Consolidate serialization code in base::HistogramDeltasSerializer.

base/metrics/histogram_delta_serializer.h

Index: base/metrics/histogram_delta_serializer.h
diff --git a/base/metrics/histogram_delta_serializer.h b/base/metrics/histogram_delta_serializer.h
new file mode 100644
index 0000000000000000000000000000000000000000..a35899d9a96fe017cd57825a8ef382a7c404d82a
--- /dev/null
+++ b/base/metrics/histogram_delta_serializer.h
@@ -0,0 +1,64 @@
+// Copyright 2013 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_DELTA_SERIALIZER_BASE_H_

[darin (slow to review), 2013/10/21 21:59:58]

nit: include guard is wrong

[Vitaly Buka (NO REVIEWS), 2013/10/21 23:05:32]

Done.

+#define BASE_METRICS_HISTOGRAM_DELTA_SERIALIZER_BASE_H_
+
+#include <string>
+#include <vector>
+
+#include "base/base_export.h"
+#include "base/basictypes.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/metrics/histogram_flattener.h"
+#include "base/metrics/histogram_snapshot_manager.h"
+
+namespace base {
+
+class HistogramBase;
+
+// Serializes and restores histograms deltas.
+class BASE_EXPORT HistogramDeltasSerializer : public HistogramFlattener {

[darin (slow to review), 2013/10/21 21:59:58]

nit: the file name and class name do not precisely match. "Delta[s]"

[Vitaly Buka (NO REVIEWS), 2013/10/21 23:05:32]

Done.

+ public:
+  // |caller_name| is string used in histograms for counting inconsistencies.
+  explicit HistogramDeltasSerializer(const std::string& caller_name);
+  virtual ~HistogramDeltasSerializer();
+
+  // Computes deltas in histogram bucket counts relative to the previous call to
+  // this method. Stores the deltas in serialized form into |serialized_deltas|.
+  // If |serialized_deltas| is NULL, no data is serialized, though the next call
+  // will compute the deltas relative to this one.
+  void PrepareAndSerializeDeltas(std::vector<std::string>* serialized_deltas);
+
+  // Deserialize deltas and add samples to corresponding histograms, creating
+  // them if necessary. Silently ignores errors in |deltas|.
+  static void DeserializeAndAddSamples(const std::vector<std::string>& deltas);

[darin (slow to review), 2013/10/21 21:59:58]

nit: Is this class really a Serializer if it provides a method to deserialize as
well? Maybe HistogramDeltaSerialization would be a better name?

nit: Use "serialized_deltas" or "deltas" for the variable name in both
functions? Be consistent.

[Vitaly Buka (NO REVIEWS), 2013/10/21 23:05:32]

Done.

+
+ private:
+  // HistogramFlattener implementation.
+  virtual void RecordDelta(const HistogramBase& histogram,
+                           const HistogramSamples& snapshot) OVERRIDE;
+  virtual void InconsistencyDetected(
+      HistogramBase::Inconsistency problem) OVERRIDE;
+  virtual void UniqueInconsistencyDetected(
+      HistogramBase::Inconsistency problem) OVERRIDE;
+  virtual void InconsistencyDetectedInLoggedCount(int amount) OVERRIDE;
+
+  // Calculates deltas in histogram counters.
+  HistogramSnapshotManager histogram_snapshot_manager_;
+
+  // Output buffer for serialized deltas.
+  std::vector<std::string>* serialized_deltas_;
+
+  // Histograms to count inconsistencies in snapshots.
+  HistogramBase* inconsistencies_histogram_;
+  HistogramBase* inconsistencies_unique_histogram_;
+  HistogramBase* inconsistent_snapshot_histogram_;
+
+  DISALLOW_COPY_AND_ASSIGN(HistogramDeltasSerializer);
+};
+
+}  // namespace base
+
+#endif  // BASE_METRICS_HISTOGRAM_DELTA_SERIALIZER_BASE_H_