LOW_MASK
"LOW MASK ", hashp->LOW_MASK,
hashp->MAX_BUCKET = hashp->LOW_MASK = nbuckets - 1;
old_bucket = (hashp->MAX_BUCKET & hashp->LOW_MASK);
hashp->LOW_MASK = hashp->HIGH_MASK;
hashp->HIGH_MASK = new_bucket | hashp->LOW_MASK;
bucket = bucket & hashp->LOW_MASK;