Implement I/O abstraction layer. Finally.
diff --git a/lib/zip_source_begin_write.c b/lib/zip_source_begin_write.c
new file mode 100644
index 0000000..a6a8563
--- /dev/null
+++ b/lib/zip_source_begin_write.c
@@ -0,0 +1,53 @@
+/*
+ zip_source_begin_write.c -- start a new file for writing
+ Copyright (C) 2014 Dieter Baron and Thomas Klausner
+
+ This file is part of libzip, a library to manipulate ZIP archives.
+ The authors can be contacted at <libzip@nih.at>
+
+ Redistribution and use in source and binary forms, with or without
+ modification, are permitted provided that the following conditions
+ are met:
+ 1. Redistributions of source code must retain the above copyright
+ notice, this list of conditions and the following disclaimer.
+ 2. 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.
+ 3. The names of the authors may not be used to endorse or promote
+ products derived from this software without specific prior
+ written permission.
+
+ THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``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 AUTHORS 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 "zipint.h"
+
+
+int
+zip_source_begin_write(struct zip_source *src)
+{
+ if (ZIP_SOURCE_IS_OPEN_WRITING(src)) {
+ zip_error_set(&src->error, ZIP_ER_INVAL, 0);
+ return -1;
+ }
+
+ if (_zip_source_call(src, NULL, 0, ZIP_SOURCE_BEGIN_WRITE) < 0) {
+ return -1;
+ }
+
+ src->write_state = ZIP_SOURCE_WRITE_OPEN;
+
+ return 0;
+}
