[rtp_rtcp] rtcp::Rpsi moved into own file

webrtc/modules/rtp_rtcp/source/rtcp_packet/rpsi.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/rpsi.h"
+
+#include "webrtc/modules/rtp_rtcp/source/byte_io.h"
+
+using webrtc::RTCPUtility::PT_PSFB;
+using webrtc::RTCPUtility::RTCPPacketPSFBRPSI;
+
+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;
+}
+
+// Reference picture selection indication (RPSI) (RFC 4585).
+//
+// 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
+//   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+//   |      PB       |0| Payload Type|    Native RPSI bit string     |
+//   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+//   |   defined per codec          ...                | Padding (0) |
+//   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+void CreateRpsi(const RTCPPacketPSFBRPSI& rpsi,
+                uint8_t padding_bytes,
+                uint8_t* buffer,
+                size_t* pos) {
+  // Native bit string should be a multiple of 8 bits.
+  assert(rpsi.NumberOfValidBits % 8 == 0);
+  AssignUWord32(buffer, pos, rpsi.SenderSSRC);
+  AssignUWord32(buffer, pos, rpsi.MediaSSRC);
+  AssignUWord8(buffer, pos, padding_bytes * 8);
+  AssignUWord8(buffer, pos, rpsi.PayloadType);
+  memcpy(buffer + *pos, rpsi.NativeBitString, rpsi.NumberOfValidBits / 8);
+  *pos += rpsi.NumberOfValidBits / 8;
+  memset(buffer + *pos, 0, padding_bytes);
+  *pos += padding_bytes;
+}
+}  // namespace
+
+bool Rpsi::Create(uint8_t* packet,
+                  size_t* index,
+                  size_t max_length,
+                  RtcpPacket::PacketReadyCallback* callback) const {
+  assert(rpsi_.NumberOfValidBits > 0);
+  while (*index + BlockLength() > max_length) {
+    if (!OnBufferFull(packet, index, callback))
+      return false;
+  }
+  const uint8_t kFmt = 3;
+  CreateHeader(kFmt, PT_PSFB, HeaderLength(), packet, index);
+  CreateRpsi(rpsi_, padding_bytes_, packet, index);
+  return true;
+}
+
+void Rpsi::WithPictureId(uint64_t picture_id) {
+  const uint32_t kPidBits = 7;
+  const uint64_t k7MsbZeroMask = 0x1ffffffffffffffULL;
+  uint8_t required_bytes = 0;
+  uint64_t shifted_pid = picture_id;
+  do {
+    ++required_bytes;
+    shifted_pid = (shifted_pid >> kPidBits) & k7MsbZeroMask;
+  } while (shifted_pid > 0);
+
+  // Convert picture id to native bit string (natively defined by the video
+  // codec).
+  int pos = 0;
+  for (int i = required_bytes - 1; i > 0; i--) {
+    rpsi_.NativeBitString[pos++] =
+        0x80 | static_cast<uint8_t>(picture_id >> (i * kPidBits));
+  }
+  rpsi_.NativeBitString[pos++] = static_cast<uint8_t>(picture_id & 0x7f);
+  rpsi_.NumberOfValidBits = pos * 8;
+
+  // Calculate padding bytes (to reach next 32-bit boundary, 1, 2 or 3 bytes).
+  padding_bytes_ = 4 - ((2 + required_bytes) % 4);
+  if (padding_bytes_ == 4) {
+    padding_bytes_ = 0;
+  }
+}
+
+
+}  // namespace rtcp
+}  // namespace webrtc