internal static PayloadHeader Decode(List <byte> buffer, int startPosition)
{
var header = new PayloadHeader();
// Decode the first byte
var position = startPosition;
if (position >= buffer.Count)
{
return(null);
}
header.FinishedBit = (buffer[position] & 128) == 128;
header.OpCode = (WebSocketOpCode)(buffer[position] & 15);
position++;
// Decode the second byte
if (position >= buffer.Count)
{
return(null);
}
header.Masked = (buffer[position] & 128) == 128;
header.PayloadLength = buffer[position] & 127;
position++;
// Calculate the real length of the payload (but exit if we don't have enough bytes)
if (header.PayloadLength == 126)
{
if (position + 1 >= buffer.Count)
{
return(null);
}
header.PayloadLength = (buffer[position++] << 8) | buffer[position++];
}
else if (header.PayloadLength == 127)
{
if (position + 7 >= buffer.Count)
{
return(null);
}
header.PayloadLength = (buffer[position++] << 56) | (buffer[position++] << 48) | (buffer[position++] << 40) | (buffer[position++] << 32) | (buffer[position++] << 24) | (buffer[position++] << 16) | (buffer[position++] << 8) | buffer[position++];
}
// Get the mask key bytes
if (header.Masked)
{
if (position + 3 >= buffer.Count)
{
return(null);
}
header.MaskKey = new byte[4];
buffer.CopyTo(position, header.MaskKey, 0, 4);
position += 4;
}
// Return decoded payload header
header.Size = position - startPosition;
return(header);
}
private Packet DecodeBuffer()
{
var position = 0;
var header = PayloadHeader.Decode(largeBuffer, position);
if (header == null)
{
return(null);
}
position += header.Size;
// Confirm that we have retrieved enough bytes, otherwise we need to wait for more data to come in
var totalExpectedSize = header.Size + header.PayloadLength;
if (largeBuffer.Count < totalExpectedSize)
{
return(null);
}
// Copy the payload into its own array, unmasking it if necessary into a readable form
var payloadBytes = new byte[header.PayloadLength];
if (header.Masked)
{
for (var i = 0; i < header.PayloadLength; i++)
{
payloadBytes[i] = (byte)(largeBuffer[position + i] ^ header.MaskKey[i % 4]);
}
}
else
{
largeBuffer.CopyTo(position, payloadBytes, 0, header.PayloadLength);
}
// Advance the position
position += header.PayloadLength;
// We only accept these types of opcode
switch (header.OpCode)
{
case WebSocketOpCode.Close:
largeBuffer.RemoveRange(0, position);
return(new Packet(RemoteEndPoint, WebSocketAction.Disconnect, "Intentional client disconnection."));
case WebSocketOpCode.Text:
case WebSocketOpCode.Continuation:
case WebSocketOpCode.Ping:
// Add to the payload
largeBuffer.RemoveRange(0, position);
incompletePayload.AddRange(payloadBytes);
// Do we have a complete payload?
if (!header.FinishedBit)
{
return(DecodeBuffer());
}
// Convert the completed payload into a string
var payloadText = Encoding.UTF8.GetString(incompletePayload.ToArray());
incompletePayload.Clear();
// Raise a text packet for processing
if (header.OpCode != WebSocketOpCode.Ping)
{
return(new Packet(RemoteEndPoint, WebSocketAction.SendText, payloadText));
}
// Send a pong and get the next packet
Send(WebSocketOpCode.Pong, payloadText);
return(DecodeBuffer());
case WebSocketOpCode.Pong:
// Simply get the next packet
largeBuffer.RemoveRange(0, position);
return(DecodeBuffer());
default:
throw new NotImplementedException("Web socket opcode " + header.OpCode + " is currently not supported.");
}
}
