1// Copyright 2013 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_DELTA_SERIALIZATION_H_
6#define BASE_METRICS_HISTOGRAM_DELTA_SERIALIZATION_H_
7
8#include <memory>
9#include <string>
10#include <vector>
11
12#include "base/base_export.h"
13#include "base/macros.h"
14#include "base/metrics/histogram_flattener.h"
15#include "base/metrics/histogram_snapshot_manager.h"
16#include "base/threading/thread_checker.h"
17
18namespace base {
19
20class HistogramBase;
21
22// Serializes and restores histograms deltas.
23class BASE_EXPORT HistogramDeltaSerialization : public HistogramFlattener {
24 public:
25  // |caller_name| is string used in histograms for counting inconsistencies.
26  explicit HistogramDeltaSerialization(const std::string& caller_name);
27  ~HistogramDeltaSerialization() override;
28
29  // Computes deltas in histogram bucket counts relative to the previous call to
30  // this method. Stores the deltas in serialized form into |serialized_deltas|.
31  // If |serialized_deltas| is null, no data is serialized, though the next call
32  // will compute the deltas relative to this one. Setting |include_persistent|
33  // will include histograms held in persistent memory (and thus may be reported
34  // elsewhere); otherwise only histograms local to this process are serialized.
35  void PrepareAndSerializeDeltas(std::vector<std::string>* serialized_deltas,
36                                 bool include_persistent);
37
38  // Deserialize deltas and add samples to corresponding histograms, creating
39  // them if necessary. Silently ignores errors in |serialized_deltas|.
40  static void DeserializeAndAddSamples(
41      const std::vector<std::string>& serialized_deltas);
42
43 private:
44  // HistogramFlattener implementation.
45  void RecordDelta(const HistogramBase& histogram,
46                   const HistogramSamples& snapshot) override;
47  void InconsistencyDetected(HistogramBase::Inconsistency problem) override;
48  void UniqueInconsistencyDetected(
49      HistogramBase::Inconsistency problem) override;
50  void InconsistencyDetectedInLoggedCount(int amount) override;
51
52  ThreadChecker thread_checker_;
53
54  // Calculates deltas in histogram counters.
55  HistogramSnapshotManager histogram_snapshot_manager_;
56
57  // Output buffer for serialized deltas.
58  std::vector<std::string>* serialized_deltas_;
59
60  // Histograms to count inconsistencies in snapshots.
61  HistogramBase* inconsistencies_histogram_;
62  HistogramBase* inconsistencies_unique_histogram_;
63  HistogramBase* inconsistent_snapshot_histogram_;
64
65  DISALLOW_COPY_AND_ASSIGN(HistogramDeltaSerialization);
66};
67
68}  // namespace base
69
70#endif  // BASE_METRICS_HISTOGRAM_DELTA_SERIALIZATION_H_
71