Create a histogram serialization mechanism in components/metrics

components/metrics/chromeos/metrics_utils.h

Index: components/metrics/chromeos/metrics_utils.h
diff --git a/components/metrics/chromeos/metrics_utils.h b/components/metrics/chromeos/metrics_utils.h
new file mode 100644
index 0000000000000000000000000000000000000000..e996d0fb0e634fec3b33ed8a856e9c89d2c8f264
--- /dev/null
+++ b/components/metrics/chromeos/metrics_utils.h
@@ -0,0 +1,48 @@
+// 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 {

[Alexei Svitkine (slow), 2014/05/15 13:43:26]

Can this have a better name? It's already in the metrics namespace - how about
SerializationUtils? (Likewise for the name of the file.)

[bsimonnet, 2014/05/15 19:23:40]

Done.

+
+// 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);

[Alexei Svitkine (slow), 2014/05/15 13:43:26]

Nit: A better name might be "ParseSample", since this function isn't actually
reading from a file.

[bsimonnet, 2014/05/15 19:23:40]

Done.

+
+// Read all samples from a file and truncate the file when done.
+void ReadAndTruncateMetricsFromFile(const std::string& filename,
+                                    ScopedVector<MetricSample>* metrics);
+
+// Serialize a sample and write it to filename.
+// The format for the message 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)
+//
+//  NB: the file will never leave the device so message_size will be written
+//  with the architecture's endianness.
+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_