Update //third_party/protobuf to version 3.

third_party/protobuf/src/google/protobuf/extension_set.h

 // Protocol Buffers - Google's data interchange format
 // Copyright 2008 Google Inc.  All rights reserved.
-// http://code.google.com/p/protobuf/
+// 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
@@ skipping 24 matching lines @@
 #ifndef GOOGLE_PROTOBUF_EXTENSION_SET_H__
 #define GOOGLE_PROTOBUF_EXTENSION_SET_H__
 
 #include <vector>
 #include <map>
 #include <utility>
 #include <string>
 
 
 #include <google/protobuf/stubs/common.h>
+#include <google/protobuf/stubs/logging.h>
+#include <google/protobuf/stubs/once.h>
+
+#include <google/protobuf/repeated_field.h>
 
 namespace google {
 
 namespace protobuf {
+  class Arena;
   class Descriptor;                                    // descriptor.h
   class FieldDescriptor;                               // descriptor.h
   class DescriptorPool;                                // descriptor.h
   class MessageLite;                                   // message_lite.h
   class Message;                                       // message.h
   class MessageFactory;                                // message.h
   class UnknownFieldSet;                               // unknown_field_set.h
   namespace io {
     class CodedInputStream;                              // coded_stream.h
     class CodedOutputStream;                             // coded_stream.h
   }
   namespace internal {
     class FieldSkipper;                                  // wire_format_lite.h
-    class RepeatedPtrFieldBase;                          // repeated_field.h
   }
-  template <typename Element> class RepeatedField;     // repeated_field.h
-  template <typename Element> class RepeatedPtrField;  // repeated_field.h
 }
 
 namespace protobuf {
 namespace internal {
 
 // Used to store values of type WireFormatLite::FieldType without having to
 // #include wire_format_lite.h.  Also, ensures that we use only one byte to
 // store these values, which is important to keep the layout of
 // ExtensionSet::Extension small.
 typedef uint8 FieldType;
@@ skipping 52 matching lines @@
       : containing_type_(containing_type) {}
   virtual ~GeneratedExtensionFinder() {}
 
   // Returns true and fills in *output if found, otherwise returns false.
   virtual bool Find(int number, ExtensionInfo* output);
 
  private:
   const MessageLite* containing_type_;
 };
 
+// A FieldSkipper used for parsing MessageSet.
+class MessageSetFieldSkipper;
+
 // Note:  extension_set_heavy.cc defines DescriptorPoolExtensionFinder for
 // finding extensions from a DescriptorPool.
 
 // This is an internal helper class intended for use within the protocol buffer
 // library and generated classes.  Clients should not use it directly.  Instead,
 // use the generated accessors such as GetExtension() of the class being
 // extended.
 //
 // This class manages extensions for a protocol message object.  The
 // message's HasExtension(), GetExtension(), MutableExtension(), and
 // ClearExtension() methods are just thin wrappers around the embedded
 // ExtensionSet.  When parsing, if a tag number is encountered which is
 // inside one of the message type's extension ranges, the tag is passed
 // off to the ExtensionSet for parsing.  Etc.
 class LIBPROTOBUF_EXPORT ExtensionSet {
  public:
   ExtensionSet();
+  explicit ExtensionSet(::google::protobuf::Arena* arena);
   ~ExtensionSet();
 
   // These are called at startup by protocol-compiler-generated code to
   // register known extensions.  The registrations are used by ParseField()
   // to look up extensions for parsed field numbers.  Note that dynamic parsing
   // does not use ParseField(); only protocol-compiler-generated parsing
   // methods do.
   static void RegisterExtension(const MessageLite* containing_type,
                                 int number, FieldType type,
                                 bool is_repeated, bool is_packed);
@@ skipping 15 matching lines @@
                     std::vector<const FieldDescriptor*>* output) const;
 
   // =================================================================
   // Accessors
   //
   // Generated message classes include type-safe templated wrappers around
   // these methods.  Generally you should use those rather than call these
   // directly, unless you are doing low-level memory management.
   //
   // When calling any of these accessors, the extension number requested
-  // MUST exist in the DescriptorPool provided to the constructor.  Otheriwse,
+  // MUST exist in the DescriptorPool provided to the constructor.  Otherwise,
   // the method will fail an assert.  Normally, though, you would not call
   // these directly; you would either call the generated accessors of your
   // message class (e.g. GetExtension()) or you would call the accessors
   // of the reflection interface.  In both cases, it is impossible to
   // trigger this assert failure:  the generated accessors only accept
   // linked-in extension types as parameters, while the Reflection interface
   // requires you to provide the FieldDescriptor describing the extension.
   //
   // When calling any of these accessors, a protocol-compiler-generated
   // implementation of the extension corresponding to the number MUST
@@ skipping 47 matching lines @@
   MessageLite* MutableMessage(int number, FieldType type,
                               const MessageLite& prototype, desc);
   MessageLite* MutableMessage(const FieldDescriptor* decsriptor,
                               MessageFactory* factory);
   // Adds the given message to the ExtensionSet, taking ownership of the
   // message object. Existing message with the same number will be deleted.
   // If "message" is NULL, this is equivalent to "ClearExtension(number)".
   void SetAllocatedMessage(int number, FieldType type,
                            const FieldDescriptor* descriptor,
                            MessageLite* message);
+  void UnsafeArenaSetAllocatedMessage(int number, FieldType type,
+                                      const FieldDescriptor* descriptor,
+                                      MessageLite* message);
   MessageLite* ReleaseMessage(int number, const MessageLite& prototype);
+  MessageLite* UnsafeArenaReleaseMessage(
+      int number, const MessageLite& prototype);
+
   MessageLite* ReleaseMessage(const FieldDescriptor* descriptor,
                               MessageFactory* factory);
 #undef desc
+  ::google::protobuf::Arena* GetArenaNoVirtual() const { return arena_; }
 
   // repeated fields -------------------------------------------------
 
+  // Fetches a RepeatedField extension by number; returns |default_value|
+  // if no such extension exists. User should not touch this directly; it is
+  // used by the GetRepeatedExtension() method.
+  const void* GetRawRepeatedField(int number, const void* default_value) const;
+  // Fetches a mutable version of a RepeatedField extension by number,
+  // instantiating one if none exists. Similar to above, user should not use
+  // this directly; it underlies MutableRepeatedExtension().
+  void* MutableRawRepeatedField(int number, FieldType field_type,
+                                bool packed, const FieldDescriptor* desc);
+
+  // This is an overload of MutableRawRepeatedField to maintain compatibility
+  // with old code using a previous API. This version of
+  // MutableRawRepeatedField() will GOOGLE_CHECK-fail on a missing extension.
+  // (E.g.: borg/clients/internal/proto1/proto2_reflection.cc.)
   void* MutableRawRepeatedField(int number);
 
   int32  GetRepeatedInt32 (int number, int index) const;
   int64  GetRepeatedInt64 (int number, int index) const;
   uint32 GetRepeatedUInt32(int number, int index) const;
   uint64 GetRepeatedUInt64(int number, int index) const;
   float  GetRepeatedFloat (int number, int index) const;
   double GetRepeatedDouble(int number, int index) const;
   bool   GetRepeatedBool  (int number, int index) const;
   int    GetRepeatedEnum  (int number, int index) const;
@@ skipping 20 matching lines @@
   void AddFloat (int number, FieldType type, bool packed, float  value, desc);
   void AddDouble(int number, FieldType type, bool packed, double value, desc);
   void AddBool  (int number, FieldType type, bool packed, bool   value, desc);
   void AddEnum  (int number, FieldType type, bool packed, int    value, desc);
   void AddString(int number, FieldType type, const string& value, desc);
   string * AddString (int number, FieldType type, desc);
   MessageLite* AddMessage(int number, FieldType type,
                           const MessageLite& prototype, desc);
   MessageLite* AddMessage(const FieldDescriptor* descriptor,
                           MessageFactory* factory);
+  void AddAllocatedMessage(const FieldDescriptor* descriptor,
+                           MessageLite* new_entry);
 #undef desc
 
   void RemoveLast(int number);
   MessageLite* ReleaseLast(int number);
   void SwapElements(int number, int index1, int index2);
 
   // -----------------------------------------------------------------
   // TODO(kenton):  Hardcore memory management accessors
 
   // =================================================================
   // convenience methods for implementing methods of Message
   //
   // These could all be implemented in terms of the other methods of this
   // class, but providing them here helps keep the generated code size down.
 
   void Clear();
   void MergeFrom(const ExtensionSet& other);
   void Swap(ExtensionSet* other);
+  void SwapExtension(ExtensionSet* other, int number);
   bool IsInitialized() const;
 
   // Parses a single extension from the input. The input should start out
   // positioned immediately after the tag.
   bool ParseField(uint32 tag, io::CodedInputStream* input,
                   ExtensionFinder* extension_finder,
                   FieldSkipper* field_skipper);
 
   // Specific versions for lite or full messages (constructs the appropriate
   // FieldSkipper automatically).  |containing_type| is the default
   // instance for the containing message; it is used only to look up the
   // extension by number.  See RegisterExtension(), above.  Unlike the other
   // methods of ExtensionSet, this only works for generated message types --
   // it looks up extensions registered using RegisterExtension().
   bool ParseField(uint32 tag, io::CodedInputStream* input,
+                  const MessageLite* containing_type);
+  bool ParseField(uint32 tag, io::CodedInputStream* input,
+                  const Message* containing_type,
+                  UnknownFieldSet* unknown_fields);
+  bool ParseField(uint32 tag, io::CodedInputStream* input,
                   const MessageLite* containing_type,
-                  UnknownFieldSet* unknown_fields);
-  bool ParseFieldHeavy(uint32 tag, io::CodedInputStream* input,
-                       const Message* containing_type,
-                       UnknownFieldSet* unknown_fields);
+                  io::CodedOutputStream* unknown_fields);
 
   // Parse an entire message in MessageSet format.  Such messages have no
   // fields, only extensions.
   bool ParseMessageSet(io::CodedInputStream* input,
                        ExtensionFinder* extension_finder,
-                       FieldSkipper* field_skipper);
+                       MessageSetFieldSkipper* field_skipper);
 
   // Specific versions for lite or full messages (constructs the appropriate
   // FieldSkipper automatically).
   bool ParseMessageSet(io::CodedInputStream* input,
-                       const MessageLite* containing_type,
+                       const MessageLite* containing_type);
+  bool ParseMessageSet(io::CodedInputStream* input,
+                       const Message* containing_type,
                        UnknownFieldSet* unknown_fields);
-  bool ParseMessageSetHeavy(io::CodedInputStream* input,
-                            const Message* containing_type,
-                            UnknownFieldSet* unknown_fields);
 
   // Write all extension fields with field numbers in the range
   //   [start_field_number, end_field_number)
   // to the output stream, using the cached sizes computed when ByteSize() was
   // last called.  Note that the range bounds are inclusive-exclusive.
   void SerializeWithCachedSizes(int start_field_number,
                                 int end_field_number,
                                 io::CodedOutputStream* output) const;
 
   // Same as SerializeWithCachedSizes, but without any bounds checking.
@@ skipping 25 matching lines @@
   int SpaceUsedExcludingSelf() const;
 
  private:
 
   // Interface of a lazily parsed singular message extension.
   class LIBPROTOBUF_EXPORT LazyMessageExtension {
    public:
     LazyMessageExtension() {}
     virtual ~LazyMessageExtension() {}
 
-    virtual LazyMessageExtension* New() const = 0;
+    virtual LazyMessageExtension* New(::google::protobuf::Arena* arena) const = 0;
     virtual const MessageLite& GetMessage(
         const MessageLite& prototype) const = 0;
     virtual MessageLite* MutableMessage(const MessageLite& prototype) = 0;
     virtual void SetAllocatedMessage(MessageLite *message) = 0;
+    virtual void UnsafeArenaSetAllocatedMessage(MessageLite *message) = 0;
     virtual MessageLite* ReleaseMessage(const MessageLite& prototype) = 0;
+    virtual MessageLite* UnsafeArenaReleaseMessage(
+        const MessageLite& prototype) = 0;
 
     virtual bool IsInitialized() const = 0;
     virtual int ByteSize() const = 0;
     virtual int SpaceUsed() const = 0;
 
     virtual void MergeFrom(const LazyMessageExtension& other) = 0;
     virtual void Clear() = 0;
 
     virtual bool ReadMessage(const MessageLite& prototype,
                              io::CodedInputStream* input) = 0;
@@ skipping 77 matching lines @@
         uint8* target) const;
     int ByteSize(int number) const;
     int MessageSetItemByteSize(int number) const;
     void Clear();
     int GetSize() const;
     void Free();
     int SpaceUsedExcludingSelf() const;
   };
 
 
+  // Merges existing Extension from other_extension
+  void InternalExtensionMergeFrom(int number, const Extension& other_extension);
+
   // Returns true and fills field_number and extension if extension is found.
+  // Note to support packed repeated field compatibility, it also fills whether
+  // the tag on wire is packed, which can be different from
+  // extension->is_packed (whether packed=true is specified).
   bool FindExtensionInfoFromTag(uint32 tag, ExtensionFinder* extension_finder,
-                                int* field_number, ExtensionInfo* extension);
+                                int* field_number, ExtensionInfo* extension,
+                                bool* was_packed_on_wire);
+
+  // Returns true and fills extension if extension is found.
+  // Note to support packed repeated field compatibility, it also fills whether
+  // the tag on wire is packed, which can be different from
+  // extension->is_packed (whether packed=true is specified).
+  bool FindExtensionInfoFromFieldNumber(int wire_type, int field_number,
+                                        ExtensionFinder* extension_finder,
+                                        ExtensionInfo* extension,
+                                        bool* was_packed_on_wire);
 
   // Parses a single extension from the input. The input should start out
   // positioned immediately after the wire tag. This method is called in
-  // ParseField() after field number is extracted from the wire tag and
-  // ExtensionInfo is found by the field number.
+  // ParseField() after field number and was_packed_on_wire is extracted from
+  // the wire tag and ExtensionInfo is found by the field number.
   bool ParseFieldWithExtensionInfo(int field_number,
+                                   bool was_packed_on_wire,
                                    const ExtensionInfo& extension,
                                    io::CodedInputStream* input,
                                    FieldSkipper* field_skipper);
 
   // Like ParseField(), but this method may parse singular message extensions
   // lazily depending on the value of FLAGS_eagerly_parse_message_sets.
-  bool ParseFieldMaybeLazily(uint32 tag, io::CodedInputStream* input,
+  bool ParseFieldMaybeLazily(int wire_type, int field_number,
+                             io::CodedInputStream* input,
                              ExtensionFinder* extension_finder,
-                             FieldSkipper* field_skipper);
+                             MessageSetFieldSkipper* field_skipper);
 
   // Gets the extension with the given number, creating it if it does not
   // already exist.  Returns true if the extension did not already exist.
   bool MaybeNewExtension(int number, const FieldDescriptor* descriptor,
                          Extension** result);
 
+  // Gets the repeated extension for the given descriptor, creating it if
+  // it does not exist.
+  Extension* MaybeNewRepeatedExtension(const FieldDescriptor* descriptor);
+
   // Parse a single MessageSet item -- called just after the item group start
   // tag has been read.
   bool ParseMessageSetItem(io::CodedInputStream* input,
                            ExtensionFinder* extension_finder,
-                           FieldSkipper* field_skipper);
-
+                           MessageSetFieldSkipper* field_skipper);
 
   // Hack:  RepeatedPtrFieldBase declares ExtensionSet as a friend.  This
   //   friendship should automatically extend to ExtensionSet::Extension, but
   //   unfortunately some older compilers (e.g. GCC 3.4.4) do not implement this
   //   correctly.  So, we must provide helpers for calling methods of that
   //   class.
 
   // Defined in extension_set_heavy.cc.
   static inline int RepeatedMessage_SpaceUsedExcludingSelf(
       RepeatedPtrFieldBase* field);
 
   // The Extension struct is small enough to be passed by value, so we use it
   // directly as the value type in the map rather than use pointers.  We use
   // a map rather than hash_map here because we expect most ExtensionSets will
   // only contain a small number of extensions whereas hash_map is optimized
   // for 100 elements or more.  Also, we want AppendToList() to order fields
   // by field number.
   std::map<int, Extension> extensions_;
-
+  ::google::protobuf::Arena* arena_;
   GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(ExtensionSet);
 };
 
 // These are just for convenience...
 inline void ExtensionSet::SetString(int number, FieldType type,
                                     const string& value,
                                     const FieldDescriptor* descriptor) {
   MutableString(number, type, descriptor)->assign(value);
 }
 inline void ExtensionSet::SetRepeatedString(int number, int index,
@@ skipping 14 matching lines @@
 
 // First we have a set of classes representing "type traits" for different
 // field types.  A type traits class knows how to implement basic accessors
 // for extensions of a particular type given an ExtensionSet.  The signature
 // for a type traits class looks like this:
 //
 //   class TypeTraits {
 //    public:
 //     typedef ? ConstType;
 //     typedef ? MutableType;
+//     // TypeTraits for singular fields and repeated fields will define the
+//     // symbol "Singular" or "Repeated" respectively. These two symbols will
+//     // be used in extension accessors to distinguish between singular
+//     // extensions and repeated extensions. If the TypeTraits for the passed
+//     // in extension doesn't have the expected symbol defined, it means the
+//     // user is passing a repeated extension to a singular accessor, or the
+//     // opposite. In that case the C++ compiler will generate an error
+//     // message "no matching member function" to inform the user.
+//     typedef ? Singular
+//     typedef ? Repeated
 //
 //     static inline ConstType Get(int number, const ExtensionSet& set);
 //     static inline void Set(int number, ConstType value, ExtensionSet* set);
 //     static inline MutableType Mutable(int number, ExtensionSet* set);
 //
 //     // Variants for repeated fields.
 //     static inline ConstType Get(int number, const ExtensionSet& set,
 //                                 int index);
 //     static inline void Set(int number, int index,
 //                            ConstType value, ExtensionSet* set);
@@ skipping 18 matching lines @@
 // -------------------------------------------------------------------
 // PrimitiveTypeTraits
 
 // Since the ExtensionSet has different methods for each primitive type,
 // we must explicitly define the methods of the type traits class for each
 // known type.
 template <typename Type>
 class PrimitiveTypeTraits {
  public:
   typedef Type ConstType;
+  typedef Type MutableType;
+  typedef PrimitiveTypeTraits<Type> Singular;
 
   static inline ConstType Get(int number, const ExtensionSet& set,
                               ConstType default_value);
   static inline void Set(int number, FieldType field_type,
                          ConstType value, ExtensionSet* set);
 };
 
 template <typename Type>
 class RepeatedPrimitiveTypeTraits {
  public:
   typedef Type ConstType;
+  typedef Type MutableType;
+  typedef RepeatedPrimitiveTypeTraits<Type> Repeated;
+
+  typedef RepeatedField<Type> RepeatedFieldType;
 
   static inline Type Get(int number, const ExtensionSet& set, int index);
   static inline void Set(int number, int index, Type value, ExtensionSet* set);
   static inline void Add(int number, FieldType field_type,
                          bool is_packed, Type value, ExtensionSet* set);
+
+  static inline const RepeatedField<ConstType>&
+      GetRepeated(int number, const ExtensionSet& set);
+  static inline RepeatedField<Type>*
+      MutableRepeated(int number, FieldType field_type,
+                      bool is_packed, ExtensionSet* set);
+
+  static const RepeatedFieldType* GetDefaultRepeatedField();
+};
+
+LIBPROTOBUF_EXPORT extern ProtobufOnceType repeated_primitive_generic_type_traits_once_init_;
+
+class LIBPROTOBUF_EXPORT RepeatedPrimitiveGenericTypeTraits {
+ private:
+  template<typename Type> friend class RepeatedPrimitiveTypeTraits;
+  static void InitializeDefaultRepeatedFields();
+  static void DestroyDefaultRepeatedFields();
+  static const RepeatedField<int32>* default_repeated_field_int32_;
+  static const RepeatedField<int64>* default_repeated_field_int64_;
+  static const RepeatedField<uint32>* default_repeated_field_uint32_;
+  static const RepeatedField<uint64>* default_repeated_field_uint64_;
+  static const RepeatedField<double>* default_repeated_field_double_;
+  static const RepeatedField<float>* default_repeated_field_float_;
+  static const RepeatedField<bool>* default_repeated_field_bool_;
 };
 
 #define PROTOBUF_DEFINE_PRIMITIVE_TYPE(TYPE, METHOD)                       \
 template<> inline TYPE PrimitiveTypeTraits<TYPE>::Get(                     \
     int number, const ExtensionSet& set, TYPE default_value) {             \
   return set.Get##METHOD(number, default_value);                           \
 }                                                                          \
 template<> inline void PrimitiveTypeTraits<TYPE>::Set(                     \
     int number, FieldType field_type, TYPE value, ExtensionSet* set) {     \
   set->Set##METHOD(number, field_type, value, NULL);                       \
 }                                                                          \
                                                                            \
 template<> inline TYPE RepeatedPrimitiveTypeTraits<TYPE>::Get(             \
     int number, const ExtensionSet& set, int index) {                      \
   return set.GetRepeated##METHOD(number, index);                           \
 }                                                                          \
 template<> inline void RepeatedPrimitiveTypeTraits<TYPE>::Set(             \
     int number, int index, TYPE value, ExtensionSet* set) {                \
   set->SetRepeated##METHOD(number, index, value);                          \
 }                                                                          \
 template<> inline void RepeatedPrimitiveTypeTraits<TYPE>::Add(             \
     int number, FieldType field_type, bool is_packed,                      \
     TYPE value, ExtensionSet* set) {                                       \
   set->Add##METHOD(number, field_type, is_packed, value, NULL);            \
+}                                                                          \
+template<> inline const RepeatedField<TYPE>*                               \
+    RepeatedPrimitiveTypeTraits<TYPE>::GetDefaultRepeatedField() {         \
+  ::google::protobuf::GoogleOnceInit(                                                          \
+      &repeated_primitive_generic_type_traits_once_init_,                  \
+      &RepeatedPrimitiveGenericTypeTraits::InitializeDefaultRepeatedFields); \
+  return RepeatedPrimitiveGenericTypeTraits::                              \
+      default_repeated_field_##TYPE##_;                                    \
+}                                                                          \
+template<> inline const RepeatedField<TYPE>&                               \
+    RepeatedPrimitiveTypeTraits<TYPE>::GetRepeated(int number,             \
+                                               const ExtensionSet& set) {  \
+  return *reinterpret_cast<const RepeatedField<TYPE>*>(                    \
+                            set.GetRawRepeatedField(                       \
+                                number, GetDefaultRepeatedField()));       \
+}                                                                          \
+template<> inline RepeatedField<TYPE>*                                     \
+    RepeatedPrimitiveTypeTraits<TYPE>::MutableRepeated(int number,         \
+                                                   FieldType field_type,   \
+                                                   bool is_packed,         \
+                                                   ExtensionSet* set) {    \
+  return reinterpret_cast<RepeatedField<TYPE>*>(                           \
+      set->MutableRawRepeatedField(number, field_type, is_packed, NULL));  \
 }
 
 PROTOBUF_DEFINE_PRIMITIVE_TYPE( int32,  Int32)
 PROTOBUF_DEFINE_PRIMITIVE_TYPE( int64,  Int64)
 PROTOBUF_DEFINE_PRIMITIVE_TYPE(uint32, UInt32)
 PROTOBUF_DEFINE_PRIMITIVE_TYPE(uint64, UInt64)
 PROTOBUF_DEFINE_PRIMITIVE_TYPE( float,  Float)
 PROTOBUF_DEFINE_PRIMITIVE_TYPE(double, Double)
 PROTOBUF_DEFINE_PRIMITIVE_TYPE(  bool,   Bool)
 
 #undef PROTOBUF_DEFINE_PRIMITIVE_TYPE
 
 // -------------------------------------------------------------------
 // StringTypeTraits
 
 // Strings support both Set() and Mutable().
 class LIBPROTOBUF_EXPORT StringTypeTraits {
  public:
   typedef const string& ConstType;
   typedef string* MutableType;
+  typedef StringTypeTraits Singular;
 
   static inline const string& Get(int number, const ExtensionSet& set,
                                   ConstType default_value) {
     return set.GetString(number, default_value);
   }
   static inline void Set(int number, FieldType field_type,
                          const string& value, ExtensionSet* set) {
     set->SetString(number, field_type, value, NULL);
   }
   static inline string* Mutable(int number, FieldType field_type,
                                 ExtensionSet* set) {
     return set->MutableString(number, field_type, NULL);
   }
 };
 
+LIBPROTOBUF_EXPORT extern ProtobufOnceType repeated_string_type_traits_once_init_;
+
 class LIBPROTOBUF_EXPORT RepeatedStringTypeTraits {
  public:
   typedef const string& ConstType;
   typedef string* MutableType;
+  typedef RepeatedStringTypeTraits Repeated;
+
+  typedef RepeatedPtrField<string> RepeatedFieldType;
 
   static inline const string& Get(int number, const ExtensionSet& set,
                                   int index) {
     return set.GetRepeatedString(number, index);
   }
   static inline void Set(int number, int index,
                          const string& value, ExtensionSet* set) {
     set->SetRepeatedString(number, index, value);
   }
   static inline string* Mutable(int number, int index, ExtensionSet* set) {
     return set->MutableRepeatedString(number, index);
   }
   static inline void Add(int number, FieldType field_type,
                          bool /*is_packed*/, const string& value,
                          ExtensionSet* set) {
     set->AddString(number, field_type, value, NULL);
   }
   static inline string* Add(int number, FieldType field_type,
                             ExtensionSet* set) {
     return set->AddString(number, field_type, NULL);
   }
+  static inline const RepeatedPtrField<string>&
+      GetRepeated(int number, const ExtensionSet& set) {
+    return *reinterpret_cast<const RepeatedPtrField<string>*>(
+        set.GetRawRepeatedField(number, GetDefaultRepeatedField()));
+  }
+
+  static inline RepeatedPtrField<string>*
+      MutableRepeated(int number, FieldType field_type,
+                      bool is_packed, ExtensionSet* set) {
+    return reinterpret_cast<RepeatedPtrField<string>*>(
+        set->MutableRawRepeatedField(number, field_type,
+                                     is_packed, NULL));
+  }
+
+  static const RepeatedFieldType* GetDefaultRepeatedField() {
+    ::google::protobuf::GoogleOnceInit(&repeated_string_type_traits_once_init_,
+                   &InitializeDefaultRepeatedFields);
+    return default_repeated_field_;
+  }
+
+ private:
+  static void InitializeDefaultRepeatedFields();
+  static void DestroyDefaultRepeatedFields();
+  static const RepeatedFieldType *default_repeated_field_;
 };
 
 // -------------------------------------------------------------------
 // EnumTypeTraits
 
 // ExtensionSet represents enums using integers internally, so we have to
 // static_cast around.
 template <typename Type, bool IsValid(int)>
 class EnumTypeTraits {
  public:
   typedef Type ConstType;
+  typedef Type MutableType;
+  typedef EnumTypeTraits<Type, IsValid> Singular;
 
   static inline ConstType Get(int number, const ExtensionSet& set,
                               ConstType default_value) {
     return static_cast<Type>(set.GetEnum(number, default_value));
   }
   static inline void Set(int number, FieldType field_type,
                          ConstType value, ExtensionSet* set) {
     GOOGLE_DCHECK(IsValid(value));
     set->SetEnum(number, field_type, value, NULL);
   }
 };
 
 template <typename Type, bool IsValid(int)>
 class RepeatedEnumTypeTraits {
  public:
   typedef Type ConstType;
+  typedef Type MutableType;
+  typedef RepeatedEnumTypeTraits<Type, IsValid> Repeated;
+
+  typedef RepeatedField<Type> RepeatedFieldType;
 
   static inline ConstType Get(int number, const ExtensionSet& set, int index) {
     return static_cast<Type>(set.GetRepeatedEnum(number, index));
   }
   static inline void Set(int number, int index,
                          ConstType value, ExtensionSet* set) {
     GOOGLE_DCHECK(IsValid(value));
     set->SetRepeatedEnum(number, index, value);
   }
   static inline void Add(int number, FieldType field_type,
                          bool is_packed, ConstType value, ExtensionSet* set) {
     GOOGLE_DCHECK(IsValid(value));
     set->AddEnum(number, field_type, is_packed, value, NULL);
   }
+  static inline const RepeatedField<Type>& GetRepeated(int number,
+                                                       const ExtensionSet&
+                                                       set) {
+    // Hack: the `Extension` struct stores a RepeatedField<int> for enums.
+    // RepeatedField<int> cannot implicitly convert to RepeatedField<EnumType>
+    // so we need to do some casting magic. See message.h for similar
+    // contortions for non-extension fields.
+    return *reinterpret_cast<const RepeatedField<Type>*>(
+        set.GetRawRepeatedField(number, GetDefaultRepeatedField()));
+  }
+
+  static inline RepeatedField<Type>* MutableRepeated(int number,
+                                                     FieldType field_type,
+                                                     bool is_packed,
+                                                     ExtensionSet* set) {
+    return reinterpret_cast<RepeatedField<Type>*>(
+        set->MutableRawRepeatedField(number, field_type, is_packed, NULL));
+  }
+
+  static const RepeatedFieldType* GetDefaultRepeatedField() {
+    // Hack: as noted above, repeated enum fields are internally stored as a
+    // RepeatedField<int>. We need to be able to instantiate global static
+    // objects to return as default (empty) repeated fields on non-existent
+    // extensions. We would not be able to know a-priori all of the enum types
+    // (values of |Type|) to instantiate all of these, so we just re-use int32's
+    // default repeated field object.
+    return reinterpret_cast<const RepeatedField<Type>*>(
+        RepeatedPrimitiveTypeTraits<int32>::GetDefaultRepeatedField());
+  }
 };
 
 // -------------------------------------------------------------------
 // MessageTypeTraits
 
 // ExtensionSet guarantees that when manipulating extensions with message
 // types, the implementation used will be the compiled-in class representing
 // that type.  So, we can static_cast down to the exact type we expect.
 template <typename Type>
 class MessageTypeTraits {
  public:
   typedef const Type& ConstType;
   typedef Type* MutableType;
+  typedef MessageTypeTraits<Type> Singular;
 
   static inline ConstType Get(int number, const ExtensionSet& set,
                               ConstType default_value) {
     return static_cast<const Type&>(
         set.GetMessage(number, default_value));
   }
   static inline MutableType Mutable(int number, FieldType field_type,
                                     ExtensionSet* set) {
     return static_cast<Type*>(
       set->MutableMessage(number, field_type, Type::default_instance(), NULL));
   }
   static inline void SetAllocated(int number, FieldType field_type,
                                   MutableType message, ExtensionSet* set) {
     set->SetAllocatedMessage(number, field_type, NULL, message);
   }
-  static inline MutableType Release(int number, FieldType field_type,
+  static inline MutableType Release(int number, FieldType /* field_type */,
                                     ExtensionSet* set) {
     return static_cast<Type*>(set->ReleaseMessage(
         number, Type::default_instance()));
   }
 };
 
+// forward declaration
+class RepeatedMessageGenericTypeTraits;
+
 template <typename Type>
 class RepeatedMessageTypeTraits {
  public:
   typedef const Type& ConstType;
   typedef Type* MutableType;
+  typedef RepeatedMessageTypeTraits<Type> Repeated;
+
+  typedef RepeatedPtrField<Type> RepeatedFieldType;
 
   static inline ConstType Get(int number, const ExtensionSet& set, int index) {
     return static_cast<const Type&>(set.GetRepeatedMessage(number, index));
   }
   static inline MutableType Mutable(int number, int index, ExtensionSet* set) {
     return static_cast<Type*>(set->MutableRepeatedMessage(number, index));
   }
   static inline MutableType Add(int number, FieldType field_type,
                                 ExtensionSet* set) {
     return static_cast<Type*>(
         set->AddMessage(number, field_type, Type::default_instance(), NULL));
   }
+  static inline const RepeatedPtrField<Type>& GetRepeated(int number,
+                                                          const ExtensionSet&
+                                                          set) {
+    // See notes above in RepeatedEnumTypeTraits::GetRepeated(): same
+    // casting hack applies here, because a RepeatedPtrField<MessageLite>
+    // cannot naturally become a RepeatedPtrType<Type> even though Type is
+    // presumably a message. google::protobuf::Message goes through similar contortions
+    // with a reinterpret_cast<>.
+    return *reinterpret_cast<const RepeatedPtrField<Type>*>(
+        set.GetRawRepeatedField(number, GetDefaultRepeatedField()));
+  }
+  static inline RepeatedPtrField<Type>* MutableRepeated(int number,
+                                                        FieldType field_type,
+                                                        bool is_packed,
+                                                        ExtensionSet* set) {
+    return reinterpret_cast<RepeatedPtrField<Type>*>(
+        set->MutableRawRepeatedField(number, field_type, is_packed, NULL));
+  }
+
+  static const RepeatedFieldType* GetDefaultRepeatedField();
 };
 
+LIBPROTOBUF_EXPORT extern ProtobufOnceType repeated_message_generic_type_traits_once_init_;
+
+// This class exists only to hold a generic default empty repeated field for all
+// message-type repeated field extensions.
+class LIBPROTOBUF_EXPORT RepeatedMessageGenericTypeTraits {
+ public:
+  typedef RepeatedPtrField< ::google::protobuf::MessageLite*> RepeatedFieldType;
+ private:
+  template<typename Type> friend class RepeatedMessageTypeTraits;
+  static void InitializeDefaultRepeatedFields();
+  static void DestroyDefaultRepeatedFields();
+  static const RepeatedFieldType* default_repeated_field_;
+};
+
+template<typename Type> inline
+    const typename RepeatedMessageTypeTraits<Type>::RepeatedFieldType*
+    RepeatedMessageTypeTraits<Type>::GetDefaultRepeatedField() {
+  ::google::protobuf::GoogleOnceInit(
+      &repeated_message_generic_type_traits_once_init_,
+      &RepeatedMessageGenericTypeTraits::InitializeDefaultRepeatedFields);
+  return reinterpret_cast<const RepeatedFieldType*>(
+      RepeatedMessageGenericTypeTraits::default_repeated_field_);
+}
+
 // -------------------------------------------------------------------
 // ExtensionIdentifier
 
 // This is the type of actual extension objects.  E.g. if you have:
 //   extends Foo with optional int32 bar = 1234;
 // then "bar" will be defined in C++ as:
 //   ExtensionIdentifier<Foo, PrimitiveTypeTraits<int32>, 1, false> bar(1234);
 //
 // Note that we could, in theory, supply the field number as a template
 // parameter, and thus make an instance of ExtensionIdentifier have no
@@ skipping 62 matching lines @@
   inline int ExtensionSize(                                                   \
       const ::google::protobuf::internal::ExtensionIdentifier<                          \
         CLASSNAME, _proto_TypeTraits, _field_type, _is_packed>& id) const {   \
     return _extensions_.ExtensionSize(id.number());                           \
   }                                                                           \
                                                                               \
   /* Singular accessors */                                                    \
   template <typename _proto_TypeTraits,                                       \
             ::google::protobuf::internal::FieldType _field_type,                        \
             bool _is_packed>                                                  \
-  inline typename _proto_TypeTraits::ConstType GetExtension(                  \
+  inline typename _proto_TypeTraits::Singular::ConstType GetExtension(        \
       const ::google::protobuf::internal::ExtensionIdentifier<                          \
         CLASSNAME, _proto_TypeTraits, _field_type, _is_packed>& id) const {   \
     return _proto_TypeTraits::Get(id.number(), _extensions_,                  \
                                   id.default_value());                        \
   }                                                                           \
                                                                               \
   template <typename _proto_TypeTraits,                                       \
             ::google::protobuf::internal::FieldType _field_type,                        \
             bool _is_packed>                                                  \
-  inline typename _proto_TypeTraits::MutableType MutableExtension(            \
+  inline typename _proto_TypeTraits::Singular::MutableType MutableExtension(  \
       const ::google::protobuf::internal::ExtensionIdentifier<                          \
         CLASSNAME, _proto_TypeTraits, _field_type, _is_packed>& id) {         \
     return _proto_TypeTraits::Mutable(id.number(), _field_type,               \
                                       &_extensions_);                         \
   }                                                                           \
                                                                               \
   template <typename _proto_TypeTraits,                                       \
             ::google::protobuf::internal::FieldType _field_type,                        \
             bool _is_packed>                                                  \
   inline void SetExtension(                                                   \
       const ::google::protobuf::internal::ExtensionIdentifier<                          \
         CLASSNAME, _proto_TypeTraits, _field_type, _is_packed>& id,           \
-      typename _proto_TypeTraits::ConstType value) {                          \
+      typename _proto_TypeTraits::Singular::ConstType value) {                \
     _proto_TypeTraits::Set(id.number(), _field_type, value, &_extensions_);   \
   }                                                                           \
                                                                               \
   template <typename _proto_TypeTraits,                                       \
             ::google::protobuf::internal::FieldType _field_type,                        \
             bool _is_packed>                                                  \
   inline void SetAllocatedExtension(                                          \
       const ::google::protobuf::internal::ExtensionIdentifier<                          \
         CLASSNAME, _proto_TypeTraits, _field_type, _is_packed>& id,           \
-      typename _proto_TypeTraits::MutableType value) {                        \
+      typename _proto_TypeTraits::Singular::MutableType value) {              \
     _proto_TypeTraits::SetAllocated(id.number(), _field_type,                 \
                                     value, &_extensions_);                    \
   }                                                                           \
   template <typename _proto_TypeTraits,                                       \
             ::google::protobuf::internal::FieldType _field_type,                        \
             bool _is_packed>                                                  \
-  inline typename _proto_TypeTraits::MutableType ReleaseExtension(            \
+  inline typename _proto_TypeTraits::Singular::MutableType ReleaseExtension(  \
       const ::google::protobuf::internal::ExtensionIdentifier<                          \
         CLASSNAME, _proto_TypeTraits, _field_type, _is_packed>& id) {         \
     return _proto_TypeTraits::Release(id.number(), _field_type,               \
                                       &_extensions_);                         \
   }                                                                           \
                                                                               \
   /* Repeated accessors */                                                    \
   template <typename _proto_TypeTraits,                                       \
             ::google::protobuf::internal::FieldType _field_type,                        \
             bool _is_packed>                                                  \
-  inline typename _proto_TypeTraits::ConstType GetExtension(                  \
+  inline typename _proto_TypeTraits::Repeated::ConstType GetExtension(        \
       const ::google::protobuf::internal::ExtensionIdentifier<                          \
         CLASSNAME, _proto_TypeTraits, _field_type, _is_packed>& id,           \
       int index) const {                                                      \
     return _proto_TypeTraits::Get(id.number(), _extensions_, index);          \
   }                                                                           \
                                                                               \
   template <typename _proto_TypeTraits,                                       \
             ::google::protobuf::internal::FieldType _field_type,                        \
             bool _is_packed>                                                  \
-  inline typename _proto_TypeTraits::MutableType MutableExtension(            \
+  inline typename _proto_TypeTraits::Repeated::MutableType MutableExtension(  \
       const ::google::protobuf::internal::ExtensionIdentifier<                          \
         CLASSNAME, _proto_TypeTraits, _field_type, _is_packed>& id,           \
       int index) {                                                            \
     return _proto_TypeTraits::Mutable(id.number(), index, &_extensions_);     \
   }                                                                           \
                                                                               \
   template <typename _proto_TypeTraits,                                       \
             ::google::protobuf::internal::FieldType _field_type,                        \
             bool _is_packed>                                                  \
   inline void SetExtension(                                                   \
       const ::google::protobuf::internal::ExtensionIdentifier<                          \
         CLASSNAME, _proto_TypeTraits, _field_type, _is_packed>& id,           \
-      int index, typename _proto_TypeTraits::ConstType value) {               \
+      int index, typename _proto_TypeTraits::Repeated::ConstType value) {     \
     _proto_TypeTraits::Set(id.number(), index, value, &_extensions_);         \
   }                                                                           \
                                                                               \
   template <typename _proto_TypeTraits,                                       \
             ::google::protobuf::internal::FieldType _field_type,                        \
             bool _is_packed>                                                  \
-  inline typename _proto_TypeTraits::MutableType AddExtension(                \
+  inline typename _proto_TypeTraits::Repeated::MutableType AddExtension(      \
       const ::google::protobuf::internal::ExtensionIdentifier<                          \
         CLASSNAME, _proto_TypeTraits, _field_type, _is_packed>& id) {         \
     return _proto_TypeTraits::Add(id.number(), _field_type, &_extensions_);   \
   }                                                                           \
                                                                               \
   template <typename _proto_TypeTraits,                                       \
             ::google::protobuf::internal::FieldType _field_type,                        \
             bool _is_packed>                                                  \
   inline void AddExtension(                                                   \
       const ::google::protobuf::internal::ExtensionIdentifier<                          \
         CLASSNAME, _proto_TypeTraits, _field_type, _is_packed>& id,           \
-      typename _proto_TypeTraits::ConstType value) {                          \
+      typename _proto_TypeTraits::Repeated::ConstType value) {                \
     _proto_TypeTraits::Add(id.number(), _field_type, _is_packed,              \
                            value, &_extensions_);                             \
+  }                                                                           \
+                                                                              \
+  template <typename _proto_TypeTraits,                                       \
+            ::google::protobuf::internal::FieldType _field_type,                        \
+            bool _is_packed>                                                  \
+  inline const typename _proto_TypeTraits::Repeated::RepeatedFieldType&       \
+      GetRepeatedExtension(                                                   \
+          const ::google::protobuf::internal::ExtensionIdentifier<                      \
+            CLASSNAME, _proto_TypeTraits, _field_type,                        \
+            _is_packed>& id) const {                                          \
+    return _proto_TypeTraits::GetRepeated(id.number(), _extensions_);         \
+  }                                                                           \
+                                                                              \
+  template <typename _proto_TypeTraits,                                       \
+            ::google::protobuf::internal::FieldType _field_type,                        \
+            bool _is_packed>                                                  \
+  inline typename _proto_TypeTraits::Repeated::RepeatedFieldType*             \
+      MutableRepeatedExtension(                                               \
+          const ::google::protobuf::internal::ExtensionIdentifier<                      \
+              CLASSNAME, _proto_TypeTraits, _field_type,                      \
+              _is_packed>& id) {                                              \
+    return _proto_TypeTraits::MutableRepeated(id.number(), _field_type,       \
+                                              _is_packed, &_extensions_);     \
   }
 
 }  // namespace internal
 }  // namespace protobuf
 
 }  // namespace google
 #endif  // GOOGLE_PROTOBUF_EXTENSION_SET_H__