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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.
…		…
406	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	416	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
407	without a system call and thus I<very> fast, but my GNU/Linux system also has	417	without a system call and thus I<very> fast, but my GNU/Linux system also has
408	C<pthread_atfork> which is even faster).	418	C<pthread_atfork> which is even faster).
409		419
410	The big advantage of this flag is that you can forget about fork (and	420	The big advantage of this flag is that you can forget about fork (and
411	forget about forgetting to tell libev about forking) when you use this	421	forget about forgetting to tell libev about forking, although you still
412	flag.	422	have to ignore C<SIGPIPE>) when you use this flag.
413		423
414	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	424	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
415	environment variable.	425	environment variable.
416		426
417	=item C<EVFLAG_NOINOTIFY>	427	=item C<EVFLAG_NOINOTIFY>
…		…
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,
		528	cobbled together in a hurry, no thought to design or interaction with
		529	others. Oh, the pain, will it ever stop...
512		530
513	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
514	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
515	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
516	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
…		…
553		571
554	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
555	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
556	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
557	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
558	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
559	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
560	cases	578	drops fds silently in similarly hard-to-detect cases.
561		579
562	This backend usually performs well under most conditions.	580	This backend usually performs well under most conditions.
563		581
564	While nominally embeddable in other event loops, this doesn't work	582	While nominally embeddable in other event loops, this doesn't work
565	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
…		…
592	On the positive side, this backend actually performed fully to	610	On the positive side, this backend actually performed fully to
593	specification in all tests and is fully embeddable, which is a rare feat	611	specification in all tests and is fully embeddable, which is a rare feat
594	among the OS-specific backends (I vastly prefer correctness over speed	612	among the OS-specific backends (I vastly prefer correctness over speed
595	hacks).	613	hacks).
596		614
597	On the negative side, the interface is I<bizarre>, with the event polling	615	On the negative side, the interface is I<bizarre> - so bizarre that
		616	even sun itself gets it wrong in their code examples: The event polling
598	function sometimes returning events to the caller even though an error	617	function sometimes returns events to the caller even though an error
599	occured, 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
600	even documented that way) - deadly for edge-triggered interfaces, but	619	even documented that way) - deadly for edge-triggered interfaces where you
		620	absolutely have to know whether an event occurred or not because you have
		621	to re-arm the watcher.
		622
601	fortunately libev seems to be able to work around it.	623	Fortunately libev seems to be able to work around these idiocies.
602		624
603	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
604	C<EVBACKEND_POLL>.	626	C<EVBACKEND_POLL>.
605		627
606	=item C<EVBACKEND_ALL>	628	=item C<EVBACKEND_ALL>
…		…
660	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>
661	and C<ev_loop_destroy>.	683	and C<ev_loop_destroy>.
662		684
663	=item ev_loop_fork (loop)	685	=item ev_loop_fork (loop)
664		686
665	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
666	reinitialise the kernel state for backends that have one. Despite the	688	to reinitialise the kernel state for backends that have one. Despite
667	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
668	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
669	child before resuming or calling C<ev_run>.	692	C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>.
670		693
		694	In addition, if you want to reuse a loop (via this function or
		695	C<EVFLAG_FORKCHECK>), you I<also> have to ignore C<SIGPIPE>.
		696
671	Again, you I<have> to call it on I<any> loop that you want to re-use after	697	Again, you I<have> to call it on I<any> loop that you want to re-use after
672	a fork, I<even if you do not plan to use the loop in the parent>. This is	698	a fork, I<even if you do not plan to use the loop in the parent>. This is
673	because some kernel interfaces *cough* I<kqueue> *cough* do funny things	699	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
674	during fork.	700	during fork.
675		701
676	On the other hand, you only need to call this function in the child	702	On the other hand, you only need to call this function in the child
…		…
746		772
747	This function is rarely useful, but when some event callback runs for a	773	This function is rarely useful, but when some event callback runs for a
748	very long time without entering the event loop, updating libev's idea of	774	very long time without entering the event loop, updating libev's idea of
749	the current time is a good idea.	775	the current time is a good idea.
750		776
751	See also L<The special problem of time updates> in the C<ev_timer> section.	777	See also L</The special problem of time updates> in the C<ev_timer> section.
752		778
753	=item ev_suspend (loop)	779	=item ev_suspend (loop)
754		780
755	=item ev_resume (loop)	781	=item ev_resume (loop)
756		782
…		…
774	without a previous call to C<ev_suspend>.	800	without a previous call to C<ev_suspend>.
775		801
776	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	802	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
777	event loop time (see C<ev_now_update>).	803	event loop time (see C<ev_now_update>).
778		804
779	=item ev_run (loop, int flags)	805	=item bool ev_run (loop, int flags)
780		806
781	Finally, this is it, the event handler. This function usually is called	807	Finally, this is it, the event handler. This function usually is called
782	after you have initialised all your watchers and you want to start	808	after you have initialised all your watchers and you want to start
783	handling events. It will ask the operating system for any new events, call	809	handling events. It will ask the operating system for any new events, call
784	the watcher callbacks, an then repeat the whole process indefinitely: This	810	the watcher callbacks, and then repeat the whole process indefinitely: This
785	is why event loops are called I<loops>.	811	is why event loops are called I<loops>.
786		812
787	If the flags argument is specified as C<0>, it will keep handling events	813	If the flags argument is specified as C<0>, it will keep handling events
788	until either no event watchers are active anymore or C<ev_break> was	814	until either no event watchers are active anymore or C<ev_break> was
789	called.	815	called.
		816
		817	The return value is false if there are no more active watchers (which
		818	usually means "all jobs done" or "deadlock"), and true in all other cases
		819	(which usually means " you should call C<ev_run> again").
790		820
791	Please note that an explicit C<ev_break> is usually better than	821	Please note that an explicit C<ev_break> is usually better than
792	relying on all watchers to be stopped when deciding when a program has	822	relying on all watchers to be stopped when deciding when a program has
793	finished (especially in interactive programs), but having a program	823	finished (especially in interactive programs), but having a program
794	that automatically loops as long as it has to and no longer by virtue	824	that automatically loops as long as it has to and no longer by virtue
795	of relying on its watchers stopping correctly, that is truly a thing of	825	of relying on its watchers stopping correctly, that is truly a thing of
796	beauty.	826	beauty.
797		827
798	This function is also I<mostly> exception-safe - you can break out of	828	This function is I<mostly> exception-safe - you can break out of a
799	a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++	829	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
800	exception and so on. This does not decrement the C<ev_depth> value, nor	830	exception and so on. This does not decrement the C<ev_depth> value, nor
801	will it clear any outstanding C<EVBREAK_ONE> breaks.	831	will it clear any outstanding C<EVBREAK_ONE> breaks.
802		832
803	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle	833	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
804	those events and any already outstanding ones, but will not wait and	834	those events and any already outstanding ones, but will not wait and
…		…
816	This is useful if you are waiting for some external event in conjunction	846	This is useful if you are waiting for some external event in conjunction
817	with something not expressible using other libev watchers (i.e. "roll your	847	with something not expressible using other libev watchers (i.e. "roll your
818	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	848	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
819	usually a better approach for this kind of thing.	849	usually a better approach for this kind of thing.
820		850
821	Here are the gory details of what C<ev_run> does:	851	Here are the gory details of what C<ev_run> does (this is for your
		852	understanding, not a guarantee that things will work exactly like this in
		853	future versions):
822		854
823	- Increment loop depth.	855	- Increment loop depth.
824	- Reset the ev_break status.	856	- Reset the ev_break status.
825	- Before the first iteration, call any pending watchers.	857	- Before the first iteration, call any pending watchers.
826	LOOP:	858	LOOP:
…		…
859	anymore.	891	anymore.
860		892
861	... queue jobs here, make sure they register event watchers as long	893	... queue jobs here, make sure they register event watchers as long
862	... as they still have work to do (even an idle watcher will do..)	894	... as they still have work to do (even an idle watcher will do..)
863	ev_run (my_loop, 0);	895	ev_run (my_loop, 0);
864	... jobs done or somebody called unloop. yeah!	896	... jobs done or somebody called break. yeah!
865		897
866	=item ev_break (loop, how)	898	=item ev_break (loop, how)
867		899
868	Can be used to make a call to C<ev_run> return early (but only after it	900	Can be used to make a call to C<ev_run> return early (but only after it
869	has processed all outstanding events). The C<how> argument must be either	901	has processed all outstanding events). The C<how> argument must be either
…		…
932	overhead for the actual polling but can deliver many events at once.	964	overhead for the actual polling but can deliver many events at once.
933		965
934	By setting a higher I<io collect interval> you allow libev to spend more	966	By setting a higher I<io collect interval> you allow libev to spend more
935	time collecting I/O events, so you can handle more events per iteration,	967	time collecting I/O events, so you can handle more events per iteration,
936	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	968	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
937	C<ev_timer>) will be not affected. Setting this to a non-null value will	969	C<ev_timer>) will not be affected. Setting this to a non-null value will
938	introduce an additional C<ev_sleep ()> call into most loop iterations. The	970	introduce an additional C<ev_sleep ()> call into most loop iterations. The
939	sleep time ensures that libev will not poll for I/O events more often then	971	sleep time ensures that libev will not poll for I/O events more often then
940	once per this interval, on average.	972	once per this interval, on average (as long as the host time resolution is
		973	good enough).
941		974
942	Likewise, by setting a higher I<timeout collect interval> you allow libev	975	Likewise, by setting a higher I<timeout collect interval> you allow libev
943	to spend more time collecting timeouts, at the expense of increased	976	to spend more time collecting timeouts, at the expense of increased
944	latency/jitter/inexactness (the watcher callback will be called	977	latency/jitter/inexactness (the watcher callback will be called
945	later). C<ev_io> watchers will not be affected. Setting this to a non-null	978	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
991	invoke the actual watchers inside another context (another thread etc.).	1024	invoke the actual watchers inside another context (another thread etc.).
992		1025
993	If you want to reset the callback, use C<ev_invoke_pending> as new	1026	If you want to reset the callback, use C<ev_invoke_pending> as new
994	callback.	1027	callback.
995		1028
996	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))	1029	=item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())
997		1030
998	Sometimes you want to share the same loop between multiple threads. This	1031	Sometimes you want to share the same loop between multiple threads. This
999	can be done relatively simply by putting mutex_lock/unlock calls around	1032	can be done relatively simply by putting mutex_lock/unlock calls around
1000	each call to a libev function.	1033	each call to a libev function.
1001		1034
1002	However, C<ev_run> can run an indefinite time, so it is not feasible	1035	However, C<ev_run> can run an indefinite time, so it is not feasible
1003	to wait for it to return. One way around this is to wake up the event	1036	to wait for it to return. One way around this is to wake up the event
1004	loop via C<ev_break> and C<av_async_send>, another way is to set these	1037	loop via C<ev_break> and C<ev_async_send>, another way is to set these
1005	I<release> and I<acquire> callbacks on the loop.	1038	I<release> and I<acquire> callbacks on the loop.
1006		1039
1007	When set, then C<release> will be called just before the thread is	1040	When set, then C<release> will be called just before the thread is
1008	suspended waiting for new events, and C<acquire> is called just	1041	suspended waiting for new events, and C<acquire> is called just
1009	afterwards.	1042	afterwards.
…		…
1149		1182
1150	=item C<EV_PREPARE>	1183	=item C<EV_PREPARE>
1151		1184
1152	=item C<EV_CHECK>	1185	=item C<EV_CHECK>
1153		1186
1154	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts	1187	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to
1155	to gather new events, and all C<ev_check> watchers are invoked just after	1188	gather new events, and all C<ev_check> watchers are queued (not invoked)
1156	C<ev_run> has gathered them, but before it invokes any callbacks for any	1189	just after C<ev_run> has gathered them, but before it queues any callbacks
		1190	for any received events. That means C<ev_prepare> watchers are the last
		1191	watchers invoked before the event loop sleeps or polls for new events, and
		1192	C<ev_check> watchers will be invoked before any other watchers of the same
		1193	or lower priority within an event loop iteration.
		1194
1157	received events. Callbacks of both watcher types can start and stop as	1195	Callbacks of both watcher types can start and stop as many watchers as
1158	many watchers as they want, and all of them will be taken into account	1196	they want, and all of them will be taken into account (for example, a
1159	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1197	C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from
1160	C<ev_run> from blocking).	1198	blocking).
1161		1199
1162	=item C<EV_EMBED>	1200	=item C<EV_EMBED>
1163		1201
1164	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1202	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1165		1203
…		…
1288		1326
1289	=item callback ev_cb (ev_TYPE *watcher)	1327	=item callback ev_cb (ev_TYPE *watcher)
1290		1328
1291	Returns the callback currently set on the watcher.	1329	Returns the callback currently set on the watcher.
1292		1330
1293	=item ev_cb_set (ev_TYPE *watcher, callback)	1331	=item ev_set_cb (ev_TYPE *watcher, callback)
1294		1332
1295	Change the callback. You can change the callback at virtually any time	1333	Change the callback. You can change the callback at virtually any time
1296	(modulo threads).	1334	(modulo threads).
1297		1335
1298	=item ev_set_priority (ev_TYPE *watcher, int priority)	1336	=item ev_set_priority (ev_TYPE *watcher, int priority)
…		…
1316	or might not have been clamped to the valid range.	1354	or might not have been clamped to the valid range.
1317		1355
1318	The default priority used by watchers when no priority has been set is	1356	The default priority used by watchers when no priority has been set is
1319	always C<0>, which is supposed to not be too high and not be too low :).	1357	always C<0>, which is supposed to not be too high and not be too low :).
1320		1358
1321	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of	1359	See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1322	priorities.	1360	priorities.
1323		1361
1324	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1362	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1325		1363
1326	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1364	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
…		…
1351	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related	1389	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1352	functions that do not need a watcher.	1390	functions that do not need a watcher.
1353		1391
1354	=back	1392	=back
1355		1393
1356	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1394	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
1357		1395	OWN COMPOSITE WATCHERS> idioms.
1358	Each watcher has, by default, a member C<void *data> that you can change
1359	and read at any time: libev will completely ignore it. This can be used
1360	to associate arbitrary data with your watcher. If you need more data and
1361	don't want to allocate memory and store a pointer to it in that data
1362	member, you can also "subclass" the watcher type and provide your own
1363	data:
1364
1365	struct my_io
1366	{
1367	ev_io io;
1368	int otherfd;
1369	void *somedata;
1370	struct whatever *mostinteresting;
1371	};
1372
1373	...
1374	struct my_io w;
1375	ev_io_init (&w.io, my_cb, fd, EV_READ);
1376
1377	And since your callback will be called with a pointer to the watcher, you
1378	can cast it back to your own type:
1379
1380	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1381	{
1382	struct my_io *w = (struct my_io *)w_;
1383	...
1384	}
1385
1386	More interesting and less C-conformant ways of casting your callback type
1387	instead have been omitted.
1388
1389	Another common scenario is to use some data structure with multiple
1390	embedded watchers:
1391
1392	struct my_biggy
1393	{
1394	int some_data;
1395	ev_timer t1;
1396	ev_timer t2;
1397	}
1398
1399	In this case getting the pointer to C<my_biggy> is a bit more
1400	complicated: Either you store the address of your C<my_biggy> struct
1401	in the C<data> member of the watcher (for woozies), or you need to use
1402	some pointer arithmetic using C<offsetof> inside your watchers (for real
1403	programmers):
1404
1405	#include <stddef.h>
1406
1407	static void
1408	t1_cb (EV_P_ ev_timer *w, int revents)
1409	{
1410	struct my_biggy big = (struct my_biggy *)
1411	(((char *)w) - offsetof (struct my_biggy, t1));
1412	}
1413
1414	static void
1415	t2_cb (EV_P_ ev_timer *w, int revents)
1416	{
1417	struct my_biggy big = (struct my_biggy *)
1418	(((char *)w) - offsetof (struct my_biggy, t2));
1419	}
1420		1396
1421	=head2 WATCHER STATES	1397	=head2 WATCHER STATES
1422		1398
1423	There are various watcher states mentioned throughout this manual -	1399	There are various watcher states mentioned throughout this manual -
1424	active, pending and so on. In this section these states and the rules to	1400	active, pending and so on. In this section these states and the rules to
1425	transition between them will be described in more detail - and while these	1401	transition between them will be described in more detail - and while these
1426	rules might look complicated, they usually do "the right thing".	1402	rules might look complicated, they usually do "the right thing".
1427		1403
1428	=over 4	1404	=over 4
1429		1405
1430	=item initialiased	1406	=item initialised
1431		1407
1432	Before a watcher can be registered with the event looop it has to be	1408	Before a watcher can be registered with the event loop it has to be
1433	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to	1409	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
1434	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.	1410	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1435		1411
1436	In this state it is simply some block of memory that is suitable for use	1412	In this state it is simply some block of memory that is suitable for
1437	in an event loop. It can be moved around, freed, reused etc. at will.	1413	use in an event loop. It can be moved around, freed, reused etc. at
		1414	will - as long as you either keep the memory contents intact, or call
		1415	C<ev_TYPE_init> again.
1438		1416
1439	=item started/running/active	1417	=item started/running/active
1440		1418
1441	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes	1419	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1442	property of the event loop, and is actively waiting for events. While in	1420	property of the event loop, and is actively waiting for events. While in
…		…
1470	latter will clear any pending state the watcher might be in, regardless	1448	latter will clear any pending state the watcher might be in, regardless
1471	of whether it was active or not, so stopping a watcher explicitly before	1449	of whether it was active or not, so stopping a watcher explicitly before
1472	freeing it is often a good idea.	1450	freeing it is often a good idea.
1473		1451
1474	While stopped (and not pending) the watcher is essentially in the	1452	While stopped (and not pending) the watcher is essentially in the
1475	initialised state, that is it can be reused, moved, modified in any way	1453	initialised state, that is, it can be reused, moved, modified in any way
1476	you wish.	1454	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1455	it again).
1477		1456
1478	=back	1457	=back
1479		1458
1480	=head2 WATCHER PRIORITY MODELS	1459	=head2 WATCHER PRIORITY MODELS
1481		1460
…		…
1610	In general you can register as many read and/or write event watchers per	1589	In general you can register as many read and/or write event watchers per
1611	fd as you want (as long as you don't confuse yourself). Setting all file	1590	fd as you want (as long as you don't confuse yourself). Setting all file
1612	descriptors to non-blocking mode is also usually a good idea (but not	1591	descriptors to non-blocking mode is also usually a good idea (but not
1613	required if you know what you are doing).	1592	required if you know what you are doing).
1614		1593
1615	If you cannot use non-blocking mode, then force the use of a
1616	known-to-be-good backend (at the time of this writing, this includes only
1617	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1618	descriptors for which non-blocking operation makes no sense (such as
1619	files) - libev doesn't guarantee any specific behaviour in that case.
1620
1621	Another thing you have to watch out for is that it is quite easy to	1594	Another thing you have to watch out for is that it is quite easy to
1622	receive "spurious" readiness notifications, that is your callback might	1595	receive "spurious" readiness notifications, that is, your callback might
1623	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1596	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1624	because there is no data. Not only are some backends known to create a	1597	because there is no data. It is very easy to get into this situation even
1625	lot of those (for example Solaris ports), it is very easy to get into	1598	with a relatively standard program structure. Thus it is best to always
1626	this situation even with a relatively standard program structure. Thus	1599	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1627	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1628	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1600	preferable to a program hanging until some data arrives.
1629		1601
1630	If you cannot run the fd in non-blocking mode (for example you should	1602	If you cannot run the fd in non-blocking mode (for example you should
1631	not play around with an Xlib connection), then you have to separately	1603	not play around with an Xlib connection), then you have to separately
1632	re-test whether a file descriptor is really ready with a known-to-be good	1604	re-test whether a file descriptor is really ready with a known-to-be good
1633	interface such as poll (fortunately in our Xlib example, Xlib already	1605	interface such as poll (fortunately in the case of Xlib, it already does
1634	does this on its own, so its quite safe to use). Some people additionally	1606	this on its own, so its quite safe to use). Some people additionally
1635	use C<SIGALRM> and an interval timer, just to be sure you won't block	1607	use C<SIGALRM> and an interval timer, just to be sure you won't block
1636	indefinitely.	1608	indefinitely.
1637		1609
1638	But really, best use non-blocking mode.	1610	But really, best use non-blocking mode.
1639		1611
…		…
1667		1639
1668	There is no workaround possible except not registering events	1640	There is no workaround possible except not registering events
1669	for potentially C<dup ()>'ed file descriptors, or to resort to	1641	for potentially C<dup ()>'ed file descriptors, or to resort to
1670	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1642	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1671		1643
		1644	=head3 The special problem of files
		1645
		1646	Many people try to use C<select> (or libev) on file descriptors
		1647	representing files, and expect it to become ready when their program
		1648	doesn't block on disk accesses (which can take a long time on their own).
		1649
		1650	However, this cannot ever work in the "expected" way - you get a readiness
		1651	notification as soon as the kernel knows whether and how much data is
		1652	there, and in the case of open files, that's always the case, so you
		1653	always get a readiness notification instantly, and your read (or possibly
		1654	write) will still block on the disk I/O.
		1655
		1656	Another way to view it is that in the case of sockets, pipes, character
		1657	devices and so on, there is another party (the sender) that delivers data
		1658	on its own, but in the case of files, there is no such thing: the disk
		1659	will not send data on its own, simply because it doesn't know what you
		1660	wish to read - you would first have to request some data.
		1661
		1662	Since files are typically not-so-well supported by advanced notification
		1663	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1664	to files, even though you should not use it. The reason for this is
		1665	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1666	usually a tty, often a pipe, but also sometimes files or special devices
		1667	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1668	F</dev/urandom>), and even though the file might better be served with
		1669	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1670	it "just works" instead of freezing.
		1671
		1672	So avoid file descriptors pointing to files when you know it (e.g. use
		1673	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1674	when you rarely read from a file instead of from a socket, and want to
		1675	reuse the same code path.
		1676
1672	=head3 The special problem of fork	1677	=head3 The special problem of fork
1673		1678
1674	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1679	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1675	useless behaviour. Libev fully supports fork, but needs to be told about	1680	useless behaviour. Libev fully supports fork, but needs to be told about
1676	it in the child.	1681	it in the child if you want to continue to use it in the child.
1677		1682
1678	To support fork in your programs, you either have to call	1683	To support fork in your child processes, you have to call C<ev_loop_fork
1679	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1684	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1680	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1685	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1681	C<EVBACKEND_POLL>.
1682		1686
1683	=head3 The special problem of SIGPIPE	1687	=head3 The special problem of SIGPIPE
1684		1688
1685	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1689	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1686	when writing to a pipe whose other end has been closed, your program gets	1690	when writing to a pipe whose other end has been closed, your program gets
…		…
1784	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1788	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1785	monotonic clock option helps a lot here).	1789	monotonic clock option helps a lot here).
1786		1790
1787	The callback is guaranteed to be invoked only I<after> its timeout has	1791	The callback is guaranteed to be invoked only I<after> its timeout has
1788	passed (not I<at>, so on systems with very low-resolution clocks this	1792	passed (not I<at>, so on systems with very low-resolution clocks this
1789	might introduce a small delay). If multiple timers become ready during the	1793	might introduce a small delay, see "the special problem of being too
		1794	early", below). If multiple timers become ready during the same loop
1790	same loop iteration then the ones with earlier time-out values are invoked	1795	iteration then the ones with earlier time-out values are invoked before
1791	before ones of the same priority with later time-out values (but this is	1796	ones of the same priority with later time-out values (but this is no
1792	no longer true when a callback calls C<ev_run> recursively).	1797	longer true when a callback calls C<ev_run> recursively).
1793		1798
1794	=head3 Be smart about timeouts	1799	=head3 Be smart about timeouts
1795		1800
1796	Many real-world problems involve some kind of timeout, usually for error	1801	Many real-world problems involve some kind of timeout, usually for error
1797	recovery. A typical example is an HTTP request - if the other side hangs,	1802	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1872		1877
1873	In this case, it would be more efficient to leave the C<ev_timer> alone,	1878	In this case, it would be more efficient to leave the C<ev_timer> alone,
1874	but remember the time of last activity, and check for a real timeout only	1879	but remember the time of last activity, and check for a real timeout only
1875	within the callback:	1880	within the callback:
1876		1881
		1882	ev_tstamp timeout = 60.;
1877	ev_tstamp last_activity; // time of last activity	1883	ev_tstamp last_activity; // time of last activity
		1884	ev_timer timer;
1878		1885
1879	static void	1886	static void
1880	callback (EV_P_ ev_timer *w, int revents)	1887	callback (EV_P_ ev_timer *w, int revents)
1881	{	1888	{
1882	ev_tstamp now = ev_now (EV_A);	1889	// calculate when the timeout would happen
1883	ev_tstamp timeout = last_activity + 60.;	1890	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1884		1891
1885	// if last_activity + 60. is older than now, we did time out	1892	// if negative, it means we the timeout already occurred
1886	if (timeout < now)	1893	if (after < 0.)
1887	{	1894	{
1888	// timeout occurred, take action	1895	// timeout occurred, take action
1889	}	1896	}
1890	else	1897	else
1891	{	1898	{
1892	// callback was invoked, but there was some activity, re-arm	1899	// callback was invoked, but there was some recent
1893	// the watcher to fire in last_activity + 60, which is	1900	// activity. simply restart the timer to time out
1894	// guaranteed to be in the future, so "again" is positive:	1901	// after "after" seconds, which is the earliest time
1895	w->repeat = timeout - now;	1902	// the timeout can occur.
		1903	ev_timer_set (w, after, 0.);
1896	ev_timer_again (EV_A_ w);	1904	ev_timer_start (EV_A_ w);
1897	}	1905	}
1898	}	1906	}
1899		1907
1900	To summarise the callback: first calculate the real timeout (defined	1908	To summarise the callback: first calculate in how many seconds the
1901	as "60 seconds after the last activity"), then check if that time has	1909	timeout will occur (by calculating the absolute time when it would occur,
1902	been reached, which means something I<did>, in fact, time out. Otherwise	1910	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1903	the callback was invoked too early (C<timeout> is in the future), so	1911	(EV_A)> from that).
1904	re-schedule the timer to fire at that future time, to see if maybe we have
1905	a timeout then.
1906		1912
1907	Note how C<ev_timer_again> is used, taking advantage of the	1913	If this value is negative, then we are already past the timeout, i.e. we
1908	C<ev_timer_again> optimisation when the timer is already running.	1914	timed out, and need to do whatever is needed in this case.
		1915
		1916	Otherwise, we now the earliest time at which the timeout would trigger,
		1917	and simply start the timer with this timeout value.
		1918
		1919	In other words, each time the callback is invoked it will check whether
		1920	the timeout occurred. If not, it will simply reschedule itself to check
		1921	again at the earliest time it could time out. Rinse. Repeat.
1909		1922
1910	This scheme causes more callback invocations (about one every 60 seconds	1923	This scheme causes more callback invocations (about one every 60 seconds
1911	minus half the average time between activity), but virtually no calls to	1924	minus half the average time between activity), but virtually no calls to
1912	libev to change the timeout.	1925	libev to change the timeout.
1913		1926
1914	To start the timer, simply initialise the watcher and set C<last_activity>	1927	To start the machinery, simply initialise the watcher and set
1915	to the current time (meaning we just have some activity :), then call the	1928	C<last_activity> to the current time (meaning there was some activity just
1916	callback, which will "do the right thing" and start the timer:	1929	now), then call the callback, which will "do the right thing" and start
		1930	the timer:
1917		1931
		1932	last_activity = ev_now (EV_A);
1918	ev_init (timer, callback);	1933	ev_init (&timer, callback);
1919	last_activity = ev_now (loop);	1934	callback (EV_A_ &timer, 0);
1920	callback (loop, timer, EV_TIMER);
1921		1935
1922	And when there is some activity, simply store the current time in	1936	When there is some activity, simply store the current time in
1923	C<last_activity>, no libev calls at all:	1937	C<last_activity>, no libev calls at all:
1924		1938
		1939	if (activity detected)
1925	last_activity = ev_now (loop);	1940	last_activity = ev_now (EV_A);
		1941
		1942	When your timeout value changes, then the timeout can be changed by simply
		1943	providing a new value, stopping the timer and calling the callback, which
		1944	will again do the right thing (for example, time out immediately :).
		1945
		1946	timeout = new_value;
		1947	ev_timer_stop (EV_A_ &timer);
		1948	callback (EV_A_ &timer, 0);
1926		1949
1927	This technique is slightly more complex, but in most cases where the	1950	This technique is slightly more complex, but in most cases where the
1928	time-out is unlikely to be triggered, much more efficient.	1951	time-out is unlikely to be triggered, much more efficient.
1929
1930	Changing the timeout is trivial as well (if it isn't hard-coded in the
1931	callback :) - just change the timeout and invoke the callback, which will
1932	fix things for you.
1933		1952
1934	=item 4. Wee, just use a double-linked list for your timeouts.	1953	=item 4. Wee, just use a double-linked list for your timeouts.
1935		1954
1936	If there is not one request, but many thousands (millions...), all	1955	If there is not one request, but many thousands (millions...), all
1937	employing some kind of timeout with the same timeout value, then one can	1956	employing some kind of timeout with the same timeout value, then one can
…		…
1964	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	1983	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1965	rather complicated, but extremely efficient, something that really pays	1984	rather complicated, but extremely efficient, something that really pays
1966	off after the first million or so of active timers, i.e. it's usually	1985	off after the first million or so of active timers, i.e. it's usually
1967	overkill :)	1986	overkill :)
1968		1987
		1988	=head3 The special problem of being too early
		1989
		1990	If you ask a timer to call your callback after three seconds, then
		1991	you expect it to be invoked after three seconds - but of course, this
		1992	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		1993	guaranteed to any precision by libev - imagine somebody suspending the
		1994	process with a STOP signal for a few hours for example.
		1995
		1996	So, libev tries to invoke your callback as soon as possible I<after> the
		1997	delay has occurred, but cannot guarantee this.
		1998
		1999	A less obvious failure mode is calling your callback too early: many event
		2000	loops compare timestamps with a "elapsed delay >= requested delay", but
		2001	this can cause your callback to be invoked much earlier than you would
		2002	expect.
		2003
		2004	To see why, imagine a system with a clock that only offers full second
		2005	resolution (think windows if you can't come up with a broken enough OS
		2006	yourself). If you schedule a one-second timer at the time 500.9, then the
		2007	event loop will schedule your timeout to elapse at a system time of 500
		2008	(500.9 truncated to the resolution) + 1, or 501.
		2009
		2010	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2011	501" and invoke the callback 0.1s after it was started, even though a
		2012	one-second delay was requested - this is being "too early", despite best
		2013	intentions.
		2014
		2015	This is the reason why libev will never invoke the callback if the elapsed
		2016	delay equals the requested delay, but only when the elapsed delay is
		2017	larger than the requested delay. In the example above, libev would only invoke
		2018	the callback at system time 502, or 1.1s after the timer was started.
		2019
		2020	So, while libev cannot guarantee that your callback will be invoked
		2021	exactly when requested, it I<can> and I<does> guarantee that the requested
		2022	delay has actually elapsed, or in other words, it always errs on the "too
		2023	late" side of things.
		2024
1969	=head3 The special problem of time updates	2025	=head3 The special problem of time updates
1970		2026
1971	Establishing the current time is a costly operation (it usually takes at	2027	Establishing the current time is a costly operation (it usually takes
1972	least two system calls): EV therefore updates its idea of the current	2028	at least one system call): EV therefore updates its idea of the current
1973	time only before and after C<ev_run> collects new events, which causes a	2029	time only before and after C<ev_run> collects new events, which causes a
1974	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2030	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1975	lots of events in one iteration.	2031	lots of events in one iteration.
1976		2032
1977	The relative timeouts are calculated relative to the C<ev_now ()>	2033	The relative timeouts are calculated relative to the C<ev_now ()>
1978	time. This is usually the right thing as this timestamp refers to the time	2034	time. This is usually the right thing as this timestamp refers to the time
1979	of the event triggering whatever timeout you are modifying/starting. If	2035	of the event triggering whatever timeout you are modifying/starting. If
1980	you suspect event processing to be delayed and you I<need> to base the	2036	you suspect event processing to be delayed and you I<need> to base the
1981	timeout on the current time, use something like this to adjust for this:	2037	timeout on the current time, use something like the following to adjust
		2038	for it:
1982		2039
1983	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2040	ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.);
1984		2041
1985	If the event loop is suspended for a long time, you can also force an	2042	If the event loop is suspended for a long time, you can also force an
1986	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2043	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1987	()>.	2044	()>, although that will push the event time of all outstanding events
		2045	further into the future.
		2046
		2047	=head3 The special problem of unsynchronised clocks
		2048
		2049	Modern systems have a variety of clocks - libev itself uses the normal
		2050	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2051	jumps).
		2052
		2053	Neither of these clocks is synchronised with each other or any other clock
		2054	on the system, so C<ev_time ()> might return a considerably different time
		2055	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2056	a call to C<gettimeofday> might return a second count that is one higher
		2057	than a directly following call to C<time>.
		2058
		2059	The moral of this is to only compare libev-related timestamps with
		2060	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2061	a second or so.
		2062
		2063	One more problem arises due to this lack of synchronisation: if libev uses
		2064	the system monotonic clock and you compare timestamps from C<ev_time>
		2065	or C<ev_now> from when you started your timer and when your callback is
		2066	invoked, you will find that sometimes the callback is a bit "early".
		2067
		2068	This is because C<ev_timer>s work in real time, not wall clock time, so
		2069	libev makes sure your callback is not invoked before the delay happened,
		2070	I<measured according to the real time>, not the system clock.
		2071
		2072	If your timeouts are based on a physical timescale (e.g. "time out this
		2073	connection after 100 seconds") then this shouldn't bother you as it is
		2074	exactly the right behaviour.
		2075
		2076	If you want to compare wall clock/system timestamps to your timers, then
		2077	you need to use C<ev_periodic>s, as these are based on the wall clock
		2078	time, where your comparisons will always generate correct results.
1988		2079
1989	=head3 The special problems of suspended animation	2080	=head3 The special problems of suspended animation
1990		2081
1991	When you leave the server world it is quite customary to hit machines that	2082	When you leave the server world it is quite customary to hit machines that
1992	can suspend/hibernate - what happens to the clocks during such a suspend?	2083	can suspend/hibernate - what happens to the clocks during such a suspend?
…		…
2036	keep up with the timer (because it takes longer than those 10 seconds to	2127	keep up with the timer (because it takes longer than those 10 seconds to
2037	do stuff) the timer will not fire more than once per event loop iteration.	2128	do stuff) the timer will not fire more than once per event loop iteration.
2038		2129
2039	=item ev_timer_again (loop, ev_timer *)	2130	=item ev_timer_again (loop, ev_timer *)
2040		2131
2041	This will act as if the timer timed out and restart it again if it is	2132	This will act as if the timer timed out, and restarts it again if it is
2042	repeating. The exact semantics are:	2133	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2134	timeout to the C<repeat> value and calling C<ev_timer_start>.
2043		2135
		2136	The exact semantics are as in the following rules, all of which will be
		2137	applied to the watcher:
		2138
		2139	=over 4
		2140
2044	If the timer is pending, its pending status is cleared.	2141	=item If the timer is pending, the pending status is always cleared.
2045		2142
2046	If the timer is started but non-repeating, stop it (as if it timed out).	2143	=item If the timer is started but non-repeating, stop it (as if it timed
		2144	out, without invoking it).
2047		2145
2048	If the timer is repeating, either start it if necessary (with the	2146	=item If the timer is repeating, make the C<repeat> value the new timeout
2049	C<repeat> value), or reset the running timer to the C<repeat> value.	2147	and start the timer, if necessary.
2050		2148
		2149	=back
		2150
2051	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2151	This sounds a bit complicated, see L</Be smart about timeouts>, above, for a
2052	usage example.	2152	usage example.
2053		2153
2054	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)	2154	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
2055		2155
2056	Returns the remaining time until a timer fires. If the timer is active,	2156	Returns the remaining time until a timer fires. If the timer is active,
…		…
2109	Periodic watchers are also timers of a kind, but they are very versatile	2209	Periodic watchers are also timers of a kind, but they are very versatile
2110	(and unfortunately a bit complex).	2210	(and unfortunately a bit complex).
2111		2211
2112	Unlike C<ev_timer>, periodic watchers are not based on real time (or	2212	Unlike C<ev_timer>, periodic watchers are not based on real time (or
2113	relative time, the physical time that passes) but on wall clock time	2213	relative time, the physical time that passes) but on wall clock time
2114	(absolute time, the thing you can read on your calender or clock). The	2214	(absolute time, the thing you can read on your calendar or clock). The
2115	difference is that wall clock time can run faster or slower than real	2215	difference is that wall clock time can run faster or slower than real
2116	time, and time jumps are not uncommon (e.g. when you adjust your	2216	time, and time jumps are not uncommon (e.g. when you adjust your
2117	wrist-watch).	2217	wrist-watch).
2118		2218
2119	You can tell a periodic watcher to trigger after some specific point	2219	You can tell a periodic watcher to trigger after some specific point
…		…
2176		2276
2177	Another way to think about it (for the mathematically inclined) is that	2277	Another way to think about it (for the mathematically inclined) is that
2178	C<ev_periodic> will try to run the callback in this mode at the next possible	2278	C<ev_periodic> will try to run the callback in this mode at the next possible
2179	time where C<time = offset (mod interval)>, regardless of any time jumps.	2279	time where C<time = offset (mod interval)>, regardless of any time jumps.
2180		2280
2181	For numerical stability it is preferable that the C<offset> value is near	2281	The C<interval> I<MUST> be positive, and for numerical stability, the
2182	C<ev_now ()> (the current time), but there is no range requirement for	2282	interval value should be higher than C<1/8192> (which is around 100
2183	this value, and in fact is often specified as zero.	2283	microseconds) and C<offset> should be higher than C<0> and should have
		2284	at most a similar magnitude as the current time (say, within a factor of
		2285	ten). Typical values for offset are, in fact, C<0> or something between
		2286	C<0> and C<interval>, which is also the recommended range.
2184		2287
2185	Note also that there is an upper limit to how often a timer can fire (CPU	2288	Note also that there is an upper limit to how often a timer can fire (CPU
2186	speed for example), so if C<interval> is very small then timing stability	2289	speed for example), so if C<interval> is very small then timing stability
2187	will of course deteriorate. Libev itself tries to be exact to be about one	2290	will of course deteriorate. Libev itself tries to be exact to be about one
2188	millisecond (if the OS supports it and the machine is fast enough).	2291	millisecond (if the OS supports it and the machine is fast enough).
…		…
2296		2399
2297	ev_periodic hourly_tick;	2400	ev_periodic hourly_tick;
2298	ev_periodic_init (&hourly_tick, clock_cb,	2401	ev_periodic_init (&hourly_tick, clock_cb,
2299	fmod (ev_now (loop), 3600.), 3600., 0);	2402	fmod (ev_now (loop), 3600.), 3600., 0);
2300	ev_periodic_start (loop, &hourly_tick);	2403	ev_periodic_start (loop, &hourly_tick);
2301		2404
2302		2405
2303	=head2 C<ev_signal> - signal me when a signal gets signalled!	2406	=head2 C<ev_signal> - signal me when a signal gets signalled!
2304		2407
2305	Signal watchers will trigger an event when the process receives a specific	2408	Signal watchers will trigger an event when the process receives a specific
2306	signal one or more times. Even though signals are very asynchronous, libev	2409	signal one or more times. Even though signals are very asynchronous, libev
…		…
2316	only within the same loop, i.e. you can watch for C<SIGINT> in your	2419	only within the same loop, i.e. you can watch for C<SIGINT> in your
2317	default loop and for C<SIGIO> in another loop, but you cannot watch for	2420	default loop and for C<SIGIO> in another loop, but you cannot watch for
2318	C<SIGINT> in both the default loop and another loop at the same time. At	2421	C<SIGINT> in both the default loop and another loop at the same time. At
2319	the moment, C<SIGCHLD> is permanently tied to the default loop.	2422	the moment, C<SIGCHLD> is permanently tied to the default loop.
2320		2423
2321	When the first watcher gets started will libev actually register something	2424	Only after the first watcher for a signal is started will libev actually
2322	with the kernel (thus it coexists with your own signal handlers as long as	2425	register something with the kernel. It thus coexists with your own signal
2323	you don't register any with libev for the same signal).	2426	handlers as long as you don't register any with libev for the same signal.
2324		2427
2325	If possible and supported, libev will install its handlers with	2428	If possible and supported, libev will install its handlers with
2326	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should	2429	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
2327	not be unduly interrupted. If you have a problem with system calls getting	2430	not be unduly interrupted. If you have a problem with system calls getting
2328	interrupted by signals you can block all signals in an C<ev_check> watcher	2431	interrupted by signals you can block all signals in an C<ev_check> watcher
…		…
2331	=head3 The special problem of inheritance over fork/execve/pthread_create	2434	=head3 The special problem of inheritance over fork/execve/pthread_create
2332		2435
2333	Both the signal mask (C<sigprocmask>) and the signal disposition	2436	Both the signal mask (C<sigprocmask>) and the signal disposition
2334	(C<sigaction>) are unspecified after starting a signal watcher (and after	2437	(C<sigaction>) are unspecified after starting a signal watcher (and after
2335	stopping it again), that is, libev might or might not block the signal,	2438	stopping it again), that is, libev might or might not block the signal,
2336	and might or might not set or restore the installed signal handler.	2439	and might or might not set or restore the installed signal handler (but
		2440	see C<EVFLAG_NOSIGMASK>).
2337		2441
2338	While this does not matter for the signal disposition (libev never	2442	While this does not matter for the signal disposition (libev never
2339	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on	2443	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
2340	C<execve>), this matters for the signal mask: many programs do not expect	2444	C<execve>), this matters for the signal mask: many programs do not expect
2341	certain signals to be blocked.	2445	certain signals to be blocked.
…		…
2512		2616
2513	=head2 C<ev_stat> - did the file attributes just change?	2617	=head2 C<ev_stat> - did the file attributes just change?
2514		2618
2515	This watches a file system path for attribute changes. That is, it calls	2619	This watches a file system path for attribute changes. That is, it calls
2516	C<stat> on that path in regular intervals (or when the OS says it changed)	2620	C<stat> on that path in regular intervals (or when the OS says it changed)
2517	and sees if it changed compared to the last time, invoking the callback if	2621	and sees if it changed compared to the last time, invoking the callback
2518	it did.	2622	if it did. Starting the watcher C<stat>'s the file, so only changes that
		2623	happen after the watcher has been started will be reported.
2519		2624
2520	The path does not need to exist: changing from "path exists" to "path does	2625	The path does not need to exist: changing from "path exists" to "path does
2521	not exist" is a status change like any other. The condition "path does not	2626	not exist" is a status change like any other. The condition "path does not
2522	exist" (or more correctly "path cannot be stat'ed") is signified by the	2627	exist" (or more correctly "path cannot be stat'ed") is signified by the
2523	C<st_nlink> field being zero (which is otherwise always forced to be at	2628	C<st_nlink> field being zero (which is otherwise always forced to be at
…		…
2753	Apart from keeping your process non-blocking (which is a useful	2858	Apart from keeping your process non-blocking (which is a useful
2754	effect on its own sometimes), idle watchers are a good place to do	2859	effect on its own sometimes), idle watchers are a good place to do
2755	"pseudo-background processing", or delay processing stuff to after the	2860	"pseudo-background processing", or delay processing stuff to after the
2756	event loop has handled all outstanding events.	2861	event loop has handled all outstanding events.
2757		2862
		2863	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2864
		2865	As long as there is at least one active idle watcher, libev will never
		2866	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2867	For this to work, the idle watcher doesn't need to be invoked at all - the
		2868	lowest priority will do.
		2869
		2870	This mode of operation can be useful together with an C<ev_check> watcher,
		2871	to do something on each event loop iteration - for example to balance load
		2872	between different connections.
		2873
		2874	See L</Abusing an ev_check watcher for its side-effect> for a longer
		2875	example.
		2876
2758	=head3 Watcher-Specific Functions and Data Members	2877	=head3 Watcher-Specific Functions and Data Members
2759		2878
2760	=over 4	2879	=over 4
2761		2880
2762	=item ev_idle_init (ev_idle *, callback)	2881	=item ev_idle_init (ev_idle *, callback)
…		…
2773	callback, free it. Also, use no error checking, as usual.	2892	callback, free it. Also, use no error checking, as usual.
2774		2893
2775	static void	2894	static void
2776	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	2895	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2777	{	2896	{
		2897	// stop the watcher
		2898	ev_idle_stop (loop, w);
		2899
		2900	// now we can free it
2778	free (w);	2901	free (w);
		2902
2779	// now do something you wanted to do when the program has	2903	// now do something you wanted to do when the program has
2780	// no longer anything immediate to do.	2904	// no longer anything immediate to do.
2781	}	2905	}
2782		2906
2783	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2907	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
…		…
2785	ev_idle_start (loop, idle_watcher);	2909	ev_idle_start (loop, idle_watcher);
2786		2910
2787		2911
2788	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2912	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2789		2913
2790	Prepare and check watchers are usually (but not always) used in pairs:	2914	Prepare and check watchers are often (but not always) used in pairs:
2791	prepare watchers get invoked before the process blocks and check watchers	2915	prepare watchers get invoked before the process blocks and check watchers
2792	afterwards.	2916	afterwards.
2793		2917
2794	You I<must not> call C<ev_run> or similar functions that enter	2918	You I<must not> call C<ev_run> (or similar functions that enter the
2795	the current event loop from either C<ev_prepare> or C<ev_check>	2919	current event loop) or C<ev_loop_fork> from either C<ev_prepare> or
2796	watchers. Other loops than the current one are fine, however. The	2920	C<ev_check> watchers. Other loops than the current one are fine,
2797	rationale behind this is that you do not need to check for recursion in	2921	however. The rationale behind this is that you do not need to check
2798	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2922	for recursion in those watchers, i.e. the sequence will always be
2799	C<ev_check> so if you have one watcher of each kind they will always be	2923	C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each
2800	called in pairs bracketing the blocking call.	2924	kind they will always be called in pairs bracketing the blocking call.
2801		2925
2802	Their main purpose is to integrate other event mechanisms into libev and	2926	Their main purpose is to integrate other event mechanisms into libev and
2803	their use is somewhat advanced. They could be used, for example, to track	2927	their use is somewhat advanced. They could be used, for example, to track
2804	variable changes, implement your own watchers, integrate net-snmp or a	2928	variable changes, implement your own watchers, integrate net-snmp or a
2805	coroutine library and lots more. They are also occasionally useful if	2929	coroutine library and lots more. They are also occasionally useful if
…		…
2823	with priority higher than or equal to the event loop and one coroutine	2947	with priority higher than or equal to the event loop and one coroutine
2824	of lower priority, but only once, using idle watchers to keep the event	2948	of lower priority, but only once, using idle watchers to keep the event
2825	loop from blocking if lower-priority coroutines are active, thus mapping	2949	loop from blocking if lower-priority coroutines are active, thus mapping
2826	low-priority coroutines to idle/background tasks).	2950	low-priority coroutines to idle/background tasks).
2827		2951
2828	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2952	When used for this purpose, it is recommended to give C<ev_check> watchers
2829	priority, to ensure that they are being run before any other watchers	2953	highest (C<EV_MAXPRI>) priority, to ensure that they are being run before
2830	after the poll (this doesn't matter for C<ev_prepare> watchers).	2954	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		2955	watchers).
2831		2956
2832	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	2957	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
2833	activate ("feed") events into libev. While libev fully supports this, they	2958	activate ("feed") events into libev. While libev fully supports this, they
2834	might get executed before other C<ev_check> watchers did their job. As	2959	might get executed before other C<ev_check> watchers did their job. As
2835	C<ev_check> watchers are often used to embed other (non-libev) event	2960	C<ev_check> watchers are often used to embed other (non-libev) event
2836	loops those other event loops might be in an unusable state until their	2961	loops those other event loops might be in an unusable state until their
2837	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	2962	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2838	others).	2963	others).
		2964
		2965	=head3 Abusing an C<ev_check> watcher for its side-effect
		2966
		2967	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		2968	useful because they are called once per event loop iteration. For
		2969	example, if you want to handle a large number of connections fairly, you
		2970	normally only do a bit of work for each active connection, and if there
		2971	is more work to do, you wait for the next event loop iteration, so other
		2972	connections have a chance of making progress.
		2973
		2974	Using an C<ev_check> watcher is almost enough: it will be called on the
		2975	next event loop iteration. However, that isn't as soon as possible -
		2976	without external events, your C<ev_check> watcher will not be invoked.
		2977
		2978	This is where C<ev_idle> watchers come in handy - all you need is a
		2979	single global idle watcher that is active as long as you have one active
		2980	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		2981	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		2982	invoked. Neither watcher alone can do that.
2839		2983
2840	=head3 Watcher-Specific Functions and Data Members	2984	=head3 Watcher-Specific Functions and Data Members
2841		2985
2842	=over 4	2986	=over 4
2843		2987
…		…
3044		3188
3045	=over 4	3189	=over 4
3046		3190
3047	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	3191	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
3048		3192
3049	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	3193	=item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)
3050		3194
3051	Configures the watcher to embed the given loop, which must be	3195	Configures the watcher to embed the given loop, which must be
3052	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	3196	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
3053	invoked automatically, otherwise it is the responsibility of the callback	3197	invoked automatically, otherwise it is the responsibility of the callback
3054	to invoke it (it will continue to be called until the sweep has been done,	3198	to invoke it (it will continue to be called until the sweep has been done,
…		…
3075	used).	3219	used).
3076		3220
3077	struct ev_loop *loop_hi = ev_default_init (0);	3221	struct ev_loop *loop_hi = ev_default_init (0);
3078	struct ev_loop *loop_lo = 0;	3222	struct ev_loop *loop_lo = 0;
3079	ev_embed embed;	3223	ev_embed embed;
3080		3224
3081	// see if there is a chance of getting one that works	3225	// see if there is a chance of getting one that works
3082	// (remember that a flags value of 0 means autodetection)	3226	// (remember that a flags value of 0 means autodetection)
3083	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3227	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
3084	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3228	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
3085	: 0;	3229	: 0;
…		…
3099	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3243	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
3100		3244
3101	struct ev_loop *loop = ev_default_init (0);	3245	struct ev_loop *loop = ev_default_init (0);
3102	struct ev_loop *loop_socket = 0;	3246	struct ev_loop *loop_socket = 0;
3103	ev_embed embed;	3247	ev_embed embed;
3104		3248
3105	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3249	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
3106	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3250	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
3107	{	3251	{
3108	ev_embed_init (&embed, 0, loop_socket);	3252	ev_embed_init (&embed, 0, loop_socket);
3109	ev_embed_start (loop, &embed);	3253	ev_embed_start (loop, &embed);
…		…
3117		3261
3118	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3262	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
3119		3263
3120	Fork watchers are called when a C<fork ()> was detected (usually because	3264	Fork watchers are called when a C<fork ()> was detected (usually because
3121	whoever is a good citizen cared to tell libev about it by calling	3265	whoever is a good citizen cared to tell libev about it by calling
3122	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the	3266	C<ev_loop_fork>). The invocation is done before the event loop blocks next
3123	event loop blocks next and before C<ev_check> watchers are being called,	3267	and before C<ev_check> watchers are being called, and only in the child
3124	and only in the child after the fork. If whoever good citizen calling	3268	after the fork. If whoever good citizen calling C<ev_default_fork> cheats
3125	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3269	and calls it in the wrong process, the fork handlers will be invoked, too,
3126	handlers will be invoked, too, of course.	3270	of course.
3127		3271
3128	=head3 The special problem of life after fork - how is it possible?	3272	=head3 The special problem of life after fork - how is it possible?
3129		3273
3130	Most uses of C<fork()> consist of forking, then some simple calls to set	3274	Most uses of C<fork ()> consist of forking, then some simple calls to set
3131	up/change the process environment, followed by a call to C<exec()>. This	3275	up/change the process environment, followed by a call to C<exec()>. This
3132	sequence should be handled by libev without any problems.	3276	sequence should be handled by libev without any problems.
3133		3277
3134	This changes when the application actually wants to do event handling	3278	This changes when the application actually wants to do event handling
3135	in the child, or both parent in child, in effect "continuing" after the	3279	in the child, or both parent in child, in effect "continuing" after the
…		…
3212	atexit (program_exits);	3356	atexit (program_exits);
3213		3357
3214		3358
3215	=head2 C<ev_async> - how to wake up an event loop	3359	=head2 C<ev_async> - how to wake up an event loop
3216		3360
3217	In general, you cannot use an C<ev_run> from multiple threads or other	3361	In general, you cannot use an C<ev_loop> from multiple threads or other
3218	asynchronous sources such as signal handlers (as opposed to multiple event	3362	asynchronous sources such as signal handlers (as opposed to multiple event
3219	loops - those are of course safe to use in different threads).	3363	loops - those are of course safe to use in different threads).
3220		3364
3221	Sometimes, however, you need to wake up an event loop you do not control,	3365	Sometimes, however, you need to wake up an event loop you do not control,
3222	for example because it belongs to another thread. This is what C<ev_async>	3366	for example because it belongs to another thread. This is what C<ev_async>
…		…
3224	it by calling C<ev_async_send>, which is thread- and signal safe.	3368	it by calling C<ev_async_send>, which is thread- and signal safe.
3225		3369
3226	This functionality is very similar to C<ev_signal> watchers, as signals,	3370	This functionality is very similar to C<ev_signal> watchers, as signals,
3227	too, are asynchronous in nature, and signals, too, will be compressed	3371	too, are asynchronous in nature, and signals, too, will be compressed
3228	(i.e. the number of callback invocations may be less than the number of	3372	(i.e. the number of callback invocations may be less than the number of
3229	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind	3373	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
3230	of "global async watchers" by using a watcher on an otherwise unused	3374	of "global async watchers" by using a watcher on an otherwise unused
3231	signal, and C<ev_feed_signal> to signal this watcher from another thread,	3375	signal, and C<ev_feed_signal> to signal this watcher from another thread,
3232	even without knowing which loop owns the signal.	3376	even without knowing which loop owns the signal.
3233
3234	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
3235	just the default loop.
3236		3377
3237	=head3 Queueing	3378	=head3 Queueing
3238		3379
3239	C<ev_async> does not support queueing of data in any way. The reason	3380	C<ev_async> does not support queueing of data in any way. The reason
3240	is that the author does not know of a simple (or any) algorithm for a	3381	is that the author does not know of a simple (or any) algorithm for a
…		…
3332	trust me.	3473	trust me.
3333		3474
3334	=item ev_async_send (loop, ev_async *)	3475	=item ev_async_send (loop, ev_async *)
3335		3476
3336	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3477	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3337	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3478	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3479	returns.
		3480
3338	C<ev_feed_event>, this call is safe to do from other threads, signal or	3481	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3339	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3482	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3340	section below on what exactly this means).	3483	embedding section below on what exactly this means).
3341		3484
3342	Note that, as with other watchers in libev, multiple events might get	3485	Note that, as with other watchers in libev, multiple events might get
3343	compressed into a single callback invocation (another way to look at this	3486	compressed into a single callback invocation (another way to look at
3344	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3487	this is that C<ev_async> watchers are level-triggered: they are set on
3345	reset when the event loop detects that).	3488	C<ev_async_send>, reset when the event loop detects that).
3346		3489
3347	This call incurs the overhead of a system call only once per event loop	3490	This call incurs the overhead of at most one extra system call per event
3348	iteration, so while the overhead might be noticeable, it doesn't apply to	3491	loop iteration, if the event loop is blocked, and no syscall at all if
3349	repeated calls to C<ev_async_send> for the same event loop.	3492	the event loop (or your program) is processing events. That means that
		3493	repeated calls are basically free (there is no need to avoid calls for
		3494	performance reasons) and that the overhead becomes smaller (typically
		3495	zero) under load.
3350		3496
3351	=item bool = ev_async_pending (ev_async *)	3497	=item bool = ev_async_pending (ev_async *)
3352		3498
3353	Returns a non-zero value when C<ev_async_send> has been called on the	3499	Returns a non-zero value when C<ev_async_send> has been called on the
3354	watcher but the event has not yet been processed (or even noted) by the	3500	watcher but the event has not yet been processed (or even noted) by the
…		…
3409	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3555	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3410		3556
3411	=item ev_feed_fd_event (loop, int fd, int revents)	3557	=item ev_feed_fd_event (loop, int fd, int revents)
3412		3558
3413	Feed an event on the given fd, as if a file descriptor backend detected	3559	Feed an event on the given fd, as if a file descriptor backend detected
3414	the given events it.	3560	the given events.
3415		3561
3416	=item ev_feed_signal_event (loop, int signum)	3562	=item ev_feed_signal_event (loop, int signum)
3417		3563
3418	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,	3564	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3419	which is async-safe.	3565	which is async-safe.
…		…
3425		3571
3426	This section explains some common idioms that are not immediately	3572	This section explains some common idioms that are not immediately
3427	obvious. Note that examples are sprinkled over the whole manual, and this	3573	obvious. Note that examples are sprinkled over the whole manual, and this
3428	section only contains stuff that wouldn't fit anywhere else.	3574	section only contains stuff that wouldn't fit anywhere else.
3429		3575
3430	=over 4	3576	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
3431		3577
3432	=item Model/nested event loop invocations and exit conditions.	3578	Each watcher has, by default, a C<void *data> member that you can read
		3579	or modify at any time: libev will completely ignore it. This can be used
		3580	to associate arbitrary data with your watcher. If you need more data and
		3581	don't want to allocate memory separately and store a pointer to it in that
		3582	data member, you can also "subclass" the watcher type and provide your own
		3583	data:
		3584
		3585	struct my_io
		3586	{
		3587	ev_io io;
		3588	int otherfd;
		3589	void *somedata;
		3590	struct whatever *mostinteresting;
		3591	};
		3592
		3593	...
		3594	struct my_io w;
		3595	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3596
		3597	And since your callback will be called with a pointer to the watcher, you
		3598	can cast it back to your own type:
		3599
		3600	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3601	{
		3602	struct my_io *w = (struct my_io *)w_;
		3603	...
		3604	}
		3605
		3606	More interesting and less C-conformant ways of casting your callback
		3607	function type instead have been omitted.
		3608
		3609	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3610
		3611	Another common scenario is to use some data structure with multiple
		3612	embedded watchers, in effect creating your own watcher that combines
		3613	multiple libev event sources into one "super-watcher":
		3614
		3615	struct my_biggy
		3616	{
		3617	int some_data;
		3618	ev_timer t1;
		3619	ev_timer t2;
		3620	}
		3621
		3622	In this case getting the pointer to C<my_biggy> is a bit more
		3623	complicated: Either you store the address of your C<my_biggy> struct in
		3624	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3625	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3626	real programmers):
		3627
		3628	#include <stddef.h>
		3629
		3630	static void
		3631	t1_cb (EV_P_ ev_timer *w, int revents)
		3632	{
		3633	struct my_biggy big = (struct my_biggy *)
		3634	(((char *)w) - offsetof (struct my_biggy, t1));
		3635	}
		3636
		3637	static void
		3638	t2_cb (EV_P_ ev_timer *w, int revents)
		3639	{
		3640	struct my_biggy big = (struct my_biggy *)
		3641	(((char *)w) - offsetof (struct my_biggy, t2));
		3642	}
		3643
		3644	=head2 AVOIDING FINISHING BEFORE RETURNING
		3645
		3646	Often you have structures like this in event-based programs:
		3647
		3648	callback ()
		3649	{
		3650	free (request);
		3651	}
		3652
		3653	request = start_new_request (..., callback);
		3654
		3655	The intent is to start some "lengthy" operation. The C<request> could be
		3656	used to cancel the operation, or do other things with it.
		3657
		3658	It's not uncommon to have code paths in C<start_new_request> that
		3659	immediately invoke the callback, for example, to report errors. Or you add
		3660	some caching layer that finds that it can skip the lengthy aspects of the
		3661	operation and simply invoke the callback with the result.
		3662
		3663	The problem here is that this will happen I<before> C<start_new_request>
		3664	has returned, so C<request> is not set.
		3665
		3666	Even if you pass the request by some safer means to the callback, you
		3667	might want to do something to the request after starting it, such as
		3668	canceling it, which probably isn't working so well when the callback has
		3669	already been invoked.
		3670
		3671	A common way around all these issues is to make sure that
		3672	C<start_new_request> I<always> returns before the callback is invoked. If
		3673	C<start_new_request> immediately knows the result, it can artificially
		3674	delay invoking the callback by using a C<prepare> or C<idle> watcher for
		3675	example, or more sneakily, by reusing an existing (stopped) watcher and
		3676	pushing it into the pending queue:
		3677
		3678	ev_set_cb (watcher, callback);
		3679	ev_feed_event (EV_A_ watcher, 0);
		3680
		3681	This way, C<start_new_request> can safely return before the callback is
		3682	invoked, while not delaying callback invocation too much.
		3683
		3684	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
3433		3685
3434	Often (especially in GUI toolkits) there are places where you have	3686	Often (especially in GUI toolkits) there are places where you have
3435	I<modal> interaction, which is most easily implemented by recursively	3687	I<modal> interaction, which is most easily implemented by recursively
3436	invoking C<ev_run>.	3688	invoking C<ev_run>.
3437		3689
3438	This brings the problem of exiting - a callback might want to finish the	3690	This brings the problem of exiting - a callback might want to finish the
3439	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but	3691	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
3440	a modal "Are you sure?" dialog is still waiting), or just the nested one	3692	a modal "Are you sure?" dialog is still waiting), or just the nested one
3441	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some	3693	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
3442	other combination: In these cases, C<ev_break> will not work alone.	3694	other combination: In these cases, a simple C<ev_break> will not work.
3443		3695
3444	The solution is to maintain "break this loop" variable for each C<ev_run>	3696	The solution is to maintain "break this loop" variable for each C<ev_run>
3445	invocation, and use a loop around C<ev_run> until the condition is	3697	invocation, and use a loop around C<ev_run> until the condition is
3446	triggered, using C<EVRUN_ONCE>:	3698	triggered, using C<EVRUN_ONCE>:
3447		3699
…		…
3449	int exit_main_loop = 0;	3701	int exit_main_loop = 0;
3450		3702
3451	while (!exit_main_loop)	3703	while (!exit_main_loop)
3452	ev_run (EV_DEFAULT_ EVRUN_ONCE);	3704	ev_run (EV_DEFAULT_ EVRUN_ONCE);
3453		3705
3454	// in a model watcher	3706	// in a modal watcher
3455	int exit_nested_loop = 0;	3707	int exit_nested_loop = 0;
3456		3708
3457	while (!exit_nested_loop)	3709	while (!exit_nested_loop)
3458	ev_run (EV_A_ EVRUN_ONCE);	3710	ev_run (EV_A_ EVRUN_ONCE);
3459		3711
…		…
3466	exit_main_loop = 1;	3718	exit_main_loop = 1;
3467		3719
3468	// exit both	3720	// exit both
3469	exit_main_loop = exit_nested_loop = 1;	3721	exit_main_loop = exit_nested_loop = 1;
3470		3722
3471	=back	3723	=head2 THREAD LOCKING EXAMPLE
		3724
		3725	Here is a fictitious example of how to run an event loop in a different
		3726	thread from where callbacks are being invoked and watchers are
		3727	created/added/removed.
		3728
		3729	For a real-world example, see the C<EV::Loop::Async> perl module,
		3730	which uses exactly this technique (which is suited for many high-level
		3731	languages).
		3732
		3733	The example uses a pthread mutex to protect the loop data, a condition
		3734	variable to wait for callback invocations, an async watcher to notify the
		3735	event loop thread and an unspecified mechanism to wake up the main thread.
		3736
		3737	First, you need to associate some data with the event loop:
		3738
		3739	typedef struct {
		3740	mutex_t lock; /* global loop lock */
		3741	ev_async async_w;
		3742	thread_t tid;
		3743	cond_t invoke_cv;
		3744	} userdata;
		3745
		3746	void prepare_loop (EV_P)
		3747	{
		3748	// for simplicity, we use a static userdata struct.
		3749	static userdata u;
		3750
		3751	ev_async_init (&u->async_w, async_cb);
		3752	ev_async_start (EV_A_ &u->async_w);
		3753
		3754	pthread_mutex_init (&u->lock, 0);
		3755	pthread_cond_init (&u->invoke_cv, 0);
		3756
		3757	// now associate this with the loop
		3758	ev_set_userdata (EV_A_ u);
		3759	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3760	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3761
		3762	// then create the thread running ev_run
		3763	pthread_create (&u->tid, 0, l_run, EV_A);
		3764	}
		3765
		3766	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3767	solely to wake up the event loop so it takes notice of any new watchers
		3768	that might have been added:
		3769
		3770	static void
		3771	async_cb (EV_P_ ev_async *w, int revents)
		3772	{
		3773	// just used for the side effects
		3774	}
		3775
		3776	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3777	protecting the loop data, respectively.
		3778
		3779	static void
		3780	l_release (EV_P)
		3781	{
		3782	userdata *u = ev_userdata (EV_A);
		3783	pthread_mutex_unlock (&u->lock);
		3784	}
		3785
		3786	static void
		3787	l_acquire (EV_P)
		3788	{
		3789	userdata *u = ev_userdata (EV_A);
		3790	pthread_mutex_lock (&u->lock);
		3791	}
		3792
		3793	The event loop thread first acquires the mutex, and then jumps straight
		3794	into C<ev_run>:
		3795
		3796	void *
		3797	l_run (void *thr_arg)
		3798	{
		3799	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3800
		3801	l_acquire (EV_A);
		3802	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3803	ev_run (EV_A_ 0);
		3804	l_release (EV_A);
		3805
		3806	return 0;
		3807	}
		3808
		3809	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3810	signal the main thread via some unspecified mechanism (signals? pipe
		3811	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3812	have been called (in a while loop because a) spurious wakeups are possible
		3813	and b) skipping inter-thread-communication when there are no pending
		3814	watchers is very beneficial):
		3815
		3816	static void
		3817	l_invoke (EV_P)
		3818	{
		3819	userdata *u = ev_userdata (EV_A);
		3820
		3821	while (ev_pending_count (EV_A))
		3822	{
		3823	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3824	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3825	}
		3826	}
		3827
		3828	Now, whenever the main thread gets told to invoke pending watchers, it
		3829	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3830	thread to continue:
		3831
		3832	static void
		3833	real_invoke_pending (EV_P)
		3834	{
		3835	userdata *u = ev_userdata (EV_A);
		3836
		3837	pthread_mutex_lock (&u->lock);
		3838	ev_invoke_pending (EV_A);
		3839	pthread_cond_signal (&u->invoke_cv);
		3840	pthread_mutex_unlock (&u->lock);
		3841	}
		3842
		3843	Whenever you want to start/stop a watcher or do other modifications to an
		3844	event loop, you will now have to lock:
		3845
		3846	ev_timer timeout_watcher;
		3847	userdata *u = ev_userdata (EV_A);
		3848
		3849	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3850
		3851	pthread_mutex_lock (&u->lock);
		3852	ev_timer_start (EV_A_ &timeout_watcher);
		3853	ev_async_send (EV_A_ &u->async_w);
		3854	pthread_mutex_unlock (&u->lock);
		3855
		3856	Note that sending the C<ev_async> watcher is required because otherwise
		3857	an event loop currently blocking in the kernel will have no knowledge
		3858	about the newly added timer. By waking up the loop it will pick up any new
		3859	watchers in the next event loop iteration.
		3860
		3861	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3862
		3863	While the overhead of a callback that e.g. schedules a thread is small, it
		3864	is still an overhead. If you embed libev, and your main usage is with some
		3865	kind of threads or coroutines, you might want to customise libev so that
		3866	doesn't need callbacks anymore.
		3867
		3868	Imagine you have coroutines that you can switch to using a function
		3869	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3870	and that due to some magic, the currently active coroutine is stored in a
		3871	global called C<current_coro>. Then you can build your own "wait for libev
		3872	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3873	the differing C<;> conventions):
		3874
		3875	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3876	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3877
		3878	That means instead of having a C callback function, you store the
		3879	coroutine to switch to in each watcher, and instead of having libev call
		3880	your callback, you instead have it switch to that coroutine.
		3881
		3882	A coroutine might now wait for an event with a function called
		3883	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3884	matter when, or whether the watcher is active or not when this function is
		3885	called):
		3886
		3887	void
		3888	wait_for_event (ev_watcher *w)
		3889	{
		3890	ev_set_cb (w, current_coro);
		3891	switch_to (libev_coro);
		3892	}
		3893
		3894	That basically suspends the coroutine inside C<wait_for_event> and
		3895	continues the libev coroutine, which, when appropriate, switches back to
		3896	this or any other coroutine.
		3897
		3898	You can do similar tricks if you have, say, threads with an event queue -
		3899	instead of storing a coroutine, you store the queue object and instead of
		3900	switching to a coroutine, you push the watcher onto the queue and notify
		3901	any waiters.
		3902
		3903	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		3904	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3905
		3906	// my_ev.h
		3907	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3908	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3909	#include "../libev/ev.h"
		3910
		3911	// my_ev.c
		3912	#define EV_H "my_ev.h"
		3913	#include "../libev/ev.c"
		3914
		3915	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3916	F<my_ev.c> into your project. When properly specifying include paths, you
		3917	can even use F<ev.h> as header file name directly.
3472		3918
3473		3919
3474	=head1 LIBEVENT EMULATION	3920	=head1 LIBEVENT EMULATION
3475		3921
3476	Libev offers a compatibility emulation layer for libevent. It cannot	3922	Libev offers a compatibility emulation layer for libevent. It cannot
…		…
3506		3952
3507	=back	3953	=back
3508		3954
3509	=head1 C++ SUPPORT	3955	=head1 C++ SUPPORT
3510		3956
		3957	=head2 C API
		3958
		3959	The normal C API should work fine when used from C++: both ev.h and the
		3960	libev sources can be compiled as C++. Therefore, code that uses the C API
		3961	will work fine.
		3962
		3963	Proper exception specifications might have to be added to callbacks passed
		3964	to libev: exceptions may be thrown only from watcher callbacks, all
		3965	other callbacks (allocator, syserr, loop acquire/release and periodic
		3966	reschedule callbacks) must not throw exceptions, and might need a C<throw
		3967	()> specification. If you have code that needs to be compiled as both C
		3968	and C++ you can use the C<EV_THROW> macro for this:
		3969
		3970	static void
		3971	fatal_error (const char *msg) EV_THROW
		3972	{
		3973	perror (msg);
		3974	abort ();
		3975	}
		3976
		3977	...
		3978	ev_set_syserr_cb (fatal_error);
		3979
		3980	The only API functions that can currently throw exceptions are C<ev_run>,
		3981	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		3982	because it runs cleanup watchers).
		3983
		3984	Throwing exceptions in watcher callbacks is only supported if libev itself
		3985	is compiled with a C++ compiler or your C and C++ environments allow
		3986	throwing exceptions through C libraries (most do).
		3987
		3988	=head2 C++ API
		3989
3511	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3990	Libev comes with some simplistic wrapper classes for C++ that mainly allow
3512	you to use some convenience methods to start/stop watchers and also change	3991	you to use some convenience methods to start/stop watchers and also change
3513	the callback model to a model using method callbacks on objects.	3992	the callback model to a model using method callbacks on objects.
3514		3993
3515	To use it,	3994	To use it,
3516		3995
3517	#include <ev++.h>	3996	#include <ev++.h>
3518		3997
3519	This automatically includes F<ev.h> and puts all of its definitions (many	3998	This automatically includes F<ev.h> and puts all of its definitions (many
3520	of them macros) into the global namespace. All C++ specific things are	3999	of them macros) into the global namespace. All C++ specific things are
3521	put into the C<ev> namespace. It should support all the same embedding	4000	put into the C<ev> namespace. It should support all the same embedding
…		…
3530	with C<operator ()> can be used as callbacks. Other types should be easy	4009	with C<operator ()> can be used as callbacks. Other types should be easy
3531	to add as long as they only need one additional pointer for context. If	4010	to add as long as they only need one additional pointer for context. If
3532	you need support for other types of functors please contact the author	4011	you need support for other types of functors please contact the author
3533	(preferably after implementing it).	4012	(preferably after implementing it).
3534		4013
		4014	For all this to work, your C++ compiler either has to use the same calling
		4015	conventions as your C compiler (for static member functions), or you have
		4016	to embed libev and compile libev itself as C++.
		4017
3535	Here is a list of things available in the C<ev> namespace:	4018	Here is a list of things available in the C<ev> namespace:
3536		4019
3537	=over 4	4020	=over 4
3538		4021
3539	=item C<ev::READ>, C<ev::WRITE> etc.	4022	=item C<ev::READ>, C<ev::WRITE> etc.
…		…
3548	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4031	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3549		4032
3550	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4033	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
3551	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4034	the same name in the C<ev> namespace, with the exception of C<ev_signal>
3552	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4035	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3553	defines by many implementations.	4036	defined by many implementations.
3554		4037
3555	All of those classes have these methods:	4038	All of those classes have these methods:
3556		4039
3557	=over 4	4040	=over 4
3558		4041
…		…
3620	void operator() (ev::io &w, int revents)	4103	void operator() (ev::io &w, int revents)
3621	{	4104	{
3622	...	4105	...
3623	}	4106	}
3624	}	4107	}
3625		4108
3626	myfunctor f;	4109	myfunctor f;
3627		4110
3628	ev::io w;	4111	ev::io w;
3629	w.set (&f);	4112	w.set (&f);
3630		4113
…		…
3648	Associates a different C<struct ev_loop> with this watcher. You can only	4131	Associates a different C<struct ev_loop> with this watcher. You can only
3649	do this when the watcher is inactive (and not pending either).	4132	do this when the watcher is inactive (and not pending either).
3650		4133
3651	=item w->set ([arguments])	4134	=item w->set ([arguments])
3652		4135
3653	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this	4136	Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>),
3654	method or a suitable start method must be called at least once. Unlike the	4137	with the same arguments. Either this method or a suitable start method
3655	C counterpart, an active watcher gets automatically stopped and restarted	4138	must be called at least once. Unlike the C counterpart, an active watcher
3656	when reconfiguring it with this method.	4139	gets automatically stopped and restarted when reconfiguring it with this
		4140	method.
		4141
		4142	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4143	clashing with the C<set (loop)> method.
3657		4144
3658	=item w->start ()	4145	=item w->start ()
3659		4146
3660	Starts the watcher. Note that there is no C<loop> argument, as the	4147	Starts the watcher. Note that there is no C<loop> argument, as the
3661	constructor already stores the event loop.	4148	constructor already stores the event loop.
…		…
3691	watchers in the constructor.	4178	watchers in the constructor.
3692		4179
3693	class myclass	4180	class myclass
3694	{	4181	{
3695	ev::io io ; void io_cb (ev::io &w, int revents);	4182	ev::io io ; void io_cb (ev::io &w, int revents);
3696	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);	4183	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3697	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4184	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3698		4185
3699	myclass (int fd)	4186	myclass (int fd)
3700	{	4187	{
3701	io .set <myclass, &myclass::io_cb > (this);	4188	io .set <myclass, &myclass::io_cb > (this);
…		…
3752	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4239	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3753		4240
3754	=item D	4241	=item D
3755		4242
3756	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4243	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3757	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4244	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3758		4245
3759	=item Ocaml	4246	=item Ocaml
3760		4247
3761	Erkki Seppala has written Ocaml bindings for libev, to be found at	4248	Erkki Seppala has written Ocaml bindings for libev, to be found at
3762	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4249	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
…		…
3765		4252
3766	Brian Maher has written a partial interface to libev for lua (at the	4253	Brian Maher has written a partial interface to libev for lua (at the
3767	time of this writing, only C<ev_io> and C<ev_timer>), to be found at	4254	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
3768	L<http://github.com/brimworks/lua-ev>.	4255	L<http://github.com/brimworks/lua-ev>.
3769		4256
		4257	=item Javascript
		4258
		4259	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4260
		4261	=item Others
		4262
		4263	There are others, and I stopped counting.
		4264
3770	=back	4265	=back
3771		4266
3772		4267
3773	=head1 MACRO MAGIC	4268	=head1 MACRO MAGIC
3774		4269
…		…
3810	suitable for use with C<EV_A>.	4305	suitable for use with C<EV_A>.
3811		4306
3812	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4307	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3813		4308
3814	Similar to the other two macros, this gives you the value of the default	4309	Similar to the other two macros, this gives you the value of the default
3815	loop, if multiple loops are supported ("ev loop default").	4310	loop, if multiple loops are supported ("ev loop default"). The default loop
		4311	will be initialised if it isn't already initialised.
		4312
		4313	For non-multiplicity builds, these macros do nothing, so you always have
		4314	to initialise the loop somewhere.
3816		4315
3817	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4316	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3818		4317
3819	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4318	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3820	default loop has been initialised (C<UC> == unchecked). Their behaviour	4319	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3965	supported). It will also not define any of the structs usually found in	4464	supported). It will also not define any of the structs usually found in
3966	F<event.h> that are not directly supported by the libev core alone.	4465	F<event.h> that are not directly supported by the libev core alone.
3967		4466
3968	In standalone mode, libev will still try to automatically deduce the	4467	In standalone mode, libev will still try to automatically deduce the
3969	configuration, but has to be more conservative.	4468	configuration, but has to be more conservative.
		4469
		4470	=item EV_USE_FLOOR
		4471
		4472	If defined to be C<1>, libev will use the C<floor ()> function for its
		4473	periodic reschedule calculations, otherwise libev will fall back on a
		4474	portable (slower) implementation. If you enable this, you usually have to
		4475	link against libm or something equivalent. Enabling this when the C<floor>
		4476	function is not available will fail, so the safe default is to not enable
		4477	this.
3970		4478
3971	=item EV_USE_MONOTONIC	4479	=item EV_USE_MONOTONIC
3972		4480
3973	If defined to be C<1>, libev will try to detect the availability of the	4481	If defined to be C<1>, libev will try to detect the availability of the
3974	monotonic clock option at both compile time and runtime. Otherwise no	4482	monotonic clock option at both compile time and runtime. Otherwise no
…		…
4059		4567
4060	If programs implement their own fd to handle mapping on win32, then this	4568	If programs implement their own fd to handle mapping on win32, then this
4061	macro can be used to override the C<close> function, useful to unregister	4569	macro can be used to override the C<close> function, useful to unregister
4062	file descriptors again. Note that the replacement function has to close	4570	file descriptors again. Note that the replacement function has to close
4063	the underlying OS handle.	4571	the underlying OS handle.
		4572
		4573	=item EV_USE_WSASOCKET
		4574
		4575	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4576	communication socket, which works better in some environments. Otherwise,
		4577	the normal C<socket> function will be used, which works better in other
		4578	environments.
4064		4579
4065	=item EV_USE_POLL	4580	=item EV_USE_POLL
4066		4581
4067	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4582	If defined to be C<1>, libev will compile in support for the C<poll>(2)
4068	backend. Otherwise it will be enabled on non-win32 platforms. It	4583	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
4104	If defined to be C<1>, libev will compile in support for the Linux inotify	4619	If defined to be C<1>, libev will compile in support for the Linux inotify
4105	interface to speed up C<ev_stat> watchers. Its actual availability will	4620	interface to speed up C<ev_stat> watchers. Its actual availability will
4106	be detected at runtime. If undefined, it will be enabled if the headers	4621	be detected at runtime. If undefined, it will be enabled if the headers
4107	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4622	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
4108		4623
		4624	=item EV_NO_SMP
		4625
		4626	If defined to be C<1>, libev will assume that memory is always coherent
		4627	between threads, that is, threads can be used, but threads never run on
		4628	different cpus (or different cpu cores). This reduces dependencies
		4629	and makes libev faster.
		4630
		4631	=item EV_NO_THREADS
		4632
		4633	If defined to be C<1>, libev will assume that it will never be called from
		4634	different threads (that includes signal handlers), which is a stronger
		4635	assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes
		4636	libev faster.
		4637
4109	=item EV_ATOMIC_T	4638	=item EV_ATOMIC_T
4110		4639
4111	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4640	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
4112	access is atomic with respect to other threads or signal contexts. No such	4641	access is atomic with respect to other threads or signal contexts. No
4113	type is easily found in the C language, so you can provide your own type	4642	such type is easily found in the C language, so you can provide your own
4114	that you know is safe for your purposes. It is used both for signal handler "locking"	4643	type that you know is safe for your purposes. It is used both for signal
4115	as well as for signal and thread safety in C<ev_async> watchers.	4644	handler "locking" as well as for signal and thread safety in C<ev_async>
		4645	watchers.
4116		4646
4117	In the absence of this define, libev will use C<sig_atomic_t volatile>	4647	In the absence of this define, libev will use C<sig_atomic_t volatile>
4118	(from F<signal.h>), which is usually good enough on most platforms.	4648	(from F<signal.h>), which is usually good enough on most platforms.
4119		4649
4120	=item EV_H (h)	4650	=item EV_H (h)
…		…
4147	will have the C<struct ev_loop *> as first argument, and you can create	4677	will have the C<struct ev_loop *> as first argument, and you can create
4148	additional independent event loops. Otherwise there will be no support	4678	additional independent event loops. Otherwise there will be no support
4149	for multiple event loops and there is no first event loop pointer	4679	for multiple event loops and there is no first event loop pointer
4150	argument. Instead, all functions act on the single default loop.	4680	argument. Instead, all functions act on the single default loop.
4151		4681
		4682	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4683	default loop when multiplicity is switched off - you always have to
		4684	initialise the loop manually in this case.
		4685
4152	=item EV_MINPRI	4686	=item EV_MINPRI
4153		4687
4154	=item EV_MAXPRI	4688	=item EV_MAXPRI
4155		4689
4156	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4690	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
4192	#define EV_USE_POLL 1	4726	#define EV_USE_POLL 1
4193	#define EV_CHILD_ENABLE 1	4727	#define EV_CHILD_ENABLE 1
4194	#define EV_ASYNC_ENABLE 1	4728	#define EV_ASYNC_ENABLE 1
4195		4729
4196	The actual value is a bitset, it can be a combination of the following	4730	The actual value is a bitset, it can be a combination of the following
4197	values:	4731	values (by default, all of these are enabled):
4198		4732
4199	=over 4	4733	=over 4
4200		4734
4201	=item C<1> - faster/larger code	4735	=item C<1> - faster/larger code
4202		4736
…		…
4206	code size by roughly 30% on amd64).	4740	code size by roughly 30% on amd64).
4207		4741
4208	When optimising for size, use of compiler flags such as C<-Os> with	4742	When optimising for size, use of compiler flags such as C<-Os> with
4209	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of	4743	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
4210	assertions.	4744	assertions.
		4745
		4746	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4747	(e.g. gcc with C<-Os>).
4211		4748
4212	=item C<2> - faster/larger data structures	4749	=item C<2> - faster/larger data structures
4213		4750
4214	Replaces the small 2-heap for timer management by a faster 4-heap, larger	4751	Replaces the small 2-heap for timer management by a faster 4-heap, larger
4215	hash table sizes and so on. This will usually further increase code size	4752	hash table sizes and so on. This will usually further increase code size
4216	and can additionally have an effect on the size of data structures at	4753	and can additionally have an effect on the size of data structures at
4217	runtime.	4754	runtime.
4218		4755
		4756	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4757	(e.g. gcc with C<-Os>).
		4758
4219	=item C<4> - full API configuration	4759	=item C<4> - full API configuration
4220		4760
4221	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and	4761	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
4222	enables multiplicity (C<EV_MULTIPLICITY>=1).	4762	enables multiplicity (C<EV_MULTIPLICITY>=1).
4223		4763
…		…
4253		4793
4254	With an intelligent-enough linker (gcc+binutils are intelligent enough	4794	With an intelligent-enough linker (gcc+binutils are intelligent enough
4255	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by	4795	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
4256	your program might be left out as well - a binary starting a timer and an	4796	your program might be left out as well - a binary starting a timer and an
4257	I/O watcher then might come out at only 5Kb.	4797	I/O watcher then might come out at only 5Kb.
		4798
		4799	=item EV_API_STATIC
		4800
		4801	If this symbol is defined (by default it is not), then all identifiers
		4802	will have static linkage. This means that libev will not export any
		4803	identifiers, and you cannot link against libev anymore. This can be useful
		4804	when you embed libev, only want to use libev functions in a single file,
		4805	and do not want its identifiers to be visible.
		4806
		4807	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4808	wants to use libev.
		4809
		4810	This option only works when libev is compiled with a C compiler, as C++
		4811	doesn't support the required declaration syntax.
4258		4812
4259	=item EV_AVOID_STDIO	4813	=item EV_AVOID_STDIO
4260		4814
4261	If this is set to C<1> at compiletime, then libev will avoid using stdio	4815	If this is set to C<1> at compiletime, then libev will avoid using stdio
4262	functions (printf, scanf, perror etc.). This will increase the code size	4816	functions (printf, scanf, perror etc.). This will increase the code size
…		…
4406	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4960	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4407		4961
4408	#include "ev_cpp.h"	4962	#include "ev_cpp.h"
4409	#include "ev.c"	4963	#include "ev.c"
4410		4964
4411	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4965	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4412		4966
4413	=head2 THREADS AND COROUTINES	4967	=head2 THREADS AND COROUTINES
4414		4968
4415	=head3 THREADS	4969	=head3 THREADS
4416		4970
…		…
4467	default loop and triggering an C<ev_async> watcher from the default loop	5021	default loop and triggering an C<ev_async> watcher from the default loop
4468	watcher callback into the event loop interested in the signal.	5022	watcher callback into the event loop interested in the signal.
4469		5023
4470	=back	5024	=back
4471		5025
4472	=head4 THREAD LOCKING EXAMPLE	5026	See also L</THREAD LOCKING EXAMPLE>.
4473
4474	Here is a fictitious example of how to run an event loop in a different
4475	thread than where callbacks are being invoked and watchers are
4476	created/added/removed.
4477
4478	For a real-world example, see the C<EV::Loop::Async> perl module,
4479	which uses exactly this technique (which is suited for many high-level
4480	languages).
4481
4482	The example uses a pthread mutex to protect the loop data, a condition
4483	variable to wait for callback invocations, an async watcher to notify the
4484	event loop thread and an unspecified mechanism to wake up the main thread.
4485
4486	First, you need to associate some data with the event loop:
4487
4488	typedef struct {
4489	mutex_t lock; /* global loop lock */
4490	ev_async async_w;
4491	thread_t tid;
4492	cond_t invoke_cv;
4493	} userdata;
4494
4495	void prepare_loop (EV_P)
4496	{
4497	// for simplicity, we use a static userdata struct.
4498	static userdata u;
4499
4500	ev_async_init (&u->async_w, async_cb);
4501	ev_async_start (EV_A_ &u->async_w);
4502
4503	pthread_mutex_init (&u->lock, 0);
4504	pthread_cond_init (&u->invoke_cv, 0);
4505
4506	// now associate this with the loop
4507	ev_set_userdata (EV_A_ u);
4508	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4509	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4510
4511	// then create the thread running ev_loop
4512	pthread_create (&u->tid, 0, l_run, EV_A);
4513	}
4514
4515	The callback for the C<ev_async> watcher does nothing: the watcher is used
4516	solely to wake up the event loop so it takes notice of any new watchers
4517	that might have been added:
4518
4519	static void
4520	async_cb (EV_P_ ev_async *w, int revents)
4521	{
4522	// just used for the side effects
4523	}
4524
4525	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4526	protecting the loop data, respectively.
4527
4528	static void
4529	l_release (EV_P)
4530	{
4531	userdata *u = ev_userdata (EV_A);
4532	pthread_mutex_unlock (&u->lock);
4533	}
4534
4535	static void
4536	l_acquire (EV_P)
4537	{
4538	userdata *u = ev_userdata (EV_A);
4539	pthread_mutex_lock (&u->lock);
4540	}
4541
4542	The event loop thread first acquires the mutex, and then jumps straight
4543	into C<ev_run>:
4544
4545	void *
4546	l_run (void *thr_arg)
4547	{
4548	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4549
4550	l_acquire (EV_A);
4551	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4552	ev_run (EV_A_ 0);
4553	l_release (EV_A);
4554
4555	return 0;
4556	}
4557
4558	Instead of invoking all pending watchers, the C<l_invoke> callback will
4559	signal the main thread via some unspecified mechanism (signals? pipe
4560	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4561	have been called (in a while loop because a) spurious wakeups are possible
4562	and b) skipping inter-thread-communication when there are no pending
4563	watchers is very beneficial):
4564
4565	static void
4566	l_invoke (EV_P)
4567	{
4568	userdata *u = ev_userdata (EV_A);
4569
4570	while (ev_pending_count (EV_A))
4571	{
4572	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4573	pthread_cond_wait (&u->invoke_cv, &u->lock);
4574	}
4575	}
4576
4577	Now, whenever the main thread gets told to invoke pending watchers, it
4578	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4579	thread to continue:
4580
4581	static void
4582	real_invoke_pending (EV_P)
4583	{
4584	userdata *u = ev_userdata (EV_A);
4585
4586	pthread_mutex_lock (&u->lock);
4587	ev_invoke_pending (EV_A);
4588	pthread_cond_signal (&u->invoke_cv);
4589	pthread_mutex_unlock (&u->lock);
4590	}
4591
4592	Whenever you want to start/stop a watcher or do other modifications to an
4593	event loop, you will now have to lock:
4594
4595	ev_timer timeout_watcher;
4596	userdata *u = ev_userdata (EV_A);
4597
4598	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4599
4600	pthread_mutex_lock (&u->lock);
4601	ev_timer_start (EV_A_ &timeout_watcher);
4602	ev_async_send (EV_A_ &u->async_w);
4603	pthread_mutex_unlock (&u->lock);
4604
4605	Note that sending the C<ev_async> watcher is required because otherwise
4606	an event loop currently blocking in the kernel will have no knowledge
4607	about the newly added timer. By waking up the loop it will pick up any new
4608	watchers in the next event loop iteration.
4609		5027
4610	=head3 COROUTINES	5028	=head3 COROUTINES
4611		5029
4612	Libev is very accommodating to coroutines ("cooperative threads"):	5030	Libev is very accommodating to coroutines ("cooperative threads"):
4613	libev fully supports nesting calls to its functions from different	5031	libev fully supports nesting calls to its functions from different
…		…
4778	requires, and its I/O model is fundamentally incompatible with the POSIX	5196	requires, and its I/O model is fundamentally incompatible with the POSIX
4779	model. Libev still offers limited functionality on this platform in	5197	model. Libev still offers limited functionality on this platform in
4780	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5198	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4781	descriptors. This only applies when using Win32 natively, not when using	5199	descriptors. This only applies when using Win32 natively, not when using
4782	e.g. cygwin. Actually, it only applies to the microsofts own compilers,	5200	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
4783	as every compielr comes with a slightly differently broken/incompatible	5201	as every compiler comes with a slightly differently broken/incompatible
4784	environment.	5202	environment.
4785		5203
4786	Lifting these limitations would basically require the full	5204	Lifting these limitations would basically require the full
4787	re-implementation of the I/O system. If you are into this kind of thing,	5205	re-implementation of the I/O system. If you are into this kind of thing,
4788	then note that glib does exactly that for you in a very portable way (note	5206	then note that glib does exactly that for you in a very portable way (note
…		…
4904	thread" or will block signals process-wide, both behaviours would	5322	thread" or will block signals process-wide, both behaviours would
4905	be compatible with libev. Interaction between C<sigprocmask> and	5323	be compatible with libev. Interaction between C<sigprocmask> and
4906	C<pthread_sigmask> could complicate things, however.	5324	C<pthread_sigmask> could complicate things, however.
4907		5325
4908	The most portable way to handle signals is to block signals in all threads	5326	The most portable way to handle signals is to block signals in all threads
4909	except the initial one, and run the default loop in the initial thread as	5327	except the initial one, and run the signal handling loop in the initial
4910	well.	5328	thread as well.
4911		5329
4912	=item C<long> must be large enough for common memory allocation sizes	5330	=item C<long> must be large enough for common memory allocation sizes
4913		5331
4914	To improve portability and simplify its API, libev uses C<long> internally	5332	To improve portability and simplify its API, libev uses C<long> internally
4915	instead of C<size_t> when allocating its data structures. On non-POSIX	5333	instead of C<size_t> when allocating its data structures. On non-POSIX
…		…
4921		5339
4922	The type C<double> is used to represent timestamps. It is required to	5340	The type C<double> is used to represent timestamps. It is required to
4923	have at least 51 bits of mantissa (and 9 bits of exponent), which is	5341	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4924	good enough for at least into the year 4000 with millisecond accuracy	5342	good enough for at least into the year 4000 with millisecond accuracy
4925	(the design goal for libev). This requirement is overfulfilled by	5343	(the design goal for libev). This requirement is overfulfilled by
4926	implementations using IEEE 754, which is basically all existing ones. With	5344	implementations using IEEE 754, which is basically all existing ones.
		5345
4927	IEEE 754 doubles, you get microsecond accuracy until at least 2200.	5346	With IEEE 754 doubles, you get microsecond accuracy until at least the
		5347	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5348	is either obsolete or somebody patched it to use C<long double> or
		5349	something like that, just kidding).
4928		5350
4929	=back	5351	=back
4930		5352
4931	If you know of other additional requirements drop me a note.	5353	If you know of other additional requirements drop me a note.
4932		5354
…		…
4994	=item Processing ev_async_send: O(number_of_async_watchers)	5416	=item Processing ev_async_send: O(number_of_async_watchers)
4995		5417
4996	=item Processing signals: O(max_signal_number)	5418	=item Processing signals: O(max_signal_number)
4997		5419
4998	Sending involves a system call I<iff> there were no other C<ev_async_send>	5420	Sending involves a system call I<iff> there were no other C<ev_async_send>
4999	calls in the current loop iteration. Checking for async and signal events	5421	calls in the current loop iteration and the loop is currently
		5422	blocked. Checking for async and signal events involves iterating over all
5000	involves iterating over all running async watchers or all signal numbers.	5423	running async watchers or all signal numbers.
5001		5424
5002	=back	5425	=back
5003		5426
5004		5427
5005	=head1 PORTING FROM LIBEV 3.X TO 4.X	5428	=head1 PORTING FROM LIBEV 3.X TO 4.X
…		…
5014	=over 4	5437	=over 4
5015		5438
5016	=item C<EV_COMPAT3> backwards compatibility mechanism	5439	=item C<EV_COMPAT3> backwards compatibility mechanism
5017		5440
5018	The backward compatibility mechanism can be controlled by	5441	The backward compatibility mechanism can be controlled by
5019	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>	5442	C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING>
5020	section.	5443	section.
5021		5444
5022	=item C<ev_default_destroy> and C<ev_default_fork> have been removed	5445	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
5023		5446
5024	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:	5447	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
…		…
5067	=over 4	5490	=over 4
5068		5491
5069	=item active	5492	=item active
5070		5493
5071	A watcher is active as long as it has been started and not yet stopped.	5494	A watcher is active as long as it has been started and not yet stopped.
5072	See L<WATCHER STATES> for details.	5495	See L</WATCHER STATES> for details.
5073		5496
5074	=item application	5497	=item application
5075		5498
5076	In this document, an application is whatever is using libev.	5499	In this document, an application is whatever is using libev.
5077		5500
…		…
5113	watchers and events.	5536	watchers and events.
5114		5537
5115	=item pending	5538	=item pending
5116		5539
5117	A watcher is pending as soon as the corresponding event has been	5540	A watcher is pending as soon as the corresponding event has been
5118	detected. See L<WATCHER STATES> for details.	5541	detected. See L</WATCHER STATES> for details.
5119		5542
5120	=item real time	5543	=item real time
5121		5544
5122	The physical time that is observed. It is apparently strictly monotonic :)	5545	The physical time that is observed. It is apparently strictly monotonic :)
5123		5546
5124	=item wall-clock time	5547	=item wall-clock time
5125		5548
5126	The time and date as shown on clocks. Unlike real time, it can actually	5549	The time and date as shown on clocks. Unlike real time, it can actually
5127	be wrong and jump forwards and backwards, e.g. when the you adjust your	5550	be wrong and jump forwards and backwards, e.g. when you adjust your
5128	clock.	5551	clock.
5129		5552
5130	=item watcher	5553	=item watcher
5131		5554
5132	A data structure that describes interest in certain events. Watchers need	5555	A data structure that describes interest in certain events. Watchers need
…		…
5135	=back	5558	=back
5136		5559
5137	=head1 AUTHOR	5560	=head1 AUTHOR
5138		5561
5139	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael	5562	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
5140	Magnusson and Emanuele Giaquinta.	5563	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
5141		5564

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