c20978e581
NOPRESUBMIT=True # cpplint errors that aren't caused by this CL. NOTRY=True NOTREECHECKS=True TBR=kwiberg@webrtc.org, kjellander@webrtc.org Bug: webrtc:7634 Change-Id: I3cca0fbaa807b563c95979cccd6d1bec32055f36 Reviewed-on: https://chromium-review.googlesource.com/562156 Commit-Queue: Edward Lemur <ehmaldonado@webrtc.org> Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org> Cr-Commit-Position: refs/heads/master@{#18919}
111 lines
3.6 KiB
C++
111 lines
3.6 KiB
C++
/*
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* Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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#ifndef WEBRTC_MODULES_VIDEO_CODING_SEQUENCE_NUMBER_UTIL_H_
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#define WEBRTC_MODULES_VIDEO_CODING_SEQUENCE_NUMBER_UTIL_H_
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#include <limits>
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#include <type_traits>
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#include "webrtc/rtc_base/mod_ops.h"
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namespace webrtc {
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// Test if the sequence number |a| is ahead or at sequence number |b|.
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//
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// If |M| is an even number and the two sequence numbers are at max distance
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// from each other, then the sequence number with the highest value is
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// considered to be ahead.
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template <typename T, T M>
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inline bool AheadOrAt(T a, T b) {
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static_assert(std::is_unsigned<T>::value,
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"Type must be an unsigned integer.");
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const T maxDist = M / 2;
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if (!(M & 1) && MinDiff<T, M>(a, b) == maxDist)
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return b < a;
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return ForwardDiff<T, M>(b, a) <= maxDist;
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}
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template <typename T>
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inline bool AheadOrAt(T a, T b) {
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static_assert(std::is_unsigned<T>::value,
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"Type must be an unsigned integer.");
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const T maxDist = std::numeric_limits<T>::max() / 2 + T(1);
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if (a - b == maxDist)
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return b < a;
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return ForwardDiff(b, a) < maxDist;
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}
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// Test if the sequence number |a| is ahead of sequence number |b|.
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//
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// If |M| is an even number and the two sequence numbers are at max distance
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// from each other, then the sequence number with the highest value is
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// considered to be ahead.
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template <typename T, T M>
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inline bool AheadOf(T a, T b) {
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static_assert(std::is_unsigned<T>::value,
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"Type must be an unsigned integer.");
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return a != b && AheadOrAt<T, M>(a, b);
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}
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template <typename T>
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inline bool AheadOf(T a, T b) {
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static_assert(std::is_unsigned<T>::value,
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"Type must be an unsigned integer.");
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return a != b && AheadOrAt(a, b);
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}
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namespace internal {
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template <typename T, typename M>
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struct SeqNumComp;
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template <typename T, T M>
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struct SeqNumComp<T, std::integral_constant<T, M>> {
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bool operator()(T a, T b) const { return AheadOf<T, M>(a, b); }
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};
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template <typename T>
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struct SeqNumComp<T, std::integral_constant<T, T(0)>> {
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bool operator()(T a, T b) const { return AheadOf<T>(a, b); }
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};
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} // namespace internal
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// Comparator used to compare sequence numbers in a continuous fashion.
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//
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// WARNING! If used to sort sequence numbers of length M then the interval
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// covered by the sequence numbers may not be larger than floor(M/2).
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template <typename T, T M = 0>
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struct AscendingSeqNumComp
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: private internal::SeqNumComp<T, std::integral_constant<T, M>> {
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bool operator()(T a, T b) const {
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return internal::SeqNumComp<T, std::integral_constant<T, M>>::operator()(a,
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b);
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}
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};
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// Comparator used to compare sequence numbers in a continuous fashion.
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//
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// WARNING! If used to sort sequence numbers of length M then the interval
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// covered by the sequence numbers may not be larger than floor(M/2).
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template <typename T, T M = 0>
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struct DescendingSeqNumComp
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: private internal::SeqNumComp<T, std::integral_constant<T, M>> {
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bool operator()(T a, T b) const {
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return internal::SeqNumComp<T, std::integral_constant<T, M>>::operator()(b,
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a);
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}
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};
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} // namespace webrtc
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#endif // WEBRTC_MODULES_VIDEO_CODING_SEQUENCE_NUMBER_UTIL_H_
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