ev_io - is this file descriptor readable or writable?ev_io - is this file descriptor readable or writable?
+
+ev_timer - relative and optionally repeating timeoutsev_periodic - to cron or not to cron?ev_signal - signal me when a signal gets signalled!You can find out the major and minor version numbers of the library +
You can find out the major and minor ABI version numbers of the library
you linked against by calling the functions ev_version_major and
ev_version_minor. If you want, you can compare against the global
symbols EV_VERSION_MAJOR and EV_VERSION_MINOR, which specify the
version of the library your program was compiled against.
These version numbers refer to the ABI version of the library, not the +release version.
Usually, it's a good idea to terminate if the major versions mismatch, -as this indicates an incompatible change. Minor versions are usually +as this indicates an incompatible change. Minor versions are usually compatible to older versions, so a larger minor version alone is usually not a problem.
Example: Make sure we haven't accidentally been linked against the wrong @@ -941,6 +946,30 @@ play around with an Xlib connection), then you have to seperately re-test whether a file descriptor is really ready with a known-to-be good interface such as poll (fortunately in our Xlib example, Xlib already does this on its own, so its quite safe to use).
+ + +Some backends (e.g kqueue, epoll) need to be told about closing a file
+descriptor (either by calling close explicitly or by any other means,
+such as dup). The reason is that you register interest in some file
+descriptor, but when it goes away, the operating system will silently drop
+this interest. If another file descriptor with the same number then is
+registered with libev, there is no efficient way to see that this is, in
+fact, a different file descriptor.
To avoid having to explicitly tell libev about such cases, libev follows
+the following policy: Each time ev_io_set is being called, libev
+will assume that this is potentially a new file descriptor, otherwise
+it is assumed that the file descriptor stays the same. That means that
+you have to call ev_io_set (or ev_io_init) when you change the
+descriptor even if the file descriptor number itself did not change.
This is how one would do it normally anyway, the important point is that +the libev application should not optimise around libev but should leave +optimisations to libev.
+ + + +ev_now ()
+ 10.) and then reset your system clock to the last year, then it will
take a year to trigger the event (unlike an ev_timer, which would trigger
-roughly 10 seconds later and of course not if you reset your system time
-again).
+roughly 10 seconds later).
They can also be used to implement vastly more complex timers, such as -triggering an event on eahc midnight, local time.
+triggering an event on each midnight, local time or other, complicated, +rules.As with timers, the callback is guarenteed to be invoked only when the
time (at) has been passed, but if multiple periodic timers become ready
during the same loop iteration then order of execution is undefined.
In this configuration the watcher triggers an event at the wallclock time
at and doesn't repeat. It will not adjust when a time jump occurs,
that is, if it is to be run at January 1st 2011 then it will run when the
system time reaches or surpasses this time.
In this mode the watcher will always be scheduled to time out at the next
-at + N * interval time (for some integer N) and then repeat, regardless
-of any time jumps.
at + N * interval time (for some integer N, which can also be negative)
+and then repeat, regardless of any time jumps.
This can be used to create timers that do not drift with respect to system time:
ev_periodic_set (&periodic, 0., 3600., 0); @@ -1138,8 +1167,11 @@ by 3600.Another way to think about it (for the mathematically inclined) is that
+ev_periodicwill try to run the callback in this mode at the next possible time wheretime = at (mod interval), regardless of any time jumps.For numerical stability it is preferable that the
atvalue is near +ev_now ()(the current time), but there is no range requirement for +this value.
In this mode the values for interval and at are both being
ignored. Instead, each time the periodic watcher gets scheduled, the
@@ -1148,7 +1180,7 @@ current time as second argument.
NOTE: This callback MUST NOT stop or destroy any periodic watcher,
ever, or make any event loop modifications. If you need to stop it,
return now + 1e30 (or so, fudge fudge) and stop it afterwards (e.g. by
-starting a prepare watcher).
ev_prepare watcher, which is legal).
Its prototype is ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
ev_tstamp now), e.g.:
static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) @@ -1178,6 +1210,13 @@ reason I omitted it as an example). when you changed some parameters or the reschedule callback would return a different time than the last time it was called (e.g. in a crond like program when the crontabs have changed). +
When repeating, this contains the offset value, otherwise this is the
+absolute point in time (the at value passed to ev_periodic_set).
Can be modified any time, but changes only take effect when the periodic
+timer fires or ev_periodic_again is being called.