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// 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 <stdint.h>
#include <map>
#include <string>
#include "base/macros.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 rendundancy as it can before
// calling for the marginal change (a.k.a., delta) in a histogram to be
// recorded.
class BASE_EXPORT HistogramSnapshotManager {
public:
explicit HistogramSnapshotManager(HistogramFlattener* histogram_flattener);
virtual ~HistogramSnapshotManager();
// Snapshot all histograms, and ask |histogram_flattener_| to record the
// delta. |flags_to_set| is used to set flags for each histogram.
// |required_flags| is used to select histograms to be recorded.
// Only histograms that have all the flags specified by the argument will be
// chosen. If all histograms should be recorded, set it to
// |Histogram::kNoFlags|.
template <class ForwardHistogramIterator>
void PrepareDeltas(ForwardHistogramIterator begin,
ForwardHistogramIterator end,
HistogramBase::Flags flags_to_set,
HistogramBase::Flags required_flags) {
for (ForwardHistogramIterator it = begin; it != end; ++it) {
(*it)->SetFlags(flags_to_set);
if (((*it)->flags() & required_flags) == required_flags)
PrepareDelta(**it);
}
}
private:
// Snapshot this histogram, and record the delta.
void PrepareDelta(const HistogramBase& histogram);
// Try to detect and fix count inconsistency of logged samples.
void InspectLoggedSamplesInconsistency(
const HistogramSamples& new_snapshot,
HistogramSamples* logged_samples);
// For histograms, track what we've already recorded (as a sample for
// each histogram) so that we can record only the delta with the next log.
// The information is indexed by the hash of the histogram name.
std::map<uint64_t, HistogramSamples*> logged_samples_;
// Set of histograms found to be corrupt and their problems, indexed
// by the hash of the histogram name.
std::map<uint64_t, int> inconsistencies_;
// |histogram_flattener_| handles the logistics of recording the histogram
// deltas.
HistogramFlattener* histogram_flattener_; // Weak.
DISALLOW_COPY_AND_ASSIGN(HistogramSnapshotManager);
};
} // namespace base
#endif // BASE_METRICS_HISTOGRAM_SNAPSHOT_MANAGER_H_