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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
…		…
103	details of the event, and then hand it over to libev by I<starting> the	105	details of the event, and then hand it over to libev by I<starting> the
104	watcher.	106	watcher.
105		107
106	=head2 FEATURES	108	=head2 FEATURES
107		109
108	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	110	Libev supports C<select>, C<poll>, the Linux-specific aio and C<epoll>
109	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	111	interfaces, the BSD-specific C<kqueue> and the Solaris-specific event port
110	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	112	mechanisms for file descriptor events (C<ev_io>), the Linux C<inotify>
111	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner	113	interface (for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
112	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative	114	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
113	timers (C<ev_timer>), absolute timers with customised rescheduling	115	timers (C<ev_timer>), absolute timers with customised rescheduling
114	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status	116	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
115	change events (C<ev_child>), and event watchers dealing with the event	117	change events (C<ev_child>), and event watchers dealing with the event
116	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and	118	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
…		…
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
…		…
257		265
258	You could override this function in high-availability programs to, say,	266	You could override this function in high-availability programs to, say,
259	free some memory if it cannot allocate memory, to use a special allocator,	267	free some memory if it cannot allocate memory, to use a special allocator,
260	or even to sleep a while and retry until some memory is available.	268	or even to sleep a while and retry until some memory is available.
261		269
		270	Example: The following is the C<realloc> function that libev itself uses
		271	which should work with C<realloc> and C<free> functions of all kinds and
		272	is probably a good basis for your own implementation.
		273
		274	static void *
		275	ev_realloc_emul (void *ptr, long size) EV_NOEXCEPT
		276	{
		277	if (size)
		278	return realloc (ptr, size);
		279
		280	free (ptr);
		281	return 0;
		282	}
		283
262	Example: Replace the libev allocator with one that waits a bit and then	284	Example: Replace the libev allocator with one that waits a bit and then
263	retries (example requires a standards-compliant C<realloc>).	285	retries.
264		286
265	static void *	287	static void *
266	persistent_realloc (void *ptr, size_t size)	288	persistent_realloc (void *ptr, size_t size)
267	{	289	{
		290	if (!size)
		291	{
		292	free (ptr);
		293	return 0;
		294	}
		295
268	for (;;)	296	for (;;)
269	{	297	{
270	void *newptr = realloc (ptr, size);	298	void *newptr = realloc (ptr, size);
271		299
272	if (newptr)	300	if (newptr)
…		…
277	}	305	}
278		306
279	...	307	...
280	ev_set_allocator (persistent_realloc);	308	ev_set_allocator (persistent_realloc);
281		309
282	=item ev_set_syserr_cb (void (*cb)(const char *msg))	310	=item ev_set_syserr_cb (void (*cb)(const char *msg) throw ())
283		311
284	Set the callback function to call on a retryable system call error (such	312	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	313	as failed select, poll, epoll_wait). The message is a printable string
286	indicating the system call or subsystem causing the problem. If this	314	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	315	callback is set, then libev will expect it to remedy the situation, no
…		…
390		418
391	If this flag bit is or'ed into the flag value (or the program runs setuid	419	If this flag bit is or'ed into the flag value (or the program runs setuid
392	or setgid) then libev will I<not> look at the environment variable	420	or setgid) then libev will I<not> look at the environment variable
393	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	421	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
394	override the flags completely if it is found in the environment. This is	422	override the flags completely if it is found in the environment. This is
395	useful to try out specific backends to test their performance, or to work	423	useful to try out specific backends to test their performance, to work
396	around bugs.	424	around bugs, or to make libev threadsafe (accessing environment variables
		425	cannot be done in a threadsafe way, but usually it works if no other
		426	thread modifies them).
397		427
398	=item C<EVFLAG_FORKCHECK>	428	=item C<EVFLAG_FORKCHECK>
399		429
400	Instead of calling C<ev_loop_fork> manually after a fork, you can also	430	Instead of calling C<ev_loop_fork> manually after a fork, you can also
401	make libev check for a fork in each iteration by enabling this flag.	431	make libev check for a fork in each iteration by enabling this flag.
402		432
403	This works by calling C<getpid ()> on every iteration of the loop,	433	This works by calling C<getpid ()> on every iteration of the loop,
404	and thus this might slow down your event loop if you do a lot of loop	434	and thus this might slow down your event loop if you do a lot of loop
405	iterations and little real work, but is usually not noticeable (on my	435	iterations and little real work, but is usually not noticeable (on my
406	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	436	GNU/Linux system for example, C<getpid> is actually a simple 5-insn
407	without a system call and thus I<very> fast, but my GNU/Linux system also has	437	sequence without a system call and thus I<very> fast, but my GNU/Linux
408	C<pthread_atfork> which is even faster).	438	system also has C<pthread_atfork> which is even faster). (Update: glibc
		439	versions 2.25 apparently removed the C<getpid> optimisation again).
409		440
410	The big advantage of this flag is that you can forget about fork (and	441	The big advantage of this flag is that you can forget about fork (and
411	forget about forgetting to tell libev about forking) when you use this	442	forget about forgetting to tell libev about forking, although you still
412	flag.	443	have to ignore C<SIGPIPE>) when you use this flag.
413		444
414	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	445	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
415	environment variable.	446	environment variable.
416		447
417	=item C<EVFLAG_NOINOTIFY>	448	=item C<EVFLAG_NOINOTIFY>
…		…
435	example) that can't properly initialise their signal masks.	466	example) that can't properly initialise their signal masks.
436		467
437	=item C<EVFLAG_NOSIGMASK>	468	=item C<EVFLAG_NOSIGMASK>
438		469
439	When this flag is specified, then libev will avoid to modify the signal	470	When this flag is specified, then libev will avoid to modify the signal
440	mask. Specifically, this means you ahve to make sure signals are unblocked	471	mask. Specifically, this means you have to make sure signals are unblocked
441	when you want to receive them.	472	when you want to receive them.
442		473
443	This behaviour is useful when you want to do your own signal handling, or	474	This behaviour is useful when you want to do your own signal handling, or
444	want to handle signals only in specific threads and want to avoid libev	475	want to handle signals only in specific threads and want to avoid libev
445	unblocking the signals.	476	unblocking the signals.
		477
		478	It's also required by POSIX in a threaded program, as libev calls
		479	C<sigprocmask>, whose behaviour is officially unspecified.
446		480
447	This flag's behaviour will become the default in future versions of libev.	481	This flag's behaviour will become the default in future versions of libev.
448		482
449	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	483	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
450		484
…		…
477	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and	511	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
478	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	512	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
479		513
480	=item C<EVBACKEND_EPOLL> (value 4, Linux)	514	=item C<EVBACKEND_EPOLL> (value 4, Linux)
481		515
482	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9	516	Use the Linux-specific epoll(7) interface (for both pre- and post-2.6.9
483	kernels).	517	kernels).
484		518
485	For few fds, this backend is a bit little slower than poll and select,	519	For few fds, this backend is a bit little slower than poll and select, but
486	but it scales phenomenally better. While poll and select usually scale	520	it scales phenomenally better. While poll and select usually scale like
487	like O(total_fds) where n is the total number of fds (or the highest fd),	521	O(total_fds) where total_fds is the total number of fds (or the highest
488	epoll scales either O(1) or O(active_fds).	522	fd), epoll scales either O(1) or O(active_fds).
489		523
490	The epoll mechanism deserves honorable mention as the most misdesigned	524	The epoll mechanism deserves honorable mention as the most misdesigned
491	of the more advanced event mechanisms: mere annoyances include silently	525	of the more advanced event mechanisms: mere annoyances include silently
492	dropping file descriptors, requiring a system call per change per file	526	dropping file descriptors, requiring a system call per change per file
493	descriptor (and unnecessary guessing of parameters), problems with dup,	527	descriptor (and unnecessary guessing of parameters), problems with dup,
…		…
496	0.1ms) and so on. The biggest issue is fork races, however - if a program	530	0.1ms) and so on. The biggest issue is fork races, however - if a program
497	forks then I<both> parent and child process have to recreate the epoll	531	forks then I<both> parent and child process have to recreate the epoll
498	set, which can take considerable time (one syscall per file descriptor)	532	set, which can take considerable time (one syscall per file descriptor)
499	and is of course hard to detect.	533	and is of course hard to detect.
500		534
501	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	535	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
502	of course I<doesn't>, and epoll just loves to report events for totally	536	but of course I<doesn't>, and epoll just loves to report events for
503	I<different> file descriptors (even already closed ones, so one cannot	537	totally I<different> file descriptors (even already closed ones, so
504	even remove them from the set) than registered in the set (especially	538	one cannot even remove them from the set) than registered in the set
505	on SMP systems). Libev tries to counter these spurious notifications by	539	(especially on SMP systems). Libev tries to counter these spurious
506	employing an additional generation counter and comparing that against the	540	notifications by employing an additional generation counter and comparing
507	events to filter out spurious ones, recreating the set when required. Last	541	that against the events to filter out spurious ones, recreating the set
		542	when required. Epoll also erroneously rounds down timeouts, but gives you
		543	no way to know when and by how much, so sometimes you have to busy-wait
		544	because epoll returns immediately despite a nonzero timeout. And last
508	not least, it also refuses to work with some file descriptors which work	545	not least, it also refuses to work with some file descriptors which work
509	perfectly fine with C<select> (files, many character devices...).	546	perfectly fine with C<select> (files, many character devices...).
510		547
511	Epoll is truly the train wreck analog among event poll mechanisms,	548	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
512	a frankenpoll, cobbled together in a hurry, no thought to design or	549	cobbled together in a hurry, no thought to design or interaction with
513	interaction with others.	550	others. Oh, the pain, will it ever stop...
514		551
515	While stopping, setting and starting an I/O watcher in the same iteration	552	While stopping, setting and starting an I/O watcher in the same iteration
516	will result in some caching, there is still a system call per such	553	will result in some caching, there is still a system call per such
517	incident (because the same I<file descriptor> could point to a different	554	incident (because the same I<file descriptor> could point to a different
518	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	555	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
530	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or	567	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
531	faster than epoll for maybe up to a hundred file descriptors, depending on	568	faster than epoll for maybe up to a hundred file descriptors, depending on
532	the usage. So sad.	569	the usage. So sad.
533		570
534	While nominally embeddable in other event loops, this feature is broken in	571	While nominally embeddable in other event loops, this feature is broken in
535	all kernel versions tested so far.	572	a lot of kernel revisions, but probably(!) works in current versions.
536		573
537	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	574	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
538	C<EVBACKEND_POLL>.	575	C<EVBACKEND_POLL>.
539		576
		577	=item C<EVBACKEND_LINUXAIO> (value 64, Linux)
		578
		579	Use the Linux-specific Linux AIO (I<not> C<< aio(7) >> but C<<
		580	io_submit(2) >>) event interface available in post-4.18 kernels (but libev
		581	only tries to use it in 4.19+).
		582
		583	This is another Linux train wreck of an event interface.
		584
		585	If this backend works for you (as of this writing, it was very
		586	experimental), it is the best event interface available on Linux and might
		587	be well worth enabling it - if it isn't available in your kernel this will
		588	be detected and this backend will be skipped.
		589
		590	This backend can batch oneshot requests and supports a user-space ring
		591	buffer to receive events. It also doesn't suffer from most of the design
		592	problems of epoll (such as not being able to remove event sources from
		593	the epoll set), and generally sounds too good to be true. Because, this
		594	being the Linux kernel, of course it suffers from a whole new set of
		595	limitations, forcing you to fall back to epoll, inheriting all its design
		596	issues.
		597
		598	For one, it is not easily embeddable (but probably could be done using
		599	an event fd at some extra overhead). It also is subject to a system wide
		600	limit that can be configured in F</proc/sys/fs/aio-max-nr>. If no AIO
		601	requests are left, this backend will be skipped during initialisation, and
		602	will switch to epoll when the loop is active.
		603
		604	Most problematic in practice, however, is that not all file descriptors
		605	work with it. For example, in Linux 5.1, TCP sockets, pipes, event fds,
		606	files, F</dev/null> and many others are supported, but ttys do not work
		607	properly (a known bug that the kernel developers don't care about, see
		608	L<https://lore.kernel.org/patchwork/patch/1047453/>), so this is not
		609	(yet?) a generic event polling interface.
		610
		611	Overall, it seems the Linux developers just don't want it to have a
		612	generic event handling mechanism other than C<select> or C<poll>.
		613
		614	To work around all these problem, the current version of libev uses its
		615	epoll backend as a fallback for file descriptor types that do not work. Or
		616	falls back completely to epoll if the kernel acts up.
		617
		618	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		619	C<EVBACKEND_POLL>.
		620
540	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	621	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
541		622
542	Kqueue deserves special mention, as at the time of this writing, it	623	Kqueue deserves special mention, as at the time this backend was
543	was broken on all BSDs except NetBSD (usually it doesn't work reliably	624	implemented, it was broken on all BSDs except NetBSD (usually it doesn't
544	with anything but sockets and pipes, except on Darwin, where of course	625	work reliably with anything but sockets and pipes, except on Darwin,
545	it's completely useless). Unlike epoll, however, whose brokenness	626	where of course it's completely useless). Unlike epoll, however, whose
546	is by design, these kqueue bugs can (and eventually will) be fixed	627	brokenness is by design, these kqueue bugs can be (and mostly have been)
547	without API changes to existing programs. For this reason it's not being	628	fixed without API changes to existing programs. For this reason it's not
548	"auto-detected" unless you explicitly specify it in the flags (i.e. using	629	being "auto-detected" on all platforms unless you explicitly specify it
549	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	630	in the flags (i.e. using C<EVBACKEND_KQUEUE>) or libev was compiled on a
550	system like NetBSD.	631	known-to-be-good (-enough) system like NetBSD.
551		632
552	You still can embed kqueue into a normal poll or select backend and use it	633	You still can embed kqueue into a normal poll or select backend and use it
553	only for sockets (after having made sure that sockets work with kqueue on	634	only for sockets (after having made sure that sockets work with kqueue on
554	the target platform). See C<ev_embed> watchers for more info.	635	the target platform). See C<ev_embed> watchers for more info.
555		636
556	It scales in the same way as the epoll backend, but the interface to the	637	It scales in the same way as the epoll backend, but the interface to the
557	kernel is more efficient (which says nothing about its actual speed, of	638	kernel is more efficient (which says nothing about its actual speed, of
558	course). While stopping, setting and starting an I/O watcher does never	639	course). While stopping, setting and starting an I/O watcher does never
559	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	640	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
560	two event changes per incident. Support for C<fork ()> is very bad (but	641	two event changes per incident. Support for C<fork ()> is very bad (you
561	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect	642	might have to leak fds on fork, but it's more sane than epoll) and it
562	cases	643	drops fds silently in similarly hard-to-detect cases.
563		644
564	This backend usually performs well under most conditions.	645	This backend usually performs well under most conditions.
565		646
566	While nominally embeddable in other event loops, this doesn't work	647	While nominally embeddable in other event loops, this doesn't work
567	everywhere, so you might need to test for this. And since it is broken	648	everywhere, so you might need to test for this. And since it is broken
…		…
596	among the OS-specific backends (I vastly prefer correctness over speed	677	among the OS-specific backends (I vastly prefer correctness over speed
597	hacks).	678	hacks).
598		679
599	On the negative side, the interface is I<bizarre> - so bizarre that	680	On the negative side, the interface is I<bizarre> - so bizarre that
600	even sun itself gets it wrong in their code examples: The event polling	681	even sun itself gets it wrong in their code examples: The event polling
601	function sometimes returning events to the caller even though an error	682	function sometimes returns events to the caller even though an error
602	occurred, but with no indication whether it has done so or not (yes, it's	683	occurred, but with no indication whether it has done so or not (yes, it's
603	even documented that way) - deadly for edge-triggered interfaces where	684	even documented that way) - deadly for edge-triggered interfaces where you
604	you absolutely have to know whether an event occurred or not because you	685	absolutely have to know whether an event occurred or not because you have
605	have to re-arm the watcher.	686	to re-arm the watcher.
606		687
607	Fortunately libev seems to be able to work around these idiocies.	688	Fortunately libev seems to be able to work around these idiocies.
608		689
609	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	690	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
610	C<EVBACKEND_POLL>.	691	C<EVBACKEND_POLL>.
…		…
640		721
641	Example: Use whatever libev has to offer, but make sure that kqueue is	722	Example: Use whatever libev has to offer, but make sure that kqueue is
642	used if available.	723	used if available.
643		724
644	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);	725	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		726
		727	Example: Similarly, on linux, you mgiht want to take advantage of the
		728	linux aio backend if possible, but fall back to something else if that
		729	isn't available.
		730
		731	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_LINUXAIO);
645		732
646	=item ev_loop_destroy (loop)	733	=item ev_loop_destroy (loop)
647		734
648	Destroys an event loop object (frees all memory and kernel state	735	Destroys an event loop object (frees all memory and kernel state
649	etc.). None of the active event watchers will be stopped in the normal	736	etc.). None of the active event watchers will be stopped in the normal
…		…
666	If you need dynamically allocated loops it is better to use C<ev_loop_new>	753	If you need dynamically allocated loops it is better to use C<ev_loop_new>
667	and C<ev_loop_destroy>.	754	and C<ev_loop_destroy>.
668		755
669	=item ev_loop_fork (loop)	756	=item ev_loop_fork (loop)
670		757
671	This function sets a flag that causes subsequent C<ev_run> iterations to	758	This function sets a flag that causes subsequent C<ev_run> iterations
672	reinitialise the kernel state for backends that have one. Despite the	759	to reinitialise the kernel state for backends that have one. Despite
673	name, you can call it anytime, but it makes most sense after forking, in	760	the name, you can call it anytime you are allowed to start or stop
674	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the	761	watchers (except inside an C<ev_prepare> callback), but it makes most
		762	sense after forking, in the child process. You I<must> call it (or use
675	child before resuming or calling C<ev_run>.	763	C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>.
676		764
		765	In addition, if you want to reuse a loop (via this function or
		766	C<EVFLAG_FORKCHECK>), you I<also> have to ignore C<SIGPIPE>.
		767
677	Again, you I<have> to call it on I<any> loop that you want to re-use after	768	Again, you I<have> to call it on I<any> loop that you want to re-use after
678	a fork, I<even if you do not plan to use the loop in the parent>. This is	769	a fork, I<even if you do not plan to use the loop in the parent>. This is
679	because some kernel interfaces *cough* I<kqueue> *cough* do funny things	770	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
680	during fork.	771	during fork.
681		772
682	On the other hand, you only need to call this function in the child	773	On the other hand, you only need to call this function in the child
…		…
752		843
753	This function is rarely useful, but when some event callback runs for a	844	This function is rarely useful, but when some event callback runs for a
754	very long time without entering the event loop, updating libev's idea of	845	very long time without entering the event loop, updating libev's idea of
755	the current time is a good idea.	846	the current time is a good idea.
756		847
757	See also L<The special problem of time updates> in the C<ev_timer> section.	848	See also L</The special problem of time updates> in the C<ev_timer> section.
758		849
759	=item ev_suspend (loop)	850	=item ev_suspend (loop)
760		851
761	=item ev_resume (loop)	852	=item ev_resume (loop)
762		853
…		…
780	without a previous call to C<ev_suspend>.	871	without a previous call to C<ev_suspend>.
781		872
782	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	873	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
783	event loop time (see C<ev_now_update>).	874	event loop time (see C<ev_now_update>).
784		875
785	=item ev_run (loop, int flags)	876	=item bool ev_run (loop, int flags)
786		877
787	Finally, this is it, the event handler. This function usually is called	878	Finally, this is it, the event handler. This function usually is called
788	after you have initialised all your watchers and you want to start	879	after you have initialised all your watchers and you want to start
789	handling events. It will ask the operating system for any new events, call	880	handling events. It will ask the operating system for any new events, call
790	the watcher callbacks, an then repeat the whole process indefinitely: This	881	the watcher callbacks, and then repeat the whole process indefinitely: This
791	is why event loops are called I<loops>.	882	is why event loops are called I<loops>.
792		883
793	If the flags argument is specified as C<0>, it will keep handling events	884	If the flags argument is specified as C<0>, it will keep handling events
794	until either no event watchers are active anymore or C<ev_break> was	885	until either no event watchers are active anymore or C<ev_break> was
795	called.	886	called.
		887
		888	The return value is false if there are no more active watchers (which
		889	usually means "all jobs done" or "deadlock"), and true in all other cases
		890	(which usually means " you should call C<ev_run> again").
796		891
797	Please note that an explicit C<ev_break> is usually better than	892	Please note that an explicit C<ev_break> is usually better than
798	relying on all watchers to be stopped when deciding when a program has	893	relying on all watchers to be stopped when deciding when a program has
799	finished (especially in interactive programs), but having a program	894	finished (especially in interactive programs), but having a program
800	that automatically loops as long as it has to and no longer by virtue	895	that automatically loops as long as it has to and no longer by virtue
801	of relying on its watchers stopping correctly, that is truly a thing of	896	of relying on its watchers stopping correctly, that is truly a thing of
802	beauty.	897	beauty.
803		898
804	This function is also I<mostly> exception-safe - you can break out of	899	This function is I<mostly> exception-safe - you can break out of a
805	a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++	900	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
806	exception and so on. This does not decrement the C<ev_depth> value, nor	901	exception and so on. This does not decrement the C<ev_depth> value, nor
807	will it clear any outstanding C<EVBREAK_ONE> breaks.	902	will it clear any outstanding C<EVBREAK_ONE> breaks.
808		903
809	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle	904	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
810	those events and any already outstanding ones, but will not wait and	905	those events and any already outstanding ones, but will not wait and
…		…
822	This is useful if you are waiting for some external event in conjunction	917	This is useful if you are waiting for some external event in conjunction
823	with something not expressible using other libev watchers (i.e. "roll your	918	with something not expressible using other libev watchers (i.e. "roll your
824	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	919	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
825	usually a better approach for this kind of thing.	920	usually a better approach for this kind of thing.
826		921
827	Here are the gory details of what C<ev_run> does:	922	Here are the gory details of what C<ev_run> does (this is for your
		923	understanding, not a guarantee that things will work exactly like this in
		924	future versions):
828		925
829	- Increment loop depth.	926	- Increment loop depth.
830	- Reset the ev_break status.	927	- Reset the ev_break status.
831	- Before the first iteration, call any pending watchers.	928	- Before the first iteration, call any pending watchers.
832	LOOP:	929	LOOP:
…		…
865	anymore.	962	anymore.
866		963
867	... queue jobs here, make sure they register event watchers as long	964	... queue jobs here, make sure they register event watchers as long
868	... as they still have work to do (even an idle watcher will do..)	965	... as they still have work to do (even an idle watcher will do..)
869	ev_run (my_loop, 0);	966	ev_run (my_loop, 0);
870	... jobs done or somebody called unloop. yeah!	967	... jobs done or somebody called break. yeah!
871		968
872	=item ev_break (loop, how)	969	=item ev_break (loop, how)
873		970
874	Can be used to make a call to C<ev_run> return early (but only after it	971	Can be used to make a call to C<ev_run> return early (but only after it
875	has processed all outstanding events). The C<how> argument must be either	972	has processed all outstanding events). The C<how> argument must be either
…		…
938	overhead for the actual polling but can deliver many events at once.	1035	overhead for the actual polling but can deliver many events at once.
939		1036
940	By setting a higher I<io collect interval> you allow libev to spend more	1037	By setting a higher I<io collect interval> you allow libev to spend more
941	time collecting I/O events, so you can handle more events per iteration,	1038	time collecting I/O events, so you can handle more events per iteration,
942	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	1039	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
943	C<ev_timer>) will be not affected. Setting this to a non-null value will	1040	C<ev_timer>) will not be affected. Setting this to a non-null value will
944	introduce an additional C<ev_sleep ()> call into most loop iterations. The	1041	introduce an additional C<ev_sleep ()> call into most loop iterations. The
945	sleep time ensures that libev will not poll for I/O events more often then	1042	sleep time ensures that libev will not poll for I/O events more often then
946	once per this interval, on average.	1043	once per this interval, on average (as long as the host time resolution is
		1044	good enough).
947		1045
948	Likewise, by setting a higher I<timeout collect interval> you allow libev	1046	Likewise, by setting a higher I<timeout collect interval> you allow libev
949	to spend more time collecting timeouts, at the expense of increased	1047	to spend more time collecting timeouts, at the expense of increased
950	latency/jitter/inexactness (the watcher callback will be called	1048	latency/jitter/inexactness (the watcher callback will be called
951	later). C<ev_io> watchers will not be affected. Setting this to a non-null	1049	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
997	invoke the actual watchers inside another context (another thread etc.).	1095	invoke the actual watchers inside another context (another thread etc.).
998		1096
999	If you want to reset the callback, use C<ev_invoke_pending> as new	1097	If you want to reset the callback, use C<ev_invoke_pending> as new
1000	callback.	1098	callback.
1001		1099
1002	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))	1100	=item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())
1003		1101
1004	Sometimes you want to share the same loop between multiple threads. This	1102	Sometimes you want to share the same loop between multiple threads. This
1005	can be done relatively simply by putting mutex_lock/unlock calls around	1103	can be done relatively simply by putting mutex_lock/unlock calls around
1006	each call to a libev function.	1104	each call to a libev function.
1007		1105
1008	However, C<ev_run> can run an indefinite time, so it is not feasible	1106	However, C<ev_run> can run an indefinite time, so it is not feasible
1009	to wait for it to return. One way around this is to wake up the event	1107	to wait for it to return. One way around this is to wake up the event
1010	loop via C<ev_break> and C<av_async_send>, another way is to set these	1108	loop via C<ev_break> and C<ev_async_send>, another way is to set these
1011	I<release> and I<acquire> callbacks on the loop.	1109	I<release> and I<acquire> callbacks on the loop.
1012		1110
1013	When set, then C<release> will be called just before the thread is	1111	When set, then C<release> will be called just before the thread is
1014	suspended waiting for new events, and C<acquire> is called just	1112	suspended waiting for new events, and C<acquire> is called just
1015	afterwards.	1113	afterwards.
…		…
1155		1253
1156	=item C<EV_PREPARE>	1254	=item C<EV_PREPARE>
1157		1255
1158	=item C<EV_CHECK>	1256	=item C<EV_CHECK>
1159		1257
1160	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts	1258	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to
1161	to gather new events, and all C<ev_check> watchers are invoked just after	1259	gather new events, and all C<ev_check> watchers are queued (not invoked)
1162	C<ev_run> has gathered them, but before it invokes any callbacks for any	1260	just after C<ev_run> has gathered them, but before it queues any callbacks
		1261	for any received events. That means C<ev_prepare> watchers are the last
		1262	watchers invoked before the event loop sleeps or polls for new events, and
		1263	C<ev_check> watchers will be invoked before any other watchers of the same
		1264	or lower priority within an event loop iteration.
		1265
1163	received events. Callbacks of both watcher types can start and stop as	1266	Callbacks of both watcher types can start and stop as many watchers as
1164	many watchers as they want, and all of them will be taken into account	1267	they want, and all of them will be taken into account (for example, a
1165	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1268	C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from
1166	C<ev_run> from blocking).	1269	blocking).
1167		1270
1168	=item C<EV_EMBED>	1271	=item C<EV_EMBED>
1169		1272
1170	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1273	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1171		1274
…		…
1294		1397
1295	=item callback ev_cb (ev_TYPE *watcher)	1398	=item callback ev_cb (ev_TYPE *watcher)
1296		1399
1297	Returns the callback currently set on the watcher.	1400	Returns the callback currently set on the watcher.
1298		1401
1299	=item ev_cb_set (ev_TYPE *watcher, callback)	1402	=item ev_set_cb (ev_TYPE *watcher, callback)
1300		1403
1301	Change the callback. You can change the callback at virtually any time	1404	Change the callback. You can change the callback at virtually any time
1302	(modulo threads).	1405	(modulo threads).
1303		1406
1304	=item ev_set_priority (ev_TYPE *watcher, int priority)	1407	=item ev_set_priority (ev_TYPE *watcher, int priority)
…		…
1322	or might not have been clamped to the valid range.	1425	or might not have been clamped to the valid range.
1323		1426
1324	The default priority used by watchers when no priority has been set is	1427	The default priority used by watchers when no priority has been set is
1325	always C<0>, which is supposed to not be too high and not be too low :).	1428	always C<0>, which is supposed to not be too high and not be too low :).
1326		1429
1327	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of	1430	See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1328	priorities.	1431	priorities.
1329		1432
1330	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1433	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1331		1434
1332	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1435	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
…		…
1357	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related	1460	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1358	functions that do not need a watcher.	1461	functions that do not need a watcher.
1359		1462
1360	=back	1463	=back
1361		1464
1362	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1465	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
1363		1466	OWN COMPOSITE WATCHERS> idioms.
1364	Each watcher has, by default, a member C<void *data> that you can change
1365	and read at any time: libev will completely ignore it. This can be used
1366	to associate arbitrary data with your watcher. If you need more data and
1367	don't want to allocate memory and store a pointer to it in that data
1368	member, you can also "subclass" the watcher type and provide your own
1369	data:
1370
1371	struct my_io
1372	{
1373	ev_io io;
1374	int otherfd;
1375	void *somedata;
1376	struct whatever *mostinteresting;
1377	};
1378
1379	...
1380	struct my_io w;
1381	ev_io_init (&w.io, my_cb, fd, EV_READ);
1382
1383	And since your callback will be called with a pointer to the watcher, you
1384	can cast it back to your own type:
1385
1386	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1387	{
1388	struct my_io *w = (struct my_io *)w_;
1389	...
1390	}
1391
1392	More interesting and less C-conformant ways of casting your callback type
1393	instead have been omitted.
1394
1395	Another common scenario is to use some data structure with multiple
1396	embedded watchers:
1397
1398	struct my_biggy
1399	{
1400	int some_data;
1401	ev_timer t1;
1402	ev_timer t2;
1403	}
1404
1405	In this case getting the pointer to C<my_biggy> is a bit more
1406	complicated: Either you store the address of your C<my_biggy> struct
1407	in the C<data> member of the watcher (for woozies), or you need to use
1408	some pointer arithmetic using C<offsetof> inside your watchers (for real
1409	programmers):
1410
1411	#include <stddef.h>
1412
1413	static void
1414	t1_cb (EV_P_ ev_timer *w, int revents)
1415	{
1416	struct my_biggy big = (struct my_biggy *)
1417	(((char *)w) - offsetof (struct my_biggy, t1));
1418	}
1419
1420	static void
1421	t2_cb (EV_P_ ev_timer *w, int revents)
1422	{
1423	struct my_biggy big = (struct my_biggy *)
1424	(((char *)w) - offsetof (struct my_biggy, t2));
1425	}
1426		1467
1427	=head2 WATCHER STATES	1468	=head2 WATCHER STATES
1428		1469
1429	There are various watcher states mentioned throughout this manual -	1470	There are various watcher states mentioned throughout this manual -
1430	active, pending and so on. In this section these states and the rules to	1471	active, pending and so on. In this section these states and the rules to
1431	transition between them will be described in more detail - and while these	1472	transition between them will be described in more detail - and while these
1432	rules might look complicated, they usually do "the right thing".	1473	rules might look complicated, they usually do "the right thing".
1433		1474
1434	=over 4	1475	=over 4
1435		1476
1436	=item initialiased	1477	=item initialised
1437		1478
1438	Before a watcher can be registered with the event looop it has to be	1479	Before a watcher can be registered with the event loop it has to be
1439	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to	1480	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
1440	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.	1481	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1441		1482
1442	In this state it is simply some block of memory that is suitable for use	1483	In this state it is simply some block of memory that is suitable for
1443	in an event loop. It can be moved around, freed, reused etc. at will.	1484	use in an event loop. It can be moved around, freed, reused etc. at
		1485	will - as long as you either keep the memory contents intact, or call
		1486	C<ev_TYPE_init> again.
1444		1487
1445	=item started/running/active	1488	=item started/running/active
1446		1489
1447	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes	1490	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1448	property of the event loop, and is actively waiting for events. While in	1491	property of the event loop, and is actively waiting for events. While in
…		…
1476	latter will clear any pending state the watcher might be in, regardless	1519	latter will clear any pending state the watcher might be in, regardless
1477	of whether it was active or not, so stopping a watcher explicitly before	1520	of whether it was active or not, so stopping a watcher explicitly before
1478	freeing it is often a good idea.	1521	freeing it is often a good idea.
1479		1522
1480	While stopped (and not pending) the watcher is essentially in the	1523	While stopped (and not pending) the watcher is essentially in the
1481	initialised state, that is it can be reused, moved, modified in any way	1524	initialised state, that is, it can be reused, moved, modified in any way
1482	you wish.	1525	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1526	it again).
1483		1527
1484	=back	1528	=back
1485		1529
1486	=head2 WATCHER PRIORITY MODELS	1530	=head2 WATCHER PRIORITY MODELS
1487		1531
…		…
1636		1680
1637	But really, best use non-blocking mode.	1681	But really, best use non-blocking mode.
1638		1682
1639	=head3 The special problem of disappearing file descriptors	1683	=head3 The special problem of disappearing file descriptors
1640		1684
1641	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1685	Some backends (e.g. kqueue, epoll, linuxaio) need to be told about closing
1642	descriptor (either due to calling C<close> explicitly or any other means,	1686	a file descriptor (either due to calling C<close> explicitly or any other
1643	such as C<dup2>). The reason is that you register interest in some file	1687	means, such as C<dup2>). The reason is that you register interest in some
1644	descriptor, but when it goes away, the operating system will silently drop	1688	file descriptor, but when it goes away, the operating system will silently
1645	this interest. If another file descriptor with the same number then is	1689	drop this interest. If another file descriptor with the same number then
1646	registered with libev, there is no efficient way to see that this is, in	1690	is registered with libev, there is no efficient way to see that this is,
1647	fact, a different file descriptor.	1691	in fact, a different file descriptor.
1648		1692
1649	To avoid having to explicitly tell libev about such cases, libev follows	1693	To avoid having to explicitly tell libev about such cases, libev follows
1650	the following policy: Each time C<ev_io_set> is being called, libev	1694	the following policy: Each time C<ev_io_set> is being called, libev
1651	will assume that this is potentially a new file descriptor, otherwise	1695	will assume that this is potentially a new file descriptor, otherwise
1652	it is assumed that the file descriptor stays the same. That means that	1696	it is assumed that the file descriptor stays the same. That means that
…		…
1680	always get a readiness notification instantly, and your read (or possibly	1724	always get a readiness notification instantly, and your read (or possibly
1681	write) will still block on the disk I/O.	1725	write) will still block on the disk I/O.
1682		1726
1683	Another way to view it is that in the case of sockets, pipes, character	1727	Another way to view it is that in the case of sockets, pipes, character
1684	devices and so on, there is another party (the sender) that delivers data	1728	devices and so on, there is another party (the sender) that delivers data
1685	on it's own, but in the case of files, there is no such thing: the disk	1729	on its own, but in the case of files, there is no such thing: the disk
1686	will not send data on it's own, simply because it doesn't know what you	1730	will not send data on its own, simply because it doesn't know what you
1687	wish to read - you would first have to request some data.	1731	wish to read - you would first have to request some data.
1688		1732
1689	Since files are typically not-so-well supported by advanced notification	1733	Since files are typically not-so-well supported by advanced notification
1690	mechanism, libev tries hard to emulate POSIX behaviour with respect	1734	mechanism, libev tries hard to emulate POSIX behaviour with respect
1691	to files, even though you should not use it. The reason for this is	1735	to files, even though you should not use it. The reason for this is
…		…
1701	when you rarely read from a file instead of from a socket, and want to	1745	when you rarely read from a file instead of from a socket, and want to
1702	reuse the same code path.	1746	reuse the same code path.
1703		1747
1704	=head3 The special problem of fork	1748	=head3 The special problem of fork
1705		1749
1706	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1750	Some backends (epoll, kqueue, probably linuxaio) do not support C<fork ()>
1707	useless behaviour. Libev fully supports fork, but needs to be told about	1751	at all or exhibit useless behaviour. Libev fully supports fork, but needs
1708	it in the child if you want to continue to use it in the child.	1752	to be told about it in the child if you want to continue to use it in the
		1753	child.
1709		1754
1710	To support fork in your child processes, you have to call C<ev_loop_fork	1755	To support fork in your child processes, you have to call C<ev_loop_fork
1711	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to	1756	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1712	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1757	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1713		1758
…		…
1815	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1860	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1816	monotonic clock option helps a lot here).	1861	monotonic clock option helps a lot here).
1817		1862
1818	The callback is guaranteed to be invoked only I<after> its timeout has	1863	The callback is guaranteed to be invoked only I<after> its timeout has
1819	passed (not I<at>, so on systems with very low-resolution clocks this	1864	passed (not I<at>, so on systems with very low-resolution clocks this
1820	might introduce a small delay). If multiple timers become ready during the	1865	might introduce a small delay, see "the special problem of being too
		1866	early", below). If multiple timers become ready during the same loop
1821	same loop iteration then the ones with earlier time-out values are invoked	1867	iteration then the ones with earlier time-out values are invoked before
1822	before ones of the same priority with later time-out values (but this is	1868	ones of the same priority with later time-out values (but this is no
1823	no longer true when a callback calls C<ev_run> recursively).	1869	longer true when a callback calls C<ev_run> recursively).
1824		1870
1825	=head3 Be smart about timeouts	1871	=head3 Be smart about timeouts
1826		1872
1827	Many real-world problems involve some kind of timeout, usually for error	1873	Many real-world problems involve some kind of timeout, usually for error
1828	recovery. A typical example is an HTTP request - if the other side hangs,	1874	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1903		1949
1904	In this case, it would be more efficient to leave the C<ev_timer> alone,	1950	In this case, it would be more efficient to leave the C<ev_timer> alone,
1905	but remember the time of last activity, and check for a real timeout only	1951	but remember the time of last activity, and check for a real timeout only
1906	within the callback:	1952	within the callback:
1907		1953
		1954	ev_tstamp timeout = 60.;
1908	ev_tstamp last_activity; // time of last activity	1955	ev_tstamp last_activity; // time of last activity
		1956	ev_timer timer;
1909		1957
1910	static void	1958	static void
1911	callback (EV_P_ ev_timer *w, int revents)	1959	callback (EV_P_ ev_timer *w, int revents)
1912	{	1960	{
1913	ev_tstamp now = ev_now (EV_A);	1961	// calculate when the timeout would happen
1914	ev_tstamp timeout = last_activity + 60.;	1962	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1915		1963
1916	// if last_activity + 60. is older than now, we did time out	1964	// if negative, it means we the timeout already occurred
1917	if (timeout < now)	1965	if (after < 0.)
1918	{	1966	{
1919	// timeout occurred, take action	1967	// timeout occurred, take action
1920	}	1968	}
1921	else	1969	else
1922	{	1970	{
1923	// callback was invoked, but there was some activity, re-arm	1971	// callback was invoked, but there was some recent
1924	// the watcher to fire in last_activity + 60, which is	1972	// activity. simply restart the timer to time out
1925	// guaranteed to be in the future, so "again" is positive:	1973	// after "after" seconds, which is the earliest time
1926	w->repeat = timeout - now;	1974	// the timeout can occur.
		1975	ev_timer_set (w, after, 0.);
1927	ev_timer_again (EV_A_ w);	1976	ev_timer_start (EV_A_ w);
1928	}	1977	}
1929	}	1978	}
1930		1979
1931	To summarise the callback: first calculate the real timeout (defined	1980	To summarise the callback: first calculate in how many seconds the
1932	as "60 seconds after the last activity"), then check if that time has	1981	timeout will occur (by calculating the absolute time when it would occur,
1933	been reached, which means something I<did>, in fact, time out. Otherwise	1982	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1934	the callback was invoked too early (C<timeout> is in the future), so	1983	(EV_A)> from that).
1935	re-schedule the timer to fire at that future time, to see if maybe we have
1936	a timeout then.
1937		1984
1938	Note how C<ev_timer_again> is used, taking advantage of the	1985	If this value is negative, then we are already past the timeout, i.e. we
1939	C<ev_timer_again> optimisation when the timer is already running.	1986	timed out, and need to do whatever is needed in this case.
		1987
		1988	Otherwise, we now the earliest time at which the timeout would trigger,
		1989	and simply start the timer with this timeout value.
		1990
		1991	In other words, each time the callback is invoked it will check whether
		1992	the timeout occurred. If not, it will simply reschedule itself to check
		1993	again at the earliest time it could time out. Rinse. Repeat.
1940		1994
1941	This scheme causes more callback invocations (about one every 60 seconds	1995	This scheme causes more callback invocations (about one every 60 seconds
1942	minus half the average time between activity), but virtually no calls to	1996	minus half the average time between activity), but virtually no calls to
1943	libev to change the timeout.	1997	libev to change the timeout.
1944		1998
1945	To start the timer, simply initialise the watcher and set C<last_activity>	1999	To start the machinery, simply initialise the watcher and set
1946	to the current time (meaning we just have some activity :), then call the	2000	C<last_activity> to the current time (meaning there was some activity just
1947	callback, which will "do the right thing" and start the timer:	2001	now), then call the callback, which will "do the right thing" and start
		2002	the timer:
1948		2003
		2004	last_activity = ev_now (EV_A);
1949	ev_init (timer, callback);	2005	ev_init (&timer, callback);
1950	last_activity = ev_now (loop);	2006	callback (EV_A_ &timer, 0);
1951	callback (loop, timer, EV_TIMER);
1952		2007
1953	And when there is some activity, simply store the current time in	2008	When there is some activity, simply store the current time in
1954	C<last_activity>, no libev calls at all:	2009	C<last_activity>, no libev calls at all:
1955		2010
		2011	if (activity detected)
1956	last_activity = ev_now (loop);	2012	last_activity = ev_now (EV_A);
		2013
		2014	When your timeout value changes, then the timeout can be changed by simply
		2015	providing a new value, stopping the timer and calling the callback, which
		2016	will again do the right thing (for example, time out immediately :).
		2017
		2018	timeout = new_value;
		2019	ev_timer_stop (EV_A_ &timer);
		2020	callback (EV_A_ &timer, 0);
1957		2021
1958	This technique is slightly more complex, but in most cases where the	2022	This technique is slightly more complex, but in most cases where the
1959	time-out is unlikely to be triggered, much more efficient.	2023	time-out is unlikely to be triggered, much more efficient.
1960
1961	Changing the timeout is trivial as well (if it isn't hard-coded in the
1962	callback :) - just change the timeout and invoke the callback, which will
1963	fix things for you.
1964		2024
1965	=item 4. Wee, just use a double-linked list for your timeouts.	2025	=item 4. Wee, just use a double-linked list for your timeouts.
1966		2026
1967	If there is not one request, but many thousands (millions...), all	2027	If there is not one request, but many thousands (millions...), all
1968	employing some kind of timeout with the same timeout value, then one can	2028	employing some kind of timeout with the same timeout value, then one can
…		…
1995	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	2055	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1996	rather complicated, but extremely efficient, something that really pays	2056	rather complicated, but extremely efficient, something that really pays
1997	off after the first million or so of active timers, i.e. it's usually	2057	off after the first million or so of active timers, i.e. it's usually
1998	overkill :)	2058	overkill :)
1999		2059
		2060	=head3 The special problem of being too early
		2061
		2062	If you ask a timer to call your callback after three seconds, then
		2063	you expect it to be invoked after three seconds - but of course, this
		2064	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		2065	guaranteed to any precision by libev - imagine somebody suspending the
		2066	process with a STOP signal for a few hours for example.
		2067
		2068	So, libev tries to invoke your callback as soon as possible I<after> the
		2069	delay has occurred, but cannot guarantee this.
		2070
		2071	A less obvious failure mode is calling your callback too early: many event
		2072	loops compare timestamps with a "elapsed delay >= requested delay", but
		2073	this can cause your callback to be invoked much earlier than you would
		2074	expect.
		2075
		2076	To see why, imagine a system with a clock that only offers full second
		2077	resolution (think windows if you can't come up with a broken enough OS
		2078	yourself). If you schedule a one-second timer at the time 500.9, then the
		2079	event loop will schedule your timeout to elapse at a system time of 500
		2080	(500.9 truncated to the resolution) + 1, or 501.
		2081
		2082	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2083	501" and invoke the callback 0.1s after it was started, even though a
		2084	one-second delay was requested - this is being "too early", despite best
		2085	intentions.
		2086
		2087	This is the reason why libev will never invoke the callback if the elapsed
		2088	delay equals the requested delay, but only when the elapsed delay is
		2089	larger than the requested delay. In the example above, libev would only invoke
		2090	the callback at system time 502, or 1.1s after the timer was started.
		2091
		2092	So, while libev cannot guarantee that your callback will be invoked
		2093	exactly when requested, it I<can> and I<does> guarantee that the requested
		2094	delay has actually elapsed, or in other words, it always errs on the "too
		2095	late" side of things.
		2096
2000	=head3 The special problem of time updates	2097	=head3 The special problem of time updates
2001		2098
2002	Establishing the current time is a costly operation (it usually takes at	2099	Establishing the current time is a costly operation (it usually takes
2003	least two system calls): EV therefore updates its idea of the current	2100	at least one system call): EV therefore updates its idea of the current
2004	time only before and after C<ev_run> collects new events, which causes a	2101	time only before and after C<ev_run> collects new events, which causes a
2005	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2102	growing difference between C<ev_now ()> and C<ev_time ()> when handling
2006	lots of events in one iteration.	2103	lots of events in one iteration.
2007		2104
2008	The relative timeouts are calculated relative to the C<ev_now ()>	2105	The relative timeouts are calculated relative to the C<ev_now ()>
2009	time. This is usually the right thing as this timestamp refers to the time	2106	time. This is usually the right thing as this timestamp refers to the time
2010	of the event triggering whatever timeout you are modifying/starting. If	2107	of the event triggering whatever timeout you are modifying/starting. If
2011	you suspect event processing to be delayed and you I<need> to base the	2108	you suspect event processing to be delayed and you I<need> to base the
2012	timeout on the current time, use something like this to adjust for this:	2109	timeout on the current time, use something like the following to adjust
		2110	for it:
2013		2111
2014	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2112	ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.);
2015		2113
2016	If the event loop is suspended for a long time, you can also force an	2114	If the event loop is suspended for a long time, you can also force an
2017	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2115	update of the time returned by C<ev_now ()> by calling C<ev_now_update
2018	()>.	2116	()>, although that will push the event time of all outstanding events
		2117	further into the future.
		2118
		2119	=head3 The special problem of unsynchronised clocks
		2120
		2121	Modern systems have a variety of clocks - libev itself uses the normal
		2122	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2123	jumps).
		2124
		2125	Neither of these clocks is synchronised with each other or any other clock
		2126	on the system, so C<ev_time ()> might return a considerably different time
		2127	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2128	a call to C<gettimeofday> might return a second count that is one higher
		2129	than a directly following call to C<time>.
		2130
		2131	The moral of this is to only compare libev-related timestamps with
		2132	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2133	a second or so.
		2134
		2135	One more problem arises due to this lack of synchronisation: if libev uses
		2136	the system monotonic clock and you compare timestamps from C<ev_time>
		2137	or C<ev_now> from when you started your timer and when your callback is
		2138	invoked, you will find that sometimes the callback is a bit "early".
		2139
		2140	This is because C<ev_timer>s work in real time, not wall clock time, so
		2141	libev makes sure your callback is not invoked before the delay happened,
		2142	I<measured according to the real time>, not the system clock.
		2143
		2144	If your timeouts are based on a physical timescale (e.g. "time out this
		2145	connection after 100 seconds") then this shouldn't bother you as it is
		2146	exactly the right behaviour.
		2147
		2148	If you want to compare wall clock/system timestamps to your timers, then
		2149	you need to use C<ev_periodic>s, as these are based on the wall clock
		2150	time, where your comparisons will always generate correct results.
2019		2151
2020	=head3 The special problems of suspended animation	2152	=head3 The special problems of suspended animation
2021		2153
2022	When you leave the server world it is quite customary to hit machines that	2154	When you leave the server world it is quite customary to hit machines that
2023	can suspend/hibernate - what happens to the clocks during such a suspend?	2155	can suspend/hibernate - what happens to the clocks during such a suspend?
…		…
2053		2185
2054	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2186	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
2055		2187
2056	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	2188	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
2057		2189
2058	Configure the timer to trigger after C<after> seconds. If C<repeat>	2190	Configure the timer to trigger after C<after> seconds (fractional and
2059	is C<0.>, then it will automatically be stopped once the timeout is	2191	negative values are supported). If C<repeat> is C<0.>, then it will
2060	reached. If it is positive, then the timer will automatically be	2192	automatically be stopped once the timeout is reached. If it is positive,
2061	configured to trigger again C<repeat> seconds later, again, and again,	2193	then the timer will automatically be configured to trigger again C<repeat>
2062	until stopped manually.	2194	seconds later, again, and again, until stopped manually.
2063		2195
2064	The timer itself will do a best-effort at avoiding drift, that is, if	2196	The timer itself will do a best-effort at avoiding drift, that is, if
2065	you configure a timer to trigger every 10 seconds, then it will normally	2197	you configure a timer to trigger every 10 seconds, then it will normally
2066	trigger at exactly 10 second intervals. If, however, your program cannot	2198	trigger at exactly 10 second intervals. If, however, your program cannot
2067	keep up with the timer (because it takes longer than those 10 seconds to	2199	keep up with the timer (because it takes longer than those 10 seconds to
2068	do stuff) the timer will not fire more than once per event loop iteration.	2200	do stuff) the timer will not fire more than once per event loop iteration.
2069		2201
2070	=item ev_timer_again (loop, ev_timer *)	2202	=item ev_timer_again (loop, ev_timer *)
2071		2203
2072	This will act as if the timer timed out and restart it again if it is	2204	This will act as if the timer timed out, and restarts it again if it is
2073	repeating. The exact semantics are:	2205	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2206	timeout to the C<repeat> value and calling C<ev_timer_start>.
2074		2207
		2208	The exact semantics are as in the following rules, all of which will be
		2209	applied to the watcher:
		2210
		2211	=over 4
		2212
2075	If the timer is pending, its pending status is cleared.	2213	=item If the timer is pending, the pending status is always cleared.
2076		2214
2077	If the timer is started but non-repeating, stop it (as if it timed out).	2215	=item If the timer is started but non-repeating, stop it (as if it timed
		2216	out, without invoking it).
2078		2217
2079	If the timer is repeating, either start it if necessary (with the	2218	=item If the timer is repeating, make the C<repeat> value the new timeout
2080	C<repeat> value), or reset the running timer to the C<repeat> value.	2219	and start the timer, if necessary.
2081		2220
		2221	=back
		2222
2082	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2223	This sounds a bit complicated, see L</Be smart about timeouts>, above, for a
2083	usage example.	2224	usage example.
2084		2225
2085	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)	2226	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
2086		2227
2087	Returns the remaining time until a timer fires. If the timer is active,	2228	Returns the remaining time until a timer fires. If the timer is active,
…		…
2140	Periodic watchers are also timers of a kind, but they are very versatile	2281	Periodic watchers are also timers of a kind, but they are very versatile
2141	(and unfortunately a bit complex).	2282	(and unfortunately a bit complex).
2142		2283
2143	Unlike C<ev_timer>, periodic watchers are not based on real time (or	2284	Unlike C<ev_timer>, periodic watchers are not based on real time (or
2144	relative time, the physical time that passes) but on wall clock time	2285	relative time, the physical time that passes) but on wall clock time
2145	(absolute time, the thing you can read on your calender or clock). The	2286	(absolute time, the thing you can read on your calendar or clock). The
2146	difference is that wall clock time can run faster or slower than real	2287	difference is that wall clock time can run faster or slower than real
2147	time, and time jumps are not uncommon (e.g. when you adjust your	2288	time, and time jumps are not uncommon (e.g. when you adjust your
2148	wrist-watch).	2289	wrist-watch).
2149		2290
2150	You can tell a periodic watcher to trigger after some specific point	2291	You can tell a periodic watcher to trigger after some specific point
…		…
2155	C<ev_timer>, which would still trigger roughly 10 seconds after starting	2296	C<ev_timer>, which would still trigger roughly 10 seconds after starting
2156	it, as it uses a relative timeout).	2297	it, as it uses a relative timeout).
2157		2298
2158	C<ev_periodic> watchers can also be used to implement vastly more complex	2299	C<ev_periodic> watchers can also be used to implement vastly more complex
2159	timers, such as triggering an event on each "midnight, local time", or	2300	timers, such as triggering an event on each "midnight, local time", or
2160	other complicated rules. This cannot be done with C<ev_timer> watchers, as	2301	other complicated rules. This cannot easily be done with C<ev_timer>
2161	those cannot react to time jumps.	2302	watchers, as those cannot react to time jumps.
2162		2303
2163	As with timers, the callback is guaranteed to be invoked only when the	2304	As with timers, the callback is guaranteed to be invoked only when the
2164	point in time where it is supposed to trigger has passed. If multiple	2305	point in time where it is supposed to trigger has passed. If multiple
2165	timers become ready during the same loop iteration then the ones with	2306	timers become ready during the same loop iteration then the ones with
2166	earlier time-out values are invoked before ones with later time-out values	2307	earlier time-out values are invoked before ones with later time-out values
…		…
2207		2348
2208	Another way to think about it (for the mathematically inclined) is that	2349	Another way to think about it (for the mathematically inclined) is that
2209	C<ev_periodic> will try to run the callback in this mode at the next possible	2350	C<ev_periodic> will try to run the callback in this mode at the next possible
2210	time where C<time = offset (mod interval)>, regardless of any time jumps.	2351	time where C<time = offset (mod interval)>, regardless of any time jumps.
2211		2352
2212	For numerical stability it is preferable that the C<offset> value is near	2353	The C<interval> I<MUST> be positive, and for numerical stability, the
2213	C<ev_now ()> (the current time), but there is no range requirement for	2354	interval value should be higher than C<1/8192> (which is around 100
2214	this value, and in fact is often specified as zero.	2355	microseconds) and C<offset> should be higher than C<0> and should have
		2356	at most a similar magnitude as the current time (say, within a factor of
		2357	ten). Typical values for offset are, in fact, C<0> or something between
		2358	C<0> and C<interval>, which is also the recommended range.
2215		2359
2216	Note also that there is an upper limit to how often a timer can fire (CPU	2360	Note also that there is an upper limit to how often a timer can fire (CPU
2217	speed for example), so if C<interval> is very small then timing stability	2361	speed for example), so if C<interval> is very small then timing stability
2218	will of course deteriorate. Libev itself tries to be exact to be about one	2362	will of course deteriorate. Libev itself tries to be exact to be about one
2219	millisecond (if the OS supports it and the machine is fast enough).	2363	millisecond (if the OS supports it and the machine is fast enough).
…		…
2249		2393
2250	NOTE: I<< This callback must always return a time that is higher than or	2394	NOTE: I<< This callback must always return a time that is higher than or
2251	equal to the passed C<now> value >>.	2395	equal to the passed C<now> value >>.
2252		2396
2253	This can be used to create very complex timers, such as a timer that	2397	This can be used to create very complex timers, such as a timer that
2254	triggers on "next midnight, local time". To do this, you would calculate the	2398	triggers on "next midnight, local time". To do this, you would calculate
2255	next midnight after C<now> and return the timestamp value for this. How	2399	the next midnight after C<now> and return the timestamp value for
2256	you do this is, again, up to you (but it is not trivial, which is the main	2400	this. Here is a (completely untested, no error checking) example on how to
2257	reason I omitted it as an example).	2401	do this:
		2402
		2403	#include <time.h>
		2404
		2405	static ev_tstamp
		2406	my_rescheduler (ev_periodic *w, ev_tstamp now)
		2407	{
		2408	time_t tnow = (time_t)now;
		2409	struct tm tm;
		2410	localtime_r (&tnow, &tm);
		2411
		2412	tm.tm_sec = tm.tm_min = tm.tm_hour = 0; // midnight current day
		2413	++tm.tm_mday; // midnight next day
		2414
		2415	return mktime (&tm);
		2416	}
		2417
		2418	Note: this code might run into trouble on days that have more then two
		2419	midnights (beginning and end).
2258		2420
2259	=back	2421	=back
2260		2422
2261	=item ev_periodic_again (loop, ev_periodic *)	2423	=item ev_periodic_again (loop, ev_periodic *)
2262		2424
…		…
2327		2489
2328	ev_periodic hourly_tick;	2490	ev_periodic hourly_tick;
2329	ev_periodic_init (&hourly_tick, clock_cb,	2491	ev_periodic_init (&hourly_tick, clock_cb,
2330	fmod (ev_now (loop), 3600.), 3600., 0);	2492	fmod (ev_now (loop), 3600.), 3600., 0);
2331	ev_periodic_start (loop, &hourly_tick);	2493	ev_periodic_start (loop, &hourly_tick);
2332		2494
2333		2495
2334	=head2 C<ev_signal> - signal me when a signal gets signalled!	2496	=head2 C<ev_signal> - signal me when a signal gets signalled!
2335		2497
2336	Signal watchers will trigger an event when the process receives a specific	2498	Signal watchers will trigger an event when the process receives a specific
2337	signal one or more times. Even though signals are very asynchronous, libev	2499	signal one or more times. Even though signals are very asynchronous, libev
…		…
2347	only within the same loop, i.e. you can watch for C<SIGINT> in your	2509	only within the same loop, i.e. you can watch for C<SIGINT> in your
2348	default loop and for C<SIGIO> in another loop, but you cannot watch for	2510	default loop and for C<SIGIO> in another loop, but you cannot watch for
2349	C<SIGINT> in both the default loop and another loop at the same time. At	2511	C<SIGINT> in both the default loop and another loop at the same time. At
2350	the moment, C<SIGCHLD> is permanently tied to the default loop.	2512	the moment, C<SIGCHLD> is permanently tied to the default loop.
2351		2513
2352	When the first watcher gets started will libev actually register something	2514	Only after the first watcher for a signal is started will libev actually
2353	with the kernel (thus it coexists with your own signal handlers as long as	2515	register something with the kernel. It thus coexists with your own signal
2354	you don't register any with libev for the same signal).	2516	handlers as long as you don't register any with libev for the same signal.
2355		2517
2356	If possible and supported, libev will install its handlers with	2518	If possible and supported, libev will install its handlers with
2357	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should	2519	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
2358	not be unduly interrupted. If you have a problem with system calls getting	2520	not be unduly interrupted. If you have a problem with system calls getting
2359	interrupted by signals you can block all signals in an C<ev_check> watcher	2521	interrupted by signals you can block all signals in an C<ev_check> watcher
…		…
2362	=head3 The special problem of inheritance over fork/execve/pthread_create	2524	=head3 The special problem of inheritance over fork/execve/pthread_create
2363		2525
2364	Both the signal mask (C<sigprocmask>) and the signal disposition	2526	Both the signal mask (C<sigprocmask>) and the signal disposition
2365	(C<sigaction>) are unspecified after starting a signal watcher (and after	2527	(C<sigaction>) are unspecified after starting a signal watcher (and after
2366	stopping it again), that is, libev might or might not block the signal,	2528	stopping it again), that is, libev might or might not block the signal,
2367	and might or might not set or restore the installed signal handler.	2529	and might or might not set or restore the installed signal handler (but
		2530	see C<EVFLAG_NOSIGMASK>).
2368		2531
2369	While this does not matter for the signal disposition (libev never	2532	While this does not matter for the signal disposition (libev never
2370	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on	2533	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
2371	C<execve>), this matters for the signal mask: many programs do not expect	2534	C<execve>), this matters for the signal mask: many programs do not expect
2372	certain signals to be blocked.	2535	certain signals to be blocked.
…		…
2543		2706
2544	=head2 C<ev_stat> - did the file attributes just change?	2707	=head2 C<ev_stat> - did the file attributes just change?
2545		2708
2546	This watches a file system path for attribute changes. That is, it calls	2709	This watches a file system path for attribute changes. That is, it calls
2547	C<stat> on that path in regular intervals (or when the OS says it changed)	2710	C<stat> on that path in regular intervals (or when the OS says it changed)
2548	and sees if it changed compared to the last time, invoking the callback if	2711	and sees if it changed compared to the last time, invoking the callback
2549	it did.	2712	if it did. Starting the watcher C<stat>'s the file, so only changes that
		2713	happen after the watcher has been started will be reported.
2550		2714
2551	The path does not need to exist: changing from "path exists" to "path does	2715	The path does not need to exist: changing from "path exists" to "path does
2552	not exist" is a status change like any other. The condition "path does not	2716	not exist" is a status change like any other. The condition "path does not
2553	exist" (or more correctly "path cannot be stat'ed") is signified by the	2717	exist" (or more correctly "path cannot be stat'ed") is signified by the
2554	C<st_nlink> field being zero (which is otherwise always forced to be at	2718	C<st_nlink> field being zero (which is otherwise always forced to be at
…		…
2784	Apart from keeping your process non-blocking (which is a useful	2948	Apart from keeping your process non-blocking (which is a useful
2785	effect on its own sometimes), idle watchers are a good place to do	2949	effect on its own sometimes), idle watchers are a good place to do
2786	"pseudo-background processing", or delay processing stuff to after the	2950	"pseudo-background processing", or delay processing stuff to after the
2787	event loop has handled all outstanding events.	2951	event loop has handled all outstanding events.
2788		2952
		2953	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2954
		2955	As long as there is at least one active idle watcher, libev will never
		2956	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2957	For this to work, the idle watcher doesn't need to be invoked at all - the
		2958	lowest priority will do.
		2959
		2960	This mode of operation can be useful together with an C<ev_check> watcher,
		2961	to do something on each event loop iteration - for example to balance load
		2962	between different connections.
		2963
		2964	See L</Abusing an ev_check watcher for its side-effect> for a longer
		2965	example.
		2966
2789	=head3 Watcher-Specific Functions and Data Members	2967	=head3 Watcher-Specific Functions and Data Members
2790		2968
2791	=over 4	2969	=over 4
2792		2970
2793	=item ev_idle_init (ev_idle *, callback)	2971	=item ev_idle_init (ev_idle *, callback)
…		…
2804	callback, free it. Also, use no error checking, as usual.	2982	callback, free it. Also, use no error checking, as usual.
2805		2983
2806	static void	2984	static void
2807	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	2985	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2808	{	2986	{
		2987	// stop the watcher
		2988	ev_idle_stop (loop, w);
		2989
		2990	// now we can free it
2809	free (w);	2991	free (w);
		2992
2810	// now do something you wanted to do when the program has	2993	// now do something you wanted to do when the program has
2811	// no longer anything immediate to do.	2994	// no longer anything immediate to do.
2812	}	2995	}
2813		2996
2814	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2997	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
…		…
2816	ev_idle_start (loop, idle_watcher);	2999	ev_idle_start (loop, idle_watcher);
2817		3000
2818		3001
2819	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	3002	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2820		3003
2821	Prepare and check watchers are usually (but not always) used in pairs:	3004	Prepare and check watchers are often (but not always) used in pairs:
2822	prepare watchers get invoked before the process blocks and check watchers	3005	prepare watchers get invoked before the process blocks and check watchers
2823	afterwards.	3006	afterwards.
2824		3007
2825	You I<must not> call C<ev_run> or similar functions that enter	3008	You I<must not> call C<ev_run> (or similar functions that enter the
2826	the current event loop from either C<ev_prepare> or C<ev_check>	3009	current event loop) or C<ev_loop_fork> from either C<ev_prepare> or
2827	watchers. Other loops than the current one are fine, however. The	3010	C<ev_check> watchers. Other loops than the current one are fine,
2828	rationale behind this is that you do not need to check for recursion in	3011	however. The rationale behind this is that you do not need to check
2829	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	3012	for recursion in those watchers, i.e. the sequence will always be
2830	C<ev_check> so if you have one watcher of each kind they will always be	3013	C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each
2831	called in pairs bracketing the blocking call.	3014	kind they will always be called in pairs bracketing the blocking call.
2832		3015
2833	Their main purpose is to integrate other event mechanisms into libev and	3016	Their main purpose is to integrate other event mechanisms into libev and
2834	their use is somewhat advanced. They could be used, for example, to track	3017	their use is somewhat advanced. They could be used, for example, to track
2835	variable changes, implement your own watchers, integrate net-snmp or a	3018	variable changes, implement your own watchers, integrate net-snmp or a
2836	coroutine library and lots more. They are also occasionally useful if	3019	coroutine library and lots more. They are also occasionally useful if
…		…
2854	with priority higher than or equal to the event loop and one coroutine	3037	with priority higher than or equal to the event loop and one coroutine
2855	of lower priority, but only once, using idle watchers to keep the event	3038	of lower priority, but only once, using idle watchers to keep the event
2856	loop from blocking if lower-priority coroutines are active, thus mapping	3039	loop from blocking if lower-priority coroutines are active, thus mapping
2857	low-priority coroutines to idle/background tasks).	3040	low-priority coroutines to idle/background tasks).
2858		3041
2859	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	3042	When used for this purpose, it is recommended to give C<ev_check> watchers
2860	priority, to ensure that they are being run before any other watchers	3043	highest (C<EV_MAXPRI>) priority, to ensure that they are being run before
2861	after the poll (this doesn't matter for C<ev_prepare> watchers).	3044	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		3045	watchers).
2862		3046
2863	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	3047	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
2864	activate ("feed") events into libev. While libev fully supports this, they	3048	activate ("feed") events into libev. While libev fully supports this, they
2865	might get executed before other C<ev_check> watchers did their job. As	3049	might get executed before other C<ev_check> watchers did their job. As
2866	C<ev_check> watchers are often used to embed other (non-libev) event	3050	C<ev_check> watchers are often used to embed other (non-libev) event
2867	loops those other event loops might be in an unusable state until their	3051	loops those other event loops might be in an unusable state until their
2868	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	3052	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2869	others).	3053	others).
		3054
		3055	=head3 Abusing an C<ev_check> watcher for its side-effect
		3056
		3057	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		3058	useful because they are called once per event loop iteration. For
		3059	example, if you want to handle a large number of connections fairly, you
		3060	normally only do a bit of work for each active connection, and if there
		3061	is more work to do, you wait for the next event loop iteration, so other
		3062	connections have a chance of making progress.
		3063
		3064	Using an C<ev_check> watcher is almost enough: it will be called on the
		3065	next event loop iteration. However, that isn't as soon as possible -
		3066	without external events, your C<ev_check> watcher will not be invoked.
		3067
		3068	This is where C<ev_idle> watchers come in handy - all you need is a
		3069	single global idle watcher that is active as long as you have one active
		3070	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		3071	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		3072	invoked. Neither watcher alone can do that.
2870		3073
2871	=head3 Watcher-Specific Functions and Data Members	3074	=head3 Watcher-Specific Functions and Data Members
2872		3075
2873	=over 4	3076	=over 4
2874		3077
…		…
3075		3278
3076	=over 4	3279	=over 4
3077		3280
3078	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	3281	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
3079		3282
3080	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	3283	=item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)
3081		3284
3082	Configures the watcher to embed the given loop, which must be	3285	Configures the watcher to embed the given loop, which must be
3083	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	3286	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
3084	invoked automatically, otherwise it is the responsibility of the callback	3287	invoked automatically, otherwise it is the responsibility of the callback
3085	to invoke it (it will continue to be called until the sweep has been done,	3288	to invoke it (it will continue to be called until the sweep has been done,
…		…
3106	used).	3309	used).
3107		3310
3108	struct ev_loop *loop_hi = ev_default_init (0);	3311	struct ev_loop *loop_hi = ev_default_init (0);
3109	struct ev_loop *loop_lo = 0;	3312	struct ev_loop *loop_lo = 0;
3110	ev_embed embed;	3313	ev_embed embed;
3111		3314
3112	// see if there is a chance of getting one that works	3315	// see if there is a chance of getting one that works
3113	// (remember that a flags value of 0 means autodetection)	3316	// (remember that a flags value of 0 means autodetection)
3114	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3317	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
3115	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3318	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
3116	: 0;	3319	: 0;
…		…
3130	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3333	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
3131		3334
3132	struct ev_loop *loop = ev_default_init (0);	3335	struct ev_loop *loop = ev_default_init (0);
3133	struct ev_loop *loop_socket = 0;	3336	struct ev_loop *loop_socket = 0;
3134	ev_embed embed;	3337	ev_embed embed;
3135		3338
3136	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3339	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
3137	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3340	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
3138	{	3341	{
3139	ev_embed_init (&embed, 0, loop_socket);	3342	ev_embed_init (&embed, 0, loop_socket);
3140	ev_embed_start (loop, &embed);	3343	ev_embed_start (loop, &embed);
…		…
3148		3351
3149	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3352	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
3150		3353
3151	Fork watchers are called when a C<fork ()> was detected (usually because	3354	Fork watchers are called when a C<fork ()> was detected (usually because
3152	whoever is a good citizen cared to tell libev about it by calling	3355	whoever is a good citizen cared to tell libev about it by calling
3153	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the	3356	C<ev_loop_fork>). The invocation is done before the event loop blocks next
3154	event loop blocks next and before C<ev_check> watchers are being called,	3357	and before C<ev_check> watchers are being called, and only in the child
3155	and only in the child after the fork. If whoever good citizen calling	3358	after the fork. If whoever good citizen calling C<ev_default_fork> cheats
3156	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3359	and calls it in the wrong process, the fork handlers will be invoked, too,
3157	handlers will be invoked, too, of course.	3360	of course.
3158		3361
3159	=head3 The special problem of life after fork - how is it possible?	3362	=head3 The special problem of life after fork - how is it possible?
3160		3363
3161	Most uses of C<fork()> consist of forking, then some simple calls to set	3364	Most uses of C<fork ()> consist of forking, then some simple calls to set
3162	up/change the process environment, followed by a call to C<exec()>. This	3365	up/change the process environment, followed by a call to C<exec()>. This
3163	sequence should be handled by libev without any problems.	3366	sequence should be handled by libev without any problems.
3164		3367
3165	This changes when the application actually wants to do event handling	3368	This changes when the application actually wants to do event handling
3166	in the child, or both parent in child, in effect "continuing" after the	3369	in the child, or both parent in child, in effect "continuing" after the
…		…
3243	atexit (program_exits);	3446	atexit (program_exits);
3244		3447
3245		3448
3246	=head2 C<ev_async> - how to wake up an event loop	3449	=head2 C<ev_async> - how to wake up an event loop
3247		3450
3248	In general, you cannot use an C<ev_run> from multiple threads or other	3451	In general, you cannot use an C<ev_loop> from multiple threads or other
3249	asynchronous sources such as signal handlers (as opposed to multiple event	3452	asynchronous sources such as signal handlers (as opposed to multiple event
3250	loops - those are of course safe to use in different threads).	3453	loops - those are of course safe to use in different threads).
3251		3454
3252	Sometimes, however, you need to wake up an event loop you do not control,	3455	Sometimes, however, you need to wake up an event loop you do not control,
3253	for example because it belongs to another thread. This is what C<ev_async>	3456	for example because it belongs to another thread. This is what C<ev_async>
…		…
3255	it by calling C<ev_async_send>, which is thread- and signal safe.	3458	it by calling C<ev_async_send>, which is thread- and signal safe.
3256		3459
3257	This functionality is very similar to C<ev_signal> watchers, as signals,	3460	This functionality is very similar to C<ev_signal> watchers, as signals,
3258	too, are asynchronous in nature, and signals, too, will be compressed	3461	too, are asynchronous in nature, and signals, too, will be compressed
3259	(i.e. the number of callback invocations may be less than the number of	3462	(i.e. the number of callback invocations may be less than the number of
3260	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind	3463	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
3261	of "global async watchers" by using a watcher on an otherwise unused	3464	of "global async watchers" by using a watcher on an otherwise unused
3262	signal, and C<ev_feed_signal> to signal this watcher from another thread,	3465	signal, and C<ev_feed_signal> to signal this watcher from another thread,
3263	even without knowing which loop owns the signal.	3466	even without knowing which loop owns the signal.
3264
3265	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
3266	just the default loop.
3267		3467
3268	=head3 Queueing	3468	=head3 Queueing
3269		3469
3270	C<ev_async> does not support queueing of data in any way. The reason	3470	C<ev_async> does not support queueing of data in any way. The reason
3271	is that the author does not know of a simple (or any) algorithm for a	3471	is that the author does not know of a simple (or any) algorithm for a
…		…
3363	trust me.	3563	trust me.
3364		3564
3365	=item ev_async_send (loop, ev_async *)	3565	=item ev_async_send (loop, ev_async *)
3366		3566
3367	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3567	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3368	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3568	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3569	returns.
		3570
3369	C<ev_feed_event>, this call is safe to do from other threads, signal or	3571	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3370	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3572	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3371	section below on what exactly this means).	3573	embedding section below on what exactly this means).
3372		3574
3373	Note that, as with other watchers in libev, multiple events might get	3575	Note that, as with other watchers in libev, multiple events might get
3374	compressed into a single callback invocation (another way to look at this	3576	compressed into a single callback invocation (another way to look at
3375	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3577	this is that C<ev_async> watchers are level-triggered: they are set on
3376	reset when the event loop detects that).	3578	C<ev_async_send>, reset when the event loop detects that).
3377		3579
3378	This call incurs the overhead of a system call only once per event loop	3580	This call incurs the overhead of at most one extra system call per event
3379	iteration, so while the overhead might be noticeable, it doesn't apply to	3581	loop iteration, if the event loop is blocked, and no syscall at all if
3380	repeated calls to C<ev_async_send> for the same event loop.	3582	the event loop (or your program) is processing events. That means that
		3583	repeated calls are basically free (there is no need to avoid calls for
		3584	performance reasons) and that the overhead becomes smaller (typically
		3585	zero) under load.
3381		3586
3382	=item bool = ev_async_pending (ev_async *)	3587	=item bool = ev_async_pending (ev_async *)
3383		3588
3384	Returns a non-zero value when C<ev_async_send> has been called on the	3589	Returns a non-zero value when C<ev_async_send> has been called on the
3385	watcher but the event has not yet been processed (or even noted) by the	3590	watcher but the event has not yet been processed (or even noted) by the
…		…
3402		3607
3403	There are some other functions of possible interest. Described. Here. Now.	3608	There are some other functions of possible interest. Described. Here. Now.
3404		3609
3405	=over 4	3610	=over 4
3406		3611
3407	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3612	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg)
3408		3613
3409	This function combines a simple timer and an I/O watcher, calls your	3614	This function combines a simple timer and an I/O watcher, calls your
3410	callback on whichever event happens first and automatically stops both	3615	callback on whichever event happens first and automatically stops both
3411	watchers. This is useful if you want to wait for a single event on an fd	3616	watchers. This is useful if you want to wait for a single event on an fd
3412	or timeout without having to allocate/configure/start/stop/free one or	3617	or timeout without having to allocate/configure/start/stop/free one or
…		…
3440	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3645	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3441		3646
3442	=item ev_feed_fd_event (loop, int fd, int revents)	3647	=item ev_feed_fd_event (loop, int fd, int revents)
3443		3648
3444	Feed an event on the given fd, as if a file descriptor backend detected	3649	Feed an event on the given fd, as if a file descriptor backend detected
3445	the given events it.	3650	the given events.
3446		3651
3447	=item ev_feed_signal_event (loop, int signum)	3652	=item ev_feed_signal_event (loop, int signum)
3448		3653
3449	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,	3654	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3450	which is async-safe.	3655	which is async-safe.
…		…
3455	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)	3660	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
3456		3661
3457	This section explains some common idioms that are not immediately	3662	This section explains some common idioms that are not immediately
3458	obvious. Note that examples are sprinkled over the whole manual, and this	3663	obvious. Note that examples are sprinkled over the whole manual, and this
3459	section only contains stuff that wouldn't fit anywhere else.	3664	section only contains stuff that wouldn't fit anywhere else.
		3665
		3666	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3667
		3668	Each watcher has, by default, a C<void *data> member that you can read
		3669	or modify at any time: libev will completely ignore it. This can be used
		3670	to associate arbitrary data with your watcher. If you need more data and
		3671	don't want to allocate memory separately and store a pointer to it in that
		3672	data member, you can also "subclass" the watcher type and provide your own
		3673	data:
		3674
		3675	struct my_io
		3676	{
		3677	ev_io io;
		3678	int otherfd;
		3679	void *somedata;
		3680	struct whatever *mostinteresting;
		3681	};
		3682
		3683	...
		3684	struct my_io w;
		3685	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3686
		3687	And since your callback will be called with a pointer to the watcher, you
		3688	can cast it back to your own type:
		3689
		3690	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3691	{
		3692	struct my_io *w = (struct my_io *)w_;
		3693	...
		3694	}
		3695
		3696	More interesting and less C-conformant ways of casting your callback
		3697	function type instead have been omitted.
		3698
		3699	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3700
		3701	Another common scenario is to use some data structure with multiple
		3702	embedded watchers, in effect creating your own watcher that combines
		3703	multiple libev event sources into one "super-watcher":
		3704
		3705	struct my_biggy
		3706	{
		3707	int some_data;
		3708	ev_timer t1;
		3709	ev_timer t2;
		3710	}
		3711
		3712	In this case getting the pointer to C<my_biggy> is a bit more
		3713	complicated: Either you store the address of your C<my_biggy> struct in
		3714	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3715	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3716	real programmers):
		3717
		3718	#include <stddef.h>
		3719
		3720	static void
		3721	t1_cb (EV_P_ ev_timer *w, int revents)
		3722	{
		3723	struct my_biggy big = (struct my_biggy *)
		3724	(((char *)w) - offsetof (struct my_biggy, t1));
		3725	}
		3726
		3727	static void
		3728	t2_cb (EV_P_ ev_timer *w, int revents)
		3729	{
		3730	struct my_biggy big = (struct my_biggy *)
		3731	(((char *)w) - offsetof (struct my_biggy, t2));
		3732	}
		3733
		3734	=head2 AVOIDING FINISHING BEFORE RETURNING
		3735
		3736	Often you have structures like this in event-based programs:
		3737
		3738	callback ()
		3739	{
		3740	free (request);
		3741	}
		3742
		3743	request = start_new_request (..., callback);
		3744
		3745	The intent is to start some "lengthy" operation. The C<request> could be
		3746	used to cancel the operation, or do other things with it.
		3747
		3748	It's not uncommon to have code paths in C<start_new_request> that
		3749	immediately invoke the callback, for example, to report errors. Or you add
		3750	some caching layer that finds that it can skip the lengthy aspects of the
		3751	operation and simply invoke the callback with the result.
		3752
		3753	The problem here is that this will happen I<before> C<start_new_request>
		3754	has returned, so C<request> is not set.
		3755
		3756	Even if you pass the request by some safer means to the callback, you
		3757	might want to do something to the request after starting it, such as
		3758	canceling it, which probably isn't working so well when the callback has
		3759	already been invoked.
		3760
		3761	A common way around all these issues is to make sure that
		3762	C<start_new_request> I<always> returns before the callback is invoked. If
		3763	C<start_new_request> immediately knows the result, it can artificially
		3764	delay invoking the callback by using a C<prepare> or C<idle> watcher for
		3765	example, or more sneakily, by reusing an existing (stopped) watcher and
		3766	pushing it into the pending queue:
		3767
		3768	ev_set_cb (watcher, callback);
		3769	ev_feed_event (EV_A_ watcher, 0);
		3770
		3771	This way, C<start_new_request> can safely return before the callback is
		3772	invoked, while not delaying callback invocation too much.
3460		3773
3461	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS	3774	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
3462		3775
3463	Often (especially in GUI toolkits) there are places where you have	3776	Often (especially in GUI toolkits) there are places where you have
3464	I<modal> interaction, which is most easily implemented by recursively	3777	I<modal> interaction, which is most easily implemented by recursively
…		…
3466		3779
3467	This brings the problem of exiting - a callback might want to finish the	3780	This brings the problem of exiting - a callback might want to finish the
3468	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but	3781	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
3469	a modal "Are you sure?" dialog is still waiting), or just the nested one	3782	a modal "Are you sure?" dialog is still waiting), or just the nested one
3470	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some	3783	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
3471	other combination: In these cases, C<ev_break> will not work alone.	3784	other combination: In these cases, a simple C<ev_break> will not work.
3472		3785
3473	The solution is to maintain "break this loop" variable for each C<ev_run>	3786	The solution is to maintain "break this loop" variable for each C<ev_run>
3474	invocation, and use a loop around C<ev_run> until the condition is	3787	invocation, and use a loop around C<ev_run> until the condition is
3475	triggered, using C<EVRUN_ONCE>:	3788	triggered, using C<EVRUN_ONCE>:
3476		3789
…		…
3478	int exit_main_loop = 0;	3791	int exit_main_loop = 0;
3479		3792
3480	while (!exit_main_loop)	3793	while (!exit_main_loop)
3481	ev_run (EV_DEFAULT_ EVRUN_ONCE);	3794	ev_run (EV_DEFAULT_ EVRUN_ONCE);
3482		3795
3483	// in a model watcher	3796	// in a modal watcher
3484	int exit_nested_loop = 0;	3797	int exit_nested_loop = 0;
3485		3798
3486	while (!exit_nested_loop)	3799	while (!exit_nested_loop)
3487	ev_run (EV_A_ EVRUN_ONCE);	3800	ev_run (EV_A_ EVRUN_ONCE);
3488		3801
…		…
3498	exit_main_loop = exit_nested_loop = 1;	3811	exit_main_loop = exit_nested_loop = 1;
3499		3812
3500	=head2 THREAD LOCKING EXAMPLE	3813	=head2 THREAD LOCKING EXAMPLE
3501		3814
3502	Here is a fictitious example of how to run an event loop in a different	3815	Here is a fictitious example of how to run an event loop in a different
3503	thread than where callbacks are being invoked and watchers are	3816	thread from where callbacks are being invoked and watchers are
3504	created/added/removed.	3817	created/added/removed.
3505		3818
3506	For a real-world example, see the C<EV::Loop::Async> perl module,	3819	For a real-world example, see the C<EV::Loop::Async> perl module,
3507	which uses exactly this technique (which is suited for many high-level	3820	which uses exactly this technique (which is suited for many high-level
3508	languages).	3821	languages).
…		…
3534	// now associate this with the loop	3847	// now associate this with the loop
3535	ev_set_userdata (EV_A_ u);	3848	ev_set_userdata (EV_A_ u);
3536	ev_set_invoke_pending_cb (EV_A_ l_invoke);	3849	ev_set_invoke_pending_cb (EV_A_ l_invoke);
3537	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);	3850	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
3538		3851
3539	// then create the thread running ev_loop	3852	// then create the thread running ev_run
3540	pthread_create (&u->tid, 0, l_run, EV_A);	3853	pthread_create (&u->tid, 0, l_run, EV_A);
3541	}	3854	}
3542		3855
3543	The callback for the C<ev_async> watcher does nothing: the watcher is used	3856	The callback for the C<ev_async> watcher does nothing: the watcher is used
3544	solely to wake up the event loop so it takes notice of any new watchers	3857	solely to wake up the event loop so it takes notice of any new watchers
…		…
3633	Note that sending the C<ev_async> watcher is required because otherwise	3946	Note that sending the C<ev_async> watcher is required because otherwise
3634	an event loop currently blocking in the kernel will have no knowledge	3947	an event loop currently blocking in the kernel will have no knowledge
3635	about the newly added timer. By waking up the loop it will pick up any new	3948	about the newly added timer. By waking up the loop it will pick up any new
3636	watchers in the next event loop iteration.	3949	watchers in the next event loop iteration.
3637		3950
3638	=back	3951	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3952
		3953	While the overhead of a callback that e.g. schedules a thread is small, it
		3954	is still an overhead. If you embed libev, and your main usage is with some
		3955	kind of threads or coroutines, you might want to customise libev so that
		3956	doesn't need callbacks anymore.
		3957
		3958	Imagine you have coroutines that you can switch to using a function
		3959	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3960	and that due to some magic, the currently active coroutine is stored in a
		3961	global called C<current_coro>. Then you can build your own "wait for libev
		3962	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3963	the differing C<;> conventions):
		3964
		3965	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3966	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3967
		3968	That means instead of having a C callback function, you store the
		3969	coroutine to switch to in each watcher, and instead of having libev call
		3970	your callback, you instead have it switch to that coroutine.
		3971
		3972	A coroutine might now wait for an event with a function called
		3973	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3974	matter when, or whether the watcher is active or not when this function is
		3975	called):
		3976
		3977	void
		3978	wait_for_event (ev_watcher *w)
		3979	{
		3980	ev_set_cb (w, current_coro);
		3981	switch_to (libev_coro);
		3982	}
		3983
		3984	That basically suspends the coroutine inside C<wait_for_event> and
		3985	continues the libev coroutine, which, when appropriate, switches back to
		3986	this or any other coroutine.
		3987
		3988	You can do similar tricks if you have, say, threads with an event queue -
		3989	instead of storing a coroutine, you store the queue object and instead of
		3990	switching to a coroutine, you push the watcher onto the queue and notify
		3991	any waiters.
		3992
		3993	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		3994	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3995
		3996	// my_ev.h
		3997	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3998	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3999	#include "../libev/ev.h"
		4000
		4001	// my_ev.c
		4002	#define EV_H "my_ev.h"
		4003	#include "../libev/ev.c"
		4004
		4005	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		4006	F<my_ev.c> into your project. When properly specifying include paths, you
		4007	can even use F<ev.h> as header file name directly.
3639		4008
3640		4009
3641	=head1 LIBEVENT EMULATION	4010	=head1 LIBEVENT EMULATION
3642		4011
3643	Libev offers a compatibility emulation layer for libevent. It cannot	4012	Libev offers a compatibility emulation layer for libevent. It cannot
…		…
3673		4042
3674	=back	4043	=back
3675		4044
3676	=head1 C++ SUPPORT	4045	=head1 C++ SUPPORT
3677		4046
		4047	=head2 C API
		4048
		4049	The normal C API should work fine when used from C++: both ev.h and the
		4050	libev sources can be compiled as C++. Therefore, code that uses the C API
		4051	will work fine.
		4052
		4053	Proper exception specifications might have to be added to callbacks passed
		4054	to libev: exceptions may be thrown only from watcher callbacks, all other
		4055	callbacks (allocator, syserr, loop acquire/release and periodic reschedule
		4056	callbacks) must not throw exceptions, and might need a C<noexcept>
		4057	specification. If you have code that needs to be compiled as both C and
		4058	C++ you can use the C<EV_NOEXCEPT> macro for this:
		4059
		4060	static void
		4061	fatal_error (const char *msg) EV_NOEXCEPT
		4062	{
		4063	perror (msg);
		4064	abort ();
		4065	}
		4066
		4067	...
		4068	ev_set_syserr_cb (fatal_error);
		4069
		4070	The only API functions that can currently throw exceptions are C<ev_run>,
		4071	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		4072	because it runs cleanup watchers).
		4073
		4074	Throwing exceptions in watcher callbacks is only supported if libev itself
		4075	is compiled with a C++ compiler or your C and C++ environments allow
		4076	throwing exceptions through C libraries (most do).
		4077
		4078	=head2 C++ API
		4079
3678	Libev comes with some simplistic wrapper classes for C++ that mainly allow	4080	Libev comes with some simplistic wrapper classes for C++ that mainly allow
3679	you to use some convenience methods to start/stop watchers and also change	4081	you to use some convenience methods to start/stop watchers and also change
3680	the callback model to a model using method callbacks on objects.	4082	the callback model to a model using method callbacks on objects.
3681		4083
3682	To use it,	4084	To use it,
3683		4085
3684	#include <ev++.h>	4086	#include <ev++.h>
3685		4087
3686	This automatically includes F<ev.h> and puts all of its definitions (many	4088	This automatically includes F<ev.h> and puts all of its definitions (many
3687	of them macros) into the global namespace. All C++ specific things are	4089	of them macros) into the global namespace. All C++ specific things are
3688	put into the C<ev> namespace. It should support all the same embedding	4090	put into the C<ev> namespace. It should support all the same embedding
…		…
3697	with C<operator ()> can be used as callbacks. Other types should be easy	4099	with C<operator ()> can be used as callbacks. Other types should be easy
3698	to add as long as they only need one additional pointer for context. If	4100	to add as long as they only need one additional pointer for context. If
3699	you need support for other types of functors please contact the author	4101	you need support for other types of functors please contact the author
3700	(preferably after implementing it).	4102	(preferably after implementing it).
3701		4103
		4104	For all this to work, your C++ compiler either has to use the same calling
		4105	conventions as your C compiler (for static member functions), or you have
		4106	to embed libev and compile libev itself as C++.
		4107
3702	Here is a list of things available in the C<ev> namespace:	4108	Here is a list of things available in the C<ev> namespace:
3703		4109
3704	=over 4	4110	=over 4
3705		4111
3706	=item C<ev::READ>, C<ev::WRITE> etc.	4112	=item C<ev::READ>, C<ev::WRITE> etc.
…		…
3715	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4121	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3716		4122
3717	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4123	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
3718	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4124	the same name in the C<ev> namespace, with the exception of C<ev_signal>
3719	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4125	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3720	defines by many implementations.	4126	defined by many implementations.
3721		4127
3722	All of those classes have these methods:	4128	All of those classes have these methods:
3723		4129
3724	=over 4	4130	=over 4
3725		4131
…		…
3787	void operator() (ev::io &w, int revents)	4193	void operator() (ev::io &w, int revents)
3788	{	4194	{
3789	...	4195	...
3790	}	4196	}
3791	}	4197	}
3792		4198
3793	myfunctor f;	4199	myfunctor f;
3794		4200
3795	ev::io w;	4201	ev::io w;
3796	w.set (&f);	4202	w.set (&f);
3797		4203
…		…
3815	Associates a different C<struct ev_loop> with this watcher. You can only	4221	Associates a different C<struct ev_loop> with this watcher. You can only
3816	do this when the watcher is inactive (and not pending either).	4222	do this when the watcher is inactive (and not pending either).
3817		4223
3818	=item w->set ([arguments])	4224	=item w->set ([arguments])
3819		4225
3820	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this	4226	Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>),
3821	method or a suitable start method must be called at least once. Unlike the	4227	with the same arguments. Either this method or a suitable start method
3822	C counterpart, an active watcher gets automatically stopped and restarted	4228	must be called at least once. Unlike the C counterpart, an active watcher
3823	when reconfiguring it with this method.	4229	gets automatically stopped and restarted when reconfiguring it with this
		4230	method.
		4231
		4232	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4233	clashing with the C<set (loop)> method.
3824		4234
3825	=item w->start ()	4235	=item w->start ()
3826		4236
3827	Starts the watcher. Note that there is no C<loop> argument, as the	4237	Starts the watcher. Note that there is no C<loop> argument, as the
3828	constructor already stores the event loop.	4238	constructor already stores the event loop.
…		…
3858	watchers in the constructor.	4268	watchers in the constructor.
3859		4269
3860	class myclass	4270	class myclass
3861	{	4271	{
3862	ev::io io ; void io_cb (ev::io &w, int revents);	4272	ev::io io ; void io_cb (ev::io &w, int revents);
3863	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);	4273	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3864	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4274	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3865		4275
3866	myclass (int fd)	4276	myclass (int fd)
3867	{	4277	{
3868	io .set <myclass, &myclass::io_cb > (this);	4278	io .set <myclass, &myclass::io_cb > (this);
…		…
3919	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4329	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3920		4330
3921	=item D	4331	=item D
3922		4332
3923	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4333	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3924	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4334	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3925		4335
3926	=item Ocaml	4336	=item Ocaml
3927		4337
3928	Erkki Seppala has written Ocaml bindings for libev, to be found at	4338	Erkki Seppala has written Ocaml bindings for libev, to be found at
3929	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4339	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
…		…
3932		4342
3933	Brian Maher has written a partial interface to libev for lua (at the	4343	Brian Maher has written a partial interface to libev for lua (at the
3934	time of this writing, only C<ev_io> and C<ev_timer>), to be found at	4344	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
3935	L<http://github.com/brimworks/lua-ev>.	4345	L<http://github.com/brimworks/lua-ev>.
3936		4346
		4347	=item Javascript
		4348
		4349	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4350
		4351	=item Others
		4352
		4353	There are others, and I stopped counting.
		4354
3937	=back	4355	=back
3938		4356
3939		4357
3940	=head1 MACRO MAGIC	4358	=head1 MACRO MAGIC
3941		4359
…		…
3977	suitable for use with C<EV_A>.	4395	suitable for use with C<EV_A>.
3978		4396
3979	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4397	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3980		4398
3981	Similar to the other two macros, this gives you the value of the default	4399	Similar to the other two macros, this gives you the value of the default
3982	loop, if multiple loops are supported ("ev loop default").	4400	loop, if multiple loops are supported ("ev loop default"). The default loop
		4401	will be initialised if it isn't already initialised.
		4402
		4403	For non-multiplicity builds, these macros do nothing, so you always have
		4404	to initialise the loop somewhere.
3983		4405
3984	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4406	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3985		4407
3986	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4408	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3987	default loop has been initialised (C<UC> == unchecked). Their behaviour	4409	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
4054	ev_vars.h	4476	ev_vars.h
4055	ev_wrap.h	4477	ev_wrap.h
4056		4478
4057	ev_win32.c required on win32 platforms only	4479	ev_win32.c required on win32 platforms only
4058		4480
4059	ev_select.c only when select backend is enabled (which is enabled by default)	4481	ev_select.c only when select backend is enabled
4060	ev_poll.c only when poll backend is enabled (disabled by default)	4482	ev_poll.c only when poll backend is enabled
4061	ev_epoll.c only when the epoll backend is enabled (disabled by default)	4483	ev_epoll.c only when the epoll backend is enabled
		4484	ev_linuxaio.c only when the linux aio backend is enabled
4062	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	4485	ev_kqueue.c only when the kqueue backend is enabled
4063	ev_port.c only when the solaris port backend is enabled (disabled by default)	4486	ev_port.c only when the solaris port backend is enabled
4064		4487
4065	F<ev.c> includes the backend files directly when enabled, so you only need	4488	F<ev.c> includes the backend files directly when enabled, so you only need
4066	to compile this single file.	4489	to compile this single file.
4067		4490
4068	=head3 LIBEVENT COMPATIBILITY API	4491	=head3 LIBEVENT COMPATIBILITY API
…		…
4132	supported). It will also not define any of the structs usually found in	4555	supported). It will also not define any of the structs usually found in
4133	F<event.h> that are not directly supported by the libev core alone.	4556	F<event.h> that are not directly supported by the libev core alone.
4134		4557
4135	In standalone mode, libev will still try to automatically deduce the	4558	In standalone mode, libev will still try to automatically deduce the
4136	configuration, but has to be more conservative.	4559	configuration, but has to be more conservative.
		4560
		4561	=item EV_USE_FLOOR
		4562
		4563	If defined to be C<1>, libev will use the C<floor ()> function for its
		4564	periodic reschedule calculations, otherwise libev will fall back on a
		4565	portable (slower) implementation. If you enable this, you usually have to
		4566	link against libm or something equivalent. Enabling this when the C<floor>
		4567	function is not available will fail, so the safe default is to not enable
		4568	this.
4137		4569
4138	=item EV_USE_MONOTONIC	4570	=item EV_USE_MONOTONIC
4139		4571
4140	If defined to be C<1>, libev will try to detect the availability of the	4572	If defined to be C<1>, libev will try to detect the availability of the
4141	monotonic clock option at both compile time and runtime. Otherwise no	4573	monotonic clock option at both compile time and runtime. Otherwise no
…		…
4227	If programs implement their own fd to handle mapping on win32, then this	4659	If programs implement their own fd to handle mapping on win32, then this
4228	macro can be used to override the C<close> function, useful to unregister	4660	macro can be used to override the C<close> function, useful to unregister
4229	file descriptors again. Note that the replacement function has to close	4661	file descriptors again. Note that the replacement function has to close
4230	the underlying OS handle.	4662	the underlying OS handle.
4231		4663
		4664	=item EV_USE_WSASOCKET
		4665
		4666	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4667	communication socket, which works better in some environments. Otherwise,
		4668	the normal C<socket> function will be used, which works better in other
		4669	environments.
		4670
4232	=item EV_USE_POLL	4671	=item EV_USE_POLL
4233		4672
4234	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4673	If defined to be C<1>, libev will compile in support for the C<poll>(2)
4235	backend. Otherwise it will be enabled on non-win32 platforms. It	4674	backend. Otherwise it will be enabled on non-win32 platforms. It
4236	takes precedence over select.	4675	takes precedence over select.
…		…
4240	If defined to be C<1>, libev will compile in support for the Linux	4679	If defined to be C<1>, libev will compile in support for the Linux
4241	C<epoll>(7) backend. Its availability will be detected at runtime,	4680	C<epoll>(7) backend. Its availability will be detected at runtime,
4242	otherwise another method will be used as fallback. This is the preferred	4681	otherwise another method will be used as fallback. This is the preferred
4243	backend for GNU/Linux systems. If undefined, it will be enabled if the	4682	backend for GNU/Linux systems. If undefined, it will be enabled if the
4244	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4683	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		4684
		4685	=item EV_USE_LINUXAIO
		4686
		4687	If defined to be C<1>, libev will compile in support for the Linux
		4688	aio backend. Due to it's currenbt limitations it has to be requested
		4689	explicitly. If undefined, it will be enabled on linux, otherwise
		4690	disabled.
4245		4691
4246	=item EV_USE_KQUEUE	4692	=item EV_USE_KQUEUE
4247		4693
4248	If defined to be C<1>, libev will compile in support for the BSD style	4694	If defined to be C<1>, libev will compile in support for the BSD style
4249	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	4695	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
4271	If defined to be C<1>, libev will compile in support for the Linux inotify	4717	If defined to be C<1>, libev will compile in support for the Linux inotify
4272	interface to speed up C<ev_stat> watchers. Its actual availability will	4718	interface to speed up C<ev_stat> watchers. Its actual availability will
4273	be detected at runtime. If undefined, it will be enabled if the headers	4719	be detected at runtime. If undefined, it will be enabled if the headers
4274	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4720	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
4275		4721
		4722	=item EV_NO_SMP
		4723
		4724	If defined to be C<1>, libev will assume that memory is always coherent
		4725	between threads, that is, threads can be used, but threads never run on
		4726	different cpus (or different cpu cores). This reduces dependencies
		4727	and makes libev faster.
		4728
		4729	=item EV_NO_THREADS
		4730
		4731	If defined to be C<1>, libev will assume that it will never be called from
		4732	different threads (that includes signal handlers), which is a stronger
		4733	assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes
		4734	libev faster.
		4735
4276	=item EV_ATOMIC_T	4736	=item EV_ATOMIC_T
4277		4737
4278	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4738	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
4279	access is atomic with respect to other threads or signal contexts. No such	4739	access is atomic with respect to other threads or signal contexts. No
4280	type is easily found in the C language, so you can provide your own type	4740	such type is easily found in the C language, so you can provide your own
4281	that you know is safe for your purposes. It is used both for signal handler "locking"	4741	type that you know is safe for your purposes. It is used both for signal
4282	as well as for signal and thread safety in C<ev_async> watchers.	4742	handler "locking" as well as for signal and thread safety in C<ev_async>
		4743	watchers.
4283		4744
4284	In the absence of this define, libev will use C<sig_atomic_t volatile>	4745	In the absence of this define, libev will use C<sig_atomic_t volatile>
4285	(from F<signal.h>), which is usually good enough on most platforms.	4746	(from F<signal.h>), which is usually good enough on most platforms.
4286		4747
4287	=item EV_H (h)	4748	=item EV_H (h)
…		…
4314	will have the C<struct ev_loop *> as first argument, and you can create	4775	will have the C<struct ev_loop *> as first argument, and you can create
4315	additional independent event loops. Otherwise there will be no support	4776	additional independent event loops. Otherwise there will be no support
4316	for multiple event loops and there is no first event loop pointer	4777	for multiple event loops and there is no first event loop pointer
4317	argument. Instead, all functions act on the single default loop.	4778	argument. Instead, all functions act on the single default loop.
4318		4779
		4780	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4781	default loop when multiplicity is switched off - you always have to
		4782	initialise the loop manually in this case.
		4783
4319	=item EV_MINPRI	4784	=item EV_MINPRI
4320		4785
4321	=item EV_MAXPRI	4786	=item EV_MAXPRI
4322		4787
4323	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4788	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
4359	#define EV_USE_POLL 1	4824	#define EV_USE_POLL 1
4360	#define EV_CHILD_ENABLE 1	4825	#define EV_CHILD_ENABLE 1
4361	#define EV_ASYNC_ENABLE 1	4826	#define EV_ASYNC_ENABLE 1
4362		4827
4363	The actual value is a bitset, it can be a combination of the following	4828	The actual value is a bitset, it can be a combination of the following
4364	values:	4829	values (by default, all of these are enabled):
4365		4830
4366	=over 4	4831	=over 4
4367		4832
4368	=item C<1> - faster/larger code	4833	=item C<1> - faster/larger code
4369		4834
…		…
4373	code size by roughly 30% on amd64).	4838	code size by roughly 30% on amd64).
4374		4839
4375	When optimising for size, use of compiler flags such as C<-Os> with	4840	When optimising for size, use of compiler flags such as C<-Os> with
4376	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of	4841	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
4377	assertions.	4842	assertions.
		4843
		4844	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4845	(e.g. gcc with C<-Os>).
4378		4846
4379	=item C<2> - faster/larger data structures	4847	=item C<2> - faster/larger data structures
4380		4848
4381	Replaces the small 2-heap for timer management by a faster 4-heap, larger	4849	Replaces the small 2-heap for timer management by a faster 4-heap, larger
4382	hash table sizes and so on. This will usually further increase code size	4850	hash table sizes and so on. This will usually further increase code size
4383	and can additionally have an effect on the size of data structures at	4851	and can additionally have an effect on the size of data structures at
4384	runtime.	4852	runtime.
4385		4853
		4854	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4855	(e.g. gcc with C<-Os>).
		4856
4386	=item C<4> - full API configuration	4857	=item C<4> - full API configuration
4387		4858
4388	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and	4859	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
4389	enables multiplicity (C<EV_MULTIPLICITY>=1).	4860	enables multiplicity (C<EV_MULTIPLICITY>=1).
4390		4861
…		…
4420		4891
4421	With an intelligent-enough linker (gcc+binutils are intelligent enough	4892	With an intelligent-enough linker (gcc+binutils are intelligent enough
4422	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by	4893	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
4423	your program might be left out as well - a binary starting a timer and an	4894	your program might be left out as well - a binary starting a timer and an
4424	I/O watcher then might come out at only 5Kb.	4895	I/O watcher then might come out at only 5Kb.
		4896
		4897	=item EV_API_STATIC
		4898
		4899	If this symbol is defined (by default it is not), then all identifiers
		4900	will have static linkage. This means that libev will not export any
		4901	identifiers, and you cannot link against libev anymore. This can be useful
		4902	when you embed libev, only want to use libev functions in a single file,
		4903	and do not want its identifiers to be visible.
		4904
		4905	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4906	wants to use libev.
		4907
		4908	This option only works when libev is compiled with a C compiler, as C++
		4909	doesn't support the required declaration syntax.
4425		4910
4426	=item EV_AVOID_STDIO	4911	=item EV_AVOID_STDIO
4427		4912
4428	If this is set to C<1> at compiletime, then libev will avoid using stdio	4913	If this is set to C<1> at compiletime, then libev will avoid using stdio
4429	functions (printf, scanf, perror etc.). This will increase the code size	4914	functions (printf, scanf, perror etc.). This will increase the code size
…		…
4573	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	5058	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4574		5059
4575	#include "ev_cpp.h"	5060	#include "ev_cpp.h"
4576	#include "ev.c"	5061	#include "ev.c"
4577		5062
4578	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	5063	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4579		5064
4580	=head2 THREADS AND COROUTINES	5065	=head2 THREADS AND COROUTINES
4581		5066
4582	=head3 THREADS	5067	=head3 THREADS
4583		5068
…		…
4634	default loop and triggering an C<ev_async> watcher from the default loop	5119	default loop and triggering an C<ev_async> watcher from the default loop
4635	watcher callback into the event loop interested in the signal.	5120	watcher callback into the event loop interested in the signal.
4636		5121
4637	=back	5122	=back
4638		5123
4639	See also L<THREAD LOCKING EXAMPLE>.	5124	See also L</THREAD LOCKING EXAMPLE>.
4640		5125
4641	=head3 COROUTINES	5126	=head3 COROUTINES
4642		5127
4643	Libev is very accommodating to coroutines ("cooperative threads"):	5128	Libev is very accommodating to coroutines ("cooperative threads"):
4644	libev fully supports nesting calls to its functions from different	5129	libev fully supports nesting calls to its functions from different
…		…
4809	requires, and its I/O model is fundamentally incompatible with the POSIX	5294	requires, and its I/O model is fundamentally incompatible with the POSIX
4810	model. Libev still offers limited functionality on this platform in	5295	model. Libev still offers limited functionality on this platform in
4811	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5296	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4812	descriptors. This only applies when using Win32 natively, not when using	5297	descriptors. This only applies when using Win32 natively, not when using
4813	e.g. cygwin. Actually, it only applies to the microsofts own compilers,	5298	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
4814	as every compielr comes with a slightly differently broken/incompatible	5299	as every compiler comes with a slightly differently broken/incompatible
4815	environment.	5300	environment.
4816		5301
4817	Lifting these limitations would basically require the full	5302	Lifting these limitations would basically require the full
4818	re-implementation of the I/O system. If you are into this kind of thing,	5303	re-implementation of the I/O system. If you are into this kind of thing,
4819	then note that glib does exactly that for you in a very portable way (note	5304	then note that glib does exactly that for you in a very portable way (note
…		…
4913	structure (guaranteed by POSIX but not by ISO C for example), but it also	5398	structure (guaranteed by POSIX but not by ISO C for example), but it also
4914	assumes that the same (machine) code can be used to call any watcher	5399	assumes that the same (machine) code can be used to call any watcher
4915	callback: The watcher callbacks have different type signatures, but libev	5400	callback: The watcher callbacks have different type signatures, but libev
4916	calls them using an C<ev_watcher *> internally.	5401	calls them using an C<ev_watcher *> internally.
4917		5402
		5403	=item null pointers and integer zero are represented by 0 bytes
		5404
		5405	Libev uses C<memset> to initialise structs and arrays to C<0> bytes, and
		5406	relies on this setting pointers and integers to null.
		5407
4918	=item pointer accesses must be thread-atomic	5408	=item pointer accesses must be thread-atomic
4919		5409
4920	Accessing a pointer value must be atomic, it must both be readable and	5410	Accessing a pointer value must be atomic, it must both be readable and
4921	writable in one piece - this is the case on all current architectures.	5411	writable in one piece - this is the case on all current architectures.
4922		5412
…		…
4935	thread" or will block signals process-wide, both behaviours would	5425	thread" or will block signals process-wide, both behaviours would
4936	be compatible with libev. Interaction between C<sigprocmask> and	5426	be compatible with libev. Interaction between C<sigprocmask> and
4937	C<pthread_sigmask> could complicate things, however.	5427	C<pthread_sigmask> could complicate things, however.
4938		5428
4939	The most portable way to handle signals is to block signals in all threads	5429	The most portable way to handle signals is to block signals in all threads
4940	except the initial one, and run the default loop in the initial thread as	5430	except the initial one, and run the signal handling loop in the initial
4941	well.	5431	thread as well.
4942		5432
4943	=item C<long> must be large enough for common memory allocation sizes	5433	=item C<long> must be large enough for common memory allocation sizes
4944		5434
4945	To improve portability and simplify its API, libev uses C<long> internally	5435	To improve portability and simplify its API, libev uses C<long> internally
4946	instead of C<size_t> when allocating its data structures. On non-POSIX	5436	instead of C<size_t> when allocating its data structures. On non-POSIX
…		…
4952		5442
4953	The type C<double> is used to represent timestamps. It is required to	5443	The type C<double> is used to represent timestamps. It is required to
4954	have at least 51 bits of mantissa (and 9 bits of exponent), which is	5444	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4955	good enough for at least into the year 4000 with millisecond accuracy	5445	good enough for at least into the year 4000 with millisecond accuracy
4956	(the design goal for libev). This requirement is overfulfilled by	5446	(the design goal for libev). This requirement is overfulfilled by
4957	implementations using IEEE 754, which is basically all existing ones. With	5447	implementations using IEEE 754, which is basically all existing ones.
		5448
4958	IEEE 754 doubles, you get microsecond accuracy until at least 2200.	5449	With IEEE 754 doubles, you get microsecond accuracy until at least the
		5450	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5451	is either obsolete or somebody patched it to use C<long double> or
		5452	something like that, just kidding).
4959		5453
4960	=back	5454	=back
4961		5455
4962	If you know of other additional requirements drop me a note.	5456	If you know of other additional requirements drop me a note.
4963		5457
…		…
5025	=item Processing ev_async_send: O(number_of_async_watchers)	5519	=item Processing ev_async_send: O(number_of_async_watchers)
5026		5520
5027	=item Processing signals: O(max_signal_number)	5521	=item Processing signals: O(max_signal_number)
5028		5522
5029	Sending involves a system call I<iff> there were no other C<ev_async_send>	5523	Sending involves a system call I<iff> there were no other C<ev_async_send>
5030	calls in the current loop iteration. Checking for async and signal events	5524	calls in the current loop iteration and the loop is currently
		5525	blocked. Checking for async and signal events involves iterating over all
5031	involves iterating over all running async watchers or all signal numbers.	5526	running async watchers or all signal numbers.
5032		5527
5033	=back	5528	=back
5034		5529
5035		5530
5036	=head1 PORTING FROM LIBEV 3.X TO 4.X	5531	=head1 PORTING FROM LIBEV 3.X TO 4.X
…		…
5045	=over 4	5540	=over 4
5046		5541
5047	=item C<EV_COMPAT3> backwards compatibility mechanism	5542	=item C<EV_COMPAT3> backwards compatibility mechanism
5048		5543
5049	The backward compatibility mechanism can be controlled by	5544	The backward compatibility mechanism can be controlled by
5050	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>	5545	C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING>
5051	section.	5546	section.
5052		5547
5053	=item C<ev_default_destroy> and C<ev_default_fork> have been removed	5548	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
5054		5549
5055	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:	5550	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
…		…
5098	=over 4	5593	=over 4
5099		5594
5100	=item active	5595	=item active
5101		5596
5102	A watcher is active as long as it has been started and not yet stopped.	5597	A watcher is active as long as it has been started and not yet stopped.
5103	See L<WATCHER STATES> for details.	5598	See L</WATCHER STATES> for details.
5104		5599
5105	=item application	5600	=item application
5106		5601
5107	In this document, an application is whatever is using libev.	5602	In this document, an application is whatever is using libev.
5108		5603
…		…
5144	watchers and events.	5639	watchers and events.
5145		5640
5146	=item pending	5641	=item pending
5147		5642
5148	A watcher is pending as soon as the corresponding event has been	5643	A watcher is pending as soon as the corresponding event has been
5149	detected. See L<WATCHER STATES> for details.	5644	detected. See L</WATCHER STATES> for details.
5150		5645
5151	=item real time	5646	=item real time
5152		5647
5153	The physical time that is observed. It is apparently strictly monotonic :)	5648	The physical time that is observed. It is apparently strictly monotonic :)
5154		5649
5155	=item wall-clock time	5650	=item wall-clock time
5156		5651
5157	The time and date as shown on clocks. Unlike real time, it can actually	5652	The time and date as shown on clocks. Unlike real time, it can actually
5158	be wrong and jump forwards and backwards, e.g. when the you adjust your	5653	be wrong and jump forwards and backwards, e.g. when you adjust your
5159	clock.	5654	clock.
5160		5655
5161	=item watcher	5656	=item watcher
5162		5657
5163	A data structure that describes interest in certain events. Watchers need	5658	A data structure that describes interest in certain events. Watchers need
…		…
5166	=back	5661	=back
5167		5662
5168	=head1 AUTHOR	5663	=head1 AUTHOR
5169		5664
5170	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael	5665	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
5171	Magnusson and Emanuele Giaquinta.	5666	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
5172		5667

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