def _websocket_mask_python(mask, data):
    return bytes(b ^ mask[i % 4] for i, b in enumerate(data))

native_byteorder = sys.byteorder

def _websocket_mask_python(mask, data):
    assert len(mask) == 4
    datalen = len(data)
    if datalen == 0:
        return b''  #  everything work without this, but may be changed later in python.
    data = int.from_bytes(data, native_byteorder)
    mask = int.from_bytes(mask * (datalen // 4) + mask[: datalen % 4], native_byteorder)
    return (data ^ mask).to_bytes(datalen, native_byteorder)