Down-integrate from internal code base.

15 files changed, 597 insertions, 178 deletions

diff --git a/src/google/protobuf/arena.cc b/src/google/protobuf/arena.cc
index 17b095aa..be0d9e34 100644
--- a/src/google/protobuf/arena.cc
+++ b/src/google/protobuf/arena.cc
@@ -30,6 +30,10 @@
 
 #include <google/protobuf/arena.h>
 
+#ifdef ADDRESS_SANITIZER
+#include <sanitizer/asan_interface.h>
+#endif
+
 namespace google {
 namespace protobuf {
 
@@ -91,6 +95,12 @@ Arena::Block* Arena::NewBlock(void* me, Block* my_last_block, size_t n,
   } else {
     b->owner = me;
   }
+#ifdef ADDRESS_SANITIZER
+  // Poison the rest of the block for ASAN. It was unpoisoned by the underlying
+  // malloc but it's not yet usable until we return it as part of an allocation.
+  ASAN_POISON_MEMORY_REGION(
+      reinterpret_cast<char*>(b) + b->pos, b->size - b->pos);
+#endif
   return b;
 }
 
@@ -152,6 +162,9 @@ void* Arena::AllocateAligned(size_t n) {
 void* Arena::AllocFromBlock(Block* b, size_t n) {
   size_t p = b->pos;
   b->pos = p + n;
+#ifdef ADDRESS_SANITIZER
+  ASAN_UNPOISON_MEMORY_REGION(reinterpret_cast<char*>(b) + p, n);
+#endif
   return reinterpret_cast<char*>(b) + p;
 }
 
diff --git a/src/google/protobuf/arena_unittest.cc b/src/google/protobuf/arena_unittest.cc
index b2281817..76a4274f 100644
--- a/src/google/protobuf/arena_unittest.cc
+++ b/src/google/protobuf/arena_unittest.cc
@@ -144,7 +144,7 @@ TEST(ArenaTest, InitialBlockTooSmall) {
   // Write to the memory we allocated; this should (but is not guaranteed to)
   // trigger a check for heap corruption if the object was allocated from the
   // initially-provided block.
-  memset(p, '\0', 128);
+  memset(p, '\0', 96);
 }
 
 TEST(ArenaTest, Parsing) {
diff --git a/src/google/protobuf/compiler/cpp/cpp_message.cc b/src/google/protobuf/compiler/cpp/cpp_message.cc
index 28ee3a9d..b42f32b8 100644
--- a/src/google/protobuf/compiler/cpp/cpp_message.cc
+++ b/src/google/protobuf/compiler/cpp/cpp_message.cc
@@ -614,7 +614,7 @@ GenerateFieldAccessorDefinitions(io::Printer* printer) {
     vars["classname"] = classname_;
     printer->Print(
       vars,
-      "inline bool $classname$::has_$oneof_name$() {\n"
+      "inline bool $classname$::has_$oneof_name$() const {\n"
       "  return $oneof_name$_case() != $cap_oneof_name$_NOT_SET;\n"
       "}\n"
       "inline void $classname$::clear_has_$oneof_name$() {\n"
@@ -975,7 +975,7 @@ GenerateClassDefinition(io::Printer* printer) {
   // Generate oneof function declarations
   for (int i = 0; i < descriptor_->oneof_decl_count(); i++) {
     printer->Print(
-        "inline bool has_$oneof_name$();\n"
+        "inline bool has_$oneof_name$() const;\n"
         "void clear_$oneof_name$();\n"
         "inline void clear_has_$oneof_name$();\n\n",
         "oneof_name", descriptor_->oneof_decl(i)->name());
diff --git a/src/google/protobuf/compiler/java/java_message.cc b/src/google/protobuf/compiler/java/java_message.cc
index 70f379bc..1171b718 100644
--- a/src/google/protobuf/compiler/java/java_message.cc
+++ b/src/google/protobuf/compiler/java/java_message.cc
@@ -306,31 +306,28 @@ void ImmutableMessageGenerator::Generate(io::Printer* printer) {
         variables["lite"]);
   }
   printer->Indent();
-  // Using builder_type, instead of Builder, prevents the Builder class from
-  // being loaded into PermGen space when the default instance is created.
-  // This optimizes the PermGen space usage for clients that do not modify
-  // messages.
-  printer->Print(
-    "// Use $classname$.newBuilder() to construct.\n"
-    "private $classname$($buildertype$ builder) {\n"
-    "  super(builder);\n"
-    "}\n",
-    "classname", descriptor_->name(),
-    "buildertype", builder_type);
-  printer->Print(
-    "private $classname$() {\n",
-    "classname", descriptor_->name());
-  printer->Indent();
-  for (int i = 0; i < descriptor_->field_count(); i++) {
-    if (!descriptor_->field(i)->containing_oneof()) {
-      field_generators_.get(descriptor_->field(i))
-          .GenerateInitializationCode(printer);
-    }
+  if (HasDescriptorMethods(descriptor_)) {
+    // Using builder_type, instead of Builder, prevents the Builder class from
+    // being loaded into PermGen space when the default instance is created.
+    // This optimizes the PermGen space usage for clients that do not modify
+    // messages.
+    printer->Print(
+      "// Use $classname$.newBuilder() to construct.\n"
+      "private $classname$($buildertype$ builder) {\n"
+      "  super(builder);\n"
+      "}\n",
+      "classname", descriptor_->name(),
+      "buildertype", builder_type);
+    printer->Print(
+      "private $classname$() {\n",
+      "classname", descriptor_->name());
+    printer->Indent();
+    GenerateInitializers(printer);
+    printer->Outdent();
+    printer->Print(
+      "}\n"
+      "\n");
   }
-  printer->Outdent();
-  printer->Print(
-    "}\n"
-    "\n");
 
   if (HasDescriptorMethods(descriptor_)) {
     printer->Print(
@@ -480,10 +477,37 @@ void ImmutableMessageGenerator::Generate(io::Printer* printer) {
     "// @@protoc_insertion_point(class_scope:$full_name$)\n",
     "full_name", descriptor_->full_name());
 
+
   // Carefully initialize the default instance in such a way that it doesn't
   // conflict with other initialization.
-  printer->Print("private static final $classname$ defaultInstance =\n"
-      "    new $classname$();\n"
+  printer->Print(
+    "private static final $classname$ defaultInstance;",
+    "classname", name_resolver_->GetImmutableClassName(descriptor_));
+  if (HasDescriptorMethods(descriptor_)) {
+    printer->Print(
+      "static {\n"
+      "  defaultInstance = new $classname$();\n"
+      "}\n"
+      "\n",
+      "classname", name_resolver_->GetImmutableClassName(descriptor_));
+  } else {
+    // LITE_RUNTIME only has one constructor.
+    printer->Print(
+      "static {\n"
+      "  try {\n"
+      "    defaultInstance = new $classname$(\n"
+      "        com.google.protobuf.Internal\n"
+      "            .EMPTY_CODED_INPUT_STREAM,\n"
+      "        com.google.protobuf.ExtensionRegistryLite\n"
+      "            .getEmptyRegistry());\n"
+      "  } catch (com.google.protobuf.InvalidProtocolBufferException e) {\n"
+      "    throw new ExceptionInInitializerError(e);\n"
+      "  }\n"
+      "}\n"
+      "\n",
+      "classname", descriptor_->name());
+  }
+  printer->Print(
       "public static $classname$ getDefaultInstance() {\n"
       "  return defaultInstance;\n"
       "}\n"
@@ -492,7 +516,7 @@ void ImmutableMessageGenerator::Generate(io::Printer* printer) {
       "  return defaultInstance;\n"
       "}\n"
       "\n",
-      "classname", descriptor_->name());
+      "classname", name_resolver_->GetImmutableClassName(descriptor_));
 
   // Extensions must be declared after the defaultInstance is initialized
   // because the defaultInstance is used by the extension to lazily retrieve
@@ -773,6 +797,7 @@ void ImmutableMessageGenerator::GenerateBuilder(io::Printer* printer) {
 
   if (HasGeneratedMethods(descriptor_)) {
     GenerateIsInitialized(printer, DONT_MEMOIZE);
+    GenerateBuilderParsingMethods(printer);
   }
 
   // oneof
@@ -1034,10 +1059,33 @@ GenerateCommonBuilderMethods(io::Printer* printer) {
       "classname", name_resolver_->GetImmutableClassName(descriptor_));
   }
 
-  printer->Print(
-    "public $classname$ buildPartial() {\n"
-    "  $classname$ result = new $classname$(this);\n",
-    "classname", name_resolver_->GetImmutableClassName(descriptor_));
+  if (HasDescriptorMethods(descriptor_)) {
+    printer->Print(
+        "public $classname$ buildPartial() {\n"
+            "  $classname$ result = new $classname$(this);\n",
+         "classname", name_resolver_->GetImmutableClassName(descriptor_));
+  } else {
+    // LITE_RUNTIME only provides a single message constructor.
+    printer->Print(
+        "public $classname$ buildPartial() {\n"
+        "  $classname$ result = null;\n"
+        "  try {\n"
+        "    result = new $classname$(\n"
+        "        com.google.protobuf.Internal\n"
+        "            .EMPTY_CODED_INPUT_STREAM,\n"
+        "        com.google.protobuf.ExtensionRegistryLite\n"
+        "            .getEmptyRegistry());\n"
+        "  } catch (com.google.protobuf.InvalidProtocolBufferException e) {\n"
+        "    throw new RuntimeException(e);\n"
+        "  }\n"
+        "  result.unknownFields = this.unknownFields;\n",
+        "classname", name_resolver_->GetImmutableClassName(descriptor_));
+
+    if (descriptor_->extension_range_count() > 0) {
+      printer->Print(
+        "  result.extensions = this.buildExtensions();\n");
+    }
+  }
 
   printer->Indent();
 
@@ -1193,6 +1241,34 @@ GenerateCommonBuilderMethods(io::Printer* printer) {
 
 // ===================================================================
 
+void ImmutableMessageGenerator::
+GenerateBuilderParsingMethods(io::Printer* printer) {
+  if (HasDescriptorMethods(descriptor_)) {
+    // LITE_RUNTIME implements this at the GeneratedMessageLite level.
+    printer->Print(
+      "public Builder mergeFrom(\n"
+      "    com.google.protobuf.CodedInputStream input,\n"
+      "    com.google.protobuf.ExtensionRegistryLite extensionRegistry)\n"
+      "    throws java.io.IOException {\n"
+      "  $classname$ parsedMessage = null;\n"
+      "  try {\n"
+      "    parsedMessage = PARSER.parsePartialFrom(input, extensionRegistry);\n"
+      "  } catch (com.google.protobuf.InvalidProtocolBufferException e) {\n"
+      "    parsedMessage = ($classname$) e.getUnfinishedMessage();\n"
+      "    throw e;\n"
+      "  } finally {\n"
+      "    if (parsedMessage != null) {\n"
+      "      mergeFrom(parsedMessage);\n"
+      "    }\n"
+      "  }\n"
+      "  return this;\n"
+      "}\n",
+      "classname", name_resolver_->GetImmutableClassName(descriptor_));
+  }
+}
+
+// ===================================================================
+
 void ImmutableMessageGenerator::GenerateIsInitialized(
     io::Printer* printer, UseMemoization useMemoization) {
   bool memoization = useMemoization == MEMOIZE;
@@ -1488,8 +1564,13 @@ GenerateParsingConstructor(io::Printer* printer) {
   printer->Indent();
 
   // Initialize all fields to default.
-  printer->Print(
-      "this();\n");
+  if (HasDescriptorMethods(descriptor_)) {
+    printer->Print(
+        "this();\n");
+  } else {
+    // LITE_RUNTIME only has one constructor.
+    GenerateInitializers(printer);
+  }
 
   // Use builder bits to track mutable repeated fields.
   int totalBuilderBits = 0;
@@ -1703,6 +1784,16 @@ void ImmutableMessageGenerator::GenerateParser(io::Printer* printer) {
       "classname", descriptor_->name());
 }
 
+// ===================================================================
+void ImmutableMessageGenerator::GenerateInitializers(io::Printer* printer) {
+  for (int i = 0; i < descriptor_->field_count(); i++) {
+    if (!descriptor_->field(i)->containing_oneof()) {
+      field_generators_.get(descriptor_->field(i))
+          .GenerateInitializationCode(printer);
+    }
+  }
+}
+
 
 }  // namespace java
 }  // namespace compiler
diff --git a/src/google/protobuf/compiler/java/java_message.h b/src/google/protobuf/compiler/java/java_message.h
index 2703016e..91eb2876 100644
--- a/src/google/protobuf/compiler/java/java_message.h
+++ b/src/google/protobuf/compiler/java/java_message.h
@@ -118,8 +118,10 @@ class ImmutableMessageGenerator : public MessageGenerator {
   void GenerateBuilder(io::Printer* printer);
   void GenerateCommonBuilderMethods(io::Printer* printer);
   void GenerateDescriptorMethods(io::Printer* printer);
+  void GenerateBuilderParsingMethods(io::Printer* printer);
   void GenerateIsInitialized(io::Printer* printer,
       UseMemoization useMemoization);
+  void GenerateInitializers(io::Printer* printer);
   void GenerateEqualsAndHashCode(io::Printer* printer);
   void GenerateParser(io::Printer* printer);
   void GenerateParsingConstructor(io::Printer* printer);
diff --git a/src/google/protobuf/compiler/parser.cc b/src/google/protobuf/compiler/parser.cc
index 0ed80d54..4b3efe48 100644
--- a/src/google/protobuf/compiler/parser.cc
+++ b/src/google/protobuf/compiler/parser.cc
@@ -1632,6 +1632,9 @@ bool Parser::ParseServiceMethod(MethodDescriptorProto* method,
   // Parse input type.
   DO(Consume("("));
   {
+    if (TryConsume("stream")) {
+      method->set_client_streaming(true);
+    }
     LocationRecorder location(method_location,
                               MethodDescriptorProto::kInputTypeFieldNumber);
     location.RecordLegacyLocation(
@@ -1644,6 +1647,9 @@ bool Parser::ParseServiceMethod(MethodDescriptorProto* method,
   DO(Consume("returns"));
   DO(Consume("("));
   {
+    if (TryConsume("stream")) {
+      method->set_server_streaming(true);
+    }
     LocationRecorder location(method_location,
                               MethodDescriptorProto::kOutputTypeFieldNumber);
     location.RecordLegacyLocation(
diff --git a/src/google/protobuf/descriptor.cc b/src/google/protobuf/descriptor.cc
index d3a60045..7bc172a8 100644
--- a/src/google/protobuf/descriptor.cc
+++ b/src/google/protobuf/descriptor.cc
@@ -1843,6 +1843,13 @@ void MethodDescriptor::CopyTo(MethodDescriptorProto* proto) const {
   if (&options() != &MethodOptions::default_instance()) {
     proto->mutable_options()->CopyFrom(options());
   }
+
+  if (client_streaming_) {
+    proto->set_client_streaming(true);
+  }
+  if (server_streaming_) {
+    proto->set_server_streaming(true);
+  }
 }
 
 // DebugString methods ===============================================
@@ -2395,10 +2402,12 @@ void MethodDescriptor::DebugString(int depth, string *contents,
       comment_printer(this, prefix, debug_string_options);
   comment_printer.AddPreComment(contents);
 
-  strings::SubstituteAndAppend(contents, "$0rpc $1(.$2) returns (.$3)",
+  strings::SubstituteAndAppend(contents, "$0rpc $1($4.$2) returns ($5.$3)",
                                prefix, name(),
                                input_type()->full_name(),
-                               output_type()->full_name());
+                               output_type()->full_name(),
+                               client_streaming() ? "stream " : "",
+                               server_streaming() ? "stream " : "");
 
   string formatted_options;
   if (FormatLineOptions(depth, options(), &formatted_options)) {
@@ -4393,6 +4402,9 @@ void DescriptorBuilder::BuildMethod(const MethodDescriptorProto& proto,
     AllocateOptions(proto.options(), result);
   }
 
+  result->client_streaming_ = proto.client_streaming();
+  result->server_streaming_ = proto.server_streaming();
+
   AddSymbol(result->full_name(), parent, result->name(),
             proto, Symbol(result));
 }
diff --git a/src/google/protobuf/descriptor.h b/src/google/protobuf/descriptor.h
index 0ee0a3f9..52df47f3 100644
--- a/src/google/protobuf/descriptor.h
+++ b/src/google/protobuf/descriptor.h
@@ -990,6 +990,11 @@ class LIBPROTOBUF_EXPORT MethodDescriptor {
   // Gets the type of protocol message which this message produces as output.
   const Descriptor* output_type() const;
 
+  // Gets whether the client streams multiple requests.
+  bool client_streaming() const;
+  // Gets whether the server streams multiple responses.
+  bool server_streaming() const;
+
   // Get options for this method.  These are specified in the .proto file by
   // placing lines like "option foo = 1234;" in curly-braces after a method
   // declaration.  Allowed options are defined by MethodOptions in
@@ -1031,6 +1036,8 @@ class LIBPROTOBUF_EXPORT MethodDescriptor {
   const Descriptor* input_type_;
   const Descriptor* output_type_;
   const MethodOptions* options_;
+  bool client_streaming_;
+  bool server_streaming_;
   // IMPORTANT:  If you add a new field, make sure to search for all instances
   // of Allocate<MethodDescriptor>() and AllocateArray<MethodDescriptor>() in
   // descriptor.cc and update them to initialize the field.
@@ -1623,6 +1630,9 @@ PROTOBUF_DEFINE_ACCESSOR(MethodDescriptor, service, const ServiceDescriptor*)
 PROTOBUF_DEFINE_ACCESSOR(MethodDescriptor, input_type, const Descriptor*)
 PROTOBUF_DEFINE_ACCESSOR(MethodDescriptor, output_type, const Descriptor*)
 PROTOBUF_DEFINE_OPTIONS_ACCESSOR(MethodDescriptor, MethodOptions);
+PROTOBUF_DEFINE_ACCESSOR(MethodDescriptor, client_streaming, bool)
+PROTOBUF_DEFINE_ACCESSOR(MethodDescriptor, server_streaming, bool)
+
 PROTOBUF_DEFINE_STRING_ACCESSOR(FileDescriptor, name)
 PROTOBUF_DEFINE_STRING_ACCESSOR(FileDescriptor, package)
 PROTOBUF_DEFINE_ACCESSOR(FileDescriptor, pool, const DescriptorPool*)
diff --git a/src/google/protobuf/descriptor.pb.cc b/src/google/protobuf/descriptor.pb.cc
index 6a67fef8..df214d44 100644
--- a/src/google/protobuf/descriptor.pb.cc
+++ b/src/google/protobuf/descriptor.pb.cc
@@ -260,11 +260,13 @@ void protobuf_AssignDesc_google_2fprotobuf_2fdescriptor_2eproto() {
       sizeof(ServiceDescriptorProto),
       GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(ServiceDescriptorProto, _internal_metadata_));
   MethodDescriptorProto_descriptor_ = file->message_type(8);
-  static const int MethodDescriptorProto_offsets_[4] = {
+  static const int MethodDescriptorProto_offsets_[6] = {
     GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(MethodDescriptorProto, name_),
     GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(MethodDescriptorProto, input_type_),
     GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(MethodDescriptorProto, output_type_),
     GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(MethodDescriptorProto, options_),
+    GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(MethodDescriptorProto, client_streaming_),
+    GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(MethodDescriptorProto, server_streaming_),
   };
   MethodDescriptorProto_reflection_ =
     ::google::protobuf::internal::GeneratedMessageReflection::NewGeneratedMessageReflection(
@@ -633,64 +635,65 @@ void protobuf_AddDesc_google_2fprotobuf_2fdescriptor_2eproto() {
     "riptorProto\022\014\n\004name\030\001 \001(\t\0226\n\006method\030\002 \003("
     "\0132&.google.protobuf.MethodDescriptorProt"
     "o\0220\n\007options\030\003 \001(\0132\037.google.protobuf.Ser"
-    "viceOptions\"\177\n\025MethodDescriptorProto\022\014\n\004"
-    "name\030\001 \001(\t\022\022\n\ninput_type\030\002 \001(\t\022\023\n\013output"
-    "_type\030\003 \001(\t\022/\n\007options\030\004 \001(\0132\036.google.pr"
-    "otobuf.MethodOptions\"\314\004\n\013FileOptions\022\024\n\014"
-    "java_package\030\001 \001(\t\022\034\n\024java_outer_classna"
-    "me\030\010 \001(\t\022\"\n\023java_multiple_files\030\n \001(\010:\005f"
-    "alse\022,\n\035java_generate_equals_and_hash\030\024 "
-    "\001(\010:\005false\022%\n\026java_string_check_utf8\030\033 \001"
-    "(\010:\005false\022F\n\014optimize_for\030\t \001(\0162).google"
-    ".protobuf.FileOptions.OptimizeMode:\005SPEE"
-    "D\022\022\n\ngo_package\030\013 \001(\t\022\"\n\023cc_generic_serv"
-    "ices\030\020 \001(\010:\005false\022$\n\025java_generic_servic"
-    "es\030\021 \001(\010:\005false\022\"\n\023py_generic_services\030\022"
-    " \001(\010:\005false\022\031\n\ndeprecated\030\027 \001(\010:\005false\022\037"
-    "\n\020cc_enable_arenas\030\037 \001(\010:\005false\022C\n\024unint"
+    "viceOptions\"\301\001\n\025MethodDescriptorProto\022\014\n"
+    "\004name\030\001 \001(\t\022\022\n\ninput_type\030\002 \001(\t\022\023\n\013outpu"
+    "t_type\030\003 \001(\t\022/\n\007options\030\004 \001(\0132\036.google.p"
+    "rotobuf.MethodOptions\022\037\n\020client_streamin"
+    "g\030\005 \001(\010:\005false\022\037\n\020server_streaming\030\006 \001(\010"
+    ":\005false\"\314\004\n\013FileOptions\022\024\n\014java_package\030"
+    "\001 \001(\t\022\034\n\024java_outer_classname\030\010 \001(\t\022\"\n\023j"
+    "ava_multiple_files\030\n \001(\010:\005false\022,\n\035java_"
+    "generate_equals_and_hash\030\024 \001(\010:\005false\022%\n"
+    "\026java_string_check_utf8\030\033 \001(\010:\005false\022F\n\014"
+    "optimize_for\030\t \001(\0162).google.protobuf.Fil"
+    "eOptions.OptimizeMode:\005SPEED\022\022\n\ngo_packa"
+    "ge\030\013 \001(\t\022\"\n\023cc_generic_services\030\020 \001(\010:\005f"
+    "alse\022$\n\025java_generic_services\030\021 \001(\010:\005fal"
+    "se\022\"\n\023py_generic_services\030\022 \001(\010:\005false\022\031"
+    "\n\ndeprecated\030\027 \001(\010:\005false\022\037\n\020cc_enable_a"
+    "renas\030\037 \001(\010:\005false\022C\n\024uninterpreted_opti"
+    "on\030\347\007 \003(\0132$.google.protobuf.Uninterprete"
+    "dOption\":\n\014OptimizeMode\022\t\n\005SPEED\020\001\022\r\n\tCO"
+    "DE_SIZE\020\002\022\020\n\014LITE_RUNTIME\020\003*\t\010\350\007\020\200\200\200\200\002\"\346"
+    "\001\n\016MessageOptions\022&\n\027message_set_wire_fo"
+    "rmat\030\001 \001(\010:\005false\022.\n\037no_standard_descrip"
+    "tor_accessor\030\002 \001(\010:\005false\022\031\n\ndeprecated\030"
+    "\003 \001(\010:\005false\022\021\n\tmap_entry\030\007 \001(\010\022C\n\024unint"
     "erpreted_option\030\347\007 \003(\0132$.google.protobuf"
-    ".UninterpretedOption\":\n\014OptimizeMode\022\t\n\005"
-    "SPEED\020\001\022\r\n\tCODE_SIZE\020\002\022\020\n\014LITE_RUNTIME\020\003"
-    "*\t\010\350\007\020\200\200\200\200\002\"\346\001\n\016MessageOptions\022&\n\027messag"
-    "e_set_wire_format\030\001 \001(\010:\005false\022.\n\037no_sta"
-    "ndard_descriptor_accessor\030\002 \001(\010:\005false\022\031"
-    "\n\ndeprecated\030\003 \001(\010:\005false\022\021\n\tmap_entry\030\007"
-    " \001(\010\022C\n\024uninterpreted_option\030\347\007 \003(\0132$.go"
-    "ogle.protobuf.UninterpretedOption*\t\010\350\007\020\200"
-    "\200\200\200\002\"\240\002\n\014FieldOptions\022:\n\005ctype\030\001 \001(\0162#.g"
-    "oogle.protobuf.FieldOptions.CType:\006STRIN"
-    "G\022\016\n\006packed\030\002 \001(\010\022\023\n\004lazy\030\005 \001(\010:\005false\022\031"
-    "\n\ndeprecated\030\003 \001(\010:\005false\022\023\n\004weak\030\n \001(\010:"
-    "\005false\022C\n\024uninterpreted_option\030\347\007 \003(\0132$."
-    "google.protobuf.UninterpretedOption\"/\n\005C"
-    "Type\022\n\n\006STRING\020\000\022\010\n\004CORD\020\001\022\020\n\014STRING_PIE"
-    "CE\020\002*\t\010\350\007\020\200\200\200\200\002\"\215\001\n\013EnumOptions\022\023\n\013allow"
-    "_alias\030\002 \001(\010\022\031\n\ndeprecated\030\003 \001(\010:\005false\022"
-    "C\n\024uninterpreted_option\030\347\007 \003(\0132$.google."
-    "protobuf.UninterpretedOption*\t\010\350\007\020\200\200\200\200\002\""
-    "}\n\020EnumValueOptions\022\031\n\ndeprecated\030\001 \001(\010:"
-    "\005false\022C\n\024uninterpreted_option\030\347\007 \003(\0132$."
-    "google.protobuf.UninterpretedOption*\t\010\350\007"
-    "\020\200\200\200\200\002\"{\n\016ServiceOptions\022\031\n\ndeprecated\030!"
-    " \001(\010:\005false\022C\n\024uninterpreted_option\030\347\007 \003"
-    "(\0132$.google.protobuf.UninterpretedOption"
-    "*\t\010\350\007\020\200\200\200\200\002\"z\n\rMethodOptions\022\031\n\ndeprecat"
-    "ed\030! \001(\010:\005false\022C\n\024uninterpreted_option\030"
-    "\347\007 \003(\0132$.google.protobuf.UninterpretedOp"
-    "tion*\t\010\350\007\020\200\200\200\200\002\"\236\002\n\023UninterpretedOption\022"
-    ";\n\004name\030\002 \003(\0132-.google.protobuf.Uninterp"
-    "retedOption.NamePart\022\030\n\020identifier_value"
-    "\030\003 \001(\t\022\032\n\022positive_int_value\030\004 \001(\004\022\032\n\022ne"
-    "gative_int_value\030\005 \001(\003\022\024\n\014double_value\030\006"
-    " \001(\001\022\024\n\014string_value\030\007 \001(\014\022\027\n\017aggregate_"
-    "value\030\010 \001(\t\0323\n\010NamePart\022\021\n\tname_part\030\001 \002"
-    "(\t\022\024\n\014is_extension\030\002 \002(\010\"\261\001\n\016SourceCodeI"
-    "nfo\022:\n\010location\030\001 \003(\0132(.google.protobuf."
-    "SourceCodeInfo.Location\032c\n\010Location\022\020\n\004p"
-    "ath\030\001 \003(\005B\002\020\001\022\020\n\004span\030\002 \003(\005B\002\020\001\022\030\n\020leadi"
-    "ng_comments\030\003 \001(\t\022\031\n\021trailing_comments\030\004"
-    " \001(\tB)\n\023com.google.protobufB\020DescriptorP"
-    "rotosH\001", 4487);
+    ".UninterpretedOption*\t\010\350\007\020\200\200\200\200\002\"\240\002\n\014Fiel"
+    "dOptions\022:\n\005ctype\030\001 \001(\0162#.google.protobu"
+    "f.FieldOptions.CType:\006STRING\022\016\n\006packed\030\002"
+    " \001(\010\022\023\n\004lazy\030\005 \001(\010:\005false\022\031\n\ndeprecated\030"
+    "\003 \001(\010:\005false\022\023\n\004weak\030\n \001(\010:\005false\022C\n\024uni"
+    "nterpreted_option\030\347\007 \003(\0132$.google.protob"
+    "uf.UninterpretedOption\"/\n\005CType\022\n\n\006STRIN"
+    "G\020\000\022\010\n\004CORD\020\001\022\020\n\014STRING_PIECE\020\002*\t\010\350\007\020\200\200\200"
+    "\200\002\"\215\001\n\013EnumOptions\022\023\n\013allow_alias\030\002 \001(\010\022"
+    "\031\n\ndeprecated\030\003 \001(\010:\005false\022C\n\024uninterpre"
+    "ted_option\030\347\007 \003(\0132$.google.protobuf.Unin"
+    "terpretedOption*\t\010\350\007\020\200\200\200\200\002\"}\n\020EnumValueO"
+    "ptions\022\031\n\ndeprecated\030\001 \001(\010:\005false\022C\n\024uni"
+    "nterpreted_option\030\347\007 \003(\0132$.google.protob"
+    "uf.UninterpretedOption*\t\010\350\007\020\200\200\200\200\002\"{\n\016Ser"
+    "viceOptions\022\031\n\ndeprecated\030! \001(\010:\005false\022C"
+    "\n\024uninterpreted_option\030\347\007 \003(\0132$.google.p"
+    "rotobuf.UninterpretedOption*\t\010\350\007\020\200\200\200\200\002\"z"
+    "\n\rMethodOptions\022\031\n\ndeprecated\030! \001(\010:\005fal"
+    "se\022C\n\024uninterpreted_option\030\347\007 \003(\0132$.goog"
+    "le.protobuf.UninterpretedOption*\t\010\350\007\020\200\200\200"
+    "\200\002\"\236\002\n\023UninterpretedOption\022;\n\004name\030\002 \003(\013"
+    "2-.google.protobuf.UninterpretedOption.N"
+    "amePart\022\030\n\020identifier_value\030\003 \001(\t\022\032\n\022pos"
+    "itive_int_value\030\004 \001(\004\022\032\n\022negative_int_va"
+    "lue\030\005 \001(\003\022\024\n\014double_value\030\006 \001(\001\022\024\n\014strin"
+    "g_value\030\007 \001(\014\022\027\n\017aggregate_value\030\010 \001(\t\0323"
+    "\n\010NamePart\022\021\n\tname_part\030\001 \002(\t\022\024\n\014is_exte"
+    "nsion\030\002 \002(\010\"\261\001\n\016SourceCodeInfo\022:\n\010locati"
+    "on\030\001 \003(\0132(.google.protobuf.SourceCodeInf"
+    "o.Location\032c\n\010Location\022\020\n\004path\030\001 \003(\005B\002\020\001"
+    "\022\020\n\004span\030\002 \003(\005B\002\020\001\022\030\n\020leading_comments\030\003"
+    " \001(\t\022\031\n\021trailing_comments\030\004 \001(\tB)\n\023com.g"
+    "oogle.protobufB\020DescriptorProtosH\001", 4554);
   ::google::protobuf::MessageFactory::InternalRegisterGeneratedFile(
     "google/protobuf/descriptor.proto", &protobuf_RegisterTypes);
   FileDescriptorSet::default_instance_ = new FileDescriptorSet();
@@ -4560,6 +4563,8 @@ const int MethodDescriptorProto::kNameFieldNumber;
 const int MethodDescriptorProto::kInputTypeFieldNumber;
 const int MethodDescriptorProto::kOutputTypeFieldNumber;
 const int MethodDescriptorProto::kOptionsFieldNumber;
+const int MethodDescriptorProto::kClientStreamingFieldNumber;
+const int MethodDescriptorProto::kServerStreamingFieldNumber;
 #endif  // !_MSC_VER
 
 MethodDescriptorProto::MethodDescriptorProto()
@@ -4587,6 +4592,8 @@ void MethodDescriptorProto::SharedCtor() {
   input_type_.UnsafeSetDefault(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
   output_type_.UnsafeSetDefault(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
   options_ = NULL;
+  client_streaming_ = false;
+  server_streaming_ = false;
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
 }
 
@@ -4630,7 +4637,18 @@ MethodDescriptorProto* MethodDescriptorProto::New(::google::protobuf::Arena* are
 }
 
 void MethodDescriptorProto::Clear() {
-  if (_has_bits_[0 / 32] & 15) {
+#define OFFSET_OF_FIELD_(f) (reinterpret_cast<char*>(      \
+  &reinterpret_cast<MethodDescriptorProto*>(16)->f) - \
+   reinterpret_cast<char*>(16))
+
+#define ZR_(first, last) do {                              \
+    size_t f = OFFSET_OF_FIELD_(first);                    \
+    size_t n = OFFSET_OF_FIELD_(last) - f + sizeof(last);  \
+    ::memset(&first, 0, n);                                \
+  } while (0)
+
+  if (_has_bits_[0 / 32] & 63) {
+    ZR_(client_streaming_, server_streaming_);
     if (has_name()) {
       name_.ClearToEmptyNoArena(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
     }
@@ -4644,6 +4662,10 @@ void MethodDescriptorProto::Clear() {
       if (options_ != NULL) options_->::google::protobuf::MethodOptions::Clear();
     }
   }
+
+#undef OFFSET_OF_FIELD_
+#undef ZR_
+
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
   if (_internal_metadata_.have_unknown_fields()) {
     mutable_unknown_fields()->Clear();
@@ -4719,6 +4741,36 @@ bool MethodDescriptorProto::MergePartialFromCodedStream(
         } else {
           goto handle_unusual;
         }
+        if (input->ExpectTag(40)) goto parse_client_streaming;
+        break;
+      }
+
+      // optional bool client_streaming = 5 [default = false];
+      case 5: {
+        if (tag == 40) {
+         parse_client_streaming:
+          DO_((::google::protobuf::internal::WireFormatLite::ReadPrimitive<
+                   bool, ::google::protobuf::internal::WireFormatLite::TYPE_BOOL>(
+                 input, &client_streaming_)));
+          set_has_client_streaming();
+        } else {
+          goto handle_unusual;
+        }
+        if (input->ExpectTag(48)) goto parse_server_streaming;
+        break;
+      }
+
+      // optional bool server_streaming = 6 [default = false];
+      case 6: {
+        if (tag == 48) {
+         parse_server_streaming:
+          DO_((::google::protobuf::internal::WireFormatLite::ReadPrimitive<
+                   bool, ::google::protobuf::internal::WireFormatLite::TYPE_BOOL>(
+                 input, &server_streaming_)));
+          set_has_server_streaming();
+        } else {
+          goto handle_unusual;
+        }
         if (input->ExpectAtEnd()) goto success;
         break;
       }
@@ -4784,6 +4836,16 @@ void MethodDescriptorProto::SerializeWithCachedSizes(
       4, *this->options_, output);
   }
 
+  // optional bool client_streaming = 5 [default = false];
+  if (has_client_streaming()) {
+    ::google::protobuf::internal::WireFormatLite::WriteBool(5, this->client_streaming(), output);
+  }
+
+  // optional bool server_streaming = 6 [default = false];
+  if (has_server_streaming()) {
+    ::google::protobuf::internal::WireFormatLite::WriteBool(6, this->server_streaming(), output);
+  }
+
   if (_internal_metadata_.have_unknown_fields()) {
     ::google::protobuf::internal::WireFormat::SerializeUnknownFields(
         unknown_fields(), output);
@@ -4834,6 +4896,16 @@ void MethodDescriptorProto::SerializeWithCachedSizes(
         4, *this->options_, target);
   }
 
+  // optional bool client_streaming = 5 [default = false];
+  if (has_client_streaming()) {
+    target = ::google::protobuf::internal::WireFormatLite::WriteBoolToArray(5, this->client_streaming(), target);
+  }
+
+  // optional bool server_streaming = 6 [default = false];
+  if (has_server_streaming()) {
+    target = ::google::protobuf::internal::WireFormatLite::WriteBoolToArray(6, this->server_streaming(), target);
+  }
+
   if (_internal_metadata_.have_unknown_fields()) {
     target = ::google::protobuf::internal::WireFormat::SerializeUnknownFieldsToArray(
         unknown_fields(), target);
@@ -4845,7 +4917,7 @@ void MethodDescriptorProto::SerializeWithCachedSizes(
 int MethodDescriptorProto::ByteSize() const {
   int total_size = 0;
 
-  if (_has_bits_[0 / 32] & 15) {
+  if (_has_bits_[0 / 32] & 63) {
     // optional string name = 1;
     if (has_name()) {
       total_size += 1 +
@@ -4874,6 +4946,16 @@ int MethodDescriptorProto::ByteSize() const {
           *this->options_);
     }
 
+    // optional bool client_streaming = 5 [default = false];
+    if (has_client_streaming()) {
+      total_size += 1 + 1;
+    }
+
+    // optional bool server_streaming = 6 [default = false];
+    if (has_server_streaming()) {
+      total_size += 1 + 1;
+    }
+
   }
   if (_internal_metadata_.have_unknown_fields()) {
     total_size +=
@@ -4916,6 +4998,12 @@ void MethodDescriptorProto::MergeFrom(const MethodDescriptorProto& from) {
     if (from.has_options()) {
       mutable_options()->::google::protobuf::MethodOptions::MergeFrom(from.options());
     }
+    if (from.has_client_streaming()) {
+      set_client_streaming(from.client_streaming());
+    }
+    if (from.has_server_streaming()) {
+      set_server_streaming(from.server_streaming());
+    }
   }
   if (from._internal_metadata_.have_unknown_fields()) {
     mutable_unknown_fields()->MergeFrom(from.unknown_fields());
@@ -4951,6 +5039,8 @@ void MethodDescriptorProto::InternalSwap(MethodDescriptorProto* other) {
   input_type_.Swap(&other->input_type_);
   output_type_.Swap(&other->output_type_);
   std::swap(options_, other->options_);
+  std::swap(client_streaming_, other->client_streaming_);
+  std::swap(server_streaming_, other->server_streaming_);
   std::swap(_has_bits_[0], other->_has_bits_[0]);
   _internal_metadata_.Swap(&other->_internal_metadata_);
   std::swap(_cached_size_, other->_cached_size_);
diff --git a/src/google/protobuf/descriptor.pb.h b/src/google/protobuf/descriptor.pb.h
index b699f22d..6bb5c6a6 100644
--- a/src/google/protobuf/descriptor.pb.h
+++ b/src/google/protobuf/descriptor.pb.h
@@ -1590,6 +1590,20 @@ class LIBPROTOBUF_EXPORT MethodDescriptorProto : public ::google::protobuf::Mess
   inline ::google::protobuf::MethodOptions* release_options();
   inline void set_allocated_options(::google::protobuf::MethodOptions* options);
 
+  // optional bool client_streaming = 5 [default = false];
+  inline bool has_client_streaming() const;
+  inline void clear_client_streaming();
+  static const int kClientStreamingFieldNumber = 5;
+  inline bool client_streaming() const;
+  inline void set_client_streaming(bool value);
+
+  // optional bool server_streaming = 6 [default = false];
+  inline bool has_server_streaming() const;
+  inline void clear_server_streaming();
+  static const int kServerStreamingFieldNumber = 6;
+  inline bool server_streaming() const;
+  inline void set_server_streaming(bool value);
+
   // @@protoc_insertion_point(class_scope:google.protobuf.MethodDescriptorProto)
  private:
   inline void set_has_name();
@@ -1600,6 +1614,10 @@ class LIBPROTOBUF_EXPORT MethodDescriptorProto : public ::google::protobuf::Mess
   inline void clear_has_output_type();
   inline void set_has_options();
   inline void clear_has_options();
+  inline void set_has_client_streaming();
+  inline void clear_has_client_streaming();
+  inline void set_has_server_streaming();
+  inline void clear_has_server_streaming();
 
   ::google::protobuf::internal::InternalMetadataWithArena _internal_metadata_;
   ::google::protobuf::uint32 _has_bits_[1];
@@ -1608,6 +1626,8 @@ class LIBPROTOBUF_EXPORT MethodDescriptorProto : public ::google::protobuf::Mess
   ::google::protobuf::internal::ArenaStringPtr input_type_;
   ::google::protobuf::internal::ArenaStringPtr output_type_;
   ::google::protobuf::MethodOptions* options_;
+  bool client_streaming_;
+  bool server_streaming_;
   friend void LIBPROTOBUF_EXPORT protobuf_AddDesc_google_2fprotobuf_2fdescriptor_2eproto();
   friend void protobuf_AssignDesc_google_2fprotobuf_2fdescriptor_2eproto();
   friend void protobuf_ShutdownFile_google_2fprotobuf_2fdescriptor_2eproto();
@@ -4968,6 +4988,54 @@ inline void MethodDescriptorProto::set_allocated_options(::google::protobuf::Met
   // @@protoc_insertion_point(field_set_allocated:google.protobuf.MethodDescriptorProto.options)
 }
 
+// optional bool client_streaming = 5 [default = false];
+inline bool MethodDescriptorProto::has_client_streaming() const {
+  return (_has_bits_[0] & 0x00000010u) != 0;
+}
+inline void MethodDescriptorProto::set_has_client_streaming() {
+  _has_bits_[0] |= 0x00000010u;
+}
+inline void MethodDescriptorProto::clear_has_client_streaming() {
+  _has_bits_[0] &= ~0x00000010u;
+}
+inline void MethodDescriptorProto::clear_client_streaming() {
+  client_streaming_ = false;
+  clear_has_client_streaming();
+}
+inline bool MethodDescriptorProto::client_streaming() const {
+  // @@protoc_insertion_point(field_get:google.protobuf.MethodDescriptorProto.client_streaming)
+  return client_streaming_;
+}
+inline void MethodDescriptorProto::set_client_streaming(bool value) {
+  set_has_client_streaming();
+  client_streaming_ = value;
+  // @@protoc_insertion_point(field_set:google.protobuf.MethodDescriptorProto.client_streaming)
+}
+
+// optional bool server_streaming = 6 [default = false];
+inline bool MethodDescriptorProto::has_server_streaming() const {
+  return (_has_bits_[0] & 0x00000020u) != 0;
+}
+inline void MethodDescriptorProto::set_has_server_streaming() {
+  _has_bits_[0] |= 0x00000020u;
+}
+inline void MethodDescriptorProto::clear_has_server_streaming() {
+  _has_bits_[0] &= ~0x00000020u;
+}
+inline void MethodDescriptorProto::clear_server_streaming() {
+  server_streaming_ = false;
+  clear_has_server_streaming();
+}
+inline bool MethodDescriptorProto::server_streaming() const {
+  // @@protoc_insertion_point(field_get:google.protobuf.MethodDescriptorProto.server_streaming)
+  return server_streaming_;
+}
+inline void MethodDescriptorProto::set_server_streaming(bool value) {
+  set_has_server_streaming();
+  server_streaming_ = value;
+  // @@protoc_insertion_point(field_set:google.protobuf.MethodDescriptorProto.server_streaming)
+}
+
 // -------------------------------------------------------------------
 
 // FileOptions
diff --git a/src/google/protobuf/descriptor.proto b/src/google/protobuf/descriptor.proto
index 0874c4e4..e17c0cc8 100644
--- a/src/google/protobuf/descriptor.proto
+++ b/src/google/protobuf/descriptor.proto
@@ -220,6 +220,11 @@ message MethodDescriptorProto {
   optional string output_type = 3;
 
   optional MethodOptions options = 4;
+
+  // Identifies if client streams multiple client messages
+  optional bool client_streaming = 5 [default=false];
+  // Identifies if server streams multiple server messages
+  optional bool server_streaming = 6 [default=false];
 }
 
 
diff --git a/src/google/protobuf/io/zero_copy_stream_impl_lite.h b/src/google/protobuf/io/zero_copy_stream_impl_lite.h
index a517161d..3e25edfa 100644
--- a/src/google/protobuf/io/zero_copy_stream_impl_lite.h
+++ b/src/google/protobuf/io/zero_copy_stream_impl_lite.h
@@ -127,8 +127,10 @@ class LIBPROTOBUF_EXPORT ArrayOutputStream : public ZeroCopyOutputStream {
 class LIBPROTOBUF_EXPORT StringOutputStream : public ZeroCopyOutputStream {
  public:
   // Create a StringOutputStream which appends bytes to the given string.
-  // The string remains property of the caller, but it MUST NOT be accessed
-  // in any way until the stream is destroyed.
+  // The string remains property of the caller, but it is mutated in arbitrary
+  // ways and MUST NOT be accessed in any way until you're done with the
+  // stream. Either be sure there's no further usage, or (safest) destroy the
+  // stream before using the contents.
   //
   // Hint:  If you call target->reserve(n) before creating the stream,
   //   the first call to Next() will return at least n bytes of buffer
diff --git a/src/google/protobuf/map.h b/src/google/protobuf/map.h
index a9937b9b..e55a6d43 100644
--- a/src/google/protobuf/map.h
+++ b/src/google/protobuf/map.h
@@ -31,10 +31,10 @@
 #ifndef GOOGLE_PROTOBUF_MAP_H__
 #define GOOGLE_PROTOBUF_MAP_H__
 
-#include <vector>
+#include <iterator>
+#include <google/protobuf/stubs/hash.h>
 
 #include <google/protobuf/map_type_handler.h>
-#include <google/protobuf/stubs/hash.h>
 
 namespace google {
 namespace protobuf {
@@ -48,7 +48,7 @@ namespace internal {
 template <typename K, typename V, FieldDescriptor::Type KeyProto,
           FieldDescriptor::Type ValueProto, int default_enum_value>
 class MapField;
-}
+}  // namespace internal
 
 // This is the class for google::protobuf::Map's internal value_type. Instead of using
 // std::pair as value_type, we use this class which provides us more control of
@@ -62,7 +62,7 @@ class MapPair {
   MapPair(const Key& other_first, const T& other_second)
       : first(other_first), second(other_second) {}
 
-  MapPair(const Key& other_first) : first(other_first), second() {}
+  explicit MapPair(const Key& other_first) : first(other_first), second() {}
 
   MapPair(const MapPair& other)
       : first(other.first), second(other.second) {}
@@ -82,52 +82,13 @@ class MapPair {
   friend class Map<Key, T>;
 };
 
-// STL-like iterator implementation for google::protobuf::Map. Users should not refer to
-// this class directly; use google::protobuf::Map<Key, T>::iterator instead.
-template <typename Key, typename T>
-class MapIterator {
- public:
-  typedef MapPair<Key, T> value_type;
-  typedef value_type* pointer;
-  typedef value_type& reference;
-  typedef MapIterator iterator;
-
-  // constructor
-  MapIterator(const typename hash_map<Key, value_type*>::iterator& it)
-      : it_(it) {}
-  MapIterator(const MapIterator& other) : it_(other.it_) {}
-  MapIterator& operator=(const MapIterator& other) {
-    it_ = other.it_;
-    return *this;
-  }
-
-  // deferenceable
-  reference operator*() const { return *it_->second; }
-  pointer operator->() const { return it_->second; }
-
-  // incrementable
-  iterator& operator++() {
-    ++it_;
-    return *this;
-  }
-  iterator operator++(int) { return iterator(it_++); }
-
-  // equality_comparable
-  bool operator==(const iterator& x) const { return it_ == x.it_; }
-  bool operator!=(const iterator& x) const { return it_ != x.it_; }
-
- private:
-  typename hash_map<Key, value_type*>::iterator it_;
-
-  friend class Map<Key, T>;
-};
-
 // google::protobuf::Map is an associative container type used to store protobuf map
 // fields. Its interface is similar to std::unordered_map. Users should use this
 // interface directly to visit or change map fields.
 template <typename Key, typename T>
 class Map {
   typedef internal::MapCppTypeHandler<T> ValueTypeHandler;
+
  public:
   typedef Key key_type;
   typedef T mapped_type;
@@ -138,9 +99,6 @@ class Map {
   typedef value_type& reference;
   typedef const value_type& const_reference;
 
-  typedef MapIterator<Key, T> iterator;
-  typedef MapIterator<Key, T> const_iterator;
-
   typedef size_t size_type;
   typedef hash<Key> hasher;
 
@@ -153,16 +111,70 @@ class Map {
   ~Map() { clear(); }
 
   // Iterators
+  class LIBPROTOBUF_EXPORT const_iterator
+      : public std::iterator<std::forward_iterator_tag, value_type, ptrdiff_t,
+                             const value_type*, const value_type&> {
+    typedef typename hash_map<Key, value_type*>::const_iterator InnerIt;
+
+   public:
+    const_iterator() {}
+    explicit const_iterator(const InnerIt& it) : it_(it) {}
+
+    const_reference operator*() const { return *it_->second; }
+    const_pointer operator->() const { return it_->second; }
+
+    const_iterator& operator++() {
+      ++it_;
+      return *this;
+    }
+    const_iterator operator++(int) { return const_iterator(it_++); }
+
+    friend bool operator==(const const_iterator& a, const const_iterator& b) {
+      return a.it_ == b.it_;
+    }
+    friend bool operator!=(const const_iterator& a, const const_iterator& b) {
+      return a.it_ != b.it_;
+    }
+
+   private:
+    InnerIt it_;
+  };
+
+  class LIBPROTOBUF_EXPORT iterator : public std::iterator<std::forward_iterator_tag, value_type> {
+    typedef typename hash_map<Key, value_type*>::iterator InnerIt;
+
+   public:
+    iterator() {}
+    explicit iterator(const InnerIt& it) : it_(it) {}
+
+    reference operator*() const { return *it_->second; }
+    pointer operator->() const { return it_->second; }
+
+    iterator& operator++() {
+      ++it_;
+      return *this;
+    }
+    iterator operator++(int) { return iterator(it_++); }
+
+    // Implicitly convertible to const_iterator.
+    operator const_iterator() const { return const_iterator(it_); }
+
+    friend bool operator==(const iterator& a, const iterator& b) {
+      return a.it_ == b.it_;
+    }
+    friend bool operator!=(const iterator& a, const iterator& b) {
+      return a.it_ != b.it_;
+    }
+
+   private:
+    friend class Map;
+    InnerIt it_;
+  };
+
   iterator begin() { return iterator(elements_.begin()); }
   iterator end() { return iterator(elements_.end()); }
-  const_iterator begin() const {
-    return const_iterator(
-        const_cast<hash_map<Key, value_type*>&>(elements_).begin());
-  }
-  const_iterator end() const {
-    return const_iterator(
-        const_cast<hash_map<Key, value_type*>&>(elements_).end());
-  }
+  const_iterator begin() const { return const_iterator(elements_.begin()); }
+  const_iterator end() const { return const_iterator(elements_.end()); }
   const_iterator cbegin() const { return begin(); }
   const_iterator cend() const { return end(); }
 
@@ -197,16 +209,30 @@ class Map {
     return elements_.count(key);
   }
   const_iterator find(const key_type& key) const {
-    // When elements_ is a const instance, find(key) returns a const iterator.
-    // However, to reduce code complexity, we use MapIterator for Map's both
-    // const and non-const iterator, which only takes non-const iterator to
-    // construct.
-    return const_iterator(
-        const_cast<hash_map<Key, value_type*>&>(elements_).find(key));
+    return const_iterator(elements_.find(key));
   }
   iterator find(const key_type& key) {
     return iterator(elements_.find(key));
   }
+  std::pair<const_iterator, const_iterator> equal_range(
+      const key_type& key) const {
+    const_iterator it = find(key);
+    if (it == end()) {
+      return std::pair<const_iterator, const_iterator>(it, it);
+    } else {
+      const_iterator begin = it++;
+      return std::pair<const_iterator, const_iterator>(begin, it);
+    }
+  }
+  std::pair<iterator, iterator> equal_range(const key_type& key) {
+    iterator it = find(key);
+    if (it == end()) {
+      return std::pair<iterator, iterator>(it, it);
+    } else {
+      iterator begin = it++;
+      return std::pair<iterator, iterator>(begin, it);
+    }
+  }
 
   // insert
   std::pair<iterator, bool> insert(const value_type& value) {
@@ -214,8 +240,9 @@ class Map {
     if (it != end()) {
       return std::pair<iterator, bool>(it, false);
     } else {
-      return elements_.insert(
-          std::pair<Key, value_type*>(value.first, new value_type(value)));
+      return std::pair<iterator, bool>(
+          iterator(elements_.insert(std::pair<Key, value_type*>(
+              value.first, new value_type(value))).first), true);
     }
   }
   template <class InputIt>
@@ -258,7 +285,10 @@ class Map {
 
   // Assign
   Map& operator=(const Map& other) {
-    insert(other.begin(), other.end());
+    if (this != &other) {
+      clear();
+      insert(other.begin(), other.end());
+    }
     return *this;
   }
 
diff --git a/src/google/protobuf/map_test.cc b/src/google/protobuf/map_test.cc
index f3583a83..f9544efb 100644
--- a/src/google/protobuf/map_test.cc
+++ b/src/google/protobuf/map_test.cc
@@ -237,6 +237,57 @@ TEST_F(MapImplTest, GetReferenceFromIterator) {
   }
 }
 
+TEST_F(MapImplTest, IteratorBasic) {
+  map_[0] = 0;
+
+  // Default constructible (per forward iterator requirements).
+  Map<int, int>::const_iterator cit;
+  Map<int, int>::iterator it;
+
+  it = map_.begin();
+  cit = it;  // Converts to const_iterator
+
+  // Can compare between them.
+  EXPECT_TRUE(it == cit);
+  EXPECT_FALSE(cit != it);
+
+  // Pre increment.
+  EXPECT_FALSE(it == ++cit);
+
+  // Post increment.
+  EXPECT_FALSE(it++ == cit);
+  EXPECT_TRUE(it == cit);
+}
+
+template <typename T>
+bool IsConstHelper(T& /*t*/) {  // NOLINT. We want to catch non-const refs here.
+  return false;
+}
+template <typename T>
+bool IsConstHelper(const T& /*t*/) {
+  return true;
+}
+
+TEST_F(MapImplTest, IteratorConstness) {
+  map_[0] = 0;
+  EXPECT_TRUE(IsConstHelper(*map_.cbegin()));
+  EXPECT_TRUE(IsConstHelper(*const_map_.begin()));
+  EXPECT_FALSE(IsConstHelper(*map_.begin()));
+}
+
+bool IsForwardIteratorHelper(std::forward_iterator_tag /*tag*/) { return true; }
+template <typename T>
+bool IsForwardIteratorHelper(T /*t*/) {
+  return false;
+}
+
+TEST_F(MapImplTest, IteratorCategory) {
+  EXPECT_TRUE(IsForwardIteratorHelper(
+      std::iterator_traits<Map<int, int>::iterator>::iterator_category()));
+  EXPECT_TRUE(IsForwardIteratorHelper(std::iterator_traits<
+      Map<int, int>::const_iterator>::iterator_category()));
+}
+
 TEST_F(MapImplTest, InsertSingle) {
   int32 key = 0;
   int32 value1 = 100;
@@ -433,11 +484,23 @@ TEST_F(MapImplTest, Assigner) {
   map_.insert(map.begin(), map.end());
 
   Map<int32, int32> other;
+  int32 key_other = 123;
+  int32 value_other = 321;
+  other[key_other] = value_other;
+  EXPECT_EQ(1, other.size());
+
   other = map_;
 
   EXPECT_EQ(2, other.size());
   EXPECT_EQ(value1, other.at(key1));
   EXPECT_EQ(value2, other.at(key2));
+  EXPECT_TRUE(other.find(key_other) == other.end());
+
+  // Self assign
+  other = other;
+  EXPECT_EQ(2, other.size());
+  EXPECT_EQ(value1, other.at(key1));
+  EXPECT_EQ(value2, other.at(key2));
 }
 
 TEST_F(MapImplTest, Rehash) {
@@ -457,6 +520,30 @@ TEST_F(MapImplTest, Rehash) {
   EXPECT_TRUE(map_.empty());
 }
 
+TEST_F(MapImplTest, EqualRange) {
+  int key = 100, key_missing = 101;
+  map_[key] = 100;
+
+  std::pair<google::protobuf::Map<int32, int32>::iterator,
+            google::protobuf::Map<int32, int32>::iterator> range = map_.equal_range(key);
+  EXPECT_TRUE(map_.find(key) == range.first);
+  EXPECT_TRUE(++map_.find(key) == range.second);
+
+  range = map_.equal_range(key_missing);
+  EXPECT_TRUE(map_.end() == range.first);
+  EXPECT_TRUE(map_.end() == range.second);
+
+  std::pair<google::protobuf::Map<int32, int32>::const_iterator,
+            google::protobuf::Map<int32, int32>::const_iterator> const_range =
+      const_map_.equal_range(key);
+  EXPECT_TRUE(const_map_.find(key) == const_range.first);
+  EXPECT_TRUE(++const_map_.find(key) == const_range.second);
+
+  const_range = const_map_.equal_range(key_missing);
+  EXPECT_TRUE(const_map_.end() == const_range.first);
+  EXPECT_TRUE(const_map_.end() == const_range.second);
+}
+
 // Map Field Reflection Test ========================================
 
 static int Func(int i, int j) {
@@ -879,15 +966,14 @@ TEST_F(MapFieldReflectionTest, RepeatedFieldRefForRegularFields) {
         entry_int32_double.get(), fd_map_int32_double->message_type()->field(1),
         Func(key, -2));
     entry_string_string->GetReflection()->SetString(
-        entry_string_string.get(), fd_map_string_string->message_type()->field(0),
-        StrFunc(key, 1));
+        entry_string_string.get(),
+        fd_map_string_string->message_type()->field(0), StrFunc(key, 1));
     entry_string_string->GetReflection()->SetString(
-        entry_string_string.get(), fd_map_string_string->message_type()->field(1),
-        StrFunc(key, -5));
+        entry_string_string.get(),
+        fd_map_string_string->message_type()->field(1), StrFunc(key, -5));
     entry_int32_foreign_message->GetReflection()->SetInt32(
         entry_int32_foreign_message.get(),
-        fd_map_int32_foreign_message->message_type()->field(0),
-        key);
+        fd_map_int32_foreign_message->message_type()->field(0), key);
     Message* value_message =
         entry_int32_foreign_message->GetReflection()->MutableMessage(
             entry_int32_foreign_message.get(),
@@ -896,10 +982,10 @@ TEST_F(MapFieldReflectionTest, RepeatedFieldRefForRegularFields) {
         value_message, value_message->GetDescriptor()->FindFieldByName("c"),
         Func(key, -6));
 
-    mmf_int32_int32.Set(i, *entry_int32_int32.get());
-    mmf_int32_double.Set(i, *entry_int32_double.get());
-    mmf_string_string.Set(i, *entry_string_string.get());
-    mmf_int32_foreign_message.Set(i, *entry_int32_foreign_message.get());
+    mmf_int32_int32.Set(i, *entry_int32_int32);
+    mmf_int32_double.Set(i, *entry_int32_double);
+    mmf_string_string.Set(i, *entry_string_string);
+    mmf_int32_foreign_message.Set(i, *entry_int32_foreign_message);
   }
 
   for (int i = 0; i < 10; i++) {
diff --git a/src/google/protobuf/wire_format_lite.cc b/src/google/protobuf/wire_format_lite.cc
index 0c784e66..50616551 100644
--- a/src/google/protobuf/wire_format_lite.cc
+++ b/src/google/protobuf/wire_format_lite.cc
@@ -57,10 +57,14 @@ const int WireFormatLite::kMessageSetMessageTag;
 
 // IBM xlC requires prefixing constants with WireFormatLite::
 const int WireFormatLite::kMessageSetItemTagsSize =
-  io::CodedOutputStream::StaticVarintSize32<WireFormatLite::kMessageSetItemStartTag>::value +
-  io::CodedOutputStream::StaticVarintSize32<WireFormatLite::kMessageSetItemEndTag>::value +
-  io::CodedOutputStream::StaticVarintSize32<WireFormatLite::kMessageSetTypeIdTag>::value +
-  io::CodedOutputStream::StaticVarintSize32<WireFormatLite::kMessageSetMessageTag>::value;
+  io::CodedOutputStream::StaticVarintSize32<
+      WireFormatLite::kMessageSetItemStartTag>::value +
+  io::CodedOutputStream::StaticVarintSize32<
+      WireFormatLite::kMessageSetItemEndTag>::value +
+  io::CodedOutputStream::StaticVarintSize32<
+      WireFormatLite::kMessageSetTypeIdTag>::value +
+  io::CodedOutputStream::StaticVarintSize32<
+      WireFormatLite::kMessageSetMessageTag>::value;
 
 const WireFormatLite::CppType
 WireFormatLite::kFieldTypeToCppTypeMap[MAX_FIELD_TYPE + 1] = {