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Revision 1.406 by root, Thu May 3 16:00:47 2012 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
…		…
347	=item struct ev_loop *ev_loop_new (unsigned int flags)	374	=item struct ev_loop *ev_loop_new (unsigned int flags)
348		375
349	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
350	could not be initialised, returns false.	377	could not be initialised, returns false.
351		378
352	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
353	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
354	default loop in the "main" or "initial" thread.	381	loop in the "main" or "initial" thread.
355		382
356	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
357	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>).
358		385
359	The following flags are supported:	386	The following flags are supported:
…		…
394	environment variable.	421	environment variable.
395		422
396	=item C<EVFLAG_NOINOTIFY>	423	=item C<EVFLAG_NOINOTIFY>
397		424
398	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
399	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
400	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
401	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.
402		429
403	=item C<EVFLAG_SIGNALFD>	430	=item C<EVFLAG_SIGNALFD>
404		431
405	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
406	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
407	delivers signals synchronously, which makes it both faster and might make	434	delivers signals synchronously, which makes it both faster and might make
408	it possible to get the queued signal data. It can also simplify signal	435	it possible to get the queued signal data. It can also simplify signal
409	handling with threads, as long as you properly block signals in your	436	handling with threads, as long as you properly block signals in your
410	threads that are not interested in handling them.	437	threads that are not interested in handling them.
411		438
412	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
413	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
414	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.
415		457
416	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	458	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
417		459
418	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
419	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,
…		…
447	=item C<EVBACKEND_EPOLL> (value 4, Linux)	489	=item C<EVBACKEND_EPOLL> (value 4, Linux)
448		490
449	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
450	kernels).	492	kernels).
451		493
452	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
453	but it scales phenomenally better. While poll and select usually scale	495	it scales phenomenally better. While poll and select usually scale like
454	like O(total_fds) where n is the total number of fds (or the highest fd),	496	O(total_fds) where total_fds is the total number of fds (or the highest
455	epoll scales either O(1) or O(active_fds).	497	fd), epoll scales either O(1) or O(active_fds).
456		498
457	The epoll mechanism deserves honorable mention as the most misdesigned	499	The epoll mechanism deserves honorable mention as the most misdesigned
458	of the more advanced event mechanisms: mere annoyances include silently	500	of the more advanced event mechanisms: mere annoyances include silently
459	dropping file descriptors, requiring a system call per change per file	501	dropping file descriptors, requiring a system call per change per file
460	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
461	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
462	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
463	take considerable time (one syscall per file descriptor) and is of course	507	set, which can take considerable time (one syscall per file descriptor)
464	hard to detect.	508	and is of course hard to detect.
465		509
466	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	510	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
467	of course I<doesn't>, and epoll just loves to report events for totally	511	but of course I<doesn't>, and epoll just loves to report events for
468	I<different> file descriptors (even already closed ones, so one cannot	512	totally I<different> file descriptors (even already closed ones, so
469	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
470	on SMP systems). Libev tries to counter these spurious notifications by	514	(especially on SMP systems). Libev tries to counter these spurious
471	employing an additional generation counter and comparing that against the	515	notifications by employing an additional generation counter and comparing
472	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
473	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
474	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...
475		526
476	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
477	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
478	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
479	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
…		…
516		567
517	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
518	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
519	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
520	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
521	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
522	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
523	cases	574	drops fds silently in similarly hard-to-detect cases
524		575
525	This backend usually performs well under most conditions.	576	This backend usually performs well under most conditions.
526		577
527	While nominally embeddable in other event loops, this doesn't work	578	While nominally embeddable in other event loops, this doesn't work
528	everywhere, so you might need to test for this. And since it is broken	579	everywhere, so you might need to test for this. And since it is broken
…		…
545	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	596	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
546		597
547	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,
548	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)).
549		600
550	Please note that Solaris event ports can deliver a lot of spurious
551	notifications, so you need to use non-blocking I/O or other means to avoid
552	blocking when no data (or space) is available.
553
554	While this backend scales well, it requires one system call per active	601	While this backend scales well, it requires one system call per active
555	file descriptor per loop iteration. For small and medium numbers of file	602	file descriptor per loop iteration. For small and medium numbers of file
556	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	603	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
557	might perform better.	604	might perform better.
558		605
559	On the positive side, with the exception of the spurious readiness	606	On the positive side, this backend actually performed fully to
560	notifications, this backend actually performed fully to specification
561	in all tests and is fully embeddable, which is a rare feat among the	607	specification in all tests and is fully embeddable, which is a rare feat
562	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.
563		620
564	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
565	C<EVBACKEND_POLL>.	622	C<EVBACKEND_POLL>.
566		623
567	=item C<EVBACKEND_ALL>	624	=item C<EVBACKEND_ALL>
568		625
569	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
570	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
571	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	628	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
572		629
573	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).
574		639
575	=back	640	=back
576		641
577	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,
578	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
…		…
607	This function is normally used on loop objects allocated by	672	This function is normally used on loop objects allocated by
608	C<ev_loop_new>, but it can also be used on the default loop returned by	673	C<ev_loop_new>, but it can also be used on the default loop returned by
609	C<ev_default_loop>, in which case it is not thread-safe.	674	C<ev_default_loop>, in which case it is not thread-safe.
610		675
611	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
612	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.
613	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>
614	and C<ev_loop_destroy>.	679	and C<ev_loop_destroy>.
615		680
616	=item ev_loop_fork (loop)	681	=item ev_loop_fork (loop)
617		682
…		…
665	prepare and check phases.	730	prepare and check phases.
666		731
667	=item unsigned int ev_depth (loop)	732	=item unsigned int ev_depth (loop)
668		733
669	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
670	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.
671		736
672	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
673	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),
674	in which case it is higher.	739	in which case it is higher.
675		740
676	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread	741	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
677	etc.), doesn't count as "exit" - consider this as a hint to avoid such	742	throwing an exception etc.), doesn't count as "exit" - consider this
678	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.
679		745
680	=item unsigned int ev_backend (loop)	746	=item unsigned int ev_backend (loop)
681		747
682	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
683	use.	749	use.
…		…
726	without a previous call to C<ev_suspend>.	792	without a previous call to C<ev_suspend>.
727		793
728	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
729	event loop time (see C<ev_now_update>).	795	event loop time (see C<ev_now_update>).
730		796
731	=item ev_run (loop, int flags)	797	=item bool ev_run (loop, int flags)
732		798
733	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
734	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
735	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
736	the watcher callbacks, an then repeat the whole process indefinitely: This	802	the watcher callbacks, and then repeat the whole process indefinitely: This
737	is why event loops are called I<loops>.	803	is why event loops are called I<loops>.
738		804
739	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
740	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
741	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").
742		812
743	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
744	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
745	finished (especially in interactive programs), but having a program	815	finished (especially in interactive programs), but having a program
746	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
747	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
748	beauty.	818	beauty.
749		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
750	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
751	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
752	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
753	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
754	events while doing lengthy calculations, to keep the program responsive.	829	events while doing lengthy calculations, to keep the program responsive.
…		…
763	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
764	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
765	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
766	usually a better approach for this kind of thing.	841	usually a better approach for this kind of thing.
767		842
768	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):
769		846
770	- Increment loop depth.	847	- Increment loop depth.
771	- Reset the ev_break status.	848	- Reset the ev_break status.
772	- Before the first iteration, call any pending watchers.	849	- Before the first iteration, call any pending watchers.
773	LOOP:	850	LOOP:
…		…
806	anymore.	883	anymore.
807		884
808	... queue jobs here, make sure they register event watchers as long	885	... queue jobs here, make sure they register event watchers as long
809	... as they still have work to do (even an idle watcher will do..)	886	... as they still have work to do (even an idle watcher will do..)
810	ev_run (my_loop, 0);	887	ev_run (my_loop, 0);
811	... jobs done or somebody called unloop. yeah!	888	... jobs done or somebody called break. yeah!
812		889
813	=item ev_break (loop, how)	890	=item ev_break (loop, how)
814		891
815	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
816	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
817	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
818	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.
819		896
820	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>.
821		898
822	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.
823		901
824	=item ev_ref (loop)	902	=item ev_ref (loop)
825		903
826	=item ev_unref (loop)	904	=item ev_unref (loop)
827		905
…		…
848	running when nothing else is active.	926	running when nothing else is active.
849		927
850	ev_signal exitsig;	928	ev_signal exitsig;
851	ev_signal_init (&exitsig, sig_cb, SIGINT);	929	ev_signal_init (&exitsig, sig_cb, SIGINT);
852	ev_signal_start (loop, &exitsig);	930	ev_signal_start (loop, &exitsig);
853	evf_unref (loop);	931	ev_unref (loop);
854		932
855	Example: For some weird reason, unregister the above signal handler again.	933	Example: For some weird reason, unregister the above signal handler again.
856		934
857	ev_ref (loop);	935	ev_ref (loop);
858	ev_signal_stop (loop, &exitsig);	936	ev_signal_stop (loop, &exitsig);
…		…
878	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.
879		957
880	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
881	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,
882	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
883	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
884	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
885	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
886	once per this interval, on average.	964	once per this interval, on average (as long as the host time resolution is
		965	good enough).
887		966
888	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
889	to spend more time collecting timeouts, at the expense of increased	968	to spend more time collecting timeouts, at the expense of increased
890	latency/jitter/inexactness (the watcher callback will be called	969	latency/jitter/inexactness (the watcher callback will be called
891	later). C<ev_io> watchers will not be affected. Setting this to a non-null	970	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
937	invoke the actual watchers inside another context (another thread etc.).	1016	invoke the actual watchers inside another context (another thread etc.).
938		1017
939	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
940	callback.	1019	callback.
941		1020
942	=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 ())
943		1022
944	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
945	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
946	each call to a libev function.	1025	each call to a libev function.
947		1026
948	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
949	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
950	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
951	I<release> and I<acquire> callbacks on the loop.	1030	I<release> and I<acquire> callbacks on the loop.
952		1031
953	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
954	suspended waiting for new events, and C<acquire> is called just	1033	suspended waiting for new events, and C<acquire> is called just
955	afterwards.	1034	afterwards.
…		…
970	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
971	document.	1050	document.
972		1051
973	=item ev_set_userdata (loop, void *data)	1052	=item ev_set_userdata (loop, void *data)
974		1053
975	=item ev_userdata (loop)	1054	=item void *ev_userdata (loop)
976		1055
977	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
978	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
979	C<0.>	1058	C<0>.
980		1059
981	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,
982	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
983	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
984	any other purpose as well.	1063	any other purpose as well.
…		…
1095		1174
1096	=item C<EV_PREPARE>	1175	=item C<EV_PREPARE>
1097		1176
1098	=item C<EV_CHECK>	1177	=item C<EV_CHECK>
1099		1178
1100	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
1101	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)
1102	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
1103	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
1104	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
1105	(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
1106	C<ev_run> from blocking).	1190	blocking).
1107		1191
1108	=item C<EV_EMBED>	1192	=item C<EV_EMBED>
1109		1193
1110	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.
1111		1195
1112	=item C<EV_FORK>	1196	=item C<EV_FORK>
1113		1197
1114	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
1115	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>).
1116		1204
1117	=item C<EV_ASYNC>	1205	=item C<EV_ASYNC>
1118		1206
1119	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>).
1120		1208
…		…
1142	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
1143	thing, so beware.	1231	thing, so beware.
1144		1232
1145	=back	1233	=back
1146		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_cb_set (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
1147	=head2 WATCHER STATES	1389	=head2 WATCHER STATES
1148		1390
1149	There are various watcher states mentioned throughout this manual -	1391	There are various watcher states mentioned throughout this manual -
1150	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
1151	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
…		…
1153		1395
1154	=over 4	1396	=over 4
1155		1397
1156	=item initialiased	1398	=item initialiased
1157		1399
1158	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
1159	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
1160	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.
1161		1403
1162	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
1163	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.
1164		1408
1165	=item started/running/active	1409	=item started/running/active
1166		1410
1167	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
1168	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
…		…
1196	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
1197	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
1198	freeing it is often a good idea.	1442	freeing it is often a good idea.
1199		1443
1200	While stopped (and not pending) the watcher is essentially in the	1444	While stopped (and not pending) the watcher is essentially in the
1201	initialised state, that is it can be reused, moved, modified in any way	1445	initialised state, that is, it can be reused, moved, modified in any way
1202	you wish.	1446	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1447	it again).
1203		1448
1204	=back	1449	=back
1205
1206	=head2 GENERIC WATCHER FUNCTIONS
1207
1208	=over 4
1209
1210	=item C<ev_init> (ev_TYPE *watcher, callback)
1211
1212	This macro initialises the generic portion of a watcher. The contents
1213	of the watcher object can be arbitrary (so C<malloc> will do). Only
1214	the generic parts of the watcher are initialised, you I<need> to call
1215	the type-specific C<ev_TYPE_set> macro afterwards to initialise the
1216	type-specific parts. For each type there is also a C<ev_TYPE_init> macro
1217	which rolls both calls into one.
1218
1219	You can reinitialise a watcher at any time as long as it has been stopped
1220	(or never started) and there are no pending events outstanding.
1221
1222	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
1223	int revents)>.
1224
1225	Example: Initialise an C<ev_io> watcher in two steps.
1226
1227	ev_io w;
1228	ev_init (&w, my_cb);
1229	ev_io_set (&w, STDIN_FILENO, EV_READ);
1230
1231	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
1232
1233	This macro initialises the type-specific parts of a watcher. You need to
1234	call C<ev_init> at least once before you call this macro, but you can
1235	call C<ev_TYPE_set> any number of times. You must not, however, call this
1236	macro on a watcher that is active (it can be pending, however, which is a
1237	difference to the C<ev_init> macro).
1238
1239	Although some watcher types do not have type-specific arguments
1240	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
1241
1242	See C<ev_init>, above, for an example.
1243
1244	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
1245
1246	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
1247	calls into a single call. This is the most convenient method to initialise
1248	a watcher. The same limitations apply, of course.
1249
1250	Example: Initialise and set an C<ev_io> watcher in one step.
1251
1252	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1253
1254	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1255
1256	Starts (activates) the given watcher. Only active watchers will receive
1257	events. If the watcher is already active nothing will happen.
1258
1259	Example: Start the C<ev_io> watcher that is being abused as example in this
1260	whole section.
1261
1262	ev_io_start (EV_DEFAULT_UC, &w);
1263
1264	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1265
1266	Stops the given watcher if active, and clears the pending status (whether
1267	the watcher was active or not).
1268
1269	It is possible that stopped watchers are pending - for example,
1270	non-repeating timers are being stopped when they become pending - but
1271	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
1272	pending. If you want to free or reuse the memory used by the watcher it is
1273	therefore a good idea to always call its C<ev_TYPE_stop> function.
1274
1275	=item bool ev_is_active (ev_TYPE *watcher)
1276
1277	Returns a true value iff the watcher is active (i.e. it has been started
1278	and not yet been stopped). As long as a watcher is active you must not modify
1279	it.
1280
1281	=item bool ev_is_pending (ev_TYPE *watcher)
1282
1283	Returns a true value iff the watcher is pending, (i.e. it has outstanding
1284	events but its callback has not yet been invoked). As long as a watcher
1285	is pending (but not active) you must not call an init function on it (but
1286	C<ev_TYPE_set> is safe), you must not change its priority, and you must
1287	make sure the watcher is available to libev (e.g. you cannot C<free ()>
1288	it).
1289
1290	=item callback ev_cb (ev_TYPE *watcher)
1291
1292	Returns the callback currently set on the watcher.
1293
1294	=item ev_cb_set (ev_TYPE *watcher, callback)
1295
1296	Change the callback. You can change the callback at virtually any time
1297	(modulo threads).
1298
1299	=item ev_set_priority (ev_TYPE *watcher, int priority)
1300
1301	=item int ev_priority (ev_TYPE *watcher)
1302
1303	Set and query the priority of the watcher. The priority is a small
1304	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1305	(default: C<-2>). Pending watchers with higher priority will be invoked
1306	before watchers with lower priority, but priority will not keep watchers
1307	from being executed (except for C<ev_idle> watchers).
1308
1309	If you need to suppress invocation when higher priority events are pending
1310	you need to look at C<ev_idle> watchers, which provide this functionality.
1311
1312	You I<must not> change the priority of a watcher as long as it is active or
1313	pending.
1314
1315	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1316	fine, as long as you do not mind that the priority value you query might
1317	or might not have been clamped to the valid range.
1318
1319	The default priority used by watchers when no priority has been set is
1320	always C<0>, which is supposed to not be too high and not be too low :).
1321
1322	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1323	priorities.
1324
1325	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1326
1327	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1328	C<loop> nor C<revents> need to be valid as long as the watcher callback
1329	can deal with that fact, as both are simply passed through to the
1330	callback.
1331
1332	=item int ev_clear_pending (loop, ev_TYPE *watcher)
1333
1334	If the watcher is pending, this function clears its pending status and
1335	returns its C<revents> bitset (as if its callback was invoked). If the
1336	watcher isn't pending it does nothing and returns C<0>.
1337
1338	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1339	callback to be invoked, which can be accomplished with this function.
1340
1341	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
1342
1343	Feeds the given event set into the event loop, as if the specified event
1344	had happened for the specified watcher (which must be a pointer to an
1345	initialised but not necessarily started event watcher). Obviously you must
1346	not free the watcher as long as it has pending events.
1347
1348	Stopping the watcher, letting libev invoke it, or calling
1349	C<ev_clear_pending> will clear the pending event, even if the watcher was
1350	not started in the first place.
1351
1352	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1353	functions that do not need a watcher.
1354
1355	=back
1356
1357
1358	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1359
1360	Each watcher has, by default, a member C<void *data> that you can change
1361	and read at any time: libev will completely ignore it. This can be used
1362	to associate arbitrary data with your watcher. If you need more data and
1363	don't want to allocate memory and store a pointer to it in that data
1364	member, you can also "subclass" the watcher type and provide your own
1365	data:
1366
1367	struct my_io
1368	{
1369	ev_io io;
1370	int otherfd;
1371	void *somedata;
1372	struct whatever *mostinteresting;
1373	};
1374
1375	...
1376	struct my_io w;
1377	ev_io_init (&w.io, my_cb, fd, EV_READ);
1378
1379	And since your callback will be called with a pointer to the watcher, you
1380	can cast it back to your own type:
1381
1382	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1383	{
1384	struct my_io *w = (struct my_io *)w_;
1385	...
1386	}
1387
1388	More interesting and less C-conformant ways of casting your callback type
1389	instead have been omitted.
1390
1391	Another common scenario is to use some data structure with multiple
1392	embedded watchers:
1393
1394	struct my_biggy
1395	{
1396	int some_data;
1397	ev_timer t1;
1398	ev_timer t2;
1399	}
1400
1401	In this case getting the pointer to C<my_biggy> is a bit more
1402	complicated: Either you store the address of your C<my_biggy> struct
1403	in the C<data> member of the watcher (for woozies), or you need to use
1404	some pointer arithmetic using C<offsetof> inside your watchers (for real
1405	programmers):
1406
1407	#include <stddef.h>
1408
1409	static void
1410	t1_cb (EV_P_ ev_timer *w, int revents)
1411	{
1412	struct my_biggy big = (struct my_biggy *)
1413	(((char *)w) - offsetof (struct my_biggy, t1));
1414	}
1415
1416	static void
1417	t2_cb (EV_P_ ev_timer *w, int revents)
1418	{
1419	struct my_biggy big = (struct my_biggy *)
1420	(((char *)w) - offsetof (struct my_biggy, t2));
1421	}
1422		1450
1423	=head2 WATCHER PRIORITY MODELS	1451	=head2 WATCHER PRIORITY MODELS
1424		1452
1425	Many event loops support I<watcher priorities>, which are usually small	1453	Many event loops support I<watcher priorities>, which are usually small
1426	integers that influence the ordering of event callback invocation	1454	integers that influence the ordering of event callback invocation
…		…
1553	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
1554	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
1555	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
1556	required if you know what you are doing).	1584	required if you know what you are doing).
1557		1585
1558	If you cannot use non-blocking mode, then force the use of a
1559	known-to-be-good backend (at the time of this writing, this includes only
1560	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1561	descriptors for which non-blocking operation makes no sense (such as
1562	files) - libev doesn't guarantee any specific behaviour in that case.
1563
1564	Another thing you have to watch out for is that it is quite easy to	1586	Another thing you have to watch out for is that it is quite easy to
1565	receive "spurious" readiness notifications, that is your callback might	1587	receive "spurious" readiness notifications, that is, your callback might
1566	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1588	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1567	because there is no data. Not only are some backends known to create a	1589	because there is no data. It is very easy to get into this situation even
1568	lot of those (for example Solaris ports), it is very easy to get into	1590	with a relatively standard program structure. Thus it is best to always
1569	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
1570	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1571	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1592	preferable to a program hanging until some data arrives.
1572		1593
1573	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
1574	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
1575	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
1576	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
1577	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
1578	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
1579	indefinitely.	1600	indefinitely.
1580		1601
1581	But really, best use non-blocking mode.	1602	But really, best use non-blocking mode.
1582		1603
…		…
1610		1631
1611	There is no workaround possible except not registering events	1632	There is no workaround possible except not registering events
1612	for potentially C<dup ()>'ed file descriptors, or to resort to	1633	for potentially C<dup ()>'ed file descriptors, or to resort to
1613	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1634	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1614		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
1615	=head3 The special problem of fork	1669	=head3 The special problem of fork
1616		1670
1617	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
1618	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
1619	it in the child.	1673	it in the child if you want to continue to use it in the child.
1620		1674
1621	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
1622	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
1623	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1677	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1624	C<EVBACKEND_POLL>.
1625		1678
1626	=head3 The special problem of SIGPIPE	1679	=head3 The special problem of SIGPIPE
1627		1680
1628	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>:
1629	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
…		…
1727	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1780	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1728	monotonic clock option helps a lot here).	1781	monotonic clock option helps a lot here).
1729		1782
1730	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
1731	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
1732	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
1733	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
1734	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
1735	no longer true when a callback calls C<ev_run> recursively).	1789	longer true when a callback calls C<ev_run> recursively).
1736		1790
1737	=head3 Be smart about timeouts	1791	=head3 Be smart about timeouts
1738		1792
1739	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
1740	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,
…		…
1815		1869
1816	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,
1817	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
1818	within the callback:	1872	within the callback:
1819		1873
		1874	ev_tstamp timeout = 60.;
1820	ev_tstamp last_activity; // time of last activity	1875	ev_tstamp last_activity; // time of last activity
		1876	ev_timer timer;
1821		1877
1822	static void	1878	static void
1823	callback (EV_P_ ev_timer *w, int revents)	1879	callback (EV_P_ ev_timer *w, int revents)
1824	{	1880	{
1825	ev_tstamp now = ev_now (EV_A);	1881	// calculate when the timeout would happen
1826	ev_tstamp timeout = last_activity + 60.;	1882	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1827		1883
1828	// if last_activity + 60. is older than now, we did time out	1884	// if negative, it means we the timeout already occurred
1829	if (timeout < now)	1885	if (after < 0.)
1830	{	1886	{
1831	// timeout occurred, take action	1887	// timeout occurred, take action
1832	}	1888	}
1833	else	1889	else
1834	{	1890	{
1835	// callback was invoked, but there was some activity, re-arm	1891	// callback was invoked, but there was some recent
1836	// the watcher to fire in last_activity + 60, which is	1892	// activity. simply restart the timer to time out
1837	// guaranteed to be in the future, so "again" is positive:	1893	// after "after" seconds, which is the earliest time
1838	w->repeat = timeout - now;	1894	// the timeout can occur.
		1895	ev_timer_set (w, after, 0.);
1839	ev_timer_again (EV_A_ w);	1896	ev_timer_start (EV_A_ w);
1840	}	1897	}
1841	}	1898	}
1842		1899
1843	To summarise the callback: first calculate the real timeout (defined	1900	To summarise the callback: first calculate in how many seconds the
1844	as "60 seconds after the last activity"), then check if that time has	1901	timeout will occur (by calculating the absolute time when it would occur,
1845	been reached, which means something I<did>, in fact, time out. Otherwise	1902	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1846	the callback was invoked too early (C<timeout> is in the future), so	1903	(EV_A)> from that).
1847	re-schedule the timer to fire at that future time, to see if maybe we have
1848	a timeout then.
1849		1904
1850	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
1851	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.
1852		1914
1853	This scheme causes more callback invocations (about one every 60 seconds	1915	This scheme causes more callback invocations (about one every 60 seconds
1854	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
1855	libev to change the timeout.	1917	libev to change the timeout.
1856		1918
1857	To start the timer, simply initialise the watcher and set C<last_activity>	1919	To start the machinery, simply initialise the watcher and set
1858	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
1859	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:
1860		1923
		1924	last_activity = ev_now (EV_A);
1861	ev_init (timer, callback);	1925	ev_init (&timer, callback);
1862	last_activity = ev_now (loop);	1926	callback (EV_A_ &timer, 0);
1863	callback (loop, timer, EV_TIMER);
1864		1927
1865	And when there is some activity, simply store the current time in	1928	When there is some activity, simply store the current time in
1866	C<last_activity>, no libev calls at all:	1929	C<last_activity>, no libev calls at all:
1867		1930
		1931	if (activity detected)
1868	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);
1869		1941
1870	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
1871	time-out is unlikely to be triggered, much more efficient.	1943	time-out is unlikely to be triggered, much more efficient.
1872
1873	Changing the timeout is trivial as well (if it isn't hard-coded in the
1874	callback :) - just change the timeout and invoke the callback, which will
1875	fix things for you.
1876		1944
1877	=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.
1878		1946
1879	If there is not one request, but many thousands (millions...), all	1947	If there is not one request, but many thousands (millions...), all
1880	employing some kind of timeout with the same timeout value, then one can	1948	employing some kind of timeout with the same timeout value, then one can
…		…
1907	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	1975	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1908	rather complicated, but extremely efficient, something that really pays	1976	rather complicated, but extremely efficient, something that really pays
1909	off after the first million or so of active timers, i.e. it's usually	1977	off after the first million or so of active timers, i.e. it's usually
1910	overkill :)	1978	overkill :)
1911		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
1912	=head3 The special problem of time updates	2017	=head3 The special problem of time updates
1913		2018
1914	Establishing the current time is a costly operation (it usually takes at	2019	Establishing the current time is a costly operation (it usually takes
1915	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
1916	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
1917	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
1918	lots of events in one iteration.	2023	lots of events in one iteration.
1919		2024
1920	The relative timeouts are calculated relative to the C<ev_now ()>	2025	The relative timeouts are calculated relative to the C<ev_now ()>
…		…
1926	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2031	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1927		2032
1928	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
1929	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
1930	()>.	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.
1931		2069
1932	=head3 The special problems of suspended animation	2070	=head3 The special problems of suspended animation
1933		2071
1934	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
1935	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?
…		…
1979	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
1980	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.
1981		2119
1982	=item ev_timer_again (loop, ev_timer *)	2120	=item ev_timer_again (loop, ev_timer *)
1983		2121
1984	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
1985	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>.
1986		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
1987	If the timer is pending, its pending status is cleared.	2131	=item If the timer is pending, the pending status is always cleared.
1988		2132
1989	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).
1990		2135
1991	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
1992	C<repeat> value), or reset the running timer to the C<repeat> value.	2137	and start the timer, if necessary.
		2138
		2139	=back
1993		2140
1994	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
1995	usage example.	2142	usage example.
1996		2143
1997	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)	2144	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
…		…
2119		2266
2120	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
2121	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
2122	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.
2123		2270
2124	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
2125	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
2126	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.
2127		2277
2128	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
2129	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
2130	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
2131	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).
…		…
2245		2395
2246	=head2 C<ev_signal> - signal me when a signal gets signalled!	2396	=head2 C<ev_signal> - signal me when a signal gets signalled!
2247		2397
2248	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
2249	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
2250	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
2251	normal event processing, like any other event.	2401	normal event processing, like any other event.
2252		2402
2253	If you want signals to be delivered truly asynchronously, just use	2403	If you want signals to be delivered truly asynchronously, just use
2254	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
2255	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
…		…
2274	=head3 The special problem of inheritance over fork/execve/pthread_create	2424	=head3 The special problem of inheritance over fork/execve/pthread_create
2275		2425
2276	Both the signal mask (C<sigprocmask>) and the signal disposition	2426	Both the signal mask (C<sigprocmask>) and the signal disposition
2277	(C<sigaction>) are unspecified after starting a signal watcher (and after	2427	(C<sigaction>) are unspecified after starting a signal watcher (and after
2278	stopping it again), that is, libev might or might not block the signal,	2428	stopping it again), that is, libev might or might not block the signal,
2279	and might or might not set or restore the installed signal handler.	2429	and might or might not set or restore the installed signal handler (but
		2430	see C<EVFLAG_NOSIGMASK>).
2280		2431
2281	While this does not matter for the signal disposition (libev never	2432	While this does not matter for the signal disposition (libev never
2282	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on	2433	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
2283	C<execve>), this matters for the signal mask: many programs do not expect	2434	C<execve>), this matters for the signal mask: many programs do not expect
2284	certain signals to be blocked.	2435	certain signals to be blocked.
…		…
2297	I<has> to modify the signal mask, at least temporarily.	2448	I<has> to modify the signal mask, at least temporarily.
2298		2449
2299	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
2300	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
2301	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>.
2302		2467
2303	=head3 Watcher-Specific Functions and Data Members	2468	=head3 Watcher-Specific Functions and Data Members
2304		2469
2305	=over 4	2470	=over 4
2306		2471
…		…
2682	Apart from keeping your process non-blocking (which is a useful	2847	Apart from keeping your process non-blocking (which is a useful
2683	effect on its own sometimes), idle watchers are a good place to do	2848	effect on its own sometimes), idle watchers are a good place to do
2684	"pseudo-background processing", or delay processing stuff to after the	2849	"pseudo-background processing", or delay processing stuff to after the
2685	event loop has handled all outstanding events.	2850	event loop has handled all outstanding events.
2686		2851
		2852	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2853
		2854	As long as there is at least one active idle watcher, libev will never
		2855	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2856	For this to work, the idle watcher doesn't need to be invoked at all - the
		2857	lowest priority will do.
		2858
		2859	This mode of operation can be useful together with an C<ev_check> watcher,
		2860	to do something on each event loop iteration - for example to balance load
		2861	between different connections.
		2862
		2863	See L<Abusing an C<ev_check> watcher for its side-effect> for a longer
		2864	example.
		2865
2687	=head3 Watcher-Specific Functions and Data Members	2866	=head3 Watcher-Specific Functions and Data Members
2688		2867
2689	=over 4	2868	=over 4
2690		2869
2691	=item ev_idle_init (ev_idle *, callback)	2870	=item ev_idle_init (ev_idle *, callback)
…		…
2714	ev_idle_start (loop, idle_watcher);	2893	ev_idle_start (loop, idle_watcher);
2715		2894
2716		2895
2717	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2896	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2718		2897
2719	Prepare and check watchers are usually (but not always) used in pairs:	2898	Prepare and check watchers are often (but not always) used in pairs:
2720	prepare watchers get invoked before the process blocks and check watchers	2899	prepare watchers get invoked before the process blocks and check watchers
2721	afterwards.	2900	afterwards.
2722		2901
2723	You I<must not> call C<ev_run> or similar functions that enter	2902	You I<must not> call C<ev_run> or similar functions that enter
2724	the current event loop from either C<ev_prepare> or C<ev_check>	2903	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
2752	with priority higher than or equal to the event loop and one coroutine	2931	with priority higher than or equal to the event loop and one coroutine
2753	of lower priority, but only once, using idle watchers to keep the event	2932	of lower priority, but only once, using idle watchers to keep the event
2754	loop from blocking if lower-priority coroutines are active, thus mapping	2933	loop from blocking if lower-priority coroutines are active, thus mapping
2755	low-priority coroutines to idle/background tasks).	2934	low-priority coroutines to idle/background tasks).
2756		2935
2757	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2936	When used for this purpose, it is recommended to give C<ev_check> watchers
2758	priority, to ensure that they are being run before any other watchers	2937	highest (C<EV_MAXPRI>) priority, to ensure that they are being run before
2759	after the poll (this doesn't matter for C<ev_prepare> watchers).	2938	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		2939	watchers).
2760		2940
2761	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	2941	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
2762	activate ("feed") events into libev. While libev fully supports this, they	2942	activate ("feed") events into libev. While libev fully supports this, they
2763	might get executed before other C<ev_check> watchers did their job. As	2943	might get executed before other C<ev_check> watchers did their job. As
2764	C<ev_check> watchers are often used to embed other (non-libev) event	2944	C<ev_check> watchers are often used to embed other (non-libev) event
2765	loops those other event loops might be in an unusable state until their	2945	loops those other event loops might be in an unusable state until their
2766	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	2946	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2767	others).	2947	others).
		2948
		2949	=head3 Abusing an C<ev_check> watcher for its side-effect
		2950
		2951	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		2952	useful because they are called once per event loop iteration. For
		2953	example, if you want to handle a large number of connections fairly, you
		2954	normally only do a bit of work for each active connection, and if there
		2955	is more work to do, you wait for the next event loop iteration, so other
		2956	connections have a chance of making progress.
		2957
		2958	Using an C<ev_check> watcher is almost enough: it will be called on the
		2959	next event loop iteration. However, that isn't as soon as possible -
		2960	without external events, your C<ev_check> watcher will not be invoked.
		2961
		2962
		2963	This is where C<ev_idle> watchers come in handy - all you need is a
		2964	single global idle watcher that is active as long as you have one active
		2965	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		2966	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		2967	invoked. Neither watcher alone can do that.
2768		2968
2769	=head3 Watcher-Specific Functions and Data Members	2969	=head3 Watcher-Specific Functions and Data Members
2770		2970
2771	=over 4	2971	=over 4
2772		2972
…		…
3090		3290
3091	=head3 Watcher-Specific Functions and Data Members	3291	=head3 Watcher-Specific Functions and Data Members
3092		3292
3093	=over 4	3293	=over 4
3094		3294
3095	=item ev_fork_init (ev_signal *, callback)	3295	=item ev_fork_init (ev_fork *, callback)
3096		3296
3097	Initialises and configures the fork watcher - it has no parameters of any	3297	Initialises and configures the fork watcher - it has no parameters of any
3098	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3298	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
3099	believe me.	3299	really.
3100		3300
3101	=back	3301	=back
3102		3302
3103		3303
		3304	=head2 C<ev_cleanup> - even the best things end
		3305
		3306	Cleanup watchers are called just before the event loop is being destroyed
		3307	by a call to C<ev_loop_destroy>.
		3308
		3309	While there is no guarantee that the event loop gets destroyed, cleanup
		3310	watchers provide a convenient method to install cleanup hooks for your
		3311	program, worker threads and so on - you just to make sure to destroy the
		3312	loop when you want them to be invoked.
		3313
		3314	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3315	all other watchers, they do not keep a reference to the event loop (which
		3316	makes a lot of sense if you think about it). Like all other watchers, you
		3317	can call libev functions in the callback, except C<ev_cleanup_start>.
		3318
		3319	=head3 Watcher-Specific Functions and Data Members
		3320
		3321	=over 4
		3322
		3323	=item ev_cleanup_init (ev_cleanup *, callback)
		3324
		3325	Initialises and configures the cleanup watcher - it has no parameters of
		3326	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3327	pointless, I assure you.
		3328
		3329	=back
		3330
		3331	Example: Register an atexit handler to destroy the default loop, so any
		3332	cleanup functions are called.
		3333
		3334	static void
		3335	program_exits (void)
		3336	{
		3337	ev_loop_destroy (EV_DEFAULT_UC);
		3338	}
		3339
		3340	...
		3341	atexit (program_exits);
		3342
		3343
3104	=head2 C<ev_async> - how to wake up an event loop	3344	=head2 C<ev_async> - how to wake up an event loop
3105		3345
3106	In general, you cannot use an C<ev_run> from multiple threads or other	3346	In general, you cannot use an C<ev_loop> from multiple threads or other
3107	asynchronous sources such as signal handlers (as opposed to multiple event	3347	asynchronous sources such as signal handlers (as opposed to multiple event
3108	loops - those are of course safe to use in different threads).	3348	loops - those are of course safe to use in different threads).
3109		3349
3110	Sometimes, however, you need to wake up an event loop you do not control,	3350	Sometimes, however, you need to wake up an event loop you do not control,
3111	for example because it belongs to another thread. This is what C<ev_async>	3351	for example because it belongs to another thread. This is what C<ev_async>
…		…
3113	it by calling C<ev_async_send>, which is thread- and signal safe.	3353	it by calling C<ev_async_send>, which is thread- and signal safe.
3114		3354
3115	This functionality is very similar to C<ev_signal> watchers, as signals,	3355	This functionality is very similar to C<ev_signal> watchers, as signals,
3116	too, are asynchronous in nature, and signals, too, will be compressed	3356	too, are asynchronous in nature, and signals, too, will be compressed
3117	(i.e. the number of callback invocations may be less than the number of	3357	(i.e. the number of callback invocations may be less than the number of
3118	C<ev_async_sent> calls).	3358	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
3119		3359	of "global async watchers" by using a watcher on an otherwise unused
3120	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3360	signal, and C<ev_feed_signal> to signal this watcher from another thread,
3121	just the default loop.	3361	even without knowing which loop owns the signal.
3122		3362
3123	=head3 Queueing	3363	=head3 Queueing
3124		3364
3125	C<ev_async> does not support queueing of data in any way. The reason	3365	C<ev_async> does not support queueing of data in any way. The reason
3126	is that the author does not know of a simple (or any) algorithm for a	3366	is that the author does not know of a simple (or any) algorithm for a
…		…
3218	trust me.	3458	trust me.
3219		3459
3220	=item ev_async_send (loop, ev_async *)	3460	=item ev_async_send (loop, ev_async *)
3221		3461
3222	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3462	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3223	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3463	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3464	returns.
		3465
3224	C<ev_feed_event>, this call is safe to do from other threads, signal or	3466	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3225	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3467	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3226	section below on what exactly this means).	3468	embedding section below on what exactly this means).
3227		3469
3228	Note that, as with other watchers in libev, multiple events might get	3470	Note that, as with other watchers in libev, multiple events might get
3229	compressed into a single callback invocation (another way to look at this	3471	compressed into a single callback invocation (another way to look at
3230	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3472	this is that C<ev_async> watchers are level-triggered: they are set on
3231	reset when the event loop detects that).	3473	C<ev_async_send>, reset when the event loop detects that).
3232		3474
3233	This call incurs the overhead of a system call only once per event loop	3475	This call incurs the overhead of at most one extra system call per event
3234	iteration, so while the overhead might be noticeable, it doesn't apply to	3476	loop iteration, if the event loop is blocked, and no syscall at all if
3235	repeated calls to C<ev_async_send> for the same event loop.	3477	the event loop (or your program) is processing events. That means that
		3478	repeated calls are basically free (there is no need to avoid calls for
		3479	performance reasons) and that the overhead becomes smaller (typically
		3480	zero) under load.
3236		3481
3237	=item bool = ev_async_pending (ev_async *)	3482	=item bool = ev_async_pending (ev_async *)
3238		3483
3239	Returns a non-zero value when C<ev_async_send> has been called on the	3484	Returns a non-zero value when C<ev_async_send> has been called on the
3240	watcher but the event has not yet been processed (or even noted) by the	3485	watcher but the event has not yet been processed (or even noted) by the
…		…
3295	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3540	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3296		3541
3297	=item ev_feed_fd_event (loop, int fd, int revents)	3542	=item ev_feed_fd_event (loop, int fd, int revents)
3298		3543
3299	Feed an event on the given fd, as if a file descriptor backend detected	3544	Feed an event on the given fd, as if a file descriptor backend detected
3300	the given events it.	3545	the given events.
3301		3546
3302	=item ev_feed_signal_event (loop, int signum)	3547	=item ev_feed_signal_event (loop, int signum)
3303		3548
3304	Feed an event as if the given signal occurred (C<loop> must be the default	3549	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3305	loop!).	3550	which is async-safe.
3306		3551
3307	=back	3552	=back
		3553
		3554
		3555	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3556
		3557	This section explains some common idioms that are not immediately
		3558	obvious. Note that examples are sprinkled over the whole manual, and this
		3559	section only contains stuff that wouldn't fit anywhere else.
		3560
		3561	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3562
		3563	Each watcher has, by default, a C<void *data> member that you can read
		3564	or modify at any time: libev will completely ignore it. This can be used
		3565	to associate arbitrary data with your watcher. If you need more data and
		3566	don't want to allocate memory separately and store a pointer to it in that
		3567	data member, you can also "subclass" the watcher type and provide your own
		3568	data:
		3569
		3570	struct my_io
		3571	{
		3572	ev_io io;
		3573	int otherfd;
		3574	void *somedata;
		3575	struct whatever *mostinteresting;
		3576	};
		3577
		3578	...
		3579	struct my_io w;
		3580	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3581
		3582	And since your callback will be called with a pointer to the watcher, you
		3583	can cast it back to your own type:
		3584
		3585	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3586	{
		3587	struct my_io *w = (struct my_io *)w_;
		3588	...
		3589	}
		3590
		3591	More interesting and less C-conformant ways of casting your callback
		3592	function type instead have been omitted.
		3593
		3594	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3595
		3596	Another common scenario is to use some data structure with multiple
		3597	embedded watchers, in effect creating your own watcher that combines
		3598	multiple libev event sources into one "super-watcher":
		3599
		3600	struct my_biggy
		3601	{
		3602	int some_data;
		3603	ev_timer t1;
		3604	ev_timer t2;
		3605	}
		3606
		3607	In this case getting the pointer to C<my_biggy> is a bit more
		3608	complicated: Either you store the address of your C<my_biggy> struct in
		3609	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3610	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3611	real programmers):
		3612
		3613	#include <stddef.h>
		3614
		3615	static void
		3616	t1_cb (EV_P_ ev_timer *w, int revents)
		3617	{
		3618	struct my_biggy big = (struct my_biggy *)
		3619	(((char *)w) - offsetof (struct my_biggy, t1));
		3620	}
		3621
		3622	static void
		3623	t2_cb (EV_P_ ev_timer *w, int revents)
		3624	{
		3625	struct my_biggy big = (struct my_biggy *)
		3626	(((char *)w) - offsetof (struct my_biggy, t2));
		3627	}
		3628
		3629	=head2 AVOIDING FINISHING BEFORE RETURNING
		3630
		3631	Often you have structures like this in event-based programs:
		3632
		3633	callback ()
		3634	{
		3635	free (request);
		3636	}
		3637
		3638	request = start_new_request (..., callback);
		3639
		3640	The intent is to start some "lengthy" operation. The C<request> could be
		3641	used to cancel the operation, or do other things with it.
		3642
		3643	It's not uncommon to have code paths in C<start_new_request> that
		3644	immediately invoke the callback, for example, to report errors. Or you add
		3645	some caching layer that finds that it can skip the lengthy aspects of the
		3646	operation and simply invoke the callback with the result.
		3647
		3648	The problem here is that this will happen I<before> C<start_new_request>
		3649	has returned, so C<request> is not set.
		3650
		3651	Even if you pass the request by some safer means to the callback, you
		3652	might want to do something to the request after starting it, such as
		3653	canceling it, which probably isn't working so well when the callback has
		3654	already been invoked.
		3655
		3656	A common way around all these issues is to make sure that
		3657	C<start_new_request> I<always> returns before the callback is invoked. If
		3658	C<start_new_request> immediately knows the result, it can artificially
		3659	delay invoking the callback by e.g. using a C<prepare> or C<idle> watcher
		3660	for example, or more sneakily, by reusing an existing (stopped) watcher
		3661	and pushing it into the pending queue:
		3662
		3663	ev_set_cb (watcher, callback);
		3664	ev_feed_event (EV_A_ watcher, 0);
		3665
		3666	This way, C<start_new_request> can safely return before the callback is
		3667	invoked, while not delaying callback invocation too much.
		3668
		3669	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3670
		3671	Often (especially in GUI toolkits) there are places where you have
		3672	I<modal> interaction, which is most easily implemented by recursively
		3673	invoking C<ev_run>.
		3674
		3675	This brings the problem of exiting - a callback might want to finish the
		3676	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3677	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3678	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3679	other combination: In these cases, C<ev_break> will not work alone.
		3680
		3681	The solution is to maintain "break this loop" variable for each C<ev_run>
		3682	invocation, and use a loop around C<ev_run> until the condition is
		3683	triggered, using C<EVRUN_ONCE>:
		3684
		3685	// main loop
		3686	int exit_main_loop = 0;
		3687
		3688	while (!exit_main_loop)
		3689	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3690
		3691	// in a modal watcher
		3692	int exit_nested_loop = 0;
		3693
		3694	while (!exit_nested_loop)
		3695	ev_run (EV_A_ EVRUN_ONCE);
		3696
		3697	To exit from any of these loops, just set the corresponding exit variable:
		3698
		3699	// exit modal loop
		3700	exit_nested_loop = 1;
		3701
		3702	// exit main program, after modal loop is finished
		3703	exit_main_loop = 1;
		3704
		3705	// exit both
		3706	exit_main_loop = exit_nested_loop = 1;
		3707
		3708	=head2 THREAD LOCKING EXAMPLE
		3709
		3710	Here is a fictitious example of how to run an event loop in a different
		3711	thread from where callbacks are being invoked and watchers are
		3712	created/added/removed.
		3713
		3714	For a real-world example, see the C<EV::Loop::Async> perl module,
		3715	which uses exactly this technique (which is suited for many high-level
		3716	languages).
		3717
		3718	The example uses a pthread mutex to protect the loop data, a condition
		3719	variable to wait for callback invocations, an async watcher to notify the
		3720	event loop thread and an unspecified mechanism to wake up the main thread.
		3721
		3722	First, you need to associate some data with the event loop:
		3723
		3724	typedef struct {
		3725	mutex_t lock; /* global loop lock */
		3726	ev_async async_w;
		3727	thread_t tid;
		3728	cond_t invoke_cv;
		3729	} userdata;
		3730
		3731	void prepare_loop (EV_P)
		3732	{
		3733	// for simplicity, we use a static userdata struct.
		3734	static userdata u;
		3735
		3736	ev_async_init (&u->async_w, async_cb);
		3737	ev_async_start (EV_A_ &u->async_w);
		3738
		3739	pthread_mutex_init (&u->lock, 0);
		3740	pthread_cond_init (&u->invoke_cv, 0);
		3741
		3742	// now associate this with the loop
		3743	ev_set_userdata (EV_A_ u);
		3744	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3745	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3746
		3747	// then create the thread running ev_run
		3748	pthread_create (&u->tid, 0, l_run, EV_A);
		3749	}
		3750
		3751	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3752	solely to wake up the event loop so it takes notice of any new watchers
		3753	that might have been added:
		3754
		3755	static void
		3756	async_cb (EV_P_ ev_async *w, int revents)
		3757	{
		3758	// just used for the side effects
		3759	}
		3760
		3761	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3762	protecting the loop data, respectively.
		3763
		3764	static void
		3765	l_release (EV_P)
		3766	{
		3767	userdata *u = ev_userdata (EV_A);
		3768	pthread_mutex_unlock (&u->lock);
		3769	}
		3770
		3771	static void
		3772	l_acquire (EV_P)
		3773	{
		3774	userdata *u = ev_userdata (EV_A);
		3775	pthread_mutex_lock (&u->lock);
		3776	}
		3777
		3778	The event loop thread first acquires the mutex, and then jumps straight
		3779	into C<ev_run>:
		3780
		3781	void *
		3782	l_run (void *thr_arg)
		3783	{
		3784	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3785
		3786	l_acquire (EV_A);
		3787	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3788	ev_run (EV_A_ 0);
		3789	l_release (EV_A);
		3790
		3791	return 0;
		3792	}
		3793
		3794	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3795	signal the main thread via some unspecified mechanism (signals? pipe
		3796	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3797	have been called (in a while loop because a) spurious wakeups are possible
		3798	and b) skipping inter-thread-communication when there are no pending
		3799	watchers is very beneficial):
		3800
		3801	static void
		3802	l_invoke (EV_P)
		3803	{
		3804	userdata *u = ev_userdata (EV_A);
		3805
		3806	while (ev_pending_count (EV_A))
		3807	{
		3808	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3809	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3810	}
		3811	}
		3812
		3813	Now, whenever the main thread gets told to invoke pending watchers, it
		3814	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3815	thread to continue:
		3816
		3817	static void
		3818	real_invoke_pending (EV_P)
		3819	{
		3820	userdata *u = ev_userdata (EV_A);
		3821
		3822	pthread_mutex_lock (&u->lock);
		3823	ev_invoke_pending (EV_A);
		3824	pthread_cond_signal (&u->invoke_cv);
		3825	pthread_mutex_unlock (&u->lock);
		3826	}
		3827
		3828	Whenever you want to start/stop a watcher or do other modifications to an
		3829	event loop, you will now have to lock:
		3830
		3831	ev_timer timeout_watcher;
		3832	userdata *u = ev_userdata (EV_A);
		3833
		3834	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3835
		3836	pthread_mutex_lock (&u->lock);
		3837	ev_timer_start (EV_A_ &timeout_watcher);
		3838	ev_async_send (EV_A_ &u->async_w);
		3839	pthread_mutex_unlock (&u->lock);
		3840
		3841	Note that sending the C<ev_async> watcher is required because otherwise
		3842	an event loop currently blocking in the kernel will have no knowledge
		3843	about the newly added timer. By waking up the loop it will pick up any new
		3844	watchers in the next event loop iteration.
		3845
		3846	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3847
		3848	While the overhead of a callback that e.g. schedules a thread is small, it
		3849	is still an overhead. If you embed libev, and your main usage is with some
		3850	kind of threads or coroutines, you might want to customise libev so that
		3851	doesn't need callbacks anymore.
		3852
		3853	Imagine you have coroutines that you can switch to using a function
		3854	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3855	and that due to some magic, the currently active coroutine is stored in a
		3856	global called C<current_coro>. Then you can build your own "wait for libev
		3857	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3858	the differing C<;> conventions):
		3859
		3860	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3861	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3862
		3863	That means instead of having a C callback function, you store the
		3864	coroutine to switch to in each watcher, and instead of having libev call
		3865	your callback, you instead have it switch to that coroutine.
		3866
		3867	A coroutine might now wait for an event with a function called
		3868	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3869	matter when, or whether the watcher is active or not when this function is
		3870	called):
		3871
		3872	void
		3873	wait_for_event (ev_watcher *w)
		3874	{
		3875	ev_cb_set (w) = current_coro;
		3876	switch_to (libev_coro);
		3877	}
		3878
		3879	That basically suspends the coroutine inside C<wait_for_event> and
		3880	continues the libev coroutine, which, when appropriate, switches back to
		3881	this or any other coroutine.
		3882
		3883	You can do similar tricks if you have, say, threads with an event queue -
		3884	instead of storing a coroutine, you store the queue object and instead of
		3885	switching to a coroutine, you push the watcher onto the queue and notify
		3886	any waiters.
		3887
		3888	To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two
		3889	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3890
		3891	// my_ev.h
		3892	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3893	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3894	#include "../libev/ev.h"
		3895
		3896	// my_ev.c
		3897	#define EV_H "my_ev.h"
		3898	#include "../libev/ev.c"
		3899
		3900	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3901	F<my_ev.c> into your project. When properly specifying include paths, you
		3902	can even use F<ev.h> as header file name directly.
3308		3903
3309		3904
3310	=head1 LIBEVENT EMULATION	3905	=head1 LIBEVENT EMULATION
3311		3906
3312	Libev offers a compatibility emulation layer for libevent. It cannot	3907	Libev offers a compatibility emulation layer for libevent. It cannot
3313	emulate the internals of libevent, so here are some usage hints:	3908	emulate the internals of libevent, so here are some usage hints:
3314		3909
3315	=over 4	3910	=over 4
		3911
		3912	=item * Only the libevent-1.4.1-beta API is being emulated.
		3913
		3914	This was the newest libevent version available when libev was implemented,
		3915	and is still mostly unchanged in 2010.
3316		3916
3317	=item * Use it by including <event.h>, as usual.	3917	=item * Use it by including <event.h>, as usual.
3318		3918
3319	=item * The following members are fully supported: ev_base, ev_callback,	3919	=item * The following members are fully supported: ev_base, ev_callback,
3320	ev_arg, ev_fd, ev_res, ev_events.	3920	ev_arg, ev_fd, ev_res, ev_events.
…		…
3326	=item * Priorities are not currently supported. Initialising priorities	3926	=item * Priorities are not currently supported. Initialising priorities
3327	will fail and all watchers will have the same priority, even though there	3927	will fail and all watchers will have the same priority, even though there
3328	is an ev_pri field.	3928	is an ev_pri field.
3329		3929
3330	=item * In libevent, the last base created gets the signals, in libev, the	3930	=item * In libevent, the last base created gets the signals, in libev, the
3331	first base created (== the default loop) gets the signals.	3931	base that registered the signal gets the signals.
3332		3932
3333	=item * Other members are not supported.	3933	=item * Other members are not supported.
3334		3934
3335	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3935	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3336	to use the libev header file and library.	3936	to use the libev header file and library.
3337		3937
3338	=back	3938	=back
3339		3939
3340	=head1 C++ SUPPORT	3940	=head1 C++ SUPPORT
		3941
		3942	=head2 C API
		3943
		3944	The normal C API should work fine when used from C++: both ev.h and the
		3945	libev sources can be compiled as C++. Therefore, code that uses the C API
		3946	will work fine.
		3947
		3948	Proper exception specifications might have to be added to callbacks passed
		3949	to libev: exceptions may be thrown only from watcher callbacks, all
		3950	other callbacks (allocator, syserr, loop acquire/release and periodioc
		3951	reschedule callbacks) must not throw exceptions, and might need a C<throw
		3952	()> specification. If you have code that needs to be compiled as both C
		3953	and C++ you can use the C<EV_THROW> macro for this:
		3954
		3955	static void
		3956	fatal_error (const char *msg) EV_THROW
		3957	{
		3958	perror (msg);
		3959	abort ();
		3960	}
		3961
		3962	...
		3963	ev_set_syserr_cb (fatal_error);
		3964
		3965	The only API functions that can currently throw exceptions are C<ev_run>,
		3966	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		3967	because it runs cleanup watchers).
		3968
		3969	Throwing exceptions in watcher callbacks is only supported if libev itself
		3970	is compiled with a C++ compiler or your C and C++ environments allow
		3971	throwing exceptions through C libraries (most do).
		3972
		3973	=head2 C++ API
3341		3974
3342	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3975	Libev comes with some simplistic wrapper classes for C++ that mainly allow
3343	you to use some convenience methods to start/stop watchers and also change	3976	you to use some convenience methods to start/stop watchers and also change
3344	the callback model to a model using method callbacks on objects.	3977	the callback model to a model using method callbacks on objects.
3345		3978
…		…
3355	Care has been taken to keep the overhead low. The only data member the C++	3988	Care has been taken to keep the overhead low. The only data member the C++
3356	classes add (compared to plain C-style watchers) is the event loop pointer	3989	classes add (compared to plain C-style watchers) is the event loop pointer
3357	that the watcher is associated with (or no additional members at all if	3990	that the watcher is associated with (or no additional members at all if
3358	you disable C<EV_MULTIPLICITY> when embedding libev).	3991	you disable C<EV_MULTIPLICITY> when embedding libev).
3359		3992
3360	Currently, functions, and static and non-static member functions can be	3993	Currently, functions, static and non-static member functions and classes
3361	used as callbacks. Other types should be easy to add as long as they only	3994	with C<operator ()> can be used as callbacks. Other types should be easy
3362	need one additional pointer for context. If you need support for other	3995	to add as long as they only need one additional pointer for context. If
3363	types of functors please contact the author (preferably after implementing	3996	you need support for other types of functors please contact the author
3364	it).	3997	(preferably after implementing it).
		3998
		3999	For all this to work, your C++ compiler either has to use the same calling
		4000	conventions as your C compiler (for static member functions), or you have
		4001	to embed libev and compile libev itself as C++.
3365		4002
3366	Here is a list of things available in the C<ev> namespace:	4003	Here is a list of things available in the C<ev> namespace:
3367		4004
3368	=over 4	4005	=over 4
3369		4006
…		…
3379	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4016	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3380		4017
3381	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4018	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
3382	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4019	the same name in the C<ev> namespace, with the exception of C<ev_signal>
3383	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4020	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3384	defines by many implementations.	4021	defined by many implementations.
3385		4022
3386	All of those classes have these methods:	4023	All of those classes have these methods:
3387		4024
3388	=over 4	4025	=over 4
3389		4026
…		…
3522	watchers in the constructor.	4159	watchers in the constructor.
3523		4160
3524	class myclass	4161	class myclass
3525	{	4162	{
3526	ev::io io ; void io_cb (ev::io &w, int revents);	4163	ev::io io ; void io_cb (ev::io &w, int revents);
3527	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);	4164	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3528	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4165	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3529		4166
3530	myclass (int fd)	4167	myclass (int fd)
3531	{	4168	{
3532	io .set <myclass, &myclass::io_cb > (this);	4169	io .set <myclass, &myclass::io_cb > (this);
…		…
3583	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4220	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3584		4221
3585	=item D	4222	=item D
3586		4223
3587	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4224	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3588	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4225	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3589		4226
3590	=item Ocaml	4227	=item Ocaml
3591		4228
3592	Erkki Seppala has written Ocaml bindings for libev, to be found at	4229	Erkki Seppala has written Ocaml bindings for libev, to be found at
3593	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4230	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
…		…
3641	suitable for use with C<EV_A>.	4278	suitable for use with C<EV_A>.
3642		4279
3643	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4280	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3644		4281
3645	Similar to the other two macros, this gives you the value of the default	4282	Similar to the other two macros, this gives you the value of the default
3646	loop, if multiple loops are supported ("ev loop default").	4283	loop, if multiple loops are supported ("ev loop default"). The default loop
		4284	will be initialised if it isn't already initialised.
		4285
		4286	For non-multiplicity builds, these macros do nothing, so you always have
		4287	to initialise the loop somewhere.
3647		4288
3648	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4289	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3649		4290
3650	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4291	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3651	default loop has been initialised (C<UC> == unchecked). Their behaviour	4292	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3796	supported). It will also not define any of the structs usually found in	4437	supported). It will also not define any of the structs usually found in
3797	F<event.h> that are not directly supported by the libev core alone.	4438	F<event.h> that are not directly supported by the libev core alone.
3798		4439
3799	In standalone mode, libev will still try to automatically deduce the	4440	In standalone mode, libev will still try to automatically deduce the
3800	configuration, but has to be more conservative.	4441	configuration, but has to be more conservative.
		4442
		4443	=item EV_USE_FLOOR
		4444
		4445	If defined to be C<1>, libev will use the C<floor ()> function for its
		4446	periodic reschedule calculations, otherwise libev will fall back on a
		4447	portable (slower) implementation. If you enable this, you usually have to
		4448	link against libm or something equivalent. Enabling this when the C<floor>
		4449	function is not available will fail, so the safe default is to not enable
		4450	this.
3801		4451
3802	=item EV_USE_MONOTONIC	4452	=item EV_USE_MONOTONIC
3803		4453
3804	If defined to be C<1>, libev will try to detect the availability of the	4454	If defined to be C<1>, libev will try to detect the availability of the
3805	monotonic clock option at both compile time and runtime. Otherwise no	4455	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3935	If defined to be C<1>, libev will compile in support for the Linux inotify	4585	If defined to be C<1>, libev will compile in support for the Linux inotify
3936	interface to speed up C<ev_stat> watchers. Its actual availability will	4586	interface to speed up C<ev_stat> watchers. Its actual availability will
3937	be detected at runtime. If undefined, it will be enabled if the headers	4587	be detected at runtime. If undefined, it will be enabled if the headers
3938	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4588	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3939		4589
		4590	=item EV_NO_SMP
		4591
		4592	If defined to be C<1>, libev will assume that memory is always coherent
		4593	between threads, that is, threads can be used, but threads never run on
		4594	different cpus (or different cpu cores). This reduces dependencies
		4595	and makes libev faster.
		4596
		4597	=item EV_NO_THREADS
		4598
		4599	If defined to be C<1>, libev will assume that it will never be called
		4600	from different threads, which is a stronger assumption than C<EV_NO_SMP>,
		4601	above. This reduces dependencies and makes libev faster.
		4602
3940	=item EV_ATOMIC_T	4603	=item EV_ATOMIC_T
3941		4604
3942	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4605	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3943	access is atomic with respect to other threads or signal contexts. No such	4606	access is atomic and serialised with respect to other threads or signal
3944	type is easily found in the C language, so you can provide your own type	4607	contexts. No such type is easily found in the C language, so you can
3945	that you know is safe for your purposes. It is used both for signal handler "locking"	4608	provide your own type that you know is safe for your purposes. It is used
3946	as well as for signal and thread safety in C<ev_async> watchers.	4609	both for signal handler "locking" as well as for signal and thread safety
		4610	in C<ev_async> watchers.
3947		4611
3948	In the absence of this define, libev will use C<sig_atomic_t volatile>	4612	In the absence of this define, libev will use C<sig_atomic_t volatile>
3949	(from F<signal.h>), which is usually good enough on most platforms.	4613	(from F<signal.h>), which is usually good enough on most platforms,
		4614	although strictly speaking using a type that also implies a memory fence
		4615	is required.
3950		4616
3951	=item EV_H (h)	4617	=item EV_H (h)
3952		4618
3953	The name of the F<ev.h> header file used to include it. The default if	4619	The name of the F<ev.h> header file used to include it. The default if
3954	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4620	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
…		…
3978	will have the C<struct ev_loop *> as first argument, and you can create	4644	will have the C<struct ev_loop *> as first argument, and you can create
3979	additional independent event loops. Otherwise there will be no support	4645	additional independent event loops. Otherwise there will be no support
3980	for multiple event loops and there is no first event loop pointer	4646	for multiple event loops and there is no first event loop pointer
3981	argument. Instead, all functions act on the single default loop.	4647	argument. Instead, all functions act on the single default loop.
3982		4648
		4649	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4650	default loop when multiplicity is switched off - you always have to
		4651	initialise the loop manually in this case.
		4652
3983	=item EV_MINPRI	4653	=item EV_MINPRI
3984		4654
3985	=item EV_MAXPRI	4655	=item EV_MAXPRI
3986		4656
3987	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4657	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
4023	#define EV_USE_POLL 1	4693	#define EV_USE_POLL 1
4024	#define EV_CHILD_ENABLE 1	4694	#define EV_CHILD_ENABLE 1
4025	#define EV_ASYNC_ENABLE 1	4695	#define EV_ASYNC_ENABLE 1
4026		4696
4027	The actual value is a bitset, it can be a combination of the following	4697	The actual value is a bitset, it can be a combination of the following
4028	values:	4698	values (by default, all of these are enabled):
4029		4699
4030	=over 4	4700	=over 4
4031		4701
4032	=item C<1> - faster/larger code	4702	=item C<1> - faster/larger code
4033		4703
…		…
4037	code size by roughly 30% on amd64).	4707	code size by roughly 30% on amd64).
4038		4708
4039	When optimising for size, use of compiler flags such as C<-Os> with	4709	When optimising for size, use of compiler flags such as C<-Os> with
4040	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of	4710	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
4041	assertions.	4711	assertions.
		4712
		4713	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4714	(e.g. gcc with C<-Os>).
4042		4715
4043	=item C<2> - faster/larger data structures	4716	=item C<2> - faster/larger data structures
4044		4717
4045	Replaces the small 2-heap for timer management by a faster 4-heap, larger	4718	Replaces the small 2-heap for timer management by a faster 4-heap, larger
4046	hash table sizes and so on. This will usually further increase code size	4719	hash table sizes and so on. This will usually further increase code size
4047	and can additionally have an effect on the size of data structures at	4720	and can additionally have an effect on the size of data structures at
4048	runtime.	4721	runtime.
4049		4722
		4723	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4724	(e.g. gcc with C<-Os>).
		4725
4050	=item C<4> - full API configuration	4726	=item C<4> - full API configuration
4051		4727
4052	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and	4728	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
4053	enables multiplicity (C<EV_MULTIPLICITY>=1).	4729	enables multiplicity (C<EV_MULTIPLICITY>=1).
4054		4730
…		…
4084		4760
4085	With an intelligent-enough linker (gcc+binutils are intelligent enough	4761	With an intelligent-enough linker (gcc+binutils are intelligent enough
4086	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by	4762	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
4087	your program might be left out as well - a binary starting a timer and an	4763	your program might be left out as well - a binary starting a timer and an
4088	I/O watcher then might come out at only 5Kb.	4764	I/O watcher then might come out at only 5Kb.
		4765
		4766	=item EV_API_STATIC
		4767
		4768	If this symbol is defined (by default it is not), then all identifiers
		4769	will have static linkage. This means that libev will not export any
		4770	identifiers, and you cannot link against libev anymore. This can be useful
		4771	when you embed libev, only want to use libev functions in a single file,
		4772	and do not want its identifiers to be visible.
		4773
		4774	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4775	wants to use libev.
		4776
		4777	This option only works when libev is compiled with a C compiler, as C++
		4778	doesn't support the required declaration syntax.
4089		4779
4090	=item EV_AVOID_STDIO	4780	=item EV_AVOID_STDIO
4091		4781
4092	If this is set to C<1> at compiletime, then libev will avoid using stdio	4782	If this is set to C<1> at compiletime, then libev will avoid using stdio
4093	functions (printf, scanf, perror etc.). This will increase the code size	4783	functions (printf, scanf, perror etc.). This will increase the code size
…		…
4237	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4927	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4238		4928
4239	#include "ev_cpp.h"	4929	#include "ev_cpp.h"
4240	#include "ev.c"	4930	#include "ev.c"
4241		4931
4242	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4932	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4243		4933
4244	=head2 THREADS AND COROUTINES	4934	=head2 THREADS AND COROUTINES
4245		4935
4246	=head3 THREADS	4936	=head3 THREADS
4247		4937
…		…
4298	default loop and triggering an C<ev_async> watcher from the default loop	4988	default loop and triggering an C<ev_async> watcher from the default loop
4299	watcher callback into the event loop interested in the signal.	4989	watcher callback into the event loop interested in the signal.
4300		4990
4301	=back	4991	=back
4302		4992
4303	=head4 THREAD LOCKING EXAMPLE	4993	See also L<THREAD LOCKING EXAMPLE>.
4304
4305	Here is a fictitious example of how to run an event loop in a different
4306	thread than where callbacks are being invoked and watchers are
4307	created/added/removed.
4308
4309	For a real-world example, see the C<EV::Loop::Async> perl module,
4310	which uses exactly this technique (which is suited for many high-level
4311	languages).
4312
4313	The example uses a pthread mutex to protect the loop data, a condition
4314	variable to wait for callback invocations, an async watcher to notify the
4315	event loop thread and an unspecified mechanism to wake up the main thread.
4316
4317	First, you need to associate some data with the event loop:
4318
4319	typedef struct {
4320	mutex_t lock; /* global loop lock */
4321	ev_async async_w;
4322	thread_t tid;
4323	cond_t invoke_cv;
4324	} userdata;
4325
4326	void prepare_loop (EV_P)
4327	{
4328	// for simplicity, we use a static userdata struct.
4329	static userdata u;
4330
4331	ev_async_init (&u->async_w, async_cb);
4332	ev_async_start (EV_A_ &u->async_w);
4333
4334	pthread_mutex_init (&u->lock, 0);
4335	pthread_cond_init (&u->invoke_cv, 0);
4336
4337	// now associate this with the loop
4338	ev_set_userdata (EV_A_ u);
4339	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4340	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4341
4342	// then create the thread running ev_loop
4343	pthread_create (&u->tid, 0, l_run, EV_A);
4344	}
4345
4346	The callback for the C<ev_async> watcher does nothing: the watcher is used
4347	solely to wake up the event loop so it takes notice of any new watchers
4348	that might have been added:
4349
4350	static void
4351	async_cb (EV_P_ ev_async *w, int revents)
4352	{
4353	// just used for the side effects
4354	}
4355
4356	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4357	protecting the loop data, respectively.
4358
4359	static void
4360	l_release (EV_P)
4361	{
4362	userdata *u = ev_userdata (EV_A);
4363	pthread_mutex_unlock (&u->lock);
4364	}
4365
4366	static void
4367	l_acquire (EV_P)
4368	{
4369	userdata *u = ev_userdata (EV_A);
4370	pthread_mutex_lock (&u->lock);
4371	}
4372
4373	The event loop thread first acquires the mutex, and then jumps straight
4374	into C<ev_run>:
4375
4376	void *
4377	l_run (void *thr_arg)
4378	{
4379	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4380
4381	l_acquire (EV_A);
4382	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4383	ev_run (EV_A_ 0);
4384	l_release (EV_A);
4385
4386	return 0;
4387	}
4388
4389	Instead of invoking all pending watchers, the C<l_invoke> callback will
4390	signal the main thread via some unspecified mechanism (signals? pipe
4391	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4392	have been called (in a while loop because a) spurious wakeups are possible
4393	and b) skipping inter-thread-communication when there are no pending
4394	watchers is very beneficial):
4395
4396	static void
4397	l_invoke (EV_P)
4398	{
4399	userdata *u = ev_userdata (EV_A);
4400
4401	while (ev_pending_count (EV_A))
4402	{
4403	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4404	pthread_cond_wait (&u->invoke_cv, &u->lock);
4405	}
4406	}
4407
4408	Now, whenever the main thread gets told to invoke pending watchers, it
4409	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4410	thread to continue:
4411
4412	static void
4413	real_invoke_pending (EV_P)
4414	{
4415	userdata *u = ev_userdata (EV_A);
4416
4417	pthread_mutex_lock (&u->lock);
4418	ev_invoke_pending (EV_A);
4419	pthread_cond_signal (&u->invoke_cv);
4420	pthread_mutex_unlock (&u->lock);
4421	}
4422
4423	Whenever you want to start/stop a watcher or do other modifications to an
4424	event loop, you will now have to lock:
4425
4426	ev_timer timeout_watcher;
4427	userdata *u = ev_userdata (EV_A);
4428
4429	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4430
4431	pthread_mutex_lock (&u->lock);
4432	ev_timer_start (EV_A_ &timeout_watcher);
4433	ev_async_send (EV_A_ &u->async_w);
4434	pthread_mutex_unlock (&u->lock);
4435
4436	Note that sending the C<ev_async> watcher is required because otherwise
4437	an event loop currently blocking in the kernel will have no knowledge
4438	about the newly added timer. By waking up the loop it will pick up any new
4439	watchers in the next event loop iteration.
4440		4994
4441	=head3 COROUTINES	4995	=head3 COROUTINES
4442		4996
4443	Libev is very accommodating to coroutines ("cooperative threads"):	4997	Libev is very accommodating to coroutines ("cooperative threads"):
4444	libev fully supports nesting calls to its functions from different	4998	libev fully supports nesting calls to its functions from different
…		…
4609	requires, and its I/O model is fundamentally incompatible with the POSIX	5163	requires, and its I/O model is fundamentally incompatible with the POSIX
4610	model. Libev still offers limited functionality on this platform in	5164	model. Libev still offers limited functionality on this platform in
4611	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5165	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4612	descriptors. This only applies when using Win32 natively, not when using	5166	descriptors. This only applies when using Win32 natively, not when using
4613	e.g. cygwin. Actually, it only applies to the microsofts own compilers,	5167	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
4614	as every compielr comes with a slightly differently broken/incompatible	5168	as every compiler comes with a slightly differently broken/incompatible
4615	environment.	5169	environment.
4616		5170
4617	Lifting these limitations would basically require the full	5171	Lifting these limitations would basically require the full
4618	re-implementation of the I/O system. If you are into this kind of thing,	5172	re-implementation of the I/O system. If you are into this kind of thing,
4619	then note that glib does exactly that for you in a very portable way (note	5173	then note that glib does exactly that for you in a very portable way (note
…		…
4713	structure (guaranteed by POSIX but not by ISO C for example), but it also	5267	structure (guaranteed by POSIX but not by ISO C for example), but it also
4714	assumes that the same (machine) code can be used to call any watcher	5268	assumes that the same (machine) code can be used to call any watcher
4715	callback: The watcher callbacks have different type signatures, but libev	5269	callback: The watcher callbacks have different type signatures, but libev
4716	calls them using an C<ev_watcher *> internally.	5270	calls them using an C<ev_watcher *> internally.
4717		5271
		5272	=item pointer accesses must be thread-atomic
		5273
		5274	Accessing a pointer value must be atomic, it must both be readable and
		5275	writable in one piece - this is the case on all current architectures.
		5276
4718	=item C<sig_atomic_t volatile> must be thread-atomic as well	5277	=item C<sig_atomic_t volatile> must be thread-atomic as well
4719		5278
4720	The type C<sig_atomic_t volatile> (or whatever is defined as	5279	The type C<sig_atomic_t volatile> (or whatever is defined as
4721	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5280	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
4722	threads. This is not part of the specification for C<sig_atomic_t>, but is	5281	threads. This is not part of the specification for C<sig_atomic_t>, but is
…		…
4747		5306
4748	The type C<double> is used to represent timestamps. It is required to	5307	The type C<double> is used to represent timestamps. It is required to
4749	have at least 51 bits of mantissa (and 9 bits of exponent), which is	5308	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4750	good enough for at least into the year 4000 with millisecond accuracy	5309	good enough for at least into the year 4000 with millisecond accuracy
4751	(the design goal for libev). This requirement is overfulfilled by	5310	(the design goal for libev). This requirement is overfulfilled by
4752	implementations using IEEE 754, which is basically all existing ones. With	5311	implementations using IEEE 754, which is basically all existing ones.
		5312
4753	IEEE 754 doubles, you get microsecond accuracy until at least 2200.	5313	With IEEE 754 doubles, you get microsecond accuracy until at least the
		5314	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5315	is either obsolete or somebody patched it to use C<long double> or
		5316	something like that, just kidding).
4754		5317
4755	=back	5318	=back
4756		5319
4757	If you know of other additional requirements drop me a note.	5320	If you know of other additional requirements drop me a note.
4758		5321
…		…
4820	=item Processing ev_async_send: O(number_of_async_watchers)	5383	=item Processing ev_async_send: O(number_of_async_watchers)
4821		5384
4822	=item Processing signals: O(max_signal_number)	5385	=item Processing signals: O(max_signal_number)
4823		5386
4824	Sending involves a system call I<iff> there were no other C<ev_async_send>	5387	Sending involves a system call I<iff> there were no other C<ev_async_send>
4825	calls in the current loop iteration. Checking for async and signal events	5388	calls in the current loop iteration and the loop is currently
		5389	blocked. Checking for async and signal events involves iterating over all
4826	involves iterating over all running async watchers or all signal numbers.	5390	running async watchers or all signal numbers.
4827		5391
4828	=back	5392	=back
4829		5393
4830		5394
4831	=head1 PORTING FROM LIBEV 3.X TO 4.X	5395	=head1 PORTING FROM LIBEV 3.X TO 4.X
4832		5396
4833	The major version 4 introduced some minor incompatible changes to the API.	5397	The major version 4 introduced some incompatible changes to the API.
4834		5398
4835	At the moment, the C<ev.h> header file tries to implement superficial	5399	At the moment, the C<ev.h> header file provides compatibility definitions
4836	compatibility, so most programs should still compile. Those might be	5400	for all changes, so most programs should still compile. The compatibility
4837	removed in later versions of libev, so better update early than late.	5401	layer might be removed in later versions of libev, so better update to the
		5402	new API early than late.
4838		5403
4839	=over 4	5404	=over 4
4840		5405
		5406	=item C<EV_COMPAT3> backwards compatibility mechanism
		5407
		5408	The backward compatibility mechanism can be controlled by
		5409	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5410	section.
		5411
4841	=item C<ev_default_destroy> and C<ev_default_fork> have been removed	5412	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
4842		5413
4843	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:	5414	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
4844		5415
4845	ev_loop_destroy (EV_DEFAULT);	5416	ev_loop_destroy (EV_DEFAULT_UC);
4846	ev_loop_fork (EV_DEFAULT);	5417	ev_loop_fork (EV_DEFAULT);
4847		5418
4848	=item function/symbol renames	5419	=item function/symbol renames
4849		5420
4850	A number of functions and symbols have been renamed:	5421	A number of functions and symbols have been renamed:
…		…
4870	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme	5441	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
4871	as all other watcher types. Note that C<ev_loop_fork> is still called	5442	as all other watcher types. Note that C<ev_loop_fork> is still called
4872	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>	5443	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
4873	typedef.	5444	typedef.
4874		5445
4875	=item C<EV_COMPAT3> backwards compatibility mechanism
4876
4877	The backward compatibility mechanism can be controlled by
4878	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
4879	section.
4880
4881	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>	5446	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
4882		5447
4883	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different	5448	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
4884	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile	5449	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
4885	and work, but the library code will of course be larger.	5450	and work, but the library code will of course be larger.
…		…
4947	The physical time that is observed. It is apparently strictly monotonic :)	5512	The physical time that is observed. It is apparently strictly monotonic :)
4948		5513
4949	=item wall-clock time	5514	=item wall-clock time
4950		5515
4951	The time and date as shown on clocks. Unlike real time, it can actually	5516	The time and date as shown on clocks. Unlike real time, it can actually
4952	be wrong and jump forwards and backwards, e.g. when the you adjust your	5517	be wrong and jump forwards and backwards, e.g. when you adjust your
4953	clock.	5518	clock.
4954		5519
4955	=item watcher	5520	=item watcher
4956		5521
4957	A data structure that describes interest in certain events. Watchers need	5522	A data structure that describes interest in certain events. Watchers need
…		…
4959		5524
4960	=back	5525	=back
4961		5526
4962	=head1 AUTHOR	5527	=head1 AUTHOR
4963		5528
4964	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5529	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5530	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4965		5531

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