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Comparing libev/ev.pod (file contents):
Revision 1.174 by root, Mon Aug 18 23:23:45 2008 UTC vs.
Revision 1.177 by root, Mon Sep 8 17:27:42 2008 UTC

… …
572Returns the current "event loop time", which is the time the event loop 572Returns the current "event loop time", which is the time the event loop
573received events and started processing them. This timestamp does not 573received events and started processing them. This timestamp does not
574change as long as callbacks are being processed, and this is also the base 574change as long as callbacks are being processed, and this is also the base
575time used for relative timers. You can treat it as the timestamp of the 575time used for relative timers. You can treat it as the timestamp of the
576event occurring (or more correctly, libev finding out about it). 576event occurring (or more correctly, libev finding out about it).
577
578=item ev_now_update (loop)
579
580Establishes the current time by querying the kernel, updating the time
581returned by C<ev_now ()> in the progress. This is a costly operation and
582is usually done automatically within C<ev_loop ()>.
583
584This function is rarely useful, but when some event callback runs for a
585very long time without entering the event loop, updating libev's idea of
586the current time is a good idea.
587
588See also "The special problem of time updates" in the C<ev_timer> section.
577 589
578=item ev_loop (loop, int flags) 590=item ev_loop (loop, int flags)
579 591
580Finally, this is it, the event handler. This function usually is called 592Finally, this is it, the event handler. This function usually is called
581after you initialised all your watchers and you want to start handling 593after you initialised all your watchers and you want to start handling
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1197times out after an hour and you reset your system clock to January last 1209times out after an hour and you reset your system clock to January last
1198year, it will still time out after (roughly) and hour. "Roughly" because 1210year, it will still time out after (roughly) and hour. "Roughly" because
1199detecting time jumps is hard, and some inaccuracies are unavoidable (the 1211detecting time jumps is hard, and some inaccuracies are unavoidable (the
1200monotonic clock option helps a lot here). 1212monotonic clock option helps a lot here).
1201 1213
1214The callback is guaranteed to be invoked only after its timeout has passed,
1215but if multiple timers become ready during the same loop iteration then
1216order of execution is undefined.
1217
1218=head3 The special problem of time updates
1219
1220Establishing the current time is a costly operation (it usually takes at
1221least two system calls): EV therefore updates its idea of the current
1222time only before and after C<ev_loop> polls for new events, which causes
1223a growing difference between C<ev_now ()> and C<ev_time ()> when handling
1224lots of events.
1225
1202The relative timeouts are calculated relative to the C<ev_now ()> 1226The relative timeouts are calculated relative to the C<ev_now ()>
1203time. This is usually the right thing as this timestamp refers to the time 1227time. This is usually the right thing as this timestamp refers to the time
1204of the event triggering whatever timeout you are modifying/starting. If 1228of the event triggering whatever timeout you are modifying/starting. If
1205you suspect event processing to be delayed and you I<need> to base the timeout 1229you suspect event processing to be delayed and you I<need> to base the
1206on the current time, use something like this to adjust for this: 1230timeout on the current time, use something like this to adjust for this:
1207 1231
1208 ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); 1232 ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1209 1233
1210The callback is guaranteed to be invoked only after its timeout has passed, 1234If the event loop is suspended for a long time, you can also force an
1211but if multiple timers become ready during the same loop iteration then 1235update of the time returned by C<ev_now ()> by calling C<ev_now_update
1212order of execution is undefined. 1236()>.
1213 1237
1214=head3 Watcher-Specific Functions and Data Members 1238=head3 Watcher-Specific Functions and Data Members
1215 1239
1216=over 4 1240=over 4
1217 1241

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