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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.
#include <stdint.h>
#include <map>
#include <memory>
#include "base/compiler_specific.h"
#include "base/macros.h"
#include "base/metrics/histogram_base.h"
#include "base/metrics/histogram_samples.h"
#include "base/metrics/persistent_memory_allocator.h"
namespace base {
class PersistentHistogramAllocator;
class PersistentSampleMapRecords;
// 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 {
// Constructs a persistent sample map using a PersistentHistogramAllocator
// as the data source for persistent records.
PersistentSampleMap(uint64_t id,
PersistentHistogramAllocator* 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;
std::unique_ptr<SampleCountIterator> Iterator() const override;
// Uses a persistent-memory |iterator| to locate and return information about
// the next record holding information for a PersistentSampleMap. The record
// could be for any Map so return the |sample_map_id| as well.
static PersistentMemoryAllocator::Reference GetNextPersistentRecord(
PersistentMemoryAllocator::Iterator& iterator,
uint64_t* sample_map_id);
// Creates a new record in an |allocator| storing count information for a
// specific sample |value| of a histogram with the given |sample_map_id|.
static PersistentMemoryAllocator::Reference CreatePersistentRecord(
PersistentMemoryAllocator* allocator,
uint64_t sample_map_id,
HistogramBase::Sample value);
// 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);
// Gets the object that manages persistent records. This returns the
// |records_| member after first initializing it if necessary.
PersistentSampleMapRecords* GetRecords();
// 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
// true for |import_everything| to force the importing of all available
// samples even if a match is found.
HistogramBase::Count* ImportSamples(HistogramBase::Sample until_value,
bool import_everything);
// All created/loaded sample values and their associated counts. The storage
// for the actual Count numbers is owned by the |records_| object and its
// underlying allocator.
std::map<HistogramBase::Sample, HistogramBase::Count*> sample_counts_;
// The allocator that manages histograms inside persistent memory. This is
// owned externally and is expected to live beyond the life of this object.
PersistentHistogramAllocator* allocator_;
// The object that manages sample records inside persistent memory. This is
// owned by the |allocator_| object (above) and so, like it, is expected to
// live beyond the life of this object. This value is lazily-initialized on
// first use via the GetRecords() accessor method.
PersistentSampleMapRecords* records_ = nullptr;
} // namespace base