Pull new version of protobuf sources.

third_party/protobuf/src/google/protobuf/extension_set.cc

Index: third_party/protobuf/src/google/protobuf/extension_set.cc
diff --git a/third_party/protobuf/src/google/protobuf/extension_set.cc b/third_party/protobuf/src/google/protobuf/extension_set.cc
index 418e068407b03f61231840fa43a586458bfb547d..c315ecaccb88b5f8ca8e5f74f980324ae602bd9e 100644
--- a/third_party/protobuf/src/google/protobuf/extension_set.cc
+++ b/third_party/protobuf/src/google/protobuf/extension_set.cc
@@ -1,6 +1,6 @@
 // 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
@@ -38,10 +38,10 @@
 #include <google/protobuf/extension_set.h>
 #include <google/protobuf/message_lite.h>
 #include <google/protobuf/io/coded_stream.h>
-#include <google/protobuf/io/zero_copy_stream_impl.h>
+#include <google/protobuf/io/zero_copy_stream_impl_lite.h>
 #include <google/protobuf/wire_format_lite_inl.h>
 #include <google/protobuf/repeated_field.h>
-#include <google/protobuf/stubs/map-util.h>
+#include <google/protobuf/stubs/map_util.h>
 
 namespace google {
 namespace protobuf {
@@ -58,6 +58,24 @@ inline WireFormatLite::CppType cpp_type(FieldType type) {
   return WireFormatLite::FieldTypeToCppType(real_type(type));
 }
 
+inline bool is_packable(WireFormatLite::WireType type) {
+  switch (type) {
+    case WireFormatLite::WIRETYPE_VARINT:
+    case WireFormatLite::WIRETYPE_FIXED64:
+    case WireFormatLite::WIRETYPE_FIXED32:
+      return true;
+    case WireFormatLite::WIRETYPE_LENGTH_DELIMITED:
+    case WireFormatLite::WIRETYPE_START_GROUP:
+    case WireFormatLite::WIRETYPE_END_GROUP:
+      return false;
+
+    // Do not add a default statement. Let the compiler complain when someone
+    // adds a new wire type.
+  }
+  GOOGLE_LOG(FATAL) << "can't reach here.";
+  return false;
+}
+
 // Registry stuff.
 typedef hash_map<pair<const MessageLite*, int>,
                  ExtensionInfo> ExtensionRegistry;
@@ -80,7 +98,7 @@ void Register(const MessageLite* containing_type,
               int number, ExtensionInfo info) {
   ::google::protobuf::GoogleOnceInit(&registry_init_, &InitRegistry);
 
-  if (!InsertIfNotPresent(registry_, make_pair(containing_type, number),
+  if (!InsertIfNotPresent(registry_, std::make_pair(containing_type, number),
                           info)) {
     GOOGLE_LOG(FATAL) << "Multiple extension registrations for type \""
                << containing_type->GetTypeName()
@@ -90,8 +108,9 @@ void Register(const MessageLite* containing_type,
 
 const ExtensionInfo* FindRegisteredExtension(
     const MessageLite* containing_type, int number) {
-  return (registry_ == NULL) ? NULL :
-         FindOrNull(*registry_, make_pair(containing_type, number));
+  return (registry_ == NULL)
+             ? NULL
+             : FindOrNull(*registry_, std::make_pair(containing_type, number));
 }
 
 }  // namespace
@@ -159,12 +178,21 @@ void ExtensionSet::RegisterMessageExtension(const MessageLite* containing_type,
 // ===================================================================
 // Constructors and basic methods.
 
-ExtensionSet::ExtensionSet() {}
+ExtensionSet::ExtensionSet(::google::protobuf::Arena* arena) : arena_(arena) {
+  if (arena_ != NULL) {
+    arena_->OwnDestructor(&extensions_);
+  }
+}
+
+ExtensionSet::ExtensionSet() : arena_(NULL) {}
 
 ExtensionSet::~ExtensionSet() {
-  for (map<int, Extension>::iterator iter = extensions_.begin();
-       iter != extensions_.end(); ++iter) {
-    iter->second.Free();
+  // Deletes all allocated extensions.
+  if (arena_ == NULL) {
+    for (map<int, Extension>::iterator iter = extensions_.begin();
+         iter != extensions_.end(); ++iter) {
+      iter->second.Free();
+    }
   }
 }
 
@@ -286,7 +314,8 @@ void ExtensionSet::Add##CAMELCASE(int number, FieldType type,                  \
     GOOGLE_DCHECK_EQ(cpp_type(extension->type), WireFormatLite::CPPTYPE_##UPPERCASE); \
     extension->is_repeated = true;                                             \
     extension->is_packed = packed;                                             \
-    extension->repeated_##LOWERCASE##_value = new RepeatedField<LOWERCASE>();  \
+    extension->repeated_##LOWERCASE##_value =                                  \
+      Arena::CreateMessage<RepeatedField<LOWERCASE> >(arena_);                 \
   } else {                                                                     \
     GOOGLE_DCHECK_TYPE(*extension, REPEATED, UPPERCASE);                              \
     GOOGLE_DCHECK_EQ(extension->is_packed, packed);                                   \
@@ -304,14 +333,90 @@ PRIMITIVE_ACCESSORS(  BOOL,   bool,   Bool)
 
 #undef PRIMITIVE_ACCESSORS
 
+const void* ExtensionSet::GetRawRepeatedField(int number,
+                                              const void* default_value) const {
+  map<int, Extension>::const_iterator iter = extensions_.find(number);
+  if (iter == extensions_.end()) {
+    return default_value;
+  }
+  // We assume that all the RepeatedField<>* pointers have the same
+  // size and alignment within the anonymous union in Extension.
+  return iter->second.repeated_int32_value;
+}
+
+void* ExtensionSet::MutableRawRepeatedField(int number, FieldType field_type,
+                                            bool packed,
+                                            const FieldDescriptor* desc) {
+  Extension* extension;
+
+  // We instantiate an empty Repeated{,Ptr}Field if one doesn't exist for this
+  // extension.
+  if (MaybeNewExtension(number, desc, &extension)) {
+    extension->is_repeated = true;
+    extension->type = field_type;
+    extension->is_packed = packed;
+
+    switch (WireFormatLite::FieldTypeToCppType(
+        static_cast<WireFormatLite::FieldType>(field_type))) {
+      case WireFormatLite::CPPTYPE_INT32:
+        extension->repeated_int32_value =
+            Arena::CreateMessage<RepeatedField<int32> >(arena_);
+        break;
+      case WireFormatLite::CPPTYPE_INT64:
+        extension->repeated_int64_value =
+            Arena::CreateMessage<RepeatedField<int64> >(arena_);
+        break;
+      case WireFormatLite::CPPTYPE_UINT32:
+        extension->repeated_uint32_value =
+            Arena::CreateMessage<RepeatedField<uint32> >(arena_);
+        break;
+      case WireFormatLite::CPPTYPE_UINT64:
+        extension->repeated_uint64_value =
+            Arena::CreateMessage<RepeatedField<uint64> >(arena_);
+        break;
+      case WireFormatLite::CPPTYPE_DOUBLE:
+        extension->repeated_double_value =
+            Arena::CreateMessage<RepeatedField<double> >(arena_);
+        break;
+      case WireFormatLite::CPPTYPE_FLOAT:
+        extension->repeated_float_value =
+            Arena::CreateMessage<RepeatedField<float> >(arena_);
+        break;
+      case WireFormatLite::CPPTYPE_BOOL:
+        extension->repeated_bool_value =
+            Arena::CreateMessage<RepeatedField<bool> >(arena_);
+        break;
+      case WireFormatLite::CPPTYPE_ENUM:
+        extension->repeated_enum_value =
+            Arena::CreateMessage<RepeatedField<int> >(arena_);
+        break;
+      case WireFormatLite::CPPTYPE_STRING:
+        extension->repeated_string_value =
+            Arena::CreateMessage<RepeatedPtrField< ::std::string> >(arena_);
+        break;
+      case WireFormatLite::CPPTYPE_MESSAGE:
+        extension->repeated_message_value =
+            Arena::CreateMessage<RepeatedPtrField<MessageLite> >(arena_);
+        break;
+    }
+  }
+
+  // We assume that all the RepeatedField<>* pointers have the same
+  // size and alignment within the anonymous union in Extension.
+  return extension->repeated_int32_value;
+}
+
+// Compatible version using old call signature. Does not create extensions when
+// the don't already exist; instead, just GOOGLE_CHECK-fails.
 void* ExtensionSet::MutableRawRepeatedField(int number) {
+  map<int, Extension>::iterator iter = extensions_.find(number);
+  GOOGLE_CHECK(iter == extensions_.end()) << "Extension not found.";
   // We assume that all the RepeatedField<>* pointers have the same
   // size and alignment within the anonymous union in Extension.
-  map<int, Extension>::const_iterator iter = extensions_.find(number);
-  GOOGLE_CHECK(iter != extensions_.end()) << "no extension numbered " << number;
   return iter->second.repeated_int32_value;
 }
 
+
 // -------------------------------------------------------------------
 // Enums
 
@@ -363,7 +468,8 @@ void ExtensionSet::AddEnum(int number, FieldType type,
     GOOGLE_DCHECK_EQ(cpp_type(extension->type), WireFormatLite::CPPTYPE_ENUM);
     extension->is_repeated = true;
     extension->is_packed = packed;
-    extension->repeated_enum_value = new RepeatedField<int>();
+    extension->repeated_enum_value =
+        Arena::CreateMessage<RepeatedField<int> >(arena_);
   } else {
     GOOGLE_DCHECK_TYPE(*extension, REPEATED, ENUM);
     GOOGLE_DCHECK_EQ(extension->is_packed, packed);
@@ -393,7 +499,7 @@ string* ExtensionSet::MutableString(int number, FieldType type,
     extension->type = type;
     GOOGLE_DCHECK_EQ(cpp_type(extension->type), WireFormatLite::CPPTYPE_STRING);
     extension->is_repeated = false;
-    extension->string_value = new string;
+    extension->string_value = Arena::Create<string>(arena_);
   } else {
     GOOGLE_DCHECK_TYPE(*extension, OPTIONAL, STRING);
   }
@@ -423,7 +529,8 @@ string* ExtensionSet::AddString(int number, FieldType type,
     GOOGLE_DCHECK_EQ(cpp_type(extension->type), WireFormatLite::CPPTYPE_STRING);
     extension->is_repeated = true;
     extension->is_packed = false;
-    extension->repeated_string_value = new RepeatedPtrField<string>();
+    extension->repeated_string_value =
+        Arena::CreateMessage<RepeatedPtrField<string> >(arena_);
   } else {
     GOOGLE_DCHECK_TYPE(*extension, REPEATED, STRING);
   }
@@ -463,7 +570,7 @@ MessageLite* ExtensionSet::MutableMessage(int number, FieldType type,
     GOOGLE_DCHECK_EQ(cpp_type(extension->type), WireFormatLite::CPPTYPE_MESSAGE);
     extension->is_repeated = false;
     extension->is_lazy = false;
-    extension->message_value = prototype.New();
+    extension->message_value = prototype.New(arena_);
     extension->is_cleared = false;
     return extension->message_value;
   } else {
@@ -495,19 +602,66 @@ void ExtensionSet::SetAllocatedMessage(int number, FieldType type,
     GOOGLE_DCHECK_EQ(cpp_type(extension->type), WireFormatLite::CPPTYPE_MESSAGE);
     extension->is_repeated = false;
     extension->is_lazy = false;
-    extension->message_value = message;
+    if (message->GetArena() == arena_) {
+      extension->message_value = message;
+    } else {
+      extension->message_value = message->New(arena_);
+      extension->message_value->CheckTypeAndMergeFrom(*message);
+      if (message->GetArena() == NULL) {
+        delete message;
+      }
+    }
   } else {
     GOOGLE_DCHECK_TYPE(*extension, OPTIONAL, MESSAGE);
     if (extension->is_lazy) {
       extension->lazymessage_value->SetAllocatedMessage(message);
     } else {
-      delete extension->message_value;
+      if (arena_ == NULL) {
+        delete extension->message_value;
+      }
+      if (message->GetArena() == arena_) {
+        extension->message_value = message;
+      } else {
+        extension->message_value = message->New(arena_);
+        extension->message_value->CheckTypeAndMergeFrom(*message);
+        if (message->GetArena() == NULL) {
+          delete message;
+        }
+      }
+    }
+  }
+  extension->is_cleared = false;
+}
+
+void ExtensionSet::UnsafeArenaSetAllocatedMessage(
+    int number, FieldType type, const FieldDescriptor* descriptor,
+    MessageLite* message) {
+  if (message == NULL) {
+    ClearExtension(number);
+    return;
+  }
+  Extension* extension;
+  if (MaybeNewExtension(number, descriptor, &extension)) {
+    extension->type = type;
+    GOOGLE_DCHECK_EQ(cpp_type(extension->type), WireFormatLite::CPPTYPE_MESSAGE);
+    extension->is_repeated = false;
+    extension->is_lazy = false;
+    extension->message_value = message;
+  } else {
+    GOOGLE_DCHECK_TYPE(*extension, OPTIONAL, MESSAGE);
+    if (extension->is_lazy) {
+      extension->lazymessage_value->UnsafeArenaSetAllocatedMessage(message);
+    } else {
+      if (arena_ == NULL) {
+        delete extension->message_value;
+      }
       extension->message_value = message;
     }
   }
   extension->is_cleared = false;
 }
 
+
 MessageLite* ExtensionSet::ReleaseMessage(int number,
                                           const MessageLite& prototype) {
   map<int, Extension>::iterator iter = extensions_.find(number);
@@ -519,7 +673,39 @@ MessageLite* ExtensionSet::ReleaseMessage(int number,
     MessageLite* ret = NULL;
     if (iter->second.is_lazy) {
       ret = iter->second.lazymessage_value->ReleaseMessage(prototype);
-      delete iter->second.lazymessage_value;
+      if (arena_ == NULL) {
+        delete iter->second.lazymessage_value;
+      }
+    } else {
+      if (arena_ == NULL) {
+        ret = iter->second.message_value;
+      } else {
+        // ReleaseMessage() always returns a heap-allocated message, and we are
+        // on an arena, so we need to make a copy of this message to return.
+        ret = (iter->second.message_value)->New();
+        ret->CheckTypeAndMergeFrom(*iter->second.message_value);
+      }
+    }
+    extensions_.erase(number);
+    return ret;
+  }
+}
+
+MessageLite* ExtensionSet::UnsafeArenaReleaseMessage(
+    int number, const MessageLite& prototype) {
+  map<int, Extension>::iterator iter = extensions_.find(number);
+  if (iter == extensions_.end()) {
+    // Not present.  Return NULL.
+    return NULL;
+  } else {
+    GOOGLE_DCHECK_TYPE(iter->second, OPTIONAL, MESSAGE);
+    MessageLite* ret = NULL;
+    if (iter->second.is_lazy) {
+      ret =
+        iter->second.lazymessage_value->UnsafeArenaReleaseMessage(prototype);
+      if (arena_ == NULL) {
+        delete iter->second.lazymessage_value;
+      }
     } else {
       ret = iter->second.message_value;
     }
@@ -556,7 +742,7 @@ MessageLite* ExtensionSet::AddMessage(int number, FieldType type,
     GOOGLE_DCHECK_EQ(cpp_type(extension->type), WireFormatLite::CPPTYPE_MESSAGE);
     extension->is_repeated = true;
     extension->repeated_message_value =
-      new RepeatedPtrField<MessageLite>();
+        Arena::CreateMessage<RepeatedPtrField<MessageLite> >(arena_);
   } else {
     GOOGLE_DCHECK_TYPE(*extension, REPEATED, MESSAGE);
   }
@@ -566,7 +752,7 @@ MessageLite* ExtensionSet::AddMessage(int number, FieldType type,
   MessageLite* result = extension->repeated_message_value
       ->AddFromCleared<GenericTypeHandler<MessageLite> >();
   if (result == NULL) {
-    result = prototype.New();
+    result = prototype.New(arena_);
     extension->repeated_message_value->AddAllocated(result);
   }
   return result;
@@ -684,138 +870,142 @@ void ExtensionSet::MergeFrom(const ExtensionSet& other) {
   for (map<int, Extension>::const_iterator iter = other.extensions_.begin();
        iter != other.extensions_.end(); ++iter) {
     const Extension& other_extension = iter->second;
+    InternalExtensionMergeFrom(iter->first, other_extension);
+  }
+}
 
-    if (other_extension.is_repeated) {
-      Extension* extension;
-      bool is_new = MaybeNewExtension(iter->first, other_extension.descriptor,
-                                      &extension);
-      if (is_new) {
-        // Extension did not already exist in set.
-        extension->type = other_extension.type;
-        extension->is_packed = other_extension.is_packed;
-        extension->is_repeated = true;
-      } else {
-        GOOGLE_DCHECK_EQ(extension->type, other_extension.type);
-        GOOGLE_DCHECK_EQ(extension->is_packed, other_extension.is_packed);
-        GOOGLE_DCHECK(extension->is_repeated);
-      }
+void ExtensionSet::InternalExtensionMergeFrom(
+  int number, const Extension& other_extension) {
+  if (other_extension.is_repeated) {
+    Extension* extension;
+    bool is_new = MaybeNewExtension(number, other_extension.descriptor,
+                                    &extension);
+    if (is_new) {
+      // Extension did not already exist in set.
+      extension->type = other_extension.type;
+      extension->is_packed = other_extension.is_packed;
+      extension->is_repeated = true;
+    } else {
+      GOOGLE_DCHECK_EQ(extension->type, other_extension.type);
+      GOOGLE_DCHECK_EQ(extension->is_packed, other_extension.is_packed);
+      GOOGLE_DCHECK(extension->is_repeated);
+    }
 
-      switch (cpp_type(other_extension.type)) {
-#define HANDLE_TYPE(UPPERCASE, LOWERCASE, REPEATED_TYPE)             \
-        case WireFormatLite::CPPTYPE_##UPPERCASE:                    \
-          if (is_new) {                                              \
-            extension->repeated_##LOWERCASE##_value =                \
-              new REPEATED_TYPE;                                     \
-          }                                                          \
-          extension->repeated_##LOWERCASE##_value->MergeFrom(        \
-            *other_extension.repeated_##LOWERCASE##_value);          \
-          break;
+    switch (cpp_type(other_extension.type)) {
+#define HANDLE_TYPE(UPPERCASE, LOWERCASE, REPEATED_TYPE)                    \
+      case WireFormatLite::CPPTYPE_##UPPERCASE:                             \
+        if (is_new) {                                                       \
+          extension->repeated_##LOWERCASE##_value =                         \
+            Arena::CreateMessage<REPEATED_TYPE >(arena_);                   \
+        }                                                                   \
+        extension->repeated_##LOWERCASE##_value->MergeFrom(                 \
+          *other_extension.repeated_##LOWERCASE##_value);                   \
+        break;
 
-        HANDLE_TYPE(  INT32,   int32, RepeatedField   <  int32>);
-        HANDLE_TYPE(  INT64,   int64, RepeatedField   <  int64>);
-        HANDLE_TYPE( UINT32,  uint32, RepeatedField   < uint32>);
-        HANDLE_TYPE( UINT64,  uint64, RepeatedField   < uint64>);
-        HANDLE_TYPE(  FLOAT,   float, RepeatedField   <  float>);
-        HANDLE_TYPE( DOUBLE,  double, RepeatedField   < double>);
-        HANDLE_TYPE(   BOOL,    bool, RepeatedField   <   bool>);
-        HANDLE_TYPE(   ENUM,    enum, RepeatedField   <    int>);
-        HANDLE_TYPE( STRING,  string, RepeatedPtrField< string>);
+      HANDLE_TYPE(  INT32,   int32, RepeatedField   <  int32>);
+      HANDLE_TYPE(  INT64,   int64, RepeatedField   <  int64>);
+      HANDLE_TYPE( UINT32,  uint32, RepeatedField   < uint32>);
+      HANDLE_TYPE( UINT64,  uint64, RepeatedField   < uint64>);
+      HANDLE_TYPE(  FLOAT,   float, RepeatedField   <  float>);
+      HANDLE_TYPE( DOUBLE,  double, RepeatedField   < double>);
+      HANDLE_TYPE(   BOOL,    bool, RepeatedField   <   bool>);
+      HANDLE_TYPE(   ENUM,    enum, RepeatedField   <    int>);
+      HANDLE_TYPE( STRING,  string, RepeatedPtrField< string>);
 #undef HANDLE_TYPE
 
-        case WireFormatLite::CPPTYPE_MESSAGE:
-          if (is_new) {
-            extension->repeated_message_value =
-              new RepeatedPtrField<MessageLite>();
-          }
-          // We can't call RepeatedPtrField<MessageLite>::MergeFrom() because
-          // it would attempt to allocate new objects.
-          RepeatedPtrField<MessageLite>* other_repeated_message =
-              other_extension.repeated_message_value;
-          for (int i = 0; i < other_repeated_message->size(); i++) {
-            const MessageLite& other_message = other_repeated_message->Get(i);
-            MessageLite* target = extension->repeated_message_value
-                     ->AddFromCleared<GenericTypeHandler<MessageLite> >();
-            if (target == NULL) {
-              target = other_message.New();
-              extension->repeated_message_value->AddAllocated(target);
-            }
-            target->CheckTypeAndMergeFrom(other_message);
+      case WireFormatLite::CPPTYPE_MESSAGE:
+        if (is_new) {
+          extension->repeated_message_value =
+              Arena::CreateMessage<RepeatedPtrField<MessageLite> >(arena_);
+        }
+        // We can't call RepeatedPtrField<MessageLite>::MergeFrom() because
+        // it would attempt to allocate new objects.
+        RepeatedPtrField<MessageLite>* other_repeated_message =
+            other_extension.repeated_message_value;
+        for (int i = 0; i < other_repeated_message->size(); i++) {
+          const MessageLite& other_message = other_repeated_message->Get(i);
+          MessageLite* target = extension->repeated_message_value
+                   ->AddFromCleared<GenericTypeHandler<MessageLite> >();
+          if (target == NULL) {
+            target = other_message.New(arena_);
+            extension->repeated_message_value->AddAllocated(target);
           }
+          target->CheckTypeAndMergeFrom(other_message);
+        }
+        break;
+    }
+  } else {
+    if (!other_extension.is_cleared) {
+      switch (cpp_type(other_extension.type)) {
+#define HANDLE_TYPE(UPPERCASE, LOWERCASE, CAMELCASE)                       \
+        case WireFormatLite::CPPTYPE_##UPPERCASE:                          \
+          Set##CAMELCASE(number, other_extension.type,                     \
+                         other_extension.LOWERCASE##_value,                \
+                         other_extension.descriptor);                      \
           break;
-      }
-    } else {
-      if (!other_extension.is_cleared) {
-        switch (cpp_type(other_extension.type)) {
-#define HANDLE_TYPE(UPPERCASE, LOWERCASE, CAMELCASE)                         \
-          case WireFormatLite::CPPTYPE_##UPPERCASE:                          \
-            Set##CAMELCASE(iter->first, other_extension.type,                \
-                           other_extension.LOWERCASE##_value,                \
-                           other_extension.descriptor);                      \
-            break;
-
-          HANDLE_TYPE( INT32,  int32,  Int32);
-          HANDLE_TYPE( INT64,  int64,  Int64);
-          HANDLE_TYPE(UINT32, uint32, UInt32);
-          HANDLE_TYPE(UINT64, uint64, UInt64);
-          HANDLE_TYPE( FLOAT,  float,  Float);
-          HANDLE_TYPE(DOUBLE, double, Double);
-          HANDLE_TYPE(  BOOL,   bool,   Bool);
-          HANDLE_TYPE(  ENUM,   enum,   Enum);
+
+        HANDLE_TYPE( INT32,  int32,  Int32);
+        HANDLE_TYPE( INT64,  int64,  Int64);
+        HANDLE_TYPE(UINT32, uint32, UInt32);
+        HANDLE_TYPE(UINT64, uint64, UInt64);
+        HANDLE_TYPE( FLOAT,  float,  Float);
+        HANDLE_TYPE(DOUBLE, double, Double);
+        HANDLE_TYPE(  BOOL,   bool,   Bool);
+        HANDLE_TYPE(  ENUM,   enum,   Enum);
 #undef HANDLE_TYPE
-          case WireFormatLite::CPPTYPE_STRING:
-            SetString(iter->first, other_extension.type,
-                      *other_extension.string_value,
-                      other_extension.descriptor);
-            break;
-          case WireFormatLite::CPPTYPE_MESSAGE: {
-            Extension* extension;
-            bool is_new = MaybeNewExtension(iter->first,
-                                            other_extension.descriptor,
-                                            &extension);
-            if (is_new) {
-              extension->type = other_extension.type;
-              extension->is_packed = other_extension.is_packed;
-              extension->is_repeated = false;
-              if (other_extension.is_lazy) {
-                extension->is_lazy = true;
-                extension->lazymessage_value =
-                    other_extension.lazymessage_value->New();
+        case WireFormatLite::CPPTYPE_STRING:
+          SetString(number, other_extension.type,
+                    *other_extension.string_value,
+                    other_extension.descriptor);
+          break;
+        case WireFormatLite::CPPTYPE_MESSAGE: {
+          Extension* extension;
+          bool is_new = MaybeNewExtension(number,
+                                          other_extension.descriptor,
+                                          &extension);
+          if (is_new) {
+            extension->type = other_extension.type;
+            extension->is_packed = other_extension.is_packed;
+            extension->is_repeated = false;
+            if (other_extension.is_lazy) {
+              extension->is_lazy = true;
+              extension->lazymessage_value =
+                  other_extension.lazymessage_value->New(arena_);
+              extension->lazymessage_value->MergeFrom(
+                  *other_extension.lazymessage_value);
+            } else {
+              extension->is_lazy = false;
+              extension->message_value =
+                  other_extension.message_value->New(arena_);
+              extension->message_value->CheckTypeAndMergeFrom(
+                  *other_extension.message_value);
+            }
+          } else {
+            GOOGLE_DCHECK_EQ(extension->type, other_extension.type);
+            GOOGLE_DCHECK_EQ(extension->is_packed,other_extension.is_packed);
+            GOOGLE_DCHECK(!extension->is_repeated);
+            if (other_extension.is_lazy) {
+              if (extension->is_lazy) {
                 extension->lazymessage_value->MergeFrom(
                     *other_extension.lazymessage_value);
               } else {
-                extension->is_lazy = false;
-                extension->message_value =
-                    other_extension.message_value->New();
                 extension->message_value->CheckTypeAndMergeFrom(
-                    *other_extension.message_value);
+                    other_extension.lazymessage_value->GetMessage(
+                        *extension->message_value));
               }
             } else {
-              GOOGLE_DCHECK_EQ(extension->type, other_extension.type);
-              GOOGLE_DCHECK_EQ(extension->is_packed,other_extension.is_packed);
-              GOOGLE_DCHECK(!extension->is_repeated);
-              if (other_extension.is_lazy) {
-                if (extension->is_lazy) {
-                  extension->lazymessage_value->MergeFrom(
-                      *other_extension.lazymessage_value);
-                } else {
-                  extension->message_value->CheckTypeAndMergeFrom(
-                      other_extension.lazymessage_value->GetMessage(
-                          *extension->message_value));
-                }
+              if (extension->is_lazy) {
+                extension->lazymessage_value->MutableMessage(
+                    *other_extension.message_value)->CheckTypeAndMergeFrom(
+                        *other_extension.message_value);
               } else {
-                if (extension->is_lazy) {
-                  extension->lazymessage_value->MutableMessage(
-                      *other_extension.message_value)->CheckTypeAndMergeFrom(
-                          *other_extension.message_value);
-                } else {
-                  extension->message_value->CheckTypeAndMergeFrom(
-                      *other_extension.message_value);
-                }
+                extension->message_value->CheckTypeAndMergeFrom(
+                    *other_extension.message_value);
               }
             }
-            extension->is_cleared = false;
-            break;
           }
+          extension->is_cleared = false;
+          break;
         }
       }
     }
@@ -823,7 +1013,73 @@ void ExtensionSet::MergeFrom(const ExtensionSet& other) {
 }
 
 void ExtensionSet::Swap(ExtensionSet* x) {
-  extensions_.swap(x->extensions_);
+  if (GetArenaNoVirtual() == x->GetArenaNoVirtual()) {
+    extensions_.swap(x->extensions_);
+  } else {
+    // TODO(cfallin, rohananil): We maybe able to optimize a case where we are
+    // swapping from heap to arena-allocated extension set, by just Own()'ing
+    // the extensions.
+    ExtensionSet extension_set;
+    extension_set.MergeFrom(*x);
+    x->Clear();
+    x->MergeFrom(*this);
+    Clear();
+    MergeFrom(extension_set);
+  }
+}
+
+void ExtensionSet::SwapExtension(ExtensionSet* other,
+                                 int number) {
+  if (this == other) return;
+  map<int, Extension>::iterator this_iter = extensions_.find(number);
+  map<int, Extension>::iterator other_iter = other->extensions_.find(number);
+
+  if (this_iter == extensions_.end() &&
+      other_iter == other->extensions_.end()) {
+    return;
+  }
+
+  if (this_iter != extensions_.end() &&
+      other_iter != other->extensions_.end()) {
+    if (GetArenaNoVirtual() == other->GetArenaNoVirtual()) {
+      using std::swap;
+      swap(this_iter->second, other_iter->second);
+    } else {
+      // TODO(cfallin, rohananil): We could further optimize these cases,
+      // especially avoid creation of ExtensionSet, and move MergeFrom logic
+      // into Extensions itself (which takes arena as an argument).
+      // We do it this way to reuse the copy-across-arenas logic already
+      // implemented in ExtensionSet's MergeFrom.
+      ExtensionSet temp;
+      temp.InternalExtensionMergeFrom(number, other_iter->second);
+      map<int, Extension>::iterator temp_iter = temp.extensions_.find(number);
+      other_iter->second.Clear();
+      other->InternalExtensionMergeFrom(number, this_iter->second);
+      this_iter->second.Clear();
+      InternalExtensionMergeFrom(number, temp_iter->second);
+    }
+    return;
+  }
+
+  if (this_iter == extensions_.end()) {
+    if (GetArenaNoVirtual() == other->GetArenaNoVirtual()) {
+      extensions_.insert(std::make_pair(number, other_iter->second));
+    } else {
+      InternalExtensionMergeFrom(number, other_iter->second);
+    }
+    other->extensions_.erase(number);
+    return;
+  }
+
+  if (other_iter == other->extensions_.end()) {
+    if (GetArenaNoVirtual() == other->GetArenaNoVirtual()) {
+      other->extensions_.insert(std::make_pair(number, this_iter->second));
+    } else {
+      other->InternalExtensionMergeFrom(number, this_iter->second);
+    }
+    extensions_.erase(number);
+    return;
+  }
 }
 
 bool ExtensionSet::IsInitialized() const {
@@ -855,41 +1111,59 @@ bool ExtensionSet::IsInitialized() const {
 }
 
 bool ExtensionSet::FindExtensionInfoFromTag(
-    uint32 tag, ExtensionFinder* extension_finder,
-    int* field_number, ExtensionInfo* extension) {
+    uint32 tag, ExtensionFinder* extension_finder, int* field_number,
+    ExtensionInfo* extension, bool* was_packed_on_wire) {
   *field_number = WireFormatLite::GetTagFieldNumber(tag);
   WireFormatLite::WireType wire_type = WireFormatLite::GetTagWireType(tag);
+  return FindExtensionInfoFromFieldNumber(wire_type, *field_number,
+                                          extension_finder, extension,
+                                          was_packed_on_wire);
+}
 
-  bool is_unknown;
-  if (!extension_finder->Find(*field_number, extension)) {
-    is_unknown = true;
-  } else if (extension->is_packed) {
-    is_unknown = (wire_type != WireFormatLite::WIRETYPE_LENGTH_DELIMITED);
-  } else {
-    WireFormatLite::WireType expected_wire_type =
-        WireFormatLite::WireTypeForFieldType(real_type(extension->type));
-    is_unknown = (wire_type != expected_wire_type);
+bool ExtensionSet::FindExtensionInfoFromFieldNumber(
+    int wire_type, int field_number, ExtensionFinder* extension_finder,
+    ExtensionInfo* extension, bool* was_packed_on_wire) {
+  if (!extension_finder->Find(field_number, extension)) {
+    return false;
   }
-  return !is_unknown;
+
+  WireFormatLite::WireType expected_wire_type =
+      WireFormatLite::WireTypeForFieldType(real_type(extension->type));
+
+  // Check if this is a packed field.
+  *was_packed_on_wire = false;
+  if (extension->is_repeated &&
+      wire_type == WireFormatLite::WIRETYPE_LENGTH_DELIMITED &&
+      is_packable(expected_wire_type)) {
+    *was_packed_on_wire = true;
+    return true;
+  }
+  // Otherwise the wire type must match.
+  return expected_wire_type == wire_type;
 }
 
 bool ExtensionSet::ParseField(uint32 tag, io::CodedInputStream* input,
                               ExtensionFinder* extension_finder,
                               FieldSkipper* field_skipper) {
   int number;
+  bool was_packed_on_wire;
   ExtensionInfo extension;
-  if (!FindExtensionInfoFromTag(tag, extension_finder, &number, &extension)) {
+  if (!FindExtensionInfoFromTag(
+      tag, extension_finder, &number, &extension, &was_packed_on_wire)) {
     return field_skipper->SkipField(input, tag);
   } else {
-    return ParseFieldWithExtensionInfo(number, extension, input, field_skipper);
+    return ParseFieldWithExtensionInfo(
+        number, was_packed_on_wire, extension, input, field_skipper);
   }
 }
 
 bool ExtensionSet::ParseFieldWithExtensionInfo(
-    int number, const ExtensionInfo& extension,
+    int number, bool was_packed_on_wire, const ExtensionInfo& extension,
     io::CodedInputStream* input,
     FieldSkipper* field_skipper) {
-  if (extension.is_packed) {
+  // Explicitly not read extension.is_packed, instead check whether the field
+  // was encoded in packed form on the wire.
+  if (was_packed_on_wire) {
     uint32 size;
     if (!input->ReadVarint32(&size)) return false;
     io::CodedInputStream::Limit limit = input->PushLimit(size);
@@ -903,7 +1177,8 @@ bool ExtensionSet::ParseFieldWithExtensionInfo(
                   CPP_LOWERCASE, WireFormatLite::TYPE_##UPPERCASE>(            \
                 input, &value)) return false;                                  \
           Add##CPP_CAMELCASE(number, WireFormatLite::TYPE_##UPPERCASE,         \
-                             true, value, extension.descriptor);               \
+                             extension.is_packed, value,                       \
+                             extension.descriptor);                            \
         }                                                                      \
         break
 
@@ -929,8 +1204,11 @@ bool ExtensionSet::ParseFieldWithExtensionInfo(
                   input, &value)) return false;
           if (extension.enum_validity_check.func(
                   extension.enum_validity_check.arg, value)) {
-            AddEnum(number, WireFormatLite::TYPE_ENUM, true, value,
-                    extension.descriptor);
+            AddEnum(number, WireFormatLite::TYPE_ENUM, extension.is_packed,
+                    value, extension.descriptor);
+          } else {
+            // Invalid value.  Treat as unknown.
+            field_skipper->SkipUnknownEnum(number, value);
           }
         }
         break;
@@ -952,9 +1230,10 @@ bool ExtensionSet::ParseFieldWithExtensionInfo(
         if (!WireFormatLite::ReadPrimitive<                                    \
                 CPP_LOWERCASE, WireFormatLite::TYPE_##UPPERCASE>(              \
                input, &value)) return false;                                   \
-        if (extension.is_repeated) {                                          \
+        if (extension.is_repeated) {                                           \
           Add##CPP_CAMELCASE(number, WireFormatLite::TYPE_##UPPERCASE,         \
-                             false, value, extension.descriptor);              \
+                             extension.is_packed, value,                       \
+                             extension.descriptor);                            \
         } else {                                                               \
           Set##CPP_CAMELCASE(number, WireFormatLite::TYPE_##UPPERCASE, value,  \
                              extension.descriptor);                            \
@@ -986,7 +1265,7 @@ bool ExtensionSet::ParseFieldWithExtensionInfo(
           // Invalid value.  Treat as unknown.
           field_skipper->SkipUnknownEnum(number, value);
         } else if (extension.is_repeated) {
-          AddEnum(number, WireFormatLite::TYPE_ENUM, false, value,
+          AddEnum(number, WireFormatLite::TYPE_ENUM, extension.is_packed, value,
                   extension.descriptor);
         } else {
           SetEnum(number, WireFormatLite::TYPE_ENUM, value,
@@ -1039,6 +1318,12 @@ bool ExtensionSet::ParseFieldWithExtensionInfo(
 }
 
 bool ExtensionSet::ParseField(uint32 tag, io::CodedInputStream* input,
+                              const MessageLite* containing_type) {
+  return ParseField(tag, input, containing_type,
+                    static_cast<UnknownFieldSet*>(NULL));
+}
+
+bool ExtensionSet::ParseField(uint32 tag, io::CodedInputStream* input,
                               const MessageLite* containing_type,
                               UnknownFieldSet* unknown_fields) {
   FieldSkipper skipper(unknown_fields);
@@ -1046,16 +1331,147 @@ bool ExtensionSet::ParseField(uint32 tag, io::CodedInputStream* input,
   return ParseField(tag, input, &finder, &skipper);
 }
 
+bool ExtensionSet::ParseField(uint32 tag, io::CodedInputStream* input,
+                              const MessageLite* containing_type,
+                              io::CodedOutputStream* unknown_fields) {
+  CodedOutputStreamFieldSkipper skipper(unknown_fields);
+  GeneratedExtensionFinder finder(containing_type);
+  return ParseField(tag, input, &finder, &skipper);
+}
+
 // Defined in extension_set_heavy.cc.
 // bool ExtensionSet::ParseFieldHeavy(uint32 tag, io::CodedInputStream* input,
 //                                    const Message* containing_type,
 //                                    UnknownFieldSet* unknown_fields)
 
+bool ExtensionSet::ParseMessageSet(io::CodedInputStream* input,
+                                   ExtensionFinder* extension_finder,
+                                   FieldSkipper* field_skipper) {
+  while (true) {
+    const uint32 tag = input->ReadTag();
+    switch (tag) {
+      case 0:
+        return true;
+      case WireFormatLite::kMessageSetItemStartTag:
+        if (!ParseMessageSetItem(input, extension_finder, field_skipper)) {
+          return false;
+        }
+        break;
+      default:
+        if (!ParseField(tag, input, extension_finder, field_skipper)) {
+          return false;
+        }
+        break;
+    }
+  }
+}
+
+bool ExtensionSet::ParseMessageSet(io::CodedInputStream* input,
+                                   const MessageLite* containing_type) {
+  return ParseMessageSet(input, containing_type,
+                         static_cast<UnknownFieldSet*>(NULL));
+}
+
+bool ExtensionSet::ParseMessageSet(io::CodedInputStream* input,
+                                   const MessageLite* containing_type,
+                                   UnknownFieldSet* unknown_fields) {
+  FieldSkipper skipper(unknown_fields);
+  GeneratedExtensionFinder finder(containing_type);
+  return ParseMessageSet(input, &finder, &skipper);
+}
+
 // Defined in extension_set_heavy.cc.
 // bool ExtensionSet::ParseMessageSetHeavy(io::CodedInputStream* input,
 //                                         const Message* containing_type,
 //                                         UnknownFieldSet* unknown_fields);
 
+bool ExtensionSet::ParseFieldMaybeLazily(
+    int wire_type, int field_number, io::CodedInputStream* input,
+    ExtensionFinder* extension_finder,
+    FieldSkipper* field_skipper) {
+  return ParseField(WireFormatLite::MakeTag(
+      field_number, static_cast<WireFormatLite::WireType>(wire_type)),
+                    input, extension_finder, field_skipper);
+}
+
+bool ExtensionSet::ParseMessageSetItem(io::CodedInputStream* input,
+                                       ExtensionFinder* extension_finder,
+                                       FieldSkipper* field_skipper) {
+  // TODO(kenton):  It would be nice to share code between this and
+  // WireFormatLite::ParseAndMergeMessageSetItem(), but I think the
+  // differences would be hard to factor out.
+
+  // This method parses a group which should contain two fields:
+  //   required int32 type_id = 2;
+  //   required data message = 3;
+
+  uint32 last_type_id = 0;
+
+  // If we see message data before the type_id, we'll append it to this so
+  // we can parse it later.
+  string message_data;
+
+  while (true) {
+    const uint32 tag = input->ReadTag();
+    if (tag == 0) return false;
+
+    switch (tag) {
+      case WireFormatLite::kMessageSetTypeIdTag: {
+        uint32 type_id;
+        if (!input->ReadVarint32(&type_id)) return false;
+        last_type_id = type_id;
+
+        if (!message_data.empty()) {
+          // We saw some message data before the type_id.  Have to parse it
+          // now.
+          io::CodedInputStream sub_input(
+              reinterpret_cast<const uint8*>(message_data.data()),
+              message_data.size());
+          if (!ParseFieldMaybeLazily(WireFormatLite::WIRETYPE_LENGTH_DELIMITED,
+                                     last_type_id, &sub_input,
+                                     extension_finder, field_skipper)) {
+            return false;
+          }
+          message_data.clear();
+        }
+
+        break;
+      }
+
+      case WireFormatLite::kMessageSetMessageTag: {
+        if (last_type_id == 0) {
+          // We haven't seen a type_id yet.  Append this data to message_data.
+          string temp;
+          uint32 length;
+          if (!input->ReadVarint32(&length)) return false;
+          if (!input->ReadString(&temp, length)) return false;
+          io::StringOutputStream output_stream(&message_data);
+          io::CodedOutputStream coded_output(&output_stream);
+          coded_output.WriteVarint32(length);
+          coded_output.WriteString(temp);
+        } else {
+          // Already saw type_id, so we can parse this directly.
+          if (!ParseFieldMaybeLazily(WireFormatLite::WIRETYPE_LENGTH_DELIMITED,
+                                     last_type_id, input,
+                                     extension_finder, field_skipper)) {
+            return false;
+          }
+        }
+
+        break;
+      }
+
+      case WireFormatLite::kMessageSetItemEndTag: {
+        return true;
+      }
+
+      default: {
+        if (!field_skipper->SkipField(input, tag)) return false;
+      }
+    }
+  }
+}
+
 void ExtensionSet::SerializeWithCachedSizes(
     int start_field_number, int end_field_number,
     io::CodedOutputStream* output) const {
@@ -1085,7 +1501,7 @@ bool ExtensionSet::MaybeNewExtension(int number,
                                      const FieldDescriptor* descriptor,
                                      Extension** result) {
   pair<map<int, Extension>::iterator, bool> insert_result =
-      extensions_.insert(make_pair(number, Extension()));
+      extensions_.insert(std::make_pair(number, Extension()));
   *result = &insert_result.first->second;
   (*result)->descriptor = descriptor;
   return insert_result.second;
@@ -1416,6 +1832,8 @@ int ExtensionSet::Extension::GetSize() const {
   return 0;
 }
 
+// This function deletes all allocated objects. This function should be only
+// called if the Extension was created with an arena.
 void ExtensionSet::Extension::Free() {
   if (is_repeated) {
     switch (cpp_type(type)) {
@@ -1457,6 +1875,69 @@ void ExtensionSet::Extension::Free() {
 // Defined in extension_set_heavy.cc.
 // int ExtensionSet::Extension::SpaceUsedExcludingSelf() const
 
+// ==================================================================
+// Default repeated field instances for iterator-compatible accessors
+
+const RepeatedStringTypeTraits::RepeatedFieldType*
+RepeatedStringTypeTraits::default_repeated_field_ = NULL;
+
+const RepeatedMessageGenericTypeTraits::RepeatedFieldType*
+RepeatedMessageGenericTypeTraits::default_repeated_field_ = NULL;
+
+#define PROTOBUF_DEFINE_DEFAULT_REPEATED(TYPE)                                 \
+    const RepeatedField<TYPE>*                                                 \
+    RepeatedPrimitiveGenericTypeTraits::default_repeated_field_##TYPE##_ = NULL;
+
+PROTOBUF_DEFINE_DEFAULT_REPEATED(int32)
+PROTOBUF_DEFINE_DEFAULT_REPEATED(int64)
+PROTOBUF_DEFINE_DEFAULT_REPEATED(uint32)
+PROTOBUF_DEFINE_DEFAULT_REPEATED(uint64)
+PROTOBUF_DEFINE_DEFAULT_REPEATED(double)
+PROTOBUF_DEFINE_DEFAULT_REPEATED(float)
+PROTOBUF_DEFINE_DEFAULT_REPEATED(bool)
+
+#undef PROTOBUF_DEFINE_DEFAULT_REPEATED
+
+struct StaticDefaultRepeatedFieldsInitializer {
+  StaticDefaultRepeatedFieldsInitializer() {
+    InitializeDefaultRepeatedFields();
+    OnShutdown(&DestroyDefaultRepeatedFields);
+  }
+} static_repeated_fields_initializer;
+
+void InitializeDefaultRepeatedFields() {
+  RepeatedStringTypeTraits::default_repeated_field_ =
+      new RepeatedStringTypeTraits::RepeatedFieldType;
+  RepeatedMessageGenericTypeTraits::default_repeated_field_ =
+      new RepeatedMessageGenericTypeTraits::RepeatedFieldType;
+  RepeatedPrimitiveGenericTypeTraits::default_repeated_field_int32_ =
+      new RepeatedField<int32>;
+  RepeatedPrimitiveGenericTypeTraits::default_repeated_field_int64_ =
+      new RepeatedField<int64>;
+  RepeatedPrimitiveGenericTypeTraits::default_repeated_field_uint32_ =
+      new RepeatedField<uint32>;
+  RepeatedPrimitiveGenericTypeTraits::default_repeated_field_uint64_ =
+      new RepeatedField<uint64>;
+  RepeatedPrimitiveGenericTypeTraits::default_repeated_field_double_ =
+      new RepeatedField<double>;
+  RepeatedPrimitiveGenericTypeTraits::default_repeated_field_float_ =
+      new RepeatedField<float>;
+  RepeatedPrimitiveGenericTypeTraits::default_repeated_field_bool_ =
+      new RepeatedField<bool>;
+}
+
+void DestroyDefaultRepeatedFields() {
+  delete RepeatedStringTypeTraits::default_repeated_field_;
+  delete RepeatedMessageGenericTypeTraits::default_repeated_field_;
+  delete RepeatedPrimitiveGenericTypeTraits::default_repeated_field_int32_;
+  delete RepeatedPrimitiveGenericTypeTraits::default_repeated_field_int64_;
+  delete RepeatedPrimitiveGenericTypeTraits::default_repeated_field_uint32_;
+  delete RepeatedPrimitiveGenericTypeTraits::default_repeated_field_uint64_;
+  delete RepeatedPrimitiveGenericTypeTraits::default_repeated_field_double_;
+  delete RepeatedPrimitiveGenericTypeTraits::default_repeated_field_float_;
+  delete RepeatedPrimitiveGenericTypeTraits::default_repeated_field_bool_;
+}
+
 }  // namespace internal
 }  // namespace protobuf
 }  // namespace google