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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
…		…
299	}	327	}
300		328
301	...	329	...
302	ev_set_syserr_cb (fatal_error);	330	ev_set_syserr_cb (fatal_error);
303		331
		332	=item ev_feed_signal (int signum)
		333
		334	This function can be used to "simulate" a signal receive. It is completely
		335	safe to call this function at any time, from any context, including signal
		336	handlers or random threads.
		337
		338	Its main use is to customise signal handling in your process, especially
		339	in the presence of threads. For example, you could block signals
		340	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		341	creating any loops), and in one thread, use C<sigwait> or any other
		342	mechanism to wait for signals, then "deliver" them to libev by calling
		343	C<ev_feed_signal>.
		344
304	=back	345	=back
305		346
306	=head1 FUNCTIONS CONTROLLING EVENT LOOPS	347	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
307		348
308	An event loop is described by a C<struct ev_loop *> (the C<struct> is	349	An event loop is described by a C<struct ev_loop *> (the C<struct> is
…		…
377		418
378	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
379	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
380	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	421	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
381	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
382	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
383	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).
384		427
385	=item C<EVFLAG_FORKCHECK>	428	=item C<EVFLAG_FORKCHECK>
386		429
387	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
388	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.
389		432
390	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,
391	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
392	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
393	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
394	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
395	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).
396		440
397	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
398	forget about forgetting to tell libev about forking) when you use this	442	forget about forgetting to tell libev about forking, although you still
399	flag.	443	have to ignore C<SIGPIPE>) when you use this flag.
400		444
401	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>
402	environment variable.	446	environment variable.
403		447
404	=item C<EVFLAG_NOINOTIFY>	448	=item C<EVFLAG_NOINOTIFY>
…		…
419		463
420	Signalfd will not be used by default as this changes your signal mask, and	464	Signalfd will not be used by default as this changes your signal mask, and
421	there are a lot of shoddy libraries and programs (glib's threadpool for	465	there are a lot of shoddy libraries and programs (glib's threadpool for
422	example) that can't properly initialise their signal masks.	466	example) that can't properly initialise their signal masks.
423		467
		468	=item C<EVFLAG_NOSIGMASK>
		469
		470	When this flag is specified, then libev will avoid to modify the signal
		471	mask. Specifically, this means you have to make sure signals are unblocked
		472	when you want to receive them.
		473
		474	This behaviour is useful when you want to do your own signal handling, or
		475	want to handle signals only in specific threads and want to avoid libev
		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.
		480
		481	This flag's behaviour will become the default in future versions of libev.
		482
424	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	483	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
425		484
426	This is your standard select(2) backend. Not I<completely> standard, as	485	This is your standard select(2) backend. Not I<completely> standard, as
427	libev tries to roll its own fd_set with no limits on the number of fds,	486	libev tries to roll its own fd_set with no limits on the number of fds,
428	but if that fails, expect a fairly low limit on the number of fds when	487	but if that fails, expect a fairly low limit on the number of fds when
…		…
455	=item C<EVBACKEND_EPOLL> (value 4, Linux)	514	=item C<EVBACKEND_EPOLL> (value 4, Linux)
456		515
457	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
458	kernels).	517	kernels).
459		518
460	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
461	but it scales phenomenally better. While poll and select usually scale	520	it scales phenomenally better. While poll and select usually scale like
462	like O(total_fds) where n is the total number of fds (or the highest fd),	521	O(total_fds) where total_fds is the total number of fds (or the highest
463	epoll scales either O(1) or O(active_fds).	522	fd), epoll scales either O(1) or O(active_fds).
464		523
465	The epoll mechanism deserves honorable mention as the most misdesigned	524	The epoll mechanism deserves honorable mention as the most misdesigned
466	of the more advanced event mechanisms: mere annoyances include silently	525	of the more advanced event mechanisms: mere annoyances include silently
467	dropping file descriptors, requiring a system call per change per file	526	dropping file descriptors, requiring a system call per change per file
468	descriptor (and unnecessary guessing of parameters), problems with dup,	527	descriptor (and unnecessary guessing of parameters), problems with dup,
…		…
471	0.1ms) and so on. The biggest issue is fork races, however - if a program	530	0.1ms) and so on. The biggest issue is fork races, however - if a program
472	forks then I<both> parent and child process have to recreate the epoll	531	forks then I<both> parent and child process have to recreate the epoll
473	set, which can take considerable time (one syscall per file descriptor)	532	set, which can take considerable time (one syscall per file descriptor)
474	and is of course hard to detect.	533	and is of course hard to detect.
475		534
476	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	535	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
477	of course I<doesn't>, and epoll just loves to report events for totally	536	but of course I<doesn't>, and epoll just loves to report events for
478	I<different> file descriptors (even already closed ones, so one cannot	537	totally I<different> file descriptors (even already closed ones, so
479	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
480	on SMP systems). Libev tries to counter these spurious notifications by	539	(especially on SMP systems). Libev tries to counter these spurious
481	employing an additional generation counter and comparing that against the	540	notifications by employing an additional generation counter and comparing
482	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
483	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
484	perfectly fine with C<select> (files, many character devices...).	546	perfectly fine with C<select> (files, many character devices...).
485		547
486	Epoll is truly the train wreck analog among event poll mechanisms.	548	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
		549	cobbled together in a hurry, no thought to design or interaction with
		550	others. Oh, the pain, will it ever stop...
487		551
488	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
489	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
490	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
491	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
…		…
503	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
504	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
505	the usage. So sad.	569	the usage. So sad.
506		570
507	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
508	all kernel versions tested so far.	572	a lot of kernel revisions, but probably(!) works in current versions.
		573
		574	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		575	C<EVBACKEND_POLL>.
		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.
		581
		582	If this backend works for you (as of this writing, it was very
		583	experimental), it is the best event interface available on linux and might
		584	be well worth enabling it - if it isn't available in your kernel this will
		585	be detected and this backend will be skipped.
		586
		587	This backend can batch oneshot requests and supports a user-space ring
		588	buffer to receive events. It also doesn't suffer from most of the design
		589	problems of epoll (such as not being able to remove event sources from
		590	the epoll set), and generally sounds too good to be true. Because, this
		591	being the linux kernel, of course it suffers from a whole new set of
		592	limitations.
		593
		594	For one, it is not easily embeddable (but probably could be done using
		595	an event fd at some extra overhead). It also is subject to a system wide
		596	limit that can be configured in F</proc/sys/fs/aio-max-nr> - each loop
		597	currently requires C<61> of this number. If no aio requests are left, this
		598	backend will be skipped during initialisation.
		599
		600	Most problematic in practise, however, is that not all file descriptors
		601	work with it. For example, in linux 5.1, tcp sockets, pipes, event fds,
		602	files, F</dev/null> and a few others are supported, but ttys do not work
		603	(probably because of a bug), so this is not (yet?) a generic event polling
		604	interface.
		605
		606	To work around this latter problem, the current version of libev uses
		607	epoll as a fallback for file deescriptor types that do not work. Epoll
		608	is used in, kind of, slow mode that hopefully avoids most of its design
		609	problems and requires 1-3 extra syscalls per active fd every iteration.
509		610
510	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	611	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
511	C<EVBACKEND_POLL>.	612	C<EVBACKEND_POLL>.
512		613
513	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	614	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
…		…
528		629
529	It scales in the same way as the epoll backend, but the interface to the	630	It scales in the same way as the epoll backend, but the interface to the
530	kernel is more efficient (which says nothing about its actual speed, of	631	kernel is more efficient (which says nothing about its actual speed, of
531	course). While stopping, setting and starting an I/O watcher does never	632	course). While stopping, setting and starting an I/O watcher does never
532	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	633	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
533	two event changes per incident. Support for C<fork ()> is very bad (but	634	two event changes per incident. Support for C<fork ()> is very bad (you
534	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect	635	might have to leak fd's on fork, but it's more sane than epoll) and it
535	cases	636	drops fds silently in similarly hard-to-detect cases.
536		637
537	This backend usually performs well under most conditions.	638	This backend usually performs well under most conditions.
538		639
539	While nominally embeddable in other event loops, this doesn't work	640	While nominally embeddable in other event loops, this doesn't work
540	everywhere, so you might need to test for this. And since it is broken	641	everywhere, so you might need to test for this. And since it is broken
…		…
557	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	658	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
558		659
559	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	660	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
560	it's really slow, but it still scales very well (O(active_fds)).	661	it's really slow, but it still scales very well (O(active_fds)).
561		662
562	Please note that Solaris event ports can deliver a lot of spurious
563	notifications, so you need to use non-blocking I/O or other means to avoid
564	blocking when no data (or space) is available.
565
566	While this backend scales well, it requires one system call per active	663	While this backend scales well, it requires one system call per active
567	file descriptor per loop iteration. For small and medium numbers of file	664	file descriptor per loop iteration. For small and medium numbers of file
568	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	665	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
569	might perform better.	666	might perform better.
570		667
571	On the positive side, with the exception of the spurious readiness	668	On the positive side, this backend actually performed fully to
572	notifications, this backend actually performed fully to specification
573	in all tests and is fully embeddable, which is a rare feat among the	669	specification in all tests and is fully embeddable, which is a rare feat
574	OS-specific backends (I vastly prefer correctness over speed hacks).	670	among the OS-specific backends (I vastly prefer correctness over speed
		671	hacks).
		672
		673	On the negative side, the interface is I<bizarre> - so bizarre that
		674	even sun itself gets it wrong in their code examples: The event polling
		675	function sometimes returns events to the caller even though an error
		676	occurred, but with no indication whether it has done so or not (yes, it's
		677	even documented that way) - deadly for edge-triggered interfaces where you
		678	absolutely have to know whether an event occurred or not because you have
		679	to re-arm the watcher.
		680
		681	Fortunately libev seems to be able to work around these idiocies.
575		682
576	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	683	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
577	C<EVBACKEND_POLL>.	684	C<EVBACKEND_POLL>.
578		685
579	=item C<EVBACKEND_ALL>	686	=item C<EVBACKEND_ALL>
580		687
581	Try all backends (even potentially broken ones that wouldn't be tried	688	Try all backends (even potentially broken ones that wouldn't be tried
582	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	689	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
583	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	690	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
584		691
585	It is definitely not recommended to use this flag.	692	It is definitely not recommended to use this flag, use whatever
		693	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		694	at all.
		695
		696	=item C<EVBACKEND_MASK>
		697
		698	Not a backend at all, but a mask to select all backend bits from a
		699	C<flags> value, in case you want to mask out any backends from a flags
		700	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
586		701
587	=back	702	=back
588		703
589	If one or more of the backend flags are or'ed into the flags value,	704	If one or more of the backend flags are or'ed into the flags value,
590	then only these backends will be tried (in the reverse order as listed	705	then only these backends will be tried (in the reverse order as listed
…		…
599		714
600	Example: Use whatever libev has to offer, but make sure that kqueue is	715	Example: Use whatever libev has to offer, but make sure that kqueue is
601	used if available.	716	used if available.
602		717
603	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);	718	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		719
		720	Example: Similarly, on linux, you mgiht want to take advantage of the
		721	linux aio backend if possible, but fall back to something else if that
		722	isn't available.
		723
		724	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_LINUXAIO);
604		725
605	=item ev_loop_destroy (loop)	726	=item ev_loop_destroy (loop)
606		727
607	Destroys an event loop object (frees all memory and kernel state	728	Destroys an event loop object (frees all memory and kernel state
608	etc.). None of the active event watchers will be stopped in the normal	729	etc.). None of the active event watchers will be stopped in the normal
…		…
625	If you need dynamically allocated loops it is better to use C<ev_loop_new>	746	If you need dynamically allocated loops it is better to use C<ev_loop_new>
626	and C<ev_loop_destroy>.	747	and C<ev_loop_destroy>.
627		748
628	=item ev_loop_fork (loop)	749	=item ev_loop_fork (loop)
629		750
630	This function sets a flag that causes subsequent C<ev_run> iterations to	751	This function sets a flag that causes subsequent C<ev_run> iterations
631	reinitialise the kernel state for backends that have one. Despite the	752	to reinitialise the kernel state for backends that have one. Despite
632	name, you can call it anytime, but it makes most sense after forking, in	753	the name, you can call it anytime you are allowed to start or stop
633	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the	754	watchers (except inside an C<ev_prepare> callback), but it makes most
		755	sense after forking, in the child process. You I<must> call it (or use
634	child before resuming or calling C<ev_run>.	756	C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>.
635		757
		758	In addition, if you want to reuse a loop (via this function or
		759	C<EVFLAG_FORKCHECK>), you I<also> have to ignore C<SIGPIPE>.
		760
636	Again, you I<have> to call it on I<any> loop that you want to re-use after	761	Again, you I<have> to call it on I<any> loop that you want to re-use after
637	a fork, I<even if you do not plan to use the loop in the parent>. This is	762	a fork, I<even if you do not plan to use the loop in the parent>. This is
638	because some kernel interfaces *cough* I<kqueue> *cough* do funny things	763	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
639	during fork.	764	during fork.
640		765
641	On the other hand, you only need to call this function in the child	766	On the other hand, you only need to call this function in the child
…		…
711		836
712	This function is rarely useful, but when some event callback runs for a	837	This function is rarely useful, but when some event callback runs for a
713	very long time without entering the event loop, updating libev's idea of	838	very long time without entering the event loop, updating libev's idea of
714	the current time is a good idea.	839	the current time is a good idea.
715		840
716	See also L<The special problem of time updates> in the C<ev_timer> section.	841	See also L</The special problem of time updates> in the C<ev_timer> section.
717		842
718	=item ev_suspend (loop)	843	=item ev_suspend (loop)
719		844
720	=item ev_resume (loop)	845	=item ev_resume (loop)
721		846
…		…
739	without a previous call to C<ev_suspend>.	864	without a previous call to C<ev_suspend>.
740		865
741	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	866	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
742	event loop time (see C<ev_now_update>).	867	event loop time (see C<ev_now_update>).
743		868
744	=item ev_run (loop, int flags)	869	=item bool ev_run (loop, int flags)
745		870
746	Finally, this is it, the event handler. This function usually is called	871	Finally, this is it, the event handler. This function usually is called
747	after you have initialised all your watchers and you want to start	872	after you have initialised all your watchers and you want to start
748	handling events. It will ask the operating system for any new events, call	873	handling events. It will ask the operating system for any new events, call
749	the watcher callbacks, an then repeat the whole process indefinitely: This	874	the watcher callbacks, and then repeat the whole process indefinitely: This
750	is why event loops are called I<loops>.	875	is why event loops are called I<loops>.
751		876
752	If the flags argument is specified as C<0>, it will keep handling events	877	If the flags argument is specified as C<0>, it will keep handling events
753	until either no event watchers are active anymore or C<ev_break> was	878	until either no event watchers are active anymore or C<ev_break> was
754	called.	879	called.
		880
		881	The return value is false if there are no more active watchers (which
		882	usually means "all jobs done" or "deadlock"), and true in all other cases
		883	(which usually means " you should call C<ev_run> again").
755		884
756	Please note that an explicit C<ev_break> is usually better than	885	Please note that an explicit C<ev_break> is usually better than
757	relying on all watchers to be stopped when deciding when a program has	886	relying on all watchers to be stopped when deciding when a program has
758	finished (especially in interactive programs), but having a program	887	finished (especially in interactive programs), but having a program
759	that automatically loops as long as it has to and no longer by virtue	888	that automatically loops as long as it has to and no longer by virtue
760	of relying on its watchers stopping correctly, that is truly a thing of	889	of relying on its watchers stopping correctly, that is truly a thing of
761	beauty.	890	beauty.
762		891
763	This function is also I<mostly> exception-safe - you can break out of	892	This function is I<mostly> exception-safe - you can break out of a
764	a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++	893	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
765	exception and so on. This does not decrement the C<ev_depth> value, nor	894	exception and so on. This does not decrement the C<ev_depth> value, nor
766	will it clear any outstanding C<EVBREAK_ONE> breaks.	895	will it clear any outstanding C<EVBREAK_ONE> breaks.
767		896
768	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle	897	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
769	those events and any already outstanding ones, but will not wait and	898	those events and any already outstanding ones, but will not wait and
…		…
781	This is useful if you are waiting for some external event in conjunction	910	This is useful if you are waiting for some external event in conjunction
782	with something not expressible using other libev watchers (i.e. "roll your	911	with something not expressible using other libev watchers (i.e. "roll your
783	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	912	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
784	usually a better approach for this kind of thing.	913	usually a better approach for this kind of thing.
785		914
786	Here are the gory details of what C<ev_run> does:	915	Here are the gory details of what C<ev_run> does (this is for your
		916	understanding, not a guarantee that things will work exactly like this in
		917	future versions):
787		918
788	- Increment loop depth.	919	- Increment loop depth.
789	- Reset the ev_break status.	920	- Reset the ev_break status.
790	- Before the first iteration, call any pending watchers.	921	- Before the first iteration, call any pending watchers.
791	LOOP:	922	LOOP:
…		…
824	anymore.	955	anymore.
825		956
826	... queue jobs here, make sure they register event watchers as long	957	... queue jobs here, make sure they register event watchers as long
827	... as they still have work to do (even an idle watcher will do..)	958	... as they still have work to do (even an idle watcher will do..)
828	ev_run (my_loop, 0);	959	ev_run (my_loop, 0);
829	... jobs done or somebody called unloop. yeah!	960	... jobs done or somebody called break. yeah!
830		961
831	=item ev_break (loop, how)	962	=item ev_break (loop, how)
832		963
833	Can be used to make a call to C<ev_run> return early (but only after it	964	Can be used to make a call to C<ev_run> return early (but only after it
834	has processed all outstanding events). The C<how> argument must be either	965	has processed all outstanding events). The C<how> argument must be either
…		…
867	running when nothing else is active.	998	running when nothing else is active.
868		999
869	ev_signal exitsig;	1000	ev_signal exitsig;
870	ev_signal_init (&exitsig, sig_cb, SIGINT);	1001	ev_signal_init (&exitsig, sig_cb, SIGINT);
871	ev_signal_start (loop, &exitsig);	1002	ev_signal_start (loop, &exitsig);
872	evf_unref (loop);	1003	ev_unref (loop);
873		1004
874	Example: For some weird reason, unregister the above signal handler again.	1005	Example: For some weird reason, unregister the above signal handler again.
875		1006
876	ev_ref (loop);	1007	ev_ref (loop);
877	ev_signal_stop (loop, &exitsig);	1008	ev_signal_stop (loop, &exitsig);
…		…
897	overhead for the actual polling but can deliver many events at once.	1028	overhead for the actual polling but can deliver many events at once.
898		1029
899	By setting a higher I<io collect interval> you allow libev to spend more	1030	By setting a higher I<io collect interval> you allow libev to spend more
900	time collecting I/O events, so you can handle more events per iteration,	1031	time collecting I/O events, so you can handle more events per iteration,
901	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	1032	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
902	C<ev_timer>) will be not affected. Setting this to a non-null value will	1033	C<ev_timer>) will not be affected. Setting this to a non-null value will
903	introduce an additional C<ev_sleep ()> call into most loop iterations. The	1034	introduce an additional C<ev_sleep ()> call into most loop iterations. The
904	sleep time ensures that libev will not poll for I/O events more often then	1035	sleep time ensures that libev will not poll for I/O events more often then
905	once per this interval, on average.	1036	once per this interval, on average (as long as the host time resolution is
		1037	good enough).
906		1038
907	Likewise, by setting a higher I<timeout collect interval> you allow libev	1039	Likewise, by setting a higher I<timeout collect interval> you allow libev
908	to spend more time collecting timeouts, at the expense of increased	1040	to spend more time collecting timeouts, at the expense of increased
909	latency/jitter/inexactness (the watcher callback will be called	1041	latency/jitter/inexactness (the watcher callback will be called
910	later). C<ev_io> watchers will not be affected. Setting this to a non-null	1042	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
956	invoke the actual watchers inside another context (another thread etc.).	1088	invoke the actual watchers inside another context (another thread etc.).
957		1089
958	If you want to reset the callback, use C<ev_invoke_pending> as new	1090	If you want to reset the callback, use C<ev_invoke_pending> as new
959	callback.	1091	callback.
960		1092
961	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))	1093	=item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())
962		1094
963	Sometimes you want to share the same loop between multiple threads. This	1095	Sometimes you want to share the same loop between multiple threads. This
964	can be done relatively simply by putting mutex_lock/unlock calls around	1096	can be done relatively simply by putting mutex_lock/unlock calls around
965	each call to a libev function.	1097	each call to a libev function.
966		1098
967	However, C<ev_run> can run an indefinite time, so it is not feasible	1099	However, C<ev_run> can run an indefinite time, so it is not feasible
968	to wait for it to return. One way around this is to wake up the event	1100	to wait for it to return. One way around this is to wake up the event
969	loop via C<ev_break> and C<av_async_send>, another way is to set these	1101	loop via C<ev_break> and C<ev_async_send>, another way is to set these
970	I<release> and I<acquire> callbacks on the loop.	1102	I<release> and I<acquire> callbacks on the loop.
971		1103
972	When set, then C<release> will be called just before the thread is	1104	When set, then C<release> will be called just before the thread is
973	suspended waiting for new events, and C<acquire> is called just	1105	suspended waiting for new events, and C<acquire> is called just
974	afterwards.	1106	afterwards.
…		…
989	See also the locking example in the C<THREADS> section later in this	1121	See also the locking example in the C<THREADS> section later in this
990	document.	1122	document.
991		1123
992	=item ev_set_userdata (loop, void *data)	1124	=item ev_set_userdata (loop, void *data)
993		1125
994	=item ev_userdata (loop)	1126	=item void *ev_userdata (loop)
995		1127
996	Set and retrieve a single C<void *> associated with a loop. When	1128	Set and retrieve a single C<void *> associated with a loop. When
997	C<ev_set_userdata> has never been called, then C<ev_userdata> returns	1129	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
998	C<0>.	1130	C<0>.
999		1131
…		…
1114		1246
1115	=item C<EV_PREPARE>	1247	=item C<EV_PREPARE>
1116		1248
1117	=item C<EV_CHECK>	1249	=item C<EV_CHECK>
1118		1250
1119	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts	1251	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to
1120	to gather new events, and all C<ev_check> watchers are invoked just after	1252	gather new events, and all C<ev_check> watchers are queued (not invoked)
1121	C<ev_run> has gathered them, but before it invokes any callbacks for any	1253	just after C<ev_run> has gathered them, but before it queues any callbacks
		1254	for any received events. That means C<ev_prepare> watchers are the last
		1255	watchers invoked before the event loop sleeps or polls for new events, and
		1256	C<ev_check> watchers will be invoked before any other watchers of the same
		1257	or lower priority within an event loop iteration.
		1258
1122	received events. Callbacks of both watcher types can start and stop as	1259	Callbacks of both watcher types can start and stop as many watchers as
1123	many watchers as they want, and all of them will be taken into account	1260	they want, and all of them will be taken into account (for example, a
1124	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1261	C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from
1125	C<ev_run> from blocking).	1262	blocking).
1126		1263
1127	=item C<EV_EMBED>	1264	=item C<EV_EMBED>
1128		1265
1129	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1266	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1130		1267
…		…
1253		1390
1254	=item callback ev_cb (ev_TYPE *watcher)	1391	=item callback ev_cb (ev_TYPE *watcher)
1255		1392
1256	Returns the callback currently set on the watcher.	1393	Returns the callback currently set on the watcher.
1257		1394
1258	=item ev_cb_set (ev_TYPE *watcher, callback)	1395	=item ev_set_cb (ev_TYPE *watcher, callback)
1259		1396
1260	Change the callback. You can change the callback at virtually any time	1397	Change the callback. You can change the callback at virtually any time
1261	(modulo threads).	1398	(modulo threads).
1262		1399
1263	=item ev_set_priority (ev_TYPE *watcher, int priority)	1400	=item ev_set_priority (ev_TYPE *watcher, int priority)
…		…
1281	or might not have been clamped to the valid range.	1418	or might not have been clamped to the valid range.
1282		1419
1283	The default priority used by watchers when no priority has been set is	1420	The default priority used by watchers when no priority has been set is
1284	always C<0>, which is supposed to not be too high and not be too low :).	1421	always C<0>, which is supposed to not be too high and not be too low :).
1285		1422
1286	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of	1423	See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1287	priorities.	1424	priorities.
1288		1425
1289	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1426	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1290		1427
1291	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1428	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
…		…
1316	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related	1453	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1317	functions that do not need a watcher.	1454	functions that do not need a watcher.
1318		1455
1319	=back	1456	=back
1320		1457
1321	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1458	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
1322		1459	OWN COMPOSITE WATCHERS> idioms.
1323	Each watcher has, by default, a member C<void *data> that you can change
1324	and read at any time: libev will completely ignore it. This can be used
1325	to associate arbitrary data with your watcher. If you need more data and
1326	don't want to allocate memory and store a pointer to it in that data
1327	member, you can also "subclass" the watcher type and provide your own
1328	data:
1329
1330	struct my_io
1331	{
1332	ev_io io;
1333	int otherfd;
1334	void *somedata;
1335	struct whatever *mostinteresting;
1336	};
1337
1338	...
1339	struct my_io w;
1340	ev_io_init (&w.io, my_cb, fd, EV_READ);
1341
1342	And since your callback will be called with a pointer to the watcher, you
1343	can cast it back to your own type:
1344
1345	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1346	{
1347	struct my_io *w = (struct my_io *)w_;
1348	...
1349	}
1350
1351	More interesting and less C-conformant ways of casting your callback type
1352	instead have been omitted.
1353
1354	Another common scenario is to use some data structure with multiple
1355	embedded watchers:
1356
1357	struct my_biggy
1358	{
1359	int some_data;
1360	ev_timer t1;
1361	ev_timer t2;
1362	}
1363
1364	In this case getting the pointer to C<my_biggy> is a bit more
1365	complicated: Either you store the address of your C<my_biggy> struct
1366	in the C<data> member of the watcher (for woozies), or you need to use
1367	some pointer arithmetic using C<offsetof> inside your watchers (for real
1368	programmers):
1369
1370	#include <stddef.h>
1371
1372	static void
1373	t1_cb (EV_P_ ev_timer *w, int revents)
1374	{
1375	struct my_biggy big = (struct my_biggy *)
1376	(((char *)w) - offsetof (struct my_biggy, t1));
1377	}
1378
1379	static void
1380	t2_cb (EV_P_ ev_timer *w, int revents)
1381	{
1382	struct my_biggy big = (struct my_biggy *)
1383	(((char *)w) - offsetof (struct my_biggy, t2));
1384	}
1385		1460
1386	=head2 WATCHER STATES	1461	=head2 WATCHER STATES
1387		1462
1388	There are various watcher states mentioned throughout this manual -	1463	There are various watcher states mentioned throughout this manual -
1389	active, pending and so on. In this section these states and the rules to	1464	active, pending and so on. In this section these states and the rules to
1390	transition between them will be described in more detail - and while these	1465	transition between them will be described in more detail - and while these
1391	rules might look complicated, they usually do "the right thing".	1466	rules might look complicated, they usually do "the right thing".
1392		1467
1393	=over 4	1468	=over 4
1394		1469
1395	=item initialiased	1470	=item initialised
1396		1471
1397	Before a watcher can be registered with the event looop it has to be	1472	Before a watcher can be registered with the event loop it has to be
1398	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to	1473	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
1399	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.	1474	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1400		1475
1401	In this state it is simply some block of memory that is suitable for use	1476	In this state it is simply some block of memory that is suitable for
1402	in an event loop. It can be moved around, freed, reused etc. at will.	1477	use in an event loop. It can be moved around, freed, reused etc. at
		1478	will - as long as you either keep the memory contents intact, or call
		1479	C<ev_TYPE_init> again.
1403		1480
1404	=item started/running/active	1481	=item started/running/active
1405		1482
1406	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes	1483	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1407	property of the event loop, and is actively waiting for events. While in	1484	property of the event loop, and is actively waiting for events. While in
…		…
1435	latter will clear any pending state the watcher might be in, regardless	1512	latter will clear any pending state the watcher might be in, regardless
1436	of whether it was active or not, so stopping a watcher explicitly before	1513	of whether it was active or not, so stopping a watcher explicitly before
1437	freeing it is often a good idea.	1514	freeing it is often a good idea.
1438		1515
1439	While stopped (and not pending) the watcher is essentially in the	1516	While stopped (and not pending) the watcher is essentially in the
1440	initialised state, that is it can be reused, moved, modified in any way	1517	initialised state, that is, it can be reused, moved, modified in any way
1441	you wish.	1518	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1519	it again).
1442		1520
1443	=back	1521	=back
1444		1522
1445	=head2 WATCHER PRIORITY MODELS	1523	=head2 WATCHER PRIORITY MODELS
1446		1524
…		…
1575	In general you can register as many read and/or write event watchers per	1653	In general you can register as many read and/or write event watchers per
1576	fd as you want (as long as you don't confuse yourself). Setting all file	1654	fd as you want (as long as you don't confuse yourself). Setting all file
1577	descriptors to non-blocking mode is also usually a good idea (but not	1655	descriptors to non-blocking mode is also usually a good idea (but not
1578	required if you know what you are doing).	1656	required if you know what you are doing).
1579		1657
1580	If you cannot use non-blocking mode, then force the use of a
1581	known-to-be-good backend (at the time of this writing, this includes only
1582	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1583	descriptors for which non-blocking operation makes no sense (such as
1584	files) - libev doesn't guarantee any specific behaviour in that case.
1585
1586	Another thing you have to watch out for is that it is quite easy to	1658	Another thing you have to watch out for is that it is quite easy to
1587	receive "spurious" readiness notifications, that is your callback might	1659	receive "spurious" readiness notifications, that is, your callback might
1588	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1660	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1589	because there is no data. Not only are some backends known to create a	1661	because there is no data. It is very easy to get into this situation even
1590	lot of those (for example Solaris ports), it is very easy to get into	1662	with a relatively standard program structure. Thus it is best to always
1591	this situation even with a relatively standard program structure. Thus	1663	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1592	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1593	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1664	preferable to a program hanging until some data arrives.
1594		1665
1595	If you cannot run the fd in non-blocking mode (for example you should	1666	If you cannot run the fd in non-blocking mode (for example you should
1596	not play around with an Xlib connection), then you have to separately	1667	not play around with an Xlib connection), then you have to separately
1597	re-test whether a file descriptor is really ready with a known-to-be good	1668	re-test whether a file descriptor is really ready with a known-to-be good
1598	interface such as poll (fortunately in our Xlib example, Xlib already	1669	interface such as poll (fortunately in the case of Xlib, it already does
1599	does this on its own, so its quite safe to use). Some people additionally	1670	this on its own, so its quite safe to use). Some people additionally
1600	use C<SIGALRM> and an interval timer, just to be sure you won't block	1671	use C<SIGALRM> and an interval timer, just to be sure you won't block
1601	indefinitely.	1672	indefinitely.
1602		1673
1603	But really, best use non-blocking mode.	1674	But really, best use non-blocking mode.
1604		1675
1605	=head3 The special problem of disappearing file descriptors	1676	=head3 The special problem of disappearing file descriptors
1606		1677
1607	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1678	Some backends (e.g. kqueue, epoll, linuxaio) need to be told about closing
1608	descriptor (either due to calling C<close> explicitly or any other means,	1679	a file descriptor (either due to calling C<close> explicitly or any other
1609	such as C<dup2>). The reason is that you register interest in some file	1680	means, such as C<dup2>). The reason is that you register interest in some
1610	descriptor, but when it goes away, the operating system will silently drop	1681	file descriptor, but when it goes away, the operating system will silently
1611	this interest. If another file descriptor with the same number then is	1682	drop this interest. If another file descriptor with the same number then
1612	registered with libev, there is no efficient way to see that this is, in	1683	is registered with libev, there is no efficient way to see that this is,
1613	fact, a different file descriptor.	1684	in fact, a different file descriptor.
1614		1685
1615	To avoid having to explicitly tell libev about such cases, libev follows	1686	To avoid having to explicitly tell libev about such cases, libev follows
1616	the following policy: Each time C<ev_io_set> is being called, libev	1687	the following policy: Each time C<ev_io_set> is being called, libev
1617	will assume that this is potentially a new file descriptor, otherwise	1688	will assume that this is potentially a new file descriptor, otherwise
1618	it is assumed that the file descriptor stays the same. That means that	1689	it is assumed that the file descriptor stays the same. That means that
…		…
1632		1703
1633	There is no workaround possible except not registering events	1704	There is no workaround possible except not registering events
1634	for potentially C<dup ()>'ed file descriptors, or to resort to	1705	for potentially C<dup ()>'ed file descriptors, or to resort to
1635	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1706	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1636		1707
		1708	=head3 The special problem of files
		1709
		1710	Many people try to use C<select> (or libev) on file descriptors
		1711	representing files, and expect it to become ready when their program
		1712	doesn't block on disk accesses (which can take a long time on their own).
		1713
		1714	However, this cannot ever work in the "expected" way - you get a readiness
		1715	notification as soon as the kernel knows whether and how much data is
		1716	there, and in the case of open files, that's always the case, so you
		1717	always get a readiness notification instantly, and your read (or possibly
		1718	write) will still block on the disk I/O.
		1719
		1720	Another way to view it is that in the case of sockets, pipes, character
		1721	devices and so on, there is another party (the sender) that delivers data
		1722	on its own, but in the case of files, there is no such thing: the disk
		1723	will not send data on its own, simply because it doesn't know what you
		1724	wish to read - you would first have to request some data.
		1725
		1726	Since files are typically not-so-well supported by advanced notification
		1727	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1728	to files, even though you should not use it. The reason for this is
		1729	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1730	usually a tty, often a pipe, but also sometimes files or special devices
		1731	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1732	F</dev/urandom>), and even though the file might better be served with
		1733	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1734	it "just works" instead of freezing.
		1735
		1736	So avoid file descriptors pointing to files when you know it (e.g. use
		1737	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1738	when you rarely read from a file instead of from a socket, and want to
		1739	reuse the same code path.
		1740
1637	=head3 The special problem of fork	1741	=head3 The special problem of fork
1638		1742
1639	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1743	Some backends (epoll, kqueue, probably linuxaio) do not support C<fork ()>
1640	useless behaviour. Libev fully supports fork, but needs to be told about	1744	at all or exhibit useless behaviour. Libev fully supports fork, but needs
1641	it in the child.	1745	to be told about it in the child if you want to continue to use it in the
		1746	child.
1642		1747
1643	To support fork in your programs, you either have to call	1748	To support fork in your child processes, you have to call C<ev_loop_fork
1644	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1749	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1645	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1750	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1646	C<EVBACKEND_POLL>.
1647		1751
1648	=head3 The special problem of SIGPIPE	1752	=head3 The special problem of SIGPIPE
1649		1753
1650	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1754	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1651	when writing to a pipe whose other end has been closed, your program gets	1755	when writing to a pipe whose other end has been closed, your program gets
…		…
1749	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1853	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1750	monotonic clock option helps a lot here).	1854	monotonic clock option helps a lot here).
1751		1855
1752	The callback is guaranteed to be invoked only I<after> its timeout has	1856	The callback is guaranteed to be invoked only I<after> its timeout has
1753	passed (not I<at>, so on systems with very low-resolution clocks this	1857	passed (not I<at>, so on systems with very low-resolution clocks this
1754	might introduce a small delay). If multiple timers become ready during the	1858	might introduce a small delay, see "the special problem of being too
		1859	early", below). If multiple timers become ready during the same loop
1755	same loop iteration then the ones with earlier time-out values are invoked	1860	iteration then the ones with earlier time-out values are invoked before
1756	before ones of the same priority with later time-out values (but this is	1861	ones of the same priority with later time-out values (but this is no
1757	no longer true when a callback calls C<ev_run> recursively).	1862	longer true when a callback calls C<ev_run> recursively).
1758		1863
1759	=head3 Be smart about timeouts	1864	=head3 Be smart about timeouts
1760		1865
1761	Many real-world problems involve some kind of timeout, usually for error	1866	Many real-world problems involve some kind of timeout, usually for error
1762	recovery. A typical example is an HTTP request - if the other side hangs,	1867	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1837		1942
1838	In this case, it would be more efficient to leave the C<ev_timer> alone,	1943	In this case, it would be more efficient to leave the C<ev_timer> alone,
1839	but remember the time of last activity, and check for a real timeout only	1944	but remember the time of last activity, and check for a real timeout only
1840	within the callback:	1945	within the callback:
1841		1946
		1947	ev_tstamp timeout = 60.;
1842	ev_tstamp last_activity; // time of last activity	1948	ev_tstamp last_activity; // time of last activity
		1949	ev_timer timer;
1843		1950
1844	static void	1951	static void
1845	callback (EV_P_ ev_timer *w, int revents)	1952	callback (EV_P_ ev_timer *w, int revents)
1846	{	1953	{
1847	ev_tstamp now = ev_now (EV_A);	1954	// calculate when the timeout would happen
1848	ev_tstamp timeout = last_activity + 60.;	1955	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1849		1956
1850	// if last_activity + 60. is older than now, we did time out	1957	// if negative, it means we the timeout already occurred
1851	if (timeout < now)	1958	if (after < 0.)
1852	{	1959	{
1853	// timeout occurred, take action	1960	// timeout occurred, take action
1854	}	1961	}
1855	else	1962	else
1856	{	1963	{
1857	// callback was invoked, but there was some activity, re-arm	1964	// callback was invoked, but there was some recent
1858	// the watcher to fire in last_activity + 60, which is	1965	// activity. simply restart the timer to time out
1859	// guaranteed to be in the future, so "again" is positive:	1966	// after "after" seconds, which is the earliest time
1860	w->repeat = timeout - now;	1967	// the timeout can occur.
		1968	ev_timer_set (w, after, 0.);
1861	ev_timer_again (EV_A_ w);	1969	ev_timer_start (EV_A_ w);
1862	}	1970	}
1863	}	1971	}
1864		1972
1865	To summarise the callback: first calculate the real timeout (defined	1973	To summarise the callback: first calculate in how many seconds the
1866	as "60 seconds after the last activity"), then check if that time has	1974	timeout will occur (by calculating the absolute time when it would occur,
1867	been reached, which means something I<did>, in fact, time out. Otherwise	1975	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1868	the callback was invoked too early (C<timeout> is in the future), so	1976	(EV_A)> from that).
1869	re-schedule the timer to fire at that future time, to see if maybe we have
1870	a timeout then.
1871		1977
1872	Note how C<ev_timer_again> is used, taking advantage of the	1978	If this value is negative, then we are already past the timeout, i.e. we
1873	C<ev_timer_again> optimisation when the timer is already running.	1979	timed out, and need to do whatever is needed in this case.
		1980
		1981	Otherwise, we now the earliest time at which the timeout would trigger,
		1982	and simply start the timer with this timeout value.
		1983
		1984	In other words, each time the callback is invoked it will check whether
		1985	the timeout occurred. If not, it will simply reschedule itself to check
		1986	again at the earliest time it could time out. Rinse. Repeat.
1874		1987
1875	This scheme causes more callback invocations (about one every 60 seconds	1988	This scheme causes more callback invocations (about one every 60 seconds
1876	minus half the average time between activity), but virtually no calls to	1989	minus half the average time between activity), but virtually no calls to
1877	libev to change the timeout.	1990	libev to change the timeout.
1878		1991
1879	To start the timer, simply initialise the watcher and set C<last_activity>	1992	To start the machinery, simply initialise the watcher and set
1880	to the current time (meaning we just have some activity :), then call the	1993	C<last_activity> to the current time (meaning there was some activity just
1881	callback, which will "do the right thing" and start the timer:	1994	now), then call the callback, which will "do the right thing" and start
		1995	the timer:
1882		1996
		1997	last_activity = ev_now (EV_A);
1883	ev_init (timer, callback);	1998	ev_init (&timer, callback);
1884	last_activity = ev_now (loop);	1999	callback (EV_A_ &timer, 0);
1885	callback (loop, timer, EV_TIMER);
1886		2000
1887	And when there is some activity, simply store the current time in	2001	When there is some activity, simply store the current time in
1888	C<last_activity>, no libev calls at all:	2002	C<last_activity>, no libev calls at all:
1889		2003
		2004	if (activity detected)
1890	last_activity = ev_now (loop);	2005	last_activity = ev_now (EV_A);
		2006
		2007	When your timeout value changes, then the timeout can be changed by simply
		2008	providing a new value, stopping the timer and calling the callback, which
		2009	will again do the right thing (for example, time out immediately :).
		2010
		2011	timeout = new_value;
		2012	ev_timer_stop (EV_A_ &timer);
		2013	callback (EV_A_ &timer, 0);
1891		2014
1892	This technique is slightly more complex, but in most cases where the	2015	This technique is slightly more complex, but in most cases where the
1893	time-out is unlikely to be triggered, much more efficient.	2016	time-out is unlikely to be triggered, much more efficient.
1894
1895	Changing the timeout is trivial as well (if it isn't hard-coded in the
1896	callback :) - just change the timeout and invoke the callback, which will
1897	fix things for you.
1898		2017
1899	=item 4. Wee, just use a double-linked list for your timeouts.	2018	=item 4. Wee, just use a double-linked list for your timeouts.
1900		2019
1901	If there is not one request, but many thousands (millions...), all	2020	If there is not one request, but many thousands (millions...), all
1902	employing some kind of timeout with the same timeout value, then one can	2021	employing some kind of timeout with the same timeout value, then one can
…		…
1929	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	2048	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1930	rather complicated, but extremely efficient, something that really pays	2049	rather complicated, but extremely efficient, something that really pays
1931	off after the first million or so of active timers, i.e. it's usually	2050	off after the first million or so of active timers, i.e. it's usually
1932	overkill :)	2051	overkill :)
1933		2052
		2053	=head3 The special problem of being too early
		2054
		2055	If you ask a timer to call your callback after three seconds, then
		2056	you expect it to be invoked after three seconds - but of course, this
		2057	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		2058	guaranteed to any precision by libev - imagine somebody suspending the
		2059	process with a STOP signal for a few hours for example.
		2060
		2061	So, libev tries to invoke your callback as soon as possible I<after> the
		2062	delay has occurred, but cannot guarantee this.
		2063
		2064	A less obvious failure mode is calling your callback too early: many event
		2065	loops compare timestamps with a "elapsed delay >= requested delay", but
		2066	this can cause your callback to be invoked much earlier than you would
		2067	expect.
		2068
		2069	To see why, imagine a system with a clock that only offers full second
		2070	resolution (think windows if you can't come up with a broken enough OS
		2071	yourself). If you schedule a one-second timer at the time 500.9, then the
		2072	event loop will schedule your timeout to elapse at a system time of 500
		2073	(500.9 truncated to the resolution) + 1, or 501.
		2074
		2075	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2076	501" and invoke the callback 0.1s after it was started, even though a
		2077	one-second delay was requested - this is being "too early", despite best
		2078	intentions.
		2079
		2080	This is the reason why libev will never invoke the callback if the elapsed
		2081	delay equals the requested delay, but only when the elapsed delay is
		2082	larger than the requested delay. In the example above, libev would only invoke
		2083	the callback at system time 502, or 1.1s after the timer was started.
		2084
		2085	So, while libev cannot guarantee that your callback will be invoked
		2086	exactly when requested, it I<can> and I<does> guarantee that the requested
		2087	delay has actually elapsed, or in other words, it always errs on the "too
		2088	late" side of things.
		2089
1934	=head3 The special problem of time updates	2090	=head3 The special problem of time updates
1935		2091
1936	Establishing the current time is a costly operation (it usually takes at	2092	Establishing the current time is a costly operation (it usually takes
1937	least two system calls): EV therefore updates its idea of the current	2093	at least one system call): EV therefore updates its idea of the current
1938	time only before and after C<ev_run> collects new events, which causes a	2094	time only before and after C<ev_run> collects new events, which causes a
1939	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2095	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1940	lots of events in one iteration.	2096	lots of events in one iteration.
1941		2097
1942	The relative timeouts are calculated relative to the C<ev_now ()>	2098	The relative timeouts are calculated relative to the C<ev_now ()>
1943	time. This is usually the right thing as this timestamp refers to the time	2099	time. This is usually the right thing as this timestamp refers to the time
1944	of the event triggering whatever timeout you are modifying/starting. If	2100	of the event triggering whatever timeout you are modifying/starting. If
1945	you suspect event processing to be delayed and you I<need> to base the	2101	you suspect event processing to be delayed and you I<need> to base the
1946	timeout on the current time, use something like this to adjust for this:	2102	timeout on the current time, use something like the following to adjust
		2103	for it:
1947		2104
1948	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2105	ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.);
1949		2106
1950	If the event loop is suspended for a long time, you can also force an	2107	If the event loop is suspended for a long time, you can also force an
1951	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2108	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1952	()>.	2109	()>, although that will push the event time of all outstanding events
		2110	further into the future.
		2111
		2112	=head3 The special problem of unsynchronised clocks
		2113
		2114	Modern systems have a variety of clocks - libev itself uses the normal
		2115	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2116	jumps).
		2117
		2118	Neither of these clocks is synchronised with each other or any other clock
		2119	on the system, so C<ev_time ()> might return a considerably different time
		2120	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2121	a call to C<gettimeofday> might return a second count that is one higher
		2122	than a directly following call to C<time>.
		2123
		2124	The moral of this is to only compare libev-related timestamps with
		2125	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2126	a second or so.
		2127
		2128	One more problem arises due to this lack of synchronisation: if libev uses
		2129	the system monotonic clock and you compare timestamps from C<ev_time>
		2130	or C<ev_now> from when you started your timer and when your callback is
		2131	invoked, you will find that sometimes the callback is a bit "early".
		2132
		2133	This is because C<ev_timer>s work in real time, not wall clock time, so
		2134	libev makes sure your callback is not invoked before the delay happened,
		2135	I<measured according to the real time>, not the system clock.
		2136
		2137	If your timeouts are based on a physical timescale (e.g. "time out this
		2138	connection after 100 seconds") then this shouldn't bother you as it is
		2139	exactly the right behaviour.
		2140
		2141	If you want to compare wall clock/system timestamps to your timers, then
		2142	you need to use C<ev_periodic>s, as these are based on the wall clock
		2143	time, where your comparisons will always generate correct results.
1953		2144
1954	=head3 The special problems of suspended animation	2145	=head3 The special problems of suspended animation
1955		2146
1956	When you leave the server world it is quite customary to hit machines that	2147	When you leave the server world it is quite customary to hit machines that
1957	can suspend/hibernate - what happens to the clocks during such a suspend?	2148	can suspend/hibernate - what happens to the clocks during such a suspend?
…		…
1987		2178
1988	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2179	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1989		2180
1990	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	2181	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1991		2182
1992	Configure the timer to trigger after C<after> seconds. If C<repeat>	2183	Configure the timer to trigger after C<after> seconds (fractional and
1993	is C<0.>, then it will automatically be stopped once the timeout is	2184	negative values are supported). If C<repeat> is C<0.>, then it will
1994	reached. If it is positive, then the timer will automatically be	2185	automatically be stopped once the timeout is reached. If it is positive,
1995	configured to trigger again C<repeat> seconds later, again, and again,	2186	then the timer will automatically be configured to trigger again C<repeat>
1996	until stopped manually.	2187	seconds later, again, and again, until stopped manually.
1997		2188
1998	The timer itself will do a best-effort at avoiding drift, that is, if	2189	The timer itself will do a best-effort at avoiding drift, that is, if
1999	you configure a timer to trigger every 10 seconds, then it will normally	2190	you configure a timer to trigger every 10 seconds, then it will normally
2000	trigger at exactly 10 second intervals. If, however, your program cannot	2191	trigger at exactly 10 second intervals. If, however, your program cannot
2001	keep up with the timer (because it takes longer than those 10 seconds to	2192	keep up with the timer (because it takes longer than those 10 seconds to
2002	do stuff) the timer will not fire more than once per event loop iteration.	2193	do stuff) the timer will not fire more than once per event loop iteration.
2003		2194
2004	=item ev_timer_again (loop, ev_timer *)	2195	=item ev_timer_again (loop, ev_timer *)
2005		2196
2006	This will act as if the timer timed out and restart it again if it is	2197	This will act as if the timer timed out, and restarts it again if it is
2007	repeating. The exact semantics are:	2198	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2199	timeout to the C<repeat> value and calling C<ev_timer_start>.
2008		2200
		2201	The exact semantics are as in the following rules, all of which will be
		2202	applied to the watcher:
		2203
		2204	=over 4
		2205
2009	If the timer is pending, its pending status is cleared.	2206	=item If the timer is pending, the pending status is always cleared.
2010		2207
2011	If the timer is started but non-repeating, stop it (as if it timed out).	2208	=item If the timer is started but non-repeating, stop it (as if it timed
		2209	out, without invoking it).
2012		2210
2013	If the timer is repeating, either start it if necessary (with the	2211	=item If the timer is repeating, make the C<repeat> value the new timeout
2014	C<repeat> value), or reset the running timer to the C<repeat> value.	2212	and start the timer, if necessary.
2015		2213
		2214	=back
		2215
2016	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2216	This sounds a bit complicated, see L</Be smart about timeouts>, above, for a
2017	usage example.	2217	usage example.
2018		2218
2019	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)	2219	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
2020		2220
2021	Returns the remaining time until a timer fires. If the timer is active,	2221	Returns the remaining time until a timer fires. If the timer is active,
…		…
2074	Periodic watchers are also timers of a kind, but they are very versatile	2274	Periodic watchers are also timers of a kind, but they are very versatile
2075	(and unfortunately a bit complex).	2275	(and unfortunately a bit complex).
2076		2276
2077	Unlike C<ev_timer>, periodic watchers are not based on real time (or	2277	Unlike C<ev_timer>, periodic watchers are not based on real time (or
2078	relative time, the physical time that passes) but on wall clock time	2278	relative time, the physical time that passes) but on wall clock time
2079	(absolute time, the thing you can read on your calender or clock). The	2279	(absolute time, the thing you can read on your calendar or clock). The
2080	difference is that wall clock time can run faster or slower than real	2280	difference is that wall clock time can run faster or slower than real
2081	time, and time jumps are not uncommon (e.g. when you adjust your	2281	time, and time jumps are not uncommon (e.g. when you adjust your
2082	wrist-watch).	2282	wrist-watch).
2083		2283
2084	You can tell a periodic watcher to trigger after some specific point	2284	You can tell a periodic watcher to trigger after some specific point
…		…
2089	C<ev_timer>, which would still trigger roughly 10 seconds after starting	2289	C<ev_timer>, which would still trigger roughly 10 seconds after starting
2090	it, as it uses a relative timeout).	2290	it, as it uses a relative timeout).
2091		2291
2092	C<ev_periodic> watchers can also be used to implement vastly more complex	2292	C<ev_periodic> watchers can also be used to implement vastly more complex
2093	timers, such as triggering an event on each "midnight, local time", or	2293	timers, such as triggering an event on each "midnight, local time", or
2094	other complicated rules. This cannot be done with C<ev_timer> watchers, as	2294	other complicated rules. This cannot easily be done with C<ev_timer>
2095	those cannot react to time jumps.	2295	watchers, as those cannot react to time jumps.
2096		2296
2097	As with timers, the callback is guaranteed to be invoked only when the	2297	As with timers, the callback is guaranteed to be invoked only when the
2098	point in time where it is supposed to trigger has passed. If multiple	2298	point in time where it is supposed to trigger has passed. If multiple
2099	timers become ready during the same loop iteration then the ones with	2299	timers become ready during the same loop iteration then the ones with
2100	earlier time-out values are invoked before ones with later time-out values	2300	earlier time-out values are invoked before ones with later time-out values
…		…
2141		2341
2142	Another way to think about it (for the mathematically inclined) is that	2342	Another way to think about it (for the mathematically inclined) is that
2143	C<ev_periodic> will try to run the callback in this mode at the next possible	2343	C<ev_periodic> will try to run the callback in this mode at the next possible
2144	time where C<time = offset (mod interval)>, regardless of any time jumps.	2344	time where C<time = offset (mod interval)>, regardless of any time jumps.
2145		2345
2146	For numerical stability it is preferable that the C<offset> value is near	2346	The C<interval> I<MUST> be positive, and for numerical stability, the
2147	C<ev_now ()> (the current time), but there is no range requirement for	2347	interval value should be higher than C<1/8192> (which is around 100
2148	this value, and in fact is often specified as zero.	2348	microseconds) and C<offset> should be higher than C<0> and should have
		2349	at most a similar magnitude as the current time (say, within a factor of
		2350	ten). Typical values for offset are, in fact, C<0> or something between
		2351	C<0> and C<interval>, which is also the recommended range.
2149		2352
2150	Note also that there is an upper limit to how often a timer can fire (CPU	2353	Note also that there is an upper limit to how often a timer can fire (CPU
2151	speed for example), so if C<interval> is very small then timing stability	2354	speed for example), so if C<interval> is very small then timing stability
2152	will of course deteriorate. Libev itself tries to be exact to be about one	2355	will of course deteriorate. Libev itself tries to be exact to be about one
2153	millisecond (if the OS supports it and the machine is fast enough).	2356	millisecond (if the OS supports it and the machine is fast enough).
…		…
2183		2386
2184	NOTE: I<< This callback must always return a time that is higher than or	2387	NOTE: I<< This callback must always return a time that is higher than or
2185	equal to the passed C<now> value >>.	2388	equal to the passed C<now> value >>.
2186		2389
2187	This can be used to create very complex timers, such as a timer that	2390	This can be used to create very complex timers, such as a timer that
2188	triggers on "next midnight, local time". To do this, you would calculate the	2391	triggers on "next midnight, local time". To do this, you would calculate
2189	next midnight after C<now> and return the timestamp value for this. How	2392	the next midnight after C<now> and return the timestamp value for
2190	you do this is, again, up to you (but it is not trivial, which is the main	2393	this. Here is a (completely untested, no error checking) example on how to
2191	reason I omitted it as an example).	2394	do this:
		2395
		2396	#include <time.h>
		2397
		2398	static ev_tstamp
		2399	my_rescheduler (ev_periodic *w, ev_tstamp now)
		2400	{
		2401	time_t tnow = (time_t)now;
		2402	struct tm tm;
		2403	localtime_r (&tnow, &tm);
		2404
		2405	tm.tm_sec = tm.tm_min = tm.tm_hour = 0; // midnight current day
		2406	++tm.tm_mday; // midnight next day
		2407
		2408	return mktime (&tm);
		2409	}
		2410
		2411	Note: this code might run into trouble on days that have more then two
		2412	midnights (beginning and end).
2192		2413
2193	=back	2414	=back
2194		2415
2195	=item ev_periodic_again (loop, ev_periodic *)	2416	=item ev_periodic_again (loop, ev_periodic *)
2196		2417
…		…
2261		2482
2262	ev_periodic hourly_tick;	2483	ev_periodic hourly_tick;
2263	ev_periodic_init (&hourly_tick, clock_cb,	2484	ev_periodic_init (&hourly_tick, clock_cb,
2264	fmod (ev_now (loop), 3600.), 3600., 0);	2485	fmod (ev_now (loop), 3600.), 3600., 0);
2265	ev_periodic_start (loop, &hourly_tick);	2486	ev_periodic_start (loop, &hourly_tick);
2266		2487
2267		2488
2268	=head2 C<ev_signal> - signal me when a signal gets signalled!	2489	=head2 C<ev_signal> - signal me when a signal gets signalled!
2269		2490
2270	Signal watchers will trigger an event when the process receives a specific	2491	Signal watchers will trigger an event when the process receives a specific
2271	signal one or more times. Even though signals are very asynchronous, libev	2492	signal one or more times. Even though signals are very asynchronous, libev
…		…
2281	only within the same loop, i.e. you can watch for C<SIGINT> in your	2502	only within the same loop, i.e. you can watch for C<SIGINT> in your
2282	default loop and for C<SIGIO> in another loop, but you cannot watch for	2503	default loop and for C<SIGIO> in another loop, but you cannot watch for
2283	C<SIGINT> in both the default loop and another loop at the same time. At	2504	C<SIGINT> in both the default loop and another loop at the same time. At
2284	the moment, C<SIGCHLD> is permanently tied to the default loop.	2505	the moment, C<SIGCHLD> is permanently tied to the default loop.
2285		2506
2286	When the first watcher gets started will libev actually register something	2507	Only after the first watcher for a signal is started will libev actually
2287	with the kernel (thus it coexists with your own signal handlers as long as	2508	register something with the kernel. It thus coexists with your own signal
2288	you don't register any with libev for the same signal).	2509	handlers as long as you don't register any with libev for the same signal.
2289		2510
2290	If possible and supported, libev will install its handlers with	2511	If possible and supported, libev will install its handlers with
2291	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should	2512	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
2292	not be unduly interrupted. If you have a problem with system calls getting	2513	not be unduly interrupted. If you have a problem with system calls getting
2293	interrupted by signals you can block all signals in an C<ev_check> watcher	2514	interrupted by signals you can block all signals in an C<ev_check> watcher
…		…
2296	=head3 The special problem of inheritance over fork/execve/pthread_create	2517	=head3 The special problem of inheritance over fork/execve/pthread_create
2297		2518
2298	Both the signal mask (C<sigprocmask>) and the signal disposition	2519	Both the signal mask (C<sigprocmask>) and the signal disposition
2299	(C<sigaction>) are unspecified after starting a signal watcher (and after	2520	(C<sigaction>) are unspecified after starting a signal watcher (and after
2300	stopping it again), that is, libev might or might not block the signal,	2521	stopping it again), that is, libev might or might not block the signal,
2301	and might or might not set or restore the installed signal handler.	2522	and might or might not set or restore the installed signal handler (but
		2523	see C<EVFLAG_NOSIGMASK>).
2302		2524
2303	While this does not matter for the signal disposition (libev never	2525	While this does not matter for the signal disposition (libev never
2304	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on	2526	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
2305	C<execve>), this matters for the signal mask: many programs do not expect	2527	C<execve>), this matters for the signal mask: many programs do not expect
2306	certain signals to be blocked.	2528	certain signals to be blocked.
…		…
2319	I<has> to modify the signal mask, at least temporarily.	2541	I<has> to modify the signal mask, at least temporarily.
2320		2542
2321	So I can't stress this enough: I<If you do not reset your signal mask when	2543	So I can't stress this enough: I<If you do not reset your signal mask when
2322	you expect it to be empty, you have a race condition in your code>. This	2544	you expect it to be empty, you have a race condition in your code>. This
2323	is not a libev-specific thing, this is true for most event libraries.	2545	is not a libev-specific thing, this is true for most event libraries.
		2546
		2547	=head3 The special problem of threads signal handling
		2548
		2549	POSIX threads has problematic signal handling semantics, specifically,
		2550	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2551	threads in a process block signals, which is hard to achieve.
		2552
		2553	When you want to use sigwait (or mix libev signal handling with your own
		2554	for the same signals), you can tackle this problem by globally blocking
		2555	all signals before creating any threads (or creating them with a fully set
		2556	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2557	loops. Then designate one thread as "signal receiver thread" which handles
		2558	these signals. You can pass on any signals that libev might be interested
		2559	in by calling C<ev_feed_signal>.
2324		2560
2325	=head3 Watcher-Specific Functions and Data Members	2561	=head3 Watcher-Specific Functions and Data Members
2326		2562
2327	=over 4	2563	=over 4
2328		2564
…		…
2463		2699
2464	=head2 C<ev_stat> - did the file attributes just change?	2700	=head2 C<ev_stat> - did the file attributes just change?
2465		2701
2466	This watches a file system path for attribute changes. That is, it calls	2702	This watches a file system path for attribute changes. That is, it calls
2467	C<stat> on that path in regular intervals (or when the OS says it changed)	2703	C<stat> on that path in regular intervals (or when the OS says it changed)
2468	and sees if it changed compared to the last time, invoking the callback if	2704	and sees if it changed compared to the last time, invoking the callback
2469	it did.	2705	if it did. Starting the watcher C<stat>'s the file, so only changes that
		2706	happen after the watcher has been started will be reported.
2470		2707
2471	The path does not need to exist: changing from "path exists" to "path does	2708	The path does not need to exist: changing from "path exists" to "path does
2472	not exist" is a status change like any other. The condition "path does not	2709	not exist" is a status change like any other. The condition "path does not
2473	exist" (or more correctly "path cannot be stat'ed") is signified by the	2710	exist" (or more correctly "path cannot be stat'ed") is signified by the
2474	C<st_nlink> field being zero (which is otherwise always forced to be at	2711	C<st_nlink> field being zero (which is otherwise always forced to be at
…		…
2704	Apart from keeping your process non-blocking (which is a useful	2941	Apart from keeping your process non-blocking (which is a useful
2705	effect on its own sometimes), idle watchers are a good place to do	2942	effect on its own sometimes), idle watchers are a good place to do
2706	"pseudo-background processing", or delay processing stuff to after the	2943	"pseudo-background processing", or delay processing stuff to after the
2707	event loop has handled all outstanding events.	2944	event loop has handled all outstanding events.
2708		2945
		2946	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2947
		2948	As long as there is at least one active idle watcher, libev will never
		2949	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2950	For this to work, the idle watcher doesn't need to be invoked at all - the
		2951	lowest priority will do.
		2952
		2953	This mode of operation can be useful together with an C<ev_check> watcher,
		2954	to do something on each event loop iteration - for example to balance load
		2955	between different connections.
		2956
		2957	See L</Abusing an ev_check watcher for its side-effect> for a longer
		2958	example.
		2959
2709	=head3 Watcher-Specific Functions and Data Members	2960	=head3 Watcher-Specific Functions and Data Members
2710		2961
2711	=over 4	2962	=over 4
2712		2963
2713	=item ev_idle_init (ev_idle *, callback)	2964	=item ev_idle_init (ev_idle *, callback)
…		…
2724	callback, free it. Also, use no error checking, as usual.	2975	callback, free it. Also, use no error checking, as usual.
2725		2976
2726	static void	2977	static void
2727	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	2978	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2728	{	2979	{
		2980	// stop the watcher
		2981	ev_idle_stop (loop, w);
		2982
		2983	// now we can free it
2729	free (w);	2984	free (w);
		2985
2730	// now do something you wanted to do when the program has	2986	// now do something you wanted to do when the program has
2731	// no longer anything immediate to do.	2987	// no longer anything immediate to do.
2732	}	2988	}
2733		2989
2734	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2990	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
…		…
2736	ev_idle_start (loop, idle_watcher);	2992	ev_idle_start (loop, idle_watcher);
2737		2993
2738		2994
2739	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2995	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2740		2996
2741	Prepare and check watchers are usually (but not always) used in pairs:	2997	Prepare and check watchers are often (but not always) used in pairs:
2742	prepare watchers get invoked before the process blocks and check watchers	2998	prepare watchers get invoked before the process blocks and check watchers
2743	afterwards.	2999	afterwards.
2744		3000
2745	You I<must not> call C<ev_run> or similar functions that enter	3001	You I<must not> call C<ev_run> (or similar functions that enter the
2746	the current event loop from either C<ev_prepare> or C<ev_check>	3002	current event loop) or C<ev_loop_fork> from either C<ev_prepare> or
2747	watchers. Other loops than the current one are fine, however. The	3003	C<ev_check> watchers. Other loops than the current one are fine,
2748	rationale behind this is that you do not need to check for recursion in	3004	however. The rationale behind this is that you do not need to check
2749	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	3005	for recursion in those watchers, i.e. the sequence will always be
2750	C<ev_check> so if you have one watcher of each kind they will always be	3006	C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each
2751	called in pairs bracketing the blocking call.	3007	kind they will always be called in pairs bracketing the blocking call.
2752		3008
2753	Their main purpose is to integrate other event mechanisms into libev and	3009	Their main purpose is to integrate other event mechanisms into libev and
2754	their use is somewhat advanced. They could be used, for example, to track	3010	their use is somewhat advanced. They could be used, for example, to track
2755	variable changes, implement your own watchers, integrate net-snmp or a	3011	variable changes, implement your own watchers, integrate net-snmp or a
2756	coroutine library and lots more. They are also occasionally useful if	3012	coroutine library and lots more. They are also occasionally useful if
…		…
2774	with priority higher than or equal to the event loop and one coroutine	3030	with priority higher than or equal to the event loop and one coroutine
2775	of lower priority, but only once, using idle watchers to keep the event	3031	of lower priority, but only once, using idle watchers to keep the event
2776	loop from blocking if lower-priority coroutines are active, thus mapping	3032	loop from blocking if lower-priority coroutines are active, thus mapping
2777	low-priority coroutines to idle/background tasks).	3033	low-priority coroutines to idle/background tasks).
2778		3034
2779	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	3035	When used for this purpose, it is recommended to give C<ev_check> watchers
2780	priority, to ensure that they are being run before any other watchers	3036	highest (C<EV_MAXPRI>) priority, to ensure that they are being run before
2781	after the poll (this doesn't matter for C<ev_prepare> watchers).	3037	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		3038	watchers).
2782		3039
2783	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	3040	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
2784	activate ("feed") events into libev. While libev fully supports this, they	3041	activate ("feed") events into libev. While libev fully supports this, they
2785	might get executed before other C<ev_check> watchers did their job. As	3042	might get executed before other C<ev_check> watchers did their job. As
2786	C<ev_check> watchers are often used to embed other (non-libev) event	3043	C<ev_check> watchers are often used to embed other (non-libev) event
2787	loops those other event loops might be in an unusable state until their	3044	loops those other event loops might be in an unusable state until their
2788	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	3045	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2789	others).	3046	others).
		3047
		3048	=head3 Abusing an C<ev_check> watcher for its side-effect
		3049
		3050	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		3051	useful because they are called once per event loop iteration. For
		3052	example, if you want to handle a large number of connections fairly, you
		3053	normally only do a bit of work for each active connection, and if there
		3054	is more work to do, you wait for the next event loop iteration, so other
		3055	connections have a chance of making progress.
		3056
		3057	Using an C<ev_check> watcher is almost enough: it will be called on the
		3058	next event loop iteration. However, that isn't as soon as possible -
		3059	without external events, your C<ev_check> watcher will not be invoked.
		3060
		3061	This is where C<ev_idle> watchers come in handy - all you need is a
		3062	single global idle watcher that is active as long as you have one active
		3063	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		3064	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		3065	invoked. Neither watcher alone can do that.
2790		3066
2791	=head3 Watcher-Specific Functions and Data Members	3067	=head3 Watcher-Specific Functions and Data Members
2792		3068
2793	=over 4	3069	=over 4
2794		3070
…		…
2995		3271
2996	=over 4	3272	=over 4
2997		3273
2998	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	3274	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
2999		3275
3000	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	3276	=item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)
3001		3277
3002	Configures the watcher to embed the given loop, which must be	3278	Configures the watcher to embed the given loop, which must be
3003	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	3279	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
3004	invoked automatically, otherwise it is the responsibility of the callback	3280	invoked automatically, otherwise it is the responsibility of the callback
3005	to invoke it (it will continue to be called until the sweep has been done,	3281	to invoke it (it will continue to be called until the sweep has been done,
…		…
3026	used).	3302	used).
3027		3303
3028	struct ev_loop *loop_hi = ev_default_init (0);	3304	struct ev_loop *loop_hi = ev_default_init (0);
3029	struct ev_loop *loop_lo = 0;	3305	struct ev_loop *loop_lo = 0;
3030	ev_embed embed;	3306	ev_embed embed;
3031		3307
3032	// see if there is a chance of getting one that works	3308	// see if there is a chance of getting one that works
3033	// (remember that a flags value of 0 means autodetection)	3309	// (remember that a flags value of 0 means autodetection)
3034	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3310	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
3035	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3311	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
3036	: 0;	3312	: 0;
…		…
3050	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3326	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
3051		3327
3052	struct ev_loop *loop = ev_default_init (0);	3328	struct ev_loop *loop = ev_default_init (0);
3053	struct ev_loop *loop_socket = 0;	3329	struct ev_loop *loop_socket = 0;
3054	ev_embed embed;	3330	ev_embed embed;
3055		3331
3056	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3332	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
3057	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3333	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
3058	{	3334	{
3059	ev_embed_init (&embed, 0, loop_socket);	3335	ev_embed_init (&embed, 0, loop_socket);
3060	ev_embed_start (loop, &embed);	3336	ev_embed_start (loop, &embed);
…		…
3068		3344
3069	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3345	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
3070		3346
3071	Fork watchers are called when a C<fork ()> was detected (usually because	3347	Fork watchers are called when a C<fork ()> was detected (usually because
3072	whoever is a good citizen cared to tell libev about it by calling	3348	whoever is a good citizen cared to tell libev about it by calling
3073	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the	3349	C<ev_loop_fork>). The invocation is done before the event loop blocks next
3074	event loop blocks next and before C<ev_check> watchers are being called,	3350	and before C<ev_check> watchers are being called, and only in the child
3075	and only in the child after the fork. If whoever good citizen calling	3351	after the fork. If whoever good citizen calling C<ev_default_fork> cheats
3076	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3352	and calls it in the wrong process, the fork handlers will be invoked, too,
3077	handlers will be invoked, too, of course.	3353	of course.
3078		3354
3079	=head3 The special problem of life after fork - how is it possible?	3355	=head3 The special problem of life after fork - how is it possible?
3080		3356
3081	Most uses of C<fork()> consist of forking, then some simple calls to set	3357	Most uses of C<fork ()> consist of forking, then some simple calls to set
3082	up/change the process environment, followed by a call to C<exec()>. This	3358	up/change the process environment, followed by a call to C<exec()>. This
3083	sequence should be handled by libev without any problems.	3359	sequence should be handled by libev without any problems.
3084		3360
3085	This changes when the application actually wants to do event handling	3361	This changes when the application actually wants to do event handling
3086	in the child, or both parent in child, in effect "continuing" after the	3362	in the child, or both parent in child, in effect "continuing" after the
…		…
3163	atexit (program_exits);	3439	atexit (program_exits);
3164		3440
3165		3441
3166	=head2 C<ev_async> - how to wake up an event loop	3442	=head2 C<ev_async> - how to wake up an event loop
3167		3443
3168	In general, you cannot use an C<ev_run> from multiple threads or other	3444	In general, you cannot use an C<ev_loop> from multiple threads or other
3169	asynchronous sources such as signal handlers (as opposed to multiple event	3445	asynchronous sources such as signal handlers (as opposed to multiple event
3170	loops - those are of course safe to use in different threads).	3446	loops - those are of course safe to use in different threads).
3171		3447
3172	Sometimes, however, you need to wake up an event loop you do not control,	3448	Sometimes, however, you need to wake up an event loop you do not control,
3173	for example because it belongs to another thread. This is what C<ev_async>	3449	for example because it belongs to another thread. This is what C<ev_async>
…		…
3175	it by calling C<ev_async_send>, which is thread- and signal safe.	3451	it by calling C<ev_async_send>, which is thread- and signal safe.
3176		3452
3177	This functionality is very similar to C<ev_signal> watchers, as signals,	3453	This functionality is very similar to C<ev_signal> watchers, as signals,
3178	too, are asynchronous in nature, and signals, too, will be compressed	3454	too, are asynchronous in nature, and signals, too, will be compressed
3179	(i.e. the number of callback invocations may be less than the number of	3455	(i.e. the number of callback invocations may be less than the number of
3180	C<ev_async_sent> calls).	3456	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
3181		3457	of "global async watchers" by using a watcher on an otherwise unused
3182	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3458	signal, and C<ev_feed_signal> to signal this watcher from another thread,
3183	just the default loop.	3459	even without knowing which loop owns the signal.
3184		3460
3185	=head3 Queueing	3461	=head3 Queueing
3186		3462
3187	C<ev_async> does not support queueing of data in any way. The reason	3463	C<ev_async> does not support queueing of data in any way. The reason
3188	is that the author does not know of a simple (or any) algorithm for a	3464	is that the author does not know of a simple (or any) algorithm for a
…		…
3280	trust me.	3556	trust me.
3281		3557
3282	=item ev_async_send (loop, ev_async *)	3558	=item ev_async_send (loop, ev_async *)
3283		3559
3284	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3560	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3285	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3561	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3562	returns.
		3563
3286	C<ev_feed_event>, this call is safe to do from other threads, signal or	3564	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3287	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3565	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3288	section below on what exactly this means).	3566	embedding section below on what exactly this means).
3289		3567
3290	Note that, as with other watchers in libev, multiple events might get	3568	Note that, as with other watchers in libev, multiple events might get
3291	compressed into a single callback invocation (another way to look at this	3569	compressed into a single callback invocation (another way to look at
3292	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3570	this is that C<ev_async> watchers are level-triggered: they are set on
3293	reset when the event loop detects that).	3571	C<ev_async_send>, reset when the event loop detects that).
3294		3572
3295	This call incurs the overhead of a system call only once per event loop	3573	This call incurs the overhead of at most one extra system call per event
3296	iteration, so while the overhead might be noticeable, it doesn't apply to	3574	loop iteration, if the event loop is blocked, and no syscall at all if
3297	repeated calls to C<ev_async_send> for the same event loop.	3575	the event loop (or your program) is processing events. That means that
		3576	repeated calls are basically free (there is no need to avoid calls for
		3577	performance reasons) and that the overhead becomes smaller (typically
		3578	zero) under load.
3298		3579
3299	=item bool = ev_async_pending (ev_async *)	3580	=item bool = ev_async_pending (ev_async *)
3300		3581
3301	Returns a non-zero value when C<ev_async_send> has been called on the	3582	Returns a non-zero value when C<ev_async_send> has been called on the
3302	watcher but the event has not yet been processed (or even noted) by the	3583	watcher but the event has not yet been processed (or even noted) by the
…		…
3319		3600
3320	There are some other functions of possible interest. Described. Here. Now.	3601	There are some other functions of possible interest. Described. Here. Now.
3321		3602
3322	=over 4	3603	=over 4
3323		3604
3324	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3605	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg)
3325		3606
3326	This function combines a simple timer and an I/O watcher, calls your	3607	This function combines a simple timer and an I/O watcher, calls your
3327	callback on whichever event happens first and automatically stops both	3608	callback on whichever event happens first and automatically stops both
3328	watchers. This is useful if you want to wait for a single event on an fd	3609	watchers. This is useful if you want to wait for a single event on an fd
3329	or timeout without having to allocate/configure/start/stop/free one or	3610	or timeout without having to allocate/configure/start/stop/free one or
…		…
3357	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3638	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3358		3639
3359	=item ev_feed_fd_event (loop, int fd, int revents)	3640	=item ev_feed_fd_event (loop, int fd, int revents)
3360		3641
3361	Feed an event on the given fd, as if a file descriptor backend detected	3642	Feed an event on the given fd, as if a file descriptor backend detected
3362	the given events it.	3643	the given events.
3363		3644
3364	=item ev_feed_signal_event (loop, int signum)	3645	=item ev_feed_signal_event (loop, int signum)
3365		3646
3366	Feed an event as if the given signal occurred (C<loop> must be the default	3647	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3367	loop!).	3648	which is async-safe.
3368		3649
3369	=back	3650	=back
		3651
		3652
		3653	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3654
		3655	This section explains some common idioms that are not immediately
		3656	obvious. Note that examples are sprinkled over the whole manual, and this
		3657	section only contains stuff that wouldn't fit anywhere else.
		3658
		3659	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3660
		3661	Each watcher has, by default, a C<void *data> member that you can read
		3662	or modify at any time: libev will completely ignore it. This can be used
		3663	to associate arbitrary data with your watcher. If you need more data and
		3664	don't want to allocate memory separately and store a pointer to it in that
		3665	data member, you can also "subclass" the watcher type and provide your own
		3666	data:
		3667
		3668	struct my_io
		3669	{
		3670	ev_io io;
		3671	int otherfd;
		3672	void *somedata;
		3673	struct whatever *mostinteresting;
		3674	};
		3675
		3676	...
		3677	struct my_io w;
		3678	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3679
		3680	And since your callback will be called with a pointer to the watcher, you
		3681	can cast it back to your own type:
		3682
		3683	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3684	{
		3685	struct my_io *w = (struct my_io *)w_;
		3686	...
		3687	}
		3688
		3689	More interesting and less C-conformant ways of casting your callback
		3690	function type instead have been omitted.
		3691
		3692	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3693
		3694	Another common scenario is to use some data structure with multiple
		3695	embedded watchers, in effect creating your own watcher that combines
		3696	multiple libev event sources into one "super-watcher":
		3697
		3698	struct my_biggy
		3699	{
		3700	int some_data;
		3701	ev_timer t1;
		3702	ev_timer t2;
		3703	}
		3704
		3705	In this case getting the pointer to C<my_biggy> is a bit more
		3706	complicated: Either you store the address of your C<my_biggy> struct in
		3707	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3708	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3709	real programmers):
		3710
		3711	#include <stddef.h>
		3712
		3713	static void
		3714	t1_cb (EV_P_ ev_timer *w, int revents)
		3715	{
		3716	struct my_biggy big = (struct my_biggy *)
		3717	(((char *)w) - offsetof (struct my_biggy, t1));
		3718	}
		3719
		3720	static void
		3721	t2_cb (EV_P_ ev_timer *w, int revents)
		3722	{
		3723	struct my_biggy big = (struct my_biggy *)
		3724	(((char *)w) - offsetof (struct my_biggy, t2));
		3725	}
		3726
		3727	=head2 AVOIDING FINISHING BEFORE RETURNING
		3728
		3729	Often you have structures like this in event-based programs:
		3730
		3731	callback ()
		3732	{
		3733	free (request);
		3734	}
		3735
		3736	request = start_new_request (..., callback);
		3737
		3738	The intent is to start some "lengthy" operation. The C<request> could be
		3739	used to cancel the operation, or do other things with it.
		3740
		3741	It's not uncommon to have code paths in C<start_new_request> that
		3742	immediately invoke the callback, for example, to report errors. Or you add
		3743	some caching layer that finds that it can skip the lengthy aspects of the
		3744	operation and simply invoke the callback with the result.
		3745
		3746	The problem here is that this will happen I<before> C<start_new_request>
		3747	has returned, so C<request> is not set.
		3748
		3749	Even if you pass the request by some safer means to the callback, you
		3750	might want to do something to the request after starting it, such as
		3751	canceling it, which probably isn't working so well when the callback has
		3752	already been invoked.
		3753
		3754	A common way around all these issues is to make sure that
		3755	C<start_new_request> I<always> returns before the callback is invoked. If
		3756	C<start_new_request> immediately knows the result, it can artificially
		3757	delay invoking the callback by using a C<prepare> or C<idle> watcher for
		3758	example, or more sneakily, by reusing an existing (stopped) watcher and
		3759	pushing it into the pending queue:
		3760
		3761	ev_set_cb (watcher, callback);
		3762	ev_feed_event (EV_A_ watcher, 0);
		3763
		3764	This way, C<start_new_request> can safely return before the callback is
		3765	invoked, while not delaying callback invocation too much.
		3766
		3767	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3768
		3769	Often (especially in GUI toolkits) there are places where you have
		3770	I<modal> interaction, which is most easily implemented by recursively
		3771	invoking C<ev_run>.
		3772
		3773	This brings the problem of exiting - a callback might want to finish the
		3774	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3775	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3776	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3777	other combination: In these cases, a simple C<ev_break> will not work.
		3778
		3779	The solution is to maintain "break this loop" variable for each C<ev_run>
		3780	invocation, and use a loop around C<ev_run> until the condition is
		3781	triggered, using C<EVRUN_ONCE>:
		3782
		3783	// main loop
		3784	int exit_main_loop = 0;
		3785
		3786	while (!exit_main_loop)
		3787	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3788
		3789	// in a modal watcher
		3790	int exit_nested_loop = 0;
		3791
		3792	while (!exit_nested_loop)
		3793	ev_run (EV_A_ EVRUN_ONCE);
		3794
		3795	To exit from any of these loops, just set the corresponding exit variable:
		3796
		3797	// exit modal loop
		3798	exit_nested_loop = 1;
		3799
		3800	// exit main program, after modal loop is finished
		3801	exit_main_loop = 1;
		3802
		3803	// exit both
		3804	exit_main_loop = exit_nested_loop = 1;
		3805
		3806	=head2 THREAD LOCKING EXAMPLE
		3807
		3808	Here is a fictitious example of how to run an event loop in a different
		3809	thread from where callbacks are being invoked and watchers are
		3810	created/added/removed.
		3811
		3812	For a real-world example, see the C<EV::Loop::Async> perl module,
		3813	which uses exactly this technique (which is suited for many high-level
		3814	languages).
		3815
		3816	The example uses a pthread mutex to protect the loop data, a condition
		3817	variable to wait for callback invocations, an async watcher to notify the
		3818	event loop thread and an unspecified mechanism to wake up the main thread.
		3819
		3820	First, you need to associate some data with the event loop:
		3821
		3822	typedef struct {
		3823	mutex_t lock; /* global loop lock */
		3824	ev_async async_w;
		3825	thread_t tid;
		3826	cond_t invoke_cv;
		3827	} userdata;
		3828
		3829	void prepare_loop (EV_P)
		3830	{
		3831	// for simplicity, we use a static userdata struct.
		3832	static userdata u;
		3833
		3834	ev_async_init (&u->async_w, async_cb);
		3835	ev_async_start (EV_A_ &u->async_w);
		3836
		3837	pthread_mutex_init (&u->lock, 0);
		3838	pthread_cond_init (&u->invoke_cv, 0);
		3839
		3840	// now associate this with the loop
		3841	ev_set_userdata (EV_A_ u);
		3842	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3843	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3844
		3845	// then create the thread running ev_run
		3846	pthread_create (&u->tid, 0, l_run, EV_A);
		3847	}
		3848
		3849	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3850	solely to wake up the event loop so it takes notice of any new watchers
		3851	that might have been added:
		3852
		3853	static void
		3854	async_cb (EV_P_ ev_async *w, int revents)
		3855	{
		3856	// just used for the side effects
		3857	}
		3858
		3859	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3860	protecting the loop data, respectively.
		3861
		3862	static void
		3863	l_release (EV_P)
		3864	{
		3865	userdata *u = ev_userdata (EV_A);
		3866	pthread_mutex_unlock (&u->lock);
		3867	}
		3868
		3869	static void
		3870	l_acquire (EV_P)
		3871	{
		3872	userdata *u = ev_userdata (EV_A);
		3873	pthread_mutex_lock (&u->lock);
		3874	}
		3875
		3876	The event loop thread first acquires the mutex, and then jumps straight
		3877	into C<ev_run>:
		3878
		3879	void *
		3880	l_run (void *thr_arg)
		3881	{
		3882	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3883
		3884	l_acquire (EV_A);
		3885	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3886	ev_run (EV_A_ 0);
		3887	l_release (EV_A);
		3888
		3889	return 0;
		3890	}
		3891
		3892	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3893	signal the main thread via some unspecified mechanism (signals? pipe
		3894	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3895	have been called (in a while loop because a) spurious wakeups are possible
		3896	and b) skipping inter-thread-communication when there are no pending
		3897	watchers is very beneficial):
		3898
		3899	static void
		3900	l_invoke (EV_P)
		3901	{
		3902	userdata *u = ev_userdata (EV_A);
		3903
		3904	while (ev_pending_count (EV_A))
		3905	{
		3906	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3907	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3908	}
		3909	}
		3910
		3911	Now, whenever the main thread gets told to invoke pending watchers, it
		3912	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3913	thread to continue:
		3914
		3915	static void
		3916	real_invoke_pending (EV_P)
		3917	{
		3918	userdata *u = ev_userdata (EV_A);
		3919
		3920	pthread_mutex_lock (&u->lock);
		3921	ev_invoke_pending (EV_A);
		3922	pthread_cond_signal (&u->invoke_cv);
		3923	pthread_mutex_unlock (&u->lock);
		3924	}
		3925
		3926	Whenever you want to start/stop a watcher or do other modifications to an
		3927	event loop, you will now have to lock:
		3928
		3929	ev_timer timeout_watcher;
		3930	userdata *u = ev_userdata (EV_A);
		3931
		3932	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3933
		3934	pthread_mutex_lock (&u->lock);
		3935	ev_timer_start (EV_A_ &timeout_watcher);
		3936	ev_async_send (EV_A_ &u->async_w);
		3937	pthread_mutex_unlock (&u->lock);
		3938
		3939	Note that sending the C<ev_async> watcher is required because otherwise
		3940	an event loop currently blocking in the kernel will have no knowledge
		3941	about the newly added timer. By waking up the loop it will pick up any new
		3942	watchers in the next event loop iteration.
		3943
		3944	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3945
		3946	While the overhead of a callback that e.g. schedules a thread is small, it
		3947	is still an overhead. If you embed libev, and your main usage is with some
		3948	kind of threads or coroutines, you might want to customise libev so that
		3949	doesn't need callbacks anymore.
		3950
		3951	Imagine you have coroutines that you can switch to using a function
		3952	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3953	and that due to some magic, the currently active coroutine is stored in a
		3954	global called C<current_coro>. Then you can build your own "wait for libev
		3955	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3956	the differing C<;> conventions):
		3957
		3958	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3959	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3960
		3961	That means instead of having a C callback function, you store the
		3962	coroutine to switch to in each watcher, and instead of having libev call
		3963	your callback, you instead have it switch to that coroutine.
		3964
		3965	A coroutine might now wait for an event with a function called
		3966	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3967	matter when, or whether the watcher is active or not when this function is
		3968	called):
		3969
		3970	void
		3971	wait_for_event (ev_watcher *w)
		3972	{
		3973	ev_set_cb (w, current_coro);
		3974	switch_to (libev_coro);
		3975	}
		3976
		3977	That basically suspends the coroutine inside C<wait_for_event> and
		3978	continues the libev coroutine, which, when appropriate, switches back to
		3979	this or any other coroutine.
		3980
		3981	You can do similar tricks if you have, say, threads with an event queue -
		3982	instead of storing a coroutine, you store the queue object and instead of
		3983	switching to a coroutine, you push the watcher onto the queue and notify
		3984	any waiters.
		3985
		3986	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		3987	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3988
		3989	// my_ev.h
		3990	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3991	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3992	#include "../libev/ev.h"
		3993
		3994	// my_ev.c
		3995	#define EV_H "my_ev.h"
		3996	#include "../libev/ev.c"
		3997
		3998	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3999	F<my_ev.c> into your project. When properly specifying include paths, you
		4000	can even use F<ev.h> as header file name directly.
3370		4001
3371		4002
3372	=head1 LIBEVENT EMULATION	4003	=head1 LIBEVENT EMULATION
3373		4004
3374	Libev offers a compatibility emulation layer for libevent. It cannot	4005	Libev offers a compatibility emulation layer for libevent. It cannot
3375	emulate the internals of libevent, so here are some usage hints:	4006	emulate the internals of libevent, so here are some usage hints:
3376		4007
3377	=over 4	4008	=over 4
		4009
		4010	=item * Only the libevent-1.4.1-beta API is being emulated.
		4011
		4012	This was the newest libevent version available when libev was implemented,
		4013	and is still mostly unchanged in 2010.
3378		4014
3379	=item * Use it by including <event.h>, as usual.	4015	=item * Use it by including <event.h>, as usual.
3380		4016
3381	=item * The following members are fully supported: ev_base, ev_callback,	4017	=item * The following members are fully supported: ev_base, ev_callback,
3382	ev_arg, ev_fd, ev_res, ev_events.	4018	ev_arg, ev_fd, ev_res, ev_events.
…		…
3399		4035
3400	=back	4036	=back
3401		4037
3402	=head1 C++ SUPPORT	4038	=head1 C++ SUPPORT
3403		4039
		4040	=head2 C API
		4041
		4042	The normal C API should work fine when used from C++: both ev.h and the
		4043	libev sources can be compiled as C++. Therefore, code that uses the C API
		4044	will work fine.
		4045
		4046	Proper exception specifications might have to be added to callbacks passed
		4047	to libev: exceptions may be thrown only from watcher callbacks, all other
		4048	callbacks (allocator, syserr, loop acquire/release and periodic reschedule
		4049	callbacks) must not throw exceptions, and might need a C<noexcept>
		4050	specification. If you have code that needs to be compiled as both C and
		4051	C++ you can use the C<EV_NOEXCEPT> macro for this:
		4052
		4053	static void
		4054	fatal_error (const char *msg) EV_NOEXCEPT
		4055	{
		4056	perror (msg);
		4057	abort ();
		4058	}
		4059
		4060	...
		4061	ev_set_syserr_cb (fatal_error);
		4062
		4063	The only API functions that can currently throw exceptions are C<ev_run>,
		4064	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		4065	because it runs cleanup watchers).
		4066
		4067	Throwing exceptions in watcher callbacks is only supported if libev itself
		4068	is compiled with a C++ compiler or your C and C++ environments allow
		4069	throwing exceptions through C libraries (most do).
		4070
		4071	=head2 C++ API
		4072
3404	Libev comes with some simplistic wrapper classes for C++ that mainly allow	4073	Libev comes with some simplistic wrapper classes for C++ that mainly allow
3405	you to use some convenience methods to start/stop watchers and also change	4074	you to use some convenience methods to start/stop watchers and also change
3406	the callback model to a model using method callbacks on objects.	4075	the callback model to a model using method callbacks on objects.
3407		4076
3408	To use it,	4077	To use it,
3409		4078
3410	#include <ev++.h>	4079	#include <ev++.h>
3411		4080
3412	This automatically includes F<ev.h> and puts all of its definitions (many	4081	This automatically includes F<ev.h> and puts all of its definitions (many
3413	of them macros) into the global namespace. All C++ specific things are	4082	of them macros) into the global namespace. All C++ specific things are
3414	put into the C<ev> namespace. It should support all the same embedding	4083	put into the C<ev> namespace. It should support all the same embedding
…		…
3417	Care has been taken to keep the overhead low. The only data member the C++	4086	Care has been taken to keep the overhead low. The only data member the C++
3418	classes add (compared to plain C-style watchers) is the event loop pointer	4087	classes add (compared to plain C-style watchers) is the event loop pointer
3419	that the watcher is associated with (or no additional members at all if	4088	that the watcher is associated with (or no additional members at all if
3420	you disable C<EV_MULTIPLICITY> when embedding libev).	4089	you disable C<EV_MULTIPLICITY> when embedding libev).
3421		4090
3422	Currently, functions, and static and non-static member functions can be	4091	Currently, functions, static and non-static member functions and classes
3423	used as callbacks. Other types should be easy to add as long as they only	4092	with C<operator ()> can be used as callbacks. Other types should be easy
3424	need one additional pointer for context. If you need support for other	4093	to add as long as they only need one additional pointer for context. If
3425	types of functors please contact the author (preferably after implementing	4094	you need support for other types of functors please contact the author
3426	it).	4095	(preferably after implementing it).
		4096
		4097	For all this to work, your C++ compiler either has to use the same calling
		4098	conventions as your C compiler (for static member functions), or you have
		4099	to embed libev and compile libev itself as C++.
3427		4100
3428	Here is a list of things available in the C<ev> namespace:	4101	Here is a list of things available in the C<ev> namespace:
3429		4102
3430	=over 4	4103	=over 4
3431		4104
…		…
3441	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4114	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3442		4115
3443	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4116	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
3444	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4117	the same name in the C<ev> namespace, with the exception of C<ev_signal>
3445	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4118	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3446	defines by many implementations.	4119	defined by many implementations.
3447		4120
3448	All of those classes have these methods:	4121	All of those classes have these methods:
3449		4122
3450	=over 4	4123	=over 4
3451		4124
…		…
3513	void operator() (ev::io &w, int revents)	4186	void operator() (ev::io &w, int revents)
3514	{	4187	{
3515	...	4188	...
3516	}	4189	}
3517	}	4190	}
3518		4191
3519	myfunctor f;	4192	myfunctor f;
3520		4193
3521	ev::io w;	4194	ev::io w;
3522	w.set (&f);	4195	w.set (&f);
3523		4196
…		…
3541	Associates a different C<struct ev_loop> with this watcher. You can only	4214	Associates a different C<struct ev_loop> with this watcher. You can only
3542	do this when the watcher is inactive (and not pending either).	4215	do this when the watcher is inactive (and not pending either).
3543		4216
3544	=item w->set ([arguments])	4217	=item w->set ([arguments])
3545		4218
3546	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this	4219	Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>),
3547	method or a suitable start method must be called at least once. Unlike the	4220	with the same arguments. Either this method or a suitable start method
3548	C counterpart, an active watcher gets automatically stopped and restarted	4221	must be called at least once. Unlike the C counterpart, an active watcher
3549	when reconfiguring it with this method.	4222	gets automatically stopped and restarted when reconfiguring it with this
		4223	method.
		4224
		4225	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4226	clashing with the C<set (loop)> method.
3550		4227
3551	=item w->start ()	4228	=item w->start ()
3552		4229
3553	Starts the watcher. Note that there is no C<loop> argument, as the	4230	Starts the watcher. Note that there is no C<loop> argument, as the
3554	constructor already stores the event loop.	4231	constructor already stores the event loop.
…		…
3584	watchers in the constructor.	4261	watchers in the constructor.
3585		4262
3586	class myclass	4263	class myclass
3587	{	4264	{
3588	ev::io io ; void io_cb (ev::io &w, int revents);	4265	ev::io io ; void io_cb (ev::io &w, int revents);
3589	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);	4266	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3590	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4267	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3591		4268
3592	myclass (int fd)	4269	myclass (int fd)
3593	{	4270	{
3594	io .set <myclass, &myclass::io_cb > (this);	4271	io .set <myclass, &myclass::io_cb > (this);
…		…
3645	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4322	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3646		4323
3647	=item D	4324	=item D
3648		4325
3649	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4326	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3650	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4327	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3651		4328
3652	=item Ocaml	4329	=item Ocaml
3653		4330
3654	Erkki Seppala has written Ocaml bindings for libev, to be found at	4331	Erkki Seppala has written Ocaml bindings for libev, to be found at
3655	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4332	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
…		…
3658		4335
3659	Brian Maher has written a partial interface to libev for lua (at the	4336	Brian Maher has written a partial interface to libev for lua (at the
3660	time of this writing, only C<ev_io> and C<ev_timer>), to be found at	4337	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
3661	L<http://github.com/brimworks/lua-ev>.	4338	L<http://github.com/brimworks/lua-ev>.
3662		4339
		4340	=item Javascript
		4341
		4342	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4343
		4344	=item Others
		4345
		4346	There are others, and I stopped counting.
		4347
3663	=back	4348	=back
3664		4349
3665		4350
3666	=head1 MACRO MAGIC	4351	=head1 MACRO MAGIC
3667		4352
…		…
3703	suitable for use with C<EV_A>.	4388	suitable for use with C<EV_A>.
3704		4389
3705	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4390	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3706		4391
3707	Similar to the other two macros, this gives you the value of the default	4392	Similar to the other two macros, this gives you the value of the default
3708	loop, if multiple loops are supported ("ev loop default").	4393	loop, if multiple loops are supported ("ev loop default"). The default loop
		4394	will be initialised if it isn't already initialised.
		4395
		4396	For non-multiplicity builds, these macros do nothing, so you always have
		4397	to initialise the loop somewhere.
3709		4398
3710	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4399	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3711		4400
3712	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4401	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3713	default loop has been initialised (C<UC> == unchecked). Their behaviour	4402	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3780	ev_vars.h	4469	ev_vars.h
3781	ev_wrap.h	4470	ev_wrap.h
3782		4471
3783	ev_win32.c required on win32 platforms only	4472	ev_win32.c required on win32 platforms only
3784		4473
3785	ev_select.c only when select backend is enabled (which is enabled by default)	4474	ev_select.c only when select backend is enabled
3786	ev_poll.c only when poll backend is enabled (disabled by default)	4475	ev_poll.c only when poll backend is enabled
3787	ev_epoll.c only when the epoll backend is enabled (disabled by default)	4476	ev_epoll.c only when the epoll backend is enabled
		4477	ev_linuxaio.c only when the linux aio backend is enabled
3788	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	4478	ev_kqueue.c only when the kqueue backend is enabled
3789	ev_port.c only when the solaris port backend is enabled (disabled by default)	4479	ev_port.c only when the solaris port backend is enabled
3790		4480
3791	F<ev.c> includes the backend files directly when enabled, so you only need	4481	F<ev.c> includes the backend files directly when enabled, so you only need
3792	to compile this single file.	4482	to compile this single file.
3793		4483
3794	=head3 LIBEVENT COMPATIBILITY API	4484	=head3 LIBEVENT COMPATIBILITY API
…		…
3858	supported). It will also not define any of the structs usually found in	4548	supported). It will also not define any of the structs usually found in
3859	F<event.h> that are not directly supported by the libev core alone.	4549	F<event.h> that are not directly supported by the libev core alone.
3860		4550
3861	In standalone mode, libev will still try to automatically deduce the	4551	In standalone mode, libev will still try to automatically deduce the
3862	configuration, but has to be more conservative.	4552	configuration, but has to be more conservative.
		4553
		4554	=item EV_USE_FLOOR
		4555
		4556	If defined to be C<1>, libev will use the C<floor ()> function for its
		4557	periodic reschedule calculations, otherwise libev will fall back on a
		4558	portable (slower) implementation. If you enable this, you usually have to
		4559	link against libm or something equivalent. Enabling this when the C<floor>
		4560	function is not available will fail, so the safe default is to not enable
		4561	this.
3863		4562
3864	=item EV_USE_MONOTONIC	4563	=item EV_USE_MONOTONIC
3865		4564
3866	If defined to be C<1>, libev will try to detect the availability of the	4565	If defined to be C<1>, libev will try to detect the availability of the
3867	monotonic clock option at both compile time and runtime. Otherwise no	4566	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3953	If programs implement their own fd to handle mapping on win32, then this	4652	If programs implement their own fd to handle mapping on win32, then this
3954	macro can be used to override the C<close> function, useful to unregister	4653	macro can be used to override the C<close> function, useful to unregister
3955	file descriptors again. Note that the replacement function has to close	4654	file descriptors again. Note that the replacement function has to close
3956	the underlying OS handle.	4655	the underlying OS handle.
3957		4656
		4657	=item EV_USE_WSASOCKET
		4658
		4659	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4660	communication socket, which works better in some environments. Otherwise,
		4661	the normal C<socket> function will be used, which works better in other
		4662	environments.
		4663
3958	=item EV_USE_POLL	4664	=item EV_USE_POLL
3959		4665
3960	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4666	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3961	backend. Otherwise it will be enabled on non-win32 platforms. It	4667	backend. Otherwise it will be enabled on non-win32 platforms. It
3962	takes precedence over select.	4668	takes precedence over select.
…		…
3966	If defined to be C<1>, libev will compile in support for the Linux	4672	If defined to be C<1>, libev will compile in support for the Linux
3967	C<epoll>(7) backend. Its availability will be detected at runtime,	4673	C<epoll>(7) backend. Its availability will be detected at runtime,
3968	otherwise another method will be used as fallback. This is the preferred	4674	otherwise another method will be used as fallback. This is the preferred
3969	backend for GNU/Linux systems. If undefined, it will be enabled if the	4675	backend for GNU/Linux systems. If undefined, it will be enabled if the
3970	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4676	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		4677
		4678	=item EV_USE_LINUXAIO
		4679
		4680	If defined to be C<1>, libev will compile in support for the Linux
		4681	aio backend. Due to it's currenbt limitations it has to be requested
		4682	explicitly. If undefined, it will be enabled on linux, otherwise
		4683	disabled.
3971		4684
3972	=item EV_USE_KQUEUE	4685	=item EV_USE_KQUEUE
3973		4686
3974	If defined to be C<1>, libev will compile in support for the BSD style	4687	If defined to be C<1>, libev will compile in support for the BSD style
3975	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	4688	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
3997	If defined to be C<1>, libev will compile in support for the Linux inotify	4710	If defined to be C<1>, libev will compile in support for the Linux inotify
3998	interface to speed up C<ev_stat> watchers. Its actual availability will	4711	interface to speed up C<ev_stat> watchers. Its actual availability will
3999	be detected at runtime. If undefined, it will be enabled if the headers	4712	be detected at runtime. If undefined, it will be enabled if the headers
4000	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4713	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
4001		4714
		4715	=item EV_NO_SMP
		4716
		4717	If defined to be C<1>, libev will assume that memory is always coherent
		4718	between threads, that is, threads can be used, but threads never run on
		4719	different cpus (or different cpu cores). This reduces dependencies
		4720	and makes libev faster.
		4721
		4722	=item EV_NO_THREADS
		4723
		4724	If defined to be C<1>, libev will assume that it will never be called from
		4725	different threads (that includes signal handlers), which is a stronger
		4726	assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes
		4727	libev faster.
		4728
4002	=item EV_ATOMIC_T	4729	=item EV_ATOMIC_T
4003		4730
4004	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4731	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
4005	access is atomic with respect to other threads or signal contexts. No such	4732	access is atomic with respect to other threads or signal contexts. No
4006	type is easily found in the C language, so you can provide your own type	4733	such type is easily found in the C language, so you can provide your own
4007	that you know is safe for your purposes. It is used both for signal handler "locking"	4734	type that you know is safe for your purposes. It is used both for signal
4008	as well as for signal and thread safety in C<ev_async> watchers.	4735	handler "locking" as well as for signal and thread safety in C<ev_async>
		4736	watchers.
4009		4737
4010	In the absence of this define, libev will use C<sig_atomic_t volatile>	4738	In the absence of this define, libev will use C<sig_atomic_t volatile>
4011	(from F<signal.h>), which is usually good enough on most platforms.	4739	(from F<signal.h>), which is usually good enough on most platforms.
4012		4740
4013	=item EV_H (h)	4741	=item EV_H (h)
…		…
4040	will have the C<struct ev_loop *> as first argument, and you can create	4768	will have the C<struct ev_loop *> as first argument, and you can create
4041	additional independent event loops. Otherwise there will be no support	4769	additional independent event loops. Otherwise there will be no support
4042	for multiple event loops and there is no first event loop pointer	4770	for multiple event loops and there is no first event loop pointer
4043	argument. Instead, all functions act on the single default loop.	4771	argument. Instead, all functions act on the single default loop.
4044		4772
		4773	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4774	default loop when multiplicity is switched off - you always have to
		4775	initialise the loop manually in this case.
		4776
4045	=item EV_MINPRI	4777	=item EV_MINPRI
4046		4778
4047	=item EV_MAXPRI	4779	=item EV_MAXPRI
4048		4780
4049	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4781	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
4085	#define EV_USE_POLL 1	4817	#define EV_USE_POLL 1
4086	#define EV_CHILD_ENABLE 1	4818	#define EV_CHILD_ENABLE 1
4087	#define EV_ASYNC_ENABLE 1	4819	#define EV_ASYNC_ENABLE 1
4088		4820
4089	The actual value is a bitset, it can be a combination of the following	4821	The actual value is a bitset, it can be a combination of the following
4090	values:	4822	values (by default, all of these are enabled):
4091		4823
4092	=over 4	4824	=over 4
4093		4825
4094	=item C<1> - faster/larger code	4826	=item C<1> - faster/larger code
4095		4827
…		…
4099	code size by roughly 30% on amd64).	4831	code size by roughly 30% on amd64).
4100		4832
4101	When optimising for size, use of compiler flags such as C<-Os> with	4833	When optimising for size, use of compiler flags such as C<-Os> with
4102	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of	4834	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
4103	assertions.	4835	assertions.
		4836
		4837	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4838	(e.g. gcc with C<-Os>).
4104		4839
4105	=item C<2> - faster/larger data structures	4840	=item C<2> - faster/larger data structures
4106		4841
4107	Replaces the small 2-heap for timer management by a faster 4-heap, larger	4842	Replaces the small 2-heap for timer management by a faster 4-heap, larger
4108	hash table sizes and so on. This will usually further increase code size	4843	hash table sizes and so on. This will usually further increase code size
4109	and can additionally have an effect on the size of data structures at	4844	and can additionally have an effect on the size of data structures at
4110	runtime.	4845	runtime.
4111		4846
		4847	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4848	(e.g. gcc with C<-Os>).
		4849
4112	=item C<4> - full API configuration	4850	=item C<4> - full API configuration
4113		4851
4114	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and	4852	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
4115	enables multiplicity (C<EV_MULTIPLICITY>=1).	4853	enables multiplicity (C<EV_MULTIPLICITY>=1).
4116		4854
…		…
4146		4884
4147	With an intelligent-enough linker (gcc+binutils are intelligent enough	4885	With an intelligent-enough linker (gcc+binutils are intelligent enough
4148	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by	4886	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
4149	your program might be left out as well - a binary starting a timer and an	4887	your program might be left out as well - a binary starting a timer and an
4150	I/O watcher then might come out at only 5Kb.	4888	I/O watcher then might come out at only 5Kb.
		4889
		4890	=item EV_API_STATIC
		4891
		4892	If this symbol is defined (by default it is not), then all identifiers
		4893	will have static linkage. This means that libev will not export any
		4894	identifiers, and you cannot link against libev anymore. This can be useful
		4895	when you embed libev, only want to use libev functions in a single file,
		4896	and do not want its identifiers to be visible.
		4897
		4898	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4899	wants to use libev.
		4900
		4901	This option only works when libev is compiled with a C compiler, as C++
		4902	doesn't support the required declaration syntax.
4151		4903
4152	=item EV_AVOID_STDIO	4904	=item EV_AVOID_STDIO
4153		4905
4154	If this is set to C<1> at compiletime, then libev will avoid using stdio	4906	If this is set to C<1> at compiletime, then libev will avoid using stdio
4155	functions (printf, scanf, perror etc.). This will increase the code size	4907	functions (printf, scanf, perror etc.). This will increase the code size
…		…
4299	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	5051	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4300		5052
4301	#include "ev_cpp.h"	5053	#include "ev_cpp.h"
4302	#include "ev.c"	5054	#include "ev.c"
4303		5055
4304	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	5056	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4305		5057
4306	=head2 THREADS AND COROUTINES	5058	=head2 THREADS AND COROUTINES
4307		5059
4308	=head3 THREADS	5060	=head3 THREADS
4309		5061
…		…
4360	default loop and triggering an C<ev_async> watcher from the default loop	5112	default loop and triggering an C<ev_async> watcher from the default loop
4361	watcher callback into the event loop interested in the signal.	5113	watcher callback into the event loop interested in the signal.
4362		5114
4363	=back	5115	=back
4364		5116
4365	=head4 THREAD LOCKING EXAMPLE	5117	See also L</THREAD LOCKING EXAMPLE>.
4366
4367	Here is a fictitious example of how to run an event loop in a different
4368	thread than where callbacks are being invoked and watchers are
4369	created/added/removed.
4370
4371	For a real-world example, see the C<EV::Loop::Async> perl module,
4372	which uses exactly this technique (which is suited for many high-level
4373	languages).
4374
4375	The example uses a pthread mutex to protect the loop data, a condition
4376	variable to wait for callback invocations, an async watcher to notify the
4377	event loop thread and an unspecified mechanism to wake up the main thread.
4378
4379	First, you need to associate some data with the event loop:
4380
4381	typedef struct {
4382	mutex_t lock; /* global loop lock */
4383	ev_async async_w;
4384	thread_t tid;
4385	cond_t invoke_cv;
4386	} userdata;
4387
4388	void prepare_loop (EV_P)
4389	{
4390	// for simplicity, we use a static userdata struct.
4391	static userdata u;
4392
4393	ev_async_init (&u->async_w, async_cb);
4394	ev_async_start (EV_A_ &u->async_w);
4395
4396	pthread_mutex_init (&u->lock, 0);
4397	pthread_cond_init (&u->invoke_cv, 0);
4398
4399	// now associate this with the loop
4400	ev_set_userdata (EV_A_ u);
4401	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4402	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4403
4404	// then create the thread running ev_loop
4405	pthread_create (&u->tid, 0, l_run, EV_A);
4406	}
4407
4408	The callback for the C<ev_async> watcher does nothing: the watcher is used
4409	solely to wake up the event loop so it takes notice of any new watchers
4410	that might have been added:
4411
4412	static void
4413	async_cb (EV_P_ ev_async *w, int revents)
4414	{
4415	// just used for the side effects
4416	}
4417
4418	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4419	protecting the loop data, respectively.
4420
4421	static void
4422	l_release (EV_P)
4423	{
4424	userdata *u = ev_userdata (EV_A);
4425	pthread_mutex_unlock (&u->lock);
4426	}
4427
4428	static void
4429	l_acquire (EV_P)
4430	{
4431	userdata *u = ev_userdata (EV_A);
4432	pthread_mutex_lock (&u->lock);
4433	}
4434
4435	The event loop thread first acquires the mutex, and then jumps straight
4436	into C<ev_run>:
4437
4438	void *
4439	l_run (void *thr_arg)
4440	{
4441	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4442
4443	l_acquire (EV_A);
4444	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4445	ev_run (EV_A_ 0);
4446	l_release (EV_A);
4447
4448	return 0;
4449	}
4450
4451	Instead of invoking all pending watchers, the C<l_invoke> callback will
4452	signal the main thread via some unspecified mechanism (signals? pipe
4453	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4454	have been called (in a while loop because a) spurious wakeups are possible
4455	and b) skipping inter-thread-communication when there are no pending
4456	watchers is very beneficial):
4457
4458	static void
4459	l_invoke (EV_P)
4460	{
4461	userdata *u = ev_userdata (EV_A);
4462
4463	while (ev_pending_count (EV_A))
4464	{
4465	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4466	pthread_cond_wait (&u->invoke_cv, &u->lock);
4467	}
4468	}
4469
4470	Now, whenever the main thread gets told to invoke pending watchers, it
4471	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4472	thread to continue:
4473
4474	static void
4475	real_invoke_pending (EV_P)
4476	{
4477	userdata *u = ev_userdata (EV_A);
4478
4479	pthread_mutex_lock (&u->lock);
4480	ev_invoke_pending (EV_A);
4481	pthread_cond_signal (&u->invoke_cv);
4482	pthread_mutex_unlock (&u->lock);
4483	}
4484
4485	Whenever you want to start/stop a watcher or do other modifications to an
4486	event loop, you will now have to lock:
4487
4488	ev_timer timeout_watcher;
4489	userdata *u = ev_userdata (EV_A);
4490
4491	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4492
4493	pthread_mutex_lock (&u->lock);
4494	ev_timer_start (EV_A_ &timeout_watcher);
4495	ev_async_send (EV_A_ &u->async_w);
4496	pthread_mutex_unlock (&u->lock);
4497
4498	Note that sending the C<ev_async> watcher is required because otherwise
4499	an event loop currently blocking in the kernel will have no knowledge
4500	about the newly added timer. By waking up the loop it will pick up any new
4501	watchers in the next event loop iteration.
4502		5118
4503	=head3 COROUTINES	5119	=head3 COROUTINES
4504		5120
4505	Libev is very accommodating to coroutines ("cooperative threads"):	5121	Libev is very accommodating to coroutines ("cooperative threads"):
4506	libev fully supports nesting calls to its functions from different	5122	libev fully supports nesting calls to its functions from different
…		…
4671	requires, and its I/O model is fundamentally incompatible with the POSIX	5287	requires, and its I/O model is fundamentally incompatible with the POSIX
4672	model. Libev still offers limited functionality on this platform in	5288	model. Libev still offers limited functionality on this platform in
4673	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5289	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4674	descriptors. This only applies when using Win32 natively, not when using	5290	descriptors. This only applies when using Win32 natively, not when using
4675	e.g. cygwin. Actually, it only applies to the microsofts own compilers,	5291	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
4676	as every compielr comes with a slightly differently broken/incompatible	5292	as every compiler comes with a slightly differently broken/incompatible
4677	environment.	5293	environment.
4678		5294
4679	Lifting these limitations would basically require the full	5295	Lifting these limitations would basically require the full
4680	re-implementation of the I/O system. If you are into this kind of thing,	5296	re-implementation of the I/O system. If you are into this kind of thing,
4681	then note that glib does exactly that for you in a very portable way (note	5297	then note that glib does exactly that for you in a very portable way (note
…		…
4775	structure (guaranteed by POSIX but not by ISO C for example), but it also	5391	structure (guaranteed by POSIX but not by ISO C for example), but it also
4776	assumes that the same (machine) code can be used to call any watcher	5392	assumes that the same (machine) code can be used to call any watcher
4777	callback: The watcher callbacks have different type signatures, but libev	5393	callback: The watcher callbacks have different type signatures, but libev
4778	calls them using an C<ev_watcher *> internally.	5394	calls them using an C<ev_watcher *> internally.
4779		5395
		5396	=item null pointers and integer zero are represented by 0 bytes
		5397
		5398	Libev uses C<memset> to initialise structs and arrays to C<0> bytes, and
		5399	relies on this setting pointers and integers to null.
		5400
4780	=item pointer accesses must be thread-atomic	5401	=item pointer accesses must be thread-atomic
4781		5402
4782	Accessing a pointer value must be atomic, it must both be readable and	5403	Accessing a pointer value must be atomic, it must both be readable and
4783	writable in one piece - this is the case on all current architectures.	5404	writable in one piece - this is the case on all current architectures.
4784		5405
…		…
4797	thread" or will block signals process-wide, both behaviours would	5418	thread" or will block signals process-wide, both behaviours would
4798	be compatible with libev. Interaction between C<sigprocmask> and	5419	be compatible with libev. Interaction between C<sigprocmask> and
4799	C<pthread_sigmask> could complicate things, however.	5420	C<pthread_sigmask> could complicate things, however.
4800		5421
4801	The most portable way to handle signals is to block signals in all threads	5422	The most portable way to handle signals is to block signals in all threads
4802	except the initial one, and run the default loop in the initial thread as	5423	except the initial one, and run the signal handling loop in the initial
4803	well.	5424	thread as well.
4804		5425
4805	=item C<long> must be large enough for common memory allocation sizes	5426	=item C<long> must be large enough for common memory allocation sizes
4806		5427
4807	To improve portability and simplify its API, libev uses C<long> internally	5428	To improve portability and simplify its API, libev uses C<long> internally
4808	instead of C<size_t> when allocating its data structures. On non-POSIX	5429	instead of C<size_t> when allocating its data structures. On non-POSIX
…		…
4814		5435
4815	The type C<double> is used to represent timestamps. It is required to	5436	The type C<double> is used to represent timestamps. It is required to
4816	have at least 51 bits of mantissa (and 9 bits of exponent), which is	5437	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4817	good enough for at least into the year 4000 with millisecond accuracy	5438	good enough for at least into the year 4000 with millisecond accuracy
4818	(the design goal for libev). This requirement is overfulfilled by	5439	(the design goal for libev). This requirement is overfulfilled by
4819	implementations using IEEE 754, which is basically all existing ones. With	5440	implementations using IEEE 754, which is basically all existing ones.
		5441
4820	IEEE 754 doubles, you get microsecond accuracy until at least 2200.	5442	With IEEE 754 doubles, you get microsecond accuracy until at least the
		5443	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5444	is either obsolete or somebody patched it to use C<long double> or
		5445	something like that, just kidding).
4821		5446
4822	=back	5447	=back
4823		5448
4824	If you know of other additional requirements drop me a note.	5449	If you know of other additional requirements drop me a note.
4825		5450
…		…
4887	=item Processing ev_async_send: O(number_of_async_watchers)	5512	=item Processing ev_async_send: O(number_of_async_watchers)
4888		5513
4889	=item Processing signals: O(max_signal_number)	5514	=item Processing signals: O(max_signal_number)
4890		5515
4891	Sending involves a system call I<iff> there were no other C<ev_async_send>	5516	Sending involves a system call I<iff> there were no other C<ev_async_send>
4892	calls in the current loop iteration. Checking for async and signal events	5517	calls in the current loop iteration and the loop is currently
		5518	blocked. Checking for async and signal events involves iterating over all
4893	involves iterating over all running async watchers or all signal numbers.	5519	running async watchers or all signal numbers.
4894		5520
4895	=back	5521	=back
4896		5522
4897		5523
4898	=head1 PORTING FROM LIBEV 3.X TO 4.X	5524	=head1 PORTING FROM LIBEV 3.X TO 4.X
…		…
4907	=over 4	5533	=over 4
4908		5534
4909	=item C<EV_COMPAT3> backwards compatibility mechanism	5535	=item C<EV_COMPAT3> backwards compatibility mechanism
4910		5536
4911	The backward compatibility mechanism can be controlled by	5537	The backward compatibility mechanism can be controlled by
4912	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>	5538	C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING>
4913	section.	5539	section.
4914		5540
4915	=item C<ev_default_destroy> and C<ev_default_fork> have been removed	5541	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
4916		5542
4917	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:	5543	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
…		…
4960	=over 4	5586	=over 4
4961		5587
4962	=item active	5588	=item active
4963		5589
4964	A watcher is active as long as it has been started and not yet stopped.	5590	A watcher is active as long as it has been started and not yet stopped.
4965	See L<WATCHER STATES> for details.	5591	See L</WATCHER STATES> for details.
4966		5592
4967	=item application	5593	=item application
4968		5594
4969	In this document, an application is whatever is using libev.	5595	In this document, an application is whatever is using libev.
4970		5596
…		…
5006	watchers and events.	5632	watchers and events.
5007		5633
5008	=item pending	5634	=item pending
5009		5635
5010	A watcher is pending as soon as the corresponding event has been	5636	A watcher is pending as soon as the corresponding event has been
5011	detected. See L<WATCHER STATES> for details.	5637	detected. See L</WATCHER STATES> for details.
5012		5638
5013	=item real time	5639	=item real time
5014		5640
5015	The physical time that is observed. It is apparently strictly monotonic :)	5641	The physical time that is observed. It is apparently strictly monotonic :)
5016		5642
5017	=item wall-clock time	5643	=item wall-clock time
5018		5644
5019	The time and date as shown on clocks. Unlike real time, it can actually	5645	The time and date as shown on clocks. Unlike real time, it can actually
5020	be wrong and jump forwards and backwards, e.g. when the you adjust your	5646	be wrong and jump forwards and backwards, e.g. when you adjust your
5021	clock.	5647	clock.
5022		5648
5023	=item watcher	5649	=item watcher
5024		5650
5025	A data structure that describes interest in certain events. Watchers need	5651	A data structure that describes interest in certain events. Watchers need
…		…
5028	=back	5654	=back
5029		5655
5030	=head1 AUTHOR	5656	=head1 AUTHOR
5031		5657
5032	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael	5658	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
5033	Magnusson and Emanuele Giaquinta.	5659	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
5034		5660

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