Revert https://codereview.chromium.org/1291903002 (protobuf roll).

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

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-// 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.
-//
-// Aug. 2008: Added Unknown Fields Comparison for messages.
-// Aug. 2009: Added different options to compare repeated fields.
-// Apr. 2010: Moved field comparison to FieldComparator.
-
-#ifndef GOOGLE_PROTOBUF_UTIL_MESSAGE_DIFFERENCER_H__
-#define GOOGLE_PROTOBUF_UTIL_MESSAGE_DIFFERENCER_H__
-
-#include <map>
-#include <set>
-#include <string>
-#include <vector>
-#include <google/protobuf/descriptor.h>  // FieldDescriptor
-#include <google/protobuf/message.h>  // Message
-#include <google/protobuf/unknown_field_set.h>
-#include <google/protobuf/util/field_comparator.h>
-
-namespace google {
-namespace protobuf {
-
-class DynamicMessageFactory;
-class FieldDescriptor;
-
-namespace io {
-class ZeroCopyOutputStream;
-class Printer;
-}
-
-namespace util {
-
-class FieldContext;  // declared below MessageDifferencer
-
-// A basic differencer that can be used to determine
-// the differences between two specified Protocol Messages. If any differences
-// are found, the Compare method will return false, and any differencer reporter
-// specified via ReportDifferencesTo will have its reporting methods called (see
-// below for implementation of the report). Based off of the original
-// ProtocolDifferencer implementation in //net/proto/protocol-differencer.h
-// (Thanks Todd!).
-//
-// MessageDifferencer REQUIRES that compared messages be the same type, defined
-// as messages that share the same descriptor.  If not, the behavior of this
-// class is undefined.
-//
-// People disagree on what MessageDifferencer should do when asked to compare
-// messages with different descriptors.  Some people think it should always
-// return false.  Others expect it to try to look for similar fields and
-// compare them anyway -- especially if the descriptors happen to be identical.
-// If we chose either of these behaviors, some set of people would find it
-// surprising, and could end up writing code expecting the other behavior
-// without realizing their error.  Therefore, we forbid that usage.
-//
-// This class is implemented based on the proto2 reflection. The performance
-// should be good enough for normal usages. However, for places where the
-// performance is extremely sensitive, there are several alternatives:
-// - Comparing serialized string
-// Downside: false negatives (there are messages that are the same but their
-// serialized strings are different).
-// - Equals code generator by compiler plugin (net/proto2/contrib/equals_plugin)
-// Downside: more generated code; maintenance overhead for the additional rule
-// (must be in sync with the original proto_library).
-//
-// Note on handling of google.protobuf.Any: MessageDifferencer automatically
-// unpacks Any::value into a Message and compares its individual fields.
-// Messages encoded in a repeated Any cannot be compared using TreatAsMap.
-//
-//
-// Note on thread-safety: MessageDifferencer is *not* thread-safe. You need to
-// guard it with a lock to use the same MessageDifferencer instance from
-// multiple threads. Note that it's fine to call static comparison methods
-// (like MessageDifferencer::Equals) concurrently.
-class LIBPROTOBUF_EXPORT MessageDifferencer {
- public:
-  // Determines whether the supplied messages are equal. Equality is defined as
-  // all fields within the two messages being set to the same value. Primitive
-  // fields and strings are compared by value while embedded messages/groups
-  // are compared as if via a recursive call. Use IgnoreField() and Compare()
-  // if some fields should be ignored in the comparison.
-  //
-  // This method REQUIRES that the two messages have the same
-  // Descriptor (message1.GetDescriptor() == message2.GetDescriptor()).
-  static bool Equals(const Message& message1, const Message& message2);
-
-  // Determines whether the supplied messages are equivalent. Equivalency is
-  // defined as all fields within the two messages having the same value. This
-  // differs from the Equals method above in that fields with default values
-  // are considered set to said value automatically. For details on how default
-  // values are defined for each field type, see http://shortn/_x2Gv6XFrWt.
-  // Also, Equivalent() ignores unknown fields. Use IgnoreField() and Compare()
-  // if some fields should be ignored in the comparison.
-  //
-  // This method REQUIRES that the two messages have the same
-  // Descriptor (message1.GetDescriptor() == message2.GetDescriptor()).
-  static bool Equivalent(const Message& message1, const Message& message2);
-
-  // Determines whether the supplied messages are approximately equal.
-  // Approximate equality is defined as all fields within the two messages
-  // being approximately equal.  Primitive (non-float) fields and strings are
-  // compared by value, floats are compared using MathUtil::AlmostEquals() and
-  // embedded messages/groups are compared as if via a recursive call. Use
-  // IgnoreField() and Compare() if some fields should be ignored in the
-  // comparison.
-  //
-  // This method REQUIRES that the two messages have the same
-  // Descriptor (message1.GetDescriptor() == message2.GetDescriptor()).
-  static bool ApproximatelyEquals(const Message& message1,
-                                  const Message& message2);
-
-  // Determines whether the supplied messages are approximately equivalent.
-  // Approximate equivalency is defined as all fields within the two messages
-  // being approximately equivalent. As in
-  // MessageDifferencer::ApproximatelyEquals, primitive (non-float) fields and
-  // strings are compared by value, floats are compared using
-  // MathUtil::AlmostEquals() and embedded messages/groups are compared as if
-  // via a recursive call. However, fields with default values are considered
-  // set to said value, as per MessageDiffencer::Equivalent. Use IgnoreField()
-  // and Compare() if some fields should be ignored in the comparison.
-  //
-  // This method REQUIRES that the two messages have the same
-  // Descriptor (message1.GetDescriptor() == message2.GetDescriptor()).
-  static bool ApproximatelyEquivalent(const Message& message1,
-                                      const Message& message2);
-
-  // Identifies an individual field in a message instance.  Used for field_path,
-  // below.
-  struct SpecificField {
-    // For known fields, "field" is filled in and "unknown_field_number" is -1.
-    // For unknown fields, "field" is NULL, "unknown_field_number" is the field
-    // number, and "unknown_field_type" is its type.
-    const FieldDescriptor* field;
-    int unknown_field_number;
-    UnknownField::Type unknown_field_type;
-
-    // If this a repeated field, "index" is the index within it.  For unknown
-    // fields, this is the index of the field among all unknown fields of the
-    // same field number and type.
-    int index;
-
-    // If "field" is a repeated field which is being treated as a map or
-    // a set (see TreatAsMap() and TreatAsSet(), below), new_index indicates
-    // the index the position to which the element has moved.  This only
-    // applies to ReportMoved() and (in the case of TreatAsMap())
-    // ReportModified().  In all other cases, "new_index" will have the same
-    // value as "index".
-    int new_index;
-
-    // For unknown fields, these are the pointers to the UnknownFieldSet
-    // containing the unknown fields. In certain cases (e.g. proto1's
-    // MessageSet, or nested groups of unknown fields), these may differ from
-    // the messages' internal UnknownFieldSets.
-    const UnknownFieldSet* unknown_field_set1;
-    const UnknownFieldSet* unknown_field_set2;
-
-    // For unknown fields, these are the index of the field within the
-    // UnknownFieldSets. One or the other will be -1 when
-    // reporting an addition or deletion.
-    int unknown_field_index1;
-    int unknown_field_index2;
-
-    SpecificField()
-        : field(NULL),
-          unknown_field_number(-1),
-          index(-1),
-          new_index(-1),
-          unknown_field_set1(NULL),
-          unknown_field_set2(NULL),
-          unknown_field_index1(-1),
-          unknown_field_index2(-1) {}
-  };
-
-  // Abstract base class from which all MessageDifferencer
-  // reporters derive. The five Report* methods below will be called when
-  // a field has been added, deleted, modified, moved, or matched. The third
-  // argument is a vector of FieldDescriptor pointers which describes the chain
-  // of fields that was taken to find the current field. For example, for a
-  // field found in an embedded message, the vector will contain two
-  // FieldDescriptors. The first will be the field of the embedded message
-  // itself and the second will be the actual field in the embedded message
-  // that was added/deleted/modified.
-  class LIBPROTOBUF_EXPORT Reporter {
-   public:
-    Reporter();
-    virtual ~Reporter();
-
-    // Reports that a field has been added into Message2.
-    virtual void ReportAdded(
-        const Message& message1, const Message& message2,
-        const vector<SpecificField>& field_path) = 0;
-
-    // Reports that a field has been deleted from Message1.
-    virtual void ReportDeleted(
-        const Message& message1,
-        const Message& message2,
-        const vector<SpecificField>& field_path) = 0;
-
-    // Reports that the value of a field has been modified.
-    virtual void ReportModified(
-        const Message& message1,
-        const Message& message2,
-        const vector<SpecificField>& field_path) = 0;
-
-    // Reports that a repeated field has been moved to another location.  This
-    // only applies when using TreatAsSet or TreatAsMap()  -- see below. Also
-    // note that for any given field, ReportModified and ReportMoved are
-    // mutually exclusive. If a field has been both moved and modified, then
-    // only ReportModified will be called.
-    virtual void ReportMoved(
-        const Message& message1,
-        const Message& message2,
-        const vector<SpecificField>& field_path) { }
-
-    // Reports that two fields match. Useful for doing side-by-side diffs.
-    // This function is mutually exclusive with ReportModified and ReportMoved.
-    // Note that you must call set_report_matches(true) before calling Compare
-    // to make use of this function.
-    virtual void ReportMatched(
-        const Message& message1,
-        const Message& message2,
-        const vector<SpecificField>& field_path) { }
-
-    // Reports that two fields would have been compared, but the
-    // comparison has been skipped because the field was marked as
-    // 'ignored' using IgnoreField().  This function is mutually
-    // exclusive with all the other Report() functions.
-    //
-    // The contract of ReportIgnored is slightly different than the
-    // other Report() functions, in that |field_path.back().index| is
-    // always equal to -1, even if the last field is repeated. This is
-    // because while the other Report() functions indicate where in a
-    // repeated field the action (Addition, Deletion, etc...)
-    // happened, when a repeated field is 'ignored', the differencer
-    // simply calls ReportIgnored on the repeated field as a whole and
-    // moves on without looking at its individual elements.
-    //
-    // Furthermore, ReportIgnored() does not indicate whether the
-    // fields were in fact equal or not, as Compare() does not inspect
-    // these fields at all. It is up to the Reporter to decide whether
-    // the fields are equal or not (perhaps with a second call to
-    // Compare()), if it cares.
-    virtual void ReportIgnored(
-        const Message& message1,
-        const Message& message2,
-        const vector<SpecificField>& field_path) { }
-
-   private:
-    GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(Reporter);
-  };
-
-  // MapKeyComparator is used to determine if two elements have the same key
-  // when comparing elements of a repeated field as a map.
-  class LIBPROTOBUF_EXPORT MapKeyComparator {
-   public:
-    MapKeyComparator();
-    virtual ~MapKeyComparator();
-
-    virtual bool IsMatch(const Message& message1,
-                         const Message& message2,
-                         const vector<SpecificField>& parent_fields) const {
-      GOOGLE_CHECK(false) << "IsMatch() is not implemented.";
-      return false;
-    }
-
-   private:
-    GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(MapKeyComparator);
-  };
-
-  // Abstract base class from which all IgnoreCriteria derive.
-  // By adding IgnoreCriteria more complex ignore logic can be implemented.
-  // IgnoreCriteria are registed with AddIgnoreCriteria. For each compared
-  // field IsIgnored is called on each added IgnoreCriteria until one returns
-  // true or all return false.
-  // IsIgnored is called for fields where at least one side has a value.
-  class LIBPROTOBUF_EXPORT IgnoreCriteria {
-   public:
-    IgnoreCriteria();
-    virtual ~IgnoreCriteria();
-
-    // Returns true if the field should be ignored.
-    virtual bool IsIgnored(
-        const Message& message1,
-        const Message& message2,
-        const FieldDescriptor* field,
-        const vector<SpecificField>& parent_fields) = 0;
-  };
-
-  // To add a Reporter, construct default here, then use ReportDifferencesTo or
-  // ReportDifferencesToString.
-  explicit MessageDifferencer();
-
-  ~MessageDifferencer();
-
-  enum MessageFieldComparison {
-    EQUAL,       // Fields must be present in both messages
-                 // for the messages to be considered the same.
-    EQUIVALENT,  // Fields with default values are considered set
-                 // for comparison purposes even if not explicitly
-                 // set in the messages themselves.  Unknown fields
-                 // are ignored.
-  };
-
-  enum Scope {
-    FULL,    // All fields of both messages are considered in the comparison.
-    PARTIAL  // Only fields present in the first message are considered; fields
-             // set only in the second message will be skipped during
-             // comparison.
-  };
-
-  // DEPRECATED. Use FieldComparator::FloatComparison instead.
-  enum FloatComparison {
-    EXACT,       // Floats and doubles are compared exactly.
-    APPROXIMATE  // Floats and doubles are compared using the
-                 // MathUtil::AlmostEquals method.
-  };
-
-  enum RepeatedFieldComparison {
-    AS_LIST,     // Repeated fields are compared in order.  Differing values at
-                 // the same index are reported using ReportModified().  If the
-                 // repeated fields have different numbers of elements, the
-                 // unpaired elements are reported using ReportAdded() or
-                 // ReportDeleted().
-    AS_SET,      // Treat all the repeated fields as sets by default.
-                 // See TreatAsSet(), as below.
-  };
-
-  // The elements of the given repeated field will be treated as a set for
-  // diffing purposes, so different orderings of the same elements will be
-  // considered equal.  Elements which are present on both sides of the
-  // comparison but which have changed position will be reported with
-  // ReportMoved().  Elements which only exist on one side or the other are
-  // reported with ReportAdded() and ReportDeleted() regardless of their
-  // positions.  ReportModified() is never used for this repeated field.  If
-  // the only differences between the compared messages is that some fields
-  // have been moved, then the comparison returns true.
-  //
-  // If the scope of comparison is set to PARTIAL, then in addition to what's
-  // above, extra values added to repeated fields of the second message will
-  // not cause the comparison to fail.
-  //
-  // Note that set comparison is currently O(k * n^2) (where n is the total
-  // number of elements, and k is the average size of each element). In theory
-  // it could be made O(n * k) with a more complex hashing implementation. Feel
-  // free to contribute one if the current implementation is too slow for you.
-  // If partial matching is also enabled, the time complexity will be O(k * n^2
-  // + n^3) in which n^3 is the time complexity of the maximum matching
-  // algorithm.
-  //
-  // REQUIRES:  field->is_repeated()
-  void TreatAsSet(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.
-  // Differences are reported similarly to TreatAsSet(), except that
-  // ReportModified() is used to report elements with the same key but
-  // different values.  Note that if an element is both moved and modified,
-  // only ReportModified() will be called.  As with TreatAsSet, if the only
-  // differences between the compared messages is that some fields have been
-  // moved, then the comparison returns true. See TreatAsSet for notes on
-  // performance.
-  //
-  // REQUIRES:  field->is_repeated()
-  // REQUIRES:  field->cpp_type() == FieldDescriptor::CPPTYPE_MESSAGE
-  // REQUIRES:  key->containing_type() == field->message_type()
-  void TreatAsMap(const FieldDescriptor* field, const FieldDescriptor* key);
-  // Same as TreatAsMap except that this method will use multiple fields as
-  // the key in comparison. All specified fields in 'key_fields' should be
-  // present in the compared elements. Two elements will be treated as having
-  // the same key iff they have the same value for every specified field. There
-  // are two steps in the comparison process. The first one is key matching.
-  // Every element from one message will be compared to every element from
-  // the other message. Only fields in 'key_fields' are compared in this step
-  // to decide if two elements have the same key. The second step is value
-  // comparison. Those pairs of elements with the same key (with equal value
-  // for every field in 'key_fields') will be compared in this step.
-  // Time complexity of the first step is O(s * m * n ^ 2) where s is the
-  // average size of the fields specified in 'key_fields', m is the number of
-  // fields in 'key_fields' and n is the number of elements. If partial
-  // matching is enabled, an extra O(n^3) will be incured by the maximum
-  // matching algorithm. The second step is O(k * n) where k is the average
-  // size of each element.
-  void TreatAsMapWithMultipleFieldsAsKey(
-      const FieldDescriptor* field,
-      const vector<const FieldDescriptor*>& key_fields);
-  // Same as TreatAsMapWithMultipleFieldsAsKey, except that each of the field
-  // do not necessarily need to be a direct subfield. Each element in
-  // key_field_paths indicate a path from the message being compared, listing
-  // successive subfield to reach the key field.
-  //
-  // REQUIRES:
-  //   for key_field_path in key_field_paths:
-  //     key_field_path[0]->containing_type() == field->message_type()
-  //     for i in [0, key_field_path.size() - 1):
-  //       key_field_path[i+1]->containing_type() ==
-  //           key_field_path[i]->message_type()
-  //       key_field_path[i]->cpp_type() == FieldDescriptor::CPPTYPE_MESSAGE
-  //       !key_field_path[i]->is_repeated()
-  void TreatAsMapWithMultipleFieldPathsAsKey(
-      const FieldDescriptor* field,
-      const vector<vector<const FieldDescriptor*> >& key_field_paths);
-
-  // Uses a custom MapKeyComparator to determine if two elements have the same
-  // key when comparing a repeated field as a map.
-  // The caller is responsible to delete the key_comparator.
-  // This method varies from TreatAsMapWithMultipleFieldsAsKey only in the
-  // first key matching step. Rather than comparing some specified fields, it
-  // will invoke the IsMatch method of the given 'key_comparator' to decide if
-  // two elements have the same key.
-  void TreatAsMapUsingKeyComparator(
-      const FieldDescriptor* field,
-      const MapKeyComparator* key_comparator);
-
-  // Add a custom ignore criteria that is evaluated in addition to the
-  // ignored fields added with IgnoreField.
-  // Takes ownership of ignore_criteria.
-  void AddIgnoreCriteria(IgnoreCriteria* ignore_criteria);
-
-  // Indicates that any field with the given descriptor should be
-  // ignored for the purposes of comparing two messages. This applies
-  // to fields nested in the message structure as well as top level
-  // ones. When the MessageDifferencer encounters an ignored field,
-  // ReportIgnored is called on the reporter, if one is specified.
-  //
-  // The only place where the field's 'ignored' status is not applied is when
-  // it is being used as a key in a field passed to TreatAsMap or is one of
-  // the fields passed to TreatAsMapWithMultipleFieldsAsKey.
-  // In this case it is compared in key matching but after that it's ignored
-  // in value comparison.
-  void IgnoreField(const FieldDescriptor* field);
-
-  // Sets the field comparator used to determine differences between protocol
-  // buffer fields. By default it's set to a DefaultFieldComparator instance.
-  // MessageDifferencer doesn't take ownership over the passed object.
-  // Note that this method must be called before Compare for the comparator to
-  // be used.
-  void set_field_comparator(FieldComparator* comparator);
-
-  // DEPRECATED. Pass a DefaultFieldComparator instance instead.
-  // Sets the fraction and margin for the float comparison of a given field.
-  // Uses MathUtil::WithinFractionOrMargin to compare the values.
-  // NOTE: this method does nothing if differencer's field comparator has been
-  //       set to a custom object.
-  //
-  // REQUIRES: field->cpp_type == FieldDescriptor::CPPTYPE_DOUBLE or
-  //           field->cpp_type == FieldDescriptor::CPPTYPE_FLOAT
-  // REQUIRES: float_comparison_ == APPROXIMATE
-  void SetFractionAndMargin(const FieldDescriptor* field, double fraction,
-                            double margin);
-
-  // Sets the type of comparison (as defined in the MessageFieldComparison
-  // enumeration above) that is used by this differencer when determining how
-  // to compare fields in messages.
-  void set_message_field_comparison(MessageFieldComparison comparison);
-
-  // Tells the differencer whether or not to report matches. This method must
-  // be called before Compare. The default for a new differencer is false.
-  void set_report_matches(bool report_matches) {
-    report_matches_ = report_matches;
-  }
-
-  // Sets the scope of the comparison (as defined in the Scope enumeration
-  // above) that is used by this differencer when determining which fields to
-  // compare between the messages.
-  void set_scope(Scope scope);
-
-  // Returns the current scope used by this differencer.
-  Scope scope();
-
-  // DEPRECATED. Pass a DefaultFieldComparator instance instead.
-  // Sets the type of comparison (as defined in the FloatComparison enumeration
-  // above) that is used by this differencer when comparing float (and double)
-  // fields in messages.
-  // NOTE: this method does nothing if differencer's field comparator has been
-  //       set to a custom object.
-  void set_float_comparison(FloatComparison comparison);
-
-  // Sets the type of comparison for repeated field (as defined in the
-  // RepeatedFieldComparison enumeration above) that is used by this
-  // differencer when compare repeated fields in messages.
-  void set_repeated_field_comparison(RepeatedFieldComparison comparison);
-
-  // Compares the two specified messages, returning true if they are the same,
-  // false otherwise. If this method returns false, any changes between the
-  // two messages will be reported if a Reporter was specified via
-  // ReportDifferencesTo (see also ReportDifferencesToString).
-  //
-  // This method REQUIRES that the two messages have the same
-  // Descriptor (message1.GetDescriptor() == message2.GetDescriptor()).
-  bool Compare(const Message& message1, const Message& message2);
-
-  // Same as above, except comparing only the list of fields specified by the
-  // two vectors of FieldDescriptors.
-  bool CompareWithFields(const Message& message1, const Message& message2,
-                         const vector<const FieldDescriptor*>& message1_fields,
-                         const vector<const FieldDescriptor*>& message2_fields);
-
-  // Automatically creates a reporter that will output the differences
-  // found (if any) to the specified output string pointer. Note that this
-  // method must be called before Compare.
-  void ReportDifferencesToString(string* output);
-
-  // Tells the MessageDifferencer to report differences via the specified
-  // reporter. Note that this method must be called before Compare for
-  // the reporter to be used. It is the responsibility of the caller to delete
-  // this object.
-  // If the provided pointer equals NULL, the MessageDifferencer stops reporting
-  // differences to any previously set reporters or output strings.
-  void ReportDifferencesTo(Reporter* reporter);
-
-  // An implementation of the MessageDifferencer Reporter that outputs
-  // any differences found in human-readable form to the supplied
-  // ZeroCopyOutputStream or Printer. If a printer is used, the delimiter
-  // *must* be '$'.
-  class LIBPROTOBUF_EXPORT StreamReporter : public Reporter {
-   public:
-    explicit StreamReporter(io::ZeroCopyOutputStream* output);
-    explicit StreamReporter(io::Printer* printer);  // delimiter '$'
-    virtual ~StreamReporter();
-
-    // When set to true, the stream reporter will also output aggregates nodes
-    // (i.e. messages and groups) whose subfields have been modified. When
-    // false, will only report the individual subfields. Defaults to false.
-    void set_report_modified_aggregates(bool report) {
-      report_modified_aggregates_ = report;
-    }
-
-    // The following are implementations of the methods described above.
-    virtual void ReportAdded(const Message& message1, const Message& message2,
-                             const vector<SpecificField>& field_path);
-
-    virtual void ReportDeleted(const Message& message1,
-                               const Message& message2,
-                               const vector<SpecificField>& field_path);
-
-    virtual void ReportModified(const Message& message1,
-                                const Message& message2,
-                                const vector<SpecificField>& field_path);
-
-    virtual void ReportMoved(const Message& message1,
-                             const Message& message2,
-                             const vector<SpecificField>& field_path);
-
-    virtual void ReportMatched(const Message& message1,
-                               const Message& message2,
-                               const vector<SpecificField>& field_path);
-
-    virtual void ReportIgnored(const Message& message1,
-                               const Message& message2,
-                               const vector<SpecificField>& field_path);
-
-   protected:
-    // Prints the specified path of fields to the buffer.
-    virtual void PrintPath(const vector<SpecificField>& field_path,
-                           bool left_side);
-
-    // Prints the value of fields to the buffer.  left_side is true if the
-    // given message is from the left side of the comparison, false if it
-    // was the right.  This is relevant only to decide whether to follow
-    // unknown_field_index1 or unknown_field_index2 when an unknown field
-    // is encountered in field_path.
-    virtual void PrintValue(const Message& message,
-                            const vector<SpecificField>& field_path,
-                            bool left_side);
-
-    // Prints the specified path of unknown fields to the buffer.
-    virtual void PrintUnknownFieldValue(const UnknownField* unknown_field);
-
-    // Just print a string
-    void Print(const string& str);
-
-   private:
-    io::Printer* printer_;
-    bool delete_printer_;
-    bool report_modified_aggregates_;
-
-    GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(StreamReporter);
-  };
-
- private:
-  // A MapKeyComparator to be used in TreatAsMapUsingKeyComparator.
-  // Implementation of this class needs to do field value comparison which
-  // relies on some private methods of MessageDifferencer. That's why this
-  // class is declared as a nested class of MessageDifferencer.
-  class MultipleFieldsMapKeyComparator;
-  // Returns true if field1's number() is less than field2's.
-  static bool FieldBefore(const FieldDescriptor* field1,
-                          const FieldDescriptor* field2);
-
-  // Combine the two lists of fields into the combined_fields output vector.
-  // All fields present in both lists will always be included in the combined
-  // list.  Fields only present in one of the lists will only appear in the
-  // combined list if the corresponding fields_scope option is set to FULL.
-  void CombineFields(const vector<const FieldDescriptor*>& fields1,
-                     Scope fields1_scope,
-                     const vector<const FieldDescriptor*>& fields2,
-                     Scope fields2_scope,
-                     vector<const FieldDescriptor*>* combined_fields);
-
-  // Internal version of the Compare method which performs the actual
-  // comparison. The parent_fields vector is a vector containing field
-  // descriptors of all fields accessed to get to this comparison operation
-  // (i.e. if the current message is an embedded message, the parent_fields
-  // vector will contain the field that has this embedded message).
-  bool Compare(const Message& message1, const Message& message2,
-               vector<SpecificField>* parent_fields);
-
-  // Compares all the unknown fields in two messages.
-  bool CompareUnknownFields(const Message& message1, const Message& message2,
-                            const google::protobuf::UnknownFieldSet&,
-                            const google::protobuf::UnknownFieldSet&,
-                            vector<SpecificField>* parent_fields);
-
-  // Compares the specified messages for the requested field lists. The field
-  // lists are modified depending on comparison settings, and then passed to
-  // CompareWithFieldsInternal.
-  bool CompareRequestedFieldsUsingSettings(
-      const Message& message1, const Message& message2,
-      const vector<const FieldDescriptor*>& message1_fields,
-      const vector<const FieldDescriptor*>& message2_fields,
-      vector<SpecificField>* parent_fields);
-
-  // Compares the specified messages with the specified field lists.
-  bool CompareWithFieldsInternal(
-      const Message& message1, const Message& message2,
-      const vector<const FieldDescriptor*>& message1_fields,
-      const vector<const FieldDescriptor*>& message2_fields,
-      vector<SpecificField>* parent_fields);
-
-  // Compares the repeated fields, and report the error.
-  bool CompareRepeatedField(const Message& message1, const Message& message2,
-                            const FieldDescriptor* field,
-                            vector<SpecificField>* parent_fields);
-
-  // Shorthand for CompareFieldValueUsingParentFields with NULL parent_fields.
-  bool CompareFieldValue(const Message& message1,
-                         const Message& message2,
-                         const FieldDescriptor* field,
-                         int index1,
-                         int index2);
-
-  // Compares the specified field on the two messages, returning
-  // true if they are the same, false otherwise. For repeated fields,
-  // this method only compares the value in the specified index. This method
-  // uses Compare functions to recurse into submessages.
-  // The parent_fields vector is used in calls to a Reporter instance calls.
-  // It can be NULL, in which case the MessageDifferencer will create new
-  // list of parent messages if it needs to recursively compare the given field.
-  // To avoid confusing users you should not set it to NULL unless you modified
-  // Reporter to handle the change of parent_fields correctly.
-  bool CompareFieldValueUsingParentFields(const Message& message1,
-                                          const Message& message2,
-                                          const FieldDescriptor* field,
-                                          int index1,
-                                          int index2,
-                                          vector<SpecificField>* parent_fields);
-
-  // Compares the specified field on the two messages, returning comparison
-  // result, as returned by appropriate FieldComparator.
-  FieldComparator::ComparisonResult GetFieldComparisonResult(
-      const Message& message1, const Message& message2,
-      const FieldDescriptor* field, int index1, int index2,
-      const FieldContext* field_context);
-
-  // Check if the two elements in the repeated field are match to each other.
-  // if the key_comprator is NULL, this function returns true when the two
-  // elements are equal.
-  bool IsMatch(const FieldDescriptor* repeated_field,
-               const MapKeyComparator* key_comparator,
-               const Message* message1, const Message* message2,
-               const vector<SpecificField>& parent_fields,
-               int index1, int index2);
-
-  // Returns true when this repeated field has been configured to be treated
-  // as a set.
-  bool IsTreatedAsSet(const FieldDescriptor* field);
-
-  // Returns true when this repeated field is to be compared as a subset, ie.
-  // has been configured to be treated as a set or map and scope is set to
-  // PARTIAL.
-  bool IsTreatedAsSubset(const FieldDescriptor* field);
-
-  // Returns true if this field is to be ignored when this
-  // MessageDifferencer compares messages.
-  bool IsIgnored(
-      const Message& message1,
-      const Message& message2,
-      const FieldDescriptor* field,
-      const vector<SpecificField>& parent_fields);
-
-  // Returns MapKeyComparator* when this field has been configured to
-  // be treated as a map.  If not, returns NULL.
-  const MapKeyComparator* GetMapKeyComparator(const FieldDescriptor* field);
-
-  // Attempts to match indices of a repeated field, so that the contained values
-  // match. Clears output vectors and sets their values to indices of paired
-  // messages, ie. if message1[0] matches message2[1], then match_list1[0] == 1
-  // and match_list2[1] == 0. The unmatched indices are indicated by -1.
-  // This method returns false if the match failed. However, it doesn't mean
-  // that the comparison succeeds when this method returns true (you need to
-  // double-check in this case).
-  bool MatchRepeatedFieldIndices(const Message& message1,
-                                 const Message& message2,
-                                 const FieldDescriptor* repeated_field,
-                                 const vector<SpecificField>& parent_fields,
-                                 vector<int>* match_list1,
-                                 vector<int>* match_list2);
-
-  // If "any" is of type google.protobuf.Any, extract its payload using
-  // DynamicMessageFactory and store in "data".
-  bool UnpackAny(const Message& any, google::protobuf::scoped_ptr<Message>* data);
-
-  // Checks if index is equal to new_index in all the specific fields.
-  static bool CheckPathChanged(const vector<SpecificField>& parent_fields);
-
-  // Defines a map between field descriptors and their MapKeyComparators.
-  // Used for repeated fields when they are configured as TreatAsMap.
-  typedef map<const FieldDescriptor*,
-              const MapKeyComparator*> FieldKeyComparatorMap;
-
-  // Defines a set to store field descriptors.  Used for repeated fields when
-  // they are configured as TreatAsSet.
-  typedef set<const FieldDescriptor*> FieldSet;
-
-  Reporter* reporter_;
-  DefaultFieldComparator default_field_comparator_;
-  FieldComparator* field_comparator_;
-  MessageFieldComparison message_field_comparison_;
-  Scope scope_;
-  RepeatedFieldComparison repeated_field_comparison_;
-
-  FieldSet set_fields_;
-  // Keeps track of MapKeyComparators that are created within
-  // MessageDifferencer. These MapKeyComparators should be deleted
-  // before MessageDifferencer is destroyed.
-  // When TreatAsMap or TreatAsMapWithMultipleFieldsAsKey is called, we don't
-  // store the supplied FieldDescriptors directly. Instead, a new
-  // MapKeyComparator is created for comparison purpose.
-  vector<MapKeyComparator*> owned_key_comparators_;
-  FieldKeyComparatorMap map_field_key_comparator_;
-  vector<IgnoreCriteria*> ignore_criteria_;
-
-  FieldSet ignored_fields_;
-
-  bool compare_unknown_fields_;
-  bool report_matches_;
-
-  string* output_string_;
-
-  google::protobuf::scoped_ptr<DynamicMessageFactory> dynamic_message_factory_;
-  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(MessageDifferencer);
-};
-
-// This class provides extra information to the FieldComparator::Compare
-// function.
-class LIBPROTOBUF_EXPORT FieldContext {
- public:
-  explicit FieldContext(
-      vector<MessageDifferencer::SpecificField>* parent_fields)
-      : parent_fields_(parent_fields) {}
-
-  vector<MessageDifferencer::SpecificField>* parent_fields() const {
-    return parent_fields_;
-  }
-
- private:
-  vector<MessageDifferencer::SpecificField>* parent_fields_;
-};
-
-}
-}
-
-}  // namespace google
-#endif  // GOOGLE_PROTOBUF_UTIL_MESSAGE_DIFFERENCER_H__