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 18 namespace base { 19 20 class HistogramBase; 21 22 // Serializes and restores histograms deltas. 23 class 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 48 ThreadChecker thread_checker_; 49 50 // Calculates deltas in histogram counters. 51 HistogramSnapshotManager histogram_snapshot_manager_; 52 53 // Output buffer for serialized deltas. 54 std::vector<std::string>* serialized_deltas_; 55 56 DISALLOW_COPY_AND_ASSIGN(HistogramDeltaSerialization); 57 }; 58 59 } // namespace base 60 61 #endif // BASE_METRICS_HISTOGRAM_DELTA_SERIALIZATION_H_ 62