Down-integrate from internal code base.

32 files changed, 2277 insertions, 1624 deletions

diff --git a/src/google/protobuf/util/field_comparator.h b/src/google/protobuf/util/field_comparator.h
index ee676265..8b83c69f 100644
--- a/src/google/protobuf/util/field_comparator.h
+++ b/src/google/protobuf/util/field_comparator.h
@@ -93,7 +93,7 @@ class LIBPROTOBUF_EXPORT FieldComparator {
 
 // Basic implementation of FieldComparator.  Supports four modes of floating
 // point value comparison: exact, approximate using MathUtil::AlmostEqual
-// method, and arbitrarilly precise using MathUtil::WithinFracionOrMargin.
+// method, and arbitrarilly precise using MathUtil::WithinFractionOrMargin.
 class LIBPROTOBUF_EXPORT DefaultFieldComparator : public FieldComparator {
  public:
   enum FloatComparison {
diff --git a/src/google/protobuf/util/field_comparator_test.cc b/src/google/protobuf/util/field_comparator_test.cc
index d3d34602..23f7d51d 100644
--- a/src/google/protobuf/util/field_comparator_test.cc
+++ b/src/google/protobuf/util/field_comparator_test.cc
@@ -35,7 +35,12 @@
 #include <google/protobuf/unittest.pb.h>
 #include <google/protobuf/descriptor.h>
 #include <google/protobuf/stubs/mathutil.h>
-
+// This gtest header is put after mathutil.h intentionally. We have to do
+// this because mathutil.h includes mathlimits.h which requires cmath not
+// being included to compile on some versions of gcc:
+//   https://github.com/google/protobuf/blob/818c5eee08840355d70d2f3bdf1a2f17986a5e70/src/google/protobuf/stubs/mathlimits.h#L48
+// and the opensource version gtest.h header includes cmath transitively
+// somehow.
 #include <gtest/gtest.h>
 
 namespace google {
diff --git a/src/google/protobuf/util/internal/datapiece.cc b/src/google/protobuf/util/internal/datapiece.cc
index ea360798..b557429f 100644
--- a/src/google/protobuf/util/internal/datapiece.cc
+++ b/src/google/protobuf/util/internal/datapiece.cc
@@ -35,8 +35,8 @@
 #include <google/protobuf/descriptor.h>
 #include <google/protobuf/util/internal/utility.h>
 #include <google/protobuf/stubs/strutil.h>
-#include <google/protobuf/stubs/mathutil.h>
 #include <google/protobuf/stubs/mathlimits.h>
+#include <google/protobuf/stubs/mathutil.h>
 
 namespace google {
 namespace protobuf {
@@ -57,13 +57,8 @@ inline Status InvalidArgument(StringPiece value_str) {
   return Status(util::error::INVALID_ARGUMENT, value_str);
 }
 
-// For general conversion between
-//     int32, int64, uint32, uint64, double and float
-// except conversion between double and float.
 template <typename To, typename From>
-StatusOr<To> NumberConvertAndCheck(From before) {
-  if (::google::protobuf::internal::is_same<From, To>::value) return before;
-  To after = static_cast<To>(before);
+StatusOr<To> ValidateNumberConversion(To after, From before) {
   if (after == before &&
       MathUtil::Sign<From>(before) == MathUtil::Sign<To>(after)) {
     return after;
@@ -76,6 +71,27 @@ StatusOr<To> NumberConvertAndCheck(From before) {
   }
 }
 
+// For general conversion between
+//     int32, int64, uint32, uint64, double and float
+// except conversion between double and float.
+template <typename To, typename From>
+StatusOr<To> NumberConvertAndCheck(From before) {
+  if (::google::protobuf::internal::is_same<From, To>::value) return before;
+
+  To after = static_cast<To>(before);
+  return ValidateNumberConversion(after, before);
+}
+
+// For conversion to integer types (int32, int64, uint32, uint64) from floating
+// point types (double, float) only.
+template <typename To, typename From>
+StatusOr<To> FloatingPointToIntConvertAndCheck(From before) {
+  if (::google::protobuf::internal::is_same<From, To>::value) return before;
+
+  To after = static_cast<To>(before);
+  return ValidateNumberConversion(after, before);
+}
+
 // For conversion between double and float only.
 template <typename To, typename From>
 StatusOr<To> FloatingPointConvertAndCheck(From before) {
@@ -96,30 +112,50 @@ StatusOr<To> FloatingPointConvertAndCheck(From before) {
 }  // namespace
 
 StatusOr<int32> DataPiece::ToInt32() const {
-  if (type_ == TYPE_STRING) {
-    return StringToNumber<int32>(safe_strto32);
-  }
+  if (type_ == TYPE_STRING) return StringToNumber<int32>(safe_strto32);
+
+  if (type_ == TYPE_DOUBLE)
+    return FloatingPointToIntConvertAndCheck<int32, double>(double_);
+
+  if (type_ == TYPE_FLOAT)
+    return FloatingPointToIntConvertAndCheck<int32, float>(float_);
+
   return GenericConvert<int32>();
 }
 
 StatusOr<uint32> DataPiece::ToUint32() const {
-  if (type_ == TYPE_STRING) {
-    return StringToNumber<uint32>(safe_strtou32);
-  }
+  if (type_ == TYPE_STRING) return StringToNumber<uint32>(safe_strtou32);
+
+  if (type_ == TYPE_DOUBLE)
+    return FloatingPointToIntConvertAndCheck<uint32, double>(double_);
+
+  if (type_ == TYPE_FLOAT)
+    return FloatingPointToIntConvertAndCheck<uint32, float>(float_);
+
   return GenericConvert<uint32>();
 }
 
 StatusOr<int64> DataPiece::ToInt64() const {
-  if (type_ == TYPE_STRING) {
-    return StringToNumber<int64>(safe_strto64);
-  }
+  if (type_ == TYPE_STRING) return StringToNumber<int64>(safe_strto64);
+
+  if (type_ == TYPE_DOUBLE)
+    return FloatingPointToIntConvertAndCheck<int64, double>(double_);
+
+  if (type_ == TYPE_FLOAT)
+    return FloatingPointToIntConvertAndCheck<int64, float>(float_);
+
   return GenericConvert<int64>();
 }
 
 StatusOr<uint64> DataPiece::ToUint64() const {
-  if (type_ == TYPE_STRING) {
-    return StringToNumber<uint64>(safe_strtou64);
-  }
+  if (type_ == TYPE_STRING) return StringToNumber<uint64>(safe_strtou64);
+
+  if (type_ == TYPE_DOUBLE)
+    return FloatingPointToIntConvertAndCheck<uint64, double>(double_);
+
+  if (type_ == TYPE_FLOAT)
+    return FloatingPointToIntConvertAndCheck<uint64, float>(float_);
+
   return GenericConvert<uint64>();
 }
 
diff --git a/src/google/protobuf/util/internal/datapiece.h b/src/google/protobuf/util/internal/datapiece.h
index 2ab3fa88..f22bfe70 100644
--- a/src/google/protobuf/util/internal/datapiece.h
+++ b/src/google/protobuf/util/internal/datapiece.h
@@ -98,7 +98,8 @@ class LIBPROTOBUF_EXPORT DataPiece {
 
   static DataPiece NullData() { return DataPiece(TYPE_NULL, 0); }
 
-  virtual ~DataPiece() {}
+  virtual ~DataPiece() {
+  }
 
   // Accessors
   Type type() const { return type_; }
diff --git a/src/google/protobuf/util/internal/default_value_objectwriter.cc b/src/google/protobuf/util/internal/default_value_objectwriter.cc
index 97b248ff..a63e560d 100644
--- a/src/google/protobuf/util/internal/default_value_objectwriter.cc
+++ b/src/google/protobuf/util/internal/default_value_objectwriter.cc
@@ -33,6 +33,7 @@
 #include <google/protobuf/stubs/hash.h>
 
 #include <google/protobuf/util/internal/constants.h>
+#include <google/protobuf/util/internal/utility.h>
 #include <google/protobuf/stubs/map_util.h>
 
 namespace google {
@@ -42,13 +43,25 @@ using util::Status;
 using util::StatusOr;
 namespace converter {
 
+namespace {
+// Helper function to convert string value to given data type by calling the
+// passed converter function on the DataPiece created from "value" argument.
+// If value is empty or if conversion fails, the default_value is returned.
+template <typename T>
+T ConvertTo(StringPiece value, StatusOr<T> (DataPiece::*converter_fn)() const,
+            T default_value) {
+  if (value.empty()) return default_value;
+  StatusOr<T> result = (DataPiece(value).*converter_fn)();
+  return result.ok() ? result.ValueOrDie() : default_value;
+}
+}  // namespace
+
 DefaultValueObjectWriter::DefaultValueObjectWriter(
     TypeResolver* type_resolver, const google::protobuf::Type& type,
     ObjectWriter* ow)
     : typeinfo_(TypeInfo::NewTypeInfo(type_resolver)),
       own_typeinfo_(true),
       type_(type),
-      disable_normalize_(false),
       current_(NULL),
       root_(NULL),
       ow_(ow) {}
@@ -165,12 +178,6 @@ DefaultValueObjectWriter* DefaultValueObjectWriter::RenderNull(
   return this;
 }
 
-DefaultValueObjectWriter*
-DefaultValueObjectWriter::DisableCaseNormalizationForNextKey() {
-  disable_normalize_ = true;
-  return this;
-}
-
 DefaultValueObjectWriter::Node::Node(const string& name,
                                      const google::protobuf::Type* type,
                                      NodeKind kind, const DataPiece& data,
@@ -178,7 +185,6 @@ DefaultValueObjectWriter::Node::Node(const string& name,
     : name_(name),
       type_(type),
       kind_(kind),
-      disable_normalize_(false),
       is_any_(false),
       data_(data),
       is_placeholder_(is_placeholder) {}
@@ -198,10 +204,6 @@ DefaultValueObjectWriter::Node* DefaultValueObjectWriter::Node::FindChild(
 }
 
 void DefaultValueObjectWriter::Node::WriteTo(ObjectWriter* ow) {
-  if (disable_normalize_) {
-    ow->DisableCaseNormalizationForNextKey();
-  }
-
   if (kind_ == PRIMITIVE) {
     ObjectWriter::RenderDataPieceTo(data_, name_, ow);
     return;
@@ -324,6 +326,7 @@ void DefaultValueObjectWriter::Node::PopulateChildren(
         }
       }
     }
+
     if (!is_map &&
         field.cardinality() ==
             google::protobuf::Field_Cardinality_CARDINALITY_REPEATED) {
@@ -336,11 +339,11 @@ void DefaultValueObjectWriter::Node::PopulateChildren(
 
     // If the child field is of primitive type, sets its data to the default
     // value of its type.
-    google::protobuf::scoped_ptr<Node> child(
-        new Node(field.json_name(), field_type, kind,
-                 kind == PRIMITIVE ? CreateDefaultDataPieceForField(field)
-                                   : DataPiece::NullData(),
-                 true));
+    google::protobuf::scoped_ptr<Node> child(new Node(
+        field.json_name(), field_type, kind,
+        kind == PRIMITIVE ? CreateDefaultDataPieceForField(field, typeinfo)
+                          : DataPiece::NullData(),
+        true));
     new_children.push_back(child.release());
   }
   // Adds all leftover nodes in children_ to the beginning of new_child.
@@ -363,41 +366,68 @@ void DefaultValueObjectWriter::MaybePopulateChildrenOfAny(Node* node) {
   }
 }
 
+DataPiece DefaultValueObjectWriter::FindEnumDefault(
+    const google::protobuf::Field& field, const TypeInfo* typeinfo) {
+  if (!field.default_value().empty()) return DataPiece(field.default_value());
+
+  const google::protobuf::Enum* enum_type =
+      typeinfo->GetEnumByTypeUrl(field.type_url());
+  if (!enum_type) {
+    GOOGLE_LOG(WARNING) << "Could not find enum with type '" << field.type_url()
+                 << "'";
+    return DataPiece::NullData();
+  }
+  // We treat the first value as the default if none is specified.
+  return enum_type->enumvalue_size() > 0
+             ? DataPiece(enum_type->enumvalue(0).name())
+             : DataPiece::NullData();
+}
+
 DataPiece DefaultValueObjectWriter::CreateDefaultDataPieceForField(
-    const google::protobuf::Field& field) {
+    const google::protobuf::Field& field, const TypeInfo* typeinfo) {
   switch (field.kind()) {
     case google::protobuf::Field_Kind_TYPE_DOUBLE: {
-      return DataPiece(static_cast<double>(0));
+      return DataPiece(ConvertTo<double>(
+          field.default_value(), &DataPiece::ToDouble, static_cast<double>(0)));
     }
     case google::protobuf::Field_Kind_TYPE_FLOAT: {
-      return DataPiece(static_cast<float>(0));
+      return DataPiece(ConvertTo<float>(
+          field.default_value(), &DataPiece::ToFloat, static_cast<float>(0)));
     }
     case google::protobuf::Field_Kind_TYPE_INT64:
     case google::protobuf::Field_Kind_TYPE_SINT64:
     case google::protobuf::Field_Kind_TYPE_SFIXED64: {
-      return DataPiece(static_cast<int64>(0));
+      return DataPiece(ConvertTo<int64>(
+          field.default_value(), &DataPiece::ToInt64, static_cast<int64>(0)));
     }
     case google::protobuf::Field_Kind_TYPE_UINT64:
     case google::protobuf::Field_Kind_TYPE_FIXED64: {
-      return DataPiece(static_cast<uint64>(0));
+      return DataPiece(ConvertTo<uint64>(
+          field.default_value(), &DataPiece::ToUint64, static_cast<uint64>(0)));
     }
     case google::protobuf::Field_Kind_TYPE_INT32:
     case google::protobuf::Field_Kind_TYPE_SINT32:
     case google::protobuf::Field_Kind_TYPE_SFIXED32: {
-      return DataPiece(static_cast<int32>(0));
+      return DataPiece(ConvertTo<int32>(
+          field.default_value(), &DataPiece::ToInt32, static_cast<int32>(0)));
     }
     case google::protobuf::Field_Kind_TYPE_BOOL: {
-      return DataPiece(false);
+      return DataPiece(
+          ConvertTo<bool>(field.default_value(), &DataPiece::ToBool, false));
     }
     case google::protobuf::Field_Kind_TYPE_STRING: {
-      return DataPiece(string());
+      return DataPiece(field.default_value());
     }
     case google::protobuf::Field_Kind_TYPE_BYTES: {
-      return DataPiece("", false);
+      return DataPiece(field.default_value(), false);
     }
     case google::protobuf::Field_Kind_TYPE_UINT32:
     case google::protobuf::Field_Kind_TYPE_FIXED32: {
-      return DataPiece(static_cast<uint32>(0));
+      return DataPiece(ConvertTo<uint32>(
+          field.default_value(), &DataPiece::ToUint32, static_cast<uint32>(0)));
+    }
+    case google::protobuf::Field_Kind_TYPE_ENUM: {
+      return FindEnumDefault(field, typeinfo);
     }
     default: { return DataPiece::NullData(); }
   }
@@ -408,7 +438,6 @@ DefaultValueObjectWriter* DefaultValueObjectWriter::StartObject(
   if (current_ == NULL) {
     root_.reset(new Node(name.ToString(), &type_, OBJECT, DataPiece::NullData(),
                          false));
-    root_->set_disable_normalize(GetAndResetDisableNormalize());
     root_->PopulateChildren(typeinfo_);
     current_ = root_.get();
     return this;
@@ -428,7 +457,6 @@ DefaultValueObjectWriter* DefaultValueObjectWriter::StartObject(
   }
 
   child->set_is_placeholder(false);
-  child->set_disable_normalize(GetAndResetDisableNormalize());
   if (child->kind() == OBJECT && child->number_of_children() == 0) {
     child->PopulateChildren(typeinfo_);
   }
@@ -454,21 +482,18 @@ DefaultValueObjectWriter* DefaultValueObjectWriter::StartList(
   if (current_ == NULL) {
     root_.reset(
         new Node(name.ToString(), &type_, LIST, DataPiece::NullData(), false));
-    root_->set_disable_normalize(GetAndResetDisableNormalize());
     current_ = root_.get();
     return this;
   }
   MaybePopulateChildrenOfAny(current_);
   Node* child = current_->FindChild(name);
   if (child == NULL || child->kind() != LIST) {
-    GOOGLE_LOG(WARNING) << "Cannot find field '" << name << "'.";
     google::protobuf::scoped_ptr<Node> node(
         new Node(name.ToString(), NULL, LIST, DataPiece::NullData(), false));
     child = node.get();
     current_->AddChild(node.release());
   }
   child->set_is_placeholder(false);
-  child->set_disable_normalize(GetAndResetDisableNormalize());
 
   stack_.push(current_);
   current_ = child;
@@ -526,7 +551,6 @@ void DefaultValueObjectWriter::RenderDataPiece(StringPiece name,
   } else {
     child->set_data(data);
   }
-  child->set_disable_normalize(GetAndResetDisableNormalize());
 }
 
 }  // namespace converter
diff --git a/src/google/protobuf/util/internal/default_value_objectwriter.h b/src/google/protobuf/util/internal/default_value_objectwriter.h
index bcb526e8..695b9dd8 100644
--- a/src/google/protobuf/util/internal/default_value_objectwriter.h
+++ b/src/google/protobuf/util/internal/default_value_objectwriter.h
@@ -98,8 +98,6 @@ class LIBPROTOBUF_EXPORT DefaultValueObjectWriter : public ObjectWriter {
 
   virtual DefaultValueObjectWriter* RenderNull(StringPiece name);
 
-  virtual DefaultValueObjectWriter* DisableCaseNormalizationForNextKey();
-
  private:
   enum NodeKind {
     PRIMITIVE = 0,
@@ -149,10 +147,6 @@ class LIBPROTOBUF_EXPORT DefaultValueObjectWriter : public ObjectWriter {
 
     void set_data(const DataPiece& data) { data_ = data; }
 
-    void set_disable_normalize(bool disable_normalize) {
-      disable_normalize_ = disable_normalize;
-    }
-
     bool is_any() { return is_any_; }
 
     void set_is_any(bool is_any) { is_any_ = is_any; }
@@ -176,8 +170,6 @@ class LIBPROTOBUF_EXPORT DefaultValueObjectWriter : public ObjectWriter {
     const google::protobuf::Type* type_;
     // The kind of this node.
     NodeKind kind_;
-    // Whether to disable case normalization of the name.
-    bool disable_normalize_;
     // Whether this is a node for "Any".
     bool is_any_;
     // The data of this node when it is a leaf node.
@@ -201,16 +193,17 @@ class LIBPROTOBUF_EXPORT DefaultValueObjectWriter : public ObjectWriter {
 
   // Creates a DataPiece containing the default value of the type of the field.
   static DataPiece CreateDefaultDataPieceForField(
-      const google::protobuf::Field& field);
-
-  // Returns disable_normalize_ and reset it to false.
-  bool GetAndResetDisableNormalize() {
-    return disable_normalize_ ? (disable_normalize_ = false, true) : false;
-  }
+      const google::protobuf::Field& field, const TypeInfo* typeinfo);
 
   // Adds or replaces the data_ of a primitive child node.
   void RenderDataPiece(StringPiece name, const DataPiece& data);
 
+  // Returns the default enum value as a DataPiece, or the first enum value if
+  // there is no default. For proto3, where we cannot specify an explicit
+  // default, a zero value will always be returned.
+  static DataPiece FindEnumDefault(const google::protobuf::Field& field,
+                                   const TypeInfo* typeinfo);
+
   // Type information for all the types used in the descriptor. Used to find
   // google::protobuf::Type of nested messages/enums.
   const TypeInfo* typeinfo_;
@@ -221,8 +214,6 @@ class LIBPROTOBUF_EXPORT DefaultValueObjectWriter : public ObjectWriter {
   // Holds copies of strings passed to RenderString.
   vector<string*> string_values_;
 
-  // Whether to disable case normalization of the next node.
-  bool disable_normalize_;
   // The current Node. Owned by its parents.
   Node* current_;
   // The root Node.
diff --git a/src/google/protobuf/util/internal/default_value_objectwriter_test.cc b/src/google/protobuf/util/internal/default_value_objectwriter_test.cc
index 237d0722..b7a537ab 100644
--- a/src/google/protobuf/util/internal/default_value_objectwriter_test.cc
+++ b/src/google/protobuf/util/internal/default_value_objectwriter_test.cc
@@ -43,21 +43,19 @@ namespace testing {
 
 using google::protobuf::testing::DefaultValueTest;
 
-// Tests to cover some basic DefaultValueObjectWriter use cases. More tests are
-// in the marshalling_test.cc and translator_integration_test.cc.
-class DefaultValueObjectWriterTest
+// Base class for setting up required state for running default values tests on
+// different descriptors.
+class BaseDefaultValueObjectWriterTest
     : public ::testing::TestWithParam<testing::TypeInfoSource> {
  protected:
-  DefaultValueObjectWriterTest()
+  explicit BaseDefaultValueObjectWriterTest(const Descriptor* descriptor)
       : helper_(GetParam()), mock_(), expects_(&mock_) {
-    helper_.ResetTypeInfo(DefaultValueTest::descriptor());
+    helper_.ResetTypeInfo(descriptor);
     testing_.reset(helper_.NewDefaultValueWriter(
-        string(kTypeServiceBaseUrl) + "/" +
-            DefaultValueTest::descriptor()->full_name(),
-        &mock_));
+        string(kTypeServiceBaseUrl) + "/" + descriptor->full_name(), &mock_));
   }
 
-  virtual ~DefaultValueObjectWriterTest() {}
+  ~BaseDefaultValueObjectWriterTest() override {}
 
   TypeInfoTestHelper helper_;
   MockObjectWriter mock_;
@@ -65,6 +63,15 @@ class DefaultValueObjectWriterTest
   google::protobuf::scoped_ptr<DefaultValueObjectWriter> testing_;
 };
 
+// Tests to cover some basic DefaultValueObjectWriter use cases. More tests are
+// in the marshalling_test.cc and translator_integration_test.cc.
+class DefaultValueObjectWriterTest : public BaseDefaultValueObjectWriterTest {
+ protected:
+  DefaultValueObjectWriterTest()
+      : BaseDefaultValueObjectWriterTest(DefaultValueTest::descriptor()) {}
+  ~DefaultValueObjectWriterTest() override {}
+};
+
 INSTANTIATE_TEST_CASE_P(DifferentTypeInfoSourceTest,
                         DefaultValueObjectWriterTest,
                         ::testing::Values(
@@ -74,6 +81,8 @@ TEST_P(DefaultValueObjectWriterTest, Empty) {
   // Set expectation
   expects_.StartObject("")
       ->RenderDouble("doubleValue", 0.0)
+      ->StartList("repeatedDouble")
+      ->EndList()
       ->RenderFloat("floatValue", 0.0)
       ->RenderInt64("int64Value", 0)
       ->RenderUint64("uint64Value", 0)
@@ -82,6 +91,7 @@ TEST_P(DefaultValueObjectWriterTest, Empty) {
       ->RenderBool("boolValue", false)
       ->RenderString("stringValue", "")
       ->RenderBytes("bytesValue", "")
+      ->RenderString("enumValue", "ENUM_FIRST")
       ->EndObject();
 
   // Actual testing
@@ -92,6 +102,8 @@ TEST_P(DefaultValueObjectWriterTest, NonDefaultDouble) {
   // Set expectation
   expects_.StartObject("")
       ->RenderDouble("doubleValue", 1.0)
+      ->StartList("repeatedDouble")
+      ->EndList()
       ->RenderFloat("floatValue", 0.0)
       ->RenderInt64("int64Value", 0)
       ->RenderUint64("uint64Value", 0)
@@ -99,6 +111,7 @@ TEST_P(DefaultValueObjectWriterTest, NonDefaultDouble) {
       ->RenderUint32("uint32Value", 0)
       ->RenderBool("boolValue", false)
       ->RenderString("stringValue", "")
+      ->RenderString("enumValue", "ENUM_FIRST")
       ->EndObject();
 
   // Actual testing
@@ -109,6 +122,8 @@ TEST_P(DefaultValueObjectWriterTest, ShouldRetainUnknownField) {
   // Set expectation
   expects_.StartObject("")
       ->RenderDouble("doubleValue", 1.0)
+      ->StartList("repeatedDouble")
+      ->EndList()
       ->RenderFloat("floatValue", 0.0)
       ->RenderInt64("int64Value", 0)
       ->RenderUint64("uint64Value", 0)
@@ -120,6 +135,7 @@ TEST_P(DefaultValueObjectWriterTest, ShouldRetainUnknownField) {
       ->StartObject("unknownObject")
       ->RenderString("unknown", "def")
       ->EndObject()
+      ->RenderString("enumValue", "ENUM_FIRST")
       ->EndObject();
 
   // Actual testing
@@ -132,6 +148,7 @@ TEST_P(DefaultValueObjectWriterTest, ShouldRetainUnknownField) {
       ->EndObject();
 }
 
+
 }  // namespace testing
 }  // namespace converter
 }  // namespace util
diff --git a/src/google/protobuf/util/internal/error_listener.h b/src/google/protobuf/util/internal/error_listener.h
index 2699684d..3f063936 100644
--- a/src/google/protobuf/util/internal/error_listener.h
+++ b/src/google/protobuf/util/internal/error_listener.h
@@ -31,11 +31,13 @@
 #ifndef GOOGLE_PROTOBUF_UTIL_CONVERTER_ERROR_LISTENER_H__
 #define GOOGLE_PROTOBUF_UTIL_CONVERTER_ERROR_LISTENER_H__
 
+#include <algorithm>
 #include <memory>
 #ifndef _SHARED_PTR_H
 #include <google/protobuf/stubs/shared_ptr.h>
 #endif
 #include <string>
+#include <vector>
 
 #include <google/protobuf/stubs/callback.h>
 #include <google/protobuf/stubs/common.h>
diff --git a/src/google/protobuf/util/internal/json_objectwriter_test.cc b/src/google/protobuf/util/internal/json_objectwriter_test.cc
index dcd60601..9d820162 100644
--- a/src/google/protobuf/util/internal/json_objectwriter_test.cc
+++ b/src/google/protobuf/util/internal/json_objectwriter_test.cc
@@ -47,8 +47,7 @@ class JsonObjectWriterTest : public ::testing::Test {
   JsonObjectWriterTest()
       : str_stream_(new StringOutputStream(&output_)),
         out_stream_(new CodedOutputStream(str_stream_)),
-        ow_(NULL) {
-  }
+        ow_(NULL) {}
 
   virtual ~JsonObjectWriterTest() {
     delete ow_;
@@ -64,36 +63,34 @@ class JsonObjectWriterTest : public ::testing::Test {
 
 TEST_F(JsonObjectWriterTest, EmptyRootObject) {
   ow_ = new JsonObjectWriter("", out_stream_);
-  ow_->StartObject("")
-     ->EndObject();
+  ow_->StartObject("")->EndObject();
   EXPECT_EQ("{}", output_.substr(0, out_stream_->ByteCount()));
 }
 
 TEST_F(JsonObjectWriterTest, EmptyObject) {
   ow_ = new JsonObjectWriter("", out_stream_);
   ow_->StartObject("")
-       ->RenderString("test", "value")
-       ->StartObject("empty")
-       ->EndObject()
-     ->EndObject();
+      ->RenderString("test", "value")
+      ->StartObject("empty")
+      ->EndObject()
+      ->EndObject();
   EXPECT_EQ("{\"test\":\"value\",\"empty\":{}}",
             output_.substr(0, out_stream_->ByteCount()));
 }
 
 TEST_F(JsonObjectWriterTest, EmptyRootList) {
   ow_ = new JsonObjectWriter("", out_stream_);
-  ow_->StartList("")
-     ->EndList();
+  ow_->StartList("")->EndList();
   EXPECT_EQ("[]", output_.substr(0, out_stream_->ByteCount()));
 }
 
 TEST_F(JsonObjectWriterTest, EmptyList) {
   ow_ = new JsonObjectWriter("", out_stream_);
   ow_->StartObject("")
-       ->RenderString("test", "value")
-       ->StartList("empty")
-       ->EndList()
-     ->EndObject();
+      ->RenderString("test", "value")
+      ->StartList("empty")
+      ->EndList()
+      ->EndObject();
   EXPECT_EQ("{\"test\":\"value\",\"empty\":[]}",
             output_.substr(0, out_stream_->ByteCount()));
 }
@@ -101,10 +98,10 @@ TEST_F(JsonObjectWriterTest, EmptyList) {
 TEST_F(JsonObjectWriterTest, ObjectInObject) {
   ow_ = new JsonObjectWriter("", out_stream_);
   ow_->StartObject("")
-       ->StartObject("nested")
-         ->RenderString("field", "value")
-       ->EndObject()
-     ->EndObject();
+      ->StartObject("nested")
+      ->RenderString("field", "value")
+      ->EndObject()
+      ->EndObject();
   EXPECT_EQ("{\"nested\":{\"field\":\"value\"}}",
             output_.substr(0, out_stream_->ByteCount()));
 }
@@ -112,10 +109,10 @@ TEST_F(JsonObjectWriterTest, ObjectInObject) {
 TEST_F(JsonObjectWriterTest, ListInObject) {
   ow_ = new JsonObjectWriter("", out_stream_);
   ow_->StartObject("")
-       ->StartList("nested")
-         ->RenderString("", "value")
-       ->EndList()
-     ->EndObject();
+      ->StartList("nested")
+      ->RenderString("", "value")
+      ->EndList()
+      ->EndObject();
   EXPECT_EQ("{\"nested\":[\"value\"]}",
             output_.substr(0, out_stream_->ByteCount()));
 }
@@ -123,10 +120,10 @@ TEST_F(JsonObjectWriterTest, ListInObject) {
 TEST_F(JsonObjectWriterTest, ObjectInList) {
   ow_ = new JsonObjectWriter("", out_stream_);
   ow_->StartList("")
-       ->StartObject("")
-         ->RenderString("field", "value")
-       ->EndObject()
-     ->EndList();
+      ->StartObject("")
+      ->RenderString("field", "value")
+      ->EndObject()
+      ->EndList();
   EXPECT_EQ("[{\"field\":\"value\"}]",
             output_.substr(0, out_stream_->ByteCount()));
 }
@@ -134,10 +131,10 @@ TEST_F(JsonObjectWriterTest, ObjectInList) {
 TEST_F(JsonObjectWriterTest, ListInList) {
   ow_ = new JsonObjectWriter("", out_stream_);
   ow_->StartList("")
-       ->StartList("")
-         ->RenderString("", "value")
-       ->EndList()
-     ->EndList();
+      ->StartList("")
+      ->RenderString("", "value")
+      ->EndList()
+      ->EndList();
   EXPECT_EQ("[[\"value\"]]", output_.substr(0, out_stream_->ByteCount()));
 }
 
@@ -156,14 +153,18 @@ TEST_F(JsonObjectWriterTest, RenderPrimitives) {
       ->EndObject();
   EXPECT_EQ(
       "{\"bool\":true,"
-      "\"double\":" + ValueAsString<double>(1.7976931348623157e+308) + ","
-      "\"float\":" + ValueAsString<float>(3.4028235e+38) + ","
-      "\"int\":-2147483648,"
-      "\"long\":\"-9223372036854775808\","
-      "\"bytes\":\"YWJyYWNhZGFicmE=\","
-      "\"string\":\"string\","
-      "\"emptybytes\":\"\","
-      "\"emptystring\":\"\"}",
+      "\"double\":" +
+          ValueAsString<double>(std::numeric_limits<double>::max()) +
+          ","
+          "\"float\":" +
+          ValueAsString<float>(std::numeric_limits<float>::max()) +
+          ","
+          "\"int\":-2147483648,"
+          "\"long\":\"-9223372036854775808\","
+          "\"bytes\":\"YWJyYWNhZGFicmE=\","
+          "\"string\":\"string\","
+          "\"emptybytes\":\"\","
+          "\"emptystring\":\"\"}",
       output_.substr(0, out_stream_->ByteCount()));
 }
 
@@ -181,81 +182,83 @@ TEST_F(JsonObjectWriterTest, BytesEncodesAsNonWebSafeBase64) {
 TEST_F(JsonObjectWriterTest, PrettyPrintList) {
   ow_ = new JsonObjectWriter(" ", out_stream_);
   ow_->StartObject("")
-       ->StartList("items")
-         ->RenderString("", "item1")
-         ->RenderString("", "item2")
-         ->RenderString("", "item3")
-       ->EndList()
-       ->StartList("empty")
-       ->EndList()
-     ->EndObject();
-  EXPECT_EQ("{\n"
-            " \"items\": [\n"
-            "  \"item1\",\n"
-            "  \"item2\",\n"
-            "  \"item3\"\n"
-            " ],\n"
-            " \"empty\": []\n"
-            "}\n",
-            output_.substr(0, out_stream_->ByteCount()));
+      ->StartList("items")
+      ->RenderString("", "item1")
+      ->RenderString("", "item2")
+      ->RenderString("", "item3")
+      ->EndList()
+      ->StartList("empty")
+      ->EndList()
+      ->EndObject();
+  EXPECT_EQ(
+      "{\n"
+      " \"items\": [\n"
+      "  \"item1\",\n"
+      "  \"item2\",\n"
+      "  \"item3\"\n"
+      " ],\n"
+      " \"empty\": []\n"
+      "}\n",
+      output_.substr(0, out_stream_->ByteCount()));
 }
 
 TEST_F(JsonObjectWriterTest, PrettyPrintObject) {
   ow_ = new JsonObjectWriter(" ", out_stream_);
   ow_->StartObject("")
-       ->StartObject("items")
-         ->RenderString("key1", "item1")
-         ->RenderString("key2", "item2")
-         ->RenderString("key3", "item3")
-       ->EndObject()
-       ->StartObject("empty")
-       ->EndObject()
-     ->EndObject();
-  EXPECT_EQ("{\n"
-            " \"items\": {\n"
-            "  \"key1\": \"item1\",\n"
-            "  \"key2\": \"item2\",\n"
-            "  \"key3\": \"item3\"\n"
-            " },\n"
-            " \"empty\": {}\n"
-            "}\n",
-            output_.substr(0, out_stream_->ByteCount()));
+      ->StartObject("items")
+      ->RenderString("key1", "item1")
+      ->RenderString("key2", "item2")
+      ->RenderString("key3", "item3")
+      ->EndObject()
+      ->StartObject("empty")
+      ->EndObject()
+      ->EndObject();
+  EXPECT_EQ(
+      "{\n"
+      " \"items\": {\n"
+      "  \"key1\": \"item1\",\n"
+      "  \"key2\": \"item2\",\n"
+      "  \"key3\": \"item3\"\n"
+      " },\n"
+      " \"empty\": {}\n"
+      "}\n",
+      output_.substr(0, out_stream_->ByteCount()));
 }
 
 TEST_F(JsonObjectWriterTest, PrettyPrintEmptyObjectInEmptyList) {
   ow_ = new JsonObjectWriter(" ", out_stream_);
   ow_->StartObject("")
-       ->StartList("list")
-         ->StartObject("")
-         ->EndObject()
-       ->EndList()
-     ->EndObject();
-  EXPECT_EQ("{\n"
-            " \"list\": [\n"
-            "  {}\n"
-            " ]\n"
-            "}\n",
-            output_.substr(0, out_stream_->ByteCount()));
+      ->StartList("list")
+      ->StartObject("")
+      ->EndObject()
+      ->EndList()
+      ->EndObject();
+  EXPECT_EQ(
+      "{\n"
+      " \"list\": [\n"
+      "  {}\n"
+      " ]\n"
+      "}\n",
+      output_.substr(0, out_stream_->ByteCount()));
 }
 
 TEST_F(JsonObjectWriterTest, PrettyPrintDoubleIndent) {
   ow_ = new JsonObjectWriter("  ", out_stream_);
   ow_->StartObject("")
-       ->RenderBool("bool", true)
-       ->RenderInt32("int", 42)
-     ->EndObject();
-  EXPECT_EQ("{\n"
-            "  \"bool\": true,\n"
-            "  \"int\": 42\n"
-            "}\n",
-            output_.substr(0, out_stream_->ByteCount()));
+      ->RenderBool("bool", true)
+      ->RenderInt32("int", 42)
+      ->EndObject();
+  EXPECT_EQ(
+      "{\n"
+      "  \"bool\": true,\n"
+      "  \"int\": 42\n"
+      "}\n",
+      output_.substr(0, out_stream_->ByteCount()));
 }
 
 TEST_F(JsonObjectWriterTest, StringsEscapedAndEnclosedInDoubleQuotes) {
   ow_ = new JsonObjectWriter("", out_stream_);
-  ow_->StartObject("")
-       ->RenderString("string", "'<>&amp;\\\"\r\n")
-     ->EndObject();
+  ow_->StartObject("")->RenderString("string", "'<>&amp;\\\"\r\n")->EndObject();
   EXPECT_EQ("{\"string\":\"'\\u003c\\u003e&amp;\\\\\\\"\\r\\n\"}",
             output_.substr(0, out_stream_->ByteCount()));
 }
@@ -263,13 +266,13 @@ TEST_F(JsonObjectWriterTest, StringsEscapedAndEnclosedInDoubleQuotes) {
 TEST_F(JsonObjectWriterTest, Stringification) {
   ow_ = new JsonObjectWriter("", out_stream_);
   ow_->StartObject("")
-       ->RenderDouble("double_nan", std::numeric_limits<double>::quiet_NaN())
-       ->RenderFloat("float_nan", std::numeric_limits<float>::quiet_NaN())
-       ->RenderDouble("double_pos", std::numeric_limits<double>::infinity())
-       ->RenderFloat("float_pos", std::numeric_limits<float>::infinity())
-       ->RenderDouble("double_neg", -std::numeric_limits<double>::infinity())
-       ->RenderFloat("float_neg", -std::numeric_limits<float>::infinity())
-     ->EndObject();
+      ->RenderDouble("double_nan", std::numeric_limits<double>::quiet_NaN())
+      ->RenderFloat("float_nan", std::numeric_limits<float>::quiet_NaN())
+      ->RenderDouble("double_pos", std::numeric_limits<double>::infinity())
+      ->RenderFloat("float_pos", std::numeric_limits<float>::infinity())
+      ->RenderDouble("double_neg", -std::numeric_limits<double>::infinity())
+      ->RenderFloat("float_neg", -std::numeric_limits<float>::infinity())
+      ->EndObject();
   EXPECT_EQ(
       "{\"double_nan\":\"NaN\","
       "\"float_nan\":\"NaN\","
diff --git a/src/google/protobuf/util/internal/json_stream_parser.cc b/src/google/protobuf/util/internal/json_stream_parser.cc
index a7ef7fe2..df916751 100644
--- a/src/google/protobuf/util/internal/json_stream_parser.cc
+++ b/src/google/protobuf/util/internal/json_stream_parser.cc
@@ -157,10 +157,10 @@ util::Status JsonStreamParser::FinishParse() {
     char* coerced = internal::UTF8CoerceToStructurallyValid(leftover_, utf8.get(), ' ');
     p_ = json_ = StringPiece(coerced, leftover_.size());
   } else {
+    p_ = json_ = leftover_;
     if (!internal::IsStructurallyValidUTF8(leftover_)) {
       return ReportFailure("Encountered non UTF-8 code points.");
     }
-    p_ = json_ = leftover_;
   }
 
   // Parse the remainder in finishing mode, which reports errors for things like
diff --git a/src/google/protobuf/util/internal/json_stream_parser_test.cc b/src/google/protobuf/util/internal/json_stream_parser_test.cc
index c833ed1f..3414826e 100644
--- a/src/google/protobuf/util/internal/json_stream_parser_test.cc
+++ b/src/google/protobuf/util/internal/json_stream_parser_test.cc
@@ -348,6 +348,7 @@ TEST_F(JsonStreamParserTest, RejectNonUtf8WhenNotCoerced) {
   for (int i = 0; i <= json.length(); ++i) {
     DoErrorTest(json, i, "Encountered non UTF-8 code points.");
   }
+  DoErrorTest("\xFF{}", 0, "Encountered non UTF-8 code points.");
 }
 
 #ifndef _MSC_VER
diff --git a/src/google/protobuf/util/internal/object_writer.h b/src/google/protobuf/util/internal/object_writer.h
index 20bd3627..e695f45e 100644
--- a/src/google/protobuf/util/internal/object_writer.h
+++ b/src/google/protobuf/util/internal/object_writer.h
@@ -101,11 +101,6 @@ class LIBPROTOBUF_EXPORT ObjectWriter {
   // Renders a Null value.
   virtual ObjectWriter* RenderNull(StringPiece name) = 0;
 
-  // Disables case normalization. Any RenderTYPE call after calling this
-  // function will output the name field as-is. No normalization is attempted on
-  // it. This setting is reset immediately after the next RenderTYPE is called.
-  virtual ObjectWriter* DisableCaseNormalizationForNextKey() { return this; }
-
   // Renders a DataPiece object to a ObjectWriter.
   static void RenderDataPieceTo(const DataPiece& data, StringPiece name,
                                 ObjectWriter* ow);
diff --git a/src/google/protobuf/util/internal/proto_writer.cc b/src/google/protobuf/util/internal/proto_writer.cc
new file mode 100644
index 00000000..47e0009e
--- /dev/null
+++ b/src/google/protobuf/util/internal/proto_writer.cc
@@ -0,0 +1,744 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/util/internal/proto_writer.h>
+
+#include <functional>
+#include <stack>
+
+#include <google/protobuf/stubs/once.h>
+#include <google/protobuf/stubs/time.h>
+#include <google/protobuf/wire_format_lite.h>
+#include <google/protobuf/util/internal/field_mask_utility.h>
+#include <google/protobuf/util/internal/object_location_tracker.h>
+#include <google/protobuf/util/internal/constants.h>
+#include <google/protobuf/util/internal/utility.h>
+#include <google/protobuf/stubs/strutil.h>
+#include <google/protobuf/stubs/map_util.h>
+#include <google/protobuf/stubs/statusor.h>
+
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+
+using google::protobuf::internal::WireFormatLite;
+using google::protobuf::io::CodedOutputStream;
+using util::error::INVALID_ARGUMENT;
+using util::Status;
+using util::StatusOr;
+
+
+ProtoWriter::ProtoWriter(TypeResolver* type_resolver,
+                         const google::protobuf::Type& type,
+                         strings::ByteSink* output, ErrorListener* listener)
+    : master_type_(type),
+      typeinfo_(TypeInfo::NewTypeInfo(type_resolver)),
+      own_typeinfo_(true),
+      done_(false),
+      element_(NULL),
+      size_insert_(),
+      output_(output),
+      buffer_(),
+      adapter_(&buffer_),
+      stream_(new CodedOutputStream(&adapter_)),
+      listener_(listener),
+      invalid_depth_(0),
+      tracker_(new ObjectLocationTracker()) {}
+
+ProtoWriter::ProtoWriter(const TypeInfo* typeinfo,
+                         const google::protobuf::Type& type,
+                         strings::ByteSink* output, ErrorListener* listener)
+    : master_type_(type),
+      typeinfo_(typeinfo),
+      own_typeinfo_(false),
+      done_(false),
+      element_(NULL),
+      size_insert_(),
+      output_(output),
+      buffer_(),
+      adapter_(&buffer_),
+      stream_(new CodedOutputStream(&adapter_)),
+      listener_(listener),
+      invalid_depth_(0),
+      tracker_(new ObjectLocationTracker()) {}
+
+ProtoWriter::~ProtoWriter() {
+  if (own_typeinfo_) {
+    delete typeinfo_;
+  }
+  if (element_ == NULL) return;
+  // Cleanup explicitly in order to avoid destructor stack overflow when input
+  // is deeply nested.
+  // Cast to BaseElement to avoid doing additional checks (like missing fields)
+  // during pop().
+  google::protobuf::scoped_ptr<BaseElement> element(
+      static_cast<BaseElement*>(element_.get())->pop<BaseElement>());
+  while (element != NULL) {
+    element.reset(element->pop<BaseElement>());
+  }
+}
+
+namespace {
+
+// Writes an INT32 field, including tag to the stream.
+inline Status WriteInt32(int field_number, const DataPiece& data,
+                         CodedOutputStream* stream) {
+  StatusOr<int32> i32 = data.ToInt32();
+  if (i32.ok()) {
+    WireFormatLite::WriteInt32(field_number, i32.ValueOrDie(), stream);
+  }
+  return i32.status();
+}
+
+// writes an SFIXED32 field, including tag, to the stream.
+inline Status WriteSFixed32(int field_number, const DataPiece& data,
+                            CodedOutputStream* stream) {
+  StatusOr<int32> i32 = data.ToInt32();
+  if (i32.ok()) {
+    WireFormatLite::WriteSFixed32(field_number, i32.ValueOrDie(), stream);
+  }
+  return i32.status();
+}
+
+// Writes an SINT32 field, including tag, to the stream.
+inline Status WriteSInt32(int field_number, const DataPiece& data,
+                          CodedOutputStream* stream) {
+  StatusOr<int32> i32 = data.ToInt32();
+  if (i32.ok()) {
+    WireFormatLite::WriteSInt32(field_number, i32.ValueOrDie(), stream);
+  }
+  return i32.status();
+}
+
+// Writes a FIXED32 field, including tag, to the stream.
+inline Status WriteFixed32(int field_number, const DataPiece& data,
+                           CodedOutputStream* stream) {
+  StatusOr<uint32> u32 = data.ToUint32();
+  if (u32.ok()) {
+    WireFormatLite::WriteFixed32(field_number, u32.ValueOrDie(), stream);
+  }
+  return u32.status();
+}
+
+// Writes a UINT32 field, including tag, to the stream.
+inline Status WriteUInt32(int field_number, const DataPiece& data,
+                          CodedOutputStream* stream) {
+  StatusOr<uint32> u32 = data.ToUint32();
+  if (u32.ok()) {
+    WireFormatLite::WriteUInt32(field_number, u32.ValueOrDie(), stream);
+  }
+  return u32.status();
+}
+
+// Writes an INT64 field, including tag, to the stream.
+inline Status WriteInt64(int field_number, const DataPiece& data,
+                         CodedOutputStream* stream) {
+  StatusOr<int64> i64 = data.ToInt64();
+  if (i64.ok()) {
+    WireFormatLite::WriteInt64(field_number, i64.ValueOrDie(), stream);
+  }
+  return i64.status();
+}
+
+// Writes an SFIXED64 field, including tag, to the stream.
+inline Status WriteSFixed64(int field_number, const DataPiece& data,
+                            CodedOutputStream* stream) {
+  StatusOr<int64> i64 = data.ToInt64();
+  if (i64.ok()) {
+    WireFormatLite::WriteSFixed64(field_number, i64.ValueOrDie(), stream);
+  }
+  return i64.status();
+}
+
+// Writes an SINT64 field, including tag, to the stream.
+inline Status WriteSInt64(int field_number, const DataPiece& data,
+                          CodedOutputStream* stream) {
+  StatusOr<int64> i64 = data.ToInt64();
+  if (i64.ok()) {
+    WireFormatLite::WriteSInt64(field_number, i64.ValueOrDie(), stream);
+  }
+  return i64.status();
+}
+
+// Writes a FIXED64 field, including tag, to the stream.
+inline Status WriteFixed64(int field_number, const DataPiece& data,
+                           CodedOutputStream* stream) {
+  StatusOr<uint64> u64 = data.ToUint64();
+  if (u64.ok()) {
+    WireFormatLite::WriteFixed64(field_number, u64.ValueOrDie(), stream);
+  }
+  return u64.status();
+}
+
+// Writes a UINT64 field, including tag, to the stream.
+inline Status WriteUInt64(int field_number, const DataPiece& data,
+                          CodedOutputStream* stream) {
+  StatusOr<uint64> u64 = data.ToUint64();
+  if (u64.ok()) {
+    WireFormatLite::WriteUInt64(field_number, u64.ValueOrDie(), stream);
+  }
+  return u64.status();
+}
+
+// Writes a DOUBLE field, including tag, to the stream.
+inline Status WriteDouble(int field_number, const DataPiece& data,
+                          CodedOutputStream* stream) {
+  StatusOr<double> d = data.ToDouble();
+  if (d.ok()) {
+    WireFormatLite::WriteDouble(field_number, d.ValueOrDie(), stream);
+  }
+  return d.status();
+}
+
+// Writes a FLOAT field, including tag, to the stream.
+inline Status WriteFloat(int field_number, const DataPiece& data,
+                         CodedOutputStream* stream) {
+  StatusOr<float> f = data.ToFloat();
+  if (f.ok()) {
+    WireFormatLite::WriteFloat(field_number, f.ValueOrDie(), stream);
+  }
+  return f.status();
+}
+
+// Writes a BOOL field, including tag, to the stream.
+inline Status WriteBool(int field_number, const DataPiece& data,
+                        CodedOutputStream* stream) {
+  StatusOr<bool> b = data.ToBool();
+  if (b.ok()) {
+    WireFormatLite::WriteBool(field_number, b.ValueOrDie(), stream);
+  }
+  return b.status();
+}
+
+// Writes a BYTES field, including tag, to the stream.
+inline Status WriteBytes(int field_number, const DataPiece& data,
+                         CodedOutputStream* stream) {
+  StatusOr<string> c = data.ToBytes();
+  if (c.ok()) {
+    WireFormatLite::WriteBytes(field_number, c.ValueOrDie(), stream);
+  }
+  return c.status();
+}
+
+// Writes a STRING field, including tag, to the stream.
+inline Status WriteString(int field_number, const DataPiece& data,
+                          CodedOutputStream* stream) {
+  StatusOr<string> s = data.ToString();
+  if (s.ok()) {
+    WireFormatLite::WriteString(field_number, s.ValueOrDie(), stream);
+  }
+  return s.status();
+}
+
+// Writes an ENUM field, including tag, to the stream.
+inline Status WriteEnum(int field_number, const DataPiece& data,
+                        const google::protobuf::Enum* enum_type,
+                        CodedOutputStream* stream) {
+  StatusOr<int> e = data.ToEnum(enum_type);
+  if (e.ok()) {
+    WireFormatLite::WriteEnum(field_number, e.ValueOrDie(), stream);
+  }
+  return e.status();
+}
+
+// Given a google::protobuf::Type, returns the set of all required fields.
+std::set<const google::protobuf::Field*> GetRequiredFields(
+    const google::protobuf::Type& type) {
+  std::set<const google::protobuf::Field*> required;
+  for (int i = 0; i < type.fields_size(); i++) {
+    const google::protobuf::Field& field = type.fields(i);
+    if (field.cardinality() ==
+        google::protobuf::Field_Cardinality_CARDINALITY_REQUIRED) {
+      required.insert(&field);
+    }
+  }
+  return required;
+}
+
+}  // namespace
+
+ProtoWriter::ProtoElement::ProtoElement(const TypeInfo* typeinfo,
+                                        const google::protobuf::Type& type,
+                                        ProtoWriter* enclosing)
+    : BaseElement(NULL),
+      ow_(enclosing),
+      parent_field_(NULL),
+      typeinfo_(typeinfo),
+      type_(type),
+      required_fields_(GetRequiredFields(type)),
+      size_index_(-1),
+      array_index_(-1) {}
+
+ProtoWriter::ProtoElement::ProtoElement(ProtoWriter::ProtoElement* parent,
+                                        const google::protobuf::Field* field,
+                                        const google::protobuf::Type& type,
+                                        bool is_list)
+    : BaseElement(parent),
+      ow_(this->parent()->ow_),
+      parent_field_(field),
+      typeinfo_(this->parent()->typeinfo_),
+      type_(type),
+      size_index_(
+          !is_list && field->kind() == google::protobuf::Field_Kind_TYPE_MESSAGE
+              ? ow_->size_insert_.size()
+              : -1),
+      array_index_(is_list ? 0 : -1) {
+  if (!is_list) {
+    if (ow_->IsRepeated(*field)) {
+      // Update array_index_ if it is an explicit list.
+      if (this->parent()->array_index_ >= 0) this->parent()->array_index_++;
+    } else {
+      this->parent()->RegisterField(field);
+    }
+
+    if (field->kind() == google::protobuf::Field_Kind_TYPE_MESSAGE) {
+      required_fields_ = GetRequiredFields(type_);
+      int start_pos = ow_->stream_->ByteCount();
+      // length of serialized message is the final buffer position minus
+      // starting buffer position, plus length adjustments for size fields
+      // of any nested messages. We start with -start_pos here, so we only
+      // need to add the final buffer position to it at the end.
+      SizeInfo info = {start_pos, -start_pos};
+      ow_->size_insert_.push_back(info);
+    }
+  }
+}
+
+ProtoWriter::ProtoElement* ProtoWriter::ProtoElement::pop() {
+  // Calls the registered error listener for any required field(s) not yet
+  // seen.
+  for (set<const google::protobuf::Field*>::iterator it =
+           required_fields_.begin();
+       it != required_fields_.end(); ++it) {
+    ow_->MissingField((*it)->name());
+  }
+  // Computes the total number of proto bytes used by a message, also adjusts
+  // the size of all parent messages by the length of this size field.
+  // If size_index_ < 0, this is not a message, so no size field is added.
+  if (size_index_ >= 0) {
+    // Add the final buffer position to compute the total length of this
+    // serialized message. The stored value (before this addition) already
+    // contains the total length of the size fields of all nested messages
+    // minus the initial buffer position.
+    ow_->size_insert_[size_index_].size += ow_->stream_->ByteCount();
+    // Calculate the length required to serialize the size field of the
+    // message, and propagate this additional size information upward to
+    // all enclosing messages.
+    int size = ow_->size_insert_[size_index_].size;
+    int length = CodedOutputStream::VarintSize32(size);
+    for (ProtoElement* e = parent(); e != NULL; e = e->parent()) {
+      // Only nested messages have size field, lists do not have size field.
+      if (e->size_index_ >= 0) {
+        ow_->size_insert_[e->size_index_].size += length;
+      }
+    }
+  }
+  return BaseElement::pop<ProtoElement>();
+}
+
+void ProtoWriter::ProtoElement::RegisterField(
+    const google::protobuf::Field* field) {
+  if (!required_fields_.empty() &&
+      field->cardinality() ==
+          google::protobuf::Field_Cardinality_CARDINALITY_REQUIRED) {
+    required_fields_.erase(field);
+  }
+}
+
+string ProtoWriter::ProtoElement::ToString() const {
+  if (parent() == NULL) return "";
+  string loc = parent()->ToString();
+  if (!ow_->IsRepeated(*parent_field_) ||
+      parent()->parent_field_ != parent_field_) {
+    string name = parent_field_->name();
+    int i = 0;
+    while (i < name.size() && (ascii_isalnum(name[i]) || name[i] == '_')) ++i;
+    if (i > 0 && i == name.size()) {  // safe field name
+      if (loc.empty()) {
+        loc = name;
+      } else {
+        StrAppend(&loc, ".", name);
+      }
+    } else {
+      StrAppend(&loc, "[\"", CEscape(name), "\"]");
+    }
+  }
+  if (ow_->IsRepeated(*parent_field_) && array_index_ > 0) {
+    StrAppend(&loc, "[", array_index_ - 1, "]");
+  }
+  return loc.empty() ? "." : loc;
+}
+
+bool ProtoWriter::ProtoElement::IsOneofIndexTaken(int32 index) {
+  return ContainsKey(oneof_indices_, index);
+}
+
+void ProtoWriter::ProtoElement::TakeOneofIndex(int32 index) {
+  InsertIfNotPresent(&oneof_indices_, index);
+}
+
+void ProtoWriter::InvalidName(StringPiece unknown_name, StringPiece message) {
+  listener_->InvalidName(location(), ToSnakeCase(unknown_name), message);
+}
+
+void ProtoWriter::InvalidValue(StringPiece type_name, StringPiece value) {
+  listener_->InvalidValue(location(), type_name, value);
+}
+
+void ProtoWriter::MissingField(StringPiece missing_name) {
+  listener_->MissingField(location(), missing_name);
+}
+
+ProtoWriter* ProtoWriter::StartObject(StringPiece name) {
+  // Starting the root message. Create the root ProtoElement and return.
+  if (element_ == NULL) {
+    if (!name.empty()) {
+      InvalidName(name, "Root element should not be named.");
+    }
+    element_.reset(new ProtoElement(typeinfo_, master_type_, this));
+    return this;
+  }
+
+  const google::protobuf::Field* field = NULL;
+  field = BeginNamed(name, false);
+  if (field == NULL) return this;
+
+  // Check to see if this field is a oneof and that no oneof in that group has
+  // already been set.
+  if (!ValidOneof(*field, name)) {
+    ++invalid_depth_;
+    return this;
+  }
+
+  const google::protobuf::Type* type = LookupType(field);
+  if (type == NULL) {
+    ++invalid_depth_;
+    InvalidName(name,
+                StrCat("Missing descriptor for field: ", field->type_url()));
+    return this;
+  }
+
+    WriteTag(*field);
+  element_.reset(new ProtoElement(element_.release(), field, *type, false));
+  return this;
+}
+
+ProtoWriter* ProtoWriter::EndObject() {
+  if (invalid_depth_ > 0) {
+    --invalid_depth_;
+    return this;
+  }
+
+  if (element_ != NULL) {
+    element_.reset(element_->pop());
+  }
+
+
+  // If ending the root element,
+  // then serialize the full message with calculated sizes.
+  if (element_ == NULL) {
+    WriteRootMessage();
+  }
+  return this;
+}
+
+ProtoWriter* ProtoWriter::StartList(StringPiece name) {
+  const google::protobuf::Field* field = BeginNamed(name, true);
+  if (field == NULL) return this;
+
+  if (!ValidOneof(*field, name)) {
+    ++invalid_depth_;
+    return this;
+  }
+
+  const google::protobuf::Type* type = LookupType(field);
+  if (type == NULL) {
+    ++invalid_depth_;
+    InvalidName(name,
+                StrCat("Missing descriptor for field: ", field->type_url()));
+    return this;
+  }
+
+  element_.reset(new ProtoElement(element_.release(), field, *type, true));
+  return this;
+}
+
+ProtoWriter* ProtoWriter::EndList() {
+  if (invalid_depth_ > 0) {
+    --invalid_depth_;
+  } else if (element_ != NULL) {
+    element_.reset(element_->pop());
+  }
+  return this;
+}
+
+ProtoWriter* ProtoWriter::RenderDataPiece(StringPiece name,
+                                          const DataPiece& data) {
+  Status status;
+  if (invalid_depth_ > 0) return this;
+
+  const google::protobuf::Field* field = Lookup(name);
+  if (field == NULL) return this;
+
+  if (!ValidOneof(*field, name)) return this;
+
+  const google::protobuf::Type* type = LookupType(field);
+  if (type == NULL) {
+    InvalidName(name,
+                StrCat("Missing descriptor for field: ", field->type_url()));
+    return this;
+  }
+
+  // Pushing a ProtoElement and then pop it off at the end for 2 purposes:
+  // error location reporting and required field accounting.
+  element_.reset(new ProtoElement(element_.release(), field, *type, false));
+
+  if (field->kind() == google::protobuf::Field_Kind_TYPE_UNKNOWN ||
+      field->kind() == google::protobuf::Field_Kind_TYPE_MESSAGE) {
+    InvalidValue(field->type_url().empty()
+                     ? google::protobuf::Field_Kind_Name(field->kind())
+                     : field->type_url(),
+                 data.ValueAsStringOrDefault(""));
+    element_.reset(element()->pop());
+    return this;
+  }
+
+  switch (field->kind()) {
+    case google::protobuf::Field_Kind_TYPE_INT32: {
+      status = WriteInt32(field->number(), data, stream_.get());
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_SFIXED32: {
+      status = WriteSFixed32(field->number(), data, stream_.get());
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_SINT32: {
+      status = WriteSInt32(field->number(), data, stream_.get());
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_FIXED32: {
+      status = WriteFixed32(field->number(), data, stream_.get());
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_UINT32: {
+      status = WriteUInt32(field->number(), data, stream_.get());
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_INT64: {
+      status = WriteInt64(field->number(), data, stream_.get());
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_SFIXED64: {
+      status = WriteSFixed64(field->number(), data, stream_.get());
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_SINT64: {
+      status = WriteSInt64(field->number(), data, stream_.get());
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_FIXED64: {
+      status = WriteFixed64(field->number(), data, stream_.get());
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_UINT64: {
+      status = WriteUInt64(field->number(), data, stream_.get());
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_DOUBLE: {
+      status = WriteDouble(field->number(), data, stream_.get());
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_FLOAT: {
+      status = WriteFloat(field->number(), data, stream_.get());
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_BOOL: {
+      status = WriteBool(field->number(), data, stream_.get());
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_BYTES: {
+      status = WriteBytes(field->number(), data, stream_.get());
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_STRING: {
+      status = WriteString(field->number(), data, stream_.get());
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_ENUM: {
+      status = WriteEnum(field->number(), data,
+                         typeinfo_->GetEnumByTypeUrl(field->type_url()),
+                         stream_.get());
+      break;
+    }
+    default:  // TYPE_GROUP or TYPE_MESSAGE
+      status = Status(INVALID_ARGUMENT, data.ToString().ValueOrDie());
+  }
+
+  if (!status.ok()) {
+    InvalidValue(google::protobuf::Field_Kind_Name(field->kind()),
+                 status.error_message());
+  }
+
+  element_.reset(element()->pop());
+  return this;
+}
+
+bool ProtoWriter::ValidOneof(const google::protobuf::Field& field,
+                             StringPiece unnormalized_name) {
+  if (element_ == NULL) return true;
+
+  if (field.oneof_index() > 0) {
+    if (element_->IsOneofIndexTaken(field.oneof_index())) {
+      InvalidValue(
+          "oneof",
+          StrCat("oneof field '",
+                 element_->type().oneofs(field.oneof_index() - 1),
+                 "' is already set. Cannot set '", unnormalized_name, "'"));
+      return false;
+    }
+    element_->TakeOneofIndex(field.oneof_index());
+  }
+  return true;
+}
+
+bool ProtoWriter::IsRepeated(const google::protobuf::Field& field) {
+  return field.cardinality() ==
+         google::protobuf::Field_Cardinality_CARDINALITY_REPEATED;
+}
+
+const google::protobuf::Field* ProtoWriter::BeginNamed(StringPiece name,
+                                                       bool is_list) {
+  if (invalid_depth_ > 0) {
+    ++invalid_depth_;
+    return NULL;
+  }
+  const google::protobuf::Field* field = Lookup(name);
+  if (field == NULL) {
+    ++invalid_depth_;
+    // InvalidName() already called in Lookup().
+    return NULL;
+  }
+  if (is_list && !IsRepeated(*field)) {
+    ++invalid_depth_;
+    InvalidName(name, "Proto field is not repeating, cannot start list.");
+    return NULL;
+  }
+  return field;
+}
+
+const google::protobuf::Field* ProtoWriter::Lookup(
+    StringPiece unnormalized_name) {
+  ProtoElement* e = element();
+  if (e == NULL) {
+    InvalidName(unnormalized_name, "Root element must be a message.");
+    return NULL;
+  }
+  if (unnormalized_name.empty()) {
+    // Objects in repeated field inherit the same field descriptor.
+    if (e->parent_field() == NULL) {
+      InvalidName(unnormalized_name, "Proto fields must have a name.");
+    } else if (!IsRepeated(*e->parent_field())) {
+      InvalidName(unnormalized_name, "Proto fields must have a name.");
+      return NULL;
+    }
+    return e->parent_field();
+  }
+  const google::protobuf::Field* field =
+      typeinfo_->FindField(&e->type(), unnormalized_name);
+  if (field == NULL) InvalidName(unnormalized_name, "Cannot find field.");
+  return field;
+}
+
+const google::protobuf::Type* ProtoWriter::LookupType(
+    const google::protobuf::Field* field) {
+  return ((field->kind() == google::protobuf::Field_Kind_TYPE_MESSAGE ||
+           field->kind() == google::protobuf::Field_Kind_TYPE_GROUP)
+              ? typeinfo_->GetTypeByTypeUrl(field->type_url())
+              : &element_->type());
+}
+
+void ProtoWriter::WriteRootMessage() {
+  GOOGLE_DCHECK(!done_);
+  int curr_pos = 0;
+  // Calls the destructor of CodedOutputStream to remove any uninitialized
+  // memory from the Cord before we read it.
+  stream_.reset(NULL);
+  const void* data;
+  int length;
+  google::protobuf::io::ArrayInputStream input_stream(buffer_.data(), buffer_.size());
+  while (input_stream.Next(&data, &length)) {
+    if (length == 0) continue;
+    int num_bytes = length;
+    // Write up to where we need to insert the size field.
+    // The number of bytes we may write is the smaller of:
+    //   - the current fragment size
+    //   - the distance to the next position where a size field needs to be
+    //     inserted.
+    if (!size_insert_.empty() &&
+        size_insert_.front().pos - curr_pos < num_bytes) {
+      num_bytes = size_insert_.front().pos - curr_pos;
+    }
+    output_->Append(static_cast<const char*>(data), num_bytes);
+    if (num_bytes < length) {
+      input_stream.BackUp(length - num_bytes);
+    }
+    curr_pos += num_bytes;
+    // Insert the size field.
+    //   size_insert_.front():      the next <index, size> pair to be written.
+    //   size_insert_.front().pos:  position of the size field.
+    //   size_insert_.front().size: the size (integer) to be inserted.
+    if (!size_insert_.empty() && curr_pos == size_insert_.front().pos) {
+      // Varint32 occupies at most 10 bytes.
+      uint8 insert_buffer[10];
+      uint8* insert_buffer_pos = CodedOutputStream::WriteVarint32ToArray(
+          size_insert_.front().size, insert_buffer);
+      output_->Append(reinterpret_cast<const char*>(insert_buffer),
+                      insert_buffer_pos - insert_buffer);
+      size_insert_.pop_front();
+    }
+  }
+  output_->Flush();
+  stream_.reset(new CodedOutputStream(&adapter_));
+  done_ = true;
+}
+
+void ProtoWriter::WriteTag(const google::protobuf::Field& field) {
+  WireFormatLite::WireType wire_type = WireFormatLite::WireTypeForFieldType(
+      static_cast<WireFormatLite::FieldType>(field.kind()));
+  stream_->WriteTag(WireFormatLite::MakeTag(field.number(), wire_type));
+}
+
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/internal/proto_writer.h b/src/google/protobuf/util/internal/proto_writer.h
new file mode 100644
index 00000000..e631e56f
--- /dev/null
+++ b/src/google/protobuf/util/internal/proto_writer.h
@@ -0,0 +1,315 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_PROTOBUF_UTIL_CONVERTER_PROTO_WRITER_H__
+#define GOOGLE_PROTOBUF_UTIL_CONVERTER_PROTO_WRITER_H__
+
+#include <deque>
+#include <google/protobuf/stubs/hash.h>
+#include <string>
+
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/io/coded_stream.h>
+#include <google/protobuf/io/zero_copy_stream_impl.h>
+#include <google/protobuf/descriptor.h>
+#include <google/protobuf/util/internal/type_info.h>
+#include <google/protobuf/util/internal/datapiece.h>
+#include <google/protobuf/util/internal/error_listener.h>
+#include <google/protobuf/util/internal/structured_objectwriter.h>
+#include <google/protobuf/util/type_resolver.h>
+#include <google/protobuf/stubs/bytestream.h>
+
+namespace google {
+namespace protobuf {
+namespace io {
+class CodedOutputStream;
+}  // namespace io
+}  // namespace protobuf
+
+
+namespace protobuf {
+class Type;
+class Field;
+}  // namespace protobuf
+
+
+namespace protobuf {
+namespace util {
+namespace converter {
+
+class ObjectLocationTracker;
+
+// An ObjectWriter that can write protobuf bytes directly from writer events.
+// This class does not support special types like Struct or Map. However, since
+// this class supports raw protobuf, it can be used to provide support for
+// special types by inheriting from it or by wrapping it.
+//
+// It also supports streaming.
+class LIBPROTOBUF_EXPORT ProtoWriter : public StructuredObjectWriter {
+ public:
+// Constructor. Does not take ownership of any parameter passed in.
+  ProtoWriter(TypeResolver* type_resolver, const google::protobuf::Type& type,
+              strings::ByteSink* output, ErrorListener* listener);
+  virtual ~ProtoWriter();
+
+  // ObjectWriter methods.
+  virtual ProtoWriter* StartObject(StringPiece name);
+  virtual ProtoWriter* EndObject();
+  virtual ProtoWriter* StartList(StringPiece name);
+  virtual ProtoWriter* EndList();
+  virtual ProtoWriter* RenderBool(StringPiece name, bool value) {
+    return RenderDataPiece(name, DataPiece(value));
+  }
+  virtual ProtoWriter* RenderInt32(StringPiece name, int32 value) {
+    return RenderDataPiece(name, DataPiece(value));
+  }
+  virtual ProtoWriter* RenderUint32(StringPiece name, uint32 value) {
+    return RenderDataPiece(name, DataPiece(value));
+  }
+  virtual ProtoWriter* RenderInt64(StringPiece name, int64 value) {
+    return RenderDataPiece(name, DataPiece(value));
+  }
+  virtual ProtoWriter* RenderUint64(StringPiece name, uint64 value) {
+    return RenderDataPiece(name, DataPiece(value));
+  }
+  virtual ProtoWriter* RenderDouble(StringPiece name, double value) {
+    return RenderDataPiece(name, DataPiece(value));
+  }
+  virtual ProtoWriter* RenderFloat(StringPiece name, float value) {
+    return RenderDataPiece(name, DataPiece(value));
+  }
+  virtual ProtoWriter* RenderString(StringPiece name, StringPiece value) {
+    return RenderDataPiece(name, DataPiece(value));
+  }
+  virtual ProtoWriter* RenderBytes(StringPiece name, StringPiece value) {
+    return RenderDataPiece(name, DataPiece(value, false));
+  }
+  virtual ProtoWriter* RenderNull(StringPiece name) {
+    return RenderDataPiece(name, DataPiece::NullData());
+  }
+
+  // Renders a DataPiece 'value' into a field whose wire type is determined
+  // from the given field 'name'.
+  virtual ProtoWriter* RenderDataPiece(StringPiece name,
+                                       const DataPiece& value);
+
+  // Returns the location tracker to use for tracking locations for errors.
+  const LocationTrackerInterface& location() {
+    return element_ != NULL ? *element_ : *tracker_;
+  }
+
+  // When true, we finished writing to output a complete message.
+  bool done() const { return done_; }
+
+  // Returns the proto stream object.
+  google::protobuf::io::CodedOutputStream* stream() { return stream_.get(); }
+
+  // Getters and mutators of invalid_depth_.
+  void IncrementInvalidDepth() { ++invalid_depth_; }
+  void DecrementInvalidDepth() { --invalid_depth_; }
+  int invalid_depth() { return invalid_depth_; }
+
+  ErrorListener* listener() { return listener_; }
+
+  const TypeInfo* typeinfo() { return typeinfo_; }
+
+ protected:
+  class LIBPROTOBUF_EXPORT ProtoElement : public BaseElement, public LocationTrackerInterface {
+   public:
+    // Constructor for the root element. No parent nor field.
+    ProtoElement(const TypeInfo* typeinfo, const google::protobuf::Type& type,
+                 ProtoWriter* enclosing);
+
+    // Constructor for a field of an element.
+    ProtoElement(ProtoElement* parent, const google::protobuf::Field* field,
+                 const google::protobuf::Type& type, bool is_list);
+
+    virtual ~ProtoElement() {}
+
+    // Called just before the destructor for clean up:
+    //   - reports any missing required fields
+    //   - computes the space needed by the size field, and augment the
+    //     length of all parent messages by this additional space.
+    //   - releases and returns the parent pointer.
+    ProtoElement* pop();
+
+    // Accessors
+    // parent_field() may be NULL if we are at root.
+    const google::protobuf::Field* parent_field() const {
+      return parent_field_;
+    }
+    const google::protobuf::Type& type() const { return type_; }
+
+    // Registers field for accounting required fields.
+    void RegisterField(const google::protobuf::Field* field);
+
+    // To report location on error messages.
+    virtual string ToString() const;
+
+    virtual ProtoElement* parent() const {
+      return static_cast<ProtoElement*>(BaseElement::parent());
+    }
+
+    // Returns true if the index is already taken by a preceeding oneof input.
+    bool IsOneofIndexTaken(int32 index);
+
+    // Marks the oneof 'index' as taken. Future inputs to this oneof will
+    // generate an error.
+    void TakeOneofIndex(int32 index);
+
+   private:
+    // Used for access to variables of the enclosing instance of
+    // ProtoWriter.
+    ProtoWriter* ow_;
+
+    // Describes the element as a field in the parent message.
+    // parent_field_ is NULL if and only if this element is the root element.
+    const google::protobuf::Field* parent_field_;
+
+    // TypeInfo to lookup types.
+    const TypeInfo* typeinfo_;
+
+    // Additional variables if this element is a message:
+    // (Root element is always a message).
+    // type_             : the type of this element.
+    // required_fields_  : set of required fields.
+    // size_index_       : index into ProtoWriter::size_insert_
+    //                     for later insertion of serialized message length.
+    const google::protobuf::Type& type_;
+    std::set<const google::protobuf::Field*> required_fields_;
+    const int size_index_;
+
+    // Tracks position in repeated fields, needed for LocationTrackerInterface.
+    int array_index_;
+
+    // Set of oneof indices already seen for the type_. Used to validate
+    // incoming messages so no more than one oneof is set.
+    hash_set<int32> oneof_indices_;
+
+    GOOGLE_DISALLOW_IMPLICIT_CONSTRUCTORS(ProtoElement);
+  };
+
+  // Container for inserting 'size' information at the 'pos' position.
+  struct SizeInfo {
+    const int pos;
+    int size;
+  };
+
+  ProtoWriter(const TypeInfo* typeinfo, const google::protobuf::Type& type,
+              strings::ByteSink* output, ErrorListener* listener);
+
+  virtual ProtoElement* element() { return element_.get(); }
+
+  // Helper methods for calling ErrorListener. See error_listener.h.
+  void InvalidName(StringPiece unknown_name, StringPiece message);
+  void InvalidValue(StringPiece type_name, StringPiece value);
+  void MissingField(StringPiece missing_name);
+
+  // Common code for BeginObject() and BeginList() that does invalid_depth_
+  // bookkeeping associated with name lookup.
+  const google::protobuf::Field* BeginNamed(StringPiece name, bool is_list);
+
+  // Lookup the field in the current element. Looks in the base descriptor
+  // and in any extension. This will report an error if the field cannot be
+  // found or if multiple matching extensions are found.
+  const google::protobuf::Field* Lookup(StringPiece name);
+
+  // Lookup the field type in the type descriptor. Returns NULL if the type
+  // is not known.
+  const google::protobuf::Type* LookupType(
+      const google::protobuf::Field* field);
+
+  // Write serialized output to the final output ByteSink, inserting all
+  // the size information for nested messages that are missing from the
+  // intermediate Cord buffer.
+  void WriteRootMessage();
+
+  // Helper method to write proto tags based on the given field.
+  void WriteTag(const google::protobuf::Field& field);
+
+
+  // Returns true if the field for type_ can be set as a oneof. If field is not
+  // a oneof type, this function does nothing and returns true.
+  // If another field for this oneof is already set, this function returns
+  // false. It also calls the appropriate error callback.
+  // unnormalized_name is used for error string.
+  bool ValidOneof(const google::protobuf::Field& field,
+                  StringPiece unnormalized_name);
+
+  // Returns true if the field is repeated.
+  bool IsRepeated(const google::protobuf::Field& field);
+
+ private:
+  // Variables for describing the structure of the input tree:
+  // master_type_: descriptor for the whole protobuf message.
+  // typeinfo_ : the TypeInfo object to lookup types.
+  const google::protobuf::Type& master_type_;
+  const TypeInfo* typeinfo_;
+  // Whether we own the typeinfo_ object.
+  bool own_typeinfo_;
+
+  // Indicates whether we finished writing root message completely.
+  bool done_;
+
+  // Variable for internal state processing:
+  // element_    : the current element.
+  // size_insert_: sizes of nested messages.
+  //               pos  - position to insert the size field.
+  //               size - size value to be inserted.
+  google::protobuf::scoped_ptr<ProtoElement> element_;
+  std::deque<SizeInfo> size_insert_;
+
+  // Variables for output generation:
+  // output_  : pointer to an external ByteSink for final user-visible output.
+  // buffer_  : buffer holding partial message before being ready for output_.
+  // adapter_ : internal adapter between CodedOutputStream and buffer_.
+  // stream_  : wrapper for writing tags and other encodings in wire format.
+  strings::ByteSink* output_;
+  string buffer_;
+  google::protobuf::io::StringOutputStream adapter_;
+  google::protobuf::scoped_ptr<google::protobuf::io::CodedOutputStream> stream_;
+
+  // Variables for error tracking and reporting:
+  // listener_     : a place to report any errors found.
+  // invalid_depth_: number of enclosing invalid nested messages.
+  // tracker_      : the root location tracker interface.
+  ErrorListener* listener_;
+  int invalid_depth_;
+  google::protobuf::scoped_ptr<LocationTrackerInterface> tracker_;
+
+  GOOGLE_DISALLOW_IMPLICIT_CONSTRUCTORS(ProtoWriter);
+};
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_CONVERTER_PROTO_WRITER_H__
diff --git a/src/google/protobuf/util/internal/protostream_objectsource.cc b/src/google/protobuf/util/internal/protostream_objectsource.cc
index 2bbb1597..034d616f 100644
--- a/src/google/protobuf/util/internal/protostream_objectsource.cc
+++ b/src/google/protobuf/util/internal/protostream_objectsource.cc
@@ -140,10 +140,10 @@ Status ProtoStreamObjectSource::WriteMessage(const google::protobuf::Type& type,
                                              bool include_start_and_end,
                                              ObjectWriter* ow) const {
 
-  const TypeRenderer* type_renderer = FindTypeRenderer(type.name());
-  if (type_renderer != NULL) {
-    return (*type_renderer)(this, type, name, ow);
-  }
+    const TypeRenderer* type_renderer = FindTypeRenderer(type.name());
+    if (type_renderer != NULL) {
+      return (*type_renderer)(this, type, name, ow);
+    }
 
   const google::protobuf::Field* field = NULL;
   string field_name;
@@ -171,7 +171,9 @@ Status ProtoStreamObjectSource::WriteMessage(const google::protobuf::Type& type,
 
     if (field->cardinality() ==
         google::protobuf::Field_Cardinality_CARDINALITY_REPEATED) {
-      if (IsMap(*field)) {
+      bool check_maps = true;
+
+      if (check_maps && IsMap(*field)) {
         ow->StartObject(field_name);
         ASSIGN_OR_RETURN(tag, RenderMap(field, field_name, tag, ow));
         ow->EndObject();
@@ -218,48 +220,32 @@ StatusOr<uint32> ProtoStreamObjectSource::RenderMap(
   const google::protobuf::Type* field_type =
       typeinfo_->GetTypeByTypeUrl(field->type_url());
   uint32 tag_to_return = 0;
-  if (IsPackable(*field) &&
-      list_tag ==
-          WireFormatLite::MakeTag(field->number(),
-                                  WireFormatLite::WIRETYPE_LENGTH_DELIMITED)) {
-    RETURN_IF_ERROR(RenderPackedMapEntry(field_type, ow));
-    tag_to_return = stream_->ReadTag();
-  } else {
-    do {
-      RETURN_IF_ERROR(RenderMapEntry(field_type, ow));
-    } while ((tag_to_return = stream_->ReadTag()) == list_tag);
-  }
-  return tag_to_return;
-}
-
-Status ProtoStreamObjectSource::RenderMapEntry(
-    const google::protobuf::Type* type, ObjectWriter* ow) const {
-  uint32 buffer32;
-  stream_->ReadVarint32(&buffer32);  // message length
-  int old_limit = stream_->PushLimit(buffer32);
-  string map_key;
-  for (uint32 tag = stream_->ReadTag(); tag != 0; tag = stream_->ReadTag()) {
-    const google::protobuf::Field* field = FindAndVerifyField(*type, tag);
-    if (field == NULL) {
-      WireFormat::SkipField(stream_, tag, NULL);
-      continue;
-    }
-    // Map field numbers are key = 1 and value = 2
-    if (field->number() == 1) {
-      map_key = ReadFieldValueAsString(*field);
-    } else if (field->number() == 2) {
-      if (map_key.empty()) {
-        return Status(util::error::INTERNAL, "Map key must be non-empty");
+  do {
+    // Render map entry message type.
+    uint32 buffer32;
+    stream_->ReadVarint32(&buffer32);  // message length
+    int old_limit = stream_->PushLimit(buffer32);
+    string map_key;
+    for (uint32 tag = stream_->ReadTag(); tag != 0; tag = stream_->ReadTag()) {
+      const google::protobuf::Field* field =
+          FindAndVerifyField(*field_type, tag);
+      if (field == NULL) {
+        WireFormat::SkipField(stream_, tag, NULL);
+        continue;
+      }
+      // Map field numbers are key = 1 and value = 2
+      if (field->number() == 1) {
+        map_key = ReadFieldValueAsString(*field);
+      } else if (field->number() == 2) {
+        if (map_key.empty()) {
+          return Status(util::error::INTERNAL, "Map key must be non-empty");
+        }
+        RETURN_IF_ERROR(RenderField(field, map_key, ow));
       }
-      // Disable case normalization for map keys as they are just data. We
-      // retain them intact.
-      ow->DisableCaseNormalizationForNextKey();
-      RETURN_IF_ERROR(RenderField(field, map_key, ow));
     }
-  }
-  stream_->PopLimit(old_limit);
-
-  return Status::OK;
+    stream_->PopLimit(old_limit);
+  } while ((tag_to_return = stream_->ReadTag()) == list_tag);
+  return tag_to_return;
 }
 
 Status ProtoStreamObjectSource::RenderPacked(
@@ -274,18 +260,6 @@ Status ProtoStreamObjectSource::RenderPacked(
   return Status::OK;
 }
 
-Status ProtoStreamObjectSource::RenderPackedMapEntry(
-    const google::protobuf::Type* type, ObjectWriter* ow) const {
-  uint32 length;
-  stream_->ReadVarint32(&length);
-  int old_limit = stream_->PushLimit(length);
-  while (stream_->BytesUntilLimit() > 0) {
-    RETURN_IF_ERROR(RenderMapEntry(type, ow));
-  }
-  stream_->PopLimit(old_limit);
-  return Status::OK;
-}
-
 Status ProtoStreamObjectSource::RenderTimestamp(
     const ProtoStreamObjectSource* os, const google::protobuf::Type& type,
     StringPiece field_name, ObjectWriter* ow) {
@@ -601,10 +575,10 @@ Status ProtoStreamObjectSource::RenderAny(const ProtoStreamObjectSource* os,
   // nested_type cannot be null at this time.
   const google::protobuf::Type* nested_type = resolved_type.ValueOrDie();
 
-  // We know the type so we can render it. Recursively parse the nested stream
-  // using a nested ProtoStreamObjectSource using our nested type information.
   google::protobuf::io::ArrayInputStream zero_copy_stream(value.data(), value.size());
   google::protobuf::io::CodedInputStream in_stream(&zero_copy_stream);
+  // We know the type so we can render it. Recursively parse the nested stream
+  // using a nested ProtoStreamObjectSource using our nested type information.
   ProtoStreamObjectSource nested_os(&in_stream, os->typeinfo_, *nested_type);
 
   // We manually call start and end object here so we can inject the @type.
@@ -676,8 +650,7 @@ void ProtoStreamObjectSource::InitRendererMap() {
       &ProtoStreamObjectSource::RenderString;
   (*renderers_)["google.protobuf.BytesValue"] =
       &ProtoStreamObjectSource::RenderBytes;
-  (*renderers_)["google.protobuf.Any"] =
-      &ProtoStreamObjectSource::RenderAny;
+  (*renderers_)["google.protobuf.Any"] = &ProtoStreamObjectSource::RenderAny;
   (*renderers_)["google.protobuf.Struct"] =
       &ProtoStreamObjectSource::RenderStruct;
   (*renderers_)["google.protobuf.Value"] =
@@ -704,87 +677,118 @@ ProtoStreamObjectSource::FindTypeRenderer(const string& type_url) {
 Status ProtoStreamObjectSource::RenderField(
     const google::protobuf::Field* field, StringPiece field_name,
     ObjectWriter* ow) const {
+  // Short-circuit message types as it tends to call WriteMessage recursively
+  // and ends up using a lot of stack space. Keep the stack usage of this
+  // message small in order to preserve stack space and not crash.
+  if (field->kind() == google::protobuf::Field_Kind_TYPE_MESSAGE) {
+    uint32 buffer32;
+    stream_->ReadVarint32(&buffer32);  // message length
+    int old_limit = stream_->PushLimit(buffer32);
+    // Get the nested message type for this field.
+    const google::protobuf::Type* type =
+        typeinfo_->GetTypeByTypeUrl(field->type_url());
+    if (type == NULL) {
+      return Status(util::error::INTERNAL,
+                    StrCat("Invalid configuration. Could not find the type: ",
+                           field->type_url()));
+    }
+
+    // Short-circuit any special type rendering to save call-stack space.
+    const TypeRenderer* type_renderer = FindTypeRenderer(type->name());
+
+    bool use_type_renderer = type_renderer != NULL;
+
+    if (use_type_renderer) {
+      RETURN_IF_ERROR((*type_renderer)(this, *type, field_name, ow));
+    } else {
+      RETURN_IF_ERROR(WriteMessage(*type, field_name, 0, true, ow));
+    }
+    if (!stream_->ConsumedEntireMessage()) {
+      return Status(util::error::INVALID_ARGUMENT,
+                    "Nested protocol message not parsed in its entirety.");
+    }
+    stream_->PopLimit(old_limit);
+  } else {
+    // Render all other non-message types.
+    return RenderNonMessageField(field, field_name, ow);
+  }
+  return Status::OK;
+}
+
+Status ProtoStreamObjectSource::RenderNonMessageField(
+    const google::protobuf::Field* field, StringPiece field_name,
+    ObjectWriter* ow) const {
+  // Temporary buffers of different types.
+  uint32 buffer32;
+  uint64 buffer64;
+  string strbuffer;
   switch (field->kind()) {
     case google::protobuf::Field_Kind_TYPE_BOOL: {
-      uint64 buffer64;
       stream_->ReadVarint64(&buffer64);
       ow->RenderBool(field_name, buffer64 != 0);
       break;
     }
     case google::protobuf::Field_Kind_TYPE_INT32: {
-      uint32 buffer32;
       stream_->ReadVarint32(&buffer32);
       ow->RenderInt32(field_name, bit_cast<int32>(buffer32));
       break;
     }
     case google::protobuf::Field_Kind_TYPE_INT64: {
-      uint64 buffer64;
       stream_->ReadVarint64(&buffer64);
       ow->RenderInt64(field_name, bit_cast<int64>(buffer64));
       break;
     }
     case google::protobuf::Field_Kind_TYPE_UINT32: {
-      uint32 buffer32;
       stream_->ReadVarint32(&buffer32);
       ow->RenderUint32(field_name, bit_cast<uint32>(buffer32));
       break;
     }
     case google::protobuf::Field_Kind_TYPE_UINT64: {
-      uint64 buffer64;
       stream_->ReadVarint64(&buffer64);
       ow->RenderUint64(field_name, bit_cast<uint64>(buffer64));
       break;
     }
     case google::protobuf::Field_Kind_TYPE_SINT32: {
-      uint32 buffer32;
       stream_->ReadVarint32(&buffer32);
       ow->RenderInt32(field_name, WireFormatLite::ZigZagDecode32(buffer32));
       break;
     }
     case google::protobuf::Field_Kind_TYPE_SINT64: {
-      uint64 buffer64;
       stream_->ReadVarint64(&buffer64);
       ow->RenderInt64(field_name, WireFormatLite::ZigZagDecode64(buffer64));
       break;
     }
     case google::protobuf::Field_Kind_TYPE_SFIXED32: {
-      uint32 buffer32;
       stream_->ReadLittleEndian32(&buffer32);
       ow->RenderInt32(field_name, bit_cast<int32>(buffer32));
       break;
     }
     case google::protobuf::Field_Kind_TYPE_SFIXED64: {
-      uint64 buffer64;
       stream_->ReadLittleEndian64(&buffer64);
       ow->RenderInt64(field_name, bit_cast<int64>(buffer64));
       break;
     }
     case google::protobuf::Field_Kind_TYPE_FIXED32: {
-      uint32 buffer32;
       stream_->ReadLittleEndian32(&buffer32);
       ow->RenderUint32(field_name, bit_cast<uint32>(buffer32));
       break;
     }
     case google::protobuf::Field_Kind_TYPE_FIXED64: {
-      uint64 buffer64;
       stream_->ReadLittleEndian64(&buffer64);
       ow->RenderUint64(field_name, bit_cast<uint64>(buffer64));
       break;
     }
     case google::protobuf::Field_Kind_TYPE_FLOAT: {
-      uint32 buffer32;
       stream_->ReadLittleEndian32(&buffer32);
       ow->RenderFloat(field_name, bit_cast<float>(buffer32));
       break;
     }
     case google::protobuf::Field_Kind_TYPE_DOUBLE: {
-      uint64 buffer64;
       stream_->ReadLittleEndian64(&buffer64);
       ow->RenderDouble(field_name, bit_cast<double>(buffer64));
       break;
     }
     case google::protobuf::Field_Kind_TYPE_ENUM: {
-      uint32 buffer32;
       stream_->ReadVarint32(&buffer32);
 
       // If the field represents an explicit NULL value, render null.
@@ -811,40 +815,15 @@ Status ProtoStreamObjectSource::RenderField(
       break;
     }
     case google::protobuf::Field_Kind_TYPE_STRING: {
-      uint32 buffer32;
-      string str;
       stream_->ReadVarint32(&buffer32);  // string size.
-      stream_->ReadString(&str, buffer32);
-      ow->RenderString(field_name, str);
+      stream_->ReadString(&strbuffer, buffer32);
+      ow->RenderString(field_name, strbuffer);
       break;
     }
     case google::protobuf::Field_Kind_TYPE_BYTES: {
-      uint32 buffer32;
       stream_->ReadVarint32(&buffer32);  // bytes size.
-      string value;
-      stream_->ReadString(&value, buffer32);
-      ow->RenderBytes(field_name, value);
-      break;
-    }
-    case google::protobuf::Field_Kind_TYPE_MESSAGE: {
-      uint32 buffer32;
-      stream_->ReadVarint32(&buffer32);  // message length
-      int old_limit = stream_->PushLimit(buffer32);
-      // Get the nested message type for this field.
-      const google::protobuf::Type* type =
-          typeinfo_->GetTypeByTypeUrl(field->type_url());
-      if (type == NULL) {
-        return Status(util::error::INTERNAL,
-                      StrCat("Invalid configuration. Could not find the type: ",
-                             field->type_url()));
-      }
-
-      RETURN_IF_ERROR(WriteMessage(*type, field_name, 0, true, ow));
-      if (!stream_->ConsumedEntireMessage()) {
-        return Status(util::error::INVALID_ARGUMENT,
-                      "Nested protocol message not parsed in its entirety.");
-      }
-      stream_->PopLimit(old_limit);
+      stream_->ReadString(&strbuffer, buffer32);
+      ow->RenderBytes(field_name, strbuffer);
       break;
     }
     default:
diff --git a/src/google/protobuf/util/internal/protostream_objectsource.h b/src/google/protobuf/util/internal/protostream_objectsource.h
index 3cd37aa1..78defa1d 100644
--- a/src/google/protobuf/util/internal/protostream_objectsource.h
+++ b/src/google/protobuf/util/internal/protostream_objectsource.h
@@ -122,20 +122,12 @@ class LIBPROTOBUF_EXPORT ProtoStreamObjectSource : public ObjectSource {
                                      StringPiece name, uint32 list_tag,
                                      ObjectWriter* ow) const;
 
-  // Renders an entry in a map, advancing stream pointers appropriately.
-  util::Status RenderMapEntry(const google::protobuf::Type* type,
-                                ObjectWriter* ow) const;
-
   // Renders a packed repeating field. A packed field is stored as:
   // {tag length item1 item2 item3} instead of the less efficient
   // {tag item1 tag item2 tag item3}.
   util::Status RenderPacked(const google::protobuf::Field* field,
                               ObjectWriter* ow) const;
 
-  // Equivalent of RenderPacked, but for map entries.
-  util::Status RenderPackedMapEntry(const google::protobuf::Type* type,
-                                      ObjectWriter* ow) const;
-
   // Renders a google.protobuf.Timestamp value to ObjectWriter
   static util::Status RenderTimestamp(const ProtoStreamObjectSource* os,
                                         const google::protobuf::Type& type,
@@ -210,6 +202,12 @@ class LIBPROTOBUF_EXPORT ProtoStreamObjectSource : public ObjectSource {
   util::Status RenderField(const google::protobuf::Field* field,
                              StringPiece field_name, ObjectWriter* ow) const;
 
+  // Same as above but renders all non-message field types. Callers don't call
+  // this function directly. They just use RenderField.
+  util::Status RenderNonMessageField(const google::protobuf::Field* field,
+                                       StringPiece field_name,
+                                       ObjectWriter* ow) const;
+
 
   // Reads field value according to Field spec in 'field' and returns the read
   // value as string. This only works for primitive datatypes (no message
@@ -238,6 +236,7 @@ class LIBPROTOBUF_EXPORT ProtoStreamObjectSource : public ObjectSource {
   // google::protobuf::Type of the message source.
   const google::protobuf::Type& type_;
 
+
   GOOGLE_DISALLOW_IMPLICIT_CONSTRUCTORS(ProtoStreamObjectSource);
 };
 
diff --git a/src/google/protobuf/util/internal/protostream_objectsource_test.cc b/src/google/protobuf/util/internal/protostream_objectsource_test.cc
index f6e5ee7a..561f6763 100644
--- a/src/google/protobuf/util/internal/protostream_objectsource_test.cc
+++ b/src/google/protobuf/util/internal/protostream_objectsource_test.cc
@@ -327,9 +327,16 @@ TEST_P(ProtostreamObjectSourceTest, RepeatingPrimitives) {
   DoTest(primitive, Primitive::descriptor());
 }
 
+TEST_P(ProtostreamObjectSourceTest, CustomJsonName) {
+  Author author;
+  author.set_id(12345);
+
+  ow_.StartObject("")->RenderUint64("@id", 12345)->EndObject();
+  DoTest(author, Author::descriptor());
+}
+
 TEST_P(ProtostreamObjectSourceTest, NestedMessage) {
   Author* author = new Author();
-  author->set_id(101L);
   author->set_name("Tolstoy");
   Book book;
   book.set_title("My Book");
@@ -338,7 +345,6 @@ TEST_P(ProtostreamObjectSourceTest, NestedMessage) {
   ow_.StartObject("")
       ->RenderString("title", "My Book")
       ->StartObject("author")
-      ->RenderUint64("id", bit_cast<uint64>(101LL))
       ->RenderString("name", "Tolstoy")
       ->EndObject()
       ->EndObject();
diff --git a/src/google/protobuf/util/internal/protostream_objectwriter.cc b/src/google/protobuf/util/internal/protostream_objectwriter.cc
index 0958997c..786bf0be 100644
--- a/src/google/protobuf/util/internal/protostream_objectwriter.cc
+++ b/src/google/protobuf/util/internal/protostream_objectwriter.cc
@@ -51,7 +51,6 @@ namespace util {
 namespace converter {
 
 using google::protobuf::internal::WireFormatLite;
-using google::protobuf::io::CodedOutputStream;
 using util::error::INVALID_ARGUMENT;
 using util::Status;
 using util::StatusOr;
@@ -60,230 +59,31 @@ using util::StatusOr;
 ProtoStreamObjectWriter::ProtoStreamObjectWriter(
     TypeResolver* type_resolver, const google::protobuf::Type& type,
     strings::ByteSink* output, ErrorListener* listener)
-    : master_type_(type),
-      typeinfo_(TypeInfo::NewTypeInfo(type_resolver)),
-      own_typeinfo_(true),
-      done_(false),
-      element_(NULL),
-      size_insert_(),
-      output_(output),
-      buffer_(),
-      adapter_(&buffer_),
-      stream_(new CodedOutputStream(&adapter_)),
-      listener_(listener),
-      invalid_depth_(0),
-      tracker_(new ObjectLocationTracker()) {}
+    : ProtoWriter(type_resolver, type, output, listener),
+      master_type_(type),
+      current_(NULL) {}
 
 ProtoStreamObjectWriter::ProtoStreamObjectWriter(
     const TypeInfo* typeinfo, const google::protobuf::Type& type,
     strings::ByteSink* output, ErrorListener* listener)
-    : master_type_(type),
-      typeinfo_(typeinfo),
-      own_typeinfo_(false),
-      done_(false),
-      element_(NULL),
-      size_insert_(),
-      output_(output),
-      buffer_(),
-      adapter_(&buffer_),
-      stream_(new CodedOutputStream(&adapter_)),
-      listener_(listener),
-      invalid_depth_(0),
-      tracker_(new ObjectLocationTracker()) {}
+    : ProtoWriter(typeinfo, type, output, listener),
+      master_type_(type),
+      current_(NULL) {}
 
 ProtoStreamObjectWriter::~ProtoStreamObjectWriter() {
-  if (own_typeinfo_) {
-    delete typeinfo_;
-  }
-  if (element_ == NULL) return;
+  if (current_ == NULL) return;
   // Cleanup explicitly in order to avoid destructor stack overflow when input
   // is deeply nested.
   // Cast to BaseElement to avoid doing additional checks (like missing fields)
   // during pop().
   google::protobuf::scoped_ptr<BaseElement> element(
-      static_cast<BaseElement*>(element_.get())->pop<BaseElement>());
+      static_cast<BaseElement*>(current_.get())->pop<BaseElement>());
   while (element != NULL) {
     element.reset(element->pop<BaseElement>());
   }
 }
 
 namespace {
-
-// Writes an INT32 field, including tag to the stream.
-inline Status WriteInt32(int field_number, const DataPiece& data,
-                         CodedOutputStream* stream) {
-  StatusOr<int32> i32 = data.ToInt32();
-  if (i32.ok()) {
-    WireFormatLite::WriteInt32(field_number, i32.ValueOrDie(), stream);
-  }
-  return i32.status();
-}
-
-// writes an SFIXED32 field, including tag, to the stream.
-inline Status WriteSFixed32(int field_number, const DataPiece& data,
-                            CodedOutputStream* stream) {
-  StatusOr<int32> i32 = data.ToInt32();
-  if (i32.ok()) {
-    WireFormatLite::WriteSFixed32(field_number, i32.ValueOrDie(), stream);
-  }
-  return i32.status();
-}
-
-// Writes an SINT32 field, including tag, to the stream.
-inline Status WriteSInt32(int field_number, const DataPiece& data,
-                          CodedOutputStream* stream) {
-  StatusOr<int32> i32 = data.ToInt32();
-  if (i32.ok()) {
-    WireFormatLite::WriteSInt32(field_number, i32.ValueOrDie(), stream);
-  }
-  return i32.status();
-}
-
-// Writes a FIXED32 field, including tag, to the stream.
-inline Status WriteFixed32(int field_number, const DataPiece& data,
-                           CodedOutputStream* stream) {
-  StatusOr<uint32> u32 = data.ToUint32();
-  if (u32.ok()) {
-    WireFormatLite::WriteFixed32(field_number, u32.ValueOrDie(), stream);
-  }
-  return u32.status();
-}
-
-// Writes a UINT32 field, including tag, to the stream.
-inline Status WriteUInt32(int field_number, const DataPiece& data,
-                          CodedOutputStream* stream) {
-  StatusOr<uint32> u32 = data.ToUint32();
-  if (u32.ok()) {
-    WireFormatLite::WriteUInt32(field_number, u32.ValueOrDie(), stream);
-  }
-  return u32.status();
-}
-
-// Writes an INT64 field, including tag, to the stream.
-inline Status WriteInt64(int field_number, const DataPiece& data,
-                         CodedOutputStream* stream) {
-  StatusOr<int64> i64 = data.ToInt64();
-  if (i64.ok()) {
-    WireFormatLite::WriteInt64(field_number, i64.ValueOrDie(), stream);
-  }
-  return i64.status();
-}
-
-// Writes an SFIXED64 field, including tag, to the stream.
-inline Status WriteSFixed64(int field_number, const DataPiece& data,
-                            CodedOutputStream* stream) {
-  StatusOr<int64> i64 = data.ToInt64();
-  if (i64.ok()) {
-    WireFormatLite::WriteSFixed64(field_number, i64.ValueOrDie(), stream);
-  }
-  return i64.status();
-}
-
-// Writes an SINT64 field, including tag, to the stream.
-inline Status WriteSInt64(int field_number, const DataPiece& data,
-                          CodedOutputStream* stream) {
-  StatusOr<int64> i64 = data.ToInt64();
-  if (i64.ok()) {
-    WireFormatLite::WriteSInt64(field_number, i64.ValueOrDie(), stream);
-  }
-  return i64.status();
-}
-
-// Writes a FIXED64 field, including tag, to the stream.
-inline Status WriteFixed64(int field_number, const DataPiece& data,
-                           CodedOutputStream* stream) {
-  StatusOr<uint64> u64 = data.ToUint64();
-  if (u64.ok()) {
-    WireFormatLite::WriteFixed64(field_number, u64.ValueOrDie(), stream);
-  }
-  return u64.status();
-}
-
-// Writes a UINT64 field, including tag, to the stream.
-inline Status WriteUInt64(int field_number, const DataPiece& data,
-                          CodedOutputStream* stream) {
-  StatusOr<uint64> u64 = data.ToUint64();
-  if (u64.ok()) {
-    WireFormatLite::WriteUInt64(field_number, u64.ValueOrDie(), stream);
-  }
-  return u64.status();
-}
-
-// Writes a DOUBLE field, including tag, to the stream.
-inline Status WriteDouble(int field_number, const DataPiece& data,
-                          CodedOutputStream* stream) {
-  StatusOr<double> d = data.ToDouble();
-  if (d.ok()) {
-    WireFormatLite::WriteDouble(field_number, d.ValueOrDie(), stream);
-  }
-  return d.status();
-}
-
-// Writes a FLOAT field, including tag, to the stream.
-inline Status WriteFloat(int field_number, const DataPiece& data,
-                         CodedOutputStream* stream) {
-  StatusOr<float> f = data.ToFloat();
-  if (f.ok()) {
-    WireFormatLite::WriteFloat(field_number, f.ValueOrDie(), stream);
-  }
-  return f.status();
-}
-
-// Writes a BOOL field, including tag, to the stream.
-inline Status WriteBool(int field_number, const DataPiece& data,
-                        CodedOutputStream* stream) {
-  StatusOr<bool> b = data.ToBool();
-  if (b.ok()) {
-    WireFormatLite::WriteBool(field_number, b.ValueOrDie(), stream);
-  }
-  return b.status();
-}
-
-// Writes a BYTES field, including tag, to the stream.
-inline Status WriteBytes(int field_number, const DataPiece& data,
-                         CodedOutputStream* stream) {
-  StatusOr<string> c = data.ToBytes();
-  if (c.ok()) {
-    WireFormatLite::WriteBytes(field_number, c.ValueOrDie(), stream);
-  }
-  return c.status();
-}
-
-// Writes a STRING field, including tag, to the stream.
-inline Status WriteString(int field_number, const DataPiece& data,
-                          CodedOutputStream* stream) {
-  StatusOr<string> s = data.ToString();
-  if (s.ok()) {
-    WireFormatLite::WriteString(field_number, s.ValueOrDie(), stream);
-  }
-  return s.status();
-}
-
-// Writes an ENUM field, including tag, to the stream.
-inline Status WriteEnum(int field_number, const DataPiece& data,
-                        const google::protobuf::Enum* enum_type,
-                        CodedOutputStream* stream) {
-  StatusOr<int> e = data.ToEnum(enum_type);
-  if (e.ok()) {
-    WireFormatLite::WriteEnum(field_number, e.ValueOrDie(), stream);
-  }
-  return e.status();
-}
-
-// Given a google::protobuf::Type, returns the set of all required fields.
-std::set<const google::protobuf::Field*> GetRequiredFields(
-    const google::protobuf::Type& type) {
-  std::set<const google::protobuf::Field*> required;
-  for (int i = 0; i < type.fields_size(); i++) {
-    const google::protobuf::Field& field = type.fields(i);
-    if (field.cardinality() ==
-        google::protobuf::Field_Cardinality_CARDINALITY_REQUIRED) {
-      required.insert(&field);
-    }
-  }
-  return required;
-}
-
 // Utility method to split a string representation of Timestamp or Duration and
 // return the parts.
 void SplitSecondsAndNanos(StringPiece input, StringPiece* seconds,
@@ -298,6 +98,78 @@ void SplitSecondsAndNanos(StringPiece input, StringPiece* seconds,
   }
 }
 
+Status GetNanosFromStringPiece(StringPiece s_nanos,
+                               const char* parse_failure_message,
+                               const char* exceeded_limit_message,
+                               int32* nanos) {
+  *nanos = 0;
+
+  // Count the number of leading 0s and consume them.
+  int num_leading_zeros = 0;
+  while (s_nanos.Consume("0")) {
+    num_leading_zeros++;
+  }
+  int32 i_nanos = 0;
+  // 's_nanos' contains fractional seconds -- i.e. 'nanos' is equal to
+  // "0." + s_nanos.ToString() seconds. An int32 is used for the
+  // conversion to 'nanos', rather than a double, so that there is no
+  // loss of precision.
+  if (!s_nanos.empty() && !safe_strto32(s_nanos.ToString(), &i_nanos)) {
+    return Status(INVALID_ARGUMENT, parse_failure_message);
+  }
+  if (i_nanos > kNanosPerSecond || i_nanos < 0) {
+    return Status(INVALID_ARGUMENT, exceeded_limit_message);
+  }
+  // s_nanos should only have digits. No whitespace.
+  if (s_nanos.find_first_not_of("0123456789") != StringPiece::npos) {
+    return Status(INVALID_ARGUMENT, parse_failure_message);
+  }
+
+  if (i_nanos > 0) {
+    // 'scale' is the number of digits to the right of the decimal
+    // point in "0." + s_nanos.ToString()
+    int32 scale = num_leading_zeros + s_nanos.size();
+    // 'conversion' converts i_nanos into nanoseconds.
+    // conversion = kNanosPerSecond / static_cast<int32>(std::pow(10, scale))
+    // For efficiency, we precompute the conversion factor.
+    int32 conversion = 0;
+    switch (scale) {
+      case 1:
+        conversion = 100000000;
+        break;
+      case 2:
+        conversion = 10000000;
+        break;
+      case 3:
+        conversion = 1000000;
+        break;
+      case 4:
+        conversion = 100000;
+        break;
+      case 5:
+        conversion = 10000;
+        break;
+      case 6:
+        conversion = 1000;
+        break;
+      case 7:
+        conversion = 100;
+        break;
+      case 8:
+        conversion = 10;
+        break;
+      case 9:
+        conversion = 1;
+        break;
+      default:
+        return Status(INVALID_ARGUMENT, exceeded_limit_message);
+    }
+    *nanos = i_nanos * conversion;
+  }
+
+  return Status::OK;
+}
+
 }  // namespace
 
 ProtoStreamObjectWriter::AnyWriter::AnyWriter(ProtoStreamObjectWriter* parent)
@@ -421,7 +293,7 @@ void ProtoStreamObjectWriter::AnyWriter::StartAny(const DataPiece& value) {
   }
   // Resolve the type url, and report an error if we failed to resolve it.
   StatusOr<const google::protobuf::Type*> resolved_type =
-      parent_->typeinfo_->ResolveTypeUrl(type_url_);
+      parent_->typeinfo()->ResolveTypeUrl(type_url_);
   if (!resolved_type.ok()) {
     parent_->InvalidValue("Any", resolved_type.status().error_message());
     invalid_ = true;
@@ -440,8 +312,8 @@ void ProtoStreamObjectWriter::AnyWriter::StartAny(const DataPiece& value) {
 
   // Create our object writer and initialize it with the first StartObject
   // call.
-  ow_.reset(new ProtoStreamObjectWriter(parent_->typeinfo_, *type, &output_,
-                                        parent_->listener_));
+  ow_.reset(new ProtoStreamObjectWriter(parent_->typeinfo(), *type, &output_,
+                                        parent_->listener()));
   ow_->StartObject("");
 }
 
@@ -453,604 +325,431 @@ void ProtoStreamObjectWriter::AnyWriter::WriteAny() {
   }
   // Render the type_url and value fields directly to the stream.
   // type_url has tag 1 and value has tag 2.
-  WireFormatLite::WriteString(1, type_url_, parent_->stream_.get());
+  WireFormatLite::WriteString(1, type_url_, parent_->stream());
   if (!data_.empty()) {
-    WireFormatLite::WriteBytes(2, data_, parent_->stream_.get());
+    WireFormatLite::WriteBytes(2, data_, parent_->stream());
   }
 }
 
-ProtoStreamObjectWriter::ProtoElement::ProtoElement(
-    const TypeInfo* typeinfo, const google::protobuf::Type& type,
-    ProtoStreamObjectWriter* enclosing)
+ProtoStreamObjectWriter::Item::Item(ProtoStreamObjectWriter* enclosing,
+                                    ItemType item_type, bool is_placeholder,
+                                    bool is_list)
     : BaseElement(NULL),
       ow_(enclosing),
       any_(),
-      field_(NULL),
-      typeinfo_(typeinfo),
-      type_(type),
-      required_fields_(GetRequiredFields(type)),
-      is_repeated_type_(false),
-      size_index_(-1),
-      array_index_(-1),
-      element_type_(GetElementType(type_)) {
-  if (element_type_ == ANY) {
+      item_type_(item_type),
+      is_placeholder_(is_placeholder),
+      is_list_(is_list) {
+  if (item_type_ == ANY) {
     any_.reset(new AnyWriter(ow_));
   }
 }
 
-ProtoStreamObjectWriter::ProtoElement::ProtoElement(
-    ProtoStreamObjectWriter::ProtoElement* parent,
-    const google::protobuf::Field* field, const google::protobuf::Type& type,
-    ElementType element_type)
+ProtoStreamObjectWriter::Item::Item(ProtoStreamObjectWriter::Item* parent,
+                                    ItemType item_type, bool is_placeholder,
+                                    bool is_list)
     : BaseElement(parent),
       ow_(this->parent()->ow_),
       any_(),
-      field_(field),
-      typeinfo_(this->parent()->typeinfo_),
-      type_(type),
-      is_repeated_type_(element_type == ProtoElement::LIST ||
-                        element_type == ProtoElement::STRUCT_LIST ||
-                        element_type == ProtoElement::MAP ||
-                        element_type == ProtoElement::STRUCT_MAP),
-      size_index_(!is_repeated_type_ &&
-                          field->kind() ==
-                              google::protobuf::Field_Kind_TYPE_MESSAGE
-                      ? ow_->size_insert_.size()
-                      : -1),
-      array_index_(is_repeated_type_ ? 0 : -1),
-      element_type_(element_type) {
-  if (!is_repeated_type_) {
-    if (field->cardinality() ==
-        google::protobuf::Field_Cardinality_CARDINALITY_REPEATED) {
-      // Update array_index_ if it is an explicit list.
-      if (this->parent()->array_index_ >= 0) this->parent()->array_index_++;
-    } else {
-      this->parent()->RegisterField(field);
-    }
-    if (field->kind() == google::protobuf::Field_Kind_TYPE_MESSAGE) {
-      required_fields_ = GetRequiredFields(type_);
-      int start_pos = ow_->stream_->ByteCount();
-      // length of serialized message is the final buffer position minus
-      // starting buffer position, plus length adjustments for size fields
-      // of any nested messages. We start with -start_pos here, so we only
-      // need to add the final buffer position to it at the end.
-      SizeInfo info = {start_pos, -start_pos};
-      ow_->size_insert_.push_back(info);
-    }
-  }
-  if (element_type == ANY) {
+      item_type_(item_type),
+      is_placeholder_(is_placeholder),
+      is_list_(is_list) {
+  if (item_type == ANY) {
     any_.reset(new AnyWriter(ow_));
   }
 }
 
-ProtoStreamObjectWriter::ProtoElement*
-ProtoStreamObjectWriter::ProtoElement::pop() {
-  // Calls the registered error listener for any required field(s) not yet
-  // seen.
-  for (set<const google::protobuf::Field*>::iterator it =
-           required_fields_.begin();
-       it != required_fields_.end(); ++it) {
-    ow_->MissingField((*it)->name());
-  }
-  // Computes the total number of proto bytes used by a message, also adjusts
-  // the size of all parent messages by the length of this size field.
-  // If size_index_ < 0, this is not a message, so no size field is added.
-  if (size_index_ >= 0) {
-    // Add the final buffer position to compute the total length of this
-    // serialized message. The stored value (before this addition) already
-    // contains the total length of the size fields of all nested messages
-    // minus the initial buffer position.
-    ow_->size_insert_[size_index_].size += ow_->stream_->ByteCount();
-    // Calculate the length required to serialize the size field of the
-    // message, and propagate this additional size information upward to
-    // all enclosing messages.
-    int size = ow_->size_insert_[size_index_].size;
-    int length = CodedOutputStream::VarintSize32(size);
-    for (ProtoElement* e = parent(); e != NULL; e = e->parent()) {
-      // Only nested messages have size field, lists do not have size field.
-      if (e->size_index_ >= 0) {
-        ow_->size_insert_[e->size_index_].size += length;
-      }
-    }
-  }
-  return BaseElement::pop<ProtoElement>();
-}
-
-void ProtoStreamObjectWriter::ProtoElement::RegisterField(
-    const google::protobuf::Field* field) {
-  if (!required_fields_.empty() &&
-      field->cardinality() ==
-          google::protobuf::Field_Cardinality_CARDINALITY_REQUIRED) {
-    required_fields_.erase(field);
-  }
-}
-
-string ProtoStreamObjectWriter::ProtoElement::ToString() const {
-  if (parent() == NULL) return "";
-  string loc = parent()->ToString();
-  if (field_->cardinality() !=
-          google::protobuf::Field_Cardinality_CARDINALITY_REPEATED ||
-      parent()->field_ != field_) {
-    string name = field_->name();
-    int i = 0;
-    while (i < name.size() && (ascii_isalnum(name[i]) || name[i] == '_')) ++i;
-    if (i > 0 && i == name.size()) {  // safe field name
-      if (loc.empty()) {
-        loc = name;
-      } else {
-        StrAppend(&loc, ".", name);
-      }
-    } else {
-      StrAppend(&loc, "[\"", CEscape(name), "\"]");
-    }
-  }
-  if (field_->cardinality() ==
-          google::protobuf::Field_Cardinality_CARDINALITY_REPEATED &&
-      array_index_ > 0) {
-    StrAppend(&loc, "[", array_index_ - 1, "]");
-  }
-  return loc.empty() ? "." : loc;
-}
-
-bool ProtoStreamObjectWriter::ProtoElement::OneofIndexTaken(int32 index) {
-  return ContainsKey(oneof_indices_, index);
-}
-
-void ProtoStreamObjectWriter::ProtoElement::TakeOneofIndex(int32 index) {
-  InsertIfNotPresent(&oneof_indices_, index);
-}
-
-bool ProtoStreamObjectWriter::ProtoElement::InsertMapKeyIfNotPresent(
+bool ProtoStreamObjectWriter::Item::InsertMapKeyIfNotPresent(
     StringPiece map_key) {
   return InsertIfNotPresent(&map_keys_, map_key.ToString());
 }
 
-inline void ProtoStreamObjectWriter::InvalidName(StringPiece unknown_name,
-                                                 StringPiece message) {
-  listener_->InvalidName(location(), ToSnakeCase(unknown_name), message);
-}
-
-inline void ProtoStreamObjectWriter::InvalidValue(StringPiece type_name,
-                                                  StringPiece value) {
-  listener_->InvalidValue(location(), type_name, value);
-}
-
-inline void ProtoStreamObjectWriter::MissingField(StringPiece missing_name) {
-  listener_->MissingField(location(), missing_name);
-}
-
 ProtoStreamObjectWriter* ProtoStreamObjectWriter::StartObject(
     StringPiece name) {
-  // Starting the root message. Create the root ProtoElement and return.
-  if (element_ == NULL) {
-    if (!name.empty()) {
-      InvalidName(name, "Root element should not be named.");
-    }
-    element_.reset(new ProtoElement(typeinfo_, master_type_, this));
+  if (invalid_depth() > 0) {
+    IncrementInvalidDepth();
+    return this;
+  }
+
+  // Starting the root message. Create the root Item and return.
+  // ANY message type does not need special handling, just set the ItemType
+  // to ANY.
+  if (current_ == NULL) {
+    ProtoWriter::StartObject(name);
+    current_.reset(new Item(
+        this, master_type_.name() == kAnyType ? Item::ANY : Item::MESSAGE,
+        false, false));
 
     // If master type is a special type that needs extra values to be written to
     // stream, we write those values.
     if (master_type_.name() == kStructType) {
-      StartStruct(NULL);
-    } else if (master_type_.name() == kStructValueType) {
-      // We got a StartObject call with google.protobuf.Value field. This means
-      // we are starting an object within google.protobuf.Value type. The only
-      // object within that type is a struct type. So start a struct.
-      const google::protobuf::Field* field = StartStructValueInStruct(NULL);
-      StartStruct(field);
+      // Struct has a map<string, Value> field called "fields".
+      // https://github.com/google/protobuf/blob/master/src/google/protobuf/struct.proto
+      // "fields": [
+      Push("fields", Item::MAP, true, true);
+      return this;
     }
-    return this;
-  }
 
-  const google::protobuf::Field* field = NULL;
-  if (element_ != NULL && element_->IsAny()) {
-    element_->any()->StartObject(name);
-    return this;
-  } else if (element_ != NULL &&
-             (element_->IsMap() || element_->IsStructMap())) {
-    if (!ValidMapKey(name)) {
-      ++invalid_depth_;
+    if (master_type_.name() == kStructValueType) {
+      // We got a StartObject call with google.protobuf.Value field. The only
+      // object within that type is a struct type. So start a struct.
+      //
+      // The struct field in Value type is named "struct_value"
+      // https://github.com/google/protobuf/blob/master/src/google/protobuf/struct.proto
+      // Also start the map field "fields" within the struct.
+      // "struct_value": {
+      //   "fields": [
+      Push("struct_value", Item::MESSAGE, true, false);
+      Push("fields", Item::MAP, true, true);
       return this;
     }
 
-    field = StartMapEntry(name);
-    if (element_->IsStructMapEntry()) {
-      // If the top element is a map entry, this means we are starting another
-      // struct within a struct.
-      field = StartStructValueInStruct(field);
+    if (master_type_.name() == kStructListValueType) {
+      InvalidValue(kStructListValueType,
+                   "Cannot start root message with ListValue.");
     }
-  } else if (element_ != NULL && element_->IsStructList()) {
-    // If the top element is a list, then we are starting a list field within a
-    // struct.
-    field = Lookup(name);
-    field = StartStructValueInStruct(field);
-  } else {
-    field = BeginNamed(name, false);
-  }
-  if (field == NULL) {
-    return this;
-  }
 
-  const google::protobuf::Type* type = LookupType(field);
-  if (type == NULL) {
-    ++invalid_depth_;
-    InvalidName(name,
-                StrCat("Missing descriptor for field: ", field->type_url()));
     return this;
   }
 
-  // Check to see if this field is a oneof and that no oneof in that group has
-  // already been set.
-  if (!ValidOneof(*field, name)) {
-    ++invalid_depth_;
+  // Send all ANY events to AnyWriter.
+  if (current_->IsAny()) {
+    current_->any()->StartObject(name);
     return this;
   }
 
-  if (field->type_url() == GetFullTypeWithUrl(kStructType)) {
-    // Start a struct object.
-    StartStruct(field);
-  } else if (field->type_url() == GetFullTypeWithUrl(kStructValueType)) {
-    // We got a StartObject call with google.protobuf.Value field. This means we
-    // are starting an object within google.protobuf.Value type. The only object
-    // within that type is a struct type. So start a struct.
-    field = StartStructValueInStruct(field);
-    StartStruct(field);
-  } else if (field->type_url() == GetFullTypeWithUrl(kAnyType)) {
-    // Begin an Any. We can't do the real work till we get the @type field.
-    WriteTag(*field);
-    element_.reset(
-        new ProtoElement(element_.release(), field, *type, ProtoElement::ANY));
-  } else if (IsMap(*field)) {
-    // Begin a map.
-    // A map is triggered by a StartObject() call if the current field has a map
-    // type. Map values are written to proto in a manner detailed in comments
-    // above StartMapEntry() function.
-    element_.reset(
-        new ProtoElement(element_.release(), field, *type, ProtoElement::MAP));
-  } else {
-      WriteTag(*field);
-    element_.reset(new ProtoElement(element_.release(), field, *type,
-                                    ProtoElement::MESSAGE));
-  }
-  return this;
-}
-
-// Proto3 maps are represented on the wire as a message with
-// "key" and a "value".
-//
-// For example, the syntax:
-// map<key_type, value_type> map_field = N;
-//
-// is represented as:
-// message MapFieldEntry {
-//   option map_entry = true;   // marks the map construct in the descriptor
-//
-//   key_type key = 1;
-//   value_type value = 2;
-// }
-// repeated MapFieldEntry map_field = N;
-//
-// See go/proto3-maps for more information.
-const google::protobuf::Field* ProtoStreamObjectWriter::StartMapEntry(
-    StringPiece name) {
-  // top of stack is already a map field
-  const google::protobuf::Field* field = element_->field();
-  const google::protobuf::Type& type = element_->type();
-  // If we come from a regular map, use MAP_ENTRY or if we come from a struct,
-  // use STRUCT_MAP_ENTRY. These values are used later in StartObject/StartList
-  // or RenderDataPiece for making appropriate decisions.
-  ProtoElement::ElementType element_type = element_->IsStructMap()
-                                               ? ProtoElement::STRUCT_MAP_ENTRY
-                                               : ProtoElement::MAP_ENTRY;
-  WriteTag(*field);
-  element_.reset(
-      new ProtoElement(element_.release(), field, type, element_type));
-  RenderDataPiece("key", DataPiece(name));
-  return BeginNamed("value", false);
-}
+  // If we are within a map, we render name as keys and send StartObject to the
+  // value field.
+  if (current_->IsMap()) {
+    if (!ValidMapKey(name)) {
+      IncrementInvalidDepth();
+      return this;
+    }
 
-// Starts a google.protobuf.Struct.
-// 'field' represents a field in a message of type google.protobuf.Struct.  A
-// struct contains a map with name 'fields'. This function starts this map as
-// well.
-// When 'field' is NULL, it means that the top level message is of struct
-// type.
-void ProtoStreamObjectWriter::StartStruct(
-    const google::protobuf::Field* field) {
-  const google::protobuf::Type* type = NULL;
-  if (field) {
-    type = LookupType(field);
-    WriteTag(*field);
-    element_.reset(new ProtoElement(element_.release(), field, *type,
-                                    ProtoElement::STRUCT));
-  }
-  const google::protobuf::Field* struct_field = BeginNamed("fields", false);
+    // Map is a repeated field of message type with a "key" and a "value" field.
+    // https://developers.google.com/protocol-buffers/docs/proto3?hl=en#maps
+    // message MapFieldEntry {
+    //   key_type key = 1;
+    //   value_type value = 2;
+    // }
+    //
+    // repeated MapFieldEntry map_field = N;
+    //
+    // That means, we render the following element within a list (hence no
+    // name):
+    // { "key": "<name>", "value": {
+    Push("", Item::MESSAGE, false, false);
+    ProtoWriter::RenderDataPiece("key", DataPiece(name));
+    Push("value", Item::MESSAGE, true, false);
+
+    // Make sure we are valid so far after starting map fields.
+    if (invalid_depth() > 0) return this;
+
+    // If top of stack is g.p.Struct type, start the struct the map field within
+    // it.
+    if (element() != NULL && IsStruct(*element()->parent_field())) {
+      // Render "fields": [
+      Push("fields", Item::MAP, true, true);
+      return this;
+    }
 
-  if (!struct_field) {
-    // It is a programmatic error if this happens. Log an error.
-    GOOGLE_LOG(ERROR) << "Invalid internal state. Cannot find 'fields' within "
-               << (field ? field->type_url() : "google.protobuf.Struct");
-    return;
+    // If top of stack is g.p.Value type, start the Struct within it.
+    if (element() != NULL && IsStructValue(*element()->parent_field())) {
+      // Render
+      // "struct_value": {
+      //   "fields": [
+      Push("struct_value", Item::MESSAGE, true, false);
+      Push("fields", Item::MAP, true, true);
+    }
+    return this;
   }
 
-  type = LookupType(struct_field);
-  element_.reset(new ProtoElement(element_.release(), struct_field, *type,
-                                  ProtoElement::STRUCT_MAP));
-}
+  const google::protobuf::Field* field = BeginNamed(name, false);
+  if (field == NULL) return this;
 
-// Starts a "struct_value" within struct.proto's google.protobuf.Value type.
-// 'field' should be of the type google.protobuf.Value.
-// Returns the field identifying "struct_value" within the given field.
-//
-// If field is NULL, then we are starting struct_value at the top-level, in
-// this case skip writing any tag information for the passed field.
-const google::protobuf::Field*
-ProtoStreamObjectWriter::StartStructValueInStruct(
-    const google::protobuf::Field* field) {
-  if (field) {
-    const google::protobuf::Type* type = LookupType(field);
-    WriteTag(*field);
-    element_.reset(new ProtoElement(element_.release(), field, *type,
-                                    ProtoElement::STRUCT_VALUE));
-  }
-  return BeginNamed("struct_value", false);
-}
-
-// Starts a "list_value" within struct.proto's google.protobuf.Value type.
-// 'field' should be of the type google.protobuf.Value.
-// Returns the field identifying "list_value" within the given field.
-//
-// If field is NULL, then we are starting list_value at the top-level, in
-// this case skip writing any tag information for the passed field.
-const google::protobuf::Field* ProtoStreamObjectWriter::StartListValueInStruct(
-    const google::protobuf::Field* field) {
-  if (field) {
-    const google::protobuf::Type* type = LookupType(field);
-    WriteTag(*field);
-    element_.reset(new ProtoElement(element_.release(), field, *type,
-                                    ProtoElement::STRUCT_VALUE));
+  if (IsStruct(*field)) {
+    // Start a struct object.
+    // Render
+    // "<name>": {
+    //   "fields": {
+    Push(name, Item::MESSAGE, false, false);
+    Push("fields", Item::MAP, true, true);
+    return this;
   }
-  const google::protobuf::Field* list_value = BeginNamed("list_value", false);
 
-  if (!list_value) {
-    // It is a programmatic error if this happens. Log an error.
-    GOOGLE_LOG(ERROR) << "Invalid internal state. Cannot find 'list_value' within "
-               << (field ? field->type_url() : "google.protobuf.Value");
-    return field;
+  if (IsStructValue(*field)) {
+    // We got a StartObject call with google.protobuf.Value field.  The only
+    // object within that type is a struct type. So start a struct.
+    // Render
+    // "<name>": {
+    //   "struct_value": {
+    //     "fields": {
+    Push(name, Item::MESSAGE, false, false);
+    Push("struct_value", Item::MESSAGE, true, false);
+    Push("fields", Item::MAP, true, true);
+    return this;
   }
 
-  return StartRepeatedValuesInListValue(list_value);
-}
-
-// Starts the repeated "values" field in struct.proto's
-// google.protobuf.ListValue type. 'field' should be of type
-// google.protobuf.ListValue.
-//
-// If field is NULL, then we are starting ListValue at the top-level, in
-// this case skip writing any tag information for the passed field.
-const google::protobuf::Field*
-ProtoStreamObjectWriter::StartRepeatedValuesInListValue(
-    const google::protobuf::Field* field) {
-  if (field) {
-    const google::protobuf::Type* type = LookupType(field);
-    WriteTag(*field);
-    element_.reset(new ProtoElement(element_.release(), field, *type,
-                                    ProtoElement::STRUCT_LIST_VALUE));
+  if (IsMap(*field)) {
+    // Begin a map. A map is triggered by a StartObject() call if the current
+    // field has a map type.
+    // A map type is always repeated, hence set is_list to true.
+    // Render
+    // "<name>": [
+    Push(name, Item::MAP, false, true);
+    return this;
   }
-  return BeginNamed("values", true);
-}
 
-void ProtoStreamObjectWriter::SkipElements() {
-  if (element_ == NULL) return;
-
-  ProtoElement::ElementType element_type = element_->element_type();
-  while (element_type == ProtoElement::STRUCT ||
-         element_type == ProtoElement::STRUCT_LIST_VALUE ||
-         element_type == ProtoElement::STRUCT_VALUE ||
-         element_type == ProtoElement::STRUCT_MAP_ENTRY ||
-         element_type == ProtoElement::MAP_ENTRY) {
-    element_.reset(element_->pop());
-    element_type =
-        element_ != NULL ? element_->element_type() : ProtoElement::MESSAGE;
-  }
+  // A regular message type. Pass it directly to ProtoWriter.
+  // Render
+  // "<name>": {
+  Push(name, IsAny(*field) ? Item::ANY : Item::MESSAGE, false, false);
+  return this;
 }
 
 ProtoStreamObjectWriter* ProtoStreamObjectWriter::EndObject() {
-  if (invalid_depth_ > 0) {
-    --invalid_depth_;
+  if (invalid_depth() > 0) {
+    DecrementInvalidDepth();
     return this;
   }
-  if (element_ != NULL && element_->IsAny()) {
-    if (element_->any()->EndObject()) {
-      return this;
-    }
-  }
-  if (element_ != NULL) {
-    element_.reset(element_->pop());
-  }
 
-  // Skip sentinel elements added to keep track of new proto3 types - map,
-  // struct.
-  SkipElements();
+  if (current_ == NULL) return this;
 
-
-  // If ending the root element,
-  // then serialize the full message with calculated sizes.
-  if (element_ == NULL) {
-    WriteRootMessage();
+  if (current_->IsAny()) {
+    if (current_->any()->EndObject()) return this;
   }
+
+  Pop();
+
   return this;
 }
 
 ProtoStreamObjectWriter* ProtoStreamObjectWriter::StartList(StringPiece name) {
-  const google::protobuf::Field* field = NULL;
+  if (invalid_depth() > 0) {
+    IncrementInvalidDepth();
+    return this;
+  }
+
   // Since we cannot have a top-level repeated item in protobuf, the only way
-  // element_ can be null when here is when we start a top-level list
-  // google.protobuf.ListValue.
-  if (element_ == NULL) {
+  // this is valid is if we start a special type google.protobuf.ListValue or
+  // google.protobuf.Value.
+  if (current_ == NULL) {
     if (!name.empty()) {
       InvalidName(name, "Root element should not be named.");
+      IncrementInvalidDepth();
+      return this;
     }
-    element_.reset(new ProtoElement(typeinfo_, master_type_, this));
 
     // If master type is a special type that needs extra values to be written to
     // stream, we write those values.
     if (master_type_.name() == kStructValueType) {
       // We got a StartList with google.protobuf.Value master type. This means
       // we have to start the "list_value" within google.protobuf.Value.
-      field = StartListValueInStruct(NULL);
-    } else if (master_type_.name() == kStructListValueType) {
+      //
+      // See
+      // https://github.com/google/protobuf/blob/master/src/google/protobuf/struct.proto
+      //
+      // Render
+      // "<name>": {
+      //   "list_value": {
+      //     "values": [  // Start this list.
+      ProtoWriter::StartObject(name);
+      current_.reset(new Item(this, Item::MESSAGE, false, false));
+      Push("list_value", Item::MESSAGE, true, false);
+      Push("values", Item::MESSAGE, true, true);
+      return this;
+    }
+
+    if (master_type_.name() == kStructListValueType) {
       // We got a StartList with google.protobuf.ListValue master type. This
       // means we have to start the "values" within google.protobuf.ListValue.
-      field = StartRepeatedValuesInListValue(NULL);
+      //
+      // Render
+      // "<name>": {
+      //   "values": [  // Start this list.
+      ProtoWriter::StartObject(name);
+      current_.reset(new Item(this, Item::MESSAGE, false, false));
+      Push("values", Item::MESSAGE, true, true);
+      return this;
     }
 
-    // field is NULL when master_type_ is anything other than
-    // google.protobuf.Value or google.protobuf.ListValue.
-    if (field) {
-      const google::protobuf::Type* type = LookupType(field);
-      element_.reset(new ProtoElement(element_.release(), field, *type,
-                                      ProtoElement::STRUCT_LIST));
-    }
+    // Send the event to ProtoWriter so proper errors can be reported.
+    //
+    // Render a regular list:
+    // "<name>": [
+    ProtoWriter::StartList(name);
+    current_.reset(new Item(this, Item::MESSAGE, false, true));
     return this;
   }
 
-  if (element_->IsAny()) {
-    element_->any()->StartList(name);
+  if (current_->IsAny()) {
+    current_->any()->StartList(name);
     return this;
   }
-  // The type of element we push to stack.
-  ProtoElement::ElementType element_type = ProtoElement::LIST;
 
-  // Check if we need to start a map. This can heppen when there is either a map
-  // or a struct type within a list.
-  if (element_->IsMap() || element_->IsStructMap()) {
+  // If the top of stack is a map, we are starting a list value within a map.
+  // Since map does not allow repeated values, this can only happen when the map
+  // value is of a special type that renders a list in JSON.  These can be one
+  // of 3 cases:
+  // i. We are rendering a list value within google.protobuf.Struct
+  // ii. We are rendering a list value within google.protobuf.Value
+  // iii. We are rendering a list value with type google.protobuf.ListValue.
+  if (current_->IsMap()) {
     if (!ValidMapKey(name)) {
-      ++invalid_depth_;
+      IncrementInvalidDepth();
       return this;
     }
 
-    field = StartMapEntry(name);
-    if (field == NULL) return this;
+    // Start the repeated map entry object.
+    // Render
+    // { "key": "<name>", "value": {
+    Push("", Item::MESSAGE, false, false);
+    ProtoWriter::RenderDataPiece("key", DataPiece(name));
+    Push("value", Item::MESSAGE, true, false);
+
+    // Make sure we are valid after pushing all above items.
+    if (invalid_depth() > 0) return this;
+
+    // case i and ii above. Start "list_value" field within g.p.Value
+    if (element() != NULL && element()->parent_field() != NULL) {
+      // Render
+      // "list_value": {
+      //   "values": [  // Start this list
+      if (IsStructValue(*element()->parent_field())) {
+        Push("list_value", Item::MESSAGE, true, false);
+        Push("values", Item::MESSAGE, true, true);
+        return this;
+      }
 
-    if (element_->IsStructMapEntry()) {
-      // If the top element is a map entry, this means we are starting a list
-      // within a struct or a map.
-      // An example sequence of calls would be
-      //    StartObject -> StartList
-      field = StartListValueInStruct(field);
-      if (field == NULL) return this;
+      // Render
+      // "values": [
+      if (IsStructListValue(*element()->parent_field())) {
+        // case iii above. Bind directly to g.p.ListValue
+        Push("values", Item::MESSAGE, true, true);
+        return this;
+      }
     }
 
-    element_type = ProtoElement::STRUCT_LIST;
-  } else if (element_->IsStructList()) {
-    // If the top element is a STRUCT_LIST, this means we are starting a list
-    // within the current list (inside a struct).
-    // An example call sequence would be
-    //    StartObject -> StartList -> StartList
-    // with StartObject starting a struct.
+    // Report an error.
+    InvalidValue("Map", StrCat("Cannot have repeated items ('", name,
+                               "') within a map."));
+    return this;
+  }
 
-    // Lookup the last list type in element stack as we are adding an element of
-    // the same type.
-    field = Lookup(name);
-    if (field == NULL) return this;
+  // When name is empty and stack is not empty, we are rendering an item within
+  // a list.
+  if (name.empty()) {
+    if (element() != NULL && element()->parent_field() != NULL) {
+      if (IsStructValue(*element()->parent_field())) {
+        // Since it is g.p.Value, we bind directly to the list_value.
+        // Render
+        // {  // g.p.Value item within the list
+        //   "list_value": {
+        //     "values": [
+        Push("", Item::MESSAGE, false, false);
+        Push("list_value", Item::MESSAGE, true, false);
+        Push("values", Item::MESSAGE, true, true);
+        return this;
+      }
 
-    field = StartListValueInStruct(field);
-    if (field == NULL) return this;
+      if (IsStructListValue(*element()->parent_field())) {
+        // Since it is g.p.ListValue, we bind to it directly.
+        // Render
+        // {  // g.p.ListValue item within the list
+        //   "values": [
+        Push("", Item::MESSAGE, false, false);
+        Push("values", Item::MESSAGE, true, true);
+        return this;
+      }
+    }
 
-    element_type = ProtoElement::STRUCT_LIST;
-  } else {
-    // Lookup field corresponding to 'name'. If it is a google.protobuf.Value
-    // or google.protobuf.ListValue type, then StartList is a valid call, start
-    // this list.
-    // We cannot use Lookup() here as it will produce InvalidName() error if the
-    // field is not found. We do not want to error here as it would cause us to
-    // report errors twice, once here and again later in BeginNamed() call.
-    // Also we ignore if the field is not found here as it is caught later.
-    field = typeinfo_->FindField(&element_->type(), name);
-
-    // Only check for oneof collisions on the first StartList call. We identify
-    // the first call with !name.empty() check. Subsequent list element calls
-    // will not have the name filled.
-    if (!name.empty() && field && !ValidOneof(*field, name)) {
-      ++invalid_depth_;
+    // Pass the event to underlying ProtoWriter.
+    Push(name, Item::MESSAGE, false, true);
+    return this;
+  }
+
+  // name is not empty
+  const google::protobuf::Field* field = Lookup(name);
+  if (field == NULL) {
+    IncrementInvalidDepth();
+    return this;
+  }
+
+  if (IsStructValue(*field)) {
+    // If g.p.Value is repeated, start that list. Otherwise, start the
+    // "list_value" within it.
+    if (IsRepeated(*field)) {
+      // Render it just like a regular repeated field.
+      // "<name>": [
+      Push(name, Item::MESSAGE, false, true);
       return this;
     }
 
-    // It is an error to try to bind to map, which behind the scenes is a list.
-    if (field && IsMap(*field)) {
-      // Push field to stack for error location tracking & reporting.
-      element_.reset(new ProtoElement(element_.release(), field,
-                                      *LookupType(field),
-                                      ProtoElement::MESSAGE));
-      InvalidValue("Map", "Cannot bind a list to map.");
-      ++invalid_depth_;
-      element_.reset(element_->pop());
+    // Start the "list_value" field.
+    // Render
+    // "<name>": {
+    //   "list_value": {
+    //     "values": [
+    Push(name, Item::MESSAGE, false, false);
+    Push("list_value", Item::MESSAGE, true, false);
+    Push("values", Item::MESSAGE, true, true);
+    return this;
+  }
+
+  if (IsStructListValue(*field)) {
+    // If g.p.ListValue is repeated, start that list. Otherwise, start the
+    // "values" within it.
+    if (IsRepeated(*field)) {
+      // Render it just like a regular repeated field.
+      // "<name>": [
+      Push(name, Item::MESSAGE, false, true);
       return this;
     }
 
-    if (field && field->type_url() == GetFullTypeWithUrl(kStructValueType)) {
-      // There are 2 cases possible:
-      //   a. g.p.Value is repeated
-      //   b. g.p.Value is not repeated
-      //
-      // For case (a), the StartList should bind to the repeated g.p.Value.
-      // For case (b), the StartList should bind to g.p.ListValue within the
-      // g.p.Value.
-      //
-      // This means, for case (a), we treat it just like any other repeated
-      // message, except we would apply an appropriate element_type so future
-      // Start or Render calls are routed appropriately.
-      if (field->cardinality() !=
-          google::protobuf::Field_Cardinality_CARDINALITY_REPEATED) {
-        field = StartListValueInStruct(field);
-      }
-      element_type = ProtoElement::STRUCT_LIST;
-    } else if (field &&
-               field->type_url() == GetFullTypeWithUrl(kStructListValueType)) {
-      // We got a StartList with google.protobuf.ListValue master type. This
-      // means we have to start the "values" within google.protobuf.ListValue.
-      field = StartRepeatedValuesInListValue(field);
-    } else {
-      // If no special types are to be bound, fall back to normal processing of
-      // StartList.
-      field = BeginNamed(name, true);
-    }
-    if (field == NULL) return this;
+    // Start the "values" field within g.p.ListValue.
+    // Render
+    // "<name>": {
+    //   "values": [
+    Push(name, Item::MESSAGE, false, false);
+    Push("values", Item::MESSAGE, true, true);
+    return this;
   }
 
-  const google::protobuf::Type* type = LookupType(field);
-  if (type == NULL) {
-    ++invalid_depth_;
-    InvalidName(name,
-                StrCat("Missing descriptor for field: ", field->type_url()));
+  // If we are here, the field should be repeated. Report an error otherwise.
+  if (!IsRepeated(*field)) {
+    IncrementInvalidDepth();
+    InvalidName(name, "Proto field is not repeating, cannot start list.");
     return this;
   }
 
-  element_.reset(
-      new ProtoElement(element_.release(), field, *type, element_type));
+  if (IsMap(*field)) {
+    InvalidValue("Map",
+                 StrCat("Cannot bind a list to map for field '", name, "'."));
+    IncrementInvalidDepth();
+    return this;
+  }
+
+  // Pass the event to ProtoWriter.
+  // Render
+  // "<name>": [
+  Push(name, Item::MESSAGE, false, true);
   return this;
 }
 
 ProtoStreamObjectWriter* ProtoStreamObjectWriter::EndList() {
-  if (invalid_depth_ > 0) {
-    --invalid_depth_;
-  } else if (element_ != NULL) {
-    if (element_->IsAny()) {
-      element_->any()->EndList();
-    } else {
-      element_.reset(element_->pop());
-      // Skip sentinel elements added to keep track of new proto3 types - map,
-      // struct.
-      SkipElements();
-    }
+  if (invalid_depth() > 0) {
+    DecrementInvalidDepth();
+    return this;
   }
 
-  // When element_ is NULL, we have reached the root message type. Write out
-  // the bytes.
-  if (element_ == NULL) {
-    WriteRootMessage();
+  if (current_ == NULL) return this;
+
+  if (current_->IsAny()) {
+    current_->any()->EndList();
+    return this;
   }
+
+  Pop();
   return this;
 }
 
@@ -1083,7 +782,7 @@ Status ProtoStreamObjectWriter::RenderStructValue(ProtoStreamObjectWriter* ow,
                     "null values are supported.");
     }
   }
-  ow->RenderDataPiece(struct_field_name, data);
+  ow->ProtoWriter::RenderDataPiece(struct_field_name, data);
   return Status::OK;
 }
 
@@ -1105,15 +804,15 @@ Status ProtoStreamObjectWriter::RenderTimestamp(ProtoStreamObjectWriter* ow,
   }
 
 
-  ow->RenderDataPiece("seconds", DataPiece(seconds));
-  ow->RenderDataPiece("nanos", DataPiece(nanos));
+  ow->ProtoWriter::RenderDataPiece("seconds", DataPiece(seconds));
+  ow->ProtoWriter::RenderDataPiece("nanos", DataPiece(nanos));
   return Status::OK;
 }
 
 static inline util::Status RenderOneFieldPath(ProtoStreamObjectWriter* ow,
                                                 StringPiece path) {
-  ow->RenderDataPiece("paths",
-                      DataPiece(ConvertFieldMaskPath(path, &ToSnakeCase)));
+  ow->ProtoWriter::RenderDataPiece(
+      "paths", DataPiece(ConvertFieldMaskPath(path, &ToSnakeCase)));
   return Status::OK;
 }
 
@@ -1162,224 +861,133 @@ Status ProtoStreamObjectWriter::RenderDuration(ProtoStreamObjectWriter* ow,
                   "Invalid duration format, failed to parse seconds");
   }
 
-  double d_nanos = 0;
-  if (!safe_strtod("0." + s_nanos.ToString(), &d_nanos)) {
-    return Status(INVALID_ARGUMENT,
-                  "Invalid duration format, failed to parse nanos seconds");
+  int32 nanos = 0;
+  Status nanos_status = GetNanosFromStringPiece(
+      s_nanos, "Invalid duration format, failed to parse nano seconds",
+      "Duration value exceeds limits", &nanos);
+  if (!nanos_status.ok()) {
+    return nanos_status;
   }
+  nanos = sign * nanos;
 
-  int32 nanos = sign * static_cast<int32>(d_nanos * kNanosPerSecond);
   int64 seconds = sign * unsigned_seconds;
-
   if (seconds > kMaxSeconds || seconds < kMinSeconds ||
       nanos <= -kNanosPerSecond || nanos >= kNanosPerSecond) {
     return Status(INVALID_ARGUMENT, "Duration value exceeds limits");
   }
 
-  ow->RenderDataPiece("seconds", DataPiece(seconds));
-  ow->RenderDataPiece("nanos", DataPiece(nanos));
+  ow->ProtoWriter::RenderDataPiece("seconds", DataPiece(seconds));
+  ow->ProtoWriter::RenderDataPiece("nanos", DataPiece(nanos));
   return Status::OK;
 }
 
 Status ProtoStreamObjectWriter::RenderWrapperType(ProtoStreamObjectWriter* ow,
                                                   const DataPiece& data) {
-  ow->RenderDataPiece("value", data);
+  ow->ProtoWriter::RenderDataPiece("value", data);
   return Status::OK;
 }
 
 ProtoStreamObjectWriter* ProtoStreamObjectWriter::RenderDataPiece(
     StringPiece name, const DataPiece& data) {
   Status status;
-  if (invalid_depth_ > 0) return this;
-  if (element_ != NULL && element_->IsAny()) {
-    element_->any()->RenderDataPiece(name, data);
+  if (invalid_depth() > 0) return this;
+
+  if (current_ == NULL) {
+    const TypeRenderer* type_renderer =
+        FindTypeRenderer(GetFullTypeWithUrl(master_type_.name()));
+    if (type_renderer == NULL) {
+      InvalidName(name, "Root element must be a message.");
+      return this;
+    }
+    // Render the special type.
+    // "<name>": {
+    //   ... Render special type ...
+    // }
+    ProtoWriter::StartObject(name);
+    status = (*type_renderer)(this, data);
+    if (!status.ok()) {
+      InvalidValue(master_type_.name(),
+                   StrCat("Field '", name, "', ", status.error_message()));
+    }
+    ProtoWriter::EndObject();
+    return this;
+  }
+
+  if (current_->IsAny()) {
+    current_->any()->RenderDataPiece(name, data);
     return this;
   }
 
   const google::protobuf::Field* field = NULL;
-  string type_url;
-  bool is_map_entry = false;
-  // We are at the root when element_ == NULL.
-  if (element_ == NULL) {
-    type_url = GetFullTypeWithUrl(master_type_.name());
-  } else {
-    if (element_->IsMap() || element_->IsStructMap()) {
-      if (!ValidMapKey(name)) return this;
-      is_map_entry = true;
-      field = StartMapEntry(name);
-    } else {
-      field = Lookup(name);
-    }
+  if (current_->IsMap()) {
+    if (!ValidMapKey(name)) return this;
+
+    // Render an item in repeated map list.
+    // { "key": "<name>", "value":
+    Push("", Item::MESSAGE, false, false);
+    ProtoWriter::RenderDataPiece("key", DataPiece(name));
+    field = Lookup("value");
     if (field == NULL) {
+      GOOGLE_LOG(DFATAL) << "Map does not have a value field.";
+      return this;
+    }
+
+    const TypeRenderer* type_renderer = FindTypeRenderer(field->type_url());
+    if (type_renderer != NULL) {
+      // Map's value type is a special type. Render it like a message:
+      // "value": {
+      //   ... Render special type ...
+      // }
+      Push("value", Item::MESSAGE, true, false);
+      status = (*type_renderer)(this, data);
+      if (!status.ok()) {
+        InvalidValue(field->type_url(),
+                     StrCat("Field '", name, "', ", status.error_message()));
+      }
+      Pop();
       return this;
     }
 
-    // Check to see if this field is a oneof and that no oneof in that group has
-    // already been set.
-    if (!ValidOneof(*field, name)) return this;
+    // If we are rendering explicit null values and the backend proto field is
+    // not of the google.protobuf.NullType type, we do nothing.
+    if (data.type() == DataPiece::TYPE_NULL &&
+        field->type_url() != kStructNullValueTypeUrl) {
+      return this;
+    }
 
-    type_url = field->type_url();
+    // Render the map value as a primitive type.
+    ProtoWriter::RenderDataPiece("value", data);
+    Pop();
+    return this;
   }
 
-  // Check if there are any well known type renderers available for type_url.
-  const TypeRenderer* type_renderer = FindTypeRenderer(type_url);
+  field = Lookup(name);
+  if (field == NULL) return this;
+
+  // Check if the field is of special type. Render it accordingly if so.
+  const TypeRenderer* type_renderer = FindTypeRenderer(field->type_url());
   if (type_renderer != NULL) {
-    // Push the current element to stack so lookups in type_renderer will
-    // find the fields. We do an EndObject soon after, which pops this. This is
-    // safe because all well-known types are messages.
-    if (element_ == NULL) {
-      element_.reset(new ProtoElement(typeinfo_, master_type_, this));
-    } else {
-      if (field) {
-        WriteTag(*field);
-        const google::protobuf::Type* type = LookupType(field);
-        element_.reset(new ProtoElement(element_.release(), field, *type,
-                                        ProtoElement::MESSAGE));
-      }
-    }
+    Push(name, Item::MESSAGE, false, false);
     status = (*type_renderer)(this, data);
     if (!status.ok()) {
-      InvalidValue(type_url,
+      InvalidValue(field->type_url(),
                    StrCat("Field '", name, "', ", status.error_message()));
     }
-    EndObject();
-    return this;
-  } else if (element_ == NULL) {  // no message type found at root
-    element_.reset(new ProtoElement(typeinfo_, master_type_, this));
-    InvalidName(name, "Root element must be a message.");
+    Pop();
     return this;
   }
 
-  if (field == NULL) {
-    return this;
-  }
-  const google::protobuf::Type* type = LookupType(field);
-  if (type == NULL) {
-    InvalidName(name,
-                StrCat("Missing descriptor for field: ", field->type_url()));
+  // If we are rendering explicit null values and the backend proto field is
+  // not of the google.protobuf.NullType type, we do nothing.
+  if (data.type() == DataPiece::TYPE_NULL &&
+      field->type_url() != kStructNullValueTypeUrl) {
     return this;
   }
 
-  // Whether we should pop at the end. Set to true if the data field is a
-  // message type, which can happen in case of struct values.
-  bool should_pop = false;
-
-  RenderSimpleDataPiece(*field, *type, data);
-
-  if (should_pop && element_ != NULL) {
-    element_.reset(element_->pop());
-  }
-
-  if (is_map_entry) {
-    // Ending map is the same as ending an object.
-    EndObject();
-  }
+  ProtoWriter::RenderDataPiece(name, data);
   return this;
 }
 
-void ProtoStreamObjectWriter::RenderSimpleDataPiece(
-    const google::protobuf::Field& field, const google::protobuf::Type& type,
-    const DataPiece& data) {
-  // If we are rendering explicit null values and the backend proto field is not
-  // of the google.protobuf.NullType type, we do nothing.
-  if (data.type() == DataPiece::TYPE_NULL &&
-      field.type_url() != kStructNullValueTypeUrl) {
-    return;
-  }
-
-  // Pushing a ProtoElement and then pop it off at the end for 2 purposes:
-  // error location reporting and required field accounting.
-  element_.reset(new ProtoElement(element_.release(), &field, type,
-                                  ProtoElement::MESSAGE));
-
-  // Make sure that field represents a simple data type.
-  if (field.kind() == google::protobuf::Field_Kind_TYPE_UNKNOWN ||
-      field.kind() == google::protobuf::Field_Kind_TYPE_MESSAGE) {
-    InvalidValue(field.type_url().empty()
-                     ? google::protobuf::Field_Kind_Name(field.kind())
-                     : field.type_url(),
-                 data.ValueAsStringOrDefault(""));
-    return;
-  }
-
-  Status status;
-  switch (field.kind()) {
-    case google::protobuf::Field_Kind_TYPE_INT32: {
-      status = WriteInt32(field.number(), data, stream_.get());
-      break;
-    }
-    case google::protobuf::Field_Kind_TYPE_SFIXED32: {
-      status = WriteSFixed32(field.number(), data, stream_.get());
-      break;
-    }
-    case google::protobuf::Field_Kind_TYPE_SINT32: {
-      status = WriteSInt32(field.number(), data, stream_.get());
-      break;
-    }
-    case google::protobuf::Field_Kind_TYPE_FIXED32: {
-      status = WriteFixed32(field.number(), data, stream_.get());
-      break;
-    }
-    case google::protobuf::Field_Kind_TYPE_UINT32: {
-      status = WriteUInt32(field.number(), data, stream_.get());
-      break;
-    }
-    case google::protobuf::Field_Kind_TYPE_INT64: {
-      status = WriteInt64(field.number(), data, stream_.get());
-      break;
-    }
-    case google::protobuf::Field_Kind_TYPE_SFIXED64: {
-      status = WriteSFixed64(field.number(), data, stream_.get());
-      break;
-    }
-    case google::protobuf::Field_Kind_TYPE_SINT64: {
-      status = WriteSInt64(field.number(), data, stream_.get());
-      break;
-    }
-    case google::protobuf::Field_Kind_TYPE_FIXED64: {
-      status = WriteFixed64(field.number(), data, stream_.get());
-      break;
-    }
-    case google::protobuf::Field_Kind_TYPE_UINT64: {
-      status = WriteUInt64(field.number(), data, stream_.get());
-      break;
-    }
-    case google::protobuf::Field_Kind_TYPE_DOUBLE: {
-      status = WriteDouble(field.number(), data, stream_.get());
-      break;
-    }
-    case google::protobuf::Field_Kind_TYPE_FLOAT: {
-      status = WriteFloat(field.number(), data, stream_.get());
-      break;
-    }
-    case google::protobuf::Field_Kind_TYPE_BOOL: {
-      status = WriteBool(field.number(), data, stream_.get());
-      break;
-    }
-    case google::protobuf::Field_Kind_TYPE_BYTES: {
-      status = WriteBytes(field.number(), data, stream_.get());
-      break;
-    }
-    case google::protobuf::Field_Kind_TYPE_STRING: {
-      status = WriteString(field.number(), data, stream_.get());
-      break;
-    }
-    case google::protobuf::Field_Kind_TYPE_ENUM: {
-      status = WriteEnum(field.number(), data,
-                         typeinfo_->GetEnumByTypeUrl(field.type_url()),
-                         stream_.get());
-      break;
-    }
-    default:  // TYPE_GROUP or TYPE_MESSAGE
-      status = Status(INVALID_ARGUMENT, data.ToString().ValueOrDie());
-  }
-  if (!status.ok()) {
-    InvalidValue(google::protobuf::Field_Kind_Name(field.kind()),
-                 status.error_message());
-  }
-  element_.reset(element_->pop());
-}
-
 // Map of functions that are responsible for rendering well known type
 // represented by the key.
 hash_map<string, ProtoStreamObjectWriter::TypeRenderer>*
@@ -1446,45 +1054,12 @@ ProtoStreamObjectWriter::FindTypeRenderer(const string& type_url) {
   return FindOrNull(*renderers_, type_url);
 }
 
-ProtoStreamObjectWriter::ProtoElement::ElementType
-ProtoStreamObjectWriter::GetElementType(const google::protobuf::Type& type) {
-  if (type.name() == kAnyType) {
-    return ProtoElement::ANY;
-  } else if (type.name() == kStructType) {
-    return ProtoElement::STRUCT;
-  } else if (type.name() == kStructValueType) {
-    return ProtoElement::STRUCT_VALUE;
-  } else if (type.name() == kStructListValueType) {
-    return ProtoElement::STRUCT_LIST_VALUE;
-  } else {
-    return ProtoElement::MESSAGE;
-  }
-}
-
-bool ProtoStreamObjectWriter::ValidOneof(const google::protobuf::Field& field,
-                                         StringPiece unnormalized_name) {
-  if (element_ == NULL) return true;
-
-  if (field.oneof_index() > 0) {
-    if (element_->OneofIndexTaken(field.oneof_index())) {
-      InvalidValue(
-          "oneof",
-          StrCat("oneof field '",
-                 element_->type().oneofs(field.oneof_index() - 1),
-                 "' is already set. Cannot set '", unnormalized_name, "'"));
-      return false;
-    }
-    element_->TakeOneofIndex(field.oneof_index());
-  }
-  return true;
-}
-
 bool ProtoStreamObjectWriter::ValidMapKey(StringPiece unnormalized_name) {
-  if (element_ == NULL) return true;
+  if (current_ == NULL) return true;
 
-  if (!element_->InsertMapKeyIfNotPresent(unnormalized_name)) {
-    InvalidName(
-        unnormalized_name,
+  if (!current_->InsertMapKeyIfNotPresent(unnormalized_name)) {
+    listener()->InvalidName(
+        location(), unnormalized_name,
         StrCat("Repeated map key: '", unnormalized_name, "' is already set."));
     return false;
   }
@@ -1492,134 +1067,30 @@ bool ProtoStreamObjectWriter::ValidMapKey(StringPiece unnormalized_name) {
   return true;
 }
 
-const google::protobuf::Field* ProtoStreamObjectWriter::BeginNamed(
-    StringPiece name, bool is_list) {
-  if (invalid_depth_ > 0) {
-    ++invalid_depth_;
-    return NULL;
-  }
-  const google::protobuf::Field* field = Lookup(name);
-  if (field == NULL) {
-    ++invalid_depth_;
-    // InvalidName() already called in Lookup().
-    return NULL;
-  }
-  if (is_list &&
-      field->cardinality() !=
-          google::protobuf::Field_Cardinality_CARDINALITY_REPEATED) {
-    ++invalid_depth_;
-    InvalidName(name, "Proto field is not repeating, cannot start list.");
-    return NULL;
-  }
-  return field;
-}
+void ProtoStreamObjectWriter::Push(StringPiece name, Item::ItemType item_type,
+                                   bool is_placeholder, bool is_list) {
+  is_list ? ProtoWriter::StartList(name) : ProtoWriter::StartObject(name);
 
-const google::protobuf::Field* ProtoStreamObjectWriter::Lookup(
-    StringPiece unnormalized_name) {
-  ProtoElement* e = element();
-  if (e == NULL) {
-    InvalidName(unnormalized_name, "Root element must be a message.");
-    return NULL;
-  }
-  if (unnormalized_name.empty()) {
-    // Objects in repeated field inherit the same field descriptor.
-    if (e->field() == NULL) {
-      InvalidName(unnormalized_name, "Proto fields must have a name.");
-    } else if (e->field()->cardinality() !=
-               google::protobuf::Field_Cardinality_CARDINALITY_REPEATED) {
-      InvalidName(unnormalized_name, "Proto fields must have a name.");
-      return NULL;
-    }
-    return e->field();
-  }
-  const google::protobuf::Field* field =
-      typeinfo_->FindField(&e->type(), unnormalized_name);
-  if (field == NULL) InvalidName(unnormalized_name, "Cannot find field.");
-  return field;
-}
-
-const google::protobuf::Type* ProtoStreamObjectWriter::LookupType(
-    const google::protobuf::Field* field) {
-  return (field->kind() == google::protobuf::Field_Kind_TYPE_MESSAGE
-              ? typeinfo_->GetTypeByTypeUrl(field->type_url())
-              : &element_->type());
+  // invalid_depth == 0 means it is a successful StartObject or StartList.
+  if (invalid_depth() == 0)
+    current_.reset(
+        new Item(current_.release(), item_type, is_placeholder, is_list));
 }
 
-// Looks up the oneof struct field based on the data type.
-StatusOr<const google::protobuf::Field*>
-ProtoStreamObjectWriter::LookupStructField(DataPiece::Type type) {
-  const google::protobuf::Field* field = NULL;
-  switch (type) {
-    // Our JSON parser parses numbers as either int64, uint64, or double.
-    case DataPiece::TYPE_INT64:
-    case DataPiece::TYPE_UINT64:
-    case DataPiece::TYPE_DOUBLE: {
-      field = Lookup("number_value");
-      break;
-    }
-    case DataPiece::TYPE_STRING: {
-      field = Lookup("string_value");
-      break;
-    }
-    case DataPiece::TYPE_BOOL: {
-      field = Lookup("bool_value");
-      break;
-    }
-    case DataPiece::TYPE_NULL: {
-      field = Lookup("null_value");
-      break;
-    }
-    default: { return Status(INVALID_ARGUMENT, "Invalid struct data type"); }
+void ProtoStreamObjectWriter::Pop() {
+  // Pop all placeholder items sending StartObject or StartList events to
+  // ProtoWriter according to is_list value.
+  while (current_ != NULL && current_->is_placeholder()) {
+    PopOneElement();
   }
-  if (field == NULL) {
-    return Status(INVALID_ARGUMENT, "Could not lookup struct field");
+  if (current_ != NULL) {
+    PopOneElement();
   }
-  return field;
 }
 
-void ProtoStreamObjectWriter::WriteRootMessage() {
-  GOOGLE_DCHECK(!done_);
-  int curr_pos = 0;
-  // Calls the destructor of CodedOutputStream to remove any uninitialized
-  // memory from the Cord before we read it.
-  stream_.reset(NULL);
-  const void* data;
-  int length;
-  google::protobuf::io::ArrayInputStream input_stream(buffer_.data(), buffer_.size());
-  while (input_stream.Next(&data, &length)) {
-    if (length == 0) continue;
-    int num_bytes = length;
-    // Write up to where we need to insert the size field.
-    // The number of bytes we may write is the smaller of:
-    //   - the current fragment size
-    //   - the distance to the next position where a size field needs to be
-    //     inserted.
-    if (!size_insert_.empty() &&
-        size_insert_.front().pos - curr_pos < num_bytes) {
-      num_bytes = size_insert_.front().pos - curr_pos;
-    }
-    output_->Append(static_cast<const char*>(data), num_bytes);
-    if (num_bytes < length) {
-      input_stream.BackUp(length - num_bytes);
-    }
-    curr_pos += num_bytes;
-    // Insert the size field.
-    //   size_insert_.front():      the next <index, size> pair to be written.
-    //   size_insert_.front().pos:  position of the size field.
-    //   size_insert_.front().size: the size (integer) to be inserted.
-    if (!size_insert_.empty() && curr_pos == size_insert_.front().pos) {
-      // Varint32 occupies at most 10 bytes.
-      uint8 insert_buffer[10];
-      uint8* insert_buffer_pos = CodedOutputStream::WriteVarint32ToArray(
-          size_insert_.front().size, insert_buffer);
-      output_->Append(reinterpret_cast<const char*>(insert_buffer),
-                      insert_buffer_pos - insert_buffer);
-      size_insert_.pop_front();
-    }
-  }
-  output_->Flush();
-  stream_.reset(new CodedOutputStream(&adapter_));
-  done_ = true;
+void ProtoStreamObjectWriter::PopOneElement() {
+  current_->is_list() ? ProtoWriter::EndList() : ProtoWriter::EndObject();
+  current_.reset(current_->pop<Item>());
 }
 
 bool ProtoStreamObjectWriter::IsMap(const google::protobuf::Field& field) {
@@ -1630,7 +1101,7 @@ bool ProtoStreamObjectWriter::IsMap(const google::protobuf::Field& field) {
     return false;
   }
   const google::protobuf::Type* field_type =
-      typeinfo_->GetTypeByTypeUrl(field.type_url());
+      typeinfo()->GetTypeByTypeUrl(field.type_url());
 
   // TODO(xiaofeng): Unify option names.
   return GetBoolOptionOrDefault(field_type->options(),
@@ -1638,12 +1109,23 @@ bool ProtoStreamObjectWriter::IsMap(const google::protobuf::Field& field) {
          GetBoolOptionOrDefault(field_type->options(), "map_entry", false);
 }
 
-void ProtoStreamObjectWriter::WriteTag(const google::protobuf::Field& field) {
-  WireFormatLite::WireType wire_type = WireFormatLite::WireTypeForFieldType(
-      static_cast<WireFormatLite::FieldType>(field.kind()));
-  stream_->WriteTag(WireFormatLite::MakeTag(field.number(), wire_type));
+bool ProtoStreamObjectWriter::IsAny(const google::protobuf::Field& field) {
+  return GetTypeWithoutUrl(field.type_url()) == kAnyType;
 }
 
+bool ProtoStreamObjectWriter::IsStruct(const google::protobuf::Field& field) {
+  return GetTypeWithoutUrl(field.type_url()) == kStructType;
+}
+
+bool ProtoStreamObjectWriter::IsStructValue(
+    const google::protobuf::Field& field) {
+  return GetTypeWithoutUrl(field.type_url()) == kStructValueType;
+}
+
+bool ProtoStreamObjectWriter::IsStructListValue(
+    const google::protobuf::Field& field) {
+  return GetTypeWithoutUrl(field.type_url()) == kStructListValueType;
+}
 
 }  // namespace converter
 }  // namespace util
diff --git a/src/google/protobuf/util/internal/protostream_objectwriter.h b/src/google/protobuf/util/internal/protostream_objectwriter.h
index 6e133679..08ac6e33 100644
--- a/src/google/protobuf/util/internal/protostream_objectwriter.h
+++ b/src/google/protobuf/util/internal/protostream_objectwriter.h
@@ -42,6 +42,7 @@
 #include <google/protobuf/util/internal/type_info.h>
 #include <google/protobuf/util/internal/datapiece.h>
 #include <google/protobuf/util/internal/error_listener.h>
+#include <google/protobuf/util/internal/proto_writer.h>
 #include <google/protobuf/util/internal/structured_objectwriter.h>
 #include <google/protobuf/util/type_resolver.h>
 #include <google/protobuf/stubs/bytestream.h>
@@ -67,9 +68,11 @@ namespace converter {
 class ObjectLocationTracker;
 
 // An ObjectWriter that can write protobuf bytes directly from writer events.
+// This class supports all special types like Struct and Map. It uses
+// the ProtoWriter class to write raw proto bytes.
 //
 // It also supports streaming.
-class LIBPROTOBUF_EXPORT ProtoStreamObjectWriter : public StructuredObjectWriter {
+class LIBPROTOBUF_EXPORT ProtoStreamObjectWriter : public ProtoWriter {
  public:
 // Constructor. Does not take ownership of any parameter passed in.
   ProtoStreamObjectWriter(TypeResolver* type_resolver,
@@ -82,56 +85,13 @@ class LIBPROTOBUF_EXPORT ProtoStreamObjectWriter : public StructuredObjectWriter
   virtual ProtoStreamObjectWriter* EndObject();
   virtual ProtoStreamObjectWriter* StartList(StringPiece name);
   virtual ProtoStreamObjectWriter* EndList();
-  virtual ProtoStreamObjectWriter* RenderBool(StringPiece name, bool value) {
-    return RenderDataPiece(name, DataPiece(value));
-  }
-  virtual ProtoStreamObjectWriter* RenderInt32(StringPiece name, int32 value) {
-    return RenderDataPiece(name, DataPiece(value));
-  }
-  virtual ProtoStreamObjectWriter* RenderUint32(StringPiece name,
-                                                uint32 value) {
-    return RenderDataPiece(name, DataPiece(value));
-  }
-  virtual ProtoStreamObjectWriter* RenderInt64(StringPiece name, int64 value) {
-    return RenderDataPiece(name, DataPiece(value));
-  }
-  virtual ProtoStreamObjectWriter* RenderUint64(StringPiece name,
-                                                uint64 value) {
-    return RenderDataPiece(name, DataPiece(value));
-  }
-  virtual ProtoStreamObjectWriter* RenderDouble(StringPiece name,
-                                                double value) {
-    return RenderDataPiece(name, DataPiece(value));
-  }
-  virtual ProtoStreamObjectWriter* RenderFloat(StringPiece name, float value) {
-    return RenderDataPiece(name, DataPiece(value));
-  }
-  virtual ProtoStreamObjectWriter* RenderString(StringPiece name,
-                                                StringPiece value) {
-    return RenderDataPiece(name, DataPiece(value));
-  }
-  virtual ProtoStreamObjectWriter* RenderBytes(StringPiece name,
-                                               StringPiece value) {
-    return RenderDataPiece(name, DataPiece(value, false));
-  }
-  virtual ProtoStreamObjectWriter* RenderNull(StringPiece name) {
-    return RenderDataPiece(name, DataPiece::NullData());
-  }
 
   // Renders a DataPiece 'value' into a field whose wire type is determined
   // from the given field 'name'.
-  ProtoStreamObjectWriter* RenderDataPiece(StringPiece name,
-                                           const DataPiece& value);
+  virtual ProtoStreamObjectWriter* RenderDataPiece(StringPiece name,
+                                                   const DataPiece& value);
 
-  // Returns the location tracker to use for tracking locations for errors.
-  const LocationTrackerInterface& location() {
-    return element_ != NULL ? *element_ : *tracker_;
-  }
-
-  // When true, we finished writing to output a complete message.
-  bool done() const { return done_; }
-
- private:
+ protected:
   // Function that renders a well known type with modified behavior.
   typedef util::Status (*TypeRenderer)(ProtoStreamObjectWriter*,
                                          const DataPiece&);
@@ -192,73 +152,37 @@ class LIBPROTOBUF_EXPORT ProtoStreamObjectWriter : public StructuredObjectWriter
     bool has_injected_value_message_;
   };
 
-  class LIBPROTOBUF_EXPORT ProtoElement : public BaseElement, public LocationTrackerInterface {
+  // Represents an item in a stack of items used to keep state between
+  // ObjectWrier events.
+  class LIBPROTOBUF_EXPORT Item : public BaseElement {
    public:
-    // Indicates the type of element. Special types like LIST, MAP, MAP_ENTRY,
-    // STRUCT etc. are used to deduce other information based on their position
-    // on the stack of elements.
-    enum ElementType {
-      MESSAGE,       // Simple message
-      LIST,          // List/repeated element
-      MAP,           // Proto3 map type
-      MAP_ENTRY,     // Proto3 map message type, with 'key' and 'value' fields
-      ANY,           // Proto3 Any type
-      STRUCT,        // Proto3 struct type
-      STRUCT_VALUE,  // Struct's Value message type
-      STRUCT_LIST,   // List type indicator within a struct
-      STRUCT_LIST_VALUE,  // Struct Value's ListValue message type
-      STRUCT_MAP,         // Struct within a struct type
-      STRUCT_MAP_ENTRY    // Struct map's entry type with 'key' and 'value'
-                          // fields
+    // Indicates the type of item.
+    enum ItemType {
+      MESSAGE,  // Simple message
+      MAP,      // Proto3 map type
+      ANY,      // Proto3 Any type
     };
 
-    // Constructor for the root element. No parent nor field.
-    ProtoElement(const TypeInfo* typeinfo, const google::protobuf::Type& type,
-                 ProtoStreamObjectWriter* enclosing);
-
-    // Constructor for a field of an element.
-    ProtoElement(ProtoElement* parent, const google::protobuf::Field* field,
-                 const google::protobuf::Type& type, ElementType element_type);
+    // Constructor for the root item.
+    Item(ProtoStreamObjectWriter* enclosing, ItemType item_type,
+         bool is_placeholder, bool is_list);
 
-    virtual ~ProtoElement() {}
+    // Constructor for a field of a message.
+    Item(Item* parent, ItemType item_type, bool is_placeholder, bool is_list);
 
-    // Called just before the destructor for clean up:
-    //   - reports any missing required fields
-    //   - computes the space needed by the size field, and augment the
-    //     length of all parent messages by this additional space.
-    //   - releases and returns the parent pointer.
-    ProtoElement* pop();
-
-    // Accessors
-    const google::protobuf::Field* field() const { return field_; }
-    const google::protobuf::Type& type() const { return type_; }
+    virtual ~Item() {}
 
     // These functions return true if the element type is corresponding to the
     // type in function name.
-    bool IsMap() { return element_type_ == MAP; }
-    bool IsStructMap() { return element_type_ == STRUCT_MAP; }
-    bool IsStructMapEntry() { return element_type_ == STRUCT_MAP_ENTRY; }
-    bool IsStructList() { return element_type_ == STRUCT_LIST; }
-    bool IsAny() { return element_type_ == ANY; }
-
-    ElementType element_type() { return element_type_; }
-
-    void RegisterField(const google::protobuf::Field* field);
-    virtual string ToString() const;
+    bool IsMap() { return item_type_ == MAP; }
+    bool IsAny() { return item_type_ == ANY; }
 
     AnyWriter* any() const { return any_.get(); }
 
-    virtual ProtoElement* parent() const {
-      return static_cast<ProtoElement*>(BaseElement::parent());
+    virtual Item* parent() const {
+      return static_cast<Item*>(BaseElement::parent());
     }
 
-    // Returns true if the index is already taken by a preceeding oneof input.
-    bool OneofIndexTaken(int32 index);
-
-    // Marks the oneof 'index' as taken. Future inputs to this oneof will
-    // generate an error.
-    void TakeOneofIndex(int32 index);
-
     // Inserts map key into hash set if and only if the key did NOT already
     // exist in hash set.
     // The hash set (map_keys_) is ONLY used to keep track of map keys.
@@ -266,6 +190,9 @@ class LIBPROTOBUF_EXPORT ProtoStreamObjectWriter : public StructuredObjectWriter
     // already present.
     bool InsertMapKeyIfNotPresent(StringPiece map_key);
 
+    bool is_placeholder() const { return is_placeholder_; }
+    bool is_list() const { return is_list_; }
+
    private:
     // Used for access to variables of the enclosing instance of
     // ProtoStreamObjectWriter.
@@ -274,126 +201,42 @@ class LIBPROTOBUF_EXPORT ProtoStreamObjectWriter : public StructuredObjectWriter
     // A writer for Any objects, handles all Any-related nonsense.
     google::protobuf::scoped_ptr<AnyWriter> any_;
 
-    // Describes the element as a field in the parent message.
-    // field_ is NULL if and only if this element is the root element.
-    const google::protobuf::Field* field_;
-
-    // TypeInfo to lookup types.
-    const TypeInfo* typeinfo_;
-
-    // Additional variables if this element is a message:
-    // (Root element is always a message).
-    // descriptor_     : describes allowed fields in the message.
-    // required_fields_: set of required fields.
-    // is_repeated_type_ : true if the element is of type list or map.
-    // size_index_     : index into ProtoStreamObjectWriter::size_insert_
-    //                   for later insertion of serialized message length.
-    const google::protobuf::Type& type_;
-    std::set<const google::protobuf::Field*> required_fields_;
-    const bool is_repeated_type_;
-    const int size_index_;
-
-    // Tracks position in repeated fields, needed for LocationTrackerInterface.
-    int array_index_;
-
     // The type of this element, see enum for permissible types.
-    ElementType element_type_;
-
-    // Set of oneof indices already seen for the type_. Used to validate
-    // incoming messages so no more than one oneof is set.
-    hash_set<int32> oneof_indices_;
+    ItemType item_type_;
 
     // Set of map keys already seen for the type_. Used to validate incoming
     // messages so no map key appears more than once.
     hash_set<string> map_keys_;
 
-    GOOGLE_DISALLOW_IMPLICIT_CONSTRUCTORS(ProtoElement);
-  };
+    // Conveys whether this Item is a placeholder or not. Placeholder items are
+    // pushed to stack to account for special types.
+    bool is_placeholder_;
 
-  // Container for inserting 'size' information at the 'pos' position.
-  struct SizeInfo {
-    const int pos;
-    int size;
+    // Conveys whether this Item is a list or not. This is used to send
+    // StartList or EndList calls to underlying ObjectWriter.
+    bool is_list_;
+
+    GOOGLE_DISALLOW_IMPLICIT_CONSTRUCTORS(Item);
   };
 
   ProtoStreamObjectWriter(const TypeInfo* typeinfo,
                           const google::protobuf::Type& type,
                           strings::ByteSink* output, ErrorListener* listener);
 
-  ProtoElement* element() { return element_.get(); }
-
-  // Helper methods for calling ErrorListener. See error_listener.h.
-  void InvalidName(StringPiece unknown_name, StringPiece message);
-  void InvalidValue(StringPiece type_name, StringPiece value);
-  void MissingField(StringPiece missing_name);
-
-  // Common code for BeginObject() and BeginList() that does invalid_depth_
-  // bookkeeping associated with name lookup.
-  const google::protobuf::Field* BeginNamed(StringPiece name, bool is_list);
-
-  // Lookup the field in the current element. Looks in the base descriptor
-  // and in any extension. This will report an error if the field cannot be
-  // found or if multiple matching extensions are found.
-  const google::protobuf::Field* Lookup(StringPiece name);
-
-  // Lookup the field type in the type descriptor. Returns NULL if the type
-  // is not known.
-  const google::protobuf::Type* LookupType(
-      const google::protobuf::Field* field);
-
-  // Looks up the oneof struct Value field depending on the type.
-  // On failure to find, it returns an appropriate error.
-  util::StatusOr<const google::protobuf::Field*> LookupStructField(
-      DataPiece::Type type);
-
-  // Starts an entry in map. This will be called after placing map element at
-  // the top of the stack. Uses this information to write map entries.
-  const google::protobuf::Field* StartMapEntry(StringPiece name);
-
-  // Starts a google.protobuf.Struct.
-  // 'field' is of type google.protobuf.Struct.
-  // If field is NULL, it indicates that the top-level message is a struct
-  // type.
-  void StartStruct(const google::protobuf::Field* field);
-
-  // Starts another struct within a struct.
-  // 'field' is of type google.protobuf.Value (see struct.proto).
-  const google::protobuf::Field* StartStructValueInStruct(
-      const google::protobuf::Field* field);
-
-  // Starts a list within a struct.
-  // 'field' is of type google.protobuf.ListValue (see struct.proto).
-  const google::protobuf::Field* StartListValueInStruct(
-      const google::protobuf::Field* field);
-
-  // Starts the repeated "values" field in struct.proto's
-  // google.protobuf.ListValue type. 'field' should be of type
-  // google.protobuf.ListValue.
-  const google::protobuf::Field* StartRepeatedValuesInListValue(
-      const google::protobuf::Field* field);
-
-  // Pops sentinel elements off the stack.
-  void SkipElements();
-
-  // Write serialized output to the final output ByteSink, inserting all
-  // the size information for nested messages that are missing from the
-  // intermediate Cord buffer.
-  void WriteRootMessage();
-
   // Returns true if the field is a map.
   bool IsMap(const google::protobuf::Field& field);
 
   // Returns true if the field is an any.
   bool IsAny(const google::protobuf::Field& field);
 
-  // Helper method to write proto tags based on the given field.
-  void WriteTag(const google::protobuf::Field& field);
+  // Returns true if the field is google.protobuf.Struct.
+  bool IsStruct(const google::protobuf::Field& field);
 
+  // Returns true if the field is google.protobuf.Value.
+  bool IsStructValue(const google::protobuf::Field& field);
 
-  // Helper function to render primitive data types in DataPiece.
-  void RenderSimpleDataPiece(const google::protobuf::Field& field,
-                             const google::protobuf::Type& type,
-                             const DataPiece& data);
+  // Returns true if the field is google.protobuf.ListValue.
+  bool IsStructListValue(const google::protobuf::Field& field);
 
   // Renders google.protobuf.Value in struct.proto. It picks the right oneof
   // type based on value's type.
@@ -417,69 +260,46 @@ class LIBPROTOBUF_EXPORT ProtoStreamObjectWriter : public StructuredObjectWriter
   static util::Status RenderWrapperType(ProtoStreamObjectWriter* ow,
                                           const DataPiece& value);
 
-  // Helper functions to create the map and find functions responsible for
-  // rendering well known types, keyed by type URL.
-  static hash_map<string, TypeRenderer>* renderers_;
   static void InitRendererMap();
   static void DeleteRendererMap();
   static TypeRenderer* FindTypeRenderer(const string& type_url);
 
-  // Returns the ProtoElement::ElementType for the given Type.
-  static ProtoElement::ElementType GetElementType(
-      const google::protobuf::Type& type);
-
-  // Returns true if the field for type_ can be set as a oneof. If field is not
-  // a oneof type, this function does nothing and returns true.
-  // If another field for this oneof is already set, this function returns
-  // false. It also calls the appropriate error callback.
-  // unnormalized_name is used for error string.
-  bool ValidOneof(const google::protobuf::Field& field,
-                  StringPiece unnormalized_name);
-
   // Returns true if the map key for type_ is not duplicated key.
   // If map key is duplicated key, this function returns false.
-  // Note that caller should make sure that the current proto element (element_)
+  // Note that caller should make sure that the current proto element (current_)
   // is of element type MAP or STRUCT_MAP.
   // It also calls the appropriate error callback and unnormalzied_name is used
   // for error string.
   bool ValidMapKey(StringPiece unnormalized_name);
 
+  // Pushes an item on to the stack. Also calls either StartObject or StartList
+  // on the underlying ObjectWriter depending on whether is_list is false or
+  // not.
+  // is_placeholder conveys whether the item is a placeholder item or not.
+  // Placeholder items are pushed when adding auxillary types' StartObject or
+  // StartList calls.
+  void Push(StringPiece name, Item::ItemType item_type, bool is_placeholder,
+            bool is_list);
+
+  // Pops items from the stack. All placeholder items are popped until a
+  // non-placeholder item is found.
+  void Pop();
+
+  // Pops one element from the stack. Calls EndObject() or EndList() on the
+  // underlying ObjectWriter depending on the value of is_list_.
+  void PopOneElement();
+
+ private:
+  // Helper functions to create the map and find functions responsible for
+  // rendering well known types, keyed by type URL.
+  static hash_map<string, TypeRenderer>* renderers_;
+
   // Variables for describing the structure of the input tree:
   // master_type_: descriptor for the whole protobuf message.
-  // typeinfo_ : the TypeInfo object to lookup types.
   const google::protobuf::Type& master_type_;
-  const TypeInfo* typeinfo_;
-  // Whether we own the typeinfo_ object.
-  bool own_typeinfo_;
-
-  // Indicates whether we finished writing root message completely.
-  bool done_;
-
-  // Variable for internal state processing:
-  // element_    : the current element.
-  // size_insert_: sizes of nested messages.
-  //               pos  - position to insert the size field.
-  //               size - size value to be inserted.
-  google::protobuf::scoped_ptr<ProtoElement> element_;
-  std::deque<SizeInfo> size_insert_;
-
-  // Variables for output generation:
-  // output_  : pointer to an external ByteSink for final user-visible output.
-  // buffer_  : buffer holding partial message before being ready for output_.
-  // adapter_ : internal adapter between CodedOutputStream and Cord buffer_.
-  // stream_  : wrapper for writing tags and other encodings in wire format.
-  strings::ByteSink* output_;
-  string buffer_;
-  google::protobuf::io::StringOutputStream adapter_;
-  google::protobuf::scoped_ptr<google::protobuf::io::CodedOutputStream> stream_;
-
-  // Variables for error tracking and reporting:
-  // listener_     : a place to report any errors found.
-  // invalid_depth_: number of enclosing invalid nested messages.
-  // tracker_      : the root location tracker interface.
-  ErrorListener* listener_;
-  int invalid_depth_;
-  google::protobuf::scoped_ptr<LocationTrackerInterface> tracker_;
+
+  // The current element, variable for internal state processing.
+  google::protobuf::scoped_ptr<Item> current_;
 
   GOOGLE_DISALLOW_IMPLICIT_CONSTRUCTORS(ProtoStreamObjectWriter);
 };
diff --git a/src/google/protobuf/util/internal/protostream_objectwriter_test.cc b/src/google/protobuf/util/internal/protostream_objectwriter_test.cc
index cb9f97f7..c7667c21 100644
--- a/src/google/protobuf/util/internal/protostream_objectwriter_test.cc
+++ b/src/google/protobuf/util/internal/protostream_objectwriter_test.cc
@@ -241,6 +241,21 @@ TEST_P(ProtoStreamObjectWriterTest, SimpleMessage) {
   CheckOutput(book);
 }
 
+TEST_P(ProtoStreamObjectWriterTest, CustomJsonName) {
+  Book book;
+  Author* robert = book.mutable_author();
+  robert->set_id(12345);
+  robert->set_name("robert");
+
+  ow_->StartObject("")
+      ->StartObject("author")
+      ->RenderUint64("@id", 12345)
+      ->RenderString("name", "robert")
+      ->EndObject()
+      ->EndObject();
+  CheckOutput(book);
+}
+
 TEST_P(ProtoStreamObjectWriterTest, PrimitiveFromStringConversion) {
   Primitive full;
   full.set_fix32(101);
@@ -796,10 +811,6 @@ TEST_P(ProtoStreamObjectWriterTest, RootNamedList) {
               InvalidName(_, StringPiece("oops"),
                           StringPiece("Root element should not be named.")))
       .With(Args<0>(HasObjectLocation("")));
-  EXPECT_CALL(listener_,
-              InvalidName(_, StringPiece(""),
-                          StringPiece("Proto fields must have a name.")))
-      .With(Args<0>(HasObjectLocation("")));
   ow_->StartList("oops")->RenderString("", "item")->EndList();
   CheckOutput(empty, 0);
 }
@@ -864,6 +875,18 @@ INSTANTIATE_TEST_CASE_P(DifferentTypeInfoSourceTest,
                         ::testing::Values(
                             testing::USE_TYPE_RESOLVER));
 
+TEST_P(ProtoStreamObjectWriterTimestampDurationTest, ParseTimestamp) {
+  TimestampDuration timestamp;
+  google::protobuf::Timestamp* ts = timestamp.mutable_ts();
+  ts->set_seconds(1448249855);
+  ts->set_nanos(33155000);
+
+  ow_->StartObject("")
+      ->RenderString("ts", "2015-11-23T03:37:35.033155Z")
+      ->EndObject();
+  CheckOutput(timestamp);
+}
+
 TEST_P(ProtoStreamObjectWriterTimestampDurationTest, InvalidTimestampError1) {
   TimestampDuration timestamp;
 
@@ -922,9 +945,66 @@ TEST_P(ProtoStreamObjectWriterTimestampDurationTest, InvalidTimestampError4) {
   CheckOutput(timestamp);
 }
 
-// TODO(skarvaje): Write a test for nanos that exceed limit. Currently, it is
-// not possible to construct a test case where nanos exceed limit because of
-// floating point arithmetic.
+TEST_P(ProtoStreamObjectWriterTimestampDurationTest, InvalidTimestampError5) {
+  TimestampDuration timestamp;
+
+  EXPECT_CALL(
+      listener_,
+      InvalidValue(_,
+                   StringPiece("type.googleapis.com/google.protobuf.Timestamp"),
+                   StringPiece("Field 'ts', Invalid time format: "
+                               "2015-11-23T03:37:35.033155   Z")));
+
+  ow_->StartObject("")
+      // Whitespace in the Timestamp nanos is not allowed.
+      ->RenderString("ts", "2015-11-23T03:37:35.033155   Z")
+      ->EndObject();
+  CheckOutput(timestamp);
+}
+
+TEST_P(ProtoStreamObjectWriterTimestampDurationTest, InvalidTimestampError6) {
+  TimestampDuration timestamp;
+
+  EXPECT_CALL(
+      listener_,
+      InvalidValue(_,
+                   StringPiece("type.googleapis.com/google.protobuf.Timestamp"),
+                   StringPiece("Field 'ts', Invalid time format: "
+                               "2015-11-23T03:37:35.033155 1234Z")));
+
+  ow_->StartObject("")
+      // Whitespace in the Timestamp nanos is not allowed.
+      ->RenderString("ts", "2015-11-23T03:37:35.033155 1234Z")
+      ->EndObject();
+  CheckOutput(timestamp);
+}
+
+TEST_P(ProtoStreamObjectWriterTimestampDurationTest, InvalidTimestampError7) {
+  TimestampDuration timestamp;
+
+  EXPECT_CALL(
+      listener_,
+      InvalidValue(_,
+                   StringPiece("type.googleapis.com/google.protobuf.Timestamp"),
+                   StringPiece("Field 'ts', Invalid time format: "
+                               "2015-11-23T03:37:35.033abc155Z")));
+
+  ow_->StartObject("")
+      // Non-numeric characters in the Timestamp nanos is not allowed.
+      ->RenderString("ts", "2015-11-23T03:37:35.033abc155Z")
+      ->EndObject();
+  CheckOutput(timestamp);
+}
+
+TEST_P(ProtoStreamObjectWriterTimestampDurationTest, ParseDuration) {
+  TimestampDuration duration;
+  google::protobuf::Duration* dur = duration.mutable_dur();
+  dur->set_seconds(1448216930);
+  dur->set_nanos(132262000);
+
+  ow_->StartObject("")->RenderString("dur", "1448216930.132262s")->EndObject();
+  CheckOutput(duration);
+}
 
 TEST_P(ProtoStreamObjectWriterTimestampDurationTest, InvalidDurationError1) {
   TimestampDuration duration;
@@ -962,7 +1042,7 @@ TEST_P(ProtoStreamObjectWriterTimestampDurationTest, InvalidDurationError3) {
       InvalidValue(
           _, StringPiece("type.googleapis.com/google.protobuf.Duration"),
           StringPiece("Field 'dur', Invalid duration format, failed to "
-                      "parse nanos seconds")));
+                      "parse nano seconds")));
 
   ow_->StartObject("")->RenderString("dur", "123.DEFs")->EndObject();
   CheckOutput(duration);
@@ -981,6 +1061,19 @@ TEST_P(ProtoStreamObjectWriterTimestampDurationTest, InvalidDurationError4) {
   CheckOutput(duration);
 }
 
+TEST_P(ProtoStreamObjectWriterTimestampDurationTest, InvalidDurationError5) {
+  TimestampDuration duration;
+
+  EXPECT_CALL(
+      listener_,
+      InvalidValue(_,
+                   StringPiece("type.googleapis.com/google.protobuf.Duration"),
+                   StringPiece("Field 'dur', Duration value exceeds limits")));
+
+  ow_->StartObject("")->RenderString("dur", "0.1000000001s")->EndObject();
+  CheckOutput(duration);
+}
+
 TEST_P(ProtoStreamObjectWriterTimestampDurationTest,
        MismatchedTimestampTypeInput) {
   TimestampDuration timestamp;
@@ -1066,12 +1159,12 @@ TEST_P(ProtoStreamObjectWriterStructTest, StructInvalidInputFailure) {
 TEST_P(ProtoStreamObjectWriterStructTest, SimpleRepeatedStructMapKeyTest) {
   EXPECT_CALL(
       listener_,
-      InvalidName(_, StringPiece("k1"),
-                  StringPiece("Repeated map key: 'k1' is already set.")));
+      InvalidName(_, StringPiece("gBike"),
+                  StringPiece("Repeated map key: 'gBike' is already set.")));
   ow_->StartObject("")
       ->StartObject("object")
-      ->RenderString("k1", "v1")
-      ->RenderString("k1", "v2")
+      ->RenderString("gBike", "v1")
+      ->RenderString("gBike", "v2")
       ->EndObject()
       ->EndObject();
 }
@@ -1121,10 +1214,11 @@ INSTANTIATE_TEST_CASE_P(DifferentTypeInfoSourceTest,
 
 TEST_P(ProtoStreamObjectWriterMapTest, MapShouldNotAcceptList) {
   MapIn mm;
-  EXPECT_CALL(listener_,
-              InvalidValue(_, StringPiece("Map"),
-                           StringPiece("Cannot bind a list to map.")))
-      .With(Args<0>(HasObjectLocation("map_input")));
+  EXPECT_CALL(
+      listener_,
+      InvalidValue(
+          _, StringPiece("Map"),
+          StringPiece("Cannot bind a list to map for field 'map_input'.")));
   ow_->StartObject("")
       ->StartList("map_input")
       ->RenderString("a", "b")
diff --git a/src/google/protobuf/util/internal/testdata/books.proto b/src/google/protobuf/util/internal/testdata/books.proto
index 6e2f109b..82b81760 100644
--- a/src/google/protobuf/util/internal/testdata/books.proto
+++ b/src/google/protobuf/util/internal/testdata/books.proto
@@ -66,7 +66,7 @@ message Publisher {
 
 // An author of a book
 message Author {
-  optional uint64 id = 1;
+  optional uint64 id = 1 [json_name = "@id"];
   optional string name = 2;
   repeated string pseudonym = 3;
   optional bool alive = 4;
diff --git a/src/google/protobuf/util/internal/testdata/default_value.proto b/src/google/protobuf/util/internal/testdata/default_value.proto
index ebbdf6ab..cccc741c 100644
--- a/src/google/protobuf/util/internal/testdata/default_value.proto
+++ b/src/google/protobuf/util/internal/testdata/default_value.proto
@@ -75,9 +75,10 @@ message DefaultValueTestCases {
   IntToStringMap int_to_string = 403;
   MixedMap mixed1 = 404;
   MixedMap2 mixed2 = 405;
-  MessageMap map_of_objects = 406;
-  MixedMap mixed_empty = 407;
-  MessageMap message_map_empty = 408;
+  MixedMap2 empty_mixed2 = 406;
+  MessageMap map_of_objects = 407;
+  MixedMap mixed_empty = 408;
+  MessageMap message_map_empty = 409;
   DoubleValueMessage double_value = 501;
   DoubleValueMessage double_value_default = 502;
 }
diff --git a/src/google/protobuf/util/internal/testdata/default_value_test.proto b/src/google/protobuf/util/internal/testdata/default_value_test.proto
index 21b85e6d..93288341 100644
--- a/src/google/protobuf/util/internal/testdata/default_value_test.proto
+++ b/src/google/protobuf/util/internal/testdata/default_value_test.proto
@@ -43,4 +43,11 @@ message DefaultValueTest {
   bool bool_value = 13;
   string string_value = 15;
   bytes bytes_value = 17 [ctype = CORD];
+
+  enum EnumDefault {
+    ENUM_FIRST = 0;
+    ENUM_SECOND = 1;
+    ENUM_THIRD = 2;
+  }
+  EnumDefault enum_value = 18;
 }
diff --git a/src/google/protobuf/util/internal/type_info.cc b/src/google/protobuf/util/internal/type_info.cc
index a45a76e3..00a8ee7a 100644
--- a/src/google/protobuf/util/internal/type_info.cc
+++ b/src/google/protobuf/util/internal/type_info.cc
@@ -136,8 +136,7 @@ class TypeInfoForTypeResolver : public TypeInfo {
     for (int i = 0; i < type->fields_size(); ++i) {
       const google::protobuf::Field& field = type->fields(i);
       StringPiece name = field.name();
-      StringPiece camel_case_name =
-          *string_storage_.insert(ToCamelCase(name)).first;
+      StringPiece camel_case_name = field.json_name();
       const StringPiece* existing = InsertOrReturnExisting(
           &camel_case_name_table_, camel_case_name, name);
       if (existing && *existing != name) {
diff --git a/src/google/protobuf/util/internal/utility.cc b/src/google/protobuf/util/internal/utility.cc
index 61899c24..1ddf2487 100644
--- a/src/google/protobuf/util/internal/utility.cc
+++ b/src/google/protobuf/util/internal/utility.cc
@@ -49,7 +49,8 @@ namespace converter {
 namespace {
 const StringPiece SkipWhiteSpace(StringPiece str) {
   StringPiece::size_type i;
-  for (i = 0; i < str.size() && isspace(str[i]); ++i) {}
+  for (i = 0; i < str.size() && isspace(str[i]); ++i) {
+  }
   GOOGLE_DCHECK(i == str.size() || !isspace(str[i]));
   return StringPiece(str, i);
 }
@@ -160,6 +161,19 @@ const google::protobuf::Field* FindFieldInTypeOrNull(
   return NULL;
 }
 
+const google::protobuf::Field* FindJsonFieldInTypeOrNull(
+    const google::protobuf::Type* type, StringPiece json_name) {
+  if (type != NULL) {
+    for (int i = 0; i < type->fields_size(); ++i) {
+      const google::protobuf::Field& field = type->fields(i);
+      if (field.json_name() == json_name) {
+        return &field;
+      }
+    }
+  }
+  return NULL;
+}
+
 const google::protobuf::EnumValue* FindEnumValueByNameOrNull(
     const google::protobuf::Enum* enum_type, StringPiece enum_name) {
   if (enum_type != NULL) {
@@ -316,16 +330,23 @@ string FloatAsString(float value) {
   return DoubleAsString(value);
 }
 
-bool SafeStrToFloat(StringPiece str, float *value) {
+bool SafeStrToFloat(StringPiece str, float* value) {
   double double_value;
   if (!safe_strtod(str, &double_value)) {
     return false;
   }
-  *value = static_cast<float>(double_value);
 
-  if (MathLimits<float>::IsInf(*value)) {
+  if (MathLimits<double>::IsInf(double_value) ||
+      MathLimits<double>::IsNaN(double_value))
+    return false;
+
+  // Fail if the value is not representable in float.
+  if (double_value > std::numeric_limits<float>::max() ||
+      double_value < -std::numeric_limits<float>::max()) {
     return false;
   }
+
+  *value = static_cast<float>(double_value);
   return true;
 }
 
diff --git a/src/google/protobuf/util/internal/utility.h b/src/google/protobuf/util/internal/utility.h
index 5ba97bd2..33df8eda 100644
--- a/src/google/protobuf/util/internal/utility.h
+++ b/src/google/protobuf/util/internal/utility.h
@@ -127,6 +127,11 @@ const google::protobuf::Option* FindOptionOrNull(
 const google::protobuf::Field* FindFieldInTypeOrNull(
     const google::protobuf::Type* type, StringPiece field_name);
 
+// Similar to FindFieldInTypeOrNull, but this looks up fields with given
+// json_name.
+const google::protobuf::Field* FindJsonFieldInTypeOrNull(
+    const google::protobuf::Type* type, StringPiece json_name);
+
 // Finds and returns the EnumValue identified by enum_name in the passed tech
 // Enum object. Returns NULL if none found.
 const google::protobuf::EnumValue* FindEnumValueByNameOrNull(
diff --git a/src/google/protobuf/util/json_format_proto3.proto b/src/google/protobuf/util/json_format_proto3.proto
index e8137677..a1e24c18 100644
--- a/src/google/protobuf/util/json_format_proto3.proto
+++ b/src/google/protobuf/util/json_format_proto3.proto
@@ -165,3 +165,12 @@ message TestListValue {
   google.protobuf.ListValue value = 1;
   repeated google.protobuf.ListValue repeated_value = 2;
 }
+
+message TestBoolValue {
+  bool bool_value = 1;
+  map<bool, int32> bool_map = 2;
+}
+
+message TestCustomJsonName {
+  int32 value = 1 [json_name = "@value"];
+}
diff --git a/src/google/protobuf/util/message_differencer.cc b/src/google/protobuf/util/message_differencer.cc
index 47237e5a..0f879dc7 100644
--- a/src/google/protobuf/util/message_differencer.cc
+++ b/src/google/protobuf/util/message_differencer.cc
@@ -238,9 +238,25 @@ void MessageDifferencer::TreatAsSet(const FieldDescriptor* field) {
   GOOGLE_CHECK(key_comparator == NULL)
       << "Cannot treat this repeated field as both Map and Set for"
       << " comparison.  Field name is: " << field->full_name();
+  GOOGLE_CHECK(list_fields_.find(field) == list_fields_.end())
+      << "Cannot treat the same field as both SET and LIST. Field name is: "
+      << field->full_name();
   set_fields_.insert(field);
 }
 
+void MessageDifferencer::TreatAsList(const FieldDescriptor* field) {
+  GOOGLE_CHECK(field->is_repeated()) << "Field must be repeated: "
+                              << field->full_name();
+  const MapKeyComparator* key_comparator = GetMapKeyComparator(field);
+  GOOGLE_CHECK(key_comparator == NULL)
+      << "Cannot treat this repeated field as both Map and Set for"
+      << " comparison.  Field name is: " << field->full_name();
+  GOOGLE_CHECK(set_fields_.find(field) == set_fields_.end())
+      << "Cannot treat the same field as both SET and LIST. Field name is: "
+      << field->full_name();
+  list_fields_.insert(field);
+}
+
 void MessageDifferencer::TreatAsMap(const FieldDescriptor* field,
                                     const FieldDescriptor* key) {
   GOOGLE_CHECK(field->is_repeated()) << "Field must be repeated: "
@@ -255,6 +271,9 @@ void MessageDifferencer::TreatAsMap(const FieldDescriptor* field,
   GOOGLE_CHECK(set_fields_.find(field) == set_fields_.end())
       << "Cannot treat this repeated field as both Map and Set for "
       << "comparison.";
+  GOOGLE_CHECK(list_fields_.find(field) == list_fields_.end())
+      << "Cannot treat this repeated field as both Map and List for "
+      << "comparison.";
   MapKeyComparator* key_comparator =
       new MultipleFieldsMapKeyComparator(this, key);
   owned_key_comparators_.push_back(key_comparator);
@@ -920,7 +939,8 @@ bool MessageDifferencer::CheckPathChanged(
 bool MessageDifferencer::IsTreatedAsSet(const FieldDescriptor* field) {
   if (!field->is_repeated()) return false;
   if (field->is_map()) return true;
-  if (repeated_field_comparison_ == AS_SET) return true;
+  if (repeated_field_comparison_ == AS_SET)
+    return list_fields_.find(field) == list_fields_.end();
   return (set_fields_.find(field) != set_fields_.end());
 }
 
diff --git a/src/google/protobuf/util/message_differencer.h b/src/google/protobuf/util/message_differencer.h
index 34c173db..3ea74e67 100644
--- a/src/google/protobuf/util/message_differencer.h
+++ b/src/google/protobuf/util/message_differencer.h
@@ -397,9 +397,16 @@ class LIBPROTOBUF_EXPORT MessageDifferencer {
   // + n^3) in which n^3 is the time complexity of the maximum matching
   // algorithm.
   //
-  // REQUIRES:  field->is_repeated()
+  // REQUIRES:  field->is_repeated() and field not registered with TreatAsList
   void TreatAsSet(const FieldDescriptor* field);
 
+  // The elements of the given repeated field will be treated as a list for
+  // diffing purposes, so different orderings of the same elements will NOT be
+  // considered equal.
+  //
+  // REQUIRED: field->is_repeated() and field not registered with TreatAsSet
+  void TreatAsList(const FieldDescriptor* field);
+
   // The elements of the given repeated field will be treated as a map for
   // diffing purposes, with |key| being the map key.  Thus, elements with the
   // same key will be compared even if they do not appear at the same index.
@@ -791,6 +798,7 @@ class LIBPROTOBUF_EXPORT MessageDifferencer {
   RepeatedFieldComparison repeated_field_comparison_;
 
   FieldSet set_fields_;
+  FieldSet list_fields_;
   // Keeps track of MapKeyComparators that are created within
   // MessageDifferencer. These MapKeyComparators should be deleted
   // before MessageDifferencer is destroyed.
diff --git a/src/google/protobuf/util/message_differencer_unittest.cc b/src/google/protobuf/util/message_differencer_unittest.cc
index 701b94ae..4e9ca348 100755
--- a/src/google/protobuf/util/message_differencer_unittest.cc
+++ b/src/google/protobuf/util/message_differencer_unittest.cc
@@ -1103,12 +1103,19 @@ TEST(MessageDifferencerTest, RepeatedFieldSetTest_Combination) {
   msg1.add_rw("change"); msg2.add_rw("change");
 
   // Compare
-  util::MessageDifferencer differencer;
-  differencer.TreatAsMap(msg1.GetDescriptor()->FindFieldByName("item"),
-                         item->GetDescriptor()->FindFieldByName("a"));
-  differencer.TreatAsSet(msg1.GetDescriptor()->FindFieldByName("rv"));
-  differencer.TreatAsSet(item->GetDescriptor()->FindFieldByName("ra"));
-  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+  util::MessageDifferencer differencer1;
+  differencer1.TreatAsMap(msg1.GetDescriptor()->FindFieldByName("item"),
+                          item->GetDescriptor()->FindFieldByName("a"));
+  differencer1.TreatAsSet(msg1.GetDescriptor()->FindFieldByName("rv"));
+  differencer1.TreatAsSet(item->GetDescriptor()->FindFieldByName("ra"));
+  EXPECT_TRUE(differencer1.Compare(msg1, msg2));
+
+  util::MessageDifferencer differencer2;
+  differencer2.TreatAsMap(msg1.GetDescriptor()->FindFieldByName("item"),
+                          item->GetDescriptor()->FindFieldByName("a"));
+  differencer2.set_repeated_field_comparison(util::MessageDifferencer::AS_SET);
+  differencer2.TreatAsList(msg1.GetDescriptor()->FindFieldByName("rw"));
+  EXPECT_TRUE(differencer2.Compare(msg1, msg2));
 }
 
 TEST(MessageDifferencerTest, RepeatedFieldMapTest_Partial) {
@@ -1168,6 +1175,11 @@ TEST(MessageDifferencerTest, RepeatedFieldSetTest_Duplicates) {
   differencer.TreatAsSet(GetFieldDescriptor(a, "rv"));
   EXPECT_TRUE(differencer.Compare(b, a));
   EXPECT_FALSE(differencer.Compare(c, a));
+
+  util::MessageDifferencer differencer1;
+  differencer1.set_repeated_field_comparison(util::MessageDifferencer::AS_SET);
+  EXPECT_TRUE(differencer1.Compare(b, a));
+  EXPECT_FALSE(differencer1.Compare(c, a));
 }
 
 TEST(MessageDifferencerTest, RepeatedFieldSetTest_PartialSimple) {
diff --git a/src/google/protobuf/util/type_resolver_util.cc b/src/google/protobuf/util/type_resolver_util.cc
index a0996954..96393903 100644
--- a/src/google/protobuf/util/type_resolver_util.cc
+++ b/src/google/protobuf/util/type_resolver_util.cc
@@ -159,7 +159,10 @@ class DescriptorPoolTypeResolver : public TypeResolver {
     }
     field->set_number(descriptor->number());
     field->set_name(descriptor->name());
-    field->set_json_name(converter::ToCamelCase(descriptor->name()));
+    field->set_json_name(descriptor->json_name());
+    if (descriptor->has_default_value()) {
+      field->set_default_value(DefaultValueAsString(descriptor));
+    }
     if (descriptor->type() == FieldDescriptor::TYPE_MESSAGE) {
       field->set_type_url(GetTypeUrl(descriptor->message_type()));
     } else if (descriptor->type() == FieldDescriptor::TYPE_ENUM) {
@@ -200,6 +203,46 @@ class DescriptorPoolTypeResolver : public TypeResolver {
     return url_prefix_ + "/" + descriptor->full_name();
   }
 
+  string DefaultValueAsString(const FieldDescriptor* descriptor) {
+    switch (descriptor->cpp_type()) {
+      case FieldDescriptor::CPPTYPE_INT32:
+        return SimpleItoa(descriptor->default_value_int32());
+        break;
+      case FieldDescriptor::CPPTYPE_INT64:
+        return SimpleItoa(descriptor->default_value_int64());
+        break;
+      case FieldDescriptor::CPPTYPE_UINT32:
+        return SimpleItoa(descriptor->default_value_uint32());
+        break;
+      case FieldDescriptor::CPPTYPE_UINT64:
+        return SimpleItoa(descriptor->default_value_uint64());
+        break;
+      case FieldDescriptor::CPPTYPE_FLOAT:
+        return SimpleFtoa(descriptor->default_value_float());
+        break;
+      case FieldDescriptor::CPPTYPE_DOUBLE:
+        return SimpleDtoa(descriptor->default_value_double());
+        break;
+      case FieldDescriptor::CPPTYPE_BOOL:
+        return descriptor->default_value_bool() ? "true" : "false";
+        break;
+      case FieldDescriptor::CPPTYPE_STRING:
+        if (descriptor->type() == FieldDescriptor::TYPE_BYTES) {
+          return CEscape(descriptor->default_value_string());
+        } else {
+          return descriptor->default_value_string();
+        }
+        break;
+      case FieldDescriptor::CPPTYPE_ENUM:
+        return descriptor->default_value_enum()->name();
+        break;
+      case FieldDescriptor::CPPTYPE_MESSAGE:
+        GOOGLE_LOG(DFATAL) << "Messages can't have default values!";
+        break;
+    }
+    return "";
+  }
+
   string url_prefix_;
   const DescriptorPool* pool_;
 };
diff --git a/src/google/protobuf/util/type_resolver_util_test.cc b/src/google/protobuf/util/type_resolver_util_test.cc
index 74b2d0da..8a0bf652 100644
--- a/src/google/protobuf/util/type_resolver_util_test.cc
+++ b/src/google/protobuf/util/type_resolver_util_test.cc
@@ -43,6 +43,7 @@
 #include <google/protobuf/map_unittest.pb.h>
 #include <google/protobuf/test_util.h>
 #include <google/protobuf/unittest.pb.h>
+#include <google/protobuf/util/json_format_proto3.pb.h>
 #include <google/protobuf/util/type_resolver.h>
 #include <google/protobuf/testing/googletest.h>
 #include <gtest/gtest.h>
@@ -332,6 +333,19 @@ TEST_F(DescriptorPoolTypeResolverTest, TestEnum) {
   EnumHasValue(type, "NEG", -1);
 }
 
+TEST_F(DescriptorPoolTypeResolverTest, TestJsonName) {
+  Type type;
+  ASSERT_TRUE(resolver_->ResolveMessageType(
+                           GetTypeUrl<protobuf_unittest::TestAllTypes>(), &type)
+                  .ok());
+  EXPECT_EQ("optionalInt32", FindField(type, "optional_int32")->json_name());
+
+  ASSERT_TRUE(resolver_->ResolveMessageType(
+                           GetTypeUrl<proto3::TestCustomJsonName>(), &type)
+                  .ok());
+  EXPECT_EQ("@value", FindField(type, "value")->json_name());
+}
+
 }  // namespace
 }  // namespace util
 }  // namespace protobuf