/// <summary>
/// Decodes a single hybi13 frame.
/// </summary>
/// <param name="context">The context for decoding.</param>
/// <param name="pBuffer">The byte pointer to start decoding process.</param>
/// <param name="length">The length of the buffer, starting at pBuffer offset.</param>
/// <param name="index">The amount of procesed bytes.</param>
/// <param name="isFinal">Whether the frame is final or not.</param>
/// <param name="decoded">The frame decoded.</param>
/// <returns>Processing state.</returns>
private static ProcessingState DecodeFrame(ProcessingContext context, byte *pBuffer, int length, out int index, out bool isFinal, out BufferSegment decoded)
{
// Default values
index = 0;
decoded = null;
// Check if we have a buffer for the mask
if (MaskBuffer == null)
{
MaskBuffer = new byte[4];
}
// Get the first part of the header
var frameType = (WebSocketFrameType)(*pBuffer & 15);
isFinal = (*pBuffer & 128) != 0;
// Must have at least some bytes
if (length == 0)
{
return(ProcessingState.InsufficientData);
}
// We only got one byte, kthx iOS
if (length == 1 && (frameType == WebSocketFrameType.Text || frameType == WebSocketFrameType.Binary))
{
return(ProcessingState.InsufficientData);
}
// Get the second part of the header
var isMasked = (*(pBuffer + 1) & 128) != 0;
var dataLength = (*(pBuffer + 1) & 127);
// Close the connection if requested
if (frameType == WebSocketFrameType.Close)
{
// Client sent us a close frame, we should close the connection
context.Channel.Close();
return(ProcessingState.Stop);
}
// We got some weird shit
if (!isMasked)
{
throw new WebSocketException("Incorrect incoming Hybi13 data format.");
}
// Validate the frame type
switch (frameType)
{
// Frames with a payload
case WebSocketFrameType.Text:
case WebSocketFrameType.Binary:
case WebSocketFrameType.Continuation:
case WebSocketFrameType.Ping:
case WebSocketFrameType.Pong:
break;
// Unrecognized frame type
default: throw new WebSocketException("Unsupported Huby13 frame (" + frameType + ") received.");
}
index = 2;
int payloadLength;
if (dataLength == 127)
{
if (length < index + 8)
{
return(ProcessingState.InsufficientData);
}
// TODO: Support little endian too
payloadLength = *(pBuffer + 2) << 56
| *(pBuffer + 3) << 48
| *(pBuffer + 4) << 40
| *(pBuffer + 5) << 32
| *(pBuffer + 6) << 24
| *(pBuffer + 7) << 16
| *(pBuffer + 8) << 8
| *(pBuffer + 9);
index += 8;
}
else if (dataLength == 126)
{
if (length < index + 2)
{
return(ProcessingState.InsufficientData);
}
// TODO: Support little endian too
payloadLength = *(pBuffer + 2) << 8
| *(pBuffer + 3);
index += 2;
}
else
{
payloadLength = dataLength;
}
// Check if we have the whole frame here
if (length < index + payloadLength + 4)
{
return(ProcessingState.InsufficientData);
}
// Get the mask bytes
MaskBuffer[0] = *(pBuffer + index);
MaskBuffer[1] = *(pBuffer + index + 1);
MaskBuffer[2] = *(pBuffer + index + 2);
MaskBuffer[3] = *(pBuffer + index + 3);
index += 4;
// Reserve a decode buffer to decode into
decoded = context.BufferReserve(payloadLength);
// Decode the body
byte *pTo = decoded.AsBytePointer();
byte *pFrom = pBuffer + index;
for (int i = 0; i < payloadLength; ++i, ++pTo, ++pFrom)
{
*pTo = (byte)((*pFrom) ^ MaskBuffer[i % 4]);
}
// Set the new index
index += payloadLength;
switch (frameType)
{
// We need to reply to the ping
case WebSocketFrameType.Ping:
{
// Send the websocket with the copy of the body (as per RFC)
context.Channel.Send(WebSocketPong.Acquire(decoded));
decoded.TryRelease();
return(ProcessingState.Stop);
}
// Pong is just used for the heartbeat
case WebSocketFrameType.Pong: return(ProcessingState.Stop);
}
// Trace a websocket event
return(ProcessingState.Success);
}
