ext/googletest/googlemock/src/gmock-matchers.cc - public/gem5 - Git at Google

 // Copyright 2007, Google Inc.
 // All rights reserved.
 //
 // 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.


 // Google Mock - a framework for writing C++ mock classes.
 //
 // This file implements Matcher<const string&>, Matcher<string>, and
 // utilities for defining matchers.

 #include "gmock/gmock-matchers.h"
 #include "gmock/gmock-generated-matchers.h"

 #include <string.h>
 #include <iostream>
 #include <sstream>
 #include <string>

 namespace testing {
 namespace internal {

 // Returns the description for a matcher defined using the MATCHER*()
 // macro where the user-supplied description string is "", if
 // 'negation' is false; otherwise returns the description of the
 // negation of the matcher.  'param_values' contains a list of strings
 // that are the print-out of the matcher's parameters.
 GTEST_API_ std::string FormatMatcherDescription(bool negation,
                                                 const char* matcher_name,
                                                 const Strings& param_values) {
   std::string result = ConvertIdentifierNameToWords(matcher_name);
   if (param_values.size() >= 1) result += " " + JoinAsTuple(param_values);
   return negation ? "not (" + result + ")" : result;
 }

 // FindMaxBipartiteMatching and its helper class.
 //
 // Uses the well-known Ford-Fulkerson max flow method to find a maximum
 // bipartite matching. Flow is considered to be from left to right.
 // There is an implicit source node that is connected to all of the left
 // nodes, and an implicit sink node that is connected to all of the
 // right nodes. All edges have unit capacity.
 //
 // Neither the flow graph nor the residual flow graph are represented
 // explicitly. Instead, they are implied by the information in 'graph' and
 // a vector<int> called 'left_' whose elements are initialized to the
 // value kUnused. This represents the initial state of the algorithm,
 // where the flow graph is empty, and the residual flow graph has the
 // following edges:
 //   - An edge from source to each left_ node
 //   - An edge from each right_ node to sink
 //   - An edge from each left_ node to each right_ node, if the
 //     corresponding edge exists in 'graph'.
 //
 // When the TryAugment() method adds a flow, it sets left_[l] = r for some
 // nodes l and r. This induces the following changes:
 //   - The edges (source, l), (l, r), and (r, sink) are added to the
 //     flow graph.
 //   - The same three edges are removed from the residual flow graph.
 //   - The reverse edges (l, source), (r, l), and (sink, r) are added
 //     to the residual flow graph, which is a directional graph
 //     representing unused flow capacity.
 //
 // When the method augments a flow (moving left_[l] from some r1 to some
 // other r2), this can be thought of as "undoing" the above steps with
 // respect to r1 and "redoing" them with respect to r2.
 //
 // It bears repeating that the flow graph and residual flow graph are
 // never represented explicitly, but can be derived by looking at the
 // information in 'graph' and in left_.
 //
 // As an optimization, there is a second vector<int> called right_ which
 // does not provide any new information. Instead, it enables more
 // efficient queries about edges entering or leaving the right-side nodes
 // of the flow or residual flow graphs. The following invariants are
 // maintained:
 //
 // left[l] == kUnused or right[left[l]] == l
 // right[r] == kUnused or left[right[r]] == r
 //
 // . [ source ]                                        .
 // .   |||                                             .
 // .   |||                                             .
 // .   ||\--> left[0]=1  ---\    right[0]=-1 ----\     .
 // .   ||                   |                    |     .
 // .   |\---> left[1]=-1    \--> right[1]=0  ---\|     .
 // .   |                                        ||     .
 // .   \----> left[2]=2  ------> right[2]=2  --\||     .
 // .                                           |||     .
 // .         elements           matchers       vvv     .
 // .                                         [ sink ]  .
 //
 // See Also:
 //   [1] Cormen, et al (2001). "Section 26.2: The Ford-Fulkerson method".
 //       "Introduction to Algorithms (Second ed.)", pp. 651-664.
 //   [2] "Ford-Fulkerson algorithm", Wikipedia,
 //       'http://en.wikipedia.org/wiki/Ford%E2%80%93Fulkerson_algorithm'
 class MaxBipartiteMatchState {
  public:
   explicit MaxBipartiteMatchState(const MatchMatrix& graph)
       : graph_(&graph),
         left_(graph_->LhsSize(), kUnused),
         right_(graph_->RhsSize(), kUnused) {}

   // Returns the edges of a maximal match, each in the form {left, right}.
   ElementMatcherPairs Compute() {
     // 'seen' is used for path finding { 0: unseen, 1: seen }.
     ::std::vector<char> seen;
     // Searches the residual flow graph for a path from each left node to
     // the sink in the residual flow graph, and if one is found, add flow
     // to the graph. It's okay to search through the left nodes once. The
     // edge from the implicit source node to each previously-visited left
     // node will have flow if that left node has any path to the sink
     // whatsoever. Subsequent augmentations can only add flow to the
     // network, and cannot take away that previous flow unit from the source.
     // Since the source-to-left edge can only carry one flow unit (or,
     // each element can be matched to only one matcher), there is no need
     // to visit the left nodes more than once looking for augmented paths.
     // The flow is known to be possible or impossible by looking at the
     // node once.
     for (size_t ilhs = 0; ilhs < graph_->LhsSize(); ++ilhs) {
       // Reset the path-marking vector and try to find a path from
       // source to sink starting at the left_[ilhs] node.
       GTEST_CHECK_(left_[ilhs] == kUnused)
           << "ilhs: " << ilhs << ", left_[ilhs]: " << left_[ilhs];
       // 'seen' initialized to 'graph_->RhsSize()' copies of 0.
       seen.assign(graph_->RhsSize(), 0);
       TryAugment(ilhs, &seen);
     }
     ElementMatcherPairs result;
     for (size_t ilhs = 0; ilhs < left_.size(); ++ilhs) {
       size_t irhs = left_[ilhs];
       if (irhs == kUnused) continue;
       result.push_back(ElementMatcherPair(ilhs, irhs));
     }
     return result;
   }

  private:
   static const size_t kUnused = static_cast<size_t>(-1);

   // Perform a depth-first search from left node ilhs to the sink.  If a
   // path is found, flow is added to the network by linking the left and
   // right vector elements corresponding each segment of the path.
   // Returns true if a path to sink was found, which means that a unit of
   // flow was added to the network. The 'seen' vector elements correspond
   // to right nodes and are marked to eliminate cycles from the search.
   //
   // Left nodes will only be explored at most once because they
   // are accessible from at most one right node in the residual flow
   // graph.
   //
   // Note that left_[ilhs] is the only element of left_ that TryAugment will
   // potentially transition from kUnused to another value. Any other
   // left_ element holding kUnused before TryAugment will be holding it
   // when TryAugment returns.
   //
   bool TryAugment(size_t ilhs, ::std::vector<char>* seen) {
     for (size_t irhs = 0; irhs < graph_->RhsSize(); ++irhs) {
       if ((*seen)[irhs]) continue;
       if (!graph_->HasEdge(ilhs, irhs)) continue;
       // There's an available edge from ilhs to irhs.
       (*seen)[irhs] = 1;
       // Next a search is performed to determine whether
       // this edge is a dead end or leads to the sink.
       //
       // right_[irhs] == kUnused means that there is residual flow from
       // right node irhs to the sink, so we can use that to finish this
       // flow path and return success.
       //
       // Otherwise there is residual flow to some ilhs. We push flow
       // along that path and call ourselves recursively to see if this
       // ultimately leads to sink.
       if (right_[irhs] == kUnused || TryAugment(right_[irhs], seen)) {
         // Add flow from left_[ilhs] to right_[irhs].
         left_[ilhs] = irhs;
         right_[irhs] = ilhs;
         return true;
       }
     }
     return false;
   }

   const MatchMatrix* graph_;  // not owned
   // Each element of the left_ vector represents a left hand side node
   // (i.e. an element) and each element of right_ is a right hand side
   // node (i.e. a matcher). The values in the left_ vector indicate
   // outflow from that node to a node on the right_ side. The values
   // in the right_ indicate inflow, and specify which left_ node is
   // feeding that right_ node, if any. For example, left_[3] == 1 means
   // there's a flow from element #3 to matcher #1. Such a flow would also
   // be redundantly represented in the right_ vector as right_[1] == 3.
   // Elements of left_ and right_ are either kUnused or mutually
   // referent. Mutually referent means that left_[right_[i]] = i and
   // right_[left_[i]] = i.
   ::std::vector<size_t> left_;
   ::std::vector<size_t> right_;

   GTEST_DISALLOW_ASSIGN_(MaxBipartiteMatchState);
 };

 const size_t MaxBipartiteMatchState::kUnused;

 GTEST_API_ ElementMatcherPairs FindMaxBipartiteMatching(const MatchMatrix& g) {
   return MaxBipartiteMatchState(g).Compute();
 }

 static void LogElementMatcherPairVec(const ElementMatcherPairs& pairs,
                                      ::std::ostream* stream) {
   typedef ElementMatcherPairs::const_iterator Iter;
   ::std::ostream& os = *stream;
   os << "{";
   const char* sep = "";
   for (Iter it = pairs.begin(); it != pairs.end(); ++it) {
     os << sep << "\n  ("
        << "element #" << it->first << ", "
        << "matcher #" << it->second << ")";
     sep = ",";
   }
   os << "\n}";
 }

 bool MatchMatrix::NextGraph() {
   for (size_t ilhs = 0; ilhs < LhsSize(); ++ilhs) {
     for (size_t irhs = 0; irhs < RhsSize(); ++irhs) {
       char& b = matched_[SpaceIndex(ilhs, irhs)];
       if (!b) {
         b = 1;
         return true;
       }
       b = 0;
     }
   }
   return false;
 }

 void MatchMatrix::Randomize() {
   for (size_t ilhs = 0; ilhs < LhsSize(); ++ilhs) {
     for (size_t irhs = 0; irhs < RhsSize(); ++irhs) {
       char& b = matched_[SpaceIndex(ilhs, irhs)];
       b = static_cast<char>(rand() & 1);  // NOLINT
     }
   }
 }

 std::string MatchMatrix::DebugString() const {
   ::std::stringstream ss;
   const char* sep = "";
   for (size_t i = 0; i < LhsSize(); ++i) {
     ss << sep;
     for (size_t j = 0; j < RhsSize(); ++j) {
       ss << HasEdge(i, j);
     }
     sep = ";";
   }
   return ss.str();
 }

 void UnorderedElementsAreMatcherImplBase::DescribeToImpl(
     ::std::ostream* os) const {
   switch (match_flags()) {
     case UnorderedMatcherRequire::ExactMatch:
       if (matcher_describers_.empty()) {
         *os << "is empty";
         return;
       }
       if (matcher_describers_.size() == 1) {
         *os << "has " << Elements(1) << " and that element ";
         matcher_describers_[0]->DescribeTo(os);
         return;
       }
       *os << "has " << Elements(matcher_describers_.size())
           << " and there exists some permutation of elements such that:\n";
       break;
     case UnorderedMatcherRequire::Superset:
       *os << "a surjection from elements to requirements exists such that:\n";
       break;
     case UnorderedMatcherRequire::Subset:
       *os << "an injection from elements to requirements exists such that:\n";
       break;
   }

   const char* sep = "";
   for (size_t i = 0; i != matcher_describers_.size(); ++i) {
     *os << sep;
     if (match_flags() == UnorderedMatcherRequire::ExactMatch) {
       *os << " - element #" << i << " ";
     } else {
       *os << " - an element ";
     }
     matcher_describers_[i]->DescribeTo(os);
     if (match_flags() == UnorderedMatcherRequire::ExactMatch) {
       sep = ", and\n";
     } else {
       sep = "\n";
     }
   }
 }

 void UnorderedElementsAreMatcherImplBase::DescribeNegationToImpl(
     ::std::ostream* os) const {
   switch (match_flags()) {
     case UnorderedMatcherRequire::ExactMatch:
       if (matcher_describers_.empty()) {
         *os << "isn't empty";
         return;
       }
       if (matcher_describers_.size() == 1) {
         *os << "doesn't have " << Elements(1) << ", or has " << Elements(1)
             << " that ";
         matcher_describers_[0]->DescribeNegationTo(os);
         return;
       }
       *os << "doesn't have " << Elements(matcher_describers_.size())
           << ", or there exists no permutation of elements such that:\n";
       break;
     case UnorderedMatcherRequire::Superset:
       *os << "no surjection from elements to requirements exists such that:\n";
       break;
     case UnorderedMatcherRequire::Subset:
       *os << "no injection from elements to requirements exists such that:\n";
       break;
   }
   const char* sep = "";
   for (size_t i = 0; i != matcher_describers_.size(); ++i) {
     *os << sep;
     if (match_flags() == UnorderedMatcherRequire::ExactMatch) {
       *os << " - element #" << i << " ";
     } else {
       *os << " - an element ";
     }
     matcher_describers_[i]->DescribeTo(os);
     if (match_flags() == UnorderedMatcherRequire::ExactMatch) {
       sep = ", and\n";
     } else {
       sep = "\n";
     }
   }
 }

 // Checks that all matchers match at least one element, and that all
 // elements match at least one matcher. This enables faster matching
 // and better error reporting.
 // Returns false, writing an explanation to 'listener', if and only
 // if the success criteria are not met.
 bool UnorderedElementsAreMatcherImplBase::VerifyMatchMatrix(
     const ::std::vector<std::string>& element_printouts,
     const MatchMatrix& matrix, MatchResultListener* listener) const {
   bool result = true;
   ::std::vector<char> element_matched(matrix.LhsSize(), 0);
   ::std::vector<char> matcher_matched(matrix.RhsSize(), 0);

   for (size_t ilhs = 0; ilhs < matrix.LhsSize(); ilhs++) {
     for (size_t irhs = 0; irhs < matrix.RhsSize(); irhs++) {
       char matched = matrix.HasEdge(ilhs, irhs);
       element_matched[ilhs] |= matched;
       matcher_matched[irhs] |= matched;
     }
   }

   if (match_flags() & UnorderedMatcherRequire::Superset) {
     const char* sep =
         "where the following matchers don't match any elements:\n";
     for (size_t mi = 0; mi < matcher_matched.size(); ++mi) {
       if (matcher_matched[mi]) continue;
       result = false;
       if (listener->IsInterested()) {
         *listener << sep << "matcher #" << mi << ": ";
         matcher_describers_[mi]->DescribeTo(listener->stream());
         sep = ",\n";
       }
     }
   }

   if (match_flags() & UnorderedMatcherRequire::Subset) {
     const char* sep =
         "where the following elements don't match any matchers:\n";
     const char* outer_sep = "";
     if (!result) {
       outer_sep = "\nand ";
     }
     for (size_t ei = 0; ei < element_matched.size(); ++ei) {
       if (element_matched[ei]) continue;
       result = false;
       if (listener->IsInterested()) {
         *listener << outer_sep << sep << "element #" << ei << ": "
                   << element_printouts[ei];
         sep = ",\n";
         outer_sep = "";
       }
     }
   }
   return result;
 }

 bool UnorderedElementsAreMatcherImplBase::FindPairing(
     const MatchMatrix& matrix, MatchResultListener* listener) const {
   ElementMatcherPairs matches = FindMaxBipartiteMatching(matrix);

   size_t max_flow = matches.size();
   if ((match_flags() & UnorderedMatcherRequire::Superset) &&
       max_flow < matrix.RhsSize()) {
     if (listener->IsInterested()) {
       *listener << "where no permutation of the elements can satisfy all "
                    "matchers, and the closest match is "
                 << max_flow << " of " << matrix.RhsSize()
                 << " matchers with the pairings:\n";
       LogElementMatcherPairVec(matches, listener->stream());
     }
     return false;
   }
   if ((match_flags() & UnorderedMatcherRequire::Subset) &&
       max_flow < matrix.LhsSize()) {
     if (listener->IsInterested()) {
       *listener
           << "where not all elements can be matched, and the closest match is "
           << max_flow << " of " << matrix.RhsSize()
           << " matchers with the pairings:\n";
       LogElementMatcherPairVec(matches, listener->stream());
     }
     return false;
   }

   if (matches.size() > 1) {
     if (listener->IsInterested()) {
       const char* sep = "where:\n";
       for (size_t mi = 0; mi < matches.size(); ++mi) {
         *listener << sep << " - element #" << matches[mi].first
                   << " is matched by matcher #" << matches[mi].second;
         sep = ",\n";
       }
     }
   }
   return true;
 }

 }  // namespace internal
 }  // namespace testing
	// Copyright 2007, Google Inc.
	// All rights reserved.
	//
	// 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.


	// Google Mock - a framework for writing C++ mock classes.
	//
	// This file implements Matcher<const string&>, Matcher<string>, and
	// utilities for defining matchers.

	#include "gmock/gmock-matchers.h"
	#include "gmock/gmock-generated-matchers.h"

	#include <string.h>
	#include <iostream>
	#include <sstream>
	#include <string>

	namespace testing {
	namespace internal {

	// Returns the description for a matcher defined using the MATCHER*()
	// macro where the user-supplied description string is "", if
	// 'negation' is false; otherwise returns the description of the
	// negation of the matcher. 'param_values' contains a list of strings
	// that are the print-out of the matcher's parameters.
	GTEST_API_ std::string FormatMatcherDescription(bool negation,
	const char* matcher_name,
	const Strings& param_values) {
	std::string result = ConvertIdentifierNameToWords(matcher_name);
	if (param_values.size() >= 1) result += " " + JoinAsTuple(param_values);
	return negation ? "not (" + result + ")" : result;
	}

	// FindMaxBipartiteMatching and its helper class.
	//
	// Uses the well-known Ford-Fulkerson max flow method to find a maximum
	// bipartite matching. Flow is considered to be from left to right.
	// There is an implicit source node that is connected to all of the left
	// nodes, and an implicit sink node that is connected to all of the
	// right nodes. All edges have unit capacity.
	//
	// Neither the flow graph nor the residual flow graph are represented
	// explicitly. Instead, they are implied by the information in 'graph' and
	// a vector<int> called 'left_' whose elements are initialized to the
	// value kUnused. This represents the initial state of the algorithm,
	// where the flow graph is empty, and the residual flow graph has the
	// following edges:
	// - An edge from source to each left_ node
	// - An edge from each right_ node to sink
	// - An edge from each left_ node to each right_ node, if the
	// corresponding edge exists in 'graph'.
	//
	// When the TryAugment() method adds a flow, it sets left_[l] = r for some
	// nodes l and r. This induces the following changes:
	// - The edges (source, l), (l, r), and (r, sink) are added to the
	// flow graph.
	// - The same three edges are removed from the residual flow graph.
	// - The reverse edges (l, source), (r, l), and (sink, r) are added
	// to the residual flow graph, which is a directional graph
	// representing unused flow capacity.
	//
	// When the method augments a flow (moving left_[l] from some r1 to some
	// other r2), this can be thought of as "undoing" the above steps with
	// respect to r1 and "redoing" them with respect to r2.
	//
	// It bears repeating that the flow graph and residual flow graph are
	// never represented explicitly, but can be derived by looking at the
	// information in 'graph' and in left_.
	//
	// As an optimization, there is a second vector<int> called right_ which
	// does not provide any new information. Instead, it enables more
	// efficient queries about edges entering or leaving the right-side nodes
	// of the flow or residual flow graphs. The following invariants are
	// maintained:
	//
	// left[l] == kUnused or right[left[l]] == l
	// right[r] == kUnused or left[right[r]] == r
	//
	// . [ source ] .
	// . \|\|\| .
	// . \|\|\| .
	// . \|\|\--> left[0]=1 ---\ right[0]=-1 ----\ .
	// . \|\| \| \| .
	// . \|\---> left[1]=-1 \--> right[1]=0 ---\\| .
	// . \| \|\| .
	// . \----> left[2]=2 ------> right[2]=2 --\\|\| .
	// . \|\|\| .
	// . elements matchers vvv .
	// . [ sink ] .
	//
	// See Also:
	// [1] Cormen, et al (2001). "Section 26.2: The Ford-Fulkerson method".
	// "Introduction to Algorithms (Second ed.)", pp. 651-664.
	// [2] "Ford-Fulkerson algorithm", Wikipedia,
	// 'http://en.wikipedia.org/wiki/Ford%E2%80%93Fulkerson_algorithm'
	class MaxBipartiteMatchState {
	public:
	explicit MaxBipartiteMatchState(const MatchMatrix& graph)
	: graph_(&graph),
	left_(graph_->LhsSize(), kUnused),
	right_(graph_->RhsSize(), kUnused) {}

	// Returns the edges of a maximal match, each in the form {left, right}.
	ElementMatcherPairs Compute() {
	// 'seen' is used for path finding { 0: unseen, 1: seen }.
	::std::vector<char> seen;
	// Searches the residual flow graph for a path from each left node to
	// the sink in the residual flow graph, and if one is found, add flow
	// to the graph. It's okay to search through the left nodes once. The
	// edge from the implicit source node to each previously-visited left
	// node will have flow if that left node has any path to the sink
	// whatsoever. Subsequent augmentations can only add flow to the
	// network, and cannot take away that previous flow unit from the source.
	// Since the source-to-left edge can only carry one flow unit (or,
	// each element can be matched to only one matcher), there is no need
	// to visit the left nodes more than once looking for augmented paths.
	// The flow is known to be possible or impossible by looking at the
	// node once.
	for (size_t ilhs = 0; ilhs < graph_->LhsSize(); ++ilhs) {
	// Reset the path-marking vector and try to find a path from
	// source to sink starting at the left_[ilhs] node.
	GTEST_CHECK_(left_[ilhs] == kUnused)
	<< "ilhs: " << ilhs << ", left_[ilhs]: " << left_[ilhs];
	// 'seen' initialized to 'graph_->RhsSize()' copies of 0.
	seen.assign(graph_->RhsSize(), 0);
	TryAugment(ilhs, &seen);
	}
	ElementMatcherPairs result;
	for (size_t ilhs = 0; ilhs < left_.size(); ++ilhs) {
	size_t irhs = left_[ilhs];
	if (irhs == kUnused) continue;
	result.push_back(ElementMatcherPair(ilhs, irhs));
	}
	return result;
	}

	private:
	static const size_t kUnused = static_cast<size_t>(-1);

	// Perform a depth-first search from left node ilhs to the sink. If a
	// path is found, flow is added to the network by linking the left and
	// right vector elements corresponding each segment of the path.
	// Returns true if a path to sink was found, which means that a unit of
	// flow was added to the network. The 'seen' vector elements correspond
	// to right nodes and are marked to eliminate cycles from the search.
	//
	// Left nodes will only be explored at most once because they
	// are accessible from at most one right node in the residual flow
	// graph.
	//
	// Note that left_[ilhs] is the only element of left_ that TryAugment will
	// potentially transition from kUnused to another value. Any other
	// left_ element holding kUnused before TryAugment will be holding it
	// when TryAugment returns.
	//
	bool TryAugment(size_t ilhs, ::std::vector<char>* seen) {
	for (size_t irhs = 0; irhs < graph_->RhsSize(); ++irhs) {
	if ((*seen)[irhs]) continue;
	if (!graph_->HasEdge(ilhs, irhs)) continue;
	// There's an available edge from ilhs to irhs.
	(*seen)[irhs] = 1;
	// Next a search is performed to determine whether
	// this edge is a dead end or leads to the sink.
	//
	// right_[irhs] == kUnused means that there is residual flow from
	// right node irhs to the sink, so we can use that to finish this
	// flow path and return success.
	//
	// Otherwise there is residual flow to some ilhs. We push flow
	// along that path and call ourselves recursively to see if this
	// ultimately leads to sink.
	if (right_[irhs] == kUnused \|\| TryAugment(right_[irhs], seen)) {
	// Add flow from left_[ilhs] to right_[irhs].
	left_[ilhs] = irhs;
	right_[irhs] = ilhs;
	return true;
	}
	}
	return false;
	}

	const MatchMatrix* graph_; // not owned
	// Each element of the left_ vector represents a left hand side node
	// (i.e. an element) and each element of right_ is a right hand side
	// node (i.e. a matcher). The values in the left_ vector indicate
	// outflow from that node to a node on the right_ side. The values
	// in the right_ indicate inflow, and specify which left_ node is
	// feeding that right_ node, if any. For example, left_[3] == 1 means
	// there's a flow from element #3 to matcher #1. Such a flow would also
	// be redundantly represented in the right_ vector as right_[1] == 3.
	// Elements of left_ and right_ are either kUnused or mutually
	// referent. Mutually referent means that left_[right_[i]] = i and
	// right_[left_[i]] = i.
	::std::vector<size_t> left_;
	::std::vector<size_t> right_;

	GTEST_DISALLOW_ASSIGN_(MaxBipartiteMatchState);
	};

	const size_t MaxBipartiteMatchState::kUnused;

	GTEST_API_ ElementMatcherPairs FindMaxBipartiteMatching(const MatchMatrix& g) {
	return MaxBipartiteMatchState(g).Compute();
	}

	static void LogElementMatcherPairVec(const ElementMatcherPairs& pairs,
	::std::ostream* stream) {
	typedef ElementMatcherPairs::const_iterator Iter;
	::std::ostream& os = *stream;
	os << "{";
	const char* sep = "";
	for (Iter it = pairs.begin(); it != pairs.end(); ++it) {
	os << sep << "\n ("
	<< "element #" << it->first << ", "
	<< "matcher #" << it->second << ")";
	sep = ",";
	}
	os << "\n}";
	}

	bool MatchMatrix::NextGraph() {
	for (size_t ilhs = 0; ilhs < LhsSize(); ++ilhs) {
	for (size_t irhs = 0; irhs < RhsSize(); ++irhs) {
	char& b = matched_[SpaceIndex(ilhs, irhs)];
	if (!b) {
	b = 1;
	return true;
	}
	b = 0;
	}
	}
	return false;
	}

	void MatchMatrix::Randomize() {
	for (size_t ilhs = 0; ilhs < LhsSize(); ++ilhs) {
	for (size_t irhs = 0; irhs < RhsSize(); ++irhs) {
	char& b = matched_[SpaceIndex(ilhs, irhs)];
	b = static_cast<char>(rand() & 1); // NOLINT
	}
	}
	}

	std::string MatchMatrix::DebugString() const {
	::std::stringstream ss;
	const char* sep = "";
	for (size_t i = 0; i < LhsSize(); ++i) {
	ss << sep;
	for (size_t j = 0; j < RhsSize(); ++j) {
	ss << HasEdge(i, j);
	}
	sep = ";";
	}
	return ss.str();
	}

	void UnorderedElementsAreMatcherImplBase::DescribeToImpl(
	::std::ostream* os) const {
	switch (match_flags()) {
	case UnorderedMatcherRequire::ExactMatch:
	if (matcher_describers_.empty()) {
	*os << "is empty";
	return;
	}
	if (matcher_describers_.size() == 1) {
	*os << "has " << Elements(1) << " and that element ";
	matcher_describers_[0]->DescribeTo(os);
	return;
	}
	*os << "has " << Elements(matcher_describers_.size())
	<< " and there exists some permutation of elements such that:\n";
	break;
	case UnorderedMatcherRequire::Superset:
	*os << "a surjection from elements to requirements exists such that:\n";
	break;
	case UnorderedMatcherRequire::Subset:
	*os << "an injection from elements to requirements exists such that:\n";
	break;
	}

	const char* sep = "";
	for (size_t i = 0; i != matcher_describers_.size(); ++i) {
	*os << sep;
	if (match_flags() == UnorderedMatcherRequire::ExactMatch) {
	*os << " - element #" << i << " ";
	} else {
	*os << " - an element ";
	}
	matcher_describers_[i]->DescribeTo(os);
	if (match_flags() == UnorderedMatcherRequire::ExactMatch) {
	sep = ", and\n";
	} else {
	sep = "\n";
	}
	}
	}

	void UnorderedElementsAreMatcherImplBase::DescribeNegationToImpl(
	::std::ostream* os) const {
	switch (match_flags()) {
	case UnorderedMatcherRequire::ExactMatch:
	if (matcher_describers_.empty()) {
	*os << "isn't empty";
	return;
	}
	if (matcher_describers_.size() == 1) {
	*os << "doesn't have " << Elements(1) << ", or has " << Elements(1)
	<< " that ";
	matcher_describers_[0]->DescribeNegationTo(os);
	return;
	}
	*os << "doesn't have " << Elements(matcher_describers_.size())
	<< ", or there exists no permutation of elements such that:\n";
	break;
	case UnorderedMatcherRequire::Superset:
	*os << "no surjection from elements to requirements exists such that:\n";
	break;
	case UnorderedMatcherRequire::Subset:
	*os << "no injection from elements to requirements exists such that:\n";
	break;
	}
	const char* sep = "";
	for (size_t i = 0; i != matcher_describers_.size(); ++i) {
	*os << sep;
	if (match_flags() == UnorderedMatcherRequire::ExactMatch) {
	*os << " - element #" << i << " ";
	} else {
	*os << " - an element ";
	}
	matcher_describers_[i]->DescribeTo(os);
	if (match_flags() == UnorderedMatcherRequire::ExactMatch) {
	sep = ", and\n";
	} else {
	sep = "\n";
	}
	}
	}

	// Checks that all matchers match at least one element, and that all
	// elements match at least one matcher. This enables faster matching
	// and better error reporting.
	// Returns false, writing an explanation to 'listener', if and only
	// if the success criteria are not met.
	bool UnorderedElementsAreMatcherImplBase::VerifyMatchMatrix(
	const ::std::vector<std::string>& element_printouts,
	const MatchMatrix& matrix, MatchResultListener* listener) const {
	bool result = true;
	::std::vector<char> element_matched(matrix.LhsSize(), 0);
	::std::vector<char> matcher_matched(matrix.RhsSize(), 0);

	for (size_t ilhs = 0; ilhs < matrix.LhsSize(); ilhs++) {
	for (size_t irhs = 0; irhs < matrix.RhsSize(); irhs++) {
	char matched = matrix.HasEdge(ilhs, irhs);
	element_matched[ilhs] \|= matched;
	matcher_matched[irhs] \|= matched;
	}
	}

	if (match_flags() & UnorderedMatcherRequire::Superset) {
	const char* sep =
	"where the following matchers don't match any elements:\n";
	for (size_t mi = 0; mi < matcher_matched.size(); ++mi) {
	if (matcher_matched[mi]) continue;
	result = false;
	if (listener->IsInterested()) {
	*listener << sep << "matcher #" << mi << ": ";
	matcher_describers_[mi]->DescribeTo(listener->stream());
	sep = ",\n";
	}
	}
	}

	if (match_flags() & UnorderedMatcherRequire::Subset) {
	const char* sep =
	"where the following elements don't match any matchers:\n";
	const char* outer_sep = "";
	if (!result) {
	outer_sep = "\nand ";
	}
	for (size_t ei = 0; ei < element_matched.size(); ++ei) {
	if (element_matched[ei]) continue;
	result = false;
	if (listener->IsInterested()) {
	*listener << outer_sep << sep << "element #" << ei << ": "
	<< element_printouts[ei];
	sep = ",\n";
	outer_sep = "";
	}
	}
	}
	return result;
	}

	bool UnorderedElementsAreMatcherImplBase::FindPairing(
	const MatchMatrix& matrix, MatchResultListener* listener) const {
	ElementMatcherPairs matches = FindMaxBipartiteMatching(matrix);

	size_t max_flow = matches.size();
	if ((match_flags() & UnorderedMatcherRequire::Superset) &&
	max_flow < matrix.RhsSize()) {
	if (listener->IsInterested()) {
	*listener << "where no permutation of the elements can satisfy all "
	"matchers, and the closest match is "
	<< max_flow << " of " << matrix.RhsSize()
	<< " matchers with the pairings:\n";
	LogElementMatcherPairVec(matches, listener->stream());
	}
	return false;
	}
	if ((match_flags() & UnorderedMatcherRequire::Subset) &&
	max_flow < matrix.LhsSize()) {
	if (listener->IsInterested()) {
	*listener
	<< "where not all elements can be matched, and the closest match is "
	<< max_flow << " of " << matrix.RhsSize()
	<< " matchers with the pairings:\n";
	LogElementMatcherPairVec(matches, listener->stream());
	}
	return false;
	}

	if (matches.size() > 1) {
	if (listener->IsInterested()) {
	const char* sep = "where:\n";
	for (size_t mi = 0; mi < matches.size(); ++mi) {
	*listener << sep << " - element #" << matches[mi].first
	<< " is matched by matcher #" << matches[mi].second;
	sep = ",\n";
	}
	}
	}
	return true;
	}

	} // namespace internal
	} // namespace testing