pub type OSSL_FUNC_digest_init_fn = Option<unsafe extern "C" fn(*mut c_void, *const ossl_param_st) -> i32>;
enum OSSL_FUNC_digest_init_fn { None, Some(unsafe extern "C" fn(*mut c_void, *const ossl_param_st) -> i32), }
No value.
Some value of type T.
T