public static async Task <FrameHeader> ReadHeader(this IDuplexStream stream, CancellationToken cancellationToken = default)
{
if (stream == null)
{
throw new ArgumentNullException(nameof(stream));
}
return((FrameHeader)(await stream.Read(1, cancellationToken)).Single());
}
private async Task <DataFrame> ReadDataFrame(CancellationToken cancellationToken = default)
{
// INS12350-Serial-API-Host-Appl.-Prg.-Guide | 6.2.1 Data frame reception timeout
// A receiving host or Z-Wave chip MUST abort reception of a Data frame if the reception has lasted for
// more than 1500ms after the reception of the SOF byte.
using (var timeoutCancelation = new CancellationTokenSource(ProtocolSettings.DataFrameWaitTime))
{
// combine the passed and the timeout cancelationtokens
using (var linkedCancellation = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken, timeoutCancelation.Token))
{
// read the length
var length = await Stream.ReadByte(linkedCancellation.Token);
// read data (payload and checksum)
var data = await Stream.Read(length, linkedCancellation.Token);
// payload (data without checksum)
var payload = data.Take(data.Length - 1).ToArray();
// checksum
var actualChecksum = data.Last();
// calculate required checksum (include length)
var expectedChecksum = new byte[] { length }.Concat(payload).CalculateLrc8Checksum();
// validate checksum
if (actualChecksum != expectedChecksum)
{
throw new ChecksumException("Checksum failure");
}
// return dataframe
return(new DataFrame((DataFrameType)payload[0], new Payload(payload.Skip(1))));
}
}
}