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// Copyright 2013 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef BASE_METRICS_HISTOGRAM_DELTA_SERIALIZATION_H_
#define BASE_METRICS_HISTOGRAM_DELTA_SERIALIZATION_H_
#include <memory>
#include <string>
#include <vector>
#include "base/base_export.h"
#include "base/memory/raw_ptr.h"
#include "base/metrics/histogram_flattener.h"
#include "base/metrics/histogram_snapshot_manager.h"
#include "base/threading/thread_checker.h"
namespace base {
class HistogramBase;
// Serializes and restores histograms deltas.
class BASE_EXPORT HistogramDeltaSerialization : public HistogramFlattener {
public:
// |caller_name| is string used in histograms for counting inconsistencies.
explicit HistogramDeltaSerialization(const std::string& caller_name);
HistogramDeltaSerialization(const HistogramDeltaSerialization&) = delete;
HistogramDeltaSerialization& operator=(const HistogramDeltaSerialization&) =
delete;
~HistogramDeltaSerialization() override;
// Computes deltas in histogram bucket counts relative to the previous call to
// this method. Stores the deltas in serialized form into |serialized_deltas|.
// If |serialized_deltas| is null, no data is serialized, though the next call
// will compute the deltas relative to this one. Setting |include_persistent|
// will include histograms held in persistent memory (and thus may be reported
// elsewhere); otherwise only histograms local to this process are serialized.
void PrepareAndSerializeDeltas(std::vector<std::string>* serialized_deltas,
bool include_persistent);
// Deserialize deltas and add samples to corresponding histograms, creating
// them if necessary. Silently ignores errors in |serialized_deltas|.
static void DeserializeAndAddSamples(
const std::vector<std::string>& serialized_deltas);
private:
// HistogramFlattener implementation.
void RecordDelta(const HistogramBase& histogram,
const HistogramSamples& snapshot) override;
ThreadChecker thread_checker_;
// Calculates deltas in histogram counters.
HistogramSnapshotManager histogram_snapshot_manager_;
// Output buffer for serialized deltas.
raw_ptr<std::vector<std::string>> serialized_deltas_;
};
} // namespace base
#endif // BASE_METRICS_HISTOGRAM_DELTA_SERIALIZATION_H_
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