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 "modules/rtp_rtcp/include/rtp_rtcp_defines.h"
14 #include "rtc_base/checks.h"
15
16 namespace webrtc {
17 namespace rtcp {
18 constexpr size_t RtcpPacket::kHeaderLength;
19
Build() const20 rtc::Buffer RtcpPacket::Build() const {
21 rtc::Buffer packet(BlockLength());
22
23 size_t length = 0;
24 bool created = Create(packet.data(), &length, packet.capacity(), nullptr);
25 RTC_DCHECK(created) << "Invalid packet is not supported.";
26 RTC_DCHECK_EQ(length, packet.size())
27 << "BlockLength mispredicted size used by Create";
28
29 return packet;
30 }
31
Build(size_t max_length,PacketReadyCallback callback) const32 bool RtcpPacket::Build(size_t max_length, PacketReadyCallback callback) const {
33 RTC_CHECK_LE(max_length, IP_PACKET_SIZE);
34 uint8_t buffer[IP_PACKET_SIZE];
35 size_t index = 0;
36 if (!Create(buffer, &index, max_length, callback))
37 return false;
38 return OnBufferFull(buffer, &index, callback);
39 }
40
OnBufferFull(uint8_t * packet,size_t * index,PacketReadyCallback callback) const41 bool RtcpPacket::OnBufferFull(uint8_t* packet,
42 size_t* index,
43 PacketReadyCallback callback) const {
44 if (*index == 0)
45 return false;
46 RTC_DCHECK(callback) << "Fragmentation not supported.";
47 callback(rtc::ArrayView<const uint8_t>(packet, *index));
48 *index = 0;
49 return true;
50 }
51
HeaderLength() const52 size_t RtcpPacket::HeaderLength() const {
53 size_t length_in_bytes = BlockLength();
54 RTC_DCHECK_GT(length_in_bytes, 0);
55 RTC_DCHECK_EQ(length_in_bytes % 4, 0)
56 << "Padding must be handled by each subclass.";
57 // Length in 32-bit words without common header.
58 return (length_in_bytes - kHeaderLength) / 4;
59 }
60
61 // From RFC 3550, RTP: A Transport Protocol for Real-Time Applications.
62 //
63 // RTP header format.
64 // 0 1 2 3
65 // 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
66 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
67 // |V=2|P| RC/FMT | PT | length |
68 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
CreateHeader(size_t count_or_format,uint8_t packet_type,size_t length,uint8_t * buffer,size_t * pos)69 void RtcpPacket::CreateHeader(
70 size_t count_or_format, // Depends on packet type.
71 uint8_t packet_type,
72 size_t length,
73 uint8_t* buffer,
74 size_t* pos) {
75 CreateHeader(count_or_format, packet_type, length, /*padding=*/false, buffer,
76 pos);
77 }
78
CreateHeader(size_t count_or_format,uint8_t packet_type,size_t length,bool padding,uint8_t * buffer,size_t * pos)79 void RtcpPacket::CreateHeader(
80 size_t count_or_format, // Depends on packet type.
81 uint8_t packet_type,
82 size_t length,
83 bool padding,
84 uint8_t* buffer,
85 size_t* pos) {
86 RTC_DCHECK_LE(length, 0xffffU);
87 RTC_DCHECK_LE(count_or_format, 0x1f);
88 constexpr uint8_t kVersionBits = 2 << 6;
89 uint8_t padding_bit = padding ? 1 << 5 : 0;
90 buffer[*pos + 0] =
91 kVersionBits | padding_bit | static_cast<uint8_t>(count_or_format);
92 buffer[*pos + 1] = packet_type;
93 buffer[*pos + 2] = (length >> 8) & 0xff;
94 buffer[*pos + 3] = length & 0xff;
95 *pos += kHeaderLength;
96 }
97
98 } // namespace rtcp
99 } // namespace webrtc
100