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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_SPARSE_HISTOGRAM_H_
      6 #define BASE_METRICS_SPARSE_HISTOGRAM_H_
      7 
      8 #include <stddef.h>
      9 #include <stdint.h>
     10 
     11 #include <map>
     12 #include <memory>
     13 #include <string>
     14 
     15 #include "base/base_export.h"
     16 #include "base/macros.h"
     17 #include "base/metrics/histogram_base.h"
     18 #include "base/metrics/histogram_samples.h"
     19 #include "base/synchronization/lock.h"
     20 
     21 namespace base {
     22 
     23 class HistogramSamples;
     24 class PersistentHistogramAllocator;
     25 class Pickle;
     26 class PickleIterator;
     27 
     28 class BASE_EXPORT SparseHistogram : public HistogramBase {
     29  public:
     30   // If there's one with same name, return the existing one. If not, create a
     31   // new one.
     32   static HistogramBase* FactoryGet(const std::string& name, int32_t flags);
     33 
     34   // Create a histogram using data in persistent storage. The allocator must
     35   // live longer than the created sparse histogram.
     36   static std::unique_ptr<HistogramBase> PersistentCreate(
     37       PersistentHistogramAllocator* allocator,
     38       const std::string& name,
     39       HistogramSamples::Metadata* meta,
     40       HistogramSamples::Metadata* logged_meta);
     41 
     42   ~SparseHistogram() override;
     43 
     44   // HistogramBase implementation:
     45   uint64_t name_hash() const override;
     46   HistogramType GetHistogramType() const override;
     47   bool HasConstructionArguments(Sample expected_minimum,
     48                                 Sample expected_maximum,
     49                                 uint32_t expected_bucket_count) const override;
     50   void Add(Sample value) override;
     51   void AddCount(Sample value, int count) override;
     52   void AddSamples(const HistogramSamples& samples) override;
     53   bool AddSamplesFromPickle(base::PickleIterator* iter) override;
     54   std::unique_ptr<HistogramSamples> SnapshotSamples() const override;
     55   std::unique_ptr<HistogramSamples> SnapshotDelta() override;
     56   std::unique_ptr<HistogramSamples> SnapshotFinalDelta() const override;
     57   void WriteHTMLGraph(std::string* output) const override;
     58   void WriteAscii(std::string* output) const override;
     59 
     60  protected:
     61   // HistogramBase implementation:
     62   bool SerializeInfoImpl(base::Pickle* pickle) const override;
     63 
     64  private:
     65   // Clients should always use FactoryGet to create SparseHistogram.
     66   explicit SparseHistogram(const std::string& name);
     67 
     68   SparseHistogram(PersistentHistogramAllocator* allocator,
     69                   const std::string& name,
     70                   HistogramSamples::Metadata* meta,
     71                   HistogramSamples::Metadata* logged_meta);
     72 
     73   friend BASE_EXPORT HistogramBase* DeserializeHistogramInfo(
     74       base::PickleIterator* iter);
     75   static HistogramBase* DeserializeInfoImpl(base::PickleIterator* iter);
     76 
     77   void GetParameters(DictionaryValue* params) const override;
     78   void GetCountAndBucketData(Count* count,
     79                              int64_t* sum,
     80                              ListValue* buckets) const override;
     81 
     82   // Helpers for emitting Ascii graphic.  Each method appends data to output.
     83   void WriteAsciiImpl(bool graph_it,
     84                       const std::string& newline,
     85                       std::string* output) const;
     86 
     87   // Write a common header message describing this histogram.
     88   void WriteAsciiHeader(const Count total_count,
     89                         std::string* output) const;
     90 
     91   // For constuctor calling.
     92   friend class SparseHistogramTest;
     93 
     94   // Protects access to |samples_|.
     95   mutable base::Lock lock_;
     96 
     97   // Flag to indicate if PrepareFinalDelta has been previously called.
     98   mutable bool final_delta_created_ = false;
     99 
    100   std::unique_ptr<HistogramSamples> samples_;
    101   std::unique_ptr<HistogramSamples> logged_samples_;
    102 
    103   DISALLOW_COPY_AND_ASSIGN(SparseHistogram);
    104 };
    105 
    106 }  // namespace base
    107 
    108 #endif  // BASE_METRICS_SPARSE_HISTOGRAM_H_
    109