From d36c0c538a545fac5d9db6ba65c525246d4efa95 Mon Sep 17 00:00:00 2001
From: Feng Xiao <xfxyjwf@gmail.com>
Date: Wed, 29 Mar 2017 14:32:48 -0700
Subject: Down-integrate from google3.

---
 src/google/protobuf/map_field.h | 529 +++++++++++++++++++++++++++++++++++-----
 1 file changed, 470 insertions(+), 59 deletions(-)

(limited to 'src/google/protobuf/map_field.h')

diff --git a/src/google/protobuf/map_field.h b/src/google/protobuf/map_field.h
index d6af8532..6d904076 100644
--- a/src/google/protobuf/map_field.h
+++ b/src/google/protobuf/map_field.h
@@ -36,6 +36,7 @@
 #include <google/protobuf/stubs/common.h>
 #include <google/protobuf/generated_message_reflection.h>
 #include <google/protobuf/arena.h>
+#include <google/protobuf/descriptor.h>
 #include <google/protobuf/map_entry.h>
 #include <google/protobuf/map_field_lite.h>
 #include <google/protobuf/map_type_handler.h>
@@ -62,14 +63,10 @@ class LIBPROTOBUF_EXPORT MapFieldBase {
   MapFieldBase()
       : arena_(NULL),
         repeated_field_(NULL),
-        entry_descriptor_(NULL),
-        assign_descriptor_callback_(NULL),
         state_(STATE_MODIFIED_MAP) {}
   explicit MapFieldBase(Arena* arena)
       : arena_(arena),
         repeated_field_(NULL),
-        entry_descriptor_(NULL),
-        assign_descriptor_callback_(NULL),
         state_(STATE_MODIFIED_MAP) {
     // Mutex's destructor needs to be called explicitly to release resources
     // acquired in its constructor.
@@ -99,11 +96,15 @@ class LIBPROTOBUF_EXPORT MapFieldBase {
 
   // Returns the number of bytes used by the repeated field, excluding
   // sizeof(*this)
-  int SpaceUsedExcludingSelf() const;
+  size_t SpaceUsedExcludingSelfLong() const;
+
+  int SpaceUsedExcludingSelf() const {
+    return internal::ToIntSize(SpaceUsedExcludingSelfLong());
+  }
 
  protected:
   // Gets the size of space used by map field.
-  virtual int SpaceUsedExcludingSelfNoLock() const;
+  virtual size_t SpaceUsedExcludingSelfNoLock() const;
 
   // Synchronizes the content in Map to RepeatedPtrField if there is any change
   // to Map after last synchronization.
@@ -124,9 +125,6 @@ class LIBPROTOBUF_EXPORT MapFieldBase {
   // Provides derived class the access to repeated field.
   void* MutableRepeatedPtrField() const;
 
-  // Creates descriptor for only one time.
-  void InitMetadataOnce() const;
-
   enum State {
     STATE_MODIFIED_MAP = 0,       // map has newly added data that has not been
                                   // synchronized to repeated field
@@ -137,13 +135,6 @@ class LIBPROTOBUF_EXPORT MapFieldBase {
 
   Arena* arena_;
   mutable RepeatedPtrField<Message>* repeated_field_;
-  // MapEntry can only be created from MapField. To create MapEntry, MapField
-  // needs to know its descriptor, because MapEntry is not generated class which
-  // cannot initialize its own descriptor by calling generated
-  // descriptor-assign-function. Thus, we need to register a callback to
-  // initialize MapEntry's descriptor.
-  const Descriptor** entry_descriptor_;
-  void (*assign_descriptor_callback_)();
 
   mutable Mutex mutex_;  // The thread to synchronize map and repeated field
                          // needs to get lock first;
@@ -211,27 +202,24 @@ class TypeDefinedMapFieldBase : public MapFieldBase {
 // This class provides access to map field using generated api. It is used for
 // internal generated message implentation only. Users should never use this
 // directly.
-template <typename Key, typename T,
+template <typename Derived, typename Key, typename T,
           WireFormatLite::FieldType kKeyFieldType,
-          WireFormatLite::FieldType kValueFieldType,
-          int default_enum_value = 0>
-class MapField : public TypeDefinedMapFieldBase<Key, T>,
-                 public MapFieldLite<Key, T, kKeyFieldType, kValueFieldType,
-                                     default_enum_value> {
+          WireFormatLite::FieldType kValueFieldType, int default_enum_value = 0>
+class MapField : public TypeDefinedMapFieldBase<Key, T> {
   // Provide utilities to parse/serialize key/value.  Provide utilities to
   // manipulate internal stored type.
   typedef MapTypeHandler<kKeyFieldType, Key> KeyTypeHandler;
   typedef MapTypeHandler<kValueFieldType, T> ValueTypeHandler;
 
   // Define message type for internal repeated field.
-  typedef MapEntry<Key, T, kKeyFieldType, kValueFieldType, default_enum_value>
-      EntryType;
+  typedef Derived EntryType;
   typedef MapEntryLite<Key, T, kKeyFieldType, kValueFieldType,
                        default_enum_value> EntryLiteType;
 
   // Define abbreviation for parent MapFieldLite
-  typedef MapFieldLite<Key, T, kKeyFieldType, kValueFieldType,
-                       default_enum_value> MapFieldLiteType;
+  typedef MapFieldLite<Derived, Key, T, kKeyFieldType, kValueFieldType,
+                       default_enum_value>
+      MapFieldLiteType;
 
   // Enum needs to be handled differently from other types because it has
   // different exposed type in google::protobuf::Map's api and repeated field's api. For
@@ -241,58 +229,62 @@ class MapField : public TypeDefinedMapFieldBase<Key, T>,
   typedef typename MapIf<kIsValueEnum, T, const T&>::type CastValueType;
 
  public:
-  MapField();
-  explicit MapField(Arena* arena);
-  // MapField doesn't own the default_entry, which means default_entry must
-  // outlive the lifetime of MapField.
-  MapField(const Message* default_entry);
-  // For tests only.
-  MapField(Arena* arena, const Message* default_entry);
-  ~MapField();
+  MapField() {}
+  explicit MapField(Arena* arena)
+      : TypeDefinedMapFieldBase<Key, T>(arena), impl_(arena) {}
 
   // Implement MapFieldBase
   bool ContainsMapKey(const MapKey& map_key) const;
   bool InsertOrLookupMapValue(const MapKey& map_key, MapValueRef* val);
   bool DeleteMapValue(const MapKey& map_key);
 
-  // Accessors
-  const Map<Key, T>& GetMap() const;
-  Map<Key, T>* MutableMap();
+  const Map<Key, T>& GetMap() const {
+    MapFieldBase::SyncMapWithRepeatedField();
+    return impl_.GetMap();
+  }
+
+  Map<Key, T>* MutableMap() {
+    MapFieldBase::SyncMapWithRepeatedField();
+    Map<Key, T>* result = impl_.MutableMap();
+    MapFieldBase::SetMapDirty();
+    return result;
+  }
 
   // Convenient methods for generated message implementation.
   int size() const;
   void Clear();
-  void MergeFrom(const MapFieldLiteType& other);
-  void Swap(MapFieldLiteType* other);
-
-  // Allocates metadata only if this MapField is part of a generated message.
-  void SetEntryDescriptor(const Descriptor** descriptor);
-  void SetAssignDescriptorCallback(void (*callback)());
+  void MergeFrom(const MapField& other);
+  void Swap(MapField* other);
+
+  // Used in the implementation of parsing. Caller should take the ownership iff
+  // arena_ is NULL.
+  EntryType* NewEntry() const { return impl_.NewEntry(); }
+  // Used in the implementation of serializing enum value type. Caller should
+  // take the ownership iff arena_ is NULL.
+  EntryType* NewEnumEntryWrapper(const Key& key, const T t) const {
+    return impl_.NewEnumEntryWrapper(key, t);
+  }
+  // Used in the implementation of serializing other value types. Caller should
+  // take the ownership iff arena_ is NULL.
+  EntryType* NewEntryWrapper(const Key& key, const T& t) const {
+    return impl_.NewEntryWrapper(key, t);
+  }
 
  private:
+  MapFieldLiteType impl_;
+
   typedef void InternalArenaConstructable_;
   typedef void DestructorSkippable_;
 
-  // MapField needs MapEntry's default instance to create new MapEntry.
-  void InitDefaultEntryOnce() const;
-
-  // Manually set default entry instance. For test only.
-  void SetDefaultEntryOnce(const EntryType* default_entry) const;
-
-  // Convenient methods to get internal google::protobuf::Map
-  const Map<Key, T>& GetInternalMap() const;
-  Map<Key, T>* MutableInternalMap();
-
   // Implements MapFieldBase
   void SyncRepeatedFieldWithMapNoLock() const;
   void SyncMapWithRepeatedFieldNoLock() const;
-  int SpaceUsedExcludingSelfNoLock() const;
+  size_t SpaceUsedExcludingSelfNoLock() const;
 
   void SetMapIteratorValue(MapIterator* map_iter) const;
 
-  mutable const EntryType* default_entry_;
-
   friend class ::google::protobuf::Arena;
+  friend class MapFieldStateTest;  // For testing, it needs raw access to impl_
 };
 
 class LIBPROTOBUF_EXPORT DynamicMapField: public TypeDefinedMapFieldBase<MapKey, MapValueRef> {
@@ -318,12 +310,395 @@ class LIBPROTOBUF_EXPORT DynamicMapField: public TypeDefinedMapFieldBase<MapKey,
   // Implements MapFieldBase
   void SyncRepeatedFieldWithMapNoLock() const;
   void SyncMapWithRepeatedFieldNoLock() const;
-  int SpaceUsedExcludingSelfNoLock() const;
+  size_t SpaceUsedExcludingSelfNoLock() const;
   void SetMapIteratorValue(MapIterator* map_iter) const;
 };
 
 }  // namespace internal
 
+#define TYPE_CHECK(EXPECTEDTYPE, METHOD)                        \
+  if (type() != EXPECTEDTYPE) {                                 \
+    GOOGLE_LOG(FATAL)                                                  \
+        << "Protocol Buffer map usage error:\n"                 \
+        << METHOD << " type does not match\n"                   \
+        << "  Expected : "                                      \
+        << FieldDescriptor::CppTypeName(EXPECTEDTYPE) << "\n"   \
+        << "  Actual   : "                                      \
+        << FieldDescriptor::CppTypeName(type());                \
+  }
+
+// MapKey is an union type for representing any possible
+// map key.
+class LIBPROTOBUF_EXPORT MapKey {
+ public:
+  MapKey() : type_(0) {
+  }
+  MapKey(const MapKey& other) : type_(0) {
+    CopyFrom(other);
+  }
+
+  ~MapKey() {
+    if (type_ == FieldDescriptor::CPPTYPE_STRING) {
+      delete val_.string_value_;
+    }
+  }
+
+  FieldDescriptor::CppType type() const {
+    if (type_ == 0) {
+      GOOGLE_LOG(FATAL)
+          << "Protocol Buffer map usage error:\n"
+          << "MapKey::type MapKey is not initialized. "
+          << "Call set methods to initialize MapKey.";
+    }
+    return (FieldDescriptor::CppType)type_;
+  }
+
+  void SetInt64Value(int64 value) {
+    SetType(FieldDescriptor::CPPTYPE_INT64);
+    val_.int64_value_ = value;
+  }
+  void SetUInt64Value(uint64 value) {
+    SetType(FieldDescriptor::CPPTYPE_UINT64);
+    val_.uint64_value_ = value;
+  }
+  void SetInt32Value(int32 value) {
+    SetType(FieldDescriptor::CPPTYPE_INT32);
+    val_.int32_value_ = value;
+  }
+  void SetUInt32Value(uint32 value) {
+    SetType(FieldDescriptor::CPPTYPE_UINT32);
+    val_.uint32_value_ = value;
+  }
+  void SetBoolValue(bool value) {
+    SetType(FieldDescriptor::CPPTYPE_BOOL);
+    val_.bool_value_ = value;
+  }
+  void SetStringValue(const string& val) {
+    SetType(FieldDescriptor::CPPTYPE_STRING);
+    *val_.string_value_ = val;
+  }
+
+  int64 GetInt64Value() const {
+    TYPE_CHECK(FieldDescriptor::CPPTYPE_INT64,
+               "MapKey::GetInt64Value");
+    return val_.int64_value_;
+  }
+  uint64 GetUInt64Value() const {
+    TYPE_CHECK(FieldDescriptor::CPPTYPE_UINT64,
+               "MapKey::GetUInt64Value");
+    return val_.uint64_value_;
+  }
+  int32 GetInt32Value() const {
+    TYPE_CHECK(FieldDescriptor::CPPTYPE_INT32,
+               "MapKey::GetInt32Value");
+    return val_.int32_value_;
+  }
+  uint32 GetUInt32Value() const {
+    TYPE_CHECK(FieldDescriptor::CPPTYPE_UINT32,
+               "MapKey::GetUInt32Value");
+    return val_.uint32_value_;
+  }
+  bool GetBoolValue() const {
+    TYPE_CHECK(FieldDescriptor::CPPTYPE_BOOL,
+               "MapKey::GetBoolValue");
+    return val_.bool_value_;
+  }
+  const string& GetStringValue() const {
+    TYPE_CHECK(FieldDescriptor::CPPTYPE_STRING,
+               "MapKey::GetStringValue");
+    return *val_.string_value_;
+  }
+
+  bool operator<(const MapKey& other) const {
+    if (type_ != other.type_) {
+      // We could define a total order that handles this case, but
+      // there currently no need.  So, for now, fail.
+      GOOGLE_LOG(FATAL) << "Unsupported: type mismatch";
+    }
+    switch (type()) {
+      case FieldDescriptor::CPPTYPE_DOUBLE:
+      case FieldDescriptor::CPPTYPE_FLOAT:
+      case FieldDescriptor::CPPTYPE_ENUM:
+      case FieldDescriptor::CPPTYPE_MESSAGE:
+        GOOGLE_LOG(FATAL) << "Unsupported";
+        return false;
+      case FieldDescriptor::CPPTYPE_STRING:
+        return *val_.string_value_ < *other.val_.string_value_;
+      case FieldDescriptor::CPPTYPE_INT64:
+        return val_.int64_value_ < other.val_.int64_value_;
+      case FieldDescriptor::CPPTYPE_INT32:
+        return val_.int32_value_ < other.val_.int32_value_;
+      case FieldDescriptor::CPPTYPE_UINT64:
+        return val_.uint64_value_ < other.val_.uint64_value_;
+      case FieldDescriptor::CPPTYPE_UINT32:
+        return val_.uint32_value_ < other.val_.uint32_value_;
+      case FieldDescriptor::CPPTYPE_BOOL:
+        return val_.bool_value_ < other.val_.bool_value_;
+    }
+    return false;
+  }
+
+  bool operator==(const MapKey& other) const {
+    if (type_ != other.type_) {
+      // To be consistent with operator<, we don't allow this either.
+      GOOGLE_LOG(FATAL) << "Unsupported: type mismatch";
+    }
+    switch (type()) {
+      case FieldDescriptor::CPPTYPE_DOUBLE:
+      case FieldDescriptor::CPPTYPE_FLOAT:
+      case FieldDescriptor::CPPTYPE_ENUM:
+      case FieldDescriptor::CPPTYPE_MESSAGE:
+        GOOGLE_LOG(FATAL) << "Unsupported";
+        break;
+      case FieldDescriptor::CPPTYPE_STRING:
+        return *val_.string_value_ == *other.val_.string_value_;
+      case FieldDescriptor::CPPTYPE_INT64:
+        return val_.int64_value_ == other.val_.int64_value_;
+      case FieldDescriptor::CPPTYPE_INT32:
+        return val_.int32_value_ == other.val_.int32_value_;
+      case FieldDescriptor::CPPTYPE_UINT64:
+        return val_.uint64_value_ == other.val_.uint64_value_;
+      case FieldDescriptor::CPPTYPE_UINT32:
+        return val_.uint32_value_ == other.val_.uint32_value_;
+      case FieldDescriptor::CPPTYPE_BOOL:
+        return val_.bool_value_ == other.val_.bool_value_;
+    }
+    GOOGLE_LOG(FATAL) << "Can't get here.";
+    return false;
+  }
+
+  void CopyFrom(const MapKey& other) {
+    SetType(other.type());
+    switch (type_) {
+      case FieldDescriptor::CPPTYPE_DOUBLE:
+      case FieldDescriptor::CPPTYPE_FLOAT:
+      case FieldDescriptor::CPPTYPE_ENUM:
+      case FieldDescriptor::CPPTYPE_MESSAGE:
+        GOOGLE_LOG(FATAL) << "Unsupported";
+        break;
+      case FieldDescriptor::CPPTYPE_STRING:
+        *val_.string_value_ = *other.val_.string_value_;
+        break;
+      case FieldDescriptor::CPPTYPE_INT64:
+        val_.int64_value_ = other.val_.int64_value_;
+        break;
+      case FieldDescriptor::CPPTYPE_INT32:
+        val_.int32_value_ = other.val_.int32_value_;
+        break;
+      case FieldDescriptor::CPPTYPE_UINT64:
+        val_.uint64_value_ = other.val_.uint64_value_;
+        break;
+      case FieldDescriptor::CPPTYPE_UINT32:
+        val_.uint32_value_ = other.val_.uint32_value_;
+        break;
+      case FieldDescriptor::CPPTYPE_BOOL:
+        val_.bool_value_ = other.val_.bool_value_;
+        break;
+    }
+  }
+
+ private:
+  template <typename K, typename V>
+  friend class internal::TypeDefinedMapFieldBase;
+  friend class MapIterator;
+  friend class internal::DynamicMapField;
+
+  union KeyValue {
+    KeyValue() {}
+    string* string_value_;
+    int64 int64_value_;
+    int32 int32_value_;
+    uint64 uint64_value_;
+    uint32 uint32_value_;
+    bool bool_value_;
+  } val_;
+
+  void SetType(FieldDescriptor::CppType type) {
+    if (type_ == type) return;
+    if (type_ == FieldDescriptor::CPPTYPE_STRING) {
+      delete val_.string_value_;
+    }
+    type_ = type;
+    if (type_ == FieldDescriptor::CPPTYPE_STRING) {
+      val_.string_value_ = new string;
+    }
+  }
+
+  // type_ is 0 or a valid FieldDescriptor::CppType.
+  int type_;
+};
+
+// MapValueRef points to a map value.
+class LIBPROTOBUF_EXPORT MapValueRef {
+ public:
+  MapValueRef() : data_(NULL), type_(0) {}
+
+  void SetInt64Value(int64 value) {
+    TYPE_CHECK(FieldDescriptor::CPPTYPE_INT64,
+               "MapValueRef::SetInt64Value");
+    *reinterpret_cast<int64*>(data_) = value;
+  }
+  void SetUInt64Value(uint64 value) {
+    TYPE_CHECK(FieldDescriptor::CPPTYPE_UINT64,
+               "MapValueRef::SetUInt64Value");
+    *reinterpret_cast<uint64*>(data_) = value;
+  }
+  void SetInt32Value(int32 value) {
+    TYPE_CHECK(FieldDescriptor::CPPTYPE_INT32,
+               "MapValueRef::SetInt32Value");
+    *reinterpret_cast<int32*>(data_) = value;
+  }
+  void SetUInt32Value(uint32 value) {
+    TYPE_CHECK(FieldDescriptor::CPPTYPE_UINT32,
+               "MapValueRef::SetUInt32Value");
+    *reinterpret_cast<uint32*>(data_) = value;
+  }
+  void SetBoolValue(bool value) {
+    TYPE_CHECK(FieldDescriptor::CPPTYPE_BOOL,
+               "MapValueRef::SetBoolValue");
+    *reinterpret_cast<bool*>(data_) = value;
+  }
+  // TODO(jieluo) - Checks that enum is member.
+  void SetEnumValue(int value) {
+    TYPE_CHECK(FieldDescriptor::CPPTYPE_ENUM,
+               "MapValueRef::SetEnumValue");
+    *reinterpret_cast<int*>(data_) = value;
+  }
+  void SetStringValue(const string& value) {
+    TYPE_CHECK(FieldDescriptor::CPPTYPE_STRING,
+               "MapValueRef::SetStringValue");
+    *reinterpret_cast<string*>(data_) = value;
+  }
+  void SetFloatValue(float value) {
+    TYPE_CHECK(FieldDescriptor::CPPTYPE_FLOAT,
+               "MapValueRef::SetFloatValue");
+    *reinterpret_cast<float*>(data_) = value;
+  }
+  void SetDoubleValue(double value) {
+    TYPE_CHECK(FieldDescriptor::CPPTYPE_DOUBLE,
+               "MapValueRef::SetDoubleValue");
+    *reinterpret_cast<double*>(data_) = value;
+  }
+
+  int64 GetInt64Value() const {
+    TYPE_CHECK(FieldDescriptor::CPPTYPE_INT64,
+               "MapValueRef::GetInt64Value");
+    return *reinterpret_cast<int64*>(data_);
+  }
+  uint64 GetUInt64Value() const {
+    TYPE_CHECK(FieldDescriptor::CPPTYPE_UINT64,
+               "MapValueRef::GetUInt64Value");
+    return *reinterpret_cast<uint64*>(data_);
+  }
+  int32 GetInt32Value() const {
+    TYPE_CHECK(FieldDescriptor::CPPTYPE_INT32,
+               "MapValueRef::GetInt32Value");
+    return *reinterpret_cast<int32*>(data_);
+  }
+  uint32 GetUInt32Value() const {
+    TYPE_CHECK(FieldDescriptor::CPPTYPE_UINT32,
+               "MapValueRef::GetUInt32Value");
+    return *reinterpret_cast<uint32*>(data_);
+  }
+  bool GetBoolValue() const {
+    TYPE_CHECK(FieldDescriptor::CPPTYPE_BOOL,
+               "MapValueRef::GetBoolValue");
+    return *reinterpret_cast<bool*>(data_);
+  }
+  int GetEnumValue() const {
+    TYPE_CHECK(FieldDescriptor::CPPTYPE_ENUM,
+               "MapValueRef::GetEnumValue");
+    return *reinterpret_cast<int*>(data_);
+  }
+  const string& GetStringValue() const {
+    TYPE_CHECK(FieldDescriptor::CPPTYPE_STRING,
+               "MapValueRef::GetStringValue");
+    return *reinterpret_cast<string*>(data_);
+  }
+  float GetFloatValue() const {
+    TYPE_CHECK(FieldDescriptor::CPPTYPE_FLOAT,
+               "MapValueRef::GetFloatValue");
+    return *reinterpret_cast<float*>(data_);
+  }
+  double GetDoubleValue() const {
+    TYPE_CHECK(FieldDescriptor::CPPTYPE_DOUBLE,
+               "MapValueRef::GetDoubleValue");
+    return *reinterpret_cast<double*>(data_);
+  }
+
+  const Message& GetMessageValue() const {
+    TYPE_CHECK(FieldDescriptor::CPPTYPE_MESSAGE,
+               "MapValueRef::GetMessageValue");
+    return *reinterpret_cast<Message*>(data_);
+  }
+
+  Message* MutableMessageValue() {
+    TYPE_CHECK(FieldDescriptor::CPPTYPE_MESSAGE,
+               "MapValueRef::MutableMessageValue");
+    return reinterpret_cast<Message*>(data_);
+  }
+
+ private:
+  template <typename Derived, typename K, typename V,
+            internal::WireFormatLite::FieldType key_wire_type,
+            internal::WireFormatLite::FieldType value_wire_type,
+            int default_enum_value>
+  friend class internal::MapField;
+  template <typename K, typename V>
+  friend class internal::TypeDefinedMapFieldBase;
+  friend class MapIterator;
+  friend class internal::GeneratedMessageReflection;
+  friend class internal::DynamicMapField;
+
+  void SetType(FieldDescriptor::CppType type) {
+    type_ = type;
+  }
+
+  FieldDescriptor::CppType type() const {
+    if (type_ == 0 || data_ == NULL) {
+      GOOGLE_LOG(FATAL)
+          << "Protocol Buffer map usage error:\n"
+          << "MapValueRef::type MapValueRef is not initialized.";
+    }
+    return (FieldDescriptor::CppType)type_;
+  }
+  void SetValue(const void* val) {
+    data_ = const_cast<void*>(val);
+  }
+  void CopyFrom(const MapValueRef& other) {
+    type_ = other.type_;
+    data_ = other.data_;
+  }
+  // Only used in DynamicMapField
+  void DeleteData() {
+    switch (type_) {
+#define HANDLE_TYPE(CPPTYPE, TYPE)                              \
+      case google::protobuf::FieldDescriptor::CPPTYPE_##CPPTYPE: {        \
+        delete reinterpret_cast<TYPE*>(data_);                  \
+        break;                                                  \
+      }
+      HANDLE_TYPE(INT32, int32);
+      HANDLE_TYPE(INT64, int64);
+      HANDLE_TYPE(UINT32, uint32);
+      HANDLE_TYPE(UINT64, uint64);
+      HANDLE_TYPE(DOUBLE, double);
+      HANDLE_TYPE(FLOAT, float);
+      HANDLE_TYPE(BOOL, bool);
+      HANDLE_TYPE(STRING, string);
+      HANDLE_TYPE(ENUM, int32);
+      HANDLE_TYPE(MESSAGE, Message);
+#undef HANDLE_TYPE
+    }
+  }
+  // data_ point to a map value. MapValueRef does not
+  // own this value.
+  void* data_;
+  // type_ is 0 or a valid FieldDescriptor::CppType.
+  int type_;
+};
+
+#undef TYPE_CHECK
+
 class LIBPROTOBUF_EXPORT MapIterator {
  public:
   MapIterator(Message* message, const FieldDescriptor* field) {
@@ -373,7 +748,7 @@ class LIBPROTOBUF_EXPORT MapIterator {
   template <typename Key, typename T>
   friend class internal::TypeDefinedMapFieldBase;
   friend class internal::DynamicMapField;
-  template <typename Key, typename T,
+  template <typename Derived, typename Key, typename T,
             internal::WireFormatLite::FieldType kKeyFieldType,
             internal::WireFormatLite::FieldType kValueFieldType,
             int default_enum_value>
@@ -392,6 +767,42 @@ class LIBPROTOBUF_EXPORT MapIterator {
 };
 
 }  // namespace protobuf
-
 }  // namespace google
+
+GOOGLE_PROTOBUF_HASH_NAMESPACE_DECLARATION_START
+template<>
+struct hash<google::protobuf::MapKey> {
+  size_t
+  operator()(const google::protobuf::MapKey& map_key) const {
+    switch (map_key.type()) {
+      case google::protobuf::FieldDescriptor::CPPTYPE_DOUBLE:
+      case google::protobuf::FieldDescriptor::CPPTYPE_FLOAT:
+      case google::protobuf::FieldDescriptor::CPPTYPE_ENUM:
+      case google::protobuf::FieldDescriptor::CPPTYPE_MESSAGE:
+        GOOGLE_LOG(FATAL) << "Unsupported";
+        break;
+      case google::protobuf::FieldDescriptor::CPPTYPE_STRING:
+        return hash<string>()(map_key.GetStringValue());
+      case google::protobuf::FieldDescriptor::CPPTYPE_INT64:
+        return hash< ::google::protobuf::int64>()(map_key.GetInt64Value());
+      case google::protobuf::FieldDescriptor::CPPTYPE_INT32:
+        return hash< ::google::protobuf::int32>()(map_key.GetInt32Value());
+      case google::protobuf::FieldDescriptor::CPPTYPE_UINT64:
+        return hash< ::google::protobuf::uint64>()(map_key.GetUInt64Value());
+      case google::protobuf::FieldDescriptor::CPPTYPE_UINT32:
+        return hash< ::google::protobuf::uint32>()(map_key.GetUInt32Value());
+      case google::protobuf::FieldDescriptor::CPPTYPE_BOOL:
+        return hash<bool>()(map_key.GetBoolValue());
+    }
+    GOOGLE_LOG(FATAL) << "Can't get here.";
+    return 0;
+  }
+  bool
+  operator()(const google::protobuf::MapKey& map_key1,
+             const google::protobuf::MapKey& map_key2) const {
+    return map_key1 < map_key2;
+  }
+};
+GOOGLE_PROTOBUF_HASH_NAMESPACE_DECLARATION_END
+
 #endif  // GOOGLE_PROTOBUF_MAP_FIELD_H__
-- 
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