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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
…		…
299	}	307	}
300		308
301	...	309	...
302	ev_set_syserr_cb (fatal_error);	310	ev_set_syserr_cb (fatal_error);
303		311
		312	=item ev_feed_signal (int signum)
		313
		314	This function can be used to "simulate" a signal receive. It is completely
		315	safe to call this function at any time, from any context, including signal
		316	handlers or random threads.
		317
		318	Its main use is to customise signal handling in your process, especially
		319	in the presence of threads. For example, you could block signals
		320	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		321	creating any loops), and in one thread, use C<sigwait> or any other
		322	mechanism to wait for signals, then "deliver" them to libev by calling
		323	C<ev_feed_signal>.
		324
304	=back	325	=back
305		326
306	=head1 FUNCTIONS CONTROLLING EVENT LOOPS	327	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
307		328
308	An event loop is described by a C<struct ev_loop *> (the C<struct> is	329	An event loop is described by a C<struct ev_loop *> (the C<struct> is
…		…
355	=item struct ev_loop *ev_loop_new (unsigned int flags)	376	=item struct ev_loop *ev_loop_new (unsigned int flags)
356		377
357	This will create and initialise a new event loop object. If the loop	378	This will create and initialise a new event loop object. If the loop
358	could not be initialised, returns false.	379	could not be initialised, returns false.
359		380
360	Note that this function I<is> thread-safe, and one common way to use	381	This function is thread-safe, and one common way to use libev with
361	libev with threads is indeed to create one loop per thread, and using the	382	threads is indeed to create one loop per thread, and using the default
362	default loop in the "main" or "initial" thread.	383	loop in the "main" or "initial" thread.
363		384
364	The flags argument can be used to specify special behaviour or specific	385	The flags argument can be used to specify special behaviour or specific
365	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	386	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
366		387
367	The following flags are supported:	388	The following flags are supported:
…		…
377		398
378	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
379	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
380	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	401	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
381	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
382	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
383	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).
384		407
385	=item C<EVFLAG_FORKCHECK>	408	=item C<EVFLAG_FORKCHECK>
386		409
387	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
388	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.
389		412
390	This works by calling C<getpid ()> on every iteration of the loop,	413	This works by calling C<getpid ()> on every iteration of the loop,
391	and thus this might slow down your event loop if you do a lot of loop	414	and thus this might slow down your event loop if you do a lot of loop
392	iterations and little real work, but is usually not noticeable (on my	415	iterations and little real work, but is usually not noticeable (on my
393	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
394	without a system call and thus I<very> fast, but my GNU/Linux system also has	417	sequence without a system call and thus I<very> fast, but my GNU/Linux
395	C<pthread_atfork> which is even faster).	418	system also has C<pthread_atfork> which is even faster). (Update: glibc
		419	versions 2.25 apparently removed the C<getpid> optimisation again).
396		420
397	The big advantage of this flag is that you can forget about fork (and	421	The big advantage of this flag is that you can forget about fork (and
398	forget about forgetting to tell libev about forking) when you use this	422	forget about forgetting to tell libev about forking, although you still
399	flag.	423	have to ignore C<SIGPIPE>) when you use this flag.
400		424
401	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	425	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
402	environment variable.	426	environment variable.
403		427
404	=item C<EVFLAG_NOINOTIFY>	428	=item C<EVFLAG_NOINOTIFY>
…		…
419		443
420	Signalfd will not be used by default as this changes your signal mask, and	444	Signalfd will not be used by default as this changes your signal mask, and
421	there are a lot of shoddy libraries and programs (glib's threadpool for	445	there are a lot of shoddy libraries and programs (glib's threadpool for
422	example) that can't properly initialise their signal masks.	446	example) that can't properly initialise their signal masks.
423		447
		448	=item C<EVFLAG_NOSIGMASK>
		449
		450	When this flag is specified, then libev will avoid to modify the signal
		451	mask. Specifically, this means you have to make sure signals are unblocked
		452	when you want to receive them.
		453
		454	This behaviour is useful when you want to do your own signal handling, or
		455	want to handle signals only in specific threads and want to avoid libev
		456	unblocking the signals.
		457
		458	It's also required by POSIX in a threaded program, as libev calls
		459	C<sigprocmask>, whose behaviour is officially unspecified.
		460
		461	This flag's behaviour will become the default in future versions of libev.
		462
424	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	463	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
425		464
426	This is your standard select(2) backend. Not I<completely> standard, as	465	This is your standard select(2) backend. Not I<completely> standard, as
427	libev tries to roll its own fd_set with no limits on the number of fds,	466	libev tries to roll its own fd_set with no limits on the number of fds,
428	but if that fails, expect a fairly low limit on the number of fds when	467	but if that fails, expect a fairly low limit on the number of fds when
…		…
455	=item C<EVBACKEND_EPOLL> (value 4, Linux)	494	=item C<EVBACKEND_EPOLL> (value 4, Linux)
456		495
457	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9	496	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
458	kernels).	497	kernels).
459		498
460	For few fds, this backend is a bit little slower than poll and select,	499	For few fds, this backend is a bit little slower than poll and select, but
461	but it scales phenomenally better. While poll and select usually scale	500	it scales phenomenally better. While poll and select usually scale like
462	like O(total_fds) where n is the total number of fds (or the highest fd),	501	O(total_fds) where total_fds is the total number of fds (or the highest
463	epoll scales either O(1) or O(active_fds).	502	fd), epoll scales either O(1) or O(active_fds).
464		503
465	The epoll mechanism deserves honorable mention as the most misdesigned	504	The epoll mechanism deserves honorable mention as the most misdesigned
466	of the more advanced event mechanisms: mere annoyances include silently	505	of the more advanced event mechanisms: mere annoyances include silently
467	dropping file descriptors, requiring a system call per change per file	506	dropping file descriptors, requiring a system call per change per file
468	descriptor (and unnecessary guessing of parameters), problems with dup,	507	descriptor (and unnecessary guessing of parameters), problems with dup,
…		…
471	0.1ms) and so on. The biggest issue is fork races, however - if a program	510	0.1ms) and so on. The biggest issue is fork races, however - if a program
472	forks then I<both> parent and child process have to recreate the epoll	511	forks then I<both> parent and child process have to recreate the epoll
473	set, which can take considerable time (one syscall per file descriptor)	512	set, which can take considerable time (one syscall per file descriptor)
474	and is of course hard to detect.	513	and is of course hard to detect.
475		514
476	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	515	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
477	of course I<doesn't>, and epoll just loves to report events for totally	516	but of course I<doesn't>, and epoll just loves to report events for
478	I<different> file descriptors (even already closed ones, so one cannot	517	totally I<different> file descriptors (even already closed ones, so
479	even remove them from the set) than registered in the set (especially	518	one cannot even remove them from the set) than registered in the set
480	on SMP systems). Libev tries to counter these spurious notifications by	519	(especially on SMP systems). Libev tries to counter these spurious
481	employing an additional generation counter and comparing that against the	520	notifications by employing an additional generation counter and comparing
482	events to filter out spurious ones, recreating the set when required. Last	521	that against the events to filter out spurious ones, recreating the set
		522	when required. Epoll also erroneously rounds down timeouts, but gives you
		523	no way to know when and by how much, so sometimes you have to busy-wait
		524	because epoll returns immediately despite a nonzero timeout. And last
483	not least, it also refuses to work with some file descriptors which work	525	not least, it also refuses to work with some file descriptors which work
484	perfectly fine with C<select> (files, many character devices...).	526	perfectly fine with C<select> (files, many character devices...).
485		527
486	Epoll is truly the train wreck analog among event poll mechanisms.	528	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
		529	cobbled together in a hurry, no thought to design or interaction with
		530	others. Oh, the pain, will it ever stop...
487		531
488	While stopping, setting and starting an I/O watcher in the same iteration	532	While stopping, setting and starting an I/O watcher in the same iteration
489	will result in some caching, there is still a system call per such	533	will result in some caching, there is still a system call per such
490	incident (because the same I<file descriptor> could point to a different	534	incident (because the same I<file descriptor> could point to a different
491	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	535	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
528		572
529	It scales in the same way as the epoll backend, but the interface to the	573	It scales in the same way as the epoll backend, but the interface to the
530	kernel is more efficient (which says nothing about its actual speed, of	574	kernel is more efficient (which says nothing about its actual speed, of
531	course). While stopping, setting and starting an I/O watcher does never	575	course). While stopping, setting and starting an I/O watcher does never
532	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	576	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
533	two event changes per incident. Support for C<fork ()> is very bad (but	577	two event changes per incident. Support for C<fork ()> is very bad (you
534	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect	578	might have to leak fd's on fork, but it's more sane than epoll) and it
535	cases	579	drops fds silently in similarly hard-to-detect cases.
536		580
537	This backend usually performs well under most conditions.	581	This backend usually performs well under most conditions.
538		582
539	While nominally embeddable in other event loops, this doesn't work	583	While nominally embeddable in other event loops, this doesn't work
540	everywhere, so you might need to test for this. And since it is broken	584	everywhere, so you might need to test for this. And since it is broken
…		…
557	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	601	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
558		602
559	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	603	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
560	it's really slow, but it still scales very well (O(active_fds)).	604	it's really slow, but it still scales very well (O(active_fds)).
561		605
562	Please note that Solaris event ports can deliver a lot of spurious
563	notifications, so you need to use non-blocking I/O or other means to avoid
564	blocking when no data (or space) is available.
565
566	While this backend scales well, it requires one system call per active	606	While this backend scales well, it requires one system call per active
567	file descriptor per loop iteration. For small and medium numbers of file	607	file descriptor per loop iteration. For small and medium numbers of file
568	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	608	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
569	might perform better.	609	might perform better.
570		610
571	On the positive side, with the exception of the spurious readiness	611	On the positive side, this backend actually performed fully to
572	notifications, this backend actually performed fully to specification
573	in all tests and is fully embeddable, which is a rare feat among the	612	specification in all tests and is fully embeddable, which is a rare feat
574	OS-specific backends (I vastly prefer correctness over speed hacks).	613	among the OS-specific backends (I vastly prefer correctness over speed
		614	hacks).
		615
		616	On the negative side, the interface is I<bizarre> - so bizarre that
		617	even sun itself gets it wrong in their code examples: The event polling
		618	function sometimes returns events to the caller even though an error
		619	occurred, but with no indication whether it has done so or not (yes, it's
		620	even documented that way) - deadly for edge-triggered interfaces where you
		621	absolutely have to know whether an event occurred or not because you have
		622	to re-arm the watcher.
		623
		624	Fortunately libev seems to be able to work around these idiocies.
575		625
576	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	626	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
577	C<EVBACKEND_POLL>.	627	C<EVBACKEND_POLL>.
578		628
579	=item C<EVBACKEND_ALL>	629	=item C<EVBACKEND_ALL>
580		630
581	Try all backends (even potentially broken ones that wouldn't be tried	631	Try all backends (even potentially broken ones that wouldn't be tried
582	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	632	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
583	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	633	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
584		634
585	It is definitely not recommended to use this flag.	635	It is definitely not recommended to use this flag, use whatever
		636	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		637	at all.
		638
		639	=item C<EVBACKEND_MASK>
		640
		641	Not a backend at all, but a mask to select all backend bits from a
		642	C<flags> value, in case you want to mask out any backends from a flags
		643	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
586		644
587	=back	645	=back
588		646
589	If one or more of the backend flags are or'ed into the flags value,	647	If one or more of the backend flags are or'ed into the flags value,
590	then only these backends will be tried (in the reverse order as listed	648	then only these backends will be tried (in the reverse order as listed
…		…
625	If you need dynamically allocated loops it is better to use C<ev_loop_new>	683	If you need dynamically allocated loops it is better to use C<ev_loop_new>
626	and C<ev_loop_destroy>.	684	and C<ev_loop_destroy>.
627		685
628	=item ev_loop_fork (loop)	686	=item ev_loop_fork (loop)
629		687
630	This function sets a flag that causes subsequent C<ev_run> iterations to	688	This function sets a flag that causes subsequent C<ev_run> iterations
631	reinitialise the kernel state for backends that have one. Despite the	689	to reinitialise the kernel state for backends that have one. Despite
632	name, you can call it anytime, but it makes most sense after forking, in	690	the name, you can call it anytime you are allowed to start or stop
633	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the	691	watchers (except inside an C<ev_prepare> callback), but it makes most
		692	sense after forking, in the child process. You I<must> call it (or use
634	child before resuming or calling C<ev_run>.	693	C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>.
635		694
		695	In addition, if you want to reuse a loop (via this function or
		696	C<EVFLAG_FORKCHECK>), you I<also> have to ignore C<SIGPIPE>.
		697
636	Again, you I<have> to call it on I<any> loop that you want to re-use after	698	Again, you I<have> to call it on I<any> loop that you want to re-use after
637	a fork, I<even if you do not plan to use the loop in the parent>. This is	699	a fork, I<even if you do not plan to use the loop in the parent>. This is
638	because some kernel interfaces *cough* I<kqueue> *cough* do funny things	700	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
639	during fork.	701	during fork.
640		702
641	On the other hand, you only need to call this function in the child	703	On the other hand, you only need to call this function in the child
…		…
677	prepare and check phases.	739	prepare and check phases.
678		740
679	=item unsigned int ev_depth (loop)	741	=item unsigned int ev_depth (loop)
680		742
681	Returns the number of times C<ev_run> was entered minus the number of	743	Returns the number of times C<ev_run> was entered minus the number of
682	times C<ev_run> was exited, in other words, the recursion depth.	744	times C<ev_run> was exited normally, in other words, the recursion depth.
683		745
684	Outside C<ev_run>, this number is zero. In a callback, this number is	746	Outside C<ev_run>, this number is zero. In a callback, this number is
685	C<1>, unless C<ev_run> was invoked recursively (or from another thread),	747	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
686	in which case it is higher.	748	in which case it is higher.
687		749
688	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread	750	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
689	etc.), doesn't count as "exit" - consider this as a hint to avoid such	751	throwing an exception etc.), doesn't count as "exit" - consider this
690	ungentleman-like behaviour unless it's really convenient.	752	as a hint to avoid such ungentleman-like behaviour unless it's really
		753	convenient, in which case it is fully supported.
691		754
692	=item unsigned int ev_backend (loop)	755	=item unsigned int ev_backend (loop)
693		756
694	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	757	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
695	use.	758	use.
…		…
710		773
711	This function is rarely useful, but when some event callback runs for a	774	This function is rarely useful, but when some event callback runs for a
712	very long time without entering the event loop, updating libev's idea of	775	very long time without entering the event loop, updating libev's idea of
713	the current time is a good idea.	776	the current time is a good idea.
714		777
715	See also L<The special problem of time updates> in the C<ev_timer> section.	778	See also L</The special problem of time updates> in the C<ev_timer> section.
716		779
717	=item ev_suspend (loop)	780	=item ev_suspend (loop)
718		781
719	=item ev_resume (loop)	782	=item ev_resume (loop)
720		783
…		…
738	without a previous call to C<ev_suspend>.	801	without a previous call to C<ev_suspend>.
739		802
740	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	803	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
741	event loop time (see C<ev_now_update>).	804	event loop time (see C<ev_now_update>).
742		805
743	=item ev_run (loop, int flags)	806	=item bool ev_run (loop, int flags)
744		807
745	Finally, this is it, the event handler. This function usually is called	808	Finally, this is it, the event handler. This function usually is called
746	after you have initialised all your watchers and you want to start	809	after you have initialised all your watchers and you want to start
747	handling events. It will ask the operating system for any new events, call	810	handling events. It will ask the operating system for any new events, call
748	the watcher callbacks, an then repeat the whole process indefinitely: This	811	the watcher callbacks, and then repeat the whole process indefinitely: This
749	is why event loops are called I<loops>.	812	is why event loops are called I<loops>.
750		813
751	If the flags argument is specified as C<0>, it will keep handling events	814	If the flags argument is specified as C<0>, it will keep handling events
752	until either no event watchers are active anymore or C<ev_break> was	815	until either no event watchers are active anymore or C<ev_break> was
753	called.	816	called.
		817
		818	The return value is false if there are no more active watchers (which
		819	usually means "all jobs done" or "deadlock"), and true in all other cases
		820	(which usually means " you should call C<ev_run> again").
754		821
755	Please note that an explicit C<ev_break> is usually better than	822	Please note that an explicit C<ev_break> is usually better than
756	relying on all watchers to be stopped when deciding when a program has	823	relying on all watchers to be stopped when deciding when a program has
757	finished (especially in interactive programs), but having a program	824	finished (especially in interactive programs), but having a program
758	that automatically loops as long as it has to and no longer by virtue	825	that automatically loops as long as it has to and no longer by virtue
759	of relying on its watchers stopping correctly, that is truly a thing of	826	of relying on its watchers stopping correctly, that is truly a thing of
760	beauty.	827	beauty.
761		828
		829	This function is I<mostly> exception-safe - you can break out of a
		830	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		831	exception and so on. This does not decrement the C<ev_depth> value, nor
		832	will it clear any outstanding C<EVBREAK_ONE> breaks.
		833
762	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle	834	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
763	those events and any already outstanding ones, but will not wait and	835	those events and any already outstanding ones, but will not wait and
764	block your process in case there are no events and will return after one	836	block your process in case there are no events and will return after one
765	iteration of the loop. This is sometimes useful to poll and handle new	837	iteration of the loop. This is sometimes useful to poll and handle new
766	events while doing lengthy calculations, to keep the program responsive.	838	events while doing lengthy calculations, to keep the program responsive.
…		…
775	This is useful if you are waiting for some external event in conjunction	847	This is useful if you are waiting for some external event in conjunction
776	with something not expressible using other libev watchers (i.e. "roll your	848	with something not expressible using other libev watchers (i.e. "roll your
777	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	849	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
778	usually a better approach for this kind of thing.	850	usually a better approach for this kind of thing.
779		851
780	Here are the gory details of what C<ev_run> does:	852	Here are the gory details of what C<ev_run> does (this is for your
		853	understanding, not a guarantee that things will work exactly like this in
		854	future versions):
781		855
782	- Increment loop depth.	856	- Increment loop depth.
783	- Reset the ev_break status.	857	- Reset the ev_break status.
784	- Before the first iteration, call any pending watchers.	858	- Before the first iteration, call any pending watchers.
785	LOOP:	859	LOOP:
…		…
818	anymore.	892	anymore.
819		893
820	... queue jobs here, make sure they register event watchers as long	894	... queue jobs here, make sure they register event watchers as long
821	... as they still have work to do (even an idle watcher will do..)	895	... as they still have work to do (even an idle watcher will do..)
822	ev_run (my_loop, 0);	896	ev_run (my_loop, 0);
823	... jobs done or somebody called unloop. yeah!	897	... jobs done or somebody called break. yeah!
824		898
825	=item ev_break (loop, how)	899	=item ev_break (loop, how)
826		900
827	Can be used to make a call to C<ev_run> return early (but only after it	901	Can be used to make a call to C<ev_run> return early (but only after it
828	has processed all outstanding events). The C<how> argument must be either	902	has processed all outstanding events). The C<how> argument must be either
829	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or	903	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
830	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.	904	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
831		905
832	This "break state" will be cleared when entering C<ev_run> again.	906	This "break state" will be cleared on the next call to C<ev_run>.
833		907
834	It is safe to call C<ev_break> from outside any C<ev_run> calls, too.	908	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		909	which case it will have no effect.
835		910
836	=item ev_ref (loop)	911	=item ev_ref (loop)
837		912
838	=item ev_unref (loop)	913	=item ev_unref (loop)
839		914
…		…
860	running when nothing else is active.	935	running when nothing else is active.
861		936
862	ev_signal exitsig;	937	ev_signal exitsig;
863	ev_signal_init (&exitsig, sig_cb, SIGINT);	938	ev_signal_init (&exitsig, sig_cb, SIGINT);
864	ev_signal_start (loop, &exitsig);	939	ev_signal_start (loop, &exitsig);
865	evf_unref (loop);	940	ev_unref (loop);
866		941
867	Example: For some weird reason, unregister the above signal handler again.	942	Example: For some weird reason, unregister the above signal handler again.
868		943
869	ev_ref (loop);	944	ev_ref (loop);
870	ev_signal_stop (loop, &exitsig);	945	ev_signal_stop (loop, &exitsig);
…		…
890	overhead for the actual polling but can deliver many events at once.	965	overhead for the actual polling but can deliver many events at once.
891		966
892	By setting a higher I<io collect interval> you allow libev to spend more	967	By setting a higher I<io collect interval> you allow libev to spend more
893	time collecting I/O events, so you can handle more events per iteration,	968	time collecting I/O events, so you can handle more events per iteration,
894	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	969	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
895	C<ev_timer>) will be not affected. Setting this to a non-null value will	970	C<ev_timer>) will not be affected. Setting this to a non-null value will
896	introduce an additional C<ev_sleep ()> call into most loop iterations. The	971	introduce an additional C<ev_sleep ()> call into most loop iterations. The
897	sleep time ensures that libev will not poll for I/O events more often then	972	sleep time ensures that libev will not poll for I/O events more often then
898	once per this interval, on average.	973	once per this interval, on average (as long as the host time resolution is
		974	good enough).
899		975
900	Likewise, by setting a higher I<timeout collect interval> you allow libev	976	Likewise, by setting a higher I<timeout collect interval> you allow libev
901	to spend more time collecting timeouts, at the expense of increased	977	to spend more time collecting timeouts, at the expense of increased
902	latency/jitter/inexactness (the watcher callback will be called	978	latency/jitter/inexactness (the watcher callback will be called
903	later). C<ev_io> watchers will not be affected. Setting this to a non-null	979	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
949	invoke the actual watchers inside another context (another thread etc.).	1025	invoke the actual watchers inside another context (another thread etc.).
950		1026
951	If you want to reset the callback, use C<ev_invoke_pending> as new	1027	If you want to reset the callback, use C<ev_invoke_pending> as new
952	callback.	1028	callback.
953		1029
954	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))	1030	=item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())
955		1031
956	Sometimes you want to share the same loop between multiple threads. This	1032	Sometimes you want to share the same loop between multiple threads. This
957	can be done relatively simply by putting mutex_lock/unlock calls around	1033	can be done relatively simply by putting mutex_lock/unlock calls around
958	each call to a libev function.	1034	each call to a libev function.
959		1035
960	However, C<ev_run> can run an indefinite time, so it is not feasible	1036	However, C<ev_run> can run an indefinite time, so it is not feasible
961	to wait for it to return. One way around this is to wake up the event	1037	to wait for it to return. One way around this is to wake up the event
962	loop via C<ev_break> and C<av_async_send>, another way is to set these	1038	loop via C<ev_break> and C<ev_async_send>, another way is to set these
963	I<release> and I<acquire> callbacks on the loop.	1039	I<release> and I<acquire> callbacks on the loop.
964		1040
965	When set, then C<release> will be called just before the thread is	1041	When set, then C<release> will be called just before the thread is
966	suspended waiting for new events, and C<acquire> is called just	1042	suspended waiting for new events, and C<acquire> is called just
967	afterwards.	1043	afterwards.
…		…
982	See also the locking example in the C<THREADS> section later in this	1058	See also the locking example in the C<THREADS> section later in this
983	document.	1059	document.
984		1060
985	=item ev_set_userdata (loop, void *data)	1061	=item ev_set_userdata (loop, void *data)
986		1062
987	=item ev_userdata (loop)	1063	=item void *ev_userdata (loop)
988		1064
989	Set and retrieve a single C<void *> associated with a loop. When	1065	Set and retrieve a single C<void *> associated with a loop. When
990	C<ev_set_userdata> has never been called, then C<ev_userdata> returns	1066	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
991	C<0.>	1067	C<0>.
992		1068
993	These two functions can be used to associate arbitrary data with a loop,	1069	These two functions can be used to associate arbitrary data with a loop,
994	and are intended solely for the C<invoke_pending_cb>, C<release> and	1070	and are intended solely for the C<invoke_pending_cb>, C<release> and
995	C<acquire> callbacks described above, but of course can be (ab-)used for	1071	C<acquire> callbacks described above, but of course can be (ab-)used for
996	any other purpose as well.	1072	any other purpose as well.
…		…
1107		1183
1108	=item C<EV_PREPARE>	1184	=item C<EV_PREPARE>
1109		1185
1110	=item C<EV_CHECK>	1186	=item C<EV_CHECK>
1111		1187
1112	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts	1188	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to
1113	to gather new events, and all C<ev_check> watchers are invoked just after	1189	gather new events, and all C<ev_check> watchers are queued (not invoked)
1114	C<ev_run> has gathered them, but before it invokes any callbacks for any	1190	just after C<ev_run> has gathered them, but before it queues any callbacks
		1191	for any received events. That means C<ev_prepare> watchers are the last
		1192	watchers invoked before the event loop sleeps or polls for new events, and
		1193	C<ev_check> watchers will be invoked before any other watchers of the same
		1194	or lower priority within an event loop iteration.
		1195
1115	received events. Callbacks of both watcher types can start and stop as	1196	Callbacks of both watcher types can start and stop as many watchers as
1116	many watchers as they want, and all of them will be taken into account	1197	they want, and all of them will be taken into account (for example, a
1117	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1198	C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from
1118	C<ev_run> from blocking).	1199	blocking).
1119		1200
1120	=item C<EV_EMBED>	1201	=item C<EV_EMBED>
1121		1202
1122	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1203	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1123		1204
…		…
1246		1327
1247	=item callback ev_cb (ev_TYPE *watcher)	1328	=item callback ev_cb (ev_TYPE *watcher)
1248		1329
1249	Returns the callback currently set on the watcher.	1330	Returns the callback currently set on the watcher.
1250		1331
1251	=item ev_cb_set (ev_TYPE *watcher, callback)	1332	=item ev_set_cb (ev_TYPE *watcher, callback)
1252		1333
1253	Change the callback. You can change the callback at virtually any time	1334	Change the callback. You can change the callback at virtually any time
1254	(modulo threads).	1335	(modulo threads).
1255		1336
1256	=item ev_set_priority (ev_TYPE *watcher, int priority)	1337	=item ev_set_priority (ev_TYPE *watcher, int priority)
…		…
1274	or might not have been clamped to the valid range.	1355	or might not have been clamped to the valid range.
1275		1356
1276	The default priority used by watchers when no priority has been set is	1357	The default priority used by watchers when no priority has been set is
1277	always C<0>, which is supposed to not be too high and not be too low :).	1358	always C<0>, which is supposed to not be too high and not be too low :).
1278		1359
1279	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of	1360	See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1280	priorities.	1361	priorities.
1281		1362
1282	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1363	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1283		1364
1284	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1365	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
…		…
1309	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related	1390	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1310	functions that do not need a watcher.	1391	functions that do not need a watcher.
1311		1392
1312	=back	1393	=back
1313		1394
1314	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1395	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
1315		1396	OWN COMPOSITE WATCHERS> idioms.
1316	Each watcher has, by default, a member C<void *data> that you can change
1317	and read at any time: libev will completely ignore it. This can be used
1318	to associate arbitrary data with your watcher. If you need more data and
1319	don't want to allocate memory and store a pointer to it in that data
1320	member, you can also "subclass" the watcher type and provide your own
1321	data:
1322
1323	struct my_io
1324	{
1325	ev_io io;
1326	int otherfd;
1327	void *somedata;
1328	struct whatever *mostinteresting;
1329	};
1330
1331	...
1332	struct my_io w;
1333	ev_io_init (&w.io, my_cb, fd, EV_READ);
1334
1335	And since your callback will be called with a pointer to the watcher, you
1336	can cast it back to your own type:
1337
1338	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1339	{
1340	struct my_io *w = (struct my_io *)w_;
1341	...
1342	}
1343
1344	More interesting and less C-conformant ways of casting your callback type
1345	instead have been omitted.
1346
1347	Another common scenario is to use some data structure with multiple
1348	embedded watchers:
1349
1350	struct my_biggy
1351	{
1352	int some_data;
1353	ev_timer t1;
1354	ev_timer t2;
1355	}
1356
1357	In this case getting the pointer to C<my_biggy> is a bit more
1358	complicated: Either you store the address of your C<my_biggy> struct
1359	in the C<data> member of the watcher (for woozies), or you need to use
1360	some pointer arithmetic using C<offsetof> inside your watchers (for real
1361	programmers):
1362
1363	#include <stddef.h>
1364
1365	static void
1366	t1_cb (EV_P_ ev_timer *w, int revents)
1367	{
1368	struct my_biggy big = (struct my_biggy *)
1369	(((char *)w) - offsetof (struct my_biggy, t1));
1370	}
1371
1372	static void
1373	t2_cb (EV_P_ ev_timer *w, int revents)
1374	{
1375	struct my_biggy big = (struct my_biggy *)
1376	(((char *)w) - offsetof (struct my_biggy, t2));
1377	}
1378		1397
1379	=head2 WATCHER STATES	1398	=head2 WATCHER STATES
1380		1399
1381	There are various watcher states mentioned throughout this manual -	1400	There are various watcher states mentioned throughout this manual -
1382	active, pending and so on. In this section these states and the rules to	1401	active, pending and so on. In this section these states and the rules to
1383	transition between them will be described in more detail - and while these	1402	transition between them will be described in more detail - and while these
1384	rules might look complicated, they usually do "the right thing".	1403	rules might look complicated, they usually do "the right thing".
1385		1404
1386	=over 4	1405	=over 4
1387		1406
1388	=item initialiased	1407	=item initialised
1389		1408
1390	Before a watcher can be registered with the event looop it has to be	1409	Before a watcher can be registered with the event loop it has to be
1391	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to	1410	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
1392	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.	1411	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1393		1412
1394	In this state it is simply some block of memory that is suitable for use	1413	In this state it is simply some block of memory that is suitable for
1395	in an event loop. It can be moved around, freed, reused etc. at will.	1414	use in an event loop. It can be moved around, freed, reused etc. at
		1415	will - as long as you either keep the memory contents intact, or call
		1416	C<ev_TYPE_init> again.
1396		1417
1397	=item started/running/active	1418	=item started/running/active
1398		1419
1399	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes	1420	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1400	property of the event loop, and is actively waiting for events. While in	1421	property of the event loop, and is actively waiting for events. While in
…		…
1428	latter will clear any pending state the watcher might be in, regardless	1449	latter will clear any pending state the watcher might be in, regardless
1429	of whether it was active or not, so stopping a watcher explicitly before	1450	of whether it was active or not, so stopping a watcher explicitly before
1430	freeing it is often a good idea.	1451	freeing it is often a good idea.
1431		1452
1432	While stopped (and not pending) the watcher is essentially in the	1453	While stopped (and not pending) the watcher is essentially in the
1433	initialised state, that is it can be reused, moved, modified in any way	1454	initialised state, that is, it can be reused, moved, modified in any way
1434	you wish.	1455	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1456	it again).
1435		1457
1436	=back	1458	=back
1437		1459
1438	=head2 WATCHER PRIORITY MODELS	1460	=head2 WATCHER PRIORITY MODELS
1439		1461
…		…
1568	In general you can register as many read and/or write event watchers per	1590	In general you can register as many read and/or write event watchers per
1569	fd as you want (as long as you don't confuse yourself). Setting all file	1591	fd as you want (as long as you don't confuse yourself). Setting all file
1570	descriptors to non-blocking mode is also usually a good idea (but not	1592	descriptors to non-blocking mode is also usually a good idea (but not
1571	required if you know what you are doing).	1593	required if you know what you are doing).
1572		1594
1573	If you cannot use non-blocking mode, then force the use of a
1574	known-to-be-good backend (at the time of this writing, this includes only
1575	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1576	descriptors for which non-blocking operation makes no sense (such as
1577	files) - libev doesn't guarantee any specific behaviour in that case.
1578
1579	Another thing you have to watch out for is that it is quite easy to	1595	Another thing you have to watch out for is that it is quite easy to
1580	receive "spurious" readiness notifications, that is your callback might	1596	receive "spurious" readiness notifications, that is, your callback might
1581	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1597	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1582	because there is no data. Not only are some backends known to create a	1598	because there is no data. It is very easy to get into this situation even
1583	lot of those (for example Solaris ports), it is very easy to get into	1599	with a relatively standard program structure. Thus it is best to always
1584	this situation even with a relatively standard program structure. Thus	1600	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1585	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1586	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1601	preferable to a program hanging until some data arrives.
1587		1602
1588	If you cannot run the fd in non-blocking mode (for example you should	1603	If you cannot run the fd in non-blocking mode (for example you should
1589	not play around with an Xlib connection), then you have to separately	1604	not play around with an Xlib connection), then you have to separately
1590	re-test whether a file descriptor is really ready with a known-to-be good	1605	re-test whether a file descriptor is really ready with a known-to-be good
1591	interface such as poll (fortunately in our Xlib example, Xlib already	1606	interface such as poll (fortunately in the case of Xlib, it already does
1592	does this on its own, so its quite safe to use). Some people additionally	1607	this on its own, so its quite safe to use). Some people additionally
1593	use C<SIGALRM> and an interval timer, just to be sure you won't block	1608	use C<SIGALRM> and an interval timer, just to be sure you won't block
1594	indefinitely.	1609	indefinitely.
1595		1610
1596	But really, best use non-blocking mode.	1611	But really, best use non-blocking mode.
1597		1612
…		…
1625		1640
1626	There is no workaround possible except not registering events	1641	There is no workaround possible except not registering events
1627	for potentially C<dup ()>'ed file descriptors, or to resort to	1642	for potentially C<dup ()>'ed file descriptors, or to resort to
1628	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1643	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1629		1644
		1645	=head3 The special problem of files
		1646
		1647	Many people try to use C<select> (or libev) on file descriptors
		1648	representing files, and expect it to become ready when their program
		1649	doesn't block on disk accesses (which can take a long time on their own).
		1650
		1651	However, this cannot ever work in the "expected" way - you get a readiness
		1652	notification as soon as the kernel knows whether and how much data is
		1653	there, and in the case of open files, that's always the case, so you
		1654	always get a readiness notification instantly, and your read (or possibly
		1655	write) will still block on the disk I/O.
		1656
		1657	Another way to view it is that in the case of sockets, pipes, character
		1658	devices and so on, there is another party (the sender) that delivers data
		1659	on its own, but in the case of files, there is no such thing: the disk
		1660	will not send data on its own, simply because it doesn't know what you
		1661	wish to read - you would first have to request some data.
		1662
		1663	Since files are typically not-so-well supported by advanced notification
		1664	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1665	to files, even though you should not use it. The reason for this is
		1666	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1667	usually a tty, often a pipe, but also sometimes files or special devices
		1668	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1669	F</dev/urandom>), and even though the file might better be served with
		1670	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1671	it "just works" instead of freezing.
		1672
		1673	So avoid file descriptors pointing to files when you know it (e.g. use
		1674	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1675	when you rarely read from a file instead of from a socket, and want to
		1676	reuse the same code path.
		1677
1630	=head3 The special problem of fork	1678	=head3 The special problem of fork
1631		1679
1632	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1680	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1633	useless behaviour. Libev fully supports fork, but needs to be told about	1681	useless behaviour. Libev fully supports fork, but needs to be told about
1634	it in the child.	1682	it in the child if you want to continue to use it in the child.
1635		1683
1636	To support fork in your programs, you either have to call	1684	To support fork in your child processes, you have to call C<ev_loop_fork
1637	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1685	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1638	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1686	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1639	C<EVBACKEND_POLL>.
1640		1687
1641	=head3 The special problem of SIGPIPE	1688	=head3 The special problem of SIGPIPE
1642		1689
1643	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1690	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1644	when writing to a pipe whose other end has been closed, your program gets	1691	when writing to a pipe whose other end has been closed, your program gets
…		…
1742	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1789	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1743	monotonic clock option helps a lot here).	1790	monotonic clock option helps a lot here).
1744		1791
1745	The callback is guaranteed to be invoked only I<after> its timeout has	1792	The callback is guaranteed to be invoked only I<after> its timeout has
1746	passed (not I<at>, so on systems with very low-resolution clocks this	1793	passed (not I<at>, so on systems with very low-resolution clocks this
1747	might introduce a small delay). If multiple timers become ready during the	1794	might introduce a small delay, see "the special problem of being too
		1795	early", below). If multiple timers become ready during the same loop
1748	same loop iteration then the ones with earlier time-out values are invoked	1796	iteration then the ones with earlier time-out values are invoked before
1749	before ones of the same priority with later time-out values (but this is	1797	ones of the same priority with later time-out values (but this is no
1750	no longer true when a callback calls C<ev_run> recursively).	1798	longer true when a callback calls C<ev_run> recursively).
1751		1799
1752	=head3 Be smart about timeouts	1800	=head3 Be smart about timeouts
1753		1801
1754	Many real-world problems involve some kind of timeout, usually for error	1802	Many real-world problems involve some kind of timeout, usually for error
1755	recovery. A typical example is an HTTP request - if the other side hangs,	1803	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1830		1878
1831	In this case, it would be more efficient to leave the C<ev_timer> alone,	1879	In this case, it would be more efficient to leave the C<ev_timer> alone,
1832	but remember the time of last activity, and check for a real timeout only	1880	but remember the time of last activity, and check for a real timeout only
1833	within the callback:	1881	within the callback:
1834		1882
		1883	ev_tstamp timeout = 60.;
1835	ev_tstamp last_activity; // time of last activity	1884	ev_tstamp last_activity; // time of last activity
		1885	ev_timer timer;
1836		1886
1837	static void	1887	static void
1838	callback (EV_P_ ev_timer *w, int revents)	1888	callback (EV_P_ ev_timer *w, int revents)
1839	{	1889	{
1840	ev_tstamp now = ev_now (EV_A);	1890	// calculate when the timeout would happen
1841	ev_tstamp timeout = last_activity + 60.;	1891	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1842		1892
1843	// if last_activity + 60. is older than now, we did time out	1893	// if negative, it means we the timeout already occurred
1844	if (timeout < now)	1894	if (after < 0.)
1845	{	1895	{
1846	// timeout occurred, take action	1896	// timeout occurred, take action
1847	}	1897	}
1848	else	1898	else
1849	{	1899	{
1850	// callback was invoked, but there was some activity, re-arm	1900	// callback was invoked, but there was some recent
1851	// the watcher to fire in last_activity + 60, which is	1901	// activity. simply restart the timer to time out
1852	// guaranteed to be in the future, so "again" is positive:	1902	// after "after" seconds, which is the earliest time
1853	w->repeat = timeout - now;	1903	// the timeout can occur.
		1904	ev_timer_set (w, after, 0.);
1854	ev_timer_again (EV_A_ w);	1905	ev_timer_start (EV_A_ w);
1855	}	1906	}
1856	}	1907	}
1857		1908
1858	To summarise the callback: first calculate the real timeout (defined	1909	To summarise the callback: first calculate in how many seconds the
1859	as "60 seconds after the last activity"), then check if that time has	1910	timeout will occur (by calculating the absolute time when it would occur,
1860	been reached, which means something I<did>, in fact, time out. Otherwise	1911	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1861	the callback was invoked too early (C<timeout> is in the future), so	1912	(EV_A)> from that).
1862	re-schedule the timer to fire at that future time, to see if maybe we have
1863	a timeout then.
1864		1913
1865	Note how C<ev_timer_again> is used, taking advantage of the	1914	If this value is negative, then we are already past the timeout, i.e. we
1866	C<ev_timer_again> optimisation when the timer is already running.	1915	timed out, and need to do whatever is needed in this case.
		1916
		1917	Otherwise, we now the earliest time at which the timeout would trigger,
		1918	and simply start the timer with this timeout value.
		1919
		1920	In other words, each time the callback is invoked it will check whether
		1921	the timeout occurred. If not, it will simply reschedule itself to check
		1922	again at the earliest time it could time out. Rinse. Repeat.
1867		1923
1868	This scheme causes more callback invocations (about one every 60 seconds	1924	This scheme causes more callback invocations (about one every 60 seconds
1869	minus half the average time between activity), but virtually no calls to	1925	minus half the average time between activity), but virtually no calls to
1870	libev to change the timeout.	1926	libev to change the timeout.
1871		1927
1872	To start the timer, simply initialise the watcher and set C<last_activity>	1928	To start the machinery, simply initialise the watcher and set
1873	to the current time (meaning we just have some activity :), then call the	1929	C<last_activity> to the current time (meaning there was some activity just
1874	callback, which will "do the right thing" and start the timer:	1930	now), then call the callback, which will "do the right thing" and start
		1931	the timer:
1875		1932
		1933	last_activity = ev_now (EV_A);
1876	ev_init (timer, callback);	1934	ev_init (&timer, callback);
1877	last_activity = ev_now (loop);	1935	callback (EV_A_ &timer, 0);
1878	callback (loop, timer, EV_TIMER);
1879		1936
1880	And when there is some activity, simply store the current time in	1937	When there is some activity, simply store the current time in
1881	C<last_activity>, no libev calls at all:	1938	C<last_activity>, no libev calls at all:
1882		1939
		1940	if (activity detected)
1883	last_activity = ev_now (loop);	1941	last_activity = ev_now (EV_A);
		1942
		1943	When your timeout value changes, then the timeout can be changed by simply
		1944	providing a new value, stopping the timer and calling the callback, which
		1945	will again do the right thing (for example, time out immediately :).
		1946
		1947	timeout = new_value;
		1948	ev_timer_stop (EV_A_ &timer);
		1949	callback (EV_A_ &timer, 0);
1884		1950
1885	This technique is slightly more complex, but in most cases where the	1951	This technique is slightly more complex, but in most cases where the
1886	time-out is unlikely to be triggered, much more efficient.	1952	time-out is unlikely to be triggered, much more efficient.
1887
1888	Changing the timeout is trivial as well (if it isn't hard-coded in the
1889	callback :) - just change the timeout and invoke the callback, which will
1890	fix things for you.
1891		1953
1892	=item 4. Wee, just use a double-linked list for your timeouts.	1954	=item 4. Wee, just use a double-linked list for your timeouts.
1893		1955
1894	If there is not one request, but many thousands (millions...), all	1956	If there is not one request, but many thousands (millions...), all
1895	employing some kind of timeout with the same timeout value, then one can	1957	employing some kind of timeout with the same timeout value, then one can
…		…
1922	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	1984	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1923	rather complicated, but extremely efficient, something that really pays	1985	rather complicated, but extremely efficient, something that really pays
1924	off after the first million or so of active timers, i.e. it's usually	1986	off after the first million or so of active timers, i.e. it's usually
1925	overkill :)	1987	overkill :)
1926		1988
		1989	=head3 The special problem of being too early
		1990
		1991	If you ask a timer to call your callback after three seconds, then
		1992	you expect it to be invoked after three seconds - but of course, this
		1993	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		1994	guaranteed to any precision by libev - imagine somebody suspending the
		1995	process with a STOP signal for a few hours for example.
		1996
		1997	So, libev tries to invoke your callback as soon as possible I<after> the
		1998	delay has occurred, but cannot guarantee this.
		1999
		2000	A less obvious failure mode is calling your callback too early: many event
		2001	loops compare timestamps with a "elapsed delay >= requested delay", but
		2002	this can cause your callback to be invoked much earlier than you would
		2003	expect.
		2004
		2005	To see why, imagine a system with a clock that only offers full second
		2006	resolution (think windows if you can't come up with a broken enough OS
		2007	yourself). If you schedule a one-second timer at the time 500.9, then the
		2008	event loop will schedule your timeout to elapse at a system time of 500
		2009	(500.9 truncated to the resolution) + 1, or 501.
		2010
		2011	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2012	501" and invoke the callback 0.1s after it was started, even though a
		2013	one-second delay was requested - this is being "too early", despite best
		2014	intentions.
		2015
		2016	This is the reason why libev will never invoke the callback if the elapsed
		2017	delay equals the requested delay, but only when the elapsed delay is
		2018	larger than the requested delay. In the example above, libev would only invoke
		2019	the callback at system time 502, or 1.1s after the timer was started.
		2020
		2021	So, while libev cannot guarantee that your callback will be invoked
		2022	exactly when requested, it I<can> and I<does> guarantee that the requested
		2023	delay has actually elapsed, or in other words, it always errs on the "too
		2024	late" side of things.
		2025
1927	=head3 The special problem of time updates	2026	=head3 The special problem of time updates
1928		2027
1929	Establishing the current time is a costly operation (it usually takes at	2028	Establishing the current time is a costly operation (it usually takes
1930	least two system calls): EV therefore updates its idea of the current	2029	at least one system call): EV therefore updates its idea of the current
1931	time only before and after C<ev_run> collects new events, which causes a	2030	time only before and after C<ev_run> collects new events, which causes a
1932	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2031	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1933	lots of events in one iteration.	2032	lots of events in one iteration.
1934		2033
1935	The relative timeouts are calculated relative to the C<ev_now ()>	2034	The relative timeouts are calculated relative to the C<ev_now ()>
1936	time. This is usually the right thing as this timestamp refers to the time	2035	time. This is usually the right thing as this timestamp refers to the time
1937	of the event triggering whatever timeout you are modifying/starting. If	2036	of the event triggering whatever timeout you are modifying/starting. If
1938	you suspect event processing to be delayed and you I<need> to base the	2037	you suspect event processing to be delayed and you I<need> to base the
1939	timeout on the current time, use something like this to adjust for this:	2038	timeout on the current time, use something like the following to adjust
		2039	for it:
1940		2040
1941	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2041	ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.);
1942		2042
1943	If the event loop is suspended for a long time, you can also force an	2043	If the event loop is suspended for a long time, you can also force an
1944	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2044	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1945	()>.	2045	()>, although that will push the event time of all outstanding events
		2046	further into the future.
		2047
		2048	=head3 The special problem of unsynchronised clocks
		2049
		2050	Modern systems have a variety of clocks - libev itself uses the normal
		2051	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2052	jumps).
		2053
		2054	Neither of these clocks is synchronised with each other or any other clock
		2055	on the system, so C<ev_time ()> might return a considerably different time
		2056	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2057	a call to C<gettimeofday> might return a second count that is one higher
		2058	than a directly following call to C<time>.
		2059
		2060	The moral of this is to only compare libev-related timestamps with
		2061	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2062	a second or so.
		2063
		2064	One more problem arises due to this lack of synchronisation: if libev uses
		2065	the system monotonic clock and you compare timestamps from C<ev_time>
		2066	or C<ev_now> from when you started your timer and when your callback is
		2067	invoked, you will find that sometimes the callback is a bit "early".
		2068
		2069	This is because C<ev_timer>s work in real time, not wall clock time, so
		2070	libev makes sure your callback is not invoked before the delay happened,
		2071	I<measured according to the real time>, not the system clock.
		2072
		2073	If your timeouts are based on a physical timescale (e.g. "time out this
		2074	connection after 100 seconds") then this shouldn't bother you as it is
		2075	exactly the right behaviour.
		2076
		2077	If you want to compare wall clock/system timestamps to your timers, then
		2078	you need to use C<ev_periodic>s, as these are based on the wall clock
		2079	time, where your comparisons will always generate correct results.
1946		2080
1947	=head3 The special problems of suspended animation	2081	=head3 The special problems of suspended animation
1948		2082
1949	When you leave the server world it is quite customary to hit machines that	2083	When you leave the server world it is quite customary to hit machines that
1950	can suspend/hibernate - what happens to the clocks during such a suspend?	2084	can suspend/hibernate - what happens to the clocks during such a suspend?
…		…
1980		2114
1981	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2115	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1982		2116
1983	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	2117	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1984		2118
1985	Configure the timer to trigger after C<after> seconds. If C<repeat>	2119	Configure the timer to trigger after C<after> seconds (fractional and
1986	is C<0.>, then it will automatically be stopped once the timeout is	2120	negative values are supported). If C<repeat> is C<0.>, then it will
1987	reached. If it is positive, then the timer will automatically be	2121	automatically be stopped once the timeout is reached. If it is positive,
1988	configured to trigger again C<repeat> seconds later, again, and again,	2122	then the timer will automatically be configured to trigger again C<repeat>
1989	until stopped manually.	2123	seconds later, again, and again, until stopped manually.
1990		2124
1991	The timer itself will do a best-effort at avoiding drift, that is, if	2125	The timer itself will do a best-effort at avoiding drift, that is, if
1992	you configure a timer to trigger every 10 seconds, then it will normally	2126	you configure a timer to trigger every 10 seconds, then it will normally
1993	trigger at exactly 10 second intervals. If, however, your program cannot	2127	trigger at exactly 10 second intervals. If, however, your program cannot
1994	keep up with the timer (because it takes longer than those 10 seconds to	2128	keep up with the timer (because it takes longer than those 10 seconds to
1995	do stuff) the timer will not fire more than once per event loop iteration.	2129	do stuff) the timer will not fire more than once per event loop iteration.
1996		2130
1997	=item ev_timer_again (loop, ev_timer *)	2131	=item ev_timer_again (loop, ev_timer *)
1998		2132
1999	This will act as if the timer timed out and restart it again if it is	2133	This will act as if the timer timed out, and restarts it again if it is
2000	repeating. The exact semantics are:	2134	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2135	timeout to the C<repeat> value and calling C<ev_timer_start>.
2001		2136
		2137	The exact semantics are as in the following rules, all of which will be
		2138	applied to the watcher:
		2139
		2140	=over 4
		2141
2002	If the timer is pending, its pending status is cleared.	2142	=item If the timer is pending, the pending status is always cleared.
2003		2143
2004	If the timer is started but non-repeating, stop it (as if it timed out).	2144	=item If the timer is started but non-repeating, stop it (as if it timed
		2145	out, without invoking it).
2005		2146
2006	If the timer is repeating, either start it if necessary (with the	2147	=item If the timer is repeating, make the C<repeat> value the new timeout
2007	C<repeat> value), or reset the running timer to the C<repeat> value.	2148	and start the timer, if necessary.
2008		2149
		2150	=back
		2151
2009	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2152	This sounds a bit complicated, see L</Be smart about timeouts>, above, for a
2010	usage example.	2153	usage example.
2011		2154
2012	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)	2155	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
2013		2156
2014	Returns the remaining time until a timer fires. If the timer is active,	2157	Returns the remaining time until a timer fires. If the timer is active,
…		…
2067	Periodic watchers are also timers of a kind, but they are very versatile	2210	Periodic watchers are also timers of a kind, but they are very versatile
2068	(and unfortunately a bit complex).	2211	(and unfortunately a bit complex).
2069		2212
2070	Unlike C<ev_timer>, periodic watchers are not based on real time (or	2213	Unlike C<ev_timer>, periodic watchers are not based on real time (or
2071	relative time, the physical time that passes) but on wall clock time	2214	relative time, the physical time that passes) but on wall clock time
2072	(absolute time, the thing you can read on your calender or clock). The	2215	(absolute time, the thing you can read on your calendar or clock). The
2073	difference is that wall clock time can run faster or slower than real	2216	difference is that wall clock time can run faster or slower than real
2074	time, and time jumps are not uncommon (e.g. when you adjust your	2217	time, and time jumps are not uncommon (e.g. when you adjust your
2075	wrist-watch).	2218	wrist-watch).
2076		2219
2077	You can tell a periodic watcher to trigger after some specific point	2220	You can tell a periodic watcher to trigger after some specific point
…		…
2082	C<ev_timer>, which would still trigger roughly 10 seconds after starting	2225	C<ev_timer>, which would still trigger roughly 10 seconds after starting
2083	it, as it uses a relative timeout).	2226	it, as it uses a relative timeout).
2084		2227
2085	C<ev_periodic> watchers can also be used to implement vastly more complex	2228	C<ev_periodic> watchers can also be used to implement vastly more complex
2086	timers, such as triggering an event on each "midnight, local time", or	2229	timers, such as triggering an event on each "midnight, local time", or
2087	other complicated rules. This cannot be done with C<ev_timer> watchers, as	2230	other complicated rules. This cannot easily be done with C<ev_timer>
2088	those cannot react to time jumps.	2231	watchers, as those cannot react to time jumps.
2089		2232
2090	As with timers, the callback is guaranteed to be invoked only when the	2233	As with timers, the callback is guaranteed to be invoked only when the
2091	point in time where it is supposed to trigger has passed. If multiple	2234	point in time where it is supposed to trigger has passed. If multiple
2092	timers become ready during the same loop iteration then the ones with	2235	timers become ready during the same loop iteration then the ones with
2093	earlier time-out values are invoked before ones with later time-out values	2236	earlier time-out values are invoked before ones with later time-out values
…		…
2134		2277
2135	Another way to think about it (for the mathematically inclined) is that	2278	Another way to think about it (for the mathematically inclined) is that
2136	C<ev_periodic> will try to run the callback in this mode at the next possible	2279	C<ev_periodic> will try to run the callback in this mode at the next possible
2137	time where C<time = offset (mod interval)>, regardless of any time jumps.	2280	time where C<time = offset (mod interval)>, regardless of any time jumps.
2138		2281
2139	For numerical stability it is preferable that the C<offset> value is near	2282	The C<interval> I<MUST> be positive, and for numerical stability, the
2140	C<ev_now ()> (the current time), but there is no range requirement for	2283	interval value should be higher than C<1/8192> (which is around 100
2141	this value, and in fact is often specified as zero.	2284	microseconds) and C<offset> should be higher than C<0> and should have
		2285	at most a similar magnitude as the current time (say, within a factor of
		2286	ten). Typical values for offset are, in fact, C<0> or something between
		2287	C<0> and C<interval>, which is also the recommended range.
2142		2288
2143	Note also that there is an upper limit to how often a timer can fire (CPU	2289	Note also that there is an upper limit to how often a timer can fire (CPU
2144	speed for example), so if C<interval> is very small then timing stability	2290	speed for example), so if C<interval> is very small then timing stability
2145	will of course deteriorate. Libev itself tries to be exact to be about one	2291	will of course deteriorate. Libev itself tries to be exact to be about one
2146	millisecond (if the OS supports it and the machine is fast enough).	2292	millisecond (if the OS supports it and the machine is fast enough).
…		…
2176		2322
2177	NOTE: I<< This callback must always return a time that is higher than or	2323	NOTE: I<< This callback must always return a time that is higher than or
2178	equal to the passed C<now> value >>.	2324	equal to the passed C<now> value >>.
2179		2325
2180	This can be used to create very complex timers, such as a timer that	2326	This can be used to create very complex timers, such as a timer that
2181	triggers on "next midnight, local time". To do this, you would calculate the	2327	triggers on "next midnight, local time". To do this, you would calculate
2182	next midnight after C<now> and return the timestamp value for this. How	2328	the next midnight after C<now> and return the timestamp value for
2183	you do this is, again, up to you (but it is not trivial, which is the main	2329	this. Here is a (completely untested, no error checking) example on how to
2184	reason I omitted it as an example).	2330	do this:
		2331
		2332	#include <time.h>
		2333
		2334	static ev_tstamp
		2335	my_rescheduler (ev_periodic *w, ev_tstamp now)
		2336	{
		2337	time_t tnow = (time_t)now;
		2338	struct tm tm;
		2339	localtime_r (&tnow, &tm);
		2340
		2341	tm.tm_sec = tm.tm_min = tm.tm_hour = 0; // midnight current day
		2342	++tm.tm_mday; // midnight next day
		2343
		2344	return mktime (&tm);
		2345	}
		2346
		2347	Note: this code might run into trouble on days that have more then two
		2348	midnights (beginning and end).
2185		2349
2186	=back	2350	=back
2187		2351
2188	=item ev_periodic_again (loop, ev_periodic *)	2352	=item ev_periodic_again (loop, ev_periodic *)
2189		2353
…		…
2254		2418
2255	ev_periodic hourly_tick;	2419	ev_periodic hourly_tick;
2256	ev_periodic_init (&hourly_tick, clock_cb,	2420	ev_periodic_init (&hourly_tick, clock_cb,
2257	fmod (ev_now (loop), 3600.), 3600., 0);	2421	fmod (ev_now (loop), 3600.), 3600., 0);
2258	ev_periodic_start (loop, &hourly_tick);	2422	ev_periodic_start (loop, &hourly_tick);
2259		2423
2260		2424
2261	=head2 C<ev_signal> - signal me when a signal gets signalled!	2425	=head2 C<ev_signal> - signal me when a signal gets signalled!
2262		2426
2263	Signal watchers will trigger an event when the process receives a specific	2427	Signal watchers will trigger an event when the process receives a specific
2264	signal one or more times. Even though signals are very asynchronous, libev	2428	signal one or more times. Even though signals are very asynchronous, libev
…		…
2274	only within the same loop, i.e. you can watch for C<SIGINT> in your	2438	only within the same loop, i.e. you can watch for C<SIGINT> in your
2275	default loop and for C<SIGIO> in another loop, but you cannot watch for	2439	default loop and for C<SIGIO> in another loop, but you cannot watch for
2276	C<SIGINT> in both the default loop and another loop at the same time. At	2440	C<SIGINT> in both the default loop and another loop at the same time. At
2277	the moment, C<SIGCHLD> is permanently tied to the default loop.	2441	the moment, C<SIGCHLD> is permanently tied to the default loop.
2278		2442
2279	When the first watcher gets started will libev actually register something	2443	Only after the first watcher for a signal is started will libev actually
2280	with the kernel (thus it coexists with your own signal handlers as long as	2444	register something with the kernel. It thus coexists with your own signal
2281	you don't register any with libev for the same signal).	2445	handlers as long as you don't register any with libev for the same signal.
2282		2446
2283	If possible and supported, libev will install its handlers with	2447	If possible and supported, libev will install its handlers with
2284	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should	2448	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
2285	not be unduly interrupted. If you have a problem with system calls getting	2449	not be unduly interrupted. If you have a problem with system calls getting
2286	interrupted by signals you can block all signals in an C<ev_check> watcher	2450	interrupted by signals you can block all signals in an C<ev_check> watcher
…		…
2289	=head3 The special problem of inheritance over fork/execve/pthread_create	2453	=head3 The special problem of inheritance over fork/execve/pthread_create
2290		2454
2291	Both the signal mask (C<sigprocmask>) and the signal disposition	2455	Both the signal mask (C<sigprocmask>) and the signal disposition
2292	(C<sigaction>) are unspecified after starting a signal watcher (and after	2456	(C<sigaction>) are unspecified after starting a signal watcher (and after
2293	stopping it again), that is, libev might or might not block the signal,	2457	stopping it again), that is, libev might or might not block the signal,
2294	and might or might not set or restore the installed signal handler.	2458	and might or might not set or restore the installed signal handler (but
		2459	see C<EVFLAG_NOSIGMASK>).
2295		2460
2296	While this does not matter for the signal disposition (libev never	2461	While this does not matter for the signal disposition (libev never
2297	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on	2462	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
2298	C<execve>), this matters for the signal mask: many programs do not expect	2463	C<execve>), this matters for the signal mask: many programs do not expect
2299	certain signals to be blocked.	2464	certain signals to be blocked.
…		…
2312	I<has> to modify the signal mask, at least temporarily.	2477	I<has> to modify the signal mask, at least temporarily.
2313		2478
2314	So I can't stress this enough: I<If you do not reset your signal mask when	2479	So I can't stress this enough: I<If you do not reset your signal mask when
2315	you expect it to be empty, you have a race condition in your code>. This	2480	you expect it to be empty, you have a race condition in your code>. This
2316	is not a libev-specific thing, this is true for most event libraries.	2481	is not a libev-specific thing, this is true for most event libraries.
		2482
		2483	=head3 The special problem of threads signal handling
		2484
		2485	POSIX threads has problematic signal handling semantics, specifically,
		2486	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2487	threads in a process block signals, which is hard to achieve.
		2488
		2489	When you want to use sigwait (or mix libev signal handling with your own
		2490	for the same signals), you can tackle this problem by globally blocking
		2491	all signals before creating any threads (or creating them with a fully set
		2492	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2493	loops. Then designate one thread as "signal receiver thread" which handles
		2494	these signals. You can pass on any signals that libev might be interested
		2495	in by calling C<ev_feed_signal>.
2317		2496
2318	=head3 Watcher-Specific Functions and Data Members	2497	=head3 Watcher-Specific Functions and Data Members
2319		2498
2320	=over 4	2499	=over 4
2321		2500
…		…
2456		2635
2457	=head2 C<ev_stat> - did the file attributes just change?	2636	=head2 C<ev_stat> - did the file attributes just change?
2458		2637
2459	This watches a file system path for attribute changes. That is, it calls	2638	This watches a file system path for attribute changes. That is, it calls
2460	C<stat> on that path in regular intervals (or when the OS says it changed)	2639	C<stat> on that path in regular intervals (or when the OS says it changed)
2461	and sees if it changed compared to the last time, invoking the callback if	2640	and sees if it changed compared to the last time, invoking the callback
2462	it did.	2641	if it did. Starting the watcher C<stat>'s the file, so only changes that
		2642	happen after the watcher has been started will be reported.
2463		2643
2464	The path does not need to exist: changing from "path exists" to "path does	2644	The path does not need to exist: changing from "path exists" to "path does
2465	not exist" is a status change like any other. The condition "path does not	2645	not exist" is a status change like any other. The condition "path does not
2466	exist" (or more correctly "path cannot be stat'ed") is signified by the	2646	exist" (or more correctly "path cannot be stat'ed") is signified by the
2467	C<st_nlink> field being zero (which is otherwise always forced to be at	2647	C<st_nlink> field being zero (which is otherwise always forced to be at
…		…
2697	Apart from keeping your process non-blocking (which is a useful	2877	Apart from keeping your process non-blocking (which is a useful
2698	effect on its own sometimes), idle watchers are a good place to do	2878	effect on its own sometimes), idle watchers are a good place to do
2699	"pseudo-background processing", or delay processing stuff to after the	2879	"pseudo-background processing", or delay processing stuff to after the
2700	event loop has handled all outstanding events.	2880	event loop has handled all outstanding events.
2701		2881
		2882	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2883
		2884	As long as there is at least one active idle watcher, libev will never
		2885	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2886	For this to work, the idle watcher doesn't need to be invoked at all - the
		2887	lowest priority will do.
		2888
		2889	This mode of operation can be useful together with an C<ev_check> watcher,
		2890	to do something on each event loop iteration - for example to balance load
		2891	between different connections.
		2892
		2893	See L</Abusing an ev_check watcher for its side-effect> for a longer
		2894	example.
		2895
2702	=head3 Watcher-Specific Functions and Data Members	2896	=head3 Watcher-Specific Functions and Data Members
2703		2897
2704	=over 4	2898	=over 4
2705		2899
2706	=item ev_idle_init (ev_idle *, callback)	2900	=item ev_idle_init (ev_idle *, callback)
…		…
2717	callback, free it. Also, use no error checking, as usual.	2911	callback, free it. Also, use no error checking, as usual.
2718		2912
2719	static void	2913	static void
2720	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	2914	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2721	{	2915	{
		2916	// stop the watcher
		2917	ev_idle_stop (loop, w);
		2918
		2919	// now we can free it
2722	free (w);	2920	free (w);
		2921
2723	// now do something you wanted to do when the program has	2922	// now do something you wanted to do when the program has
2724	// no longer anything immediate to do.	2923	// no longer anything immediate to do.
2725	}	2924	}
2726		2925
2727	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2926	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
…		…
2729	ev_idle_start (loop, idle_watcher);	2928	ev_idle_start (loop, idle_watcher);
2730		2929
2731		2930
2732	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2931	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2733		2932
2734	Prepare and check watchers are usually (but not always) used in pairs:	2933	Prepare and check watchers are often (but not always) used in pairs:
2735	prepare watchers get invoked before the process blocks and check watchers	2934	prepare watchers get invoked before the process blocks and check watchers
2736	afterwards.	2935	afterwards.
2737		2936
2738	You I<must not> call C<ev_run> or similar functions that enter	2937	You I<must not> call C<ev_run> (or similar functions that enter the
2739	the current event loop from either C<ev_prepare> or C<ev_check>	2938	current event loop) or C<ev_loop_fork> from either C<ev_prepare> or
2740	watchers. Other loops than the current one are fine, however. The	2939	C<ev_check> watchers. Other loops than the current one are fine,
2741	rationale behind this is that you do not need to check for recursion in	2940	however. The rationale behind this is that you do not need to check
2742	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2941	for recursion in those watchers, i.e. the sequence will always be
2743	C<ev_check> so if you have one watcher of each kind they will always be	2942	C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each
2744	called in pairs bracketing the blocking call.	2943	kind they will always be called in pairs bracketing the blocking call.
2745		2944
2746	Their main purpose is to integrate other event mechanisms into libev and	2945	Their main purpose is to integrate other event mechanisms into libev and
2747	their use is somewhat advanced. They could be used, for example, to track	2946	their use is somewhat advanced. They could be used, for example, to track
2748	variable changes, implement your own watchers, integrate net-snmp or a	2947	variable changes, implement your own watchers, integrate net-snmp or a
2749	coroutine library and lots more. They are also occasionally useful if	2948	coroutine library and lots more. They are also occasionally useful if
…		…
2767	with priority higher than or equal to the event loop and one coroutine	2966	with priority higher than or equal to the event loop and one coroutine
2768	of lower priority, but only once, using idle watchers to keep the event	2967	of lower priority, but only once, using idle watchers to keep the event
2769	loop from blocking if lower-priority coroutines are active, thus mapping	2968	loop from blocking if lower-priority coroutines are active, thus mapping
2770	low-priority coroutines to idle/background tasks).	2969	low-priority coroutines to idle/background tasks).
2771		2970
2772	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2971	When used for this purpose, it is recommended to give C<ev_check> watchers
2773	priority, to ensure that they are being run before any other watchers	2972	highest (C<EV_MAXPRI>) priority, to ensure that they are being run before
2774	after the poll (this doesn't matter for C<ev_prepare> watchers).	2973	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		2974	watchers).
2775		2975
2776	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	2976	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
2777	activate ("feed") events into libev. While libev fully supports this, they	2977	activate ("feed") events into libev. While libev fully supports this, they
2778	might get executed before other C<ev_check> watchers did their job. As	2978	might get executed before other C<ev_check> watchers did their job. As
2779	C<ev_check> watchers are often used to embed other (non-libev) event	2979	C<ev_check> watchers are often used to embed other (non-libev) event
2780	loops those other event loops might be in an unusable state until their	2980	loops those other event loops might be in an unusable state until their
2781	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	2981	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2782	others).	2982	others).
		2983
		2984	=head3 Abusing an C<ev_check> watcher for its side-effect
		2985
		2986	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		2987	useful because they are called once per event loop iteration. For
		2988	example, if you want to handle a large number of connections fairly, you
		2989	normally only do a bit of work for each active connection, and if there
		2990	is more work to do, you wait for the next event loop iteration, so other
		2991	connections have a chance of making progress.
		2992
		2993	Using an C<ev_check> watcher is almost enough: it will be called on the
		2994	next event loop iteration. However, that isn't as soon as possible -
		2995	without external events, your C<ev_check> watcher will not be invoked.
		2996
		2997	This is where C<ev_idle> watchers come in handy - all you need is a
		2998	single global idle watcher that is active as long as you have one active
		2999	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		3000	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		3001	invoked. Neither watcher alone can do that.
2783		3002
2784	=head3 Watcher-Specific Functions and Data Members	3003	=head3 Watcher-Specific Functions and Data Members
2785		3004
2786	=over 4	3005	=over 4
2787		3006
…		…
2988		3207
2989	=over 4	3208	=over 4
2990		3209
2991	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	3210	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
2992		3211
2993	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	3212	=item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)
2994		3213
2995	Configures the watcher to embed the given loop, which must be	3214	Configures the watcher to embed the given loop, which must be
2996	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	3215	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2997	invoked automatically, otherwise it is the responsibility of the callback	3216	invoked automatically, otherwise it is the responsibility of the callback
2998	to invoke it (it will continue to be called until the sweep has been done,	3217	to invoke it (it will continue to be called until the sweep has been done,
…		…
3019	used).	3238	used).
3020		3239
3021	struct ev_loop *loop_hi = ev_default_init (0);	3240	struct ev_loop *loop_hi = ev_default_init (0);
3022	struct ev_loop *loop_lo = 0;	3241	struct ev_loop *loop_lo = 0;
3023	ev_embed embed;	3242	ev_embed embed;
3024		3243
3025	// see if there is a chance of getting one that works	3244	// see if there is a chance of getting one that works
3026	// (remember that a flags value of 0 means autodetection)	3245	// (remember that a flags value of 0 means autodetection)
3027	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3246	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
3028	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3247	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
3029	: 0;	3248	: 0;
…		…
3043	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3262	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
3044		3263
3045	struct ev_loop *loop = ev_default_init (0);	3264	struct ev_loop *loop = ev_default_init (0);
3046	struct ev_loop *loop_socket = 0;	3265	struct ev_loop *loop_socket = 0;
3047	ev_embed embed;	3266	ev_embed embed;
3048		3267
3049	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3268	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
3050	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3269	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
3051	{	3270	{
3052	ev_embed_init (&embed, 0, loop_socket);	3271	ev_embed_init (&embed, 0, loop_socket);
3053	ev_embed_start (loop, &embed);	3272	ev_embed_start (loop, &embed);
…		…
3061		3280
3062	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3281	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
3063		3282
3064	Fork watchers are called when a C<fork ()> was detected (usually because	3283	Fork watchers are called when a C<fork ()> was detected (usually because
3065	whoever is a good citizen cared to tell libev about it by calling	3284	whoever is a good citizen cared to tell libev about it by calling
3066	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the	3285	C<ev_loop_fork>). The invocation is done before the event loop blocks next
3067	event loop blocks next and before C<ev_check> watchers are being called,	3286	and before C<ev_check> watchers are being called, and only in the child
3068	and only in the child after the fork. If whoever good citizen calling	3287	after the fork. If whoever good citizen calling C<ev_default_fork> cheats
3069	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3288	and calls it in the wrong process, the fork handlers will be invoked, too,
3070	handlers will be invoked, too, of course.	3289	of course.
3071		3290
3072	=head3 The special problem of life after fork - how is it possible?	3291	=head3 The special problem of life after fork - how is it possible?
3073		3292
3074	Most uses of C<fork()> consist of forking, then some simple calls to set	3293	Most uses of C<fork ()> consist of forking, then some simple calls to set
3075	up/change the process environment, followed by a call to C<exec()>. This	3294	up/change the process environment, followed by a call to C<exec()>. This
3076	sequence should be handled by libev without any problems.	3295	sequence should be handled by libev without any problems.
3077		3296
3078	This changes when the application actually wants to do event handling	3297	This changes when the application actually wants to do event handling
3079	in the child, or both parent in child, in effect "continuing" after the	3298	in the child, or both parent in child, in effect "continuing" after the
…		…
3156	atexit (program_exits);	3375	atexit (program_exits);
3157		3376
3158		3377
3159	=head2 C<ev_async> - how to wake up an event loop	3378	=head2 C<ev_async> - how to wake up an event loop
3160		3379
3161	In general, you cannot use an C<ev_run> from multiple threads or other	3380	In general, you cannot use an C<ev_loop> from multiple threads or other
3162	asynchronous sources such as signal handlers (as opposed to multiple event	3381	asynchronous sources such as signal handlers (as opposed to multiple event
3163	loops - those are of course safe to use in different threads).	3382	loops - those are of course safe to use in different threads).
3164		3383
3165	Sometimes, however, you need to wake up an event loop you do not control,	3384	Sometimes, however, you need to wake up an event loop you do not control,
3166	for example because it belongs to another thread. This is what C<ev_async>	3385	for example because it belongs to another thread. This is what C<ev_async>
…		…
3168	it by calling C<ev_async_send>, which is thread- and signal safe.	3387	it by calling C<ev_async_send>, which is thread- and signal safe.
3169		3388
3170	This functionality is very similar to C<ev_signal> watchers, as signals,	3389	This functionality is very similar to C<ev_signal> watchers, as signals,
3171	too, are asynchronous in nature, and signals, too, will be compressed	3390	too, are asynchronous in nature, and signals, too, will be compressed
3172	(i.e. the number of callback invocations may be less than the number of	3391	(i.e. the number of callback invocations may be less than the number of
3173	C<ev_async_sent> calls).	3392	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
3174		3393	of "global async watchers" by using a watcher on an otherwise unused
3175	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3394	signal, and C<ev_feed_signal> to signal this watcher from another thread,
3176	just the default loop.	3395	even without knowing which loop owns the signal.
3177		3396
3178	=head3 Queueing	3397	=head3 Queueing
3179		3398
3180	C<ev_async> does not support queueing of data in any way. The reason	3399	C<ev_async> does not support queueing of data in any way. The reason
3181	is that the author does not know of a simple (or any) algorithm for a	3400	is that the author does not know of a simple (or any) algorithm for a
…		…
3273	trust me.	3492	trust me.
3274		3493
3275	=item ev_async_send (loop, ev_async *)	3494	=item ev_async_send (loop, ev_async *)
3276		3495
3277	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3496	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3278	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3497	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3498	returns.
		3499
3279	C<ev_feed_event>, this call is safe to do from other threads, signal or	3500	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3280	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3501	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3281	section below on what exactly this means).	3502	embedding section below on what exactly this means).
3282		3503
3283	Note that, as with other watchers in libev, multiple events might get	3504	Note that, as with other watchers in libev, multiple events might get
3284	compressed into a single callback invocation (another way to look at this	3505	compressed into a single callback invocation (another way to look at
3285	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3506	this is that C<ev_async> watchers are level-triggered: they are set on
3286	reset when the event loop detects that).	3507	C<ev_async_send>, reset when the event loop detects that).
3287		3508
3288	This call incurs the overhead of a system call only once per event loop	3509	This call incurs the overhead of at most one extra system call per event
3289	iteration, so while the overhead might be noticeable, it doesn't apply to	3510	loop iteration, if the event loop is blocked, and no syscall at all if
3290	repeated calls to C<ev_async_send> for the same event loop.	3511	the event loop (or your program) is processing events. That means that
		3512	repeated calls are basically free (there is no need to avoid calls for
		3513	performance reasons) and that the overhead becomes smaller (typically
		3514	zero) under load.
3291		3515
3292	=item bool = ev_async_pending (ev_async *)	3516	=item bool = ev_async_pending (ev_async *)
3293		3517
3294	Returns a non-zero value when C<ev_async_send> has been called on the	3518	Returns a non-zero value when C<ev_async_send> has been called on the
3295	watcher but the event has not yet been processed (or even noted) by the	3519	watcher but the event has not yet been processed (or even noted) by the
…		…
3312		3536
3313	There are some other functions of possible interest. Described. Here. Now.	3537	There are some other functions of possible interest. Described. Here. Now.
3314		3538
3315	=over 4	3539	=over 4
3316		3540
3317	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3541	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg)
3318		3542
3319	This function combines a simple timer and an I/O watcher, calls your	3543	This function combines a simple timer and an I/O watcher, calls your
3320	callback on whichever event happens first and automatically stops both	3544	callback on whichever event happens first and automatically stops both
3321	watchers. This is useful if you want to wait for a single event on an fd	3545	watchers. This is useful if you want to wait for a single event on an fd
3322	or timeout without having to allocate/configure/start/stop/free one or	3546	or timeout without having to allocate/configure/start/stop/free one or
…		…
3350	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3574	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3351		3575
3352	=item ev_feed_fd_event (loop, int fd, int revents)	3576	=item ev_feed_fd_event (loop, int fd, int revents)
3353		3577
3354	Feed an event on the given fd, as if a file descriptor backend detected	3578	Feed an event on the given fd, as if a file descriptor backend detected
3355	the given events it.	3579	the given events.
3356		3580
3357	=item ev_feed_signal_event (loop, int signum)	3581	=item ev_feed_signal_event (loop, int signum)
3358		3582
3359	Feed an event as if the given signal occurred (C<loop> must be the default	3583	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3360	loop!).	3584	which is async-safe.
3361		3585
3362	=back	3586	=back
		3587
		3588
		3589	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3590
		3591	This section explains some common idioms that are not immediately
		3592	obvious. Note that examples are sprinkled over the whole manual, and this
		3593	section only contains stuff that wouldn't fit anywhere else.
		3594
		3595	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3596
		3597	Each watcher has, by default, a C<void *data> member that you can read
		3598	or modify at any time: libev will completely ignore it. This can be used
		3599	to associate arbitrary data with your watcher. If you need more data and
		3600	don't want to allocate memory separately and store a pointer to it in that
		3601	data member, you can also "subclass" the watcher type and provide your own
		3602	data:
		3603
		3604	struct my_io
		3605	{
		3606	ev_io io;
		3607	int otherfd;
		3608	void *somedata;
		3609	struct whatever *mostinteresting;
		3610	};
		3611
		3612	...
		3613	struct my_io w;
		3614	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3615
		3616	And since your callback will be called with a pointer to the watcher, you
		3617	can cast it back to your own type:
		3618
		3619	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3620	{
		3621	struct my_io *w = (struct my_io *)w_;
		3622	...
		3623	}
		3624
		3625	More interesting and less C-conformant ways of casting your callback
		3626	function type instead have been omitted.
		3627
		3628	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3629
		3630	Another common scenario is to use some data structure with multiple
		3631	embedded watchers, in effect creating your own watcher that combines
		3632	multiple libev event sources into one "super-watcher":
		3633
		3634	struct my_biggy
		3635	{
		3636	int some_data;
		3637	ev_timer t1;
		3638	ev_timer t2;
		3639	}
		3640
		3641	In this case getting the pointer to C<my_biggy> is a bit more
		3642	complicated: Either you store the address of your C<my_biggy> struct in
		3643	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3644	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3645	real programmers):
		3646
		3647	#include <stddef.h>
		3648
		3649	static void
		3650	t1_cb (EV_P_ ev_timer *w, int revents)
		3651	{
		3652	struct my_biggy big = (struct my_biggy *)
		3653	(((char *)w) - offsetof (struct my_biggy, t1));
		3654	}
		3655
		3656	static void
		3657	t2_cb (EV_P_ ev_timer *w, int revents)
		3658	{
		3659	struct my_biggy big = (struct my_biggy *)
		3660	(((char *)w) - offsetof (struct my_biggy, t2));
		3661	}
		3662
		3663	=head2 AVOIDING FINISHING BEFORE RETURNING
		3664
		3665	Often you have structures like this in event-based programs:
		3666
		3667	callback ()
		3668	{
		3669	free (request);
		3670	}
		3671
		3672	request = start_new_request (..., callback);
		3673
		3674	The intent is to start some "lengthy" operation. The C<request> could be
		3675	used to cancel the operation, or do other things with it.
		3676
		3677	It's not uncommon to have code paths in C<start_new_request> that
		3678	immediately invoke the callback, for example, to report errors. Or you add
		3679	some caching layer that finds that it can skip the lengthy aspects of the
		3680	operation and simply invoke the callback with the result.
		3681
		3682	The problem here is that this will happen I<before> C<start_new_request>
		3683	has returned, so C<request> is not set.
		3684
		3685	Even if you pass the request by some safer means to the callback, you
		3686	might want to do something to the request after starting it, such as
		3687	canceling it, which probably isn't working so well when the callback has
		3688	already been invoked.
		3689
		3690	A common way around all these issues is to make sure that
		3691	C<start_new_request> I<always> returns before the callback is invoked. If
		3692	C<start_new_request> immediately knows the result, it can artificially
		3693	delay invoking the callback by using a C<prepare> or C<idle> watcher for
		3694	example, or more sneakily, by reusing an existing (stopped) watcher and
		3695	pushing it into the pending queue:
		3696
		3697	ev_set_cb (watcher, callback);
		3698	ev_feed_event (EV_A_ watcher, 0);
		3699
		3700	This way, C<start_new_request> can safely return before the callback is
		3701	invoked, while not delaying callback invocation too much.
		3702
		3703	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3704
		3705	Often (especially in GUI toolkits) there are places where you have
		3706	I<modal> interaction, which is most easily implemented by recursively
		3707	invoking C<ev_run>.
		3708
		3709	This brings the problem of exiting - a callback might want to finish the
		3710	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3711	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3712	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3713	other combination: In these cases, a simple C<ev_break> will not work.
		3714
		3715	The solution is to maintain "break this loop" variable for each C<ev_run>
		3716	invocation, and use a loop around C<ev_run> until the condition is
		3717	triggered, using C<EVRUN_ONCE>:
		3718
		3719	// main loop
		3720	int exit_main_loop = 0;
		3721
		3722	while (!exit_main_loop)
		3723	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3724
		3725	// in a modal watcher
		3726	int exit_nested_loop = 0;
		3727
		3728	while (!exit_nested_loop)
		3729	ev_run (EV_A_ EVRUN_ONCE);
		3730
		3731	To exit from any of these loops, just set the corresponding exit variable:
		3732
		3733	// exit modal loop
		3734	exit_nested_loop = 1;
		3735
		3736	// exit main program, after modal loop is finished
		3737	exit_main_loop = 1;
		3738
		3739	// exit both
		3740	exit_main_loop = exit_nested_loop = 1;
		3741
		3742	=head2 THREAD LOCKING EXAMPLE
		3743
		3744	Here is a fictitious example of how to run an event loop in a different
		3745	thread from where callbacks are being invoked and watchers are
		3746	created/added/removed.
		3747
		3748	For a real-world example, see the C<EV::Loop::Async> perl module,
		3749	which uses exactly this technique (which is suited for many high-level
		3750	languages).
		3751
		3752	The example uses a pthread mutex to protect the loop data, a condition
		3753	variable to wait for callback invocations, an async watcher to notify the
		3754	event loop thread and an unspecified mechanism to wake up the main thread.
		3755
		3756	First, you need to associate some data with the event loop:
		3757
		3758	typedef struct {
		3759	mutex_t lock; /* global loop lock */
		3760	ev_async async_w;
		3761	thread_t tid;
		3762	cond_t invoke_cv;
		3763	} userdata;
		3764
		3765	void prepare_loop (EV_P)
		3766	{
		3767	// for simplicity, we use a static userdata struct.
		3768	static userdata u;
		3769
		3770	ev_async_init (&u->async_w, async_cb);
		3771	ev_async_start (EV_A_ &u->async_w);
		3772
		3773	pthread_mutex_init (&u->lock, 0);
		3774	pthread_cond_init (&u->invoke_cv, 0);
		3775
		3776	// now associate this with the loop
		3777	ev_set_userdata (EV_A_ u);
		3778	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3779	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3780
		3781	// then create the thread running ev_run
		3782	pthread_create (&u->tid, 0, l_run, EV_A);
		3783	}
		3784
		3785	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3786	solely to wake up the event loop so it takes notice of any new watchers
		3787	that might have been added:
		3788
		3789	static void
		3790	async_cb (EV_P_ ev_async *w, int revents)
		3791	{
		3792	// just used for the side effects
		3793	}
		3794
		3795	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3796	protecting the loop data, respectively.
		3797
		3798	static void
		3799	l_release (EV_P)
		3800	{
		3801	userdata *u = ev_userdata (EV_A);
		3802	pthread_mutex_unlock (&u->lock);
		3803	}
		3804
		3805	static void
		3806	l_acquire (EV_P)
		3807	{
		3808	userdata *u = ev_userdata (EV_A);
		3809	pthread_mutex_lock (&u->lock);
		3810	}
		3811
		3812	The event loop thread first acquires the mutex, and then jumps straight
		3813	into C<ev_run>:
		3814
		3815	void *
		3816	l_run (void *thr_arg)
		3817	{
		3818	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3819
		3820	l_acquire (EV_A);
		3821	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3822	ev_run (EV_A_ 0);
		3823	l_release (EV_A);
		3824
		3825	return 0;
		3826	}
		3827
		3828	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3829	signal the main thread via some unspecified mechanism (signals? pipe
		3830	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3831	have been called (in a while loop because a) spurious wakeups are possible
		3832	and b) skipping inter-thread-communication when there are no pending
		3833	watchers is very beneficial):
		3834
		3835	static void
		3836	l_invoke (EV_P)
		3837	{
		3838	userdata *u = ev_userdata (EV_A);
		3839
		3840	while (ev_pending_count (EV_A))
		3841	{
		3842	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3843	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3844	}
		3845	}
		3846
		3847	Now, whenever the main thread gets told to invoke pending watchers, it
		3848	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3849	thread to continue:
		3850
		3851	static void
		3852	real_invoke_pending (EV_P)
		3853	{
		3854	userdata *u = ev_userdata (EV_A);
		3855
		3856	pthread_mutex_lock (&u->lock);
		3857	ev_invoke_pending (EV_A);
		3858	pthread_cond_signal (&u->invoke_cv);
		3859	pthread_mutex_unlock (&u->lock);
		3860	}
		3861
		3862	Whenever you want to start/stop a watcher or do other modifications to an
		3863	event loop, you will now have to lock:
		3864
		3865	ev_timer timeout_watcher;
		3866	userdata *u = ev_userdata (EV_A);
		3867
		3868	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3869
		3870	pthread_mutex_lock (&u->lock);
		3871	ev_timer_start (EV_A_ &timeout_watcher);
		3872	ev_async_send (EV_A_ &u->async_w);
		3873	pthread_mutex_unlock (&u->lock);
		3874
		3875	Note that sending the C<ev_async> watcher is required because otherwise
		3876	an event loop currently blocking in the kernel will have no knowledge
		3877	about the newly added timer. By waking up the loop it will pick up any new
		3878	watchers in the next event loop iteration.
		3879
		3880	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3881
		3882	While the overhead of a callback that e.g. schedules a thread is small, it
		3883	is still an overhead. If you embed libev, and your main usage is with some
		3884	kind of threads or coroutines, you might want to customise libev so that
		3885	doesn't need callbacks anymore.
		3886
		3887	Imagine you have coroutines that you can switch to using a function
		3888	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3889	and that due to some magic, the currently active coroutine is stored in a
		3890	global called C<current_coro>. Then you can build your own "wait for libev
		3891	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3892	the differing C<;> conventions):
		3893
		3894	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3895	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3896
		3897	That means instead of having a C callback function, you store the
		3898	coroutine to switch to in each watcher, and instead of having libev call
		3899	your callback, you instead have it switch to that coroutine.
		3900
		3901	A coroutine might now wait for an event with a function called
		3902	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3903	matter when, or whether the watcher is active or not when this function is
		3904	called):
		3905
		3906	void
		3907	wait_for_event (ev_watcher *w)
		3908	{
		3909	ev_set_cb (w, current_coro);
		3910	switch_to (libev_coro);
		3911	}
		3912
		3913	That basically suspends the coroutine inside C<wait_for_event> and
		3914	continues the libev coroutine, which, when appropriate, switches back to
		3915	this or any other coroutine.
		3916
		3917	You can do similar tricks if you have, say, threads with an event queue -
		3918	instead of storing a coroutine, you store the queue object and instead of
		3919	switching to a coroutine, you push the watcher onto the queue and notify
		3920	any waiters.
		3921
		3922	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		3923	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3924
		3925	// my_ev.h
		3926	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3927	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3928	#include "../libev/ev.h"
		3929
		3930	// my_ev.c
		3931	#define EV_H "my_ev.h"
		3932	#include "../libev/ev.c"
		3933
		3934	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3935	F<my_ev.c> into your project. When properly specifying include paths, you
		3936	can even use F<ev.h> as header file name directly.
3363		3937
3364		3938
3365	=head1 LIBEVENT EMULATION	3939	=head1 LIBEVENT EMULATION
3366		3940
3367	Libev offers a compatibility emulation layer for libevent. It cannot	3941	Libev offers a compatibility emulation layer for libevent. It cannot
3368	emulate the internals of libevent, so here are some usage hints:	3942	emulate the internals of libevent, so here are some usage hints:
3369		3943
3370	=over 4	3944	=over 4
		3945
		3946	=item * Only the libevent-1.4.1-beta API is being emulated.
		3947
		3948	This was the newest libevent version available when libev was implemented,
		3949	and is still mostly unchanged in 2010.
3371		3950
3372	=item * Use it by including <event.h>, as usual.	3951	=item * Use it by including <event.h>, as usual.
3373		3952
3374	=item * The following members are fully supported: ev_base, ev_callback,	3953	=item * The following members are fully supported: ev_base, ev_callback,
3375	ev_arg, ev_fd, ev_res, ev_events.	3954	ev_arg, ev_fd, ev_res, ev_events.
…		…
3392		3971
3393	=back	3972	=back
3394		3973
3395	=head1 C++ SUPPORT	3974	=head1 C++ SUPPORT
3396		3975
		3976	=head2 C API
		3977
		3978	The normal C API should work fine when used from C++: both ev.h and the
		3979	libev sources can be compiled as C++. Therefore, code that uses the C API
		3980	will work fine.
		3981
		3982	Proper exception specifications might have to be added to callbacks passed
		3983	to libev: exceptions may be thrown only from watcher callbacks, all
		3984	other callbacks (allocator, syserr, loop acquire/release and periodic
		3985	reschedule callbacks) must not throw exceptions, and might need a C<throw
		3986	()> specification. If you have code that needs to be compiled as both C
		3987	and C++ you can use the C<EV_THROW> macro for this:
		3988
		3989	static void
		3990	fatal_error (const char *msg) EV_THROW
		3991	{
		3992	perror (msg);
		3993	abort ();
		3994	}
		3995
		3996	...
		3997	ev_set_syserr_cb (fatal_error);
		3998
		3999	The only API functions that can currently throw exceptions are C<ev_run>,
		4000	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		4001	because it runs cleanup watchers).
		4002
		4003	Throwing exceptions in watcher callbacks is only supported if libev itself
		4004	is compiled with a C++ compiler or your C and C++ environments allow
		4005	throwing exceptions through C libraries (most do).
		4006
		4007	=head2 C++ API
		4008
3397	Libev comes with some simplistic wrapper classes for C++ that mainly allow	4009	Libev comes with some simplistic wrapper classes for C++ that mainly allow
3398	you to use some convenience methods to start/stop watchers and also change	4010	you to use some convenience methods to start/stop watchers and also change
3399	the callback model to a model using method callbacks on objects.	4011	the callback model to a model using method callbacks on objects.
3400		4012
3401	To use it,	4013	To use it,
3402		4014
3403	#include <ev++.h>	4015	#include <ev++.h>
3404		4016
3405	This automatically includes F<ev.h> and puts all of its definitions (many	4017	This automatically includes F<ev.h> and puts all of its definitions (many
3406	of them macros) into the global namespace. All C++ specific things are	4018	of them macros) into the global namespace. All C++ specific things are
3407	put into the C<ev> namespace. It should support all the same embedding	4019	put into the C<ev> namespace. It should support all the same embedding
…		…
3410	Care has been taken to keep the overhead low. The only data member the C++	4022	Care has been taken to keep the overhead low. The only data member the C++
3411	classes add (compared to plain C-style watchers) is the event loop pointer	4023	classes add (compared to plain C-style watchers) is the event loop pointer
3412	that the watcher is associated with (or no additional members at all if	4024	that the watcher is associated with (or no additional members at all if
3413	you disable C<EV_MULTIPLICITY> when embedding libev).	4025	you disable C<EV_MULTIPLICITY> when embedding libev).
3414		4026
3415	Currently, functions, and static and non-static member functions can be	4027	Currently, functions, static and non-static member functions and classes
3416	used as callbacks. Other types should be easy to add as long as they only	4028	with C<operator ()> can be used as callbacks. Other types should be easy
3417	need one additional pointer for context. If you need support for other	4029	to add as long as they only need one additional pointer for context. If
3418	types of functors please contact the author (preferably after implementing	4030	you need support for other types of functors please contact the author
3419	it).	4031	(preferably after implementing it).
		4032
		4033	For all this to work, your C++ compiler either has to use the same calling
		4034	conventions as your C compiler (for static member functions), or you have
		4035	to embed libev and compile libev itself as C++.
3420		4036
3421	Here is a list of things available in the C<ev> namespace:	4037	Here is a list of things available in the C<ev> namespace:
3422		4038
3423	=over 4	4039	=over 4
3424		4040
…		…
3434	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4050	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3435		4051
3436	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4052	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
3437	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4053	the same name in the C<ev> namespace, with the exception of C<ev_signal>
3438	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4054	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3439	defines by many implementations.	4055	defined by many implementations.
3440		4056
3441	All of those classes have these methods:	4057	All of those classes have these methods:
3442		4058
3443	=over 4	4059	=over 4
3444		4060
…		…
3506	void operator() (ev::io &w, int revents)	4122	void operator() (ev::io &w, int revents)
3507	{	4123	{
3508	...	4124	...
3509	}	4125	}
3510	}	4126	}
3511		4127
3512	myfunctor f;	4128	myfunctor f;
3513		4129
3514	ev::io w;	4130	ev::io w;
3515	w.set (&f);	4131	w.set (&f);
3516		4132
…		…
3534	Associates a different C<struct ev_loop> with this watcher. You can only	4150	Associates a different C<struct ev_loop> with this watcher. You can only
3535	do this when the watcher is inactive (and not pending either).	4151	do this when the watcher is inactive (and not pending either).
3536		4152
3537	=item w->set ([arguments])	4153	=item w->set ([arguments])
3538		4154
3539	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this	4155	Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>),
3540	method or a suitable start method must be called at least once. Unlike the	4156	with the same arguments. Either this method or a suitable start method
3541	C counterpart, an active watcher gets automatically stopped and restarted	4157	must be called at least once. Unlike the C counterpart, an active watcher
3542	when reconfiguring it with this method.	4158	gets automatically stopped and restarted when reconfiguring it with this
		4159	method.
		4160
		4161	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4162	clashing with the C<set (loop)> method.
3543		4163
3544	=item w->start ()	4164	=item w->start ()
3545		4165
3546	Starts the watcher. Note that there is no C<loop> argument, as the	4166	Starts the watcher. Note that there is no C<loop> argument, as the
3547	constructor already stores the event loop.	4167	constructor already stores the event loop.
…		…
3577	watchers in the constructor.	4197	watchers in the constructor.
3578		4198
3579	class myclass	4199	class myclass
3580	{	4200	{
3581	ev::io io ; void io_cb (ev::io &w, int revents);	4201	ev::io io ; void io_cb (ev::io &w, int revents);
3582	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);	4202	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3583	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4203	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3584		4204
3585	myclass (int fd)	4205	myclass (int fd)
3586	{	4206	{
3587	io .set <myclass, &myclass::io_cb > (this);	4207	io .set <myclass, &myclass::io_cb > (this);
…		…
3638	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4258	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3639		4259
3640	=item D	4260	=item D
3641		4261
3642	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4262	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3643	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4263	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3644		4264
3645	=item Ocaml	4265	=item Ocaml
3646		4266
3647	Erkki Seppala has written Ocaml bindings for libev, to be found at	4267	Erkki Seppala has written Ocaml bindings for libev, to be found at
3648	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4268	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
…		…
3651		4271
3652	Brian Maher has written a partial interface to libev for lua (at the	4272	Brian Maher has written a partial interface to libev for lua (at the
3653	time of this writing, only C<ev_io> and C<ev_timer>), to be found at	4273	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
3654	L<http://github.com/brimworks/lua-ev>.	4274	L<http://github.com/brimworks/lua-ev>.
3655		4275
		4276	=item Javascript
		4277
		4278	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4279
		4280	=item Others
		4281
		4282	There are others, and I stopped counting.
		4283
3656	=back	4284	=back
3657		4285
3658		4286
3659	=head1 MACRO MAGIC	4287	=head1 MACRO MAGIC
3660		4288
…		…
3696	suitable for use with C<EV_A>.	4324	suitable for use with C<EV_A>.
3697		4325
3698	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4326	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3699		4327
3700	Similar to the other two macros, this gives you the value of the default	4328	Similar to the other two macros, this gives you the value of the default
3701	loop, if multiple loops are supported ("ev loop default").	4329	loop, if multiple loops are supported ("ev loop default"). The default loop
		4330	will be initialised if it isn't already initialised.
		4331
		4332	For non-multiplicity builds, these macros do nothing, so you always have
		4333	to initialise the loop somewhere.
3702		4334
3703	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4335	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3704		4336
3705	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4337	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3706	default loop has been initialised (C<UC> == unchecked). Their behaviour	4338	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3773	ev_vars.h	4405	ev_vars.h
3774	ev_wrap.h	4406	ev_wrap.h
3775		4407
3776	ev_win32.c required on win32 platforms only	4408	ev_win32.c required on win32 platforms only
3777		4409
3778	ev_select.c only when select backend is enabled (which is enabled by default)	4410	ev_select.c only when select backend is enabled
3779	ev_poll.c only when poll backend is enabled (disabled by default)	4411	ev_poll.c only when poll backend is enabled
3780	ev_epoll.c only when the epoll backend is enabled (disabled by default)	4412	ev_epoll.c only when the epoll backend is enabled
3781	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	4413	ev_kqueue.c only when the kqueue backend is enabled
3782	ev_port.c only when the solaris port backend is enabled (disabled by default)	4414	ev_port.c only when the solaris port backend is enabled
3783		4415
3784	F<ev.c> includes the backend files directly when enabled, so you only need	4416	F<ev.c> includes the backend files directly when enabled, so you only need
3785	to compile this single file.	4417	to compile this single file.
3786		4418
3787	=head3 LIBEVENT COMPATIBILITY API	4419	=head3 LIBEVENT COMPATIBILITY API
…		…
3851	supported). It will also not define any of the structs usually found in	4483	supported). It will also not define any of the structs usually found in
3852	F<event.h> that are not directly supported by the libev core alone.	4484	F<event.h> that are not directly supported by the libev core alone.
3853		4485
3854	In standalone mode, libev will still try to automatically deduce the	4486	In standalone mode, libev will still try to automatically deduce the
3855	configuration, but has to be more conservative.	4487	configuration, but has to be more conservative.
		4488
		4489	=item EV_USE_FLOOR
		4490
		4491	If defined to be C<1>, libev will use the C<floor ()> function for its
		4492	periodic reschedule calculations, otherwise libev will fall back on a
		4493	portable (slower) implementation. If you enable this, you usually have to
		4494	link against libm or something equivalent. Enabling this when the C<floor>
		4495	function is not available will fail, so the safe default is to not enable
		4496	this.
3856		4497
3857	=item EV_USE_MONOTONIC	4498	=item EV_USE_MONOTONIC
3858		4499
3859	If defined to be C<1>, libev will try to detect the availability of the	4500	If defined to be C<1>, libev will try to detect the availability of the
3860	monotonic clock option at both compile time and runtime. Otherwise no	4501	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3945		4586
3946	If programs implement their own fd to handle mapping on win32, then this	4587	If programs implement their own fd to handle mapping on win32, then this
3947	macro can be used to override the C<close> function, useful to unregister	4588	macro can be used to override the C<close> function, useful to unregister
3948	file descriptors again. Note that the replacement function has to close	4589	file descriptors again. Note that the replacement function has to close
3949	the underlying OS handle.	4590	the underlying OS handle.
		4591
		4592	=item EV_USE_WSASOCKET
		4593
		4594	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4595	communication socket, which works better in some environments. Otherwise,
		4596	the normal C<socket> function will be used, which works better in other
		4597	environments.
3950		4598
3951	=item EV_USE_POLL	4599	=item EV_USE_POLL
3952		4600
3953	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4601	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3954	backend. Otherwise it will be enabled on non-win32 platforms. It	4602	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3990	If defined to be C<1>, libev will compile in support for the Linux inotify	4638	If defined to be C<1>, libev will compile in support for the Linux inotify
3991	interface to speed up C<ev_stat> watchers. Its actual availability will	4639	interface to speed up C<ev_stat> watchers. Its actual availability will
3992	be detected at runtime. If undefined, it will be enabled if the headers	4640	be detected at runtime. If undefined, it will be enabled if the headers
3993	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4641	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3994		4642
		4643	=item EV_NO_SMP
		4644
		4645	If defined to be C<1>, libev will assume that memory is always coherent
		4646	between threads, that is, threads can be used, but threads never run on
		4647	different cpus (or different cpu cores). This reduces dependencies
		4648	and makes libev faster.
		4649
		4650	=item EV_NO_THREADS
		4651
		4652	If defined to be C<1>, libev will assume that it will never be called from
		4653	different threads (that includes signal handlers), which is a stronger
		4654	assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes
		4655	libev faster.
		4656
3995	=item EV_ATOMIC_T	4657	=item EV_ATOMIC_T
3996		4658
3997	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4659	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3998	access is atomic with respect to other threads or signal contexts. No such	4660	access is atomic with respect to other threads or signal contexts. No
3999	type is easily found in the C language, so you can provide your own type	4661	such type is easily found in the C language, so you can provide your own
4000	that you know is safe for your purposes. It is used both for signal handler "locking"	4662	type that you know is safe for your purposes. It is used both for signal
4001	as well as for signal and thread safety in C<ev_async> watchers.	4663	handler "locking" as well as for signal and thread safety in C<ev_async>
		4664	watchers.
4002		4665
4003	In the absence of this define, libev will use C<sig_atomic_t volatile>	4666	In the absence of this define, libev will use C<sig_atomic_t volatile>
4004	(from F<signal.h>), which is usually good enough on most platforms.	4667	(from F<signal.h>), which is usually good enough on most platforms.
4005		4668
4006	=item EV_H (h)	4669	=item EV_H (h)
…		…
4033	will have the C<struct ev_loop *> as first argument, and you can create	4696	will have the C<struct ev_loop *> as first argument, and you can create
4034	additional independent event loops. Otherwise there will be no support	4697	additional independent event loops. Otherwise there will be no support
4035	for multiple event loops and there is no first event loop pointer	4698	for multiple event loops and there is no first event loop pointer
4036	argument. Instead, all functions act on the single default loop.	4699	argument. Instead, all functions act on the single default loop.
4037		4700
		4701	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4702	default loop when multiplicity is switched off - you always have to
		4703	initialise the loop manually in this case.
		4704
4038	=item EV_MINPRI	4705	=item EV_MINPRI
4039		4706
4040	=item EV_MAXPRI	4707	=item EV_MAXPRI
4041		4708
4042	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4709	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
4078	#define EV_USE_POLL 1	4745	#define EV_USE_POLL 1
4079	#define EV_CHILD_ENABLE 1	4746	#define EV_CHILD_ENABLE 1
4080	#define EV_ASYNC_ENABLE 1	4747	#define EV_ASYNC_ENABLE 1
4081		4748
4082	The actual value is a bitset, it can be a combination of the following	4749	The actual value is a bitset, it can be a combination of the following
4083	values:	4750	values (by default, all of these are enabled):
4084		4751
4085	=over 4	4752	=over 4
4086		4753
4087	=item C<1> - faster/larger code	4754	=item C<1> - faster/larger code
4088		4755
…		…
4092	code size by roughly 30% on amd64).	4759	code size by roughly 30% on amd64).
4093		4760
4094	When optimising for size, use of compiler flags such as C<-Os> with	4761	When optimising for size, use of compiler flags such as C<-Os> with
4095	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of	4762	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
4096	assertions.	4763	assertions.
		4764
		4765	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4766	(e.g. gcc with C<-Os>).
4097		4767
4098	=item C<2> - faster/larger data structures	4768	=item C<2> - faster/larger data structures
4099		4769
4100	Replaces the small 2-heap for timer management by a faster 4-heap, larger	4770	Replaces the small 2-heap for timer management by a faster 4-heap, larger
4101	hash table sizes and so on. This will usually further increase code size	4771	hash table sizes and so on. This will usually further increase code size
4102	and can additionally have an effect on the size of data structures at	4772	and can additionally have an effect on the size of data structures at
4103	runtime.	4773	runtime.
4104		4774
		4775	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4776	(e.g. gcc with C<-Os>).
		4777
4105	=item C<4> - full API configuration	4778	=item C<4> - full API configuration
4106		4779
4107	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and	4780	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
4108	enables multiplicity (C<EV_MULTIPLICITY>=1).	4781	enables multiplicity (C<EV_MULTIPLICITY>=1).
4109		4782
…		…
4139		4812
4140	With an intelligent-enough linker (gcc+binutils are intelligent enough	4813	With an intelligent-enough linker (gcc+binutils are intelligent enough
4141	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by	4814	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
4142	your program might be left out as well - a binary starting a timer and an	4815	your program might be left out as well - a binary starting a timer and an
4143	I/O watcher then might come out at only 5Kb.	4816	I/O watcher then might come out at only 5Kb.
		4817
		4818	=item EV_API_STATIC
		4819
		4820	If this symbol is defined (by default it is not), then all identifiers
		4821	will have static linkage. This means that libev will not export any
		4822	identifiers, and you cannot link against libev anymore. This can be useful
		4823	when you embed libev, only want to use libev functions in a single file,
		4824	and do not want its identifiers to be visible.
		4825
		4826	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4827	wants to use libev.
		4828
		4829	This option only works when libev is compiled with a C compiler, as C++
		4830	doesn't support the required declaration syntax.
4144		4831
4145	=item EV_AVOID_STDIO	4832	=item EV_AVOID_STDIO
4146		4833
4147	If this is set to C<1> at compiletime, then libev will avoid using stdio	4834	If this is set to C<1> at compiletime, then libev will avoid using stdio
4148	functions (printf, scanf, perror etc.). This will increase the code size	4835	functions (printf, scanf, perror etc.). This will increase the code size
…		…
4292	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4979	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4293		4980
4294	#include "ev_cpp.h"	4981	#include "ev_cpp.h"
4295	#include "ev.c"	4982	#include "ev.c"
4296		4983
4297	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4984	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4298		4985
4299	=head2 THREADS AND COROUTINES	4986	=head2 THREADS AND COROUTINES
4300		4987
4301	=head3 THREADS	4988	=head3 THREADS
4302		4989
…		…
4353	default loop and triggering an C<ev_async> watcher from the default loop	5040	default loop and triggering an C<ev_async> watcher from the default loop
4354	watcher callback into the event loop interested in the signal.	5041	watcher callback into the event loop interested in the signal.
4355		5042
4356	=back	5043	=back
4357		5044
4358	=head4 THREAD LOCKING EXAMPLE	5045	See also L</THREAD LOCKING EXAMPLE>.
4359
4360	Here is a fictitious example of how to run an event loop in a different
4361	thread than where callbacks are being invoked and watchers are
4362	created/added/removed.
4363
4364	For a real-world example, see the C<EV::Loop::Async> perl module,
4365	which uses exactly this technique (which is suited for many high-level
4366	languages).
4367
4368	The example uses a pthread mutex to protect the loop data, a condition
4369	variable to wait for callback invocations, an async watcher to notify the
4370	event loop thread and an unspecified mechanism to wake up the main thread.
4371
4372	First, you need to associate some data with the event loop:
4373
4374	typedef struct {
4375	mutex_t lock; /* global loop lock */
4376	ev_async async_w;
4377	thread_t tid;
4378	cond_t invoke_cv;
4379	} userdata;
4380
4381	void prepare_loop (EV_P)
4382	{
4383	// for simplicity, we use a static userdata struct.
4384	static userdata u;
4385
4386	ev_async_init (&u->async_w, async_cb);
4387	ev_async_start (EV_A_ &u->async_w);
4388
4389	pthread_mutex_init (&u->lock, 0);
4390	pthread_cond_init (&u->invoke_cv, 0);
4391
4392	// now associate this with the loop
4393	ev_set_userdata (EV_A_ u);
4394	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4395	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4396
4397	// then create the thread running ev_loop
4398	pthread_create (&u->tid, 0, l_run, EV_A);
4399	}
4400
4401	The callback for the C<ev_async> watcher does nothing: the watcher is used
4402	solely to wake up the event loop so it takes notice of any new watchers
4403	that might have been added:
4404
4405	static void
4406	async_cb (EV_P_ ev_async *w, int revents)
4407	{
4408	// just used for the side effects
4409	}
4410
4411	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4412	protecting the loop data, respectively.
4413
4414	static void
4415	l_release (EV_P)
4416	{
4417	userdata *u = ev_userdata (EV_A);
4418	pthread_mutex_unlock (&u->lock);
4419	}
4420
4421	static void
4422	l_acquire (EV_P)
4423	{
4424	userdata *u = ev_userdata (EV_A);
4425	pthread_mutex_lock (&u->lock);
4426	}
4427
4428	The event loop thread first acquires the mutex, and then jumps straight
4429	into C<ev_run>:
4430
4431	void *
4432	l_run (void *thr_arg)
4433	{
4434	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4435
4436	l_acquire (EV_A);
4437	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4438	ev_run (EV_A_ 0);
4439	l_release (EV_A);
4440
4441	return 0;
4442	}
4443
4444	Instead of invoking all pending watchers, the C<l_invoke> callback will
4445	signal the main thread via some unspecified mechanism (signals? pipe
4446	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4447	have been called (in a while loop because a) spurious wakeups are possible
4448	and b) skipping inter-thread-communication when there are no pending
4449	watchers is very beneficial):
4450
4451	static void
4452	l_invoke (EV_P)
4453	{
4454	userdata *u = ev_userdata (EV_A);
4455
4456	while (ev_pending_count (EV_A))
4457	{
4458	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4459	pthread_cond_wait (&u->invoke_cv, &u->lock);
4460	}
4461	}
4462
4463	Now, whenever the main thread gets told to invoke pending watchers, it
4464	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4465	thread to continue:
4466
4467	static void
4468	real_invoke_pending (EV_P)
4469	{
4470	userdata *u = ev_userdata (EV_A);
4471
4472	pthread_mutex_lock (&u->lock);
4473	ev_invoke_pending (EV_A);
4474	pthread_cond_signal (&u->invoke_cv);
4475	pthread_mutex_unlock (&u->lock);
4476	}
4477
4478	Whenever you want to start/stop a watcher or do other modifications to an
4479	event loop, you will now have to lock:
4480
4481	ev_timer timeout_watcher;
4482	userdata *u = ev_userdata (EV_A);
4483
4484	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4485
4486	pthread_mutex_lock (&u->lock);
4487	ev_timer_start (EV_A_ &timeout_watcher);
4488	ev_async_send (EV_A_ &u->async_w);
4489	pthread_mutex_unlock (&u->lock);
4490
4491	Note that sending the C<ev_async> watcher is required because otherwise
4492	an event loop currently blocking in the kernel will have no knowledge
4493	about the newly added timer. By waking up the loop it will pick up any new
4494	watchers in the next event loop iteration.
4495		5046
4496	=head3 COROUTINES	5047	=head3 COROUTINES
4497		5048
4498	Libev is very accommodating to coroutines ("cooperative threads"):	5049	Libev is very accommodating to coroutines ("cooperative threads"):
4499	libev fully supports nesting calls to its functions from different	5050	libev fully supports nesting calls to its functions from different
…		…
4664	requires, and its I/O model is fundamentally incompatible with the POSIX	5215	requires, and its I/O model is fundamentally incompatible with the POSIX
4665	model. Libev still offers limited functionality on this platform in	5216	model. Libev still offers limited functionality on this platform in
4666	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5217	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4667	descriptors. This only applies when using Win32 natively, not when using	5218	descriptors. This only applies when using Win32 natively, not when using
4668	e.g. cygwin. Actually, it only applies to the microsofts own compilers,	5219	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
4669	as every compielr comes with a slightly differently broken/incompatible	5220	as every compiler comes with a slightly differently broken/incompatible
4670	environment.	5221	environment.
4671		5222
4672	Lifting these limitations would basically require the full	5223	Lifting these limitations would basically require the full
4673	re-implementation of the I/O system. If you are into this kind of thing,	5224	re-implementation of the I/O system. If you are into this kind of thing,
4674	then note that glib does exactly that for you in a very portable way (note	5225	then note that glib does exactly that for you in a very portable way (note
…		…
4768	structure (guaranteed by POSIX but not by ISO C for example), but it also	5319	structure (guaranteed by POSIX but not by ISO C for example), but it also
4769	assumes that the same (machine) code can be used to call any watcher	5320	assumes that the same (machine) code can be used to call any watcher
4770	callback: The watcher callbacks have different type signatures, but libev	5321	callback: The watcher callbacks have different type signatures, but libev
4771	calls them using an C<ev_watcher *> internally.	5322	calls them using an C<ev_watcher *> internally.
4772		5323
		5324	=item null pointers and integer zero are represented by 0 bytes
		5325
		5326	Libev uses C<memset> to initialise structs and arrays to C<0> bytes, and
		5327	relies on this setting pointers and integers to null.
		5328
4773	=item pointer accesses must be thread-atomic	5329	=item pointer accesses must be thread-atomic
4774		5330
4775	Accessing a pointer value must be atomic, it must both be readable and	5331	Accessing a pointer value must be atomic, it must both be readable and
4776	writable in one piece - this is the case on all current architectures.	5332	writable in one piece - this is the case on all current architectures.
4777		5333
…		…
4790	thread" or will block signals process-wide, both behaviours would	5346	thread" or will block signals process-wide, both behaviours would
4791	be compatible with libev. Interaction between C<sigprocmask> and	5347	be compatible with libev. Interaction between C<sigprocmask> and
4792	C<pthread_sigmask> could complicate things, however.	5348	C<pthread_sigmask> could complicate things, however.
4793		5349
4794	The most portable way to handle signals is to block signals in all threads	5350	The most portable way to handle signals is to block signals in all threads
4795	except the initial one, and run the default loop in the initial thread as	5351	except the initial one, and run the signal handling loop in the initial
4796	well.	5352	thread as well.
4797		5353
4798	=item C<long> must be large enough for common memory allocation sizes	5354	=item C<long> must be large enough for common memory allocation sizes
4799		5355
4800	To improve portability and simplify its API, libev uses C<long> internally	5356	To improve portability and simplify its API, libev uses C<long> internally
4801	instead of C<size_t> when allocating its data structures. On non-POSIX	5357	instead of C<size_t> when allocating its data structures. On non-POSIX
…		…
4807		5363
4808	The type C<double> is used to represent timestamps. It is required to	5364	The type C<double> is used to represent timestamps. It is required to
4809	have at least 51 bits of mantissa (and 9 bits of exponent), which is	5365	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4810	good enough for at least into the year 4000 with millisecond accuracy	5366	good enough for at least into the year 4000 with millisecond accuracy
4811	(the design goal for libev). This requirement is overfulfilled by	5367	(the design goal for libev). This requirement is overfulfilled by
4812	implementations using IEEE 754, which is basically all existing ones. With	5368	implementations using IEEE 754, which is basically all existing ones.
		5369
4813	IEEE 754 doubles, you get microsecond accuracy until at least 2200.	5370	With IEEE 754 doubles, you get microsecond accuracy until at least the
		5371	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5372	is either obsolete or somebody patched it to use C<long double> or
		5373	something like that, just kidding).
4814		5374
4815	=back	5375	=back
4816		5376
4817	If you know of other additional requirements drop me a note.	5377	If you know of other additional requirements drop me a note.
4818		5378
…		…
4880	=item Processing ev_async_send: O(number_of_async_watchers)	5440	=item Processing ev_async_send: O(number_of_async_watchers)
4881		5441
4882	=item Processing signals: O(max_signal_number)	5442	=item Processing signals: O(max_signal_number)
4883		5443
4884	Sending involves a system call I<iff> there were no other C<ev_async_send>	5444	Sending involves a system call I<iff> there were no other C<ev_async_send>
4885	calls in the current loop iteration. Checking for async and signal events	5445	calls in the current loop iteration and the loop is currently
		5446	blocked. Checking for async and signal events involves iterating over all
4886	involves iterating over all running async watchers or all signal numbers.	5447	running async watchers or all signal numbers.
4887		5448
4888	=back	5449	=back
4889		5450
4890		5451
4891	=head1 PORTING FROM LIBEV 3.X TO 4.X	5452	=head1 PORTING FROM LIBEV 3.X TO 4.X
…		…
4900	=over 4	5461	=over 4
4901		5462
4902	=item C<EV_COMPAT3> backwards compatibility mechanism	5463	=item C<EV_COMPAT3> backwards compatibility mechanism
4903		5464
4904	The backward compatibility mechanism can be controlled by	5465	The backward compatibility mechanism can be controlled by
4905	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>	5466	C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING>
4906	section.	5467	section.
4907		5468
4908	=item C<ev_default_destroy> and C<ev_default_fork> have been removed	5469	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
4909		5470
4910	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:	5471	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
…		…
4953	=over 4	5514	=over 4
4954		5515
4955	=item active	5516	=item active
4956		5517
4957	A watcher is active as long as it has been started and not yet stopped.	5518	A watcher is active as long as it has been started and not yet stopped.
4958	See L<WATCHER STATES> for details.	5519	See L</WATCHER STATES> for details.
4959		5520
4960	=item application	5521	=item application
4961		5522
4962	In this document, an application is whatever is using libev.	5523	In this document, an application is whatever is using libev.
4963		5524
…		…
4999	watchers and events.	5560	watchers and events.
5000		5561
5001	=item pending	5562	=item pending
5002		5563
5003	A watcher is pending as soon as the corresponding event has been	5564	A watcher is pending as soon as the corresponding event has been
5004	detected. See L<WATCHER STATES> for details.	5565	detected. See L</WATCHER STATES> for details.
5005		5566
5006	=item real time	5567	=item real time
5007		5568
5008	The physical time that is observed. It is apparently strictly monotonic :)	5569	The physical time that is observed. It is apparently strictly monotonic :)
5009		5570
5010	=item wall-clock time	5571	=item wall-clock time
5011		5572
5012	The time and date as shown on clocks. Unlike real time, it can actually	5573	The time and date as shown on clocks. Unlike real time, it can actually
5013	be wrong and jump forwards and backwards, e.g. when the you adjust your	5574	be wrong and jump forwards and backwards, e.g. when you adjust your
5014	clock.	5575	clock.
5015		5576
5016	=item watcher	5577	=item watcher
5017		5578
5018	A data structure that describes interest in certain events. Watchers need	5579	A data structure that describes interest in certain events. Watchers need
…		…
5021	=back	5582	=back
5022		5583
5023	=head1 AUTHOR	5584	=head1 AUTHOR
5024		5585
5025	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael	5586	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
5026	Magnusson and Emanuele Giaquinta.	5587	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
5027		5588

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