1 // Copyright 2013 The Chromium Authors 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/memory/raw_ptr.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 28 HistogramDeltaSerialization(const HistogramDeltaSerialization&) = delete; 29 HistogramDeltaSerialization& operator=(const HistogramDeltaSerialization&) = 30 delete; 31 32 ~HistogramDeltaSerialization() override; 33 34 // Computes deltas in histogram bucket counts relative to the previous call to 35 // this method. Stores the deltas in serialized form into |serialized_deltas|. 36 // If |serialized_deltas| is null, no data is serialized, though the next call 37 // will compute the deltas relative to this one. Setting |include_persistent| 38 // will include histograms held in persistent memory (and thus may be reported 39 // elsewhere); otherwise only histograms local to this process are serialized. 40 void PrepareAndSerializeDeltas(std::vector<std::string>* serialized_deltas, 41 bool include_persistent); 42 43 // Deserialize deltas and add samples to corresponding histograms, creating 44 // them if necessary. Silently ignores errors in |serialized_deltas|. 45 static void DeserializeAndAddSamples( 46 const std::vector<std::string>& serialized_deltas); 47 48 private: 49 // HistogramFlattener implementation. 50 void RecordDelta(const HistogramBase& histogram, 51 const HistogramSamples& snapshot) override; 52 53 ThreadChecker thread_checker_; 54 55 // Calculates deltas in histogram counters. 56 HistogramSnapshotManager histogram_snapshot_manager_; 57 58 // Output buffer for serialized deltas. 59 raw_ptr<std::vector<std::string>> serialized_deltas_; 60 }; 61 62 } // namespace base 63 64 #endif // BASE_METRICS_HISTOGRAM_DELTA_SERIALIZATION_H_ 65