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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.
…		…
435	example) that can't properly initialise their signal masks.	445	example) that can't properly initialise their signal masks.
436		446
437	=item C<EVFLAG_NOSIGMASK>	447	=item C<EVFLAG_NOSIGMASK>
438		448
439	When this flag is specified, then libev will avoid to modify the signal	449	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	450	mask. Specifically, this means you have to make sure signals are unblocked
441	when you want to receive them.	451	when you want to receive them.
442		452
443	This behaviour is useful when you want to do your own signal handling, or	453	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	454	want to handle signals only in specific threads and want to avoid libev
445	unblocking the signals.	455	unblocking the signals.
		456
		457	It's also required by POSIX in a threaded program, as libev calls
		458	C<sigprocmask>, whose behaviour is officially unspecified.
446		459
447	This flag's behaviour will become the default in future versions of libev.	460	This flag's behaviour will become the default in future versions of libev.
448		461
449	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	462	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
450		463
…		…
480	=item C<EVBACKEND_EPOLL> (value 4, Linux)	493	=item C<EVBACKEND_EPOLL> (value 4, Linux)
481		494
482	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9	495	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
483	kernels).	496	kernels).
484		497
485	For few fds, this backend is a bit little slower than poll and select,	498	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	499	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),	500	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).	501	fd), epoll scales either O(1) or O(active_fds).
489		502
490	The epoll mechanism deserves honorable mention as the most misdesigned	503	The epoll mechanism deserves honorable mention as the most misdesigned
491	of the more advanced event mechanisms: mere annoyances include silently	504	of the more advanced event mechanisms: mere annoyances include silently
492	dropping file descriptors, requiring a system call per change per file	505	dropping file descriptors, requiring a system call per change per file
493	descriptor (and unnecessary guessing of parameters), problems with dup,	506	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	509	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	510	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)	511	set, which can take considerable time (one syscall per file descriptor)
499	and is of course hard to detect.	512	and is of course hard to detect.
500		513
501	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	514	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	515	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	516	totally I<different> file descriptors (even already closed ones, so
504	even remove them from the set) than registered in the set (especially	517	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	518	(especially on SMP systems). Libev tries to counter these spurious
506	employing an additional generation counter and comparing that against the	519	notifications by employing an additional generation counter and comparing
507	events to filter out spurious ones, recreating the set when required. Last	520	that against the events to filter out spurious ones, recreating the set
		521	when required. Epoll also erroneously rounds down timeouts, but gives you
		522	no way to know when and by how much, so sometimes you have to busy-wait
		523	because epoll returns immediately despite a nonzero timeout. And last
508	not least, it also refuses to work with some file descriptors which work	524	not least, it also refuses to work with some file descriptors which work
509	perfectly fine with C<select> (files, many character devices...).	525	perfectly fine with C<select> (files, many character devices...).
510		526
511	Epoll is truly the train wreck analog among event poll mechanisms,	527	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	528	cobbled together in a hurry, no thought to design or interaction with
513	interaction with others.	529	others. Oh, the pain, will it ever stop...
514		530
515	While stopping, setting and starting an I/O watcher in the same iteration	531	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	532	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	533	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	534	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
555		571
556	It scales in the same way as the epoll backend, but the interface to the	572	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	573	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	574	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	575	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	576	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	577	might have to leak fd's on fork, but it's more sane than epoll) and it
562	cases	578	drops fds silently in similarly hard-to-detect cases.
563		579
564	This backend usually performs well under most conditions.	580	This backend usually performs well under most conditions.
565		581
566	While nominally embeddable in other event loops, this doesn't work	582	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	583	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	612	among the OS-specific backends (I vastly prefer correctness over speed
597	hacks).	613	hacks).
598		614
599	On the negative side, the interface is I<bizarre> - so bizarre that	615	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	616	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	617	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	618	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	619	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	620	absolutely have to know whether an event occurred or not because you have
605	have to re-arm the watcher.	621	to re-arm the watcher.
606		622
607	Fortunately libev seems to be able to work around these idiocies.	623	Fortunately libev seems to be able to work around these idiocies.
608		624
609	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	625	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
610	C<EVBACKEND_POLL>.	626	C<EVBACKEND_POLL>.
…		…
666	If you need dynamically allocated loops it is better to use C<ev_loop_new>	682	If you need dynamically allocated loops it is better to use C<ev_loop_new>
667	and C<ev_loop_destroy>.	683	and C<ev_loop_destroy>.
668		684
669	=item ev_loop_fork (loop)	685	=item ev_loop_fork (loop)
670		686
671	This function sets a flag that causes subsequent C<ev_run> iterations to	687	This function sets a flag that causes subsequent C<ev_run> iterations
672	reinitialise the kernel state for backends that have one. Despite the	688	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	689	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	690	watchers (except inside an C<ev_prepare> callback), but it makes most
		691	sense after forking, in the child process. You I<must> call it (or use
675	child before resuming or calling C<ev_run>.	692	C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>.
676		693
677	Again, you I<have> to call it on I<any> loop that you want to re-use after	694	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	695	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	696	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
680	during fork.	697	during fork.
681		698
682	On the other hand, you only need to call this function in the child	699	On the other hand, you only need to call this function in the child
…		…
752		769
753	This function is rarely useful, but when some event callback runs for a	770	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	771	very long time without entering the event loop, updating libev's idea of
755	the current time is a good idea.	772	the current time is a good idea.
756		773
757	See also L<The special problem of time updates> in the C<ev_timer> section.	774	See also L</The special problem of time updates> in the C<ev_timer> section.
758		775
759	=item ev_suspend (loop)	776	=item ev_suspend (loop)
760		777
761	=item ev_resume (loop)	778	=item ev_resume (loop)
762		779
…		…
780	without a previous call to C<ev_suspend>.	797	without a previous call to C<ev_suspend>.
781		798
782	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	799	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
783	event loop time (see C<ev_now_update>).	800	event loop time (see C<ev_now_update>).
784		801
785	=item ev_run (loop, int flags)	802	=item bool ev_run (loop, int flags)
786		803
787	Finally, this is it, the event handler. This function usually is called	804	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	805	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	806	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	807	the watcher callbacks, and then repeat the whole process indefinitely: This
791	is why event loops are called I<loops>.	808	is why event loops are called I<loops>.
792		809
793	If the flags argument is specified as C<0>, it will keep handling events	810	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	811	until either no event watchers are active anymore or C<ev_break> was
795	called.	812	called.
		813
		814	The return value is false if there are no more active watchers (which
		815	usually means "all jobs done" or "deadlock"), and true in all other cases
		816	(which usually means " you should call C<ev_run> again").
796		817
797	Please note that an explicit C<ev_break> is usually better than	818	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	819	relying on all watchers to be stopped when deciding when a program has
799	finished (especially in interactive programs), but having a program	820	finished (especially in interactive programs), but having a program
800	that automatically loops as long as it has to and no longer by virtue	821	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	822	of relying on its watchers stopping correctly, that is truly a thing of
802	beauty.	823	beauty.
803		824
804	This function is also I<mostly> exception-safe - you can break out of	825	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++	826	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	827	exception and so on. This does not decrement the C<ev_depth> value, nor
807	will it clear any outstanding C<EVBREAK_ONE> breaks.	828	will it clear any outstanding C<EVBREAK_ONE> breaks.
808		829
809	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle	830	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	831	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	843	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	844	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	845	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.	846	usually a better approach for this kind of thing.
826		847
827	Here are the gory details of what C<ev_run> does:	848	Here are the gory details of what C<ev_run> does (this is for your
		849	understanding, not a guarantee that things will work exactly like this in
		850	future versions):
828		851
829	- Increment loop depth.	852	- Increment loop depth.
830	- Reset the ev_break status.	853	- Reset the ev_break status.
831	- Before the first iteration, call any pending watchers.	854	- Before the first iteration, call any pending watchers.
832	LOOP:	855	LOOP:
…		…
865	anymore.	888	anymore.
866		889
867	... queue jobs here, make sure they register event watchers as long	890	... 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..)	891	... as they still have work to do (even an idle watcher will do..)
869	ev_run (my_loop, 0);	892	ev_run (my_loop, 0);
870	... jobs done or somebody called unloop. yeah!	893	... jobs done or somebody called break. yeah!
871		894
872	=item ev_break (loop, how)	895	=item ev_break (loop, how)
873		896
874	Can be used to make a call to C<ev_run> return early (but only after it	897	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	898	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.	961	overhead for the actual polling but can deliver many events at once.
939		962
940	By setting a higher I<io collect interval> you allow libev to spend more	963	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,	964	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	965	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	966	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	967	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	968	sleep time ensures that libev will not poll for I/O events more often then
946	once per this interval, on average.	969	once per this interval, on average (as long as the host time resolution is
		970	good enough).
947		971
948	Likewise, by setting a higher I<timeout collect interval> you allow libev	972	Likewise, by setting a higher I<timeout collect interval> you allow libev
949	to spend more time collecting timeouts, at the expense of increased	973	to spend more time collecting timeouts, at the expense of increased
950	latency/jitter/inexactness (the watcher callback will be called	974	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	975	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.).	1021	invoke the actual watchers inside another context (another thread etc.).
998		1022
999	If you want to reset the callback, use C<ev_invoke_pending> as new	1023	If you want to reset the callback, use C<ev_invoke_pending> as new
1000	callback.	1024	callback.
1001		1025
1002	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))	1026	=item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())
1003		1027
1004	Sometimes you want to share the same loop between multiple threads. This	1028	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	1029	can be done relatively simply by putting mutex_lock/unlock calls around
1006	each call to a libev function.	1030	each call to a libev function.
1007		1031
1008	However, C<ev_run> can run an indefinite time, so it is not feasible	1032	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	1033	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	1034	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.	1035	I<release> and I<acquire> callbacks on the loop.
1012		1036
1013	When set, then C<release> will be called just before the thread is	1037	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	1038	suspended waiting for new events, and C<acquire> is called just
1015	afterwards.	1039	afterwards.
…		…
1155		1179
1156	=item C<EV_PREPARE>	1180	=item C<EV_PREPARE>
1157		1181
1158	=item C<EV_CHECK>	1182	=item C<EV_CHECK>
1159		1183
1160	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts	1184	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	1185	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	1186	just after C<ev_run> has gathered them, but before it queues any callbacks
		1187	for any received events. That means C<ev_prepare> watchers are the last
		1188	watchers invoked before the event loop sleeps or polls for new events, and
		1189	C<ev_check> watchers will be invoked before any other watchers of the same
		1190	or lower priority within an event loop iteration.
		1191
1163	received events. Callbacks of both watcher types can start and stop as	1192	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	1193	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	1194	C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from
1166	C<ev_run> from blocking).	1195	blocking).
1167		1196
1168	=item C<EV_EMBED>	1197	=item C<EV_EMBED>
1169		1198
1170	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1199	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1171		1200
…		…
1294		1323
1295	=item callback ev_cb (ev_TYPE *watcher)	1324	=item callback ev_cb (ev_TYPE *watcher)
1296		1325
1297	Returns the callback currently set on the watcher.	1326	Returns the callback currently set on the watcher.
1298		1327
1299	=item ev_cb_set (ev_TYPE *watcher, callback)	1328	=item ev_set_cb (ev_TYPE *watcher, callback)
1300		1329
1301	Change the callback. You can change the callback at virtually any time	1330	Change the callback. You can change the callback at virtually any time
1302	(modulo threads).	1331	(modulo threads).
1303		1332
1304	=item ev_set_priority (ev_TYPE *watcher, int priority)	1333	=item ev_set_priority (ev_TYPE *watcher, int priority)
…		…
1322	or might not have been clamped to the valid range.	1351	or might not have been clamped to the valid range.
1323		1352
1324	The default priority used by watchers when no priority has been set is	1353	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 :).	1354	always C<0>, which is supposed to not be too high and not be too low :).
1326		1355
1327	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of	1356	See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1328	priorities.	1357	priorities.
1329		1358
1330	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1359	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1331		1360
1332	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1361	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	1386	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1358	functions that do not need a watcher.	1387	functions that do not need a watcher.
1359		1388
1360	=back	1389	=back
1361		1390
1362	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1391	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
1363		1392	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		1393
1427	=head2 WATCHER STATES	1394	=head2 WATCHER STATES
1428		1395
1429	There are various watcher states mentioned throughout this manual -	1396	There are various watcher states mentioned throughout this manual -
1430	active, pending and so on. In this section these states and the rules to	1397	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	1398	transition between them will be described in more detail - and while these
1432	rules might look complicated, they usually do "the right thing".	1399	rules might look complicated, they usually do "the right thing".
1433		1400
1434	=over 4	1401	=over 4
1435		1402
1436	=item initialiased	1403	=item initialised
1437		1404
1438	Before a watcher can be registered with the event looop it has to be	1405	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	1406	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.	1407	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1441		1408
1442	In this state it is simply some block of memory that is suitable for use	1409	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.	1410	use in an event loop. It can be moved around, freed, reused etc. at
		1411	will - as long as you either keep the memory contents intact, or call
		1412	C<ev_TYPE_init> again.
1444		1413
1445	=item started/running/active	1414	=item started/running/active
1446		1415
1447	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes	1416	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	1417	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	1445	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	1446	of whether it was active or not, so stopping a watcher explicitly before
1478	freeing it is often a good idea.	1447	freeing it is often a good idea.
1479		1448
1480	While stopped (and not pending) the watcher is essentially in the	1449	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	1450	initialised state, that is, it can be reused, moved, modified in any way
1482	you wish.	1451	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1452	it again).
1483		1453
1484	=back	1454	=back
1485		1455
1486	=head2 WATCHER PRIORITY MODELS	1456	=head2 WATCHER PRIORITY MODELS
1487		1457
…		…
1680	always get a readiness notification instantly, and your read (or possibly	1650	always get a readiness notification instantly, and your read (or possibly
1681	write) will still block on the disk I/O.	1651	write) will still block on the disk I/O.
1682		1652
1683	Another way to view it is that in the case of sockets, pipes, character	1653	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	1654	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	1655	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	1656	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.	1657	wish to read - you would first have to request some data.
1688		1658
1689	Since files are typically not-so-well supported by advanced notification	1659	Since files are typically not-so-well supported by advanced notification
1690	mechanism, libev tries hard to emulate POSIX behaviour with respect	1660	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	1661	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	1785	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1816	monotonic clock option helps a lot here).	1786	monotonic clock option helps a lot here).
1817		1787
1818	The callback is guaranteed to be invoked only I<after> its timeout has	1788	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	1789	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	1790	might introduce a small delay, see "the special problem of being too
		1791	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	1792	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	1793	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).	1794	longer true when a callback calls C<ev_run> recursively).
1824		1795
1825	=head3 Be smart about timeouts	1796	=head3 Be smart about timeouts
1826		1797
1827	Many real-world problems involve some kind of timeout, usually for error	1798	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,	1799	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1903		1874
1904	In this case, it would be more efficient to leave the C<ev_timer> alone,	1875	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	1876	but remember the time of last activity, and check for a real timeout only
1906	within the callback:	1877	within the callback:
1907		1878
		1879	ev_tstamp timeout = 60.;
1908	ev_tstamp last_activity; // time of last activity	1880	ev_tstamp last_activity; // time of last activity
		1881	ev_timer timer;
1909		1882
1910	static void	1883	static void
1911	callback (EV_P_ ev_timer *w, int revents)	1884	callback (EV_P_ ev_timer *w, int revents)
1912	{	1885	{
1913	ev_tstamp now = ev_now (EV_A);	1886	// calculate when the timeout would happen
1914	ev_tstamp timeout = last_activity + 60.;	1887	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1915		1888
1916	// if last_activity + 60. is older than now, we did time out	1889	// if negative, it means we the timeout already occurred
1917	if (timeout < now)	1890	if (after < 0.)
1918	{	1891	{
1919	// timeout occurred, take action	1892	// timeout occurred, take action
1920	}	1893	}
1921	else	1894	else
1922	{	1895	{
1923	// callback was invoked, but there was some activity, re-arm	1896	// callback was invoked, but there was some recent
1924	// the watcher to fire in last_activity + 60, which is	1897	// activity. simply restart the timer to time out
1925	// guaranteed to be in the future, so "again" is positive:	1898	// after "after" seconds, which is the earliest time
1926	w->repeat = timeout - now;	1899	// the timeout can occur.
		1900	ev_timer_set (w, after, 0.);
1927	ev_timer_again (EV_A_ w);	1901	ev_timer_start (EV_A_ w);
1928	}	1902	}
1929	}	1903	}
1930		1904
1931	To summarise the callback: first calculate the real timeout (defined	1905	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	1906	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	1907	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	1908	(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		1909
1938	Note how C<ev_timer_again> is used, taking advantage of the	1910	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.	1911	timed out, and need to do whatever is needed in this case.
		1912
		1913	Otherwise, we now the earliest time at which the timeout would trigger,
		1914	and simply start the timer with this timeout value.
		1915
		1916	In other words, each time the callback is invoked it will check whether
		1917	the timeout occurred. If not, it will simply reschedule itself to check
		1918	again at the earliest time it could time out. Rinse. Repeat.
1940		1919
1941	This scheme causes more callback invocations (about one every 60 seconds	1920	This scheme causes more callback invocations (about one every 60 seconds
1942	minus half the average time between activity), but virtually no calls to	1921	minus half the average time between activity), but virtually no calls to
1943	libev to change the timeout.	1922	libev to change the timeout.
1944		1923
1945	To start the timer, simply initialise the watcher and set C<last_activity>	1924	To start the machinery, simply initialise the watcher and set
1946	to the current time (meaning we just have some activity :), then call the	1925	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:	1926	now), then call the callback, which will "do the right thing" and start
		1927	the timer:
1948		1928
		1929	last_activity = ev_now (EV_A);
1949	ev_init (timer, callback);	1930	ev_init (&timer, callback);
1950	last_activity = ev_now (loop);	1931	callback (EV_A_ &timer, 0);
1951	callback (loop, timer, EV_TIMER);
1952		1932
1953	And when there is some activity, simply store the current time in	1933	When there is some activity, simply store the current time in
1954	C<last_activity>, no libev calls at all:	1934	C<last_activity>, no libev calls at all:
1955		1935
		1936	if (activity detected)
1956	last_activity = ev_now (loop);	1937	last_activity = ev_now (EV_A);
		1938
		1939	When your timeout value changes, then the timeout can be changed by simply
		1940	providing a new value, stopping the timer and calling the callback, which
		1941	will again do the right thing (for example, time out immediately :).
		1942
		1943	timeout = new_value;
		1944	ev_timer_stop (EV_A_ &timer);
		1945	callback (EV_A_ &timer, 0);
1957		1946
1958	This technique is slightly more complex, but in most cases where the	1947	This technique is slightly more complex, but in most cases where the
1959	time-out is unlikely to be triggered, much more efficient.	1948	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		1949
1965	=item 4. Wee, just use a double-linked list for your timeouts.	1950	=item 4. Wee, just use a double-linked list for your timeouts.
1966		1951
1967	If there is not one request, but many thousands (millions...), all	1952	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	1953	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	1980	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	1981	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	1982	off after the first million or so of active timers, i.e. it's usually
1998	overkill :)	1983	overkill :)
1999		1984
		1985	=head3 The special problem of being too early
		1986
		1987	If you ask a timer to call your callback after three seconds, then
		1988	you expect it to be invoked after three seconds - but of course, this
		1989	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		1990	guaranteed to any precision by libev - imagine somebody suspending the
		1991	process with a STOP signal for a few hours for example.
		1992
		1993	So, libev tries to invoke your callback as soon as possible I<after> the
		1994	delay has occurred, but cannot guarantee this.
		1995
		1996	A less obvious failure mode is calling your callback too early: many event
		1997	loops compare timestamps with a "elapsed delay >= requested delay", but
		1998	this can cause your callback to be invoked much earlier than you would
		1999	expect.
		2000
		2001	To see why, imagine a system with a clock that only offers full second
		2002	resolution (think windows if you can't come up with a broken enough OS
		2003	yourself). If you schedule a one-second timer at the time 500.9, then the
		2004	event loop will schedule your timeout to elapse at a system time of 500
		2005	(500.9 truncated to the resolution) + 1, or 501.
		2006
		2007	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2008	501" and invoke the callback 0.1s after it was started, even though a
		2009	one-second delay was requested - this is being "too early", despite best
		2010	intentions.
		2011
		2012	This is the reason why libev will never invoke the callback if the elapsed
		2013	delay equals the requested delay, but only when the elapsed delay is
		2014	larger than the requested delay. In the example above, libev would only invoke
		2015	the callback at system time 502, or 1.1s after the timer was started.
		2016
		2017	So, while libev cannot guarantee that your callback will be invoked
		2018	exactly when requested, it I<can> and I<does> guarantee that the requested
		2019	delay has actually elapsed, or in other words, it always errs on the "too
		2020	late" side of things.
		2021
2000	=head3 The special problem of time updates	2022	=head3 The special problem of time updates
2001		2023
2002	Establishing the current time is a costly operation (it usually takes at	2024	Establishing the current time is a costly operation (it usually takes
2003	least two system calls): EV therefore updates its idea of the current	2025	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	2026	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	2027	growing difference between C<ev_now ()> and C<ev_time ()> when handling
2006	lots of events in one iteration.	2028	lots of events in one iteration.
2007		2029
2008	The relative timeouts are calculated relative to the C<ev_now ()>	2030	The relative timeouts are calculated relative to the C<ev_now ()>
…		…
2014	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2036	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
2015		2037
2016	If the event loop is suspended for a long time, you can also force an	2038	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	2039	update of the time returned by C<ev_now ()> by calling C<ev_now_update
2018	()>.	2040	()>.
		2041
		2042	=head3 The special problem of unsynchronised clocks
		2043
		2044	Modern systems have a variety of clocks - libev itself uses the normal
		2045	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2046	jumps).
		2047
		2048	Neither of these clocks is synchronised with each other or any other clock
		2049	on the system, so C<ev_time ()> might return a considerably different time
		2050	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2051	a call to C<gettimeofday> might return a second count that is one higher
		2052	than a directly following call to C<time>.
		2053
		2054	The moral of this is to only compare libev-related timestamps with
		2055	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2056	a second or so.
		2057
		2058	One more problem arises due to this lack of synchronisation: if libev uses
		2059	the system monotonic clock and you compare timestamps from C<ev_time>
		2060	or C<ev_now> from when you started your timer and when your callback is
		2061	invoked, you will find that sometimes the callback is a bit "early".
		2062
		2063	This is because C<ev_timer>s work in real time, not wall clock time, so
		2064	libev makes sure your callback is not invoked before the delay happened,
		2065	I<measured according to the real time>, not the system clock.
		2066
		2067	If your timeouts are based on a physical timescale (e.g. "time out this
		2068	connection after 100 seconds") then this shouldn't bother you as it is
		2069	exactly the right behaviour.
		2070
		2071	If you want to compare wall clock/system timestamps to your timers, then
		2072	you need to use C<ev_periodic>s, as these are based on the wall clock
		2073	time, where your comparisons will always generate correct results.
2019		2074
2020	=head3 The special problems of suspended animation	2075	=head3 The special problems of suspended animation
2021		2076
2022	When you leave the server world it is quite customary to hit machines that	2077	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?	2078	can suspend/hibernate - what happens to the clocks during such a suspend?
…		…
2067	keep up with the timer (because it takes longer than those 10 seconds to	2122	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.	2123	do stuff) the timer will not fire more than once per event loop iteration.
2069		2124
2070	=item ev_timer_again (loop, ev_timer *)	2125	=item ev_timer_again (loop, ev_timer *)
2071		2126
2072	This will act as if the timer timed out and restart it again if it is	2127	This will act as if the timer timed out, and restarts it again if it is
2073	repeating. The exact semantics are:	2128	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2129	timeout to the C<repeat> value and calling C<ev_timer_start>.
2074		2130
		2131	The exact semantics are as in the following rules, all of which will be
		2132	applied to the watcher:
		2133
		2134	=over 4
		2135
2075	If the timer is pending, its pending status is cleared.	2136	=item If the timer is pending, the pending status is always cleared.
2076		2137
2077	If the timer is started but non-repeating, stop it (as if it timed out).	2138	=item If the timer is started but non-repeating, stop it (as if it timed
		2139	out, without invoking it).
2078		2140
2079	If the timer is repeating, either start it if necessary (with the	2141	=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.	2142	and start the timer, if necessary.
2081		2143
		2144	=back
		2145
2082	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2146	This sounds a bit complicated, see L</Be smart about timeouts>, above, for a
2083	usage example.	2147	usage example.
2084		2148
2085	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)	2149	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
2086		2150
2087	Returns the remaining time until a timer fires. If the timer is active,	2151	Returns the remaining time until a timer fires. If the timer is active,
…		…
2207		2271
2208	Another way to think about it (for the mathematically inclined) is that	2272	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	2273	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.	2274	time where C<time = offset (mod interval)>, regardless of any time jumps.
2211		2275
2212	For numerical stability it is preferable that the C<offset> value is near	2276	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	2277	interval value should be higher than C<1/8192> (which is around 100
2214	this value, and in fact is often specified as zero.	2278	microseconds) and C<offset> should be higher than C<0> and should have
		2279	at most a similar magnitude as the current time (say, within a factor of
		2280	ten). Typical values for offset are, in fact, C<0> or something between
		2281	C<0> and C<interval>, which is also the recommended range.
2215		2282
2216	Note also that there is an upper limit to how often a timer can fire (CPU	2283	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	2284	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	2285	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).	2286	millisecond (if the OS supports it and the machine is fast enough).
…		…
2327		2394
2328	ev_periodic hourly_tick;	2395	ev_periodic hourly_tick;
2329	ev_periodic_init (&hourly_tick, clock_cb,	2396	ev_periodic_init (&hourly_tick, clock_cb,
2330	fmod (ev_now (loop), 3600.), 3600., 0);	2397	fmod (ev_now (loop), 3600.), 3600., 0);
2331	ev_periodic_start (loop, &hourly_tick);	2398	ev_periodic_start (loop, &hourly_tick);
2332		2399
2333		2400
2334	=head2 C<ev_signal> - signal me when a signal gets signalled!	2401	=head2 C<ev_signal> - signal me when a signal gets signalled!
2335		2402
2336	Signal watchers will trigger an event when the process receives a specific	2403	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	2404	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	2414	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	2415	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	2416	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.	2417	the moment, C<SIGCHLD> is permanently tied to the default loop.
2351		2418
2352	When the first watcher gets started will libev actually register something	2419	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	2420	register something with the kernel. It thus coexists with your own signal
2354	you don't register any with libev for the same signal).	2421	handlers as long as you don't register any with libev for the same signal.
2355		2422
2356	If possible and supported, libev will install its handlers with	2423	If possible and supported, libev will install its handlers with
2357	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should	2424	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	2425	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	2426	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	2429	=head3 The special problem of inheritance over fork/execve/pthread_create
2363		2430
2364	Both the signal mask (C<sigprocmask>) and the signal disposition	2431	Both the signal mask (C<sigprocmask>) and the signal disposition
2365	(C<sigaction>) are unspecified after starting a signal watcher (and after	2432	(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,	2433	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.	2434	and might or might not set or restore the installed signal handler (but
		2435	see C<EVFLAG_NOSIGMASK>).
2368		2436
2369	While this does not matter for the signal disposition (libev never	2437	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	2438	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	2439	C<execve>), this matters for the signal mask: many programs do not expect
2372	certain signals to be blocked.	2440	certain signals to be blocked.
…		…
2543		2611
2544	=head2 C<ev_stat> - did the file attributes just change?	2612	=head2 C<ev_stat> - did the file attributes just change?
2545		2613
2546	This watches a file system path for attribute changes. That is, it calls	2614	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)	2615	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	2616	and sees if it changed compared to the last time, invoking the callback
2549	it did.	2617	if it did. Starting the watcher C<stat>'s the file, so only changes that
		2618	happen after the watcher has been started will be reported.
2550		2619
2551	The path does not need to exist: changing from "path exists" to "path does	2620	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	2621	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	2622	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	2623	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	2853	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	2854	effect on its own sometimes), idle watchers are a good place to do
2786	"pseudo-background processing", or delay processing stuff to after the	2855	"pseudo-background processing", or delay processing stuff to after the
2787	event loop has handled all outstanding events.	2856	event loop has handled all outstanding events.
2788		2857
		2858	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2859
		2860	As long as there is at least one active idle watcher, libev will never
		2861	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2862	For this to work, the idle watcher doesn't need to be invoked at all - the
		2863	lowest priority will do.
		2864
		2865	This mode of operation can be useful together with an C<ev_check> watcher,
		2866	to do something on each event loop iteration - for example to balance load
		2867	between different connections.
		2868
		2869	See L</Abusing an ev_check watcher for its side-effect> for a longer
		2870	example.
		2871
2789	=head3 Watcher-Specific Functions and Data Members	2872	=head3 Watcher-Specific Functions and Data Members
2790		2873
2791	=over 4	2874	=over 4
2792		2875
2793	=item ev_idle_init (ev_idle *, callback)	2876	=item ev_idle_init (ev_idle *, callback)
…		…
2804	callback, free it. Also, use no error checking, as usual.	2887	callback, free it. Also, use no error checking, as usual.
2805		2888
2806	static void	2889	static void
2807	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	2890	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2808	{	2891	{
		2892	// stop the watcher
		2893	ev_idle_stop (loop, w);
		2894
		2895	// now we can free it
2809	free (w);	2896	free (w);
		2897
2810	// now do something you wanted to do when the program has	2898	// now do something you wanted to do when the program has
2811	// no longer anything immediate to do.	2899	// no longer anything immediate to do.
2812	}	2900	}
2813		2901
2814	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2902	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
…		…
2816	ev_idle_start (loop, idle_watcher);	2904	ev_idle_start (loop, idle_watcher);
2817		2905
2818		2906
2819	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2907	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2820		2908
2821	Prepare and check watchers are usually (but not always) used in pairs:	2909	Prepare and check watchers are often (but not always) used in pairs:
2822	prepare watchers get invoked before the process blocks and check watchers	2910	prepare watchers get invoked before the process blocks and check watchers
2823	afterwards.	2911	afterwards.
2824		2912
2825	You I<must not> call C<ev_run> or similar functions that enter	2913	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>	2914	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	2915	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	2916	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,	2917	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	2918	C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each
2831	called in pairs bracketing the blocking call.	2919	kind they will always be called in pairs bracketing the blocking call.
2832		2920
2833	Their main purpose is to integrate other event mechanisms into libev and	2921	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	2922	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	2923	variable changes, implement your own watchers, integrate net-snmp or a
2836	coroutine library and lots more. They are also occasionally useful if	2924	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	2942	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	2943	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	2944	loop from blocking if lower-priority coroutines are active, thus mapping
2857	low-priority coroutines to idle/background tasks).	2945	low-priority coroutines to idle/background tasks).
2858		2946
2859	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2947	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	2948	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).	2949	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		2950	watchers).
2862		2951
2863	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	2952	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	2953	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	2954	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	2955	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	2956	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	2957	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2869	others).	2958	others).
		2959
		2960	=head3 Abusing an C<ev_check> watcher for its side-effect
		2961
		2962	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		2963	useful because they are called once per event loop iteration. For
		2964	example, if you want to handle a large number of connections fairly, you
		2965	normally only do a bit of work for each active connection, and if there
		2966	is more work to do, you wait for the next event loop iteration, so other
		2967	connections have a chance of making progress.
		2968
		2969	Using an C<ev_check> watcher is almost enough: it will be called on the
		2970	next event loop iteration. However, that isn't as soon as possible -
		2971	without external events, your C<ev_check> watcher will not be invoked.
		2972
		2973	This is where C<ev_idle> watchers come in handy - all you need is a
		2974	single global idle watcher that is active as long as you have one active
		2975	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		2976	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		2977	invoked. Neither watcher alone can do that.
2870		2978
2871	=head3 Watcher-Specific Functions and Data Members	2979	=head3 Watcher-Specific Functions and Data Members
2872		2980
2873	=over 4	2981	=over 4
2874		2982
…		…
3075		3183
3076	=over 4	3184	=over 4
3077		3185
3078	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	3186	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
3079		3187
3080	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	3188	=item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)
3081		3189
3082	Configures the watcher to embed the given loop, which must be	3190	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	3191	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	3192	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,	3193	to invoke it (it will continue to be called until the sweep has been done,
…		…
3106	used).	3214	used).
3107		3215
3108	struct ev_loop *loop_hi = ev_default_init (0);	3216	struct ev_loop *loop_hi = ev_default_init (0);
3109	struct ev_loop *loop_lo = 0;	3217	struct ev_loop *loop_lo = 0;
3110	ev_embed embed;	3218	ev_embed embed;
3111		3219
3112	// see if there is a chance of getting one that works	3220	// see if there is a chance of getting one that works
3113	// (remember that a flags value of 0 means autodetection)	3221	// (remember that a flags value of 0 means autodetection)
3114	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3222	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
3115	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3223	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
3116	: 0;	3224	: 0;
…		…
3130	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3238	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
3131		3239
3132	struct ev_loop *loop = ev_default_init (0);	3240	struct ev_loop *loop = ev_default_init (0);
3133	struct ev_loop *loop_socket = 0;	3241	struct ev_loop *loop_socket = 0;
3134	ev_embed embed;	3242	ev_embed embed;
3135		3243
3136	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3244	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
3137	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3245	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
3138	{	3246	{
3139	ev_embed_init (&embed, 0, loop_socket);	3247	ev_embed_init (&embed, 0, loop_socket);
3140	ev_embed_start (loop, &embed);	3248	ev_embed_start (loop, &embed);
…		…
3148		3256
3149	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3257	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
3150		3258
3151	Fork watchers are called when a C<fork ()> was detected (usually because	3259	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	3260	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	3261	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,	3262	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	3263	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	3264	and calls it in the wrong process, the fork handlers will be invoked, too,
3157	handlers will be invoked, too, of course.	3265	of course.
3158		3266
3159	=head3 The special problem of life after fork - how is it possible?	3267	=head3 The special problem of life after fork - how is it possible?
3160		3268
3161	Most uses of C<fork()> consist of forking, then some simple calls to set	3269	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	3270	up/change the process environment, followed by a call to C<exec()>. This
3163	sequence should be handled by libev without any problems.	3271	sequence should be handled by libev without any problems.
3164		3272
3165	This changes when the application actually wants to do event handling	3273	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	3274	in the child, or both parent in child, in effect "continuing" after the
…		…
3243	atexit (program_exits);	3351	atexit (program_exits);
3244		3352
3245		3353
3246	=head2 C<ev_async> - how to wake up an event loop	3354	=head2 C<ev_async> - how to wake up an event loop
3247		3355
3248	In general, you cannot use an C<ev_run> from multiple threads or other	3356	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	3357	asynchronous sources such as signal handlers (as opposed to multiple event
3250	loops - those are of course safe to use in different threads).	3358	loops - those are of course safe to use in different threads).
3251		3359
3252	Sometimes, however, you need to wake up an event loop you do not control,	3360	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>	3361	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.	3363	it by calling C<ev_async_send>, which is thread- and signal safe.
3256		3364
3257	This functionality is very similar to C<ev_signal> watchers, as signals,	3365	This functionality is very similar to C<ev_signal> watchers, as signals,
3258	too, are asynchronous in nature, and signals, too, will be compressed	3366	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	3367	(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	3368	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	3369	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,	3370	signal, and C<ev_feed_signal> to signal this watcher from another thread,
3263	even without knowing which loop owns the signal.	3371	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		3372
3268	=head3 Queueing	3373	=head3 Queueing
3269		3374
3270	C<ev_async> does not support queueing of data in any way. The reason	3375	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	3376	is that the author does not know of a simple (or any) algorithm for a
…		…
3363	trust me.	3468	trust me.
3364		3469
3365	=item ev_async_send (loop, ev_async *)	3470	=item ev_async_send (loop, ev_async *)
3366		3471
3367	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3472	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	3473	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3474	returns.
		3475
3369	C<ev_feed_event>, this call is safe to do from other threads, signal or	3476	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	3477	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3371	section below on what exactly this means).	3478	embedding section below on what exactly this means).
3372		3479
3373	Note that, as with other watchers in libev, multiple events might get	3480	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	3481	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>,	3482	this is that C<ev_async> watchers are level-triggered: they are set on
3376	reset when the event loop detects that).	3483	C<ev_async_send>, reset when the event loop detects that).
3377		3484
3378	This call incurs the overhead of a system call only once per event loop	3485	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	3486	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.	3487	the event loop (or your program) is processing events. That means that
		3488	repeated calls are basically free (there is no need to avoid calls for
		3489	performance reasons) and that the overhead becomes smaller (typically
		3490	zero) under load.
3381		3491
3382	=item bool = ev_async_pending (ev_async *)	3492	=item bool = ev_async_pending (ev_async *)
3383		3493
3384	Returns a non-zero value when C<ev_async_send> has been called on the	3494	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	3495	watcher but the event has not yet been processed (or even noted) by the
…		…
3440	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3550	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3441		3551
3442	=item ev_feed_fd_event (loop, int fd, int revents)	3552	=item ev_feed_fd_event (loop, int fd, int revents)
3443		3553
3444	Feed an event on the given fd, as if a file descriptor backend detected	3554	Feed an event on the given fd, as if a file descriptor backend detected
3445	the given events it.	3555	the given events.
3446		3556
3447	=item ev_feed_signal_event (loop, int signum)	3557	=item ev_feed_signal_event (loop, int signum)
3448		3558
3449	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,	3559	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3450	which is async-safe.	3560	which is async-safe.
…		…
3455	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)	3565	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
3456		3566
3457	This section explains some common idioms that are not immediately	3567	This section explains some common idioms that are not immediately
3458	obvious. Note that examples are sprinkled over the whole manual, and this	3568	obvious. Note that examples are sprinkled over the whole manual, and this
3459	section only contains stuff that wouldn't fit anywhere else.	3569	section only contains stuff that wouldn't fit anywhere else.
		3570
		3571	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3572
		3573	Each watcher has, by default, a C<void *data> member that you can read
		3574	or modify at any time: libev will completely ignore it. This can be used
		3575	to associate arbitrary data with your watcher. If you need more data and
		3576	don't want to allocate memory separately and store a pointer to it in that
		3577	data member, you can also "subclass" the watcher type and provide your own
		3578	data:
		3579
		3580	struct my_io
		3581	{
		3582	ev_io io;
		3583	int otherfd;
		3584	void *somedata;
		3585	struct whatever *mostinteresting;
		3586	};
		3587
		3588	...
		3589	struct my_io w;
		3590	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3591
		3592	And since your callback will be called with a pointer to the watcher, you
		3593	can cast it back to your own type:
		3594
		3595	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3596	{
		3597	struct my_io *w = (struct my_io *)w_;
		3598	...
		3599	}
		3600
		3601	More interesting and less C-conformant ways of casting your callback
		3602	function type instead have been omitted.
		3603
		3604	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3605
		3606	Another common scenario is to use some data structure with multiple
		3607	embedded watchers, in effect creating your own watcher that combines
		3608	multiple libev event sources into one "super-watcher":
		3609
		3610	struct my_biggy
		3611	{
		3612	int some_data;
		3613	ev_timer t1;
		3614	ev_timer t2;
		3615	}
		3616
		3617	In this case getting the pointer to C<my_biggy> is a bit more
		3618	complicated: Either you store the address of your C<my_biggy> struct in
		3619	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3620	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3621	real programmers):
		3622
		3623	#include <stddef.h>
		3624
		3625	static void
		3626	t1_cb (EV_P_ ev_timer *w, int revents)
		3627	{
		3628	struct my_biggy big = (struct my_biggy *)
		3629	(((char *)w) - offsetof (struct my_biggy, t1));
		3630	}
		3631
		3632	static void
		3633	t2_cb (EV_P_ ev_timer *w, int revents)
		3634	{
		3635	struct my_biggy big = (struct my_biggy *)
		3636	(((char *)w) - offsetof (struct my_biggy, t2));
		3637	}
		3638
		3639	=head2 AVOIDING FINISHING BEFORE RETURNING
		3640
		3641	Often you have structures like this in event-based programs:
		3642
		3643	callback ()
		3644	{
		3645	free (request);
		3646	}
		3647
		3648	request = start_new_request (..., callback);
		3649
		3650	The intent is to start some "lengthy" operation. The C<request> could be
		3651	used to cancel the operation, or do other things with it.
		3652
		3653	It's not uncommon to have code paths in C<start_new_request> that
		3654	immediately invoke the callback, for example, to report errors. Or you add
		3655	some caching layer that finds that it can skip the lengthy aspects of the
		3656	operation and simply invoke the callback with the result.
		3657
		3658	The problem here is that this will happen I<before> C<start_new_request>
		3659	has returned, so C<request> is not set.
		3660
		3661	Even if you pass the request by some safer means to the callback, you
		3662	might want to do something to the request after starting it, such as
		3663	canceling it, which probably isn't working so well when the callback has
		3664	already been invoked.
		3665
		3666	A common way around all these issues is to make sure that
		3667	C<start_new_request> I<always> returns before the callback is invoked. If
		3668	C<start_new_request> immediately knows the result, it can artificially
		3669	delay invoking the callback by using a C<prepare> or C<idle> watcher for
		3670	example, or more sneakily, by reusing an existing (stopped) watcher and
		3671	pushing it into the pending queue:
		3672
		3673	ev_set_cb (watcher, callback);
		3674	ev_feed_event (EV_A_ watcher, 0);
		3675
		3676	This way, C<start_new_request> can safely return before the callback is
		3677	invoked, while not delaying callback invocation too much.
3460		3678
3461	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS	3679	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
3462		3680
3463	Often (especially in GUI toolkits) there are places where you have	3681	Often (especially in GUI toolkits) there are places where you have
3464	I<modal> interaction, which is most easily implemented by recursively	3682	I<modal> interaction, which is most easily implemented by recursively
…		…
3466		3684
3467	This brings the problem of exiting - a callback might want to finish the	3685	This brings the problem of exiting - a callback might want to finish the
3468	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but	3686	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
3469	a modal "Are you sure?" dialog is still waiting), or just the nested one	3687	a modal "Are you sure?" dialog is still waiting), or just the nested one
3470	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some	3688	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
3471	other combination: In these cases, C<ev_break> will not work alone.	3689	other combination: In these cases, a simple C<ev_break> will not work.
3472		3690
3473	The solution is to maintain "break this loop" variable for each C<ev_run>	3691	The solution is to maintain "break this loop" variable for each C<ev_run>
3474	invocation, and use a loop around C<ev_run> until the condition is	3692	invocation, and use a loop around C<ev_run> until the condition is
3475	triggered, using C<EVRUN_ONCE>:	3693	triggered, using C<EVRUN_ONCE>:
3476		3694
…		…
3478	int exit_main_loop = 0;	3696	int exit_main_loop = 0;
3479		3697
3480	while (!exit_main_loop)	3698	while (!exit_main_loop)
3481	ev_run (EV_DEFAULT_ EVRUN_ONCE);	3699	ev_run (EV_DEFAULT_ EVRUN_ONCE);
3482		3700
3483	// in a model watcher	3701	// in a modal watcher
3484	int exit_nested_loop = 0;	3702	int exit_nested_loop = 0;
3485		3703
3486	while (!exit_nested_loop)	3704	while (!exit_nested_loop)
3487	ev_run (EV_A_ EVRUN_ONCE);	3705	ev_run (EV_A_ EVRUN_ONCE);
3488		3706
…		…
3498	exit_main_loop = exit_nested_loop = 1;	3716	exit_main_loop = exit_nested_loop = 1;
3499		3717
3500	=head2 THREAD LOCKING EXAMPLE	3718	=head2 THREAD LOCKING EXAMPLE
3501		3719
3502	Here is a fictitious example of how to run an event loop in a different	3720	Here is a fictitious example of how to run an event loop in a different
3503	thread than where callbacks are being invoked and watchers are	3721	thread from where callbacks are being invoked and watchers are
3504	created/added/removed.	3722	created/added/removed.
3505		3723
3506	For a real-world example, see the C<EV::Loop::Async> perl module,	3724	For a real-world example, see the C<EV::Loop::Async> perl module,
3507	which uses exactly this technique (which is suited for many high-level	3725	which uses exactly this technique (which is suited for many high-level
3508	languages).	3726	languages).
…		…
3534	// now associate this with the loop	3752	// now associate this with the loop
3535	ev_set_userdata (EV_A_ u);	3753	ev_set_userdata (EV_A_ u);
3536	ev_set_invoke_pending_cb (EV_A_ l_invoke);	3754	ev_set_invoke_pending_cb (EV_A_ l_invoke);
3537	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);	3755	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
3538		3756
3539	// then create the thread running ev_loop	3757	// then create the thread running ev_run
3540	pthread_create (&u->tid, 0, l_run, EV_A);	3758	pthread_create (&u->tid, 0, l_run, EV_A);
3541	}	3759	}
3542		3760
3543	The callback for the C<ev_async> watcher does nothing: the watcher is used	3761	The callback for the C<ev_async> watcher does nothing: the watcher is used
3544	solely to wake up the event loop so it takes notice of any new watchers	3762	solely to wake up the event loop so it takes notice of any new watchers
…		…
3633	Note that sending the C<ev_async> watcher is required because otherwise	3851	Note that sending the C<ev_async> watcher is required because otherwise
3634	an event loop currently blocking in the kernel will have no knowledge	3852	an event loop currently blocking in the kernel will have no knowledge
3635	about the newly added timer. By waking up the loop it will pick up any new	3853	about the newly added timer. By waking up the loop it will pick up any new
3636	watchers in the next event loop iteration.	3854	watchers in the next event loop iteration.
3637		3855
3638	=back	3856	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3857
		3858	While the overhead of a callback that e.g. schedules a thread is small, it
		3859	is still an overhead. If you embed libev, and your main usage is with some
		3860	kind of threads or coroutines, you might want to customise libev so that
		3861	doesn't need callbacks anymore.
		3862
		3863	Imagine you have coroutines that you can switch to using a function
		3864	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3865	and that due to some magic, the currently active coroutine is stored in a
		3866	global called C<current_coro>. Then you can build your own "wait for libev
		3867	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3868	the differing C<;> conventions):
		3869
		3870	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3871	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3872
		3873	That means instead of having a C callback function, you store the
		3874	coroutine to switch to in each watcher, and instead of having libev call
		3875	your callback, you instead have it switch to that coroutine.
		3876
		3877	A coroutine might now wait for an event with a function called
		3878	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3879	matter when, or whether the watcher is active or not when this function is
		3880	called):
		3881
		3882	void
		3883	wait_for_event (ev_watcher *w)
		3884	{
		3885	ev_set_cb (w, current_coro);
		3886	switch_to (libev_coro);
		3887	}
		3888
		3889	That basically suspends the coroutine inside C<wait_for_event> and
		3890	continues the libev coroutine, which, when appropriate, switches back to
		3891	this or any other coroutine.
		3892
		3893	You can do similar tricks if you have, say, threads with an event queue -
		3894	instead of storing a coroutine, you store the queue object and instead of
		3895	switching to a coroutine, you push the watcher onto the queue and notify
		3896	any waiters.
		3897
		3898	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		3899	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3900
		3901	// my_ev.h
		3902	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3903	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3904	#include "../libev/ev.h"
		3905
		3906	// my_ev.c
		3907	#define EV_H "my_ev.h"
		3908	#include "../libev/ev.c"
		3909
		3910	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3911	F<my_ev.c> into your project. When properly specifying include paths, you
		3912	can even use F<ev.h> as header file name directly.
3639		3913
3640		3914
3641	=head1 LIBEVENT EMULATION	3915	=head1 LIBEVENT EMULATION
3642		3916
3643	Libev offers a compatibility emulation layer for libevent. It cannot	3917	Libev offers a compatibility emulation layer for libevent. It cannot
…		…
3673		3947
3674	=back	3948	=back
3675		3949
3676	=head1 C++ SUPPORT	3950	=head1 C++ SUPPORT
3677		3951
		3952	=head2 C API
		3953
		3954	The normal C API should work fine when used from C++: both ev.h and the
		3955	libev sources can be compiled as C++. Therefore, code that uses the C API
		3956	will work fine.
		3957
		3958	Proper exception specifications might have to be added to callbacks passed
		3959	to libev: exceptions may be thrown only from watcher callbacks, all
		3960	other callbacks (allocator, syserr, loop acquire/release and periodic
		3961	reschedule callbacks) must not throw exceptions, and might need a C<throw
		3962	()> specification. If you have code that needs to be compiled as both C
		3963	and C++ you can use the C<EV_THROW> macro for this:
		3964
		3965	static void
		3966	fatal_error (const char *msg) EV_THROW
		3967	{
		3968	perror (msg);
		3969	abort ();
		3970	}
		3971
		3972	...
		3973	ev_set_syserr_cb (fatal_error);
		3974
		3975	The only API functions that can currently throw exceptions are C<ev_run>,
		3976	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		3977	because it runs cleanup watchers).
		3978
		3979	Throwing exceptions in watcher callbacks is only supported if libev itself
		3980	is compiled with a C++ compiler or your C and C++ environments allow
		3981	throwing exceptions through C libraries (most do).
		3982
		3983	=head2 C++ API
		3984
3678	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3985	Libev comes with some simplistic wrapper classes for C++ that mainly allow
3679	you to use some convenience methods to start/stop watchers and also change	3986	you to use some convenience methods to start/stop watchers and also change
3680	the callback model to a model using method callbacks on objects.	3987	the callback model to a model using method callbacks on objects.
3681		3988
3682	To use it,	3989	To use it,
3683		3990
3684	#include <ev++.h>	3991	#include <ev++.h>
3685		3992
3686	This automatically includes F<ev.h> and puts all of its definitions (many	3993	This automatically includes F<ev.h> and puts all of its definitions (many
3687	of them macros) into the global namespace. All C++ specific things are	3994	of them macros) into the global namespace. All C++ specific things are
3688	put into the C<ev> namespace. It should support all the same embedding	3995	put into the C<ev> namespace. It should support all the same embedding
…		…
3697	with C<operator ()> can be used as callbacks. Other types should be easy	4004	with C<operator ()> can be used as callbacks. Other types should be easy
3698	to add as long as they only need one additional pointer for context. If	4005	to add as long as they only need one additional pointer for context. If
3699	you need support for other types of functors please contact the author	4006	you need support for other types of functors please contact the author
3700	(preferably after implementing it).	4007	(preferably after implementing it).
3701		4008
		4009	For all this to work, your C++ compiler either has to use the same calling
		4010	conventions as your C compiler (for static member functions), or you have
		4011	to embed libev and compile libev itself as C++.
		4012
3702	Here is a list of things available in the C<ev> namespace:	4013	Here is a list of things available in the C<ev> namespace:
3703		4014
3704	=over 4	4015	=over 4
3705		4016
3706	=item C<ev::READ>, C<ev::WRITE> etc.	4017	=item C<ev::READ>, C<ev::WRITE> etc.
…		…
3715	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4026	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3716		4027
3717	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4028	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
3718	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4029	the same name in the C<ev> namespace, with the exception of C<ev_signal>
3719	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4030	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3720	defines by many implementations.	4031	defined by many implementations.
3721		4032
3722	All of those classes have these methods:	4033	All of those classes have these methods:
3723		4034
3724	=over 4	4035	=over 4
3725		4036
…		…
3787	void operator() (ev::io &w, int revents)	4098	void operator() (ev::io &w, int revents)
3788	{	4099	{
3789	...	4100	...
3790	}	4101	}
3791	}	4102	}
3792		4103
3793	myfunctor f;	4104	myfunctor f;
3794		4105
3795	ev::io w;	4106	ev::io w;
3796	w.set (&f);	4107	w.set (&f);
3797		4108
…		…
3815	Associates a different C<struct ev_loop> with this watcher. You can only	4126	Associates a different C<struct ev_loop> with this watcher. You can only
3816	do this when the watcher is inactive (and not pending either).	4127	do this when the watcher is inactive (and not pending either).
3817		4128
3818	=item w->set ([arguments])	4129	=item w->set ([arguments])
3819		4130
3820	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this	4131	Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>),
3821	method or a suitable start method must be called at least once. Unlike the	4132	with the same arguments. Either this method or a suitable start method
3822	C counterpart, an active watcher gets automatically stopped and restarted	4133	must be called at least once. Unlike the C counterpart, an active watcher
3823	when reconfiguring it with this method.	4134	gets automatically stopped and restarted when reconfiguring it with this
		4135	method.
		4136
		4137	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4138	clashing with the C<set (loop)> method.
3824		4139
3825	=item w->start ()	4140	=item w->start ()
3826		4141
3827	Starts the watcher. Note that there is no C<loop> argument, as the	4142	Starts the watcher. Note that there is no C<loop> argument, as the
3828	constructor already stores the event loop.	4143	constructor already stores the event loop.
…		…
3858	watchers in the constructor.	4173	watchers in the constructor.
3859		4174
3860	class myclass	4175	class myclass
3861	{	4176	{
3862	ev::io io ; void io_cb (ev::io &w, int revents);	4177	ev::io io ; void io_cb (ev::io &w, int revents);
3863	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);	4178	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3864	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4179	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3865		4180
3866	myclass (int fd)	4181	myclass (int fd)
3867	{	4182	{
3868	io .set <myclass, &myclass::io_cb > (this);	4183	io .set <myclass, &myclass::io_cb > (this);
…		…
3919	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4234	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3920		4235
3921	=item D	4236	=item D
3922		4237
3923	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4238	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3924	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4239	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3925		4240
3926	=item Ocaml	4241	=item Ocaml
3927		4242
3928	Erkki Seppala has written Ocaml bindings for libev, to be found at	4243	Erkki Seppala has written Ocaml bindings for libev, to be found at
3929	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4244	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
…		…
3932		4247
3933	Brian Maher has written a partial interface to libev for lua (at the	4248	Brian Maher has written a partial interface to libev for lua (at the
3934	time of this writing, only C<ev_io> and C<ev_timer>), to be found at	4249	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
3935	L<http://github.com/brimworks/lua-ev>.	4250	L<http://github.com/brimworks/lua-ev>.
3936		4251
		4252	=item Javascript
		4253
		4254	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4255
		4256	=item Others
		4257
		4258	There are others, and I stopped counting.
		4259
3937	=back	4260	=back
3938		4261
3939		4262
3940	=head1 MACRO MAGIC	4263	=head1 MACRO MAGIC
3941		4264
…		…
3977	suitable for use with C<EV_A>.	4300	suitable for use with C<EV_A>.
3978		4301
3979	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4302	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3980		4303
3981	Similar to the other two macros, this gives you the value of the default	4304	Similar to the other two macros, this gives you the value of the default
3982	loop, if multiple loops are supported ("ev loop default").	4305	loop, if multiple loops are supported ("ev loop default"). The default loop
		4306	will be initialised if it isn't already initialised.
		4307
		4308	For non-multiplicity builds, these macros do nothing, so you always have
		4309	to initialise the loop somewhere.
3983		4310
3984	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4311	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3985		4312
3986	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4313	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3987	default loop has been initialised (C<UC> == unchecked). Their behaviour	4314	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
4132	supported). It will also not define any of the structs usually found in	4459	supported). It will also not define any of the structs usually found in
4133	F<event.h> that are not directly supported by the libev core alone.	4460	F<event.h> that are not directly supported by the libev core alone.
4134		4461
4135	In standalone mode, libev will still try to automatically deduce the	4462	In standalone mode, libev will still try to automatically deduce the
4136	configuration, but has to be more conservative.	4463	configuration, but has to be more conservative.
		4464
		4465	=item EV_USE_FLOOR
		4466
		4467	If defined to be C<1>, libev will use the C<floor ()> function for its
		4468	periodic reschedule calculations, otherwise libev will fall back on a
		4469	portable (slower) implementation. If you enable this, you usually have to
		4470	link against libm or something equivalent. Enabling this when the C<floor>
		4471	function is not available will fail, so the safe default is to not enable
		4472	this.
4137		4473
4138	=item EV_USE_MONOTONIC	4474	=item EV_USE_MONOTONIC
4139		4475
4140	If defined to be C<1>, libev will try to detect the availability of the	4476	If defined to be C<1>, libev will try to detect the availability of the
4141	monotonic clock option at both compile time and runtime. Otherwise no	4477	monotonic clock option at both compile time and runtime. Otherwise no
…		…
4226		4562
4227	If programs implement their own fd to handle mapping on win32, then this	4563	If programs implement their own fd to handle mapping on win32, then this
4228	macro can be used to override the C<close> function, useful to unregister	4564	macro can be used to override the C<close> function, useful to unregister
4229	file descriptors again. Note that the replacement function has to close	4565	file descriptors again. Note that the replacement function has to close
4230	the underlying OS handle.	4566	the underlying OS handle.
		4567
		4568	=item EV_USE_WSASOCKET
		4569
		4570	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4571	communication socket, which works better in some environments. Otherwise,
		4572	the normal C<socket> function will be used, which works better in other
		4573	environments.
4231		4574
4232	=item EV_USE_POLL	4575	=item EV_USE_POLL
4233		4576
4234	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4577	If defined to be C<1>, libev will compile in support for the C<poll>(2)
4235	backend. Otherwise it will be enabled on non-win32 platforms. It	4578	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
4271	If defined to be C<1>, libev will compile in support for the Linux inotify	4614	If defined to be C<1>, libev will compile in support for the Linux inotify
4272	interface to speed up C<ev_stat> watchers. Its actual availability will	4615	interface to speed up C<ev_stat> watchers. Its actual availability will
4273	be detected at runtime. If undefined, it will be enabled if the headers	4616	be detected at runtime. If undefined, it will be enabled if the headers
4274	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4617	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
4275		4618
		4619	=item EV_NO_SMP
		4620
		4621	If defined to be C<1>, libev will assume that memory is always coherent
		4622	between threads, that is, threads can be used, but threads never run on
		4623	different cpus (or different cpu cores). This reduces dependencies
		4624	and makes libev faster.
		4625
		4626	=item EV_NO_THREADS
		4627
		4628	If defined to be C<1>, libev will assume that it will never be called from
		4629	different threads (that includes signal handlers), which is a stronger
		4630	assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes
		4631	libev faster.
		4632
4276	=item EV_ATOMIC_T	4633	=item EV_ATOMIC_T
4277		4634
4278	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4635	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
4279	access is atomic with respect to other threads or signal contexts. No such	4636	access is atomic with respect to other threads or signal contexts. No
4280	type is easily found in the C language, so you can provide your own type	4637	such type is easily found in the C language, so you can provide your own
4281	that you know is safe for your purposes. It is used both for signal handler "locking"	4638	type that you know is safe for your purposes. It is used both for signal
4282	as well as for signal and thread safety in C<ev_async> watchers.	4639	handler "locking" as well as for signal and thread safety in C<ev_async>
		4640	watchers.
4283		4641
4284	In the absence of this define, libev will use C<sig_atomic_t volatile>	4642	In the absence of this define, libev will use C<sig_atomic_t volatile>
4285	(from F<signal.h>), which is usually good enough on most platforms.	4643	(from F<signal.h>), which is usually good enough on most platforms.
4286		4644
4287	=item EV_H (h)	4645	=item EV_H (h)
…		…
4314	will have the C<struct ev_loop *> as first argument, and you can create	4672	will have the C<struct ev_loop *> as first argument, and you can create
4315	additional independent event loops. Otherwise there will be no support	4673	additional independent event loops. Otherwise there will be no support
4316	for multiple event loops and there is no first event loop pointer	4674	for multiple event loops and there is no first event loop pointer
4317	argument. Instead, all functions act on the single default loop.	4675	argument. Instead, all functions act on the single default loop.
4318		4676
		4677	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4678	default loop when multiplicity is switched off - you always have to
		4679	initialise the loop manually in this case.
		4680
4319	=item EV_MINPRI	4681	=item EV_MINPRI
4320		4682
4321	=item EV_MAXPRI	4683	=item EV_MAXPRI
4322		4684
4323	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4685	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
4359	#define EV_USE_POLL 1	4721	#define EV_USE_POLL 1
4360	#define EV_CHILD_ENABLE 1	4722	#define EV_CHILD_ENABLE 1
4361	#define EV_ASYNC_ENABLE 1	4723	#define EV_ASYNC_ENABLE 1
4362		4724
4363	The actual value is a bitset, it can be a combination of the following	4725	The actual value is a bitset, it can be a combination of the following
4364	values:	4726	values (by default, all of these are enabled):
4365		4727
4366	=over 4	4728	=over 4
4367		4729
4368	=item C<1> - faster/larger code	4730	=item C<1> - faster/larger code
4369		4731
…		…
4373	code size by roughly 30% on amd64).	4735	code size by roughly 30% on amd64).
4374		4736
4375	When optimising for size, use of compiler flags such as C<-Os> with	4737	When optimising for size, use of compiler flags such as C<-Os> with
4376	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of	4738	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
4377	assertions.	4739	assertions.
		4740
		4741	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4742	(e.g. gcc with C<-Os>).
4378		4743
4379	=item C<2> - faster/larger data structures	4744	=item C<2> - faster/larger data structures
4380		4745
4381	Replaces the small 2-heap for timer management by a faster 4-heap, larger	4746	Replaces the small 2-heap for timer management by a faster 4-heap, larger
4382	hash table sizes and so on. This will usually further increase code size	4747	hash table sizes and so on. This will usually further increase code size
4383	and can additionally have an effect on the size of data structures at	4748	and can additionally have an effect on the size of data structures at
4384	runtime.	4749	runtime.
4385		4750
		4751	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4752	(e.g. gcc with C<-Os>).
		4753
4386	=item C<4> - full API configuration	4754	=item C<4> - full API configuration
4387		4755
4388	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and	4756	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
4389	enables multiplicity (C<EV_MULTIPLICITY>=1).	4757	enables multiplicity (C<EV_MULTIPLICITY>=1).
4390		4758
…		…
4420		4788
4421	With an intelligent-enough linker (gcc+binutils are intelligent enough	4789	With an intelligent-enough linker (gcc+binutils are intelligent enough
4422	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by	4790	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
4423	your program might be left out as well - a binary starting a timer and an	4791	your program might be left out as well - a binary starting a timer and an
4424	I/O watcher then might come out at only 5Kb.	4792	I/O watcher then might come out at only 5Kb.
		4793
		4794	=item EV_API_STATIC
		4795
		4796	If this symbol is defined (by default it is not), then all identifiers
		4797	will have static linkage. This means that libev will not export any
		4798	identifiers, and you cannot link against libev anymore. This can be useful
		4799	when you embed libev, only want to use libev functions in a single file,
		4800	and do not want its identifiers to be visible.
		4801
		4802	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4803	wants to use libev.
		4804
		4805	This option only works when libev is compiled with a C compiler, as C++
		4806	doesn't support the required declaration syntax.
4425		4807
4426	=item EV_AVOID_STDIO	4808	=item EV_AVOID_STDIO
4427		4809
4428	If this is set to C<1> at compiletime, then libev will avoid using stdio	4810	If this is set to C<1> at compiletime, then libev will avoid using stdio
4429	functions (printf, scanf, perror etc.). This will increase the code size	4811	functions (printf, scanf, perror etc.). This will increase the code size
…		…
4573	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4955	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4574		4956
4575	#include "ev_cpp.h"	4957	#include "ev_cpp.h"
4576	#include "ev.c"	4958	#include "ev.c"
4577		4959
4578	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4960	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4579		4961
4580	=head2 THREADS AND COROUTINES	4962	=head2 THREADS AND COROUTINES
4581		4963
4582	=head3 THREADS	4964	=head3 THREADS
4583		4965
…		…
4634	default loop and triggering an C<ev_async> watcher from the default loop	5016	default loop and triggering an C<ev_async> watcher from the default loop
4635	watcher callback into the event loop interested in the signal.	5017	watcher callback into the event loop interested in the signal.
4636		5018
4637	=back	5019	=back
4638		5020
4639	See also L<THREAD LOCKING EXAMPLE>.	5021	See also L</THREAD LOCKING EXAMPLE>.
4640		5022
4641	=head3 COROUTINES	5023	=head3 COROUTINES
4642		5024
4643	Libev is very accommodating to coroutines ("cooperative threads"):	5025	Libev is very accommodating to coroutines ("cooperative threads"):
4644	libev fully supports nesting calls to its functions from different	5026	libev fully supports nesting calls to its functions from different
…		…
4809	requires, and its I/O model is fundamentally incompatible with the POSIX	5191	requires, and its I/O model is fundamentally incompatible with the POSIX
4810	model. Libev still offers limited functionality on this platform in	5192	model. Libev still offers limited functionality on this platform in
4811	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5193	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4812	descriptors. This only applies when using Win32 natively, not when using	5194	descriptors. This only applies when using Win32 natively, not when using
4813	e.g. cygwin. Actually, it only applies to the microsofts own compilers,	5195	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
4814	as every compielr comes with a slightly differently broken/incompatible	5196	as every compiler comes with a slightly differently broken/incompatible
4815	environment.	5197	environment.
4816		5198
4817	Lifting these limitations would basically require the full	5199	Lifting these limitations would basically require the full
4818	re-implementation of the I/O system. If you are into this kind of thing,	5200	re-implementation of the I/O system. If you are into this kind of thing,
4819	then note that glib does exactly that for you in a very portable way (note	5201	then note that glib does exactly that for you in a very portable way (note
…		…
4935	thread" or will block signals process-wide, both behaviours would	5317	thread" or will block signals process-wide, both behaviours would
4936	be compatible with libev. Interaction between C<sigprocmask> and	5318	be compatible with libev. Interaction between C<sigprocmask> and
4937	C<pthread_sigmask> could complicate things, however.	5319	C<pthread_sigmask> could complicate things, however.
4938		5320
4939	The most portable way to handle signals is to block signals in all threads	5321	The most portable way to handle signals is to block signals in all threads
4940	except the initial one, and run the default loop in the initial thread as	5322	except the initial one, and run the signal handling loop in the initial
4941	well.	5323	thread as well.
4942		5324
4943	=item C<long> must be large enough for common memory allocation sizes	5325	=item C<long> must be large enough for common memory allocation sizes
4944		5326
4945	To improve portability and simplify its API, libev uses C<long> internally	5327	To improve portability and simplify its API, libev uses C<long> internally
4946	instead of C<size_t> when allocating its data structures. On non-POSIX	5328	instead of C<size_t> when allocating its data structures. On non-POSIX
…		…
4952		5334
4953	The type C<double> is used to represent timestamps. It is required to	5335	The type C<double> is used to represent timestamps. It is required to
4954	have at least 51 bits of mantissa (and 9 bits of exponent), which is	5336	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4955	good enough for at least into the year 4000 with millisecond accuracy	5337	good enough for at least into the year 4000 with millisecond accuracy
4956	(the design goal for libev). This requirement is overfulfilled by	5338	(the design goal for libev). This requirement is overfulfilled by
4957	implementations using IEEE 754, which is basically all existing ones. With	5339	implementations using IEEE 754, which is basically all existing ones.
		5340
4958	IEEE 754 doubles, you get microsecond accuracy until at least 2200.	5341	With IEEE 754 doubles, you get microsecond accuracy until at least the
		5342	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5343	is either obsolete or somebody patched it to use C<long double> or
		5344	something like that, just kidding).
4959		5345
4960	=back	5346	=back
4961		5347
4962	If you know of other additional requirements drop me a note.	5348	If you know of other additional requirements drop me a note.
4963		5349
…		…
5025	=item Processing ev_async_send: O(number_of_async_watchers)	5411	=item Processing ev_async_send: O(number_of_async_watchers)
5026		5412
5027	=item Processing signals: O(max_signal_number)	5413	=item Processing signals: O(max_signal_number)
5028		5414
5029	Sending involves a system call I<iff> there were no other C<ev_async_send>	5415	Sending involves a system call I<iff> there were no other C<ev_async_send>
5030	calls in the current loop iteration. Checking for async and signal events	5416	calls in the current loop iteration and the loop is currently
		5417	blocked. Checking for async and signal events involves iterating over all
5031	involves iterating over all running async watchers or all signal numbers.	5418	running async watchers or all signal numbers.
5032		5419
5033	=back	5420	=back
5034		5421
5035		5422
5036	=head1 PORTING FROM LIBEV 3.X TO 4.X	5423	=head1 PORTING FROM LIBEV 3.X TO 4.X
…		…
5045	=over 4	5432	=over 4
5046		5433
5047	=item C<EV_COMPAT3> backwards compatibility mechanism	5434	=item C<EV_COMPAT3> backwards compatibility mechanism
5048		5435
5049	The backward compatibility mechanism can be controlled by	5436	The backward compatibility mechanism can be controlled by
5050	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>	5437	C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING>
5051	section.	5438	section.
5052		5439
5053	=item C<ev_default_destroy> and C<ev_default_fork> have been removed	5440	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
5054		5441
5055	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:	5442	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
…		…
5098	=over 4	5485	=over 4
5099		5486
5100	=item active	5487	=item active
5101		5488
5102	A watcher is active as long as it has been started and not yet stopped.	5489	A watcher is active as long as it has been started and not yet stopped.
5103	See L<WATCHER STATES> for details.	5490	See L</WATCHER STATES> for details.
5104		5491
5105	=item application	5492	=item application
5106		5493
5107	In this document, an application is whatever is using libev.	5494	In this document, an application is whatever is using libev.
5108		5495
…		…
5144	watchers and events.	5531	watchers and events.
5145		5532
5146	=item pending	5533	=item pending
5147		5534
5148	A watcher is pending as soon as the corresponding event has been	5535	A watcher is pending as soon as the corresponding event has been
5149	detected. See L<WATCHER STATES> for details.	5536	detected. See L</WATCHER STATES> for details.
5150		5537
5151	=item real time	5538	=item real time
5152		5539
5153	The physical time that is observed. It is apparently strictly monotonic :)	5540	The physical time that is observed. It is apparently strictly monotonic :)
5154		5541
5155	=item wall-clock time	5542	=item wall-clock time
5156		5543
5157	The time and date as shown on clocks. Unlike real time, it can actually	5544	The time and date as shown on clocks. Unlike real time, it can actually
5158	be wrong and jump forwards and backwards, e.g. when the you adjust your	5545	be wrong and jump forwards and backwards, e.g. when you adjust your
5159	clock.	5546	clock.
5160		5547
5161	=item watcher	5548	=item watcher
5162		5549
5163	A data structure that describes interest in certain events. Watchers need	5550	A data structure that describes interest in certain events. Watchers need
…		…
5166	=back	5553	=back
5167		5554
5168	=head1 AUTHOR	5555	=head1 AUTHOR
5169		5556
5170	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael	5557	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
5171	Magnusson and Emanuele Giaquinta.	5558	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
5172		5559

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