/// <summary>
/// Decodes RTMP packet header.
/// </summary>
/// <param name="context">RTMP protocol state.</param>
/// <param name="lastHeader">Previous header.</param>
/// <param name="stream">Buffer to be decoded.</param>
/// <returns>Decoded RTMP header.</returns>
public static RtmpHeader DecodeHeader(RtmpContext context, RtmpHeader lastHeader, ByteBuffer stream) {
byte headerByte = stream.Get();
int headerValue;
int byteCount = 1;
if ((headerByte & 0x3f) == 0) {
// Two byte header
headerValue = ((int)headerByte & 0xff) << 8 | ((int)stream.Get() & 0xff);
byteCount = 2;
} else if ((headerByte & 0x3f) == 1) {
// Three byte header
headerValue = ((int)headerByte & 0xff) << 16 | ((int)stream.Get() & 0xff) << 8 | ((int)stream.Get() & 0xff);
byteCount = 3;
} else {
// Single byte header
headerValue = (int)headerByte & 0xff;
byteCount = 1;
}
byte channelId = DecodeChannelId(headerValue, byteCount);
byte headerSize = DecodeHeaderSize(headerValue, byteCount);
RtmpHeader header = new RtmpHeader();
header.ChannelId = channelId;
header.IsTimerRelative = (HeaderType)headerSize != HeaderType.HeaderNew;
if ((HeaderType)headerSize != HeaderType.HeaderNew && lastHeader == null) {
#if !SILVERLIGHT
if (log.IsErrorEnabled)
log.Error(string.Format("Last header null not new, headerSize: {0}, channelId {1}", headerSize, channelId));
#endif
lastHeader = new RtmpHeader();
lastHeader.ChannelId = channelId;
lastHeader.IsTimerRelative = (HeaderType)headerSize != HeaderType.HeaderNew;
}
#if !SILVERLIGHT
if (log.IsDebugEnabled)
log.Debug(__Res.GetString(__Res.Rtmp_DecodeHeader, Enum.GetName(typeof(HeaderType), (HeaderType)headerSize)));
#endif
switch ((HeaderType)headerSize) {
case HeaderType.HeaderNew:
header.Timer = stream.ReadUInt24();// ReadUnsignedMediumInt();
header.Size = stream.ReadUInt24();// ReadMediumInt();
header.DataType = stream.Get();
header.StreamId = stream.ReadReverseInt();
break;
case HeaderType.HeaderSameSource:
header.Timer = stream.ReadUInt24();// ReadUnsignedMediumInt();
header.Size = stream.ReadUInt24();// ReadMediumInt();
header.DataType = stream.Get();
header.StreamId = lastHeader.StreamId;
break;
case HeaderType.HeaderTimerChange:
header.Timer = stream.ReadUInt24();//ReadUnsignedMediumInt();
header.Size = lastHeader.Size;
header.DataType = lastHeader.DataType;
header.StreamId = lastHeader.StreamId;
break;
case HeaderType.HeaderContinue:
header.Timer = lastHeader.Timer;
header.Size = lastHeader.Size;
header.DataType = lastHeader.DataType;
header.StreamId = lastHeader.StreamId;
header.IsTimerRelative = lastHeader.IsTimerRelative;
break;
default:
#if !SILVERLIGHT
log.Error("Unexpected header size: " + headerSize);
#endif
return null;
}
if (header.Timer >= 0xffffff) {
//Extended timestamp
header.Timer = stream.GetInt();
}
return header;
}
