h.h = hash_record(tdb, off);
gnum = use_bits(&h, TDB_SUBLEVEL_HASH_BITS-TDB_HASH_GROUP_BITS);
h.group_start = subhash + sizeof(struct tdb_used_record)
h.h = hash_record(tdb, off);
gnum = use_bits(&h, TDB_SUBLEVEL_HASH_BITS-TDB_HASH_GROUP_BITS);
h.group_start = subhash + sizeof(struct tdb_used_record)