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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/base/attributes.h"
#include "absl/strings/string_view.h"
#include "api/array_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 {
using value_type = typename BufferClassT::value_type;
ByteBufferWriterT() { Construct(nullptr, kDefaultCapacity); }
ByteBufferWriterT(const value_type* bytes, size_t len) {
Construct(bytes, len);
ByteBufferWriterT(const ByteBufferWriterT&) = delete;
ByteBufferWriterT& operator=(const ByteBufferWriterT&) = delete;
const value_type* Data() const { return; }
size_t Length() const { return buffer_.size(); }
size_t Capacity() const { return buffer_.capacity(); }
rtc::ArrayView<const value_type> DataView() const {
return rtc::MakeArrayView(Data(), Length());
// Accessor that returns a string_view, independent of underlying type.
// Intended to provide access for existing users that expect char*
// when the underlying type changes to uint8_t.
// TODO( Delete when users are converted.
absl::string_view DataAsStringView() const {
return absl::string_view(reinterpret_cast<const char*>(Data()), Length());
const char* DataAsCharPointer() const {
return reinterpret_cast<const char*>(Data());
// Write value to the buffer. Resizes the buffer when it is
// neccessary.
void WriteUInt8(uint8_t val) {
WriteBytesInternal(reinterpret_cast<const value_type*>(&val), 1);
void WriteUInt16(uint16_t val) {
uint16_t v = HostToNetwork16(val);
WriteBytesInternal(reinterpret_cast<const value_type*>(&v), 2);
void WriteUInt24(uint32_t val) {
uint32_t v = HostToNetwork32(val);
value_type* start = reinterpret_cast<value_type*>(&v);
WriteBytesInternal(start, 3);
void WriteUInt32(uint32_t val) {
uint32_t v = HostToNetwork32(val);
WriteBytesInternal(reinterpret_cast<const value_type*>(&v), 4);
void WriteUInt64(uint64_t val) {
uint64_t v = HostToNetwork64(val);
WriteBytesInternal(reinterpret_cast<const value_type*>(&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).
value_type byte = static_cast<value_type>(val) | 0x80;
WriteBytesInternal(&byte, 1);
val >>= 7;
value_type last_byte = static_cast<value_type>(val);
WriteBytesInternal(&last_byte, 1);
void WriteString(absl::string_view val) {
WriteBytesInternal(reinterpret_cast<const value_type*>(,
// Write an array of bytes (uint8_t)
void WriteBytes(const uint8_t* val, size_t len) {
WriteBytesInternal(reinterpret_cast<const value_type*>(val), len);
// Reserves the given number of bytes and returns a value_type* that can be
// written into. Useful for functions that require a value_type* buffer and
// not a ByteBufferWriter.
value_type* 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 value_type* bytes, size_t size) {
if (bytes) {
buffer_.AppendData(bytes, size);
} else {
void WriteBytesInternal(const value_type* val, size_t len) {
buffer_.AppendData(val, len);
BufferClassT buffer_;
// There are sensible ways to define these, but they aren't needed in our code
// base.
class ByteBufferWriter : public ByteBufferWriterT<BufferT<uint8_t>> {
ByteBufferWriter(const uint8_t* 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 {
explicit ByteBufferReader(
rtc::ArrayView<const uint8_t> bytes ABSL_ATTRIBUTE_LIFETIME_BOUND);
explicit ByteBufferReader(const ByteBufferWriter& buf);
ByteBufferReader(const ByteBufferReader&) = delete;
ByteBufferReader& operator=(const ByteBufferReader&) = delete;
const uint8_t* Data() const { return bytes_ + start_; }
// Returns number of unprocessed bytes.
size_t Length() const { return end_ - start_; }
// Returns a view of the unprocessed data. Does not move current position.
rtc::ArrayView<const uint8_t> DataView() const {
return rtc::ArrayView<const uint8_t>(bytes_ + start_, 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);
// Copies the val.size() next bytes into
bool ReadBytes(rtc::ArrayView<uint8_t> val);
// 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);
// Same as `ReadString` except that the returned string_view will point into
// the internal buffer (no additional buffer allocation).
bool ReadStringView(absl::string_view* 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 uint8_t* bytes, size_t size);
bool ReadBytes(uint8_t* val, size_t len);
const uint8_t* bytes_;
size_t size_;
size_t start_;
size_t end_;
} // namespace rtc