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99e5aedc21
Summary: Without this the math doesn't really make sense, since it's done in whole intervals of seconds. Reviewed By: sharmafb Differential Revision: D21614903 fbshipit-source-id: 1bd9fddb9c667de1ae509340feedc0058befd50c
43 lines
1.5 KiB
C++
43 lines
1.5 KiB
C++
// Copyright 2004-present Facebook. All Rights Reserved.
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#include "SlidingWindowRateLimiter.h"
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#include <cmath>
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namespace quic {
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bool SlidingWindowRateLimiter::check(TimePoint time) {
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// This is the first time point.
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if (!currentWindowStartPoint_) {
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currentWindowStartPoint_ = time;
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}
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auto timeElapsedSinceCurWindow =
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std::chrono::duration_cast<std::chrono::microseconds>(
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time - currentWindowStartPoint_.value());
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// A full window has elapsed.
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if (timeElapsedSinceCurWindow > window_) {
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double windowsElapsed = timeElapsedSinceCurWindow.count() / window_.count();
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currentWindowStartPoint_.value() +=
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std::chrono::microseconds(uint64_t(window_.count() * windowsElapsed));
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// If more than one window has elapsed, there were zero in the previous
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// window.
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countInPrevWindow_ = windowsElapsed == 1 ? countInCurWindow_ : 0;
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countInCurWindow_ = 0;
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timeElapsedSinceCurWindow =
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std::chrono::duration_cast<std::chrono::microseconds>(
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time - currentWindowStartPoint_.value());
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}
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// The weighted count accounts for the "sliding" window by using the
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// previous windows average rate over the time that has elapsed in the
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// current window.
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double weightedCount = countInPrevWindow_ *
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(static_cast<double>((window_ - timeElapsedSinceCurWindow).count()) /
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window_.count()) +
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countInCurWindow_ + 1;
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bool limited = std::trunc(weightedCount) > count_;
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countInCurWindow_ = limited ? countInCurWindow_ : countInCurWindow_ + 1;
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return limited;
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}
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} // namespace quic
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