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Side by Side Diff: webrtc/base/bucketratetracker.cc

Issue 1279433006: Add a rate tracker that tracks rate over a given interval split up into buckets that accumulate uni… (Closed) Base URL: https://chromium.googlesource.com/external/webrtc.git@master
Patch Set: win64 fix Created 5 years, 4 months ago
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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/bucketratetracker.h"
12
13 #include <stddef.h>
14 #include <assert.h>
15
16 #include <algorithm>
17
18 #include "webrtc/base/timeutils.h"
19
20 namespace rtc {
21
22 BucketRateTracker::BucketRateTracker(
23 uint32 bucket_milliseconds, size_t bucket_count)
24 : bucket_milliseconds_(bucket_milliseconds),
25 bucket_count_(bucket_count),
26 sample_buckets_(new size_t[bucket_count + 1]),
27 bucket_start_time_(~0u) {
28 assert(bucket_milliseconds > 0u);
29 assert(bucket_count > 0u);
30 }
31
32 BucketRateTracker::~BucketRateTracker() {
33 delete[] sample_buckets_;
34 }
35
36 double BucketRateTracker::ComputeCurrentRate(
37 uint32 interval_milliseconds) const {
38 if (bucket_start_time_ == ~0u) {
39 return 0.0;
40 }
41 uint32 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 available_interval_milliseconds = std::min<uint32>(
45 interval_milliseconds,
46 bucket_milliseconds_ * static_cast<uint32>(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 milliseconds_to_skip;
53 if (current_time > initialization_time_ + available_interval_milliseconds) {
54 uint32 time_to_skip = current_time - bucket_start_time_ +
55 static_cast<uint32>(bucket_count_) * bucket_milliseconds_ -
56 available_interval_milliseconds;
57 buckets_to_skip = time_to_skip / bucket_milliseconds_;
58 milliseconds_to_skip = time_to_skip % bucket_milliseconds_;
59 } else {
60 buckets_to_skip = bucket_count_ - current_bucket_;
61 milliseconds_to_skip = 0u;
62 available_interval_milliseconds = current_time - initialization_time_;
63 }
64 // If we're skipping all buckets that means that there have been no samples
65 // within the sampling interval so report 0.
66 if (buckets_to_skip > bucket_count_ ||
67 available_interval_milliseconds == 0u) {
68 return 0.0;
69 }
70 size_t start_bucket = NextBucketIndex(current_bucket_ + buckets_to_skip);
71 // Only count a portion of the first bucket according to how much of the
72 // first bucket is within the current interval.
73 size_t total_samples = sample_buckets_[start_bucket] *
74 (bucket_milliseconds_ - milliseconds_to_skip) /
75 bucket_milliseconds_;
76 // All other buckets in the interval are counted in their entirety.
77 for (size_t i = NextBucketIndex(start_bucket);
78 i != NextBucketIndex(current_bucket_);
79 i = NextBucketIndex(i)) {
80 total_samples += sample_buckets_[i];
81 }
82 // Convert to samples per second.
83 return static_cast<double>(total_samples * 1000u) /
84 static_cast<double>(available_interval_milliseconds);
85 }
86
87 void BucketRateTracker::AddSamples(size_t sample_count) {
88 EnsureInitialized();
89 uint32 current_time = Time();
90 // Advance the current bucket as needed for the current time, and reset
91 // bucket counts as we advance.
92 for (size_t i = 0u; i <= bucket_count_ &&
93 current_time >= bucket_start_time_ + bucket_milliseconds_; ++i) {
94 bucket_start_time_ += bucket_milliseconds_;
95 current_bucket_ = NextBucketIndex(current_bucket_);
96 sample_buckets_[current_bucket_] = 0u;
97 }
98 // Ensure that bucket_start_time_ is updated appropriately if we've expired
99 // the entire buffer of samples.
100 bucket_start_time_ += bucket_milliseconds_ *
101 ((current_time - bucket_start_time_) / bucket_milliseconds_);
102 // Add all samples in the bucket that includes the current time.
103 sample_buckets_[current_bucket_] += sample_count;
104 }
105
106 uint32 BucketRateTracker::Time() const {
107 return rtc::Time();
108 }
109
110 void BucketRateTracker::EnsureInitialized() {
111 if (bucket_start_time_ == ~0u) {
112 initialization_time_ = Time();
113 bucket_start_time_ = initialization_time_;
114 current_bucket_ = 0u;
115 // We only need to initialize the first bucket because we reset buckets when
116 // current_bucket_ increments.
117 sample_buckets_[current_bucket_] = 0u;
118 }
119 }
120
121 size_t BucketRateTracker::NextBucketIndex(size_t bucket_index) const {
122 return (bucket_index + 1u) % (bucket_count_ + 1u);
123 }
124
125 } // namespace rtc
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