tor-browser

The Tor Browser
git clone https://git.dasho.dev/tor-browser.git
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rtcp_packet.cc (3335B)

      1 /*
      2 *  Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
      3 *
      4 *  Use of this source code is governed by a BSD-style license
      5 *  that can be found in the LICENSE file in the root of the source
      6 *  tree. An additional intellectual property rights grant can be found
      7 *  in the file PATENTS.  All contributing project authors may
      8 *  be found in the AUTHORS file in the root of the source tree.
      9 */
     10 
     11 #include "modules/rtp_rtcp/source/rtcp_packet.h"
     12 
     13 #include <cstddef>
     14 #include <cstdint>
     15 
     16 #include "api/array_view.h"
     17 #include "modules/rtp_rtcp/include/rtp_rtcp_defines.h"
     18 #include "rtc_base/buffer.h"
     19 #include "rtc_base/checks.h"
     20 
     21 namespace webrtc {
     22 namespace rtcp {
     23 
     24 Buffer RtcpPacket::Build() const {
     25  Buffer packet(BlockLength());
     26 
     27  size_t length = 0;
     28  bool created = Create(packet.data(), &length, packet.capacity(), nullptr);
     29  RTC_DCHECK(created) << "Invalid packet is not supported.";
     30  RTC_DCHECK_EQ(length, packet.size())
     31      << "BlockLength mispredicted size used by Create";
     32 
     33  return packet;
     34 }
     35 
     36 bool RtcpPacket::Build(size_t max_length, PacketReadyCallback callback) const {
     37  RTC_CHECK_LE(max_length, IP_PACKET_SIZE);
     38  uint8_t buffer[IP_PACKET_SIZE];
     39  size_t index = 0;
     40  if (!Create(buffer, &index, max_length, callback))
     41    return false;
     42  return OnBufferFull(buffer, &index, callback);
     43 }
     44 
     45 bool RtcpPacket::OnBufferFull(uint8_t* packet,
     46                              size_t* index,
     47                              PacketReadyCallback callback) const {
     48  if (*index == 0)
     49    return false;
     50  RTC_DCHECK(callback) << "Fragmentation not supported.";
     51  callback(ArrayView<const uint8_t>(packet, *index));
     52  *index = 0;
     53  return true;
     54 }
     55 
     56 size_t RtcpPacket::HeaderLength() const {
     57  size_t length_in_bytes = BlockLength();
     58  RTC_DCHECK_GT(length_in_bytes, 0);
     59  RTC_DCHECK_EQ(length_in_bytes % 4, 0)
     60      << "Padding must be handled by each subclass.";
     61  // Length in 32-bit words without common header.
     62  return (length_in_bytes - kHeaderLength) / 4;
     63 }
     64 
     65 // From RFC 3550, RTP: A Transport Protocol for Real-Time Applications.
     66 //
     67 // RTP header format.
     68 //   0                   1                   2                   3
     69 //   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
     70 //  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     71 //  |V=2|P| RC/FMT  |      PT       |             length            |
     72 //  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     73 void RtcpPacket::CreateHeader(
     74    size_t count_or_format,  // Depends on packet type.
     75    uint8_t packet_type,
     76    size_t length,
     77    uint8_t* buffer,
     78    size_t* pos) {
     79  CreateHeader(count_or_format, packet_type, length, /*padding=*/false, buffer,
     80               pos);
     81 }
     82 
     83 void RtcpPacket::CreateHeader(
     84    size_t count_or_format,  // Depends on packet type.
     85    uint8_t packet_type,
     86    size_t length,
     87    bool padding,
     88    uint8_t* buffer,
     89    size_t* pos) {
     90  RTC_DCHECK_LE(length, 0xffffU);
     91  RTC_DCHECK_LE(count_or_format, 0x1f);
     92  constexpr uint8_t kVersionBits = 2 << 6;
     93  uint8_t padding_bit = padding ? 1 << 5 : 0;
     94  buffer[*pos + 0] =
     95      kVersionBits | padding_bit | static_cast<uint8_t>(count_or_format);
     96  buffer[*pos + 1] = packet_type;
     97  buffer[*pos + 2] = (length >> 8) & 0xff;
     98  buffer[*pos + 3] = length & 0xff;
     99  *pos += kHeaderLength;
    100 }
    101 
    102 }  // namespace rtcp
    103 }  // namespace webrtc