NDSLOT
off = NDSLOT(low);
off = NDSLOT(fdp->fd_nfiles - 1);
for (minoff = NDSLOT(0); off >= minoff; --off)
return ((fdp->fd_map[NDSLOT(fd)] & NDBIT(fd)) != 0);
fdp->fd_map[NDSLOT(fd)] |= NDBIT(fd);
fdp->fd_map[NDSLOT(fd)] &= ~NDBIT(fd);
off = NDSLOT(fdp->fd_nfiles - 1);
for (minoff = NDSLOT(0); off >= minoff; --off)