Measure bandwidth for chromoting video channel

remoting/base/rate_counter.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.
+
+// RateCounter is defined to measure average rate over a given time window.
+// Rate is reported as the sum of values recorded divided by the time window.
+// This can be used for measuring bandwidth, bitrate, etc.
+
+// This class is thread-safe.
+
+#ifndef REMOTING_BASE_RATE_COUNTER_H_
+#define REMOTING_BASE_RATE_COUNTER_H_
+
+#include <queue>
+#include <utility>
+
+#include "base/basictypes.h"
+#include "base/synchronization/lock.h"
+#include "base/time.h"
+
+namespace remoting {
+
+class RateCounter {
+ public:
+  // Construct a counter for a specific time window.
+  RateCounter(base::TimeDelta time_window);
+
+  virtual ~RateCounter();
+
+  // Record the data point.
+  void Record(int64 value);
+
+  // Report the rate recorded. At the beginning of recording the numbers before
+  // |time_window| is reached the reported rate will not be accurate.
+  double Rate();
+
+ private:
+  // Helper function to evict old data points.
+  void Evict(base::Time current_time);
+
+  // A data point consists of a timestamp and a data value.
+  typedef std::pair<base::Time, int64> DataPoint;
+
+  // Duration of the time window.
+  base::TimeDelta time_window_;
+
+  // Protects |data_points_| and |sum_|.
+  base::Lock lock_;
+
+  // Keep the values of all the data points in a queue.
+  std::queue<DataPoint> data_points_;
+
+  // Sum of values in |data_points_|.
+  int64 sum_;
+
+  DISALLOW_COPY_AND_ASSIGN(RateCounter);
+};
+
+}  // namespace remoting
+
+#endif  // REMOTING_BASE_RATE_COUNTER_H_