[rtp_rtcp] rtcp::Tmmbn moved into own file

webrtc/modules/rtp_rtcp/source/rtcp_packet/tmmbn.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/tmmbn.h"
+
+#include "webrtc/base/logging.h"
+#include "webrtc/modules/rtp_rtcp/source/byte_io.h"
+
+using webrtc::RTCPUtility::PT_RTPFB;
+using webrtc::RTCPUtility::RTCPPacketRTPFBTMMBN;
+using webrtc::RTCPUtility::RTCPPacketRTPFBTMMBRItem;
+
+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 AssignUWord32(uint8_t* buffer, size_t* offset, uint32_t value) {

[tommi, 2016/01/11 15:45:40]

empty line above this one

+  ByteWriter<uint32_t>::WriteBigEndian(buffer + *offset, value);
+  *offset += 4;
+}
+
+void ComputeMantissaAnd6bitBase2Exponent(uint32_t input_base10,
+                                         uint8_t bits_mantissa,
+                                         uint32_t* mantissa,
+                                         uint8_t* exp) {
+  // input_base10 = mantissa * 2^exp
+  assert(bits_mantissa <= 32);
+  uint32_t mantissa_max = (1 << bits_mantissa) - 1;
+  uint8_t exponent = 0;
+  for (uint32_t i = 0; i < 64; ++i) {
+    if (input_base10 <= (mantissa_max << i)) {
+      exponent = i;
+      break;
+    }
+  }
+  *exp = exponent;
+  *mantissa = (input_base10 >> exponent);
+}
+
+void CreateTmmbrItem(const RTCPPacketRTPFBTMMBRItem& tmmbr_item,
+                     uint8_t* buffer,
+                     size_t* pos) {
+  uint32_t bitrate_bps = tmmbr_item.MaxTotalMediaBitRate * 1000;
+  uint32_t mantissa = 0;
+  uint8_t exp = 0;
+  ComputeMantissaAnd6bitBase2Exponent(bitrate_bps, 17, &mantissa, &exp);
+
+  AssignUWord32(buffer, pos, tmmbr_item.SSRC);
+  AssignUWord8(buffer, pos, (exp << 2) + ((mantissa >> 15) & 0x03));
+  AssignUWord8(buffer, pos, mantissa >> 7);
+  AssignUWord8(buffer, pos, (mantissa << 1) +
+                            ((tmmbr_item.MeasuredOverhead >> 8) & 0x01));
+  AssignUWord8(buffer, pos, tmmbr_item.MeasuredOverhead);
+}
+
+// Temporary Maximum Media Stream Bit Rate Notification (TMMBN) (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                             |
+//   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+//   | MxTBR Exp |  MxTBR Mantissa                 |Measured Overhead|
+//   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+void CreateTmmbn(const RTCPPacketRTPFBTMMBN& tmmbn,
+                 const std::vector<RTCPPacketRTPFBTMMBRItem>& tmmbn_items,
+                 uint8_t* buffer,
+                 size_t* pos) {
+  AssignUWord32(buffer, pos, tmmbn.SenderSSRC);
+  AssignUWord32(buffer, pos, kUnusedMediaSourceSsrc0);
+  for (uint8_t i = 0; i < tmmbn_items.size(); ++i) {
+    CreateTmmbrItem(tmmbn_items[i], buffer, pos);
+  }
+}
+}  // namespace
+
+bool Tmmbn::WithTmmbr(uint32_t ssrc, uint32_t bitrate_kbps, uint16_t overhead) {
+  assert(overhead <= 0x1ff);

[tommi, 2016/01/11 15:45:40]

use RTC_DCHECK

+  if (tmmbn_items_.size() >= kMaxNumberOfTmmbrs) {

[tommi, 2016/01/11 15:45:40]

assuming single threaded?  If so, please use ThreadChecker

+    LOG(LS_WARNING) << "Max TMMBN size reached.";
+    return false;
+  }
+  RTCPPacketRTPFBTMMBRItem tmmbn_item;
+  tmmbn_item.SSRC = ssrc;
+  tmmbn_item.MaxTotalMediaBitRate = bitrate_kbps;
+  tmmbn_item.MeasuredOverhead = overhead;
+  tmmbn_items_.push_back(tmmbn_item);
+  return true;
+}
+
+bool Tmmbn::Create(uint8_t* packet,
+                   size_t* index,
+                   size_t max_length,
+                   RtcpPacket::PacketReadyCallback* callback) const {
+  while (*index + BlockLength() > max_length) {

[tommi, 2016/01/11 15:45:40]

would also be good to state the threading model here.

+    if (!OnBufferFull(packet, index, callback))
+      return false;
+  }
+  const uint8_t kFmt = 4;
+  CreateHeader(kFmt, PT_RTPFB, HeaderLength(), packet, index);
+  CreateTmmbn(tmmbn_, tmmbn_items_, packet, index);
+  return true;
+}
+
+}  // namespace rtcp
+}  // namespace webrtc