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

Comparing libev/ev.pod (file contents):
Revision 1.16 by root, Mon Nov 12 08:47:14 2007 UTC vs.
Revision 1.25 by root, Mon Nov 12 21:51:14 2007 UTC

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39	F<README.embed> in the libev distribution. If libev was configured without	39	F<README.embed> in the libev distribution. If libev was configured without
40	support for multiple event loops, then all functions taking an initial	40	support for multiple event loops, then all functions taking an initial
41	argument of name C<loop> (which is always of type C<struct ev_loop *>)	41	argument of name C<loop> (which is always of type C<struct ev_loop *>)
42	will not have this argument.	42	will not have this argument.
43		43
44	=head1 TIME AND OTHER GLOBAL FUNCTIONS	44	=head1 TIME REPRESENTATION
45		45
46	Libev represents time as a single floating point number, representing the	46	Libev represents time as a single floating point number, representing the
47	(fractional) number of seconds since the (POSIX) epoch (somewhere near	47	(fractional) number of seconds since the (POSIX) epoch (somewhere near
48	the beginning of 1970, details are complicated, don't ask). This type is	48	the beginning of 1970, details are complicated, don't ask). This type is
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
		52	=head1 GLOBAL FUNCTIONS
		53
		54	These functions can be called anytime, even before initialising the
		55	library in any way.
51		56
52	=over 4	57	=over 4
53		58
54	=item ev_tstamp ev_time ()	59	=item ev_tstamp ev_time ()
55		60
…		…
99	An event loop is described by a C<struct ev_loop *>. The library knows two	104	An event loop is described by a C<struct ev_loop *>. The library knows two
100	types of such loops, the I<default> loop, which supports signals and child	105	types of such loops, the I<default> loop, which supports signals and child
101	events, and dynamically created loops which do not.	106	events, and dynamically created loops which do not.
102		107
103	If you use threads, a common model is to run the default event loop	108	If you use threads, a common model is to run the default event loop
104	in your main thread (or in a separate thrad) and for each thread you	109	in your main thread (or in a separate thread) and for each thread you
105	create, you also create another event loop. Libev itself does no locking	110	create, you also create another event loop. Libev itself does no locking
106	whatsoever, so if you mix calls to the same event loop in different	111	whatsoever, so if you mix calls to the same event loop in different
107	threads, make sure you lock (this is usually a bad idea, though, even if	112	threads, make sure you lock (this is usually a bad idea, though, even if
108	done correctly, because it's hideous and inefficient).	113	done correctly, because it's hideous and inefficient).
109		114
…		…
236		241
237	=item ev_unloop (loop, how)	242	=item ev_unloop (loop, how)
238		243
239	Can be used to make a call to C<ev_loop> return early (but only after it	244	Can be used to make a call to C<ev_loop> return early (but only after it
240	has processed all outstanding events). The C<how> argument must be either	245	has processed all outstanding events). The C<how> argument must be either
241	C<EVUNLOOP_ONCE>, which will make the innermost C<ev_loop> call return, or	246	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
242	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	247	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
243		248
244	=item ev_ref (loop)	249	=item ev_ref (loop)
245		250
246	=item ev_unref (loop)	251	=item ev_unref (loop)
…		…
412	in each iteration of the event loop (This behaviour is called	417	in each iteration of the event loop (This behaviour is called
413	level-triggering because you keep receiving events as long as the	418	level-triggering because you keep receiving events as long as the
414	condition persists. Remember you can stop the watcher if you don't want to	419	condition persists. Remember you can stop the watcher if you don't want to
415	act on the event and neither want to receive future events).	420	act on the event and neither want to receive future events).
416		421
417	In general you can register as many read and/or write event watchers oer	422	In general you can register as many read and/or write event watchers per
418	fd as you want (as long as you don't confuse yourself). Setting all file	423	fd as you want (as long as you don't confuse yourself). Setting all file
419	descriptors to non-blocking mode is also usually a good idea (but not	424	descriptors to non-blocking mode is also usually a good idea (but not
420	required if you know what you are doing).	425	required if you know what you are doing).
421		426
422	You have to be careful with dup'ed file descriptors, though. Some backends	427	You have to be careful with dup'ed file descriptors, though. Some backends
423	(the linux epoll backend is a notable example) cannot handle dup'ed file	428	(the linux epoll backend is a notable example) cannot handle dup'ed file
424	descriptors correctly if you register interest in two or more fds pointing	429	descriptors correctly if you register interest in two or more fds pointing
425	to the same file/socket etc. description.	430	to the same underlying file/socket etc. description (that is, they share
		431	the same underlying "file open").
426		432
427	If you must do this, then force the use of a known-to-be-good backend	433	If you must do this, then force the use of a known-to-be-good backend
428	(at the time of this writing, this includes only EVMETHOD_SELECT and	434	(at the time of this writing, this includes only EVMETHOD_SELECT and
429	EVMETHOD_POLL).	435	EVMETHOD_POLL).
430		436
…		…
444		450
445	Timer watchers are simple relative timers that generate an event after a	451	Timer watchers are simple relative timers that generate an event after a
446	given time, and optionally repeating in regular intervals after that.	452	given time, and optionally repeating in regular intervals after that.
447		453
448	The timers are based on real time, that is, if you register an event that	454	The timers are based on real time, that is, if you register an event that
449	times out after an hour and youreset your system clock to last years	455	times out after an hour and you reset your system clock to last years
450	time, it will still time out after (roughly) and hour. "Roughly" because	456	time, it will still time out after (roughly) and hour. "Roughly" because
451	detecting time jumps is hard, and soem inaccuracies are unavoidable (the	457	detecting time jumps is hard, and soem inaccuracies are unavoidable (the
452	monotonic clock option helps a lot here).	458	monotonic clock option helps a lot here).
453		459
454	The relative timeouts are calculated relative to the C<ev_now ()>	460	The relative timeouts are calculated relative to the C<ev_now ()>
455	time. This is usually the right thing as this timestamp refers to the time	461	time. This is usually the right thing as this timestamp refers to the time
456	of the event triggering whatever timeout you are modifying/starting. If	462	of the event triggering whatever timeout you are modifying/starting. If
457	you suspect event processing to be delayed and you need to base the timeout	463	you suspect event processing to be delayed and you need to base the timeout
458	ion the current time, use something like this to adjust for this:	464	on the current time, use something like this to adjust for this:
459		465
460	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	466	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
461		467
462	=over 4	468	=over 4
463		469
…		…
471	later, again, and again, until stopped manually.	477	later, again, and again, until stopped manually.
472		478
473	The timer itself will do a best-effort at avoiding drift, that is, if you	479	The timer itself will do a best-effort at avoiding drift, that is, if you
474	configure a timer to trigger every 10 seconds, then it will trigger at	480	configure a timer to trigger every 10 seconds, then it will trigger at
475	exactly 10 second intervals. If, however, your program cannot keep up with	481	exactly 10 second intervals. If, however, your program cannot keep up with
476	the timer (ecause it takes longer than those 10 seconds to do stuff) the	482	the timer (because it takes longer than those 10 seconds to do stuff) the
477	timer will not fire more than once per event loop iteration.	483	timer will not fire more than once per event loop iteration.
478		484
479	=item ev_timer_again (loop)	485	=item ev_timer_again (loop)
480		486
481	This will act as if the timer timed out and restart it again if it is	487	This will act as if the timer timed out and restart it again if it is
…		…
558	In this mode the values for C<interval> and C<at> are both being	564	In this mode the values for C<interval> and C<at> are both being
559	ignored. Instead, each time the periodic watcher gets scheduled, the	565	ignored. Instead, each time the periodic watcher gets scheduled, the
560	reschedule callback will be called with the watcher as first, and the	566	reschedule callback will be called with the watcher as first, and the
561	current time as second argument.	567	current time as second argument.
562		568
563	NOTE: I<This callback MUST NOT stop or destroy the periodic or any other	569	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
564	periodic watcher, ever, or make any event loop modifications>. If you need	570	ever, or make any event loop modifications>. If you need to stop it,
565	to stop it, return C<now + 1e30> (or so, fudge fudge) and stop it afterwards.	571	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
566		572	starting a prepare watcher).
567	Also, I<< this callback must always return a time that is later than the
568	passed C<now> value >>. Not even C<now> itself will be ok.
569		573
570	Its prototype is C<ev_tstamp (reschedule_cb)(struct ev_periodic w,	574	Its prototype is C<ev_tstamp (reschedule_cb)(struct ev_periodic w,
571	ev_tstamp now)>, e.g.:	575	ev_tstamp now)>, e.g.:
572		576
573	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	577	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
…		…
578	It must return the next time to trigger, based on the passed time value	582	It must return the next time to trigger, based on the passed time value
579	(that is, the lowest time value larger than to the second argument). It	583	(that is, the lowest time value larger than to the second argument). It
580	will usually be called just before the callback will be triggered, but	584	will usually be called just before the callback will be triggered, but
581	might be called at other times, too.	585	might be called at other times, too.
582		586
		587	NOTE: I<< This callback must always return a time that is later than the
		588	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.
		589
583	This can be used to create very complex timers, such as a timer that	590	This can be used to create very complex timers, such as a timer that
584	triggers on each midnight, local time. To do this, you would calculate the	591	triggers on each midnight, local time. To do this, you would calculate the
585	next midnight after C<now> and return the timestamp value for this. How you do this	592	next midnight after C<now> and return the timestamp value for this. How
586	is, again, up to you (but it is not trivial).	593	you do this is, again, up to you (but it is not trivial, which is the main
		594	reason I omitted it as an example).
587		595
588	=back	596	=back
589		597
590	=item ev_periodic_again (loop, ev_periodic *)	598	=item ev_periodic_again (loop, ev_periodic *)
591		599
…		…
670	=back	678	=back
671		679
672	=head2 C<ev_prepare> and C<ev_check> - customise your event loop	680	=head2 C<ev_prepare> and C<ev_check> - customise your event loop
673		681
674	Prepare and check watchers are usually (but not always) used in tandem:	682	Prepare and check watchers are usually (but not always) used in tandem:
675	Prepare watchers get invoked before the process blocks and check watchers	683	prepare watchers get invoked before the process blocks and check watchers
676	afterwards.	684	afterwards.
677		685
678	Their main purpose is to integrate other event mechanisms into libev. This	686	Their main purpose is to integrate other event mechanisms into libev. This
679	could be used, for example, to track variable changes, implement your own	687	could be used, for example, to track variable changes, implement your own
680	watchers, integrate net-snmp or a coroutine library and lots more.	688	watchers, integrate net-snmp or a coroutine library and lots more.
…		…
683	to be watched by the other library, registering C<ev_io> watchers for	691	to be watched by the other library, registering C<ev_io> watchers for
684	them and starting an C<ev_timer> watcher for any timeouts (many libraries	692	them and starting an C<ev_timer> watcher for any timeouts (many libraries
685	provide just this functionality). Then, in the check watcher you check for	693	provide just this functionality). Then, in the check watcher you check for
686	any events that occured (by checking the pending status of all watchers	694	any events that occured (by checking the pending status of all watchers
687	and stopping them) and call back into the library. The I/O and timer	695	and stopping them) and call back into the library. The I/O and timer
688	callbacks will never actually be called (but must be valid neverthelles,	696	callbacks will never actually be called (but must be valid nevertheless,
689	because you never know, you know?).	697	because you never know, you know?).
690		698
691	As another example, the Perl Coro module uses these hooks to integrate	699	As another example, the Perl Coro module uses these hooks to integrate
692	coroutines into libev programs, by yielding to other active coroutines	700	coroutines into libev programs, by yielding to other active coroutines
693	during each prepare and only letting the process block if no coroutines	701	during each prepare and only letting the process block if no coroutines
694	are ready to run (its actually more complicated, it only runs coroutines	702	are ready to run (it's actually more complicated: it only runs coroutines
695	with priority higher than the event loop and one lower priority once,	703	with priority higher than or equal to the event loop and one coroutine
696	using idle watchers to keep the event loop from blocking if lower-priority	704	of lower priority, but only once, using idle watchers to keep the event
697	coroutines exist, thus mapping low-priority coroutines to idle/background	705	loop from blocking if lower-priority coroutines are active, thus mapping
698	tasks).	706	low-priority coroutines to idle/background tasks).
699		707
700	=over 4	708	=over 4
701		709
702	=item ev_prepare_init (ev_prepare *, callback)	710	=item ev_prepare_init (ev_prepare *, callback)
703		711
…		…
718	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	726	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
719		727
720	This function combines a simple timer and an I/O watcher, calls your	728	This function combines a simple timer and an I/O watcher, calls your
721	callback on whichever event happens first and automatically stop both	729	callback on whichever event happens first and automatically stop both
722	watchers. This is useful if you want to wait for a single event on an fd	730	watchers. This is useful if you want to wait for a single event on an fd
723	or timeout without havign to allocate/configure/start/stop/free one or	731	or timeout without having to allocate/configure/start/stop/free one or
724	more watchers yourself.	732	more watchers yourself.
725		733
726	If C<fd> is less than 0, then no I/O watcher will be started and events	734	If C<fd> is less than 0, then no I/O watcher will be started and events
727	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	735	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
728	C<events> set will be craeted and started.	736	C<events> set will be craeted and started.
…		…
731	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	739	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
732	repeat = 0) will be started. While C<0> is a valid timeout, it is of	740	repeat = 0) will be started. While C<0> is a valid timeout, it is of
733	dubious value.	741	dubious value.
734		742
735	The callback has the type C<void (cb)(int revents, void arg)> and gets	743	The callback has the type C<void (cb)(int revents, void arg)> and gets
736	passed an events set like normal event callbacks (with a combination of	744	passed an C<revents> set like normal event callbacks (a combination of
737	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	745	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
738	value passed to C<ev_once>:	746	value passed to C<ev_once>:
739		747
740	static void stdin_ready (int revents, void *arg)	748	static void stdin_ready (int revents, void *arg)
741	{	749	{
…		…
762		770
763	Feed an event as if the given signal occured (loop must be the default loop!).	771	Feed an event as if the given signal occured (loop must be the default loop!).
764		772
765	=back	773	=back
766		774
		775	=head1 LIBEVENT EMULATION
		776
		777	Libev offers a compatibility emulation layer for libevent. It cannot
		778	emulate the internals of libevent, so here are some usage hints:
		779
		780	=over 4
		781
		782	=item * Use it by including <event.h>, as usual.
		783
		784	=item * The following members are fully supported: ev_base, ev_callback,
		785	ev_arg, ev_fd, ev_res, ev_events.
		786
		787	=item * Avoid using ev_flags and the EVLIST_*-macros, while it is
		788	maintained by libev, it does not work exactly the same way as in libevent (consider
		789	it a private API).
		790
		791	=item * Priorities are not currently supported. Initialising priorities
		792	will fail and all watchers will have the same priority, even though there
		793	is an ev_pri field.
		794
		795	=item * Other members are not supported.
		796
		797	=item * The libev emulation is I<not> ABI compatible to libevent, you need
		798	to use the libev header file and library.
		799
		800	=back
		801
		802	=head1 C++ SUPPORT
		803
		804	TBD.
		805
767	=head1 AUTHOR	806	=head1 AUTHOR
768		807
769	Marc Lehmann <libev@schmorp.de>.	808	Marc Lehmann <libev@schmorp.de>.
770		809

Comparing libev/ev.pod (file contents): Revision 1.16 by root, Mon Nov 12 08:47:14 2007 UTC vs. Revision 1.25 by root, Mon Nov 12 21:51:14 2007 UTC

Diff Legend

Comparing libev/ev.pod (file contents):
Revision 1.16 by root, Mon Nov 12 08:47:14 2007 UTC vs.
Revision 1.25 by root, Mon Nov 12 21:51:14 2007 UTC