-struct rng *rng_create (void);
-void rng_destroy (struct rng *);
-void rng_seed (struct rng *, const void *, size_t);
-void rng_get_bytes (struct rng *, void *, size_t);
-int rng_get_int (struct rng *);
-unsigned rng_get_unsigned (struct rng *);
-double rng_get_double (struct rng *);
-double rng_get_double_normal (struct rng *);