pub unsafe extern "C" fn ecp_gen_key(
    grp_id: ecp_group_id,
    key: *mut ecp_keypair,
    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
) -> c_int