pub unsafe extern "C" fn pk_sign_restartable(
    ctx: *mut pk_context,
    md_alg: md_type_t,
    hash: *const c_uchar,
    hash_len: size_t,
    sig: *mut c_uchar,
    sig_len: *mut size_t,
    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,
    rs_ctx: *mut pk_restart_ctx
) -> c_int