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// Copyright 2016 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
// PersistentSampleMap implements HistogramSamples interface. It is used
// by the SparseHistogram class to store samples in persistent memory which
// allows it to be shared between processes or live across restarts.
#ifndef BASE_METRICS_PERSISTENT_SAMPLE_MAP_H_
#define BASE_METRICS_PERSISTENT_SAMPLE_MAP_H_
#include <stdint.h>
#include <map>
#include "base/compiler_specific.h"
#include "base/macros.h"
#include "base/memory/scoped_ptr.h"
#include "base/metrics/histogram_base.h"
#include "base/metrics/histogram_samples.h"
#include "base/metrics/persistent_memory_allocator.h"
namespace base {
// The logic here is similar to that of SampleMap but with different data
// structures. Changes here likely need to be duplicated there.
class BASE_EXPORT PersistentSampleMap : public HistogramSamples {
public:
PersistentSampleMap(uint64_t id,
PersistentMemoryAllocator* allocator,
Metadata* meta);
~PersistentSampleMap() override;
// HistogramSamples:
void Accumulate(HistogramBase::Sample value,
HistogramBase::Count count) override;
HistogramBase::Count GetCount(HistogramBase::Sample value) const override;
HistogramBase::Count TotalCount() const override;
scoped_ptr<SampleCountIterator> Iterator() const override;
protected:
// Performs arithemetic. |op| is ADD or SUBTRACT.
bool AddSubtractImpl(SampleCountIterator* iter, Operator op) override;
// Gets a pointer to a "count" corresponding to a given |value|. Returns NULL
// if sample does not exist.
HistogramBase::Count* GetSampleCountStorage(HistogramBase::Sample value);
// Gets a pointer to a "count" corresponding to a given |value|, creating
// the sample (initialized to zero) if it does not already exists.
HistogramBase::Count* GetOrCreateSampleCountStorage(
HistogramBase::Sample value);
private:
enum : HistogramBase::Sample { kAllSamples = -1 };
// Imports samples from persistent memory by iterating over all sample
// records found therein, adding them to the sample_counts_ map. If a
// count for the sample |until_value| is found, stop the import and return
// a pointer to that counter. If that value is not found, null will be
// returned after all currently available samples have been loaded. Pass
// kAllSamples to force the importing of all available samples.
HistogramBase::Count* ImportSamples(HistogramBase::Sample until_value);
// All created/loaded sample values and their associated counts. The storage
// for the actual Count numbers is owned by the |allocator_|.
std::map<HistogramBase::Sample, HistogramBase::Count*> sample_counts_;
// The persistent memory allocator holding samples and an iterator through it.
PersistentMemoryAllocator* allocator_;
PersistentMemoryAllocator::Iterator sample_iter_;
DISALLOW_COPY_AND_ASSIGN(PersistentSampleMap);
};
} // namespace base
#endif // BASE_METRICS_PERSISTENT_SAMPLE_MAP_H_
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