pub unsafe extern "C" fn ecdh_compute_shared( grp: *mut ecp_group, z: *mut mpi, Q: *const ecp_point, d: *const mpi, 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