ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.323 by root, Sun Oct 24 18:01:26 2010 UTC vs.
Revision 1.445 by root, Fri Dec 21 06:54:30 2018 UTC

		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
…		…
77	on event-based programming, nor will it introduce event-based programming	79	on event-based programming, nor will it introduce event-based programming
78	with libev.	80	with libev.
79		81
80	Familiarity with event based programming techniques in general is assumed	82	Familiarity with event based programming techniques in general is assumed
81	throughout this document.	83	throughout this document.
		84
		85	=head1 WHAT TO READ WHEN IN A HURRY
		86
		87	This manual tries to be very detailed, but unfortunately, this also makes
		88	it very long. If you just want to know the basics of libev, I suggest
		89	reading L</ANATOMY OF A WATCHER>, then the L</EXAMPLE PROGRAM> above and
		90	look up the missing functions in L</GLOBAL FUNCTIONS> and the C<ev_io> and
		91	C<ev_timer> sections in L</WATCHER TYPES>.
82		92
83	=head1 ABOUT LIBEV	93	=head1 ABOUT LIBEV
84		94
85	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
86	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
…		…
166	=item ev_tstamp ev_time ()	176	=item ev_tstamp ev_time ()
167		177
168	Returns the current time as libev would use it. Please note that the	178	Returns the current time as libev would use it. Please note that the
169	C<ev_now> function is usually faster and also often returns the timestamp	179	C<ev_now> function is usually faster and also often returns the timestamp
170	you actually want to know. Also interesting is the combination of	180	you actually want to know. Also interesting is the combination of
171	C<ev_update_now> and C<ev_now>.	181	C<ev_now_update> and C<ev_now>.
172		182
173	=item ev_sleep (ev_tstamp interval)	183	=item ev_sleep (ev_tstamp interval)
174		184
175	Sleep for the given interval: The current thread will be blocked until	185	Sleep for the given interval: The current thread will be blocked
176	either it is interrupted or the given time interval has passed. Basically	186	until either it is interrupted or the given time interval has
		187	passed (approximately - it might return a bit earlier even if not
		188	interrupted). Returns immediately if C<< interval <= 0 >>.
		189
177	this is a sub-second-resolution C<sleep ()>.	190	Basically this is a sub-second-resolution C<sleep ()>.
		191
		192	The range of the C<interval> is limited - libev only guarantees to work
		193	with sleep times of up to one day (C<< interval <= 86400 >>).
178		194
179	=item int ev_version_major ()	195	=item int ev_version_major ()
180		196
181	=item int ev_version_minor ()	197	=item int ev_version_minor ()
182		198
…		…
233	the current system, you would need to look at C<ev_embeddable_backends ()	249	the current system, you would need to look at C<ev_embeddable_backends ()
234	& ev_supported_backends ()>, likewise for recommended ones.	250	& ev_supported_backends ()>, likewise for recommended ones.
235		251
236	See the description of C<ev_embed> watchers for more info.	252	See the description of C<ev_embed> watchers for more info.
237		253
238	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	254	=item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())
239		255
240	Sets the allocation function to use (the prototype is similar - the	256	Sets the allocation function to use (the prototype is similar - the
241	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	257	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
242	used to allocate and free memory (no surprises here). If it returns zero	258	used to allocate and free memory (no surprises here). If it returns zero
243	when memory needs to be allocated (C<size != 0>), the library might abort	259	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
269	}	285	}
270		286
271	...	287	...
272	ev_set_allocator (persistent_realloc);	288	ev_set_allocator (persistent_realloc);
273		289
274	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	290	=item ev_set_syserr_cb (void (*cb)(const char *msg) throw ())
275		291
276	Set the callback function to call on a retryable system call error (such	292	Set the callback function to call on a retryable system call error (such
277	as failed select, poll, epoll_wait). The message is a printable string	293	as failed select, poll, epoll_wait). The message is a printable string
278	indicating the system call or subsystem causing the problem. If this	294	indicating the system call or subsystem causing the problem. If this
279	callback is set, then libev will expect it to remedy the situation, no	295	callback is set, then libev will expect it to remedy the situation, no
…		…
291	}	307	}
292		308
293	...	309	...
294	ev_set_syserr_cb (fatal_error);	310	ev_set_syserr_cb (fatal_error);
295		311
		312	=item ev_feed_signal (int signum)
		313
		314	This function can be used to "simulate" a signal receive. It is completely
		315	safe to call this function at any time, from any context, including signal
		316	handlers or random threads.
		317
		318	Its main use is to customise signal handling in your process, especially
		319	in the presence of threads. For example, you could block signals
		320	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		321	creating any loops), and in one thread, use C<sigwait> or any other
		322	mechanism to wait for signals, then "deliver" them to libev by calling
		323	C<ev_feed_signal>.
		324
296	=back	325	=back
297		326
298	=head1 FUNCTIONS CONTROLLING EVENT LOOPS	327	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
299		328
300	An event loop is described by a C<struct ev_loop *> (the C<struct> is	329	An event loop is described by a C<struct ev_loop *> (the C<struct> is
301	I<not> optional in this case unless libev 3 compatibility is disabled, as	330	I<not> optional in this case unless libev 3 compatibility is disabled, as
302	libev 3 had an C<ev_loop> function colliding with the struct name).	331	libev 3 had an C<ev_loop> function colliding with the struct name).
303		332
304	The library knows two types of such loops, the I<default> loop, which	333	The library knows two types of such loops, the I<default> loop, which
305	supports signals and child events, and dynamically created event loops	334	supports child process events, and dynamically created event loops which
306	which do not.	335	do not.
307		336
308	=over 4	337	=over 4
309		338
310	=item struct ev_loop *ev_default_loop (unsigned int flags)	339	=item struct ev_loop *ev_default_loop (unsigned int flags)
311		340
…		…
347	=item struct ev_loop *ev_loop_new (unsigned int flags)	376	=item struct ev_loop *ev_loop_new (unsigned int flags)
348		377
349	This will create and initialise a new event loop object. If the loop	378	This will create and initialise a new event loop object. If the loop
350	could not be initialised, returns false.	379	could not be initialised, returns false.
351		380
352	Note that this function I<is> thread-safe, and one common way to use	381	This function is thread-safe, and one common way to use libev with
353	libev with threads is indeed to create one loop per thread, and using the	382	threads is indeed to create one loop per thread, and using the default
354	default loop in the "main" or "initial" thread.	383	loop in the "main" or "initial" thread.
355		384
356	The flags argument can be used to specify special behaviour or specific	385	The flags argument can be used to specify special behaviour or specific
357	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	386	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
358		387
359	The following flags are supported:	388	The following flags are supported:
…		…
369		398
370	If this flag bit is or'ed into the flag value (or the program runs setuid	399	If this flag bit is or'ed into the flag value (or the program runs setuid
371	or setgid) then libev will I<not> look at the environment variable	400	or setgid) then libev will I<not> look at the environment variable
372	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	401	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
373	override the flags completely if it is found in the environment. This is	402	override the flags completely if it is found in the environment. This is
374	useful to try out specific backends to test their performance, or to work	403	useful to try out specific backends to test their performance, to work
375	around bugs.	404	around bugs, or to make libev threadsafe (accessing environment variables
		405	cannot be done in a threadsafe way, but usually it works if no other
		406	thread modifies them).
376		407
377	=item C<EVFLAG_FORKCHECK>	408	=item C<EVFLAG_FORKCHECK>
378		409
379	Instead of calling C<ev_loop_fork> manually after a fork, you can also	410	Instead of calling C<ev_loop_fork> manually after a fork, you can also
380	make libev check for a fork in each iteration by enabling this flag.	411	make libev check for a fork in each iteration by enabling this flag.
381		412
382	This works by calling C<getpid ()> on every iteration of the loop,	413	This works by calling C<getpid ()> on every iteration of the loop,
383	and thus this might slow down your event loop if you do a lot of loop	414	and thus this might slow down your event loop if you do a lot of loop
384	iterations and little real work, but is usually not noticeable (on my	415	iterations and little real work, but is usually not noticeable (on my
385	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	416	GNU/Linux system for example, C<getpid> is actually a simple 5-insn
386	without a system call and thus I<very> fast, but my GNU/Linux system also has	417	sequence without a system call and thus I<very> fast, but my GNU/Linux
387	C<pthread_atfork> which is even faster).	418	system also has C<pthread_atfork> which is even faster). (Update: glibc
		419	versions 2.25 apparently removed the C<getpid> optimisation again).
388		420
389	The big advantage of this flag is that you can forget about fork (and	421	The big advantage of this flag is that you can forget about fork (and
390	forget about forgetting to tell libev about forking) when you use this	422	forget about forgetting to tell libev about forking, although you still
391	flag.	423	have to ignore C<SIGPIPE>) when you use this flag.
392		424
393	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	425	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
394	environment variable.	426	environment variable.
395		427
396	=item C<EVFLAG_NOINOTIFY>	428	=item C<EVFLAG_NOINOTIFY>
397		429
398	When this flag is specified, then libev will not attempt to use the	430	When this flag is specified, then libev will not attempt to use the
399	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and	431	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
400	testing, this flag can be useful to conserve inotify file descriptors, as	432	testing, this flag can be useful to conserve inotify file descriptors, as
401	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.	433	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
402		434
403	=item C<EVFLAG_SIGNALFD>	435	=item C<EVFLAG_SIGNALFD>
404		436
405	When this flag is specified, then libev will attempt to use the	437	When this flag is specified, then libev will attempt to use the
406	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API	438	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
407	delivers signals synchronously, which makes it both faster and might make	439	delivers signals synchronously, which makes it both faster and might make
408	it possible to get the queued signal data. It can also simplify signal	440	it possible to get the queued signal data. It can also simplify signal
409	handling with threads, as long as you properly block signals in your	441	handling with threads, as long as you properly block signals in your
410	threads that are not interested in handling them.	442	threads that are not interested in handling them.
411		443
412	Signalfd will not be used by default as this changes your signal mask, and	444	Signalfd will not be used by default as this changes your signal mask, and
413	there are a lot of shoddy libraries and programs (glib's threadpool for	445	there are a lot of shoddy libraries and programs (glib's threadpool for
414	example) that can't properly initialise their signal masks.	446	example) that can't properly initialise their signal masks.
		447
		448	=item C<EVFLAG_NOSIGMASK>
		449
		450	When this flag is specified, then libev will avoid to modify the signal
		451	mask. Specifically, this means you have to make sure signals are unblocked
		452	when you want to receive them.
		453
		454	This behaviour is useful when you want to do your own signal handling, or
		455	want to handle signals only in specific threads and want to avoid libev
		456	unblocking the signals.
		457
		458	It's also required by POSIX in a threaded program, as libev calls
		459	C<sigprocmask>, whose behaviour is officially unspecified.
		460
		461	This flag's behaviour will become the default in future versions of libev.
415		462
416	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	463	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
417		464
418	This is your standard select(2) backend. Not I<completely> standard, as	465	This is your standard select(2) backend. Not I<completely> standard, as
419	libev tries to roll its own fd_set with no limits on the number of fds,	466	libev tries to roll its own fd_set with no limits on the number of fds,
…		…
447	=item C<EVBACKEND_EPOLL> (value 4, Linux)	494	=item C<EVBACKEND_EPOLL> (value 4, Linux)
448		495
449	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9	496	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
450	kernels).	497	kernels).
451		498
452	For few fds, this backend is a bit little slower than poll and select,	499	For few fds, this backend is a bit little slower than poll and select, but
453	but it scales phenomenally better. While poll and select usually scale	500	it scales phenomenally better. While poll and select usually scale like
454	like O(total_fds) where n is the total number of fds (or the highest fd),	501	O(total_fds) where total_fds is the total number of fds (or the highest
455	epoll scales either O(1) or O(active_fds).	502	fd), epoll scales either O(1) or O(active_fds).
456		503
457	The epoll mechanism deserves honorable mention as the most misdesigned	504	The epoll mechanism deserves honorable mention as the most misdesigned
458	of the more advanced event mechanisms: mere annoyances include silently	505	of the more advanced event mechanisms: mere annoyances include silently
459	dropping file descriptors, requiring a system call per change per file	506	dropping file descriptors, requiring a system call per change per file
460	descriptor (and unnecessary guessing of parameters), problems with dup and	507	descriptor (and unnecessary guessing of parameters), problems with dup,
		508	returning before the timeout value, resulting in additional iterations
		509	(and only giving 5ms accuracy while select on the same platform gives
461	so on. The biggest issue is fork races, however - if a program forks then	510	0.1ms) and so on. The biggest issue is fork races, however - if a program
462	I<both> parent and child process have to recreate the epoll set, which can	511	forks then I<both> parent and child process have to recreate the epoll
463	take considerable time (one syscall per file descriptor) and is of course	512	set, which can take considerable time (one syscall per file descriptor)
464	hard to detect.	513	and is of course hard to detect.
465		514
466	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	515	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
467	of course I<doesn't>, and epoll just loves to report events for totally	516	but of course I<doesn't>, and epoll just loves to report events for
468	I<different> file descriptors (even already closed ones, so one cannot	517	totally I<different> file descriptors (even already closed ones, so
469	even remove them from the set) than registered in the set (especially	518	one cannot even remove them from the set) than registered in the set
470	on SMP systems). Libev tries to counter these spurious notifications by	519	(especially on SMP systems). Libev tries to counter these spurious
471	employing an additional generation counter and comparing that against the	520	notifications by employing an additional generation counter and comparing
472	events to filter out spurious ones, recreating the set when required. Last	521	that against the events to filter out spurious ones, recreating the set
		522	when required. Epoll also erroneously rounds down timeouts, but gives you
		523	no way to know when and by how much, so sometimes you have to busy-wait
		524	because epoll returns immediately despite a nonzero timeout. And last
473	not least, it also refuses to work with some file descriptors which work	525	not least, it also refuses to work with some file descriptors which work
474	perfectly fine with C<select> (files, many character devices...).	526	perfectly fine with C<select> (files, many character devices...).
		527
		528	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
		529	cobbled together in a hurry, no thought to design or interaction with
		530	others. Oh, the pain, will it ever stop...
475		531
476	While stopping, setting and starting an I/O watcher in the same iteration	532	While stopping, setting and starting an I/O watcher in the same iteration
477	will result in some caching, there is still a system call per such	533	will result in some caching, there is still a system call per such
478	incident (because the same I<file descriptor> could point to a different	534	incident (because the same I<file descriptor> could point to a different
479	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	535	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
516		572
517	It scales in the same way as the epoll backend, but the interface to the	573	It scales in the same way as the epoll backend, but the interface to the
518	kernel is more efficient (which says nothing about its actual speed, of	574	kernel is more efficient (which says nothing about its actual speed, of
519	course). While stopping, setting and starting an I/O watcher does never	575	course). While stopping, setting and starting an I/O watcher does never
520	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	576	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
521	two event changes per incident. Support for C<fork ()> is very bad (but	577	two event changes per incident. Support for C<fork ()> is very bad (you
522	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect	578	might have to leak fd's on fork, but it's more sane than epoll) and it
523	cases	579	drops fds silently in similarly hard-to-detect cases.
524		580
525	This backend usually performs well under most conditions.	581	This backend usually performs well under most conditions.
526		582
527	While nominally embeddable in other event loops, this doesn't work	583	While nominally embeddable in other event loops, this doesn't work
528	everywhere, so you might need to test for this. And since it is broken	584	everywhere, so you might need to test for this. And since it is broken
…		…
545	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	601	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
546		602
547	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	603	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
548	it's really slow, but it still scales very well (O(active_fds)).	604	it's really slow, but it still scales very well (O(active_fds)).
549		605
550	Please note that Solaris event ports can deliver a lot of spurious
551	notifications, so you need to use non-blocking I/O or other means to avoid
552	blocking when no data (or space) is available.
553
554	While this backend scales well, it requires one system call per active	606	While this backend scales well, it requires one system call per active
555	file descriptor per loop iteration. For small and medium numbers of file	607	file descriptor per loop iteration. For small and medium numbers of file
556	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	608	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
557	might perform better.	609	might perform better.
558		610
559	On the positive side, with the exception of the spurious readiness	611	On the positive side, this backend actually performed fully to
560	notifications, this backend actually performed fully to specification
561	in all tests and is fully embeddable, which is a rare feat among the	612	specification in all tests and is fully embeddable, which is a rare feat
562	OS-specific backends (I vastly prefer correctness over speed hacks).	613	among the OS-specific backends (I vastly prefer correctness over speed
		614	hacks).
		615
		616	On the negative side, the interface is I<bizarre> - so bizarre that
		617	even sun itself gets it wrong in their code examples: The event polling
		618	function sometimes returns events to the caller even though an error
		619	occurred, but with no indication whether it has done so or not (yes, it's
		620	even documented that way) - deadly for edge-triggered interfaces where you
		621	absolutely have to know whether an event occurred or not because you have
		622	to re-arm the watcher.
		623
		624	Fortunately libev seems to be able to work around these idiocies.
563		625
564	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	626	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
565	C<EVBACKEND_POLL>.	627	C<EVBACKEND_POLL>.
566		628
567	=item C<EVBACKEND_ALL>	629	=item C<EVBACKEND_ALL>
568		630
569	Try all backends (even potentially broken ones that wouldn't be tried	631	Try all backends (even potentially broken ones that wouldn't be tried
570	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	632	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
571	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	633	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
572		634
573	It is definitely not recommended to use this flag.	635	It is definitely not recommended to use this flag, use whatever
		636	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		637	at all.
		638
		639	=item C<EVBACKEND_MASK>
		640
		641	Not a backend at all, but a mask to select all backend bits from a
		642	C<flags> value, in case you want to mask out any backends from a flags
		643	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
574		644
575	=back	645	=back
576		646
577	If one or more of the backend flags are or'ed into the flags value,	647	If one or more of the backend flags are or'ed into the flags value,
578	then only these backends will be tried (in the reverse order as listed	648	then only these backends will be tried (in the reverse order as listed
…		…
607	This function is normally used on loop objects allocated by	677	This function is normally used on loop objects allocated by
608	C<ev_loop_new>, but it can also be used on the default loop returned by	678	C<ev_loop_new>, but it can also be used on the default loop returned by
609	C<ev_default_loop>, in which case it is not thread-safe.	679	C<ev_default_loop>, in which case it is not thread-safe.
610		680
611	Note that it is not advisable to call this function on the default loop	681	Note that it is not advisable to call this function on the default loop
612	except in the rare occasion where you really need to free it's resources.	682	except in the rare occasion where you really need to free its resources.
613	If you need dynamically allocated loops it is better to use C<ev_loop_new>	683	If you need dynamically allocated loops it is better to use C<ev_loop_new>
614	and C<ev_loop_destroy>.	684	and C<ev_loop_destroy>.
615		685
616	=item ev_loop_fork (loop)	686	=item ev_loop_fork (loop)
617		687
618	This function sets a flag that causes subsequent C<ev_run> iterations to	688	This function sets a flag that causes subsequent C<ev_run> iterations
619	reinitialise the kernel state for backends that have one. Despite the	689	to reinitialise the kernel state for backends that have one. Despite
620	name, you can call it anytime, but it makes most sense after forking, in	690	the name, you can call it anytime you are allowed to start or stop
621	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the	691	watchers (except inside an C<ev_prepare> callback), but it makes most
		692	sense after forking, in the child process. You I<must> call it (or use
622	child before resuming or calling C<ev_run>.	693	C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>.
623		694
		695	In addition, if you want to reuse a loop (via this function or
		696	C<EVFLAG_FORKCHECK>), you I<also> have to ignore C<SIGPIPE>.
		697
624	Again, you I<have> to call it on I<any> loop that you want to re-use after	698	Again, you I<have> to call it on I<any> loop that you want to re-use after
625	a fork, I<even if you do not plan to use the loop in the parent>. This is	699	a fork, I<even if you do not plan to use the loop in the parent>. This is
626	because some kernel interfaces *cough* I<kqueue> *cough* do funny things	700	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
627	during fork.	701	during fork.
628		702
629	On the other hand, you only need to call this function in the child	703	On the other hand, you only need to call this function in the child
…		…
665	prepare and check phases.	739	prepare and check phases.
666		740
667	=item unsigned int ev_depth (loop)	741	=item unsigned int ev_depth (loop)
668		742
669	Returns the number of times C<ev_run> was entered minus the number of	743	Returns the number of times C<ev_run> was entered minus the number of
670	times C<ev_run> was exited, in other words, the recursion depth.	744	times C<ev_run> was exited normally, in other words, the recursion depth.
671		745
672	Outside C<ev_run>, this number is zero. In a callback, this number is	746	Outside C<ev_run>, this number is zero. In a callback, this number is
673	C<1>, unless C<ev_run> was invoked recursively (or from another thread),	747	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
674	in which case it is higher.	748	in which case it is higher.
675		749
676	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread	750	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
677	etc.), doesn't count as "exit" - consider this as a hint to avoid such	751	throwing an exception etc.), doesn't count as "exit" - consider this
678	ungentleman-like behaviour unless it's really convenient.	752	as a hint to avoid such ungentleman-like behaviour unless it's really
		753	convenient, in which case it is fully supported.
679		754
680	=item unsigned int ev_backend (loop)	755	=item unsigned int ev_backend (loop)
681		756
682	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	757	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
683	use.	758	use.
…		…
698		773
699	This function is rarely useful, but when some event callback runs for a	774	This function is rarely useful, but when some event callback runs for a
700	very long time without entering the event loop, updating libev's idea of	775	very long time without entering the event loop, updating libev's idea of
701	the current time is a good idea.	776	the current time is a good idea.
702		777
703	See also L<The special problem of time updates> in the C<ev_timer> section.	778	See also L</The special problem of time updates> in the C<ev_timer> section.
704		779
705	=item ev_suspend (loop)	780	=item ev_suspend (loop)
706		781
707	=item ev_resume (loop)	782	=item ev_resume (loop)
708		783
…		…
726	without a previous call to C<ev_suspend>.	801	without a previous call to C<ev_suspend>.
727		802
728	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	803	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
729	event loop time (see C<ev_now_update>).	804	event loop time (see C<ev_now_update>).
730		805
731	=item ev_run (loop, int flags)	806	=item bool ev_run (loop, int flags)
732		807
733	Finally, this is it, the event handler. This function usually is called	808	Finally, this is it, the event handler. This function usually is called
734	after you have initialised all your watchers and you want to start	809	after you have initialised all your watchers and you want to start
735	handling events. It will ask the operating system for any new events, call	810	handling events. It will ask the operating system for any new events, call
736	the watcher callbacks, an then repeat the whole process indefinitely: This	811	the watcher callbacks, and then repeat the whole process indefinitely: This
737	is why event loops are called I<loops>.	812	is why event loops are called I<loops>.
738		813
739	If the flags argument is specified as C<0>, it will keep handling events	814	If the flags argument is specified as C<0>, it will keep handling events
740	until either no event watchers are active anymore or C<ev_break> was	815	until either no event watchers are active anymore or C<ev_break> was
741	called.	816	called.
		817
		818	The return value is false if there are no more active watchers (which
		819	usually means "all jobs done" or "deadlock"), and true in all other cases
		820	(which usually means " you should call C<ev_run> again").
742		821
743	Please note that an explicit C<ev_break> is usually better than	822	Please note that an explicit C<ev_break> is usually better than
744	relying on all watchers to be stopped when deciding when a program has	823	relying on all watchers to be stopped when deciding when a program has
745	finished (especially in interactive programs), but having a program	824	finished (especially in interactive programs), but having a program
746	that automatically loops as long as it has to and no longer by virtue	825	that automatically loops as long as it has to and no longer by virtue
747	of relying on its watchers stopping correctly, that is truly a thing of	826	of relying on its watchers stopping correctly, that is truly a thing of
748	beauty.	827	beauty.
749		828
		829	This function is I<mostly> exception-safe - you can break out of a
		830	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		831	exception and so on. This does not decrement the C<ev_depth> value, nor
		832	will it clear any outstanding C<EVBREAK_ONE> breaks.
		833
750	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle	834	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
751	those events and any already outstanding ones, but will not wait and	835	those events and any already outstanding ones, but will not wait and
752	block your process in case there are no events and will return after one	836	block your process in case there are no events and will return after one
753	iteration of the loop. This is sometimes useful to poll and handle new	837	iteration of the loop. This is sometimes useful to poll and handle new
754	events while doing lengthy calculations, to keep the program responsive.	838	events while doing lengthy calculations, to keep the program responsive.
…		…
763	This is useful if you are waiting for some external event in conjunction	847	This is useful if you are waiting for some external event in conjunction
764	with something not expressible using other libev watchers (i.e. "roll your	848	with something not expressible using other libev watchers (i.e. "roll your
765	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	849	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
766	usually a better approach for this kind of thing.	850	usually a better approach for this kind of thing.
767		851
768	Here are the gory details of what C<ev_run> does:	852	Here are the gory details of what C<ev_run> does (this is for your
		853	understanding, not a guarantee that things will work exactly like this in
		854	future versions):
769		855
770	- Increment loop depth.	856	- Increment loop depth.
771	- Reset the ev_break status.	857	- Reset the ev_break status.
772	- Before the first iteration, call any pending watchers.	858	- Before the first iteration, call any pending watchers.
773	LOOP:	859	LOOP:
…		…
806	anymore.	892	anymore.
807		893
808	... queue jobs here, make sure they register event watchers as long	894	... queue jobs here, make sure they register event watchers as long
809	... as they still have work to do (even an idle watcher will do..)	895	... as they still have work to do (even an idle watcher will do..)
810	ev_run (my_loop, 0);	896	ev_run (my_loop, 0);
811	... jobs done or somebody called unloop. yeah!	897	... jobs done or somebody called break. yeah!
812		898
813	=item ev_break (loop, how)	899	=item ev_break (loop, how)
814		900
815	Can be used to make a call to C<ev_run> return early (but only after it	901	Can be used to make a call to C<ev_run> return early (but only after it
816	has processed all outstanding events). The C<how> argument must be either	902	has processed all outstanding events). The C<how> argument must be either
817	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or	903	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
818	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.	904	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
819		905
820	This "unloop state" will be cleared when entering C<ev_run> again.	906	This "break state" will be cleared on the next call to C<ev_run>.
821		907
822	It is safe to call C<ev_break> from outside any C<ev_run> calls. ##TODO##	908	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		909	which case it will have no effect.
823		910
824	=item ev_ref (loop)	911	=item ev_ref (loop)
825		912
826	=item ev_unref (loop)	913	=item ev_unref (loop)
827		914
…		…
848	running when nothing else is active.	935	running when nothing else is active.
849		936
850	ev_signal exitsig;	937	ev_signal exitsig;
851	ev_signal_init (&exitsig, sig_cb, SIGINT);	938	ev_signal_init (&exitsig, sig_cb, SIGINT);
852	ev_signal_start (loop, &exitsig);	939	ev_signal_start (loop, &exitsig);
853	evf_unref (loop);	940	ev_unref (loop);
854		941
855	Example: For some weird reason, unregister the above signal handler again.	942	Example: For some weird reason, unregister the above signal handler again.
856		943
857	ev_ref (loop);	944	ev_ref (loop);
858	ev_signal_stop (loop, &exitsig);	945	ev_signal_stop (loop, &exitsig);
…		…
878	overhead for the actual polling but can deliver many events at once.	965	overhead for the actual polling but can deliver many events at once.
879		966
880	By setting a higher I<io collect interval> you allow libev to spend more	967	By setting a higher I<io collect interval> you allow libev to spend more
881	time collecting I/O events, so you can handle more events per iteration,	968	time collecting I/O events, so you can handle more events per iteration,
882	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	969	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
883	C<ev_timer>) will be not affected. Setting this to a non-null value will	970	C<ev_timer>) will not be affected. Setting this to a non-null value will
884	introduce an additional C<ev_sleep ()> call into most loop iterations. The	971	introduce an additional C<ev_sleep ()> call into most loop iterations. The
885	sleep time ensures that libev will not poll for I/O events more often then	972	sleep time ensures that libev will not poll for I/O events more often then
886	once per this interval, on average.	973	once per this interval, on average (as long as the host time resolution is
		974	good enough).
887		975
888	Likewise, by setting a higher I<timeout collect interval> you allow libev	976	Likewise, by setting a higher I<timeout collect interval> you allow libev
889	to spend more time collecting timeouts, at the expense of increased	977	to spend more time collecting timeouts, at the expense of increased
890	latency/jitter/inexactness (the watcher callback will be called	978	latency/jitter/inexactness (the watcher callback will be called
891	later). C<ev_io> watchers will not be affected. Setting this to a non-null	979	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
937	invoke the actual watchers inside another context (another thread etc.).	1025	invoke the actual watchers inside another context (another thread etc.).
938		1026
939	If you want to reset the callback, use C<ev_invoke_pending> as new	1027	If you want to reset the callback, use C<ev_invoke_pending> as new
940	callback.	1028	callback.
941		1029
942	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))	1030	=item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())
943		1031
944	Sometimes you want to share the same loop between multiple threads. This	1032	Sometimes you want to share the same loop between multiple threads. This
945	can be done relatively simply by putting mutex_lock/unlock calls around	1033	can be done relatively simply by putting mutex_lock/unlock calls around
946	each call to a libev function.	1034	each call to a libev function.
947		1035
948	However, C<ev_run> can run an indefinite time, so it is not feasible	1036	However, C<ev_run> can run an indefinite time, so it is not feasible
949	to wait for it to return. One way around this is to wake up the event	1037	to wait for it to return. One way around this is to wake up the event
950	loop via C<ev_break> and C<av_async_send>, another way is to set these	1038	loop via C<ev_break> and C<ev_async_send>, another way is to set these
951	I<release> and I<acquire> callbacks on the loop.	1039	I<release> and I<acquire> callbacks on the loop.
952		1040
953	When set, then C<release> will be called just before the thread is	1041	When set, then C<release> will be called just before the thread is
954	suspended waiting for new events, and C<acquire> is called just	1042	suspended waiting for new events, and C<acquire> is called just
955	afterwards.	1043	afterwards.
…		…
970	See also the locking example in the C<THREADS> section later in this	1058	See also the locking example in the C<THREADS> section later in this
971	document.	1059	document.
972		1060
973	=item ev_set_userdata (loop, void *data)	1061	=item ev_set_userdata (loop, void *data)
974		1062
975	=item ev_userdata (loop)	1063	=item void *ev_userdata (loop)
976		1064
977	Set and retrieve a single C<void *> associated with a loop. When	1065	Set and retrieve a single C<void *> associated with a loop. When
978	C<ev_set_userdata> has never been called, then C<ev_userdata> returns	1066	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
979	C<0.>	1067	C<0>.
980		1068
981	These two functions can be used to associate arbitrary data with a loop,	1069	These two functions can be used to associate arbitrary data with a loop,
982	and are intended solely for the C<invoke_pending_cb>, C<release> and	1070	and are intended solely for the C<invoke_pending_cb>, C<release> and
983	C<acquire> callbacks described above, but of course can be (ab-)used for	1071	C<acquire> callbacks described above, but of course can be (ab-)used for
984	any other purpose as well.	1072	any other purpose as well.
…		…
1095		1183
1096	=item C<EV_PREPARE>	1184	=item C<EV_PREPARE>
1097		1185
1098	=item C<EV_CHECK>	1186	=item C<EV_CHECK>
1099		1187
1100	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts	1188	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to
1101	to gather new events, and all C<ev_check> watchers are invoked just after	1189	gather new events, and all C<ev_check> watchers are queued (not invoked)
1102	C<ev_run> has gathered them, but before it invokes any callbacks for any	1190	just after C<ev_run> has gathered them, but before it queues any callbacks
		1191	for any received events. That means C<ev_prepare> watchers are the last
		1192	watchers invoked before the event loop sleeps or polls for new events, and
		1193	C<ev_check> watchers will be invoked before any other watchers of the same
		1194	or lower priority within an event loop iteration.
		1195
1103	received events. Callbacks of both watcher types can start and stop as	1196	Callbacks of both watcher types can start and stop as many watchers as
1104	many watchers as they want, and all of them will be taken into account	1197	they want, and all of them will be taken into account (for example, a
1105	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1198	C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from
1106	C<ev_run> from blocking).	1199	blocking).
1107		1200
1108	=item C<EV_EMBED>	1201	=item C<EV_EMBED>
1109		1202
1110	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1203	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1111		1204
1112	=item C<EV_FORK>	1205	=item C<EV_FORK>
1113		1206
1114	The event loop has been resumed in the child process after fork (see	1207	The event loop has been resumed in the child process after fork (see
1115	C<ev_fork>).	1208	C<ev_fork>).
		1209
		1210	=item C<EV_CLEANUP>
		1211
		1212	The event loop is about to be destroyed (see C<ev_cleanup>).
1116		1213
1117	=item C<EV_ASYNC>	1214	=item C<EV_ASYNC>
1118		1215
1119	The given async watcher has been asynchronously notified (see C<ev_async>).	1216	The given async watcher has been asynchronously notified (see C<ev_async>).
1120		1217
…		…
1142	programs, though, as the fd could already be closed and reused for another	1239	programs, though, as the fd could already be closed and reused for another
1143	thing, so beware.	1240	thing, so beware.
1144		1241
1145	=back	1242	=back
1146		1243
		1244	=head2 GENERIC WATCHER FUNCTIONS
		1245
		1246	=over 4
		1247
		1248	=item C<ev_init> (ev_TYPE *watcher, callback)
		1249
		1250	This macro initialises the generic portion of a watcher. The contents
		1251	of the watcher object can be arbitrary (so C<malloc> will do). Only
		1252	the generic parts of the watcher are initialised, you I<need> to call
		1253	the type-specific C<ev_TYPE_set> macro afterwards to initialise the
		1254	type-specific parts. For each type there is also a C<ev_TYPE_init> macro
		1255	which rolls both calls into one.
		1256
		1257	You can reinitialise a watcher at any time as long as it has been stopped
		1258	(or never started) and there are no pending events outstanding.
		1259
		1260	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
		1261	int revents)>.
		1262
		1263	Example: Initialise an C<ev_io> watcher in two steps.
		1264
		1265	ev_io w;
		1266	ev_init (&w, my_cb);
		1267	ev_io_set (&w, STDIN_FILENO, EV_READ);
		1268
		1269	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
		1270
		1271	This macro initialises the type-specific parts of a watcher. You need to
		1272	call C<ev_init> at least once before you call this macro, but you can
		1273	call C<ev_TYPE_set> any number of times. You must not, however, call this
		1274	macro on a watcher that is active (it can be pending, however, which is a
		1275	difference to the C<ev_init> macro).
		1276
		1277	Although some watcher types do not have type-specific arguments
		1278	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
		1279
		1280	See C<ev_init>, above, for an example.
		1281
		1282	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
		1283
		1284	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
		1285	calls into a single call. This is the most convenient method to initialise
		1286	a watcher. The same limitations apply, of course.
		1287
		1288	Example: Initialise and set an C<ev_io> watcher in one step.
		1289
		1290	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1291
		1292	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
		1293
		1294	Starts (activates) the given watcher. Only active watchers will receive
		1295	events. If the watcher is already active nothing will happen.
		1296
		1297	Example: Start the C<ev_io> watcher that is being abused as example in this
		1298	whole section.
		1299
		1300	ev_io_start (EV_DEFAULT_UC, &w);
		1301
		1302	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
		1303
		1304	Stops the given watcher if active, and clears the pending status (whether
		1305	the watcher was active or not).
		1306
		1307	It is possible that stopped watchers are pending - for example,
		1308	non-repeating timers are being stopped when they become pending - but
		1309	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
		1310	pending. If you want to free or reuse the memory used by the watcher it is
		1311	therefore a good idea to always call its C<ev_TYPE_stop> function.
		1312
		1313	=item bool ev_is_active (ev_TYPE *watcher)
		1314
		1315	Returns a true value iff the watcher is active (i.e. it has been started
		1316	and not yet been stopped). As long as a watcher is active you must not modify
		1317	it.
		1318
		1319	=item bool ev_is_pending (ev_TYPE *watcher)
		1320
		1321	Returns a true value iff the watcher is pending, (i.e. it has outstanding
		1322	events but its callback has not yet been invoked). As long as a watcher
		1323	is pending (but not active) you must not call an init function on it (but
		1324	C<ev_TYPE_set> is safe), you must not change its priority, and you must
		1325	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		1326	it).
		1327
		1328	=item callback ev_cb (ev_TYPE *watcher)
		1329
		1330	Returns the callback currently set on the watcher.
		1331
		1332	=item ev_set_cb (ev_TYPE *watcher, callback)
		1333
		1334	Change the callback. You can change the callback at virtually any time
		1335	(modulo threads).
		1336
		1337	=item ev_set_priority (ev_TYPE *watcher, int priority)
		1338
		1339	=item int ev_priority (ev_TYPE *watcher)
		1340
		1341	Set and query the priority of the watcher. The priority is a small
		1342	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		1343	(default: C<-2>). Pending watchers with higher priority will be invoked
		1344	before watchers with lower priority, but priority will not keep watchers
		1345	from being executed (except for C<ev_idle> watchers).
		1346
		1347	If you need to suppress invocation when higher priority events are pending
		1348	you need to look at C<ev_idle> watchers, which provide this functionality.
		1349
		1350	You I<must not> change the priority of a watcher as long as it is active or
		1351	pending.
		1352
		1353	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1354	fine, as long as you do not mind that the priority value you query might
		1355	or might not have been clamped to the valid range.
		1356
		1357	The default priority used by watchers when no priority has been set is
		1358	always C<0>, which is supposed to not be too high and not be too low :).
		1359
		1360	See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
		1361	priorities.
		1362
		1363	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		1364
		1365	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		1366	C<loop> nor C<revents> need to be valid as long as the watcher callback
		1367	can deal with that fact, as both are simply passed through to the
		1368	callback.
		1369
		1370	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		1371
		1372	If the watcher is pending, this function clears its pending status and
		1373	returns its C<revents> bitset (as if its callback was invoked). If the
		1374	watcher isn't pending it does nothing and returns C<0>.
		1375
		1376	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1377	callback to be invoked, which can be accomplished with this function.
		1378
		1379	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1380
		1381	Feeds the given event set into the event loop, as if the specified event
		1382	had happened for the specified watcher (which must be a pointer to an
		1383	initialised but not necessarily started event watcher). Obviously you must
		1384	not free the watcher as long as it has pending events.
		1385
		1386	Stopping the watcher, letting libev invoke it, or calling
		1387	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1388	not started in the first place.
		1389
		1390	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1391	functions that do not need a watcher.
		1392
		1393	=back
		1394
		1395	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
		1396	OWN COMPOSITE WATCHERS> idioms.
		1397
1147	=head2 WATCHER STATES	1398	=head2 WATCHER STATES
1148		1399
1149	There are various watcher states mentioned throughout this manual -	1400	There are various watcher states mentioned throughout this manual -
1150	active, pending and so on. In this section these states and the rules to	1401	active, pending and so on. In this section these states and the rules to
1151	transition between them will be described in more detail - and while these	1402	transition between them will be described in more detail - and while these
1152	rules might look complicated, they usually do "the right thing".	1403	rules might look complicated, they usually do "the right thing".
1153		1404
1154	=over 4	1405	=over 4
1155		1406
1156	=item initialiased	1407	=item initialised
1157		1408
1158	Before a watcher can be registered with the event looop it has to be	1409	Before a watcher can be registered with the event loop it has to be
1159	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to	1410	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
1160	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.	1411	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1161		1412
1162	In this state it is simply some block of memory that is suitable for use	1413	In this state it is simply some block of memory that is suitable for
1163	in an event loop. It can be moved around, freed, reused etc. at will.	1414	use in an event loop. It can be moved around, freed, reused etc. at
		1415	will - as long as you either keep the memory contents intact, or call
		1416	C<ev_TYPE_init> again.
1164		1417
1165	=item started/running/active	1418	=item started/running/active
1166		1419
1167	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes	1420	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1168	property of the event loop, and is actively waiting for events. While in	1421	property of the event loop, and is actively waiting for events. While in
…		…
1196	latter will clear any pending state the watcher might be in, regardless	1449	latter will clear any pending state the watcher might be in, regardless
1197	of whether it was active or not, so stopping a watcher explicitly before	1450	of whether it was active or not, so stopping a watcher explicitly before
1198	freeing it is often a good idea.	1451	freeing it is often a good idea.
1199		1452
1200	While stopped (and not pending) the watcher is essentially in the	1453	While stopped (and not pending) the watcher is essentially in the
1201	initialised state, that is it can be reused, moved, modified in any way	1454	initialised state, that is, it can be reused, moved, modified in any way
1202	you wish.	1455	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1456	it again).
1203		1457
1204	=back	1458	=back
1205
1206	=head2 GENERIC WATCHER FUNCTIONS
1207
1208	=over 4
1209
1210	=item C<ev_init> (ev_TYPE *watcher, callback)
1211
1212	This macro initialises the generic portion of a watcher. The contents
1213	of the watcher object can be arbitrary (so C<malloc> will do). Only
1214	the generic parts of the watcher are initialised, you I<need> to call
1215	the type-specific C<ev_TYPE_set> macro afterwards to initialise the
1216	type-specific parts. For each type there is also a C<ev_TYPE_init> macro
1217	which rolls both calls into one.
1218
1219	You can reinitialise a watcher at any time as long as it has been stopped
1220	(or never started) and there are no pending events outstanding.
1221
1222	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
1223	int revents)>.
1224
1225	Example: Initialise an C<ev_io> watcher in two steps.
1226
1227	ev_io w;
1228	ev_init (&w, my_cb);
1229	ev_io_set (&w, STDIN_FILENO, EV_READ);
1230
1231	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
1232
1233	This macro initialises the type-specific parts of a watcher. You need to
1234	call C<ev_init> at least once before you call this macro, but you can
1235	call C<ev_TYPE_set> any number of times. You must not, however, call this
1236	macro on a watcher that is active (it can be pending, however, which is a
1237	difference to the C<ev_init> macro).
1238
1239	Although some watcher types do not have type-specific arguments
1240	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
1241
1242	See C<ev_init>, above, for an example.
1243
1244	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
1245
1246	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
1247	calls into a single call. This is the most convenient method to initialise
1248	a watcher. The same limitations apply, of course.
1249
1250	Example: Initialise and set an C<ev_io> watcher in one step.
1251
1252	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1253
1254	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1255
1256	Starts (activates) the given watcher. Only active watchers will receive
1257	events. If the watcher is already active nothing will happen.
1258
1259	Example: Start the C<ev_io> watcher that is being abused as example in this
1260	whole section.
1261
1262	ev_io_start (EV_DEFAULT_UC, &w);
1263
1264	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1265
1266	Stops the given watcher if active, and clears the pending status (whether
1267	the watcher was active or not).
1268
1269	It is possible that stopped watchers are pending - for example,
1270	non-repeating timers are being stopped when they become pending - but
1271	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
1272	pending. If you want to free or reuse the memory used by the watcher it is
1273	therefore a good idea to always call its C<ev_TYPE_stop> function.
1274
1275	=item bool ev_is_active (ev_TYPE *watcher)
1276
1277	Returns a true value iff the watcher is active (i.e. it has been started
1278	and not yet been stopped). As long as a watcher is active you must not modify
1279	it.
1280
1281	=item bool ev_is_pending (ev_TYPE *watcher)
1282
1283	Returns a true value iff the watcher is pending, (i.e. it has outstanding
1284	events but its callback has not yet been invoked). As long as a watcher
1285	is pending (but not active) you must not call an init function on it (but
1286	C<ev_TYPE_set> is safe), you must not change its priority, and you must
1287	make sure the watcher is available to libev (e.g. you cannot C<free ()>
1288	it).
1289
1290	=item callback ev_cb (ev_TYPE *watcher)
1291
1292	Returns the callback currently set on the watcher.
1293
1294	=item ev_cb_set (ev_TYPE *watcher, callback)
1295
1296	Change the callback. You can change the callback at virtually any time
1297	(modulo threads).
1298
1299	=item ev_set_priority (ev_TYPE *watcher, int priority)
1300
1301	=item int ev_priority (ev_TYPE *watcher)
1302
1303	Set and query the priority of the watcher. The priority is a small
1304	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1305	(default: C<-2>). Pending watchers with higher priority will be invoked
1306	before watchers with lower priority, but priority will not keep watchers
1307	from being executed (except for C<ev_idle> watchers).
1308
1309	If you need to suppress invocation when higher priority events are pending
1310	you need to look at C<ev_idle> watchers, which provide this functionality.
1311
1312	You I<must not> change the priority of a watcher as long as it is active or
1313	pending.
1314
1315	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1316	fine, as long as you do not mind that the priority value you query might
1317	or might not have been clamped to the valid range.
1318
1319	The default priority used by watchers when no priority has been set is
1320	always C<0>, which is supposed to not be too high and not be too low :).
1321
1322	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1323	priorities.
1324
1325	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1326
1327	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1328	C<loop> nor C<revents> need to be valid as long as the watcher callback
1329	can deal with that fact, as both are simply passed through to the
1330	callback.
1331
1332	=item int ev_clear_pending (loop, ev_TYPE *watcher)
1333
1334	If the watcher is pending, this function clears its pending status and
1335	returns its C<revents> bitset (as if its callback was invoked). If the
1336	watcher isn't pending it does nothing and returns C<0>.
1337
1338	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1339	callback to be invoked, which can be accomplished with this function.
1340
1341	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
1342
1343	Feeds the given event set into the event loop, as if the specified event
1344	had happened for the specified watcher (which must be a pointer to an
1345	initialised but not necessarily started event watcher). Obviously you must
1346	not free the watcher as long as it has pending events.
1347
1348	Stopping the watcher, letting libev invoke it, or calling
1349	C<ev_clear_pending> will clear the pending event, even if the watcher was
1350	not started in the first place.
1351
1352	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1353	functions that do not need a watcher.
1354
1355	=back
1356
1357
1358	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1359
1360	Each watcher has, by default, a member C<void *data> that you can change
1361	and read at any time: libev will completely ignore it. This can be used
1362	to associate arbitrary data with your watcher. If you need more data and
1363	don't want to allocate memory and store a pointer to it in that data
1364	member, you can also "subclass" the watcher type and provide your own
1365	data:
1366
1367	struct my_io
1368	{
1369	ev_io io;
1370	int otherfd;
1371	void *somedata;
1372	struct whatever *mostinteresting;
1373	};
1374
1375	...
1376	struct my_io w;
1377	ev_io_init (&w.io, my_cb, fd, EV_READ);
1378
1379	And since your callback will be called with a pointer to the watcher, you
1380	can cast it back to your own type:
1381
1382	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1383	{
1384	struct my_io *w = (struct my_io *)w_;
1385	...
1386	}
1387
1388	More interesting and less C-conformant ways of casting your callback type
1389	instead have been omitted.
1390
1391	Another common scenario is to use some data structure with multiple
1392	embedded watchers:
1393
1394	struct my_biggy
1395	{
1396	int some_data;
1397	ev_timer t1;
1398	ev_timer t2;
1399	}
1400
1401	In this case getting the pointer to C<my_biggy> is a bit more
1402	complicated: Either you store the address of your C<my_biggy> struct
1403	in the C<data> member of the watcher (for woozies), or you need to use
1404	some pointer arithmetic using C<offsetof> inside your watchers (for real
1405	programmers):
1406
1407	#include <stddef.h>
1408
1409	static void
1410	t1_cb (EV_P_ ev_timer *w, int revents)
1411	{
1412	struct my_biggy big = (struct my_biggy *)
1413	(((char *)w) - offsetof (struct my_biggy, t1));
1414	}
1415
1416	static void
1417	t2_cb (EV_P_ ev_timer *w, int revents)
1418	{
1419	struct my_biggy big = (struct my_biggy *)
1420	(((char *)w) - offsetof (struct my_biggy, t2));
1421	}
1422		1459
1423	=head2 WATCHER PRIORITY MODELS	1460	=head2 WATCHER PRIORITY MODELS
1424		1461
1425	Many event loops support I<watcher priorities>, which are usually small	1462	Many event loops support I<watcher priorities>, which are usually small
1426	integers that influence the ordering of event callback invocation	1463	integers that influence the ordering of event callback invocation
…		…
1553	In general you can register as many read and/or write event watchers per	1590	In general you can register as many read and/or write event watchers per
1554	fd as you want (as long as you don't confuse yourself). Setting all file	1591	fd as you want (as long as you don't confuse yourself). Setting all file
1555	descriptors to non-blocking mode is also usually a good idea (but not	1592	descriptors to non-blocking mode is also usually a good idea (but not
1556	required if you know what you are doing).	1593	required if you know what you are doing).
1557		1594
1558	If you cannot use non-blocking mode, then force the use of a
1559	known-to-be-good backend (at the time of this writing, this includes only
1560	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1561	descriptors for which non-blocking operation makes no sense (such as
1562	files) - libev doesn't guarantee any specific behaviour in that case.
1563
1564	Another thing you have to watch out for is that it is quite easy to	1595	Another thing you have to watch out for is that it is quite easy to
1565	receive "spurious" readiness notifications, that is your callback might	1596	receive "spurious" readiness notifications, that is, your callback might
1566	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1597	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1567	because there is no data. Not only are some backends known to create a	1598	because there is no data. It is very easy to get into this situation even
1568	lot of those (for example Solaris ports), it is very easy to get into	1599	with a relatively standard program structure. Thus it is best to always
1569	this situation even with a relatively standard program structure. Thus	1600	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1570	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1571	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1601	preferable to a program hanging until some data arrives.
1572		1602
1573	If you cannot run the fd in non-blocking mode (for example you should	1603	If you cannot run the fd in non-blocking mode (for example you should
1574	not play around with an Xlib connection), then you have to separately	1604	not play around with an Xlib connection), then you have to separately
1575	re-test whether a file descriptor is really ready with a known-to-be good	1605	re-test whether a file descriptor is really ready with a known-to-be good
1576	interface such as poll (fortunately in our Xlib example, Xlib already	1606	interface such as poll (fortunately in the case of Xlib, it already does
1577	does this on its own, so its quite safe to use). Some people additionally	1607	this on its own, so its quite safe to use). Some people additionally
1578	use C<SIGALRM> and an interval timer, just to be sure you won't block	1608	use C<SIGALRM> and an interval timer, just to be sure you won't block
1579	indefinitely.	1609	indefinitely.
1580		1610
1581	But really, best use non-blocking mode.	1611	But really, best use non-blocking mode.
1582		1612
…		…
1610		1640
1611	There is no workaround possible except not registering events	1641	There is no workaround possible except not registering events
1612	for potentially C<dup ()>'ed file descriptors, or to resort to	1642	for potentially C<dup ()>'ed file descriptors, or to resort to
1613	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1643	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1614		1644
		1645	=head3 The special problem of files
		1646
		1647	Many people try to use C<select> (or libev) on file descriptors
		1648	representing files, and expect it to become ready when their program
		1649	doesn't block on disk accesses (which can take a long time on their own).
		1650
		1651	However, this cannot ever work in the "expected" way - you get a readiness
		1652	notification as soon as the kernel knows whether and how much data is
		1653	there, and in the case of open files, that's always the case, so you
		1654	always get a readiness notification instantly, and your read (or possibly
		1655	write) will still block on the disk I/O.
		1656
		1657	Another way to view it is that in the case of sockets, pipes, character
		1658	devices and so on, there is another party (the sender) that delivers data
		1659	on its own, but in the case of files, there is no such thing: the disk
		1660	will not send data on its own, simply because it doesn't know what you
		1661	wish to read - you would first have to request some data.
		1662
		1663	Since files are typically not-so-well supported by advanced notification
		1664	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1665	to files, even though you should not use it. The reason for this is
		1666	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1667	usually a tty, often a pipe, but also sometimes files or special devices
		1668	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1669	F</dev/urandom>), and even though the file might better be served with
		1670	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1671	it "just works" instead of freezing.
		1672
		1673	So avoid file descriptors pointing to files when you know it (e.g. use
		1674	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1675	when you rarely read from a file instead of from a socket, and want to
		1676	reuse the same code path.
		1677
1615	=head3 The special problem of fork	1678	=head3 The special problem of fork
1616		1679
1617	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1680	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1618	useless behaviour. Libev fully supports fork, but needs to be told about	1681	useless behaviour. Libev fully supports fork, but needs to be told about
1619	it in the child.	1682	it in the child if you want to continue to use it in the child.
1620		1683
1621	To support fork in your programs, you either have to call	1684	To support fork in your child processes, you have to call C<ev_loop_fork
1622	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1685	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1623	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1686	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1624	C<EVBACKEND_POLL>.
1625		1687
1626	=head3 The special problem of SIGPIPE	1688	=head3 The special problem of SIGPIPE
1627		1689
1628	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1690	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1629	when writing to a pipe whose other end has been closed, your program gets	1691	when writing to a pipe whose other end has been closed, your program gets
…		…
1727	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1789	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1728	monotonic clock option helps a lot here).	1790	monotonic clock option helps a lot here).
1729		1791
1730	The callback is guaranteed to be invoked only I<after> its timeout has	1792	The callback is guaranteed to be invoked only I<after> its timeout has
1731	passed (not I<at>, so on systems with very low-resolution clocks this	1793	passed (not I<at>, so on systems with very low-resolution clocks this
1732	might introduce a small delay). If multiple timers become ready during the	1794	might introduce a small delay, see "the special problem of being too
		1795	early", below). If multiple timers become ready during the same loop
1733	same loop iteration then the ones with earlier time-out values are invoked	1796	iteration then the ones with earlier time-out values are invoked before
1734	before ones of the same priority with later time-out values (but this is	1797	ones of the same priority with later time-out values (but this is no
1735	no longer true when a callback calls C<ev_run> recursively).	1798	longer true when a callback calls C<ev_run> recursively).
1736		1799
1737	=head3 Be smart about timeouts	1800	=head3 Be smart about timeouts
1738		1801
1739	Many real-world problems involve some kind of timeout, usually for error	1802	Many real-world problems involve some kind of timeout, usually for error
1740	recovery. A typical example is an HTTP request - if the other side hangs,	1803	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1815		1878
1816	In this case, it would be more efficient to leave the C<ev_timer> alone,	1879	In this case, it would be more efficient to leave the C<ev_timer> alone,
1817	but remember the time of last activity, and check for a real timeout only	1880	but remember the time of last activity, and check for a real timeout only
1818	within the callback:	1881	within the callback:
1819		1882
		1883	ev_tstamp timeout = 60.;
1820	ev_tstamp last_activity; // time of last activity	1884	ev_tstamp last_activity; // time of last activity
		1885	ev_timer timer;
1821		1886
1822	static void	1887	static void
1823	callback (EV_P_ ev_timer *w, int revents)	1888	callback (EV_P_ ev_timer *w, int revents)
1824	{	1889	{
1825	ev_tstamp now = ev_now (EV_A);	1890	// calculate when the timeout would happen
1826	ev_tstamp timeout = last_activity + 60.;	1891	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1827		1892
1828	// if last_activity + 60. is older than now, we did time out	1893	// if negative, it means we the timeout already occurred
1829	if (timeout < now)	1894	if (after < 0.)
1830	{	1895	{
1831	// timeout occurred, take action	1896	// timeout occurred, take action
1832	}	1897	}
1833	else	1898	else
1834	{	1899	{
1835	// callback was invoked, but there was some activity, re-arm	1900	// callback was invoked, but there was some recent
1836	// the watcher to fire in last_activity + 60, which is	1901	// activity. simply restart the timer to time out
1837	// guaranteed to be in the future, so "again" is positive:	1902	// after "after" seconds, which is the earliest time
1838	w->repeat = timeout - now;	1903	// the timeout can occur.
		1904	ev_timer_set (w, after, 0.);
1839	ev_timer_again (EV_A_ w);	1905	ev_timer_start (EV_A_ w);
1840	}	1906	}
1841	}	1907	}
1842		1908
1843	To summarise the callback: first calculate the real timeout (defined	1909	To summarise the callback: first calculate in how many seconds the
1844	as "60 seconds after the last activity"), then check if that time has	1910	timeout will occur (by calculating the absolute time when it would occur,
1845	been reached, which means something I<did>, in fact, time out. Otherwise	1911	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1846	the callback was invoked too early (C<timeout> is in the future), so	1912	(EV_A)> from that).
1847	re-schedule the timer to fire at that future time, to see if maybe we have
1848	a timeout then.
1849		1913
1850	Note how C<ev_timer_again> is used, taking advantage of the	1914	If this value is negative, then we are already past the timeout, i.e. we
1851	C<ev_timer_again> optimisation when the timer is already running.	1915	timed out, and need to do whatever is needed in this case.
		1916
		1917	Otherwise, we now the earliest time at which the timeout would trigger,
		1918	and simply start the timer with this timeout value.
		1919
		1920	In other words, each time the callback is invoked it will check whether
		1921	the timeout occurred. If not, it will simply reschedule itself to check
		1922	again at the earliest time it could time out. Rinse. Repeat.
1852		1923
1853	This scheme causes more callback invocations (about one every 60 seconds	1924	This scheme causes more callback invocations (about one every 60 seconds
1854	minus half the average time between activity), but virtually no calls to	1925	minus half the average time between activity), but virtually no calls to
1855	libev to change the timeout.	1926	libev to change the timeout.
1856		1927
1857	To start the timer, simply initialise the watcher and set C<last_activity>	1928	To start the machinery, simply initialise the watcher and set
1858	to the current time (meaning we just have some activity :), then call the	1929	C<last_activity> to the current time (meaning there was some activity just
1859	callback, which will "do the right thing" and start the timer:	1930	now), then call the callback, which will "do the right thing" and start
		1931	the timer:
1860		1932
		1933	last_activity = ev_now (EV_A);
1861	ev_init (timer, callback);	1934	ev_init (&timer, callback);
1862	last_activity = ev_now (loop);	1935	callback (EV_A_ &timer, 0);
1863	callback (loop, timer, EV_TIMER);
1864		1936
1865	And when there is some activity, simply store the current time in	1937	When there is some activity, simply store the current time in
1866	C<last_activity>, no libev calls at all:	1938	C<last_activity>, no libev calls at all:
1867		1939
		1940	if (activity detected)
1868	last_activity = ev_now (loop);	1941	last_activity = ev_now (EV_A);
		1942
		1943	When your timeout value changes, then the timeout can be changed by simply
		1944	providing a new value, stopping the timer and calling the callback, which
		1945	will again do the right thing (for example, time out immediately :).
		1946
		1947	timeout = new_value;
		1948	ev_timer_stop (EV_A_ &timer);
		1949	callback (EV_A_ &timer, 0);
1869		1950
1870	This technique is slightly more complex, but in most cases where the	1951	This technique is slightly more complex, but in most cases where the
1871	time-out is unlikely to be triggered, much more efficient.	1952	time-out is unlikely to be triggered, much more efficient.
1872
1873	Changing the timeout is trivial as well (if it isn't hard-coded in the
1874	callback :) - just change the timeout and invoke the callback, which will
1875	fix things for you.
1876		1953
1877	=item 4. Wee, just use a double-linked list for your timeouts.	1954	=item 4. Wee, just use a double-linked list for your timeouts.
1878		1955
1879	If there is not one request, but many thousands (millions...), all	1956	If there is not one request, but many thousands (millions...), all
1880	employing some kind of timeout with the same timeout value, then one can	1957	employing some kind of timeout with the same timeout value, then one can
…		…
1907	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	1984	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1908	rather complicated, but extremely efficient, something that really pays	1985	rather complicated, but extremely efficient, something that really pays
1909	off after the first million or so of active timers, i.e. it's usually	1986	off after the first million or so of active timers, i.e. it's usually
1910	overkill :)	1987	overkill :)
1911		1988
		1989	=head3 The special problem of being too early
		1990
		1991	If you ask a timer to call your callback after three seconds, then
		1992	you expect it to be invoked after three seconds - but of course, this
		1993	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		1994	guaranteed to any precision by libev - imagine somebody suspending the
		1995	process with a STOP signal for a few hours for example.
		1996
		1997	So, libev tries to invoke your callback as soon as possible I<after> the
		1998	delay has occurred, but cannot guarantee this.
		1999
		2000	A less obvious failure mode is calling your callback too early: many event
		2001	loops compare timestamps with a "elapsed delay >= requested delay", but
		2002	this can cause your callback to be invoked much earlier than you would
		2003	expect.
		2004
		2005	To see why, imagine a system with a clock that only offers full second
		2006	resolution (think windows if you can't come up with a broken enough OS
		2007	yourself). If you schedule a one-second timer at the time 500.9, then the
		2008	event loop will schedule your timeout to elapse at a system time of 500
		2009	(500.9 truncated to the resolution) + 1, or 501.
		2010
		2011	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2012	501" and invoke the callback 0.1s after it was started, even though a
		2013	one-second delay was requested - this is being "too early", despite best
		2014	intentions.
		2015
		2016	This is the reason why libev will never invoke the callback if the elapsed
		2017	delay equals the requested delay, but only when the elapsed delay is
		2018	larger than the requested delay. In the example above, libev would only invoke
		2019	the callback at system time 502, or 1.1s after the timer was started.
		2020
		2021	So, while libev cannot guarantee that your callback will be invoked
		2022	exactly when requested, it I<can> and I<does> guarantee that the requested
		2023	delay has actually elapsed, or in other words, it always errs on the "too
		2024	late" side of things.
		2025
1912	=head3 The special problem of time updates	2026	=head3 The special problem of time updates
1913		2027
1914	Establishing the current time is a costly operation (it usually takes at	2028	Establishing the current time is a costly operation (it usually takes
1915	least two system calls): EV therefore updates its idea of the current	2029	at least one system call): EV therefore updates its idea of the current
1916	time only before and after C<ev_run> collects new events, which causes a	2030	time only before and after C<ev_run> collects new events, which causes a
1917	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2031	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1918	lots of events in one iteration.	2032	lots of events in one iteration.
1919		2033
1920	The relative timeouts are calculated relative to the C<ev_now ()>	2034	The relative timeouts are calculated relative to the C<ev_now ()>
1921	time. This is usually the right thing as this timestamp refers to the time	2035	time. This is usually the right thing as this timestamp refers to the time
1922	of the event triggering whatever timeout you are modifying/starting. If	2036	of the event triggering whatever timeout you are modifying/starting. If
1923	you suspect event processing to be delayed and you I<need> to base the	2037	you suspect event processing to be delayed and you I<need> to base the
1924	timeout on the current time, use something like this to adjust for this:	2038	timeout on the current time, use something like the following to adjust
		2039	for it:
1925		2040
1926	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2041	ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.);
1927		2042
1928	If the event loop is suspended for a long time, you can also force an	2043	If the event loop is suspended for a long time, you can also force an
1929	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2044	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1930	()>.	2045	()>, although that will push the event time of all outstanding events
		2046	further into the future.
		2047
		2048	=head3 The special problem of unsynchronised clocks
		2049
		2050	Modern systems have a variety of clocks - libev itself uses the normal
		2051	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2052	jumps).
		2053
		2054	Neither of these clocks is synchronised with each other or any other clock
		2055	on the system, so C<ev_time ()> might return a considerably different time
		2056	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2057	a call to C<gettimeofday> might return a second count that is one higher
		2058	than a directly following call to C<time>.
		2059
		2060	The moral of this is to only compare libev-related timestamps with
		2061	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2062	a second or so.
		2063
		2064	One more problem arises due to this lack of synchronisation: if libev uses
		2065	the system monotonic clock and you compare timestamps from C<ev_time>
		2066	or C<ev_now> from when you started your timer and when your callback is
		2067	invoked, you will find that sometimes the callback is a bit "early".
		2068
		2069	This is because C<ev_timer>s work in real time, not wall clock time, so
		2070	libev makes sure your callback is not invoked before the delay happened,
		2071	I<measured according to the real time>, not the system clock.
		2072
		2073	If your timeouts are based on a physical timescale (e.g. "time out this
		2074	connection after 100 seconds") then this shouldn't bother you as it is
		2075	exactly the right behaviour.
		2076
		2077	If you want to compare wall clock/system timestamps to your timers, then
		2078	you need to use C<ev_periodic>s, as these are based on the wall clock
		2079	time, where your comparisons will always generate correct results.
1931		2080
1932	=head3 The special problems of suspended animation	2081	=head3 The special problems of suspended animation
1933		2082
1934	When you leave the server world it is quite customary to hit machines that	2083	When you leave the server world it is quite customary to hit machines that
1935	can suspend/hibernate - what happens to the clocks during such a suspend?	2084	can suspend/hibernate - what happens to the clocks during such a suspend?
…		…
1965		2114
1966	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2115	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1967		2116
1968	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	2117	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1969		2118
1970	Configure the timer to trigger after C<after> seconds. If C<repeat>	2119	Configure the timer to trigger after C<after> seconds (fractional and
1971	is C<0.>, then it will automatically be stopped once the timeout is	2120	negative values are supported). If C<repeat> is C<0.>, then it will
1972	reached. If it is positive, then the timer will automatically be	2121	automatically be stopped once the timeout is reached. If it is positive,
1973	configured to trigger again C<repeat> seconds later, again, and again,	2122	then the timer will automatically be configured to trigger again C<repeat>
1974	until stopped manually.	2123	seconds later, again, and again, until stopped manually.
1975		2124
1976	The timer itself will do a best-effort at avoiding drift, that is, if	2125	The timer itself will do a best-effort at avoiding drift, that is, if
1977	you configure a timer to trigger every 10 seconds, then it will normally	2126	you configure a timer to trigger every 10 seconds, then it will normally
1978	trigger at exactly 10 second intervals. If, however, your program cannot	2127	trigger at exactly 10 second intervals. If, however, your program cannot
1979	keep up with the timer (because it takes longer than those 10 seconds to	2128	keep up with the timer (because it takes longer than those 10 seconds to
1980	do stuff) the timer will not fire more than once per event loop iteration.	2129	do stuff) the timer will not fire more than once per event loop iteration.
1981		2130
1982	=item ev_timer_again (loop, ev_timer *)	2131	=item ev_timer_again (loop, ev_timer *)
1983		2132
1984	This will act as if the timer timed out and restart it again if it is	2133	This will act as if the timer timed out, and restarts it again if it is
1985	repeating. The exact semantics are:	2134	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2135	timeout to the C<repeat> value and calling C<ev_timer_start>.
1986		2136
		2137	The exact semantics are as in the following rules, all of which will be
		2138	applied to the watcher:
		2139
		2140	=over 4
		2141
1987	If the timer is pending, its pending status is cleared.	2142	=item If the timer is pending, the pending status is always cleared.
1988		2143
1989	If the timer is started but non-repeating, stop it (as if it timed out).	2144	=item If the timer is started but non-repeating, stop it (as if it timed
		2145	out, without invoking it).
1990		2146
1991	If the timer is repeating, either start it if necessary (with the	2147	=item If the timer is repeating, make the C<repeat> value the new timeout
1992	C<repeat> value), or reset the running timer to the C<repeat> value.	2148	and start the timer, if necessary.
1993		2149
		2150	=back
		2151
1994	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2152	This sounds a bit complicated, see L</Be smart about timeouts>, above, for a
1995	usage example.	2153	usage example.
1996		2154
1997	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)	2155	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1998		2156
1999	Returns the remaining time until a timer fires. If the timer is active,	2157	Returns the remaining time until a timer fires. If the timer is active,
…		…
2052	Periodic watchers are also timers of a kind, but they are very versatile	2210	Periodic watchers are also timers of a kind, but they are very versatile
2053	(and unfortunately a bit complex).	2211	(and unfortunately a bit complex).
2054		2212
2055	Unlike C<ev_timer>, periodic watchers are not based on real time (or	2213	Unlike C<ev_timer>, periodic watchers are not based on real time (or
2056	relative time, the physical time that passes) but on wall clock time	2214	relative time, the physical time that passes) but on wall clock time
2057	(absolute time, the thing you can read on your calender or clock). The	2215	(absolute time, the thing you can read on your calendar or clock). The
2058	difference is that wall clock time can run faster or slower than real	2216	difference is that wall clock time can run faster or slower than real
2059	time, and time jumps are not uncommon (e.g. when you adjust your	2217	time, and time jumps are not uncommon (e.g. when you adjust your
2060	wrist-watch).	2218	wrist-watch).
2061		2219
2062	You can tell a periodic watcher to trigger after some specific point	2220	You can tell a periodic watcher to trigger after some specific point
…		…
2067	C<ev_timer>, which would still trigger roughly 10 seconds after starting	2225	C<ev_timer>, which would still trigger roughly 10 seconds after starting
2068	it, as it uses a relative timeout).	2226	it, as it uses a relative timeout).
2069		2227
2070	C<ev_periodic> watchers can also be used to implement vastly more complex	2228	C<ev_periodic> watchers can also be used to implement vastly more complex
2071	timers, such as triggering an event on each "midnight, local time", or	2229	timers, such as triggering an event on each "midnight, local time", or
2072	other complicated rules. This cannot be done with C<ev_timer> watchers, as	2230	other complicated rules. This cannot easily be done with C<ev_timer>
2073	those cannot react to time jumps.	2231	watchers, as those cannot react to time jumps.
2074		2232
2075	As with timers, the callback is guaranteed to be invoked only when the	2233	As with timers, the callback is guaranteed to be invoked only when the
2076	point in time where it is supposed to trigger has passed. If multiple	2234	point in time where it is supposed to trigger has passed. If multiple
2077	timers become ready during the same loop iteration then the ones with	2235	timers become ready during the same loop iteration then the ones with
2078	earlier time-out values are invoked before ones with later time-out values	2236	earlier time-out values are invoked before ones with later time-out values
…		…
2119		2277
2120	Another way to think about it (for the mathematically inclined) is that	2278	Another way to think about it (for the mathematically inclined) is that
2121	C<ev_periodic> will try to run the callback in this mode at the next possible	2279	C<ev_periodic> will try to run the callback in this mode at the next possible
2122	time where C<time = offset (mod interval)>, regardless of any time jumps.	2280	time where C<time = offset (mod interval)>, regardless of any time jumps.
2123		2281
2124	For numerical stability it is preferable that the C<offset> value is near	2282	The C<interval> I<MUST> be positive, and for numerical stability, the
2125	C<ev_now ()> (the current time), but there is no range requirement for	2283	interval value should be higher than C<1/8192> (which is around 100
2126	this value, and in fact is often specified as zero.	2284	microseconds) and C<offset> should be higher than C<0> and should have
		2285	at most a similar magnitude as the current time (say, within a factor of
		2286	ten). Typical values for offset are, in fact, C<0> or something between
		2287	C<0> and C<interval>, which is also the recommended range.
2127		2288
2128	Note also that there is an upper limit to how often a timer can fire (CPU	2289	Note also that there is an upper limit to how often a timer can fire (CPU
2129	speed for example), so if C<interval> is very small then timing stability	2290	speed for example), so if C<interval> is very small then timing stability
2130	will of course deteriorate. Libev itself tries to be exact to be about one	2291	will of course deteriorate. Libev itself tries to be exact to be about one
2131	millisecond (if the OS supports it and the machine is fast enough).	2292	millisecond (if the OS supports it and the machine is fast enough).
…		…
2161		2322
2162	NOTE: I<< This callback must always return a time that is higher than or	2323	NOTE: I<< This callback must always return a time that is higher than or
2163	equal to the passed C<now> value >>.	2324	equal to the passed C<now> value >>.
2164		2325
2165	This can be used to create very complex timers, such as a timer that	2326	This can be used to create very complex timers, such as a timer that
2166	triggers on "next midnight, local time". To do this, you would calculate the	2327	triggers on "next midnight, local time". To do this, you would calculate
2167	next midnight after C<now> and return the timestamp value for this. How	2328	the next midnight after C<now> and return the timestamp value for
2168	you do this is, again, up to you (but it is not trivial, which is the main	2329	this. Here is a (completely untested, no error checking) example on how to
2169	reason I omitted it as an example).	2330	do this:
		2331
		2332	#include <time.h>
		2333
		2334	static ev_tstamp
		2335	my_rescheduler (ev_periodic *w, ev_tstamp now)
		2336	{
		2337	time_t tnow = (time_t)now;
		2338	struct tm tm;
		2339	localtime_r (&tnow, &tm);
		2340
		2341	tm.tm_sec = tm.tm_min = tm.tm_hour = 0; // midnight current day
		2342	++tm.tm_mday; // midnight next day
		2343
		2344	return mktime (&tm);
		2345	}
		2346
		2347	Note: this code might run into trouble on days that have more then two
		2348	midnights (beginning and end).
2170		2349
2171	=back	2350	=back
2172		2351
2173	=item ev_periodic_again (loop, ev_periodic *)	2352	=item ev_periodic_again (loop, ev_periodic *)
2174		2353
…		…
2239		2418
2240	ev_periodic hourly_tick;	2419	ev_periodic hourly_tick;
2241	ev_periodic_init (&hourly_tick, clock_cb,	2420	ev_periodic_init (&hourly_tick, clock_cb,
2242	fmod (ev_now (loop), 3600.), 3600., 0);	2421	fmod (ev_now (loop), 3600.), 3600., 0);
2243	ev_periodic_start (loop, &hourly_tick);	2422	ev_periodic_start (loop, &hourly_tick);
2244		2423
2245		2424
2246	=head2 C<ev_signal> - signal me when a signal gets signalled!	2425	=head2 C<ev_signal> - signal me when a signal gets signalled!
2247		2426
2248	Signal watchers will trigger an event when the process receives a specific	2427	Signal watchers will trigger an event when the process receives a specific
2249	signal one or more times. Even though signals are very asynchronous, libev	2428	signal one or more times. Even though signals are very asynchronous, libev
2250	will try it's best to deliver signals synchronously, i.e. as part of the	2429	will try its best to deliver signals synchronously, i.e. as part of the
2251	normal event processing, like any other event.	2430	normal event processing, like any other event.
2252		2431
2253	If you want signals to be delivered truly asynchronously, just use	2432	If you want signals to be delivered truly asynchronously, just use
2254	C<sigaction> as you would do without libev and forget about sharing	2433	C<sigaction> as you would do without libev and forget about sharing
2255	the signal. You can even use C<ev_async> from a signal handler to	2434	the signal. You can even use C<ev_async> from a signal handler to
…		…
2259	only within the same loop, i.e. you can watch for C<SIGINT> in your	2438	only within the same loop, i.e. you can watch for C<SIGINT> in your
2260	default loop and for C<SIGIO> in another loop, but you cannot watch for	2439	default loop and for C<SIGIO> in another loop, but you cannot watch for
2261	C<SIGINT> in both the default loop and another loop at the same time. At	2440	C<SIGINT> in both the default loop and another loop at the same time. At
2262	the moment, C<SIGCHLD> is permanently tied to the default loop.	2441	the moment, C<SIGCHLD> is permanently tied to the default loop.
2263		2442
2264	When the first watcher gets started will libev actually register something	2443	Only after the first watcher for a signal is started will libev actually
2265	with the kernel (thus it coexists with your own signal handlers as long as	2444	register something with the kernel. It thus coexists with your own signal
2266	you don't register any with libev for the same signal).	2445	handlers as long as you don't register any with libev for the same signal.
2267		2446
2268	If possible and supported, libev will install its handlers with	2447	If possible and supported, libev will install its handlers with
2269	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should	2448	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
2270	not be unduly interrupted. If you have a problem with system calls getting	2449	not be unduly interrupted. If you have a problem with system calls getting
2271	interrupted by signals you can block all signals in an C<ev_check> watcher	2450	interrupted by signals you can block all signals in an C<ev_check> watcher
…		…
2274	=head3 The special problem of inheritance over fork/execve/pthread_create	2453	=head3 The special problem of inheritance over fork/execve/pthread_create
2275		2454
2276	Both the signal mask (C<sigprocmask>) and the signal disposition	2455	Both the signal mask (C<sigprocmask>) and the signal disposition
2277	(C<sigaction>) are unspecified after starting a signal watcher (and after	2456	(C<sigaction>) are unspecified after starting a signal watcher (and after
2278	stopping it again), that is, libev might or might not block the signal,	2457	stopping it again), that is, libev might or might not block the signal,
2279	and might or might not set or restore the installed signal handler.	2458	and might or might not set or restore the installed signal handler (but
		2459	see C<EVFLAG_NOSIGMASK>).
2280		2460
2281	While this does not matter for the signal disposition (libev never	2461	While this does not matter for the signal disposition (libev never
2282	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on	2462	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
2283	C<execve>), this matters for the signal mask: many programs do not expect	2463	C<execve>), this matters for the signal mask: many programs do not expect
2284	certain signals to be blocked.	2464	certain signals to be blocked.
…		…
2297	I<has> to modify the signal mask, at least temporarily.	2477	I<has> to modify the signal mask, at least temporarily.
2298		2478
2299	So I can't stress this enough: I<If you do not reset your signal mask when	2479	So I can't stress this enough: I<If you do not reset your signal mask when
2300	you expect it to be empty, you have a race condition in your code>. This	2480	you expect it to be empty, you have a race condition in your code>. This
2301	is not a libev-specific thing, this is true for most event libraries.	2481	is not a libev-specific thing, this is true for most event libraries.
		2482
		2483	=head3 The special problem of threads signal handling
		2484
		2485	POSIX threads has problematic signal handling semantics, specifically,
		2486	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2487	threads in a process block signals, which is hard to achieve.
		2488
		2489	When you want to use sigwait (or mix libev signal handling with your own
		2490	for the same signals), you can tackle this problem by globally blocking
		2491	all signals before creating any threads (or creating them with a fully set
		2492	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2493	loops. Then designate one thread as "signal receiver thread" which handles
		2494	these signals. You can pass on any signals that libev might be interested
		2495	in by calling C<ev_feed_signal>.
2302		2496
2303	=head3 Watcher-Specific Functions and Data Members	2497	=head3 Watcher-Specific Functions and Data Members
2304		2498
2305	=over 4	2499	=over 4
2306		2500
…		…
2441		2635
2442	=head2 C<ev_stat> - did the file attributes just change?	2636	=head2 C<ev_stat> - did the file attributes just change?
2443		2637
2444	This watches a file system path for attribute changes. That is, it calls	2638	This watches a file system path for attribute changes. That is, it calls
2445	C<stat> on that path in regular intervals (or when the OS says it changed)	2639	C<stat> on that path in regular intervals (or when the OS says it changed)
2446	and sees if it changed compared to the last time, invoking the callback if	2640	and sees if it changed compared to the last time, invoking the callback
2447	it did.	2641	if it did. Starting the watcher C<stat>'s the file, so only changes that
		2642	happen after the watcher has been started will be reported.
2448		2643
2449	The path does not need to exist: changing from "path exists" to "path does	2644	The path does not need to exist: changing from "path exists" to "path does
2450	not exist" is a status change like any other. The condition "path does not	2645	not exist" is a status change like any other. The condition "path does not
2451	exist" (or more correctly "path cannot be stat'ed") is signified by the	2646	exist" (or more correctly "path cannot be stat'ed") is signified by the
2452	C<st_nlink> field being zero (which is otherwise always forced to be at	2647	C<st_nlink> field being zero (which is otherwise always forced to be at
…		…
2682	Apart from keeping your process non-blocking (which is a useful	2877	Apart from keeping your process non-blocking (which is a useful
2683	effect on its own sometimes), idle watchers are a good place to do	2878	effect on its own sometimes), idle watchers are a good place to do
2684	"pseudo-background processing", or delay processing stuff to after the	2879	"pseudo-background processing", or delay processing stuff to after the
2685	event loop has handled all outstanding events.	2880	event loop has handled all outstanding events.
2686		2881
		2882	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2883
		2884	As long as there is at least one active idle watcher, libev will never
		2885	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2886	For this to work, the idle watcher doesn't need to be invoked at all - the
		2887	lowest priority will do.
		2888
		2889	This mode of operation can be useful together with an C<ev_check> watcher,
		2890	to do something on each event loop iteration - for example to balance load
		2891	between different connections.
		2892
		2893	See L</Abusing an ev_check watcher for its side-effect> for a longer
		2894	example.
		2895
2687	=head3 Watcher-Specific Functions and Data Members	2896	=head3 Watcher-Specific Functions and Data Members
2688		2897
2689	=over 4	2898	=over 4
2690		2899
2691	=item ev_idle_init (ev_idle *, callback)	2900	=item ev_idle_init (ev_idle *, callback)
…		…
2702	callback, free it. Also, use no error checking, as usual.	2911	callback, free it. Also, use no error checking, as usual.
2703		2912
2704	static void	2913	static void
2705	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	2914	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2706	{	2915	{
		2916	// stop the watcher
		2917	ev_idle_stop (loop, w);
		2918
		2919	// now we can free it
2707	free (w);	2920	free (w);
		2921
2708	// now do something you wanted to do when the program has	2922	// now do something you wanted to do when the program has
2709	// no longer anything immediate to do.	2923	// no longer anything immediate to do.
2710	}	2924	}
2711		2925
2712	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2926	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
…		…
2714	ev_idle_start (loop, idle_watcher);	2928	ev_idle_start (loop, idle_watcher);
2715		2929
2716		2930
2717	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2931	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2718		2932
2719	Prepare and check watchers are usually (but not always) used in pairs:	2933	Prepare and check watchers are often (but not always) used in pairs:
2720	prepare watchers get invoked before the process blocks and check watchers	2934	prepare watchers get invoked before the process blocks and check watchers
2721	afterwards.	2935	afterwards.
2722		2936
2723	You I<must not> call C<ev_run> or similar functions that enter	2937	You I<must not> call C<ev_run> (or similar functions that enter the
2724	the current event loop from either C<ev_prepare> or C<ev_check>	2938	current event loop) or C<ev_loop_fork> from either C<ev_prepare> or
2725	watchers. Other loops than the current one are fine, however. The	2939	C<ev_check> watchers. Other loops than the current one are fine,
2726	rationale behind this is that you do not need to check for recursion in	2940	however. The rationale behind this is that you do not need to check
2727	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2941	for recursion in those watchers, i.e. the sequence will always be
2728	C<ev_check> so if you have one watcher of each kind they will always be	2942	C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each
2729	called in pairs bracketing the blocking call.	2943	kind they will always be called in pairs bracketing the blocking call.
2730		2944
2731	Their main purpose is to integrate other event mechanisms into libev and	2945	Their main purpose is to integrate other event mechanisms into libev and
2732	their use is somewhat advanced. They could be used, for example, to track	2946	their use is somewhat advanced. They could be used, for example, to track
2733	variable changes, implement your own watchers, integrate net-snmp or a	2947	variable changes, implement your own watchers, integrate net-snmp or a
2734	coroutine library and lots more. They are also occasionally useful if	2948	coroutine library and lots more. They are also occasionally useful if
…		…
2752	with priority higher than or equal to the event loop and one coroutine	2966	with priority higher than or equal to the event loop and one coroutine
2753	of lower priority, but only once, using idle watchers to keep the event	2967	of lower priority, but only once, using idle watchers to keep the event
2754	loop from blocking if lower-priority coroutines are active, thus mapping	2968	loop from blocking if lower-priority coroutines are active, thus mapping
2755	low-priority coroutines to idle/background tasks).	2969	low-priority coroutines to idle/background tasks).
2756		2970
2757	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2971	When used for this purpose, it is recommended to give C<ev_check> watchers
2758	priority, to ensure that they are being run before any other watchers	2972	highest (C<EV_MAXPRI>) priority, to ensure that they are being run before
2759	after the poll (this doesn't matter for C<ev_prepare> watchers).	2973	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		2974	watchers).
2760		2975
2761	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	2976	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
2762	activate ("feed") events into libev. While libev fully supports this, they	2977	activate ("feed") events into libev. While libev fully supports this, they
2763	might get executed before other C<ev_check> watchers did their job. As	2978	might get executed before other C<ev_check> watchers did their job. As
2764	C<ev_check> watchers are often used to embed other (non-libev) event	2979	C<ev_check> watchers are often used to embed other (non-libev) event
2765	loops those other event loops might be in an unusable state until their	2980	loops those other event loops might be in an unusable state until their
2766	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	2981	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2767	others).	2982	others).
		2983
		2984	=head3 Abusing an C<ev_check> watcher for its side-effect
		2985
		2986	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		2987	useful because they are called once per event loop iteration. For
		2988	example, if you want to handle a large number of connections fairly, you
		2989	normally only do a bit of work for each active connection, and if there
		2990	is more work to do, you wait for the next event loop iteration, so other
		2991	connections have a chance of making progress.
		2992
		2993	Using an C<ev_check> watcher is almost enough: it will be called on the
		2994	next event loop iteration. However, that isn't as soon as possible -
		2995	without external events, your C<ev_check> watcher will not be invoked.
		2996
		2997	This is where C<ev_idle> watchers come in handy - all you need is a
		2998	single global idle watcher that is active as long as you have one active
		2999	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		3000	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		3001	invoked. Neither watcher alone can do that.
2768		3002
2769	=head3 Watcher-Specific Functions and Data Members	3003	=head3 Watcher-Specific Functions and Data Members
2770		3004
2771	=over 4	3005	=over 4
2772		3006
…		…
2973		3207
2974	=over 4	3208	=over 4
2975		3209
2976	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	3210	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
2977		3211
2978	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	3212	=item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)
2979		3213
2980	Configures the watcher to embed the given loop, which must be	3214	Configures the watcher to embed the given loop, which must be
2981	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	3215	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2982	invoked automatically, otherwise it is the responsibility of the callback	3216	invoked automatically, otherwise it is the responsibility of the callback
2983	to invoke it (it will continue to be called until the sweep has been done,	3217	to invoke it (it will continue to be called until the sweep has been done,
…		…
3004	used).	3238	used).
3005		3239
3006	struct ev_loop *loop_hi = ev_default_init (0);	3240	struct ev_loop *loop_hi = ev_default_init (0);
3007	struct ev_loop *loop_lo = 0;	3241	struct ev_loop *loop_lo = 0;
3008	ev_embed embed;	3242	ev_embed embed;
3009		3243
3010	// see if there is a chance of getting one that works	3244	// see if there is a chance of getting one that works
3011	// (remember that a flags value of 0 means autodetection)	3245	// (remember that a flags value of 0 means autodetection)
3012	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3246	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
3013	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3247	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
3014	: 0;	3248	: 0;
…		…
3028	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3262	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
3029		3263
3030	struct ev_loop *loop = ev_default_init (0);	3264	struct ev_loop *loop = ev_default_init (0);
3031	struct ev_loop *loop_socket = 0;	3265	struct ev_loop *loop_socket = 0;
3032	ev_embed embed;	3266	ev_embed embed;
3033		3267
3034	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3268	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
3035	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3269	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
3036	{	3270	{
3037	ev_embed_init (&embed, 0, loop_socket);	3271	ev_embed_init (&embed, 0, loop_socket);
3038	ev_embed_start (loop, &embed);	3272	ev_embed_start (loop, &embed);
…		…
3046		3280
3047	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3281	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
3048		3282
3049	Fork watchers are called when a C<fork ()> was detected (usually because	3283	Fork watchers are called when a C<fork ()> was detected (usually because
3050	whoever is a good citizen cared to tell libev about it by calling	3284	whoever is a good citizen cared to tell libev about it by calling
3051	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the	3285	C<ev_loop_fork>). The invocation is done before the event loop blocks next
3052	event loop blocks next and before C<ev_check> watchers are being called,	3286	and before C<ev_check> watchers are being called, and only in the child
3053	and only in the child after the fork. If whoever good citizen calling	3287	after the fork. If whoever good citizen calling C<ev_default_fork> cheats
3054	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3288	and calls it in the wrong process, the fork handlers will be invoked, too,
3055	handlers will be invoked, too, of course.	3289	of course.
3056		3290
3057	=head3 The special problem of life after fork - how is it possible?	3291	=head3 The special problem of life after fork - how is it possible?
3058		3292
3059	Most uses of C<fork()> consist of forking, then some simple calls to set	3293	Most uses of C<fork ()> consist of forking, then some simple calls to set
3060	up/change the process environment, followed by a call to C<exec()>. This	3294	up/change the process environment, followed by a call to C<exec()>. This
3061	sequence should be handled by libev without any problems.	3295	sequence should be handled by libev without any problems.
3062		3296
3063	This changes when the application actually wants to do event handling	3297	This changes when the application actually wants to do event handling
3064	in the child, or both parent in child, in effect "continuing" after the	3298	in the child, or both parent in child, in effect "continuing" after the
…		…
3090		3324
3091	=head3 Watcher-Specific Functions and Data Members	3325	=head3 Watcher-Specific Functions and Data Members
3092		3326
3093	=over 4	3327	=over 4
3094		3328
3095	=item ev_fork_init (ev_signal *, callback)	3329	=item ev_fork_init (ev_fork *, callback)
3096		3330
3097	Initialises and configures the fork watcher - it has no parameters of any	3331	Initialises and configures the fork watcher - it has no parameters of any
3098	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3332	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
3099	believe me.	3333	really.
3100		3334
3101	=back	3335	=back
3102		3336
3103		3337
		3338	=head2 C<ev_cleanup> - even the best things end
		3339
		3340	Cleanup watchers are called just before the event loop is being destroyed
		3341	by a call to C<ev_loop_destroy>.
		3342
		3343	While there is no guarantee that the event loop gets destroyed, cleanup
		3344	watchers provide a convenient method to install cleanup hooks for your
		3345	program, worker threads and so on - you just to make sure to destroy the
		3346	loop when you want them to be invoked.
		3347
		3348	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3349	all other watchers, they do not keep a reference to the event loop (which
		3350	makes a lot of sense if you think about it). Like all other watchers, you
		3351	can call libev functions in the callback, except C<ev_cleanup_start>.
		3352
		3353	=head3 Watcher-Specific Functions and Data Members
		3354
		3355	=over 4
		3356
		3357	=item ev_cleanup_init (ev_cleanup *, callback)
		3358
		3359	Initialises and configures the cleanup watcher - it has no parameters of
		3360	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3361	pointless, I assure you.
		3362
		3363	=back
		3364
		3365	Example: Register an atexit handler to destroy the default loop, so any
		3366	cleanup functions are called.
		3367
		3368	static void
		3369	program_exits (void)
		3370	{
		3371	ev_loop_destroy (EV_DEFAULT_UC);
		3372	}
		3373
		3374	...
		3375	atexit (program_exits);
		3376
		3377
3104	=head2 C<ev_async> - how to wake up an event loop	3378	=head2 C<ev_async> - how to wake up an event loop
3105		3379
3106	In general, you cannot use an C<ev_run> from multiple threads or other	3380	In general, you cannot use an C<ev_loop> from multiple threads or other
3107	asynchronous sources such as signal handlers (as opposed to multiple event	3381	asynchronous sources such as signal handlers (as opposed to multiple event
3108	loops - those are of course safe to use in different threads).	3382	loops - those are of course safe to use in different threads).
3109		3383
3110	Sometimes, however, you need to wake up an event loop you do not control,	3384	Sometimes, however, you need to wake up an event loop you do not control,
3111	for example because it belongs to another thread. This is what C<ev_async>	3385	for example because it belongs to another thread. This is what C<ev_async>
…		…
3113	it by calling C<ev_async_send>, which is thread- and signal safe.	3387	it by calling C<ev_async_send>, which is thread- and signal safe.
3114		3388
3115	This functionality is very similar to C<ev_signal> watchers, as signals,	3389	This functionality is very similar to C<ev_signal> watchers, as signals,
3116	too, are asynchronous in nature, and signals, too, will be compressed	3390	too, are asynchronous in nature, and signals, too, will be compressed
3117	(i.e. the number of callback invocations may be less than the number of	3391	(i.e. the number of callback invocations may be less than the number of
3118	C<ev_async_sent> calls).	3392	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
3119		3393	of "global async watchers" by using a watcher on an otherwise unused
3120	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3394	signal, and C<ev_feed_signal> to signal this watcher from another thread,
3121	just the default loop.	3395	even without knowing which loop owns the signal.
3122		3396
3123	=head3 Queueing	3397	=head3 Queueing
3124		3398
3125	C<ev_async> does not support queueing of data in any way. The reason	3399	C<ev_async> does not support queueing of data in any way. The reason
3126	is that the author does not know of a simple (or any) algorithm for a	3400	is that the author does not know of a simple (or any) algorithm for a
…		…
3218	trust me.	3492	trust me.
3219		3493
3220	=item ev_async_send (loop, ev_async *)	3494	=item ev_async_send (loop, ev_async *)
3221		3495
3222	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3496	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3223	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3497	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3498	returns.
		3499
3224	C<ev_feed_event>, this call is safe to do from other threads, signal or	3500	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3225	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3501	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3226	section below on what exactly this means).	3502	embedding section below on what exactly this means).
3227		3503
3228	Note that, as with other watchers in libev, multiple events might get	3504	Note that, as with other watchers in libev, multiple events might get
3229	compressed into a single callback invocation (another way to look at this	3505	compressed into a single callback invocation (another way to look at
3230	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3506	this is that C<ev_async> watchers are level-triggered: they are set on
3231	reset when the event loop detects that).	3507	C<ev_async_send>, reset when the event loop detects that).
3232		3508
3233	This call incurs the overhead of a system call only once per event loop	3509	This call incurs the overhead of at most one extra system call per event
3234	iteration, so while the overhead might be noticeable, it doesn't apply to	3510	loop iteration, if the event loop is blocked, and no syscall at all if
3235	repeated calls to C<ev_async_send> for the same event loop.	3511	the event loop (or your program) is processing events. That means that
		3512	repeated calls are basically free (there is no need to avoid calls for
		3513	performance reasons) and that the overhead becomes smaller (typically
		3514	zero) under load.
3236		3515
3237	=item bool = ev_async_pending (ev_async *)	3516	=item bool = ev_async_pending (ev_async *)
3238		3517
3239	Returns a non-zero value when C<ev_async_send> has been called on the	3518	Returns a non-zero value when C<ev_async_send> has been called on the
3240	watcher but the event has not yet been processed (or even noted) by the	3519	watcher but the event has not yet been processed (or even noted) by the
…		…
3257		3536
3258	There are some other functions of possible interest. Described. Here. Now.	3537	There are some other functions of possible interest. Described. Here. Now.
3259		3538
3260	=over 4	3539	=over 4
3261		3540
3262	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3541	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg)
3263		3542
3264	This function combines a simple timer and an I/O watcher, calls your	3543	This function combines a simple timer and an I/O watcher, calls your
3265	callback on whichever event happens first and automatically stops both	3544	callback on whichever event happens first and automatically stops both
3266	watchers. This is useful if you want to wait for a single event on an fd	3545	watchers. This is useful if you want to wait for a single event on an fd
3267	or timeout without having to allocate/configure/start/stop/free one or	3546	or timeout without having to allocate/configure/start/stop/free one or
…		…
3295	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3574	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3296		3575
3297	=item ev_feed_fd_event (loop, int fd, int revents)	3576	=item ev_feed_fd_event (loop, int fd, int revents)
3298		3577
3299	Feed an event on the given fd, as if a file descriptor backend detected	3578	Feed an event on the given fd, as if a file descriptor backend detected
3300	the given events it.	3579	the given events.
3301		3580
3302	=item ev_feed_signal_event (loop, int signum)	3581	=item ev_feed_signal_event (loop, int signum)
3303		3582
3304	Feed an event as if the given signal occurred (C<loop> must be the default	3583	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3305	loop!).	3584	which is async-safe.
3306		3585
3307	=back	3586	=back
		3587
		3588
		3589	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3590
		3591	This section explains some common idioms that are not immediately
		3592	obvious. Note that examples are sprinkled over the whole manual, and this
		3593	section only contains stuff that wouldn't fit anywhere else.
		3594
		3595	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3596
		3597	Each watcher has, by default, a C<void *data> member that you can read
		3598	or modify at any time: libev will completely ignore it. This can be used
		3599	to associate arbitrary data with your watcher. If you need more data and
		3600	don't want to allocate memory separately and store a pointer to it in that
		3601	data member, you can also "subclass" the watcher type and provide your own
		3602	data:
		3603
		3604	struct my_io
		3605	{
		3606	ev_io io;
		3607	int otherfd;
		3608	void *somedata;
		3609	struct whatever *mostinteresting;
		3610	};
		3611
		3612	...
		3613	struct my_io w;
		3614	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3615
		3616	And since your callback will be called with a pointer to the watcher, you
		3617	can cast it back to your own type:
		3618
		3619	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3620	{
		3621	struct my_io *w = (struct my_io *)w_;
		3622	...
		3623	}
		3624
		3625	More interesting and less C-conformant ways of casting your callback
		3626	function type instead have been omitted.
		3627
		3628	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3629
		3630	Another common scenario is to use some data structure with multiple
		3631	embedded watchers, in effect creating your own watcher that combines
		3632	multiple libev event sources into one "super-watcher":
		3633
		3634	struct my_biggy
		3635	{
		3636	int some_data;
		3637	ev_timer t1;
		3638	ev_timer t2;
		3639	}
		3640
		3641	In this case getting the pointer to C<my_biggy> is a bit more
		3642	complicated: Either you store the address of your C<my_biggy> struct in
		3643	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3644	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3645	real programmers):
		3646
		3647	#include <stddef.h>
		3648
		3649	static void
		3650	t1_cb (EV_P_ ev_timer *w, int revents)
		3651	{
		3652	struct my_biggy big = (struct my_biggy *)
		3653	(((char *)w) - offsetof (struct my_biggy, t1));
		3654	}
		3655
		3656	static void
		3657	t2_cb (EV_P_ ev_timer *w, int revents)
		3658	{
		3659	struct my_biggy big = (struct my_biggy *)
		3660	(((char *)w) - offsetof (struct my_biggy, t2));
		3661	}
		3662
		3663	=head2 AVOIDING FINISHING BEFORE RETURNING
		3664
		3665	Often you have structures like this in event-based programs:
		3666
		3667	callback ()
		3668	{
		3669	free (request);
		3670	}
		3671
		3672	request = start_new_request (..., callback);
		3673
		3674	The intent is to start some "lengthy" operation. The C<request> could be
		3675	used to cancel the operation, or do other things with it.
		3676
		3677	It's not uncommon to have code paths in C<start_new_request> that
		3678	immediately invoke the callback, for example, to report errors. Or you add
		3679	some caching layer that finds that it can skip the lengthy aspects of the
		3680	operation and simply invoke the callback with the result.
		3681
		3682	The problem here is that this will happen I<before> C<start_new_request>
		3683	has returned, so C<request> is not set.
		3684
		3685	Even if you pass the request by some safer means to the callback, you
		3686	might want to do something to the request after starting it, such as
		3687	canceling it, which probably isn't working so well when the callback has
		3688	already been invoked.
		3689
		3690	A common way around all these issues is to make sure that
		3691	C<start_new_request> I<always> returns before the callback is invoked. If
		3692	C<start_new_request> immediately knows the result, it can artificially
		3693	delay invoking the callback by using a C<prepare> or C<idle> watcher for
		3694	example, or more sneakily, by reusing an existing (stopped) watcher and
		3695	pushing it into the pending queue:
		3696
		3697	ev_set_cb (watcher, callback);
		3698	ev_feed_event (EV_A_ watcher, 0);
		3699
		3700	This way, C<start_new_request> can safely return before the callback is
		3701	invoked, while not delaying callback invocation too much.
		3702
		3703	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3704
		3705	Often (especially in GUI toolkits) there are places where you have
		3706	I<modal> interaction, which is most easily implemented by recursively
		3707	invoking C<ev_run>.
		3708
		3709	This brings the problem of exiting - a callback might want to finish the
		3710	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3711	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3712	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3713	other combination: In these cases, a simple C<ev_break> will not work.
		3714
		3715	The solution is to maintain "break this loop" variable for each C<ev_run>
		3716	invocation, and use a loop around C<ev_run> until the condition is
		3717	triggered, using C<EVRUN_ONCE>:
		3718
		3719	// main loop
		3720	int exit_main_loop = 0;
		3721
		3722	while (!exit_main_loop)
		3723	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3724
		3725	// in a modal watcher
		3726	int exit_nested_loop = 0;
		3727
		3728	while (!exit_nested_loop)
		3729	ev_run (EV_A_ EVRUN_ONCE);
		3730
		3731	To exit from any of these loops, just set the corresponding exit variable:
		3732
		3733	// exit modal loop
		3734	exit_nested_loop = 1;
		3735
		3736	// exit main program, after modal loop is finished
		3737	exit_main_loop = 1;
		3738
		3739	// exit both
		3740	exit_main_loop = exit_nested_loop = 1;
		3741
		3742	=head2 THREAD LOCKING EXAMPLE
		3743
		3744	Here is a fictitious example of how to run an event loop in a different
		3745	thread from where callbacks are being invoked and watchers are
		3746	created/added/removed.
		3747
		3748	For a real-world example, see the C<EV::Loop::Async> perl module,
		3749	which uses exactly this technique (which is suited for many high-level
		3750	languages).
		3751
		3752	The example uses a pthread mutex to protect the loop data, a condition
		3753	variable to wait for callback invocations, an async watcher to notify the
		3754	event loop thread and an unspecified mechanism to wake up the main thread.
		3755
		3756	First, you need to associate some data with the event loop:
		3757
		3758	typedef struct {
		3759	mutex_t lock; /* global loop lock */
		3760	ev_async async_w;
		3761	thread_t tid;
		3762	cond_t invoke_cv;
		3763	} userdata;
		3764
		3765	void prepare_loop (EV_P)
		3766	{
		3767	// for simplicity, we use a static userdata struct.
		3768	static userdata u;
		3769
		3770	ev_async_init (&u->async_w, async_cb);
		3771	ev_async_start (EV_A_ &u->async_w);
		3772
		3773	pthread_mutex_init (&u->lock, 0);
		3774	pthread_cond_init (&u->invoke_cv, 0);
		3775
		3776	// now associate this with the loop
		3777	ev_set_userdata (EV_A_ u);
		3778	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3779	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3780
		3781	// then create the thread running ev_run
		3782	pthread_create (&u->tid, 0, l_run, EV_A);
		3783	}
		3784
		3785	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3786	solely to wake up the event loop so it takes notice of any new watchers
		3787	that might have been added:
		3788
		3789	static void
		3790	async_cb (EV_P_ ev_async *w, int revents)
		3791	{
		3792	// just used for the side effects
		3793	}
		3794
		3795	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3796	protecting the loop data, respectively.
		3797
		3798	static void
		3799	l_release (EV_P)
		3800	{
		3801	userdata *u = ev_userdata (EV_A);
		3802	pthread_mutex_unlock (&u->lock);
		3803	}
		3804
		3805	static void
		3806	l_acquire (EV_P)
		3807	{
		3808	userdata *u = ev_userdata (EV_A);
		3809	pthread_mutex_lock (&u->lock);
		3810	}
		3811
		3812	The event loop thread first acquires the mutex, and then jumps straight
		3813	into C<ev_run>:
		3814
		3815	void *
		3816	l_run (void *thr_arg)
		3817	{
		3818	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3819
		3820	l_acquire (EV_A);
		3821	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3822	ev_run (EV_A_ 0);
		3823	l_release (EV_A);
		3824
		3825	return 0;
		3826	}
		3827
		3828	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3829	signal the main thread via some unspecified mechanism (signals? pipe
		3830	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3831	have been called (in a while loop because a) spurious wakeups are possible
		3832	and b) skipping inter-thread-communication when there are no pending
		3833	watchers is very beneficial):
		3834
		3835	static void
		3836	l_invoke (EV_P)
		3837	{
		3838	userdata *u = ev_userdata (EV_A);
		3839
		3840	while (ev_pending_count (EV_A))
		3841	{
		3842	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3843	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3844	}
		3845	}
		3846
		3847	Now, whenever the main thread gets told to invoke pending watchers, it
		3848	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3849	thread to continue:
		3850
		3851	static void
		3852	real_invoke_pending (EV_P)
		3853	{
		3854	userdata *u = ev_userdata (EV_A);
		3855
		3856	pthread_mutex_lock (&u->lock);
		3857	ev_invoke_pending (EV_A);
		3858	pthread_cond_signal (&u->invoke_cv);
		3859	pthread_mutex_unlock (&u->lock);
		3860	}
		3861
		3862	Whenever you want to start/stop a watcher or do other modifications to an
		3863	event loop, you will now have to lock:
		3864
		3865	ev_timer timeout_watcher;
		3866	userdata *u = ev_userdata (EV_A);
		3867
		3868	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3869
		3870	pthread_mutex_lock (&u->lock);
		3871	ev_timer_start (EV_A_ &timeout_watcher);
		3872	ev_async_send (EV_A_ &u->async_w);
		3873	pthread_mutex_unlock (&u->lock);
		3874
		3875	Note that sending the C<ev_async> watcher is required because otherwise
		3876	an event loop currently blocking in the kernel will have no knowledge
		3877	about the newly added timer. By waking up the loop it will pick up any new
		3878	watchers in the next event loop iteration.
		3879
		3880	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3881
		3882	While the overhead of a callback that e.g. schedules a thread is small, it
		3883	is still an overhead. If you embed libev, and your main usage is with some
		3884	kind of threads or coroutines, you might want to customise libev so that
		3885	doesn't need callbacks anymore.
		3886
		3887	Imagine you have coroutines that you can switch to using a function
		3888	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3889	and that due to some magic, the currently active coroutine is stored in a
		3890	global called C<current_coro>. Then you can build your own "wait for libev
		3891	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3892	the differing C<;> conventions):
		3893
		3894	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3895	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3896
		3897	That means instead of having a C callback function, you store the
		3898	coroutine to switch to in each watcher, and instead of having libev call
		3899	your callback, you instead have it switch to that coroutine.
		3900
		3901	A coroutine might now wait for an event with a function called
		3902	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3903	matter when, or whether the watcher is active or not when this function is
		3904	called):
		3905
		3906	void
		3907	wait_for_event (ev_watcher *w)
		3908	{
		3909	ev_set_cb (w, current_coro);
		3910	switch_to (libev_coro);
		3911	}
		3912
		3913	That basically suspends the coroutine inside C<wait_for_event> and
		3914	continues the libev coroutine, which, when appropriate, switches back to
		3915	this or any other coroutine.
		3916
		3917	You can do similar tricks if you have, say, threads with an event queue -
		3918	instead of storing a coroutine, you store the queue object and instead of
		3919	switching to a coroutine, you push the watcher onto the queue and notify
		3920	any waiters.
		3921
		3922	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		3923	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3924
		3925	// my_ev.h
		3926	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3927	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3928	#include "../libev/ev.h"
		3929
		3930	// my_ev.c
		3931	#define EV_H "my_ev.h"
		3932	#include "../libev/ev.c"
		3933
		3934	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3935	F<my_ev.c> into your project. When properly specifying include paths, you
		3936	can even use F<ev.h> as header file name directly.
3308		3937
3309		3938
3310	=head1 LIBEVENT EMULATION	3939	=head1 LIBEVENT EMULATION
3311		3940
3312	Libev offers a compatibility emulation layer for libevent. It cannot	3941	Libev offers a compatibility emulation layer for libevent. It cannot
3313	emulate the internals of libevent, so here are some usage hints:	3942	emulate the internals of libevent, so here are some usage hints:
3314		3943
3315	=over 4	3944	=over 4
		3945
		3946	=item * Only the libevent-1.4.1-beta API is being emulated.
		3947
		3948	This was the newest libevent version available when libev was implemented,
		3949	and is still mostly unchanged in 2010.
3316		3950
3317	=item * Use it by including <event.h>, as usual.	3951	=item * Use it by including <event.h>, as usual.
3318		3952
3319	=item * The following members are fully supported: ev_base, ev_callback,	3953	=item * The following members are fully supported: ev_base, ev_callback,
3320	ev_arg, ev_fd, ev_res, ev_events.	3954	ev_arg, ev_fd, ev_res, ev_events.
…		…
3326	=item * Priorities are not currently supported. Initialising priorities	3960	=item * Priorities are not currently supported. Initialising priorities
3327	will fail and all watchers will have the same priority, even though there	3961	will fail and all watchers will have the same priority, even though there
3328	is an ev_pri field.	3962	is an ev_pri field.
3329		3963
3330	=item * In libevent, the last base created gets the signals, in libev, the	3964	=item * In libevent, the last base created gets the signals, in libev, the
3331	first base created (== the default loop) gets the signals.	3965	base that registered the signal gets the signals.
3332		3966
3333	=item * Other members are not supported.	3967	=item * Other members are not supported.
3334		3968
3335	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3969	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3336	to use the libev header file and library.	3970	to use the libev header file and library.
3337		3971
3338	=back	3972	=back
3339		3973
3340	=head1 C++ SUPPORT	3974	=head1 C++ SUPPORT
		3975
		3976	=head2 C API
		3977
		3978	The normal C API should work fine when used from C++: both ev.h and the
		3979	libev sources can be compiled as C++. Therefore, code that uses the C API
		3980	will work fine.
		3981
		3982	Proper exception specifications might have to be added to callbacks passed
		3983	to libev: exceptions may be thrown only from watcher callbacks, all other
		3984	callbacks (allocator, syserr, loop acquire/release and periodic reschedule
		3985	callbacks) must not throw exceptions, and might need a C<noexcept>
		3986	specification. If you have code that needs to be compiled as both C and
		3987	C++ you can use the C<EV_NOEXCEPT> macro for this:
		3988
		3989	static void
		3990	fatal_error (const char *msg) EV_NOEXCEPT
		3991	{
		3992	perror (msg);
		3993	abort ();
		3994	}
		3995
		3996	...
		3997	ev_set_syserr_cb (fatal_error);
		3998
		3999	The only API functions that can currently throw exceptions are C<ev_run>,
		4000	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		4001	because it runs cleanup watchers).
		4002
		4003	Throwing exceptions in watcher callbacks is only supported if libev itself
		4004	is compiled with a C++ compiler or your C and C++ environments allow
		4005	throwing exceptions through C libraries (most do).
		4006
		4007	=head2 C++ API
3341		4008
3342	Libev comes with some simplistic wrapper classes for C++ that mainly allow	4009	Libev comes with some simplistic wrapper classes for C++ that mainly allow
3343	you to use some convenience methods to start/stop watchers and also change	4010	you to use some convenience methods to start/stop watchers and also change
3344	the callback model to a model using method callbacks on objects.	4011	the callback model to a model using method callbacks on objects.
3345		4012
3346	To use it,	4013	To use it,
3347		4014
3348	#include <ev++.h>	4015	#include <ev++.h>
3349		4016
3350	This automatically includes F<ev.h> and puts all of its definitions (many	4017	This automatically includes F<ev.h> and puts all of its definitions (many
3351	of them macros) into the global namespace. All C++ specific things are	4018	of them macros) into the global namespace. All C++ specific things are
3352	put into the C<ev> namespace. It should support all the same embedding	4019	put into the C<ev> namespace. It should support all the same embedding
…		…
3355	Care has been taken to keep the overhead low. The only data member the C++	4022	Care has been taken to keep the overhead low. The only data member the C++
3356	classes add (compared to plain C-style watchers) is the event loop pointer	4023	classes add (compared to plain C-style watchers) is the event loop pointer
3357	that the watcher is associated with (or no additional members at all if	4024	that the watcher is associated with (or no additional members at all if
3358	you disable C<EV_MULTIPLICITY> when embedding libev).	4025	you disable C<EV_MULTIPLICITY> when embedding libev).
3359		4026
3360	Currently, functions, and static and non-static member functions can be	4027	Currently, functions, static and non-static member functions and classes
3361	used as callbacks. Other types should be easy to add as long as they only	4028	with C<operator ()> can be used as callbacks. Other types should be easy
3362	need one additional pointer for context. If you need support for other	4029	to add as long as they only need one additional pointer for context. If
3363	types of functors please contact the author (preferably after implementing	4030	you need support for other types of functors please contact the author
3364	it).	4031	(preferably after implementing it).
		4032
		4033	For all this to work, your C++ compiler either has to use the same calling
		4034	conventions as your C compiler (for static member functions), or you have
		4035	to embed libev and compile libev itself as C++.
3365		4036
3366	Here is a list of things available in the C<ev> namespace:	4037	Here is a list of things available in the C<ev> namespace:
3367		4038
3368	=over 4	4039	=over 4
3369		4040
…		…
3379	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4050	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3380		4051
3381	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4052	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
3382	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4053	the same name in the C<ev> namespace, with the exception of C<ev_signal>
3383	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4054	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3384	defines by many implementations.	4055	defined by many implementations.
3385		4056
3386	All of those classes have these methods:	4057	All of those classes have these methods:
3387		4058
3388	=over 4	4059	=over 4
3389		4060
…		…
3451	void operator() (ev::io &w, int revents)	4122	void operator() (ev::io &w, int revents)
3452	{	4123	{
3453	...	4124	...
3454	}	4125	}
3455	}	4126	}
3456		4127
3457	myfunctor f;	4128	myfunctor f;
3458		4129
3459	ev::io w;	4130	ev::io w;
3460	w.set (&f);	4131	w.set (&f);
3461		4132
…		…
3479	Associates a different C<struct ev_loop> with this watcher. You can only	4150	Associates a different C<struct ev_loop> with this watcher. You can only
3480	do this when the watcher is inactive (and not pending either).	4151	do this when the watcher is inactive (and not pending either).
3481		4152
3482	=item w->set ([arguments])	4153	=item w->set ([arguments])
3483		4154
3484	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this	4155	Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>),
3485	method or a suitable start method must be called at least once. Unlike the	4156	with the same arguments. Either this method or a suitable start method
3486	C counterpart, an active watcher gets automatically stopped and restarted	4157	must be called at least once. Unlike the C counterpart, an active watcher
3487	when reconfiguring it with this method.	4158	gets automatically stopped and restarted when reconfiguring it with this
		4159	method.
		4160
		4161	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4162	clashing with the C<set (loop)> method.
3488		4163
3489	=item w->start ()	4164	=item w->start ()
3490		4165
3491	Starts the watcher. Note that there is no C<loop> argument, as the	4166	Starts the watcher. Note that there is no C<loop> argument, as the
3492	constructor already stores the event loop.	4167	constructor already stores the event loop.
…		…
3522	watchers in the constructor.	4197	watchers in the constructor.
3523		4198
3524	class myclass	4199	class myclass
3525	{	4200	{
3526	ev::io io ; void io_cb (ev::io &w, int revents);	4201	ev::io io ; void io_cb (ev::io &w, int revents);
3527	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);	4202	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3528	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4203	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3529		4204
3530	myclass (int fd)	4205	myclass (int fd)
3531	{	4206	{
3532	io .set <myclass, &myclass::io_cb > (this);	4207	io .set <myclass, &myclass::io_cb > (this);
…		…
3583	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4258	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3584		4259
3585	=item D	4260	=item D
3586		4261
3587	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4262	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3588	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4263	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3589		4264
3590	=item Ocaml	4265	=item Ocaml
3591		4266
3592	Erkki Seppala has written Ocaml bindings for libev, to be found at	4267	Erkki Seppala has written Ocaml bindings for libev, to be found at
3593	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4268	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
…		…
3596		4271
3597	Brian Maher has written a partial interface to libev for lua (at the	4272	Brian Maher has written a partial interface to libev for lua (at the
3598	time of this writing, only C<ev_io> and C<ev_timer>), to be found at	4273	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
3599	L<http://github.com/brimworks/lua-ev>.	4274	L<http://github.com/brimworks/lua-ev>.
3600		4275
		4276	=item Javascript
		4277
		4278	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4279
		4280	=item Others
		4281
		4282	There are others, and I stopped counting.
		4283
3601	=back	4284	=back
3602		4285
3603		4286
3604	=head1 MACRO MAGIC	4287	=head1 MACRO MAGIC
3605		4288
…		…
3641	suitable for use with C<EV_A>.	4324	suitable for use with C<EV_A>.
3642		4325
3643	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4326	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3644		4327
3645	Similar to the other two macros, this gives you the value of the default	4328	Similar to the other two macros, this gives you the value of the default
3646	loop, if multiple loops are supported ("ev loop default").	4329	loop, if multiple loops are supported ("ev loop default"). The default loop
		4330	will be initialised if it isn't already initialised.
		4331
		4332	For non-multiplicity builds, these macros do nothing, so you always have
		4333	to initialise the loop somewhere.
3647		4334
3648	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4335	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3649		4336
3650	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4337	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3651	default loop has been initialised (C<UC> == unchecked). Their behaviour	4338	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3718	ev_vars.h	4405	ev_vars.h
3719	ev_wrap.h	4406	ev_wrap.h
3720		4407
3721	ev_win32.c required on win32 platforms only	4408	ev_win32.c required on win32 platforms only
3722		4409
3723	ev_select.c only when select backend is enabled (which is enabled by default)	4410	ev_select.c only when select backend is enabled
3724	ev_poll.c only when poll backend is enabled (disabled by default)	4411	ev_poll.c only when poll backend is enabled
3725	ev_epoll.c only when the epoll backend is enabled (disabled by default)	4412	ev_epoll.c only when the epoll backend is enabled
3726	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	4413	ev_kqueue.c only when the kqueue backend is enabled
3727	ev_port.c only when the solaris port backend is enabled (disabled by default)	4414	ev_port.c only when the solaris port backend is enabled
3728		4415
3729	F<ev.c> includes the backend files directly when enabled, so you only need	4416	F<ev.c> includes the backend files directly when enabled, so you only need
3730	to compile this single file.	4417	to compile this single file.
3731		4418
3732	=head3 LIBEVENT COMPATIBILITY API	4419	=head3 LIBEVENT COMPATIBILITY API
…		…
3796	supported). It will also not define any of the structs usually found in	4483	supported). It will also not define any of the structs usually found in
3797	F<event.h> that are not directly supported by the libev core alone.	4484	F<event.h> that are not directly supported by the libev core alone.
3798		4485
3799	In standalone mode, libev will still try to automatically deduce the	4486	In standalone mode, libev will still try to automatically deduce the
3800	configuration, but has to be more conservative.	4487	configuration, but has to be more conservative.
		4488
		4489	=item EV_USE_FLOOR
		4490
		4491	If defined to be C<1>, libev will use the C<floor ()> function for its
		4492	periodic reschedule calculations, otherwise libev will fall back on a
		4493	portable (slower) implementation. If you enable this, you usually have to
		4494	link against libm or something equivalent. Enabling this when the C<floor>
		4495	function is not available will fail, so the safe default is to not enable
		4496	this.
3801		4497
3802	=item EV_USE_MONOTONIC	4498	=item EV_USE_MONOTONIC
3803		4499
3804	If defined to be C<1>, libev will try to detect the availability of the	4500	If defined to be C<1>, libev will try to detect the availability of the
3805	monotonic clock option at both compile time and runtime. Otherwise no	4501	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3890		4586
3891	If programs implement their own fd to handle mapping on win32, then this	4587	If programs implement their own fd to handle mapping on win32, then this
3892	macro can be used to override the C<close> function, useful to unregister	4588	macro can be used to override the C<close> function, useful to unregister
3893	file descriptors again. Note that the replacement function has to close	4589	file descriptors again. Note that the replacement function has to close
3894	the underlying OS handle.	4590	the underlying OS handle.
		4591
		4592	=item EV_USE_WSASOCKET
		4593
		4594	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4595	communication socket, which works better in some environments. Otherwise,
		4596	the normal C<socket> function will be used, which works better in other
		4597	environments.
3895		4598
3896	=item EV_USE_POLL	4599	=item EV_USE_POLL
3897		4600
3898	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4601	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3899	backend. Otherwise it will be enabled on non-win32 platforms. It	4602	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3935	If defined to be C<1>, libev will compile in support for the Linux inotify	4638	If defined to be C<1>, libev will compile in support for the Linux inotify
3936	interface to speed up C<ev_stat> watchers. Its actual availability will	4639	interface to speed up C<ev_stat> watchers. Its actual availability will
3937	be detected at runtime. If undefined, it will be enabled if the headers	4640	be detected at runtime. If undefined, it will be enabled if the headers
3938	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4641	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3939		4642
		4643	=item EV_NO_SMP
		4644
		4645	If defined to be C<1>, libev will assume that memory is always coherent
		4646	between threads, that is, threads can be used, but threads never run on
		4647	different cpus (or different cpu cores). This reduces dependencies
		4648	and makes libev faster.
		4649
		4650	=item EV_NO_THREADS
		4651
		4652	If defined to be C<1>, libev will assume that it will never be called from
		4653	different threads (that includes signal handlers), which is a stronger
		4654	assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes
		4655	libev faster.
		4656
3940	=item EV_ATOMIC_T	4657	=item EV_ATOMIC_T
3941		4658
3942	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4659	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3943	access is atomic with respect to other threads or signal contexts. No such	4660	access is atomic with respect to other threads or signal contexts. No
3944	type is easily found in the C language, so you can provide your own type	4661	such type is easily found in the C language, so you can provide your own
3945	that you know is safe for your purposes. It is used both for signal handler "locking"	4662	type that you know is safe for your purposes. It is used both for signal
3946	as well as for signal and thread safety in C<ev_async> watchers.	4663	handler "locking" as well as for signal and thread safety in C<ev_async>
		4664	watchers.
3947		4665
3948	In the absence of this define, libev will use C<sig_atomic_t volatile>	4666	In the absence of this define, libev will use C<sig_atomic_t volatile>
3949	(from F<signal.h>), which is usually good enough on most platforms.	4667	(from F<signal.h>), which is usually good enough on most platforms.
3950		4668
3951	=item EV_H (h)	4669	=item EV_H (h)
…		…
3978	will have the C<struct ev_loop *> as first argument, and you can create	4696	will have the C<struct ev_loop *> as first argument, and you can create
3979	additional independent event loops. Otherwise there will be no support	4697	additional independent event loops. Otherwise there will be no support
3980	for multiple event loops and there is no first event loop pointer	4698	for multiple event loops and there is no first event loop pointer
3981	argument. Instead, all functions act on the single default loop.	4699	argument. Instead, all functions act on the single default loop.
3982		4700
		4701	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4702	default loop when multiplicity is switched off - you always have to
		4703	initialise the loop manually in this case.
		4704
3983	=item EV_MINPRI	4705	=item EV_MINPRI
3984		4706
3985	=item EV_MAXPRI	4707	=item EV_MAXPRI
3986		4708
3987	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4709	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
4023	#define EV_USE_POLL 1	4745	#define EV_USE_POLL 1
4024	#define EV_CHILD_ENABLE 1	4746	#define EV_CHILD_ENABLE 1
4025	#define EV_ASYNC_ENABLE 1	4747	#define EV_ASYNC_ENABLE 1
4026		4748
4027	The actual value is a bitset, it can be a combination of the following	4749	The actual value is a bitset, it can be a combination of the following
4028	values:	4750	values (by default, all of these are enabled):
4029		4751
4030	=over 4	4752	=over 4
4031		4753
4032	=item C<1> - faster/larger code	4754	=item C<1> - faster/larger code
4033		4755
…		…
4037	code size by roughly 30% on amd64).	4759	code size by roughly 30% on amd64).
4038		4760
4039	When optimising for size, use of compiler flags such as C<-Os> with	4761	When optimising for size, use of compiler flags such as C<-Os> with
4040	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of	4762	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
4041	assertions.	4763	assertions.
		4764
		4765	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4766	(e.g. gcc with C<-Os>).
4042		4767
4043	=item C<2> - faster/larger data structures	4768	=item C<2> - faster/larger data structures
4044		4769
4045	Replaces the small 2-heap for timer management by a faster 4-heap, larger	4770	Replaces the small 2-heap for timer management by a faster 4-heap, larger
4046	hash table sizes and so on. This will usually further increase code size	4771	hash table sizes and so on. This will usually further increase code size
4047	and can additionally have an effect on the size of data structures at	4772	and can additionally have an effect on the size of data structures at
4048	runtime.	4773	runtime.
4049		4774
		4775	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4776	(e.g. gcc with C<-Os>).
		4777
4050	=item C<4> - full API configuration	4778	=item C<4> - full API configuration
4051		4779
4052	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and	4780	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
4053	enables multiplicity (C<EV_MULTIPLICITY>=1).	4781	enables multiplicity (C<EV_MULTIPLICITY>=1).
4054		4782
…		…
4084		4812
4085	With an intelligent-enough linker (gcc+binutils are intelligent enough	4813	With an intelligent-enough linker (gcc+binutils are intelligent enough
4086	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by	4814	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
4087	your program might be left out as well - a binary starting a timer and an	4815	your program might be left out as well - a binary starting a timer and an
4088	I/O watcher then might come out at only 5Kb.	4816	I/O watcher then might come out at only 5Kb.
		4817
		4818	=item EV_API_STATIC
		4819
		4820	If this symbol is defined (by default it is not), then all identifiers
		4821	will have static linkage. This means that libev will not export any
		4822	identifiers, and you cannot link against libev anymore. This can be useful
		4823	when you embed libev, only want to use libev functions in a single file,
		4824	and do not want its identifiers to be visible.
		4825
		4826	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4827	wants to use libev.
		4828
		4829	This option only works when libev is compiled with a C compiler, as C++
		4830	doesn't support the required declaration syntax.
4089		4831
4090	=item EV_AVOID_STDIO	4832	=item EV_AVOID_STDIO
4091		4833
4092	If this is set to C<1> at compiletime, then libev will avoid using stdio	4834	If this is set to C<1> at compiletime, then libev will avoid using stdio
4093	functions (printf, scanf, perror etc.). This will increase the code size	4835	functions (printf, scanf, perror etc.). This will increase the code size
…		…
4237	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4979	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4238		4980
4239	#include "ev_cpp.h"	4981	#include "ev_cpp.h"
4240	#include "ev.c"	4982	#include "ev.c"
4241		4983
4242	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4984	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4243		4985
4244	=head2 THREADS AND COROUTINES	4986	=head2 THREADS AND COROUTINES
4245		4987
4246	=head3 THREADS	4988	=head3 THREADS
4247		4989
…		…
4298	default loop and triggering an C<ev_async> watcher from the default loop	5040	default loop and triggering an C<ev_async> watcher from the default loop
4299	watcher callback into the event loop interested in the signal.	5041	watcher callback into the event loop interested in the signal.
4300		5042
4301	=back	5043	=back
4302		5044
4303	=head4 THREAD LOCKING EXAMPLE	5045	See also L</THREAD LOCKING EXAMPLE>.
4304
4305	Here is a fictitious example of how to run an event loop in a different
4306	thread than where callbacks are being invoked and watchers are
4307	created/added/removed.
4308
4309	For a real-world example, see the C<EV::Loop::Async> perl module,
4310	which uses exactly this technique (which is suited for many high-level
4311	languages).
4312
4313	The example uses a pthread mutex to protect the loop data, a condition
4314	variable to wait for callback invocations, an async watcher to notify the
4315	event loop thread and an unspecified mechanism to wake up the main thread.
4316
4317	First, you need to associate some data with the event loop:
4318
4319	typedef struct {
4320	mutex_t lock; /* global loop lock */
4321	ev_async async_w;
4322	thread_t tid;
4323	cond_t invoke_cv;
4324	} userdata;
4325
4326	void prepare_loop (EV_P)
4327	{
4328	// for simplicity, we use a static userdata struct.
4329	static userdata u;
4330
4331	ev_async_init (&u->async_w, async_cb);
4332	ev_async_start (EV_A_ &u->async_w);
4333
4334	pthread_mutex_init (&u->lock, 0);
4335	pthread_cond_init (&u->invoke_cv, 0);
4336
4337	// now associate this with the loop
4338	ev_set_userdata (EV_A_ u);
4339	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4340	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4341
4342	// then create the thread running ev_loop
4343	pthread_create (&u->tid, 0, l_run, EV_A);
4344	}
4345
4346	The callback for the C<ev_async> watcher does nothing: the watcher is used
4347	solely to wake up the event loop so it takes notice of any new watchers
4348	that might have been added:
4349
4350	static void
4351	async_cb (EV_P_ ev_async *w, int revents)
4352	{
4353	// just used for the side effects
4354	}
4355
4356	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4357	protecting the loop data, respectively.
4358
4359	static void
4360	l_release (EV_P)
4361	{
4362	userdata *u = ev_userdata (EV_A);
4363	pthread_mutex_unlock (&u->lock);
4364	}
4365
4366	static void
4367	l_acquire (EV_P)
4368	{
4369	userdata *u = ev_userdata (EV_A);
4370	pthread_mutex_lock (&u->lock);
4371	}
4372
4373	The event loop thread first acquires the mutex, and then jumps straight
4374	into C<ev_run>:
4375
4376	void *
4377	l_run (void *thr_arg)
4378	{
4379	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4380
4381	l_acquire (EV_A);
4382	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4383	ev_run (EV_A_ 0);
4384	l_release (EV_A);
4385
4386	return 0;
4387	}
4388
4389	Instead of invoking all pending watchers, the C<l_invoke> callback will
4390	signal the main thread via some unspecified mechanism (signals? pipe
4391	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4392	have been called (in a while loop because a) spurious wakeups are possible
4393	and b) skipping inter-thread-communication when there are no pending
4394	watchers is very beneficial):
4395
4396	static void
4397	l_invoke (EV_P)
4398	{
4399	userdata *u = ev_userdata (EV_A);
4400
4401	while (ev_pending_count (EV_A))
4402	{
4403	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4404	pthread_cond_wait (&u->invoke_cv, &u->lock);
4405	}
4406	}
4407
4408	Now, whenever the main thread gets told to invoke pending watchers, it
4409	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4410	thread to continue:
4411
4412	static void
4413	real_invoke_pending (EV_P)
4414	{
4415	userdata *u = ev_userdata (EV_A);
4416
4417	pthread_mutex_lock (&u->lock);
4418	ev_invoke_pending (EV_A);
4419	pthread_cond_signal (&u->invoke_cv);
4420	pthread_mutex_unlock (&u->lock);
4421	}
4422
4423	Whenever you want to start/stop a watcher or do other modifications to an
4424	event loop, you will now have to lock:
4425
4426	ev_timer timeout_watcher;
4427	userdata *u = ev_userdata (EV_A);
4428
4429	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4430
4431	pthread_mutex_lock (&u->lock);
4432	ev_timer_start (EV_A_ &timeout_watcher);
4433	ev_async_send (EV_A_ &u->async_w);
4434	pthread_mutex_unlock (&u->lock);
4435
4436	Note that sending the C<ev_async> watcher is required because otherwise
4437	an event loop currently blocking in the kernel will have no knowledge
4438	about the newly added timer. By waking up the loop it will pick up any new
4439	watchers in the next event loop iteration.
4440		5046
4441	=head3 COROUTINES	5047	=head3 COROUTINES
4442		5048
4443	Libev is very accommodating to coroutines ("cooperative threads"):	5049	Libev is very accommodating to coroutines ("cooperative threads"):
4444	libev fully supports nesting calls to its functions from different	5050	libev fully supports nesting calls to its functions from different
…		…
4609	requires, and its I/O model is fundamentally incompatible with the POSIX	5215	requires, and its I/O model is fundamentally incompatible with the POSIX
4610	model. Libev still offers limited functionality on this platform in	5216	model. Libev still offers limited functionality on this platform in
4611	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5217	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4612	descriptors. This only applies when using Win32 natively, not when using	5218	descriptors. This only applies when using Win32 natively, not when using
4613	e.g. cygwin. Actually, it only applies to the microsofts own compilers,	5219	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
4614	as every compielr comes with a slightly differently broken/incompatible	5220	as every compiler comes with a slightly differently broken/incompatible
4615	environment.	5221	environment.
4616		5222
4617	Lifting these limitations would basically require the full	5223	Lifting these limitations would basically require the full
4618	re-implementation of the I/O system. If you are into this kind of thing,	5224	re-implementation of the I/O system. If you are into this kind of thing,
4619	then note that glib does exactly that for you in a very portable way (note	5225	then note that glib does exactly that for you in a very portable way (note
…		…
4713	structure (guaranteed by POSIX but not by ISO C for example), but it also	5319	structure (guaranteed by POSIX but not by ISO C for example), but it also
4714	assumes that the same (machine) code can be used to call any watcher	5320	assumes that the same (machine) code can be used to call any watcher
4715	callback: The watcher callbacks have different type signatures, but libev	5321	callback: The watcher callbacks have different type signatures, but libev
4716	calls them using an C<ev_watcher *> internally.	5322	calls them using an C<ev_watcher *> internally.
4717		5323
		5324	=item null pointers and integer zero are represented by 0 bytes
		5325
		5326	Libev uses C<memset> to initialise structs and arrays to C<0> bytes, and
		5327	relies on this setting pointers and integers to null.
		5328
		5329	=item pointer accesses must be thread-atomic
		5330
		5331	Accessing a pointer value must be atomic, it must both be readable and
		5332	writable in one piece - this is the case on all current architectures.
		5333
4718	=item C<sig_atomic_t volatile> must be thread-atomic as well	5334	=item C<sig_atomic_t volatile> must be thread-atomic as well
4719		5335
4720	The type C<sig_atomic_t volatile> (or whatever is defined as	5336	The type C<sig_atomic_t volatile> (or whatever is defined as
4721	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5337	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
4722	threads. This is not part of the specification for C<sig_atomic_t>, but is	5338	threads. This is not part of the specification for C<sig_atomic_t>, but is
…		…
4730	thread" or will block signals process-wide, both behaviours would	5346	thread" or will block signals process-wide, both behaviours would
4731	be compatible with libev. Interaction between C<sigprocmask> and	5347	be compatible with libev. Interaction between C<sigprocmask> and
4732	C<pthread_sigmask> could complicate things, however.	5348	C<pthread_sigmask> could complicate things, however.
4733		5349
4734	The most portable way to handle signals is to block signals in all threads	5350	The most portable way to handle signals is to block signals in all threads
4735	except the initial one, and run the default loop in the initial thread as	5351	except the initial one, and run the signal handling loop in the initial
4736	well.	5352	thread as well.
4737		5353
4738	=item C<long> must be large enough for common memory allocation sizes	5354	=item C<long> must be large enough for common memory allocation sizes
4739		5355
4740	To improve portability and simplify its API, libev uses C<long> internally	5356	To improve portability and simplify its API, libev uses C<long> internally
4741	instead of C<size_t> when allocating its data structures. On non-POSIX	5357	instead of C<size_t> when allocating its data structures. On non-POSIX
…		…
4747		5363
4748	The type C<double> is used to represent timestamps. It is required to	5364	The type C<double> is used to represent timestamps. It is required to
4749	have at least 51 bits of mantissa (and 9 bits of exponent), which is	5365	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4750	good enough for at least into the year 4000 with millisecond accuracy	5366	good enough for at least into the year 4000 with millisecond accuracy
4751	(the design goal for libev). This requirement is overfulfilled by	5367	(the design goal for libev). This requirement is overfulfilled by
4752	implementations using IEEE 754, which is basically all existing ones. With	5368	implementations using IEEE 754, which is basically all existing ones.
		5369
4753	IEEE 754 doubles, you get microsecond accuracy until at least 2200.	5370	With IEEE 754 doubles, you get microsecond accuracy until at least the
		5371	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5372	is either obsolete or somebody patched it to use C<long double> or
		5373	something like that, just kidding).
4754		5374
4755	=back	5375	=back
4756		5376
4757	If you know of other additional requirements drop me a note.	5377	If you know of other additional requirements drop me a note.
4758		5378
…		…
4820	=item Processing ev_async_send: O(number_of_async_watchers)	5440	=item Processing ev_async_send: O(number_of_async_watchers)
4821		5441
4822	=item Processing signals: O(max_signal_number)	5442	=item Processing signals: O(max_signal_number)
4823		5443
4824	Sending involves a system call I<iff> there were no other C<ev_async_send>	5444	Sending involves a system call I<iff> there were no other C<ev_async_send>
4825	calls in the current loop iteration. Checking for async and signal events	5445	calls in the current loop iteration and the loop is currently
		5446	blocked. Checking for async and signal events involves iterating over all
4826	involves iterating over all running async watchers or all signal numbers.	5447	running async watchers or all signal numbers.
4827		5448
4828	=back	5449	=back
4829		5450
4830		5451
4831	=head1 PORTING FROM LIBEV 3.X TO 4.X	5452	=head1 PORTING FROM LIBEV 3.X TO 4.X
4832		5453
4833	The major version 4 introduced some minor incompatible changes to the API.	5454	The major version 4 introduced some incompatible changes to the API.
4834		5455
4835	At the moment, the C<ev.h> header file tries to implement superficial	5456	At the moment, the C<ev.h> header file provides compatibility definitions
4836	compatibility, so most programs should still compile. Those might be	5457	for all changes, so most programs should still compile. The compatibility
4837	removed in later versions of libev, so better update early than late.	5458	layer might be removed in later versions of libev, so better update to the
		5459	new API early than late.
4838		5460
4839	=over 4	5461	=over 4
4840		5462
		5463	=item C<EV_COMPAT3> backwards compatibility mechanism
		5464
		5465	The backward compatibility mechanism can be controlled by
		5466	C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING>
		5467	section.
		5468
4841	=item C<ev_default_destroy> and C<ev_default_fork> have been removed	5469	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
4842		5470
4843	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:	5471	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
4844		5472
4845	ev_loop_destroy (EV_DEFAULT);	5473	ev_loop_destroy (EV_DEFAULT_UC);
4846	ev_loop_fork (EV_DEFAULT);	5474	ev_loop_fork (EV_DEFAULT);
4847		5475
4848	=item function/symbol renames	5476	=item function/symbol renames
4849		5477
4850	A number of functions and symbols have been renamed:	5478	A number of functions and symbols have been renamed:
…		…
4870	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme	5498	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
4871	as all other watcher types. Note that C<ev_loop_fork> is still called	5499	as all other watcher types. Note that C<ev_loop_fork> is still called
4872	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>	5500	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
4873	typedef.	5501	typedef.
4874		5502
4875	=item C<EV_COMPAT3> backwards compatibility mechanism
4876
4877	The backward compatibility mechanism can be controlled by
4878	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
4879	section.
4880
4881	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>	5503	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
4882		5504
4883	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different	5505	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
4884	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile	5506	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
4885	and work, but the library code will of course be larger.	5507	and work, but the library code will of course be larger.
…		…
4892	=over 4	5514	=over 4
4893		5515
4894	=item active	5516	=item active
4895		5517
4896	A watcher is active as long as it has been started and not yet stopped.	5518	A watcher is active as long as it has been started and not yet stopped.
4897	See L<WATCHER STATES> for details.	5519	See L</WATCHER STATES> for details.
4898		5520
4899	=item application	5521	=item application
4900		5522
4901	In this document, an application is whatever is using libev.	5523	In this document, an application is whatever is using libev.
4902		5524
…		…
4938	watchers and events.	5560	watchers and events.
4939		5561
4940	=item pending	5562	=item pending
4941		5563
4942	A watcher is pending as soon as the corresponding event has been	5564	A watcher is pending as soon as the corresponding event has been
4943	detected. See L<WATCHER STATES> for details.	5565	detected. See L</WATCHER STATES> for details.
4944		5566
4945	=item real time	5567	=item real time
4946		5568
4947	The physical time that is observed. It is apparently strictly monotonic :)	5569	The physical time that is observed. It is apparently strictly monotonic :)
4948		5570
4949	=item wall-clock time	5571	=item wall-clock time
4950		5572
4951	The time and date as shown on clocks. Unlike real time, it can actually	5573	The time and date as shown on clocks. Unlike real time, it can actually
4952	be wrong and jump forwards and backwards, e.g. when the you adjust your	5574	be wrong and jump forwards and backwards, e.g. when you adjust your
4953	clock.	5575	clock.
4954		5576
4955	=item watcher	5577	=item watcher
4956		5578
4957	A data structure that describes interest in certain events. Watchers need	5579	A data structure that describes interest in certain events. Watchers need
…		…
4959		5581
4960	=back	5582	=back
4961		5583
4962	=head1 AUTHOR	5584	=head1 AUTHOR
4963		5585
4964	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5586	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5587	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4965		5588

Diff Legend

–	Removed lines
+	Added lines
<	Changed lines
>	Changed lines