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097fc347ec
This is in prep for the migration of all unwrappers to SequenceNumberUnwrapper as a standard implementation. This moves the SeqNumUnwapper to its own header and adds 2 methods to SeqNumUnwrapper which are defined by other unwrappers: * PeekUnwrap * Reset It also adds two implementations for RtpTimestamps and RtpSequenceNumbers. Bug: webrtc:13982 Change-Id: I5baefb2de1db92fe1bb600760bd63b71e9310eb5 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/288742 Commit-Queue: Evan Shrubsole <eshr@webrtc.org> Reviewed-by: Harald Alvestrand <hta@webrtc.org> Auto-Submit: Evan Shrubsole <eshr@webrtc.org> Cr-Commit-Position: refs/heads/main@{#39030}
80 lines
2.3 KiB
C++
80 lines
2.3 KiB
C++
/*
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* Copyright (c) 2022 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 RTC_BASE_NUMERICS_SEQUENCE_NUMBER_UNWRAPPER_H_
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#define RTC_BASE_NUMERICS_SEQUENCE_NUMBER_UNWRAPPER_H_
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#include <stdint.h>
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#include <limits>
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#include "absl/types/optional.h"
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#include "rtc_base/numerics/sequence_number_util.h"
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namespace webrtc {
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// A sequence number unwrapper where the first unwrapped value equals the
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// first value being unwrapped.
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template <typename T, T M = 0>
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class SeqNumUnwrapper {
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static_assert(
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std::is_unsigned<T>::value &&
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std::numeric_limits<T>::max() < std::numeric_limits<int64_t>::max(),
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"Type unwrapped must be an unsigned integer smaller than int64_t.");
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public:
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// Unwraps `value` and updates the internal state of the unwrapper.
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int64_t Unwrap(T value) {
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if (!last_value_) {
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last_unwrapped_ = {value};
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} else {
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last_unwrapped_ += Delta(*last_value_, value);
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}
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last_value_ = value;
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return last_unwrapped_;
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}
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// Returns the `value` without updating the internal state of the unwrapper.
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int64_t PeekUnwrap(T value) const {
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if (!last_value_) {
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return value;
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}
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return last_unwrapped_ + Delta(*last_value_, value);
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}
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// Resets the unwrapper to its initial state. Unwrapped sequence numbers will
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// being at 0 after resetting.
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void Reset() {
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last_unwrapped_ = 0;
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last_value_.reset();
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}
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private:
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static int64_t Delta(T last_value, T new_value) {
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constexpr int64_t kBackwardAdjustment =
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M == 0 ? int64_t{std::numeric_limits<T>::max()} + 1 : M;
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int64_t result = ForwardDiff<T, M>(last_value, new_value);
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if (!AheadOrAt<T, M>(new_value, last_value)) {
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result -= kBackwardAdjustment;
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}
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return result;
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}
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int64_t last_unwrapped_ = 0;
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absl::optional<T> last_value_;
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};
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using RtpTimestampUnwrapper = SeqNumUnwrapper<uint32_t>;
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using RtpSequenceNumberUnwrapper = SeqNumUnwrapper<uint16_t>;
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} // namespace webrtc
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#endif // RTC_BASE_NUMERICS_SEQUENCE_NUMBER_UNWRAPPER_H_
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