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 #include "webrtc/base/ratetracker.h"
12
13 #include <stddef.h>
14
15 #include <algorithm>
16
17 #include "webrtc/base/checks.h"
18 #include "webrtc/base/timeutils.h"
19
20 namespace rtc {
21
RateTracker(uint32_t bucket_milliseconds,size_t bucket_count)22 RateTracker::RateTracker(uint32_t bucket_milliseconds, size_t bucket_count)
23 : bucket_milliseconds_(bucket_milliseconds),
24 bucket_count_(bucket_count),
25 sample_buckets_(new size_t[bucket_count + 1]),
26 total_sample_count_(0u),
27 bucket_start_time_milliseconds_(~0u) {
28 RTC_CHECK(bucket_milliseconds > 0u);
29 RTC_CHECK(bucket_count > 0u);
30 }
31
~RateTracker()32 RateTracker::~RateTracker() {
33 delete[] sample_buckets_;
34 }
35
ComputeRateForInterval(uint32_t interval_milliseconds) const36 double RateTracker::ComputeRateForInterval(
37 uint32_t interval_milliseconds) const {
38 if (bucket_start_time_milliseconds_ == ~0u) {
39 return 0.0;
40 }
41 uint32_t current_time = Time();
42 // Calculate which buckets to sum up given the current time. If the time
43 // has passed to a new bucket then we have to skip some of the oldest buckets.
44 uint32_t available_interval_milliseconds = std::min<uint32_t>(
45 interval_milliseconds,
46 bucket_milliseconds_ * static_cast<uint32_t>(bucket_count_));
47 // number of old buckets (i.e. after the current bucket in the ring buffer)
48 // that are expired given our current time interval.
49 size_t buckets_to_skip;
50 // Number of milliseconds of the first bucket that are not a portion of the
51 // current interval.
52 uint32_t milliseconds_to_skip;
53 if (current_time >
54 initialization_time_milliseconds_ + available_interval_milliseconds) {
55 uint32_t time_to_skip =
56 current_time - bucket_start_time_milliseconds_ +
57 static_cast<uint32_t>(bucket_count_) * bucket_milliseconds_ -
58 available_interval_milliseconds;
59 buckets_to_skip = time_to_skip / bucket_milliseconds_;
60 milliseconds_to_skip = time_to_skip % bucket_milliseconds_;
61 } else {
62 buckets_to_skip = bucket_count_ - current_bucket_;
63 milliseconds_to_skip = 0u;
64 available_interval_milliseconds =
65 TimeDiff(current_time, initialization_time_milliseconds_);
66 }
67 // If we're skipping all buckets that means that there have been no samples
68 // within the sampling interval so report 0.
69 if (buckets_to_skip > bucket_count_ ||
70 available_interval_milliseconds == 0u) {
71 return 0.0;
72 }
73 size_t start_bucket = NextBucketIndex(current_bucket_ + buckets_to_skip);
74 // Only count a portion of the first bucket according to how much of the
75 // first bucket is within the current interval.
76 size_t total_samples = ((sample_buckets_[start_bucket] *
77 (bucket_milliseconds_ - milliseconds_to_skip)) +
78 (bucket_milliseconds_ >> 1)) /
79 bucket_milliseconds_;
80 // All other buckets in the interval are counted in their entirety.
81 for (size_t i = NextBucketIndex(start_bucket);
82 i != NextBucketIndex(current_bucket_);
83 i = NextBucketIndex(i)) {
84 total_samples += sample_buckets_[i];
85 }
86 // Convert to samples per second.
87 return static_cast<double>(total_samples * 1000u) /
88 static_cast<double>(available_interval_milliseconds);
89 }
90
ComputeTotalRate() const91 double RateTracker::ComputeTotalRate() const {
92 if (bucket_start_time_milliseconds_ == ~0u) {
93 return 0.0;
94 }
95 uint32_t current_time = Time();
96 if (TimeIsLaterOrEqual(current_time, initialization_time_milliseconds_)) {
97 return 0.0;
98 }
99 return static_cast<double>(total_sample_count_ * 1000u) /
100 static_cast<double>(
101 TimeDiff(current_time, initialization_time_milliseconds_));
102 }
103
TotalSampleCount() const104 size_t RateTracker::TotalSampleCount() const {
105 return total_sample_count_;
106 }
107
AddSamples(size_t sample_count)108 void RateTracker::AddSamples(size_t sample_count) {
109 EnsureInitialized();
110 uint32_t current_time = Time();
111 // Advance the current bucket as needed for the current time, and reset
112 // bucket counts as we advance.
113 for (size_t i = 0u; i <= bucket_count_ &&
114 current_time >= bucket_start_time_milliseconds_ + bucket_milliseconds_;
115 ++i) {
116 bucket_start_time_milliseconds_ += bucket_milliseconds_;
117 current_bucket_ = NextBucketIndex(current_bucket_);
118 sample_buckets_[current_bucket_] = 0u;
119 }
120 // Ensure that bucket_start_time_milliseconds_ is updated appropriately if
121 // the entire buffer of samples has been expired.
122 bucket_start_time_milliseconds_ += bucket_milliseconds_ *
123 ((current_time - bucket_start_time_milliseconds_) / bucket_milliseconds_);
124 // Add all samples in the bucket that includes the current time.
125 sample_buckets_[current_bucket_] += sample_count;
126 total_sample_count_ += sample_count;
127 }
128
Time() const129 uint32_t RateTracker::Time() const {
130 return rtc::Time();
131 }
132
EnsureInitialized()133 void RateTracker::EnsureInitialized() {
134 if (bucket_start_time_milliseconds_ == ~0u) {
135 initialization_time_milliseconds_ = Time();
136 bucket_start_time_milliseconds_ = initialization_time_milliseconds_;
137 current_bucket_ = 0u;
138 // We only need to initialize the first bucket because we reset buckets when
139 // current_bucket_ increments.
140 sample_buckets_[current_bucket_] = 0u;
141 }
142 }
143
NextBucketIndex(size_t bucket_index) const144 size_t RateTracker::NextBucketIndex(size_t bucket_index) const {
145 return (bucket_index + 1u) % (bucket_count_ + 1u);
146 }
147
148 } // namespace rtc
149