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Revision 1.362 by root, Sun Jan 30 21:10:13 2011 UTC vs.
Revision 1.367 by root, Sun Feb 20 02:56:23 2011 UTC

… …
2151 2151
2152Another way to think about it (for the mathematically inclined) is that 2152Another way to think about it (for the mathematically inclined) is that
2153C<ev_periodic> will try to run the callback in this mode at the next possible 2153C<ev_periodic> will try to run the callback in this mode at the next possible
2154time where C<time = offset (mod interval)>, regardless of any time jumps. 2154time where C<time = offset (mod interval)>, regardless of any time jumps.
2155 2155
2156For numerical stability it is preferable that the C<offset> value is near 2156The C<interval> I<MUST> be positive, and for numerical stability, the
2157C<ev_now ()> (the current time), but there is no range requirement for 2157interval value should be higher than C<1/8192> (which is around 100
2158this value, and in fact is often specified as zero. 2158microseconds) and C<offset> should be higher than C<0> and should have
2159at most a similar magnitude as the current time (say, within a factor of
2160ten). Typical values for offset are, in fact, C<0> or something between
2161C<0> and C<interval>, which is also the recommended range.
2159 2162
2160Note also that there is an upper limit to how often a timer can fire (CPU 2163Note also that there is an upper limit to how often a timer can fire (CPU
2161speed for example), so if C<interval> is very small then timing stability 2164speed for example), so if C<interval> is very small then timing stability
2162will of course deteriorate. Libev itself tries to be exact to be about one 2165will of course deteriorate. Libev itself tries to be exact to be about one
2163millisecond (if the OS supports it and the machine is fast enough). 2166millisecond (if the OS supports it and the machine is fast enough).
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3188 atexit (program_exits); 3191 atexit (program_exits);
3189 3192
3190 3193
3191=head2 C<ev_async> - how to wake up an event loop 3194=head2 C<ev_async> - how to wake up an event loop
3192 3195
3193In general, you cannot use an C<ev_run> from multiple threads or other 3196In general, you cannot use an C<ev_loop> from multiple threads or other
3194asynchronous sources such as signal handlers (as opposed to multiple event 3197asynchronous sources such as signal handlers (as opposed to multiple event
3195loops - those are of course safe to use in different threads). 3198loops - those are of course safe to use in different threads).
3196 3199
3197Sometimes, however, you need to wake up an event loop you do not control, 3200Sometimes, however, you need to wake up an event loop you do not control,
3198for example because it belongs to another thread. This is what C<ev_async> 3201for example because it belongs to another thread. This is what C<ev_async>
… …
3308trust me. 3311trust me.
3309 3312
3310=item ev_async_send (loop, ev_async *) 3313=item ev_async_send (loop, ev_async *)
3311 3314
3312Sends/signals/activates the given C<ev_async> watcher, that is, feeds 3315Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3313an C<EV_ASYNC> event on the watcher into the event loop. Unlike 3316an C<EV_ASYNC> event on the watcher into the event loop, and instantly
3317returns.
3318
3314C<ev_feed_event>, this call is safe to do from other threads, signal or 3319Unlike C<ev_feed_event>, this call is safe to do from other threads,
3315similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding 3320signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3316section below on what exactly this means). 3321embedding section below on what exactly this means).
3317 3322
3318Note that, as with other watchers in libev, multiple events might get 3323Note that, as with other watchers in libev, multiple events might get
3319compressed into a single callback invocation (another way to look at this 3324compressed into a single callback invocation (another way to look at this
3320is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, 3325is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
3321reset when the event loop detects that). 3326reset when the event loop detects that).
… …
4202F<event.h> that are not directly supported by the libev core alone. 4207F<event.h> that are not directly supported by the libev core alone.
4203 4208
4204In standalone mode, libev will still try to automatically deduce the 4209In standalone mode, libev will still try to automatically deduce the
4205configuration, but has to be more conservative. 4210configuration, but has to be more conservative.
4206 4211
4212=item EV_USE_FLOOR
4213
4214If defined to be C<1>, libev will use the C<floor ()> function for its
4215periodic reschedule calculations, otherwise libev will fall back on a
4216portable (slower) implementation. If you enable this, you usually have to
4217link against libm or something equivalent. Enabling this when the C<floor>
4218function is not available will fail, so the safe default is to not enable
4219this.
4220
4207=item EV_USE_MONOTONIC 4221=item EV_USE_MONOTONIC
4208 4222
4209If defined to be C<1>, libev will try to detect the availability of the 4223If defined to be C<1>, libev will try to detect the availability of the
4210monotonic clock option at both compile time and runtime. Otherwise no 4224monotonic clock option at both compile time and runtime. Otherwise no
4211use of the monotonic clock option will be attempted. If you enable this, 4225use of the monotonic clock option will be attempted. If you enable this,
… …
5222The physical time that is observed. It is apparently strictly monotonic :) 5236The physical time that is observed. It is apparently strictly monotonic :)
5223 5237
5224=item wall-clock time 5238=item wall-clock time
5225 5239
5226The time and date as shown on clocks. Unlike real time, it can actually 5240The time and date as shown on clocks. Unlike real time, it can actually
5227be wrong and jump forwards and backwards, e.g. when the you adjust your 5241be wrong and jump forwards and backwards, e.g. when you adjust your
5228clock. 5242clock.
5229 5243
5230=item watcher 5244=item watcher
5231 5245
5232A data structure that describes interest in certain events. Watchers need 5246A data structure that describes interest in certain events. Watchers need
… …
5235=back 5249=back
5236 5250
5237=head1 AUTHOR 5251=head1 AUTHOR
5238 5252
5239Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael 5253Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
5240Magnusson and Emanuele Giaquinta. 5254Magnusson and Emanuele Giaquinta, and minor corrections by many others.
5241 5255

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