/// <summary>
/// Read a WebSocket frame from the stream
/// </summary>
/// <param name="fromStream">The stream to read from</param>
/// <param name="intoBuffer">The buffer to read into</param>
/// <param name="cancellationToken">the cancellation token</param>
/// <returns>A websocket frame</returns>
public static async Task<WebSocketFrame> ReadAsync(System.IO.Stream fromStream, ArraySegment<byte> intoBuffer, CancellationToken cancellationToken)
{
// allocate a small buffer to read small chunks of data from the stream
var smallBuffer = new ArraySegment<byte>(new byte[8]);
await BinaryReaderWriter.ReadExactly(2, fromStream, smallBuffer, cancellationToken);
byte byte1 = smallBuffer.Array[0];
byte byte2 = smallBuffer.Array[1];
// process first byte
byte finBitFlag = 0x80;
byte opCodeFlag = 0x0F;
bool isFinBitSet = (byte1 & finBitFlag) == finBitFlag;
WebSocketOpCode opCode = (WebSocketOpCode) (byte1 & opCodeFlag);
// read and process second byte
byte maskFlag = 0x80;
bool isMaskBitSet = (byte2 & maskFlag) == maskFlag;
uint len = await ReadLength(byte2, smallBuffer, fromStream, cancellationToken);
int count = (int)len;
try
{
// use the masking key to decode the data if needed
if (isMaskBitSet)
{
ArraySegment<byte> maskKey = new ArraySegment<byte>(smallBuffer.Array, 0, WebSocketFrameCommon.MaskKeyLength);
await BinaryReaderWriter.ReadExactly(maskKey.Count, fromStream, maskKey, cancellationToken);
await BinaryReaderWriter.ReadExactly(count, fromStream, intoBuffer, cancellationToken);
ArraySegment<byte> payloadToMask = new ArraySegment<byte>(intoBuffer.Array, intoBuffer.Offset, count);
WebSocketFrameCommon.ToggleMask(maskKey, payloadToMask);
}
else
{
await BinaryReaderWriter.ReadExactly(count, fromStream, intoBuffer, cancellationToken);
}
}
catch (InternalBufferOverflowException e)
{
throw new InternalBufferOverflowException($"Supplied buffer too small to read {0} bytes from {Enum.GetName(typeof(WebSocketOpCode), opCode)} frame", e);
}
if (opCode == WebSocketOpCode.ConnectionClose)
{
return DecodeCloseFrame(isFinBitSet, opCode, count, intoBuffer);
}
else
{
// note that by this point the payload will be populated
return new WebSocketFrame(isFinBitSet, opCode, count);
}
}
/// <summary>
/// The last read could not be completed because the read buffer was too small.
/// We need to continue reading bytes off the stream.
/// Not to be confused with a continuation frame
/// </summary>
/// <param name="fromStream">The stream to read from</param>
/// <param name="intoBuffer">The buffer to read into</param>
/// <param name="readCursor">The previous partial websocket frame read plus cursor information</param>
/// <param name="cancellationToken">the cancellation token</param>
/// <returns>A websocket frame</returns>
public static async Task <WebSocketReadCursor> ReadFromCursorAsync(System.IO.Stream fromStream,
ArraySegment <byte> intoBuffer, WebSocketReadCursor readCursor, CancellationToken cancellationToken)
{
var remainingFrame = readCursor.WebSocketFrame;
var minCount = CalculateNumBytesToRead(readCursor.NumBytesLeftToRead, intoBuffer.Count);
await BinaryReaderWriter.ReadExactly(minCount, fromStream, intoBuffer, cancellationToken);
if (remainingFrame.MaskKey.Count > 0)
{
ArraySegment <byte> payloadToMask =
new ArraySegment <byte>(intoBuffer.Array, intoBuffer.Offset, minCount);
WebSocketFrameCommon.ToggleMask(remainingFrame.MaskKey, payloadToMask);
}
return(new WebSocketReadCursor(remainingFrame, minCount, readCursor.NumBytesLeftToRead - minCount));
}
