struct hash_backend *get_hash_backend(const char *name);
void put_hash_backend(struct hash_backend *backend);
int hash(const char *backend_name, const char *hash_name,
struct hash_backend *get_hash_backend(const char *name);
void put_hash_backend(struct hash_backend *backend);
int hash(const char *backend_name, const char *hash_name,