ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.327 by root, Sun Oct 24 20:05:43 2010 UTC vs.
Revision 1.401 by root, Wed Apr 18 06:06:04 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.
…		…
1114	The event loop has been resumed in the child process after fork (see	1193	The event loop has been resumed in the child process after fork (see
1115	C<ev_fork>).	1194	C<ev_fork>).
1116		1195
1117	=item C<EV_CLEANUP>	1196	=item C<EV_CLEANUP>
1118		1197
1119	The event loop is abotu to be destroyed (see C<ev_cleanup>).	1198	The event loop is about to be destroyed (see C<ev_cleanup>).
1120		1199
1121	=item C<EV_ASYNC>	1200	=item C<EV_ASYNC>
1122		1201
1123	The given async watcher has been asynchronously notified (see C<ev_async>).	1202	The given async watcher has been asynchronously notified (see C<ev_async>).
1124		1203
…		…
1146	programs, though, as the fd could already be closed and reused for another	1225	programs, though, as the fd could already be closed and reused for another
1147	thing, so beware.	1226	thing, so beware.
1148		1227
1149	=back	1228	=back
1150		1229
		1230	=head2 GENERIC WATCHER FUNCTIONS
		1231
		1232	=over 4
		1233
		1234	=item C<ev_init> (ev_TYPE *watcher, callback)
		1235
		1236	This macro initialises the generic portion of a watcher. The contents
		1237	of the watcher object can be arbitrary (so C<malloc> will do). Only
		1238	the generic parts of the watcher are initialised, you I<need> to call
		1239	the type-specific C<ev_TYPE_set> macro afterwards to initialise the
		1240	type-specific parts. For each type there is also a C<ev_TYPE_init> macro
		1241	which rolls both calls into one.
		1242
		1243	You can reinitialise a watcher at any time as long as it has been stopped
		1244	(or never started) and there are no pending events outstanding.
		1245
		1246	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
		1247	int revents)>.
		1248
		1249	Example: Initialise an C<ev_io> watcher in two steps.
		1250
		1251	ev_io w;
		1252	ev_init (&w, my_cb);
		1253	ev_io_set (&w, STDIN_FILENO, EV_READ);
		1254
		1255	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
		1256
		1257	This macro initialises the type-specific parts of a watcher. You need to
		1258	call C<ev_init> at least once before you call this macro, but you can
		1259	call C<ev_TYPE_set> any number of times. You must not, however, call this
		1260	macro on a watcher that is active (it can be pending, however, which is a
		1261	difference to the C<ev_init> macro).
		1262
		1263	Although some watcher types do not have type-specific arguments
		1264	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
		1265
		1266	See C<ev_init>, above, for an example.
		1267
		1268	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
		1269
		1270	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
		1271	calls into a single call. This is the most convenient method to initialise
		1272	a watcher. The same limitations apply, of course.
		1273
		1274	Example: Initialise and set an C<ev_io> watcher in one step.
		1275
		1276	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1277
		1278	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
		1279
		1280	Starts (activates) the given watcher. Only active watchers will receive
		1281	events. If the watcher is already active nothing will happen.
		1282
		1283	Example: Start the C<ev_io> watcher that is being abused as example in this
		1284	whole section.
		1285
		1286	ev_io_start (EV_DEFAULT_UC, &w);
		1287
		1288	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
		1289
		1290	Stops the given watcher if active, and clears the pending status (whether
		1291	the watcher was active or not).
		1292
		1293	It is possible that stopped watchers are pending - for example,
		1294	non-repeating timers are being stopped when they become pending - but
		1295	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
		1296	pending. If you want to free or reuse the memory used by the watcher it is
		1297	therefore a good idea to always call its C<ev_TYPE_stop> function.
		1298
		1299	=item bool ev_is_active (ev_TYPE *watcher)
		1300
		1301	Returns a true value iff the watcher is active (i.e. it has been started
		1302	and not yet been stopped). As long as a watcher is active you must not modify
		1303	it.
		1304
		1305	=item bool ev_is_pending (ev_TYPE *watcher)
		1306
		1307	Returns a true value iff the watcher is pending, (i.e. it has outstanding
		1308	events but its callback has not yet been invoked). As long as a watcher
		1309	is pending (but not active) you must not call an init function on it (but
		1310	C<ev_TYPE_set> is safe), you must not change its priority, and you must
		1311	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		1312	it).
		1313
		1314	=item callback ev_cb (ev_TYPE *watcher)
		1315
		1316	Returns the callback currently set on the watcher.
		1317
		1318	=item ev_cb_set (ev_TYPE *watcher, callback)
		1319
		1320	Change the callback. You can change the callback at virtually any time
		1321	(modulo threads).
		1322
		1323	=item ev_set_priority (ev_TYPE *watcher, int priority)
		1324
		1325	=item int ev_priority (ev_TYPE *watcher)
		1326
		1327	Set and query the priority of the watcher. The priority is a small
		1328	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		1329	(default: C<-2>). Pending watchers with higher priority will be invoked
		1330	before watchers with lower priority, but priority will not keep watchers
		1331	from being executed (except for C<ev_idle> watchers).
		1332
		1333	If you need to suppress invocation when higher priority events are pending
		1334	you need to look at C<ev_idle> watchers, which provide this functionality.
		1335
		1336	You I<must not> change the priority of a watcher as long as it is active or
		1337	pending.
		1338
		1339	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1340	fine, as long as you do not mind that the priority value you query might
		1341	or might not have been clamped to the valid range.
		1342
		1343	The default priority used by watchers when no priority has been set is
		1344	always C<0>, which is supposed to not be too high and not be too low :).
		1345
		1346	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
		1347	priorities.
		1348
		1349	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		1350
		1351	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		1352	C<loop> nor C<revents> need to be valid as long as the watcher callback
		1353	can deal with that fact, as both are simply passed through to the
		1354	callback.
		1355
		1356	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		1357
		1358	If the watcher is pending, this function clears its pending status and
		1359	returns its C<revents> bitset (as if its callback was invoked). If the
		1360	watcher isn't pending it does nothing and returns C<0>.
		1361
		1362	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1363	callback to be invoked, which can be accomplished with this function.
		1364
		1365	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1366
		1367	Feeds the given event set into the event loop, as if the specified event
		1368	had happened for the specified watcher (which must be a pointer to an
		1369	initialised but not necessarily started event watcher). Obviously you must
		1370	not free the watcher as long as it has pending events.
		1371
		1372	Stopping the watcher, letting libev invoke it, or calling
		1373	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1374	not started in the first place.
		1375
		1376	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1377	functions that do not need a watcher.
		1378
		1379	=back
		1380
		1381	See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR
		1382	OWN COMPOSITE WATCHERS> idioms.
		1383
1151	=head2 WATCHER STATES	1384	=head2 WATCHER STATES
1152		1385
1153	There are various watcher states mentioned throughout this manual -	1386	There are various watcher states mentioned throughout this manual -
1154	active, pending and so on. In this section these states and the rules to	1387	active, pending and so on. In this section these states and the rules to
1155	transition between them will be described in more detail - and while these	1388	transition between them will be described in more detail - and while these
…		…
1157		1390
1158	=over 4	1391	=over 4
1159		1392
1160	=item initialiased	1393	=item initialiased
1161		1394
1162	Before a watcher can be registered with the event looop it has to be	1395	Before a watcher can be registered with the event loop it has to be
1163	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to	1396	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
1164	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.	1397	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1165		1398
1166	In this state it is simply some block of memory that is suitable for use	1399	In this state it is simply some block of memory that is suitable for
1167	in an event loop. It can be moved around, freed, reused etc. at will.	1400	use in an event loop. It can be moved around, freed, reused etc. at
		1401	will - as long as you either keep the memory contents intact, or call
		1402	C<ev_TYPE_init> again.
1168		1403
1169	=item started/running/active	1404	=item started/running/active
1170		1405
1171	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes	1406	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1172	property of the event loop, and is actively waiting for events. While in	1407	property of the event loop, and is actively waiting for events. While in
…		…
1200	latter will clear any pending state the watcher might be in, regardless	1435	latter will clear any pending state the watcher might be in, regardless
1201	of whether it was active or not, so stopping a watcher explicitly before	1436	of whether it was active or not, so stopping a watcher explicitly before
1202	freeing it is often a good idea.	1437	freeing it is often a good idea.
1203		1438
1204	While stopped (and not pending) the watcher is essentially in the	1439	While stopped (and not pending) the watcher is essentially in the
1205	initialised state, that is it can be reused, moved, modified in any way	1440	initialised state, that is, it can be reused, moved, modified in any way
1206	you wish.	1441	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1442	it again).
1207		1443
1208	=back	1444	=back
1209
1210	=head2 GENERIC WATCHER FUNCTIONS
1211
1212	=over 4
1213
1214	=item C<ev_init> (ev_TYPE *watcher, callback)
1215
1216	This macro initialises the generic portion of a watcher. The contents
1217	of the watcher object can be arbitrary (so C<malloc> will do). Only
1218	the generic parts of the watcher are initialised, you I<need> to call
1219	the type-specific C<ev_TYPE_set> macro afterwards to initialise the
1220	type-specific parts. For each type there is also a C<ev_TYPE_init> macro
1221	which rolls both calls into one.
1222
1223	You can reinitialise a watcher at any time as long as it has been stopped
1224	(or never started) and there are no pending events outstanding.
1225
1226	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
1227	int revents)>.
1228
1229	Example: Initialise an C<ev_io> watcher in two steps.
1230
1231	ev_io w;
1232	ev_init (&w, my_cb);
1233	ev_io_set (&w, STDIN_FILENO, EV_READ);
1234
1235	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
1236
1237	This macro initialises the type-specific parts of a watcher. You need to
1238	call C<ev_init> at least once before you call this macro, but you can
1239	call C<ev_TYPE_set> any number of times. You must not, however, call this
1240	macro on a watcher that is active (it can be pending, however, which is a
1241	difference to the C<ev_init> macro).
1242
1243	Although some watcher types do not have type-specific arguments
1244	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
1245
1246	See C<ev_init>, above, for an example.
1247
1248	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
1249
1250	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
1251	calls into a single call. This is the most convenient method to initialise
1252	a watcher. The same limitations apply, of course.
1253
1254	Example: Initialise and set an C<ev_io> watcher in one step.
1255
1256	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1257
1258	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1259
1260	Starts (activates) the given watcher. Only active watchers will receive
1261	events. If the watcher is already active nothing will happen.
1262
1263	Example: Start the C<ev_io> watcher that is being abused as example in this
1264	whole section.
1265
1266	ev_io_start (EV_DEFAULT_UC, &w);
1267
1268	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1269
1270	Stops the given watcher if active, and clears the pending status (whether
1271	the watcher was active or not).
1272
1273	It is possible that stopped watchers are pending - for example,
1274	non-repeating timers are being stopped when they become pending - but
1275	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
1276	pending. If you want to free or reuse the memory used by the watcher it is
1277	therefore a good idea to always call its C<ev_TYPE_stop> function.
1278
1279	=item bool ev_is_active (ev_TYPE *watcher)
1280
1281	Returns a true value iff the watcher is active (i.e. it has been started
1282	and not yet been stopped). As long as a watcher is active you must not modify
1283	it.
1284
1285	=item bool ev_is_pending (ev_TYPE *watcher)
1286
1287	Returns a true value iff the watcher is pending, (i.e. it has outstanding
1288	events but its callback has not yet been invoked). As long as a watcher
1289	is pending (but not active) you must not call an init function on it (but
1290	C<ev_TYPE_set> is safe), you must not change its priority, and you must
1291	make sure the watcher is available to libev (e.g. you cannot C<free ()>
1292	it).
1293
1294	=item callback ev_cb (ev_TYPE *watcher)
1295
1296	Returns the callback currently set on the watcher.
1297
1298	=item ev_cb_set (ev_TYPE *watcher, callback)
1299
1300	Change the callback. You can change the callback at virtually any time
1301	(modulo threads).
1302
1303	=item ev_set_priority (ev_TYPE *watcher, int priority)
1304
1305	=item int ev_priority (ev_TYPE *watcher)
1306
1307	Set and query the priority of the watcher. The priority is a small
1308	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1309	(default: C<-2>). Pending watchers with higher priority will be invoked
1310	before watchers with lower priority, but priority will not keep watchers
1311	from being executed (except for C<ev_idle> watchers).
1312
1313	If you need to suppress invocation when higher priority events are pending
1314	you need to look at C<ev_idle> watchers, which provide this functionality.
1315
1316	You I<must not> change the priority of a watcher as long as it is active or
1317	pending.
1318
1319	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1320	fine, as long as you do not mind that the priority value you query might
1321	or might not have been clamped to the valid range.
1322
1323	The default priority used by watchers when no priority has been set is
1324	always C<0>, which is supposed to not be too high and not be too low :).
1325
1326	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1327	priorities.
1328
1329	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1330
1331	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1332	C<loop> nor C<revents> need to be valid as long as the watcher callback
1333	can deal with that fact, as both are simply passed through to the
1334	callback.
1335
1336	=item int ev_clear_pending (loop, ev_TYPE *watcher)
1337
1338	If the watcher is pending, this function clears its pending status and
1339	returns its C<revents> bitset (as if its callback was invoked). If the
1340	watcher isn't pending it does nothing and returns C<0>.
1341
1342	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1343	callback to be invoked, which can be accomplished with this function.
1344
1345	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
1346
1347	Feeds the given event set into the event loop, as if the specified event
1348	had happened for the specified watcher (which must be a pointer to an
1349	initialised but not necessarily started event watcher). Obviously you must
1350	not free the watcher as long as it has pending events.
1351
1352	Stopping the watcher, letting libev invoke it, or calling
1353	C<ev_clear_pending> will clear the pending event, even if the watcher was
1354	not started in the first place.
1355
1356	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1357	functions that do not need a watcher.
1358
1359	=back
1360
1361
1362	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1363
1364	Each watcher has, by default, a member C<void *data> that you can change
1365	and read at any time: libev will completely ignore it. This can be used
1366	to associate arbitrary data with your watcher. If you need more data and
1367	don't want to allocate memory and store a pointer to it in that data
1368	member, you can also "subclass" the watcher type and provide your own
1369	data:
1370
1371	struct my_io
1372	{
1373	ev_io io;
1374	int otherfd;
1375	void *somedata;
1376	struct whatever *mostinteresting;
1377	};
1378
1379	...
1380	struct my_io w;
1381	ev_io_init (&w.io, my_cb, fd, EV_READ);
1382
1383	And since your callback will be called with a pointer to the watcher, you
1384	can cast it back to your own type:
1385
1386	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1387	{
1388	struct my_io *w = (struct my_io *)w_;
1389	...
1390	}
1391
1392	More interesting and less C-conformant ways of casting your callback type
1393	instead have been omitted.
1394
1395	Another common scenario is to use some data structure with multiple
1396	embedded watchers:
1397
1398	struct my_biggy
1399	{
1400	int some_data;
1401	ev_timer t1;
1402	ev_timer t2;
1403	}
1404
1405	In this case getting the pointer to C<my_biggy> is a bit more
1406	complicated: Either you store the address of your C<my_biggy> struct
1407	in the C<data> member of the watcher (for woozies), or you need to use
1408	some pointer arithmetic using C<offsetof> inside your watchers (for real
1409	programmers):
1410
1411	#include <stddef.h>
1412
1413	static void
1414	t1_cb (EV_P_ ev_timer *w, int revents)
1415	{
1416	struct my_biggy big = (struct my_biggy *)
1417	(((char *)w) - offsetof (struct my_biggy, t1));
1418	}
1419
1420	static void
1421	t2_cb (EV_P_ ev_timer *w, int revents)
1422	{
1423	struct my_biggy big = (struct my_biggy *)
1424	(((char *)w) - offsetof (struct my_biggy, t2));
1425	}
1426		1445
1427	=head2 WATCHER PRIORITY MODELS	1446	=head2 WATCHER PRIORITY MODELS
1428		1447
1429	Many event loops support I<watcher priorities>, which are usually small	1448	Many event loops support I<watcher priorities>, which are usually small
1430	integers that influence the ordering of event callback invocation	1449	integers that influence the ordering of event callback invocation
…		…
1557	In general you can register as many read and/or write event watchers per	1576	In general you can register as many read and/or write event watchers per
1558	fd as you want (as long as you don't confuse yourself). Setting all file	1577	fd as you want (as long as you don't confuse yourself). Setting all file
1559	descriptors to non-blocking mode is also usually a good idea (but not	1578	descriptors to non-blocking mode is also usually a good idea (but not
1560	required if you know what you are doing).	1579	required if you know what you are doing).
1561		1580
1562	If you cannot use non-blocking mode, then force the use of a
1563	known-to-be-good backend (at the time of this writing, this includes only
1564	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1565	descriptors for which non-blocking operation makes no sense (such as
1566	files) - libev doesn't guarantee any specific behaviour in that case.
1567
1568	Another thing you have to watch out for is that it is quite easy to	1581	Another thing you have to watch out for is that it is quite easy to
1569	receive "spurious" readiness notifications, that is your callback might	1582	receive "spurious" readiness notifications, that is, your callback might
1570	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1583	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1571	because there is no data. Not only are some backends known to create a	1584	because there is no data. It is very easy to get into this situation even
1572	lot of those (for example Solaris ports), it is very easy to get into	1585	with a relatively standard program structure. Thus it is best to always
1573	this situation even with a relatively standard program structure. Thus	1586	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1574	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1575	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1587	preferable to a program hanging until some data arrives.
1576		1588
1577	If you cannot run the fd in non-blocking mode (for example you should	1589	If you cannot run the fd in non-blocking mode (for example you should
1578	not play around with an Xlib connection), then you have to separately	1590	not play around with an Xlib connection), then you have to separately
1579	re-test whether a file descriptor is really ready with a known-to-be good	1591	re-test whether a file descriptor is really ready with a known-to-be good
1580	interface such as poll (fortunately in our Xlib example, Xlib already	1592	interface such as poll (fortunately in the case of Xlib, it already does
1581	does this on its own, so its quite safe to use). Some people additionally	1593	this on its own, so its quite safe to use). Some people additionally
1582	use C<SIGALRM> and an interval timer, just to be sure you won't block	1594	use C<SIGALRM> and an interval timer, just to be sure you won't block
1583	indefinitely.	1595	indefinitely.
1584		1596
1585	But really, best use non-blocking mode.	1597	But really, best use non-blocking mode.
1586		1598
…		…
1614		1626
1615	There is no workaround possible except not registering events	1627	There is no workaround possible except not registering events
1616	for potentially C<dup ()>'ed file descriptors, or to resort to	1628	for potentially C<dup ()>'ed file descriptors, or to resort to
1617	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1629	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1618		1630
		1631	=head3 The special problem of files
		1632
		1633	Many people try to use C<select> (or libev) on file descriptors
		1634	representing files, and expect it to become ready when their program
		1635	doesn't block on disk accesses (which can take a long time on their own).
		1636
		1637	However, this cannot ever work in the "expected" way - you get a readiness
		1638	notification as soon as the kernel knows whether and how much data is
		1639	there, and in the case of open files, that's always the case, so you
		1640	always get a readiness notification instantly, and your read (or possibly
		1641	write) will still block on the disk I/O.
		1642
		1643	Another way to view it is that in the case of sockets, pipes, character
		1644	devices and so on, there is another party (the sender) that delivers data
		1645	on its own, but in the case of files, there is no such thing: the disk
		1646	will not send data on its own, simply because it doesn't know what you
		1647	wish to read - you would first have to request some data.
		1648
		1649	Since files are typically not-so-well supported by advanced notification
		1650	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1651	to files, even though you should not use it. The reason for this is
		1652	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1653	usually a tty, often a pipe, but also sometimes files or special devices
		1654	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1655	F</dev/urandom>), and even though the file might better be served with
		1656	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1657	it "just works" instead of freezing.
		1658
		1659	So avoid file descriptors pointing to files when you know it (e.g. use
		1660	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1661	when you rarely read from a file instead of from a socket, and want to
		1662	reuse the same code path.
		1663
1619	=head3 The special problem of fork	1664	=head3 The special problem of fork
1620		1665
1621	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1666	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1622	useless behaviour. Libev fully supports fork, but needs to be told about	1667	useless behaviour. Libev fully supports fork, but needs to be told about
1623	it in the child.	1668	it in the child if you want to continue to use it in the child.
1624		1669
1625	To support fork in your programs, you either have to call	1670	To support fork in your child processes, you have to call C<ev_loop_fork
1626	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1671	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1627	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1672	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1628	C<EVBACKEND_POLL>.
1629		1673
1630	=head3 The special problem of SIGPIPE	1674	=head3 The special problem of SIGPIPE
1631		1675
1632	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1676	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1633	when writing to a pipe whose other end has been closed, your program gets	1677	when writing to a pipe whose other end has been closed, your program gets
…		…
1731	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1775	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1732	monotonic clock option helps a lot here).	1776	monotonic clock option helps a lot here).
1733		1777
1734	The callback is guaranteed to be invoked only I<after> its timeout has	1778	The callback is guaranteed to be invoked only I<after> its timeout has
1735	passed (not I<at>, so on systems with very low-resolution clocks this	1779	passed (not I<at>, so on systems with very low-resolution clocks this
1736	might introduce a small delay). If multiple timers become ready during the	1780	might introduce a small delay, see "the special problem of being too
		1781	early", below). If multiple timers become ready during the same loop
1737	same loop iteration then the ones with earlier time-out values are invoked	1782	iteration then the ones with earlier time-out values are invoked before
1738	before ones of the same priority with later time-out values (but this is	1783	ones of the same priority with later time-out values (but this is no
1739	no longer true when a callback calls C<ev_run> recursively).	1784	longer true when a callback calls C<ev_run> recursively).
1740		1785
1741	=head3 Be smart about timeouts	1786	=head3 Be smart about timeouts
1742		1787
1743	Many real-world problems involve some kind of timeout, usually for error	1788	Many real-world problems involve some kind of timeout, usually for error
1744	recovery. A typical example is an HTTP request - if the other side hangs,	1789	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1819		1864
1820	In this case, it would be more efficient to leave the C<ev_timer> alone,	1865	In this case, it would be more efficient to leave the C<ev_timer> alone,
1821	but remember the time of last activity, and check for a real timeout only	1866	but remember the time of last activity, and check for a real timeout only
1822	within the callback:	1867	within the callback:
1823		1868
		1869	ev_tstamp timeout = 60.;
1824	ev_tstamp last_activity; // time of last activity	1870	ev_tstamp last_activity; // time of last activity
		1871	ev_timer timer;
1825		1872
1826	static void	1873	static void
1827	callback (EV_P_ ev_timer *w, int revents)	1874	callback (EV_P_ ev_timer *w, int revents)
1828	{	1875	{
1829	ev_tstamp now = ev_now (EV_A);	1876	// calculate when the timeout would happen
1830	ev_tstamp timeout = last_activity + 60.;	1877	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1831		1878
1832	// if last_activity + 60. is older than now, we did time out	1879	// if negative, it means we the timeout already occured
1833	if (timeout < now)	1880	if (after < 0.)
1834	{	1881	{
1835	// timeout occurred, take action	1882	// timeout occurred, take action
1836	}	1883	}
1837	else	1884	else
1838	{	1885	{
1839	// callback was invoked, but there was some activity, re-arm	1886	// callback was invoked, but there was some recent
1840	// the watcher to fire in last_activity + 60, which is	1887	// activity. simply restart the timer to time out
1841	// guaranteed to be in the future, so "again" is positive:	1888	// after "after" seconds, which is the earliest time
1842	w->repeat = timeout - now;	1889	// the timeout can occur.
		1890	ev_timer_set (w, after, 0.);
1843	ev_timer_again (EV_A_ w);	1891	ev_timer_start (EV_A_ w);
1844	}	1892	}
1845	}	1893	}
1846		1894
1847	To summarise the callback: first calculate the real timeout (defined	1895	To summarise the callback: first calculate in how many seconds the
1848	as "60 seconds after the last activity"), then check if that time has	1896	timeout will occur (by calculating the absolute time when it would occur,
1849	been reached, which means something I<did>, in fact, time out. Otherwise	1897	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1850	the callback was invoked too early (C<timeout> is in the future), so	1898	(EV_A)> from that).
1851	re-schedule the timer to fire at that future time, to see if maybe we have
1852	a timeout then.
1853		1899
1854	Note how C<ev_timer_again> is used, taking advantage of the	1900	If this value is negative, then we are already past the timeout, i.e. we
1855	C<ev_timer_again> optimisation when the timer is already running.	1901	timed out, and need to do whatever is needed in this case.
		1902
		1903	Otherwise, we now the earliest time at which the timeout would trigger,
		1904	and simply start the timer with this timeout value.
		1905
		1906	In other words, each time the callback is invoked it will check whether
		1907	the timeout cocured. If not, it will simply reschedule itself to check
		1908	again at the earliest time it could time out. Rinse. Repeat.
1856		1909
1857	This scheme causes more callback invocations (about one every 60 seconds	1910	This scheme causes more callback invocations (about one every 60 seconds
1858	minus half the average time between activity), but virtually no calls to	1911	minus half the average time between activity), but virtually no calls to
1859	libev to change the timeout.	1912	libev to change the timeout.
1860		1913
1861	To start the timer, simply initialise the watcher and set C<last_activity>	1914	To start the machinery, simply initialise the watcher and set
1862	to the current time (meaning we just have some activity :), then call the	1915	C<last_activity> to the current time (meaning there was some activity just
1863	callback, which will "do the right thing" and start the timer:	1916	now), then call the callback, which will "do the right thing" and start
		1917	the timer:
1864		1918
		1919	last_activity = ev_now (EV_A);
1865	ev_init (timer, callback);	1920	ev_init (&timer, callback);
1866	last_activity = ev_now (loop);	1921	callback (EV_A_ &timer, 0);
1867	callback (loop, timer, EV_TIMER);
1868		1922
1869	And when there is some activity, simply store the current time in	1923	When there is some activity, simply store the current time in
1870	C<last_activity>, no libev calls at all:	1924	C<last_activity>, no libev calls at all:
1871		1925
		1926	if (activity detected)
1872	last_activity = ev_now (loop);	1927	last_activity = ev_now (EV_A);
		1928
		1929	When your timeout value changes, then the timeout can be changed by simply
		1930	providing a new value, stopping the timer and calling the callback, which
		1931	will agaion do the right thing (for example, time out immediately :).
		1932
		1933	timeout = new_value;
		1934	ev_timer_stop (EV_A_ &timer);
		1935	callback (EV_A_ &timer, 0);
1873		1936
1874	This technique is slightly more complex, but in most cases where the	1937	This technique is slightly more complex, but in most cases where the
1875	time-out is unlikely to be triggered, much more efficient.	1938	time-out is unlikely to be triggered, much more efficient.
1876
1877	Changing the timeout is trivial as well (if it isn't hard-coded in the
1878	callback :) - just change the timeout and invoke the callback, which will
1879	fix things for you.
1880		1939
1881	=item 4. Wee, just use a double-linked list for your timeouts.	1940	=item 4. Wee, just use a double-linked list for your timeouts.
1882		1941
1883	If there is not one request, but many thousands (millions...), all	1942	If there is not one request, but many thousands (millions...), all
1884	employing some kind of timeout with the same timeout value, then one can	1943	employing some kind of timeout with the same timeout value, then one can
…		…
1911	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	1970	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1912	rather complicated, but extremely efficient, something that really pays	1971	rather complicated, but extremely efficient, something that really pays
1913	off after the first million or so of active timers, i.e. it's usually	1972	off after the first million or so of active timers, i.e. it's usually
1914	overkill :)	1973	overkill :)
1915		1974
		1975	=head3 The special problem of being too early
		1976
		1977	If you ask a timer to call your callback after three seconds, then
		1978	you expect it to be invoked after three seconds - but of course, this
		1979	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		1980	guaranteed to any precision by libev - imagine somebody suspending the
		1981	process with a STOP signal for a few hours for example.
		1982
		1983	So, libev tries to invoke your callback as soon as possible I<after> the
		1984	delay has occurred, but cannot guarantee this.
		1985
		1986	A less obvious failure mode is calling your callback too early: many event
		1987	loops compare timestamps with a "elapsed delay >= requested delay", but
		1988	this can cause your callback to be invoked much earlier than you would
		1989	expect.
		1990
		1991	To see why, imagine a system with a clock that only offers full second
		1992	resolution (think windows if you can't come up with a broken enough OS
		1993	yourself). If you schedule a one-second timer at the time 500.9, then the
		1994	event loop will schedule your timeout to elapse at a system time of 500
		1995	(500.9 truncated to the resolution) + 1, or 501.
		1996
		1997	If an event library looks at the timeout 0.1s later, it will see "501 >=
		1998	501" and invoke the callback 0.1s after it was started, even though a
		1999	one-second delay was requested - this is being "too early", despite best
		2000	intentions.
		2001
		2002	This is the reason why libev will never invoke the callback if the elapsed
		2003	delay equals the requested delay, but only when the elapsed delay is
		2004	larger than the requested delay. In the example above, libev would only invoke
		2005	the callback at system time 502, or 1.1s after the timer was started.
		2006
		2007	So, while libev cannot guarantee that your callback will be invoked
		2008	exactly when requested, it I<can> and I<does> guarantee that the requested
		2009	delay has actually elapsed, or in other words, it always errs on the "too
		2010	late" side of things.
		2011
1916	=head3 The special problem of time updates	2012	=head3 The special problem of time updates
1917		2013
1918	Establishing the current time is a costly operation (it usually takes at	2014	Establishing the current time is a costly operation (it usually takes
1919	least two system calls): EV therefore updates its idea of the current	2015	at least one system call): EV therefore updates its idea of the current
1920	time only before and after C<ev_run> collects new events, which causes a	2016	time only before and after C<ev_run> collects new events, which causes a
1921	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2017	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1922	lots of events in one iteration.	2018	lots of events in one iteration.
1923		2019
1924	The relative timeouts are calculated relative to the C<ev_now ()>	2020	The relative timeouts are calculated relative to the C<ev_now ()>
…		…
1930	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2026	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1931		2027
1932	If the event loop is suspended for a long time, you can also force an	2028	If the event loop is suspended for a long time, you can also force an
1933	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2029	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1934	()>.	2030	()>.
		2031
		2032	=head3 The special problem of unsynchronised clocks
		2033
		2034	Modern systems have a variety of clocks - libev itself uses the normal
		2035	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2036	jumps).
		2037
		2038	Neither of these clocks is synchronised with each other or any other clock
		2039	on the system, so C<ev_time ()> might return a considerably different time
		2040	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2041	a call to C<gettimeofday> might return a second count that is one higher
		2042	than a directly following call to C<time>.
		2043
		2044	The moral of this is to only compare libev-related timestamps with
		2045	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2046	a second or so.
		2047
		2048	One more problem arises due to this lack of synchronisation: if libev uses
		2049	the system monotonic clock and you compare timestamps from C<ev_time>
		2050	or C<ev_now> from when you started your timer and when your callback is
		2051	invoked, you will find that sometimes the callback is a bit "early".
		2052
		2053	This is because C<ev_timer>s work in real time, not wall clock time, so
		2054	libev makes sure your callback is not invoked before the delay happened,
		2055	I<measured according to the real time>, not the system clock.
		2056
		2057	If your timeouts are based on a physical timescale (e.g. "time out this
		2058	connection after 100 seconds") then this shouldn't bother you as it is
		2059	exactly the right behaviour.
		2060
		2061	If you want to compare wall clock/system timestamps to your timers, then
		2062	you need to use C<ev_periodic>s, as these are based on the wall clock
		2063	time, where your comparisons will always generate correct results.
1935		2064
1936	=head3 The special problems of suspended animation	2065	=head3 The special problems of suspended animation
1937		2066
1938	When you leave the server world it is quite customary to hit machines that	2067	When you leave the server world it is quite customary to hit machines that
1939	can suspend/hibernate - what happens to the clocks during such a suspend?	2068	can suspend/hibernate - what happens to the clocks during such a suspend?
…		…
1983	keep up with the timer (because it takes longer than those 10 seconds to	2112	keep up with the timer (because it takes longer than those 10 seconds to
1984	do stuff) the timer will not fire more than once per event loop iteration.	2113	do stuff) the timer will not fire more than once per event loop iteration.
1985		2114
1986	=item ev_timer_again (loop, ev_timer *)	2115	=item ev_timer_again (loop, ev_timer *)
1987		2116
1988	This will act as if the timer timed out and restart it again if it is	2117	This will act as if the timer timed out, and restarts it again if it is
1989	repeating. The exact semantics are:	2118	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2119	timeout to the C<repeat> value and calling C<ev_timer_start>.
1990		2120
		2121	The exact semantics are as in the following rules, all of which will be
		2122	applied to the watcher:
		2123
		2124	=over 4
		2125
1991	If the timer is pending, its pending status is cleared.	2126	=item If the timer is pending, the pending status is always cleared.
1992		2127
1993	If the timer is started but non-repeating, stop it (as if it timed out).	2128	=item If the timer is started but non-repeating, stop it (as if it timed
		2129	out, without invoking it).
1994		2130
1995	If the timer is repeating, either start it if necessary (with the	2131	=item If the timer is repeating, make the C<repeat> value the new timeout
1996	C<repeat> value), or reset the running timer to the C<repeat> value.	2132	and start the timer, if necessary.
		2133
		2134	=back
1997		2135
1998	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2136	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1999	usage example.	2137	usage example.
2000		2138
2001	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)	2139	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
…		…
2123		2261
2124	Another way to think about it (for the mathematically inclined) is that	2262	Another way to think about it (for the mathematically inclined) is that
2125	C<ev_periodic> will try to run the callback in this mode at the next possible	2263	C<ev_periodic> will try to run the callback in this mode at the next possible
2126	time where C<time = offset (mod interval)>, regardless of any time jumps.	2264	time where C<time = offset (mod interval)>, regardless of any time jumps.
2127		2265
2128	For numerical stability it is preferable that the C<offset> value is near	2266	The C<interval> I<MUST> be positive, and for numerical stability, the
2129	C<ev_now ()> (the current time), but there is no range requirement for	2267	interval value should be higher than C<1/8192> (which is around 100
2130	this value, and in fact is often specified as zero.	2268	microseconds) and C<offset> should be higher than C<0> and should have
		2269	at most a similar magnitude as the current time (say, within a factor of
		2270	ten). Typical values for offset are, in fact, C<0> or something between
		2271	C<0> and C<interval>, which is also the recommended range.
2131		2272
2132	Note also that there is an upper limit to how often a timer can fire (CPU	2273	Note also that there is an upper limit to how often a timer can fire (CPU
2133	speed for example), so if C<interval> is very small then timing stability	2274	speed for example), so if C<interval> is very small then timing stability
2134	will of course deteriorate. Libev itself tries to be exact to be about one	2275	will of course deteriorate. Libev itself tries to be exact to be about one
2135	millisecond (if the OS supports it and the machine is fast enough).	2276	millisecond (if the OS supports it and the machine is fast enough).
…		…
2249		2390
2250	=head2 C<ev_signal> - signal me when a signal gets signalled!	2391	=head2 C<ev_signal> - signal me when a signal gets signalled!
2251		2392
2252	Signal watchers will trigger an event when the process receives a specific	2393	Signal watchers will trigger an event when the process receives a specific
2253	signal one or more times. Even though signals are very asynchronous, libev	2394	signal one or more times. Even though signals are very asynchronous, libev
2254	will try it's best to deliver signals synchronously, i.e. as part of the	2395	will try its best to deliver signals synchronously, i.e. as part of the
2255	normal event processing, like any other event.	2396	normal event processing, like any other event.
2256		2397
2257	If you want signals to be delivered truly asynchronously, just use	2398	If you want signals to be delivered truly asynchronously, just use
2258	C<sigaction> as you would do without libev and forget about sharing	2399	C<sigaction> as you would do without libev and forget about sharing
2259	the signal. You can even use C<ev_async> from a signal handler to	2400	the signal. You can even use C<ev_async> from a signal handler to
…		…
2278	=head3 The special problem of inheritance over fork/execve/pthread_create	2419	=head3 The special problem of inheritance over fork/execve/pthread_create
2279		2420
2280	Both the signal mask (C<sigprocmask>) and the signal disposition	2421	Both the signal mask (C<sigprocmask>) and the signal disposition
2281	(C<sigaction>) are unspecified after starting a signal watcher (and after	2422	(C<sigaction>) are unspecified after starting a signal watcher (and after
2282	stopping it again), that is, libev might or might not block the signal,	2423	stopping it again), that is, libev might or might not block the signal,
2283	and might or might not set or restore the installed signal handler.	2424	and might or might not set or restore the installed signal handler (but
		2425	see C<EVFLAG_NOSIGMASK>).
2284		2426
2285	While this does not matter for the signal disposition (libev never	2427	While this does not matter for the signal disposition (libev never
2286	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on	2428	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
2287	C<execve>), this matters for the signal mask: many programs do not expect	2429	C<execve>), this matters for the signal mask: many programs do not expect
2288	certain signals to be blocked.	2430	certain signals to be blocked.
…		…
2301	I<has> to modify the signal mask, at least temporarily.	2443	I<has> to modify the signal mask, at least temporarily.
2302		2444
2303	So I can't stress this enough: I<If you do not reset your signal mask when	2445	So I can't stress this enough: I<If you do not reset your signal mask when
2304	you expect it to be empty, you have a race condition in your code>. This	2446	you expect it to be empty, you have a race condition in your code>. This
2305	is not a libev-specific thing, this is true for most event libraries.	2447	is not a libev-specific thing, this is true for most event libraries.
		2448
		2449	=head3 The special problem of threads signal handling
		2450
		2451	POSIX threads has problematic signal handling semantics, specifically,
		2452	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2453	threads in a process block signals, which is hard to achieve.
		2454
		2455	When you want to use sigwait (or mix libev signal handling with your own
		2456	for the same signals), you can tackle this problem by globally blocking
		2457	all signals before creating any threads (or creating them with a fully set
		2458	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2459	loops. Then designate one thread as "signal receiver thread" which handles
		2460	these signals. You can pass on any signals that libev might be interested
		2461	in by calling C<ev_feed_signal>.
2306		2462
2307	=head3 Watcher-Specific Functions and Data Members	2463	=head3 Watcher-Specific Functions and Data Members
2308		2464
2309	=over 4	2465	=over 4
2310		2466
…		…
3098		3254
3099	=item ev_fork_init (ev_fork *, callback)	3255	=item ev_fork_init (ev_fork *, callback)
3100		3256
3101	Initialises and configures the fork watcher - it has no parameters of any	3257	Initialises and configures the fork watcher - it has no parameters of any
3102	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3258	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
3103	believe me.	3259	really.
3104		3260
3105	=back	3261	=back
3106		3262
3107		3263
3108	=head2 C<ev_cleanup> - even the best things end	3264	=head2 C<ev_cleanup> - even the best things end
3109		3265
3110	Cleanup watchers are called just before the event loop they are registered	3266	Cleanup watchers are called just before the event loop is being destroyed
3111	with is being destroyed.	3267	by a call to C<ev_loop_destroy>.
3112		3268
3113	While there is no guarantee that the event loop gets destroyed, cleanup	3269	While there is no guarantee that the event loop gets destroyed, cleanup
3114	watchers provide a convenient method to install cleanup hooks for your	3270	watchers provide a convenient method to install cleanup hooks for your
3115	program, worker threads and so on - you just to make sure to destroy the	3271	program, worker threads and so on - you just to make sure to destroy the
3116	loop when you want them to be invoked.	3272	loop when you want them to be invoked.
…		…
3126		3282
3127	=item ev_cleanup_init (ev_cleanup *, callback)	3283	=item ev_cleanup_init (ev_cleanup *, callback)
3128		3284
3129	Initialises and configures the cleanup watcher - it has no parameters of	3285	Initialises and configures the cleanup watcher - it has no parameters of
3130	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly	3286	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
3131	pointless, believe me.	3287	pointless, I assure you.
3132		3288
3133	=back	3289	=back
3134		3290
3135	Example: Register an atexit handler to destroy the default loop, so any	3291	Example: Register an atexit handler to destroy the default loop, so any
3136	cleanup functions are called.	3292	cleanup functions are called.
…		…
3145	atexit (program_exits);	3301	atexit (program_exits);
3146		3302
3147		3303
3148	=head2 C<ev_async> - how to wake up an event loop	3304	=head2 C<ev_async> - how to wake up an event loop
3149		3305
3150	In general, you cannot use an C<ev_run> from multiple threads or other	3306	In general, you cannot use an C<ev_loop> from multiple threads or other
3151	asynchronous sources such as signal handlers (as opposed to multiple event	3307	asynchronous sources such as signal handlers (as opposed to multiple event
3152	loops - those are of course safe to use in different threads).	3308	loops - those are of course safe to use in different threads).
3153		3309
3154	Sometimes, however, you need to wake up an event loop you do not control,	3310	Sometimes, however, you need to wake up an event loop you do not control,
3155	for example because it belongs to another thread. This is what C<ev_async>	3311	for example because it belongs to another thread. This is what C<ev_async>
…		…
3157	it by calling C<ev_async_send>, which is thread- and signal safe.	3313	it by calling C<ev_async_send>, which is thread- and signal safe.
3158		3314
3159	This functionality is very similar to C<ev_signal> watchers, as signals,	3315	This functionality is very similar to C<ev_signal> watchers, as signals,
3160	too, are asynchronous in nature, and signals, too, will be compressed	3316	too, are asynchronous in nature, and signals, too, will be compressed
3161	(i.e. the number of callback invocations may be less than the number of	3317	(i.e. the number of callback invocations may be less than the number of
3162	C<ev_async_sent> calls).	3318	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
3163		3319	of "global async watchers" by using a watcher on an otherwise unused
3164	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3320	signal, and C<ev_feed_signal> to signal this watcher from another thread,
3165	just the default loop.	3321	even without knowing which loop owns the signal.
3166		3322
3167	=head3 Queueing	3323	=head3 Queueing
3168		3324
3169	C<ev_async> does not support queueing of data in any way. The reason	3325	C<ev_async> does not support queueing of data in any way. The reason
3170	is that the author does not know of a simple (or any) algorithm for a	3326	is that the author does not know of a simple (or any) algorithm for a
…		…
3262	trust me.	3418	trust me.
3263		3419
3264	=item ev_async_send (loop, ev_async *)	3420	=item ev_async_send (loop, ev_async *)
3265		3421
3266	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3422	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3267	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3423	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3424	returns.
		3425
3268	C<ev_feed_event>, this call is safe to do from other threads, signal or	3426	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3269	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3427	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3270	section below on what exactly this means).	3428	embedding section below on what exactly this means).
3271		3429
3272	Note that, as with other watchers in libev, multiple events might get	3430	Note that, as with other watchers in libev, multiple events might get
3273	compressed into a single callback invocation (another way to look at this	3431	compressed into a single callback invocation (another way to look at
3274	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3432	this is that C<ev_async> watchers are level-triggered: they are set on
3275	reset when the event loop detects that).	3433	C<ev_async_send>, reset when the event loop detects that).
3276		3434
3277	This call incurs the overhead of a system call only once per event loop	3435	This call incurs the overhead of at most one extra system call per event
3278	iteration, so while the overhead might be noticeable, it doesn't apply to	3436	loop iteration, if the event loop is blocked, and no syscall at all if
3279	repeated calls to C<ev_async_send> for the same event loop.	3437	the event loop (or your program) is processing events. That means that
		3438	repeated calls are basically free (there is no need to avoid calls for
		3439	performance reasons) and that the overhead becomes smaller (typically
		3440	zero) under load.
3280		3441
3281	=item bool = ev_async_pending (ev_async *)	3442	=item bool = ev_async_pending (ev_async *)
3282		3443
3283	Returns a non-zero value when C<ev_async_send> has been called on the	3444	Returns a non-zero value when C<ev_async_send> has been called on the
3284	watcher but the event has not yet been processed (or even noted) by the	3445	watcher but the event has not yet been processed (or even noted) by the
…		…
3339	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3500	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3340		3501
3341	=item ev_feed_fd_event (loop, int fd, int revents)	3502	=item ev_feed_fd_event (loop, int fd, int revents)
3342		3503
3343	Feed an event on the given fd, as if a file descriptor backend detected	3504	Feed an event on the given fd, as if a file descriptor backend detected
3344	the given events it.	3505	the given events.
3345		3506
3346	=item ev_feed_signal_event (loop, int signum)	3507	=item ev_feed_signal_event (loop, int signum)
3347		3508
3348	Feed an event as if the given signal occurred (C<loop> must be the default	3509	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3349	loop!).	3510	which is async-safe.
3350		3511
3351	=back	3512	=back
		3513
		3514
		3515	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3516
		3517	This section explains some common idioms that are not immediately
		3518	obvious. Note that examples are sprinkled over the whole manual, and this
		3519	section only contains stuff that wouldn't fit anywhere else.
		3520
		3521	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3522
		3523	Each watcher has, by default, a C<void *data> member that you can read
		3524	or modify at any time: libev will completely ignore it. This can be used
		3525	to associate arbitrary data with your watcher. If you need more data and
		3526	don't want to allocate memory separately and store a pointer to it in that
		3527	data member, you can also "subclass" the watcher type and provide your own
		3528	data:
		3529
		3530	struct my_io
		3531	{
		3532	ev_io io;
		3533	int otherfd;
		3534	void *somedata;
		3535	struct whatever *mostinteresting;
		3536	};
		3537
		3538	...
		3539	struct my_io w;
		3540	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3541
		3542	And since your callback will be called with a pointer to the watcher, you
		3543	can cast it back to your own type:
		3544
		3545	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3546	{
		3547	struct my_io *w = (struct my_io *)w_;
		3548	...
		3549	}
		3550
		3551	More interesting and less C-conformant ways of casting your callback
		3552	function type instead have been omitted.
		3553
		3554	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3555
		3556	Another common scenario is to use some data structure with multiple
		3557	embedded watchers, in effect creating your own watcher that combines
		3558	multiple libev event sources into one "super-watcher":
		3559
		3560	struct my_biggy
		3561	{
		3562	int some_data;
		3563	ev_timer t1;
		3564	ev_timer t2;
		3565	}
		3566
		3567	In this case getting the pointer to C<my_biggy> is a bit more
		3568	complicated: Either you store the address of your C<my_biggy> struct in
		3569	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3570	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3571	real programmers):
		3572
		3573	#include <stddef.h>
		3574
		3575	static void
		3576	t1_cb (EV_P_ ev_timer *w, int revents)
		3577	{
		3578	struct my_biggy big = (struct my_biggy *)
		3579	(((char *)w) - offsetof (struct my_biggy, t1));
		3580	}
		3581
		3582	static void
		3583	t2_cb (EV_P_ ev_timer *w, int revents)
		3584	{
		3585	struct my_biggy big = (struct my_biggy *)
		3586	(((char *)w) - offsetof (struct my_biggy, t2));
		3587	}
		3588
		3589	=head2 AVOIDING FINISHING BEFORE RETURNING
		3590
		3591	Often you have structures like this in event-based programs:
		3592
		3593	callback ()
		3594	{
		3595	free (request);
		3596	}
		3597
		3598	request = start_new_request (..., callback);
		3599
		3600	The intent is to start some "lengthy" operation. The C<request> could be
		3601	used to cancel the operation, or do other things with it.
		3602
		3603	It's not uncommon to have code paths in C<start_new_request> that
		3604	immediately invoke the callback, for example, to report errors. Or you add
		3605	some caching layer that finds that it can skip the lengthy aspects of the
		3606	operation and simply invoke the callback with the result.
		3607
		3608	The problem here is that this will happen I<before> C<start_new_request>
		3609	has returned, so C<request> is not set.
		3610
		3611	Even if you pass the request by some safer means to the callback, you
		3612	might want to do something to the request after starting it, such as
		3613	canceling it, which probably isn't working so well when the callback has
		3614	already been invoked.
		3615
		3616	A common way around all these issues is to make sure that
		3617	C<start_new_request> I<always> returns before the callback is invoked. If
		3618	C<start_new_request> immediately knows the result, it can artificially
		3619	delay invoking the callback by e.g. using a C<prepare> or C<idle> watcher
		3620	for example, or more sneakily, by reusing an existing (stopped) watcher
		3621	and pushing it into the pending queue:
		3622
		3623	ev_set_cb (watcher, callback);
		3624	ev_feed_event (EV_A_ watcher, 0);
		3625
		3626	This way, C<start_new_request> can safely return before the callback is
		3627	invoked, while not delaying callback invocation too much.
		3628
		3629	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3630
		3631	Often (especially in GUI toolkits) there are places where you have
		3632	I<modal> interaction, which is most easily implemented by recursively
		3633	invoking C<ev_run>.
		3634
		3635	This brings the problem of exiting - a callback might want to finish the
		3636	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3637	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3638	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3639	other combination: In these cases, C<ev_break> will not work alone.
		3640
		3641	The solution is to maintain "break this loop" variable for each C<ev_run>
		3642	invocation, and use a loop around C<ev_run> until the condition is
		3643	triggered, using C<EVRUN_ONCE>:
		3644
		3645	// main loop
		3646	int exit_main_loop = 0;
		3647
		3648	while (!exit_main_loop)
		3649	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3650
		3651	// in a modal watcher
		3652	int exit_nested_loop = 0;
		3653
		3654	while (!exit_nested_loop)
		3655	ev_run (EV_A_ EVRUN_ONCE);
		3656
		3657	To exit from any of these loops, just set the corresponding exit variable:
		3658
		3659	// exit modal loop
		3660	exit_nested_loop = 1;
		3661
		3662	// exit main program, after modal loop is finished
		3663	exit_main_loop = 1;
		3664
		3665	// exit both
		3666	exit_main_loop = exit_nested_loop = 1;
		3667
		3668	=head2 THREAD LOCKING EXAMPLE
		3669
		3670	Here is a fictitious example of how to run an event loop in a different
		3671	thread from where callbacks are being invoked and watchers are
		3672	created/added/removed.
		3673
		3674	For a real-world example, see the C<EV::Loop::Async> perl module,
		3675	which uses exactly this technique (which is suited for many high-level
		3676	languages).
		3677
		3678	The example uses a pthread mutex to protect the loop data, a condition
		3679	variable to wait for callback invocations, an async watcher to notify the
		3680	event loop thread and an unspecified mechanism to wake up the main thread.
		3681
		3682	First, you need to associate some data with the event loop:
		3683
		3684	typedef struct {
		3685	mutex_t lock; /* global loop lock */
		3686	ev_async async_w;
		3687	thread_t tid;
		3688	cond_t invoke_cv;
		3689	} userdata;
		3690
		3691	void prepare_loop (EV_P)
		3692	{
		3693	// for simplicity, we use a static userdata struct.
		3694	static userdata u;
		3695
		3696	ev_async_init (&u->async_w, async_cb);
		3697	ev_async_start (EV_A_ &u->async_w);
		3698
		3699	pthread_mutex_init (&u->lock, 0);
		3700	pthread_cond_init (&u->invoke_cv, 0);
		3701
		3702	// now associate this with the loop
		3703	ev_set_userdata (EV_A_ u);
		3704	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3705	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3706
		3707	// then create the thread running ev_run
		3708	pthread_create (&u->tid, 0, l_run, EV_A);
		3709	}
		3710
		3711	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3712	solely to wake up the event loop so it takes notice of any new watchers
		3713	that might have been added:
		3714
		3715	static void
		3716	async_cb (EV_P_ ev_async *w, int revents)
		3717	{
		3718	// just used for the side effects
		3719	}
		3720
		3721	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3722	protecting the loop data, respectively.
		3723
		3724	static void
		3725	l_release (EV_P)
		3726	{
		3727	userdata *u = ev_userdata (EV_A);
		3728	pthread_mutex_unlock (&u->lock);
		3729	}
		3730
		3731	static void
		3732	l_acquire (EV_P)
		3733	{
		3734	userdata *u = ev_userdata (EV_A);
		3735	pthread_mutex_lock (&u->lock);
		3736	}
		3737
		3738	The event loop thread first acquires the mutex, and then jumps straight
		3739	into C<ev_run>:
		3740
		3741	void *
		3742	l_run (void *thr_arg)
		3743	{
		3744	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3745
		3746	l_acquire (EV_A);
		3747	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3748	ev_run (EV_A_ 0);
		3749	l_release (EV_A);
		3750
		3751	return 0;
		3752	}
		3753
		3754	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3755	signal the main thread via some unspecified mechanism (signals? pipe
		3756	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3757	have been called (in a while loop because a) spurious wakeups are possible
		3758	and b) skipping inter-thread-communication when there are no pending
		3759	watchers is very beneficial):
		3760
		3761	static void
		3762	l_invoke (EV_P)
		3763	{
		3764	userdata *u = ev_userdata (EV_A);
		3765
		3766	while (ev_pending_count (EV_A))
		3767	{
		3768	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3769	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3770	}
		3771	}
		3772
		3773	Now, whenever the main thread gets told to invoke pending watchers, it
		3774	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3775	thread to continue:
		3776
		3777	static void
		3778	real_invoke_pending (EV_P)
		3779	{
		3780	userdata *u = ev_userdata (EV_A);
		3781
		3782	pthread_mutex_lock (&u->lock);
		3783	ev_invoke_pending (EV_A);
		3784	pthread_cond_signal (&u->invoke_cv);
		3785	pthread_mutex_unlock (&u->lock);
		3786	}
		3787
		3788	Whenever you want to start/stop a watcher or do other modifications to an
		3789	event loop, you will now have to lock:
		3790
		3791	ev_timer timeout_watcher;
		3792	userdata *u = ev_userdata (EV_A);
		3793
		3794	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3795
		3796	pthread_mutex_lock (&u->lock);
		3797	ev_timer_start (EV_A_ &timeout_watcher);
		3798	ev_async_send (EV_A_ &u->async_w);
		3799	pthread_mutex_unlock (&u->lock);
		3800
		3801	Note that sending the C<ev_async> watcher is required because otherwise
		3802	an event loop currently blocking in the kernel will have no knowledge
		3803	about the newly added timer. By waking up the loop it will pick up any new
		3804	watchers in the next event loop iteration.
		3805
		3806	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3807
		3808	While the overhead of a callback that e.g. schedules a thread is small, it
		3809	is still an overhead. If you embed libev, and your main usage is with some
		3810	kind of threads or coroutines, you might want to customise libev so that
		3811	doesn't need callbacks anymore.
		3812
		3813	Imagine you have coroutines that you can switch to using a function
		3814	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3815	and that due to some magic, the currently active coroutine is stored in a
		3816	global called C<current_coro>. Then you can build your own "wait for libev
		3817	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3818	the differing C<;> conventions):
		3819
		3820	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3821	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3822
		3823	That means instead of having a C callback function, you store the
		3824	coroutine to switch to in each watcher, and instead of having libev call
		3825	your callback, you instead have it switch to that coroutine.
		3826
		3827	A coroutine might now wait for an event with a function called
		3828	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3829	matter when, or whether the watcher is active or not when this function is
		3830	called):
		3831
		3832	void
		3833	wait_for_event (ev_watcher *w)
		3834	{
		3835	ev_cb_set (w) = current_coro;
		3836	switch_to (libev_coro);
		3837	}
		3838
		3839	That basically suspends the coroutine inside C<wait_for_event> and
		3840	continues the libev coroutine, which, when appropriate, switches back to
		3841	this or any other coroutine.
		3842
		3843	You can do similar tricks if you have, say, threads with an event queue -
		3844	instead of storing a coroutine, you store the queue object and instead of
		3845	switching to a coroutine, you push the watcher onto the queue and notify
		3846	any waiters.
		3847
		3848	To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two
		3849	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3850
		3851	// my_ev.h
		3852	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3853	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3854	#include "../libev/ev.h"
		3855
		3856	// my_ev.c
		3857	#define EV_H "my_ev.h"
		3858	#include "../libev/ev.c"
		3859
		3860	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3861	F<my_ev.c> into your project. When properly specifying include paths, you
		3862	can even use F<ev.h> as header file name directly.
3352		3863
3353		3864
3354	=head1 LIBEVENT EMULATION	3865	=head1 LIBEVENT EMULATION
3355		3866
3356	Libev offers a compatibility emulation layer for libevent. It cannot	3867	Libev offers a compatibility emulation layer for libevent. It cannot
3357	emulate the internals of libevent, so here are some usage hints:	3868	emulate the internals of libevent, so here are some usage hints:
3358		3869
3359	=over 4	3870	=over 4
		3871
		3872	=item * Only the libevent-1.4.1-beta API is being emulated.
		3873
		3874	This was the newest libevent version available when libev was implemented,
		3875	and is still mostly unchanged in 2010.
3360		3876
3361	=item * Use it by including <event.h>, as usual.	3877	=item * Use it by including <event.h>, as usual.
3362		3878
3363	=item * The following members are fully supported: ev_base, ev_callback,	3879	=item * The following members are fully supported: ev_base, ev_callback,
3364	ev_arg, ev_fd, ev_res, ev_events.	3880	ev_arg, ev_fd, ev_res, ev_events.
…		…
3370	=item * Priorities are not currently supported. Initialising priorities	3886	=item * Priorities are not currently supported. Initialising priorities
3371	will fail and all watchers will have the same priority, even though there	3887	will fail and all watchers will have the same priority, even though there
3372	is an ev_pri field.	3888	is an ev_pri field.
3373		3889
3374	=item * In libevent, the last base created gets the signals, in libev, the	3890	=item * In libevent, the last base created gets the signals, in libev, the
3375	first base created (== the default loop) gets the signals.	3891	base that registered the signal gets the signals.
3376		3892
3377	=item * Other members are not supported.	3893	=item * Other members are not supported.
3378		3894
3379	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3895	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3380	to use the libev header file and library.	3896	to use the libev header file and library.
3381		3897
3382	=back	3898	=back
3383		3899
3384	=head1 C++ SUPPORT	3900	=head1 C++ SUPPORT
		3901
		3902	=head2 C API
		3903
		3904	The normal C API should work fine when used from C++: both ev.h and the
		3905	libev sources can be compiled as C++. Therefore, code that uses the C API
		3906	will work fine.
		3907
		3908	Proper exception specifications might have to be added to callbacks passed
		3909	to libev: exceptions may be thrown only from watcher callbacks, all
		3910	other callbacks (allocator, syserr, loop acquire/release and periodioc
		3911	reschedule callbacks) must not throw exceptions, and might need a C<throw
		3912	()> specification. If you have code that needs to be compiled as both C
		3913	and C++ you can use the C<EV_THROW> macro for this:
		3914
		3915	static void
		3916	fatal_error (const char *msg) EV_THROW
		3917	{
		3918	perror (msg);
		3919	abort ();
		3920	}
		3921
		3922	...
		3923	ev_set_syserr_cb (fatal_error);
		3924
		3925	The only API functions that can currently throw exceptions are C<ev_run>,
		3926	C<ev_inoke> and C<ev_invoke_pending>.
		3927
		3928	Throwing exceptions in watcher callbacks is only supported if libev itself
		3929	is compiled with a C++ compiler or your C and C++ environments allow
		3930	throwing exceptions through C libraries (most do).
		3931
		3932	=head2 C++ API
3385		3933
3386	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3934	Libev comes with some simplistic wrapper classes for C++ that mainly allow
3387	you to use some convenience methods to start/stop watchers and also change	3935	you to use some convenience methods to start/stop watchers and also change
3388	the callback model to a model using method callbacks on objects.	3936	the callback model to a model using method callbacks on objects.
3389		3937
…		…
3399	Care has been taken to keep the overhead low. The only data member the C++	3947	Care has been taken to keep the overhead low. The only data member the C++
3400	classes add (compared to plain C-style watchers) is the event loop pointer	3948	classes add (compared to plain C-style watchers) is the event loop pointer
3401	that the watcher is associated with (or no additional members at all if	3949	that the watcher is associated with (or no additional members at all if
3402	you disable C<EV_MULTIPLICITY> when embedding libev).	3950	you disable C<EV_MULTIPLICITY> when embedding libev).
3403		3951
3404	Currently, functions, and static and non-static member functions can be	3952	Currently, functions, static and non-static member functions and classes
3405	used as callbacks. Other types should be easy to add as long as they only	3953	with C<operator ()> can be used as callbacks. Other types should be easy
3406	need one additional pointer for context. If you need support for other	3954	to add as long as they only need one additional pointer for context. If
3407	types of functors please contact the author (preferably after implementing	3955	you need support for other types of functors please contact the author
3408	it).	3956	(preferably after implementing it).
		3957
		3958	For all this to work, your C++ compiler either has to use the same calling
		3959	conventions as your C compiler (for static member functions), or you have
		3960	to embed libev and compile libev itself as C++.
3409		3961
3410	Here is a list of things available in the C<ev> namespace:	3962	Here is a list of things available in the C<ev> namespace:
3411		3963
3412	=over 4	3964	=over 4
3413		3965
…		…
3423	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	3975	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3424		3976
3425	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	3977	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
3426	the same name in the C<ev> namespace, with the exception of C<ev_signal>	3978	the same name in the C<ev> namespace, with the exception of C<ev_signal>
3427	which is called C<ev::sig> to avoid clashes with the C<signal> macro	3979	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3428	defines by many implementations.	3980	defined by many implementations.
3429		3981
3430	All of those classes have these methods:	3982	All of those classes have these methods:
3431		3983
3432	=over 4	3984	=over 4
3433		3985
…		…
3566	watchers in the constructor.	4118	watchers in the constructor.
3567		4119
3568	class myclass	4120	class myclass
3569	{	4121	{
3570	ev::io io ; void io_cb (ev::io &w, int revents);	4122	ev::io io ; void io_cb (ev::io &w, int revents);
3571	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);	4123	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3572	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4124	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3573		4125
3574	myclass (int fd)	4126	myclass (int fd)
3575	{	4127	{
3576	io .set <myclass, &myclass::io_cb > (this);	4128	io .set <myclass, &myclass::io_cb > (this);
…		…
3627	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4179	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3628		4180
3629	=item D	4181	=item D
3630		4182
3631	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4183	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3632	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4184	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3633		4185
3634	=item Ocaml	4186	=item Ocaml
3635		4187
3636	Erkki Seppala has written Ocaml bindings for libev, to be found at	4188	Erkki Seppala has written Ocaml bindings for libev, to be found at
3637	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4189	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
…		…
3685	suitable for use with C<EV_A>.	4237	suitable for use with C<EV_A>.
3686		4238
3687	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4239	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3688		4240
3689	Similar to the other two macros, this gives you the value of the default	4241	Similar to the other two macros, this gives you the value of the default
3690	loop, if multiple loops are supported ("ev loop default").	4242	loop, if multiple loops are supported ("ev loop default"). The default loop
		4243	will be initialised if it isn't already initialised.
		4244
		4245	For non-multiplicity builds, these macros do nothing, so you always have
		4246	to initialise the loop somewhere.
3691		4247
3692	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4248	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3693		4249
3694	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4250	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3695	default loop has been initialised (C<UC> == unchecked). Their behaviour	4251	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3840	supported). It will also not define any of the structs usually found in	4396	supported). It will also not define any of the structs usually found in
3841	F<event.h> that are not directly supported by the libev core alone.	4397	F<event.h> that are not directly supported by the libev core alone.
3842		4398
3843	In standalone mode, libev will still try to automatically deduce the	4399	In standalone mode, libev will still try to automatically deduce the
3844	configuration, but has to be more conservative.	4400	configuration, but has to be more conservative.
		4401
		4402	=item EV_USE_FLOOR
		4403
		4404	If defined to be C<1>, libev will use the C<floor ()> function for its
		4405	periodic reschedule calculations, otherwise libev will fall back on a
		4406	portable (slower) implementation. If you enable this, you usually have to
		4407	link against libm or something equivalent. Enabling this when the C<floor>
		4408	function is not available will fail, so the safe default is to not enable
		4409	this.
3845		4410
3846	=item EV_USE_MONOTONIC	4411	=item EV_USE_MONOTONIC
3847		4412
3848	If defined to be C<1>, libev will try to detect the availability of the	4413	If defined to be C<1>, libev will try to detect the availability of the
3849	monotonic clock option at both compile time and runtime. Otherwise no	4414	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3979	If defined to be C<1>, libev will compile in support for the Linux inotify	4544	If defined to be C<1>, libev will compile in support for the Linux inotify
3980	interface to speed up C<ev_stat> watchers. Its actual availability will	4545	interface to speed up C<ev_stat> watchers. Its actual availability will
3981	be detected at runtime. If undefined, it will be enabled if the headers	4546	be detected at runtime. If undefined, it will be enabled if the headers
3982	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4547	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3983		4548
		4549	=item EV_NO_SMP
		4550
		4551	If defined to be C<1>, libev will assume that memory is always coherent
		4552	between threads, that is, threads can be used, but threads never run on
		4553	different cpus (or different cpu cores). This reduces dependencies
		4554	and makes libev faster.
		4555
		4556	=item EV_NO_THREADS
		4557
		4558	If defined to be C<1>, libev will assume that it will never be called
		4559	from different threads, which is a stronger assumption than C<EV_NO_SMP>,
		4560	above. This reduces dependencies and makes libev faster.
		4561
3984	=item EV_ATOMIC_T	4562	=item EV_ATOMIC_T
3985		4563
3986	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4564	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3987	access is atomic with respect to other threads or signal contexts. No such	4565	access is atomic and serialised with respect to other threads or signal
3988	type is easily found in the C language, so you can provide your own type	4566	contexts. No such type is easily found in the C language, so you can
3989	that you know is safe for your purposes. It is used both for signal handler "locking"	4567	provide your own type that you know is safe for your purposes. It is used
3990	as well as for signal and thread safety in C<ev_async> watchers.	4568	both for signal handler "locking" as well as for signal and thread safety
		4569	in C<ev_async> watchers.
3991		4570
3992	In the absence of this define, libev will use C<sig_atomic_t volatile>	4571	In the absence of this define, libev will use C<sig_atomic_t volatile>
3993	(from F<signal.h>), which is usually good enough on most platforms.	4572	(from F<signal.h>), which is usually good enough on most platforms,
		4573	although strictly speaking using a type that also implies a memory fence
		4574	is required.
3994		4575
3995	=item EV_H (h)	4576	=item EV_H (h)
3996		4577
3997	The name of the F<ev.h> header file used to include it. The default if	4578	The name of the F<ev.h> header file used to include it. The default if
3998	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4579	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
…		…
4022	will have the C<struct ev_loop *> as first argument, and you can create	4603	will have the C<struct ev_loop *> as first argument, and you can create
4023	additional independent event loops. Otherwise there will be no support	4604	additional independent event loops. Otherwise there will be no support
4024	for multiple event loops and there is no first event loop pointer	4605	for multiple event loops and there is no first event loop pointer
4025	argument. Instead, all functions act on the single default loop.	4606	argument. Instead, all functions act on the single default loop.
4026		4607
		4608	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4609	default loop when multiplicity is switched off - you always have to
		4610	initialise the loop manually in this case.
		4611
4027	=item EV_MINPRI	4612	=item EV_MINPRI
4028		4613
4029	=item EV_MAXPRI	4614	=item EV_MAXPRI
4030		4615
4031	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4616	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
4067	#define EV_USE_POLL 1	4652	#define EV_USE_POLL 1
4068	#define EV_CHILD_ENABLE 1	4653	#define EV_CHILD_ENABLE 1
4069	#define EV_ASYNC_ENABLE 1	4654	#define EV_ASYNC_ENABLE 1
4070		4655
4071	The actual value is a bitset, it can be a combination of the following	4656	The actual value is a bitset, it can be a combination of the following
4072	values:	4657	values (by default, all of these are enabled):
4073		4658
4074	=over 4	4659	=over 4
4075		4660
4076	=item C<1> - faster/larger code	4661	=item C<1> - faster/larger code
4077		4662
…		…
4081	code size by roughly 30% on amd64).	4666	code size by roughly 30% on amd64).
4082		4667
4083	When optimising for size, use of compiler flags such as C<-Os> with	4668	When optimising for size, use of compiler flags such as C<-Os> with
4084	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of	4669	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
4085	assertions.	4670	assertions.
		4671
		4672	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4673	(e.g. gcc with C<-Os>).
4086		4674
4087	=item C<2> - faster/larger data structures	4675	=item C<2> - faster/larger data structures
4088		4676
4089	Replaces the small 2-heap for timer management by a faster 4-heap, larger	4677	Replaces the small 2-heap for timer management by a faster 4-heap, larger
4090	hash table sizes and so on. This will usually further increase code size	4678	hash table sizes and so on. This will usually further increase code size
4091	and can additionally have an effect on the size of data structures at	4679	and can additionally have an effect on the size of data structures at
4092	runtime.	4680	runtime.
4093		4681
		4682	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4683	(e.g. gcc with C<-Os>).
		4684
4094	=item C<4> - full API configuration	4685	=item C<4> - full API configuration
4095		4686
4096	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and	4687	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
4097	enables multiplicity (C<EV_MULTIPLICITY>=1).	4688	enables multiplicity (C<EV_MULTIPLICITY>=1).
4098		4689
…		…
4128		4719
4129	With an intelligent-enough linker (gcc+binutils are intelligent enough	4720	With an intelligent-enough linker (gcc+binutils are intelligent enough
4130	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by	4721	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
4131	your program might be left out as well - a binary starting a timer and an	4722	your program might be left out as well - a binary starting a timer and an
4132	I/O watcher then might come out at only 5Kb.	4723	I/O watcher then might come out at only 5Kb.
		4724
		4725	=item EV_API_STATIC
		4726
		4727	If this symbol is defined (by default it is not), then all identifiers
		4728	will have static linkage. This means that libev will not export any
		4729	identifiers, and you cannot link against libev anymore. This can be useful
		4730	when you embed libev, only want to use libev functions in a single file,
		4731	and do not want its identifiers to be visible.
		4732
		4733	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4734	wants to use libev.
		4735
		4736	This option only works when libev is compiled with a C compiler, as C++
		4737	doesn't support the required declaration syntax.
4133		4738
4134	=item EV_AVOID_STDIO	4739	=item EV_AVOID_STDIO
4135		4740
4136	If this is set to C<1> at compiletime, then libev will avoid using stdio	4741	If this is set to C<1> at compiletime, then libev will avoid using stdio
4137	functions (printf, scanf, perror etc.). This will increase the code size	4742	functions (printf, scanf, perror etc.). This will increase the code size
…		…
4281	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4886	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4282		4887
4283	#include "ev_cpp.h"	4888	#include "ev_cpp.h"
4284	#include "ev.c"	4889	#include "ev.c"
4285		4890
4286	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4891	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4287		4892
4288	=head2 THREADS AND COROUTINES	4893	=head2 THREADS AND COROUTINES
4289		4894
4290	=head3 THREADS	4895	=head3 THREADS
4291		4896
…		…
4342	default loop and triggering an C<ev_async> watcher from the default loop	4947	default loop and triggering an C<ev_async> watcher from the default loop
4343	watcher callback into the event loop interested in the signal.	4948	watcher callback into the event loop interested in the signal.
4344		4949
4345	=back	4950	=back
4346		4951
4347	=head4 THREAD LOCKING EXAMPLE	4952	See also L<THREAD LOCKING EXAMPLE>.
4348
4349	Here is a fictitious example of how to run an event loop in a different
4350	thread than where callbacks are being invoked and watchers are
4351	created/added/removed.
4352
4353	For a real-world example, see the C<EV::Loop::Async> perl module,
4354	which uses exactly this technique (which is suited for many high-level
4355	languages).
4356
4357	The example uses a pthread mutex to protect the loop data, a condition
4358	variable to wait for callback invocations, an async watcher to notify the
4359	event loop thread and an unspecified mechanism to wake up the main thread.
4360
4361	First, you need to associate some data with the event loop:
4362
4363	typedef struct {
4364	mutex_t lock; /* global loop lock */
4365	ev_async async_w;
4366	thread_t tid;
4367	cond_t invoke_cv;
4368	} userdata;
4369
4370	void prepare_loop (EV_P)
4371	{
4372	// for simplicity, we use a static userdata struct.
4373	static userdata u;
4374
4375	ev_async_init (&u->async_w, async_cb);
4376	ev_async_start (EV_A_ &u->async_w);
4377
4378	pthread_mutex_init (&u->lock, 0);
4379	pthread_cond_init (&u->invoke_cv, 0);
4380
4381	// now associate this with the loop
4382	ev_set_userdata (EV_A_ u);
4383	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4384	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4385
4386	// then create the thread running ev_loop
4387	pthread_create (&u->tid, 0, l_run, EV_A);
4388	}
4389
4390	The callback for the C<ev_async> watcher does nothing: the watcher is used
4391	solely to wake up the event loop so it takes notice of any new watchers
4392	that might have been added:
4393
4394	static void
4395	async_cb (EV_P_ ev_async *w, int revents)
4396	{
4397	// just used for the side effects
4398	}
4399
4400	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4401	protecting the loop data, respectively.
4402
4403	static void
4404	l_release (EV_P)
4405	{
4406	userdata *u = ev_userdata (EV_A);
4407	pthread_mutex_unlock (&u->lock);
4408	}
4409
4410	static void
4411	l_acquire (EV_P)
4412	{
4413	userdata *u = ev_userdata (EV_A);
4414	pthread_mutex_lock (&u->lock);
4415	}
4416
4417	The event loop thread first acquires the mutex, and then jumps straight
4418	into C<ev_run>:
4419
4420	void *
4421	l_run (void *thr_arg)
4422	{
4423	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4424
4425	l_acquire (EV_A);
4426	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4427	ev_run (EV_A_ 0);
4428	l_release (EV_A);
4429
4430	return 0;
4431	}
4432
4433	Instead of invoking all pending watchers, the C<l_invoke> callback will
4434	signal the main thread via some unspecified mechanism (signals? pipe
4435	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4436	have been called (in a while loop because a) spurious wakeups are possible
4437	and b) skipping inter-thread-communication when there are no pending
4438	watchers is very beneficial):
4439
4440	static void
4441	l_invoke (EV_P)
4442	{
4443	userdata *u = ev_userdata (EV_A);
4444
4445	while (ev_pending_count (EV_A))
4446	{
4447	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4448	pthread_cond_wait (&u->invoke_cv, &u->lock);
4449	}
4450	}
4451
4452	Now, whenever the main thread gets told to invoke pending watchers, it
4453	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4454	thread to continue:
4455
4456	static void
4457	real_invoke_pending (EV_P)
4458	{
4459	userdata *u = ev_userdata (EV_A);
4460
4461	pthread_mutex_lock (&u->lock);
4462	ev_invoke_pending (EV_A);
4463	pthread_cond_signal (&u->invoke_cv);
4464	pthread_mutex_unlock (&u->lock);
4465	}
4466
4467	Whenever you want to start/stop a watcher or do other modifications to an
4468	event loop, you will now have to lock:
4469
4470	ev_timer timeout_watcher;
4471	userdata *u = ev_userdata (EV_A);
4472
4473	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4474
4475	pthread_mutex_lock (&u->lock);
4476	ev_timer_start (EV_A_ &timeout_watcher);
4477	ev_async_send (EV_A_ &u->async_w);
4478	pthread_mutex_unlock (&u->lock);
4479
4480	Note that sending the C<ev_async> watcher is required because otherwise
4481	an event loop currently blocking in the kernel will have no knowledge
4482	about the newly added timer. By waking up the loop it will pick up any new
4483	watchers in the next event loop iteration.
4484		4953
4485	=head3 COROUTINES	4954	=head3 COROUTINES
4486		4955
4487	Libev is very accommodating to coroutines ("cooperative threads"):	4956	Libev is very accommodating to coroutines ("cooperative threads"):
4488	libev fully supports nesting calls to its functions from different	4957	libev fully supports nesting calls to its functions from different
…		…
4653	requires, and its I/O model is fundamentally incompatible with the POSIX	5122	requires, and its I/O model is fundamentally incompatible with the POSIX
4654	model. Libev still offers limited functionality on this platform in	5123	model. Libev still offers limited functionality on this platform in
4655	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5124	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4656	descriptors. This only applies when using Win32 natively, not when using	5125	descriptors. This only applies when using Win32 natively, not when using
4657	e.g. cygwin. Actually, it only applies to the microsofts own compilers,	5126	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
4658	as every compielr comes with a slightly differently broken/incompatible	5127	as every compiler comes with a slightly differently broken/incompatible
4659	environment.	5128	environment.
4660		5129
4661	Lifting these limitations would basically require the full	5130	Lifting these limitations would basically require the full
4662	re-implementation of the I/O system. If you are into this kind of thing,	5131	re-implementation of the I/O system. If you are into this kind of thing,
4663	then note that glib does exactly that for you in a very portable way (note	5132	then note that glib does exactly that for you in a very portable way (note
…		…
4757	structure (guaranteed by POSIX but not by ISO C for example), but it also	5226	structure (guaranteed by POSIX but not by ISO C for example), but it also
4758	assumes that the same (machine) code can be used to call any watcher	5227	assumes that the same (machine) code can be used to call any watcher
4759	callback: The watcher callbacks have different type signatures, but libev	5228	callback: The watcher callbacks have different type signatures, but libev
4760	calls them using an C<ev_watcher *> internally.	5229	calls them using an C<ev_watcher *> internally.
4761		5230
		5231	=item pointer accesses must be thread-atomic
		5232
		5233	Accessing a pointer value must be atomic, it must both be readable and
		5234	writable in one piece - this is the case on all current architectures.
		5235
4762	=item C<sig_atomic_t volatile> must be thread-atomic as well	5236	=item C<sig_atomic_t volatile> must be thread-atomic as well
4763		5237
4764	The type C<sig_atomic_t volatile> (or whatever is defined as	5238	The type C<sig_atomic_t volatile> (or whatever is defined as
4765	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5239	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
4766	threads. This is not part of the specification for C<sig_atomic_t>, but is	5240	threads. This is not part of the specification for C<sig_atomic_t>, but is
…		…
4791		5265
4792	The type C<double> is used to represent timestamps. It is required to	5266	The type C<double> is used to represent timestamps. It is required to
4793	have at least 51 bits of mantissa (and 9 bits of exponent), which is	5267	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4794	good enough for at least into the year 4000 with millisecond accuracy	5268	good enough for at least into the year 4000 with millisecond accuracy
4795	(the design goal for libev). This requirement is overfulfilled by	5269	(the design goal for libev). This requirement is overfulfilled by
4796	implementations using IEEE 754, which is basically all existing ones. With	5270	implementations using IEEE 754, which is basically all existing ones.
		5271
4797	IEEE 754 doubles, you get microsecond accuracy until at least 2200.	5272	With IEEE 754 doubles, you get microsecond accuracy until at least the
		5273	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5274	is either obsolete or somebody patched it to use C<long double> or
		5275	something like that, just kidding).
4798		5276
4799	=back	5277	=back
4800		5278
4801	If you know of other additional requirements drop me a note.	5279	If you know of other additional requirements drop me a note.
4802		5280
…		…
4864	=item Processing ev_async_send: O(number_of_async_watchers)	5342	=item Processing ev_async_send: O(number_of_async_watchers)
4865		5343
4866	=item Processing signals: O(max_signal_number)	5344	=item Processing signals: O(max_signal_number)
4867		5345
4868	Sending involves a system call I<iff> there were no other C<ev_async_send>	5346	Sending involves a system call I<iff> there were no other C<ev_async_send>
4869	calls in the current loop iteration. Checking for async and signal events	5347	calls in the current loop iteration and the loop is currently
		5348	blocked. Checking for async and signal events involves iterating over all
4870	involves iterating over all running async watchers or all signal numbers.	5349	running async watchers or all signal numbers.
4871		5350
4872	=back	5351	=back
4873		5352
4874		5353
4875	=head1 PORTING FROM LIBEV 3.X TO 4.X	5354	=head1 PORTING FROM LIBEV 3.X TO 4.X
4876		5355
4877	The major version 4 introduced some minor incompatible changes to the API.	5356	The major version 4 introduced some incompatible changes to the API.
4878		5357
4879	At the moment, the C<ev.h> header file tries to implement superficial	5358	At the moment, the C<ev.h> header file provides compatibility definitions
4880	compatibility, so most programs should still compile. Those might be	5359	for all changes, so most programs should still compile. The compatibility
4881	removed in later versions of libev, so better update early than late.	5360	layer might be removed in later versions of libev, so better update to the
		5361	new API early than late.
4882		5362
4883	=over 4	5363	=over 4
		5364
		5365	=item C<EV_COMPAT3> backwards compatibility mechanism
		5366
		5367	The backward compatibility mechanism can be controlled by
		5368	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5369	section.
4884		5370
4885	=item C<ev_default_destroy> and C<ev_default_fork> have been removed	5371	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
4886		5372
4887	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:	5373	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
4888		5374
…		…
4914	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme	5400	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
4915	as all other watcher types. Note that C<ev_loop_fork> is still called	5401	as all other watcher types. Note that C<ev_loop_fork> is still called
4916	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>	5402	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
4917	typedef.	5403	typedef.
4918		5404
4919	=item C<EV_COMPAT3> backwards compatibility mechanism
4920
4921	The backward compatibility mechanism can be controlled by
4922	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
4923	section.
4924
4925	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>	5405	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
4926		5406
4927	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different	5407	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
4928	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile	5408	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
4929	and work, but the library code will of course be larger.	5409	and work, but the library code will of course be larger.
…		…
4991	The physical time that is observed. It is apparently strictly monotonic :)	5471	The physical time that is observed. It is apparently strictly monotonic :)
4992		5472
4993	=item wall-clock time	5473	=item wall-clock time
4994		5474
4995	The time and date as shown on clocks. Unlike real time, it can actually	5475	The time and date as shown on clocks. Unlike real time, it can actually
4996	be wrong and jump forwards and backwards, e.g. when the you adjust your	5476	be wrong and jump forwards and backwards, e.g. when you adjust your
4997	clock.	5477	clock.
4998		5478
4999	=item watcher	5479	=item watcher
5000		5480
5001	A data structure that describes interest in certain events. Watchers need	5481	A data structure that describes interest in certain events. Watchers need
…		…
5003		5483
5004	=back	5484	=back
5005		5485
5006	=head1 AUTHOR	5486	=head1 AUTHOR
5007		5487
5008	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5488	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5489	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
5009		5490

Diff Legend

–	Removed lines
+	Added lines
<	Changed lines
>	Changed lines