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1 /* | |
2 * Copyright (c) 2013 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/rate_statistics.h" | |
12 | |
13 #include <algorithm> | |
14 | |
15 #include "webrtc/base/checks.h" | |
16 | |
17 namespace webrtc { | |
18 | |
19 RateStatistics::RateStatistics(int64_t window_size_ms, float scale) | |
20 : buckets_(new Bucket[window_size_ms]()), | |
21 accumulated_count_(0), | |
22 num_samples_(0), | |
23 oldest_time_(-window_size_ms), | |
24 oldest_index_(0), | |
25 scale_(scale), | |
26 max_window_size_ms_(window_size_ms), | |
27 current_window_size_ms_(max_window_size_ms_) {} | |
28 | |
29 RateStatistics::~RateStatistics() {} | |
30 | |
31 void RateStatistics::Reset() { | |
32 accumulated_count_ = 0; | |
33 num_samples_ = 0; | |
34 oldest_time_ = -max_window_size_ms_; | |
35 oldest_index_ = 0; | |
36 current_window_size_ms_ = max_window_size_ms_; | |
37 for (int64_t i = 0; i < max_window_size_ms_; i++) | |
38 buckets_[i] = Bucket(); | |
39 } | |
40 | |
41 void RateStatistics::Update(size_t count, int64_t now_ms) { | |
42 if (now_ms < oldest_time_) { | |
43 // Too old data is ignored. | |
44 return; | |
45 } | |
46 | |
47 EraseOld(now_ms); | |
48 | |
49 // First ever sample, reset window to start now. | |
50 if (!IsInitialized()) | |
51 oldest_time_ = now_ms; | |
52 | |
53 uint32_t now_offset = static_cast<uint32_t>(now_ms - oldest_time_); | |
54 RTC_DCHECK_LT(now_offset, max_window_size_ms_); | |
55 uint32_t index = oldest_index_ + now_offset; | |
56 if (index >= max_window_size_ms_) | |
57 index -= max_window_size_ms_; | |
58 buckets_[index].sum += count; | |
59 ++buckets_[index].samples; | |
60 accumulated_count_ += count; | |
61 ++num_samples_; | |
62 } | |
63 | |
64 rtc::Optional<uint32_t> RateStatistics::Rate(int64_t now_ms) const { | |
65 // Yeah, this const_cast ain't pretty, but the alternative is to declare most | |
66 // of the members as mutable... | |
67 const_cast<RateStatistics*>(this)->EraseOld(now_ms); | |
68 | |
69 // If window is a single bucket or there is only one sample in a data set that | |
70 // has not grown to the full window size, treat this as rate unavailable. | |
71 int64_t active_window_size = now_ms - oldest_time_ + 1; | |
72 if (num_samples_ == 0 || active_window_size <= 1 || | |
73 (num_samples_ <= 1 && active_window_size < current_window_size_ms_)) { | |
74 return rtc::Optional<uint32_t>(); | |
75 } | |
76 | |
77 float scale = scale_ / active_window_size; | |
78 return rtc::Optional<uint32_t>( | |
79 static_cast<uint32_t>(accumulated_count_ * scale + 0.5f)); | |
80 } | |
81 | |
82 void RateStatistics::EraseOld(int64_t now_ms) { | |
83 if (!IsInitialized()) | |
84 return; | |
85 | |
86 // New oldest time that is included in data set. | |
87 int64_t new_oldest_time = now_ms - current_window_size_ms_ + 1; | |
88 | |
89 // New oldest time is older than the current one, no need to cull data. | |
90 if (new_oldest_time <= oldest_time_) | |
91 return; | |
92 | |
93 // Loop over buckets and remove too old data points. | |
94 while (num_samples_ > 0 && oldest_time_ < new_oldest_time) { | |
95 const Bucket& oldest_bucket = buckets_[oldest_index_]; | |
96 RTC_DCHECK_GE(accumulated_count_, oldest_bucket.sum); | |
97 RTC_DCHECK_GE(num_samples_, oldest_bucket.samples); | |
98 accumulated_count_ -= oldest_bucket.sum; | |
99 num_samples_ -= oldest_bucket.samples; | |
100 buckets_[oldest_index_] = Bucket(); | |
101 if (++oldest_index_ >= max_window_size_ms_) | |
102 oldest_index_ = 0; | |
103 ++oldest_time_; | |
104 } | |
105 oldest_time_ = new_oldest_time; | |
106 } | |
107 | |
108 bool RateStatistics::SetWindowSize(int64_t window_size_ms, int64_t now_ms) { | |
109 if (window_size_ms <= 0 || window_size_ms > max_window_size_ms_) | |
110 return false; | |
111 | |
112 current_window_size_ms_ = window_size_ms; | |
113 EraseOld(now_ms); | |
114 return true; | |
115 } | |
116 | |
117 bool RateStatistics::IsInitialized() const { | |
118 return oldest_time_ != -max_window_size_ms_; | |
119 } | |
120 | |
121 } // namespace webrtc | |
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