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Revision 1.379 by root, Tue Jul 12 23:32:10 2011 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
…		…
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_update_now> 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))
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))
275		289
276	Set the callback function to call on a retryable system call error (such	290	Set the callback function to call on a retryable system call error (such
277	as failed select, poll, epoll_wait). The message is a printable string	291	as failed select, poll, epoll_wait). The message is a printable string
278	indicating the system call or subsystem causing the problem. If this	292	indicating the system call or subsystem causing the problem. If this
279	callback is set, then libev will expect it to remedy the situation, no	293	callback is set, then libev will expect it to remedy the situation, no
…		…
291	}	305	}
292		306
293	...	307	...
294	ev_set_syserr_cb (fatal_error);	308	ev_set_syserr_cb (fatal_error);
295		309
		310	=item ev_feed_signal (int signum)
		311
		312	This function can be used to "simulate" a signal receive. It is completely
		313	safe to call this function at any time, from any context, including signal
		314	handlers or random threads.
		315
		316	Its main use is to customise signal handling in your process, especially
		317	in the presence of threads. For example, you could block signals
		318	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		319	creating any loops), and in one thread, use C<sigwait> or any other
		320	mechanism to wait for signals, then "deliver" them to libev by calling
		321	C<ev_feed_signal>.
		322
296	=back	323	=back
297		324
298	=head1 FUNCTIONS CONTROLLING EVENT LOOPS	325	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
299		326
300	An event loop is described by a C<struct ev_loop *> (the C<struct> is	327	An event loop is described by a C<struct ev_loop *> (the C<struct> is
301	I<not> optional in this case unless libev 3 compatibility is disabled, as	328	I<not> optional in this case unless libev 3 compatibility is disabled, as
302	libev 3 had an C<ev_loop> function colliding with the struct name).	329	libev 3 had an C<ev_loop> function colliding with the struct name).
303		330
304	The library knows two types of such loops, the I<default> loop, which	331	The library knows two types of such loops, the I<default> loop, which
305	supports signals and child events, and dynamically created event loops	332	supports child process events, and dynamically created event loops which
306	which do not.	333	do not.
307		334
308	=over 4	335	=over 4
309		336
310	=item struct ev_loop *ev_default_loop (unsigned int flags)	337	=item struct ev_loop *ev_default_loop (unsigned int flags)
311		338
…		…
342	Example: Restrict libev to the select and poll backends, and do not allow	369	Example: Restrict libev to the select and poll backends, and do not allow
343	environment settings to be taken into account:	370	environment settings to be taken into account:
344		371
345	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	372	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
346		373
347	Example: Use whatever libev has to offer, but make sure that kqueue is
348	used if available (warning, breaks stuff, best use only with your own
349	private event loop and only if you know the OS supports your types of
350	fds):
351
352	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
353
354	=item struct ev_loop *ev_loop_new (unsigned int flags)	374	=item struct ev_loop *ev_loop_new (unsigned int flags)
355		375
356	This will create and initialise a new event loop object. If the loop	376	This will create and initialise a new event loop object. If the loop
357	could not be initialised, returns false.	377	could not be initialised, returns false.
358		378
359	Note that this function I<is> thread-safe, and one common way to use	379	This function is thread-safe, and one common way to use libev with
360	libev with threads is indeed to create one loop per thread, and using the	380	threads is indeed to create one loop per thread, and using the default
361	default loop in the "main" or "initial" thread.	381	loop in the "main" or "initial" thread.
362		382
363	The flags argument can be used to specify special behaviour or specific	383	The flags argument can be used to specify special behaviour or specific
364	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	384	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
365		385
366	The following flags are supported:	386	The following flags are supported:
…		…
401	environment variable.	421	environment variable.
402		422
403	=item C<EVFLAG_NOINOTIFY>	423	=item C<EVFLAG_NOINOTIFY>
404		424
405	When this flag is specified, then libev will not attempt to use the	425	When this flag is specified, then libev will not attempt to use the
406	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and	426	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
407	testing, this flag can be useful to conserve inotify file descriptors, as	427	testing, this flag can be useful to conserve inotify file descriptors, as
408	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.	428	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
409		429
410	=item C<EVFLAG_SIGNALFD>	430	=item C<EVFLAG_SIGNALFD>
411		431
412	When this flag is specified, then libev will attempt to use the	432	When this flag is specified, then libev will attempt to use the
413	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API	433	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
414	delivers signals synchronously, which makes it both faster and might make	434	delivers signals synchronously, which makes it both faster and might make
415	it possible to get the queued signal data. It can also simplify signal	435	it possible to get the queued signal data. It can also simplify signal
416	handling with threads, as long as you properly block signals in your	436	handling with threads, as long as you properly block signals in your
417	threads that are not interested in handling them.	437	threads that are not interested in handling them.
418		438
419	Signalfd will not be used by default as this changes your signal mask, and	439	Signalfd will not be used by default as this changes your signal mask, and
420	there are a lot of shoddy libraries and programs (glib's threadpool for	440	there are a lot of shoddy libraries and programs (glib's threadpool for
421	example) that can't properly initialise their signal masks.	441	example) that can't properly initialise their signal masks.
		442
		443	=item C<EVFLAG_NOSIGMASK>
		444
		445	When this flag is specified, then libev will avoid to modify the signal
		446	mask. Specifically, this means you have to make sure signals are unblocked
		447	when you want to receive them.
		448
		449	This behaviour is useful when you want to do your own signal handling, or
		450	want to handle signals only in specific threads and want to avoid libev
		451	unblocking the signals.
		452
		453	It's also required by POSIX in a threaded program, as libev calls
		454	C<sigprocmask>, whose behaviour is officially unspecified.
		455
		456	This flag's behaviour will become the default in future versions of libev.
422		457
423	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	458	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
424		459
425	This is your standard select(2) backend. Not I<completely> standard, as	460	This is your standard select(2) backend. Not I<completely> standard, as
426	libev tries to roll its own fd_set with no limits on the number of fds,	461	libev tries to roll its own fd_set with no limits on the number of fds,
…		…
454	=item C<EVBACKEND_EPOLL> (value 4, Linux)	489	=item C<EVBACKEND_EPOLL> (value 4, Linux)
455		490
456	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9	491	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
457	kernels).	492	kernels).
458		493
459	For few fds, this backend is a bit little slower than poll and select,	494	For few fds, this backend is a bit little slower than poll and select, but
460	but it scales phenomenally better. While poll and select usually scale	495	it scales phenomenally better. While poll and select usually scale like
461	like O(total_fds) where n is the total number of fds (or the highest fd),	496	O(total_fds) where total_fds is the total number of fds (or the highest
462	epoll scales either O(1) or O(active_fds).	497	fd), epoll scales either O(1) or O(active_fds).
463		498
464	The epoll mechanism deserves honorable mention as the most misdesigned	499	The epoll mechanism deserves honorable mention as the most misdesigned
465	of the more advanced event mechanisms: mere annoyances include silently	500	of the more advanced event mechanisms: mere annoyances include silently
466	dropping file descriptors, requiring a system call per change per file	501	dropping file descriptors, requiring a system call per change per file
467	descriptor (and unnecessary guessing of parameters), problems with dup and	502	descriptor (and unnecessary guessing of parameters), problems with dup,
		503	returning before the timeout value, resulting in additional iterations
		504	(and only giving 5ms accuracy while select on the same platform gives
468	so on. The biggest issue is fork races, however - if a program forks then	505	0.1ms) and so on. The biggest issue is fork races, however - if a program
469	I<both> parent and child process have to recreate the epoll set, which can	506	forks then I<both> parent and child process have to recreate the epoll
470	take considerable time (one syscall per file descriptor) and is of course	507	set, which can take considerable time (one syscall per file descriptor)
471	hard to detect.	508	and is of course hard to detect.
472		509
473	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	510	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
474	of course I<doesn't>, and epoll just loves to report events for totally	511	but of course I<doesn't>, and epoll just loves to report events for
475	I<different> file descriptors (even already closed ones, so one cannot	512	totally I<different> file descriptors (even already closed ones, so
476	even remove them from the set) than registered in the set (especially	513	one cannot even remove them from the set) than registered in the set
477	on SMP systems). Libev tries to counter these spurious notifications by	514	(especially on SMP systems). Libev tries to counter these spurious
478	employing an additional generation counter and comparing that against the	515	notifications by employing an additional generation counter and comparing
479	events to filter out spurious ones, recreating the set when required. Last	516	that against the events to filter out spurious ones, recreating the set
		517	when required. Epoll also erroneously rounds down timeouts, but gives you
		518	no way to know when and by how much, so sometimes you have to busy-wait
		519	because epoll returns immediately despite a nonzero timeout. And last
480	not least, it also refuses to work with some file descriptors which work	520	not least, it also refuses to work with some file descriptors which work
481	perfectly fine with C<select> (files, many character devices...).	521	perfectly fine with C<select> (files, many character devices...).
		522
		523	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
		524	cobbled together in a hurry, no thought to design or interaction with
		525	others. Oh, the pain, will it ever stop...
482		526
483	While stopping, setting and starting an I/O watcher in the same iteration	527	While stopping, setting and starting an I/O watcher in the same iteration
484	will result in some caching, there is still a system call per such	528	will result in some caching, there is still a system call per such
485	incident (because the same I<file descriptor> could point to a different	529	incident (because the same I<file descriptor> could point to a different
486	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	530	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
552	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	596	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
553		597
554	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	598	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
555	it's really slow, but it still scales very well (O(active_fds)).	599	it's really slow, but it still scales very well (O(active_fds)).
556		600
557	Please note that Solaris event ports can deliver a lot of spurious
558	notifications, so you need to use non-blocking I/O or other means to avoid
559	blocking when no data (or space) is available.
560
561	While this backend scales well, it requires one system call per active	601	While this backend scales well, it requires one system call per active
562	file descriptor per loop iteration. For small and medium numbers of file	602	file descriptor per loop iteration. For small and medium numbers of file
563	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	603	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
564	might perform better.	604	might perform better.
565		605
566	On the positive side, with the exception of the spurious readiness	606	On the positive side, this backend actually performed fully to
567	notifications, this backend actually performed fully to specification
568	in all tests and is fully embeddable, which is a rare feat among the	607	specification in all tests and is fully embeddable, which is a rare feat
569	OS-specific backends (I vastly prefer correctness over speed hacks).	608	among the OS-specific backends (I vastly prefer correctness over speed
		609	hacks).
		610
		611	On the negative side, the interface is I<bizarre> - so bizarre that
		612	even sun itself gets it wrong in their code examples: The event polling
		613	function sometimes returns events to the caller even though an error
		614	occurred, but with no indication whether it has done so or not (yes, it's
		615	even documented that way) - deadly for edge-triggered interfaces where you
		616	absolutely have to know whether an event occurred or not because you have
		617	to re-arm the watcher.
		618
		619	Fortunately libev seems to be able to work around these idiocies.
570		620
571	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	621	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
572	C<EVBACKEND_POLL>.	622	C<EVBACKEND_POLL>.
573		623
574	=item C<EVBACKEND_ALL>	624	=item C<EVBACKEND_ALL>
575		625
576	Try all backends (even potentially broken ones that wouldn't be tried	626	Try all backends (even potentially broken ones that wouldn't be tried
577	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	627	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
578	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	628	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
579		629
580	It is definitely not recommended to use this flag.	630	It is definitely not recommended to use this flag, use whatever
		631	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		632	at all.
		633
		634	=item C<EVBACKEND_MASK>
		635
		636	Not a backend at all, but a mask to select all backend bits from a
		637	C<flags> value, in case you want to mask out any backends from a flags
		638	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
581		639
582	=back	640	=back
583		641
584	If one or more of the backend flags are or'ed into the flags value,	642	If one or more of the backend flags are or'ed into the flags value,
585	then only these backends will be tried (in the reverse order as listed	643	then only these backends will be tried (in the reverse order as listed
…		…
589	Example: Try to create a event loop that uses epoll and nothing else.	647	Example: Try to create a event loop that uses epoll and nothing else.
590		648
591	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	649	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
592	if (!epoller)	650	if (!epoller)
593	fatal ("no epoll found here, maybe it hides under your chair");	651	fatal ("no epoll found here, maybe it hides under your chair");
		652
		653	Example: Use whatever libev has to offer, but make sure that kqueue is
		654	used if available.
		655
		656	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
594		657
595	=item ev_loop_destroy (loop)	658	=item ev_loop_destroy (loop)
596		659
597	Destroys an event loop object (frees all memory and kernel state	660	Destroys an event loop object (frees all memory and kernel state
598	etc.). None of the active event watchers will be stopped in the normal	661	etc.). None of the active event watchers will be stopped in the normal
…		…
609	This function is normally used on loop objects allocated by	672	This function is normally used on loop objects allocated by
610	C<ev_loop_new>, but it can also be used on the default loop returned by	673	C<ev_loop_new>, but it can also be used on the default loop returned by
611	C<ev_default_loop>, in which case it is not thread-safe.	674	C<ev_default_loop>, in which case it is not thread-safe.
612		675
613	Note that it is not advisable to call this function on the default loop	676	Note that it is not advisable to call this function on the default loop
614	except in the rare occasion where you really need to free it's resources.	677	except in the rare occasion where you really need to free its resources.
615	If you need dynamically allocated loops it is better to use C<ev_loop_new>	678	If you need dynamically allocated loops it is better to use C<ev_loop_new>
616	and C<ev_loop_destroy>.	679	and C<ev_loop_destroy>.
617		680
618	=item ev_loop_fork (loop)	681	=item ev_loop_fork (loop)
619		682
…		…
667	prepare and check phases.	730	prepare and check phases.
668		731
669	=item unsigned int ev_depth (loop)	732	=item unsigned int ev_depth (loop)
670		733
671	Returns the number of times C<ev_run> was entered minus the number of	734	Returns the number of times C<ev_run> was entered minus the number of
672	times C<ev_run> was exited, in other words, the recursion depth.	735	times C<ev_run> was exited normally, in other words, the recursion depth.
673		736
674	Outside C<ev_run>, this number is zero. In a callback, this number is	737	Outside C<ev_run>, this number is zero. In a callback, this number is
675	C<1>, unless C<ev_run> was invoked recursively (or from another thread),	738	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
676	in which case it is higher.	739	in which case it is higher.
677		740
678	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread	741	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
679	etc.), doesn't count as "exit" - consider this as a hint to avoid such	742	throwing an exception etc.), doesn't count as "exit" - consider this
680	ungentleman-like behaviour unless it's really convenient.	743	as a hint to avoid such ungentleman-like behaviour unless it's really
		744	convenient, in which case it is fully supported.
681		745
682	=item unsigned int ev_backend (loop)	746	=item unsigned int ev_backend (loop)
683		747
684	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	748	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
685	use.	749	use.
…		…
747	finished (especially in interactive programs), but having a program	811	finished (especially in interactive programs), but having a program
748	that automatically loops as long as it has to and no longer by virtue	812	that automatically loops as long as it has to and no longer by virtue
749	of relying on its watchers stopping correctly, that is truly a thing of	813	of relying on its watchers stopping correctly, that is truly a thing of
750	beauty.	814	beauty.
751		815
		816	This function is also I<mostly> exception-safe - you can break out of
		817	a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		818	exception and so on. This does not decrement the C<ev_depth> value, nor
		819	will it clear any outstanding C<EVBREAK_ONE> breaks.
		820
752	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle	821	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
753	those events and any already outstanding ones, but will not wait and	822	those events and any already outstanding ones, but will not wait and
754	block your process in case there are no events and will return after one	823	block your process in case there are no events and will return after one
755	iteration of the loop. This is sometimes useful to poll and handle new	824	iteration of the loop. This is sometimes useful to poll and handle new
756	events while doing lengthy calculations, to keep the program responsive.	825	events while doing lengthy calculations, to keep the program responsive.
…		…
765	This is useful if you are waiting for some external event in conjunction	834	This is useful if you are waiting for some external event in conjunction
766	with something not expressible using other libev watchers (i.e. "roll your	835	with something not expressible using other libev watchers (i.e. "roll your
767	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	836	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
768	usually a better approach for this kind of thing.	837	usually a better approach for this kind of thing.
769		838
770	Here are the gory details of what C<ev_run> does:	839	Here are the gory details of what C<ev_run> does (this is for your
		840	understanding, not a guarantee that things will work exactly like this in
		841	future versions):
771		842
772	- Increment loop depth.	843	- Increment loop depth.
773	- Reset the ev_break status.	844	- Reset the ev_break status.
774	- Before the first iteration, call any pending watchers.	845	- Before the first iteration, call any pending watchers.
775	LOOP:	846	LOOP:
…		…
808	anymore.	879	anymore.
809		880
810	... queue jobs here, make sure they register event watchers as long	881	... queue jobs here, make sure they register event watchers as long
811	... as they still have work to do (even an idle watcher will do..)	882	... as they still have work to do (even an idle watcher will do..)
812	ev_run (my_loop, 0);	883	ev_run (my_loop, 0);
813	... jobs done or somebody called unloop. yeah!	884	... jobs done or somebody called break. yeah!
814		885
815	=item ev_break (loop, how)	886	=item ev_break (loop, how)
816		887
817	Can be used to make a call to C<ev_run> return early (but only after it	888	Can be used to make a call to C<ev_run> return early (but only after it
818	has processed all outstanding events). The C<how> argument must be either	889	has processed all outstanding events). The C<how> argument must be either
819	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or	890	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
820	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.	891	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
821		892
822	This "unloop state" will be cleared when entering C<ev_run> again.	893	This "break state" will be cleared on the next call to C<ev_run>.
823		894
824	It is safe to call C<ev_break> from outside any C<ev_run> calls. ##TODO##	895	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		896	which case it will have no effect.
825		897
826	=item ev_ref (loop)	898	=item ev_ref (loop)
827		899
828	=item ev_unref (loop)	900	=item ev_unref (loop)
829		901
…		…
850	running when nothing else is active.	922	running when nothing else is active.
851		923
852	ev_signal exitsig;	924	ev_signal exitsig;
853	ev_signal_init (&exitsig, sig_cb, SIGINT);	925	ev_signal_init (&exitsig, sig_cb, SIGINT);
854	ev_signal_start (loop, &exitsig);	926	ev_signal_start (loop, &exitsig);
855	evf_unref (loop);	927	ev_unref (loop);
856		928
857	Example: For some weird reason, unregister the above signal handler again.	929	Example: For some weird reason, unregister the above signal handler again.
858		930
859	ev_ref (loop);	931	ev_ref (loop);
860	ev_signal_stop (loop, &exitsig);	932	ev_signal_stop (loop, &exitsig);
…		…
880	overhead for the actual polling but can deliver many events at once.	952	overhead for the actual polling but can deliver many events at once.
881		953
882	By setting a higher I<io collect interval> you allow libev to spend more	954	By setting a higher I<io collect interval> you allow libev to spend more
883	time collecting I/O events, so you can handle more events per iteration,	955	time collecting I/O events, so you can handle more events per iteration,
884	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	956	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
885	C<ev_timer>) will be not affected. Setting this to a non-null value will	957	C<ev_timer>) will not be affected. Setting this to a non-null value will
886	introduce an additional C<ev_sleep ()> call into most loop iterations. The	958	introduce an additional C<ev_sleep ()> call into most loop iterations. The
887	sleep time ensures that libev will not poll for I/O events more often then	959	sleep time ensures that libev will not poll for I/O events more often then
888	once per this interval, on average.	960	once per this interval, on average (as long as the host time resolution is
		961	good enough).
889		962
890	Likewise, by setting a higher I<timeout collect interval> you allow libev	963	Likewise, by setting a higher I<timeout collect interval> you allow libev
891	to spend more time collecting timeouts, at the expense of increased	964	to spend more time collecting timeouts, at the expense of increased
892	latency/jitter/inexactness (the watcher callback will be called	965	latency/jitter/inexactness (the watcher callback will be called
893	later). C<ev_io> watchers will not be affected. Setting this to a non-null	966	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
972	See also the locking example in the C<THREADS> section later in this	1045	See also the locking example in the C<THREADS> section later in this
973	document.	1046	document.
974		1047
975	=item ev_set_userdata (loop, void *data)	1048	=item ev_set_userdata (loop, void *data)
976		1049
977	=item ev_userdata (loop)	1050	=item void *ev_userdata (loop)
978		1051
979	Set and retrieve a single C<void *> associated with a loop. When	1052	Set and retrieve a single C<void *> associated with a loop. When
980	C<ev_set_userdata> has never been called, then C<ev_userdata> returns	1053	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
981	C<0.>	1054	C<0>.
982		1055
983	These two functions can be used to associate arbitrary data with a loop,	1056	These two functions can be used to associate arbitrary data with a loop,
984	and are intended solely for the C<invoke_pending_cb>, C<release> and	1057	and are intended solely for the C<invoke_pending_cb>, C<release> and
985	C<acquire> callbacks described above, but of course can be (ab-)used for	1058	C<acquire> callbacks described above, but of course can be (ab-)used for
986	any other purpose as well.	1059	any other purpose as well.
…		…
1114	=item C<EV_FORK>	1187	=item C<EV_FORK>
1115		1188
1116	The event loop has been resumed in the child process after fork (see	1189	The event loop has been resumed in the child process after fork (see
1117	C<ev_fork>).	1190	C<ev_fork>).
1118		1191
		1192	=item C<EV_CLEANUP>
		1193
		1194	The event loop is about to be destroyed (see C<ev_cleanup>).
		1195
1119	=item C<EV_ASYNC>	1196	=item C<EV_ASYNC>
1120		1197
1121	The given async watcher has been asynchronously notified (see C<ev_async>).	1198	The given async watcher has been asynchronously notified (see C<ev_async>).
1122		1199
1123	=item C<EV_CUSTOM>	1200	=item C<EV_CUSTOM>
…		…
1144	programs, though, as the fd could already be closed and reused for another	1221	programs, though, as the fd could already be closed and reused for another
1145	thing, so beware.	1222	thing, so beware.
1146		1223
1147	=back	1224	=back
1148		1225
		1226	=head2 GENERIC WATCHER FUNCTIONS
		1227
		1228	=over 4
		1229
		1230	=item C<ev_init> (ev_TYPE *watcher, callback)
		1231
		1232	This macro initialises the generic portion of a watcher. The contents
		1233	of the watcher object can be arbitrary (so C<malloc> will do). Only
		1234	the generic parts of the watcher are initialised, you I<need> to call
		1235	the type-specific C<ev_TYPE_set> macro afterwards to initialise the
		1236	type-specific parts. For each type there is also a C<ev_TYPE_init> macro
		1237	which rolls both calls into one.
		1238
		1239	You can reinitialise a watcher at any time as long as it has been stopped
		1240	(or never started) and there are no pending events outstanding.
		1241
		1242	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
		1243	int revents)>.
		1244
		1245	Example: Initialise an C<ev_io> watcher in two steps.
		1246
		1247	ev_io w;
		1248	ev_init (&w, my_cb);
		1249	ev_io_set (&w, STDIN_FILENO, EV_READ);
		1250
		1251	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
		1252
		1253	This macro initialises the type-specific parts of a watcher. You need to
		1254	call C<ev_init> at least once before you call this macro, but you can
		1255	call C<ev_TYPE_set> any number of times. You must not, however, call this
		1256	macro on a watcher that is active (it can be pending, however, which is a
		1257	difference to the C<ev_init> macro).
		1258
		1259	Although some watcher types do not have type-specific arguments
		1260	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
		1261
		1262	See C<ev_init>, above, for an example.
		1263
		1264	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
		1265
		1266	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
		1267	calls into a single call. This is the most convenient method to initialise
		1268	a watcher. The same limitations apply, of course.
		1269
		1270	Example: Initialise and set an C<ev_io> watcher in one step.
		1271
		1272	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1273
		1274	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
		1275
		1276	Starts (activates) the given watcher. Only active watchers will receive
		1277	events. If the watcher is already active nothing will happen.
		1278
		1279	Example: Start the C<ev_io> watcher that is being abused as example in this
		1280	whole section.
		1281
		1282	ev_io_start (EV_DEFAULT_UC, &w);
		1283
		1284	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
		1285
		1286	Stops the given watcher if active, and clears the pending status (whether
		1287	the watcher was active or not).
		1288
		1289	It is possible that stopped watchers are pending - for example,
		1290	non-repeating timers are being stopped when they become pending - but
		1291	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
		1292	pending. If you want to free or reuse the memory used by the watcher it is
		1293	therefore a good idea to always call its C<ev_TYPE_stop> function.
		1294
		1295	=item bool ev_is_active (ev_TYPE *watcher)
		1296
		1297	Returns a true value iff the watcher is active (i.e. it has been started
		1298	and not yet been stopped). As long as a watcher is active you must not modify
		1299	it.
		1300
		1301	=item bool ev_is_pending (ev_TYPE *watcher)
		1302
		1303	Returns a true value iff the watcher is pending, (i.e. it has outstanding
		1304	events but its callback has not yet been invoked). As long as a watcher
		1305	is pending (but not active) you must not call an init function on it (but
		1306	C<ev_TYPE_set> is safe), you must not change its priority, and you must
		1307	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		1308	it).
		1309
		1310	=item callback ev_cb (ev_TYPE *watcher)
		1311
		1312	Returns the callback currently set on the watcher.
		1313
		1314	=item ev_cb_set (ev_TYPE *watcher, callback)
		1315
		1316	Change the callback. You can change the callback at virtually any time
		1317	(modulo threads).
		1318
		1319	=item ev_set_priority (ev_TYPE *watcher, int priority)
		1320
		1321	=item int ev_priority (ev_TYPE *watcher)
		1322
		1323	Set and query the priority of the watcher. The priority is a small
		1324	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		1325	(default: C<-2>). Pending watchers with higher priority will be invoked
		1326	before watchers with lower priority, but priority will not keep watchers
		1327	from being executed (except for C<ev_idle> watchers).
		1328
		1329	If you need to suppress invocation when higher priority events are pending
		1330	you need to look at C<ev_idle> watchers, which provide this functionality.
		1331
		1332	You I<must not> change the priority of a watcher as long as it is active or
		1333	pending.
		1334
		1335	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1336	fine, as long as you do not mind that the priority value you query might
		1337	or might not have been clamped to the valid range.
		1338
		1339	The default priority used by watchers when no priority has been set is
		1340	always C<0>, which is supposed to not be too high and not be too low :).
		1341
		1342	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
		1343	priorities.
		1344
		1345	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		1346
		1347	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		1348	C<loop> nor C<revents> need to be valid as long as the watcher callback
		1349	can deal with that fact, as both are simply passed through to the
		1350	callback.
		1351
		1352	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		1353
		1354	If the watcher is pending, this function clears its pending status and
		1355	returns its C<revents> bitset (as if its callback was invoked). If the
		1356	watcher isn't pending it does nothing and returns C<0>.
		1357
		1358	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1359	callback to be invoked, which can be accomplished with this function.
		1360
		1361	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1362
		1363	Feeds the given event set into the event loop, as if the specified event
		1364	had happened for the specified watcher (which must be a pointer to an
		1365	initialised but not necessarily started event watcher). Obviously you must
		1366	not free the watcher as long as it has pending events.
		1367
		1368	Stopping the watcher, letting libev invoke it, or calling
		1369	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1370	not started in the first place.
		1371
		1372	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1373	functions that do not need a watcher.
		1374
		1375	=back
		1376
		1377	See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR
		1378	OWN COMPOSITE WATCHERS> idioms.
		1379
1149	=head2 WATCHER STATES	1380	=head2 WATCHER STATES
1150		1381
1151	There are various watcher states mentioned throughout this manual -	1382	There are various watcher states mentioned throughout this manual -
1152	active, pending and so on. In this section these states and the rules to	1383	active, pending and so on. In this section these states and the rules to
1153	transition between them will be described in more detail - and while these	1384	transition between them will be described in more detail - and while these
…		…
1155		1386
1156	=over 4	1387	=over 4
1157		1388
1158	=item initialiased	1389	=item initialiased
1159		1390
1160	Before a watcher can be registered with the event looop it has to be	1391	Before a watcher can be registered with the event loop it has to be
1161	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to	1392	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
1162	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.	1393	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1163		1394
1164	In this state it is simply some block of memory that is suitable for use	1395	In this state it is simply some block of memory that is suitable for
1165	in an event loop. It can be moved around, freed, reused etc. at will.	1396	use in an event loop. It can be moved around, freed, reused etc. at
		1397	will - as long as you either keep the memory contents intact, or call
		1398	C<ev_TYPE_init> again.
1166		1399
1167	=item started/running/active	1400	=item started/running/active
1168		1401
1169	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes	1402	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1170	property of the event loop, and is actively waiting for events. While in	1403	property of the event loop, and is actively waiting for events. While in
…		…
1198	latter will clear any pending state the watcher might be in, regardless	1431	latter will clear any pending state the watcher might be in, regardless
1199	of whether it was active or not, so stopping a watcher explicitly before	1432	of whether it was active or not, so stopping a watcher explicitly before
1200	freeing it is often a good idea.	1433	freeing it is often a good idea.
1201		1434
1202	While stopped (and not pending) the watcher is essentially in the	1435	While stopped (and not pending) the watcher is essentially in the
1203	initialised state, that is it can be reused, moved, modified in any way	1436	initialised state, that is, it can be reused, moved, modified in any way
1204	you wish.	1437	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1438	it again).
1205		1439
1206	=back	1440	=back
1207
1208	=head2 GENERIC WATCHER FUNCTIONS
1209
1210	=over 4
1211
1212	=item C<ev_init> (ev_TYPE *watcher, callback)
1213
1214	This macro initialises the generic portion of a watcher. The contents
1215	of the watcher object can be arbitrary (so C<malloc> will do). Only
1216	the generic parts of the watcher are initialised, you I<need> to call
1217	the type-specific C<ev_TYPE_set> macro afterwards to initialise the
1218	type-specific parts. For each type there is also a C<ev_TYPE_init> macro
1219	which rolls both calls into one.
1220
1221	You can reinitialise a watcher at any time as long as it has been stopped
1222	(or never started) and there are no pending events outstanding.
1223
1224	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
1225	int revents)>.
1226
1227	Example: Initialise an C<ev_io> watcher in two steps.
1228
1229	ev_io w;
1230	ev_init (&w, my_cb);
1231	ev_io_set (&w, STDIN_FILENO, EV_READ);
1232
1233	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
1234
1235	This macro initialises the type-specific parts of a watcher. You need to
1236	call C<ev_init> at least once before you call this macro, but you can
1237	call C<ev_TYPE_set> any number of times. You must not, however, call this
1238	macro on a watcher that is active (it can be pending, however, which is a
1239	difference to the C<ev_init> macro).
1240
1241	Although some watcher types do not have type-specific arguments
1242	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
1243
1244	See C<ev_init>, above, for an example.
1245
1246	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
1247
1248	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
1249	calls into a single call. This is the most convenient method to initialise
1250	a watcher. The same limitations apply, of course.
1251
1252	Example: Initialise and set an C<ev_io> watcher in one step.
1253
1254	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1255
1256	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1257
1258	Starts (activates) the given watcher. Only active watchers will receive
1259	events. If the watcher is already active nothing will happen.
1260
1261	Example: Start the C<ev_io> watcher that is being abused as example in this
1262	whole section.
1263
1264	ev_io_start (EV_DEFAULT_UC, &w);
1265
1266	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1267
1268	Stops the given watcher if active, and clears the pending status (whether
1269	the watcher was active or not).
1270
1271	It is possible that stopped watchers are pending - for example,
1272	non-repeating timers are being stopped when they become pending - but
1273	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
1274	pending. If you want to free or reuse the memory used by the watcher it is
1275	therefore a good idea to always call its C<ev_TYPE_stop> function.
1276
1277	=item bool ev_is_active (ev_TYPE *watcher)
1278
1279	Returns a true value iff the watcher is active (i.e. it has been started
1280	and not yet been stopped). As long as a watcher is active you must not modify
1281	it.
1282
1283	=item bool ev_is_pending (ev_TYPE *watcher)
1284
1285	Returns a true value iff the watcher is pending, (i.e. it has outstanding
1286	events but its callback has not yet been invoked). As long as a watcher
1287	is pending (but not active) you must not call an init function on it (but
1288	C<ev_TYPE_set> is safe), you must not change its priority, and you must
1289	make sure the watcher is available to libev (e.g. you cannot C<free ()>
1290	it).
1291
1292	=item callback ev_cb (ev_TYPE *watcher)
1293
1294	Returns the callback currently set on the watcher.
1295
1296	=item ev_cb_set (ev_TYPE *watcher, callback)
1297
1298	Change the callback. You can change the callback at virtually any time
1299	(modulo threads).
1300
1301	=item ev_set_priority (ev_TYPE *watcher, int priority)
1302
1303	=item int ev_priority (ev_TYPE *watcher)
1304
1305	Set and query the priority of the watcher. The priority is a small
1306	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1307	(default: C<-2>). Pending watchers with higher priority will be invoked
1308	before watchers with lower priority, but priority will not keep watchers
1309	from being executed (except for C<ev_idle> watchers).
1310
1311	If you need to suppress invocation when higher priority events are pending
1312	you need to look at C<ev_idle> watchers, which provide this functionality.
1313
1314	You I<must not> change the priority of a watcher as long as it is active or
1315	pending.
1316
1317	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1318	fine, as long as you do not mind that the priority value you query might
1319	or might not have been clamped to the valid range.
1320
1321	The default priority used by watchers when no priority has been set is
1322	always C<0>, which is supposed to not be too high and not be too low :).
1323
1324	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1325	priorities.
1326
1327	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1328
1329	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1330	C<loop> nor C<revents> need to be valid as long as the watcher callback
1331	can deal with that fact, as both are simply passed through to the
1332	callback.
1333
1334	=item int ev_clear_pending (loop, ev_TYPE *watcher)
1335
1336	If the watcher is pending, this function clears its pending status and
1337	returns its C<revents> bitset (as if its callback was invoked). If the
1338	watcher isn't pending it does nothing and returns C<0>.
1339
1340	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1341	callback to be invoked, which can be accomplished with this function.
1342
1343	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
1344
1345	Feeds the given event set into the event loop, as if the specified event
1346	had happened for the specified watcher (which must be a pointer to an
1347	initialised but not necessarily started event watcher). Obviously you must
1348	not free the watcher as long as it has pending events.
1349
1350	Stopping the watcher, letting libev invoke it, or calling
1351	C<ev_clear_pending> will clear the pending event, even if the watcher was
1352	not started in the first place.
1353
1354	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1355	functions that do not need a watcher.
1356
1357	=back
1358
1359
1360	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1361
1362	Each watcher has, by default, a member C<void *data> that you can change
1363	and read at any time: libev will completely ignore it. This can be used
1364	to associate arbitrary data with your watcher. If you need more data and
1365	don't want to allocate memory and store a pointer to it in that data
1366	member, you can also "subclass" the watcher type and provide your own
1367	data:
1368
1369	struct my_io
1370	{
1371	ev_io io;
1372	int otherfd;
1373	void *somedata;
1374	struct whatever *mostinteresting;
1375	};
1376
1377	...
1378	struct my_io w;
1379	ev_io_init (&w.io, my_cb, fd, EV_READ);
1380
1381	And since your callback will be called with a pointer to the watcher, you
1382	can cast it back to your own type:
1383
1384	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1385	{
1386	struct my_io *w = (struct my_io *)w_;
1387	...
1388	}
1389
1390	More interesting and less C-conformant ways of casting your callback type
1391	instead have been omitted.
1392
1393	Another common scenario is to use some data structure with multiple
1394	embedded watchers:
1395
1396	struct my_biggy
1397	{
1398	int some_data;
1399	ev_timer t1;
1400	ev_timer t2;
1401	}
1402
1403	In this case getting the pointer to C<my_biggy> is a bit more
1404	complicated: Either you store the address of your C<my_biggy> struct
1405	in the C<data> member of the watcher (for woozies), or you need to use
1406	some pointer arithmetic using C<offsetof> inside your watchers (for real
1407	programmers):
1408
1409	#include <stddef.h>
1410
1411	static void
1412	t1_cb (EV_P_ ev_timer *w, int revents)
1413	{
1414	struct my_biggy big = (struct my_biggy *)
1415	(((char *)w) - offsetof (struct my_biggy, t1));
1416	}
1417
1418	static void
1419	t2_cb (EV_P_ ev_timer *w, int revents)
1420	{
1421	struct my_biggy big = (struct my_biggy *)
1422	(((char *)w) - offsetof (struct my_biggy, t2));
1423	}
1424		1441
1425	=head2 WATCHER PRIORITY MODELS	1442	=head2 WATCHER PRIORITY MODELS
1426		1443
1427	Many event loops support I<watcher priorities>, which are usually small	1444	Many event loops support I<watcher priorities>, which are usually small
1428	integers that influence the ordering of event callback invocation	1445	integers that influence the ordering of event callback invocation
…		…
1555	In general you can register as many read and/or write event watchers per	1572	In general you can register as many read and/or write event watchers per
1556	fd as you want (as long as you don't confuse yourself). Setting all file	1573	fd as you want (as long as you don't confuse yourself). Setting all file
1557	descriptors to non-blocking mode is also usually a good idea (but not	1574	descriptors to non-blocking mode is also usually a good idea (but not
1558	required if you know what you are doing).	1575	required if you know what you are doing).
1559		1576
1560	If you cannot use non-blocking mode, then force the use of a
1561	known-to-be-good backend (at the time of this writing, this includes only
1562	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1563	descriptors for which non-blocking operation makes no sense (such as
1564	files) - libev doesn't guarantee any specific behaviour in that case.
1565
1566	Another thing you have to watch out for is that it is quite easy to	1577	Another thing you have to watch out for is that it is quite easy to
1567	receive "spurious" readiness notifications, that is your callback might	1578	receive "spurious" readiness notifications, that is, your callback might
1568	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1579	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1569	because there is no data. Not only are some backends known to create a	1580	because there is no data. It is very easy to get into this situation even
1570	lot of those (for example Solaris ports), it is very easy to get into	1581	with a relatively standard program structure. Thus it is best to always
1571	this situation even with a relatively standard program structure. Thus	1582	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1572	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1573	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1583	preferable to a program hanging until some data arrives.
1574		1584
1575	If you cannot run the fd in non-blocking mode (for example you should	1585	If you cannot run the fd in non-blocking mode (for example you should
1576	not play around with an Xlib connection), then you have to separately	1586	not play around with an Xlib connection), then you have to separately
1577	re-test whether a file descriptor is really ready with a known-to-be good	1587	re-test whether a file descriptor is really ready with a known-to-be good
1578	interface such as poll (fortunately in our Xlib example, Xlib already	1588	interface such as poll (fortunately in the case of Xlib, it already does
1579	does this on its own, so its quite safe to use). Some people additionally	1589	this on its own, so its quite safe to use). Some people additionally
1580	use C<SIGALRM> and an interval timer, just to be sure you won't block	1590	use C<SIGALRM> and an interval timer, just to be sure you won't block
1581	indefinitely.	1591	indefinitely.
1582		1592
1583	But really, best use non-blocking mode.	1593	But really, best use non-blocking mode.
1584		1594
…		…
1612		1622
1613	There is no workaround possible except not registering events	1623	There is no workaround possible except not registering events
1614	for potentially C<dup ()>'ed file descriptors, or to resort to	1624	for potentially C<dup ()>'ed file descriptors, or to resort to
1615	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1625	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1616		1626
		1627	=head3 The special problem of files
		1628
		1629	Many people try to use C<select> (or libev) on file descriptors
		1630	representing files, and expect it to become ready when their program
		1631	doesn't block on disk accesses (which can take a long time on their own).
		1632
		1633	However, this cannot ever work in the "expected" way - you get a readiness
		1634	notification as soon as the kernel knows whether and how much data is
		1635	there, and in the case of open files, that's always the case, so you
		1636	always get a readiness notification instantly, and your read (or possibly
		1637	write) will still block on the disk I/O.
		1638
		1639	Another way to view it is that in the case of sockets, pipes, character
		1640	devices and so on, there is another party (the sender) that delivers data
		1641	on its own, but in the case of files, there is no such thing: the disk
		1642	will not send data on its own, simply because it doesn't know what you
		1643	wish to read - you would first have to request some data.
		1644
		1645	Since files are typically not-so-well supported by advanced notification
		1646	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1647	to files, even though you should not use it. The reason for this is
		1648	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1649	usually a tty, often a pipe, but also sometimes files or special devices
		1650	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1651	F</dev/urandom>), and even though the file might better be served with
		1652	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1653	it "just works" instead of freezing.
		1654
		1655	So avoid file descriptors pointing to files when you know it (e.g. use
		1656	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1657	when you rarely read from a file instead of from a socket, and want to
		1658	reuse the same code path.
		1659
1617	=head3 The special problem of fork	1660	=head3 The special problem of fork
1618		1661
1619	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1662	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1620	useless behaviour. Libev fully supports fork, but needs to be told about	1663	useless behaviour. Libev fully supports fork, but needs to be told about
1621	it in the child.	1664	it in the child if you want to continue to use it in the child.
1622		1665
1623	To support fork in your programs, you either have to call	1666	To support fork in your child processes, you have to call C<ev_loop_fork
1624	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1667	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1625	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1668	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1626	C<EVBACKEND_POLL>.
1627		1669
1628	=head3 The special problem of SIGPIPE	1670	=head3 The special problem of SIGPIPE
1629		1671
1630	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1672	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1631	when writing to a pipe whose other end has been closed, your program gets	1673	when writing to a pipe whose other end has been closed, your program gets
…		…
1981	keep up with the timer (because it takes longer than those 10 seconds to	2023	keep up with the timer (because it takes longer than those 10 seconds to
1982	do stuff) the timer will not fire more than once per event loop iteration.	2024	do stuff) the timer will not fire more than once per event loop iteration.
1983		2025
1984	=item ev_timer_again (loop, ev_timer *)	2026	=item ev_timer_again (loop, ev_timer *)
1985		2027
1986	This will act as if the timer timed out and restart it again if it is	2028	This will act as if the timer timed out and restarts it again if it is
1987	repeating. The exact semantics are:	2029	repeating. The exact semantics are:
1988		2030
1989	If the timer is pending, its pending status is cleared.	2031	If the timer is pending, its pending status is cleared.
1990		2032
1991	If the timer is started but non-repeating, stop it (as if it timed out).	2033	If the timer is started but non-repeating, stop it (as if it timed out).
…		…
2121		2163
2122	Another way to think about it (for the mathematically inclined) is that	2164	Another way to think about it (for the mathematically inclined) is that
2123	C<ev_periodic> will try to run the callback in this mode at the next possible	2165	C<ev_periodic> will try to run the callback in this mode at the next possible
2124	time where C<time = offset (mod interval)>, regardless of any time jumps.	2166	time where C<time = offset (mod interval)>, regardless of any time jumps.
2125		2167
2126	For numerical stability it is preferable that the C<offset> value is near	2168	The C<interval> I<MUST> be positive, and for numerical stability, the
2127	C<ev_now ()> (the current time), but there is no range requirement for	2169	interval value should be higher than C<1/8192> (which is around 100
2128	this value, and in fact is often specified as zero.	2170	microseconds) and C<offset> should be higher than C<0> and should have
		2171	at most a similar magnitude as the current time (say, within a factor of
		2172	ten). Typical values for offset are, in fact, C<0> or something between
		2173	C<0> and C<interval>, which is also the recommended range.
2129		2174
2130	Note also that there is an upper limit to how often a timer can fire (CPU	2175	Note also that there is an upper limit to how often a timer can fire (CPU
2131	speed for example), so if C<interval> is very small then timing stability	2176	speed for example), so if C<interval> is very small then timing stability
2132	will of course deteriorate. Libev itself tries to be exact to be about one	2177	will of course deteriorate. Libev itself tries to be exact to be about one
2133	millisecond (if the OS supports it and the machine is fast enough).	2178	millisecond (if the OS supports it and the machine is fast enough).
…		…
2247		2292
2248	=head2 C<ev_signal> - signal me when a signal gets signalled!	2293	=head2 C<ev_signal> - signal me when a signal gets signalled!
2249		2294
2250	Signal watchers will trigger an event when the process receives a specific	2295	Signal watchers will trigger an event when the process receives a specific
2251	signal one or more times. Even though signals are very asynchronous, libev	2296	signal one or more times. Even though signals are very asynchronous, libev
2252	will try it's best to deliver signals synchronously, i.e. as part of the	2297	will try its best to deliver signals synchronously, i.e. as part of the
2253	normal event processing, like any other event.	2298	normal event processing, like any other event.
2254		2299
2255	If you want signals to be delivered truly asynchronously, just use	2300	If you want signals to be delivered truly asynchronously, just use
2256	C<sigaction> as you would do without libev and forget about sharing	2301	C<sigaction> as you would do without libev and forget about sharing
2257	the signal. You can even use C<ev_async> from a signal handler to	2302	the signal. You can even use C<ev_async> from a signal handler to
…		…
2276	=head3 The special problem of inheritance over fork/execve/pthread_create	2321	=head3 The special problem of inheritance over fork/execve/pthread_create
2277		2322
2278	Both the signal mask (C<sigprocmask>) and the signal disposition	2323	Both the signal mask (C<sigprocmask>) and the signal disposition
2279	(C<sigaction>) are unspecified after starting a signal watcher (and after	2324	(C<sigaction>) are unspecified after starting a signal watcher (and after
2280	stopping it again), that is, libev might or might not block the signal,	2325	stopping it again), that is, libev might or might not block the signal,
2281	and might or might not set or restore the installed signal handler.	2326	and might or might not set or restore the installed signal handler (but
		2327	see C<EVFLAG_NOSIGMASK>).
2282		2328
2283	While this does not matter for the signal disposition (libev never	2329	While this does not matter for the signal disposition (libev never
2284	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on	2330	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
2285	C<execve>), this matters for the signal mask: many programs do not expect	2331	C<execve>), this matters for the signal mask: many programs do not expect
2286	certain signals to be blocked.	2332	certain signals to be blocked.
…		…
2299	I<has> to modify the signal mask, at least temporarily.	2345	I<has> to modify the signal mask, at least temporarily.
2300		2346
2301	So I can't stress this enough: I<If you do not reset your signal mask when	2347	So I can't stress this enough: I<If you do not reset your signal mask when
2302	you expect it to be empty, you have a race condition in your code>. This	2348	you expect it to be empty, you have a race condition in your code>. This
2303	is not a libev-specific thing, this is true for most event libraries.	2349	is not a libev-specific thing, this is true for most event libraries.
		2350
		2351	=head3 The special problem of threads signal handling
		2352
		2353	POSIX threads has problematic signal handling semantics, specifically,
		2354	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2355	threads in a process block signals, which is hard to achieve.
		2356
		2357	When you want to use sigwait (or mix libev signal handling with your own
		2358	for the same signals), you can tackle this problem by globally blocking
		2359	all signals before creating any threads (or creating them with a fully set
		2360	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2361	loops. Then designate one thread as "signal receiver thread" which handles
		2362	these signals. You can pass on any signals that libev might be interested
		2363	in by calling C<ev_feed_signal>.
2304		2364
2305	=head3 Watcher-Specific Functions and Data Members	2365	=head3 Watcher-Specific Functions and Data Members
2306		2366
2307	=over 4	2367	=over 4
2308		2368
…		…
3092		3152
3093	=head3 Watcher-Specific Functions and Data Members	3153	=head3 Watcher-Specific Functions and Data Members
3094		3154
3095	=over 4	3155	=over 4
3096		3156
3097	=item ev_fork_init (ev_signal *, callback)	3157	=item ev_fork_init (ev_fork *, callback)
3098		3158
3099	Initialises and configures the fork watcher - it has no parameters of any	3159	Initialises and configures the fork watcher - it has no parameters of any
3100	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3160	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
3101	believe me.	3161	really.
3102		3162
3103	=back	3163	=back
3104		3164
3105		3165
		3166	=head2 C<ev_cleanup> - even the best things end
		3167
		3168	Cleanup watchers are called just before the event loop is being destroyed
		3169	by a call to C<ev_loop_destroy>.
		3170
		3171	While there is no guarantee that the event loop gets destroyed, cleanup
		3172	watchers provide a convenient method to install cleanup hooks for your
		3173	program, worker threads and so on - you just to make sure to destroy the
		3174	loop when you want them to be invoked.
		3175
		3176	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3177	all other watchers, they do not keep a reference to the event loop (which
		3178	makes a lot of sense if you think about it). Like all other watchers, you
		3179	can call libev functions in the callback, except C<ev_cleanup_start>.
		3180
		3181	=head3 Watcher-Specific Functions and Data Members
		3182
		3183	=over 4
		3184
		3185	=item ev_cleanup_init (ev_cleanup *, callback)
		3186
		3187	Initialises and configures the cleanup watcher - it has no parameters of
		3188	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3189	pointless, I assure you.
		3190
		3191	=back
		3192
		3193	Example: Register an atexit handler to destroy the default loop, so any
		3194	cleanup functions are called.
		3195
		3196	static void
		3197	program_exits (void)
		3198	{
		3199	ev_loop_destroy (EV_DEFAULT_UC);
		3200	}
		3201
		3202	...
		3203	atexit (program_exits);
		3204
		3205
3106	=head2 C<ev_async> - how to wake up an event loop	3206	=head2 C<ev_async> - how to wake up an event loop
3107		3207
3108	In general, you cannot use an C<ev_run> from multiple threads or other	3208	In general, you cannot use an C<ev_loop> from multiple threads or other
3109	asynchronous sources such as signal handlers (as opposed to multiple event	3209	asynchronous sources such as signal handlers (as opposed to multiple event
3110	loops - those are of course safe to use in different threads).	3210	loops - those are of course safe to use in different threads).
3111		3211
3112	Sometimes, however, you need to wake up an event loop you do not control,	3212	Sometimes, however, you need to wake up an event loop you do not control,
3113	for example because it belongs to another thread. This is what C<ev_async>	3213	for example because it belongs to another thread. This is what C<ev_async>
…		…
3115	it by calling C<ev_async_send>, which is thread- and signal safe.	3215	it by calling C<ev_async_send>, which is thread- and signal safe.
3116		3216
3117	This functionality is very similar to C<ev_signal> watchers, as signals,	3217	This functionality is very similar to C<ev_signal> watchers, as signals,
3118	too, are asynchronous in nature, and signals, too, will be compressed	3218	too, are asynchronous in nature, and signals, too, will be compressed
3119	(i.e. the number of callback invocations may be less than the number of	3219	(i.e. the number of callback invocations may be less than the number of
3120	C<ev_async_sent> calls).	3220	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
3121		3221	of "global async watchers" by using a watcher on an otherwise unused
3122	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3222	signal, and C<ev_feed_signal> to signal this watcher from another thread,
3123	just the default loop.	3223	even without knowing which loop owns the signal.
3124		3224
3125	=head3 Queueing	3225	=head3 Queueing
3126		3226
3127	C<ev_async> does not support queueing of data in any way. The reason	3227	C<ev_async> does not support queueing of data in any way. The reason
3128	is that the author does not know of a simple (or any) algorithm for a	3228	is that the author does not know of a simple (or any) algorithm for a
…		…
3220	trust me.	3320	trust me.
3221		3321
3222	=item ev_async_send (loop, ev_async *)	3322	=item ev_async_send (loop, ev_async *)
3223		3323
3224	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3324	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3225	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3325	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3326	returns.
		3327
3226	C<ev_feed_event>, this call is safe to do from other threads, signal or	3328	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3227	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3329	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3228	section below on what exactly this means).	3330	embedding section below on what exactly this means).
3229		3331
3230	Note that, as with other watchers in libev, multiple events might get	3332	Note that, as with other watchers in libev, multiple events might get
3231	compressed into a single callback invocation (another way to look at this	3333	compressed into a single callback invocation (another way to look at
3232	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3334	this is that C<ev_async> watchers are level-triggered: they are set on
3233	reset when the event loop detects that).	3335	C<ev_async_send>, reset when the event loop detects that).
3234		3336
3235	This call incurs the overhead of a system call only once per event loop	3337	This call incurs the overhead of at most one extra system call per event
3236	iteration, so while the overhead might be noticeable, it doesn't apply to	3338	loop iteration, if the event loop is blocked, and no syscall at all if
3237	repeated calls to C<ev_async_send> for the same event loop.	3339	the event loop (or your program) is processing events. That means that
		3340	repeated calls are basically free (there is no need to avoid calls for
		3341	performance reasons) and that the overhead becomes smaller (typically
		3342	zero) under load.
3238		3343
3239	=item bool = ev_async_pending (ev_async *)	3344	=item bool = ev_async_pending (ev_async *)
3240		3345
3241	Returns a non-zero value when C<ev_async_send> has been called on the	3346	Returns a non-zero value when C<ev_async_send> has been called on the
3242	watcher but the event has not yet been processed (or even noted) by the	3347	watcher but the event has not yet been processed (or even noted) by the
…		…
3301	Feed an event on the given fd, as if a file descriptor backend detected	3406	Feed an event on the given fd, as if a file descriptor backend detected
3302	the given events it.	3407	the given events it.
3303		3408
3304	=item ev_feed_signal_event (loop, int signum)	3409	=item ev_feed_signal_event (loop, int signum)
3305		3410
3306	Feed an event as if the given signal occurred (C<loop> must be the default	3411	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3307	loop!).	3412	which is async-safe.
3308		3413
3309	=back	3414	=back
		3415
		3416
		3417	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3418
		3419	This section explains some common idioms that are not immediately
		3420	obvious. Note that examples are sprinkled over the whole manual, and this
		3421	section only contains stuff that wouldn't fit anywhere else.
		3422
		3423	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3424
		3425	Each watcher has, by default, a C<void *data> member that you can read
		3426	or modify at any time: libev will completely ignore it. This can be used
		3427	to associate arbitrary data with your watcher. If you need more data and
		3428	don't want to allocate memory separately and store a pointer to it in that
		3429	data member, you can also "subclass" the watcher type and provide your own
		3430	data:
		3431
		3432	struct my_io
		3433	{
		3434	ev_io io;
		3435	int otherfd;
		3436	void *somedata;
		3437	struct whatever *mostinteresting;
		3438	};
		3439
		3440	...
		3441	struct my_io w;
		3442	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3443
		3444	And since your callback will be called with a pointer to the watcher, you
		3445	can cast it back to your own type:
		3446
		3447	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3448	{
		3449	struct my_io *w = (struct my_io *)w_;
		3450	...
		3451	}
		3452
		3453	More interesting and less C-conformant ways of casting your callback
		3454	function type instead have been omitted.
		3455
		3456	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3457
		3458	Another common scenario is to use some data structure with multiple
		3459	embedded watchers, in effect creating your own watcher that combines
		3460	multiple libev event sources into one "super-watcher":
		3461
		3462	struct my_biggy
		3463	{
		3464	int some_data;
		3465	ev_timer t1;
		3466	ev_timer t2;
		3467	}
		3468
		3469	In this case getting the pointer to C<my_biggy> is a bit more
		3470	complicated: Either you store the address of your C<my_biggy> struct in
		3471	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3472	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3473	real programmers):
		3474
		3475	#include <stddef.h>
		3476
		3477	static void
		3478	t1_cb (EV_P_ ev_timer *w, int revents)
		3479	{
		3480	struct my_biggy big = (struct my_biggy *)
		3481	(((char *)w) - offsetof (struct my_biggy, t1));
		3482	}
		3483
		3484	static void
		3485	t2_cb (EV_P_ ev_timer *w, int revents)
		3486	{
		3487	struct my_biggy big = (struct my_biggy *)
		3488	(((char *)w) - offsetof (struct my_biggy, t2));
		3489	}
		3490
		3491	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3492
		3493	Often (especially in GUI toolkits) there are places where you have
		3494	I<modal> interaction, which is most easily implemented by recursively
		3495	invoking C<ev_run>.
		3496
		3497	This brings the problem of exiting - a callback might want to finish the
		3498	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3499	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3500	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3501	other combination: In these cases, C<ev_break> will not work alone.
		3502
		3503	The solution is to maintain "break this loop" variable for each C<ev_run>
		3504	invocation, and use a loop around C<ev_run> until the condition is
		3505	triggered, using C<EVRUN_ONCE>:
		3506
		3507	// main loop
		3508	int exit_main_loop = 0;
		3509
		3510	while (!exit_main_loop)
		3511	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3512
		3513	// in a model watcher
		3514	int exit_nested_loop = 0;
		3515
		3516	while (!exit_nested_loop)
		3517	ev_run (EV_A_ EVRUN_ONCE);
		3518
		3519	To exit from any of these loops, just set the corresponding exit variable:
		3520
		3521	// exit modal loop
		3522	exit_nested_loop = 1;
		3523
		3524	// exit main program, after modal loop is finished
		3525	exit_main_loop = 1;
		3526
		3527	// exit both
		3528	exit_main_loop = exit_nested_loop = 1;
		3529
		3530	=head2 THREAD LOCKING EXAMPLE
		3531
		3532	Here is a fictitious example of how to run an event loop in a different
		3533	thread from where callbacks are being invoked and watchers are
		3534	created/added/removed.
		3535
		3536	For a real-world example, see the C<EV::Loop::Async> perl module,
		3537	which uses exactly this technique (which is suited for many high-level
		3538	languages).
		3539
		3540	The example uses a pthread mutex to protect the loop data, a condition
		3541	variable to wait for callback invocations, an async watcher to notify the
		3542	event loop thread and an unspecified mechanism to wake up the main thread.
		3543
		3544	First, you need to associate some data with the event loop:
		3545
		3546	typedef struct {
		3547	mutex_t lock; /* global loop lock */
		3548	ev_async async_w;
		3549	thread_t tid;
		3550	cond_t invoke_cv;
		3551	} userdata;
		3552
		3553	void prepare_loop (EV_P)
		3554	{
		3555	// for simplicity, we use a static userdata struct.
		3556	static userdata u;
		3557
		3558	ev_async_init (&u->async_w, async_cb);
		3559	ev_async_start (EV_A_ &u->async_w);
		3560
		3561	pthread_mutex_init (&u->lock, 0);
		3562	pthread_cond_init (&u->invoke_cv, 0);
		3563
		3564	// now associate this with the loop
		3565	ev_set_userdata (EV_A_ u);
		3566	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3567	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3568
		3569	// then create the thread running ev_run
		3570	pthread_create (&u->tid, 0, l_run, EV_A);
		3571	}
		3572
		3573	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3574	solely to wake up the event loop so it takes notice of any new watchers
		3575	that might have been added:
		3576
		3577	static void
		3578	async_cb (EV_P_ ev_async *w, int revents)
		3579	{
		3580	// just used for the side effects
		3581	}
		3582
		3583	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3584	protecting the loop data, respectively.
		3585
		3586	static void
		3587	l_release (EV_P)
		3588	{
		3589	userdata *u = ev_userdata (EV_A);
		3590	pthread_mutex_unlock (&u->lock);
		3591	}
		3592
		3593	static void
		3594	l_acquire (EV_P)
		3595	{
		3596	userdata *u = ev_userdata (EV_A);
		3597	pthread_mutex_lock (&u->lock);
		3598	}
		3599
		3600	The event loop thread first acquires the mutex, and then jumps straight
		3601	into C<ev_run>:
		3602
		3603	void *
		3604	l_run (void *thr_arg)
		3605	{
		3606	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3607
		3608	l_acquire (EV_A);
		3609	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3610	ev_run (EV_A_ 0);
		3611	l_release (EV_A);
		3612
		3613	return 0;
		3614	}
		3615
		3616	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3617	signal the main thread via some unspecified mechanism (signals? pipe
		3618	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3619	have been called (in a while loop because a) spurious wakeups are possible
		3620	and b) skipping inter-thread-communication when there are no pending
		3621	watchers is very beneficial):
		3622
		3623	static void
		3624	l_invoke (EV_P)
		3625	{
		3626	userdata *u = ev_userdata (EV_A);
		3627
		3628	while (ev_pending_count (EV_A))
		3629	{
		3630	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3631	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3632	}
		3633	}
		3634
		3635	Now, whenever the main thread gets told to invoke pending watchers, it
		3636	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3637	thread to continue:
		3638
		3639	static void
		3640	real_invoke_pending (EV_P)
		3641	{
		3642	userdata *u = ev_userdata (EV_A);
		3643
		3644	pthread_mutex_lock (&u->lock);
		3645	ev_invoke_pending (EV_A);
		3646	pthread_cond_signal (&u->invoke_cv);
		3647	pthread_mutex_unlock (&u->lock);
		3648	}
		3649
		3650	Whenever you want to start/stop a watcher or do other modifications to an
		3651	event loop, you will now have to lock:
		3652
		3653	ev_timer timeout_watcher;
		3654	userdata *u = ev_userdata (EV_A);
		3655
		3656	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3657
		3658	pthread_mutex_lock (&u->lock);
		3659	ev_timer_start (EV_A_ &timeout_watcher);
		3660	ev_async_send (EV_A_ &u->async_w);
		3661	pthread_mutex_unlock (&u->lock);
		3662
		3663	Note that sending the C<ev_async> watcher is required because otherwise
		3664	an event loop currently blocking in the kernel will have no knowledge
		3665	about the newly added timer. By waking up the loop it will pick up any new
		3666	watchers in the next event loop iteration.
		3667
		3668	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3669
		3670	While the overhead of a callback that e.g. schedules a thread is small, it
		3671	is still an overhead. If you embed libev, and your main usage is with some
		3672	kind of threads or coroutines, you might want to customise libev so that
		3673	doesn't need callbacks anymore.
		3674
		3675	Imagine you have coroutines that you can switch to using a function
		3676	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3677	and that due to some magic, the currently active coroutine is stored in a
		3678	global called C<current_coro>. Then you can build your own "wait for libev
		3679	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3680	the differing C<;> conventions):
		3681
		3682	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3683	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3684
		3685	That means instead of having a C callback function, you store the
		3686	coroutine to switch to in each watcher, and instead of having libev call
		3687	your callback, you instead have it switch to that coroutine.
		3688
		3689	A coroutine might now wait for an event with a function called
		3690	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3691	matter when, or whether the watcher is active or not when this function is
		3692	called):
		3693
		3694	void
		3695	wait_for_event (ev_watcher *w)
		3696	{
		3697	ev_cb_set (w) = current_coro;
		3698	switch_to (libev_coro);
		3699	}
		3700
		3701	That basically suspends the coroutine inside C<wait_for_event> and
		3702	continues the libev coroutine, which, when appropriate, switches back to
		3703	this or any other coroutine. I am sure if you sue this your own :)
		3704
		3705	You can do similar tricks if you have, say, threads with an event queue -
		3706	instead of storing a coroutine, you store the queue object and instead of
		3707	switching to a coroutine, you push the watcher onto the queue and notify
		3708	any waiters.
		3709
		3710	To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two
		3711	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3712
		3713	// my_ev.h
		3714	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3715	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3716	#include "../libev/ev.h"
		3717
		3718	// my_ev.c
		3719	#define EV_H "my_ev.h"
		3720	#include "../libev/ev.c"
		3721
		3722	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3723	F<my_ev.c> into your project. When properly specifying include paths, you
		3724	can even use F<ev.h> as header file name directly.
3310		3725
3311		3726
3312	=head1 LIBEVENT EMULATION	3727	=head1 LIBEVENT EMULATION
3313		3728
3314	Libev offers a compatibility emulation layer for libevent. It cannot	3729	Libev offers a compatibility emulation layer for libevent. It cannot
3315	emulate the internals of libevent, so here are some usage hints:	3730	emulate the internals of libevent, so here are some usage hints:
3316		3731
3317	=over 4	3732	=over 4
		3733
		3734	=item * Only the libevent-1.4.1-beta API is being emulated.
		3735
		3736	This was the newest libevent version available when libev was implemented,
		3737	and is still mostly unchanged in 2010.
3318		3738
3319	=item * Use it by including <event.h>, as usual.	3739	=item * Use it by including <event.h>, as usual.
3320		3740
3321	=item * The following members are fully supported: ev_base, ev_callback,	3741	=item * The following members are fully supported: ev_base, ev_callback,
3322	ev_arg, ev_fd, ev_res, ev_events.	3742	ev_arg, ev_fd, ev_res, ev_events.
…		…
3328	=item * Priorities are not currently supported. Initialising priorities	3748	=item * Priorities are not currently supported. Initialising priorities
3329	will fail and all watchers will have the same priority, even though there	3749	will fail and all watchers will have the same priority, even though there
3330	is an ev_pri field.	3750	is an ev_pri field.
3331		3751
3332	=item * In libevent, the last base created gets the signals, in libev, the	3752	=item * In libevent, the last base created gets the signals, in libev, the
3333	first base created (== the default loop) gets the signals.	3753	base that registered the signal gets the signals.
3334		3754
3335	=item * Other members are not supported.	3755	=item * Other members are not supported.
3336		3756
3337	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3757	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3338	to use the libev header file and library.	3758	to use the libev header file and library.
…		…
3357	Care has been taken to keep the overhead low. The only data member the C++	3777	Care has been taken to keep the overhead low. The only data member the C++
3358	classes add (compared to plain C-style watchers) is the event loop pointer	3778	classes add (compared to plain C-style watchers) is the event loop pointer
3359	that the watcher is associated with (or no additional members at all if	3779	that the watcher is associated with (or no additional members at all if
3360	you disable C<EV_MULTIPLICITY> when embedding libev).	3780	you disable C<EV_MULTIPLICITY> when embedding libev).
3361		3781
3362	Currently, functions, and static and non-static member functions can be	3782	Currently, functions, static and non-static member functions and classes
3363	used as callbacks. Other types should be easy to add as long as they only	3783	with C<operator ()> can be used as callbacks. Other types should be easy
3364	need one additional pointer for context. If you need support for other	3784	to add as long as they only need one additional pointer for context. If
3365	types of functors please contact the author (preferably after implementing	3785	you need support for other types of functors please contact the author
3366	it).	3786	(preferably after implementing it).
3367		3787
3368	Here is a list of things available in the C<ev> namespace:	3788	Here is a list of things available in the C<ev> namespace:
3369		3789
3370	=over 4	3790	=over 4
3371		3791
…		…
3524	watchers in the constructor.	3944	watchers in the constructor.
3525		3945
3526	class myclass	3946	class myclass
3527	{	3947	{
3528	ev::io io ; void io_cb (ev::io &w, int revents);	3948	ev::io io ; void io_cb (ev::io &w, int revents);
3529	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);	3949	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3530	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3950	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3531		3951
3532	myclass (int fd)	3952	myclass (int fd)
3533	{	3953	{
3534	io .set <myclass, &myclass::io_cb > (this);	3954	io .set <myclass, &myclass::io_cb > (this);
…		…
3585	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4005	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3586		4006
3587	=item D	4007	=item D
3588		4008
3589	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4009	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3590	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4010	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3591		4011
3592	=item Ocaml	4012	=item Ocaml
3593		4013
3594	Erkki Seppala has written Ocaml bindings for libev, to be found at	4014	Erkki Seppala has written Ocaml bindings for libev, to be found at
3595	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4015	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
…		…
3798	supported). It will also not define any of the structs usually found in	4218	supported). It will also not define any of the structs usually found in
3799	F<event.h> that are not directly supported by the libev core alone.	4219	F<event.h> that are not directly supported by the libev core alone.
3800		4220
3801	In standalone mode, libev will still try to automatically deduce the	4221	In standalone mode, libev will still try to automatically deduce the
3802	configuration, but has to be more conservative.	4222	configuration, but has to be more conservative.
		4223
		4224	=item EV_USE_FLOOR
		4225
		4226	If defined to be C<1>, libev will use the C<floor ()> function for its
		4227	periodic reschedule calculations, otherwise libev will fall back on a
		4228	portable (slower) implementation. If you enable this, you usually have to
		4229	link against libm or something equivalent. Enabling this when the C<floor>
		4230	function is not available will fail, so the safe default is to not enable
		4231	this.
3803		4232
3804	=item EV_USE_MONOTONIC	4233	=item EV_USE_MONOTONIC
3805		4234
3806	If defined to be C<1>, libev will try to detect the availability of the	4235	If defined to be C<1>, libev will try to detect the availability of the
3807	monotonic clock option at both compile time and runtime. Otherwise no	4236	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3940	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4369	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3941		4370
3942	=item EV_ATOMIC_T	4371	=item EV_ATOMIC_T
3943		4372
3944	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4373	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3945	access is atomic with respect to other threads or signal contexts. No such	4374	access is atomic and serialised with respect to other threads or signal
3946	type is easily found in the C language, so you can provide your own type	4375	contexts. No such type is easily found in the C language, so you can
3947	that you know is safe for your purposes. It is used both for signal handler "locking"	4376	provide your own type that you know is safe for your purposes. It is used
3948	as well as for signal and thread safety in C<ev_async> watchers.	4377	both for signal handler "locking" as well as for signal and thread safety
		4378	in C<ev_async> watchers.
3949		4379
3950	In the absence of this define, libev will use C<sig_atomic_t volatile>	4380	In the absence of this define, libev will use C<sig_atomic_t volatile>
3951	(from F<signal.h>), which is usually good enough on most platforms.	4381	(from F<signal.h>), which is usually good enough on most platforms,
		4382	although strictly speaking using a type that also implies a memory fence
		4383	is required.
3952		4384
3953	=item EV_H (h)	4385	=item EV_H (h)
3954		4386
3955	The name of the F<ev.h> header file used to include it. The default if	4387	The name of the F<ev.h> header file used to include it. The default if
3956	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4388	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
…		…
4239	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4671	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4240		4672
4241	#include "ev_cpp.h"	4673	#include "ev_cpp.h"
4242	#include "ev.c"	4674	#include "ev.c"
4243		4675
4244	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4676	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4245		4677
4246	=head2 THREADS AND COROUTINES	4678	=head2 THREADS AND COROUTINES
4247		4679
4248	=head3 THREADS	4680	=head3 THREADS
4249		4681
…		…
4300	default loop and triggering an C<ev_async> watcher from the default loop	4732	default loop and triggering an C<ev_async> watcher from the default loop
4301	watcher callback into the event loop interested in the signal.	4733	watcher callback into the event loop interested in the signal.
4302		4734
4303	=back	4735	=back
4304		4736
4305	=head4 THREAD LOCKING EXAMPLE	4737	See also L<THREAD LOCKING EXAMPLE>.
4306
4307	Here is a fictitious example of how to run an event loop in a different
4308	thread than where callbacks are being invoked and watchers are
4309	created/added/removed.
4310
4311	For a real-world example, see the C<EV::Loop::Async> perl module,
4312	which uses exactly this technique (which is suited for many high-level
4313	languages).
4314
4315	The example uses a pthread mutex to protect the loop data, a condition
4316	variable to wait for callback invocations, an async watcher to notify the
4317	event loop thread and an unspecified mechanism to wake up the main thread.
4318
4319	First, you need to associate some data with the event loop:
4320
4321	typedef struct {
4322	mutex_t lock; /* global loop lock */
4323	ev_async async_w;
4324	thread_t tid;
4325	cond_t invoke_cv;
4326	} userdata;
4327
4328	void prepare_loop (EV_P)
4329	{
4330	// for simplicity, we use a static userdata struct.
4331	static userdata u;
4332
4333	ev_async_init (&u->async_w, async_cb);
4334	ev_async_start (EV_A_ &u->async_w);
4335
4336	pthread_mutex_init (&u->lock, 0);
4337	pthread_cond_init (&u->invoke_cv, 0);
4338
4339	// now associate this with the loop
4340	ev_set_userdata (EV_A_ u);
4341	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4342	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4343
4344	// then create the thread running ev_loop
4345	pthread_create (&u->tid, 0, l_run, EV_A);
4346	}
4347
4348	The callback for the C<ev_async> watcher does nothing: the watcher is used
4349	solely to wake up the event loop so it takes notice of any new watchers
4350	that might have been added:
4351
4352	static void
4353	async_cb (EV_P_ ev_async *w, int revents)
4354	{
4355	// just used for the side effects
4356	}
4357
4358	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4359	protecting the loop data, respectively.
4360
4361	static void
4362	l_release (EV_P)
4363	{
4364	userdata *u = ev_userdata (EV_A);
4365	pthread_mutex_unlock (&u->lock);
4366	}
4367
4368	static void
4369	l_acquire (EV_P)
4370	{
4371	userdata *u = ev_userdata (EV_A);
4372	pthread_mutex_lock (&u->lock);
4373	}
4374
4375	The event loop thread first acquires the mutex, and then jumps straight
4376	into C<ev_run>:
4377
4378	void *
4379	l_run (void *thr_arg)
4380	{
4381	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4382
4383	l_acquire (EV_A);
4384	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4385	ev_run (EV_A_ 0);
4386	l_release (EV_A);
4387
4388	return 0;
4389	}
4390
4391	Instead of invoking all pending watchers, the C<l_invoke> callback will
4392	signal the main thread via some unspecified mechanism (signals? pipe
4393	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4394	have been called (in a while loop because a) spurious wakeups are possible
4395	and b) skipping inter-thread-communication when there are no pending
4396	watchers is very beneficial):
4397
4398	static void
4399	l_invoke (EV_P)
4400	{
4401	userdata *u = ev_userdata (EV_A);
4402
4403	while (ev_pending_count (EV_A))
4404	{
4405	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4406	pthread_cond_wait (&u->invoke_cv, &u->lock);
4407	}
4408	}
4409
4410	Now, whenever the main thread gets told to invoke pending watchers, it
4411	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4412	thread to continue:
4413
4414	static void
4415	real_invoke_pending (EV_P)
4416	{
4417	userdata *u = ev_userdata (EV_A);
4418
4419	pthread_mutex_lock (&u->lock);
4420	ev_invoke_pending (EV_A);
4421	pthread_cond_signal (&u->invoke_cv);
4422	pthread_mutex_unlock (&u->lock);
4423	}
4424
4425	Whenever you want to start/stop a watcher or do other modifications to an
4426	event loop, you will now have to lock:
4427
4428	ev_timer timeout_watcher;
4429	userdata *u = ev_userdata (EV_A);
4430
4431	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4432
4433	pthread_mutex_lock (&u->lock);
4434	ev_timer_start (EV_A_ &timeout_watcher);
4435	ev_async_send (EV_A_ &u->async_w);
4436	pthread_mutex_unlock (&u->lock);
4437
4438	Note that sending the C<ev_async> watcher is required because otherwise
4439	an event loop currently blocking in the kernel will have no knowledge
4440	about the newly added timer. By waking up the loop it will pick up any new
4441	watchers in the next event loop iteration.
4442		4738
4443	=head3 COROUTINES	4739	=head3 COROUTINES
4444		4740
4445	Libev is very accommodating to coroutines ("cooperative threads"):	4741	Libev is very accommodating to coroutines ("cooperative threads"):
4446	libev fully supports nesting calls to its functions from different	4742	libev fully supports nesting calls to its functions from different
…		…
4611	requires, and its I/O model is fundamentally incompatible with the POSIX	4907	requires, and its I/O model is fundamentally incompatible with the POSIX
4612	model. Libev still offers limited functionality on this platform in	4908	model. Libev still offers limited functionality on this platform in
4613	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4909	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4614	descriptors. This only applies when using Win32 natively, not when using	4910	descriptors. This only applies when using Win32 natively, not when using
4615	e.g. cygwin. Actually, it only applies to the microsofts own compilers,	4911	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
4616	as every compielr comes with a slightly differently broken/incompatible	4912	as every compiler comes with a slightly differently broken/incompatible
4617	environment.	4913	environment.
4618		4914
4619	Lifting these limitations would basically require the full	4915	Lifting these limitations would basically require the full
4620	re-implementation of the I/O system. If you are into this kind of thing,	4916	re-implementation of the I/O system. If you are into this kind of thing,
4621	then note that glib does exactly that for you in a very portable way (note	4917	then note that glib does exactly that for you in a very portable way (note
…		…
4715	structure (guaranteed by POSIX but not by ISO C for example), but it also	5011	structure (guaranteed by POSIX but not by ISO C for example), but it also
4716	assumes that the same (machine) code can be used to call any watcher	5012	assumes that the same (machine) code can be used to call any watcher
4717	callback: The watcher callbacks have different type signatures, but libev	5013	callback: The watcher callbacks have different type signatures, but libev
4718	calls them using an C<ev_watcher *> internally.	5014	calls them using an C<ev_watcher *> internally.
4719		5015
		5016	=item pointer accesses must be thread-atomic
		5017
		5018	Accessing a pointer value must be atomic, it must both be readable and
		5019	writable in one piece - this is the case on all current architectures.
		5020
4720	=item C<sig_atomic_t volatile> must be thread-atomic as well	5021	=item C<sig_atomic_t volatile> must be thread-atomic as well
4721		5022
4722	The type C<sig_atomic_t volatile> (or whatever is defined as	5023	The type C<sig_atomic_t volatile> (or whatever is defined as
4723	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5024	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
4724	threads. This is not part of the specification for C<sig_atomic_t>, but is	5025	threads. This is not part of the specification for C<sig_atomic_t>, but is
…		…
4749		5050
4750	The type C<double> is used to represent timestamps. It is required to	5051	The type C<double> is used to represent timestamps. It is required to
4751	have at least 51 bits of mantissa (and 9 bits of exponent), which is	5052	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4752	good enough for at least into the year 4000 with millisecond accuracy	5053	good enough for at least into the year 4000 with millisecond accuracy
4753	(the design goal for libev). This requirement is overfulfilled by	5054	(the design goal for libev). This requirement is overfulfilled by
4754	implementations using IEEE 754, which is basically all existing ones. With	5055	implementations using IEEE 754, which is basically all existing ones.
		5056
4755	IEEE 754 doubles, you get microsecond accuracy until at least 2200.	5057	With IEEE 754 doubles, you get microsecond accuracy until at least the
		5058	year 2255 (and millisecond accuray till the year 287396 - by then, libev
		5059	is either obsolete or somebody patched it to use C<long double> or
		5060	something like that, just kidding).
4756		5061
4757	=back	5062	=back
4758		5063
4759	If you know of other additional requirements drop me a note.	5064	If you know of other additional requirements drop me a note.
4760		5065
…		…
4822	=item Processing ev_async_send: O(number_of_async_watchers)	5127	=item Processing ev_async_send: O(number_of_async_watchers)
4823		5128
4824	=item Processing signals: O(max_signal_number)	5129	=item Processing signals: O(max_signal_number)
4825		5130
4826	Sending involves a system call I<iff> there were no other C<ev_async_send>	5131	Sending involves a system call I<iff> there were no other C<ev_async_send>
4827	calls in the current loop iteration. Checking for async and signal events	5132	calls in the current loop iteration and the loop is currently
		5133	blocked. Checking for async and signal events involves iterating over all
4828	involves iterating over all running async watchers or all signal numbers.	5134	running async watchers or all signal numbers.
4829		5135
4830	=back	5136	=back
4831		5137
4832		5138
4833	=head1 PORTING FROM LIBEV 3.X TO 4.X	5139	=head1 PORTING FROM LIBEV 3.X TO 4.X
4834		5140
4835	The major version 4 introduced some minor incompatible changes to the API.	5141	The major version 4 introduced some incompatible changes to the API.
4836		5142
4837	At the moment, the C<ev.h> header file tries to implement superficial	5143	At the moment, the C<ev.h> header file provides compatibility definitions
4838	compatibility, so most programs should still compile. Those might be	5144	for all changes, so most programs should still compile. The compatibility
4839	removed in later versions of libev, so better update early than late.	5145	layer might be removed in later versions of libev, so better update to the
		5146	new API early than late.
4840		5147
4841	=over 4	5148	=over 4
4842		5149
		5150	=item C<EV_COMPAT3> backwards compatibility mechanism
		5151
		5152	The backward compatibility mechanism can be controlled by
		5153	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5154	section.
		5155
4843	=item C<ev_default_destroy> and C<ev_default_fork> have been removed	5156	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
4844		5157
4845	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:	5158	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
4846		5159
4847	ev_loop_destroy (EV_DEFAULT);	5160	ev_loop_destroy (EV_DEFAULT_UC);
4848	ev_loop_fork (EV_DEFAULT);	5161	ev_loop_fork (EV_DEFAULT);
4849		5162
4850	=item function/symbol renames	5163	=item function/symbol renames
4851		5164
4852	A number of functions and symbols have been renamed:	5165	A number of functions and symbols have been renamed:
…		…
4872	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme	5185	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
4873	as all other watcher types. Note that C<ev_loop_fork> is still called	5186	as all other watcher types. Note that C<ev_loop_fork> is still called
4874	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>	5187	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
4875	typedef.	5188	typedef.
4876		5189
4877	=item C<EV_COMPAT3> backwards compatibility mechanism
4878
4879	The backward compatibility mechanism can be controlled by
4880	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
4881	section.
4882
4883	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>	5190	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
4884		5191
4885	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different	5192	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
4886	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile	5193	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
4887	and work, but the library code will of course be larger.	5194	and work, but the library code will of course be larger.
…		…
4949	The physical time that is observed. It is apparently strictly monotonic :)	5256	The physical time that is observed. It is apparently strictly monotonic :)
4950		5257
4951	=item wall-clock time	5258	=item wall-clock time
4952		5259
4953	The time and date as shown on clocks. Unlike real time, it can actually	5260	The time and date as shown on clocks. Unlike real time, it can actually
4954	be wrong and jump forwards and backwards, e.g. when the you adjust your	5261	be wrong and jump forwards and backwards, e.g. when you adjust your
4955	clock.	5262	clock.
4956		5263
4957	=item watcher	5264	=item watcher
4958		5265
4959	A data structure that describes interest in certain events. Watchers need	5266	A data structure that describes interest in certain events. Watchers need
…		…
4961		5268
4962	=back	5269	=back
4963		5270
4964	=head1 AUTHOR	5271	=head1 AUTHOR
4965		5272
4966	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5273	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5274	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4967		5275

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