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/*
* Copyright (c) 2023 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/optional_blob_encoding.h"
#include <cstddef>
#include <cstdint>
#include <optional>
#include <string>
#include <vector>
#include "absl/strings/string_view.h"
#include "rtc_base/bit_buffer.h"
#include "rtc_base/bitstream_reader.h"
#include "rtc_base/checks.h"
namespace webrtc {
std::string EncodeOptionalBlobs(
const std::vector<std::optional<std::string>>& blobs) {
if (blobs.empty()) {
return {};
}
size_t reserve_size_bits = 1;
size_t num_blobs_present = 0;
for (const auto& blob : blobs) {
if (blob.has_value()) {
++num_blobs_present;
reserve_size_bits +=
(BitBufferWriter::kMaxLeb128Length.bytes() + blob->size()) * 8;
}
}
if (num_blobs_present == 0) {
return {};
}
const bool all_blobs_present = num_blobs_present == blobs.size();
if (!all_blobs_present) {
reserve_size_bits += blobs.size();
}
std::vector<uint8_t> buffer((reserve_size_bits + 7) / 8);
BitBufferWriter writer(buffer.data(), buffer.size());
// Write present bits if all blobs are not present.
writer.WriteBits(all_blobs_present, 1);
if (!all_blobs_present) {
for (const auto& blob : blobs) {
writer.WriteBits(blob.has_value(), 1);
}
}
// Byte align the writer.
writer.ConsumeBits(writer.RemainingBitCount() % 8);
// Write blobs.
for (const auto& blob : blobs) {
if (blob.has_value()) {
writer.WriteLeb128(blob->length());
writer.WriteString(*blob);
}
}
size_t bytes_written;
size_t bits_written;
writer.GetCurrentOffset(&bytes_written, &bits_written);
RTC_CHECK_EQ(bits_written, 0);
RTC_CHECK_LE(bytes_written, buffer.size());
return std::string(buffer.data(), buffer.data() + bytes_written);
}
std::vector<std::optional<std::string>> DecodeOptionalBlobs(
absl::string_view encoded_blobs,
size_t num_of_blobs) {
std::vector<std::optional<std::string>> res(num_of_blobs);
if (encoded_blobs.empty() || num_of_blobs == 0) {
return res;
}
BitstreamReader reader(encoded_blobs);
const bool all_blobs_present = reader.ReadBit();
// Read present bits if all blobs are not present.
std::vector<uint8_t> present;
if (!all_blobs_present) {
present.resize(num_of_blobs);
for (size_t i = 0; i < num_of_blobs; ++i) {
present[i] = reader.ReadBit();
}
}
// Byte align the reader.
reader.ConsumeBits(reader.RemainingBitCount() % 8);
// Read the blobs.
for (size_t i = 0; i < num_of_blobs; ++i) {
if (!all_blobs_present && !present[i]) {
continue;
}
res[i] = reader.ReadString(reader.ReadLeb128());
}
// The result is only valid if exactly all bits was consumed during decoding.
if (!reader.Ok() || reader.RemainingBitCount() > 0) {
return {};
}
return res;
}
} // namespace webrtc
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