/* We may need backfilling, if we read a lonely key to make */
/* a singleton, but its bitw will not fit in. Then we need to */
/* process it normally, which means reading it again. So we */
/* need to unread it first. Luckily the filter is empty at that */
/* point */
/* We may need backfilling, if we read a lonely key to make */
/* a singleton, but its bitw will not fit in. Then we need to */
/* process it normally, which means reading it again. So we */
/* need to unread it first. Luckily the filter is empty at that */
/* point */