Match only prefixes of histogram names.

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 <stddef.h>
 
 #include "base/metrics/histogram.h"
 #include "base/metrics/histogram_samples.h"
 #include "base/metrics/metrics_hashes.h"
 #include "base/metrics/sample_map.h"
 #include "base/metrics/statistics_recorder.h"
+#include "base/strings/string_util.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace base {
 
 HistogramTester::HistogramTester() {
   StatisticsRecorder::Initialize();  // Safe to call multiple times.
 
   // Record any histogram data that exists when the object is created so it can
   // be subtracted later.
   StatisticsRecorder::Histograms histograms;
   StatisticsRecorder::GetSnapshot(std::string(), &histograms);
   for (const auto& histogram : histograms) {
     histograms_snapshot_[histogram->histogram_name()] =
         histogram->SnapshotSamples();
   }
 }
 
 HistogramTester::~HistogramTester() {
 }
 
 void HistogramTester::ExpectUniqueSample(
     const std::string& name,
-    base::HistogramBase::Sample sample,
-    base::HistogramBase::Count expected_count) const {
-  base::HistogramBase* histogram =
-      base::StatisticsRecorder::FindHistogram(name);
+    HistogramBase::Sample sample,
+    HistogramBase::Count expected_count) const {
+  HistogramBase* histogram = StatisticsRecorder::FindHistogram(name);
   EXPECT_NE(nullptr, histogram) << "Histogram \"" << name
                                 << "\" does not exist.";
 
   if (histogram) {
-    std::unique_ptr<base::HistogramSamples> samples =
-        histogram->SnapshotSamples();
+    std::unique_ptr<HistogramSamples> samples = histogram->SnapshotSamples();
     CheckBucketCount(name, sample, expected_count, *samples);
     CheckTotalCount(name, expected_count, *samples);
   }
 }
 
 void HistogramTester::ExpectBucketCount(
     const std::string& name,
-    base::HistogramBase::Sample sample,
-    base::HistogramBase::Count expected_count) const {
-  base::HistogramBase* histogram =
-      base::StatisticsRecorder::FindHistogram(name);
+    HistogramBase::Sample sample,
+    HistogramBase::Count expected_count) const {
+  HistogramBase* histogram = StatisticsRecorder::FindHistogram(name);
   EXPECT_NE(nullptr, histogram) << "Histogram \"" << name
                                 << "\" does not exist.";
 
   if (histogram) {
-    std::unique_ptr<base::HistogramSamples> samples =
-        histogram->SnapshotSamples();
+    std::unique_ptr<HistogramSamples> samples = histogram->SnapshotSamples();
     CheckBucketCount(name, sample, expected_count, *samples);
   }
 }
 
 void HistogramTester::ExpectTotalCount(const std::string& name,
-                                       base::HistogramBase::Count count) const {
-  base::HistogramBase* histogram =
-      base::StatisticsRecorder::FindHistogram(name);
+                                       HistogramBase::Count count) const {
+  HistogramBase* histogram = StatisticsRecorder::FindHistogram(name);
   if (histogram) {
-    std::unique_ptr<base::HistogramSamples> samples =
-        histogram->SnapshotSamples();
+    std::unique_ptr<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.";
   }
 }
 
-void HistogramTester::ExpectTimeBucketCount(
-    const std::string& name,
-    base::TimeDelta sample,
-    base::HistogramBase::Count count) const {
+void HistogramTester::ExpectTimeBucketCount(const std::string& name,
+                                            TimeDelta sample,
+                                            HistogramBase::Count count) const {
   ExpectBucketCount(name, sample.InMilliseconds(), count);
 }
 
 std::vector<Bucket> HistogramTester::GetAllSamples(
     const std::string& name) const {
   std::vector<Bucket> samples;
   std::unique_ptr<HistogramSamples> snapshot =
       GetHistogramSamplesSinceCreation(name);
   if (snapshot) {
     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"
+    const std::string& prefix) const {
+  EXPECT_TRUE(prefix.find('.') != std::string::npos)
+      << "|prefix| 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);
+  // Find candidate matches by using the logic built into GetSnapshot().
+  StatisticsRecorder::Histograms candidate_matches;
+  StatisticsRecorder::GetSnapshot(prefix, &candidate_matches);
 
   CountsMap result;
-  for (base::HistogramBase* histogram : query_matches) {
+  for (HistogramBase* histogram : candidate_matches) {
+    if (!StartsWith(histogram->histogram_name(), prefix,
+                    CompareCase::SENSITIVE)) {
+      continue;
+    }
     std::unique_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;
 }
 
@@ skipping 12 matching lines @@
         new SampleMap(HashMetricName(histogram_name)));
   }
   std::unique_ptr<HistogramSamples> named_samples =
       histogram->SnapshotSamples();
   auto original_samples_it = histograms_snapshot_.find(histogram_name);
   if (original_samples_it != histograms_snapshot_.end())
     named_samples->Subtract(*original_samples_it->second.get());
   return named_samples;
 }
 
-void HistogramTester::CheckBucketCount(
-    const std::string& name,
-    base::HistogramBase::Sample sample,
-    base::HistogramBase::Count expected_count,
-    const base::HistogramSamples& samples) const {
+void HistogramTester::CheckBucketCount(const std::string& name,
+                                       HistogramBase::Sample sample,
+                                       HistogramBase::Count expected_count,
+                                       const HistogramSamples& samples) const {
   int actual_count = samples.GetCount(sample);
   auto histogram_data = histograms_snapshot_.find(name);
   if (histogram_data != histograms_snapshot_.end())
     actual_count -= histogram_data->second->GetCount(sample);
 
   EXPECT_EQ(expected_count, actual_count)
       << "Histogram \"" << name
       << "\" does not have the right number of samples (" << expected_count
       << ") in the expected bucket (" << sample << "). It has (" << actual_count
       << ").";
 }
 
-void HistogramTester::CheckTotalCount(
-    const std::string& name,
-    base::HistogramBase::Count expected_count,
-    const base::HistogramSamples& samples) const {
+void HistogramTester::CheckTotalCount(const std::string& name,
+                                      HistogramBase::Count expected_count,
+                                      const HistogramSamples& samples) const {
   int actual_count = samples.TotalCount();
   auto histogram_data = histograms_snapshot_.find(name);
   if (histogram_data != histograms_snapshot_.end())
     actual_count -= histogram_data->second->TotalCount();
 
   EXPECT_EQ(expected_count, actual_count)
       << "Histogram \"" << name
       << "\" does not have the right total number of samples ("
       << expected_count << "). It has (" << actual_count << ").";
 }
 
 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