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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
…		…
43		45
44	int	46	int
45	main (void)	47	main (void)
46	{	48	{
47	// use the default event loop unless you have special needs	49	// use the default event loop unless you have special needs
48	struct ev_loop *loop = ev_default_loop (0);	50	struct ev_loop *loop = EV_DEFAULT;
49		51
50	// initialise an io watcher, then start it	52	// initialise an io watcher, then start it
51	// this one will watch for stdin to become readable	53	// this one will watch for stdin to become readable
52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	54	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
53	ev_io_start (loop, &stdin_watcher);	55	ev_io_start (loop, &stdin_watcher);
…		…
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 THE EVENT LOOP	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
312	This will initialise the default event loop if it hasn't been initialised	341	This returns the "default" event loop object, which is what you should
313	yet and return it. If the default loop could not be initialised, returns	342	normally use when you just need "the event loop". Event loop objects and
314	false. If it already was initialised it simply returns it (and ignores the	343	the C<flags> parameter are described in more detail in the entry for
315	flags. If that is troubling you, check C<ev_backend ()> afterwards).	344	C<ev_loop_new>.
		345
		346	If the default loop is already initialised then this function simply
		347	returns it (and ignores the flags. If that is troubling you, check
		348	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		349	flags, which should almost always be C<0>, unless the caller is also the
		350	one calling C<ev_run> or otherwise qualifies as "the main program".
316		351
317	If you don't know what event loop to use, use the one returned from this	352	If you don't know what event loop to use, use the one returned from this
318	function.	353	function (or via the C<EV_DEFAULT> macro).
319		354
320	Note that this function is I<not> thread-safe, so if you want to use it	355	Note that this function is I<not> thread-safe, so if you want to use it
321	from multiple threads, you have to lock (note also that this is unlikely,	356	from multiple threads, you have to employ some kind of mutex (note also
322	as loops cannot be shared easily between threads anyway).	357	that this case is unlikely, as loops cannot be shared easily between
		358	threads anyway).
323		359
324	The default loop is the only loop that can handle C<ev_signal> and	360	The default loop is the only loop that can handle C<ev_child> watchers,
325	C<ev_child> watchers, and to do this, it always registers a handler	361	and to do this, it always registers a handler for C<SIGCHLD>. If this is
326	for C<SIGCHLD>. If this is a problem for your application you can either	362	a problem for your application you can either create a dynamic loop with
327	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	363	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
328	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	364	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
329	C<ev_default_init>.	365
		366	Example: This is the most typical usage.
		367
		368	if (!ev_default_loop (0))
		369	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		370
		371	Example: Restrict libev to the select and poll backends, and do not allow
		372	environment settings to be taken into account:
		373
		374	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		375
		376	=item struct ev_loop *ev_loop_new (unsigned int flags)
		377
		378	This will create and initialise a new event loop object. If the loop
		379	could not be initialised, returns false.
		380
		381	This function is thread-safe, and one common way to use libev with
		382	threads is indeed to create one loop per thread, and using the default
		383	loop in the "main" or "initial" thread.
330		384
331	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
332	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>).
333		387
334	The following flags are supported:	388	The following flags are supported:
…		…
344		398
345	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
346	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
347	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	401	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
348	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
349	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
350	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).
351		407
352	=item C<EVFLAG_FORKCHECK>	408	=item C<EVFLAG_FORKCHECK>
353		409
354	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
355	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.
356		412
357	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,
358	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
359	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
360	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
361	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
362	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).
363		420
364	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
365	forget about forgetting to tell libev about forking) when you use this	422	forget about forgetting to tell libev about forking, although you still
366	flag.	423	have to ignore C<SIGPIPE>) when you use this flag.
367		424
368	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>
369	environment variable.	426	environment variable.
370		427
371	=item C<EVFLAG_NOINOTIFY>	428	=item C<EVFLAG_NOINOTIFY>
372		429
373	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
374	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
375	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
376	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.
377		434
378	=item C<EVFLAG_SIGNALFD>	435	=item C<EVFLAG_SIGNALFD>
379		436
380	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
381	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
382	delivers signals synchronously, which makes it both faster and might make	439	delivers signals synchronously, which makes it both faster and might make
383	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
384	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
385	threads that are not interested in handling them.	442	threads that are not interested in handling them.
386		443
387	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
388	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
389	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.
390		462
391	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	463	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
392		464
393	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
394	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,
…		…
422	=item C<EVBACKEND_EPOLL> (value 4, Linux)	494	=item C<EVBACKEND_EPOLL> (value 4, Linux)
423		495
424	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
425	kernels).	497	kernels).
426		498
427	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
428	but it scales phenomenally better. While poll and select usually scale	500	it scales phenomenally better. While poll and select usually scale like
429	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
430	epoll scales either O(1) or O(active_fds).	502	fd), epoll scales either O(1) or O(active_fds).
431		503
432	The epoll mechanism deserves honorable mention as the most misdesigned	504	The epoll mechanism deserves honorable mention as the most misdesigned
433	of the more advanced event mechanisms: mere annoyances include silently	505	of the more advanced event mechanisms: mere annoyances include silently
434	dropping file descriptors, requiring a system call per change per file	506	dropping file descriptors, requiring a system call per change per file
435	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
436	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
437	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
438	take considerable time (one syscall per file descriptor) and is of course	512	set, which can take considerable time (one syscall per file descriptor)
439	hard to detect.	513	and is of course hard to detect.
440		514
441	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	515	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
442	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
443	I<different> file descriptors (even already closed ones, so one cannot	517	totally I<different> file descriptors (even already closed ones, so
444	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
445	on SMP systems). Libev tries to counter these spurious notifications by	519	(especially on SMP systems). Libev tries to counter these spurious
446	employing an additional generation counter and comparing that against the	520	notifications by employing an additional generation counter and comparing
447	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
448	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
449	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...
450		531
451	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
452	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
453	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
454	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
…		…
491		572
492	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
493	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
494	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
495	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
496	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
497	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
498	cases	579	drops fds silently in similarly hard-to-detect cases.
499		580
500	This backend usually performs well under most conditions.	581	This backend usually performs well under most conditions.
501		582
502	While nominally embeddable in other event loops, this doesn't work	583	While nominally embeddable in other event loops, this doesn't work
503	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
…		…
520	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	601	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
521		602
522	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,
523	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)).
524		605
525	Please note that Solaris event ports can deliver a lot of spurious
526	notifications, so you need to use non-blocking I/O or other means to avoid
527	blocking when no data (or space) is available.
528
529	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
530	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
531	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	608	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
532	might perform better.	609	might perform better.
533		610
534	On the positive side, with the exception of the spurious readiness	611	On the positive side, this backend actually performed fully to
535	notifications, this backend actually performed fully to specification
536	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
537	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.
538		625
539	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
540	C<EVBACKEND_POLL>.	627	C<EVBACKEND_POLL>.
541		628
542	=item C<EVBACKEND_ALL>	629	=item C<EVBACKEND_ALL>
543		630
544	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
545	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
546	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	633	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
547		634
548	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).
549		644
550	=back	645	=back
551		646
552	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,
553	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
554	here). If none are specified, all backends in C<ev_recommended_backends	649	here). If none are specified, all backends in C<ev_recommended_backends
555	()> will be tried.	650	()> will be tried.
556		651
557	Example: This is the most typical usage.
558
559	if (!ev_default_loop (0))
560	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
561
562	Example: Restrict libev to the select and poll backends, and do not allow
563	environment settings to be taken into account:
564
565	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
566
567	Example: Use whatever libev has to offer, but make sure that kqueue is
568	used if available (warning, breaks stuff, best use only with your own
569	private event loop and only if you know the OS supports your types of
570	fds):
571
572	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
573
574	=item struct ev_loop *ev_loop_new (unsigned int flags)
575
576	Similar to C<ev_default_loop>, but always creates a new event loop that is
577	always distinct from the default loop.
578
579	Note that this function I<is> thread-safe, and one common way to use
580	libev with threads is indeed to create one loop per thread, and using the
581	default loop in the "main" or "initial" thread.
582
583	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.
584		653
585	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	654	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
586	if (!epoller)	655	if (!epoller)
587	fatal ("no epoll found here, maybe it hides under your chair");	656	fatal ("no epoll found here, maybe it hides under your chair");
588		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);
		662
589	=item ev_default_destroy ()	663	=item ev_loop_destroy (loop)
590		664
591	Destroys the default loop (frees all memory and kernel state etc.). None	665	Destroys an event loop object (frees all memory and kernel state
592	of the active event watchers will be stopped in the normal sense, so	666	etc.). None of the active event watchers will be stopped in the normal
593	e.g. C<ev_is_active> might still return true. It is your responsibility to	667	sense, so e.g. C<ev_is_active> might still return true. It is your
594	either stop all watchers cleanly yourself I<before> calling this function,	668	responsibility to either stop all watchers cleanly yourself I<before>
595	or cope with the fact afterwards (which is usually the easiest thing, you	669	calling this function, or cope with the fact afterwards (which is usually
596	can just ignore the watchers and/or C<free ()> them for example).	670	the easiest thing, you can just ignore the watchers and/or C<free ()> them
		671	for example).
597		672
598	Note that certain global state, such as signal state (and installed signal	673	Note that certain global state, such as signal state (and installed signal
599	handlers), will not be freed by this function, and related watchers (such	674	handlers), will not be freed by this function, and related watchers (such
600	as signal and child watchers) would need to be stopped manually.	675	as signal and child watchers) would need to be stopped manually.
601		676
602	In general it is not advisable to call this function except in the	677	This function is normally used on loop objects allocated by
603	rare occasion where you really need to free e.g. the signal handling	678	C<ev_loop_new>, but it can also be used on the default loop returned by
		679	C<ev_default_loop>, in which case it is not thread-safe.
		680
		681	Note that it is not advisable to call this function on the default loop
		682	except in the rare occasion where you really need to free its resources.
604	pipe fds. If you need dynamically allocated loops it is better to use	683	If you need dynamically allocated loops it is better to use C<ev_loop_new>
605	C<ev_loop_new> and C<ev_loop_destroy>.	684	and C<ev_loop_destroy>.
606		685
607	=item ev_loop_destroy (loop)	686	=item ev_loop_fork (loop)
608
609	Like C<ev_default_destroy>, but destroys an event loop created by an
610	earlier call to C<ev_loop_new>.
611
612	=item ev_default_fork ()
613		687
614	This function sets a flag that causes subsequent C<ev_run> iterations	688	This function sets a flag that causes subsequent C<ev_run> iterations
615	to reinitialise the kernel state for backends that have one. Despite the	689	to reinitialise the kernel state for backends that have one. Despite
616	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
617	the child process (or both child and parent, but that again makes little	691	watchers (except inside an C<ev_prepare> callback), but it makes most
618	sense). You I<must> call it in the child before using any of the libev	692	sense after forking, in the child process. You I<must> call it (or use
619	functions, and it will only take effect at the next C<ev_run> iteration.	693	C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>.
620		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
621	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
622	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
623	because some kernel interfaces *cough* I<kqueue> *cough* do funny things	700	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
624	during fork.	701	during fork.
625		702
626	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
…		…
629	call it at all (in fact, C<epoll> is so badly broken that it makes a	706	call it at all (in fact, C<epoll> is so badly broken that it makes a
630	difference, but libev will usually detect this case on its own and do a	707	difference, but libev will usually detect this case on its own and do a
631	costly reset of the backend).	708	costly reset of the backend).
632		709
633	The function itself is quite fast and it's usually not a problem to call	710	The function itself is quite fast and it's usually not a problem to call
634	it just in case after a fork. To make this easy, the function will fit in	711	it just in case after a fork.
635	quite nicely into a call to C<pthread_atfork>:
636		712
		713	Example: Automate calling C<ev_loop_fork> on the default loop when
		714	using pthreads.
		715
		716	static void
		717	post_fork_child (void)
		718	{
		719	ev_loop_fork (EV_DEFAULT);
		720	}
		721
		722	...
637	pthread_atfork (0, 0, ev_default_fork);	723	pthread_atfork (0, 0, post_fork_child);
638
639	=item ev_loop_fork (loop)
640
641	Like C<ev_default_fork>, but acts on an event loop created by
642	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
643	after fork that you want to re-use in the child, and how you keep track of
644	them is entirely your own problem.
645		724
646	=item int ev_is_default_loop (loop)	725	=item int ev_is_default_loop (loop)
647		726
648	Returns true when the given loop is, in fact, the default loop, and false	727	Returns true when the given loop is, in fact, the default loop, and false
649	otherwise.	728	otherwise.
…		…
660	prepare and check phases.	739	prepare and check phases.
661		740
662	=item unsigned int ev_depth (loop)	741	=item unsigned int ev_depth (loop)
663		742
664	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
665	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.
666		745
667	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
668	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),
669	in which case it is higher.	748	in which case it is higher.
670		749
671	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread	750	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
672	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
673	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.
674		754
675	=item unsigned int ev_backend (loop)	755	=item unsigned int ev_backend (loop)
676		756
677	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
678	use.	758	use.
…		…
693		773
694	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
695	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
696	the current time is a good idea.	776	the current time is a good idea.
697		777
698	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.
699		779
700	=item ev_suspend (loop)	780	=item ev_suspend (loop)
701		781
702	=item ev_resume (loop)	782	=item ev_resume (loop)
703		783
…		…
721	without a previous call to C<ev_suspend>.	801	without a previous call to C<ev_suspend>.
722		802
723	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
724	event loop time (see C<ev_now_update>).	804	event loop time (see C<ev_now_update>).
725		805
726	=item ev_run (loop, int flags)	806	=item bool ev_run (loop, int flags)
727		807
728	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
729	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
730	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
731	the watcher callbacks, an then repeat the whole process indefinitely: This	811	the watcher callbacks, and then repeat the whole process indefinitely: This
732	is why event loops are called I<loops>.	812	is why event loops are called I<loops>.
733		813
734	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
735	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
736	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").
737		821
738	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
739	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
740	finished (especially in interactive programs), but having a program	824	finished (especially in interactive programs), but having a program
741	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
742	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
743	beauty.	827	beauty.
744		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
745	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
746	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
747	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
748	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
749	events while doing lengthy calculations, to keep the program responsive.	838	events while doing lengthy calculations, to keep the program responsive.
…		…
758	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
759	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
760	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
761	usually a better approach for this kind of thing.	850	usually a better approach for this kind of thing.
762		851
763	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):
764		855
765	- Increment loop depth.	856	- Increment loop depth.
766	- Reset the ev_break status.	857	- Reset the ev_break status.
767	- Before the first iteration, call any pending watchers.	858	- Before the first iteration, call any pending watchers.
768	LOOP:	859	LOOP:
…		…
801	anymore.	892	anymore.
802		893
803	... queue jobs here, make sure they register event watchers as long	894	... queue jobs here, make sure they register event watchers as long
804	... 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..)
805	ev_run (my_loop, 0);	896	ev_run (my_loop, 0);
806	... jobs done or somebody called unloop. yeah!	897	... jobs done or somebody called break. yeah!
807		898
808	=item ev_break (loop, how)	899	=item ev_break (loop, how)
809		900
810	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
811	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
812	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
813	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.
814		905
815	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>.
816		907
817	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.
818		910
819	=item ev_ref (loop)	911	=item ev_ref (loop)
820		912
821	=item ev_unref (loop)	913	=item ev_unref (loop)
822		914
…		…
843	running when nothing else is active.	935	running when nothing else is active.
844		936
845	ev_signal exitsig;	937	ev_signal exitsig;
846	ev_signal_init (&exitsig, sig_cb, SIGINT);	938	ev_signal_init (&exitsig, sig_cb, SIGINT);
847	ev_signal_start (loop, &exitsig);	939	ev_signal_start (loop, &exitsig);
848	evf_unref (loop);	940	ev_unref (loop);
849		941
850	Example: For some weird reason, unregister the above signal handler again.	942	Example: For some weird reason, unregister the above signal handler again.
851		943
852	ev_ref (loop);	944	ev_ref (loop);
853	ev_signal_stop (loop, &exitsig);	945	ev_signal_stop (loop, &exitsig);
…		…
873	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.
874		966
875	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
876	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,
877	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
878	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
879	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
880	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
881	once per this interval, on average.	973	once per this interval, on average (as long as the host time resolution is
		974	good enough).
882		975
883	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
884	to spend more time collecting timeouts, at the expense of increased	977	to spend more time collecting timeouts, at the expense of increased
885	latency/jitter/inexactness (the watcher callback will be called	978	latency/jitter/inexactness (the watcher callback will be called
886	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
…		…
932	invoke the actual watchers inside another context (another thread etc.).	1025	invoke the actual watchers inside another context (another thread etc.).
933		1026
934	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
935	callback.	1028	callback.
936		1029
937	=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 ())
938		1031
939	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
940	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
941	each call to a libev function.	1034	each call to a libev function.
942		1035
943	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
944	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
945	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
946	I<release> and I<acquire> callbacks on the loop.	1039	I<release> and I<acquire> callbacks on the loop.
947		1040
948	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
949	suspended waiting for new events, and C<acquire> is called just	1042	suspended waiting for new events, and C<acquire> is called just
950	afterwards.	1043	afterwards.
…		…
965	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
966	document.	1059	document.
967		1060
968	=item ev_set_userdata (loop, void *data)	1061	=item ev_set_userdata (loop, void *data)
969		1062
970	=item ev_userdata (loop)	1063	=item void *ev_userdata (loop)
971		1064
972	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
973	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
974	C<0.>	1067	C<0>.
975		1068
976	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,
977	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
978	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
979	any other purpose as well.	1072	any other purpose as well.
…		…
1090		1183
1091	=item C<EV_PREPARE>	1184	=item C<EV_PREPARE>
1092		1185
1093	=item C<EV_CHECK>	1186	=item C<EV_CHECK>
1094		1187
1095	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
1096	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)
1097	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
1098	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
1099	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
1100	(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
1101	C<ev_run> from blocking).	1199	blocking).
1102		1200
1103	=item C<EV_EMBED>	1201	=item C<EV_EMBED>
1104		1202
1105	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.
1106		1204
1107	=item C<EV_FORK>	1205	=item C<EV_FORK>
1108		1206
1109	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
1110	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>).
1111		1213
1112	=item C<EV_ASYNC>	1214	=item C<EV_ASYNC>
1113		1215
1114	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>).
1115		1217
…		…
1137	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
1138	thing, so beware.	1240	thing, so beware.
1139		1241
1140	=back	1242	=back
1141		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
1142	=head2 WATCHER STATES	1398	=head2 WATCHER STATES
1143		1399
1144	There are various watcher states mentioned throughout this manual -	1400	There are various watcher states mentioned throughout this manual -
1145	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
1146	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
1147	rules might look complicated, they usually do "the right thing".	1403	rules might look complicated, they usually do "the right thing".
1148		1404
1149	=over 4	1405	=over 4
1150		1406
1151	=item initialiased	1407	=item initialised
1152		1408
1153	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
1154	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
1155	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.
1156		1412
1157	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
1158	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.
1159		1417
1160	=item started/running/active	1418	=item started/running/active
1161		1419
1162	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
1163	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
…		…
1191	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
1192	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
1193	freeing it is often a good idea.	1451	freeing it is often a good idea.
1194		1452
1195	While stopped (and not pending) the watcher is essentially in the	1453	While stopped (and not pending) the watcher is essentially in the
1196	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
1197	you wish.	1455	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1456	it again).
1198		1457
1199	=back	1458	=back
1200
1201	=head2 GENERIC WATCHER FUNCTIONS
1202
1203	=over 4
1204
1205	=item C<ev_init> (ev_TYPE *watcher, callback)
1206
1207	This macro initialises the generic portion of a watcher. The contents
1208	of the watcher object can be arbitrary (so C<malloc> will do). Only
1209	the generic parts of the watcher are initialised, you I<need> to call
1210	the type-specific C<ev_TYPE_set> macro afterwards to initialise the
1211	type-specific parts. For each type there is also a C<ev_TYPE_init> macro
1212	which rolls both calls into one.
1213
1214	You can reinitialise a watcher at any time as long as it has been stopped
1215	(or never started) and there are no pending events outstanding.
1216
1217	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
1218	int revents)>.
1219
1220	Example: Initialise an C<ev_io> watcher in two steps.
1221
1222	ev_io w;
1223	ev_init (&w, my_cb);
1224	ev_io_set (&w, STDIN_FILENO, EV_READ);
1225
1226	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
1227
1228	This macro initialises the type-specific parts of a watcher. You need to
1229	call C<ev_init> at least once before you call this macro, but you can
1230	call C<ev_TYPE_set> any number of times. You must not, however, call this
1231	macro on a watcher that is active (it can be pending, however, which is a
1232	difference to the C<ev_init> macro).
1233
1234	Although some watcher types do not have type-specific arguments
1235	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
1236
1237	See C<ev_init>, above, for an example.
1238
1239	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
1240
1241	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
1242	calls into a single call. This is the most convenient method to initialise
1243	a watcher. The same limitations apply, of course.
1244
1245	Example: Initialise and set an C<ev_io> watcher in one step.
1246
1247	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1248
1249	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1250
1251	Starts (activates) the given watcher. Only active watchers will receive
1252	events. If the watcher is already active nothing will happen.
1253
1254	Example: Start the C<ev_io> watcher that is being abused as example in this
1255	whole section.
1256
1257	ev_io_start (EV_DEFAULT_UC, &w);
1258
1259	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1260
1261	Stops the given watcher if active, and clears the pending status (whether
1262	the watcher was active or not).
1263
1264	It is possible that stopped watchers are pending - for example,
1265	non-repeating timers are being stopped when they become pending - but
1266	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
1267	pending. If you want to free or reuse the memory used by the watcher it is
1268	therefore a good idea to always call its C<ev_TYPE_stop> function.
1269
1270	=item bool ev_is_active (ev_TYPE *watcher)
1271
1272	Returns a true value iff the watcher is active (i.e. it has been started
1273	and not yet been stopped). As long as a watcher is active you must not modify
1274	it.
1275
1276	=item bool ev_is_pending (ev_TYPE *watcher)
1277
1278	Returns a true value iff the watcher is pending, (i.e. it has outstanding
1279	events but its callback has not yet been invoked). As long as a watcher
1280	is pending (but not active) you must not call an init function on it (but
1281	C<ev_TYPE_set> is safe), you must not change its priority, and you must
1282	make sure the watcher is available to libev (e.g. you cannot C<free ()>
1283	it).
1284
1285	=item callback ev_cb (ev_TYPE *watcher)
1286
1287	Returns the callback currently set on the watcher.
1288
1289	=item ev_cb_set (ev_TYPE *watcher, callback)
1290
1291	Change the callback. You can change the callback at virtually any time
1292	(modulo threads).
1293
1294	=item ev_set_priority (ev_TYPE *watcher, int priority)
1295
1296	=item int ev_priority (ev_TYPE *watcher)
1297
1298	Set and query the priority of the watcher. The priority is a small
1299	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1300	(default: C<-2>). Pending watchers with higher priority will be invoked
1301	before watchers with lower priority, but priority will not keep watchers
1302	from being executed (except for C<ev_idle> watchers).
1303
1304	If you need to suppress invocation when higher priority events are pending
1305	you need to look at C<ev_idle> watchers, which provide this functionality.
1306
1307	You I<must not> change the priority of a watcher as long as it is active or
1308	pending.
1309
1310	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1311	fine, as long as you do not mind that the priority value you query might
1312	or might not have been clamped to the valid range.
1313
1314	The default priority used by watchers when no priority has been set is
1315	always C<0>, which is supposed to not be too high and not be too low :).
1316
1317	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1318	priorities.
1319
1320	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1321
1322	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1323	C<loop> nor C<revents> need to be valid as long as the watcher callback
1324	can deal with that fact, as both are simply passed through to the
1325	callback.
1326
1327	=item int ev_clear_pending (loop, ev_TYPE *watcher)
1328
1329	If the watcher is pending, this function clears its pending status and
1330	returns its C<revents> bitset (as if its callback was invoked). If the
1331	watcher isn't pending it does nothing and returns C<0>.
1332
1333	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1334	callback to be invoked, which can be accomplished with this function.
1335
1336	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
1337
1338	Feeds the given event set into the event loop, as if the specified event
1339	had happened for the specified watcher (which must be a pointer to an
1340	initialised but not necessarily started event watcher). Obviously you must
1341	not free the watcher as long as it has pending events.
1342
1343	Stopping the watcher, letting libev invoke it, or calling
1344	C<ev_clear_pending> will clear the pending event, even if the watcher was
1345	not started in the first place.
1346
1347	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1348	functions that do not need a watcher.
1349
1350	=back
1351
1352
1353	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1354
1355	Each watcher has, by default, a member C<void *data> that you can change
1356	and read at any time: libev will completely ignore it. This can be used
1357	to associate arbitrary data with your watcher. If you need more data and
1358	don't want to allocate memory and store a pointer to it in that data
1359	member, you can also "subclass" the watcher type and provide your own
1360	data:
1361
1362	struct my_io
1363	{
1364	ev_io io;
1365	int otherfd;
1366	void *somedata;
1367	struct whatever *mostinteresting;
1368	};
1369
1370	...
1371	struct my_io w;
1372	ev_io_init (&w.io, my_cb, fd, EV_READ);
1373
1374	And since your callback will be called with a pointer to the watcher, you
1375	can cast it back to your own type:
1376
1377	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1378	{
1379	struct my_io *w = (struct my_io *)w_;
1380	...
1381	}
1382
1383	More interesting and less C-conformant ways of casting your callback type
1384	instead have been omitted.
1385
1386	Another common scenario is to use some data structure with multiple
1387	embedded watchers:
1388
1389	struct my_biggy
1390	{
1391	int some_data;
1392	ev_timer t1;
1393	ev_timer t2;
1394	}
1395
1396	In this case getting the pointer to C<my_biggy> is a bit more
1397	complicated: Either you store the address of your C<my_biggy> struct
1398	in the C<data> member of the watcher (for woozies), or you need to use
1399	some pointer arithmetic using C<offsetof> inside your watchers (for real
1400	programmers):
1401
1402	#include <stddef.h>
1403
1404	static void
1405	t1_cb (EV_P_ ev_timer *w, int revents)
1406	{
1407	struct my_biggy big = (struct my_biggy *)
1408	(((char *)w) - offsetof (struct my_biggy, t1));
1409	}
1410
1411	static void
1412	t2_cb (EV_P_ ev_timer *w, int revents)
1413	{
1414	struct my_biggy big = (struct my_biggy *)
1415	(((char *)w) - offsetof (struct my_biggy, t2));
1416	}
1417		1459
1418	=head2 WATCHER PRIORITY MODELS	1460	=head2 WATCHER PRIORITY MODELS
1419		1461
1420	Many event loops support I<watcher priorities>, which are usually small	1462	Many event loops support I<watcher priorities>, which are usually small
1421	integers that influence the ordering of event callback invocation	1463	integers that influence the ordering of event callback invocation
…		…
1548	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
1549	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
1550	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
1551	required if you know what you are doing).	1593	required if you know what you are doing).
1552		1594
1553	If you cannot use non-blocking mode, then force the use of a
1554	known-to-be-good backend (at the time of this writing, this includes only
1555	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1556	descriptors for which non-blocking operation makes no sense (such as
1557	files) - libev doesn't guarantee any specific behaviour in that case.
1558
1559	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
1560	receive "spurious" readiness notifications, that is your callback might	1596	receive "spurious" readiness notifications, that is, your callback might
1561	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
1562	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
1563	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
1564	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
1565	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1566	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1601	preferable to a program hanging until some data arrives.
1567		1602
1568	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
1569	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
1570	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
1571	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
1572	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
1573	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
1574	indefinitely.	1609	indefinitely.
1575		1610
1576	But really, best use non-blocking mode.	1611	But really, best use non-blocking mode.
1577		1612
…		…
1605		1640
1606	There is no workaround possible except not registering events	1641	There is no workaround possible except not registering events
1607	for potentially C<dup ()>'ed file descriptors, or to resort to	1642	for potentially C<dup ()>'ed file descriptors, or to resort to
1608	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1643	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1609		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
1610	=head3 The special problem of fork	1678	=head3 The special problem of fork
1611		1679
1612	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
1613	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
1614	it in the child.	1682	it in the child if you want to continue to use it in the child.
1615		1683
1616	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
1617	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
1618	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1686	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1619	C<EVBACKEND_POLL>.
1620		1687
1621	=head3 The special problem of SIGPIPE	1688	=head3 The special problem of SIGPIPE
1622		1689
1623	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>:
1624	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
…		…
1722	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1789	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1723	monotonic clock option helps a lot here).	1790	monotonic clock option helps a lot here).
1724		1791
1725	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
1726	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
1727	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
1728	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
1729	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
1730	no longer true when a callback calls C<ev_run> recursively).	1798	longer true when a callback calls C<ev_run> recursively).
1731		1799
1732	=head3 Be smart about timeouts	1800	=head3 Be smart about timeouts
1733		1801
1734	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
1735	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,
…		…
1810		1878
1811	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,
1812	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
1813	within the callback:	1881	within the callback:
1814		1882
		1883	ev_tstamp timeout = 60.;
1815	ev_tstamp last_activity; // time of last activity	1884	ev_tstamp last_activity; // time of last activity
		1885	ev_timer timer;
1816		1886
1817	static void	1887	static void
1818	callback (EV_P_ ev_timer *w, int revents)	1888	callback (EV_P_ ev_timer *w, int revents)
1819	{	1889	{
1820	ev_tstamp now = ev_now (EV_A);	1890	// calculate when the timeout would happen
1821	ev_tstamp timeout = last_activity + 60.;	1891	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1822		1892
1823	// if last_activity + 60. is older than now, we did time out	1893	// if negative, it means we the timeout already occurred
1824	if (timeout < now)	1894	if (after < 0.)
1825	{	1895	{
1826	// timeout occurred, take action	1896	// timeout occurred, take action
1827	}	1897	}
1828	else	1898	else
1829	{	1899	{
1830	// callback was invoked, but there was some activity, re-arm	1900	// callback was invoked, but there was some recent
1831	// the watcher to fire in last_activity + 60, which is	1901	// activity. simply restart the timer to time out
1832	// guaranteed to be in the future, so "again" is positive:	1902	// after "after" seconds, which is the earliest time
1833	w->repeat = timeout - now;	1903	// the timeout can occur.
		1904	ev_timer_set (w, after, 0.);
1834	ev_timer_again (EV_A_ w);	1905	ev_timer_start (EV_A_ w);
1835	}	1906	}
1836	}	1907	}
1837		1908
1838	To summarise the callback: first calculate the real timeout (defined	1909	To summarise the callback: first calculate in how many seconds the
1839	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,
1840	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
1841	the callback was invoked too early (C<timeout> is in the future), so	1912	(EV_A)> from that).
1842	re-schedule the timer to fire at that future time, to see if maybe we have
1843	a timeout then.
1844		1913
1845	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
1846	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.
1847		1923
1848	This scheme causes more callback invocations (about one every 60 seconds	1924	This scheme causes more callback invocations (about one every 60 seconds
1849	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
1850	libev to change the timeout.	1926	libev to change the timeout.
1851		1927
1852	To start the timer, simply initialise the watcher and set C<last_activity>	1928	To start the machinery, simply initialise the watcher and set
1853	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
1854	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:
1855		1932
		1933	last_activity = ev_now (EV_A);
1856	ev_init (timer, callback);	1934	ev_init (&timer, callback);
1857	last_activity = ev_now (loop);	1935	callback (EV_A_ &timer, 0);
1858	callback (loop, timer, EV_TIMER);
1859		1936
1860	And when there is some activity, simply store the current time in	1937	When there is some activity, simply store the current time in
1861	C<last_activity>, no libev calls at all:	1938	C<last_activity>, no libev calls at all:
1862		1939
		1940	if (activity detected)
1863	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);
1864		1950
1865	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
1866	time-out is unlikely to be triggered, much more efficient.	1952	time-out is unlikely to be triggered, much more efficient.
1867
1868	Changing the timeout is trivial as well (if it isn't hard-coded in the
1869	callback :) - just change the timeout and invoke the callback, which will
1870	fix things for you.
1871		1953
1872	=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.
1873		1955
1874	If there is not one request, but many thousands (millions...), all	1956	If there is not one request, but many thousands (millions...), all
1875	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
…		…
1902	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
1903	rather complicated, but extremely efficient, something that really pays	1985	rather complicated, but extremely efficient, something that really pays
1904	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
1905	overkill :)	1987	overkill :)
1906		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
1907	=head3 The special problem of time updates	2026	=head3 The special problem of time updates
1908		2027
1909	Establishing the current time is a costly operation (it usually takes at	2028	Establishing the current time is a costly operation (it usually takes
1910	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
1911	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
1912	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
1913	lots of events in one iteration.	2032	lots of events in one iteration.
1914		2033
1915	The relative timeouts are calculated relative to the C<ev_now ()>	2034	The relative timeouts are calculated relative to the C<ev_now ()>
1916	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
1917	of the event triggering whatever timeout you are modifying/starting. If	2036	of the event triggering whatever timeout you are modifying/starting. If
1918	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
1919	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:
1920		2040
1921	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2041	ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.);
1922		2042
1923	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
1924	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
1925	()>.	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.
1926		2080
1927	=head3 The special problems of suspended animation	2081	=head3 The special problems of suspended animation
1928		2082
1929	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
1930	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?
…		…
1960		2114
1961	=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)
1962		2116
1963	=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)
1964		2118
1965	Configure the timer to trigger after C<after> seconds. If C<repeat>	2119	Configure the timer to trigger after C<after> seconds (fractional and
1966	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
1967	reached. If it is positive, then the timer will automatically be	2121	automatically be stopped once the timeout is reached. If it is positive,
1968	configured to trigger again C<repeat> seconds later, again, and again,	2122	then the timer will automatically be configured to trigger again C<repeat>
1969	until stopped manually.	2123	seconds later, again, and again, until stopped manually.
1970		2124
1971	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
1972	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
1973	trigger at exactly 10 second intervals. If, however, your program cannot	2127	trigger at exactly 10 second intervals. If, however, your program cannot
1974	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
1975	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.
1976		2130
1977	=item ev_timer_again (loop, ev_timer *)	2131	=item ev_timer_again (loop, ev_timer *)
1978		2132
1979	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
1980	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>.
1981		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
1982	If the timer is pending, its pending status is cleared.	2142	=item If the timer is pending, the pending status is always cleared.
1983		2143
1984	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).
1985		2146
1986	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
1987	C<repeat> value), or reset the running timer to the C<repeat> value.	2148	and start the timer, if necessary.
1988		2149
		2150	=back
		2151
1989	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
1990	usage example.	2153	usage example.
1991		2154
1992	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)	2155	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1993		2156
1994	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,
…		…
2047	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
2048	(and unfortunately a bit complex).	2211	(and unfortunately a bit complex).
2049		2212
2050	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
2051	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
2052	(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
2053	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
2054	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
2055	wrist-watch).	2218	wrist-watch).
2056		2219
2057	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
…		…
2114		2277
2115	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
2116	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
2117	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.
2118		2281
2119	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
2120	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
2121	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.
2122		2288
2123	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
2124	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
2125	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
2126	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).
…		…
2234		2400
2235	ev_periodic hourly_tick;	2401	ev_periodic hourly_tick;
2236	ev_periodic_init (&hourly_tick, clock_cb,	2402	ev_periodic_init (&hourly_tick, clock_cb,
2237	fmod (ev_now (loop), 3600.), 3600., 0);	2403	fmod (ev_now (loop), 3600.), 3600., 0);
2238	ev_periodic_start (loop, &hourly_tick);	2404	ev_periodic_start (loop, &hourly_tick);
2239		2405
2240		2406
2241	=head2 C<ev_signal> - signal me when a signal gets signalled!	2407	=head2 C<ev_signal> - signal me when a signal gets signalled!
2242		2408
2243	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
2244	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
2245	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
2246	normal event processing, like any other event.	2412	normal event processing, like any other event.
2247		2413
2248	If you want signals to be delivered truly asynchronously, just use	2414	If you want signals to be delivered truly asynchronously, just use
2249	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
2250	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
…		…
2254	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
2255	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
2256	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
2257	the moment, C<SIGCHLD> is permanently tied to the default loop.	2423	the moment, C<SIGCHLD> is permanently tied to the default loop.
2258		2424
2259	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
2260	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
2261	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.
2262		2428
2263	If possible and supported, libev will install its handlers with	2429	If possible and supported, libev will install its handlers with
2264	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should	2430	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
2265	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
2266	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
…		…
2269	=head3 The special problem of inheritance over fork/execve/pthread_create	2435	=head3 The special problem of inheritance over fork/execve/pthread_create
2270		2436
2271	Both the signal mask (C<sigprocmask>) and the signal disposition	2437	Both the signal mask (C<sigprocmask>) and the signal disposition
2272	(C<sigaction>) are unspecified after starting a signal watcher (and after	2438	(C<sigaction>) are unspecified after starting a signal watcher (and after
2273	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,
2274	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>).
2275		2442
2276	While this does not matter for the signal disposition (libev never	2443	While this does not matter for the signal disposition (libev never
2277	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
2278	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
2279	certain signals to be blocked.	2446	certain signals to be blocked.
…		…
2292	I<has> to modify the signal mask, at least temporarily.	2459	I<has> to modify the signal mask, at least temporarily.
2293		2460
2294	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
2295	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
2296	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>.
2297		2478
2298	=head3 Watcher-Specific Functions and Data Members	2479	=head3 Watcher-Specific Functions and Data Members
2299		2480
2300	=over 4	2481	=over 4
2301		2482
…		…
2436		2617
2437	=head2 C<ev_stat> - did the file attributes just change?	2618	=head2 C<ev_stat> - did the file attributes just change?
2438		2619
2439	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
2440	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)
2441	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
2442	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.
2443		2625
2444	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
2445	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
2446	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
2447	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
…		…
2677	Apart from keeping your process non-blocking (which is a useful	2859	Apart from keeping your process non-blocking (which is a useful
2678	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
2679	"pseudo-background processing", or delay processing stuff to after the	2861	"pseudo-background processing", or delay processing stuff to after the
2680	event loop has handled all outstanding events.	2862	event loop has handled all outstanding events.
2681		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
2682	=head3 Watcher-Specific Functions and Data Members	2878	=head3 Watcher-Specific Functions and Data Members
2683		2879
2684	=over 4	2880	=over 4
2685		2881
2686	=item ev_idle_init (ev_idle *, callback)	2882	=item ev_idle_init (ev_idle *, callback)
…		…
2697	callback, free it. Also, use no error checking, as usual.	2893	callback, free it. Also, use no error checking, as usual.
2698		2894
2699	static void	2895	static void
2700	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	2896	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2701	{	2897	{
		2898	// stop the watcher
		2899	ev_idle_stop (loop, w);
		2900
		2901	// now we can free it
2702	free (w);	2902	free (w);
		2903
2703	// now do something you wanted to do when the program has	2904	// now do something you wanted to do when the program has
2704	// no longer anything immediate to do.	2905	// no longer anything immediate to do.
2705	}	2906	}
2706		2907
2707	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2908	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
…		…
2709	ev_idle_start (loop, idle_watcher);	2910	ev_idle_start (loop, idle_watcher);
2710		2911
2711		2912
2712	=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!
2713		2914
2714	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:
2715	prepare watchers get invoked before the process blocks and check watchers	2916	prepare watchers get invoked before the process blocks and check watchers
2716	afterwards.	2917	afterwards.
2717		2918
2718	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
2719	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
2720	watchers. Other loops than the current one are fine, however. The	2921	C<ev_check> watchers. Other loops than the current one are fine,
2721	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
2722	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
2723	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
2724	called in pairs bracketing the blocking call.	2925	kind they will always be called in pairs bracketing the blocking call.
2725		2926
2726	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
2727	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
2728	variable changes, implement your own watchers, integrate net-snmp or a	2929	variable changes, implement your own watchers, integrate net-snmp or a
2729	coroutine library and lots more. They are also occasionally useful if	2930	coroutine library and lots more. They are also occasionally useful if
…		…
2747	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
2748	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
2749	loop from blocking if lower-priority coroutines are active, thus mapping	2950	loop from blocking if lower-priority coroutines are active, thus mapping
2750	low-priority coroutines to idle/background tasks).	2951	low-priority coroutines to idle/background tasks).
2751		2952
2752	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
2753	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
2754	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).
2755		2957
2756	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
2757	activate ("feed") events into libev. While libev fully supports this, they	2959	activate ("feed") events into libev. While libev fully supports this, they
2758	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
2759	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
2760	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
2761	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
2762	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.
2763		2984
2764	=head3 Watcher-Specific Functions and Data Members	2985	=head3 Watcher-Specific Functions and Data Members
2765		2986
2766	=over 4	2987	=over 4
2767		2988
…		…
2968		3189
2969	=over 4	3190	=over 4
2970		3191
2971	=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)
2972		3193
2973	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	3194	=item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)
2974		3195
2975	Configures the watcher to embed the given loop, which must be	3196	Configures the watcher to embed the given loop, which must be
2976	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
2977	invoked automatically, otherwise it is the responsibility of the callback	3198	invoked automatically, otherwise it is the responsibility of the callback
2978	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,
…		…
2999	used).	3220	used).
3000		3221
3001	struct ev_loop *loop_hi = ev_default_init (0);	3222	struct ev_loop *loop_hi = ev_default_init (0);
3002	struct ev_loop *loop_lo = 0;	3223	struct ev_loop *loop_lo = 0;
3003	ev_embed embed;	3224	ev_embed embed;
3004		3225
3005	// see if there is a chance of getting one that works	3226	// see if there is a chance of getting one that works
3006	// (remember that a flags value of 0 means autodetection)	3227	// (remember that a flags value of 0 means autodetection)
3007	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3228	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
3008	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3229	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
3009	: 0;	3230	: 0;
…		…
3023	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3244	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
3024		3245
3025	struct ev_loop *loop = ev_default_init (0);	3246	struct ev_loop *loop = ev_default_init (0);
3026	struct ev_loop *loop_socket = 0;	3247	struct ev_loop *loop_socket = 0;
3027	ev_embed embed;	3248	ev_embed embed;
3028		3249
3029	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3250	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
3030	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3251	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
3031	{	3252	{
3032	ev_embed_init (&embed, 0, loop_socket);	3253	ev_embed_init (&embed, 0, loop_socket);
3033	ev_embed_start (loop, &embed);	3254	ev_embed_start (loop, &embed);
…		…
3041		3262
3042	=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
3043		3264
3044	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
3045	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
3046	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
3047	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
3048	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
3049	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,
3050	handlers will be invoked, too, of course.	3271	of course.
3051		3272
3052	=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?
3053		3274
3054	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
3055	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
3056	sequence should be handled by libev without any problems.	3277	sequence should be handled by libev without any problems.
3057		3278
3058	This changes when the application actually wants to do event handling	3279	This changes when the application actually wants to do event handling
3059	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
…		…
3075	disadvantage of having to use multiple event loops (which do not support	3296	disadvantage of having to use multiple event loops (which do not support
3076	signal watchers).	3297	signal watchers).
3077		3298
3078	When this is not possible, or you want to use the default loop for	3299	When this is not possible, or you want to use the default loop for
3079	other reasons, then in the process that wants to start "fresh", call	3300	other reasons, then in the process that wants to start "fresh", call
3080	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3301	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
3081	the default loop will "orphan" (not stop) all registered watchers, so you	3302	Destroying the default loop will "orphan" (not stop) all registered
3082	have to be careful not to execute code that modifies those watchers. Note	3303	watchers, so you have to be careful not to execute code that modifies
3083	also that in that case, you have to re-register any signal watchers.	3304	those watchers. Note also that in that case, you have to re-register any
		3305	signal watchers.
3084		3306
3085	=head3 Watcher-Specific Functions and Data Members	3307	=head3 Watcher-Specific Functions and Data Members
3086		3308
3087	=over 4	3309	=over 4
3088		3310
3089	=item ev_fork_init (ev_signal *, callback)	3311	=item ev_fork_init (ev_fork *, callback)
3090		3312
3091	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
3092	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,
3093	believe me.	3315	really.
3094		3316
3095	=back	3317	=back
3096		3318
3097		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
3098	=head2 C<ev_async> - how to wake up an event loop	3360	=head2 C<ev_async> - how to wake up an event loop
3099		3361
3100	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
3101	asynchronous sources such as signal handlers (as opposed to multiple event	3363	asynchronous sources such as signal handlers (as opposed to multiple event
3102	loops - those are of course safe to use in different threads).	3364	loops - those are of course safe to use in different threads).
3103		3365
3104	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,
3105	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>
…		…
3107	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.
3108		3370
3109	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,
3110	too, are asynchronous in nature, and signals, too, will be compressed	3372	too, are asynchronous in nature, and signals, too, will be compressed
3111	(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
3112	C<ev_async_sent> calls).	3374	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
3113		3375	of "global async watchers" by using a watcher on an otherwise unused
3114	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,
3115	just the default loop.	3377	even without knowing which loop owns the signal.
3116		3378
3117	=head3 Queueing	3379	=head3 Queueing
3118		3380
3119	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
3120	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
…		…
3212	trust me.	3474	trust me.
3213		3475
3214	=item ev_async_send (loop, ev_async *)	3476	=item ev_async_send (loop, ev_async *)
3215		3477
3216	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
3217	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
3218	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,
3219	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
3220	section below on what exactly this means).	3484	embedding section below on what exactly this means).
3221		3485
3222	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
3223	compressed into a single callback invocation (another way to look at this	3487	compressed into a single callback invocation (another way to look at
3224	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
3225	reset when the event loop detects that).	3489	C<ev_async_send>, reset when the event loop detects that).
3226		3490
3227	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
3228	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
3229	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.
3230		3497
3231	=item bool = ev_async_pending (ev_async *)	3498	=item bool = ev_async_pending (ev_async *)
3232		3499
3233	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
3234	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
…		…
3251		3518
3252	There are some other functions of possible interest. Described. Here. Now.	3519	There are some other functions of possible interest. Described. Here. Now.
3253		3520
3254	=over 4	3521	=over 4
3255		3522
3256	=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)
3257		3524
3258	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
3259	callback on whichever event happens first and automatically stops both	3526	callback on whichever event happens first and automatically stops both
3260	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
3261	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
…		…
3289	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3556	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3290		3557
3291	=item ev_feed_fd_event (loop, int fd, int revents)	3558	=item ev_feed_fd_event (loop, int fd, int revents)
3292		3559
3293	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
3294	the given events it.	3561	the given events.
3295		3562
3296	=item ev_feed_signal_event (loop, int signum)	3563	=item ev_feed_signal_event (loop, int signum)
3297		3564
3298	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>,
3299	loop!).	3566	which is async-safe.
3300		3567
3301	=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.
3302		3919
3303		3920
3304	=head1 LIBEVENT EMULATION	3921	=head1 LIBEVENT EMULATION
3305		3922
3306	Libev offers a compatibility emulation layer for libevent. It cannot	3923	Libev offers a compatibility emulation layer for libevent. It cannot
3307	emulate the internals of libevent, so here are some usage hints:	3924	emulate the internals of libevent, so here are some usage hints:
3308		3925
3309	=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.
3310		3932
3311	=item * Use it by including <event.h>, as usual.	3933	=item * Use it by including <event.h>, as usual.
3312		3934
3313	=item * The following members are fully supported: ev_base, ev_callback,	3935	=item * The following members are fully supported: ev_base, ev_callback,
3314	ev_arg, ev_fd, ev_res, ev_events.	3936	ev_arg, ev_fd, ev_res, ev_events.
…		…
3320	=item * Priorities are not currently supported. Initialising priorities	3942	=item * Priorities are not currently supported. Initialising priorities
3321	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
3322	is an ev_pri field.	3944	is an ev_pri field.
3323		3945
3324	=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
3325	first base created (== the default loop) gets the signals.	3947	base that registered the signal gets the signals.
3326		3948
3327	=item * Other members are not supported.	3949	=item * Other members are not supported.
3328		3950
3329	=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
3330	to use the libev header file and library.	3952	to use the libev header file and library.
3331		3953
3332	=back	3954	=back
3333		3955
3334	=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
3335		3990
3336	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
3337	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
3338	the callback model to a model using method callbacks on objects.	3993	the callback model to a model using method callbacks on objects.
3339		3994
3340	To use it,	3995	To use it,
3341		3996
3342	#include <ev++.h>	3997	#include <ev++.h>
3343		3998
3344	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
3345	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
3346	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
…		…
3349	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++
3350	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
3351	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
3352	you disable C<EV_MULTIPLICITY> when embedding libev).	4007	you disable C<EV_MULTIPLICITY> when embedding libev).
3353		4008
3354	Currently, functions, and static and non-static member functions can be	4009	Currently, functions, static and non-static member functions and classes
3355	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
3356	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
3357	types of functors please contact the author (preferably after implementing	4012	you need support for other types of functors please contact the author
3358	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++.
3359		4018
3360	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:
3361		4020
3362	=over 4	4021	=over 4
3363		4022
…		…
3373	=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.
3374		4033
3375	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
3376	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>
3377	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
3378	defines by many implementations.	4037	defined by many implementations.
3379		4038
3380	All of those classes have these methods:	4039	All of those classes have these methods:
3381		4040
3382	=over 4	4041	=over 4
3383		4042
…		…
3445	void operator() (ev::io &w, int revents)	4104	void operator() (ev::io &w, int revents)
3446	{	4105	{
3447	...	4106	...
3448	}	4107	}
3449	}	4108	}
3450		4109
3451	myfunctor f;	4110	myfunctor f;
3452		4111
3453	ev::io w;	4112	ev::io w;
3454	w.set (&f);	4113	w.set (&f);
3455		4114
…		…
3473	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
3474	do this when the watcher is inactive (and not pending either).	4133	do this when the watcher is inactive (and not pending either).
3475		4134
3476	=item w->set ([arguments])	4135	=item w->set ([arguments])
3477		4136
3478	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>),
3479	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
3480	C counterpart, an active watcher gets automatically stopped and restarted	4139	must be called at least once. Unlike the C counterpart, an active watcher
3481	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.
3482		4145
3483	=item w->start ()	4146	=item w->start ()
3484		4147
3485	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
3486	constructor already stores the event loop.	4149	constructor already stores the event loop.
…		…
3516	watchers in the constructor.	4179	watchers in the constructor.
3517		4180
3518	class myclass	4181	class myclass
3519	{	4182	{
3520	ev::io io ; void io_cb (ev::io &w, int revents);	4183	ev::io io ; void io_cb (ev::io &w, int revents);
3521	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);	4184	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3522	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4185	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3523		4186
3524	myclass (int fd)	4187	myclass (int fd)
3525	{	4188	{
3526	io .set <myclass, &myclass::io_cb > (this);	4189	io .set <myclass, &myclass::io_cb > (this);
…		…
3577	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4240	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3578		4241
3579	=item D	4242	=item D
3580		4243
3581	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
3582	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>.
3583		4246
3584	=item Ocaml	4247	=item Ocaml
3585		4248
3586	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
3587	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4250	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
…		…
3590		4253
3591	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
3592	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
3593	L<http://github.com/brimworks/lua-ev>.	4256	L<http://github.com/brimworks/lua-ev>.
3594		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
3595	=back	4266	=back
3596		4267
3597		4268
3598	=head1 MACRO MAGIC	4269	=head1 MACRO MAGIC
3599		4270
…		…
3635	suitable for use with C<EV_A>.	4306	suitable for use with C<EV_A>.
3636		4307
3637	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4308	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3638		4309
3639	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
3640	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.
3641		4316
3642	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4317	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3643		4318
3644	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
3645	default loop has been initialised (C<UC> == unchecked). Their behaviour	4320	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3712	ev_vars.h	4387	ev_vars.h
3713	ev_wrap.h	4388	ev_wrap.h
3714		4389
3715	ev_win32.c required on win32 platforms only	4390	ev_win32.c required on win32 platforms only
3716		4391
3717	ev_select.c only when select backend is enabled (which is enabled by default)	4392	ev_select.c only when select backend is enabled
3718	ev_poll.c only when poll backend is enabled (disabled by default)	4393	ev_poll.c only when poll backend is enabled
3719	ev_epoll.c only when the epoll backend is enabled (disabled by default)	4394	ev_epoll.c only when the epoll backend is enabled
3720	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	4395	ev_kqueue.c only when the kqueue backend is enabled
3721	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
3722		4397
3723	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
3724	to compile this single file.	4399	to compile this single file.
3725		4400
3726	=head3 LIBEVENT COMPATIBILITY API	4401	=head3 LIBEVENT COMPATIBILITY API
…		…
3790	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
3791	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.
3792		4467
3793	In standalone mode, libev will still try to automatically deduce the	4468	In standalone mode, libev will still try to automatically deduce the
3794	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.
3795		4479
3796	=item EV_USE_MONOTONIC	4480	=item EV_USE_MONOTONIC
3797		4481
3798	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
3799	monotonic clock option at both compile time and runtime. Otherwise no	4483	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3884		4568
3885	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
3886	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
3887	file descriptors again. Note that the replacement function has to close	4571	file descriptors again. Note that the replacement function has to close
3888	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.
3889		4580
3890	=item EV_USE_POLL	4581	=item EV_USE_POLL
3891		4582
3892	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)
3893	backend. Otherwise it will be enabled on non-win32 platforms. It	4584	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3929	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
3930	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
3931	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
3932	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4623	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3933		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
3934	=item EV_ATOMIC_T	4639	=item EV_ATOMIC_T
3935		4640
3936	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
3937	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
3938	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
3939	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
3940	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.
3941		4647
3942	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>
3943	(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.
3944		4650
3945	=item EV_H (h)	4651	=item EV_H (h)
…		…
3972	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
3973	additional independent event loops. Otherwise there will be no support	4679	additional independent event loops. Otherwise there will be no support
3974	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
3975	argument. Instead, all functions act on the single default loop.	4681	argument. Instead, all functions act on the single default loop.
3976		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
3977	=item EV_MINPRI	4687	=item EV_MINPRI
3978		4688
3979	=item EV_MAXPRI	4689	=item EV_MAXPRI
3980		4690
3981	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
…		…
4017	#define EV_USE_POLL 1	4727	#define EV_USE_POLL 1
4018	#define EV_CHILD_ENABLE 1	4728	#define EV_CHILD_ENABLE 1
4019	#define EV_ASYNC_ENABLE 1	4729	#define EV_ASYNC_ENABLE 1
4020		4730
4021	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
4022	values:	4732	values (by default, all of these are enabled):
4023		4733
4024	=over 4	4734	=over 4
4025		4735
4026	=item C<1> - faster/larger code	4736	=item C<1> - faster/larger code
4027		4737
…		…
4031	code size by roughly 30% on amd64).	4741	code size by roughly 30% on amd64).
4032		4742
4033	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
4034	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
4035	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>).
4036		4749
4037	=item C<2> - faster/larger data structures	4750	=item C<2> - faster/larger data structures
4038		4751
4039	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
4040	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
4041	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
4042	runtime.	4755	runtime.
4043		4756
		4757	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4758	(e.g. gcc with C<-Os>).
		4759
4044	=item C<4> - full API configuration	4760	=item C<4> - full API configuration
4045		4761
4046	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
4047	enables multiplicity (C<EV_MULTIPLICITY>=1).	4763	enables multiplicity (C<EV_MULTIPLICITY>=1).
4048		4764
…		…
4078		4794
4079	With an intelligent-enough linker (gcc+binutils are intelligent enough	4795	With an intelligent-enough linker (gcc+binutils are intelligent enough
4080	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
4081	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
4082	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.
4083		4813
4084	=item EV_AVOID_STDIO	4814	=item EV_AVOID_STDIO
4085		4815
4086	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
4087	functions (printf, scanf, perror etc.). This will increase the code size	4817	functions (printf, scanf, perror etc.). This will increase the code size
…		…
4231	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:
4232		4962
4233	#include "ev_cpp.h"	4963	#include "ev_cpp.h"
4234	#include "ev.c"	4964	#include "ev.c"
4235		4965
4236	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4966	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4237		4967
4238	=head2 THREADS AND COROUTINES	4968	=head2 THREADS AND COROUTINES
4239		4969
4240	=head3 THREADS	4970	=head3 THREADS
4241		4971
…		…
4292	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
4293	watcher callback into the event loop interested in the signal.	5023	watcher callback into the event loop interested in the signal.
4294		5024
4295	=back	5025	=back
4296		5026
4297	=head4 THREAD LOCKING EXAMPLE	5027	See also L</THREAD LOCKING EXAMPLE>.
4298
4299	Here is a fictitious example of how to run an event loop in a different
4300	thread than where callbacks are being invoked and watchers are
4301	created/added/removed.
4302
4303	For a real-world example, see the C<EV::Loop::Async> perl module,
4304	which uses exactly this technique (which is suited for many high-level
4305	languages).
4306
4307	The example uses a pthread mutex to protect the loop data, a condition
4308	variable to wait for callback invocations, an async watcher to notify the
4309	event loop thread and an unspecified mechanism to wake up the main thread.
4310
4311	First, you need to associate some data with the event loop:
4312
4313	typedef struct {
4314	mutex_t lock; /* global loop lock */
4315	ev_async async_w;
4316	thread_t tid;
4317	cond_t invoke_cv;
4318	} userdata;
4319
4320	void prepare_loop (EV_P)
4321	{
4322	// for simplicity, we use a static userdata struct.
4323	static userdata u;
4324
4325	ev_async_init (&u->async_w, async_cb);
4326	ev_async_start (EV_A_ &u->async_w);
4327
4328	pthread_mutex_init (&u->lock, 0);
4329	pthread_cond_init (&u->invoke_cv, 0);
4330
4331	// now associate this with the loop
4332	ev_set_userdata (EV_A_ u);
4333	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4334	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4335
4336	// then create the thread running ev_loop
4337	pthread_create (&u->tid, 0, l_run, EV_A);
4338	}
4339
4340	The callback for the C<ev_async> watcher does nothing: the watcher is used
4341	solely to wake up the event loop so it takes notice of any new watchers
4342	that might have been added:
4343
4344	static void
4345	async_cb (EV_P_ ev_async *w, int revents)
4346	{
4347	// just used for the side effects
4348	}
4349
4350	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4351	protecting the loop data, respectively.
4352
4353	static void
4354	l_release (EV_P)
4355	{
4356	userdata *u = ev_userdata (EV_A);
4357	pthread_mutex_unlock (&u->lock);
4358	}
4359
4360	static void
4361	l_acquire (EV_P)
4362	{
4363	userdata *u = ev_userdata (EV_A);
4364	pthread_mutex_lock (&u->lock);
4365	}
4366
4367	The event loop thread first acquires the mutex, and then jumps straight
4368	into C<ev_run>:
4369
4370	void *
4371	l_run (void *thr_arg)
4372	{
4373	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4374
4375	l_acquire (EV_A);
4376	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4377	ev_run (EV_A_ 0);
4378	l_release (EV_A);
4379
4380	return 0;
4381	}
4382
4383	Instead of invoking all pending watchers, the C<l_invoke> callback will
4384	signal the main thread via some unspecified mechanism (signals? pipe
4385	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4386	have been called (in a while loop because a) spurious wakeups are possible
4387	and b) skipping inter-thread-communication when there are no pending
4388	watchers is very beneficial):
4389
4390	static void
4391	l_invoke (EV_P)
4392	{
4393	userdata *u = ev_userdata (EV_A);
4394
4395	while (ev_pending_count (EV_A))
4396	{
4397	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4398	pthread_cond_wait (&u->invoke_cv, &u->lock);
4399	}
4400	}
4401
4402	Now, whenever the main thread gets told to invoke pending watchers, it
4403	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4404	thread to continue:
4405
4406	static void
4407	real_invoke_pending (EV_P)
4408	{
4409	userdata *u = ev_userdata (EV_A);
4410
4411	pthread_mutex_lock (&u->lock);
4412	ev_invoke_pending (EV_A);
4413	pthread_cond_signal (&u->invoke_cv);
4414	pthread_mutex_unlock (&u->lock);
4415	}
4416
4417	Whenever you want to start/stop a watcher or do other modifications to an
4418	event loop, you will now have to lock:
4419
4420	ev_timer timeout_watcher;
4421	userdata *u = ev_userdata (EV_A);
4422
4423	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4424
4425	pthread_mutex_lock (&u->lock);
4426	ev_timer_start (EV_A_ &timeout_watcher);
4427	ev_async_send (EV_A_ &u->async_w);
4428	pthread_mutex_unlock (&u->lock);
4429
4430	Note that sending the C<ev_async> watcher is required because otherwise
4431	an event loop currently blocking in the kernel will have no knowledge
4432	about the newly added timer. By waking up the loop it will pick up any new
4433	watchers in the next event loop iteration.
4434		5028
4435	=head3 COROUTINES	5029	=head3 COROUTINES
4436		5030
4437	Libev is very accommodating to coroutines ("cooperative threads"):	5031	Libev is very accommodating to coroutines ("cooperative threads"):
4438	libev fully supports nesting calls to its functions from different	5032	libev fully supports nesting calls to its functions from different
…		…
4603	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
4604	model. Libev still offers limited functionality on this platform in	5198	model. Libev still offers limited functionality on this platform in
4605	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
4606	descriptors. This only applies when using Win32 natively, not when using	5200	descriptors. This only applies when using Win32 natively, not when using
4607	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,
4608	as every compielr comes with a slightly differently broken/incompatible	5202	as every compiler comes with a slightly differently broken/incompatible
4609	environment.	5203	environment.
4610		5204
4611	Lifting these limitations would basically require the full	5205	Lifting these limitations would basically require the full
4612	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,
4613	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
…		…
4707	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
4708	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
4709	callback: The watcher callbacks have different type signatures, but libev	5303	callback: The watcher callbacks have different type signatures, but libev
4710	calls them using an C<ev_watcher *> internally.	5304	calls them using an C<ev_watcher *> internally.
4711		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
4712	=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
4713		5317
4714	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
4715	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
4716	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
…		…
4724	thread" or will block signals process-wide, both behaviours would	5328	thread" or will block signals process-wide, both behaviours would
4725	be compatible with libev. Interaction between C<sigprocmask> and	5329	be compatible with libev. Interaction between C<sigprocmask> and
4726	C<pthread_sigmask> could complicate things, however.	5330	C<pthread_sigmask> could complicate things, however.
4727		5331
4728	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
4729	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
4730	well.	5334	thread as well.
4731		5335
4732	=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
4733		5337
4734	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
4735	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
…		…
4741		5345
4742	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
4743	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
4744	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
4745	(the design goal for libev). This requirement is overfulfilled by	5349	(the design goal for libev). This requirement is overfulfilled by
4746	implementations using IEEE 754, which is basically all existing ones. With	5350	implementations using IEEE 754, which is basically all existing ones.
		5351
4747	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).
4748		5356
4749	=back	5357	=back
4750		5358
4751	If you know of other additional requirements drop me a note.	5359	If you know of other additional requirements drop me a note.
4752		5360
…		…
4814	=item Processing ev_async_send: O(number_of_async_watchers)	5422	=item Processing ev_async_send: O(number_of_async_watchers)
4815		5423
4816	=item Processing signals: O(max_signal_number)	5424	=item Processing signals: O(max_signal_number)
4817		5425
4818	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>
4819	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
4820	involves iterating over all running async watchers or all signal numbers.	5429	running async watchers or all signal numbers.
4821		5430
4822	=back	5431	=back
4823		5432
4824		5433
4825	=head1 PORTING FROM LIBEV 3.X TO 4.X	5434	=head1 PORTING FROM LIBEV 3.X TO 4.X
4826		5435
4827	The major version 4 introduced some minor incompatible changes to the API.	5436	The major version 4 introduced some incompatible changes to the API.
4828		5437
4829	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
4830	compatibility, so most programs should still compile. Those might be	5439	for all changes, so most programs should still compile. The compatibility
4831	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.
4832		5442
4833	=over 4	5443	=over 4
		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
		5451	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5452
		5453	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5454
		5455	ev_loop_destroy (EV_DEFAULT_UC);
		5456	ev_loop_fork (EV_DEFAULT);
4834		5457
4835	=item function/symbol renames	5458	=item function/symbol renames
4836		5459
4837	A number of functions and symbols have been renamed:	5460	A number of functions and symbols have been renamed:
4838		5461
…		…
4857	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
4858	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
4859	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>
4860	typedef.	5483	typedef.
4861		5484
4862	=item C<EV_COMPAT3> backwards compatibility mechanism
4863
4864	The backward compatibility mechanism can be controlled by
4865	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
4866	section.
4867
4868	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>	5485	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
4869		5486
4870	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
4871	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile	5488	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
4872	and work, but the library code will of course be larger.	5489	and work, but the library code will of course be larger.
…		…
4879	=over 4	5496	=over 4
4880		5497
4881	=item active	5498	=item active
4882		5499
4883	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.
4884	See L<WATCHER STATES> for details.	5501	See L</WATCHER STATES> for details.
4885		5502
4886	=item application	5503	=item application
4887		5504
4888	In this document, an application is whatever is using libev.	5505	In this document, an application is whatever is using libev.
4889		5506
…		…
4925	watchers and events.	5542	watchers and events.
4926		5543
4927	=item pending	5544	=item pending
4928		5545
4929	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
4930	detected. See L<WATCHER STATES> for details.	5547	detected. See L</WATCHER STATES> for details.
4931		5548
4932	=item real time	5549	=item real time
4933		5550
4934	The physical time that is observed. It is apparently strictly monotonic :)	5551	The physical time that is observed. It is apparently strictly monotonic :)
4935		5552
4936	=item wall-clock time	5553	=item wall-clock time
4937		5554
4938	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
4939	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
4940	clock.	5557	clock.
4941		5558
4942	=item watcher	5559	=item watcher
4943		5560
4944	A data structure that describes interest in certain events. Watchers need	5561	A data structure that describes interest in certain events. Watchers need
…		…
4946		5563
4947	=back	5564	=back
4948		5565
4949	=head1 AUTHOR	5566	=head1 AUTHOR
4950		5567
4951	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.
4952		5570

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