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Revision 1.425 by root, Tue Jan 22 03:53:01 2013 UTC

…		…
58	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
59		59
60	// now wait for events to arrive	60	// now wait for events to arrive
61	ev_run (loop, 0);	61	ev_run (loop, 0);
62		62
63	// unloop was called, so exit	63	// break was called, so exit
64	return 0;	64	return 0;
65	}	65	}
66		66
67	=head1 ABOUT THIS DOCUMENT	67	=head1 ABOUT THIS DOCUMENT
68		68
…		…
77	on event-based programming, nor will it introduce event-based programming	77	on event-based programming, nor will it introduce event-based programming
78	with libev.	78	with libev.
79		79
80	Familiarity with event based programming techniques in general is assumed	80	Familiarity with event based programming techniques in general is assumed
81	throughout this document.	81	throughout this document.
		82
		83	=head1 WHAT TO READ WHEN IN A HURRY
		84
		85	This manual tries to be very detailed, but unfortunately, this also makes
		86	it very long. If you just want to know the basics of libev, I suggest
		87	reading L</ANATOMY OF A WATCHER>, then the L</EXAMPLE PROGRAM> above and
		88	look up the missing functions in L</GLOBAL FUNCTIONS> and the C<ev_io> and
		89	C<ev_timer> sections in L</WATCHER TYPES>.
82		90
83	=head1 ABOUT LIBEV	91	=head1 ABOUT LIBEV
84		92
85	Libev is an event loop: you register interest in certain events (such as a	93	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	94	file descriptor being readable or a timeout occurring), and it will manage
…		…
166	=item ev_tstamp ev_time ()	174	=item ev_tstamp ev_time ()
167		175
168	Returns the current time as libev would use it. Please note that the	176	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	177	C<ev_now> function is usually faster and also often returns the timestamp
170	you actually want to know. Also interesting is the combination of	178	you actually want to know. Also interesting is the combination of
171	C<ev_update_now> and C<ev_now>.	179	C<ev_now_update> and C<ev_now>.
172		180
173	=item ev_sleep (ev_tstamp interval)	181	=item ev_sleep (ev_tstamp interval)
174		182
175	Sleep for the given interval: The current thread will be blocked until	183	Sleep for the given interval: The current thread will be blocked
176	either it is interrupted or the given time interval has passed. Basically	184	until either it is interrupted or the given time interval has
		185	passed (approximately - it might return a bit earlier even if not
		186	interrupted). Returns immediately if C<< interval <= 0 >>.
		187
177	this is a sub-second-resolution C<sleep ()>.	188	Basically this is a sub-second-resolution C<sleep ()>.
		189
		190	The range of the C<interval> is limited - libev only guarantees to work
		191	with sleep times of up to one day (C<< interval <= 86400 >>).
178		192
179	=item int ev_version_major ()	193	=item int ev_version_major ()
180		194
181	=item int ev_version_minor ()	195	=item int ev_version_minor ()
182		196
…		…
233	the current system, you would need to look at C<ev_embeddable_backends ()	247	the current system, you would need to look at C<ev_embeddable_backends ()
234	& ev_supported_backends ()>, likewise for recommended ones.	248	& ev_supported_backends ()>, likewise for recommended ones.
235		249
236	See the description of C<ev_embed> watchers for more info.	250	See the description of C<ev_embed> watchers for more info.
237		251
238	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	252	=item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())
239		253
240	Sets the allocation function to use (the prototype is similar - the	254	Sets the allocation function to use (the prototype is similar - the
241	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	255	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
242	used to allocate and free memory (no surprises here). If it returns zero	256	used to allocate and free memory (no surprises here). If it returns zero
243	when memory needs to be allocated (C<size != 0>), the library might abort	257	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
269	}	283	}
270		284
271	...	285	...
272	ev_set_allocator (persistent_realloc);	286	ev_set_allocator (persistent_realloc);
273		287
274	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	288	=item ev_set_syserr_cb (void (*cb)(const char *msg) throw ())
275		289
276	Set the callback function to call on a retryable system call error (such	290	Set the callback function to call on a retryable system call error (such
277	as failed select, poll, epoll_wait). The message is a printable string	291	as failed select, poll, epoll_wait). The message is a printable string
278	indicating the system call or subsystem causing the problem. If this	292	indicating the system call or subsystem causing the problem. If this
279	callback is set, then libev will expect it to remedy the situation, no	293	callback is set, then libev will expect it to remedy the situation, no
…		…
291	}	305	}
292		306
293	...	307	...
294	ev_set_syserr_cb (fatal_error);	308	ev_set_syserr_cb (fatal_error);
295		309
		310	=item ev_feed_signal (int signum)
		311
		312	This function can be used to "simulate" a signal receive. It is completely
		313	safe to call this function at any time, from any context, including signal
		314	handlers or random threads.
		315
		316	Its main use is to customise signal handling in your process, especially
		317	in the presence of threads. For example, you could block signals
		318	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		319	creating any loops), and in one thread, use C<sigwait> or any other
		320	mechanism to wait for signals, then "deliver" them to libev by calling
		321	C<ev_feed_signal>.
		322
296	=back	323	=back
297		324
298	=head1 FUNCTIONS CONTROLLING EVENT LOOPS	325	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
299		326
300	An event loop is described by a C<struct ev_loop *> (the C<struct> is	327	An event loop is described by a C<struct ev_loop *> (the C<struct> is
301	I<not> optional in this case unless libev 3 compatibility is disabled, as	328	I<not> optional in this case unless libev 3 compatibility is disabled, as
302	libev 3 had an C<ev_loop> function colliding with the struct name).	329	libev 3 had an C<ev_loop> function colliding with the struct name).
303		330
304	The library knows two types of such loops, the I<default> loop, which	331	The library knows two types of such loops, the I<default> loop, which
305	supports signals and child events, and dynamically created event loops	332	supports child process events, and dynamically created event loops which
306	which do not.	333	do not.
307		334
308	=over 4	335	=over 4
309		336
310	=item struct ev_loop *ev_default_loop (unsigned int flags)	337	=item struct ev_loop *ev_default_loop (unsigned int flags)
311		338
…		…
342	Example: Restrict libev to the select and poll backends, and do not allow	369	Example: Restrict libev to the select and poll backends, and do not allow
343	environment settings to be taken into account:	370	environment settings to be taken into account:
344		371
345	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	372	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
346		373
347	Example: Use whatever libev has to offer, but make sure that kqueue is
348	used if available (warning, breaks stuff, best use only with your own
349	private event loop and only if you know the OS supports your types of
350	fds):
351
352	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
353
354	=item struct ev_loop *ev_loop_new (unsigned int flags)	374	=item struct ev_loop *ev_loop_new (unsigned int flags)
355		375
356	This will create and initialise a new event loop object. If the loop	376	This will create and initialise a new event loop object. If the loop
357	could not be initialised, returns false.	377	could not be initialised, returns false.
358		378
359	Note that this function I<is> thread-safe, and one common way to use	379	This function is thread-safe, and one common way to use libev with
360	libev with threads is indeed to create one loop per thread, and using the	380	threads is indeed to create one loop per thread, and using the default
361	default loop in the "main" or "initial" thread.	381	loop in the "main" or "initial" thread.
362		382
363	The flags argument can be used to specify special behaviour or specific	383	The flags argument can be used to specify special behaviour or specific
364	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	384	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
365		385
366	The following flags are supported:	386	The following flags are supported:
…		…
401	environment variable.	421	environment variable.
402		422
403	=item C<EVFLAG_NOINOTIFY>	423	=item C<EVFLAG_NOINOTIFY>
404		424
405	When this flag is specified, then libev will not attempt to use the	425	When this flag is specified, then libev will not attempt to use the
406	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and	426	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
407	testing, this flag can be useful to conserve inotify file descriptors, as	427	testing, this flag can be useful to conserve inotify file descriptors, as
408	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.	428	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
409		429
410	=item C<EVFLAG_SIGNALFD>	430	=item C<EVFLAG_SIGNALFD>
411		431
412	When this flag is specified, then libev will attempt to use the	432	When this flag is specified, then libev will attempt to use the
413	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API	433	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
414	delivers signals synchronously, which makes it both faster and might make	434	delivers signals synchronously, which makes it both faster and might make
415	it possible to get the queued signal data. It can also simplify signal	435	it possible to get the queued signal data. It can also simplify signal
416	handling with threads, as long as you properly block signals in your	436	handling with threads, as long as you properly block signals in your
417	threads that are not interested in handling them.	437	threads that are not interested in handling them.
418		438
419	Signalfd will not be used by default as this changes your signal mask, and	439	Signalfd will not be used by default as this changes your signal mask, and
420	there are a lot of shoddy libraries and programs (glib's threadpool for	440	there are a lot of shoddy libraries and programs (glib's threadpool for
421	example) that can't properly initialise their signal masks.	441	example) that can't properly initialise their signal masks.
		442
		443	=item C<EVFLAG_NOSIGMASK>
		444
		445	When this flag is specified, then libev will avoid to modify the signal
		446	mask. Specifically, this means you have to make sure signals are unblocked
		447	when you want to receive them.
		448
		449	This behaviour is useful when you want to do your own signal handling, or
		450	want to handle signals only in specific threads and want to avoid libev
		451	unblocking the signals.
		452
		453	It's also required by POSIX in a threaded program, as libev calls
		454	C<sigprocmask>, whose behaviour is officially unspecified.
		455
		456	This flag's behaviour will become the default in future versions of libev.
422		457
423	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	458	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
424		459
425	This is your standard select(2) backend. Not I<completely> standard, as	460	This is your standard select(2) backend. Not I<completely> standard, as
426	libev tries to roll its own fd_set with no limits on the number of fds,	461	libev tries to roll its own fd_set with no limits on the number of fds,
…		…
454	=item C<EVBACKEND_EPOLL> (value 4, Linux)	489	=item C<EVBACKEND_EPOLL> (value 4, Linux)
455		490
456	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9	491	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
457	kernels).	492	kernels).
458		493
459	For few fds, this backend is a bit little slower than poll and select,	494	For few fds, this backend is a bit little slower than poll and select, but
460	but it scales phenomenally better. While poll and select usually scale	495	it scales phenomenally better. While poll and select usually scale like
461	like O(total_fds) where n is the total number of fds (or the highest fd),	496	O(total_fds) where total_fds is the total number of fds (or the highest
462	epoll scales either O(1) or O(active_fds).	497	fd), epoll scales either O(1) or O(active_fds).
463		498
464	The epoll mechanism deserves honorable mention as the most misdesigned	499	The epoll mechanism deserves honorable mention as the most misdesigned
465	of the more advanced event mechanisms: mere annoyances include silently	500	of the more advanced event mechanisms: mere annoyances include silently
466	dropping file descriptors, requiring a system call per change per file	501	dropping file descriptors, requiring a system call per change per file
467	descriptor (and unnecessary guessing of parameters), problems with dup and	502	descriptor (and unnecessary guessing of parameters), problems with dup,
		503	returning before the timeout value, resulting in additional iterations
		504	(and only giving 5ms accuracy while select on the same platform gives
468	so on. The biggest issue is fork races, however - if a program forks then	505	0.1ms) and so on. The biggest issue is fork races, however - if a program
469	I<both> parent and child process have to recreate the epoll set, which can	506	forks then I<both> parent and child process have to recreate the epoll
470	take considerable time (one syscall per file descriptor) and is of course	507	set, which can take considerable time (one syscall per file descriptor)
471	hard to detect.	508	and is of course hard to detect.
472		509
473	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	510	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
474	of course I<doesn't>, and epoll just loves to report events for totally	511	but of course I<doesn't>, and epoll just loves to report events for
475	I<different> file descriptors (even already closed ones, so one cannot	512	totally I<different> file descriptors (even already closed ones, so
476	even remove them from the set) than registered in the set (especially	513	one cannot even remove them from the set) than registered in the set
477	on SMP systems). Libev tries to counter these spurious notifications by	514	(especially on SMP systems). Libev tries to counter these spurious
478	employing an additional generation counter and comparing that against the	515	notifications by employing an additional generation counter and comparing
479	events to filter out spurious ones, recreating the set when required. Last	516	that against the events to filter out spurious ones, recreating the set
		517	when required. Epoll also erroneously rounds down timeouts, but gives you
		518	no way to know when and by how much, so sometimes you have to busy-wait
		519	because epoll returns immediately despite a nonzero timeout. And last
480	not least, it also refuses to work with some file descriptors which work	520	not least, it also refuses to work with some file descriptors which work
481	perfectly fine with C<select> (files, many character devices...).	521	perfectly fine with C<select> (files, many character devices...).
		522
		523	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
		524	cobbled together in a hurry, no thought to design or interaction with
		525	others. Oh, the pain, will it ever stop...
482		526
483	While stopping, setting and starting an I/O watcher in the same iteration	527	While stopping, setting and starting an I/O watcher in the same iteration
484	will result in some caching, there is still a system call per such	528	will result in some caching, there is still a system call per such
485	incident (because the same I<file descriptor> could point to a different	529	incident (because the same I<file descriptor> could point to a different
486	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	530	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
523		567
524	It scales in the same way as the epoll backend, but the interface to the	568	It scales in the same way as the epoll backend, but the interface to the
525	kernel is more efficient (which says nothing about its actual speed, of	569	kernel is more efficient (which says nothing about its actual speed, of
526	course). While stopping, setting and starting an I/O watcher does never	570	course). While stopping, setting and starting an I/O watcher does never
527	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	571	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
528	two event changes per incident. Support for C<fork ()> is very bad (but	572	two event changes per incident. Support for C<fork ()> is very bad (you
529	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect	573	might have to leak fd's on fork, but it's more sane than epoll) and it
530	cases	574	drops fds silently in similarly hard-to-detect cases.
531		575
532	This backend usually performs well under most conditions.	576	This backend usually performs well under most conditions.
533		577
534	While nominally embeddable in other event loops, this doesn't work	578	While nominally embeddable in other event loops, this doesn't work
535	everywhere, so you might need to test for this. And since it is broken	579	everywhere, so you might need to test for this. And since it is broken
…		…
552	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	596	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
553		597
554	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	598	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
555	it's really slow, but it still scales very well (O(active_fds)).	599	it's really slow, but it still scales very well (O(active_fds)).
556		600
557	Please note that Solaris event ports can deliver a lot of spurious
558	notifications, so you need to use non-blocking I/O or other means to avoid
559	blocking when no data (or space) is available.
560
561	While this backend scales well, it requires one system call per active	601	While this backend scales well, it requires one system call per active
562	file descriptor per loop iteration. For small and medium numbers of file	602	file descriptor per loop iteration. For small and medium numbers of file
563	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	603	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
564	might perform better.	604	might perform better.
565		605
566	On the positive side, with the exception of the spurious readiness	606	On the positive side, this backend actually performed fully to
567	notifications, this backend actually performed fully to specification
568	in all tests and is fully embeddable, which is a rare feat among the	607	specification in all tests and is fully embeddable, which is a rare feat
569	OS-specific backends (I vastly prefer correctness over speed hacks).	608	among the OS-specific backends (I vastly prefer correctness over speed
		609	hacks).
		610
		611	On the negative side, the interface is I<bizarre> - so bizarre that
		612	even sun itself gets it wrong in their code examples: The event polling
		613	function sometimes returns events to the caller even though an error
		614	occurred, but with no indication whether it has done so or not (yes, it's
		615	even documented that way) - deadly for edge-triggered interfaces where you
		616	absolutely have to know whether an event occurred or not because you have
		617	to re-arm the watcher.
		618
		619	Fortunately libev seems to be able to work around these idiocies.
570		620
571	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	621	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
572	C<EVBACKEND_POLL>.	622	C<EVBACKEND_POLL>.
573		623
574	=item C<EVBACKEND_ALL>	624	=item C<EVBACKEND_ALL>
575		625
576	Try all backends (even potentially broken ones that wouldn't be tried	626	Try all backends (even potentially broken ones that wouldn't be tried
577	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	627	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
578	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	628	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
579		629
580	It is definitely not recommended to use this flag.	630	It is definitely not recommended to use this flag, use whatever
		631	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		632	at all.
		633
		634	=item C<EVBACKEND_MASK>
		635
		636	Not a backend at all, but a mask to select all backend bits from a
		637	C<flags> value, in case you want to mask out any backends from a flags
		638	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
581		639
582	=back	640	=back
583		641
584	If one or more of the backend flags are or'ed into the flags value,	642	If one or more of the backend flags are or'ed into the flags value,
585	then only these backends will be tried (in the reverse order as listed	643	then only these backends will be tried (in the reverse order as listed
…		…
589	Example: Try to create a event loop that uses epoll and nothing else.	647	Example: Try to create a event loop that uses epoll and nothing else.
590		648
591	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	649	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
592	if (!epoller)	650	if (!epoller)
593	fatal ("no epoll found here, maybe it hides under your chair");	651	fatal ("no epoll found here, maybe it hides under your chair");
		652
		653	Example: Use whatever libev has to offer, but make sure that kqueue is
		654	used if available.
		655
		656	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
594		657
595	=item ev_loop_destroy (loop)	658	=item ev_loop_destroy (loop)
596		659
597	Destroys an event loop object (frees all memory and kernel state	660	Destroys an event loop object (frees all memory and kernel state
598	etc.). None of the active event watchers will be stopped in the normal	661	etc.). None of the active event watchers will be stopped in the normal
…		…
609	This function is normally used on loop objects allocated by	672	This function is normally used on loop objects allocated by
610	C<ev_loop_new>, but it can also be used on the default loop returned by	673	C<ev_loop_new>, but it can also be used on the default loop returned by
611	C<ev_default_loop>, in which case it is not thread-safe.	674	C<ev_default_loop>, in which case it is not thread-safe.
612		675
613	Note that it is not advisable to call this function on the default loop	676	Note that it is not advisable to call this function on the default loop
614	except in the rare occasion where you really need to free it's resources.	677	except in the rare occasion where you really need to free its resources.
615	If you need dynamically allocated loops it is better to use C<ev_loop_new>	678	If you need dynamically allocated loops it is better to use C<ev_loop_new>
616	and C<ev_loop_destroy>.	679	and C<ev_loop_destroy>.
617		680
618	=item ev_loop_fork (loop)	681	=item ev_loop_fork (loop)
619		682
…		…
667	prepare and check phases.	730	prepare and check phases.
668		731
669	=item unsigned int ev_depth (loop)	732	=item unsigned int ev_depth (loop)
670		733
671	Returns the number of times C<ev_run> was entered minus the number of	734	Returns the number of times C<ev_run> was entered minus the number of
672	times C<ev_run> was exited, in other words, the recursion depth.	735	times C<ev_run> was exited normally, in other words, the recursion depth.
673		736
674	Outside C<ev_run>, this number is zero. In a callback, this number is	737	Outside C<ev_run>, this number is zero. In a callback, this number is
675	C<1>, unless C<ev_run> was invoked recursively (or from another thread),	738	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
676	in which case it is higher.	739	in which case it is higher.
677		740
678	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread	741	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
679	etc.), doesn't count as "exit" - consider this as a hint to avoid such	742	throwing an exception etc.), doesn't count as "exit" - consider this
680	ungentleman-like behaviour unless it's really convenient.	743	as a hint to avoid such ungentleman-like behaviour unless it's really
		744	convenient, in which case it is fully supported.
681		745
682	=item unsigned int ev_backend (loop)	746	=item unsigned int ev_backend (loop)
683		747
684	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	748	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
685	use.	749	use.
…		…
700		764
701	This function is rarely useful, but when some event callback runs for a	765	This function is rarely useful, but when some event callback runs for a
702	very long time without entering the event loop, updating libev's idea of	766	very long time without entering the event loop, updating libev's idea of
703	the current time is a good idea.	767	the current time is a good idea.
704		768
705	See also L<The special problem of time updates> in the C<ev_timer> section.	769	See also L</The special problem of time updates> in the C<ev_timer> section.
706		770
707	=item ev_suspend (loop)	771	=item ev_suspend (loop)
708		772
709	=item ev_resume (loop)	773	=item ev_resume (loop)
710		774
…		…
728	without a previous call to C<ev_suspend>.	792	without a previous call to C<ev_suspend>.
729		793
730	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	794	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
731	event loop time (see C<ev_now_update>).	795	event loop time (see C<ev_now_update>).
732		796
733	=item ev_run (loop, int flags)	797	=item bool ev_run (loop, int flags)
734		798
735	Finally, this is it, the event handler. This function usually is called	799	Finally, this is it, the event handler. This function usually is called
736	after you have initialised all your watchers and you want to start	800	after you have initialised all your watchers and you want to start
737	handling events. It will ask the operating system for any new events, call	801	handling events. It will ask the operating system for any new events, call
738	the watcher callbacks, an then repeat the whole process indefinitely: This	802	the watcher callbacks, and then repeat the whole process indefinitely: This
739	is why event loops are called I<loops>.	803	is why event loops are called I<loops>.
740		804
741	If the flags argument is specified as C<0>, it will keep handling events	805	If the flags argument is specified as C<0>, it will keep handling events
742	until either no event watchers are active anymore or C<ev_break> was	806	until either no event watchers are active anymore or C<ev_break> was
743	called.	807	called.
		808
		809	The return value is false if there are no more active watchers (which
		810	usually means "all jobs done" or "deadlock"), and true in all other cases
		811	(which usually means " you should call C<ev_run> again").
744		812
745	Please note that an explicit C<ev_break> is usually better than	813	Please note that an explicit C<ev_break> is usually better than
746	relying on all watchers to be stopped when deciding when a program has	814	relying on all watchers to be stopped when deciding when a program has
747	finished (especially in interactive programs), but having a program	815	finished (especially in interactive programs), but having a program
748	that automatically loops as long as it has to and no longer by virtue	816	that automatically loops as long as it has to and no longer by virtue
749	of relying on its watchers stopping correctly, that is truly a thing of	817	of relying on its watchers stopping correctly, that is truly a thing of
750	beauty.	818	beauty.
751		819
		820	This function is I<mostly> exception-safe - you can break out of a
		821	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		822	exception and so on. This does not decrement the C<ev_depth> value, nor
		823	will it clear any outstanding C<EVBREAK_ONE> breaks.
		824
752	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle	825	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
753	those events and any already outstanding ones, but will not wait and	826	those events and any already outstanding ones, but will not wait and
754	block your process in case there are no events and will return after one	827	block your process in case there are no events and will return after one
755	iteration of the loop. This is sometimes useful to poll and handle new	828	iteration of the loop. This is sometimes useful to poll and handle new
756	events while doing lengthy calculations, to keep the program responsive.	829	events while doing lengthy calculations, to keep the program responsive.
…		…
765	This is useful if you are waiting for some external event in conjunction	838	This is useful if you are waiting for some external event in conjunction
766	with something not expressible using other libev watchers (i.e. "roll your	839	with something not expressible using other libev watchers (i.e. "roll your
767	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	840	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
768	usually a better approach for this kind of thing.	841	usually a better approach for this kind of thing.
769		842
770	Here are the gory details of what C<ev_run> does:	843	Here are the gory details of what C<ev_run> does (this is for your
		844	understanding, not a guarantee that things will work exactly like this in
		845	future versions):
771		846
772	- Increment loop depth.	847	- Increment loop depth.
773	- Reset the ev_break status.	848	- Reset the ev_break status.
774	- Before the first iteration, call any pending watchers.	849	- Before the first iteration, call any pending watchers.
775	LOOP:	850	LOOP:
…		…
808	anymore.	883	anymore.
809		884
810	... queue jobs here, make sure they register event watchers as long	885	... queue jobs here, make sure they register event watchers as long
811	... as they still have work to do (even an idle watcher will do..)	886	... as they still have work to do (even an idle watcher will do..)
812	ev_run (my_loop, 0);	887	ev_run (my_loop, 0);
813	... jobs done or somebody called unloop. yeah!	888	... jobs done or somebody called break. yeah!
814		889
815	=item ev_break (loop, how)	890	=item ev_break (loop, how)
816		891
817	Can be used to make a call to C<ev_run> return early (but only after it	892	Can be used to make a call to C<ev_run> return early (but only after it
818	has processed all outstanding events). The C<how> argument must be either	893	has processed all outstanding events). The C<how> argument must be either
819	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or	894	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
820	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.	895	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
821		896
822	This "unloop state" will be cleared when entering C<ev_run> again.	897	This "break state" will be cleared on the next call to C<ev_run>.
823		898
824	It is safe to call C<ev_break> from outside any C<ev_run> calls. ##TODO##	899	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		900	which case it will have no effect.
825		901
826	=item ev_ref (loop)	902	=item ev_ref (loop)
827		903
828	=item ev_unref (loop)	904	=item ev_unref (loop)
829		905
…		…
850	running when nothing else is active.	926	running when nothing else is active.
851		927
852	ev_signal exitsig;	928	ev_signal exitsig;
853	ev_signal_init (&exitsig, sig_cb, SIGINT);	929	ev_signal_init (&exitsig, sig_cb, SIGINT);
854	ev_signal_start (loop, &exitsig);	930	ev_signal_start (loop, &exitsig);
855	evf_unref (loop);	931	ev_unref (loop);
856		932
857	Example: For some weird reason, unregister the above signal handler again.	933	Example: For some weird reason, unregister the above signal handler again.
858		934
859	ev_ref (loop);	935	ev_ref (loop);
860	ev_signal_stop (loop, &exitsig);	936	ev_signal_stop (loop, &exitsig);
…		…
880	overhead for the actual polling but can deliver many events at once.	956	overhead for the actual polling but can deliver many events at once.
881		957
882	By setting a higher I<io collect interval> you allow libev to spend more	958	By setting a higher I<io collect interval> you allow libev to spend more
883	time collecting I/O events, so you can handle more events per iteration,	959	time collecting I/O events, so you can handle more events per iteration,
884	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	960	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
885	C<ev_timer>) will be not affected. Setting this to a non-null value will	961	C<ev_timer>) will not be affected. Setting this to a non-null value will
886	introduce an additional C<ev_sleep ()> call into most loop iterations. The	962	introduce an additional C<ev_sleep ()> call into most loop iterations. The
887	sleep time ensures that libev will not poll for I/O events more often then	963	sleep time ensures that libev will not poll for I/O events more often then
888	once per this interval, on average.	964	once per this interval, on average (as long as the host time resolution is
		965	good enough).
889		966
890	Likewise, by setting a higher I<timeout collect interval> you allow libev	967	Likewise, by setting a higher I<timeout collect interval> you allow libev
891	to spend more time collecting timeouts, at the expense of increased	968	to spend more time collecting timeouts, at the expense of increased
892	latency/jitter/inexactness (the watcher callback will be called	969	latency/jitter/inexactness (the watcher callback will be called
893	later). C<ev_io> watchers will not be affected. Setting this to a non-null	970	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
939	invoke the actual watchers inside another context (another thread etc.).	1016	invoke the actual watchers inside another context (another thread etc.).
940		1017
941	If you want to reset the callback, use C<ev_invoke_pending> as new	1018	If you want to reset the callback, use C<ev_invoke_pending> as new
942	callback.	1019	callback.
943		1020
944	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))	1021	=item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())
945		1022
946	Sometimes you want to share the same loop between multiple threads. This	1023	Sometimes you want to share the same loop between multiple threads. This
947	can be done relatively simply by putting mutex_lock/unlock calls around	1024	can be done relatively simply by putting mutex_lock/unlock calls around
948	each call to a libev function.	1025	each call to a libev function.
949		1026
950	However, C<ev_run> can run an indefinite time, so it is not feasible	1027	However, C<ev_run> can run an indefinite time, so it is not feasible
951	to wait for it to return. One way around this is to wake up the event	1028	to wait for it to return. One way around this is to wake up the event
952	loop via C<ev_break> and C<av_async_send>, another way is to set these	1029	loop via C<ev_break> and C<ev_async_send>, another way is to set these
953	I<release> and I<acquire> callbacks on the loop.	1030	I<release> and I<acquire> callbacks on the loop.
954		1031
955	When set, then C<release> will be called just before the thread is	1032	When set, then C<release> will be called just before the thread is
956	suspended waiting for new events, and C<acquire> is called just	1033	suspended waiting for new events, and C<acquire> is called just
957	afterwards.	1034	afterwards.
…		…
972	See also the locking example in the C<THREADS> section later in this	1049	See also the locking example in the C<THREADS> section later in this
973	document.	1050	document.
974		1051
975	=item ev_set_userdata (loop, void *data)	1052	=item ev_set_userdata (loop, void *data)
976		1053
977	=item ev_userdata (loop)	1054	=item void *ev_userdata (loop)
978		1055
979	Set and retrieve a single C<void *> associated with a loop. When	1056	Set and retrieve a single C<void *> associated with a loop. When
980	C<ev_set_userdata> has never been called, then C<ev_userdata> returns	1057	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
981	C<0.>	1058	C<0>.
982		1059
983	These two functions can be used to associate arbitrary data with a loop,	1060	These two functions can be used to associate arbitrary data with a loop,
984	and are intended solely for the C<invoke_pending_cb>, C<release> and	1061	and are intended solely for the C<invoke_pending_cb>, C<release> and
985	C<acquire> callbacks described above, but of course can be (ab-)used for	1062	C<acquire> callbacks described above, but of course can be (ab-)used for
986	any other purpose as well.	1063	any other purpose as well.
…		…
1097		1174
1098	=item C<EV_PREPARE>	1175	=item C<EV_PREPARE>
1099		1176
1100	=item C<EV_CHECK>	1177	=item C<EV_CHECK>
1101		1178
1102	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts	1179	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to
1103	to gather new events, and all C<ev_check> watchers are invoked just after	1180	gather new events, and all C<ev_check> watchers are queued (not invoked)
1104	C<ev_run> has gathered them, but before it invokes any callbacks for any	1181	just after C<ev_run> has gathered them, but before it queues any callbacks
		1182	for any received events. That means C<ev_prepare> watchers are the last
		1183	watchers invoked before the event loop sleeps or polls for new events, and
		1184	C<ev_check> watchers will be invoked before any other watchers of the same
		1185	or lower priority within an event loop iteration.
		1186
1105	received events. Callbacks of both watcher types can start and stop as	1187	Callbacks of both watcher types can start and stop as many watchers as
1106	many watchers as they want, and all of them will be taken into account	1188	they want, and all of them will be taken into account (for example, a
1107	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1189	C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from
1108	C<ev_run> from blocking).	1190	blocking).
1109		1191
1110	=item C<EV_EMBED>	1192	=item C<EV_EMBED>
1111		1193
1112	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1194	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1113		1195
1114	=item C<EV_FORK>	1196	=item C<EV_FORK>
1115		1197
1116	The event loop has been resumed in the child process after fork (see	1198	The event loop has been resumed in the child process after fork (see
1117	C<ev_fork>).	1199	C<ev_fork>).
		1200
		1201	=item C<EV_CLEANUP>
		1202
		1203	The event loop is about to be destroyed (see C<ev_cleanup>).
1118		1204
1119	=item C<EV_ASYNC>	1205	=item C<EV_ASYNC>
1120		1206
1121	The given async watcher has been asynchronously notified (see C<ev_async>).	1207	The given async watcher has been asynchronously notified (see C<ev_async>).
1122		1208
…		…
1144	programs, though, as the fd could already be closed and reused for another	1230	programs, though, as the fd could already be closed and reused for another
1145	thing, so beware.	1231	thing, so beware.
1146		1232
1147	=back	1233	=back
1148		1234
		1235	=head2 GENERIC WATCHER FUNCTIONS
		1236
		1237	=over 4
		1238
		1239	=item C<ev_init> (ev_TYPE *watcher, callback)
		1240
		1241	This macro initialises the generic portion of a watcher. The contents
		1242	of the watcher object can be arbitrary (so C<malloc> will do). Only
		1243	the generic parts of the watcher are initialised, you I<need> to call
		1244	the type-specific C<ev_TYPE_set> macro afterwards to initialise the
		1245	type-specific parts. For each type there is also a C<ev_TYPE_init> macro
		1246	which rolls both calls into one.
		1247
		1248	You can reinitialise a watcher at any time as long as it has been stopped
		1249	(or never started) and there are no pending events outstanding.
		1250
		1251	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
		1252	int revents)>.
		1253
		1254	Example: Initialise an C<ev_io> watcher in two steps.
		1255
		1256	ev_io w;
		1257	ev_init (&w, my_cb);
		1258	ev_io_set (&w, STDIN_FILENO, EV_READ);
		1259
		1260	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
		1261
		1262	This macro initialises the type-specific parts of a watcher. You need to
		1263	call C<ev_init> at least once before you call this macro, but you can
		1264	call C<ev_TYPE_set> any number of times. You must not, however, call this
		1265	macro on a watcher that is active (it can be pending, however, which is a
		1266	difference to the C<ev_init> macro).
		1267
		1268	Although some watcher types do not have type-specific arguments
		1269	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
		1270
		1271	See C<ev_init>, above, for an example.
		1272
		1273	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
		1274
		1275	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
		1276	calls into a single call. This is the most convenient method to initialise
		1277	a watcher. The same limitations apply, of course.
		1278
		1279	Example: Initialise and set an C<ev_io> watcher in one step.
		1280
		1281	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1282
		1283	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
		1284
		1285	Starts (activates) the given watcher. Only active watchers will receive
		1286	events. If the watcher is already active nothing will happen.
		1287
		1288	Example: Start the C<ev_io> watcher that is being abused as example in this
		1289	whole section.
		1290
		1291	ev_io_start (EV_DEFAULT_UC, &w);
		1292
		1293	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
		1294
		1295	Stops the given watcher if active, and clears the pending status (whether
		1296	the watcher was active or not).
		1297
		1298	It is possible that stopped watchers are pending - for example,
		1299	non-repeating timers are being stopped when they become pending - but
		1300	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
		1301	pending. If you want to free or reuse the memory used by the watcher it is
		1302	therefore a good idea to always call its C<ev_TYPE_stop> function.
		1303
		1304	=item bool ev_is_active (ev_TYPE *watcher)
		1305
		1306	Returns a true value iff the watcher is active (i.e. it has been started
		1307	and not yet been stopped). As long as a watcher is active you must not modify
		1308	it.
		1309
		1310	=item bool ev_is_pending (ev_TYPE *watcher)
		1311
		1312	Returns a true value iff the watcher is pending, (i.e. it has outstanding
		1313	events but its callback has not yet been invoked). As long as a watcher
		1314	is pending (but not active) you must not call an init function on it (but
		1315	C<ev_TYPE_set> is safe), you must not change its priority, and you must
		1316	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		1317	it).
		1318
		1319	=item callback ev_cb (ev_TYPE *watcher)
		1320
		1321	Returns the callback currently set on the watcher.
		1322
		1323	=item ev_set_cb (ev_TYPE *watcher, callback)
		1324
		1325	Change the callback. You can change the callback at virtually any time
		1326	(modulo threads).
		1327
		1328	=item ev_set_priority (ev_TYPE *watcher, int priority)
		1329
		1330	=item int ev_priority (ev_TYPE *watcher)
		1331
		1332	Set and query the priority of the watcher. The priority is a small
		1333	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		1334	(default: C<-2>). Pending watchers with higher priority will be invoked
		1335	before watchers with lower priority, but priority will not keep watchers
		1336	from being executed (except for C<ev_idle> watchers).
		1337
		1338	If you need to suppress invocation when higher priority events are pending
		1339	you need to look at C<ev_idle> watchers, which provide this functionality.
		1340
		1341	You I<must not> change the priority of a watcher as long as it is active or
		1342	pending.
		1343
		1344	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1345	fine, as long as you do not mind that the priority value you query might
		1346	or might not have been clamped to the valid range.
		1347
		1348	The default priority used by watchers when no priority has been set is
		1349	always C<0>, which is supposed to not be too high and not be too low :).
		1350
		1351	See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
		1352	priorities.
		1353
		1354	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		1355
		1356	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		1357	C<loop> nor C<revents> need to be valid as long as the watcher callback
		1358	can deal with that fact, as both are simply passed through to the
		1359	callback.
		1360
		1361	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		1362
		1363	If the watcher is pending, this function clears its pending status and
		1364	returns its C<revents> bitset (as if its callback was invoked). If the
		1365	watcher isn't pending it does nothing and returns C<0>.
		1366
		1367	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1368	callback to be invoked, which can be accomplished with this function.
		1369
		1370	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1371
		1372	Feeds the given event set into the event loop, as if the specified event
		1373	had happened for the specified watcher (which must be a pointer to an
		1374	initialised but not necessarily started event watcher). Obviously you must
		1375	not free the watcher as long as it has pending events.
		1376
		1377	Stopping the watcher, letting libev invoke it, or calling
		1378	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1379	not started in the first place.
		1380
		1381	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1382	functions that do not need a watcher.
		1383
		1384	=back
		1385
		1386	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
		1387	OWN COMPOSITE WATCHERS> idioms.
		1388
1149	=head2 WATCHER STATES	1389	=head2 WATCHER STATES
1150		1390
1151	There are various watcher states mentioned throughout this manual -	1391	There are various watcher states mentioned throughout this manual -
1152	active, pending and so on. In this section these states and the rules to	1392	active, pending and so on. In this section these states and the rules to
1153	transition between them will be described in more detail - and while these	1393	transition between them will be described in more detail - and while these
1154	rules might look complicated, they usually do "the right thing".	1394	rules might look complicated, they usually do "the right thing".
1155		1395
1156	=over 4	1396	=over 4
1157		1397
1158	=item initialiased	1398	=item initialised
1159		1399
1160	Before a watcher can be registered with the event looop it has to be	1400	Before a watcher can be registered with the event loop it has to be
1161	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to	1401	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
1162	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.	1402	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1163		1403
1164	In this state it is simply some block of memory that is suitable for use	1404	In this state it is simply some block of memory that is suitable for
1165	in an event loop. It can be moved around, freed, reused etc. at will.	1405	use in an event loop. It can be moved around, freed, reused etc. at
		1406	will - as long as you either keep the memory contents intact, or call
		1407	C<ev_TYPE_init> again.
1166		1408
1167	=item started/running/active	1409	=item started/running/active
1168		1410
1169	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes	1411	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1170	property of the event loop, and is actively waiting for events. While in	1412	property of the event loop, and is actively waiting for events. While in
…		…
1198	latter will clear any pending state the watcher might be in, regardless	1440	latter will clear any pending state the watcher might be in, regardless
1199	of whether it was active or not, so stopping a watcher explicitly before	1441	of whether it was active or not, so stopping a watcher explicitly before
1200	freeing it is often a good idea.	1442	freeing it is often a good idea.
1201		1443
1202	While stopped (and not pending) the watcher is essentially in the	1444	While stopped (and not pending) the watcher is essentially in the
1203	initialised state, that is it can be reused, moved, modified in any way	1445	initialised state, that is, it can be reused, moved, modified in any way
1204	you wish.	1446	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1447	it again).
1205		1448
1206	=back	1449	=back
1207
1208	=head2 GENERIC WATCHER FUNCTIONS
1209
1210	=over 4
1211
1212	=item C<ev_init> (ev_TYPE *watcher, callback)
1213
1214	This macro initialises the generic portion of a watcher. The contents
1215	of the watcher object can be arbitrary (so C<malloc> will do). Only
1216	the generic parts of the watcher are initialised, you I<need> to call
1217	the type-specific C<ev_TYPE_set> macro afterwards to initialise the
1218	type-specific parts. For each type there is also a C<ev_TYPE_init> macro
1219	which rolls both calls into one.
1220
1221	You can reinitialise a watcher at any time as long as it has been stopped
1222	(or never started) and there are no pending events outstanding.
1223
1224	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
1225	int revents)>.
1226
1227	Example: Initialise an C<ev_io> watcher in two steps.
1228
1229	ev_io w;
1230	ev_init (&w, my_cb);
1231	ev_io_set (&w, STDIN_FILENO, EV_READ);
1232
1233	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
1234
1235	This macro initialises the type-specific parts of a watcher. You need to
1236	call C<ev_init> at least once before you call this macro, but you can
1237	call C<ev_TYPE_set> any number of times. You must not, however, call this
1238	macro on a watcher that is active (it can be pending, however, which is a
1239	difference to the C<ev_init> macro).
1240
1241	Although some watcher types do not have type-specific arguments
1242	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
1243
1244	See C<ev_init>, above, for an example.
1245
1246	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
1247
1248	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
1249	calls into a single call. This is the most convenient method to initialise
1250	a watcher. The same limitations apply, of course.
1251
1252	Example: Initialise and set an C<ev_io> watcher in one step.
1253
1254	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1255
1256	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1257
1258	Starts (activates) the given watcher. Only active watchers will receive
1259	events. If the watcher is already active nothing will happen.
1260
1261	Example: Start the C<ev_io> watcher that is being abused as example in this
1262	whole section.
1263
1264	ev_io_start (EV_DEFAULT_UC, &w);
1265
1266	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1267
1268	Stops the given watcher if active, and clears the pending status (whether
1269	the watcher was active or not).
1270
1271	It is possible that stopped watchers are pending - for example,
1272	non-repeating timers are being stopped when they become pending - but
1273	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
1274	pending. If you want to free or reuse the memory used by the watcher it is
1275	therefore a good idea to always call its C<ev_TYPE_stop> function.
1276
1277	=item bool ev_is_active (ev_TYPE *watcher)
1278
1279	Returns a true value iff the watcher is active (i.e. it has been started
1280	and not yet been stopped). As long as a watcher is active you must not modify
1281	it.
1282
1283	=item bool ev_is_pending (ev_TYPE *watcher)
1284
1285	Returns a true value iff the watcher is pending, (i.e. it has outstanding
1286	events but its callback has not yet been invoked). As long as a watcher
1287	is pending (but not active) you must not call an init function on it (but
1288	C<ev_TYPE_set> is safe), you must not change its priority, and you must
1289	make sure the watcher is available to libev (e.g. you cannot C<free ()>
1290	it).
1291
1292	=item callback ev_cb (ev_TYPE *watcher)
1293
1294	Returns the callback currently set on the watcher.
1295
1296	=item ev_cb_set (ev_TYPE *watcher, callback)
1297
1298	Change the callback. You can change the callback at virtually any time
1299	(modulo threads).
1300
1301	=item ev_set_priority (ev_TYPE *watcher, int priority)
1302
1303	=item int ev_priority (ev_TYPE *watcher)
1304
1305	Set and query the priority of the watcher. The priority is a small
1306	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1307	(default: C<-2>). Pending watchers with higher priority will be invoked
1308	before watchers with lower priority, but priority will not keep watchers
1309	from being executed (except for C<ev_idle> watchers).
1310
1311	If you need to suppress invocation when higher priority events are pending
1312	you need to look at C<ev_idle> watchers, which provide this functionality.
1313
1314	You I<must not> change the priority of a watcher as long as it is active or
1315	pending.
1316
1317	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1318	fine, as long as you do not mind that the priority value you query might
1319	or might not have been clamped to the valid range.
1320
1321	The default priority used by watchers when no priority has been set is
1322	always C<0>, which is supposed to not be too high and not be too low :).
1323
1324	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1325	priorities.
1326
1327	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1328
1329	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1330	C<loop> nor C<revents> need to be valid as long as the watcher callback
1331	can deal with that fact, as both are simply passed through to the
1332	callback.
1333
1334	=item int ev_clear_pending (loop, ev_TYPE *watcher)
1335
1336	If the watcher is pending, this function clears its pending status and
1337	returns its C<revents> bitset (as if its callback was invoked). If the
1338	watcher isn't pending it does nothing and returns C<0>.
1339
1340	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1341	callback to be invoked, which can be accomplished with this function.
1342
1343	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
1344
1345	Feeds the given event set into the event loop, as if the specified event
1346	had happened for the specified watcher (which must be a pointer to an
1347	initialised but not necessarily started event watcher). Obviously you must
1348	not free the watcher as long as it has pending events.
1349
1350	Stopping the watcher, letting libev invoke it, or calling
1351	C<ev_clear_pending> will clear the pending event, even if the watcher was
1352	not started in the first place.
1353
1354	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1355	functions that do not need a watcher.
1356
1357	=back
1358
1359
1360	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1361
1362	Each watcher has, by default, a member C<void *data> that you can change
1363	and read at any time: libev will completely ignore it. This can be used
1364	to associate arbitrary data with your watcher. If you need more data and
1365	don't want to allocate memory and store a pointer to it in that data
1366	member, you can also "subclass" the watcher type and provide your own
1367	data:
1368
1369	struct my_io
1370	{
1371	ev_io io;
1372	int otherfd;
1373	void *somedata;
1374	struct whatever *mostinteresting;
1375	};
1376
1377	...
1378	struct my_io w;
1379	ev_io_init (&w.io, my_cb, fd, EV_READ);
1380
1381	And since your callback will be called with a pointer to the watcher, you
1382	can cast it back to your own type:
1383
1384	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1385	{
1386	struct my_io *w = (struct my_io *)w_;
1387	...
1388	}
1389
1390	More interesting and less C-conformant ways of casting your callback type
1391	instead have been omitted.
1392
1393	Another common scenario is to use some data structure with multiple
1394	embedded watchers:
1395
1396	struct my_biggy
1397	{
1398	int some_data;
1399	ev_timer t1;
1400	ev_timer t2;
1401	}
1402
1403	In this case getting the pointer to C<my_biggy> is a bit more
1404	complicated: Either you store the address of your C<my_biggy> struct
1405	in the C<data> member of the watcher (for woozies), or you need to use
1406	some pointer arithmetic using C<offsetof> inside your watchers (for real
1407	programmers):
1408
1409	#include <stddef.h>
1410
1411	static void
1412	t1_cb (EV_P_ ev_timer *w, int revents)
1413	{
1414	struct my_biggy big = (struct my_biggy *)
1415	(((char *)w) - offsetof (struct my_biggy, t1));
1416	}
1417
1418	static void
1419	t2_cb (EV_P_ ev_timer *w, int revents)
1420	{
1421	struct my_biggy big = (struct my_biggy *)
1422	(((char *)w) - offsetof (struct my_biggy, t2));
1423	}
1424		1450
1425	=head2 WATCHER PRIORITY MODELS	1451	=head2 WATCHER PRIORITY MODELS
1426		1452
1427	Many event loops support I<watcher priorities>, which are usually small	1453	Many event loops support I<watcher priorities>, which are usually small
1428	integers that influence the ordering of event callback invocation	1454	integers that influence the ordering of event callback invocation
…		…
1555	In general you can register as many read and/or write event watchers per	1581	In general you can register as many read and/or write event watchers per
1556	fd as you want (as long as you don't confuse yourself). Setting all file	1582	fd as you want (as long as you don't confuse yourself). Setting all file
1557	descriptors to non-blocking mode is also usually a good idea (but not	1583	descriptors to non-blocking mode is also usually a good idea (but not
1558	required if you know what you are doing).	1584	required if you know what you are doing).
1559		1585
1560	If you cannot use non-blocking mode, then force the use of a
1561	known-to-be-good backend (at the time of this writing, this includes only
1562	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1563	descriptors for which non-blocking operation makes no sense (such as
1564	files) - libev doesn't guarantee any specific behaviour in that case.
1565
1566	Another thing you have to watch out for is that it is quite easy to	1586	Another thing you have to watch out for is that it is quite easy to
1567	receive "spurious" readiness notifications, that is your callback might	1587	receive "spurious" readiness notifications, that is, your callback might
1568	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1588	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1569	because there is no data. Not only are some backends known to create a	1589	because there is no data. It is very easy to get into this situation even
1570	lot of those (for example Solaris ports), it is very easy to get into	1590	with a relatively standard program structure. Thus it is best to always
1571	this situation even with a relatively standard program structure. Thus	1591	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1572	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1573	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1592	preferable to a program hanging until some data arrives.
1574		1593
1575	If you cannot run the fd in non-blocking mode (for example you should	1594	If you cannot run the fd in non-blocking mode (for example you should
1576	not play around with an Xlib connection), then you have to separately	1595	not play around with an Xlib connection), then you have to separately
1577	re-test whether a file descriptor is really ready with a known-to-be good	1596	re-test whether a file descriptor is really ready with a known-to-be good
1578	interface such as poll (fortunately in our Xlib example, Xlib already	1597	interface such as poll (fortunately in the case of Xlib, it already does
1579	does this on its own, so its quite safe to use). Some people additionally	1598	this on its own, so its quite safe to use). Some people additionally
1580	use C<SIGALRM> and an interval timer, just to be sure you won't block	1599	use C<SIGALRM> and an interval timer, just to be sure you won't block
1581	indefinitely.	1600	indefinitely.
1582		1601
1583	But really, best use non-blocking mode.	1602	But really, best use non-blocking mode.
1584		1603
…		…
1612		1631
1613	There is no workaround possible except not registering events	1632	There is no workaround possible except not registering events
1614	for potentially C<dup ()>'ed file descriptors, or to resort to	1633	for potentially C<dup ()>'ed file descriptors, or to resort to
1615	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1634	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1616		1635
		1636	=head3 The special problem of files
		1637
		1638	Many people try to use C<select> (or libev) on file descriptors
		1639	representing files, and expect it to become ready when their program
		1640	doesn't block on disk accesses (which can take a long time on their own).
		1641
		1642	However, this cannot ever work in the "expected" way - you get a readiness
		1643	notification as soon as the kernel knows whether and how much data is
		1644	there, and in the case of open files, that's always the case, so you
		1645	always get a readiness notification instantly, and your read (or possibly
		1646	write) will still block on the disk I/O.
		1647
		1648	Another way to view it is that in the case of sockets, pipes, character
		1649	devices and so on, there is another party (the sender) that delivers data
		1650	on its own, but in the case of files, there is no such thing: the disk
		1651	will not send data on its own, simply because it doesn't know what you
		1652	wish to read - you would first have to request some data.
		1653
		1654	Since files are typically not-so-well supported by advanced notification
		1655	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1656	to files, even though you should not use it. The reason for this is
		1657	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1658	usually a tty, often a pipe, but also sometimes files or special devices
		1659	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1660	F</dev/urandom>), and even though the file might better be served with
		1661	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1662	it "just works" instead of freezing.
		1663
		1664	So avoid file descriptors pointing to files when you know it (e.g. use
		1665	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1666	when you rarely read from a file instead of from a socket, and want to
		1667	reuse the same code path.
		1668
1617	=head3 The special problem of fork	1669	=head3 The special problem of fork
1618		1670
1619	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1671	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1620	useless behaviour. Libev fully supports fork, but needs to be told about	1672	useless behaviour. Libev fully supports fork, but needs to be told about
1621	it in the child.	1673	it in the child if you want to continue to use it in the child.
1622		1674
1623	To support fork in your programs, you either have to call	1675	To support fork in your child processes, you have to call C<ev_loop_fork
1624	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1676	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1625	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1677	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1626	C<EVBACKEND_POLL>.
1627		1678
1628	=head3 The special problem of SIGPIPE	1679	=head3 The special problem of SIGPIPE
1629		1680
1630	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1681	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1631	when writing to a pipe whose other end has been closed, your program gets	1682	when writing to a pipe whose other end has been closed, your program gets
…		…
1729	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1780	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1730	monotonic clock option helps a lot here).	1781	monotonic clock option helps a lot here).
1731		1782
1732	The callback is guaranteed to be invoked only I<after> its timeout has	1783	The callback is guaranteed to be invoked only I<after> its timeout has
1733	passed (not I<at>, so on systems with very low-resolution clocks this	1784	passed (not I<at>, so on systems with very low-resolution clocks this
1734	might introduce a small delay). If multiple timers become ready during the	1785	might introduce a small delay, see "the special problem of being too
		1786	early", below). If multiple timers become ready during the same loop
1735	same loop iteration then the ones with earlier time-out values are invoked	1787	iteration then the ones with earlier time-out values are invoked before
1736	before ones of the same priority with later time-out values (but this is	1788	ones of the same priority with later time-out values (but this is no
1737	no longer true when a callback calls C<ev_run> recursively).	1789	longer true when a callback calls C<ev_run> recursively).
1738		1790
1739	=head3 Be smart about timeouts	1791	=head3 Be smart about timeouts
1740		1792
1741	Many real-world problems involve some kind of timeout, usually for error	1793	Many real-world problems involve some kind of timeout, usually for error
1742	recovery. A typical example is an HTTP request - if the other side hangs,	1794	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1817		1869
1818	In this case, it would be more efficient to leave the C<ev_timer> alone,	1870	In this case, it would be more efficient to leave the C<ev_timer> alone,
1819	but remember the time of last activity, and check for a real timeout only	1871	but remember the time of last activity, and check for a real timeout only
1820	within the callback:	1872	within the callback:
1821		1873
		1874	ev_tstamp timeout = 60.;
1822	ev_tstamp last_activity; // time of last activity	1875	ev_tstamp last_activity; // time of last activity
		1876	ev_timer timer;
1823		1877
1824	static void	1878	static void
1825	callback (EV_P_ ev_timer *w, int revents)	1879	callback (EV_P_ ev_timer *w, int revents)
1826	{	1880	{
1827	ev_tstamp now = ev_now (EV_A);	1881	// calculate when the timeout would happen
1828	ev_tstamp timeout = last_activity + 60.;	1882	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1829		1883
1830	// if last_activity + 60. is older than now, we did time out	1884	// if negative, it means we the timeout already occurred
1831	if (timeout < now)	1885	if (after < 0.)
1832	{	1886	{
1833	// timeout occurred, take action	1887	// timeout occurred, take action
1834	}	1888	}
1835	else	1889	else
1836	{	1890	{
1837	// callback was invoked, but there was some activity, re-arm	1891	// callback was invoked, but there was some recent
1838	// the watcher to fire in last_activity + 60, which is	1892	// activity. simply restart the timer to time out
1839	// guaranteed to be in the future, so "again" is positive:	1893	// after "after" seconds, which is the earliest time
1840	w->repeat = timeout - now;	1894	// the timeout can occur.
		1895	ev_timer_set (w, after, 0.);
1841	ev_timer_again (EV_A_ w);	1896	ev_timer_start (EV_A_ w);
1842	}	1897	}
1843	}	1898	}
1844		1899
1845	To summarise the callback: first calculate the real timeout (defined	1900	To summarise the callback: first calculate in how many seconds the
1846	as "60 seconds after the last activity"), then check if that time has	1901	timeout will occur (by calculating the absolute time when it would occur,
1847	been reached, which means something I<did>, in fact, time out. Otherwise	1902	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1848	the callback was invoked too early (C<timeout> is in the future), so	1903	(EV_A)> from that).
1849	re-schedule the timer to fire at that future time, to see if maybe we have
1850	a timeout then.
1851		1904
1852	Note how C<ev_timer_again> is used, taking advantage of the	1905	If this value is negative, then we are already past the timeout, i.e. we
1853	C<ev_timer_again> optimisation when the timer is already running.	1906	timed out, and need to do whatever is needed in this case.
		1907
		1908	Otherwise, we now the earliest time at which the timeout would trigger,
		1909	and simply start the timer with this timeout value.
		1910
		1911	In other words, each time the callback is invoked it will check whether
		1912	the timeout occurred. If not, it will simply reschedule itself to check
		1913	again at the earliest time it could time out. Rinse. Repeat.
1854		1914
1855	This scheme causes more callback invocations (about one every 60 seconds	1915	This scheme causes more callback invocations (about one every 60 seconds
1856	minus half the average time between activity), but virtually no calls to	1916	minus half the average time between activity), but virtually no calls to
1857	libev to change the timeout.	1917	libev to change the timeout.
1858		1918
1859	To start the timer, simply initialise the watcher and set C<last_activity>	1919	To start the machinery, simply initialise the watcher and set
1860	to the current time (meaning we just have some activity :), then call the	1920	C<last_activity> to the current time (meaning there was some activity just
1861	callback, which will "do the right thing" and start the timer:	1921	now), then call the callback, which will "do the right thing" and start
		1922	the timer:
1862		1923
		1924	last_activity = ev_now (EV_A);
1863	ev_init (timer, callback);	1925	ev_init (&timer, callback);
1864	last_activity = ev_now (loop);	1926	callback (EV_A_ &timer, 0);
1865	callback (loop, timer, EV_TIMER);
1866		1927
1867	And when there is some activity, simply store the current time in	1928	When there is some activity, simply store the current time in
1868	C<last_activity>, no libev calls at all:	1929	C<last_activity>, no libev calls at all:
1869		1930
		1931	if (activity detected)
1870	last_activity = ev_now (loop);	1932	last_activity = ev_now (EV_A);
		1933
		1934	When your timeout value changes, then the timeout can be changed by simply
		1935	providing a new value, stopping the timer and calling the callback, which
		1936	will again do the right thing (for example, time out immediately :).
		1937
		1938	timeout = new_value;
		1939	ev_timer_stop (EV_A_ &timer);
		1940	callback (EV_A_ &timer, 0);
1871		1941
1872	This technique is slightly more complex, but in most cases where the	1942	This technique is slightly more complex, but in most cases where the
1873	time-out is unlikely to be triggered, much more efficient.	1943	time-out is unlikely to be triggered, much more efficient.
1874
1875	Changing the timeout is trivial as well (if it isn't hard-coded in the
1876	callback :) - just change the timeout and invoke the callback, which will
1877	fix things for you.
1878		1944
1879	=item 4. Wee, just use a double-linked list for your timeouts.	1945	=item 4. Wee, just use a double-linked list for your timeouts.
1880		1946
1881	If there is not one request, but many thousands (millions...), all	1947	If there is not one request, but many thousands (millions...), all
1882	employing some kind of timeout with the same timeout value, then one can	1948	employing some kind of timeout with the same timeout value, then one can
…		…
1909	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	1975	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1910	rather complicated, but extremely efficient, something that really pays	1976	rather complicated, but extremely efficient, something that really pays
1911	off after the first million or so of active timers, i.e. it's usually	1977	off after the first million or so of active timers, i.e. it's usually
1912	overkill :)	1978	overkill :)
1913		1979
		1980	=head3 The special problem of being too early
		1981
		1982	If you ask a timer to call your callback after three seconds, then
		1983	you expect it to be invoked after three seconds - but of course, this
		1984	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		1985	guaranteed to any precision by libev - imagine somebody suspending the
		1986	process with a STOP signal for a few hours for example.
		1987
		1988	So, libev tries to invoke your callback as soon as possible I<after> the
		1989	delay has occurred, but cannot guarantee this.
		1990
		1991	A less obvious failure mode is calling your callback too early: many event
		1992	loops compare timestamps with a "elapsed delay >= requested delay", but
		1993	this can cause your callback to be invoked much earlier than you would
		1994	expect.
		1995
		1996	To see why, imagine a system with a clock that only offers full second
		1997	resolution (think windows if you can't come up with a broken enough OS
		1998	yourself). If you schedule a one-second timer at the time 500.9, then the
		1999	event loop will schedule your timeout to elapse at a system time of 500
		2000	(500.9 truncated to the resolution) + 1, or 501.
		2001
		2002	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2003	501" and invoke the callback 0.1s after it was started, even though a
		2004	one-second delay was requested - this is being "too early", despite best
		2005	intentions.
		2006
		2007	This is the reason why libev will never invoke the callback if the elapsed
		2008	delay equals the requested delay, but only when the elapsed delay is
		2009	larger than the requested delay. In the example above, libev would only invoke
		2010	the callback at system time 502, or 1.1s after the timer was started.
		2011
		2012	So, while libev cannot guarantee that your callback will be invoked
		2013	exactly when requested, it I<can> and I<does> guarantee that the requested
		2014	delay has actually elapsed, or in other words, it always errs on the "too
		2015	late" side of things.
		2016
1914	=head3 The special problem of time updates	2017	=head3 The special problem of time updates
1915		2018
1916	Establishing the current time is a costly operation (it usually takes at	2019	Establishing the current time is a costly operation (it usually takes
1917	least two system calls): EV therefore updates its idea of the current	2020	at least one system call): EV therefore updates its idea of the current
1918	time only before and after C<ev_run> collects new events, which causes a	2021	time only before and after C<ev_run> collects new events, which causes a
1919	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2022	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1920	lots of events in one iteration.	2023	lots of events in one iteration.
1921		2024
1922	The relative timeouts are calculated relative to the C<ev_now ()>	2025	The relative timeouts are calculated relative to the C<ev_now ()>
…		…
1928	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2031	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1929		2032
1930	If the event loop is suspended for a long time, you can also force an	2033	If the event loop is suspended for a long time, you can also force an
1931	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2034	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1932	()>.	2035	()>.
		2036
		2037	=head3 The special problem of unsynchronised clocks
		2038
		2039	Modern systems have a variety of clocks - libev itself uses the normal
		2040	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2041	jumps).
		2042
		2043	Neither of these clocks is synchronised with each other or any other clock
		2044	on the system, so C<ev_time ()> might return a considerably different time
		2045	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2046	a call to C<gettimeofday> might return a second count that is one higher
		2047	than a directly following call to C<time>.
		2048
		2049	The moral of this is to only compare libev-related timestamps with
		2050	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2051	a second or so.
		2052
		2053	One more problem arises due to this lack of synchronisation: if libev uses
		2054	the system monotonic clock and you compare timestamps from C<ev_time>
		2055	or C<ev_now> from when you started your timer and when your callback is
		2056	invoked, you will find that sometimes the callback is a bit "early".
		2057
		2058	This is because C<ev_timer>s work in real time, not wall clock time, so
		2059	libev makes sure your callback is not invoked before the delay happened,
		2060	I<measured according to the real time>, not the system clock.
		2061
		2062	If your timeouts are based on a physical timescale (e.g. "time out this
		2063	connection after 100 seconds") then this shouldn't bother you as it is
		2064	exactly the right behaviour.
		2065
		2066	If you want to compare wall clock/system timestamps to your timers, then
		2067	you need to use C<ev_periodic>s, as these are based on the wall clock
		2068	time, where your comparisons will always generate correct results.
1933		2069
1934	=head3 The special problems of suspended animation	2070	=head3 The special problems of suspended animation
1935		2071
1936	When you leave the server world it is quite customary to hit machines that	2072	When you leave the server world it is quite customary to hit machines that
1937	can suspend/hibernate - what happens to the clocks during such a suspend?	2073	can suspend/hibernate - what happens to the clocks during such a suspend?
…		…
1981	keep up with the timer (because it takes longer than those 10 seconds to	2117	keep up with the timer (because it takes longer than those 10 seconds to
1982	do stuff) the timer will not fire more than once per event loop iteration.	2118	do stuff) the timer will not fire more than once per event loop iteration.
1983		2119
1984	=item ev_timer_again (loop, ev_timer *)	2120	=item ev_timer_again (loop, ev_timer *)
1985		2121
1986	This will act as if the timer timed out and restart it again if it is	2122	This will act as if the timer timed out, and restarts it again if it is
1987	repeating. The exact semantics are:	2123	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2124	timeout to the C<repeat> value and calling C<ev_timer_start>.
1988		2125
		2126	The exact semantics are as in the following rules, all of which will be
		2127	applied to the watcher:
		2128
		2129	=over 4
		2130
1989	If the timer is pending, its pending status is cleared.	2131	=item If the timer is pending, the pending status is always cleared.
1990		2132
1991	If the timer is started but non-repeating, stop it (as if it timed out).	2133	=item If the timer is started but non-repeating, stop it (as if it timed
		2134	out, without invoking it).
1992		2135
1993	If the timer is repeating, either start it if necessary (with the	2136	=item If the timer is repeating, make the C<repeat> value the new timeout
1994	C<repeat> value), or reset the running timer to the C<repeat> value.	2137	and start the timer, if necessary.
1995		2138
		2139	=back
		2140
1996	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2141	This sounds a bit complicated, see L</Be smart about timeouts>, above, for a
1997	usage example.	2142	usage example.
1998		2143
1999	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)	2144	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
2000		2145
2001	Returns the remaining time until a timer fires. If the timer is active,	2146	Returns the remaining time until a timer fires. If the timer is active,
…		…
2121		2266
2122	Another way to think about it (for the mathematically inclined) is that	2267	Another way to think about it (for the mathematically inclined) is that
2123	C<ev_periodic> will try to run the callback in this mode at the next possible	2268	C<ev_periodic> will try to run the callback in this mode at the next possible
2124	time where C<time = offset (mod interval)>, regardless of any time jumps.	2269	time where C<time = offset (mod interval)>, regardless of any time jumps.
2125		2270
2126	For numerical stability it is preferable that the C<offset> value is near	2271	The C<interval> I<MUST> be positive, and for numerical stability, the
2127	C<ev_now ()> (the current time), but there is no range requirement for	2272	interval value should be higher than C<1/8192> (which is around 100
2128	this value, and in fact is often specified as zero.	2273	microseconds) and C<offset> should be higher than C<0> and should have
		2274	at most a similar magnitude as the current time (say, within a factor of
		2275	ten). Typical values for offset are, in fact, C<0> or something between
		2276	C<0> and C<interval>, which is also the recommended range.
2129		2277
2130	Note also that there is an upper limit to how often a timer can fire (CPU	2278	Note also that there is an upper limit to how often a timer can fire (CPU
2131	speed for example), so if C<interval> is very small then timing stability	2279	speed for example), so if C<interval> is very small then timing stability
2132	will of course deteriorate. Libev itself tries to be exact to be about one	2280	will of course deteriorate. Libev itself tries to be exact to be about one
2133	millisecond (if the OS supports it and the machine is fast enough).	2281	millisecond (if the OS supports it and the machine is fast enough).
…		…
2247		2395
2248	=head2 C<ev_signal> - signal me when a signal gets signalled!	2396	=head2 C<ev_signal> - signal me when a signal gets signalled!
2249		2397
2250	Signal watchers will trigger an event when the process receives a specific	2398	Signal watchers will trigger an event when the process receives a specific
2251	signal one or more times. Even though signals are very asynchronous, libev	2399	signal one or more times. Even though signals are very asynchronous, libev
2252	will try it's best to deliver signals synchronously, i.e. as part of the	2400	will try its best to deliver signals synchronously, i.e. as part of the
2253	normal event processing, like any other event.	2401	normal event processing, like any other event.
2254		2402
2255	If you want signals to be delivered truly asynchronously, just use	2403	If you want signals to be delivered truly asynchronously, just use
2256	C<sigaction> as you would do without libev and forget about sharing	2404	C<sigaction> as you would do without libev and forget about sharing
2257	the signal. You can even use C<ev_async> from a signal handler to	2405	the signal. You can even use C<ev_async> from a signal handler to
…		…
2276	=head3 The special problem of inheritance over fork/execve/pthread_create	2424	=head3 The special problem of inheritance over fork/execve/pthread_create
2277		2425
2278	Both the signal mask (C<sigprocmask>) and the signal disposition	2426	Both the signal mask (C<sigprocmask>) and the signal disposition
2279	(C<sigaction>) are unspecified after starting a signal watcher (and after	2427	(C<sigaction>) are unspecified after starting a signal watcher (and after
2280	stopping it again), that is, libev might or might not block the signal,	2428	stopping it again), that is, libev might or might not block the signal,
2281	and might or might not set or restore the installed signal handler.	2429	and might or might not set or restore the installed signal handler (but
		2430	see C<EVFLAG_NOSIGMASK>).
2282		2431
2283	While this does not matter for the signal disposition (libev never	2432	While this does not matter for the signal disposition (libev never
2284	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on	2433	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
2285	C<execve>), this matters for the signal mask: many programs do not expect	2434	C<execve>), this matters for the signal mask: many programs do not expect
2286	certain signals to be blocked.	2435	certain signals to be blocked.
…		…
2299	I<has> to modify the signal mask, at least temporarily.	2448	I<has> to modify the signal mask, at least temporarily.
2300		2449
2301	So I can't stress this enough: I<If you do not reset your signal mask when	2450	So I can't stress this enough: I<If you do not reset your signal mask when
2302	you expect it to be empty, you have a race condition in your code>. This	2451	you expect it to be empty, you have a race condition in your code>. This
2303	is not a libev-specific thing, this is true for most event libraries.	2452	is not a libev-specific thing, this is true for most event libraries.
		2453
		2454	=head3 The special problem of threads signal handling
		2455
		2456	POSIX threads has problematic signal handling semantics, specifically,
		2457	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2458	threads in a process block signals, which is hard to achieve.
		2459
		2460	When you want to use sigwait (or mix libev signal handling with your own
		2461	for the same signals), you can tackle this problem by globally blocking
		2462	all signals before creating any threads (or creating them with a fully set
		2463	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2464	loops. Then designate one thread as "signal receiver thread" which handles
		2465	these signals. You can pass on any signals that libev might be interested
		2466	in by calling C<ev_feed_signal>.
2304		2467
2305	=head3 Watcher-Specific Functions and Data Members	2468	=head3 Watcher-Specific Functions and Data Members
2306		2469
2307	=over 4	2470	=over 4
2308		2471
…		…
2443		2606
2444	=head2 C<ev_stat> - did the file attributes just change?	2607	=head2 C<ev_stat> - did the file attributes just change?
2445		2608
2446	This watches a file system path for attribute changes. That is, it calls	2609	This watches a file system path for attribute changes. That is, it calls
2447	C<stat> on that path in regular intervals (or when the OS says it changed)	2610	C<stat> on that path in regular intervals (or when the OS says it changed)
2448	and sees if it changed compared to the last time, invoking the callback if	2611	and sees if it changed compared to the last time, invoking the callback
2449	it did.	2612	if it did. Starting the watcher C<stat>'s the file, so only changes that
		2613	happen after the watcher has been started will be reported.
2450		2614
2451	The path does not need to exist: changing from "path exists" to "path does	2615	The path does not need to exist: changing from "path exists" to "path does
2452	not exist" is a status change like any other. The condition "path does not	2616	not exist" is a status change like any other. The condition "path does not
2453	exist" (or more correctly "path cannot be stat'ed") is signified by the	2617	exist" (or more correctly "path cannot be stat'ed") is signified by the
2454	C<st_nlink> field being zero (which is otherwise always forced to be at	2618	C<st_nlink> field being zero (which is otherwise always forced to be at
…		…
2684	Apart from keeping your process non-blocking (which is a useful	2848	Apart from keeping your process non-blocking (which is a useful
2685	effect on its own sometimes), idle watchers are a good place to do	2849	effect on its own sometimes), idle watchers are a good place to do
2686	"pseudo-background processing", or delay processing stuff to after the	2850	"pseudo-background processing", or delay processing stuff to after the
2687	event loop has handled all outstanding events.	2851	event loop has handled all outstanding events.
2688		2852
		2853	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2854
		2855	As long as there is at least one active idle watcher, libev will never
		2856	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2857	For this to work, the idle watcher doesn't need to be invoked at all - the
		2858	lowest priority will do.
		2859
		2860	This mode of operation can be useful together with an C<ev_check> watcher,
		2861	to do something on each event loop iteration - for example to balance load
		2862	between different connections.
		2863
		2864	See L</Abusing an ev_check watcher for its side-effect> for a longer
		2865	example.
		2866
2689	=head3 Watcher-Specific Functions and Data Members	2867	=head3 Watcher-Specific Functions and Data Members
2690		2868
2691	=over 4	2869	=over 4
2692		2870
2693	=item ev_idle_init (ev_idle *, callback)	2871	=item ev_idle_init (ev_idle *, callback)
…		…
2704	callback, free it. Also, use no error checking, as usual.	2882	callback, free it. Also, use no error checking, as usual.
2705		2883
2706	static void	2884	static void
2707	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	2885	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2708	{	2886	{
		2887	// stop the watcher
		2888	ev_idle_stop (loop, w);
		2889
		2890	// now we can free it
2709	free (w);	2891	free (w);
		2892
2710	// now do something you wanted to do when the program has	2893	// now do something you wanted to do when the program has
2711	// no longer anything immediate to do.	2894	// no longer anything immediate to do.
2712	}	2895	}
2713		2896
2714	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2897	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
…		…
2716	ev_idle_start (loop, idle_watcher);	2899	ev_idle_start (loop, idle_watcher);
2717		2900
2718		2901
2719	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2902	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2720		2903
2721	Prepare and check watchers are usually (but not always) used in pairs:	2904	Prepare and check watchers are often (but not always) used in pairs:
2722	prepare watchers get invoked before the process blocks and check watchers	2905	prepare watchers get invoked before the process blocks and check watchers
2723	afterwards.	2906	afterwards.
2724		2907
2725	You I<must not> call C<ev_run> or similar functions that enter	2908	You I<must not> call C<ev_run> or similar functions that enter
2726	the current event loop from either C<ev_prepare> or C<ev_check>	2909	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
2754	with priority higher than or equal to the event loop and one coroutine	2937	with priority higher than or equal to the event loop and one coroutine
2755	of lower priority, but only once, using idle watchers to keep the event	2938	of lower priority, but only once, using idle watchers to keep the event
2756	loop from blocking if lower-priority coroutines are active, thus mapping	2939	loop from blocking if lower-priority coroutines are active, thus mapping
2757	low-priority coroutines to idle/background tasks).	2940	low-priority coroutines to idle/background tasks).
2758		2941
2759	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2942	When used for this purpose, it is recommended to give C<ev_check> watchers
2760	priority, to ensure that they are being run before any other watchers	2943	highest (C<EV_MAXPRI>) priority, to ensure that they are being run before
2761	after the poll (this doesn't matter for C<ev_prepare> watchers).	2944	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		2945	watchers).
2762		2946
2763	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	2947	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
2764	activate ("feed") events into libev. While libev fully supports this, they	2948	activate ("feed") events into libev. While libev fully supports this, they
2765	might get executed before other C<ev_check> watchers did their job. As	2949	might get executed before other C<ev_check> watchers did their job. As
2766	C<ev_check> watchers are often used to embed other (non-libev) event	2950	C<ev_check> watchers are often used to embed other (non-libev) event
2767	loops those other event loops might be in an unusable state until their	2951	loops those other event loops might be in an unusable state until their
2768	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	2952	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2769	others).	2953	others).
		2954
		2955	=head3 Abusing an C<ev_check> watcher for its side-effect
		2956
		2957	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		2958	useful because they are called once per event loop iteration. For
		2959	example, if you want to handle a large number of connections fairly, you
		2960	normally only do a bit of work for each active connection, and if there
		2961	is more work to do, you wait for the next event loop iteration, so other
		2962	connections have a chance of making progress.
		2963
		2964	Using an C<ev_check> watcher is almost enough: it will be called on the
		2965	next event loop iteration. However, that isn't as soon as possible -
		2966	without external events, your C<ev_check> watcher will not be invoked.
		2967
		2968	This is where C<ev_idle> watchers come in handy - all you need is a
		2969	single global idle watcher that is active as long as you have one active
		2970	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		2971	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		2972	invoked. Neither watcher alone can do that.
2770		2973
2771	=head3 Watcher-Specific Functions and Data Members	2974	=head3 Watcher-Specific Functions and Data Members
2772		2975
2773	=over 4	2976	=over 4
2774		2977
…		…
2975		3178
2976	=over 4	3179	=over 4
2977		3180
2978	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	3181	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
2979		3182
2980	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	3183	=item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)
2981		3184
2982	Configures the watcher to embed the given loop, which must be	3185	Configures the watcher to embed the given loop, which must be
2983	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	3186	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2984	invoked automatically, otherwise it is the responsibility of the callback	3187	invoked automatically, otherwise it is the responsibility of the callback
2985	to invoke it (it will continue to be called until the sweep has been done,	3188	to invoke it (it will continue to be called until the sweep has been done,
…		…
3048		3251
3049	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3252	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
3050		3253
3051	Fork watchers are called when a C<fork ()> was detected (usually because	3254	Fork watchers are called when a C<fork ()> was detected (usually because
3052	whoever is a good citizen cared to tell libev about it by calling	3255	whoever is a good citizen cared to tell libev about it by calling
3053	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the	3256	C<ev_loop_fork>). The invocation is done before the event loop blocks next
3054	event loop blocks next and before C<ev_check> watchers are being called,	3257	and before C<ev_check> watchers are being called, and only in the child
3055	and only in the child after the fork. If whoever good citizen calling	3258	after the fork. If whoever good citizen calling C<ev_default_fork> cheats
3056	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3259	and calls it in the wrong process, the fork handlers will be invoked, too,
3057	handlers will be invoked, too, of course.	3260	of course.
3058		3261
3059	=head3 The special problem of life after fork - how is it possible?	3262	=head3 The special problem of life after fork - how is it possible?
3060		3263
3061	Most uses of C<fork()> consist of forking, then some simple calls to set	3264	Most uses of C<fork()> consist of forking, then some simple calls to set
3062	up/change the process environment, followed by a call to C<exec()>. This	3265	up/change the process environment, followed by a call to C<exec()>. This
…		…
3092		3295
3093	=head3 Watcher-Specific Functions and Data Members	3296	=head3 Watcher-Specific Functions and Data Members
3094		3297
3095	=over 4	3298	=over 4
3096		3299
3097	=item ev_fork_init (ev_signal *, callback)	3300	=item ev_fork_init (ev_fork *, callback)
3098		3301
3099	Initialises and configures the fork watcher - it has no parameters of any	3302	Initialises and configures the fork watcher - it has no parameters of any
3100	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3303	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
3101	believe me.	3304	really.
3102		3305
3103	=back	3306	=back
3104		3307
3105		3308
		3309	=head2 C<ev_cleanup> - even the best things end
		3310
		3311	Cleanup watchers are called just before the event loop is being destroyed
		3312	by a call to C<ev_loop_destroy>.
		3313
		3314	While there is no guarantee that the event loop gets destroyed, cleanup
		3315	watchers provide a convenient method to install cleanup hooks for your
		3316	program, worker threads and so on - you just to make sure to destroy the
		3317	loop when you want them to be invoked.
		3318
		3319	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3320	all other watchers, they do not keep a reference to the event loop (which
		3321	makes a lot of sense if you think about it). Like all other watchers, you
		3322	can call libev functions in the callback, except C<ev_cleanup_start>.
		3323
		3324	=head3 Watcher-Specific Functions and Data Members
		3325
		3326	=over 4
		3327
		3328	=item ev_cleanup_init (ev_cleanup *, callback)
		3329
		3330	Initialises and configures the cleanup watcher - it has no parameters of
		3331	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3332	pointless, I assure you.
		3333
		3334	=back
		3335
		3336	Example: Register an atexit handler to destroy the default loop, so any
		3337	cleanup functions are called.
		3338
		3339	static void
		3340	program_exits (void)
		3341	{
		3342	ev_loop_destroy (EV_DEFAULT_UC);
		3343	}
		3344
		3345	...
		3346	atexit (program_exits);
		3347
		3348
3106	=head2 C<ev_async> - how to wake up an event loop	3349	=head2 C<ev_async> - how to wake up an event loop
3107		3350
3108	In general, you cannot use an C<ev_run> from multiple threads or other	3351	In general, you cannot use an C<ev_loop> from multiple threads or other
3109	asynchronous sources such as signal handlers (as opposed to multiple event	3352	asynchronous sources such as signal handlers (as opposed to multiple event
3110	loops - those are of course safe to use in different threads).	3353	loops - those are of course safe to use in different threads).
3111		3354
3112	Sometimes, however, you need to wake up an event loop you do not control,	3355	Sometimes, however, you need to wake up an event loop you do not control,
3113	for example because it belongs to another thread. This is what C<ev_async>	3356	for example because it belongs to another thread. This is what C<ev_async>
…		…
3115	it by calling C<ev_async_send>, which is thread- and signal safe.	3358	it by calling C<ev_async_send>, which is thread- and signal safe.
3116		3359
3117	This functionality is very similar to C<ev_signal> watchers, as signals,	3360	This functionality is very similar to C<ev_signal> watchers, as signals,
3118	too, are asynchronous in nature, and signals, too, will be compressed	3361	too, are asynchronous in nature, and signals, too, will be compressed
3119	(i.e. the number of callback invocations may be less than the number of	3362	(i.e. the number of callback invocations may be less than the number of
3120	C<ev_async_sent> calls).	3363	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
3121		3364	of "global async watchers" by using a watcher on an otherwise unused
3122	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3365	signal, and C<ev_feed_signal> to signal this watcher from another thread,
3123	just the default loop.	3366	even without knowing which loop owns the signal.
3124		3367
3125	=head3 Queueing	3368	=head3 Queueing
3126		3369
3127	C<ev_async> does not support queueing of data in any way. The reason	3370	C<ev_async> does not support queueing of data in any way. The reason
3128	is that the author does not know of a simple (or any) algorithm for a	3371	is that the author does not know of a simple (or any) algorithm for a
…		…
3220	trust me.	3463	trust me.
3221		3464
3222	=item ev_async_send (loop, ev_async *)	3465	=item ev_async_send (loop, ev_async *)
3223		3466
3224	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3467	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3225	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3468	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3469	returns.
		3470
3226	C<ev_feed_event>, this call is safe to do from other threads, signal or	3471	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3227	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3472	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3228	section below on what exactly this means).	3473	embedding section below on what exactly this means).
3229		3474
3230	Note that, as with other watchers in libev, multiple events might get	3475	Note that, as with other watchers in libev, multiple events might get
3231	compressed into a single callback invocation (another way to look at this	3476	compressed into a single callback invocation (another way to look at
3232	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3477	this is that C<ev_async> watchers are level-triggered: they are set on
3233	reset when the event loop detects that).	3478	C<ev_async_send>, reset when the event loop detects that).
3234		3479
3235	This call incurs the overhead of a system call only once per event loop	3480	This call incurs the overhead of at most one extra system call per event
3236	iteration, so while the overhead might be noticeable, it doesn't apply to	3481	loop iteration, if the event loop is blocked, and no syscall at all if
3237	repeated calls to C<ev_async_send> for the same event loop.	3482	the event loop (or your program) is processing events. That means that
		3483	repeated calls are basically free (there is no need to avoid calls for
		3484	performance reasons) and that the overhead becomes smaller (typically
		3485	zero) under load.
3238		3486
3239	=item bool = ev_async_pending (ev_async *)	3487	=item bool = ev_async_pending (ev_async *)
3240		3488
3241	Returns a non-zero value when C<ev_async_send> has been called on the	3489	Returns a non-zero value when C<ev_async_send> has been called on the
3242	watcher but the event has not yet been processed (or even noted) by the	3490	watcher but the event has not yet been processed (or even noted) by the
…		…
3297	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3545	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3298		3546
3299	=item ev_feed_fd_event (loop, int fd, int revents)	3547	=item ev_feed_fd_event (loop, int fd, int revents)
3300		3548
3301	Feed an event on the given fd, as if a file descriptor backend detected	3549	Feed an event on the given fd, as if a file descriptor backend detected
3302	the given events it.	3550	the given events.
3303		3551
3304	=item ev_feed_signal_event (loop, int signum)	3552	=item ev_feed_signal_event (loop, int signum)
3305		3553
3306	Feed an event as if the given signal occurred (C<loop> must be the default	3554	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3307	loop!).	3555	which is async-safe.
3308		3556
3309	=back	3557	=back
		3558
		3559
		3560	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3561
		3562	This section explains some common idioms that are not immediately
		3563	obvious. Note that examples are sprinkled over the whole manual, and this
		3564	section only contains stuff that wouldn't fit anywhere else.
		3565
		3566	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3567
		3568	Each watcher has, by default, a C<void *data> member that you can read
		3569	or modify at any time: libev will completely ignore it. This can be used
		3570	to associate arbitrary data with your watcher. If you need more data and
		3571	don't want to allocate memory separately and store a pointer to it in that
		3572	data member, you can also "subclass" the watcher type and provide your own
		3573	data:
		3574
		3575	struct my_io
		3576	{
		3577	ev_io io;
		3578	int otherfd;
		3579	void *somedata;
		3580	struct whatever *mostinteresting;
		3581	};
		3582
		3583	...
		3584	struct my_io w;
		3585	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3586
		3587	And since your callback will be called with a pointer to the watcher, you
		3588	can cast it back to your own type:
		3589
		3590	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3591	{
		3592	struct my_io *w = (struct my_io *)w_;
		3593	...
		3594	}
		3595
		3596	More interesting and less C-conformant ways of casting your callback
		3597	function type instead have been omitted.
		3598
		3599	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3600
		3601	Another common scenario is to use some data structure with multiple
		3602	embedded watchers, in effect creating your own watcher that combines
		3603	multiple libev event sources into one "super-watcher":
		3604
		3605	struct my_biggy
		3606	{
		3607	int some_data;
		3608	ev_timer t1;
		3609	ev_timer t2;
		3610	}
		3611
		3612	In this case getting the pointer to C<my_biggy> is a bit more
		3613	complicated: Either you store the address of your C<my_biggy> struct in
		3614	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3615	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3616	real programmers):
		3617
		3618	#include <stddef.h>
		3619
		3620	static void
		3621	t1_cb (EV_P_ ev_timer *w, int revents)
		3622	{
		3623	struct my_biggy big = (struct my_biggy *)
		3624	(((char *)w) - offsetof (struct my_biggy, t1));
		3625	}
		3626
		3627	static void
		3628	t2_cb (EV_P_ ev_timer *w, int revents)
		3629	{
		3630	struct my_biggy big = (struct my_biggy *)
		3631	(((char *)w) - offsetof (struct my_biggy, t2));
		3632	}
		3633
		3634	=head2 AVOIDING FINISHING BEFORE RETURNING
		3635
		3636	Often you have structures like this in event-based programs:
		3637
		3638	callback ()
		3639	{
		3640	free (request);
		3641	}
		3642
		3643	request = start_new_request (..., callback);
		3644
		3645	The intent is to start some "lengthy" operation. The C<request> could be
		3646	used to cancel the operation, or do other things with it.
		3647
		3648	It's not uncommon to have code paths in C<start_new_request> that
		3649	immediately invoke the callback, for example, to report errors. Or you add
		3650	some caching layer that finds that it can skip the lengthy aspects of the
		3651	operation and simply invoke the callback with the result.
		3652
		3653	The problem here is that this will happen I<before> C<start_new_request>
		3654	has returned, so C<request> is not set.
		3655
		3656	Even if you pass the request by some safer means to the callback, you
		3657	might want to do something to the request after starting it, such as
		3658	canceling it, which probably isn't working so well when the callback has
		3659	already been invoked.
		3660
		3661	A common way around all these issues is to make sure that
		3662	C<start_new_request> I<always> returns before the callback is invoked. If
		3663	C<start_new_request> immediately knows the result, it can artificially
		3664	delay invoking the callback by using a C<prepare> or C<idle> watcher for
		3665	example, or more sneakily, by reusing an existing (stopped) watcher and
		3666	pushing it into the pending queue:
		3667
		3668	ev_set_cb (watcher, callback);
		3669	ev_feed_event (EV_A_ watcher, 0);
		3670
		3671	This way, C<start_new_request> can safely return before the callback is
		3672	invoked, while not delaying callback invocation too much.
		3673
		3674	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3675
		3676	Often (especially in GUI toolkits) there are places where you have
		3677	I<modal> interaction, which is most easily implemented by recursively
		3678	invoking C<ev_run>.
		3679
		3680	This brings the problem of exiting - a callback might want to finish the
		3681	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3682	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3683	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3684	other combination: In these cases, a simple C<ev_break> will not work.
		3685
		3686	The solution is to maintain "break this loop" variable for each C<ev_run>
		3687	invocation, and use a loop around C<ev_run> until the condition is
		3688	triggered, using C<EVRUN_ONCE>:
		3689
		3690	// main loop
		3691	int exit_main_loop = 0;
		3692
		3693	while (!exit_main_loop)
		3694	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3695
		3696	// in a modal watcher
		3697	int exit_nested_loop = 0;
		3698
		3699	while (!exit_nested_loop)
		3700	ev_run (EV_A_ EVRUN_ONCE);
		3701
		3702	To exit from any of these loops, just set the corresponding exit variable:
		3703
		3704	// exit modal loop
		3705	exit_nested_loop = 1;
		3706
		3707	// exit main program, after modal loop is finished
		3708	exit_main_loop = 1;
		3709
		3710	// exit both
		3711	exit_main_loop = exit_nested_loop = 1;
		3712
		3713	=head2 THREAD LOCKING EXAMPLE
		3714
		3715	Here is a fictitious example of how to run an event loop in a different
		3716	thread from where callbacks are being invoked and watchers are
		3717	created/added/removed.
		3718
		3719	For a real-world example, see the C<EV::Loop::Async> perl module,
		3720	which uses exactly this technique (which is suited for many high-level
		3721	languages).
		3722
		3723	The example uses a pthread mutex to protect the loop data, a condition
		3724	variable to wait for callback invocations, an async watcher to notify the
		3725	event loop thread and an unspecified mechanism to wake up the main thread.
		3726
		3727	First, you need to associate some data with the event loop:
		3728
		3729	typedef struct {
		3730	mutex_t lock; /* global loop lock */
		3731	ev_async async_w;
		3732	thread_t tid;
		3733	cond_t invoke_cv;
		3734	} userdata;
		3735
		3736	void prepare_loop (EV_P)
		3737	{
		3738	// for simplicity, we use a static userdata struct.
		3739	static userdata u;
		3740
		3741	ev_async_init (&u->async_w, async_cb);
		3742	ev_async_start (EV_A_ &u->async_w);
		3743
		3744	pthread_mutex_init (&u->lock, 0);
		3745	pthread_cond_init (&u->invoke_cv, 0);
		3746
		3747	// now associate this with the loop
		3748	ev_set_userdata (EV_A_ u);
		3749	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3750	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3751
		3752	// then create the thread running ev_run
		3753	pthread_create (&u->tid, 0, l_run, EV_A);
		3754	}
		3755
		3756	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3757	solely to wake up the event loop so it takes notice of any new watchers
		3758	that might have been added:
		3759
		3760	static void
		3761	async_cb (EV_P_ ev_async *w, int revents)
		3762	{
		3763	// just used for the side effects
		3764	}
		3765
		3766	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3767	protecting the loop data, respectively.
		3768
		3769	static void
		3770	l_release (EV_P)
		3771	{
		3772	userdata *u = ev_userdata (EV_A);
		3773	pthread_mutex_unlock (&u->lock);
		3774	}
		3775
		3776	static void
		3777	l_acquire (EV_P)
		3778	{
		3779	userdata *u = ev_userdata (EV_A);
		3780	pthread_mutex_lock (&u->lock);
		3781	}
		3782
		3783	The event loop thread first acquires the mutex, and then jumps straight
		3784	into C<ev_run>:
		3785
		3786	void *
		3787	l_run (void *thr_arg)
		3788	{
		3789	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3790
		3791	l_acquire (EV_A);
		3792	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3793	ev_run (EV_A_ 0);
		3794	l_release (EV_A);
		3795
		3796	return 0;
		3797	}
		3798
		3799	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3800	signal the main thread via some unspecified mechanism (signals? pipe
		3801	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3802	have been called (in a while loop because a) spurious wakeups are possible
		3803	and b) skipping inter-thread-communication when there are no pending
		3804	watchers is very beneficial):
		3805
		3806	static void
		3807	l_invoke (EV_P)
		3808	{
		3809	userdata *u = ev_userdata (EV_A);
		3810
		3811	while (ev_pending_count (EV_A))
		3812	{
		3813	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3814	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3815	}
		3816	}
		3817
		3818	Now, whenever the main thread gets told to invoke pending watchers, it
		3819	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3820	thread to continue:
		3821
		3822	static void
		3823	real_invoke_pending (EV_P)
		3824	{
		3825	userdata *u = ev_userdata (EV_A);
		3826
		3827	pthread_mutex_lock (&u->lock);
		3828	ev_invoke_pending (EV_A);
		3829	pthread_cond_signal (&u->invoke_cv);
		3830	pthread_mutex_unlock (&u->lock);
		3831	}
		3832
		3833	Whenever you want to start/stop a watcher or do other modifications to an
		3834	event loop, you will now have to lock:
		3835
		3836	ev_timer timeout_watcher;
		3837	userdata *u = ev_userdata (EV_A);
		3838
		3839	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3840
		3841	pthread_mutex_lock (&u->lock);
		3842	ev_timer_start (EV_A_ &timeout_watcher);
		3843	ev_async_send (EV_A_ &u->async_w);
		3844	pthread_mutex_unlock (&u->lock);
		3845
		3846	Note that sending the C<ev_async> watcher is required because otherwise
		3847	an event loop currently blocking in the kernel will have no knowledge
		3848	about the newly added timer. By waking up the loop it will pick up any new
		3849	watchers in the next event loop iteration.
		3850
		3851	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3852
		3853	While the overhead of a callback that e.g. schedules a thread is small, it
		3854	is still an overhead. If you embed libev, and your main usage is with some
		3855	kind of threads or coroutines, you might want to customise libev so that
		3856	doesn't need callbacks anymore.
		3857
		3858	Imagine you have coroutines that you can switch to using a function
		3859	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3860	and that due to some magic, the currently active coroutine is stored in a
		3861	global called C<current_coro>. Then you can build your own "wait for libev
		3862	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3863	the differing C<;> conventions):
		3864
		3865	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3866	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3867
		3868	That means instead of having a C callback function, you store the
		3869	coroutine to switch to in each watcher, and instead of having libev call
		3870	your callback, you instead have it switch to that coroutine.
		3871
		3872	A coroutine might now wait for an event with a function called
		3873	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3874	matter when, or whether the watcher is active or not when this function is
		3875	called):
		3876
		3877	void
		3878	wait_for_event (ev_watcher *w)
		3879	{
		3880	ev_set_cb (w, current_coro);
		3881	switch_to (libev_coro);
		3882	}
		3883
		3884	That basically suspends the coroutine inside C<wait_for_event> and
		3885	continues the libev coroutine, which, when appropriate, switches back to
		3886	this or any other coroutine.
		3887
		3888	You can do similar tricks if you have, say, threads with an event queue -
		3889	instead of storing a coroutine, you store the queue object and instead of
		3890	switching to a coroutine, you push the watcher onto the queue and notify
		3891	any waiters.
		3892
		3893	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		3894	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3895
		3896	// my_ev.h
		3897	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3898	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3899	#include "../libev/ev.h"
		3900
		3901	// my_ev.c
		3902	#define EV_H "my_ev.h"
		3903	#include "../libev/ev.c"
		3904
		3905	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3906	F<my_ev.c> into your project. When properly specifying include paths, you
		3907	can even use F<ev.h> as header file name directly.
3310		3908
3311		3909
3312	=head1 LIBEVENT EMULATION	3910	=head1 LIBEVENT EMULATION
3313		3911
3314	Libev offers a compatibility emulation layer for libevent. It cannot	3912	Libev offers a compatibility emulation layer for libevent. It cannot
3315	emulate the internals of libevent, so here are some usage hints:	3913	emulate the internals of libevent, so here are some usage hints:
3316		3914
3317	=over 4	3915	=over 4
		3916
		3917	=item * Only the libevent-1.4.1-beta API is being emulated.
		3918
		3919	This was the newest libevent version available when libev was implemented,
		3920	and is still mostly unchanged in 2010.
3318		3921
3319	=item * Use it by including <event.h>, as usual.	3922	=item * Use it by including <event.h>, as usual.
3320		3923
3321	=item * The following members are fully supported: ev_base, ev_callback,	3924	=item * The following members are fully supported: ev_base, ev_callback,
3322	ev_arg, ev_fd, ev_res, ev_events.	3925	ev_arg, ev_fd, ev_res, ev_events.
…		…
3328	=item * Priorities are not currently supported. Initialising priorities	3931	=item * Priorities are not currently supported. Initialising priorities
3329	will fail and all watchers will have the same priority, even though there	3932	will fail and all watchers will have the same priority, even though there
3330	is an ev_pri field.	3933	is an ev_pri field.
3331		3934
3332	=item * In libevent, the last base created gets the signals, in libev, the	3935	=item * In libevent, the last base created gets the signals, in libev, the
3333	first base created (== the default loop) gets the signals.	3936	base that registered the signal gets the signals.
3334		3937
3335	=item * Other members are not supported.	3938	=item * Other members are not supported.
3336		3939
3337	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3940	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3338	to use the libev header file and library.	3941	to use the libev header file and library.
3339		3942
3340	=back	3943	=back
3341		3944
3342	=head1 C++ SUPPORT	3945	=head1 C++ SUPPORT
		3946
		3947	=head2 C API
		3948
		3949	The normal C API should work fine when used from C++: both ev.h and the
		3950	libev sources can be compiled as C++. Therefore, code that uses the C API
		3951	will work fine.
		3952
		3953	Proper exception specifications might have to be added to callbacks passed
		3954	to libev: exceptions may be thrown only from watcher callbacks, all
		3955	other callbacks (allocator, syserr, loop acquire/release and periodic
		3956	reschedule callbacks) must not throw exceptions, and might need a C<throw
		3957	()> specification. If you have code that needs to be compiled as both C
		3958	and C++ you can use the C<EV_THROW> macro for this:
		3959
		3960	static void
		3961	fatal_error (const char *msg) EV_THROW
		3962	{
		3963	perror (msg);
		3964	abort ();
		3965	}
		3966
		3967	...
		3968	ev_set_syserr_cb (fatal_error);
		3969
		3970	The only API functions that can currently throw exceptions are C<ev_run>,
		3971	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		3972	because it runs cleanup watchers).
		3973
		3974	Throwing exceptions in watcher callbacks is only supported if libev itself
		3975	is compiled with a C++ compiler or your C and C++ environments allow
		3976	throwing exceptions through C libraries (most do).
		3977
		3978	=head2 C++ API
3343		3979
3344	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3980	Libev comes with some simplistic wrapper classes for C++ that mainly allow
3345	you to use some convenience methods to start/stop watchers and also change	3981	you to use some convenience methods to start/stop watchers and also change
3346	the callback model to a model using method callbacks on objects.	3982	the callback model to a model using method callbacks on objects.
3347		3983
…		…
3357	Care has been taken to keep the overhead low. The only data member the C++	3993	Care has been taken to keep the overhead low. The only data member the C++
3358	classes add (compared to plain C-style watchers) is the event loop pointer	3994	classes add (compared to plain C-style watchers) is the event loop pointer
3359	that the watcher is associated with (or no additional members at all if	3995	that the watcher is associated with (or no additional members at all if
3360	you disable C<EV_MULTIPLICITY> when embedding libev).	3996	you disable C<EV_MULTIPLICITY> when embedding libev).
3361		3997
3362	Currently, functions, and static and non-static member functions can be	3998	Currently, functions, static and non-static member functions and classes
3363	used as callbacks. Other types should be easy to add as long as they only	3999	with C<operator ()> can be used as callbacks. Other types should be easy
3364	need one additional pointer for context. If you need support for other	4000	to add as long as they only need one additional pointer for context. If
3365	types of functors please contact the author (preferably after implementing	4001	you need support for other types of functors please contact the author
3366	it).	4002	(preferably after implementing it).
		4003
		4004	For all this to work, your C++ compiler either has to use the same calling
		4005	conventions as your C compiler (for static member functions), or you have
		4006	to embed libev and compile libev itself as C++.
3367		4007
3368	Here is a list of things available in the C<ev> namespace:	4008	Here is a list of things available in the C<ev> namespace:
3369		4009
3370	=over 4	4010	=over 4
3371		4011
…		…
3381	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4021	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3382		4022
3383	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4023	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
3384	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4024	the same name in the C<ev> namespace, with the exception of C<ev_signal>
3385	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4025	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3386	defines by many implementations.	4026	defined by many implementations.
3387		4027
3388	All of those classes have these methods:	4028	All of those classes have these methods:
3389		4029
3390	=over 4	4030	=over 4
3391		4031
…		…
3481	Associates a different C<struct ev_loop> with this watcher. You can only	4121	Associates a different C<struct ev_loop> with this watcher. You can only
3482	do this when the watcher is inactive (and not pending either).	4122	do this when the watcher is inactive (and not pending either).
3483		4123
3484	=item w->set ([arguments])	4124	=item w->set ([arguments])
3485		4125
3486	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this	4126	Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>),
3487	method or a suitable start method must be called at least once. Unlike the	4127	with the same arguments. Either this method or a suitable start method
3488	C counterpart, an active watcher gets automatically stopped and restarted	4128	must be called at least once. Unlike the C counterpart, an active watcher
3489	when reconfiguring it with this method.	4129	gets automatically stopped and restarted when reconfiguring it with this
		4130	method.
		4131
		4132	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4133	clashing with the C<set (loop)> method.
3490		4134
3491	=item w->start ()	4135	=item w->start ()
3492		4136
3493	Starts the watcher. Note that there is no C<loop> argument, as the	4137	Starts the watcher. Note that there is no C<loop> argument, as the
3494	constructor already stores the event loop.	4138	constructor already stores the event loop.
…		…
3524	watchers in the constructor.	4168	watchers in the constructor.
3525		4169
3526	class myclass	4170	class myclass
3527	{	4171	{
3528	ev::io io ; void io_cb (ev::io &w, int revents);	4172	ev::io io ; void io_cb (ev::io &w, int revents);
3529	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);	4173	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3530	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4174	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3531		4175
3532	myclass (int fd)	4176	myclass (int fd)
3533	{	4177	{
3534	io .set <myclass, &myclass::io_cb > (this);	4178	io .set <myclass, &myclass::io_cb > (this);
…		…
3585	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4229	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3586		4230
3587	=item D	4231	=item D
3588		4232
3589	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4233	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3590	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4234	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3591		4235
3592	=item Ocaml	4236	=item Ocaml
3593		4237
3594	Erkki Seppala has written Ocaml bindings for libev, to be found at	4238	Erkki Seppala has written Ocaml bindings for libev, to be found at
3595	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4239	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
…		…
3598		4242
3599	Brian Maher has written a partial interface to libev for lua (at the	4243	Brian Maher has written a partial interface to libev for lua (at the
3600	time of this writing, only C<ev_io> and C<ev_timer>), to be found at	4244	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
3601	L<http://github.com/brimworks/lua-ev>.	4245	L<http://github.com/brimworks/lua-ev>.
3602		4246
		4247	=item Javascript
		4248
		4249	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4250
		4251	=item Others
		4252
		4253	There are others, and I stopped counting.
		4254
3603	=back	4255	=back
3604		4256
3605		4257
3606	=head1 MACRO MAGIC	4258	=head1 MACRO MAGIC
3607		4259
…		…
3643	suitable for use with C<EV_A>.	4295	suitable for use with C<EV_A>.
3644		4296
3645	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4297	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3646		4298
3647	Similar to the other two macros, this gives you the value of the default	4299	Similar to the other two macros, this gives you the value of the default
3648	loop, if multiple loops are supported ("ev loop default").	4300	loop, if multiple loops are supported ("ev loop default"). The default loop
		4301	will be initialised if it isn't already initialised.
		4302
		4303	For non-multiplicity builds, these macros do nothing, so you always have
		4304	to initialise the loop somewhere.
3649		4305
3650	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4306	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3651		4307
3652	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4308	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3653	default loop has been initialised (C<UC> == unchecked). Their behaviour	4309	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3798	supported). It will also not define any of the structs usually found in	4454	supported). It will also not define any of the structs usually found in
3799	F<event.h> that are not directly supported by the libev core alone.	4455	F<event.h> that are not directly supported by the libev core alone.
3800		4456
3801	In standalone mode, libev will still try to automatically deduce the	4457	In standalone mode, libev will still try to automatically deduce the
3802	configuration, but has to be more conservative.	4458	configuration, but has to be more conservative.
		4459
		4460	=item EV_USE_FLOOR
		4461
		4462	If defined to be C<1>, libev will use the C<floor ()> function for its
		4463	periodic reschedule calculations, otherwise libev will fall back on a
		4464	portable (slower) implementation. If you enable this, you usually have to
		4465	link against libm or something equivalent. Enabling this when the C<floor>
		4466	function is not available will fail, so the safe default is to not enable
		4467	this.
3803		4468
3804	=item EV_USE_MONOTONIC	4469	=item EV_USE_MONOTONIC
3805		4470
3806	If defined to be C<1>, libev will try to detect the availability of the	4471	If defined to be C<1>, libev will try to detect the availability of the
3807	monotonic clock option at both compile time and runtime. Otherwise no	4472	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3892		4557
3893	If programs implement their own fd to handle mapping on win32, then this	4558	If programs implement their own fd to handle mapping on win32, then this
3894	macro can be used to override the C<close> function, useful to unregister	4559	macro can be used to override the C<close> function, useful to unregister
3895	file descriptors again. Note that the replacement function has to close	4560	file descriptors again. Note that the replacement function has to close
3896	the underlying OS handle.	4561	the underlying OS handle.
		4562
		4563	=item EV_USE_WSASOCKET
		4564
		4565	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4566	communication socket, which works better in some environments. Otherwise,
		4567	the normal C<socket> function will be used, which works better in other
		4568	environments.
3897		4569
3898	=item EV_USE_POLL	4570	=item EV_USE_POLL
3899		4571
3900	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4572	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3901	backend. Otherwise it will be enabled on non-win32 platforms. It	4573	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3937	If defined to be C<1>, libev will compile in support for the Linux inotify	4609	If defined to be C<1>, libev will compile in support for the Linux inotify
3938	interface to speed up C<ev_stat> watchers. Its actual availability will	4610	interface to speed up C<ev_stat> watchers. Its actual availability will
3939	be detected at runtime. If undefined, it will be enabled if the headers	4611	be detected at runtime. If undefined, it will be enabled if the headers
3940	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4612	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3941		4613
		4614	=item EV_NO_SMP
		4615
		4616	If defined to be C<1>, libev will assume that memory is always coherent
		4617	between threads, that is, threads can be used, but threads never run on
		4618	different cpus (or different cpu cores). This reduces dependencies
		4619	and makes libev faster.
		4620
		4621	=item EV_NO_THREADS
		4622
		4623	If defined to be C<1>, libev will assume that it will never be called
		4624	from different threads, which is a stronger assumption than C<EV_NO_SMP>,
		4625	above. This reduces dependencies and makes libev faster.
		4626
3942	=item EV_ATOMIC_T	4627	=item EV_ATOMIC_T
3943		4628
3944	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4629	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3945	access is atomic with respect to other threads or signal contexts. No such	4630	access is atomic with respect to other threads or signal contexts. No
3946	type is easily found in the C language, so you can provide your own type	4631	such type is easily found in the C language, so you can provide your own
3947	that you know is safe for your purposes. It is used both for signal handler "locking"	4632	type that you know is safe for your purposes. It is used both for signal
3948	as well as for signal and thread safety in C<ev_async> watchers.	4633	handler "locking" as well as for signal and thread safety in C<ev_async>
		4634	watchers.
3949		4635
3950	In the absence of this define, libev will use C<sig_atomic_t volatile>	4636	In the absence of this define, libev will use C<sig_atomic_t volatile>
3951	(from F<signal.h>), which is usually good enough on most platforms.	4637	(from F<signal.h>), which is usually good enough on most platforms.
3952		4638
3953	=item EV_H (h)	4639	=item EV_H (h)
…		…
3980	will have the C<struct ev_loop *> as first argument, and you can create	4666	will have the C<struct ev_loop *> as first argument, and you can create
3981	additional independent event loops. Otherwise there will be no support	4667	additional independent event loops. Otherwise there will be no support
3982	for multiple event loops and there is no first event loop pointer	4668	for multiple event loops and there is no first event loop pointer
3983	argument. Instead, all functions act on the single default loop.	4669	argument. Instead, all functions act on the single default loop.
3984		4670
		4671	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4672	default loop when multiplicity is switched off - you always have to
		4673	initialise the loop manually in this case.
		4674
3985	=item EV_MINPRI	4675	=item EV_MINPRI
3986		4676
3987	=item EV_MAXPRI	4677	=item EV_MAXPRI
3988		4678
3989	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4679	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
4025	#define EV_USE_POLL 1	4715	#define EV_USE_POLL 1
4026	#define EV_CHILD_ENABLE 1	4716	#define EV_CHILD_ENABLE 1
4027	#define EV_ASYNC_ENABLE 1	4717	#define EV_ASYNC_ENABLE 1
4028		4718
4029	The actual value is a bitset, it can be a combination of the following	4719	The actual value is a bitset, it can be a combination of the following
4030	values:	4720	values (by default, all of these are enabled):
4031		4721
4032	=over 4	4722	=over 4
4033		4723
4034	=item C<1> - faster/larger code	4724	=item C<1> - faster/larger code
4035		4725
…		…
4039	code size by roughly 30% on amd64).	4729	code size by roughly 30% on amd64).
4040		4730
4041	When optimising for size, use of compiler flags such as C<-Os> with	4731	When optimising for size, use of compiler flags such as C<-Os> with
4042	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of	4732	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
4043	assertions.	4733	assertions.
		4734
		4735	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4736	(e.g. gcc with C<-Os>).
4044		4737
4045	=item C<2> - faster/larger data structures	4738	=item C<2> - faster/larger data structures
4046		4739
4047	Replaces the small 2-heap for timer management by a faster 4-heap, larger	4740	Replaces the small 2-heap for timer management by a faster 4-heap, larger
4048	hash table sizes and so on. This will usually further increase code size	4741	hash table sizes and so on. This will usually further increase code size
4049	and can additionally have an effect on the size of data structures at	4742	and can additionally have an effect on the size of data structures at
4050	runtime.	4743	runtime.
4051		4744
		4745	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4746	(e.g. gcc with C<-Os>).
		4747
4052	=item C<4> - full API configuration	4748	=item C<4> - full API configuration
4053		4749
4054	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and	4750	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
4055	enables multiplicity (C<EV_MULTIPLICITY>=1).	4751	enables multiplicity (C<EV_MULTIPLICITY>=1).
4056		4752
…		…
4086		4782
4087	With an intelligent-enough linker (gcc+binutils are intelligent enough	4783	With an intelligent-enough linker (gcc+binutils are intelligent enough
4088	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by	4784	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
4089	your program might be left out as well - a binary starting a timer and an	4785	your program might be left out as well - a binary starting a timer and an
4090	I/O watcher then might come out at only 5Kb.	4786	I/O watcher then might come out at only 5Kb.
		4787
		4788	=item EV_API_STATIC
		4789
		4790	If this symbol is defined (by default it is not), then all identifiers
		4791	will have static linkage. This means that libev will not export any
		4792	identifiers, and you cannot link against libev anymore. This can be useful
		4793	when you embed libev, only want to use libev functions in a single file,
		4794	and do not want its identifiers to be visible.
		4795
		4796	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4797	wants to use libev.
		4798
		4799	This option only works when libev is compiled with a C compiler, as C++
		4800	doesn't support the required declaration syntax.
4091		4801
4092	=item EV_AVOID_STDIO	4802	=item EV_AVOID_STDIO
4093		4803
4094	If this is set to C<1> at compiletime, then libev will avoid using stdio	4804	If this is set to C<1> at compiletime, then libev will avoid using stdio
4095	functions (printf, scanf, perror etc.). This will increase the code size	4805	functions (printf, scanf, perror etc.). This will increase the code size
…		…
4239	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4949	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4240		4950
4241	#include "ev_cpp.h"	4951	#include "ev_cpp.h"
4242	#include "ev.c"	4952	#include "ev.c"
4243		4953
4244	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4954	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4245		4955
4246	=head2 THREADS AND COROUTINES	4956	=head2 THREADS AND COROUTINES
4247		4957
4248	=head3 THREADS	4958	=head3 THREADS
4249		4959
…		…
4300	default loop and triggering an C<ev_async> watcher from the default loop	5010	default loop and triggering an C<ev_async> watcher from the default loop
4301	watcher callback into the event loop interested in the signal.	5011	watcher callback into the event loop interested in the signal.
4302		5012
4303	=back	5013	=back
4304		5014
4305	=head4 THREAD LOCKING EXAMPLE	5015	See also L</THREAD LOCKING EXAMPLE>.
4306
4307	Here is a fictitious example of how to run an event loop in a different
4308	thread than where callbacks are being invoked and watchers are
4309	created/added/removed.
4310
4311	For a real-world example, see the C<EV::Loop::Async> perl module,
4312	which uses exactly this technique (which is suited for many high-level
4313	languages).
4314
4315	The example uses a pthread mutex to protect the loop data, a condition
4316	variable to wait for callback invocations, an async watcher to notify the
4317	event loop thread and an unspecified mechanism to wake up the main thread.
4318
4319	First, you need to associate some data with the event loop:
4320
4321	typedef struct {
4322	mutex_t lock; /* global loop lock */
4323	ev_async async_w;
4324	thread_t tid;
4325	cond_t invoke_cv;
4326	} userdata;
4327
4328	void prepare_loop (EV_P)
4329	{
4330	// for simplicity, we use a static userdata struct.
4331	static userdata u;
4332
4333	ev_async_init (&u->async_w, async_cb);
4334	ev_async_start (EV_A_ &u->async_w);
4335
4336	pthread_mutex_init (&u->lock, 0);
4337	pthread_cond_init (&u->invoke_cv, 0);
4338
4339	// now associate this with the loop
4340	ev_set_userdata (EV_A_ u);
4341	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4342	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4343
4344	// then create the thread running ev_loop
4345	pthread_create (&u->tid, 0, l_run, EV_A);
4346	}
4347
4348	The callback for the C<ev_async> watcher does nothing: the watcher is used
4349	solely to wake up the event loop so it takes notice of any new watchers
4350	that might have been added:
4351
4352	static void
4353	async_cb (EV_P_ ev_async *w, int revents)
4354	{
4355	// just used for the side effects
4356	}
4357
4358	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4359	protecting the loop data, respectively.
4360
4361	static void
4362	l_release (EV_P)
4363	{
4364	userdata *u = ev_userdata (EV_A);
4365	pthread_mutex_unlock (&u->lock);
4366	}
4367
4368	static void
4369	l_acquire (EV_P)
4370	{
4371	userdata *u = ev_userdata (EV_A);
4372	pthread_mutex_lock (&u->lock);
4373	}
4374
4375	The event loop thread first acquires the mutex, and then jumps straight
4376	into C<ev_run>:
4377
4378	void *
4379	l_run (void *thr_arg)
4380	{
4381	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4382
4383	l_acquire (EV_A);
4384	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4385	ev_run (EV_A_ 0);
4386	l_release (EV_A);
4387
4388	return 0;
4389	}
4390
4391	Instead of invoking all pending watchers, the C<l_invoke> callback will
4392	signal the main thread via some unspecified mechanism (signals? pipe
4393	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4394	have been called (in a while loop because a) spurious wakeups are possible
4395	and b) skipping inter-thread-communication when there are no pending
4396	watchers is very beneficial):
4397
4398	static void
4399	l_invoke (EV_P)
4400	{
4401	userdata *u = ev_userdata (EV_A);
4402
4403	while (ev_pending_count (EV_A))
4404	{
4405	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4406	pthread_cond_wait (&u->invoke_cv, &u->lock);
4407	}
4408	}
4409
4410	Now, whenever the main thread gets told to invoke pending watchers, it
4411	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4412	thread to continue:
4413
4414	static void
4415	real_invoke_pending (EV_P)
4416	{
4417	userdata *u = ev_userdata (EV_A);
4418
4419	pthread_mutex_lock (&u->lock);
4420	ev_invoke_pending (EV_A);
4421	pthread_cond_signal (&u->invoke_cv);
4422	pthread_mutex_unlock (&u->lock);
4423	}
4424
4425	Whenever you want to start/stop a watcher or do other modifications to an
4426	event loop, you will now have to lock:
4427
4428	ev_timer timeout_watcher;
4429	userdata *u = ev_userdata (EV_A);
4430
4431	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4432
4433	pthread_mutex_lock (&u->lock);
4434	ev_timer_start (EV_A_ &timeout_watcher);
4435	ev_async_send (EV_A_ &u->async_w);
4436	pthread_mutex_unlock (&u->lock);
4437
4438	Note that sending the C<ev_async> watcher is required because otherwise
4439	an event loop currently blocking in the kernel will have no knowledge
4440	about the newly added timer. By waking up the loop it will pick up any new
4441	watchers in the next event loop iteration.
4442		5016
4443	=head3 COROUTINES	5017	=head3 COROUTINES
4444		5018
4445	Libev is very accommodating to coroutines ("cooperative threads"):	5019	Libev is very accommodating to coroutines ("cooperative threads"):
4446	libev fully supports nesting calls to its functions from different	5020	libev fully supports nesting calls to its functions from different
…		…
4611	requires, and its I/O model is fundamentally incompatible with the POSIX	5185	requires, and its I/O model is fundamentally incompatible with the POSIX
4612	model. Libev still offers limited functionality on this platform in	5186	model. Libev still offers limited functionality on this platform in
4613	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5187	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4614	descriptors. This only applies when using Win32 natively, not when using	5188	descriptors. This only applies when using Win32 natively, not when using
4615	e.g. cygwin. Actually, it only applies to the microsofts own compilers,	5189	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
4616	as every compielr comes with a slightly differently broken/incompatible	5190	as every compiler comes with a slightly differently broken/incompatible
4617	environment.	5191	environment.
4618		5192
4619	Lifting these limitations would basically require the full	5193	Lifting these limitations would basically require the full
4620	re-implementation of the I/O system. If you are into this kind of thing,	5194	re-implementation of the I/O system. If you are into this kind of thing,
4621	then note that glib does exactly that for you in a very portable way (note	5195	then note that glib does exactly that for you in a very portable way (note
…		…
4715	structure (guaranteed by POSIX but not by ISO C for example), but it also	5289	structure (guaranteed by POSIX but not by ISO C for example), but it also
4716	assumes that the same (machine) code can be used to call any watcher	5290	assumes that the same (machine) code can be used to call any watcher
4717	callback: The watcher callbacks have different type signatures, but libev	5291	callback: The watcher callbacks have different type signatures, but libev
4718	calls them using an C<ev_watcher *> internally.	5292	calls them using an C<ev_watcher *> internally.
4719		5293
		5294	=item pointer accesses must be thread-atomic
		5295
		5296	Accessing a pointer value must be atomic, it must both be readable and
		5297	writable in one piece - this is the case on all current architectures.
		5298
4720	=item C<sig_atomic_t volatile> must be thread-atomic as well	5299	=item C<sig_atomic_t volatile> must be thread-atomic as well
4721		5300
4722	The type C<sig_atomic_t volatile> (or whatever is defined as	5301	The type C<sig_atomic_t volatile> (or whatever is defined as
4723	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5302	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
4724	threads. This is not part of the specification for C<sig_atomic_t>, but is	5303	threads. This is not part of the specification for C<sig_atomic_t>, but is
…		…
4732	thread" or will block signals process-wide, both behaviours would	5311	thread" or will block signals process-wide, both behaviours would
4733	be compatible with libev. Interaction between C<sigprocmask> and	5312	be compatible with libev. Interaction between C<sigprocmask> and
4734	C<pthread_sigmask> could complicate things, however.	5313	C<pthread_sigmask> could complicate things, however.
4735		5314
4736	The most portable way to handle signals is to block signals in all threads	5315	The most portable way to handle signals is to block signals in all threads
4737	except the initial one, and run the default loop in the initial thread as	5316	except the initial one, and run the signal handling loop in the initial
4738	well.	5317	thread as well.
4739		5318
4740	=item C<long> must be large enough for common memory allocation sizes	5319	=item C<long> must be large enough for common memory allocation sizes
4741		5320
4742	To improve portability and simplify its API, libev uses C<long> internally	5321	To improve portability and simplify its API, libev uses C<long> internally
4743	instead of C<size_t> when allocating its data structures. On non-POSIX	5322	instead of C<size_t> when allocating its data structures. On non-POSIX
…		…
4749		5328
4750	The type C<double> is used to represent timestamps. It is required to	5329	The type C<double> is used to represent timestamps. It is required to
4751	have at least 51 bits of mantissa (and 9 bits of exponent), which is	5330	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4752	good enough for at least into the year 4000 with millisecond accuracy	5331	good enough for at least into the year 4000 with millisecond accuracy
4753	(the design goal for libev). This requirement is overfulfilled by	5332	(the design goal for libev). This requirement is overfulfilled by
4754	implementations using IEEE 754, which is basically all existing ones. With	5333	implementations using IEEE 754, which is basically all existing ones.
		5334
4755	IEEE 754 doubles, you get microsecond accuracy until at least 2200.	5335	With IEEE 754 doubles, you get microsecond accuracy until at least the
		5336	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5337	is either obsolete or somebody patched it to use C<long double> or
		5338	something like that, just kidding).
4756		5339
4757	=back	5340	=back
4758		5341
4759	If you know of other additional requirements drop me a note.	5342	If you know of other additional requirements drop me a note.
4760		5343
…		…
4822	=item Processing ev_async_send: O(number_of_async_watchers)	5405	=item Processing ev_async_send: O(number_of_async_watchers)
4823		5406
4824	=item Processing signals: O(max_signal_number)	5407	=item Processing signals: O(max_signal_number)
4825		5408
4826	Sending involves a system call I<iff> there were no other C<ev_async_send>	5409	Sending involves a system call I<iff> there were no other C<ev_async_send>
4827	calls in the current loop iteration. Checking for async and signal events	5410	calls in the current loop iteration and the loop is currently
		5411	blocked. Checking for async and signal events involves iterating over all
4828	involves iterating over all running async watchers or all signal numbers.	5412	running async watchers or all signal numbers.
4829		5413
4830	=back	5414	=back
4831		5415
4832		5416
4833	=head1 PORTING FROM LIBEV 3.X TO 4.X	5417	=head1 PORTING FROM LIBEV 3.X TO 4.X
4834		5418
4835	The major version 4 introduced some minor incompatible changes to the API.	5419	The major version 4 introduced some incompatible changes to the API.
4836		5420
4837	At the moment, the C<ev.h> header file tries to implement superficial	5421	At the moment, the C<ev.h> header file provides compatibility definitions
4838	compatibility, so most programs should still compile. Those might be	5422	for all changes, so most programs should still compile. The compatibility
4839	removed in later versions of libev, so better update early than late.	5423	layer might be removed in later versions of libev, so better update to the
		5424	new API early than late.
4840		5425
4841	=over 4	5426	=over 4
4842		5427
		5428	=item C<EV_COMPAT3> backwards compatibility mechanism
		5429
		5430	The backward compatibility mechanism can be controlled by
		5431	C<EV_COMPAT3>. See L</PREPROCESSOR SYMBOLS/MACROS> in the L</EMBEDDING>
		5432	section.
		5433
4843	=item C<ev_default_destroy> and C<ev_default_fork> have been removed	5434	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
4844		5435
4845	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:	5436	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
4846		5437
4847	ev_loop_destroy (EV_DEFAULT);	5438	ev_loop_destroy (EV_DEFAULT_UC);
4848	ev_loop_fork (EV_DEFAULT);	5439	ev_loop_fork (EV_DEFAULT);
4849		5440
4850	=item function/symbol renames	5441	=item function/symbol renames
4851		5442
4852	A number of functions and symbols have been renamed:	5443	A number of functions and symbols have been renamed:
…		…
4872	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme	5463	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
4873	as all other watcher types. Note that C<ev_loop_fork> is still called	5464	as all other watcher types. Note that C<ev_loop_fork> is still called
4874	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>	5465	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
4875	typedef.	5466	typedef.
4876		5467
4877	=item C<EV_COMPAT3> backwards compatibility mechanism
4878
4879	The backward compatibility mechanism can be controlled by
4880	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
4881	section.
4882
4883	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>	5468	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
4884		5469
4885	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different	5470	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
4886	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile	5471	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
4887	and work, but the library code will of course be larger.	5472	and work, but the library code will of course be larger.
…		…
4894	=over 4	5479	=over 4
4895		5480
4896	=item active	5481	=item active
4897		5482
4898	A watcher is active as long as it has been started and not yet stopped.	5483	A watcher is active as long as it has been started and not yet stopped.
4899	See L<WATCHER STATES> for details.	5484	See L</WATCHER STATES> for details.
4900		5485
4901	=item application	5486	=item application
4902		5487
4903	In this document, an application is whatever is using libev.	5488	In this document, an application is whatever is using libev.
4904		5489
…		…
4940	watchers and events.	5525	watchers and events.
4941		5526
4942	=item pending	5527	=item pending
4943		5528
4944	A watcher is pending as soon as the corresponding event has been	5529	A watcher is pending as soon as the corresponding event has been
4945	detected. See L<WATCHER STATES> for details.	5530	detected. See L</WATCHER STATES> for details.
4946		5531
4947	=item real time	5532	=item real time
4948		5533
4949	The physical time that is observed. It is apparently strictly monotonic :)	5534	The physical time that is observed. It is apparently strictly monotonic :)
4950		5535
4951	=item wall-clock time	5536	=item wall-clock time
4952		5537
4953	The time and date as shown on clocks. Unlike real time, it can actually	5538	The time and date as shown on clocks. Unlike real time, it can actually
4954	be wrong and jump forwards and backwards, e.g. when the you adjust your	5539	be wrong and jump forwards and backwards, e.g. when you adjust your
4955	clock.	5540	clock.
4956		5541
4957	=item watcher	5542	=item watcher
4958		5543
4959	A data structure that describes interest in certain events. Watchers need	5544	A data structure that describes interest in certain events. Watchers need
…		…
4961		5546
4962	=back	5547	=back
4963		5548
4964	=head1 AUTHOR	5549	=head1 AUTHOR
4965		5550
4966	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5551	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5552	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4967		5553

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