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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
…		…
157	When libev detects a usage error such as a negative timer interval, then	159	When libev detects a usage error such as a negative timer interval, then
158	it will print a diagnostic message and abort (via the C<assert> mechanism,	160	it will print a diagnostic message and abort (via the C<assert> mechanism,
159	so C<NDEBUG> will disable this checking): these are programming errors in	161	so C<NDEBUG> will disable this checking): these are programming errors in
160	the libev caller and need to be fixed there.	162	the libev caller and need to be fixed there.
161		163
		164	Via the C<EV_FREQUENT> macro you can compile in and/or enable extensive
		165	consistency checking code inside libev that can be used to check for
		166	internal inconsistencies, suually caused by application bugs.
		167
162	Libev also has a few internal error-checking C<assert>ions, and also has	168	Libev also has a few internal error-checking C<assert>ions. These do not
163	extensive consistency checking code. These do not trigger under normal
164	circumstances, as they indicate either a bug in libev or worse.	169	trigger under normal circumstances, as they indicate either a bug in libev
		170	or worse.
165		171
166		172
167	=head1 GLOBAL FUNCTIONS	173	=head1 GLOBAL FUNCTIONS
168		174
169	These functions can be called anytime, even before initialising the	175	These functions can be called anytime, even before initialising the
…		…
174	=item ev_tstamp ev_time ()	180	=item ev_tstamp ev_time ()
175		181
176	Returns the current time as libev would use it. Please note that the	182	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	183	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	184	you actually want to know. Also interesting is the combination of
179	C<ev_update_now> and C<ev_now>.	185	C<ev_now_update> and C<ev_now>.
180		186
181	=item ev_sleep (ev_tstamp interval)	187	=item ev_sleep (ev_tstamp interval)
182		188
183	Sleep for the given interval: The current thread will be blocked until	189	Sleep for the given interval: The current thread will be blocked
184	either it is interrupted or the given time interval has passed. Basically	190	until either it is interrupted or the given time interval has
		191	passed (approximately - it might return a bit earlier even if not
		192	interrupted). Returns immediately if C<< interval <= 0 >>.
		193
185	this is a sub-second-resolution C<sleep ()>.	194	Basically this is a sub-second-resolution C<sleep ()>.
		195
		196	The range of the C<interval> is limited - libev only guarantees to work
		197	with sleep times of up to one day (C<< interval <= 86400 >>).
186		198
187	=item int ev_version_major ()	199	=item int ev_version_major ()
188		200
189	=item int ev_version_minor ()	201	=item int ev_version_minor ()
190		202
…		…
241	the current system, you would need to look at C<ev_embeddable_backends ()	253	the current system, you would need to look at C<ev_embeddable_backends ()
242	& ev_supported_backends ()>, likewise for recommended ones.	254	& ev_supported_backends ()>, likewise for recommended ones.
243		255
244	See the description of C<ev_embed> watchers for more info.	256	See the description of C<ev_embed> watchers for more info.
245		257
246	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	258	=item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())
247		259
248	Sets the allocation function to use (the prototype is similar - the	260	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	261	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	262	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	263	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
257		269
258	You could override this function in high-availability programs to, say,	270	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,	271	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.	272	or even to sleep a while and retry until some memory is available.
261		273
		274	Example: The following is the C<realloc> function that libev itself uses
		275	which should work with C<realloc> and C<free> functions of all kinds and
		276	is probably a good basis for your own implementation.
		277
		278	static void *
		279	ev_realloc_emul (void *ptr, long size) EV_NOEXCEPT
		280	{
		281	if (size)
		282	return realloc (ptr, size);
		283
		284	free (ptr);
		285	return 0;
		286	}
		287
262	Example: Replace the libev allocator with one that waits a bit and then	288	Example: Replace the libev allocator with one that waits a bit and then
263	retries (example requires a standards-compliant C<realloc>).	289	retries.
264		290
265	static void *	291	static void *
266	persistent_realloc (void *ptr, size_t size)	292	persistent_realloc (void *ptr, size_t size)
267	{	293	{
		294	if (!size)
		295	{
		296	free (ptr);
		297	return 0;
		298	}
		299
268	for (;;)	300	for (;;)
269	{	301	{
270	void *newptr = realloc (ptr, size);	302	void *newptr = realloc (ptr, size);
271		303
272	if (newptr)	304	if (newptr)
…		…
277	}	309	}
278		310
279	...	311	...
280	ev_set_allocator (persistent_realloc);	312	ev_set_allocator (persistent_realloc);
281		313
282	=item ev_set_syserr_cb (void (*cb)(const char *msg))	314	=item ev_set_syserr_cb (void (*cb)(const char *msg) throw ())
283		315
284	Set the callback function to call on a retryable system call error (such	316	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	317	as failed select, poll, epoll_wait). The message is a printable string
286	indicating the system call or subsystem causing the problem. If this	318	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	319	callback is set, then libev will expect it to remedy the situation, no
…		…
390		422
391	If this flag bit is or'ed into the flag value (or the program runs setuid	423	If this flag bit is or'ed into the flag value (or the program runs setuid
392	or setgid) then libev will I<not> look at the environment variable	424	or setgid) then libev will I<not> look at the environment variable
393	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	425	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
394	override the flags completely if it is found in the environment. This is	426	override the flags completely if it is found in the environment. This is
395	useful to try out specific backends to test their performance, or to work	427	useful to try out specific backends to test their performance, to work
396	around bugs.	428	around bugs, or to make libev threadsafe (accessing environment variables
		429	cannot be done in a threadsafe way, but usually it works if no other
		430	thread modifies them).
397		431
398	=item C<EVFLAG_FORKCHECK>	432	=item C<EVFLAG_FORKCHECK>
399		433
400	Instead of calling C<ev_loop_fork> manually after a fork, you can also	434	Instead of calling C<ev_loop_fork> manually after a fork, you can also
401	make libev check for a fork in each iteration by enabling this flag.	435	make libev check for a fork in each iteration by enabling this flag.
402		436
403	This works by calling C<getpid ()> on every iteration of the loop,	437	This works by calling C<getpid ()> on every iteration of the loop,
404	and thus this might slow down your event loop if you do a lot of loop	438	and thus this might slow down your event loop if you do a lot of loop
405	iterations and little real work, but is usually not noticeable (on my	439	iterations and little real work, but is usually not noticeable (on my
406	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	440	GNU/Linux system for example, C<getpid> is actually a simple 5-insn
407	without a system call and thus I<very> fast, but my GNU/Linux system also has	441	sequence without a system call and thus I<very> fast, but my GNU/Linux
408	C<pthread_atfork> which is even faster).	442	system also has C<pthread_atfork> which is even faster). (Update: glibc
		443	versions 2.25 apparently removed the C<getpid> optimisation again).
409		444
410	The big advantage of this flag is that you can forget about fork (and	445	The big advantage of this flag is that you can forget about fork (and
411	forget about forgetting to tell libev about forking) when you use this	446	forget about forgetting to tell libev about forking, although you still
412	flag.	447	have to ignore C<SIGPIPE>) when you use this flag.
413		448
414	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	449	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
415	environment variable.	450	environment variable.
416		451
417	=item C<EVFLAG_NOINOTIFY>	452	=item C<EVFLAG_NOINOTIFY>
…		…
435	example) that can't properly initialise their signal masks.	470	example) that can't properly initialise their signal masks.
436		471
437	=item C<EVFLAG_NOSIGMASK>	472	=item C<EVFLAG_NOSIGMASK>
438		473
439	When this flag is specified, then libev will avoid to modify the signal	474	When this flag is specified, then libev will avoid to modify the signal
440	mask. Specifically, this means you ahve to make sure signals are unblocked	475	mask. Specifically, this means you have to make sure signals are unblocked
441	when you want to receive them.	476	when you want to receive them.
442		477
443	This behaviour is useful when you want to do your own signal handling, or	478	This behaviour is useful when you want to do your own signal handling, or
444	want to handle signals only in specific threads and want to avoid libev	479	want to handle signals only in specific threads and want to avoid libev
445	unblocking the signals.	480	unblocking the signals.
446		481
447	This flag's behaviour will become the default in future versions of libev.	482	It's also required by POSIX in a threaded program, as libev calls
		483	C<sigprocmask>, whose behaviour is officially unspecified.
		484
		485	=item C<EVFLAG_NOTIMERFD>
		486
		487	When this flag is specified, the libev will avoid using a C<timerfd> to
		488	detect time jumps. It will still be able to detect time jumps, but takes
		489	longer and has a lower accuracy in doing so, but saves a file descriptor
		490	per loop.
		491
		492	The current implementation only tries to use a C<timerfd> when the first
		493	C<ev_periodic> watcher is started and falls back on other methods if it
		494	cannot be created, but this behaviour might change in the future.
448		495
449	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	496	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
450		497
451	This is your standard select(2) backend. Not I<completely> standard, as	498	This is your standard select(2) backend. Not I<completely> standard, as
452	libev tries to roll its own fd_set with no limits on the number of fds,	499	libev tries to roll its own fd_set with no limits on the number of fds,
…		…
477	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and	524	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
478	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	525	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
479		526
480	=item C<EVBACKEND_EPOLL> (value 4, Linux)	527	=item C<EVBACKEND_EPOLL> (value 4, Linux)
481		528
482	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9	529	Use the Linux-specific epoll(7) interface (for both pre- and post-2.6.9
483	kernels).	530	kernels).
484		531
485	For few fds, this backend is a bit little slower than poll and select,	532	For few fds, this backend is a bit little slower than poll and select, but
486	but it scales phenomenally better. While poll and select usually scale	533	it scales phenomenally better. While poll and select usually scale like
487	like O(total_fds) where n is the total number of fds (or the highest fd),	534	O(total_fds) where total_fds is the total number of fds (or the highest
488	epoll scales either O(1) or O(active_fds).	535	fd), epoll scales either O(1) or O(active_fds).
489		536
490	The epoll mechanism deserves honorable mention as the most misdesigned	537	The epoll mechanism deserves honorable mention as the most misdesigned
491	of the more advanced event mechanisms: mere annoyances include silently	538	of the more advanced event mechanisms: mere annoyances include silently
492	dropping file descriptors, requiring a system call per change per file	539	dropping file descriptors, requiring a system call per change per file
493	descriptor (and unnecessary guessing of parameters), problems with dup,	540	descriptor (and unnecessary guessing of parameters), problems with dup,
…		…
496	0.1ms) and so on. The biggest issue is fork races, however - if a program	543	0.1ms) and so on. The biggest issue is fork races, however - if a program
497	forks then I<both> parent and child process have to recreate the epoll	544	forks then I<both> parent and child process have to recreate the epoll
498	set, which can take considerable time (one syscall per file descriptor)	545	set, which can take considerable time (one syscall per file descriptor)
499	and is of course hard to detect.	546	and is of course hard to detect.
500		547
501	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	548	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
502	of course I<doesn't>, and epoll just loves to report events for totally	549	but of course I<doesn't>, and epoll just loves to report events for
503	I<different> file descriptors (even already closed ones, so one cannot	550	totally I<different> file descriptors (even already closed ones, so
504	even remove them from the set) than registered in the set (especially	551	one cannot even remove them from the set) than registered in the set
505	on SMP systems). Libev tries to counter these spurious notifications by	552	(especially on SMP systems). Libev tries to counter these spurious
506	employing an additional generation counter and comparing that against the	553	notifications by employing an additional generation counter and comparing
507	events to filter out spurious ones, recreating the set when required. Last	554	that against the events to filter out spurious ones, recreating the set
		555	when required. Epoll also erroneously rounds down timeouts, but gives you
		556	no way to know when and by how much, so sometimes you have to busy-wait
		557	because epoll returns immediately despite a nonzero timeout. And last
508	not least, it also refuses to work with some file descriptors which work	558	not least, it also refuses to work with some file descriptors which work
509	perfectly fine with C<select> (files, many character devices...).	559	perfectly fine with C<select> (files, many character devices...).
510		560
511	Epoll is truly the train wreck analog among event poll mechanisms,	561	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
512	a frankenpoll, cobbled together in a hurry, no thought to design or	562	cobbled together in a hurry, no thought to design or interaction with
513	interaction with others.	563	others. Oh, the pain, will it ever stop...
514		564
515	While stopping, setting and starting an I/O watcher in the same iteration	565	While stopping, setting and starting an I/O watcher in the same iteration
516	will result in some caching, there is still a system call per such	566	will result in some caching, there is still a system call per such
517	incident (because the same I<file descriptor> could point to a different	567	incident (because the same I<file descriptor> could point to a different
518	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	568	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
530	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or	580	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
531	faster than epoll for maybe up to a hundred file descriptors, depending on	581	faster than epoll for maybe up to a hundred file descriptors, depending on
532	the usage. So sad.	582	the usage. So sad.
533		583
534	While nominally embeddable in other event loops, this feature is broken in	584	While nominally embeddable in other event loops, this feature is broken in
535	all kernel versions tested so far.	585	a lot of kernel revisions, but probably(!) works in current versions.
536		586
537	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	587	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
538	C<EVBACKEND_POLL>.	588	C<EVBACKEND_POLL>.
539		589
		590	=item C<EVBACKEND_LINUXAIO> (value 64, Linux)
		591
		592	Use the Linux-specific Linux AIO (I<not> C<< aio(7) >> but C<<
		593	io_submit(2) >>) event interface available in post-4.18 kernels (but libev
		594	only tries to use it in 4.19+).
		595
		596	This is another Linux train wreck of an event interface.
		597
		598	If this backend works for you (as of this writing, it was very
		599	experimental), it is the best event interface available on Linux and might
		600	be well worth enabling it - if it isn't available in your kernel this will
		601	be detected and this backend will be skipped.
		602
		603	This backend can batch oneshot requests and supports a user-space ring
		604	buffer to receive events. It also doesn't suffer from most of the design
		605	problems of epoll (such as not being able to remove event sources from
		606	the epoll set), and generally sounds too good to be true. Because, this
		607	being the Linux kernel, of course it suffers from a whole new set of
		608	limitations, forcing you to fall back to epoll, inheriting all its design
		609	issues.
		610
		611	For one, it is not easily embeddable (but probably could be done using
		612	an event fd at some extra overhead). It also is subject to a system wide
		613	limit that can be configured in F</proc/sys/fs/aio-max-nr>. If no AIO
		614	requests are left, this backend will be skipped during initialisation, and
		615	will switch to epoll when the loop is active.
		616
		617	Most problematic in practice, however, is that not all file descriptors
		618	work with it. For example, in Linux 5.1, TCP sockets, pipes, event fds,
		619	files, F</dev/null> and many others are supported, but ttys do not work
		620	properly (a known bug that the kernel developers don't care about, see
		621	L<https://lore.kernel.org/patchwork/patch/1047453/>), so this is not
		622	(yet?) a generic event polling interface.
		623
		624	Overall, it seems the Linux developers just don't want it to have a
		625	generic event handling mechanism other than C<select> or C<poll>.
		626
		627	To work around all these problem, the current version of libev uses its
		628	epoll backend as a fallback for file descriptor types that do not work. Or
		629	falls back completely to epoll if the kernel acts up.
		630
		631	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		632	C<EVBACKEND_POLL>.
		633
540	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	634	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
541		635
542	Kqueue deserves special mention, as at the time of this writing, it	636	Kqueue deserves special mention, as at the time this backend was
543	was broken on all BSDs except NetBSD (usually it doesn't work reliably	637	implemented, it was broken on all BSDs except NetBSD (usually it doesn't
544	with anything but sockets and pipes, except on Darwin, where of course	638	work reliably with anything but sockets and pipes, except on Darwin,
545	it's completely useless). Unlike epoll, however, whose brokenness	639	where of course it's completely useless). Unlike epoll, however, whose
546	is by design, these kqueue bugs can (and eventually will) be fixed	640	brokenness is by design, these kqueue bugs can be (and mostly have been)
547	without API changes to existing programs. For this reason it's not being	641	fixed without API changes to existing programs. For this reason it's not
548	"auto-detected" unless you explicitly specify it in the flags (i.e. using	642	being "auto-detected" on all platforms unless you explicitly specify it
549	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	643	in the flags (i.e. using C<EVBACKEND_KQUEUE>) or libev was compiled on a
550	system like NetBSD.	644	known-to-be-good (-enough) system like NetBSD.
551		645
552	You still can embed kqueue into a normal poll or select backend and use it	646	You still can embed kqueue into a normal poll or select backend and use it
553	only for sockets (after having made sure that sockets work with kqueue on	647	only for sockets (after having made sure that sockets work with kqueue on
554	the target platform). See C<ev_embed> watchers for more info.	648	the target platform). See C<ev_embed> watchers for more info.
555		649
556	It scales in the same way as the epoll backend, but the interface to the	650	It scales in the same way as the epoll backend, but the interface to the
557	kernel is more efficient (which says nothing about its actual speed, of	651	kernel is more efficient (which says nothing about its actual speed, of
558	course). While stopping, setting and starting an I/O watcher does never	652	course). While stopping, setting and starting an I/O watcher does never
559	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	653	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
560	two event changes per incident. Support for C<fork ()> is very bad (but	654	two event changes per incident. Support for C<fork ()> is very bad (you
561	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect	655	might have to leak fds on fork, but it's more sane than epoll) and it
562	cases	656	drops fds silently in similarly hard-to-detect cases.
563		657
564	This backend usually performs well under most conditions.	658	This backend usually performs well under most conditions.
565		659
566	While nominally embeddable in other event loops, this doesn't work	660	While nominally embeddable in other event loops, this doesn't work
567	everywhere, so you might need to test for this. And since it is broken	661	everywhere, so you might need to test for this. And since it is broken
…		…
596	among the OS-specific backends (I vastly prefer correctness over speed	690	among the OS-specific backends (I vastly prefer correctness over speed
597	hacks).	691	hacks).
598		692
599	On the negative side, the interface is I<bizarre> - so bizarre that	693	On the negative side, the interface is I<bizarre> - so bizarre that
600	even sun itself gets it wrong in their code examples: The event polling	694	even sun itself gets it wrong in their code examples: The event polling
601	function sometimes returning events to the caller even though an error	695	function sometimes returns events to the caller even though an error
602	occurred, but with no indication whether it has done so or not (yes, it's	696	occurred, but with no indication whether it has done so or not (yes, it's
603	even documented that way) - deadly for edge-triggered interfaces where	697	even documented that way) - deadly for edge-triggered interfaces where you
604	you absolutely have to know whether an event occurred or not because you	698	absolutely have to know whether an event occurred or not because you have
605	have to re-arm the watcher.	699	to re-arm the watcher.
606		700
607	Fortunately libev seems to be able to work around these idiocies.	701	Fortunately libev seems to be able to work around these idiocies.
608		702
609	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	703	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
610	C<EVBACKEND_POLL>.	704	C<EVBACKEND_POLL>.
…		…
640		734
641	Example: Use whatever libev has to offer, but make sure that kqueue is	735	Example: Use whatever libev has to offer, but make sure that kqueue is
642	used if available.	736	used if available.
643		737
644	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);	738	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		739
		740	Example: Similarly, on linux, you mgiht want to take advantage of the
		741	linux aio backend if possible, but fall back to something else if that
		742	isn't available.
		743
		744	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_LINUXAIO);
645		745
646	=item ev_loop_destroy (loop)	746	=item ev_loop_destroy (loop)
647		747
648	Destroys an event loop object (frees all memory and kernel state	748	Destroys an event loop object (frees all memory and kernel state
649	etc.). None of the active event watchers will be stopped in the normal	749	etc.). None of the active event watchers will be stopped in the normal
…		…
666	If you need dynamically allocated loops it is better to use C<ev_loop_new>	766	If you need dynamically allocated loops it is better to use C<ev_loop_new>
667	and C<ev_loop_destroy>.	767	and C<ev_loop_destroy>.
668		768
669	=item ev_loop_fork (loop)	769	=item ev_loop_fork (loop)
670		770
671	This function sets a flag that causes subsequent C<ev_run> iterations to	771	This function sets a flag that causes subsequent C<ev_run> iterations
672	reinitialise the kernel state for backends that have one. Despite the	772	to reinitialise the kernel state for backends that have one. Despite
673	name, you can call it anytime, but it makes most sense after forking, in	773	the name, you can call it anytime you are allowed to start or stop
674	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the	774	watchers (except inside an C<ev_prepare> callback), but it makes most
		775	sense after forking, in the child process. You I<must> call it (or use
675	child before resuming or calling C<ev_run>.	776	C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>.
676		777
		778	In addition, if you want to reuse a loop (via this function or
		779	C<EVFLAG_FORKCHECK>), you I<also> have to ignore C<SIGPIPE>.
		780
677	Again, you I<have> to call it on I<any> loop that you want to re-use after	781	Again, you I<have> to call it on I<any> loop that you want to re-use after
678	a fork, I<even if you do not plan to use the loop in the parent>. This is	782	a fork, I<even if you do not plan to use the loop in the parent>. This is
679	because some kernel interfaces *cough* I<kqueue> *cough* do funny things	783	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
680	during fork.	784	during fork.
681		785
682	On the other hand, you only need to call this function in the child	786	On the other hand, you only need to call this function in the child
…		…
752		856
753	This function is rarely useful, but when some event callback runs for a	857	This function is rarely useful, but when some event callback runs for a
754	very long time without entering the event loop, updating libev's idea of	858	very long time without entering the event loop, updating libev's idea of
755	the current time is a good idea.	859	the current time is a good idea.
756		860
757	See also L<The special problem of time updates> in the C<ev_timer> section.	861	See also L</The special problem of time updates> in the C<ev_timer> section.
758		862
759	=item ev_suspend (loop)	863	=item ev_suspend (loop)
760		864
761	=item ev_resume (loop)	865	=item ev_resume (loop)
762		866
…		…
780	without a previous call to C<ev_suspend>.	884	without a previous call to C<ev_suspend>.
781		885
782	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	886	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
783	event loop time (see C<ev_now_update>).	887	event loop time (see C<ev_now_update>).
784		888
785	=item ev_run (loop, int flags)	889	=item bool ev_run (loop, int flags)
786		890
787	Finally, this is it, the event handler. This function usually is called	891	Finally, this is it, the event handler. This function usually is called
788	after you have initialised all your watchers and you want to start	892	after you have initialised all your watchers and you want to start
789	handling events. It will ask the operating system for any new events, call	893	handling events. It will ask the operating system for any new events, call
790	the watcher callbacks, an then repeat the whole process indefinitely: This	894	the watcher callbacks, and then repeat the whole process indefinitely: This
791	is why event loops are called I<loops>.	895	is why event loops are called I<loops>.
792		896
793	If the flags argument is specified as C<0>, it will keep handling events	897	If the flags argument is specified as C<0>, it will keep handling events
794	until either no event watchers are active anymore or C<ev_break> was	898	until either no event watchers are active anymore or C<ev_break> was
795	called.	899	called.
		900
		901	The return value is false if there are no more active watchers (which
		902	usually means "all jobs done" or "deadlock"), and true in all other cases
		903	(which usually means " you should call C<ev_run> again").
796		904
797	Please note that an explicit C<ev_break> is usually better than	905	Please note that an explicit C<ev_break> is usually better than
798	relying on all watchers to be stopped when deciding when a program has	906	relying on all watchers to be stopped when deciding when a program has
799	finished (especially in interactive programs), but having a program	907	finished (especially in interactive programs), but having a program
800	that automatically loops as long as it has to and no longer by virtue	908	that automatically loops as long as it has to and no longer by virtue
801	of relying on its watchers stopping correctly, that is truly a thing of	909	of relying on its watchers stopping correctly, that is truly a thing of
802	beauty.	910	beauty.
803		911
804	This function is also I<mostly> exception-safe - you can break out of	912	This function is I<mostly> exception-safe - you can break out of a
805	a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++	913	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
806	exception and so on. This does not decrement the C<ev_depth> value, nor	914	exception and so on. This does not decrement the C<ev_depth> value, nor
807	will it clear any outstanding C<EVBREAK_ONE> breaks.	915	will it clear any outstanding C<EVBREAK_ONE> breaks.
808		916
809	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle	917	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
810	those events and any already outstanding ones, but will not wait and	918	those events and any already outstanding ones, but will not wait and
…		…
822	This is useful if you are waiting for some external event in conjunction	930	This is useful if you are waiting for some external event in conjunction
823	with something not expressible using other libev watchers (i.e. "roll your	931	with something not expressible using other libev watchers (i.e. "roll your
824	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	932	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
825	usually a better approach for this kind of thing.	933	usually a better approach for this kind of thing.
826		934
827	Here are the gory details of what C<ev_run> does:	935	Here are the gory details of what C<ev_run> does (this is for your
		936	understanding, not a guarantee that things will work exactly like this in
		937	future versions):
828		938
829	- Increment loop depth.	939	- Increment loop depth.
830	- Reset the ev_break status.	940	- Reset the ev_break status.
831	- Before the first iteration, call any pending watchers.	941	- Before the first iteration, call any pending watchers.
832	LOOP:	942	LOOP:
…		…
865	anymore.	975	anymore.
866		976
867	... queue jobs here, make sure they register event watchers as long	977	... queue jobs here, make sure they register event watchers as long
868	... as they still have work to do (even an idle watcher will do..)	978	... as they still have work to do (even an idle watcher will do..)
869	ev_run (my_loop, 0);	979	ev_run (my_loop, 0);
870	... jobs done or somebody called unloop. yeah!	980	... jobs done or somebody called break. yeah!
871		981
872	=item ev_break (loop, how)	982	=item ev_break (loop, how)
873		983
874	Can be used to make a call to C<ev_run> return early (but only after it	984	Can be used to make a call to C<ev_run> return early (but only after it
875	has processed all outstanding events). The C<how> argument must be either	985	has processed all outstanding events). The C<how> argument must be either
…		…
938	overhead for the actual polling but can deliver many events at once.	1048	overhead for the actual polling but can deliver many events at once.
939		1049
940	By setting a higher I<io collect interval> you allow libev to spend more	1050	By setting a higher I<io collect interval> you allow libev to spend more
941	time collecting I/O events, so you can handle more events per iteration,	1051	time collecting I/O events, so you can handle more events per iteration,
942	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	1052	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
943	C<ev_timer>) will be not affected. Setting this to a non-null value will	1053	C<ev_timer>) will not be affected. Setting this to a non-null value will
944	introduce an additional C<ev_sleep ()> call into most loop iterations. The	1054	introduce an additional C<ev_sleep ()> call into most loop iterations. The
945	sleep time ensures that libev will not poll for I/O events more often then	1055	sleep time ensures that libev will not poll for I/O events more often then
946	once per this interval, on average.	1056	once per this interval, on average (as long as the host time resolution is
		1057	good enough).
947		1058
948	Likewise, by setting a higher I<timeout collect interval> you allow libev	1059	Likewise, by setting a higher I<timeout collect interval> you allow libev
949	to spend more time collecting timeouts, at the expense of increased	1060	to spend more time collecting timeouts, at the expense of increased
950	latency/jitter/inexactness (the watcher callback will be called	1061	latency/jitter/inexactness (the watcher callback will be called
951	later). C<ev_io> watchers will not be affected. Setting this to a non-null	1062	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
997	invoke the actual watchers inside another context (another thread etc.).	1108	invoke the actual watchers inside another context (another thread etc.).
998		1109
999	If you want to reset the callback, use C<ev_invoke_pending> as new	1110	If you want to reset the callback, use C<ev_invoke_pending> as new
1000	callback.	1111	callback.
1001		1112
1002	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))	1113	=item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())
1003		1114
1004	Sometimes you want to share the same loop between multiple threads. This	1115	Sometimes you want to share the same loop between multiple threads. This
1005	can be done relatively simply by putting mutex_lock/unlock calls around	1116	can be done relatively simply by putting mutex_lock/unlock calls around
1006	each call to a libev function.	1117	each call to a libev function.
1007		1118
1008	However, C<ev_run> can run an indefinite time, so it is not feasible	1119	However, C<ev_run> can run an indefinite time, so it is not feasible
1009	to wait for it to return. One way around this is to wake up the event	1120	to wait for it to return. One way around this is to wake up the event
1010	loop via C<ev_break> and C<av_async_send>, another way is to set these	1121	loop via C<ev_break> and C<ev_async_send>, another way is to set these
1011	I<release> and I<acquire> callbacks on the loop.	1122	I<release> and I<acquire> callbacks on the loop.
1012		1123
1013	When set, then C<release> will be called just before the thread is	1124	When set, then C<release> will be called just before the thread is
1014	suspended waiting for new events, and C<acquire> is called just	1125	suspended waiting for new events, and C<acquire> is called just
1015	afterwards.	1126	afterwards.
…		…
1107	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher	1218	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
1108	*) >>), and you can stop watching for events at any time by calling the	1219	*) >>), and you can stop watching for events at any time by calling the
1109	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.	1220	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
1110		1221
1111	As long as your watcher is active (has been started but not stopped) you	1222	As long as your watcher is active (has been started but not stopped) you
1112	must not touch the values stored in it. Most specifically you must never	1223	must not touch the values stored in it except when explicitly documented
1113	reinitialise it or call its C<ev_TYPE_set> macro.	1224	otherwise. Most specifically you must never reinitialise it or call its
		1225	C<ev_TYPE_set> macro.
1114		1226
1115	Each and every callback receives the event loop pointer as first, the	1227	Each and every callback receives the event loop pointer as first, the
1116	registered watcher structure as second, and a bitset of received events as	1228	registered watcher structure as second, and a bitset of received events as
1117	third argument.	1229	third argument.
1118		1230
…		…
1155		1267
1156	=item C<EV_PREPARE>	1268	=item C<EV_PREPARE>
1157		1269
1158	=item C<EV_CHECK>	1270	=item C<EV_CHECK>
1159		1271
1160	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts	1272	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to
1161	to gather new events, and all C<ev_check> watchers are invoked just after	1273	gather new events, and all C<ev_check> watchers are queued (not invoked)
1162	C<ev_run> has gathered them, but before it invokes any callbacks for any	1274	just after C<ev_run> has gathered them, but before it queues any callbacks
		1275	for any received events. That means C<ev_prepare> watchers are the last
		1276	watchers invoked before the event loop sleeps or polls for new events, and
		1277	C<ev_check> watchers will be invoked before any other watchers of the same
		1278	or lower priority within an event loop iteration.
		1279
1163	received events. Callbacks of both watcher types can start and stop as	1280	Callbacks of both watcher types can start and stop as many watchers as
1164	many watchers as they want, and all of them will be taken into account	1281	they want, and all of them will be taken into account (for example, a
1165	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1282	C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from
1166	C<ev_run> from blocking).	1283	blocking).
1167		1284
1168	=item C<EV_EMBED>	1285	=item C<EV_EMBED>
1169		1286
1170	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1287	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1171		1288
…		…
1279		1396
1280	=item bool ev_is_active (ev_TYPE *watcher)	1397	=item bool ev_is_active (ev_TYPE *watcher)
1281		1398
1282	Returns a true value iff the watcher is active (i.e. it has been started	1399	Returns a true value iff the watcher is active (i.e. it has been started
1283	and not yet been stopped). As long as a watcher is active you must not modify	1400	and not yet been stopped). As long as a watcher is active you must not modify
1284	it.	1401	it unless documented otherwise.
1285		1402
1286	=item bool ev_is_pending (ev_TYPE *watcher)	1403	=item bool ev_is_pending (ev_TYPE *watcher)
1287		1404
1288	Returns a true value iff the watcher is pending, (i.e. it has outstanding	1405	Returns a true value iff the watcher is pending, (i.e. it has outstanding
1289	events but its callback has not yet been invoked). As long as a watcher	1406	events but its callback has not yet been invoked). As long as a watcher
…		…
1294		1411
1295	=item callback ev_cb (ev_TYPE *watcher)	1412	=item callback ev_cb (ev_TYPE *watcher)
1296		1413
1297	Returns the callback currently set on the watcher.	1414	Returns the callback currently set on the watcher.
1298		1415
1299	=item ev_cb_set (ev_TYPE *watcher, callback)	1416	=item ev_set_cb (ev_TYPE *watcher, callback)
1300		1417
1301	Change the callback. You can change the callback at virtually any time	1418	Change the callback. You can change the callback at virtually any time
1302	(modulo threads).	1419	(modulo threads).
1303		1420
1304	=item ev_set_priority (ev_TYPE *watcher, int priority)	1421	=item ev_set_priority (ev_TYPE *watcher, int priority)
…		…
1322	or might not have been clamped to the valid range.	1439	or might not have been clamped to the valid range.
1323		1440
1324	The default priority used by watchers when no priority has been set is	1441	The default priority used by watchers when no priority has been set is
1325	always C<0>, which is supposed to not be too high and not be too low :).	1442	always C<0>, which is supposed to not be too high and not be too low :).
1326		1443
1327	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of	1444	See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1328	priorities.	1445	priorities.
1329		1446
1330	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1447	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1331		1448
1332	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1449	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
…		…
1357	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related	1474	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1358	functions that do not need a watcher.	1475	functions that do not need a watcher.
1359		1476
1360	=back	1477	=back
1361		1478
1362	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1479	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
1363		1480	OWN COMPOSITE WATCHERS> idioms.
1364	Each watcher has, by default, a member C<void *data> that you can change
1365	and read at any time: libev will completely ignore it. This can be used
1366	to associate arbitrary data with your watcher. If you need more data and
1367	don't want to allocate memory and store a pointer to it in that data
1368	member, you can also "subclass" the watcher type and provide your own
1369	data:
1370
1371	struct my_io
1372	{
1373	ev_io io;
1374	int otherfd;
1375	void *somedata;
1376	struct whatever *mostinteresting;
1377	};
1378
1379	...
1380	struct my_io w;
1381	ev_io_init (&w.io, my_cb, fd, EV_READ);
1382
1383	And since your callback will be called with a pointer to the watcher, you
1384	can cast it back to your own type:
1385
1386	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1387	{
1388	struct my_io *w = (struct my_io *)w_;
1389	...
1390	}
1391
1392	More interesting and less C-conformant ways of casting your callback type
1393	instead have been omitted.
1394
1395	Another common scenario is to use some data structure with multiple
1396	embedded watchers:
1397
1398	struct my_biggy
1399	{
1400	int some_data;
1401	ev_timer t1;
1402	ev_timer t2;
1403	}
1404
1405	In this case getting the pointer to C<my_biggy> is a bit more
1406	complicated: Either you store the address of your C<my_biggy> struct
1407	in the C<data> member of the watcher (for woozies), or you need to use
1408	some pointer arithmetic using C<offsetof> inside your watchers (for real
1409	programmers):
1410
1411	#include <stddef.h>
1412
1413	static void
1414	t1_cb (EV_P_ ev_timer *w, int revents)
1415	{
1416	struct my_biggy big = (struct my_biggy *)
1417	(((char *)w) - offsetof (struct my_biggy, t1));
1418	}
1419
1420	static void
1421	t2_cb (EV_P_ ev_timer *w, int revents)
1422	{
1423	struct my_biggy big = (struct my_biggy *)
1424	(((char *)w) - offsetof (struct my_biggy, t2));
1425	}
1426		1481
1427	=head2 WATCHER STATES	1482	=head2 WATCHER STATES
1428		1483
1429	There are various watcher states mentioned throughout this manual -	1484	There are various watcher states mentioned throughout this manual -
1430	active, pending and so on. In this section these states and the rules to	1485	active, pending and so on. In this section these states and the rules to
1431	transition between them will be described in more detail - and while these	1486	transition between them will be described in more detail - and while these
1432	rules might look complicated, they usually do "the right thing".	1487	rules might look complicated, they usually do "the right thing".
1433		1488
1434	=over 4	1489	=over 4
1435		1490
1436	=item initialiased	1491	=item initialised
1437		1492
1438	Before a watcher can be registered with the event looop it has to be	1493	Before a watcher can be registered with the event loop it has to be
1439	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to	1494	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
1440	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.	1495	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1441		1496
1442	In this state it is simply some block of memory that is suitable for use	1497	In this state it is simply some block of memory that is suitable for
1443	in an event loop. It can be moved around, freed, reused etc. at will.	1498	use in an event loop. It can be moved around, freed, reused etc. at
		1499	will - as long as you either keep the memory contents intact, or call
		1500	C<ev_TYPE_init> again.
1444		1501
1445	=item started/running/active	1502	=item started/running/active
1446		1503
1447	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes	1504	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1448	property of the event loop, and is actively waiting for events. While in	1505	property of the event loop, and is actively waiting for events. While in
…		…
1476	latter will clear any pending state the watcher might be in, regardless	1533	latter will clear any pending state the watcher might be in, regardless
1477	of whether it was active or not, so stopping a watcher explicitly before	1534	of whether it was active or not, so stopping a watcher explicitly before
1478	freeing it is often a good idea.	1535	freeing it is often a good idea.
1479		1536
1480	While stopped (and not pending) the watcher is essentially in the	1537	While stopped (and not pending) the watcher is essentially in the
1481	initialised state, that is it can be reused, moved, modified in any way	1538	initialised state, that is, it can be reused, moved, modified in any way
1482	you wish.	1539	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1540	it again).
1483		1541
1484	=back	1542	=back
1485		1543
1486	=head2 WATCHER PRIORITY MODELS	1544	=head2 WATCHER PRIORITY MODELS
1487		1545
1488	Many event loops support I<watcher priorities>, which are usually small	1546	Many event loops support I<watcher priorities>, which are usually small
1489	integers that influence the ordering of event callback invocation	1547	integers that influence the ordering of event callback invocation
1490	between watchers in some way, all else being equal.	1548	between watchers in some way, all else being equal.
1491		1549
1492	In libev, Watcher priorities can be set using C<ev_set_priority>. See its	1550	In libev, watcher priorities can be set using C<ev_set_priority>. See its
1493	description for the more technical details such as the actual priority	1551	description for the more technical details such as the actual priority
1494	range.	1552	range.
1495		1553
1496	There are two common ways how these these priorities are being interpreted	1554	There are two common ways how these these priorities are being interpreted
1497	by event loops:	1555	by event loops:
…		…
1591		1649
1592	This section describes each watcher in detail, but will not repeat	1650	This section describes each watcher in detail, but will not repeat
1593	information given in the last section. Any initialisation/set macros,	1651	information given in the last section. Any initialisation/set macros,
1594	functions and members specific to the watcher type are explained.	1652	functions and members specific to the watcher type are explained.
1595		1653
1596	Members are additionally marked with either I<[read-only]>, meaning that,	1654	Most members are additionally marked with either I<[read-only]>, meaning
1597	while the watcher is active, you can look at the member and expect some	1655	that, while the watcher is active, you can look at the member and expect
1598	sensible content, but you must not modify it (you can modify it while the	1656	some sensible content, but you must not modify it (you can modify it while
1599	watcher is stopped to your hearts content), or I<[read-write]>, which	1657	the watcher is stopped to your hearts content), or I<[read-write]>, which
1600	means you can expect it to have some sensible content while the watcher	1658	means you can expect it to have some sensible content while the watcher is
1601	is active, but you can also modify it. Modifying it may not do something	1659	active, but you can also modify it (within the same thread as the event
		1660	loop, i.e. without creating data races). Modifying it may not do something
1602	sensible or take immediate effect (or do anything at all), but libev will	1661	sensible or take immediate effect (or do anything at all), but libev will
1603	not crash or malfunction in any way.	1662	not crash or malfunction in any way.
1604		1663
		1664	In any case, the documentation for each member will explain what the
		1665	effects are, and if there are any additional access restrictions.
1605		1666
1606	=head2 C<ev_io> - is this file descriptor readable or writable?	1667	=head2 C<ev_io> - is this file descriptor readable or writable?
1607		1668
1608	I/O watchers check whether a file descriptor is readable or writable	1669	I/O watchers check whether a file descriptor is readable or writable
1609	in each iteration of the event loop, or, more precisely, when reading	1670	in each iteration of the event loop, or, more precisely, when reading
…		…
1636		1697
1637	But really, best use non-blocking mode.	1698	But really, best use non-blocking mode.
1638		1699
1639	=head3 The special problem of disappearing file descriptors	1700	=head3 The special problem of disappearing file descriptors
1640		1701
1641	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1702	Some backends (e.g. kqueue, epoll, linuxaio) need to be told about closing
1642	descriptor (either due to calling C<close> explicitly or any other means,	1703	a file descriptor (either due to calling C<close> explicitly or any other
1643	such as C<dup2>). The reason is that you register interest in some file	1704	means, such as C<dup2>). The reason is that you register interest in some
1644	descriptor, but when it goes away, the operating system will silently drop	1705	file descriptor, but when it goes away, the operating system will silently
1645	this interest. If another file descriptor with the same number then is	1706	drop this interest. If another file descriptor with the same number then
1646	registered with libev, there is no efficient way to see that this is, in	1707	is registered with libev, there is no efficient way to see that this is,
1647	fact, a different file descriptor.	1708	in fact, a different file descriptor.
1648		1709
1649	To avoid having to explicitly tell libev about such cases, libev follows	1710	To avoid having to explicitly tell libev about such cases, libev follows
1650	the following policy: Each time C<ev_io_set> is being called, libev	1711	the following policy: Each time C<ev_io_set> is being called, libev
1651	will assume that this is potentially a new file descriptor, otherwise	1712	will assume that this is potentially a new file descriptor, otherwise
1652	it is assumed that the file descriptor stays the same. That means that	1713	it is assumed that the file descriptor stays the same. That means that
…		…
1680	always get a readiness notification instantly, and your read (or possibly	1741	always get a readiness notification instantly, and your read (or possibly
1681	write) will still block on the disk I/O.	1742	write) will still block on the disk I/O.
1682		1743
1683	Another way to view it is that in the case of sockets, pipes, character	1744	Another way to view it is that in the case of sockets, pipes, character
1684	devices and so on, there is another party (the sender) that delivers data	1745	devices and so on, there is another party (the sender) that delivers data
1685	on it's own, but in the case of files, there is no such thing: the disk	1746	on its own, but in the case of files, there is no such thing: the disk
1686	will not send data on it's own, simply because it doesn't know what you	1747	will not send data on its own, simply because it doesn't know what you
1687	wish to read - you would first have to request some data.	1748	wish to read - you would first have to request some data.
1688		1749
1689	Since files are typically not-so-well supported by advanced notification	1750	Since files are typically not-so-well supported by advanced notification
1690	mechanism, libev tries hard to emulate POSIX behaviour with respect	1751	mechanism, libev tries hard to emulate POSIX behaviour with respect
1691	to files, even though you should not use it. The reason for this is	1752	to files, even though you should not use it. The reason for this is
…		…
1701	when you rarely read from a file instead of from a socket, and want to	1762	when you rarely read from a file instead of from a socket, and want to
1702	reuse the same code path.	1763	reuse the same code path.
1703		1764
1704	=head3 The special problem of fork	1765	=head3 The special problem of fork
1705		1766
1706	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1767	Some backends (epoll, kqueue, linuxaio, iouring) do not support C<fork ()>
1707	useless behaviour. Libev fully supports fork, but needs to be told about	1768	at all or exhibit useless behaviour. Libev fully supports fork, but needs
1708	it in the child if you want to continue to use it in the child.	1769	to be told about it in the child if you want to continue to use it in the
		1770	child.
1709		1771
1710	To support fork in your child processes, you have to call C<ev_loop_fork	1772	To support fork in your child processes, you have to call C<ev_loop_fork
1711	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to	1773	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1712	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1774	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1713		1775
…		…
1768	=item ev_io_init (ev_io *, callback, int fd, int events)	1830	=item ev_io_init (ev_io *, callback, int fd, int events)
1769		1831
1770	=item ev_io_set (ev_io *, int fd, int events)	1832	=item ev_io_set (ev_io *, int fd, int events)
1771		1833
1772	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1834	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1773	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or	1835	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE>, both
1774	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.	1836	C<EV_READ | EV_WRITE> or C<0>, to express the desire to receive the given
		1837	events.
1775		1838
1776	=item int fd [read-only]	1839	Note that setting the C<events> to C<0> and starting the watcher is
		1840	supported, but not specially optimized - if your program sometimes happens
		1841	to generate this combination this is fine, but if it is easy to avoid
		1842	starting an io watcher watching for no events you should do so.
1777		1843
1778	The file descriptor being watched.	1844	=item ev_io_modify (ev_io *, int events)
1779		1845
		1846	Similar to C<ev_io_set>, but only changes the requested events. Using this
		1847	might be faster with some backends, as libev can assume that the C<fd>
		1848	still refers to the same underlying file description, something it cannot
		1849	do when using C<ev_io_set>.
		1850
		1851	=item int fd [no-modify]
		1852
		1853	The file descriptor being watched. While it can be read at any time, you
		1854	must not modify this member even when the watcher is stopped - always use
		1855	C<ev_io_set> for that.
		1856
1780	=item int events [read-only]	1857	=item int events [no-modify]
1781		1858
1782	The events being watched.	1859	The set of events the fd is being watched for, among other flags. Remember
		1860	that this is a bit set - to test for C<EV_READ>, use C<< w->events &
		1861	EV_READ >>, and similarly for C<EV_WRITE>.
		1862
		1863	As with C<fd>, you must not modify this member even when the watcher is
		1864	stopped, always use C<ev_io_set> or C<ev_io_modify> for that.
1783		1865
1784	=back	1866	=back
1785		1867
1786	=head3 Examples	1868	=head3 Examples
1787		1869
…		…
1815	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1897	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1816	monotonic clock option helps a lot here).	1898	monotonic clock option helps a lot here).
1817		1899
1818	The callback is guaranteed to be invoked only I<after> its timeout has	1900	The callback is guaranteed to be invoked only I<after> its timeout has
1819	passed (not I<at>, so on systems with very low-resolution clocks this	1901	passed (not I<at>, so on systems with very low-resolution clocks this
1820	might introduce a small delay). If multiple timers become ready during the	1902	might introduce a small delay, see "the special problem of being too
		1903	early", below). If multiple timers become ready during the same loop
1821	same loop iteration then the ones with earlier time-out values are invoked	1904	iteration then the ones with earlier time-out values are invoked before
1822	before ones of the same priority with later time-out values (but this is	1905	ones of the same priority with later time-out values (but this is no
1823	no longer true when a callback calls C<ev_run> recursively).	1906	longer true when a callback calls C<ev_run> recursively).
1824		1907
1825	=head3 Be smart about timeouts	1908	=head3 Be smart about timeouts
1826		1909
1827	Many real-world problems involve some kind of timeout, usually for error	1910	Many real-world problems involve some kind of timeout, usually for error
1828	recovery. A typical example is an HTTP request - if the other side hangs,	1911	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1903		1986
1904	In this case, it would be more efficient to leave the C<ev_timer> alone,	1987	In this case, it would be more efficient to leave the C<ev_timer> alone,
1905	but remember the time of last activity, and check for a real timeout only	1988	but remember the time of last activity, and check for a real timeout only
1906	within the callback:	1989	within the callback:
1907		1990
		1991	ev_tstamp timeout = 60.;
1908	ev_tstamp last_activity; // time of last activity	1992	ev_tstamp last_activity; // time of last activity
		1993	ev_timer timer;
1909		1994
1910	static void	1995	static void
1911	callback (EV_P_ ev_timer *w, int revents)	1996	callback (EV_P_ ev_timer *w, int revents)
1912	{	1997	{
1913	ev_tstamp now = ev_now (EV_A);	1998	// calculate when the timeout would happen
1914	ev_tstamp timeout = last_activity + 60.;	1999	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1915		2000
1916	// if last_activity + 60. is older than now, we did time out	2001	// if negative, it means we the timeout already occurred
1917	if (timeout < now)	2002	if (after < 0.)
1918	{	2003	{
1919	// timeout occurred, take action	2004	// timeout occurred, take action
1920	}	2005	}
1921	else	2006	else
1922	{	2007	{
1923	// callback was invoked, but there was some activity, re-arm	2008	// callback was invoked, but there was some recent
1924	// the watcher to fire in last_activity + 60, which is	2009	// activity. simply restart the timer to time out
1925	// guaranteed to be in the future, so "again" is positive:	2010	// after "after" seconds, which is the earliest time
1926	w->repeat = timeout - now;	2011	// the timeout can occur.
		2012	ev_timer_set (w, after, 0.);
1927	ev_timer_again (EV_A_ w);	2013	ev_timer_start (EV_A_ w);
1928	}	2014	}
1929	}	2015	}
1930		2016
1931	To summarise the callback: first calculate the real timeout (defined	2017	To summarise the callback: first calculate in how many seconds the
1932	as "60 seconds after the last activity"), then check if that time has	2018	timeout will occur (by calculating the absolute time when it would occur,
1933	been reached, which means something I<did>, in fact, time out. Otherwise	2019	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1934	the callback was invoked too early (C<timeout> is in the future), so	2020	(EV_A)> from that).
1935	re-schedule the timer to fire at that future time, to see if maybe we have
1936	a timeout then.
1937		2021
1938	Note how C<ev_timer_again> is used, taking advantage of the	2022	If this value is negative, then we are already past the timeout, i.e. we
1939	C<ev_timer_again> optimisation when the timer is already running.	2023	timed out, and need to do whatever is needed in this case.
		2024
		2025	Otherwise, we now the earliest time at which the timeout would trigger,
		2026	and simply start the timer with this timeout value.
		2027
		2028	In other words, each time the callback is invoked it will check whether
		2029	the timeout occurred. If not, it will simply reschedule itself to check
		2030	again at the earliest time it could time out. Rinse. Repeat.
1940		2031
1941	This scheme causes more callback invocations (about one every 60 seconds	2032	This scheme causes more callback invocations (about one every 60 seconds
1942	minus half the average time between activity), but virtually no calls to	2033	minus half the average time between activity), but virtually no calls to
1943	libev to change the timeout.	2034	libev to change the timeout.
1944		2035
1945	To start the timer, simply initialise the watcher and set C<last_activity>	2036	To start the machinery, simply initialise the watcher and set
1946	to the current time (meaning we just have some activity :), then call the	2037	C<last_activity> to the current time (meaning there was some activity just
1947	callback, which will "do the right thing" and start the timer:	2038	now), then call the callback, which will "do the right thing" and start
		2039	the timer:
1948		2040
		2041	last_activity = ev_now (EV_A);
1949	ev_init (timer, callback);	2042	ev_init (&timer, callback);
1950	last_activity = ev_now (loop);	2043	callback (EV_A_ &timer, 0);
1951	callback (loop, timer, EV_TIMER);
1952		2044
1953	And when there is some activity, simply store the current time in	2045	When there is some activity, simply store the current time in
1954	C<last_activity>, no libev calls at all:	2046	C<last_activity>, no libev calls at all:
1955		2047
		2048	if (activity detected)
1956	last_activity = ev_now (loop);	2049	last_activity = ev_now (EV_A);
		2050
		2051	When your timeout value changes, then the timeout can be changed by simply
		2052	providing a new value, stopping the timer and calling the callback, which
		2053	will again do the right thing (for example, time out immediately :).
		2054
		2055	timeout = new_value;
		2056	ev_timer_stop (EV_A_ &timer);
		2057	callback (EV_A_ &timer, 0);
1957		2058
1958	This technique is slightly more complex, but in most cases where the	2059	This technique is slightly more complex, but in most cases where the
1959	time-out is unlikely to be triggered, much more efficient.	2060	time-out is unlikely to be triggered, much more efficient.
1960
1961	Changing the timeout is trivial as well (if it isn't hard-coded in the
1962	callback :) - just change the timeout and invoke the callback, which will
1963	fix things for you.
1964		2061
1965	=item 4. Wee, just use a double-linked list for your timeouts.	2062	=item 4. Wee, just use a double-linked list for your timeouts.
1966		2063
1967	If there is not one request, but many thousands (millions...), all	2064	If there is not one request, but many thousands (millions...), all
1968	employing some kind of timeout with the same timeout value, then one can	2065	employing some kind of timeout with the same timeout value, then one can
…		…
1995	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	2092	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1996	rather complicated, but extremely efficient, something that really pays	2093	rather complicated, but extremely efficient, something that really pays
1997	off after the first million or so of active timers, i.e. it's usually	2094	off after the first million or so of active timers, i.e. it's usually
1998	overkill :)	2095	overkill :)
1999		2096
		2097	=head3 The special problem of being too early
		2098
		2099	If you ask a timer to call your callback after three seconds, then
		2100	you expect it to be invoked after three seconds - but of course, this
		2101	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		2102	guaranteed to any precision by libev - imagine somebody suspending the
		2103	process with a STOP signal for a few hours for example.
		2104
		2105	So, libev tries to invoke your callback as soon as possible I<after> the
		2106	delay has occurred, but cannot guarantee this.
		2107
		2108	A less obvious failure mode is calling your callback too early: many event
		2109	loops compare timestamps with a "elapsed delay >= requested delay", but
		2110	this can cause your callback to be invoked much earlier than you would
		2111	expect.
		2112
		2113	To see why, imagine a system with a clock that only offers full second
		2114	resolution (think windows if you can't come up with a broken enough OS
		2115	yourself). If you schedule a one-second timer at the time 500.9, then the
		2116	event loop will schedule your timeout to elapse at a system time of 500
		2117	(500.9 truncated to the resolution) + 1, or 501.
		2118
		2119	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2120	501" and invoke the callback 0.1s after it was started, even though a
		2121	one-second delay was requested - this is being "too early", despite best
		2122	intentions.
		2123
		2124	This is the reason why libev will never invoke the callback if the elapsed
		2125	delay equals the requested delay, but only when the elapsed delay is
		2126	larger than the requested delay. In the example above, libev would only invoke
		2127	the callback at system time 502, or 1.1s after the timer was started.
		2128
		2129	So, while libev cannot guarantee that your callback will be invoked
		2130	exactly when requested, it I<can> and I<does> guarantee that the requested
		2131	delay has actually elapsed, or in other words, it always errs on the "too
		2132	late" side of things.
		2133
2000	=head3 The special problem of time updates	2134	=head3 The special problem of time updates
2001		2135
2002	Establishing the current time is a costly operation (it usually takes at	2136	Establishing the current time is a costly operation (it usually takes
2003	least two system calls): EV therefore updates its idea of the current	2137	at least one system call): EV therefore updates its idea of the current
2004	time only before and after C<ev_run> collects new events, which causes a	2138	time only before and after C<ev_run> collects new events, which causes a
2005	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2139	growing difference between C<ev_now ()> and C<ev_time ()> when handling
2006	lots of events in one iteration.	2140	lots of events in one iteration.
2007		2141
2008	The relative timeouts are calculated relative to the C<ev_now ()>	2142	The relative timeouts are calculated relative to the C<ev_now ()>
2009	time. This is usually the right thing as this timestamp refers to the time	2143	time. This is usually the right thing as this timestamp refers to the time
2010	of the event triggering whatever timeout you are modifying/starting. If	2144	of the event triggering whatever timeout you are modifying/starting. If
2011	you suspect event processing to be delayed and you I<need> to base the	2145	you suspect event processing to be delayed and you I<need> to base the
2012	timeout on the current time, use something like this to adjust for this:	2146	timeout on the current time, use something like the following to adjust
		2147	for it:
2013		2148
2014	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2149	ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.);
2015		2150
2016	If the event loop is suspended for a long time, you can also force an	2151	If the event loop is suspended for a long time, you can also force an
2017	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2152	update of the time returned by C<ev_now ()> by calling C<ev_now_update
2018	()>.	2153	()>, although that will push the event time of all outstanding events
		2154	further into the future.
		2155
		2156	=head3 The special problem of unsynchronised clocks
		2157
		2158	Modern systems have a variety of clocks - libev itself uses the normal
		2159	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2160	jumps).
		2161
		2162	Neither of these clocks is synchronised with each other or any other clock
		2163	on the system, so C<ev_time ()> might return a considerably different time
		2164	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2165	a call to C<gettimeofday> might return a second count that is one higher
		2166	than a directly following call to C<time>.
		2167
		2168	The moral of this is to only compare libev-related timestamps with
		2169	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2170	a second or so.
		2171
		2172	One more problem arises due to this lack of synchronisation: if libev uses
		2173	the system monotonic clock and you compare timestamps from C<ev_time>
		2174	or C<ev_now> from when you started your timer and when your callback is
		2175	invoked, you will find that sometimes the callback is a bit "early".
		2176
		2177	This is because C<ev_timer>s work in real time, not wall clock time, so
		2178	libev makes sure your callback is not invoked before the delay happened,
		2179	I<measured according to the real time>, not the system clock.
		2180
		2181	If your timeouts are based on a physical timescale (e.g. "time out this
		2182	connection after 100 seconds") then this shouldn't bother you as it is
		2183	exactly the right behaviour.
		2184
		2185	If you want to compare wall clock/system timestamps to your timers, then
		2186	you need to use C<ev_periodic>s, as these are based on the wall clock
		2187	time, where your comparisons will always generate correct results.
2019		2188
2020	=head3 The special problems of suspended animation	2189	=head3 The special problems of suspended animation
2021		2190
2022	When you leave the server world it is quite customary to hit machines that	2191	When you leave the server world it is quite customary to hit machines that
2023	can suspend/hibernate - what happens to the clocks during such a suspend?	2192	can suspend/hibernate - what happens to the clocks during such a suspend?
…		…
2053		2222
2054	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2223	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
2055		2224
2056	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	2225	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
2057		2226
2058	Configure the timer to trigger after C<after> seconds. If C<repeat>	2227	Configure the timer to trigger after C<after> seconds (fractional and
2059	is C<0.>, then it will automatically be stopped once the timeout is	2228	negative values are supported). If C<repeat> is C<0.>, then it will
2060	reached. If it is positive, then the timer will automatically be	2229	automatically be stopped once the timeout is reached. If it is positive,
2061	configured to trigger again C<repeat> seconds later, again, and again,	2230	then the timer will automatically be configured to trigger again C<repeat>
2062	until stopped manually.	2231	seconds later, again, and again, until stopped manually.
2063		2232
2064	The timer itself will do a best-effort at avoiding drift, that is, if	2233	The timer itself will do a best-effort at avoiding drift, that is, if
2065	you configure a timer to trigger every 10 seconds, then it will normally	2234	you configure a timer to trigger every 10 seconds, then it will normally
2066	trigger at exactly 10 second intervals. If, however, your program cannot	2235	trigger at exactly 10 second intervals. If, however, your program cannot
2067	keep up with the timer (because it takes longer than those 10 seconds to	2236	keep up with the timer (because it takes longer than those 10 seconds to
2068	do stuff) the timer will not fire more than once per event loop iteration.	2237	do stuff) the timer will not fire more than once per event loop iteration.
2069		2238
2070	=item ev_timer_again (loop, ev_timer *)	2239	=item ev_timer_again (loop, ev_timer *)
2071		2240
2072	This will act as if the timer timed out and restart it again if it is	2241	This will act as if the timer timed out, and restarts it again if it is
2073	repeating. The exact semantics are:	2242	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2243	timeout to the C<repeat> value and calling C<ev_timer_start>.
2074		2244
		2245	The exact semantics are as in the following rules, all of which will be
		2246	applied to the watcher:
		2247
		2248	=over 4
		2249
2075	If the timer is pending, its pending status is cleared.	2250	=item If the timer is pending, the pending status is always cleared.
2076		2251
2077	If the timer is started but non-repeating, stop it (as if it timed out).	2252	=item If the timer is started but non-repeating, stop it (as if it timed
		2253	out, without invoking it).
2078		2254
2079	If the timer is repeating, either start it if necessary (with the	2255	=item If the timer is repeating, make the C<repeat> value the new timeout
2080	C<repeat> value), or reset the running timer to the C<repeat> value.	2256	and start the timer, if necessary.
2081		2257
		2258	=back
		2259
2082	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2260	This sounds a bit complicated, see L</Be smart about timeouts>, above, for a
2083	usage example.	2261	usage example.
2084		2262
2085	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)	2263	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
2086		2264
2087	Returns the remaining time until a timer fires. If the timer is active,	2265	Returns the remaining time until a timer fires. If the timer is active,
…		…
2140	Periodic watchers are also timers of a kind, but they are very versatile	2318	Periodic watchers are also timers of a kind, but they are very versatile
2141	(and unfortunately a bit complex).	2319	(and unfortunately a bit complex).
2142		2320
2143	Unlike C<ev_timer>, periodic watchers are not based on real time (or	2321	Unlike C<ev_timer>, periodic watchers are not based on real time (or
2144	relative time, the physical time that passes) but on wall clock time	2322	relative time, the physical time that passes) but on wall clock time
2145	(absolute time, the thing you can read on your calender or clock). The	2323	(absolute time, the thing you can read on your calendar or clock). The
2146	difference is that wall clock time can run faster or slower than real	2324	difference is that wall clock time can run faster or slower than real
2147	time, and time jumps are not uncommon (e.g. when you adjust your	2325	time, and time jumps are not uncommon (e.g. when you adjust your
2148	wrist-watch).	2326	wrist-watch).
2149		2327
2150	You can tell a periodic watcher to trigger after some specific point	2328	You can tell a periodic watcher to trigger after some specific point
…		…
2155	C<ev_timer>, which would still trigger roughly 10 seconds after starting	2333	C<ev_timer>, which would still trigger roughly 10 seconds after starting
2156	it, as it uses a relative timeout).	2334	it, as it uses a relative timeout).
2157		2335
2158	C<ev_periodic> watchers can also be used to implement vastly more complex	2336	C<ev_periodic> watchers can also be used to implement vastly more complex
2159	timers, such as triggering an event on each "midnight, local time", or	2337	timers, such as triggering an event on each "midnight, local time", or
2160	other complicated rules. This cannot be done with C<ev_timer> watchers, as	2338	other complicated rules. This cannot easily be done with C<ev_timer>
2161	those cannot react to time jumps.	2339	watchers, as those cannot react to time jumps.
2162		2340
2163	As with timers, the callback is guaranteed to be invoked only when the	2341	As with timers, the callback is guaranteed to be invoked only when the
2164	point in time where it is supposed to trigger has passed. If multiple	2342	point in time where it is supposed to trigger has passed. If multiple
2165	timers become ready during the same loop iteration then the ones with	2343	timers become ready during the same loop iteration then the ones with
2166	earlier time-out values are invoked before ones with later time-out values	2344	earlier time-out values are invoked before ones with later time-out values
…		…
2207		2385
2208	Another way to think about it (for the mathematically inclined) is that	2386	Another way to think about it (for the mathematically inclined) is that
2209	C<ev_periodic> will try to run the callback in this mode at the next possible	2387	C<ev_periodic> will try to run the callback in this mode at the next possible
2210	time where C<time = offset (mod interval)>, regardless of any time jumps.	2388	time where C<time = offset (mod interval)>, regardless of any time jumps.
2211		2389
2212	For numerical stability it is preferable that the C<offset> value is near	2390	The C<interval> I<MUST> be positive, and for numerical stability, the
2213	C<ev_now ()> (the current time), but there is no range requirement for	2391	interval value should be higher than C<1/8192> (which is around 100
2214	this value, and in fact is often specified as zero.	2392	microseconds) and C<offset> should be higher than C<0> and should have
		2393	at most a similar magnitude as the current time (say, within a factor of
		2394	ten). Typical values for offset are, in fact, C<0> or something between
		2395	C<0> and C<interval>, which is also the recommended range.
2215		2396
2216	Note also that there is an upper limit to how often a timer can fire (CPU	2397	Note also that there is an upper limit to how often a timer can fire (CPU
2217	speed for example), so if C<interval> is very small then timing stability	2398	speed for example), so if C<interval> is very small then timing stability
2218	will of course deteriorate. Libev itself tries to be exact to be about one	2399	will of course deteriorate. Libev itself tries to be exact to be about one
2219	millisecond (if the OS supports it and the machine is fast enough).	2400	millisecond (if the OS supports it and the machine is fast enough).
…		…
2249		2430
2250	NOTE: I<< This callback must always return a time that is higher than or	2431	NOTE: I<< This callback must always return a time that is higher than or
2251	equal to the passed C<now> value >>.	2432	equal to the passed C<now> value >>.
2252		2433
2253	This can be used to create very complex timers, such as a timer that	2434	This can be used to create very complex timers, such as a timer that
2254	triggers on "next midnight, local time". To do this, you would calculate the	2435	triggers on "next midnight, local time". To do this, you would calculate
2255	next midnight after C<now> and return the timestamp value for this. How	2436	the next midnight after C<now> and return the timestamp value for
2256	you do this is, again, up to you (but it is not trivial, which is the main	2437	this. Here is a (completely untested, no error checking) example on how to
2257	reason I omitted it as an example).	2438	do this:
		2439
		2440	#include <time.h>
		2441
		2442	static ev_tstamp
		2443	my_rescheduler (ev_periodic *w, ev_tstamp now)
		2444	{
		2445	time_t tnow = (time_t)now;
		2446	struct tm tm;
		2447	localtime_r (&tnow, &tm);
		2448
		2449	tm.tm_sec = tm.tm_min = tm.tm_hour = 0; // midnight current day
		2450	++tm.tm_mday; // midnight next day
		2451
		2452	return mktime (&tm);
		2453	}
		2454
		2455	Note: this code might run into trouble on days that have more then two
		2456	midnights (beginning and end).
2258		2457
2259	=back	2458	=back
2260		2459
2261	=item ev_periodic_again (loop, ev_periodic *)	2460	=item ev_periodic_again (loop, ev_periodic *)
2262		2461
…		…
2327		2526
2328	ev_periodic hourly_tick;	2527	ev_periodic hourly_tick;
2329	ev_periodic_init (&hourly_tick, clock_cb,	2528	ev_periodic_init (&hourly_tick, clock_cb,
2330	fmod (ev_now (loop), 3600.), 3600., 0);	2529	fmod (ev_now (loop), 3600.), 3600., 0);
2331	ev_periodic_start (loop, &hourly_tick);	2530	ev_periodic_start (loop, &hourly_tick);
2332		2531
2333		2532
2334	=head2 C<ev_signal> - signal me when a signal gets signalled!	2533	=head2 C<ev_signal> - signal me when a signal gets signalled!
2335		2534
2336	Signal watchers will trigger an event when the process receives a specific	2535	Signal watchers will trigger an event when the process receives a specific
2337	signal one or more times. Even though signals are very asynchronous, libev	2536	signal one or more times. Even though signals are very asynchronous, libev
…		…
2347	only within the same loop, i.e. you can watch for C<SIGINT> in your	2546	only within the same loop, i.e. you can watch for C<SIGINT> in your
2348	default loop and for C<SIGIO> in another loop, but you cannot watch for	2547	default loop and for C<SIGIO> in another loop, but you cannot watch for
2349	C<SIGINT> in both the default loop and another loop at the same time. At	2548	C<SIGINT> in both the default loop and another loop at the same time. At
2350	the moment, C<SIGCHLD> is permanently tied to the default loop.	2549	the moment, C<SIGCHLD> is permanently tied to the default loop.
2351		2550
2352	When the first watcher gets started will libev actually register something	2551	Only after the first watcher for a signal is started will libev actually
2353	with the kernel (thus it coexists with your own signal handlers as long as	2552	register something with the kernel. It thus coexists with your own signal
2354	you don't register any with libev for the same signal).	2553	handlers as long as you don't register any with libev for the same signal.
2355		2554
2356	If possible and supported, libev will install its handlers with	2555	If possible and supported, libev will install its handlers with
2357	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should	2556	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
2358	not be unduly interrupted. If you have a problem with system calls getting	2557	not be unduly interrupted. If you have a problem with system calls getting
2359	interrupted by signals you can block all signals in an C<ev_check> watcher	2558	interrupted by signals you can block all signals in an C<ev_check> watcher
…		…
2362	=head3 The special problem of inheritance over fork/execve/pthread_create	2561	=head3 The special problem of inheritance over fork/execve/pthread_create
2363		2562
2364	Both the signal mask (C<sigprocmask>) and the signal disposition	2563	Both the signal mask (C<sigprocmask>) and the signal disposition
2365	(C<sigaction>) are unspecified after starting a signal watcher (and after	2564	(C<sigaction>) are unspecified after starting a signal watcher (and after
2366	stopping it again), that is, libev might or might not block the signal,	2565	stopping it again), that is, libev might or might not block the signal,
2367	and might or might not set or restore the installed signal handler.	2566	and might or might not set or restore the installed signal handler (but
		2567	see C<EVFLAG_NOSIGMASK>).
2368		2568
2369	While this does not matter for the signal disposition (libev never	2569	While this does not matter for the signal disposition (libev never
2370	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on	2570	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
2371	C<execve>), this matters for the signal mask: many programs do not expect	2571	C<execve>), this matters for the signal mask: many programs do not expect
2372	certain signals to be blocked.	2572	certain signals to be blocked.
…		…
2543		2743
2544	=head2 C<ev_stat> - did the file attributes just change?	2744	=head2 C<ev_stat> - did the file attributes just change?
2545		2745
2546	This watches a file system path for attribute changes. That is, it calls	2746	This watches a file system path for attribute changes. That is, it calls
2547	C<stat> on that path in regular intervals (or when the OS says it changed)	2747	C<stat> on that path in regular intervals (or when the OS says it changed)
2548	and sees if it changed compared to the last time, invoking the callback if	2748	and sees if it changed compared to the last time, invoking the callback
2549	it did.	2749	if it did. Starting the watcher C<stat>'s the file, so only changes that
		2750	happen after the watcher has been started will be reported.
2550		2751
2551	The path does not need to exist: changing from "path exists" to "path does	2752	The path does not need to exist: changing from "path exists" to "path does
2552	not exist" is a status change like any other. The condition "path does not	2753	not exist" is a status change like any other. The condition "path does not
2553	exist" (or more correctly "path cannot be stat'ed") is signified by the	2754	exist" (or more correctly "path cannot be stat'ed") is signified by the
2554	C<st_nlink> field being zero (which is otherwise always forced to be at	2755	C<st_nlink> field being zero (which is otherwise always forced to be at
…		…
2784	Apart from keeping your process non-blocking (which is a useful	2985	Apart from keeping your process non-blocking (which is a useful
2785	effect on its own sometimes), idle watchers are a good place to do	2986	effect on its own sometimes), idle watchers are a good place to do
2786	"pseudo-background processing", or delay processing stuff to after the	2987	"pseudo-background processing", or delay processing stuff to after the
2787	event loop has handled all outstanding events.	2988	event loop has handled all outstanding events.
2788		2989
		2990	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2991
		2992	As long as there is at least one active idle watcher, libev will never
		2993	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2994	For this to work, the idle watcher doesn't need to be invoked at all - the
		2995	lowest priority will do.
		2996
		2997	This mode of operation can be useful together with an C<ev_check> watcher,
		2998	to do something on each event loop iteration - for example to balance load
		2999	between different connections.
		3000
		3001	See L</Abusing an ev_check watcher for its side-effect> for a longer
		3002	example.
		3003
2789	=head3 Watcher-Specific Functions and Data Members	3004	=head3 Watcher-Specific Functions and Data Members
2790		3005
2791	=over 4	3006	=over 4
2792		3007
2793	=item ev_idle_init (ev_idle *, callback)	3008	=item ev_idle_init (ev_idle *, callback)
…		…
2804	callback, free it. Also, use no error checking, as usual.	3019	callback, free it. Also, use no error checking, as usual.
2805		3020
2806	static void	3021	static void
2807	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	3022	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2808	{	3023	{
		3024	// stop the watcher
		3025	ev_idle_stop (loop, w);
		3026
		3027	// now we can free it
2809	free (w);	3028	free (w);
		3029
2810	// now do something you wanted to do when the program has	3030	// now do something you wanted to do when the program has
2811	// no longer anything immediate to do.	3031	// no longer anything immediate to do.
2812	}	3032	}
2813		3033
2814	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	3034	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
…		…
2816	ev_idle_start (loop, idle_watcher);	3036	ev_idle_start (loop, idle_watcher);
2817		3037
2818		3038
2819	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	3039	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2820		3040
2821	Prepare and check watchers are usually (but not always) used in pairs:	3041	Prepare and check watchers are often (but not always) used in pairs:
2822	prepare watchers get invoked before the process blocks and check watchers	3042	prepare watchers get invoked before the process blocks and check watchers
2823	afterwards.	3043	afterwards.
2824		3044
2825	You I<must not> call C<ev_run> or similar functions that enter	3045	You I<must not> call C<ev_run> (or similar functions that enter the
2826	the current event loop from either C<ev_prepare> or C<ev_check>	3046	current event loop) or C<ev_loop_fork> from either C<ev_prepare> or
2827	watchers. Other loops than the current one are fine, however. The	3047	C<ev_check> watchers. Other loops than the current one are fine,
2828	rationale behind this is that you do not need to check for recursion in	3048	however. The rationale behind this is that you do not need to check
2829	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	3049	for recursion in those watchers, i.e. the sequence will always be
2830	C<ev_check> so if you have one watcher of each kind they will always be	3050	C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each
2831	called in pairs bracketing the blocking call.	3051	kind they will always be called in pairs bracketing the blocking call.
2832		3052
2833	Their main purpose is to integrate other event mechanisms into libev and	3053	Their main purpose is to integrate other event mechanisms into libev and
2834	their use is somewhat advanced. They could be used, for example, to track	3054	their use is somewhat advanced. They could be used, for example, to track
2835	variable changes, implement your own watchers, integrate net-snmp or a	3055	variable changes, implement your own watchers, integrate net-snmp or a
2836	coroutine library and lots more. They are also occasionally useful if	3056	coroutine library and lots more. They are also occasionally useful if
…		…
2854	with priority higher than or equal to the event loop and one coroutine	3074	with priority higher than or equal to the event loop and one coroutine
2855	of lower priority, but only once, using idle watchers to keep the event	3075	of lower priority, but only once, using idle watchers to keep the event
2856	loop from blocking if lower-priority coroutines are active, thus mapping	3076	loop from blocking if lower-priority coroutines are active, thus mapping
2857	low-priority coroutines to idle/background tasks).	3077	low-priority coroutines to idle/background tasks).
2858		3078
2859	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	3079	When used for this purpose, it is recommended to give C<ev_check> watchers
2860	priority, to ensure that they are being run before any other watchers	3080	highest (C<EV_MAXPRI>) priority, to ensure that they are being run before
2861	after the poll (this doesn't matter for C<ev_prepare> watchers).	3081	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		3082	watchers).
2862		3083
2863	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	3084	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
2864	activate ("feed") events into libev. While libev fully supports this, they	3085	activate ("feed") events into libev. While libev fully supports this, they
2865	might get executed before other C<ev_check> watchers did their job. As	3086	might get executed before other C<ev_check> watchers did their job. As
2866	C<ev_check> watchers are often used to embed other (non-libev) event	3087	C<ev_check> watchers are often used to embed other (non-libev) event
2867	loops those other event loops might be in an unusable state until their	3088	loops those other event loops might be in an unusable state until their
2868	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	3089	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2869	others).	3090	others).
		3091
		3092	=head3 Abusing an C<ev_check> watcher for its side-effect
		3093
		3094	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		3095	useful because they are called once per event loop iteration. For
		3096	example, if you want to handle a large number of connections fairly, you
		3097	normally only do a bit of work for each active connection, and if there
		3098	is more work to do, you wait for the next event loop iteration, so other
		3099	connections have a chance of making progress.
		3100
		3101	Using an C<ev_check> watcher is almost enough: it will be called on the
		3102	next event loop iteration. However, that isn't as soon as possible -
		3103	without external events, your C<ev_check> watcher will not be invoked.
		3104
		3105	This is where C<ev_idle> watchers come in handy - all you need is a
		3106	single global idle watcher that is active as long as you have one active
		3107	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		3108	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		3109	invoked. Neither watcher alone can do that.
2870		3110
2871	=head3 Watcher-Specific Functions and Data Members	3111	=head3 Watcher-Specific Functions and Data Members
2872		3112
2873	=over 4	3113	=over 4
2874		3114
…		…
3075		3315
3076	=over 4	3316	=over 4
3077		3317
3078	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	3318	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
3079		3319
3080	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	3320	=item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)
3081		3321
3082	Configures the watcher to embed the given loop, which must be	3322	Configures the watcher to embed the given loop, which must be
3083	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	3323	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
3084	invoked automatically, otherwise it is the responsibility of the callback	3324	invoked automatically, otherwise it is the responsibility of the callback
3085	to invoke it (it will continue to be called until the sweep has been done,	3325	to invoke it (it will continue to be called until the sweep has been done,
…		…
3106	used).	3346	used).
3107		3347
3108	struct ev_loop *loop_hi = ev_default_init (0);	3348	struct ev_loop *loop_hi = ev_default_init (0);
3109	struct ev_loop *loop_lo = 0;	3349	struct ev_loop *loop_lo = 0;
3110	ev_embed embed;	3350	ev_embed embed;
3111		3351
3112	// see if there is a chance of getting one that works	3352	// see if there is a chance of getting one that works
3113	// (remember that a flags value of 0 means autodetection)	3353	// (remember that a flags value of 0 means autodetection)
3114	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3354	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
3115	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3355	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
3116	: 0;	3356	: 0;
…		…
3130	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3370	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
3131		3371
3132	struct ev_loop *loop = ev_default_init (0);	3372	struct ev_loop *loop = ev_default_init (0);
3133	struct ev_loop *loop_socket = 0;	3373	struct ev_loop *loop_socket = 0;
3134	ev_embed embed;	3374	ev_embed embed;
3135		3375
3136	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3376	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
3137	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3377	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
3138	{	3378	{
3139	ev_embed_init (&embed, 0, loop_socket);	3379	ev_embed_init (&embed, 0, loop_socket);
3140	ev_embed_start (loop, &embed);	3380	ev_embed_start (loop, &embed);
…		…
3148		3388
3149	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3389	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
3150		3390
3151	Fork watchers are called when a C<fork ()> was detected (usually because	3391	Fork watchers are called when a C<fork ()> was detected (usually because
3152	whoever is a good citizen cared to tell libev about it by calling	3392	whoever is a good citizen cared to tell libev about it by calling
3153	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the	3393	C<ev_loop_fork>). The invocation is done before the event loop blocks next
3154	event loop blocks next and before C<ev_check> watchers are being called,	3394	and before C<ev_check> watchers are being called, and only in the child
3155	and only in the child after the fork. If whoever good citizen calling	3395	after the fork. If whoever good citizen calling C<ev_default_fork> cheats
3156	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3396	and calls it in the wrong process, the fork handlers will be invoked, too,
3157	handlers will be invoked, too, of course.	3397	of course.
3158		3398
3159	=head3 The special problem of life after fork - how is it possible?	3399	=head3 The special problem of life after fork - how is it possible?
3160		3400
3161	Most uses of C<fork()> consist of forking, then some simple calls to set	3401	Most uses of C<fork ()> consist of forking, then some simple calls to set
3162	up/change the process environment, followed by a call to C<exec()>. This	3402	up/change the process environment, followed by a call to C<exec()>. This
3163	sequence should be handled by libev without any problems.	3403	sequence should be handled by libev without any problems.
3164		3404
3165	This changes when the application actually wants to do event handling	3405	This changes when the application actually wants to do event handling
3166	in the child, or both parent in child, in effect "continuing" after the	3406	in the child, or both parent in child, in effect "continuing" after the
…		…
3243	atexit (program_exits);	3483	atexit (program_exits);
3244		3484
3245		3485
3246	=head2 C<ev_async> - how to wake up an event loop	3486	=head2 C<ev_async> - how to wake up an event loop
3247		3487
3248	In general, you cannot use an C<ev_run> from multiple threads or other	3488	In general, you cannot use an C<ev_loop> from multiple threads or other
3249	asynchronous sources such as signal handlers (as opposed to multiple event	3489	asynchronous sources such as signal handlers (as opposed to multiple event
3250	loops - those are of course safe to use in different threads).	3490	loops - those are of course safe to use in different threads).
3251		3491
3252	Sometimes, however, you need to wake up an event loop you do not control,	3492	Sometimes, however, you need to wake up an event loop you do not control,
3253	for example because it belongs to another thread. This is what C<ev_async>	3493	for example because it belongs to another thread. This is what C<ev_async>
…		…
3255	it by calling C<ev_async_send>, which is thread- and signal safe.	3495	it by calling C<ev_async_send>, which is thread- and signal safe.
3256		3496
3257	This functionality is very similar to C<ev_signal> watchers, as signals,	3497	This functionality is very similar to C<ev_signal> watchers, as signals,
3258	too, are asynchronous in nature, and signals, too, will be compressed	3498	too, are asynchronous in nature, and signals, too, will be compressed
3259	(i.e. the number of callback invocations may be less than the number of	3499	(i.e. the number of callback invocations may be less than the number of
3260	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind	3500	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
3261	of "global async watchers" by using a watcher on an otherwise unused	3501	of "global async watchers" by using a watcher on an otherwise unused
3262	signal, and C<ev_feed_signal> to signal this watcher from another thread,	3502	signal, and C<ev_feed_signal> to signal this watcher from another thread,
3263	even without knowing which loop owns the signal.	3503	even without knowing which loop owns the signal.
3264
3265	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
3266	just the default loop.
3267		3504
3268	=head3 Queueing	3505	=head3 Queueing
3269		3506
3270	C<ev_async> does not support queueing of data in any way. The reason	3507	C<ev_async> does not support queueing of data in any way. The reason
3271	is that the author does not know of a simple (or any) algorithm for a	3508	is that the author does not know of a simple (or any) algorithm for a
…		…
3363	trust me.	3600	trust me.
3364		3601
3365	=item ev_async_send (loop, ev_async *)	3602	=item ev_async_send (loop, ev_async *)
3366		3603
3367	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3604	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3368	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3605	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3606	returns.
		3607
3369	C<ev_feed_event>, this call is safe to do from other threads, signal or	3608	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3370	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3609	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3371	section below on what exactly this means).	3610	embedding section below on what exactly this means).
3372		3611
3373	Note that, as with other watchers in libev, multiple events might get	3612	Note that, as with other watchers in libev, multiple events might get
3374	compressed into a single callback invocation (another way to look at this	3613	compressed into a single callback invocation (another way to look at
3375	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3614	this is that C<ev_async> watchers are level-triggered: they are set on
3376	reset when the event loop detects that).	3615	C<ev_async_send>, reset when the event loop detects that).
3377		3616
3378	This call incurs the overhead of a system call only once per event loop	3617	This call incurs the overhead of at most one extra system call per event
3379	iteration, so while the overhead might be noticeable, it doesn't apply to	3618	loop iteration, if the event loop is blocked, and no syscall at all if
3380	repeated calls to C<ev_async_send> for the same event loop.	3619	the event loop (or your program) is processing events. That means that
		3620	repeated calls are basically free (there is no need to avoid calls for
		3621	performance reasons) and that the overhead becomes smaller (typically
		3622	zero) under load.
3381		3623
3382	=item bool = ev_async_pending (ev_async *)	3624	=item bool = ev_async_pending (ev_async *)
3383		3625
3384	Returns a non-zero value when C<ev_async_send> has been called on the	3626	Returns a non-zero value when C<ev_async_send> has been called on the
3385	watcher but the event has not yet been processed (or even noted) by the	3627	watcher but the event has not yet been processed (or even noted) by the
…		…
3402		3644
3403	There are some other functions of possible interest. Described. Here. Now.	3645	There are some other functions of possible interest. Described. Here. Now.
3404		3646
3405	=over 4	3647	=over 4
3406		3648
3407	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3649	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg)
3408		3650
3409	This function combines a simple timer and an I/O watcher, calls your	3651	This function combines a simple timer and an I/O watcher, calls your
3410	callback on whichever event happens first and automatically stops both	3652	callback on whichever event happens first and automatically stops both
3411	watchers. This is useful if you want to wait for a single event on an fd	3653	watchers. This is useful if you want to wait for a single event on an fd
3412	or timeout without having to allocate/configure/start/stop/free one or	3654	or timeout without having to allocate/configure/start/stop/free one or
…		…
3440	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3682	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3441		3683
3442	=item ev_feed_fd_event (loop, int fd, int revents)	3684	=item ev_feed_fd_event (loop, int fd, int revents)
3443		3685
3444	Feed an event on the given fd, as if a file descriptor backend detected	3686	Feed an event on the given fd, as if a file descriptor backend detected
3445	the given events it.	3687	the given events.
3446		3688
3447	=item ev_feed_signal_event (loop, int signum)	3689	=item ev_feed_signal_event (loop, int signum)
3448		3690
3449	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,	3691	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3450	which is async-safe.	3692	which is async-safe.
…		…
3455	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)	3697	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
3456		3698
3457	This section explains some common idioms that are not immediately	3699	This section explains some common idioms that are not immediately
3458	obvious. Note that examples are sprinkled over the whole manual, and this	3700	obvious. Note that examples are sprinkled over the whole manual, and this
3459	section only contains stuff that wouldn't fit anywhere else.	3701	section only contains stuff that wouldn't fit anywhere else.
		3702
		3703	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3704
		3705	Each watcher has, by default, a C<void *data> member that you can read
		3706	or modify at any time: libev will completely ignore it. This can be used
		3707	to associate arbitrary data with your watcher. If you need more data and
		3708	don't want to allocate memory separately and store a pointer to it in that
		3709	data member, you can also "subclass" the watcher type and provide your own
		3710	data:
		3711
		3712	struct my_io
		3713	{
		3714	ev_io io;
		3715	int otherfd;
		3716	void *somedata;
		3717	struct whatever *mostinteresting;
		3718	};
		3719
		3720	...
		3721	struct my_io w;
		3722	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3723
		3724	And since your callback will be called with a pointer to the watcher, you
		3725	can cast it back to your own type:
		3726
		3727	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3728	{
		3729	struct my_io *w = (struct my_io *)w_;
		3730	...
		3731	}
		3732
		3733	More interesting and less C-conformant ways of casting your callback
		3734	function type instead have been omitted.
		3735
		3736	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3737
		3738	Another common scenario is to use some data structure with multiple
		3739	embedded watchers, in effect creating your own watcher that combines
		3740	multiple libev event sources into one "super-watcher":
		3741
		3742	struct my_biggy
		3743	{
		3744	int some_data;
		3745	ev_timer t1;
		3746	ev_timer t2;
		3747	}
		3748
		3749	In this case getting the pointer to C<my_biggy> is a bit more
		3750	complicated: Either you store the address of your C<my_biggy> struct in
		3751	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3752	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3753	real programmers):
		3754
		3755	#include <stddef.h>
		3756
		3757	static void
		3758	t1_cb (EV_P_ ev_timer *w, int revents)
		3759	{
		3760	struct my_biggy big = (struct my_biggy *)
		3761	(((char *)w) - offsetof (struct my_biggy, t1));
		3762	}
		3763
		3764	static void
		3765	t2_cb (EV_P_ ev_timer *w, int revents)
		3766	{
		3767	struct my_biggy big = (struct my_biggy *)
		3768	(((char *)w) - offsetof (struct my_biggy, t2));
		3769	}
		3770
		3771	=head2 AVOIDING FINISHING BEFORE RETURNING
		3772
		3773	Often you have structures like this in event-based programs:
		3774
		3775	callback ()
		3776	{
		3777	free (request);
		3778	}
		3779
		3780	request = start_new_request (..., callback);
		3781
		3782	The intent is to start some "lengthy" operation. The C<request> could be
		3783	used to cancel the operation, or do other things with it.
		3784
		3785	It's not uncommon to have code paths in C<start_new_request> that
		3786	immediately invoke the callback, for example, to report errors. Or you add
		3787	some caching layer that finds that it can skip the lengthy aspects of the
		3788	operation and simply invoke the callback with the result.
		3789
		3790	The problem here is that this will happen I<before> C<start_new_request>
		3791	has returned, so C<request> is not set.
		3792
		3793	Even if you pass the request by some safer means to the callback, you
		3794	might want to do something to the request after starting it, such as
		3795	canceling it, which probably isn't working so well when the callback has
		3796	already been invoked.
		3797
		3798	A common way around all these issues is to make sure that
		3799	C<start_new_request> I<always> returns before the callback is invoked. If
		3800	C<start_new_request> immediately knows the result, it can artificially
		3801	delay invoking the callback by using a C<prepare> or C<idle> watcher for
		3802	example, or more sneakily, by reusing an existing (stopped) watcher and
		3803	pushing it into the pending queue:
		3804
		3805	ev_set_cb (watcher, callback);
		3806	ev_feed_event (EV_A_ watcher, 0);
		3807
		3808	This way, C<start_new_request> can safely return before the callback is
		3809	invoked, while not delaying callback invocation too much.
3460		3810
3461	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS	3811	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
3462		3812
3463	Often (especially in GUI toolkits) there are places where you have	3813	Often (especially in GUI toolkits) there are places where you have
3464	I<modal> interaction, which is most easily implemented by recursively	3814	I<modal> interaction, which is most easily implemented by recursively
…		…
3466		3816
3467	This brings the problem of exiting - a callback might want to finish the	3817	This brings the problem of exiting - a callback might want to finish the
3468	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but	3818	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
3469	a modal "Are you sure?" dialog is still waiting), or just the nested one	3819	a modal "Are you sure?" dialog is still waiting), or just the nested one
3470	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some	3820	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
3471	other combination: In these cases, C<ev_break> will not work alone.	3821	other combination: In these cases, a simple C<ev_break> will not work.
3472		3822
3473	The solution is to maintain "break this loop" variable for each C<ev_run>	3823	The solution is to maintain "break this loop" variable for each C<ev_run>
3474	invocation, and use a loop around C<ev_run> until the condition is	3824	invocation, and use a loop around C<ev_run> until the condition is
3475	triggered, using C<EVRUN_ONCE>:	3825	triggered, using C<EVRUN_ONCE>:
3476		3826
…		…
3478	int exit_main_loop = 0;	3828	int exit_main_loop = 0;
3479		3829
3480	while (!exit_main_loop)	3830	while (!exit_main_loop)
3481	ev_run (EV_DEFAULT_ EVRUN_ONCE);	3831	ev_run (EV_DEFAULT_ EVRUN_ONCE);
3482		3832
3483	// in a model watcher	3833	// in a modal watcher
3484	int exit_nested_loop = 0;	3834	int exit_nested_loop = 0;
3485		3835
3486	while (!exit_nested_loop)	3836	while (!exit_nested_loop)
3487	ev_run (EV_A_ EVRUN_ONCE);	3837	ev_run (EV_A_ EVRUN_ONCE);
3488		3838
…		…
3498	exit_main_loop = exit_nested_loop = 1;	3848	exit_main_loop = exit_nested_loop = 1;
3499		3849
3500	=head2 THREAD LOCKING EXAMPLE	3850	=head2 THREAD LOCKING EXAMPLE
3501		3851
3502	Here is a fictitious example of how to run an event loop in a different	3852	Here is a fictitious example of how to run an event loop in a different
3503	thread than where callbacks are being invoked and watchers are	3853	thread from where callbacks are being invoked and watchers are
3504	created/added/removed.	3854	created/added/removed.
3505		3855
3506	For a real-world example, see the C<EV::Loop::Async> perl module,	3856	For a real-world example, see the C<EV::Loop::Async> perl module,
3507	which uses exactly this technique (which is suited for many high-level	3857	which uses exactly this technique (which is suited for many high-level
3508	languages).	3858	languages).
…		…
3534	// now associate this with the loop	3884	// now associate this with the loop
3535	ev_set_userdata (EV_A_ u);	3885	ev_set_userdata (EV_A_ u);
3536	ev_set_invoke_pending_cb (EV_A_ l_invoke);	3886	ev_set_invoke_pending_cb (EV_A_ l_invoke);
3537	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);	3887	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
3538		3888
3539	// then create the thread running ev_loop	3889	// then create the thread running ev_run
3540	pthread_create (&u->tid, 0, l_run, EV_A);	3890	pthread_create (&u->tid, 0, l_run, EV_A);
3541	}	3891	}
3542		3892
3543	The callback for the C<ev_async> watcher does nothing: the watcher is used	3893	The callback for the C<ev_async> watcher does nothing: the watcher is used
3544	solely to wake up the event loop so it takes notice of any new watchers	3894	solely to wake up the event loop so it takes notice of any new watchers
…		…
3633	Note that sending the C<ev_async> watcher is required because otherwise	3983	Note that sending the C<ev_async> watcher is required because otherwise
3634	an event loop currently blocking in the kernel will have no knowledge	3984	an event loop currently blocking in the kernel will have no knowledge
3635	about the newly added timer. By waking up the loop it will pick up any new	3985	about the newly added timer. By waking up the loop it will pick up any new
3636	watchers in the next event loop iteration.	3986	watchers in the next event loop iteration.
3637		3987
3638	=back	3988	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3989
		3990	While the overhead of a callback that e.g. schedules a thread is small, it
		3991	is still an overhead. If you embed libev, and your main usage is with some
		3992	kind of threads or coroutines, you might want to customise libev so that
		3993	doesn't need callbacks anymore.
		3994
		3995	Imagine you have coroutines that you can switch to using a function
		3996	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3997	and that due to some magic, the currently active coroutine is stored in a
		3998	global called C<current_coro>. Then you can build your own "wait for libev
		3999	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		4000	the differing C<;> conventions):
		4001
		4002	#define EV_CB_DECLARE(type) struct my_coro *cb;
		4003	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		4004
		4005	That means instead of having a C callback function, you store the
		4006	coroutine to switch to in each watcher, and instead of having libev call
		4007	your callback, you instead have it switch to that coroutine.
		4008
		4009	A coroutine might now wait for an event with a function called
		4010	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		4011	matter when, or whether the watcher is active or not when this function is
		4012	called):
		4013
		4014	void
		4015	wait_for_event (ev_watcher *w)
		4016	{
		4017	ev_set_cb (w, current_coro);
		4018	switch_to (libev_coro);
		4019	}
		4020
		4021	That basically suspends the coroutine inside C<wait_for_event> and
		4022	continues the libev coroutine, which, when appropriate, switches back to
		4023	this or any other coroutine.
		4024
		4025	You can do similar tricks if you have, say, threads with an event queue -
		4026	instead of storing a coroutine, you store the queue object and instead of
		4027	switching to a coroutine, you push the watcher onto the queue and notify
		4028	any waiters.
		4029
		4030	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		4031	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		4032
		4033	// my_ev.h
		4034	#define EV_CB_DECLARE(type) struct my_coro *cb;
		4035	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		4036	#include "../libev/ev.h"
		4037
		4038	// my_ev.c
		4039	#define EV_H "my_ev.h"
		4040	#include "../libev/ev.c"
		4041
		4042	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		4043	F<my_ev.c> into your project. When properly specifying include paths, you
		4044	can even use F<ev.h> as header file name directly.
3639		4045
3640		4046
3641	=head1 LIBEVENT EMULATION	4047	=head1 LIBEVENT EMULATION
3642		4048
3643	Libev offers a compatibility emulation layer for libevent. It cannot	4049	Libev offers a compatibility emulation layer for libevent. It cannot
…		…
3673		4079
3674	=back	4080	=back
3675		4081
3676	=head1 C++ SUPPORT	4082	=head1 C++ SUPPORT
3677		4083
		4084	=head2 C API
		4085
		4086	The normal C API should work fine when used from C++: both ev.h and the
		4087	libev sources can be compiled as C++. Therefore, code that uses the C API
		4088	will work fine.
		4089
		4090	Proper exception specifications might have to be added to callbacks passed
		4091	to libev: exceptions may be thrown only from watcher callbacks, all other
		4092	callbacks (allocator, syserr, loop acquire/release and periodic reschedule
		4093	callbacks) must not throw exceptions, and might need a C<noexcept>
		4094	specification. If you have code that needs to be compiled as both C and
		4095	C++ you can use the C<EV_NOEXCEPT> macro for this:
		4096
		4097	static void
		4098	fatal_error (const char *msg) EV_NOEXCEPT
		4099	{
		4100	perror (msg);
		4101	abort ();
		4102	}
		4103
		4104	...
		4105	ev_set_syserr_cb (fatal_error);
		4106
		4107	The only API functions that can currently throw exceptions are C<ev_run>,
		4108	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		4109	because it runs cleanup watchers).
		4110
		4111	Throwing exceptions in watcher callbacks is only supported if libev itself
		4112	is compiled with a C++ compiler or your C and C++ environments allow
		4113	throwing exceptions through C libraries (most do).
		4114
		4115	=head2 C++ API
		4116
3678	Libev comes with some simplistic wrapper classes for C++ that mainly allow	4117	Libev comes with some simplistic wrapper classes for C++ that mainly allow
3679	you to use some convenience methods to start/stop watchers and also change	4118	you to use some convenience methods to start/stop watchers and also change
3680	the callback model to a model using method callbacks on objects.	4119	the callback model to a model using method callbacks on objects.
3681		4120
3682	To use it,	4121	To use it,
3683		4122
3684	#include <ev++.h>	4123	#include <ev++.h>
3685		4124
3686	This automatically includes F<ev.h> and puts all of its definitions (many	4125	This automatically includes F<ev.h> and puts all of its definitions (many
3687	of them macros) into the global namespace. All C++ specific things are	4126	of them macros) into the global namespace. All C++ specific things are
3688	put into the C<ev> namespace. It should support all the same embedding	4127	put into the C<ev> namespace. It should support all the same embedding
…		…
3697	with C<operator ()> can be used as callbacks. Other types should be easy	4136	with C<operator ()> can be used as callbacks. Other types should be easy
3698	to add as long as they only need one additional pointer for context. If	4137	to add as long as they only need one additional pointer for context. If
3699	you need support for other types of functors please contact the author	4138	you need support for other types of functors please contact the author
3700	(preferably after implementing it).	4139	(preferably after implementing it).
3701		4140
		4141	For all this to work, your C++ compiler either has to use the same calling
		4142	conventions as your C compiler (for static member functions), or you have
		4143	to embed libev and compile libev itself as C++.
		4144
3702	Here is a list of things available in the C<ev> namespace:	4145	Here is a list of things available in the C<ev> namespace:
3703		4146
3704	=over 4	4147	=over 4
3705		4148
3706	=item C<ev::READ>, C<ev::WRITE> etc.	4149	=item C<ev::READ>, C<ev::WRITE> etc.
…		…
3715	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4158	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3716		4159
3717	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4160	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
3718	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4161	the same name in the C<ev> namespace, with the exception of C<ev_signal>
3719	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4162	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3720	defines by many implementations.	4163	defined by many implementations.
3721		4164
3722	All of those classes have these methods:	4165	All of those classes have these methods:
3723		4166
3724	=over 4	4167	=over 4
3725		4168
…		…
3787	void operator() (ev::io &w, int revents)	4230	void operator() (ev::io &w, int revents)
3788	{	4231	{
3789	...	4232	...
3790	}	4233	}
3791	}	4234	}
3792		4235
3793	myfunctor f;	4236	myfunctor f;
3794		4237
3795	ev::io w;	4238	ev::io w;
3796	w.set (&f);	4239	w.set (&f);
3797		4240
…		…
3815	Associates a different C<struct ev_loop> with this watcher. You can only	4258	Associates a different C<struct ev_loop> with this watcher. You can only
3816	do this when the watcher is inactive (and not pending either).	4259	do this when the watcher is inactive (and not pending either).
3817		4260
3818	=item w->set ([arguments])	4261	=item w->set ([arguments])
3819		4262
3820	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this	4263	Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>),
3821	method or a suitable start method must be called at least once. Unlike the	4264	with the same arguments. Either this method or a suitable start method
3822	C counterpart, an active watcher gets automatically stopped and restarted	4265	must be called at least once. Unlike the C counterpart, an active watcher
3823	when reconfiguring it with this method.	4266	gets automatically stopped and restarted when reconfiguring it with this
		4267	method.
		4268
		4269	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4270	clashing with the C<set (loop)> method.
		4271
		4272	For C<ev::io> watchers there is an additional C<set> method that acepts a
		4273	new event mask only, and internally calls C<ev_io_modfify>.
3824		4274
3825	=item w->start ()	4275	=item w->start ()
3826		4276
3827	Starts the watcher. Note that there is no C<loop> argument, as the	4277	Starts the watcher. Note that there is no C<loop> argument, as the
3828	constructor already stores the event loop.	4278	constructor already stores the event loop.
…		…
3858	watchers in the constructor.	4308	watchers in the constructor.
3859		4309
3860	class myclass	4310	class myclass
3861	{	4311	{
3862	ev::io io ; void io_cb (ev::io &w, int revents);	4312	ev::io io ; void io_cb (ev::io &w, int revents);
3863	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);	4313	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3864	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4314	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3865		4315
3866	myclass (int fd)	4316	myclass (int fd)
3867	{	4317	{
3868	io .set <myclass, &myclass::io_cb > (this);	4318	io .set <myclass, &myclass::io_cb > (this);
…		…
3919	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4369	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3920		4370
3921	=item D	4371	=item D
3922		4372
3923	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4373	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3924	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4374	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3925		4375
3926	=item Ocaml	4376	=item Ocaml
3927		4377
3928	Erkki Seppala has written Ocaml bindings for libev, to be found at	4378	Erkki Seppala has written Ocaml bindings for libev, to be found at
3929	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4379	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
…		…
3932		4382
3933	Brian Maher has written a partial interface to libev for lua (at the	4383	Brian Maher has written a partial interface to libev for lua (at the
3934	time of this writing, only C<ev_io> and C<ev_timer>), to be found at	4384	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
3935	L<http://github.com/brimworks/lua-ev>.	4385	L<http://github.com/brimworks/lua-ev>.
3936		4386
		4387	=item Javascript
		4388
		4389	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4390
		4391	=item Others
		4392
		4393	There are others, and I stopped counting.
		4394
3937	=back	4395	=back
3938		4396
3939		4397
3940	=head1 MACRO MAGIC	4398	=head1 MACRO MAGIC
3941		4399
…		…
3977	suitable for use with C<EV_A>.	4435	suitable for use with C<EV_A>.
3978		4436
3979	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4437	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3980		4438
3981	Similar to the other two macros, this gives you the value of the default	4439	Similar to the other two macros, this gives you the value of the default
3982	loop, if multiple loops are supported ("ev loop default").	4440	loop, if multiple loops are supported ("ev loop default"). The default loop
		4441	will be initialised if it isn't already initialised.
		4442
		4443	For non-multiplicity builds, these macros do nothing, so you always have
		4444	to initialise the loop somewhere.
3983		4445
3984	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4446	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3985		4447
3986	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4448	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3987	default loop has been initialised (C<UC> == unchecked). Their behaviour	4449	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
4054	ev_vars.h	4516	ev_vars.h
4055	ev_wrap.h	4517	ev_wrap.h
4056		4518
4057	ev_win32.c required on win32 platforms only	4519	ev_win32.c required on win32 platforms only
4058		4520
4059	ev_select.c only when select backend is enabled (which is enabled by default)	4521	ev_select.c only when select backend is enabled
4060	ev_poll.c only when poll backend is enabled (disabled by default)	4522	ev_poll.c only when poll backend is enabled
4061	ev_epoll.c only when the epoll backend is enabled (disabled by default)	4523	ev_epoll.c only when the epoll backend is enabled
		4524	ev_linuxaio.c only when the linux aio backend is enabled
		4525	ev_iouring.c only when the linux io_uring backend is enabled
4062	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	4526	ev_kqueue.c only when the kqueue backend is enabled
4063	ev_port.c only when the solaris port backend is enabled (disabled by default)	4527	ev_port.c only when the solaris port backend is enabled
4064		4528
4065	F<ev.c> includes the backend files directly when enabled, so you only need	4529	F<ev.c> includes the backend files directly when enabled, so you only need
4066	to compile this single file.	4530	to compile this single file.
4067		4531
4068	=head3 LIBEVENT COMPATIBILITY API	4532	=head3 LIBEVENT COMPATIBILITY API
…		…
4132	supported). It will also not define any of the structs usually found in	4596	supported). It will also not define any of the structs usually found in
4133	F<event.h> that are not directly supported by the libev core alone.	4597	F<event.h> that are not directly supported by the libev core alone.
4134		4598
4135	In standalone mode, libev will still try to automatically deduce the	4599	In standalone mode, libev will still try to automatically deduce the
4136	configuration, but has to be more conservative.	4600	configuration, but has to be more conservative.
		4601
		4602	=item EV_USE_FLOOR
		4603
		4604	If defined to be C<1>, libev will use the C<floor ()> function for its
		4605	periodic reschedule calculations, otherwise libev will fall back on a
		4606	portable (slower) implementation. If you enable this, you usually have to
		4607	link against libm or something equivalent. Enabling this when the C<floor>
		4608	function is not available will fail, so the safe default is to not enable
		4609	this.
4137		4610
4138	=item EV_USE_MONOTONIC	4611	=item EV_USE_MONOTONIC
4139		4612
4140	If defined to be C<1>, libev will try to detect the availability of the	4613	If defined to be C<1>, libev will try to detect the availability of the
4141	monotonic clock option at both compile time and runtime. Otherwise no	4614	monotonic clock option at both compile time and runtime. Otherwise no
…		…
4178	available and will probe for kernel support at runtime. This will improve	4651	available and will probe for kernel support at runtime. This will improve
4179	C<ev_signal> and C<ev_async> performance and reduce resource consumption.	4652	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
4180	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc	4653	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
4181	2.7 or newer, otherwise disabled.	4654	2.7 or newer, otherwise disabled.
4182		4655
		4656	=item EV_USE_SIGNALFD
		4657
		4658	If defined to be C<1>, then libev will assume that C<signalfd ()> is
		4659	available and will probe for kernel support at runtime. This enables
		4660	the use of EVFLAG_SIGNALFD for faster and simpler signal handling. If
		4661	undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		4662	2.7 or newer, otherwise disabled.
		4663
		4664	=item EV_USE_TIMERFD
		4665
		4666	If defined to be C<1>, then libev will assume that C<timerfd ()> is
		4667	available and will probe for kernel support at runtime. This allows
		4668	libev to detect time jumps accurately. If undefined, it will be enabled
		4669	if the headers indicate GNU/Linux + Glibc 2.8 or newer and define
		4670	C<TFD_TIMER_CANCEL_ON_SET>, otherwise disabled.
		4671
		4672	=item EV_USE_EVENTFD
		4673
		4674	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		4675	available and will probe for kernel support at runtime. This will improve
		4676	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		4677	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		4678	2.7 or newer, otherwise disabled.
		4679
4183	=item EV_USE_SELECT	4680	=item EV_USE_SELECT
4184		4681
4185	If undefined or defined to be C<1>, libev will compile in support for the	4682	If undefined or defined to be C<1>, libev will compile in support for the
4186	C<select>(2) backend. No attempt at auto-detection will be done: if no	4683	C<select>(2) backend. No attempt at auto-detection will be done: if no
4187	other method takes over, select will be it. Otherwise the select backend	4684	other method takes over, select will be it. Otherwise the select backend
…		…
4227	If programs implement their own fd to handle mapping on win32, then this	4724	If programs implement their own fd to handle mapping on win32, then this
4228	macro can be used to override the C<close> function, useful to unregister	4725	macro can be used to override the C<close> function, useful to unregister
4229	file descriptors again. Note that the replacement function has to close	4726	file descriptors again. Note that the replacement function has to close
4230	the underlying OS handle.	4727	the underlying OS handle.
4231		4728
		4729	=item EV_USE_WSASOCKET
		4730
		4731	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4732	communication socket, which works better in some environments. Otherwise,
		4733	the normal C<socket> function will be used, which works better in other
		4734	environments.
		4735
4232	=item EV_USE_POLL	4736	=item EV_USE_POLL
4233		4737
4234	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4738	If defined to be C<1>, libev will compile in support for the C<poll>(2)
4235	backend. Otherwise it will be enabled on non-win32 platforms. It	4739	backend. Otherwise it will be enabled on non-win32 platforms. It
4236	takes precedence over select.	4740	takes precedence over select.
…		…
4240	If defined to be C<1>, libev will compile in support for the Linux	4744	If defined to be C<1>, libev will compile in support for the Linux
4241	C<epoll>(7) backend. Its availability will be detected at runtime,	4745	C<epoll>(7) backend. Its availability will be detected at runtime,
4242	otherwise another method will be used as fallback. This is the preferred	4746	otherwise another method will be used as fallback. This is the preferred
4243	backend for GNU/Linux systems. If undefined, it will be enabled if the	4747	backend for GNU/Linux systems. If undefined, it will be enabled if the
4244	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4748	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		4749
		4750	=item EV_USE_LINUXAIO
		4751
		4752	If defined to be C<1>, libev will compile in support for the Linux aio
		4753	backend (C<EV_USE_EPOLL> must also be enabled). If undefined, it will be
		4754	enabled on linux, otherwise disabled.
		4755
		4756	=item EV_USE_IOURING
		4757
		4758	If defined to be C<1>, libev will compile in support for the Linux
		4759	io_uring backend (C<EV_USE_EPOLL> must also be enabled). Due to it's
		4760	current limitations it has to be requested explicitly. If undefined, it
		4761	will be enabled on linux, otherwise disabled.
4245		4762
4246	=item EV_USE_KQUEUE	4763	=item EV_USE_KQUEUE
4247		4764
4248	If defined to be C<1>, libev will compile in support for the BSD style	4765	If defined to be C<1>, libev will compile in support for the BSD style
4249	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	4766	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
4271	If defined to be C<1>, libev will compile in support for the Linux inotify	4788	If defined to be C<1>, libev will compile in support for the Linux inotify
4272	interface to speed up C<ev_stat> watchers. Its actual availability will	4789	interface to speed up C<ev_stat> watchers. Its actual availability will
4273	be detected at runtime. If undefined, it will be enabled if the headers	4790	be detected at runtime. If undefined, it will be enabled if the headers
4274	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4791	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
4275		4792
		4793	=item EV_NO_SMP
		4794
		4795	If defined to be C<1>, libev will assume that memory is always coherent
		4796	between threads, that is, threads can be used, but threads never run on
		4797	different cpus (or different cpu cores). This reduces dependencies
		4798	and makes libev faster.
		4799
		4800	=item EV_NO_THREADS
		4801
		4802	If defined to be C<1>, libev will assume that it will never be called from
		4803	different threads (that includes signal handlers), which is a stronger
		4804	assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes
		4805	libev faster.
		4806
4276	=item EV_ATOMIC_T	4807	=item EV_ATOMIC_T
4277		4808
4278	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4809	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
4279	access is atomic with respect to other threads or signal contexts. No such	4810	access is atomic with respect to other threads or signal contexts. No
4280	type is easily found in the C language, so you can provide your own type	4811	such type is easily found in the C language, so you can provide your own
4281	that you know is safe for your purposes. It is used both for signal handler "locking"	4812	type that you know is safe for your purposes. It is used both for signal
4282	as well as for signal and thread safety in C<ev_async> watchers.	4813	handler "locking" as well as for signal and thread safety in C<ev_async>
		4814	watchers.
4283		4815
4284	In the absence of this define, libev will use C<sig_atomic_t volatile>	4816	In the absence of this define, libev will use C<sig_atomic_t volatile>
4285	(from F<signal.h>), which is usually good enough on most platforms.	4817	(from F<signal.h>), which is usually good enough on most platforms.
4286		4818
4287	=item EV_H (h)	4819	=item EV_H (h)
…		…
4314	will have the C<struct ev_loop *> as first argument, and you can create	4846	will have the C<struct ev_loop *> as first argument, and you can create
4315	additional independent event loops. Otherwise there will be no support	4847	additional independent event loops. Otherwise there will be no support
4316	for multiple event loops and there is no first event loop pointer	4848	for multiple event loops and there is no first event loop pointer
4317	argument. Instead, all functions act on the single default loop.	4849	argument. Instead, all functions act on the single default loop.
4318		4850
		4851	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4852	default loop when multiplicity is switched off - you always have to
		4853	initialise the loop manually in this case.
		4854
4319	=item EV_MINPRI	4855	=item EV_MINPRI
4320		4856
4321	=item EV_MAXPRI	4857	=item EV_MAXPRI
4322		4858
4323	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4859	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
4359	#define EV_USE_POLL 1	4895	#define EV_USE_POLL 1
4360	#define EV_CHILD_ENABLE 1	4896	#define EV_CHILD_ENABLE 1
4361	#define EV_ASYNC_ENABLE 1	4897	#define EV_ASYNC_ENABLE 1
4362		4898
4363	The actual value is a bitset, it can be a combination of the following	4899	The actual value is a bitset, it can be a combination of the following
4364	values:	4900	values (by default, all of these are enabled):
4365		4901
4366	=over 4	4902	=over 4
4367		4903
4368	=item C<1> - faster/larger code	4904	=item C<1> - faster/larger code
4369		4905
…		…
4373	code size by roughly 30% on amd64).	4909	code size by roughly 30% on amd64).
4374		4910
4375	When optimising for size, use of compiler flags such as C<-Os> with	4911	When optimising for size, use of compiler flags such as C<-Os> with
4376	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of	4912	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
4377	assertions.	4913	assertions.
		4914
		4915	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4916	(e.g. gcc with C<-Os>).
4378		4917
4379	=item C<2> - faster/larger data structures	4918	=item C<2> - faster/larger data structures
4380		4919
4381	Replaces the small 2-heap for timer management by a faster 4-heap, larger	4920	Replaces the small 2-heap for timer management by a faster 4-heap, larger
4382	hash table sizes and so on. This will usually further increase code size	4921	hash table sizes and so on. This will usually further increase code size
4383	and can additionally have an effect on the size of data structures at	4922	and can additionally have an effect on the size of data structures at
4384	runtime.	4923	runtime.
4385		4924
		4925	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4926	(e.g. gcc with C<-Os>).
		4927
4386	=item C<4> - full API configuration	4928	=item C<4> - full API configuration
4387		4929
4388	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and	4930	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
4389	enables multiplicity (C<EV_MULTIPLICITY>=1).	4931	enables multiplicity (C<EV_MULTIPLICITY>=1).
4390		4932
…		…
4420		4962
4421	With an intelligent-enough linker (gcc+binutils are intelligent enough	4963	With an intelligent-enough linker (gcc+binutils are intelligent enough
4422	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by	4964	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
4423	your program might be left out as well - a binary starting a timer and an	4965	your program might be left out as well - a binary starting a timer and an
4424	I/O watcher then might come out at only 5Kb.	4966	I/O watcher then might come out at only 5Kb.
		4967
		4968	=item EV_API_STATIC
		4969
		4970	If this symbol is defined (by default it is not), then all identifiers
		4971	will have static linkage. This means that libev will not export any
		4972	identifiers, and you cannot link against libev anymore. This can be useful
		4973	when you embed libev, only want to use libev functions in a single file,
		4974	and do not want its identifiers to be visible.
		4975
		4976	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4977	wants to use libev.
		4978
		4979	This option only works when libev is compiled with a C compiler, as C++
		4980	doesn't support the required declaration syntax.
4425		4981
4426	=item EV_AVOID_STDIO	4982	=item EV_AVOID_STDIO
4427		4983
4428	If this is set to C<1> at compiletime, then libev will avoid using stdio	4984	If this is set to C<1> at compiletime, then libev will avoid using stdio
4429	functions (printf, scanf, perror etc.). This will increase the code size	4985	functions (printf, scanf, perror etc.). This will increase the code size
…		…
4487	in. If set to C<1>, then verification code will be compiled in, but not	5043	in. If set to C<1>, then verification code will be compiled in, but not
4488	called. If set to C<2>, then the internal verification code will be	5044	called. If set to C<2>, then the internal verification code will be
4489	called once per loop, which can slow down libev. If set to C<3>, then the	5045	called once per loop, which can slow down libev. If set to C<3>, then the
4490	verification code will be called very frequently, which will slow down	5046	verification code will be called very frequently, which will slow down
4491	libev considerably.	5047	libev considerably.
		5048
		5049	Verification errors are reported via C's C<assert> mechanism, so if you
		5050	disable that (e.g. by defining C<NDEBUG>) then no errors will be reported.
4492		5051
4493	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it	5052	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
4494	will be C<0>.	5053	will be C<0>.
4495		5054
4496	=item EV_COMMON	5055	=item EV_COMMON
…		…
4573	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	5132	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4574		5133
4575	#include "ev_cpp.h"	5134	#include "ev_cpp.h"
4576	#include "ev.c"	5135	#include "ev.c"
4577		5136
4578	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	5137	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4579		5138
4580	=head2 THREADS AND COROUTINES	5139	=head2 THREADS AND COROUTINES
4581		5140
4582	=head3 THREADS	5141	=head3 THREADS
4583		5142
…		…
4634	default loop and triggering an C<ev_async> watcher from the default loop	5193	default loop and triggering an C<ev_async> watcher from the default loop
4635	watcher callback into the event loop interested in the signal.	5194	watcher callback into the event loop interested in the signal.
4636		5195
4637	=back	5196	=back
4638		5197
4639	See also L<THREAD LOCKING EXAMPLE>.	5198	See also L</THREAD LOCKING EXAMPLE>.
4640		5199
4641	=head3 COROUTINES	5200	=head3 COROUTINES
4642		5201
4643	Libev is very accommodating to coroutines ("cooperative threads"):	5202	Libev is very accommodating to coroutines ("cooperative threads"):
4644	libev fully supports nesting calls to its functions from different	5203	libev fully supports nesting calls to its functions from different
…		…
4809	requires, and its I/O model is fundamentally incompatible with the POSIX	5368	requires, and its I/O model is fundamentally incompatible with the POSIX
4810	model. Libev still offers limited functionality on this platform in	5369	model. Libev still offers limited functionality on this platform in
4811	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5370	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4812	descriptors. This only applies when using Win32 natively, not when using	5371	descriptors. This only applies when using Win32 natively, not when using
4813	e.g. cygwin. Actually, it only applies to the microsofts own compilers,	5372	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
4814	as every compielr comes with a slightly differently broken/incompatible	5373	as every compiler comes with a slightly differently broken/incompatible
4815	environment.	5374	environment.
4816		5375
4817	Lifting these limitations would basically require the full	5376	Lifting these limitations would basically require the full
4818	re-implementation of the I/O system. If you are into this kind of thing,	5377	re-implementation of the I/O system. If you are into this kind of thing,
4819	then note that glib does exactly that for you in a very portable way (note	5378	then note that glib does exactly that for you in a very portable way (note
…		…
4913	structure (guaranteed by POSIX but not by ISO C for example), but it also	5472	structure (guaranteed by POSIX but not by ISO C for example), but it also
4914	assumes that the same (machine) code can be used to call any watcher	5473	assumes that the same (machine) code can be used to call any watcher
4915	callback: The watcher callbacks have different type signatures, but libev	5474	callback: The watcher callbacks have different type signatures, but libev
4916	calls them using an C<ev_watcher *> internally.	5475	calls them using an C<ev_watcher *> internally.
4917		5476
		5477	=item null pointers and integer zero are represented by 0 bytes
		5478
		5479	Libev uses C<memset> to initialise structs and arrays to C<0> bytes, and
		5480	relies on this setting pointers and integers to null.
		5481
4918	=item pointer accesses must be thread-atomic	5482	=item pointer accesses must be thread-atomic
4919		5483
4920	Accessing a pointer value must be atomic, it must both be readable and	5484	Accessing a pointer value must be atomic, it must both be readable and
4921	writable in one piece - this is the case on all current architectures.	5485	writable in one piece - this is the case on all current architectures.
4922		5486
…		…
4935	thread" or will block signals process-wide, both behaviours would	5499	thread" or will block signals process-wide, both behaviours would
4936	be compatible with libev. Interaction between C<sigprocmask> and	5500	be compatible with libev. Interaction between C<sigprocmask> and
4937	C<pthread_sigmask> could complicate things, however.	5501	C<pthread_sigmask> could complicate things, however.
4938		5502
4939	The most portable way to handle signals is to block signals in all threads	5503	The most portable way to handle signals is to block signals in all threads
4940	except the initial one, and run the default loop in the initial thread as	5504	except the initial one, and run the signal handling loop in the initial
4941	well.	5505	thread as well.
4942		5506
4943	=item C<long> must be large enough for common memory allocation sizes	5507	=item C<long> must be large enough for common memory allocation sizes
4944		5508
4945	To improve portability and simplify its API, libev uses C<long> internally	5509	To improve portability and simplify its API, libev uses C<long> internally
4946	instead of C<size_t> when allocating its data structures. On non-POSIX	5510	instead of C<size_t> when allocating its data structures. On non-POSIX
…		…
4952		5516
4953	The type C<double> is used to represent timestamps. It is required to	5517	The type C<double> is used to represent timestamps. It is required to
4954	have at least 51 bits of mantissa (and 9 bits of exponent), which is	5518	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4955	good enough for at least into the year 4000 with millisecond accuracy	5519	good enough for at least into the year 4000 with millisecond accuracy
4956	(the design goal for libev). This requirement is overfulfilled by	5520	(the design goal for libev). This requirement is overfulfilled by
4957	implementations using IEEE 754, which is basically all existing ones. With	5521	implementations using IEEE 754, which is basically all existing ones.
		5522
4958	IEEE 754 doubles, you get microsecond accuracy until at least 2200.	5523	With IEEE 754 doubles, you get microsecond accuracy until at least the
		5524	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5525	is either obsolete or somebody patched it to use C<long double> or
		5526	something like that, just kidding).
4959		5527
4960	=back	5528	=back
4961		5529
4962	If you know of other additional requirements drop me a note.	5530	If you know of other additional requirements drop me a note.
4963		5531
…		…
5025	=item Processing ev_async_send: O(number_of_async_watchers)	5593	=item Processing ev_async_send: O(number_of_async_watchers)
5026		5594
5027	=item Processing signals: O(max_signal_number)	5595	=item Processing signals: O(max_signal_number)
5028		5596
5029	Sending involves a system call I<iff> there were no other C<ev_async_send>	5597	Sending involves a system call I<iff> there were no other C<ev_async_send>
5030	calls in the current loop iteration. Checking for async and signal events	5598	calls in the current loop iteration and the loop is currently
		5599	blocked. Checking for async and signal events involves iterating over all
5031	involves iterating over all running async watchers or all signal numbers.	5600	running async watchers or all signal numbers.
5032		5601
5033	=back	5602	=back
5034		5603
5035		5604
5036	=head1 PORTING FROM LIBEV 3.X TO 4.X	5605	=head1 PORTING FROM LIBEV 3.X TO 4.X
…		…
5045	=over 4	5614	=over 4
5046		5615
5047	=item C<EV_COMPAT3> backwards compatibility mechanism	5616	=item C<EV_COMPAT3> backwards compatibility mechanism
5048		5617
5049	The backward compatibility mechanism can be controlled by	5618	The backward compatibility mechanism can be controlled by
5050	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>	5619	C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING>
5051	section.	5620	section.
5052		5621
5053	=item C<ev_default_destroy> and C<ev_default_fork> have been removed	5622	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
5054		5623
5055	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:	5624	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
…		…
5098	=over 4	5667	=over 4
5099		5668
5100	=item active	5669	=item active
5101		5670
5102	A watcher is active as long as it has been started and not yet stopped.	5671	A watcher is active as long as it has been started and not yet stopped.
5103	See L<WATCHER STATES> for details.	5672	See L</WATCHER STATES> for details.
5104		5673
5105	=item application	5674	=item application
5106		5675
5107	In this document, an application is whatever is using libev.	5676	In this document, an application is whatever is using libev.
5108		5677
…		…
5144	watchers and events.	5713	watchers and events.
5145		5714
5146	=item pending	5715	=item pending
5147		5716
5148	A watcher is pending as soon as the corresponding event has been	5717	A watcher is pending as soon as the corresponding event has been
5149	detected. See L<WATCHER STATES> for details.	5718	detected. See L</WATCHER STATES> for details.
5150		5719
5151	=item real time	5720	=item real time
5152		5721
5153	The physical time that is observed. It is apparently strictly monotonic :)	5722	The physical time that is observed. It is apparently strictly monotonic :)
5154		5723
5155	=item wall-clock time	5724	=item wall-clock time
5156		5725
5157	The time and date as shown on clocks. Unlike real time, it can actually	5726	The time and date as shown on clocks. Unlike real time, it can actually
5158	be wrong and jump forwards and backwards, e.g. when the you adjust your	5727	be wrong and jump forwards and backwards, e.g. when you adjust your
5159	clock.	5728	clock.
5160		5729
5161	=item watcher	5730	=item watcher
5162		5731
5163	A data structure that describes interest in certain events. Watchers need	5732	A data structure that describes interest in certain events. Watchers need
…		…
5166	=back	5735	=back
5167		5736
5168	=head1 AUTHOR	5737	=head1 AUTHOR
5169		5738
5170	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael	5739	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
5171	Magnusson and Emanuele Giaquinta.	5740	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
5172		5741

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