/**
* Constructs a message from its binary representation.
* @param binMessage the binary array that contains the encoded message
* @param offset the index where the message starts.
* @param arrayLen the length of the message
* @return a Message object constructed from the binMessage array
* @throws StunException ILLEGAL_ARGUMENT if one or more of the arguments
* have invalid values.
*/
public static Message Decode(byte[] binMessage, int offset, int arrayLen)
{
arrayLen = Math.Min(binMessage.Length, arrayLen);
if (binMessage == null || arrayLen - offset < Message.HEADER_LENGTH)
{
throw new StunException(StunException.ILLEGAL_ARGUMENT,
"The given binary array is not a valid StunMessage");
}
int messageType = (int)(((binMessage[offset++] << 8) & 0xff00) | (binMessage[offset++] & 0xFF));
int mti = (int)messageType;
Message message;
if (Message.IsResponseType(messageType))
{
message = new Response();
}
else
{
message = new Request();
}
message.SetMessageType(messageType);
int length = (int)(((binMessage[offset++] << 8) & 0xff00) | (binMessage[offset++] & 0xFF));
if (arrayLen - offset - TRANSACTION_ID_LENGTH < length)
{
throw new StunException(StunException.ILLEGAL_ARGUMENT,
"The given binary array does not seem to "
+ "contain a whole StunMessage");
}
byte[] tranID = new byte[TRANSACTION_ID_LENGTH];
for (int x = 0; x < TRANSACTION_ID_LENGTH; x++)
{
tranID[x] = binMessage[offset + x];
}
message.SetTransactionID(tranID);
offset += TRANSACTION_ID_LENGTH;
while (offset - Message.HEADER_LENGTH < length)
{
Attribute att = AttributeDecoder.decode(binMessage,
offset,
(length - offset));
if (att != null)
{
message.AddAttribute(att);
offset += att.GetDataLength() + Attribute.HEADER_LENGTH;
}
else
{
offset += Attribute.HEADER_LENGTH;
}
}
return(message);
}
