// Copyright (c) 2012 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. #ifndef BASE_METRICS_HISTOGRAM_SNAPSHOT_MANAGER_H_ #define BASE_METRICS_HISTOGRAM_SNAPSHOT_MANAGER_H_ #include #include #include #include #include #include "base/base_export.h" #include "base/gtest_prod_util.h" #include "base/memory/raw_ptr.h" #include "base/metrics/histogram_base.h" namespace base { class HistogramSamples; class HistogramFlattener; // HistogramSnapshotManager handles the logistics of gathering up available // histograms for recording either to disk or for transmission (such as from // renderer to browser, or from browser to UMA upload). Since histograms can sit // in memory for an extended period of time, and are vulnerable to memory // corruption, this class also validates as much redundancy as it can before // calling for the marginal change (a.k.a., delta) in a histogram to be // recorded. class BASE_EXPORT HistogramSnapshotManager final { public: explicit HistogramSnapshotManager(HistogramFlattener* histogram_flattener); HistogramSnapshotManager(const HistogramSnapshotManager&) = delete; HistogramSnapshotManager& operator=(const HistogramSnapshotManager&) = delete; ~HistogramSnapshotManager(); // Snapshots all histograms and asks |histogram_flattener_| to record the // delta. |flags_to_set| is used to set flags for each histogram. // |required_flags| is used to select which histograms to record. Only // histograms with all of the required flags are selected. If all histograms // should be recorded, use |Histogram::kNoFlags| as the required flag. void PrepareDeltas(const std::vector& histograms, HistogramBase::Flags flags_to_set, HistogramBase::Flags required_flags); // When the collection is not so simple as can be done using a single // iterator, the steps can be performed separately. Call PerpareDelta() // as many times as necessary. PrepareFinalDelta() works like PrepareDelta() // except that it does not update the previous logged values and can thus // be used with read-only files. void PrepareDelta(HistogramBase* histogram); void PrepareFinalDelta(const HistogramBase* histogram); private: FRIEND_TEST_ALL_PREFIXES(HistogramSnapshotManagerTest, CheckMerge); // During a snapshot, samples are acquired and aggregated. This structure // contains all the information for a given histogram that persists between // collections. struct SampleInfo { // The set of inconsistencies (flags) already seen for the histogram. // See HistogramBase::Inconsistency for values. uint32_t inconsistencies = 0; }; // Capture and hold samples from a histogram. This does all the heavy // lifting for PrepareDelta() and PrepareAbsolute(). void PrepareSamples(const HistogramBase* histogram, std::unique_ptr samples); // |histogram_flattener_| handles the logistics of recording the histogram // deltas. const raw_ptr histogram_flattener_; // Weak. // For histograms, track what has been previously seen, indexed // by the hash of the histogram name. std::map known_histograms_; // A flag indicating if a thread is currently doing an operation. This is // used to check against concurrent access which is not supported. A Thread- // Checker is not sufficient because it may be guarded by at outside lock // (as is the case with cronet). std::atomic is_active_; }; } // namespace base #endif // BASE_METRICS_HISTOGRAM_SNAPSHOT_MANAGER_H_