HASHVAL_SEEDLEN
uint8_t seed[HASHVAL_SEEDLEN];
hash(const uint8_t seed[static HASHVAL_SEEDLEN], const void *key, size_t len,
blake2s_init(&B, sizeof h, seed, HASHVAL_SEEDLEN);
hashval_init(thmap_query_t *query, const uint8_t seed[static HASHVAL_SEEDLEN],