byte[] offBuf = new byte[cnt];
        int pos = 0;
        while ( pos < cnt ) {
            int r = is.read(offBuf, pos, offBuf.length - pos);
            if ( r < 0 ) {
                fail("EOF while reading");
            }
            pos += r;
        }

        for ( int i = 0; i < offBuf.length; i++ ) {
            if ( offBuf[ i ] != 0 ) {