fast modulo op to get hash bucket

The rule to map a key to its bucket can simply be to use the key signature (modulo the number of table buckets) as the table bucket ID:

    bucket_id = f_hash(key) % n_buckets;

By selecting the number of buckets to be a power of two, the modulo operator can be replaced by a bitwise AND logical operation:

    bucket_id = f_hash(key) & (n_buckets - 1);