/// <summary>
/// This method reads bytes from the underlying input stream and performs the following tasks:
/// 1. Keeps track of how many bytes we've read
/// 2. Un-escapes bytes if necessary and verifies the checksum.
/// </summary>
/// <returns></returns>
public byte Read()
{
if (RemainingBytes == 0)
{
throw new XBeeParseException("Packet has read all of its bytes");
}
var b = TakeFromBuffer(ParseTimeLeft);
if (XBeePacket.IsSpecialByte(b))
{
Logger.LowDebug("Read special byte that needs to be unescaped");
if (b == (byte)XBeePacket.SpecialByte.Escape)
{
Logger.LowDebug("found escape byte");
// read next byte
b = TakeFromBuffer(ParseTimeLeft);
Logger.LowDebug("next byte is " + ByteUtils.FormatByte(b));
b = (byte)(0x20 ^ b);
Logger.LowDebug("unescaped (xor) byte is " + ByteUtils.FormatByte(b));
_escapedBytes++;
}
else
{
// TODO some responses such as AT Response for node discover do not escape the bytes?? shouldn't occur if AP mode is 2?
// while reading remote at response Found unescaped special byte base10=19,base16=0x13,base2=00010011 at position 5
Logger.LowDebug("Found unescaped special byte " + ByteUtils.FormatByte(b) + " at position " + BytesRead);
}
}
BytesRead++;
// do this only after reading length bytes
if (BytesRead > 2)
{
// when verifying checksum you must add the checksum that we are verifying
// checksum should only include unescaped bytes!!!!
// when computing checksum, do not include start byte, length, or checksum; when verifying, include checksum
_checksum.AddByte(b);
//Logger.LowDebug("Read byte " + ByteUtils.FormatByte(b)
// + " at position " + BytesRead
// + ", packet length is " + Length.Get16BitValue()
// + ", #escapeBytes is " + _escapedBytes
// + ", remaining bytes is " + RemainingBytes);
// escape bytes are not included in the stated packet length
if (FrameDataBytesRead >= (Length + 1))
{
// this is checksum and final byte of packet
Logger.LowDebug("Checksum byte is " + b);
if (!_checksum.Verify())
{
throw new XBeeParseException("Checksum is incorrect. Expected 0xff, but got 0x"
+ ByteUtils.ToBase16(_checksum.GetChecksum()));
}
}
}
return(b);
}
private void ParsePackets()
#endif
{
#if WINDOWS_UWP
while (!ct.IsCancellationRequested)
#else
while (!_finished)
#endif
{
try
{
var b = TakeFromBuffer();
#if WINDOWS_UWP
if (ct.IsCancellationRequested)
{
return;
}
#else
if (_finished)
{
return;
}
#endif
if (!XBeePacket.IsStartByte(b))
{
continue;
}
var packet = ParsePacket();
if (Logger.IsActive(LogLevel.Debug))
{
Logger.Debug("Received " + packet.GetType().Name + ": " + packet);
}
var listeners = _packetListeners.ToArray();
for (var i = 0; i < listeners.Length; i++)
{
var packetListener = (IPacketListener)listeners[i];
if (!packetListener.Finished)
{
packetListener.ProcessPacket(packet);
}
if (packetListener.Finished)
{
RemovePacketListener(packetListener);
}
}
}
catch (XBeeTimeoutException)
{
Logger.LowDebug("Incomplete packet received");
}
catch (XBeeParseException)
{
Logger.Warn("Errors occured while parsing received packet");
}
#if !WINDOWS_UWP
catch (ThreadAbortException)
{
Logger.Debug("Thread aborted");
return;
}
#endif
catch (Exception e)
{
Logger.Error("Unexpected exception occured while parsing packet. " + e.Message);
}
}
}
