Measure bandwidth for chromoting video channel

remoting/base/running_average.h

+// Copyright (c) 2011 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.
+
+// RunningAverage defined in this file is used to generate statistics for
+// bandwidth, latency and other performance metrics for remoting. Usually
+// these data come in as a stream and fluctuates a lot. They are processed by

[simonmorris, 2011/04/04 10:27:34]

"this...comes...fluctuates" or "these...come...fluctuate".

[Alpha Left Google, 2011/04/05 00:16:06]

Done.

[Alpha Left Google, 2011/04/05 00:16:06]

Done.

+// this class to generate a more stable value by taking average within a
+// window of data points.
+
+// All classes defined are thread-safe.
+
+#ifndef REMOTING_BASE_RUNNING_AVERAGE_H_
+#define REMOTING_BASE_RUNNING_AVERAGE_H_
+
+#include <deque>
+
+#include "base/basictypes.h"
+#include "base/synchronization/lock.h"
+#include "base/time.h"
+
+namespace remoting {
+
+class RunningAverage {
+ public:
+  // Construct a running average counter for a specific window size. The most
+  // |windows_size| recent values are kept and the average is reported.

[simonmorris, 2011/04/04 10:27:34]

"|windows_size| most recent", not "most |windows_size| recent".

[Alpha Left Google, 2011/04/05 00:16:06]

Done.

+  RunningAverage(int window_size);
+
+  virtual ~RunningAverage();
+
+  // Record the provided data point.
+  void Record(int64 value);
+
+  // Return the average of data points in the last window.
+  int64 Average();

[simonmorris, 2011/04/04 10:27:34]

Is int64 better than the expected double?

[Alpha Left Google, 2011/04/05 00:16:06]

In a later patch this is changed to double.

+
+ private:
+  // Size of the window. This is of type size_t to avoid casting when comparing
+  // with the size of |data_points_|.
+  size_t window_size_;
+
+  // Protects |data_points_| and |sum_|.
+  base::Lock lock_;
+
+  // Keep the values of all the data points.
+  std::deque<int64> data_points_;
+
+  // Sum of values in |data_points_|.
+  int64 sum_;
+
+  DISALLOW_COPY_AND_ASSIGN(RunningAverage);
+};
+
+}  // namespace remoting
+
+#endif  // REMOTING_BASE_RUNNING_AVERAGE_H_