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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
…		…
165		175
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 interetsing 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
…		…
193	as this indicates an incompatible change. Minor versions are usually	209	as this indicates an incompatible change. Minor versions are usually
194	compatible to older versions, so a larger minor version alone is usually	210	compatible to older versions, so a larger minor version alone is usually
195	not a problem.	211	not a problem.
196		212
197	Example: Make sure we haven't accidentally been linked against the wrong	213	Example: Make sure we haven't accidentally been linked against the wrong
198	version (note, however, that this will not detect ABI mismatches :).	214	version (note, however, that this will not detect other ABI mismatches,
		215	such as LFS or reentrancy).
199		216
200	assert (("libev version mismatch",	217	assert (("libev version mismatch",
201	ev_version_major () == EV_VERSION_MAJOR	218	ev_version_major () == EV_VERSION_MAJOR
202	&& ev_version_minor () >= EV_VERSION_MINOR));	219	&& ev_version_minor () >= EV_VERSION_MINOR));
203		220
…		…
225	probe for if you specify no backends explicitly.	242	probe for if you specify no backends explicitly.
226		243
227	=item unsigned int ev_embeddable_backends ()	244	=item unsigned int ev_embeddable_backends ()
228		245
229	Returns the set of backends that are embeddable in other event loops. This	246	Returns the set of backends that are embeddable in other event loops. This
230	is the theoretical, all-platform, value. To find which backends	247	value is platform-specific but can include backends not available on the
231	might be supported on the current system, you would need to look at	248	current system. To find which embeddable backends might be supported on
232	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	249	the current system, you would need to look at C<ev_embeddable_backends ()
233	recommended ones.	250	& ev_supported_backends ()>, likewise for recommended ones.
234		251
235	See the description of C<ev_embed> watchers for more info.	252	See the description of C<ev_embed> watchers for more info.
236		253
237	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	254	=item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())
238		255
239	Sets the allocation function to use (the prototype is similar - the	256	Sets the allocation function to use (the prototype is similar - the
240	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
241	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
242	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
…		…
268	}	285	}
269		286
270	...	287	...
271	ev_set_allocator (persistent_realloc);	288	ev_set_allocator (persistent_realloc);
272		289
273	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	290	=item ev_set_syserr_cb (void (*cb)(const char *msg) throw ())
274		291
275	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
276	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
277	indicating the system call or subsystem causing the problem. If this	294	indicating the system call or subsystem causing the problem. If this
278	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
…		…
290	}	307	}
291		308
292	...	309	...
293	ev_set_syserr_cb (fatal_error);	310	ev_set_syserr_cb (fatal_error);
294		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
295	=back	325	=back
296		326
297	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	327	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
298		328
299	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
300	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
301	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).
302		332
303	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
304	supports signals and child events, and dynamically created event loops	334	supports child process events, and dynamically created event loops which
305	which do not.	335	do not.
306		336
307	=over 4	337	=over 4
308		338
309	=item struct ev_loop *ev_default_loop (unsigned int flags)	339	=item struct ev_loop *ev_default_loop (unsigned int flags)
310		340
311	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
312	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
313	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
314	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".
315		351
316	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
317	function.	353	function (or via the C<EV_DEFAULT> macro).
318		354
319	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
320	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
321	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).
322		359
323	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,
324	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
325	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
326	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
327	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	364	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
328	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.
329		384
330	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
331	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>).
332		387
333	The following flags are supported:	388	The following flags are supported:
…		…
343		398
344	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
345	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
346	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	401	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
347	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
348	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
349	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).
350		407
351	=item C<EVFLAG_FORKCHECK>	408	=item C<EVFLAG_FORKCHECK>
352		409
353	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
354	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.
355		412
356	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,
357	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
358	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
359	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
360	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
361	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).
362		420
363	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
364	forget about forgetting to tell libev about forking) when you use this	422	forget about forgetting to tell libev about forking, although you still
365	flag.	423	have to ignore C<SIGPIPE>) when you use this flag.
366		424
367	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>
368	environment variable.	426	environment variable.
369		427
370	=item C<EVFLAG_NOINOTIFY>	428	=item C<EVFLAG_NOINOTIFY>
371		429
372	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
373	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
374	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
375	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.
376		434
377	=item C<EVFLAG_SIGNALFD>	435	=item C<EVFLAG_SIGNALFD>
378		436
379	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
380	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
381	delivers signals synchronously, which makes it both faster and might make	439	delivers signals synchronously, which makes it both faster and might make
382	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
383	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
384	threads that are not interested in handling them.	442	threads that are not interested in handling them.
385		443
386	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
387	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
388	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.
389		462
390	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	463	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
391		464
392	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
393	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,
…		…
421	=item C<EVBACKEND_EPOLL> (value 4, Linux)	494	=item C<EVBACKEND_EPOLL> (value 4, Linux)
422		495
423	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
424	kernels).	497	kernels).
425		498
426	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
427	but it scales phenomenally better. While poll and select usually scale	500	it scales phenomenally better. While poll and select usually scale like
428	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
429	epoll scales either O(1) or O(active_fds).	502	fd), epoll scales either O(1) or O(active_fds).
430		503
431	The epoll mechanism deserves honorable mention as the most misdesigned	504	The epoll mechanism deserves honorable mention as the most misdesigned
432	of the more advanced event mechanisms: mere annoyances include silently	505	of the more advanced event mechanisms: mere annoyances include silently
433	dropping file descriptors, requiring a system call per change per file	506	dropping file descriptors, requiring a system call per change per file
434	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
435	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
436	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
437	take considerable time (one syscall per file descriptor) and is of course	512	set, which can take considerable time (one syscall per file descriptor)
438	hard to detect.	513	and is of course hard to detect.
439		514
440	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	515	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
441	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
442	I<different> file descriptors (even already closed ones, so one cannot	517	totally I<different> file descriptors (even already closed ones, so
443	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
444	on SMP systems). Libev tries to counter these spurious notifications by	519	(especially on SMP systems). Libev tries to counter these spurious
445	employing an additional generation counter and comparing that against the	520	notifications by employing an additional generation counter and comparing
446	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
447	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
448	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...
449		531
450	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
451	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
452	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
453	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
…		…
490		572
491	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
492	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
493	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
494	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
495	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
496	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
497	cases	579	drops fds silently in similarly hard-to-detect cases.
498		580
499	This backend usually performs well under most conditions.	581	This backend usually performs well under most conditions.
500		582
501	While nominally embeddable in other event loops, this doesn't work	583	While nominally embeddable in other event loops, this doesn't work
502	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
…		…
519	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	601	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
520		602
521	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,
522	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)).
523		605
524	Please note that Solaris event ports can deliver a lot of spurious
525	notifications, so you need to use non-blocking I/O or other means to avoid
526	blocking when no data (or space) is available.
527
528	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
529	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
530	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	608	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
531	might perform better.	609	might perform better.
532		610
533	On the positive side, with the exception of the spurious readiness	611	On the positive side, this backend actually performed fully to
534	notifications, this backend actually performed fully to specification
535	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
536	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.
537		625
538	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
539	C<EVBACKEND_POLL>.	627	C<EVBACKEND_POLL>.
540		628
541	=item C<EVBACKEND_ALL>	629	=item C<EVBACKEND_ALL>
542		630
543	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
544	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
545	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	633	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
546		634
547	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).
548		644
549	=back	645	=back
550		646
551	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,
552	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
553	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
554	()> will be tried.	650	()> will be tried.
555		651
556	Example: This is the most typical usage.
557
558	if (!ev_default_loop (0))
559	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
560
561	Example: Restrict libev to the select and poll backends, and do not allow
562	environment settings to be taken into account:
563
564	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
565
566	Example: Use whatever libev has to offer, but make sure that kqueue is
567	used if available (warning, breaks stuff, best use only with your own
568	private event loop and only if you know the OS supports your types of
569	fds):
570
571	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
572
573	=item struct ev_loop *ev_loop_new (unsigned int flags)
574
575	Similar to C<ev_default_loop>, but always creates a new event loop that is
576	always distinct from the default loop.
577
578	Note that this function I<is> thread-safe, and one common way to use
579	libev with threads is indeed to create one loop per thread, and using the
580	default loop in the "main" or "initial" thread.
581
582	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.
583		653
584	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	654	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
585	if (!epoller)	655	if (!epoller)
586	fatal ("no epoll found here, maybe it hides under your chair");	656	fatal ("no epoll found here, maybe it hides under your chair");
587		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
588	=item ev_default_destroy ()	663	=item ev_loop_destroy (loop)
589		664
590	Destroys the default loop (frees all memory and kernel state etc.). None	665	Destroys an event loop object (frees all memory and kernel state
591	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
592	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
593	either stop all watchers cleanly yourself I<before> calling this function,	668	responsibility to either stop all watchers cleanly yourself I<before>
594	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
595	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).
596		672
597	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
598	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
599	as signal and child watchers) would need to be stopped manually.	675	as signal and child watchers) would need to be stopped manually.
600		676
601	In general it is not advisable to call this function except in the	677	This function is normally used on loop objects allocated by
602	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.
603	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>
604	C<ev_loop_new> and C<ev_loop_destroy>.	684	and C<ev_loop_destroy>.
605		685
606	=item ev_loop_destroy (loop)	686	=item ev_loop_fork (loop)
607
608	Like C<ev_default_destroy>, but destroys an event loop created by an
609	earlier call to C<ev_loop_new>.
610
611	=item ev_default_fork ()
612		687
613	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
614	to reinitialise the kernel state for backends that have one. Despite the	689	to reinitialise the kernel state for backends that have one. Despite
615	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
616	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
617	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
618	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>.
619		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
620	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
621	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
622	because some kernel interfaces *cough* I<kqueue> *cough* do funny things	700	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
623	during fork.	701	during fork.
624		702
625	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
…		…
628	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
629	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
630	costly reset of the backend).	708	costly reset of the backend).
631		709
632	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
633	it just in case after a fork. To make this easy, the function will fit in	711	it just in case after a fork.
634	quite nicely into a call to C<pthread_atfork>:
635		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	...
636	pthread_atfork (0, 0, ev_default_fork);	723	pthread_atfork (0, 0, post_fork_child);
637
638	=item ev_loop_fork (loop)
639
640	Like C<ev_default_fork>, but acts on an event loop created by
641	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
642	after fork that you want to re-use in the child, and how you keep track of
643	them is entirely your own problem.
644		724
645	=item int ev_is_default_loop (loop)	725	=item int ev_is_default_loop (loop)
646		726
647	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
648	otherwise.	728	otherwise.
…		…
659	prepare and check phases.	739	prepare and check phases.
660		740
661	=item unsigned int ev_depth (loop)	741	=item unsigned int ev_depth (loop)
662		742
663	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
664	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.
665		745
666	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
667	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),
668	in which case it is higher.	748	in which case it is higher.
669		749
670	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread	750	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
671	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
672	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.
673		754
674	=item unsigned int ev_backend (loop)	755	=item unsigned int ev_backend (loop)
675		756
676	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
677	use.	758	use.
…		…
692		773
693	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
694	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
695	the current time is a good idea.	776	the current time is a good idea.
696		777
697	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.
698		779
699	=item ev_suspend (loop)	780	=item ev_suspend (loop)
700		781
701	=item ev_resume (loop)	782	=item ev_resume (loop)
702		783
…		…
720	without a previous call to C<ev_suspend>.	801	without a previous call to C<ev_suspend>.
721		802
722	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
723	event loop time (see C<ev_now_update>).	804	event loop time (see C<ev_now_update>).
724		805
725	=item ev_run (loop, int flags)	806	=item bool ev_run (loop, int flags)
726		807
727	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
728	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
729	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
730	the watcher callbacks, an then repeat the whole process indefinitely: This	811	the watcher callbacks, and then repeat the whole process indefinitely: This
731	is why event loops are called I<loops>.	812	is why event loops are called I<loops>.
732		813
733	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
734	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
735	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").
736		821
737	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
738	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
739	finished (especially in interactive programs), but having a program	824	finished (especially in interactive programs), but having a program
740	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
741	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
742	beauty.	827	beauty.
743		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
744	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
745	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
746	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
747	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
748	events while doing lengthy calculations, to keep the program responsive.	838	events while doing lengthy calculations, to keep the program responsive.
…		…
757	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
758	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
759	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
760	usually a better approach for this kind of thing.	850	usually a better approach for this kind of thing.
761		851
762	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):
763		855
764	- Increment loop depth.	856	- Increment loop depth.
765	- Reset the ev_break status.	857	- Reset the ev_break status.
766	- Before the first iteration, call any pending watchers.	858	- Before the first iteration, call any pending watchers.
767	LOOP:	859	LOOP:
…		…
800	anymore.	892	anymore.
801		893
802	... queue jobs here, make sure they register event watchers as long	894	... queue jobs here, make sure they register event watchers as long
803	... 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..)
804	ev_run (my_loop, 0);	896	ev_run (my_loop, 0);
805	... jobs done or somebody called unloop. yeah!	897	... jobs done or somebody called break. yeah!
806		898
807	=item ev_break (loop, how)	899	=item ev_break (loop, how)
808		900
809	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
810	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
811	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
812	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.
813		905
814	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>.
815		907
816	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.
817		910
818	=item ev_ref (loop)	911	=item ev_ref (loop)
819		912
820	=item ev_unref (loop)	913	=item ev_unref (loop)
821		914
…		…
842	running when nothing else is active.	935	running when nothing else is active.
843		936
844	ev_signal exitsig;	937	ev_signal exitsig;
845	ev_signal_init (&exitsig, sig_cb, SIGINT);	938	ev_signal_init (&exitsig, sig_cb, SIGINT);
846	ev_signal_start (loop, &exitsig);	939	ev_signal_start (loop, &exitsig);
847	evf_unref (loop);	940	ev_unref (loop);
848		941
849	Example: For some weird reason, unregister the above signal handler again.	942	Example: For some weird reason, unregister the above signal handler again.
850		943
851	ev_ref (loop);	944	ev_ref (loop);
852	ev_signal_stop (loop, &exitsig);	945	ev_signal_stop (loop, &exitsig);
…		…
872	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.
873		966
874	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
875	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,
876	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
877	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
878	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
879	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
880	once per this interval, on average.	973	once per this interval, on average (as long as the host time resolution is
		974	good enough).
881		975
882	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
883	to spend more time collecting timeouts, at the expense of increased	977	to spend more time collecting timeouts, at the expense of increased
884	latency/jitter/inexactness (the watcher callback will be called	978	latency/jitter/inexactness (the watcher callback will be called
885	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
…		…
931	invoke the actual watchers inside another context (another thread etc.).	1025	invoke the actual watchers inside another context (another thread etc.).
932		1026
933	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
934	callback.	1028	callback.
935		1029
936	=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 ())
937		1031
938	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
939	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
940	each call to a libev function.	1034	each call to a libev function.
941		1035
942	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
943	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
944	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
945	I<release> and I<acquire> callbacks on the loop.	1039	I<release> and I<acquire> callbacks on the loop.
946		1040
947	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
948	suspended waiting for new events, and C<acquire> is called just	1042	suspended waiting for new events, and C<acquire> is called just
949	afterwards.	1043	afterwards.
…		…
964	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
965	document.	1059	document.
966		1060
967	=item ev_set_userdata (loop, void *data)	1061	=item ev_set_userdata (loop, void *data)
968		1062
969	=item ev_userdata (loop)	1063	=item void *ev_userdata (loop)
970		1064
971	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
972	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
973	C<0.>	1067	C<0>.
974		1068
975	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,
976	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
977	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
978	any other purpose as well.	1072	any other purpose as well.
…		…
1089		1183
1090	=item C<EV_PREPARE>	1184	=item C<EV_PREPARE>
1091		1185
1092	=item C<EV_CHECK>	1186	=item C<EV_CHECK>
1093		1187
1094	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
1095	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)
1096	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
1097	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
1098	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
1099	(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
1100	C<ev_run> from blocking).	1199	blocking).
1101		1200
1102	=item C<EV_EMBED>	1201	=item C<EV_EMBED>
1103		1202
1104	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.
1105		1204
1106	=item C<EV_FORK>	1205	=item C<EV_FORK>
1107		1206
1108	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
1109	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>).
1110		1213
1111	=item C<EV_ASYNC>	1214	=item C<EV_ASYNC>
1112		1215
1113	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>).
1114		1217
…		…
1136	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
1137	thing, so beware.	1240	thing, so beware.
1138		1241
1139	=back	1242	=back
1140		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
1141	=head2 WATCHER STATES	1398	=head2 WATCHER STATES
1142		1399
1143	There are various watcher states mentioned throughout this manual -	1400	There are various watcher states mentioned throughout this manual -
1144	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
1145	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
1146	rules might look complicated, they usually do "the right thing".	1403	rules might look complicated, they usually do "the right thing".
1147		1404
1148	=over 4	1405	=over 4
1149		1406
1150	=item initialiased	1407	=item initialised
1151		1408
1152	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
1153	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
1154	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.
1155		1412
1156	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
1157	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.
1158		1417
1159	=item started/running/active	1418	=item started/running/active
1160		1419
1161	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
1162	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
…		…
1190	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
1191	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
1192	freeing it is often a good idea.	1451	freeing it is often a good idea.
1193		1452
1194	While stopped (and not pending) the watcher is essentially in the	1453	While stopped (and not pending) the watcher is essentially in the
1195	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
1196	you wish.	1455	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1456	it again).
1197		1457
1198	=back	1458	=back
1199
1200	=head2 GENERIC WATCHER FUNCTIONS
1201
1202	=over 4
1203
1204	=item C<ev_init> (ev_TYPE *watcher, callback)
1205
1206	This macro initialises the generic portion of a watcher. The contents
1207	of the watcher object can be arbitrary (so C<malloc> will do). Only
1208	the generic parts of the watcher are initialised, you I<need> to call
1209	the type-specific C<ev_TYPE_set> macro afterwards to initialise the
1210	type-specific parts. For each type there is also a C<ev_TYPE_init> macro
1211	which rolls both calls into one.
1212
1213	You can reinitialise a watcher at any time as long as it has been stopped
1214	(or never started) and there are no pending events outstanding.
1215
1216	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
1217	int revents)>.
1218
1219	Example: Initialise an C<ev_io> watcher in two steps.
1220
1221	ev_io w;
1222	ev_init (&w, my_cb);
1223	ev_io_set (&w, STDIN_FILENO, EV_READ);
1224
1225	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
1226
1227	This macro initialises the type-specific parts of a watcher. You need to
1228	call C<ev_init> at least once before you call this macro, but you can
1229	call C<ev_TYPE_set> any number of times. You must not, however, call this
1230	macro on a watcher that is active (it can be pending, however, which is a
1231	difference to the C<ev_init> macro).
1232
1233	Although some watcher types do not have type-specific arguments
1234	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
1235
1236	See C<ev_init>, above, for an example.
1237
1238	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
1239
1240	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
1241	calls into a single call. This is the most convenient method to initialise
1242	a watcher. The same limitations apply, of course.
1243
1244	Example: Initialise and set an C<ev_io> watcher in one step.
1245
1246	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1247
1248	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1249
1250	Starts (activates) the given watcher. Only active watchers will receive
1251	events. If the watcher is already active nothing will happen.
1252
1253	Example: Start the C<ev_io> watcher that is being abused as example in this
1254	whole section.
1255
1256	ev_io_start (EV_DEFAULT_UC, &w);
1257
1258	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1259
1260	Stops the given watcher if active, and clears the pending status (whether
1261	the watcher was active or not).
1262
1263	It is possible that stopped watchers are pending - for example,
1264	non-repeating timers are being stopped when they become pending - but
1265	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
1266	pending. If you want to free or reuse the memory used by the watcher it is
1267	therefore a good idea to always call its C<ev_TYPE_stop> function.
1268
1269	=item bool ev_is_active (ev_TYPE *watcher)
1270
1271	Returns a true value iff the watcher is active (i.e. it has been started
1272	and not yet been stopped). As long as a watcher is active you must not modify
1273	it.
1274
1275	=item bool ev_is_pending (ev_TYPE *watcher)
1276
1277	Returns a true value iff the watcher is pending, (i.e. it has outstanding
1278	events but its callback has not yet been invoked). As long as a watcher
1279	is pending (but not active) you must not call an init function on it (but
1280	C<ev_TYPE_set> is safe), you must not change its priority, and you must
1281	make sure the watcher is available to libev (e.g. you cannot C<free ()>
1282	it).
1283
1284	=item callback ev_cb (ev_TYPE *watcher)
1285
1286	Returns the callback currently set on the watcher.
1287
1288	=item ev_cb_set (ev_TYPE *watcher, callback)
1289
1290	Change the callback. You can change the callback at virtually any time
1291	(modulo threads).
1292
1293	=item ev_set_priority (ev_TYPE *watcher, int priority)
1294
1295	=item int ev_priority (ev_TYPE *watcher)
1296
1297	Set and query the priority of the watcher. The priority is a small
1298	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1299	(default: C<-2>). Pending watchers with higher priority will be invoked
1300	before watchers with lower priority, but priority will not keep watchers
1301	from being executed (except for C<ev_idle> watchers).
1302
1303	If you need to suppress invocation when higher priority events are pending
1304	you need to look at C<ev_idle> watchers, which provide this functionality.
1305
1306	You I<must not> change the priority of a watcher as long as it is active or
1307	pending.
1308
1309	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1310	fine, as long as you do not mind that the priority value you query might
1311	or might not have been clamped to the valid range.
1312
1313	The default priority used by watchers when no priority has been set is
1314	always C<0>, which is supposed to not be too high and not be too low :).
1315
1316	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1317	priorities.
1318
1319	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1320
1321	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1322	C<loop> nor C<revents> need to be valid as long as the watcher callback
1323	can deal with that fact, as both are simply passed through to the
1324	callback.
1325
1326	=item int ev_clear_pending (loop, ev_TYPE *watcher)
1327
1328	If the watcher is pending, this function clears its pending status and
1329	returns its C<revents> bitset (as if its callback was invoked). If the
1330	watcher isn't pending it does nothing and returns C<0>.
1331
1332	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1333	callback to be invoked, which can be accomplished with this function.
1334
1335	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
1336
1337	Feeds the given event set into the event loop, as if the specified event
1338	had happened for the specified watcher (which must be a pointer to an
1339	initialised but not necessarily started event watcher). Obviously you must
1340	not free the watcher as long as it has pending events.
1341
1342	Stopping the watcher, letting libev invoke it, or calling
1343	C<ev_clear_pending> will clear the pending event, even if the watcher was
1344	not started in the first place.
1345
1346	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1347	functions that do not need a watcher.
1348
1349	=back
1350
1351
1352	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1353
1354	Each watcher has, by default, a member C<void *data> that you can change
1355	and read at any time: libev will completely ignore it. This can be used
1356	to associate arbitrary data with your watcher. If you need more data and
1357	don't want to allocate memory and store a pointer to it in that data
1358	member, you can also "subclass" the watcher type and provide your own
1359	data:
1360
1361	struct my_io
1362	{
1363	ev_io io;
1364	int otherfd;
1365	void *somedata;
1366	struct whatever *mostinteresting;
1367	};
1368
1369	...
1370	struct my_io w;
1371	ev_io_init (&w.io, my_cb, fd, EV_READ);
1372
1373	And since your callback will be called with a pointer to the watcher, you
1374	can cast it back to your own type:
1375
1376	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1377	{
1378	struct my_io *w = (struct my_io *)w_;
1379	...
1380	}
1381
1382	More interesting and less C-conformant ways of casting your callback type
1383	instead have been omitted.
1384
1385	Another common scenario is to use some data structure with multiple
1386	embedded watchers:
1387
1388	struct my_biggy
1389	{
1390	int some_data;
1391	ev_timer t1;
1392	ev_timer t2;
1393	}
1394
1395	In this case getting the pointer to C<my_biggy> is a bit more
1396	complicated: Either you store the address of your C<my_biggy> struct
1397	in the C<data> member of the watcher (for woozies), or you need to use
1398	some pointer arithmetic using C<offsetof> inside your watchers (for real
1399	programmers):
1400
1401	#include <stddef.h>
1402
1403	static void
1404	t1_cb (EV_P_ ev_timer *w, int revents)
1405	{
1406	struct my_biggy big = (struct my_biggy *)
1407	(((char *)w) - offsetof (struct my_biggy, t1));
1408	}
1409
1410	static void
1411	t2_cb (EV_P_ ev_timer *w, int revents)
1412	{
1413	struct my_biggy big = (struct my_biggy *)
1414	(((char *)w) - offsetof (struct my_biggy, t2));
1415	}
1416		1459
1417	=head2 WATCHER PRIORITY MODELS	1460	=head2 WATCHER PRIORITY MODELS
1418		1461
1419	Many event loops support I<watcher priorities>, which are usually small	1462	Many event loops support I<watcher priorities>, which are usually small
1420	integers that influence the ordering of event callback invocation	1463	integers that influence the ordering of event callback invocation
…		…
1547	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
1548	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
1549	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
1550	required if you know what you are doing).	1593	required if you know what you are doing).
1551		1594
1552	If you cannot use non-blocking mode, then force the use of a
1553	known-to-be-good backend (at the time of this writing, this includes only
1554	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1555	descriptors for which non-blocking operation makes no sense (such as
1556	files) - libev doesn't guarantee any specific behaviour in that case.
1557
1558	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
1559	receive "spurious" readiness notifications, that is your callback might	1596	receive "spurious" readiness notifications, that is, your callback might
1560	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
1561	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
1562	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
1563	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
1564	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1565	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1601	preferable to a program hanging until some data arrives.
1566		1602
1567	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
1568	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
1569	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
1570	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
1571	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
1572	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
1573	indefinitely.	1609	indefinitely.
1574		1610
1575	But really, best use non-blocking mode.	1611	But really, best use non-blocking mode.
1576		1612
…		…
1604		1640
1605	There is no workaround possible except not registering events	1641	There is no workaround possible except not registering events
1606	for potentially C<dup ()>'ed file descriptors, or to resort to	1642	for potentially C<dup ()>'ed file descriptors, or to resort to
1607	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1643	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1608		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
1609	=head3 The special problem of fork	1678	=head3 The special problem of fork
1610		1679
1611	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
1612	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
1613	it in the child.	1682	it in the child if you want to continue to use it in the child.
1614		1683
1615	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
1616	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
1617	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1686	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1618	C<EVBACKEND_POLL>.
1619		1687
1620	=head3 The special problem of SIGPIPE	1688	=head3 The special problem of SIGPIPE
1621		1689
1622	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>:
1623	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
…		…
1721	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1789	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1722	monotonic clock option helps a lot here).	1790	monotonic clock option helps a lot here).
1723		1791
1724	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
1725	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
1726	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
1727	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
1728	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
1729	no longer true when a callback calls C<ev_run> recursively).	1798	longer true when a callback calls C<ev_run> recursively).
1730		1799
1731	=head3 Be smart about timeouts	1800	=head3 Be smart about timeouts
1732		1801
1733	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
1734	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,
…		…
1809		1878
1810	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,
1811	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
1812	within the callback:	1881	within the callback:
1813		1882
		1883	ev_tstamp timeout = 60.;
1814	ev_tstamp last_activity; // time of last activity	1884	ev_tstamp last_activity; // time of last activity
		1885	ev_timer timer;
1815		1886
1816	static void	1887	static void
1817	callback (EV_P_ ev_timer *w, int revents)	1888	callback (EV_P_ ev_timer *w, int revents)
1818	{	1889	{
1819	ev_tstamp now = ev_now (EV_A);	1890	// calculate when the timeout would happen
1820	ev_tstamp timeout = last_activity + 60.;	1891	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1821		1892
1822	// if last_activity + 60. is older than now, we did time out	1893	// if negative, it means we the timeout already occurred
1823	if (timeout < now)	1894	if (after < 0.)
1824	{	1895	{
1825	// timeout occurred, take action	1896	// timeout occurred, take action
1826	}	1897	}
1827	else	1898	else
1828	{	1899	{
1829	// callback was invoked, but there was some activity, re-arm	1900	// callback was invoked, but there was some recent
1830	// the watcher to fire in last_activity + 60, which is	1901	// activity. simply restart the timer to time out
1831	// guaranteed to be in the future, so "again" is positive:	1902	// after "after" seconds, which is the earliest time
1832	w->repeat = timeout - now;	1903	// the timeout can occur.
		1904	ev_timer_set (w, after, 0.);
1833	ev_timer_again (EV_A_ w);	1905	ev_timer_start (EV_A_ w);
1834	}	1906	}
1835	}	1907	}
1836		1908
1837	To summarise the callback: first calculate the real timeout (defined	1909	To summarise the callback: first calculate in how many seconds the
1838	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,
1839	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
1840	the callback was invoked too early (C<timeout> is in the future), so	1912	(EV_A)> from that).
1841	re-schedule the timer to fire at that future time, to see if maybe we have
1842	a timeout then.
1843		1913
1844	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
1845	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.
1846		1923
1847	This scheme causes more callback invocations (about one every 60 seconds	1924	This scheme causes more callback invocations (about one every 60 seconds
1848	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
1849	libev to change the timeout.	1926	libev to change the timeout.
1850		1927
1851	To start the timer, simply initialise the watcher and set C<last_activity>	1928	To start the machinery, simply initialise the watcher and set
1852	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
1853	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:
1854		1932
		1933	last_activity = ev_now (EV_A);
1855	ev_init (timer, callback);	1934	ev_init (&timer, callback);
1856	last_activity = ev_now (loop);	1935	callback (EV_A_ &timer, 0);
1857	callback (loop, timer, EV_TIMER);
1858		1936
1859	And when there is some activity, simply store the current time in	1937	When there is some activity, simply store the current time in
1860	C<last_activity>, no libev calls at all:	1938	C<last_activity>, no libev calls at all:
1861		1939
		1940	if (activity detected)
1862	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);
1863		1950
1864	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
1865	time-out is unlikely to be triggered, much more efficient.	1952	time-out is unlikely to be triggered, much more efficient.
1866
1867	Changing the timeout is trivial as well (if it isn't hard-coded in the
1868	callback :) - just change the timeout and invoke the callback, which will
1869	fix things for you.
1870		1953
1871	=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.
1872		1955
1873	If there is not one request, but many thousands (millions...), all	1956	If there is not one request, but many thousands (millions...), all
1874	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
…		…
1901	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
1902	rather complicated, but extremely efficient, something that really pays	1985	rather complicated, but extremely efficient, something that really pays
1903	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
1904	overkill :)	1987	overkill :)
1905		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
1906	=head3 The special problem of time updates	2026	=head3 The special problem of time updates
1907		2027
1908	Establishing the current time is a costly operation (it usually takes at	2028	Establishing the current time is a costly operation (it usually takes
1909	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
1910	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
1911	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
1912	lots of events in one iteration.	2032	lots of events in one iteration.
1913		2033
1914	The relative timeouts are calculated relative to the C<ev_now ()>	2034	The relative timeouts are calculated relative to the C<ev_now ()>
1915	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
1916	of the event triggering whatever timeout you are modifying/starting. If	2036	of the event triggering whatever timeout you are modifying/starting. If
1917	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
1918	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:
1919		2040
1920	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2041	ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.);
1921		2042
1922	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
1923	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
1924	()>.	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.
1925		2080
1926	=head3 The special problems of suspended animation	2081	=head3 The special problems of suspended animation
1927		2082
1928	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
1929	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?
…		…
1959		2114
1960	=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)
1961		2116
1962	=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)
1963		2118
1964	Configure the timer to trigger after C<after> seconds. If C<repeat>	2119	Configure the timer to trigger after C<after> seconds (fractional and
1965	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
1966	reached. If it is positive, then the timer will automatically be	2121	automatically be stopped once the timeout is reached. If it is positive,
1967	configured to trigger again C<repeat> seconds later, again, and again,	2122	then the timer will automatically be configured to trigger again C<repeat>
1968	until stopped manually.	2123	seconds later, again, and again, until stopped manually.
1969		2124
1970	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
1971	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
1972	trigger at exactly 10 second intervals. If, however, your program cannot	2127	trigger at exactly 10 second intervals. If, however, your program cannot
1973	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
1974	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.
1975		2130
1976	=item ev_timer_again (loop, ev_timer *)	2131	=item ev_timer_again (loop, ev_timer *)
1977		2132
1978	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
1979	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>.
1980		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
1981	If the timer is pending, its pending status is cleared.	2142	=item If the timer is pending, the pending status is always cleared.
1982		2143
1983	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).
1984		2146
1985	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
1986	C<repeat> value), or reset the running timer to the C<repeat> value.	2148	and start the timer, if necessary.
1987		2149
		2150	=back
		2151
1988	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
1989	usage example.	2153	usage example.
1990		2154
1991	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)	2155	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1992		2156
1993	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,
…		…
2046	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
2047	(and unfortunately a bit complex).	2211	(and unfortunately a bit complex).
2048		2212
2049	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
2050	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
2051	(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
2052	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
2053	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
2054	wrist-watch).	2218	wrist-watch).
2055		2219
2056	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
…		…
2113		2277
2114	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
2115	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
2116	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.
2117		2281
2118	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
2119	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
2120	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.
2121		2288
2122	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
2123	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
2124	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
2125	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).
…		…
2233		2400
2234	ev_periodic hourly_tick;	2401	ev_periodic hourly_tick;
2235	ev_periodic_init (&hourly_tick, clock_cb,	2402	ev_periodic_init (&hourly_tick, clock_cb,
2236	fmod (ev_now (loop), 3600.), 3600., 0);	2403	fmod (ev_now (loop), 3600.), 3600., 0);
2237	ev_periodic_start (loop, &hourly_tick);	2404	ev_periodic_start (loop, &hourly_tick);
2238		2405
2239		2406
2240	=head2 C<ev_signal> - signal me when a signal gets signalled!	2407	=head2 C<ev_signal> - signal me when a signal gets signalled!
2241		2408
2242	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
2243	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
2244	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
2245	normal event processing, like any other event.	2412	normal event processing, like any other event.
2246		2413
2247	If you want signals to be delivered truly asynchronously, just use	2414	If you want signals to be delivered truly asynchronously, just use
2248	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
2249	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
…		…
2253	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
2254	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
2255	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
2256	the moment, C<SIGCHLD> is permanently tied to the default loop.	2423	the moment, C<SIGCHLD> is permanently tied to the default loop.
2257		2424
2258	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
2259	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
2260	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.
2261		2428
2262	If possible and supported, libev will install its handlers with	2429	If possible and supported, libev will install its handlers with
2263	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should	2430	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
2264	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
2265	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
…		…
2268	=head3 The special problem of inheritance over fork/execve/pthread_create	2435	=head3 The special problem of inheritance over fork/execve/pthread_create
2269		2436
2270	Both the signal mask (C<sigprocmask>) and the signal disposition	2437	Both the signal mask (C<sigprocmask>) and the signal disposition
2271	(C<sigaction>) are unspecified after starting a signal watcher (and after	2438	(C<sigaction>) are unspecified after starting a signal watcher (and after
2272	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,
2273	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>).
2274		2442
2275	While this does not matter for the signal disposition (libev never	2443	While this does not matter for the signal disposition (libev never
2276	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
2277	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
2278	certain signals to be blocked.	2446	certain signals to be blocked.
…		…
2291	I<has> to modify the signal mask, at least temporarily.	2459	I<has> to modify the signal mask, at least temporarily.
2292		2460
2293	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
2294	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
2295	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>.
2296		2478
2297	=head3 Watcher-Specific Functions and Data Members	2479	=head3 Watcher-Specific Functions and Data Members
2298		2480
2299	=over 4	2481	=over 4
2300		2482
…		…
2435		2617
2436	=head2 C<ev_stat> - did the file attributes just change?	2618	=head2 C<ev_stat> - did the file attributes just change?
2437		2619
2438	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
2439	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)
2440	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
2441	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.
2442		2625
2443	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
2444	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
2445	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
2446	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
…		…
2676	Apart from keeping your process non-blocking (which is a useful	2859	Apart from keeping your process non-blocking (which is a useful
2677	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
2678	"pseudo-background processing", or delay processing stuff to after the	2861	"pseudo-background processing", or delay processing stuff to after the
2679	event loop has handled all outstanding events.	2862	event loop has handled all outstanding events.
2680		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
2681	=head3 Watcher-Specific Functions and Data Members	2878	=head3 Watcher-Specific Functions and Data Members
2682		2879
2683	=over 4	2880	=over 4
2684		2881
2685	=item ev_idle_init (ev_idle *, callback)	2882	=item ev_idle_init (ev_idle *, callback)
…		…
2696	callback, free it. Also, use no error checking, as usual.	2893	callback, free it. Also, use no error checking, as usual.
2697		2894
2698	static void	2895	static void
2699	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	2896	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2700	{	2897	{
		2898	// stop the watcher
		2899	ev_idle_stop (loop, w);
		2900
		2901	// now we can free it
2701	free (w);	2902	free (w);
		2903
2702	// now do something you wanted to do when the program has	2904	// now do something you wanted to do when the program has
2703	// no longer anything immediate to do.	2905	// no longer anything immediate to do.
2704	}	2906	}
2705		2907
2706	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2908	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
…		…
2708	ev_idle_start (loop, idle_watcher);	2910	ev_idle_start (loop, idle_watcher);
2709		2911
2710		2912
2711	=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!
2712		2914
2713	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:
2714	prepare watchers get invoked before the process blocks and check watchers	2916	prepare watchers get invoked before the process blocks and check watchers
2715	afterwards.	2917	afterwards.
2716		2918
2717	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
2718	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
2719	watchers. Other loops than the current one are fine, however. The	2921	C<ev_check> watchers. Other loops than the current one are fine,
2720	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
2721	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
2722	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
2723	called in pairs bracketing the blocking call.	2925	kind they will always be called in pairs bracketing the blocking call.
2724		2926
2725	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
2726	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
2727	variable changes, implement your own watchers, integrate net-snmp or a	2929	variable changes, implement your own watchers, integrate net-snmp or a
2728	coroutine library and lots more. They are also occasionally useful if	2930	coroutine library and lots more. They are also occasionally useful if
…		…
2746	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
2747	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
2748	loop from blocking if lower-priority coroutines are active, thus mapping	2950	loop from blocking if lower-priority coroutines are active, thus mapping
2749	low-priority coroutines to idle/background tasks).	2951	low-priority coroutines to idle/background tasks).
2750		2952
2751	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
2752	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
2753	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).
2754		2957
2755	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
2756	activate ("feed") events into libev. While libev fully supports this, they	2959	activate ("feed") events into libev. While libev fully supports this, they
2757	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
2758	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
2759	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
2760	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
2761	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.
2762		2984
2763	=head3 Watcher-Specific Functions and Data Members	2985	=head3 Watcher-Specific Functions and Data Members
2764		2986
2765	=over 4	2987	=over 4
2766		2988
…		…
2967		3189
2968	=over 4	3190	=over 4
2969		3191
2970	=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)
2971		3193
2972	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	3194	=item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)
2973		3195
2974	Configures the watcher to embed the given loop, which must be	3196	Configures the watcher to embed the given loop, which must be
2975	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
2976	invoked automatically, otherwise it is the responsibility of the callback	3198	invoked automatically, otherwise it is the responsibility of the callback
2977	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,
…		…
2998	used).	3220	used).
2999		3221
3000	struct ev_loop *loop_hi = ev_default_init (0);	3222	struct ev_loop *loop_hi = ev_default_init (0);
3001	struct ev_loop *loop_lo = 0;	3223	struct ev_loop *loop_lo = 0;
3002	ev_embed embed;	3224	ev_embed embed;
3003		3225
3004	// see if there is a chance of getting one that works	3226	// see if there is a chance of getting one that works
3005	// (remember that a flags value of 0 means autodetection)	3227	// (remember that a flags value of 0 means autodetection)
3006	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3228	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
3007	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3229	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
3008	: 0;	3230	: 0;
…		…
3022	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3244	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
3023		3245
3024	struct ev_loop *loop = ev_default_init (0);	3246	struct ev_loop *loop = ev_default_init (0);
3025	struct ev_loop *loop_socket = 0;	3247	struct ev_loop *loop_socket = 0;
3026	ev_embed embed;	3248	ev_embed embed;
3027		3249
3028	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3250	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
3029	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3251	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
3030	{	3252	{
3031	ev_embed_init (&embed, 0, loop_socket);	3253	ev_embed_init (&embed, 0, loop_socket);
3032	ev_embed_start (loop, &embed);	3254	ev_embed_start (loop, &embed);
…		…
3040		3262
3041	=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
3042		3264
3043	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
3044	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
3045	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
3046	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
3047	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
3048	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,
3049	handlers will be invoked, too, of course.	3271	of course.
3050		3272
3051	=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?
3052		3274
3053	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
3054	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
3055	sequence should be handled by libev without any problems.	3277	sequence should be handled by libev without any problems.
3056		3278
3057	This changes when the application actually wants to do event handling	3279	This changes when the application actually wants to do event handling
3058	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
…		…
3074	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
3075	signal watchers).	3297	signal watchers).
3076		3298
3077	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
3078	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
3079	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3301	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
3080	the default loop will "orphan" (not stop) all registered watchers, so you	3302	Destroying the default loop will "orphan" (not stop) all registered
3081	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
3082	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.
3083		3306
3084	=head3 Watcher-Specific Functions and Data Members	3307	=head3 Watcher-Specific Functions and Data Members
3085		3308
3086	=over 4	3309	=over 4
3087		3310
3088	=item ev_fork_init (ev_signal *, callback)	3311	=item ev_fork_init (ev_fork *, callback)
3089		3312
3090	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
3091	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,
3092	believe me.	3315	really.
3093		3316
3094	=back	3317	=back
3095		3318
3096		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
3097	=head2 C<ev_async> - how to wake up an event loop	3360	=head2 C<ev_async> - how to wake up an event loop
3098		3361
3099	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
3100	asynchronous sources such as signal handlers (as opposed to multiple event	3363	asynchronous sources such as signal handlers (as opposed to multiple event
3101	loops - those are of course safe to use in different threads).	3364	loops - those are of course safe to use in different threads).
3102		3365
3103	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,
3104	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>
…		…
3106	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.
3107		3370
3108	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,
3109	too, are asynchronous in nature, and signals, too, will be compressed	3372	too, are asynchronous in nature, and signals, too, will be compressed
3110	(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
3111	C<ev_async_sent> calls).	3374	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
3112		3375	of "global async watchers" by using a watcher on an otherwise unused
3113	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,
3114	just the default loop.	3377	even without knowing which loop owns the signal.
3115		3378
3116	=head3 Queueing	3379	=head3 Queueing
3117		3380
3118	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
3119	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
…		…
3211	trust me.	3474	trust me.
3212		3475
3213	=item ev_async_send (loop, ev_async *)	3476	=item ev_async_send (loop, ev_async *)
3214		3477
3215	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
3216	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
3217	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,
3218	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
3219	section below on what exactly this means).	3484	embedding section below on what exactly this means).
3220		3485
3221	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
3222	compressed into a single callback invocation (another way to look at this	3487	compressed into a single callback invocation (another way to look at
3223	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
3224	reset when the event loop detects that).	3489	C<ev_async_send>, reset when the event loop detects that).
3225		3490
3226	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
3227	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
3228	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.
3229		3497
3230	=item bool = ev_async_pending (ev_async *)	3498	=item bool = ev_async_pending (ev_async *)
3231		3499
3232	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
3233	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
…		…
3250		3518
3251	There are some other functions of possible interest. Described. Here. Now.	3519	There are some other functions of possible interest. Described. Here. Now.
3252		3520
3253	=over 4	3521	=over 4
3254		3522
3255	=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)
3256		3524
3257	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
3258	callback on whichever event happens first and automatically stops both	3526	callback on whichever event happens first and automatically stops both
3259	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
3260	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
…		…
3288	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3556	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3289		3557
3290	=item ev_feed_fd_event (loop, int fd, int revents)	3558	=item ev_feed_fd_event (loop, int fd, int revents)
3291		3559
3292	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
3293	the given events it.	3561	the given events.
3294		3562
3295	=item ev_feed_signal_event (loop, int signum)	3563	=item ev_feed_signal_event (loop, int signum)
3296		3564
3297	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>,
3298	loop!).	3566	which is async-safe.
3299		3567
3300	=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.
3301		3919
3302		3920
3303	=head1 LIBEVENT EMULATION	3921	=head1 LIBEVENT EMULATION
3304		3922
3305	Libev offers a compatibility emulation layer for libevent. It cannot	3923	Libev offers a compatibility emulation layer for libevent. It cannot
3306	emulate the internals of libevent, so here are some usage hints:	3924	emulate the internals of libevent, so here are some usage hints:
3307		3925
3308	=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.
3309		3932
3310	=item * Use it by including <event.h>, as usual.	3933	=item * Use it by including <event.h>, as usual.
3311		3934
3312	=item * The following members are fully supported: ev_base, ev_callback,	3935	=item * The following members are fully supported: ev_base, ev_callback,
3313	ev_arg, ev_fd, ev_res, ev_events.	3936	ev_arg, ev_fd, ev_res, ev_events.
…		…
3319	=item * Priorities are not currently supported. Initialising priorities	3942	=item * Priorities are not currently supported. Initialising priorities
3320	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
3321	is an ev_pri field.	3944	is an ev_pri field.
3322		3945
3323	=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
3324	first base created (== the default loop) gets the signals.	3947	base that registered the signal gets the signals.
3325		3948
3326	=item * Other members are not supported.	3949	=item * Other members are not supported.
3327		3950
3328	=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
3329	to use the libev header file and library.	3952	to use the libev header file and library.
3330		3953
3331	=back	3954	=back
3332		3955
3333	=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
3334		3990
3335	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
3336	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
3337	the callback model to a model using method callbacks on objects.	3993	the callback model to a model using method callbacks on objects.
3338		3994
3339	To use it,	3995	To use it,
3340		3996
3341	#include <ev++.h>	3997	#include <ev++.h>
3342		3998
3343	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
3344	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
3345	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
…		…
3348	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++
3349	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
3350	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
3351	you disable C<EV_MULTIPLICITY> when embedding libev).	4007	you disable C<EV_MULTIPLICITY> when embedding libev).
3352		4008
3353	Currently, functions, and static and non-static member functions can be	4009	Currently, functions, static and non-static member functions and classes
3354	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
3355	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
3356	types of functors please contact the author (preferably after implementing	4012	you need support for other types of functors please contact the author
3357	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++.
3358		4018
3359	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:
3360		4020
3361	=over 4	4021	=over 4
3362		4022
…		…
3372	=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.
3373		4033
3374	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
3375	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>
3376	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
3377	defines by many implementations.	4037	defined by many implementations.
3378		4038
3379	All of those classes have these methods:	4039	All of those classes have these methods:
3380		4040
3381	=over 4	4041	=over 4
3382		4042
…		…
3444	void operator() (ev::io &w, int revents)	4104	void operator() (ev::io &w, int revents)
3445	{	4105	{
3446	...	4106	...
3447	}	4107	}
3448	}	4108	}
3449		4109
3450	myfunctor f;	4110	myfunctor f;
3451		4111
3452	ev::io w;	4112	ev::io w;
3453	w.set (&f);	4113	w.set (&f);
3454		4114
…		…
3472	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
3473	do this when the watcher is inactive (and not pending either).	4133	do this when the watcher is inactive (and not pending either).
3474		4134
3475	=item w->set ([arguments])	4135	=item w->set ([arguments])
3476		4136
3477	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>),
3478	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
3479	C counterpart, an active watcher gets automatically stopped and restarted	4139	must be called at least once. Unlike the C counterpart, an active watcher
3480	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.
3481		4145
3482	=item w->start ()	4146	=item w->start ()
3483		4147
3484	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
3485	constructor already stores the event loop.	4149	constructor already stores the event loop.
…		…
3515	watchers in the constructor.	4179	watchers in the constructor.
3516		4180
3517	class myclass	4181	class myclass
3518	{	4182	{
3519	ev::io io ; void io_cb (ev::io &w, int revents);	4183	ev::io io ; void io_cb (ev::io &w, int revents);
3520	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);	4184	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3521	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4185	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3522		4186
3523	myclass (int fd)	4187	myclass (int fd)
3524	{	4188	{
3525	io .set <myclass, &myclass::io_cb > (this);	4189	io .set <myclass, &myclass::io_cb > (this);
…		…
3576	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4240	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3577		4241
3578	=item D	4242	=item D
3579		4243
3580	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
3581	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>.
3582		4246
3583	=item Ocaml	4247	=item Ocaml
3584		4248
3585	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
3586	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4250	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
…		…
3589		4253
3590	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
3591	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
3592	L<http://github.com/brimworks/lua-ev>.	4256	L<http://github.com/brimworks/lua-ev>.
3593		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
3594	=back	4266	=back
3595		4267
3596		4268
3597	=head1 MACRO MAGIC	4269	=head1 MACRO MAGIC
3598		4270
…		…
3634	suitable for use with C<EV_A>.	4306	suitable for use with C<EV_A>.
3635		4307
3636	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4308	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3637		4309
3638	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
3639	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.
3640		4316
3641	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4317	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3642		4318
3643	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
3644	default loop has been initialised (C<UC> == unchecked). Their behaviour	4320	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3711	ev_vars.h	4387	ev_vars.h
3712	ev_wrap.h	4388	ev_wrap.h
3713		4389
3714	ev_win32.c required on win32 platforms only	4390	ev_win32.c required on win32 platforms only
3715		4391
3716	ev_select.c only when select backend is enabled (which is enabled by default)	4392	ev_select.c only when select backend is enabled
3717	ev_poll.c only when poll backend is enabled (disabled by default)	4393	ev_poll.c only when poll backend is enabled
3718	ev_epoll.c only when the epoll backend is enabled (disabled by default)	4394	ev_epoll.c only when the epoll backend is enabled
3719	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	4395	ev_kqueue.c only when the kqueue backend is enabled
3720	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
3721		4397
3722	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
3723	to compile this single file.	4399	to compile this single file.
3724		4400
3725	=head3 LIBEVENT COMPATIBILITY API	4401	=head3 LIBEVENT COMPATIBILITY API
…		…
3789	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
3790	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.
3791		4467
3792	In standalone mode, libev will still try to automatically deduce the	4468	In standalone mode, libev will still try to automatically deduce the
3793	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.
3794		4479
3795	=item EV_USE_MONOTONIC	4480	=item EV_USE_MONOTONIC
3796		4481
3797	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
3798	monotonic clock option at both compile time and runtime. Otherwise no	4483	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3883		4568
3884	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
3885	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
3886	file descriptors again. Note that the replacement function has to close	4571	file descriptors again. Note that the replacement function has to close
3887	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.
3888		4580
3889	=item EV_USE_POLL	4581	=item EV_USE_POLL
3890		4582
3891	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)
3892	backend. Otherwise it will be enabled on non-win32 platforms. It	4584	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3928	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
3929	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
3930	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
3931	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4623	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3932		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
3933	=item EV_ATOMIC_T	4639	=item EV_ATOMIC_T
3934		4640
3935	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
3936	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
3937	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
3938	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
3939	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.
3940		4647
3941	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>
3942	(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.
3943		4650
3944	=item EV_H (h)	4651	=item EV_H (h)
…		…
3971	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
3972	additional independent event loops. Otherwise there will be no support	4679	additional independent event loops. Otherwise there will be no support
3973	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
3974	argument. Instead, all functions act on the single default loop.	4681	argument. Instead, all functions act on the single default loop.
3975		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
3976	=item EV_MINPRI	4687	=item EV_MINPRI
3977		4688
3978	=item EV_MAXPRI	4689	=item EV_MAXPRI
3979		4690
3980	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
…		…
4016	#define EV_USE_POLL 1	4727	#define EV_USE_POLL 1
4017	#define EV_CHILD_ENABLE 1	4728	#define EV_CHILD_ENABLE 1
4018	#define EV_ASYNC_ENABLE 1	4729	#define EV_ASYNC_ENABLE 1
4019		4730
4020	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
4021	values:	4732	values (by default, all of these are enabled):
4022		4733
4023	=over 4	4734	=over 4
4024		4735
4025	=item C<1> - faster/larger code	4736	=item C<1> - faster/larger code
4026		4737
…		…
4030	code size by roughly 30% on amd64).	4741	code size by roughly 30% on amd64).
4031		4742
4032	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
4033	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
4034	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>).
4035		4749
4036	=item C<2> - faster/larger data structures	4750	=item C<2> - faster/larger data structures
4037		4751
4038	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
4039	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
4040	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
4041	runtime.	4755	runtime.
4042		4756
		4757	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4758	(e.g. gcc with C<-Os>).
		4759
4043	=item C<4> - full API configuration	4760	=item C<4> - full API configuration
4044		4761
4045	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
4046	enables multiplicity (C<EV_MULTIPLICITY>=1).	4763	enables multiplicity (C<EV_MULTIPLICITY>=1).
4047		4764
…		…
4077		4794
4078	With an intelligent-enough linker (gcc+binutils are intelligent enough	4795	With an intelligent-enough linker (gcc+binutils are intelligent enough
4079	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
4080	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
4081	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.
4082		4813
4083	=item EV_AVOID_STDIO	4814	=item EV_AVOID_STDIO
4084		4815
4085	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
4086	functions (printf, scanf, perror etc.). This will increase the code size	4817	functions (printf, scanf, perror etc.). This will increase the code size
…		…
4230	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:
4231		4962
4232	#include "ev_cpp.h"	4963	#include "ev_cpp.h"
4233	#include "ev.c"	4964	#include "ev.c"
4234		4965
4235	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4966	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4236		4967
4237	=head2 THREADS AND COROUTINES	4968	=head2 THREADS AND COROUTINES
4238		4969
4239	=head3 THREADS	4970	=head3 THREADS
4240		4971
…		…
4291	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
4292	watcher callback into the event loop interested in the signal.	5023	watcher callback into the event loop interested in the signal.
4293		5024
4294	=back	5025	=back
4295		5026
4296	=head4 THREAD LOCKING EXAMPLE	5027	See also L</THREAD LOCKING EXAMPLE>.
4297
4298	Here is a fictitious example of how to run an event loop in a different
4299	thread than where callbacks are being invoked and watchers are
4300	created/added/removed.
4301
4302	For a real-world example, see the C<EV::Loop::Async> perl module,
4303	which uses exactly this technique (which is suited for many high-level
4304	languages).
4305
4306	The example uses a pthread mutex to protect the loop data, a condition
4307	variable to wait for callback invocations, an async watcher to notify the
4308	event loop thread and an unspecified mechanism to wake up the main thread.
4309
4310	First, you need to associate some data with the event loop:
4311
4312	typedef struct {
4313	mutex_t lock; /* global loop lock */
4314	ev_async async_w;
4315	thread_t tid;
4316	cond_t invoke_cv;
4317	} userdata;
4318
4319	void prepare_loop (EV_P)
4320	{
4321	// for simplicity, we use a static userdata struct.
4322	static userdata u;
4323
4324	ev_async_init (&u->async_w, async_cb);
4325	ev_async_start (EV_A_ &u->async_w);
4326
4327	pthread_mutex_init (&u->lock, 0);
4328	pthread_cond_init (&u->invoke_cv, 0);
4329
4330	// now associate this with the loop
4331	ev_set_userdata (EV_A_ u);
4332	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4333	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4334
4335	// then create the thread running ev_loop
4336	pthread_create (&u->tid, 0, l_run, EV_A);
4337	}
4338
4339	The callback for the C<ev_async> watcher does nothing: the watcher is used
4340	solely to wake up the event loop so it takes notice of any new watchers
4341	that might have been added:
4342
4343	static void
4344	async_cb (EV_P_ ev_async *w, int revents)
4345	{
4346	// just used for the side effects
4347	}
4348
4349	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4350	protecting the loop data, respectively.
4351
4352	static void
4353	l_release (EV_P)
4354	{
4355	userdata *u = ev_userdata (EV_A);
4356	pthread_mutex_unlock (&u->lock);
4357	}
4358
4359	static void
4360	l_acquire (EV_P)
4361	{
4362	userdata *u = ev_userdata (EV_A);
4363	pthread_mutex_lock (&u->lock);
4364	}
4365
4366	The event loop thread first acquires the mutex, and then jumps straight
4367	into C<ev_run>:
4368
4369	void *
4370	l_run (void *thr_arg)
4371	{
4372	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4373
4374	l_acquire (EV_A);
4375	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4376	ev_run (EV_A_ 0);
4377	l_release (EV_A);
4378
4379	return 0;
4380	}
4381
4382	Instead of invoking all pending watchers, the C<l_invoke> callback will
4383	signal the main thread via some unspecified mechanism (signals? pipe
4384	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4385	have been called (in a while loop because a) spurious wakeups are possible
4386	and b) skipping inter-thread-communication when there are no pending
4387	watchers is very beneficial):
4388
4389	static void
4390	l_invoke (EV_P)
4391	{
4392	userdata *u = ev_userdata (EV_A);
4393
4394	while (ev_pending_count (EV_A))
4395	{
4396	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4397	pthread_cond_wait (&u->invoke_cv, &u->lock);
4398	}
4399	}
4400
4401	Now, whenever the main thread gets told to invoke pending watchers, it
4402	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4403	thread to continue:
4404
4405	static void
4406	real_invoke_pending (EV_P)
4407	{
4408	userdata *u = ev_userdata (EV_A);
4409
4410	pthread_mutex_lock (&u->lock);
4411	ev_invoke_pending (EV_A);
4412	pthread_cond_signal (&u->invoke_cv);
4413	pthread_mutex_unlock (&u->lock);
4414	}
4415
4416	Whenever you want to start/stop a watcher or do other modifications to an
4417	event loop, you will now have to lock:
4418
4419	ev_timer timeout_watcher;
4420	userdata *u = ev_userdata (EV_A);
4421
4422	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4423
4424	pthread_mutex_lock (&u->lock);
4425	ev_timer_start (EV_A_ &timeout_watcher);
4426	ev_async_send (EV_A_ &u->async_w);
4427	pthread_mutex_unlock (&u->lock);
4428
4429	Note that sending the C<ev_async> watcher is required because otherwise
4430	an event loop currently blocking in the kernel will have no knowledge
4431	about the newly added timer. By waking up the loop it will pick up any new
4432	watchers in the next event loop iteration.
4433		5028
4434	=head3 COROUTINES	5029	=head3 COROUTINES
4435		5030
4436	Libev is very accommodating to coroutines ("cooperative threads"):	5031	Libev is very accommodating to coroutines ("cooperative threads"):
4437	libev fully supports nesting calls to its functions from different	5032	libev fully supports nesting calls to its functions from different
…		…
4602	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
4603	model. Libev still offers limited functionality on this platform in	5198	model. Libev still offers limited functionality on this platform in
4604	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
4605	descriptors. This only applies when using Win32 natively, not when using	5200	descriptors. This only applies when using Win32 natively, not when using
4606	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,
4607	as every compielr comes with a slightly differently broken/incompatible	5202	as every compiler comes with a slightly differently broken/incompatible
4608	environment.	5203	environment.
4609		5204
4610	Lifting these limitations would basically require the full	5205	Lifting these limitations would basically require the full
4611	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,
4612	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
…		…
4706	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
4707	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
4708	callback: The watcher callbacks have different type signatures, but libev	5303	callback: The watcher callbacks have different type signatures, but libev
4709	calls them using an C<ev_watcher *> internally.	5304	calls them using an C<ev_watcher *> internally.
4710		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
4711	=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
4712		5317
4713	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
4714	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
4715	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
…		…
4723	thread" or will block signals process-wide, both behaviours would	5328	thread" or will block signals process-wide, both behaviours would
4724	be compatible with libev. Interaction between C<sigprocmask> and	5329	be compatible with libev. Interaction between C<sigprocmask> and
4725	C<pthread_sigmask> could complicate things, however.	5330	C<pthread_sigmask> could complicate things, however.
4726		5331
4727	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
4728	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
4729	well.	5334	thread as well.
4730		5335
4731	=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
4732		5337
4733	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
4734	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
…		…
4740		5345
4741	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
4742	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
4743	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
4744	(the design goal for libev). This requirement is overfulfilled by	5349	(the design goal for libev). This requirement is overfulfilled by
4745	implementations using IEEE 754, which is basically all existing ones. With	5350	implementations using IEEE 754, which is basically all existing ones.
		5351
4746	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).
4747		5356
4748	=back	5357	=back
4749		5358
4750	If you know of other additional requirements drop me a note.	5359	If you know of other additional requirements drop me a note.
4751		5360
…		…
4813	=item Processing ev_async_send: O(number_of_async_watchers)	5422	=item Processing ev_async_send: O(number_of_async_watchers)
4814		5423
4815	=item Processing signals: O(max_signal_number)	5424	=item Processing signals: O(max_signal_number)
4816		5425
4817	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>
4818	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
4819	involves iterating over all running async watchers or all signal numbers.	5429	running async watchers or all signal numbers.
4820		5430
4821	=back	5431	=back
4822		5432
4823		5433
4824	=head1 PORTING FROM LIBEV 3.X TO 4.X	5434	=head1 PORTING FROM LIBEV 3.X TO 4.X
4825		5435
4826	The major version 4 introduced some minor incompatible changes to the API.	5436	The major version 4 introduced some incompatible changes to the API.
4827		5437
4828	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
4829	compatibility, so most programs should still compile. Those might be	5439	for all changes, so most programs should still compile. The compatibility
4830	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.
4831		5442
4832	=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);
4833		5457
4834	=item function/symbol renames	5458	=item function/symbol renames
4835		5459
4836	A number of functions and symbols have been renamed:	5460	A number of functions and symbols have been renamed:
4837		5461
…		…
4856	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
4857	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
4858	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>
4859	typedef.	5483	typedef.
4860		5484
4861	=item C<EV_COMPAT3> backwards compatibility mechanism
4862
4863	The backward compatibility mechanism can be controlled by
4864	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
4865	section.
4866
4867	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>	5485	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
4868		5486
4869	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
4870	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile	5488	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
4871	and work, but the library code will of course be larger.	5489	and work, but the library code will of course be larger.
…		…
4878	=over 4	5496	=over 4
4879		5497
4880	=item active	5498	=item active
4881		5499
4882	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.
4883	See L<WATCHER STATES> for details.	5501	See L</WATCHER STATES> for details.
4884		5502
4885	=item application	5503	=item application
4886		5504
4887	In this document, an application is whatever is using libev.	5505	In this document, an application is whatever is using libev.
4888		5506
…		…
4924	watchers and events.	5542	watchers and events.
4925		5543
4926	=item pending	5544	=item pending
4927		5545
4928	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
4929	detected. See L<WATCHER STATES> for details.	5547	detected. See L</WATCHER STATES> for details.
4930		5548
4931	=item real time	5549	=item real time
4932		5550
4933	The physical time that is observed. It is apparently strictly monotonic :)	5551	The physical time that is observed. It is apparently strictly monotonic :)
4934		5552
4935	=item wall-clock time	5553	=item wall-clock time
4936		5554
4937	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
4938	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
4939	clock.	5557	clock.
4940		5558
4941	=item watcher	5559	=item watcher
4942		5560
4943	A data structure that describes interest in certain events. Watchers need	5561	A data structure that describes interest in certain events. Watchers need
…		…
4945		5563
4946	=back	5564	=back
4947		5565
4948	=head1 AUTHOR	5566	=head1 AUTHOR
4949		5567
4950	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.
4951		5570

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