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707e3d187c
BitstreamReader allows to write easier to reader parser Bug: None Change-Id: I9da88c86ee04be4c0b06e181e409a915ba1a5123 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/231232 Commit-Queue: Danil Chapovalov <danilchap@webrtc.org> Reviewed-by: Björn Terelius <terelius@webrtc.org> Cr-Commit-Position: refs/heads/main@{#34939}
77 lines
2.1 KiB
C++
77 lines
2.1 KiB
C++
/*
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* Copyright (c) 2018 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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#include "logging/rtc_event_log/encoder/var_int.h"
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#include "rtc_base/bitstream_reader.h"
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#include "rtc_base/checks.h"
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// TODO(eladalon): Add unit tests.
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namespace webrtc {
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const size_t kMaxVarIntLengthBytes = 10; // ceil(64 / 7.0) is 10.
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std::string EncodeVarInt(uint64_t input) {
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std::string output;
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output.reserve(kMaxVarIntLengthBytes);
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do {
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uint8_t byte = static_cast<uint8_t>(input & 0x7f);
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input >>= 7;
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if (input > 0) {
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byte |= 0x80;
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}
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output += byte;
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} while (input > 0);
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RTC_DCHECK_GE(output.size(), 1u);
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RTC_DCHECK_LE(output.size(), kMaxVarIntLengthBytes);
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return output;
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}
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// There is some code duplication between the flavors of this function.
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// For performance's sake, it's best to just keep it.
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std::pair<bool, absl::string_view> DecodeVarInt(absl::string_view input,
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uint64_t* output) {
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RTC_DCHECK(output);
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uint64_t decoded = 0;
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for (size_t i = 0; i < input.length() && i < kMaxVarIntLengthBytes; ++i) {
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decoded += (static_cast<uint64_t>(input[i] & 0x7f)
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<< static_cast<uint64_t>(7 * i));
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if (!(input[i] & 0x80)) {
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*output = decoded;
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return {true, input.substr(i + 1)};
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}
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}
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return {false, input};
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}
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// There is some code duplication between the flavors of this function.
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// For performance's sake, it's best to just keep it.
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uint64_t DecodeVarInt(BitstreamReader& input) {
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uint64_t decoded = 0;
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for (size_t i = 0; i < kMaxVarIntLengthBytes; ++i) {
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uint8_t byte = input.Read<uint8_t>();
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decoded +=
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(static_cast<uint64_t>(byte & 0x7f) << static_cast<uint64_t>(7 * i));
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if (!(byte & 0x80)) {
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return decoded;
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}
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}
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input.Invalidate();
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return 0;
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}
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} // namespace webrtc
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