private int WriteByte(byte[] buffer, int offset, WriteBuffer writeBuffer)
{
// The body of this method should rather be inlined where it is called, but doing so seems to cause a huge
// (>5x) perf hit.
var currentByte = buffer[offset];
if (this.previousWasEscapeByte)
{
this.previousWasEscapeByte = false;
this.crc = Crc.AddCrcCcitt(this.crc, currentByte);
currentByte = (byte)(currentByte ^ Frame.EscapeXor);
++offset;
}
else
{
if (currentByte < Frame.InvalidStart)
{
this.crc = Crc.AddCrcCcitt(this.crc, currentByte);
++offset;
}
else
{
currentByte = Frame.EscapeByte;
this.previousWasEscapeByte = true;
}
}
writeBuffer[writeBuffer.Count++] = currentByte;
return(offset);
}
private bool ReadByte(ReadBuffer readBuffer)
{
var currentByte = readBuffer[readBuffer.Index++];
switch (this.state)
{
case State.BeforeFrame:
if (currentByte == Frame.BeginOfFrame)
{
this.state = State.InFrame;
}
else
{
this.outOfFrameByteReceived(currentByte);
}
break;
case State.InFrame:
if (currentByte < Frame.InvalidStart)
{
this.crc = Crc.AddCrcCcitt(this.crc, currentByte);
this.decodedQueue.Enqueue(currentByte);
}
else
{
switch (currentByte)
{
case Frame.EscapeByte:
this.state = State.InFrameEscaped;
break;
case Frame.BeginOfFrame:
this.decodedQueue.Clear();
this.crc = 0xFFFF;
break;
case Frame.EndOfFrame:
this.state = State.AfterFrame;
if (this.crc != 0xF0B8)
{
this.decodedQueue.Clear();
}
return(false);
default:
this.state = State.AfterFrame;
this.decodedQueue.Clear();
break;
}
}
break;
case State.InFrameEscaped:
if (currentByte >= Frame.InvalidStart)
{
this.state = State.AfterFrame;
this.decodedQueue.Clear();
}
currentByte = (byte)(currentByte ^ Frame.EscapeXor);
this.crc = Crc.AddCrcCcitt(this.crc, currentByte);
this.decodedQueue.Enqueue(currentByte);
this.state = State.InFrame;
break;
}
return(true);
}