private (SequencePosition consumed, SequencePosition examined) ReadFrames(ref ReadOnlySequence <byte> buffer)
{
buffer.Debug($"BUFFER len: {buffer.Length}, start: {buffer.Start.GetInteger()}, end: {buffer.End.GetInteger()}");
const int MinPossibleFrameLength = 6;
if (buffer.Length < MinPossibleFrameLength)
{
Debug.WriteLine($"SMALL_BUFFER {buffer.Length}");
return(buffer.Start, buffer.End);
}
var seq = new SequenceReader <byte>(buffer);
byte apduLength = 0;
var foundStart = seq.TryAdvanceTo(0x68, advancePastDelimiter: true) && seq.TryRead(out apduLength);
if (!foundStart)
{
seq.Debug("NO_START_BYTE");
return(seq.Position, seq.Position);
}
var validApduLength = apduLength == 4 || (apduLength >= Constants.NoPrefix.MinFrameILength && apduLength <= Constants.MaxApduLength);
if (!validApduLength)
{
seq.Debug("INVALID_APDU", apduLength);
OnError(ErrorCode.InvalidApduLength, null);
return(seq.Position, seq.Position);
}
var isThereEnoughData = seq.Remaining >= apduLength;
if (!isThereEnoughData)
{
seq.Debug("NOT_ENOUGH_DATA", apduLength);
return(buffer.Start, seq.Position);
}
var success = TryCreateFrameSpan(in seq, apduLength, out var frameSpan);
if (!success)
{
seq.Debug("FAILED_FRAME_SPAN");
OnError(ErrorCode.FailedToCreateFrameSpan, null);
return(seq.Position, seq.Position);
}
seq.Debug("FRAME_READ", apduLength);
frameSpan.Debug("FRAME");
var(error, frame) = Bytes.ReadFrame(frameSpan);
if (error == ErrorCode.None)
{
OnFrameRead(frame);
}
else
{
Stats.IncrementFrameReadErrors();
OnError(error, null);
}
var at = buffer.GetPosition(apduLength, seq.Position);
return(at, at);
}