These functions can be called anytime, even before initialising the +library in any way.
time = at (mod interval), regardless of any time jumps.<
ignored. Instead, each time the periodic watcher gets scheduled, the
reschedule callback will be called with the watcher as first, and the
current time as second argument.
- NOTE: This callback MUST NOT stop or destroy the periodic or any other
-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.
Also, this callback must always return a time that is later than the
-passed now value. Not even now itself will be ok.
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).
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) @@ -586,10 +589,13 @@ ev_tstamp now), e.g.: (that is, the lowest time value larger than to the second argument). It will usually be called just before the callback will be triggered, but might be called at other times, too. +NOTE: This callback must always return a time that is later than the +passed
nowvalue. Not evennowitself will do, it must be larger.This can be used to create very complex timers, such as a timer that triggers on each midnight, local time. To do this, you would calculate the -next midnight after
+next midnight afternowand return the timestamp value for this. How you do this -is, again, up to you (but it is not trivial).nowand return the timestamp value for this. How +you do this is, again, up to you (but it is not trivial, which is the main +reason I omitted it as an example).
ev_prepare and ev_check - customise your event loopPrepare and check watchers are usually (but not always) used in tandem: -Prepare watchers get invoked before the process blocks and check watchers +prepare watchers get invoked before the process blocks and check watchers afterwards.
Their main purpose is to integrate other event mechanisms into libev. This
could be used, for example, to track variable changes, implement your own
@@ -683,16 +689,16 @@ them and starting an ev_timer watcher for any timeouts (many librar
provide just this functionality). Then, in the check watcher you check for
any events that occured (by checking the pending status of all watchers
and stopping them) and call back into the library. The I/O and timer
-callbacks will never actually be called (but must be valid neverthelles,
+callbacks will never actually be called (but must be valid nevertheless,
because you never know, you know?).
As another example, the Perl Coro module uses these hooks to integrate coroutines into libev programs, by yielding to other active coroutines during each prepare and only letting the process block if no coroutines -are ready to run (its actually more complicated, it only runs coroutines -with priority higher than the event loop and one lower priority once, -using idle watchers to keep the event loop from blocking if lower-priority -coroutines exist, thus mapping low-priority coroutines to idle/background -tasks).
+are ready to run (it's actually more complicated: it only runs coroutines +with priority higher than or equal to the event loop and one coroutine +of lower priority, but only once, using idle watchers to keep the event +loop from blocking if lower-priority coroutines are active, thus mapping +low-priority coroutines to idle/background tasks).ev_timer watcher with after = timeout0 is a valid timeout, it is of
dubious value.
The callback has the type void (*cb)(int revents, void *arg) and gets
-passed an events set like normal event callbacks (with a combination of
+passed an revents set like normal event callbacks (a combination of
EV_ERROR, EV_READ, EV_WRITE or EV_TIMEOUT) and the arg
value passed to ev_once:
static void stdin_ready (int revents, void *arg) @@ -755,6 +761,16 @@ the given events it.
TBD.
+ +TBD.
+