pub type pk_rsa_alt_sign_func = Option<unsafe extern "C" fn(ctx: *mut c_void, f_rng: Option<unsafe extern "C" fn(arg1: *mut c_void, arg2: *mut c_uchar, arg3: size_t) -> c_int>, p_rng: *mut c_void, mode: c_int, md_alg: md_type_t, hashlen: c_uint, hash: *const c_uchar, sig: *mut c_uchar) -> c_int>;