base/test/statistics_delta_reader.h

   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 #ifndef BASE_TEST_STATISTICS_DELTA_READER_H_
   6 #define BASE_TEST_STATISTICS_DELTA_READER_H_
   7
   8 #include <map>
   9 #include <string>
  10
  11 #include "base/basictypes.h"
  12 #include "base/memory/scoped_ptr.h"
  13 #include "base/metrics/histogram_samples.h"
  14
  15 namespace base {
  16
  17 // This class acts as a differential reader for histogram samples, enabling
  18 // tests to check that metrics were recorded as they should be.
  19 // Before using this class, StatisticsRecoder must be initialized.
  20 class StatisticsDeltaReader {
  21  public:
  22   StatisticsDeltaReader();
  23   ~StatisticsDeltaReader();
  24
  25   // Returns the histogram data accumulated since this instance was created.
  26   // Returns NULL if no samples are available.
  27   scoped_ptr<HistogramSamples> GetHistogramSamplesSinceCreation(
  28       const std::string& histogram_name);
  29
  30  private:
  31   // Used to determine the histogram changes made during this instance's
  32   // lifecycle. This instance takes ownership of the samples, which are deleted
  33   // when the instance is destroyed.
  34   std::map<std::string, HistogramSamples*> original_samples_;
  35
  36   DISALLOW_COPY_AND_ASSIGN(StatisticsDeltaReader);
  37 };
  38
  39 }  // namespace base
  40
  41 #endif  // BASE_TEST_STATISTICS_DELTA_READER_H_