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* Copyright 2004 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 <stddef.h>
#include <stdint.h>
#include <string>
#include "absl/strings/string_view.h"
#include "rtc_base/buffer.h"
#include "rtc_base/byte_order.h"
// Reads/Writes from/to buffer using network byte order (big endian)
namespace rtc {
template <class BufferClassT>
class ByteBufferWriterT {
ByteBufferWriterT() { Construct(nullptr, kDefaultCapacity); }
ByteBufferWriterT(const char* bytes, size_t len) { Construct(bytes, len); }
ByteBufferWriterT(const ByteBufferWriterT&) = delete;
ByteBufferWriterT& operator=(const ByteBufferWriterT&) = delete;
const char* Data() const { return; }
size_t Length() const { return buffer_.size(); }
size_t Capacity() const { return buffer_.capacity(); }
// Write value to the buffer. Resizes the buffer when it is
// neccessary.
void WriteUInt8(uint8_t val) {
WriteBytes(reinterpret_cast<const char*>(&val), 1);
void WriteUInt16(uint16_t val) {
uint16_t v = HostToNetwork16(val);
WriteBytes(reinterpret_cast<const char*>(&v), 2);
void WriteUInt24(uint32_t val) {
uint32_t v = HostToNetwork32(val);
char* start = reinterpret_cast<char*>(&v);
WriteBytes(start, 3);
void WriteUInt32(uint32_t val) {
uint32_t v = HostToNetwork32(val);
WriteBytes(reinterpret_cast<const char*>(&v), 4);
void WriteUInt64(uint64_t val) {
uint64_t v = HostToNetwork64(val);
WriteBytes(reinterpret_cast<const char*>(&v), 8);
// Serializes an unsigned varint in the format described by
// with the caveat that integers are 64-bit, not 128-bit.
void WriteUVarint(uint64_t val) {
while (val >= 0x80) {
// Write 7 bits at a time, then set the msb to a continuation byte
// (msb=1).
char byte = static_cast<char>(val) | 0x80;
WriteBytes(&byte, 1);
val >>= 7;
char last_byte = static_cast<char>(val);
WriteBytes(&last_byte, 1);
void WriteString(absl::string_view val) {
WriteBytes(, val.size());
void WriteBytes(const char* val, size_t len) { buffer_.AppendData(val, len); }
// Reserves the given number of bytes and returns a char* that can be written
// into. Useful for functions that require a char* buffer and not a
// ByteBufferWriter.
char* ReserveWriteBuffer(size_t len) {
buffer_.SetSize(buffer_.size() + len);
// Resize the buffer to the specified `size`.
void Resize(size_t size) { buffer_.SetSize(size); }
// Clears the contents of the buffer. After this, Length() will be 0.
void Clear() { buffer_.Clear(); }
static constexpr size_t kDefaultCapacity = 4096;
void Construct(const char* bytes, size_t size) {
if (bytes) {
buffer_.AppendData(bytes, size);
} else {
BufferClassT buffer_;
// There are sensible ways to define these, but they aren't needed in our code
// base.
class ByteBufferWriter : public ByteBufferWriterT<BufferT<char>> {
ByteBufferWriter(const char* bytes, size_t len);
ByteBufferWriter(const ByteBufferWriter&) = delete;
ByteBufferWriter& operator=(const ByteBufferWriter&) = delete;
// The ByteBufferReader references the passed data, i.e. the pointer must be
// valid during the lifetime of the reader.
class ByteBufferReader {
ByteBufferReader(const char* bytes, size_t len);
// Initializes buffer from a zero-terminated string.
explicit ByteBufferReader(const char* bytes);
explicit ByteBufferReader(const Buffer& buf);
explicit ByteBufferReader(const ByteBufferWriter& buf);
ByteBufferReader(const ByteBufferReader&) = delete;
ByteBufferReader& operator=(const ByteBufferReader&) = delete;
// Returns start of unprocessed data.
const char* Data() const { return bytes_ + start_; }
// Returns number of unprocessed bytes.
size_t Length() const { return end_ - start_; }
// Read a next value from the buffer. Return false if there isn't
// enough data left for the specified type.
bool ReadUInt8(uint8_t* val);
bool ReadUInt16(uint16_t* val);
bool ReadUInt24(uint32_t* val);
bool ReadUInt32(uint32_t* val);
bool ReadUInt64(uint64_t* val);
bool ReadUVarint(uint64_t* val);
bool ReadBytes(char* val, size_t len);
// Appends next `len` bytes from the buffer to `val`. Returns false
// if there is less than `len` bytes left.
bool ReadString(std::string* val, size_t len);
// Moves current position `size` bytes forward. Returns false if
// there is less than `size` bytes left in the buffer. Consume doesn't
// permanently remove data, so remembered read positions are still valid
// after this call.
bool Consume(size_t size);
void Construct(const char* bytes, size_t size);
const char* bytes_;
size_t size_;
size_t start_;
size_t end_;
} // namespace rtc