从XLST生成低阶不可打印字符

I'm trying to use XSLT text output to generate a file (in a file format that I'm not in control of), and while it is mostly text, it includes low-order non-printable characters as flags, including characters that are not valid within an XLST file (according to the XSLT specification).I'm trying to use XSLT text output to generate