1// Copyright (c) 2011 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#ifndef REMOTING_BASE_RATE_COUNTER_H_
6#define REMOTING_BASE_RATE_COUNTER_H_
7
8#include <queue>
9#include <utility>
10
11#include "base/basictypes.h"
12#include "base/threading/non_thread_safe.h"
13#include "base/time/time.h"
14
15namespace remoting {
16
17// Measures average rate per second of a sequence of point rate samples
18// over a specified time window. This can be used to measure bandwidth, frame
19// rates, etc.
20class RateCounter : public base::NonThreadSafe {
21 public:
22  // Constructs a rate counter over the specified |time_window|.
23  explicit RateCounter(base::TimeDelta time_window);
24  virtual ~RateCounter();
25
26  // Records a point event count to include in the rate.
27  void Record(int64 value);
28
29  // Returns the rate-per-second of values recorded over the time window.
30  // Note that rates reported before |time_window| has elapsed are not accurate.
31  double Rate();
32
33  // Overrides the current time for testing.
34  void SetCurrentTimeForTest(base::Time current_time);
35
36 private:
37  // Type used to store data points with timestamps.
38  typedef std::pair<base::Time, int64> DataPoint;
39
40  // Removes data points more than |time_window| older than |current_time|.
41  void EvictOldDataPoints(base::Time current_time);
42
43  // Returns the current time specified for test, if set, or base::Time::Now().
44  base::Time CurrentTime() const;
45
46  // Time window over which to calculate the rate.
47  const base::TimeDelta time_window_;
48
49  // Queue containing data points in the order in which they were recorded.
50  std::queue<DataPoint> data_points_;
51
52  // Sum of values in |data_points_|.
53  int64 sum_;
54
55  // If set, used to calculate the running average, in place of Now().
56  base::Time current_time_for_test_;
57
58  DISALLOW_COPY_AND_ASSIGN(RateCounter);
59};
60
61}  // namespace remoting
62
63#endif  // REMOTING_BASE_RATE_COUNTER_H_
64