Create a histogram serialization mechanism in components/metrics

components/metrics/chromeos/metrics_utils.h

+// Copyright 2014 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 COMPONENTS_METRICS_CHROMEOS_METRICS_UTILS_H_
+#define COMPONENTS_METRICS_CHROMEOS_METRICS_UTILS_H_
+
+#include <string>
+
+#include "base/memory/scoped_ptr.h"
+#include "base/memory/scoped_vector.h"
+
+namespace metrics {
+
+class MetricSample;
+
+// Metrics helpers to serialize and deserialize metrics collected by
+// ChromeOS.
+namespace MetricsUtils {
+
+// Deserialize a sample passed as a string and return a sample.
+// The return value will either be a scoped_ptr to a Metric sample (if the
+// deserialization was successful) or a NULL scoped_ptr.
+scoped_ptr<MetricSample> ReadSample(const std::string& sample);
+
+// Read all samples from a file and truncate the file when done.
+void ReadAndTruncateMetricsFromFile(const std::string& filename,
+                                    ScopedVector<MetricSample>* metrics);
+
+// Serialize a metric and write it to filename.

[Luigi Semenzato, 2014/05/12 23:04:48]

Use "sample" instead of "metric" is possible.  (It's at least partly my fault
that we abuse the word "metric", it's really only plural with that meaning.)

+// The format for the message wrote is:

[Luigi Semenzato, 2014/05/12 23:04:48]

Typo.

+//  message_size, serialized_message
+// where
+//  * message_size is the total length of the message (message_size +
+//    serialized_message) on 4 bytes
+//  * serialized_message is the serialized version of sample (using ToString)
+bool WriteMetricToFile(MetricSample* sample, const std::string& filename);

[gauravsh, 2014/05/12 22:53:10]

The input could const MetricSample* sample?

+
+// Maximum length of a serialized message
+const int kMessageMaxLength = 1024;
+
+}  // namespace MetricsUtils
+}  // namespace metrics
+
+#endif  // COMPONENTS_METRICS_CHROMEOS_METRICS_UTILS_H_