[beep4j-user] seqno incrementing past 4 gigabytes

[Thomson, M. <Mar...@an...>]

There are two places in beep4j where the rollover of the seqno field
isn't correctly handled.  Of course, given that you need to send 4
gigabytes of data over a single channel to reach this point, it's
probably a little theoretical...

First is in SlidingWindow.remaining(), which currently uses:

        return getEnd() - position;

This doesn't work if the end has just rolled around to zero, but the
positioning hasn't.  This should look like:

        if (position < start) {
            return (int) ((start + windowSize) % modulo - position);
        } else {
            return (int) (start - position + windowSize);
        }

The other place is in the incrementing of the seqno in
DefaultChannelController.  This doesn't roll over at all, so when 4Gb
comes around, things will probably break.  I've added a method
getNextSeqno that does the incrementing and rollover...

    private long getNextSeqno(int messageSize) {
        long nextSeqno = this.seqno;
        this.seqno = (this.seqno + messageSize) % (1L << 32);
        return nextSeqno;
    }

Ta,
Martin 

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