src/google/protobuf/map_entry.h

// Protocol Buffers - Google's data interchange format
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#ifndef GOOGLE_PROTOBUF_MAP_ENTRY_H__
#define GOOGLE_PROTOBUF_MAP_ENTRY_H__

#include "google/protobuf/port.h"
#include "google/protobuf/generated_message_reflection.h"
#include "google/protobuf/map_entry_lite.h"
#include "google/protobuf/map_type_handler.h"
#include "google/protobuf/reflection_ops.h"
#include "google/protobuf/unknown_field_set.h"
#include "google/protobuf/wire_format_lite.h"

// Must be included last.
#include "google/protobuf/port_def.inc"

#ifdef SWIG
#error "You cannot SWIG proto headers"
#endif

namespace google {
namespace protobuf {
class Arena;
namespace internal {
template <typename Derived, typename Key, typename Value,
          WireFormatLite::FieldType kKeyFieldType,
          WireFormatLite::FieldType kValueFieldType>
class MapField;
}
}  // namespace protobuf
}  // namespace google

namespace google {
namespace protobuf {
namespace internal {

// MapEntry is the returned google::protobuf::Message when calling AddMessage of
// google::protobuf::Reflection. In order to let it work with generated message
// reflection, its in-memory type is the same as generated message with the same
// fields. However, in order to decide the in-memory type of key/value, we need
// to know both their cpp type in generated api and proto type. In
// implementation, all in-memory types have related wire format functions to
// support except ArenaStringPtr. Therefore, we need to define another type with
// supporting wire format functions. Since this type is only used as return type
// of MapEntry accessors, it's named MapEntry accessor type.
//
// cpp type:               the type visible to users in public API.
// proto type:             WireFormatLite::FieldType of the field.
// in-memory type:         type of the data member used to stored this field.
// MapEntry accessor type: type used in MapEntry getters/mutators to access the
//                         field.
//
// cpp type | proto type  | in-memory type | MapEntry accessor type
// int32_t    TYPE_INT32    int32_t          int32_t
// int32_t    TYPE_FIXED32  int32_t          int32_t
// string     TYPE_STRING   ArenaStringPtr   string
// FooEnum    TYPE_ENUM     int              int
// FooMessage TYPE_MESSAGE  FooMessage*      FooMessage
//
// The in-memory types of primitive types can be inferred from its proto type,
// while we need to explicitly specify the cpp type if proto type is
// TYPE_MESSAGE to infer the in-memory type.
template <typename Derived, typename Key, typename Value,
          WireFormatLite::FieldType kKeyFieldType,
          WireFormatLite::FieldType kValueFieldType>
class MapEntry : public MapEntryImpl<Derived, Message, Key, Value,
                                     kKeyFieldType, kValueFieldType> {
 public:
  constexpr MapEntry() {}
  explicit MapEntry(Arena* arena)
      : MapEntryImpl<Derived, Message, Key, Value, kKeyFieldType,
                     kValueFieldType>(arena) {}
  MapEntry(const MapEntry&) = delete;
  MapEntry& operator=(const MapEntry&) = delete;
  ~MapEntry() override {
    Message::_internal_metadata_.template Delete<UnknownFieldSet>();
  }
  typedef void InternalArenaConstructable_;
  typedef void DestructorSkippable_;

  typedef typename MapEntryImpl<Derived, Message, Key, Value, kKeyFieldType,
                                kValueFieldType>::KeyTypeHandler KeyTypeHandler;
  typedef
      typename MapEntryImpl<Derived, Message, Key, Value, kKeyFieldType,
                            kValueFieldType>::ValueTypeHandler ValueTypeHandler;
  size_t SpaceUsedLong() const override {
    size_t size = sizeof(Derived);
    size += KeyTypeHandler::SpaceUsedInMapEntryLong(this->key_);
    size += ValueTypeHandler::SpaceUsedInMapEntryLong(this->value_);
    return size;
  }

 private:
  friend class ::PROTOBUF_NAMESPACE_ID::Arena;
  template <typename C, typename K, typename V,
            WireFormatLite::FieldType k_wire_type, WireFormatLite::FieldType>
  friend class internal::MapField;
};

}  // namespace internal
}  // namespace protobuf
}  // namespace google

#include "google/protobuf/port_undef.inc"

#endif  // GOOGLE_PROTOBUF_MAP_ENTRY_H__