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

Comparing libev/ev.pod (file contents):
Revision 1.354 by root, Tue Jan 11 01:40:25 2011 UTC vs.
Revision 1.443 by root, Thu Aug 30 21:51:15 2018 UTC

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		1	=encoding utf-8
		2
1	=head1 NAME	3	=head1 NAME
2		4
3	libev - a high performance full-featured event loop written in C	5	libev - a high performance full-featured event loop written in C
4		6
5	=head1 SYNOPSIS	7	=head1 SYNOPSIS
58	ev_timer_start (loop, &timeout_watcher);	60	ev_timer_start (loop, &timeout_watcher);
59		61
60	// now wait for events to arrive	62	// now wait for events to arrive
61	ev_run (loop, 0);	63	ev_run (loop, 0);
62		64
63	// unloop was called, so exit	65	// break was called, so exit
64	return 0;	66	return 0;
65	}	67	}
66		68
67	=head1 ABOUT THIS DOCUMENT	69	=head1 ABOUT THIS DOCUMENT
68		70
…		…
82		84
83	=head1 WHAT TO READ WHEN IN A HURRY	85	=head1 WHAT TO READ WHEN IN A HURRY
84		86
85	This manual tries to be very detailed, but unfortunately, this also makes	87	This manual tries to be very detailed, but unfortunately, this also makes
86	it very long. If you just want to know the basics of libev, I suggest	88	it very long. If you just want to know the basics of libev, I suggest
87	reading L<ANATOMY OF A WATCHER>, then the L<EXAMPLE PROGRAM> above and	89	reading L</ANATOMY OF A WATCHER>, then the L</EXAMPLE PROGRAM> above and
88	look up the missing functions in L<GLOBAL FUNCTIONS> and the C<ev_io> and	90	look up the missing functions in L</GLOBAL FUNCTIONS> and the C<ev_io> and
89	C<ev_timer> sections in L<WATCHER TYPES>.	91	C<ev_timer> sections in L</WATCHER TYPES>.
90		92
91	=head1 ABOUT LIBEV	93	=head1 ABOUT LIBEV
92		94
93	Libev is an event loop: you register interest in certain events (such as a	95	Libev is an event loop: you register interest in certain events (such as a
94	file descriptor being readable or a timeout occurring), and it will manage	96	file descriptor being readable or a timeout occurring), and it will manage
…		…
174	=item ev_tstamp ev_time ()	176	=item ev_tstamp ev_time ()
175		177
176	Returns the current time as libev would use it. Please note that the	178	Returns the current time as libev would use it. Please note that the
177	C<ev_now> function is usually faster and also often returns the timestamp	179	C<ev_now> function is usually faster and also often returns the timestamp
178	you actually want to know. Also interesting is the combination of	180	you actually want to know. Also interesting is the combination of
179	C<ev_update_now> and C<ev_now>.	181	C<ev_now_update> and C<ev_now>.
180		182
181	=item ev_sleep (ev_tstamp interval)	183	=item ev_sleep (ev_tstamp interval)
182		184
183	Sleep for the given interval: The current thread will be blocked until	185	Sleep for the given interval: The current thread will be blocked
184	either it is interrupted or the given time interval has passed. Basically	186	until either it is interrupted or the given time interval has
		187	passed (approximately - it might return a bit earlier even if not
		188	interrupted). Returns immediately if C<< interval <= 0 >>.
		189
185	this is a sub-second-resolution C<sleep ()>.	190	Basically this is a sub-second-resolution C<sleep ()>.
		191
		192	The range of the C<interval> is limited - libev only guarantees to work
		193	with sleep times of up to one day (C<< interval <= 86400 >>).
186		194
187	=item int ev_version_major ()	195	=item int ev_version_major ()
188		196
189	=item int ev_version_minor ()	197	=item int ev_version_minor ()
190		198
…		…
241	the current system, you would need to look at C<ev_embeddable_backends ()	249	the current system, you would need to look at C<ev_embeddable_backends ()
242	& ev_supported_backends ()>, likewise for recommended ones.	250	& ev_supported_backends ()>, likewise for recommended ones.
243		251
244	See the description of C<ev_embed> watchers for more info.	252	See the description of C<ev_embed> watchers for more info.
245		253
246	=item ev_set_allocator (void (cb)(void *ptr, long size))	254	=item ev_set_allocator (void (cb)(void *ptr, long size) throw ())
247		255
248	Sets the allocation function to use (the prototype is similar - the	256	Sets the allocation function to use (the prototype is similar - the
249	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	257	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
250	used to allocate and free memory (no surprises here). If it returns zero	258	used to allocate and free memory (no surprises here). If it returns zero
251	when memory needs to be allocated (C<size != 0>), the library might abort	259	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
277	}	285	}
278		286
279	...	287	...
280	ev_set_allocator (persistent_realloc);	288	ev_set_allocator (persistent_realloc);
281		289
282	=item ev_set_syserr_cb (void (cb)(const char msg))	290	=item ev_set_syserr_cb (void (cb)(const char msg) throw ())
283		291
284	Set the callback function to call on a retryable system call error (such	292	Set the callback function to call on a retryable system call error (such
285	as failed select, poll, epoll_wait). The message is a printable string	293	as failed select, poll, epoll_wait). The message is a printable string
286	indicating the system call or subsystem causing the problem. If this	294	indicating the system call or subsystem causing the problem. If this
287	callback is set, then libev will expect it to remedy the situation, no	295	callback is set, then libev will expect it to remedy the situation, no
…		…
390		398
391	If this flag bit is or'ed into the flag value (or the program runs setuid	399	If this flag bit is or'ed into the flag value (or the program runs setuid
392	or setgid) then libev will I<not> look at the environment variable	400	or setgid) then libev will I<not> look at the environment variable
393	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	401	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
394	override the flags completely if it is found in the environment. This is	402	override the flags completely if it is found in the environment. This is
395	useful to try out specific backends to test their performance, or to work	403	useful to try out specific backends to test their performance, to work
396	around bugs.	404	around bugs, or to make libev threadsafe (accessing environment variables
		405	cannot be done in a threadsafe way, but usually it works if no other
		406	thread modifies them).
397		407
398	=item C<EVFLAG_FORKCHECK>	408	=item C<EVFLAG_FORKCHECK>
399		409
400	Instead of calling C<ev_loop_fork> manually after a fork, you can also	410	Instead of calling C<ev_loop_fork> manually after a fork, you can also
401	make libev check for a fork in each iteration by enabling this flag.	411	make libev check for a fork in each iteration by enabling this flag.
402		412
403	This works by calling C<getpid ()> on every iteration of the loop,	413	This works by calling C<getpid ()> on every iteration of the loop,
404	and thus this might slow down your event loop if you do a lot of loop	414	and thus this might slow down your event loop if you do a lot of loop
405	iterations and little real work, but is usually not noticeable (on my	415	iterations and little real work, but is usually not noticeable (on my
406	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	416	GNU/Linux system for example, C<getpid> is actually a simple 5-insn
407	without a system call and thus I<very> fast, but my GNU/Linux system also has	417	sequence without a system call and thus I<very> fast, but my GNU/Linux
408	C<pthread_atfork> which is even faster).	418	system also has C<pthread_atfork> which is even faster). (Update: glibc
		419	versions 2.25 apparently removed the C<getpid> optimisation again).
409		420
410	The big advantage of this flag is that you can forget about fork (and	421	The big advantage of this flag is that you can forget about fork (and
411	forget about forgetting to tell libev about forking) when you use this	422	forget about forgetting to tell libev about forking, although you still
412	flag.	423	have to ignore C<SIGPIPE>) when you use this flag.
413		424
414	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	425	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
415	environment variable.	426	environment variable.
416		427
417	=item C<EVFLAG_NOINOTIFY>	428	=item C<EVFLAG_NOINOTIFY>
…		…
435	example) that can't properly initialise their signal masks.	446	example) that can't properly initialise their signal masks.
436		447
437	=item C<EVFLAG_NOSIGMASK>	448	=item C<EVFLAG_NOSIGMASK>
438		449
439	When this flag is specified, then libev will avoid to modify the signal	450	When this flag is specified, then libev will avoid to modify the signal
440	mask. Specifically, this means you ahve to make sure signals are unblocked	451	mask. Specifically, this means you have to make sure signals are unblocked
441	when you want to receive them.	452	when you want to receive them.
442		453
443	This behaviour is useful when you want to do your own signal handling, or	454	This behaviour is useful when you want to do your own signal handling, or
444	want to handle signals only in specific threads and want to avoid libev	455	want to handle signals only in specific threads and want to avoid libev
445	unblocking the signals.	456	unblocking the signals.
		457
		458	It's also required by POSIX in a threaded program, as libev calls
		459	C<sigprocmask>, whose behaviour is officially unspecified.
446		460
447	This flag's behaviour will become the default in future versions of libev.	461	This flag's behaviour will become the default in future versions of libev.
448		462
449	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	463	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
450		464
…		…
480	=item C<EVBACKEND_EPOLL> (value 4, Linux)	494	=item C<EVBACKEND_EPOLL> (value 4, Linux)
481		495
482	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9	496	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
483	kernels).	497	kernels).
484		498
485	For few fds, this backend is a bit little slower than poll and select,	499	For few fds, this backend is a bit little slower than poll and select, but
486	but it scales phenomenally better. While poll and select usually scale	500	it scales phenomenally better. While poll and select usually scale like
487	like O(total_fds) where n is the total number of fds (or the highest fd),	501	O(total_fds) where total_fds is the total number of fds (or the highest
488	epoll scales either O(1) or O(active_fds).	502	fd), epoll scales either O(1) or O(active_fds).
489		503
490	The epoll mechanism deserves honorable mention as the most misdesigned	504	The epoll mechanism deserves honorable mention as the most misdesigned
491	of the more advanced event mechanisms: mere annoyances include silently	505	of the more advanced event mechanisms: mere annoyances include silently
492	dropping file descriptors, requiring a system call per change per file	506	dropping file descriptors, requiring a system call per change per file
493	descriptor (and unnecessary guessing of parameters), problems with dup,	507	descriptor (and unnecessary guessing of parameters), problems with dup,
…		…
496	0.1ms) and so on. The biggest issue is fork races, however - if a program	510	0.1ms) and so on. The biggest issue is fork races, however - if a program
497	forks then I<both> parent and child process have to recreate the epoll	511	forks then I<both> parent and child process have to recreate the epoll
498	set, which can take considerable time (one syscall per file descriptor)	512	set, which can take considerable time (one syscall per file descriptor)
499	and is of course hard to detect.	513	and is of course hard to detect.
500		514
501	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	515	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
502	of course I<doesn't>, and epoll just loves to report events for totally	516	but of course I<doesn't>, and epoll just loves to report events for
503	I<different> file descriptors (even already closed ones, so one cannot	517	totally I<different> file descriptors (even already closed ones, so
504	even remove them from the set) than registered in the set (especially	518	one cannot even remove them from the set) than registered in the set
505	on SMP systems). Libev tries to counter these spurious notifications by	519	(especially on SMP systems). Libev tries to counter these spurious
506	employing an additional generation counter and comparing that against the	520	notifications by employing an additional generation counter and comparing
507	events to filter out spurious ones, recreating the set when required. Last	521	that against the events to filter out spurious ones, recreating the set
		522	when required. Epoll also erroneously rounds down timeouts, but gives you
		523	no way to know when and by how much, so sometimes you have to busy-wait
		524	because epoll returns immediately despite a nonzero timeout. And last
508	not least, it also refuses to work with some file descriptors which work	525	not least, it also refuses to work with some file descriptors which work
509	perfectly fine with C<select> (files, many character devices...).	526	perfectly fine with C<select> (files, many character devices...).
510		527
511	Epoll is truly the train wreck analog among event poll mechanisms,	528	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
512	a frankenpoll, cobbled together in a hurry, no thought to design or	529	cobbled together in a hurry, no thought to design or interaction with
513	interaction with others.	530	others. Oh, the pain, will it ever stop...
514		531
515	While stopping, setting and starting an I/O watcher in the same iteration	532	While stopping, setting and starting an I/O watcher in the same iteration
516	will result in some caching, there is still a system call per such	533	will result in some caching, there is still a system call per such
517	incident (because the same I<file descriptor> could point to a different	534	incident (because the same I<file descriptor> could point to a different
518	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	535	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
555		572
556	It scales in the same way as the epoll backend, but the interface to the	573	It scales in the same way as the epoll backend, but the interface to the
557	kernel is more efficient (which says nothing about its actual speed, of	574	kernel is more efficient (which says nothing about its actual speed, of
558	course). While stopping, setting and starting an I/O watcher does never	575	course). While stopping, setting and starting an I/O watcher does never
559	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	576	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
560	two event changes per incident. Support for C<fork ()> is very bad (but	577	two event changes per incident. Support for C<fork ()> is very bad (you
561	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect	578	might have to leak fd's on fork, but it's more sane than epoll) and it
562	cases	579	drops fds silently in similarly hard-to-detect cases.
563		580
564	This backend usually performs well under most conditions.	581	This backend usually performs well under most conditions.
565		582
566	While nominally embeddable in other event loops, this doesn't work	583	While nominally embeddable in other event loops, this doesn't work
567	everywhere, so you might need to test for this. And since it is broken	584	everywhere, so you might need to test for this. And since it is broken
…		…
596	among the OS-specific backends (I vastly prefer correctness over speed	613	among the OS-specific backends (I vastly prefer correctness over speed
597	hacks).	614	hacks).
598		615
599	On the negative side, the interface is I<bizarre> - so bizarre that	616	On the negative side, the interface is I<bizarre> - so bizarre that
600	even sun itself gets it wrong in their code examples: The event polling	617	even sun itself gets it wrong in their code examples: The event polling
601	function sometimes returning events to the caller even though an error	618	function sometimes returns events to the caller even though an error
602	occurred, but with no indication whether it has done so or not (yes, it's	619	occurred, but with no indication whether it has done so or not (yes, it's
603	even documented that way) - deadly for edge-triggered interfaces where	620	even documented that way) - deadly for edge-triggered interfaces where you
604	you absolutely have to know whether an event occurred or not because you	621	absolutely have to know whether an event occurred or not because you have
605	have to re-arm the watcher.	622	to re-arm the watcher.
606		623
607	Fortunately libev seems to be able to work around these idiocies.	624	Fortunately libev seems to be able to work around these idiocies.
608		625
609	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	626	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
610	C<EVBACKEND_POLL>.	627	C<EVBACKEND_POLL>.
…		…
666	If you need dynamically allocated loops it is better to use C<ev_loop_new>	683	If you need dynamically allocated loops it is better to use C<ev_loop_new>
667	and C<ev_loop_destroy>.	684	and C<ev_loop_destroy>.
668		685
669	=item ev_loop_fork (loop)	686	=item ev_loop_fork (loop)
670		687
671	This function sets a flag that causes subsequent C<ev_run> iterations to	688	This function sets a flag that causes subsequent C<ev_run> iterations
672	reinitialise the kernel state for backends that have one. Despite the	689	to reinitialise the kernel state for backends that have one. Despite
673	name, you can call it anytime, but it makes most sense after forking, in	690	the name, you can call it anytime you are allowed to start or stop
674	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the	691	watchers (except inside an C<ev_prepare> callback), but it makes most
		692	sense after forking, in the child process. You I<must> call it (or use
675	child before resuming or calling C<ev_run>.	693	C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>.
676		694
		695	In addition, if you want to reuse a loop (via this function or
		696	C<EVFLAG_FORKCHECK>), you I<also> have to ignore C<SIGPIPE>.
		697
677	Again, you I<have> to call it on I<any> loop that you want to re-use after	698	Again, you I<have> to call it on I<any> loop that you want to re-use after
678	a fork, I<even if you do not plan to use the loop in the parent>. This is	699	a fork, I<even if you do not plan to use the loop in the parent>. This is
679	because some kernel interfaces cough I<kqueue> cough do funny things	700	because some kernel interfaces cough I<kqueue> cough do funny things
680	during fork.	701	during fork.
681		702
682	On the other hand, you only need to call this function in the child	703	On the other hand, you only need to call this function in the child
…		…
752		773
753	This function is rarely useful, but when some event callback runs for a	774	This function is rarely useful, but when some event callback runs for a
754	very long time without entering the event loop, updating libev's idea of	775	very long time without entering the event loop, updating libev's idea of
755	the current time is a good idea.	776	the current time is a good idea.
756		777
757	See also L<The special problem of time updates> in the C<ev_timer> section.	778	See also L</The special problem of time updates> in the C<ev_timer> section.
758		779
759	=item ev_suspend (loop)	780	=item ev_suspend (loop)
760		781
761	=item ev_resume (loop)	782	=item ev_resume (loop)
762		783
…		…
780	without a previous call to C<ev_suspend>.	801	without a previous call to C<ev_suspend>.
781		802
782	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	803	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
783	event loop time (see C<ev_now_update>).	804	event loop time (see C<ev_now_update>).
784		805
785	=item ev_run (loop, int flags)	806	=item bool ev_run (loop, int flags)
786		807
787	Finally, this is it, the event handler. This function usually is called	808	Finally, this is it, the event handler. This function usually is called
788	after you have initialised all your watchers and you want to start	809	after you have initialised all your watchers and you want to start
789	handling events. It will ask the operating system for any new events, call	810	handling events. It will ask the operating system for any new events, call
790	the watcher callbacks, an then repeat the whole process indefinitely: This	811	the watcher callbacks, and then repeat the whole process indefinitely: This
791	is why event loops are called I<loops>.	812	is why event loops are called I<loops>.
792		813
793	If the flags argument is specified as C<0>, it will keep handling events	814	If the flags argument is specified as C<0>, it will keep handling events
794	until either no event watchers are active anymore or C<ev_break> was	815	until either no event watchers are active anymore or C<ev_break> was
795	called.	816	called.
		817
		818	The return value is false if there are no more active watchers (which
		819	usually means "all jobs done" or "deadlock"), and true in all other cases
		820	(which usually means " you should call C<ev_run> again").
796		821
797	Please note that an explicit C<ev_break> is usually better than	822	Please note that an explicit C<ev_break> is usually better than
798	relying on all watchers to be stopped when deciding when a program has	823	relying on all watchers to be stopped when deciding when a program has
799	finished (especially in interactive programs), but having a program	824	finished (especially in interactive programs), but having a program
800	that automatically loops as long as it has to and no longer by virtue	825	that automatically loops as long as it has to and no longer by virtue
801	of relying on its watchers stopping correctly, that is truly a thing of	826	of relying on its watchers stopping correctly, that is truly a thing of
802	beauty.	827	beauty.
803		828
804	This function is also I<mostly> exception-safe - you can break out of	829	This function is I<mostly> exception-safe - you can break out of a
805	a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++	830	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
806	exception and so on. This does not decrement the C<ev_depth> value, nor	831	exception and so on. This does not decrement the C<ev_depth> value, nor
807	will it clear any outstanding C<EVBREAK_ONE> breaks.	832	will it clear any outstanding C<EVBREAK_ONE> breaks.
808		833
809	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle	834	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
810	those events and any already outstanding ones, but will not wait and	835	those events and any already outstanding ones, but will not wait and
…		…
822	This is useful if you are waiting for some external event in conjunction	847	This is useful if you are waiting for some external event in conjunction
823	with something not expressible using other libev watchers (i.e. "roll your	848	with something not expressible using other libev watchers (i.e. "roll your
824	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	849	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
825	usually a better approach for this kind of thing.	850	usually a better approach for this kind of thing.
826		851
827	Here are the gory details of what C<ev_run> does:	852	Here are the gory details of what C<ev_run> does (this is for your
		853	understanding, not a guarantee that things will work exactly like this in
		854	future versions):
828		855
829	- Increment loop depth.	856	- Increment loop depth.
830	- Reset the ev_break status.	857	- Reset the ev_break status.
831	- Before the first iteration, call any pending watchers.	858	- Before the first iteration, call any pending watchers.
832	LOOP:	859	LOOP:
…		…
865	anymore.	892	anymore.
866		893
867	... queue jobs here, make sure they register event watchers as long	894	... queue jobs here, make sure they register event watchers as long
868	... as they still have work to do (even an idle watcher will do..)	895	... as they still have work to do (even an idle watcher will do..)
869	ev_run (my_loop, 0);	896	ev_run (my_loop, 0);
870	... jobs done or somebody called unloop. yeah!	897	... jobs done or somebody called break. yeah!
871		898
872	=item ev_break (loop, how)	899	=item ev_break (loop, how)
873		900
874	Can be used to make a call to C<ev_run> return early (but only after it	901	Can be used to make a call to C<ev_run> return early (but only after it
875	has processed all outstanding events). The C<how> argument must be either	902	has processed all outstanding events). The C<how> argument must be either
…		…
938	overhead for the actual polling but can deliver many events at once.	965	overhead for the actual polling but can deliver many events at once.
939		966
940	By setting a higher I<io collect interval> you allow libev to spend more	967	By setting a higher I<io collect interval> you allow libev to spend more
941	time collecting I/O events, so you can handle more events per iteration,	968	time collecting I/O events, so you can handle more events per iteration,
942	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	969	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
943	C<ev_timer>) will be not affected. Setting this to a non-null value will	970	C<ev_timer>) will not be affected. Setting this to a non-null value will
944	introduce an additional C<ev_sleep ()> call into most loop iterations. The	971	introduce an additional C<ev_sleep ()> call into most loop iterations. The
945	sleep time ensures that libev will not poll for I/O events more often then	972	sleep time ensures that libev will not poll for I/O events more often then
946	once per this interval, on average.	973	once per this interval, on average (as long as the host time resolution is
		974	good enough).
947		975
948	Likewise, by setting a higher I<timeout collect interval> you allow libev	976	Likewise, by setting a higher I<timeout collect interval> you allow libev
949	to spend more time collecting timeouts, at the expense of increased	977	to spend more time collecting timeouts, at the expense of increased
950	latency/jitter/inexactness (the watcher callback will be called	978	latency/jitter/inexactness (the watcher callback will be called
951	later). C<ev_io> watchers will not be affected. Setting this to a non-null	979	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
997	invoke the actual watchers inside another context (another thread etc.).	1025	invoke the actual watchers inside another context (another thread etc.).
998		1026
999	If you want to reset the callback, use C<ev_invoke_pending> as new	1027	If you want to reset the callback, use C<ev_invoke_pending> as new
1000	callback.	1028	callback.
1001		1029
1002	=item ev_set_loop_release_cb (loop, void (release)(EV_P), void (acquire)(EV_P))	1030	=item ev_set_loop_release_cb (loop, void (release)(EV_P) throw (), void (acquire)(EV_P) throw ())
1003		1031
1004	Sometimes you want to share the same loop between multiple threads. This	1032	Sometimes you want to share the same loop between multiple threads. This
1005	can be done relatively simply by putting mutex_lock/unlock calls around	1033	can be done relatively simply by putting mutex_lock/unlock calls around
1006	each call to a libev function.	1034	each call to a libev function.
1007		1035
1008	However, C<ev_run> can run an indefinite time, so it is not feasible	1036	However, C<ev_run> can run an indefinite time, so it is not feasible
1009	to wait for it to return. One way around this is to wake up the event	1037	to wait for it to return. One way around this is to wake up the event
1010	loop via C<ev_break> and C<av_async_send>, another way is to set these	1038	loop via C<ev_break> and C<ev_async_send>, another way is to set these
1011	I<release> and I<acquire> callbacks on the loop.	1039	I<release> and I<acquire> callbacks on the loop.
1012		1040
1013	When set, then C<release> will be called just before the thread is	1041	When set, then C<release> will be called just before the thread is
1014	suspended waiting for new events, and C<acquire> is called just	1042	suspended waiting for new events, and C<acquire> is called just
1015	afterwards.	1043	afterwards.
…		…
1155		1183
1156	=item C<EV_PREPARE>	1184	=item C<EV_PREPARE>
1157		1185
1158	=item C<EV_CHECK>	1186	=item C<EV_CHECK>
1159		1187
1160	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts	1188	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to
1161	to gather new events, and all C<ev_check> watchers are invoked just after	1189	gather new events, and all C<ev_check> watchers are queued (not invoked)
1162	C<ev_run> has gathered them, but before it invokes any callbacks for any	1190	just after C<ev_run> has gathered them, but before it queues any callbacks
		1191	for any received events. That means C<ev_prepare> watchers are the last
		1192	watchers invoked before the event loop sleeps or polls for new events, and
		1193	C<ev_check> watchers will be invoked before any other watchers of the same
		1194	or lower priority within an event loop iteration.
		1195
1163	received events. Callbacks of both watcher types can start and stop as	1196	Callbacks of both watcher types can start and stop as many watchers as
1164	many watchers as they want, and all of them will be taken into account	1197	they want, and all of them will be taken into account (for example, a
1165	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1198	C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from
1166	C<ev_run> from blocking).	1199	blocking).
1167		1200
1168	=item C<EV_EMBED>	1201	=item C<EV_EMBED>
1169		1202
1170	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1203	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1171		1204
…		…
1294		1327
1295	=item callback ev_cb (ev_TYPE *watcher)	1328	=item callback ev_cb (ev_TYPE *watcher)
1296		1329
1297	Returns the callback currently set on the watcher.	1330	Returns the callback currently set on the watcher.
1298		1331
1299	=item ev_cb_set (ev_TYPE *watcher, callback)	1332	=item ev_set_cb (ev_TYPE *watcher, callback)
1300		1333
1301	Change the callback. You can change the callback at virtually any time	1334	Change the callback. You can change the callback at virtually any time
1302	(modulo threads).	1335	(modulo threads).
1303		1336
1304	=item ev_set_priority (ev_TYPE *watcher, int priority)	1337	=item ev_set_priority (ev_TYPE *watcher, int priority)
…		…
1322	or might not have been clamped to the valid range.	1355	or might not have been clamped to the valid range.
1323		1356
1324	The default priority used by watchers when no priority has been set is	1357	The default priority used by watchers when no priority has been set is
1325	always C<0>, which is supposed to not be too high and not be too low :).	1358	always C<0>, which is supposed to not be too high and not be too low :).
1326		1359
1327	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of	1360	See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1328	priorities.	1361	priorities.
1329		1362
1330	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1363	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1331		1364
1332	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1365	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
…		…
1357	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related	1390	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1358	functions that do not need a watcher.	1391	functions that do not need a watcher.
1359		1392
1360	=back	1393	=back
1361		1394
1362	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1395	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
1363		1396	OWN COMPOSITE WATCHERS> idioms.
1364	Each watcher has, by default, a member C<void *data> that you can change
1365	and read at any time: libev will completely ignore it. This can be used
1366	to associate arbitrary data with your watcher. If you need more data and
1367	don't want to allocate memory and store a pointer to it in that data
1368	member, you can also "subclass" the watcher type and provide your own
1369	data:
1370
1371	struct my_io
1372	{
1373	ev_io io;
1374	int otherfd;
1375	void *somedata;
1376	struct whatever *mostinteresting;
1377	};
1378
1379	...
1380	struct my_io w;
1381	ev_io_init (&w.io, my_cb, fd, EV_READ);
1382
1383	And since your callback will be called with a pointer to the watcher, you
1384	can cast it back to your own type:
1385
1386	static void my_cb (struct ev_loop loop, ev_io w_, int revents)
1387	{
1388	struct my_io w = (struct my_io )w_;
1389	...
1390	}
1391
1392	More interesting and less C-conformant ways of casting your callback type
1393	instead have been omitted.
1394
1395	Another common scenario is to use some data structure with multiple
1396	embedded watchers:
1397
1398	struct my_biggy
1399	{
1400	int some_data;
1401	ev_timer t1;
1402	ev_timer t2;
1403	}
1404
1405	In this case getting the pointer to C<my_biggy> is a bit more
1406	complicated: Either you store the address of your C<my_biggy> struct
1407	in the C<data> member of the watcher (for woozies), or you need to use
1408	some pointer arithmetic using C<offsetof> inside your watchers (for real
1409	programmers):
1410
1411	#include <stddef.h>
1412
1413	static void
1414	t1_cb (EV_P_ ev_timer *w, int revents)
1415	{
1416	struct my_biggy big = (struct my_biggy *)
1417	(((char *)w) - offsetof (struct my_biggy, t1));
1418	}
1419
1420	static void
1421	t2_cb (EV_P_ ev_timer *w, int revents)
1422	{
1423	struct my_biggy big = (struct my_biggy *)
1424	(((char *)w) - offsetof (struct my_biggy, t2));
1425	}
1426		1397
1427	=head2 WATCHER STATES	1398	=head2 WATCHER STATES
1428		1399
1429	There are various watcher states mentioned throughout this manual -	1400	There are various watcher states mentioned throughout this manual -
1430	active, pending and so on. In this section these states and the rules to	1401	active, pending and so on. In this section these states and the rules to
1431	transition between them will be described in more detail - and while these	1402	transition between them will be described in more detail - and while these
1432	rules might look complicated, they usually do "the right thing".	1403	rules might look complicated, they usually do "the right thing".
1433		1404
1434	=over 4	1405	=over 4
1435		1406
1436	=item initialiased	1407	=item initialised
1437		1408
1438	Before a watcher can be registered with the event looop it has to be	1409	Before a watcher can be registered with the event loop it has to be
1439	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to	1410	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
1440	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.	1411	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1441		1412
1442	In this state it is simply some block of memory that is suitable for use	1413	In this state it is simply some block of memory that is suitable for
1443	in an event loop. It can be moved around, freed, reused etc. at will.	1414	use in an event loop. It can be moved around, freed, reused etc. at
		1415	will - as long as you either keep the memory contents intact, or call
		1416	C<ev_TYPE_init> again.
1444		1417
1445	=item started/running/active	1418	=item started/running/active
1446		1419
1447	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes	1420	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1448	property of the event loop, and is actively waiting for events. While in	1421	property of the event loop, and is actively waiting for events. While in
…		…
1476	latter will clear any pending state the watcher might be in, regardless	1449	latter will clear any pending state the watcher might be in, regardless
1477	of whether it was active or not, so stopping a watcher explicitly before	1450	of whether it was active or not, so stopping a watcher explicitly before
1478	freeing it is often a good idea.	1451	freeing it is often a good idea.
1479		1452
1480	While stopped (and not pending) the watcher is essentially in the	1453	While stopped (and not pending) the watcher is essentially in the
1481	initialised state, that is it can be reused, moved, modified in any way	1454	initialised state, that is, it can be reused, moved, modified in any way
1482	you wish.	1455	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1456	it again).
1483		1457
1484	=back	1458	=back
1485		1459
1486	=head2 WATCHER PRIORITY MODELS	1460	=head2 WATCHER PRIORITY MODELS
1487		1461
…		…
1680	always get a readiness notification instantly, and your read (or possibly	1654	always get a readiness notification instantly, and your read (or possibly
1681	write) will still block on the disk I/O.	1655	write) will still block on the disk I/O.
1682		1656
1683	Another way to view it is that in the case of sockets, pipes, character	1657	Another way to view it is that in the case of sockets, pipes, character
1684	devices and so on, there is another party (the sender) that delivers data	1658	devices and so on, there is another party (the sender) that delivers data
1685	on it's own, but in the case of files, there is no such thing: the disk	1659	on its own, but in the case of files, there is no such thing: the disk
1686	will not send data on it's own, simply because it doesn't know what you	1660	will not send data on its own, simply because it doesn't know what you
1687	wish to read - you would first have to request some data.	1661	wish to read - you would first have to request some data.
1688		1662
1689	Since files are typically not-so-well supported by advanced notification	1663	Since files are typically not-so-well supported by advanced notification
1690	mechanism, libev tries hard to emulate POSIX behaviour with respect	1664	mechanism, libev tries hard to emulate POSIX behaviour with respect
1691	to files, even though you should not use it. The reason for this is	1665	to files, even though you should not use it. The reason for this is
…		…
1815	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1789	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1816	monotonic clock option helps a lot here).	1790	monotonic clock option helps a lot here).
1817		1791
1818	The callback is guaranteed to be invoked only I<after> its timeout has	1792	The callback is guaranteed to be invoked only I<after> its timeout has
1819	passed (not I<at>, so on systems with very low-resolution clocks this	1793	passed (not I<at>, so on systems with very low-resolution clocks this
1820	might introduce a small delay). If multiple timers become ready during the	1794	might introduce a small delay, see "the special problem of being too
		1795	early", below). If multiple timers become ready during the same loop
1821	same loop iteration then the ones with earlier time-out values are invoked	1796	iteration then the ones with earlier time-out values are invoked before
1822	before ones of the same priority with later time-out values (but this is	1797	ones of the same priority with later time-out values (but this is no
1823	no longer true when a callback calls C<ev_run> recursively).	1798	longer true when a callback calls C<ev_run> recursively).
1824		1799
1825	=head3 Be smart about timeouts	1800	=head3 Be smart about timeouts
1826		1801
1827	Many real-world problems involve some kind of timeout, usually for error	1802	Many real-world problems involve some kind of timeout, usually for error
1828	recovery. A typical example is an HTTP request - if the other side hangs,	1803	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1903		1878
1904	In this case, it would be more efficient to leave the C<ev_timer> alone,	1879	In this case, it would be more efficient to leave the C<ev_timer> alone,
1905	but remember the time of last activity, and check for a real timeout only	1880	but remember the time of last activity, and check for a real timeout only
1906	within the callback:	1881	within the callback:
1907		1882
		1883	ev_tstamp timeout = 60.;
1908	ev_tstamp last_activity; // time of last activity	1884	ev_tstamp last_activity; // time of last activity
		1885	ev_timer timer;
1909		1886
1910	static void	1887	static void
1911	callback (EV_P_ ev_timer *w, int revents)	1888	callback (EV_P_ ev_timer *w, int revents)
1912	{	1889	{
1913	ev_tstamp now = ev_now (EV_A);	1890	// calculate when the timeout would happen
1914	ev_tstamp timeout = last_activity + 60.;	1891	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1915		1892
1916	// if last_activity + 60. is older than now, we did time out	1893	// if negative, it means we the timeout already occurred
1917	if (timeout < now)	1894	if (after < 0.)
1918	{	1895	{
1919	// timeout occurred, take action	1896	// timeout occurred, take action
1920	}	1897	}
1921	else	1898	else
1922	{	1899	{
1923	// callback was invoked, but there was some activity, re-arm	1900	// callback was invoked, but there was some recent
1924	// the watcher to fire in last_activity + 60, which is	1901	// activity. simply restart the timer to time out
1925	// guaranteed to be in the future, so "again" is positive:	1902	// after "after" seconds, which is the earliest time
1926	w->repeat = timeout - now;	1903	// the timeout can occur.
		1904	ev_timer_set (w, after, 0.);
1927	ev_timer_again (EV_A_ w);	1905	ev_timer_start (EV_A_ w);
1928	}	1906	}
1929	}	1907	}
1930		1908
1931	To summarise the callback: first calculate the real timeout (defined	1909	To summarise the callback: first calculate in how many seconds the
1932	as "60 seconds after the last activity"), then check if that time has	1910	timeout will occur (by calculating the absolute time when it would occur,
1933	been reached, which means something I<did>, in fact, time out. Otherwise	1911	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1934	the callback was invoked too early (C<timeout> is in the future), so	1912	(EV_A)> from that).
1935	re-schedule the timer to fire at that future time, to see if maybe we have
1936	a timeout then.
1937		1913
1938	Note how C<ev_timer_again> is used, taking advantage of the	1914	If this value is negative, then we are already past the timeout, i.e. we
1939	C<ev_timer_again> optimisation when the timer is already running.	1915	timed out, and need to do whatever is needed in this case.
		1916
		1917	Otherwise, we now the earliest time at which the timeout would trigger,
		1918	and simply start the timer with this timeout value.
		1919
		1920	In other words, each time the callback is invoked it will check whether
		1921	the timeout occurred. If not, it will simply reschedule itself to check
		1922	again at the earliest time it could time out. Rinse. Repeat.
1940		1923
1941	This scheme causes more callback invocations (about one every 60 seconds	1924	This scheme causes more callback invocations (about one every 60 seconds
1942	minus half the average time between activity), but virtually no calls to	1925	minus half the average time between activity), but virtually no calls to
1943	libev to change the timeout.	1926	libev to change the timeout.
1944		1927
1945	To start the timer, simply initialise the watcher and set C<last_activity>	1928	To start the machinery, simply initialise the watcher and set
1946	to the current time (meaning we just have some activity :), then call the	1929	C<last_activity> to the current time (meaning there was some activity just
1947	callback, which will "do the right thing" and start the timer:	1930	now), then call the callback, which will "do the right thing" and start
		1931	the timer:
1948		1932
		1933	last_activity = ev_now (EV_A);
1949	ev_init (timer, callback);	1934	ev_init (&timer, callback);
1950	last_activity = ev_now (loop);	1935	callback (EV_A_ &timer, 0);
1951	callback (loop, timer, EV_TIMER);
1952		1936
1953	And when there is some activity, simply store the current time in	1937	When there is some activity, simply store the current time in
1954	C<last_activity>, no libev calls at all:	1938	C<last_activity>, no libev calls at all:
1955		1939
		1940	if (activity detected)
1956	last_activity = ev_now (loop);	1941	last_activity = ev_now (EV_A);
		1942
		1943	When your timeout value changes, then the timeout can be changed by simply
		1944	providing a new value, stopping the timer and calling the callback, which
		1945	will again do the right thing (for example, time out immediately :).
		1946
		1947	timeout = new_value;
		1948	ev_timer_stop (EV_A_ &timer);
		1949	callback (EV_A_ &timer, 0);
1957		1950
1958	This technique is slightly more complex, but in most cases where the	1951	This technique is slightly more complex, but in most cases where the
1959	time-out is unlikely to be triggered, much more efficient.	1952	time-out is unlikely to be triggered, much more efficient.
1960
1961	Changing the timeout is trivial as well (if it isn't hard-coded in the
1962	callback :) - just change the timeout and invoke the callback, which will
1963	fix things for you.
1964		1953
1965	=item 4. Wee, just use a double-linked list for your timeouts.	1954	=item 4. Wee, just use a double-linked list for your timeouts.
1966		1955
1967	If there is not one request, but many thousands (millions...), all	1956	If there is not one request, but many thousands (millions...), all
1968	employing some kind of timeout with the same timeout value, then one can	1957	employing some kind of timeout with the same timeout value, then one can
…		…
1995	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	1984	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1996	rather complicated, but extremely efficient, something that really pays	1985	rather complicated, but extremely efficient, something that really pays
1997	off after the first million or so of active timers, i.e. it's usually	1986	off after the first million or so of active timers, i.e. it's usually
1998	overkill :)	1987	overkill :)
1999		1988
		1989	=head3 The special problem of being too early
		1990
		1991	If you ask a timer to call your callback after three seconds, then
		1992	you expect it to be invoked after three seconds - but of course, this
		1993	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		1994	guaranteed to any precision by libev - imagine somebody suspending the
		1995	process with a STOP signal for a few hours for example.
		1996
		1997	So, libev tries to invoke your callback as soon as possible I<after> the
		1998	delay has occurred, but cannot guarantee this.
		1999
		2000	A less obvious failure mode is calling your callback too early: many event
		2001	loops compare timestamps with a "elapsed delay >= requested delay", but
		2002	this can cause your callback to be invoked much earlier than you would
		2003	expect.
		2004
		2005	To see why, imagine a system with a clock that only offers full second
		2006	resolution (think windows if you can't come up with a broken enough OS
		2007	yourself). If you schedule a one-second timer at the time 500.9, then the
		2008	event loop will schedule your timeout to elapse at a system time of 500
		2009	(500.9 truncated to the resolution) + 1, or 501.
		2010
		2011	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2012	501" and invoke the callback 0.1s after it was started, even though a
		2013	one-second delay was requested - this is being "too early", despite best
		2014	intentions.
		2015
		2016	This is the reason why libev will never invoke the callback if the elapsed
		2017	delay equals the requested delay, but only when the elapsed delay is
		2018	larger than the requested delay. In the example above, libev would only invoke
		2019	the callback at system time 502, or 1.1s after the timer was started.
		2020
		2021	So, while libev cannot guarantee that your callback will be invoked
		2022	exactly when requested, it I<can> and I<does> guarantee that the requested
		2023	delay has actually elapsed, or in other words, it always errs on the "too
		2024	late" side of things.
		2025
2000	=head3 The special problem of time updates	2026	=head3 The special problem of time updates
2001		2027
2002	Establishing the current time is a costly operation (it usually takes at	2028	Establishing the current time is a costly operation (it usually takes
2003	least two system calls): EV therefore updates its idea of the current	2029	at least one system call): EV therefore updates its idea of the current
2004	time only before and after C<ev_run> collects new events, which causes a	2030	time only before and after C<ev_run> collects new events, which causes a
2005	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2031	growing difference between C<ev_now ()> and C<ev_time ()> when handling
2006	lots of events in one iteration.	2032	lots of events in one iteration.
2007		2033
2008	The relative timeouts are calculated relative to the C<ev_now ()>	2034	The relative timeouts are calculated relative to the C<ev_now ()>
2009	time. This is usually the right thing as this timestamp refers to the time	2035	time. This is usually the right thing as this timestamp refers to the time
2010	of the event triggering whatever timeout you are modifying/starting. If	2036	of the event triggering whatever timeout you are modifying/starting. If
2011	you suspect event processing to be delayed and you I<need> to base the	2037	you suspect event processing to be delayed and you I<need> to base the
2012	timeout on the current time, use something like this to adjust for this:	2038	timeout on the current time, use something like the following to adjust
		2039	for it:
2013		2040
2014	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2041	ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.);
2015		2042
2016	If the event loop is suspended for a long time, you can also force an	2043	If the event loop is suspended for a long time, you can also force an
2017	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2044	update of the time returned by C<ev_now ()> by calling C<ev_now_update
2018	()>.	2045	()>, although that will push the event time of all outstanding events
		2046	further into the future.
		2047
		2048	=head3 The special problem of unsynchronised clocks
		2049
		2050	Modern systems have a variety of clocks - libev itself uses the normal
		2051	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2052	jumps).
		2053
		2054	Neither of these clocks is synchronised with each other or any other clock
		2055	on the system, so C<ev_time ()> might return a considerably different time
		2056	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2057	a call to C<gettimeofday> might return a second count that is one higher
		2058	than a directly following call to C<time>.
		2059
		2060	The moral of this is to only compare libev-related timestamps with
		2061	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2062	a second or so.
		2063
		2064	One more problem arises due to this lack of synchronisation: if libev uses
		2065	the system monotonic clock and you compare timestamps from C<ev_time>
		2066	or C<ev_now> from when you started your timer and when your callback is
		2067	invoked, you will find that sometimes the callback is a bit "early".
		2068
		2069	This is because C<ev_timer>s work in real time, not wall clock time, so
		2070	libev makes sure your callback is not invoked before the delay happened,
		2071	I<measured according to the real time>, not the system clock.
		2072
		2073	If your timeouts are based on a physical timescale (e.g. "time out this
		2074	connection after 100 seconds") then this shouldn't bother you as it is
		2075	exactly the right behaviour.
		2076
		2077	If you want to compare wall clock/system timestamps to your timers, then
		2078	you need to use C<ev_periodic>s, as these are based on the wall clock
		2079	time, where your comparisons will always generate correct results.
2019		2080
2020	=head3 The special problems of suspended animation	2081	=head3 The special problems of suspended animation
2021		2082
2022	When you leave the server world it is quite customary to hit machines that	2083	When you leave the server world it is quite customary to hit machines that
2023	can suspend/hibernate - what happens to the clocks during such a suspend?	2084	can suspend/hibernate - what happens to the clocks during such a suspend?
…		…
2053		2114
2054	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2115	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
2055		2116
2056	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	2117	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
2057		2118
2058	Configure the timer to trigger after C<after> seconds. If C<repeat>	2119	Configure the timer to trigger after C<after> seconds (fractional and
2059	is C<0.>, then it will automatically be stopped once the timeout is	2120	negative values are supported). If C<repeat> is C<0.>, then it will
2060	reached. If it is positive, then the timer will automatically be	2121	automatically be stopped once the timeout is reached. If it is positive,
2061	configured to trigger again C<repeat> seconds later, again, and again,	2122	then the timer will automatically be configured to trigger again C<repeat>
2062	until stopped manually.	2123	seconds later, again, and again, until stopped manually.
2063		2124
2064	The timer itself will do a best-effort at avoiding drift, that is, if	2125	The timer itself will do a best-effort at avoiding drift, that is, if
2065	you configure a timer to trigger every 10 seconds, then it will normally	2126	you configure a timer to trigger every 10 seconds, then it will normally
2066	trigger at exactly 10 second intervals. If, however, your program cannot	2127	trigger at exactly 10 second intervals. If, however, your program cannot
2067	keep up with the timer (because it takes longer than those 10 seconds to	2128	keep up with the timer (because it takes longer than those 10 seconds to
2068	do stuff) the timer will not fire more than once per event loop iteration.	2129	do stuff) the timer will not fire more than once per event loop iteration.
2069		2130
2070	=item ev_timer_again (loop, ev_timer *)	2131	=item ev_timer_again (loop, ev_timer *)
2071		2132
2072	This will act as if the timer timed out and restart it again if it is	2133	This will act as if the timer timed out, and restarts it again if it is
2073	repeating. The exact semantics are:	2134	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2135	timeout to the C<repeat> value and calling C<ev_timer_start>.
2074		2136
		2137	The exact semantics are as in the following rules, all of which will be
		2138	applied to the watcher:
		2139
		2140	=over 4
		2141
2075	If the timer is pending, its pending status is cleared.	2142	=item If the timer is pending, the pending status is always cleared.
2076		2143
2077	If the timer is started but non-repeating, stop it (as if it timed out).	2144	=item If the timer is started but non-repeating, stop it (as if it timed
		2145	out, without invoking it).
2078		2146
2079	If the timer is repeating, either start it if necessary (with the	2147	=item If the timer is repeating, make the C<repeat> value the new timeout
2080	C<repeat> value), or reset the running timer to the C<repeat> value.	2148	and start the timer, if necessary.
2081		2149
		2150	=back
		2151
2082	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2152	This sounds a bit complicated, see L</Be smart about timeouts>, above, for a
2083	usage example.	2153	usage example.
2084		2154
2085	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)	2155	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
2086		2156
2087	Returns the remaining time until a timer fires. If the timer is active,	2157	Returns the remaining time until a timer fires. If the timer is active,
…		…
2140	Periodic watchers are also timers of a kind, but they are very versatile	2210	Periodic watchers are also timers of a kind, but they are very versatile
2141	(and unfortunately a bit complex).	2211	(and unfortunately a bit complex).
2142		2212
2143	Unlike C<ev_timer>, periodic watchers are not based on real time (or	2213	Unlike C<ev_timer>, periodic watchers are not based on real time (or
2144	relative time, the physical time that passes) but on wall clock time	2214	relative time, the physical time that passes) but on wall clock time
2145	(absolute time, the thing you can read on your calender or clock). The	2215	(absolute time, the thing you can read on your calendar or clock). The
2146	difference is that wall clock time can run faster or slower than real	2216	difference is that wall clock time can run faster or slower than real
2147	time, and time jumps are not uncommon (e.g. when you adjust your	2217	time, and time jumps are not uncommon (e.g. when you adjust your
2148	wrist-watch).	2218	wrist-watch).
2149		2219
2150	You can tell a periodic watcher to trigger after some specific point	2220	You can tell a periodic watcher to trigger after some specific point
…		…
2207		2277
2208	Another way to think about it (for the mathematically inclined) is that	2278	Another way to think about it (for the mathematically inclined) is that
2209	C<ev_periodic> will try to run the callback in this mode at the next possible	2279	C<ev_periodic> will try to run the callback in this mode at the next possible
2210	time where C<time = offset (mod interval)>, regardless of any time jumps.	2280	time where C<time = offset (mod interval)>, regardless of any time jumps.
2211		2281
2212	For numerical stability it is preferable that the C<offset> value is near	2282	The C<interval> I<MUST> be positive, and for numerical stability, the
2213	C<ev_now ()> (the current time), but there is no range requirement for	2283	interval value should be higher than C<1/8192> (which is around 100
2214	this value, and in fact is often specified as zero.	2284	microseconds) and C<offset> should be higher than C<0> and should have
		2285	at most a similar magnitude as the current time (say, within a factor of
		2286	ten). Typical values for offset are, in fact, C<0> or something between
		2287	C<0> and C<interval>, which is also the recommended range.
2215		2288
2216	Note also that there is an upper limit to how often a timer can fire (CPU	2289	Note also that there is an upper limit to how often a timer can fire (CPU
2217	speed for example), so if C<interval> is very small then timing stability	2290	speed for example), so if C<interval> is very small then timing stability
2218	will of course deteriorate. Libev itself tries to be exact to be about one	2291	will of course deteriorate. Libev itself tries to be exact to be about one
2219	millisecond (if the OS supports it and the machine is fast enough).	2292	millisecond (if the OS supports it and the machine is fast enough).
…		…
2327		2400
2328	ev_periodic hourly_tick;	2401	ev_periodic hourly_tick;
2329	ev_periodic_init (&hourly_tick, clock_cb,	2402	ev_periodic_init (&hourly_tick, clock_cb,
2330	fmod (ev_now (loop), 3600.), 3600., 0);	2403	fmod (ev_now (loop), 3600.), 3600., 0);
2331	ev_periodic_start (loop, &hourly_tick);	2404	ev_periodic_start (loop, &hourly_tick);
2332		2405
2333		2406
2334	=head2 C<ev_signal> - signal me when a signal gets signalled!	2407	=head2 C<ev_signal> - signal me when a signal gets signalled!
2335		2408
2336	Signal watchers will trigger an event when the process receives a specific	2409	Signal watchers will trigger an event when the process receives a specific
2337	signal one or more times. Even though signals are very asynchronous, libev	2410	signal one or more times. Even though signals are very asynchronous, libev
…		…
2347	only within the same loop, i.e. you can watch for C<SIGINT> in your	2420	only within the same loop, i.e. you can watch for C<SIGINT> in your
2348	default loop and for C<SIGIO> in another loop, but you cannot watch for	2421	default loop and for C<SIGIO> in another loop, but you cannot watch for
2349	C<SIGINT> in both the default loop and another loop at the same time. At	2422	C<SIGINT> in both the default loop and another loop at the same time. At
2350	the moment, C<SIGCHLD> is permanently tied to the default loop.	2423	the moment, C<SIGCHLD> is permanently tied to the default loop.
2351		2424
2352	When the first watcher gets started will libev actually register something	2425	Only after the first watcher for a signal is started will libev actually
2353	with the kernel (thus it coexists with your own signal handlers as long as	2426	register something with the kernel. It thus coexists with your own signal
2354	you don't register any with libev for the same signal).	2427	handlers as long as you don't register any with libev for the same signal.
2355		2428
2356	If possible and supported, libev will install its handlers with	2429	If possible and supported, libev will install its handlers with
2357	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should	2430	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
2358	not be unduly interrupted. If you have a problem with system calls getting	2431	not be unduly interrupted. If you have a problem with system calls getting
2359	interrupted by signals you can block all signals in an C<ev_check> watcher	2432	interrupted by signals you can block all signals in an C<ev_check> watcher
…		…
2362	=head3 The special problem of inheritance over fork/execve/pthread_create	2435	=head3 The special problem of inheritance over fork/execve/pthread_create
2363		2436
2364	Both the signal mask (C<sigprocmask>) and the signal disposition	2437	Both the signal mask (C<sigprocmask>) and the signal disposition
2365	(C<sigaction>) are unspecified after starting a signal watcher (and after	2438	(C<sigaction>) are unspecified after starting a signal watcher (and after
2366	stopping it again), that is, libev might or might not block the signal,	2439	stopping it again), that is, libev might or might not block the signal,
2367	and might or might not set or restore the installed signal handler.	2440	and might or might not set or restore the installed signal handler (but
		2441	see C<EVFLAG_NOSIGMASK>).
2368		2442
2369	While this does not matter for the signal disposition (libev never	2443	While this does not matter for the signal disposition (libev never
2370	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on	2444	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
2371	C<execve>), this matters for the signal mask: many programs do not expect	2445	C<execve>), this matters for the signal mask: many programs do not expect
2372	certain signals to be blocked.	2446	certain signals to be blocked.
…		…
2543		2617
2544	=head2 C<ev_stat> - did the file attributes just change?	2618	=head2 C<ev_stat> - did the file attributes just change?
2545		2619
2546	This watches a file system path for attribute changes. That is, it calls	2620	This watches a file system path for attribute changes. That is, it calls
2547	C<stat> on that path in regular intervals (or when the OS says it changed)	2621	C<stat> on that path in regular intervals (or when the OS says it changed)
2548	and sees if it changed compared to the last time, invoking the callback if	2622	and sees if it changed compared to the last time, invoking the callback
2549	it did.	2623	if it did. Starting the watcher C<stat>'s the file, so only changes that
		2624	happen after the watcher has been started will be reported.
2550		2625
2551	The path does not need to exist: changing from "path exists" to "path does	2626	The path does not need to exist: changing from "path exists" to "path does
2552	not exist" is a status change like any other. The condition "path does not	2627	not exist" is a status change like any other. The condition "path does not
2553	exist" (or more correctly "path cannot be stat'ed") is signified by the	2628	exist" (or more correctly "path cannot be stat'ed") is signified by the
2554	C<st_nlink> field being zero (which is otherwise always forced to be at	2629	C<st_nlink> field being zero (which is otherwise always forced to be at
…		…
2784	Apart from keeping your process non-blocking (which is a useful	2859	Apart from keeping your process non-blocking (which is a useful
2785	effect on its own sometimes), idle watchers are a good place to do	2860	effect on its own sometimes), idle watchers are a good place to do
2786	"pseudo-background processing", or delay processing stuff to after the	2861	"pseudo-background processing", or delay processing stuff to after the
2787	event loop has handled all outstanding events.	2862	event loop has handled all outstanding events.
2788		2863
		2864	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2865
		2866	As long as there is at least one active idle watcher, libev will never
		2867	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2868	For this to work, the idle watcher doesn't need to be invoked at all - the
		2869	lowest priority will do.
		2870
		2871	This mode of operation can be useful together with an C<ev_check> watcher,
		2872	to do something on each event loop iteration - for example to balance load
		2873	between different connections.
		2874
		2875	See L</Abusing an ev_check watcher for its side-effect> for a longer
		2876	example.
		2877
2789	=head3 Watcher-Specific Functions and Data Members	2878	=head3 Watcher-Specific Functions and Data Members
2790		2879
2791	=over 4	2880	=over 4
2792		2881
2793	=item ev_idle_init (ev_idle *, callback)	2882	=item ev_idle_init (ev_idle *, callback)
…		…
2804	callback, free it. Also, use no error checking, as usual.	2893	callback, free it. Also, use no error checking, as usual.
2805		2894
2806	static void	2895	static void
2807	idle_cb (struct ev_loop loop, ev_idle w, int revents)	2896	idle_cb (struct ev_loop loop, ev_idle w, int revents)
2808	{	2897	{
		2898	// stop the watcher
		2899	ev_idle_stop (loop, w);
		2900
		2901	// now we can free it
2809	free (w);	2902	free (w);
		2903
2810	// now do something you wanted to do when the program has	2904	// now do something you wanted to do when the program has
2811	// no longer anything immediate to do.	2905	// no longer anything immediate to do.
2812	}	2906	}
2813		2907
2814	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2908	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
…		…
2816	ev_idle_start (loop, idle_watcher);	2910	ev_idle_start (loop, idle_watcher);
2817		2911
2818		2912
2819	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2913	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2820		2914
2821	Prepare and check watchers are usually (but not always) used in pairs:	2915	Prepare and check watchers are often (but not always) used in pairs:
2822	prepare watchers get invoked before the process blocks and check watchers	2916	prepare watchers get invoked before the process blocks and check watchers
2823	afterwards.	2917	afterwards.
2824		2918
2825	You I<must not> call C<ev_run> or similar functions that enter	2919	You I<must not> call C<ev_run> (or similar functions that enter the
2826	the current event loop from either C<ev_prepare> or C<ev_check>	2920	current event loop) or C<ev_loop_fork> from either C<ev_prepare> or
2827	watchers. Other loops than the current one are fine, however. The	2921	C<ev_check> watchers. Other loops than the current one are fine,
2828	rationale behind this is that you do not need to check for recursion in	2922	however. The rationale behind this is that you do not need to check
2829	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2923	for recursion in those watchers, i.e. the sequence will always be
2830	C<ev_check> so if you have one watcher of each kind they will always be	2924	C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each
2831	called in pairs bracketing the blocking call.	2925	kind they will always be called in pairs bracketing the blocking call.
2832		2926
2833	Their main purpose is to integrate other event mechanisms into libev and	2927	Their main purpose is to integrate other event mechanisms into libev and
2834	their use is somewhat advanced. They could be used, for example, to track	2928	their use is somewhat advanced. They could be used, for example, to track
2835	variable changes, implement your own watchers, integrate net-snmp or a	2929	variable changes, implement your own watchers, integrate net-snmp or a
2836	coroutine library and lots more. They are also occasionally useful if	2930	coroutine library and lots more. They are also occasionally useful if
…		…
2854	with priority higher than or equal to the event loop and one coroutine	2948	with priority higher than or equal to the event loop and one coroutine
2855	of lower priority, but only once, using idle watchers to keep the event	2949	of lower priority, but only once, using idle watchers to keep the event
2856	loop from blocking if lower-priority coroutines are active, thus mapping	2950	loop from blocking if lower-priority coroutines are active, thus mapping
2857	low-priority coroutines to idle/background tasks).	2951	low-priority coroutines to idle/background tasks).
2858		2952
2859	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2953	When used for this purpose, it is recommended to give C<ev_check> watchers
2860	priority, to ensure that they are being run before any other watchers	2954	highest (C<EV_MAXPRI>) priority, to ensure that they are being run before
2861	after the poll (this doesn't matter for C<ev_prepare> watchers).	2955	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		2956	watchers).
2862		2957
2863	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	2958	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
2864	activate ("feed") events into libev. While libev fully supports this, they	2959	activate ("feed") events into libev. While libev fully supports this, they
2865	might get executed before other C<ev_check> watchers did their job. As	2960	might get executed before other C<ev_check> watchers did their job. As
2866	C<ev_check> watchers are often used to embed other (non-libev) event	2961	C<ev_check> watchers are often used to embed other (non-libev) event
2867	loops those other event loops might be in an unusable state until their	2962	loops those other event loops might be in an unusable state until their
2868	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	2963	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2869	others).	2964	others).
		2965
		2966	=head3 Abusing an C<ev_check> watcher for its side-effect
		2967
		2968	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		2969	useful because they are called once per event loop iteration. For
		2970	example, if you want to handle a large number of connections fairly, you
		2971	normally only do a bit of work for each active connection, and if there
		2972	is more work to do, you wait for the next event loop iteration, so other
		2973	connections have a chance of making progress.
		2974
		2975	Using an C<ev_check> watcher is almost enough: it will be called on the
		2976	next event loop iteration. However, that isn't as soon as possible -
		2977	without external events, your C<ev_check> watcher will not be invoked.
		2978
		2979	This is where C<ev_idle> watchers come in handy - all you need is a
		2980	single global idle watcher that is active as long as you have one active
		2981	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		2982	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		2983	invoked. Neither watcher alone can do that.
2870		2984
2871	=head3 Watcher-Specific Functions and Data Members	2985	=head3 Watcher-Specific Functions and Data Members
2872		2986
2873	=over 4	2987	=over 4
2874		2988
…		…
3075		3189
3076	=over 4	3190	=over 4
3077		3191
3078	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)	3192	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)
3079		3193
3080	=item ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)	3194	=item ev_embed_set (ev_embed , struct ev_loop embedded_loop)
3081		3195
3082	Configures the watcher to embed the given loop, which must be	3196	Configures the watcher to embed the given loop, which must be
3083	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	3197	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
3084	invoked automatically, otherwise it is the responsibility of the callback	3198	invoked automatically, otherwise it is the responsibility of the callback
3085	to invoke it (it will continue to be called until the sweep has been done,	3199	to invoke it (it will continue to be called until the sweep has been done,
…		…
3106	used).	3220	used).
3107		3221
3108	struct ev_loop *loop_hi = ev_default_init (0);	3222	struct ev_loop *loop_hi = ev_default_init (0);
3109	struct ev_loop *loop_lo = 0;	3223	struct ev_loop *loop_lo = 0;
3110	ev_embed embed;	3224	ev_embed embed;
3111		3225
3112	// see if there is a chance of getting one that works	3226	// see if there is a chance of getting one that works
3113	// (remember that a flags value of 0 means autodetection)	3227	// (remember that a flags value of 0 means autodetection)
3114	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3228	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
3115	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3229	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
3116	: 0;	3230	: 0;
…		…
3130	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3244	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
3131		3245
3132	struct ev_loop *loop = ev_default_init (0);	3246	struct ev_loop *loop = ev_default_init (0);
3133	struct ev_loop *loop_socket = 0;	3247	struct ev_loop *loop_socket = 0;
3134	ev_embed embed;	3248	ev_embed embed;
3135		3249
3136	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3250	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
3137	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3251	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
3138	{	3252	{
3139	ev_embed_init (&embed, 0, loop_socket);	3253	ev_embed_init (&embed, 0, loop_socket);
3140	ev_embed_start (loop, &embed);	3254	ev_embed_start (loop, &embed);
…		…
3148		3262
3149	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3263	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
3150		3264
3151	Fork watchers are called when a C<fork ()> was detected (usually because	3265	Fork watchers are called when a C<fork ()> was detected (usually because
3152	whoever is a good citizen cared to tell libev about it by calling	3266	whoever is a good citizen cared to tell libev about it by calling
3153	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the	3267	C<ev_loop_fork>). The invocation is done before the event loop blocks next
3154	event loop blocks next and before C<ev_check> watchers are being called,	3268	and before C<ev_check> watchers are being called, and only in the child
3155	and only in the child after the fork. If whoever good citizen calling	3269	after the fork. If whoever good citizen calling C<ev_default_fork> cheats
3156	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3270	and calls it in the wrong process, the fork handlers will be invoked, too,
3157	handlers will be invoked, too, of course.	3271	of course.
3158		3272
3159	=head3 The special problem of life after fork - how is it possible?	3273	=head3 The special problem of life after fork - how is it possible?
3160		3274
3161	Most uses of C<fork()> consist of forking, then some simple calls to set	3275	Most uses of C<fork ()> consist of forking, then some simple calls to set
3162	up/change the process environment, followed by a call to C<exec()>. This	3276	up/change the process environment, followed by a call to C<exec()>. This
3163	sequence should be handled by libev without any problems.	3277	sequence should be handled by libev without any problems.
3164		3278
3165	This changes when the application actually wants to do event handling	3279	This changes when the application actually wants to do event handling
3166	in the child, or both parent in child, in effect "continuing" after the	3280	in the child, or both parent in child, in effect "continuing" after the
…		…
3243	atexit (program_exits);	3357	atexit (program_exits);
3244		3358
3245		3359
3246	=head2 C<ev_async> - how to wake up an event loop	3360	=head2 C<ev_async> - how to wake up an event loop
3247		3361
3248	In general, you cannot use an C<ev_run> from multiple threads or other	3362	In general, you cannot use an C<ev_loop> from multiple threads or other
3249	asynchronous sources such as signal handlers (as opposed to multiple event	3363	asynchronous sources such as signal handlers (as opposed to multiple event
3250	loops - those are of course safe to use in different threads).	3364	loops - those are of course safe to use in different threads).
3251		3365
3252	Sometimes, however, you need to wake up an event loop you do not control,	3366	Sometimes, however, you need to wake up an event loop you do not control,
3253	for example because it belongs to another thread. This is what C<ev_async>	3367	for example because it belongs to another thread. This is what C<ev_async>
…		…
3255	it by calling C<ev_async_send>, which is thread- and signal safe.	3369	it by calling C<ev_async_send>, which is thread- and signal safe.
3256		3370
3257	This functionality is very similar to C<ev_signal> watchers, as signals,	3371	This functionality is very similar to C<ev_signal> watchers, as signals,
3258	too, are asynchronous in nature, and signals, too, will be compressed	3372	too, are asynchronous in nature, and signals, too, will be compressed
3259	(i.e. the number of callback invocations may be less than the number of	3373	(i.e. the number of callback invocations may be less than the number of
3260	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind	3374	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
3261	of "global async watchers" by using a watcher on an otherwise unused	3375	of "global async watchers" by using a watcher on an otherwise unused
3262	signal, and C<ev_feed_signal> to signal this watcher from another thread,	3376	signal, and C<ev_feed_signal> to signal this watcher from another thread,
3263	even without knowing which loop owns the signal.	3377	even without knowing which loop owns the signal.
3264
3265	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
3266	just the default loop.
3267		3378
3268	=head3 Queueing	3379	=head3 Queueing
3269		3380
3270	C<ev_async> does not support queueing of data in any way. The reason	3381	C<ev_async> does not support queueing of data in any way. The reason
3271	is that the author does not know of a simple (or any) algorithm for a	3382	is that the author does not know of a simple (or any) algorithm for a
…		…
3363	trust me.	3474	trust me.
3364		3475
3365	=item ev_async_send (loop, ev_async *)	3476	=item ev_async_send (loop, ev_async *)
3366		3477
3367	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3478	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3368	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3479	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3480	returns.
		3481
3369	C<ev_feed_event>, this call is safe to do from other threads, signal or	3482	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3370	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3483	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3371	section below on what exactly this means).	3484	embedding section below on what exactly this means).
3372		3485
3373	Note that, as with other watchers in libev, multiple events might get	3486	Note that, as with other watchers in libev, multiple events might get
3374	compressed into a single callback invocation (another way to look at this	3487	compressed into a single callback invocation (another way to look at
3375	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3488	this is that C<ev_async> watchers are level-triggered: they are set on
3376	reset when the event loop detects that).	3489	C<ev_async_send>, reset when the event loop detects that).
3377		3490
3378	This call incurs the overhead of a system call only once per event loop	3491	This call incurs the overhead of at most one extra system call per event
3379	iteration, so while the overhead might be noticeable, it doesn't apply to	3492	loop iteration, if the event loop is blocked, and no syscall at all if
3380	repeated calls to C<ev_async_send> for the same event loop.	3493	the event loop (or your program) is processing events. That means that
		3494	repeated calls are basically free (there is no need to avoid calls for
		3495	performance reasons) and that the overhead becomes smaller (typically
		3496	zero) under load.
3381		3497
3382	=item bool = ev_async_pending (ev_async *)	3498	=item bool = ev_async_pending (ev_async *)
3383		3499
3384	Returns a non-zero value when C<ev_async_send> has been called on the	3500	Returns a non-zero value when C<ev_async_send> has been called on the
3385	watcher but the event has not yet been processed (or even noted) by the	3501	watcher but the event has not yet been processed (or even noted) by the
…		…
3402		3518
3403	There are some other functions of possible interest. Described. Here. Now.	3519	There are some other functions of possible interest. Described. Here. Now.
3404		3520
3405	=over 4	3521	=over 4
3406		3522
3407	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3523	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg)
3408		3524
3409	This function combines a simple timer and an I/O watcher, calls your	3525	This function combines a simple timer and an I/O watcher, calls your
3410	callback on whichever event happens first and automatically stops both	3526	callback on whichever event happens first and automatically stops both
3411	watchers. This is useful if you want to wait for a single event on an fd	3527	watchers. This is useful if you want to wait for a single event on an fd
3412	or timeout without having to allocate/configure/start/stop/free one or	3528	or timeout without having to allocate/configure/start/stop/free one or
…		…
3440	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3556	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3441		3557
3442	=item ev_feed_fd_event (loop, int fd, int revents)	3558	=item ev_feed_fd_event (loop, int fd, int revents)
3443		3559
3444	Feed an event on the given fd, as if a file descriptor backend detected	3560	Feed an event on the given fd, as if a file descriptor backend detected
3445	the given events it.	3561	the given events.
3446		3562
3447	=item ev_feed_signal_event (loop, int signum)	3563	=item ev_feed_signal_event (loop, int signum)
3448		3564
3449	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,	3565	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3450	which is async-safe.	3566	which is async-safe.
…		…
3456		3572
3457	This section explains some common idioms that are not immediately	3573	This section explains some common idioms that are not immediately
3458	obvious. Note that examples are sprinkled over the whole manual, and this	3574	obvious. Note that examples are sprinkled over the whole manual, and this
3459	section only contains stuff that wouldn't fit anywhere else.	3575	section only contains stuff that wouldn't fit anywhere else.
3460		3576
3461	=over 4	3577	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
3462		3578
3463	=item Model/nested event loop invocations and exit conditions.	3579	Each watcher has, by default, a C<void *data> member that you can read
		3580	or modify at any time: libev will completely ignore it. This can be used
		3581	to associate arbitrary data with your watcher. If you need more data and
		3582	don't want to allocate memory separately and store a pointer to it in that
		3583	data member, you can also "subclass" the watcher type and provide your own
		3584	data:
		3585
		3586	struct my_io
		3587	{
		3588	ev_io io;
		3589	int otherfd;
		3590	void *somedata;
		3591	struct whatever *mostinteresting;
		3592	};
		3593
		3594	...
		3595	struct my_io w;
		3596	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3597
		3598	And since your callback will be called with a pointer to the watcher, you
		3599	can cast it back to your own type:
		3600
		3601	static void my_cb (struct ev_loop loop, ev_io w_, int revents)
		3602	{
		3603	struct my_io w = (struct my_io )w_;
		3604	...
		3605	}
		3606
		3607	More interesting and less C-conformant ways of casting your callback
		3608	function type instead have been omitted.
		3609
		3610	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3611
		3612	Another common scenario is to use some data structure with multiple
		3613	embedded watchers, in effect creating your own watcher that combines
		3614	multiple libev event sources into one "super-watcher":
		3615
		3616	struct my_biggy
		3617	{
		3618	int some_data;
		3619	ev_timer t1;
		3620	ev_timer t2;
		3621	}
		3622
		3623	In this case getting the pointer to C<my_biggy> is a bit more
		3624	complicated: Either you store the address of your C<my_biggy> struct in
		3625	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3626	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3627	real programmers):
		3628
		3629	#include <stddef.h>
		3630
		3631	static void
		3632	t1_cb (EV_P_ ev_timer *w, int revents)
		3633	{
		3634	struct my_biggy big = (struct my_biggy *)
		3635	(((char *)w) - offsetof (struct my_biggy, t1));
		3636	}
		3637
		3638	static void
		3639	t2_cb (EV_P_ ev_timer *w, int revents)
		3640	{
		3641	struct my_biggy big = (struct my_biggy *)
		3642	(((char *)w) - offsetof (struct my_biggy, t2));
		3643	}
		3644
		3645	=head2 AVOIDING FINISHING BEFORE RETURNING
		3646
		3647	Often you have structures like this in event-based programs:
		3648
		3649	callback ()
		3650	{
		3651	free (request);
		3652	}
		3653
		3654	request = start_new_request (..., callback);
		3655
		3656	The intent is to start some "lengthy" operation. The C<request> could be
		3657	used to cancel the operation, or do other things with it.
		3658
		3659	It's not uncommon to have code paths in C<start_new_request> that
		3660	immediately invoke the callback, for example, to report errors. Or you add
		3661	some caching layer that finds that it can skip the lengthy aspects of the
		3662	operation and simply invoke the callback with the result.
		3663
		3664	The problem here is that this will happen I<before> C<start_new_request>
		3665	has returned, so C<request> is not set.
		3666
		3667	Even if you pass the request by some safer means to the callback, you
		3668	might want to do something to the request after starting it, such as
		3669	canceling it, which probably isn't working so well when the callback has
		3670	already been invoked.
		3671
		3672	A common way around all these issues is to make sure that
		3673	C<start_new_request> I<always> returns before the callback is invoked. If
		3674	C<start_new_request> immediately knows the result, it can artificially
		3675	delay invoking the callback by using a C<prepare> or C<idle> watcher for
		3676	example, or more sneakily, by reusing an existing (stopped) watcher and
		3677	pushing it into the pending queue:
		3678
		3679	ev_set_cb (watcher, callback);
		3680	ev_feed_event (EV_A_ watcher, 0);
		3681
		3682	This way, C<start_new_request> can safely return before the callback is
		3683	invoked, while not delaying callback invocation too much.
		3684
		3685	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
3464		3686
3465	Often (especially in GUI toolkits) there are places where you have	3687	Often (especially in GUI toolkits) there are places where you have
3466	I<modal> interaction, which is most easily implemented by recursively	3688	I<modal> interaction, which is most easily implemented by recursively
3467	invoking C<ev_run>.	3689	invoking C<ev_run>.
3468		3690
3469	This brings the problem of exiting - a callback might want to finish the	3691	This brings the problem of exiting - a callback might want to finish the
3470	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but	3692	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
3471	a modal "Are you sure?" dialog is still waiting), or just the nested one	3693	a modal "Are you sure?" dialog is still waiting), or just the nested one
3472	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some	3694	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
3473	other combination: In these cases, C<ev_break> will not work alone.	3695	other combination: In these cases, a simple C<ev_break> will not work.
3474		3696
3475	The solution is to maintain "break this loop" variable for each C<ev_run>	3697	The solution is to maintain "break this loop" variable for each C<ev_run>
3476	invocation, and use a loop around C<ev_run> until the condition is	3698	invocation, and use a loop around C<ev_run> until the condition is
3477	triggered, using C<EVRUN_ONCE>:	3699	triggered, using C<EVRUN_ONCE>:
3478		3700
…		…
3480	int exit_main_loop = 0;	3702	int exit_main_loop = 0;
3481		3703
3482	while (!exit_main_loop)	3704	while (!exit_main_loop)
3483	ev_run (EV_DEFAULT_ EVRUN_ONCE);	3705	ev_run (EV_DEFAULT_ EVRUN_ONCE);
3484		3706
3485	// in a model watcher	3707	// in a modal watcher
3486	int exit_nested_loop = 0;	3708	int exit_nested_loop = 0;
3487		3709
3488	while (!exit_nested_loop)	3710	while (!exit_nested_loop)
3489	ev_run (EV_A_ EVRUN_ONCE);	3711	ev_run (EV_A_ EVRUN_ONCE);
3490		3712
…		…
3497	exit_main_loop = 1;	3719	exit_main_loop = 1;
3498		3720
3499	// exit both	3721	// exit both
3500	exit_main_loop = exit_nested_loop = 1;	3722	exit_main_loop = exit_nested_loop = 1;
3501		3723
3502	=item Thread locking example	3724	=head2 THREAD LOCKING EXAMPLE
3503		3725
3504	Here is a fictitious example of how to run an event loop in a different	3726	Here is a fictitious example of how to run an event loop in a different
3505	thread than where callbacks are being invoked and watchers are	3727	thread from where callbacks are being invoked and watchers are
3506	created/added/removed.	3728	created/added/removed.
3507		3729
3508	For a real-world example, see the C<EV::Loop::Async> perl module,	3730	For a real-world example, see the C<EV::Loop::Async> perl module,
3509	which uses exactly this technique (which is suited for many high-level	3731	which uses exactly this technique (which is suited for many high-level
3510	languages).	3732	languages).
…		…
3536	// now associate this with the loop	3758	// now associate this with the loop
3537	ev_set_userdata (EV_A_ u);	3759	ev_set_userdata (EV_A_ u);
3538	ev_set_invoke_pending_cb (EV_A_ l_invoke);	3760	ev_set_invoke_pending_cb (EV_A_ l_invoke);
3539	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);	3761	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
3540		3762
3541	// then create the thread running ev_loop	3763	// then create the thread running ev_run
3542	pthread_create (&u->tid, 0, l_run, EV_A);	3764	pthread_create (&u->tid, 0, l_run, EV_A);
3543	}	3765	}
3544		3766
3545	The callback for the C<ev_async> watcher does nothing: the watcher is used	3767	The callback for the C<ev_async> watcher does nothing: the watcher is used
3546	solely to wake up the event loop so it takes notice of any new watchers	3768	solely to wake up the event loop so it takes notice of any new watchers
…		…
3635	Note that sending the C<ev_async> watcher is required because otherwise	3857	Note that sending the C<ev_async> watcher is required because otherwise
3636	an event loop currently blocking in the kernel will have no knowledge	3858	an event loop currently blocking in the kernel will have no knowledge
3637	about the newly added timer. By waking up the loop it will pick up any new	3859	about the newly added timer. By waking up the loop it will pick up any new
3638	watchers in the next event loop iteration.	3860	watchers in the next event loop iteration.
3639		3861
3640	=back	3862	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3863
		3864	While the overhead of a callback that e.g. schedules a thread is small, it
		3865	is still an overhead. If you embed libev, and your main usage is with some
		3866	kind of threads or coroutines, you might want to customise libev so that
		3867	doesn't need callbacks anymore.
		3868
		3869	Imagine you have coroutines that you can switch to using a function
		3870	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3871	and that due to some magic, the currently active coroutine is stored in a
		3872	global called C<current_coro>. Then you can build your own "wait for libev
		3873	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3874	the differing C<;> conventions):
		3875
		3876	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3877	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3878
		3879	That means instead of having a C callback function, you store the
		3880	coroutine to switch to in each watcher, and instead of having libev call
		3881	your callback, you instead have it switch to that coroutine.
		3882
		3883	A coroutine might now wait for an event with a function called
		3884	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3885	matter when, or whether the watcher is active or not when this function is
		3886	called):
		3887
		3888	void
		3889	wait_for_event (ev_watcher *w)
		3890	{
		3891	ev_set_cb (w, current_coro);
		3892	switch_to (libev_coro);
		3893	}
		3894
		3895	That basically suspends the coroutine inside C<wait_for_event> and
		3896	continues the libev coroutine, which, when appropriate, switches back to
		3897	this or any other coroutine.
		3898
		3899	You can do similar tricks if you have, say, threads with an event queue -
		3900	instead of storing a coroutine, you store the queue object and instead of
		3901	switching to a coroutine, you push the watcher onto the queue and notify
		3902	any waiters.
		3903
		3904	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		3905	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3906
		3907	// my_ev.h
		3908	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3909	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3910	#include "../libev/ev.h"
		3911
		3912	// my_ev.c
		3913	#define EV_H "my_ev.h"
		3914	#include "../libev/ev.c"
		3915
		3916	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3917	F<my_ev.c> into your project. When properly specifying include paths, you
		3918	can even use F<ev.h> as header file name directly.
3641		3919
3642		3920
3643	=head1 LIBEVENT EMULATION	3921	=head1 LIBEVENT EMULATION
3644		3922
3645	Libev offers a compatibility emulation layer for libevent. It cannot	3923	Libev offers a compatibility emulation layer for libevent. It cannot
…		…
3675		3953
3676	=back	3954	=back
3677		3955
3678	=head1 C++ SUPPORT	3956	=head1 C++ SUPPORT
3679		3957
		3958	=head2 C API
		3959
		3960	The normal C API should work fine when used from C++: both ev.h and the
		3961	libev sources can be compiled as C++. Therefore, code that uses the C API
		3962	will work fine.
		3963
		3964	Proper exception specifications might have to be added to callbacks passed
		3965	to libev: exceptions may be thrown only from watcher callbacks, all
		3966	other callbacks (allocator, syserr, loop acquire/release and periodic
		3967	reschedule callbacks) must not throw exceptions, and might need a C<throw
		3968	()> specification. If you have code that needs to be compiled as both C
		3969	and C++ you can use the C<EV_THROW> macro for this:
		3970
		3971	static void
		3972	fatal_error (const char *msg) EV_THROW
		3973	{
		3974	perror (msg);
		3975	abort ();
		3976	}
		3977
		3978	...
		3979	ev_set_syserr_cb (fatal_error);
		3980
		3981	The only API functions that can currently throw exceptions are C<ev_run>,
		3982	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		3983	because it runs cleanup watchers).
		3984
		3985	Throwing exceptions in watcher callbacks is only supported if libev itself
		3986	is compiled with a C++ compiler or your C and C++ environments allow
		3987	throwing exceptions through C libraries (most do).
		3988
		3989	=head2 C++ API
		3990
3680	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3991	Libev comes with some simplistic wrapper classes for C++ that mainly allow
3681	you to use some convenience methods to start/stop watchers and also change	3992	you to use some convenience methods to start/stop watchers and also change
3682	the callback model to a model using method callbacks on objects.	3993	the callback model to a model using method callbacks on objects.
3683		3994
3684	To use it,	3995	To use it,
3685		3996
3686	#include <ev++.h>	3997	#include <ev++.h>
3687		3998
3688	This automatically includes F<ev.h> and puts all of its definitions (many	3999	This automatically includes F<ev.h> and puts all of its definitions (many
3689	of them macros) into the global namespace. All C++ specific things are	4000	of them macros) into the global namespace. All C++ specific things are
3690	put into the C<ev> namespace. It should support all the same embedding	4001	put into the C<ev> namespace. It should support all the same embedding
…		…
3699	with C<operator ()> can be used as callbacks. Other types should be easy	4010	with C<operator ()> can be used as callbacks. Other types should be easy
3700	to add as long as they only need one additional pointer for context. If	4011	to add as long as they only need one additional pointer for context. If
3701	you need support for other types of functors please contact the author	4012	you need support for other types of functors please contact the author
3702	(preferably after implementing it).	4013	(preferably after implementing it).
3703		4014
		4015	For all this to work, your C++ compiler either has to use the same calling
		4016	conventions as your C compiler (for static member functions), or you have
		4017	to embed libev and compile libev itself as C++.
		4018
3704	Here is a list of things available in the C<ev> namespace:	4019	Here is a list of things available in the C<ev> namespace:
3705		4020
3706	=over 4	4021	=over 4
3707		4022
3708	=item C<ev::READ>, C<ev::WRITE> etc.	4023	=item C<ev::READ>, C<ev::WRITE> etc.
…		…
3717	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4032	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3718		4033
3719	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4034	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
3720	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4035	the same name in the C<ev> namespace, with the exception of C<ev_signal>
3721	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4036	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3722	defines by many implementations.	4037	defined by many implementations.
3723		4038
3724	All of those classes have these methods:	4039	All of those classes have these methods:
3725		4040
3726	=over 4	4041	=over 4
3727		4042
…		…
3789	void operator() (ev::io &w, int revents)	4104	void operator() (ev::io &w, int revents)
3790	{	4105	{
3791	...	4106	...
3792	}	4107	}
3793	}	4108	}
3794		4109
3795	myfunctor f;	4110	myfunctor f;
3796		4111
3797	ev::io w;	4112	ev::io w;
3798	w.set (&f);	4113	w.set (&f);
3799		4114
…		…
3817	Associates a different C<struct ev_loop> with this watcher. You can only	4132	Associates a different C<struct ev_loop> with this watcher. You can only
3818	do this when the watcher is inactive (and not pending either).	4133	do this when the watcher is inactive (and not pending either).
3819		4134
3820	=item w->set ([arguments])	4135	=item w->set ([arguments])
3821		4136
3822	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this	4137	Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>),
3823	method or a suitable start method must be called at least once. Unlike the	4138	with the same arguments. Either this method or a suitable start method
3824	C counterpart, an active watcher gets automatically stopped and restarted	4139	must be called at least once. Unlike the C counterpart, an active watcher
3825	when reconfiguring it with this method.	4140	gets automatically stopped and restarted when reconfiguring it with this
		4141	method.
		4142
		4143	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4144	clashing with the C<set (loop)> method.
3826		4145
3827	=item w->start ()	4146	=item w->start ()
3828		4147
3829	Starts the watcher. Note that there is no C<loop> argument, as the	4148	Starts the watcher. Note that there is no C<loop> argument, as the
3830	constructor already stores the event loop.	4149	constructor already stores the event loop.
…		…
3860	watchers in the constructor.	4179	watchers in the constructor.
3861		4180
3862	class myclass	4181	class myclass
3863	{	4182	{
3864	ev::io io ; void io_cb (ev::io &w, int revents);	4183	ev::io io ; void io_cb (ev::io &w, int revents);
3865	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);	4184	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3866	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4185	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3867		4186
3868	myclass (int fd)	4187	myclass (int fd)
3869	{	4188	{
3870	io .set <myclass, &myclass::io_cb > (this);	4189	io .set <myclass, &myclass::io_cb > (this);
…		…
3921	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4240	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3922		4241
3923	=item D	4242	=item D
3924		4243
3925	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4244	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3926	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4245	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3927		4246
3928	=item Ocaml	4247	=item Ocaml
3929		4248
3930	Erkki Seppala has written Ocaml bindings for libev, to be found at	4249	Erkki Seppala has written Ocaml bindings for libev, to be found at
3931	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4250	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
…		…
3934		4253
3935	Brian Maher has written a partial interface to libev for lua (at the	4254	Brian Maher has written a partial interface to libev for lua (at the
3936	time of this writing, only C<ev_io> and C<ev_timer>), to be found at	4255	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
3937	L<http://github.com/brimworks/lua-ev>.	4256	L<http://github.com/brimworks/lua-ev>.
3938		4257
		4258	=item Javascript
		4259
		4260	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4261
		4262	=item Others
		4263
		4264	There are others, and I stopped counting.
		4265
3939	=back	4266	=back
3940		4267
3941		4268
3942	=head1 MACRO MAGIC	4269	=head1 MACRO MAGIC
3943		4270
…		…
3979	suitable for use with C<EV_A>.	4306	suitable for use with C<EV_A>.
3980		4307
3981	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4308	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3982		4309
3983	Similar to the other two macros, this gives you the value of the default	4310	Similar to the other two macros, this gives you the value of the default
3984	loop, if multiple loops are supported ("ev loop default").	4311	loop, if multiple loops are supported ("ev loop default"). The default loop
		4312	will be initialised if it isn't already initialised.
		4313
		4314	For non-multiplicity builds, these macros do nothing, so you always have
		4315	to initialise the loop somewhere.
3985		4316
3986	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4317	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3987		4318
3988	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4319	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3989	default loop has been initialised (C<UC> == unchecked). Their behaviour	4320	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
4056	ev_vars.h	4387	ev_vars.h
4057	ev_wrap.h	4388	ev_wrap.h
4058		4389
4059	ev_win32.c required on win32 platforms only	4390	ev_win32.c required on win32 platforms only
4060		4391
4061	ev_select.c only when select backend is enabled (which is enabled by default)	4392	ev_select.c only when select backend is enabled
4062	ev_poll.c only when poll backend is enabled (disabled by default)	4393	ev_poll.c only when poll backend is enabled
4063	ev_epoll.c only when the epoll backend is enabled (disabled by default)	4394	ev_epoll.c only when the epoll backend is enabled
4064	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	4395	ev_kqueue.c only when the kqueue backend is enabled
4065	ev_port.c only when the solaris port backend is enabled (disabled by default)	4396	ev_port.c only when the solaris port backend is enabled
4066		4397
4067	F<ev.c> includes the backend files directly when enabled, so you only need	4398	F<ev.c> includes the backend files directly when enabled, so you only need
4068	to compile this single file.	4399	to compile this single file.
4069		4400
4070	=head3 LIBEVENT COMPATIBILITY API	4401	=head3 LIBEVENT COMPATIBILITY API
…		…
4134	supported). It will also not define any of the structs usually found in	4465	supported). It will also not define any of the structs usually found in
4135	F<event.h> that are not directly supported by the libev core alone.	4466	F<event.h> that are not directly supported by the libev core alone.
4136		4467
4137	In standalone mode, libev will still try to automatically deduce the	4468	In standalone mode, libev will still try to automatically deduce the
4138	configuration, but has to be more conservative.	4469	configuration, but has to be more conservative.
		4470
		4471	=item EV_USE_FLOOR
		4472
		4473	If defined to be C<1>, libev will use the C<floor ()> function for its
		4474	periodic reschedule calculations, otherwise libev will fall back on a
		4475	portable (slower) implementation. If you enable this, you usually have to
		4476	link against libm or something equivalent. Enabling this when the C<floor>
		4477	function is not available will fail, so the safe default is to not enable
		4478	this.
4139		4479
4140	=item EV_USE_MONOTONIC	4480	=item EV_USE_MONOTONIC
4141		4481
4142	If defined to be C<1>, libev will try to detect the availability of the	4482	If defined to be C<1>, libev will try to detect the availability of the
4143	monotonic clock option at both compile time and runtime. Otherwise no	4483	monotonic clock option at both compile time and runtime. Otherwise no
…		…
4228		4568
4229	If programs implement their own fd to handle mapping on win32, then this	4569	If programs implement their own fd to handle mapping on win32, then this
4230	macro can be used to override the C<close> function, useful to unregister	4570	macro can be used to override the C<close> function, useful to unregister
4231	file descriptors again. Note that the replacement function has to close	4571	file descriptors again. Note that the replacement function has to close
4232	the underlying OS handle.	4572	the underlying OS handle.
		4573
		4574	=item EV_USE_WSASOCKET
		4575
		4576	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4577	communication socket, which works better in some environments. Otherwise,
		4578	the normal C<socket> function will be used, which works better in other
		4579	environments.
4233		4580
4234	=item EV_USE_POLL	4581	=item EV_USE_POLL
4235		4582
4236	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4583	If defined to be C<1>, libev will compile in support for the C<poll>(2)
4237	backend. Otherwise it will be enabled on non-win32 platforms. It	4584	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
4273	If defined to be C<1>, libev will compile in support for the Linux inotify	4620	If defined to be C<1>, libev will compile in support for the Linux inotify
4274	interface to speed up C<ev_stat> watchers. Its actual availability will	4621	interface to speed up C<ev_stat> watchers. Its actual availability will
4275	be detected at runtime. If undefined, it will be enabled if the headers	4622	be detected at runtime. If undefined, it will be enabled if the headers
4276	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4623	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
4277		4624
		4625	=item EV_NO_SMP
		4626
		4627	If defined to be C<1>, libev will assume that memory is always coherent
		4628	between threads, that is, threads can be used, but threads never run on
		4629	different cpus (or different cpu cores). This reduces dependencies
		4630	and makes libev faster.
		4631
		4632	=item EV_NO_THREADS
		4633
		4634	If defined to be C<1>, libev will assume that it will never be called from
		4635	different threads (that includes signal handlers), which is a stronger
		4636	assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes
		4637	libev faster.
		4638
4278	=item EV_ATOMIC_T	4639	=item EV_ATOMIC_T
4279		4640
4280	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4641	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
4281	access is atomic with respect to other threads or signal contexts. No such	4642	access is atomic with respect to other threads or signal contexts. No
4282	type is easily found in the C language, so you can provide your own type	4643	such type is easily found in the C language, so you can provide your own
4283	that you know is safe for your purposes. It is used both for signal handler "locking"	4644	type that you know is safe for your purposes. It is used both for signal
4284	as well as for signal and thread safety in C<ev_async> watchers.	4645	handler "locking" as well as for signal and thread safety in C<ev_async>
		4646	watchers.
4285		4647
4286	In the absence of this define, libev will use C<sig_atomic_t volatile>	4648	In the absence of this define, libev will use C<sig_atomic_t volatile>
4287	(from F<signal.h>), which is usually good enough on most platforms.	4649	(from F<signal.h>), which is usually good enough on most platforms.
4288		4650
4289	=item EV_H (h)	4651	=item EV_H (h)
…		…
4316	will have the C<struct ev_loop *> as first argument, and you can create	4678	will have the C<struct ev_loop *> as first argument, and you can create
4317	additional independent event loops. Otherwise there will be no support	4679	additional independent event loops. Otherwise there will be no support
4318	for multiple event loops and there is no first event loop pointer	4680	for multiple event loops and there is no first event loop pointer
4319	argument. Instead, all functions act on the single default loop.	4681	argument. Instead, all functions act on the single default loop.
4320		4682
		4683	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4684	default loop when multiplicity is switched off - you always have to
		4685	initialise the loop manually in this case.
		4686
4321	=item EV_MINPRI	4687	=item EV_MINPRI
4322		4688
4323	=item EV_MAXPRI	4689	=item EV_MAXPRI
4324		4690
4325	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4691	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
4361	#define EV_USE_POLL 1	4727	#define EV_USE_POLL 1
4362	#define EV_CHILD_ENABLE 1	4728	#define EV_CHILD_ENABLE 1
4363	#define EV_ASYNC_ENABLE 1	4729	#define EV_ASYNC_ENABLE 1
4364		4730
4365	The actual value is a bitset, it can be a combination of the following	4731	The actual value is a bitset, it can be a combination of the following
4366	values:	4732	values (by default, all of these are enabled):
4367		4733
4368	=over 4	4734	=over 4
4369		4735
4370	=item C<1> - faster/larger code	4736	=item C<1> - faster/larger code
4371		4737
…		…
4375	code size by roughly 30% on amd64).	4741	code size by roughly 30% on amd64).
4376		4742
4377	When optimising for size, use of compiler flags such as C<-Os> with	4743	When optimising for size, use of compiler flags such as C<-Os> with
4378	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of	4744	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
4379	assertions.	4745	assertions.
		4746
		4747	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4748	(e.g. gcc with C<-Os>).
4380		4749
4381	=item C<2> - faster/larger data structures	4750	=item C<2> - faster/larger data structures
4382		4751
4383	Replaces the small 2-heap for timer management by a faster 4-heap, larger	4752	Replaces the small 2-heap for timer management by a faster 4-heap, larger
4384	hash table sizes and so on. This will usually further increase code size	4753	hash table sizes and so on. This will usually further increase code size
4385	and can additionally have an effect on the size of data structures at	4754	and can additionally have an effect on the size of data structures at
4386	runtime.	4755	runtime.
4387		4756
		4757	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4758	(e.g. gcc with C<-Os>).
		4759
4388	=item C<4> - full API configuration	4760	=item C<4> - full API configuration
4389		4761
4390	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and	4762	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
4391	enables multiplicity (C<EV_MULTIPLICITY>=1).	4763	enables multiplicity (C<EV_MULTIPLICITY>=1).
4392		4764
…		…
4422		4794
4423	With an intelligent-enough linker (gcc+binutils are intelligent enough	4795	With an intelligent-enough linker (gcc+binutils are intelligent enough
4424	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by	4796	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
4425	your program might be left out as well - a binary starting a timer and an	4797	your program might be left out as well - a binary starting a timer and an
4426	I/O watcher then might come out at only 5Kb.	4798	I/O watcher then might come out at only 5Kb.
		4799
		4800	=item EV_API_STATIC
		4801
		4802	If this symbol is defined (by default it is not), then all identifiers
		4803	will have static linkage. This means that libev will not export any
		4804	identifiers, and you cannot link against libev anymore. This can be useful
		4805	when you embed libev, only want to use libev functions in a single file,
		4806	and do not want its identifiers to be visible.
		4807
		4808	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4809	wants to use libev.
		4810
		4811	This option only works when libev is compiled with a C compiler, as C++
		4812	doesn't support the required declaration syntax.
4427		4813
4428	=item EV_AVOID_STDIO	4814	=item EV_AVOID_STDIO
4429		4815
4430	If this is set to C<1> at compiletime, then libev will avoid using stdio	4816	If this is set to C<1> at compiletime, then libev will avoid using stdio
4431	functions (printf, scanf, perror etc.). This will increase the code size	4817	functions (printf, scanf, perror etc.). This will increase the code size
…		…
4575	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4961	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4576		4962
4577	#include "ev_cpp.h"	4963	#include "ev_cpp.h"
4578	#include "ev.c"	4964	#include "ev.c"
4579		4965
4580	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4966	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4581		4967
4582	=head2 THREADS AND COROUTINES	4968	=head2 THREADS AND COROUTINES
4583		4969
4584	=head3 THREADS	4970	=head3 THREADS
4585		4971
…		…
4636	default loop and triggering an C<ev_async> watcher from the default loop	5022	default loop and triggering an C<ev_async> watcher from the default loop
4637	watcher callback into the event loop interested in the signal.	5023	watcher callback into the event loop interested in the signal.
4638		5024
4639	=back	5025	=back
4640		5026
4641	See also L<Thread locking example>.	5027	See also L</THREAD LOCKING EXAMPLE>.
4642		5028
4643	=head3 COROUTINES	5029	=head3 COROUTINES
4644		5030
4645	Libev is very accommodating to coroutines ("cooperative threads"):	5031	Libev is very accommodating to coroutines ("cooperative threads"):
4646	libev fully supports nesting calls to its functions from different	5032	libev fully supports nesting calls to its functions from different
…		…
4811	requires, and its I/O model is fundamentally incompatible with the POSIX	5197	requires, and its I/O model is fundamentally incompatible with the POSIX
4812	model. Libev still offers limited functionality on this platform in	5198	model. Libev still offers limited functionality on this platform in
4813	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5199	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4814	descriptors. This only applies when using Win32 natively, not when using	5200	descriptors. This only applies when using Win32 natively, not when using
4815	e.g. cygwin. Actually, it only applies to the microsofts own compilers,	5201	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
4816	as every compielr comes with a slightly differently broken/incompatible	5202	as every compiler comes with a slightly differently broken/incompatible
4817	environment.	5203	environment.
4818		5204
4819	Lifting these limitations would basically require the full	5205	Lifting these limitations would basically require the full
4820	re-implementation of the I/O system. If you are into this kind of thing,	5206	re-implementation of the I/O system. If you are into this kind of thing,
4821	then note that glib does exactly that for you in a very portable way (note	5207	then note that glib does exactly that for you in a very portable way (note
…		…
4915	structure (guaranteed by POSIX but not by ISO C for example), but it also	5301	structure (guaranteed by POSIX but not by ISO C for example), but it also
4916	assumes that the same (machine) code can be used to call any watcher	5302	assumes that the same (machine) code can be used to call any watcher
4917	callback: The watcher callbacks have different type signatures, but libev	5303	callback: The watcher callbacks have different type signatures, but libev
4918	calls them using an C<ev_watcher *> internally.	5304	calls them using an C<ev_watcher *> internally.
4919		5305
		5306	=item null pointers and integer zero are represented by 0 bytes
		5307
		5308	Libev uses C<memset> to initialise structs and arrays to C<0> bytes, and
		5309	relies on this setting pointers and integers to null.
		5310
4920	=item pointer accesses must be thread-atomic	5311	=item pointer accesses must be thread-atomic
4921		5312
4922	Accessing a pointer value must be atomic, it must both be readable and	5313	Accessing a pointer value must be atomic, it must both be readable and
4923	writable in one piece - this is the case on all current architectures.	5314	writable in one piece - this is the case on all current architectures.
4924		5315
…		…
4937	thread" or will block signals process-wide, both behaviours would	5328	thread" or will block signals process-wide, both behaviours would
4938	be compatible with libev. Interaction between C<sigprocmask> and	5329	be compatible with libev. Interaction between C<sigprocmask> and
4939	C<pthread_sigmask> could complicate things, however.	5330	C<pthread_sigmask> could complicate things, however.
4940		5331
4941	The most portable way to handle signals is to block signals in all threads	5332	The most portable way to handle signals is to block signals in all threads
4942	except the initial one, and run the default loop in the initial thread as	5333	except the initial one, and run the signal handling loop in the initial
4943	well.	5334	thread as well.
4944		5335
4945	=item C<long> must be large enough for common memory allocation sizes	5336	=item C<long> must be large enough for common memory allocation sizes
4946		5337
4947	To improve portability and simplify its API, libev uses C<long> internally	5338	To improve portability and simplify its API, libev uses C<long> internally
4948	instead of C<size_t> when allocating its data structures. On non-POSIX	5339	instead of C<size_t> when allocating its data structures. On non-POSIX
…		…
4954		5345
4955	The type C<double> is used to represent timestamps. It is required to	5346	The type C<double> is used to represent timestamps. It is required to
4956	have at least 51 bits of mantissa (and 9 bits of exponent), which is	5347	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4957	good enough for at least into the year 4000 with millisecond accuracy	5348	good enough for at least into the year 4000 with millisecond accuracy
4958	(the design goal for libev). This requirement is overfulfilled by	5349	(the design goal for libev). This requirement is overfulfilled by
4959	implementations using IEEE 754, which is basically all existing ones. With	5350	implementations using IEEE 754, which is basically all existing ones.
		5351
4960	IEEE 754 doubles, you get microsecond accuracy until at least 2200.	5352	With IEEE 754 doubles, you get microsecond accuracy until at least the
		5353	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5354	is either obsolete or somebody patched it to use C<long double> or
		5355	something like that, just kidding).
4961		5356
4962	=back	5357	=back
4963		5358
4964	If you know of other additional requirements drop me a note.	5359	If you know of other additional requirements drop me a note.
4965		5360
…		…
5027	=item Processing ev_async_send: O(number_of_async_watchers)	5422	=item Processing ev_async_send: O(number_of_async_watchers)
5028		5423
5029	=item Processing signals: O(max_signal_number)	5424	=item Processing signals: O(max_signal_number)
5030		5425
5031	Sending involves a system call I<iff> there were no other C<ev_async_send>	5426	Sending involves a system call I<iff> there were no other C<ev_async_send>
5032	calls in the current loop iteration. Checking for async and signal events	5427	calls in the current loop iteration and the loop is currently
		5428	blocked. Checking for async and signal events involves iterating over all
5033	involves iterating over all running async watchers or all signal numbers.	5429	running async watchers or all signal numbers.
5034		5430
5035	=back	5431	=back
5036		5432
5037		5433
5038	=head1 PORTING FROM LIBEV 3.X TO 4.X	5434	=head1 PORTING FROM LIBEV 3.X TO 4.X
…		…
5047	=over 4	5443	=over 4
5048		5444
5049	=item C<EV_COMPAT3> backwards compatibility mechanism	5445	=item C<EV_COMPAT3> backwards compatibility mechanism
5050		5446
5051	The backward compatibility mechanism can be controlled by	5447	The backward compatibility mechanism can be controlled by
5052	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>	5448	C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING>
5053	section.	5449	section.
5054		5450
5055	=item C<ev_default_destroy> and C<ev_default_fork> have been removed	5451	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
5056		5452
5057	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:	5453	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
…		…
5100	=over 4	5496	=over 4
5101		5497
5102	=item active	5498	=item active
5103		5499
5104	A watcher is active as long as it has been started and not yet stopped.	5500	A watcher is active as long as it has been started and not yet stopped.
5105	See L<WATCHER STATES> for details.	5501	See L</WATCHER STATES> for details.
5106		5502
5107	=item application	5503	=item application
5108		5504
5109	In this document, an application is whatever is using libev.	5505	In this document, an application is whatever is using libev.
5110		5506
…		…
5146	watchers and events.	5542	watchers and events.
5147		5543
5148	=item pending	5544	=item pending
5149		5545
5150	A watcher is pending as soon as the corresponding event has been	5546	A watcher is pending as soon as the corresponding event has been
5151	detected. See L<WATCHER STATES> for details.	5547	detected. See L</WATCHER STATES> for details.
5152		5548
5153	=item real time	5549	=item real time
5154		5550
5155	The physical time that is observed. It is apparently strictly monotonic :)	5551	The physical time that is observed. It is apparently strictly monotonic :)
5156		5552
5157	=item wall-clock time	5553	=item wall-clock time
5158		5554
5159	The time and date as shown on clocks. Unlike real time, it can actually	5555	The time and date as shown on clocks. Unlike real time, it can actually
5160	be wrong and jump forwards and backwards, e.g. when the you adjust your	5556	be wrong and jump forwards and backwards, e.g. when you adjust your
5161	clock.	5557	clock.
5162		5558
5163	=item watcher	5559	=item watcher
5164		5560
5165	A data structure that describes interest in certain events. Watchers need	5561	A data structure that describes interest in certain events. Watchers need
…		…
5168	=back	5564	=back
5169		5565
5170	=head1 AUTHOR	5566	=head1 AUTHOR
5171		5567
5172	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael	5568	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
5173	Magnusson and Emanuele Giaquinta.	5569	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
5174		5570

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Comparing libev/ev.pod (file contents): Revision 1.354 by root, Tue Jan 11 01:40:25 2011 UTC vs. Revision 1.443 by root, Thu Aug 30 21:51:15 2018 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.354 by root, Tue Jan 11 01:40:25 2011 UTC vs.
Revision 1.443 by root, Thu Aug 30 21:51:15 2018 UTC