base/test/histogram_tester.h: Add a way to query a whole family of related

base/test/histogram_tester.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/test/histogram_tester.h"
 
 #include "base/metrics/histogram.h"
 #include "base/metrics/histogram_samples.h"
 #include "base/metrics/statistics_recorder.h"
 #include "base/stl_util.h"
@@ skipping 55 matching lines @@
       base::StatisticsRecorder::FindHistogram(name);
   if (histogram) {
     scoped_ptr<base::HistogramSamples> samples(histogram->SnapshotSamples());
     CheckTotalCount(name, count, *samples);
   } else {
     // No histogram means there were zero samples.
     EXPECT_EQ(count, 0) << "Histogram \"" << name << "\" does not exist.";
   }
 }
 
-std::vector<Bucket> HistogramTester::GetAllSamples(const std::string& name) {
+std::vector<Bucket> HistogramTester::GetAllSamples(
+    const std::string& name) const {
   std::vector<Bucket> samples;
   scoped_ptr<HistogramSamples> snapshot =
       GetHistogramSamplesSinceCreation(name);
   for (auto it = snapshot->Iterator(); !it->Done(); it->Next()) {
     HistogramBase::Sample sample;
     HistogramBase::Count count;
     it->Get(&sample, nullptr, &count);
     samples.push_back(Bucket(sample, count));
   }
   return samples;
 }
 
+HistogramTester::CountsMap HistogramTester::GetTotalCountsForPrefix(
+    const std::string& query) const {
+  EXPECT_TRUE(query.find('.') != std::string::npos)
+      << "|query| ought to contain at least one period, to avoid matching too"
+      << " many histograms.";
+
+  // Find matches by using the prefix-matching logic built into GetSnapshot().
+  StatisticsRecorder::Histograms query_matches;
+  StatisticsRecorder::GetSnapshot(query, &query_matches);
+
+  CountsMap result;
+  for (base::HistogramBase* histogram : query_matches) {
+    scoped_ptr<HistogramSamples> new_samples =
+        GetHistogramSamplesSinceCreation(histogram->histogram_name());
+    // Omit unchanged histograms from the result.
+    if (new_samples->TotalCount()) {
+      result[histogram->histogram_name()] = new_samples->TotalCount();
+    }
+  }
+  return result;
+}
+
 scoped_ptr<HistogramSamples> HistogramTester::GetHistogramSamplesSinceCreation(
-    const std::string& histogram_name) {
+    const std::string& histogram_name) const {
   HistogramBase* histogram = StatisticsRecorder::FindHistogram(histogram_name);
   if (!histogram)
     return scoped_ptr<HistogramSamples>();
   scoped_ptr<HistogramSamples> named_samples(histogram->SnapshotSamples());
-  HistogramSamples* named_original_samples =
-      histograms_snapshot_[histogram_name];
-  if (named_original_samples)
-    named_samples->Subtract(*named_original_samples);
+  auto original_samples_it = histograms_snapshot_.find(histogram_name);
+  if (original_samples_it != histograms_snapshot_.end())
+    named_samples->Subtract(*original_samples_it->second);
   return named_samples.Pass();
 }
 
 void HistogramTester::CheckBucketCount(
     const std::string& name,
     base::HistogramBase::Sample sample,
     base::HistogramBase::Count expected_count,
     const base::HistogramSamples& samples) const {
   int actual_count = samples.GetCount(sample);
   std::map<std::string, HistogramSamples*>::const_iterator histogram_data;
@@ skipping 26 matching lines @@
 
 bool Bucket::operator==(const Bucket& other) const {
   return min == other.min && count == other.count;
 }
 
 void PrintTo(const Bucket& bucket, std::ostream* os) {
   *os << "Bucket " << bucket.min << ": " << bucket.count;
 }
 
 }  // namespace base