1// Copyright (c) 2012 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_METRICS_HISTOGRAM_SAMPLES_H_
6#define BASE_METRICS_HISTOGRAM_SAMPLES_H_
7
8#include "base/basictypes.h"
9#include "base/metrics/histogram_base.h"
10#include "base/memory/scoped_ptr.h"
11
12class Pickle;
13class PickleIterator;
14
15namespace base {
16
17class SampleCountIterator;
18
19// HistogramSamples is a container storing all samples of a histogram.
20class BASE_EXPORT HistogramSamples {
21 public:
22  HistogramSamples();
23  virtual ~HistogramSamples();
24
25  virtual void Accumulate(HistogramBase::Sample value,
26                          HistogramBase::Count count) = 0;
27  virtual HistogramBase::Count GetCount(HistogramBase::Sample value) const = 0;
28  virtual HistogramBase::Count TotalCount() const = 0;
29
30  virtual void Add(const HistogramSamples& other);
31
32  // Add from serialized samples.
33  virtual bool AddFromPickle(PickleIterator* iter);
34
35  virtual void Subtract(const HistogramSamples& other);
36
37  virtual scoped_ptr<SampleCountIterator> Iterator() const = 0;
38  virtual bool Serialize(Pickle* pickle) const;
39
40  // Accessor fuctions.
41  int64 sum() const { return sum_; }
42  HistogramBase::Count redundant_count() const { return redundant_count_; }
43
44 protected:
45  // Based on |op| type, add or subtract sample counts data from the iterator.
46  enum Operator { ADD, SUBTRACT };
47  virtual bool AddSubtractImpl(SampleCountIterator* iter, Operator op) = 0;
48
49  void IncreaseSum(int64 diff);
50  void IncreaseRedundantCount(HistogramBase::Count diff);
51
52 private:
53  int64 sum_;
54
55  // |redundant_count_| helps identify memory corruption. It redundantly stores
56  // the total number of samples accumulated in the histogram. We can compare
57  // this count to the sum of the counts (TotalCount() function), and detect
58  // problems. Note, depending on the implementation of different histogram
59  // types, there might be races during histogram accumulation and snapshotting
60  // that we choose to accept. In this case, the tallies might mismatch even
61  // when no memory corruption has happened.
62  HistogramBase::Count redundant_count_;
63};
64
65class BASE_EXPORT SampleCountIterator {
66 public:
67  virtual ~SampleCountIterator();
68
69  virtual bool Done() const = 0;
70  virtual void Next() = 0;
71
72  // Get the sample and count at current position.
73  // |min| |max| and |count| can be NULL if the value is not of interest.
74  // Requires: !Done();
75  virtual void Get(HistogramBase::Sample* min,
76                   HistogramBase::Sample* max,
77                   HistogramBase::Count* count) const = 0;
78
79  // Get the index of current histogram bucket.
80  // For histograms that don't use predefined buckets, it returns false.
81  // Requires: !Done();
82  virtual bool GetBucketIndex(size_t* index) const;
83};
84
85}  // namespace base
86
87#endif  // BASE_METRICS_HISTOGRAM_SAMPLES_H_
88