[ViewVC] Diff of: cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.17 by root, Mon Nov 12 08:57:03 2007 UTC vs.
Revision 1.27 by root, Wed Nov 14 05:02:07 2007 UTC

…		…
49	called C<ev_tstamp>, which is what you should use too. It usually aliases	49	called C<ev_tstamp>, which is what you should use too. It usually aliases
50	to the double type in C.	50	to the double type in C.
51		51
52	=head1 GLOBAL FUNCTIONS	52	=head1 GLOBAL FUNCTIONS
53		53
		54	These functions can be called anytime, even before initialising the
		55	library in any way.
		56
54	=over 4	57	=over 4
55		58
56	=item ev_tstamp ev_time ()	59	=item ev_tstamp ev_time ()
57		60
58	Returns the current time as libev would use it.	61	Returns the current time as libev would use it. Please note that the
		62	C<ev_now> function is usually faster and also often returns the timestamp
		63	you actually want to know.
59		64
60	=item int ev_version_major ()	65	=item int ev_version_major ()
61		66
62	=item int ev_version_minor ()	67	=item int ev_version_minor ()
63		68
…		…
234		239
235	This flags value could be used to implement alternative looping	240	This flags value could be used to implement alternative looping
236	constructs, but the C<prepare> and C<check> watchers provide a better and	241	constructs, but the C<prepare> and C<check> watchers provide a better and
237	more generic mechanism.	242	more generic mechanism.
238		243
		244	Here are the gory details of what ev_loop does:
		245
		246	1. If there are no active watchers (reference count is zero), return.
		247	2. Queue and immediately call all prepare watchers.
		248	3. If we have been forked, recreate the kernel state.
		249	4. Update the kernel state with all outstanding changes.
		250	5. Update the "event loop time".
		251	6. Calculate for how long to block.
		252	7. Block the process, waiting for events.
		253	8. Update the "event loop time" and do time jump handling.
		254	9. Queue all outstanding timers.
		255	10. Queue all outstanding periodics.
		256	11. If no events are pending now, queue all idle watchers.
		257	12. Queue all check watchers.
		258	13. Call all queued watchers in reverse order (i.e. check watchers first).
		259	14. If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
		260	was used, return, otherwise continue with step #1.
		261
239	=item ev_unloop (loop, how)	262	=item ev_unloop (loop, how)
240		263
241	Can be used to make a call to C<ev_loop> return early (but only after it	264	Can be used to make a call to C<ev_loop> return early (but only after it
242	has processed all outstanding events). The C<how> argument must be either	265	has processed all outstanding events). The C<how> argument must be either
243	C<EVUNLOOP_ONCE>, which will make the innermost C<ev_loop> call return, or	266	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
244	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	267	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
245		268
246	=item ev_ref (loop)	269	=item ev_ref (loop)
247		270
248	=item ev_unref (loop)	271	=item ev_unref (loop)
…		…
414	in each iteration of the event loop (This behaviour is called	437	in each iteration of the event loop (This behaviour is called
415	level-triggering because you keep receiving events as long as the	438	level-triggering because you keep receiving events as long as the
416	condition persists. Remember you can stop the watcher if you don't want to	439	condition persists. Remember you can stop the watcher if you don't want to
417	act on the event and neither want to receive future events).	440	act on the event and neither want to receive future events).
418		441
419	In general you can register as many read and/or write event watchers oer	442	In general you can register as many read and/or write event watchers per
420	fd as you want (as long as you don't confuse yourself). Setting all file	443	fd as you want (as long as you don't confuse yourself). Setting all file
421	descriptors to non-blocking mode is also usually a good idea (but not	444	descriptors to non-blocking mode is also usually a good idea (but not
422	required if you know what you are doing).	445	required if you know what you are doing).
423		446
424	You have to be careful with dup'ed file descriptors, though. Some backends	447	You have to be careful with dup'ed file descriptors, though. Some backends
425	(the linux epoll backend is a notable example) cannot handle dup'ed file	448	(the linux epoll backend is a notable example) cannot handle dup'ed file
426	descriptors correctly if you register interest in two or more fds pointing	449	descriptors correctly if you register interest in two or more fds pointing
427	to the same file/socket etc. description.	450	to the same underlying file/socket etc. description (that is, they share
		451	the same underlying "file open").
428		452
429	If you must do this, then force the use of a known-to-be-good backend	453	If you must do this, then force the use of a known-to-be-good backend
430	(at the time of this writing, this includes only EVMETHOD_SELECT and	454	(at the time of this writing, this includes only EVMETHOD_SELECT and
431	EVMETHOD_POLL).	455	EVMETHOD_POLL).
432		456
…		…
446		470
447	Timer watchers are simple relative timers that generate an event after a	471	Timer watchers are simple relative timers that generate an event after a
448	given time, and optionally repeating in regular intervals after that.	472	given time, and optionally repeating in regular intervals after that.
449		473
450	The timers are based on real time, that is, if you register an event that	474	The timers are based on real time, that is, if you register an event that
451	times out after an hour and youreset your system clock to last years	475	times out after an hour and you reset your system clock to last years
452	time, it will still time out after (roughly) and hour. "Roughly" because	476	time, it will still time out after (roughly) and hour. "Roughly" because
453	detecting time jumps is hard, and soem inaccuracies are unavoidable (the	477	detecting time jumps is hard, and soem inaccuracies are unavoidable (the
454	monotonic clock option helps a lot here).	478	monotonic clock option helps a lot here).
455		479
456	The relative timeouts are calculated relative to the C<ev_now ()>	480	The relative timeouts are calculated relative to the C<ev_now ()>
457	time. This is usually the right thing as this timestamp refers to the time	481	time. This is usually the right thing as this timestamp refers to the time
458	of the event triggering whatever timeout you are modifying/starting. If	482	of the event triggering whatever timeout you are modifying/starting. If
459	you suspect event processing to be delayed and you need to base the timeout	483	you suspect event processing to be delayed and you need to base the timeout
460	ion the current time, use something like this to adjust for this:	484	on the current time, use something like this to adjust for this:
461		485
462	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	486	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
463		487
464	=over 4	488	=over 4
465		489
…		…
473	later, again, and again, until stopped manually.	497	later, again, and again, until stopped manually.
474		498
475	The timer itself will do a best-effort at avoiding drift, that is, if you	499	The timer itself will do a best-effort at avoiding drift, that is, if you
476	configure a timer to trigger every 10 seconds, then it will trigger at	500	configure a timer to trigger every 10 seconds, then it will trigger at
477	exactly 10 second intervals. If, however, your program cannot keep up with	501	exactly 10 second intervals. If, however, your program cannot keep up with
478	the timer (ecause it takes longer than those 10 seconds to do stuff) the	502	the timer (because it takes longer than those 10 seconds to do stuff) the
479	timer will not fire more than once per event loop iteration.	503	timer will not fire more than once per event loop iteration.
480		504
481	=item ev_timer_again (loop)	505	=item ev_timer_again (loop)
482		506
483	This will act as if the timer timed out and restart it again if it is	507	This will act as if the timer timed out and restart it again if it is
…		…
560	In this mode the values for C<interval> and C<at> are both being	584	In this mode the values for C<interval> and C<at> are both being
561	ignored. Instead, each time the periodic watcher gets scheduled, the	585	ignored. Instead, each time the periodic watcher gets scheduled, the
562	reschedule callback will be called with the watcher as first, and the	586	reschedule callback will be called with the watcher as first, and the
563	current time as second argument.	587	current time as second argument.
564		588
565	NOTE: I<This callback MUST NOT stop or destroy the periodic or any other	589	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
566	periodic watcher, ever, or make any event loop modifications>. If you need	590	ever, or make any event loop modifications>. If you need to stop it,
567	to stop it, return C<now + 1e30> (or so, fudge fudge) and stop it afterwards.	591	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
568		592	starting a prepare watcher).
569	Also, I<< this callback must always return a time that is later than the
570	passed C<now> value >>. Not even C<now> itself will be ok.
571		593
572	Its prototype is C<ev_tstamp (reschedule_cb)(struct ev_periodic w,	594	Its prototype is C<ev_tstamp (reschedule_cb)(struct ev_periodic w,
573	ev_tstamp now)>, e.g.:	595	ev_tstamp now)>, e.g.:
574		596
575	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	597	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
…		…
580	It must return the next time to trigger, based on the passed time value	602	It must return the next time to trigger, based on the passed time value
581	(that is, the lowest time value larger than to the second argument). It	603	(that is, the lowest time value larger than to the second argument). It
582	will usually be called just before the callback will be triggered, but	604	will usually be called just before the callback will be triggered, but
583	might be called at other times, too.	605	might be called at other times, too.
584		606
		607	NOTE: I<< This callback must always return a time that is later than the
		608	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.
		609
585	This can be used to create very complex timers, such as a timer that	610	This can be used to create very complex timers, such as a timer that
586	triggers on each midnight, local time. To do this, you would calculate the	611	triggers on each midnight, local time. To do this, you would calculate the
587	next midnight after C<now> and return the timestamp value for this. How you do this	612	next midnight after C<now> and return the timestamp value for this. How
588	is, again, up to you (but it is not trivial).	613	you do this is, again, up to you (but it is not trivial, which is the main
		614	reason I omitted it as an example).
589		615
590	=back	616	=back
591		617
592	=item ev_periodic_again (loop, ev_periodic *)	618	=item ev_periodic_again (loop, ev_periodic *)
593		619
…		…
672	=back	698	=back
673		699
674	=head2 C<ev_prepare> and C<ev_check> - customise your event loop	700	=head2 C<ev_prepare> and C<ev_check> - customise your event loop
675		701
676	Prepare and check watchers are usually (but not always) used in tandem:	702	Prepare and check watchers are usually (but not always) used in tandem:
677	Prepare watchers get invoked before the process blocks and check watchers	703	prepare watchers get invoked before the process blocks and check watchers
678	afterwards.	704	afterwards.
679		705
680	Their main purpose is to integrate other event mechanisms into libev. This	706	Their main purpose is to integrate other event mechanisms into libev. This
681	could be used, for example, to track variable changes, implement your own	707	could be used, for example, to track variable changes, implement your own
682	watchers, integrate net-snmp or a coroutine library and lots more.	708	watchers, integrate net-snmp or a coroutine library and lots more.
…		…
685	to be watched by the other library, registering C<ev_io> watchers for	711	to be watched by the other library, registering C<ev_io> watchers for
686	them and starting an C<ev_timer> watcher for any timeouts (many libraries	712	them and starting an C<ev_timer> watcher for any timeouts (many libraries
687	provide just this functionality). Then, in the check watcher you check for	713	provide just this functionality). Then, in the check watcher you check for
688	any events that occured (by checking the pending status of all watchers	714	any events that occured (by checking the pending status of all watchers
689	and stopping them) and call back into the library. The I/O and timer	715	and stopping them) and call back into the library. The I/O and timer
690	callbacks will never actually be called (but must be valid neverthelles,	716	callbacks will never actually be called (but must be valid nevertheless,
691	because you never know, you know?).	717	because you never know, you know?).
692		718
693	As another example, the Perl Coro module uses these hooks to integrate	719	As another example, the Perl Coro module uses these hooks to integrate
694	coroutines into libev programs, by yielding to other active coroutines	720	coroutines into libev programs, by yielding to other active coroutines
695	during each prepare and only letting the process block if no coroutines	721	during each prepare and only letting the process block if no coroutines
696	are ready to run (its actually more complicated, it only runs coroutines	722	are ready to run (it's actually more complicated: it only runs coroutines
697	with priority higher than the event loop and one lower priority once,	723	with priority higher than or equal to the event loop and one coroutine
698	using idle watchers to keep the event loop from blocking if lower-priority	724	of lower priority, but only once, using idle watchers to keep the event
699	coroutines exist, thus mapping low-priority coroutines to idle/background	725	loop from blocking if lower-priority coroutines are active, thus mapping
700	tasks).	726	low-priority coroutines to idle/background tasks).
701		727
702	=over 4	728	=over 4
703		729
704	=item ev_prepare_init (ev_prepare *, callback)	730	=item ev_prepare_init (ev_prepare *, callback)
705		731
…		…
720	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	746	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
721		747
722	This function combines a simple timer and an I/O watcher, calls your	748	This function combines a simple timer and an I/O watcher, calls your
723	callback on whichever event happens first and automatically stop both	749	callback on whichever event happens first and automatically stop both
724	watchers. This is useful if you want to wait for a single event on an fd	750	watchers. This is useful if you want to wait for a single event on an fd
725	or timeout without havign to allocate/configure/start/stop/free one or	751	or timeout without having to allocate/configure/start/stop/free one or
726	more watchers yourself.	752	more watchers yourself.
727		753
728	If C<fd> is less than 0, then no I/O watcher will be started and events	754	If C<fd> is less than 0, then no I/O watcher will be started and events
729	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	755	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
730	C<events> set will be craeted and started.	756	C<events> set will be craeted and started.
…		…
733	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	759	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
734	repeat = 0) will be started. While C<0> is a valid timeout, it is of	760	repeat = 0) will be started. While C<0> is a valid timeout, it is of
735	dubious value.	761	dubious value.
736		762
737	The callback has the type C<void (cb)(int revents, void arg)> and gets	763	The callback has the type C<void (cb)(int revents, void arg)> and gets
738	passed an events set like normal event callbacks (with a combination of	764	passed an C<revents> set like normal event callbacks (a combination of
739	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	765	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
740	value passed to C<ev_once>:	766	value passed to C<ev_once>:
741		767
742	static void stdin_ready (int revents, void *arg)	768	static void stdin_ready (int revents, void *arg)
743	{	769	{
…		…
764		790
765	Feed an event as if the given signal occured (loop must be the default loop!).	791	Feed an event as if the given signal occured (loop must be the default loop!).
766		792
767	=back	793	=back
768		794
		795	=head1 LIBEVENT EMULATION
		796
		797	Libev offers a compatibility emulation layer for libevent. It cannot
		798	emulate the internals of libevent, so here are some usage hints:
		799
		800	=over 4
		801
		802	=item * Use it by including <event.h>, as usual.
		803
		804	=item * The following members are fully supported: ev_base, ev_callback,
		805	ev_arg, ev_fd, ev_res, ev_events.
		806
		807	=item * Avoid using ev_flags and the EVLIST_*-macros, while it is
		808	maintained by libev, it does not work exactly the same way as in libevent (consider
		809	it a private API).
		810
		811	=item * Priorities are not currently supported. Initialising priorities
		812	will fail and all watchers will have the same priority, even though there
		813	is an ev_pri field.
		814
		815	=item * Other members are not supported.
		816
		817	=item * The libev emulation is I<not> ABI compatible to libevent, you need
		818	to use the libev header file and library.
		819
		820	=back
		821
		822	=head1 C++ SUPPORT
		823
		824	TBD.
		825
769	=head1 AUTHOR	826	=head1 AUTHOR
770		827
771	Marc Lehmann <libev@schmorp.de>.	828	Marc Lehmann <libev@schmorp.de>.
772		829

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Comparing libev/ev.pod (file contents): Revision 1.17 by root, Mon Nov 12 08:57:03 2007 UTC vs. Revision 1.27 by root, Wed Nov 14 05:02:07 2007 UTC

Diff Legend

Comparing libev/ev.pod (file contents):
Revision 1.17 by root, Mon Nov 12 08:57:03 2007 UTC vs.
Revision 1.27 by root, Wed Nov 14 05:02:07 2007 UTC