include/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/generated_message_reflection.h>
#include <google/protobuf/map_entry_lite.h>
#include <google/protobuf/map_type_handler.h>
#include <google/protobuf/metadata.h>
#include <google/protobuf/reflection_ops.h>
#include <google/protobuf/unknown_field_set.h>
#include <google/protobuf/wire_format_lite_inl.h>

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

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      TYPE_INT32    int32            int32
// int32      TYPE_FIXED32  int32            int32
// 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.  Moreover, default_enum_value is
// used to initialize enum field in proto2.
template <typename Derived, typename Key, typename Value,
          WireFormatLite::FieldType kKeyFieldType,
          WireFormatLite::FieldType kValueFieldType, int default_enum_value>
class MapEntry
    : public MapEntryImpl<Derived, Message, Key, Value, kKeyFieldType,
                          kValueFieldType, default_enum_value> {
 public:
  MapEntry() : _internal_metadata_(NULL) {}
  explicit MapEntry(Arena* arena)
      : MapEntryImpl<Derived, Message, Key, Value, kKeyFieldType,
                     kValueFieldType, default_enum_value>(arena),
        _internal_metadata_(arena) {}
  typedef void InternalArenaConstructable_;
  typedef void DestructorSkippable_;

  InternalMetadataWithArena _internal_metadata_;

 private:
  friend class ::google::protobuf::Arena;
  template <typename C, typename K, typename V,
            WireFormatLite::FieldType k_wire_type, WireFormatLite::FieldType,
            int default_enum>
  friend class internal::MapField;
  friend class internal::GeneratedMessageReflection;

  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(MapEntry);
};

// Specialization for the full runtime
template <typename Derived, typename Key, typename Value,
          WireFormatLite::FieldType kKeyFieldType,
          WireFormatLite::FieldType kValueFieldType, int default_enum_value>
struct MapEntryHelper<MapEntry<Derived, Key, Value, kKeyFieldType,
                               kValueFieldType, default_enum_value> >
    : MapEntryHelper<MapEntryLite<Derived, Key, Value, kKeyFieldType,
                                  kValueFieldType, default_enum_value> > {
  explicit MapEntryHelper(const MapPair<Key, Value>& map_pair)
      : MapEntryHelper<MapEntryLite<Derived, Key, Value, kKeyFieldType,
                                    kValueFieldType, default_enum_value> >(
            map_pair) {}
};

template <typename Derived, typename K, typename V,
          WireFormatLite::FieldType key, WireFormatLite::FieldType value,
          int default_enum>
struct DeconstructMapEntry<MapEntry<Derived, K, V, key, value, default_enum> > {
  typedef K Key;
  typedef V Value;
  static const WireFormatLite::FieldType kKeyFieldType = key;
  static const WireFormatLite::FieldType kValueFieldType = value;
  static const int default_enum_value = default_enum;
};

}  // namespace internal
}  // namespace protobuf

}  // namespace google
#endif  // GOOGLE_PROTOBUF_MAP_ENTRY_H__