Mainloop
========

Not every program is strictly sequential. Sometimes, an event-driven
model is much easier to grasp. A fine example of such a program could
be a railway server. It has a separate connection to each station
and also to each train, so that it knows where each of them is (and
that neither a train nor a station have got missing). So it has to wait
for events coming from these connections and handle them appropriately.
It also processes other events that it has itself generated -- for
example various timers telling that a train is scheduled to depart
from some station.

The mainloop module takes care of the low-level part of event-driven
programs: it calls the OS to monitor file activity, to interrupt
the program at the right moment to serve a timer, and so on. The
programmer only defines hooks that should be called to handle
the events and calls mainloop functions to schedule them.

// TODO Example?

- <<conventions,Conventions>>
- <<time,Time and timers>>
- <<file,Activity on file descriptors>>
- <<hooks,Loop hooks>>
- <<process,Child processes>>
- <<control,Control of the mainloop>>

!!ucw/mainloop.h