base/test/statistics_delta_reader.cc

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "base/test/statistics_delta_reader.h"
   6
   7 #include "base/metrics/histogram.h"
   8 #include "base/metrics/statistics_recorder.h"
   9 #include "base/stl_util.h"
  10
  11 namespace base {
  12
  13 StatisticsDeltaReader::StatisticsDeltaReader() {
  14   // Record any histogram data that exists when the object is created so it can
  15   // be subtracted later.
  16   StatisticsRecorder::Histograms histograms;
  17   StatisticsRecorder::GetSnapshot(std::string(), &histograms);
  18   for (size_t i = 0; i < histograms.size(); ++i) {
  19     original_samples_[histograms[i]->histogram_name()] =
  20         histograms[i]->SnapshotSamples().release();
  21   }
  22 }
  23
  24 StatisticsDeltaReader::~StatisticsDeltaReader() {
  25   STLDeleteValues(&original_samples_);
  26 }
  27
  28 scoped_ptr<HistogramSamples>
  29     StatisticsDeltaReader::GetHistogramSamplesSinceCreation(
  30         const std::string& histogram_name) {
  31   HistogramBase* histogram = StatisticsRecorder::FindHistogram(histogram_name);
  32   if (!histogram)
  33     return scoped_ptr<HistogramSamples>();
  34   scoped_ptr<HistogramSamples> named_samples(histogram->SnapshotSamples());
  35   HistogramSamples* named_original_samples = original_samples_[histogram_name];
  36   if (named_original_samples)
  37     named_samples->Subtract(*named_original_samples);
  38   return named_samples.Pass();
  39 }
  40
  41 }  // namespace base