Idfxt

This pull request is for the sake of conversation, not necessarily with the intent to merge.  yet. 
const reference.

Also this interface seems questionable to me.  At minimum the raw pointer is violating the coding standard.  But beyond that I'm am not a fan of exposing the c data structure at all.  Can you provide a more friendly C++ class around that thing, therefore hiding the c.  What you do privately is not so much my concern.