Update //third_party/protobuf to version 3.

third_party/protobuf/src/google/protobuf/util/message_differencer.cc

Index: third_party/protobuf/src/google/protobuf/util/message_differencer.cc
diff --git a/third_party/protobuf/src/google/protobuf/util/message_differencer.cc b/third_party/protobuf/src/google/protobuf/util/message_differencer.cc
new file mode 100644
index 0000000000000000000000000000000000000000..0f879dc72be18d3b3895319ecd162997f5f98419
--- /dev/null
+++ b/third_party/protobuf/src/google/protobuf/util/message_differencer.cc
@@ -0,0 +1,1686 @@
+// 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.
+
+// Author: jschorr@google.com (Joseph Schorr)
+//  Based on original Protocol Buffers design by
+//  Sanjay Ghemawat, Jeff Dean, and others.
+//
+// This file defines static methods and classes for comparing Protocol
+// Messages (see //google/protobuf/util/message_differencer.h for more
+// information).
+
+#include <google/protobuf/util/message_differencer.h>
+
+#include <algorithm>
+#include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
+#include <utility>
+
+#include <google/protobuf/stubs/callback.h>
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/stubs/stringprintf.h>
+#include <google/protobuf/any.h>
+#include <google/protobuf/io/printer.h>
+#include <google/protobuf/io/zero_copy_stream.h>
+#include <google/protobuf/io/zero_copy_stream_impl.h>
+#include <google/protobuf/dynamic_message.h>
+#include <google/protobuf/text_format.h>
+#include <google/protobuf/util/field_comparator.h>
+#include <google/protobuf/stubs/strutil.h>
+
+namespace google {
+namespace protobuf {
+
+namespace util {
+
+// When comparing a repeated field as map, MultipleFieldMapKeyComparator can
+// be used to specify multiple fields as key for key comparison.
+// Two elements of a repeated field will be regarded as having the same key
+// iff they have the same value for every specified key field.
+// Note that you can also specify only one field as key.
+class MessageDifferencer::MultipleFieldsMapKeyComparator
+    : public MessageDifferencer::MapKeyComparator {
+ public:
+  MultipleFieldsMapKeyComparator(
+      MessageDifferencer* message_differencer,
+      const vector<vector<const FieldDescriptor*> >& key_field_paths)
+        : message_differencer_(message_differencer),
+          key_field_paths_(key_field_paths) {
+    GOOGLE_CHECK(!key_field_paths_.empty());
+    for (int i = 0; i < key_field_paths_.size(); ++i) {
+      GOOGLE_CHECK(!key_field_paths_[i].empty());
+    }
+  }
+  MultipleFieldsMapKeyComparator(
+      MessageDifferencer* message_differencer,
+      const FieldDescriptor* key)
+        : message_differencer_(message_differencer) {
+    vector<const FieldDescriptor*> key_field_path;
+    key_field_path.push_back(key);
+    key_field_paths_.push_back(key_field_path);
+  }
+  virtual bool IsMatch(
+      const Message& message1,
+      const Message& message2,
+      const vector<SpecificField>& parent_fields) const {
+    for (int i = 0; i < key_field_paths_.size(); ++i) {
+      if (!IsMatchInternal(message1, message2, parent_fields,
+                           key_field_paths_[i], 0)) {
+        return false;
+      }
+    }
+    return true;
+  }
+ private:
+  bool IsMatchInternal(
+      const Message& message1,
+      const Message& message2,
+      const vector<SpecificField>& parent_fields,
+      const vector<const FieldDescriptor*>& key_field_path,
+      int path_index) const {
+    const FieldDescriptor* field = key_field_path[path_index];
+    vector<SpecificField> current_parent_fields(parent_fields);
+    if (path_index == key_field_path.size() - 1) {
+      if (field->is_repeated()) {
+        if (!message_differencer_->CompareRepeatedField(
+            message1, message2, field, &current_parent_fields)) {
+          return false;
+        }
+      } else {
+        if (!message_differencer_->CompareFieldValueUsingParentFields(
+            message1, message2, field, -1, -1, &current_parent_fields)) {
+          return false;
+        }
+      }
+      return true;
+    } else {
+      const Reflection* reflection1 = message1.GetReflection();
+      const Reflection* reflection2 = message2.GetReflection();
+      bool has_field1 = reflection1->HasField(message1, field);
+      bool has_field2 = reflection2->HasField(message2, field);
+      if (!has_field1 && !has_field2) {
+        return true;
+      }
+      if (has_field1 != has_field2) {
+        return false;
+      }
+      SpecificField specific_field;
+      specific_field.field = field;
+      current_parent_fields.push_back(specific_field);
+      return IsMatchInternal(
+          reflection1->GetMessage(message1, field),
+          reflection2->GetMessage(message2, field),
+          current_parent_fields,
+          key_field_path,
+          path_index + 1);
+    }
+  }
+  MessageDifferencer* message_differencer_;
+  vector<vector<const FieldDescriptor*> > key_field_paths_;
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(MultipleFieldsMapKeyComparator);
+};
+
+bool MessageDifferencer::Equals(const Message& message1,
+                                const Message& message2) {
+  MessageDifferencer differencer;
+
+  return differencer.Compare(message1, message2);
+}
+
+bool MessageDifferencer::Equivalent(const Message& message1,
+                                    const Message& message2) {
+  MessageDifferencer differencer;
+  differencer.set_message_field_comparison(MessageDifferencer::EQUIVALENT);
+
+  return differencer.Compare(message1, message2);
+}
+
+bool MessageDifferencer::ApproximatelyEquals(const Message& message1,
+                                             const Message& message2) {
+  MessageDifferencer differencer;
+  differencer.set_float_comparison(
+      MessageDifferencer::APPROXIMATE);
+
+  return differencer.Compare(message1, message2);
+}
+
+bool MessageDifferencer::ApproximatelyEquivalent(const Message& message1,
+                                                 const Message& message2) {
+  MessageDifferencer differencer;
+  differencer.set_message_field_comparison(MessageDifferencer::EQUIVALENT);
+  differencer.set_float_comparison(MessageDifferencer::APPROXIMATE);
+
+  return differencer.Compare(message1, message2);
+}
+
+// ===========================================================================
+
+MessageDifferencer::MessageDifferencer()
+    : reporter_(NULL),
+      field_comparator_(NULL),
+      message_field_comparison_(EQUAL),
+      scope_(FULL),
+      repeated_field_comparison_(AS_LIST),
+      report_matches_(false),
+      output_string_(NULL) { }
+
+MessageDifferencer::~MessageDifferencer() {
+  for (int i = 0; i < owned_key_comparators_.size(); ++i) {
+    delete owned_key_comparators_[i];
+  }
+  for (int i = 0; i < ignore_criteria_.size(); ++i) {
+    delete ignore_criteria_[i];
+  }
+}
+
+void MessageDifferencer::set_field_comparator(FieldComparator* comparator) {
+  GOOGLE_CHECK(comparator) << "Field comparator can't be NULL.";
+  field_comparator_ = comparator;
+}
+
+void MessageDifferencer::set_message_field_comparison(
+    MessageFieldComparison comparison) {
+  message_field_comparison_ = comparison;
+}
+
+void MessageDifferencer::set_scope(Scope scope) {
+  scope_ = scope;
+}
+
+MessageDifferencer::Scope MessageDifferencer::scope() {
+  return scope_;
+}
+
+void MessageDifferencer::set_float_comparison(FloatComparison comparison) {
+  default_field_comparator_.set_float_comparison(
+      comparison == EXACT ?
+      DefaultFieldComparator::EXACT : DefaultFieldComparator::APPROXIMATE);
+}
+
+void MessageDifferencer::set_repeated_field_comparison(
+    RepeatedFieldComparison comparison) {
+  repeated_field_comparison_ = comparison;
+}
+
+void MessageDifferencer::TreatAsSet(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(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: "
+                               << field->full_name();
+  GOOGLE_CHECK_EQ(FieldDescriptor::CPPTYPE_MESSAGE, field->cpp_type())
+      << "Field has to be message type.  Field name is: "
+      << field->full_name();
+  GOOGLE_CHECK(key->containing_type() == field->message_type())
+      << key->full_name()
+      << " must be a direct subfield within the repeated field "
+      << field->full_name() << ", not " << key->containing_type()->full_name();
+  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);
+  map_field_key_comparator_[field] = key_comparator;
+}
+
+void MessageDifferencer::TreatAsMapWithMultipleFieldsAsKey(
+    const FieldDescriptor* field,
+    const vector<const FieldDescriptor*>& key_fields) {
+  vector<vector<const FieldDescriptor*> > key_field_paths;
+  for (int i = 0; i < key_fields.size(); ++i) {
+    vector<const FieldDescriptor*> key_field_path;
+    key_field_path.push_back(key_fields[i]);
+    key_field_paths.push_back(key_field_path);
+  }
+  TreatAsMapWithMultipleFieldPathsAsKey(field, key_field_paths);
+}
+
+void MessageDifferencer::TreatAsMapWithMultipleFieldPathsAsKey(
+    const FieldDescriptor* field,
+    const vector<vector<const FieldDescriptor*> >& key_field_paths) {
+  GOOGLE_CHECK(field->is_repeated()) << "Field must be repeated: "
+                              << field->full_name();
+  GOOGLE_CHECK_EQ(FieldDescriptor::CPPTYPE_MESSAGE, field->cpp_type())
+      << "Field has to be message type.  Field name is: "
+      << field->full_name();
+  for (int i = 0; i < key_field_paths.size(); ++i) {
+    const vector<const FieldDescriptor*>& key_field_path = key_field_paths[i];
+    for (int j = 0; j < key_field_path.size(); ++j) {
+      const FieldDescriptor* parent_field =
+          j == 0 ? field : key_field_path[j - 1];
+      const FieldDescriptor* child_field = key_field_path[j];
+      GOOGLE_CHECK(child_field->containing_type() == parent_field->message_type())
+          << child_field->full_name()
+          << " must be a direct subfield within the field: "
+          << parent_field->full_name();
+      if (j != 0) {
+        GOOGLE_CHECK_EQ(FieldDescriptor::CPPTYPE_MESSAGE, parent_field->cpp_type())
+            << parent_field->full_name() << " has to be of type message.";
+        GOOGLE_CHECK(!parent_field->is_repeated())
+            << parent_field->full_name() << " cannot be a repeated field.";
+      }
+    }
+  }
+  GOOGLE_CHECK(set_fields_.find(field) == set_fields_.end())
+      << "Cannot treat this repeated field as both Map and Set for "
+      << "comparison.";
+  MapKeyComparator* key_comparator =
+      new MultipleFieldsMapKeyComparator(this, key_field_paths);
+  owned_key_comparators_.push_back(key_comparator);
+  map_field_key_comparator_[field] = key_comparator;
+}
+
+void MessageDifferencer::TreatAsMapUsingKeyComparator(
+    const FieldDescriptor* field,
+    const MapKeyComparator* key_comparator) {
+  GOOGLE_CHECK(field->is_repeated()) << "Field must be repeated: "
+                               << field->full_name();
+  GOOGLE_CHECK_EQ(FieldDescriptor::CPPTYPE_MESSAGE, field->cpp_type())
+      << "Field has to be message type.  Field name is: "
+      << field->full_name();
+  GOOGLE_CHECK(set_fields_.find(field) == set_fields_.end())
+      << "Cannot treat this repeated field as both Map and Set for "
+      << "comparison.";
+  map_field_key_comparator_[field] = key_comparator;
+}
+
+void MessageDifferencer::AddIgnoreCriteria(IgnoreCriteria* ignore_criteria) {
+  ignore_criteria_.push_back(ignore_criteria);
+}
+
+void MessageDifferencer::IgnoreField(const FieldDescriptor* field) {
+  ignored_fields_.insert(field);
+}
+
+void MessageDifferencer::SetFractionAndMargin(const FieldDescriptor* field,
+                                              double fraction, double margin) {
+  default_field_comparator_.SetFractionAndMargin(field, fraction, margin);
+}
+
+void MessageDifferencer::ReportDifferencesToString(string* output) {
+  GOOGLE_DCHECK(output) << "Specified output string was NULL";
+
+  output_string_ = output;
+  output_string_->clear();
+}
+
+void MessageDifferencer::ReportDifferencesTo(Reporter* reporter) {
+  // If an output string is set, clear it to prevent
+  // it superceding the specified reporter.
+  if (output_string_) {
+    output_string_ = NULL;
+  }
+
+  reporter_ = reporter;
+}
+
+bool MessageDifferencer::FieldBefore(const FieldDescriptor* field1,
+                                     const FieldDescriptor* field2) {
+  // Handle sentinel values (i.e. make sure NULLs are always ordered
+  // at the end of the list).
+  if (field1 == NULL) {
+    return false;
+  }
+
+  if (field2 == NULL) {
+    return true;
+  }
+
+  // Always order fields by their tag number
+  return (field1->number() < field2->number());
+}
+
+bool MessageDifferencer::Compare(const Message& message1,
+                                 const Message& message2) {
+  vector<SpecificField> parent_fields;
+
+  bool result = false;
+
+  // Setup the internal reporter if need be.
+  if (output_string_) {
+    io::StringOutputStream output_stream(output_string_);
+    StreamReporter reporter(&output_stream);
+    reporter_ = &reporter;
+    result = Compare(message1, message2, &parent_fields);
+    reporter_ = NULL;
+  } else {
+    result = Compare(message1, message2, &parent_fields);
+  }
+
+  return result;
+}
+
+bool MessageDifferencer::CompareWithFields(
+    const Message& message1,
+    const Message& message2,
+    const vector<const FieldDescriptor*>& message1_fields_arg,
+    const vector<const FieldDescriptor*>& message2_fields_arg) {
+  if (message1.GetDescriptor() != message2.GetDescriptor()) {
+    GOOGLE_LOG(DFATAL) << "Comparison between two messages with different "
+                << "descriptors.";
+    return false;
+  }
+
+  vector<SpecificField> parent_fields;
+
+  bool result = false;
+
+  vector<const FieldDescriptor*> message1_fields(message1_fields_arg);
+  vector<const FieldDescriptor*> message2_fields(message2_fields_arg);
+
+  std::sort(message1_fields.begin(), message1_fields.end(), FieldBefore);
+  std::sort(message2_fields.begin(), message2_fields.end(), FieldBefore);
+  // Append NULL sentinel values.
+  message1_fields.push_back(NULL);
+  message2_fields.push_back(NULL);
+
+  // Setup the internal reporter if need be.
+  if (output_string_) {
+    io::StringOutputStream output_stream(output_string_);
+    StreamReporter reporter(&output_stream);
+    reporter_ = &reporter;
+    result = CompareRequestedFieldsUsingSettings(
+        message1, message2, message1_fields, message2_fields, &parent_fields);
+    reporter_ = NULL;
+  } else {
+    result = CompareRequestedFieldsUsingSettings(
+        message1, message2, message1_fields, message2_fields, &parent_fields);
+  }
+
+  return result;
+}
+
+bool MessageDifferencer::Compare(
+    const Message& message1,
+    const Message& message2,
+    vector<SpecificField>* parent_fields) {
+  const Descriptor* descriptor1 = message1.GetDescriptor();
+  const Descriptor* descriptor2 = message2.GetDescriptor();
+  if (descriptor1 != descriptor2) {
+    GOOGLE_LOG(DFATAL) << "Comparison between two messages with different "
+                << "descriptors.";
+    return false;
+  }
+  // Expand google.protobuf.Any payload if possible.
+  if (descriptor1->full_name() == internal::kAnyFullTypeName) {
+    google::protobuf::scoped_ptr<Message> data1;
+    google::protobuf::scoped_ptr<Message> data2;
+    if (UnpackAny(message1, &data1) && UnpackAny(message2, &data2)) {
+      return Compare(*data1, *data2, parent_fields);
+    }
+  }
+  const Reflection* reflection1 = message1.GetReflection();
+  const Reflection* reflection2 = message2.GetReflection();
+
+  // Retrieve all the set fields, including extensions.
+  vector<const FieldDescriptor*> message1_fields;
+  vector<const FieldDescriptor*> message2_fields;
+
+  reflection1->ListFields(message1, &message1_fields);
+  reflection2->ListFields(message2, &message2_fields);
+
+  // Add sentinel values to deal with the
+  // case where the number of the fields in
+  // each list are different.
+  message1_fields.push_back(NULL);
+  message2_fields.push_back(NULL);
+
+  bool unknown_compare_result = true;
+  // Ignore unknown fields in EQUIVALENT mode
+  if (message_field_comparison_ != EQUIVALENT) {
+    const google::protobuf::UnknownFieldSet* unknown_field_set1 =
+        &reflection1->GetUnknownFields(message1);
+    const google::protobuf::UnknownFieldSet* unknown_field_set2 =
+        &reflection2->GetUnknownFields(message2);
+    if (!CompareUnknownFields(message1, message2,
+                              *unknown_field_set1, *unknown_field_set2,
+                              parent_fields)) {
+      if (reporter_ == NULL) {
+        return false;
+      };
+      unknown_compare_result = false;
+    }
+  }
+
+  return CompareRequestedFieldsUsingSettings(
+      message1, message2,
+      message1_fields, message2_fields,
+      parent_fields) && unknown_compare_result;
+}
+
+bool MessageDifferencer::CompareRequestedFieldsUsingSettings(
+    const Message& message1,
+    const Message& message2,
+    const vector<const FieldDescriptor*>& message1_fields,
+    const vector<const FieldDescriptor*>& message2_fields,
+    vector<SpecificField>* parent_fields) {
+  if (scope_ == FULL) {
+    if (message_field_comparison_ == EQUIVALENT) {
+      // We need to merge the field lists of both messages (i.e.
+      // we are merely checking for a difference in field values,
+      // rather than the addition or deletion of fields).
+      vector<const FieldDescriptor*> fields_union;
+      CombineFields(message1_fields, FULL, message2_fields, FULL,
+                    &fields_union);
+      return CompareWithFieldsInternal(message1, message2, fields_union,
+                                       fields_union, parent_fields);
+    } else {
+      // Simple equality comparison, use the unaltered field lists.
+      return CompareWithFieldsInternal(message1, message2, message1_fields,
+                                       message2_fields, parent_fields);
+    }
+  } else {
+    if (message_field_comparison_ == EQUIVALENT) {
+      // We use the list of fields for message1 for both messages when
+      // comparing.  This way, extra fields in message2 are ignored,
+      // and missing fields in message2 use their default value.
+      return CompareWithFieldsInternal(message1, message2, message1_fields,
+                                       message1_fields, parent_fields);
+    } else {
+      // We need to consider the full list of fields for message1
+      // but only the intersection for message2.  This way, any fields
+      // only present in message2 will be ignored, but any fields only
+      // present in message1 will be marked as a difference.
+      vector<const FieldDescriptor*> fields_intersection;
+      CombineFields(message1_fields, PARTIAL, message2_fields, PARTIAL,
+                    &fields_intersection);
+      return CompareWithFieldsInternal(message1, message2, message1_fields,
+                                       fields_intersection, parent_fields);
+    }
+  }
+}
+
+void MessageDifferencer::CombineFields(
+    const vector<const FieldDescriptor*>& fields1,
+    Scope fields1_scope,
+    const vector<const FieldDescriptor*>& fields2,
+    Scope fields2_scope,
+    vector<const FieldDescriptor*>* combined_fields) {
+
+  int index1 = 0;
+  int index2 = 0;
+
+  while (index1 < fields1.size() && index2 < fields2.size()) {
+    const FieldDescriptor* field1 = fields1[index1];
+    const FieldDescriptor* field2 = fields2[index2];
+
+    if (FieldBefore(field1, field2)) {
+      if (fields1_scope == FULL) {
+        combined_fields->push_back(fields1[index1]);
+      }
+      ++index1;
+    } else if (FieldBefore(field2, field1)) {
+      if (fields2_scope == FULL) {
+        combined_fields->push_back(fields2[index2]);
+      }
+      ++index2;
+    } else {
+      combined_fields->push_back(fields1[index1]);
+      ++index1;
+      ++index2;
+    }
+  }
+}
+
+bool MessageDifferencer::CompareWithFieldsInternal(
+    const Message& message1,
+    const Message& message2,
+    const vector<const FieldDescriptor*>& message1_fields,
+    const vector<const FieldDescriptor*>& message2_fields,
+    vector<SpecificField>* parent_fields) {
+  bool isDifferent = false;
+  int field_index1 = 0;
+  int field_index2 = 0;
+
+  const Reflection* reflection1 = message1.GetReflection();
+  const Reflection* reflection2 = message2.GetReflection();
+
+  while (true) {
+    const FieldDescriptor* field1 = message1_fields[field_index1];
+    const FieldDescriptor* field2 = message2_fields[field_index2];
+
+    // Once we have reached sentinel values, we are done the comparison.
+    if (field1 == NULL && field2 == NULL) {
+      break;
+    }
+
+    // Check for differences in the field itself.
+    if (FieldBefore(field1, field2)) {
+      // Field 1 is not in the field list for message 2.
+      if (IsIgnored(message1, message2, field1, *parent_fields)) {
+        // We are ignoring field1. Report the ignore and move on to
+        // the next field in message1_fields.
+        if (reporter_ != NULL) {
+          SpecificField specific_field;
+          specific_field.field = field1;
+
+          parent_fields->push_back(specific_field);
+          reporter_->ReportIgnored(message1, message2, *parent_fields);
+          parent_fields->pop_back();
+        }
+        ++field_index1;
+        continue;
+      }
+
+      if (reporter_ != NULL) {
+        int count = field1->is_repeated() ?
+            reflection1->FieldSize(message1, field1) : 1;
+
+        for (int i = 0; i < count; ++i) {
+          SpecificField specific_field;
+          specific_field.field = field1;
+          specific_field.index = field1->is_repeated() ? i : -1;
+
+          parent_fields->push_back(specific_field);
+          reporter_->ReportDeleted(message1, message2, *parent_fields);
+          parent_fields->pop_back();
+        }
+
+        isDifferent = true;
+      } else {
+        return false;
+      }
+
+      ++field_index1;
+      continue;
+    } else if (FieldBefore(field2, field1)) {
+      // Field 2 is not in the field list for message 1.
+      if (IsIgnored(message1, message2, field2, *parent_fields)) {
+        // We are ignoring field2. Report the ignore and move on to
+        // the next field in message2_fields.
+        if (reporter_ != NULL) {
+          SpecificField specific_field;
+          specific_field.field = field2;
+
+          parent_fields->push_back(specific_field);
+          reporter_->ReportIgnored(message1, message2, *parent_fields);
+          parent_fields->pop_back();
+        }
+        ++field_index2;
+        continue;
+      }
+
+      if (reporter_ != NULL) {
+        int count = field2->is_repeated() ?
+            reflection2->FieldSize(message2, field2) : 1;
+
+        for (int i = 0; i < count; ++i) {
+          SpecificField specific_field;
+          specific_field.field = field2;
+          specific_field.index = field2->is_repeated() ? i : -1;
+          specific_field.new_index = specific_field.index;
+
+          parent_fields->push_back(specific_field);
+          reporter_->ReportAdded(message1, message2, *parent_fields);
+          parent_fields->pop_back();
+        }
+
+        isDifferent = true;
+      } else {
+        return false;
+      }
+
+      ++field_index2;
+      continue;
+    }
+
+    // By this point, field1 and field2 are guarenteed to point to the same
+    // field, so we can now compare the values.
+    if (IsIgnored(message1, message2, field1, *parent_fields)) {
+      // Ignore this field. Report and move on.
+      if (reporter_ != NULL) {
+        SpecificField specific_field;
+        specific_field.field = field1;
+
+        parent_fields->push_back(specific_field);
+        reporter_->ReportIgnored(message1, message2, *parent_fields);
+        parent_fields->pop_back();
+      }
+
+      ++field_index1;
+      ++field_index2;
+      continue;
+    }
+
+    bool fieldDifferent = false;
+    if (field1->is_repeated()) {
+      fieldDifferent = !CompareRepeatedField(message1, message2, field1,
+                                             parent_fields);
+      if (fieldDifferent) {
+        if (reporter_ == NULL) return false;
+        isDifferent = true;
+      }
+    } else {
+      fieldDifferent = !CompareFieldValueUsingParentFields(
+          message1, message2, field1, -1, -1, parent_fields);
+
+      // If we have found differences, either report them or terminate if
+      // no reporter is present.
+      if (fieldDifferent && reporter_ == NULL) {
+        return false;
+      }
+
+      if (reporter_ != NULL) {
+        SpecificField specific_field;
+        specific_field.field = field1;
+        parent_fields->push_back(specific_field);
+        if (fieldDifferent) {
+          reporter_->ReportModified(message1, message2, *parent_fields);
+          isDifferent = true;
+        } else if (report_matches_) {
+          reporter_->ReportMatched(message1, message2, *parent_fields);
+        }
+        parent_fields->pop_back();
+      }
+    }
+    // Increment the field indicies.
+    ++field_index1;
+    ++field_index2;
+  }
+
+  return !isDifferent;
+}
+
+bool MessageDifferencer::IsMatch(const FieldDescriptor* repeated_field,
+                                 const MapKeyComparator* key_comparator,
+                                 const Message* message1,
+                                 const Message* message2,
+                                 const vector<SpecificField>& parent_fields,
+                                 int index1, int index2) {
+  vector<SpecificField> current_parent_fields(parent_fields);
+  if (repeated_field->cpp_type() != FieldDescriptor::CPPTYPE_MESSAGE) {
+    return CompareFieldValueUsingParentFields(
+        *message1, *message2, repeated_field, index1, index2,
+        &current_parent_fields);
+  }
+  // Back up the Reporter and output_string_.  They will be reset in the
+  // following code.
+  Reporter* backup_reporter = reporter_;
+  string* output_string = output_string_;
+  reporter_ = NULL;
+  output_string_ = NULL;
+  bool match;
+
+  if (key_comparator == NULL) {
+    match = CompareFieldValueUsingParentFields(
+        *message1, *message2, repeated_field, index1, index2,
+        &current_parent_fields);
+  } else {
+    const Reflection* reflection1 = message1->GetReflection();
+    const Reflection* reflection2 = message2->GetReflection();
+    const Message& m1 =
+        reflection1->GetRepeatedMessage(*message1, repeated_field, index1);
+    const Message& m2 =
+        reflection2->GetRepeatedMessage(*message2, repeated_field, index2);
+    SpecificField specific_field;
+    specific_field.field = repeated_field;
+    current_parent_fields.push_back(specific_field);
+    match = key_comparator->IsMatch(m1, m2, current_parent_fields);
+  }
+
+  reporter_ = backup_reporter;
+  output_string_ = output_string;
+  return match;
+}
+
+bool MessageDifferencer::CompareRepeatedField(
+    const Message& message1,
+    const Message& message2,
+    const FieldDescriptor* repeated_field,
+    vector<SpecificField>* parent_fields) {
+  // the input FieldDescriptor is guaranteed to be repeated field.
+  const Reflection* reflection1 = message1.GetReflection();
+  const Reflection* reflection2 = message2.GetReflection();
+  const int count1 = reflection1->FieldSize(message1, repeated_field);
+  const int count2 = reflection2->FieldSize(message2, repeated_field);
+  const bool treated_as_subset = IsTreatedAsSubset(repeated_field);
+
+  // If the field is not treated as subset and no detailed reports is needed,
+  // we do a quick check on the number of the elements to avoid unnecessary
+  // comparison.
+  if (count1 != count2 && reporter_ == NULL && !treated_as_subset) {
+    return false;
+  }
+  // A match can never be found if message1 has more items than message2.
+  if (count1 > count2 && reporter_ == NULL) {
+    return false;
+  }
+
+  // These two list are used for store the index of the correspondent
+  // element in peer repeated field.
+  vector<int> match_list1;
+  vector<int> match_list2;
+
+  // Try to match indices of the repeated fields. Return false if match fails
+  // and there's no detailed report needed.
+  if (!MatchRepeatedFieldIndices(message1, message2, repeated_field,
+                                 *parent_fields, &match_list1, &match_list2) &&
+      reporter_ == NULL) {
+    return false;
+  }
+
+  bool fieldDifferent = false;
+  SpecificField specific_field;
+  specific_field.field = repeated_field;
+
+  // At this point, we have already matched pairs of fields (with the reporting
+  // to be done later). Now to check if the paired elements are different.
+  for (int i = 0; i < count1; i++) {
+    if (match_list1[i] == -1) continue;
+    specific_field.index = i;
+    specific_field.new_index = match_list1[i];
+
+    const bool result = CompareFieldValueUsingParentFields(
+        message1, message2, repeated_field, i, specific_field.new_index,
+        parent_fields);
+
+    // If we have found differences, either report them or terminate if
+    // no reporter is present. Note that ReportModified, ReportMoved, and
+    // ReportMatched are all mutually exclusive.
+    if (!result) {
+      if (reporter_ == NULL) return false;
+      parent_fields->push_back(specific_field);
+      reporter_->ReportModified(message1, message2, *parent_fields);
+      parent_fields->pop_back();
+      fieldDifferent = true;
+    } else if (reporter_ != NULL &&
+               specific_field.index != specific_field.new_index) {
+      parent_fields->push_back(specific_field);
+      reporter_->ReportMoved(message1, message2, *parent_fields);
+      parent_fields->pop_back();
+    } else if (report_matches_ && reporter_ != NULL) {
+      parent_fields->push_back(specific_field);
+      reporter_->ReportMatched(message1, message2, *parent_fields);
+      parent_fields->pop_back();
+    }
+  }
+
+  // Report any remaining additions or deletions.
+  for (int i = 0; i < count2; ++i) {
+    if (match_list2[i] != -1) continue;
+    if (!treated_as_subset) {
+      fieldDifferent = true;
+    }
+
+    if (reporter_ == NULL) continue;
+    specific_field.index = i;
+    specific_field.new_index = i;
+    parent_fields->push_back(specific_field);
+    reporter_->ReportAdded(message1, message2, *parent_fields);
+    parent_fields->pop_back();
+  }
+
+  for (int i = 0; i < count1; ++i) {
+    if (match_list1[i] != -1) continue;
+    specific_field.index = i;
+    parent_fields->push_back(specific_field);
+    reporter_->ReportDeleted(message1, message2, *parent_fields);
+    parent_fields->pop_back();
+    fieldDifferent = true;
+  }
+  return !fieldDifferent;
+}
+
+bool MessageDifferencer::CompareFieldValue(const Message& message1,
+                                           const Message& message2,
+                                           const FieldDescriptor* field,
+                                           int index1,
+                                           int index2) {
+  return CompareFieldValueUsingParentFields(message1, message2, field, index1,
+                                            index2, NULL);
+}
+
+bool MessageDifferencer::CompareFieldValueUsingParentFields(
+    const Message& message1, const Message& message2,
+    const FieldDescriptor* field, int index1, int index2,
+    vector<SpecificField>* parent_fields) {
+  FieldContext field_context(parent_fields);
+  FieldComparator::ComparisonResult result = GetFieldComparisonResult(
+      message1, message2, field, index1, index2, &field_context);
+
+  if (field->cpp_type() == FieldDescriptor::CPPTYPE_MESSAGE &&
+      result == FieldComparator::RECURSE) {
+    // Get the nested messages and compare them using one of the Compare
+    // methods.
+    const Reflection* reflection1 = message1.GetReflection();
+    const Reflection* reflection2 = message2.GetReflection();
+    const Message& m1 = field->is_repeated() ?
+        reflection1->GetRepeatedMessage(message1, field, index1) :
+        reflection1->GetMessage(message1, field);
+    const Message& m2 = field->is_repeated() ?
+        reflection2->GetRepeatedMessage(message2, field, index2) :
+        reflection2->GetMessage(message2, field);
+
+    // parent_fields is used in calls to Reporter methods.
+    if (parent_fields != NULL) {
+      // Append currently compared field to the end of parent_fields.
+      SpecificField specific_field;
+      specific_field.field = field;
+      specific_field.index = index1;
+      specific_field.new_index = index2;
+      parent_fields->push_back(specific_field);
+      const bool compare_result = Compare(m1, m2, parent_fields);
+      parent_fields->pop_back();
+      return compare_result;
+    } else {
+      // Recreates parent_fields as if m1 and m2 had no parents.
+      return Compare(m1, m2);
+    }
+  } else {
+    return (result == FieldComparator::SAME);
+  }
+}
+
+bool MessageDifferencer::CheckPathChanged(
+    const vector<SpecificField>& field_path) {
+  for (int i = 0; i < field_path.size(); ++i) {
+    if (field_path[i].index != field_path[i].new_index) return true;
+  }
+  return false;
+}
+
+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 list_fields_.find(field) == list_fields_.end();
+  return (set_fields_.find(field) != set_fields_.end());
+}
+
+bool MessageDifferencer::IsTreatedAsSubset(const FieldDescriptor* field) {
+  return scope_ == PARTIAL &&
+      (IsTreatedAsSet(field) || GetMapKeyComparator(field) != NULL);
+}
+
+bool MessageDifferencer::IsIgnored(
+    const Message& message1,
+    const Message& message2,
+    const FieldDescriptor* field,
+    const vector<SpecificField>& parent_fields) {
+  if (ignored_fields_.find(field) != ignored_fields_.end()) {
+    return true;
+  }
+  for (int i = 0; i < ignore_criteria_.size(); ++i) {
+    if (ignore_criteria_[i]->IsIgnored(message1, message2, field,
+                                       parent_fields)) {
+      return true;
+    }
+  }
+  return false;
+}
+
+bool MessageDifferencer::IsUnknownFieldIgnored(
+    const Message& message1, const Message& message2,
+    const SpecificField& field, const vector<SpecificField>& parent_fields) {
+  for (int i = 0; i < ignore_criteria_.size(); ++i) {
+    if (ignore_criteria_[i]->IsUnknownFieldIgnored(message1, message2, field,
+                                                   parent_fields)) {
+      return true;
+    }
+  }
+  return false;
+}
+
+const MessageDifferencer::MapKeyComparator* MessageDifferencer
+    ::GetMapKeyComparator(const FieldDescriptor* field) {
+  if (!field->is_repeated()) return NULL;
+  if (map_field_key_comparator_.find(field) !=
+      map_field_key_comparator_.end()) {
+    return map_field_key_comparator_[field];
+  }
+  return NULL;
+}
+
+namespace {
+
+typedef pair<int, const UnknownField*> IndexUnknownFieldPair;
+
+struct UnknownFieldOrdering {
+  inline bool operator()(const IndexUnknownFieldPair& a,
+                         const IndexUnknownFieldPair& b) const {
+    if (a.second->number() < b.second->number()) return true;
+    if (a.second->number() > b.second->number()) return false;
+    return a.second->type() < b.second->type();
+  }
+};
+
+}  // namespace
+
+bool MessageDifferencer::UnpackAny(const Message& any,
+                                   google::protobuf::scoped_ptr<Message>* data) {
+  const Reflection* reflection = any.GetReflection();
+  const FieldDescriptor* type_url_field;
+  const FieldDescriptor* value_field;
+  if (!internal::GetAnyFieldDescriptors(any, &type_url_field, &value_field)) {
+    return false;
+  }
+  const string& type_url = reflection->GetString(any, type_url_field);
+  string full_type_name;
+  if (!internal::ParseAnyTypeUrl(type_url, &full_type_name)) {
+    return false;
+  }
+
+  const google::protobuf::Descriptor* desc =
+      any.GetDescriptor()->file()->pool()->FindMessageTypeByName(
+          full_type_name);
+  if (desc == NULL) {
+    GOOGLE_LOG(ERROR) << "Proto type '" << full_type_name << "' not found";
+    return false;
+  }
+
+  if (dynamic_message_factory_ == NULL) {
+    dynamic_message_factory_.reset(new DynamicMessageFactory());
+  }
+  data->reset(dynamic_message_factory_->GetPrototype(desc)->New());
+  string serialized_value = reflection->GetString(any, value_field);
+  if (!(*data)->ParseFromString(serialized_value)) {
+    GOOGLE_LOG(ERROR) << "Failed to parse value for " << full_type_name;
+    return false;
+  }
+  return true;
+}
+
+bool MessageDifferencer::CompareUnknownFields(
+    const Message& message1, const Message& message2,
+    const google::protobuf::UnknownFieldSet& unknown_field_set1,
+    const google::protobuf::UnknownFieldSet& unknown_field_set2,
+    vector<SpecificField>* parent_field) {
+  // Ignore unknown fields in EQUIVALENT mode.
+  if (message_field_comparison_ == EQUIVALENT) return true;
+
+  if (unknown_field_set1.empty() && unknown_field_set2.empty()) {
+    return true;
+  }
+
+  bool is_different = false;
+
+  // We first sort the unknown fields by field number and type (in other words,
+  // in tag order), making sure to preserve ordering of values with the same
+  // tag.  This allows us to report only meaningful differences between the
+  // two sets -- that is, differing values for the same tag.  We use
+  // IndexUnknownFieldPairs to keep track of the field's original index for
+  // reporting purposes.
+  vector<IndexUnknownFieldPair> fields1;  // unknown_field_set1, sorted
+  vector<IndexUnknownFieldPair> fields2;  // unknown_field_set2, sorted
+  fields1.reserve(unknown_field_set1.field_count());
+  fields2.reserve(unknown_field_set2.field_count());
+
+  for (int i = 0; i < unknown_field_set1.field_count(); i++) {
+    fields1.push_back(std::make_pair(i, &unknown_field_set1.field(i)));
+  }
+  for (int i = 0; i < unknown_field_set2.field_count(); i++) {
+    fields2.push_back(std::make_pair(i, &unknown_field_set2.field(i)));
+  }
+
+  UnknownFieldOrdering is_before;
+  std::stable_sort(fields1.begin(), fields1.end(), is_before);
+  std::stable_sort(fields2.begin(), fields2.end(), is_before);
+
+  // In order to fill in SpecificField::index, we have to keep track of how
+  // many values we've seen with the same field number and type.
+  // current_repeated points at the first field in this range, and
+  // current_repeated_start{1,2} are the indexes of the first field in the
+  // range within fields1 and fields2.
+  const UnknownField* current_repeated = NULL;
+  int current_repeated_start1 = 0;
+  int current_repeated_start2 = 0;
+
+  // Now that we have two sorted lists, we can detect fields which appear only
+  // in one list or the other by traversing them simultaneously.
+  int index1 = 0;
+  int index2 = 0;
+  while (index1 < fields1.size() || index2 < fields2.size()) {
+    enum { ADDITION, DELETION, MODIFICATION, COMPARE_GROUPS,
+      NO_CHANGE } change_type;
+
+    // focus_field is the field we're currently reporting on.  (In the case
+    // of a modification, it's the field on the left side.)
+    const UnknownField* focus_field;
+    bool match = false;
+
+    if (index2 == fields2.size() ||
+        (index1 < fields1.size() &&
+          is_before(fields1[index1], fields2[index2]))) {
+      // fields1[index1] is not present in fields2.
+      change_type = DELETION;
+      focus_field = fields1[index1].second;
+    } else if (index1 == fields1.size() ||
+               is_before(fields2[index2], fields1[index1])) {
+      // fields2[index2] is not present in fields1.
+      if (scope_ == PARTIAL) {
+        // Ignore.
+        ++index2;
+        continue;
+      }
+      change_type = ADDITION;
+      focus_field = fields2[index2].second;
+    } else {
+      // Field type and number are the same.  See if the values differ.
+      change_type = MODIFICATION;
+      focus_field = fields1[index1].second;
+
+      switch (focus_field->type()) {
+        case UnknownField::TYPE_VARINT:
+          match = fields1[index1].second->varint() ==
+                  fields2[index2].second->varint();
+          break;
+        case UnknownField::TYPE_FIXED32:
+          match = fields1[index1].second->fixed32() ==
+                  fields2[index2].second->fixed32();
+          break;
+        case UnknownField::TYPE_FIXED64:
+          match = fields1[index1].second->fixed64() ==
+                  fields2[index2].second->fixed64();
+          break;
+        case UnknownField::TYPE_LENGTH_DELIMITED:
+          match = fields1[index1].second->length_delimited() ==
+                  fields2[index2].second->length_delimited();
+          break;
+        case UnknownField::TYPE_GROUP:
+          // We must deal with this later, after building the SpecificField.
+          change_type = COMPARE_GROUPS;
+          break;
+      }
+      if (match && change_type != COMPARE_GROUPS) {
+        change_type = NO_CHANGE;
+      }
+    }
+
+    if (current_repeated == NULL ||
+        focus_field->number() != current_repeated->number() ||
+        focus_field->type() != current_repeated->type()) {
+      // We've started a new repeated field.
+      current_repeated = focus_field;
+      current_repeated_start1 = index1;
+      current_repeated_start2 = index2;
+    }
+
+    if (change_type == NO_CHANGE && reporter_ == NULL) {
+      // Fields were already compared and matched and we have no reporter.
+      ++index1;
+      ++index2;
+      continue;
+    }
+
+    // Build the SpecificField.  This is slightly complicated.
+    SpecificField specific_field;
+    specific_field.unknown_field_number = focus_field->number();
+    specific_field.unknown_field_type = focus_field->type();
+
+    specific_field.unknown_field_set1 = &unknown_field_set1;
+    specific_field.unknown_field_set2 = &unknown_field_set2;
+
+    if (change_type != ADDITION) {
+      specific_field.unknown_field_index1 = fields1[index1].first;
+    }
+    if (change_type != DELETION) {
+      specific_field.unknown_field_index2 = fields2[index2].first;
+    }
+
+    // Calculate the field index.
+    if (change_type == ADDITION) {
+      specific_field.index = index2 - current_repeated_start2;
+      specific_field.new_index = index2 - current_repeated_start2;
+    } else {
+      specific_field.index = index1 - current_repeated_start1;
+      specific_field.new_index = index2 - current_repeated_start2;
+    }
+
+    if (IsUnknownFieldIgnored(message1, message2, specific_field,
+                              *parent_field)) {
+      if (reporter_ != NULL) {
+        parent_field->push_back(specific_field);
+        reporter_->ReportUnknownFieldIgnored(message1, message2, *parent_field);
+        parent_field->pop_back();
+      }
+      return true;
+    }
+
+    if (change_type == ADDITION || change_type == DELETION ||
+        change_type == MODIFICATION) {
+      if (reporter_ == NULL) {
+        // We found a difference and we have no reproter.
+        return false;
+      }
+      is_different = true;
+    }
+
+    parent_field->push_back(specific_field);
+
+    switch (change_type) {
+      case ADDITION:
+        reporter_->ReportAdded(message1, message2, *parent_field);
+        ++index2;
+        break;
+      case DELETION:
+        reporter_->ReportDeleted(message1, message2, *parent_field);
+        ++index1;
+        break;
+      case MODIFICATION:
+        reporter_->ReportModified(message1, message2, *parent_field);
+        ++index1;
+        ++index2;
+        break;
+      case COMPARE_GROUPS:
+        if (!CompareUnknownFields(message1, message2,
+                                  fields1[index1].second->group(),
+                                  fields2[index2].second->group(),
+                                  parent_field)) {
+          if (reporter_ == NULL) return false;
+          is_different = true;
+          reporter_->ReportModified(message1, message2, *parent_field);
+        }
+        ++index1;
+        ++index2;
+        break;
+      case NO_CHANGE:
+        ++index1;
+        ++index2;
+        if (report_matches_) {
+          reporter_->ReportMatched(message1, message2, *parent_field);
+        }
+    }
+
+    parent_field->pop_back();
+  }
+
+  return !is_different;
+}
+
+namespace {
+
+// Find maximum bipartite matching using the argumenting path algorithm.
+class MaximumMatcher {
+ public:
+  typedef ResultCallback2<bool, int, int> NodeMatchCallback;
+  // MaximumMatcher takes ownership of the passed in callback and uses it to
+  // determine whether a node on the left side of the bipartial graph matches
+  // a node on the right side. count1 is the number of nodes on the left side
+  // of the graph and count2 to is the number of nodes on the right side.
+  // Every node is referred to using 0-based indices.
+  // If a maximum match is found, the result will be stored in match_list1 and
+  // match_list2. match_list1[i] == j means the i-th node on the left side is
+  // matched to the j-th node on the right side and match_list2[x] == y means
+  // the x-th node on the right side is matched to y-th node on the left side.
+  // match_list1[i] == -1 means the node is not matched. Same with match_list2.
+  MaximumMatcher(int count1, int count2, NodeMatchCallback* callback,
+                 vector<int>* match_list1, vector<int>* match_list2);
+  // Find a maximum match and return the number of matched node pairs.
+  // If early_return is true, this method will return 0 immediately when it
+  // finds that not all nodes on the left side can be matched.
+  int FindMaximumMatch(bool early_return);
+ private:
+  // Determines whether the node on the left side of the bipartial graph
+  // matches the one on the right side.
+  bool Match(int left, int right);
+  // Find an argumenting path starting from the node v on the left side. If a
+  // path can be found, update match_list2_ to reflect the path and return
+  // true.
+  bool FindArgumentPathDFS(int v, vector<bool>* visited);
+
+  int count1_;
+  int count2_;
+  google::protobuf::scoped_ptr<NodeMatchCallback> match_callback_;
+  map<pair<int, int>, bool> cached_match_results_;
+  vector<int>* match_list1_;
+  vector<int>* match_list2_;
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(MaximumMatcher);
+};
+
+MaximumMatcher::MaximumMatcher(int count1, int count2,
+                               NodeMatchCallback* callback,
+                               vector<int>* match_list1,
+                               vector<int>* match_list2)
+    : count1_(count1), count2_(count2), match_callback_(callback),
+      match_list1_(match_list1), match_list2_(match_list2) {
+  match_list1_->assign(count1, -1);
+  match_list2_->assign(count2, -1);
+}
+
+int MaximumMatcher::FindMaximumMatch(bool early_return) {
+  int result = 0;
+  for (int i = 0; i < count1_; ++i) {
+    vector<bool> visited(count1_);
+    if (FindArgumentPathDFS(i, &visited)) {
+      ++result;
+    } else if (early_return) {
+      return 0;
+    }
+  }
+  // Backfill match_list1_ as we only filled match_list2_ when finding
+  // argumenting pathes.
+  for (int i = 0; i < count2_; ++i) {
+    if ((*match_list2_)[i] != -1) {
+      (*match_list1_)[(*match_list2_)[i]] = i;
+    }
+  }
+  return result;
+}
+
+bool MaximumMatcher::Match(int left, int right) {
+  pair<int, int> p(left, right);
+  map<pair<int, int>, bool>::iterator it = cached_match_results_.find(p);
+  if (it != cached_match_results_.end()) {
+    return it->second;
+  }
+  cached_match_results_[p] = match_callback_->Run(left, right);
+  return cached_match_results_[p];
+}
+
+bool MaximumMatcher::FindArgumentPathDFS(int v, vector<bool>* visited) {
+  (*visited)[v] = true;
+  // We try to match those un-matched nodes on the right side first. This is
+  // the step that the navie greedy matching algorithm uses. In the best cases
+  // where the greedy algorithm can find a maximum matching, we will always
+  // find a match in this step and the performance will be identical to the
+  // greedy algorithm.
+  for (int i = 0; i < count2_; ++i) {
+    int matched = (*match_list2_)[i];
+    if (matched == -1 && Match(v, i)) {
+      (*match_list2_)[i] = v;
+      return true;
+    }
+  }
+  // Then we try those already matched nodes and see if we can find an
+  // alternaive match for the node matched to them.
+  // The greedy algorithm will stop before this and fail to produce the
+  // correct result.
+  for (int i = 0; i < count2_; ++i) {
+    int matched = (*match_list2_)[i];
+    if (matched != -1 && Match(v, i)) {
+      if (!(*visited)[matched] && FindArgumentPathDFS(matched, visited)) {
+        (*match_list2_)[i] = v;
+        return true;
+      }
+    }
+  }
+  return false;
+}
+
+}  // namespace
+
+bool MessageDifferencer::MatchRepeatedFieldIndices(
+    const Message& message1,
+    const Message& message2,
+    const FieldDescriptor* repeated_field,
+    const vector<SpecificField>& parent_fields,
+    vector<int>* match_list1,
+    vector<int>* match_list2) {
+  const int count1 =
+      message1.GetReflection()->FieldSize(message1, repeated_field);
+  const int count2 =
+      message2.GetReflection()->FieldSize(message2, repeated_field);
+  const MapKeyComparator* key_comparator = GetMapKeyComparator(repeated_field);
+
+  match_list1->assign(count1, -1);
+  match_list2->assign(count2, -1);
+
+  SpecificField specific_field;
+  specific_field.field = repeated_field;
+
+  bool success = true;
+  // Find potential match if this is a special repeated field.
+  if (key_comparator != NULL || IsTreatedAsSet(repeated_field)) {
+    if (scope_ == PARTIAL) {
+      // When partial matching is enabled, Compare(a, b) && Compare(a, c)
+      // doesn't neccessarily imply Compare(b, c). Therefore a naive greedy
+      // algorithm will fail to find a maximum matching.
+      // Here we use the argumenting path algorithm.
+      MaximumMatcher::NodeMatchCallback* callback =
+          google::protobuf::internal::NewPermanentCallback(
+              this, &MessageDifferencer::IsMatch,
+              repeated_field, key_comparator,
+              &message1, &message2, parent_fields);
+      MaximumMatcher matcher(count1, count2, callback, match_list1,
+                             match_list2);
+      // If diff info is not needed, we should end the matching process as
+      // soon as possible if not all items can be matched.
+      bool early_return = (reporter_ == NULL);
+      int match_count = matcher.FindMaximumMatch(early_return);
+      if (match_count != count1 && reporter_ == NULL) return false;
+      success = success && (match_count == count1);
+    } else {
+      for (int i = 0; i < count1; ++i) {
+        // Indicates any matched elements for this repeated field.
+        bool match = false;
+
+        specific_field.index = i;
+        specific_field.new_index = i;
+
+        for (int j = 0; j < count2; j++) {
+          if (match_list2->at(j) != -1) continue;
+          specific_field.index = i;
+          specific_field.new_index = j;
+
+          match = IsMatch(repeated_field, key_comparator,
+                          &message1, &message2, parent_fields, i, j);
+
+          if (match) {
+            match_list1->at(specific_field.index) = specific_field.new_index;
+            match_list2->at(specific_field.new_index) = specific_field.index;
+            break;
+          }
+        }
+        if (!match && reporter_ == NULL) return false;
+        success = success && match;
+      }
+    }
+  } else {
+    // If this field should be treated as list, just label the match_list.
+    for (int i = 0; i < count1 && i < count2; i++) {
+      match_list1->at(i) = i;
+      match_list2->at(i) = i;
+    }
+  }
+
+  return success;
+}
+
+FieldComparator::ComparisonResult MessageDifferencer::GetFieldComparisonResult(
+    const Message& message1, const Message& message2,
+    const FieldDescriptor* field, int index1, int index2,
+    const FieldContext* field_context) {
+  FieldComparator* comparator = field_comparator_ != NULL ?
+      field_comparator_ : &default_field_comparator_;
+  return comparator->Compare(message1, message2, field,
+                             index1, index2, field_context);
+}
+
+// ===========================================================================
+
+MessageDifferencer::Reporter::Reporter() { }
+MessageDifferencer::Reporter::~Reporter() {}
+
+// ===========================================================================
+
+MessageDifferencer::MapKeyComparator::MapKeyComparator() {}
+MessageDifferencer::MapKeyComparator::~MapKeyComparator() {}
+
+// ===========================================================================
+
+MessageDifferencer::IgnoreCriteria::IgnoreCriteria() {}
+MessageDifferencer::IgnoreCriteria::~IgnoreCriteria() {}
+
+// ===========================================================================
+
+// Note that the printer's delimiter is not used, because if we are given a
+// printer, we don't know its delimiter.
+MessageDifferencer::StreamReporter::StreamReporter(
+    io::ZeroCopyOutputStream* output) : printer_(new io::Printer(output, '$')),
+                                        delete_printer_(true),
+                                        report_modified_aggregates_(false) { }
+
+MessageDifferencer::StreamReporter::StreamReporter(
+    io::Printer* printer) : printer_(printer),
+                            delete_printer_(false),
+                            report_modified_aggregates_(false) { }
+
+MessageDifferencer::StreamReporter::~StreamReporter() {
+  if (delete_printer_) delete printer_;
+}
+
+void MessageDifferencer::StreamReporter::PrintPath(
+    const vector<SpecificField>& field_path, bool left_side) {
+  for (int i = 0; i < field_path.size(); ++i) {
+    if (i > 0) {
+      printer_->Print(".");
+    }
+
+    SpecificField specific_field = field_path[i];
+
+    if (specific_field.field != NULL) {
+      if (specific_field.field->is_extension()) {
+        printer_->Print("($name$)", "name",
+                        specific_field.field->full_name());
+      } else {
+        printer_->PrintRaw(specific_field.field->name());
+      }
+    } else {
+      printer_->PrintRaw(SimpleItoa(specific_field.unknown_field_number));
+    }
+    if (left_side && specific_field.index >= 0) {
+      printer_->Print("[$name$]", "name", SimpleItoa(specific_field.index));
+    }
+    if (!left_side && specific_field.new_index >= 0) {
+      printer_->Print("[$name$]", "name", SimpleItoa(specific_field.new_index));
+    }
+  }
+}
+
+void MessageDifferencer::
+StreamReporter::PrintValue(const Message& message,
+                           const vector<SpecificField>& field_path,
+                           bool left_side) {
+  const SpecificField& specific_field = field_path.back();
+  const FieldDescriptor* field = specific_field.field;
+  if (field != NULL) {
+    string output;
+    int index = left_side ? specific_field.index : specific_field.new_index;
+    if (field->cpp_type() == FieldDescriptor::CPPTYPE_MESSAGE) {
+      const Reflection* reflection = message.GetReflection();
+      const Message& field_message = field->is_repeated() ?
+          reflection->GetRepeatedMessage(message, field, index) :
+          reflection->GetMessage(message, field);
+      output = field_message.ShortDebugString();
+      if (output.empty()) {
+        printer_->Print("{ }");
+      } else {
+        printer_->Print("{ $name$ }", "name", output);
+      }
+    } else {
+      TextFormat::PrintFieldValueToString(message, field, index, &output);
+      printer_->PrintRaw(output);
+    }
+  } else {
+    const UnknownFieldSet* unknown_fields =
+        (left_side ?
+         specific_field.unknown_field_set1 :
+         specific_field.unknown_field_set2);
+    const UnknownField* unknown_field = &unknown_fields->field(
+        left_side ?
+        specific_field.unknown_field_index1 :
+        specific_field.unknown_field_index2);
+    PrintUnknownFieldValue(unknown_field);
+  }
+}
+
+void MessageDifferencer::
+StreamReporter::PrintUnknownFieldValue(const UnknownField* unknown_field) {
+  GOOGLE_CHECK(unknown_field != NULL) << " Cannot print NULL unknown_field.";
+
+  string output;
+  switch (unknown_field->type()) {
+    case UnknownField::TYPE_VARINT:
+      output = SimpleItoa(unknown_field->varint());
+      break;
+    case UnknownField::TYPE_FIXED32:
+      output = StrCat("0x", strings::Hex(unknown_field->fixed32(),
+                                         strings::ZERO_PAD_8));
+      break;
+    case UnknownField::TYPE_FIXED64:
+      output = StrCat("0x", strings::Hex(unknown_field->fixed64(),
+                                         strings::ZERO_PAD_16));
+      break;
+    case UnknownField::TYPE_LENGTH_DELIMITED:
+      output = StringPrintf("\"%s\"",
+          CEscape(unknown_field->length_delimited()).c_str());
+      break;
+    case UnknownField::TYPE_GROUP:
+      // TODO(kenton):  Print the contents of the group like we do for
+      //   messages.  Requires an equivalent of ShortDebugString() for
+      //   UnknownFieldSet.
+      output = "{ ... }";
+      break;
+  }
+  printer_->PrintRaw(output);
+}
+
+void MessageDifferencer::StreamReporter::Print(const string& str) {
+  printer_->Print(str.c_str());
+}
+
+void MessageDifferencer::StreamReporter::ReportAdded(
+    const Message& message1,
+    const Message& message2,
+    const vector<SpecificField>& field_path) {
+  printer_->Print("added: ");
+  PrintPath(field_path, false);
+  printer_->Print(": ");
+  PrintValue(message2, field_path, false);
+  printer_->Print("\n");  // Print for newlines.
+}
+
+void MessageDifferencer::StreamReporter::ReportDeleted(
+    const Message& message1,
+    const Message& message2,
+    const vector<SpecificField>& field_path) {
+  printer_->Print("deleted: ");
+  PrintPath(field_path, true);
+  printer_->Print(": ");
+  PrintValue(message1, field_path, true);
+  printer_->Print("\n");  // Print for newlines
+}
+
+void MessageDifferencer::StreamReporter::ReportModified(
+    const Message& message1,
+    const Message& message2,
+    const vector<SpecificField>& field_path) {
+  if (!report_modified_aggregates_ && field_path.back().field == NULL) {
+    if (field_path.back().unknown_field_type == UnknownField::TYPE_GROUP) {
+      // Any changes to the subfields have already been printed.
+      return;
+    }
+  } else if (!report_modified_aggregates_) {
+    if (field_path.back().field->cpp_type() ==
+        FieldDescriptor::CPPTYPE_MESSAGE) {
+      // Any changes to the subfields have already been printed.
+      return;
+    }
+  }
+
+  printer_->Print("modified: ");
+  PrintPath(field_path, true);
+  if (CheckPathChanged(field_path)) {
+    printer_->Print(" -> ");
+    PrintPath(field_path, false);
+  }
+  printer_->Print(": ");
+  PrintValue(message1, field_path, true);
+  printer_->Print(" -> ");
+  PrintValue(message2, field_path, false);
+  printer_->Print("\n");  // Print for newlines.
+}
+
+void MessageDifferencer::StreamReporter::ReportMoved(
+    const Message& message1,
+    const Message& message2,
+    const vector<SpecificField>& field_path) {
+  printer_->Print("moved: ");
+  PrintPath(field_path, true);
+  printer_->Print(" -> ");
+  PrintPath(field_path, false);
+  printer_->Print(" : ");
+  PrintValue(message1, field_path, true);
+  printer_->Print("\n");  // Print for newlines.
+}
+
+void MessageDifferencer::StreamReporter::ReportMatched(
+    const Message& message1,
+    const Message& message2,
+    const vector<SpecificField>& field_path) {
+  printer_->Print("matched: ");
+  PrintPath(field_path, true);
+  if (CheckPathChanged(field_path)) {
+    printer_->Print(" -> ");
+    PrintPath(field_path, false);
+  }
+  printer_->Print(" : ");
+  PrintValue(message1, field_path, true);
+  printer_->Print("\n");  // Print for newlines.
+}
+
+void MessageDifferencer::StreamReporter::ReportIgnored(
+    const Message& message1,
+    const Message& message2,
+    const vector<SpecificField>& field_path) {
+  printer_->Print("ignored: ");
+  PrintPath(field_path, true);
+  if (CheckPathChanged(field_path)) {
+    printer_->Print(" -> ");
+    PrintPath(field_path, false);
+  }
+  printer_->Print("\n");  // Print for newlines.
+}
+
+void MessageDifferencer::StreamReporter::ReportUnknownFieldIgnored(
+    const Message& message1, const Message& message2,
+    const vector<SpecificField>& field_path) {
+  printer_->Print("ignored: ");
+  PrintPath(field_path, true);
+  if (CheckPathChanged(field_path)) {
+    printer_->Print(" -> ");
+    PrintPath(field_path, false);
+  }
+  printer_->Print("\n");  // Print for newlines.
+}
+
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google