cast: cleanup rtp header and parsing

media/cast/net/rtp/rtp_parser.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "media/cast/net/rtp/rtp_parser.h"
 
 #include "base/big_endian.h"
 #include "base/logging.h"
 #include "media/cast/cast_defines.h"
 #include "media/cast/net/rtp/rtp_defines.h"
@@ skipping 33 matching lines @@
 
   // Parse the RTP header.  See
   // http://en.wikipedia.org/wiki/Real-time_Transport_Protocol for an
   // explanation of the standard RTP packet header.
   uint8 bits;
   if (!reader.ReadU8(&bits))
     return false;
   const uint8 version = bits >> 6;
   if (version != 2)
     return false;
+  header->num_csrcs = bits & kRtpNumCsrcsMask;
   if (bits & kRtpExtensionBitMask)
     return false;  // We lack the implementation to skip over an extension.
   if (!reader.ReadU8(&bits))
     return false;
   header->marker = !!(bits & kRtpMarkerBitMask);
   header->payload_type = bits & ~kRtpMarkerBitMask;
   if (header->payload_type != expected_payload_type_)
     return false;  // Punt: Unexpected payload type.
   if (!reader.ReadU16(&header->sequence_number) ||
       !reader.ReadU32(&header->rtp_timestamp) ||
       !reader.ReadU32(&header->sender_ssrc)) {
     return false;
   }
   if (header->sender_ssrc != expected_sender_ssrc_)
     return false;  // Punt: Sender's SSRC does not match the expected one.
 
   // Parse the Cast header.  Note that, from the RTP protocol's perspective, the
   // Cast header is part of the payload (and not meant to be an extension
   // header).
   if (!reader.ReadU8(&bits))
     return false;
   header->is_key_frame = !!(bits & kCastKeyFrameBitMask);
-  const bool includes_specific_frame_reference =
-      !!(bits & kCastReferenceFrameIdBitMask);
+  header->is_reference = !!(bits & kCastReferenceFrameIdBitMask);
   uint8 truncated_frame_id;
   if (!reader.ReadU8(&truncated_frame_id) ||
       !reader.ReadU16(&header->packet_id) ||
       !reader.ReadU16(&header->max_packet_id)) {
     return false;
   }
   // Sanity-check: Do the packet ID values make sense w.r.t. each other?
   if (header->max_packet_id < header->packet_id)
     return false;
   uint8 truncated_reference_frame_id;
-  if (!includes_specific_frame_reference) {
+  if (!header->is_reference) {
     // By default, a key frame only references itself; and non-key frames
     // reference their direct predecessor.
     truncated_reference_frame_id = truncated_frame_id;
     if (!header->is_key_frame)
       --truncated_reference_frame_id;
   } else if (!reader.ReadU8(&truncated_reference_frame_id)) {
     return false;
   }
 
   for (int i = 0; i < (bits & kCastExtensionCountmask); i++) {
     uint16 type_and_size;
     if (!reader.ReadU16(&type_and_size))
       return false;
     base::StringPiece tmp;
     if (!reader.ReadPiece(&tmp, type_and_size & 0x3ff))
       return false;
     base::BigEndianReader chunk(tmp.data(), tmp.size());
     switch (type_and_size >> 10) {
       case kCastRtpExtensionAdaptiveLatency:
         if (!chunk.ReadU16(&header->new_playout_delay_ms))
           return false;
-
     }
   }
 
   // Only the lower 8 bits of the |frame_id| were serialized, so do some magic
   // to restore the upper 24 bits.
   //
   // Note: The call to |frame_id_wrap_helper_| has side effects, so we must not
   // call it until we know the entire deserialization will succeed.
   header->frame_id =
       frame_id_wrap_helper_.MapTo32bitsFrameId(truncated_frame_id);
   // When the upper 24 bits are restored to |reference_frame_id|, make sure
   // |reference_frame_id| will be strictly less than or equal to |frame_id|.
   if (truncated_reference_frame_id <= truncated_frame_id)
     header->reference_frame_id = header->frame_id & 0xffffff00;
   else
     header->reference_frame_id = (header->frame_id & 0xffffff00) - 0x00000100;
   header->reference_frame_id |= truncated_reference_frame_id;
 
   // All remaining data in the packet is the payload.
   *payload_data = reinterpret_cast<const uint8*>(reader.ptr());
   *payload_size = reader.remaining();
 
   return true;
 }
 
 }  // namespace cast
 }  // namespace media