3 files changed, 204 insertions, 0 deletions
diff --git a/base/metrics/histogram_flattener.h b/base/metrics/histogram_flattener.h
new file mode 100644
index 0000000..edb1511
--- /dev/null
+++ b/base/metrics/histogram_flattener.h
@@ -0,0 +1,40 @@
+// 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_FLATTENER_H_
+#define BASE_METRICS_HISTOGRAM_FLATTENER_H_
+
+#include <map>
+#include <string>
+
+#include "base/basictypes.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/metrics/histogram.h"
+
+namespace base {
+
+// HistogramFlattener is an interface for the logistics of gathering up
+// available histograms for recording. The implementors handle the exact lower
+// level recording mechanism, or error report mechanism.
+class BASE_EXPORT HistogramFlattener {
+ public:
+  virtual void RecordDelta(const base::Histogram& histogram,
+                           const base::Histogram::SampleSet& snapshot) = 0;
+
+  // Record various errors found during attempts to record histograms.
+  virtual void InconsistencyDetected(int problem) = 0;
+  virtual void UniqueInconsistencyDetected(int problem) = 0;
+  virtual void SnapshotProblemResolved(int amount) = 0;
+
+ protected:
+  HistogramFlattener() {}
+  virtual ~HistogramFlattener() {}
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(HistogramFlattener);
+};
+
+}  // namespace base
+
+#endif  // BASE_METRICS_HISTOGRAM_FLATTENER_H_
diff --git a/base/metrics/histogram_snapshot_manager.cc b/base/metrics/histogram_snapshot_manager.cc
new file mode 100644
index 0000000..b325f73
--- /dev/null
+++ b/base/metrics/histogram_snapshot_manager.cc
@@ -0,0 +1,104 @@
+// 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.
+
+#include "base/metrics/histogram_snapshot_manager.h"
+
+using base::Histogram;
+using base::StatisticsRecorder;
+
+namespace base {
+
+HistogramSnapshotManager::HistogramSnapshotManager(
+    HistogramFlattener* histogram_flattener)
+    : histogram_flattener_(histogram_flattener) {
+  DCHECK(histogram_flattener_);
+}
+
+HistogramSnapshotManager::~HistogramSnapshotManager() {}
+
+void HistogramSnapshotManager::PrepareDeltas(Histogram::Flags flag_to_set,
+                                             bool record_only_uma) {
+  StatisticsRecorder::Histograms histograms;
+  StatisticsRecorder::GetHistograms(&histograms);
+  for (StatisticsRecorder::Histograms::const_iterator it = histograms.begin();
+       histograms.end() != it;
+       ++it) {
+    (*it)->SetFlags(flag_to_set);
+    if (record_only_uma &&
+        0 == ((*it)->flags() & Histogram::kUmaTargetedHistogramFlag))
+      continue;
+    PrepareDelta(**it);
+  }
+}
+
+void HistogramSnapshotManager::PrepareDelta(const Histogram& histogram) {
+  DCHECK(histogram_flattener_);
+
+  // Get up-to-date snapshot of sample stats.
+  Histogram::SampleSet snapshot;
+  histogram.SnapshotSample(&snapshot);
+  const std::string& histogram_name = histogram.histogram_name();
+
+  int corruption = histogram.FindCorruption(snapshot);
+
+  // Crash if we detect that our histograms have been overwritten.  This may be
+  // a fair distance from the memory smasher, but we hope to correlate these
+  // crashes with other events, such as plugins, or usage patterns, etc.
+  if (Histogram::BUCKET_ORDER_ERROR & corruption) {
+    // The checksum should have caught this, so crash separately if it didn't.
+    CHECK_NE(0, Histogram::RANGE_CHECKSUM_ERROR & corruption);
+    CHECK(false);  // Crash for the bucket order corruption.
+  }
+  // Checksum corruption might not have caused order corruption.
+  CHECK_EQ(0, Histogram::RANGE_CHECKSUM_ERROR & corruption);
+
+  if (corruption) {
+    NOTREACHED();
+    histogram_flattener_->InconsistencyDetected(corruption);
+    // Don't record corrupt data to metrics survices.
+    if (NULL == inconsistencies_.get())
+      inconsistencies_.reset(new ProblemMap);
+    int old_corruption = (*inconsistencies_)[histogram_name];
+    if (old_corruption == (corruption | old_corruption))
+      return;  // We've already seen this corruption for this histogram.
+    (*inconsistencies_)[histogram_name] |= corruption;
+    histogram_flattener_->UniqueInconsistencyDetected(corruption);
+    return;
+  }
+
+  // Find the already recorded stats, or create an empty set. Remove from our
+  // snapshot anything that we've already recorded.
+  LoggedSampleMap::iterator it = logged_samples_.find(histogram_name);
+  Histogram::SampleSet* already_logged;
+  if (logged_samples_.end() == it) {
+    // Add new entry
+    already_logged = &logged_samples_[histogram.histogram_name()];
+    already_logged->Resize(histogram);  // Complete initialization.
+  } else {
+    already_logged = &(it->second);
+    int64 discrepancy(already_logged->TotalCount() -
+                      already_logged->redundant_count());
+    if (discrepancy) {
+      NOTREACHED();  // Already_logged has become corrupt.
+      int problem = static_cast<int>(discrepancy);
+      if (problem != discrepancy)
+        problem = INT_MAX;
+      histogram_flattener_->SnapshotProblemResolved(problem);
+      // With no valid baseline, we'll act like we've recorded everything in our
+      // snapshot.
+      already_logged->Subtract(*already_logged);
+      already_logged->Add(snapshot);
+    }
+    // Deduct any stats we've already logged from our snapshot.
+    snapshot.Subtract(*already_logged);
+  }
+
+  // Snapshot now contains only a delta to what we've already_logged.
+  if (snapshot.redundant_count() > 0) {
+    histogram_flattener_->RecordDelta(histogram, snapshot);
+    // Add new data into our running total.
+    already_logged->Add(snapshot);
+  }
+}
+}  // namespace base
diff --git a/base/metrics/histogram_snapshot_manager.h b/base/metrics/histogram_snapshot_manager.h
new file mode 100644
index 0000000..a945ac7
--- /dev/null
+++ b/base/metrics/histogram_snapshot_manager.h
@@ -0,0 +1,60 @@
+// 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 <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_