BytesRef matchOutput = null;

        int index = 0;
        while (start + index < src.length) {
            final int codePoint = Character.codePointAt(src, start + index, src.length);
            if (fst.findTargetArc(ignoreCase ? Character.toLowerCase(codePoint) : codePoint, scratchArc, scratchArc, fstReader) == null) {
                return matchOutput;
            }