Jeff Pohlmeyer has been working with the hiperfifo.c example source code,

and while doing so it became apparent that the current timeout system for
the socket API really was a bit awkward since it become quite some work to
be sure we have the correct timeout set.

Jeff then provided the new CURLMOPT_TIMERFUNCTION that is yet another
callback the app can set to get to know when the general timeout time
changes and thus for an application like hiperfifo.c it makes everything a
lot easier and nicer. There's a CURLMOPT_TIMERDATA option too of course in
good old libcurl tradition.