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 subclass of MetricSample or NULL if the
+// sample could not be parsed.
+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.
+// The format for the message wrote is:
+//  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(const MetricSample& sample, const std::string& filename);
+
+// Maximum length of a serialized message
+const int kMessageMaxLength = 1024;
+
+}  // namespace MetricsUtils
+}  // namespace metrics
+
+#endif  // COMPONENTS_METRICS_CHROMEOS_METRICS_UTILS_H_