.java

    public static boolean isConstantInitial(ByteList byteList) {
        int c, len;
        int nlen = byteList.realSize();
        Encoding enc = byteList.getEncoding();

        if (nlen < 1) return false;
        int byte0 = byteList.get(0);
        if (byte0 < 128) return enc.isUpper(byte0);

        byte[] bytes = byteList.getUnsafeBytes();
        int begin = byteList.begin();
        int end = begin + nlen;
        c = StringSupport.preciseLength(enc, bytes, begin, end);
        if (!StringSupport.MBCLEN_CHARFOUND_P(c)) return false;
        len = StringSupport.MBCLEN_CHARFOUND_LEN(c);
        c = StringSupport.codePoint(enc, bytes, begin, end);
        if (enc.isUnicode()) {
            if (enc.isUpper(c)) return true;
            if (enc.isLower(c)) return false;
            if (enc.isCodeCType(c, UnicodeCodeRange.TITLECASELETTER.getCType())) return true;
        } else {
            /* fallback to case-folding */
            IntHolder holder = new IntHolder();
            holder.value = begin;
            byte[] fold = new byte[Config.ENC_GET_CASE_FOLD_CODES_MAX_NUM];
            int r = enc.mbcCaseFold(Config.CASE_FOLD, bytes, holder, end, fold);
            if (r > 0 && (r != len || ByteList.memcmp(fold, 0, bytes, begin, r) != 0))
                return true;
        }
        return false;
    }