1 /*
2  *  Copyright 2015 The WebRTC Project Authors. All rights reserved.
3  *
4  *  Use of this source code is governed by a BSD-style license
5  *  that can be found in the LICENSE file in the root of the source
6  *  tree. An additional intellectual property rights grant can be found
7  *  in the file PATENTS.  All contributing project authors may
8  *  be found in the AUTHORS file in the root of the source tree.
9  */
10 
11 #ifndef WEBRTC_BASE_RATETRACKER_H_
12 #define WEBRTC_BASE_RATETRACKER_H_
13 
14 #include <stdlib.h>
15 #include "webrtc/base/basictypes.h"
16 
17 namespace rtc {
18 
19 // Computes units per second over a given interval by tracking the units over
20 // each bucket of a given size and calculating the instantaneous rate assuming
21 // that over each bucket the rate was constant.
22 class RateTracker {
23  public:
24   RateTracker(uint32_t bucket_milliseconds, size_t bucket_count);
25   virtual ~RateTracker();
26 
27   // Computes the average rate over the most recent interval_milliseconds,
28   // or if the first sample was added within this period, computes the rate
29   // since the first sample was added.
30   double ComputeRateForInterval(uint32_t interval_milliseconds) const;
31 
32   // Computes the average rate over the rate tracker's recording interval
33   // of bucket_milliseconds * bucket_count.
ComputeRate()34   double ComputeRate() const {
35     return ComputeRateForInterval(bucket_milliseconds_ *
36                                   static_cast<uint32_t>(bucket_count_));
37   }
38 
39   // Computes the average rate since the first sample was added to the
40   // rate tracker.
41   double ComputeTotalRate() const;
42 
43   // The total number of samples added.
44   size_t TotalSampleCount() const;
45 
46   // Reads the current time in order to determine the appropriate bucket for
47   // these samples, and increments the count for that bucket by sample_count.
48   void AddSamples(size_t sample_count);
49 
50  protected:
51   // overrideable for tests
52   virtual uint32_t Time() const;
53 
54  private:
55   void EnsureInitialized();
56   size_t NextBucketIndex(size_t bucket_index) const;
57 
58   const uint32_t bucket_milliseconds_;
59   const size_t bucket_count_;
60   size_t* sample_buckets_;
61   size_t total_sample_count_;
62   size_t current_bucket_;
63   uint32_t bucket_start_time_milliseconds_;
64   uint32_t initialization_time_milliseconds_;
65 };
66 
67 }  // namespace rtc
68 
69 #endif  // WEBRTC_BASE_RATETRACKER_H_
70