public String tk_lstring() {
        StringBuffer sb = new StringBuffer();
        if (tk_m(tk_lstr_start)) {
            for (;;) {
                if (ch == 0) {
                    break;
                }
                if (ch == QUOT) {
                    if (m(1, QUOT)) {
                        sb.append(QUOT);
                        next();
                    } else {
                        break;
                    }
                } else {
                    sb.append(ch);
                }
                next();
            }
            next();
        }
        return sb.toString();
    }