private boolean notAvailable(long index, int mask, AtomicLongArray sBuffer, long expectedSeq) {
        final int seqOffset = calcCircularLongElementOffset(index, mask);
        final long seq = lvLongElement(sBuffer, seqOffset);
        if (seq < expectedSeq) {
            return true;
        }
        return false;
    }
{@inheritDoc}
<p>
Because return null indicates queue is empty we cannot simply rely on next element visibility for poll
and must test producer index when next element is not visible.
jctools-core/src/main/java/org/jctools/queues/atomic/MpmcAtomicArrayQueue.java