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/*
* Copyright (c) 2018 The WebRTC project authors. All Rights Reserved.
*
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
*/
#include "logging/rtc_event_log/encoder/var_int.h"
#include <cstddef>
#include <cstdint>
#include <string>
#include <utility>
#include "absl/strings/string_view.h"
#include "rtc_base/bitstream_reader.h"
#include "rtc_base/checks.h"
// TODO(eladalon): Add unit tests.
namespace webrtc {
const size_t kMaxVarIntLengthBytes = 10; // ceil(64 / 7.0) is 10.
std::string EncodeVarInt(uint64_t input) {
std::string output;
output.reserve(kMaxVarIntLengthBytes);
do {
uint8_t byte = static_cast<uint8_t>(input & 0x7f);
input >>= 7;
if (input > 0) {
byte |= 0x80;
}
output += byte;
} while (input > 0);
RTC_DCHECK_GE(output.size(), 1u);
RTC_DCHECK_LE(output.size(), kMaxVarIntLengthBytes);
return output;
}
// There is some code duplication between the flavors of this function.
// For performance's sake, it's best to just keep it.
std::pair<bool, absl::string_view> DecodeVarInt(absl::string_view input,
uint64_t* output) {
RTC_DCHECK(output);
uint64_t decoded = 0;
for (size_t i = 0; i < input.length() && i < kMaxVarIntLengthBytes; ++i) {
decoded += (static_cast<uint64_t>(input[i] & 0x7f)
<< static_cast<uint64_t>(7 * i));
if (!(input[i] & 0x80)) {
*output = decoded;
return {true, input.substr(i + 1)};
}
}
return {false, input};
}
// There is some code duplication between the flavors of this function.
// For performance's sake, it's best to just keep it.
uint64_t DecodeVarInt(BitstreamReader& input) {
uint64_t decoded = 0;
for (size_t i = 0; i < kMaxVarIntLengthBytes; ++i) {
uint8_t byte = input.Read<uint8_t>();
decoded +=
(static_cast<uint64_t>(byte & 0x7f) << static_cast<uint64_t>(7 * i));
if (!(byte & 0x80)) {
return decoded;
}
}
input.Invalidate();
return 0;
}
} // namespace webrtc
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