diff --git a/Makefile.am b/Makefile.am
index 0eb8020..b506ef3 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -8,28 +8,29 @@
 # the right time.
 SUBDIRS = . src
 
-# Always include gtest in distributions.
+# Always include gmock in distributions.
 DIST_SUBDIRS = $(subdirs) src conformance
 
-# Build gtest before we build protobuf tests.  We don't add gtest to SUBDIRS
-# because then "make check" would also build and run all of gtest's own tests,
+# Build gmock before we build protobuf tests.  We don't add gmock to SUBDIRS
+# because then "make check" would also build and run all of gmock's own tests,
 # which takes a lot of time and is generally not useful to us.  Also, we don't
-# want "make install" to recurse into gtest since we don't want to overwrite
-# the installed version of gtest if there is one.
+# want "make install" to recurse into gmock since we don't want to overwrite
+# the installed version of gmock if there is one.
 check-local:
-	@echo "Making lib/libgtest.a lib/libgtest_main.a in gtest"
-	@cd gtest && $(MAKE) $(AM_MAKEFLAGS) lib/libgtest.la lib/libgtest_main.la
+	@echo "Making lib/libgmock.a lib/libgmock_main.a in gmock"
+	@cd gmock && $(MAKE) $(AM_MAKEFLAGS) lib/libgmock.la lib/libgmock_main.la
+	@cd gmock/gtest && $(MAKE) $(AM_MAKEFLAGS) lib/libgtest.la lib/libgtest_main.la
 
-# We would like to clean gtest when "make clean" is invoked.  But we have to
+# We would like to clean gmock when "make clean" is invoked.  But we have to
 # be careful because clean-local is also invoked during "make distclean", but
-# "make distclean" already recurses into gtest because it's listed among the
-# DIST_SUBDIRS.  distclean will delete gtest/Makefile, so if we then try to
+# "make distclean" already recurses into gmock because it's listed among the
+# DIST_SUBDIRS.  distclean will delete gmock/Makefile, so if we then try to
 # cd to the directory again and "make clean" it will fail.  So, check that the
 # Makefile exists before recursing.
 clean-local:
-	@if test -e gtest/Makefile; then \
-	  echo "Making clean in gtest"; \
-	  cd gtest && $(MAKE) $(AM_MAKEFLAGS) clean; \
+	@if test -e gmock/Makefile; then \
+	  echo "Making clean in gmock"; \
+	  cd gmock && $(MAKE) $(AM_MAKEFLAGS) clean; \
 	fi; \
 	if test -e conformance/Makefile; then \
 	  echo "Making clean in conformance"; \
diff --git a/README.md b/README.md
index 51377ad..a974d30 100644
--- a/README.md
+++ b/README.md
@@ -15,12 +15,12 @@
 
     $ ./autogen.sh
 
-This will download gtest source (which is used for C++ Protocol Buffer
+This will download gmock source (which is used for C++ Protocol Buffer
 unit-tests) to the current directory and run automake, autoconf, etc.
 to generate the configure script and various template makefiles.
 
 You can skip this step if you are using a release package (which already
-contains gtest and the configure script).
+contains gmock and the configure script).
 
 To build and install the C++ Protocol Buffer runtime and the Protocol
 Buffer compiler (protoc) execute the following:
diff --git a/autogen.sh b/autogen.sh
index 08966c6..8160313 100755
--- a/autogen.sh
+++ b/autogen.sh
@@ -15,27 +15,18 @@
   exit 1
 fi
 
-# Check that gtest is present.  Usually it is already there since the
+# Check that gmock is present.  Usually it is already there since the
 # directory is set up as an SVN external.
-if test ! -e gtest; then
-  echo "Google Test not present.  Fetching gtest-1.7.0 from the web..."
-  curl -O https://googletest.googlecode.com/files/gtest-1.7.0.zip
-  unzip -q gtest-1.7.0.zip
-  rm gtest-1.7.0.zip
-  mv gtest-1.7.0 gtest
+if test ! -e gmock; then
+  echo "Google Mock not present.  Fetching gmock-1.7.0 from the web..."
+  curl -O https://googlemock.googlecode.com/files/gmock-1.7.0.zip
+  unzip -q gmock-1.7.0.zip
+  rm gmock-1.7.0.zip
+  mv gmock-1.7.0 gmock
 fi
 
 set -ex
 
-# Temporary hack:  Must change C runtime library to "multi-threaded DLL",
-#   otherwise it will be set to "multi-threaded static" when MSVC upgrades
-#   the project file to MSVC 2005/2008.  vladl of Google Test says gtest will
-#   probably change their default to match, then this will be unnecessary.
-#   One of these mappings converts the debug configuration and the other
-#   converts the release configuration.  I don't know which is which.
-sed -i -e 's/RuntimeLibrary="5"/RuntimeLibrary="3"/g;
-           s/RuntimeLibrary="4"/RuntimeLibrary="2"/g;' gtest/msvc/*.vcproj
-
 # TODO(kenton):  Remove the ",no-obsolete" part and fix the resulting warnings.
 autoreconf -f -i -Wall,no-obsolete
 
diff --git a/cmake/README.md b/cmake/README.md
index 1d5c8bc..0abe078 100644
--- a/cmake/README.md
+++ b/cmake/README.md
@@ -5,17 +5,17 @@
 Compiling and Installing
 ========================
 
-1. Check whether a gtest directory exists in the upper level directory. If you
-   checkout the code from github via "git clone", this gtest directory won't
+1. Check whether a gmock directory exists in the upper level directory. If you
+   checkout the code from github via "git clone", this gmock directory won't
    exist and you won't be able to build protobuf unit-tests. Consider using one
    of the release tar balls instead:
 
         https://github.com/google/protobuf/releases
 
    These release tar balls are more stable versions of protobuf and already
-   have the gtest directory included.
+   have the gmock directory included.
 
-   You can also download gtest by yourself and put it in the right place.
+   You can also download gmock by yourself and put it in the right place.
 
    If you absolutely don't want to build and run protobuf unit-tests, skip
    this step and use protobuf at your own risk.
@@ -29,7 +29,7 @@
         $ cd build
         $ cmake -G "Visual Studio 9 2008" ..
 
-   If you don't have gtest, skip the build of tests by turning off the
+   If you don't have gmock, skip the build of tests by turning off the
    BUILD_TESTING option:
 
         $ cmake -G "Visutal Studio 9 2008" -DBUILD_TESTING=OFF ..
diff --git a/cmake/extract_includes.bat.in b/cmake/extract_includes.bat.in
index b2e9444..d0c6dbf 100644
--- a/cmake/extract_includes.bat.in
+++ b/cmake/extract_includes.bat.in
@@ -11,6 +11,7 @@
 mkdir include\google\protobuf\compiler\ruby
 mkdir include\google\protobuf\io
 mkdir include\google\protobuf\stubs
+mkdir include\google\protobuf\util
 copy ${PROTOBUF_SOURCE_WIN32_PATH}\..\src\google\protobuf\any.h include\google\protobuf\any.h
 copy ${PROTOBUF_SOURCE_WIN32_PATH}\..\src\google\protobuf\any.pb.h include\google\protobuf\any.pb.h
 copy ${PROTOBUF_SOURCE_WIN32_PATH}\..\src\google\protobuf\api.pb.h include\google\protobuf\api.pb.h
@@ -98,6 +99,11 @@
 copy ${PROTOBUF_SOURCE_WIN32_PATH}\..\src\google\protobuf\timestamp.pb.h include\google\protobuf\timestamp.pb.h
 copy ${PROTOBUF_SOURCE_WIN32_PATH}\..\src\google\protobuf\type.pb.h include\google\protobuf\type.pb.h
 copy ${PROTOBUF_SOURCE_WIN32_PATH}\..\src\google\protobuf\unknown_field_set.h include\google\protobuf\unknown_field_set.h
+copy ${PROTOBUF_SOURCE_WIN32_PATH}\..\src\google\protobuf\util\field_comparator.h include\google\protobuf\util\field_comparator.h
+copy ${PROTOBUF_SOURCE_WIN32_PATH}\..\src\google\protobuf\util\json_util.h include\google\protobuf\util\json_util.h
+copy ${PROTOBUF_SOURCE_WIN32_PATH}\..\src\google\protobuf\util\message_differencer.h include\google\protobuf\util\message_differencer.h
+copy ${PROTOBUF_SOURCE_WIN32_PATH}\..\src\google\protobuf\util\type_resolver.h include\google\protobuf\util\type_resolver.h
+copy ${PROTOBUF_SOURCE_WIN32_PATH}\..\src\google\protobuf\util\type_resolver_util.h include\google\protobuf\util\type_resolver_util.h
 copy ${PROTOBUF_SOURCE_WIN32_PATH}\..\src\google\protobuf\wire_format.h include\google\protobuf\wire_format.h
 copy ${PROTOBUF_SOURCE_WIN32_PATH}\..\src\google\protobuf\wire_format_lite.h include\google\protobuf\wire_format_lite.h
 copy ${PROTOBUF_SOURCE_WIN32_PATH}\..\src\google\protobuf\wire_format_lite_inl.h include\google\protobuf\wire_format_lite_inl.h
diff --git a/cmake/libprotobuf-lite.cmake b/cmake/libprotobuf-lite.cmake
index 32c2d02..8d995df 100644
--- a/cmake/libprotobuf-lite.cmake
+++ b/cmake/libprotobuf-lite.cmake
@@ -10,9 +10,14 @@
   ${protobuf_source_dir}/src/google/protobuf/repeated_field.cc
   ${protobuf_source_dir}/src/google/protobuf/stubs/atomicops_internals_x86_gcc.cc
   ${protobuf_source_dir}/src/google/protobuf/stubs/atomicops_internals_x86_msvc.cc
+  ${protobuf_source_dir}/src/google/protobuf/stubs/bytestream.cc
   ${protobuf_source_dir}/src/google/protobuf/stubs/common.cc
   ${protobuf_source_dir}/src/google/protobuf/stubs/once.cc
+  ${protobuf_source_dir}/src/google/protobuf/stubs/status.cc
+  ${protobuf_source_dir}/src/google/protobuf/stubs/statusor.cc
+  ${protobuf_source_dir}/src/google/protobuf/stubs/stringpiece.cc
   ${protobuf_source_dir}/src/google/protobuf/stubs/stringprintf.cc
+  ${protobuf_source_dir}/src/google/protobuf/stubs/time.cc
   ${protobuf_source_dir}/src/google/protobuf/wire_format_lite.cc
 )
 
diff --git a/cmake/libprotobuf.cmake b/cmake/libprotobuf.cmake
index b1f2dc3..850d93a 100644
--- a/cmake/libprotobuf.cmake
+++ b/cmake/libprotobuf.cmake
@@ -24,6 +24,7 @@
   ${protobuf_source_dir}/src/google/protobuf/service.cc
   ${protobuf_source_dir}/src/google/protobuf/source_context.pb.cc
   ${protobuf_source_dir}/src/google/protobuf/struct.pb.cc
+  ${protobuf_source_dir}/src/google/protobuf/stubs/mathlimits.cc
   ${protobuf_source_dir}/src/google/protobuf/stubs/structurally_valid.cc
   ${protobuf_source_dir}/src/google/protobuf/stubs/strutil.cc
   ${protobuf_source_dir}/src/google/protobuf/stubs/substitute.cc
@@ -31,6 +32,22 @@
   ${protobuf_source_dir}/src/google/protobuf/timestamp.pb.cc
   ${protobuf_source_dir}/src/google/protobuf/type.pb.cc
   ${protobuf_source_dir}/src/google/protobuf/unknown_field_set.cc
+  ${protobuf_source_dir}/src/google/protobuf/util/field_comparator.cc
+  ${protobuf_source_dir}/src/google/protobuf/util/internal/datapiece.cc
+  ${protobuf_source_dir}/src/google/protobuf/util/internal/default_value_objectwriter.cc
+  ${protobuf_source_dir}/src/google/protobuf/util/internal/error_listener.cc
+  ${protobuf_source_dir}/src/google/protobuf/util/internal/field_mask_utility.cc
+  ${protobuf_source_dir}/src/google/protobuf/util/internal/json_escaping.cc
+  ${protobuf_source_dir}/src/google/protobuf/util/internal/json_objectwriter.cc
+  ${protobuf_source_dir}/src/google/protobuf/util/internal/json_stream_parser.cc
+  ${protobuf_source_dir}/src/google/protobuf/util/internal/object_writer.cc
+  ${protobuf_source_dir}/src/google/protobuf/util/internal/protostream_objectsource.cc
+  ${protobuf_source_dir}/src/google/protobuf/util/internal/protostream_objectwriter.cc
+  ${protobuf_source_dir}/src/google/protobuf/util/internal/type_info.cc
+  ${protobuf_source_dir}/src/google/protobuf/util/internal/utility.cc
+  ${protobuf_source_dir}/src/google/protobuf/util/json_util.cc
+  ${protobuf_source_dir}/src/google/protobuf/util/message_differencer.cc
+  ${protobuf_source_dir}/src/google/protobuf/util/type_resolver_util.cc
   ${protobuf_source_dir}/src/google/protobuf/wire_format.cc
   ${protobuf_source_dir}/src/google/protobuf/wrappers.pb.cc
 )
diff --git a/cmake/tests.cmake b/cmake/tests.cmake
index 8fb5eef..4396a65 100644
--- a/cmake/tests.cmake
+++ b/cmake/tests.cmake
@@ -1,10 +1,13 @@
-include_directories(
-  ${protobuf_source_dir}/gtest/include
-  ${protobuf_source_dir}/gtest)
+if (NOT EXISTS "${PROJECT_SOURCE_DIR}/../gmock/CMakeLists.txt")
+  message(FATAL_ERROR "Cannot find gmock directory.")
+endif()
 
-add_library(gtest STATIC ${protobuf_source_dir}/gtest/src/gtest-all.cc)
-add_library(gtest_main STATIC ${protobuf_source_dir}/gtest/src/gtest_main.cc)
-target_link_libraries(gtest_main gtest)
+add_subdirectory(../gmock ${PROJECT_BINARY_DIR}/gmock)
+
+include_directories(
+  ${protobuf_source_dir}/gmock/gtest/include
+  ${protobuf_source_dir}/gmock/include
+)
 
 set(lite_test_protos
   google/protobuf/map_lite_unittest.proto
@@ -39,6 +42,15 @@
   google/protobuf/unittest_preserve_unknown_enum2.proto
   google/protobuf/unittest_proto3_arena.proto
   google/protobuf/unittest_well_known_types.proto
+  google/protobuf/util/internal/testdata/anys.proto
+  google/protobuf/util/internal/testdata/books.proto
+  google/protobuf/util/internal/testdata/default_value.proto
+  google/protobuf/util/internal/testdata/default_value_test.proto
+  google/protobuf/util/internal/testdata/field_mask.proto
+  google/protobuf/util/internal/testdata/maps.proto
+  google/protobuf/util/internal/testdata/struct.proto
+  google/protobuf/util/internal/testdata/timestamp_duration.proto
+  google/protobuf/util/json_format_proto3.proto
 )
 
 macro(compile_proto_file filename)
@@ -46,10 +58,10 @@
   get_filename_component(basename ${filename} NAME_WE)
   add_custom_command(
     OUTPUT ${protobuf_source_dir}/src/${dirname}/${basename}.pb.cc
+    DEPENDS protoc ${protobuf_source_dir}/src/${dirname}/${basename}.proto
     COMMAND protoc ${protobuf_source_dir}/src/${dirname}/${basename}.proto
         --proto_path=${protobuf_source_dir}/src
         --cpp_out=${protobuf_source_dir}/src
-    DEPENDS protoc
   )
 endmacro(compile_proto_file)
 
@@ -113,21 +125,35 @@
   ${protobuf_source_dir}/src/google/protobuf/reflection_ops_unittest.cc
   ${protobuf_source_dir}/src/google/protobuf/repeated_field_reflection_unittest.cc
   ${protobuf_source_dir}/src/google/protobuf/repeated_field_unittest.cc
+  ${protobuf_source_dir}/src/google/protobuf/stubs/bytestream_unittest.cc
   ${protobuf_source_dir}/src/google/protobuf/stubs/common_unittest.cc
   ${protobuf_source_dir}/src/google/protobuf/stubs/once_unittest.cc
+  ${protobuf_source_dir}/src/google/protobuf/stubs/status_test.cc
+  ${protobuf_source_dir}/src/google/protobuf/stubs/statusor_test.cc
+  ${protobuf_source_dir}/src/google/protobuf/stubs/stringpiece_unittest.cc
   ${protobuf_source_dir}/src/google/protobuf/stubs/stringprintf_unittest.cc
   ${protobuf_source_dir}/src/google/protobuf/stubs/structurally_valid_unittest.cc
   ${protobuf_source_dir}/src/google/protobuf/stubs/strutil_unittest.cc
   ${protobuf_source_dir}/src/google/protobuf/stubs/template_util_unittest.cc
+  ${protobuf_source_dir}/src/google/protobuf/stubs/time_test.cc
   ${protobuf_source_dir}/src/google/protobuf/stubs/type_traits_unittest.cc
   ${protobuf_source_dir}/src/google/protobuf/text_format_unittest.cc
   ${protobuf_source_dir}/src/google/protobuf/unknown_field_set_unittest.cc
+  ${protobuf_source_dir}/src/google/protobuf/util/field_comparator_test.cc
+  ${protobuf_source_dir}/src/google/protobuf/util/internal/default_value_objectwriter_test.cc
+  ${protobuf_source_dir}/src/google/protobuf/util/internal/json_objectwriter_test.cc
+  ${protobuf_source_dir}/src/google/protobuf/util/internal/json_stream_parser_test.cc
+  ${protobuf_source_dir}/src/google/protobuf/util/internal/protostream_objectsource_test.cc
+  ${protobuf_source_dir}/src/google/protobuf/util/internal/protostream_objectwriter_test.cc
+  ${protobuf_source_dir}/src/google/protobuf/util/internal/type_info_test_helper.cc
+  ${protobuf_source_dir}/src/google/protobuf/util/json_util_test.cc
+  ${protobuf_source_dir}/src/google/protobuf/util/type_resolver_util_test.cc
   ${protobuf_source_dir}/src/google/protobuf/well_known_types_unittest.cc
   ${protobuf_source_dir}/src/google/protobuf/wire_format_unittest.cc
 )
 
 add_executable(tests ${tests_files} ${common_test_files} ${tests_proto_files} ${lite_test_proto_files})
-target_link_libraries(tests libprotoc libprotobuf gtest_main)
+target_link_libraries(tests libprotoc libprotobuf gmock_main)
 
 set(test_plugin_files
   ${protobuf_source_dir}/src/google/protobuf/compiler/mock_code_generator.cc
@@ -137,7 +163,7 @@
 )
 
 add_executable(test_plugin ${test_plugin_files})
-target_link_libraries(test_plugin libprotoc libprotobuf gtest)
+target_link_libraries(test_plugin libprotoc libprotobuf gmock)
 
 set(lite_test_files
   ${protobuf_source_dir}/src/google/protobuf/arena_test_util.cc
diff --git a/configure.ac b/configure.ac
index 8018cc7..764e5d4 100644
--- a/configure.ac
+++ b/configure.ac
@@ -157,12 +157,12 @@
     ;;
 esac
 
-# HACK:  Make gtest's configure script pick up our copy of CFLAGS and CXXFLAGS,
-#   since the flags added by ACX_CHECK_SUNCC must be used when compiling gtest
+# HACK:  Make gmock's configure script pick up our copy of CFLAGS and CXXFLAGS,
+#   since the flags added by ACX_CHECK_SUNCC must be used when compiling gmock
 #   too.
 export CFLAGS
 export CXXFLAGS
-AC_CONFIG_SUBDIRS([gtest])
+AC_CONFIG_SUBDIRS([gmock])
 
 AC_CONFIG_FILES([Makefile src/Makefile conformance/Makefile protobuf.pc protobuf-lite.pc])
 AC_OUTPUT
diff --git a/src/Makefile.am b/src/Makefile.am
index ac6ec6f..de6a88e 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -139,7 +139,12 @@
   google/protobuf/compiler/objectivec/objectivec_helpers.h      \
   google/protobuf/compiler/python/python_generator.h            \
   google/protobuf/compiler/ruby/ruby_generator.h                \
-  google/protobuf/compiler/csharp/csharp_generator.h
+  google/protobuf/compiler/csharp/csharp_generator.h            \
+  google/protobuf/util/type_resolver.h                          \
+  google/protobuf/util/type_resolver_util.h                     \
+  google/protobuf/util/json_util.h                              \
+  google/protobuf/util/field_comparator.h                       \
+  google/protobuf/util/message_differencer.h
 
 lib_LTLIBRARIES = libprotobuf-lite.la libprotobuf.la libprotoc.la
 
@@ -148,13 +153,25 @@
 libprotobuf_lite_la_SOURCES =                                  \
   google/protobuf/stubs/atomicops_internals_x86_gcc.cc         \
   google/protobuf/stubs/atomicops_internals_x86_msvc.cc        \
+  google/protobuf/stubs/bytestream.cc                          \
+  google/protobuf/stubs/bytestream.h                           \
   google/protobuf/stubs/common.cc                              \
-  google/protobuf/stubs/once.cc                                \
   google/protobuf/stubs/hash.h                                 \
   google/protobuf/stubs/map_util.h                             \
+  google/protobuf/stubs/mathutil.h                             \
+  google/protobuf/stubs/once.cc                                \
   google/protobuf/stubs/shared_ptr.h                           \
+  google/protobuf/stubs/status.cc                              \
+  google/protobuf/stubs/status.h                               \
+  google/protobuf/stubs/status_macros.h                        \
+  google/protobuf/stubs/statusor.cc                            \
+  google/protobuf/stubs/statusor.h                             \
+  google/protobuf/stubs/stringpiece.cc                         \
+  google/protobuf/stubs/stringpiece.h                          \
   google/protobuf/stubs/stringprintf.cc                        \
   google/protobuf/stubs/stringprintf.h                         \
+  google/protobuf/stubs/time.cc                                \
+  google/protobuf/stubs/time.h                                 \
   google/protobuf/arena.cc                                     \
   google/protobuf/arenastring.cc                               \
   google/protobuf/extension_set.cc                             \
@@ -173,6 +190,8 @@
   $(libprotobuf_lite_la_SOURCES)                               \
   google/protobuf/any.pb.cc                                    \
   google/protobuf/api.pb.cc                                    \
+  google/protobuf/stubs/mathlimits.h                           \
+  google/protobuf/stubs/mathlimits.cc                          \
   google/protobuf/any.cc                                       \
   google/protobuf/descriptor.cc                                \
   google/protobuf/descriptor_database.cc                       \
@@ -207,7 +226,39 @@
   google/protobuf/io/tokenizer.cc                              \
   google/protobuf/io/zero_copy_stream_impl.cc                  \
   google/protobuf/compiler/importer.cc                         \
-  google/protobuf/compiler/parser.cc
+  google/protobuf/compiler/parser.cc                           \
+  google/protobuf/util/field_comparator.cc                     \
+  google/protobuf/util/internal/constants.h                    \
+  google/protobuf/util/internal/datapiece.cc                   \
+  google/protobuf/util/internal/datapiece.h                    \
+  google/protobuf/util/internal/default_value_objectwriter.cc  \
+  google/protobuf/util/internal/default_value_objectwriter.h   \
+  google/protobuf/util/internal/error_listener.cc              \
+  google/protobuf/util/internal/error_listener.h               \
+  google/protobuf/util/internal/field_mask_utility.cc          \
+  google/protobuf/util/internal/field_mask_utility.h           \
+  google/protobuf/util/internal/json_escaping.cc               \
+  google/protobuf/util/internal/json_escaping.h                \
+  google/protobuf/util/internal/json_objectwriter.cc           \
+  google/protobuf/util/internal/json_objectwriter.h            \
+  google/protobuf/util/internal/json_stream_parser.cc          \
+  google/protobuf/util/internal/json_stream_parser.h           \
+  google/protobuf/util/internal/location_tracker.h             \
+  google/protobuf/util/internal/object_source.h                \
+  google/protobuf/util/internal/object_writer.cc               \
+  google/protobuf/util/internal/object_writer.h                \
+  google/protobuf/util/internal/object_writer.h                \
+  google/protobuf/util/internal/protostream_objectsource.cc    \
+  google/protobuf/util/internal/protostream_objectsource.h     \
+  google/protobuf/util/internal/protostream_objectwriter.cc    \
+  google/protobuf/util/internal/protostream_objectwriter.h     \
+  google/protobuf/util/internal/type_info.cc                   \
+  google/protobuf/util/internal/type_info.h                    \
+  google/protobuf/util/internal/utility.cc                     \
+  google/protobuf/util/internal/utility.h                      \
+  google/protobuf/util/json_util.cc                            \
+  google/protobuf/util/type_resolver_util.cc                   \
+  google/protobuf/util/message_differencer.cc
 nodist_libprotobuf_la_SOURCES = $(nodist_libprotobuf_lite_la_SOURCES)
 
 libprotoc_la_LIBADD = $(PTHREAD_LIBS) libprotobuf.la
@@ -386,35 +437,44 @@
 
 # Tests ==============================================================
 
-protoc_inputs =                                                \
-  google/protobuf/any_test.proto                               \
-  google/protobuf/map_lite_unittest.proto                      \
-  google/protobuf/map_proto2_unittest.proto                    \
-  google/protobuf/map_unittest.proto                           \
-  google/protobuf/unittest.proto                               \
-  google/protobuf/unittest_arena.proto                         \
-  google/protobuf/unittest_custom_options.proto                \
-  google/protobuf/unittest_drop_unknown_fields.proto           \
-  google/protobuf/unittest_embed_optimize_for.proto            \
-  google/protobuf/unittest_empty.proto                         \
-  google/protobuf/unittest_enormous_descriptor.proto           \
-  google/protobuf/unittest_import_lite.proto                   \
-  google/protobuf/unittest_import.proto                        \
-  google/protobuf/unittest_import_public_lite.proto            \
-  google/protobuf/unittest_import_public.proto                 \
-  google/protobuf/unittest_lite_imports_nonlite.proto          \
-  google/protobuf/unittest_lite.proto                          \
-  google/protobuf/unittest_mset.proto                          \
-  google/protobuf/unittest_no_arena_import.proto               \
-  google/protobuf/unittest_no_arena.proto                      \
-  google/protobuf/unittest_no_field_presence.proto             \
-  google/protobuf/unittest_no_generic_services.proto           \
-  google/protobuf/unittest_optimize_for.proto                  \
-  google/protobuf/unittest_preserve_unknown_enum.proto         \
-  google/protobuf/unittest_preserve_unknown_enum2.proto        \
-  google/protobuf/unittest_proto3_arena.proto                  \
-  google/protobuf/unittest_well_known_types.proto              \
-  google/protobuf/compiler/cpp/cpp_test_bad_identifiers.proto  \
+protoc_inputs =                                                   \
+  google/protobuf/any_test.proto                                  \
+  google/protobuf/compiler/cpp/cpp_test_bad_identifiers.proto     \
+  google/protobuf/map_lite_unittest.proto                         \
+  google/protobuf/map_proto2_unittest.proto                       \
+  google/protobuf/map_unittest.proto                              \
+  google/protobuf/unittest_arena.proto                            \
+  google/protobuf/unittest_custom_options.proto                   \
+  google/protobuf/unittest_drop_unknown_fields.proto              \
+  google/protobuf/unittest_embed_optimize_for.proto               \
+  google/protobuf/unittest_empty.proto                            \
+  google/protobuf/unittest_enormous_descriptor.proto              \
+  google/protobuf/unittest_import_lite.proto                      \
+  google/protobuf/unittest_import.proto                           \
+  google/protobuf/unittest_import_public_lite.proto               \
+  google/protobuf/unittest_import_public.proto                    \
+  google/protobuf/unittest_lite_imports_nonlite.proto             \
+  google/protobuf/unittest_lite.proto                             \
+  google/protobuf/unittest_mset.proto                             \
+  google/protobuf/unittest_no_arena_import.proto                  \
+  google/protobuf/unittest_no_arena.proto                         \
+  google/protobuf/unittest_no_field_presence.proto                \
+  google/protobuf/unittest_no_generic_services.proto              \
+  google/protobuf/unittest_optimize_for.proto                     \
+  google/protobuf/unittest_preserve_unknown_enum2.proto           \
+  google/protobuf/unittest_preserve_unknown_enum.proto            \
+  google/protobuf/unittest.proto                                  \
+  google/protobuf/unittest_proto3_arena.proto                     \
+  google/protobuf/unittest_well_known_types.proto                 \
+  google/protobuf/util/internal/testdata/anys.proto               \
+  google/protobuf/util/internal/testdata/books.proto              \
+  google/protobuf/util/internal/testdata/default_value.proto      \
+  google/protobuf/util/internal/testdata/default_value_test.proto \
+  google/protobuf/util/internal/testdata/field_mask.proto         \
+  google/protobuf/util/internal/testdata/maps.proto               \
+  google/protobuf/util/internal/testdata/struct.proto             \
+  google/protobuf/util/internal/testdata/timestamp_duration.proto \
+  google/protobuf/util/json_format_proto3.proto                   \
   google/protobuf/compiler/cpp/cpp_test_large_enum_value.proto
 
 EXTRA_DIST =                                                   \
@@ -451,58 +511,76 @@
   google/protobuf/unittest_import_public_lite.pb.cc            \
   google/protobuf/unittest_import_public_lite.pb.h
 
-protoc_outputs =                                               \
-  $(protoc_lite_outputs)                                       \
-  google/protobuf/any_test.pb.cc                               \
-  google/protobuf/any_test.pb.h                                \
-  google/protobuf/map_proto2_unittest.pb.cc                    \
-  google/protobuf/map_proto2_unittest.pb.h                     \
-  google/protobuf/map_unittest.pb.cc                           \
-  google/protobuf/map_unittest.pb.h                            \
-  google/protobuf/unittest.pb.cc                               \
-  google/protobuf/unittest.pb.h                                \
-  google/protobuf/unittest_arena.pb.cc                         \
-  google/protobuf/unittest_arena.pb.h                          \
-  google/protobuf/unittest_custom_options.pb.cc                \
-  google/protobuf/unittest_custom_options.pb.h                 \
-  google/protobuf/unittest_drop_unknown_fields.pb.cc           \
-  google/protobuf/unittest_drop_unknown_fields.pb.h            \
-  google/protobuf/unittest_embed_optimize_for.pb.cc            \
-  google/protobuf/unittest_embed_optimize_for.pb.h             \
-  google/protobuf/unittest_empty.pb.cc                         \
-  google/protobuf/unittest_empty.pb.h                          \
-  google/protobuf/unittest_enormous_descriptor.pb.cc           \
-  google/protobuf/unittest_enormous_descriptor.pb.h            \
-  google/protobuf/unittest_import.pb.cc                        \
-  google/protobuf/unittest_import.pb.h                         \
-  google/protobuf/unittest_import_public.pb.cc                 \
-  google/protobuf/unittest_import_public.pb.h                  \
-  google/protobuf/unittest_lite_imports_nonlite.pb.cc          \
-  google/protobuf/unittest_lite_imports_nonlite.pb.h           \
-  google/protobuf/unittest_mset.pb.cc                          \
-  google/protobuf/unittest_mset.pb.h                           \
-  google/protobuf/unittest_no_arena.pb.cc                      \
-  google/protobuf/unittest_no_arena.pb.h                       \
-  google/protobuf/unittest_no_arena_import.pb.cc               \
-  google/protobuf/unittest_no_arena_import.pb.h                \
-  google/protobuf/unittest_no_field_presence.pb.cc             \
-  google/protobuf/unittest_no_field_presence.pb.h              \
-  google/protobuf/unittest_no_generic_services.pb.cc           \
-  google/protobuf/unittest_no_generic_services.pb.h            \
-  google/protobuf/unittest_optimize_for.pb.cc                  \
-  google/protobuf/unittest_optimize_for.pb.h                   \
-  google/protobuf/unittest_preserve_unknown_enum.pb.cc         \
-  google/protobuf/unittest_preserve_unknown_enum.pb.h          \
-  google/protobuf/unittest_preserve_unknown_enum2.pb.cc        \
-  google/protobuf/unittest_preserve_unknown_enum2.pb.h         \
-  google/protobuf/unittest_proto3_arena.pb.cc                  \
-  google/protobuf/unittest_proto3_arena.pb.h                   \
-  google/protobuf/unittest_well_known_types.pb.cc              \
-  google/protobuf/unittest_well_known_types.pb.h               \
-  google/protobuf/compiler/cpp/cpp_test_large_enum_value.pb.cc \
-  google/protobuf/compiler/cpp/cpp_test_large_enum_value.pb.h  \
-  google/protobuf/compiler/cpp/cpp_test_bad_identifiers.pb.cc  \
-  google/protobuf/compiler/cpp/cpp_test_bad_identifiers.pb.h
+protoc_outputs =                                                  \
+  $(protoc_lite_outputs)                                          \
+  google/protobuf/any_test.pb.cc                                  \
+  google/protobuf/any_test.pb.h                                   \
+  google/protobuf/compiler/cpp/cpp_test_bad_identifiers.pb.cc     \
+  google/protobuf/compiler/cpp/cpp_test_bad_identifiers.pb.h      \
+  google/protobuf/compiler/cpp/cpp_test_large_enum_value.pb.cc    \
+  google/protobuf/compiler/cpp/cpp_test_large_enum_value.pb.h     \
+  google/protobuf/map_proto2_unittest.pb.cc                       \
+  google/protobuf/map_proto2_unittest.pb.h                        \
+  google/protobuf/map_unittest.pb.cc                              \
+  google/protobuf/map_unittest.pb.h                               \
+  google/protobuf/unittest_arena.pb.cc                            \
+  google/protobuf/unittest_arena.pb.h                             \
+  google/protobuf/unittest_custom_options.pb.cc                   \
+  google/protobuf/unittest_custom_options.pb.h                    \
+  google/protobuf/unittest_drop_unknown_fields.pb.cc              \
+  google/protobuf/unittest_drop_unknown_fields.pb.h               \
+  google/protobuf/unittest_embed_optimize_for.pb.cc               \
+  google/protobuf/unittest_embed_optimize_for.pb.h                \
+  google/protobuf/unittest_empty.pb.cc                            \
+  google/protobuf/unittest_empty.pb.h                             \
+  google/protobuf/unittest_enormous_descriptor.pb.cc              \
+  google/protobuf/unittest_enormous_descriptor.pb.h               \
+  google/protobuf/unittest_import.pb.cc                           \
+  google/protobuf/unittest_import.pb.h                            \
+  google/protobuf/unittest_import_public.pb.cc                    \
+  google/protobuf/unittest_import_public.pb.h                     \
+  google/protobuf/unittest_lite_imports_nonlite.pb.cc             \
+  google/protobuf/unittest_lite_imports_nonlite.pb.h              \
+  google/protobuf/unittest_mset.pb.cc                             \
+  google/protobuf/unittest_mset.pb.h                              \
+  google/protobuf/unittest_no_arena_import.pb.cc                  \
+  google/protobuf/unittest_no_arena_import.pb.h                   \
+  google/protobuf/unittest_no_arena.pb.cc                         \
+  google/protobuf/unittest_no_arena.pb.h                          \
+  google/protobuf/unittest_no_field_presence.pb.cc                \
+  google/protobuf/unittest_no_field_presence.pb.h                 \
+  google/protobuf/unittest_no_generic_services.pb.cc              \
+  google/protobuf/unittest_no_generic_services.pb.h               \
+  google/protobuf/unittest_optimize_for.pb.cc                     \
+  google/protobuf/unittest_optimize_for.pb.h                      \
+  google/protobuf/unittest.pb.cc                                  \
+  google/protobuf/unittest.pb.h                                   \
+  google/protobuf/unittest_preserve_unknown_enum2.pb.cc           \
+  google/protobuf/unittest_preserve_unknown_enum2.pb.h            \
+  google/protobuf/unittest_preserve_unknown_enum.pb.cc            \
+  google/protobuf/unittest_preserve_unknown_enum.pb.h             \
+  google/protobuf/unittest_proto3_arena.pb.cc                     \
+  google/protobuf/unittest_proto3_arena.pb.h                      \
+  google/protobuf/unittest_well_known_types.pb.cc                 \
+  google/protobuf/unittest_well_known_types.pb.h                  \
+  google/protobuf/util/internal/testdata/anys.pb.cc               \
+  google/protobuf/util/internal/testdata/anys.pb.h                \
+  google/protobuf/util/internal/testdata/books.pb.cc              \
+  google/protobuf/util/internal/testdata/books.pb.h               \
+  google/protobuf/util/internal/testdata/default_value.pb.cc      \
+  google/protobuf/util/internal/testdata/default_value.pb.h       \
+  google/protobuf/util/internal/testdata/default_value_test.pb.cc \
+  google/protobuf/util/internal/testdata/default_value_test.pb.h  \
+  google/protobuf/util/internal/testdata/field_mask.pb.cc         \
+  google/protobuf/util/internal/testdata/field_mask.pb.h          \
+  google/protobuf/util/internal/testdata/maps.pb.cc               \
+  google/protobuf/util/internal/testdata/maps.pb.h                \
+  google/protobuf/util/internal/testdata/struct.pb.cc             \
+  google/protobuf/util/internal/testdata/struct.pb.h              \
+  google/protobuf/util/internal/testdata/timestamp_duration.pb.cc \
+  google/protobuf/util/internal/testdata/timestamp_duration.pb.h  \
+  google/protobuf/util/json_format_proto3.pb.cc                   \
+  google/protobuf/util/json_format_proto3.pb.h
 
 BUILT_SOURCES = $(protoc_outputs)
 
@@ -541,21 +619,27 @@
 check_PROGRAMS = protoc protobuf-test protobuf-lazy-descriptor-test \
                  protobuf-lite-test test_plugin $(GZCHECKPROGRAMS)
 protobuf_test_LDADD = $(PTHREAD_LIBS) libprotobuf.la libprotoc.la \
-                      $(top_builddir)/gtest/lib/libgtest.la       \
-                      $(top_builddir)/gtest/lib/libgtest_main.la
-protobuf_test_CPPFLAGS = -I$(top_srcdir)/gtest/include         \
-                         -I$(top_builddir)/gtest/include
+                      $(top_builddir)/gmock/gtest/lib/libgtest.la \
+                      $(top_builddir)/gmock/lib/libgmock.la       \
+                      $(top_builddir)/gmock/lib/libgmock_main.la
+protobuf_test_CPPFLAGS = -I$(top_builddir)/gmock/gtest/include \
+                         -I$(top_builddir)/gmock/include
 # Disable optimization for tests unless the user explicitly asked for it,
 # since test_util.cc takes forever to compile with optimization (with GCC).
 # See configure.ac for more info.
 protobuf_test_CXXFLAGS = $(NO_OPT_CXXFLAGS)
 protobuf_test_SOURCES =                                        \
+  google/protobuf/stubs/bytestream_unittest.cc                 \
   google/protobuf/stubs/common_unittest.cc                     \
   google/protobuf/stubs/once_unittest.cc                       \
-  google/protobuf/stubs/strutil_unittest.cc                    \
-  google/protobuf/stubs/structurally_valid_unittest.cc         \
+  google/protobuf/stubs/statusor_test.cc                       \
+  google/protobuf/stubs/status_test.cc                         \
+  google/protobuf/stubs/stringpiece_unittest.cc                \
   google/protobuf/stubs/stringprintf_unittest.cc               \
+  google/protobuf/stubs/structurally_valid_unittest.cc         \
+  google/protobuf/stubs/strutil_unittest.cc                    \
   google/protobuf/stubs/template_util_unittest.cc              \
+  google/protobuf/stubs/time_test.cc                           \
   google/protobuf/stubs/type_traits_unittest.cc                \
   google/protobuf/any_test.cc                                  \
   google/protobuf/arenastring_unittest.cc                      \
@@ -598,16 +682,28 @@
   google/protobuf/compiler/python/python_plugin_unittest.cc    \
   google/protobuf/compiler/ruby/ruby_generator_unittest.cc     \
   google/protobuf/compiler/csharp/csharp_generator_unittest.cc \
+  google/protobuf/util/field_comparator_test.cc                \
+  google/protobuf/util/internal/default_value_objectwriter_test.cc \
+  google/protobuf/util/internal/json_objectwriter_test.cc      \
+  google/protobuf/util/internal/json_stream_parser_test.cc     \
+  google/protobuf/util/internal/protostream_objectsource_test.cc \
+  google/protobuf/util/internal/protostream_objectwriter_test.cc \
+  google/protobuf/util/internal/type_info_test_helper.cc       \
+  google/protobuf/util/json_util_test.cc                       \
+  google/protobuf/util/type_resolver_util_test.cc              \
   $(COMMON_TEST_SOURCES)
+
+
 nodist_protobuf_test_SOURCES = $(protoc_outputs)
 
 # Run cpp_unittest again with PROTOBUF_TEST_NO_DESCRIPTORS defined.
 protobuf_lazy_descriptor_test_LDADD = $(PTHREAD_LIBS) libprotobuf.la \
                       libprotoc.la                                   \
-                      $(top_builddir)/gtest/lib/libgtest.la          \
-                      $(top_builddir)/gtest/lib/libgtest_main.la
-protobuf_lazy_descriptor_test_CPPFLAGS = -I$(top_srcdir)/gtest/include    \
-                                         -I$(top_builddir)/gtest/include  \
+                      $(top_builddir)/gmock/gtest/lib/libgtest.la    \
+                      $(top_builddir)/gmock/lib/libgmock.la          \
+                      $(top_builddir)/gmock/lib/libgmock_main.la
+protobuf_lazy_descriptor_test_CPPFLAGS = -I$(top_builddir)/gmock/include       \
+                                         -I$(top_builddir)/gmock/gtest/include \
                                          -DPROTOBUF_TEST_NO_DESCRIPTORS
 protobuf_lazy_descriptor_test_CXXFLAGS = $(NO_OPT_CXXFLAGS)
 protobuf_lazy_descriptor_test_SOURCES =                        \
@@ -632,9 +728,8 @@
 
 # Test plugin binary.
 test_plugin_LDADD = $(PTHREAD_LIBS) libprotobuf.la libprotoc.la \
-                    $(top_builddir)/gtest/lib/libgtest.la
-test_plugin_CPPFLAGS = -I$(top_srcdir)/gtest/include         \
-                       -I$(top_builddir)/gtest/include
+                    $(top_builddir)/gmock/gtest/lib/libgtest.la
+test_plugin_CPPFLAGS = -I$(top_builddir)/gmock/gtest/include
 test_plugin_SOURCES =                                          \
   google/protobuf/compiler/mock_code_generator.cc              \
   google/protobuf/testing/file.cc                              \
diff --git a/src/google/protobuf/compiler/cpp/cpp_message.cc b/src/google/protobuf/compiler/cpp/cpp_message.cc
index af85919..17f67a7 100644
--- a/src/google/protobuf/compiler/cpp/cpp_message.cc
+++ b/src/google/protobuf/compiler/cpp/cpp_message.cc
@@ -621,7 +621,7 @@
     // has_$name$() methods.
     vars["has_array_index"] = SimpleItoa(field->index() / 32);
     vars["has_mask"] = StrCat(strings::Hex(1u << (field->index() % 32),
-                                           strings::Hex::ZERO_PAD_8));
+                                           strings::ZERO_PAD_8));
     printer->Print(vars,
       "$inline$"
       "bool $classname$::has_$name$() const {\n"
@@ -3364,7 +3364,7 @@
   vector<string> parts;
   for (int i = 0; i < masks.size(); i++) {
     if (masks[i] == 0) continue;
-    string m = StrCat("0x", strings::Hex(masks[i], strings::Hex::ZERO_PAD_8));
+    string m = StrCat("0x", strings::Hex(masks[i], strings::ZERO_PAD_8));
     // Each xor evaluates to 0 if the expected bits are present.
     parts.push_back(StrCat("((_has_bits_[", i, "] & ", m, ") ^ ", m, ")"));
   }
@@ -3659,7 +3659,7 @@
         printer->Print(
           "if ((_has_bits_[$i$] & 0x$mask$) != 0x$mask$) return false;\n",
           "i", SimpleItoa(i),
-          "mask", StrCat(strings::Hex(mask, strings::Hex::ZERO_PAD_8)));
+          "mask", StrCat(strings::Hex(mask, strings::ZERO_PAD_8)));
       }
     }
   }
diff --git a/src/google/protobuf/stubs/bytestream.cc b/src/google/protobuf/stubs/bytestream.cc
new file mode 100644
index 0000000..f4af6a5
--- /dev/null
+++ b/src/google/protobuf/stubs/bytestream.cc
@@ -0,0 +1,196 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/stubs/bytestream.h>
+
+#include <string.h>
+#include <algorithm>
+
+namespace google {
+namespace protobuf {
+namespace strings {
+
+void ByteSource::CopyTo(ByteSink* sink, size_t n) {
+  while (n > 0) {
+    StringPiece fragment = Peek();
+    if (fragment.empty()) {
+      GOOGLE_LOG(DFATAL) << "ByteSource::CopyTo() overran input.";
+      break;
+    }
+    std::size_t fragment_size = std::min<std::size_t>(n, fragment.size());
+    sink->Append(fragment.data(), fragment_size);
+    Skip(fragment_size);
+    n -= fragment_size;
+  }
+}
+
+void ByteSink::Flush() {}
+
+void UncheckedArrayByteSink::Append(const char* data, size_t n) {
+  if (data != dest_) {
+    // Catch cases where the pointer returned by GetAppendBuffer() was modified.
+    GOOGLE_DCHECK(!(dest_ <= data && data < (dest_ + n)))
+        << "Append() data[] overlaps with dest_[]";
+    memcpy(dest_, data, n);
+  }
+  dest_ += n;
+}
+
+CheckedArrayByteSink::CheckedArrayByteSink(char* outbuf, size_t capacity)
+    : outbuf_(outbuf), capacity_(capacity), size_(0), overflowed_(false) {
+}
+
+void CheckedArrayByteSink::Append(const char* bytes, size_t n) {
+  size_t available = capacity_ - size_;
+  if (n > available) {
+    n = available;
+    overflowed_ = true;
+  }
+  if (n > 0 && bytes != (outbuf_ + size_)) {
+    // Catch cases where the pointer returned by GetAppendBuffer() was modified.
+    GOOGLE_DCHECK(!(outbuf_ <= bytes && bytes < (outbuf_ + capacity_)))
+        << "Append() bytes[] overlaps with outbuf_[]";
+    memcpy(outbuf_ + size_, bytes, n);
+  }
+  size_ += n;
+}
+
+GrowingArrayByteSink::GrowingArrayByteSink(size_t estimated_size)
+    : capacity_(estimated_size),
+      buf_(new char[estimated_size]),
+      size_(0) {
+}
+
+GrowingArrayByteSink::~GrowingArrayByteSink() {
+  delete[] buf_;  // Just in case the user didn't call GetBuffer.
+}
+
+void GrowingArrayByteSink::Append(const char* bytes, size_t n) {
+  size_t available = capacity_ - size_;
+  if (bytes != (buf_ + size_)) {
+    // Catch cases where the pointer returned by GetAppendBuffer() was modified.
+    // We need to test for this before calling Expand() which may reallocate.
+    GOOGLE_DCHECK(!(buf_ <= bytes && bytes < (buf_ + capacity_)))
+        << "Append() bytes[] overlaps with buf_[]";
+  }
+  if (n > available) {
+    Expand(n - available);
+  }
+  if (n > 0 && bytes != (buf_ + size_)) {
+    memcpy(buf_ + size_, bytes, n);
+  }
+  size_ += n;
+}
+
+char* GrowingArrayByteSink::GetBuffer(size_t* nbytes) {
+  ShrinkToFit();
+  char* b = buf_;
+  *nbytes = size_;
+  buf_ = NULL;
+  size_ = capacity_ = 0;
+  return b;
+}
+
+void GrowingArrayByteSink::Expand(size_t amount) {  // Expand by at least 50%.
+  size_t new_capacity = std::max(capacity_ + amount, (3 * capacity_) / 2);
+  char* bigger = new char[new_capacity];
+  memcpy(bigger, buf_, size_);
+  delete[] buf_;
+  buf_ = bigger;
+  capacity_ = new_capacity;
+}
+
+void GrowingArrayByteSink::ShrinkToFit() {
+  // Shrink only if the buffer is large and size_ is less than 3/4
+  // of capacity_.
+  if (capacity_ > 256 && size_ < (3 * capacity_) / 4) {
+    char* just_enough = new char[size_];
+    memcpy(just_enough, buf_, size_);
+    delete[] buf_;
+    buf_ = just_enough;
+    capacity_ = size_;
+  }
+}
+
+void StringByteSink::Append(const char* data, size_t n) {
+  dest_->append(data, n);
+}
+
+size_t ArrayByteSource::Available() const {
+  return input_.size();
+}
+
+StringPiece ArrayByteSource::Peek() {
+  return input_;
+}
+
+void ArrayByteSource::Skip(size_t n) {
+  GOOGLE_DCHECK_LE(n, input_.size());
+  input_.remove_prefix(n);
+}
+
+LimitByteSource::LimitByteSource(ByteSource *source, size_t limit)
+  : source_(source),
+    limit_(limit) {
+}
+
+size_t LimitByteSource::Available() const {
+  size_t available = source_->Available();
+  if (available > limit_) {
+    available = limit_;
+  }
+
+  return available;
+}
+
+StringPiece LimitByteSource::Peek() {
+  StringPiece piece(source_->Peek());
+  if (piece.size() > limit_) {
+    piece.set(piece.data(), limit_);
+  }
+
+  return piece;
+}
+
+void LimitByteSource::Skip(size_t n) {
+  GOOGLE_DCHECK_LE(n, limit_);
+  source_->Skip(n);
+  limit_ -= n;
+}
+
+void LimitByteSource::CopyTo(ByteSink *sink, size_t n) {
+  GOOGLE_DCHECK_LE(n, limit_);
+  source_->CopyTo(sink, n);
+  limit_ -= n;
+}
+
+}  // namespace strings
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/stubs/bytestream.h b/src/google/protobuf/stubs/bytestream.h
new file mode 100644
index 0000000..c9c9a76
--- /dev/null
+++ b/src/google/protobuf/stubs/bytestream.h
@@ -0,0 +1,348 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// This file declares the ByteSink and ByteSource abstract interfaces. These
+// interfaces represent objects that consume (ByteSink) or produce (ByteSource)
+// a sequence of bytes. Using these abstract interfaces in your APIs can help
+// make your code work with a variety of input and output types.
+//
+// This file also declares the following commonly used implementations of these
+// interfaces.
+//
+//   ByteSink:
+//      UncheckedArrayByteSink  Writes to an array, without bounds checking
+//      CheckedArrayByteSink    Writes to an array, with bounds checking
+//      GrowingArrayByteSink    Allocates and writes to a growable buffer
+//      StringByteSink          Writes to an STL string
+//      NullByteSink            Consumes a never-ending stream of bytes
+//
+//   ByteSource:
+//      ArrayByteSource         Reads from an array or string/StringPiece
+//      LimitedByteSource       Limits the number of bytes read from an
+
+#ifndef GOOGLE_PROTOBUF_STUBS_BYTESTREAM_H_
+#define GOOGLE_PROTOBUF_STUBS_BYTESTREAM_H_
+
+#include <stddef.h>
+#include <string>
+
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/stubs/stringpiece.h>
+
+class CordByteSink;
+class MemBlock;
+
+namespace google {
+namespace protobuf {
+namespace strings {
+
+// An abstract interface for an object that consumes a sequence of bytes. This
+// interface offers 3 different ways to append data, and a Flush() function.
+//
+// Example:
+//
+//   string my_data;
+//   ...
+//   ByteSink* sink = ...
+//   sink->Append(my_data.data(), my_data.size());
+//   sink->Flush();
+//
+class ByteSink {
+ public:
+  ByteSink() {}
+  virtual ~ByteSink() {}
+
+  // Appends the "n" bytes starting at "bytes".
+  virtual void Append(const char* bytes, size_t n) = 0;
+
+  // Flushes internal buffers. The default implemenation does nothing. ByteSink
+  // subclasses may use internal buffers that require calling Flush() at the end
+  // of the stream.
+  virtual void Flush();
+
+ private:
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(ByteSink);
+};
+
+// An abstract interface for an object that produces a fixed-size sequence of
+// bytes.
+//
+// Example:
+//
+//   ByteSource* source = ...
+//   while (source->Available() > 0) {
+//     StringPiece data = source->Peek();
+//     ... do something with "data" ...
+//     source->Skip(data.length());
+//   }
+//
+class ByteSource {
+ public:
+  ByteSource() {}
+  virtual ~ByteSource() {}
+
+  // Returns the number of bytes left to read from the source. Available()
+  // should decrease by N each time Skip(N) is called. Available() may not
+  // increase. Available() returning 0 indicates that the ByteSource is
+  // exhausted.
+  //
+  // Note: Size() may have been a more appropriate name as it's more
+  //       indicative of the fixed-size nature of a ByteSource.
+  virtual size_t Available() const = 0;
+
+  // Returns a StringPiece of the next contiguous region of the source. Does not
+  // reposition the source. The returned region is empty iff Available() == 0.
+  //
+  // The returned region is valid until the next call to Skip() or until this
+  // object is destroyed, whichever occurs first.
+  //
+  // The length of the returned StringPiece will be <= Available().
+  virtual StringPiece Peek() = 0;
+
+  // Skips the next n bytes. Invalidates any StringPiece returned by a previous
+  // call to Peek().
+  //
+  // REQUIRES: Available() >= n
+  virtual void Skip(size_t n) = 0;
+
+  // Writes the next n bytes in this ByteSource to the given ByteSink, and
+  // advances this ByteSource past the copied bytes. The default implementation
+  // of this method just copies the bytes normally, but subclasses might
+  // override CopyTo to optimize certain cases.
+  //
+  // REQUIRES: Available() >= n
+  virtual void CopyTo(ByteSink* sink, size_t n);
+
+ private:
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(ByteSource);
+};
+
+//
+// Some commonly used implementations of ByteSink
+//
+
+// Implementation of ByteSink that writes to an unsized byte array. No
+// bounds-checking is performed--it is the caller's responsibility to ensure
+// that the destination array is large enough.
+//
+// Example:
+//
+//   char buf[10];
+//   UncheckedArrayByteSink sink(buf);
+//   sink.Append("hi", 2);    // OK
+//   sink.Append(data, 100);  // WOOPS! Overflows buf[10].
+//
+class UncheckedArrayByteSink : public ByteSink {
+ public:
+  explicit UncheckedArrayByteSink(char* dest) : dest_(dest) {}
+  virtual void Append(const char* data, size_t n);
+
+  // Returns the current output pointer so that a caller can see how many bytes
+  // were produced.
+  //
+  // Note: this method is not part of the ByteSink interface.
+  char* CurrentDestination() const { return dest_; }
+
+ private:
+  char* dest_;
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(UncheckedArrayByteSink);
+};
+
+// Implementation of ByteSink that writes to a sized byte array. This sink will
+// not write more than "capacity" bytes to outbuf. Once "capacity" bytes are
+// appended, subsequent bytes will be ignored and Overflowed() will return true.
+// Overflowed() does not cause a runtime error (i.e., it does not CHECK fail).
+//
+// Example:
+//
+//   char buf[10];
+//   CheckedArrayByteSink sink(buf, 10);
+//   sink.Append("hi", 2);    // OK
+//   sink.Append(data, 100);  // Will only write 8 more bytes
+//
+class CheckedArrayByteSink : public ByteSink {
+ public:
+  CheckedArrayByteSink(char* outbuf, size_t capacity);
+  virtual void Append(const char* bytes, size_t n);
+
+  // Returns the number of bytes actually written to the sink.
+  size_t NumberOfBytesWritten() const { return size_; }
+
+  // Returns true if any bytes were discarded, i.e., if there was an
+  // attempt to write more than 'capacity' bytes.
+  bool Overflowed() const { return overflowed_; }
+
+ private:
+  char* outbuf_;
+  const size_t capacity_;
+  size_t size_;
+  bool overflowed_;
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(CheckedArrayByteSink);
+};
+
+// Implementation of ByteSink that allocates an internal buffer (a char array)
+// and expands it as needed to accomodate appended data (similar to a string),
+// and allows the caller to take ownership of the internal buffer via the
+// GetBuffer() method. The buffer returned from GetBuffer() must be deleted by
+// the caller with delete[]. GetBuffer() also sets the internal buffer to be
+// empty, and subsequent appends to the sink will create a new buffer. The
+// destructor will free the internal buffer if GetBuffer() was not called.
+//
+// Example:
+//
+//   GrowingArrayByteSink sink(10);
+//   sink.Append("hi", 2);
+//   sink.Append(data, n);
+//   const char* buf = sink.GetBuffer();  // Ownership transferred
+//   delete[] buf;
+//
+class GrowingArrayByteSink : public strings::ByteSink {
+ public:
+  explicit GrowingArrayByteSink(size_t estimated_size);
+  virtual ~GrowingArrayByteSink();
+  virtual void Append(const char* bytes, size_t n);
+
+  // Returns the allocated buffer, and sets nbytes to its size. The caller takes
+  // ownership of the buffer and must delete it with delete[].
+  char* GetBuffer(size_t* nbytes);
+
+ private:
+  void Expand(size_t amount);
+  void ShrinkToFit();
+
+  size_t capacity_;
+  char* buf_;
+  size_t size_;
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(GrowingArrayByteSink);
+};
+
+// Implementation of ByteSink that appends to the given string.
+// Existing contents of "dest" are not modified; new data is appended.
+//
+// Example:
+//
+//   string dest = "Hello ";
+//   StringByteSink sink(&dest);
+//   sink.Append("World", 5);
+//   assert(dest == "Hello World");
+//
+class StringByteSink : public ByteSink {
+ public:
+  explicit StringByteSink(string* dest) : dest_(dest) {}
+  virtual void Append(const char* data, size_t n);
+
+ private:
+  string* dest_;
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(StringByteSink);
+};
+
+// Implementation of ByteSink that discards all data.
+//
+// Example:
+//
+//   NullByteSink sink;
+//   sink.Append(data, data.size());  // All data ignored.
+//
+class NullByteSink : public ByteSink {
+ public:
+  NullByteSink() {}
+  virtual void Append(const char *data, size_t n) {}
+
+ private:
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(NullByteSink);
+};
+
+//
+// Some commonly used implementations of ByteSource
+//
+
+// Implementation of ByteSource that reads from a StringPiece.
+//
+// Example:
+//
+//   string data = "Hello";
+//   ArrayByteSource source(data);
+//   assert(source.Available() == 5);
+//   assert(source.Peek() == "Hello");
+//
+class ArrayByteSource : public ByteSource {
+ public:
+  explicit ArrayByteSource(StringPiece s) : input_(s) {}
+
+  virtual size_t Available() const;
+  virtual StringPiece Peek();
+  virtual void Skip(size_t n);
+
+ private:
+  StringPiece   input_;
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(ArrayByteSource);
+};
+
+// Implementation of ByteSource that wraps another ByteSource, limiting the
+// number of bytes returned.
+//
+// The caller maintains ownership of the underlying source, and may not use the
+// underlying source while using the LimitByteSource object.  The underlying
+// source's pointer is advanced by n bytes every time this LimitByteSource
+// object is advanced by n.
+//
+// Example:
+//
+//   string data = "Hello World";
+//   ArrayByteSource abs(data);
+//   assert(abs.Available() == data.size());
+//
+//   LimitByteSource limit(abs, 5);
+//   assert(limit.Available() == 5);
+//   assert(limit.Peek() == "Hello");
+//
+class LimitByteSource : public ByteSource {
+ public:
+  // Returns at most "limit" bytes from "source".
+  LimitByteSource(ByteSource* source, size_t limit);
+
+  virtual size_t Available() const;
+  virtual StringPiece Peek();
+  virtual void Skip(size_t n);
+
+  // We override CopyTo so that we can forward to the underlying source, in
+  // case it has an efficient implementation of CopyTo.
+  virtual void CopyTo(ByteSink* sink, size_t n);
+
+ private:
+  ByteSource* source_;
+  size_t limit_;
+};
+
+}  // namespace strings
+}  // namespace protobuf
+}  // namespace google
+
+#endif  // GOOGLE_PROTOBUF_STUBS_BYTESTREAM_H_
diff --git a/src/google/protobuf/stubs/bytestream_unittest.cc b/src/google/protobuf/stubs/bytestream_unittest.cc
new file mode 100644
index 0000000..06f114a
--- /dev/null
+++ b/src/google/protobuf/stubs/bytestream_unittest.cc
@@ -0,0 +1,146 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/stubs/bytestream.h>
+
+#include <stdio.h>
+#include <string.h>
+#include <algorithm>
+
+#include <google/protobuf/testing/googletest.h>
+#include <gtest/gtest.h>
+
+namespace google {
+namespace protobuf {
+namespace strings {
+namespace {
+
+// We use this class instead of ArrayByteSource to simulate a ByteSource that
+// contains multiple fragments.  ArrayByteSource returns the entire array in
+// one fragment.
+class MockByteSource : public ByteSource {
+ public:
+  MockByteSource(StringPiece data, int block_size)
+    : data_(data), block_size_(block_size) {}
+
+  size_t Available() const { return data_.size(); }
+  StringPiece Peek() {
+    return data_.substr(0, block_size_);
+  }
+  void Skip(size_t n) { data_.remove_prefix(n); }
+
+ private:
+  StringPiece data_;
+  int block_size_;
+};
+
+TEST(ByteSourceTest, CopyTo) {
+  StringPiece data("Hello world!");
+  MockByteSource source(data, 3);
+  string str;
+  StringByteSink sink(&str);
+
+  source.CopyTo(&sink, data.size());
+  EXPECT_EQ(data, str);
+}
+
+TEST(ByteSourceTest, CopySubstringTo) {
+  StringPiece data("Hello world!");
+  MockByteSource source(data, 3);
+  source.Skip(1);
+  string str;
+  StringByteSink sink(&str);
+
+  source.CopyTo(&sink, data.size() - 2);
+  EXPECT_EQ(data.substr(1, data.size() - 2), str);
+  EXPECT_EQ("!", source.Peek());
+}
+
+TEST(ByteSourceTest, LimitByteSource) {
+  StringPiece data("Hello world!");
+  MockByteSource source(data, 3);
+  LimitByteSource limit_source(&source, 6);
+  EXPECT_EQ(6, limit_source.Available());
+  limit_source.Skip(1);
+  EXPECT_EQ(5, limit_source.Available());
+
+  {
+    string str;
+    StringByteSink sink(&str);
+    limit_source.CopyTo(&sink, limit_source.Available());
+    EXPECT_EQ("ello ", str);
+    EXPECT_EQ(0, limit_source.Available());
+    EXPECT_EQ(6, source.Available());
+  }
+
+  {
+    string str;
+    StringByteSink sink(&str);
+    source.CopyTo(&sink, source.Available());
+    EXPECT_EQ("world!", str);
+    EXPECT_EQ(0, source.Available());
+  }
+}
+
+TEST(ByteSourceTest, CopyToStringByteSink) {
+  StringPiece data("Hello world!");
+  MockByteSource source(data, 3);
+  string str;
+  StringByteSink sink(&str);
+  source.CopyTo(&sink, data.size());
+  EXPECT_EQ(data, str);
+}
+
+// Verify that ByteSink is subclassable and Flush() overridable.
+class FlushingByteSink : public StringByteSink {
+ public:
+  explicit FlushingByteSink(string* dest) : StringByteSink(dest) {}
+  virtual void Flush() { Append("z", 1); }
+ private:
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(FlushingByteSink);
+};
+
+// Write and Flush via the ByteSink superclass interface.
+void WriteAndFlush(ByteSink* s) {
+  s->Append("abc", 3);
+  s->Flush();
+}
+
+TEST(ByteSinkTest, Flush) {
+  string str;
+  FlushingByteSink f_sink(&str);
+  WriteAndFlush(&f_sink);
+  EXPECT_STREQ("abcz", str.c_str());
+}
+
+}  // namespace
+}  // namespace strings
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/stubs/casts.h b/src/google/protobuf/stubs/casts.h
index cccf65a..be65284 100644
--- a/src/google/protobuf/stubs/casts.h
+++ b/src/google/protobuf/stubs/casts.h
@@ -111,12 +111,22 @@
   return *static_cast<ToAsPointer>(&f);
 }
 
+template<typename To, typename From>
+inline To bit_cast(const From& from) {
+  GOOGLE_COMPILE_ASSERT(sizeof(From) == sizeof(To),
+                        bit_cast_with_different_sizes);
+  To dest;
+  memcpy(&dest, &from, sizeof(dest));
+  return dest;
+}
+
 }  // namespace internal
 
 // We made these internal so that they would show up as such in the docs,
 // but we don't want to stick "internal::" in front of them everywhere.
 using internal::implicit_cast;
 using internal::down_cast;
+using internal::bit_cast;
 
 }  // namespace protobuf
 }  // namespace google
diff --git a/src/google/protobuf/stubs/common.cc b/src/google/protobuf/stubs/common.cc
index 54e00cc..b895d91 100644
--- a/src/google/protobuf/stubs/common.cc
+++ b/src/google/protobuf/stubs/common.cc
@@ -32,6 +32,8 @@
 
 #include <google/protobuf/stubs/common.h>
 #include <google/protobuf/stubs/once.h>
+#include <google/protobuf/stubs/status.h>
+#include <google/protobuf/stubs/stringpiece.h>
 #include <stdio.h>
 #include <errno.h>
 #include <vector>
@@ -148,6 +150,17 @@
   return *this;
 }
 
+LogMessage& LogMessage::operator<<(const StringPiece& value) {
+  message_ += value.ToString();
+  return *this;
+}
+
+LogMessage& LogMessage::operator<<(
+    const ::google::protobuf::util::Status& status) {
+  message_ += status.ToString();
+  return *this;
+}
+
 // Since this is just for logging, we don't care if the current locale changes
 // the results -- in fact, we probably prefer that.  So we use snprintf()
 // instead of Simple*toa().
diff --git a/src/google/protobuf/stubs/common.h b/src/google/protobuf/stubs/common.h
index 49d1602..34d79f4 100644
--- a/src/google/protobuf/stubs/common.h
+++ b/src/google/protobuf/stubs/common.h
@@ -48,6 +48,26 @@
 #include <stdint.h>
 #endif
 
+#undef PROTOBUF_LITTLE_ENDIAN
+#ifdef _MSC_VER
+  #if defined(_M_IX86) && \
+      !defined(PROTOBUF_DISABLE_LITTLE_ENDIAN_OPT_FOR_TEST)
+    #define PROTOBUF_LITTLE_ENDIAN 1
+  #endif
+  #if _MSC_VER >= 1300
+    // If MSVC has "/RTCc" set, it will complain about truncating casts at
+    // runtime.  This file contains some intentional truncating casts.
+    #pragma runtime_checks("c", off)
+  #endif
+#else
+  #include <sys/param.h>   // __BYTE_ORDER
+  #if ((defined(__LITTLE_ENDIAN__) && !defined(__BIG_ENDIAN__)) || \
+         (defined(__BYTE_ORDER) && __BYTE_ORDER == __LITTLE_ENDIAN)) && \
+      !defined(PROTOBUF_DISABLE_LITTLE_ENDIAN_OPT_FOR_TEST)
+    #define PROTOBUF_LITTLE_ENDIAN 1
+  #endif
+#endif
+
 #ifndef PROTOBUF_USE_EXCEPTIONS
 #if defined(_MSC_VER) && defined(_CPPUNWIND)
   #define PROTOBUF_USE_EXCEPTIONS 1
@@ -100,6 +120,12 @@
   TypeName(const TypeName&);                           \
   void operator=(const TypeName&)
 
+#undef GOOGLE_DISALLOW_IMPLICIT_CONSTRUCTORS
+#define GOOGLE_DISALLOW_IMPLICIT_CONSTRUCTORS(TypeName) \
+  TypeName();                                           \
+  TypeName(const TypeName&);                            \
+  void operator=(const TypeName&)
+
 #if defined(_MSC_VER) && defined(PROTOBUF_USE_DLLS)
   #ifdef LIBPROTOBUF_EXPORTS
     #define LIBPROTOBUF_EXPORT __declspec(dllexport)
@@ -660,6 +686,10 @@
 #endif
 };
 
+class StringPiece;
+namespace util {
+class Status;
+}
 namespace internal {
 
 class LogFinisher;
@@ -678,6 +708,8 @@
   LogMessage& operator<<(unsigned long value);
   LogMessage& operator<<(double value);
   LogMessage& operator<<(void* value);
+  LogMessage& operator<<(const StringPiece& value);
+  LogMessage& operator<<(const ::google::protobuf::util::Status& status);
 
  private:
   friend class LogFinisher;
@@ -696,6 +728,11 @@
   void operator=(LogMessage& other);
 };
 
+template<typename T>
+bool IsOk(T status) { return status.ok(); }
+template<>
+inline bool IsOk(bool status) { return status; }
+
 }  // namespace internal
 
 // Undef everything in case we're being mixed with some other Google library
@@ -717,6 +754,7 @@
 
 #undef GOOGLE_DLOG
 #undef GOOGLE_DCHECK
+#undef GOOGLE_DCHECK_OK
 #undef GOOGLE_DCHECK_EQ
 #undef GOOGLE_DCHECK_NE
 #undef GOOGLE_DCHECK_LT
@@ -733,7 +771,7 @@
 
 #define GOOGLE_CHECK(EXPRESSION) \
   GOOGLE_LOG_IF(FATAL, !(EXPRESSION)) << "CHECK failed: " #EXPRESSION ": "
-#define GOOGLE_CHECK_OK(A) GOOGLE_CHECK(A)
+#define GOOGLE_CHECK_OK(A) GOOGLE_CHECK(::google::protobuf::internal::IsOk(A))
 #define GOOGLE_CHECK_EQ(A, B) GOOGLE_CHECK((A) == (B))
 #define GOOGLE_CHECK_NE(A, B) GOOGLE_CHECK((A) != (B))
 #define GOOGLE_CHECK_LT(A, B) GOOGLE_CHECK((A) <  (B))
@@ -760,6 +798,7 @@
 #define GOOGLE_DLOG GOOGLE_LOG_IF(INFO, false)
 
 #define GOOGLE_DCHECK(EXPRESSION) while(false) GOOGLE_CHECK(EXPRESSION)
+#define GOOGLE_DCHECK_OK(E) GOOGLE_DCHECK(::google::protobuf::internal::IsOk(E))
 #define GOOGLE_DCHECK_EQ(A, B) GOOGLE_DCHECK((A) == (B))
 #define GOOGLE_DCHECK_NE(A, B) GOOGLE_DCHECK((A) != (B))
 #define GOOGLE_DCHECK_LT(A, B) GOOGLE_DCHECK((A) <  (B))
@@ -772,6 +811,7 @@
 #define GOOGLE_DLOG GOOGLE_LOG
 
 #define GOOGLE_DCHECK    GOOGLE_CHECK
+#define GOOGLE_DCHECK_OK GOOGLE_CHECK_OK
 #define GOOGLE_DCHECK_EQ GOOGLE_CHECK_EQ
 #define GOOGLE_DCHECK_NE GOOGLE_CHECK_NE
 #define GOOGLE_DCHECK_LT GOOGLE_CHECK_LT
@@ -883,6 +923,30 @@
   GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(Closure);
 };
 
+template<typename R, typename A1>
+class LIBPROTOBUF_EXPORT ResultCallback1 {
+ public:
+  ResultCallback1() {}
+  virtual ~ResultCallback1() {}
+
+  virtual R Run(A1) = 0;
+
+ private:
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(ResultCallback1);
+};
+
+template<typename R, typename A1, typename A2>
+class LIBPROTOBUF_EXPORT ResultCallback2 {
+ public:
+  ResultCallback2() {}
+  virtual ~ResultCallback2() {}
+
+  virtual R Run(A1,A2) = 0;
+
+ private:
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(ResultCallback2);
+};
+
 namespace internal {
 
 class LIBPROTOBUF_EXPORT FunctionClosure0 : public Closure {
@@ -1021,6 +1085,96 @@
   Arg2 arg2_;
 };
 
+template<typename R, typename Arg1>
+class FunctionResultCallback_0_1 : public ResultCallback1<R, Arg1> {
+ public:
+  typedef R (*FunctionType)(Arg1 arg1);
+
+  FunctionResultCallback_0_1(FunctionType function, bool self_deleting)
+      : function_(function), self_deleting_(self_deleting) {}
+  ~FunctionResultCallback_0_1() {}
+
+  R Run(Arg1 a1) {
+    bool needs_delete = self_deleting_;  // read in case callback deletes
+    R result = function_(a1);
+    if (needs_delete) delete this;
+    return result;
+  }
+
+ private:
+  FunctionType function_;
+  bool self_deleting_;
+};
+
+template<typename R, typename P1, typename A1>
+class FunctionResultCallback_1_1 : public ResultCallback1<R, A1> {
+ public:
+  typedef R (*FunctionType)(P1, A1);
+
+  FunctionResultCallback_1_1(FunctionType function, bool self_deleting,
+                             P1 p1)
+      : function_(function), self_deleting_(self_deleting), p1_(p1) {}
+  ~FunctionResultCallback_1_1() {}
+
+  R Run(A1 a1) {
+    bool needs_delete = self_deleting_;  // read in case callback deletes
+    R result = function_(p1_, a1);
+    if (needs_delete) delete this;
+    return result;
+  }
+
+ private:
+  FunctionType function_;
+  bool self_deleting_;
+  P1 p1_;
+};
+
+// Duplicate this again in the type_traits.h, due to dependency problems.
+template <class T> struct internal_remove_reference;
+template<typename T> struct internal_remove_reference { typedef T type; };
+template<typename T> struct internal_remove_reference<T&> { typedef T type; };
+
+template <typename T>
+struct InternalConstRef {
+  typedef typename internal_remove_reference<T>::type base_type;
+  typedef const base_type& type;
+};
+
+template <typename R, typename T, typename P1, typename P2, typename P3,
+          typename P4, typename P5, typename A1, typename A2>
+class MethodResultCallback_5_2 : public ResultCallback2<R, A1, A2> {
+ public:
+  typedef R (T::*MethodType)(P1, P2, P3, P4, P5, A1, A2);
+  MethodResultCallback_5_2(T* object, MethodType method, bool self_deleting,
+                           P1 p1, P2 p2, P3 p3, P4 p4, P5 p5)
+      : object_(object),
+        method_(method),
+        self_deleting_(self_deleting),
+        p1_(p1),
+        p2_(p2),
+        p3_(p3),
+        p4_(p4),
+        p5_(p5) {}
+  ~MethodResultCallback_5_2() {}
+
+  R Run(A1 a1, A2 a2) {
+    bool needs_delete = self_deleting_;
+    R result = (object_->*method_)(p1_, p2_, p3_, p4_, p5_, a1, a2);
+    if (needs_delete) delete this;
+    return result;
+  }
+
+ private:
+  T* object_;
+  MethodType method_;
+  bool self_deleting_;
+  typename internal_remove_reference<P1>::type p1_;
+  typename internal_remove_reference<P2>::type p2_;
+  typename internal_remove_reference<P3>::type p3_;
+  typename internal_remove_reference<P4>::type p4_;
+  typename internal_remove_reference<P5>::type p5_;
+};
+
 }  // namespace internal
 
 // See Closure.
@@ -1106,6 +1260,48 @@
     object, method, false, arg1, arg2);
 }
 
+// See ResultCallback1
+template<typename R, typename A1>
+inline ResultCallback1<R, A1>* NewCallback(R (*function)(A1)) {
+  return new internal::FunctionResultCallback_0_1<R, A1>(function, true);
+}
+
+// See ResultCallback1
+template<typename R, typename A1>
+inline ResultCallback1<R, A1>* NewPermanentCallback(R (*function)(A1)) {
+  return new internal::FunctionResultCallback_0_1<R, A1>(function, false);
+}
+
+// See ResultCallback1
+template<typename R, typename P1, typename A1>
+inline ResultCallback1<R, A1>* NewCallback(R (*function)(P1, A1), P1 p1) {
+  return new internal::FunctionResultCallback_1_1<R, P1, A1>(
+      function, true, p1);
+}
+
+// See ResultCallback1
+template<typename R, typename P1, typename A1>
+inline ResultCallback1<R, A1>* NewPermanentCallback(
+    R (*function)(P1, A1), P1 p1) {
+  return new internal::FunctionResultCallback_1_1<R, P1, A1>(
+      function, false, p1);
+}
+
+// See MethodResultCallback_5_2
+template <typename R, typename T, typename P1, typename P2, typename P3,
+          typename P4, typename P5, typename A1, typename A2>
+inline ResultCallback2<R, A1, A2>* NewPermanentCallback(
+    T* object, R (T::*function)(P1, P2, P3, P4, P5, A1, A2),
+    typename internal::InternalConstRef<P1>::type p1,
+    typename internal::InternalConstRef<P2>::type p2,
+    typename internal::InternalConstRef<P3>::type p3,
+    typename internal::InternalConstRef<P4>::type p4,
+    typename internal::InternalConstRef<P5>::type p5) {
+  return new internal::MethodResultCallback_5_2<R, T, P1, P2, P3, P4, P5, A1,
+                                                A2>(object, function, false, p1,
+                                                    p2, p3, p4, p5);
+}
+
 // A function which does nothing.  Useful for creating no-op callbacks, e.g.:
 //   Closure* nothing = NewCallback(&DoNothing);
 void LIBPROTOBUF_EXPORT DoNothing();
@@ -1226,9 +1422,114 @@
 }  // namespace internal
 
 // ===================================================================
+// from google3/base/port.h
+
+// The following guarantees declaration of the byte swap functions, and
+// defines __BYTE_ORDER for MSVC
+#ifdef _MSC_VER
+#include <stdlib.h>  // NOLINT(build/include)
+#define __BYTE_ORDER __LITTLE_ENDIAN
+#define bswap_16(x) _byteswap_ushort(x)
+#define bswap_32(x) _byteswap_ulong(x)
+#define bswap_64(x) _byteswap_uint64(x)
+
+#elif defined(__APPLE__)
+// Mac OS X / Darwin features
+#include <libkern/OSByteOrder.h>
+#define bswap_16(x) OSSwapInt16(x)
+#define bswap_32(x) OSSwapInt32(x)
+#define bswap_64(x) OSSwapInt64(x)
+
+#elif defined(__GLIBC__) || defined(__CYGWIN__)
+#include <byteswap.h>  // IWYU pragma: export
+
+#else
+
+static inline uint16 bswap_16(uint16 x) {
+  return static_cast<uint16>(((x & 0xFF) << 8) | ((x & 0xFF00) >> 8));
+}
+#define bswap_16(x) bswap_16(x)
+static inline uint32 bswap_32(uint32 x) {
+  return (((x & 0xFF) << 24) |
+          ((x & 0xFF00) << 8) |
+          ((x & 0xFF0000) >> 8) |
+          ((x & 0xFF000000) >> 24));
+}
+#define bswap_32(x) bswap_32(x)
+static inline uint64 bswap_64(uint64 x) {
+  return (((x & GG_ULONGLONG(0xFF)) << 56) |
+          ((x & GG_ULONGLONG(0xFF00)) << 40) |
+          ((x & GG_ULONGLONG(0xFF0000)) << 24) |
+          ((x & GG_ULONGLONG(0xFF000000)) << 8) |
+          ((x & GG_ULONGLONG(0xFF00000000)) >> 8) |
+          ((x & GG_ULONGLONG(0xFF0000000000)) >> 24) |
+          ((x & GG_ULONGLONG(0xFF000000000000)) >> 40) |
+          ((x & GG_ULONGLONG(0xFF00000000000000)) >> 56));
+}
+#define bswap_64(x) bswap_64(x)
+
+#endif
+
+// ===================================================================
 // from google3/util/endian/endian.h
 LIBPROTOBUF_EXPORT uint32 ghtonl(uint32 x);
 
+class BigEndian {
+ public:
+#ifdef PROTOBUF_LITTLE_ENDIAN
+
+  static uint16 FromHost16(uint16 x) { return bswap_16(x); }
+  static uint16 ToHost16(uint16 x) { return bswap_16(x); }
+
+  static uint32 FromHost32(uint32 x) { return bswap_32(x); }
+  static uint32 ToHost32(uint32 x) { return bswap_32(x); }
+
+  static uint64 FromHost64(uint64 x) { return bswap_64(x); }
+  static uint64 ToHost64(uint64 x) { return bswap_64(x); }
+
+  static bool IsLittleEndian() { return true; }
+
+#else
+
+  static uint16 FromHost16(uint16 x) { return x; }
+  static uint16 ToHost16(uint16 x) { return x; }
+
+  static uint32 FromHost32(uint32 x) { return x; }
+  static uint32 ToHost32(uint32 x) { return x; }
+
+  static uint64 FromHost64(uint64 x) { return x; }
+  static uint64 ToHost64(uint64 x) { return x; }
+
+  static bool IsLittleEndian() { return false; }
+
+#endif /* ENDIAN */
+
+  // Functions to do unaligned loads and stores in big-endian order.
+  static uint16 Load16(const void *p) {
+    return ToHost16(GOOGLE_UNALIGNED_LOAD16(p));
+  }
+
+  static void Store16(void *p, uint16 v) {
+    GOOGLE_UNALIGNED_STORE16(p, FromHost16(v));
+  }
+
+  static uint32 Load32(const void *p) {
+    return ToHost32(GOOGLE_UNALIGNED_LOAD32(p));
+  }
+
+  static void Store32(void *p, uint32 v) {
+    GOOGLE_UNALIGNED_STORE32(p, FromHost32(v));
+  }
+
+  static uint64 Load64(const void *p) {
+    return ToHost64(GOOGLE_UNALIGNED_LOAD64(p));
+  }
+
+  static void Store64(void *p, uint64 v) {
+    GOOGLE_UNALIGNED_STORE64(p, FromHost64(v));
+  }
+};
+
 // ===================================================================
 // Shutdown support.
 
diff --git a/src/google/protobuf/stubs/mathlimits.cc b/src/google/protobuf/stubs/mathlimits.cc
new file mode 100644
index 0000000..0373b2b
--- /dev/null
+++ b/src/google/protobuf/stubs/mathlimits.cc
@@ -0,0 +1,144 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// All Rights Reserved.
+//
+// Author: Maxim Lifantsev
+//
+
+#include <google/protobuf/stubs/mathlimits.h>
+
+#include <google/protobuf/stubs/common.h>
+
+namespace google {
+namespace protobuf {
+
+// MSVC++ 2005 and older compilers think the header declaration was a
+// definition, and erroneously flag these as a duplicate definition.
+#if defined(COMPILER_MSVC) || __cpluscplus < 201103L
+
+#define DEF_COMMON_LIMITS(Type)
+#define DEF_UNSIGNED_INT_LIMITS(Type)
+#define DEF_SIGNED_INT_LIMITS(Type)
+#define DEF_PRECISION_LIMITS(Type)
+
+#else
+
+#define DEF_COMMON_LIMITS(Type) \
+const bool MathLimits<Type>::kIsSigned; \
+const bool MathLimits<Type>::kIsInteger; \
+const int MathLimits<Type>::kMin10Exp; \
+const int MathLimits<Type>::kMax10Exp;
+
+#define DEF_UNSIGNED_INT_LIMITS(Type) \
+DEF_COMMON_LIMITS(Type) \
+const Type MathLimits<Type>::kPosMin; \
+const Type MathLimits<Type>::kPosMax; \
+const Type MathLimits<Type>::kMin; \
+const Type MathLimits<Type>::kMax; \
+const Type MathLimits<Type>::kEpsilon; \
+const Type MathLimits<Type>::kStdError;
+
+#define DEF_SIGNED_INT_LIMITS(Type) \
+DEF_UNSIGNED_INT_LIMITS(Type) \
+const Type MathLimits<Type>::kNegMin; \
+const Type MathLimits<Type>::kNegMax;
+
+#define DEF_PRECISION_LIMITS(Type) \
+const int MathLimits<Type>::kPrecisionDigits;
+
+#endif  // not COMPILER_MSVC
+
+// http://en.wikipedia.org/wiki/Quadruple_precision_floating-point_format#Double-double_arithmetic
+// With some compilers (gcc 4.6.x) on some platforms (powerpc64),
+// "long double" is implemented as a pair of double: "double double" format.
+// This causes a problem with epsilon (eps).
+// eps is the smallest positive number such that 1.0 + eps > 1.0
+//
+// Normal format:  1.0 + e = 1.0...01      // N-1 zeros for N fraction bits
+// D-D format:     1.0 + e = 1.000...0001  // epsilon can be very small
+//
+// In the normal format, 1.0 + e has to fit in one stretch of bits.
+// The maximum rounding error is half of eps.
+//
+// In the double-double format, 1.0 + e splits across two doubles:
+// 1.0 in the high double, e in the low double, and they do not have to
+// be contiguous.  The maximum rounding error on a value close to 1.0 is
+// much larger than eps.
+//
+// Some code checks for errors by comparing a computed value to a golden
+// value +/- some multiple of the maximum rounding error.  The maximum
+// rounding error is not available so we use eps as an approximation
+// instead.  That fails when long double is in the double-double format.
+// Therefore, we define kStdError as a multiple of
+// max(DBL_EPSILON * DBL_EPSILON, kEpsilon) rather than a multiple of kEpsilon.
+
+#define DEF_FP_LIMITS(Type, PREFIX) \
+DEF_COMMON_LIMITS(Type) \
+const Type MathLimits<Type>::kPosMin = PREFIX##_MIN; \
+const Type MathLimits<Type>::kPosMax = PREFIX##_MAX; \
+const Type MathLimits<Type>::kMin = -MathLimits<Type>::kPosMax; \
+const Type MathLimits<Type>::kMax = MathLimits<Type>::kPosMax; \
+const Type MathLimits<Type>::kNegMin = -MathLimits<Type>::kPosMin; \
+const Type MathLimits<Type>::kNegMax = -MathLimits<Type>::kPosMax; \
+const Type MathLimits<Type>::kEpsilon = PREFIX##_EPSILON; \
+/* 32 is 5 bits of mantissa error; should be adequate for common errors */ \
+const Type MathLimits<Type>::kStdError = \
+  32 * (DBL_EPSILON * DBL_EPSILON > MathLimits<Type>::kEpsilon \
+      ? DBL_EPSILON * DBL_EPSILON : MathLimits<Type>::kEpsilon); \
+DEF_PRECISION_LIMITS(Type) \
+const Type MathLimits<Type>::kNaN = HUGE_VAL - HUGE_VAL; \
+const Type MathLimits<Type>::kPosInf = HUGE_VAL; \
+const Type MathLimits<Type>::kNegInf = -HUGE_VAL;
+
+// The following are *not* casts!
+DEF_SIGNED_INT_LIMITS(int8)
+DEF_SIGNED_INT_LIMITS(int16)  // NOLINT(readability/casting)
+DEF_SIGNED_INT_LIMITS(int32)  // NOLINT(readability/casting)
+DEF_SIGNED_INT_LIMITS(int64)  // NOLINT(readability/casting)
+DEF_UNSIGNED_INT_LIMITS(uint8)
+DEF_UNSIGNED_INT_LIMITS(uint16)  // NOLINT(readability/casting)
+DEF_UNSIGNED_INT_LIMITS(uint32)  // NOLINT(readability/casting)
+DEF_UNSIGNED_INT_LIMITS(uint64)  // NOLINT(readability/casting)
+
+DEF_SIGNED_INT_LIMITS(long int)
+DEF_UNSIGNED_INT_LIMITS(unsigned long int)
+
+DEF_FP_LIMITS(float, FLT)
+DEF_FP_LIMITS(double, DBL)
+DEF_FP_LIMITS(long double, LDBL);
+
+#undef DEF_COMMON_LIMITS
+#undef DEF_SIGNED_INT_LIMITS
+#undef DEF_UNSIGNED_INT_LIMITS
+#undef DEF_FP_LIMITS
+#undef DEF_PRECISION_LIMITS
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/stubs/mathlimits.h b/src/google/protobuf/stubs/mathlimits.h
new file mode 100644
index 0000000..39957d6
--- /dev/null
+++ b/src/google/protobuf/stubs/mathlimits.h
@@ -0,0 +1,277 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// All Rights Reserved.
+//
+// Author: Maxim Lifantsev
+//
+// Useful integer and floating point limits and type traits.
+//
+// This partially replaces/duplictes numeric_limits<> from <limits>.
+// We get a Google-style class that we have a greater control over
+// and thus can add new features to it or fix whatever happens to be broken in
+// numeric_limits for the compilers we use.
+//
+
+#ifndef UTIL_MATH_MATHLIMITS_H__
+#define UTIL_MATH_MATHLIMITS_H__
+
+// <math.h> lacks a lot of prototypes. However, this file needs <math.h> to
+// access old-fashioned isinf et al. Even worse more: this file must not
+// include <cmath> because that breaks the definition of isinf with gcc 4.9.
+//
+// TODO(mec): after C++11 everywhere, use <cmath> and std::isinf in this file.
+#include <math.h>
+#include <string.h>
+
+#include <cfloat>
+
+// ========================================================================= //
+
+// Useful integer and floating point limits and type traits.
+// This is just for the documentation;
+// real members are defined in our specializations below.
+namespace google {
+namespace protobuf {
+template<typename T> struct MathLimits {
+  // Type name.
+  typedef T Type;
+  // Unsigned version of the Type with the same byte size.
+  // Same as Type for floating point and unsigned types.
+  typedef T UnsignedType;
+  // If the type supports negative values.
+  static const bool kIsSigned;
+  // If the type supports only integer values.
+  static const bool kIsInteger;
+  // Magnitude-wise smallest representable positive value.
+  static const Type kPosMin;
+  // Magnitude-wise largest representable positive value.
+  static const Type kPosMax;
+  // Smallest representable value.
+  static const Type kMin;
+  // Largest representable value.
+  static const Type kMax;
+  // Magnitude-wise smallest representable negative value.
+  // Present only if kIsSigned.
+  static const Type kNegMin;
+  // Magnitude-wise largest representable negative value.
+  // Present only if kIsSigned.
+  static const Type kNegMax;
+  // Smallest integer x such that 10^x is representable.
+  static const int kMin10Exp;
+  // Largest integer x such that 10^x is representable.
+  static const int kMax10Exp;
+  // Smallest positive value such that Type(1) + kEpsilon != Type(1)
+  static const Type kEpsilon;
+  // Typical rounding error that is enough to cover
+  // a few simple floating-point operations.
+  // Slightly larger than kEpsilon to account for a few rounding errors.
+  // Is zero if kIsInteger.
+  static const Type kStdError;
+  // Number of decimal digits of mantissa precision.
+  // Present only if !kIsInteger.
+  static const int kPrecisionDigits;
+  // Not a number, i.e. result of 0/0.
+  // Present only if !kIsInteger.
+  static const Type kNaN;
+  // Positive infinity, i.e. result of 1/0.
+  // Present only if !kIsInteger.
+  static const Type kPosInf;
+  // Negative infinity, i.e. result of -1/0.
+  // Present only if !kIsInteger.
+  static const Type kNegInf;
+
+  // NOTE: Special floating point values behave
+  // in a special (but mathematically-logical) way
+  // in terms of (in)equalty comparison and mathematical operations
+  // -- see out unittest for examples.
+
+  // Special floating point value testers.
+  // Present in integer types for convenience.
+  static bool IsFinite(const Type x);
+  static bool IsNaN(const Type x);
+  static bool IsInf(const Type x);
+  static bool IsPosInf(const Type x);
+  static bool IsNegInf(const Type x);
+};
+
+// ========================================================================= //
+
+// All #define-s below are simply to refactor the declarations of
+// MathLimits template specializations.
+// They are all #undef-ined below.
+
+// The hoop-jumping in *_INT_(MAX|MIN) below is so that the compiler does not
+// get an overflow while computing the constants.
+
+#define SIGNED_INT_MAX(Type) \
+  (((Type(1) << (sizeof(Type)*8 - 2)) - 1) + (Type(1) << (sizeof(Type)*8 - 2)))
+
+#define SIGNED_INT_MIN(Type) \
+  (-(Type(1) << (sizeof(Type)*8 - 2)) - (Type(1) << (sizeof(Type)*8 - 2)))
+
+#define UNSIGNED_INT_MAX(Type) \
+  (((Type(1) << (sizeof(Type)*8 - 1)) - 1) + (Type(1) << (sizeof(Type)*8 - 1)))
+
+// Compile-time selected log10-related constants for integer types.
+#define SIGNED_MAX_10_EXP(Type) \
+  (sizeof(Type) == 1 ? 2 : ( \
+    sizeof(Type) == 2 ? 4 : ( \
+      sizeof(Type) == 4 ? 9 : ( \
+        sizeof(Type) == 8 ? 18 : -1))))
+
+#define UNSIGNED_MAX_10_EXP(Type) \
+  (sizeof(Type) == 1 ? 2 : ( \
+    sizeof(Type) == 2 ? 4 : ( \
+      sizeof(Type) == 4 ? 9 : ( \
+        sizeof(Type) == 8 ? 19 : -1))))
+
+#define DECL_INT_LIMIT_FUNCS \
+  static bool IsFinite(const Type /*x*/) { return true; } \
+  static bool IsNaN(const Type /*x*/) { return false; } \
+  static bool IsInf(const Type /*x*/) { return false; } \
+  static bool IsPosInf(const Type /*x*/) { return false; } \
+  static bool IsNegInf(const Type /*x*/) { return false; }
+
+#define DECL_SIGNED_INT_LIMITS(IntType, UnsignedIntType) \
+template<> \
+struct MathLimits<IntType> { \
+  typedef IntType Type; \
+  typedef UnsignedIntType UnsignedType; \
+  static const bool kIsSigned = true; \
+  static const bool kIsInteger = true; \
+  static const Type kPosMin = 1; \
+  static const Type kPosMax = SIGNED_INT_MAX(Type); \
+  static const Type kMin = SIGNED_INT_MIN(Type); \
+  static const Type kMax = kPosMax; \
+  static const Type kNegMin = -1; \
+  static const Type kNegMax = kMin; \
+  static const int kMin10Exp = 0; \
+  static const int kMax10Exp = SIGNED_MAX_10_EXP(Type); \
+  static const Type kEpsilon = 1; \
+  static const Type kStdError = 0; \
+  DECL_INT_LIMIT_FUNCS \
+};
+
+#define DECL_UNSIGNED_INT_LIMITS(IntType) \
+template<> \
+struct MathLimits<IntType> { \
+  typedef IntType Type; \
+  typedef IntType UnsignedType; \
+  static const bool kIsSigned = false; \
+  static const bool kIsInteger = true; \
+  static const Type kPosMin = 1; \
+  static const Type kPosMax = UNSIGNED_INT_MAX(Type); \
+  static const Type kMin = 0; \
+  static const Type kMax = kPosMax; \
+  static const int kMin10Exp = 0; \
+  static const int kMax10Exp = UNSIGNED_MAX_10_EXP(Type); \
+  static const Type kEpsilon = 1; \
+  static const Type kStdError = 0; \
+  DECL_INT_LIMIT_FUNCS \
+};
+
+DECL_SIGNED_INT_LIMITS(signed char, unsigned char)
+DECL_SIGNED_INT_LIMITS(signed short int, unsigned short int)
+DECL_SIGNED_INT_LIMITS(signed int, unsigned int)
+DECL_SIGNED_INT_LIMITS(signed long int, unsigned long int)
+DECL_SIGNED_INT_LIMITS(signed long long int, unsigned long long int)
+DECL_UNSIGNED_INT_LIMITS(unsigned char)
+DECL_UNSIGNED_INT_LIMITS(unsigned short int)
+DECL_UNSIGNED_INT_LIMITS(unsigned int)
+DECL_UNSIGNED_INT_LIMITS(unsigned long int)
+DECL_UNSIGNED_INT_LIMITS(unsigned long long int)
+
+#undef DECL_SIGNED_INT_LIMITS
+#undef DECL_UNSIGNED_INT_LIMITS
+#undef SIGNED_INT_MAX
+#undef SIGNED_INT_MIN
+#undef UNSIGNED_INT_MAX
+#undef SIGNED_MAX_10_EXP
+#undef UNSIGNED_MAX_10_EXP
+#undef DECL_INT_LIMIT_FUNCS
+
+// ========================================================================= //
+#ifdef WIN32  // Lacks built-in isnan() and isinf()
+#define DECL_FP_LIMIT_FUNCS \
+  static bool IsFinite(const Type x) { return _finite(x); } \
+  static bool IsNaN(const Type x) { return _isnan(x); } \
+  static bool IsInf(const Type x) { return (_fpclass(x) & (_FPCLASS_NINF | _FPCLASS_PINF)) != 0; } \
+  static bool IsPosInf(const Type x) { return _fpclass(x) == _FPCLASS_PINF; } \
+  static bool IsNegInf(const Type x) { return _fpclass(x) == _FPCLASS_NINF; }
+#else
+#define DECL_FP_LIMIT_FUNCS \
+  static bool IsFinite(const Type x) { return !isinf(x)  &&  !isnan(x); } \
+  static bool IsNaN(const Type x) { return isnan(x); } \
+  static bool IsInf(const Type x) { return isinf(x); } \
+  static bool IsPosInf(const Type x) { return isinf(x)  &&  x > 0; } \
+  static bool IsNegInf(const Type x) { return isinf(x)  &&  x < 0; }
+#endif
+
+// We can't put floating-point constant values in the header here because
+// such constants are not considered to be primitive-type constants by gcc.
+// CAVEAT: Hence, they are going to be initialized only during
+// the global objects construction time.
+#define DECL_FP_LIMITS(FP_Type, PREFIX) \
+template<> \
+struct MathLimits<FP_Type> { \
+  typedef FP_Type Type; \
+  typedef FP_Type UnsignedType; \
+  static const bool kIsSigned = true; \
+  static const bool kIsInteger = false; \
+  static const Type kPosMin; \
+  static const Type kPosMax; \
+  static const Type kMin; \
+  static const Type kMax; \
+  static const Type kNegMin; \
+  static const Type kNegMax; \
+  static const int kMin10Exp = PREFIX##_MIN_10_EXP; \
+  static const int kMax10Exp = PREFIX##_MAX_10_EXP; \
+  static const Type kEpsilon; \
+  static const Type kStdError; \
+  static const int kPrecisionDigits = PREFIX##_DIG; \
+  static const Type kNaN; \
+  static const Type kPosInf; \
+  static const Type kNegInf; \
+  DECL_FP_LIMIT_FUNCS \
+};
+
+DECL_FP_LIMITS(float, FLT)
+DECL_FP_LIMITS(double, DBL)
+DECL_FP_LIMITS(long double, LDBL)
+
+#undef DECL_FP_LIMITS
+#undef DECL_FP_LIMIT_FUNCS
+
+// ========================================================================= //
+}  // namespace protobuf
+}  // namespace google
+
+#endif  // UTIL_MATH_MATHLIMITS_H__
diff --git a/src/google/protobuf/stubs/mathutil.h b/src/google/protobuf/stubs/mathutil.h
new file mode 100644
index 0000000..87ca5e9
--- /dev/null
+++ b/src/google/protobuf/stubs/mathutil.h
@@ -0,0 +1,149 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#ifndef GOOGLE_PROTOBUF_STUBS_MATHUTIL_H_
+#define GOOGLE_PROTOBUF_STUBS_MATHUTIL_H_
+
+#include <float.h>
+#include <math.h>
+
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/stubs/mathlimits.h>
+
+namespace google {
+namespace protobuf {
+namespace internal {
+template<typename T>
+bool IsNan(T value) {
+  return false;
+}
+template<>
+inline bool IsNan(float value) { return isnan(value); }
+template<>
+inline bool IsNan(double value) { return isnan(value); }
+
+template<typename T>
+bool AlmostEquals(T a, T b) {
+  return a == b;
+}
+template<>
+inline bool AlmostEquals(float a, float b) {
+  return fabs(a - b) < 32 * FLT_EPSILON;
+}
+
+template<>
+inline bool AlmostEquals(double a, double b) {
+  return fabs(a - b) < 32 * DBL_EPSILON;
+}
+}  // namespace internal
+
+class MathUtil {
+ public:
+  template<typename T>
+  static T Sign(T value) {
+    if (value == T(0) || ::google::protobuf::internal::IsNan<T>(value)) {
+      return value;
+    }
+    return value > T(0) ? value : -value;
+  }
+
+  template<typename T>
+  static bool AlmostEquals(T a, T b) {
+    return ::google::protobuf::internal::AlmostEquals(a, b);
+  }
+
+  // Largest of two values.
+  // Works correctly for special floating point values.
+  // Note: 0.0 and -0.0 are not differentiated by Max (Max(0.0, -0.0) is -0.0),
+  // which should be OK because, although they (can) have different
+  // bit representation, they are observably the same when examined
+  // with arithmetic and (in)equality operators.
+  template<typename T>
+  static T Max(const T x, const T y) {
+    return MathLimits<T>::IsNaN(x) || x > y ? x : y;
+  }
+
+  // Absolute value of x
+  // Works correctly for unsigned types and
+  // for special floating point values.
+  // Note: 0.0 and -0.0 are not differentiated by Abs (Abs(0.0) is -0.0),
+  // which should be OK: see the comment for Max above.
+  template<typename T>
+  static T Abs(const T x) {
+    return x > T(0) ? x : -x;
+  }
+
+  // Absolute value of the difference between two numbers.
+  // Works correctly for signed types and special floating point values.
+  template<typename T>
+  static typename MathLimits<T>::UnsignedType AbsDiff(const T x, const T y) {
+    // Carries out arithmetic as unsigned to avoid overflow.
+    typedef typename MathLimits<T>::UnsignedType R;
+    return x > y ? R(x) - R(y) : R(y) - R(x);
+  }
+
+  // If two (usually floating point) numbers are within a certain
+  // fraction of their magnitude or within a certain absolute margin of error.
+  // This is the same as the following but faster:
+  //   WithinFraction(x, y, fraction)  ||  WithinMargin(x, y, margin)
+  // E.g. WithinFraction(0.0, 1e-10, 1e-5) is false but
+  //      WithinFractionOrMargin(0.0, 1e-10, 1e-5, 1e-5) is true.
+  template<typename T>
+  static bool WithinFractionOrMargin(const T x, const T y,
+                                     const T fraction, const T margin);
+};
+
+template<typename T>
+bool MathUtil::WithinFractionOrMargin(const T x, const T y,
+                                      const T fraction, const T margin) {
+  // Not just "0 <= fraction" to fool the compiler for unsigned types.
+  GOOGLE_DCHECK((T(0) < fraction || T(0) == fraction) &&
+         fraction < T(1) &&
+         margin >= T(0));
+
+  // Template specialization will convert the if() condition to a constant,
+  // which will cause the compiler to generate code for either the "if" part
+  // or the "then" part.  In this way we avoid a compiler warning
+  // about a potential integer overflow in crosstool v12 (gcc 4.3.1).
+  if (MathLimits<T>::kIsInteger) {
+    return x == y;
+  } else {
+    // IsFinite checks are to make kPosInf and kNegInf not within fraction
+    if (!MathLimits<T>::IsFinite(x) && !MathLimits<T>::IsFinite(y)) {
+      return false;
+    }
+    T relative_margin = static_cast<T>(fraction * Max(Abs(x), Abs(y)));
+    return AbsDiff(x, y) <= Max(margin, relative_margin);
+  }
+}
+
+}  // namespace protobuf
+}  // namespace google
+
+#endif  // GOOGLE_PROTOBUF_STUBS_MATHUTIL_H_
diff --git a/src/google/protobuf/stubs/status.cc b/src/google/protobuf/stubs/status.cc
new file mode 100644
index 0000000..9a68fad
--- /dev/null
+++ b/src/google/protobuf/stubs/status.cc
@@ -0,0 +1,133 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#include <google/protobuf/stubs/status.h>
+
+#include <stdint.h>
+#include <stdio.h>
+#include <utility>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace error {
+inline string CodeEnumToString(error::Code code) {
+  switch (code) {
+    case OK:
+      return "OK";
+    case CANCELLED:
+      return "CANCELLED";
+    case UNKNOWN:
+      return "UNKNOWN";
+    case INVALID_ARGUMENT:
+      return "INVALID_ARGUMENT";
+    case DEADLINE_EXCEEDED:
+      return "DEADLINE_EXCEEDED";
+    case NOT_FOUND:
+      return "NOT_FOUND";
+    case ALREADY_EXISTS:
+      return "ALREADY_EXISTS";
+    case PERMISSION_DENIED:
+      return "PERMISSION_DENIED";
+    case UNAUTHENTICATED:
+      return "UNAUTHENTICATED";
+    case RESOURCE_EXHAUSTED:
+      return "RESOURCE_EXHAUSTED";
+    case FAILED_PRECONDITION:
+      return "FAILED_PRECONDITION";
+    case ABORTED:
+      return "ABORTED";
+    case OUT_OF_RANGE:
+      return "OUT_OF_RANGE";
+    case UNIMPLEMENTED:
+      return "UNIMPLEMENTED";
+    case INTERNAL:
+      return "INTERNAL";
+    case UNAVAILABLE:
+      return "UNAVAILABLE";
+    case DATA_LOSS:
+      return "DATA_LOSS";
+  }
+
+  // No default clause, clang will abort if a code is missing from
+  // above switch.
+  return "UNKNOWN";
+}
+}  // namespace error.
+
+const Status Status::OK = Status();
+const Status Status::CANCELLED = Status(error::CANCELLED, "");
+const Status Status::UNKNOWN = Status(error::UNKNOWN, "");
+
+Status::Status() : error_code_(error::OK) {
+}
+
+Status::Status(error::Code error_code, StringPiece error_message)
+    : error_code_(error_code) {
+  if (error_code != error::OK) {
+    error_message_ = error_message.ToString();
+  }
+}
+
+Status::Status(const Status& other)
+    : error_code_(other.error_code_), error_message_(other.error_message_) {
+}
+
+Status& Status::operator=(const Status& other) {
+  error_code_ = other.error_code_;
+  error_message_ = other.error_message_;
+  return *this;
+}
+
+bool Status::operator==(const Status& x) const {
+  return error_code_ == x.error_code_ &&
+      error_message_ == x.error_message_;
+}
+
+string Status::ToString() const {
+  if (error_code_ == error::OK) {
+    return "OK";
+  } else {
+    if (error_message_.empty()) {
+      return error::CodeEnumToString(error_code_);
+    } else {
+      return error::CodeEnumToString(error_code_) + ":" +
+          error_message_;
+    }
+  }
+}
+
+ostream& operator<<(ostream& os, const Status& x) {
+  os << x.ToString();
+  return os;
+}
+
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/stubs/status.h b/src/google/protobuf/stubs/status.h
new file mode 100644
index 0000000..34d6cf1
--- /dev/null
+++ b/src/google/protobuf/stubs/status.h
@@ -0,0 +1,116 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#ifndef GOOGLE_PROTOBUF_STUBS_STATUS_H_
+#define GOOGLE_PROTOBUF_STUBS_STATUS_H_
+
+#include <iosfwd>
+#include <string>
+
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/stubs/stringpiece.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace error {
+// These values must match error codes defined in google/rpc/code.proto.
+enum Code {
+  OK = 0,
+  CANCELLED = 1,
+  UNKNOWN = 2,
+  INVALID_ARGUMENT = 3,
+  DEADLINE_EXCEEDED = 4,
+  NOT_FOUND = 5,
+  ALREADY_EXISTS = 6,
+  PERMISSION_DENIED = 7,
+  UNAUTHENTICATED = 16,
+  RESOURCE_EXHAUSTED = 8,
+  FAILED_PRECONDITION = 9,
+  ABORTED = 10,
+  OUT_OF_RANGE = 11,
+  UNIMPLEMENTED = 12,
+  INTERNAL = 13,
+  UNAVAILABLE = 14,
+  DATA_LOSS = 15,
+};
+}  // namespace error
+
+class Status {
+ public:
+  // Creates a "successful" status.
+  Status();
+
+  // Create a status in the canonical error space with the specified
+  // code, and error message.  If "code == 0", error_message is
+  // ignored and a Status object identical to Status::OK is
+  // constructed.
+  Status(error::Code error_code, StringPiece error_message);
+  Status(const Status&);
+  Status& operator=(const Status& x);
+  ~Status() {}
+
+  // Some pre-defined Status objects
+  static const Status OK;             // Identical to 0-arg constructor
+  static const Status CANCELLED;
+  static const Status UNKNOWN;
+
+  // Accessor
+  bool ok() const {
+    return error_code_ == error::OK;
+  }
+  int error_code() const {
+    return error_code_;
+  }
+  StringPiece error_message() const {
+    return error_message_;
+  }
+
+  bool operator==(const Status& x) const;
+  bool operator!=(const Status& x) const {
+    return !operator==(x);
+  }
+
+  // Return a combination of the error code name and message.
+  string ToString() const;
+
+ private:
+  error::Code error_code_;
+  string error_message_;
+};
+
+// Prints a human-readable representation of 'x' to 'os'.
+ostream& operator<<(ostream& os, const Status& x);
+
+#define EXPECT_OK(value) EXPECT_TRUE((value).ok())
+
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_STUBS_STATUS_H_
diff --git a/src/google/protobuf/stubs/status_macros.h b/src/google/protobuf/stubs/status_macros.h
new file mode 100644
index 0000000..743e79a
--- /dev/null
+++ b/src/google/protobuf/stubs/status_macros.h
@@ -0,0 +1,89 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// From: util/task/contrib/status_macros/status_macros.h
+
+#ifndef GOOGLE_PROTOBUF_STUBS_STATUS_MACROS_H_
+#define GOOGLE_PROTOBUF_STUBS_STATUS_MACROS_H_
+
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/stubs/status.h>
+#include <google/protobuf/stubs/statusor.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+
+// Run a command that returns a util::Status.  If the called code returns an
+// error status, return that status up out of this method too.
+//
+// Example:
+//   RETURN_IF_ERROR(DoThings(4));
+#define RETURN_IF_ERROR(expr) \
+  do { \
+    /* Using _status below to avoid capture problems if expr is "status". */ \
+    const ::google::protobuf::util::Status _status = (expr); \
+    if (GOOGLE_PREDICT_FALSE(!_status.ok())) return _status; \
+  } while (0)
+
+// Internal helper for concatenating macro values.
+#define STATUS_MACROS_CONCAT_NAME_INNER(x, y) x##y
+#define STATUS_MACROS_CONCAT_NAME(x, y) STATUS_MACROS_CONCAT_NAME_INNER(x, y)
+
+template<typename T>
+Status DoAssignOrReturn(T& lhs, StatusOr<T> result) {
+  if (result.ok()) {
+    lhs = result.ValueOrDie();
+  }
+  return result.status();
+}
+
+#define ASSIGN_OR_RETURN_IMPL(status, lhs, rexpr) \
+  Status status = DoAssignOrReturn(lhs, (rexpr)); \
+  if (GOOGLE_PREDICT_FALSE(!status.ok())) return status;
+
+// Executes an expression that returns a util::StatusOr, extracting its value
+// into the variable defined by lhs (or returning on error).
+//
+// Example: Assigning to an existing value
+//   ValueType value;
+//   ASSIGN_OR_RETURN(value, MaybeGetValue(arg));
+//
+// WARNING: ASSIGN_OR_RETURN expands into multiple statements; it cannot be used
+//  in a single statement (e.g. as the body of an if statement without {})!
+#define ASSIGN_OR_RETURN(lhs, rexpr) \
+  ASSIGN_OR_RETURN_IMPL( \
+      STATUS_MACROS_CONCAT_NAME(_status_or_value, __COUNTER__), lhs, rexpr);
+
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
+
+#endif  // GOOGLE_PROTOBUF_STUBS_STATUS_H_
diff --git a/src/google/protobuf/stubs/status_test.cc b/src/google/protobuf/stubs/status_test.cc
new file mode 100644
index 0000000..c70c33c
--- /dev/null
+++ b/src/google/protobuf/stubs/status_test.cc
@@ -0,0 +1,131 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#include <google/protobuf/stubs/status.h>
+
+#include <stdio.h>
+
+#include <google/protobuf/testing/googletest.h>
+#include <gtest/gtest.h>
+
+namespace google {
+namespace protobuf {
+namespace {
+TEST(Status, Empty) {
+  util::Status status;
+  EXPECT_EQ(util::error::OK, util::Status::OK.error_code());
+  EXPECT_EQ("OK", util::Status::OK.ToString());
+}
+
+TEST(Status, GenericCodes) {
+  EXPECT_EQ(util::error::OK, util::Status::OK.error_code());
+  EXPECT_EQ(util::error::CANCELLED, util::Status::CANCELLED.error_code());
+  EXPECT_EQ(util::error::UNKNOWN, util::Status::UNKNOWN.error_code());
+}
+
+TEST(Status, ConstructorZero) {
+  util::Status status(util::error::OK, "msg");
+  EXPECT_TRUE(status.ok());
+  EXPECT_EQ("OK", status.ToString());
+}
+
+TEST(Status, CheckOK) {
+  util::Status status;
+  GOOGLE_CHECK_OK(status);
+  GOOGLE_CHECK_OK(status) << "Failed";
+  GOOGLE_DCHECK_OK(status) << "Failed";
+}
+
+TEST(Status, ErrorMessage) {
+  util::Status status(util::error::INVALID_ARGUMENT, "");
+  EXPECT_FALSE(status.ok());
+  EXPECT_EQ("", status.error_message().ToString());
+  EXPECT_EQ("INVALID_ARGUMENT", status.ToString());
+  status = util::Status(util::error::INVALID_ARGUMENT, "msg");
+  EXPECT_FALSE(status.ok());
+  EXPECT_EQ("msg", status.error_message().ToString());
+  EXPECT_EQ("INVALID_ARGUMENT:msg", status.ToString());
+  status = util::Status(util::error::OK, "msg");
+  EXPECT_TRUE(status.ok());
+  EXPECT_EQ("", status.error_message().ToString());
+  EXPECT_EQ("OK", status.ToString());
+}
+
+TEST(Status, Copy) {
+  util::Status a(util::error::UNKNOWN, "message");
+  util::Status b(a);
+  ASSERT_EQ(a.ToString(), b.ToString());
+}
+
+TEST(Status, Assign) {
+  util::Status a(util::error::UNKNOWN, "message");
+  util::Status b;
+  b = a;
+  ASSERT_EQ(a.ToString(), b.ToString());
+}
+
+TEST(Status, AssignEmpty) {
+  util::Status a(util::error::UNKNOWN, "message");
+  util::Status b;
+  a = b;
+  ASSERT_EQ(string("OK"), a.ToString());
+  ASSERT_TRUE(b.ok());
+  ASSERT_TRUE(a.ok());
+}
+
+TEST(Status, EqualsOK) {
+  ASSERT_EQ(util::Status::OK, util::Status());
+}
+
+TEST(Status, EqualsSame) {
+  const util::Status a = util::Status(util::error::CANCELLED, "message");
+  const util::Status b = util::Status(util::error::CANCELLED, "message");
+  ASSERT_EQ(a, b);
+}
+
+TEST(Status, EqualsCopy) {
+  const util::Status a = util::Status(util::error::CANCELLED, "message");
+  const util::Status b = a;
+  ASSERT_EQ(a, b);
+}
+
+TEST(Status, EqualsDifferentCode) {
+  const util::Status a = util::Status(util::error::CANCELLED, "message");
+  const util::Status b = util::Status(util::error::UNKNOWN, "message");
+  ASSERT_NE(a, b);
+}
+
+TEST(Status, EqualsDifferentMessage) {
+  const util::Status a = util::Status(util::error::CANCELLED, "message");
+  const util::Status b = util::Status(util::error::CANCELLED, "another");
+  ASSERT_NE(a, b);
+}
+}  // namespace
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/stubs/statusor.cc b/src/google/protobuf/stubs/statusor.cc
new file mode 100644
index 0000000..48d1402
--- /dev/null
+++ b/src/google/protobuf/stubs/statusor.cc
@@ -0,0 +1,46 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/stubs/statusor.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace internal {
+
+void StatusOrHelper::Crash(const Status& status) {
+  GOOGLE_LOG(FATAL) << "Attempting to fetch value instead of handling error "
+                    << status.ToString();
+}
+
+}  // namespace internal
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/stubs/statusor.h b/src/google/protobuf/stubs/statusor.h
new file mode 100644
index 0000000..9495107
--- /dev/null
+++ b/src/google/protobuf/stubs/statusor.h
@@ -0,0 +1,259 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// StatusOr<T> is the union of a Status object and a T
+// object. StatusOr models the concept of an object that is either a
+// usable value, or an error Status explaining why such a value is
+// not present. To this end, StatusOr<T> does not allow its Status
+// value to be Status::OK. Further, StatusOr<T*> does not allow the
+// contained pointer to be NULL.
+//
+// The primary use-case for StatusOr<T> is as the return value of a
+// function which may fail.
+//
+// Example client usage for a StatusOr<T>, where T is not a pointer:
+//
+//  StatusOr<float> result = DoBigCalculationThatCouldFail();
+//  if (result.ok()) {
+//    float answer = result.ValueOrDie();
+//    printf("Big calculation yielded: %f", answer);
+//  } else {
+//    LOG(ERROR) << result.status();
+//  }
+//
+// Example client usage for a StatusOr<T*>:
+//
+//  StatusOr<Foo*> result = FooFactory::MakeNewFoo(arg);
+//  if (result.ok()) {
+//    std::unique_ptr<Foo> foo(result.ValueOrDie());
+//    foo->DoSomethingCool();
+//  } else {
+//    LOG(ERROR) << result.status();
+//  }
+//
+// Example client usage for a StatusOr<std::unique_ptr<T>>:
+//
+//  StatusOr<std::unique_ptr<Foo>> result = FooFactory::MakeNewFoo(arg);
+//  if (result.ok()) {
+//    std::unique_ptr<Foo> foo = result.ConsumeValueOrDie();
+//    foo->DoSomethingCool();
+//  } else {
+//    LOG(ERROR) << result.status();
+//  }
+//
+// Example factory implementation returning StatusOr<T*>:
+//
+//  StatusOr<Foo*> FooFactory::MakeNewFoo(int arg) {
+//    if (arg <= 0) {
+//      return ::util::Status(::util::error::INVALID_ARGUMENT,
+//                            "Arg must be positive");
+//    } else {
+//      return new Foo(arg);
+//    }
+//  }
+//
+
+#ifndef GOOGLE_PROTOBUF_STUBS_STATUSOR_H_
+#define GOOGLE_PROTOBUF_STUBS_STATUSOR_H_
+
+#include <new>
+#include <string>
+#include <utility>
+
+#include <google/protobuf/stubs/status.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+
+template<typename T>
+class StatusOr {
+  template<typename U> friend class StatusOr;
+
+ public:
+  // Construct a new StatusOr with Status::UNKNOWN status
+  StatusOr();
+
+  // Construct a new StatusOr with the given non-ok status. After calling
+  // this constructor, calls to ValueOrDie() will CHECK-fail.
+  //
+  // NOTE: Not explicit - we want to use StatusOr<T> as a return
+  // value, so it is convenient and sensible to be able to do 'return
+  // Status()' when the return type is StatusOr<T>.
+  //
+  // REQUIRES: status != Status::OK. This requirement is DCHECKed.
+  // In optimized builds, passing Status::OK here will have the effect
+  // of passing PosixErrorSpace::EINVAL as a fallback.
+  StatusOr(const Status& status);  // NOLINT
+
+  // Construct a new StatusOr with the given value. If T is a plain pointer,
+  // value must not be NULL. After calling this constructor, calls to
+  // ValueOrDie() will succeed, and calls to status() will return OK.
+  //
+  // NOTE: Not explicit - we want to use StatusOr<T> as a return type
+  // so it is convenient and sensible to be able to do 'return T()'
+  // when when the return type is StatusOr<T>.
+  //
+  // REQUIRES: if T is a plain pointer, value != NULL. This requirement is
+  // DCHECKed. In optimized builds, passing a NULL pointer here will have
+  // the effect of passing PosixErrorSpace::EINVAL as a fallback.
+  StatusOr(const T& value);  // NOLINT
+
+  // Copy constructor.
+  StatusOr(const StatusOr& other);
+
+  // Conversion copy constructor, T must be copy constructible from U
+  template<typename U>
+  StatusOr(const StatusOr<U>& other);
+
+  // Assignment operator.
+  StatusOr& operator=(const StatusOr& other);
+
+  // Conversion assignment operator, T must be assignable from U
+  template<typename U>
+  StatusOr& operator=(const StatusOr<U>& other);
+
+  // Returns a reference to our status. If this contains a T, then
+  // returns Status::OK.
+  const Status& status() const;
+
+  // Returns this->status().ok()
+  bool ok() const;
+
+  // Returns a reference to our current value, or CHECK-fails if !this->ok().
+  // If you need to initialize a T object from the stored value,
+  // ConsumeValueOrDie() may be more efficient.
+  const T& ValueOrDie() const;
+
+ private:
+  Status status_;
+  T value_;
+};
+
+////////////////////////////////////////////////////////////////////////////////
+// Implementation details for StatusOr<T>
+
+namespace internal {
+
+class StatusOrHelper {
+ public:
+  // Move type-agnostic error handling to the .cc.
+  static void Crash(const util::Status& status);
+
+  // Customized behavior for StatusOr<T> vs. StatusOr<T*>
+  template<typename T>
+  struct Specialize;
+};
+
+template<typename T>
+struct StatusOrHelper::Specialize {
+  // For non-pointer T, a reference can never be NULL.
+  static inline bool IsValueNull(const T& t) { return false; }
+};
+
+template<typename T>
+struct StatusOrHelper::Specialize<T*> {
+  static inline bool IsValueNull(const T* t) { return t == NULL; }
+};
+
+}  // namespace internal
+
+template<typename T>
+inline StatusOr<T>::StatusOr()
+    : status_(util::Status::UNKNOWN) {
+}
+
+template<typename T>
+inline StatusOr<T>::StatusOr(const Status& status) {
+  if (status.ok()) {
+    status_ = Status(error::INTERNAL, "Status::OK is not a valid argument.");
+  } else {
+    status_ = status;
+  }
+}
+
+template<typename T>
+inline StatusOr<T>::StatusOr(const T& value) {
+  if (internal::StatusOrHelper::Specialize<T>::IsValueNull(value)) {
+    status_ = Status(error::INTERNAL, "NULL is not a vaild argument.");
+  } else {
+    status_ = Status::OK;
+    value_ = value;
+  }
+}
+
+template<typename T>
+inline StatusOr<T>::StatusOr(const StatusOr<T>& other)
+    : status_(other.status_), value_(other.value_) {
+}
+
+template<typename T>
+inline StatusOr<T>& StatusOr<T>::operator=(const StatusOr<T>& other) {
+  status_ = other.status_;
+  value_ = other.value_;
+  return *this;
+}
+
+template<typename T>
+template<typename U>
+inline StatusOr<T>::StatusOr(const StatusOr<U>& other)
+    : status_(other.status_), value_(other.value_) {
+}
+
+template<typename T>
+template<typename U>
+inline StatusOr<T>& StatusOr<T>::operator=(const StatusOr<U>& other) {
+  status_ = other.status_;
+  value_ = other.value_;
+  return *this;
+}
+
+template<typename T>
+inline const Status& StatusOr<T>::status() const {
+  return status_;
+}
+
+template<typename T>
+inline bool StatusOr<T>::ok() const {
+  return status().ok();
+}
+
+template<typename T>
+inline const T& StatusOr<T>::ValueOrDie() const {
+  if (!status_.ok()) {
+    internal::StatusOrHelper::Crash(status_);
+  }
+  return value_;
+}
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
+
+#endif  // GOOGLE_PROTOBUF_STUBS_STATUSOR_H_
diff --git a/src/google/protobuf/stubs/statusor_test.cc b/src/google/protobuf/stubs/statusor_test.cc
new file mode 100644
index 0000000..6e2a9e5
--- /dev/null
+++ b/src/google/protobuf/stubs/statusor_test.cc
@@ -0,0 +1,274 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/stubs/statusor.h>
+
+#include <errno.h>
+#include <memory>
+
+#include <google/protobuf/testing/googletest.h>
+#include <gtest/gtest.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace {
+
+class Base1 {
+ public:
+  virtual ~Base1() {}
+  int pad;
+};
+
+class Base2 {
+ public:
+  virtual ~Base2() {}
+  int yetotherpad;
+};
+
+class Derived : public Base1, public Base2 {
+ public:
+  virtual ~Derived() {}
+  int evenmorepad;
+};
+
+class CopyNoAssign {
+ public:
+  explicit CopyNoAssign(int value) : foo(value) {}
+  CopyNoAssign(const CopyNoAssign& other) : foo(other.foo) {}
+  int foo;
+ private:
+  const CopyNoAssign& operator=(const CopyNoAssign&);
+};
+
+TEST(StatusOr, TestDefaultCtor) {
+  StatusOr<int> thing;
+  EXPECT_FALSE(thing.ok());
+  EXPECT_EQ(Status::UNKNOWN, thing.status());
+}
+
+TEST(StatusOr, TestStatusCtor) {
+  StatusOr<int> thing(Status::CANCELLED);
+  EXPECT_FALSE(thing.ok());
+  EXPECT_EQ(Status::CANCELLED, thing.status());
+}
+
+TEST(StatusOr, TestValueCtor) {
+  const int kI = 4;
+  StatusOr<int> thing(kI);
+  EXPECT_TRUE(thing.ok());
+  EXPECT_EQ(kI, thing.ValueOrDie());
+}
+
+TEST(StatusOr, TestCopyCtorStatusOk) {
+  const int kI = 4;
+  StatusOr<int> original(kI);
+  StatusOr<int> copy(original);
+  EXPECT_EQ(original.status(), copy.status());
+  EXPECT_EQ(original.ValueOrDie(), copy.ValueOrDie());
+}
+
+TEST(StatusOr, TestCopyCtorStatusNotOk) {
+  StatusOr<int> original(Status::CANCELLED);
+  StatusOr<int> copy(original);
+  EXPECT_EQ(original.status(), copy.status());
+}
+
+TEST(StatusOr, TestCopyCtorStatusOKConverting) {
+  const int kI = 4;
+  StatusOr<int>    original(kI);
+  StatusOr<double> copy(original);
+  EXPECT_EQ(original.status(), copy.status());
+  EXPECT_EQ(original.ValueOrDie(), copy.ValueOrDie());
+}
+
+TEST(StatusOr, TestCopyCtorStatusNotOkConverting) {
+  StatusOr<int>    original(Status::CANCELLED);
+  StatusOr<double> copy(original);
+  EXPECT_EQ(original.status(), copy.status());
+}
+
+TEST(StatusOr, TestAssignmentStatusOk) {
+  const int kI = 4;
+  StatusOr<int> source(kI);
+  StatusOr<int> target;
+  target = source;
+  EXPECT_EQ(source.status(), target.status());
+  EXPECT_EQ(source.ValueOrDie(), target.ValueOrDie());
+}
+
+TEST(StatusOr, TestAssignmentStatusNotOk) {
+  StatusOr<int> source(Status::CANCELLED);
+  StatusOr<int> target;
+  target = source;
+  EXPECT_EQ(source.status(), target.status());
+}
+
+TEST(StatusOr, TestAssignmentStatusOKConverting) {
+  const int kI = 4;
+  StatusOr<int>    source(kI);
+  StatusOr<double> target;
+  target = source;
+  EXPECT_EQ(source.status(), target.status());
+  EXPECT_DOUBLE_EQ(source.ValueOrDie(), target.ValueOrDie());
+}
+
+TEST(StatusOr, TestAssignmentStatusNotOkConverting) {
+  StatusOr<int>    source(Status::CANCELLED);
+  StatusOr<double> target;
+  target = source;
+  EXPECT_EQ(source.status(), target.status());
+}
+
+TEST(StatusOr, TestStatus) {
+  StatusOr<int> good(4);
+  EXPECT_TRUE(good.ok());
+  StatusOr<int> bad(Status::CANCELLED);
+  EXPECT_FALSE(bad.ok());
+  EXPECT_EQ(Status::CANCELLED, bad.status());
+}
+
+TEST(StatusOr, TestValue) {
+  const int kI = 4;
+  StatusOr<int> thing(kI);
+  EXPECT_EQ(kI, thing.ValueOrDie());
+}
+
+TEST(StatusOr, TestValueConst) {
+  const int kI = 4;
+  const StatusOr<int> thing(kI);
+  EXPECT_EQ(kI, thing.ValueOrDie());
+}
+
+TEST(StatusOr, TestPointerDefaultCtor) {
+  StatusOr<int*> thing;
+  EXPECT_FALSE(thing.ok());
+  EXPECT_EQ(Status::UNKNOWN, thing.status());
+}
+
+TEST(StatusOr, TestPointerStatusCtor) {
+  StatusOr<int*> thing(Status::CANCELLED);
+  EXPECT_FALSE(thing.ok());
+  EXPECT_EQ(Status::CANCELLED, thing.status());
+}
+
+TEST(StatusOr, TestPointerValueCtor) {
+  const int kI = 4;
+  StatusOr<const int*> thing(&kI);
+  EXPECT_TRUE(thing.ok());
+  EXPECT_EQ(&kI, thing.ValueOrDie());
+}
+
+TEST(StatusOr, TestPointerCopyCtorStatusOk) {
+  const int kI = 0;
+  StatusOr<const int*> original(&kI);
+  StatusOr<const int*> copy(original);
+  EXPECT_EQ(original.status(), copy.status());
+  EXPECT_EQ(original.ValueOrDie(), copy.ValueOrDie());
+}
+
+TEST(StatusOr, TestPointerCopyCtorStatusNotOk) {
+  StatusOr<int*> original(Status::CANCELLED);
+  StatusOr<int*> copy(original);
+  EXPECT_EQ(original.status(), copy.status());
+}
+
+TEST(StatusOr, TestPointerCopyCtorStatusOKConverting) {
+  Derived derived;
+  StatusOr<Derived*> original(&derived);
+  StatusOr<Base2*>   copy(original);
+  EXPECT_EQ(original.status(), copy.status());
+  EXPECT_EQ(static_cast<const Base2*>(original.ValueOrDie()),
+            copy.ValueOrDie());
+}
+
+TEST(StatusOr, TestPointerCopyCtorStatusNotOkConverting) {
+  StatusOr<Derived*> original(Status::CANCELLED);
+  StatusOr<Base2*>   copy(original);
+  EXPECT_EQ(original.status(), copy.status());
+}
+
+TEST(StatusOr, TestPointerAssignmentStatusOk) {
+  const int kI = 0;
+  StatusOr<const int*> source(&kI);
+  StatusOr<const int*> target;
+  target = source;
+  EXPECT_EQ(source.status(), target.status());
+  EXPECT_EQ(source.ValueOrDie(), target.ValueOrDie());
+}
+
+TEST(StatusOr, TestPointerAssignmentStatusNotOk) {
+  StatusOr<int*> source(Status::CANCELLED);
+  StatusOr<int*> target;
+  target = source;
+  EXPECT_EQ(source.status(), target.status());
+}
+
+TEST(StatusOr, TestPointerAssignmentStatusOKConverting) {
+  Derived derived;
+  StatusOr<Derived*> source(&derived);
+  StatusOr<Base2*>   target;
+  target = source;
+  EXPECT_EQ(source.status(), target.status());
+  EXPECT_EQ(static_cast<const Base2*>(source.ValueOrDie()),
+            target.ValueOrDie());
+}
+
+TEST(StatusOr, TestPointerAssignmentStatusNotOkConverting) {
+  StatusOr<Derived*> source(Status::CANCELLED);
+  StatusOr<Base2*>   target;
+  target = source;
+  EXPECT_EQ(source.status(), target.status());
+}
+
+TEST(StatusOr, TestPointerStatus) {
+  const int kI = 0;
+  StatusOr<const int*> good(&kI);
+  EXPECT_TRUE(good.ok());
+  StatusOr<const int*> bad(Status::CANCELLED);
+  EXPECT_EQ(Status::CANCELLED, bad.status());
+}
+
+TEST(StatusOr, TestPointerValue) {
+  const int kI = 0;
+  StatusOr<const int*> thing(&kI);
+  EXPECT_EQ(&kI, thing.ValueOrDie());
+}
+
+TEST(StatusOr, TestPointerValueConst) {
+  const int kI = 0;
+  const StatusOr<const int*> thing(&kI);
+  EXPECT_EQ(&kI, thing.ValueOrDie());
+}
+
+}  // namespace
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/stubs/stringpiece.cc b/src/google/protobuf/stubs/stringpiece.cc
new file mode 100644
index 0000000..989474b
--- /dev/null
+++ b/src/google/protobuf/stubs/stringpiece.cc
@@ -0,0 +1,268 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#include <google/protobuf/stubs/stringpiece.h>
+
+#include <string.h>
+#include <algorithm>
+#include <climits>
+#include <string>
+#include <ostream>
+
+namespace google {
+namespace protobuf {
+std::ostream& operator<<(std::ostream& o, StringPiece piece) {
+  o.write(piece.data(), piece.size());
+  return o;
+}
+
+// Out-of-line error path.
+void StringPiece::LogFatalSizeTooBig(size_t size, const char* details) {
+  GOOGLE_LOG(FATAL) << "size too big: " << size << " details: " << details;
+}
+
+StringPiece::StringPiece(StringPiece x, stringpiece_ssize_type pos)
+    : ptr_(x.ptr_ + pos), length_(x.length_ - pos) {
+  GOOGLE_DCHECK_LE(0, pos);
+  GOOGLE_DCHECK_LE(pos, x.length_);
+}
+
+StringPiece::StringPiece(StringPiece x,
+                         stringpiece_ssize_type pos,
+                         stringpiece_ssize_type len)
+    : ptr_(x.ptr_ + pos), length_(std::min(len, x.length_ - pos)) {
+  GOOGLE_DCHECK_LE(0, pos);
+  GOOGLE_DCHECK_LE(pos, x.length_);
+  GOOGLE_DCHECK_GE(len, 0);
+}
+
+void StringPiece::CopyToString(string* target) const {
+  target->assign(ptr_, length_);
+}
+
+void StringPiece::AppendToString(string* target) const {
+  target->append(ptr_, length_);
+}
+
+bool StringPiece::Consume(StringPiece x) {
+  if (starts_with(x)) {
+    ptr_ += x.length_;
+    length_ -= x.length_;
+    return true;
+  }
+  return false;
+}
+
+bool StringPiece::ConsumeFromEnd(StringPiece x) {
+  if (ends_with(x)) {
+    length_ -= x.length_;
+    return true;
+  }
+  return false;
+}
+
+stringpiece_ssize_type StringPiece::copy(char* buf,
+                                         size_type n,
+                                         size_type pos) const {
+  stringpiece_ssize_type ret = std::min(length_ - pos, n);
+  memcpy(buf, ptr_ + pos, ret);
+  return ret;
+}
+
+bool StringPiece::contains(StringPiece s) const {
+  return find(s, 0) != npos;
+}
+
+stringpiece_ssize_type StringPiece::find(StringPiece s, size_type pos) const {
+  if (length_ <= 0 || pos > static_cast<size_type>(length_)) {
+    if (length_ == 0 && pos == 0 && s.length_ == 0) return 0;
+    return npos;
+  }
+  const char *result = std::search(ptr_ + pos, ptr_ + length_,
+                                   s.ptr_, s.ptr_ + s.length_);
+  return result == ptr_ + length_ ? npos : result - ptr_;
+}
+
+stringpiece_ssize_type StringPiece::find(char c, size_type pos) const {
+  if (length_ <= 0 || pos >= static_cast<size_type>(length_)) {
+    return npos;
+  }
+  const char* result = static_cast<const char*>(
+      memchr(ptr_ + pos, c, length_ - pos));
+  return result != NULL ? result - ptr_ : npos;
+}
+
+stringpiece_ssize_type StringPiece::rfind(StringPiece s, size_type pos) const {
+  if (length_ < s.length_) return npos;
+  const size_t ulen = length_;
+  if (s.length_ == 0) return std::min(ulen, pos);
+
+  const char* last = ptr_ + std::min(ulen - s.length_, pos) + s.length_;
+  const char* result = std::find_end(ptr_, last, s.ptr_, s.ptr_ + s.length_);
+  return result != last ? result - ptr_ : npos;
+}
+
+// Search range is [0..pos] inclusive.  If pos == npos, search everything.
+stringpiece_ssize_type StringPiece::rfind(char c, size_type pos) const {
+  // Note: memrchr() is not available on Windows.
+  if (length_ <= 0) return npos;
+  for (stringpiece_ssize_type i =
+      std::min(pos, static_cast<size_type>(length_ - 1));
+       i >= 0; --i) {
+    if (ptr_[i] == c) {
+      return i;
+    }
+  }
+  return npos;
+}
+
+// For each character in characters_wanted, sets the index corresponding
+// to the ASCII code of that character to 1 in table.  This is used by
+// the find_.*_of methods below to tell whether or not a character is in
+// the lookup table in constant time.
+// The argument `table' must be an array that is large enough to hold all
+// the possible values of an unsigned char.  Thus it should be be declared
+// as follows:
+//   bool table[UCHAR_MAX + 1]
+static inline void BuildLookupTable(StringPiece characters_wanted,
+                                    bool* table) {
+  const stringpiece_ssize_type length = characters_wanted.length();
+  const char* const data = characters_wanted.data();
+  for (stringpiece_ssize_type i = 0; i < length; ++i) {
+    table[static_cast<unsigned char>(data[i])] = true;
+  }
+}
+
+stringpiece_ssize_type StringPiece::find_first_of(StringPiece s,
+                                                  size_type pos) const {
+  if (length_ <= 0 || s.length_ <= 0) {
+    return npos;
+  }
+  // Avoid the cost of BuildLookupTable() for a single-character search.
+  if (s.length_ == 1) return find_first_of(s.ptr_[0], pos);
+
+  bool lookup[UCHAR_MAX + 1] = { false };
+  BuildLookupTable(s, lookup);
+  for (stringpiece_ssize_type i = pos; i < length_; ++i) {
+    if (lookup[static_cast<unsigned char>(ptr_[i])]) {
+      return i;
+    }
+  }
+  return npos;
+}
+
+stringpiece_ssize_type StringPiece::find_first_not_of(StringPiece s,
+                                                      size_type pos) const {
+  if (length_ <= 0) return npos;
+  if (s.length_ <= 0) return 0;
+  // Avoid the cost of BuildLookupTable() for a single-character search.
+  if (s.length_ == 1) return find_first_not_of(s.ptr_[0], pos);
+
+  bool lookup[UCHAR_MAX + 1] = { false };
+  BuildLookupTable(s, lookup);
+  for (stringpiece_ssize_type i = pos; i < length_; ++i) {
+    if (!lookup[static_cast<unsigned char>(ptr_[i])]) {
+      return i;
+    }
+  }
+  return npos;
+}
+
+stringpiece_ssize_type StringPiece::find_first_not_of(char c,
+                                                      size_type pos) const {
+  if (length_ <= 0) return npos;
+
+  for (; pos < static_cast<size_type>(length_); ++pos) {
+    if (ptr_[pos] != c) {
+      return pos;
+    }
+  }
+  return npos;
+}
+
+stringpiece_ssize_type StringPiece::find_last_of(StringPiece s,
+                                                 size_type pos) const {
+  if (length_ <= 0 || s.length_ <= 0) return npos;
+  // Avoid the cost of BuildLookupTable() for a single-character search.
+  if (s.length_ == 1) return find_last_of(s.ptr_[0], pos);
+
+  bool lookup[UCHAR_MAX + 1] = { false };
+  BuildLookupTable(s, lookup);
+  for (stringpiece_ssize_type i =
+       std::min(pos, static_cast<size_type>(length_ - 1)); i >= 0; --i) {
+    if (lookup[static_cast<unsigned char>(ptr_[i])]) {
+      return i;
+    }
+  }
+  return npos;
+}
+
+stringpiece_ssize_type StringPiece::find_last_not_of(StringPiece s,
+                                                     size_type pos) const {
+  if (length_ <= 0) return npos;
+
+  stringpiece_ssize_type i = std::min(pos, static_cast<size_type>(length_ - 1));
+  if (s.length_ <= 0) return i;
+
+  // Avoid the cost of BuildLookupTable() for a single-character search.
+  if (s.length_ == 1) return find_last_not_of(s.ptr_[0], pos);
+
+  bool lookup[UCHAR_MAX + 1] = { false };
+  BuildLookupTable(s, lookup);
+  for (; i >= 0; --i) {
+    if (!lookup[static_cast<unsigned char>(ptr_[i])]) {
+      return i;
+    }
+  }
+  return npos;
+}
+
+stringpiece_ssize_type StringPiece::find_last_not_of(char c,
+                                                     size_type pos) const {
+  if (length_ <= 0) return npos;
+
+  for (stringpiece_ssize_type i =
+       std::min(pos, static_cast<size_type>(length_ - 1)); i >= 0; --i) {
+    if (ptr_[i] != c) {
+      return i;
+    }
+  }
+  return npos;
+}
+
+StringPiece StringPiece::substr(size_type pos, size_type n) const {
+  if (pos > length_) pos = length_;
+  if (n > length_ - pos) n = length_ - pos;
+  return StringPiece(ptr_ + pos, n);
+}
+
+const StringPiece::size_type StringPiece::npos = size_type(-1);
+
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/stubs/stringpiece.h b/src/google/protobuf/stubs/stringpiece.h
new file mode 100644
index 0000000..5d4d5fe
--- /dev/null
+++ b/src/google/protobuf/stubs/stringpiece.h
@@ -0,0 +1,437 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// A StringPiece points to part or all of a string, Cord, double-quoted string
+// literal, or other string-like object.  A StringPiece does *not* own the
+// string to which it points.  A StringPiece is not null-terminated.
+//
+// You can use StringPiece as a function or method parameter.  A StringPiece
+// parameter can receive a double-quoted string literal argument, a "const
+// char*" argument, a string argument, or a StringPiece argument with no data
+// copying.  Systematic use of StringPiece for arguments reduces data
+// copies and strlen() calls.
+//
+// Prefer passing StringPieces by value:
+//   void MyFunction(StringPiece arg);
+// If circumstances require, you may also pass by const reference:
+//   void MyFunction(const StringPiece& arg);  // not preferred
+// Both of these have the same lifetime semantics.  Passing by value
+// generates slightly smaller code.  For more discussion, see the thread
+// go/stringpiecebyvalue on c-users.
+//
+// StringPiece is also suitable for local variables if you know that
+// the lifetime of the underlying object is longer than the lifetime
+// of your StringPiece variable.
+//
+// Beware of binding a StringPiece to a temporary:
+//   StringPiece sp = obj.MethodReturningString();  // BAD: lifetime problem
+//
+// This code is okay:
+//   string str = obj.MethodReturningString();  // str owns its contents
+//   StringPiece sp(str);  // GOOD, because str outlives sp
+//
+// StringPiece is sometimes a poor choice for a return value and usually a poor
+// choice for a data member.  If you do use a StringPiece this way, it is your
+// responsibility to ensure that the object pointed to by the StringPiece
+// outlives the StringPiece.
+//
+// A StringPiece may represent just part of a string; thus the name "Piece".
+// For example, when splitting a string, vector<StringPiece> is a natural data
+// type for the output.  For another example, a Cord is a non-contiguous,
+// potentially very long string-like object.  The Cord class has an interface
+// that iteratively provides StringPiece objects that point to the
+// successive pieces of a Cord object.
+//
+// A StringPiece is not null-terminated.  If you write code that scans a
+// StringPiece, you must check its length before reading any characters.
+// Common idioms that work on null-terminated strings do not work on
+// StringPiece objects.
+//
+// There are several ways to create a null StringPiece:
+//   StringPiece()
+//   StringPiece(NULL)
+//   StringPiece(NULL, 0)
+// For all of the above, sp.data() == NULL, sp.length() == 0,
+// and sp.empty() == true.  Also, if you create a StringPiece with
+// a non-NULL pointer then sp.data() != NULL.  Once created,
+// sp.data() will stay either NULL or not-NULL, except if you call
+// sp.clear() or sp.set().
+//
+// Thus, you can use StringPiece(NULL) to signal an out-of-band value
+// that is different from other StringPiece values.  This is similar
+// to the way that const char* p1 = NULL; is different from
+// const char* p2 = "";.
+//
+// There are many ways to create an empty StringPiece:
+//   StringPiece()
+//   StringPiece(NULL)
+//   StringPiece(NULL, 0)
+//   StringPiece("")
+//   StringPiece("", 0)
+//   StringPiece("abcdef", 0)
+//   StringPiece("abcdef"+6, 0)
+// For all of the above, sp.length() will be 0 and sp.empty() will be true.
+// For some empty StringPiece values, sp.data() will be NULL.
+// For some empty StringPiece values, sp.data() will not be NULL.
+//
+// Be careful not to confuse: null StringPiece and empty StringPiece.
+// The set of empty StringPieces properly includes the set of null StringPieces.
+// That is, every null StringPiece is an empty StringPiece,
+// but some non-null StringPieces are empty Stringpieces too.
+//
+// All empty StringPiece values compare equal to each other.
+// Even a null StringPieces compares equal to a non-null empty StringPiece:
+//  StringPiece() == StringPiece("", 0)
+//  StringPiece(NULL) == StringPiece("abc", 0)
+//  StringPiece(NULL, 0) == StringPiece("abcdef"+6, 0)
+//
+// Look carefully at this example:
+//   StringPiece("") == NULL
+// True or false?  TRUE, because StringPiece::operator== converts
+// the right-hand side from NULL to StringPiece(NULL),
+// and then compares two zero-length spans of characters.
+// However, we are working to make this example produce a compile error.
+//
+// Suppose you want to write:
+//   bool TestWhat?(StringPiece sp) { return sp == NULL; }  // BAD
+// Do not do that.  Write one of these instead:
+//   bool TestNull(StringPiece sp) { return sp.data() == NULL; }
+//   bool TestEmpty(StringPiece sp) { return sp.empty(); }
+// The intent of TestWhat? is unclear.  Did you mean TestNull or TestEmpty?
+// Right now, TestWhat? behaves likes TestEmpty.
+// We are working to make TestWhat? produce a compile error.
+// TestNull is good to test for an out-of-band signal.
+// TestEmpty is good to test for an empty StringPiece.
+//
+// Caveats (again):
+// (1) The lifetime of the pointed-to string (or piece of a string)
+//     must be longer than the lifetime of the StringPiece.
+// (2) There may or may not be a '\0' character after the end of
+//     StringPiece data.
+// (3) A null StringPiece is empty.
+//     An empty StringPiece may or may not be a null StringPiece.
+
+#ifndef GOOGLE_PROTOBUF_STUBS_STRINGPIECE_H_
+#define GOOGLE_PROTOBUF_STUBS_STRINGPIECE_H_
+
+#include <assert.h>
+#include <stddef.h>
+#include <string.h>
+#include <iosfwd>
+#include <limits>
+#include <string>
+
+#include <google/protobuf/stubs/common.h>
+
+namespace google {
+namespace protobuf {
+// StringPiece has *two* size types.
+// StringPiece::size_type
+//   is unsigned
+//   is 32 bits in LP32, 64 bits in LP64, 64 bits in LLP64
+//   no future changes intended
+// stringpiece_ssize_type
+//   is signed
+//   is 32 bits in LP32, 64 bits in LP64, 64 bits in LLP64
+//   future changes intended: http://go/64BitStringPiece
+//
+typedef string::difference_type stringpiece_ssize_type;
+
+// STRINGPIECE_CHECK_SIZE protects us from 32-bit overflows.
+// TODO(mec): delete this after stringpiece_ssize_type goes 64 bit.
+#if !defined(NDEBUG)
+#define STRINGPIECE_CHECK_SIZE 1
+#elif defined(_FORTIFY_SOURCE) && _FORTIFY_SOURCE > 0
+#define STRINGPIECE_CHECK_SIZE 1
+#else
+#define STRINGPIECE_CHECK_SIZE 0
+#endif
+
+class StringPiece {
+ private:
+  const char* ptr_;
+  stringpiece_ssize_type length_;
+
+  // Prevent overflow in debug mode or fortified mode.
+  // sizeof(stringpiece_ssize_type) may be smaller than sizeof(size_t).
+  static stringpiece_ssize_type CheckedSsizeTFromSizeT(size_t size) {
+#if STRINGPIECE_CHECK_SIZE > 0
+    if (size > static_cast<size_t>(
+        std::numeric_limits<stringpiece_ssize_type>::max())) {
+      // Some people grep for this message in logs
+      // so take care if you ever change it.
+      LogFatalSizeTooBig(size, "size_t to int conversion");
+    }
+#endif
+    return static_cast<stringpiece_ssize_type>(size);
+  }
+
+  // Out-of-line error path.
+  static void LogFatalSizeTooBig(size_t size, const char* details);
+
+ public:
+  // We provide non-explicit singleton constructors so users can pass
+  // in a "const char*" or a "string" wherever a "StringPiece" is
+  // expected.
+  //
+  // Style guide exception granted:
+  // http://goto/style-guide-exception-20978288
+  StringPiece() : ptr_(NULL), length_(0) {}
+
+  StringPiece(const char* str)  // NOLINT(runtime/explicit)
+      : ptr_(str), length_(0) {
+    if (str != NULL) {
+      length_ = CheckedSsizeTFromSizeT(strlen(str));
+    }
+  }
+
+  template <class Allocator>
+  StringPiece(  // NOLINT(runtime/explicit)
+      const std::basic_string<char, std::char_traits<char>, Allocator>& str)
+      : ptr_(str.data()), length_(0) {
+    length_ = CheckedSsizeTFromSizeT(str.size());
+  }
+#if defined(HAS_GLOBAL_STRING)
+  template <class Allocator>
+  StringPiece(  // NOLINT(runtime/explicit)
+      const basic_string<char, std::char_traits<char>, Allocator>& str)
+      : ptr_(str.data()), length_(0) {
+    length_ = CheckedSsizeTFromSizeT(str.size());
+  }
+#endif
+
+  StringPiece(const char* offset, stringpiece_ssize_type len)
+      : ptr_(offset), length_(len) {
+    assert(len >= 0);
+  }
+
+  // Substring of another StringPiece.
+  // pos must be non-negative and <= x.length().
+  StringPiece(StringPiece x, stringpiece_ssize_type pos);
+  // Substring of another StringPiece.
+  // pos must be non-negative and <= x.length().
+  // len must be non-negative and will be pinned to at most x.length() - pos.
+  StringPiece(StringPiece x,
+              stringpiece_ssize_type pos,
+              stringpiece_ssize_type len);
+
+  // data() may return a pointer to a buffer with embedded NULs, and the
+  // returned buffer may or may not be null terminated.  Therefore it is
+  // typically a mistake to pass data() to a routine that expects a NUL
+  // terminated string.
+  const char* data() const { return ptr_; }
+  stringpiece_ssize_type size() const { return length_; }
+  stringpiece_ssize_type length() const { return length_; }
+  bool empty() const { return length_ == 0; }
+
+  void clear() {
+    ptr_ = NULL;
+    length_ = 0;
+  }
+
+  void set(const char* data, stringpiece_ssize_type len) {
+    assert(len >= 0);
+    ptr_ = data;
+    length_ = len;
+  }
+
+  void set(const char* str) {
+    ptr_ = str;
+    if (str != NULL)
+      length_ = CheckedSsizeTFromSizeT(strlen(str));
+    else
+      length_ = 0;
+  }
+
+  void set(const void* data, stringpiece_ssize_type len) {
+    ptr_ = reinterpret_cast<const char*>(data);
+    length_ = len;
+  }
+
+  char operator[](stringpiece_ssize_type i) const {
+    assert(0 <= i);
+    assert(i < length_);
+    return ptr_[i];
+  }
+
+  void remove_prefix(stringpiece_ssize_type n) {
+    assert(length_ >= n);
+    ptr_ += n;
+    length_ -= n;
+  }
+
+  void remove_suffix(stringpiece_ssize_type n) {
+    assert(length_ >= n);
+    length_ -= n;
+  }
+
+  // returns {-1, 0, 1}
+  int compare(StringPiece x) const {
+    const stringpiece_ssize_type min_size =
+        length_ < x.length_ ? length_ : x.length_;
+    int r = memcmp(ptr_, x.ptr_, min_size);
+    if (r < 0) return -1;
+    if (r > 0) return 1;
+    if (length_ < x.length_) return -1;
+    if (length_ > x.length_) return 1;
+    return 0;
+  }
+
+  string as_string() const {
+    return ToString();
+  }
+  // We also define ToString() here, since many other string-like
+  // interfaces name the routine that converts to a C++ string
+  // "ToString", and it's confusing to have the method that does that
+  // for a StringPiece be called "as_string()".  We also leave the
+  // "as_string()" method defined here for existing code.
+  string ToString() const {
+    if (ptr_ == NULL) return string();
+    return string(data(), size());
+  }
+
+  operator string() const {
+    return ToString();
+  }
+
+  void CopyToString(string* target) const;
+  void AppendToString(string* target) const;
+
+  bool starts_with(StringPiece x) const {
+    return (length_ >= x.length_) && (memcmp(ptr_, x.ptr_, x.length_) == 0);
+  }
+
+  bool ends_with(StringPiece x) const {
+    return ((length_ >= x.length_) &&
+            (memcmp(ptr_ + (length_-x.length_), x.ptr_, x.length_) == 0));
+  }
+
+  // Checks whether StringPiece starts with x and if so advances the beginning
+  // of it to past the match.  It's basically a shortcut for starts_with
+  // followed by remove_prefix.
+  bool Consume(StringPiece x);
+  // Like above but for the end of the string.
+  bool ConsumeFromEnd(StringPiece x);
+
+  // standard STL container boilerplate
+  typedef char value_type;
+  typedef const char* pointer;
+  typedef const char& reference;
+  typedef const char& const_reference;
+  typedef size_t size_type;
+  typedef ptrdiff_t difference_type;
+  static const size_type npos;
+  typedef const char* const_iterator;
+  typedef const char* iterator;
+  typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
+  typedef std::reverse_iterator<iterator> reverse_iterator;
+  iterator begin() const { return ptr_; }
+  iterator end() const { return ptr_ + length_; }
+  const_reverse_iterator rbegin() const {
+    return const_reverse_iterator(ptr_ + length_);
+  }
+  const_reverse_iterator rend() const {
+    return const_reverse_iterator(ptr_);
+  }
+  stringpiece_ssize_type max_size() const { return length_; }
+  stringpiece_ssize_type capacity() const { return length_; }
+
+  // cpplint.py emits a false positive [build/include_what_you_use]
+  stringpiece_ssize_type copy(char* buf, size_type n, size_type pos = 0) const;  // NOLINT
+
+  bool contains(StringPiece s) const;
+
+  stringpiece_ssize_type find(StringPiece s, size_type pos = 0) const;
+  stringpiece_ssize_type find(char c, size_type pos = 0) const;
+  stringpiece_ssize_type rfind(StringPiece s, size_type pos = npos) const;
+  stringpiece_ssize_type rfind(char c, size_type pos = npos) const;
+
+  stringpiece_ssize_type find_first_of(StringPiece s, size_type pos = 0) const;
+  stringpiece_ssize_type find_first_of(char c, size_type pos = 0) const {
+    return find(c, pos);
+  }
+  stringpiece_ssize_type find_first_not_of(StringPiece s,
+                                           size_type pos = 0) const;
+  stringpiece_ssize_type find_first_not_of(char c, size_type pos = 0) const;
+  stringpiece_ssize_type find_last_of(StringPiece s,
+                                      size_type pos = npos) const;
+  stringpiece_ssize_type find_last_of(char c, size_type pos = npos) const {
+    return rfind(c, pos);
+  }
+  stringpiece_ssize_type find_last_not_of(StringPiece s,
+                                          size_type pos = npos) const;
+  stringpiece_ssize_type find_last_not_of(char c, size_type pos = npos) const;
+
+  StringPiece substr(size_type pos, size_type n = npos) const;
+};
+
+// This large function is defined inline so that in a fairly common case where
+// one of the arguments is a literal, the compiler can elide a lot of the
+// following comparisons.
+inline bool operator==(StringPiece x, StringPiece y) {
+  stringpiece_ssize_type len = x.size();
+  if (len != y.size()) {
+    return false;
+  }
+
+  return x.data() == y.data() || len <= 0 ||
+      memcmp(x.data(), y.data(), len) == 0;
+}
+
+inline bool operator!=(StringPiece x, StringPiece y) {
+  return !(x == y);
+}
+
+inline bool operator<(StringPiece x, StringPiece y) {
+  const stringpiece_ssize_type min_size =
+      x.size() < y.size() ? x.size() : y.size();
+  const int r = memcmp(x.data(), y.data(), min_size);
+  return (r < 0) || (r == 0 && x.size() < y.size());
+}
+
+inline bool operator>(StringPiece x, StringPiece y) {
+  return y < x;
+}
+
+inline bool operator<=(StringPiece x, StringPiece y) {
+  return !(x > y);
+}
+
+inline bool operator>=(StringPiece x, StringPiece y) {
+  return !(x < y);
+}
+
+// allow StringPiece to be logged
+extern std::ostream& operator<<(std::ostream& o, StringPiece piece);
+
+}  // namespace protobuf
+}  // namespace google
+
+#endif  // STRINGS_STRINGPIECE_H_
diff --git a/src/google/protobuf/stubs/stringpiece_unittest.cc b/src/google/protobuf/stubs/stringpiece_unittest.cc
new file mode 100644
index 0000000..9b5dae1
--- /dev/null
+++ b/src/google/protobuf/stubs/stringpiece_unittest.cc
@@ -0,0 +1,793 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#include <google/protobuf/stubs/stringpiece.h>
+
+#include <iterator>
+#include <map>
+#include <string>
+#include <utility>
+#include <vector>
+
+#include <google/protobuf/testing/googletest.h>
+#include <gtest/gtest.h>
+
+namespace google {
+namespace protobuf {
+namespace {
+TEST(StringPiece, Ctor) {
+  {
+    // Null.
+    StringPiece s10;
+    EXPECT_TRUE(s10.data() == NULL);
+    EXPECT_EQ(0, s10.length());
+  }
+
+  {
+    // const char* without length.
+    const char* hello = "hello";
+    StringPiece s20(hello);
+    EXPECT_TRUE(s20.data() == hello);
+    EXPECT_EQ(5, s20.length());
+
+    // const char* with length.
+    StringPiece s21(hello, 4);
+    EXPECT_TRUE(s21.data() == hello);
+    EXPECT_EQ(4, s21.length());
+
+    // Not recommended, but valid C++
+    StringPiece s22(hello, 6);
+    EXPECT_TRUE(s22.data() == hello);
+    EXPECT_EQ(6, s22.length());
+  }
+
+  {
+    // std::string.
+    std::string hola = "hola";
+    StringPiece s30(hola);
+    EXPECT_TRUE(s30.data() == hola.data());
+    EXPECT_EQ(4, s30.length());
+
+    // std::string with embedded '\0'.
+    hola.push_back('\0');
+    hola.append("h2");
+    hola.push_back('\0');
+    StringPiece s31(hola);
+    EXPECT_TRUE(s31.data() == hola.data());
+    EXPECT_EQ(8, s31.length());
+  }
+
+#if defined(HAS_GLOBAL_STRING)
+  {
+    // ::string
+    string bonjour = "bonjour";
+    StringPiece s40(bonjour);
+    EXPECT_TRUE(s40.data() == bonjour.data());
+    EXPECT_EQ(7, s40.length());
+  }
+#endif
+
+  // TODO(mec): StringPiece(StringPiece x, int pos);
+  // TODO(mec): StringPiece(StringPiece x, int pos, int len);
+  // TODO(mec): StringPiece(const StringPiece&);
+}
+
+TEST(StringPiece, STLComparator) {
+  string s1("foo");
+  string s2("bar");
+  string s3("baz");
+
+  StringPiece p1(s1);
+  StringPiece p2(s2);
+  StringPiece p3(s3);
+
+  typedef std::map<StringPiece, int> TestMap;
+  TestMap map;
+
+  map.insert(std::make_pair(p1, 0));
+  map.insert(std::make_pair(p2, 1));
+  map.insert(std::make_pair(p3, 2));
+  EXPECT_EQ(map.size(), 3);
+
+  TestMap::const_iterator iter = map.begin();
+  EXPECT_EQ(iter->second, 1);
+  ++iter;
+  EXPECT_EQ(iter->second, 2);
+  ++iter;
+  EXPECT_EQ(iter->second, 0);
+  ++iter;
+  EXPECT_TRUE(iter == map.end());
+
+  TestMap::iterator new_iter = map.find("zot");
+  EXPECT_TRUE(new_iter == map.end());
+
+  new_iter = map.find("bar");
+  EXPECT_TRUE(new_iter != map.end());
+
+  map.erase(new_iter);
+  EXPECT_EQ(map.size(), 2);
+
+  iter = map.begin();
+  EXPECT_EQ(iter->second, 2);
+  ++iter;
+  EXPECT_EQ(iter->second, 0);
+  ++iter;
+  EXPECT_TRUE(iter == map.end());
+}
+
+TEST(StringPiece, ComparisonOperators) {
+#define COMPARE(result, op, x, y) \
+  EXPECT_EQ(result, StringPiece((x)) op StringPiece((y))); \
+  EXPECT_EQ(result, StringPiece((x)).compare(StringPiece((y))) op 0)
+
+  COMPARE(true, ==, "",   "");
+  COMPARE(true, ==, "", NULL);
+  COMPARE(true, ==, NULL, "");
+  COMPARE(true, ==, "a",  "a");
+  COMPARE(true, ==, "aa", "aa");
+  COMPARE(false, ==, "a",  "");
+  COMPARE(false, ==, "",   "a");
+  COMPARE(false, ==, "a",  "b");
+  COMPARE(false, ==, "a",  "aa");
+  COMPARE(false, ==, "aa", "a");
+
+  COMPARE(false, !=, "",   "");
+  COMPARE(false, !=, "a",  "a");
+  COMPARE(false, !=, "aa", "aa");
+  COMPARE(true, !=, "a",  "");
+  COMPARE(true, !=, "",   "a");
+  COMPARE(true, !=, "a",  "b");
+  COMPARE(true, !=, "a",  "aa");
+  COMPARE(true, !=, "aa", "a");
+
+  COMPARE(true, <, "a",  "b");
+  COMPARE(true, <, "a",  "aa");
+  COMPARE(true, <, "aa", "b");
+  COMPARE(true, <, "aa", "bb");
+  COMPARE(false, <, "a",  "a");
+  COMPARE(false, <, "b",  "a");
+  COMPARE(false, <, "aa", "a");
+  COMPARE(false, <, "b",  "aa");
+  COMPARE(false, <, "bb", "aa");
+
+  COMPARE(true, <=, "a",  "a");
+  COMPARE(true, <=, "a",  "b");
+  COMPARE(true, <=, "a",  "aa");
+  COMPARE(true, <=, "aa", "b");
+  COMPARE(true, <=, "aa", "bb");
+  COMPARE(false, <=, "b",  "a");
+  COMPARE(false, <=, "aa", "a");
+  COMPARE(false, <=, "b",  "aa");
+  COMPARE(false, <=, "bb", "aa");
+
+  COMPARE(false, >=, "a",  "b");
+  COMPARE(false, >=, "a",  "aa");
+  COMPARE(false, >=, "aa", "b");
+  COMPARE(false, >=, "aa", "bb");
+  COMPARE(true, >=, "a",  "a");
+  COMPARE(true, >=, "b",  "a");
+  COMPARE(true, >=, "aa", "a");
+  COMPARE(true, >=, "b",  "aa");
+  COMPARE(true, >=, "bb", "aa");
+
+  COMPARE(false, >, "a",  "a");
+  COMPARE(false, >, "a",  "b");
+  COMPARE(false, >, "a",  "aa");
+  COMPARE(false, >, "aa", "b");
+  COMPARE(false, >, "aa", "bb");
+  COMPARE(true, >, "b",  "a");
+  COMPARE(true, >, "aa", "a");
+  COMPARE(true, >, "b",  "aa");
+  COMPARE(true, >, "bb", "aa");
+
+  string x;
+  for (int i = 0; i < 256; i++) {
+    x += 'a';
+    string y = x;
+    COMPARE(true, ==, x, y);
+    for (int j = 0; j < i; j++) {
+      string z = x;
+      z[j] = 'b';       // Differs in position 'j'
+      COMPARE(false, ==, x, z);
+      COMPARE(true, <, x, z);
+      COMPARE(true, >, z, x);
+      if (j + 1 < i) {
+        z[j + 1] = 'A';  // Differs in position 'j+1' as well
+        COMPARE(false, ==, x, z);
+        COMPARE(true, <, x, z);
+        COMPARE(true, >, z, x);
+        z[j + 1] = 'z';  // Differs in position 'j+1' as well
+        COMPARE(false, ==, x, z);
+        COMPARE(true, <, x, z);
+        COMPARE(true, >, z, x);
+      }
+    }
+  }
+
+#undef COMPARE
+}
+
+TEST(StringPiece, STL1) {
+  const StringPiece a("abcdefghijklmnopqrstuvwxyz");
+  const StringPiece b("abc");
+  const StringPiece c("xyz");
+  const StringPiece d("foobar");
+  const StringPiece e;
+  string temp("123");
+  temp += '\0';
+  temp += "456";
+  const StringPiece f(temp);
+
+  EXPECT_EQ(a[6], 'g');
+  EXPECT_EQ(b[0], 'a');
+  EXPECT_EQ(c[2], 'z');
+  EXPECT_EQ(f[3], '\0');
+  EXPECT_EQ(f[5], '5');
+
+  EXPECT_EQ(*d.data(), 'f');
+  EXPECT_EQ(d.data()[5], 'r');
+  EXPECT_TRUE(e.data() == NULL);
+
+  EXPECT_EQ(*a.begin(), 'a');
+  EXPECT_EQ(*(b.begin() + 2), 'c');
+  EXPECT_EQ(*(c.end() - 1), 'z');
+
+  EXPECT_EQ(*a.rbegin(), 'z');
+  EXPECT_EQ(*(b.rbegin() + 2), 'a');
+  EXPECT_EQ(*(c.rend() - 1), 'x');
+  EXPECT_TRUE(a.rbegin() + 26 == a.rend());
+
+  EXPECT_EQ(a.size(), 26);
+  EXPECT_EQ(b.size(), 3);
+  EXPECT_EQ(c.size(), 3);
+  EXPECT_EQ(d.size(), 6);
+  EXPECT_EQ(e.size(), 0);
+  EXPECT_EQ(f.size(), 7);
+
+  EXPECT_TRUE(!d.empty());
+  EXPECT_TRUE(d.begin() != d.end());
+  EXPECT_TRUE(d.begin() + 6 == d.end());
+
+  EXPECT_TRUE(e.empty());
+  EXPECT_TRUE(e.begin() == e.end());
+
+  EXPECT_GE(a.max_size(), a.capacity());
+  EXPECT_GE(a.capacity(), a.size());
+
+  char buf[4] = { '%', '%', '%', '%' };
+  EXPECT_EQ(a.copy(buf, 4), 4);
+  EXPECT_EQ(buf[0], a[0]);
+  EXPECT_EQ(buf[1], a[1]);
+  EXPECT_EQ(buf[2], a[2]);
+  EXPECT_EQ(buf[3], a[3]);
+  EXPECT_EQ(a.copy(buf, 3, 7), 3);
+  EXPECT_EQ(buf[0], a[7]);
+  EXPECT_EQ(buf[1], a[8]);
+  EXPECT_EQ(buf[2], a[9]);
+  EXPECT_EQ(buf[3], a[3]);
+  EXPECT_EQ(c.copy(buf, 99), 3);
+  EXPECT_EQ(buf[0], c[0]);
+  EXPECT_EQ(buf[1], c[1]);
+  EXPECT_EQ(buf[2], c[2]);
+  EXPECT_EQ(buf[3], a[3]);
+}
+
+// Separated from STL1() because some compilers produce an overly
+// large stack frame for the combined function.
+TEST(StringPiece, STL2) {
+  const StringPiece a("abcdefghijklmnopqrstuvwxyz");
+  const StringPiece b("abc");
+  const StringPiece c("xyz");
+  StringPiece d("foobar");
+  const StringPiece e;
+  const StringPiece f("123" "\0" "456", 7);
+
+  d.clear();
+  EXPECT_EQ(d.size(), 0);
+  EXPECT_TRUE(d.empty());
+  EXPECT_TRUE(d.data() == NULL);
+  EXPECT_TRUE(d.begin() == d.end());
+
+  EXPECT_EQ(StringPiece::npos, string::npos);
+
+  EXPECT_EQ(a.find(b), 0);
+  EXPECT_EQ(a.find(b, 1), StringPiece::npos);
+  EXPECT_EQ(a.find(c), 23);
+  EXPECT_EQ(a.find(c, 9), 23);
+  EXPECT_EQ(a.find(c, StringPiece::npos), StringPiece::npos);
+  EXPECT_EQ(b.find(c), StringPiece::npos);
+  EXPECT_EQ(b.find(c, StringPiece::npos), StringPiece::npos);
+  EXPECT_EQ(a.find(d), 0);
+  EXPECT_EQ(a.find(e), 0);
+  EXPECT_EQ(a.find(d, 12), 12);
+  EXPECT_EQ(a.find(e, 17), 17);
+  StringPiece g("xx not found bb");
+  EXPECT_EQ(a.find(g), StringPiece::npos);
+  // empty string nonsense
+  EXPECT_EQ(d.find(b), StringPiece::npos);
+  EXPECT_EQ(e.find(b), StringPiece::npos);
+  EXPECT_EQ(d.find(b, 4), StringPiece::npos);
+  EXPECT_EQ(e.find(b, 7), StringPiece::npos);
+
+  size_t empty_search_pos = string().find(string());
+  EXPECT_EQ(d.find(d), empty_search_pos);
+  EXPECT_EQ(d.find(e), empty_search_pos);
+  EXPECT_EQ(e.find(d), empty_search_pos);
+  EXPECT_EQ(e.find(e), empty_search_pos);
+  EXPECT_EQ(d.find(d, 4), string().find(string(), 4));
+  EXPECT_EQ(d.find(e, 4), string().find(string(), 4));
+  EXPECT_EQ(e.find(d, 4), string().find(string(), 4));
+  EXPECT_EQ(e.find(e, 4), string().find(string(), 4));
+
+  EXPECT_EQ(a.find('a'), 0);
+  EXPECT_EQ(a.find('c'), 2);
+  EXPECT_EQ(a.find('z'), 25);
+  EXPECT_EQ(a.find('$'), StringPiece::npos);
+  EXPECT_EQ(a.find('\0'), StringPiece::npos);
+  EXPECT_EQ(f.find('\0'), 3);
+  EXPECT_EQ(f.find('3'), 2);
+  EXPECT_EQ(f.find('5'), 5);
+  EXPECT_EQ(g.find('o'), 4);
+  EXPECT_EQ(g.find('o', 4), 4);
+  EXPECT_EQ(g.find('o', 5), 8);
+  EXPECT_EQ(a.find('b', 5), StringPiece::npos);
+  // empty string nonsense
+  EXPECT_EQ(d.find('\0'), StringPiece::npos);
+  EXPECT_EQ(e.find('\0'), StringPiece::npos);
+  EXPECT_EQ(d.find('\0', 4), StringPiece::npos);
+  EXPECT_EQ(e.find('\0', 7), StringPiece::npos);
+  EXPECT_EQ(d.find('x'), StringPiece::npos);
+  EXPECT_EQ(e.find('x'), StringPiece::npos);
+  EXPECT_EQ(d.find('x', 4), StringPiece::npos);
+  EXPECT_EQ(e.find('x', 7), StringPiece::npos);
+
+  EXPECT_EQ(a.rfind(b), 0);
+  EXPECT_EQ(a.rfind(b, 1), 0);
+  EXPECT_EQ(a.rfind(c), 23);
+  EXPECT_EQ(a.rfind(c, 22), StringPiece::npos);
+  EXPECT_EQ(a.rfind(c, 1), StringPiece::npos);
+  EXPECT_EQ(a.rfind(c, 0), StringPiece::npos);
+  EXPECT_EQ(b.rfind(c), StringPiece::npos);
+  EXPECT_EQ(b.rfind(c, 0), StringPiece::npos);
+  EXPECT_EQ(a.rfind(d), a.as_string().rfind(string()));
+  EXPECT_EQ(a.rfind(e), a.as_string().rfind(string()));
+  EXPECT_EQ(a.rfind(d, 12), 12);
+  EXPECT_EQ(a.rfind(e, 17), 17);
+  EXPECT_EQ(a.rfind(g), StringPiece::npos);
+  EXPECT_EQ(d.rfind(b), StringPiece::npos);
+  EXPECT_EQ(e.rfind(b), StringPiece::npos);
+  EXPECT_EQ(d.rfind(b, 4), StringPiece::npos);
+  EXPECT_EQ(e.rfind(b, 7), StringPiece::npos);
+  // empty string nonsense
+  EXPECT_EQ(d.rfind(d, 4), string().rfind(string()));
+  EXPECT_EQ(e.rfind(d, 7), string().rfind(string()));
+  EXPECT_EQ(d.rfind(e, 4), string().rfind(string()));
+  EXPECT_EQ(e.rfind(e, 7), string().rfind(string()));
+  EXPECT_EQ(d.rfind(d), string().rfind(string()));
+  EXPECT_EQ(e.rfind(d), string().rfind(string()));
+  EXPECT_EQ(d.rfind(e), string().rfind(string()));
+  EXPECT_EQ(e.rfind(e), string().rfind(string()));
+
+  EXPECT_EQ(g.rfind('o'), 8);
+  EXPECT_EQ(g.rfind('q'), StringPiece::npos);
+  EXPECT_EQ(g.rfind('o', 8), 8);
+  EXPECT_EQ(g.rfind('o', 7), 4);
+  EXPECT_EQ(g.rfind('o', 3), StringPiece::npos);
+  EXPECT_EQ(f.rfind('\0'), 3);
+  EXPECT_EQ(f.rfind('\0', 12), 3);
+  EXPECT_EQ(f.rfind('3'), 2);
+  EXPECT_EQ(f.rfind('5'), 5);
+  // empty string nonsense
+  EXPECT_EQ(d.rfind('o'), StringPiece::npos);
+  EXPECT_EQ(e.rfind('o'), StringPiece::npos);
+  EXPECT_EQ(d.rfind('o', 4), StringPiece::npos);
+  EXPECT_EQ(e.rfind('o', 7), StringPiece::npos);
+
+  EXPECT_EQ(a.find_first_of(b), 0);
+  EXPECT_EQ(a.find_first_of(b, 0), 0);
+  EXPECT_EQ(a.find_first_of(b, 1), 1);
+  EXPECT_EQ(a.find_first_of(b, 2), 2);
+  EXPECT_EQ(a.find_first_of(b, 3), StringPiece::npos);
+  EXPECT_EQ(a.find_first_of(c), 23);
+  EXPECT_EQ(a.find_first_of(c, 23), 23);
+  EXPECT_EQ(a.find_first_of(c, 24), 24);
+  EXPECT_EQ(a.find_first_of(c, 25), 25);
+  EXPECT_EQ(a.find_first_of(c, 26), StringPiece::npos);
+  EXPECT_EQ(g.find_first_of(b), 13);
+  EXPECT_EQ(g.find_first_of(c), 0);
+  EXPECT_EQ(a.find_first_of(f), StringPiece::npos);
+  EXPECT_EQ(f.find_first_of(a), StringPiece::npos);
+  // empty string nonsense
+  EXPECT_EQ(a.find_first_of(d), StringPiece::npos);
+  EXPECT_EQ(a.find_first_of(e), StringPiece::npos);
+  EXPECT_EQ(d.find_first_of(b), StringPiece::npos);
+  EXPECT_EQ(e.find_first_of(b), StringPiece::npos);
+  EXPECT_EQ(d.find_first_of(d), StringPiece::npos);
+  EXPECT_EQ(e.find_first_of(d), StringPiece::npos);
+  EXPECT_EQ(d.find_first_of(e), StringPiece::npos);
+  EXPECT_EQ(e.find_first_of(e), StringPiece::npos);
+
+  EXPECT_EQ(a.find_first_not_of(b), 3);
+  EXPECT_EQ(a.find_first_not_of(c), 0);
+  EXPECT_EQ(b.find_first_not_of(a), StringPiece::npos);
+  EXPECT_EQ(c.find_first_not_of(a), StringPiece::npos);
+  EXPECT_EQ(f.find_first_not_of(a), 0);
+  EXPECT_EQ(a.find_first_not_of(f), 0);
+  EXPECT_EQ(a.find_first_not_of(d), 0);
+  EXPECT_EQ(a.find_first_not_of(e), 0);
+  // empty string nonsense
+  EXPECT_EQ(d.find_first_not_of(a), StringPiece::npos);
+  EXPECT_EQ(e.find_first_not_of(a), StringPiece::npos);
+  EXPECT_EQ(d.find_first_not_of(d), StringPiece::npos);
+  EXPECT_EQ(e.find_first_not_of(d), StringPiece::npos);
+  EXPECT_EQ(d.find_first_not_of(e), StringPiece::npos);
+  EXPECT_EQ(e.find_first_not_of(e), StringPiece::npos);
+
+  StringPiece h("====");
+  EXPECT_EQ(h.find_first_not_of('='), StringPiece::npos);
+  EXPECT_EQ(h.find_first_not_of('=', 3), StringPiece::npos);
+  EXPECT_EQ(h.find_first_not_of('\0'), 0);
+  EXPECT_EQ(g.find_first_not_of('x'), 2);
+  EXPECT_EQ(f.find_first_not_of('\0'), 0);
+  EXPECT_EQ(f.find_first_not_of('\0', 3), 4);
+  EXPECT_EQ(f.find_first_not_of('\0', 2), 2);
+  // empty string nonsense
+  EXPECT_EQ(d.find_first_not_of('x'), StringPiece::npos);
+  EXPECT_EQ(e.find_first_not_of('x'), StringPiece::npos);
+  EXPECT_EQ(d.find_first_not_of('\0'), StringPiece::npos);
+  EXPECT_EQ(e.find_first_not_of('\0'), StringPiece::npos);
+
+  //  StringPiece g("xx not found bb");
+  StringPiece i("56");
+  EXPECT_EQ(h.find_last_of(a), StringPiece::npos);
+  EXPECT_EQ(g.find_last_of(a), g.size()-1);
+  EXPECT_EQ(a.find_last_of(b), 2);
+  EXPECT_EQ(a.find_last_of(c), a.size()-1);
+  EXPECT_EQ(f.find_last_of(i), 6);
+  EXPECT_EQ(a.find_last_of('a'), 0);
+  EXPECT_EQ(a.find_last_of('b'), 1);
+  EXPECT_EQ(a.find_last_of('z'), 25);
+  EXPECT_EQ(a.find_last_of('a', 5), 0);
+  EXPECT_EQ(a.find_last_of('b', 5), 1);
+  EXPECT_EQ(a.find_last_of('b', 0), StringPiece::npos);
+  EXPECT_EQ(a.find_last_of('z', 25), 25);
+  EXPECT_EQ(a.find_last_of('z', 24), StringPiece::npos);
+  EXPECT_EQ(f.find_last_of(i, 5), 5);
+  EXPECT_EQ(f.find_last_of(i, 6), 6);
+  EXPECT_EQ(f.find_last_of(a, 4), StringPiece::npos);
+  // empty string nonsense
+  EXPECT_EQ(f.find_last_of(d), StringPiece::npos);
+  EXPECT_EQ(f.find_last_of(e), StringPiece::npos);
+  EXPECT_EQ(f.find_last_of(d, 4), StringPiece::npos);
+  EXPECT_EQ(f.find_last_of(e, 4), StringPiece::npos);
+  EXPECT_EQ(d.find_last_of(d), StringPiece::npos);
+  EXPECT_EQ(d.find_last_of(e), StringPiece::npos);
+  EXPECT_EQ(e.find_last_of(d), StringPiece::npos);
+  EXPECT_EQ(e.find_last_of(e), StringPiece::npos);
+  EXPECT_EQ(d.find_last_of(f), StringPiece::npos);
+  EXPECT_EQ(e.find_last_of(f), StringPiece::npos);
+  EXPECT_EQ(d.find_last_of(d, 4), StringPiece::npos);
+  EXPECT_EQ(d.find_last_of(e, 4), StringPiece::npos);
+  EXPECT_EQ(e.find_last_of(d, 4), StringPiece::npos);
+  EXPECT_EQ(e.find_last_of(e, 4), StringPiece::npos);
+  EXPECT_EQ(d.find_last_of(f, 4), StringPiece::npos);
+  EXPECT_EQ(e.find_last_of(f, 4), StringPiece::npos);
+
+  EXPECT_EQ(a.find_last_not_of(b), a.size()-1);
+  EXPECT_EQ(a.find_last_not_of(c), 22);
+  EXPECT_EQ(b.find_last_not_of(a), StringPiece::npos);
+  EXPECT_EQ(b.find_last_not_of(b), StringPiece::npos);
+  EXPECT_EQ(f.find_last_not_of(i), 4);
+  EXPECT_EQ(a.find_last_not_of(c, 24), 22);
+  EXPECT_EQ(a.find_last_not_of(b, 3), 3);
+  EXPECT_EQ(a.find_last_not_of(b, 2), StringPiece::npos);
+  // empty string nonsense
+  EXPECT_EQ(f.find_last_not_of(d), f.size()-1);
+  EXPECT_EQ(f.find_last_not_of(e), f.size()-1);
+  EXPECT_EQ(f.find_last_not_of(d, 4), 4);
+  EXPECT_EQ(f.find_last_not_of(e, 4), 4);
+  EXPECT_EQ(d.find_last_not_of(d), StringPiece::npos);
+  EXPECT_EQ(d.find_last_not_of(e), StringPiece::npos);
+  EXPECT_EQ(e.find_last_not_of(d), StringPiece::npos);
+  EXPECT_EQ(e.find_last_not_of(e), StringPiece::npos);
+  EXPECT_EQ(d.find_last_not_of(f), StringPiece::npos);
+  EXPECT_EQ(e.find_last_not_of(f), StringPiece::npos);
+  EXPECT_EQ(d.find_last_not_of(d, 4), StringPiece::npos);
+  EXPECT_EQ(d.find_last_not_of(e, 4), StringPiece::npos);
+  EXPECT_EQ(e.find_last_not_of(d, 4), StringPiece::npos);
+  EXPECT_EQ(e.find_last_not_of(e, 4), StringPiece::npos);
+  EXPECT_EQ(d.find_last_not_of(f, 4), StringPiece::npos);
+  EXPECT_EQ(e.find_last_not_of(f, 4), StringPiece::npos);
+
+  EXPECT_EQ(h.find_last_not_of('x'), h.size() - 1);
+  EXPECT_EQ(h.find_last_not_of('='), StringPiece::npos);
+  EXPECT_EQ(b.find_last_not_of('c'), 1);
+  EXPECT_EQ(h.find_last_not_of('x', 2), 2);
+  EXPECT_EQ(h.find_last_not_of('=', 2), StringPiece::npos);
+  EXPECT_EQ(b.find_last_not_of('b', 1), 0);
+  // empty string nonsense
+  EXPECT_EQ(d.find_last_not_of('x'), StringPiece::npos);
+  EXPECT_EQ(e.find_last_not_of('x'), StringPiece::npos);
+  EXPECT_EQ(d.find_last_not_of('\0'), StringPiece::npos);
+  EXPECT_EQ(e.find_last_not_of('\0'), StringPiece::npos);
+
+  EXPECT_EQ(a.substr(0, 3), b);
+  EXPECT_EQ(a.substr(23), c);
+  EXPECT_EQ(a.substr(23, 3), c);
+  EXPECT_EQ(a.substr(23, 99), c);
+  EXPECT_EQ(a.substr(0), a);
+  EXPECT_EQ(a.substr(3, 2), "de");
+  // empty string nonsense
+  EXPECT_EQ(a.substr(99, 2), e);
+  EXPECT_EQ(d.substr(99), e);
+  EXPECT_EQ(d.substr(0, 99), e);
+  EXPECT_EQ(d.substr(99, 99), e);
+  // use of npos
+  EXPECT_EQ(a.substr(0, StringPiece::npos), a);
+  EXPECT_EQ(a.substr(23, StringPiece::npos), c);
+  EXPECT_EQ(a.substr(StringPiece::npos, 0), e);
+  EXPECT_EQ(a.substr(StringPiece::npos, 1), e);
+  EXPECT_EQ(a.substr(StringPiece::npos, StringPiece::npos), e);
+
+  // Substring constructors.
+  EXPECT_EQ(StringPiece(a, 0, 3), b);
+  EXPECT_EQ(StringPiece(a, 23), c);
+  EXPECT_EQ(StringPiece(a, 23, 3), c);
+  EXPECT_EQ(StringPiece(a, 23, 99), c);
+  EXPECT_EQ(StringPiece(a, 0), a);
+  EXPECT_EQ(StringPiece(a, 3, 2), "de");
+  // empty string nonsense
+  EXPECT_EQ(StringPiece(d, 0, 99), e);
+  // Verify that they work taking an actual string, not just a StringPiece.
+  string a2 = a.as_string();
+  EXPECT_EQ(StringPiece(a2, 0, 3), b);
+  EXPECT_EQ(StringPiece(a2, 23), c);
+  EXPECT_EQ(StringPiece(a2, 23, 3), c);
+  EXPECT_EQ(StringPiece(a2, 23, 99), c);
+  EXPECT_EQ(StringPiece(a2, 0), a);
+  EXPECT_EQ(StringPiece(a2, 3, 2), "de");
+}
+
+TEST(StringPiece, Custom) {
+  StringPiece a("foobar");
+  string s1("123");
+  s1 += '\0';
+  s1 += "456";
+  StringPiece b(s1);
+  StringPiece e;
+  string s2;
+
+  // CopyToString
+  a.CopyToString(&s2);
+  EXPECT_EQ(s2.size(), 6);
+  EXPECT_EQ(s2, "foobar");
+  b.CopyToString(&s2);
+  EXPECT_EQ(s2.size(), 7);
+  EXPECT_EQ(s1, s2);
+  e.CopyToString(&s2);
+  EXPECT_TRUE(s2.empty());
+
+  // AppendToString
+  s2.erase();
+  a.AppendToString(&s2);
+  EXPECT_EQ(s2.size(), 6);
+  EXPECT_EQ(s2, "foobar");
+  a.AppendToString(&s2);
+  EXPECT_EQ(s2.size(), 12);
+  EXPECT_EQ(s2, "foobarfoobar");
+
+  // starts_with
+  EXPECT_TRUE(a.starts_with(a));
+  EXPECT_TRUE(a.starts_with("foo"));
+  EXPECT_TRUE(a.starts_with(e));
+  EXPECT_TRUE(b.starts_with(s1));
+  EXPECT_TRUE(b.starts_with(b));
+  EXPECT_TRUE(b.starts_with(e));
+  EXPECT_TRUE(e.starts_with(""));
+  EXPECT_TRUE(!a.starts_with(b));
+  EXPECT_TRUE(!b.starts_with(a));
+  EXPECT_TRUE(!e.starts_with(a));
+
+  // ends with
+  EXPECT_TRUE(a.ends_with(a));
+  EXPECT_TRUE(a.ends_with("bar"));
+  EXPECT_TRUE(a.ends_with(e));
+  EXPECT_TRUE(b.ends_with(s1));
+  EXPECT_TRUE(b.ends_with(b));
+  EXPECT_TRUE(b.ends_with(e));
+  EXPECT_TRUE(e.ends_with(""));
+  EXPECT_TRUE(!a.ends_with(b));
+  EXPECT_TRUE(!b.ends_with(a));
+  EXPECT_TRUE(!e.ends_with(a));
+
+  // remove_prefix
+  StringPiece c(a);
+  c.remove_prefix(3);
+  EXPECT_EQ(c, "bar");
+  c = a;
+  c.remove_prefix(0);
+  EXPECT_EQ(c, a);
+  c.remove_prefix(c.size());
+  EXPECT_EQ(c, e);
+
+  // remove_suffix
+  c = a;
+  c.remove_suffix(3);
+  EXPECT_EQ(c, "foo");
+  c = a;
+  c.remove_suffix(0);
+  EXPECT_EQ(c, a);
+  c.remove_suffix(c.size());
+  EXPECT_EQ(c, e);
+
+  // set
+  c.set("foobar", 6);
+  EXPECT_EQ(c, a);
+  c.set("foobar", 0);
+  EXPECT_EQ(c, e);
+  c.set("foobar", 7);
+  EXPECT_NE(c, a);
+
+  c.set("foobar");
+  EXPECT_EQ(c, a);
+
+  c.set(static_cast<const void*>("foobar"), 6);
+  EXPECT_EQ(c, a);
+  c.set(static_cast<const void*>("foobar"), 0);
+  EXPECT_EQ(c, e);
+  c.set(static_cast<const void*>("foobar"), 7);
+  EXPECT_NE(c, a);
+
+  // as_string
+  string s3(a.as_string().c_str(), 7);
+  EXPECT_EQ(c, s3);
+  string s4(e.as_string());
+  EXPECT_TRUE(s4.empty());
+
+  // ToString
+  {
+    string s5(a.ToString().c_str(), 7);
+    EXPECT_EQ(c, s5);
+    string s6(e.ToString());
+    EXPECT_TRUE(s6.empty());
+  }
+
+  // Consume
+  a.set("foobar");
+  EXPECT_TRUE(a.Consume("foo"));
+  EXPECT_EQ(a, "bar");
+  EXPECT_FALSE(a.Consume("foo"));
+  EXPECT_FALSE(a.Consume("barbar"));
+  EXPECT_FALSE(a.Consume("ar"));
+  EXPECT_EQ(a, "bar");
+
+  a.set("foobar");
+  EXPECT_TRUE(a.ConsumeFromEnd("bar"));
+  EXPECT_EQ(a, "foo");
+  EXPECT_FALSE(a.ConsumeFromEnd("bar"));
+  EXPECT_FALSE(a.ConsumeFromEnd("foofoo"));
+  EXPECT_FALSE(a.ConsumeFromEnd("fo"));
+  EXPECT_EQ(a, "foo");
+}
+
+TEST(StringPiece, Contains) {
+  StringPiece a("abcdefg");
+  StringPiece b("abcd");
+  StringPiece c("efg");
+  StringPiece d("gh");
+  EXPECT_TRUE(a.contains(b));
+  EXPECT_TRUE(a.contains(c));
+  EXPECT_TRUE(!a.contains(d));
+}
+
+TEST(StringPiece, NULLInput) {
+  // we used to crash here, but now we don't.
+  StringPiece s(NULL);
+  EXPECT_EQ(s.data(), (const char*)NULL);
+  EXPECT_EQ(s.size(), 0);
+
+  s.set(NULL);
+  EXPECT_EQ(s.data(), (const char*)NULL);
+  EXPECT_EQ(s.size(), 0);
+
+  // .ToString() on a StringPiece with NULL should produce the empty string.
+  EXPECT_EQ("", s.ToString());
+  EXPECT_EQ("", s.as_string());
+}
+
+TEST(StringPiece, Comparisons2) {
+  StringPiece abc("abcdefghijklmnopqrstuvwxyz");
+
+  // check comparison operations on strings longer than 4 bytes.
+  EXPECT_EQ(abc, StringPiece("abcdefghijklmnopqrstuvwxyz"));
+  EXPECT_EQ(abc.compare(StringPiece("abcdefghijklmnopqrstuvwxyz")), 0);
+
+  EXPECT_LT(abc, StringPiece("abcdefghijklmnopqrstuvwxzz"));
+  EXPECT_LT(abc.compare(StringPiece("abcdefghijklmnopqrstuvwxzz")), 0);
+
+  EXPECT_GT(abc, StringPiece("abcdefghijklmnopqrstuvwxyy"));
+  EXPECT_GT(abc.compare(StringPiece("abcdefghijklmnopqrstuvwxyy")), 0);
+
+  // starts_with
+  EXPECT_TRUE(abc.starts_with(abc));
+  EXPECT_TRUE(abc.starts_with("abcdefghijklm"));
+  EXPECT_TRUE(!abc.starts_with("abcdefguvwxyz"));
+
+  // ends_with
+  EXPECT_TRUE(abc.ends_with(abc));
+  EXPECT_TRUE(!abc.ends_with("abcdefguvwxyz"));
+  EXPECT_TRUE(abc.ends_with("nopqrstuvwxyz"));
+}
+
+TEST(ComparisonOpsTest, StringCompareNotAmbiguous) {
+  EXPECT_EQ("hello", string("hello"));
+  EXPECT_LT("hello", string("world"));
+}
+
+TEST(ComparisonOpsTest, HeterogenousStringPieceEquals) {
+  EXPECT_EQ(StringPiece("hello"), string("hello"));
+  EXPECT_EQ("hello", StringPiece("hello"));
+}
+
+TEST(FindOneCharTest, EdgeCases) {
+  StringPiece a("xxyyyxx");
+
+  // Set a = "xyyyx".
+  a.remove_prefix(1);
+  a.remove_suffix(1);
+
+  EXPECT_EQ(0, a.find('x'));
+  EXPECT_EQ(0, a.find('x', 0));
+  EXPECT_EQ(4, a.find('x', 1));
+  EXPECT_EQ(4, a.find('x', 4));
+  EXPECT_EQ(StringPiece::npos, a.find('x', 5));
+
+  EXPECT_EQ(4, a.rfind('x'));
+  EXPECT_EQ(4, a.rfind('x', 5));
+  EXPECT_EQ(4, a.rfind('x', 4));
+  EXPECT_EQ(0, a.rfind('x', 3));
+  EXPECT_EQ(0, a.rfind('x', 0));
+
+  // Set a = "yyy".
+  a.remove_prefix(1);
+  a.remove_suffix(1);
+
+  EXPECT_EQ(StringPiece::npos, a.find('x'));
+  EXPECT_EQ(StringPiece::npos, a.rfind('x'));
+}
+
+#ifndef NDEBUG
+TEST(NonNegativeLenTest, NonNegativeLen) {
+  EXPECT_DEATH(StringPiece("xyz", -1), "len >= 0");
+}
+#endif  // ndef DEBUG
+
+}  // namespace
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/stubs/strutil.cc b/src/google/protobuf/stubs/strutil.cc
index 7ecc17e..99e8bf1 100644
--- a/src/google/protobuf/stubs/strutil.cc
+++ b/src/google/protobuf/stubs/strutil.cc
@@ -31,6 +31,7 @@
 // from google3/strings/strutil.cc
 
 #include <google/protobuf/stubs/strutil.h>
+
 #include <errno.h>
 #include <float.h>    // FLT_DIG and DBL_DIG
 #include <limits>
@@ -38,6 +39,8 @@
 #include <stdio.h>
 #include <iterator>
 
+#include <google/protobuf/stubs/stl_util.h>
+
 #ifdef _WIN32
 // MSVC has only _snprintf, not snprintf.
 //
@@ -309,17 +312,6 @@
 
 #define IS_OCTAL_DIGIT(c) (((c) >= '0') && ((c) <= '7'))
 
-inline int hex_digit_to_int(char c) {
-  /* Assume ASCII. */
-  assert('0' == 0x30 && 'A' == 0x41 && 'a' == 0x61);
-  assert(isxdigit(c));
-  int x = static_cast<unsigned char>(c);
-  if (x > '9') {
-    x += 9;
-  }
-  return x & 0xf;
-}
-
 // Protocol buffers doesn't ever care about errors, but I don't want to remove
 // the code.
 #define LOG_STRING(LEVEL, VECTOR) GOOGLE_LOG_IF(LEVEL, false)
@@ -652,14 +644,15 @@
   return true;
 }
 
-inline bool safe_parse_positive_int(
-    string text, int32* value_p) {
+template<typename IntType>
+bool safe_parse_positive_int(
+    string text, IntType* value_p) {
   int base = 10;
-  int32 value = 0;
-  const int32 vmax = std::numeric_limits<int32>::max();
+  IntType value = 0;
+  const IntType vmax = std::numeric_limits<IntType>::max();
   assert(vmax > 0);
   assert(vmax >= base);
-  const int32 vmax_over_base = vmax / base;
+  const IntType vmax_over_base = vmax / base;
   const char* start = text.data();
   const char* end = start + text.size();
   // loop over digits
@@ -685,14 +678,15 @@
   return true;
 }
 
-inline bool safe_parse_negative_int(
-    string text, int32* value_p) {
+template<typename IntType>
+bool safe_parse_negative_int(
+    const string& text, IntType* value_p) {
   int base = 10;
-  int32 value = 0;
-  const int32 vmin = std::numeric_limits<int32>::min();
+  IntType value = 0;
+  const IntType vmin = std::numeric_limits<IntType>::min();
   assert(vmin < 0);
   assert(vmin <= 0 - base);
-  int32 vmin_over_base = vmin / base;
+  IntType vmin_over_base = vmin / base;
   // 2003 c++ standard [expr.mul]
   // "... the sign of the remainder is implementation-defined."
   // Although (vmin/base)*base + vmin%base is always vmin.
@@ -725,7 +719,8 @@
   return true;
 }
 
-bool safe_int(string text, int32* value_p) {
+template<typename IntType>
+bool safe_int_internal(string text, IntType* value_p) {
   *value_p = 0;
   bool negative;
   if (!safe_parse_sign(&text, &negative)) {
@@ -738,6 +733,16 @@
   }
 }
 
+template<typename IntType>
+bool safe_uint_internal(string text, IntType* value_p) {
+  *value_p = 0;
+  bool negative;
+  if (!safe_parse_sign(&text, &negative) || negative) {
+    return false;
+  }
+  return safe_parse_positive_int(text, value_p);
+}
+
 // ----------------------------------------------------------------------
 // FastIntToBuffer()
 // FastInt64ToBuffer()
@@ -1236,6 +1241,41 @@
   return buffer;
 }
 
+static int memcasecmp(const char *s1, const char *s2, size_t len) {
+  const unsigned char *us1 = reinterpret_cast<const unsigned char *>(s1);
+  const unsigned char *us2 = reinterpret_cast<const unsigned char *>(s2);
+
+  for ( int i = 0; i < len; i++ ) {
+    const int diff =
+      static_cast<int>(static_cast<unsigned char>(ascii_tolower(us1[i]))) -
+      static_cast<int>(static_cast<unsigned char>(ascii_tolower(us2[i])));
+    if (diff != 0) return diff;
+  }
+  return 0;
+}
+
+inline bool CaseEqual(StringPiece s1, StringPiece s2) {
+  if (s1.size() != s2.size()) return false;
+  return memcasecmp(s1.data(), s2.data(), s1.size()) == 0;
+}
+
+bool safe_strtob(StringPiece str, bool* value) {
+  GOOGLE_CHECK(value != NULL) << "NULL output boolean given.";
+  if (CaseEqual(str, "true") || CaseEqual(str, "t") ||
+      CaseEqual(str, "yes") || CaseEqual(str, "y") ||
+      CaseEqual(str, "1")) {
+    *value = true;
+    return true;
+  }
+  if (CaseEqual(str, "false") || CaseEqual(str, "f") ||
+      CaseEqual(str, "no") || CaseEqual(str, "n") ||
+      CaseEqual(str, "0")) {
+    *value = false;
+    return true;
+  }
+  return false;
+}
+
 bool safe_strtof(const char* str, float* value) {
   char* endptr;
   errno = 0;  // errno only gets set on errors
@@ -1247,6 +1287,34 @@
   return *str != 0 && *endptr == 0 && errno == 0;
 }
 
+bool safe_strtod(const char* str, double* value) {
+  char* endptr;
+  *value = strtod(str, &endptr);
+  if (endptr != str) {
+    while (ascii_isspace(*endptr)) ++endptr;
+  }
+  // Ignore range errors from strtod.  The values it
+  // returns on underflow and overflow are the right
+  // fallback in a robust setting.
+  return *str != '\0' && *endptr == '\0';
+}
+
+bool safe_strto32(const string& str, int32* value) {
+  return safe_int_internal(str, value);
+}
+
+bool safe_strtou32(const string& str, uint32* value) {
+  return safe_uint_internal(str, value);
+}
+
+bool safe_strto64(const string& str, int64* value) {
+  return safe_int_internal(str, value);
+}
+
+bool safe_strtou64(const string& str, uint64* value) {
+  return safe_uint_internal(str, value);
+}
+
 char* FloatToBuffer(float value, char* buffer) {
   // FLT_DIG is 6 for IEEE-754 floats, which are used on almost all
   // platforms these days.  Just in case some system exists where FLT_DIG
@@ -1518,5 +1586,661 @@
   return num_replacements;
 }
 
+int CalculateBase64EscapedLen(int input_len, bool do_padding) {
+  // Base64 encodes three bytes of input at a time. If the input is not
+  // divisible by three, we pad as appropriate.
+  //
+  // (from http://tools.ietf.org/html/rfc3548)
+  // Special processing is performed if fewer than 24 bits are available
+  // at the end of the data being encoded.  A full encoding quantum is
+  // always completed at the end of a quantity.  When fewer than 24 input
+  // bits are available in an input group, zero bits are added (on the
+  // right) to form an integral number of 6-bit groups.  Padding at the
+  // end of the data is performed using the '=' character.  Since all base
+  // 64 input is an integral number of octets, only the following cases
+  // can arise:
+
+
+  // Base64 encodes each three bytes of input into four bytes of output.
+  int len = (input_len / 3) * 4;
+
+  if (input_len % 3 == 0) {
+    // (from http://tools.ietf.org/html/rfc3548)
+    // (1) the final quantum of encoding input is an integral multiple of 24
+    // bits; here, the final unit of encoded output will be an integral
+    // multiple of 4 characters with no "=" padding,
+  } else if (input_len % 3 == 1) {
+    // (from http://tools.ietf.org/html/rfc3548)
+    // (2) the final quantum of encoding input is exactly 8 bits; here, the
+    // final unit of encoded output will be two characters followed by two
+    // "=" padding characters, or
+    len += 2;
+    if (do_padding) {
+      len += 2;
+    }
+  } else {  // (input_len % 3 == 2)
+    // (from http://tools.ietf.org/html/rfc3548)
+    // (3) the final quantum of encoding input is exactly 16 bits; here, the
+    // final unit of encoded output will be three characters followed by one
+    // "=" padding character.
+    len += 3;
+    if (do_padding) {
+      len += 1;
+    }
+  }
+
+  assert(len >= input_len);  // make sure we didn't overflow
+  return len;
+}
+
+// Base64Escape does padding, so this calculation includes padding.
+int CalculateBase64EscapedLen(int input_len) {
+  return CalculateBase64EscapedLen(input_len, true);
+}
+
+// ----------------------------------------------------------------------
+// int Base64Unescape() - base64 decoder
+// int Base64Escape() - base64 encoder
+// int WebSafeBase64Unescape() - Google's variation of base64 decoder
+// int WebSafeBase64Escape() - Google's variation of base64 encoder
+//
+// Check out
+// http://tools.ietf.org/html/rfc2045 for formal description, but what we
+// care about is that...
+//   Take the encoded stuff in groups of 4 characters and turn each
+//   character into a code 0 to 63 thus:
+//           A-Z map to 0 to 25
+//           a-z map to 26 to 51
+//           0-9 map to 52 to 61
+//           +(- for WebSafe) maps to 62
+//           /(_ for WebSafe) maps to 63
+//   There will be four numbers, all less than 64 which can be represented
+//   by a 6 digit binary number (aaaaaa, bbbbbb, cccccc, dddddd respectively).
+//   Arrange the 6 digit binary numbers into three bytes as such:
+//   aaaaaabb bbbbcccc ccdddddd
+//   Equals signs (one or two) are used at the end of the encoded block to
+//   indicate that the text was not an integer multiple of three bytes long.
+// ----------------------------------------------------------------------
+
+int Base64UnescapeInternal(const char *src_param, int szsrc,
+                           char *dest, int szdest,
+                           const signed char* unbase64) {
+  static const char kPad64Equals = '=';
+  static const char kPad64Dot = '.';
+
+  int decode = 0;
+  int destidx = 0;
+  int state = 0;
+  unsigned int ch = 0;
+  unsigned int temp = 0;
+
+  // If "char" is signed by default, using *src as an array index results in
+  // accessing negative array elements. Treat the input as a pointer to
+  // unsigned char to avoid this.
+  const unsigned char *src = reinterpret_cast<const unsigned char*>(src_param);
+
+  // The GET_INPUT macro gets the next input character, skipping
+  // over any whitespace, and stopping when we reach the end of the
+  // string or when we read any non-data character.  The arguments are
+  // an arbitrary identifier (used as a label for goto) and the number
+  // of data bytes that must remain in the input to avoid aborting the
+  // loop.
+#define GET_INPUT(label, remain)                 \
+  label:                                         \
+    --szsrc;                                     \
+    ch = *src++;                                 \
+    decode = unbase64[ch];                       \
+    if (decode < 0) {                            \
+      if (ascii_isspace(ch) && szsrc >= remain)  \
+        goto label;                              \
+      state = 4 - remain;                        \
+      break;                                     \
+    }
+
+  // if dest is null, we're just checking to see if it's legal input
+  // rather than producing output.  (I suspect this could just be done
+  // with a regexp...).  We duplicate the loop so this test can be
+  // outside it instead of in every iteration.
+
+  if (dest) {
+    // This loop consumes 4 input bytes and produces 3 output bytes
+    // per iteration.  We can't know at the start that there is enough
+    // data left in the string for a full iteration, so the loop may
+    // break out in the middle; if so 'state' will be set to the
+    // number of input bytes read.
+
+    while (szsrc >= 4)  {
+      // We'll start by optimistically assuming that the next four
+      // bytes of the string (src[0..3]) are four good data bytes
+      // (that is, no nulls, whitespace, padding chars, or illegal
+      // chars).  We need to test src[0..2] for nulls individually
+      // before constructing temp to preserve the property that we
+      // never read past a null in the string (no matter how long
+      // szsrc claims the string is).
+
+      if (!src[0] || !src[1] || !src[2] ||
+          (temp = ((unsigned(unbase64[src[0]]) << 18) |
+                   (unsigned(unbase64[src[1]]) << 12) |
+                   (unsigned(unbase64[src[2]]) << 6) |
+                   (unsigned(unbase64[src[3]])))) & 0x80000000) {
+        // Iff any of those four characters was bad (null, illegal,
+        // whitespace, padding), then temp's high bit will be set
+        // (because unbase64[] is -1 for all bad characters).
+        //
+        // We'll back up and resort to the slower decoder, which knows
+        // how to handle those cases.
+
+        GET_INPUT(first, 4);
+        temp = decode;
+        GET_INPUT(second, 3);
+        temp = (temp << 6) | decode;
+        GET_INPUT(third, 2);
+        temp = (temp << 6) | decode;
+        GET_INPUT(fourth, 1);
+        temp = (temp << 6) | decode;
+      } else {
+        // We really did have four good data bytes, so advance four
+        // characters in the string.
+
+        szsrc -= 4;
+        src += 4;
+        decode = -1;
+        ch = '\0';
+      }
+
+      // temp has 24 bits of input, so write that out as three bytes.
+
+      if (destidx+3 > szdest) return -1;
+      dest[destidx+2] = temp;
+      temp >>= 8;
+      dest[destidx+1] = temp;
+      temp >>= 8;
+      dest[destidx] = temp;
+      destidx += 3;
+    }
+  } else {
+    while (szsrc >= 4)  {
+      if (!src[0] || !src[1] || !src[2] ||
+          (temp = ((unsigned(unbase64[src[0]]) << 18) |
+                   (unsigned(unbase64[src[1]]) << 12) |
+                   (unsigned(unbase64[src[2]]) << 6) |
+                   (unsigned(unbase64[src[3]])))) & 0x80000000) {
+        GET_INPUT(first_no_dest, 4);
+        GET_INPUT(second_no_dest, 3);
+        GET_INPUT(third_no_dest, 2);
+        GET_INPUT(fourth_no_dest, 1);
+      } else {
+        szsrc -= 4;
+        src += 4;
+        decode = -1;
+        ch = '\0';
+      }
+      destidx += 3;
+    }
+  }
+
+#undef GET_INPUT
+
+  // if the loop terminated because we read a bad character, return
+  // now.
+  if (decode < 0 && ch != '\0' &&
+      ch != kPad64Equals && ch != kPad64Dot && !ascii_isspace(ch))
+    return -1;
+
+  if (ch == kPad64Equals || ch == kPad64Dot) {
+    // if we stopped by hitting an '=' or '.', un-read that character -- we'll
+    // look at it again when we count to check for the proper number of
+    // equals signs at the end.
+    ++szsrc;
+    --src;
+  } else {
+    // This loop consumes 1 input byte per iteration.  It's used to
+    // clean up the 0-3 input bytes remaining when the first, faster
+    // loop finishes.  'temp' contains the data from 'state' input
+    // characters read by the first loop.
+    while (szsrc > 0)  {
+      --szsrc;
+      ch = *src++;
+      decode = unbase64[ch];
+      if (decode < 0) {
+        if (ascii_isspace(ch)) {
+          continue;
+        } else if (ch == '\0') {
+          break;
+        } else if (ch == kPad64Equals || ch == kPad64Dot) {
+          // back up one character; we'll read it again when we check
+          // for the correct number of pad characters at the end.
+          ++szsrc;
+          --src;
+          break;
+        } else {
+          return -1;
+        }
+      }
+
+      // Each input character gives us six bits of output.
+      temp = (temp << 6) | decode;
+      ++state;
+      if (state == 4) {
+        // If we've accumulated 24 bits of output, write that out as
+        // three bytes.
+        if (dest) {
+          if (destidx+3 > szdest) return -1;
+          dest[destidx+2] = temp;
+          temp >>= 8;
+          dest[destidx+1] = temp;
+          temp >>= 8;
+          dest[destidx] = temp;
+        }
+        destidx += 3;
+        state = 0;
+        temp = 0;
+      }
+    }
+  }
+
+  // Process the leftover data contained in 'temp' at the end of the input.
+  int expected_equals = 0;
+  switch (state) {
+    case 0:
+      // Nothing left over; output is a multiple of 3 bytes.
+      break;
+
+    case 1:
+      // Bad input; we have 6 bits left over.
+      return -1;
+
+    case 2:
+      // Produce one more output byte from the 12 input bits we have left.
+      if (dest) {
+        if (destidx+1 > szdest) return -1;
+        temp >>= 4;
+        dest[destidx] = temp;
+      }
+      ++destidx;
+      expected_equals = 2;
+      break;
+
+    case 3:
+      // Produce two more output bytes from the 18 input bits we have left.
+      if (dest) {
+        if (destidx+2 > szdest) return -1;
+        temp >>= 2;
+        dest[destidx+1] = temp;
+        temp >>= 8;
+        dest[destidx] = temp;
+      }
+      destidx += 2;
+      expected_equals = 1;
+      break;
+
+    default:
+      // state should have no other values at this point.
+      GOOGLE_LOG(FATAL) << "This can't happen; base64 decoder state = " << state;
+  }
+
+  // The remainder of the string should be all whitespace, mixed with
+  // exactly 0 equals signs, or exactly 'expected_equals' equals
+  // signs.  (Always accepting 0 equals signs is a google extension
+  // not covered in the RFC, as is accepting dot as the pad character.)
+
+  int equals = 0;
+  while (szsrc > 0 && *src) {
+    if (*src == kPad64Equals || *src == kPad64Dot)
+      ++equals;
+    else if (!ascii_isspace(*src))
+      return -1;
+    --szsrc;
+    ++src;
+  }
+
+  return (equals == 0 || equals == expected_equals) ? destidx : -1;
+}
+
+// The arrays below were generated by the following code
+// #include <sys/time.h>
+// #include <stdlib.h>
+// #include <string.h>
+// main()
+// {
+//   static const char Base64[] =
+//     "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+//   char *pos;
+//   int idx, i, j;
+//   printf("    ");
+//   for (i = 0; i < 255; i += 8) {
+//     for (j = i; j < i + 8; j++) {
+//       pos = strchr(Base64, j);
+//       if ((pos == NULL) || (j == 0))
+//         idx = -1;
+//       else
+//         idx = pos - Base64;
+//       if (idx == -1)
+//         printf(" %2d,     ", idx);
+//       else
+//         printf(" %2d/*%c*/,", idx, j);
+//     }
+//     printf("\n    ");
+//   }
+// }
+//
+// where the value of "Base64[]" was replaced by one of the base-64 conversion
+// tables from the functions below.
+static const signed char kUnBase64[] = {
+  -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
+  -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
+  -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
+  -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
+  -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
+  -1,      -1,      -1,      62/*+*/, -1,      -1,      -1,      63/*/ */,
+  52/*0*/, 53/*1*/, 54/*2*/, 55/*3*/, 56/*4*/, 57/*5*/, 58/*6*/, 59/*7*/,
+  60/*8*/, 61/*9*/, -1,      -1,      -1,      -1,      -1,      -1,
+  -1,       0/*A*/,  1/*B*/,  2/*C*/,  3/*D*/,  4/*E*/,  5/*F*/,  6/*G*/,
+  07/*H*/,  8/*I*/,  9/*J*/, 10/*K*/, 11/*L*/, 12/*M*/, 13/*N*/, 14/*O*/,
+  15/*P*/, 16/*Q*/, 17/*R*/, 18/*S*/, 19/*T*/, 20/*U*/, 21/*V*/, 22/*W*/,
+  23/*X*/, 24/*Y*/, 25/*Z*/, -1,      -1,      -1,      -1,      -1,
+  -1,      26/*a*/, 27/*b*/, 28/*c*/, 29/*d*/, 30/*e*/, 31/*f*/, 32/*g*/,
+  33/*h*/, 34/*i*/, 35/*j*/, 36/*k*/, 37/*l*/, 38/*m*/, 39/*n*/, 40/*o*/,
+  41/*p*/, 42/*q*/, 43/*r*/, 44/*s*/, 45/*t*/, 46/*u*/, 47/*v*/, 48/*w*/,
+  49/*x*/, 50/*y*/, 51/*z*/, -1,      -1,      -1,      -1,      -1,
+  -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
+  -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
+  -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
+  -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
+  -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
+  -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
+  -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
+  -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
+  -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
+  -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
+  -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
+  -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
+  -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
+  -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
+  -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
+  -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1
+};
+static const signed char kUnWebSafeBase64[] = {
+  -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
+  -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
+  -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
+  -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
+  -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
+  -1,      -1,      -1,      -1,      -1,      62/*-*/, -1,      -1,
+  52/*0*/, 53/*1*/, 54/*2*/, 55/*3*/, 56/*4*/, 57/*5*/, 58/*6*/, 59/*7*/,
+  60/*8*/, 61/*9*/, -1,      -1,      -1,      -1,      -1,      -1,
+  -1,       0/*A*/,  1/*B*/,  2/*C*/,  3/*D*/,  4/*E*/,  5/*F*/,  6/*G*/,
+  07/*H*/,  8/*I*/,  9/*J*/, 10/*K*/, 11/*L*/, 12/*M*/, 13/*N*/, 14/*O*/,
+  15/*P*/, 16/*Q*/, 17/*R*/, 18/*S*/, 19/*T*/, 20/*U*/, 21/*V*/, 22/*W*/,
+  23/*X*/, 24/*Y*/, 25/*Z*/, -1,      -1,      -1,      -1,      63/*_*/,
+  -1,      26/*a*/, 27/*b*/, 28/*c*/, 29/*d*/, 30/*e*/, 31/*f*/, 32/*g*/,
+  33/*h*/, 34/*i*/, 35/*j*/, 36/*k*/, 37/*l*/, 38/*m*/, 39/*n*/, 40/*o*/,
+  41/*p*/, 42/*q*/, 43/*r*/, 44/*s*/, 45/*t*/, 46/*u*/, 47/*v*/, 48/*w*/,
+  49/*x*/, 50/*y*/, 51/*z*/, -1,      -1,      -1,      -1,      -1,
+  -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
+  -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
+  -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
+  -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
+  -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
+  -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
+  -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
+  -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
+  -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
+  -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
+  -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
+  -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
+  -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
+  -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
+  -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1,
+  -1,      -1,      -1,      -1,      -1,      -1,      -1,      -1
+};
+
+int WebSafeBase64Unescape(const char *src, int szsrc, char *dest, int szdest) {
+  return Base64UnescapeInternal(src, szsrc, dest, szdest, kUnWebSafeBase64);
+}
+
+static bool Base64UnescapeInternal(const char* src, int slen, string* dest,
+                                   const signed char* unbase64) {
+  // Determine the size of the output string.  Base64 encodes every 3 bytes into
+  // 4 characters.  any leftover chars are added directly for good measure.
+  // This is documented in the base64 RFC: http://tools.ietf.org/html/rfc3548
+  const int dest_len = 3 * (slen / 4) + (slen % 4);
+
+  dest->resize(dest_len);
+
+  // We are getting the destination buffer by getting the beginning of the
+  // string and converting it into a char *.
+  const int len = Base64UnescapeInternal(src, slen, string_as_array(dest),
+                                         dest_len, unbase64);
+  if (len < 0) {
+    dest->clear();
+    return false;
+  }
+
+  // could be shorter if there was padding
+  GOOGLE_DCHECK_LE(len, dest_len);
+  dest->erase(len);
+
+  return true;
+}
+
+bool Base64Unescape(StringPiece src, string* dest) {
+  return Base64UnescapeInternal(src.data(), src.size(), dest, kUnBase64);
+}
+
+bool WebSafeBase64Unescape(StringPiece src, string* dest) {
+  return Base64UnescapeInternal(src.data(), src.size(), dest, kUnWebSafeBase64);
+}
+
+int Base64EscapeInternal(const unsigned char *src, int szsrc,
+                         char *dest, int szdest, const char *base64,
+                         bool do_padding) {
+  static const char kPad64 = '=';
+
+  if (szsrc <= 0) return 0;
+
+  if (szsrc * 4 > szdest * 3) return 0;
+
+  char *cur_dest = dest;
+  const unsigned char *cur_src = src;
+
+  char *limit_dest = dest + szdest;
+  const unsigned char *limit_src = src + szsrc;
+
+  // Three bytes of data encodes to four characters of cyphertext.
+  // So we can pump through three-byte chunks atomically.
+  while (cur_src < limit_src - 3) {  // keep going as long as we have >= 32 bits
+    uint32 in = BigEndian::Load32(cur_src) >> 8;
+
+    cur_dest[0] = base64[in >> 18];
+    in &= 0x3FFFF;
+    cur_dest[1] = base64[in >> 12];
+    in &= 0xFFF;
+    cur_dest[2] = base64[in >> 6];
+    in &= 0x3F;
+    cur_dest[3] = base64[in];
+
+    cur_dest += 4;
+    cur_src += 3;
+  }
+  // To save time, we didn't update szdest or szsrc in the loop.  So do it now.
+  szdest = limit_dest - cur_dest;
+  szsrc = limit_src - cur_src;
+
+  /* now deal with the tail (<=3 bytes) */
+  switch (szsrc) {
+    case 0:
+      // Nothing left; nothing more to do.
+      break;
+    case 1: {
+      // One byte left: this encodes to two characters, and (optionally)
+      // two pad characters to round out the four-character cypherblock.
+      if ((szdest -= 2) < 0) return 0;
+      uint32 in = cur_src[0];
+      cur_dest[0] = base64[in >> 2];
+      in &= 0x3;
+      cur_dest[1] = base64[in << 4];
+      cur_dest += 2;
+      if (do_padding) {
+        if ((szdest -= 2) < 0) return 0;
+        cur_dest[0] = kPad64;
+        cur_dest[1] = kPad64;
+        cur_dest += 2;
+      }
+      break;
+    }
+    case 2: {
+      // Two bytes left: this encodes to three characters, and (optionally)
+      // one pad character to round out the four-character cypherblock.
+      if ((szdest -= 3) < 0) return 0;
+      uint32 in = BigEndian::Load16(cur_src);
+      cur_dest[0] = base64[in >> 10];
+      in &= 0x3FF;
+      cur_dest[1] = base64[in >> 4];
+      in &= 0x00F;
+      cur_dest[2] = base64[in << 2];
+      cur_dest += 3;
+      if (do_padding) {
+        if ((szdest -= 1) < 0) return 0;
+        cur_dest[0] = kPad64;
+        cur_dest += 1;
+      }
+      break;
+    }
+    case 3: {
+      // Three bytes left: same as in the big loop above.  We can't do this in
+      // the loop because the loop above always reads 4 bytes, and the fourth
+      // byte is past the end of the input.
+      if ((szdest -= 4) < 0) return 0;
+      uint32 in = (cur_src[0] << 16) + BigEndian::Load16(cur_src + 1);
+      cur_dest[0] = base64[in >> 18];
+      in &= 0x3FFFF;
+      cur_dest[1] = base64[in >> 12];
+      in &= 0xFFF;
+      cur_dest[2] = base64[in >> 6];
+      in &= 0x3F;
+      cur_dest[3] = base64[in];
+      cur_dest += 4;
+      break;
+    }
+    default:
+      // Should not be reached: blocks of 4 bytes are handled
+      // in the while loop before this switch statement.
+      GOOGLE_LOG(FATAL) << "Logic problem? szsrc = " << szsrc;
+      break;
+  }
+  return (cur_dest - dest);
+}
+
+static const char kBase64Chars[] =
+"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+
+static const char kWebSafeBase64Chars[] =
+"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_";
+
+int Base64Escape(const unsigned char *src, int szsrc, char *dest, int szdest) {
+  return Base64EscapeInternal(src, szsrc, dest, szdest, kBase64Chars, true);
+}
+int WebSafeBase64Escape(const unsigned char *src, int szsrc, char *dest,
+                        int szdest, bool do_padding) {
+  return Base64EscapeInternal(src, szsrc, dest, szdest,
+                              kWebSafeBase64Chars, do_padding);
+}
+
+void Base64EscapeInternal(const unsigned char* src, int szsrc,
+                          string* dest, bool do_padding,
+                          const char* base64_chars) {
+  const int calc_escaped_size =
+    CalculateBase64EscapedLen(szsrc, do_padding);
+  dest->resize(calc_escaped_size);
+  const int escaped_len = Base64EscapeInternal(src, szsrc,
+                                               string_as_array(dest),
+                                               dest->size(),
+                                               base64_chars,
+                                               do_padding);
+  GOOGLE_DCHECK_EQ(calc_escaped_size, escaped_len);
+  dest->erase(escaped_len);
+}
+
+void Base64Escape(const unsigned char *src, int szsrc,
+                  string* dest, bool do_padding) {
+  Base64EscapeInternal(src, szsrc, dest, do_padding, kBase64Chars);
+}
+
+void WebSafeBase64Escape(const unsigned char *src, int szsrc,
+                         string *dest, bool do_padding) {
+  Base64EscapeInternal(src, szsrc, dest, do_padding, kWebSafeBase64Chars);
+}
+
+void Base64Escape(StringPiece src, string* dest) {
+  Base64Escape(reinterpret_cast<const unsigned char*>(src.data()),
+               src.size(), dest, true);
+}
+
+void WebSafeBase64Escape(StringPiece src, string* dest) {
+  WebSafeBase64Escape(reinterpret_cast<const unsigned char*>(src.data()),
+                      src.size(), dest, false);
+}
+
+void WebSafeBase64EscapeWithPadding(StringPiece src, string* dest) {
+  WebSafeBase64Escape(reinterpret_cast<const unsigned char*>(src.data()),
+                      src.size(), dest, true);
+}
+
+// Helper to append a Unicode code point to a string as UTF8, without bringing
+// in any external dependencies.
+int EncodeAsUTF8Char(uint32 code_point, char* output) {
+  uint32 tmp = 0;
+  int len = 0;
+  if (code_point <= 0x7f) {
+    tmp = code_point;
+    len = 1;
+  } else if (code_point <= 0x07ff) {
+    tmp = 0x0000c080 |
+        ((code_point & 0x07c0) << 2) |
+        (code_point & 0x003f);
+    len = 2;
+  } else if (code_point <= 0xffff) {
+    tmp = 0x00e08080 |
+        ((code_point & 0xf000) << 4) |
+        ((code_point & 0x0fc0) << 2) |
+        (code_point & 0x003f);
+    len = 3;
+  } else {
+    // UTF-16 is only defined for code points up to 0x10FFFF, and UTF-8 is
+    // normally only defined up to there as well.
+    tmp = 0xf0808080 |
+        ((code_point & 0x1c0000) << 6) |
+        ((code_point & 0x03f000) << 4) |
+        ((code_point & 0x000fc0) << 2) |
+        (code_point & 0x003f);
+    len = 4;
+  }
+  tmp = ghtonl(tmp);
+  memcpy(output, reinterpret_cast<const char*>(&tmp) + sizeof(tmp) - len, len);
+  return len;
+}
+
+// Table of UTF-8 character lengths, based on first byte
+static const unsigned char kUTF8LenTbl[256] = {
+  1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1,
+  1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1,
+  1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1,
+  1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1,
+
+  1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1,
+  1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1,
+  2,2,2,2,2,2,2,2, 2,2,2,2,2,2,2,2, 2,2,2,2,2,2,2,2, 2,2,2,2,2,2,2,2,
+  3,3,3,3,3,3,3,3, 3,3,3,3,3,3,3,3, 4,4,4,4,4,4,4,4, 4,4,4,4,4,4,4,4
+};
+
+// Return length of a single UTF-8 source character
+int UTF8FirstLetterNumBytes(const char* src, int len) {
+  if (len == 0) {
+    return 0;
+  }
+  return kUTF8LenTbl[*reinterpret_cast<const uint8*>(src)];
+}
+
 }  // namespace protobuf
 }  // namespace google
diff --git a/src/google/protobuf/stubs/strutil.h b/src/google/protobuf/stubs/strutil.h
index 397122e..b22066b 100644
--- a/src/google/protobuf/stubs/strutil.h
+++ b/src/google/protobuf/stubs/strutil.h
@@ -36,6 +36,7 @@
 #include <stdlib.h>
 #include <vector>
 #include <google/protobuf/stubs/common.h>
+#include <google/protobuf/stubs/stringpiece.h>
 
 namespace google {
 namespace protobuf {
@@ -72,7 +73,33 @@
 }
 
 inline bool ascii_isspace(char c) {
-  return c == ' ';
+  return c == ' ' || c == '\t' || c == '\n' || c == '\v' || c == '\f' ||
+      c == '\r';
+}
+
+inline bool ascii_isupper(char c) {
+  return c >= 'A' && c <= 'Z';
+}
+
+inline bool ascii_islower(char c) {
+  return c >= 'a' && c <= 'z';
+}
+
+inline char ascii_toupper(char c) {
+  return ascii_islower(c) ? c - ('a' - 'A') : c;
+}
+
+inline char ascii_tolower(char c) {
+  return ascii_isupper(c) ? c + ('a' - 'A') : c;
+}
+
+inline int hex_digit_to_int(char c) {
+  /* Assume ASCII. */
+  int x = static_cast<unsigned char>(c);
+  if (x > '9') {
+    x += 9;
+  }
+  return x & 0xf;
 }
 
 // ----------------------------------------------------------------------
@@ -360,12 +387,59 @@
 }
 
 // ----------------------------------------------------------------------
+// safe_strtob()
 // safe_strto32()
+// safe_strtou32()
+// safe_strto64()
+// safe_strtou64()
+// safe_strtof()
+// safe_strtod()
 // ----------------------------------------------------------------------
-LIBPROTOBUF_EXPORT bool safe_int(string text, int32* value_p);
+LIBPROTOBUF_EXPORT bool safe_strtob(StringPiece str, bool* value);
 
-inline bool safe_strto32(string text, int32* value) {
-  return safe_int(text, value);
+LIBPROTOBUF_EXPORT bool safe_strto32(const string& str, int32* value);
+LIBPROTOBUF_EXPORT bool safe_strtou32(const string& str, uint32* value);
+inline bool safe_strto32(const char* str, int32* value) {
+  return safe_strto32(string(str), value);
+}
+inline bool safe_strto32(StringPiece str, int32* value) {
+  return safe_strto32(str.ToString(), value);
+}
+inline bool safe_strtou32(const char* str, uint32* value) {
+  return safe_strtou32(string(str), value);
+}
+inline bool safe_strtou32(StringPiece str, uint32* value) {
+  return safe_strtou32(str.ToString(), value);
+}
+
+LIBPROTOBUF_EXPORT bool safe_strto64(const string& str, int64* value);
+LIBPROTOBUF_EXPORT bool safe_strtou64(const string& str, uint64* value);
+inline bool safe_strto64(const char* str, int64* value) {
+  return safe_strto64(string(str), value);
+}
+inline bool safe_strto64(StringPiece str, int64* value) {
+  return safe_strto64(str.ToString(), value);
+}
+inline bool safe_strtou64(const char* str, uint64* value) {
+  return safe_strtou64(string(str), value);
+}
+inline bool safe_strtou64(StringPiece str, uint64* value) {
+  return safe_strtou64(str.ToString(), value);
+}
+
+LIBPROTOBUF_EXPORT bool safe_strtof(const char* str, float* value);
+LIBPROTOBUF_EXPORT bool safe_strtod(const char* str, double* value);
+inline bool safe_strtof(const string& str, float* value) {
+  return safe_strtof(str.c_str(), value);
+}
+inline bool safe_strtod(const string& str, double* value) {
+  return safe_strtod(str.c_str(), value);
+}
+inline bool safe_strtof(StringPiece str, float* value) {
+  return safe_strtof(str.ToString(), value);
+}
+inline bool safe_strtod(StringPiece str, double* value) {
+  return safe_strtod(str.ToString(), value);
 }
 
 // ----------------------------------------------------------------------
@@ -451,6 +525,10 @@
   return buffer;
 }
 
+inline string SimpleBtoa(bool value) {
+  return value ? "true" : "false";
+}
+
 // ----------------------------------------------------------------------
 // SimpleItoa()
 //    Description: converts an integer to a string.
@@ -497,28 +575,30 @@
 
 namespace strings {
 
+enum PadSpec {
+  NO_PAD = 1,
+  ZERO_PAD_2,
+  ZERO_PAD_3,
+  ZERO_PAD_4,
+  ZERO_PAD_5,
+  ZERO_PAD_6,
+  ZERO_PAD_7,
+  ZERO_PAD_8,
+  ZERO_PAD_9,
+  ZERO_PAD_10,
+  ZERO_PAD_11,
+  ZERO_PAD_12,
+  ZERO_PAD_13,
+  ZERO_PAD_14,
+  ZERO_PAD_15,
+  ZERO_PAD_16,
+};
+
 struct Hex {
   uint64 value;
-  enum PadSpec {
-    NONE = 1,
-    ZERO_PAD_2,
-    ZERO_PAD_3,
-    ZERO_PAD_4,
-    ZERO_PAD_5,
-    ZERO_PAD_6,
-    ZERO_PAD_7,
-    ZERO_PAD_8,
-    ZERO_PAD_9,
-    ZERO_PAD_10,
-    ZERO_PAD_11,
-    ZERO_PAD_12,
-    ZERO_PAD_13,
-    ZERO_PAD_14,
-    ZERO_PAD_15,
-    ZERO_PAD_16,
-  } spec;
+  enum PadSpec spec;
   template <class Int>
-  explicit Hex(Int v, PadSpec s = NONE)
+  explicit Hex(Int v, PadSpec s = NO_PAD)
       : spec(s) {
     // Prevent sign-extension by casting integers to
     // their unsigned counterparts.
@@ -571,6 +651,9 @@
   AlphaNum(const string& str)
       : piece_data_(str.data()), piece_size_(str.size()) {}
 
+  AlphaNum(StringPiece str)
+      : piece_data_(str.data()), piece_size_(str.size()) {}
+
   size_t size() const { return piece_size_; }
   const char *data() const { return piece_data_; }
 
@@ -692,6 +775,12 @@
 }
 
 // ----------------------------------------------------------------------
+// ToHex()
+//    Return a lower-case hex string representation of the given integer.
+// ----------------------------------------------------------------------
+LIBPROTOBUF_EXPORT string ToHex(uint64 num);
+
+// ----------------------------------------------------------------------
 // GlobalReplaceSubstring()
 //    Replaces all instances of a substring in a string.  Does nothing
 //    if 'substring' is empty.  Returns the number of replacements.
@@ -702,6 +791,83 @@
                                               const string& replacement,
                                               string* s);
 
+// ----------------------------------------------------------------------
+// Base64Unescape()
+//    Converts "src" which is encoded in Base64 to its binary equivalent and
+//    writes it to "dest". If src contains invalid characters, dest is cleared
+//    and the function returns false. Returns true on success.
+// ----------------------------------------------------------------------
+LIBPROTOBUF_EXPORT bool Base64Unescape(StringPiece src, string* dest);
+
+// ----------------------------------------------------------------------
+// WebSafeBase64Unescape()
+//    This is a variation of Base64Unescape which uses '-' instead of '+', and
+//    '_' instead of '/'. src is not null terminated, instead specify len. I
+//    recommend that slen<szdest, but we honor szdest anyway.
+//    RETURNS the length of dest, or -1 if src contains invalid chars.
+
+//    The variation that stores into a string clears the string first, and
+//    returns false (with dest empty) if src contains invalid chars; for
+//    this version src and dest must be different strings.
+// ----------------------------------------------------------------------
+LIBPROTOBUF_EXPORT int WebSafeBase64Unescape(const char* src, int slen,
+                                             char* dest, int szdest);
+LIBPROTOBUF_EXPORT bool WebSafeBase64Unescape(StringPiece src, string* dest);
+
+// Return the length to use for the output buffer given to the base64 escape
+// routines. Make sure to use the same value for do_padding in both.
+// This function may return incorrect results if given input_len values that
+// are extremely high, which should happen rarely.
+LIBPROTOBUF_EXPORT int CalculateBase64EscapedLen(int input_len,
+                                                 bool do_padding);
+// Use this version when calling Base64Escape without a do_padding arg.
+LIBPROTOBUF_EXPORT int CalculateBase64EscapedLen(int input_len);
+
+// ----------------------------------------------------------------------
+// Base64Escape()
+// WebSafeBase64Escape()
+//    Encode "src" to "dest" using base64 encoding.
+//    src is not null terminated, instead specify len.
+//    'dest' should have at least CalculateBase64EscapedLen() length.
+//    RETURNS the length of dest.
+//    The WebSafe variation use '-' instead of '+' and '_' instead of '/'
+//    so that we can place the out in the URL or cookies without having
+//    to escape them.  It also has an extra parameter "do_padding",
+//    which when set to false will prevent padding with "=".
+// ----------------------------------------------------------------------
+LIBPROTOBUF_EXPORT int Base64Escape(const unsigned char* src, int slen,
+                                    char* dest, int szdest);
+LIBPROTOBUF_EXPORT int WebSafeBase64Escape(
+    const unsigned char* src, int slen, char* dest,
+    int szdest, bool do_padding);
+// Encode src into dest with padding.
+LIBPROTOBUF_EXPORT void Base64Escape(StringPiece src, string* dest);
+// Encode src into dest web-safely without padding.
+LIBPROTOBUF_EXPORT void WebSafeBase64Escape(StringPiece src, string* dest);
+// Encode src into dest web-safely with padding.
+LIBPROTOBUF_EXPORT void WebSafeBase64EscapeWithPadding(StringPiece src,
+                                                       string* dest);
+
+LIBPROTOBUF_EXPORT void Base64Escape(const unsigned char* src, int szsrc,
+                                     string* dest, bool do_padding);
+LIBPROTOBUF_EXPORT void WebSafeBase64Escape(const unsigned char* src, int szsrc,
+                                            string* dest, bool do_padding);
+
+static const int UTFmax = 4;
+// ----------------------------------------------------------------------
+// EncodeAsUTF8Char()
+//  Helper to append a Unicode code point to a string as UTF8, without bringing
+//  in any external dependencies. The output buffer must be as least 4 bytes
+//  large.
+// ----------------------------------------------------------------------
+LIBPROTOBUF_EXPORT int EncodeAsUTF8Char(uint32 code_point, char* output);
+
+// ----------------------------------------------------------------------
+// UTF8FirstLetterNumBytes()
+//   Length of the first UTF-8 character.
+// ----------------------------------------------------------------------
+LIBPROTOBUF_EXPORT int UTF8FirstLetterNumBytes(const char* src, int len);
+
 }  // namespace protobuf
 }  // namespace google
 
diff --git a/src/google/protobuf/stubs/strutil_unittest.cc b/src/google/protobuf/stubs/strutil_unittest.cc
index 7f27dca..3e84932 100644
--- a/src/google/protobuf/stubs/strutil_unittest.cc
+++ b/src/google/protobuf/stubs/strutil_unittest.cc
@@ -32,9 +32,11 @@
 
 #include <google/protobuf/stubs/strutil.h>
 
+#include <locale.h>
+
+#include <google/protobuf/stubs/stl_util.h>
 #include <google/protobuf/testing/googletest.h>
 #include <gtest/gtest.h>
-#include <locale.h>
 
 namespace google {
 namespace protobuf {
@@ -68,6 +70,738 @@
   setlocale(LC_NUMERIC, old_locale.c_str());
 }
 
+#define EXPECT_EQ_ARRAY(len, x, y, msg)                     \
+  for (int j = 0; j < len; ++j) {                           \
+    EXPECT_EQ(x[j], y[j]) << "" # x << " != " # y           \
+                          << " byte " << j << ": " << msg;  \
+  }
+
+static struct {
+  int plain_length;
+  const char* plaintext;
+  const char* cyphertext;
+} base64_tests[] = {
+  // Empty string.
+  { 0, "", ""},
+
+  // Basic bit patterns;
+  // values obtained with "echo -n '...' | uuencode -m test"
+
+  { 1, "\000", "AA==" },
+  { 1, "\001", "AQ==" },
+  { 1, "\002", "Ag==" },
+  { 1, "\004", "BA==" },
+  { 1, "\010", "CA==" },
+  { 1, "\020", "EA==" },
+  { 1, "\040", "IA==" },
+  { 1, "\100", "QA==" },
+  { 1, "\200", "gA==" },
+
+  { 1, "\377", "/w==" },
+  { 1, "\376", "/g==" },
+  { 1, "\375", "/Q==" },
+  { 1, "\373", "+w==" },
+  { 1, "\367", "9w==" },
+  { 1, "\357", "7w==" },
+  { 1, "\337", "3w==" },
+  { 1, "\277", "vw==" },
+  { 1, "\177", "fw==" },
+  { 2, "\000\000", "AAA=" },
+  { 2, "\000\001", "AAE=" },
+  { 2, "\000\002", "AAI=" },
+  { 2, "\000\004", "AAQ=" },
+  { 2, "\000\010", "AAg=" },
+  { 2, "\000\020", "ABA=" },
+  { 2, "\000\040", "ACA=" },
+  { 2, "\000\100", "AEA=" },
+  { 2, "\000\200", "AIA=" },
+  { 2, "\001\000", "AQA=" },
+  { 2, "\002\000", "AgA=" },
+  { 2, "\004\000", "BAA=" },
+  { 2, "\010\000", "CAA=" },
+  { 2, "\020\000", "EAA=" },
+  { 2, "\040\000", "IAA=" },
+  { 2, "\100\000", "QAA=" },
+  { 2, "\200\000", "gAA=" },
+
+  { 2, "\377\377", "//8=" },
+  { 2, "\377\376", "//4=" },
+  { 2, "\377\375", "//0=" },
+  { 2, "\377\373", "//s=" },
+  { 2, "\377\367", "//c=" },
+  { 2, "\377\357", "/+8=" },
+  { 2, "\377\337", "/98=" },
+  { 2, "\377\277", "/78=" },
+  { 2, "\377\177", "/38=" },
+  { 2, "\376\377", "/v8=" },
+  { 2, "\375\377", "/f8=" },
+  { 2, "\373\377", "+/8=" },
+  { 2, "\367\377", "9/8=" },
+  { 2, "\357\377", "7/8=" },
+  { 2, "\337\377", "3/8=" },
+  { 2, "\277\377", "v/8=" },
+  { 2, "\177\377", "f/8=" },
+
+  { 3, "\000\000\000", "AAAA" },
+  { 3, "\000\000\001", "AAAB" },
+  { 3, "\000\000\002", "AAAC" },
+  { 3, "\000\000\004", "AAAE" },
+  { 3, "\000\000\010", "AAAI" },
+  { 3, "\000\000\020", "AAAQ" },
+  { 3, "\000\000\040", "AAAg" },
+  { 3, "\000\000\100", "AABA" },
+  { 3, "\000\000\200", "AACA" },
+  { 3, "\000\001\000", "AAEA" },
+  { 3, "\000\002\000", "AAIA" },
+  { 3, "\000\004\000", "AAQA" },
+  { 3, "\000\010\000", "AAgA" },
+  { 3, "\000\020\000", "ABAA" },
+  { 3, "\000\040\000", "ACAA" },
+  { 3, "\000\100\000", "AEAA" },
+  { 3, "\000\200\000", "AIAA" },
+  { 3, "\001\000\000", "AQAA" },
+  { 3, "\002\000\000", "AgAA" },
+  { 3, "\004\000\000", "BAAA" },
+  { 3, "\010\000\000", "CAAA" },
+  { 3, "\020\000\000", "EAAA" },
+  { 3, "\040\000\000", "IAAA" },
+  { 3, "\100\000\000", "QAAA" },
+  { 3, "\200\000\000", "gAAA" },
+
+  { 3, "\377\377\377", "////" },
+  { 3, "\377\377\376", "///+" },
+  { 3, "\377\377\375", "///9" },
+  { 3, "\377\377\373", "///7" },
+  { 3, "\377\377\367", "///3" },
+  { 3, "\377\377\357", "///v" },
+  { 3, "\377\377\337", "///f" },
+  { 3, "\377\377\277", "//+/" },
+  { 3, "\377\377\177", "//9/" },
+  { 3, "\377\376\377", "//7/" },
+  { 3, "\377\375\377", "//3/" },
+  { 3, "\377\373\377", "//v/" },
+  { 3, "\377\367\377", "//f/" },
+  { 3, "\377\357\377", "/+//" },
+  { 3, "\377\337\377", "/9//" },
+  { 3, "\377\277\377", "/7//" },
+  { 3, "\377\177\377", "/3//" },
+  { 3, "\376\377\377", "/v//" },
+  { 3, "\375\377\377", "/f//" },
+  { 3, "\373\377\377", "+///" },
+  { 3, "\367\377\377", "9///" },
+  { 3, "\357\377\377", "7///" },
+  { 3, "\337\377\377", "3///" },
+  { 3, "\277\377\377", "v///" },
+  { 3, "\177\377\377", "f///" },
+
+  // Random numbers: values obtained with
+  //
+  //  #! /bin/bash
+  //  dd bs=$1 count=1 if=/dev/random of=/tmp/bar.random
+  //  od -N $1 -t o1 /tmp/bar.random
+  //  uuencode -m test < /tmp/bar.random
+  //
+  // where $1 is the number of bytes (2, 3)
+
+  { 2, "\243\361", "o/E=" },
+  { 2, "\024\167", "FHc=" },
+  { 2, "\313\252", "y6o=" },
+  { 2, "\046\041", "JiE=" },
+  { 2, "\145\236", "ZZ4=" },
+  { 2, "\254\325", "rNU=" },
+  { 2, "\061\330", "Mdg=" },
+  { 2, "\245\032", "pRo=" },
+  { 2, "\006\000", "BgA=" },
+  { 2, "\375\131", "/Vk=" },
+  { 2, "\303\210", "w4g=" },
+  { 2, "\040\037", "IB8=" },
+  { 2, "\261\372", "sfo=" },
+  { 2, "\335\014", "3Qw=" },
+  { 2, "\233\217", "m48=" },
+  { 2, "\373\056", "+y4=" },
+  { 2, "\247\232", "p5o=" },
+  { 2, "\107\053", "Rys=" },
+  { 2, "\204\077", "hD8=" },
+  { 2, "\276\211", "vok=" },
+  { 2, "\313\110", "y0g=" },
+  { 2, "\363\376", "8/4=" },
+  { 2, "\251\234", "qZw=" },
+  { 2, "\103\262", "Q7I=" },
+  { 2, "\142\312", "Yso=" },
+  { 2, "\067\211", "N4k=" },
+  { 2, "\220\001", "kAE=" },
+  { 2, "\152\240", "aqA=" },
+  { 2, "\367\061", "9zE=" },
+  { 2, "\133\255", "W60=" },
+  { 2, "\176\035", "fh0=" },
+  { 2, "\032\231", "Gpk=" },
+
+  { 3, "\013\007\144", "Cwdk" },
+  { 3, "\030\112\106", "GEpG" },
+  { 3, "\047\325\046", "J9Um" },
+  { 3, "\310\160\022", "yHAS" },
+  { 3, "\131\100\237", "WUCf" },
+  { 3, "\064\342\134", "NOJc" },
+  { 3, "\010\177\004", "CH8E" },
+  { 3, "\345\147\205", "5WeF" },
+  { 3, "\300\343\360", "wOPw" },
+  { 3, "\061\240\201", "MaCB" },
+  { 3, "\225\333\044", "ldsk" },
+  { 3, "\215\137\352", "jV/q" },
+  { 3, "\371\147\160", "+Wdw" },
+  { 3, "\030\320\051", "GNAp" },
+  { 3, "\044\174\241", "JHyh" },
+  { 3, "\260\127\037", "sFcf" },
+  { 3, "\111\045\033", "SSUb" },
+  { 3, "\202\114\107", "gkxH" },
+  { 3, "\057\371\042", "L/ki" },
+  { 3, "\223\247\244", "k6ek" },
+  { 3, "\047\216\144", "J45k" },
+  { 3, "\203\070\327", "gzjX" },
+  { 3, "\247\140\072", "p2A6" },
+  { 3, "\124\115\116", "VE1O" },
+  { 3, "\157\162\050", "b3Io" },
+  { 3, "\357\223\004", "75ME" },
+  { 3, "\052\117\156", "Kk9u" },
+  { 3, "\347\154\000", "52wA" },
+  { 3, "\303\012\142", "wwpi" },
+  { 3, "\060\035\362", "MB3y" },
+  { 3, "\130\226\361", "WJbx" },
+  { 3, "\173\013\071", "ews5" },
+  { 3, "\336\004\027", "3gQX" },
+  { 3, "\357\366\234", "7/ac" },
+  { 3, "\353\304\111", "68RJ" },
+  { 3, "\024\264\131", "FLRZ" },
+  { 3, "\075\114\251", "PUyp" },
+  { 3, "\315\031\225", "zRmV" },
+  { 3, "\154\201\276", "bIG+" },
+  { 3, "\200\066\072", "gDY6" },
+  { 3, "\142\350\267", "Yui3" },
+  { 3, "\033\000\166", "GwB2" },
+  { 3, "\210\055\077", "iC0/" },
+  { 3, "\341\037\124", "4R9U" },
+  { 3, "\161\103\152", "cUNq" },
+  { 3, "\270\142\131", "uGJZ" },
+  { 3, "\337\076\074", "3z48" },
+  { 3, "\375\106\362", "/Uby" },
+  { 3, "\227\301\127", "l8FX" },
+  { 3, "\340\002\234", "4AKc" },
+  { 3, "\121\064\033", "UTQb" },
+  { 3, "\157\134\143", "b1xj" },
+  { 3, "\247\055\327", "py3X" },
+  { 3, "\340\142\005", "4GIF" },
+  { 3, "\060\260\143", "MLBj" },
+  { 3, "\075\203\170", "PYN4" },
+  { 3, "\143\160\016", "Y3AO" },
+  { 3, "\313\013\063", "ywsz" },
+  { 3, "\174\236\135", "fJ5d" },
+  { 3, "\103\047\026", "QycW" },
+  { 3, "\365\005\343", "9QXj" },
+  { 3, "\271\160\223", "uXCT" },
+  { 3, "\362\255\172", "8q16" },
+  { 3, "\113\012\015", "SwoN" },
+
+  // various lengths, generated by this python script:
+  //
+  // from string import lowercase as lc
+  // for i in range(27):
+  //   print '{ %2d, "%s",%s "%s" },' % (i, lc[:i], ' ' * (26-i),
+  //                                     lc[:i].encode('base64').strip())
+
+  {  0, "",                           "" },
+  {  1, "a",                          "YQ==" },
+  {  2, "ab",                         "YWI=" },
+  {  3, "abc",                        "YWJj" },
+  {  4, "abcd",                       "YWJjZA==" },
+  {  5, "abcde",                      "YWJjZGU=" },
+  {  6, "abcdef",                     "YWJjZGVm" },
+  {  7, "abcdefg",                    "YWJjZGVmZw==" },
+  {  8, "abcdefgh",                   "YWJjZGVmZ2g=" },
+  {  9, "abcdefghi",                  "YWJjZGVmZ2hp" },
+  { 10, "abcdefghij",                 "YWJjZGVmZ2hpag==" },
+  { 11, "abcdefghijk",                "YWJjZGVmZ2hpams=" },
+  { 12, "abcdefghijkl",               "YWJjZGVmZ2hpamts" },
+  { 13, "abcdefghijklm",              "YWJjZGVmZ2hpamtsbQ==" },
+  { 14, "abcdefghijklmn",             "YWJjZGVmZ2hpamtsbW4=" },
+  { 15, "abcdefghijklmno",            "YWJjZGVmZ2hpamtsbW5v" },
+  { 16, "abcdefghijklmnop",           "YWJjZGVmZ2hpamtsbW5vcA==" },
+  { 17, "abcdefghijklmnopq",          "YWJjZGVmZ2hpamtsbW5vcHE=" },
+  { 18, "abcdefghijklmnopqr",         "YWJjZGVmZ2hpamtsbW5vcHFy" },
+  { 19, "abcdefghijklmnopqrs",        "YWJjZGVmZ2hpamtsbW5vcHFycw==" },
+  { 20, "abcdefghijklmnopqrst",       "YWJjZGVmZ2hpamtsbW5vcHFyc3Q=" },
+  { 21, "abcdefghijklmnopqrstu",      "YWJjZGVmZ2hpamtsbW5vcHFyc3R1" },
+  { 22, "abcdefghijklmnopqrstuv",     "YWJjZGVmZ2hpamtsbW5vcHFyc3R1dg==" },
+  { 23, "abcdefghijklmnopqrstuvw",    "YWJjZGVmZ2hpamtsbW5vcHFyc3R1dnc=" },
+  { 24, "abcdefghijklmnopqrstuvwx",   "YWJjZGVmZ2hpamtsbW5vcHFyc3R1dnd4" },
+  { 25, "abcdefghijklmnopqrstuvwxy",  "YWJjZGVmZ2hpamtsbW5vcHFyc3R1dnd4eQ==" },
+  { 26, "abcdefghijklmnopqrstuvwxyz", "YWJjZGVmZ2hpamtsbW5vcHFyc3R1dnd4eXo=" },
+};
+
+static struct {
+  const char* plaintext;
+  const char* cyphertext;
+} base64_strings[] = {
+  // Some google quotes
+  // Cyphertext created with "uuencode (GNU sharutils) 4.6.3"
+  // (Note that we're testing the websafe encoding, though, so if
+  // you add messages, be sure to run "tr -- '+/' '-_'" on the output)
+  { "I was always good at math and science, and I never realized "
+    "that was unusual or somehow undesirable. So one of the things "
+    "I care a lot about is helping to remove that stigma, "
+    "to show girls that you can be feminine, you can like the things "
+    "that girls like, but you can also be really good at technology. "
+    "You can be really good at building things."
+    " - Marissa Meyer, Newsweek, 2010-12-22" "\n",
+
+    "SSB3YXMgYWx3YXlzIGdvb2QgYXQgbWF0aCBhbmQgc2NpZW5jZSwgYW5kIEkg"
+    "bmV2ZXIgcmVhbGl6ZWQgdGhhdCB3YXMgdW51c3VhbCBvciBzb21laG93IHVu"
+    "ZGVzaXJhYmxlLiBTbyBvbmUgb2YgdGhlIHRoaW5ncyBJIGNhcmUgYSBsb3Qg"
+    "YWJvdXQgaXMgaGVscGluZyB0byByZW1vdmUgdGhhdCBzdGlnbWEsIHRvIHNo"
+    "b3cgZ2lybHMgdGhhdCB5b3UgY2FuIGJlIGZlbWluaW5lLCB5b3UgY2FuIGxp"
+    "a2UgdGhlIHRoaW5ncyB0aGF0IGdpcmxzIGxpa2UsIGJ1dCB5b3UgY2FuIGFs"
+    "c28gYmUgcmVhbGx5IGdvb2QgYXQgdGVjaG5vbG9neS4gWW91IGNhbiBiZSBy"
+    "ZWFsbHkgZ29vZCBhdCBidWlsZGluZyB0aGluZ3MuIC0gTWFyaXNzYSBNZXll"
+    "ciwgTmV3c3dlZWssIDIwMTAtMTItMjIK" },
+
+  { "Typical first year for a new cluster: "
+    "~0.5 overheating "
+    "~1 PDU failure "
+    "~1 rack-move "
+    "~1 network rewiring "
+    "~20 rack failures "
+    "~5 racks go wonky "
+    "~8 network maintenances "
+    "~12 router reloads "
+    "~3 router failures "
+    "~dozens of minor 30-second blips for dns "
+    "~1000 individual machine failures "
+    "~thousands of hard drive failures "
+    "slow disks, bad memory, misconfigured machines, flaky machines, etc."
+    " - Jeff Dean, The Joys of Real Hardware" "\n",
+
+    "VHlwaWNhbCBmaXJzdCB5ZWFyIGZvciBhIG5ldyBjbHVzdGVyOiB-MC41IG92"
+    "ZXJoZWF0aW5nIH4xIFBEVSBmYWlsdXJlIH4xIHJhY2stbW92ZSB-MSBuZXR3"
+    "b3JrIHJld2lyaW5nIH4yMCByYWNrIGZhaWx1cmVzIH41IHJhY2tzIGdvIHdv"
+    "bmt5IH44IG5ldHdvcmsgbWFpbnRlbmFuY2VzIH4xMiByb3V0ZXIgcmVsb2Fk"
+    "cyB-MyByb3V0ZXIgZmFpbHVyZXMgfmRvemVucyBvZiBtaW5vciAzMC1zZWNv"
+    "bmQgYmxpcHMgZm9yIGRucyB-MTAwMCBpbmRpdmlkdWFsIG1hY2hpbmUgZmFp"
+    "bHVyZXMgfnRob3VzYW5kcyBvZiBoYXJkIGRyaXZlIGZhaWx1cmVzIHNsb3cg"
+    "ZGlza3MsIGJhZCBtZW1vcnksIG1pc2NvbmZpZ3VyZWQgbWFjaGluZXMsIGZs"
+    "YWt5IG1hY2hpbmVzLCBldGMuIC0gSmVmZiBEZWFuLCBUaGUgSm95cyBvZiBS"
+    "ZWFsIEhhcmR3YXJlCg" },
+
+  { "I'm the head of the webspam team at Google.  "
+    "That means that if you type your name into Google and get porn back, "
+    "it's my fault. Unless you're a porn star, in which case porn is a "
+    "completely reasonable response."
+    " - Matt Cutts, Google Plus" "\n",
+
+    "SSdtIHRoZSBoZWFkIG9mIHRoZSB3ZWJzcGFtIHRlYW0gYXQgR29vZ2xlLiAg"
+    "VGhhdCBtZWFucyB0aGF0IGlmIHlvdSB0eXBlIHlvdXIgbmFtZSBpbnRvIEdv"
+    "b2dsZSBhbmQgZ2V0IHBvcm4gYmFjaywgaXQncyBteSBmYXVsdC4gVW5sZXNz"
+    "IHlvdSdyZSBhIHBvcm4gc3RhciwgaW4gd2hpY2ggY2FzZSBwb3JuIGlzIGEg"
+    "Y29tcGxldGVseSByZWFzb25hYmxlIHJlc3BvbnNlLiAtIE1hdHQgQ3V0dHMs"
+    "IEdvb2dsZSBQbHVzCg" },
+
+  { "It will still be a long time before machines approach human intelligence. "
+    "But luckily, machines don't actually have to be intelligent; "
+    "they just have to fake it. Access to a wealth of information, "
+    "combined with a rudimentary decision-making capacity, "
+    "can often be almost as useful. Of course, the results are better yet "
+    "when coupled with intelligence. A reference librarian with access to "
+    "a good search engine is a formidable tool."
+    " - Craig Silverstein, Siemens Pictures of the Future, Spring 2004" "\n",
+
+    "SXQgd2lsbCBzdGlsbCBiZSBhIGxvbmcgdGltZSBiZWZvcmUgbWFjaGluZXMg"
+    "YXBwcm9hY2ggaHVtYW4gaW50ZWxsaWdlbmNlLiBCdXQgbHVja2lseSwgbWFj"
+    "aGluZXMgZG9uJ3QgYWN0dWFsbHkgaGF2ZSB0byBiZSBpbnRlbGxpZ2VudDsg"
+    "dGhleSBqdXN0IGhhdmUgdG8gZmFrZSBpdC4gQWNjZXNzIHRvIGEgd2VhbHRo"
+    "IG9mIGluZm9ybWF0aW9uLCBjb21iaW5lZCB3aXRoIGEgcnVkaW1lbnRhcnkg"
+    "ZGVjaXNpb24tbWFraW5nIGNhcGFjaXR5LCBjYW4gb2Z0ZW4gYmUgYWxtb3N0"
+    "IGFzIHVzZWZ1bC4gT2YgY291cnNlLCB0aGUgcmVzdWx0cyBhcmUgYmV0dGVy"
+    "IHlldCB3aGVuIGNvdXBsZWQgd2l0aCBpbnRlbGxpZ2VuY2UuIEEgcmVmZXJl"
+    "bmNlIGxpYnJhcmlhbiB3aXRoIGFjY2VzcyB0byBhIGdvb2Qgc2VhcmNoIGVu"
+    "Z2luZSBpcyBhIGZvcm1pZGFibGUgdG9vbC4gLSBDcmFpZyBTaWx2ZXJzdGVp"
+    "biwgU2llbWVucyBQaWN0dXJlcyBvZiB0aGUgRnV0dXJlLCBTcHJpbmcgMjAw"
+    "NAo" },
+
+  // Degenerate edge case
+  { "",
+    "" },
+};
+
+TEST(Base64, EscapeAndUnescape) {
+  // Check the short strings; this tests the math (and boundaries)
+  for (int i = 0; i < sizeof(base64_tests) / sizeof(base64_tests[0]); ++i) {
+    char encode_buffer[100];
+    int encode_length;
+    char decode_buffer[100];
+    int decode_length;
+    int cypher_length;
+    string decode_str;
+
+    const unsigned char* unsigned_plaintext =
+      reinterpret_cast<const unsigned char*>(base64_tests[i].plaintext);
+
+    StringPiece plaintext(base64_tests[i].plaintext,
+                          base64_tests[i].plain_length);
+
+    cypher_length = strlen(base64_tests[i].cyphertext);
+
+    // The basic escape function:
+    memset(encode_buffer, 0, sizeof(encode_buffer));
+    encode_length = Base64Escape(unsigned_plaintext,
+                                 base64_tests[i].plain_length,
+                                 encode_buffer,
+                                 sizeof(encode_buffer));
+    //    Is it of the expected length?
+    EXPECT_EQ(encode_length, cypher_length);
+    // Would it have been okay to allocate only CalculateBase64EscapeLen()?
+    EXPECT_EQ(CalculateBase64EscapedLen(base64_tests[i].plain_length),
+              encode_length);
+
+    //    Is it the expected encoded value?
+    EXPECT_STREQ(encode_buffer, base64_tests[i].cyphertext);
+
+    // If we encode it into a buffer of exactly the right length...
+    memset(encode_buffer, 0, sizeof(encode_buffer));
+    encode_length = Base64Escape(unsigned_plaintext,
+                                          base64_tests[i].plain_length,
+                                          encode_buffer,
+                                          cypher_length);
+    //    Is it still of the expected length?
+    EXPECT_EQ(encode_length, cypher_length);
+
+    //    And is the value still correct?  (i.e., not losing the last byte)
+    EXPECT_STREQ(encode_buffer, base64_tests[i].cyphertext);
+
+    // If we decode it back:
+    decode_str.clear();
+    EXPECT_TRUE(Base64Unescape(
+        StringPiece(encode_buffer, cypher_length), &decode_str));
+
+    //    Is it of the expected length?
+    EXPECT_EQ(base64_tests[i].plain_length, decode_str.length());
+
+    //    Is it the expected decoded value?
+    EXPECT_EQ(plaintext, decode_str);
+
+    // Let's try with a pre-populated string.
+    string encoded("this junk should be ignored");
+    Base64Escape(string(base64_tests[i].plaintext,
+                        base64_tests[i].plain_length),
+                 &encoded);
+    EXPECT_EQ(encoded, string(encode_buffer, cypher_length));
+
+    string decoded("this junk should be ignored");
+    EXPECT_TRUE(Base64Unescape(
+        StringPiece(encode_buffer, cypher_length), &decoded));
+    EXPECT_EQ(decoded.size(), base64_tests[i].plain_length);
+    EXPECT_EQ_ARRAY(decoded.size(), decoded, base64_tests[i].plaintext, i);
+
+    // Our decoder treats the padding '=' characters at the end as
+    // optional (but if there are any, there must be the correct
+    // number of them.)  If encode_buffer has any, run some additional
+    // tests that fiddle with them.
+    char* first_equals = strchr(encode_buffer, '=');
+    if (first_equals) {
+      // How many equals signs does the string start with?
+      int equals = (*(first_equals+1) == '=') ? 2 : 1;
+
+      // Try chopping off the equals sign(s) entirely.  The decoder
+      // should still be okay with this.
+      string decoded2("this junk should also be ignored");
+      *first_equals = '\0';
+      EXPECT_TRUE(Base64Unescape(
+          StringPiece(encode_buffer, first_equals - encode_buffer), &decoded2));
+      EXPECT_EQ(decoded.size(), base64_tests[i].plain_length);
+      EXPECT_EQ_ARRAY(decoded.size(), decoded, base64_tests[i].plaintext, i);
+
+      // Now test chopping off the equals sign(s) and adding
+      // whitespace.  Our decoder should still accept this.
+      decoded2.assign("this junk should be ignored");
+      *first_equals = ' ';
+      *(first_equals+1) = '\0';
+      EXPECT_TRUE(Base64Unescape(
+          StringPiece(encode_buffer, first_equals - encode_buffer + 1),
+          &decoded2));
+      EXPECT_EQ(decoded.size(), base64_tests[i].plain_length);
+      EXPECT_EQ_ARRAY(decoded.size(), decoded, base64_tests[i].plaintext, i);
+
+      // Now stick a bad character at the end of the string.  The decoder
+      // should refuse this string.
+      decoded2.assign("this junk should be ignored");
+      *first_equals = '?';
+      *(first_equals+1) = '\0';
+      EXPECT_TRUE(
+          !Base64Unescape(
+              StringPiece(encode_buffer, first_equals - encode_buffer + 1),
+              &decoded2));
+
+      int len;
+
+      // Test whitespace mixed with the padding.  (eg "AA = = ")  The
+      // decoder should accept this.
+      if (equals == 2) {
+        snprintf(first_equals, 6, " = = ");
+        len = first_equals - encode_buffer + 5;
+      } else {
+        snprintf(first_equals, 6, " = ");
+        len = first_equals - encode_buffer + 3;
+      }
+      decoded2.assign("this junk should be ignored");
+      EXPECT_TRUE(
+          Base64Unescape(StringPiece(encode_buffer, len), &decoded2));
+      EXPECT_EQ(decoded.size(), base64_tests[i].plain_length);
+      EXPECT_EQ_ARRAY(decoded.size(), decoded, base64_tests[i].plaintext, i);
+
+      // Test whitespace mixed with the padding, but with the wrong
+      // number of equals signs (eg "AA = ").  The decoder should
+      // refuse these strings.
+      if (equals == 1) {
+        snprintf(first_equals, 6, " = = ");
+        len = first_equals - encode_buffer + 5;
+      } else {
+        snprintf(first_equals, 6, " = ");
+        len = first_equals - encode_buffer + 3;
+      }
+      EXPECT_TRUE(
+          !Base64Unescape(StringPiece(encode_buffer, len), &decoded2));
+    }
+
+    // Cool! the basic Base64 encoder/decoder works.
+    // Let's try the alternate alphabet: tr -- '+/' '-_'
+
+    char websafe[100];
+    memset(websafe, 0, sizeof(websafe));
+    strncpy(websafe, base64_tests[i].cyphertext, cypher_length);
+    for (int c = 0; c < sizeof(websafe); ++c) {
+      if ('+' == websafe[c]) { websafe[c] = '-'; }
+      if ('/' == websafe[c]) { websafe[c] = '_'; }
+    }
+
+    // The websafe escape function:
+    memset(encode_buffer, 0, sizeof(encode_buffer));
+    encode_length = WebSafeBase64Escape(unsigned_plaintext,
+                                                 base64_tests[i].plain_length,
+                                                 encode_buffer,
+                                                 sizeof(encode_buffer),
+                                                 true);
+    //    Is it of the expected length?
+    EXPECT_EQ(encode_length, cypher_length);
+    EXPECT_EQ(
+        CalculateBase64EscapedLen(base64_tests[i].plain_length, true),
+        encode_length);
+
+    //    Is it the expected encoded value?
+    EXPECT_STREQ(encode_buffer, websafe);
+
+    //    If we encode it into a buffer of exactly the right length...
+    memset(encode_buffer, 0, sizeof(encode_buffer));
+    encode_length = WebSafeBase64Escape(unsigned_plaintext,
+                                                 base64_tests[i].plain_length,
+                                                 encode_buffer,
+                                                 cypher_length,
+                                                 true);
+    //    Is it still of the expected length?
+    EXPECT_EQ(encode_length, cypher_length);
+
+    //    And is the value still correct?  (i.e., not losing the last byte)
+    EXPECT_STREQ(encode_buffer, websafe);
+
+    //    Let's try the string version of the encoder
+    encoded = "this junk should be ignored";
+    WebSafeBase64Escape(
+        unsigned_plaintext, base64_tests[i].plain_length,
+        &encoded, true);
+    EXPECT_EQ(encoded.size(), cypher_length);
+    EXPECT_STREQ(encoded.c_str(), websafe);
+
+    //    If we decode it back:
+    memset(decode_buffer, 0, sizeof(decode_buffer));
+    decode_length = WebSafeBase64Unescape(encode_buffer,
+                                                   cypher_length,
+                                                   decode_buffer,
+                                                   sizeof(decode_buffer));
+
+    //    Is it of the expected length?
+    EXPECT_EQ(decode_length, base64_tests[i].plain_length);
+
+    //    Is it the expected decoded value?
+    EXPECT_EQ(0,
+              memcmp(decode_buffer, base64_tests[i].plaintext, decode_length));
+
+    //    If we decode it into a buffer of exactly the right length...
+    memset(decode_buffer, 0, sizeof(decode_buffer));
+    decode_length = WebSafeBase64Unescape(encode_buffer,
+                                                   cypher_length,
+                                                   decode_buffer,
+                                                   decode_length);
+
+    //    Is it still of the expected length?
+    EXPECT_EQ(decode_length, base64_tests[i].plain_length);
+
+    //    And is it the expected decoded value?
+    EXPECT_EQ(0,
+              memcmp(decode_buffer, base64_tests[i].plaintext, decode_length));
+
+    // Try using '.' for the pad character.
+    for (int c = cypher_length - 1; c >= 0 && '=' == encode_buffer[c]; --c) {
+      encode_buffer[c] = '.';
+    }
+
+    // If we decode it back:
+    memset(decode_buffer, 0, sizeof(decode_buffer));
+    decode_length = WebSafeBase64Unescape(encode_buffer,
+                                                   cypher_length,
+                                                   decode_buffer,
+                                                   sizeof(decode_buffer));
+
+    // Is it of the expected length?
+    EXPECT_EQ(decode_length, base64_tests[i].plain_length);
+
+    // Is it the expected decoded value?
+    EXPECT_EQ(0,
+              memcmp(decode_buffer, base64_tests[i].plaintext, decode_length));
+
+    // If we decode it into a buffer of exactly the right length...
+    memset(decode_buffer, 0, sizeof(decode_buffer));
+    decode_length = WebSafeBase64Unescape(encode_buffer,
+                                                   cypher_length,
+                                                   decode_buffer,
+                                                   decode_length);
+
+    // Is it still of the expected length?
+    EXPECT_EQ(decode_length, base64_tests[i].plain_length);
+
+    // And is it the expected decoded value?
+    EXPECT_EQ(0,
+              memcmp(decode_buffer, base64_tests[i].plaintext, decode_length));
+
+    // Let's try the string version of the decoder
+    decoded = "this junk should be ignored";
+    EXPECT_TRUE(WebSafeBase64Unescape(
+        StringPiece(encode_buffer, cypher_length), &decoded));
+    EXPECT_EQ(decoded.size(), base64_tests[i].plain_length);
+    EXPECT_EQ_ARRAY(decoded.size(), decoded, base64_tests[i].plaintext, i);
+
+    // Okay! the websafe Base64 encoder/decoder works.
+    // Let's try the unpadded version
+
+    for (int c = 0; c < sizeof(websafe); ++c) {
+      if ('=' == websafe[c]) {
+        websafe[c] = '\0';
+        cypher_length = c;
+        break;
+      }
+    }
+
+    // The websafe escape function:
+    memset(encode_buffer, 0, sizeof(encode_buffer));
+    encode_length = WebSafeBase64Escape(unsigned_plaintext,
+                                                 base64_tests[i].plain_length,
+                                                 encode_buffer,
+                                                 sizeof(encode_buffer),
+                                                 false);
+    //    Is it of the expected length?
+    EXPECT_EQ(encode_length, cypher_length);
+    EXPECT_EQ(
+        CalculateBase64EscapedLen(base64_tests[i].plain_length, false),
+        encode_length);
+
+    //    Is it the expected encoded value?
+    EXPECT_STREQ(encode_buffer, websafe);
+
+    //    If we encode it into a buffer of exactly the right length...
+    memset(encode_buffer, 0, sizeof(encode_buffer));
+    encode_length = WebSafeBase64Escape(unsigned_plaintext,
+                                                 base64_tests[i].plain_length,
+                                                 encode_buffer,
+                                                 cypher_length,
+                                                 false);
+    //    Is it still of the expected length?
+    EXPECT_EQ(encode_length, cypher_length);
+
+    //    And is the value still correct?  (i.e., not losing the last byte)
+    EXPECT_STREQ(encode_buffer, websafe);
+
+    // Let's try the (other) string version of the encoder
+    string plain(base64_tests[i].plaintext, base64_tests[i].plain_length);
+    encoded = "this junk should be ignored";
+    WebSafeBase64Escape(plain, &encoded);
+    EXPECT_EQ(encoded.size(), cypher_length);
+    EXPECT_STREQ(encoded.c_str(), websafe);
+
+    //    If we decode it back:
+    memset(decode_buffer, 0, sizeof(decode_buffer));
+    decode_length = WebSafeBase64Unescape(encode_buffer,
+                                                   cypher_length,
+                                                   decode_buffer,
+                                                   sizeof(decode_buffer));
+
+    //    Is it of the expected length?
+    EXPECT_EQ(decode_length, base64_tests[i].plain_length);
+
+    //    Is it the expected decoded value?
+    EXPECT_EQ(0,
+              memcmp(decode_buffer, base64_tests[i].plaintext, decode_length));
+
+    //    If we decode it into a buffer of exactly the right length...
+    memset(decode_buffer, 0, sizeof(decode_buffer));
+    decode_length = WebSafeBase64Unescape(encode_buffer,
+                                                   cypher_length,
+                                                   decode_buffer,
+                                                   decode_length);
+
+    //    Is it still of the expected length?
+    EXPECT_EQ(decode_length, base64_tests[i].plain_length);
+
+    //    And is it the expected decoded value?
+    EXPECT_EQ(0,
+              memcmp(decode_buffer, base64_tests[i].plaintext, decode_length));
+
+
+    // Let's try the string version of the decoder
+    decoded = "this junk should be ignored";
+    EXPECT_TRUE(WebSafeBase64Unescape(
+        StringPiece(encode_buffer, cypher_length), &decoded));
+    EXPECT_EQ(decoded.size(), base64_tests[i].plain_length);
+    EXPECT_EQ_ARRAY(decoded.size(), decoded, base64_tests[i].plaintext, i);
+
+    // This value works.  Try the next.
+  }
+
+  // Now try the long strings, this tests the streaming
+  for (int i = 0; i < sizeof(base64_strings) / sizeof(base64_strings[0]);
+       ++i) {
+
+    const unsigned char* unsigned_plaintext =
+      reinterpret_cast<const unsigned char*>(base64_strings[i].plaintext);
+    int plain_length = strlen(base64_strings[i].plaintext);
+    int cypher_length = strlen(base64_strings[i].cyphertext);
+    vector<char> buffer(cypher_length+1);
+    int encode_length = WebSafeBase64Escape(unsigned_plaintext,
+                                                     plain_length,
+                                                     &buffer[0],
+                                                     buffer.size(),
+                                                     false);
+    EXPECT_EQ(cypher_length, encode_length);
+    EXPECT_EQ(
+        CalculateBase64EscapedLen(plain_length, false), encode_length);
+    buffer[ encode_length ] = '\0';
+    EXPECT_STREQ(base64_strings[i].cyphertext, &buffer[0]);
+  }
+
+  // Verify the behavior when decoding bad data
+  {
+    const char* bad_data = "ab-/";
+    string buf;
+    EXPECT_FALSE(Base64Unescape(StringPiece(bad_data), &buf));
+    EXPECT_TRUE(!WebSafeBase64Unescape(bad_data, &buf));
+    EXPECT_TRUE(buf.empty());
+  }
+}
+
 }  // anonymous namespace
 }  // namespace protobuf
 }  // namespace google
diff --git a/src/google/protobuf/stubs/time.cc b/src/google/protobuf/stubs/time.cc
new file mode 100644
index 0000000..73b99af
--- /dev/null
+++ b/src/google/protobuf/stubs/time.cc
@@ -0,0 +1,364 @@
+#include <google/protobuf/stubs/time.h>
+
+#include <google/protobuf/stubs/stringprintf.h>
+#include <google/protobuf/stubs/strutil.h>
+
+namespace google {
+namespace protobuf {
+namespace internal {
+
+namespace {
+static const int64 kSecondsPerMinute = 60;
+static const int64 kSecondsPerHour = 3600;
+static const int64 kSecondsPerDay = kSecondsPerHour * 24;
+static const int64 kSecondsPer400Years =
+    kSecondsPerDay * (400 * 365 + 400 / 4 - 3);
+// Seconds from 0001-01-01T00:00:00 to 1970-01-01T:00:00:00
+static const int64 kSecondsFromEraToEpoch = 62135596800LL;
+// The range of timestamp values we support.
+static const int64 kMinTime = -62135596800LL;  // 0001-01-01T00:00:00
+static const int64 kMaxTime = 253402300799LL;  // 9999-12-31T23:59:59
+
+static const int kNanosPerSecond = 1000000000;
+static const int kNanosPerMillisecond = 1000000;
+static const int kNanosPerMicrosecond = 1000;
+
+// Count the seconds from the given year (start at Jan 1, 00:00) to 100 years
+// after.
+int64 SecondsPer100Years(int year) {
+  if (year % 400 == 0 || year % 400 > 300) {
+    return kSecondsPerDay * (100 * 365 + 100 / 4);
+  } else {
+    return kSecondsPerDay * (100 * 365 + 100 / 4 - 1);
+  }
+}
+
+// Count the seconds from the given year (start at Jan 1, 00:00) to 4 years
+// after.
+int64 SecondsPer4Years(int year) {
+  if ((year % 100 == 0 || year % 100 > 96) &&
+      !(year % 400 == 0 || year % 400 > 396)) {
+    // No leap years.
+    return kSecondsPerDay * (4 * 365);
+  } else {
+    // One leap years.
+    return kSecondsPerDay * (4 * 365 + 1);
+  }
+}
+
+bool IsLeapYear(int year) {
+  return year % 400 == 0 || (year % 4 == 0 && year % 100 != 0);
+}
+
+int64 SecondsPerYear(int year) {
+  return kSecondsPerDay * (IsLeapYear(year) ? 366 : 365);
+}
+
+static const int kDaysInMonth[13] = {
+  0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
+};
+
+int64 SecondsPerMonth(int month, bool leap) {
+  if (month == 2 && leap) {
+    return kSecondsPerDay * (kDaysInMonth[month] + 1);
+  }
+  return kSecondsPerDay * kDaysInMonth[month];
+}
+
+static const int kDaysSinceJan[13] = {
+  0, 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334,
+};
+
+bool ValidateDateTime(const DateTime& time) {
+  if (time.year < 1 || time.year > 9999 ||
+      time.month < 1 || time.month > 12 ||
+      time.day < 1 || time.day > 31 ||
+      time.hour < 0 || time.hour > 23 ||
+      time.minute < 0 || time.minute > 59 ||
+      time.second < 0 || time.second > 59) {
+    return false;
+  }
+  if (time.month == 2 && IsLeapYear(time.year)) {
+    return time.month <= kDaysInMonth[time.month] + 1;
+  } else {
+    return time.month <= kDaysInMonth[time.month];
+  }
+}
+
+// Count the number of seconds elapsed from 0001-01-01T00:00:00 to the given
+// time.
+int64 SecondsSinceCommonEra(const DateTime& time) {
+  int64 result = 0;
+  // Years should be between 1 and 9999.
+  assert(time.year >= 1 && time.year <= 9999);
+  int year = 1;
+  if ((time.year - year) >= 400) {
+    int count_400years = (time.year - year) / 400;
+    result += kSecondsPer400Years * count_400years;
+    year += count_400years * 400;
+  }
+  while ((time.year - year) >= 100) {
+    result += SecondsPer100Years(year);
+    year += 100;
+  }
+  while ((time.year - year) >= 4) {
+    result += SecondsPer4Years(year);
+    year += 4;
+  }
+  while (time.year > year) {
+    result += SecondsPerYear(year);
+    ++year;
+  }
+  // Months should be between 1 and 12.
+  assert(time.month >= 1 && time.month <= 12);
+  int month = time.month;
+  result += kSecondsPerDay * kDaysSinceJan[month];
+  if (month > 2 && IsLeapYear(year)) {
+    result += kSecondsPerDay;
+  }
+  assert(time.day >= 1 &&
+         time.day <= (month == 2 && IsLeapYear(year)
+                          ? kDaysInMonth[month] + 1
+                          : kDaysInMonth[month]));
+  result += kSecondsPerDay * (time.day - 1);
+  result += kSecondsPerHour * time.hour +
+      kSecondsPerMinute * time.minute +
+      time.second;
+  return result;
+}
+
+// Format nanoseconds with either 3, 6, or 9 digits depending on the required
+// precision to represent the exact value.
+string FormatNanos(int32 nanos) {
+  if (nanos % kNanosPerMillisecond == 0) {
+    return StringPrintf("%03d", nanos / kNanosPerMillisecond);
+  } else if (nanos % kNanosPerMicrosecond == 0) {
+    return StringPrintf("%06d", nanos / kNanosPerMicrosecond);
+  } else {
+    return StringPrintf("%09d", nanos);
+  }
+}
+
+// Parses an integer from a null-terminated char sequence. The method
+// consumes at most "width" chars. Returns a pointer after the consumed
+// integer, or NULL if the data does not start with an integer or the
+// integer value does not fall in the range of [min_value, max_value].
+const char* ParseInt(const char* data, int width, int min_value,
+                     int max_value, int* result) {
+  if (!ascii_isdigit(*data)) {
+    return NULL;
+  }
+  int value = 0;
+  for (int i = 0; i < width; ++i, ++data) {
+    if (ascii_isdigit(*data)) {
+      value = value * 10 + (*data - '0');
+    } else {
+      break;
+    }
+  }
+  if (value >= min_value && value <= max_value) {
+    *result = value;
+    return data;
+  } else {
+    return NULL;
+  }
+}
+
+// Consumes the fractional parts of a second into nanos. For example,
+// "010" will be parsed to 10000000 nanos.
+const char* ParseNanos(const char* data, int32* nanos) {
+  if (!ascii_isdigit(*data)) {
+    return NULL;
+  }
+  int value = 0;
+  int len = 0;
+  // Consume as many digits as there are but only take the first 9 into
+  // account.
+  while (ascii_isdigit(*data)) {
+    if (len < 9) {
+      value = value * 10 + *data - '0';
+    }
+    ++len;
+    ++data;
+  }
+  while (len < 9) {
+    value = value * 10;
+    ++len;
+  }
+  *nanos = value;
+  return data;
+}
+
+const char* ParseTimezoneOffset(const char* data, int64* offset) {
+  // Accept format "HH:MM". E.g., "08:00"
+  int hour;
+  if ((data = ParseInt(data, 2, 0, 23, &hour)) == NULL) {
+    return NULL;
+  }
+  if (*data++ != ':') {
+    return NULL;
+  }
+  int minute;
+  if ((data = ParseInt(data, 2, 0, 59, &minute)) == NULL) {
+    return NULL;
+  }
+  *offset = (hour * 60 + minute) * 60;
+  return data;
+}
+}  // namespace
+
+bool SecondsToDateTime(int64 seconds, DateTime* time) {
+  if (seconds < kMinTime || seconds > kMaxTime) {
+    return false;
+  }
+  // It's easier to calcuate the DateTime starting from 0001-01-01T00:00:00
+  seconds = seconds + kSecondsFromEraToEpoch;
+  int year = 1;
+  if (seconds >= kSecondsPer400Years) {
+    int count_400years = seconds / kSecondsPer400Years;
+    year += 400 * count_400years;
+    seconds %= kSecondsPer400Years;
+  }
+  while (seconds >= SecondsPer100Years(year)) {
+    seconds -= SecondsPer100Years(year);
+    year += 100;
+  }
+  while (seconds >= SecondsPer4Years(year)) {
+    seconds -= SecondsPer4Years(year);
+    year += 4;
+  }
+  while (seconds >= SecondsPerYear(year)) {
+    seconds -= SecondsPerYear(year);
+    year += 1;
+  }
+  bool leap = IsLeapYear(year);
+  int month = 1;
+  while (seconds >= SecondsPerMonth(month, leap)) {
+    seconds -= SecondsPerMonth(month, leap);
+    ++month;
+  }
+  int day = 1 + seconds / kSecondsPerDay;
+  seconds %= kSecondsPerDay;
+  int hour = seconds / kSecondsPerHour;
+  seconds %= kSecondsPerHour;
+  int minute = seconds / kSecondsPerMinute;
+  seconds %= kSecondsPerMinute;
+  time->year = year;
+  time->month = month;
+  time->day = day;
+  time->hour = hour;
+  time->minute = minute;
+  time->second = static_cast<int>(seconds);
+  return true;
+}
+
+bool DateTimeToSeconds(const DateTime& time, int64* seconds) {
+  if (!ValidateDateTime(time)) {
+    return false;
+  }
+  *seconds = SecondsSinceCommonEra(time) - kSecondsFromEraToEpoch;
+  return true;
+}
+
+void GetCurrentTime(int64* seconds, int32* nanos) {
+  // TODO(xiaofeng): Improve the accuracy of this implementation (or just
+  // remove this method from protobuf).
+  *seconds = time(NULL);
+  *nanos = 0;
+}
+
+string FormatTime(int64 seconds, int32 nanos) {
+  DateTime time;
+  if (nanos < 0 || nanos > 999999999 || !SecondsToDateTime(seconds, &time)) {
+    return "InvalidTime";
+  }
+  string result = StringPrintf("%04d-%02d-%02dT%02d:%02d:%02d",
+                               time.year, time.month, time.day,
+                               time.hour, time.minute, time.second);
+  if (nanos != 0) {
+    result += "." + FormatNanos(nanos);
+  }
+  return result + "Z";
+}
+
+bool ParseTime(const string& value, int64* seconds, int32* nanos) {
+  DateTime time;
+  const char* data = value.c_str();
+  // We only accept:
+  //   Z-normalized: 2015-05-20T13:29:35.120Z
+  //   With UTC offset: 2015-05-20T13:29:35.120-08:00
+
+  // Parse year
+  if ((data = ParseInt(data, 4, 1, 9999, &time.year)) == NULL) {
+    return false;
+  }
+  // Expect '-'
+  if (*data++ != '-') return false;
+  // Parse month
+  if ((data = ParseInt(data, 2, 1, 12, &time.month)) == NULL) {
+    return false;
+  }
+  // Expect '-'
+  if (*data++ != '-') return false;
+  // Parse day
+  if ((data = ParseInt(data, 2, 1, 31, &time.day)) == NULL) {
+    return false;
+  }
+  // Expect 'T'
+  if (*data++ != 'T') return false;
+  // Parse hour
+  if ((data = ParseInt(data, 2, 0, 23, &time.hour)) == NULL) {
+    return false;
+  }
+  // Expect ':'
+  if (*data++ != ':') return false;
+  // Parse minute
+  if ((data = ParseInt(data, 2, 0, 59, &time.minute)) == NULL) {
+    return false;
+  }
+  // Expect ':'
+  if (*data++ != ':') return false;
+  // Parse second
+  if ((data = ParseInt(data, 2, 0, 59, &time.second)) == NULL) {
+    return false;
+  }
+  if (!DateTimeToSeconds(time, seconds)) {
+    return false;
+  }
+  // Parse nanoseconds.
+  if (*data == '.') {
+    ++data;
+    // Parse nanoseconds.
+    if ((data = ParseNanos(data, nanos)) == NULL) {
+      return false;
+    }
+  } else {
+    *nanos = 0;
+  }
+  // Parse UTC offsets.
+  if (*data == 'Z') {
+    ++data;
+  } else if (*data == '+') {
+    ++data;
+    int64 offset;
+    if ((data = ParseTimezoneOffset(data, &offset)) == NULL) {
+      return false;
+    }
+    *seconds -= offset;
+  } else if (*data == '-') {
+    ++data;
+    int64 offset;
+    if ((data = ParseTimezoneOffset(data, &offset)) == NULL) {
+      return false;
+    }
+    *seconds += offset;
+  } else {
+    return false;
+  }
+  // Done with parsing.
+  return *data == 0;
+}
+
+}  // namespace internal
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/stubs/time.h b/src/google/protobuf/stubs/time.h
new file mode 100644
index 0000000..0f641dc
--- /dev/null
+++ b/src/google/protobuf/stubs/time.h
@@ -0,0 +1,75 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#ifndef GOOGLE_PROTOBUF_STUBS_TIME_H_
+#define GOOGLE_PROTOBUF_STUBS_TIME_H_
+
+#include <google/protobuf/stubs/common.h>
+
+namespace google {
+namespace protobuf {
+namespace internal {
+
+struct DateTime {
+  int year;
+  int month;
+  int day;
+  int hour;
+  int minute;
+  int second;
+};
+
+// Converts a timestamp (seconds elapsed since 1970-01-01T00:00:00, could be
+// negative to represent time before 1970-01-01) to DateTime. Returns false
+// if the timestamp is not in the range between 0001-01-01T00:00:00 and
+// 9999-12-31T23:59:59.
+bool SecondsToDateTime(int64 seconds, DateTime* time);
+// Converts DateTime to a timestamp (seconds since 1970-01-01T00:00:00).
+// Returns false if the DateTime is not valid or is not in the valid range.
+bool DateTimeToSeconds(const DateTime& time, int64* seconds);
+
+void GetCurrentTime(int64* seconds, int32* nanos);
+
+// Formats a time string in RFC3339 fromat.
+//
+// For example, "2015-05-20T13:29:35.120Z". For nanos, 0, 3, 6 or 9 fractional
+// digits will be used depending on how many are required to represent the exact
+// value.
+//
+// Note that "nanos" must in the range of [0, 999999999].
+string FormatTime(int64 seconds, int32 nanos);
+// Parses a time string. This method accepts RFC3339 date/time string with UTC
+// offset. For example, "2015-05-20T13:29:35.120-08:00".
+bool ParseTime(const string& vaule, int64* seconds, int32* nanos);
+
+}  // namespace internal
+}  // namespace protobuf
+}  // namespace google
+
+#endif  // GOOGLE_PROTOBUF_STUBS_TIME_H_
diff --git a/src/google/protobuf/stubs/time_test.cc b/src/google/protobuf/stubs/time_test.cc
new file mode 100644
index 0000000..59e9d1c
--- /dev/null
+++ b/src/google/protobuf/stubs/time_test.cc
@@ -0,0 +1,208 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#include <google/protobuf/stubs/time.h>
+
+#include <google/protobuf/testing/googletest.h>
+#include <gtest/gtest.h>
+
+namespace google {
+namespace protobuf {
+namespace internal {
+namespace {
+static const int64 kSecondsPerDay = 3600 * 24;
+
+// For DateTime, tests will mostly focuse on the date part because that's
+// the tricky one.
+int64 CreateTimestamp(int year, int month, int day) {
+  DateTime time;
+  time.year = year;
+  time.month = month;
+  time.day = day;
+  time.hour = time.minute = time.second = 0;
+  int64 result;
+  GOOGLE_CHECK(DateTimeToSeconds(time, &result));
+  // Check that a roundtrip produces the same result.
+  GOOGLE_CHECK(SecondsToDateTime(result, &time));
+  GOOGLE_CHECK(time.year == year);
+  GOOGLE_CHECK(time.month == month);
+  GOOGLE_CHECK(time.day == day);
+  return result;
+}
+
+TEST(DateTimeTest, SimpleTime) {
+  DateTime time;
+  ASSERT_TRUE(SecondsToDateTime(1, &time));
+  EXPECT_EQ(1970, time.year);
+  EXPECT_EQ(1, time.month);
+  EXPECT_EQ(1, time.day);
+  EXPECT_EQ(0, time.hour);
+  EXPECT_EQ(0, time.minute);
+  EXPECT_EQ(1, time.second);
+  int64 seconds;
+  ASSERT_TRUE(DateTimeToSeconds(time, &seconds));
+  EXPECT_EQ(1, seconds);
+
+  ASSERT_TRUE(SecondsToDateTime(-1, &time));
+  EXPECT_EQ(1969, time.year);
+  EXPECT_EQ(12, time.month);
+  EXPECT_EQ(31, time.day);
+  EXPECT_EQ(23, time.hour);
+  EXPECT_EQ(59, time.minute);
+  EXPECT_EQ(59, time.second);
+  ASSERT_TRUE(DateTimeToSeconds(time, &seconds));
+  EXPECT_EQ(-1, seconds);
+
+  DateTime start, end;
+  start.year = 1;
+  start.month = 1;
+  start.day = 1;
+  start.hour = 0;
+  start.minute = 0;
+  start.second = 0;
+  end.year = 9999;
+  end.month = 12;
+  end.day = 31;
+  end.hour = 23;
+  end.minute = 59;
+  end.second = 59;
+  int64 start_time, end_time;
+  ASSERT_TRUE(DateTimeToSeconds(start, &start_time));
+  ASSERT_TRUE(DateTimeToSeconds(end, &end_time));
+  EXPECT_EQ(315537897599LL, end_time - start_time);
+  ASSERT_TRUE(SecondsToDateTime(start_time, &time));
+  ASSERT_TRUE(DateTimeToSeconds(time, &seconds));
+  EXPECT_EQ(start_time, seconds);
+  ASSERT_TRUE(SecondsToDateTime(end_time, &time));
+  ASSERT_TRUE(DateTimeToSeconds(time, &seconds));
+  EXPECT_EQ(end_time, seconds);
+}
+
+TEST(DateTimeTest, DayInMonths) {
+  // Check that month boundaries are handled correctly.
+  EXPECT_EQ(kSecondsPerDay,
+            CreateTimestamp(2015, 1, 1) - CreateTimestamp(2014, 12, 31));
+  EXPECT_EQ(kSecondsPerDay,
+            CreateTimestamp(2015, 2, 1) - CreateTimestamp(2015, 1, 31));
+  EXPECT_EQ(kSecondsPerDay,
+            CreateTimestamp(2015, 3, 1) - CreateTimestamp(2015, 2, 28));
+  EXPECT_EQ(kSecondsPerDay,
+            CreateTimestamp(2015, 4, 1) - CreateTimestamp(2015, 3, 31));
+  EXPECT_EQ(kSecondsPerDay,
+            CreateTimestamp(2015, 5, 1) - CreateTimestamp(2015, 4, 30));
+  EXPECT_EQ(kSecondsPerDay,
+            CreateTimestamp(2015, 6, 1) - CreateTimestamp(2015, 5, 31));
+  EXPECT_EQ(kSecondsPerDay,
+            CreateTimestamp(2015, 7, 1) - CreateTimestamp(2015, 6, 30));
+  EXPECT_EQ(kSecondsPerDay,
+            CreateTimestamp(2015, 8, 1) - CreateTimestamp(2015, 7, 31));
+  EXPECT_EQ(kSecondsPerDay,
+            CreateTimestamp(2015, 9, 1) - CreateTimestamp(2015, 8, 31));
+  EXPECT_EQ(kSecondsPerDay,
+            CreateTimestamp(2015, 10, 1) - CreateTimestamp(2015, 9, 30));
+  EXPECT_EQ(kSecondsPerDay,
+            CreateTimestamp(2015, 11, 1) - CreateTimestamp(2015, 10, 31));
+  EXPECT_EQ(kSecondsPerDay,
+            CreateTimestamp(2015, 12, 1) - CreateTimestamp(2015, 11, 30));
+  EXPECT_EQ(kSecondsPerDay,
+            CreateTimestamp(2016, 1, 1) - CreateTimestamp(2015, 12, 31));
+}
+
+TEST(DateTimeTest, LeapYear) {
+  // Non-leap year.
+  EXPECT_EQ(kSecondsPerDay,
+            CreateTimestamp(2015, 3, 1) - CreateTimestamp(2015, 2, 28));
+  // Leap year.
+  EXPECT_EQ(kSecondsPerDay,
+            CreateTimestamp(2016, 3, 1) - CreateTimestamp(2016, 2, 29));
+  // Non-leap year.
+  EXPECT_EQ(kSecondsPerDay,
+            CreateTimestamp(2100, 3, 1) - CreateTimestamp(2100, 2, 28));
+  // Leap year.
+  EXPECT_EQ(kSecondsPerDay,
+            CreateTimestamp(2400, 3, 1) - CreateTimestamp(2400, 2, 29));
+}
+
+TEST(DateTimeTest, StringFormat) {
+  DateTime start, end;
+  start.year = 1;
+  start.month = 1;
+  start.day = 1;
+  start.hour = 0;
+  start.minute = 0;
+  start.second = 0;
+  end.year = 9999;
+  end.month = 12;
+  end.day = 31;
+  end.hour = 23;
+  end.minute = 59;
+  end.second = 59;
+  int64 start_time, end_time;
+  ASSERT_TRUE(DateTimeToSeconds(start, &start_time));
+  ASSERT_TRUE(DateTimeToSeconds(end, &end_time));
+
+  EXPECT_EQ("0001-01-01T00:00:00Z", FormatTime(start_time, 0));
+  EXPECT_EQ("9999-12-31T23:59:59Z", FormatTime(end_time, 0));
+
+  // Make sure the nanoseconds part is formated correctly.
+  EXPECT_EQ("1970-01-01T00:00:00.010Z", FormatTime(0, 10000000));
+  EXPECT_EQ("1970-01-01T00:00:00.000010Z", FormatTime(0, 10000));
+  EXPECT_EQ("1970-01-01T00:00:00.000000010Z", FormatTime(0, 10));
+}
+
+TEST(DateTimeTest, ParseString) {
+  int64 seconds;
+  int32 nanos;
+  ASSERT_TRUE(ParseTime("0001-01-01T00:00:00Z", &seconds, &nanos));
+  EXPECT_EQ("0001-01-01T00:00:00Z", FormatTime(seconds, nanos));
+  ASSERT_TRUE(ParseTime("9999-12-31T23:59:59.999999999Z", &seconds, &nanos));
+  EXPECT_EQ("9999-12-31T23:59:59.999999999Z", FormatTime(seconds, nanos));
+
+  // Test time zone offsets.
+  ASSERT_TRUE(ParseTime("1970-01-01T00:00:00-08:00", &seconds, &nanos));
+  EXPECT_EQ("1970-01-01T08:00:00Z", FormatTime(seconds, nanos));
+  ASSERT_TRUE(ParseTime("1970-01-01T00:00:00+08:00", &seconds, &nanos));
+  EXPECT_EQ("1969-12-31T16:00:00Z", FormatTime(seconds, nanos));
+
+  // Test nanoseconds.
+  ASSERT_TRUE(ParseTime("1970-01-01T00:00:00.01Z", &seconds, &nanos));
+  EXPECT_EQ("1970-01-01T00:00:00.010Z", FormatTime(seconds, nanos));
+  ASSERT_TRUE(ParseTime("1970-01-01T00:00:00.00001-08:00", &seconds, &nanos));
+  EXPECT_EQ("1970-01-01T08:00:00.000010Z", FormatTime(seconds, nanos));
+  ASSERT_TRUE(ParseTime("1970-01-01T00:00:00.00000001+08:00", &seconds, &nanos));
+  EXPECT_EQ("1969-12-31T16:00:00.000000010Z", FormatTime(seconds, nanos));
+  // Fractional parts less than 1 nanosecond will be ignored.
+  ASSERT_TRUE(ParseTime("1970-01-01T00:00:00.0123456789Z", &seconds, &nanos));
+  EXPECT_EQ("1970-01-01T00:00:00.012345678Z", FormatTime(seconds, nanos));
+}
+
+}  // namespace
+}  // namespace internal
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/text_format.cc b/src/google/protobuf/text_format.cc
index 61dfa5d..4d8c1f9 100644
--- a/src/google/protobuf/text_format.cc
+++ b/src/google/protobuf/text_format.cc
@@ -1880,7 +1880,7 @@
         generator.Print(field_number);
         generator.Print(": 0x");
         generator.Print(
-            StrCat(strings::Hex(field.fixed32(), strings::Hex::ZERO_PAD_8)));
+            StrCat(strings::Hex(field.fixed32(), strings::ZERO_PAD_8)));
         if (single_line_mode_) {
           generator.Print(" ");
         } else {
@@ -1892,7 +1892,7 @@
         generator.Print(field_number);
         generator.Print(": 0x");
         generator.Print(
-            StrCat(strings::Hex(field.fixed64(), strings::Hex::ZERO_PAD_16)));
+            StrCat(strings::Hex(field.fixed64(), strings::ZERO_PAD_16)));
         if (single_line_mode_) {
           generator.Print(" ");
         } else {
diff --git a/src/google/protobuf/util/field_comparator.cc b/src/google/protobuf/util/field_comparator.cc
new file mode 100644
index 0000000..b7676a8
--- /dev/null
+++ b/src/google/protobuf/util/field_comparator.cc
@@ -0,0 +1,187 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Author: ksroka@google.com (Krzysztof Sroka)
+
+#include <google/protobuf/util/field_comparator.h>
+
+#include <string>
+
+#include <google/protobuf/descriptor.h>
+#include <google/protobuf/message.h>
+#include <google/protobuf/stubs/map_util.h>
+#include <google/protobuf/stubs/mathlimits.h>
+#include <google/protobuf/stubs/mathutil.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+
+FieldComparator::FieldComparator() {}
+FieldComparator::~FieldComparator() {}
+
+DefaultFieldComparator::DefaultFieldComparator()
+    : float_comparison_(EXACT),
+      treat_nan_as_equal_(false),
+      has_default_tolerance_(false) {
+}
+
+DefaultFieldComparator::~DefaultFieldComparator() {}
+
+FieldComparator::ComparisonResult DefaultFieldComparator::Compare(
+      const google::protobuf::Message& message_1,
+      const google::protobuf::Message& message_2,
+      const google::protobuf::FieldDescriptor* field,
+      int index_1, int index_2,
+      const google::protobuf::util::FieldContext* field_context) {
+  const Reflection* reflection_1 = message_1.GetReflection();
+  const Reflection* reflection_2 = message_2.GetReflection();
+
+  switch (field->cpp_type()) {
+#define COMPARE_FIELD(METHOD)                                              \
+    if (field->is_repeated()) {                                            \
+      return ResultFromBoolean(Compare##METHOD(                            \
+          *field,                                                          \
+          reflection_1->GetRepeated##METHOD(message_1, field, index_1),    \
+          reflection_2->GetRepeated##METHOD(message_2, field, index_2)));  \
+    } else {                                                               \
+      return ResultFromBoolean(Compare##METHOD(                            \
+          *field,                                                          \
+          reflection_1->Get##METHOD(message_1, field),                     \
+          reflection_2->Get##METHOD(message_2, field)));                   \
+    }                                                                      \
+    break;  // Make sure no fall-through is introduced.
+
+    case FieldDescriptor::CPPTYPE_BOOL:
+      COMPARE_FIELD(Bool);
+    case FieldDescriptor::CPPTYPE_DOUBLE:
+      COMPARE_FIELD(Double);
+    case FieldDescriptor::CPPTYPE_ENUM:
+      COMPARE_FIELD(Enum);
+    case FieldDescriptor::CPPTYPE_FLOAT:
+      COMPARE_FIELD(Float);
+    case FieldDescriptor::CPPTYPE_INT32:
+      COMPARE_FIELD(Int32);
+    case FieldDescriptor::CPPTYPE_INT64:
+      COMPARE_FIELD(Int64);
+    case FieldDescriptor::CPPTYPE_STRING:
+      COMPARE_FIELD(String);
+    case FieldDescriptor::CPPTYPE_UINT32:
+      COMPARE_FIELD(UInt32);
+    case FieldDescriptor::CPPTYPE_UINT64:
+      COMPARE_FIELD(UInt64);
+
+#undef COMPARE_FIELD
+
+    case FieldDescriptor::CPPTYPE_MESSAGE:
+      return RECURSE;
+
+    default:
+      GOOGLE_LOG(FATAL) << "No comparison code for field " << field->full_name()
+                 << " of CppType = " << field->cpp_type();
+  }
+}
+
+void DefaultFieldComparator::SetDefaultFractionAndMargin(double fraction,
+                                                         double margin) {
+  default_tolerance_ = Tolerance(fraction, margin);
+  has_default_tolerance_ = true;
+}
+
+void DefaultFieldComparator::SetFractionAndMargin(const FieldDescriptor* field,
+                                                  double fraction,
+                                                  double margin) {
+  GOOGLE_CHECK(FieldDescriptor::CPPTYPE_FLOAT == field->cpp_type() ||
+        FieldDescriptor::CPPTYPE_DOUBLE == field->cpp_type())
+      << "Field has to be float or double type. Field name is: "
+      << field->full_name();
+  map_tolerance_[field] = Tolerance(fraction, margin);
+}
+
+bool DefaultFieldComparator::CompareDouble(const FieldDescriptor& field,
+                                           double value_1, double value_2) {
+  return CompareDoubleOrFloat(field, value_1, value_2);
+}
+
+bool DefaultFieldComparator::CompareEnum(const FieldDescriptor& field,
+                                         const EnumValueDescriptor* value_1,
+                                         const EnumValueDescriptor* value_2) {
+  return value_1->number() == value_2->number();
+}
+
+bool DefaultFieldComparator::CompareFloat(const FieldDescriptor& field,
+                                          float value_1, float value_2) {
+  return CompareDoubleOrFloat(field, value_1, value_2);
+}
+
+template<typename T>
+bool DefaultFieldComparator::CompareDoubleOrFloat(const FieldDescriptor& field,
+                                                  T value_1, T value_2) {
+  if (value_1 == value_2) {
+    // Covers +inf and -inf (which are not within margin or fraction of
+    // themselves), and is a shortcut for finite values.
+    return true;
+  } else if (float_comparison_ == EXACT) {
+    if (treat_nan_as_equal_ &&
+        MathLimits<T>::IsNaN(value_1) && MathLimits<T>::IsNaN(value_2)) {
+      return true;
+    }
+    return false;
+  } else {
+    if (treat_nan_as_equal_ &&
+        MathLimits<T>::IsNaN(value_1) && MathLimits<T>::IsNaN(value_2)) {
+      return true;
+    }
+    // float_comparison_ == APPROXIMATE covers two use cases.
+    Tolerance* tolerance = FindOrNull(map_tolerance_, &field);
+    if (tolerance == NULL && has_default_tolerance_) {
+      tolerance = &default_tolerance_;
+    }
+    if (tolerance == NULL) {
+      return MathUtil::AlmostEquals(value_1, value_2);
+    } else {
+      // Use user-provided fraction and margin. Since they are stored as
+      // doubles, we explicitely cast them to types of values provided. This
+      // is very likely to fail if provided values are not numeric.
+      return MathUtil::WithinFractionOrMargin(
+          value_1, value_2, static_cast<T>(tolerance->fraction),
+          static_cast<T>(tolerance->margin));
+    }
+  }
+}
+
+FieldComparator::ComparisonResult DefaultFieldComparator::ResultFromBoolean(
+    bool boolean_result) const {
+  return boolean_result ? FieldComparator::SAME : FieldComparator::DIFFERENT;
+}
+
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/field_comparator.h b/src/google/protobuf/util/field_comparator.h
new file mode 100644
index 0000000..5e893f9
--- /dev/null
+++ b/src/google/protobuf/util/field_comparator.h
@@ -0,0 +1,259 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Author: ksroka@google.com (Krzysztof Sroka)
+
+#ifndef GOOGLE_PROTOBUF_UTIL_FIELD_COMPARATOR_H__
+#define GOOGLE_PROTOBUF_UTIL_FIELD_COMPARATOR_H__
+
+#include <map>
+#include <string>
+
+#include <google/protobuf/stubs/common.h>
+
+namespace google {
+namespace protobuf {
+
+class Message;
+class EnumValueDescriptor;
+class FieldDescriptor;
+
+namespace util {
+
+struct FieldContext;
+
+// Base class specifying the interface for comparing protocol buffer fields.
+// Regular users should consider using or subclassing DefaultFieldComparator
+// rather than this interface.
+// Currently, this does not support comparing unknown fields.
+class LIBPROTOBUF_EXPORT FieldComparator {
+ public:
+  FieldComparator();
+  virtual ~FieldComparator();
+
+  enum ComparisonResult {
+    SAME,       // Compared fields are equal. In case of comparing submessages,
+                // user should not recursively compare their contents.
+    DIFFERENT,  // Compared fields are different. In case of comparing
+                // submessages, user should not recursively compare their
+                // contents.
+    RECURSE,    // Compared submessages need to be compared recursively.
+                // FieldComparator does not specify the semantics of recursive
+                // comparison. This value should not be returned for simple
+                // values.
+  };
+
+  // Compares the values of a field in two protocol buffer messages.
+  // Returns SAME or DIFFERENT for simple values, and SAME, DIFFERENT or RECURSE
+  // for submessages. Returning RECURSE for fields not being submessages is
+  // illegal.
+  // In case the given FieldDescriptor points to a repeated field, the indices
+  // need to be valid. Otherwise they should be ignored.
+  //
+  // FieldContext contains information about the specific instances of the
+  // fields being compared, versus FieldDescriptor which only contains general
+  // type information about the fields.
+  virtual ComparisonResult Compare(
+      const google::protobuf::Message& message_1,
+      const google::protobuf::Message& message_2,
+      const google::protobuf::FieldDescriptor* field,
+      int index_1, int index_2,
+      const google::protobuf::util::FieldContext* field_context) = 0;
+
+ private:
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(FieldComparator);
+};
+
+// Basic implementation of FieldComparator.  Supports four modes of floating
+// point value comparison: exact, approximate using MathUtil::AlmostEqual
+// method, and arbitrarilly precise using MathUtil::WithinFracionOrMargin.
+class LIBPROTOBUF_EXPORT DefaultFieldComparator : public FieldComparator {
+ public:
+  enum FloatComparison {
+     EXACT,               // Floats and doubles are compared exactly.
+     APPROXIMATE,         // Floats and doubles are compared using the
+                          // MathUtil::AlmostEqual method or
+                          // MathUtil::WithinFractionOrMargin method.
+     // TODO(ksroka): Introduce third value to differenciate uses of AlmostEqual
+     //               and WithinFractionOrMargin.
+  };
+
+  // Creates new comparator with float comparison set to EXACT.
+  DefaultFieldComparator();
+
+  virtual ~DefaultFieldComparator();
+
+  virtual ComparisonResult Compare(
+      const google::protobuf::Message& message_1,
+      const google::protobuf::Message& message_2,
+      const google::protobuf::FieldDescriptor* field,
+      int index_1, int index_2,
+      const google::protobuf::util::FieldContext* field_context);
+
+  void set_float_comparison(FloatComparison float_comparison) {
+    float_comparison_ = float_comparison;
+  }
+
+  FloatComparison float_comparison() const {
+    return float_comparison_;
+  }
+
+  // Set whether the FieldComparator shall treat floats or doubles that are both
+  // NaN as equal (treat_nan_as_equal = true) or as different
+  // (treat_nan_as_equal = false). Default is treating NaNs always as different.
+  void set_treat_nan_as_equal(bool treat_nan_as_equal) {
+    treat_nan_as_equal_ = treat_nan_as_equal;
+  }
+
+  bool treat_nan_as_equal() const {
+    return treat_nan_as_equal_;
+  }
+
+  // Sets the fraction and margin for the float comparison of a given field.
+  // Uses MathUtil::WithinFractionOrMargin to compare the values.
+  //
+  // REQUIRES: field->cpp_type == FieldDescriptor::CPPTYPE_DOUBLE or
+  //           field->cpp_type == FieldDescriptor::CPPTYPE_FLOAT
+  // REQUIRES: float_comparison_ == APPROXIMATE
+  void SetFractionAndMargin(const FieldDescriptor* field, double fraction,
+                            double margin);
+
+  // Sets the fraction and margin for the float comparison of all float and
+  // double fields, unless a field has been given a specific setting via
+  // SetFractionAndMargin() above.
+  // Uses MathUtil::WithinFractionOrMargin to compare the values.
+  //
+  // REQUIRES: float_comparison_ == APPROXIMATE
+  void SetDefaultFractionAndMargin(double fraction, double margin);
+
+ private:
+  // Defines the tolerance for floating point comparison (fraction and margin).
+  struct Tolerance {
+    double fraction;
+    double margin;
+    Tolerance()
+        : fraction(0.0),
+          margin(0.0) {}
+    Tolerance(double f, double m)
+        : fraction(f),
+          margin(m) {}
+  };
+
+  // Defines the map to store the tolerances for floating point comparison.
+  typedef map<const FieldDescriptor*, Tolerance> ToleranceMap;
+
+  // The following methods get executed when CompareFields is called for the
+  // basic types (instead of submessages). They return true on success. One
+  // can use ResultFromBoolean() to convert that boolean to a ComparisonResult
+  // value.
+  bool CompareBool(const google::protobuf::FieldDescriptor& field,
+                   bool value_1, bool value_2) {
+    return value_1 == value_2;
+  }
+
+  // Uses CompareDoubleOrFloat, a helper function used by both CompareDouble and
+  // CompareFloat.
+  bool CompareDouble(const google::protobuf::FieldDescriptor& field,
+                     double value_1, double value_2);
+
+  bool CompareEnum(const google::protobuf::FieldDescriptor& field,
+                   const EnumValueDescriptor* value_1,
+                   const EnumValueDescriptor* value_2);
+
+  // Uses CompareDoubleOrFloat, a helper function used by both CompareDouble and
+  // CompareFloat.
+  bool CompareFloat(const google::protobuf::FieldDescriptor& field,
+                    float value_1, float value_2);
+
+  bool CompareInt32(const google::protobuf::FieldDescriptor& field,
+                    int32 value_1, int32 value_2) {
+    return value_1 == value_2;
+  }
+
+  bool CompareInt64(const google::protobuf::FieldDescriptor& field,
+                    int64 value_1, int64 value_2) {
+    return value_1 == value_2;
+  }
+
+  bool CompareString(const google::protobuf::FieldDescriptor& field,
+                     const string& value_1, const string& value_2) {
+    return value_1 == value_2;
+  }
+
+  bool CompareUInt32(const google::protobuf::FieldDescriptor& field,
+                     uint32 value_1, uint32 value_2) {
+    return value_1 == value_2;
+  }
+
+  bool CompareUInt64(const google::protobuf::FieldDescriptor& field,
+                     uint64 value_1, uint64 value_2) {
+    return value_1 == value_2;
+  }
+
+  // This function is used by CompareDouble and CompareFloat to avoid code
+  // duplication. There are no checks done against types of the values passed,
+  // but it's likely to fail if passed non-numeric arguments.
+  template<typename T>
+  bool CompareDoubleOrFloat(const google::protobuf::FieldDescriptor& field,
+                            T value_1, T value_2);
+
+  // Returns FieldComparator::SAME if boolean_result is true and
+  // FieldComparator::DIFFERENT otherwise.
+  ComparisonResult ResultFromBoolean(bool boolean_result) const;
+
+  FloatComparison float_comparison_;
+
+  // If true, floats and doubles that are both NaN are considered to be
+  // equal. Otherwise, two floats or doubles that are NaN are considered to be
+  // different.
+  bool treat_nan_as_equal_;
+
+  // True iff default_tolerance_ has been explicitly set.
+  //
+  // If false, then the default tolerance for flaots and doubles is that which
+  // is used by MathUtil::AlmostEquals().
+  bool has_default_tolerance_;
+
+  // Default float/double tolerance. Only meaningful if
+  // has_default_tolerance_ == true.
+  Tolerance default_tolerance_;
+
+  // Field-specific float/double tolerances, which override any default for
+  // those particular fields.
+  ToleranceMap map_tolerance_;
+
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(DefaultFieldComparator);
+};
+
+}  // namespace util
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_FIELD_COMPARATOR_H__
diff --git a/src/google/protobuf/util/field_comparator_test.cc b/src/google/protobuf/util/field_comparator_test.cc
new file mode 100644
index 0000000..748c7d1
--- /dev/null
+++ b/src/google/protobuf/util/field_comparator_test.cc
@@ -0,0 +1,483 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Author: ksroka@google.com (Krzysztof Sroka)
+
+#include <google/protobuf/util/field_comparator.h>
+
+#include <google/protobuf/unittest.pb.h>
+#include <google/protobuf/descriptor.h>
+#include <gtest/gtest.h>
+#include <google/protobuf/stubs/mathutil.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace {
+
+using protobuf_unittest::TestAllTypes;
+
+class DefaultFieldComparatorTest : public ::testing::Test {
+ protected:
+  void SetUp() {
+    descriptor_ = TestAllTypes::descriptor();
+  }
+
+  const Descriptor* descriptor_;
+  DefaultFieldComparator comparator_;
+  TestAllTypes message_1_;
+  TestAllTypes message_2_;
+};
+
+TEST_F(DefaultFieldComparatorTest, RecursesIntoGroup) {
+  const FieldDescriptor* field =
+      descriptor_->FindFieldByName("optionalgroup");
+  EXPECT_EQ(FieldComparator::RECURSE,
+            comparator_.Compare(message_1_, message_2_, field, -1, -1, NULL));
+}
+
+TEST_F(DefaultFieldComparatorTest, RecursesIntoNestedMessage) {
+  const FieldDescriptor* field =
+      descriptor_->FindFieldByName("optional_nested_message");
+  EXPECT_EQ(FieldComparator::RECURSE,
+            comparator_.Compare(message_1_, message_2_, field, -1, -1, NULL));
+}
+
+TEST_F(DefaultFieldComparatorTest, RecursesIntoForeignMessage) {
+  const FieldDescriptor* field =
+      descriptor_->FindFieldByName("optional_foreign_message");
+  EXPECT_EQ(FieldComparator::RECURSE,
+            comparator_.Compare(message_1_, message_2_, field, -1, -1, NULL));
+}
+
+TEST_F(DefaultFieldComparatorTest, Int32Comparison) {
+  const FieldDescriptor* field = descriptor_->FindFieldByName("optional_int32");
+  message_1_.set_optional_int32(1);
+  message_2_.set_optional_int32(1);
+
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_, field, -1, -1, NULL));
+
+  message_2_.set_optional_int32(-1);
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_, field, -1, -1, NULL));
+}
+
+TEST_F(DefaultFieldComparatorTest, Int64Comparison) {
+  const FieldDescriptor* field = descriptor_->FindFieldByName("optional_int64");
+  message_1_.set_optional_int64(1L);
+  message_2_.set_optional_int64(1L);
+
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_, field, -1, -1, NULL));
+
+  message_2_.set_optional_int64(-1L);
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_, field, -1, -1, NULL));
+}
+
+TEST_F(DefaultFieldComparatorTest, UInt32Comparison) {
+  const FieldDescriptor* field =
+      descriptor_->FindFieldByName("optional_uint32");
+  message_1_.set_optional_uint32(1);
+  message_2_.set_optional_uint32(1);
+
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_, field, -1, -1, NULL));
+
+  message_2_.set_optional_uint32(2);
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_, field, -1, -1, NULL));
+}
+
+TEST_F(DefaultFieldComparatorTest, UInt64Comparison) {
+  const FieldDescriptor* field =
+      descriptor_->FindFieldByName("optional_uint64");
+  message_1_.set_optional_uint64(1L);
+  message_2_.set_optional_uint64(1L);
+
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_, field, -1, -1, NULL));
+
+  message_2_.set_optional_uint64(2L);
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_, field, -1, -1, NULL));
+}
+
+TEST_F(DefaultFieldComparatorTest, BooleanComparison) {
+  const FieldDescriptor* field =
+      descriptor_->FindFieldByName("optional_bool");
+  message_1_.set_optional_bool(true);
+  message_2_.set_optional_bool(true);
+
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_, field, -1, -1, NULL));
+
+  message_2_.set_optional_bool(false);
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_, field, -1, -1, NULL));
+}
+
+TEST_F(DefaultFieldComparatorTest, EnumComparison) {
+  const FieldDescriptor* field =
+      descriptor_->FindFieldByName("optional_nested_enum");
+  message_1_.set_optional_nested_enum(TestAllTypes::BAR);
+  message_2_.set_optional_nested_enum(TestAllTypes::BAR);
+
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_, field, -1, -1, NULL));
+
+  message_2_.set_optional_nested_enum(TestAllTypes::BAZ);
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_, field, -1, -1, NULL));
+}
+
+TEST_F(DefaultFieldComparatorTest, StringComparison) {
+  const FieldDescriptor* field =
+      descriptor_->FindFieldByName("optional_string");
+  message_1_.set_optional_string("foo");
+  message_2_.set_optional_string("foo");
+
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_, field, -1, -1, NULL));
+
+  message_2_.set_optional_string("bar");
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_, field, -1, -1, NULL));
+}
+
+TEST_F(DefaultFieldComparatorTest, FloatingPointComparisonExact) {
+  const FieldDescriptor* field_float =
+      descriptor_->FindFieldByName("optional_float");
+  const FieldDescriptor* field_double =
+      descriptor_->FindFieldByName("optional_double");
+
+  message_1_.set_optional_float(0.1f);
+  message_2_.set_optional_float(0.1f);
+  message_1_.set_optional_double(0.1);
+  message_2_.set_optional_double(0.1);
+
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_,
+                                field_float, -1, -1, NULL));
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_,
+                                field_double, -1, -1, NULL));
+
+  message_2_.set_optional_float(0.2f);
+  message_2_.set_optional_double(0.2);
+
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_,
+                                field_float, -1, -1, NULL));
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_,
+                                field_double, -1, -1, NULL));
+}
+
+TEST_F(DefaultFieldComparatorTest, FloatingPointComparisonApproximate) {
+  const FieldDescriptor* field_float =
+      descriptor_->FindFieldByName("optional_float");
+  const FieldDescriptor* field_double =
+      descriptor_->FindFieldByName("optional_double");
+
+  message_1_.set_optional_float(2.300005f);
+  message_2_.set_optional_float(2.300006f);
+  message_1_.set_optional_double(2.3000000000000003);
+  message_2_.set_optional_double(2.3000000000000007);
+
+  // Approximate comparison depends on MathUtil, so we assert on MathUtil
+  // results first to check if that's where the failure was introduced.
+  ASSERT_NE(message_1_.optional_float(), message_2_.optional_float());
+  ASSERT_NE(message_1_.optional_double(), message_2_.optional_double());
+  ASSERT_TRUE(MathUtil::AlmostEquals(message_1_.optional_float(),
+                                     message_2_.optional_float()));
+  ASSERT_TRUE(MathUtil::AlmostEquals(message_1_.optional_double(),
+                                     message_2_.optional_double()));
+
+  // DefaultFieldComparator's default float comparison mode is EXACT.
+  ASSERT_EQ(DefaultFieldComparator::EXACT, comparator_.float_comparison());
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_,
+                                field_float, -1, -1, NULL));
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_,
+                                field_double, -1, -1, NULL));
+
+  comparator_.set_float_comparison(DefaultFieldComparator::APPROXIMATE);
+
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_,
+                                field_float, -1, -1, NULL));
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_,
+                                field_double, -1, -1, NULL));
+}
+
+TEST_F(DefaultFieldComparatorTest, FloatingPointComparisonTreatNaNsAsEqual) {
+  const FieldDescriptor* field_float =
+      descriptor_->FindFieldByName("optional_float");
+  const FieldDescriptor* field_double =
+      descriptor_->FindFieldByName("optional_double");
+
+  message_1_.set_optional_float(MathLimits<float>::kNaN);
+  message_2_.set_optional_float(MathLimits<float>::kNaN);
+  message_1_.set_optional_double(MathLimits<double>::kNaN);
+  message_2_.set_optional_double(MathLimits<double>::kNaN);
+
+  // DefaultFieldComparator's default float comparison mode is EXACT with
+  // treating NaNs as different.
+  ASSERT_EQ(DefaultFieldComparator::EXACT, comparator_.float_comparison());
+  ASSERT_EQ(false, comparator_.treat_nan_as_equal());
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_,
+                                field_float, -1, -1, NULL));
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_,
+                                field_double, -1, -1, NULL));
+  comparator_.set_float_comparison(DefaultFieldComparator::APPROXIMATE);
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_,
+                                field_float, -1, -1, NULL));
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_,
+                                field_double, -1, -1, NULL));
+
+  comparator_.set_treat_nan_as_equal(true);
+  ASSERT_EQ(true, comparator_.treat_nan_as_equal());
+  comparator_.set_float_comparison(DefaultFieldComparator::EXACT);
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_,
+                                field_float, -1, -1, NULL));
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_,
+                                field_double, -1, -1, NULL));
+  comparator_.set_float_comparison(DefaultFieldComparator::APPROXIMATE);
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_,
+                                field_float, -1, -1, NULL));
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_,
+                                field_double, -1, -1, NULL));
+}
+
+TEST_F(DefaultFieldComparatorTest,
+       FloatingPointComparisonWithinFractionOrMargin) {
+  const FieldDescriptor* field_float =
+      descriptor_->FindFieldByName("optional_float");
+  const FieldDescriptor* field_double =
+      descriptor_->FindFieldByName("optional_double");
+
+  message_1_.set_optional_float(100.0f);
+  message_2_.set_optional_float(109.9f);
+  message_1_.set_optional_double(100.0);
+  message_2_.set_optional_double(109.9);
+
+  comparator_.set_float_comparison(DefaultFieldComparator::APPROXIMATE);
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_,
+                                field_float, -1, -1, NULL));
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_,
+                                field_double, -1, -1, NULL));
+
+  // Should fail since the fraction is too low.
+  comparator_.SetFractionAndMargin(field_float, 0.01, 0.0);
+  comparator_.SetFractionAndMargin(field_double, 0.01, 0.0);
+
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_,
+                                field_float, -1, -1, NULL));
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_,
+                                field_double, -1, -1, NULL));
+
+  // Should fail since the margin is too low.
+  comparator_.SetFractionAndMargin(field_float, 0.0, 9.0);
+  comparator_.SetFractionAndMargin(field_double, 0.0, 9.0);
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_,
+                                field_float, -1, -1, NULL));
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_,
+                                field_double, -1, -1, NULL));
+
+  // Should succeed since the fraction is high enough.
+  comparator_.SetFractionAndMargin(field_float, 0.2, 0.0);
+  comparator_.SetFractionAndMargin(field_double, 0.2, 0.0);
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_,
+                                field_float, -1, -1, NULL));
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_,
+                                field_double, -1, -1, NULL));
+
+  // Should succeed since the margin is high enough.
+  comparator_.SetFractionAndMargin(field_float, 0.0, 10.0);
+  comparator_.SetFractionAndMargin(field_double, 0.0, 10.0);
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_,
+                                field_float, -1, -1, NULL));
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_,
+                                field_double, -1, -1, NULL));
+
+  // Setting values for one of the fields should not affect the other.
+  comparator_.SetFractionAndMargin(field_double, 0.0, 0.0);
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_,
+                                field_float, -1, -1, NULL));
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_,
+                                field_double, -1, -1, NULL));
+
+  // +inf should be equal even though they are not technically within margin or
+  // fraction.
+  message_1_.set_optional_float(numeric_limits<float>::infinity());
+  message_2_.set_optional_float(numeric_limits<float>::infinity());
+  message_1_.set_optional_double(numeric_limits<double>::infinity());
+  message_2_.set_optional_double(numeric_limits<double>::infinity());
+  comparator_.SetFractionAndMargin(field_float, 0.0, 0.0);
+  comparator_.SetFractionAndMargin(field_double, 0.0, 0.0);
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_,
+                                field_float, -1, -1, NULL));
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_,
+                                field_double, -1, -1, NULL));
+
+  // -inf should be equal even though they are not technically within margin or
+  // fraction.
+  message_1_.set_optional_float(-numeric_limits<float>::infinity());
+  message_2_.set_optional_float(-numeric_limits<float>::infinity());
+  message_1_.set_optional_double(-numeric_limits<double>::infinity());
+  message_2_.set_optional_double(-numeric_limits<double>::infinity());
+  comparator_.SetFractionAndMargin(field_float, 0.0, 0.0);
+  comparator_.SetFractionAndMargin(field_double, 0.0, 0.0);
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_,
+                                field_float, -1, -1, NULL));
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_,
+                                field_double, -1, -1, NULL));
+}
+
+TEST_F(DefaultFieldComparatorTest,
+       FloatingPointComparisonWithinDefaultFractionOrMargin) {
+  const FieldDescriptor* field_float =
+      descriptor_->FindFieldByName("optional_float");
+  const FieldDescriptor* field_double =
+      descriptor_->FindFieldByName("optional_double");
+
+  message_1_.set_optional_float(100.0f);
+  message_2_.set_optional_float(109.9f);
+  message_1_.set_optional_double(100.0);
+  message_2_.set_optional_double(109.9);
+
+  comparator_.set_float_comparison(DefaultFieldComparator::APPROXIMATE);
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_,
+                                field_float, -1, -1, NULL));
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_,
+                                field_double, -1, -1, NULL));
+
+  // Set default fraction and margin.
+  comparator_.SetDefaultFractionAndMargin(0.01, 0.0);
+
+  // Float comparisons should fail since the fraction is too low.
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_,
+                                field_float, -1, -1, NULL));
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_,
+                                field_double, -1, -1, NULL));
+
+  // Set field-specific fraction and margin for one field (field_float) but not
+  // the other (field_double)
+  comparator_.SetFractionAndMargin(field_float, 0.2, 0.0);
+
+  // The field with the override should succeed, since its field-specific
+  // fraction is high enough.
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_,
+                                field_float, -1, -1, NULL));
+  // The field with no override should fail, since the default fraction is too
+  // low
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_,
+                                field_double, -1, -1, NULL));
+
+  // Set the default fraction and margin high enough so that fields that use
+  // the default should succeed
+  comparator_.SetDefaultFractionAndMargin(0.2, 0.0);
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_,
+                                field_double, -1, -1, NULL));
+
+  // The field with an override should still be OK
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_,
+                                field_float, -1, -1, NULL));
+
+  // Set fraction and margin for the field with an override to be too low
+  comparator_.SetFractionAndMargin(field_float, 0.01, 0.0);
+
+  // Now our default is high enough but field_float's override is too low.
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_,
+                                field_float, -1, -1, NULL));
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_,
+                                field_double, -1, -1, NULL));
+}
+
+// Simple test checking whether we compare values at correct indices.
+TEST_F(DefaultFieldComparatorTest, RepeatedFieldComparison) {
+  const FieldDescriptor* field =
+      descriptor_->FindFieldByName("repeated_string");
+
+  message_1_.add_repeated_string("foo");
+  message_1_.add_repeated_string("bar");
+  message_2_.add_repeated_string("bar");
+  message_2_.add_repeated_string("baz");
+
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_, field, 0, 0, NULL));
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_, field, 1, 1, NULL));
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_, field, 1, 0, NULL));
+}
+
+}  // namespace util
+}  // namespace protobuf
+}  // namespace
+}  // namespace google
diff --git a/src/google/protobuf/util/internal/constants.h b/src/google/protobuf/util/internal/constants.h
new file mode 100644
index 0000000..0cb8f6e
--- /dev/null
+++ b/src/google/protobuf/util/internal/constants.h
@@ -0,0 +1,93 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_PROTOBUF_UTIL_CONVERTER_CONSTANTS_H__
+#define GOOGLE_PROTOBUF_UTIL_CONVERTER_CONSTANTS_H__
+
+#include <google/protobuf/stubs/common.h>
+
+// This file contains constants used by //net/proto2/util/converter.
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+// Prefix for type URLs.
+const char kTypeServiceBaseUrl[] = "type.googleapis.com";
+
+// Format string for RFC3339 timestamp formatting.
+const char kRfc3339TimeFormat[] = "%Y-%m-%dT%H:%M:%S";
+
+// Minimum seconds allowed in a google.protobuf.TimeStamp or Duration value.
+const int64 kMinSeconds = -315576000000;
+
+// Maximum seconds allowed in a google.protobuf.TimeStamp or Duration value.
+const int64 kMaxSeconds = 315576000000;
+
+// Nano seconds in a second.
+const int32 kNanosPerSecond = 1000000000;
+
+// Type url representing NULL values in google.protobuf.Struct type.
+const char kStructNullValueTypeUrl[] =
+    "type.googleapis.com/google.protobuf.NullValue";
+
+// Type string for google.protobuf.Struct
+const char kStructType[] = "google.protobuf.Struct";
+
+// Type string for struct.proto's google.protobuf.Value value type.
+const char kStructValueType[] = "google.protobuf.Value";
+
+// Type string for struct.proto's google.protobuf.ListValue value type.
+const char kStructListValueType[] = "google.protobuf.ListValue";
+
+// Type string for google.protobuf.Timestamp
+const char kTimestampType[] = "google.protobuf.Timestamp";
+
+// Type string for google.protobuf.Duration
+const char kDurationType[] = "google.protobuf.Duration";
+
+// Type URL for struct value type google.protobuf.Value
+const char kStructValueTypeUrl[] = "type.googleapis.com/google.protobuf.Value";
+
+// Type URL for struct value type google.protobuf.Value
+const char kStructTypeUrl[] = "type.googleapis.com/google.protobuf.Struct";
+
+// Type string for google.protobuf.Any
+const char kAnyType[] = "google.protobuf.Any";
+
+// The type URL of google.protobuf.FieldMask;
+const char kFieldMaskTypeUrl[] =
+    "type.googleapis.com/google.protobuf.FieldMask";
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_CONVERTER_CONSTANTS_H__
diff --git a/src/google/protobuf/util/internal/datapiece.cc b/src/google/protobuf/util/internal/datapiece.cc
new file mode 100644
index 0000000..72b737e
--- /dev/null
+++ b/src/google/protobuf/util/internal/datapiece.cc
@@ -0,0 +1,285 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/util/internal/datapiece.h>
+
+#include <google/protobuf/struct.pb.h>
+#include <google/protobuf/type.pb.h>
+#include <google/protobuf/descriptor.h>
+#include <google/protobuf/util/internal/utility.h>
+#include <google/protobuf/stubs/strutil.h>
+#include <google/protobuf/stubs/mathutil.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+
+using google::protobuf::EnumDescriptor;
+using google::protobuf::EnumValueDescriptor;
+;
+;
+using util::error::Code;
+using util::Status;
+using util::StatusOr;
+
+namespace {
+
+inline Status InvalidArgument(StringPiece value_str) {
+  return Status(util::error::INVALID_ARGUMENT, value_str);
+}
+
+// For general conversion between
+//     int32, int64, uint32, uint64, double and float
+// except conversion between double and float.
+template <typename To, typename From>
+StatusOr<To> NumberConvertAndCheck(From before) {
+  if (::google::protobuf::internal::is_same<From, To>::value) return before;
+  To after = static_cast<To>(before);
+  if (after == before &&
+      MathUtil::Sign<From>(before) == MathUtil::Sign<To>(after)) {
+    return after;
+  } else {
+    return InvalidArgument(::google::protobuf::internal::is_integral<From>::value
+                               ? ValueAsString(before)
+                               : ::google::protobuf::internal::is_same<From, double>::value
+                                     ? DoubleAsString(before)
+                                     : FloatAsString(before));
+  }
+}
+
+// For conversion between double and float only.
+template <typename To, typename From>
+StatusOr<To> FloatingPointConvertAndCheck(From before) {
+  if (isnan(before)) return std::numeric_limits<To>::quiet_NaN();
+
+  To after = static_cast<To>(before);
+  if (MathUtil::AlmostEquals<To>(after, before)) {
+    return after;
+  } else {
+    return InvalidArgument(::google::protobuf::internal::is_same<From, double>::value
+                               ? DoubleAsString(before)
+                               : FloatAsString(before));
+  }
+}
+
+}  // namespace
+
+StatusOr<int32> DataPiece::ToInt32() const {
+  if (type_ == TYPE_STRING) {
+    return StringToNumber<int32>(safe_strto32);
+  }
+  return GenericConvert<int32>();
+}
+
+StatusOr<uint32> DataPiece::ToUint32() const {
+  if (type_ == TYPE_STRING) {
+    return StringToNumber<uint32>(safe_strtou32);
+  }
+  return GenericConvert<uint32>();
+}
+
+StatusOr<int64> DataPiece::ToInt64() const {
+  if (type_ == TYPE_STRING) {
+    return StringToNumber<int64>(safe_strto64);
+  }
+  return GenericConvert<int64>();
+}
+
+StatusOr<uint64> DataPiece::ToUint64() const {
+  if (type_ == TYPE_STRING) {
+    return StringToNumber<uint64>(safe_strtou64);
+  }
+  return GenericConvert<uint64>();
+}
+
+StatusOr<double> DataPiece::ToDouble() const {
+  if (type_ == TYPE_FLOAT) {
+    return FloatingPointConvertAndCheck<double, float>(float_);
+  }
+  if (type_ == TYPE_STRING) {
+    if (str_ == "Infinity") return std::numeric_limits<double>::infinity();
+    if (str_ == "-Infinity") return -std::numeric_limits<double>::infinity();
+    if (str_ == "NaN") return std::numeric_limits<double>::quiet_NaN();
+    return StringToNumber<double>(safe_strtod);
+  }
+  return GenericConvert<double>();
+}
+
+StatusOr<float> DataPiece::ToFloat() const {
+  if (type_ == TYPE_DOUBLE) {
+    return FloatingPointConvertAndCheck<float, double>(double_);
+  }
+  if (type_ == TYPE_STRING) {
+    if (str_ == "Infinity") return std::numeric_limits<float>::infinity();
+    if (str_ == "-Infinity") return -std::numeric_limits<float>::infinity();
+    if (str_ == "NaN") return std::numeric_limits<float>::quiet_NaN();
+    // SafeStrToFloat() is used instead of safe_strtof() because the later
+    // does not fail on inputs like SimpleDtoa(DBL_MAX).
+    return StringToNumber<float>(SafeStrToFloat);
+  }
+  return GenericConvert<float>();
+}
+
+StatusOr<bool> DataPiece::ToBool() const {
+  switch (type_) {
+    case TYPE_BOOL:
+      return bool_;
+    case TYPE_STRING:
+      return StringToNumber<bool>(safe_strtob);
+    default:
+      return InvalidArgument(
+          ValueAsStringOrDefault("Wrong type. Cannot convert to Bool."));
+  }
+}
+
+StatusOr<string> DataPiece::ToString() const {
+  switch (type_) {
+    case TYPE_STRING:
+      return str_.ToString();
+    case TYPE_BYTES: {
+      string base64;
+      WebSafeBase64Escape(str_, &base64);
+      return base64;
+    }
+    default:
+      return InvalidArgument(
+          ValueAsStringOrDefault("Cannot convert to string."));
+  }
+}
+
+string DataPiece::ValueAsStringOrDefault(StringPiece default_string) const {
+  switch (type_) {
+    case TYPE_INT32:
+      return SimpleItoa(i32_);
+    case TYPE_INT64:
+      return SimpleItoa(i64_);
+    case TYPE_UINT32:
+      return SimpleItoa(u32_);
+    case TYPE_UINT64:
+      return SimpleItoa(u64_);
+    case TYPE_DOUBLE:
+      return DoubleAsString(double_);
+    case TYPE_FLOAT:
+      return FloatAsString(float_);
+    case TYPE_BOOL:
+      return SimpleBtoa(bool_);
+    case TYPE_STRING:
+      return StrCat("\"", str_.ToString(), "\"");
+    case TYPE_BYTES: {
+      string base64;
+      WebSafeBase64Escape(str_, &base64);
+      return StrCat("\"", base64, "\"");
+    }
+    case TYPE_NULL:
+      return "null";
+    default:
+      return default_string.ToString();
+  }
+}
+
+StatusOr<string> DataPiece::ToBytes() const {
+  if (type_ == TYPE_BYTES) return str_.ToString();
+  if (type_ == TYPE_STRING) {
+    string decoded;
+    if (!WebSafeBase64Unescape(str_, &decoded)) {
+      if (!Base64Unescape(str_, &decoded)) {
+        return InvalidArgument(
+            ValueAsStringOrDefault("Invalid data in input."));
+      }
+    }
+    return decoded;
+  } else {
+    return InvalidArgument(ValueAsStringOrDefault(
+        "Wrong type. Only String or Bytes can be converted to Bytes."));
+  }
+}
+
+StatusOr<int> DataPiece::ToEnum(const google::protobuf::Enum* enum_type) const {
+  if (type_ == TYPE_NULL) return google::protobuf::NULL_VALUE;
+
+  if (type_ == TYPE_STRING) {
+    // First try the given value as a name.
+    string enum_name = str_.ToString();
+    const google::protobuf::EnumValue* value =
+        FindEnumValueByNameOrNull(enum_type, enum_name);
+    if (value != NULL) return value->number();
+    // Next try a normalized name.
+    for (string::iterator it = enum_name.begin(); it != enum_name.end(); ++it) {
+      *it = *it == '-' ? '_' : ascii_toupper(*it);
+    }
+    value = FindEnumValueByNameOrNull(enum_type, enum_name);
+    if (value != NULL) return value->number();
+  } else {
+    StatusOr<int32> value = ToInt32();
+    if (value.ok()) {
+      if (const google::protobuf::EnumValue* enum_value =
+              FindEnumValueByNumberOrNull(enum_type, value.ValueOrDie())) {
+        return enum_value->number();
+      }
+    }
+  }
+  return InvalidArgument(
+      ValueAsStringOrDefault("Cannot find enum with given value."));
+}
+
+template <typename To>
+StatusOr<To> DataPiece::GenericConvert() const {
+  switch (type_) {
+    case TYPE_INT32:
+      return NumberConvertAndCheck<To, int32>(i32_);
+    case TYPE_INT64:
+      return NumberConvertAndCheck<To, int64>(i64_);
+    case TYPE_UINT32:
+      return NumberConvertAndCheck<To, uint32>(u32_);
+    case TYPE_UINT64:
+      return NumberConvertAndCheck<To, uint64>(u64_);
+    case TYPE_DOUBLE:
+      return NumberConvertAndCheck<To, double>(double_);
+    case TYPE_FLOAT:
+      return NumberConvertAndCheck<To, float>(float_);
+    default:  // TYPE_ENUM, TYPE_STRING, TYPE_CORD, TYPE_BOOL
+      return InvalidArgument(ValueAsStringOrDefault(
+          "Wrong type. Bool, Enum, String and Cord not supported in "
+          "GenericConvert."));
+  }
+}
+
+template <typename To>
+StatusOr<To> DataPiece::StringToNumber(bool (*func)(StringPiece, To*)) const {
+  To result;
+  if (func(str_, &result)) return result;
+  return InvalidArgument(StrCat("\"", str_.ToString(), "\""));
+}
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/internal/datapiece.h b/src/google/protobuf/util/internal/datapiece.h
new file mode 100644
index 0000000..3094725
--- /dev/null
+++ b/src/google/protobuf/util/internal/datapiece.h
@@ -0,0 +1,212 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_PROTOBUF_UTIL_CONVERTER_DATAPIECE_H__
+#define GOOGLE_PROTOBUF_UTIL_CONVERTER_DATAPIECE_H__
+
+#include <string>
+
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/stubs/stringpiece.h>
+#include <google/protobuf/stubs/statusor.h>
+
+
+namespace google {
+namespace protobuf {
+class Enum;
+}  // namespace protobuf
+
+
+namespace protobuf {
+namespace util {
+namespace converter {
+
+// Container for a single piece of data together with its data type.
+//
+// For primitive types (int32, int64, uint32, uint64, double, float, bool),
+// the data is stored by value.
+//
+// For string, a StringPiece is stored. For Cord, a pointer to Cord is stored.
+// Just like StringPiece, the DataPiece class does not own the storage for
+// the actual string or Cord, so it is the user's responsiblity to guarantee
+// that the underlying storage is still valid when the DataPiece is accessed.
+class LIBPROTOBUF_EXPORT DataPiece {
+ public:
+  // Identifies data type of the value.
+  // These are the types supported by DataPiece.
+  enum Type {
+    TYPE_INT32 = 1,
+    TYPE_INT64 = 2,
+    TYPE_UINT32 = 3,
+    TYPE_UINT64 = 4,
+    TYPE_DOUBLE = 5,
+    TYPE_FLOAT = 6,
+    TYPE_BOOL = 7,
+    TYPE_ENUM = 8,
+    TYPE_STRING = 9,
+    TYPE_BYTES = 10,
+    TYPE_NULL = 11,  // explicit NULL type
+  };
+
+  // Constructors and Destructor
+  explicit DataPiece(const int32 value) : type_(TYPE_INT32), i32_(value) {}
+  explicit DataPiece(const int64 value) : type_(TYPE_INT64), i64_(value) {}
+  explicit DataPiece(const uint32 value) : type_(TYPE_UINT32), u32_(value) {}
+  explicit DataPiece(const uint64 value) : type_(TYPE_UINT64), u64_(value) {}
+  explicit DataPiece(const double value) : type_(TYPE_DOUBLE), double_(value) {}
+  explicit DataPiece(const float value) : type_(TYPE_FLOAT), float_(value) {}
+  explicit DataPiece(const bool value) : type_(TYPE_BOOL), bool_(value) {}
+  explicit DataPiece(StringPiece value)
+      : type_(TYPE_STRING),
+        str_(StringPiecePod::CreateFromStringPiece(value)) {}
+  // Constructor for bytes. The second parameter is not used.
+  explicit DataPiece(StringPiece value, bool dummy)
+      : type_(TYPE_BYTES), str_(StringPiecePod::CreateFromStringPiece(value)) {}
+  DataPiece(const DataPiece& r) : type_(r.type_), str_(r.str_) {}
+  DataPiece& operator=(const DataPiece& x) {
+    type_ = x.type_;
+    str_ = x.str_;
+    return *this;
+  }
+
+  static DataPiece NullData() { return DataPiece(TYPE_NULL, 0); }
+
+  virtual ~DataPiece() {}
+
+  // Accessors
+  Type type() const { return type_; }
+
+  StringPiece str() const {
+    GOOGLE_LOG_IF(DFATAL, type_ != TYPE_STRING) << "Not a string type.";
+    return str_;
+  }
+
+
+  // Parses, casts or converts the value stored in the DataPiece into an int32.
+  util::StatusOr<int32> ToInt32() const;
+
+  // Parses, casts or converts the value stored in the DataPiece into a uint32.
+  util::StatusOr<uint32> ToUint32() const;
+
+  // Parses, casts or converts the value stored in the DataPiece into an int64.
+  util::StatusOr<int64> ToInt64() const;
+
+  // Parses, casts or converts the value stored in the DataPiece into a uint64.
+  util::StatusOr<uint64> ToUint64() const;
+
+  // Parses, casts or converts the value stored in the DataPiece into a double.
+  util::StatusOr<double> ToDouble() const;
+
+  // Parses, casts or converts the value stored in the DataPiece into a float.
+  util::StatusOr<float> ToFloat() const;
+
+  // Parses, casts or converts the value stored in the DataPiece into a bool.
+  util::StatusOr<bool> ToBool() const;
+
+  // Parses, casts or converts the value stored in the DataPiece into a string.
+  util::StatusOr<string> ToString() const;
+
+  // Tries to convert the value contained in this datapiece to string. If the
+  // conversion fails, it returns the default_string.
+  string ValueAsStringOrDefault(StringPiece default_string) const;
+
+  util::StatusOr<string> ToBytes() const;
+
+  // Converts a value into protocol buffer enum number. If the value is a
+  // string, first attempts conversion by name, trying names as follows:
+  //   1) the directly provided string value.
+  //   2) the value upper-cased and replacing '-' by '_'
+  // If the value is not a string, attempts to convert to a 32-bit integer.
+  // If none of these succeeds, returns a conversion error status.
+  util::StatusOr<int> ToEnum(const google::protobuf::Enum* enum_type) const;
+
+ private:
+  // Disallow implicit constructor.
+  DataPiece();
+
+  // Helper to create NULL or ENUM types.
+  DataPiece(Type type, int32 val) : type_(type), i32_(val) {}
+
+  // For numeric conversion between
+  //     int32, int64, uint32, uint64, double, float and bool
+  template <typename To>
+  util::StatusOr<To> GenericConvert() const;
+
+  // For conversion from string to
+  //     int32, int64, uint32, uint64, double, float and bool
+  template <typename To>
+  util::StatusOr<To> StringToNumber(bool (*func)(StringPiece, To*)) const;
+
+  // Data type for this piece of data.
+  Type type_;
+
+  // StringPiece is not a POD and can not be used in an union (pre C++11). We
+  // need a POD version of it.
+  struct StringPiecePod {
+    const char* data;
+    int size;
+
+    // Create from a StringPiece.
+    static StringPiecePod CreateFromStringPiece(StringPiece str) {
+      StringPiecePod pod;
+      pod.data = str.data();
+      pod.size = str.size();
+      return pod;
+    }
+
+    // Cast to StringPiece.
+    operator StringPiece() const { return StringPiece(data, size); }
+
+    bool operator==(const char* value) const {
+      return StringPiece(data, size) == StringPiece(value);
+    }
+
+    string ToString() const { return string(data, size); }
+  };
+
+  // Stored piece of data.
+  union {
+    const int32 i32_;
+    const int64 i64_;
+    const uint32 u32_;
+    const uint64 u64_;
+    const double double_;
+    const float float_;
+    const bool bool_;
+    StringPiecePod str_;
+  };
+};
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_CONVERTER_DATAPIECE_H__
diff --git a/src/google/protobuf/util/internal/default_value_objectwriter.cc b/src/google/protobuf/util/internal/default_value_objectwriter.cc
new file mode 100644
index 0000000..267e2cd
--- /dev/null
+++ b/src/google/protobuf/util/internal/default_value_objectwriter.cc
@@ -0,0 +1,515 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/util/internal/default_value_objectwriter.h>
+
+#include <google/protobuf/stubs/hash.h>
+
+#include <google/protobuf/util/internal/constants.h>
+#include <google/protobuf/stubs/map_util.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+using util::Status;
+using util::StatusOr;
+namespace converter {
+
+DefaultValueObjectWriter::DefaultValueObjectWriter(
+    TypeResolver* type_resolver, const google::protobuf::Type& type,
+    ObjectWriter* ow)
+    : typeinfo_(TypeInfo::NewTypeInfo(type_resolver)),
+      type_(type),
+      disable_normalize_(false),
+      current_(NULL),
+      root_(NULL),
+      ow_(ow) {}
+
+DefaultValueObjectWriter::~DefaultValueObjectWriter() {
+  for (int i = 0; i < string_values_.size(); ++i) {
+    delete string_values_[i];
+  }
+}
+
+DefaultValueObjectWriter* DefaultValueObjectWriter::RenderBool(StringPiece name,
+                                                               bool value) {
+  if (current_ == NULL) {
+    ow_->RenderBool(name, value);
+  } else {
+    RenderDataPiece(name, DataPiece(value));
+  }
+  return this;
+}
+
+DefaultValueObjectWriter* DefaultValueObjectWriter::RenderInt32(
+    StringPiece name, int32 value) {
+  if (current_ == NULL) {
+    ow_->RenderInt32(name, value);
+  } else {
+    RenderDataPiece(name, DataPiece(value));
+  }
+  return this;
+}
+
+DefaultValueObjectWriter* DefaultValueObjectWriter::RenderUint32(
+    StringPiece name, uint32 value) {
+  if (current_ == NULL) {
+    ow_->RenderUint32(name, value);
+  } else {
+    RenderDataPiece(name, DataPiece(value));
+  }
+  return this;
+}
+
+DefaultValueObjectWriter* DefaultValueObjectWriter::RenderInt64(
+    StringPiece name, int64 value) {
+  if (current_ == NULL) {
+    ow_->RenderInt64(name, value);
+  } else {
+    RenderDataPiece(name, DataPiece(value));
+  }
+  return this;
+}
+
+DefaultValueObjectWriter* DefaultValueObjectWriter::RenderUint64(
+    StringPiece name, uint64 value) {
+  if (current_ == NULL) {
+    ow_->RenderUint64(name, value);
+  } else {
+    RenderDataPiece(name, DataPiece(value));
+  }
+  return this;
+}
+
+DefaultValueObjectWriter* DefaultValueObjectWriter::RenderDouble(
+    StringPiece name, double value) {
+  if (current_ == NULL) {
+    ow_->RenderDouble(name, value);
+  } else {
+    RenderDataPiece(name, DataPiece(value));
+  }
+  return this;
+}
+
+DefaultValueObjectWriter* DefaultValueObjectWriter::RenderFloat(
+    StringPiece name, float value) {
+  if (current_ == NULL) {
+    ow_->RenderBool(name, value);
+  } else {
+    RenderDataPiece(name, DataPiece(value));
+  }
+  return this;
+}
+
+DefaultValueObjectWriter* DefaultValueObjectWriter::RenderString(
+    StringPiece name, StringPiece value) {
+  if (current_ == NULL) {
+    ow_->RenderString(name, value);
+  } else {
+    // Since StringPiece is essentially a pointer, takes a copy of "value" to
+    // avoid ownership issues.
+    string_values_.push_back(new string(value.ToString()));
+    RenderDataPiece(name, DataPiece(*string_values_.back()));
+  }
+  return this;
+}
+
+DefaultValueObjectWriter* DefaultValueObjectWriter::RenderBytes(
+    StringPiece name, StringPiece value) {
+  if (current_ == NULL) {
+    ow_->RenderBytes(name, value);
+  } else {
+    RenderDataPiece(name, DataPiece(value));
+  }
+  return this;
+}
+
+DefaultValueObjectWriter* DefaultValueObjectWriter::RenderNull(
+    StringPiece name) {
+  if (current_ == NULL) {
+    ow_->RenderNull(name);
+  } else {
+    RenderDataPiece(name, DataPiece::NullData());
+  }
+  return this;
+}
+
+DefaultValueObjectWriter*
+DefaultValueObjectWriter::DisableCaseNormalizationForNextKey() {
+  disable_normalize_ = true;
+  return this;
+}
+
+DefaultValueObjectWriter::Node::Node(const string& name,
+                                     const google::protobuf::Type* type,
+                                     NodeKind kind, const DataPiece& data,
+                                     bool is_placeholder)
+    : name_(name),
+      type_(type),
+      kind_(kind),
+      disable_normalize_(false),
+      is_any_(false),
+      data_(data),
+      is_placeholder_(is_placeholder) {}
+
+DefaultValueObjectWriter::Node* DefaultValueObjectWriter::Node::FindChild(
+    StringPiece name) {
+  if (name.empty() || kind_ != OBJECT) {
+    return NULL;
+  }
+  for (int i = 0; i < children_.size(); ++i) {
+    Node* child = children_[i];
+    if (child->name() == name) {
+      return child;
+    }
+  }
+  return NULL;
+}
+
+void DefaultValueObjectWriter::Node::WriteTo(ObjectWriter* ow) {
+  if (disable_normalize_) {
+    ow->DisableCaseNormalizationForNextKey();
+  }
+  if (kind_ == PRIMITIVE) {
+    ObjectWriter::RenderDataPieceTo(data_, name_, ow);
+    return;
+  }
+  if (is_placeholder_) {
+    // If is_placeholder_ = true, we didn't see this node in the response, so
+    // skip output.
+    return;
+  }
+  if (kind_ == LIST) {
+    ow->StartList(name_);
+  } else {
+    ow->StartObject(name_);
+  }
+  for (int i = 0; i < children_.size(); ++i) {
+    Node* child = children_[i];
+    child->WriteTo(ow);
+  }
+  if (kind_ == LIST) {
+    ow->EndList();
+  } else {
+    ow->EndObject();
+  }
+}
+
+const google::protobuf::Type* DefaultValueObjectWriter::Node::GetMapValueType(
+    const google::protobuf::Type& found_type, TypeInfo* typeinfo) {
+  // If this field is a map, we should use the type of its "Value" as
+  // the type of the child node.
+  for (int i = 0; i < found_type.fields_size(); ++i) {
+    const google::protobuf::Field& sub_field = found_type.fields(i);
+    if (sub_field.number() != 2) {
+      continue;
+    }
+    if (sub_field.kind() != google::protobuf::Field_Kind_TYPE_MESSAGE) {
+      // This map's value type is not a message type. We don't need to
+      // get the field_type in this case.
+      break;
+    }
+    util::StatusOr<const google::protobuf::Type*> sub_type =
+        typeinfo->ResolveTypeUrl(sub_field.type_url());
+    if (!sub_type.ok()) {
+      GOOGLE_LOG(WARNING) << "Cannot resolve type '" << sub_field.type_url() << "'.";
+    } else {
+      return sub_type.ValueOrDie();
+    }
+    break;
+  }
+  return NULL;
+}
+
+void DefaultValueObjectWriter::Node::PopulateChildren(TypeInfo* typeinfo) {
+  // Ignores well known types that don't require automatically populating their
+  // primitive children. For type "Any", we only populate its children when the
+  // "@type" field is set.
+  // TODO(tsun): remove "kStructValueType" from the list. It's being checked
+  //     now because of a bug in the tool-chain that causes the "oneof_index"
+  //     of kStructValueType to not be set correctly.
+  if (type_ == NULL || type_->name() == kAnyType ||
+      type_->name() == kStructType || type_->name() == kTimestampType ||
+      type_->name() == kDurationType || type_->name() == kStructValueType) {
+    return;
+  }
+  std::vector<Node*> new_children;
+  hash_map<string, int> orig_children_map;
+
+  // Creates a map of child nodes to speed up lookup.
+  for (int i = 0; i < children_.size(); ++i) {
+    InsertIfNotPresent(&orig_children_map, children_[i]->name_, i);
+  }
+
+  for (int i = 0; i < type_->fields_size(); ++i) {
+    const google::protobuf::Field& field = type_->fields(i);
+    hash_map<string, int>::iterator found =
+        orig_children_map.find(field.name());
+    // If the child field has already been set, we just add it to the new list
+    // of children.
+    if (found != orig_children_map.end()) {
+      new_children.push_back(children_[found->second]);
+      children_[found->second] = NULL;
+      continue;
+    }
+
+    const google::protobuf::Type* field_type = NULL;
+    bool is_map = false;
+    NodeKind kind = PRIMITIVE;
+
+    if (field.kind() == google::protobuf::Field_Kind_TYPE_MESSAGE) {
+      kind = OBJECT;
+      util::StatusOr<const google::protobuf::Type*> found_result =
+          typeinfo->ResolveTypeUrl(field.type_url());
+      if (!found_result.ok()) {
+        // "field" is of an unknown type.
+        GOOGLE_LOG(WARNING) << "Cannot resolve type '" << field.type_url() << "'.";
+      } else {
+        const google::protobuf::Type* found_type = found_result.ValueOrDie();
+        is_map = IsMap(field, *found_type);
+
+        if (!is_map) {
+          field_type = found_type;
+        } else {
+          // If this field is a map, we should use the type of its "Value" as
+          // the type of the child node.
+          field_type = GetMapValueType(*found_type, typeinfo);
+          kind = MAP;
+        }
+      }
+    }
+    if (!is_map &&
+        field.cardinality() ==
+            google::protobuf::Field_Cardinality_CARDINALITY_REPEATED) {
+      kind = LIST;
+    }
+    // If the child field is of primitive type, sets its data to the default
+    // value of its type.
+    // If oneof_index() != 0, the child field is part of a "oneof", which means
+    // the child field is optional and we shouldn't populate its default value.
+    google::protobuf::scoped_ptr<Node> child(
+        new Node(field.name(), field_type, kind,
+                 ((kind == PRIMITIVE && field.oneof_index() == 0)
+                      ? CreateDefaultDataPieceForField(field)
+                      : DataPiece::NullData()),
+                 true));
+    new_children.push_back(child.release());
+  }
+  // Adds all leftover nodes in children_ to the beginning of new_child.
+  for (int i = 0; i < children_.size(); ++i) {
+    if (children_[i] == NULL) {
+      continue;
+    }
+    new_children.insert(new_children.begin(), children_[i]);
+    children_[i] = NULL;
+  }
+  children_.swap(new_children);
+}
+
+void DefaultValueObjectWriter::MaybePopulateChildrenOfAny(Node* node) {
+  // If this is an "Any" node with "@type" already given and no other children
+  // have been added, populates its children.
+  if (node != NULL && node->is_any() && node->type() != NULL &&
+      node->type()->name() != kAnyType && node->number_of_children() == 1) {
+    node->PopulateChildren(typeinfo_.get());
+  }
+}
+
+DataPiece DefaultValueObjectWriter::CreateDefaultDataPieceForField(
+    const google::protobuf::Field& field) {
+  switch (field.kind()) {
+    case google::protobuf::Field_Kind_TYPE_DOUBLE: {
+      return DataPiece(static_cast<double>(0));
+    }
+    case google::protobuf::Field_Kind_TYPE_FLOAT: {
+      return DataPiece(static_cast<float>(0));
+    }
+    case google::protobuf::Field_Kind_TYPE_INT64:
+    case google::protobuf::Field_Kind_TYPE_SINT64:
+    case google::protobuf::Field_Kind_TYPE_SFIXED64: {
+      return DataPiece(static_cast<int64>(0));
+    }
+    case google::protobuf::Field_Kind_TYPE_UINT64:
+    case google::protobuf::Field_Kind_TYPE_FIXED64: {
+      return DataPiece(static_cast<uint64>(0));
+    }
+    case google::protobuf::Field_Kind_TYPE_INT32:
+    case google::protobuf::Field_Kind_TYPE_SINT32:
+    case google::protobuf::Field_Kind_TYPE_SFIXED32: {
+      return DataPiece(static_cast<int32>(0));
+    }
+    case google::protobuf::Field_Kind_TYPE_BOOL: {
+      return DataPiece(false);
+    }
+    case google::protobuf::Field_Kind_TYPE_STRING: {
+      return DataPiece(string());
+    }
+    case google::protobuf::Field_Kind_TYPE_BYTES: {
+      return DataPiece("", false);
+    }
+    case google::protobuf::Field_Kind_TYPE_UINT32:
+    case google::protobuf::Field_Kind_TYPE_FIXED32: {
+      return DataPiece(static_cast<uint32>(0));
+    }
+    default: { return DataPiece::NullData(); }
+  }
+}
+
+DefaultValueObjectWriter* DefaultValueObjectWriter::StartObject(
+    StringPiece name) {
+  if (current_ == NULL) {
+    root_.reset(new Node(name.ToString(), &type_, OBJECT, DataPiece::NullData(),
+                         false));
+    root_->set_disable_normalize(GetAndResetDisableNormalize());
+    root_->PopulateChildren(typeinfo_.get());
+    current_ = root_.get();
+    return this;
+  }
+  MaybePopulateChildrenOfAny(current_);
+  Node* child = current_->FindChild(name);
+  if (current_->kind() == LIST || current_->kind() == MAP || child == NULL) {
+    // If current_ is a list or a map node, we should create a new child and use
+    // the type of current_ as the type of the new child.
+    google::protobuf::scoped_ptr<Node> node(new Node(
+        name.ToString(), ((current_->kind() == LIST || current_->kind() == MAP)
+                              ? current_->type()
+                              : NULL),
+        OBJECT, DataPiece::NullData(), false));
+    child = node.get();
+    current_->AddChild(node.release());
+  }
+
+  child->set_is_placeholder(false);
+  child->set_disable_normalize(GetAndResetDisableNormalize());
+  if (child->kind() == OBJECT && child->number_of_children() == 0) {
+    child->PopulateChildren(typeinfo_.get());
+  }
+
+  stack_.push(current_);
+  current_ = child;
+  return this;
+}
+
+DefaultValueObjectWriter* DefaultValueObjectWriter::EndObject() {
+  if (stack_.empty()) {
+    // The root object ends here. Writes out the tree.
+    WriteRoot();
+    return this;
+  }
+  current_ = stack_.top();
+  stack_.pop();
+  return this;
+}
+
+DefaultValueObjectWriter* DefaultValueObjectWriter::StartList(
+    StringPiece name) {
+  if (current_ == NULL) {
+    root_.reset(
+        new Node(name.ToString(), &type_, LIST, DataPiece::NullData(), false));
+    root_->set_disable_normalize(GetAndResetDisableNormalize());
+    current_ = root_.get();
+    return this;
+  }
+  MaybePopulateChildrenOfAny(current_);
+  Node* child = current_->FindChild(name);
+  if (child == NULL || child->kind() != LIST) {
+    GOOGLE_LOG(WARNING) << "Cannot find field '" << name << "'.";
+    google::protobuf::scoped_ptr<Node> node(
+        new Node(name.ToString(), NULL, LIST, DataPiece::NullData(), false));
+    child = node.get();
+    current_->AddChild(node.release());
+  }
+  child->set_is_placeholder(false);
+  child->set_disable_normalize(GetAndResetDisableNormalize());
+
+  stack_.push(current_);
+  current_ = child;
+  return this;
+}
+
+void DefaultValueObjectWriter::WriteRoot() {
+  root_->WriteTo(ow_);
+  root_.reset(NULL);
+  current_ = NULL;
+}
+
+DefaultValueObjectWriter* DefaultValueObjectWriter::EndList() {
+  if (stack_.empty()) {
+    WriteRoot();
+    return this;
+  }
+  current_ = stack_.top();
+  stack_.pop();
+  return this;
+}
+
+void DefaultValueObjectWriter::RenderDataPiece(StringPiece name,
+                                               const DataPiece& data) {
+  MaybePopulateChildrenOfAny(current_);
+  util::StatusOr<string> data_string = data.ToString();
+  if (current_->type() != NULL && current_->type()->name() == kAnyType &&
+      name == "@type" && data_string.ok()) {
+    const string& string_value = data_string.ValueOrDie();
+    // If the type of current_ is "Any" and its "@type" field is being set here,
+    // sets the type of current_ to be the type specified by the "@type".
+    util::StatusOr<const google::protobuf::Type*> found_type =
+        typeinfo_->ResolveTypeUrl(string_value);
+    if (!found_type.ok()) {
+      GOOGLE_LOG(WARNING) << "Failed to resolve type '" << string_value << "'.";
+    } else {
+      current_->set_type(found_type.ValueOrDie());
+    }
+    current_->set_is_any(true);
+    // If the "@type" field is placed after other fields, we should populate
+    // other children of primitive type now. Otherwise, we should wait until the
+    // first value field is rendered before we populate the children, because
+    // the "value" field of a Any message could be omitted.
+    if (current_->number_of_children() > 1 && current_->type() != NULL) {
+      current_->PopulateChildren(typeinfo_.get());
+    }
+  }
+  Node* child = current_->FindChild(name);
+  if (child == NULL || child->kind() != PRIMITIVE) {
+    GOOGLE_LOG(WARNING) << "Cannot find primitive field '" << name << "'.";
+    // No children are found, creates a new child.
+    google::protobuf::scoped_ptr<Node> node(
+        new Node(name.ToString(), NULL, PRIMITIVE, data, false));
+    child = node.get();
+    current_->AddChild(node.release());
+  } else {
+    child->set_data(data);
+  }
+  child->set_disable_normalize(GetAndResetDisableNormalize());
+}
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/internal/default_value_objectwriter.h b/src/google/protobuf/util/internal/default_value_objectwriter.h
new file mode 100644
index 0000000..ae013aa
--- /dev/null
+++ b/src/google/protobuf/util/internal/default_value_objectwriter.h
@@ -0,0 +1,238 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_PROTOBUF_UTIL_CONVERTER_DEFAULT_VALUE_OBJECTWRITER_H__
+#define GOOGLE_PROTOBUF_UTIL_CONVERTER_DEFAULT_VALUE_OBJECTWRITER_H__
+
+#include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
+#include <stack>
+#include <vector>
+
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/util/internal/type_info.h>
+#include <google/protobuf/util/internal/datapiece.h>
+#include <google/protobuf/util/internal/object_writer.h>
+#include <google/protobuf/util/internal/utility.h>
+#include <google/protobuf/util/type_resolver.h>
+#include <google/protobuf/stubs/stringpiece.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+
+// An ObjectWriter that renders non-repeated primitive fields of proto messages
+// with their default values. DefaultValueObjectWriter holds objects, lists and
+// fields it receives in a tree structure and writes them out to another
+// ObjectWriter when EndObject() is called on the root object. It also writes
+// out all non-repeated primitive fields that haven't been explicitly rendered
+// with their default values (0 for numbers, "" for strings, etc).
+class DefaultValueObjectWriter : public ObjectWriter {
+ public:
+  DefaultValueObjectWriter(TypeResolver* type_resolver,
+                           const google::protobuf::Type& type,
+                           ObjectWriter* ow);
+
+  virtual ~DefaultValueObjectWriter();
+
+  // ObjectWriter methods.
+  virtual DefaultValueObjectWriter* StartObject(StringPiece name);
+
+  virtual DefaultValueObjectWriter* EndObject();
+
+  virtual DefaultValueObjectWriter* StartList(StringPiece name);
+
+  virtual DefaultValueObjectWriter* EndList();
+
+  virtual DefaultValueObjectWriter* RenderBool(StringPiece name, bool value);
+
+  virtual DefaultValueObjectWriter* RenderInt32(StringPiece name, int32 value);
+
+  virtual DefaultValueObjectWriter* RenderUint32(StringPiece name,
+                                                 uint32 value);
+
+  virtual DefaultValueObjectWriter* RenderInt64(StringPiece name, int64 value);
+
+  virtual DefaultValueObjectWriter* RenderUint64(StringPiece name,
+                                                 uint64 value);
+
+  virtual DefaultValueObjectWriter* RenderDouble(StringPiece name,
+                                                 double value);
+
+  virtual DefaultValueObjectWriter* RenderFloat(StringPiece name, float value);
+
+  virtual DefaultValueObjectWriter* RenderString(StringPiece name,
+                                                 StringPiece value);
+  virtual DefaultValueObjectWriter* RenderBytes(StringPiece name,
+                                                StringPiece value);
+
+  virtual DefaultValueObjectWriter* RenderNull(StringPiece name);
+
+  virtual DefaultValueObjectWriter* DisableCaseNormalizationForNextKey();
+
+ private:
+  enum NodeKind {
+    PRIMITIVE = 0,
+    OBJECT = 1,
+    LIST = 2,
+    MAP = 3,
+  };
+
+  // "Node" represents a node in the tree that holds the input of
+  // DefaultValueObjectWriter.
+  class Node {
+   public:
+    Node(const string& name, const google::protobuf::Type* type, NodeKind kind,
+         const DataPiece& data, bool is_placeholder);
+    virtual ~Node() {
+      for (int i = 0; i < children_.size(); ++i) {
+        delete children_[i];
+      }
+    }
+
+    // Adds a child to this node. Takes ownership of this child.
+    void AddChild(Node* child) { children_.push_back(child); }
+
+    // Finds the child given its name.
+    Node* FindChild(StringPiece name);
+
+    // Populates children of this Node based on its type. If there are already
+    // children created, they will be merged to the result. Caller should pass
+    // in TypeInfo for looking up types of the children.
+    void PopulateChildren(TypeInfo* typeinfo);
+
+    // If this node is a leaf (has data), writes the current node to the
+    // ObjectWriter; if not, then recursively writes the children to the
+    // ObjectWriter.
+    void WriteTo(ObjectWriter* ow);
+
+    // Accessors
+    const string& name() const { return name_; }
+
+    const google::protobuf::Type* type() { return type_; }
+
+    void set_type(const google::protobuf::Type* type) { type_ = type; }
+
+    NodeKind kind() { return kind_; }
+
+    int number_of_children() { return children_.size(); }
+
+    void set_data(const DataPiece& data) { data_ = data; }
+
+    void set_disable_normalize(bool disable_normalize) {
+      disable_normalize_ = disable_normalize;
+    }
+
+    bool is_any() { return is_any_; }
+
+    void set_is_any(bool is_any) { is_any_ = is_any; }
+
+    void set_is_placeholder(bool is_placeholder) {
+      is_placeholder_ = is_placeholder;
+    }
+
+   private:
+    // Returns the Value Type of a map given the Type of the map entry and a
+    // TypeInfo instance.
+    const google::protobuf::Type* GetMapValueType(
+        const google::protobuf::Type& entry_type, TypeInfo* typeinfo);
+
+    // The name of this node.
+    string name_;
+    // google::protobuf::Type of this node. Owned by TypeInfo.
+    const google::protobuf::Type* type_;
+    // The kind of this node.
+    NodeKind kind_;
+    // Whether to disable case normalization of the name.
+    bool disable_normalize_;
+    // Whether this is a node for "Any".
+    bool is_any_;
+    // The data of this node when it is a leaf node.
+    DataPiece data_;
+    // Children of this node.
+    std::vector<Node*> children_;
+    // Whether this node is a placeholder for an object or list automatically
+    // generated when creating the parent node. Should be set to false after
+    // the parent node's StartObject()/StartList() method is called with this
+    // node's name.
+    bool is_placeholder_;
+  };
+
+  // Populates children of "node" if it is an "any" Node and its real type has
+  // been given.
+  void MaybePopulateChildrenOfAny(Node* node);
+
+  // Writes the root_ node to ow_ and resets the root_ and current_ pointer to
+  // NULL.
+  void WriteRoot();
+
+  // Creates a DataPiece containing the default value of the type of the field.
+  static DataPiece CreateDefaultDataPieceForField(
+      const google::protobuf::Field& field);
+
+  // Returns disable_normalize_ and reset it to false.
+  bool GetAndResetDisableNormalize() {
+    return disable_normalize_ ? (disable_normalize_ = false, true) : false;
+  }
+
+  // Adds or replaces the data_ of a primitive child node.
+  void RenderDataPiece(StringPiece name, const DataPiece& data);
+
+  // Type information for all the types used in the descriptor. Used to find
+  // google::protobuf::Type of nested messages/enums.
+  google::protobuf::scoped_ptr<TypeInfo> typeinfo_;
+  // google::protobuf::Type of the root message type.
+  const google::protobuf::Type& type_;
+  // Holds copies of strings passed to RenderString.
+  vector<string*> string_values_;
+
+  // Whether to disable case normalization of the next node.
+  bool disable_normalize_;
+  // The current Node. Owned by its parents.
+  Node* current_;
+  // The root Node.
+  google::protobuf::scoped_ptr<Node> root_;
+  // The stack to hold the path of Nodes from current_ to root_;
+  std::stack<Node*> stack_;
+
+  ObjectWriter* ow_;
+
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(DefaultValueObjectWriter);
+};
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_CONVERTER_DEFAULT_VALUE_OBJECTWRITER_H__
diff --git a/src/google/protobuf/util/internal/default_value_objectwriter_test.cc b/src/google/protobuf/util/internal/default_value_objectwriter_test.cc
new file mode 100644
index 0000000..593c710
--- /dev/null
+++ b/src/google/protobuf/util/internal/default_value_objectwriter_test.cc
@@ -0,0 +1,139 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/util/internal/default_value_objectwriter.h>
+#include <google/protobuf/util/internal/expecting_objectwriter.h>
+#include <google/protobuf/util/internal/testdata/default_value_test.pb.h>
+#include <google/protobuf/util/internal/type_info_test_helper.h>
+#include <google/protobuf/util/internal/constants.h>
+#include <gtest/gtest.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+namespace testing {
+
+using google::protobuf::testing::DefaultValueTest;
+
+// Tests to cover some basic DefaultValueObjectWriter use cases. More tests are
+// in the marshalling_test.cc and translator_integration_test.cc.
+class DefaultValueObjectWriterTest
+    : public ::testing::TestWithParam<testing::TypeInfoSource> {
+ protected:
+  DefaultValueObjectWriterTest()
+      : helper_(GetParam()), mock_(), expects_(&mock_) {
+    helper_.ResetTypeInfo(DefaultValueTest::descriptor());
+    testing_.reset(helper_.NewDefaultValueWriter(
+        string(kTypeServiceBaseUrl) + "/" +
+            DefaultValueTest::descriptor()->full_name(),
+        &mock_));
+  }
+
+  virtual ~DefaultValueObjectWriterTest() {}
+
+  TypeInfoTestHelper helper_;
+  MockObjectWriter mock_;
+  ExpectingObjectWriter expects_;
+  google::protobuf::scoped_ptr<DefaultValueObjectWriter> testing_;
+};
+
+INSTANTIATE_TEST_CASE_P(DifferentTypeInfoSourceTest,
+                        DefaultValueObjectWriterTest,
+                        ::testing::Values(
+                            testing::USE_TYPE_RESOLVER));
+
+TEST_P(DefaultValueObjectWriterTest, Empty) {
+  // Set expectation
+  expects_.StartObject("")
+      ->RenderDouble("double_value", 0.0)
+      ->RenderFloat("float_value", 0.0)
+      ->RenderInt64("int64_value", 0)
+      ->RenderUint64("uint64_value", 0)
+      ->RenderInt32("int32_value", 0)
+      ->RenderUint32("uint32_value", 0)
+      ->RenderBool("bool_value", false)
+      ->RenderString("string_value", "")
+      ->RenderBytes("bytes_value", "")
+      ->EndObject();
+
+  // Actual testing
+  testing_->StartObject("")->EndObject();
+}
+
+TEST_P(DefaultValueObjectWriterTest, NonDefaultDouble) {
+  // Set expectation
+  expects_.StartObject("")
+      ->RenderDouble("double_value", 1.0)
+      ->RenderFloat("float_value", 0.0)
+      ->RenderInt64("int64_value", 0)
+      ->RenderUint64("uint64_value", 0)
+      ->RenderInt32("int32_value", 0)
+      ->RenderUint32("uint32_value", 0)
+      ->RenderBool("bool_value", false)
+      ->RenderString("string_value", "")
+      ->EndObject();
+
+  // Actual testing
+  testing_->StartObject("")->RenderDouble("double_value", 1.0)->EndObject();
+}
+
+TEST_P(DefaultValueObjectWriterTest, ShouldRetainUnknownField) {
+  // Set expectation
+  expects_.StartObject("")
+      ->RenderDouble("double_value", 1.0)
+      ->RenderFloat("float_value", 0.0)
+      ->RenderInt64("int64_value", 0)
+      ->RenderUint64("uint64_value", 0)
+      ->RenderInt32("int32_value", 0)
+      ->RenderUint32("uint32_value", 0)
+      ->RenderBool("bool_value", false)
+      ->RenderString("string_value", "")
+      ->RenderString("unknown", "abc")
+      ->StartObject("unknown_object")
+      ->RenderString("unknown", "def")
+      ->EndObject()
+      ->EndObject();
+
+  // Actual testing
+  testing_->StartObject("")
+      ->RenderDouble("double_value", 1.0)
+      ->RenderString("unknown", "abc")
+      ->StartObject("unknown_object")
+      ->RenderString("unknown", "def")
+      ->EndObject()
+      ->EndObject();
+}
+
+}  // namespace testing
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/internal/error_listener.cc b/src/google/protobuf/util/internal/error_listener.cc
new file mode 100644
index 0000000..538307b
--- /dev/null
+++ b/src/google/protobuf/util/internal/error_listener.cc
@@ -0,0 +1,42 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/util/internal/error_listener.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/internal/error_listener.h b/src/google/protobuf/util/internal/error_listener.h
new file mode 100644
index 0000000..9b907df
--- /dev/null
+++ b/src/google/protobuf/util/internal/error_listener.h
@@ -0,0 +1,99 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_PROTOBUF_UTIL_CONVERTER_ERROR_LISTENER_H__
+#define GOOGLE_PROTOBUF_UTIL_CONVERTER_ERROR_LISTENER_H__
+
+#include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
+#include <string>
+
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/util/internal/location_tracker.h>
+#include <google/protobuf/stubs/stringpiece.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+
+// Interface for error listener.
+class LIBPROTOBUF_EXPORT ErrorListener {
+ public:
+  virtual ~ErrorListener() {}
+
+  // Reports an invalid name at the given location.
+  virtual void InvalidName(const LocationTrackerInterface& loc,
+                           StringPiece unknown_name, StringPiece message) = 0;
+
+  // Reports an invalid value for a field.
+  virtual void InvalidValue(const LocationTrackerInterface& loc,
+                            StringPiece type_name, StringPiece value) = 0;
+
+  // Reports a missing required field.
+  virtual void MissingField(const LocationTrackerInterface& loc,
+                            StringPiece missing_name) = 0;
+
+ protected:
+  ErrorListener() {}
+
+ private:
+  // Do not add any data members to this class.
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(ErrorListener);
+};
+
+// An error listener that ignores all errors.
+class LIBPROTOBUF_EXPORT NoopErrorListener : public ErrorListener {
+ public:
+  NoopErrorListener() {}
+  virtual ~NoopErrorListener() {}
+
+  virtual void InvalidName(const LocationTrackerInterface& loc,
+                           StringPiece unknown_name, StringPiece message) {}
+
+  virtual void InvalidValue(const LocationTrackerInterface& loc,
+                            StringPiece type_name, StringPiece value) {}
+
+  virtual void MissingField(const LocationTrackerInterface& loc,
+                            StringPiece missing_name) {}
+
+ private:
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(NoopErrorListener);
+};
+
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_CONVERTER_ERROR_LISTENER_H__
diff --git a/src/google/protobuf/util/internal/expecting_objectwriter.h b/src/google/protobuf/util/internal/expecting_objectwriter.h
new file mode 100644
index 0000000..7509622
--- /dev/null
+++ b/src/google/protobuf/util/internal/expecting_objectwriter.h
@@ -0,0 +1,238 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_PROTOBUF_UTIL_CONVERTER_EXPECTING_OBJECTWRITER_H__
+#define GOOGLE_PROTOBUF_UTIL_CONVERTER_EXPECTING_OBJECTWRITER_H__
+
+// An implementation of ObjectWriter that automatically sets the
+// gmock expectations for the response to a method. Every method
+// returns the object itself for chaining.
+//
+// Usage:
+//   // Setup
+//   MockObjectWriter mock;
+//   ExpectingObjectWriter ow(&mock);
+//
+//   // Set expectation
+//   ow.StartObject("")
+//       ->RenderString("key", "value")
+//     ->EndObject();
+//
+//   // Actual testing
+//   mock.StartObject(StringPiece())
+//         ->RenderString("key", "value")
+//       ->EndObject();
+
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/util/internal/object_writer.h>
+#include <gmock/gmock.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+
+using testing::IsEmpty;
+using testing::NanSensitiveDoubleEq;
+using testing::NanSensitiveFloatEq;
+using testing::Return;
+using testing::StrEq;
+using testing::TypedEq;
+
+class MockObjectWriter : public ObjectWriter {
+ public:
+  MockObjectWriter() {}
+
+  MOCK_METHOD1(StartObject, ObjectWriter*(StringPiece));
+  MOCK_METHOD0(EndObject, ObjectWriter*());
+  MOCK_METHOD1(StartList, ObjectWriter*(StringPiece));
+  MOCK_METHOD0(EndList, ObjectWriter*());
+  MOCK_METHOD2(RenderBool, ObjectWriter*(StringPiece, const bool));
+  MOCK_METHOD2(RenderInt32, ObjectWriter*(StringPiece, const int32));
+  MOCK_METHOD2(RenderUint32, ObjectWriter*(StringPiece, const uint32));
+  MOCK_METHOD2(RenderInt64, ObjectWriter*(StringPiece, const int64));
+  MOCK_METHOD2(RenderUint64, ObjectWriter*(StringPiece, const uint64));
+  MOCK_METHOD2(RenderDouble, ObjectWriter*(StringPiece, const double));
+  MOCK_METHOD2(RenderFloat, ObjectWriter*(StringPiece, const float));
+  MOCK_METHOD2(RenderString, ObjectWriter*(StringPiece, StringPiece));
+  MOCK_METHOD2(RenderBytes, ObjectWriter*(StringPiece, StringPiece));
+  MOCK_METHOD1(RenderNull, ObjectWriter*(StringPiece));
+};
+
+class ExpectingObjectWriter : public ObjectWriter {
+ public:
+  explicit ExpectingObjectWriter(MockObjectWriter* mock) : mock_(mock) {}
+
+  virtual ObjectWriter* StartObject(StringPiece name) {
+    (name.empty()
+         ? EXPECT_CALL(*mock_, StartObject(IsEmpty()))
+         : EXPECT_CALL(*mock_, StartObject(StrEq(name.ToString()))))
+        .WillOnce(Return(mock_))
+        .RetiresOnSaturation();
+    return this;
+  }
+
+  virtual ObjectWriter* EndObject() {
+    EXPECT_CALL(*mock_, EndObject())
+        .WillOnce(Return(mock_))
+        .RetiresOnSaturation();
+    return this;
+  }
+
+  virtual ObjectWriter* StartList(StringPiece name) {
+    (name.empty()
+         ? EXPECT_CALL(*mock_, StartList(IsEmpty()))
+         : EXPECT_CALL(*mock_, StartList(StrEq(name.ToString()))))
+        .WillOnce(Return(mock_))
+        .RetiresOnSaturation();
+    return this;
+  }
+
+  virtual ObjectWriter* EndList() {
+    EXPECT_CALL(*mock_, EndList())
+        .WillOnce(Return(mock_))
+        .RetiresOnSaturation();
+    return this;
+  }
+
+  virtual ObjectWriter* RenderBool(StringPiece name, const bool value) {
+    (name.empty()
+         ? EXPECT_CALL(*mock_, RenderBool(IsEmpty(), TypedEq<bool>(value)))
+         : EXPECT_CALL(*mock_, RenderBool(StrEq(name.ToString()),
+                                          TypedEq<bool>(value))))
+        .WillOnce(Return(mock_))
+        .RetiresOnSaturation();
+    return this;
+  }
+
+  virtual ObjectWriter* RenderInt32(StringPiece name, const int32 value) {
+    (name.empty()
+         ? EXPECT_CALL(*mock_, RenderInt32(IsEmpty(), TypedEq<int32>(value)))
+         : EXPECT_CALL(*mock_, RenderInt32(StrEq(name.ToString()),
+                                           TypedEq<int32>(value))))
+        .WillOnce(Return(mock_))
+        .RetiresOnSaturation();
+    return this;
+  }
+
+  virtual ObjectWriter* RenderUint32(StringPiece name, const uint32 value) {
+    (name.empty()
+         ? EXPECT_CALL(*mock_, RenderUint32(IsEmpty(), TypedEq<uint32>(value)))
+         : EXPECT_CALL(*mock_, RenderUint32(StrEq(name.ToString()),
+                                            TypedEq<uint32>(value))))
+        .WillOnce(Return(mock_))
+        .RetiresOnSaturation();
+    return this;
+  }
+
+  virtual ObjectWriter* RenderInt64(StringPiece name, const int64 value) {
+    (name.empty()
+         ? EXPECT_CALL(*mock_, RenderInt64(IsEmpty(), TypedEq<int64>(value)))
+         : EXPECT_CALL(*mock_, RenderInt64(StrEq(name.ToString()),
+                                           TypedEq<int64>(value))))
+        .WillOnce(Return(mock_))
+        .RetiresOnSaturation();
+    return this;
+  }
+
+  virtual ObjectWriter* RenderUint64(StringPiece name, const uint64 value) {
+    (name.empty()
+         ? EXPECT_CALL(*mock_, RenderUint64(IsEmpty(), TypedEq<uint64>(value)))
+         : EXPECT_CALL(*mock_, RenderUint64(StrEq(name.ToString()),
+                                            TypedEq<uint64>(value))))
+        .WillOnce(Return(mock_))
+        .RetiresOnSaturation();
+    return this;
+  }
+
+  virtual ObjectWriter* RenderDouble(StringPiece name, const double value) {
+    (name.empty()
+         ? EXPECT_CALL(*mock_, RenderDouble(IsEmpty(),
+                                            NanSensitiveDoubleEq(value)))
+         : EXPECT_CALL(*mock_, RenderDouble(StrEq(name.ToString()),
+                                            NanSensitiveDoubleEq(value))))
+        .WillOnce(Return(mock_))
+        .RetiresOnSaturation();
+    return this;
+  }
+
+  virtual ObjectWriter* RenderFloat(StringPiece name, const float value) {
+    (name.empty()
+         ? EXPECT_CALL(*mock_, RenderFloat(IsEmpty(),
+                                           NanSensitiveFloatEq(value)))
+         : EXPECT_CALL(*mock_, RenderFloat(StrEq(name.ToString()),
+                                           NanSensitiveFloatEq(value))))
+        .WillOnce(Return(mock_))
+        .RetiresOnSaturation();
+    return this;
+  }
+
+  virtual ObjectWriter* RenderString(StringPiece name, StringPiece value) {
+    (name.empty()
+         ? EXPECT_CALL(*mock_, RenderString(IsEmpty(),
+               TypedEq<StringPiece>(value.ToString())))
+         : EXPECT_CALL(*mock_, RenderString(StrEq(name.ToString()),
+               TypedEq<StringPiece>(value.ToString()))))
+        .WillOnce(Return(mock_))
+        .RetiresOnSaturation();
+    return this;
+  }
+  virtual ObjectWriter* RenderBytes(StringPiece name, StringPiece value) {
+    (name.empty()
+         ? EXPECT_CALL(*mock_, RenderBytes(IsEmpty(), TypedEq<StringPiece>(
+                                                          value.ToString())))
+         : EXPECT_CALL(*mock_,
+                       RenderBytes(StrEq(name.ToString()),
+                                   TypedEq<StringPiece>(value.ToString()))))
+        .WillOnce(Return(mock_))
+        .RetiresOnSaturation();
+    return this;
+  }
+
+  virtual ObjectWriter* RenderNull(StringPiece name) {
+    (name.empty() ? EXPECT_CALL(*mock_, RenderNull(IsEmpty()))
+                  : EXPECT_CALL(*mock_, RenderNull(StrEq(name.ToString())))
+                        .WillOnce(Return(mock_))
+                        .RetiresOnSaturation());
+    return this;
+  }
+
+ private:
+  MockObjectWriter* mock_;
+
+  GOOGLE_DISALLOW_IMPLICIT_CONSTRUCTORS(ExpectingObjectWriter);
+};
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_CONVERTER_EXPECTING_OBJECTWRITER_H__
diff --git a/src/google/protobuf/util/internal/field_mask_utility.cc b/src/google/protobuf/util/internal/field_mask_utility.cc
new file mode 100644
index 0000000..9246895
--- /dev/null
+++ b/src/google/protobuf/util/internal/field_mask_utility.cc
@@ -0,0 +1,228 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/util/internal/field_mask_utility.h>
+
+#include <google/protobuf/stubs/strutil.h>
+#include <google/protobuf/stubs/status_macros.h>
+
+namespace google {
+
+namespace protobuf {
+namespace util {
+namespace converter {
+
+namespace {
+inline util::Status CallPathSink(PathSinkCallback path_sink,
+                                   StringPiece arg) {
+  return path_sink->Run(arg);
+}
+
+util::Status CreatePublicError(util::error::Code code,
+                                 const string& message) {
+  return util::Status(code, message);
+}
+
+// Appends a FieldMask path segment to a prefix.
+string AppendPathSegmentToPrefix(StringPiece prefix, StringPiece segment) {
+  if (prefix.empty()) {
+    return segment.ToString();
+  }
+  if (segment.empty()) {
+    return prefix.ToString();
+  }
+  // If the segment is a map key, appends it to the prefix without the ".".
+  if (segment.starts_with("[\"")) {
+    return StrCat(prefix, segment);
+  }
+  return StrCat(prefix, ".", segment);
+}
+
+}  // namespace
+
+string ConvertFieldMaskPath(const StringPiece path,
+                            ConverterCallback converter) {
+  string result;
+  result.reserve(path.size() << 1);
+
+  bool is_quoted = false;
+  bool is_escaping = false;
+  int current_segment_start = 0;
+
+  // Loops until 1 passed the end of the input to make handling the last
+  // segment easier.
+  for (size_t i = 0; i <= path.size(); ++i) {
+    // Outputs quoted string as-is.
+    if (is_quoted) {
+      if (i == path.size()) {
+        break;
+      }
+      result.push_back(path[i]);
+      if (is_escaping) {
+        is_escaping = false;
+      } else if (path[i] == '\\') {
+        is_escaping = true;
+      } else if (path[i] == '\"') {
+        current_segment_start = i + 1;
+        is_quoted = false;
+      }
+      continue;
+    }
+    if (i == path.size() || path[i] == '.' || path[i] == '(' ||
+        path[i] == ')' || path[i] == '\"') {
+      result += converter(
+          path.substr(current_segment_start, i - current_segment_start));
+      if (i < path.size()) {
+        result.push_back(path[i]);
+      }
+      current_segment_start = i + 1;
+    }
+    if (i < path.size() && path[i] == '\"') {
+      is_quoted = true;
+    }
+  }
+  return result;
+}
+
+util::Status DecodeCompactFieldMaskPaths(StringPiece paths,
+                                           PathSinkCallback path_sink) {
+  stack<string> prefix;
+  int length = paths.length();
+  int previous_position = 0;
+  bool in_map_key = false;
+  bool is_escaping = false;
+  // Loops until 1 passed the end of the input to make the handle of the last
+  // segment easier.
+  for (int i = 0; i <= length; ++i) {
+    if (i != length) {
+      // Skips everything in a map key until we hit the end of it, which is
+      // marked by an un-escaped '"' immediately followed by a ']'.
+      if (in_map_key) {
+        if (is_escaping) {
+          is_escaping = false;
+          continue;
+        }
+        if (paths[i] == '\\') {
+          is_escaping = true;
+          continue;
+        }
+        if (paths[i] != '\"') {
+          continue;
+        }
+        // Un-escaped '"' must be followed with a ']'.
+        if (i >= length - 1 || paths[i + 1] != ']') {
+          return CreatePublicError(
+              util::error::INVALID_ARGUMENT,
+              StrCat("Invalid FieldMask '", paths,
+                     "'. Map keys should be represented as [\"some_key\"]."));
+        }
+        // The end of the map key ("\"]") has been found.
+        in_map_key = false;
+        // Skips ']'.
+        i++;
+        // Checks whether the key ends at the end of a path segment.
+        if (i < length - 1 && paths[i + 1] != '.' && paths[i + 1] != ',' &&
+            paths[i + 1] != ')' && paths[i + 1] != '(') {
+          return CreatePublicError(
+              util::error::INVALID_ARGUMENT,
+              StrCat("Invalid FieldMask '", paths,
+                     "'. Map keys should be at the end of a path segment."));
+        }
+        is_escaping = false;
+        continue;
+      }
+
+      // We are not in a map key, look for the start of one.
+      if (paths[i] == '[') {
+        if (i >= length - 1 || paths[i + 1] != '\"') {
+          return CreatePublicError(
+              util::error::INVALID_ARGUMENT,
+              StrCat("Invalid FieldMask '", paths,
+                     "'. Map keys should be represented as [\"some_key\"]."));
+        }
+        // "[\"" starts a map key.
+        in_map_key = true;
+        i++;  // Skips the '\"'.
+        continue;
+      }
+      // If the current character is not a special character (',', '(' or ')'),
+      // continue to the next.
+      if (paths[i] != ',' && paths[i] != ')' && paths[i] != '(') {
+        continue;
+      }
+    }
+    // Gets the current segment - sub-string between previous position (after
+    // '(', ')', ',', or the beginning of the input) and the current position.
+    StringPiece segment =
+        paths.substr(previous_position, i - previous_position);
+    string current_prefix = prefix.empty() ? "" : prefix.top();
+
+    if (i < length && paths[i] == '(') {
+      // Builds a prefix and save it into the stack.
+      prefix.push(AppendPathSegmentToPrefix(current_prefix, segment));
+    } else if (!segment.empty()) {
+      // When the current charactor is ')', ',' or the current position has
+      // passed the end of the input, builds and outputs a new paths by
+      // concatenating the last prefix with the current segment.
+      RETURN_IF_ERROR(CallPathSink(
+          path_sink, AppendPathSegmentToPrefix(current_prefix, segment)));
+    }
+
+    // Removes the last prefix after seeing a ')'.
+    if (i < length && paths[i] == ')') {
+      if (prefix.empty()) {
+        return CreatePublicError(
+            util::error::INVALID_ARGUMENT,
+            StrCat("Invalid FieldMask '", paths,
+                   "'. Cannot find matching '(' for all ')'."));
+      }
+      prefix.pop();
+    }
+    previous_position = i + 1;
+  }
+  if (in_map_key) {
+    return CreatePublicError(
+        util::error::INVALID_ARGUMENT,
+        StrCat("Invalid FieldMask '", paths,
+               "'. Cannot find matching ']' for all '['."));
+  }
+  if (!prefix.empty()) {
+    return CreatePublicError(
+        util::error::INVALID_ARGUMENT,
+        StrCat("Invalid FieldMask '", paths,
+               "'. Cannot find matching ')' for all '('."));
+  }
+  return util::Status::OK;
+}
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/internal/field_mask_utility.h b/src/google/protobuf/util/internal/field_mask_utility.h
new file mode 100644
index 0000000..59f36f7
--- /dev/null
+++ b/src/google/protobuf/util/internal/field_mask_utility.h
@@ -0,0 +1,72 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// FieldMask related utility methods.
+
+#ifndef GOOGLE_PROTOBUF_UTIL_CONVERTER_FIELD_MASK_UTILITY_H__
+#define GOOGLE_PROTOBUF_UTIL_CONVERTER_FIELD_MASK_UTILITY_H__
+
+#include <functional>
+#include <stack>
+
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/stubs/stringpiece.h>
+#include <google/protobuf/stubs/status.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+
+typedef string (*ConverterCallback)(StringPiece);
+typedef ResultCallback1<util::Status, StringPiece>* PathSinkCallback;
+
+// Applies a 'converter' to each segment of a FieldMask path and returns the
+// result. Quoted strings in the 'path' are copied to the output as-is without
+// converting their content. Escaping is supported within quoted strings.
+// For example, "ab\"_c" will be returned as "ab\"_c" without any changes.
+string ConvertFieldMaskPath(const StringPiece path,
+                            ConverterCallback converter);
+
+// Decodes a compact list of FieldMasks. For example, "a.b,a.c.d,a.c.e" will be
+// decoded into a list of field paths - "a.b", "a.c.d", "a.c.e". And the results
+// will be sent to 'path_sink', i.e. 'path_sink' will be called once per
+// resulting path.
+// Note that we also support Apiary style FieldMask form. The above example in
+// the Apiary style will look like "a.b,a.c(d,e)".
+util::Status DecodeCompactFieldMaskPaths(StringPiece paths,
+                                           PathSinkCallback path_sink);
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_CONVERTER_FIELD_MASK_UTILITY_H__
diff --git a/src/google/protobuf/util/internal/json_escaping.cc b/src/google/protobuf/util/internal/json_escaping.cc
new file mode 100644
index 0000000..5ac2342
--- /dev/null
+++ b/src/google/protobuf/util/internal/json_escaping.cc
@@ -0,0 +1,403 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/util/internal/json_escaping.h>
+
+#include <google/protobuf/stubs/common.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+
+namespace {
+
+// Array of hex characters for conversion to hex.
+static const char kHex[] = "0123456789abcdef";
+
+// Characters 0x00 to 0x9f are very commonly used, so we provide a special
+// table lookup.
+//
+// For unicode code point ch < 0xa0:
+// kCommonEscapes[ch] is the escaped string of ch, if escaping is needed;
+//                    or an empty string, if escaping is not needed.
+static const char kCommonEscapes[160][7] = {
+  // C0 (ASCII and derivatives) control characters
+  "\\u0000", "\\u0001", "\\u0002", "\\u0003",  // 0x00
+  "\\u0004", "\\u0005", "\\u0006", "\\u0007",
+  "\\b",     "\\t",     "\\n",     "\\u000b",
+  "\\f",     "\\r",     "\\u000e", "\\u000f",
+  "\\u0010", "\\u0011", "\\u0012", "\\u0013",  // 0x10
+  "\\u0014", "\\u0015", "\\u0016", "\\u0017",
+  "\\u0018", "\\u0019", "\\u001a", "\\u001b",
+  "\\u001c", "\\u001d", "\\u001e", "\\u001f",
+  // Escaping of " and \ are required by www.json.org string definition.
+  // Escaping of < and > are required for HTML security.
+  "", "", "\\\"", "", "",        "", "",        "",  // 0x20
+  "", "", "",     "", "",        "", "",        "",
+  "", "", "",     "", "",        "", "",        "",  // 0x30
+  "", "", "",     "", "\\u003c", "", "\\u003e", "",
+  "", "", "",     "", "",        "", "",        "",  // 0x40
+  "", "", "",     "", "",        "", "",        "",
+  "", "", "",     "", "",        "", "",        "",  // 0x50
+  "", "", "",     "", "\\\\",    "", "",        "",
+  "", "", "",     "", "",        "", "",        "",  // 0x60
+  "", "", "",     "", "",        "", "",        "",
+  "", "", "",     "", "",        "", "",        "",  // 0x70
+  "", "", "",     "", "",        "", "",        "\\u007f",
+  // C1 (ISO 8859 and Unicode) extended control characters
+  "\\u0080", "\\u0081", "\\u0082", "\\u0083",  // 0x80
+  "\\u0084", "\\u0085", "\\u0086", "\\u0087",
+  "\\u0088", "\\u0089", "\\u008a", "\\u008b",
+  "\\u008c", "\\u008d", "\\u008e", "\\u008f",
+  "\\u0090", "\\u0091", "\\u0092", "\\u0093",  // 0x90
+  "\\u0094", "\\u0095", "\\u0096", "\\u0097",
+  "\\u0098", "\\u0099", "\\u009a", "\\u009b",
+  "\\u009c", "\\u009d", "\\u009e", "\\u009f"
+};
+
+// Determines if the given char value is a unicode high-surrogate code unit.
+// Such values do not represent characters by themselves, but are used in the
+// representation of supplementary characters in the utf-16 encoding.
+inline bool IsHighSurrogate(uint16 c) {
+  // Optimized form of:
+  // return c >= kMinHighSurrogate && c <= kMaxHighSurrogate;
+  // (Reduced from 3 ALU instructions to 2 ALU instructions)
+  return (c & ~(JsonEscaping::kMaxHighSurrogate -
+                JsonEscaping::kMinHighSurrogate))
+      == JsonEscaping::kMinHighSurrogate;
+}
+
+// Determines if the given char value is a unicode low-surrogate code unit.
+// Such values do not represent characters by themselves, but are used in the
+// representation of supplementary characters in the utf-16 encoding.
+inline bool IsLowSurrogate(uint16 c) {
+  // Optimized form of:
+  // return c >= kMinLowSurrogate && c <= kMaxLowSurrogate;
+  // (Reduced from 3 ALU instructions to 2 ALU instructions)
+  return (c & ~(JsonEscaping::kMaxLowSurrogate -
+                JsonEscaping::kMinLowSurrogate))
+      == JsonEscaping::kMinLowSurrogate;
+}
+
+// Determines if the given char value is a unicode surrogate code unit (either
+// high-surrogate or low-surrogate).
+inline bool IsSurrogate(uint32 c) {
+  // Optimized form of:
+  // return c >= kMinHighSurrogate && c <= kMaxLowSurrogate;
+  // (Reduced from 3 ALU instructions to 2 ALU instructions)
+  return (c & 0xfffff800) == JsonEscaping::kMinHighSurrogate;
+}
+
+// Returns true if the given unicode code point cp is
+// in the supplementary character range.
+inline bool IsSupplementalCodePoint(uint32 cp) {
+  // Optimized form of:
+  // return kMinSupplementaryCodePoint <= cp && cp <= kMaxCodePoint;
+  // (Reduced from 3 ALU instructions to 2 ALU instructions)
+  return (cp & ~(JsonEscaping::kMinSupplementaryCodePoint - 1))
+      < JsonEscaping::kMaxCodePoint;
+}
+
+// Returns true if the given unicode code point cp is a valid
+// unicode code point (i.e. in the range 0 <= cp <= kMaxCodePoint).
+inline bool IsValidCodePoint(uint32 cp) {
+  return cp <= JsonEscaping::kMaxCodePoint;
+}
+
+// Converts the specified surrogate pair to its supplementary code point value.
+// It is the callers' responsibility to validate the specified surrogate pair.
+inline uint32 ToCodePoint(uint16 high, uint16 low) {
+  // Optimized form of:
+  // return ((high - kMinHighSurrogate) << 10)
+  //     + (low - kMinLowSurrogate)
+  //     + kMinSupplementaryCodePoint;
+  // (Reduced from 5 ALU instructions to 3 ALU instructions)
+  return (high << 10) + low +
+      (JsonEscaping::kMinSupplementaryCodePoint
+       - (static_cast<unsigned>(JsonEscaping::kMinHighSurrogate) << 10)
+       - JsonEscaping::kMinLowSurrogate);
+}
+
+// Returns the low surrogate for the given unicode code point. The result is
+// meaningless if the given code point is not a supplementary character.
+inline uint16 ToLowSurrogate(uint32 cp) {
+  return (cp & (JsonEscaping::kMaxLowSurrogate
+                - JsonEscaping::kMinLowSurrogate))
+      + JsonEscaping::kMinLowSurrogate;
+}
+
+// Returns the high surrogate for the given unicode code point. The result is
+// meaningless if the given code point is not a supplementary character.
+inline uint16 ToHighSurrogate(uint32 cp) {
+  return (cp >> 10) + (JsonEscaping::kMinHighSurrogate -
+                       (JsonEscaping::kMinSupplementaryCodePoint >> 10));
+}
+
+// Input str is encoded in UTF-8. A unicode code point could be encoded in
+// UTF-8 using anywhere from 1 to 4 characters, and it could span multiple
+// reads of the ByteSource.
+//
+// This function reads the next unicode code point from the input (str) at
+// the given position (index), taking into account any left-over partial
+// code point from the previous iteration (cp), together with the number
+// of characters left to read to complete this code point (num_left).
+//
+// This function assumes that the input (str) is valid at the given position
+// (index). In order words, at least one character could be read successfully.
+//
+// The code point read (partial or complete) is stored in (cp). Upon return,
+// (num_left) stores the number of characters that has yet to be read in
+// order to complete the current unicode code point. If the read is complete,
+// then (num_left) is 0. Also, (num_read) is the number of characters read.
+//
+// Returns false if we encounter an invalid UTF-8 string. Returns true
+// otherwise, including the case when we reach the end of the input (str)
+// before a complete unicode code point is read.
+bool ReadCodePoint(StringPiece str, int index,
+                   uint32 *cp, int* num_left, int *num_read) {
+  if (*num_left == 0) {
+    // Last read was complete. Start reading a new unicode code point.
+    *cp = str[index++];
+    *num_read = 1;
+    // The length of the code point is determined from reading the first byte.
+    //
+    // If the first byte is between:
+    //    0..0x7f: that's the value of the code point.
+    // 0x80..0xbf: <invalid>
+    // 0xc0..0xdf: 11-bit code point encoded in 2 bytes.
+    //                                   bit 10-6, bit 5-0
+    // 0xe0..0xef: 16-bit code point encoded in 3 bytes.
+    //                        bit 15-12, bit 11-6, bit 5-0
+    // 0xf0..0xf7: 21-bit code point encoded in 4 bytes.
+    //             bit 20-18, bit 17-12, bit 11-6, bit 5-0
+    // 0xf8..0xff: <invalid>
+    //
+    // Meaning of each bit:
+    // <msb> bit 7: 0 - single byte code point: bits 6-0 are values.
+    //              1 - multibyte code point
+    //       bit 6: 0 - subsequent bytes of multibyte code point:
+    //                  bits 5-0 are values.
+    //              1 - first byte of multibyte code point
+    //       bit 5: 0 - first byte of 2-byte code point: bits 4-0 are values.
+    //              1 - first byte of code point with >= 3 bytes.
+    //       bit 4: 0 - first byte of 3-byte code point: bits 3-0 are values.
+    //              1 - first byte of code point with >= 4 bytes.
+    //       bit 3: 0 - first byte of 4-byte code point: bits 2-0 are values.
+    //              1 - reserved for future expansion.
+    if (*cp <= 0x7f) {
+      return true;
+    } else if (*cp <= 0xbf) {
+      return false;
+    } else if (*cp <= 0xdf) {
+      *cp &= 0x1f;
+      *num_left = 1;
+    } else if (*cp <= 0xef) {
+      *cp &= 0x0f;
+      *num_left = 2;
+    } else if (*cp <= 0xf7) {
+      *cp &= 0x07;
+      *num_left = 3;
+    } else {
+      return false;
+    }
+  } else {
+    // Last read was partial. Initialize num_read to 0 and continue reading
+    // the last unicode code point.
+    *num_read = 0;
+  }
+  while (*num_left > 0 && index < str.size()) {
+    uint32 ch = str[index++];
+    --(*num_left);
+    ++(*num_read);
+    *cp = (*cp << 6) | (ch & 0x3f);
+    if (ch < 0x80 || ch > 0xbf) return false;
+  }
+  return *num_left > 0 || (!IsSurrogate(*cp) && IsValidCodePoint(*cp));
+}
+
+// Stores the 16-bit unicode code point as its hexadecimal digits in buffer
+// and returns a StringPiece that points to this buffer. The input buffer needs
+// to be at least 6 bytes long.
+StringPiece ToHex(uint16 cp, char* buffer) {
+  buffer[5] = kHex[cp & 0x0f];
+  cp >>= 4;
+  buffer[4] = kHex[cp & 0x0f];
+  cp >>= 4;
+  buffer[3] = kHex[cp & 0x0f];
+  cp >>= 4;
+  buffer[2] = kHex[cp & 0x0f];
+  return StringPiece(buffer, 0, 6);
+}
+
+// Stores the 32-bit unicode code point as its hexadecimal digits in buffer
+// and returns a StringPiece that points to this buffer. The input buffer needs
+// to be at least 12 bytes long.
+StringPiece ToSurrogateHex(uint32 cp, char* buffer) {
+  uint16 low = ToLowSurrogate(cp);
+  uint16 high = ToHighSurrogate(cp);
+
+  buffer[11] = kHex[low & 0x0f];
+  low >>= 4;
+  buffer[10] = kHex[low & 0x0f];
+  low >>= 4;
+  buffer[9] = kHex[low & 0x0f];
+  low >>= 4;
+  buffer[8] = kHex[low & 0x0f];
+
+  buffer[5] = kHex[high & 0x0f];
+  high >>= 4;
+  buffer[4] = kHex[high & 0x0f];
+  high >>= 4;
+  buffer[3] = kHex[high & 0x0f];
+  high >>= 4;
+  buffer[2] = kHex[high & 0x0f];
+
+  return StringPiece(buffer, 12);
+}
+
+// If the given unicode code point needs escaping, then returns the
+// escaped form. The returned StringPiece either points to statically
+// pre-allocated char[] or to the given buffer. The input buffer needs
+// to be at least 12 bytes long.
+//
+// If the given unicode code point does not need escaping, an empty
+// StringPiece is returned.
+StringPiece EscapeCodePoint(uint32 cp, char* buffer) {
+  if (cp < 0xa0) return kCommonEscapes[cp];
+  switch (cp) {
+    // These are not required by json spec
+    // but used to prevent security bugs in javascript.
+    case 0xfeff:  // Zero width no-break space
+    case 0xfff9:  // Interlinear annotation anchor
+    case 0xfffa:  // Interlinear annotation separator
+    case 0xfffb:  // Interlinear annotation terminator
+
+    case 0x00ad:  // Soft-hyphen
+    case 0x06dd:  // Arabic end of ayah
+    case 0x070f:  // Syriac abbreviation mark
+    case 0x17b4:  // Khmer vowel inherent Aq
+    case 0x17b5:  // Khmer vowel inherent Aa
+      return ToHex(cp, buffer);
+
+    default:
+      if ((cp >= 0x0600 && cp <= 0x0603) ||  // Arabic signs
+          (cp >= 0x200b && cp <= 0x200f) ||  // Zero width etc.
+          (cp >= 0x2028 && cp <= 0x202e) ||  // Separators etc.
+          (cp >= 0x2060 && cp <= 0x2064) ||  // Invisible etc.
+          (cp >= 0x206a && cp <= 0x206f)) {  // Shaping etc.
+        return ToHex(cp, buffer);
+      }
+
+      if (cp == 0x000e0001 ||                        // Language tag
+          (cp >= 0x0001d173 && cp <= 0x0001d17a) ||  // Music formatting
+          (cp >= 0x000e0020 && cp <= 0x000e007f)) {  // TAG symbols
+        return ToSurrogateHex(cp, buffer);
+      }
+  }
+  return StringPiece();
+}
+
+// Tries to escape the given code point first. If the given code point
+// does not need to be escaped, but force_output is true, then render
+// the given multi-byte code point in UTF8 in the buffer and returns it.
+StringPiece EscapeCodePoint(uint32 cp, char* buffer, bool force_output) {
+  StringPiece sp = EscapeCodePoint(cp, buffer);
+  if (force_output && sp.empty()) {
+    buffer[5] = (cp & 0x3f) | 0x80;
+    cp >>= 6;
+    if (cp <= 0x1f) {
+      buffer[4] = cp | 0xc0;
+      sp.set(buffer + 4, 2);
+      return sp;
+    }
+    buffer[4] = (cp & 0x3f) | 0x80;
+    cp >>= 6;
+    if (cp <= 0x0f) {
+      buffer[3] = cp | 0xe0;
+      sp.set(buffer + 3, 3);
+      return sp;
+    }
+    buffer[3] = (cp & 0x3f) | 0x80;
+    buffer[2] = ((cp >> 6) & 0x07) | 0xf0;
+    sp.set(buffer + 2, 4);
+  }
+  return sp;
+}
+
+}  // namespace
+
+void JsonEscaping::Escape(strings::ByteSource* input,
+                          strings::ByteSink* output) {
+  char buffer[12] = "\\udead\\ubee";
+  uint32 cp = 0;     // Current unicode code point.
+  int num_left = 0;  // Num of chars to read to complete the code point.
+  while (input->Available() > 0) {
+    StringPiece str = input->Peek();
+    StringPiece escaped;
+    int i = 0;
+    int num_read;
+    bool ok;
+    bool cp_was_split = num_left > 0;
+    // Loop until we encounter either
+    //   i) a code point that needs to be escaped; or
+    //  ii) a split code point is completely read; or
+    // iii) a character that is not a valid utf8; or
+    //  iv) end of the StringPiece str is reached.
+    do {
+      ok = ReadCodePoint(str, i, &cp, &num_left, &num_read);
+      if (num_left > 0 || !ok) break;  // case iii or iv
+      escaped = EscapeCodePoint(cp, buffer, cp_was_split);
+      if (!escaped.empty()) break;     // case i or ii
+      i += num_read;
+      num_read = 0;
+    } while (i < str.length());        // case iv
+    // First copy the un-escaped prefix, if any, to the output ByteSink.
+    if (i > 0) input->CopyTo(output, i);
+    if (num_read > 0) input->Skip(num_read);
+    if (!ok) {
+      // Case iii: Report error.
+      // TODO(wpoon): Add error reporting.
+      num_left = 0;
+    } else if (num_left == 0 && !escaped.empty()) {
+      // Case i or ii: Append the escaped code point to the output ByteSink.
+      output->Append(escaped.data(), escaped.size());
+    }
+  }
+  if (num_left > 0) {
+    // Treat as case iii: report error.
+    // TODO(wpoon): Add error reporting.
+  }
+}
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/internal/json_escaping.h b/src/google/protobuf/util/internal/json_escaping.h
new file mode 100644
index 0000000..e3e329f
--- /dev/null
+++ b/src/google/protobuf/util/internal/json_escaping.h
@@ -0,0 +1,91 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef NET_PROTO2_UTIL_CONVERTER_STRINGS_JSON_ESCAPING_H_
+#define NET_PROTO2_UTIL_CONVERTER_STRINGS_JSON_ESCAPING_H_
+
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/stubs/bytestream.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+
+class JsonEscaping {
+ public:
+  // The minimum value of a unicode high-surrogate code unit in the utf-16
+  // encoding. A high-surrogate is also known as a leading-surrogate.
+  // See http://www.unicode.org/glossary/#high_surrogate_code_unit
+  static const uint16 kMinHighSurrogate = 0xd800;
+
+  // The maximum value of a unicide high-surrogate code unit in the utf-16
+  // encoding. A high-surrogate is also known as a leading-surrogate.
+  // See http://www.unicode.org/glossary/#high_surrogate_code_unit
+  static const uint16 kMaxHighSurrogate = 0xdbff;
+
+  // The minimum value of a unicode low-surrogate code unit in the utf-16
+  // encoding. A low-surrogate is also known as a trailing-surrogate.
+  // See http://www.unicode.org/glossary/#low_surrogate_code_unit
+  static const uint16 kMinLowSurrogate = 0xdc00;
+
+  // The maximum value of a unicode low-surrogate code unit in the utf-16
+  // encoding. A low-surrogate is also known as a trailing surrogate.
+  // See http://www.unicode.org/glossary/#low_surrogate_code_unit
+  static const uint16 kMaxLowSurrogate = 0xdfff;
+
+  // The minimum value of a unicode supplementary code point.
+  // See http://www.unicode.org/glossary/#supplementary_code_point
+  static const uint32 kMinSupplementaryCodePoint = 0x010000;
+
+  // The minimum value of a unicode code point.
+  // See http://www.unicode.org/glossary/#code_point
+  static const uint32 kMinCodePoint = 0x000000;
+
+  // The maximum value of a unicode code point.
+  // See http://www.unicode.org/glossary/#code_point
+  static const uint32 kMaxCodePoint = 0x10ffff;
+
+  JsonEscaping() {}
+  virtual ~JsonEscaping() {}
+
+  // Escape the given ByteSource to the given ByteSink.
+  static void Escape(strings::ByteSource* input, strings::ByteSink* output);
+
+ private:
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(JsonEscaping);
+};
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+
+#endif  // NET_PROTO2_UTIL_CONVERTER_STRINGS_JSON_ESCAPING_H_
+}  // namespace google
diff --git a/src/google/protobuf/util/internal/json_objectwriter.cc b/src/google/protobuf/util/internal/json_objectwriter.cc
new file mode 100644
index 0000000..d14ae10
--- /dev/null
+++ b/src/google/protobuf/util/internal/json_objectwriter.cc
@@ -0,0 +1,175 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/util/internal/json_objectwriter.h>
+
+#include <math.h>
+
+#include <google/protobuf/stubs/casts.h>
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/util/internal/utility.h>
+#include <google/protobuf/util/internal/json_escaping.h>
+#include <google/protobuf/stubs/strutil.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+
+using strings::ArrayByteSource;
+
+JsonObjectWriter::~JsonObjectWriter() {
+  if (!element_->is_root()) {
+    GOOGLE_LOG(WARNING) << "JsonObjectWriter was not fully closed.";
+  }
+}
+
+JsonObjectWriter* JsonObjectWriter::StartObject(StringPiece name) {
+  WritePrefix(name);
+  WriteChar('{');
+  Push();
+  return this;
+}
+
+JsonObjectWriter* JsonObjectWriter::EndObject() {
+  Pop();
+  WriteChar('}');
+  if (element()->is_root()) NewLine();
+  return this;
+}
+
+JsonObjectWriter* JsonObjectWriter::StartList(StringPiece name) {
+  WritePrefix(name);
+  WriteChar('[');
+  Push();
+  return this;
+}
+
+JsonObjectWriter* JsonObjectWriter::EndList() {
+  Pop();
+  WriteChar(']');
+  if (element()->is_root()) NewLine();
+  return this;
+}
+
+JsonObjectWriter* JsonObjectWriter::RenderBool(StringPiece name,
+                                               const bool value) {
+  return RenderSimple(name, value ? "true" : "false");
+}
+
+JsonObjectWriter* JsonObjectWriter::RenderInt32(StringPiece name,
+                                                const int32 value) {
+  return RenderSimple(name, SimpleItoa(value));
+}
+
+JsonObjectWriter* JsonObjectWriter::RenderUint32(StringPiece name,
+                                                 const uint32 value) {
+  return RenderSimple(name, SimpleItoa(value));
+}
+
+JsonObjectWriter* JsonObjectWriter::RenderInt64(StringPiece name,
+                                                const int64 value) {
+  WritePrefix(name);
+  WriteChar('"');
+  stream_->WriteString(SimpleItoa(value));
+  WriteChar('"');
+  return this;
+}
+
+JsonObjectWriter* JsonObjectWriter::RenderUint64(StringPiece name,
+                                                 const uint64 value) {
+  WritePrefix(name);
+  WriteChar('"');
+  stream_->WriteString(SimpleItoa(value));
+  WriteChar('"');
+  return this;
+}
+
+JsonObjectWriter* JsonObjectWriter::RenderDouble(StringPiece name,
+                                                 const double value) {
+  if (isfinite(value)) return RenderSimple(name, SimpleDtoa(value));
+
+  // Render quoted with NaN/Infinity-aware DoubleAsString.
+  return RenderString(name, DoubleAsString(value));
+}
+
+JsonObjectWriter* JsonObjectWriter::RenderFloat(StringPiece name,
+                                                const float value) {
+  if (isfinite(value)) return RenderSimple(name, SimpleFtoa(value));
+
+  // Render quoted with NaN/Infinity-aware FloatAsString.
+  return RenderString(name, FloatAsString(value));
+}
+
+JsonObjectWriter* JsonObjectWriter::RenderString(StringPiece name,
+                                                 StringPiece value) {
+  WritePrefix(name);
+  WriteChar('"');
+  ArrayByteSource source(value);
+  JsonEscaping::Escape(&source, &sink_);
+  WriteChar('"');
+  return this;
+}
+
+JsonObjectWriter* JsonObjectWriter::RenderBytes(StringPiece name,
+                                                StringPiece value) {
+  WritePrefix(name);
+  string base64;
+  WebSafeBase64EscapeWithPadding(value, &base64);
+  WriteChar('"');
+  // TODO(wpoon): Consider a ByteSink solution that writes the base64 bytes
+  //              directly to the stream, rather than first putting them
+  //              into a string and then writing them to the stream.
+  stream_->WriteRaw(base64.data(), base64.size());
+  WriteChar('"');
+  return this;
+}
+
+JsonObjectWriter* JsonObjectWriter::RenderNull(StringPiece name) {
+  return RenderSimple(name, "null");
+}
+
+void JsonObjectWriter::WritePrefix(StringPiece name) {
+  bool not_first = !element()->is_first();
+  if (not_first) WriteChar(',');
+  if (not_first || !element()->is_root()) NewLine();
+  if (!name.empty()) {
+    WriteChar('"');
+    ArrayByteSource source(name);
+    JsonEscaping::Escape(&source, &sink_);
+    stream_->WriteString("\":");
+    if (!indent_string_.empty()) WriteChar(' ');
+  }
+}
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/internal/json_objectwriter.h b/src/google/protobuf/util/internal/json_objectwriter.h
new file mode 100644
index 0000000..761a0a1
--- /dev/null
+++ b/src/google/protobuf/util/internal/json_objectwriter.h
@@ -0,0 +1,206 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_PROTOBUF_UTIL_CONVERTER_JSON_OBJECTWRITER_H__
+#define GOOGLE_PROTOBUF_UTIL_CONVERTER_JSON_OBJECTWRITER_H__
+
+#include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
+#include <string>
+
+#include <google/protobuf/io/coded_stream.h>
+#include <google/protobuf/util/internal/structured_objectwriter.h>
+#include <google/protobuf/stubs/bytestream.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+
+// An ObjectWriter implementation that outputs JSON. This ObjectWriter
+// supports writing a compact form or a pretty printed form.
+//
+// Sample usage:
+//   string output;
+//   StringOutputStream* str_stream = new StringOutputStream(&output);
+//   CodedOutputStream* out_stream = new CodedOutputStream(str_stream);
+//   JsonObjectWriter* ow = new JsonObjectWriter("  ", out_stream);
+//   ow->StartObject("")
+//       ->RenderString("name", "value")
+//       ->RenderString("emptystring", string())
+//       ->StartObject("nested")
+//         ->RenderInt64("light", 299792458);
+//         ->RenderDouble("pi", 3.141592653589793);
+//       ->EndObject()
+//       ->StartList("empty")
+//       ->EndList()
+//     ->EndObject();
+//
+// And then the output string would become:
+// {
+//   "name": "value",
+//   "emptystring": "",
+//   "nested": {
+//     "light": "299792458",
+//     "pi": 3.141592653589793
+//   },
+//   "empty": []
+// }
+//
+// JsonObjectWriter does not validate if calls actually result in valid JSON.
+// For example, passing an empty name when one would be required won't result
+// in an error, just an invalid output.
+//
+// Note that all int64 and uint64 are rendered as strings instead of numbers.
+// This is because JavaScript parses numbers as 64-bit float thus int64 and
+// uint64 would lose precision if rendered as numbers.
+//
+// JsonObjectWriter is thread-unsafe.
+class LIBPROTOBUF_EXPORT JsonObjectWriter : public StructuredObjectWriter {
+ public:
+  JsonObjectWriter(StringPiece indent_string,
+                   google::protobuf::io::CodedOutputStream* out)
+      : element_(new Element(NULL)),
+        stream_(out), sink_(out),
+        indent_string_(indent_string.ToString()) {
+  }
+  virtual ~JsonObjectWriter();
+
+  // ObjectWriter methods.
+  virtual JsonObjectWriter* StartObject(StringPiece name);
+  virtual JsonObjectWriter* EndObject();
+  virtual JsonObjectWriter* StartList(StringPiece name);
+  virtual JsonObjectWriter* EndList();
+  virtual JsonObjectWriter* RenderBool(StringPiece name, bool value);
+  virtual JsonObjectWriter* RenderInt32(StringPiece name, int32 value);
+  virtual JsonObjectWriter* RenderUint32(StringPiece name, uint32 value);
+  virtual JsonObjectWriter* RenderInt64(StringPiece name, int64 value);
+  virtual JsonObjectWriter* RenderUint64(StringPiece name, uint64 value);
+  virtual JsonObjectWriter* RenderDouble(StringPiece name, double value);
+  virtual JsonObjectWriter* RenderFloat(StringPiece name, float value);
+  virtual JsonObjectWriter* RenderString(StringPiece name, StringPiece value);
+  virtual JsonObjectWriter* RenderBytes(StringPiece name, StringPiece value);
+  virtual JsonObjectWriter* RenderNull(StringPiece name);
+
+ protected:
+  class LIBPROTOBUF_EXPORT Element : public BaseElement {
+   public:
+    explicit Element(Element* parent) : BaseElement(parent), is_first_(true) {}
+
+    // Called before each field of the Element is to be processed.
+    // Returns true if this is the first call (processing the first field).
+    bool is_first() {
+      if (is_first_) {
+        is_first_ = false;
+        return true;
+      }
+      return false;
+    }
+
+   private:
+    bool is_first_;
+
+    GOOGLE_DISALLOW_IMPLICIT_CONSTRUCTORS(Element);
+  };
+
+  virtual Element* element() { return element_.get(); }
+
+ private:
+  class LIBPROTOBUF_EXPORT ByteSinkWrapper : public strings::ByteSink {
+   public:
+    explicit ByteSinkWrapper(google::protobuf::io::CodedOutputStream* stream)
+        : stream_(stream) {}
+    virtual ~ByteSinkWrapper() {}
+
+    // ByteSink methods.
+    virtual void Append(const char* bytes, size_t n) {
+      stream_->WriteRaw(bytes, n);
+    }
+
+   private:
+    google::protobuf::io::CodedOutputStream* stream_;
+
+    GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(ByteSinkWrapper);
+  };
+
+  // Renders a simple value as a string. By default all non-string Render
+  // methods convert their argument to a string and call this method. This
+  // method can then be used to render the simple value without escaping it.
+  JsonObjectWriter* RenderSimple(StringPiece name, const string& value) {
+    WritePrefix(name);
+    stream_->WriteString(value);
+    return this;
+  }
+
+  // Pushes a new element to the stack.
+  void Push() { element_.reset(new Element(element_.release())); }
+
+  // Pops an element off of the stack and deletes the popped element.
+  void Pop() {
+    bool needs_newline = !element_->is_first();
+    element_.reset(element_->pop<Element>());
+    if (needs_newline) NewLine();
+  }
+
+  // If pretty printing is enabled, this will write a newline to the output,
+  // followed by optional indentation. Otherwise this method is a noop.
+  void NewLine() {
+    if (!indent_string_.empty()) {
+      WriteChar('\n');
+      for (int i = 0; i < element()->level(); i++) {
+        stream_->WriteString(indent_string_);
+      }
+    }
+  }
+
+  // Writes a prefix. This will write out any pretty printing and
+  // commas that are required, followed by the name and a ':' if
+  // the name is not null.
+  void WritePrefix(StringPiece name);
+
+  // Writes an individual character to the output.
+  void WriteChar(const char c) { stream_->WriteRaw(&c, sizeof(c)); }
+
+  google::protobuf::scoped_ptr<Element> element_;
+  google::protobuf::io::CodedOutputStream* stream_;
+  ByteSinkWrapper sink_;
+  const string indent_string_;
+
+  GOOGLE_DISALLOW_IMPLICIT_CONSTRUCTORS(JsonObjectWriter);
+};
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_CONVERTER_JSON_OBJECTWRITER_H__
diff --git a/src/google/protobuf/util/internal/json_objectwriter_test.cc b/src/google/protobuf/util/internal/json_objectwriter_test.cc
new file mode 100644
index 0000000..c8fff8b
--- /dev/null
+++ b/src/google/protobuf/util/internal/json_objectwriter_test.cc
@@ -0,0 +1,284 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/util/internal/json_objectwriter.h>
+
+#include <google/protobuf/io/zero_copy_stream_impl_lite.h>
+#include <gtest/gtest.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+
+using google::protobuf::io::CodedOutputStream;
+using google::protobuf::io::StringOutputStream;
+
+class JsonObjectWriterTest : public ::testing::Test {
+ protected:
+  JsonObjectWriterTest()
+      : str_stream_(new StringOutputStream(&output_)),
+        out_stream_(new CodedOutputStream(str_stream_)),
+        ow_(NULL) {}
+
+  virtual ~JsonObjectWriterTest() {
+    delete ow_;
+    delete out_stream_;
+    delete str_stream_;
+  }
+
+  string output_;
+  StringOutputStream* const str_stream_;
+  CodedOutputStream* const out_stream_;
+  ObjectWriter* ow_;
+};
+
+TEST_F(JsonObjectWriterTest, EmptyRootObject) {
+  ow_ = new JsonObjectWriter("", out_stream_);
+  ow_->StartObject("")->EndObject();
+  EXPECT_EQ("{}", output_.substr(0, out_stream_->ByteCount()));
+}
+
+TEST_F(JsonObjectWriterTest, EmptyObject) {
+  ow_ = new JsonObjectWriter("", out_stream_);
+  ow_->StartObject("")
+      ->RenderString("test", "value")
+      ->StartObject("empty")
+      ->EndObject()
+      ->EndObject();
+  EXPECT_EQ("{\"test\":\"value\",\"empty\":{}}",
+            output_.substr(0, out_stream_->ByteCount()));
+}
+
+TEST_F(JsonObjectWriterTest, EmptyRootList) {
+  ow_ = new JsonObjectWriter("", out_stream_);
+  ow_->StartList("")->EndList();
+  EXPECT_EQ("[]", output_.substr(0, out_stream_->ByteCount()));
+}
+
+TEST_F(JsonObjectWriterTest, EmptyList) {
+  ow_ = new JsonObjectWriter("", out_stream_);
+  ow_->StartObject("")
+      ->RenderString("test", "value")
+      ->StartList("empty")
+      ->EndList()
+      ->EndObject();
+  EXPECT_EQ("{\"test\":\"value\",\"empty\":[]}",
+            output_.substr(0, out_stream_->ByteCount()));
+}
+
+TEST_F(JsonObjectWriterTest, ObjectInObject) {
+  ow_ = new JsonObjectWriter("", out_stream_);
+  ow_->StartObject("")
+      ->StartObject("nested")
+      ->RenderString("field", "value")
+      ->EndObject()
+      ->EndObject();
+  EXPECT_EQ("{\"nested\":{\"field\":\"value\"}}",
+            output_.substr(0, out_stream_->ByteCount()));
+}
+
+TEST_F(JsonObjectWriterTest, ListInObject) {
+  ow_ = new JsonObjectWriter("", out_stream_);
+  ow_->StartObject("")
+      ->StartList("nested")
+      ->RenderString("", "value")
+      ->EndList()
+      ->EndObject();
+  EXPECT_EQ("{\"nested\":[\"value\"]}",
+            output_.substr(0, out_stream_->ByteCount()));
+}
+
+TEST_F(JsonObjectWriterTest, ObjectInList) {
+  ow_ = new JsonObjectWriter("", out_stream_);
+  ow_->StartList("")
+      ->StartObject("")
+      ->RenderString("field", "value")
+      ->EndObject()
+      ->EndList();
+  EXPECT_EQ("[{\"field\":\"value\"}]",
+            output_.substr(0, out_stream_->ByteCount()));
+}
+
+TEST_F(JsonObjectWriterTest, ListInList) {
+  ow_ = new JsonObjectWriter("", out_stream_);
+  ow_->StartList("")
+      ->StartList("")
+      ->RenderString("", "value")
+      ->EndList()
+      ->EndList();
+  EXPECT_EQ("[[\"value\"]]", output_.substr(0, out_stream_->ByteCount()));
+}
+
+TEST_F(JsonObjectWriterTest, RenderPrimitives) {
+  ow_ = new JsonObjectWriter("", out_stream_);
+  ow_->StartObject("")
+      ->RenderBool("bool", true)
+      ->RenderDouble("double", std::numeric_limits<double>::max())
+      ->RenderFloat("float", std::numeric_limits<float>::max())
+      ->RenderInt32("int", std::numeric_limits<int32>::min())
+      ->RenderInt64("long", std::numeric_limits<int64>::min())
+      ->RenderBytes("bytes", "abracadabra")
+      ->RenderString("string", "string")
+      ->RenderBytes("emptybytes", "")
+      ->RenderString("emptystring", string())
+      ->EndObject();
+  EXPECT_EQ(
+      "{\"bool\":true,"
+      "\"double\":1.7976931348623157e+308,"
+      "\"float\":3.4028235e+38,"
+      "\"int\":-2147483648,"
+      "\"long\":\"-9223372036854775808\","
+      "\"bytes\":\"YWJyYWNhZGFicmE=\","
+      "\"string\":\"string\","
+      "\"emptybytes\":\"\","
+      "\"emptystring\":\"\"}",
+      output_.substr(0, out_stream_->ByteCount()));
+}
+
+TEST_F(JsonObjectWriterTest, BytesEncodesAsWebSafeBase64) {
+  string s;
+  s.push_back('\377');
+  s.push_back('\357');
+  ow_ = new JsonObjectWriter("", out_stream_);
+  ow_->StartObject("")->RenderBytes("bytes", s)->EndObject();
+  // Non-web-safe would encode this as "/+8="
+  EXPECT_EQ("{\"bytes\":\"_-8=\"}",
+            output_.substr(0, out_stream_->ByteCount()));
+}
+
+TEST_F(JsonObjectWriterTest, PrettyPrintList) {
+  ow_ = new JsonObjectWriter(" ", out_stream_);
+  ow_->StartObject("")
+      ->StartList("items")
+      ->RenderString("", "item1")
+      ->RenderString("", "item2")
+      ->RenderString("", "item3")
+      ->EndList()
+      ->StartList("empty")
+      ->EndList()
+      ->EndObject();
+  EXPECT_EQ(
+      "{\n"
+      " \"items\": [\n"
+      "  \"item1\",\n"
+      "  \"item2\",\n"
+      "  \"item3\"\n"
+      " ],\n"
+      " \"empty\": []\n"
+      "}\n",
+      output_.substr(0, out_stream_->ByteCount()));
+}
+
+TEST_F(JsonObjectWriterTest, PrettyPrintObject) {
+  ow_ = new JsonObjectWriter(" ", out_stream_);
+  ow_->StartObject("")
+      ->StartObject("items")
+      ->RenderString("key1", "item1")
+      ->RenderString("key2", "item2")
+      ->RenderString("key3", "item3")
+      ->EndObject()
+      ->StartObject("empty")
+      ->EndObject()
+      ->EndObject();
+  EXPECT_EQ(
+      "{\n"
+      " \"items\": {\n"
+      "  \"key1\": \"item1\",\n"
+      "  \"key2\": \"item2\",\n"
+      "  \"key3\": \"item3\"\n"
+      " },\n"
+      " \"empty\": {}\n"
+      "}\n",
+      output_.substr(0, out_stream_->ByteCount()));
+}
+
+TEST_F(JsonObjectWriterTest, PrettyPrintEmptyObjectInEmptyList) {
+  ow_ = new JsonObjectWriter(" ", out_stream_);
+  ow_->StartObject("")
+      ->StartList("list")
+      ->StartObject("")
+      ->EndObject()
+      ->EndList()
+      ->EndObject();
+  EXPECT_EQ(
+      "{\n"
+      " \"list\": [\n"
+      "  {}\n"
+      " ]\n"
+      "}\n",
+      output_.substr(0, out_stream_->ByteCount()));
+}
+
+TEST_F(JsonObjectWriterTest, PrettyPrintDoubleIndent) {
+  ow_ = new JsonObjectWriter("  ", out_stream_);
+  ow_->StartObject("")
+      ->RenderBool("bool", true)
+      ->RenderInt32("int", 42)
+      ->EndObject();
+  EXPECT_EQ(
+      "{\n"
+      "  \"bool\": true,\n"
+      "  \"int\": 42\n"
+      "}\n",
+      output_.substr(0, out_stream_->ByteCount()));
+}
+
+TEST_F(JsonObjectWriterTest, StringsEscapedAndEnclosedInDoubleQuotes) {
+  ow_ = new JsonObjectWriter("", out_stream_);
+  ow_->StartObject("")->RenderString("string", "'<>&amp;\\\"\r\n")->EndObject();
+  EXPECT_EQ("{\"string\":\"'\\u003c\\u003e&amp;\\\\\\\"\\r\\n\"}",
+            output_.substr(0, out_stream_->ByteCount()));
+}
+
+TEST_F(JsonObjectWriterTest, Stringification) {
+  ow_ = new JsonObjectWriter("", out_stream_);
+  ow_->StartObject("")
+      ->RenderDouble("double_nan", std::numeric_limits<double>::quiet_NaN())
+      ->RenderFloat("float_nan", std::numeric_limits<float>::quiet_NaN())
+      ->RenderDouble("double_pos", std::numeric_limits<double>::infinity())
+      ->RenderFloat("float_pos", std::numeric_limits<float>::infinity())
+      ->RenderDouble("double_neg", -std::numeric_limits<double>::infinity())
+      ->RenderFloat("float_neg", -std::numeric_limits<float>::infinity())
+      ->EndObject();
+  EXPECT_EQ(
+      "{\"double_nan\":\"NaN\","
+      "\"float_nan\":\"NaN\","
+      "\"double_pos\":\"Infinity\","
+      "\"float_pos\":\"Infinity\","
+      "\"double_neg\":\"-Infinity\","
+      "\"float_neg\":\"-Infinity\"}",
+      output_.substr(0, out_stream_->ByteCount()));
+}
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/internal/json_stream_parser.cc b/src/google/protobuf/util/internal/json_stream_parser.cc
new file mode 100644
index 0000000..d439a22
--- /dev/null
+++ b/src/google/protobuf/util/internal/json_stream_parser.cc
@@ -0,0 +1,740 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/util/internal/json_stream_parser.h>
+
+#include <algorithm>
+#include <cctype>
+#include <cerrno>
+#include <cstdlib>
+#include <cstring>
+#include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
+
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/stubs/strutil.h>
+#include <google/protobuf/util/internal/object_writer.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+
+// Allow these symbols to be referenced as util::Status, util::error::* in
+// this file.
+using util::Status;
+namespace error {
+using util::error::INTERNAL;
+using util::error::INVALID_ARGUMENT;
+}  // namespace error
+
+namespace converter {
+
+// Number of digits in a unicode escape sequence (/uXXXX)
+static const int kUnicodeEscapedLength = 6;
+
+// Length of the true, false, and null literals.
+static const int true_len = strlen("true");
+static const int false_len = strlen("false");
+static const int null_len = strlen("null");
+
+inline bool IsLetter(char c) {
+  return ('a' <= c && c <= 'z') || ('A' <= c && c <= 'Z') || (c == '_') ||
+         (c == '$');
+}
+
+inline bool IsAlphanumeric(char c) {
+  return IsLetter(c) || ('0' <= c && c <= '9');
+}
+
+static bool ConsumeKey(StringPiece* input, StringPiece* key) {
+  if (input->empty() || !IsLetter((*input)[0])) return false;
+  int len = 1;
+  for (; len < input->size(); ++len) {
+    if (!IsAlphanumeric((*input)[len])) {
+      break;
+    }
+  }
+  *key = StringPiece(input->data(), len);
+  *input = StringPiece(input->data() + len, input->size() - len);
+  return true;
+}
+
+static bool MatchKey(StringPiece input) {
+  return !input.empty() && IsLetter(input[0]);
+}
+
+JsonStreamParser::JsonStreamParser(ObjectWriter* ow)
+    : ow_(ow),
+      stack_(),
+      leftover_(),
+      json_(),
+      p_(),
+      key_(),
+      key_storage_(),
+      finishing_(false),
+      parsed_(),
+      parsed_storage_(),
+      string_open_(0),
+      utf8_storage_(),
+      utf8_length_(0) {
+  // Initialize the stack with a single value to be parsed.
+  stack_.push(VALUE);
+}
+
+JsonStreamParser::~JsonStreamParser() {}
+
+util::Status JsonStreamParser::Parse(StringPiece json) {
+  return ParseChunk(json);
+}
+
+util::Status JsonStreamParser::FinishParse() {
+  // If we do not expect anything and there is nothing left to parse we're all
+  // done.
+  if (stack_.empty() && leftover_.empty()) {
+    return util::Status::OK;
+  }
+  // Parse the remainder in finishing mode, which reports errors for things like
+  // unterminated strings or unknown tokens that would normally be retried.
+  p_ = json_ = StringPiece(leftover_);
+  finishing_ = true;
+  util::Status result = RunParser();
+  if (result.ok()) {
+    SkipWhitespace();
+    if (!p_.empty()) {
+      result = ReportFailure("Parsing terminated before end of input.");
+    }
+  }
+  return result;
+}
+
+util::Status JsonStreamParser::ParseChunk(StringPiece chunk) {
+  // If we have leftovers from a previous chunk, append the new chunk to it and
+  // create a new StringPiece pointing at the string's data. This could be
+  // large but we rely on the chunks to be small, assuming they are fragments
+  // of a Cord.
+  if (!leftover_.empty()) {
+    chunk.AppendToString(&leftover_);
+    p_ = json_ = StringPiece(leftover_);
+  } else {
+    p_ = json_ = chunk;
+  }
+
+  finishing_ = false;
+  util::Status result = RunParser();
+  if (!result.ok()) return result;
+
+  SkipWhitespace();
+  if (p_.empty()) {
+    // If we parsed everything we had, clear the leftover.
+    leftover_.clear();
+  } else {
+    // If we do not expect anything i.e. stack is empty, and we have non-empty
+    // string left to parse, we report an error.
+    if (stack_.empty()) {
+      return ReportFailure("Parsing terminated before end of input.");
+    }
+    // If we expect future data i.e. stack is non-empty, and we have some
+    // unparsed data left, we save it for later parse.
+    leftover_ = p_.ToString();
+  }
+  return util::Status::OK;
+}
+
+util::Status JsonStreamParser::RunParser() {
+  while (!stack_.empty()) {
+    ParseType type = stack_.top();
+    TokenType t = (string_open_ == 0) ? GetNextTokenType() : BEGIN_STRING;
+    stack_.pop();
+    util::Status result;
+    switch (type) {
+      case VALUE:
+        result = ParseValue(t);
+        break;
+
+      case OBJ_MID:
+        result = ParseObjectMid(t);
+        break;
+
+      case ENTRY:
+        result = ParseEntry(t);
+        break;
+
+      case ENTRY_MID:
+        result = ParseEntryMid(t);
+        break;
+
+      case ARRAY_VALUE:
+        result = ParseArrayValue(t);
+        break;
+
+      case ARRAY_MID:
+        result = ParseArrayMid(t);
+        break;
+
+      default:
+        result = util::Status(util::error::INTERNAL,
+                              StrCat("Unknown parse type: ", type));
+        break;
+    }
+    if (!result.ok()) {
+      // If we were cancelled, save our state and try again later.
+      if (!finishing_ && result == util::Status::CANCELLED) {
+        stack_.push(type);
+        // If we have a key we still need to render, make sure to save off the
+        // contents in our own storage.
+        if (!key_.empty() && key_storage_.empty()) {
+          key_.AppendToString(&key_storage_);
+          key_ = StringPiece(key_storage_);
+        }
+        result = util::Status::OK;
+      }
+      return result;
+    }
+  }
+  return util::Status::OK;
+}
+
+util::Status JsonStreamParser::ParseValue(TokenType type) {
+  switch (type) {
+    case BEGIN_OBJECT:
+      return HandleBeginObject();
+    case BEGIN_ARRAY:
+      return HandleBeginArray();
+    case BEGIN_STRING:
+      return ParseString();
+    case BEGIN_NUMBER:
+      return ParseNumber();
+    case BEGIN_TRUE:
+      return ParseTrue();
+    case BEGIN_FALSE:
+      return ParseFalse();
+    case BEGIN_NULL:
+      return ParseNull();
+    case UNKNOWN:
+      return ReportUnknown("Expected a value.");
+    default: {
+      // Special case for having been cut off while parsing, wait for more data.
+      // This handles things like 'fals' being at the end of the string, we
+      // don't know if the next char would be e, completing it, or something
+      // else, making it invalid.
+      if (!finishing_ && p_.length() < false_len) {
+        return util::Status::CANCELLED;
+      }
+      return ReportFailure("Unexpected token.");
+    }
+  }
+}
+
+util::Status JsonStreamParser::ParseString() {
+  util::Status result = ParseStringHelper();
+  if (result.ok()) {
+    ow_->RenderString(key_, parsed_);
+    key_.clear();
+    parsed_.clear();
+    parsed_storage_.clear();
+  }
+  return result;
+}
+
+util::Status JsonStreamParser::ParseStringHelper() {
+  // If we haven't seen the start quote, grab it and remember it for later.
+  if (string_open_ == 0) {
+    string_open_ = *p_.data();
+    GOOGLE_DCHECK(string_open_ == '\"' || string_open_ == '\'');
+    Advance();
+  }
+  // Track where we last copied data from so we can minimize copying.
+  const char* last = p_.data();
+  while (!p_.empty()) {
+    const char* data = p_.data();
+    if (*data == '\\') {
+      // We're about to handle an escape, copy all bytes from last to data.
+      if (last < data) {
+        parsed_storage_.append(last, data - last);
+        last = data;
+      }
+      // If we ran out of string after the \, cancel or report an error
+      // depending on if we expect more data later.
+      if (p_.length() == 1) {
+        if (!finishing_) {
+          return util::Status::CANCELLED;
+        }
+        return ReportFailure("Closing quote expected in string.");
+      }
+      // Parse a unicode escape if we found \u in the string.
+      if (data[1] == 'u') {
+        util::Status result = ParseUnicodeEscape();
+        if (!result.ok()) {
+          return result;
+        }
+        // Move last pointer past the unicode escape and continue.
+        last = p_.data();
+        continue;
+      }
+      // Handle the standard set of backslash-escaped characters.
+      switch (data[1]) {
+        case 'b':
+          parsed_storage_.push_back('\b');
+          break;
+        case 'f':
+          parsed_storage_.push_back('\f');
+          break;
+        case 'n':
+          parsed_storage_.push_back('\n');
+          break;
+        case 'r':
+          parsed_storage_.push_back('\r');
+          break;
+        case 't':
+          parsed_storage_.push_back('\t');
+          break;
+        case 'v':
+          parsed_storage_.push_back('\v');
+          break;
+        default:
+          parsed_storage_.push_back(data[1]);
+      }
+      // We handled two characters, so advance past them and continue.
+      p_.remove_prefix(2);
+      last = p_.data();
+      continue;
+    }
+    // If we found the closing quote note it, advance past it, and return.
+    if (*data == string_open_) {
+      // If we didn't copy anything, reuse the input buffer.
+      if (parsed_storage_.empty()) {
+        parsed_ = StringPiece(last, data - last);
+      } else {
+        if (last < data) {
+          parsed_storage_.append(last, data - last);
+          last = data;
+        }
+        parsed_ = StringPiece(parsed_storage_);
+      }
+      // Clear the quote char so next time we try to parse a string we'll
+      // start fresh.
+      string_open_ = 0;
+      Advance();
+      return util::Status::OK;
+    }
+    // Normal character, just advance past it.
+    Advance();
+  }
+  // If we ran out of characters, copy over what we have so far.
+  if (last < p_.data()) {
+    parsed_storage_.append(last, p_.data() - last);
+  }
+  // If we didn't find the closing quote but we expect more data, cancel for now
+  if (!finishing_) {
+    return util::Status::CANCELLED;
+  }
+  // End of string reached without a closing quote, report an error.
+  string_open_ = 0;
+  return ReportFailure("Closing quote expected in string.");
+}
+
+// Converts a unicode escaped character to a decimal value stored in a char32
+// for use in UTF8 encoding utility.  We assume that str begins with \uhhhh and
+// convert that from the hex number to a decimal value.
+//
+// There are some security exploits with UTF-8 that we should be careful of:
+//   - http://www.unicode.org/reports/tr36/#UTF-8_Exploit
+//   - http://sites/intl-eng/design-guide/core-application
+util::Status JsonStreamParser::ParseUnicodeEscape() {
+  if (p_.length() < kUnicodeEscapedLength) {
+    if (!finishing_) {
+      return util::Status::CANCELLED;
+    }
+    return ReportFailure("Illegal hex string.");
+  }
+  GOOGLE_DCHECK_EQ('\\', p_.data()[0]);
+  GOOGLE_DCHECK_EQ('u', p_.data()[1]);
+  uint32 code = 0;
+  for (int i = 2; i < kUnicodeEscapedLength; ++i) {
+    if (!isxdigit(p_.data()[i])) {
+      return ReportFailure("Invalid escape sequence.");
+    }
+    code = (code << 4) + hex_digit_to_int(p_.data()[i]);
+  }
+  char buf[UTFmax];
+  int len = EncodeAsUTF8Char(code, buf);
+  // Advance past the unicode escape.
+  p_.remove_prefix(kUnicodeEscapedLength);
+  parsed_storage_.append(buf, len);
+  return util::Status::OK;
+}
+
+util::Status JsonStreamParser::ParseNumber() {
+  NumberResult number;
+  util::Status result = ParseNumberHelper(&number);
+  if (result.ok()) {
+    switch (number.type) {
+      case NumberResult::DOUBLE:
+        ow_->RenderDouble(key_, number.double_val);
+        key_.clear();
+        break;
+
+      case NumberResult::INT:
+        ow_->RenderInt64(key_, number.int_val);
+        key_.clear();
+        break;
+
+      case NumberResult::UINT:
+        ow_->RenderUint64(key_, number.uint_val);
+        key_.clear();
+        break;
+
+      default:
+        return ReportFailure("Unable to parse number.");
+    }
+  }
+  return result;
+}
+
+util::Status JsonStreamParser::ParseNumberHelper(NumberResult* result) {
+  const char* data = p_.data();
+  int length = p_.length();
+
+  // Look for the first non-numeric character, or the end of the string.
+  int index = 0;
+  bool floating = false;
+  bool negative = data[index] == '-';
+  // Find the first character that cannot be part of the number. Along the way
+  // detect if the number needs to be parsed as a double.
+  // Note that this restricts numbers to the JSON specification, so for example
+  // we do not support hex or octal notations.
+  for (; index < length; ++index) {
+    char c = data[index];
+    if (isdigit(c)) continue;
+    if (c == '.' || c == 'e' || c == 'E') {
+      floating = true;
+      continue;
+    }
+    if (c == '+' || c == '-') continue;
+    // Not a valid number character, break out.
+    break;
+  }
+
+  // If the entire input is a valid number, and we may have more content in the
+  // future, we abort for now and resume when we know more.
+  if (index == length && !finishing_) {
+    return util::Status::CANCELLED;
+  }
+
+  // Create a string containing just the number, so we can use safe_strtoX
+  string number = p_.substr(0, index).ToString();
+
+  // Floating point number, parse as a double.
+  if (floating) {
+    if (!safe_strtod(number, &result->double_val)) {
+      return ReportFailure("Unable to parse number.");
+    }
+    result->type = NumberResult::DOUBLE;
+    p_.remove_prefix(index);
+    return util::Status::OK;
+  }
+
+  // Positive non-floating point number, parse as a uint64.
+  if (!negative) {
+    if (!safe_strtou64(number, &result->uint_val)) {
+      return ReportFailure("Unable to parse number.");
+    }
+    result->type = NumberResult::UINT;
+    p_.remove_prefix(index);
+    return util::Status::OK;
+  }
+
+  // Negative non-floating point number, parse as an int64.
+  if (!safe_strto64(number, &result->int_val)) {
+    return ReportFailure("Unable to parse number.");
+  }
+  result->type = NumberResult::INT;
+  p_.remove_prefix(index);
+  return util::Status::OK;
+}
+
+util::Status JsonStreamParser::HandleBeginObject() {
+  GOOGLE_DCHECK_EQ('{', *p_.data());
+  Advance();
+  ow_->StartObject(key_);
+  key_.clear();
+  stack_.push(ENTRY);
+  return util::Status::OK;
+}
+
+util::Status JsonStreamParser::ParseObjectMid(TokenType type) {
+  if (type == UNKNOWN) {
+    return ReportUnknown("Expected , or } after key:value pair.");
+  }
+
+  // Object is complete, advance past the comma and render the EndObject.
+  if (type == END_OBJECT) {
+    Advance();
+    ow_->EndObject();
+    return util::Status::OK;
+  }
+  // Found a comma, advance past it and get ready for an entry.
+  if (type == VALUE_SEPARATOR) {
+    Advance();
+    stack_.push(ENTRY);
+    return util::Status::OK;
+  }
+  // Illegal token after key:value pair.
+  return ReportFailure("Expected , or } after key:value pair.");
+}
+
+util::Status JsonStreamParser::ParseEntry(TokenType type) {
+  if (type == UNKNOWN) {
+    return ReportUnknown("Expected an object key or }.");
+  }
+
+  // Close the object and return. This allows for trailing commas.
+  if (type == END_OBJECT) {
+    ow_->EndObject();
+    Advance();
+    return util::Status::OK;
+  }
+
+  util::Status result;
+  if (type == BEGIN_STRING) {
+    // Key is a string (standard JSON), parse it and store the string.
+    result = ParseStringHelper();
+    if (result.ok()) {
+      key_storage_.clear();
+      if (!parsed_storage_.empty()) {
+        parsed_storage_.swap(key_storage_);
+        key_ = StringPiece(key_storage_);
+      } else {
+        key_ = parsed_;
+      }
+      parsed_.clear();
+    }
+  } else if (type == BEGIN_KEY) {
+    // Key is a bare key (back compat), create a StringPiece pointing to it.
+    result = ParseKey();
+  } else {
+    // Unknown key type, report an error.
+    result = ReportFailure("Expected an object key or }.");
+  }
+  // On success we next expect an entry mid ':' then an object mid ',' or '}'
+  if (result.ok()) {
+    stack_.push(OBJ_MID);
+    stack_.push(ENTRY_MID);
+  }
+  return result;
+}
+
+util::Status JsonStreamParser::ParseEntryMid(TokenType type) {
+  if (type == UNKNOWN) {
+    return ReportUnknown("Expected : between key:value pair.");
+  }
+  if (type == ENTRY_SEPARATOR) {
+    Advance();
+    stack_.push(VALUE);
+    return util::Status::OK;
+  }
+  return ReportFailure("Expected : between key:value pair.");
+}
+
+util::Status JsonStreamParser::HandleBeginArray() {
+  GOOGLE_DCHECK_EQ('[', *p_.data());
+  Advance();
+  ow_->StartList(key_);
+  key_.clear();
+  stack_.push(ARRAY_VALUE);
+  return util::Status::OK;
+}
+
+util::Status JsonStreamParser::ParseArrayValue(TokenType type) {
+  if (type == UNKNOWN) {
+    return ReportUnknown("Expected a value or ] within an array.");
+  }
+
+  if (type == END_ARRAY) {
+    ow_->EndList();
+    Advance();
+    return util::Status::OK;
+  }
+
+  // The ParseValue call may push something onto the stack so we need to make
+  // sure an ARRAY_MID is after it, so we push it on now.
+  stack_.push(ARRAY_MID);
+  util::Status result = ParseValue(type);
+  if (result == util::Status::CANCELLED) {
+    // If we were cancelled, pop back off the ARRAY_MID so we don't try to
+    // push it on again when we try over.
+    stack_.pop();
+  }
+  return result;
+}
+
+util::Status JsonStreamParser::ParseArrayMid(TokenType type) {
+  if (type == UNKNOWN) {
+    return ReportUnknown("Expected , or ] after array value.");
+  }
+
+  if (type == END_ARRAY) {
+    ow_->EndList();
+    Advance();
+    return util::Status::OK;
+  }
+
+  // Found a comma, advance past it and expect an array value next.
+  if (type == VALUE_SEPARATOR) {
+    Advance();
+    stack_.push(ARRAY_VALUE);
+    return util::Status::OK;
+  }
+  // Illegal token after array value.
+  return ReportFailure("Expected , or ] after array value.");
+}
+
+util::Status JsonStreamParser::ParseTrue() {
+  ow_->RenderBool(key_, true);
+  key_.clear();
+  p_.remove_prefix(true_len);
+  return util::Status::OK;
+}
+
+util::Status JsonStreamParser::ParseFalse() {
+  ow_->RenderBool(key_, false);
+  key_.clear();
+  p_.remove_prefix(false_len);
+  return util::Status::OK;
+}
+
+util::Status JsonStreamParser::ParseNull() {
+  ow_->RenderNull(key_);
+  key_.clear();
+  p_.remove_prefix(null_len);
+  return util::Status::OK;
+}
+
+util::Status JsonStreamParser::ReportFailure(StringPiece message) {
+  static const int kContextLength = 20;
+  const char* p_start = p_.data();
+  const char* json_start = json_.data();
+  const char* begin = max(p_start - kContextLength, json_start);
+  const char* end = min(p_start + kContextLength, json_start + json_.size());
+  StringPiece segment(begin, end - begin);
+  string location(p_start - begin, ' ');
+  location.push_back('^');
+  return util::Status(util::error::INVALID_ARGUMENT,
+                      StrCat(message, "\n", segment, "\n", location));
+}
+
+util::Status JsonStreamParser::ReportUnknown(StringPiece message) {
+  // If we aren't finishing the parse, cancel parsing and try later.
+  if (!finishing_) {
+    return util::Status::CANCELLED;
+  }
+  if (p_.empty()) {
+    return ReportFailure(StrCat("Unexpected end of string. ", message));
+  }
+  return ReportFailure(message);
+}
+
+void JsonStreamParser::SkipWhitespace() {
+  while (!p_.empty() && ascii_isspace(*p_.data())) {
+    Advance();
+  }
+}
+
+void JsonStreamParser::Advance() {
+  // Advance by moving one UTF8 character while making sure we don't go beyond
+  // the length of StringPiece.
+  p_.remove_prefix(
+      min<int>(p_.length(), UTF8FirstLetterNumBytes(p_.data(), p_.length())));
+}
+
+util::Status JsonStreamParser::ParseKey() {
+  StringPiece original = p_;
+  if (!ConsumeKey(&p_, &key_)) {
+    return ReportFailure("Invalid key or variable name.");
+  }
+  // If we consumed everything but expect more data, reset p_ and cancel since
+  // we can't know if the key was complete or not.
+  if (!finishing_ && p_.empty()) {
+    p_ = original;
+    return util::Status::CANCELLED;
+  }
+  // Since we aren't using the key storage, clear it out.
+  key_storage_.clear();
+  return util::Status::OK;
+}
+
+JsonStreamParser::TokenType JsonStreamParser::GetNextTokenType() {
+  SkipWhitespace();
+
+  int size = p_.size();
+  if (size == 0) {
+    // If we ran out of data, report unknown and we'll place the previous parse
+    // type onto the stack and try again when we have more data.
+    return UNKNOWN;
+  }
+  // TODO(sven): Split this method based on context since different contexts
+  // support different tokens. Would slightly speed up processing?
+  const char* data = p_.data();
+  if (*data == '\"' || *data == '\'') return BEGIN_STRING;
+  if (*data == '-' || ('0' <= *data && *data <= '9')) {
+    return BEGIN_NUMBER;
+  }
+  if (size >= true_len && !strncmp(data, "true", true_len)) {
+    return BEGIN_TRUE;
+  }
+  if (size >= false_len && !strncmp(data, "false", false_len)) {
+    return BEGIN_FALSE;
+  }
+  if (size >= null_len && !strncmp(data, "null", null_len)) {
+    return BEGIN_NULL;
+  }
+  if (*data == '{') return BEGIN_OBJECT;
+  if (*data == '}') return END_OBJECT;
+  if (*data == '[') return BEGIN_ARRAY;
+  if (*data == ']') return END_ARRAY;
+  if (*data == ':') return ENTRY_SEPARATOR;
+  if (*data == ',') return VALUE_SEPARATOR;
+  if (MatchKey(p_)) {
+    return BEGIN_KEY;
+  }
+
+  // We don't know that we necessarily have an invalid token here, just that we
+  // can't parse what we have so far. So we don't report an error and just
+  // return UNKNOWN so we can try again later when we have more data, or if we
+  // finish and we have leftovers.
+  return UNKNOWN;
+}
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/internal/json_stream_parser.h b/src/google/protobuf/util/internal/json_stream_parser.h
new file mode 100644
index 0000000..17b094a
--- /dev/null
+++ b/src/google/protobuf/util/internal/json_stream_parser.h
@@ -0,0 +1,256 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_PROTOBUF_UTIL_CONVERTER_JSON_STREAM_PARSER_H__
+#define GOOGLE_PROTOBUF_UTIL_CONVERTER_JSON_STREAM_PARSER_H__
+
+#include <stack>
+#include <string>
+
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/stubs/stringpiece.h>
+#include <google/protobuf/stubs/status.h>
+
+namespace google {
+namespace util {
+class Status;
+}  // namespace util
+
+namespace protobuf {
+namespace util {
+namespace converter {
+
+class ObjectWriter;
+
+// A JSON parser that can parse a stream of JSON chunks rather than needing the
+// entire JSON string up front. It is a modified version of the parser in
+// //net/proto/json/json-parser.h that has been changed in the following ways:
+// - Changed from recursion to an explicit stack to allow resumption
+// - Added support for int64 and uint64 numbers
+// - Removed support for octal and decimal escapes
+// - Removed support for numeric keys
+// - Removed support for functions (javascript)
+// - Removed some lax-comma support (but kept trailing comma support)
+// - Writes directly to an ObjectWriter rather than using subclassing
+//
+// Here is an example usage:
+// JsonStreamParser parser(ow_.get());
+// util::Status result = parser.Parse(chunk1);
+// result.Update(parser.Parse(chunk2));
+// result.Update(parser.FinishParse());
+// GOOGLE_DCHECK(result.ok()) << "Failed to parse JSON";
+//
+// This parser is thread-compatible as long as only one thread is calling a
+// Parse() method at a time.
+class LIBPROTOBUF_EXPORT JsonStreamParser {
+ public:
+  // Creates a JsonStreamParser that will write to the given ObjectWriter.
+  explicit JsonStreamParser(ObjectWriter* ow);
+  virtual ~JsonStreamParser();
+
+  // Parse a JSON string (UTF-8 encoded).
+  util::Status Parse(StringPiece json);
+
+  // Finish parsing the JSON string.
+  util::Status FinishParse();
+
+ private:
+  enum TokenType {
+    BEGIN_STRING,     // " or '
+    BEGIN_NUMBER,     // - or digit
+    BEGIN_TRUE,       // true
+    BEGIN_FALSE,      // false
+    BEGIN_NULL,       // null
+    BEGIN_OBJECT,     // {
+    END_OBJECT,       // }
+    BEGIN_ARRAY,      // [
+    END_ARRAY,        // ]
+    ENTRY_SEPARATOR,  // :
+    VALUE_SEPARATOR,  // ,
+    BEGIN_KEY,        // letter, _, $ or digit.  Must begin with non-digit
+    UNKNOWN           // Unknown token or we ran out of the stream.
+  };
+
+  enum ParseType {
+    VALUE,        // Expects a {, [, true, false, null, string or number
+    OBJ_MID,      // Expects a ',' or }
+    ENTRY,        // Expects a key or }
+    ENTRY_MID,    // Expects a :
+    ARRAY_VALUE,  // Expects a value or ]
+    ARRAY_MID     // Expects a ',' or ]
+  };
+
+  // Holds the result of parsing a number
+  struct NumberResult {
+    enum Type { DOUBLE, INT, UINT };
+    Type type;
+    union {
+      double double_val;
+      int64 int_val;
+      uint64 uint_val;
+    };
+  };
+
+  // Parses a single chunk of JSON, returning an error if the JSON was invalid.
+  util::Status ParseChunk(StringPiece json);
+
+  // Runs the parser based on stack_ and p_, until the stack is empty or p_ runs
+  // out of data. If we unexpectedly run out of p_ we push the latest back onto
+  // the stack and return.
+  util::Status RunParser();
+
+  // Parses a value from p_ and writes it to ow_.
+  // A value may be an object, array, true, false, null, string or number.
+  util::Status ParseValue(TokenType type);
+
+  // Parses a string and writes it out to the ow_.
+  util::Status ParseString();
+
+  // Parses a string, storing the result in parsed_.
+  util::Status ParseStringHelper();
+
+  // This function parses unicode escape sequences in strings. It returns an
+  // error when there's a parsing error, either the size is not the expected
+  // size or a character is not a hex digit.  When it returns str will contain
+  // what has been successfully parsed so far.
+  util::Status ParseUnicodeEscape();
+
+  // Expects p_ to point to a JSON number, writes the number to the writer using
+  // the appropriate Render method based on the type of number.
+  util::Status ParseNumber();
+
+  // Parse a number into a NumberResult, reporting an error if no number could
+  // be parsed. This method will try to parse into a uint64, int64, or double
+  // based on whether the number was positive or negative or had a decimal
+  // component.
+  util::Status ParseNumberHelper(NumberResult* result);
+
+  // Handles a { during parsing of a value.
+  util::Status HandleBeginObject();
+
+  // Parses from the ENTRY state.
+  util::Status ParseEntry(TokenType type);
+
+  // Parses from the ENTRY_MID state.
+  util::Status ParseEntryMid(TokenType type);
+
+  // Parses from the OBJ_MID state.
+  util::Status ParseObjectMid(TokenType type);
+
+  // Handles a [ during parsing of a value.
+  util::Status HandleBeginArray();
+
+  // Parses from the ARRAY_VALUE state.
+  util::Status ParseArrayValue(TokenType type);
+
+  // Parses from the ARRAY_MID state.
+  util::Status ParseArrayMid(TokenType type);
+
+  // Expects p_ to point to an unquoted literal
+  util::Status ParseTrue();
+  util::Status ParseFalse();
+  util::Status ParseNull();
+
+  // Report a failure as a util::Status.
+  util::Status ReportFailure(StringPiece message);
+
+  // Report a failure due to an UNKNOWN token type. We check if we hit the
+  // end of the stream and if we're finishing or not to detect what type of
+  // status to return in this case.
+  util::Status ReportUnknown(StringPiece message);
+
+  // Advance p_ past all whitespace or until the end of the string.
+  void SkipWhitespace();
+
+  // Advance p_ one UTF-8 character
+  void Advance();
+
+  // Expects p_ to point to the beginning of a key.
+  util::Status ParseKey();
+
+  // Return the type of the next token at p_.
+  TokenType GetNextTokenType();
+
+  // The object writer to write parse events to.
+  ObjectWriter* ow_;
+
+  // The stack of parsing we still need to do. When the stack runs empty we will
+  // have parsed a single value from the root (e.g. an object or list).
+  std::stack<ParseType> stack_;
+
+  // Contains any leftover text from a previous chunk that we weren't able to
+  // fully parse, for example the start of a key or number.
+  string leftover_;
+
+  // The current chunk of JSON being parsed. Primarily used for providing
+  // context during error reporting.
+  StringPiece json_;
+
+  // A pointer within the current JSON being parsed, used to track location.
+  StringPiece p_;
+
+  // Stores the last key read, as we separate parsing of keys and values.
+  StringPiece key_;
+
+  // Storage for key_ if we need to keep ownership, for example between chunks
+  // or if the key was unescaped from a JSON string.
+  string key_storage_;
+
+  // True during the FinishParse() call, so we know that any errors are fatal.
+  // For example an unterminated string will normally result in cancelling and
+  // trying during the next chunk, but during FinishParse() it is an error.
+  bool finishing_;
+
+  // String we parsed during a call to ParseStringHelper().
+  StringPiece parsed_;
+
+  // Storage for the string we parsed. This may be empty if the string was able
+  // to be parsed directly from the input.
+  string parsed_storage_;
+
+  // The character that opened the string, either ' or ".
+  // A value of 0 indicates that string parsing is not in process.
+  char string_open_;
+
+  // Storage for utf8-coerced bytes.
+  google::protobuf::scoped_array<char> utf8_storage_;
+
+  // Length of the storage for utf8-coerced bytes.
+  int utf8_length_;
+
+  GOOGLE_DISALLOW_IMPLICIT_CONSTRUCTORS(JsonStreamParser);
+};
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_CONVERTER_JSON_STREAM_PARSER_H__
diff --git a/src/google/protobuf/util/internal/json_stream_parser_test.cc b/src/google/protobuf/util/internal/json_stream_parser_test.cc
new file mode 100644
index 0000000..bd8ed13
--- /dev/null
+++ b/src/google/protobuf/util/internal/json_stream_parser_test.cc
@@ -0,0 +1,697 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/util/internal/json_stream_parser.h>
+
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/stubs/time.h>
+#include <google/protobuf/util/internal/expecting_objectwriter.h>
+#include <google/protobuf/util/internal/object_writer.h>
+#include <google/protobuf/stubs/strutil.h>
+#include <gtest/gtest.h>
+#include <google/protobuf/stubs/status.h>
+
+
+namespace google {
+namespace protobuf {
+namespace util {
+using util::Status;
+namespace error {
+using util::error::INVALID_ARGUMENT;
+}  // namespace error
+namespace converter {
+
+using util::Status;
+
+// Tests for the JSON Stream Parser. These tests are intended to be
+// comprehensive and cover the following:
+//
+// Positive tests:
+// - true, false, null
+// - empty object or array.
+// - negative and positive double and int, unsigned int
+// - single and double quoted strings
+// - string key, unquoted key, numeric key
+// - array containing array, object, value
+// - object containing array, object, value
+// - unicode handling in strings
+// - ascii escaping (\b, \f, \n, \r, \t, \v)
+// - trailing commas
+//
+// Negative tests:
+// - illegal literals
+// - mismatched quotes failure on strings
+// - unterminated string failure
+// - unexpected end of string failure
+// - mismatched object and array closing
+// - Failure to close array or object
+// - numbers too large
+// - invalid unicode escapes.
+// - invalid unicode sequences.
+// - numbers as keys
+//
+// For each test we split the input string on every possible character to ensure
+// the parser is able to handle arbitrarily split input for all cases. We also
+// do a final test of the entire test case one character at a time.
+class JsonStreamParserTest : public ::testing::Test {
+ protected:
+  JsonStreamParserTest() : mock_(), ow_(&mock_) {}
+  virtual ~JsonStreamParserTest() {}
+
+  util::Status RunTest(StringPiece json, int split) {
+    JsonStreamParser parser(&mock_);
+
+    // Special case for split == length, test parsing one character at a time.
+    if (split == json.length()) {
+      GOOGLE_LOG(INFO) << "Testing split every char: " << json;
+      for (int i = 0; i < json.length(); ++i) {
+        StringPiece single = json.substr(i, 1);
+        util::Status result = parser.Parse(single);
+        if (!result.ok()) {
+          return result;
+        }
+      }
+      return parser.FinishParse();
+    }
+
+    // Normal case, split at the split point and parse two substrings.
+    StringPiece first = json.substr(0, split);
+    StringPiece rest = json.substr(split);
+    GOOGLE_LOG(INFO) << "Testing split: " << first << "><" << rest;
+    util::Status result = parser.Parse(first);
+    if (result.ok()) {
+      result = parser.Parse(rest);
+      if (result.ok()) {
+        result = parser.FinishParse();
+      }
+    }
+    return result;
+  }
+
+  void DoTest(StringPiece json, int split) {
+    util::Status result = RunTest(json, split);
+    if (!result.ok()) {
+      GOOGLE_LOG(WARNING) << result;
+    }
+    EXPECT_OK(result);
+  }
+
+  void DoErrorTest(StringPiece json, int split, StringPiece error_prefix) {
+    util::Status result = RunTest(json, split);
+    EXPECT_EQ(util::error::INVALID_ARGUMENT, result.error_code());
+    StringPiece error_message(result.error_message());
+    EXPECT_EQ(error_prefix, error_message.substr(0, error_prefix.size()));
+  }
+
+
+  MockObjectWriter mock_;
+  ExpectingObjectWriter ow_;
+};
+
+
+// Positive tests
+
+// - true, false, null
+TEST_F(JsonStreamParserTest, SimpleTrue) {
+  StringPiece str = "true";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.RenderBool("", true);
+    DoTest(str, i);
+  }
+}
+
+TEST_F(JsonStreamParserTest, SimpleFalse) {
+  StringPiece str = "false";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.RenderBool("", false);
+    DoTest(str, i);
+  }
+}
+
+TEST_F(JsonStreamParserTest, SimpleNull) {
+  StringPiece str = "null";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.RenderNull("");
+    DoTest(str, i);
+  }
+}
+
+// - empty object and array.
+TEST_F(JsonStreamParserTest, EmptyObject) {
+  StringPiece str = "{}";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartObject("")->EndObject();
+    DoTest(str, i);
+  }
+}
+
+TEST_F(JsonStreamParserTest, EmptyList) {
+  StringPiece str = "[]";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartList("")->EndList();
+    DoTest(str, i);
+  }
+}
+
+// - negative and positive double and int, unsigned int
+TEST_F(JsonStreamParserTest, SimpleDouble) {
+  StringPiece str = "42.5";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.RenderDouble("", 42.5);
+    DoTest(str, i);
+  }
+}
+
+TEST_F(JsonStreamParserTest, ScientificDouble) {
+  StringPiece str = "1.2345e-10";
+  for (int i = 0; i < str.length(); ++i) {
+    ow_.RenderDouble("", 1.2345e-10);
+    DoTest(str, i);
+  }
+}
+
+TEST_F(JsonStreamParserTest, SimpleNegativeDouble) {
+  StringPiece str = "-1045.235";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.RenderDouble("", -1045.235);
+    DoTest(str, i);
+  }
+}
+
+TEST_F(JsonStreamParserTest, SimpleInt) {
+  StringPiece str = "123456";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.RenderUint64("", 123456);
+    DoTest(str, i);
+  }
+}
+
+TEST_F(JsonStreamParserTest, SimpleNegativeInt) {
+  StringPiece str = "-79497823553162765";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.RenderInt64("", -79497823553162765LL);
+    DoTest(str, i);
+  }
+}
+
+TEST_F(JsonStreamParserTest, SimpleUnsignedInt) {
+  StringPiece str = "11779497823553162765";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.RenderUint64("", 11779497823553162765ULL);
+    DoTest(str, i);
+  }
+}
+
+// - single and double quoted strings
+TEST_F(JsonStreamParserTest, EmptyDoubleQuotedString) {
+  StringPiece str = "\"\"";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.RenderString("", "");
+    DoTest(str, i);
+  }
+}
+
+TEST_F(JsonStreamParserTest, EmptySingleQuotedString) {
+  StringPiece str = "''";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.RenderString("", "");
+    DoTest(str, i);
+  }
+}
+
+TEST_F(JsonStreamParserTest, SimpleDoubleQuotedString) {
+  StringPiece str = "\"Some String\"";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.RenderString("", "Some String");
+    DoTest(str, i);
+  }
+}
+
+TEST_F(JsonStreamParserTest, SimpleSingleQuotedString) {
+  StringPiece str = "'Another String'";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.RenderString("", "Another String");
+    DoTest(str, i);
+  }
+}
+
+// - string key, unquoted key, numeric key
+TEST_F(JsonStreamParserTest, ObjectKeyTypes) {
+  StringPiece str =
+      "{'s': true, \"d\": false, key: null, snake_key: [], camelKey: {}}";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartObject("")
+        ->RenderBool("s", true)
+        ->RenderBool("d", false)
+        ->RenderNull("key")
+        ->StartList("snake_key")
+        ->EndList()
+        ->StartObject("camelKey")
+        ->EndObject()
+        ->EndObject();
+    DoTest(str, i);
+  }
+}
+
+// - array containing array, object, values (true, false, null, num, string)
+TEST_F(JsonStreamParserTest, ArrayValues) {
+  StringPiece str =
+      "[true, false, null, 'a string', \"another string\", [22, -127, 45.3, "
+      "-1056.4, 11779497823553162765], {'key': true}]";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartList("")
+        ->RenderBool("", true)
+        ->RenderBool("", false)
+        ->RenderNull("")
+        ->RenderString("", "a string")
+        ->RenderString("", "another string")
+        ->StartList("")
+        ->RenderUint64("", 22)
+        ->RenderInt64("", -127)
+        ->RenderDouble("", 45.3)
+        ->RenderDouble("", -1056.4)
+        ->RenderUint64("", 11779497823553162765ULL)
+        ->EndList()
+        ->StartObject("")
+        ->RenderBool("key", true)
+        ->EndObject()
+        ->EndList();
+    DoTest(str, i);
+  }
+}
+
+// - object containing array, object, value (true, false, null, num, string)
+TEST_F(JsonStreamParserTest, ObjectValues) {
+  StringPiece str =
+      "{t: true, f: false, n: null, s: 'a string', d: \"another string\", pi: "
+      "22, ni: -127, pd: 45.3, nd: -1056.4, pl: 11779497823553162765, l: [[]], "
+      "o: {'key': true}}";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartObject("")
+        ->RenderBool("t", true)
+        ->RenderBool("f", false)
+        ->RenderNull("n")
+        ->RenderString("s", "a string")
+        ->RenderString("d", "another string")
+        ->RenderUint64("pi", 22)
+        ->RenderInt64("ni", -127)
+        ->RenderDouble("pd", 45.3)
+        ->RenderDouble("nd", -1056.4)
+        ->RenderUint64("pl", 11779497823553162765ULL)
+        ->StartList("l")
+        ->StartList("")
+        ->EndList()
+        ->EndList()
+        ->StartObject("o")
+        ->RenderBool("key", true)
+        ->EndObject()
+        ->EndObject();
+    DoTest(str, i);
+  }
+}
+
+// - unicode handling in strings
+TEST_F(JsonStreamParserTest, UnicodeEscaping) {
+  StringPiece str = "[\"\\u0639\\u0631\\u0628\\u0649\"]";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartList("")->RenderString("", "\u0639\u0631\u0628\u0649")->EndList();
+    DoTest(str, i);
+  }
+}
+
+// - ascii escaping (\b, \f, \n, \r, \t, \v)
+TEST_F(JsonStreamParserTest, AsciiEscaping) {
+  StringPiece str =
+      "[\"\\b\", \"\\ning\", \"test\\f\", \"\\r\\t\", \"test\\\\\\ving\"]";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartList("")
+        ->RenderString("", "\b")
+        ->RenderString("", "\ning")
+        ->RenderString("", "test\f")
+        ->RenderString("", "\r\t")
+        ->RenderString("", "test\\\ving")
+        ->EndList();
+    DoTest(str, i);
+  }
+}
+
+// - trailing commas, we support a single trailing comma but no internal commas.
+TEST_F(JsonStreamParserTest, TrailingCommas) {
+  StringPiece str = "[['a',true,], {b: null,},]";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartList("")
+        ->StartList("")
+        ->RenderString("", "a")
+        ->RenderBool("", true)
+        ->EndList()
+        ->StartObject("")
+        ->RenderNull("b")
+        ->EndObject()
+        ->EndList();
+    DoTest(str, i);
+  }
+}
+
+// Negative tests
+
+// illegal literals
+TEST_F(JsonStreamParserTest, ExtraTextAfterTrue) {
+  StringPiece str = "truee";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.RenderBool("", true);
+    DoErrorTest(str, i, "Parsing terminated before end of input.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, InvalidNumberDashOnly) {
+  StringPiece str = "-";
+  for (int i = 0; i <= str.length(); ++i) {
+    DoErrorTest(str, i, "Unable to parse number.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, InvalidNumberDashName) {
+  StringPiece str = "-foo";
+  for (int i = 0; i <= str.length(); ++i) {
+    DoErrorTest(str, i, "Unable to parse number.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, InvalidLiteralInArray) {
+  StringPiece str = "[nule]";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartList("");
+    DoErrorTest(str, i, "Unexpected token.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, InvalidLiteralInObject) {
+  StringPiece str = "{123false}";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartObject("");
+    DoErrorTest(str, i, "Expected an object key or }.");
+  }
+}
+
+// mismatched quotes failure on strings
+TEST_F(JsonStreamParserTest, MismatchedSingleQuotedLiteral) {
+  StringPiece str = "'Some str\"";
+  for (int i = 0; i <= str.length(); ++i) {
+    DoErrorTest(str, i, "Closing quote expected in string.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, MismatchedDoubleQuotedLiteral) {
+  StringPiece str = "\"Another string that ends poorly!'";
+  for (int i = 0; i <= str.length(); ++i) {
+    DoErrorTest(str, i, "Closing quote expected in string.");
+  }
+}
+
+// unterminated strings
+TEST_F(JsonStreamParserTest, UnterminatedLiteralString) {
+  StringPiece str = "\"Forgot the rest of i";
+  for (int i = 0; i <= str.length(); ++i) {
+    DoErrorTest(str, i, "Closing quote expected in string.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, UnterminatedStringEscape) {
+  StringPiece str = "\"Forgot the rest of \\";
+  for (int i = 0; i <= str.length(); ++i) {
+    DoErrorTest(str, i, "Closing quote expected in string.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, UnterminatedStringInArray) {
+  StringPiece str = "[\"Forgot to close the string]";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartList("");
+    DoErrorTest(str, i, "Closing quote expected in string.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, UnterminatedStringInObject) {
+  StringPiece str = "{f: \"Forgot to close the string}";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartObject("");
+    DoErrorTest(str, i, "Closing quote expected in string.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, UnterminatedObject) {
+  StringPiece str = "{";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartObject("");
+    DoErrorTest(str, i, "Unexpected end of string.");
+  }
+}
+
+
+// mismatched object and array closing
+TEST_F(JsonStreamParserTest, MismatchedCloseObject) {
+  StringPiece str = "{'key': true]";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartObject("")->RenderBool("key", true);
+    DoErrorTest(str, i, "Expected , or } after key:value pair.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, MismatchedCloseArray) {
+  StringPiece str = "[true, null}";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartList("")->RenderBool("", true)->RenderNull("");
+    DoErrorTest(str, i, "Expected , or ] after array value.");
+  }
+}
+
+// Invalid object keys.
+TEST_F(JsonStreamParserTest, InvalidNumericObjectKey) {
+  StringPiece str = "{42: true}";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartObject("");
+    DoErrorTest(str, i, "Expected an object key or }.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, InvalidLiteralObjectInObject) {
+  StringPiece str = "{{bob: true}}";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartObject("");
+    DoErrorTest(str, i, "Expected an object key or }.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, InvalidLiteralArrayInObject) {
+  StringPiece str = "{[null]}";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartObject("");
+    DoErrorTest(str, i, "Expected an object key or }.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, InvalidLiteralValueInObject) {
+  StringPiece str = "{false}";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartObject("");
+    DoErrorTest(str, i, "Expected an object key or }.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, MissingColonAfterStringInObject) {
+  StringPiece str = "{\"key\"}";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartObject("");
+    DoErrorTest(str, i, "Expected : between key:value pair.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, MissingColonAfterKeyInObject) {
+  StringPiece str = "{key}";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartObject("");
+    DoErrorTest(str, i, "Expected : between key:value pair.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, EndOfTextAfterKeyInObject) {
+  StringPiece str = "{key";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartObject("");
+    DoErrorTest(str, i, "Unexpected end of string.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, MissingValueAfterColonInObject) {
+  StringPiece str = "{key:}";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartObject("");
+    DoErrorTest(str, i, "Unexpected token.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, MissingCommaBetweenObjectEntries) {
+  StringPiece str = "{key:20 'hello': true}";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartObject("")->RenderUint64("key", 20);
+    DoErrorTest(str, i, "Expected , or } after key:value pair.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, InvalidLiteralAsObjectKey) {
+  StringPiece str = "{false: 20}";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartObject("");
+    DoErrorTest(str, i, "Expected an object key or }.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, ExtraCharactersAfterObject) {
+  StringPiece str = "{}}";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartObject("")->EndObject();
+    DoErrorTest(str, i, "Parsing terminated before end of input.");
+  }
+}
+
+// numbers too large
+TEST_F(JsonStreamParserTest, PositiveNumberTooBig) {
+  StringPiece str = "[18446744073709551616]";  // 2^64
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartList("");
+    DoErrorTest(str, i, "Unable to parse number.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, NegativeNumberTooBig) {
+  StringPiece str = "[-18446744073709551616]";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartList("");
+    DoErrorTest(str, i, "Unable to parse number.");
+  }
+}
+
+/*
+TODO(sven): Fail parsing when parsing a double that is too large.
+
+TEST_F(JsonStreamParserTest, DoubleTooBig) {
+  StringPiece str = "[184464073709551232321616.45]";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartList("");
+    DoErrorTest(str, i, "Unable to parse number");
+  }
+}
+*/
+
+// invalid unicode sequence.
+TEST_F(JsonStreamParserTest, UnicodeEscapeCutOff) {
+  StringPiece str = "\"\\u12";
+  for (int i = 0; i <= str.length(); ++i) {
+    DoErrorTest(str, i, "Illegal hex string.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, UnicodeEscapeInvalidCharacters) {
+  StringPiece str = "\"\\u12$4hello";
+  for (int i = 0; i <= str.length(); ++i) {
+    DoErrorTest(str, i, "Invalid escape sequence.");
+  }
+}
+
+// Extra commas with an object or array.
+TEST_F(JsonStreamParserTest, ExtraCommaInObject) {
+  StringPiece str = "{'k1': true,,'k2': false}";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartObject("")->RenderBool("k1", true);
+    DoErrorTest(str, i, "Expected an object key or }.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, ExtraCommaInArray) {
+  StringPiece str = "[true,,false}";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartList("")->RenderBool("", true);
+    DoErrorTest(str, i, "Unexpected token.");
+  }
+}
+
+// Extra text beyond end of value.
+TEST_F(JsonStreamParserTest, ExtraTextAfterLiteral) {
+  StringPiece str = "'hello', 'world'";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.RenderString("", "hello");
+    DoErrorTest(str, i, "Parsing terminated before end of input.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, ExtraTextAfterObject) {
+  StringPiece str = "{'key': true} 'oops'";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartObject("")->RenderBool("key", true)->EndObject();
+    DoErrorTest(str, i, "Parsing terminated before end of input.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, ExtraTextAfterArray) {
+  StringPiece str = "[null] 'oops'";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartList("")->RenderNull("")->EndList();
+    DoErrorTest(str, i, "Parsing terminated before end of input.");
+  }
+}
+
+// Random unknown text in the value.
+TEST_F(JsonStreamParserTest, UnknownCharactersAsValue) {
+  StringPiece str = "*&#25";
+  for (int i = 0; i <= str.length(); ++i) {
+    DoErrorTest(str, i, "Expected a value.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, UnknownCharactersInArray) {
+  StringPiece str = "[*&#25]";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartList("");
+    DoErrorTest(str, i, "Expected a value or ] within an array.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, UnknownCharactersInObject) {
+  StringPiece str = "{'key': *&#25}";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartObject("");
+    DoErrorTest(str, i, "Expected a value.");
+  }
+}
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/internal/location_tracker.h b/src/google/protobuf/util/internal/location_tracker.h
new file mode 100644
index 0000000..0864b05
--- /dev/null
+++ b/src/google/protobuf/util/internal/location_tracker.h
@@ -0,0 +1,65 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_PROTOBUF_UTIL_CONVERTER_LOCATION_TRACKER_H__
+#define GOOGLE_PROTOBUF_UTIL_CONVERTER_LOCATION_TRACKER_H__
+
+#include <string>
+
+#include <google/protobuf/stubs/common.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+
+// LocationTrackerInterface is an interface for classes that track
+// the location information for the purpose of error reporting.
+class LIBPROTOBUF_EXPORT LocationTrackerInterface {
+ public:
+  virtual ~LocationTrackerInterface() {}
+
+  // Returns the object location as human readable string.
+  virtual string ToString() const = 0;
+
+ protected:
+  LocationTrackerInterface() {}
+
+ private:
+  // Please do not add any data members to this class.
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(LocationTrackerInterface);
+};
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_CONVERTER_LOCATION_TRACKER_H__
diff --git a/src/google/protobuf/util/internal/mock_error_listener.h b/src/google/protobuf/util/internal/mock_error_listener.h
new file mode 100644
index 0000000..591c35d
--- /dev/null
+++ b/src/google/protobuf/util/internal/mock_error_listener.h
@@ -0,0 +1,63 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_PROTOBUF_UTIL_CONVERTER_MOCK_ERROR_LISTENER_H__
+#define GOOGLE_PROTOBUF_UTIL_CONVERTER_MOCK_ERROR_LISTENER_H__
+
+#include <google/protobuf/stubs/stringpiece.h>
+#include <google/protobuf/util/internal/error_listener.h>
+#include <google/protobuf/util/internal/location_tracker.h>
+#include <gmock/gmock.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+
+class MockErrorListener : public ErrorListener {
+ public:
+  MockErrorListener() {}
+  virtual ~MockErrorListener() {}
+
+  MOCK_METHOD3(InvalidName, void(const LocationTrackerInterface& loc,
+                                 StringPiece unknown_name,
+                                 StringPiece message));
+  MOCK_METHOD3(InvalidValue, void(const LocationTrackerInterface& loc,
+                                  StringPiece type_name, StringPiece value));
+  MOCK_METHOD2(MissingField, void(const LocationTrackerInterface& loc,
+                                  StringPiece missing_name));
+};
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_CONVERTER_MOCK_ERROR_LISTENER_H__
diff --git a/src/google/protobuf/util/internal/object_location_tracker.h b/src/google/protobuf/util/internal/object_location_tracker.h
new file mode 100644
index 0000000..8586cec
--- /dev/null
+++ b/src/google/protobuf/util/internal/object_location_tracker.h
@@ -0,0 +1,64 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_PROTOBUF_UTIL_CONVERTER_OBJECT_LOCATION_TRACKER_H__
+#define GOOGLE_PROTOBUF_UTIL_CONVERTER_OBJECT_LOCATION_TRACKER_H__
+
+#include <string>
+
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/util/internal/location_tracker.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+
+// An empty concrete implementation of LocationTrackerInterface.
+class ObjectLocationTracker : public LocationTrackerInterface {
+ public:
+  // Creates an empty location tracker.
+  ObjectLocationTracker() {}
+
+  virtual ~ObjectLocationTracker() {}
+
+  // Returns empty because nothing is tracked.
+  virtual string ToString() const { return ""; }
+
+ private:
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(ObjectLocationTracker);
+};
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_CONVERTER_OBJECT_LOCATION_TRACKER_H__
diff --git a/src/google/protobuf/util/internal/object_source.h b/src/google/protobuf/util/internal/object_source.h
new file mode 100644
index 0000000..2c31cfb
--- /dev/null
+++ b/src/google/protobuf/util/internal/object_source.h
@@ -0,0 +1,79 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_PROTOBUF_UTIL_CONVERTER_OBJECT_SOURCE_H__
+#define GOOGLE_PROTOBUF_UTIL_CONVERTER_OBJECT_SOURCE_H__
+
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/stubs/stringpiece.h>
+#include <google/protobuf/stubs/status.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+
+class ObjectWriter;
+
+// An ObjectSource is anything that can write to an ObjectWriter.
+// Implementation of this interface typically provide constructors or
+// factory methods to create an instance based on some source data, for
+// example, a character stream, or protobuf.
+//
+// Derived classes could be thread-unsafe.
+class LIBPROTOBUF_EXPORT ObjectSource {
+ public:
+  virtual ~ObjectSource() {}
+
+  // Writes to the ObjectWriter
+  virtual util::Status WriteTo(ObjectWriter* ow) const {
+    return NamedWriteTo("", ow);
+  }
+
+  // Writes to the ObjectWriter with a custom name for the message.
+  // This is useful when you chain ObjectSource together by embedding one
+  // within another.
+  virtual util::Status NamedWriteTo(StringPiece name,
+                                      ObjectWriter* ow) const = 0;
+
+ protected:
+  ObjectSource() {}
+
+ private:
+  // Do not add any data members to this class.
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(ObjectSource);
+};
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_CONVERTER_OBJECT_SOURCE_H__
diff --git a/src/google/protobuf/util/internal/object_writer.cc b/src/google/protobuf/util/internal/object_writer.cc
new file mode 100644
index 0000000..57cc08a
--- /dev/null
+++ b/src/google/protobuf/util/internal/object_writer.cc
@@ -0,0 +1,92 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/util/internal/object_writer.h>
+
+#include <google/protobuf/util/internal/datapiece.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+
+// static
+void ObjectWriter::RenderDataPieceTo(const DataPiece& data, StringPiece name,
+                                     ObjectWriter* ow) {
+  switch (data.type()) {
+    case DataPiece::TYPE_INT32: {
+      ow->RenderInt32(name, data.ToInt32().ValueOrDie());
+      break;
+    }
+    case DataPiece::TYPE_INT64: {
+      ow->RenderInt64(name, data.ToInt64().ValueOrDie());
+      break;
+    }
+    case DataPiece::TYPE_UINT32: {
+      ow->RenderUint32(name, data.ToUint32().ValueOrDie());
+      break;
+    }
+    case DataPiece::TYPE_UINT64: {
+      ow->RenderUint64(name, data.ToUint64().ValueOrDie());
+      break;
+    }
+    case DataPiece::TYPE_DOUBLE: {
+      ow->RenderDouble(name, data.ToDouble().ValueOrDie());
+      break;
+    }
+    case DataPiece::TYPE_FLOAT: {
+      ow->RenderFloat(name, data.ToFloat().ValueOrDie());
+      break;
+    }
+    case DataPiece::TYPE_BOOL: {
+      ow->RenderBool(name, data.ToBool().ValueOrDie());
+      break;
+    }
+    case DataPiece::TYPE_STRING: {
+      ow->RenderString(name, data.ToString().ValueOrDie());
+      break;
+    }
+    case DataPiece::TYPE_BYTES: {
+      ow->RenderBytes(name, data.ToBytes().ValueOrDie());
+      break;
+    }
+    case DataPiece::TYPE_NULL: {
+      ow->RenderNull(name);
+      break;
+    }
+    default:
+      break;
+  }
+}
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/internal/object_writer.h b/src/google/protobuf/util/internal/object_writer.h
new file mode 100644
index 0000000..20bd362
--- /dev/null
+++ b/src/google/protobuf/util/internal/object_writer.h
@@ -0,0 +1,126 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_PROTOBUF_UTIL_CONVERTER_OBJECT_WRITER_H__
+#define GOOGLE_PROTOBUF_UTIL_CONVERTER_OBJECT_WRITER_H__
+
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/stubs/stringpiece.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+
+class DataPiece;
+
+// An ObjectWriter is an interface for writing a stream of events
+// representing objects and collections. Implementation of this
+// interface can be used to write an object stream to an in-memory
+// structure, protobufs, JSON, XML, or any other output format
+// desired. The ObjectSource interface is typically used as the
+// source of an object stream.
+//
+// See JsonObjectWriter for a sample implementation of ObjectWriter
+// and its use.
+//
+// Derived classes could be thread-unsafe.
+//
+// TODO(xinb): seems like a prime candidate to apply the RAII paradigm
+// and get rid the need to call EndXXX().
+class LIBPROTOBUF_EXPORT ObjectWriter {
+ public:
+  virtual ~ObjectWriter() {}
+
+  // Starts an object. If the name is empty, the object will not be named.
+  virtual ObjectWriter* StartObject(StringPiece name) = 0;
+
+  // Ends an object.
+  virtual ObjectWriter* EndObject() = 0;
+
+  // Starts a list. If the name is empty, the list will not be named.
+  virtual ObjectWriter* StartList(StringPiece name) = 0;
+
+  // Ends a list.
+  virtual ObjectWriter* EndList() = 0;
+
+  // Renders a boolean value.
+  virtual ObjectWriter* RenderBool(StringPiece name, bool value) = 0;
+
+  // Renders an 32-bit integer value.
+  virtual ObjectWriter* RenderInt32(StringPiece name, int32 value) = 0;
+
+  // Renders an 32-bit unsigned integer value.
+  virtual ObjectWriter* RenderUint32(StringPiece name, uint32 value) = 0;
+
+  // Renders a 64-bit integer value.
+  virtual ObjectWriter* RenderInt64(StringPiece name, int64 value) = 0;
+
+  // Renders an 64-bit unsigned integer value.
+  virtual ObjectWriter* RenderUint64(StringPiece name, uint64 value) = 0;
+
+  // Renders a double value.
+  virtual ObjectWriter* RenderDouble(StringPiece name, double value) = 0;
+
+  // Renders a float value.
+  virtual ObjectWriter* RenderFloat(StringPiece name, float value) = 0;
+
+  // Renders a StringPiece value. This is for rendering strings.
+  virtual ObjectWriter* RenderString(StringPiece name, StringPiece value) = 0;
+
+  // Renders a bytes value.
+  virtual ObjectWriter* RenderBytes(StringPiece name, StringPiece value) = 0;
+
+  // Renders a Null value.
+  virtual ObjectWriter* RenderNull(StringPiece name) = 0;
+
+  // Disables case normalization. Any RenderTYPE call after calling this
+  // function will output the name field as-is. No normalization is attempted on
+  // it. This setting is reset immediately after the next RenderTYPE is called.
+  virtual ObjectWriter* DisableCaseNormalizationForNextKey() { return this; }
+
+  // Renders a DataPiece object to a ObjectWriter.
+  static void RenderDataPieceTo(const DataPiece& data, StringPiece name,
+                                ObjectWriter* ow);
+
+ protected:
+  ObjectWriter() {}
+
+ private:
+  // Do not add any data members to this class.
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(ObjectWriter);
+};
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_CONVERTER_OBJECT_WRITER_H__
diff --git a/src/google/protobuf/util/internal/protostream_objectsource.cc b/src/google/protobuf/util/internal/protostream_objectsource.cc
new file mode 100644
index 0000000..53a0e47
--- /dev/null
+++ b/src/google/protobuf/util/internal/protostream_objectsource.cc
@@ -0,0 +1,1051 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/util/internal/protostream_objectsource.h>
+
+#include <utility>
+
+#include <google/protobuf/stubs/casts.h>
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/stubs/stringprintf.h>
+#include <google/protobuf/stubs/time.h>
+#include <google/protobuf/io/coded_stream.h>
+#include <google/protobuf/io/zero_copy_stream_impl.h>
+#include <google/protobuf/descriptor.h>
+#include <google/protobuf/wire_format.h>
+#include <google/protobuf/wire_format_lite.h>
+#include <google/protobuf/util/internal/field_mask_utility.h>
+#include <google/protobuf/util/internal/constants.h>
+#include <google/protobuf/util/internal/utility.h>
+#include <google/protobuf/stubs/strutil.h>
+#include <google/protobuf/stubs/map_util.h>
+#include <google/protobuf/stubs/status_macros.h>
+
+
+namespace google {
+namespace protobuf {
+namespace util {
+using util::Status;
+using util::StatusOr;
+namespace error {
+using util::error::Code;
+using util::error::INTERNAL;
+}
+namespace converter {
+
+using google::protobuf::Descriptor;
+using google::protobuf::EnumValueDescriptor;
+using google::protobuf::FieldDescriptor;
+using google::protobuf::internal::WireFormat;
+using google::protobuf::internal::WireFormatLite;
+using util::Status;
+using util::StatusOr;
+
+namespace {
+// Finds a field with the given number. NULL if none found.
+const google::protobuf::Field* FindFieldByNumber(
+    const google::protobuf::Type& type, int number);
+
+// Returns true if the field is packable.
+bool IsPackable(const google::protobuf::Field& field);
+
+// Finds an enum value with the given number. NULL if none found.
+const google::protobuf::EnumValue* FindEnumValueByNumber(
+    const google::protobuf::Enum& tech_enum, int number);
+
+// Utility function to format nanos.
+const string FormatNanos(uint32 nanos);
+}  // namespace
+
+
+ProtoStreamObjectSource::ProtoStreamObjectSource(
+    google::protobuf::io::CodedInputStream* stream, TypeResolver* type_resolver,
+    const google::protobuf::Type& type)
+    : stream_(stream),
+      typeinfo_(TypeInfo::NewTypeInfo(type_resolver)),
+      own_typeinfo_(true),
+      type_(type) {
+  GOOGLE_LOG_IF(DFATAL, stream == NULL) << "Input stream is NULL.";
+}
+
+ProtoStreamObjectSource::ProtoStreamObjectSource(
+    google::protobuf::io::CodedInputStream* stream, TypeInfo* typeinfo,
+    const google::protobuf::Type& type)
+    : stream_(stream), typeinfo_(typeinfo), own_typeinfo_(false), type_(type) {
+  GOOGLE_LOG_IF(DFATAL, stream == NULL) << "Input stream is NULL.";
+}
+
+ProtoStreamObjectSource::~ProtoStreamObjectSource() {
+  if (own_typeinfo_) {
+    delete typeinfo_;
+  }
+}
+
+Status ProtoStreamObjectSource::NamedWriteTo(StringPiece name,
+                                             ObjectWriter* ow) const {
+  return WriteMessage(type_, name, 0, true, ow);
+}
+
+const google::protobuf::Field* ProtoStreamObjectSource::FindAndVerifyField(
+    const google::protobuf::Type& type, uint32 tag) const {
+  // Lookup the new field in the type by tag number.
+  const google::protobuf::Field* field = FindFieldByNumber(type, tag >> 3);
+  // Verify if the field corresponds to the wire type in tag.
+  // If there is any discrepancy, mark the field as not found.
+  if (field != NULL) {
+    WireFormatLite::WireType expected_type =
+        WireFormatLite::WireTypeForFieldType(
+            static_cast<WireFormatLite::FieldType>(field->kind()));
+    WireFormatLite::WireType actual_type = WireFormatLite::GetTagWireType(tag);
+    if (actual_type != expected_type &&
+        (!IsPackable(*field) ||
+         actual_type != WireFormatLite::WIRETYPE_LENGTH_DELIMITED)) {
+      field = NULL;
+    }
+  }
+  return field;
+}
+
+Status ProtoStreamObjectSource::WriteMessage(const google::protobuf::Type& type,
+                                             StringPiece name,
+                                             const uint32 end_tag,
+                                             bool include_start_and_end,
+                                             ObjectWriter* ow) const {
+  const TypeRenderer* type_renderer = FindTypeRenderer(type.name());
+  if (type_renderer != NULL) {
+    return (*type_renderer)(this, type, name, ow);
+  }
+
+  const google::protobuf::Field* field = NULL;
+  string field_name;
+  // last_tag set to dummy value that is different from tag.
+  uint32 tag = stream_->ReadTag(), last_tag = tag + 1;
+
+  if (include_start_and_end) {
+    ow->StartObject(name);
+  }
+  while (tag != end_tag) {
+    if (tag != last_tag) {  // Update field only if tag is changed.
+      last_tag = tag;
+      field = FindAndVerifyField(type, tag);
+      if (field != NULL) {
+        field_name = field->name();
+      }
+    }
+    if (field == NULL) {
+      // If we didn't find a field, skip this unknown tag.
+      // TODO(wpoon): Check return boolean value.
+      WireFormat::SkipField(stream_, tag, NULL);
+      tag = stream_->ReadTag();
+      continue;
+    }
+
+    if (field->cardinality() ==
+        google::protobuf::Field_Cardinality_CARDINALITY_REPEATED) {
+      if (IsMap(*field)) {
+        ow->StartObject(field_name);
+        ASSIGN_OR_RETURN(tag, RenderMap(field, field_name, tag, ow));
+        ow->EndObject();
+      } else {
+        ASSIGN_OR_RETURN(tag, RenderList(field, field_name, tag, ow));
+      }
+    } else {
+      // Render the field.
+      RETURN_IF_ERROR(RenderField(field, field_name, ow));
+      tag = stream_->ReadTag();
+    }
+  }
+  if (include_start_and_end) {
+    ow->EndObject();
+  }
+  return Status::OK;
+}
+
+StatusOr<uint32> ProtoStreamObjectSource::RenderList(
+    const google::protobuf::Field* field, StringPiece name, uint32 list_tag,
+    ObjectWriter* ow) const {
+  uint32 tag_to_return = 0;
+  ow->StartList(name);
+  if (IsPackable(*field) &&
+      list_tag ==
+          WireFormatLite::MakeTag(field->number(),
+                                  WireFormatLite::WIRETYPE_LENGTH_DELIMITED)) {
+    RETURN_IF_ERROR(RenderPacked(field, ow));
+    // Since packed fields have a single tag, read another tag from stream to
+    // return.
+    tag_to_return = stream_->ReadTag();
+  } else {
+    do {
+      RETURN_IF_ERROR(RenderField(field, "", ow));
+    } while ((tag_to_return = stream_->ReadTag()) == list_tag);
+  }
+  ow->EndList();
+  return tag_to_return;
+}
+
+StatusOr<uint32> ProtoStreamObjectSource::RenderMap(
+    const google::protobuf::Field* field, StringPiece name, uint32 list_tag,
+    ObjectWriter* ow) const {
+  const google::protobuf::Type* field_type =
+      typeinfo_->GetType(field->type_url());
+  uint32 tag_to_return = 0;
+  if (IsPackable(*field) &&
+      list_tag ==
+          WireFormatLite::MakeTag(field->number(),
+                                  WireFormatLite::WIRETYPE_LENGTH_DELIMITED)) {
+    RETURN_IF_ERROR(RenderPackedMapEntry(field_type, ow));
+    tag_to_return = stream_->ReadTag();
+  } else {
+    do {
+      RETURN_IF_ERROR(RenderMapEntry(field_type, ow));
+    } while ((tag_to_return = stream_->ReadTag()) == list_tag);
+  }
+  return tag_to_return;
+}
+
+Status ProtoStreamObjectSource::RenderMapEntry(
+    const google::protobuf::Type* type, ObjectWriter* ow) const {
+  uint32 buffer32;
+  stream_->ReadVarint32(&buffer32);  // message length
+  int old_limit = stream_->PushLimit(buffer32);
+  string map_key;
+  for (uint32 tag = stream_->ReadTag(); tag != 0; tag = stream_->ReadTag()) {
+    const google::protobuf::Field* field = FindAndVerifyField(*type, tag);
+    if (field == NULL) {
+      WireFormat::SkipField(stream_, tag, NULL);
+      continue;
+    }
+    // Map field numbers are key = 1 and value = 2
+    if (field->number() == 1) {
+      map_key = ReadFieldValueAsString(*field);
+    } else if (field->number() == 2) {
+      if (map_key.empty()) {
+        return Status(util::error::INTERNAL, "Map key must be non-empty");
+      }
+      // Disable case normalization for map keys as they are just data. We
+      // retain them intact.
+      ow->DisableCaseNormalizationForNextKey();
+      RETURN_IF_ERROR(RenderField(field, map_key, ow));
+    }
+  }
+  stream_->PopLimit(old_limit);
+
+  return Status::OK;
+}
+
+Status ProtoStreamObjectSource::RenderPacked(
+    const google::protobuf::Field* field, ObjectWriter* ow) const {
+  uint32 length;
+  stream_->ReadVarint32(&length);
+  int old_limit = stream_->PushLimit(length);
+  while (stream_->BytesUntilLimit() > 0) {
+    RETURN_IF_ERROR(RenderField(field, StringPiece(), ow));
+  }
+  stream_->PopLimit(old_limit);
+  return Status::OK;
+}
+
+Status ProtoStreamObjectSource::RenderPackedMapEntry(
+    const google::protobuf::Type* type, ObjectWriter* ow) const {
+  uint32 length;
+  stream_->ReadVarint32(&length);
+  int old_limit = stream_->PushLimit(length);
+  while (stream_->BytesUntilLimit() > 0) {
+    RETURN_IF_ERROR(RenderMapEntry(type, ow));
+  }
+  stream_->PopLimit(old_limit);
+  return Status::OK;
+}
+
+Status ProtoStreamObjectSource::RenderTimestamp(
+    const ProtoStreamObjectSource* os, const google::protobuf::Type& type,
+    StringPiece field_name, ObjectWriter* ow) {
+  pair<int64, int32> p = os->ReadSecondsAndNanos(type);
+  int64 seconds = p.first;
+  int32 nanos = p.second;
+  if (seconds > kMaxSeconds || seconds < kMinSeconds) {
+    return Status(
+        util::error::INTERNAL,
+        StrCat("Timestamp seconds exceeds limit for field: ", field_name));
+  }
+
+  if (nanos < 0 || nanos >= kNanosPerSecond) {
+    return Status(
+        util::error::INTERNAL,
+        StrCat("Timestamp nanos exceeds limit for field: ", field_name));
+  }
+
+  ow->RenderString(field_name,
+                   ::google::protobuf::internal::FormatTime(seconds, nanos));
+
+  return Status::OK;
+}
+
+Status ProtoStreamObjectSource::RenderDuration(
+    const ProtoStreamObjectSource* os, const google::protobuf::Type& type,
+    StringPiece field_name, ObjectWriter* ow) {
+  pair<int64, int32> p = os->ReadSecondsAndNanos(type);
+  int64 seconds = p.first;
+  int32 nanos = p.second;
+  if (seconds > kMaxSeconds || seconds < kMinSeconds) {
+    return Status(
+        util::error::INTERNAL,
+        StrCat("Duration seconds exceeds limit for field: ", field_name));
+  }
+
+  if (nanos <= -kNanosPerSecond || nanos >= kNanosPerSecond) {
+    return Status(
+        util::error::INTERNAL,
+        StrCat("Duration nanos exceeds limit for field: ", field_name));
+  }
+
+  string sign = "";
+  if (seconds < 0) {
+    if (nanos > 0) {
+      return Status(util::error::INTERNAL,
+                    StrCat(
+                        "Duration nanos is non-negative, but seconds is "
+                        "negative for field: ",
+                        field_name));
+    }
+    sign = "-";
+    seconds = -seconds;
+    nanos = -nanos;
+  } else if (seconds == 0 && nanos < 0) {
+    sign = "-";
+    nanos = -nanos;
+  }
+  string formatted_duration = StringPrintf("%s%lld%ss", sign.c_str(), seconds,
+                                           FormatNanos(nanos).c_str());
+  ow->RenderString(field_name, formatted_duration);
+  return Status::OK;
+}
+
+Status ProtoStreamObjectSource::RenderDouble(const ProtoStreamObjectSource* os,
+                                             const google::protobuf::Type& type,
+                                             StringPiece field_name,
+                                             ObjectWriter* ow) {
+  uint32 tag = os->stream_->ReadTag();
+  uint64 buffer64 = 0;  // default value of Double wrapper value
+  if (tag != 0) {
+    os->stream_->ReadLittleEndian64(&buffer64);
+    os->stream_->ReadTag();
+  }
+  ow->RenderDouble(field_name, bit_cast<double>(buffer64));
+  return Status::OK;
+}
+
+Status ProtoStreamObjectSource::RenderFloat(const ProtoStreamObjectSource* os,
+                                            const google::protobuf::Type& type,
+                                            StringPiece field_name,
+                                            ObjectWriter* ow) {
+  uint32 tag = os->stream_->ReadTag();
+  uint32 buffer32 = 0;  // default value of Float wrapper value
+  if (tag != 0) {
+    os->stream_->ReadLittleEndian32(&buffer32);
+    os->stream_->ReadTag();
+  }
+  ow->RenderFloat(field_name, bit_cast<float>(buffer32));
+  return Status::OK;
+}
+
+Status ProtoStreamObjectSource::RenderInt64(const ProtoStreamObjectSource* os,
+                                            const google::protobuf::Type& type,
+                                            StringPiece field_name,
+                                            ObjectWriter* ow) {
+  uint32 tag = os->stream_->ReadTag();
+  uint64 buffer64 = 0;  // default value of Int64 wrapper value
+  if (tag != 0) {
+    os->stream_->ReadVarint64(&buffer64);
+    os->stream_->ReadTag();
+  }
+  ow->RenderInt64(field_name, bit_cast<int64>(buffer64));
+  return Status::OK;
+}
+
+Status ProtoStreamObjectSource::RenderUInt64(const ProtoStreamObjectSource* os,
+                                             const google::protobuf::Type& type,
+                                             StringPiece field_name,
+                                             ObjectWriter* ow) {
+  uint32 tag = os->stream_->ReadTag();
+  uint64 buffer64 = 0;  // default value of UInt64 wrapper value
+  if (tag != 0) {
+    os->stream_->ReadVarint64(&buffer64);
+    os->stream_->ReadTag();
+  }
+  ow->RenderUint64(field_name, bit_cast<uint64>(buffer64));
+  return Status::OK;
+}
+
+Status ProtoStreamObjectSource::RenderInt32(const ProtoStreamObjectSource* os,
+                                            const google::protobuf::Type& type,
+                                            StringPiece field_name,
+                                            ObjectWriter* ow) {
+  uint32 tag = os->stream_->ReadTag();
+  uint32 buffer32 = 0;  // default value of Int32 wrapper value
+  if (tag != 0) {
+    os->stream_->ReadVarint32(&buffer32);
+    os->stream_->ReadTag();
+  }
+  ow->RenderInt32(field_name, bit_cast<int32>(buffer32));
+  return Status::OK;
+}
+
+Status ProtoStreamObjectSource::RenderUInt32(const ProtoStreamObjectSource* os,
+                                             const google::protobuf::Type& type,
+                                             StringPiece field_name,
+                                             ObjectWriter* ow) {
+  uint32 tag = os->stream_->ReadTag();
+  uint32 buffer32 = 0;  // default value of UInt32 wrapper value
+  if (tag != 0) {
+    os->stream_->ReadVarint32(&buffer32);
+    os->stream_->ReadTag();
+  }
+  ow->RenderUint32(field_name, bit_cast<uint32>(buffer32));
+  return Status::OK;
+}
+
+Status ProtoStreamObjectSource::RenderBool(const ProtoStreamObjectSource* os,
+                                           const google::protobuf::Type& type,
+                                           StringPiece field_name,
+                                           ObjectWriter* ow) {
+  uint32 tag = os->stream_->ReadTag();
+  uint64 buffer64 = 0;  // results in 'false' value as default, which is the
+                        // default value of Bool wrapper
+  if (tag != 0) {
+    os->stream_->ReadVarint64(&buffer64);
+    os->stream_->ReadTag();
+  }
+  ow->RenderBool(field_name, buffer64 != 0);
+  return Status::OK;
+}
+
+Status ProtoStreamObjectSource::RenderString(const ProtoStreamObjectSource* os,
+                                             const google::protobuf::Type& type,
+                                             StringPiece field_name,
+                                             ObjectWriter* ow) {
+  uint32 tag = os->stream_->ReadTag();
+  uint32 buffer32;
+  string str;  // default value of empty for String wrapper
+  if (tag != 0) {
+    os->stream_->ReadVarint32(&buffer32);  // string size.
+    os->stream_->ReadString(&str, buffer32);
+    os->stream_->ReadTag();
+  }
+  ow->RenderString(field_name, str);
+  return Status::OK;
+}
+
+Status ProtoStreamObjectSource::RenderBytes(const ProtoStreamObjectSource* os,
+                                            const google::protobuf::Type& type,
+                                            StringPiece field_name,
+                                            ObjectWriter* ow) {
+  uint32 tag = os->stream_->ReadTag();
+  uint32 buffer32;
+  string str;
+  if (tag != 0) {
+    os->stream_->ReadVarint32(&buffer32);
+    os->stream_->ReadString(&str, buffer32);
+    os->stream_->ReadTag();
+  }
+  ow->RenderBytes(field_name, str);
+  return Status::OK;
+}
+
+Status ProtoStreamObjectSource::RenderStruct(const ProtoStreamObjectSource* os,
+                                             const google::protobuf::Type& type,
+                                             StringPiece field_name,
+                                             ObjectWriter* ow) {
+  const google::protobuf::Field* field = NULL;
+  uint32 tag = os->stream_->ReadTag();
+  ow->StartObject(field_name);
+  while (tag != 0) {
+    field = os->FindAndVerifyField(type, tag);
+    // google.protobuf.Struct has only one field that is a map. Hence we use
+    // RenderMap to render that field.
+    if (os->IsMap(*field)) {
+      ASSIGN_OR_RETURN(tag, os->RenderMap(field, field_name, tag, ow));
+    }
+  }
+  ow->EndObject();
+  return Status::OK;
+}
+
+Status ProtoStreamObjectSource::RenderStructValue(
+    const ProtoStreamObjectSource* os, const google::protobuf::Type& type,
+    StringPiece field_name, ObjectWriter* ow) {
+  const google::protobuf::Field* field = NULL;
+  for (uint32 tag = os->stream_->ReadTag(); tag != 0;
+       tag = os->stream_->ReadTag()) {
+    field = os->FindAndVerifyField(type, tag);
+    if (field == NULL) {
+      WireFormat::SkipField(os->stream_, tag, NULL);
+      continue;
+    }
+    RETURN_IF_ERROR(os->RenderField(field, field_name, ow));
+  }
+  return Status::OK;
+}
+
+// TODO(skarvaje): Avoid code duplication of for loops and SkipField logic.
+Status ProtoStreamObjectSource::RenderStructListValue(
+    const ProtoStreamObjectSource* os, const google::protobuf::Type& type,
+    StringPiece field_name, ObjectWriter* ow) {
+  uint32 tag = os->stream_->ReadTag();
+
+  // Render empty list when we find empty ListValue message.
+  if (tag == 0) {
+    ow->StartList(field_name);
+    ow->EndList();
+    return Status::OK;
+  }
+
+  while (tag != 0) {
+    const google::protobuf::Field* field = os->FindAndVerifyField(type, tag);
+    if (field == NULL) {
+      WireFormat::SkipField(os->stream_, tag, NULL);
+      tag = os->stream_->ReadTag();
+      continue;
+    }
+    ASSIGN_OR_RETURN(tag, os->RenderList(field, field_name, tag, ow));
+  }
+  return Status::OK;
+}
+
+Status ProtoStreamObjectSource::RenderAny(const ProtoStreamObjectSource* os,
+                                          const google::protobuf::Type& type,
+                                          StringPiece field_name,
+                                          ObjectWriter* ow) {
+  // An Any is of the form { string type_url = 1; bytes value = 2; }
+  uint32 tag;
+  string type_url;
+  string value;
+
+  // First read out the type_url and value from the proto stream
+  for (tag = os->stream_->ReadTag(); tag != 0; tag = os->stream_->ReadTag()) {
+    const google::protobuf::Field* field = os->FindAndVerifyField(type, tag);
+    if (field == NULL) {
+      WireFormat::SkipField(os->stream_, tag, NULL);
+      continue;
+    }
+    // 'type_url' has field number of 1 and 'value' has field number 2
+    // //google/protobuf/any.proto
+    if (field->number() == 1) {
+      // read type_url
+      uint32 type_url_size;
+      os->stream_->ReadVarint32(&type_url_size);
+      os->stream_->ReadString(&type_url, type_url_size);
+    } else if (field->number() == 2) {
+      // read value
+      uint32 value_size;
+      os->stream_->ReadVarint32(&value_size);
+      os->stream_->ReadString(&value, value_size);
+    }
+  }
+
+  // If there is no value, we don't lookup the type, we just output it (if
+  // present). If both type and value are empty we output an empty object.
+  if (value.empty()) {
+    ow->StartObject(field_name);
+    if (!type_url.empty()) {
+      ow->RenderString("@type", type_url);
+    }
+    ow->EndObject();
+    return util::Status::OK;
+  }
+
+  // If there is a value but no type, we cannot render it, so report an error.
+  if (type_url.empty()) {
+    // TODO(sven): Add an external message once those are ready.
+    return util::Status(util::error::INTERNAL,
+                        "Invalid Any, the type_url is missing.");
+  }
+
+  util::StatusOr<const google::protobuf::Type*> resolved_type =
+      os->typeinfo_->ResolveTypeUrl(type_url);
+
+  if (!resolved_type.ok()) {
+    // Convert into an internal error, since this means the backend gave us
+    // an invalid response (missing or invalid type information).
+    return util::Status(util::error::INTERNAL,
+                        resolved_type.status().error_message());
+  }
+  // nested_type cannot be null at this time.
+  const google::protobuf::Type* nested_type = resolved_type.ValueOrDie();
+
+  // We know the type so we can render it. Recursively parse the nested stream
+  // using a nested ProtoStreamObjectSource using our nested type information.
+  google::protobuf::io::ArrayInputStream zero_copy_stream(value.data(), value.size());
+  google::protobuf::io::CodedInputStream in_stream(&zero_copy_stream);
+  ProtoStreamObjectSource nested_os(&in_stream, os->typeinfo_, *nested_type);
+
+  // We manually call start and end object here so we can inject the @type.
+  ow->StartObject(field_name);
+  ow->RenderString("@type", type_url);
+  util::Status result =
+      nested_os.WriteMessage(nested_os.type_, "value", 0, false, ow);
+  ow->EndObject();
+  return result;
+}
+
+Status ProtoStreamObjectSource::RenderFieldMask(
+    const ProtoStreamObjectSource* os, const google::protobuf::Type& type,
+    StringPiece field_name, ObjectWriter* ow) {
+  string combined;
+  uint32 buffer32;
+  uint32 paths_field_tag = 0;
+  for (uint32 tag = os->stream_->ReadTag(); tag != 0;
+       tag = os->stream_->ReadTag()) {
+    if (paths_field_tag == 0) {
+      const google::protobuf::Field* field = os->FindAndVerifyField(type, tag);
+      if (field != NULL && field->number() == 1 &&
+          field->name() == "paths") {
+        paths_field_tag = tag;
+      }
+    }
+    if (paths_field_tag != tag) {
+      return util::Status(util::error::INTERNAL,
+                          "Invalid FieldMask, unexpected field.");
+    }
+    string str;
+    os->stream_->ReadVarint32(&buffer32);  // string size.
+    os->stream_->ReadString(&str, buffer32);
+    if (!combined.empty()) {
+      combined.append(",");
+    }
+    combined.append(ConvertFieldMaskPath(str, &ToCamelCase));
+  }
+  ow->RenderString(field_name, combined);
+  return Status::OK;
+}
+
+hash_map<string, ProtoStreamObjectSource::TypeRenderer>*
+ProtoStreamObjectSource::CreateRendererMap() {
+  hash_map<string, ProtoStreamObjectSource::TypeRenderer>* result =
+      new hash_map<string, ProtoStreamObjectSource::TypeRenderer>();
+  (*result)["google.protobuf.Timestamp"] =
+      &ProtoStreamObjectSource::RenderTimestamp;
+  (*result)["google.protobuf.Duration"] =
+      &ProtoStreamObjectSource::RenderDuration;
+  (*result)["google.protobuf.DoubleValue"] =
+      &ProtoStreamObjectSource::RenderDouble;
+  (*result)["google.protobuf.FloatValue"] =
+      &ProtoStreamObjectSource::RenderFloat;
+  (*result)["google.protobuf.Int64Value"] =
+      &ProtoStreamObjectSource::RenderInt64;
+  (*result)["google.protobuf.UInt64Value"] =
+      &ProtoStreamObjectSource::RenderUInt64;
+  (*result)["google.protobuf.Int32Value"] =
+      &ProtoStreamObjectSource::RenderInt32;
+  (*result)["google.protobuf.UInt32Value"] =
+      &ProtoStreamObjectSource::RenderUInt32;
+  (*result)["google.protobuf.BoolValue"] = &ProtoStreamObjectSource::RenderBool;
+  (*result)["google.protobuf.StringValue"] =
+      &ProtoStreamObjectSource::RenderString;
+  (*result)["google.protobuf.BytesValue"] =
+      &ProtoStreamObjectSource::RenderBytes;
+  (*result)["google.protobuf.Any"] = &ProtoStreamObjectSource::RenderAny;
+  (*result)["google.protobuf.Struct"] = &ProtoStreamObjectSource::RenderStruct;
+  (*result)["google.protobuf.Value"] =
+      &ProtoStreamObjectSource::RenderStructValue;
+  (*result)["google.protobuf.ListValue"] =
+      &ProtoStreamObjectSource::RenderStructListValue;
+  (*result)["google.protobuf.FieldMask"] =
+      &ProtoStreamObjectSource::RenderFieldMask;
+  return result;
+}
+
+// static
+ProtoStreamObjectSource::TypeRenderer*
+ProtoStreamObjectSource::FindTypeRenderer(const string& type_url) {
+  static hash_map<string, TypeRenderer>* renderers = CreateRendererMap();
+  return FindOrNull(*renderers, type_url);
+}
+
+Status ProtoStreamObjectSource::RenderField(
+    const google::protobuf::Field* field, StringPiece field_name,
+    ObjectWriter* ow) const {
+  switch (field->kind()) {
+    case google::protobuf::Field_Kind_TYPE_BOOL: {
+      uint64 buffer64;
+      stream_->ReadVarint64(&buffer64);
+      ow->RenderBool(field_name, buffer64 != 0);
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_INT32: {
+      uint32 buffer32;
+      stream_->ReadVarint32(&buffer32);
+      ow->RenderInt32(field_name, bit_cast<int32>(buffer32));
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_INT64: {
+      uint64 buffer64;
+      stream_->ReadVarint64(&buffer64);
+      ow->RenderInt64(field_name, bit_cast<int64>(buffer64));
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_UINT32: {
+      uint32 buffer32;
+      stream_->ReadVarint32(&buffer32);
+      ow->RenderUint32(field_name, bit_cast<uint32>(buffer32));
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_UINT64: {
+      uint64 buffer64;
+      stream_->ReadVarint64(&buffer64);
+      ow->RenderUint64(field_name, bit_cast<uint64>(buffer64));
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_SINT32: {
+      uint32 buffer32;
+      stream_->ReadVarint32(&buffer32);
+      ow->RenderInt32(field_name, WireFormatLite::ZigZagDecode32(buffer32));
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_SINT64: {
+      uint64 buffer64;
+      stream_->ReadVarint64(&buffer64);
+      ow->RenderInt64(field_name, WireFormatLite::ZigZagDecode64(buffer64));
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_SFIXED32: {
+      uint32 buffer32;
+      stream_->ReadLittleEndian32(&buffer32);
+      ow->RenderInt32(field_name, bit_cast<int32>(buffer32));
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_SFIXED64: {
+      uint64 buffer64;
+      stream_->ReadLittleEndian64(&buffer64);
+      ow->RenderInt64(field_name, bit_cast<int64>(buffer64));
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_FIXED32: {
+      uint32 buffer32;
+      stream_->ReadLittleEndian32(&buffer32);
+      ow->RenderUint32(field_name, bit_cast<uint32>(buffer32));
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_FIXED64: {
+      uint64 buffer64;
+      stream_->ReadLittleEndian64(&buffer64);
+      ow->RenderUint64(field_name, bit_cast<uint64>(buffer64));
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_FLOAT: {
+      uint32 buffer32;
+      stream_->ReadLittleEndian32(&buffer32);
+      ow->RenderFloat(field_name, bit_cast<float>(buffer32));
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_DOUBLE: {
+      uint64 buffer64;
+      stream_->ReadLittleEndian64(&buffer64);
+      ow->RenderDouble(field_name, bit_cast<double>(buffer64));
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_ENUM: {
+      uint32 buffer32;
+      stream_->ReadVarint32(&buffer32);
+
+      // If the field represents an explicit NULL value, render null.
+      if (field->type_url() == kStructNullValueTypeUrl) {
+        ow->RenderNull(field_name);
+        break;
+      }
+
+      // Get the nested enum type for this field.
+      // TODO(skarvaje): Avoid string manipulation. Find ways to speed this
+      // up.
+      const google::protobuf::Enum* en = typeinfo_->GetEnum(field->type_url());
+      // Lookup the name of the enum, and render that. Skips unknown enums.
+      if (en != NULL) {
+        const google::protobuf::EnumValue* enum_value =
+            FindEnumValueByNumber(*en, buffer32);
+        if (enum_value != NULL) {
+          ow->RenderString(field_name, enum_value->name());
+        }
+      } else {
+        GOOGLE_LOG(INFO) << "Unkown enum skipped: " << field->type_url();
+      }
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_STRING: {
+      uint32 buffer32;
+      string str;
+      stream_->ReadVarint32(&buffer32);  // string size.
+      stream_->ReadString(&str, buffer32);
+      ow->RenderString(field_name, str);
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_BYTES: {
+      uint32 buffer32;
+      stream_->ReadVarint32(&buffer32);  // bytes size.
+      string value;
+      stream_->ReadString(&value, buffer32);
+      ow->RenderBytes(field_name, value);
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_MESSAGE: {
+      uint32 buffer32;
+      stream_->ReadVarint32(&buffer32);  // message length
+      int old_limit = stream_->PushLimit(buffer32);
+      // Get the nested message type for this field.
+      const google::protobuf::Type* type =
+          typeinfo_->GetType(field->type_url());
+      if (type == NULL) {
+        return Status(util::error::INTERNAL,
+                      StrCat("Invalid configuration. Could not find the type: ",
+                             field->type_url()));
+      }
+      RETURN_IF_ERROR(WriteMessage(*type, field_name, 0, true, ow));
+      if (!stream_->ConsumedEntireMessage()) {
+        return Status(util::error::INVALID_ARGUMENT,
+                      "Nested protocol message not parsed in its entirety.");
+      }
+      stream_->PopLimit(old_limit);
+      break;
+    }
+    default:
+      break;
+  }
+  return Status::OK;
+}
+
+// TODO(skarvaje): Fix this to avoid code duplication.
+const string ProtoStreamObjectSource::ReadFieldValueAsString(
+    const google::protobuf::Field& field) const {
+  string result;
+  switch (field.kind()) {
+    case google::protobuf::Field_Kind_TYPE_BOOL: {
+      uint64 buffer64;
+      stream_->ReadVarint64(&buffer64);
+      result = buffer64 != 0 ? "true" : "false";
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_INT32: {
+      uint32 buffer32;
+      stream_->ReadVarint32(&buffer32);
+      result = SimpleItoa(bit_cast<int32>(buffer32));
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_INT64: {
+      uint64 buffer64;
+      stream_->ReadVarint64(&buffer64);
+      result = SimpleItoa(bit_cast<int64>(buffer64));
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_UINT32: {
+      uint32 buffer32;
+      stream_->ReadVarint32(&buffer32);
+      result = SimpleItoa(bit_cast<uint32>(buffer32));
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_UINT64: {
+      uint64 buffer64;
+      stream_->ReadVarint64(&buffer64);
+      result = SimpleItoa(bit_cast<uint64>(buffer64));
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_SINT32: {
+      uint32 buffer32;
+      stream_->ReadVarint32(&buffer32);
+      result = SimpleItoa(WireFormatLite::ZigZagDecode32(buffer32));
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_SINT64: {
+      uint64 buffer64;
+      stream_->ReadVarint64(&buffer64);
+      result = SimpleItoa(WireFormatLite::ZigZagDecode64(buffer64));
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_SFIXED32: {
+      uint32 buffer32;
+      stream_->ReadLittleEndian32(&buffer32);
+      result = SimpleItoa(bit_cast<int32>(buffer32));
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_SFIXED64: {
+      uint64 buffer64;
+      stream_->ReadLittleEndian64(&buffer64);
+      result = SimpleItoa(bit_cast<int64>(buffer64));
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_FIXED32: {
+      uint32 buffer32;
+      stream_->ReadLittleEndian32(&buffer32);
+      result = SimpleItoa(bit_cast<uint32>(buffer32));
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_FIXED64: {
+      uint64 buffer64;
+      stream_->ReadLittleEndian64(&buffer64);
+      result = SimpleItoa(bit_cast<uint64>(buffer64));
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_FLOAT: {
+      uint32 buffer32;
+      stream_->ReadLittleEndian32(&buffer32);
+      result = SimpleFtoa(bit_cast<float>(buffer32));
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_DOUBLE: {
+      uint64 buffer64;
+      stream_->ReadLittleEndian64(&buffer64);
+      result = SimpleDtoa(bit_cast<double>(buffer64));
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_ENUM: {
+      uint32 buffer32;
+      stream_->ReadVarint32(&buffer32);
+      // Get the nested enum type for this field.
+      // TODO(skarvaje): Avoid string manipulation. Find ways to speed this
+      // up.
+      const google::protobuf::Enum* en = typeinfo_->GetEnum(field.type_url());
+      // Lookup the name of the enum, and render that. Skips unknown enums.
+      if (en != NULL) {
+        const google::protobuf::EnumValue* enum_value =
+            FindEnumValueByNumber(*en, buffer32);
+        if (enum_value != NULL) {
+          result = enum_value->name();
+        }
+      }
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_STRING: {
+      uint32 buffer32;
+      stream_->ReadVarint32(&buffer32);  // string size.
+      stream_->ReadString(&result, buffer32);
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_BYTES: {
+      uint32 buffer32;
+      stream_->ReadVarint32(&buffer32);  // bytes size.
+      stream_->ReadString(&result, buffer32);
+      break;
+    }
+    default:
+      break;
+  }
+  return result;
+}
+
+// Field is a map if it is a repeated message and it has an option "map_type".
+// TODO(skarvaje): Consider pre-computing the IsMap() into Field directly.
+bool ProtoStreamObjectSource::IsMap(
+    const google::protobuf::Field& field) const {
+  const google::protobuf::Type* field_type =
+      typeinfo_->GetType(field.type_url());
+
+  // TODO(xiaofeng): Unify option names.
+  return field.kind() == google::protobuf::Field_Kind_TYPE_MESSAGE &&
+         (GetBoolOptionOrDefault(field_type->options(),
+                                 "google.protobuf.MessageOptions.map_entry", false) ||
+          GetBoolOptionOrDefault(field_type->options(), "map_entry", false));
+}
+
+std::pair<int64, int32> ProtoStreamObjectSource::ReadSecondsAndNanos(
+    const google::protobuf::Type& type) const {
+  uint64 seconds = 0;
+  uint32 nanos = 0;
+  uint32 tag = 0;
+  int64 signed_seconds = 0;
+  int64 signed_nanos = 0;
+
+  for (tag = stream_->ReadTag(); tag != 0; tag = stream_->ReadTag()) {
+    const google::protobuf::Field* field = FindAndVerifyField(type, tag);
+    if (field == NULL) {
+      WireFormat::SkipField(stream_, tag, NULL);
+      continue;
+    }
+    // 'seconds' has field number of 1 and 'nanos' has field number 2
+    // //google/protobuf/timestamp.proto & duration.proto
+    if (field->number() == 1) {
+      // read seconds
+      stream_->ReadVarint64(&seconds);
+      signed_seconds = bit_cast<int64>(seconds);
+    } else if (field->number() == 2) {
+      // read nanos
+      stream_->ReadVarint32(&nanos);
+      signed_nanos = bit_cast<int32>(nanos);
+    }
+  }
+  return std::pair<int64, int32>(signed_seconds, signed_nanos);
+}
+
+namespace {
+// TODO(skarvaje): Speed this up by not doing a linear scan.
+const google::protobuf::Field* FindFieldByNumber(
+    const google::protobuf::Type& type, int number) {
+  for (int i = 0; i < type.fields_size(); ++i) {
+    if (type.fields(i).number() == number) {
+      return &type.fields(i);
+    }
+  }
+  return NULL;
+}
+
+// TODO(skarvaje): Replace FieldDescriptor by implementing IsTypePackable()
+// using tech Field.
+bool IsPackable(const google::protobuf::Field& field) {
+  return field.cardinality() ==
+             google::protobuf::Field_Cardinality_CARDINALITY_REPEATED &&
+         google::protobuf::FieldDescriptor::IsTypePackable(
+             static_cast<google::protobuf::FieldDescriptor::Type>(field.kind()));
+}
+
+// TODO(skarvaje): Speed this up by not doing a linear scan.
+const google::protobuf::EnumValue* FindEnumValueByNumber(
+    const google::protobuf::Enum& tech_enum, int number) {
+  for (int i = 0; i < tech_enum.enumvalue_size(); ++i) {
+    const google::protobuf::EnumValue& ev = tech_enum.enumvalue(i);
+    if (ev.number() == number) {
+      return &ev;
+    }
+  }
+  return NULL;
+}
+
+// TODO(skarvaje): Look into optimizing this by not doing computation on
+// double.
+const string FormatNanos(uint32 nanos) {
+  const char* format =
+      (nanos % 1000 != 0) ? "%.9f" : (nanos % 1000000 != 0) ? "%.6f" : "%.3f";
+  string formatted =
+      StringPrintf(format, static_cast<double>(nanos) / kNanosPerSecond);
+  // remove the leading 0 before decimal.
+  return formatted.substr(1);
+}
+}  // namespace
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/internal/protostream_objectsource.h b/src/google/protobuf/util/internal/protostream_objectsource.h
new file mode 100644
index 0000000..4a4e6bb
--- /dev/null
+++ b/src/google/protobuf/util/internal/protostream_objectsource.h
@@ -0,0 +1,245 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_PROTOBUF_UTIL_CONVERTER_PROTOSTREAM_OBJECTSOURCE_H__
+#define GOOGLE_PROTOBUF_UTIL_CONVERTER_PROTOSTREAM_OBJECTSOURCE_H__
+
+#include <functional>
+#include <google/protobuf/stubs/hash.h>
+#include <string>
+
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/type.pb.h>
+#include <google/protobuf/util/internal/object_source.h>
+#include <google/protobuf/util/internal/object_writer.h>
+#include <google/protobuf/util/internal/type_info.h>
+#include <google/protobuf/util/type_resolver.h>
+#include <google/protobuf/stubs/stringpiece.h>
+#include <google/protobuf/stubs/status.h>
+#include <google/protobuf/stubs/statusor.h>
+
+
+
+namespace google {
+namespace protobuf {
+class Field;
+class Type;
+}  // namespace protobuf
+
+
+namespace protobuf {
+namespace util {
+namespace converter {
+
+class TypeInfo;
+
+// An ObjectSource that can parse a stream of bytes as a protocol buffer.
+// This implementation uses a tech Type for tag lookup.
+//
+// Sample usage: (suppose input is: string proto)
+//   ArrayInputStream arr_stream(proto.data(), proto.size());
+//   CodedInputStream in_stream(&arr_stream);
+//   ProtoStreamObjectSource os(&in_stream, /*ServiceTypeInfo*/ typeinfo,
+//                              <your message google::protobuf::Type>);
+//
+//   Status status = os.WriteTo(<some ObjectWriter>);
+class LIBPROTOBUF_EXPORT ProtoStreamObjectSource : public ObjectSource {
+ public:
+  ProtoStreamObjectSource(google::protobuf::io::CodedInputStream* stream,
+                          TypeResolver* type_resolver,
+                          const google::protobuf::Type& type);
+
+  virtual ~ProtoStreamObjectSource();
+
+  virtual util::Status NamedWriteTo(StringPiece name, ObjectWriter* ow) const;
+
+ protected:
+  // Writes a proto2 Message to the ObjectWriter. When the given end_tag is
+  // found this method will complete, allowing it to be used for parsing both
+  // nested messages (end with 0) and nested groups (end with group end tag).
+  // The include_start_and_end parameter allows this method to be called when
+  // already inside of an object, and skip calling StartObject and EndObject.
+  virtual util::Status WriteMessage(const google::protobuf::Type& descriptor,
+                                      StringPiece name, const uint32 end_tag,
+                                      bool include_start_and_end,
+                                      ObjectWriter* ow) const;
+
+ private:
+  ProtoStreamObjectSource(google::protobuf::io::CodedInputStream* stream,
+                          TypeInfo* typeinfo,
+                          const google::protobuf::Type& type);
+  // Function that renders a well known type with a modified behavior.
+  typedef util::Status (*TypeRenderer)(const ProtoStreamObjectSource*,
+                                         const google::protobuf::Type&,
+                                         StringPiece, ObjectWriter*);
+
+  // Looks up a field and verify its consistency with wire type in tag.
+  const google::protobuf::Field* FindAndVerifyField(
+      const google::protobuf::Type& type, uint32 tag) const;
+
+  // TODO(skarvaje): Mark these methods as non-const as they modify internal
+  // state (stream_).
+  //
+  // Renders a repeating field (packed or unpacked).
+  // Returns the next tag after reading all sequential repeating elements. The
+  // caller should use this tag before reading more tags from the stream.
+  util::StatusOr<uint32> RenderList(const google::protobuf::Field* field,
+                                      StringPiece name, uint32 list_tag,
+                                      ObjectWriter* ow) const;
+  // Renders a NWP map.
+  // Returns the next tag after reading all map entries. The caller should use
+  // this tag before reading more tags from the stream.
+  util::StatusOr<uint32> RenderMap(const google::protobuf::Field* field,
+                                     StringPiece name, uint32 list_tag,
+                                     ObjectWriter* ow) const;
+
+  // Renders an entry in a map, advancing stream pointers appropriately.
+  util::Status RenderMapEntry(const google::protobuf::Type* type,
+                                ObjectWriter* ow) const;
+
+  // Renders a packed repeating field. A packed field is stored as:
+  // {tag length item1 item2 item3} instead of the less efficient
+  // {tag item1 tag item2 tag item3}.
+  util::Status RenderPacked(const google::protobuf::Field* field,
+                              ObjectWriter* ow) const;
+
+  // Equivalent of RenderPacked, but for map entries.
+  util::Status RenderPackedMapEntry(const google::protobuf::Type* type,
+                                      ObjectWriter* ow) const;
+
+  // Renders a google.protobuf.Timestamp value to ObjectWriter
+  static util::Status RenderTimestamp(const ProtoStreamObjectSource* os,
+                                        const google::protobuf::Type& type,
+                                        StringPiece name, ObjectWriter* ow);
+
+  // Renders a google.protobuf.Duration value to ObjectWriter
+  static util::Status RenderDuration(const ProtoStreamObjectSource* os,
+                                       const google::protobuf::Type& type,
+                                       StringPiece name, ObjectWriter* ow);
+
+  // Following RenderTYPE functions render well known types in
+  // google/protobuf/wrappers.proto corresponding to TYPE.
+  static util::Status RenderDouble(const ProtoStreamObjectSource* os,
+                                     const google::protobuf::Type& type,
+                                     StringPiece name, ObjectWriter* ow);
+  static util::Status RenderFloat(const ProtoStreamObjectSource* os,
+                                    const google::protobuf::Type& type,
+                                    StringPiece name, ObjectWriter* ow);
+  static util::Status RenderInt64(const ProtoStreamObjectSource* os,
+                                    const google::protobuf::Type& type,
+                                    StringPiece name, ObjectWriter* ow);
+  static util::Status RenderUInt64(const ProtoStreamObjectSource* os,
+                                     const google::protobuf::Type& type,
+                                     StringPiece name, ObjectWriter* ow);
+  static util::Status RenderInt32(const ProtoStreamObjectSource* os,
+                                    const google::protobuf::Type& type,
+                                    StringPiece name, ObjectWriter* ow);
+  static util::Status RenderUInt32(const ProtoStreamObjectSource* os,
+                                     const google::protobuf::Type& type,
+                                     StringPiece name, ObjectWriter* ow);
+  static util::Status RenderBool(const ProtoStreamObjectSource* os,
+                                   const google::protobuf::Type& type,
+                                   StringPiece name, ObjectWriter* ow);
+  static util::Status RenderString(const ProtoStreamObjectSource* os,
+                                     const google::protobuf::Type& type,
+                                     StringPiece name, ObjectWriter* ow);
+  static util::Status RenderBytes(const ProtoStreamObjectSource* os,
+                                    const google::protobuf::Type& type,
+                                    StringPiece name, ObjectWriter* ow);
+
+  // Renders a google.protobuf.Struct to ObjectWriter.
+  static util::Status RenderStruct(const ProtoStreamObjectSource* os,
+                                     const google::protobuf::Type& type,
+                                     StringPiece name, ObjectWriter* ow);
+
+  // Helper to render google.protobuf.Struct's Value fields to ObjectWriter.
+  static util::Status RenderStructValue(const ProtoStreamObjectSource* os,
+                                          const google::protobuf::Type& type,
+                                          StringPiece name, ObjectWriter* ow);
+
+  // Helper to render google.protobuf.Struct's ListValue fields to ObjectWriter.
+  static util::Status RenderStructListValue(
+      const ProtoStreamObjectSource* os,
+      const google::protobuf::Type& type,
+      StringPiece name, ObjectWriter* ow);
+
+  // Render the "Any" type.
+  static util::Status RenderAny(const ProtoStreamObjectSource* os,
+                                  const google::protobuf::Type& type,
+                                  StringPiece name, ObjectWriter* ow);
+
+  // Render the "FieldMask" type.
+  static util::Status RenderFieldMask(const ProtoStreamObjectSource* os,
+                                        const google::protobuf::Type& type,
+                                        StringPiece name, ObjectWriter* ow);
+
+  static hash_map<string, TypeRenderer>* CreateRendererMap();
+  static TypeRenderer* FindTypeRenderer(const string& type_url);
+
+  // Renders a field value to the ObjectWriter.
+  util::Status RenderField(const google::protobuf::Field* field,
+                             StringPiece field_name, ObjectWriter* ow) const;
+
+  // Reads field value according to Field spec in 'field' and returns the read
+  // value as string. This only works for primitive datatypes (no message
+  // types).
+  const string ReadFieldValueAsString(
+      const google::protobuf::Field& field) const;
+
+  // Utility function to detect proto maps. The 'field' MUST be repeated.
+  bool IsMap(const google::protobuf::Field& field) const;
+
+  // Utility to read int64 and int32 values from a message type in stream_.
+  // Used for reading google.protobuf.Timestamp and Duration messages.
+  std::pair<int64, int32> ReadSecondsAndNanos(
+      const google::protobuf::Type& type) const;
+
+  // Input stream to read from. Ownership rests with the caller.
+  google::protobuf::io::CodedInputStream* stream_;
+
+  // Type information for all the types used in the descriptor. Used to find
+  // google::protobuf::Type of nested messages/enums.
+  TypeInfo* typeinfo_;
+  // Whether this class owns the typeinfo_ object. If true the typeinfo_ object
+  // should be deleted in the destructor.
+  bool own_typeinfo_;
+
+  // google::protobuf::Type of the message source.
+  const google::protobuf::Type& type_;
+
+  GOOGLE_DISALLOW_IMPLICIT_CONSTRUCTORS(ProtoStreamObjectSource);
+};
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_CONVERTER_PROTOSTREAM_OBJECTSOURCE_H__
diff --git a/src/google/protobuf/util/internal/protostream_objectsource_test.cc b/src/google/protobuf/util/internal/protostream_objectsource_test.cc
new file mode 100644
index 0000000..630393f
--- /dev/null
+++ b/src/google/protobuf/util/internal/protostream_objectsource_test.cc
@@ -0,0 +1,824 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/util/internal/protostream_objectsource.h>
+
+#include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
+#include <sstream>
+
+#include <google/protobuf/stubs/casts.h>
+#include <google/protobuf/any.pb.h>
+#include <google/protobuf/io/coded_stream.h>
+#include <google/protobuf/io/zero_copy_stream_impl_lite.h>
+#include <google/protobuf/descriptor.h>
+#include <google/protobuf/util/internal/expecting_objectwriter.h>
+#include <google/protobuf/util/internal/testdata/books.pb.h>
+#include <google/protobuf/util/internal/testdata/field_mask.pb.h>
+#include <google/protobuf/util/internal/type_info_test_helper.h>
+#include <google/protobuf/util/internal/constants.h>
+#include <google/protobuf/stubs/strutil.h>
+#include <google/protobuf/util/internal/testdata/anys.pb.h>
+#include <google/protobuf/util/internal/testdata/maps.pb.h>
+#include <google/protobuf/util/internal/testdata/struct.pb.h>
+#include <gtest/gtest.h>
+
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+
+using google::protobuf::Descriptor;
+using google::protobuf::DescriptorPool;
+using google::protobuf::FileDescriptorProto;
+using google::protobuf::Message;
+using google::protobuf::io::ArrayInputStream;
+using google::protobuf::io::CodedInputStream;
+using util::Status;
+using google::protobuf::testing::Author;
+using google::protobuf::testing::BadAuthor;
+using google::protobuf::testing::BadNestedBook;
+using google::protobuf::testing::Book;
+using google::protobuf::testing::Book_Label;
+using google::protobuf::testing::NestedBook;
+using google::protobuf::testing::PackedPrimitive;
+using google::protobuf::testing::Primitive;
+using google::protobuf::testing::more_author;
+using google::protobuf::testing::maps::MapOut;
+using google::protobuf::testing::anys::AnyOut;
+using google::protobuf::testing::anys::AnyM;
+using google::protobuf::testing::FieldMaskTest;
+using google::protobuf::testing::NestedFieldMask;
+using google::protobuf::testing::structs::StructType;
+using ::testing::_;
+
+
+namespace {
+string GetTypeUrl(const Descriptor* descriptor) {
+  return string(kTypeServiceBaseUrl) + "/" + descriptor->full_name();
+}
+}  // namespace
+
+class ProtostreamObjectSourceTest
+    : public ::testing::TestWithParam<testing::TypeInfoSource> {
+ protected:
+  ProtostreamObjectSourceTest() : helper_(GetParam()), mock_(), ow_(&mock_) {
+    helper_.ResetTypeInfo(Book::descriptor());
+  }
+
+  virtual ~ProtostreamObjectSourceTest() {}
+
+  void DoTest(const Message& msg, const Descriptor* descriptor) {
+    Status status = ExecuteTest(msg, descriptor);
+    EXPECT_EQ(Status::OK, status);
+  }
+
+  Status ExecuteTest(const Message& msg, const Descriptor* descriptor) {
+    ostringstream oss;
+    msg.SerializePartialToOstream(&oss);
+    string proto = oss.str();
+    ArrayInputStream arr_stream(proto.data(), proto.size());
+    CodedInputStream in_stream(&arr_stream);
+
+    google::protobuf::scoped_ptr<ProtoStreamObjectSource> os(
+        helper_.NewProtoSource(&in_stream, GetTypeUrl(descriptor)));
+    return os->WriteTo(&mock_);
+  }
+
+  void PrepareExpectingObjectWriterForRepeatedPrimitive() {
+    ow_.StartObject("")
+        ->StartList("rep_fix32")
+        ->RenderUint32("", bit_cast<uint32>(3201))
+        ->RenderUint32("", bit_cast<uint32>(0))
+        ->RenderUint32("", bit_cast<uint32>(3202))
+        ->EndList()
+        ->StartList("rep_u32")
+        ->RenderUint32("", bit_cast<uint32>(3203))
+        ->RenderUint32("", bit_cast<uint32>(0))
+        ->EndList()
+        ->StartList("rep_i32")
+        ->RenderInt32("", 0)
+        ->RenderInt32("", 3204)
+        ->RenderInt32("", 3205)
+        ->EndList()
+        ->StartList("rep_sf32")
+        ->RenderInt32("", 3206)
+        ->RenderInt32("", 0)
+        ->EndList()
+        ->StartList("rep_s32")
+        ->RenderInt32("", 0)
+        ->RenderInt32("", 3207)
+        ->RenderInt32("", 3208)
+        ->EndList()
+        ->StartList("rep_fix64")
+        ->RenderUint64("", bit_cast<uint64>(6401L))
+        ->RenderUint64("", bit_cast<uint64>(0L))
+        ->EndList()
+        ->StartList("rep_u64")
+        ->RenderUint64("", bit_cast<uint64>(0L))
+        ->RenderUint64("", bit_cast<uint64>(6402L))
+        ->RenderUint64("", bit_cast<uint64>(6403L))
+        ->EndList()
+        ->StartList("rep_i64")
+        ->RenderInt64("", 6404L)
+        ->RenderInt64("", 0L)
+        ->EndList()
+        ->StartList("rep_sf64")
+        ->RenderInt64("", 0L)
+        ->RenderInt64("", 6405L)
+        ->RenderInt64("", 6406L)
+        ->EndList()
+        ->StartList("rep_s64")
+        ->RenderInt64("", 6407L)
+        ->RenderInt64("", 0L)
+        ->EndList()
+        ->StartList("rep_float")
+        ->RenderFloat("", 0.0f)
+        ->RenderFloat("", 32.1f)
+        ->RenderFloat("", 32.2f)
+        ->EndList()
+        ->StartList("rep_double")
+        ->RenderDouble("", 64.1L)
+        ->RenderDouble("", 0.0L)
+        ->EndList()
+        ->StartList("rep_bool")
+        ->RenderBool("", true)
+        ->RenderBool("", false)
+        ->EndList()
+        ->EndObject();
+  }
+
+  Primitive PrepareRepeatedPrimitive() {
+    Primitive primitive;
+    primitive.add_rep_fix32(3201);
+    primitive.add_rep_fix32(0);
+    primitive.add_rep_fix32(3202);
+    primitive.add_rep_u32(3203);
+    primitive.add_rep_u32(0);
+    primitive.add_rep_i32(0);
+    primitive.add_rep_i32(3204);
+    primitive.add_rep_i32(3205);
+    primitive.add_rep_sf32(3206);
+    primitive.add_rep_sf32(0);
+    primitive.add_rep_s32(0);
+    primitive.add_rep_s32(3207);
+    primitive.add_rep_s32(3208);
+    primitive.add_rep_fix64(6401L);
+    primitive.add_rep_fix64(0L);
+    primitive.add_rep_u64(0L);
+    primitive.add_rep_u64(6402L);
+    primitive.add_rep_u64(6403L);
+    primitive.add_rep_i64(6404L);
+    primitive.add_rep_i64(0L);
+    primitive.add_rep_sf64(0L);
+    primitive.add_rep_sf64(6405L);
+    primitive.add_rep_sf64(6406L);
+    primitive.add_rep_s64(6407L);
+    primitive.add_rep_s64(0L);
+    primitive.add_rep_float(0.0f);
+    primitive.add_rep_float(32.1f);
+    primitive.add_rep_float(32.2f);
+    primitive.add_rep_double(64.1L);
+    primitive.add_rep_double(0.0);
+    primitive.add_rep_bool(true);
+    primitive.add_rep_bool(false);
+
+    PrepareExpectingObjectWriterForRepeatedPrimitive();
+    return primitive;
+  }
+
+  PackedPrimitive PreparePackedPrimitive() {
+    PackedPrimitive primitive;
+    primitive.add_rep_fix32(3201);
+    primitive.add_rep_fix32(0);
+    primitive.add_rep_fix32(3202);
+    primitive.add_rep_u32(3203);
+    primitive.add_rep_u32(0);
+    primitive.add_rep_i32(0);
+    primitive.add_rep_i32(3204);
+    primitive.add_rep_i32(3205);
+    primitive.add_rep_sf32(3206);
+    primitive.add_rep_sf32(0);
+    primitive.add_rep_s32(0);
+    primitive.add_rep_s32(3207);
+    primitive.add_rep_s32(3208);
+    primitive.add_rep_fix64(6401L);
+    primitive.add_rep_fix64(0L);
+    primitive.add_rep_u64(0L);
+    primitive.add_rep_u64(6402L);
+    primitive.add_rep_u64(6403L);
+    primitive.add_rep_i64(6404L);
+    primitive.add_rep_i64(0L);
+    primitive.add_rep_sf64(0L);
+    primitive.add_rep_sf64(6405L);
+    primitive.add_rep_sf64(6406L);
+    primitive.add_rep_s64(6407L);
+    primitive.add_rep_s64(0L);
+    primitive.add_rep_float(0.0f);
+    primitive.add_rep_float(32.1f);
+    primitive.add_rep_float(32.2f);
+    primitive.add_rep_double(64.1L);
+    primitive.add_rep_double(0.0);
+    primitive.add_rep_bool(true);
+    primitive.add_rep_bool(false);
+
+    PrepareExpectingObjectWriterForRepeatedPrimitive();
+    return primitive;
+  }
+
+  testing::TypeInfoTestHelper helper_;
+
+  ::testing::NiceMock<MockObjectWriter> mock_;
+  ExpectingObjectWriter ow_;
+};
+
+INSTANTIATE_TEST_CASE_P(DifferentTypeInfoSourceTest,
+                        ProtostreamObjectSourceTest,
+                        ::testing::Values(
+                            testing::USE_TYPE_RESOLVER));
+
+TEST_P(ProtostreamObjectSourceTest, EmptyMessage) {
+  Book empty;
+  ow_.StartObject("")->EndObject();
+  DoTest(empty, Book::descriptor());
+}
+
+TEST_P(ProtostreamObjectSourceTest, Primitives) {
+  Primitive primitive;
+  primitive.set_fix32(3201);
+  primitive.set_u32(3202);
+  primitive.set_i32(3203);
+  primitive.set_sf32(3204);
+  primitive.set_s32(3205);
+  primitive.set_fix64(6401L);
+  primitive.set_u64(6402L);
+  primitive.set_i64(6403L);
+  primitive.set_sf64(6404L);
+  primitive.set_s64(6405L);
+  primitive.set_str("String Value");
+  primitive.set_bytes("Some Bytes");
+  primitive.set_float_(32.1f);
+  primitive.set_double_(64.1L);
+  primitive.set_bool_(true);
+
+  ow_.StartObject("")
+      ->RenderUint32("fix32", bit_cast<uint32>(3201))
+      ->RenderUint32("u32", bit_cast<uint32>(3202))
+      ->RenderInt32("i32", 3203)
+      ->RenderInt32("sf32", 3204)
+      ->RenderInt32("s32", 3205)
+      ->RenderUint64("fix64", bit_cast<uint64>(6401L))
+      ->RenderUint64("u64", bit_cast<uint64>(6402L))
+      ->RenderInt64("i64", 6403L)
+      ->RenderInt64("sf64", 6404L)
+      ->RenderInt64("s64", 6405L)
+      ->RenderString("str", "String Value")
+      ->RenderBytes("bytes", "Some Bytes")
+      ->RenderFloat("float", 32.1f)
+      ->RenderDouble("double", 64.1L)
+      ->RenderBool("bool", true)
+      ->EndObject();
+  DoTest(primitive, Primitive::descriptor());
+}
+
+TEST_P(ProtostreamObjectSourceTest, RepeatingPrimitives) {
+  Primitive primitive = PrepareRepeatedPrimitive();
+  primitive.add_rep_str("String One");
+  primitive.add_rep_str("String Two");
+  primitive.add_rep_bytes("Some Bytes");
+
+  ow_.StartList("rep_str")
+      ->RenderString("", "String One")
+      ->RenderString("", "String Two")
+      ->EndList()
+      ->StartList("rep_bytes")
+      ->RenderBytes("", "Some Bytes")
+      ->EndList();
+  DoTest(primitive, Primitive::descriptor());
+}
+
+TEST_P(ProtostreamObjectSourceTest, NestedMessage) {
+  Author* author = new Author();
+  author->set_id(101L);
+  author->set_name("Tolstoy");
+  Book book;
+  book.set_title("My Book");
+  book.set_allocated_author(author);
+
+  ow_.StartObject("")
+      ->RenderString("title", "My Book")
+      ->StartObject("author")
+      ->RenderUint64("id", bit_cast<uint64>(101L))
+      ->RenderString("name", "Tolstoy")
+      ->EndObject()
+      ->EndObject();
+  DoTest(book, Book::descriptor());
+}
+
+TEST_P(ProtostreamObjectSourceTest, RepeatingField) {
+  Author author;
+  author.set_alive(false);
+  author.set_name("john");
+  author.add_pseudonym("phil");
+  author.add_pseudonym("bob");
+
+  ow_.StartObject("")
+      ->RenderBool("alive", false)
+      ->RenderString("name", "john")
+      ->StartList("pseudonym")
+      ->RenderString("", "phil")
+      ->RenderString("", "bob")
+      ->EndList()
+      ->EndObject();
+  DoTest(author, Author::descriptor());
+}
+
+TEST_P(ProtostreamObjectSourceTest, PackedRepeatingFields) {
+  DoTest(PreparePackedPrimitive(), PackedPrimitive::descriptor());
+}
+
+TEST_P(ProtostreamObjectSourceTest, NonPackedPackableFieldsActuallyPacked) {
+  // Protostream is packed, but parse with non-packed Primitive.
+  DoTest(PreparePackedPrimitive(), Primitive::descriptor());
+}
+
+TEST_P(ProtostreamObjectSourceTest, PackedPackableFieldNotActuallyPacked) {
+  // Protostream is not packed, but parse with PackedPrimitive.
+  DoTest(PrepareRepeatedPrimitive(), PackedPrimitive::descriptor());
+}
+
+TEST_P(ProtostreamObjectSourceTest, BadAuthor) {
+  Author author;
+  author.set_alive(false);
+  author.set_name("john");
+  author.set_id(1234L);
+  author.add_pseudonym("phil");
+  author.add_pseudonym("bob");
+
+  ow_.StartObject("")
+      ->StartList("alive")
+      ->RenderBool("", false)
+      ->EndList()
+      ->StartList("name")
+      ->RenderUint64("", static_cast<uint64>('j'))
+      ->RenderUint64("", static_cast<uint64>('o'))
+      ->RenderUint64("", static_cast<uint64>('h'))
+      ->RenderUint64("", static_cast<uint64>('n'))
+      ->EndList()
+      ->RenderString("pseudonym", "phil")
+      ->RenderString("pseudonym", "bob")
+      ->EndObject();
+  // Protostream created with Author, but parsed with BadAuthor.
+  DoTest(author, BadAuthor::descriptor());
+}
+
+TEST_P(ProtostreamObjectSourceTest, NestedBookToBadNestedBook) {
+  Book* book = new Book();
+  book->set_length(250);
+  book->set_published(2014L);
+  NestedBook nested;
+  nested.set_allocated_book(book);
+
+  ow_.StartObject("")
+      ->StartList("book")
+      ->RenderUint32("", 24)  // tag for field length (3 << 3)
+      ->RenderUint32("", 250)
+      ->RenderUint32("", 32)  // tag for field published (4 << 3)
+      ->RenderUint32("", 2014)
+      ->EndList()
+      ->EndObject();
+  // Protostream created with NestedBook, but parsed with BadNestedBook.
+  DoTest(nested, BadNestedBook::descriptor());
+}
+
+TEST_P(ProtostreamObjectSourceTest, BadNestedBookToNestedBook) {
+  BadNestedBook nested;
+  nested.add_book(1);
+  nested.add_book(2);
+  nested.add_book(3);
+  nested.add_book(4);
+  nested.add_book(5);
+  nested.add_book(6);
+  nested.add_book(7);
+
+  ow_.StartObject("")->StartObject("book")->EndObject()->EndObject();
+  // Protostream created with BadNestedBook, but parsed with NestedBook.
+  DoTest(nested, NestedBook::descriptor());
+}
+
+TEST_P(ProtostreamObjectSourceTest,
+       LongRepeatedListDoesNotBreakIntoMultipleJsonLists) {
+  Book book;
+
+  int repeat = 10000;
+  for (int i = 0; i < repeat; ++i) {
+    Book_Label* label = book.add_labels();
+    label->set_key(StrCat("i", i));
+    label->set_value(StrCat("v", i));
+  }
+
+  // Make sure StartList and EndList are called exactly once (see b/18227499 for
+  // problems when this doesn't happen)
+  EXPECT_CALL(mock_, StartList(_)).Times(1);
+  EXPECT_CALL(mock_, EndList()).Times(1);
+
+  DoTest(book, Book::descriptor());
+}
+
+class ProtostreamObjectSourceMapsTest : public ProtostreamObjectSourceTest {
+ protected:
+  ProtostreamObjectSourceMapsTest() {
+    helper_.ResetTypeInfo(MapOut::descriptor());
+  }
+};
+
+INSTANTIATE_TEST_CASE_P(DifferentTypeInfoSourceTest,
+                        ProtostreamObjectSourceMapsTest,
+                        ::testing::Values(
+                            testing::USE_TYPE_RESOLVER));
+
+// Tests JSON map.
+//
+// This is the example expected output.
+// {
+//   "map1": {
+//     "key1": {
+//       "foo": "foovalue"
+//     },
+//     "key2": {
+//       "foo": "barvalue"
+//     }
+//   },
+//   "map2": {
+//     "nestedself": {
+//       "map1": {
+//         "nested_key1": {
+//           "foo": "nested_foo"
+//         }
+//       },
+//       "bar": "nested_bar_string"
+//     }
+//   },
+//   "map3": {
+//     "111": "one one one"
+//   },
+//   "bar": "top bar"
+// }
+TEST_P(ProtostreamObjectSourceMapsTest, MapsTest) {
+  MapOut out;
+  (*out.mutable_map1())["key1"].set_foo("foovalue");
+  (*out.mutable_map1())["key2"].set_foo("barvalue");
+
+  MapOut* nested_value = &(*out.mutable_map2())["nestedself"];
+  (*nested_value->mutable_map1())["nested_key1"].set_foo("nested_foo");
+  nested_value->set_bar("nested_bar_string");
+
+  (*out.mutable_map3())[111] = "one one one";
+
+  out.set_bar("top bar");
+
+  ow_.StartObject("")
+      ->StartObject("map1")
+      ->StartObject("key1")
+      ->RenderString("foo", "foovalue")
+      ->EndObject()
+      ->StartObject("key2")
+      ->RenderString("foo", "barvalue")
+      ->EndObject()
+      ->StartObject("map2")
+      ->StartObject("nestedself")
+      ->StartObject("map1")
+      ->StartObject("nested_key1")
+      ->RenderString("foo", "nested_foo")
+      ->EndObject()
+      ->EndObject()
+      ->RenderString("bar", "nested_bar_string")
+      ->EndObject()
+      ->EndObject()
+      ->StartObject("map3")
+      ->RenderString("111", "one one one")
+      ->EndObject()
+      ->EndObject()
+      ->RenderString("bar", "top bar")
+      ->EndObject();
+
+  DoTest(out, MapOut::descriptor());
+}
+
+class ProtostreamObjectSourceAnysTest : public ProtostreamObjectSourceTest {
+ protected:
+  ProtostreamObjectSourceAnysTest() {
+    helper_.ResetTypeInfo(AnyOut::descriptor(),
+                          google::protobuf::Any::descriptor());
+  }
+};
+
+INSTANTIATE_TEST_CASE_P(DifferentTypeInfoSourceTest,
+                        ProtostreamObjectSourceAnysTest,
+                        ::testing::Values(
+                            testing::USE_TYPE_RESOLVER));
+
+// Tests JSON any support.
+//
+// This is the example expected output.
+// {
+//   "any": {
+//     "@type": "type.googleapis.com/google.protobuf.testing.anys.AnyM"
+//     "foo": "foovalue"
+//   }
+// }
+TEST_P(ProtostreamObjectSourceAnysTest, BasicAny) {
+  AnyOut out;
+  ::google::protobuf::Any* any = out.mutable_any();
+
+  AnyM m;
+  m.set_foo("foovalue");
+  any->PackFrom(m);
+
+  ow_.StartObject("")
+      ->StartObject("any")
+      ->RenderString("@type",
+                     "type.googleapis.com/google.protobuf.testing.anys.AnyM")
+      ->RenderString("foo", "foovalue")
+      ->EndObject()
+      ->EndObject();
+
+  DoTest(out, AnyOut::descriptor());
+}
+
+TEST_P(ProtostreamObjectSourceAnysTest, RecursiveAny) {
+  AnyOut out;
+  ::google::protobuf::Any* any = out.mutable_any();
+  any->set_type_url("type.googleapis.com/google.protobuf.Any");
+
+  ::google::protobuf::Any nested_any;
+  nested_any.set_type_url(
+      "type.googleapis.com/google.protobuf.testing.anys.AnyM");
+
+  AnyM m;
+  m.set_foo("foovalue");
+  nested_any.set_value(m.SerializeAsString());
+
+  any->set_value(nested_any.SerializeAsString());
+
+  ow_.StartObject("")
+      ->StartObject("any")
+      ->RenderString("@type", "type.googleapis.com/google.protobuf.Any")
+      ->StartObject("value")
+      ->RenderString("@type",
+                     "type.googleapis.com/google.protobuf.testing.anys.AnyM")
+      ->RenderString("foo", "foovalue")
+      ->EndObject()
+      ->EndObject()
+      ->EndObject();
+
+  DoTest(out, AnyOut::descriptor());
+}
+
+TEST_P(ProtostreamObjectSourceAnysTest, DoubleRecursiveAny) {
+  AnyOut out;
+  ::google::protobuf::Any* any = out.mutable_any();
+  any->set_type_url("type.googleapis.com/google.protobuf.Any");
+
+  ::google::protobuf::Any nested_any;
+  nested_any.set_type_url("type.googleapis.com/google.protobuf.Any");
+
+  ::google::protobuf::Any second_nested_any;
+  second_nested_any.set_type_url(
+      "type.googleapis.com/google.protobuf.testing.anys.AnyM");
+
+  AnyM m;
+  m.set_foo("foovalue");
+  second_nested_any.set_value(m.SerializeAsString());
+  nested_any.set_value(second_nested_any.SerializeAsString());
+  any->set_value(nested_any.SerializeAsString());
+
+  ow_.StartObject("")
+      ->StartObject("any")
+      ->RenderString("@type", "type.googleapis.com/google.protobuf.Any")
+      ->StartObject("value")
+      ->RenderString("@type", "type.googleapis.com/google.protobuf.Any")
+      ->StartObject("value")
+      ->RenderString("@type",
+                     "type.googleapis.com/google.protobuf.testing.anys.AnyM")
+      ->RenderString("foo", "foovalue")
+      ->EndObject()
+      ->EndObject()
+      ->EndObject()
+      ->EndObject();
+
+  DoTest(out, AnyOut::descriptor());
+}
+
+TEST_P(ProtostreamObjectSourceAnysTest, EmptyAnyOutputsEmptyObject) {
+  AnyOut out;
+  out.mutable_any();
+
+  ow_.StartObject("")->StartObject("any")->EndObject()->EndObject();
+
+  DoTest(out, AnyOut::descriptor());
+}
+
+TEST_P(ProtostreamObjectSourceAnysTest, EmptyWithTypeAndNoValueOutputsType) {
+  AnyOut out;
+  out.mutable_any()->set_type_url("foo.googleapis.com/my.Type");
+
+  ow_.StartObject("")
+      ->StartObject("any")
+      ->RenderString("@type", "foo.googleapis.com/my.Type")
+      ->EndObject()
+      ->EndObject();
+
+  DoTest(out, AnyOut::descriptor());
+}
+
+TEST_P(ProtostreamObjectSourceAnysTest, MissingTypeUrlError) {
+  AnyOut out;
+  ::google::protobuf::Any* any = out.mutable_any();
+
+  AnyM m;
+  m.set_foo("foovalue");
+  any->set_value(m.SerializeAsString());
+
+  // We start the "AnyOut" part and then fail when we hit the Any object.
+  ow_.StartObject("");
+
+  Status status = ExecuteTest(out, AnyOut::descriptor());
+  EXPECT_EQ(util::error::INTERNAL, status.error_code());
+}
+
+TEST_P(ProtostreamObjectSourceAnysTest, UnknownTypeServiceError) {
+  AnyOut out;
+  ::google::protobuf::Any* any = out.mutable_any();
+  any->set_type_url("foo.googleapis.com/my.own.Type");
+
+  AnyM m;
+  m.set_foo("foovalue");
+  any->set_value(m.SerializeAsString());
+
+  // We start the "AnyOut" part and then fail when we hit the Any object.
+  ow_.StartObject("");
+
+  Status status = ExecuteTest(out, AnyOut::descriptor());
+  EXPECT_EQ(util::error::INTERNAL, status.error_code());
+}
+
+TEST_P(ProtostreamObjectSourceAnysTest, UnknownTypeError) {
+  AnyOut out;
+  ::google::protobuf::Any* any = out.mutable_any();
+  any->set_type_url("type.googleapis.com/unknown.Type");
+
+  AnyM m;
+  m.set_foo("foovalue");
+  any->set_value(m.SerializeAsString());
+
+  // We start the "AnyOut" part and then fail when we hit the Any object.
+  ow_.StartObject("");
+
+  Status status = ExecuteTest(out, AnyOut::descriptor());
+  EXPECT_EQ(util::error::INTERNAL, status.error_code());
+}
+
+class ProtostreamObjectSourceStructTest : public ProtostreamObjectSourceTest {
+ protected:
+  ProtostreamObjectSourceStructTest() {
+    helper_.ResetTypeInfo(StructType::descriptor(),
+                          google::protobuf::Struct::descriptor());
+  }
+};
+
+INSTANTIATE_TEST_CASE_P(DifferentTypeInfoSourceTest,
+                        ProtostreamObjectSourceStructTest,
+                        ::testing::Values(
+                            testing::USE_TYPE_RESOLVER));
+
+// Tests struct
+//
+//  "object": {
+//    "k1": 123,
+//    "k2": true
+//  }
+TEST_P(ProtostreamObjectSourceStructTest, StructRenderSuccess) {
+  StructType out;
+  google::protobuf::Struct* s = out.mutable_object();
+  s->mutable_fields()->operator[]("k1").set_number_value(123);
+  s->mutable_fields()->operator[]("k2").set_bool_value(true);
+
+  ow_.StartObject("")
+      ->StartObject("object")
+      ->RenderDouble("k1", 123)
+      ->RenderBool("k2", true)
+      ->EndObject()
+      ->EndObject();
+
+  DoTest(out, StructType::descriptor());
+}
+
+TEST_P(ProtostreamObjectSourceStructTest, MissingValueSkipsField) {
+  StructType out;
+  google::protobuf::Struct* s = out.mutable_object();
+  s->mutable_fields()->operator[]("k1");
+
+  ow_.StartObject("")->StartObject("object")->EndObject()->EndObject();
+
+  DoTest(out, StructType::descriptor());
+}
+
+class ProtostreamObjectSourceFieldMaskTest
+    : public ProtostreamObjectSourceTest {
+ protected:
+  ProtostreamObjectSourceFieldMaskTest() {
+    helper_.ResetTypeInfo(FieldMaskTest::descriptor(),
+                          google::protobuf::FieldMask::descriptor());
+  }
+};
+
+INSTANTIATE_TEST_CASE_P(DifferentTypeInfoSourceTest,
+                        ProtostreamObjectSourceFieldMaskTest,
+                        ::testing::Values(
+                            testing::USE_TYPE_RESOLVER));
+
+TEST_P(ProtostreamObjectSourceFieldMaskTest, FieldMaskRenderSuccess) {
+  FieldMaskTest out;
+  out.set_id("1");
+  out.mutable_single_mask()->add_paths("path1");
+  out.mutable_single_mask()->add_paths("snake_case_path2");
+  ::google::protobuf::FieldMask* mask = out.add_repeated_mask();
+  mask->add_paths("path3");
+  mask = out.add_repeated_mask();
+  mask->add_paths("snake_case_path4");
+  mask->add_paths("path5");
+  NestedFieldMask* nested = out.add_nested_mask();
+  nested->set_data("data");
+  nested->mutable_single_mask()->add_paths("nested.path1");
+  nested->mutable_single_mask()->add_paths("nested_field.snake_case_path2");
+  mask = nested->add_repeated_mask();
+  mask->add_paths("nested_field.path3");
+  mask->add_paths("nested.snake_case_path4");
+  mask = nested->add_repeated_mask();
+  mask->add_paths("nested.path5");
+  mask = nested->add_repeated_mask();
+  mask->add_paths(
+      "snake_case.map_field[\"map_key_should_be_ignored\"].nested_snake_case."
+      "map_field[\"map_key_sho\\\"uld_be_ignored\"]");
+
+  ow_.StartObject("")
+      ->RenderString("id", "1")
+      ->RenderString("single_mask", "path1,snakeCasePath2")
+      ->StartList("repeated_mask")
+      ->RenderString("", "path3")
+      ->RenderString("", "snakeCasePath4,path5")
+      ->EndList()
+      ->StartList("nested_mask")
+      ->StartObject("")
+      ->RenderString("data", "data")
+      ->RenderString("single_mask", "nested.path1,nestedField.snakeCasePath2")
+      ->StartList("repeated_mask")
+      ->RenderString("", "nestedField.path3,nested.snakeCasePath4")
+      ->RenderString("", "nested.path5")
+      ->RenderString("",
+                     "snakeCase.mapField[\"map_key_should_be_ignored\"]."
+                     "nestedSnakeCase.mapField[\"map_key_sho\\\"uld_be_"
+                     "ignored\"]")
+      ->EndList()
+      ->EndObject()
+      ->EndList()
+      ->EndObject();
+
+  DoTest(out, FieldMaskTest::descriptor());
+}
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/internal/protostream_objectwriter.cc b/src/google/protobuf/util/internal/protostream_objectwriter.cc
new file mode 100644
index 0000000..f9ddbf3
--- /dev/null
+++ b/src/google/protobuf/util/internal/protostream_objectwriter.cc
@@ -0,0 +1,1557 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/util/internal/protostream_objectwriter.h>
+
+#include <functional>
+#include <stack>
+
+#include <google/protobuf/stubs/time.h>
+#include <google/protobuf/wire_format_lite.h>
+#include <google/protobuf/util/internal/field_mask_utility.h>
+#include <google/protobuf/util/internal/object_location_tracker.h>
+#include <google/protobuf/util/internal/constants.h>
+#include <google/protobuf/util/internal/utility.h>
+#include <google/protobuf/stubs/strutil.h>
+#include <google/protobuf/stubs/map_util.h>
+#include <google/protobuf/stubs/statusor.h>
+
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+
+using google::protobuf::internal::WireFormatLite;
+using google::protobuf::io::CodedOutputStream;
+using util::error::INVALID_ARGUMENT;
+using util::Status;
+using util::StatusOr;
+
+
+ProtoStreamObjectWriter::ProtoStreamObjectWriter(
+    TypeResolver* type_resolver, const google::protobuf::Type& type,
+    strings::ByteSink* output, ErrorListener* listener)
+    : master_type_(type),
+      typeinfo_(TypeInfo::NewTypeInfo(type_resolver)),
+      own_typeinfo_(true),
+      done_(false),
+      element_(NULL),
+      size_insert_(),
+      output_(output),
+      buffer_(),
+      adapter_(&buffer_),
+      stream_(new CodedOutputStream(&adapter_)),
+      listener_(listener),
+      invalid_depth_(0),
+      tracker_(new ObjectLocationTracker()) {}
+
+ProtoStreamObjectWriter::ProtoStreamObjectWriter(
+    TypeInfo* typeinfo, const google::protobuf::Type& type,
+    strings::ByteSink* output, ErrorListener* listener)
+    : master_type_(type),
+      typeinfo_(typeinfo),
+      own_typeinfo_(false),
+      done_(false),
+      element_(NULL),
+      size_insert_(),
+      output_(output),
+      buffer_(),
+      adapter_(&buffer_),
+      stream_(new CodedOutputStream(&adapter_)),
+      listener_(listener),
+      invalid_depth_(0),
+      tracker_(new ObjectLocationTracker()) {}
+
+ProtoStreamObjectWriter::~ProtoStreamObjectWriter() {
+  // Cleanup explicitly in order to avoid destructor stack overflow when input
+  // is deeply nested.
+  while (element_ != NULL) {
+    element_.reset(element_->pop());
+  }
+  if (own_typeinfo_) {
+    delete typeinfo_;
+  }
+}
+
+namespace {
+
+// Writes an INT32 field, including tag to the stream.
+inline Status WriteInt32(int field_number, const DataPiece& data,
+                         CodedOutputStream* stream) {
+  StatusOr<int32> i32 = data.ToInt32();
+  if (i32.ok()) {
+    WireFormatLite::WriteInt32(field_number, i32.ValueOrDie(), stream);
+  }
+  return i32.status();
+}
+
+// writes an SFIXED32 field, including tag, to the stream.
+inline Status WriteSFixed32(int field_number, const DataPiece& data,
+                            CodedOutputStream* stream) {
+  StatusOr<int32> i32 = data.ToInt32();
+  if (i32.ok()) {
+    WireFormatLite::WriteSFixed32(field_number, i32.ValueOrDie(), stream);
+  }
+  return i32.status();
+}
+
+// Writes an SINT32 field, including tag, to the stream.
+inline Status WriteSInt32(int field_number, const DataPiece& data,
+                          CodedOutputStream* stream) {
+  StatusOr<int32> i32 = data.ToInt32();
+  if (i32.ok()) {
+    WireFormatLite::WriteSInt32(field_number, i32.ValueOrDie(), stream);
+  }
+  return i32.status();
+}
+
+// Writes a FIXED32 field, including tag, to the stream.
+inline Status WriteFixed32(int field_number, const DataPiece& data,
+                           CodedOutputStream* stream) {
+  StatusOr<uint32> u32 = data.ToUint32();
+  if (u32.ok()) {
+    WireFormatLite::WriteFixed32(field_number, u32.ValueOrDie(), stream);
+  }
+  return u32.status();
+}
+
+// Writes a UINT32 field, including tag, to the stream.
+inline Status WriteUInt32(int field_number, const DataPiece& data,
+                          CodedOutputStream* stream) {
+  StatusOr<uint32> u32 = data.ToUint32();
+  if (u32.ok()) {
+    WireFormatLite::WriteUInt32(field_number, u32.ValueOrDie(), stream);
+  }
+  return u32.status();
+}
+
+// Writes an INT64 field, including tag, to the stream.
+inline Status WriteInt64(int field_number, const DataPiece& data,
+                         CodedOutputStream* stream) {
+  StatusOr<int64> i64 = data.ToInt64();
+  if (i64.ok()) {
+    WireFormatLite::WriteInt64(field_number, i64.ValueOrDie(), stream);
+  }
+  return i64.status();
+}
+
+// Writes an SFIXED64 field, including tag, to the stream.
+inline Status WriteSFixed64(int field_number, const DataPiece& data,
+                            CodedOutputStream* stream) {
+  StatusOr<int64> i64 = data.ToInt64();
+  if (i64.ok()) {
+    WireFormatLite::WriteSFixed64(field_number, i64.ValueOrDie(), stream);
+  }
+  return i64.status();
+}
+
+// Writes an SINT64 field, including tag, to the stream.
+inline Status WriteSInt64(int field_number, const DataPiece& data,
+                          CodedOutputStream* stream) {
+  StatusOr<int64> i64 = data.ToInt64();
+  if (i64.ok()) {
+    WireFormatLite::WriteSInt64(field_number, i64.ValueOrDie(), stream);
+  }
+  return i64.status();
+}
+
+// Writes a FIXED64 field, including tag, to the stream.
+inline Status WriteFixed64(int field_number, const DataPiece& data,
+                           CodedOutputStream* stream) {
+  StatusOr<uint64> u64 = data.ToUint64();
+  if (u64.ok()) {
+    WireFormatLite::WriteFixed64(field_number, u64.ValueOrDie(), stream);
+  }
+  return u64.status();
+}
+
+// Writes a UINT64 field, including tag, to the stream.
+inline Status WriteUInt64(int field_number, const DataPiece& data,
+                          CodedOutputStream* stream) {
+  StatusOr<uint64> u64 = data.ToUint64();
+  if (u64.ok()) {
+    WireFormatLite::WriteUInt64(field_number, u64.ValueOrDie(), stream);
+  }
+  return u64.status();
+}
+
+// Writes a DOUBLE field, including tag, to the stream.
+inline Status WriteDouble(int field_number, const DataPiece& data,
+                          CodedOutputStream* stream) {
+  StatusOr<double> d = data.ToDouble();
+  if (d.ok()) {
+    WireFormatLite::WriteDouble(field_number, d.ValueOrDie(), stream);
+  }
+  return d.status();
+}
+
+// Writes a FLOAT field, including tag, to the stream.
+inline Status WriteFloat(int field_number, const DataPiece& data,
+                         CodedOutputStream* stream) {
+  StatusOr<float> f = data.ToFloat();
+  if (f.ok()) {
+    WireFormatLite::WriteFloat(field_number, f.ValueOrDie(), stream);
+  }
+  return f.status();
+}
+
+// Writes a BOOL field, including tag, to the stream.
+inline Status WriteBool(int field_number, const DataPiece& data,
+                        CodedOutputStream* stream) {
+  StatusOr<bool> b = data.ToBool();
+  if (b.ok()) {
+    WireFormatLite::WriteBool(field_number, b.ValueOrDie(), stream);
+  }
+  return b.status();
+}
+
+// Writes a BYTES field, including tag, to the stream.
+inline Status WriteBytes(int field_number, const DataPiece& data,
+                         CodedOutputStream* stream) {
+  StatusOr<string> c = data.ToBytes();
+  if (c.ok()) {
+    WireFormatLite::WriteBytes(field_number, c.ValueOrDie(), stream);
+  }
+  return c.status();
+}
+
+// Writes a STRING field, including tag, to the stream.
+inline Status WriteString(int field_number, const DataPiece& data,
+                          CodedOutputStream* stream) {
+  StatusOr<string> s = data.ToString();
+  if (s.ok()) {
+    WireFormatLite::WriteString(field_number, s.ValueOrDie(), stream);
+  }
+  return s.status();
+}
+
+// Writes an ENUM field, including tag, to the stream.
+inline Status WriteEnum(int field_number, const DataPiece& data,
+                        const google::protobuf::Enum* enum_type,
+                        CodedOutputStream* stream) {
+  StatusOr<int> e = data.ToEnum(enum_type);
+  if (e.ok()) {
+    WireFormatLite::WriteEnum(field_number, e.ValueOrDie(), stream);
+  }
+  return e.status();
+}
+
+// Given a google::protobuf::Type, returns the set of all required fields.
+std::set<const google::protobuf::Field*> GetRequiredFields(
+    const google::protobuf::Type& type) {
+  std::set<const google::protobuf::Field*> required;
+  for (int i = 0; i < type.fields_size(); i++) {
+    const google::protobuf::Field& field = type.fields(i);
+    if (field.cardinality() ==
+        google::protobuf::Field_Cardinality_CARDINALITY_REQUIRED) {
+      required.insert(&field);
+    }
+  }
+  return required;
+}
+
+// Utility method to split a string representation of Timestamp or Duration and
+// return the parts.
+void SplitSecondsAndNanos(StringPiece input, StringPiece* seconds,
+                          StringPiece* nanos) {
+  size_t idx = input.rfind('.');
+  if (idx != string::npos) {
+    *seconds = input.substr(0, idx);
+    *nanos = input.substr(idx + 1);
+  } else {
+    *seconds = input;
+    *nanos = StringPiece();
+  }
+}
+
+}  // namespace
+
+ProtoStreamObjectWriter::AnyWriter::AnyWriter(ProtoStreamObjectWriter* parent)
+    : parent_(parent),
+      ow_(),
+      invalid_(false),
+      data_(),
+      output_(&data_),
+      depth_(0),
+      has_injected_value_message_(false) {}
+
+ProtoStreamObjectWriter::AnyWriter::~AnyWriter() {}
+
+void ProtoStreamObjectWriter::AnyWriter::StartObject(StringPiece name) {
+  ++depth_;
+  // If an object writer is absent, that means we have not called StartAny()
+  // before reaching here. This is an invalid state. StartAny() gets called
+  // whenever we see an "@type" being rendered (see AnyWriter::RenderDataPiece).
+  if (ow_ == NULL) {
+    // Make sure we are not already in an invalid state. This avoids making
+    // multiple unnecessary InvalidValue calls.
+    if (!invalid_) {
+      parent_->InvalidValue("Any",
+                            StrCat("Missing or invalid @type for any field in ",
+                                   parent_->master_type_.name()));
+      invalid_ = true;
+    }
+  } else if (!has_injected_value_message_ || depth_ != 1 || name != "value") {
+    // We don't propagate to ow_ StartObject("value") calls for nested Anys or
+    // Struct at depth 1 as they are nested one level deep with an injected
+    // "value" field.
+    ow_->StartObject(name);
+  }
+}
+
+bool ProtoStreamObjectWriter::AnyWriter::EndObject() {
+  --depth_;
+  // As long as depth_ >= 0, we know we haven't reached the end of Any.
+  // Propagate these EndObject() calls to the contained ow_.  If we are in a
+  // nested Any or Struct type, ignore the second to last EndObject call (depth_
+  // == -1)
+  if (ow_ != NULL && (!has_injected_value_message_ || depth_ >= 0)) {
+    ow_->EndObject();
+  }
+  // A negative depth_ implies that we have reached the end of Any
+  // object. Now we write out its contents.
+  if (depth_ < 0) {
+    WriteAny();
+    return false;
+  }
+  return true;
+}
+
+void ProtoStreamObjectWriter::AnyWriter::StartList(StringPiece name) {
+  ++depth_;
+  // We expect ow_ to be present as this call only makes sense inside an Any.
+  if (ow_ == NULL) {
+    if (!invalid_) {
+      parent_->InvalidValue("Any",
+                            StrCat("Missing or invalid @type for any field in ",
+                                   parent_->master_type_.name()));
+      invalid_ = true;
+    }
+  } else {
+    ow_->StartList(name);
+  }
+}
+
+void ProtoStreamObjectWriter::AnyWriter::EndList() {
+  --depth_;
+  if (depth_ < 0) {
+    GOOGLE_LOG(DFATAL) << "Mismatched EndList found, should not be possible";
+    depth_ = 0;
+  }
+  // We don't write an error on the close, only on the open
+  if (ow_ != NULL) {
+    ow_->EndList();
+  }
+}
+
+void ProtoStreamObjectWriter::AnyWriter::RenderDataPiece(
+    StringPiece name, const DataPiece& value) {
+  // Start an Any only at depth_ 0. Other RenderDataPiece calls with "@type"
+  // should go to the contained ow_ as they indicate nested Anys.
+  if (depth_ == 0 && ow_ == NULL && name == "@type") {
+    StartAny(value);
+  } else if (ow_ == NULL) {
+    if (!invalid_) {
+      parent_->InvalidValue("Any",
+                            StrCat("Missing or invalid @type for any field in ",
+                                   parent_->master_type_.name()));
+      invalid_ = true;
+    }
+  } else {
+    // Check to see if the data needs to be rendered with well-known-type
+    // renderer.
+    const TypeRenderer* type_renderer =
+        FindTypeRenderer(GetFullTypeWithUrl(ow_->master_type_.name()));
+    if (type_renderer) {
+      // TODO(rikka): Don't just ignore the util::Status object!
+      (*type_renderer)(ow_.get(), value);
+    } else {
+      ow_->RenderDataPiece(name, value);
+    }
+  }
+}
+
+void ProtoStreamObjectWriter::AnyWriter::StartAny(const DataPiece& value) {
+  // Figure out the type url. This is a copy-paste from WriteString but we also
+  // need the value, so we can't just call through to that.
+  if (value.type() == DataPiece::TYPE_STRING) {
+    type_url_ = value.str().ToString();
+  } else {
+    StatusOr<string> s = value.ToString();
+    if (!s.ok()) {
+      parent_->InvalidValue("String", s.status().error_message());
+      invalid_ = true;
+      return;
+    }
+    type_url_ = s.ValueOrDie();
+  }
+  // Resolve the type url, and report an error if we failed to resolve it.
+  StatusOr<const google::protobuf::Type*> resolved_type =
+      parent_->typeinfo_->ResolveTypeUrl(type_url_);
+  if (!resolved_type.ok()) {
+    parent_->InvalidValue("Any", resolved_type.status().error_message());
+    invalid_ = true;
+    return;
+  }
+  // At this point, type is never null.
+  const google::protobuf::Type* type = resolved_type.ValueOrDie();
+
+  // If this is the case of an Any in an Any or Struct in an Any, we need to
+  // expect a StartObject call with "value" while we're at depth_ 0, which we
+  // should ignore (not propagate to our nested object writer). We also need to
+  // ignore the second-to-last EndObject call, and not propagate that either.
+  if (type->name() == kAnyType || type->name() == kStructType) {
+    has_injected_value_message_ = true;
+  }
+
+  // Create our object writer and initialize it with the first StartObject
+  // call.
+  ow_.reset(new ProtoStreamObjectWriter(parent_->typeinfo_, *type, &output_,
+                                        parent_->listener_));
+  ow_->StartObject("");
+}
+
+void ProtoStreamObjectWriter::AnyWriter::WriteAny() {
+  if (ow_ == NULL) {
+    // If we had no object writer, we never got any content, so just return
+    // immediately, which is equivalent to writing an empty Any.
+    return;
+  }
+  // Render the type_url and value fields directly to the stream.
+  // type_url has tag 1 and value has tag 2.
+  WireFormatLite::WriteString(1, type_url_, parent_->stream_.get());
+  if (!data_.empty()) {
+    WireFormatLite::WriteBytes(2, data_, parent_->stream_.get());
+  }
+}
+
+ProtoStreamObjectWriter::ProtoElement::ProtoElement(
+    TypeInfo* typeinfo, const google::protobuf::Type& type,
+    ProtoStreamObjectWriter* enclosing)
+    : BaseElement(NULL),
+      ow_(enclosing),
+      any_(),
+      field_(NULL),
+      typeinfo_(typeinfo),
+      type_(type),
+      required_fields_(GetRequiredFields(type)),
+      is_repeated_type_(false),
+      size_index_(-1),
+      array_index_(-1),
+      element_type_(GetElementType(type_)) {
+  if (element_type_ == ANY) {
+    any_.reset(new AnyWriter(ow_));
+  }
+}
+
+ProtoStreamObjectWriter::ProtoElement::ProtoElement(
+    ProtoStreamObjectWriter::ProtoElement* parent,
+    const google::protobuf::Field* field, const google::protobuf::Type& type,
+    ElementType element_type)
+    : BaseElement(parent),
+      ow_(this->parent()->ow_),
+      any_(),
+      field_(field),
+      typeinfo_(this->parent()->typeinfo_),
+      type_(type),
+      is_repeated_type_(element_type == ProtoElement::LIST ||
+                        element_type == ProtoElement::STRUCT_LIST ||
+                        element_type == ProtoElement::MAP ||
+                        element_type == ProtoElement::STRUCT_MAP),
+      size_index_(!is_repeated_type_ &&
+                          field->kind() ==
+                              google::protobuf::Field_Kind_TYPE_MESSAGE
+                      ? ow_->size_insert_.size()
+                      : -1),
+      array_index_(is_repeated_type_ ? 0 : -1),
+      element_type_(element_type) {
+  if (!is_repeated_type_) {
+    if (field->cardinality() ==
+        google::protobuf::Field_Cardinality_CARDINALITY_REPEATED) {
+      // Update array_index_ if it is an explicit list.
+      if (this->parent()->array_index_ >= 0) this->parent()->array_index_++;
+    } else {
+      this->parent()->RegisterField(field);
+    }
+    if (field->kind() == google::protobuf::Field_Kind_TYPE_MESSAGE) {
+      required_fields_ = GetRequiredFields(type_);
+      int start_pos = ow_->stream_->ByteCount();
+      // length of serialized message is the final buffer position minus
+      // starting buffer position, plus length adjustments for size fields
+      // of any nested messages. We start with -start_pos here, so we only
+      // need to add the final buffer position to it at the end.
+      SizeInfo info = {start_pos, -start_pos};
+      ow_->size_insert_.push_back(info);
+    }
+  }
+  if (element_type == ANY) {
+    any_.reset(new AnyWriter(ow_));
+  }
+}
+
+ProtoStreamObjectWriter::ProtoElement*
+ProtoStreamObjectWriter::ProtoElement::pop() {
+  // Calls the registered error listener for any required field(s) not yet
+  // seen.
+  for (set<const google::protobuf::Field*>::iterator it =
+           required_fields_.begin();
+       it != required_fields_.end(); ++it) {
+    ow_->MissingField((*it)->name());
+  }
+  // Computes the total number of proto bytes used by a message, also adjusts
+  // the size of all parent messages by the length of this size field.
+  // If size_index_ < 0, this is not a message, so no size field is added.
+  if (size_index_ >= 0) {
+    // Add the final buffer position to compute the total length of this
+    // serialized message. The stored value (before this addition) already
+    // contains the total length of the size fields of all nested messages
+    // minus the initial buffer position.
+    ow_->size_insert_[size_index_].size += ow_->stream_->ByteCount();
+    // Calculate the length required to serialize the size field of the
+    // message, and propagate this additional size information upward to
+    // all enclosing messages.
+    int size = ow_->size_insert_[size_index_].size;
+    int length = CodedOutputStream::VarintSize32(size);
+    for (ProtoElement* e = parent(); e != NULL; e = e->parent()) {
+      // Only nested messages have size field, lists do not have size field.
+      if (e->size_index_ >= 0) {
+        ow_->size_insert_[e->size_index_].size += length;
+      }
+    }
+  }
+  return BaseElement::pop<ProtoElement>();
+}
+
+void ProtoStreamObjectWriter::ProtoElement::RegisterField(
+    const google::protobuf::Field* field) {
+  if (!required_fields_.empty() &&
+      field->cardinality() ==
+          google::protobuf::Field_Cardinality_CARDINALITY_REQUIRED) {
+    required_fields_.erase(field);
+  }
+}
+
+string ProtoStreamObjectWriter::ProtoElement::ToString() const {
+  if (parent() == NULL) return "";
+  string loc = parent()->ToString();
+  if (field_->cardinality() !=
+          google::protobuf::Field_Cardinality_CARDINALITY_REPEATED ||
+      parent()->field_ != field_) {
+    string name = field_->name();
+    int i = 0;
+    while (i < name.size() && (ascii_isalnum(name[i]) || name[i] == '_')) ++i;
+    if (i > 0 && i == name.size()) {  // safe field name
+      if (loc.empty()) {
+        loc = name;
+      } else {
+        StrAppend(&loc, ".", name);
+      }
+    } else {
+      StrAppend(&loc, "[\"", CEscape(name), "\"]");
+    }
+  }
+  if (field_->cardinality() ==
+          google::protobuf::Field_Cardinality_CARDINALITY_REPEATED &&
+      array_index_ > 0) {
+    StrAppend(&loc, "[", array_index_ - 1, "]");
+  }
+  return loc.empty() ? "." : loc;
+}
+
+inline void ProtoStreamObjectWriter::InvalidName(StringPiece unknown_name,
+                                                 StringPiece message) {
+  listener_->InvalidName(location(), ToSnakeCase(unknown_name), message);
+}
+
+inline void ProtoStreamObjectWriter::InvalidValue(StringPiece type_name,
+                                                  StringPiece value) {
+  listener_->InvalidValue(location(), type_name, value);
+}
+
+inline void ProtoStreamObjectWriter::MissingField(StringPiece missing_name) {
+  listener_->MissingField(location(), missing_name);
+}
+
+ProtoStreamObjectWriter* ProtoStreamObjectWriter::StartObject(
+    StringPiece name) {
+  // Starting the root message. Create the root ProtoElement and return.
+  if (element_ == NULL) {
+    if (!name.empty()) {
+      InvalidName(name, "Root element should not be named.");
+    }
+    element_.reset(new ProtoElement(typeinfo_, master_type_, this));
+
+    // If master type is a special type that needs extra values to be written to
+    // stream, we write those values.
+    if (master_type_.name() == kStructType) {
+      StartStruct(NULL);
+    } else if (master_type_.name() == kStructValueType) {
+      // We got a StartObject call with google.protobuf.Value field. This means
+      // we are starting an object within google.protobuf.Value type. The only
+      // object within that type is a struct type. So start a struct.
+      const google::protobuf::Field* field = StartStructValueInStruct(NULL);
+      StartStruct(field);
+    }
+    return this;
+  }
+
+  const google::protobuf::Field* field = NULL;
+  if (element_ != NULL && element_->IsAny()) {
+    element_->any()->StartObject(name);
+    return this;
+  } else if (element_ != NULL &&
+             (element_->IsMap() || element_->IsStructMap())) {
+    field = StartMapEntry(name);
+    if (element_->IsStructMapEntry()) {
+      // If the top element is a map entry, this means we are starting another
+      // struct within a struct.
+      field = StartStructValueInStruct(field);
+    }
+  } else if (element_ != NULL && element_->IsStructList()) {
+    // If the top element is a list, then we are starting a list field within a
+    // struct.
+    field = Lookup(name);
+    field = StartStructValueInStruct(field);
+  } else {
+    field = BeginNamed(name, false);
+  }
+  if (field == NULL) {
+    return this;
+  }
+
+  const google::protobuf::Type* type = LookupType(field);
+  if (type == NULL) {
+    ++invalid_depth_;
+    InvalidName(name,
+                StrCat("Missing descriptor for field: ", field->type_url()));
+    return this;
+  }
+
+  if (field->type_url() == GetFullTypeWithUrl(kStructType)) {
+    // Start a struct object.
+    StartStruct(field);
+  } else if (field->type_url() == GetFullTypeWithUrl(kStructValueType)) {
+    // We got a StartObject call with google.protobuf.Value field. This means we
+    // are starting an object within google.protobuf.Value type. The only object
+    // within that type is a struct type. So start a struct.
+    field = StartStructValueInStruct(field);
+    StartStruct(field);
+  } else if (field->type_url() == GetFullTypeWithUrl(kAnyType)) {
+    // Begin an Any. We can't do the real work till we get the @type field.
+    WriteTag(*field);
+    element_.reset(
+        new ProtoElement(element_.release(), field, *type, ProtoElement::ANY));
+  } else if (IsMap(*field)) {
+    // Begin a map.
+    // A map is triggered by a StartObject() call if the current field has a map
+    // type. Map values are written to proto in a manner detailed in comments
+    // above StartMapEntry() function.
+    element_.reset(
+        new ProtoElement(element_.release(), field, *type, ProtoElement::MAP));
+  } else {
+    WriteTag(*field);
+    element_.reset(new ProtoElement(element_.release(), field, *type,
+                                    ProtoElement::MESSAGE));
+  }
+  return this;
+}
+
+// Proto3 maps are represented on the wire as a message with
+// "key" and a "value".
+//
+// For example, the syntax:
+// map<key_type, value_type> map_field = N;
+//
+// is represented as:
+// message MapFieldEntry {
+//   option map_entry = true;   // marks the map construct in the descriptor
+//
+//   key_type key = 1;
+//   value_type value = 2;
+// }
+// repeated MapFieldEntry map_field = N;
+//
+// See go/proto3-maps for more information.
+const google::protobuf::Field* ProtoStreamObjectWriter::StartMapEntry(
+    StringPiece name) {
+  // top of stack is already a map field
+  const google::protobuf::Field* field = element_->field();
+  const google::protobuf::Type& type = element_->type();
+  // If we come from a regular map, use MAP_ENTRY or if we come from a struct,
+  // use STRUCT_MAP_ENTRY. These values are used later in StartObject/StartList
+  // or RenderDataPiece for making appropriate decisions.
+  ProtoElement::ElementType element_type = element_->IsStructMap()
+                                               ? ProtoElement::STRUCT_MAP_ENTRY
+                                               : ProtoElement::MAP_ENTRY;
+  WriteTag(*field);
+  element_.reset(
+      new ProtoElement(element_.release(), field, type, element_type));
+  RenderDataPiece("key", DataPiece(name));
+  return BeginNamed("value", false);
+}
+
+// Starts a google.protobuf.Struct.
+// 'field' represents a field in a message of type google.protobuf.Struct.  A
+// struct contains a map with name 'fields'. This function starts this map as
+// well.
+// When 'field' is NULL, it means that the top level message is of struct
+// type.
+void ProtoStreamObjectWriter::StartStruct(
+    const google::protobuf::Field* field) {
+  const google::protobuf::Type* type = NULL;
+  if (field) {
+    type = LookupType(field);
+    WriteTag(*field);
+    element_.reset(new ProtoElement(element_.release(), field, *type,
+                                    ProtoElement::STRUCT));
+  }
+  const google::protobuf::Field* struct_field = BeginNamed("fields", false);
+
+  if (!struct_field) {
+    // It is a programmatic error if this happens. Log an error.
+    GOOGLE_LOG(ERROR) << "Invalid internal state. Cannot find 'fields' within "
+               << (field ? field->type_url() : "google.protobuf.Struct");
+    return;
+  }
+
+  type = LookupType(struct_field);
+  element_.reset(new ProtoElement(element_.release(), struct_field, *type,
+                                  ProtoElement::STRUCT_MAP));
+}
+
+// Starts a "struct_value" within struct.proto's google.protobuf.Value type.
+// 'field' should be of the type google.protobuf.Value.
+// Returns the field identifying "struct_value" within the given field.
+//
+// If field is NULL, then we are starting struct_value at the top-level, in
+// this case skip writing any tag information for the passed field.
+const google::protobuf::Field*
+ProtoStreamObjectWriter::StartStructValueInStruct(
+    const google::protobuf::Field* field) {
+  if (field) {
+    const google::protobuf::Type* type = LookupType(field);
+    WriteTag(*field);
+    element_.reset(new ProtoElement(element_.release(), field, *type,
+                                    ProtoElement::STRUCT_VALUE));
+  }
+  return BeginNamed("struct_value", false);
+}
+
+// Starts a "list_value" within struct.proto's google.protobuf.Value type.
+// 'field' should be of the type google.protobuf.Value.
+// Returns the field identifying "list_value" within the given field.
+//
+// If field is NULL, then we are starting list_value at the top-level, in
+// this case skip writing any tag information for the passed field.
+const google::protobuf::Field* ProtoStreamObjectWriter::StartListValueInStruct(
+    const google::protobuf::Field* field) {
+  if (field) {
+    const google::protobuf::Type* type = LookupType(field);
+    WriteTag(*field);
+    element_.reset(new ProtoElement(element_.release(), field, *type,
+                                    ProtoElement::STRUCT_VALUE));
+  }
+  const google::protobuf::Field* list_value = BeginNamed("list_value", false);
+
+  if (!list_value) {
+    // It is a programmatic error if this happens. Log an error.
+    GOOGLE_LOG(ERROR) << "Invalid internal state. Cannot find 'list_value' within "
+               << (field ? field->type_url() : "google.protobuf.Value");
+    return field;
+  }
+
+  return StartRepeatedValuesInListValue(list_value);
+}
+
+// Starts the repeated "values" field in struct.proto's
+// google.protobuf.ListValue type. 'field' should be of type
+// google.protobuf.ListValue.
+//
+// If field is NULL, then we are starting ListValue at the top-level, in
+// this case skip writing any tag information for the passed field.
+const google::protobuf::Field*
+ProtoStreamObjectWriter::StartRepeatedValuesInListValue(
+    const google::protobuf::Field* field) {
+  if (field) {
+    const google::protobuf::Type* type = LookupType(field);
+    WriteTag(*field);
+    element_.reset(new ProtoElement(element_.release(), field, *type,
+                                    ProtoElement::STRUCT_LIST_VALUE));
+  }
+  return BeginNamed("values", true);
+}
+
+void ProtoStreamObjectWriter::SkipElements() {
+  if (element_ == NULL) return;
+
+  ProtoElement::ElementType element_type = element_->element_type();
+  while (element_type == ProtoElement::STRUCT ||
+         element_type == ProtoElement::STRUCT_LIST_VALUE ||
+         element_type == ProtoElement::STRUCT_VALUE ||
+         element_type == ProtoElement::STRUCT_MAP_ENTRY ||
+         element_type == ProtoElement::MAP_ENTRY) {
+    element_.reset(element_->pop());
+    element_type =
+        element_ != NULL ? element_->element_type() : ProtoElement::MESSAGE;
+  }
+}
+
+ProtoStreamObjectWriter* ProtoStreamObjectWriter::EndObject() {
+  if (invalid_depth_ > 0) {
+    --invalid_depth_;
+    return this;
+  }
+  if (element_ != NULL && element_->IsAny()) {
+    if (element_->any()->EndObject()) {
+      return this;
+    }
+  }
+  if (element_ != NULL) {
+    element_.reset(element_->pop());
+  }
+
+  // Skip sentinel elements added to keep track of new proto3 types - map,
+  // struct.
+  SkipElements();
+
+  // If ending the root element,
+  // then serialize the full message with calculated sizes.
+  if (element_ == NULL) {
+    WriteRootMessage();
+  }
+  return this;
+}
+
+ProtoStreamObjectWriter* ProtoStreamObjectWriter::StartList(StringPiece name) {
+  const google::protobuf::Field* field = NULL;
+  // Since we cannot have a top-level repeated item in protobuf, the only way
+  // element_ can be null when here is when we start a top-level list
+  // google.protobuf.ListValue.
+  if (element_ == NULL) {
+    if (!name.empty()) {
+      InvalidName(name, "Root element should not be named.");
+    }
+    element_.reset(new ProtoElement(typeinfo_, master_type_, this));
+
+    // If master type is a special type that needs extra values to be written to
+    // stream, we write those values.
+    if (master_type_.name() == kStructValueType) {
+      // We got a StartList with google.protobuf.Value master type. This means
+      // we have to start the "list_value" within google.protobuf.Value.
+      field = StartListValueInStruct(NULL);
+    } else if (master_type_.name() == kStructListValueType) {
+      // We got a StartList with google.protobuf.ListValue master type. This
+      // means we have to start the "values" within google.protobuf.ListValue.
+      field = StartRepeatedValuesInListValue(NULL);
+    }
+
+    // field is NULL when master_type_ is anything other than
+    // google.protobuf.Value or google.protobuf.ListValue.
+    if (field) {
+      const google::protobuf::Type* type = LookupType(field);
+      element_.reset(new ProtoElement(element_.release(), field, *type,
+                                      ProtoElement::STRUCT_LIST));
+    }
+    return this;
+  }
+
+  if (element_->IsAny()) {
+    element_->any()->StartList(name);
+    return this;
+  }
+  // The type of element we push to stack.
+  ProtoElement::ElementType element_type = ProtoElement::LIST;
+
+  // Check if we need to start a map. This can heppen when there is either a map
+  // or a struct type within a list.
+  if (element_->IsMap() || element_->IsStructMap()) {
+    field = StartMapEntry(name);
+    if (field == NULL) return this;
+
+    if (element_->IsStructMapEntry()) {
+      // If the top element is a map entry, this means we are starting a list
+      // within a struct or a map.
+      // An example sequence of calls would be
+      //    StartObject -> StartList
+      field = StartListValueInStruct(field);
+      if (field == NULL) return this;
+    }
+
+    element_type = ProtoElement::STRUCT_LIST;
+  } else if (element_->IsStructList()) {
+    // If the top element is a STRUCT_LIST, this means we are starting a list
+    // within the current list (inside a struct).
+    // An example call sequence would be
+    //    StartObject -> StartList -> StartList
+    // with StartObject starting a struct.
+
+    // Lookup the last list type in element stack as we are adding an element of
+    // the same type.
+    field = Lookup(name);
+    if (field == NULL) return this;
+
+    field = StartListValueInStruct(field);
+    if (field == NULL) return this;
+
+    element_type = ProtoElement::STRUCT_LIST;
+  } else {
+    // Lookup field corresponding to 'name'. If it is a google.protobuf.Value
+    // or google.protobuf.ListValue type, then StartList is a valid call, start
+    // this list.
+    // We cannot use Lookup() here as it will produce InvalidName() error if the
+    // field is not found. We do not want to error here as it would cause us to
+    // report errors twice, once here and again later in BeginNamed() call.
+    // Also we ignore if the field is not found here as it is caught later.
+    field = typeinfo_->FindField(&element_->type(), name);
+
+    // It is an error to try to bind to map, which behind the scenes is a list.
+    if (field && IsMap(*field)) {
+      // Push field to stack for error location tracking & reporting.
+      element_.reset(new ProtoElement(element_.release(), field,
+                                      *LookupType(field),
+                                      ProtoElement::MESSAGE));
+      InvalidValue("Map", "Cannot bind a list to map.");
+      ++invalid_depth_;
+      element_->pop();
+      return this;
+    }
+
+    if (field && field->type_url() == GetFullTypeWithUrl(kStructValueType)) {
+      // There are 2 cases possible:
+      //   a. g.p.Value is repeated
+      //   b. g.p.Value is not repeated
+      //
+      // For case (a), the StartList should bind to the repeated g.p.Value.
+      // For case (b), the StartList should bind to g.p.ListValue within the
+      // g.p.Value.
+      //
+      // This means, for case (a), we treat it just like any other repeated
+      // message, except we would apply an appropriate element_type so future
+      // Start or Render calls are routed appropriately.
+      if (field->cardinality() !=
+          google::protobuf::Field_Cardinality_CARDINALITY_REPEATED) {
+        field = StartListValueInStruct(field);
+      }
+      element_type = ProtoElement::STRUCT_LIST;
+    } else if (field &&
+               field->type_url() == GetFullTypeWithUrl(kStructListValueType)) {
+      // We got a StartList with google.protobuf.ListValue master type. This
+      // means we have to start the "values" within google.protobuf.ListValue.
+      field = StartRepeatedValuesInListValue(field);
+    } else {
+      // If no special types are to be bound, fall back to normal processing of
+      // StartList.
+      field = BeginNamed(name, true);
+    }
+    if (field == NULL) return this;
+  }
+
+  const google::protobuf::Type* type = LookupType(field);
+  if (type == NULL) {
+    ++invalid_depth_;
+    InvalidName(name,
+                StrCat("Missing descriptor for field: ", field->type_url()));
+    return this;
+  }
+
+  element_.reset(
+      new ProtoElement(element_.release(), field, *type, element_type));
+  return this;
+}
+
+ProtoStreamObjectWriter* ProtoStreamObjectWriter::EndList() {
+  if (invalid_depth_ > 0) {
+    --invalid_depth_;
+  } else if (element_ != NULL) {
+    if (element_->IsAny()) {
+      element_->any()->EndList();
+    } else {
+      element_.reset(element_->pop());
+      // Skip sentinel elements added to keep track of new proto3 types - map,
+      // struct.
+      SkipElements();
+    }
+  }
+
+  // When element_ is NULL, we have reached the root message type. Write out
+  // the bytes.
+  if (element_ == NULL) {
+    WriteRootMessage();
+  }
+  return this;
+}
+
+Status ProtoStreamObjectWriter::RenderStructValue(ProtoStreamObjectWriter* ow,
+                                                  const DataPiece& data) {
+  string struct_field_name;
+  switch (data.type()) {
+    // Our JSON parser parses numbers as either int64, uint64, or double.
+    case DataPiece::TYPE_INT64:
+    case DataPiece::TYPE_UINT64:
+    case DataPiece::TYPE_DOUBLE: {
+      struct_field_name = "number_value";
+      break;
+    }
+    case DataPiece::TYPE_STRING: {
+      struct_field_name = "string_value";
+      break;
+    }
+    case DataPiece::TYPE_BOOL: {
+      struct_field_name = "bool_value";
+      break;
+    }
+    case DataPiece::TYPE_NULL: {
+      struct_field_name = "null_value";
+      break;
+    }
+    default: {
+      return Status(INVALID_ARGUMENT,
+                    "Invalid struct data type. Only number, string, boolean or "
+                    "null values are supported.");
+    }
+  }
+  ow->RenderDataPiece(struct_field_name, data);
+  return Status::OK;
+}
+
+Status ProtoStreamObjectWriter::RenderTimestamp(ProtoStreamObjectWriter* ow,
+                                                const DataPiece& data) {
+  if (data.type() != DataPiece::TYPE_STRING) {
+    return Status(INVALID_ARGUMENT,
+                  StrCat("Invalid data type for timestamp, value is ",
+                         data.ValueAsStringOrDefault("")));
+  }
+
+  StringPiece value(data.str());
+
+  int64 seconds;
+  int32 nanos;
+  if (!::google::protobuf::internal::ParseTime(value.ToString(), &seconds,
+                                               &nanos)) {
+    return Status(INVALID_ARGUMENT, StrCat("Invalid time format: ", value));
+  }
+
+
+  ow->RenderDataPiece("seconds", DataPiece(seconds));
+  ow->RenderDataPiece("nanos", DataPiece(nanos));
+  return Status::OK;
+}
+
+static inline util::Status RenderOneFieldPath(ProtoStreamObjectWriter* ow,
+                                                StringPiece path) {
+  ow->RenderDataPiece("paths",
+                      DataPiece(ConvertFieldMaskPath(path, &ToSnakeCase)));
+  return Status::OK;
+}
+
+Status ProtoStreamObjectWriter::RenderFieldMask(ProtoStreamObjectWriter* ow,
+                                                const DataPiece& data) {
+  if (data.type() != DataPiece::TYPE_STRING) {
+    return Status(INVALID_ARGUMENT,
+                  StrCat("Invalid data type for field mask, value is ",
+                         data.ValueAsStringOrDefault("")));
+  }
+
+  // TODO(tsun): figure out how to do proto descriptor based snake case
+  // conversions as much as possible. Because ToSnakeCase sometimes returns the
+  // wrong value.
+  google::protobuf::scoped_ptr<ResultCallback1<util::Status, StringPiece> > callback(
+      NewPermanentCallback(&RenderOneFieldPath, ow));
+  return DecodeCompactFieldMaskPaths(data.str(), callback.get());
+}
+
+Status ProtoStreamObjectWriter::RenderDuration(ProtoStreamObjectWriter* ow,
+                                               const DataPiece& data) {
+  if (data.type() != DataPiece::TYPE_STRING) {
+    return Status(INVALID_ARGUMENT,
+                  StrCat("Invalid data type for duration, value is ",
+                         data.ValueAsStringOrDefault("")));
+  }
+
+  StringPiece value(data.str());
+
+  if (!value.ends_with("s")) {
+    return Status(INVALID_ARGUMENT,
+                  "Illegal duration format; duration must end with 's'");
+  }
+  value = value.substr(0, value.size() - 1);
+  int sign = 1;
+  if (value.starts_with("-")) {
+    sign = -1;
+    value = value.substr(1);
+  }
+
+  StringPiece s_secs, s_nanos;
+  SplitSecondsAndNanos(value, &s_secs, &s_nanos);
+  uint64 unsigned_seconds;
+  if (!safe_strtou64(s_secs, &unsigned_seconds)) {
+    return Status(INVALID_ARGUMENT,
+                  "Invalid duration format, failed to parse seconds");
+  }
+
+  double d_nanos = 0;
+  if (!safe_strtod("0." + s_nanos.ToString(), &d_nanos)) {
+    return Status(INVALID_ARGUMENT,
+                  "Invalid duration format, failed to parse nanos seconds");
+  }
+
+  int32 nanos = sign * static_cast<int32>(d_nanos * kNanosPerSecond);
+  int64 seconds = sign * unsigned_seconds;
+
+  if (seconds > kMaxSeconds || seconds < kMinSeconds ||
+      nanos <= -kNanosPerSecond || nanos >= kNanosPerSecond) {
+    return Status(INVALID_ARGUMENT, "Duration value exceeds limits");
+  }
+
+  ow->RenderDataPiece("seconds", DataPiece(seconds));
+  ow->RenderDataPiece("nanos", DataPiece(nanos));
+  return Status::OK;
+}
+
+Status ProtoStreamObjectWriter::RenderWrapperType(ProtoStreamObjectWriter* ow,
+                                                  const DataPiece& data) {
+  ow->RenderDataPiece("value", data);
+  return Status::OK;
+}
+
+ProtoStreamObjectWriter* ProtoStreamObjectWriter::RenderDataPiece(
+    StringPiece name, const DataPiece& data) {
+  Status status;
+  if (invalid_depth_ > 0) return this;
+  if (element_ != NULL && element_->IsAny()) {
+    element_->any()->RenderDataPiece(name, data);
+    return this;
+  }
+
+  const google::protobuf::Field* field = NULL;
+  string type_url;
+  bool is_map_entry = false;
+  if (element_ == NULL) {
+    type_url = GetFullTypeWithUrl(master_type_.name());
+  } else {
+    if (element_->IsMap() || element_->IsStructMap()) {
+      is_map_entry = true;
+      field = StartMapEntry(name);
+    } else {
+      field = Lookup(name);
+    }
+    if (field == NULL) {
+      return this;
+    }
+    type_url = field->type_url();
+  }
+
+  // Check if there are any well known type renderers available for type_url.
+  const TypeRenderer* type_renderer = FindTypeRenderer(type_url);
+  if (type_renderer != NULL) {
+    // Push the current element to stack so lookups in type_renderer will
+    // find the fields. We do an EndObject soon after, which pops this. This is
+    // safe because all well-known types are messages.
+    if (element_ == NULL) {
+      element_.reset(new ProtoElement(typeinfo_, master_type_, this));
+    } else {
+      if (field) {
+        WriteTag(*field);
+        const google::protobuf::Type* type = LookupType(field);
+        element_.reset(new ProtoElement(element_.release(), field, *type,
+                                        ProtoElement::MESSAGE));
+      }
+    }
+    status = (*type_renderer)(this, data);
+    if (!status.ok()) {
+      InvalidValue(type_url,
+                   StrCat("Field '", name, "', ", status.error_message()));
+    }
+    EndObject();
+    return this;
+  } else if (element_ == NULL) {  // no message type found at root
+    element_.reset(new ProtoElement(typeinfo_, master_type_, this));
+    InvalidName(name, "Root element must be a message.");
+    return this;
+  }
+
+  if (field == NULL) {
+    return this;
+  }
+  const google::protobuf::Type* type = LookupType(field);
+  if (type == NULL) {
+    InvalidName(name,
+                StrCat("Missing descriptor for field: ", field->type_url()));
+    return this;
+  }
+
+  // Whether we should pop at the end. Set to true if the data field is a
+  // message type, which can happen in case of struct values.
+  bool should_pop = false;
+
+  RenderSimpleDataPiece(*field, *type, data);
+
+  if (should_pop && element_ != NULL) {
+    element_.reset(element_->pop());
+  }
+
+  if (is_map_entry) {
+    // Ending map is the same as ending an object.
+    EndObject();
+  }
+  return this;
+}
+
+void ProtoStreamObjectWriter::RenderSimpleDataPiece(
+    const google::protobuf::Field& field, const google::protobuf::Type& type,
+    const DataPiece& data) {
+  // If we are rendering explicit null values and the backend proto field is not
+  // of the google.protobuf.NullType type, we do nothing.
+  if (data.type() == DataPiece::TYPE_NULL &&
+      field.type_url() != kStructNullValueTypeUrl) {
+    return;
+  }
+
+  // Pushing a ProtoElement and then pop it off at the end for 2 purposes:
+  // error location reporting and required field accounting.
+  element_.reset(new ProtoElement(element_.release(), &field, type,
+                                  ProtoElement::MESSAGE));
+
+  // Make sure that field represents a simple data type.
+  if (field.kind() == google::protobuf::Field_Kind_TYPE_UNKNOWN ||
+      field.kind() == google::protobuf::Field_Kind_TYPE_MESSAGE) {
+    InvalidValue(field.type_url().empty()
+                     ? google::protobuf::Field_Kind_Name(field.kind())
+                     : field.type_url(),
+                 data.ValueAsStringOrDefault(""));
+    return;
+  }
+
+  Status status;
+  switch (field.kind()) {
+    case google::protobuf::Field_Kind_TYPE_INT32: {
+      status = WriteInt32(field.number(), data, stream_.get());
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_SFIXED32: {
+      status = WriteSFixed32(field.number(), data, stream_.get());
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_SINT32: {
+      status = WriteSInt32(field.number(), data, stream_.get());
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_FIXED32: {
+      status = WriteFixed32(field.number(), data, stream_.get());
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_UINT32: {
+      status = WriteUInt32(field.number(), data, stream_.get());
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_INT64: {
+      status = WriteInt64(field.number(), data, stream_.get());
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_SFIXED64: {
+      status = WriteSFixed64(field.number(), data, stream_.get());
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_SINT64: {
+      status = WriteSInt64(field.number(), data, stream_.get());
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_FIXED64: {
+      status = WriteFixed64(field.number(), data, stream_.get());
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_UINT64: {
+      status = WriteUInt64(field.number(), data, stream_.get());
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_DOUBLE: {
+      status = WriteDouble(field.number(), data, stream_.get());
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_FLOAT: {
+      status = WriteFloat(field.number(), data, stream_.get());
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_BOOL: {
+      status = WriteBool(field.number(), data, stream_.get());
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_BYTES: {
+      status = WriteBytes(field.number(), data, stream_.get());
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_STRING: {
+      status = WriteString(field.number(), data, stream_.get());
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_ENUM: {
+      status = WriteEnum(field.number(), data,
+                         typeinfo_->GetEnum(field.type_url()), stream_.get());
+      break;
+    }
+    default:  // TYPE_GROUP or TYPE_MESSAGE
+      status = Status(INVALID_ARGUMENT, data.ToString().ValueOrDie());
+  }
+  if (!status.ok()) {
+    InvalidValue(google::protobuf::Field_Kind_Name(field.kind()),
+                 status.error_message());
+  }
+  element_.reset(element_->pop());
+}
+
+// Map of functions that are responsible for rendering well known type
+// represented by the key.
+hash_map<string, ProtoStreamObjectWriter::TypeRenderer>*
+ProtoStreamObjectWriter::CreateRendererMap() {
+  google::protobuf::scoped_ptr<hash_map<string, ProtoStreamObjectWriter::TypeRenderer> >
+      result(new hash_map<string, ProtoStreamObjectWriter::TypeRenderer>());
+  (*result)["type.googleapis.com/google.protobuf.Timestamp"] =
+      &ProtoStreamObjectWriter::RenderTimestamp;
+  (*result)["type.googleapis.com/google.protobuf.Duration"] =
+      &ProtoStreamObjectWriter::RenderDuration;
+  (*result)["type.googleapis.com/google.protobuf.FieldMask"] =
+      &ProtoStreamObjectWriter::RenderFieldMask;
+  (*result)["type.googleapis.com/google.protobuf.Double"] =
+      &ProtoStreamObjectWriter::RenderWrapperType;
+  (*result)["type.googleapis.com/google.protobuf.Float"] =
+      &ProtoStreamObjectWriter::RenderWrapperType;
+  (*result)["type.googleapis.com/google.protobuf.Int64"] =
+      &ProtoStreamObjectWriter::RenderWrapperType;
+  (*result)["type.googleapis.com/google.protobuf.UInt64"] =
+      &ProtoStreamObjectWriter::RenderWrapperType;
+  (*result)["type.googleapis.com/google.protobuf.Int32"] =
+      &ProtoStreamObjectWriter::RenderWrapperType;
+  (*result)["type.googleapis.com/google.protobuf.UInt32"] =
+      &ProtoStreamObjectWriter::RenderWrapperType;
+  (*result)["type.googleapis.com/google.protobuf.Bool"] =
+      &ProtoStreamObjectWriter::RenderWrapperType;
+  (*result)["type.googleapis.com/google.protobuf.String"] =
+      &ProtoStreamObjectWriter::RenderWrapperType;
+  (*result)["type.googleapis.com/google.protobuf.Bytes"] =
+      &ProtoStreamObjectWriter::RenderWrapperType;
+  (*result)["type.googleapis.com/google.protobuf.DoubleValue"] =
+      &ProtoStreamObjectWriter::RenderWrapperType;
+  (*result)["type.googleapis.com/google.protobuf.FloatValue"] =
+      &ProtoStreamObjectWriter::RenderWrapperType;
+  (*result)["type.googleapis.com/google.protobuf.Int64Value"] =
+      &ProtoStreamObjectWriter::RenderWrapperType;
+  (*result)["type.googleapis.com/google.protobuf.UInt64Value"] =
+      &ProtoStreamObjectWriter::RenderWrapperType;
+  (*result)["type.googleapis.com/google.protobuf.Int32Value"] =
+      &ProtoStreamObjectWriter::RenderWrapperType;
+  (*result)["type.googleapis.com/google.protobuf.UInt32Value"] =
+      &ProtoStreamObjectWriter::RenderWrapperType;
+  (*result)["type.googleapis.com/google.protobuf.BoolValue"] =
+      &ProtoStreamObjectWriter::RenderWrapperType;
+  (*result)["type.googleapis.com/google.protobuf.StringValue"] =
+      &ProtoStreamObjectWriter::RenderWrapperType;
+  (*result)["type.googleapis.com/google.protobuf.BytesValue"] =
+      &ProtoStreamObjectWriter::RenderWrapperType;
+  (*result)["type.googleapis.com/google.protobuf.Value"] =
+      &ProtoStreamObjectWriter::RenderStructValue;
+  return result.release();
+}
+
+ProtoStreamObjectWriter::TypeRenderer*
+ProtoStreamObjectWriter::FindTypeRenderer(const string& type_url) {
+  static hash_map<string, TypeRenderer>* renderers = CreateRendererMap();
+  return FindOrNull(*renderers, type_url);
+}
+
+ProtoStreamObjectWriter::ProtoElement::ElementType
+ProtoStreamObjectWriter::GetElementType(const google::protobuf::Type& type) {
+  if (type.name() == kAnyType) {
+    return ProtoElement::ANY;
+  } else if (type.name() == kStructType) {
+    return ProtoElement::STRUCT;
+  } else if (type.name() == kStructValueType) {
+    return ProtoElement::STRUCT_VALUE;
+  } else if (type.name() == kStructListValueType) {
+    return ProtoElement::STRUCT_LIST_VALUE;
+  } else {
+    return ProtoElement::MESSAGE;
+  }
+}
+
+const google::protobuf::Field* ProtoStreamObjectWriter::BeginNamed(
+    StringPiece name, bool is_list) {
+  if (invalid_depth_ > 0) {
+    ++invalid_depth_;
+    return NULL;
+  }
+  const google::protobuf::Field* field = Lookup(name);
+  if (field == NULL) {
+    ++invalid_depth_;
+    // InvalidName() already called in Lookup().
+    return NULL;
+  }
+  if (is_list &&
+      field->cardinality() !=
+          google::protobuf::Field_Cardinality_CARDINALITY_REPEATED) {
+    ++invalid_depth_;
+    InvalidName(name, "Proto field is not repeating, cannot start list.");
+    return NULL;
+  }
+  return field;
+}
+
+const google::protobuf::Field* ProtoStreamObjectWriter::Lookup(
+    StringPiece unnormalized_name) {
+  ProtoElement* e = element();
+  if (e == NULL) {
+    InvalidName(unnormalized_name, "Root element must be a message.");
+    return NULL;
+  }
+  if (unnormalized_name.empty()) {
+    // Objects in repeated field inherit the same field descriptor.
+    if (e->field() == NULL) {
+      InvalidName(unnormalized_name, "Proto fields must have a name.");
+    } else if (e->field()->cardinality() !=
+               google::protobuf::Field_Cardinality_CARDINALITY_REPEATED) {
+      InvalidName(unnormalized_name, "Proto fields must have a name.");
+      return NULL;
+    }
+    return e->field();
+  }
+  const google::protobuf::Field* field =
+      typeinfo_->FindField(&e->type(), unnormalized_name);
+  if (field == NULL) InvalidName(unnormalized_name, "Cannot find field.");
+  return field;
+}
+
+const google::protobuf::Type* ProtoStreamObjectWriter::LookupType(
+    const google::protobuf::Field* field) {
+  return (field->kind() == google::protobuf::Field_Kind_TYPE_MESSAGE
+              ? typeinfo_->GetType(field->type_url())
+              : &element_->type());
+}
+
+// Looks up the oneof struct field based on the data type.
+StatusOr<const google::protobuf::Field*>
+ProtoStreamObjectWriter::LookupStructField(DataPiece::Type type) {
+  const google::protobuf::Field* field = NULL;
+  switch (type) {
+    // Our JSON parser parses numbers as either int64, uint64, or double.
+    case DataPiece::TYPE_INT64:
+    case DataPiece::TYPE_UINT64:
+    case DataPiece::TYPE_DOUBLE: {
+      field = Lookup("number_value");
+      break;
+    }
+    case DataPiece::TYPE_STRING: {
+      field = Lookup("string_value");
+      break;
+    }
+    case DataPiece::TYPE_BOOL: {
+      field = Lookup("bool_value");
+      break;
+    }
+    case DataPiece::TYPE_NULL: {
+      field = Lookup("null_value");
+      break;
+    }
+    default: { return Status(INVALID_ARGUMENT, "Invalid struct data type"); }
+  }
+  if (field == NULL) {
+    return Status(INVALID_ARGUMENT, "Could not lookup struct field");
+  }
+  return field;
+}
+
+void ProtoStreamObjectWriter::WriteRootMessage() {
+  GOOGLE_DCHECK(!done_);
+  int curr_pos = 0;
+  // Calls the destructor of CodedOutputStream to remove any uninitialized
+  // memory from the Cord before we read it.
+  stream_.reset(NULL);
+  const void* data;
+  int length;
+  google::protobuf::io::ArrayInputStream input_stream(buffer_.data(), buffer_.size());
+  while (input_stream.Next(&data, &length)) {
+    if (length == 0) continue;
+    int num_bytes = length;
+    // Write up to where we need to insert the size field.
+    // The number of bytes we may write is the smaller of:
+    //   - the current fragment size
+    //   - the distance to the next position where a size field needs to be
+    //     inserted.
+    if (!size_insert_.empty() &&
+        size_insert_.front().pos - curr_pos < num_bytes) {
+      num_bytes = size_insert_.front().pos - curr_pos;
+    }
+    output_->Append(static_cast<const char*>(data), num_bytes);
+    if (num_bytes < length) {
+      input_stream.BackUp(length - num_bytes);
+    }
+    curr_pos += num_bytes;
+    // Insert the size field.
+    //   size_insert_.front():      the next <index, size> pair to be written.
+    //   size_insert_.front().pos:  position of the size field.
+    //   size_insert_.front().size: the size (integer) to be inserted.
+    if (!size_insert_.empty() && curr_pos == size_insert_.front().pos) {
+      // Varint32 occupies at most 10 bytes.
+      uint8 insert_buffer[10];
+      uint8* insert_buffer_pos = CodedOutputStream::WriteVarint32ToArray(
+          size_insert_.front().size, insert_buffer);
+      output_->Append(reinterpret_cast<const char*>(insert_buffer),
+                      insert_buffer_pos - insert_buffer);
+      size_insert_.pop_front();
+    }
+  }
+  output_->Flush();
+  stream_.reset(new CodedOutputStream(&adapter_));
+  done_ = true;
+}
+
+bool ProtoStreamObjectWriter::IsMap(const google::protobuf::Field& field) {
+  if (field.type_url().empty() ||
+      field.kind() != google::protobuf::Field_Kind_TYPE_MESSAGE ||
+      field.cardinality() !=
+          google::protobuf::Field_Cardinality_CARDINALITY_REPEATED) {
+    return false;
+  }
+  const google::protobuf::Type* field_type =
+      typeinfo_->GetType(field.type_url());
+
+  return GetBoolOptionOrDefault(field_type->options(),
+                                "google.protobuf.MessageOptions.map_entry", false);
+}
+
+void ProtoStreamObjectWriter::WriteTag(const google::protobuf::Field& field) {
+  WireFormatLite::WireType wire_type = WireFormatLite::WireTypeForFieldType(
+      static_cast<WireFormatLite::FieldType>(field.kind()));
+  stream_->WriteTag(WireFormatLite::MakeTag(field.number(), wire_type));
+}
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/internal/protostream_objectwriter.h b/src/google/protobuf/util/internal/protostream_objectwriter.h
new file mode 100644
index 0000000..f17278b
--- /dev/null
+++ b/src/google/protobuf/util/internal/protostream_objectwriter.h
@@ -0,0 +1,455 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_PROTOBUF_UTIL_CONVERTER_PROTOSTREAM_OBJECTWRITER_H__
+#define GOOGLE_PROTOBUF_UTIL_CONVERTER_PROTOSTREAM_OBJECTWRITER_H__
+
+#include <deque>
+#include <google/protobuf/stubs/hash.h>
+#include <string>
+
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/io/coded_stream.h>
+#include <google/protobuf/io/zero_copy_stream_impl.h>
+#include <google/protobuf/descriptor.h>
+#include <google/protobuf/util/internal/type_info.h>
+#include <google/protobuf/util/internal/datapiece.h>
+#include <google/protobuf/util/internal/error_listener.h>
+#include <google/protobuf/util/internal/structured_objectwriter.h>
+#include <google/protobuf/util/type_resolver.h>
+#include <google/protobuf/stubs/bytestream.h>
+
+namespace google {
+namespace protobuf {
+namespace io {
+class CodedOutputStream;
+}  // namespace io
+}  // namespace protobuf
+
+
+namespace protobuf {
+class Type;
+class Field;
+}  // namespace protobuf
+
+
+namespace protobuf {
+namespace util {
+namespace converter {
+
+class ObjectLocationTracker;
+
+// An ObjectWriter that can write protobuf bytes directly from writer events.
+//
+// It also supports streaming.
+class LIBPROTOBUF_EXPORT ProtoStreamObjectWriter : public StructuredObjectWriter {
+ public:
+  // Constructor. Does not take ownership of any parameter passed in.
+  ProtoStreamObjectWriter(TypeResolver* type_resolver,
+                          const google::protobuf::Type& type,
+                          strings::ByteSink* output, ErrorListener* listener);
+  virtual ~ProtoStreamObjectWriter();
+
+  // ObjectWriter methods.
+  virtual ProtoStreamObjectWriter* StartObject(StringPiece name);
+  virtual ProtoStreamObjectWriter* EndObject();
+  virtual ProtoStreamObjectWriter* StartList(StringPiece name);
+  virtual ProtoStreamObjectWriter* EndList();
+  virtual ProtoStreamObjectWriter* RenderBool(StringPiece name,
+                                              const bool value) {
+    return RenderDataPiece(name, DataPiece(value));
+  }
+  virtual ProtoStreamObjectWriter* RenderInt32(StringPiece name,
+                                               const int32 value) {
+    return RenderDataPiece(name, DataPiece(value));
+  }
+  virtual ProtoStreamObjectWriter* RenderUint32(StringPiece name,
+                                                const uint32 value) {
+    return RenderDataPiece(name, DataPiece(value));
+  }
+  virtual ProtoStreamObjectWriter* RenderInt64(StringPiece name,
+                                               const int64 value) {
+    return RenderDataPiece(name, DataPiece(value));
+  }
+  virtual ProtoStreamObjectWriter* RenderUint64(StringPiece name,
+                                                const uint64 value) {
+    return RenderDataPiece(name, DataPiece(value));
+  }
+  virtual ProtoStreamObjectWriter* RenderDouble(StringPiece name,
+                                                const double value) {
+    return RenderDataPiece(name, DataPiece(value));
+  }
+  virtual ProtoStreamObjectWriter* RenderFloat(StringPiece name,
+                                               const float value) {
+    return RenderDataPiece(name, DataPiece(value));
+  }
+  virtual ProtoStreamObjectWriter* RenderString(StringPiece name,
+                                                StringPiece value) {
+    return RenderDataPiece(name, DataPiece(value));
+  }
+  virtual ProtoStreamObjectWriter* RenderBytes(StringPiece name,
+                                               StringPiece value) {
+    return RenderDataPiece(name, DataPiece(value, false));
+  }
+  virtual ProtoStreamObjectWriter* RenderNull(StringPiece name) {
+    return RenderDataPiece(name, DataPiece::NullData());
+  }
+
+  // Renders a DataPiece 'value' into a field whose wire type is determined
+  // from the given field 'name'.
+  ProtoStreamObjectWriter* RenderDataPiece(StringPiece name,
+                                           const DataPiece& value);
+
+  // Returns the location tracker to use for tracking locations for errors.
+  const LocationTrackerInterface& location() {
+    return element_ != NULL ? *element_ : *tracker_;
+  }
+
+  // When true, we finished writing to output a complete message.
+  bool done() const { return done_; }
+
+ private:
+  // Function that renders a well known type with modified behavior.
+  typedef util::Status (*TypeRenderer)(ProtoStreamObjectWriter*,
+                                         const DataPiece&);
+
+  // Handles writing Anys out using nested object writers and the like.
+  class LIBPROTOBUF_EXPORT AnyWriter {
+   public:
+    explicit AnyWriter(ProtoStreamObjectWriter* parent);
+    ~AnyWriter();
+
+    // Passes a StartObject call through to the Any writer.
+    void StartObject(StringPiece name);
+
+    // Passes an EndObject call through to the Any. Returns true if the any
+    // handled the EndObject call, false if the Any is now all done and is no
+    // longer needed.
+    bool EndObject();
+
+    // Passes a StartList call through to the Any writer.
+    void StartList(StringPiece name);
+
+    // Passes an EndList call through to the Any writer.
+    void EndList();
+
+    // Renders a data piece on the any.
+    void RenderDataPiece(StringPiece name, const DataPiece& value);
+
+   private:
+    // Handles starting up the any once we have a type.
+    void StartAny(const DataPiece& value);
+
+    // Writes the Any out to the parent writer in its serialized form.
+    void WriteAny();
+
+    // The parent of this writer, needed for various bits such as type info and
+    // the listeners.
+    ProtoStreamObjectWriter* parent_;
+
+    // The nested object writer, used to write events.
+    google::protobuf::scoped_ptr<ProtoStreamObjectWriter> ow_;
+
+    // The type_url_ that this Any represents.
+    string type_url_;
+
+    // Whether this any is invalid. This allows us to only report an invalid
+    // Any message a single time rather than every time we get a nested field.
+    bool invalid_;
+
+    // The output data and wrapping ByteSink.
+    string data_;
+    strings::StringByteSink output_;
+
+    // The depth within the Any, so we can track when we're done.
+    int depth_;
+
+    // True if the message type contained in Any has a special "value" message
+    // injected. This is true for well-known message types like Any or Struct.
+    bool has_injected_value_message_;
+  };
+
+  class LIBPROTOBUF_EXPORT ProtoElement : public BaseElement, public LocationTrackerInterface {
+   public:
+    // Indicates the type of element. Special types like LIST, MAP, MAP_ENTRY,
+    // STRUCT etc. are used to deduce other information based on their position
+    // on the stack of elements.
+    enum ElementType {
+      MESSAGE,       // Simple message
+      LIST,          // List/repeated element
+      MAP,           // Proto3 map type
+      MAP_ENTRY,     // Proto3 map message type, with 'key' and 'value' fields
+      ANY,           // Proto3 Any type
+      STRUCT,        // Proto3 struct type
+      STRUCT_VALUE,  // Struct's Value message type
+      STRUCT_LIST,   // List type indicator within a struct
+      STRUCT_LIST_VALUE,  // Struct Value's ListValue message type
+      STRUCT_MAP,         // Struct within a struct type
+      STRUCT_MAP_ENTRY    // Struct map's entry type with 'key' and 'value'
+                          // fields
+    };
+
+    // Constructor for the root element. No parent nor field.
+    ProtoElement(TypeInfo* typeinfo, const google::protobuf::Type& type,
+                 ProtoStreamObjectWriter* enclosing);
+
+    // Constructor for a field of an element.
+    ProtoElement(ProtoElement* parent, const google::protobuf::Field* field,
+                 const google::protobuf::Type& type, ElementType element_type);
+
+    virtual ~ProtoElement() {}
+
+    // Called just before the destructor for clean up:
+    //   - reports any missing required fields
+    //   - computes the space needed by the size field, and augment the
+    //     length of all parent messages by this additional space.
+    //   - releases and returns the parent pointer.
+    ProtoElement* pop();
+
+    // Accessors
+    const google::protobuf::Field* field() const { return field_; }
+    const google::protobuf::Type& type() const { return type_; }
+
+    // These functions return true if the element type is corresponding to the
+    // type in function name.
+    bool IsMap() { return element_type_ == MAP; }
+    bool IsStructMap() { return element_type_ == STRUCT_MAP; }
+    bool IsStructMapEntry() { return element_type_ == STRUCT_MAP_ENTRY; }
+    bool IsStructList() { return element_type_ == STRUCT_LIST; }
+    bool IsAny() { return element_type_ == ANY; }
+
+    ElementType element_type() { return element_type_; }
+
+    void RegisterField(const google::protobuf::Field* field);
+    virtual string ToString() const;
+
+    AnyWriter* any() const { return any_.get(); }
+
+    virtual ProtoElement* parent() const {
+      return static_cast<ProtoElement*>(BaseElement::parent());
+    }
+
+   private:
+    // Used for access to variables of the enclosing instance of
+    // ProtoStreamObjectWriter.
+    ProtoStreamObjectWriter* ow_;
+
+    // A writer for Any objects, handles all Any-related nonsense.
+    google::protobuf::scoped_ptr<AnyWriter> any_;
+
+    // Describes the element as a field in the parent message.
+    // field_ is NULL if and only if this element is the root element.
+    const google::protobuf::Field* field_;
+
+    // TypeInfo to lookup types.
+    TypeInfo* typeinfo_;
+
+    // Additional variables if this element is a message:
+    // (Root element is always a message).
+    // descriptor_     : describes allowed fields in the message.
+    // required_fields_: set of required fields.
+    // is_repeated_type_ : true if the element is of type list or map.
+    // size_index_     : index into ProtoStreamObjectWriter::size_insert_
+    //                   for later insertion of serialized message length.
+    const google::protobuf::Type& type_;
+    std::set<const google::protobuf::Field*> required_fields_;
+    const bool is_repeated_type_;
+    const int size_index_;
+
+    // Tracks position in repeated fields, needed for LocationTrackerInterface.
+    int array_index_;
+
+    // The type of this element, see enum for permissible types.
+    ElementType element_type_;
+
+    GOOGLE_DISALLOW_IMPLICIT_CONSTRUCTORS(ProtoElement);
+  };
+
+  // Container for inserting 'size' information at the 'pos' position.
+  struct SizeInfo {
+    const int pos;
+    int size;
+  };
+
+  ProtoStreamObjectWriter(TypeInfo* typeinfo,
+                          const google::protobuf::Type& type,
+                          strings::ByteSink* output, ErrorListener* listener);
+
+  ProtoElement* element() { return element_.get(); }
+
+  // Helper methods for calling ErrorListener. See error_listener.h.
+  void InvalidName(StringPiece unknown_name, StringPiece message);
+  void InvalidValue(StringPiece type_name, StringPiece value);
+  void MissingField(StringPiece missing_name);
+
+  // Common code for BeginObject() and BeginList() that does invalid_depth_
+  // bookkeeping associated with name lookup.
+  const google::protobuf::Field* BeginNamed(StringPiece name, bool is_list);
+
+  // Lookup the field in the current element. Looks in the base descriptor
+  // and in any extension. This will report an error if the field cannot be
+  // found or if multiple matching extensions are found.
+  const google::protobuf::Field* Lookup(StringPiece name);
+
+  // Lookup the field type in the type descriptor. Returns NULL if the type
+  // is not known.
+  const google::protobuf::Type* LookupType(
+      const google::protobuf::Field* field);
+
+  // Looks up the oneof struct Value field depending on the type.
+  // On failure to find, it returns an appropriate error.
+  util::StatusOr<const google::protobuf::Field*> LookupStructField(
+      DataPiece::Type type);
+
+  // Starts an entry in map. This will be called after placing map element at
+  // the top of the stack. Uses this information to write map entries.
+  const google::protobuf::Field* StartMapEntry(StringPiece name);
+
+  // Starts a google.protobuf.Struct.
+  // 'field' is of type google.protobuf.Struct.
+  // If field is NULL, it indicates that the top-level message is a struct
+  // type.
+  void StartStruct(const google::protobuf::Field* field);
+
+  // Starts another struct within a struct.
+  // 'field' is of type google.protobuf.Value (see struct.proto).
+  const google::protobuf::Field* StartStructValueInStruct(
+      const google::protobuf::Field* field);
+
+  // Starts a list within a struct.
+  // 'field' is of type google.protobuf.ListValue (see struct.proto).
+  const google::protobuf::Field* StartListValueInStruct(
+      const google::protobuf::Field* field);
+
+  // Starts the repeated "values" field in struct.proto's
+  // google.protobuf.ListValue type. 'field' should be of type
+  // google.protobuf.ListValue.
+  const google::protobuf::Field* StartRepeatedValuesInListValue(
+      const google::protobuf::Field* field);
+
+  // Pops sentinel elements off the stack.
+  void SkipElements();
+
+  // Write serialized output to the final output ByteSink, inserting all
+  // the size information for nested messages that are missing from the
+  // intermediate Cord buffer.
+  void WriteRootMessage();
+
+  // Returns true if the field is a map.
+  bool IsMap(const google::protobuf::Field& field);
+
+  // Returns true if the field is an any.
+  bool IsAny(const google::protobuf::Field& field);
+
+  // Helper method to write proto tags based on the given field.
+  void WriteTag(const google::protobuf::Field& field);
+
+  // Helper function to render primitive data types in DataPiece.
+  void RenderSimpleDataPiece(const google::protobuf::Field& field,
+                             const google::protobuf::Type& type,
+                             const DataPiece& data);
+
+  // Renders google.protobuf.Value in struct.proto. It picks the right oneof
+  // type based on value's type.
+  static util::Status RenderStructValue(ProtoStreamObjectWriter* ow,
+                                          const DataPiece& value);
+
+  // Renders google.protobuf.Timestamp value.
+  static util::Status RenderTimestamp(ProtoStreamObjectWriter* ow,
+                                        const DataPiece& value);
+
+  // Renders google.protobuf.FieldMask value.
+  static util::Status RenderFieldMask(ProtoStreamObjectWriter* ow,
+                                        const DataPiece& value);
+
+  // Renders google.protobuf.Duration value.
+  static util::Status RenderDuration(ProtoStreamObjectWriter* ow,
+                                       const DataPiece& value);
+
+  // Renders wrapper message types for primitive types in
+  // google/protobuf/wrappers.proto.
+  static util::Status RenderWrapperType(ProtoStreamObjectWriter* ow,
+                                          const DataPiece& value);
+
+  // Helper functions to create the map and find functions responsible for
+  // rendering well known types, keyed by type URL.
+  static hash_map<string, TypeRenderer>* CreateRendererMap();
+  static TypeRenderer* FindTypeRenderer(const string& type_url);
+
+  // Returns the ProtoElement::ElementType for the given Type.
+  static ProtoElement::ElementType GetElementType(
+      const google::protobuf::Type& type);
+
+  // Variables for describing the structure of the input tree:
+  // master_type_: descriptor for the whole protobuf message.
+  // typeinfo_ : the TypeInfo object to lookup types.
+  const google::protobuf::Type& master_type_;
+  TypeInfo* typeinfo_;
+  // Whether we own the typeinfo_ object.
+  bool own_typeinfo_;
+
+  // Indicates whether we finished writing root message completely.
+  bool done_;
+
+  // Variable for internal state processing:
+  // element_    : the current element.
+  // size_insert_: sizes of nested messages.
+  //               pos  - position to insert the size field.
+  //               size - size value to be inserted.
+  google::protobuf::scoped_ptr<ProtoElement> element_;
+  std::deque<SizeInfo> size_insert_;
+
+  // Variables for output generation:
+  // output_  : pointer to an external ByteSink for final user-visible output.
+  // buffer_  : buffer holding partial message before being ready for output_.
+  // adapter_ : internal adapter between CodedOutputStream and Cord buffer_.
+  // stream_  : wrapper for writing tags and other encodings in wire format.
+  strings::ByteSink* output_;
+  string buffer_;
+  google::protobuf::io::StringOutputStream adapter_;
+  google::protobuf::scoped_ptr<google::protobuf::io::CodedOutputStream> stream_;
+
+  // Variables for error tracking and reporting:
+  // listener_     : a place to report any errors found.
+  // invalid_depth_: number of enclosing invalid nested messages.
+  // tracker_      : the root location tracker interface.
+  ErrorListener* listener_;
+  int invalid_depth_;
+  google::protobuf::scoped_ptr<LocationTrackerInterface> tracker_;
+
+  GOOGLE_DISALLOW_IMPLICIT_CONSTRUCTORS(ProtoStreamObjectWriter);
+};
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_CONVERTER_PROTOSTREAM_OBJECTWRITER_H__
diff --git a/src/google/protobuf/util/internal/protostream_objectwriter_test.cc b/src/google/protobuf/util/internal/protostream_objectwriter_test.cc
new file mode 100644
index 0000000..bd4f29f
--- /dev/null
+++ b/src/google/protobuf/util/internal/protostream_objectwriter_test.cc
@@ -0,0 +1,1513 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/util/internal/protostream_objectwriter.h>
+
+#include <stddef.h>  // For size_t
+
+#include <google/protobuf/field_mask.pb.h>
+#include <google/protobuf/timestamp.pb.h>
+#include <google/protobuf/wrappers.pb.h>
+#include <google/protobuf/io/zero_copy_stream_impl_lite.h>
+#include <google/protobuf/descriptor.pb.h>
+#include <google/protobuf/descriptor.h>
+#include <google/protobuf/dynamic_message.h>
+#include <google/protobuf/message.h>
+#include <google/protobuf/util/internal/mock_error_listener.h>
+#include <google/protobuf/util/internal/testdata/books.pb.h>
+#include <google/protobuf/util/internal/testdata/field_mask.pb.h>
+#include <google/protobuf/util/internal/type_info_test_helper.h>
+#include <google/protobuf/util/internal/constants.h>
+#include <google/protobuf/stubs/bytestream.h>
+#include <google/protobuf/stubs/strutil.h>
+#include <google/protobuf/util/internal/testdata/anys.pb.h>
+#include <google/protobuf/util/internal/testdata/maps.pb.h>
+#include <google/protobuf/util/internal/testdata/struct.pb.h>
+#include <google/protobuf/util/internal/testdata/timestamp_duration.pb.h>
+#include <gtest/gtest.h>
+
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+
+using google::protobuf::testing::Author;
+using google::protobuf::testing::Book;
+using google::protobuf::testing::Book_Data;
+using google::protobuf::testing::Primitive;
+using google::protobuf::testing::Publisher;
+using google::protobuf::Descriptor;
+using google::protobuf::DescriptorPool;
+using google::protobuf::DynamicMessageFactory;
+using google::protobuf::FileDescriptorProto;
+using google::protobuf::Message;
+using google::protobuf::io::ArrayInputStream;
+using strings::GrowingArrayByteSink;
+using ::testing::_;
+using ::testing::Args;
+using google::protobuf::testing::anys::AnyM;
+using google::protobuf::testing::anys::AnyOut;
+using google::protobuf::testing::FieldMaskTest;
+using google::protobuf::testing::maps::MapIn;
+using google::protobuf::testing::structs::StructType;
+using google::protobuf::testing::timestampduration::TimestampDuration;
+
+
+namespace {
+string GetTypeUrl(const Descriptor* descriptor) {
+  return string(kTypeServiceBaseUrl) + "/" + descriptor->full_name();
+}
+}  // namespace
+
+class BaseProtoStreamObjectWriterTest
+    : public ::testing::TestWithParam<testing::TypeInfoSource> {
+ protected:
+  BaseProtoStreamObjectWriterTest()
+      : helper_(GetParam()),
+        listener_(),
+        output_(new GrowingArrayByteSink(1000)),
+        ow_() {}
+
+  explicit BaseProtoStreamObjectWriterTest(const Descriptor* descriptor)
+      : helper_(GetParam()),
+        listener_(),
+        output_(new GrowingArrayByteSink(1000)),
+        ow_() {
+    vector<const Descriptor*> descriptors;
+    descriptors.push_back(descriptor);
+    ResetTypeInfo(descriptors);
+  }
+
+  explicit BaseProtoStreamObjectWriterTest(
+      vector<const Descriptor*> descriptors)
+      : helper_(GetParam()),
+        listener_(),
+        output_(new GrowingArrayByteSink(1000)),
+        ow_() {
+    ResetTypeInfo(descriptors);
+  }
+
+  void ResetTypeInfo(vector<const Descriptor*> descriptors) {
+    GOOGLE_CHECK(!descriptors.empty()) << "Must have at least one descriptor!";
+    helper_.ResetTypeInfo(descriptors);
+    ow_.reset(helper_.NewProtoWriter(GetTypeUrl(descriptors[0]), output_.get(),
+                                     &listener_));
+  }
+
+  virtual ~BaseProtoStreamObjectWriterTest() {}
+
+  void CheckOutput(const Message& expected, int expected_length) {
+    size_t nbytes;
+    google::protobuf::scoped_array<char> buffer(output_->GetBuffer(&nbytes));
+    if (expected_length >= 0) {
+      EXPECT_EQ(expected_length, nbytes);
+    }
+    string str(buffer.get(), nbytes);
+
+    std::stringbuf str_buf(str, std::ios_base::in);
+    std::istream istream(&str_buf);
+    google::protobuf::scoped_ptr<Message> message(expected.New());
+    message->ParsePartialFromIstream(&istream);
+
+    EXPECT_EQ(expected.DebugString(), message->DebugString());
+  }
+
+  void CheckOutput(const Message& expected) { CheckOutput(expected, -1); }
+
+  const google::protobuf::Type* GetType(const Descriptor* descriptor) {
+    return helper_.GetTypeInfo()->GetType(GetTypeUrl(descriptor));
+  }
+
+  testing::TypeInfoTestHelper helper_;
+  MockErrorListener listener_;
+  google::protobuf::scoped_ptr<GrowingArrayByteSink> output_;
+  google::protobuf::scoped_ptr<ProtoStreamObjectWriter> ow_;
+};
+
+MATCHER_P(HasObjectLocation, expected,
+          "Verifies the expected object location") {
+  string actual = std::tr1::get<0>(arg).ToString();
+  if (actual.compare(expected) == 0) return true;
+  *result_listener << "actual location is: " << actual;
+  return false;
+}
+
+class ProtoStreamObjectWriterTest : public BaseProtoStreamObjectWriterTest {
+ protected:
+  ProtoStreamObjectWriterTest()
+      : BaseProtoStreamObjectWriterTest(Book::descriptor()) {}
+
+  virtual ~ProtoStreamObjectWriterTest() {}
+};
+
+INSTANTIATE_TEST_CASE_P(DifferentTypeInfoSourceTest,
+                        ProtoStreamObjectWriterTest,
+                        ::testing::Values(
+                            testing::USE_TYPE_RESOLVER));
+
+TEST_P(ProtoStreamObjectWriterTest, EmptyObject) {
+  Book empty;
+  ow_->StartObject("")->EndObject();
+  CheckOutput(empty, 0);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, SimpleObject) {
+  string content("My content");
+
+  Book book;
+  book.set_title("My Title");
+  book.set_length(222);
+  book.set_content(content);
+
+  ow_->StartObject("")
+      ->RenderString("title", "My Title")
+      ->RenderInt32("length", 222)
+      ->RenderBytes("content", content)
+      ->EndObject();
+  CheckOutput(book);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, SimpleMessage) {
+  Book book;
+  book.set_title("Some Book");
+  book.set_length(102);
+  Publisher* publisher = book.mutable_publisher();
+  publisher->set_name("My Publisher");
+  Author* robert = book.mutable_author();
+  robert->set_alive(true);
+  robert->set_name("robert");
+  robert->add_pseudonym("bob");
+  robert->add_pseudonym("bobby");
+  robert->add_friend_()->set_name("john");
+
+  ow_->StartObject("")
+      ->RenderString("title", "Some Book")
+      ->RenderInt32("length", 102)
+      ->StartObject("publisher")
+      ->RenderString("name", "My Publisher")
+      ->EndObject()
+      ->StartObject("author")
+      ->RenderBool("alive", true)
+      ->RenderString("name", "robert")
+      ->StartList("pseudonym")
+      ->RenderString("", "bob")
+      ->RenderString("", "bobby")
+      ->EndList()
+      ->StartList("friend")
+      ->StartObject("")
+      ->RenderString("name", "john")
+      ->EndObject()
+      ->EndList()
+      ->EndObject()
+      ->EndObject();
+  CheckOutput(book);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, PrimitiveFromStringConversion) {
+  Primitive full;
+  full.set_fix32(101);
+  full.set_u32(102);
+  full.set_i32(-103);
+  full.set_sf32(-104);
+  full.set_s32(-105);
+  full.set_fix64(40000000001L);
+  full.set_u64(40000000002L);
+  full.set_i64(-40000000003L);
+  full.set_sf64(-40000000004L);
+  full.set_s64(-40000000005L);
+  full.set_str("string1");
+  full.set_bytes("Some Bytes");
+  full.set_float_(3.14f);
+  full.set_double_(-4.05L);
+  full.set_bool_(true);
+  full.add_rep_fix32(201);
+  full.add_rep_u32(202);
+  full.add_rep_i32(-203);
+  full.add_rep_sf32(-204);
+  full.add_rep_s32(-205);
+  full.add_rep_fix64(80000000001L);
+  full.add_rep_u64(80000000002L);
+  full.add_rep_i64(-80000000003L);
+  full.add_rep_sf64(-80000000004L);
+  full.add_rep_s64(-80000000005L);
+  full.add_rep_str("string2");
+  full.add_rep_bytes("More Bytes");
+  full.add_rep_float(6.14f);
+  full.add_rep_double(-8.05L);
+  full.add_rep_bool(false);
+
+  ow_.reset(helper_.NewProtoWriter(GetTypeUrl(Primitive::descriptor()),
+                                   output_.get(), &listener_));
+
+  ow_->StartObject("")
+      ->RenderString("fix32", "101")
+      ->RenderString("u32", "102")
+      ->RenderString("i32", "-103")
+      ->RenderString("sf32", "-104")
+      ->RenderString("s32", "-105")
+      ->RenderString("fix64", "40000000001")
+      ->RenderString("u64", "40000000002")
+      ->RenderString("i64", "-40000000003")
+      ->RenderString("sf64", "-40000000004")
+      ->RenderString("s64", "-40000000005")
+      ->RenderString("str", "string1")
+      ->RenderString("bytes", "U29tZSBCeXRlcw==")  // "Some Bytes"
+      ->RenderString("float", "3.14")
+      ->RenderString("double", "-4.05")
+      ->RenderString("bool", "true")
+      ->StartList("rep_fix32")
+      ->RenderString("", "201")
+      ->EndList()
+      ->StartList("rep_u32")
+      ->RenderString("", "202")
+      ->EndList()
+      ->StartList("rep_i32")
+      ->RenderString("", "-203")
+      ->EndList()
+      ->StartList("rep_sf32")
+      ->RenderString("", "-204")
+      ->EndList()
+      ->StartList("rep_s32")
+      ->RenderString("", "-205")
+      ->EndList()
+      ->StartList("rep_fix64")
+      ->RenderString("", "80000000001")
+      ->EndList()
+      ->StartList("rep_u64")
+      ->RenderString("", "80000000002")
+      ->EndList()
+      ->StartList("rep_i64")
+      ->RenderString("", "-80000000003")
+      ->EndList()
+      ->StartList("rep_sf64")
+      ->RenderString("", "-80000000004")
+      ->EndList()
+      ->StartList("rep_s64")
+      ->RenderString("", "-80000000005")
+      ->EndList()
+      ->StartList("rep_str")
+      ->RenderString("", "string2")
+      ->EndList()
+      ->StartList("rep_bytes")
+      ->RenderString("", "TW9yZSBCeXRlcw==")  // "More Bytes"
+      ->EndList()
+      ->StartList("rep_float")
+      ->RenderString("", "6.14")
+      ->EndList()
+      ->StartList("rep_double")
+      ->RenderString("", "-8.05")
+      ->EndList()
+      ->StartList("rep_bool")
+      ->RenderString("", "false")
+      ->EndList()
+      ->EndObject();
+  CheckOutput(full);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, InfinityInputTest) {
+  Primitive full;
+  full.set_double_(std::numeric_limits<double>::infinity());
+  full.set_float_(std::numeric_limits<float>::infinity());
+  full.set_str("-Infinity");
+
+  ow_.reset(helper_.NewProtoWriter(GetTypeUrl(Primitive::descriptor()),
+                                   output_.get(), &listener_));
+
+  EXPECT_CALL(listener_, InvalidValue(_, StringPiece("TYPE_INT32"),
+                                      StringPiece("\"Infinity\"")))
+      .With(Args<0>(HasObjectLocation("i32")));
+  EXPECT_CALL(listener_, InvalidValue(_, StringPiece("TYPE_UINT32"),
+                                      StringPiece("\"Infinity\"")))
+      .With(Args<0>(HasObjectLocation("u32")));
+  EXPECT_CALL(listener_, InvalidValue(_, StringPiece("TYPE_SFIXED64"),
+                                      StringPiece("\"-Infinity\"")))
+      .With(Args<0>(HasObjectLocation("sf64")));
+  EXPECT_CALL(listener_, InvalidValue(_, StringPiece("TYPE_BOOL"),
+                                      StringPiece("\"Infinity\"")))
+      .With(Args<0>(HasObjectLocation("bool")));
+
+  ow_->StartObject("")
+      ->RenderString("double", "Infinity")
+      ->RenderString("float", "Infinity")
+      ->RenderString("i32", "Infinity")
+      ->RenderString("u32", "Infinity")
+      ->RenderString("sf64", "-Infinity")
+      ->RenderString("str", "-Infinity")
+      ->RenderString("bool", "Infinity")
+      ->EndObject();
+  CheckOutput(full);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, NaNInputTest) {
+  Primitive full;
+  full.set_double_(std::numeric_limits<double>::quiet_NaN());
+  full.set_float_(std::numeric_limits<float>::quiet_NaN());
+  full.set_str("NaN");
+
+  ow_.reset(helper_.NewProtoWriter(GetTypeUrl(Primitive::descriptor()),
+                                   output_.get(), &listener_));
+
+  EXPECT_CALL(listener_, InvalidValue(_, StringPiece("TYPE_INT32"),
+                                      StringPiece("\"NaN\"")))
+      .With(Args<0>(HasObjectLocation("i32")));
+  EXPECT_CALL(listener_, InvalidValue(_, StringPiece("TYPE_UINT32"),
+                                      StringPiece("\"NaN\"")))
+      .With(Args<0>(HasObjectLocation("u32")));
+  EXPECT_CALL(listener_, InvalidValue(_, StringPiece("TYPE_SFIXED64"),
+                                      StringPiece("\"NaN\"")))
+      .With(Args<0>(HasObjectLocation("sf64")));
+  EXPECT_CALL(listener_,
+              InvalidValue(_, StringPiece("TYPE_BOOL"), StringPiece("\"NaN\"")))
+      .With(Args<0>(HasObjectLocation("bool")));
+
+  ow_->StartObject("")
+      ->RenderString("double", "NaN")
+      ->RenderString("float", "NaN")
+      ->RenderString("i32", "NaN")
+      ->RenderString("u32", "NaN")
+      ->RenderString("sf64", "NaN")
+      ->RenderString("str", "NaN")
+      ->RenderString("bool", "NaN")
+      ->EndObject();
+
+  CheckOutput(full);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, ImplicitPrimitiveList) {
+  Book expected;
+  Author* author = expected.mutable_author();
+  author->set_name("The Author");
+  author->add_pseudonym("first");
+  author->add_pseudonym("second");
+
+  ow_->StartObject("")
+      ->StartObject("author")
+      ->RenderString("name", "The Author")
+      ->RenderString("pseudonym", "first")
+      ->RenderString("pseudonym", "second")
+      ->EndObject()
+      ->EndObject();
+  CheckOutput(expected);
+}
+
+TEST_P(ProtoStreamObjectWriterTest,
+       LastWriteWinsOnNonRepeatedPrimitiveFieldWithDuplicates) {
+  Book expected;
+  Author* author = expected.mutable_author();
+  author->set_name("second");
+
+  ow_->StartObject("")
+      ->StartObject("author")
+      ->RenderString("name", "first")
+      ->RenderString("name", "second")
+      ->EndObject()
+      ->EndObject();
+  CheckOutput(expected);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, ExplicitPrimitiveList) {
+  Book expected;
+  Author* author = expected.mutable_author();
+  author->set_name("The Author");
+  author->add_pseudonym("first");
+  author->add_pseudonym("second");
+
+  ow_->StartObject("")
+      ->StartObject("author")
+      ->RenderString("name", "The Author")
+      ->StartList("pseudonym")
+      ->RenderString("", "first")
+      ->RenderString("", "second")
+      ->EndList()
+      ->EndObject()
+      ->EndObject();
+  CheckOutput(expected);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, NonRepeatedExplicitPrimitiveList) {
+  Book expected;
+  expected.set_allocated_author(new Author());
+
+  EXPECT_CALL(
+      listener_,
+      InvalidName(
+          _, StringPiece("name"),
+          StringPiece("Proto field is not repeating, cannot start list.")))
+      .With(Args<0>(HasObjectLocation("author")));
+  ow_->StartObject("")
+      ->StartObject("author")
+      ->StartList("name")
+      ->RenderString("", "first")
+      ->RenderString("", "second")
+      ->EndList()
+      ->EndObject()
+      ->EndObject();
+  CheckOutput(expected);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, ImplicitMessageList) {
+  Book expected;
+  Author* outer = expected.mutable_author();
+  outer->set_name("outer");
+  outer->set_alive(true);
+  Author* first = outer->add_friend_();
+  first->set_name("first");
+  Author* second = outer->add_friend_();
+  second->set_name("second");
+
+  ow_->StartObject("")
+      ->StartObject("author")
+      ->RenderString("name", "outer")
+      ->RenderBool("alive", true)
+      ->StartObject("friend")
+      ->RenderString("name", "first")
+      ->EndObject()
+      ->StartObject("friend")
+      ->RenderString("name", "second")
+      ->EndObject()
+      ->EndObject()
+      ->EndObject();
+  CheckOutput(expected);
+}
+
+TEST_P(ProtoStreamObjectWriterTest,
+       LastWriteWinsOnNonRepeatedMessageFieldWithDuplicates) {
+  Book expected;
+  Author* author = expected.mutable_author();
+  author->set_name("The Author");
+  Publisher* publisher = expected.mutable_publisher();
+  publisher->set_name("second");
+
+  ow_->StartObject("")
+      ->StartObject("author")
+      ->RenderString("name", "The Author")
+      ->EndObject()
+      ->StartObject("publisher")
+      ->RenderString("name", "first")
+      ->EndObject()
+      ->StartObject("publisher")
+      ->RenderString("name", "second")
+      ->EndObject()
+      ->EndObject();
+  CheckOutput(expected);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, ExplicitMessageList) {
+  Book expected;
+  Author* outer = expected.mutable_author();
+  outer->set_name("outer");
+  outer->set_alive(true);
+  Author* first = outer->add_friend_();
+  first->set_name("first");
+  Author* second = outer->add_friend_();
+  second->set_name("second");
+
+  ow_->StartObject("")
+      ->StartObject("author")
+      ->RenderString("name", "outer")
+      ->RenderBool("alive", true)
+      ->StartList("friend")
+      ->StartObject("")
+      ->RenderString("name", "first")
+      ->EndObject()
+      ->StartObject("")
+      ->RenderString("name", "second")
+      ->EndObject()
+      ->EndList()
+      ->EndObject()
+      ->EndObject();
+  CheckOutput(expected);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, NonRepeatedExplicitMessageList) {
+  Book expected;
+  Author* author = expected.mutable_author();
+  author->set_name("The Author");
+
+  EXPECT_CALL(
+      listener_,
+      InvalidName(
+          _, StringPiece("publisher"),
+          StringPiece("Proto field is not repeating, cannot start list.")))
+      .With(Args<0>(HasObjectLocation("")));
+  ow_->StartObject("")
+      ->StartObject("author")
+      ->RenderString("name", "The Author")
+      ->EndObject()
+      ->StartList("publisher")
+      ->StartObject("")
+      ->RenderString("name", "first")
+      ->EndObject()
+      ->StartObject("")
+      ->RenderString("name", "second")
+      ->EndObject()
+      ->EndList()
+      ->EndObject();
+  CheckOutput(expected);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, UnknownFieldAtRoot) {
+  Book empty;
+
+  EXPECT_CALL(listener_, InvalidName(_, StringPiece("unknown"),
+                                     StringPiece("Cannot find field.")))
+      .With(Args<0>(HasObjectLocation("")));
+  ow_->StartObject("")->RenderString("unknown", "Nope!")->EndObject();
+  CheckOutput(empty, 0);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, UnknownFieldAtAuthorFriend) {
+  Book expected;
+  Author* paul = expected.mutable_author();
+  paul->set_name("Paul");
+  Author* mark = paul->add_friend_();
+  mark->set_name("Mark");
+  Author* john = paul->add_friend_();
+  john->set_name("John");
+  Author* luke = paul->add_friend_();
+  luke->set_name("Luke");
+
+  EXPECT_CALL(listener_, InvalidName(_, StringPiece("address"),
+                                     StringPiece("Cannot find field.")))
+      .With(Args<0>(HasObjectLocation("author.friend[1]")));
+  ow_->StartObject("")
+      ->StartObject("author")
+      ->RenderString("name", "Paul")
+      ->StartList("friend")
+      ->StartObject("")
+      ->RenderString("name", "Mark")
+      ->EndObject()
+      ->StartObject("")
+      ->RenderString("name", "John")
+      ->RenderString("address", "Patmos")
+      ->EndObject()
+      ->StartObject("")
+      ->RenderString("name", "Luke")
+      ->EndObject()
+      ->EndList()
+      ->EndObject()
+      ->EndObject();
+  CheckOutput(expected);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, UnknownObjectAtRoot) {
+  Book empty;
+
+  EXPECT_CALL(listener_, InvalidName(_, StringPiece("unknown"),
+                                     StringPiece("Cannot find field.")))
+      .With(Args<0>(HasObjectLocation("")));
+  ow_->StartObject("")->StartObject("unknown")->EndObject()->EndObject();
+  CheckOutput(empty, 0);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, UnknownObjectAtAuthor) {
+  Book expected;
+  Author* author = expected.mutable_author();
+  author->set_name("William");
+  author->add_pseudonym("Bill");
+
+  EXPECT_CALL(listener_, InvalidName(_, StringPiece("wife"),
+                                     StringPiece("Cannot find field.")))
+      .With(Args<0>(HasObjectLocation("author")));
+  ow_->StartObject("")
+      ->StartObject("author")
+      ->RenderString("name", "William")
+      ->StartObject("wife")
+      ->RenderString("name", "Hilary")
+      ->EndObject()
+      ->RenderString("pseudonym", "Bill")
+      ->EndObject()
+      ->EndObject();
+  CheckOutput(expected);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, UnknownListAtRoot) {
+  Book empty;
+
+  EXPECT_CALL(listener_, InvalidName(_, StringPiece("unknown"),
+                                     StringPiece("Cannot find field.")))
+      .With(Args<0>(HasObjectLocation("")));
+  ow_->StartObject("")->StartList("unknown")->EndList()->EndObject();
+  CheckOutput(empty, 0);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, UnknownListAtPublisher) {
+  Book expected;
+  expected.set_title("Brainwashing");
+  Publisher* publisher = expected.mutable_publisher();
+  publisher->set_name("propaganda");
+
+  EXPECT_CALL(listener_, InvalidName(_, StringPiece("alliance"),
+                                     StringPiece("Cannot find field.")))
+      .With(Args<0>(HasObjectLocation("publisher")));
+  ow_->StartObject("")
+      ->StartObject("publisher")
+      ->RenderString("name", "propaganda")
+      ->StartList("alliance")
+      ->EndList()
+      ->EndObject()
+      ->RenderString("title", "Brainwashing")
+      ->EndObject();
+  CheckOutput(expected);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, MissingRequiredField) {
+  Book expected;
+  expected.set_title("My Title");
+  expected.set_allocated_publisher(new Publisher());
+
+  EXPECT_CALL(listener_, MissingField(_, StringPiece("name")))
+      .With(Args<0>(HasObjectLocation("publisher")));
+  ow_->StartObject("")
+      ->StartObject("publisher")
+      ->EndObject()
+      ->RenderString("title", "My Title")
+      ->EndObject();
+  CheckOutput(expected);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, InvalidFieldValueAtRoot) {
+  Book empty;
+
+  EXPECT_CALL(listener_, InvalidValue(_, StringPiece("TYPE_UINT32"),
+                                      StringPiece("\"garbage\"")))
+      .With(Args<0>(HasObjectLocation("length")));
+  ow_->StartObject("")->RenderString("length", "garbage")->EndObject();
+  CheckOutput(empty, 0);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, MultipleInvalidFieldValues) {
+  Book expected;
+  expected.set_title("My Title");
+
+  EXPECT_CALL(listener_, InvalidValue(_, StringPiece("TYPE_UINT32"),
+                                      StringPiece("\"-400\"")))
+      .With(Args<0>(HasObjectLocation("length")));
+  EXPECT_CALL(listener_, InvalidValue(_, StringPiece("TYPE_INT64"),
+                                      StringPiece("\"3.14\"")))
+      .With(Args<0>(HasObjectLocation("published")));
+  ow_->StartObject("")
+      ->RenderString("length", "-400")
+      ->RenderString("published", "3.14")
+      ->RenderString("title", "My Title")
+      ->EndObject();
+  CheckOutput(expected);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, UnnamedFieldAtRoot) {
+  Book empty;
+
+  EXPECT_CALL(listener_,
+              InvalidName(_, StringPiece(""),
+                          StringPiece("Proto fields must have a name.")))
+      .With(Args<0>(HasObjectLocation("")));
+  ow_->StartObject("")->RenderFloat("", 3.14)->EndObject();
+  CheckOutput(empty, 0);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, UnnamedFieldAtAuthor) {
+  Book expected;
+  expected.set_title("noname");
+  expected.set_allocated_author(new Author());
+
+  EXPECT_CALL(listener_,
+              InvalidName(_, StringPiece(""),
+                          StringPiece("Proto fields must have a name.")))
+      .With(Args<0>(HasObjectLocation("author")));
+  ow_->StartObject("")
+      ->StartObject("author")
+      ->RenderInt32("", 123)
+      ->EndObject()
+      ->RenderString("title", "noname")
+      ->EndObject();
+  CheckOutput(expected);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, UnnamedListAtRoot) {
+  Book expected;
+  expected.set_title("noname");
+
+  EXPECT_CALL(listener_,
+              InvalidName(_, StringPiece(""),
+                          StringPiece("Proto fields must have a name.")))
+      .With(Args<0>(HasObjectLocation("")));
+  ow_->StartObject("")
+      ->StartList("")
+      ->EndList()
+      ->RenderString("title", "noname")
+      ->EndObject();
+  CheckOutput(expected);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, RootNamedObject) {
+  Book expected;
+  expected.set_title("Annie");
+
+  EXPECT_CALL(listener_,
+              InvalidName(_, StringPiece("oops"),
+                          StringPiece("Root element should not be named.")))
+      .With(Args<0>(HasObjectLocation("")));
+  ow_->StartObject("oops")->RenderString("title", "Annie")->EndObject();
+  CheckOutput(expected, 7);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, RootNamedList) {
+  Book empty;
+
+  EXPECT_CALL(listener_,
+              InvalidName(_, StringPiece("oops"),
+                          StringPiece("Root element should not be named.")))
+      .With(Args<0>(HasObjectLocation("")));
+  EXPECT_CALL(listener_,
+              InvalidName(_, StringPiece(""),
+                          StringPiece("Proto fields must have a name.")))
+      .With(Args<0>(HasObjectLocation("")));
+  ow_->StartList("oops")->RenderString("", "item")->EndList();
+  CheckOutput(empty, 0);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, RootUnnamedField) {
+  Book empty;
+
+  EXPECT_CALL(listener_,
+              InvalidName(_, StringPiece(""),
+                          StringPiece("Root element must be a message.")))
+      .With(Args<0>(HasObjectLocation("")));
+  ow_->RenderBool("", true);
+  CheckOutput(empty, 0);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, RootNamedField) {
+  Book empty;
+
+  EXPECT_CALL(listener_,
+              InvalidName(_, StringPiece("oops"),
+                          StringPiece("Root element must be a message.")))
+      .With(Args<0>(HasObjectLocation("")));
+  ow_->RenderBool("oops", true);
+  CheckOutput(empty, 0);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, NullValue) {
+  Book empty;
+
+  ow_->RenderNull("");
+  CheckOutput(empty, 0);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, NullValueForMessageField) {
+  Book empty;
+
+  ow_->RenderNull("author");
+  CheckOutput(empty, 0);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, NullValueForPrimitiveField) {
+  Book empty;
+
+  ow_->RenderNull("length");
+  CheckOutput(empty, 0);
+}
+
+class ProtoStreamObjectWriterTimestampDurationTest
+    : public BaseProtoStreamObjectWriterTest {
+ protected:
+  ProtoStreamObjectWriterTimestampDurationTest() {
+    vector<const Descriptor*> descriptors;
+    descriptors.push_back(TimestampDuration::descriptor());
+    descriptors.push_back(google::protobuf::Timestamp::descriptor());
+    descriptors.push_back(google::protobuf::Duration::descriptor());
+    ResetTypeInfo(descriptors);
+  }
+};
+
+TEST_P(ProtoStreamObjectWriterTimestampDurationTest, InvalidTimestampError1) {
+  TimestampDuration timestamp;
+
+  EXPECT_CALL(
+      listener_,
+      InvalidValue(_,
+                   StringPiece("type.googleapis.com/google.protobuf.Timestamp"),
+                   StringPiece(
+                       "Field 'ts', Illegal timestamp format; timestamps "
+                       "must end with 'Z'")));
+
+  ow_->StartObject("")->RenderString("ts", "")->EndObject();
+  CheckOutput(timestamp);
+}
+
+TEST_P(ProtoStreamObjectWriterTimestampDurationTest, InvalidTimestampError2) {
+  TimestampDuration timestamp;
+
+  EXPECT_CALL(
+      listener_,
+      InvalidValue(
+          _, StringPiece("type.googleapis.com/google.protobuf.Timestamp"),
+          StringPiece(
+              "Field 'ts', Invalid time format: Failed to parse input")));
+
+  ow_->StartObject("")->RenderString("ts", "Z")->EndObject();
+  CheckOutput(timestamp);
+}
+
+TEST_P(ProtoStreamObjectWriterTimestampDurationTest, InvalidTimestampError3) {
+  TimestampDuration timestamp;
+
+  EXPECT_CALL(
+      listener_,
+      InvalidValue(_,
+                   StringPiece("type.googleapis.com/google.protobuf.Timestamp"),
+                   StringPiece(
+                       "Field 'ts', Invalid time format, failed to parse nano "
+                       "seconds")));
+
+  ow_->StartObject("")
+      ->RenderString("ts", "1970-01-01T00:00:00.ABZ")
+      ->EndObject();
+  CheckOutput(timestamp);
+}
+
+TEST_P(ProtoStreamObjectWriterTimestampDurationTest, InvalidTimestampError4) {
+  TimestampDuration timestamp;
+
+  EXPECT_CALL(
+      listener_,
+      InvalidValue(_,
+                   StringPiece("type.googleapis.com/google.protobuf.Timestamp"),
+                   StringPiece("Field 'ts', Timestamp value exceeds limits")));
+
+  ow_->StartObject("")
+      ->RenderString("ts", "-8032-10-18T00:00:00.000Z")
+      ->EndObject();
+  CheckOutput(timestamp);
+}
+
+// TODO(skarvaje): Write a test for nanos that exceed limit. Currently, it is
+// not possible to construct a test case where nanos exceed limit because of
+// floating point arithmetic.
+
+TEST_P(ProtoStreamObjectWriterTimestampDurationTest, InvalidDurationError1) {
+  TimestampDuration duration;
+
+  EXPECT_CALL(
+      listener_,
+      InvalidValue(_,
+                   StringPiece("type.googleapis.com/google.protobuf.Duration"),
+                   StringPiece(
+                       "Field 'dur', Illegal duration format; duration must "
+                       "end with 's'")));
+
+  ow_->StartObject("")->RenderString("dur", "")->EndObject();
+  CheckOutput(duration);
+}
+
+TEST_P(ProtoStreamObjectWriterTimestampDurationTest, InvalidDurationError2) {
+  TimestampDuration duration;
+
+  EXPECT_CALL(
+      listener_,
+      InvalidValue(_,
+                   StringPiece("type.googleapis.com/google.protobuf.Duration"),
+                   StringPiece(
+                       "Field 'dur', Invalid duration format, failed to parse "
+                       "seconds")));
+
+  ow_->StartObject("")->RenderString("dur", "s")->EndObject();
+  CheckOutput(duration);
+}
+
+TEST_P(ProtoStreamObjectWriterTimestampDurationTest, InvalidDurationError3) {
+  TimestampDuration duration;
+
+  EXPECT_CALL(
+      listener_,
+      InvalidValue(_,
+                   StringPiece("type.googleapis.com/google.protobuf.Duration"),
+                   StringPiece(
+                       "Field 'dur', Invalid duration format, failed to "
+                       "parse nanos seconds")));
+
+  ow_->StartObject("")->RenderString("dur", "123.DEFs")->EndObject();
+  CheckOutput(duration);
+}
+
+TEST_P(ProtoStreamObjectWriterTimestampDurationTest, InvalidDurationError4) {
+  TimestampDuration duration;
+
+  EXPECT_CALL(
+      listener_,
+      InvalidValue(_,
+                   StringPiece("type.googleapis.com/google.protobuf.Duration"),
+                   StringPiece("Field 'dur', Duration value exceeds limits")));
+
+  ow_->StartObject("")->RenderString("dur", "315576000002s")->EndObject();
+  CheckOutput(duration);
+}
+
+TEST_P(ProtoStreamObjectWriterTimestampDurationTest,
+       MismatchedTimestampTypeInput) {
+  TimestampDuration timestamp;
+  EXPECT_CALL(
+      listener_,
+      InvalidValue(
+          _, StringPiece("type.googleapis.com/google.protobuf.Timestamp"),
+          StringPiece(
+              "Field 'ts', Invalid data type for timestamp, value is null")))
+      .With(Args<0>(HasObjectLocation("ts")));
+  ow_->StartObject("")->RenderNull("ts")->EndObject();
+  CheckOutput(timestamp);
+}
+
+TEST_P(ProtoStreamObjectWriterTimestampDurationTest,
+       MismatchedDurationTypeInput) {
+  TimestampDuration duration;
+  EXPECT_CALL(
+      listener_,
+      InvalidValue(
+          _, StringPiece("type.googleapis.com/google.protobuf.Duration"),
+          StringPiece(
+              "Field 'dur', Invalid data type for duration, value is null")))
+      .With(Args<0>(HasObjectLocation("dur")));
+  ow_->StartObject("")->RenderNull("dur")->EndObject();
+  CheckOutput(duration);
+}
+
+class ProtoStreamObjectWriterStructTest
+    : public BaseProtoStreamObjectWriterTest {
+ protected:
+  ProtoStreamObjectWriterStructTest() {
+    vector<const Descriptor*> descriptors;
+    descriptors.push_back(StructType::descriptor());
+    descriptors.push_back(google::protobuf::Struct::descriptor());
+    ResetTypeInfo(descriptors);
+  }
+};
+
+// TODO(skarvaje): Write tests for failure cases.
+TEST_P(ProtoStreamObjectWriterStructTest, StructRenderSuccess) {
+  StructType struct_type;
+  google::protobuf::Struct* s = struct_type.mutable_object();
+  s->mutable_fields()->operator[]("k1").set_number_value(123);
+  s->mutable_fields()->operator[]("k2").set_bool_value(true);
+
+  ow_->StartObject("")
+      ->StartObject("object")
+      ->RenderDouble("k1", 123)
+      ->RenderBool("k2", true)
+      ->EndObject()
+      ->EndObject();
+  CheckOutput(struct_type);
+}
+
+TEST_P(ProtoStreamObjectWriterStructTest, StructNullInputSuccess) {
+  StructType struct_type;
+  EXPECT_CALL(listener_,
+              InvalidName(_, StringPiece(""),
+                          StringPiece("Proto fields must have a name.")))
+      .With(Args<0>(HasObjectLocation("")));
+  ow_->StartObject("")->RenderNull("")->EndObject();
+  CheckOutput(struct_type);
+}
+
+TEST_P(ProtoStreamObjectWriterStructTest, StructInvalidInputFailure) {
+  StructType struct_type;
+  EXPECT_CALL(
+      listener_,
+      InvalidValue(_, StringPiece("type.googleapis.com/google.protobuf.Struct"),
+                   StringPiece("true")))
+      .With(Args<0>(HasObjectLocation("object")));
+
+  ow_->StartObject("")->RenderBool("object", true)->EndObject();
+  CheckOutput(struct_type);
+}
+
+class ProtoStreamObjectWriterMapTest : public BaseProtoStreamObjectWriterTest {
+ protected:
+  ProtoStreamObjectWriterMapTest()
+      : BaseProtoStreamObjectWriterTest(MapIn::descriptor()) {}
+};
+
+TEST_P(ProtoStreamObjectWriterMapTest, MapShouldNotAcceptList) {
+  MapIn mm;
+  EXPECT_CALL(listener_,
+              InvalidValue(_, StringPiece("Map"),
+                           StringPiece("Cannot bind a list to map.")))
+      .With(Args<0>(HasObjectLocation("map_input")));
+  ow_->StartObject("")
+      ->StartList("map_input")
+      ->RenderString("a", "b")
+      ->EndList()
+      ->EndObject();
+  CheckOutput(mm);
+}
+
+class ProtoStreamObjectWriterAnyTest : public BaseProtoStreamObjectWriterTest {
+ protected:
+  ProtoStreamObjectWriterAnyTest() {
+    vector<const Descriptor*> descriptors;
+    descriptors.push_back(AnyOut::descriptor());
+    descriptors.push_back(google::protobuf::DoubleValue::descriptor());
+    descriptors.push_back(google::protobuf::Any::descriptor());
+    ResetTypeInfo(descriptors);
+  }
+};
+
+TEST_P(ProtoStreamObjectWriterAnyTest, AnyRenderSuccess) {
+  AnyOut any;
+  google::protobuf::Any* any_type = any.mutable_any();
+  any_type->set_type_url("type.googleapis.com/google.protobuf.DoubleValue");
+  google::protobuf::DoubleValue d;
+  d.set_value(40.2);
+  any_type->set_value(d.SerializeAsString());
+
+  ow_->StartObject("")
+      ->StartObject("any")
+      ->RenderString("@type", "type.googleapis.com/google.protobuf.DoubleValue")
+      ->RenderDouble("value", 40.2)
+      ->EndObject()
+      ->EndObject();
+  CheckOutput(any);
+}
+
+TEST_P(ProtoStreamObjectWriterAnyTest, RecursiveAny) {
+  AnyOut out;
+  ::google::protobuf::Any* any = out.mutable_any();
+  any->set_type_url("type.googleapis.com/google.protobuf.Any");
+
+  ::google::protobuf::Any nested_any;
+  nested_any.set_type_url(
+      "type.googleapis.com/google.protobuf.testing.anys.AnyM");
+
+  AnyM m;
+  m.set_foo("foovalue");
+  nested_any.set_value(m.SerializeAsString());
+
+  any->set_value(nested_any.SerializeAsString());
+
+  ow_->StartObject("")
+      ->StartObject("any")
+      ->RenderString("@type", "type.googleapis.com/google.protobuf.Any")
+      ->StartObject("value")
+      ->RenderString("@type",
+                     "type.googleapis.com/google.protobuf.testing.anys.AnyM")
+      ->RenderString("foo", "foovalue")
+      ->EndObject()
+      ->EndObject()
+      ->EndObject();
+
+  CheckOutput(out, 115);
+}
+
+TEST_P(ProtoStreamObjectWriterAnyTest, DoubleRecursiveAny) {
+  AnyOut out;
+  ::google::protobuf::Any* any = out.mutable_any();
+  any->set_type_url("type.googleapis.com/google.protobuf.Any");
+
+  ::google::protobuf::Any nested_any;
+  nested_any.set_type_url("type.googleapis.com/google.protobuf.Any");
+
+  ::google::protobuf::Any second_nested_any;
+  second_nested_any.set_type_url(
+      "type.googleapis.com/google.protobuf.testing.anys.AnyM");
+
+  AnyM m;
+  m.set_foo("foovalue");
+  second_nested_any.set_value(m.SerializeAsString());
+
+  nested_any.set_value(second_nested_any.SerializeAsString());
+  any->set_value(nested_any.SerializeAsString());
+
+  ow_->StartObject("")
+      ->StartObject("any")
+      ->RenderString("@type", "type.googleapis.com/google.protobuf.Any")
+      ->StartObject("value")
+      ->RenderString("@type", "type.googleapis.com/google.protobuf.Any")
+      ->StartObject("value")
+      ->RenderString("@type",
+                     "type.googleapis.com/google.protobuf.testing.anys.AnyM")
+      ->RenderString("foo", "foovalue")
+      ->EndObject()
+      ->EndObject()
+      ->EndObject()
+      ->EndObject();
+
+  CheckOutput(out, 159);
+}
+
+TEST_P(ProtoStreamObjectWriterAnyTest, EmptyAnyFromEmptyObject) {
+  AnyOut out;
+  out.mutable_any();
+
+  ow_->StartObject("")->StartObject("any")->EndObject()->EndObject();
+
+  CheckOutput(out, 2);
+}
+
+TEST_P(ProtoStreamObjectWriterAnyTest, AnyWithoutTypeUrlFails1) {
+  AnyOut any;
+
+  EXPECT_CALL(listener_,
+              InvalidValue(_, StringPiece("Any"),
+                           StringPiece(
+                               "Missing or invalid @type for any field in "
+                               "google.protobuf.testing.anys.AnyOut")));
+
+  ow_->StartObject("")
+      ->StartObject("any")
+      ->StartObject("another")
+      ->EndObject()
+      ->EndObject()
+      ->EndObject();
+  CheckOutput(any);
+}
+
+TEST_P(ProtoStreamObjectWriterAnyTest, AnyWithoutTypeUrlFails2) {
+  AnyOut any;
+
+  EXPECT_CALL(listener_,
+              InvalidValue(_, StringPiece("Any"),
+                           StringPiece(
+                               "Missing or invalid @type for any field in "
+                               "google.protobuf.testing.anys.AnyOut")));
+
+  ow_->StartObject("")
+      ->StartObject("any")
+      ->StartList("another")
+      ->EndObject()
+      ->EndObject()
+      ->EndObject();
+  CheckOutput(any);
+}
+
+TEST_P(ProtoStreamObjectWriterAnyTest, AnyWithoutTypeUrlFails3) {
+  AnyOut any;
+
+  EXPECT_CALL(listener_,
+              InvalidValue(_, StringPiece("Any"),
+                           StringPiece(
+                               "Missing or invalid @type for any field in "
+                               "google.protobuf.testing.anys.AnyOut")));
+
+  ow_->StartObject("")
+      ->StartObject("any")
+      ->RenderString("value", "somevalue")
+      ->EndObject()
+      ->EndObject();
+  CheckOutput(any);
+}
+
+TEST_P(ProtoStreamObjectWriterAnyTest, AnyWithInvalidTypeUrlFails) {
+  AnyOut any;
+
+  EXPECT_CALL(
+      listener_,
+      InvalidValue(_, StringPiece("Any"),
+                   StringPiece(
+                       "Invalid type URL, type URLs must be of the form "
+                       "'type.googleapis.com/<typename>', got: "
+                       "type.other.com/some.Type")));
+
+  ow_->StartObject("")
+      ->StartObject("any")
+      ->RenderString("@type", "type.other.com/some.Type")
+      ->RenderDouble("value", 40.2)
+      ->EndObject()
+      ->EndObject();
+  CheckOutput(any);
+}
+
+TEST_P(ProtoStreamObjectWriterAnyTest, AnyWithUnknownTypeFails) {
+  AnyOut any;
+
+  EXPECT_CALL(
+      listener_,
+      InvalidValue(_, StringPiece("Any"),
+                   StringPiece("Invalid type URL, unknown type: some.Type")));
+  ow_->StartObject("")
+      ->StartObject("any")
+      ->RenderString("@type", "type.googleapis.com/some.Type")
+      ->RenderDouble("value", 40.2)
+      ->EndObject()
+      ->EndObject();
+  CheckOutput(any);
+}
+
+TEST_P(ProtoStreamObjectWriterAnyTest, AnyNullInputFails) {
+  AnyOut any;
+
+  ow_->StartObject("")->RenderNull("any")->EndObject();
+  CheckOutput(any);
+}
+
+class ProtoStreamObjectWriterFieldMaskTest
+    : public BaseProtoStreamObjectWriterTest {
+ protected:
+  ProtoStreamObjectWriterFieldMaskTest() {
+    vector<const Descriptor*> descriptors;
+    descriptors.push_back(FieldMaskTest::descriptor());
+    descriptors.push_back(google::protobuf::FieldMask::descriptor());
+    ResetTypeInfo(descriptors);
+  }
+};
+
+TEST_P(ProtoStreamObjectWriterFieldMaskTest, SimpleFieldMaskTest) {
+  FieldMaskTest expected;
+  expected.set_id("1");
+  expected.mutable_single_mask()->add_paths("path1");
+
+  ow_->StartObject("");
+  ow_->RenderString("id", "1");
+  ow_->RenderString("single_mask", "path1");
+  ow_->EndObject();
+
+  CheckOutput(expected);
+}
+
+TEST_P(ProtoStreamObjectWriterFieldMaskTest, MutipleMasksInCompactForm) {
+  FieldMaskTest expected;
+  expected.set_id("1");
+  expected.mutable_single_mask()->add_paths("camel_case1");
+  expected.mutable_single_mask()->add_paths("camel_case2");
+  expected.mutable_single_mask()->add_paths("camel_case3");
+
+  ow_->StartObject("");
+  ow_->RenderString("id", "1");
+  ow_->RenderString("single_mask", "camelCase1,camelCase2,camelCase3");
+  ow_->EndObject();
+
+  CheckOutput(expected);
+}
+
+TEST_P(ProtoStreamObjectWriterFieldMaskTest, RepeatedFieldMaskTest) {
+  FieldMaskTest expected;
+  expected.set_id("1");
+  google::protobuf::FieldMask* mask = expected.add_repeated_mask();
+  mask->add_paths("field1");
+  mask->add_paths("field2");
+  expected.add_repeated_mask()->add_paths("field3");
+
+  ow_->StartObject("");
+  ow_->RenderString("id", "1");
+  ow_->StartList("repeated_mask");
+  ow_->RenderString("", "field1,field2");
+  ow_->RenderString("", "field3");
+  ow_->EndList();
+  ow_->EndObject();
+
+  CheckOutput(expected);
+}
+
+TEST_P(ProtoStreamObjectWriterFieldMaskTest, EmptyFieldMaskTest) {
+  FieldMaskTest expected;
+  expected.set_id("1");
+
+  ow_->StartObject("");
+  ow_->RenderString("id", "1");
+  ow_->RenderString("single_mask", "");
+  ow_->EndObject();
+
+  CheckOutput(expected);
+}
+
+TEST_P(ProtoStreamObjectWriterFieldMaskTest, MaskUsingApiaryStyleShouldWork) {
+  FieldMaskTest expected;
+  expected.set_id("1");
+
+  ow_->StartObject("");
+  ow_->RenderString("id", "1");
+  // Case1
+  ow_->RenderString("single_mask",
+                    "outerField(camelCase1,camelCase2,camelCase3)");
+  expected.mutable_single_mask()->add_paths("outer_field.camel_case1");
+  expected.mutable_single_mask()->add_paths("outer_field.camel_case2");
+  expected.mutable_single_mask()->add_paths("outer_field.camel_case3");
+
+  ow_->StartList("repeated_mask");
+
+  ow_->RenderString("", "a(field1,field2)");
+  google::protobuf::FieldMask* mask = expected.add_repeated_mask();
+  mask->add_paths("a.field1");
+  mask->add_paths("a.field2");
+
+  ow_->RenderString("", "a(field3)");
+  mask = expected.add_repeated_mask();
+  mask->add_paths("a.field3");
+
+  ow_->RenderString("", "a()");
+  expected.add_repeated_mask();
+
+  ow_->RenderString("", "a(,)");
+  expected.add_repeated_mask();
+
+  ow_->RenderString("", "a(field1(field2(field3)))");
+  mask = expected.add_repeated_mask();
+  mask->add_paths("a.field1.field2.field3");
+
+  ow_->RenderString("", "a(field1(field2(field3,field4),field5),field6)");
+  mask = expected.add_repeated_mask();
+  mask->add_paths("a.field1.field2.field3");
+  mask->add_paths("a.field1.field2.field4");
+  mask->add_paths("a.field1.field5");
+  mask->add_paths("a.field6");
+
+  ow_->RenderString("", "a(id,field1(id,field2(field3,field4),field5),field6)");
+  mask = expected.add_repeated_mask();
+  mask->add_paths("a.id");
+  mask->add_paths("a.field1.id");
+  mask->add_paths("a.field1.field2.field3");
+  mask->add_paths("a.field1.field2.field4");
+  mask->add_paths("a.field1.field5");
+  mask->add_paths("a.field6");
+
+  ow_->RenderString("", "a(((field3,field4)))");
+  mask = expected.add_repeated_mask();
+  mask->add_paths("a.field3");
+  mask->add_paths("a.field4");
+
+  ow_->EndList();
+  ow_->EndObject();
+
+  CheckOutput(expected);
+}
+
+TEST_P(ProtoStreamObjectWriterFieldMaskTest, MoreCloseThanOpenParentheses) {
+  EXPECT_CALL(
+      listener_,
+      InvalidValue(_,
+                   StringPiece("type.googleapis.com/google.protobuf.FieldMask"),
+                   StringPiece(
+                       "Field 'single_mask', Invalid FieldMask 'a(b,c))'. "
+                       "Cannot find matching '(' for all ')'.")));
+
+  ow_->StartObject("");
+  ow_->RenderString("id", "1");
+  ow_->RenderString("single_mask", "a(b,c))");
+  ow_->EndObject();
+}
+
+TEST_P(ProtoStreamObjectWriterFieldMaskTest, MoreOpenThanCloseParentheses) {
+  EXPECT_CALL(
+      listener_,
+      InvalidValue(
+          _, StringPiece("type.googleapis.com/google.protobuf.FieldMask"),
+          StringPiece(
+              "Field 'single_mask', Invalid FieldMask 'a(((b,c)'. Cannot "
+              "find matching ')' for all '('.")));
+
+  ow_->StartObject("");
+  ow_->RenderString("id", "1");
+  ow_->RenderString("single_mask", "a(((b,c)");
+  ow_->EndObject();
+}
+
+TEST_P(ProtoStreamObjectWriterFieldMaskTest, PathWithMapKeyShouldWork) {
+  FieldMaskTest expected;
+  expected.mutable_single_mask()->add_paths("path.to.map[\"key1\"]");
+  expected.mutable_single_mask()->add_paths(
+      "path.to.map[\"e\\\"[]][scape\\\"\"]");
+  expected.mutable_single_mask()->add_paths("path.to.map[\"key2\"]");
+
+  ow_->StartObject("");
+  ow_->RenderString("single_mask",
+                    "path.to.map[\"key1\"],path.to.map[\"e\\\"[]][scape\\\"\"],"
+                    "path.to.map[\"key2\"]");
+  ow_->EndObject();
+
+  CheckOutput(expected);
+}
+
+TEST_P(ProtoStreamObjectWriterFieldMaskTest,
+       MapKeyMustBeAtTheEndOfAPathSegment) {
+  EXPECT_CALL(
+      listener_,
+      InvalidValue(_,
+                   StringPiece("type.googleapis.com/google.protobuf.FieldMask"),
+                   StringPiece(
+                       "Field 'single_mask', Invalid FieldMask "
+                       "'path.to.map[\"key1\"]a,path.to.map[\"key2\"]'. "
+                       "Map keys should be at the end of a path segment.")));
+
+  ow_->StartObject("");
+  ow_->RenderString("single_mask",
+                    "path.to.map[\"key1\"]a,path.to.map[\"key2\"]");
+  ow_->EndObject();
+}
+
+TEST_P(ProtoStreamObjectWriterFieldMaskTest, MapKeyMustEnd) {
+  EXPECT_CALL(
+      listener_,
+      InvalidValue(_,
+                   StringPiece("type.googleapis.com/google.protobuf.FieldMask"),
+                   StringPiece(
+                       "Field 'single_mask', Invalid FieldMask "
+                       "'path.to.map[\"key1\"'. Map keys should be "
+                       "represented as [\"some_key\"].")));
+
+  ow_->StartObject("");
+  ow_->RenderString("single_mask", "path.to.map[\"key1\"");
+  ow_->EndObject();
+}
+
+TEST_P(ProtoStreamObjectWriterFieldMaskTest, MapKeyMustBeEscapedCorrectly) {
+  EXPECT_CALL(
+      listener_,
+      InvalidValue(_,
+                   StringPiece("type.googleapis.com/google.protobuf.FieldMask"),
+                   StringPiece(
+                       "Field 'single_mask', Invalid FieldMask "
+                       "'path.to.map[\"ke\"y1\"]'. Map keys should be "
+                       "represented as [\"some_key\"].")));
+
+  ow_->StartObject("");
+  ow_->RenderString("single_mask", "path.to.map[\"ke\"y1\"]");
+  ow_->EndObject();
+}
+
+TEST_P(ProtoStreamObjectWriterFieldMaskTest, MapKeyCanContainAnyChars) {
+  FieldMaskTest expected;
+  expected.mutable_single_mask()->add_paths(
+      "path.to.map[\"(),[],\\\"'!@#$%^&*123_|War孙天涌,./?><\\\\\"]");
+  expected.mutable_single_mask()->add_paths("path.to.map[\"key2\"]");
+
+  ow_->StartObject("");
+  ow_->RenderString(
+      "single_mask",
+      "path.to.map[\"(),[],\\\"'!@#$%^&*123_|War孙天涌,./?><\\\\\"],"
+      "path.to.map[\"key2\"]");
+  ow_->EndObject();
+
+  CheckOutput(expected);
+}
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/internal/snake2camel_objectwriter.h b/src/google/protobuf/util/internal/snake2camel_objectwriter.h
new file mode 100644
index 0000000..1a32bc5
--- /dev/null
+++ b/src/google/protobuf/util/internal/snake2camel_objectwriter.h
@@ -0,0 +1,187 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_PROTOBUF_UTIL_CONVERTER_SNAKE2CAMEL_OBJECTWRITER_H__
+#define GOOGLE_PROTOBUF_UTIL_CONVERTER_SNAKE2CAMEL_OBJECTWRITER_H__
+
+#include <string>
+
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/stubs/strutil.h>
+#include <google/protobuf/stubs/stringpiece.h>
+#include <google/protobuf/util/internal/object_writer.h>
+#include <google/protobuf/util/internal/utility.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+
+// Snake2CamelObjectWriter is an ObjectWriter than translates each field name
+// from snake_case to camelCase. Typical usage is:
+//     ProtoStreamObjectSource psos(...);
+//     JsonObjectWriter jow(...);
+//     Snake2CamelObjectWriter snake_to_camel(&jow);
+//     psos.writeTo(&snake_to_camel);
+class Snake2CamelObjectWriter : public ObjectWriter {
+ public:
+  explicit Snake2CamelObjectWriter(ObjectWriter* ow)
+      : ow_(ow), normalize_case_(true) {}
+  virtual ~Snake2CamelObjectWriter() {}
+
+  // ObjectWriter methods.
+  virtual Snake2CamelObjectWriter* StartObject(StringPiece name) {
+    ow_->StartObject(ShouldNormalizeCase(name)
+                         ? StringPiece(StringPiece(ToCamelCase(name)))
+                         : name);
+    return this;
+  }
+
+  virtual Snake2CamelObjectWriter* EndObject() {
+    ow_->EndObject();
+    return this;
+  }
+
+  virtual Snake2CamelObjectWriter* StartList(StringPiece name) {
+    ow_->StartList(ShouldNormalizeCase(name) ? StringPiece(ToCamelCase(name))
+                                             : name);
+    return this;
+  }
+
+  virtual Snake2CamelObjectWriter* EndList() {
+    ow_->EndList();
+    return this;
+  }
+
+  virtual Snake2CamelObjectWriter* RenderBool(StringPiece name, bool value) {
+    ow_->RenderBool(
+        ShouldNormalizeCase(name) ? StringPiece(ToCamelCase(name)) : name,
+        value);
+    return this;
+  }
+
+  virtual Snake2CamelObjectWriter* RenderInt32(StringPiece name, int32 value) {
+    ow_->RenderInt32(
+        ShouldNormalizeCase(name) ? StringPiece(ToCamelCase(name)) : name,
+        value);
+    return this;
+  }
+
+  virtual Snake2CamelObjectWriter* RenderUint32(StringPiece name,
+                                                uint32 value) {
+    ow_->RenderUint32(
+        ShouldNormalizeCase(name) ? StringPiece(ToCamelCase(name)) : name,
+        value);
+    return this;
+  }
+
+  virtual Snake2CamelObjectWriter* RenderInt64(StringPiece name, int64 value) {
+    ow_->RenderInt64(
+        ShouldNormalizeCase(name) ? StringPiece(ToCamelCase(name)) : name,
+        value);
+    return this;
+  }
+
+  virtual Snake2CamelObjectWriter* RenderUint64(StringPiece name,
+                                                uint64 value) {
+    ow_->RenderUint64(
+        ShouldNormalizeCase(name) ? StringPiece(ToCamelCase(name)) : name,
+        value);
+    return this;
+  }
+
+  virtual Snake2CamelObjectWriter* RenderDouble(StringPiece name,
+                                                double value) {
+    ow_->RenderDouble(
+        ShouldNormalizeCase(name) ? StringPiece(ToCamelCase(name)) : name,
+        value);
+    return this;
+  }
+
+  virtual Snake2CamelObjectWriter* RenderFloat(StringPiece name, float value) {
+    ow_->RenderFloat(
+        ShouldNormalizeCase(name) ? StringPiece(ToCamelCase(name)) : name,
+        value);
+    return this;
+  }
+
+  virtual Snake2CamelObjectWriter* RenderString(StringPiece name,
+                                                StringPiece value) {
+    ow_->RenderString(
+        ShouldNormalizeCase(name) ? StringPiece(ToCamelCase(name)) : name,
+        value);
+    return this;
+  }
+
+  virtual Snake2CamelObjectWriter* RenderBytes(StringPiece name,
+                                               StringPiece value) {
+    ow_->RenderBytes(
+        ShouldNormalizeCase(name) ? StringPiece(ToCamelCase(name)) : name,
+        value);
+    return this;
+  }
+
+  virtual Snake2CamelObjectWriter* RenderNull(StringPiece name) {
+    ow_->RenderNull(ShouldNormalizeCase(name) ? StringPiece(ToCamelCase(name))
+                                              : name);
+    return this;
+  }
+
+  virtual Snake2CamelObjectWriter* DisableCaseNormalizationForNextKey() {
+    normalize_case_ = false;
+    return this;
+  }
+
+ private:
+  ObjectWriter* ow_;
+  bool normalize_case_;
+
+  bool ShouldNormalizeCase(StringPiece name) {
+    if (normalize_case_) {
+      return !IsCamel(name);
+    } else {
+      normalize_case_ = true;
+      return false;
+    }
+  }
+
+  bool IsCamel(StringPiece name) {
+    return name.empty() || (ascii_islower(name[0]) && !name.contains("_"));
+  }
+
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(Snake2CamelObjectWriter);
+};
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_CONVERTER_SNAKE2CAMEL_OBJECTWRITER_H__
diff --git a/src/google/protobuf/util/internal/snake2camel_objectwriter_test.cc b/src/google/protobuf/util/internal/snake2camel_objectwriter_test.cc
new file mode 100644
index 0000000..67388c3
--- /dev/null
+++ b/src/google/protobuf/util/internal/snake2camel_objectwriter_test.cc
@@ -0,0 +1,311 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/util/internal/snake2camel_objectwriter.h>
+#include <google/protobuf/util/internal/expecting_objectwriter.h>
+#include <gtest/gtest.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+
+class Snake2CamelObjectWriterTest : public ::testing::Test {
+ protected:
+  Snake2CamelObjectWriterTest() : mock_(), expects_(&mock_), testing_(&mock_) {}
+  virtual ~Snake2CamelObjectWriterTest() {}
+
+  MockObjectWriter mock_;
+  ExpectingObjectWriter expects_;
+  Snake2CamelObjectWriter testing_;
+};
+
+TEST_F(Snake2CamelObjectWriterTest, Empty) {
+  // Set expectation
+  expects_.StartObject("")->EndObject();
+
+  // Actual testing
+  testing_.StartObject("")->EndObject();
+}
+
+TEST_F(Snake2CamelObjectWriterTest, UnderscoresOnly) {
+  // Set expectation
+  expects_.StartObject("")
+      ->RenderInt32("", 1)
+      ->RenderInt32("", 2)
+      ->RenderInt32("", 3)
+      ->RenderInt32("", 4)
+      ->RenderInt32("", 5)
+      ->EndObject();
+
+  // Actual testing
+  testing_.StartObject("")
+      ->RenderInt32("_", 1)
+      ->RenderInt32("__", 2)
+      ->RenderInt32("___", 3)
+      ->RenderInt32("____", 4)
+      ->RenderInt32("_____", 5)
+      ->EndObject();
+}
+
+TEST_F(Snake2CamelObjectWriterTest, LowercaseOnly) {
+  // Set expectation
+  expects_.StartObject("")
+      ->RenderString("key", "value")
+      ->RenderString("abracadabra", "magic")
+      ->EndObject();
+
+  // Actual testing
+  testing_.StartObject("")
+      ->RenderString("key", "value")
+      ->RenderString("abracadabra", "magic")
+      ->EndObject();
+}
+
+TEST_F(Snake2CamelObjectWriterTest, UppercaseOnly) {
+  // Set expectation
+  expects_.StartObject("")
+      ->RenderString("key", "VALUE")
+      ->RenderString("abracadabra", "MAGIC")
+      ->EndObject();
+
+  // Actual testing
+  testing_.StartObject("")
+      ->RenderString("KEY", "VALUE")
+      ->RenderString("ABRACADABRA", "MAGIC")
+      ->EndObject();
+}
+
+TEST_F(Snake2CamelObjectWriterTest, CamelCase) {
+  // Set expectation
+  expects_.StartObject("")
+      ->RenderString("camelCase", "camelCase")
+      ->RenderString("theQuickBrownFoxJumpsOverTheLazyDog",
+                     "theQuickBrownFoxJumpsOverTheLazyDog")
+      ->EndObject();
+
+  // Actual testing
+  testing_.StartObject("")
+      ->RenderString("camelCase", "camelCase")
+      ->RenderString("theQuickBrownFoxJumpsOverTheLazyDog",
+                     "theQuickBrownFoxJumpsOverTheLazyDog")
+      ->EndObject();
+}
+
+TEST_F(Snake2CamelObjectWriterTest, FirstCapCamelCase) {
+  // Sets expectation
+  expects_.StartObject("camel")
+      ->RenderString("camelCase", "CamelCase")
+      ->RenderString("theQuickBrownFoxJumpsOverTheLazyDog",
+                     "TheQuickBrownFoxJumpsOverTheLazyDog")
+      ->EndObject();
+
+  // Actual testing
+  testing_.StartObject("Camel")
+      ->RenderString("CamelCase", "CamelCase")
+      ->RenderString("TheQuickBrownFoxJumpsOverTheLazyDog",
+                     "TheQuickBrownFoxJumpsOverTheLazyDog")
+      ->EndObject();
+}
+
+TEST_F(Snake2CamelObjectWriterTest, LastCapCamelCase) {
+  // Sets expectation
+  expects_.StartObject("lastCapCamelCasE")->EndObject();
+
+  // Actual testing
+  testing_.StartObject("lastCapCamelCasE")->EndObject();
+}
+
+TEST_F(Snake2CamelObjectWriterTest, MixedCapCamelCase) {
+  // Sets expectation
+  expects_.StartObject("googleIsTheBest")
+      ->RenderFloat("iLoveGOOGLE", 1.61803f)
+      ->RenderFloat("goGoogleGO", 2.71828f)
+      ->RenderFloat("gBikeISCool", 3.14159f)
+      ->EndObject();
+
+  // Actual testing
+  testing_.StartObject("GOOGLEIsTheBest")
+      ->RenderFloat("ILoveGOOGLE", 1.61803f)
+      ->RenderFloat("GOGoogleGO", 2.71828f)
+      ->RenderFloat("GBikeISCool", 3.14159f)
+      ->EndObject();
+}
+
+TEST_F(Snake2CamelObjectWriterTest, MixedCase) {
+  // Sets expectation
+  expects_.StartObject("snakeCaseCamelCase")
+      ->RenderBool("camelCaseSnakeCase", false)
+      ->RenderBool("mixedCamelAndUnderScores", false)
+      ->RenderBool("goGOOGLEGo", true)
+      ->EndObject();
+
+  // Actual testing
+  testing_.StartObject("snake_case_camelCase")
+      ->RenderBool("camelCase_snake_case", false)
+      ->RenderBool("MixedCamel_And_UnderScores", false)
+      ->RenderBool("Go_GOOGLEGo", true)
+      ->EndObject();
+}
+
+TEST_F(Snake2CamelObjectWriterTest, SnakeCase) {
+  // Sets expectation
+  expects_.StartObject("")
+      ->RenderString("snakeCase", "snake_case")
+      ->RenderString("theQuickBrownFoxJumpsOverTheLazyDog",
+                     "the_quick_brown_fox_jumps_over_the_lazy_dog")
+      ->EndObject();
+
+  // Actual testing
+  testing_.StartObject("")
+      ->RenderString("snake_case", "snake_case")
+      ->RenderString("the_quick_brown_fox_jumps_over_the_lazy_dog",
+                     "the_quick_brown_fox_jumps_over_the_lazy_dog")
+      ->EndObject();
+}
+
+TEST_F(Snake2CamelObjectWriterTest, FirstCapSnakeCase) {
+  // Sets expectation
+  expects_.StartObject("firstCapSnakeCase")
+      ->RenderBool("helloWorld", true)
+      ->EndObject();
+
+  // Actual testing
+  testing_.StartObject("First_Cap_Snake_Case")
+      ->RenderBool("Hello_World", true)
+      ->EndObject();
+}
+
+TEST_F(Snake2CamelObjectWriterTest, AllCapSnakeCase) {
+  // Sets expectation
+  expects_.StartObject("allCAPSNAKECASE")
+      ->RenderDouble("nyseGOOGL", 600.0L)
+      ->RenderDouble("aBCDE", 1.0L)
+      ->RenderDouble("klMNOP", 2.0L)
+      ->RenderDouble("abcIJKPQRXYZ", 3.0L)
+      ->EndObject();
+
+  // Actual testing
+  testing_.StartObject("ALL_CAP_SNAKE_CASE")
+      ->RenderDouble("NYSE_GOOGL", 600.0L)
+      ->RenderDouble("A_B_C_D_E", 1.0L)
+      ->RenderDouble("KL_MN_OP", 2.0L)
+      ->RenderDouble("ABC_IJK_PQR_XYZ", 3.0L)
+      ->EndObject();
+}
+
+TEST_F(Snake2CamelObjectWriterTest, RepeatedUnderScoreSnakeCase) {
+  // Sets expectation
+  expects_.StartObject("")
+      ->RenderInt32("doubleUnderscoreSnakeCase", 2)
+      ->RenderInt32("tripleUnderscoreFirstCap", 3)
+      ->RenderInt32("quadrupleUNDERSCOREALLCAP", 4)
+      ->EndObject();
+
+  // Actual testing
+  testing_.StartObject("")
+      ->RenderInt32("double__underscore__snake__case", 2)
+      ->RenderInt32("Triple___Underscore___First___Cap", 3)
+      ->RenderInt32("QUADRUPLE____UNDERSCORE____ALL____CAP", 4)
+      ->EndObject();
+}
+
+TEST_F(Snake2CamelObjectWriterTest, LeadingUnderscoreSnakeCase) {
+  // Sets expectation
+  expects_.StartObject("leadingUnderscoreSnakeCase")
+      ->RenderUint32("leadingDoubleUnderscore", 2)
+      ->RenderUint32("leadingTripleUnderscoreFirstCap", 3)
+      ->RenderUint32("leadingQUADRUPLEUNDERSCOREALLCAP", 4)
+      ->EndObject();
+
+  // Actual testing
+  testing_.StartObject("_leading_underscore_snake_case")
+      ->RenderUint32("__leading_double_underscore", 2)
+      ->RenderUint32("___Leading_Triple_Underscore_First_Cap", 3)
+      ->RenderUint32("____LEADING_QUADRUPLE_UNDERSCORE_ALL_CAP", 4)
+      ->EndObject();
+}
+
+TEST_F(Snake2CamelObjectWriterTest, TrailingUnderscoreSnakeCase) {
+  // Sets expectation
+  expects_.StartObject("trailingUnderscoreSnakeCase")
+      ->RenderInt64("trailingDoubleUnderscore", 2L)
+      ->RenderInt64("trailingTripleUnderscoreFirstCap", 3L)
+      ->RenderInt64("trailingQUADRUPLEUNDERSCOREALLCAP", 4L)
+      ->EndObject();
+
+  // Actual testing
+  testing_.StartObject("trailing_underscore_snake_case")
+      ->RenderInt64("trailing_double_underscore__", 2L)
+      ->RenderInt64("Trailing_Triple_Underscore_First_Cap___", 3L)
+      ->RenderInt64("TRAILING_QUADRUPLE_UNDERSCORE_ALL_CAP____", 4L)
+      ->EndObject();
+}
+
+TEST_F(Snake2CamelObjectWriterTest, EnclosingUnderscoreSnakeCase) {
+  // Sets expectation
+  expects_.StartObject("enclosingUnderscoreSnakeCase")
+      ->RenderUint64("enclosingDoubleUnderscore", 2L)
+      ->RenderUint64("enclosingTripleUnderscoreFirstCap", 3L)
+      ->RenderUint64("enclosingQUADRUPLEUNDERSCOREALLCAP", 4L)
+      ->EndObject();
+
+  // Actual testing
+  testing_.StartObject("_enclosing_underscore_snake_case_")
+      ->RenderUint64("__enclosing_double_underscore__", 2L)
+      ->RenderUint64("___Enclosing_Triple_Underscore_First_Cap___", 3L)
+      ->RenderUint64("____ENCLOSING_QUADRUPLE_UNDERSCORE_ALL_CAP____", 4L)
+      ->EndObject();
+}
+
+TEST_F(Snake2CamelObjectWriterTest, DisableCaseNormalizationOnlyDisablesFirst) {
+  // Sets expectation
+  expects_.StartObject("")
+      ->RenderString("snakeCase", "snake_case")
+      ->RenderString(
+            "the_quick_brown_fox_jumps_over_the_lazy_dog",  // case retained
+            "the_quick_brown_fox_jumps_over_the_lazy_dog")
+      ->RenderBool("theSlowFox", true)  // disable case not in effect
+      ->EndObject();
+
+  // Actual testing
+  testing_.StartObject("")
+      ->RenderString("snake_case", "snake_case")
+      ->DisableCaseNormalizationForNextKey()
+      ->RenderString("the_quick_brown_fox_jumps_over_the_lazy_dog",
+                     "the_quick_brown_fox_jumps_over_the_lazy_dog")
+      ->RenderBool("the_slow_fox", true)
+      ->EndObject();
+}
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/internal/structured_objectwriter.h b/src/google/protobuf/util/internal/structured_objectwriter.h
new file mode 100644
index 0000000..3f065d6
--- /dev/null
+++ b/src/google/protobuf/util/internal/structured_objectwriter.h
@@ -0,0 +1,118 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_PROTOBUF_UTIL_CONVERTER_STRUCTURED_OBJECTWRITER_H__
+#define GOOGLE_PROTOBUF_UTIL_CONVERTER_STRUCTURED_OBJECTWRITER_H__
+
+#include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
+
+#include <google/protobuf/stubs/casts.h>
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/util/internal/object_writer.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+
+// An StructuredObjectWriter is an ObjectWriter for writing
+// tree-structured data in a stream of events representing objects
+// and collections. Implementation of this interface can be used to
+// write an object stream to an in-memory structure, protobufs,
+// JSON, XML, or any other output format desired. The ObjectSource
+// interface is typically used as the source of an object stream.
+//
+// See JsonObjectWriter for a sample implementation of
+// StructuredObjectWriter and its use.
+//
+// Derived classes could be thread-unsafe.
+class LIBPROTOBUF_EXPORT StructuredObjectWriter : public ObjectWriter {
+ public:
+  virtual ~StructuredObjectWriter() {}
+
+ protected:
+  // A base element class for subclasses to extend, makes tracking state easier.
+  //
+  // StructuredObjectWriter behaves as a visitor. BaseElement represents a node
+  // in the input tree. Implementation of StructuredObjectWriter should also
+  // extend BaseElement to keep track of the location in the input tree.
+  class LIBPROTOBUF_EXPORT BaseElement {
+   public:
+    // Takes ownership of the parent Element.
+    explicit BaseElement(BaseElement* parent)
+        : parent_(parent), level_(parent == NULL ? 0 : parent->level() + 1) {}
+    virtual ~BaseElement() {}
+
+    // Releases ownership of the parent and returns a pointer to it.
+    template <typename ElementType>
+    ElementType* pop() {
+      return down_cast<ElementType*>(parent_.release());
+    }
+
+    // Returns true if this element is the root.
+    bool is_root() const { return parent_ == NULL; }
+
+    // Returns the number of hops from this element to the root element.
+    int level() const { return level_; }
+
+   protected:
+    // Returns pointer to parent element without releasing ownership.
+    virtual BaseElement* parent() const { return parent_.get(); }
+
+   private:
+    // Pointer to the parent Element.
+    google::protobuf::scoped_ptr<BaseElement> parent_;
+
+    // Number of hops to the root Element.
+    // The root Element has NULL parent_ and a level_ of 0.
+    const int level_;
+
+    GOOGLE_DISALLOW_IMPLICIT_CONSTRUCTORS(BaseElement);
+  };
+
+  StructuredObjectWriter() {}
+
+  // Returns the current element. Used for indentation and name overrides.
+  virtual BaseElement* element() = 0;
+
+ private:
+  // Do not add any data members to this class.
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(StructuredObjectWriter);
+};
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_CONVERTER_STRUCTURED_OBJECTWRITER_H__
diff --git a/src/google/protobuf/util/internal/testdata/anys.proto b/src/google/protobuf/util/internal/testdata/anys.proto
new file mode 100644
index 0000000..18c59cb
--- /dev/null
+++ b/src/google/protobuf/util/internal/testdata/anys.proto
@@ -0,0 +1,53 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Proto to test Proto3 Any serialization.
+syntax = "proto3";
+
+package google.protobuf.testing.anys;
+option java_package = "com.google.protobuf.testing.anys";
+
+import "google/protobuf/any.proto";
+
+message AnyIn {
+  string something = 1;
+}
+
+message AnyOut {
+  google.protobuf.Any any = 1;
+}
+
+message AnyM {
+  string foo = 1;
+}
+
+service TestService {
+  rpc Call(AnyIn) returns (AnyOut);
+}
diff --git a/src/google/protobuf/util/internal/testdata/books.proto b/src/google/protobuf/util/internal/testdata/books.proto
new file mode 100644
index 0000000..6e2f109
--- /dev/null
+++ b/src/google/protobuf/util/internal/testdata/books.proto
@@ -0,0 +1,171 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Author: sven@google.com (Sven Mawson)
+//
+// Sample protos for testing.
+syntax = "proto2";
+
+package google.protobuf.testing;
+
+// A book
+message Book {
+  optional string title = 1;
+  optional Author author = 2;
+  optional uint32 length = 3;
+  optional int64 published = 4;
+  optional bytes content = 5;
+
+  optional group Data = 6 {
+    optional uint32 year = 7;
+    optional string copyright = 8;
+  }
+
+  message Label {
+    optional string key = 1;
+    optional string value = 2;
+  }
+
+  optional Publisher publisher = 9;
+  repeated Label labels = 10;
+
+  extensions 200 to 499;
+}
+
+// A publisher of a book, tests required fields.
+message Publisher {
+  required string name = 1;
+}
+
+// An author of a book
+message Author {
+  optional uint64 id = 1;
+  optional string name = 2;
+  repeated string pseudonym = 3;
+  optional bool alive = 4;
+  repeated Author friend = 5;
+}
+
+// For testing resiliency of our protostream parser.
+// Field numbers of Author are reused for something else.
+message BadAuthor {
+  optional string id = 1;  // non-length-delimited to length-delimited.
+  repeated uint64 name = 2;  // string to repeated (both length-delimited).
+  optional string pseudonym = 3;  // Repeated to optional.
+  repeated bool alive = 4 [packed=true];  // Optional to repeated.
+}
+
+// All primitive types
+message Primitive {
+  // 32 bit numbers:
+  optional fixed32 fix32 = 1;
+  optional uint32 u32 = 2;
+  optional int32 i32 = 3;
+  optional sfixed32 sf32 = 4;
+  optional sint32 s32 = 5;
+
+  // 64 bit numbers:
+  optional fixed64 fix64 = 6;
+  optional uint64 u64 = 7;
+  optional int64 i64 = 8;
+  optional sfixed64 sf64 = 9;
+  optional sint64 s64 = 10;
+
+  // The other stuff.
+  optional string str = 11;
+  optional bytes bytes = 12;
+  optional float float = 13;
+  optional double double = 14;
+  optional bool bool = 15;
+
+  // repeated 32 bit numbers:
+  repeated fixed32 rep_fix32 = 16;
+  repeated uint32 rep_u32 = 17;
+  repeated int32 rep_i32 = 18;
+  repeated sfixed32 rep_sf32 = 19;
+  repeated sint32 rep_s32 = 20;
+
+  // repeated 64 bit numbers:
+  repeated fixed64 rep_fix64 = 21;
+  repeated uint64 rep_u64 = 22;
+  repeated int64 rep_i64 = 23;
+  repeated sfixed64 rep_sf64 = 24;
+  repeated sint64 rep_s64 = 25;
+
+  // repeated other stuff:
+  repeated string rep_str = 26;
+  repeated bytes rep_bytes = 27;
+  repeated float rep_float = 28;
+  repeated double rep_double = 29;
+  repeated bool rep_bool = 30;
+}
+
+// Test packed versions of all repeated primitives.
+// The field numbers should match their non-packed version in Primitive message.
+message PackedPrimitive {
+  // repeated 32 bit numbers:
+  repeated fixed32 rep_fix32 = 16 [packed=true];
+  repeated uint32 rep_u32 = 17 [packed=true];
+  repeated int32 rep_i32 = 18 [packed=true];
+  repeated sfixed32 rep_sf32 = 19 [packed=true];
+  repeated sint32 rep_s32 = 20 [packed=true];
+
+  // repeated 64 bit numbers:
+  repeated fixed64 rep_fix64 = 21 [packed=true];
+  repeated uint64 rep_u64 = 22 [packed=true];
+  repeated int64 rep_i64 = 23 [packed=true];
+  repeated sfixed64 rep_sf64 = 24 [packed=true];
+  repeated sint64 rep_s64 = 25 [packed=true];
+
+  // repeated other stuff:
+  repeated float rep_float = 28 [packed=true];
+  repeated double rep_double = 29 [packed=true];
+  repeated bool rep_bool = 30 [packed=true];
+}
+
+// Test extensions.
+extend Book {
+  repeated Author more_author = 201;
+}
+
+// Test nested extensions.
+message NestedBook {
+  extend Book {
+    optional NestedBook another_book = 301;
+  }
+  // Recurse
+  optional Book book = 1;
+}
+
+// For testing resiliency of our protostream parser.
+// Field number of NestedBook is reused for something else.
+message BadNestedBook {
+  repeated uint32 book = 1 [packed=true];  // Packed to optional message.
+}
diff --git a/src/google/protobuf/util/internal/testdata/default_value.proto b/src/google/protobuf/util/internal/testdata/default_value.proto
new file mode 100644
index 0000000..ecfc811
--- /dev/null
+++ b/src/google/protobuf/util/internal/testdata/default_value.proto
@@ -0,0 +1,162 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+syntax = "proto3";
+
+package google.protobuf.testing;
+
+import "google/protobuf/any.proto";
+import "google/protobuf/struct.proto";
+import "google/protobuf/wrappers.proto";
+
+message DefaultValueTestCases {
+  DoubleMessage empty_double = 1;
+  DoubleMessage double_with_default_value = 2;
+  DoubleMessage double_with_nondefault_value = 3;
+  DoubleMessage repeated_double = 4;
+  DoubleMessage nested_message = 5;
+  DoubleMessage repeated_nested_message = 6;
+  StructMessage empty_struct = 201;
+  StructMessage empty_struct2 = 202;
+  StructMessage struct_with_null_value = 203;
+  StructMessage struct_with_values = 204;
+  StructMessage struct_with_nested_struct = 205;
+  StructMessage struct_with_nested_list = 206;
+  StructMessage struct_with_list_of_nulls = 207;
+  StructMessage struct_with_list_of_lists = 208;
+  StructMessage struct_with_list_of_structs = 209;
+  google.protobuf.Struct top_level_struct = 210;
+  ValueMessage value_wrapper_simple = 212;
+  ValueMessage value_wrapper_with_struct = 213;
+  ValueMessage value_wrapper_with_list = 214;
+  ListValueMessage list_value_wrapper = 215;
+  google.protobuf.Value top_level_value_simple = 216;
+  google.protobuf.Value top_level_value_with_struct = 217;
+  google.protobuf.Value top_level_value_with_list = 218;
+  google.protobuf.ListValue top_level_listvalue = 219;
+  AnyMessage empty_any = 301;
+  AnyMessage type_only_any = 302;
+  AnyMessage recursive_any = 303;
+  AnyMessage any_with_message_value = 304;
+  AnyMessage any_with_nested_message = 305;
+  AnyMessage any_with_message_containing_map = 306;
+  AnyMessage any_with_message_containing_struct = 307;
+  google.protobuf.Any top_level_any = 308;
+  StringtoIntMap empty_map = 401;
+  StringtoIntMap string_to_int = 402;
+  IntToStringMap int_to_string = 403;
+  MixedMap mixed1 = 404;
+  MixedMap2 mixed2 = 405;
+  MessageMap map_of_objects = 406;
+  DoubleValueMessage double_value = 501;
+  DoubleValueMessage double_value_default = 502;
+}
+
+message DoubleMessage {
+  double double_value = 1;
+  repeated double repeated_double = 2;
+  DoubleMessage nested_message = 3;
+  repeated DoubleMessage repeated_nested_message = 4;
+  google.protobuf.DoubleValue double_wrapper = 100;
+}
+
+message StructMessage {
+  google.protobuf.Struct struct = 1;
+}
+
+message ValueMessage {
+  google.protobuf.Value value = 1;
+}
+
+message ListValueMessage {
+  google.protobuf.ListValue shopping_list = 1;
+}
+message RequestMessage {
+  string content = 1;
+}
+
+// A test service.
+service DefaultValueTestService {
+  // A test method.
+  rpc Call(RequestMessage) returns (DefaultValueTestCases);
+}
+
+message AnyMessage {
+  google.protobuf.Any any = 1;
+  AnyData data = 2;
+}
+
+message AnyData {
+  int32 attr = 1;
+  string str = 2;
+  repeated string msgs = 3;
+  AnyData nested_data = 4;
+  map<string, string> map_data = 7;
+  google.protobuf.Struct struct_data = 8;
+  repeated AnyData repeated_data = 9;
+}
+
+message StringtoIntMap {
+  map<string, int32> map = 1;
+}
+
+message IntToStringMap {
+  map<int32, string> map = 1;
+}
+
+message MixedMap {
+  string msg = 1;
+  map<string, float> map = 2;
+  int32 int_value = 3;
+}
+
+message MixedMap2 {
+  enum E {
+    E0 = 0;
+    E1 = 1;
+    E2 = 2;
+    E3 = 3;
+  }
+  map<int32, bool> map = 1;
+  E ee = 2;
+  string msg = 4;
+}
+
+message MessageMap {
+  message M {
+    int32 inner_int = 1;
+    string inner_text = 2;
+  }
+  map<string, M> map = 1;
+}
+
+message DoubleValueMessage {
+  google.protobuf.DoubleValue double = 1;
+}
diff --git a/src/google/protobuf/util/internal/testdata/default_value_test.proto b/src/google/protobuf/util/internal/testdata/default_value_test.proto
new file mode 100644
index 0000000..21b85e6
--- /dev/null
+++ b/src/google/protobuf/util/internal/testdata/default_value_test.proto
@@ -0,0 +1,46 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+syntax = "proto3";
+
+package google.protobuf.testing;
+
+message DefaultValueTest {
+  double double_value = 1;
+  repeated double repeated_double = 2;
+  float float_value = 3;
+  int64 int64_value = 5;
+  uint64 uint64_value = 7;
+  int32 int32_value = 9;
+  uint32 uint32_value = 11;
+  bool bool_value = 13;
+  string string_value = 15;
+  bytes bytes_value = 17 [ctype = CORD];
+}
diff --git a/src/google/protobuf/util/internal/testdata/field_mask.proto b/src/google/protobuf/util/internal/testdata/field_mask.proto
new file mode 100644
index 0000000..e8b2bc5
--- /dev/null
+++ b/src/google/protobuf/util/internal/testdata/field_mask.proto
@@ -0,0 +1,71 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+syntax = "proto3";
+
+package google.protobuf.testing;
+
+import "google/protobuf/field_mask.proto";
+
+message NestedFieldMask {
+  string data = 1;
+  google.protobuf.FieldMask single_mask = 2;
+  repeated google.protobuf.FieldMask repeated_mask = 3;
+}
+
+message FieldMaskTest {
+  string id = 1;
+  google.protobuf.FieldMask single_mask = 2;
+  repeated google.protobuf.FieldMask repeated_mask = 3;
+  repeated NestedFieldMask nested_mask = 4;
+}
+
+message FieldMaskTestCases {
+  FieldMaskWrapper single_mask = 1;
+  FieldMaskWrapper multiple_mask = 2;
+  FieldMaskWrapper snake_camel = 3;
+  FieldMaskWrapper empty_field = 4;
+  FieldMaskWrapper apiary_format1 = 5;
+  FieldMaskWrapper apiary_format2 = 6;
+  FieldMaskWrapper apiary_format3 = 7;
+  FieldMaskWrapper map_key1 = 8;
+  FieldMaskWrapper map_key2 = 9;
+  FieldMaskWrapper map_key3 = 10;
+  FieldMaskWrapper map_key4 = 11;
+  FieldMaskWrapper map_key5 = 12;
+}
+
+message FieldMaskWrapper {
+  google.protobuf.FieldMask mask = 1;
+}
+
+service FieldMaskTestService {
+  rpc Call(FieldMaskTestCases) returns (FieldMaskTestCases);
+}
diff --git a/src/google/protobuf/util/internal/testdata/maps.proto b/src/google/protobuf/util/internal/testdata/maps.proto
new file mode 100644
index 0000000..7fb42a2
--- /dev/null
+++ b/src/google/protobuf/util/internal/testdata/maps.proto
@@ -0,0 +1,57 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Proto to test proto3 maps.
+syntax = "proto3";
+
+package google.protobuf.testing.maps;
+option java_package = "com.google.protobuf.testing.maps";
+
+message MapIn {
+  string other = 1;
+  repeated string things = 2;
+  map<string, string> map_input = 3;
+}
+
+message MapOut {
+  map<string, MapM> map1 = 1;
+  map<string, MapOut> map2 = 2;
+  map<int32, string> map3 = 3;
+  string bar = 4;
+}
+
+message MapM {
+  string foo = 1;
+}
+
+service TestService {
+  rpc Call1(MapIn) returns (MapOut);
+  rpc Call2(MapIn) returns (MapOut);
+}
diff --git a/src/google/protobuf/util/internal/testdata/struct.proto b/src/google/protobuf/util/internal/testdata/struct.proto
new file mode 100644
index 0000000..c15aba0
--- /dev/null
+++ b/src/google/protobuf/util/internal/testdata/struct.proto
@@ -0,0 +1,45 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Proto to test proto3 struct.
+syntax = "proto3";
+
+package google.protobuf.testing.structs;
+option java_package = "com.google.protobuf.testing.structs";
+
+import "google/protobuf/struct.proto";
+
+message StructType {
+  google.protobuf.Struct object = 1;
+}
+
+service TestService {
+  rpc Call(StructType) returns (StructType);
+}
diff --git a/src/google/protobuf/util/internal/testdata/timestamp_duration.proto b/src/google/protobuf/util/internal/testdata/timestamp_duration.proto
new file mode 100644
index 0000000..56351f1
--- /dev/null
+++ b/src/google/protobuf/util/internal/testdata/timestamp_duration.proto
@@ -0,0 +1,47 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Proto to test proto3 Timestamp and Duration.
+syntax = "proto3";
+
+package google.protobuf.testing.timestampduration;
+option java_package = "com.google.protobuf.testing.timestampduration";
+
+import "google/protobuf/timestamp.proto";
+import "google/protobuf/duration.proto";
+
+message TimestampDuration {
+  google.protobuf.Timestamp ts = 1;
+  google.protobuf.Duration dur = 2;
+}
+
+service TestService {
+  rpc Call(TimestampDuration) returns (TimestampDuration);
+}
diff --git a/src/google/protobuf/util/internal/testdata/wrappers.proto b/src/google/protobuf/util/internal/testdata/wrappers.proto
new file mode 100644
index 0000000..eabc99f
--- /dev/null
+++ b/src/google/protobuf/util/internal/testdata/wrappers.proto
@@ -0,0 +1,100 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+syntax = "proto3";
+
+package google.protobuf.testing;
+
+import "google/protobuf/wrappers.proto";
+
+// Top-level test cases proto used by MarshallingTest. See description
+// at the top of the class MarshallingTest for details on how to write
+// test cases.
+message WrappersTestCases {
+  DoubleWrapper double_wrapper = 1;
+  FloatWrapper float_wrapper = 2;
+  Int64Wrapper int64_wrapper = 3;
+  UInt64Wrapper uint64_wrapper = 4;
+  Int32Wrapper int32_wrapper = 5;
+  UInt32Wrapper uint32_wrapper = 6;
+  BoolWrapper bool_wrapper = 7;
+  StringWrapper string_wrapper = 8;
+  BytesWrapper bytes_wrapper = 9;
+
+  DoubleWrapper double_wrapper_default = 10;
+  FloatWrapper float_wrapper_default = 11;
+  Int64Wrapper int64_wrapper_default = 12;
+  UInt64Wrapper uint64_wrapper_default = 13;
+  Int32Wrapper int32_wrapper_default = 14;
+  UInt32Wrapper uint32_wrapper_default = 15;
+  BoolWrapper bool_wrapper_default = 16;
+  StringWrapper string_wrapper_default = 17;
+  BytesWrapper bytes_wrapper_default = 18;
+}
+
+message DoubleWrapper {
+  google.protobuf.DoubleValue double = 1;
+}
+
+message FloatWrapper {
+  google.protobuf.FloatValue float = 1;
+}
+
+message Int64Wrapper {
+  google.protobuf.Int64Value int64 = 1;
+}
+
+message UInt64Wrapper {
+  google.protobuf.UInt64Value uint64 = 1;
+}
+
+message Int32Wrapper {
+  google.protobuf.Int32Value int32 = 1;
+}
+
+message UInt32Wrapper {
+  google.protobuf.UInt32Value uint32 = 1;
+}
+
+message BoolWrapper {
+  google.protobuf.BoolValue bool = 1;
+}
+
+message StringWrapper {
+  google.protobuf.StringValue string = 1;
+}
+
+message BytesWrapper {
+  google.protobuf.BytesValue bytes = 1;
+}
+
+service WrappersTestService {
+  rpc Call(WrappersTestCases) returns (WrappersTestCases);
+}
diff --git a/src/google/protobuf/util/internal/type_info.cc b/src/google/protobuf/util/internal/type_info.cc
new file mode 100644
index 0000000..6392e18
--- /dev/null
+++ b/src/google/protobuf/util/internal/type_info.cc
@@ -0,0 +1,171 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/util/internal/type_info.h>
+
+#include <map>
+#include <set>
+
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/type.pb.h>
+#include <google/protobuf/stubs/stringpiece.h>
+#include <google/protobuf/stubs/map_util.h>
+#include <google/protobuf/stubs/status.h>
+#include <google/protobuf/stubs/statusor.h>
+#include <google/protobuf/util/internal/utility.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+
+namespace {
+
+// A TypeInfo that looks up information provided by a TypeResolver.
+class TypeInfoForTypeResolver : public TypeInfo {
+ public:
+  explicit TypeInfoForTypeResolver(TypeResolver* type_resolver)
+      : type_resolver_(type_resolver) {}
+
+  virtual ~TypeInfoForTypeResolver() {
+    DeleteCachedTypes(&cached_types_);
+    DeleteCachedTypes(&cached_enums_);
+  }
+
+  virtual util::StatusOr<const google::protobuf::Type*> ResolveTypeUrl(
+      StringPiece type_url) {
+    map<StringPiece, StatusOrType>::iterator it = cached_types_.find(type_url);
+    if (it != cached_types_.end()) {
+      return it->second;
+    }
+    // Stores the string value so it can be referenced using StringPiece in the
+    // cached_types_ map.
+    const string& string_type_url =
+        *string_storage_.insert(type_url.ToString()).first;
+    google::protobuf::scoped_ptr<google::protobuf::Type> type(new google::protobuf::Type());
+    util::Status status =
+        type_resolver_->ResolveMessageType(string_type_url, type.get());
+    StatusOrType result =
+        status.ok() ? StatusOrType(type.release()) : StatusOrType(status);
+    cached_types_[string_type_url] = result;
+    return result;
+  }
+
+  virtual const google::protobuf::Type* GetType(StringPiece type_url) {
+    StatusOrType result = ResolveTypeUrl(type_url);
+    return result.ok() ? result.ValueOrDie() : NULL;
+  }
+
+  virtual const google::protobuf::Enum* GetEnum(StringPiece type_url) {
+    map<StringPiece, StatusOrEnum>::iterator it = cached_enums_.find(type_url);
+    if (it != cached_enums_.end()) {
+      return it->second.ok() ? it->second.ValueOrDie() : NULL;
+    }
+    // Stores the string value so it can be referenced using StringPiece in the
+    // cached_enums_ map.
+    const string& string_type_url =
+        *string_storage_.insert(type_url.ToString()).first;
+    google::protobuf::scoped_ptr<google::protobuf::Enum> enum_type(
+        new google::protobuf::Enum());
+    util::Status status =
+        type_resolver_->ResolveEnumType(string_type_url, enum_type.get());
+    StatusOrEnum result =
+        status.ok() ? StatusOrEnum(enum_type.release()) : StatusOrEnum(status);
+    cached_enums_[string_type_url] = result;
+    return result.ok() ? result.ValueOrDie() : NULL;
+  }
+
+  virtual const google::protobuf::Field* FindField(
+      const google::protobuf::Type* type, StringPiece camel_case_name) {
+    if (indexed_types_.find(type) == indexed_types_.end()) {
+      PopulateNameLookupTable(type);
+      indexed_types_.insert(type);
+    }
+    StringPiece name =
+        FindWithDefault(camel_case_name_table_, camel_case_name, StringPiece());
+    if (name.empty()) {
+      // Didn't find a mapping. Use whatever provided.
+      name = camel_case_name;
+    }
+    return FindFieldInTypeOrNull(type, name);
+  }
+
+ private:
+  typedef util::StatusOr<const google::protobuf::Type*> StatusOrType;
+  typedef util::StatusOr<const google::protobuf::Enum*> StatusOrEnum;
+
+  template <typename T>
+  static void DeleteCachedTypes(map<StringPiece, T>* cached_types) {
+    for (typename map<StringPiece, T>::iterator it = cached_types->begin();
+         it != cached_types->end(); ++it) {
+      if (it->second.ok()) {
+        delete it->second.ValueOrDie();
+      }
+    }
+  }
+
+  void PopulateNameLookupTable(const google::protobuf::Type* type) {
+    for (int i = 0; i < type->fields_size(); ++i) {
+      const google::protobuf::Field& field = type->fields(i);
+      StringPiece name = field.name();
+      StringPiece camel_case_name =
+          *string_storage_.insert(ToCamelCase(name)).first;
+      const StringPiece* existing = InsertOrReturnExisting(
+          &camel_case_name_table_, camel_case_name, name);
+      if (existing && *existing != name) {
+        GOOGLE_LOG(WARNING) << "Field '" << name << "' and '" << *existing
+                     << "' map to the same camel case name '" << camel_case_name
+                     << "'.";
+      }
+    }
+  }
+
+  TypeResolver* type_resolver_;
+
+  // Stores string values that will be referenced by StringPieces in
+  // cached_types_, cached_enums_ and camel_case_name_table_.
+  set<string> string_storage_;
+
+  map<StringPiece, StatusOrType> cached_types_;
+  map<StringPiece, StatusOrEnum> cached_enums_;
+
+  set<const google::protobuf::Type*> indexed_types_;
+  map<StringPiece, StringPiece> camel_case_name_table_;
+};
+}  // namespace
+
+TypeInfo* TypeInfo::NewTypeInfo(TypeResolver* type_resolver) {
+  return new TypeInfoForTypeResolver(type_resolver);
+}
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/internal/type_info.h b/src/google/protobuf/util/internal/type_info.h
new file mode 100644
index 0000000..04ed78d
--- /dev/null
+++ b/src/google/protobuf/util/internal/type_info.h
@@ -0,0 +1,87 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_PROTOBUF_UTIL_CONVERTER_TYPE_INFO_H__
+#define GOOGLE_PROTOBUF_UTIL_CONVERTER_TYPE_INFO_H__
+
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/type.pb.h>
+#include <google/protobuf/util/type_resolver.h>
+#include <google/protobuf/stubs/stringpiece.h>
+#include <google/protobuf/stubs/status.h>
+#include <google/protobuf/stubs/statusor.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+// Internal helper class for type resolving. Note that this class is not
+// thread-safe and should only be accessed in one thread.
+class TypeInfo {
+ public:
+  TypeInfo() {}
+  virtual ~TypeInfo() {}
+
+  // Resolves a type url into a Type. If the type url is invalid, returns
+  // INVALID_ARGUMENT error status. If the type url is valid but the
+  // corresponding type cannot be found, returns a NOT_FOUND error status.
+  //
+  // This TypeInfo class retains the ownership of the returned pointer.
+  virtual util::StatusOr<const google::protobuf::Type*> ResolveTypeUrl(
+      StringPiece type_url) = 0;
+
+  // Resolves a type url into a Type. Like ResolveTypeUrl() but returns
+  // NULL if the type url is invalid or the type cannot be found.
+  //
+  // This TypeInfo class retains the ownership of the returned pointer.
+  virtual const google::protobuf::Type* GetType(StringPiece type_url) = 0;
+
+  // Resolves a type url for an enum. Returns NULL if the type url is
+  // invalid or the type cannot be found.
+  //
+  // This TypeInfo class retains the ownership of the returned pointer.
+  virtual const google::protobuf::Enum* GetEnum(StringPiece type_url) = 0;
+
+  // Looks up a field in the specified type given a CamelCase name.
+  virtual const google::protobuf::Field* FindField(
+      const google::protobuf::Type* type, StringPiece camel_case_name) = 0;
+
+  static TypeInfo* NewTypeInfo(TypeResolver* type_resolver);
+
+ private:
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(TypeInfo);
+};
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_CONVERTER_TYPE_INFO_H__
diff --git a/src/google/protobuf/util/internal/type_info_test_helper.cc b/src/google/protobuf/util/internal/type_info_test_helper.cc
new file mode 100644
index 0000000..f7aea85
--- /dev/null
+++ b/src/google/protobuf/util/internal/type_info_test_helper.cc
@@ -0,0 +1,130 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/util/internal/type_info_test_helper.h>
+
+#include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
+#include <vector>
+
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/descriptor.h>
+#include <google/protobuf/util/internal/default_value_objectwriter.h>
+#include <google/protobuf/util/internal/type_info.h>
+#include <google/protobuf/util/internal/constants.h>
+#include <google/protobuf/util/internal/protostream_objectsource.h>
+#include <google/protobuf/util/internal/protostream_objectwriter.h>
+#include <google/protobuf/util/type_resolver.h>
+#include <google/protobuf/util/type_resolver_util.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+namespace testing {
+
+
+void TypeInfoTestHelper::ResetTypeInfo(
+    const vector<const Descriptor*>& descriptors) {
+  switch (type_) {
+    case USE_TYPE_RESOLVER: {
+      const DescriptorPool* pool = descriptors[0]->file()->pool();
+      for (int i = 1; i < descriptors.size(); ++i) {
+        GOOGLE_CHECK(pool == descriptors[i]->file()->pool())
+            << "Descriptors from different pools are not supported.";
+      }
+      type_resolver_.reset(
+          NewTypeResolverForDescriptorPool(kTypeServiceBaseUrl, pool));
+      typeinfo_.reset(TypeInfo::NewTypeInfo(type_resolver_.get()));
+      return;
+    }
+  }
+  GOOGLE_LOG(FATAL) << "Can not reach here.";
+}
+
+void TypeInfoTestHelper::ResetTypeInfo(const Descriptor* descriptor) {
+  vector<const Descriptor*> descriptors;
+  descriptors.push_back(descriptor);
+  ResetTypeInfo(descriptors);
+}
+
+void TypeInfoTestHelper::ResetTypeInfo(const Descriptor* descriptor1,
+                                       const Descriptor* descriptor2) {
+  vector<const Descriptor*> descriptors;
+  descriptors.push_back(descriptor1);
+  descriptors.push_back(descriptor2);
+  ResetTypeInfo(descriptors);
+}
+
+TypeInfo* TypeInfoTestHelper::GetTypeInfo() { return typeinfo_.get(); }
+
+ProtoStreamObjectSource* TypeInfoTestHelper::NewProtoSource(
+    io::CodedInputStream* coded_input, const string& type_url) {
+  const google::protobuf::Type* type = typeinfo_->GetType(type_url);
+  switch (type_) {
+    case USE_TYPE_RESOLVER: {
+      return new ProtoStreamObjectSource(coded_input, type_resolver_.get(),
+                                         *type);
+    }
+  }
+  GOOGLE_LOG(FATAL) << "Can not reach here.";
+}
+
+ProtoStreamObjectWriter* TypeInfoTestHelper::NewProtoWriter(
+    const string& type_url, strings::ByteSink* output,
+    ErrorListener* listener) {
+  const google::protobuf::Type* type = typeinfo_->GetType(type_url);
+  switch (type_) {
+    case USE_TYPE_RESOLVER: {
+      return new ProtoStreamObjectWriter(type_resolver_.get(), *type, output,
+                                         listener);
+    }
+  }
+  GOOGLE_LOG(FATAL) << "Can not reach here.";
+}
+
+DefaultValueObjectWriter* TypeInfoTestHelper::NewDefaultValueWriter(
+    const string& type_url, ObjectWriter* writer) {
+  const google::protobuf::Type* type = typeinfo_->GetType(type_url);
+  switch (type_) {
+    case USE_TYPE_RESOLVER: {
+      return new DefaultValueObjectWriter(type_resolver_.get(), *type, writer);
+    }
+  }
+  GOOGLE_LOG(FATAL) << "Can not reach here.";
+}
+
+}  // namespace testing
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/internal/type_info_test_helper.h b/src/google/protobuf/util/internal/type_info_test_helper.h
new file mode 100644
index 0000000..6916a73
--- /dev/null
+++ b/src/google/protobuf/util/internal/type_info_test_helper.h
@@ -0,0 +1,98 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_PROTOBUF_UTIL_CONVERTER_TYPE_INFO_TEST_HELPER_H__
+#define GOOGLE_PROTOBUF_UTIL_CONVERTER_TYPE_INFO_TEST_HELPER_H__
+
+#include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
+#include <vector>
+
+#include <google/protobuf/io/coded_stream.h>
+#include <google/protobuf/descriptor.h>
+#include <google/protobuf/util/internal/type_info.h>
+#include <google/protobuf/util/internal/default_value_objectwriter.h>
+#include <google/protobuf/util/internal/protostream_objectsource.h>
+#include <google/protobuf/util/internal/protostream_objectwriter.h>
+#include <google/protobuf/util/type_resolver.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+namespace testing {
+
+enum TypeInfoSource {
+  USE_TYPE_RESOLVER,
+};
+
+// In the unit-tests we want to test two scenarios: one with type info from
+// ServiceTypeInfo, the other with type info from TypeResolver. This class
+// wraps the detail of where the type info is from and provides the same
+// interface so the same unit-test code can test both scenarios.
+class TypeInfoTestHelper {
+ public:
+  explicit TypeInfoTestHelper(TypeInfoSource type) : type_(type) {}
+
+  // Creates a TypeInfo object for the given set of descriptors.
+  void ResetTypeInfo(const vector<const Descriptor*>& descriptors);
+
+  // Convinent overloads.
+  void ResetTypeInfo(const Descriptor* descriptor);
+  void ResetTypeInfo(const Descriptor* descriptor1,
+                     const Descriptor* descriptor2);
+
+  // Returns the TypeInfo created after ResetTypeInfo.
+  TypeInfo* GetTypeInfo();
+
+  ProtoStreamObjectSource* NewProtoSource(io::CodedInputStream* coded_input,
+                                          const string& type_url);
+
+  ProtoStreamObjectWriter* NewProtoWriter(const string& type_url,
+                                          strings::ByteSink* output,
+                                          ErrorListener* listener);
+
+  DefaultValueObjectWriter* NewDefaultValueWriter(const string& type_url,
+                                                  ObjectWriter* writer);
+
+ private:
+  TypeInfoSource type_;
+  google::protobuf::scoped_ptr<TypeInfo> typeinfo_;
+  google::protobuf::scoped_ptr<TypeResolver> type_resolver_;
+};
+}  // namespace testing
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_CONVERTER_TYPE_INFO_TEST_HELPER_H__
diff --git a/src/google/protobuf/util/internal/utility.cc b/src/google/protobuf/util/internal/utility.cc
new file mode 100644
index 0000000..b6ec19b
--- /dev/null
+++ b/src/google/protobuf/util/internal/utility.cc
@@ -0,0 +1,332 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/util/internal/utility.h>
+
+#include <cmath>
+#include <algorithm>
+#include <utility>
+
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/wrappers.pb.h>
+#include <google/protobuf/descriptor.pb.h>
+#include <google/protobuf/descriptor.h>
+#include <google/protobuf/util/internal/constants.h>
+#include <google/protobuf/stubs/strutil.h>
+#include <google/protobuf/stubs/map_util.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+
+namespace {
+const StringPiece SkipWhiteSpace(StringPiece str) {
+  StringPiece::size_type i;
+  for (i = 0; i < str.size() && isspace(str[i]); ++i) {}
+  GOOGLE_DCHECK(i == str.size() || !isspace(str[i]));
+  return StringPiece(str, i);
+}
+}  // namespace
+
+bool GetBoolOptionOrDefault(
+    const google::protobuf::RepeatedPtrField<google::protobuf::Option>& options,
+    const string& option_name, bool default_value) {
+  const google::protobuf::Option* opt = FindOptionOrNull(options, option_name);
+  if (opt == NULL) {
+    return default_value;
+  }
+  return GetBoolFromAny(opt->value());
+}
+
+int64 GetInt64OptionOrDefault(
+    const google::protobuf::RepeatedPtrField<google::protobuf::Option>& options,
+    const string& option_name, int64 default_value) {
+  const google::protobuf::Option* opt = FindOptionOrNull(options, option_name);
+  if (opt == NULL) {
+    return default_value;
+  }
+  return GetInt64FromAny(opt->value());
+}
+
+double GetDoubleOptionOrDefault(
+    const google::protobuf::RepeatedPtrField<google::protobuf::Option>& options,
+    const string& option_name, double default_value) {
+  const google::protobuf::Option* opt = FindOptionOrNull(options, option_name);
+  if (opt == NULL) {
+    return default_value;
+  }
+  return GetDoubleFromAny(opt->value());
+}
+
+string GetStringOptionOrDefault(
+    const google::protobuf::RepeatedPtrField<google::protobuf::Option>& options,
+    const string& option_name, const string& default_value) {
+  const google::protobuf::Option* opt = FindOptionOrNull(options, option_name);
+  if (opt == NULL) {
+    return default_value;
+  }
+  return GetStringFromAny(opt->value());
+}
+
+template <typename T>
+void ParseFromAny(const string& data, T* result) {
+  result->ParseFromString(data);
+}
+
+// Returns a boolean value contained in Any type.
+// TODO(skarvaje): Add type checking & error messages here.
+bool GetBoolFromAny(const google::protobuf::Any& any) {
+  google::protobuf::BoolValue b;
+  ParseFromAny(any.value(), &b);
+  return b.value();
+}
+
+int64 GetInt64FromAny(const google::protobuf::Any& any) {
+  google::protobuf::Int64Value i;
+  ParseFromAny(any.value(), &i);
+  return i.value();
+}
+
+double GetDoubleFromAny(const google::protobuf::Any& any) {
+  google::protobuf::DoubleValue i;
+  ParseFromAny(any.value(), &i);
+  return i.value();
+}
+
+string GetStringFromAny(const google::protobuf::Any& any) {
+  google::protobuf::StringValue s;
+  ParseFromAny(any.value(), &s);
+  return s.value();
+}
+
+const StringPiece GetTypeWithoutUrl(StringPiece type_url) {
+  size_t idx = type_url.rfind('/');
+  return type_url.substr(idx + 1);
+}
+
+const string GetFullTypeWithUrl(StringPiece simple_type) {
+  return StrCat(kTypeServiceBaseUrl, "/", simple_type);
+}
+
+const google::protobuf::Option* FindOptionOrNull(
+    const google::protobuf::RepeatedPtrField<google::protobuf::Option>& options,
+    const string& option_name) {
+  for (int i = 0; i < options.size(); ++i) {
+    const google::protobuf::Option& opt = options.Get(i);
+    if (opt.name() == option_name) {
+      return &opt;
+    }
+  }
+  return NULL;
+}
+
+const google::protobuf::Field* FindFieldInTypeOrNull(
+    const google::protobuf::Type* type, StringPiece field_name) {
+  if (type != NULL) {
+    for (int i = 0; i < type->fields_size(); ++i) {
+      const google::protobuf::Field& field = type->fields(i);
+      if (field.name() == field_name) {
+        return &field;
+      }
+    }
+  }
+  return NULL;
+}
+
+const google::protobuf::EnumValue* FindEnumValueByNameOrNull(
+    const google::protobuf::Enum* enum_type, StringPiece enum_name) {
+  if (enum_type != NULL) {
+    for (int i = 0; i < enum_type->enumvalue_size(); ++i) {
+      const google::protobuf::EnumValue& enum_value = enum_type->enumvalue(i);
+      if (enum_value.name() == enum_name) {
+        return &enum_value;
+      }
+    }
+  }
+  return NULL;
+}
+
+const google::protobuf::EnumValue* FindEnumValueByNumberOrNull(
+    const google::protobuf::Enum* enum_type, int32 value) {
+  if (enum_type != NULL) {
+    for (int i = 0; i < enum_type->enumvalue_size(); ++i) {
+      const google::protobuf::EnumValue& enum_value = enum_type->enumvalue(i);
+      if (enum_value.number() == value) {
+        return &enum_value;
+      }
+    }
+  }
+  return NULL;
+}
+
+string ToCamelCase(const StringPiece input) {
+  bool capitalize_next = false;
+  bool was_cap = true;
+  bool is_cap = false;
+  bool first_word = true;
+  string result;
+  result.reserve(input.size());
+
+  for (size_t i = 0; i < input.size(); ++i, was_cap = is_cap) {
+    is_cap = ascii_isupper(input[i]);
+    if (input[i] == '_') {
+      capitalize_next = true;
+      if (!result.empty()) first_word = false;
+      continue;
+    } else if (first_word) {
+      // Consider when the current character B is capitalized,
+      // first word ends when:
+      // 1) following a lowercase:   "...aB..."
+      // 2) followed by a lowercase: "...ABc..."
+      if (!result.empty() && is_cap &&
+          (!was_cap || (i + 1 < input.size() && ascii_islower(input[i + 1])))) {
+        first_word = false;
+      } else {
+        result.push_back(ascii_tolower(input[i]));
+        continue;
+      }
+    } else if (capitalize_next) {
+      capitalize_next = false;
+      if (ascii_islower(input[i])) {
+        result.push_back(ascii_toupper(input[i]));
+        continue;
+      }
+    }
+    result.push_back(input[i]);
+  }
+  return result;
+}
+
+string ToSnakeCase(StringPiece input) {
+  bool was_not_underscore = false;  // Initialize to false for case 1 (below)
+  bool was_not_cap = false;
+  string result;
+  result.reserve(input.size() << 1);
+
+  for (size_t i = 0; i < input.size(); ++i) {
+    if (ascii_isupper(input[i])) {
+      // Consider when the current character B is capitalized:
+      // 1) At beginning of input:   "B..." => "b..."
+      //    (e.g. "Biscuit" => "biscuit")
+      // 2) Following a lowercase:   "...aB..." => "...a_b..."
+      //    (e.g. "gBike" => "g_bike")
+      // 3) At the end of input:     "...AB" => "...ab"
+      //    (e.g. "GoogleLAB" => "google_lab")
+      // 4) Followed by a lowercase: "...ABc..." => "...a_bc..."
+      //    (e.g. "GBike" => "g_bike")
+      if (was_not_underscore &&               //            case 1 out
+          (was_not_cap ||                     // case 2 in, case 3 out
+           (i + 1 < input.size() &&           //            case 3 out
+            ascii_islower(input[i + 1])))) {  // case 4 in
+        // We add an underscore for case 2 and case 4.
+        result.push_back('_');
+      }
+      result.push_back(ascii_tolower(input[i]));
+      was_not_underscore = true;
+      was_not_cap = false;
+    } else {
+      result.push_back(input[i]);
+      was_not_underscore = input[i] != '_';
+      was_not_cap = true;
+    }
+  }
+  return result;
+}
+
+set<string>* well_known_types_ = NULL;
+GOOGLE_PROTOBUF_DECLARE_ONCE(well_known_types_init_);
+const char* well_known_types_name_array_[] = {
+    "google.protobuf.Timestamp",   "google.protobuf.Duration",
+    "google.protobuf.DoubleValue", "google.protobuf.FloatValue",
+    "google.protobuf.Int64Value",  "google.protobuf.UInt64Value",
+    "google.protobuf.Int32Value",  "google.protobuf.UInt32Value",
+    "google.protobuf.BoolValue",   "google.protobuf.StringValue",
+    "google.protobuf.BytesValue",  "google.protobuf.FieldMask"};
+
+void DeleteWellKnownTypes() { delete well_known_types_; }
+
+void InitWellKnownTypes() {
+  well_known_types_ = new set<string>;
+  for (int i = 0; i < GOOGLE_ARRAYSIZE(well_known_types_name_array_); ++i) {
+    well_known_types_->insert(well_known_types_name_array_[i]);
+  }
+  google::protobuf::internal::OnShutdown(&DeleteWellKnownTypes);
+}
+
+bool IsWellKnownType(const string& type_name) {
+  InitWellKnownTypes();
+  return ContainsKey(*well_known_types_, type_name);
+}
+
+bool IsValidBoolString(const string& bool_string) {
+  return bool_string == "true" || bool_string == "false" ||
+         bool_string == "1" || bool_string == "0";
+}
+
+bool IsMap(const google::protobuf::Field& field,
+           const google::protobuf::Type& type) {
+  return (field.cardinality() ==
+              google::protobuf::Field_Cardinality_CARDINALITY_REPEATED &&
+          GetBoolOptionOrDefault(type.options(),
+                                 "google.protobuf.MessageOptions.map_entry", false));
+}
+
+string DoubleAsString(double value) {
+  if (value == std::numeric_limits<double>::infinity()) return "Infinity";
+  if (value == -std::numeric_limits<double>::infinity()) return "-Infinity";
+  if (isnan(value)) return "NaN";
+
+  return SimpleDtoa(value);
+}
+
+string FloatAsString(float value) {
+  if (isfinite(value)) return SimpleFtoa(value);
+  return DoubleAsString(value);
+}
+
+bool SafeStrToFloat(StringPiece str, float *value) {
+  double double_value;
+  if (!safe_strtod(str, &double_value)) {
+    return false;
+  }
+  *value = static_cast<float>(double_value);
+
+  if ((*value ==  numeric_limits<float>::infinity()) ||
+      (*value == -numeric_limits<float>::infinity())) {
+    return false;
+  }
+  return true;
+}
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/internal/utility.h b/src/google/protobuf/util/internal/utility.h
new file mode 100644
index 0000000..56ae1a2
--- /dev/null
+++ b/src/google/protobuf/util/internal/utility.h
@@ -0,0 +1,187 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_PROTOBUF_UTIL_CONVERTER_UTILITY_H__
+#define GOOGLE_PROTOBUF_UTIL_CONVERTER_UTILITY_H__
+
+#include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
+#include <string>
+#include <utility>
+
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/type.pb.h>
+#include <google/protobuf/repeated_field.h>
+#include <google/protobuf/stubs/stringpiece.h>
+#include <google/protobuf/stubs/strutil.h>
+#include <google/protobuf/stubs/status.h>
+#include <google/protobuf/stubs/statusor.h>
+
+
+namespace google {
+namespace protobuf {
+class Method;
+class Any;
+class Bool;
+class Option;
+class Field;
+class Type;
+class Enum;
+class EnumValue;
+}  // namespace protobuf
+
+
+namespace protobuf {
+namespace util {
+namespace converter {
+// Finds the tech option identified by option_name. Parses the boolean value and
+// returns it.
+// When the option with the given name is not found, default_value is returned.
+bool GetBoolOptionOrDefault(
+    const google::protobuf::RepeatedPtrField<google::protobuf::Option>& options,
+    const string& option_name, bool default_value);
+
+// Returns int64 option value. If the option isn't found, returns the
+// default_value.
+int64 GetInt64OptionOrDefault(
+    const google::protobuf::RepeatedPtrField<google::protobuf::Option>& options,
+    const string& option_name, int64 default_value);
+
+// Returns double option value. If the option isn't found, returns the
+// default_value.
+double GetDoubleOptionOrDefault(
+    const google::protobuf::RepeatedPtrField<google::protobuf::Option>& options,
+    const string& option_name, double default_value);
+
+// Returns string option value. If the option isn't found, returns the
+// default_value.
+string GetStringOptionOrDefault(
+    const google::protobuf::RepeatedPtrField<google::protobuf::Option>& options,
+    const string& option_name, const string& default_value);
+
+// Returns a boolean value contained in Any type.
+// TODO(skarvaje): Make these utilities dealing with Any types more generic,
+// add more error checking and move to a more public/sharable location so others
+// can use.
+bool GetBoolFromAny(const google::protobuf::Any& any);
+
+// Returns int64 value contained in Any type.
+int64 GetInt64FromAny(const google::protobuf::Any& any);
+
+// Returns double value contained in Any type.
+double GetDoubleFromAny(const google::protobuf::Any& any);
+
+// Returns string value contained in Any type.
+string GetStringFromAny(const google::protobuf::Any& any);
+
+// Returns the type string without the url prefix. e.g.: If the passed type is
+// 'type.googleapis.com/tech.type.Bool', the returned value is 'tech.type.Bool'.
+const StringPiece GetTypeWithoutUrl(StringPiece type_url);
+
+// Returns the simple_type with the base type url (kTypeServiceBaseUrl)
+// prefixed.
+//
+// E.g:
+// GetFullTypeWithUrl("google.protobuf.Timestamp") returns the string
+// "type.googleapis.com/google.protobuf.Timestamp".
+const string GetFullTypeWithUrl(StringPiece simple_type);
+
+// Finds and returns option identified by name and option_name within the
+// provided map. Returns NULL if none found.
+const google::protobuf::Option* FindOptionOrNull(
+    const google::protobuf::RepeatedPtrField<google::protobuf::Option>& options,
+    const string& option_name);
+
+// Finds and returns the field identified by field_name in the passed tech Type
+// object. Returns NULL if none found.
+const google::protobuf::Field* FindFieldInTypeOrNull(
+    const google::protobuf::Type* type, StringPiece field_name);
+
+// Finds and returns the EnumValue identified by enum_name in the passed tech
+// Enum object. Returns NULL if none found.
+const google::protobuf::EnumValue* FindEnumValueByNameOrNull(
+    const google::protobuf::Enum* enum_type, StringPiece enum_name);
+
+// Finds and returns the EnumValue identified by value in the passed tech
+// Enum object. Returns NULL if none found.
+const google::protobuf::EnumValue* FindEnumValueByNumberOrNull(
+    const google::protobuf::Enum* enum_type, int32 value);
+
+// Converts input to camel-case and returns it.
+// Tests are in wrappers/translator/snake2camel_objectwriter_test.cc
+// TODO(skarvaje): Isolate tests for this function and put them in
+// utility_test.cc
+string ToCamelCase(const StringPiece input);
+
+// Converts input to snake_case and returns it.
+string ToSnakeCase(StringPiece input);
+
+// Returns true if type_name represents a well-known type.
+bool IsWellKnownType(const string& type_name);
+
+// Returns true if 'bool_string' represents a valid boolean value. Only "true",
+// "false", "0" and "1" are allowed.
+bool IsValidBoolString(const string& bool_string);
+
+// Returns true if "field" is a protobuf map field based on its type.
+bool IsMap(const google::protobuf::Field& field,
+           const google::protobuf::Type& type);
+
+// Infinity/NaN-aware conversion to string.
+string DoubleAsString(double value);
+string FloatAsString(float value);
+
+// Convert from int32, int64, uint32, uint64, double or float to string.
+template <typename T>
+string ValueAsString(T value) {
+  return SimpleItoa(value);
+}
+
+template <>
+inline string ValueAsString(float value) {
+  return FloatAsString(value);
+}
+
+template <>
+inline string ValueAsString(double value) {
+  return DoubleAsString(value);
+}
+
+// Converts a string to float. Unlike safe_strtof, conversion will fail if the
+// value fits into double but not float (e.g., DBL_MAX).
+bool SafeStrToFloat(StringPiece str, float* value);
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_CONVERTER_UTILITY_H__
diff --git a/src/google/protobuf/util/json_format_proto3.proto b/src/google/protobuf/util/json_format_proto3.proto
new file mode 100644
index 0000000..7a28286
--- /dev/null
+++ b/src/google/protobuf/util/json_format_proto3.proto
@@ -0,0 +1,157 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+syntax = "proto3";
+
+package proto3;
+
+
+import "google/protobuf/duration.proto";
+import "google/protobuf/timestamp.proto";
+import "google/protobuf/wrappers.proto";
+import "google/protobuf/struct.proto";
+import "google/protobuf/any.proto";
+import "google/protobuf/field_mask.proto";
+
+enum EnumType {
+  FOO = 0;
+  BAR = 1;
+}
+
+message MessageType {
+  int32 value = 1;
+}
+
+message TestMessage {
+  bool bool_value = 1;
+  int32 int32_value = 2;
+  int64 int64_value = 3;
+  uint32 uint32_value = 4;
+  uint64 uint64_value = 5;
+  float float_value = 6;
+  double double_value = 7;
+  string string_value = 8;
+  bytes bytes_value = 9;
+  EnumType enum_value = 10;
+  MessageType message_value = 11;
+
+  repeated bool repeated_bool_value = 21;
+  repeated int32 repeated_int32_value = 22;
+  repeated int64 repeated_int64_value = 23;
+  repeated uint32 repeated_uint32_value = 24;
+  repeated uint64 repeated_uint64_value = 25;
+  repeated float repeated_float_value = 26;
+  repeated double repeated_double_value = 27;
+  repeated string repeated_string_value = 28;
+  repeated bytes repeated_bytes_value = 29;
+  repeated EnumType repeated_enum_value = 30;
+  repeated MessageType repeated_message_value = 31;
+}
+
+message TestOneof {
+  // In JSON format oneof fields behave mostly the same as optional
+  // fields except that:
+  //   1. Oneof fields have field presence information and will be
+  //      printed if it's set no matter whether it's the default value.
+  //   2. Multiple oneof fields in the same oneof cannot appear at the
+  //      same time in the input.
+  oneof oneof_value {
+    int32 oneof_int32_value = 1;
+    string oneof_string_value = 2;
+    bytes oneof_bytes_value = 3;
+    EnumType oneof_enum_value = 4;
+    MessageType oneof_message_value = 5;
+  }
+}
+
+message TestMap {
+  map<bool, int32> bool_map = 1;
+  map<int32, int32> int32_map = 2;
+  map<int64, int32> int64_map = 3;
+  map<uint32, int32> uint32_map = 4;
+  map<uint64, int32> uint64_map = 5;
+  map<string, int32> string_map = 6;
+}
+
+message TestWrapper {
+  google.protobuf.BoolValue bool_value = 1;
+  google.protobuf.Int32Value int32_value = 2;
+  google.protobuf.Int64Value int64_value = 3;
+  google.protobuf.UInt32Value uint32_value = 4;
+  google.protobuf.UInt64Value uint64_value = 5;
+  google.protobuf.FloatValue float_value = 6;
+  google.protobuf.DoubleValue double_value = 7;
+  google.protobuf.StringValue string_value = 8;
+  google.protobuf.BytesValue bytes_value = 9;
+
+  repeated google.protobuf.BoolValue repeated_bool_value = 11;
+  repeated google.protobuf.Int32Value repeated_int32_value = 12;
+  repeated google.protobuf.Int64Value repeated_int64_value = 13;
+  repeated google.protobuf.UInt32Value repeated_uint32_value = 14;
+  repeated google.protobuf.UInt64Value repeated_uint64_value = 15;
+  repeated google.protobuf.FloatValue repeated_float_value = 16;
+  repeated google.protobuf.DoubleValue repeated_double_value = 17;
+  repeated google.protobuf.StringValue repeated_string_value = 18;
+  repeated google.protobuf.BytesValue repeated_bytes_value = 19;
+}
+
+message TestTimestamp {
+  google.protobuf.Timestamp value = 1;
+  repeated google.protobuf.Timestamp repeated_value = 2;
+}
+
+message TestDuration {
+  google.protobuf.Duration value = 1;
+  repeated google.protobuf.Duration repeated_value = 2;
+}
+
+message TestFieldMask {
+  google.protobuf.FieldMask value = 1;
+}
+
+message TestStruct {
+  google.protobuf.Struct value = 1;
+  repeated google.protobuf.Struct repeated_value = 2;
+}
+
+message TestAny {
+  google.protobuf.Any value = 1;
+  repeated google.protobuf.Any repeated_value = 2;
+}
+
+message TestValue {
+  google.protobuf.Value value = 1;
+  repeated google.protobuf.Value repeated_value = 2;
+}
+
+message TestListValue {
+  google.protobuf.ListValue value = 1;
+  repeated google.protobuf.ListValue repeated_value = 2;
+}
diff --git a/src/google/protobuf/util/json_util.cc b/src/google/protobuf/util/json_util.cc
new file mode 100644
index 0000000..6cd40fd
--- /dev/null
+++ b/src/google/protobuf/util/json_util.cc
@@ -0,0 +1,142 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/util/json_util.h>
+
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/io/coded_stream.h>
+#include <google/protobuf/io/zero_copy_stream.h>
+#include <google/protobuf/util/internal/default_value_objectwriter.h>
+#include <google/protobuf/util/internal/snake2camel_objectwriter.h>
+#include <google/protobuf/util/internal/error_listener.h>
+#include <google/protobuf/util/internal/json_objectwriter.h>
+#include <google/protobuf/util/internal/json_stream_parser.h>
+#include <google/protobuf/util/internal/protostream_objectsource.h>
+#include <google/protobuf/util/internal/protostream_objectwriter.h>
+#include <google/protobuf/util/type_resolver.h>
+#include <google/protobuf/util/type_resolver_util.h>
+#include <google/protobuf/stubs/bytestream.h>
+#include <google/protobuf/stubs/status_macros.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+
+namespace internal {
+void ZeroCopyStreamByteSink::Append(const char* bytes, size_t len) {
+  while (len > 0) {
+    void* buffer;
+    int length;
+    if (!stream_->Next(&buffer, &length)) {
+      // There isn't a way for ByteSink to report errors.
+      return;
+    }
+    if (len < length) {
+      memcpy(buffer, bytes, len);
+      stream_->BackUp(length - len);
+      break;
+    } else {
+      memcpy(buffer, bytes, length);
+      bytes += length;
+      len -= length;
+    }
+  }
+}
+}  // namespace internal
+
+util::Status BinaryToJsonStream(TypeResolver* resolver,
+                                  const string& type_url,
+                                  io::ZeroCopyInputStream* binary_input,
+                                  io::ZeroCopyOutputStream* json_output,
+                                  const JsonOptions& options) {
+  io::CodedInputStream in_stream(binary_input);
+  google::protobuf::Type type;
+  RETURN_IF_ERROR(resolver->ResolveMessageType(type_url, &type));
+  converter::ProtoStreamObjectSource proto_source(&in_stream, resolver, type);
+  io::CodedOutputStream out_stream(json_output);
+  converter::JsonObjectWriter json_writer(options.add_whitespace ? " " : "",
+                                          &out_stream);
+  converter::Snake2CamelObjectWriter snake2camel_writer(&json_writer);
+  if (options.always_print_primitive_fields) {
+    converter::DefaultValueObjectWriter default_value_writer(
+        resolver, type, &snake2camel_writer);
+    return proto_source.WriteTo(&default_value_writer);
+  } else {
+    return proto_source.WriteTo(&snake2camel_writer);
+  }
+}
+
+util::Status BinaryToJsonString(TypeResolver* resolver,
+                                  const string& type_url,
+                                  const string& binary_input,
+                                  string* json_output,
+                                  const JsonOptions& options) {
+  io::ArrayInputStream input_stream(binary_input.data(), binary_input.size());
+  io::StringOutputStream output_stream(json_output);
+  return BinaryToJsonStream(resolver, type_url, &input_stream, &output_stream,
+                            options);
+}
+
+util::Status JsonToBinaryStream(TypeResolver* resolver,
+                                  const string& type_url,
+                                  io::ZeroCopyInputStream* json_input,
+                                  io::ZeroCopyOutputStream* binary_output) {
+  google::protobuf::Type type;
+  RETURN_IF_ERROR(resolver->ResolveMessageType(type_url, &type));
+  internal::ZeroCopyStreamByteSink sink(binary_output);
+  converter::NoopErrorListener listener;
+  converter::ProtoStreamObjectWriter proto_writer(resolver, type, &sink,
+                                                  &listener);
+
+  converter::JsonStreamParser parser(&proto_writer);
+  const void* buffer;
+  int length;
+  while (json_input->Next(&buffer, &length)) {
+    if (length == 0) continue;
+    RETURN_IF_ERROR(
+        parser.Parse(StringPiece(static_cast<const char*>(buffer), length)));
+  }
+  RETURN_IF_ERROR(parser.FinishParse());
+
+  return util::Status::OK;
+}
+
+util::Status JsonToBinaryString(TypeResolver* resolver,
+                                  const string& type_url,
+                                  const string& json_input,
+                                  string* binary_output) {
+  io::ArrayInputStream input_stream(json_input.data(), json_input.size());
+  io::StringOutputStream output_stream(binary_output);
+  return JsonToBinaryStream(resolver, type_url, &input_stream, &output_stream);
+}
+
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/json_util.h b/src/google/protobuf/util/json_util.h
new file mode 100644
index 0000000..8659448
--- /dev/null
+++ b/src/google/protobuf/util/json_util.h
@@ -0,0 +1,132 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Utility functions to convert between protobuf binary format and proto3 JSON
+// format.
+#ifndef GOOGLE_PROTOBUF_UTIL_JSON_UTIL_H__
+#define GOOGLE_PROTOBUF_UTIL_JSON_UTIL_H__
+
+#include <google/protobuf/util/type_resolver.h>
+#include <google/protobuf/stubs/bytestream.h>
+
+namespace google {
+namespace protobuf {
+namespace io {
+class ZeroCopyInputStream;
+class ZeroCopyOutputStream;
+}  // namespace io
+namespace util {
+
+struct JsonOptions {
+  // Whether to add spaces, line breaks and indentation to make the JSON output
+  // easy to read.
+  bool add_whitespace;
+  // Whether to always print primitive fields. By default primitive fields with
+  // default values will be omitted in JSON joutput. For example, an int32 field
+  // set to 0 will be omitted. Set this flag to true will override the default
+  // behavior and print primitive fields regardless of their values.
+  bool always_print_primitive_fields;
+
+  JsonOptions() : add_whitespace(false),
+                  always_print_primitive_fields(false) {
+  }
+};
+
+// Converts protobuf binary data to JSON.
+// The conversion will fail if:
+//   1. TypeResolver fails to resolve a type.
+//   2. input is not valid protobuf wire format, or conflicts with the type
+//      information returned by TypeResolver.
+// Note that unknown fields will be discarded silently.
+util::Status BinaryToJsonStream(TypeResolver* resolver,
+                                  const string& type_url,
+                                  io::ZeroCopyInputStream* binary_input,
+                                  io::ZeroCopyOutputStream* json_output,
+                                  const JsonOptions& options);
+
+inline util::Status BinaryToJsonStream(
+    TypeResolver* resolver, const string& type_url,
+    io::ZeroCopyInputStream* binary_input,
+    io::ZeroCopyOutputStream* json_output) {
+  return BinaryToJsonStream(resolver, type_url, binary_input, json_output,
+                            JsonOptions());
+}
+
+util::Status BinaryToJsonString(TypeResolver* resolver,
+                                  const string& type_url,
+                                  const string& binary_input,
+                                  string* json_output,
+                                  const JsonOptions& options);
+
+inline util::Status BinaryToJsonString(TypeResolver* resolver,
+                                         const string& type_url,
+                                         const string& binary_input,
+                                         string* json_output) {
+  return BinaryToJsonString(resolver, type_url, binary_input, json_output,
+                            JsonOptions());
+}
+
+// Converts JSON data to protobuf binary format.
+// The conversion will fail if:
+//   1. TypeResolver fails to resolve a type.
+//   2. input is not valid JSON format, or conflicts with the type
+//      information returned by TypeResolver.
+//   3. input has unknown fields.
+util::Status JsonToBinaryStream(TypeResolver* resolver,
+                                  const string& type_url,
+                                  io::ZeroCopyInputStream* json_input,
+                                  io::ZeroCopyOutputStream* binary_output);
+
+util::Status JsonToBinaryString(TypeResolver* resolver,
+                                  const string& type_url,
+                                  const string& json_input,
+                                  string* binary_output);
+
+namespace internal {
+// Internal helper class. Put in the header so we can write unit-tests for it.
+class LIBPROTOBUF_EXPORT ZeroCopyStreamByteSink : public strings::ByteSink {
+ public:
+  explicit ZeroCopyStreamByteSink(io::ZeroCopyOutputStream* stream)
+      : stream_(stream) {}
+
+  virtual void Append(const char* bytes, size_t len);
+
+ private:
+  io::ZeroCopyOutputStream* stream_;
+
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(ZeroCopyStreamByteSink);
+};
+}  // namespace internal
+
+}  // namespace util
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_JSON_UTIL_H__
diff --git a/src/google/protobuf/util/json_util_test.cc b/src/google/protobuf/util/json_util_test.cc
new file mode 100644
index 0000000..8399b40
--- /dev/null
+++ b/src/google/protobuf/util/json_util_test.cc
@@ -0,0 +1,277 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/util/json_util.h>
+
+#include <list>
+#include <string>
+
+#include <google/protobuf/io/zero_copy_stream.h>
+#include <google/protobuf/util/json_format_proto3.pb.h>
+#include <google/protobuf/util/type_resolver.h>
+#include <google/protobuf/util/type_resolver_util.h>
+#include <gtest/gtest.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace {
+
+using proto3::FOO;
+using proto3::BAR;
+using proto3::TestMessage;
+
+static const char kTypeUrlPrefix[] = "type.googleapis.com";
+
+static string GetTypeUrl(const Descriptor* message) {
+  return string(kTypeUrlPrefix) + "/" + message->full_name();
+}
+
+// As functions defined in json_util.h are just thin wrappers around the
+// JSON conversion code in //net/proto2/util/converter, in this test we
+// only cover some very basic cases to make sure the wrappers have forwarded
+// parameters to the underlying implementation correctly. More detailed
+// tests are contained in the //net/proto2/util/converter directory.
+class JsonUtilTest : public testing::Test {
+ protected:
+  JsonUtilTest() {
+    resolver_.reset(NewTypeResolverForDescriptorPool(
+        kTypeUrlPrefix, DescriptorPool::generated_pool()));
+  }
+
+  string ToJson(const Message& message, const JsonOptions& options) {
+    string result;
+    GOOGLE_CHECK_OK(BinaryToJsonString(resolver_.get(),
+                                GetTypeUrl(message.GetDescriptor()),
+                                message.SerializeAsString(), &result, options));
+    return result;
+  }
+
+  bool FromJson(const string& json, Message* message) {
+    string binary;
+    GOOGLE_CHECK_OK(JsonToBinaryString(
+        resolver_.get(), GetTypeUrl(message->GetDescriptor()), json, &binary));
+    return message->ParseFromString(binary);
+  }
+
+  google::protobuf::scoped_ptr<TypeResolver> resolver_;
+};
+
+TEST_F(JsonUtilTest, TestWhitespaces) {
+  TestMessage m;
+  m.mutable_message_value();
+
+  JsonOptions options;
+  EXPECT_EQ("{\"messageValue\":{}}", ToJson(m, options));
+  options.add_whitespace = true;
+  EXPECT_EQ(
+      "{\n"
+      " \"messageValue\": {}\n"
+      "}\n",
+      ToJson(m, options));
+}
+
+TEST_F(JsonUtilTest, TestDefaultValues) {
+  TestMessage m;
+  JsonOptions options;
+  EXPECT_EQ("{}", ToJson(m, options));
+  options.always_print_primitive_fields = true;
+  EXPECT_EQ(
+      "{\"boolValue\":false,"
+      "\"int32Value\":0,"
+      "\"int64Value\":\"0\","
+      "\"uint32Value\":0,"
+      "\"uint64Value\":\"0\","
+      "\"floatValue\":0,"
+      "\"doubleValue\":0,"
+      "\"stringValue\":\"\","
+      "\"bytesValue\":\"\","
+      // TODO(xiaofeng): The default enum value should be FOO. I believe
+      // this is a bug in DefaultValueObjectWriter.
+      "\"enumValue\":null"
+      "}",
+      ToJson(m, options));
+}
+
+TEST_F(JsonUtilTest, ParseMessage) {
+  // Some random message but good enough to verify that the parsing warpper
+  // functions are working properly.
+  string input =
+      "{\n"
+      "  \"int32Value\": 1024,\n"
+      "  \"repeatedInt32Value\": [1, 2],\n"
+      "  \"messageValue\": {\n"
+      "    \"value\": 2048\n"
+      "  },\n"
+      "  \"repeatedMessageValue\": [\n"
+      "    {\"value\": 40}, {\"value\": 96}\n"
+      "  ]\n"
+      "}\n";
+  TestMessage m;
+  ASSERT_TRUE(FromJson(input, &m));
+  EXPECT_EQ(1024, m.int32_value());
+  ASSERT_EQ(2, m.repeated_int32_value_size());
+  EXPECT_EQ(1, m.repeated_int32_value(0));
+  EXPECT_EQ(2, m.repeated_int32_value(1));
+  EXPECT_EQ(2048, m.message_value().value());
+  ASSERT_EQ(2, m.repeated_message_value_size());
+  EXPECT_EQ(40, m.repeated_message_value(0).value());
+  EXPECT_EQ(96, m.repeated_message_value(1).value());
+}
+
+typedef pair<char*, int> Segment;
+// A ZeroCopyOutputStream that writes to multiple buffers.
+class SegmentedZeroCopyOutputStream : public io::ZeroCopyOutputStream {
+ public:
+  explicit SegmentedZeroCopyOutputStream(list<Segment> segments)
+      : segments_(segments), last_segment_(NULL, 0), byte_count_(0) {}
+
+  virtual bool Next(void** buffer, int* length) {
+    if (segments_.empty()) {
+      return false;
+    }
+    last_segment_ = segments_.front();
+    segments_.pop_front();
+    *buffer = last_segment_.first;
+    *length = last_segment_.second;
+    byte_count_ += *length;
+    return true;
+  }
+
+  virtual void BackUp(int length) {
+    GOOGLE_CHECK(length <= last_segment_.second);
+    segments_.push_front(
+        Segment(last_segment_.first + last_segment_.second - length, length));
+    last_segment_ = Segment(last_segment_.first, last_segment_.second - length);
+    byte_count_ -= length;
+  }
+
+  virtual int64 ByteCount() const { return byte_count_; }
+
+ private:
+  list<Segment> segments_;
+  Segment last_segment_;
+  int64 byte_count_;
+};
+
+// This test splits the output buffer and also the input data into multiple
+// segments and checks that the implementation of ZeroCopyStreamByteSink
+// handles all possible cases correctly.
+TEST(ZeroCopyStreamByteSinkTest, TestAllInputOutputPatterns) {
+  static const int kOutputBufferLength = 10;
+  // An exhaustive test takes too long, skip some combinations to make the test
+  // run faster.
+  static const int kSkippedPatternCount = 7;
+
+  char buffer[kOutputBufferLength];
+  for (int split_pattern = 0; split_pattern < (1 << (kOutputBufferLength - 1));
+       split_pattern += kSkippedPatternCount) {
+    // Split the buffer into small segments according to the split_pattern.
+    list<Segment> segments;
+    int segment_start = 0;
+    for (int i = 0; i < kOutputBufferLength - 1; ++i) {
+      if (split_pattern & (1 << i)) {
+        segments.push_back(
+            Segment(buffer + segment_start, i - segment_start + 1));
+        segment_start = i + 1;
+      }
+    }
+    segments.push_back(
+        Segment(buffer + segment_start, kOutputBufferLength - segment_start));
+
+    // Write exactly 10 bytes through the ByteSink.
+    string input_data = "0123456789";
+    for (int input_pattern = 0; input_pattern < (1 << (input_data.size() - 1));
+         input_pattern += kSkippedPatternCount) {
+      memset(buffer, 0, sizeof(buffer));
+      {
+        SegmentedZeroCopyOutputStream output_stream(segments);
+        internal::ZeroCopyStreamByteSink byte_sink(&output_stream);
+        int start = 0;
+        for (int j = 0; j < input_data.length() - 1; ++j) {
+          if (input_pattern & (1 << j)) {
+            byte_sink.Append(&input_data[start], j - start + 1);
+            start = j + 1;
+          }
+        }
+        byte_sink.Append(&input_data[start], input_data.length() - start);
+      }
+      EXPECT_EQ(input_data, string(buffer, input_data.length()));
+    }
+
+    // Write only 9 bytes through the ByteSink.
+    input_data = "012345678";
+    for (int input_pattern = 0; input_pattern < (1 << (input_data.size() - 1));
+         input_pattern += kSkippedPatternCount) {
+      memset(buffer, 0, sizeof(buffer));
+      {
+        SegmentedZeroCopyOutputStream output_stream(segments);
+        internal::ZeroCopyStreamByteSink byte_sink(&output_stream);
+        int start = 0;
+        for (int j = 0; j < input_data.length() - 1; ++j) {
+          if (input_pattern & (1 << j)) {
+            byte_sink.Append(&input_data[start], j - start + 1);
+            start = j + 1;
+          }
+        }
+        byte_sink.Append(&input_data[start], input_data.length() - start);
+      }
+      EXPECT_EQ(input_data, string(buffer, input_data.length()));
+      EXPECT_EQ(0, buffer[input_data.length()]);
+    }
+
+    // Write 11 bytes through the ByteSink. The extra byte will just
+    // be ignored.
+    input_data = "0123456789A";
+    for (int input_pattern = 0; input_pattern < (1 << (input_data.size() - 1));
+         input_pattern += kSkippedPatternCount) {
+      memset(buffer, 0, sizeof(buffer));
+      {
+        SegmentedZeroCopyOutputStream output_stream(segments);
+        internal::ZeroCopyStreamByteSink byte_sink(&output_stream);
+        int start = 0;
+        for (int j = 0; j < input_data.length() - 1; ++j) {
+          if (input_pattern & (1 << j)) {
+            byte_sink.Append(&input_data[start], j - start + 1);
+            start = j + 1;
+          }
+        }
+        byte_sink.Append(&input_data[start], input_data.length() - start);
+      }
+      EXPECT_EQ(input_data.substr(0, kOutputBufferLength),
+                string(buffer, kOutputBufferLength));
+    }
+  }
+}
+
+}  // namespace
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/message_differencer.cc b/src/google/protobuf/util/message_differencer.cc
new file mode 100644
index 0000000..5048563
--- /dev/null
+++ b/src/google/protobuf/util/message_differencer.cc
@@ -0,0 +1,1629 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Author: jschorr@google.com (Joseph Schorr)
+//  Based on original Protocol Buffers design by
+//  Sanjay Ghemawat, Jeff Dean, and others.
+//
+// This file defines static methods and classes for comparing Protocol
+// Messages (see //google/protobuf/util/message_differencer.h for more
+// information).
+
+#include <google/protobuf/util/message_differencer.h>
+
+#include <algorithm>
+#include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
+#include <utility>
+
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/stubs/stringprintf.h>
+#include <google/protobuf/any.h>
+#include <google/protobuf/io/printer.h>
+#include <google/protobuf/io/zero_copy_stream.h>
+#include <google/protobuf/io/zero_copy_stream_impl.h>
+#include <google/protobuf/dynamic_message.h>
+#include <google/protobuf/text_format.h>
+#include <google/protobuf/util/field_comparator.h>
+#include <google/protobuf/stubs/strutil.h>
+
+namespace google {
+namespace protobuf {
+
+namespace util {
+
+// When comparing a repeated field as map, MultipleFieldMapKeyComparator can
+// be used to specify multiple fields as key for key comparison.
+// Two elements of a repeated field will be regarded as having the same key
+// iff they have the same value for every specified key field.
+// Note that you can also specify only one field as key.
+class MessageDifferencer::MultipleFieldsMapKeyComparator
+    : public MessageDifferencer::MapKeyComparator {
+ public:
+  MultipleFieldsMapKeyComparator(
+      MessageDifferencer* message_differencer,
+      const vector<vector<const FieldDescriptor*> >& key_field_paths)
+        : message_differencer_(message_differencer),
+          key_field_paths_(key_field_paths) {
+    GOOGLE_CHECK(!key_field_paths_.empty());
+    for (int i = 0; i < key_field_paths_.size(); ++i) {
+      GOOGLE_CHECK(!key_field_paths_[i].empty());
+    }
+  }
+  MultipleFieldsMapKeyComparator(
+      MessageDifferencer* message_differencer,
+      const FieldDescriptor* key)
+        : message_differencer_(message_differencer) {
+    vector<const FieldDescriptor*> key_field_path;
+    key_field_path.push_back(key);
+    key_field_paths_.push_back(key_field_path);
+  }
+  bool IsMatch(
+      const Message& message1,
+      const Message& message2,
+      const vector<SpecificField>& parent_fields) const override {
+    for (int i = 0; i < key_field_paths_.size(); ++i) {
+      if (!IsMatchInternal(message1, message2, parent_fields,
+                           key_field_paths_[i], 0)) {
+        return false;
+      }
+    }
+    return true;
+  }
+ private:
+  bool IsMatchInternal(
+      const Message& message1,
+      const Message& message2,
+      const vector<SpecificField>& parent_fields,
+      const vector<const FieldDescriptor*>& key_field_path,
+      int path_index) const {
+    const FieldDescriptor* field = key_field_path[path_index];
+    vector<SpecificField> current_parent_fields(parent_fields);
+    if (path_index == key_field_path.size() - 1) {
+      if (field->is_repeated()) {
+        if (!message_differencer_->CompareRepeatedField(
+            message1, message2, field, &current_parent_fields)) {
+          return false;
+        }
+      } else {
+        if (!message_differencer_->CompareFieldValueUsingParentFields(
+            message1, message2, field, -1, -1, &current_parent_fields)) {
+          return false;
+        }
+      }
+      return true;
+    } else {
+      const Reflection* reflection1 = message1.GetReflection();
+      const Reflection* reflection2 = message2.GetReflection();
+      bool has_field1 = reflection1->HasField(message1, field);
+      bool has_field2 = reflection2->HasField(message2, field);
+      if (!has_field1 && !has_field2) {
+        return true;
+      }
+      if (has_field1 != has_field2) {
+        return false;
+      }
+      SpecificField specific_field;
+      specific_field.field = field;
+      current_parent_fields.push_back(specific_field);
+      return IsMatchInternal(
+          reflection1->GetMessage(message1, field),
+          reflection2->GetMessage(message2, field),
+          current_parent_fields,
+          key_field_path,
+          path_index + 1);
+    }
+  }
+  MessageDifferencer* message_differencer_;
+  vector<vector<const FieldDescriptor*> > key_field_paths_;
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(MultipleFieldsMapKeyComparator);
+};
+
+bool MessageDifferencer::Equals(const Message& message1,
+                                const Message& message2) {
+  MessageDifferencer differencer;
+
+  return differencer.Compare(message1, message2);
+}
+
+bool MessageDifferencer::Equivalent(const Message& message1,
+                                    const Message& message2) {
+  MessageDifferencer differencer;
+  differencer.set_message_field_comparison(MessageDifferencer::EQUIVALENT);
+
+  return differencer.Compare(message1, message2);
+}
+
+bool MessageDifferencer::ApproximatelyEquals(const Message& message1,
+                                             const Message& message2) {
+  MessageDifferencer differencer;
+  differencer.set_float_comparison(
+      MessageDifferencer::APPROXIMATE);
+
+  return differencer.Compare(message1, message2);
+}
+
+bool MessageDifferencer::ApproximatelyEquivalent(const Message& message1,
+                                                 const Message& message2) {
+  MessageDifferencer differencer;
+  differencer.set_message_field_comparison(MessageDifferencer::EQUIVALENT);
+  differencer.set_float_comparison(MessageDifferencer::APPROXIMATE);
+
+  return differencer.Compare(message1, message2);
+}
+
+// ===========================================================================
+
+MessageDifferencer::MessageDifferencer()
+    : reporter_(NULL),
+      field_comparator_(NULL),
+      message_field_comparison_(EQUAL),
+      scope_(FULL),
+      repeated_field_comparison_(AS_LIST),
+      report_matches_(false),
+      output_string_(NULL) { }
+
+MessageDifferencer::~MessageDifferencer() {
+  for (int i = 0; i < owned_key_comparators_.size(); ++i) {
+    delete owned_key_comparators_[i];
+  }
+  for (int i = 0; i < ignore_criteria_.size(); ++i) {
+    delete ignore_criteria_[i];
+  }
+}
+
+void MessageDifferencer::set_field_comparator(FieldComparator* comparator) {
+  GOOGLE_CHECK(comparator) << "Field comparator can't be NULL.";
+  field_comparator_ = comparator;
+}
+
+void MessageDifferencer::set_message_field_comparison(
+    MessageFieldComparison comparison) {
+  message_field_comparison_ = comparison;
+}
+
+void MessageDifferencer::set_scope(Scope scope) {
+  scope_ = scope;
+}
+
+MessageDifferencer::Scope MessageDifferencer::scope() {
+  return scope_;
+}
+
+void MessageDifferencer::set_float_comparison(FloatComparison comparison) {
+  default_field_comparator_.set_float_comparison(
+      comparison == EXACT ?
+      DefaultFieldComparator::EXACT : DefaultFieldComparator::APPROXIMATE);
+}
+
+void MessageDifferencer::set_repeated_field_comparison(
+    RepeatedFieldComparison comparison) {
+  repeated_field_comparison_ = comparison;
+}
+
+void MessageDifferencer::TreatAsSet(const FieldDescriptor* field) {
+  GOOGLE_CHECK(field->is_repeated()) << "Field must be repeated: "
+                               << field->full_name();
+  const MapKeyComparator* key_comparator = GetMapKeyComparator(field);
+  GOOGLE_CHECK(key_comparator == NULL)
+      << "Cannot treat this repeated field as both Map and Set for"
+      << " comparison.  Field name is: " << field->full_name();
+  set_fields_.insert(field);
+}
+
+void MessageDifferencer::TreatAsMap(const FieldDescriptor* field,
+                                    const FieldDescriptor* key) {
+  GOOGLE_CHECK(field->is_repeated()) << "Field must be repeated: "
+                               << field->full_name();
+  GOOGLE_CHECK_EQ(FieldDescriptor::CPPTYPE_MESSAGE, field->cpp_type())
+      << "Field has to be message type.  Field name is: "
+      << field->full_name();
+  GOOGLE_CHECK(key->containing_type() == field->message_type())
+      << key->full_name()
+      << " must be a direct subfield within the repeated field "
+      << field->full_name() << ", not " << key->containing_type()->full_name();
+  GOOGLE_CHECK(set_fields_.find(field) == set_fields_.end())
+      << "Cannot treat this repeated field as both Map and Set for "
+      << "comparison.";
+  MapKeyComparator* key_comparator =
+      new MultipleFieldsMapKeyComparator(this, key);
+  owned_key_comparators_.push_back(key_comparator);
+  map_field_key_comparator_[field] = key_comparator;
+}
+
+void MessageDifferencer::TreatAsMapWithMultipleFieldsAsKey(
+    const FieldDescriptor* field,
+    const vector<const FieldDescriptor*>& key_fields) {
+  vector<vector<const FieldDescriptor*> > key_field_paths;
+  for (int i = 0; i < key_fields.size(); ++i) {
+    vector<const FieldDescriptor*> key_field_path;
+    key_field_path.push_back(key_fields[i]);
+    key_field_paths.push_back(key_field_path);
+  }
+  TreatAsMapWithMultipleFieldPathsAsKey(field, key_field_paths);
+}
+
+void MessageDifferencer::TreatAsMapWithMultipleFieldPathsAsKey(
+    const FieldDescriptor* field,
+    const vector<vector<const FieldDescriptor*> >& key_field_paths) {
+  GOOGLE_CHECK(field->is_repeated()) << "Field must be repeated: "
+                              << field->full_name();
+  GOOGLE_CHECK_EQ(FieldDescriptor::CPPTYPE_MESSAGE, field->cpp_type())
+      << "Field has to be message type.  Field name is: "
+      << field->full_name();
+  for (int i = 0; i < key_field_paths.size(); ++i) {
+    const vector<const FieldDescriptor*>& key_field_path = key_field_paths[i];
+    for (int j = 0; j < key_field_path.size(); ++j) {
+      const FieldDescriptor* parent_field =
+          j == 0 ? field : key_field_path[j - 1];
+      const FieldDescriptor* child_field = key_field_path[j];
+      GOOGLE_CHECK(child_field->containing_type() == parent_field->message_type())
+          << child_field->full_name()
+          << " must be a direct subfield within the field: "
+          << parent_field->full_name();
+      if (j != 0) {
+        GOOGLE_CHECK_EQ(FieldDescriptor::CPPTYPE_MESSAGE, parent_field->cpp_type())
+            << parent_field->full_name() << " has to be of type message.";
+        GOOGLE_CHECK(!parent_field->is_repeated())
+            << parent_field->full_name() << " cannot be a repeated field.";
+      }
+    }
+  }
+  GOOGLE_CHECK(set_fields_.find(field) == set_fields_.end())
+      << "Cannot treat this repeated field as both Map and Set for "
+      << "comparison.";
+  MapKeyComparator* key_comparator =
+      new MultipleFieldsMapKeyComparator(this, key_field_paths);
+  owned_key_comparators_.push_back(key_comparator);
+  map_field_key_comparator_[field] = key_comparator;
+}
+
+void MessageDifferencer::TreatAsMapUsingKeyComparator(
+    const FieldDescriptor* field,
+    const MapKeyComparator* key_comparator) {
+  GOOGLE_CHECK(field->is_repeated()) << "Field must be repeated: "
+                               << field->full_name();
+  GOOGLE_CHECK_EQ(FieldDescriptor::CPPTYPE_MESSAGE, field->cpp_type())
+      << "Field has to be message type.  Field name is: "
+      << field->full_name();
+  GOOGLE_CHECK(set_fields_.find(field) == set_fields_.end())
+      << "Cannot treat this repeated field as both Map and Set for "
+      << "comparison.";
+  map_field_key_comparator_[field] = key_comparator;
+}
+
+void MessageDifferencer::AddIgnoreCriteria(IgnoreCriteria* ignore_criteria) {
+  ignore_criteria_.push_back(ignore_criteria);
+}
+
+void MessageDifferencer::IgnoreField(const FieldDescriptor* field) {
+  ignored_fields_.insert(field);
+}
+
+void MessageDifferencer::SetFractionAndMargin(const FieldDescriptor* field,
+                                              double fraction, double margin) {
+  default_field_comparator_.SetFractionAndMargin(field, fraction, margin);
+}
+
+void MessageDifferencer::ReportDifferencesToString(string* output) {
+  GOOGLE_DCHECK(output) << "Specified output string was NULL";
+
+  output_string_ = output;
+  output_string_->clear();
+}
+
+void MessageDifferencer::ReportDifferencesTo(Reporter* reporter) {
+  // If an output string is set, clear it to prevent
+  // it superceding the specified reporter.
+  if (output_string_) {
+    output_string_ = NULL;
+  }
+
+  reporter_ = reporter;
+}
+
+bool MessageDifferencer::FieldBefore(const FieldDescriptor* field1,
+                                     const FieldDescriptor* field2) {
+  // Handle sentinel values (i.e. make sure NULLs are always ordered
+  // at the end of the list).
+  if (field1 == NULL) {
+    return false;
+  }
+
+  if (field2 == NULL) {
+    return true;
+  }
+
+  // Always order fields by their tag number
+  return (field1->number() < field2->number());
+}
+
+bool MessageDifferencer::Compare(const Message& message1,
+                                 const Message& message2) {
+  vector<SpecificField> parent_fields;
+
+  bool result = false;
+
+  // Setup the internal reporter if need be.
+  if (output_string_) {
+    io::StringOutputStream output_stream(output_string_);
+    StreamReporter reporter(&output_stream);
+    reporter_ = &reporter;
+    result = Compare(message1, message2, &parent_fields);
+    reporter_ = NULL;
+  } else {
+    result = Compare(message1, message2, &parent_fields);
+  }
+
+  return result;
+}
+
+bool MessageDifferencer::CompareWithFields(
+    const Message& message1,
+    const Message& message2,
+    const vector<const FieldDescriptor*>& message1_fields_arg,
+    const vector<const FieldDescriptor*>& message2_fields_arg) {
+  if (message1.GetDescriptor() != message2.GetDescriptor()) {
+    GOOGLE_LOG(DFATAL) << "Comparison between two messages with different "
+                << "descriptors.";
+    return false;
+  }
+
+  vector<SpecificField> parent_fields;
+
+  bool result = false;
+
+  vector<const FieldDescriptor*> message1_fields(message1_fields_arg);
+  vector<const FieldDescriptor*> message2_fields(message2_fields_arg);
+
+  std::sort(message1_fields.begin(), message1_fields.end(), FieldBefore);
+  std::sort(message2_fields.begin(), message2_fields.end(), FieldBefore);
+  // Append NULL sentinel values.
+  message1_fields.push_back(NULL);
+  message2_fields.push_back(NULL);
+
+  // Setup the internal reporter if need be.
+  if (output_string_) {
+    io::StringOutputStream output_stream(output_string_);
+    StreamReporter reporter(&output_stream);
+    reporter_ = &reporter;
+    result = CompareRequestedFieldsUsingSettings(
+        message1, message2, message1_fields, message2_fields, &parent_fields);
+    reporter_ = NULL;
+  } else {
+    result = CompareRequestedFieldsUsingSettings(
+        message1, message2, message1_fields, message2_fields, &parent_fields);
+  }
+
+  return result;
+}
+
+bool MessageDifferencer::Compare(
+    const Message& message1,
+    const Message& message2,
+    vector<SpecificField>* parent_fields) {
+  const Descriptor* descriptor1 = message1.GetDescriptor();
+  const Descriptor* descriptor2 = message2.GetDescriptor();
+  if (descriptor1 != descriptor2) {
+    GOOGLE_LOG(DFATAL) << "Comparison between two messages with different "
+                << "descriptors.";
+    return false;
+  }
+  // Expand google.protobuf.Any payload if possible.
+  if (descriptor1->full_name() == internal::kAnyFullTypeName) {
+    google::protobuf::scoped_ptr<Message> data1;
+    google::protobuf::scoped_ptr<Message> data2;
+    if (UnpackAny(message1, &data1) && UnpackAny(message2, &data2)) {
+      return Compare(*data1, *data2, parent_fields);
+    }
+  }
+  const Reflection* reflection1 = message1.GetReflection();
+  const Reflection* reflection2 = message2.GetReflection();
+
+  // Retrieve all the set fields, including extensions.
+  vector<const FieldDescriptor*> message1_fields;
+  vector<const FieldDescriptor*> message2_fields;
+
+  reflection1->ListFields(message1, &message1_fields);
+  reflection2->ListFields(message2, &message2_fields);
+
+  // Add sentinel values to deal with the
+  // case where the number of the fields in
+  // each list are different.
+  message1_fields.push_back(NULL);
+  message2_fields.push_back(NULL);
+
+  bool unknown_compare_result = true;
+  // Ignore unknown fields in EQUIVALENT mode
+  if (message_field_comparison_ != EQUIVALENT) {
+    const google::protobuf::UnknownFieldSet* unknown_field_set1 =
+        &reflection1->GetUnknownFields(message1);
+    const google::protobuf::UnknownFieldSet* unknown_field_set2 =
+        &reflection2->GetUnknownFields(message2);
+    if (!CompareUnknownFields(message1, message2,
+                              *unknown_field_set1, *unknown_field_set2,
+                              parent_fields)) {
+      if (reporter_ == NULL) {
+        return false;
+      };
+      unknown_compare_result = false;
+    }
+  }
+
+  return CompareRequestedFieldsUsingSettings(
+      message1, message2,
+      message1_fields, message2_fields,
+      parent_fields) && unknown_compare_result;
+}
+
+bool MessageDifferencer::CompareRequestedFieldsUsingSettings(
+    const Message& message1,
+    const Message& message2,
+    const vector<const FieldDescriptor*>& message1_fields,
+    const vector<const FieldDescriptor*>& message2_fields,
+    vector<SpecificField>* parent_fields) {
+  if (scope_ == FULL) {
+    if (message_field_comparison_ == EQUIVALENT) {
+      // We need to merge the field lists of both messages (i.e.
+      // we are merely checking for a difference in field values,
+      // rather than the addition or deletion of fields).
+      vector<const FieldDescriptor*> fields_union;
+      CombineFields(message1_fields, FULL, message2_fields, FULL,
+                    &fields_union);
+      return CompareWithFieldsInternal(message1, message2, fields_union,
+                                       fields_union, parent_fields);
+    } else {
+      // Simple equality comparison, use the unaltered field lists.
+      return CompareWithFieldsInternal(message1, message2, message1_fields,
+                                       message2_fields, parent_fields);
+    }
+  } else {
+    if (message_field_comparison_ == EQUIVALENT) {
+      // We use the list of fields for message1 for both messages when
+      // comparing.  This way, extra fields in message2 are ignored,
+      // and missing fields in message2 use their default value.
+      return CompareWithFieldsInternal(message1, message2, message1_fields,
+                                       message1_fields, parent_fields);
+    } else {
+      // We need to consider the full list of fields for message1
+      // but only the intersection for message2.  This way, any fields
+      // only present in message2 will be ignored, but any fields only
+      // present in message1 will be marked as a difference.
+      vector<const FieldDescriptor*> fields_intersection;
+      CombineFields(message1_fields, PARTIAL, message2_fields, PARTIAL,
+                    &fields_intersection);
+      return CompareWithFieldsInternal(message1, message2, message1_fields,
+                                       fields_intersection, parent_fields);
+    }
+  }
+}
+
+void MessageDifferencer::CombineFields(
+    const vector<const FieldDescriptor*>& fields1,
+    Scope fields1_scope,
+    const vector<const FieldDescriptor*>& fields2,
+    Scope fields2_scope,
+    vector<const FieldDescriptor*>* combined_fields) {
+
+  int index1 = 0;
+  int index2 = 0;
+
+  while (index1 < fields1.size() && index2 < fields2.size()) {
+    const FieldDescriptor* field1 = fields1[index1];
+    const FieldDescriptor* field2 = fields2[index2];
+
+    if (FieldBefore(field1, field2)) {
+      if (fields1_scope == FULL) {
+        combined_fields->push_back(fields1[index1]);
+      }
+      ++index1;
+    } else if (FieldBefore(field2, field1)) {
+      if (fields2_scope == FULL) {
+        combined_fields->push_back(fields2[index2]);
+      }
+      ++index2;
+    } else {
+      combined_fields->push_back(fields1[index1]);
+      ++index1;
+      ++index2;
+    }
+  }
+}
+
+bool MessageDifferencer::CompareWithFieldsInternal(
+    const Message& message1,
+    const Message& message2,
+    const vector<const FieldDescriptor*>& message1_fields,
+    const vector<const FieldDescriptor*>& message2_fields,
+    vector<SpecificField>* parent_fields) {
+  bool isDifferent = false;
+  int field_index1 = 0;
+  int field_index2 = 0;
+
+  const Reflection* reflection1 = message1.GetReflection();
+  const Reflection* reflection2 = message2.GetReflection();
+
+  while (true) {
+    const FieldDescriptor* field1 = message1_fields[field_index1];
+    const FieldDescriptor* field2 = message2_fields[field_index2];
+
+    // Once we have reached sentinel values, we are done the comparison.
+    if (field1 == NULL && field2 == NULL) {
+      break;
+    }
+
+    // Check for differences in the field itself.
+    if (FieldBefore(field1, field2)) {
+      // Field 1 is not in the field list for message 2.
+      if (IsIgnored(message1, message2, field1, *parent_fields)) {
+        // We are ignoring field1. Report the ignore and move on to
+        // the next field in message1_fields.
+        if (reporter_ != NULL) {
+          SpecificField specific_field;
+          specific_field.field = field1;
+
+          parent_fields->push_back(specific_field);
+          reporter_->ReportIgnored(message1, message2, *parent_fields);
+          parent_fields->pop_back();
+        }
+        ++field_index1;
+        continue;
+      }
+
+      if (reporter_ != NULL) {
+        int count = field1->is_repeated() ?
+            reflection1->FieldSize(message1, field1) : 1;
+
+        for (int i = 0; i < count; ++i) {
+          SpecificField specific_field;
+          specific_field.field = field1;
+          specific_field.index = field1->is_repeated() ? i : -1;
+
+          parent_fields->push_back(specific_field);
+          reporter_->ReportDeleted(message1, message2, *parent_fields);
+          parent_fields->pop_back();
+        }
+
+        isDifferent = true;
+      } else {
+        return false;
+      }
+
+      ++field_index1;
+      continue;
+    } else if (FieldBefore(field2, field1)) {
+      // Field 2 is not in the field list for message 1.
+      if (IsIgnored(message1, message2, field2, *parent_fields)) {
+        // We are ignoring field2. Report the ignore and move on to
+        // the next field in message2_fields.
+        if (reporter_ != NULL) {
+          SpecificField specific_field;
+          specific_field.field = field2;
+
+          parent_fields->push_back(specific_field);
+          reporter_->ReportIgnored(message1, message2, *parent_fields);
+          parent_fields->pop_back();
+        }
+        ++field_index2;
+        continue;
+      }
+
+      if (reporter_ != NULL) {
+        int count = field2->is_repeated() ?
+            reflection2->FieldSize(message2, field2) : 1;
+
+        for (int i = 0; i < count; ++i) {
+          SpecificField specific_field;
+          specific_field.field = field2;
+          specific_field.index = field2->is_repeated() ? i : -1;
+          specific_field.new_index = specific_field.index;
+
+          parent_fields->push_back(specific_field);
+          reporter_->ReportAdded(message1, message2, *parent_fields);
+          parent_fields->pop_back();
+        }
+
+        isDifferent = true;
+      } else {
+        return false;
+      }
+
+      ++field_index2;
+      continue;
+    }
+
+    // By this point, field1 and field2 are guarenteed to point to the same
+    // field, so we can now compare the values.
+    if (IsIgnored(message1, message2, field1, *parent_fields)) {
+      // Ignore this field. Report and move on.
+      if (reporter_ != NULL) {
+        SpecificField specific_field;
+        specific_field.field = field1;
+
+        parent_fields->push_back(specific_field);
+        reporter_->ReportIgnored(message1, message2, *parent_fields);
+        parent_fields->pop_back();
+      }
+
+      ++field_index1;
+      ++field_index2;
+      continue;
+    }
+
+    bool fieldDifferent = false;
+    if (field1->is_repeated()) {
+      fieldDifferent = !CompareRepeatedField(message1, message2, field1,
+                                             parent_fields);
+      if (fieldDifferent) {
+        if (reporter_ == NULL) return false;
+        isDifferent = true;
+      }
+    } else {
+      fieldDifferent = !CompareFieldValueUsingParentFields(
+          message1, message2, field1, -1, -1, parent_fields);
+
+      // If we have found differences, either report them or terminate if
+      // no reporter is present.
+      if (fieldDifferent && reporter_ == NULL) {
+        return false;
+      }
+
+      if (reporter_ != NULL) {
+        SpecificField specific_field;
+        specific_field.field = field1;
+        parent_fields->push_back(specific_field);
+        if (fieldDifferent) {
+          reporter_->ReportModified(message1, message2, *parent_fields);
+          isDifferent = true;
+        } else if (report_matches_) {
+          reporter_->ReportMatched(message1, message2, *parent_fields);
+        }
+        parent_fields->pop_back();
+      }
+    }
+    // Increment the field indicies.
+    ++field_index1;
+    ++field_index2;
+  }
+
+  return !isDifferent;
+}
+
+bool MessageDifferencer::IsMatch(const FieldDescriptor* repeated_field,
+                                 const MapKeyComparator* key_comparator,
+                                 const Message* message1,
+                                 const Message* message2,
+                                 const vector<SpecificField>& parent_fields,
+                                 int index1, int index2) {
+  vector<SpecificField> current_parent_fields(parent_fields);
+  if (repeated_field->cpp_type() != FieldDescriptor::CPPTYPE_MESSAGE) {
+    return CompareFieldValueUsingParentFields(
+        *message1, *message2, repeated_field, index1, index2,
+        &current_parent_fields);
+  }
+  // Back up the Reporter and output_string_.  They will be reset in the
+  // following code.
+  Reporter* backup_reporter = reporter_;
+  string* output_string = output_string_;
+  reporter_ = NULL;
+  output_string_ = NULL;
+  bool match;
+
+  if (key_comparator == NULL) {
+    match = CompareFieldValueUsingParentFields(
+        *message1, *message2, repeated_field, index1, index2,
+        &current_parent_fields);
+  } else {
+    const Reflection* reflection1 = message1->GetReflection();
+    const Reflection* reflection2 = message2->GetReflection();
+    const Message& m1 =
+        reflection1->GetRepeatedMessage(*message1, repeated_field, index1);
+    const Message& m2 =
+        reflection2->GetRepeatedMessage(*message2, repeated_field, index2);
+    SpecificField specific_field;
+    specific_field.field = repeated_field;
+    current_parent_fields.push_back(specific_field);
+    match = key_comparator->IsMatch(m1, m2, current_parent_fields);
+  }
+
+  reporter_ = backup_reporter;
+  output_string_ = output_string;
+  return match;
+}
+
+bool MessageDifferencer::CompareRepeatedField(
+    const Message& message1,
+    const Message& message2,
+    const FieldDescriptor* repeated_field,
+    vector<SpecificField>* parent_fields) {
+  // the input FieldDescriptor is guaranteed to be repeated field.
+  const Reflection* reflection1 = message1.GetReflection();
+  const Reflection* reflection2 = message2.GetReflection();
+  const int count1 = reflection1->FieldSize(message1, repeated_field);
+  const int count2 = reflection2->FieldSize(message2, repeated_field);
+  const bool treated_as_subset = IsTreatedAsSubset(repeated_field);
+
+  // If the field is not treated as subset and no detailed reports is needed,
+  // we do a quick check on the number of the elements to avoid unnecessary
+  // comparison.
+  if (count1 != count2 && reporter_ == NULL && !treated_as_subset) {
+    return false;
+  }
+  // A match can never be found if message1 has more items than message2.
+  if (count1 > count2 && reporter_ == NULL) {
+    return false;
+  }
+
+  // These two list are used for store the index of the correspondent
+  // element in peer repeated field.
+  vector<int> match_list1;
+  vector<int> match_list2;
+
+  // Try to match indices of the repeated fields. Return false if match fails
+  // and there's no detailed report needed.
+  if (!MatchRepeatedFieldIndices(message1, message2, repeated_field,
+                                 *parent_fields, &match_list1, &match_list2) &&
+      reporter_ == NULL) {
+    return false;
+  }
+
+  bool fieldDifferent = false;
+  SpecificField specific_field;
+  specific_field.field = repeated_field;
+
+  // At this point, we have already matched pairs of fields (with the reporting
+  // to be done later). Now to check if the paired elements are different.
+  for (int i = 0; i < count1; i++) {
+    if (match_list1[i] == -1) continue;
+    specific_field.index = i;
+    specific_field.new_index = match_list1[i];
+
+    const bool result = CompareFieldValueUsingParentFields(
+        message1, message2, repeated_field, i, specific_field.new_index,
+        parent_fields);
+
+    // If we have found differences, either report them or terminate if
+    // no reporter is present. Note that ReportModified, ReportMoved, and
+    // ReportMatched are all mutually exclusive.
+    if (!result) {
+      if (reporter_ == NULL) return false;
+      parent_fields->push_back(specific_field);
+      reporter_->ReportModified(message1, message2, *parent_fields);
+      parent_fields->pop_back();
+      fieldDifferent = true;
+    } else if (reporter_ != NULL &&
+               specific_field.index != specific_field.new_index) {
+      parent_fields->push_back(specific_field);
+      reporter_->ReportMoved(message1, message2, *parent_fields);
+      parent_fields->pop_back();
+    } else if (report_matches_ && reporter_ != NULL) {
+      parent_fields->push_back(specific_field);
+      reporter_->ReportMatched(message1, message2, *parent_fields);
+      parent_fields->pop_back();
+    }
+  }
+
+  // Report any remaining additions or deletions.
+  for (int i = 0; i < count2; ++i) {
+    if (match_list2[i] != -1) continue;
+    if (!treated_as_subset) {
+      fieldDifferent = true;
+    }
+
+    if (reporter_ == NULL) continue;
+    specific_field.index = i;
+    specific_field.new_index = i;
+    parent_fields->push_back(specific_field);
+    reporter_->ReportAdded(message1, message2, *parent_fields);
+    parent_fields->pop_back();
+  }
+
+  for (int i = 0; i < count1; ++i) {
+    if (match_list1[i] != -1) continue;
+    specific_field.index = i;
+    parent_fields->push_back(specific_field);
+    reporter_->ReportDeleted(message1, message2, *parent_fields);
+    parent_fields->pop_back();
+    fieldDifferent = true;
+  }
+  return !fieldDifferent;
+}
+
+bool MessageDifferencer::CompareFieldValue(const Message& message1,
+                                           const Message& message2,
+                                           const FieldDescriptor* field,
+                                           int index1,
+                                           int index2) {
+  return CompareFieldValueUsingParentFields(message1, message2, field, index1,
+                                            index2, NULL);
+}
+
+bool MessageDifferencer::CompareFieldValueUsingParentFields(
+    const Message& message1, const Message& message2,
+    const FieldDescriptor* field, int index1, int index2,
+    vector<SpecificField>* parent_fields) {
+  FieldContext field_context(parent_fields);
+  FieldComparator::ComparisonResult result = GetFieldComparisonResult(
+      message1, message2, field, index1, index2, &field_context);
+
+  if (field->cpp_type() == FieldDescriptor::CPPTYPE_MESSAGE &&
+      result == FieldComparator::RECURSE) {
+    // Get the nested messages and compare them using one of the Compare
+    // methods.
+    const Reflection* reflection1 = message1.GetReflection();
+    const Reflection* reflection2 = message2.GetReflection();
+    const Message& m1 = field->is_repeated() ?
+        reflection1->GetRepeatedMessage(message1, field, index1) :
+        reflection1->GetMessage(message1, field);
+    const Message& m2 = field->is_repeated() ?
+        reflection2->GetRepeatedMessage(message2, field, index2) :
+        reflection2->GetMessage(message2, field);
+
+    // parent_fields is used in calls to Reporter methods.
+    if (parent_fields != NULL) {
+      // Append currently compared field to the end of parent_fields.
+      SpecificField specific_field;
+      specific_field.field = field;
+      specific_field.index = index1;
+      specific_field.new_index = index2;
+      parent_fields->push_back(specific_field);
+      const bool compare_result = Compare(m1, m2, parent_fields);
+      parent_fields->pop_back();
+      return compare_result;
+    } else {
+      // Recreates parent_fields as if m1 and m2 had no parents.
+      return Compare(m1, m2);
+    }
+  } else {
+    return (result == FieldComparator::SAME);
+  }
+}
+
+bool MessageDifferencer::CheckPathChanged(
+    const vector<SpecificField>& field_path) {
+  for (int i = 0; i < field_path.size(); ++i) {
+    if (field_path[i].index != field_path[i].new_index) return true;
+  }
+  return false;
+}
+
+bool MessageDifferencer::IsTreatedAsSet(const FieldDescriptor* field) {
+  if (!field->is_repeated()) return false;
+  if (field->is_map()) return true;
+  if (repeated_field_comparison_ == AS_SET) return true;
+  return (set_fields_.find(field) != set_fields_.end());
+}
+
+bool MessageDifferencer::IsTreatedAsSubset(const FieldDescriptor* field) {
+  return scope_ == PARTIAL &&
+      (IsTreatedAsSet(field) || GetMapKeyComparator(field) != NULL);
+}
+
+bool MessageDifferencer::IsIgnored(
+    const Message& message1,
+    const Message& message2,
+    const FieldDescriptor* field,
+    const vector<SpecificField>& parent_fields) {
+  if (ignored_fields_.find(field) != ignored_fields_.end()) {
+    return true;
+  }
+  for (int i = 0; i < ignore_criteria_.size(); ++i) {
+    if (ignore_criteria_[i]->IsIgnored(message1, message2, field,
+                                       parent_fields)) {
+      return true;
+    }
+  }
+  return false;
+}
+
+const MessageDifferencer::MapKeyComparator* MessageDifferencer
+    ::GetMapKeyComparator(const FieldDescriptor* field) {
+  if (!field->is_repeated()) return NULL;
+  if (map_field_key_comparator_.find(field) !=
+      map_field_key_comparator_.end()) {
+    return map_field_key_comparator_[field];
+  }
+  return NULL;
+}
+
+namespace {
+
+typedef pair<int, const UnknownField*> IndexUnknownFieldPair;
+
+struct UnknownFieldOrdering {
+  inline bool operator()(const IndexUnknownFieldPair& a,
+                         const IndexUnknownFieldPair& b) const {
+    if (a.second->number() < b.second->number()) return true;
+    if (a.second->number() > b.second->number()) return false;
+    return a.second->type() < b.second->type();
+  }
+};
+
+}  // namespace
+
+bool MessageDifferencer::UnpackAny(const Message& any,
+                                   google::protobuf::scoped_ptr<Message>* data) {
+  const Reflection* reflection = any.GetReflection();
+  const FieldDescriptor* type_url_field;
+  const FieldDescriptor* value_field;
+  if (!internal::GetAnyFieldDescriptors(any, &type_url_field, &value_field)) {
+    return false;
+  }
+  const string& type_url = reflection->GetString(any, type_url_field);
+  string full_type_name;
+  if (!internal::ParseAnyTypeUrl(type_url, &full_type_name)) {
+    return false;
+  }
+
+  const google::protobuf::Descriptor* desc =
+      any.GetDescriptor()->file()->pool()->FindMessageTypeByName(
+          full_type_name);
+  if (desc == NULL) {
+    GOOGLE_LOG(ERROR) << "Proto type '" << full_type_name << "' not found";
+    return false;
+  }
+
+  if (dynamic_message_factory_ == NULL) {
+    dynamic_message_factory_.reset(new DynamicMessageFactory());
+  }
+  data->reset(dynamic_message_factory_->GetPrototype(desc)->New());
+  string serialized_value = reflection->GetString(any, value_field);
+  if (!(*data)->ParseFromString(serialized_value)) {
+    GOOGLE_LOG(ERROR) << "Failed to parse value for " << full_type_name;
+    return false;
+  }
+  return true;
+}
+
+bool MessageDifferencer::CompareUnknownFields(
+    const Message& message1, const Message& message2,
+    const google::protobuf::UnknownFieldSet& unknown_field_set1,
+    const google::protobuf::UnknownFieldSet& unknown_field_set2,
+    vector<SpecificField>* parent_field) {
+  // Ignore unknown fields in EQUIVALENT mode.
+  if (message_field_comparison_ == EQUIVALENT) return true;
+
+  if (unknown_field_set1.empty() && unknown_field_set2.empty()) {
+    return true;
+  }
+
+  bool is_different = false;
+
+  // We first sort the unknown fields by field number and type (in other words,
+  // in tag order), making sure to preserve ordering of values with the same
+  // tag.  This allows us to report only meaningful differences between the
+  // two sets -- that is, differing values for the same tag.  We use
+  // IndexUnknownFieldPairs to keep track of the field's original index for
+  // reporting purposes.
+  vector<IndexUnknownFieldPair> fields1;  // unknown_field_set1, sorted
+  vector<IndexUnknownFieldPair> fields2;  // unknown_field_set2, sorted
+  fields1.reserve(unknown_field_set1.field_count());
+  fields2.reserve(unknown_field_set2.field_count());
+
+  for (int i = 0; i < unknown_field_set1.field_count(); i++) {
+    fields1.push_back(std::make_pair(i, &unknown_field_set1.field(i)));
+  }
+  for (int i = 0; i < unknown_field_set2.field_count(); i++) {
+    fields2.push_back(std::make_pair(i, &unknown_field_set2.field(i)));
+  }
+
+  UnknownFieldOrdering is_before;
+  std::stable_sort(fields1.begin(), fields1.end(), is_before);
+  std::stable_sort(fields2.begin(), fields2.end(), is_before);
+
+  // In order to fill in SpecificField::index, we have to keep track of how
+  // many values we've seen with the same field number and type.
+  // current_repeated points at the first field in this range, and
+  // current_repeated_start{1,2} are the indexes of the first field in the
+  // range within fields1 and fields2.
+  const UnknownField* current_repeated = NULL;
+  int current_repeated_start1 = 0;
+  int current_repeated_start2 = 0;
+
+  // Now that we have two sorted lists, we can detect fields which appear only
+  // in one list or the other by traversing them simultaneously.
+  int index1 = 0;
+  int index2 = 0;
+  while (index1 < fields1.size() || index2 < fields2.size()) {
+    enum { ADDITION, DELETION, MODIFICATION, COMPARE_GROUPS,
+      NO_CHANGE } change_type;
+
+    // focus_field is the field we're currently reporting on.  (In the case
+    // of a modification, it's the field on the left side.)
+    const UnknownField* focus_field;
+    bool match = false;
+
+    if (index2 == fields2.size() ||
+        (index1 < fields1.size() &&
+          is_before(fields1[index1], fields2[index2]))) {
+      // fields1[index1] is not present in fields2.
+      change_type = DELETION;
+      focus_field = fields1[index1].second;
+    } else if (index1 == fields1.size() ||
+               is_before(fields2[index2], fields1[index1])) {
+      // fields2[index2] is not present in fields1.
+      if (scope_ == PARTIAL) {
+        // Ignore.
+        ++index2;
+        continue;
+      }
+      change_type = ADDITION;
+      focus_field = fields2[index2].second;
+    } else {
+      // Field type and number are the same.  See if the values differ.
+      change_type = MODIFICATION;
+      focus_field = fields1[index1].second;
+
+      switch (focus_field->type()) {
+        case UnknownField::TYPE_VARINT:
+          match = fields1[index1].second->varint() ==
+                  fields2[index2].second->varint();
+          break;
+        case UnknownField::TYPE_FIXED32:
+          match = fields1[index1].second->fixed32() ==
+                  fields2[index2].second->fixed32();
+          break;
+        case UnknownField::TYPE_FIXED64:
+          match = fields1[index1].second->fixed64() ==
+                  fields2[index2].second->fixed64();
+          break;
+        case UnknownField::TYPE_LENGTH_DELIMITED:
+          match = fields1[index1].second->length_delimited() ==
+                  fields2[index2].second->length_delimited();
+          break;
+        case UnknownField::TYPE_GROUP:
+          // We must deal with this later, after building the SpecificField.
+          change_type = COMPARE_GROUPS;
+          break;
+      }
+      if (match && change_type != COMPARE_GROUPS) {
+        change_type = NO_CHANGE;
+      }
+    }
+
+    if (current_repeated == NULL ||
+        focus_field->number() != current_repeated->number() ||
+        focus_field->type() != current_repeated->type()) {
+      // We've started a new repeated field.
+      current_repeated = focus_field;
+      current_repeated_start1 = index1;
+      current_repeated_start2 = index2;
+    }
+
+    if (change_type == NO_CHANGE && reporter_ == NULL) {
+      // Fields were already compared and matched and we have no reporter.
+      ++index1;
+      ++index2;
+      continue;
+    }
+
+    if (change_type == ADDITION || change_type == DELETION ||
+        change_type == MODIFICATION) {
+      if (reporter_ == NULL) {
+        // We found a difference and we have no reproter.
+        return false;
+      }
+      is_different = true;
+    }
+
+    // Build the SpecificField.  This is slightly complicated.
+    SpecificField specific_field;
+    specific_field.unknown_field_number = focus_field->number();
+    specific_field.unknown_field_type = focus_field->type();
+
+    specific_field.unknown_field_set1 = &unknown_field_set1;
+    specific_field.unknown_field_set2 = &unknown_field_set2;
+
+    if (change_type != ADDITION) {
+      specific_field.unknown_field_index1 = fields1[index1].first;
+    }
+    if (change_type != DELETION) {
+      specific_field.unknown_field_index2 = fields2[index2].first;
+    }
+
+    // Calculate the field index.
+    if (change_type == ADDITION) {
+      specific_field.index = index2 - current_repeated_start2;
+      specific_field.new_index = index2 - current_repeated_start2;
+    } else {
+      specific_field.index = index1 - current_repeated_start1;
+      specific_field.new_index = index2 - current_repeated_start2;
+    }
+
+    parent_field->push_back(specific_field);
+
+    switch (change_type) {
+      case ADDITION:
+        reporter_->ReportAdded(message1, message2, *parent_field);
+        ++index2;
+        break;
+      case DELETION:
+        reporter_->ReportDeleted(message1, message2, *parent_field);
+        ++index1;
+        break;
+      case MODIFICATION:
+        reporter_->ReportModified(message1, message2, *parent_field);
+        ++index1;
+        ++index2;
+        break;
+      case COMPARE_GROUPS:
+        if (!CompareUnknownFields(message1, message2,
+                                  fields1[index1].second->group(),
+                                  fields2[index2].second->group(),
+                                  parent_field)) {
+          if (reporter_ == NULL) return false;
+          is_different = true;
+          reporter_->ReportModified(message1, message2, *parent_field);
+        }
+        ++index1;
+        ++index2;
+        break;
+      case NO_CHANGE:
+        ++index1;
+        ++index2;
+        if (report_matches_) {
+          reporter_->ReportMatched(message1, message2, *parent_field);
+        }
+    }
+
+    parent_field->pop_back();
+  }
+
+  return !is_different;
+}
+
+namespace {
+
+// Find maximum bipartite matching using the argumenting path algorithm.
+class MaximumMatcher {
+ public:
+  typedef ResultCallback2<bool, int, int> NodeMatchCallback;
+  // MaximumMatcher takes ownership of the passed in callback and uses it to
+  // determine whether a node on the left side of the bipartial graph matches
+  // a node on the right side. count1 is the number of nodes on the left side
+  // of the graph and count2 to is the number of nodes on the right side.
+  // Every node is referred to using 0-based indices.
+  // If a maximum match is found, the result will be stored in match_list1 and
+  // match_list2. match_list1[i] == j means the i-th node on the left side is
+  // matched to the j-th node on the right side and match_list2[x] == y means
+  // the x-th node on the right side is matched to y-th node on the left side.
+  // match_list1[i] == -1 means the node is not matched. Same with match_list2.
+  MaximumMatcher(int count1, int count2, NodeMatchCallback* callback,
+                 vector<int>* match_list1, vector<int>* match_list2);
+  // Find a maximum match and return the number of matched node pairs.
+  // If early_return is true, this method will return 0 immediately when it
+  // finds that not all nodes on the left side can be matched.
+  int FindMaximumMatch(bool early_return);
+ private:
+  // Determines whether the node on the left side of the bipartial graph
+  // matches the one on the right side.
+  bool Match(int left, int right);
+  // Find an argumenting path starting from the node v on the left side. If a
+  // path can be found, update match_list2_ to reflect the path and return
+  // true.
+  bool FindArgumentPathDFS(int v, vector<bool>* visited);
+
+  int count1_;
+  int count2_;
+  google::protobuf::scoped_ptr<NodeMatchCallback> match_callback_;
+  map<pair<int, int>, bool> cached_match_results_;
+  vector<int>* match_list1_;
+  vector<int>* match_list2_;
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(MaximumMatcher);
+};
+
+MaximumMatcher::MaximumMatcher(int count1, int count2,
+                               NodeMatchCallback* callback,
+                               vector<int>* match_list1,
+                               vector<int>* match_list2)
+    : count1_(count1), count2_(count2), match_callback_(callback),
+      match_list1_(match_list1), match_list2_(match_list2) {
+  match_list1_->assign(count1, -1);
+  match_list2_->assign(count2, -1);
+}
+
+int MaximumMatcher::FindMaximumMatch(bool early_return) {
+  int result = 0;
+  for (int i = 0; i < count1_; ++i) {
+    vector<bool> visited(count1_);
+    if (FindArgumentPathDFS(i, &visited)) {
+      ++result;
+    } else if (early_return) {
+      return 0;
+    }
+  }
+  // Backfill match_list1_ as we only filled match_list2_ when finding
+  // argumenting pathes.
+  for (int i = 0; i < count2_; ++i) {
+    if ((*match_list2_)[i] != -1) {
+      (*match_list1_)[(*match_list2_)[i]] = i;
+    }
+  }
+  return result;
+}
+
+bool MaximumMatcher::Match(int left, int right) {
+  pair<int, int> p(left, right);
+  map<pair<int, int>, bool>::iterator it = cached_match_results_.find(p);
+  if (it != cached_match_results_.end()) {
+    return it->second;
+  }
+  cached_match_results_[p] = match_callback_->Run(left, right);
+  return cached_match_results_[p];
+}
+
+bool MaximumMatcher::FindArgumentPathDFS(int v, vector<bool>* visited) {
+  (*visited)[v] = true;
+  // We try to match those un-matched nodes on the right side first. This is
+  // the step that the navie greedy matching algorithm uses. In the best cases
+  // where the greedy algorithm can find a maximum matching, we will always
+  // find a match in this step and the performance will be identical to the
+  // greedy algorithm.
+  for (int i = 0; i < count2_; ++i) {
+    int matched = (*match_list2_)[i];
+    if (matched == -1 && Match(v, i)) {
+      (*match_list2_)[i] = v;
+      return true;
+    }
+  }
+  // Then we try those already matched nodes and see if we can find an
+  // alternaive match for the node matched to them.
+  // The greedy algorithm will stop before this and fail to produce the
+  // correct result.
+  for (int i = 0; i < count2_; ++i) {
+    int matched = (*match_list2_)[i];
+    if (matched != -1 && Match(v, i)) {
+      if (!(*visited)[matched] && FindArgumentPathDFS(matched, visited)) {
+        (*match_list2_)[i] = v;
+        return true;
+      }
+    }
+  }
+  return false;
+}
+
+}  // namespace
+
+bool MessageDifferencer::MatchRepeatedFieldIndices(
+    const Message& message1,
+    const Message& message2,
+    const FieldDescriptor* repeated_field,
+    const vector<SpecificField>& parent_fields,
+    vector<int>* match_list1,
+    vector<int>* match_list2) {
+  const int count1 =
+      message1.GetReflection()->FieldSize(message1, repeated_field);
+  const int count2 =
+      message2.GetReflection()->FieldSize(message2, repeated_field);
+  const MapKeyComparator* key_comparator = GetMapKeyComparator(repeated_field);
+
+  match_list1->assign(count1, -1);
+  match_list2->assign(count2, -1);
+
+  SpecificField specific_field;
+  specific_field.field = repeated_field;
+
+  bool success = true;
+  // Find potential match if this is a special repeated field.
+  if (key_comparator != NULL || IsTreatedAsSet(repeated_field)) {
+    if (scope_ == PARTIAL) {
+      // When partial matching is enabled, Compare(a, b) && Compare(a, c)
+      // doesn't neccessarily imply Compare(b, c). Therefore a naive greedy
+      // algorithm will fail to find a maximum matching.
+      // Here we use the argumenting path algorithm.
+      MaximumMatcher::NodeMatchCallback* callback = NewPermanentCallback(
+          this, &MessageDifferencer::IsMatch, repeated_field, key_comparator,
+          &message1, &message2, parent_fields);
+      MaximumMatcher matcher(count1, count2, callback, match_list1,
+                             match_list2);
+      // If diff info is not needed, we should end the matching process as
+      // soon as possible if not all items can be matched.
+      bool early_return = (reporter_ == NULL);
+      int match_count = matcher.FindMaximumMatch(early_return);
+      if (match_count != count1 && reporter_ == NULL) return false;
+      success = success && (match_count == count1);
+    } else {
+      for (int i = 0; i < count1; ++i) {
+        // Indicates any matched elements for this repeated field.
+        bool match = false;
+
+        specific_field.index = i;
+        specific_field.new_index = i;
+
+        for (int j = 0; j < count2; j++) {
+          if (match_list2->at(j) != -1) continue;
+          specific_field.index = i;
+          specific_field.new_index = j;
+
+          match = IsMatch(repeated_field, key_comparator,
+                          &message1, &message2, parent_fields, i, j);
+
+          if (match) {
+            match_list1->at(specific_field.index) = specific_field.new_index;
+            match_list2->at(specific_field.new_index) = specific_field.index;
+            break;
+          }
+        }
+        if (!match && reporter_ == NULL) return false;
+        success = success && match;
+      }
+    }
+  } else {
+    // If this field should be treated as list, just label the match_list.
+    for (int i = 0; i < count1 && i < count2; i++) {
+      match_list1->at(i) = i;
+      match_list2->at(i) = i;
+    }
+  }
+
+  return success;
+}
+
+FieldComparator::ComparisonResult MessageDifferencer::GetFieldComparisonResult(
+    const Message& message1, const Message& message2,
+    const FieldDescriptor* field, int index1, int index2,
+    const FieldContext* field_context) {
+  FieldComparator* comparator = field_comparator_ != NULL ?
+      field_comparator_ : &default_field_comparator_;
+  return comparator->Compare(message1, message2, field,
+                             index1, index2, field_context);
+}
+
+// ===========================================================================
+
+MessageDifferencer::Reporter::Reporter() { }
+MessageDifferencer::Reporter::~Reporter() {}
+
+// ===========================================================================
+
+MessageDifferencer::MapKeyComparator::MapKeyComparator() {}
+MessageDifferencer::MapKeyComparator::~MapKeyComparator() {}
+
+// ===========================================================================
+
+MessageDifferencer::IgnoreCriteria::IgnoreCriteria() {}
+MessageDifferencer::IgnoreCriteria::~IgnoreCriteria() {}
+
+// ===========================================================================
+
+// Note that the printer's delimiter is not used, because if we are given a
+// printer, we don't know its delimiter.
+MessageDifferencer::StreamReporter::StreamReporter(
+    io::ZeroCopyOutputStream* output) : printer_(new io::Printer(output, '$')),
+                                        delete_printer_(true),
+                                        report_modified_aggregates_(false) { }
+
+MessageDifferencer::StreamReporter::StreamReporter(
+    io::Printer* printer) : printer_(printer),
+                            delete_printer_(false),
+                            report_modified_aggregates_(false) { }
+
+MessageDifferencer::StreamReporter::~StreamReporter() {
+  if (delete_printer_) delete printer_;
+}
+
+void MessageDifferencer::StreamReporter::PrintPath(
+    const vector<SpecificField>& field_path, bool left_side) {
+  for (int i = 0; i < field_path.size(); ++i) {
+    if (i > 0) {
+      printer_->Print(".");
+    }
+
+    SpecificField specific_field = field_path[i];
+
+    if (specific_field.field != NULL) {
+      if (specific_field.field->is_extension()) {
+        printer_->Print("($name$)", "name",
+                        specific_field.field->full_name());
+      } else {
+        printer_->PrintRaw(specific_field.field->name());
+      }
+    } else {
+      printer_->PrintRaw(SimpleItoa(specific_field.unknown_field_number));
+    }
+    if (left_side && specific_field.index >= 0) {
+      printer_->Print("[$name$]", "name", SimpleItoa(specific_field.index));
+    }
+    if (!left_side && specific_field.new_index >= 0) {
+      printer_->Print("[$name$]", "name", SimpleItoa(specific_field.new_index));
+    }
+  }
+}
+
+void MessageDifferencer::
+StreamReporter::PrintValue(const Message& message,
+                           const vector<SpecificField>& field_path,
+                           bool left_side) {
+  const SpecificField& specific_field = field_path.back();
+  const FieldDescriptor* field = specific_field.field;
+  if (field != NULL) {
+    string output;
+    int index = left_side ? specific_field.index : specific_field.new_index;
+    if (field->cpp_type() == FieldDescriptor::CPPTYPE_MESSAGE) {
+      const Reflection* reflection = message.GetReflection();
+      const Message& field_message = field->is_repeated() ?
+          reflection->GetRepeatedMessage(message, field, index) :
+          reflection->GetMessage(message, field);
+      output = field_message.ShortDebugString();
+      if (output.empty()) {
+        printer_->Print("{ }");
+      } else {
+        printer_->Print("{ $name$ }", "name", output);
+      }
+    } else {
+      TextFormat::PrintFieldValueToString(message, field, index, &output);
+      printer_->PrintRaw(output);
+    }
+  } else {
+    const UnknownFieldSet* unknown_fields =
+        (left_side ?
+         specific_field.unknown_field_set1 :
+         specific_field.unknown_field_set2);
+    const UnknownField* unknown_field = &unknown_fields->field(
+        left_side ?
+        specific_field.unknown_field_index1 :
+        specific_field.unknown_field_index2);
+    PrintUnknownFieldValue(unknown_field);
+  }
+}
+
+void MessageDifferencer::
+StreamReporter::PrintUnknownFieldValue(const UnknownField* unknown_field) {
+  GOOGLE_CHECK(unknown_field != NULL) << " Cannot print NULL unknown_field.";
+
+  string output;
+  switch (unknown_field->type()) {
+    case UnknownField::TYPE_VARINT:
+      output = SimpleItoa(unknown_field->varint());
+      break;
+    case UnknownField::TYPE_FIXED32:
+      output = StrCat("0x", strings::Hex(unknown_field->fixed32(),
+                                         strings::ZERO_PAD_8));
+      break;
+    case UnknownField::TYPE_FIXED64:
+      output = StrCat("0x", strings::Hex(unknown_field->fixed64(),
+                                         strings::ZERO_PAD_16));
+      break;
+    case UnknownField::TYPE_LENGTH_DELIMITED:
+      output = StringPrintf("\"%s\"",
+          CEscape(unknown_field->length_delimited()).c_str());
+      break;
+    case UnknownField::TYPE_GROUP:
+      // TODO(kenton):  Print the contents of the group like we do for
+      //   messages.  Requires an equivalent of ShortDebugString() for
+      //   UnknownFieldSet.
+      output = "{ ... }";
+      break;
+  }
+  printer_->PrintRaw(output);
+}
+
+void MessageDifferencer::StreamReporter::Print(const string& str) {
+  printer_->Print(str.c_str());
+}
+
+void MessageDifferencer::StreamReporter::ReportAdded(
+    const Message& message1,
+    const Message& message2,
+    const vector<SpecificField>& field_path) {
+  printer_->Print("added: ");
+  PrintPath(field_path, false);
+  printer_->Print(": ");
+  PrintValue(message2, field_path, false);
+  printer_->Print("\n");  // Print for newlines.
+}
+
+void MessageDifferencer::StreamReporter::ReportDeleted(
+    const Message& message1,
+    const Message& message2,
+    const vector<SpecificField>& field_path) {
+  printer_->Print("deleted: ");
+  PrintPath(field_path, true);
+  printer_->Print(": ");
+  PrintValue(message1, field_path, true);
+  printer_->Print("\n");  // Print for newlines
+}
+
+void MessageDifferencer::StreamReporter::ReportModified(
+    const Message& message1,
+    const Message& message2,
+    const vector<SpecificField>& field_path) {
+  if (!report_modified_aggregates_ && field_path.back().field == NULL) {
+    if (field_path.back().unknown_field_type == UnknownField::TYPE_GROUP) {
+      // Any changes to the subfields have already been printed.
+      return;
+    }
+  } else if (!report_modified_aggregates_) {
+    if (field_path.back().field->cpp_type() ==
+        FieldDescriptor::CPPTYPE_MESSAGE) {
+      // Any changes to the subfields have already been printed.
+      return;
+    }
+  }
+
+  printer_->Print("modified: ");
+  PrintPath(field_path, true);
+  if (CheckPathChanged(field_path)) {
+    printer_->Print(" -> ");
+    PrintPath(field_path, false);
+  }
+  printer_->Print(": ");
+  PrintValue(message1, field_path, true);
+  printer_->Print(" -> ");
+  PrintValue(message2, field_path, false);
+  printer_->Print("\n");  // Print for newlines.
+}
+
+void MessageDifferencer::StreamReporter::ReportMoved(
+    const Message& message1,
+    const Message& message2,
+    const vector<SpecificField>& field_path) {
+  printer_->Print("moved: ");
+  PrintPath(field_path, true);
+  printer_->Print(" -> ");
+  PrintPath(field_path, false);
+  printer_->Print(" : ");
+  PrintValue(message1, field_path, true);
+  printer_->Print("\n");  // Print for newlines.
+}
+
+void MessageDifferencer::StreamReporter::ReportMatched(
+    const Message& message1,
+    const Message& message2,
+    const vector<SpecificField>& field_path) {
+  printer_->Print("matched: ");
+  PrintPath(field_path, true);
+  if (CheckPathChanged(field_path)) {
+    printer_->Print(" -> ");
+    PrintPath(field_path, false);
+  }
+  printer_->Print(" : ");
+  PrintValue(message1, field_path, true);
+  printer_->Print("\n");  // Print for newlines.
+}
+
+void MessageDifferencer::StreamReporter::ReportIgnored(
+    const Message& message1,
+    const Message& message2,
+    const vector<SpecificField>& field_path) {
+  printer_->Print("ignored: ");
+  PrintPath(field_path, true);
+  if (CheckPathChanged(field_path)) {
+    printer_->Print(" -> ");
+    PrintPath(field_path, false);
+  }
+  printer_->Print("\n");  // Print for newlines.
+}
+
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/message_differencer.h b/src/google/protobuf/util/message_differencer.h
new file mode 100644
index 0000000..0554889
--- /dev/null
+++ b/src/google/protobuf/util/message_differencer.h
@@ -0,0 +1,817 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Author: jschorr@google.com (Joseph Schorr)
+//  Based on original Protocol Buffers design by
+//  Sanjay Ghemawat, Jeff Dean, and others.
+//
+// This file defines static methods and classes for comparing Protocol
+// Messages.
+//
+// Aug. 2008: Added Unknown Fields Comparison for messages.
+// Aug. 2009: Added different options to compare repeated fields.
+// Apr. 2010: Moved field comparison to FieldComparator.
+
+#ifndef GOOGLE_PROTOBUF_UTIL_MESSAGE_DIFFERENCER_H__
+#define GOOGLE_PROTOBUF_UTIL_MESSAGE_DIFFERENCER_H__
+
+#include <map>
+#include <set>
+#include <string>
+#include <vector>
+#include <google/protobuf/descriptor.h>  // FieldDescriptor
+#include <google/protobuf/message.h>  // Message
+#include <google/protobuf/unknown_field_set.h>
+#include <google/protobuf/util/field_comparator.h>
+
+namespace google {
+namespace protobuf {
+
+class DynamicMessageFactory;
+class FieldDescriptor;
+
+namespace io {
+class ZeroCopyOutputStream;
+class Printer;
+}
+
+namespace util {
+
+class FieldContext;  // declared below MessageDifferencer
+
+// A basic differencer that can be used to determine
+// the differences between two specified Protocol Messages. If any differences
+// are found, the Compare method will return false, and any differencer reporter
+// specified via ReportDifferencesTo will have its reporting methods called (see
+// below for implementation of the report). Based off of the original
+// ProtocolDifferencer implementation in //net/proto/protocol-differencer.h
+// (Thanks Todd!).
+//
+// MessageDifferencer REQUIRES that compared messages be the same type, defined
+// as messages that share the same descriptor.  If not, the behavior of this
+// class is undefined.
+//
+// People disagree on what MessageDifferencer should do when asked to compare
+// messages with different descriptors.  Some people think it should always
+// return false.  Others expect it to try to look for similar fields and
+// compare them anyway -- especially if the descriptors happen to be identical.
+// If we chose either of these behaviors, some set of people would find it
+// surprising, and could end up writing code expecting the other behavior
+// without realizing their error.  Therefore, we forbid that usage.
+//
+// This class is implemented based on the proto2 reflection. The performance
+// should be good enough for normal usages. However, for places where the
+// performance is extremely sensitive, there are several alternatives:
+// - Comparing serialized string
+// Downside: false negatives (there are messages that are the same but their
+// serialized strings are different).
+// - Equals code generator by compiler plugin (net/proto2/contrib/equals_plugin)
+// Downside: more generated code; maintenance overhead for the additional rule
+// (must be in sync with the original proto_library).
+//
+// Note on handling of google.protobuf.Any: MessageDifferencer automatically
+// unpacks Any::value into a Message and compares its individual fields.
+// Messages encoded in a repeated Any cannot be compared using TreatAsMap.
+//
+//
+// Note on thread-safety: MessageDifferencer is *not* thread-safe. You need to
+// guard it with a lock to use the same MessageDifferencer instance from
+// multiple threads. Note that it's fine to call static comparison methods
+// (like MessageDifferencer::Equals) concurrently.
+class LIBPROTOBUF_EXPORT MessageDifferencer {
+ public:
+  // Determines whether the supplied messages are equal. Equality is defined as
+  // all fields within the two messages being set to the same value. Primitive
+  // fields and strings are compared by value while embedded messages/groups
+  // are compared as if via a recursive call. Use IgnoreField() and Compare()
+  // if some fields should be ignored in the comparison.
+  //
+  // This method REQUIRES that the two messages have the same
+  // Descriptor (message1.GetDescriptor() == message2.GetDescriptor()).
+  static bool Equals(const Message& message1, const Message& message2);
+
+  // Determines whether the supplied messages are equivalent. Equivalency is
+  // defined as all fields within the two messages having the same value. This
+  // differs from the Equals method above in that fields with default values
+  // are considered set to said value automatically. For details on how default
+  // values are defined for each field type, see http://shortn/_x2Gv6XFrWt.
+  // Also, Equivalent() ignores unknown fields. Use IgnoreField() and Compare()
+  // if some fields should be ignored in the comparison.
+  //
+  // This method REQUIRES that the two messages have the same
+  // Descriptor (message1.GetDescriptor() == message2.GetDescriptor()).
+  static bool Equivalent(const Message& message1, const Message& message2);
+
+  // Determines whether the supplied messages are approximately equal.
+  // Approximate equality is defined as all fields within the two messages
+  // being approximately equal.  Primitive (non-float) fields and strings are
+  // compared by value, floats are compared using MathUtil::AlmostEquals() and
+  // embedded messages/groups are compared as if via a recursive call. Use
+  // IgnoreField() and Compare() if some fields should be ignored in the
+  // comparison.
+  //
+  // This method REQUIRES that the two messages have the same
+  // Descriptor (message1.GetDescriptor() == message2.GetDescriptor()).
+  static bool ApproximatelyEquals(const Message& message1,
+                                  const Message& message2);
+
+  // Determines whether the supplied messages are approximately equivalent.
+  // Approximate equivalency is defined as all fields within the two messages
+  // being approximately equivalent. As in
+  // MessageDifferencer::ApproximatelyEquals, primitive (non-float) fields and
+  // strings are compared by value, floats are compared using
+  // MathUtil::AlmostEquals() and embedded messages/groups are compared as if
+  // via a recursive call. However, fields with default values are considered
+  // set to said value, as per MessageDiffencer::Equivalent. Use IgnoreField()
+  // and Compare() if some fields should be ignored in the comparison.
+  //
+  // This method REQUIRES that the two messages have the same
+  // Descriptor (message1.GetDescriptor() == message2.GetDescriptor()).
+  static bool ApproximatelyEquivalent(const Message& message1,
+                                      const Message& message2);
+
+  // Identifies an individual field in a message instance.  Used for field_path,
+  // below.
+  struct SpecificField {
+    // For known fields, "field" is filled in and "unknown_field_number" is -1.
+    // For unknown fields, "field" is NULL, "unknown_field_number" is the field
+    // number, and "unknown_field_type" is its type.
+    const FieldDescriptor* field;
+    int unknown_field_number;
+    UnknownField::Type unknown_field_type;
+
+    // If this a repeated field, "index" is the index within it.  For unknown
+    // fields, this is the index of the field among all unknown fields of the
+    // same field number and type.
+    int index;
+
+    // If "field" is a repeated field which is being treated as a map or
+    // a set (see TreatAsMap() and TreatAsSet(), below), new_index indicates
+    // the index the position to which the element has moved.  This only
+    // applies to ReportMoved() and (in the case of TreatAsMap())
+    // ReportModified().  In all other cases, "new_index" will have the same
+    // value as "index".
+    int new_index;
+
+    // For unknown fields, these are the pointers to the UnknownFieldSet
+    // containing the unknown fields. In certain cases (e.g. proto1's
+    // MessageSet, or nested groups of unknown fields), these may differ from
+    // the messages' internal UnknownFieldSets.
+    const UnknownFieldSet* unknown_field_set1;
+    const UnknownFieldSet* unknown_field_set2;
+
+    // For unknown fields, these are the index of the field within the
+    // UnknownFieldSets. One or the other will be -1 when
+    // reporting an addition or deletion.
+    int unknown_field_index1;
+    int unknown_field_index2;
+
+    SpecificField()
+        : field(NULL),
+          unknown_field_number(-1),
+          index(-1),
+          new_index(-1),
+          unknown_field_set1(NULL),
+          unknown_field_set2(NULL),
+          unknown_field_index1(-1),
+          unknown_field_index2(-1) {}
+  };
+
+  // Abstract base class from which all MessageDifferencer
+  // reporters derive. The five Report* methods below will be called when
+  // a field has been added, deleted, modified, moved, or matched. The third
+  // argument is a vector of FieldDescriptor pointers which describes the chain
+  // of fields that was taken to find the current field. For example, for a
+  // field found in an embedded message, the vector will contain two
+  // FieldDescriptors. The first will be the field of the embedded message
+  // itself and the second will be the actual field in the embedded message
+  // that was added/deleted/modified.
+  class LIBPROTOBUF_EXPORT Reporter {
+   public:
+    Reporter();
+    virtual ~Reporter();
+
+    // Reports that a field has been added into Message2.
+    virtual void ReportAdded(
+        const Message& message1, const Message& message2,
+        const vector<SpecificField>& field_path) = 0;
+
+    // Reports that a field has been deleted from Message1.
+    virtual void ReportDeleted(
+        const Message& message1,
+        const Message& message2,
+        const vector<SpecificField>& field_path) = 0;
+
+    // Reports that the value of a field has been modified.
+    virtual void ReportModified(
+        const Message& message1,
+        const Message& message2,
+        const vector<SpecificField>& field_path) = 0;
+
+    // Reports that a repeated field has been moved to another location.  This
+    // only applies when using TreatAsSet or TreatAsMap()  -- see below. Also
+    // note that for any given field, ReportModified and ReportMoved are
+    // mutually exclusive. If a field has been both moved and modified, then
+    // only ReportModified will be called.
+    virtual void ReportMoved(
+        const Message& message1,
+        const Message& message2,
+        const vector<SpecificField>& field_path) { }
+
+    // Reports that two fields match. Useful for doing side-by-side diffs.
+    // This function is mutually exclusive with ReportModified and ReportMoved.
+    // Note that you must call set_report_matches(true) before calling Compare
+    // to make use of this function.
+    virtual void ReportMatched(
+        const Message& message1,
+        const Message& message2,
+        const vector<SpecificField>& field_path) { }
+
+    // Reports that two fields would have been compared, but the
+    // comparison has been skipped because the field was marked as
+    // 'ignored' using IgnoreField().  This function is mutually
+    // exclusive with all the other Report() functions.
+    //
+    // The contract of ReportIgnored is slightly different than the
+    // other Report() functions, in that |field_path.back().index| is
+    // always equal to -1, even if the last field is repeated. This is
+    // because while the other Report() functions indicate where in a
+    // repeated field the action (Addition, Deletion, etc...)
+    // happened, when a repeated field is 'ignored', the differencer
+    // simply calls ReportIgnored on the repeated field as a whole and
+    // moves on without looking at its individual elements.
+    //
+    // Furthermore, ReportIgnored() does not indicate whether the
+    // fields were in fact equal or not, as Compare() does not inspect
+    // these fields at all. It is up to the Reporter to decide whether
+    // the fields are equal or not (perhaps with a second call to
+    // Compare()), if it cares.
+    virtual void ReportIgnored(
+        const Message& message1,
+        const Message& message2,
+        const vector<SpecificField>& field_path) { }
+
+   private:
+    GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(Reporter);
+  };
+
+  // MapKeyComparator is used to determine if two elements have the same key
+  // when comparing elements of a repeated field as a map.
+  class LIBPROTOBUF_EXPORT MapKeyComparator {
+   public:
+    MapKeyComparator();
+    virtual ~MapKeyComparator();
+
+    // The first IsMatch without parent_fields is only for backward
+    // compatibility. New users should override the second one instead.
+    //
+    // Deprecated.
+    // TODO(ykzhu): remove this function.
+    virtual bool IsMatch(const Message& message1,
+                         const Message& message2) const {
+      GOOGLE_CHECK(false) << "This function shouldn't get called";
+      return false;
+    }
+    virtual bool IsMatch(const Message& message1,
+                         const Message& message2,
+                         const vector<SpecificField>& parent_fields) const {
+      return IsMatch(message1, message2);
+    }
+
+   private:
+    GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(MapKeyComparator);
+  };
+
+  // Abstract base class from which all IgnoreCriteria derive.
+  // By adding IgnoreCriteria more complex ignore logic can be implemented.
+  // IgnoreCriteria are registed with AddIgnoreCriteria. For each compared
+  // field IsIgnored is called on each added IgnoreCriteria until one returns
+  // true or all return false.
+  // IsIgnored is called for fields where at least one side has a value.
+  class LIBPROTOBUF_EXPORT IgnoreCriteria {
+   public:
+    IgnoreCriteria();
+    virtual ~IgnoreCriteria();
+
+    // Returns true if the field should be ignored.
+    virtual bool IsIgnored(
+        const Message& message1,
+        const Message& message2,
+        const FieldDescriptor* field,
+        const vector<SpecificField>& parent_fields) = 0;
+  };
+
+  // To add a Reporter, construct default here, then use ReportDifferencesTo or
+  // ReportDifferencesToString.
+  explicit MessageDifferencer();
+
+  ~MessageDifferencer();
+
+  enum MessageFieldComparison {
+    EQUAL,       // Fields must be present in both messages
+                 // for the messages to be considered the same.
+    EQUIVALENT,  // Fields with default values are considered set
+                 // for comparison purposes even if not explicitly
+                 // set in the messages themselves.  Unknown fields
+                 // are ignored.
+  };
+
+  enum Scope {
+    FULL,    // All fields of both messages are considered in the comparison.
+    PARTIAL  // Only fields present in the first message are considered; fields
+             // set only in the second message will be skipped during
+             // comparison.
+  };
+
+  // DEPRECATED. Use FieldComparator::FloatComparison instead.
+  enum FloatComparison {
+    EXACT,       // Floats and doubles are compared exactly.
+    APPROXIMATE  // Floats and doubles are compared using the
+                 // MathUtil::AlmostEquals method.
+  };
+
+  enum RepeatedFieldComparison {
+    AS_LIST,     // Repeated fields are compared in order.  Differing values at
+                 // the same index are reported using ReportModified().  If the
+                 // repeated fields have different numbers of elements, the
+                 // unpaired elements are reported using ReportAdded() or
+                 // ReportDeleted().
+    AS_SET,      // Treat all the repeated fields as sets by default.
+                 // See TreatAsSet(), as below.
+  };
+
+  // The elements of the given repeated field will be treated as a set for
+  // diffing purposes, so different orderings of the same elements will be
+  // considered equal.  Elements which are present on both sides of the
+  // comparison but which have changed position will be reported with
+  // ReportMoved().  Elements which only exist on one side or the other are
+  // reported with ReportAdded() and ReportDeleted() regardless of their
+  // positions.  ReportModified() is never used for this repeated field.  If
+  // the only differences between the compared messages is that some fields
+  // have been moved, then the comparison returns true.
+  //
+  // If the scope of comparison is set to PARTIAL, then in addition to what's
+  // above, extra values added to repeated fields of the second message will
+  // not cause the comparison to fail.
+  //
+  // Note that set comparison is currently O(k * n^2) (where n is the total
+  // number of elements, and k is the average size of each element). In theory
+  // it could be made O(n * k) with a more complex hashing implementation. Feel
+  // free to contribute one if the current implementation is too slow for you.
+  // If partial matching is also enabled, the time complexity will be O(k * n^2
+  // + n^3) in which n^3 is the time complexity of the maximum matching
+  // algorithm.
+  //
+  // REQUIRES:  field->is_repeated()
+  void TreatAsSet(const FieldDescriptor* field);
+
+  // The elements of the given repeated field will be treated as a map for
+  // diffing purposes, with |key| being the map key.  Thus, elements with the
+  // same key will be compared even if they do not appear at the same index.
+  // Differences are reported similarly to TreatAsSet(), except that
+  // ReportModified() is used to report elements with the same key but
+  // different values.  Note that if an element is both moved and modified,
+  // only ReportModified() will be called.  As with TreatAsSet, if the only
+  // differences between the compared messages is that some fields have been
+  // moved, then the comparison returns true. See TreatAsSet for notes on
+  // performance.
+  //
+  // REQUIRES:  field->is_repeated()
+  // REQUIRES:  field->cpp_type() == FieldDescriptor::CPPTYPE_MESSAGE
+  // REQUIRES:  key->containing_type() == field->message_type()
+  void TreatAsMap(const FieldDescriptor* field, const FieldDescriptor* key);
+  // Same as TreatAsMap except that this method will use multiple fields as
+  // the key in comparison. All specified fields in 'key_fields' should be
+  // present in the compared elements. Two elements will be treated as having
+  // the same key iff they have the same value for every specified field. There
+  // are two steps in the comparison process. The first one is key matching.
+  // Every element from one message will be compared to every element from
+  // the other message. Only fields in 'key_fields' are compared in this step
+  // to decide if two elements have the same key. The second step is value
+  // comparison. Those pairs of elements with the same key (with equal value
+  // for every field in 'key_fields') will be compared in this step.
+  // Time complexity of the first step is O(s * m * n ^ 2) where s is the
+  // average size of the fields specified in 'key_fields', m is the number of
+  // fields in 'key_fields' and n is the number of elements. If partial
+  // matching is enabled, an extra O(n^3) will be incured by the maximum
+  // matching algorithm. The second step is O(k * n) where k is the average
+  // size of each element.
+  void TreatAsMapWithMultipleFieldsAsKey(
+      const FieldDescriptor* field,
+      const vector<const FieldDescriptor*>& key_fields);
+  // Same as TreatAsMapWithMultipleFieldsAsKey, except that each of the field
+  // do not necessarily need to be a direct subfield. Each element in
+  // key_field_paths indicate a path from the message being compared, listing
+  // successive subfield to reach the key field.
+  //
+  // REQUIRES:
+  //   for key_field_path in key_field_paths:
+  //     key_field_path[0]->containing_type() == field->message_type()
+  //     for i in [0, key_field_path.size() - 1):
+  //       key_field_path[i+1]->containing_type() ==
+  //           key_field_path[i]->message_type()
+  //       key_field_path[i]->cpp_type() == FieldDescriptor::CPPTYPE_MESSAGE
+  //       !key_field_path[i]->is_repeated()
+  void TreatAsMapWithMultipleFieldPathsAsKey(
+      const FieldDescriptor* field,
+      const vector<vector<const FieldDescriptor*> >& key_field_paths);
+
+  // Uses a custom MapKeyComparator to determine if two elements have the same
+  // key when comparing a repeated field as a map.
+  // The caller is responsible to delete the key_comparator.
+  // This method varies from TreatAsMapWithMultipleFieldsAsKey only in the
+  // first key matching step. Rather than comparing some specified fields, it
+  // will invoke the IsMatch method of the given 'key_comparator' to decide if
+  // two elements have the same key.
+  void TreatAsMapUsingKeyComparator(
+      const FieldDescriptor* field,
+      const MapKeyComparator* key_comparator);
+
+  // Add a custom ignore criteria that is evaluated in addition to the
+  // ignored fields added with IgnoreField.
+  // Takes ownership of ignore_criteria.
+  void AddIgnoreCriteria(IgnoreCriteria* ignore_criteria);
+
+  // Indicates that any field with the given descriptor should be
+  // ignored for the purposes of comparing two messages. This applies
+  // to fields nested in the message structure as well as top level
+  // ones. When the MessageDifferencer encounters an ignored field,
+  // ReportIgnored is called on the reporter, if one is specified.
+  //
+  // The only place where the field's 'ignored' status is not applied is when
+  // it is being used as a key in a field passed to TreatAsMap or is one of
+  // the fields passed to TreatAsMapWithMultipleFieldsAsKey.
+  // In this case it is compared in key matching but after that it's ignored
+  // in value comparison.
+  void IgnoreField(const FieldDescriptor* field);
+
+  // Sets the field comparator used to determine differences between protocol
+  // buffer fields. By default it's set to a DefaultFieldComparator instance.
+  // MessageDifferencer doesn't take ownership over the passed object.
+  // Note that this method must be called before Compare for the comparator to
+  // be used.
+  void set_field_comparator(FieldComparator* comparator);
+
+  // DEPRECATED. Pass a DefaultFieldComparator instance instead.
+  // Sets the fraction and margin for the float comparison of a given field.
+  // Uses MathUtil::WithinFractionOrMargin to compare the values.
+  // NOTE: this method does nothing if differencer's field comparator has been
+  //       set to a custom object.
+  //
+  // REQUIRES: field->cpp_type == FieldDescriptor::CPPTYPE_DOUBLE or
+  //           field->cpp_type == FieldDescriptor::CPPTYPE_FLOAT
+  // REQUIRES: float_comparison_ == APPROXIMATE
+  void SetFractionAndMargin(const FieldDescriptor* field, double fraction,
+                            double margin);
+
+  // Sets the type of comparison (as defined in the MessageFieldComparison
+  // enumeration above) that is used by this differencer when determining how
+  // to compare fields in messages.
+  void set_message_field_comparison(MessageFieldComparison comparison);
+
+  // Tells the differencer whether or not to report matches. This method must
+  // be called before Compare. The default for a new differencer is false.
+  void set_report_matches(bool report_matches) {
+    report_matches_ = report_matches;
+  }
+
+  // Sets the scope of the comparison (as defined in the Scope enumeration
+  // above) that is used by this differencer when determining which fields to
+  // compare between the messages.
+  void set_scope(Scope scope);
+
+  // Returns the current scope used by this differencer.
+  Scope scope();
+
+  // DEPRECATED. Pass a DefaultFieldComparator instance instead.
+  // Sets the type of comparison (as defined in the FloatComparison enumeration
+  // above) that is used by this differencer when comparing float (and double)
+  // fields in messages.
+  // NOTE: this method does nothing if differencer's field comparator has been
+  //       set to a custom object.
+  void set_float_comparison(FloatComparison comparison);
+
+  // Sets the type of comparison for repeated field (as defined in the
+  // RepeatedFieldComparison enumeration above) that is used by this
+  // differencer when compare repeated fields in messages.
+  void set_repeated_field_comparison(RepeatedFieldComparison comparison);
+
+  // Compares the two specified messages, returning true if they are the same,
+  // false otherwise. If this method returns false, any changes between the
+  // two messages will be reported if a Reporter was specified via
+  // ReportDifferencesTo (see also ReportDifferencesToString).
+  //
+  // This method REQUIRES that the two messages have the same
+  // Descriptor (message1.GetDescriptor() == message2.GetDescriptor()).
+  bool Compare(const Message& message1, const Message& message2);
+
+  // Same as above, except comparing only the list of fields specified by the
+  // two vectors of FieldDescriptors.
+  bool CompareWithFields(const Message& message1, const Message& message2,
+                         const vector<const FieldDescriptor*>& message1_fields,
+                         const vector<const FieldDescriptor*>& message2_fields);
+
+  // Automatically creates a reporter that will output the differences
+  // found (if any) to the specified output string pointer. Note that this
+  // method must be called before Compare.
+  void ReportDifferencesToString(string* output);
+
+  // Tells the MessageDifferencer to report differences via the specified
+  // reporter. Note that this method must be called before Compare for
+  // the reporter to be used. It is the responsibility of the caller to delete
+  // this object.
+  // If the provided pointer equals NULL, the MessageDifferencer stops reporting
+  // differences to any previously set reporters or output strings.
+  void ReportDifferencesTo(Reporter* reporter);
+
+  // An implementation of the MessageDifferencer Reporter that outputs
+  // any differences found in human-readable form to the supplied
+  // ZeroCopyOutputStream or Printer. If a printer is used, the delimiter
+  // *must* be '$'.
+  class LIBPROTOBUF_EXPORT StreamReporter : public Reporter {
+   public:
+    explicit StreamReporter(io::ZeroCopyOutputStream* output);
+    explicit StreamReporter(io::Printer* printer);  // delimiter '$'
+    virtual ~StreamReporter();
+
+    // When set to true, the stream reporter will also output aggregates nodes
+    // (i.e. messages and groups) whose subfields have been modified. When
+    // false, will only report the individual subfields. Defaults to false.
+    void set_report_modified_aggregates(bool report) {
+      report_modified_aggregates_ = report;
+    }
+
+    // The following are implementations of the methods described above.
+    virtual void ReportAdded(const Message& message1, const Message& message2,
+                             const vector<SpecificField>& field_path);
+
+    virtual void ReportDeleted(const Message& message1,
+                               const Message& message2,
+                               const vector<SpecificField>& field_path);
+
+    virtual void ReportModified(const Message& message1,
+                                const Message& message2,
+                                const vector<SpecificField>& field_path);
+
+    virtual void ReportMoved(const Message& message1,
+                             const Message& message2,
+                             const vector<SpecificField>& field_path);
+
+    virtual void ReportMatched(const Message& message1,
+                               const Message& message2,
+                               const vector<SpecificField>& field_path);
+
+    virtual void ReportIgnored(const Message& message1,
+                               const Message& message2,
+                               const vector<SpecificField>& field_path);
+
+   protected:
+    // Prints the specified path of fields to the buffer.
+    virtual void PrintPath(const vector<SpecificField>& field_path,
+                           bool left_side);
+
+    // Prints the value of fields to the buffer.  left_side is true if the
+    // given message is from the left side of the comparison, false if it
+    // was the right.  This is relevant only to decide whether to follow
+    // unknown_field_index1 or unknown_field_index2 when an unknown field
+    // is encountered in field_path.
+    virtual void PrintValue(const Message& message,
+                            const vector<SpecificField>& field_path,
+                            bool left_side);
+
+    // Prints the specified path of unknown fields to the buffer.
+    virtual void PrintUnknownFieldValue(const UnknownField* unknown_field);
+
+    // Just print a string
+    void Print(const string& str);
+
+   private:
+    io::Printer* printer_;
+    bool delete_printer_;
+    bool report_modified_aggregates_;
+
+    GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(StreamReporter);
+  };
+
+ private:
+  // A MapKeyComparator to be used in TreatAsMapUsingKeyComparator.
+  // Implementation of this class needs to do field value comparison which
+  // relies on some private methods of MessageDifferencer. That's why this
+  // class is declared as a nested class of MessageDifferencer.
+  class MultipleFieldsMapKeyComparator;
+  // Returns true if field1's number() is less than field2's.
+  static bool FieldBefore(const FieldDescriptor* field1,
+                          const FieldDescriptor* field2);
+
+  // Combine the two lists of fields into the combined_fields output vector.
+  // All fields present in both lists will always be included in the combined
+  // list.  Fields only present in one of the lists will only appear in the
+  // combined list if the corresponding fields_scope option is set to FULL.
+  void CombineFields(const vector<const FieldDescriptor*>& fields1,
+                     Scope fields1_scope,
+                     const vector<const FieldDescriptor*>& fields2,
+                     Scope fields2_scope,
+                     vector<const FieldDescriptor*>* combined_fields);
+
+  // Internal version of the Compare method which performs the actual
+  // comparison. The parent_fields vector is a vector containing field
+  // descriptors of all fields accessed to get to this comparison operation
+  // (i.e. if the current message is an embedded message, the parent_fields
+  // vector will contain the field that has this embedded message).
+  bool Compare(const Message& message1, const Message& message2,
+               vector<SpecificField>* parent_fields);
+
+  // Compares all the unknown fields in two messages.
+  bool CompareUnknownFields(const Message& message1, const Message& message2,
+                            const google::protobuf::UnknownFieldSet&,
+                            const google::protobuf::UnknownFieldSet&,
+                            vector<SpecificField>* parent_fields);
+
+  // Compares the specified messages for the requested field lists. The field
+  // lists are modified depending on comparison settings, and then passed to
+  // CompareWithFieldsInternal.
+  bool CompareRequestedFieldsUsingSettings(
+      const Message& message1, const Message& message2,
+      const vector<const FieldDescriptor*>& message1_fields,
+      const vector<const FieldDescriptor*>& message2_fields,
+      vector<SpecificField>* parent_fields);
+
+  // Compares the specified messages with the specified field lists.
+  bool CompareWithFieldsInternal(
+      const Message& message1, const Message& message2,
+      const vector<const FieldDescriptor*>& message1_fields,
+      const vector<const FieldDescriptor*>& message2_fields,
+      vector<SpecificField>* parent_fields);
+
+  // Compares the repeated fields, and report the error.
+  bool CompareRepeatedField(const Message& message1, const Message& message2,
+                            const FieldDescriptor* field,
+                            vector<SpecificField>* parent_fields);
+
+  // Shorthand for CompareFieldValueUsingParentFields with NULL parent_fields.
+  bool CompareFieldValue(const Message& message1,
+                         const Message& message2,
+                         const FieldDescriptor* field,
+                         int index1,
+                         int index2);
+
+  // Compares the specified field on the two messages, returning
+  // true if they are the same, false otherwise. For repeated fields,
+  // this method only compares the value in the specified index. This method
+  // uses Compare functions to recurse into submessages.
+  // The parent_fields vector is used in calls to a Reporter instance calls.
+  // It can be NULL, in which case the MessageDifferencer will create new
+  // list of parent messages if it needs to recursively compare the given field.
+  // To avoid confusing users you should not set it to NULL unless you modified
+  // Reporter to handle the change of parent_fields correctly.
+  bool CompareFieldValueUsingParentFields(const Message& message1,
+                                          const Message& message2,
+                                          const FieldDescriptor* field,
+                                          int index1,
+                                          int index2,
+                                          vector<SpecificField>* parent_fields);
+
+  // Compares the specified field on the two messages, returning comparison
+  // result, as returned by appropriate FieldComparator.
+  FieldComparator::ComparisonResult GetFieldComparisonResult(
+      const Message& message1, const Message& message2,
+      const FieldDescriptor* field, int index1, int index2,
+      const FieldContext* field_context);
+
+  // Check if the two elements in the repeated field are match to each other.
+  // if the key_comprator is NULL, this function returns true when the two
+  // elements are equal.
+  bool IsMatch(const FieldDescriptor* repeated_field,
+               const MapKeyComparator* key_comparator,
+               const Message* message1, const Message* message2,
+               const vector<SpecificField>& parent_fields,
+               int index1, int index2);
+
+  // Returns true when this repeated field has been configured to be treated
+  // as a set.
+  bool IsTreatedAsSet(const FieldDescriptor* field);
+
+  // Returns true when this repeated field is to be compared as a subset, ie.
+  // has been configured to be treated as a set or map and scope is set to
+  // PARTIAL.
+  bool IsTreatedAsSubset(const FieldDescriptor* field);
+
+  // Returns true if this field is to be ignored when this
+  // MessageDifferencer compares messages.
+  bool IsIgnored(
+      const Message& message1,
+      const Message& message2,
+      const FieldDescriptor* field,
+      const vector<SpecificField>& parent_fields);
+
+  // Returns MapKeyComparator* when this field has been configured to
+  // be treated as a map.  If not, returns NULL.
+  const MapKeyComparator* GetMapKeyComparator(const FieldDescriptor* field);
+
+  // Attempts to match indices of a repeated field, so that the contained values
+  // match. Clears output vectors and sets their values to indices of paired
+  // messages, ie. if message1[0] matches message2[1], then match_list1[0] == 1
+  // and match_list2[1] == 0. The unmatched indices are indicated by -1.
+  // This method returns false if the match failed. However, it doesn't mean
+  // that the comparison succeeds when this method returns true (you need to
+  // double-check in this case).
+  bool MatchRepeatedFieldIndices(const Message& message1,
+                                 const Message& message2,
+                                 const FieldDescriptor* repeated_field,
+                                 const vector<SpecificField>& parent_fields,
+                                 vector<int>* match_list1,
+                                 vector<int>* match_list2);
+
+  // If "any" is of type google.protobuf.Any, extract its payload using
+  // DynamicMessageFactory and store in "data".
+  bool UnpackAny(const Message& any, google::protobuf::scoped_ptr<Message>* data);
+
+  // Checks if index is equal to new_index in all the specific fields.
+  static bool CheckPathChanged(const vector<SpecificField>& parent_fields);
+
+  // Defines a map between field descriptors and their MapKeyComparators.
+  // Used for repeated fields when they are configured as TreatAsMap.
+  typedef map<const FieldDescriptor*,
+              const MapKeyComparator*> FieldKeyComparatorMap;
+
+  // Defines a set to store field descriptors.  Used for repeated fields when
+  // they are configured as TreatAsSet.
+  typedef set<const FieldDescriptor*> FieldSet;
+
+  Reporter* reporter_;
+  DefaultFieldComparator default_field_comparator_;
+  FieldComparator* field_comparator_;
+  MessageFieldComparison message_field_comparison_;
+  Scope scope_;
+  RepeatedFieldComparison repeated_field_comparison_;
+
+  FieldSet set_fields_;
+  // Keeps track of MapKeyComparators that are created within
+  // MessageDifferencer. These MapKeyComparators should be deleted
+  // before MessageDifferencer is destroyed.
+  // When TreatAsMap or TreatAsMapWithMultipleFieldsAsKey is called, we don't
+  // store the supplied FieldDescriptors directly. Instead, a new
+  // MapKeyComparator is created for comparison purpose.
+  vector<MapKeyComparator*> owned_key_comparators_;
+  FieldKeyComparatorMap map_field_key_comparator_;
+  vector<IgnoreCriteria*> ignore_criteria_;
+
+  FieldSet ignored_fields_;
+
+  bool compare_unknown_fields_;
+  bool report_matches_;
+
+  string* output_string_;
+
+  google::protobuf::scoped_ptr<DynamicMessageFactory> dynamic_message_factory_;
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(MessageDifferencer);
+};
+
+// This class provides extra information to the FieldComparator::Compare
+// function.
+class LIBPROTOBUF_EXPORT FieldContext {
+ public:
+  explicit FieldContext(
+      vector<MessageDifferencer::SpecificField>* parent_fields)
+      : parent_fields_(parent_fields) {}
+
+  vector<MessageDifferencer::SpecificField>* parent_fields() const {
+    return parent_fields_;
+  }
+
+ private:
+  vector<MessageDifferencer::SpecificField>* parent_fields_;
+};
+
+}
+}
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_MESSAGE_DIFFERENCER_H__
diff --git a/src/google/protobuf/util/message_differencer_unittest.cc b/src/google/protobuf/util/message_differencer_unittest.cc
new file mode 100755
index 0000000..bd19f69
--- /dev/null
+++ b/src/google/protobuf/util/message_differencer_unittest.cc
@@ -0,0 +1,3132 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Author: jschorr@google.com (Joseph Schorr)
+//  Based on original Protocol Buffers design by
+//  Sanjay Ghemawat, Jeff Dean, and others.
+//
+// TODO(ksroka): Move some of these tests to field_comparator_test.cc.
+
+#include <algorithm>
+#include <string>
+#include <vector>
+
+
+#include <google/protobuf/util/field_comparator.h>
+#include <google/protobuf/util/message_differencer.h>
+#include <google/protobuf/util/message_differencer_unittest.pb.h>
+#include <google/protobuf/text_format.h>
+#include <google/protobuf/wire_format.h>
+#include <google/protobuf/io/zero_copy_stream_impl.h>
+#include <google/protobuf/io/coded_stream.h>
+#include <google/protobuf/any_test.pb.h>
+#include <google/protobuf/map_unittest.pb.h>
+#include <google/protobuf/unittest.pb.h>
+#include <google/protobuf/map_test_util.h>
+#include <google/protobuf/test_util.h>
+
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/stubs/strutil.h>
+#include <google/protobuf/testing/googletest.h>
+#include <gtest/gtest.h>
+
+namespace google {
+namespace protobuf {
+
+namespace {
+
+
+const FieldDescriptor* GetFieldDescriptor(
+    const Message& message, const string& field_name) {
+  vector<string> field_path =
+      Split(field_name, ".", true);
+  const Descriptor* descriptor = message.GetDescriptor();
+  const FieldDescriptor* field = NULL;
+  for (int i = 0; i < field_path.size(); i++) {
+    field = descriptor->FindFieldByName(field_path[i]);
+    descriptor = field->message_type();
+  }
+  return field;
+}
+
+void ExpectEqualsWithDifferencer(util::MessageDifferencer* differencer,
+                                 const Message& msg1,
+                                 const Message& msg2) {
+  differencer->set_scope(util::MessageDifferencer::FULL);
+  EXPECT_TRUE(differencer->Compare(msg1, msg2));
+
+  differencer->set_scope(util::MessageDifferencer::PARTIAL);
+  EXPECT_TRUE(differencer->Compare(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, BasicEqualityTest) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  // Compare
+  EXPECT_TRUE(util::MessageDifferencer::Equals(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, BasicInequalityTest) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  msg1.set_optional_int32(-1);
+
+  // Compare
+  EXPECT_FALSE(util::MessageDifferencer::Equals(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, RepeatedFieldInequalityTest) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  msg1.add_repeated_int32(-1);
+
+  // Compare
+  EXPECT_FALSE(util::MessageDifferencer::Equals(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, MapFieldEqualityTest) {
+  // Create the testing protos
+  unittest::TestMap msg1;
+  unittest::TestMap msg2;
+
+  MapTestUtil::MapReflectionTester tester(unittest::TestMap::descriptor());
+  tester.SetMapFieldsViaReflection(&msg1);
+  tester.SetMapFieldsViaReflection(&msg2);
+  tester.SwapMapsViaReflection(&msg1);
+
+  // Compare
+  EXPECT_TRUE(util::MessageDifferencer::Equals(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, BasicPartialEqualityTest) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  // Compare
+  util::MessageDifferencer differencer;
+  differencer.set_scope(util::MessageDifferencer::PARTIAL);
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, PartialEqualityTestExtraField) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  msg1.clear_optional_int32();
+
+  // Compare
+  util::MessageDifferencer differencer;
+  differencer.set_scope(util::MessageDifferencer::PARTIAL);
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, PartialEqualityTestSkipRequiredField) {
+  // Create the testing protos
+  unittest::TestRequired msg1;
+  unittest::TestRequired msg2;
+
+  msg1.set_a(401);
+  msg2.set_a(401);
+  msg2.set_b(402);
+
+  // Compare
+  util::MessageDifferencer differencer;
+  differencer.set_scope(util::MessageDifferencer::PARTIAL);
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, BasicPartialInequalityTest) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  msg1.set_optional_int32(-1);
+
+  // Compare
+  util::MessageDifferencer differencer;
+  differencer.set_scope(util::MessageDifferencer::PARTIAL);
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, PartialInequalityMissingFieldTest) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  msg2.clear_optional_int32();
+
+  // Compare
+  util::MessageDifferencer differencer;
+  differencer.set_scope(util::MessageDifferencer::PARTIAL);
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, RepeatedFieldPartialInequalityTest) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  msg1.add_repeated_int32(-1);
+
+  // Compare
+  util::MessageDifferencer differencer;
+  differencer.set_scope(util::MessageDifferencer::PARTIAL);
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, BasicEquivalencyTest) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  // Compare
+  EXPECT_TRUE(util::MessageDifferencer::Equivalent(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, EquivalencyNotEqualTest) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  msg1.clear_optional_int32();
+  msg2.set_optional_int32(0);
+
+  // Compare
+  EXPECT_FALSE(util::MessageDifferencer::Equals(msg1, msg2));
+  EXPECT_TRUE(util::MessageDifferencer::Equivalent(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, BasicInequivalencyTest) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  msg1.set_optional_int32(-1);
+
+  // Compare
+  EXPECT_FALSE(util::MessageDifferencer::Equivalent(msg1, msg2));
+}
+
+
+TEST(MessageDifferencerTest, BasicEquivalencyNonSetTest) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  // Compare
+  EXPECT_TRUE(util::MessageDifferencer::Equivalent(msg1, msg2));
+}
+
+
+TEST(MessageDifferencerTest, BasicInequivalencyNonSetTest) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  msg1.set_optional_int32(-1);
+
+  // Compare
+  EXPECT_FALSE(util::MessageDifferencer::Equivalent(msg1, msg2));
+}
+
+
+TEST(MessageDifferencerTest, BasicPartialEquivalencyTest) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  // Compare
+  util::MessageDifferencer differencer;
+  differencer.set_message_field_comparison(
+      util::MessageDifferencer::EQUIVALENT);
+  differencer.set_scope(util::MessageDifferencer::PARTIAL);
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, PartialEquivalencyNotEqualTest) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  msg1.set_optional_int32(0);
+  msg2.clear_optional_int32();
+
+  // Compare
+  EXPECT_FALSE(util::MessageDifferencer::Equals(msg1, msg2));
+  util::MessageDifferencer differencer;
+  differencer.set_message_field_comparison(
+      util::MessageDifferencer::EQUIVALENT);
+  differencer.set_scope(util::MessageDifferencer::PARTIAL);
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, PartialEquivalencyTestExtraField) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  msg1.clear_optional_int32();
+
+  // Compare
+  util::MessageDifferencer differencer;
+  differencer.set_message_field_comparison(
+      util::MessageDifferencer::EQUIVALENT);
+  differencer.set_scope(util::MessageDifferencer::PARTIAL);
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, PartialEquivalencyTestSkipRequiredField) {
+  // Create the testing protos
+  unittest::TestRequired msg1;
+  unittest::TestRequired msg2;
+
+  msg1.set_a(401);
+  msg2.set_a(401);
+  msg2.set_b(402);
+
+  // Compare
+  util::MessageDifferencer differencer;
+  differencer.set_message_field_comparison(
+      util::MessageDifferencer::EQUIVALENT);
+  differencer.set_scope(util::MessageDifferencer::PARTIAL);
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, BasicPartialInequivalencyTest) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  msg1.set_optional_int32(-1);
+
+  // Compare
+  util::MessageDifferencer differencer;
+  differencer.set_message_field_comparison(
+      util::MessageDifferencer::EQUIVALENT);
+  differencer.set_scope(util::MessageDifferencer::PARTIAL);
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, BasicPartialEquivalencyNonSetTest) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  // Compare
+  util::MessageDifferencer differencer;
+  differencer.set_message_field_comparison(
+      util::MessageDifferencer::EQUIVALENT);
+  differencer.set_scope(util::MessageDifferencer::PARTIAL);
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, BasicPartialInequivalencyNonSetTest) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  msg1.set_optional_int32(-1);
+
+  // Compare
+  util::MessageDifferencer differencer;
+  differencer.set_message_field_comparison(
+      util::MessageDifferencer::EQUIVALENT);
+  differencer.set_scope(util::MessageDifferencer::PARTIAL);
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, ApproximateEqualityTest) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  // Compare
+  EXPECT_TRUE(util::MessageDifferencer::ApproximatelyEquals(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, ApproximateModifiedEqualityTest) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  const float v1 = 2.300005f;
+  const float v2 = 2.300006f;
+  msg1.set_optional_float(v1);
+  msg2.set_optional_float(v2);
+
+  // Compare
+  ASSERT_NE(v1, v2) << "Should not be the same: " << v1 << ", " << v2;
+  ASSERT_FLOAT_EQ(v1, v2) << "Should be approx. equal: " << v1 << ", " << v2;
+  EXPECT_FALSE(util::MessageDifferencer::Equals(msg1, msg2));
+  EXPECT_TRUE(util::MessageDifferencer::ApproximatelyEquals(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, ApproximateEquivalencyTest) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  // Compare
+  EXPECT_TRUE(util::MessageDifferencer::ApproximatelyEquivalent(msg1,
+                                                                msg2));
+}
+
+TEST(MessageDifferencerTest, ApproximateModifiedEquivalencyTest) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  // Modify the approximateness requirement
+  const float v1 = 2.300005f;
+  const float v2 = 2.300006f;
+  msg1.set_optional_float(v1);
+  msg2.set_optional_float(v2);
+
+  // Compare
+  ASSERT_NE(v1, v2) << "Should not be the same: " << v1 << ", " << v2;
+  ASSERT_FLOAT_EQ(v1, v2) << "Should be approx. equal: " << v1 << ", " << v2;
+  EXPECT_FALSE(util::MessageDifferencer::Equals(msg1, msg2));
+  EXPECT_TRUE(util::MessageDifferencer::ApproximatelyEquivalent(msg1,
+                                                                msg2));
+
+  // Modify the equivalency requirement too
+  msg1.clear_optional_int32();
+  msg2.set_optional_int32(0);
+
+  // Compare. Now should only pass on ApproximatelyEquivalent
+  EXPECT_FALSE(util::MessageDifferencer::Equals(msg1, msg2));
+  EXPECT_FALSE(util::MessageDifferencer::Equivalent(msg1, msg2));
+  EXPECT_FALSE(util::MessageDifferencer::ApproximatelyEquals(msg1, msg2));
+  EXPECT_TRUE(util::MessageDifferencer::ApproximatelyEquivalent(msg1,
+                                                                msg2));
+}
+
+TEST(MessageDifferencerTest, ApproximateInequivalencyTest) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  // Should fail on equivalency
+  msg1.set_optional_int32(-1);
+  EXPECT_FALSE(util::MessageDifferencer::ApproximatelyEquivalent(msg1,
+                                                                 msg2));
+
+  // Make these fields the same again.
+  msg1.set_optional_int32(0);
+  msg2.set_optional_int32(0);
+  EXPECT_TRUE(util::MessageDifferencer::ApproximatelyEquivalent(msg1,
+                                                                msg2));
+
+  // Should fail on approximate equality check
+  const float v1 = 2.3f;
+  const float v2 = 9.3f;
+  msg1.set_optional_float(v1);
+  msg2.set_optional_float(v2);
+  EXPECT_FALSE(util::MessageDifferencer::ApproximatelyEquivalent(msg1,
+                                                                 msg2));
+}
+
+TEST(MessageDifferencerTest, WithinFractionOrMarginFloatTest) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  // Should fail on approximate equality check
+  const float v1 = 100.0f;
+  const float v2 = 109.9f;
+  msg1.set_optional_float(v1);
+  msg2.set_optional_float(v2);
+
+  // Compare
+  util::MessageDifferencer differencer;
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+  const FieldDescriptor* fd =
+      msg1.GetDescriptor()->FindFieldByName("optional_float");
+
+  // Set float comparison to exact, margin and fraction value should not matter.
+  differencer.set_float_comparison(util::MessageDifferencer::EXACT);
+  // Set margin for float comparison.
+  differencer.SetFractionAndMargin(fd, 0.0, 10.0);
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+
+  // Margin and fraction float comparison is activated when float comparison is
+  // set to approximate.
+  differencer.set_float_comparison(util::MessageDifferencer::APPROXIMATE);
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+
+  // Test out float comparison with fraction.
+  differencer.SetFractionAndMargin(fd, 0.2, 0.0);
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+
+  // Should fail since the fraction is smaller than error.
+  differencer.SetFractionAndMargin(fd, 0.01, 0.0);
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+
+  // Should pass if either fraction or margin are satisfied.
+  differencer.SetFractionAndMargin(fd, 0.01, 10.0);
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+
+  // Make sure that the margin and fraction only affects the field that it was
+  // set for.
+  msg1.set_default_float(v1);
+  msg2.set_default_float(v2);
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+  msg1.set_default_float(v1);
+  msg2.set_default_float(v1);
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, WithinFractionOrMarginDoubleTest) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  // Should fail on approximate equality check
+  const double v1 = 100.0;
+  const double v2 = 109.9;
+  msg1.set_optional_double(v1);
+  msg2.set_optional_double(v2);
+
+  // Compare
+  util::MessageDifferencer differencer;
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+
+  // Set comparison to exact, margin and fraction value should not matter.
+  differencer.set_float_comparison(util::MessageDifferencer::EXACT);
+  // Set margin for float comparison.
+  const FieldDescriptor* fd =
+      msg1.GetDescriptor()->FindFieldByName("optional_double");
+  differencer.SetFractionAndMargin(fd, 0.0, 10.0);
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+
+  // Margin and fraction comparison is activated when float comparison is
+  // set to approximate.
+  differencer.set_float_comparison(util::MessageDifferencer::APPROXIMATE);
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+
+  // Test out comparison with fraction.
+  differencer.SetFractionAndMargin(fd, 0.2, 0.0);
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+
+  // Should fail since the fraction is smaller than error.
+  differencer.SetFractionAndMargin(fd, 0.01, 0.0);
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+
+  // Should pass if either fraction or margin are satisfied.
+  differencer.SetFractionAndMargin(fd, 0.01, 10.0);
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+
+  // Make sure that the margin and fraction only affects the field that it was
+  // set for.
+  msg1.set_default_double(v1);
+  msg2.set_default_double(v2);
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+  msg1.set_default_double(v1);
+  msg2.set_default_double(v1);
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, WithinDefaultFractionOrMarginDoubleTest) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  // Should fail on approximate equality check
+  const double v1 = 100.0;
+  const double v2 = 109.9;
+  msg1.set_optional_double(v1);
+  msg2.set_optional_double(v2);
+
+  util::MessageDifferencer differencer;
+
+  // Compare
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+
+  // Set up a custom field comparitor, with a default fraction and margin for
+  // float and double comparison.
+  util::DefaultFieldComparator field_comparitor;
+  field_comparitor.SetDefaultFractionAndMargin(0.0, 10.0);
+  differencer.set_field_comparator(&field_comparitor);
+
+  // Set comparison to exact, margin and fraction value should not matter.
+  field_comparitor.set_float_comparison(util::DefaultFieldComparator::EXACT);
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+
+  // Margin and fraction comparison is activated when float comparison is
+  // set to approximate.
+  field_comparitor.set_float_comparison(
+      util::DefaultFieldComparator::APPROXIMATE);
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+
+  // Test out comparison with fraction.
+  field_comparitor.SetDefaultFractionAndMargin(0.2, 0.0);
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+
+  // Should fail since the fraction is smaller than error.
+  field_comparitor.SetDefaultFractionAndMargin(0.01, 0.0);
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+
+  // Should pass if either fraction or margin are satisfied.
+  field_comparitor.SetDefaultFractionAndMargin(0.01, 10.0);
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+
+  // Make sure that the default margin and fraction affects all fields
+  msg1.set_default_double(v1);
+  msg2.set_default_double(v2);
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, BasicFieldOrderingsTest) {
+  // Create the testing protos
+  unittest::TestFieldOrderings msg1;
+  unittest::TestFieldOrderings msg2;
+
+  TestUtil::SetAllFieldsAndExtensions(&msg1);
+  TestUtil::SetAllFieldsAndExtensions(&msg2);
+
+  // Compare
+  EXPECT_TRUE(util::MessageDifferencer::Equals(msg1, msg2));
+}
+
+
+TEST(MessageDifferencerTest, BasicFieldOrderingInequalityTest) {
+  // Create the testing protos
+  unittest::TestFieldOrderings msg1;
+  unittest::TestFieldOrderings msg2;
+
+  TestUtil::SetAllFieldsAndExtensions(&msg1);
+  TestUtil::SetAllFieldsAndExtensions(&msg2);
+
+  msg1.set_my_float(15.00);
+  msg2.set_my_float(16.00);
+
+  // Compare
+  EXPECT_FALSE(util::MessageDifferencer::Equals(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, BasicExtensionTest) {
+  // Create the testing protos
+  unittest::TestAllExtensions msg1;
+  unittest::TestAllExtensions msg2;
+
+  TestUtil::SetAllExtensions(&msg1);
+  TestUtil::SetAllExtensions(&msg2);
+
+  // Compare
+  EXPECT_TRUE(util::MessageDifferencer::Equals(msg1, msg2));
+}
+
+
+TEST(MessageDifferencerTest, BasicExtensionInequalityTest) {
+  // Create the testing protos
+  unittest::TestAllExtensions msg1;
+  unittest::TestAllExtensions msg2;
+
+  TestUtil::SetAllExtensions(&msg1);
+  TestUtil::SetAllExtensions(&msg2);
+
+  msg1.SetExtension(unittest::optional_int32_extension, 101);
+  msg2.SetExtension(unittest::optional_int32_extension, 102);
+
+  // Compare
+  EXPECT_FALSE(util::MessageDifferencer::Equals(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, OneofTest) {
+  // Create the testing protos
+  unittest::TestOneof2 msg1;
+  unittest::TestOneof2 msg2;
+
+  TestUtil::SetOneof1(&msg1);
+  TestUtil::SetOneof1(&msg2);
+
+  // Compare
+  EXPECT_TRUE(util::MessageDifferencer::Equals(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, OneofInequalityTest) {
+  // Create the testing protos
+  unittest::TestOneof2 msg1;
+  unittest::TestOneof2 msg2;
+
+  TestUtil::SetOneof1(&msg1);
+  TestUtil::SetOneof2(&msg2);
+
+  // Compare
+  EXPECT_FALSE(util::MessageDifferencer::Equals(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, UnknownFieldPartialEqualTest) {
+  unittest::TestEmptyMessage empty1;
+  unittest::TestEmptyMessage empty2;
+
+  UnknownFieldSet* unknown1 = empty1.mutable_unknown_fields();
+  UnknownFieldSet* unknown2 = empty2.mutable_unknown_fields();
+
+  unknown1->AddVarint(243, 122);
+  unknown1->AddLengthDelimited(245, "abc");
+  unknown1->AddGroup(246)->AddFixed32(248, 1);
+  unknown1->mutable_field(2)->mutable_group()->AddFixed32(248, 2);
+
+  unknown2->AddVarint(243, 122);
+  unknown2->AddLengthDelimited(245, "abc");
+  unknown2->AddGroup(246)->AddFixed32(248, 1);
+  unknown2->mutable_field(2)->mutable_group()->AddFixed32(248, 2);
+
+  util::MessageDifferencer differencer;
+  differencer.set_scope(util::MessageDifferencer::PARTIAL);
+  EXPECT_TRUE(differencer.Compare(empty1, empty2));
+}
+
+TEST(MessageDifferencerTest, SpecifiedFieldsEqualityAllTest) {
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  vector<const FieldDescriptor*> fields1;
+  vector<const FieldDescriptor*> fields2;
+  msg1.GetReflection()->ListFields(msg1, &fields1);
+  msg2.GetReflection()->ListFields(msg2, &fields2);
+
+  util::MessageDifferencer differencer;
+  EXPECT_TRUE(differencer.CompareWithFields(msg1, msg2, fields1, fields2));
+}
+
+TEST(MessageDifferencerTest, SpecifiedFieldsInequalityAllTest) {
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+
+  vector<const FieldDescriptor*> fields1;
+  vector<const FieldDescriptor*> fields2;
+  msg1.GetReflection()->ListFields(msg1, &fields1);
+  msg2.GetReflection()->ListFields(msg2, &fields2);
+
+  util::MessageDifferencer differencer;
+  EXPECT_FALSE(differencer.CompareWithFields(msg1, msg2, fields1, fields2));
+}
+
+TEST(MessageDifferencerTest, SpecifiedFieldsEmptyListAlwaysSucceeds) {
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+
+  vector<const FieldDescriptor*> empty_fields;
+
+  util::MessageDifferencer differencer;
+  EXPECT_TRUE(differencer.CompareWithFields(msg1, msg2,
+                                            empty_fields, empty_fields));
+
+  TestUtil::SetAllFields(&msg2);
+  EXPECT_TRUE(differencer.CompareWithFields(msg1, msg2,
+                                            empty_fields, empty_fields));
+}
+
+TEST(MessageDifferencerTest, SpecifiedFieldsCompareWithSelf) {
+  unittest::TestAllTypes msg1;
+  TestUtil::SetAllFields(&msg1);
+
+  vector<const FieldDescriptor*> fields;
+  msg1.GetReflection()->ListFields(msg1, &fields);
+
+  util::MessageDifferencer differencer;
+  EXPECT_TRUE(differencer.CompareWithFields(msg1, msg1, fields, fields));
+
+  {
+    // Compare with a subset of fields.
+    vector<const FieldDescriptor*> compare_fields;
+    for (int i = 0; i < fields.size(); ++i) {
+      if (i % 2 == 0) {
+        compare_fields.push_back(fields[i]);
+      }
+    }
+    EXPECT_TRUE(differencer.CompareWithFields(msg1, msg1,
+                                              compare_fields, compare_fields));
+  }
+  {
+    // Specify a different set of fields to compare, even though we're using the
+    // same message. This should fail, since we are explicitly saying that the
+    // set of fields are different.
+    vector<const FieldDescriptor*> compare_fields1;
+    vector<const FieldDescriptor*> compare_fields2;
+    for (int i = 0; i < fields.size(); ++i) {
+      if (i % 2 == 0) {
+        compare_fields1.push_back(fields[i]);
+      } else {
+        compare_fields2.push_back(fields[i]);
+      }
+    }
+    EXPECT_FALSE(differencer.CompareWithFields(
+        msg1, msg1, compare_fields1, compare_fields2));
+  }
+}
+
+TEST(MessageDifferencerTest, SpecifiedFieldsEqualityAllShuffledTest) {
+  // This is a public function, so make sure there are no assumptions about the
+  // list of fields. Randomly shuffle them to make sure that they are properly
+  // ordered for comparison.
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  vector<const FieldDescriptor*> fields1;
+  vector<const FieldDescriptor*> fields2;
+  msg1.GetReflection()->ListFields(msg1, &fields1);
+  msg2.GetReflection()->ListFields(msg2, &fields2);
+
+  std::random_shuffle(fields1.begin(), fields1.end());
+  std::random_shuffle(fields2.begin(), fields2.end());
+
+  util::MessageDifferencer differencer;
+  EXPECT_TRUE(differencer.CompareWithFields(msg1, msg2, fields1, fields2));
+}
+
+TEST(MessageDifferencerTest, SpecifiedFieldsSubsetEqualityTest) {
+  // Specify a set of fields to compare. All the fields are equal.
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  vector<const FieldDescriptor*> fields1;
+  msg1.GetReflection()->ListFields(msg1, &fields1);
+
+  vector<const FieldDescriptor*> compare_fields;
+  // Only compare the field descriptors with even indices.
+  for (int i = 0; i < fields1.size(); ++i) {
+    if (i % 2 == 0) {
+      compare_fields.push_back(fields1[i]);
+    }
+  }
+
+  util::MessageDifferencer differencer;
+  EXPECT_TRUE(differencer.CompareWithFields(msg1, msg2,
+                                            compare_fields, compare_fields));
+}
+
+TEST(MessageDifferencerTest,
+     SpecifiedFieldsSubsetIgnoresOtherFieldDifferencesTest) {
+  // Specify a set of fields to compare, but clear all the other fields in one
+  // of the messages. This should fail a regular compare, but CompareWithFields
+  // should succeed.
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  vector<const FieldDescriptor*> fields1;
+  const Reflection* reflection = msg1.GetReflection();
+  reflection->ListFields(msg1, &fields1);
+
+  vector<const FieldDescriptor*> compare_fields;
+  // Only compare the field descriptors with even indices.
+  for (int i = 0; i < fields1.size(); ++i) {
+    if (i % 2 == 0) {
+      compare_fields.push_back(fields1[i]);
+    } else {
+      reflection->ClearField(&msg2, fields1[i]);
+    }
+  }
+
+  util::MessageDifferencer differencer;
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+  EXPECT_TRUE(differencer.CompareWithFields(msg1, msg2,
+                                            compare_fields, compare_fields));
+}
+
+TEST(MessageDifferencerTest, SpecifiedFieldsDetectsDifferencesTest) {
+  // Change all of the repeated fields in one of the messages, and use only
+  // those fields for comparison.
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+  TestUtil::ModifyRepeatedFields(&msg2);
+
+  vector<const FieldDescriptor*> fields1;
+  msg1.GetReflection()->ListFields(msg1, &fields1);
+
+  vector<const FieldDescriptor*> compare_fields;
+  // Only compare the repeated field descriptors.
+  for (int i = 0; i < fields1.size(); ++i) {
+    if (fields1[i]->is_repeated()) {
+      compare_fields.push_back(fields1[i]);
+    }
+  }
+
+  util::MessageDifferencer differencer;
+  EXPECT_FALSE(differencer.CompareWithFields(msg1, msg2,
+                                             compare_fields, compare_fields));
+}
+
+TEST(MessageDifferencerTest, SpecifiedFieldsEquivalenceAllTest) {
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  vector<const FieldDescriptor*> fields1;
+  vector<const FieldDescriptor*> fields2;
+  msg1.GetReflection()->ListFields(msg1, &fields1);
+  msg2.GetReflection()->ListFields(msg2, &fields2);
+
+  util::MessageDifferencer differencer;
+  differencer.set_message_field_comparison(
+      util::MessageDifferencer::EQUIVALENT);
+  EXPECT_TRUE(differencer.CompareWithFields(msg1, msg2, fields1, fields2));
+}
+
+TEST(MessageDifferencerTest,
+     SpecifiedFieldsEquivalenceIgnoresOtherFieldDifferencesTest) {
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+  const Descriptor* desc = msg1.GetDescriptor();
+
+  const FieldDescriptor* optional_int32_desc =
+      desc->FindFieldByName("optional_int32");
+  const FieldDescriptor* optional_int64_desc =
+      desc->FindFieldByName("optional_int64");
+  const FieldDescriptor* default_int64_desc =
+      desc->FindFieldByName("default_int64");
+  ASSERT_TRUE(optional_int32_desc != NULL);
+  ASSERT_TRUE(optional_int64_desc != NULL);
+  ASSERT_TRUE(default_int64_desc != NULL);
+  msg1.set_optional_int32(0);
+  msg2.set_optional_int64(0);
+  msg1.set_default_int64(default_int64_desc->default_value_int64());
+
+  // Set a field to a non-default value so we know that field selection is
+  // actually doing something.
+  msg2.set_optional_uint64(23);
+
+  vector<const FieldDescriptor*> fields1;
+  vector<const FieldDescriptor*> fields2;
+  fields1.push_back(optional_int32_desc);
+  fields1.push_back(default_int64_desc);
+
+  fields2.push_back(optional_int64_desc);
+
+  util::MessageDifferencer differencer;
+  EXPECT_FALSE(differencer.CompareWithFields(msg1, msg2, fields1, fields2));
+  differencer.set_message_field_comparison(
+      util::MessageDifferencer::EQUIVALENT);
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+  EXPECT_TRUE(differencer.CompareWithFields(msg1, msg2, fields1, fields2));
+}
+
+TEST(MessageDifferencerTest, RepeatedFieldSetTest_SetOfSet) {
+  // Create the testing protos
+  protobuf_unittest::TestDiffMessage msg1;
+  protobuf_unittest::TestDiffMessage msg2;
+
+  protobuf_unittest::TestDiffMessage::Item* item = msg1.add_item();
+  item->add_ra(1); item->add_ra(2); item->add_ra(3);
+  item = msg1.add_item();
+  item->add_ra(5); item->add_ra(6);
+  item = msg1.add_item();
+  item->add_ra(1); item->add_ra(3);
+  item = msg1.add_item();
+  item->add_ra(6); item->add_ra(7); item->add_ra(8);
+
+  item = msg2.add_item();
+  item->add_ra(6); item->add_ra(5);
+  item = msg2.add_item();
+  item->add_ra(6); item->add_ra(8); item->add_ra(7);
+  item = msg2.add_item();
+  item->add_ra(1); item->add_ra(3);
+  item = msg2.add_item();
+  item->add_ra(3); item->add_ra(2); item->add_ra(1);
+
+  // Compare
+  util::MessageDifferencer differencer;
+  differencer.set_repeated_field_comparison(util::MessageDifferencer::AS_SET);
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, RepeatedFieldSetTest_Combination) {
+  // Create the testing protos
+  protobuf_unittest::TestDiffMessage msg1;
+  protobuf_unittest::TestDiffMessage msg2;
+  // Treat "item" as Map, with key = "a"
+  // Treat "item.ra" also as Set
+  // Treat "rv" as Set
+  // Treat "rw" as List
+  protobuf_unittest::TestDiffMessage::Item* item = msg1.add_item();
+  item->set_a(3);
+  item->add_ra(1); item->add_ra(2); item->add_ra(3);
+  item = msg1.add_item();
+  item->set_a(4);
+  item->add_ra(5); item->add_ra(6);
+  item = msg1.add_item();
+  item->set_a(1);
+  item->add_ra(1); item->add_ra(3);
+  item = msg1.add_item();
+  item->set_a(2);
+  item->add_ra(6); item->add_ra(7); item->add_ra(8);
+
+  item = msg2.add_item();
+  item->set_a(4);
+  item->add_ra(6); item->add_ra(5);
+  item = msg2.add_item();
+  item->set_a(2);
+  item->add_ra(6); item->add_ra(8); item->add_ra(7);
+  item = msg2.add_item();
+  item->set_a(1);
+  item->add_ra(1); item->add_ra(3);
+  item = msg2.add_item();
+  item->set_a(3);
+  item->add_ra(3); item->add_ra(2); item->add_ra(1);
+
+  msg1.add_rv(3);
+  msg1.add_rv(4);
+  msg1.add_rv(7);
+  msg1.add_rv(0);
+  msg2.add_rv(4);
+  msg2.add_rv(3);
+  msg2.add_rv(0);
+  msg2.add_rv(7);
+
+  msg1.add_rw("nothing"); msg2.add_rw("nothing");
+  msg1.add_rw("should"); msg2.add_rw("should");
+  msg1.add_rw("change"); msg2.add_rw("change");
+
+  // Compare
+  util::MessageDifferencer differencer;
+  differencer.TreatAsMap(msg1.GetDescriptor()->FindFieldByName("item"),
+                         item->GetDescriptor()->FindFieldByName("a"));
+  differencer.TreatAsSet(msg1.GetDescriptor()->FindFieldByName("rv"));
+  differencer.TreatAsSet(item->GetDescriptor()->FindFieldByName("ra"));
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, RepeatedFieldMapTest_Partial) {
+  protobuf_unittest::TestDiffMessage msg1;
+  // message msg1 {
+  //   item { a: 1; b: "11" }
+  // }
+  protobuf_unittest::TestDiffMessage::Item* item = msg1.add_item();
+  item->set_a(1);
+  item->set_b("11");
+
+  protobuf_unittest::TestDiffMessage msg2;
+  // message msg2 {
+  //   item { a: 2; b: "22" }
+  //   item { a: 1; b: "11" }
+  // }
+  item = msg2.add_item();
+  item->set_a(2);
+  item->set_b("22");
+  item = msg2.add_item();
+  item->set_a(1);
+  item->set_b("11");
+
+  // Compare
+  util::MessageDifferencer differencer;
+  differencer.TreatAsMap(GetFieldDescriptor(msg1, "item"),
+                         GetFieldDescriptor(msg1, "item.a"));
+  differencer.set_scope(util::MessageDifferencer::PARTIAL);
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, RepeatedFieldSetTest_Duplicates) {
+  protobuf_unittest::TestDiffMessage a, b, c;
+  // message a: {
+  //   rv: 0
+  //   rv: 1
+  //   rv: 0
+  // }
+  a.add_rv(0);
+  a.add_rv(1);
+  a.add_rv(0);
+  // message b: {
+  //   rv: 0
+  //   rv: 0
+  //   rv: 1
+  // }
+  b.add_rv(0);
+  b.add_rv(0);
+  b.add_rv(1);
+  // message c: {
+  //   rv: 0
+  //   rv: 1
+  // }
+  c.add_rv(0);
+  c.add_rv(1);
+  util::MessageDifferencer differencer;
+  differencer.TreatAsSet(GetFieldDescriptor(a, "rv"));
+  EXPECT_TRUE(differencer.Compare(b, a));
+  EXPECT_FALSE(differencer.Compare(c, a));
+}
+
+TEST(MessageDifferencerTest, RepeatedFieldSetTest_PartialSimple) {
+  protobuf_unittest::TestDiffMessage a, b, c;
+  // message a: {
+  //   rm { c: 1 }
+  //   rm { c: 0 }
+  // }
+  a.add_rm()->set_c(1);
+  a.add_rm()->set_c(0);
+  // message b: {
+  //   rm { c: 1 }
+  //   rm {}
+  // }
+  b.add_rm()->set_c(1);
+  b.add_rm();
+  // message c: {
+  //   rm {}
+  //   rm { c: 1 }
+  // }
+  c.add_rm();
+  c.add_rm()->set_c(1);
+  util::MessageDifferencer differencer;
+  differencer.set_scope(util::MessageDifferencer::PARTIAL);
+  differencer.TreatAsSet(GetFieldDescriptor(a, "rm"));
+  EXPECT_TRUE(differencer.Compare(b, a));
+  EXPECT_TRUE(differencer.Compare(c, a));
+}
+
+TEST(MessageDifferencerTest, RepeatedFieldSetTest_Partial) {
+  protobuf_unittest::TestDiffMessage msg1, msg2;
+  // message msg1: {
+  //   rm { a: 1 }
+  //   rm { b: 2 }
+  //   rm { c: 3 }
+  // }
+  msg1.add_rm()->set_a(1);
+  msg1.add_rm()->set_b(2);
+  msg1.add_rm()->set_c(3);
+  // message msg2: {
+  //   rm { a: 1; c: 3 }
+  //   rm { b: 2; c: 3 }
+  //   rm { b: 2 }
+  // }
+  protobuf_unittest::TestField* field = msg2.add_rm();
+  field->set_a(1);
+  field->set_c(3);
+  field = msg2.add_rm();
+  field->set_b(2);
+  field->set_c(3);
+  field = msg2.add_rm();
+  field->set_b(2);
+
+  util::MessageDifferencer differencer;
+  differencer.set_scope(util::MessageDifferencer::PARTIAL);
+  differencer.TreatAsSet(GetFieldDescriptor(msg1, "rm"));
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, RepeatedFieldMapTest_MultipleFieldsAsKey) {
+  protobuf_unittest::TestDiffMessage msg1;
+  protobuf_unittest::TestDiffMessage msg2;
+  // Treat "item" as Map, with key = ("a", "ra")
+  // Treat "item.ra" as Set
+  protobuf_unittest::TestDiffMessage::Item* item = msg1.add_item();
+  // key => value: (1, {2, 3}) => "a"
+  item->set_a(1);
+  item->add_ra(2);
+  item->add_ra(3);
+  item->set_b("a");
+  item = msg1.add_item();
+  // key => value: (2, {1, 3}) => "b"
+  item->set_a(2);
+  item->add_ra(1);
+  item->add_ra(3);
+  item->set_b("b");
+  item = msg1.add_item();
+  // key => value: (1, {1, 3}) => "c"
+  item->set_a(1);
+  item->add_ra(1);
+  item->add_ra(3);
+  item->set_b("c");
+
+  item = msg2.add_item();
+  // key => value: (1, {1, 3}) => "c"
+  item->set_a(1);
+  item->add_ra(3);
+  item->add_ra(1);
+  item->set_b("c");
+  item = msg2.add_item();
+  // key => value: (1, {2, 3}) => "a"
+  item->set_a(1);
+  item->add_ra(3);
+  item->add_ra(2);
+  item->set_b("a");
+  item = msg2.add_item();
+  // key => value: (2, {1, 3}) => "b"
+  item->set_a(2);
+  item->add_ra(3);
+  item->add_ra(1);
+  item->set_b("b");
+
+  // Compare
+  util::MessageDifferencer differencer;
+  differencer.TreatAsSet(GetFieldDescriptor(msg1, "item.ra"));
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+  vector<const FieldDescriptor*> key_fields;
+  key_fields.push_back(GetFieldDescriptor(msg1, "item.a"));
+  key_fields.push_back(GetFieldDescriptor(msg1, "item.ra"));
+  differencer.TreatAsMapWithMultipleFieldsAsKey(
+      GetFieldDescriptor(msg1, "item"), key_fields);
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+
+  // Introduce some differences.
+  msg1.clear_item();
+  msg2.clear_item();
+  item = msg1.add_item();
+  item->set_a(4);
+  item->add_ra(5);
+  item->add_ra(6);
+  item->set_b("hello");
+  item = msg2.add_item();
+  item->set_a(4);
+  item->add_ra(6);
+  item->add_ra(5);
+  item->set_b("world");
+  string output;
+  differencer.ReportDifferencesToString(&output);
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+  EXPECT_EQ(
+      "moved: item[0].ra[0] -> item[0].ra[1] : 5\n"
+      "moved: item[0].ra[1] -> item[0].ra[0] : 6\n"
+      "modified: item[0].b: \"hello\" -> \"world\"\n",
+      output);
+}
+
+TEST(MessageDifferencerTest, RepeatedFieldMapTest_MultipleFieldPathsAsKey) {
+  protobuf_unittest::TestDiffMessage msg1;
+  protobuf_unittest::TestDiffMessage msg2;
+  // Treat "item" as Map, with key = ("m.a", "m.rc")
+  // Treat "item.m.rc" as Set
+  protobuf_unittest::TestDiffMessage::Item* item = msg1.add_item();
+  // key => value: (1, {2, 3}) => "a"
+  item->mutable_m()->set_a(1);
+  item->mutable_m()->add_rc(2);
+  item->mutable_m()->add_rc(3);
+  item->set_b("a");
+  item = msg1.add_item();
+  // key => value: (2, {1, 3}) => "b"
+  item->mutable_m()->set_a(2);
+  item->mutable_m()->add_rc(1);
+  item->mutable_m()->add_rc(3);
+  item->set_b("b");
+  item = msg1.add_item();
+  // key => value: (1, {1, 3}) => "c"
+  item->mutable_m()->set_a(1);
+  item->mutable_m()->add_rc(1);
+  item->mutable_m()->add_rc(3);
+  item->set_b("c");
+
+  item = msg2.add_item();
+  // key => value: (1, {1, 3}) => "c"
+  item->mutable_m()->set_a(1);
+  item->mutable_m()->add_rc(3);
+  item->mutable_m()->add_rc(1);
+  item->set_b("c");
+  item = msg2.add_item();
+  // key => value: (1, {2, 3}) => "a"
+  item->mutable_m()->set_a(1);
+  item->mutable_m()->add_rc(3);
+  item->mutable_m()->add_rc(2);
+  item->set_b("a");
+  item = msg2.add_item();
+  // key => value: (2, {1, 3}) => "b"
+  item->mutable_m()->set_a(2);
+  item->mutable_m()->add_rc(3);
+  item->mutable_m()->add_rc(1);
+  item->set_b("b");
+
+  // Compare
+  util::MessageDifferencer differencer;
+  differencer.TreatAsSet(GetFieldDescriptor(msg1, "item.m.rc"));
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+  vector<vector<const FieldDescriptor*> > key_field_paths;
+  vector<const FieldDescriptor*> key_field_path1;
+  key_field_path1.push_back(GetFieldDescriptor(msg1, "item.m"));
+  key_field_path1.push_back(GetFieldDescriptor(msg1, "item.m.a"));
+  vector<const FieldDescriptor*> key_field_path2;
+  key_field_path2.push_back(GetFieldDescriptor(msg1, "item.m"));
+  key_field_path2.push_back(GetFieldDescriptor(msg1, "item.m.rc"));
+  key_field_paths.push_back(key_field_path1);
+  key_field_paths.push_back(key_field_path2);
+  differencer.TreatAsMapWithMultipleFieldPathsAsKey(
+      GetFieldDescriptor(msg1, "item"), key_field_paths);
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+
+  // Introduce some differences.
+  msg1.clear_item();
+  msg2.clear_item();
+  item = msg1.add_item();
+  item->mutable_m()->set_a(4);
+  item->mutable_m()->add_rc(5);
+  item->mutable_m()->add_rc(6);
+  item->set_b("hello");
+  item = msg2.add_item();
+  item->mutable_m()->set_a(4);
+  item->mutable_m()->add_rc(6);
+  item->mutable_m()->add_rc(5);
+  item->set_b("world");
+  string output;
+  differencer.ReportDifferencesToString(&output);
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+  EXPECT_EQ(
+      "modified: item[0].b: \"hello\" -> \"world\"\n"
+      "moved: item[0].m.rc[0] -> item[0].m.rc[1] : 5\n"
+      "moved: item[0].m.rc[1] -> item[0].m.rc[0] : 6\n",
+      output);
+}
+
+TEST(MessageDifferencerTest, RepeatedFieldMapTest_IgnoredKeyFields) {
+  protobuf_unittest::TestDiffMessage msg1;
+  protobuf_unittest::TestDiffMessage msg2;
+  // Treat "item" as Map, with key = ("a", "ra")
+  protobuf_unittest::TestDiffMessage::Item* item = msg1.add_item();
+  item->set_a(1);
+  item->add_ra(2);
+  item->set_b("hello");
+  item = msg2.add_item();
+  item->set_a(1);
+  item->add_ra(3);
+  item->set_b("world");
+  // Compare
+  util::MessageDifferencer differencer;
+  vector<const FieldDescriptor*> key_fields;
+  key_fields.push_back(GetFieldDescriptor(msg1, "item.a"));
+  key_fields.push_back(GetFieldDescriptor(msg1, "item.ra"));
+  differencer.TreatAsMapWithMultipleFieldsAsKey(
+      GetFieldDescriptor(msg1, "item"), key_fields);
+  string output;
+  differencer.ReportDifferencesToString(&output);
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+  EXPECT_EQ(
+      "added: item[0]: { a: 1 ra: 3 b: \"world\" }\n"
+      "deleted: item[0]: { a: 1 ra: 2 b: \"hello\" }\n",
+      output);
+  // Ignored fields that are listed as parts of the key are still used
+  // in key comparison, but they're not used in value comparison.
+  differencer.IgnoreField(GetFieldDescriptor(msg1, "item.ra"));
+  output.clear();
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+  EXPECT_EQ(
+      "added: item[0]: { a: 1 ra: 3 b: \"world\" }\n"
+      "deleted: item[0]: { a: 1 ra: 2 b: \"hello\" }\n",
+      output);
+  // Ignoring a field in the key is different from treating the left fields
+  // as key. That is:
+  //   (key = ("a", "ra") && ignore "ra") != (key = ("a") && ignore "ra")
+  util::MessageDifferencer differencer2;
+  differencer2.TreatAsMap(GetFieldDescriptor(msg1, "item"),
+                          GetFieldDescriptor(msg1, "item.a"));
+  differencer2.IgnoreField(GetFieldDescriptor(msg1, "item.ra"));
+  output.clear();
+  differencer2.ReportDifferencesToString(&output);
+  EXPECT_FALSE(differencer2.Compare(msg1, msg2));
+  EXPECT_EQ(
+      "ignored: item[0].ra\n"
+      "modified: item[0].b: \"hello\" -> \"world\"\n",
+      output);
+}
+
+static const char* const kIgnoredFields[] = {"rm.b", "rm.m.b"};
+
+class TestIgnorer : public util::MessageDifferencer::IgnoreCriteria {
+ public:
+  bool IsIgnored(
+      const Message& message1, const Message& message2,
+      const FieldDescriptor* field,
+      const vector<util::MessageDifferencer::SpecificField>& parent_fields)
+      override {
+    string name = "";
+    for (int i = 0; i < parent_fields.size(); ++i) {
+      name += parent_fields[i].field->name() + ".";
+    }
+    name += field->name();
+    for (int i = 0; i < GOOGLE_ARRAYSIZE(kIgnoredFields); ++i) {
+      if (name.compare(kIgnoredFields[i]) == 0) {
+        return true;
+      }
+    }
+    return false;
+  }
+};
+
+TEST(MessageDifferencerTest, TreatRepeatedFieldAsSetWithIgnoredFields) {
+  protobuf_unittest::TestDiffMessage msg1;
+  protobuf_unittest::TestDiffMessage msg2;
+  TextFormat::MergeFromString("rm { a: 11\n b: 12 }", &msg1);
+  TextFormat::MergeFromString("rm { a: 11\n b: 13 }", &msg2);
+  util::MessageDifferencer differ;
+  differ.TreatAsSet(GetFieldDescriptor(msg1, "rm"));
+  differ.AddIgnoreCriteria(new TestIgnorer);
+  EXPECT_TRUE(differ.Compare(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, TreatRepeatedFieldAsMapWithIgnoredKeyFields) {
+  protobuf_unittest::TestDiffMessage msg1;
+  protobuf_unittest::TestDiffMessage msg2;
+  TextFormat::MergeFromString("rm { a: 11\n m { a: 12\n b: 13\n } }", &msg1);
+  TextFormat::MergeFromString("rm { a: 11\n m { a: 12\n b: 14\n } }", &msg2);
+  util::MessageDifferencer differ;
+  differ.TreatAsMap(GetFieldDescriptor(msg1, "rm"),
+                    GetFieldDescriptor(msg1, "rm.m"));
+  differ.AddIgnoreCriteria(new TestIgnorer);
+  EXPECT_TRUE(differ.Compare(msg1, msg2));
+}
+
+// Takes the product of all elements of item.ra as the key for key comparison.
+class ValueProductMapKeyComparator
+    : public util::MessageDifferencer::MapKeyComparator {
+ public:
+  virtual bool IsMatch(const Message &message1,
+                       const Message &message2) const {
+    const Reflection* reflection1 = message1.GetReflection();
+    const Reflection* reflection2 = message2.GetReflection();
+    // FieldDescriptor for item.ra
+    const FieldDescriptor* ra_field =
+        message1.GetDescriptor()->FindFieldByName("ra");
+    // Get the product of all elements in item.ra
+    int result1 = 1, result2 = 1;
+    for (int i = 0; i < reflection1->FieldSize(message1, ra_field); ++i) {
+      result1 *= reflection1->GetRepeatedInt32(message1, ra_field, i);
+    }
+    for (int i = 0; i < reflection2->FieldSize(message2, ra_field); ++i) {
+      result2 *= reflection2->GetRepeatedInt32(message2, ra_field, i);
+    }
+    return result1 == result2;
+  }
+};
+
+TEST(MessageDifferencerTest, RepeatedFieldMapTest_CustomMapKeyComparator) {
+  protobuf_unittest::TestDiffMessage msg1;
+  protobuf_unittest::TestDiffMessage msg2;
+  // Treat "item" as Map, using custom key comparator to determine if two
+  // elements have the same key.
+  protobuf_unittest::TestDiffMessage::Item* item = msg1.add_item();
+  item->add_ra(6);
+  item->add_ra(35);
+  item->set_b("hello");
+  item = msg2.add_item();
+  item->add_ra(10);
+  item->add_ra(21);
+  item->set_b("hello");
+  util::MessageDifferencer differencer;
+  ValueProductMapKeyComparator key_comparator;
+  differencer.TreatAsMapUsingKeyComparator(
+      GetFieldDescriptor(msg1, "item"), &key_comparator);
+  string output;
+  differencer.ReportDifferencesToString(&output);
+  // Though the above two messages have different values for item.ra, they
+  // are regarded as having the same key because 6 * 35 == 10 * 21. That's
+  // how the key comparator determines if the two have the same key.
+  // However, in value comparison, all fields of the message are taken into
+  // consideration, so they are different because their item.ra fields have
+  // different values using normal value comparison.
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+  EXPECT_EQ(
+      "modified: item[0].ra[0]: 6 -> 10\n"
+      "modified: item[0].ra[1]: 35 -> 21\n",
+      output);
+  differencer.IgnoreField(GetFieldDescriptor(msg1, "item.ra"));
+  output.clear();
+  // item.ra is ignored in value comparison, so the two messages equal.
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+  EXPECT_EQ("ignored: item[0].ra\n", output);
+}
+
+TEST(MessageDifferencerTest, RepeatedFieldSetTest_Subset) {
+  protobuf_unittest::TestDiffMessage msg1;
+  protobuf_unittest::TestDiffMessage msg2;
+
+  msg1.add_rv(3);
+  msg1.add_rv(8);
+  msg1.add_rv(2);
+  msg2.add_rv(2);
+  msg2.add_rv(3);
+  msg2.add_rv(5);
+  msg2.add_rv(8);
+
+  util::MessageDifferencer differencer;
+
+  // Fail with only partial scope set.
+  differencer.set_scope(util::MessageDifferencer::PARTIAL);
+  differencer.set_repeated_field_comparison(util::MessageDifferencer::AS_LIST);
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+
+  // Fail with only set-like comparison set.
+  differencer.set_scope(util::MessageDifferencer::FULL);
+  differencer.set_repeated_field_comparison(util::MessageDifferencer::AS_SET);
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+
+  // Succeed with scope and repeated field comparison set properly.
+  differencer.set_scope(util::MessageDifferencer::PARTIAL);
+  differencer.set_repeated_field_comparison(util::MessageDifferencer::AS_SET);
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, IgnoreField_Single) {
+  protobuf_unittest::TestField msg1;
+  protobuf_unittest::TestField msg2;
+
+  msg1.set_c(3);
+  msg1.add_rc(1);
+
+  msg2.set_c(5);
+  msg2.add_rc(1);
+
+  util::MessageDifferencer differencer;
+  differencer.IgnoreField(GetFieldDescriptor(msg1, "c"));
+
+  ExpectEqualsWithDifferencer(&differencer, msg1, msg2);
+}
+
+TEST(MessageDifferencerTest, IgnoreField_Repeated) {
+  protobuf_unittest::TestField msg1;
+  protobuf_unittest::TestField msg2;
+
+  msg1.set_c(3);
+  msg1.add_rc(1);
+  msg1.add_rc(2);
+
+  msg2.set_c(3);
+  msg2.add_rc(1);
+  msg2.add_rc(3);
+
+  util::MessageDifferencer differencer;
+  differencer.IgnoreField(GetFieldDescriptor(msg1, "rc"));
+
+  ExpectEqualsWithDifferencer(&differencer, msg1, msg2);
+}
+
+TEST(MessageDifferencerTest, IgnoreField_Message) {
+  protobuf_unittest::TestDiffMessage msg1;
+  protobuf_unittest::TestDiffMessage msg2;
+
+  protobuf_unittest::TestField* field;
+
+  field = msg1.add_rm();
+  field->set_c(3);
+
+  field = msg2.add_rm();
+  field->set_c(4);
+
+  util::MessageDifferencer differencer;
+  differencer.IgnoreField(GetFieldDescriptor(msg1, "rm"));
+
+  ExpectEqualsWithDifferencer(&differencer, msg1, msg2);
+}
+
+TEST(MessageDifferencerTest, IgnoreField_Group) {
+  protobuf_unittest::TestDiffMessage msg1;
+  protobuf_unittest::TestDiffMessage msg2;
+
+  protobuf_unittest::TestDiffMessage::Item* item;
+
+  item = msg1.add_item();
+  item->set_a(3);
+
+  item = msg2.add_item();
+  item->set_a(4);
+
+  util::MessageDifferencer differencer;
+  differencer.IgnoreField(GetFieldDescriptor(msg1, "item"));
+
+  ExpectEqualsWithDifferencer(&differencer, msg1, msg2);
+}
+
+TEST(MessageDifferencerTest, IgnoreField_Missing) {
+  protobuf_unittest::TestField msg1;
+  protobuf_unittest::TestField msg2;
+
+  msg1.set_c(3);
+  msg1.add_rc(1);
+
+  msg2.add_rc(1);
+
+  util::MessageDifferencer differencer;
+  differencer.IgnoreField(GetFieldDescriptor(msg1, "c"));
+
+  ExpectEqualsWithDifferencer(&differencer, msg1, msg2);
+  ExpectEqualsWithDifferencer(&differencer, msg2, msg1);
+}
+
+TEST(MessageDifferencerTest, IgnoreField_Multiple) {
+  protobuf_unittest::TestField msg1;
+  protobuf_unittest::TestField msg2;
+
+  msg1.set_c(3);
+  msg1.add_rc(1);
+  msg1.add_rc(2);
+
+  msg2.set_c(5);
+  msg2.add_rc(1);
+  msg2.add_rc(3);
+
+  const FieldDescriptor* c = GetFieldDescriptor(msg1, "c");
+  const FieldDescriptor* rc = GetFieldDescriptor(msg1, "rc");
+
+  { // Ignore c
+    util::MessageDifferencer differencer;
+    differencer.IgnoreField(c);
+
+    EXPECT_FALSE(differencer.Compare(msg1, msg2));
+  }
+  { // Ignore rc
+    util::MessageDifferencer differencer;
+    differencer.IgnoreField(rc);
+
+    EXPECT_FALSE(differencer.Compare(msg1, msg2));
+  }
+  { // Ignore both
+    util::MessageDifferencer differencer;
+    differencer.IgnoreField(c);
+    differencer.IgnoreField(rc);
+
+    ExpectEqualsWithDifferencer(&differencer, msg1, msg2);
+  }
+}
+
+TEST(MessageDifferencerTest, IgnoreField_NestedMessage) {
+  protobuf_unittest::TestDiffMessage msg1;
+  protobuf_unittest::TestDiffMessage msg2;
+
+  protobuf_unittest::TestField* field;
+
+  field = msg1.add_rm();
+  field->set_c(3);
+  field->add_rc(1);
+
+  field = msg2.add_rm();
+  field->set_c(4);
+  field->add_rc(1);
+
+  util::MessageDifferencer differencer;
+  differencer.IgnoreField(GetFieldDescriptor(msg1, "rm.c"));
+
+  ExpectEqualsWithDifferencer(&differencer, msg1, msg2);
+}
+
+TEST(MessageDifferencerTest, IgnoreField_NestedGroup) {
+  protobuf_unittest::TestDiffMessage msg1;
+  protobuf_unittest::TestDiffMessage msg2;
+
+  protobuf_unittest::TestDiffMessage::Item* item;
+
+  item = msg1.add_item();
+  item->set_a(3);
+  item->set_b("foo");
+
+  item = msg2.add_item();
+  item->set_a(4);
+  item->set_b("foo");
+
+  util::MessageDifferencer differencer;
+  differencer.IgnoreField(GetFieldDescriptor(msg1, "item.a"));
+
+  ExpectEqualsWithDifferencer(&differencer, msg1, msg2);
+}
+
+TEST(MessageDifferencerTest, IgnoreField_InsideSet) {
+  protobuf_unittest::TestDiffMessage msg1;
+  protobuf_unittest::TestDiffMessage msg2;
+
+  protobuf_unittest::TestDiffMessage::Item* item;
+
+  item = msg1.add_item();
+  item->set_a(1);
+  item->set_b("foo");
+  item->add_ra(1);
+
+  item = msg1.add_item();
+  item->set_a(2);
+  item->set_b("bar");
+  item->add_ra(2);
+
+  item = msg2.add_item();
+  item->set_a(2);
+  item->set_b("bar");
+  item->add_ra(2);
+
+  item = msg2.add_item();
+  item->set_a(1);
+  item->set_b("baz");
+  item->add_ra(1);
+
+  const FieldDescriptor* item_desc = GetFieldDescriptor(msg1, "item");
+  const FieldDescriptor* b = GetFieldDescriptor(msg1, "item.b");
+
+  util::MessageDifferencer differencer;
+  differencer.IgnoreField(b);
+  differencer.TreatAsSet(item_desc);
+
+  ExpectEqualsWithDifferencer(&differencer, msg1, msg2);
+}
+
+TEST(MessageDifferencerTest, IgnoreField_InsideMap) {
+  protobuf_unittest::TestDiffMessage msg1;
+  protobuf_unittest::TestDiffMessage msg2;
+
+  protobuf_unittest::TestDiffMessage::Item* item;
+
+  item = msg1.add_item();
+  item->set_a(1);
+  item->set_b("foo");
+  item->add_ra(1);
+
+  item = msg1.add_item();
+  item->set_a(2);
+  item->set_b("bar");
+  item->add_ra(2);
+
+  item = msg2.add_item();
+  item->set_a(2);
+  item->set_b("bar");
+  item->add_ra(2);
+
+  item = msg2.add_item();
+  item->set_a(1);
+  item->set_b("baz");
+  item->add_ra(1);
+
+  const FieldDescriptor* item_desc = GetFieldDescriptor(msg1, "item");
+  const FieldDescriptor* a = GetFieldDescriptor(msg1, "item.a");
+  const FieldDescriptor* b = GetFieldDescriptor(msg1, "item.b");
+
+  util::MessageDifferencer differencer;
+  differencer.IgnoreField(b);
+  differencer.TreatAsMap(item_desc, a);
+
+  ExpectEqualsWithDifferencer(&differencer, msg1, msg2);
+}
+
+TEST(MessageDifferencerTest, IgnoreField_DoesNotIgnoreKey) {
+  protobuf_unittest::TestDiffMessage msg1;
+  protobuf_unittest::TestDiffMessage msg2;
+
+  protobuf_unittest::TestDiffMessage::Item* item;
+
+  item = msg1.add_item();
+  item->set_a(1);
+  item->set_b("foo");
+  item->add_ra(1);
+
+  item = msg2.add_item();
+  item->set_a(2);
+  item->set_b("foo");
+  item->add_ra(1);
+
+  const FieldDescriptor* item_desc = GetFieldDescriptor(msg1, "item");
+  const FieldDescriptor* a = GetFieldDescriptor(msg1, "item.a");
+
+  util::MessageDifferencer differencer;
+  differencer.IgnoreField(a);
+  differencer.TreatAsMap(item_desc, a);
+
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, IgnoreField_TrumpsCompareWithFields) {
+  protobuf_unittest::TestField msg1;
+  protobuf_unittest::TestField msg2;
+
+  msg1.set_c(3);
+  msg1.add_rc(1);
+  msg1.add_rc(2);
+
+  msg2.set_c(3);
+  msg2.add_rc(1);
+  msg2.add_rc(3);
+
+  const FieldDescriptor* c = GetFieldDescriptor(msg1, "c");
+  const FieldDescriptor* rc = GetFieldDescriptor(msg1, "rc");
+
+  vector<const FieldDescriptor*> fields;
+  fields.push_back(c);
+  fields.push_back(rc);
+
+  util::MessageDifferencer differencer;
+  differencer.IgnoreField(rc);
+
+  differencer.set_scope(util::MessageDifferencer::FULL);
+  EXPECT_TRUE(differencer.CompareWithFields(msg1, msg2, fields, fields));
+
+  differencer.set_scope(util::MessageDifferencer::PARTIAL);
+  EXPECT_TRUE(differencer.CompareWithFields(msg1, msg2, fields, fields));
+}
+
+
+// Test class to save a copy of the last field_context.parent_fields() vector
+// passed to the comparison function.
+class ParentSavingFieldComparator : public util::FieldComparator {
+ public:
+  ParentSavingFieldComparator() {}
+
+  virtual ComparisonResult Compare(
+      const google::protobuf::Message& message_1,
+      const google::protobuf::Message& message_2,
+      const google::protobuf::FieldDescriptor* field,
+      int index_1, int index_2,
+      const google::protobuf::util::FieldContext* field_context) {
+    if (field_context)
+      parent_fields_ = *(field_context->parent_fields());
+    if (field->cpp_type() == FieldDescriptor::CPPTYPE_MESSAGE) {
+      return RECURSE;
+    } else {
+      return SAME;
+    }
+  }
+
+  vector<google::protobuf::util::MessageDifferencer::SpecificField> parent_fields() {
+    return parent_fields_;
+  }
+
+ private:
+  vector<google::protobuf::util::MessageDifferencer::SpecificField> parent_fields_;
+};
+
+// Tests if MessageDifferencer sends the parent fields in the FieldContext
+// parameter.
+TEST(MessageDifferencerTest, FieldContextParentFieldsTest) {
+  protobuf_unittest::TestDiffMessage msg1;
+  msg1.add_rm()->set_c(1);
+  protobuf_unittest::TestDiffMessage msg2;
+  msg2.add_rm()->set_c(1);
+
+  ParentSavingFieldComparator field_comparator;
+  util::MessageDifferencer differencer;
+  differencer.set_field_comparator(&field_comparator);
+  differencer.Compare(msg1, msg2);
+
+  // We want only one parent with the name "rm"
+  ASSERT_EQ(1, field_comparator.parent_fields().size());
+  EXPECT_EQ("rm", field_comparator.parent_fields()[0].field->name());
+}
+
+
+class ComparisonTest : public testing::Test {
+ protected:
+  ComparisonTest() : use_equivalency_(false), repeated_field_as_set_(false) {
+    // Setup the test.
+    TestUtil::SetAllFields(&proto1_);
+    TestUtil::SetAllFields(&proto2_);
+
+    TestUtil::SetAllExtensions(&proto1ex_);
+    TestUtil::SetAllExtensions(&proto2ex_);
+
+    TestUtil::SetAllFieldsAndExtensions(&orderings_proto1_);
+    TestUtil::SetAllFieldsAndExtensions(&orderings_proto2_);
+
+    unknown1_ = empty1_.mutable_unknown_fields();
+    unknown2_ = empty2_.mutable_unknown_fields();
+  }
+
+  ~ComparisonTest() { }
+
+  void SetSpecialFieldOption(const Message& message,
+                              util::MessageDifferencer* d) {
+    if (!ignored_field_.empty()) {
+      d->IgnoreField(GetFieldDescriptor(message, ignored_field_));
+    }
+
+    if (repeated_field_as_set_) {
+      d->set_repeated_field_comparison(util::MessageDifferencer::AS_SET);
+    }
+
+    if (!set_field_.empty()) {
+      d->TreatAsSet(GetFieldDescriptor(message, set_field_));
+    }
+
+    if (!map_field_.empty() && !map_key_.empty()) {
+      d->TreatAsMap(GetFieldDescriptor(message, map_field_),
+                    GetFieldDescriptor(message, map_field_ + "." + map_key_));
+    }
+  }
+
+  string Run(const Message& msg1, const Message& msg2) {
+    string output;
+
+    // Setup the comparison.
+    util::MessageDifferencer differencer;
+    differencer.ReportDifferencesToString(&output);
+
+    if (use_equivalency_) {
+      differencer.set_message_field_comparison(
+          util::MessageDifferencer::EQUIVALENT);
+    }
+
+    SetSpecialFieldOption(msg1, &differencer);
+
+    // Conduct the comparison.
+    EXPECT_FALSE(differencer.Compare(msg1, msg2));
+
+    return output;
+  }
+
+  string Run() {
+    return Run(proto1_, proto2_);
+  }
+
+  string RunOrder() {
+    return Run(orderings_proto1_, orderings_proto2_);
+  }
+
+  string RunEx() {
+    return Run(proto1ex_, proto2ex_);
+  }
+
+  string RunDiff() {
+    return Run(proto1diff_, proto2diff_);
+  }
+
+  string RunUn() {
+    return Run(empty1_, empty2_);
+  }
+
+  void use_equivalency() {
+    use_equivalency_ = true;
+  }
+
+  void repeated_field_as_set() {
+    repeated_field_as_set_ = true;
+  }
+
+  void field_as_set(const string& field) {
+    set_field_ = field;
+  }
+
+  void field_as_map(const string& field, const string& key) {
+    map_field_ = field;
+    map_key_   = key;
+  }
+
+  void ignore_field(const string& field) {
+    ignored_field_ = field;
+  }
+
+  unittest::TestAllTypes proto1_;
+  unittest::TestAllTypes proto2_;
+
+  unittest::TestFieldOrderings orderings_proto1_;
+  unittest::TestFieldOrderings orderings_proto2_;
+
+  unittest::TestAllExtensions proto1ex_;
+  unittest::TestAllExtensions proto2ex_;
+
+  unittest::TestDiffMessage proto1diff_;
+  unittest::TestDiffMessage proto2diff_;
+
+  unittest::TestEmptyMessage empty1_;
+  unittest::TestEmptyMessage empty2_;
+
+  UnknownFieldSet* unknown1_;
+  UnknownFieldSet* unknown2_;
+
+  bool use_equivalency_;
+  bool repeated_field_as_set_;
+
+  string set_field_;
+  string map_field_;
+  string map_key_;
+  string ignored_field_;
+};
+
+// Basic tests.
+TEST_F(ComparisonTest, AdditionTest) {
+  proto1_.clear_optional_int32();
+
+  EXPECT_EQ("added: optional_int32: 101\n",
+            Run());
+}
+
+TEST_F(ComparisonTest, Addition_OrderTest) {
+  orderings_proto1_.clear_my_int();
+
+  EXPECT_EQ("added: my_int: 1\n",
+            RunOrder());
+}
+
+TEST_F(ComparisonTest, DeletionTest) {
+  proto2_.clear_optional_int32();
+
+  EXPECT_EQ("deleted: optional_int32: 101\n",
+            Run());
+}
+
+TEST_F(ComparisonTest, Deletion_OrderTest) {
+  orderings_proto2_.clear_my_string();
+
+  EXPECT_EQ("deleted: my_string: \"foo\"\n",
+            RunOrder());
+}
+
+TEST_F(ComparisonTest, RepeatedDeletionTest) {
+  proto2_.clear_repeated_int32();
+
+  EXPECT_EQ("deleted: repeated_int32[0]: 201\n"
+            "deleted: repeated_int32[1]: 301\n",
+            Run());
+}
+
+TEST_F(ComparisonTest, ModificationTest) {
+  proto1_.set_optional_int32(-1);
+
+  EXPECT_EQ("modified: optional_int32: -1 -> 101\n",
+            Run());
+}
+
+// Basic equivalency tests.
+TEST_F(ComparisonTest, EquivalencyAdditionTest) {
+  use_equivalency();
+
+  proto1_.clear_optional_int32();
+
+  EXPECT_EQ("modified: optional_int32: 0 -> 101\n",
+            Run());
+}
+
+TEST_F(ComparisonTest, EquivalencyDeletionTest) {
+  use_equivalency();
+
+  proto2_.clear_optional_int32();
+
+  EXPECT_EQ("modified: optional_int32: 101 -> 0\n",
+            Run());
+}
+
+// Group tests.
+TEST_F(ComparisonTest, GroupAdditionTest) {
+  proto1_.mutable_optionalgroup()->clear_a();
+
+  EXPECT_EQ("added: optionalgroup.a: 117\n",
+            Run());
+}
+
+TEST_F(ComparisonTest, GroupDeletionTest) {
+  proto2_.mutable_optionalgroup()->clear_a();
+
+  EXPECT_EQ("deleted: optionalgroup.a: 117\n",
+            Run());
+}
+
+TEST_F(ComparisonTest, GroupModificationTest) {
+  proto1_.mutable_optionalgroup()->set_a(2);
+
+  EXPECT_EQ("modified: optionalgroup.a: 2 -> 117\n",
+            Run());
+}
+
+TEST_F(ComparisonTest, GroupFullAdditionTest) {
+  proto1_.clear_optionalgroup();
+
+  // Note the difference in the output between this and GroupAdditionTest.
+  EXPECT_EQ("added: optionalgroup: { a: 117 }\n",
+            Run());
+}
+
+TEST_F(ComparisonTest, GroupFullDeletionTest) {
+  proto2_.clear_optionalgroup();
+
+  EXPECT_EQ("deleted: optionalgroup: { a: 117 }\n",
+            Run());
+}
+
+TEST_F(ComparisonTest, RepeatedSetOptionTest) {
+  repeated_field_as_set();
+
+  proto2_.clear_repeatedgroup();
+  proto1_.clear_repeatedgroup();
+  proto1_.add_repeatedgroup()->set_a(317);
+  proto2_.add_repeatedgroup()->set_a(909);
+  proto2_.add_repeatedgroup()->set_a(907);
+  proto1_.add_repeatedgroup()->set_a(904);
+  proto1_.add_repeatedgroup()->set_a(907);
+  proto1_.add_repeatedgroup()->set_a(909);
+
+  EXPECT_EQ("moved: repeatedgroup[2] -> repeatedgroup[1] : { a: 907 }\n"
+            "moved: repeatedgroup[3] -> repeatedgroup[0] : { a: 909 }\n"
+            "deleted: repeatedgroup[0]: { a: 317 }\n"
+            "deleted: repeatedgroup[1]: { a: 904 }\n",
+            Run());
+}
+
+TEST_F(ComparisonTest, RepeatedSetOptionTest_Ex) {
+  repeated_field_as_set();
+
+  proto1ex_.ClearExtension(protobuf_unittest::repeated_nested_message_extension);
+  proto2ex_.ClearExtension(protobuf_unittest::repeated_nested_message_extension);
+  proto2ex_.AddExtension(protobuf_unittest::repeated_nested_message_extension)
+      ->set_bb(909);
+  proto2ex_.AddExtension(protobuf_unittest::repeated_nested_message_extension)
+      ->set_bb(907);
+  proto1ex_.AddExtension(protobuf_unittest::repeated_nested_message_extension)
+      ->set_bb(904);
+  proto1ex_.AddExtension(protobuf_unittest::repeated_nested_message_extension)
+      ->set_bb(907);
+  proto1ex_.AddExtension(protobuf_unittest::repeated_nested_message_extension)
+      ->set_bb(909);
+
+  EXPECT_EQ("moved: (protobuf_unittest.repeated_nested_message_extension)[2] ->"
+            " (protobuf_unittest.repeated_nested_message_extension)[0] :"
+            " { bb: 909 }\n"
+            "deleted: (protobuf_unittest.repeated_nested_message_extension)[0]:"
+            " { bb: 904 }\n",
+            RunEx());
+}
+
+TEST_F(ComparisonTest, RepeatedMapFieldTest_Group) {
+  field_as_map("repeatedgroup", "a");
+  proto1_.clear_repeatedgroup();
+  proto2_.clear_repeatedgroup();
+
+  proto1_.add_repeatedgroup()->set_a(317);  // deleted
+  proto1_.add_repeatedgroup()->set_a(904);  // deleted
+  proto1_.add_repeatedgroup()->set_a(907);  // moved from
+  proto1_.add_repeatedgroup()->set_a(909);  // moved from
+
+  proto2_.add_repeatedgroup()->set_a(909);  // moved to
+  proto2_.add_repeatedgroup()->set_a(318);  // added
+  proto2_.add_repeatedgroup()->set_a(907);  // moved to
+
+  EXPECT_EQ("moved: repeatedgroup[3] -> repeatedgroup[0] : { a: 909 }\n"
+            "added: repeatedgroup[1]: { a: 318 }\n"
+            "deleted: repeatedgroup[0]: { a: 317 }\n"
+            "deleted: repeatedgroup[1]: { a: 904 }\n",
+            Run());
+}
+
+TEST_F(ComparisonTest, RepeatedMapFieldTest_MessageKey) {
+  // Use m as key, but use b as value.
+  field_as_map("item", "m");
+
+  protobuf_unittest::TestDiffMessage msg1;
+  protobuf_unittest::TestDiffMessage msg2;
+  protobuf_unittest::TestDiffMessage::Item* item = msg1.add_item();
+
+  // The following code creates one deletion, one addition and two moved fields
+  // on the messages.
+  item->mutable_m()->set_c(0);
+  item->set_b("first");
+  item = msg1.add_item();
+  item->mutable_m()->set_c(2);
+  item->set_b("second");
+  item = msg1.add_item(); item->set_b("null");  // empty key moved
+  item = msg1.add_item();
+  item->mutable_m()->set_c(3);
+  item->set_b("third");   // deletion
+  item = msg1.add_item();
+  item->mutable_m()->set_c(2);
+  item->set_b("second");  // duplicated key ( deletion )
+  item = msg2.add_item();
+  item->mutable_m()->set_c(2);
+  item->set_b("second");  // modification
+  item = msg2.add_item();
+  item->mutable_m()->set_c(4);
+  item->set_b("fourth");  // addition
+  item = msg2.add_item();
+  item->mutable_m()->set_c(0);
+  item->set_b("fist");    // move with change
+  item = msg2.add_item(); item->set_b("null");
+
+  EXPECT_EQ(
+      "modified: item[0].b -> item[2].b: \"first\" -> \"fist\"\n"
+      "moved: item[1] -> item[0] : { b: \"second\" m { c: 2 } }\n"
+      "moved: item[2] -> item[3] : { b: \"null\" }\n"
+      "added: item[1]: { b: \"fourth\" m { c: 4 } }\n"
+      "deleted: item[3]: { b: \"third\" m { c: 3 } }\n"
+      "deleted: item[4]: { b: \"second\" m { c: 2 } }\n",
+      Run(msg1, msg2));
+}
+
+TEST_F(ComparisonTest, RepeatedFieldSetTest_SetOfSet) {
+  repeated_field_as_set();
+  // Create the testing protos
+  protobuf_unittest::TestDiffMessage msg1;
+  protobuf_unittest::TestDiffMessage msg2;
+
+  protobuf_unittest::TestDiffMessage::Item* item = msg1.add_item();
+  item->add_ra(1); item->add_ra(2); item->add_ra(3);
+  item = msg1.add_item();
+  item->add_ra(5); item->add_ra(6);
+  item = msg1.add_item();
+  item->add_ra(1); item->add_ra(3);
+  item = msg1.add_item();
+  item->add_ra(6); item->add_ra(7); item->add_ra(8);
+
+  item = msg2.add_item();
+  item->add_ra(6); item->add_ra(5);
+  item = msg2.add_item();
+  item->add_ra(6); item->add_ra(8);
+  item = msg2.add_item();
+  item->add_ra(1); item->add_ra(3);
+  item = msg2.add_item();
+  item->add_ra(3); item->add_ra(2); item->add_ra(1);
+
+  // Compare
+  EXPECT_EQ("moved: item[0].ra[0] -> item[3].ra[2] : 1\n"
+            "moved: item[0].ra[2] -> item[3].ra[0] : 3\n"
+            "moved: item[0] -> item[3] : { ra: 1 ra: 2 ra: 3 }\n"
+            "moved: item[1].ra[0] -> item[0].ra[1] : 5\n"
+            "moved: item[1].ra[1] -> item[0].ra[0] : 6\n"
+            "moved: item[1] -> item[0] : { ra: 5 ra: 6 }\n"
+            "added: item[1]: { ra: 6 ra: 8 }\n"
+            "deleted: item[3]: { ra: 6 ra: 7 ra: 8 }\n",
+            Run(msg1, msg2));
+}
+
+TEST_F(ComparisonTest, RepeatedMapFieldTest_RepeatedKey) {
+  // used rb as a key, but b is the value.
+  repeated_field_as_set();
+  field_as_map("item", "rb");
+
+  protobuf_unittest::TestDiffMessage msg1;
+  protobuf_unittest::TestDiffMessage msg2;
+  protobuf_unittest::TestDiffMessage::Item* item = msg1.add_item();
+  item->add_rb("a");
+  item->add_rb("b");
+  item->set_b("first");
+
+  item = msg2.add_item();
+  item->add_rb("c");
+  item->set_b("second");
+
+  item = msg2.add_item();
+  item->add_rb("b");
+  item->add_rb("a");
+  item->set_b("fist");
+
+
+  EXPECT_EQ("modified: item[0].b -> item[1].b: \"first\" -> \"fist\"\n"
+            "moved: item[0].rb[0] -> item[1].rb[1] : \"a\"\n"
+            "moved: item[0].rb[1] -> item[1].rb[0] : \"b\"\n"
+            "added: item[0]: { b: \"second\" rb: \"c\" }\n",
+            Run(msg1, msg2));
+}
+
+TEST_F(ComparisonTest, RepeatedMapFieldTest_RepeatedMessageKey) {
+  field_as_map("item", "rm");
+
+  protobuf_unittest::TestDiffMessage msg1;
+  protobuf_unittest::TestDiffMessage msg2;
+  protobuf_unittest::TestDiffMessage::Item* item = msg1.add_item();
+  protobuf_unittest::TestField* key = item->add_rm();
+  key->set_c(2); key->add_rc(10); key->add_rc(10);
+  item = msg1.add_item(); key = item->add_rm();
+  key->set_c(0); key->add_rc(1); key->add_rc(2);
+  key = item->add_rm();
+  key->set_c(0);
+  item->add_rb("first");
+
+  item = msg2.add_item();
+  item->CopyFrom(msg1.item(1));
+  item->add_rb("second");
+
+  EXPECT_EQ("added: item[0].rb[1]: \"second\"\n"
+            "deleted: item[0]: { rm { c: 2 rc: 10 rc: 10 } }\n",
+            Run(msg1, msg2));
+}
+
+TEST_F(ComparisonTest, RepeatedSetOptionTest_Unknown) {
+  // Currently, as_set option doens't have affects on unknown field.
+  // If needed, this feature will be added by request.
+  repeated_field_as_set();
+  unknown1_->AddGroup(245)->AddFixed32(248, 1);
+  unknown2_->AddGroup(245)->AddFixed32(248, 3);
+  unknown2_->AddGroup(245)->AddFixed32(248, 1);
+
+  // We expect it behaves the same as normal comparison.
+  EXPECT_EQ("modified: 245[0].248[0]: 0x00000001 -> 0x00000003\n"
+            "added: 245[1]: { ... }\n",
+            RunUn());
+}
+
+TEST_F(ComparisonTest, Matching_Unknown) {
+  unknown1_->AddGroup(245)->AddFixed32(248, 1);
+  unknown2_->AddGroup(245)->AddFixed32(248, 1);
+  unknown1_->AddGroup(245)->AddFixed32(248, 3);
+  unknown2_->AddGroup(245)->AddFixed32(248, 3);
+  unknown2_->AddLengthDelimited(242, "cat");
+  unknown2_->AddGroup(246)->AddFixed32(248, 4);
+
+  // report_match is false so only added/modified fields are expected.
+  EXPECT_EQ("added: 242[0]: \"cat\"\n"
+            "added: 246[0]: { ... }\n",
+            RunUn());
+}
+
+TEST_F(ComparisonTest, RepeatedSetFieldTest) {
+  field_as_set("repeatedgroup");
+
+  proto1_.clear_repeatedgroup();
+  proto2_.clear_repeatedgroup();
+  proto2_.add_repeatedgroup()->set_a(909);
+  proto2_.add_repeatedgroup()->set_a(907);
+  proto1_.add_repeatedgroup()->set_a(317);
+  proto1_.add_repeatedgroup()->set_a(904);
+  proto1_.add_repeatedgroup()->set_a(907);
+  proto1_.add_repeatedgroup()->set_a(909);
+
+  EXPECT_EQ("moved: repeatedgroup[2] -> repeatedgroup[1] : { a: 907 }\n"
+            "moved: repeatedgroup[3] -> repeatedgroup[0] : { a: 909 }\n"
+            "deleted: repeatedgroup[0]: { a: 317 }\n"
+            "deleted: repeatedgroup[1]: { a: 904 }\n",
+            Run());
+}
+
+// Embedded message tests.
+TEST_F(ComparisonTest, EmbeddedAdditionTest) {
+  proto1_.mutable_optional_nested_message()->clear_bb();
+
+  EXPECT_EQ("added: optional_nested_message.bb: 118\n",
+            Run());
+}
+
+TEST_F(ComparisonTest, EmbeddedDeletionTest) {
+  proto2_.mutable_optional_nested_message()->clear_bb();
+
+  EXPECT_EQ("deleted: optional_nested_message.bb: 118\n",
+            Run());
+}
+
+TEST_F(ComparisonTest, EmbeddedModificationTest) {
+  proto1_.mutable_optional_nested_message()->set_bb(2);
+
+  EXPECT_EQ("modified: optional_nested_message.bb: 2 -> 118\n",
+            Run());
+}
+
+TEST_F(ComparisonTest, EmbeddedFullAdditionTest) {
+  proto1_.clear_optional_nested_message();
+
+  EXPECT_EQ("added: optional_nested_message: { bb: 118 }\n",
+            Run());
+}
+
+TEST_F(ComparisonTest, EmbeddedPartialAdditionTest) {
+  proto1_.clear_optional_nested_message();
+  proto2_.mutable_optional_nested_message()->clear_bb();
+
+  EXPECT_EQ("added: optional_nested_message: { }\n",
+            Run());
+}
+
+TEST_F(ComparisonTest, EmbeddedFullDeletionTest) {
+  proto2_.clear_optional_nested_message();
+
+  EXPECT_EQ("deleted: optional_nested_message: { bb: 118 }\n",
+            Run());
+}
+
+// Repeated element tests.
+TEST_F(ComparisonTest, BasicRepeatedTest) {
+  proto1_.clear_repeated_int32();
+  proto2_.clear_repeated_int32();
+
+  proto1_.add_repeated_int32(500);
+  proto1_.add_repeated_int32(501);
+  proto1_.add_repeated_int32(502);
+  proto1_.add_repeated_int32(503);
+  proto1_.add_repeated_int32(500);
+
+  proto2_.add_repeated_int32(500);
+  proto2_.add_repeated_int32(509);
+  proto2_.add_repeated_int32(502);
+  proto2_.add_repeated_int32(504);
+
+  EXPECT_EQ("modified: repeated_int32[1]: 501 -> 509\n"
+            "modified: repeated_int32[3]: 503 -> 504\n"
+            "deleted: repeated_int32[4]: 500\n",
+            Run());
+}
+
+TEST_F(ComparisonTest, BasicRepeatedTest_SetOption) {
+  repeated_field_as_set();
+  proto1_.clear_repeated_int32();
+  proto2_.clear_repeated_int32();
+
+  proto1_.add_repeated_int32(501);
+  proto1_.add_repeated_int32(502);
+  proto1_.add_repeated_int32(503);
+  proto1_.add_repeated_int32(500);
+  proto1_.add_repeated_int32(500);
+
+  proto2_.add_repeated_int32(500);
+  proto2_.add_repeated_int32(509);
+  proto2_.add_repeated_int32(503);
+  proto2_.add_repeated_int32(502);
+  proto2_.add_repeated_int32(504);
+
+  EXPECT_EQ("moved: repeated_int32[1] -> repeated_int32[3] : 502\n"
+            "moved: repeated_int32[3] -> repeated_int32[0] : 500\n"
+            "added: repeated_int32[1]: 509\n"
+            "added: repeated_int32[4]: 504\n"
+            "deleted: repeated_int32[0]: 501\n"
+            "deleted: repeated_int32[4]: 500\n",
+            Run());
+}
+
+TEST_F(ComparisonTest, BasicRepeatedTest_SetField) {
+  field_as_set("repeated_int32");
+  proto1_.clear_repeated_int32();
+  proto2_.clear_repeated_int32();
+
+  proto1_.add_repeated_int32(501);
+  proto1_.add_repeated_int32(502);
+  proto1_.add_repeated_int32(503);
+  proto1_.add_repeated_int32(500);
+  proto1_.add_repeated_int32(500);
+
+  proto2_.add_repeated_int32(500);
+  proto2_.add_repeated_int32(509);
+  proto2_.add_repeated_int32(503);
+  proto2_.add_repeated_int32(502);
+  proto2_.add_repeated_int32(504);
+
+  EXPECT_EQ("moved: repeated_int32[1] -> repeated_int32[3] : 502\n"
+            "moved: repeated_int32[3] -> repeated_int32[0] : 500\n"
+            "added: repeated_int32[1]: 509\n"
+            "added: repeated_int32[4]: 504\n"
+            "deleted: repeated_int32[0]: 501\n"
+            "deleted: repeated_int32[4]: 500\n",
+            Run());
+}
+
+// Multiple action tests.
+TEST_F(ComparisonTest, AddDeleteTest) {
+  proto1_.clear_optional_int32();
+  proto2_.clear_optional_int64();
+
+  EXPECT_EQ("added: optional_int32: 101\n"
+            "deleted: optional_int64: 102\n",
+            Run());
+}
+
+TEST_F(ComparisonTest, AddDelete_FieldOrderingTest) {
+  orderings_proto1_.ClearExtension(unittest::my_extension_string);
+  orderings_proto2_.clear_my_int();
+
+  EXPECT_EQ("deleted: my_int: 1\n"
+            "added: (protobuf_unittest.my_extension_string): \"bar\"\n",
+            RunOrder());
+}
+
+TEST_F(ComparisonTest, AllThreeTest) {
+  proto1_.clear_optional_int32();
+  proto2_.clear_optional_float();
+  proto2_.set_optional_string("hello world!");
+
+  EXPECT_EQ("added: optional_int32: 101\n"
+            "deleted: optional_float: 111\n"
+            "modified: optional_string: \"115\" -> \"hello world!\"\n",
+            Run());
+}
+
+TEST_F(ComparisonTest, SandwhichTest) {
+  proto1_.clear_optional_int64();
+  proto1_.clear_optional_uint32();
+
+  proto2_.clear_optional_uint64();
+
+  EXPECT_EQ("added: optional_int64: 102\n"
+            "added: optional_uint32: 103\n"
+            "deleted: optional_uint64: 104\n",
+            Run());
+}
+
+TEST_F(ComparisonTest, IgnoredNoChangeTest) {
+  proto1diff_.set_v(3);
+  proto2diff_.set_v(3);
+  proto2diff_.set_w("foo");
+
+  ignore_field("v");
+
+  EXPECT_EQ("ignored: v\n"
+            "added: w: \"foo\"\n",
+            RunDiff());
+}
+
+TEST_F(ComparisonTest, IgnoredAddTest) {
+  proto2diff_.set_v(3);
+  proto2diff_.set_w("foo");
+
+  ignore_field("v");
+
+  EXPECT_EQ("ignored: v\n"
+            "added: w: \"foo\"\n",
+            RunDiff());
+}
+
+TEST_F(ComparisonTest, IgnoredDeleteTest) {
+  proto1diff_.set_v(3);
+  proto2diff_.set_w("foo");
+
+  ignore_field("v");
+
+  EXPECT_EQ("ignored: v\n"
+            "added: w: \"foo\"\n",
+            RunDiff());
+}
+
+TEST_F(ComparisonTest, IgnoredModifyTest) {
+  proto1diff_.set_v(3);
+  proto2diff_.set_v(4);
+  proto2diff_.set_w("foo");
+
+  ignore_field("v");
+
+  EXPECT_EQ("ignored: v\n"
+            "added: w: \"foo\"\n",
+            RunDiff());
+}
+
+TEST_F(ComparisonTest, IgnoredRepeatedAddTest) {
+  proto1diff_.add_rv(3);
+  proto1diff_.add_rv(4);
+
+  proto2diff_.add_rv(3);
+  proto2diff_.add_rv(4);
+  proto2diff_.add_rv(5);
+
+  proto2diff_.set_w("foo");
+
+  ignore_field("rv");
+
+  EXPECT_EQ("ignored: rv\n"
+            "added: w: \"foo\"\n",
+            RunDiff());
+}
+
+TEST_F(ComparisonTest, IgnoredRepeatedDeleteTest) {
+  proto1diff_.add_rv(3);
+  proto1diff_.add_rv(4);
+  proto1diff_.add_rv(5);
+
+  proto2diff_.add_rv(3);
+  proto2diff_.add_rv(4);
+
+  proto2diff_.set_w("foo");
+
+  ignore_field("rv");
+
+  EXPECT_EQ("ignored: rv\n"
+            "added: w: \"foo\"\n",
+            RunDiff());
+}
+
+TEST_F(ComparisonTest, IgnoredRepeatedModifyTest) {
+  proto1diff_.add_rv(3);
+  proto1diff_.add_rv(4);
+
+  proto2diff_.add_rv(3);
+  proto2diff_.add_rv(5);
+
+  proto2diff_.set_w("foo");
+
+  ignore_field("rv");
+
+  EXPECT_EQ("ignored: rv\n"
+            "added: w: \"foo\"\n",
+            RunDiff());
+}
+
+TEST_F(ComparisonTest, IgnoredWholeNestedMessage) {
+  proto1diff_.mutable_m()->set_c(3);
+  proto2diff_.mutable_m()->set_c(4);
+
+  proto2diff_.set_w("foo");
+
+  ignore_field("m");
+
+  EXPECT_EQ("added: w: \"foo\"\n"
+            "ignored: m\n",
+            RunDiff());
+}
+
+TEST_F(ComparisonTest, IgnoredNestedField) {
+  proto1diff_.mutable_m()->set_c(3);
+  proto2diff_.mutable_m()->set_c(4);
+
+  proto2diff_.set_w("foo");
+
+  ignore_field("m.c");
+
+  EXPECT_EQ("added: w: \"foo\"\n"
+            "ignored: m.c\n",
+            RunDiff());
+}
+
+TEST_F(ComparisonTest, IgnoredRepeatedNested) {
+  proto1diff_.add_rm()->set_c(0);
+  proto1diff_.add_rm()->set_c(1);
+  proto2diff_.add_rm()->set_c(2);
+  proto2diff_.add_rm()->set_c(3);
+
+  proto2diff_.set_w("foo");
+
+  ignore_field("rm.c");
+
+  EXPECT_EQ("ignored: rm[0].c\n"
+            "ignored: rm[1].c\n"
+            "added: w: \"foo\"\n",
+            RunDiff());
+}
+
+TEST_F(ComparisonTest, IgnoredNestedRepeated) {
+  proto1diff_.mutable_m()->add_rc(23);
+  proto1diff_.mutable_m()->add_rc(24);
+  proto2diff_.mutable_m()->add_rc(25);
+
+  proto2diff_.set_w("foo");
+
+  ignore_field("m.rc");
+
+  EXPECT_EQ("added: w: \"foo\"\n"
+            "ignored: m.rc\n",
+            RunDiff());
+}
+
+TEST_F(ComparisonTest, ExtensionTest) {
+  proto1ex_.SetExtension(unittest::optional_int32_extension, 401);
+  proto2ex_.SetExtension(unittest::optional_int32_extension, 402);
+
+  proto1ex_.ClearExtension(unittest::optional_int64_extension);
+  proto2ex_.SetExtension(unittest::optional_int64_extension, 403);
+
+  EXPECT_EQ(
+      "modified: (protobuf_unittest.optional_int32_extension): 401 -> 402\n"
+      "added: (protobuf_unittest.optional_int64_extension): 403\n",
+      RunEx());
+}
+
+TEST_F(ComparisonTest, MatchedUnknownFieldTagTest) {
+  unknown1_->AddVarint(240, 122);
+  unknown2_->AddVarint(240, 121);
+  unknown1_->AddFixed32(241, 1);
+  unknown2_->AddFixed64(241, 2);
+  unknown1_->AddLengthDelimited(242, "cat");
+  unknown2_->AddLengthDelimited(242, "dog");
+
+  EXPECT_EQ(
+      "modified: 240[0]: 122 -> 121\n"
+      "deleted: 241[0]: 0x00000001\n"
+      "added: 241[0]: 0x0000000000000002\n"
+      "modified: 242[0]: \"cat\" -> \"dog\"\n",
+      RunUn());
+}
+
+TEST_F(ComparisonTest, UnmatchedUnknownFieldTagTest) {
+  unknown1_->AddFixed32(243, 1);
+  unknown2_->AddVarint(244, 2);
+  unknown2_->AddVarint(244, 4);
+
+  EXPECT_EQ(
+      "deleted: 243[0]: 0x00000001\n"
+      "added: 244[0]: 2\n"
+      "added: 244[1]: 4\n",
+      RunUn());
+}
+
+TEST_F(ComparisonTest, DifferentSizedUnknownFieldTest) {
+  unknown1_->AddVarint(240, 1);
+  unknown1_->AddVarint(240, 3);
+  unknown1_->AddVarint(240, 4);
+  unknown2_->AddVarint(240, 2);
+  unknown2_->AddVarint(240, 3);
+  unknown2_->AddVarint(240, 2);
+  unknown2_->AddVarint(240, 5);
+
+  EXPECT_EQ(
+      "modified: 240[0]: 1 -> 2\n"
+      "modified: 240[2]: 4 -> 2\n"
+      "added: 240[3]: 5\n",
+      RunUn());
+}
+
+TEST_F(ComparisonTest, UnknownFieldsAll) {
+  unknown1_->AddVarint(243, 122);
+  unknown1_->AddFixed64(244, 0x0172356);
+  unknown1_->AddFixed64(244, 0x098);
+  unknown1_->AddGroup(245)->AddFixed32(248, 1);
+  unknown1_->mutable_field(3)->mutable_group()->AddFixed32(248, 2);
+  unknown1_->AddGroup(249)->AddFixed64(250, 1);
+
+  unknown2_->AddVarint(243, 121);
+  unknown2_->AddLengthDelimited(73882, "test 123");
+  unknown2_->AddGroup(245)->AddFixed32(248, 3);
+  unknown2_->AddGroup(247);
+
+  EXPECT_EQ(
+      "modified: 243[0]: 122 -> 121\n"
+      "deleted: 244[0]: 0x0000000000172356\n"
+      "deleted: 244[1]: 0x0000000000000098\n"
+      "modified: 245[0].248[0]: 0x00000001 -> 0x00000003\n"
+      "deleted: 245[0].248[1]: 0x00000002\n"
+      "added: 247[0]: { ... }\n"
+      "deleted: 249[0]: { ... }\n"
+      "added: 73882[0]: \"test 123\"\n",
+      RunUn());
+}
+
+TEST_F(ComparisonTest, EquivalentIgnoresUnknown) {
+  unittest::ForeignMessage message1, message2;
+
+  message1.set_c(5);
+  message1.mutable_unknown_fields()->AddVarint(123, 456);
+  message2.set_c(5);
+  message2.mutable_unknown_fields()->AddVarint(321, 654);
+
+  EXPECT_FALSE(util::MessageDifferencer::Equals(message1, message2));
+  EXPECT_TRUE(util::MessageDifferencer::Equivalent(message1, message2));
+}
+
+class MatchingTest : public testing::Test {
+ public:
+  typedef util::MessageDifferencer MessageDifferencer;
+
+ protected:
+  MatchingTest() {
+  }
+
+  ~MatchingTest() {
+  }
+
+  string RunWithResult(MessageDifferencer* differencer,
+                              const Message& msg1, const Message& msg2,
+                              bool result) {
+    string output;
+    io::StringOutputStream output_stream(&output);
+    MessageDifferencer::StreamReporter reporter(&output_stream);
+    reporter.set_report_modified_aggregates(true);
+    differencer->set_report_matches(true);
+    differencer->ReportDifferencesTo(&reporter);
+    if (result) {
+      EXPECT_TRUE(differencer->Compare(msg1, msg2));
+    } else {
+      EXPECT_FALSE(differencer->Compare(msg1, msg2));
+    }
+    return output;
+  }
+
+ private:
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(MatchingTest);
+};
+
+TEST_F(MatchingTest, StreamReporterMatching) {
+  protobuf_unittest::TestField msg1, msg2;
+  msg1.set_c(72);
+  msg2.set_c(72);
+  msg1.add_rc(13);
+  msg2.add_rc(13);
+  msg1.add_rc(17);
+  msg2.add_rc(17);
+  string output;
+  MessageDifferencer differencer;
+  differencer.set_report_matches(true);
+  differencer.ReportDifferencesToString(&output);
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+  EXPECT_EQ(
+      "matched: c : 72\n"
+      "matched: rc[0] : 13\n"
+      "matched: rc[1] : 17\n",
+      output);
+}
+
+TEST_F(MatchingTest, DontReportMatchedWhenIgnoring) {
+  protobuf_unittest::TestField msg1, msg2;
+  msg1.set_c(72);
+  msg2.set_c(72);
+  msg1.add_rc(13);
+  msg2.add_rc(13);
+  msg1.add_rc(17);
+  msg2.add_rc(17);
+  string output;
+  MessageDifferencer differencer;
+  differencer.set_report_matches(true);
+  differencer.ReportDifferencesToString(&output);
+
+  differencer.IgnoreField(msg1.GetDescriptor()->FindFieldByName("c"));
+
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+  EXPECT_EQ(
+      "ignored: c\n"
+      "matched: rc[0] : 13\n"
+      "matched: rc[1] : 17\n",
+      output);
+}
+
+TEST_F(MatchingTest, ReportMatchedForMovedFields) {
+  protobuf_unittest::TestDiffMessage msg1, msg2;
+  protobuf_unittest::TestDiffMessage::Item* item = msg1.add_item();
+  item->set_a(53);
+  item->set_b("hello");
+  item = msg2.add_item();
+  item->set_a(27);
+  item = msg2.add_item();
+  item->set_a(53);
+  item->set_b("hello");
+  item = msg1.add_item();
+  item->set_a(27);
+  MessageDifferencer differencer;
+  const FieldDescriptor* desc;
+  desc = msg1.GetDescriptor()->FindFieldByName("item");
+  differencer.TreatAsSet(desc);
+
+  EXPECT_EQ(
+      "matched: item[0].a -> item[1].a : 53\n"
+      "matched: item[0].b -> item[1].b : \"hello\"\n"
+      "moved: item[0] -> item[1] : { a: 53 b: \"hello\" }\n"
+      "matched: item[1].a -> item[0].a : 27\n"
+      "moved: item[1] -> item[0] : { a: 27 }\n",
+      RunWithResult(&differencer, msg1, msg2, true));
+}
+
+TEST_F(MatchingTest, MatchesAppearInPostTraversalOrderForMovedFields) {
+  protobuf_unittest::TestDiffMessage msg1, msg2;
+  protobuf_unittest::TestDiffMessage::Item* item;
+  protobuf_unittest::TestField* field;
+
+  const FieldDescriptor* desc;
+  const FieldDescriptor* nested_desc;
+  const FieldDescriptor* double_nested_desc;
+  desc = msg1.GetDescriptor()->FindFieldByName("item");
+  nested_desc = desc->message_type()->FindFieldByName("rm");
+  double_nested_desc = nested_desc->message_type()->FindFieldByName("rc");
+  MessageDifferencer differencer;
+  differencer.TreatAsSet(desc);
+  differencer.TreatAsSet(nested_desc);
+  differencer.TreatAsSet(double_nested_desc);
+
+  item = msg1.add_item();
+  field = item->add_rm();
+  field->set_c(1);
+  field->add_rc(2);
+  field->add_rc(3);
+  field = item->add_rm();
+  field->set_c(4);
+  field->add_rc(5);
+  field->add_rc(6);
+  field->add_rc(7);
+  item = msg2.add_item();
+  field = item->add_rm();
+  field->set_c(4);
+  field->add_rc(7);
+  field->add_rc(6);
+  field->add_rc(5);
+  field = item->add_rm();
+  field->set_c(1);
+  field->add_rc(3);
+  field->add_rc(2);
+  item = msg1.add_item();
+  field = item->add_rm();
+  field->set_c(8);
+  field->add_rc(10);
+  field->add_rc(11);
+  field->add_rc(9);
+  item = msg2.add_item();
+  field = item->add_rm();
+  field->set_c(8);
+  field->add_rc(9);
+  field->add_rc(10);
+  field->add_rc(11);
+
+  EXPECT_EQ(
+      "matched: item[0].rm[0].c -> item[0].rm[1].c : 1\n"
+      "moved: item[0].rm[0].rc[0] -> item[0].rm[1].rc[1] : 2\n"
+      "moved: item[0].rm[0].rc[1] -> item[0].rm[1].rc[0] : 3\n"
+      "moved: item[0].rm[0] -> item[0].rm[1] : { c: 1 rc: 2 rc: 3 }\n"
+      "matched: item[0].rm[1].c -> item[0].rm[0].c : 4\n"
+      "moved: item[0].rm[1].rc[0] -> item[0].rm[0].rc[2] : 5\n"
+      "matched: item[0].rm[1].rc[1] -> item[0].rm[0].rc[1] : 6\n"
+      "moved: item[0].rm[1].rc[2] -> item[0].rm[0].rc[0] : 7\n"
+      "moved: item[0].rm[1] -> item[0].rm[0] : { c: 4 rc: 5 rc: 6 rc: 7 }\n"
+      "matched: item[0] : { rm { c: 1 rc: 2 rc: 3 }"
+                          " rm { c: 4 rc: 5 rc: 6 rc: 7 } }\n"
+      "matched: item[1].rm[0].c : 8\n"
+      "moved: item[1].rm[0].rc[0] -> item[1].rm[0].rc[1] : 10\n"
+      "moved: item[1].rm[0].rc[1] -> item[1].rm[0].rc[2] : 11\n"
+      "moved: item[1].rm[0].rc[2] -> item[1].rm[0].rc[0] : 9\n"
+      "matched: item[1].rm[0] : { c: 8 rc: 10 rc: 11 rc: 9 }\n"
+      "matched: item[1] : { rm { c: 8 rc: 10 rc: 11 rc: 9 } }\n",
+      RunWithResult(&differencer, msg1, msg2, true));
+}
+
+TEST_F(MatchingTest, MatchAndModifiedInterleaveProperly) {
+  protobuf_unittest::TestDiffMessage msg1, msg2;
+  protobuf_unittest::TestDiffMessage::Item* item;
+  protobuf_unittest::TestField* field;
+
+  const FieldDescriptor* desc;
+  const FieldDescriptor* nested_key;
+  const FieldDescriptor* nested_desc;
+  const FieldDescriptor* double_nested_key;
+  const FieldDescriptor* double_nested_desc;
+  desc = msg1.GetDescriptor()->FindFieldByName("item");
+  nested_key = desc->message_type()->FindFieldByName("a");
+  nested_desc = desc->message_type()->FindFieldByName("rm");
+  double_nested_key = nested_desc->message_type()->FindFieldByName("c");
+  double_nested_desc = nested_desc->message_type()->FindFieldByName("rc");
+
+  MessageDifferencer differencer;
+  differencer.TreatAsMap(desc, nested_key);
+  differencer.TreatAsMap(nested_desc, double_nested_key);
+  differencer.TreatAsSet(double_nested_desc);
+
+  item = msg1.add_item();
+  item->set_a(1);
+  field = item->add_rm();
+  field->set_c(2);
+  field->add_rc(3);
+  field->add_rc(4);
+  field = item->add_rm();
+  field->set_c(5);
+  field->add_rc(6);
+  field->add_rc(7);
+  field->add_rc(8);
+  item = msg1.add_item();
+  item->set_a(9);
+  field = item->add_rm();
+  field->set_c(10);
+  field->add_rc(11);
+  field->add_rc(12);
+  field = item->add_rm();
+  field->set_c(13);
+
+  item = msg2.add_item();
+  item->set_a(1);
+  field = item->add_rm();
+  field->set_c(5);
+  field->add_rc(8);
+  field->add_rc(8);
+  field->add_rc(6);
+  field = item->add_rm();
+  field->set_c(3);
+  field->add_rc(2);
+  field->add_rc(4);
+  item = msg2.add_item();
+  item->set_a(9);
+  field = item->add_rm();
+  field->set_c(10);
+  field->add_rc(12);
+  field->add_rc(11);
+  field = item->add_rm();
+  field->set_c(13);
+
+  EXPECT_EQ(
+      "matched: item[0].a : 1\n"
+      "matched: item[0].rm[1].c -> item[0].rm[0].c : 5\n"
+      "moved: item[0].rm[1].rc[0] -> item[0].rm[0].rc[2] : 6\n"
+      "moved: item[0].rm[1].rc[2] -> item[0].rm[0].rc[0] : 8\n"
+      "added: item[0].rm[0].rc[1]: 8\n"
+      "deleted: item[0].rm[1].rc[1]: 7\n"
+      "modified: item[0].rm[1] -> item[0].rm[0]: { c: 5 rc: 6 rc: 7 rc: 8 } ->"
+                                               " { c: 5 rc: 8 rc: 8 rc: 6 }\n"
+      "added: item[0].rm[1]: { c: 3 rc: 2 rc: 4 }\n"
+      "deleted: item[0].rm[0]: { c: 2 rc: 3 rc: 4 }\n"
+      "modified: item[0]: { a: 1 rm { c: 2 rc: 3 rc: 4 }"
+                               " rm { c: 5 rc: 6 rc: 7 rc: 8 } } ->"
+                        " { a: 1 rm { c: 5 rc: 8 rc: 8 rc: 6 }"
+                               " rm { c: 3 rc: 2 rc: 4 } }\n"
+      "matched: item[1].a : 9\n"
+      "matched: item[1].rm[0].c : 10\n"
+      "moved: item[1].rm[0].rc[0] -> item[1].rm[0].rc[1] : 11\n"
+      "moved: item[1].rm[0].rc[1] -> item[1].rm[0].rc[0] : 12\n"
+      "matched: item[1].rm[0] : { c: 10 rc: 11 rc: 12 }\n"
+      "matched: item[1].rm[1].c : 13\n"
+      "matched: item[1].rm[1] : { c: 13 }\n"
+      "matched: item[1] : { a: 9 rm { c: 10 rc: 11 rc: 12 } rm { c: 13 } }\n",
+      RunWithResult(&differencer, msg1, msg2, false));
+}
+
+TEST_F(MatchingTest, MatchingWorksWithExtensions) {
+  protobuf_unittest::TestAllExtensions msg1, msg2;
+  protobuf_unittest::TestAllTypes::NestedMessage* nested;
+  using protobuf_unittest::repeated_nested_message_extension;
+
+  const FileDescriptor* descriptor;
+  const FieldDescriptor* desc;
+  const FieldDescriptor* nested_key;
+  descriptor = msg1.GetDescriptor()->file();
+  desc = descriptor->FindExtensionByName("repeated_nested_message_extension");
+  ASSERT_FALSE(desc == NULL);
+  nested_key = desc->message_type()->FindFieldByName("bb");
+
+  MessageDifferencer differencer;
+  differencer.TreatAsMap(desc, nested_key);
+
+  nested = msg1.AddExtension(repeated_nested_message_extension);
+  nested->set_bb(7);
+  nested = msg1.AddExtension(repeated_nested_message_extension);
+  nested->set_bb(13);
+  nested = msg1.AddExtension(repeated_nested_message_extension);
+  nested->set_bb(11);
+  nested = msg2.AddExtension(repeated_nested_message_extension);
+  nested->set_bb(11);
+  nested = msg2.AddExtension(repeated_nested_message_extension);
+  nested->set_bb(13);
+  nested = msg2.AddExtension(repeated_nested_message_extension);
+  nested->set_bb(7);
+
+  EXPECT_EQ(
+      "matched: (protobuf_unittest.repeated_nested_message_extension)[0].bb ->"
+              " (protobuf_unittest.repeated_nested_message_extension)[2].bb : 7\n"
+      "moved: (protobuf_unittest.repeated_nested_message_extension)[0] ->"
+            " (protobuf_unittest.repeated_nested_message_extension)[2] :"
+                " { bb: 7 }\n"
+      "matched: (protobuf_unittest.repeated_nested_message_extension)[1].bb :"
+                  " 13\n"
+      "matched: (protobuf_unittest.repeated_nested_message_extension)[1] :"
+                  " { bb: 13 }\n"
+      "matched: (protobuf_unittest.repeated_nested_message_extension)[2].bb ->"
+              " (protobuf_unittest.repeated_nested_message_extension)[0].bb :"
+                  " 11\n"
+      "moved: (protobuf_unittest.repeated_nested_message_extension)[2] ->"
+            " (protobuf_unittest.repeated_nested_message_extension)[0] :"
+                " { bb: 11 }\n",
+      RunWithResult(&differencer, msg1, msg2, true));
+}
+
+TEST(AnyTest, Simple) {
+  protobuf_unittest::TestField value1, value2;
+  value1.set_a(20);
+  value2.set_a(21);
+
+  protobuf_unittest::TestAny m1, m2;
+  m1.mutable_any_value()->PackFrom(value1);
+  m2.mutable_any_value()->PackFrom(value2);
+  util::MessageDifferencer message_differencer;
+  string difference_string;
+  message_differencer.ReportDifferencesToString(&difference_string);
+  EXPECT_FALSE(message_differencer.Compare(m1, m2));
+  EXPECT_EQ("modified: any_value.a: 20 -> 21\n", difference_string);
+}
+
+TEST(Anytest, TreatAsSet) {
+  protobuf_unittest::TestField value1, value2;
+  value1.set_a(20);
+  value1.set_b(30);
+  value2.set_a(20);
+  value2.set_b(31);
+
+  protobuf_unittest::TestAny m1, m2;
+  m1.add_repeated_any_value()->PackFrom(value1);
+  m1.add_repeated_any_value()->PackFrom(value2);
+  m2.add_repeated_any_value()->PackFrom(value2);
+  m2.add_repeated_any_value()->PackFrom(value1);
+
+  util::MessageDifferencer message_differencer;
+  message_differencer.TreatAsSet(GetFieldDescriptor(m1, "repeated_any_value"));
+  EXPECT_TRUE(message_differencer.Compare(m1, m2));
+}
+
+
+}  // namespace
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/message_differencer_unittest.proto b/src/google/protobuf/util/message_differencer_unittest.proto
new file mode 100644
index 0000000..698775f
--- /dev/null
+++ b/src/google/protobuf/util/message_differencer_unittest.proto
@@ -0,0 +1,74 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Author: kenton@google.com (Kenton Varda)
+//  Based on original Protocol Buffers design by
+//  Sanjay Ghemawat, Jeff Dean, and others.
+//
+// This file contains messages for testing repeated field comparison
+
+syntax = "proto2";
+package protobuf_unittest;
+
+option optimize_for = SPEED;
+
+message TestField {
+  optional int32 a = 3;
+  optional int32 b = 4;
+  optional int32 c = 1;
+  repeated int32 rc = 2;
+  optional TestField m = 5;
+
+  extend TestDiffMessage {
+    optional TestField tf = 100;
+  }
+}
+
+message TestDiffMessage {
+  repeated group Item = 1 {
+    optional int32  a  =  2;     // Test basic repeated field comparison.
+    optional string b  =  4;     // Test basic repeated field comparison.
+    repeated int32  ra =  3;     // Test SetOfSet Comparison.
+    repeated string rb =  5;     // Test TreatAsMap when key is repeated
+    optional TestField m  = 6;   // Test TreatAsMap when key is a message
+    repeated TestField rm = 7;   // Test TreatAsMap when key is a repeated
+                                 // message
+  }
+
+  optional int32  v  = 13 [deprecated = true];
+  optional string w  = 14;
+  optional TestField m  = 15;
+  repeated int32  rv = 11;       // Test for combinations
+  repeated string rw = 10;       // Test for combinations
+  repeated TestField rm = 12 [deprecated = true];    // Test for combinations
+
+  extensions 100 to 199;
+}
+
diff --git a/src/google/protobuf/util/type_resolver.h b/src/google/protobuf/util/type_resolver.h
new file mode 100644
index 0000000..77d4416
--- /dev/null
+++ b/src/google/protobuf/util/type_resolver.h
@@ -0,0 +1,75 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_PROTOBUF_UTIL_TYPE_RESOLVER_H__
+#define GOOGLE_PROTOBUF_UTIL_TYPE_RESOLVER_H__
+
+#include <string>
+
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/stubs/status.h>
+
+
+namespace google {
+namespace protobuf {
+class Type;
+class Enum;
+}  // namespace protobuf
+
+
+namespace protobuf {
+class DescriptorPool;
+namespace util {
+
+// Abstract interface for a type resovler.
+//
+// Implementations of this interface must be thread-safe.
+class LIBPROTOBUF_EXPORT TypeResolver {
+ public:
+  TypeResolver() {}
+  virtual ~TypeResolver() {}
+
+  // Resolves a type url for a message type.
+  virtual util::Status ResolveMessageType(
+      const string& type_url, google::protobuf::Type* message_type) = 0;
+
+  // Resolves a type url for an enum type.
+  virtual util::Status ResolveEnumType(const string& type_url,
+                                         google::protobuf::Enum* enum_type) = 0;
+
+ private:
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(TypeResolver);
+};
+
+}  // namespace util
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_TYPE_RESOLVER_H__
diff --git a/src/google/protobuf/util/type_resolver_util.cc b/src/google/protobuf/util/type_resolver_util.cc
new file mode 100644
index 0000000..053a4ed
--- /dev/null
+++ b/src/google/protobuf/util/type_resolver_util.cc
@@ -0,0 +1,212 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/util/type_resolver_util.h>
+
+#include <google/protobuf/type.pb.h>
+#include <google/protobuf/wrappers.pb.h>
+#include <google/protobuf/descriptor.pb.h>
+#include <google/protobuf/descriptor.h>
+#include <google/protobuf/util/type_resolver.h>
+#include <google/protobuf/stubs/status.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace {
+using google::protobuf::BoolValue;
+using google::protobuf::Enum;
+using google::protobuf::EnumValue;
+using google::protobuf::Field;
+using google::protobuf::Option;
+using google::protobuf::Type;
+
+using util::Status;
+using util::error::INVALID_ARGUMENT;
+using util::error::NOT_FOUND;
+
+bool SplitTypeUrl(const string& type_url,
+                  string* url_prefix,
+                  string* message_name) {
+  size_t pos = type_url.find_last_of("/");
+  if (pos == string::npos) {
+    return false;
+  }
+  *url_prefix = type_url.substr(0, pos);
+  *message_name = type_url.substr(pos + 1);
+  return true;
+}
+
+
+class DescriptorPoolTypeResolver : public TypeResolver {
+ public:
+  DescriptorPoolTypeResolver(const string& url_prefix,
+                             const DescriptorPool* pool)
+      : url_prefix_(url_prefix), pool_(pool) {
+  }
+
+  Status ResolveMessageType(const string& type_url, Type* type) {
+    string url_prefix, message_name;
+    if (!SplitTypeUrl(type_url, &url_prefix, &message_name) ||
+        url_prefix != url_prefix_) {
+      return Status(INVALID_ARGUMENT, "Failed to parse type url: " + type_url);
+    }
+    if (url_prefix != url_prefix_) {
+      return Status(INVALID_ARGUMENT,
+                    "Cannot resolve types from URL: " + url_prefix);
+    }
+    const Descriptor* descriptor = pool_->FindMessageTypeByName(message_name);
+    if (descriptor == NULL) {
+      return Status(NOT_FOUND, "Cannot found the type: " + message_name);
+    }
+    ConvertDescriptor(descriptor, type);
+    return Status();
+  }
+
+  Status ResolveEnumType(const string& type_url, Enum* enum_type) {
+    string url_prefix, type_name;
+    if (!SplitTypeUrl(type_url, &url_prefix, &type_name) ||
+        url_prefix != url_prefix_) {
+      return Status(INVALID_ARGUMENT, "Failed to parse type url: " + type_url);
+    }
+    if (url_prefix != url_prefix_) {
+      return Status(INVALID_ARGUMENT,
+                    "Cannot resolve types from URL: " + url_prefix);
+    }
+    const EnumDescriptor* descriptor = pool_->FindEnumTypeByName(type_name);
+    if (descriptor == NULL) {
+      return Status(NOT_FOUND, "Cannot found the type: " + type_name);
+    }
+    ConvertEnumDescriptor(descriptor, enum_type);
+    return Status();
+  }
+
+ private:
+  void ConvertDescriptor(const Descriptor* descriptor, Type* type) {
+    type->Clear();
+    type->set_name(descriptor->full_name());
+    for (int i = 0; i < descriptor->field_count(); ++i) {
+      const FieldDescriptor* field = descriptor->field(i);
+      if (field->type() == FieldDescriptor::TYPE_GROUP) {
+        // Group fields cannot be represented with Type. We discard them.
+        continue;
+      }
+      ConvertFieldDescriptor(descriptor->field(i), type->add_fields());
+    }
+    for (int i = 0; i < descriptor->oneof_decl_count(); ++i) {
+      type->add_oneofs(descriptor->oneof_decl(i)->name());
+    }
+    type->mutable_source_context()->set_file_name(descriptor->file()->name());
+    ConvertMessageOptions(descriptor->options(), type->mutable_options());
+  }
+
+  void ConvertMessageOptions(const MessageOptions& options,
+                             RepeatedPtrField<Option>* output) {
+    if (options.map_entry()) {
+      Option* option = output->Add();
+      option->set_name("map_entry");
+      BoolValue value;
+      value.set_value(true);
+      option->mutable_value()->PackFrom(value);
+    }
+
+    // TODO(xiaofeng): Set other "options"?
+  }
+
+  void ConvertFieldDescriptor(const FieldDescriptor* descriptor, Field* field) {
+    field->set_kind(static_cast<Field::Kind>(descriptor->type()));
+    switch (descriptor->label()) {
+      case FieldDescriptor::LABEL_OPTIONAL:
+        field->set_cardinality(Field::CARDINALITY_OPTIONAL);
+        break;
+      case FieldDescriptor::LABEL_REPEATED:
+        field->set_cardinality(Field::CARDINALITY_REPEATED);
+        break;
+      case FieldDescriptor::LABEL_REQUIRED:
+        field->set_cardinality(Field::CARDINALITY_REQUIRED);
+        break;
+    }
+    field->set_number(descriptor->number());
+    field->set_name(descriptor->name());
+    if (descriptor->type() == FieldDescriptor::TYPE_MESSAGE) {
+      field->set_type_url(GetTypeUrl(descriptor->message_type()));
+    } else if (descriptor->type() == FieldDescriptor::TYPE_ENUM) {
+      field->set_type_url(GetTypeUrl(descriptor->enum_type()));
+    }
+    if (descriptor->containing_oneof() != NULL) {
+      field->set_oneof_index(descriptor->containing_oneof()->index() + 1);
+    }
+    if (descriptor->is_packed()) {
+      field->set_packed(true);
+    }
+
+    // TODO(xiaofeng): Set other field "options"?
+  }
+
+  void ConvertEnumDescriptor(const EnumDescriptor* descriptor,
+                             Enum* enum_type) {
+    enum_type->Clear();
+    enum_type->set_name(descriptor->full_name());
+    enum_type->mutable_source_context()->set_file_name(
+        descriptor->file()->name());
+    for (int i = 0; i < descriptor->value_count(); ++i) {
+      const EnumValueDescriptor* value_descriptor = descriptor->value(i);
+      EnumValue* value =
+          enum_type->mutable_enumvalue()->Add();
+      value->set_name(value_descriptor->name());
+      value->set_number(value_descriptor->number());
+
+      // TODO(xiaofeng): Set EnumValue options.
+    }
+    // TODO(xiaofeng): Set Enum "options".
+  }
+
+  string GetTypeUrl(const Descriptor* descriptor) {
+    return url_prefix_ + "/" + descriptor->full_name();
+  }
+
+  string GetTypeUrl(const EnumDescriptor* descriptor) {
+    return url_prefix_ + "/" + descriptor->full_name();
+  }
+
+  string url_prefix_;
+  const DescriptorPool* pool_;
+};
+
+}  // namespace
+
+TypeResolver* NewTypeResolverForDescriptorPool(
+    const string& url_prefix, const DescriptorPool* pool) {
+  return new DescriptorPoolTypeResolver(url_prefix, pool);
+}
+
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/type_resolver_util.h b/src/google/protobuf/util/type_resolver_util.h
new file mode 100644
index 0000000..00cf9c1
--- /dev/null
+++ b/src/google/protobuf/util/type_resolver_util.h
@@ -0,0 +1,52 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_PROTOBUF_UTIL_TYPE_RESOLVER_UTIL_H__
+#define GOOGLE_PROTOBUF_UTIL_TYPE_RESOLVER_UTIL_H__
+
+#include <string>
+
+#include <google/protobuf/stubs/common.h>
+namespace google {
+namespace protobuf {
+class DescriptorPool;
+namespace util {
+class TypeResolver;
+
+// Creates a TypeResolver that serves type information in the given descriptor
+// pool. Caller takes ownership of the returned TypeResolver.
+TypeResolver* NewTypeResolverForDescriptorPool(
+    const string& url_prefix, const DescriptorPool* pool);
+
+}  // namespace util
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_TYPE_RESOLVER_UTIL_H__
diff --git a/src/google/protobuf/util/type_resolver_util_test.cc b/src/google/protobuf/util/type_resolver_util_test.cc
new file mode 100644
index 0000000..b56bf98
--- /dev/null
+++ b/src/google/protobuf/util/type_resolver_util_test.cc
@@ -0,0 +1,338 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/util/type_resolver_util.h>
+
+#include <limits>
+#include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
+#include <string>
+#include <vector>
+
+#include <google/protobuf/type.pb.h>
+#include <google/protobuf/wrappers.pb.h>
+#include <google/protobuf/map_unittest.pb.h>
+#include <google/protobuf/test_util.h>
+#include <google/protobuf/unittest.pb.h>
+#include <google/protobuf/util/type_resolver.h>
+#include <google/protobuf/testing/googletest.h>
+#include <gtest/gtest.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace {
+using google::protobuf::Type;
+using google::protobuf::Enum;
+using google::protobuf::Field;
+using google::protobuf::Option;
+using google::protobuf::BoolValue;
+
+static const char kUrlPrefix[] = "type.googleapis.com";
+
+class DescriptorPoolTypeResolverTest : public testing::Test {
+ public:
+  DescriptorPoolTypeResolverTest() {
+    resolver_.reset(NewTypeResolverForDescriptorPool(
+        kUrlPrefix, DescriptorPool::generated_pool()));
+  }
+
+  const Field* FindField(const Type& type, const string& name) {
+    for (int i = 0; i < type.fields_size(); ++i) {
+      const Field& field = type.fields(i);
+      if (field.name() == name) {
+        return &field;
+      }
+    }
+    return NULL;
+  }
+
+  bool HasField(const Type& type, const string& name) {
+    return FindField(type, name) != NULL;
+  }
+
+  bool HasField(const Type& type, Field::Cardinality cardinality,
+                Field::Field::Kind kind, const string& name, int number) {
+    const Field* field = FindField(type, name);
+    if (field == NULL) {
+      return false;
+    }
+    return field->cardinality() == cardinality &&
+        field->kind() == kind && field->number() == number;
+  }
+
+  bool CheckFieldTypeUrl(const Type& type, const string& name,
+                         const string& type_url) {
+    const Field* field = FindField(type, name);
+    if (field == NULL) {
+      return false;
+    }
+    return field->type_url() == type_url;
+  }
+
+  bool FieldInOneof(const Type& type, const string& name,
+                    const string& oneof_name) {
+    const Field* field = FindField(type, name);
+    if (field == NULL || field->oneof_index() <= 0 ||
+        field->oneof_index() > type.oneofs_size()) {
+      return false;
+    }
+    return type.oneofs(field->oneof_index() - 1) == oneof_name;
+  }
+
+  bool IsPacked(const Type& type, const string& name) {
+    const Field* field = FindField(type, name);
+    if (field == NULL) {
+      return false;
+    }
+    return field->packed();
+  }
+
+  bool EnumHasValue(const Enum& type, const string& name, int number) {
+    for (int i = 0; i < type.enumvalue_size(); ++i) {
+      if (type.enumvalue(i).name() == name &&
+          type.enumvalue(i).number() == number) {
+        return true;
+      }
+    }
+    return false;
+  }
+
+  bool HasBoolOption(const RepeatedPtrField<Option>& options,
+                     const string& name, bool value) {
+    for (int i = 0; i < options.size(); ++i) {
+      const Option& option = options.Get(i);
+      if (option.name() == name) {
+        BoolValue bool_value;
+        if (option.value().UnpackTo(&bool_value) &&
+            bool_value.value() == value) {
+          return true;
+        }
+      }
+    }
+    return false;
+  }
+
+  string GetTypeUrl(string full_name) {
+    return kUrlPrefix + string("/") + full_name;
+  }
+
+  template<typename T>
+  string GetTypeUrl() {
+    return GetTypeUrl(T::descriptor()->full_name());
+  }
+
+ protected:
+  google::protobuf::scoped_ptr<TypeResolver> resolver_;
+};
+
+TEST_F(DescriptorPoolTypeResolverTest, TestAllTypes) {
+  Type type;
+  ASSERT_TRUE(resolver_->ResolveMessageType(
+      GetTypeUrl<protobuf_unittest::TestAllTypes>(), &type).ok());
+  // Check all optional fields.
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_OPTIONAL,
+                       Field::TYPE_INT32, "optional_int32", 1));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_OPTIONAL,
+                       Field::TYPE_INT64, "optional_int64", 2));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_OPTIONAL,
+                       Field::TYPE_UINT32, "optional_uint32", 3));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_OPTIONAL,
+                       Field::TYPE_UINT64, "optional_uint64", 4));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_OPTIONAL,
+                       Field::TYPE_SINT32, "optional_sint32", 5));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_OPTIONAL,
+                       Field::TYPE_SINT64, "optional_sint64", 6));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_OPTIONAL,
+                       Field::TYPE_FIXED32, "optional_fixed32", 7));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_OPTIONAL,
+                       Field::TYPE_FIXED64, "optional_fixed64", 8));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_OPTIONAL,
+                       Field::TYPE_SFIXED32, "optional_sfixed32", 9));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_OPTIONAL,
+                       Field::TYPE_SFIXED64, "optional_sfixed64", 10));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_OPTIONAL,
+                       Field::TYPE_FLOAT, "optional_float", 11));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_OPTIONAL,
+                       Field::TYPE_DOUBLE, "optional_double", 12));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_OPTIONAL,
+                       Field::TYPE_BOOL, "optional_bool", 13));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_OPTIONAL,
+                       Field::TYPE_STRING, "optional_string", 14));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_OPTIONAL,
+                       Field::TYPE_BYTES, "optional_bytes", 15));
+
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_OPTIONAL,
+                       Field::TYPE_MESSAGE, "optional_nested_message", 18));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_OPTIONAL,
+                       Field::TYPE_MESSAGE, "optional_foreign_message", 19));
+
+  EXPECT_TRUE(CheckFieldTypeUrl(
+      type, "optional_nested_message",
+      GetTypeUrl<protobuf_unittest::TestAllTypes::NestedMessage>()));
+  EXPECT_TRUE(CheckFieldTypeUrl(
+      type, "optional_foreign_message",
+      GetTypeUrl<protobuf_unittest::ForeignMessage>()));
+
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_OPTIONAL,
+                       Field::TYPE_ENUM, "optional_nested_enum", 21));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_OPTIONAL,
+                       Field::TYPE_ENUM, "optional_foreign_enum", 22));
+
+  EXPECT_TRUE(CheckFieldTypeUrl(
+      type, "optional_nested_enum",
+      GetTypeUrl("protobuf_unittest.TestAllTypes.NestedEnum")));
+  EXPECT_TRUE(CheckFieldTypeUrl(
+      type, "optional_foreign_enum",
+      GetTypeUrl("protobuf_unittest.ForeignEnum")));
+
+  // Check all repeated fields.
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_REPEATED,
+                       Field::TYPE_INT32, "repeated_int32", 31));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_REPEATED,
+                       Field::TYPE_INT64, "repeated_int64", 32));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_REPEATED,
+                       Field::TYPE_UINT32, "repeated_uint32", 33));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_REPEATED,
+                       Field::TYPE_UINT64, "repeated_uint64", 34));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_REPEATED,
+                       Field::TYPE_SINT32, "repeated_sint32", 35));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_REPEATED,
+                       Field::TYPE_SINT64, "repeated_sint64", 36));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_REPEATED,
+                       Field::TYPE_FIXED32, "repeated_fixed32", 37));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_REPEATED,
+                       Field::TYPE_FIXED64, "repeated_fixed64", 38));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_REPEATED,
+                       Field::TYPE_SFIXED32, "repeated_sfixed32", 39));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_REPEATED,
+                       Field::TYPE_SFIXED64, "repeated_sfixed64", 40));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_REPEATED,
+                       Field::TYPE_FLOAT, "repeated_float", 41));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_REPEATED,
+                       Field::TYPE_DOUBLE, "repeated_double", 42));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_REPEATED,
+                       Field::TYPE_BOOL, "repeated_bool", 43));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_REPEATED,
+                       Field::TYPE_STRING, "repeated_string", 44));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_REPEATED,
+                       Field::TYPE_BYTES, "repeated_bytes", 45));
+
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_REPEATED,
+                       Field::TYPE_MESSAGE, "repeated_nested_message", 48));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_REPEATED,
+                       Field::TYPE_MESSAGE, "repeated_foreign_message", 49));
+
+  EXPECT_TRUE(CheckFieldTypeUrl(
+      type, "repeated_nested_message",
+      GetTypeUrl<protobuf_unittest::TestAllTypes::NestedMessage>()));
+  EXPECT_TRUE(CheckFieldTypeUrl(
+      type, "repeated_foreign_message",
+      GetTypeUrl<protobuf_unittest::ForeignMessage>()));
+
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_REPEATED,
+                       Field::TYPE_ENUM, "repeated_nested_enum", 51));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_REPEATED,
+                       Field::TYPE_ENUM, "repeated_foreign_enum", 52));
+
+  EXPECT_TRUE(CheckFieldTypeUrl(
+      type, "repeated_nested_enum",
+      GetTypeUrl("protobuf_unittest.TestAllTypes.NestedEnum")));
+  EXPECT_TRUE(CheckFieldTypeUrl(
+      type, "repeated_foreign_enum",
+      GetTypeUrl("protobuf_unittest.ForeignEnum")));
+
+  // Groups are discarded when converting to Type.
+  const Descriptor* descriptor = protobuf_unittest::TestAllTypes::descriptor();
+  EXPECT_TRUE(descriptor->FindFieldByName("optionalgroup") != NULL);
+  EXPECT_TRUE(descriptor->FindFieldByName("repeatedgroup") != NULL);
+  ASSERT_FALSE(HasField(type, "optionalgroup"));
+  ASSERT_FALSE(HasField(type, "repeatedgroup"));
+}
+
+TEST_F(DescriptorPoolTypeResolverTest, TestPackedField) {
+  Type type;
+  ASSERT_TRUE(resolver_->ResolveMessageType(
+      GetTypeUrl<protobuf_unittest::TestPackedTypes>(), &type).ok());
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_REPEATED,
+                       Field::TYPE_INT32, "packed_int32", 90));
+  EXPECT_TRUE(IsPacked(type, "packed_int32"));
+}
+
+TEST_F(DescriptorPoolTypeResolverTest, TestOneof) {
+  Type type;
+  ASSERT_TRUE(resolver_->ResolveMessageType(
+      GetTypeUrl<protobuf_unittest::TestAllTypes>(), &type).ok());
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_OPTIONAL,
+                       Field::TYPE_UINT32, "oneof_uint32", 111));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_OPTIONAL,
+                       Field::TYPE_MESSAGE, "oneof_nested_message", 112));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_OPTIONAL,
+                       Field::TYPE_STRING, "oneof_string", 113));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_OPTIONAL,
+                       Field::TYPE_BYTES, "oneof_bytes", 114));
+  EXPECT_TRUE(FieldInOneof(type, "oneof_uint32", "oneof_field"));
+  EXPECT_TRUE(FieldInOneof(type, "oneof_nested_message", "oneof_field"));
+  EXPECT_TRUE(FieldInOneof(type, "oneof_string", "oneof_field"));
+  EXPECT_TRUE(FieldInOneof(type, "oneof_bytes", "oneof_field"));
+}
+
+TEST_F(DescriptorPoolTypeResolverTest, TestMap) {
+  Type type;
+  ASSERT_TRUE(resolver_->ResolveMessageType(
+      GetTypeUrl<protobuf_unittest::TestMap>(), &type).ok());
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_REPEATED,
+                       Field::TYPE_MESSAGE, "map_int32_int32", 1));
+  EXPECT_TRUE(CheckFieldTypeUrl(
+      type, "map_int32_int32",
+      GetTypeUrl("protobuf_unittest.TestMap.MapInt32Int32Entry")));
+
+  ASSERT_TRUE(resolver_->ResolveMessageType(
+      GetTypeUrl("protobuf_unittest.TestMap.MapInt32Int32Entry"),
+      &type).ok());
+  EXPECT_TRUE(HasBoolOption(type.options(), "map_entry", true));
+}
+
+TEST_F(DescriptorPoolTypeResolverTest, TestEnum) {
+  Enum type;
+  ASSERT_TRUE(resolver_->ResolveEnumType(
+      GetTypeUrl("protobuf_unittest.TestAllTypes.NestedEnum"), &type).ok());
+  EnumHasValue(type, "FOO", 1);
+  EnumHasValue(type, "BAR", 2);
+  EnumHasValue(type, "BAZ", 3);
+  EnumHasValue(type, "NEG", -1);
+}
+
+}  // namespace
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google