Entity encoding for XML - script?

Following on the web service question, has anybody seen a script that can encode (and double-encode) strings with entities for safe use in XML? https://en.wikipedia.org/wiki/List_of_XML_and_HTML_character_entity_references

Have you looked through Chris RG's site, for example http://reb4.me/r3/altxml . Years ago, I had also used http://earl.strain.at/space/rebXR - I don't remember what's in that package, but it may provide a starting point.

Thanks for those links-- those do look like a great start, esp Chris's site.