1 /*
2 * Copyright (c) 2016 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 "rtc_base/rate_limiter.h"
12
13 #include <limits>
14
15 #include "absl/types/optional.h"
16 #include "system_wrappers/include/clock.h"
17
18 namespace webrtc {
19
RateLimiter(Clock * clock,int64_t max_window_ms)20 RateLimiter::RateLimiter(Clock* clock, int64_t max_window_ms)
21 : clock_(clock),
22 current_rate_(max_window_ms, RateStatistics::kBpsScale),
23 window_size_ms_(max_window_ms),
24 max_rate_bps_(std::numeric_limits<uint32_t>::max()) {}
25
~RateLimiter()26 RateLimiter::~RateLimiter() {}
27
28 // Usage note: This class is intended be usable in a scenario where different
29 // threads may call each of the the different method. For instance, a network
30 // thread trying to send data calling TryUseRate(), the bandwidth estimator
31 // calling SetMaxRate() and a timed maintenance thread periodically updating
32 // the RTT.
TryUseRate(size_t packet_size_bytes)33 bool RateLimiter::TryUseRate(size_t packet_size_bytes) {
34 MutexLock lock(&lock_);
35 int64_t now_ms = clock_->TimeInMilliseconds();
36 absl::optional<uint32_t> current_rate = current_rate_.Rate(now_ms);
37 if (current_rate) {
38 // If there is a current rate, check if adding bytes would cause maximum
39 // bitrate target to be exceeded. If there is NOT a valid current rate,
40 // allow allocating rate even if target is exceeded. This prevents
41 // problems
42 // at very low rates, where for instance retransmissions would never be
43 // allowed due to too high bitrate caused by a single packet.
44
45 size_t bitrate_addition_bps =
46 (packet_size_bytes * 8 * 1000) / window_size_ms_;
47 if (*current_rate + bitrate_addition_bps > max_rate_bps_)
48 return false;
49 }
50
51 current_rate_.Update(packet_size_bytes, now_ms);
52 return true;
53 }
54
SetMaxRate(uint32_t max_rate_bps)55 void RateLimiter::SetMaxRate(uint32_t max_rate_bps) {
56 MutexLock lock(&lock_);
57 max_rate_bps_ = max_rate_bps;
58 }
59
60 // Set the window size over which to measure the current bitrate.
61 // For retransmissions, this is typically the RTT.
SetWindowSize(int64_t window_size_ms)62 bool RateLimiter::SetWindowSize(int64_t window_size_ms) {
63 MutexLock lock(&lock_);
64 window_size_ms_ = window_size_ms;
65 return current_rate_.SetWindowSize(window_size_ms,
66 clock_->TimeInMilliseconds());
67 }
68
69 } // namespace webrtc
70