public Task SendAsync(ArraySegment <byte> buffer, WebSocketMessageType messageType, bool compressed, bool endOfMessage, CancellationToken cancellationToken)
{
if (messageType != WebSocketMessageType.Text && messageType != WebSocketMessageType.Binary)
{
throw new ArgumentException("Invalid message type", nameof(messageType));
}
WebSocketValidationHelper.ValidateArraySegment(buffer, nameof(buffer));
try
{
WebSocketValidationHelper.ThrowIfInvalidState(_state, _disposed, _validSendStates);
ThrowIfOperationInProgress(_lastSendTask);
}
catch (Exception ex)
{
return(TargetFrameworksHelper.FromException(ex));
}
WebSocketMessageOpcode opcode = _lastSendWasFragment ? WebSocketMessageOpcode.Continuation : (messageType == WebSocketMessageType.Binary ? WebSocketMessageOpcode.Binary : WebSocketMessageOpcode.Text);
Task sendTask = SendFrameAsync(opcode, compressed, endOfMessage, buffer, cancellationToken);
_lastSendWasFragment = !endOfMessage;
_lastSendTask = sendTask;
return(sendTask);
}
private int WriteFrameToSendBuffer(WebSocketMessageOpcode opcode, bool compressed, bool endOfMessage, ArraySegment <byte> payloadBuffer)
{
EnsureBufferLength(ref _sendBuffer, payloadBuffer.Count + MAX_MESSAGE_HEADER_LENGTH);
int headerLength = WriteHeader(opcode, _sendBuffer, payloadBuffer, compressed, endOfMessage);
if (payloadBuffer.Count > 0)
{
Buffer.BlockCopy(payloadBuffer.Array, payloadBuffer.Offset, _sendBuffer, headerLength, payloadBuffer.Count);
}
return(headerLength + payloadBuffer.Count);
}
private Task SendFrameLockAcquiredNonCancelableAsync(WebSocketMessageOpcode opcode, bool compressed, bool endOfMessage, ArraySegment <byte> payloadBuffer)
{
Task writeTask = null;
bool releaseSemaphore = true;
try
{
int sendBytes = WriteFrameToSendBuffer(opcode, compressed, endOfMessage, payloadBuffer);
writeTask = _stream.WriteAsync(_sendBuffer, 0, sendBytes, CancellationToken.None);
if (writeTask.IsCompleted)
{
writeTask.GetAwaiter().GetResult();
return(TargetFrameworksHelper.CompletedTask);
}
releaseSemaphore = false;
}
catch (Exception ex)
{
return(TargetFrameworksHelper.FromException(_state == WebSocketState.Aborted ? CreateOperationCanceledException(ex) : new WebSocketException(WebSocketError.ConnectionClosedPrematurely, ex)));
}
finally
{
if (releaseSemaphore)
{
_sendFrameAsyncLock.Release();
}
}
return(writeTask.ContinueWith((task, source) =>
{
CompressionWebSocket webSocket = (CompressionWebSocket)source;
webSocket._sendFrameAsyncLock.Release();
try
{
task.GetAwaiter().GetResult();
}
catch (Exception ex)
{
throw webSocket._state == WebSocketState.Aborted ? CreateOperationCanceledException(ex) : new WebSocketException(WebSocketError.ConnectionClosedPrematurely, ex);
}
}, this, CancellationToken.None, TaskContinuationOptions.ExecuteSynchronously, TaskScheduler.Default));
}
private async Task SendFrameFallbackAsync(WebSocketMessageOpcode opcode, bool compressed, bool endOfMessage, ArraySegment <byte> payloadBuffer, CancellationToken cancellationToken)
{
await _sendFrameAsyncLock.WaitAsync().ConfigureAwait(false);
try
{
int sendBytes = WriteFrameToSendBuffer(opcode, compressed, endOfMessage, payloadBuffer);
using (cancellationToken.Register(source => ((CompressionWebSocket)source).Abort(), this))
{
await _stream.WriteAsync(_sendBuffer, 0, sendBytes, cancellationToken).ConfigureAwait(false);
}
}
catch (Exception exc)
{
throw _state == WebSocketState.Aborted ? CreateOperationCanceledException(exc, cancellationToken) : new WebSocketException(WebSocketError.ConnectionClosedPrematurely, exc);
}
finally
{
_sendFrameAsyncLock.Release();
}
}
private static int WriteHeader(WebSocketMessageOpcode opcode, byte[] sendBuffer, ArraySegment <byte> payload, bool compressed, bool endOfMessage)
{
// Client header format:
// 1 bit - FIN - 1 if this is the final fragment in the message (it could be the only fragment), otherwise 0
// 1 bit - RSV1 - Per-Message Compressed - 1 if this is the first fragment of compressed message, otherwise 0
// 1 bit - RSV2 - Reserved - 0
// 1 bit - RSV3 - Reserved - 0
// 4 bits - Opcode - How to interpret the payload
// - 0x0 - continuation
// - 0x1 - text
// - 0x2 - binary
// - 0x8 - connection close
// - 0x9 - ping
// - 0xA - pong
// - (0x3 to 0x7, 0xB-0xF - reserved)
// 1 bit - Masked - 1 if the payload is masked, 0 if it's not. Must be 1 for the client. This is only server and we use always 0
// 7 bits, 7+16 bits, or 7+64 bits - Payload length
// - For length 0 through 125, 7 bits storing the length
// - For lengths 126 through 2^16, 7 bits storing the value 126, followed by 16 bits storing the length
// - For lengths 2^16+1 through 2^64, 7 bits storing the value 127, followed by 64 bytes storing the length
// 0 or 4 bytes - Mask, if Masked is 1 - random value XOR'd with each 4 bytes of the payload, round-robin
// Length bytes - Payload data
sendBuffer[0] = (byte)opcode;
if (compressed && (opcode != WebSocketMessageOpcode.Continuation))
{
sendBuffer[0] |= 0x40;
}
if (endOfMessage)
{
sendBuffer[0] |= 0x80;
}
int headerLength;
if (payload.Count <= 125)
{
sendBuffer[1] = (byte)payload.Count;
headerLength = 2;
}
else if (payload.Count <= ushort.MaxValue)
{
sendBuffer[1] = 126;
sendBuffer[2] = (byte)(payload.Count / 256);
sendBuffer[3] = (byte)payload.Count;
headerLength = 2 + sizeof(ushort);
}
else
{
sendBuffer[1] = 127;
int length = payload.Count;
for (int i = 9; i >= 2; i--)
{
sendBuffer[i] = (byte)length;
length = length / 256;
}
headerLength = 2 + sizeof(ulong);
}
return(headerLength);
}
private Task SendFrameAsync(WebSocketMessageOpcode opcode, bool compressed, bool endOfMessage, ArraySegment <byte> payloadBuffer, CancellationToken cancellationToken)
{
return(cancellationToken.CanBeCanceled || !_sendFrameAsyncLock.Wait(0) ?
SendFrameFallbackAsync(opcode, compressed, endOfMessage, payloadBuffer, cancellationToken) :
SendFrameLockAcquiredNonCancelableAsync(opcode, compressed, endOfMessage, payloadBuffer));
}
