def _windows_covers(windows, rrtype):
    """
    Check to see if an NSECx windows list covers a type.

    :param list windows: An NSEC or NSEC3 windows list.
    :param int rrtype: The dns.rdatatype to test.
    :return: True if the windows covers the type; False if not.
    """
    window = rrtype // 256
    for win in windows:
        if win[0] == window:
            bitmap = win[1]
            offset = rrtype % 256
            byte = offset // 8
            if bitmap and len(bitmap) >= byte + 1:
                bit = offset % 8
                return bool(bitmap[byte] & 128 >> bit)
    return False
