webrtc/modules/rtp_rtcp/source/rtcp_packet/sdes.cc

/*
 *  Copyright (c) 2016 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 "webrtc/modules/rtp_rtcp/source/rtcp_packet/sdes.h"

#include "webrtc/base/logging.h"
#include "webrtc/modules/rtp_rtcp/source/byte_io.h"

using webrtc::RTCPUtility::PT_SDES;

namespace webrtc {
namespace rtcp {
namespace {
void AssignUWord8(uint8_t* buffer, size_t* offset, uint8_t value) {
  buffer[(*offset)++] = value;
}

void AssignUWord32(uint8_t* buffer, size_t* offset, uint32_t value) {
  ByteWriter<uint32_t>::WriteBigEndian(buffer + *offset, value);
  *offset += 4;
}
// Source Description (SDES) (RFC 3550).
//
//         0                   1                   2                   3
//         0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
//        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// header |V=2|P|    SC   |  PT=SDES=202  |             length            |
//        +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
// chunk  |                          SSRC/CSRC_1                          |
//   1    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
//        |                           SDES items                          |
//        |                              ...                              |
//        +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
// chunk  |                          SSRC/CSRC_2                          |
//   2    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
//        |                           SDES items                          |
//        |                              ...                              |
//        +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
//
// Canonical End-Point Identifier SDES Item (CNAME)
//
//    0                   1                   2                   3
//    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
//   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
//   |    CNAME=1    |     length    | user and domain name        ...
//   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
void CreateSdes(const std::vector<Sdes::Chunk>& chunks,
                uint8_t* buffer,
                size_t* pos) {
  const uint8_t kSdesItemType = 1;
  for (std::vector<Sdes::Chunk>::const_iterator it = chunks.begin();
       it != chunks.end(); ++it) {
    AssignUWord32(buffer, pos, (*it).ssrc);
    AssignUWord8(buffer, pos, kSdesItemType);
    AssignUWord8(buffer, pos, (*it).name.length());
    memcpy(buffer + *pos, (*it).name.data(), (*it).name.length());
    *pos += (*it).name.length();
    memset(buffer + *pos, 0, (*it).null_octets);
    *pos += (*it).null_octets;
  }
}
}  // namespace

bool Sdes::Create(uint8_t* packet,
                  size_t* index,
                  size_t max_length,
                  RtcpPacket::PacketReadyCallback* callback) const {
  assert(!chunks_.empty());
  while (*index + BlockLength() > max_length) {
    if (!OnBufferFull(packet, index, callback))
      return false;
  }
  CreateHeader(chunks_.size(), PT_SDES, HeaderLength(), packet, index);
  CreateSdes(chunks_, packet, index);
  return true;
}

bool Sdes::WithCName(uint32_t ssrc, const std::string& cname) {
  assert(cname.length() <= 0xff);
  if (chunks_.size() >= kMaxNumberOfChunks) {
    LOG(LS_WARNING) << "Max SDES chunks reached.";
    return false;
  }
  // In each chunk, the list of items must be terminated by one or more null
  // octets. The next chunk must start on a 32-bit boundary.
  // CNAME (1 byte) | length (1 byte) | name | padding.
  int null_octets = 4 - ((2 + cname.length()) % 4);
  Chunk chunk;
  chunk.ssrc = ssrc;
  chunk.name = cname;
  chunk.null_octets = null_octets;
  chunks_.push_back(chunk);
  return true;
}

size_t Sdes::BlockLength() const {
  // Header (4 bytes).
  // Chunk:
  // SSRC/CSRC (4 bytes) | CNAME (1 byte) | length (1 byte) | name | padding.
  size_t length = kHeaderLength;
  for (const Chunk& chunk : chunks_)
    length += 6 + chunk.name.length() + chunk.null_octets;
  assert(length % 4 == 0);
  return length;
}
}  // namespace rtcp
}  // namespace webrtc