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		1	=encoding utf-8
		2
1	=head1 NAME	3	=head1 NAME
2		4
3	libev - a high performance full-featured event loop written in C	5	libev - a high performance full-featured event loop written in C
4		6
5	=head1 SYNOPSIS	7	=head1 SYNOPSIS
…		…
58	ev_timer_start (loop, &timeout_watcher);	60	ev_timer_start (loop, &timeout_watcher);
59		61
60	// now wait for events to arrive	62	// now wait for events to arrive
61	ev_run (loop, 0);	63	ev_run (loop, 0);
62		64
63	// unloop was called, so exit	65	// break was called, so exit
64	return 0;	66	return 0;
65	}	67	}
66		68
67	=head1 ABOUT THIS DOCUMENT	69	=head1 ABOUT THIS DOCUMENT
68		70
…		…
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
…		…
342	Example: Restrict libev to the select and poll backends, and do not allow	371	Example: Restrict libev to the select and poll backends, and do not allow
343	environment settings to be taken into account:	372	environment settings to be taken into account:
344		373
345	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	374	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
346		375
347	Example: Use whatever libev has to offer, but make sure that kqueue is
348	used if available (warning, breaks stuff, best use only with your own
349	private event loop and only if you know the OS supports your types of
350	fds):
351
352	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
353
354	=item struct ev_loop *ev_loop_new (unsigned int flags)	376	=item struct ev_loop *ev_loop_new (unsigned int flags)
355		377
356	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
357	could not be initialised, returns false.	379	could not be initialised, returns false.
358		380
359	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
360	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
361	default loop in the "main" or "initial" thread.	383	loop in the "main" or "initial" thread.
362		384
363	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
364	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>).
365		387
366	The following flags are supported:	388	The following flags are supported:
…		…
376		398
377	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
378	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
379	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	401	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
380	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
381	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
382	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).
383		407
384	=item C<EVFLAG_FORKCHECK>	408	=item C<EVFLAG_FORKCHECK>
385		409
386	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
387	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.
388		412
389	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,
390	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
391	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
392	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
393	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
394	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).
395		420
396	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
397	forget about forgetting to tell libev about forking) when you use this	422	forget about forgetting to tell libev about forking, although you still
398	flag.	423	have to ignore C<SIGPIPE>) when you use this flag.
399		424
400	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>
401	environment variable.	426	environment variable.
402		427
403	=item C<EVFLAG_NOINOTIFY>	428	=item C<EVFLAG_NOINOTIFY>
404		429
405	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
406	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
407	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
408	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.
409		434
410	=item C<EVFLAG_SIGNALFD>	435	=item C<EVFLAG_SIGNALFD>
411		436
412	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
413	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
414	delivers signals synchronously, which makes it both faster and might make	439	delivers signals synchronously, which makes it both faster and might make
415	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
416	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
417	threads that are not interested in handling them.	442	threads that are not interested in handling them.
418		443
419	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
420	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
421	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.
422		462
423	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	463	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
424		464
425	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
426	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,
…		…
454	=item C<EVBACKEND_EPOLL> (value 4, Linux)	494	=item C<EVBACKEND_EPOLL> (value 4, Linux)
455		495
456	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
457	kernels).	497	kernels).
458		498
459	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
460	but it scales phenomenally better. While poll and select usually scale	500	it scales phenomenally better. While poll and select usually scale like
461	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
462	epoll scales either O(1) or O(active_fds).	502	fd), epoll scales either O(1) or O(active_fds).
463		503
464	The epoll mechanism deserves honorable mention as the most misdesigned	504	The epoll mechanism deserves honorable mention as the most misdesigned
465	of the more advanced event mechanisms: mere annoyances include silently	505	of the more advanced event mechanisms: mere annoyances include silently
466	dropping file descriptors, requiring a system call per change per file	506	dropping file descriptors, requiring a system call per change per file
467	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
468	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
469	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
470	take considerable time (one syscall per file descriptor) and is of course	512	set, which can take considerable time (one syscall per file descriptor)
471	hard to detect.	513	and is of course hard to detect.
472		514
473	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	515	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
474	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
475	I<different> file descriptors (even already closed ones, so one cannot	517	totally I<different> file descriptors (even already closed ones, so
476	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
477	on SMP systems). Libev tries to counter these spurious notifications by	519	(especially on SMP systems). Libev tries to counter these spurious
478	employing an additional generation counter and comparing that against the	520	notifications by employing an additional generation counter and comparing
479	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
480	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
481	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...
482		531
483	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
484	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
485	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
486	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
…		…
523		572
524	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
525	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
526	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
527	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
528	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
529	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
530	cases	579	drops fds silently in similarly hard-to-detect cases.
531		580
532	This backend usually performs well under most conditions.	581	This backend usually performs well under most conditions.
533		582
534	While nominally embeddable in other event loops, this doesn't work	583	While nominally embeddable in other event loops, this doesn't work
535	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
…		…
552	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	601	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
553		602
554	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,
555	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)).
556		605
557	Please note that Solaris event ports can deliver a lot of spurious
558	notifications, so you need to use non-blocking I/O or other means to avoid
559	blocking when no data (or space) is available.
560
561	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
562	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
563	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	608	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
564	might perform better.	609	might perform better.
565		610
566	On the positive side, with the exception of the spurious readiness	611	On the positive side, this backend actually performed fully to
567	notifications, this backend actually performed fully to specification
568	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
569	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.
570		625
571	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
572	C<EVBACKEND_POLL>.	627	C<EVBACKEND_POLL>.
573		628
574	=item C<EVBACKEND_ALL>	629	=item C<EVBACKEND_ALL>
575		630
576	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
577	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
578	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	633	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
579		634
580	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).
581		644
582	=back	645	=back
583		646
584	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,
585	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
…		…
589	Example: Try to create a event loop that uses epoll and nothing else.	652	Example: Try to create a event loop that uses epoll and nothing else.
590		653
591	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	654	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
592	if (!epoller)	655	if (!epoller)
593	fatal ("no epoll found here, maybe it hides under your chair");	656	fatal ("no epoll found here, maybe it hides under your chair");
		657
		658	Example: Use whatever libev has to offer, but make sure that kqueue is
		659	used if available.
		660
		661	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
594		662
595	=item ev_loop_destroy (loop)	663	=item ev_loop_destroy (loop)
596		664
597	Destroys an event loop object (frees all memory and kernel state	665	Destroys an event loop object (frees all memory and kernel state
598	etc.). None of the active event watchers will be stopped in the normal	666	etc.). None of the active event watchers will be stopped in the normal
…		…
609	This function is normally used on loop objects allocated by	677	This function is normally used on loop objects allocated by
610	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
611	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.
612		680
613	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
614	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.
615	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>
616	and C<ev_loop_destroy>.	684	and C<ev_loop_destroy>.
617		685
618	=item ev_loop_fork (loop)	686	=item ev_loop_fork (loop)
619		687
620	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
621	reinitialise the kernel state for backends that have one. Despite the	689	to reinitialise the kernel state for backends that have one. Despite
622	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
623	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
624	child before resuming or calling C<ev_run>.	693	C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>.
625		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
626	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
627	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
628	because some kernel interfaces *cough* I<kqueue> *cough* do funny things	700	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
629	during fork.	701	during fork.
630		702
631	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
…		…
667	prepare and check phases.	739	prepare and check phases.
668		740
669	=item unsigned int ev_depth (loop)	741	=item unsigned int ev_depth (loop)
670		742
671	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
672	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.
673		745
674	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
675	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),
676	in which case it is higher.	748	in which case it is higher.
677		749
678	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread	750	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
679	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
680	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.
681		754
682	=item unsigned int ev_backend (loop)	755	=item unsigned int ev_backend (loop)
683		756
684	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
685	use.	758	use.
…		…
700		773
701	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
702	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
703	the current time is a good idea.	776	the current time is a good idea.
704		777
705	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.
706		779
707	=item ev_suspend (loop)	780	=item ev_suspend (loop)
708		781
709	=item ev_resume (loop)	782	=item ev_resume (loop)
710		783
…		…
728	without a previous call to C<ev_suspend>.	801	without a previous call to C<ev_suspend>.
729		802
730	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
731	event loop time (see C<ev_now_update>).	804	event loop time (see C<ev_now_update>).
732		805
733	=item ev_run (loop, int flags)	806	=item bool ev_run (loop, int flags)
734		807
735	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
736	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
737	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
738	the watcher callbacks, an then repeat the whole process indefinitely: This	811	the watcher callbacks, and then repeat the whole process indefinitely: This
739	is why event loops are called I<loops>.	812	is why event loops are called I<loops>.
740		813
741	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
742	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
743	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").
744		821
745	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
746	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
747	finished (especially in interactive programs), but having a program	824	finished (especially in interactive programs), but having a program
748	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
749	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
750	beauty.	827	beauty.
751		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
752	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
753	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
754	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
755	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
756	events while doing lengthy calculations, to keep the program responsive.	838	events while doing lengthy calculations, to keep the program responsive.
…		…
765	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
766	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
767	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
768	usually a better approach for this kind of thing.	850	usually a better approach for this kind of thing.
769		851
770	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):
771		855
772	- Increment loop depth.	856	- Increment loop depth.
773	- Reset the ev_break status.	857	- Reset the ev_break status.
774	- Before the first iteration, call any pending watchers.	858	- Before the first iteration, call any pending watchers.
775	LOOP:	859	LOOP:
…		…
808	anymore.	892	anymore.
809		893
810	... queue jobs here, make sure they register event watchers as long	894	... queue jobs here, make sure they register event watchers as long
811	... 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..)
812	ev_run (my_loop, 0);	896	ev_run (my_loop, 0);
813	... jobs done or somebody called unloop. yeah!	897	... jobs done or somebody called break. yeah!
814		898
815	=item ev_break (loop, how)	899	=item ev_break (loop, how)
816		900
817	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
818	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
819	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
820	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.
821		905
822	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>.
823		907
824	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.
825		910
826	=item ev_ref (loop)	911	=item ev_ref (loop)
827		912
828	=item ev_unref (loop)	913	=item ev_unref (loop)
829		914
…		…
850	running when nothing else is active.	935	running when nothing else is active.
851		936
852	ev_signal exitsig;	937	ev_signal exitsig;
853	ev_signal_init (&exitsig, sig_cb, SIGINT);	938	ev_signal_init (&exitsig, sig_cb, SIGINT);
854	ev_signal_start (loop, &exitsig);	939	ev_signal_start (loop, &exitsig);
855	evf_unref (loop);	940	ev_unref (loop);
856		941
857	Example: For some weird reason, unregister the above signal handler again.	942	Example: For some weird reason, unregister the above signal handler again.
858		943
859	ev_ref (loop);	944	ev_ref (loop);
860	ev_signal_stop (loop, &exitsig);	945	ev_signal_stop (loop, &exitsig);
…		…
880	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.
881		966
882	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
883	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,
884	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
885	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
886	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
887	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
888	once per this interval, on average.	973	once per this interval, on average (as long as the host time resolution is
		974	good enough).
889		975
890	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
891	to spend more time collecting timeouts, at the expense of increased	977	to spend more time collecting timeouts, at the expense of increased
892	latency/jitter/inexactness (the watcher callback will be called	978	latency/jitter/inexactness (the watcher callback will be called
893	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
…		…
939	invoke the actual watchers inside another context (another thread etc.).	1025	invoke the actual watchers inside another context (another thread etc.).
940		1026
941	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
942	callback.	1028	callback.
943		1029
944	=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 ())
945		1031
946	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
947	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
948	each call to a libev function.	1034	each call to a libev function.
949		1035
950	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
951	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
952	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
953	I<release> and I<acquire> callbacks on the loop.	1039	I<release> and I<acquire> callbacks on the loop.
954		1040
955	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
956	suspended waiting for new events, and C<acquire> is called just	1042	suspended waiting for new events, and C<acquire> is called just
957	afterwards.	1043	afterwards.
…		…
972	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
973	document.	1059	document.
974		1060
975	=item ev_set_userdata (loop, void *data)	1061	=item ev_set_userdata (loop, void *data)
976		1062
977	=item ev_userdata (loop)	1063	=item void *ev_userdata (loop)
978		1064
979	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
980	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
981	C<0.>	1067	C<0>.
982		1068
983	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,
984	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
985	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
986	any other purpose as well.	1072	any other purpose as well.
…		…
1097		1183
1098	=item C<EV_PREPARE>	1184	=item C<EV_PREPARE>
1099		1185
1100	=item C<EV_CHECK>	1186	=item C<EV_CHECK>
1101		1187
1102	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
1103	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)
1104	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
1105	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
1106	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
1107	(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
1108	C<ev_run> from blocking).	1199	blocking).
1109		1200
1110	=item C<EV_EMBED>	1201	=item C<EV_EMBED>
1111		1202
1112	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.
1113		1204
1114	=item C<EV_FORK>	1205	=item C<EV_FORK>
1115		1206
1116	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
1117	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>).
1118		1213
1119	=item C<EV_ASYNC>	1214	=item C<EV_ASYNC>
1120		1215
1121	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>).
1122		1217
…		…
1144	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
1145	thing, so beware.	1240	thing, so beware.
1146		1241
1147	=back	1242	=back
1148		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
1149	=head2 WATCHER STATES	1398	=head2 WATCHER STATES
1150		1399
1151	There are various watcher states mentioned throughout this manual -	1400	There are various watcher states mentioned throughout this manual -
1152	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
1153	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
1154	rules might look complicated, they usually do "the right thing".	1403	rules might look complicated, they usually do "the right thing".
1155		1404
1156	=over 4	1405	=over 4
1157		1406
1158	=item initialiased	1407	=item initialised
1159		1408
1160	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
1161	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
1162	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.
1163		1412
1164	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
1165	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.
1166		1417
1167	=item started/running/active	1418	=item started/running/active
1168		1419
1169	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
1170	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
…		…
1198	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
1199	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
1200	freeing it is often a good idea.	1451	freeing it is often a good idea.
1201		1452
1202	While stopped (and not pending) the watcher is essentially in the	1453	While stopped (and not pending) the watcher is essentially in the
1203	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
1204	you wish.	1455	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1456	it again).
1205		1457
1206	=back	1458	=back
1207
1208	=head2 GENERIC WATCHER FUNCTIONS
1209
1210	=over 4
1211
1212	=item C<ev_init> (ev_TYPE *watcher, callback)
1213
1214	This macro initialises the generic portion of a watcher. The contents
1215	of the watcher object can be arbitrary (so C<malloc> will do). Only
1216	the generic parts of the watcher are initialised, you I<need> to call
1217	the type-specific C<ev_TYPE_set> macro afterwards to initialise the
1218	type-specific parts. For each type there is also a C<ev_TYPE_init> macro
1219	which rolls both calls into one.
1220
1221	You can reinitialise a watcher at any time as long as it has been stopped
1222	(or never started) and there are no pending events outstanding.
1223
1224	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
1225	int revents)>.
1226
1227	Example: Initialise an C<ev_io> watcher in two steps.
1228
1229	ev_io w;
1230	ev_init (&w, my_cb);
1231	ev_io_set (&w, STDIN_FILENO, EV_READ);
1232
1233	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
1234
1235	This macro initialises the type-specific parts of a watcher. You need to
1236	call C<ev_init> at least once before you call this macro, but you can
1237	call C<ev_TYPE_set> any number of times. You must not, however, call this
1238	macro on a watcher that is active (it can be pending, however, which is a
1239	difference to the C<ev_init> macro).
1240
1241	Although some watcher types do not have type-specific arguments
1242	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
1243
1244	See C<ev_init>, above, for an example.
1245
1246	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
1247
1248	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
1249	calls into a single call. This is the most convenient method to initialise
1250	a watcher. The same limitations apply, of course.
1251
1252	Example: Initialise and set an C<ev_io> watcher in one step.
1253
1254	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1255
1256	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1257
1258	Starts (activates) the given watcher. Only active watchers will receive
1259	events. If the watcher is already active nothing will happen.
1260
1261	Example: Start the C<ev_io> watcher that is being abused as example in this
1262	whole section.
1263
1264	ev_io_start (EV_DEFAULT_UC, &w);
1265
1266	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1267
1268	Stops the given watcher if active, and clears the pending status (whether
1269	the watcher was active or not).
1270
1271	It is possible that stopped watchers are pending - for example,
1272	non-repeating timers are being stopped when they become pending - but
1273	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
1274	pending. If you want to free or reuse the memory used by the watcher it is
1275	therefore a good idea to always call its C<ev_TYPE_stop> function.
1276
1277	=item bool ev_is_active (ev_TYPE *watcher)
1278
1279	Returns a true value iff the watcher is active (i.e. it has been started
1280	and not yet been stopped). As long as a watcher is active you must not modify
1281	it.
1282
1283	=item bool ev_is_pending (ev_TYPE *watcher)
1284
1285	Returns a true value iff the watcher is pending, (i.e. it has outstanding
1286	events but its callback has not yet been invoked). As long as a watcher
1287	is pending (but not active) you must not call an init function on it (but
1288	C<ev_TYPE_set> is safe), you must not change its priority, and you must
1289	make sure the watcher is available to libev (e.g. you cannot C<free ()>
1290	it).
1291
1292	=item callback ev_cb (ev_TYPE *watcher)
1293
1294	Returns the callback currently set on the watcher.
1295
1296	=item ev_cb_set (ev_TYPE *watcher, callback)
1297
1298	Change the callback. You can change the callback at virtually any time
1299	(modulo threads).
1300
1301	=item ev_set_priority (ev_TYPE *watcher, int priority)
1302
1303	=item int ev_priority (ev_TYPE *watcher)
1304
1305	Set and query the priority of the watcher. The priority is a small
1306	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1307	(default: C<-2>). Pending watchers with higher priority will be invoked
1308	before watchers with lower priority, but priority will not keep watchers
1309	from being executed (except for C<ev_idle> watchers).
1310
1311	If you need to suppress invocation when higher priority events are pending
1312	you need to look at C<ev_idle> watchers, which provide this functionality.
1313
1314	You I<must not> change the priority of a watcher as long as it is active or
1315	pending.
1316
1317	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1318	fine, as long as you do not mind that the priority value you query might
1319	or might not have been clamped to the valid range.
1320
1321	The default priority used by watchers when no priority has been set is
1322	always C<0>, which is supposed to not be too high and not be too low :).
1323
1324	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1325	priorities.
1326
1327	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1328
1329	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1330	C<loop> nor C<revents> need to be valid as long as the watcher callback
1331	can deal with that fact, as both are simply passed through to the
1332	callback.
1333
1334	=item int ev_clear_pending (loop, ev_TYPE *watcher)
1335
1336	If the watcher is pending, this function clears its pending status and
1337	returns its C<revents> bitset (as if its callback was invoked). If the
1338	watcher isn't pending it does nothing and returns C<0>.
1339
1340	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1341	callback to be invoked, which can be accomplished with this function.
1342
1343	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
1344
1345	Feeds the given event set into the event loop, as if the specified event
1346	had happened for the specified watcher (which must be a pointer to an
1347	initialised but not necessarily started event watcher). Obviously you must
1348	not free the watcher as long as it has pending events.
1349
1350	Stopping the watcher, letting libev invoke it, or calling
1351	C<ev_clear_pending> will clear the pending event, even if the watcher was
1352	not started in the first place.
1353
1354	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1355	functions that do not need a watcher.
1356
1357	=back
1358
1359
1360	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1361
1362	Each watcher has, by default, a member C<void *data> that you can change
1363	and read at any time: libev will completely ignore it. This can be used
1364	to associate arbitrary data with your watcher. If you need more data and
1365	don't want to allocate memory and store a pointer to it in that data
1366	member, you can also "subclass" the watcher type and provide your own
1367	data:
1368
1369	struct my_io
1370	{
1371	ev_io io;
1372	int otherfd;
1373	void *somedata;
1374	struct whatever *mostinteresting;
1375	};
1376
1377	...
1378	struct my_io w;
1379	ev_io_init (&w.io, my_cb, fd, EV_READ);
1380
1381	And since your callback will be called with a pointer to the watcher, you
1382	can cast it back to your own type:
1383
1384	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1385	{
1386	struct my_io *w = (struct my_io *)w_;
1387	...
1388	}
1389
1390	More interesting and less C-conformant ways of casting your callback type
1391	instead have been omitted.
1392
1393	Another common scenario is to use some data structure with multiple
1394	embedded watchers:
1395
1396	struct my_biggy
1397	{
1398	int some_data;
1399	ev_timer t1;
1400	ev_timer t2;
1401	}
1402
1403	In this case getting the pointer to C<my_biggy> is a bit more
1404	complicated: Either you store the address of your C<my_biggy> struct
1405	in the C<data> member of the watcher (for woozies), or you need to use
1406	some pointer arithmetic using C<offsetof> inside your watchers (for real
1407	programmers):
1408
1409	#include <stddef.h>
1410
1411	static void
1412	t1_cb (EV_P_ ev_timer *w, int revents)
1413	{
1414	struct my_biggy big = (struct my_biggy *)
1415	(((char *)w) - offsetof (struct my_biggy, t1));
1416	}
1417
1418	static void
1419	t2_cb (EV_P_ ev_timer *w, int revents)
1420	{
1421	struct my_biggy big = (struct my_biggy *)
1422	(((char *)w) - offsetof (struct my_biggy, t2));
1423	}
1424		1459
1425	=head2 WATCHER PRIORITY MODELS	1460	=head2 WATCHER PRIORITY MODELS
1426		1461
1427	Many event loops support I<watcher priorities>, which are usually small	1462	Many event loops support I<watcher priorities>, which are usually small
1428	integers that influence the ordering of event callback invocation	1463	integers that influence the ordering of event callback invocation
…		…
1555	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
1556	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
1557	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
1558	required if you know what you are doing).	1593	required if you know what you are doing).
1559		1594
1560	If you cannot use non-blocking mode, then force the use of a
1561	known-to-be-good backend (at the time of this writing, this includes only
1562	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1563	descriptors for which non-blocking operation makes no sense (such as
1564	files) - libev doesn't guarantee any specific behaviour in that case.
1565
1566	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
1567	receive "spurious" readiness notifications, that is your callback might	1596	receive "spurious" readiness notifications, that is, your callback might
1568	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
1569	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
1570	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
1571	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
1572	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1573	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1601	preferable to a program hanging until some data arrives.
1574		1602
1575	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
1576	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
1577	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
1578	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
1579	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
1580	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
1581	indefinitely.	1609	indefinitely.
1582		1610
1583	But really, best use non-blocking mode.	1611	But really, best use non-blocking mode.
1584		1612
…		…
1612		1640
1613	There is no workaround possible except not registering events	1641	There is no workaround possible except not registering events
1614	for potentially C<dup ()>'ed file descriptors, or to resort to	1642	for potentially C<dup ()>'ed file descriptors, or to resort to
1615	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1643	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1616		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
1617	=head3 The special problem of fork	1678	=head3 The special problem of fork
1618		1679
1619	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
1620	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
1621	it in the child.	1682	it in the child if you want to continue to use it in the child.
1622		1683
1623	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
1624	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
1625	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1686	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1626	C<EVBACKEND_POLL>.
1627		1687
1628	=head3 The special problem of SIGPIPE	1688	=head3 The special problem of SIGPIPE
1629		1689
1630	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>:
1631	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
…		…
1729	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1789	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1730	monotonic clock option helps a lot here).	1790	monotonic clock option helps a lot here).
1731		1791
1732	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
1733	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
1734	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
1735	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
1736	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
1737	no longer true when a callback calls C<ev_run> recursively).	1798	longer true when a callback calls C<ev_run> recursively).
1738		1799
1739	=head3 Be smart about timeouts	1800	=head3 Be smart about timeouts
1740		1801
1741	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
1742	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,
…		…
1817		1878
1818	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,
1819	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
1820	within the callback:	1881	within the callback:
1821		1882
		1883	ev_tstamp timeout = 60.;
1822	ev_tstamp last_activity; // time of last activity	1884	ev_tstamp last_activity; // time of last activity
		1885	ev_timer timer;
1823		1886
1824	static void	1887	static void
1825	callback (EV_P_ ev_timer *w, int revents)	1888	callback (EV_P_ ev_timer *w, int revents)
1826	{	1889	{
1827	ev_tstamp now = ev_now (EV_A);	1890	// calculate when the timeout would happen
1828	ev_tstamp timeout = last_activity + 60.;	1891	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1829		1892
1830	// if last_activity + 60. is older than now, we did time out	1893	// if negative, it means we the timeout already occurred
1831	if (timeout < now)	1894	if (after < 0.)
1832	{	1895	{
1833	// timeout occurred, take action	1896	// timeout occurred, take action
1834	}	1897	}
1835	else	1898	else
1836	{	1899	{
1837	// callback was invoked, but there was some activity, re-arm	1900	// callback was invoked, but there was some recent
1838	// the watcher to fire in last_activity + 60, which is	1901	// activity. simply restart the timer to time out
1839	// guaranteed to be in the future, so "again" is positive:	1902	// after "after" seconds, which is the earliest time
1840	w->repeat = timeout - now;	1903	// the timeout can occur.
		1904	ev_timer_set (w, after, 0.);
1841	ev_timer_again (EV_A_ w);	1905	ev_timer_start (EV_A_ w);
1842	}	1906	}
1843	}	1907	}
1844		1908
1845	To summarise the callback: first calculate the real timeout (defined	1909	To summarise the callback: first calculate in how many seconds the
1846	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,
1847	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
1848	the callback was invoked too early (C<timeout> is in the future), so	1912	(EV_A)> from that).
1849	re-schedule the timer to fire at that future time, to see if maybe we have
1850	a timeout then.
1851		1913
1852	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
1853	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.
1854		1923
1855	This scheme causes more callback invocations (about one every 60 seconds	1924	This scheme causes more callback invocations (about one every 60 seconds
1856	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
1857	libev to change the timeout.	1926	libev to change the timeout.
1858		1927
1859	To start the timer, simply initialise the watcher and set C<last_activity>	1928	To start the machinery, simply initialise the watcher and set
1860	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
1861	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:
1862		1932
		1933	last_activity = ev_now (EV_A);
1863	ev_init (timer, callback);	1934	ev_init (&timer, callback);
1864	last_activity = ev_now (loop);	1935	callback (EV_A_ &timer, 0);
1865	callback (loop, timer, EV_TIMER);
1866		1936
1867	And when there is some activity, simply store the current time in	1937	When there is some activity, simply store the current time in
1868	C<last_activity>, no libev calls at all:	1938	C<last_activity>, no libev calls at all:
1869		1939
		1940	if (activity detected)
1870	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);
1871		1950
1872	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
1873	time-out is unlikely to be triggered, much more efficient.	1952	time-out is unlikely to be triggered, much more efficient.
1874
1875	Changing the timeout is trivial as well (if it isn't hard-coded in the
1876	callback :) - just change the timeout and invoke the callback, which will
1877	fix things for you.
1878		1953
1879	=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.
1880		1955
1881	If there is not one request, but many thousands (millions...), all	1956	If there is not one request, but many thousands (millions...), all
1882	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
…		…
1909	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
1910	rather complicated, but extremely efficient, something that really pays	1985	rather complicated, but extremely efficient, something that really pays
1911	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
1912	overkill :)	1987	overkill :)
1913		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
1914	=head3 The special problem of time updates	2026	=head3 The special problem of time updates
1915		2027
1916	Establishing the current time is a costly operation (it usually takes at	2028	Establishing the current time is a costly operation (it usually takes
1917	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
1918	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
1919	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
1920	lots of events in one iteration.	2032	lots of events in one iteration.
1921		2033
1922	The relative timeouts are calculated relative to the C<ev_now ()>	2034	The relative timeouts are calculated relative to the C<ev_now ()>
1923	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
1924	of the event triggering whatever timeout you are modifying/starting. If	2036	of the event triggering whatever timeout you are modifying/starting. If
1925	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
1926	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:
1927		2040
1928	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2041	ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.);
1929		2042
1930	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
1931	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
1932	()>.	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.
1933		2080
1934	=head3 The special problems of suspended animation	2081	=head3 The special problems of suspended animation
1935		2082
1936	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
1937	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?
…		…
1967		2114
1968	=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)
1969		2116
1970	=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)
1971		2118
1972	Configure the timer to trigger after C<after> seconds. If C<repeat>	2119	Configure the timer to trigger after C<after> seconds (fractional and
1973	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
1974	reached. If it is positive, then the timer will automatically be	2121	automatically be stopped once the timeout is reached. If it is positive,
1975	configured to trigger again C<repeat> seconds later, again, and again,	2122	then the timer will automatically be configured to trigger again C<repeat>
1976	until stopped manually.	2123	seconds later, again, and again, until stopped manually.
1977		2124
1978	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
1979	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
1980	trigger at exactly 10 second intervals. If, however, your program cannot	2127	trigger at exactly 10 second intervals. If, however, your program cannot
1981	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
1982	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.
1983		2130
1984	=item ev_timer_again (loop, ev_timer *)	2131	=item ev_timer_again (loop, ev_timer *)
1985		2132
1986	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
1987	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>.
1988		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
1989	If the timer is pending, its pending status is cleared.	2142	=item If the timer is pending, the pending status is always cleared.
1990		2143
1991	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).
1992		2146
1993	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
1994	C<repeat> value), or reset the running timer to the C<repeat> value.	2148	and start the timer, if necessary.
1995		2149
		2150	=back
		2151
1996	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
1997	usage example.	2153	usage example.
1998		2154
1999	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)	2155	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
2000		2156
2001	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,
…		…
2054	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
2055	(and unfortunately a bit complex).	2211	(and unfortunately a bit complex).
2056		2212
2057	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
2058	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
2059	(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
2060	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
2061	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
2062	wrist-watch).	2218	wrist-watch).
2063		2219
2064	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
…		…
2121		2277
2122	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
2123	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
2124	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.
2125		2281
2126	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
2127	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
2128	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.
2129		2288
2130	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
2131	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
2132	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
2133	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).
…		…
2241		2400
2242	ev_periodic hourly_tick;	2401	ev_periodic hourly_tick;
2243	ev_periodic_init (&hourly_tick, clock_cb,	2402	ev_periodic_init (&hourly_tick, clock_cb,
2244	fmod (ev_now (loop), 3600.), 3600., 0);	2403	fmod (ev_now (loop), 3600.), 3600., 0);
2245	ev_periodic_start (loop, &hourly_tick);	2404	ev_periodic_start (loop, &hourly_tick);
2246		2405
2247		2406
2248	=head2 C<ev_signal> - signal me when a signal gets signalled!	2407	=head2 C<ev_signal> - signal me when a signal gets signalled!
2249		2408
2250	Signal watchers will trigger an event when the process receives a specific	2409	Signal watchers will trigger an event when the process receives a specific
2251	signal one or more times. Even though signals are very asynchronous, libev	2410	signal one or more times. Even though signals are very asynchronous, libev
2252	will try it's best to deliver signals synchronously, i.e. as part of the	2411	will try its best to deliver signals synchronously, i.e. as part of the
2253	normal event processing, like any other event.	2412	normal event processing, like any other event.
2254		2413
2255	If you want signals to be delivered truly asynchronously, just use	2414	If you want signals to be delivered truly asynchronously, just use
2256	C<sigaction> as you would do without libev and forget about sharing	2415	C<sigaction> as you would do without libev and forget about sharing
2257	the signal. You can even use C<ev_async> from a signal handler to	2416	the signal. You can even use C<ev_async> from a signal handler to
…		…
2261	only within the same loop, i.e. you can watch for C<SIGINT> in your	2420	only within the same loop, i.e. you can watch for C<SIGINT> in your
2262	default loop and for C<SIGIO> in another loop, but you cannot watch for	2421	default loop and for C<SIGIO> in another loop, but you cannot watch for
2263	C<SIGINT> in both the default loop and another loop at the same time. At	2422	C<SIGINT> in both the default loop and another loop at the same time. At
2264	the moment, C<SIGCHLD> is permanently tied to the default loop.	2423	the moment, C<SIGCHLD> is permanently tied to the default loop.
2265		2424
2266	When the first watcher gets started will libev actually register something	2425	Only after the first watcher for a signal is started will libev actually
2267	with the kernel (thus it coexists with your own signal handlers as long as	2426	register something with the kernel. It thus coexists with your own signal
2268	you don't register any with libev for the same signal).	2427	handlers as long as you don't register any with libev for the same signal.
2269		2428
2270	If possible and supported, libev will install its handlers with	2429	If possible and supported, libev will install its handlers with
2271	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should	2430	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
2272	not be unduly interrupted. If you have a problem with system calls getting	2431	not be unduly interrupted. If you have a problem with system calls getting
2273	interrupted by signals you can block all signals in an C<ev_check> watcher	2432	interrupted by signals you can block all signals in an C<ev_check> watcher
…		…
2276	=head3 The special problem of inheritance over fork/execve/pthread_create	2435	=head3 The special problem of inheritance over fork/execve/pthread_create
2277		2436
2278	Both the signal mask (C<sigprocmask>) and the signal disposition	2437	Both the signal mask (C<sigprocmask>) and the signal disposition
2279	(C<sigaction>) are unspecified after starting a signal watcher (and after	2438	(C<sigaction>) are unspecified after starting a signal watcher (and after
2280	stopping it again), that is, libev might or might not block the signal,	2439	stopping it again), that is, libev might or might not block the signal,
2281	and might or might not set or restore the installed signal handler.	2440	and might or might not set or restore the installed signal handler (but
		2441	see C<EVFLAG_NOSIGMASK>).
2282		2442
2283	While this does not matter for the signal disposition (libev never	2443	While this does not matter for the signal disposition (libev never
2284	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on	2444	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
2285	C<execve>), this matters for the signal mask: many programs do not expect	2445	C<execve>), this matters for the signal mask: many programs do not expect
2286	certain signals to be blocked.	2446	certain signals to be blocked.
…		…
2299	I<has> to modify the signal mask, at least temporarily.	2459	I<has> to modify the signal mask, at least temporarily.
2300		2460
2301	So I can't stress this enough: I<If you do not reset your signal mask when	2461	So I can't stress this enough: I<If you do not reset your signal mask when
2302	you expect it to be empty, you have a race condition in your code>. This	2462	you expect it to be empty, you have a race condition in your code>. This
2303	is not a libev-specific thing, this is true for most event libraries.	2463	is not a libev-specific thing, this is true for most event libraries.
		2464
		2465	=head3 The special problem of threads signal handling
		2466
		2467	POSIX threads has problematic signal handling semantics, specifically,
		2468	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2469	threads in a process block signals, which is hard to achieve.
		2470
		2471	When you want to use sigwait (or mix libev signal handling with your own
		2472	for the same signals), you can tackle this problem by globally blocking
		2473	all signals before creating any threads (or creating them with a fully set
		2474	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2475	loops. Then designate one thread as "signal receiver thread" which handles
		2476	these signals. You can pass on any signals that libev might be interested
		2477	in by calling C<ev_feed_signal>.
2304		2478
2305	=head3 Watcher-Specific Functions and Data Members	2479	=head3 Watcher-Specific Functions and Data Members
2306		2480
2307	=over 4	2481	=over 4
2308		2482
…		…
2443		2617
2444	=head2 C<ev_stat> - did the file attributes just change?	2618	=head2 C<ev_stat> - did the file attributes just change?
2445		2619
2446	This watches a file system path for attribute changes. That is, it calls	2620	This watches a file system path for attribute changes. That is, it calls
2447	C<stat> on that path in regular intervals (or when the OS says it changed)	2621	C<stat> on that path in regular intervals (or when the OS says it changed)
2448	and sees if it changed compared to the last time, invoking the callback if	2622	and sees if it changed compared to the last time, invoking the callback
2449	it did.	2623	if it did. Starting the watcher C<stat>'s the file, so only changes that
		2624	happen after the watcher has been started will be reported.
2450		2625
2451	The path does not need to exist: changing from "path exists" to "path does	2626	The path does not need to exist: changing from "path exists" to "path does
2452	not exist" is a status change like any other. The condition "path does not	2627	not exist" is a status change like any other. The condition "path does not
2453	exist" (or more correctly "path cannot be stat'ed") is signified by the	2628	exist" (or more correctly "path cannot be stat'ed") is signified by the
2454	C<st_nlink> field being zero (which is otherwise always forced to be at	2629	C<st_nlink> field being zero (which is otherwise always forced to be at
…		…
2684	Apart from keeping your process non-blocking (which is a useful	2859	Apart from keeping your process non-blocking (which is a useful
2685	effect on its own sometimes), idle watchers are a good place to do	2860	effect on its own sometimes), idle watchers are a good place to do
2686	"pseudo-background processing", or delay processing stuff to after the	2861	"pseudo-background processing", or delay processing stuff to after the
2687	event loop has handled all outstanding events.	2862	event loop has handled all outstanding events.
2688		2863
		2864	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2865
		2866	As long as there is at least one active idle watcher, libev will never
		2867	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2868	For this to work, the idle watcher doesn't need to be invoked at all - the
		2869	lowest priority will do.
		2870
		2871	This mode of operation can be useful together with an C<ev_check> watcher,
		2872	to do something on each event loop iteration - for example to balance load
		2873	between different connections.
		2874
		2875	See L</Abusing an ev_check watcher for its side-effect> for a longer
		2876	example.
		2877
2689	=head3 Watcher-Specific Functions and Data Members	2878	=head3 Watcher-Specific Functions and Data Members
2690		2879
2691	=over 4	2880	=over 4
2692		2881
2693	=item ev_idle_init (ev_idle *, callback)	2882	=item ev_idle_init (ev_idle *, callback)
…		…
2704	callback, free it. Also, use no error checking, as usual.	2893	callback, free it. Also, use no error checking, as usual.
2705		2894
2706	static void	2895	static void
2707	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	2896	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2708	{	2897	{
		2898	// stop the watcher
		2899	ev_idle_stop (loop, w);
		2900
		2901	// now we can free it
2709	free (w);	2902	free (w);
		2903
2710	// now do something you wanted to do when the program has	2904	// now do something you wanted to do when the program has
2711	// no longer anything immediate to do.	2905	// no longer anything immediate to do.
2712	}	2906	}
2713		2907
2714	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2908	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
…		…
2716	ev_idle_start (loop, idle_watcher);	2910	ev_idle_start (loop, idle_watcher);
2717		2911
2718		2912
2719	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2913	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2720		2914
2721	Prepare and check watchers are usually (but not always) used in pairs:	2915	Prepare and check watchers are often (but not always) used in pairs:
2722	prepare watchers get invoked before the process blocks and check watchers	2916	prepare watchers get invoked before the process blocks and check watchers
2723	afterwards.	2917	afterwards.
2724		2918
2725	You I<must not> call C<ev_run> or similar functions that enter	2919	You I<must not> call C<ev_run> (or similar functions that enter the
2726	the current event loop from either C<ev_prepare> or C<ev_check>	2920	current event loop) or C<ev_loop_fork> from either C<ev_prepare> or
2727	watchers. Other loops than the current one are fine, however. The	2921	C<ev_check> watchers. Other loops than the current one are fine,
2728	rationale behind this is that you do not need to check for recursion in	2922	however. The rationale behind this is that you do not need to check
2729	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2923	for recursion in those watchers, i.e. the sequence will always be
2730	C<ev_check> so if you have one watcher of each kind they will always be	2924	C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each
2731	called in pairs bracketing the blocking call.	2925	kind they will always be called in pairs bracketing the blocking call.
2732		2926
2733	Their main purpose is to integrate other event mechanisms into libev and	2927	Their main purpose is to integrate other event mechanisms into libev and
2734	their use is somewhat advanced. They could be used, for example, to track	2928	their use is somewhat advanced. They could be used, for example, to track
2735	variable changes, implement your own watchers, integrate net-snmp or a	2929	variable changes, implement your own watchers, integrate net-snmp or a
2736	coroutine library and lots more. They are also occasionally useful if	2930	coroutine library and lots more. They are also occasionally useful if
…		…
2754	with priority higher than or equal to the event loop and one coroutine	2948	with priority higher than or equal to the event loop and one coroutine
2755	of lower priority, but only once, using idle watchers to keep the event	2949	of lower priority, but only once, using idle watchers to keep the event
2756	loop from blocking if lower-priority coroutines are active, thus mapping	2950	loop from blocking if lower-priority coroutines are active, thus mapping
2757	low-priority coroutines to idle/background tasks).	2951	low-priority coroutines to idle/background tasks).
2758		2952
2759	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2953	When used for this purpose, it is recommended to give C<ev_check> watchers
2760	priority, to ensure that they are being run before any other watchers	2954	highest (C<EV_MAXPRI>) priority, to ensure that they are being run before
2761	after the poll (this doesn't matter for C<ev_prepare> watchers).	2955	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		2956	watchers).
2762		2957
2763	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	2958	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
2764	activate ("feed") events into libev. While libev fully supports this, they	2959	activate ("feed") events into libev. While libev fully supports this, they
2765	might get executed before other C<ev_check> watchers did their job. As	2960	might get executed before other C<ev_check> watchers did their job. As
2766	C<ev_check> watchers are often used to embed other (non-libev) event	2961	C<ev_check> watchers are often used to embed other (non-libev) event
2767	loops those other event loops might be in an unusable state until their	2962	loops those other event loops might be in an unusable state until their
2768	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	2963	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2769	others).	2964	others).
		2965
		2966	=head3 Abusing an C<ev_check> watcher for its side-effect
		2967
		2968	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		2969	useful because they are called once per event loop iteration. For
		2970	example, if you want to handle a large number of connections fairly, you
		2971	normally only do a bit of work for each active connection, and if there
		2972	is more work to do, you wait for the next event loop iteration, so other
		2973	connections have a chance of making progress.
		2974
		2975	Using an C<ev_check> watcher is almost enough: it will be called on the
		2976	next event loop iteration. However, that isn't as soon as possible -
		2977	without external events, your C<ev_check> watcher will not be invoked.
		2978
		2979	This is where C<ev_idle> watchers come in handy - all you need is a
		2980	single global idle watcher that is active as long as you have one active
		2981	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		2982	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		2983	invoked. Neither watcher alone can do that.
2770		2984
2771	=head3 Watcher-Specific Functions and Data Members	2985	=head3 Watcher-Specific Functions and Data Members
2772		2986
2773	=over 4	2987	=over 4
2774		2988
…		…
2975		3189
2976	=over 4	3190	=over 4
2977		3191
2978	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	3192	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
2979		3193
2980	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	3194	=item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)
2981		3195
2982	Configures the watcher to embed the given loop, which must be	3196	Configures the watcher to embed the given loop, which must be
2983	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	3197	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2984	invoked automatically, otherwise it is the responsibility of the callback	3198	invoked automatically, otherwise it is the responsibility of the callback
2985	to invoke it (it will continue to be called until the sweep has been done,	3199	to invoke it (it will continue to be called until the sweep has been done,
…		…
3006	used).	3220	used).
3007		3221
3008	struct ev_loop *loop_hi = ev_default_init (0);	3222	struct ev_loop *loop_hi = ev_default_init (0);
3009	struct ev_loop *loop_lo = 0;	3223	struct ev_loop *loop_lo = 0;
3010	ev_embed embed;	3224	ev_embed embed;
3011		3225
3012	// see if there is a chance of getting one that works	3226	// see if there is a chance of getting one that works
3013	// (remember that a flags value of 0 means autodetection)	3227	// (remember that a flags value of 0 means autodetection)
3014	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3228	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
3015	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3229	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
3016	: 0;	3230	: 0;
…		…
3030	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3244	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
3031		3245
3032	struct ev_loop *loop = ev_default_init (0);	3246	struct ev_loop *loop = ev_default_init (0);
3033	struct ev_loop *loop_socket = 0;	3247	struct ev_loop *loop_socket = 0;
3034	ev_embed embed;	3248	ev_embed embed;
3035		3249
3036	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3250	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
3037	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3251	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
3038	{	3252	{
3039	ev_embed_init (&embed, 0, loop_socket);	3253	ev_embed_init (&embed, 0, loop_socket);
3040	ev_embed_start (loop, &embed);	3254	ev_embed_start (loop, &embed);
…		…
3048		3262
3049	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3263	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
3050		3264
3051	Fork watchers are called when a C<fork ()> was detected (usually because	3265	Fork watchers are called when a C<fork ()> was detected (usually because
3052	whoever is a good citizen cared to tell libev about it by calling	3266	whoever is a good citizen cared to tell libev about it by calling
3053	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the	3267	C<ev_loop_fork>). The invocation is done before the event loop blocks next
3054	event loop blocks next and before C<ev_check> watchers are being called,	3268	and before C<ev_check> watchers are being called, and only in the child
3055	and only in the child after the fork. If whoever good citizen calling	3269	after the fork. If whoever good citizen calling C<ev_default_fork> cheats
3056	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3270	and calls it in the wrong process, the fork handlers will be invoked, too,
3057	handlers will be invoked, too, of course.	3271	of course.
3058		3272
3059	=head3 The special problem of life after fork - how is it possible?	3273	=head3 The special problem of life after fork - how is it possible?
3060		3274
3061	Most uses of C<fork()> consist of forking, then some simple calls to set	3275	Most uses of C<fork ()> consist of forking, then some simple calls to set
3062	up/change the process environment, followed by a call to C<exec()>. This	3276	up/change the process environment, followed by a call to C<exec()>. This
3063	sequence should be handled by libev without any problems.	3277	sequence should be handled by libev without any problems.
3064		3278
3065	This changes when the application actually wants to do event handling	3279	This changes when the application actually wants to do event handling
3066	in the child, or both parent in child, in effect "continuing" after the	3280	in the child, or both parent in child, in effect "continuing" after the
…		…
3092		3306
3093	=head3 Watcher-Specific Functions and Data Members	3307	=head3 Watcher-Specific Functions and Data Members
3094		3308
3095	=over 4	3309	=over 4
3096		3310
3097	=item ev_fork_init (ev_signal *, callback)	3311	=item ev_fork_init (ev_fork *, callback)
3098		3312
3099	Initialises and configures the fork watcher - it has no parameters of any	3313	Initialises and configures the fork watcher - it has no parameters of any
3100	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3314	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
3101	believe me.	3315	really.
3102		3316
3103	=back	3317	=back
3104		3318
3105		3319
		3320	=head2 C<ev_cleanup> - even the best things end
		3321
		3322	Cleanup watchers are called just before the event loop is being destroyed
		3323	by a call to C<ev_loop_destroy>.
		3324
		3325	While there is no guarantee that the event loop gets destroyed, cleanup
		3326	watchers provide a convenient method to install cleanup hooks for your
		3327	program, worker threads and so on - you just to make sure to destroy the
		3328	loop when you want them to be invoked.
		3329
		3330	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3331	all other watchers, they do not keep a reference to the event loop (which
		3332	makes a lot of sense if you think about it). Like all other watchers, you
		3333	can call libev functions in the callback, except C<ev_cleanup_start>.
		3334
		3335	=head3 Watcher-Specific Functions and Data Members
		3336
		3337	=over 4
		3338
		3339	=item ev_cleanup_init (ev_cleanup *, callback)
		3340
		3341	Initialises and configures the cleanup watcher - it has no parameters of
		3342	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3343	pointless, I assure you.
		3344
		3345	=back
		3346
		3347	Example: Register an atexit handler to destroy the default loop, so any
		3348	cleanup functions are called.
		3349
		3350	static void
		3351	program_exits (void)
		3352	{
		3353	ev_loop_destroy (EV_DEFAULT_UC);
		3354	}
		3355
		3356	...
		3357	atexit (program_exits);
		3358
		3359
3106	=head2 C<ev_async> - how to wake up an event loop	3360	=head2 C<ev_async> - how to wake up an event loop
3107		3361
3108	In general, you cannot use an C<ev_run> from multiple threads or other	3362	In general, you cannot use an C<ev_loop> from multiple threads or other
3109	asynchronous sources such as signal handlers (as opposed to multiple event	3363	asynchronous sources such as signal handlers (as opposed to multiple event
3110	loops - those are of course safe to use in different threads).	3364	loops - those are of course safe to use in different threads).
3111		3365
3112	Sometimes, however, you need to wake up an event loop you do not control,	3366	Sometimes, however, you need to wake up an event loop you do not control,
3113	for example because it belongs to another thread. This is what C<ev_async>	3367	for example because it belongs to another thread. This is what C<ev_async>
…		…
3115	it by calling C<ev_async_send>, which is thread- and signal safe.	3369	it by calling C<ev_async_send>, which is thread- and signal safe.
3116		3370
3117	This functionality is very similar to C<ev_signal> watchers, as signals,	3371	This functionality is very similar to C<ev_signal> watchers, as signals,
3118	too, are asynchronous in nature, and signals, too, will be compressed	3372	too, are asynchronous in nature, and signals, too, will be compressed
3119	(i.e. the number of callback invocations may be less than the number of	3373	(i.e. the number of callback invocations may be less than the number of
3120	C<ev_async_sent> calls).	3374	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
3121		3375	of "global async watchers" by using a watcher on an otherwise unused
3122	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3376	signal, and C<ev_feed_signal> to signal this watcher from another thread,
3123	just the default loop.	3377	even without knowing which loop owns the signal.
3124		3378
3125	=head3 Queueing	3379	=head3 Queueing
3126		3380
3127	C<ev_async> does not support queueing of data in any way. The reason	3381	C<ev_async> does not support queueing of data in any way. The reason
3128	is that the author does not know of a simple (or any) algorithm for a	3382	is that the author does not know of a simple (or any) algorithm for a
…		…
3220	trust me.	3474	trust me.
3221		3475
3222	=item ev_async_send (loop, ev_async *)	3476	=item ev_async_send (loop, ev_async *)
3223		3477
3224	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3478	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3225	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3479	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3480	returns.
		3481
3226	C<ev_feed_event>, this call is safe to do from other threads, signal or	3482	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3227	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3483	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3228	section below on what exactly this means).	3484	embedding section below on what exactly this means).
3229		3485
3230	Note that, as with other watchers in libev, multiple events might get	3486	Note that, as with other watchers in libev, multiple events might get
3231	compressed into a single callback invocation (another way to look at this	3487	compressed into a single callback invocation (another way to look at
3232	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3488	this is that C<ev_async> watchers are level-triggered: they are set on
3233	reset when the event loop detects that).	3489	C<ev_async_send>, reset when the event loop detects that).
3234		3490
3235	This call incurs the overhead of a system call only once per event loop	3491	This call incurs the overhead of at most one extra system call per event
3236	iteration, so while the overhead might be noticeable, it doesn't apply to	3492	loop iteration, if the event loop is blocked, and no syscall at all if
3237	repeated calls to C<ev_async_send> for the same event loop.	3493	the event loop (or your program) is processing events. That means that
		3494	repeated calls are basically free (there is no need to avoid calls for
		3495	performance reasons) and that the overhead becomes smaller (typically
		3496	zero) under load.
3238		3497
3239	=item bool = ev_async_pending (ev_async *)	3498	=item bool = ev_async_pending (ev_async *)
3240		3499
3241	Returns a non-zero value when C<ev_async_send> has been called on the	3500	Returns a non-zero value when C<ev_async_send> has been called on the
3242	watcher but the event has not yet been processed (or even noted) by the	3501	watcher but the event has not yet been processed (or even noted) by the
…		…
3259		3518
3260	There are some other functions of possible interest. Described. Here. Now.	3519	There are some other functions of possible interest. Described. Here. Now.
3261		3520
3262	=over 4	3521	=over 4
3263		3522
3264	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3523	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg)
3265		3524
3266	This function combines a simple timer and an I/O watcher, calls your	3525	This function combines a simple timer and an I/O watcher, calls your
3267	callback on whichever event happens first and automatically stops both	3526	callback on whichever event happens first and automatically stops both
3268	watchers. This is useful if you want to wait for a single event on an fd	3527	watchers. This is useful if you want to wait for a single event on an fd
3269	or timeout without having to allocate/configure/start/stop/free one or	3528	or timeout without having to allocate/configure/start/stop/free one or
…		…
3297	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3556	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3298		3557
3299	=item ev_feed_fd_event (loop, int fd, int revents)	3558	=item ev_feed_fd_event (loop, int fd, int revents)
3300		3559
3301	Feed an event on the given fd, as if a file descriptor backend detected	3560	Feed an event on the given fd, as if a file descriptor backend detected
3302	the given events it.	3561	the given events.
3303		3562
3304	=item ev_feed_signal_event (loop, int signum)	3563	=item ev_feed_signal_event (loop, int signum)
3305		3564
3306	Feed an event as if the given signal occurred (C<loop> must be the default	3565	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3307	loop!).	3566	which is async-safe.
3308		3567
3309	=back	3568	=back
		3569
		3570
		3571	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3572
		3573	This section explains some common idioms that are not immediately
		3574	obvious. Note that examples are sprinkled over the whole manual, and this
		3575	section only contains stuff that wouldn't fit anywhere else.
		3576
		3577	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3578
		3579	Each watcher has, by default, a C<void *data> member that you can read
		3580	or modify at any time: libev will completely ignore it. This can be used
		3581	to associate arbitrary data with your watcher. If you need more data and
		3582	don't want to allocate memory separately and store a pointer to it in that
		3583	data member, you can also "subclass" the watcher type and provide your own
		3584	data:
		3585
		3586	struct my_io
		3587	{
		3588	ev_io io;
		3589	int otherfd;
		3590	void *somedata;
		3591	struct whatever *mostinteresting;
		3592	};
		3593
		3594	...
		3595	struct my_io w;
		3596	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3597
		3598	And since your callback will be called with a pointer to the watcher, you
		3599	can cast it back to your own type:
		3600
		3601	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3602	{
		3603	struct my_io *w = (struct my_io *)w_;
		3604	...
		3605	}
		3606
		3607	More interesting and less C-conformant ways of casting your callback
		3608	function type instead have been omitted.
		3609
		3610	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3611
		3612	Another common scenario is to use some data structure with multiple
		3613	embedded watchers, in effect creating your own watcher that combines
		3614	multiple libev event sources into one "super-watcher":
		3615
		3616	struct my_biggy
		3617	{
		3618	int some_data;
		3619	ev_timer t1;
		3620	ev_timer t2;
		3621	}
		3622
		3623	In this case getting the pointer to C<my_biggy> is a bit more
		3624	complicated: Either you store the address of your C<my_biggy> struct in
		3625	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3626	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3627	real programmers):
		3628
		3629	#include <stddef.h>
		3630
		3631	static void
		3632	t1_cb (EV_P_ ev_timer *w, int revents)
		3633	{
		3634	struct my_biggy big = (struct my_biggy *)
		3635	(((char *)w) - offsetof (struct my_biggy, t1));
		3636	}
		3637
		3638	static void
		3639	t2_cb (EV_P_ ev_timer *w, int revents)
		3640	{
		3641	struct my_biggy big = (struct my_biggy *)
		3642	(((char *)w) - offsetof (struct my_biggy, t2));
		3643	}
		3644
		3645	=head2 AVOIDING FINISHING BEFORE RETURNING
		3646
		3647	Often you have structures like this in event-based programs:
		3648
		3649	callback ()
		3650	{
		3651	free (request);
		3652	}
		3653
		3654	request = start_new_request (..., callback);
		3655
		3656	The intent is to start some "lengthy" operation. The C<request> could be
		3657	used to cancel the operation, or do other things with it.
		3658
		3659	It's not uncommon to have code paths in C<start_new_request> that
		3660	immediately invoke the callback, for example, to report errors. Or you add
		3661	some caching layer that finds that it can skip the lengthy aspects of the
		3662	operation and simply invoke the callback with the result.
		3663
		3664	The problem here is that this will happen I<before> C<start_new_request>
		3665	has returned, so C<request> is not set.
		3666
		3667	Even if you pass the request by some safer means to the callback, you
		3668	might want to do something to the request after starting it, such as
		3669	canceling it, which probably isn't working so well when the callback has
		3670	already been invoked.
		3671
		3672	A common way around all these issues is to make sure that
		3673	C<start_new_request> I<always> returns before the callback is invoked. If
		3674	C<start_new_request> immediately knows the result, it can artificially
		3675	delay invoking the callback by using a C<prepare> or C<idle> watcher for
		3676	example, or more sneakily, by reusing an existing (stopped) watcher and
		3677	pushing it into the pending queue:
		3678
		3679	ev_set_cb (watcher, callback);
		3680	ev_feed_event (EV_A_ watcher, 0);
		3681
		3682	This way, C<start_new_request> can safely return before the callback is
		3683	invoked, while not delaying callback invocation too much.
		3684
		3685	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3686
		3687	Often (especially in GUI toolkits) there are places where you have
		3688	I<modal> interaction, which is most easily implemented by recursively
		3689	invoking C<ev_run>.
		3690
		3691	This brings the problem of exiting - a callback might want to finish the
		3692	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3693	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3694	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3695	other combination: In these cases, a simple C<ev_break> will not work.
		3696
		3697	The solution is to maintain "break this loop" variable for each C<ev_run>
		3698	invocation, and use a loop around C<ev_run> until the condition is
		3699	triggered, using C<EVRUN_ONCE>:
		3700
		3701	// main loop
		3702	int exit_main_loop = 0;
		3703
		3704	while (!exit_main_loop)
		3705	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3706
		3707	// in a modal watcher
		3708	int exit_nested_loop = 0;
		3709
		3710	while (!exit_nested_loop)
		3711	ev_run (EV_A_ EVRUN_ONCE);
		3712
		3713	To exit from any of these loops, just set the corresponding exit variable:
		3714
		3715	// exit modal loop
		3716	exit_nested_loop = 1;
		3717
		3718	// exit main program, after modal loop is finished
		3719	exit_main_loop = 1;
		3720
		3721	// exit both
		3722	exit_main_loop = exit_nested_loop = 1;
		3723
		3724	=head2 THREAD LOCKING EXAMPLE
		3725
		3726	Here is a fictitious example of how to run an event loop in a different
		3727	thread from where callbacks are being invoked and watchers are
		3728	created/added/removed.
		3729
		3730	For a real-world example, see the C<EV::Loop::Async> perl module,
		3731	which uses exactly this technique (which is suited for many high-level
		3732	languages).
		3733
		3734	The example uses a pthread mutex to protect the loop data, a condition
		3735	variable to wait for callback invocations, an async watcher to notify the
		3736	event loop thread and an unspecified mechanism to wake up the main thread.
		3737
		3738	First, you need to associate some data with the event loop:
		3739
		3740	typedef struct {
		3741	mutex_t lock; /* global loop lock */
		3742	ev_async async_w;
		3743	thread_t tid;
		3744	cond_t invoke_cv;
		3745	} userdata;
		3746
		3747	void prepare_loop (EV_P)
		3748	{
		3749	// for simplicity, we use a static userdata struct.
		3750	static userdata u;
		3751
		3752	ev_async_init (&u->async_w, async_cb);
		3753	ev_async_start (EV_A_ &u->async_w);
		3754
		3755	pthread_mutex_init (&u->lock, 0);
		3756	pthread_cond_init (&u->invoke_cv, 0);
		3757
		3758	// now associate this with the loop
		3759	ev_set_userdata (EV_A_ u);
		3760	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3761	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3762
		3763	// then create the thread running ev_run
		3764	pthread_create (&u->tid, 0, l_run, EV_A);
		3765	}
		3766
		3767	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3768	solely to wake up the event loop so it takes notice of any new watchers
		3769	that might have been added:
		3770
		3771	static void
		3772	async_cb (EV_P_ ev_async *w, int revents)
		3773	{
		3774	// just used for the side effects
		3775	}
		3776
		3777	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3778	protecting the loop data, respectively.
		3779
		3780	static void
		3781	l_release (EV_P)
		3782	{
		3783	userdata *u = ev_userdata (EV_A);
		3784	pthread_mutex_unlock (&u->lock);
		3785	}
		3786
		3787	static void
		3788	l_acquire (EV_P)
		3789	{
		3790	userdata *u = ev_userdata (EV_A);
		3791	pthread_mutex_lock (&u->lock);
		3792	}
		3793
		3794	The event loop thread first acquires the mutex, and then jumps straight
		3795	into C<ev_run>:
		3796
		3797	void *
		3798	l_run (void *thr_arg)
		3799	{
		3800	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3801
		3802	l_acquire (EV_A);
		3803	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3804	ev_run (EV_A_ 0);
		3805	l_release (EV_A);
		3806
		3807	return 0;
		3808	}
		3809
		3810	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3811	signal the main thread via some unspecified mechanism (signals? pipe
		3812	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3813	have been called (in a while loop because a) spurious wakeups are possible
		3814	and b) skipping inter-thread-communication when there are no pending
		3815	watchers is very beneficial):
		3816
		3817	static void
		3818	l_invoke (EV_P)
		3819	{
		3820	userdata *u = ev_userdata (EV_A);
		3821
		3822	while (ev_pending_count (EV_A))
		3823	{
		3824	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3825	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3826	}
		3827	}
		3828
		3829	Now, whenever the main thread gets told to invoke pending watchers, it
		3830	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3831	thread to continue:
		3832
		3833	static void
		3834	real_invoke_pending (EV_P)
		3835	{
		3836	userdata *u = ev_userdata (EV_A);
		3837
		3838	pthread_mutex_lock (&u->lock);
		3839	ev_invoke_pending (EV_A);
		3840	pthread_cond_signal (&u->invoke_cv);
		3841	pthread_mutex_unlock (&u->lock);
		3842	}
		3843
		3844	Whenever you want to start/stop a watcher or do other modifications to an
		3845	event loop, you will now have to lock:
		3846
		3847	ev_timer timeout_watcher;
		3848	userdata *u = ev_userdata (EV_A);
		3849
		3850	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3851
		3852	pthread_mutex_lock (&u->lock);
		3853	ev_timer_start (EV_A_ &timeout_watcher);
		3854	ev_async_send (EV_A_ &u->async_w);
		3855	pthread_mutex_unlock (&u->lock);
		3856
		3857	Note that sending the C<ev_async> watcher is required because otherwise
		3858	an event loop currently blocking in the kernel will have no knowledge
		3859	about the newly added timer. By waking up the loop it will pick up any new
		3860	watchers in the next event loop iteration.
		3861
		3862	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3863
		3864	While the overhead of a callback that e.g. schedules a thread is small, it
		3865	is still an overhead. If you embed libev, and your main usage is with some
		3866	kind of threads or coroutines, you might want to customise libev so that
		3867	doesn't need callbacks anymore.
		3868
		3869	Imagine you have coroutines that you can switch to using a function
		3870	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3871	and that due to some magic, the currently active coroutine is stored in a
		3872	global called C<current_coro>. Then you can build your own "wait for libev
		3873	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3874	the differing C<;> conventions):
		3875
		3876	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3877	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3878
		3879	That means instead of having a C callback function, you store the
		3880	coroutine to switch to in each watcher, and instead of having libev call
		3881	your callback, you instead have it switch to that coroutine.
		3882
		3883	A coroutine might now wait for an event with a function called
		3884	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3885	matter when, or whether the watcher is active or not when this function is
		3886	called):
		3887
		3888	void
		3889	wait_for_event (ev_watcher *w)
		3890	{
		3891	ev_set_cb (w, current_coro);
		3892	switch_to (libev_coro);
		3893	}
		3894
		3895	That basically suspends the coroutine inside C<wait_for_event> and
		3896	continues the libev coroutine, which, when appropriate, switches back to
		3897	this or any other coroutine.
		3898
		3899	You can do similar tricks if you have, say, threads with an event queue -
		3900	instead of storing a coroutine, you store the queue object and instead of
		3901	switching to a coroutine, you push the watcher onto the queue and notify
		3902	any waiters.
		3903
		3904	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		3905	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3906
		3907	// my_ev.h
		3908	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3909	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3910	#include "../libev/ev.h"
		3911
		3912	// my_ev.c
		3913	#define EV_H "my_ev.h"
		3914	#include "../libev/ev.c"
		3915
		3916	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3917	F<my_ev.c> into your project. When properly specifying include paths, you
		3918	can even use F<ev.h> as header file name directly.
3310		3919
3311		3920
3312	=head1 LIBEVENT EMULATION	3921	=head1 LIBEVENT EMULATION
3313		3922
3314	Libev offers a compatibility emulation layer for libevent. It cannot	3923	Libev offers a compatibility emulation layer for libevent. It cannot
3315	emulate the internals of libevent, so here are some usage hints:	3924	emulate the internals of libevent, so here are some usage hints:
3316		3925
3317	=over 4	3926	=over 4
		3927
		3928	=item * Only the libevent-1.4.1-beta API is being emulated.
		3929
		3930	This was the newest libevent version available when libev was implemented,
		3931	and is still mostly unchanged in 2010.
3318		3932
3319	=item * Use it by including <event.h>, as usual.	3933	=item * Use it by including <event.h>, as usual.
3320		3934
3321	=item * The following members are fully supported: ev_base, ev_callback,	3935	=item * The following members are fully supported: ev_base, ev_callback,
3322	ev_arg, ev_fd, ev_res, ev_events.	3936	ev_arg, ev_fd, ev_res, ev_events.
…		…
3328	=item * Priorities are not currently supported. Initialising priorities	3942	=item * Priorities are not currently supported. Initialising priorities
3329	will fail and all watchers will have the same priority, even though there	3943	will fail and all watchers will have the same priority, even though there
3330	is an ev_pri field.	3944	is an ev_pri field.
3331		3945
3332	=item * In libevent, the last base created gets the signals, in libev, the	3946	=item * In libevent, the last base created gets the signals, in libev, the
3333	first base created (== the default loop) gets the signals.	3947	base that registered the signal gets the signals.
3334		3948
3335	=item * Other members are not supported.	3949	=item * Other members are not supported.
3336		3950
3337	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3951	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3338	to use the libev header file and library.	3952	to use the libev header file and library.
3339		3953
3340	=back	3954	=back
3341		3955
3342	=head1 C++ SUPPORT	3956	=head1 C++ SUPPORT
		3957
		3958	=head2 C API
		3959
		3960	The normal C API should work fine when used from C++: both ev.h and the
		3961	libev sources can be compiled as C++. Therefore, code that uses the C API
		3962	will work fine.
		3963
		3964	Proper exception specifications might have to be added to callbacks passed
		3965	to libev: exceptions may be thrown only from watcher callbacks, all
		3966	other callbacks (allocator, syserr, loop acquire/release and periodic
		3967	reschedule callbacks) must not throw exceptions, and might need a C<throw
		3968	()> specification. If you have code that needs to be compiled as both C
		3969	and C++ you can use the C<EV_THROW> macro for this:
		3970
		3971	static void
		3972	fatal_error (const char *msg) EV_THROW
		3973	{
		3974	perror (msg);
		3975	abort ();
		3976	}
		3977
		3978	...
		3979	ev_set_syserr_cb (fatal_error);
		3980
		3981	The only API functions that can currently throw exceptions are C<ev_run>,
		3982	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		3983	because it runs cleanup watchers).
		3984
		3985	Throwing exceptions in watcher callbacks is only supported if libev itself
		3986	is compiled with a C++ compiler or your C and C++ environments allow
		3987	throwing exceptions through C libraries (most do).
		3988
		3989	=head2 C++ API
3343		3990
3344	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3991	Libev comes with some simplistic wrapper classes for C++ that mainly allow
3345	you to use some convenience methods to start/stop watchers and also change	3992	you to use some convenience methods to start/stop watchers and also change
3346	the callback model to a model using method callbacks on objects.	3993	the callback model to a model using method callbacks on objects.
3347		3994
3348	To use it,	3995	To use it,
3349		3996
3350	#include <ev++.h>	3997	#include <ev++.h>
3351		3998
3352	This automatically includes F<ev.h> and puts all of its definitions (many	3999	This automatically includes F<ev.h> and puts all of its definitions (many
3353	of them macros) into the global namespace. All C++ specific things are	4000	of them macros) into the global namespace. All C++ specific things are
3354	put into the C<ev> namespace. It should support all the same embedding	4001	put into the C<ev> namespace. It should support all the same embedding
…		…
3357	Care has been taken to keep the overhead low. The only data member the C++	4004	Care has been taken to keep the overhead low. The only data member the C++
3358	classes add (compared to plain C-style watchers) is the event loop pointer	4005	classes add (compared to plain C-style watchers) is the event loop pointer
3359	that the watcher is associated with (or no additional members at all if	4006	that the watcher is associated with (or no additional members at all if
3360	you disable C<EV_MULTIPLICITY> when embedding libev).	4007	you disable C<EV_MULTIPLICITY> when embedding libev).
3361		4008
3362	Currently, functions, and static and non-static member functions can be	4009	Currently, functions, static and non-static member functions and classes
3363	used as callbacks. Other types should be easy to add as long as they only	4010	with C<operator ()> can be used as callbacks. Other types should be easy
3364	need one additional pointer for context. If you need support for other	4011	to add as long as they only need one additional pointer for context. If
3365	types of functors please contact the author (preferably after implementing	4012	you need support for other types of functors please contact the author
3366	it).	4013	(preferably after implementing it).
		4014
		4015	For all this to work, your C++ compiler either has to use the same calling
		4016	conventions as your C compiler (for static member functions), or you have
		4017	to embed libev and compile libev itself as C++.
3367		4018
3368	Here is a list of things available in the C<ev> namespace:	4019	Here is a list of things available in the C<ev> namespace:
3369		4020
3370	=over 4	4021	=over 4
3371		4022
…		…
3381	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4032	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3382		4033
3383	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4034	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
3384	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4035	the same name in the C<ev> namespace, with the exception of C<ev_signal>
3385	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4036	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3386	defines by many implementations.	4037	defined by many implementations.
3387		4038
3388	All of those classes have these methods:	4039	All of those classes have these methods:
3389		4040
3390	=over 4	4041	=over 4
3391		4042
…		…
3453	void operator() (ev::io &w, int revents)	4104	void operator() (ev::io &w, int revents)
3454	{	4105	{
3455	...	4106	...
3456	}	4107	}
3457	}	4108	}
3458		4109
3459	myfunctor f;	4110	myfunctor f;
3460		4111
3461	ev::io w;	4112	ev::io w;
3462	w.set (&f);	4113	w.set (&f);
3463		4114
…		…
3481	Associates a different C<struct ev_loop> with this watcher. You can only	4132	Associates a different C<struct ev_loop> with this watcher. You can only
3482	do this when the watcher is inactive (and not pending either).	4133	do this when the watcher is inactive (and not pending either).
3483		4134
3484	=item w->set ([arguments])	4135	=item w->set ([arguments])
3485		4136
3486	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this	4137	Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>),
3487	method or a suitable start method must be called at least once. Unlike the	4138	with the same arguments. Either this method or a suitable start method
3488	C counterpart, an active watcher gets automatically stopped and restarted	4139	must be called at least once. Unlike the C counterpart, an active watcher
3489	when reconfiguring it with this method.	4140	gets automatically stopped and restarted when reconfiguring it with this
		4141	method.
		4142
		4143	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4144	clashing with the C<set (loop)> method.
3490		4145
3491	=item w->start ()	4146	=item w->start ()
3492		4147
3493	Starts the watcher. Note that there is no C<loop> argument, as the	4148	Starts the watcher. Note that there is no C<loop> argument, as the
3494	constructor already stores the event loop.	4149	constructor already stores the event loop.
…		…
3524	watchers in the constructor.	4179	watchers in the constructor.
3525		4180
3526	class myclass	4181	class myclass
3527	{	4182	{
3528	ev::io io ; void io_cb (ev::io &w, int revents);	4183	ev::io io ; void io_cb (ev::io &w, int revents);
3529	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);	4184	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3530	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4185	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3531		4186
3532	myclass (int fd)	4187	myclass (int fd)
3533	{	4188	{
3534	io .set <myclass, &myclass::io_cb > (this);	4189	io .set <myclass, &myclass::io_cb > (this);
…		…
3585	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4240	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3586		4241
3587	=item D	4242	=item D
3588		4243
3589	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4244	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3590	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4245	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3591		4246
3592	=item Ocaml	4247	=item Ocaml
3593		4248
3594	Erkki Seppala has written Ocaml bindings for libev, to be found at	4249	Erkki Seppala has written Ocaml bindings for libev, to be found at
3595	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4250	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
…		…
3598		4253
3599	Brian Maher has written a partial interface to libev for lua (at the	4254	Brian Maher has written a partial interface to libev for lua (at the
3600	time of this writing, only C<ev_io> and C<ev_timer>), to be found at	4255	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
3601	L<http://github.com/brimworks/lua-ev>.	4256	L<http://github.com/brimworks/lua-ev>.
3602		4257
		4258	=item Javascript
		4259
		4260	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4261
		4262	=item Others
		4263
		4264	There are others, and I stopped counting.
		4265
3603	=back	4266	=back
3604		4267
3605		4268
3606	=head1 MACRO MAGIC	4269	=head1 MACRO MAGIC
3607		4270
…		…
3643	suitable for use with C<EV_A>.	4306	suitable for use with C<EV_A>.
3644		4307
3645	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4308	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3646		4309
3647	Similar to the other two macros, this gives you the value of the default	4310	Similar to the other two macros, this gives you the value of the default
3648	loop, if multiple loops are supported ("ev loop default").	4311	loop, if multiple loops are supported ("ev loop default"). The default loop
		4312	will be initialised if it isn't already initialised.
		4313
		4314	For non-multiplicity builds, these macros do nothing, so you always have
		4315	to initialise the loop somewhere.
3649		4316
3650	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4317	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3651		4318
3652	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4319	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3653	default loop has been initialised (C<UC> == unchecked). Their behaviour	4320	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3720	ev_vars.h	4387	ev_vars.h
3721	ev_wrap.h	4388	ev_wrap.h
3722		4389
3723	ev_win32.c required on win32 platforms only	4390	ev_win32.c required on win32 platforms only
3724		4391
3725	ev_select.c only when select backend is enabled (which is enabled by default)	4392	ev_select.c only when select backend is enabled
3726	ev_poll.c only when poll backend is enabled (disabled by default)	4393	ev_poll.c only when poll backend is enabled
3727	ev_epoll.c only when the epoll backend is enabled (disabled by default)	4394	ev_epoll.c only when the epoll backend is enabled
3728	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	4395	ev_kqueue.c only when the kqueue backend is enabled
3729	ev_port.c only when the solaris port backend is enabled (disabled by default)	4396	ev_port.c only when the solaris port backend is enabled
3730		4397
3731	F<ev.c> includes the backend files directly when enabled, so you only need	4398	F<ev.c> includes the backend files directly when enabled, so you only need
3732	to compile this single file.	4399	to compile this single file.
3733		4400
3734	=head3 LIBEVENT COMPATIBILITY API	4401	=head3 LIBEVENT COMPATIBILITY API
…		…
3798	supported). It will also not define any of the structs usually found in	4465	supported). It will also not define any of the structs usually found in
3799	F<event.h> that are not directly supported by the libev core alone.	4466	F<event.h> that are not directly supported by the libev core alone.
3800		4467
3801	In standalone mode, libev will still try to automatically deduce the	4468	In standalone mode, libev will still try to automatically deduce the
3802	configuration, but has to be more conservative.	4469	configuration, but has to be more conservative.
		4470
		4471	=item EV_USE_FLOOR
		4472
		4473	If defined to be C<1>, libev will use the C<floor ()> function for its
		4474	periodic reschedule calculations, otherwise libev will fall back on a
		4475	portable (slower) implementation. If you enable this, you usually have to
		4476	link against libm or something equivalent. Enabling this when the C<floor>
		4477	function is not available will fail, so the safe default is to not enable
		4478	this.
3803		4479
3804	=item EV_USE_MONOTONIC	4480	=item EV_USE_MONOTONIC
3805		4481
3806	If defined to be C<1>, libev will try to detect the availability of the	4482	If defined to be C<1>, libev will try to detect the availability of the
3807	monotonic clock option at both compile time and runtime. Otherwise no	4483	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3892		4568
3893	If programs implement their own fd to handle mapping on win32, then this	4569	If programs implement their own fd to handle mapping on win32, then this
3894	macro can be used to override the C<close> function, useful to unregister	4570	macro can be used to override the C<close> function, useful to unregister
3895	file descriptors again. Note that the replacement function has to close	4571	file descriptors again. Note that the replacement function has to close
3896	the underlying OS handle.	4572	the underlying OS handle.
		4573
		4574	=item EV_USE_WSASOCKET
		4575
		4576	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4577	communication socket, which works better in some environments. Otherwise,
		4578	the normal C<socket> function will be used, which works better in other
		4579	environments.
3897		4580
3898	=item EV_USE_POLL	4581	=item EV_USE_POLL
3899		4582
3900	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4583	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3901	backend. Otherwise it will be enabled on non-win32 platforms. It	4584	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3937	If defined to be C<1>, libev will compile in support for the Linux inotify	4620	If defined to be C<1>, libev will compile in support for the Linux inotify
3938	interface to speed up C<ev_stat> watchers. Its actual availability will	4621	interface to speed up C<ev_stat> watchers. Its actual availability will
3939	be detected at runtime. If undefined, it will be enabled if the headers	4622	be detected at runtime. If undefined, it will be enabled if the headers
3940	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4623	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3941		4624
		4625	=item EV_NO_SMP
		4626
		4627	If defined to be C<1>, libev will assume that memory is always coherent
		4628	between threads, that is, threads can be used, but threads never run on
		4629	different cpus (or different cpu cores). This reduces dependencies
		4630	and makes libev faster.
		4631
		4632	=item EV_NO_THREADS
		4633
		4634	If defined to be C<1>, libev will assume that it will never be called from
		4635	different threads (that includes signal handlers), which is a stronger
		4636	assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes
		4637	libev faster.
		4638
3942	=item EV_ATOMIC_T	4639	=item EV_ATOMIC_T
3943		4640
3944	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4641	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3945	access is atomic with respect to other threads or signal contexts. No such	4642	access is atomic with respect to other threads or signal contexts. No
3946	type is easily found in the C language, so you can provide your own type	4643	such type is easily found in the C language, so you can provide your own
3947	that you know is safe for your purposes. It is used both for signal handler "locking"	4644	type that you know is safe for your purposes. It is used both for signal
3948	as well as for signal and thread safety in C<ev_async> watchers.	4645	handler "locking" as well as for signal and thread safety in C<ev_async>
		4646	watchers.
3949		4647
3950	In the absence of this define, libev will use C<sig_atomic_t volatile>	4648	In the absence of this define, libev will use C<sig_atomic_t volatile>
3951	(from F<signal.h>), which is usually good enough on most platforms.	4649	(from F<signal.h>), which is usually good enough on most platforms.
3952		4650
3953	=item EV_H (h)	4651	=item EV_H (h)
…		…
3980	will have the C<struct ev_loop *> as first argument, and you can create	4678	will have the C<struct ev_loop *> as first argument, and you can create
3981	additional independent event loops. Otherwise there will be no support	4679	additional independent event loops. Otherwise there will be no support
3982	for multiple event loops and there is no first event loop pointer	4680	for multiple event loops and there is no first event loop pointer
3983	argument. Instead, all functions act on the single default loop.	4681	argument. Instead, all functions act on the single default loop.
3984		4682
		4683	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4684	default loop when multiplicity is switched off - you always have to
		4685	initialise the loop manually in this case.
		4686
3985	=item EV_MINPRI	4687	=item EV_MINPRI
3986		4688
3987	=item EV_MAXPRI	4689	=item EV_MAXPRI
3988		4690
3989	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4691	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
4025	#define EV_USE_POLL 1	4727	#define EV_USE_POLL 1
4026	#define EV_CHILD_ENABLE 1	4728	#define EV_CHILD_ENABLE 1
4027	#define EV_ASYNC_ENABLE 1	4729	#define EV_ASYNC_ENABLE 1
4028		4730
4029	The actual value is a bitset, it can be a combination of the following	4731	The actual value is a bitset, it can be a combination of the following
4030	values:	4732	values (by default, all of these are enabled):
4031		4733
4032	=over 4	4734	=over 4
4033		4735
4034	=item C<1> - faster/larger code	4736	=item C<1> - faster/larger code
4035		4737
…		…
4039	code size by roughly 30% on amd64).	4741	code size by roughly 30% on amd64).
4040		4742
4041	When optimising for size, use of compiler flags such as C<-Os> with	4743	When optimising for size, use of compiler flags such as C<-Os> with
4042	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of	4744	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
4043	assertions.	4745	assertions.
		4746
		4747	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4748	(e.g. gcc with C<-Os>).
4044		4749
4045	=item C<2> - faster/larger data structures	4750	=item C<2> - faster/larger data structures
4046		4751
4047	Replaces the small 2-heap for timer management by a faster 4-heap, larger	4752	Replaces the small 2-heap for timer management by a faster 4-heap, larger
4048	hash table sizes and so on. This will usually further increase code size	4753	hash table sizes and so on. This will usually further increase code size
4049	and can additionally have an effect on the size of data structures at	4754	and can additionally have an effect on the size of data structures at
4050	runtime.	4755	runtime.
4051		4756
		4757	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4758	(e.g. gcc with C<-Os>).
		4759
4052	=item C<4> - full API configuration	4760	=item C<4> - full API configuration
4053		4761
4054	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and	4762	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
4055	enables multiplicity (C<EV_MULTIPLICITY>=1).	4763	enables multiplicity (C<EV_MULTIPLICITY>=1).
4056		4764
…		…
4086		4794
4087	With an intelligent-enough linker (gcc+binutils are intelligent enough	4795	With an intelligent-enough linker (gcc+binutils are intelligent enough
4088	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by	4796	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
4089	your program might be left out as well - a binary starting a timer and an	4797	your program might be left out as well - a binary starting a timer and an
4090	I/O watcher then might come out at only 5Kb.	4798	I/O watcher then might come out at only 5Kb.
		4799
		4800	=item EV_API_STATIC
		4801
		4802	If this symbol is defined (by default it is not), then all identifiers
		4803	will have static linkage. This means that libev will not export any
		4804	identifiers, and you cannot link against libev anymore. This can be useful
		4805	when you embed libev, only want to use libev functions in a single file,
		4806	and do not want its identifiers to be visible.
		4807
		4808	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4809	wants to use libev.
		4810
		4811	This option only works when libev is compiled with a C compiler, as C++
		4812	doesn't support the required declaration syntax.
4091		4813
4092	=item EV_AVOID_STDIO	4814	=item EV_AVOID_STDIO
4093		4815
4094	If this is set to C<1> at compiletime, then libev will avoid using stdio	4816	If this is set to C<1> at compiletime, then libev will avoid using stdio
4095	functions (printf, scanf, perror etc.). This will increase the code size	4817	functions (printf, scanf, perror etc.). This will increase the code size
…		…
4239	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4961	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4240		4962
4241	#include "ev_cpp.h"	4963	#include "ev_cpp.h"
4242	#include "ev.c"	4964	#include "ev.c"
4243		4965
4244	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4966	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4245		4967
4246	=head2 THREADS AND COROUTINES	4968	=head2 THREADS AND COROUTINES
4247		4969
4248	=head3 THREADS	4970	=head3 THREADS
4249		4971
…		…
4300	default loop and triggering an C<ev_async> watcher from the default loop	5022	default loop and triggering an C<ev_async> watcher from the default loop
4301	watcher callback into the event loop interested in the signal.	5023	watcher callback into the event loop interested in the signal.
4302		5024
4303	=back	5025	=back
4304		5026
4305	=head4 THREAD LOCKING EXAMPLE	5027	See also L</THREAD LOCKING EXAMPLE>.
4306
4307	Here is a fictitious example of how to run an event loop in a different
4308	thread than where callbacks are being invoked and watchers are
4309	created/added/removed.
4310
4311	For a real-world example, see the C<EV::Loop::Async> perl module,
4312	which uses exactly this technique (which is suited for many high-level
4313	languages).
4314
4315	The example uses a pthread mutex to protect the loop data, a condition
4316	variable to wait for callback invocations, an async watcher to notify the
4317	event loop thread and an unspecified mechanism to wake up the main thread.
4318
4319	First, you need to associate some data with the event loop:
4320
4321	typedef struct {
4322	mutex_t lock; /* global loop lock */
4323	ev_async async_w;
4324	thread_t tid;
4325	cond_t invoke_cv;
4326	} userdata;
4327
4328	void prepare_loop (EV_P)
4329	{
4330	// for simplicity, we use a static userdata struct.
4331	static userdata u;
4332
4333	ev_async_init (&u->async_w, async_cb);
4334	ev_async_start (EV_A_ &u->async_w);
4335
4336	pthread_mutex_init (&u->lock, 0);
4337	pthread_cond_init (&u->invoke_cv, 0);
4338
4339	// now associate this with the loop
4340	ev_set_userdata (EV_A_ u);
4341	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4342	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4343
4344	// then create the thread running ev_loop
4345	pthread_create (&u->tid, 0, l_run, EV_A);
4346	}
4347
4348	The callback for the C<ev_async> watcher does nothing: the watcher is used
4349	solely to wake up the event loop so it takes notice of any new watchers
4350	that might have been added:
4351
4352	static void
4353	async_cb (EV_P_ ev_async *w, int revents)
4354	{
4355	// just used for the side effects
4356	}
4357
4358	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4359	protecting the loop data, respectively.
4360
4361	static void
4362	l_release (EV_P)
4363	{
4364	userdata *u = ev_userdata (EV_A);
4365	pthread_mutex_unlock (&u->lock);
4366	}
4367
4368	static void
4369	l_acquire (EV_P)
4370	{
4371	userdata *u = ev_userdata (EV_A);
4372	pthread_mutex_lock (&u->lock);
4373	}
4374
4375	The event loop thread first acquires the mutex, and then jumps straight
4376	into C<ev_run>:
4377
4378	void *
4379	l_run (void *thr_arg)
4380	{
4381	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4382
4383	l_acquire (EV_A);
4384	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4385	ev_run (EV_A_ 0);
4386	l_release (EV_A);
4387
4388	return 0;
4389	}
4390
4391	Instead of invoking all pending watchers, the C<l_invoke> callback will
4392	signal the main thread via some unspecified mechanism (signals? pipe
4393	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4394	have been called (in a while loop because a) spurious wakeups are possible
4395	and b) skipping inter-thread-communication when there are no pending
4396	watchers is very beneficial):
4397
4398	static void
4399	l_invoke (EV_P)
4400	{
4401	userdata *u = ev_userdata (EV_A);
4402
4403	while (ev_pending_count (EV_A))
4404	{
4405	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4406	pthread_cond_wait (&u->invoke_cv, &u->lock);
4407	}
4408	}
4409
4410	Now, whenever the main thread gets told to invoke pending watchers, it
4411	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4412	thread to continue:
4413
4414	static void
4415	real_invoke_pending (EV_P)
4416	{
4417	userdata *u = ev_userdata (EV_A);
4418
4419	pthread_mutex_lock (&u->lock);
4420	ev_invoke_pending (EV_A);
4421	pthread_cond_signal (&u->invoke_cv);
4422	pthread_mutex_unlock (&u->lock);
4423	}
4424
4425	Whenever you want to start/stop a watcher or do other modifications to an
4426	event loop, you will now have to lock:
4427
4428	ev_timer timeout_watcher;
4429	userdata *u = ev_userdata (EV_A);
4430
4431	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4432
4433	pthread_mutex_lock (&u->lock);
4434	ev_timer_start (EV_A_ &timeout_watcher);
4435	ev_async_send (EV_A_ &u->async_w);
4436	pthread_mutex_unlock (&u->lock);
4437
4438	Note that sending the C<ev_async> watcher is required because otherwise
4439	an event loop currently blocking in the kernel will have no knowledge
4440	about the newly added timer. By waking up the loop it will pick up any new
4441	watchers in the next event loop iteration.
4442		5028
4443	=head3 COROUTINES	5029	=head3 COROUTINES
4444		5030
4445	Libev is very accommodating to coroutines ("cooperative threads"):	5031	Libev is very accommodating to coroutines ("cooperative threads"):
4446	libev fully supports nesting calls to its functions from different	5032	libev fully supports nesting calls to its functions from different
…		…
4611	requires, and its I/O model is fundamentally incompatible with the POSIX	5197	requires, and its I/O model is fundamentally incompatible with the POSIX
4612	model. Libev still offers limited functionality on this platform in	5198	model. Libev still offers limited functionality on this platform in
4613	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5199	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4614	descriptors. This only applies when using Win32 natively, not when using	5200	descriptors. This only applies when using Win32 natively, not when using
4615	e.g. cygwin. Actually, it only applies to the microsofts own compilers,	5201	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
4616	as every compielr comes with a slightly differently broken/incompatible	5202	as every compiler comes with a slightly differently broken/incompatible
4617	environment.	5203	environment.
4618		5204
4619	Lifting these limitations would basically require the full	5205	Lifting these limitations would basically require the full
4620	re-implementation of the I/O system. If you are into this kind of thing,	5206	re-implementation of the I/O system. If you are into this kind of thing,
4621	then note that glib does exactly that for you in a very portable way (note	5207	then note that glib does exactly that for you in a very portable way (note
…		…
4715	structure (guaranteed by POSIX but not by ISO C for example), but it also	5301	structure (guaranteed by POSIX but not by ISO C for example), but it also
4716	assumes that the same (machine) code can be used to call any watcher	5302	assumes that the same (machine) code can be used to call any watcher
4717	callback: The watcher callbacks have different type signatures, but libev	5303	callback: The watcher callbacks have different type signatures, but libev
4718	calls them using an C<ev_watcher *> internally.	5304	calls them using an C<ev_watcher *> internally.
4719		5305
		5306	=item null pointers and integer zero are represented by 0 bytes
		5307
		5308	Libev uses C<memset> to initialise structs and arrays to C<0> bytes, and
		5309	relies on this setting pointers and integers to null.
		5310
		5311	=item pointer accesses must be thread-atomic
		5312
		5313	Accessing a pointer value must be atomic, it must both be readable and
		5314	writable in one piece - this is the case on all current architectures.
		5315
4720	=item C<sig_atomic_t volatile> must be thread-atomic as well	5316	=item C<sig_atomic_t volatile> must be thread-atomic as well
4721		5317
4722	The type C<sig_atomic_t volatile> (or whatever is defined as	5318	The type C<sig_atomic_t volatile> (or whatever is defined as
4723	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5319	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
4724	threads. This is not part of the specification for C<sig_atomic_t>, but is	5320	threads. This is not part of the specification for C<sig_atomic_t>, but is
…		…
4732	thread" or will block signals process-wide, both behaviours would	5328	thread" or will block signals process-wide, both behaviours would
4733	be compatible with libev. Interaction between C<sigprocmask> and	5329	be compatible with libev. Interaction between C<sigprocmask> and
4734	C<pthread_sigmask> could complicate things, however.	5330	C<pthread_sigmask> could complicate things, however.
4735		5331
4736	The most portable way to handle signals is to block signals in all threads	5332	The most portable way to handle signals is to block signals in all threads
4737	except the initial one, and run the default loop in the initial thread as	5333	except the initial one, and run the signal handling loop in the initial
4738	well.	5334	thread as well.
4739		5335
4740	=item C<long> must be large enough for common memory allocation sizes	5336	=item C<long> must be large enough for common memory allocation sizes
4741		5337
4742	To improve portability and simplify its API, libev uses C<long> internally	5338	To improve portability and simplify its API, libev uses C<long> internally
4743	instead of C<size_t> when allocating its data structures. On non-POSIX	5339	instead of C<size_t> when allocating its data structures. On non-POSIX
…		…
4749		5345
4750	The type C<double> is used to represent timestamps. It is required to	5346	The type C<double> is used to represent timestamps. It is required to
4751	have at least 51 bits of mantissa (and 9 bits of exponent), which is	5347	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4752	good enough for at least into the year 4000 with millisecond accuracy	5348	good enough for at least into the year 4000 with millisecond accuracy
4753	(the design goal for libev). This requirement is overfulfilled by	5349	(the design goal for libev). This requirement is overfulfilled by
4754	implementations using IEEE 754, which is basically all existing ones. With	5350	implementations using IEEE 754, which is basically all existing ones.
		5351
4755	IEEE 754 doubles, you get microsecond accuracy until at least 2200.	5352	With IEEE 754 doubles, you get microsecond accuracy until at least the
		5353	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5354	is either obsolete or somebody patched it to use C<long double> or
		5355	something like that, just kidding).
4756		5356
4757	=back	5357	=back
4758		5358
4759	If you know of other additional requirements drop me a note.	5359	If you know of other additional requirements drop me a note.
4760		5360
…		…
4822	=item Processing ev_async_send: O(number_of_async_watchers)	5422	=item Processing ev_async_send: O(number_of_async_watchers)
4823		5423
4824	=item Processing signals: O(max_signal_number)	5424	=item Processing signals: O(max_signal_number)
4825		5425
4826	Sending involves a system call I<iff> there were no other C<ev_async_send>	5426	Sending involves a system call I<iff> there were no other C<ev_async_send>
4827	calls in the current loop iteration. Checking for async and signal events	5427	calls in the current loop iteration and the loop is currently
		5428	blocked. Checking for async and signal events involves iterating over all
4828	involves iterating over all running async watchers or all signal numbers.	5429	running async watchers or all signal numbers.
4829		5430
4830	=back	5431	=back
4831		5432
4832		5433
4833	=head1 PORTING FROM LIBEV 3.X TO 4.X	5434	=head1 PORTING FROM LIBEV 3.X TO 4.X
4834		5435
4835	The major version 4 introduced some minor incompatible changes to the API.	5436	The major version 4 introduced some incompatible changes to the API.
4836		5437
4837	At the moment, the C<ev.h> header file tries to implement superficial	5438	At the moment, the C<ev.h> header file provides compatibility definitions
4838	compatibility, so most programs should still compile. Those might be	5439	for all changes, so most programs should still compile. The compatibility
4839	removed in later versions of libev, so better update early than late.	5440	layer might be removed in later versions of libev, so better update to the
		5441	new API early than late.
4840		5442
4841	=over 4	5443	=over 4
4842		5444
		5445	=item C<EV_COMPAT3> backwards compatibility mechanism
		5446
		5447	The backward compatibility mechanism can be controlled by
		5448	C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING>
		5449	section.
		5450
4843	=item C<ev_default_destroy> and C<ev_default_fork> have been removed	5451	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
4844		5452
4845	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:	5453	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
4846		5454
4847	ev_loop_destroy (EV_DEFAULT);	5455	ev_loop_destroy (EV_DEFAULT_UC);
4848	ev_loop_fork (EV_DEFAULT);	5456	ev_loop_fork (EV_DEFAULT);
4849		5457
4850	=item function/symbol renames	5458	=item function/symbol renames
4851		5459
4852	A number of functions and symbols have been renamed:	5460	A number of functions and symbols have been renamed:
…		…
4872	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme	5480	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
4873	as all other watcher types. Note that C<ev_loop_fork> is still called	5481	as all other watcher types. Note that C<ev_loop_fork> is still called
4874	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>	5482	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
4875	typedef.	5483	typedef.
4876		5484
4877	=item C<EV_COMPAT3> backwards compatibility mechanism
4878
4879	The backward compatibility mechanism can be controlled by
4880	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
4881	section.
4882
4883	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>	5485	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
4884		5486
4885	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different	5487	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
4886	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile	5488	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
4887	and work, but the library code will of course be larger.	5489	and work, but the library code will of course be larger.
…		…
4894	=over 4	5496	=over 4
4895		5497
4896	=item active	5498	=item active
4897		5499
4898	A watcher is active as long as it has been started and not yet stopped.	5500	A watcher is active as long as it has been started and not yet stopped.
4899	See L<WATCHER STATES> for details.	5501	See L</WATCHER STATES> for details.
4900		5502
4901	=item application	5503	=item application
4902		5504
4903	In this document, an application is whatever is using libev.	5505	In this document, an application is whatever is using libev.
4904		5506
…		…
4940	watchers and events.	5542	watchers and events.
4941		5543
4942	=item pending	5544	=item pending
4943		5545
4944	A watcher is pending as soon as the corresponding event has been	5546	A watcher is pending as soon as the corresponding event has been
4945	detected. See L<WATCHER STATES> for details.	5547	detected. See L</WATCHER STATES> for details.
4946		5548
4947	=item real time	5549	=item real time
4948		5550
4949	The physical time that is observed. It is apparently strictly monotonic :)	5551	The physical time that is observed. It is apparently strictly monotonic :)
4950		5552
4951	=item wall-clock time	5553	=item wall-clock time
4952		5554
4953	The time and date as shown on clocks. Unlike real time, it can actually	5555	The time and date as shown on clocks. Unlike real time, it can actually
4954	be wrong and jump forwards and backwards, e.g. when the you adjust your	5556	be wrong and jump forwards and backwards, e.g. when you adjust your
4955	clock.	5557	clock.
4956		5558
4957	=item watcher	5559	=item watcher
4958		5560
4959	A data structure that describes interest in certain events. Watchers need	5561	A data structure that describes interest in certain events. Watchers need
…		…
4961		5563
4962	=back	5564	=back
4963		5565
4964	=head1 AUTHOR	5566	=head1 AUTHOR
4965		5567
4966	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5568	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5569	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4967		5570

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