tor-browser

The Tor Browser
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fir.cc (4454B)

      1 /*
      2 *  Copyright (c) 2016 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/fir.h"
     12 
     13 #include <cstddef>
     14 #include <cstdint>
     15 
     16 #include "modules/rtp_rtcp/source/byte_io.h"
     17 #include "modules/rtp_rtcp/source/rtcp_packet/common_header.h"
     18 #include "modules/rtp_rtcp/source/rtcp_packet/psfb.h"
     19 #include "rtc_base/checks.h"
     20 #include "rtc_base/logging.h"
     21 
     22 namespace webrtc {
     23 namespace rtcp {
     24 // RFC 4585: Feedback format.
     25 // Common packet format:
     26 //
     27 //   0                   1                   2                   3
     28 //   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
     29 //  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     30 //  |V=2|P|   FMT   |       PT      |          length               |
     31 //  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     32 //  |                  SSRC of packet sender                        |
     33 //  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     34 //  |             SSRC of media source (unused) = 0                 |
     35 //  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     36 //  :            Feedback Control Information (FCI)                 :
     37 //  :                                                               :
     38 // Full intra request (FIR) (RFC 5104).
     39 // The Feedback Control Information (FCI) for the Full Intra Request
     40 // consists of one or more FCI entries.
     41 // FCI:
     42 //   0                   1                   2                   3
     43 //   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
     44 //  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     45 //  |                              SSRC                             |
     46 //  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     47 //  | Seq nr.       |    Reserved = 0                               |
     48 //  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     49 
     50 Fir::Fir() = default;
     51 
     52 Fir::Fir(const Fir& fir) = default;
     53 
     54 Fir::~Fir() = default;
     55 
     56 bool Fir::Parse(const CommonHeader& packet) {
     57  RTC_DCHECK_EQ(packet.type(), kPacketType);
     58  RTC_DCHECK_EQ(packet.fmt(), kFeedbackMessageType);
     59 
     60  // The FCI field MUST contain one or more FIR entries.
     61  if (packet.payload_size_bytes() < kCommonFeedbackLength + kFciLength) {
     62    RTC_LOG(LS_WARNING) << "Packet is too small to be a valid FIR packet.";
     63    return false;
     64  }
     65 
     66  if ((packet.payload_size_bytes() - kCommonFeedbackLength) % kFciLength != 0) {
     67    RTC_LOG(LS_WARNING) << "Invalid size for a valid FIR packet.";
     68    return false;
     69  }
     70 
     71  ParseCommonFeedback(packet.payload());
     72 
     73  size_t number_of_fci_items =
     74      (packet.payload_size_bytes() - kCommonFeedbackLength) / kFciLength;
     75  const uint8_t* next_fci = packet.payload() + kCommonFeedbackLength;
     76  items_.resize(number_of_fci_items);
     77  for (Request& request : items_) {
     78    request.ssrc = ByteReader<uint32_t>::ReadBigEndian(next_fci);
     79    request.seq_nr = ByteReader<uint8_t>::ReadBigEndian(next_fci + 4);
     80    next_fci += kFciLength;
     81  }
     82  return true;
     83 }
     84 
     85 size_t Fir::BlockLength() const {
     86  return kHeaderLength + kCommonFeedbackLength + kFciLength * items_.size();
     87 }
     88 
     89 bool Fir::Create(uint8_t* packet,
     90                 size_t* index,
     91                 size_t max_length,
     92                 PacketReadyCallback callback) const {
     93  RTC_DCHECK(!items_.empty());
     94  while (*index + BlockLength() > max_length) {
     95    if (!OnBufferFull(packet, index, callback))
     96      return false;
     97  }
     98  size_t index_end = *index + BlockLength();
     99  CreateHeader(kFeedbackMessageType, kPacketType, HeaderLength(), packet,
    100               index);
    101  RTC_DCHECK_EQ(Psfb::media_ssrc(), 0);
    102  CreateCommonFeedback(packet + *index);
    103  *index += kCommonFeedbackLength;
    104 
    105  constexpr uint32_t kReserved = 0;
    106  for (const Request& request : items_) {
    107    ByteWriter<uint32_t>::WriteBigEndian(packet + *index, request.ssrc);
    108    ByteWriter<uint8_t>::WriteBigEndian(packet + *index + 4, request.seq_nr);
    109    ByteWriter<uint32_t, 3>::WriteBigEndian(packet + *index + 5, kReserved);
    110    *index += kFciLength;
    111  }
    112  RTC_CHECK_EQ(*index, index_end);
    113  return true;
    114 }
    115 }  // namespace rtcp
    116 }  // namespace webrtc