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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 
12 class Pickle;
13 class PickleIterator;
14 
15 namespace base {
16 
17 class SampleCountIterator;
18 
19 // HistogramSamples is a container storing all samples of a histogram.
20 class 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.
sum()41   int64 sum() const { return sum_; }
redundant_count()42   HistogramBase::Count redundant_count() const {
43     return subtle::NoBarrier_Load(&redundant_count_);
44   }
45 
46  protected:
47   // Based on |op| type, add or subtract sample counts data from the iterator.
48   enum Operator { ADD, SUBTRACT };
49   virtual bool AddSubtractImpl(SampleCountIterator* iter, Operator op) = 0;
50 
51   void IncreaseSum(int64 diff);
52   void IncreaseRedundantCount(HistogramBase::Count diff);
53 
54  private:
55   int64 sum_;
56 
57   // |redundant_count_| helps identify memory corruption. It redundantly stores
58   // the total number of samples accumulated in the histogram. We can compare
59   // this count to the sum of the counts (TotalCount() function), and detect
60   // problems. Note, depending on the implementation of different histogram
61   // types, there might be races during histogram accumulation and snapshotting
62   // that we choose to accept. In this case, the tallies might mismatch even
63   // when no memory corruption has happened.
64   HistogramBase::AtomicCount redundant_count_;
65 };
66 
67 class BASE_EXPORT SampleCountIterator {
68  public:
69   virtual ~SampleCountIterator();
70 
71   virtual bool Done() const = 0;
72   virtual void Next() = 0;
73 
74   // Get the sample and count at current position.
75   // |min| |max| and |count| can be NULL if the value is not of interest.
76   // Requires: !Done();
77   virtual void Get(HistogramBase::Sample* min,
78                    HistogramBase::Sample* max,
79                    HistogramBase::Count* count) const = 0;
80 
81   // Get the index of current histogram bucket.
82   // For histograms that don't use predefined buckets, it returns false.
83   // Requires: !Done();
84   virtual bool GetBucketIndex(size_t* index) const;
85 };
86 
87 }  // namespace base
88 
89 #endif  // BASE_METRICS_HISTOGRAM_SAMPLES_H_
90