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/histogram_samples.h"
   9 #include "base/metrics/statistics_recorder.h"
  10 #include "base/stl_util.h"
  11
  12 namespace base {
  13
  14 StatisticsDeltaReader::StatisticsDeltaReader() {
  15   StatisticsRecorder::Initialize();  // Safe to call multiple times.
  16
  17   // Record any histogram data that exists when the object is created so it can
  18   // be subtracted later.
  19   StatisticsRecorder::Histograms histograms;
  20   StatisticsRecorder::GetSnapshot(std::string(), &histograms);
  21   for (size_t i = 0; i < histograms.size(); ++i) {
  22     original_samples_[histograms[i]->histogram_name()] =
  23         histograms[i]->SnapshotSamples().release();
  24   }
  25 }
  26
  27 StatisticsDeltaReader::~StatisticsDeltaReader() {
  28   STLDeleteValues(&original_samples_);
  29 }
  30
  31 scoped_ptr<HistogramSamples>
  32     StatisticsDeltaReader::GetHistogramSamplesSinceCreation(
  33         const std::string& histogram_name) {
  34   HistogramBase* histogram = StatisticsRecorder::FindHistogram(histogram_name);
  35   if (!histogram)
  36     return scoped_ptr<HistogramSamples>();
  37   scoped_ptr<HistogramSamples> named_samples(histogram->SnapshotSamples());
  38   HistogramSamples* named_original_samples = original_samples_[histogram_name];
  39   if (named_original_samples)
  40     named_samples->Subtract(*named_original_samples);
  41   return named_samples.Pass();
  42 }
  43
  44 }  // namespace base