Hi, i recently coded it in more 'readable' c++ code. Can share with you if u want, i guess?
It's a "one pole complex filter", and miller has suggested previously on this list that it is indeed basically a wrapper for the same code as the cpole~ object, with some other stuff thrown in to calculate the coefficients. ( https://lists.puredata.info/pipermail/pd-list/2014-07/107391.html )
cheers, Matt