Drawing a path with subtracted text using Core Graphics

Drawing a path with subtracted text using Core Graphics

Creating filled paths in Core Graphics is straight-forward, as is creating
filled text. But I am yet to find examples of paths filled EXCEPT for text
in a sub-path. My experiments with text drawing modes, clipping etc have
got me nowhere.
Here's an example (created in photoshop). How would you go about creating
the foreground shape in Core Graphics?

I would mention that this technique appears to be used heavily in an
upcoming version of a major mobile OS, but I don't want to fall afoul of
SO's NDA-police ;)