public byte[] AnalyzeMessage(MemoryStream data)
{
if (data.Length - data.Position < 4)
{
return(null);
}
long origin = data.Position;
DatagramReader r = new DatagramReader(data);
ushort dmid = r.ReadUShort();
Type type = this.SelectMessageType(dmid);
if (type == null)
{
// clear stream
data.SetLength(0);
data.Position = 0;
return(null);
}
ushort size = r.ReadUShort();
if (data.Length - data.Position < size)
{
// roll back
data.Position = origin;
return(null);
}
byte[] bytes = new byte[4 + size];
data.Position = origin;
if (data.Read(bytes, 0, bytes.Length) < bytes.Length)
{
// roll back
data.Position = origin;
return(null);
}
return(bytes);
}
// deserialize datagram-message via data which contains 4-byte meta-data
public DatagramMessage DepackMessage(byte[] data)
{
if (data == null || data.Length < 4)
{
throw new Exception("Message data is null or data.Length is too small.");
}
MemoryStream m = new MemoryStream(data);
DatagramReader r = new DatagramReader(m);
ushort dmid = r.ReadUShort();
ushort size = r.ReadUShort();
byte[] bytes = r.ReadBytes(size);
Type type = this.SelectMessageType(dmid);
if (type == null)
{
throw new Exception("The type of message is not found for dmid=" + dmid);
}
DatagramMessage message = this.DeserializeMessage(type, bytes);
return(message);
}