Histograms - Support histograms for Plugins, GPU

base/metrics/histogram_snapshot_manager.h

+// 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_
+#pragma once
+
+#include <map>
+#include <string>
+
+#include "base/basictypes.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/metrics/histogram.h"
+#include "base/metrics/histogram_flattener.h"
+
+namespace base {
+
+// 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. The arguments allow selecting only a subset of histograms for
+  // recording, or to set a flag in each recorded histogram.
+  void PrepareDeltas(base::Histogram::Flags flags_to_set, bool record_only_uma);
+
+ private:
+  // Maintain a map of histogram names to the sample stats we've recorded.
+  typedef std::map<std::string, base::Histogram::SampleSet> LoggedSampleMap;
+  // List of histograms names, and their encontered corruptions.
+  typedef std::map<std::string, int> ProblemMap;
+
+  // Snapshot this histogram, and record the delta.
+  void PrepareDelta(const base::Histogram& histogram);
+
+  // 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.
+  LoggedSampleMap logged_samples_;
+
+  // List of histograms found corrupt to be corrupt, and their problems.
+  scoped_ptr<ProblemMap> 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_