[rtp_rtcp] rtcp::Fir moved into own file

webrtc/modules/rtp_rtcp/source/rtcp_packet/fir.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/fir.h"
+
+#include "webrtc/base/checks.h"
+#include "webrtc/base/logging.h"
+#include "webrtc/modules/rtp_rtcp/source/byte_io.h"
+
+using webrtc::RTCPUtility::PT_PSFB;
+using webrtc::RTCPUtility::RTCPPacketPSFBFIR;
+using webrtc::RTCPUtility::RTCPPacketPSFBFIRItem;
+
+namespace webrtc {
+namespace rtcp {
+namespace {
+const uint32_t kUnusedMediaSourceSsrc0 = 0;
+
+void AssignUWord8(uint8_t* buffer, size_t* offset, uint8_t value) {
+  buffer[(*offset)++] = value;
+}
+
+void AssignUWord24(uint8_t* buffer, size_t* offset, uint32_t value) {
+  ByteWriter<uint32_t, 3>::WriteBigEndian(buffer + *offset, value);
+  *offset += 3;
+}
+
+void AssignUWord32(uint8_t* buffer, size_t* offset, uint32_t value) {
+  ByteWriter<uint32_t>::WriteBigEndian(buffer + *offset, value);
+  *offset += 4;
+}
+
+// Full intra request (FIR) (RFC 5104).
+//
+// FCI:
+//
+//    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
+//   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+//   |                              SSRC                             |
+//   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+//   | Seq nr.       |    Reserved                                   |
+//   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+void CreateFir(const RTCPPacketPSFBFIR& fir,
+               const RTCPPacketPSFBFIRItem& fir_item,
+               uint8_t* buffer,
+               size_t* pos) {
+  AssignUWord32(buffer, pos, fir.SenderSSRC);
+  AssignUWord32(buffer, pos, kUnusedMediaSourceSsrc0);
+  AssignUWord32(buffer, pos, fir_item.SSRC);
+  AssignUWord8(buffer, pos, fir_item.CommandSequenceNumber);
+  AssignUWord24(buffer, pos, 0);
+}
+}  // namespace
+
+bool Fir::Create(uint8_t* packet,
+                 size_t* index,
+                 size_t max_length,
+                 RtcpPacket::PacketReadyCallback* callback) const {
+  while (*index + BlockLength() > max_length) {
+    if (!OnBufferFull(packet, index, callback))
+      return false;
+  }
+  const uint8_t kFmt = 4;
+  CreateHeader(kFmt, PT_PSFB, HeaderLength(), packet, index);
+  CreateFir(fir_, fir_item_, packet, index);
+  return true;
+}
+
+}  // namespace rtcp
+}  // namespace webrtc