remoting/base/rate_counter.h

   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
  15 namespace 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.
  20 class 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_