Windows file path to uri (iri?) using xpath functions

Is it possible to get from a windows file path:

C:\workspace\xml\abc.xml

To a uri/iri [insert correct terminology here] understandable by Saxon:

file:///c:/workspace/xml/abc.xml

Currently I do this manually, but there seems to be a raft of new uri
related functions mostly about encoding, but I'm hoping one does this
annoying task for me.

thanks
andrew