[rtp_rtcp] rtcp::Sdes moved into own file

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