public override ValueTask WriteAsync(ReadOnlyMemory <byte> buffer, CancellationToken cancellationToken = default)
{
CheckWriteArguments();
if (buffer.IsEmpty)
{
return(ValueTask.CompletedTask); // return immediately if no bytes to write; no need for overhead.
}
SerialStreamWriteRequest result = new SerialStreamWriteRequest(cancellationToken, buffer);
_writeQueue.Enqueue(result);
EnsureIOLoopRunning();
return(new ValueTask(result.Task));
}
public override Task WriteAsync(byte[] array, int offset, int count, CancellationToken cancellationToken)
{
CheckWriteArguments(array, offset, count);
if (count == 0)
{
return(Task.CompletedTask); // return immediately if no bytes to write; no need for overhead.
}
ReadOnlyMemory <byte> buffer = new ReadOnlyMemory <byte>(array, offset, count);
SerialStreamWriteRequest result = new SerialStreamWriteRequest(cancellationToken, buffer);
_writeQueue.Enqueue(result);
EnsureIOLoopRunning();
return(result.Task);
}
private unsafe int ProcessWrite(SerialStreamIORequest r)
{
SerialStreamWriteRequest writeRequest = (SerialStreamWriteRequest)r;
ReadOnlySpan <byte> buff = writeRequest.Buffer.Span;
fixed(byte *bufPtr = buff)
{
// assumes dequeue-ing happens on a single thread
int numBytes = Interop.Serial.Write(_handle, bufPtr, buff.Length);
if (numBytes <= 0)
{
Interop.ErrorInfo lastError = Interop.Sys.GetLastErrorInfo();
// ignore EWOULDBLOCK since we handle timeout elsewhere
// numBytes == 0 means that there might be an error
if (lastError.Error != Interop.Error.SUCCESS && lastError.Error != Interop.Error.EWOULDBLOCK)
{
r.Complete(Interop.GetIOException(lastError));
}
}
else
{
writeRequest.ProcessBytes(numBytes);
if (writeRequest.Buffer.Length == 0)
{
writeRequest.Complete();
}
return(numBytes);
}
}
return(0);
}
