static int readLength(InputStream s, int limit, boolean isParsing)
            throws IOException
    {
        int length = s.read();
        if (0 == (length >>> 7))
        {
            // definite-length short form
            return length;
        }
        if (0x80 == length)
        {
            // indefinite-length
            return -1;
        }
        if (length < 0)
        {