[ViewVC] Diff of: cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.320 by root, Fri Oct 22 10:48:54 2010 UTC vs.
Revision 1.346 by root, Wed Nov 10 14:50:54 2010 UTC

…		…
43		43
44	int	44	int
45	main (void)	45	main (void)
46	{	46	{
47	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
48	struct ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = EV_DEFAULT;
49		49
50	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
51	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
52	ev_io_init (&stdin_watcher, stdin_cb, /STDIN_FILENO/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /STDIN_FILENO/ 0, EV_READ);
53	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
…		…
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
…		…
165		173
166	=item ev_tstamp ev_time ()	174	=item ev_tstamp ev_time ()
167		175
168	Returns the current time as libev would use it. Please note that the	176	Returns the current time as libev would use it. Please note that the
169	C<ev_now> function is usually faster and also often returns the timestamp	177	C<ev_now> function is usually faster and also often returns the timestamp
170	you actually want to know. Also interetsing 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 until
…		…
233	the current system, you would need to look at C<ev_embeddable_backends ()	241	the current system, you would need to look at C<ev_embeddable_backends ()
234	& ev_supported_backends ()>, likewise for recommended ones.	242	& ev_supported_backends ()>, likewise for recommended ones.
235		243
236	See the description of C<ev_embed> watchers for more info.	244	See the description of C<ev_embed> watchers for more info.
237		245
238	=item ev_set_allocator (void (cb)(void *ptr, long size)) [NOT REENTRANT]	246	=item ev_set_allocator (void (cb)(void *ptr, long size))
239		247
240	Sets the allocation function to use (the prototype is similar - the	248	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	249	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	250	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	251	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
269	}	277	}
270		278
271	...	279	...
272	ev_set_allocator (persistent_realloc);	280	ev_set_allocator (persistent_realloc);
273		281
274	=item ev_set_syserr_cb (void (cb)(const char msg)); [NOT REENTRANT]	282	=item ev_set_syserr_cb (void (cb)(const char msg))
275		283
276	Set the callback function to call on a retryable system call error (such	284	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	285	as failed select, poll, epoll_wait). The message is a printable string
278	indicating the system call or subsystem causing the problem. If this	286	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	287	callback is set, then libev will expect it to remedy the situation, no
…		…
293	...	301	...
294	ev_set_syserr_cb (fatal_error);	302	ev_set_syserr_cb (fatal_error);
295		303
296	=back	304	=back
297		305
298	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	306	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
299		307
300	An event loop is described by a C<struct ev_loop *> (the C<struct> is	308	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	309	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).	310	libev 3 had an C<ev_loop> function colliding with the struct name).
303		311
304	The library knows two types of such loops, the I<default> loop, which	312	The library knows two types of such loops, the I<default> loop, which
305	supports signals and child events, and dynamically created event loops	313	supports child process events, and dynamically created event loops which
306	which do not.	314	do not.
307		315
308	=over 4	316	=over 4
309		317
310	=item struct ev_loop *ev_default_loop (unsigned int flags)	318	=item struct ev_loop *ev_default_loop (unsigned int flags)
311		319
312	This will initialise the default event loop if it hasn't been initialised	320	This returns the "default" event loop object, which is what you should
313	yet and return it. If the default loop could not be initialised, returns	321	normally use when you just need "the event loop". Event loop objects and
314	false. If it already was initialised it simply returns it (and ignores the	322	the C<flags> parameter are described in more detail in the entry for
315	flags. If that is troubling you, check C<ev_backend ()> afterwards).	323	C<ev_loop_new>.
		324
		325	If the default loop is already initialised then this function simply
		326	returns it (and ignores the flags. If that is troubling you, check
		327	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		328	flags, which should almost always be C<0>, unless the caller is also the
		329	one calling C<ev_run> or otherwise qualifies as "the main program".
316		330
317	If you don't know what event loop to use, use the one returned from this	331	If you don't know what event loop to use, use the one returned from this
318	function.	332	function (or via the C<EV_DEFAULT> macro).
319		333
320	Note that this function is I<not> thread-safe, so if you want to use it	334	Note that this function is I<not> thread-safe, so if you want to use it
321	from multiple threads, you have to lock (note also that this is unlikely,	335	from multiple threads, you have to employ some kind of mutex (note also
322	as loops cannot be shared easily between threads anyway).	336	that this case is unlikely, as loops cannot be shared easily between
		337	threads anyway).
323		338
324	The default loop is the only loop that can handle C<ev_signal> and	339	The default loop is the only loop that can handle C<ev_child> watchers,
325	C<ev_child> watchers, and to do this, it always registers a handler	340	and to do this, it always registers a handler for C<SIGCHLD>. If this is
326	for C<SIGCHLD>. If this is a problem for your application you can either	341	a problem for your application you can either create a dynamic loop with
327	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	342	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
328	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	343	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
329	C<ev_default_init>.	344
		345	Example: This is the most typical usage.
		346
		347	if (!ev_default_loop (0))
		348	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		349
		350	Example: Restrict libev to the select and poll backends, and do not allow
		351	environment settings to be taken into account:
		352
		353	ev_default_loop (EVBACKEND_POLL \| EVBACKEND_SELECT \| EVFLAG_NOENV);
		354
		355	=item struct ev_loop *ev_loop_new (unsigned int flags)
		356
		357	This will create and initialise a new event loop object. If the loop
		358	could not be initialised, returns false.
		359
		360	This function is thread-safe, and one common way to use libev with
		361	threads is indeed to create one loop per thread, and using the default
		362	loop in the "main" or "initial" thread.
330		363
331	The flags argument can be used to specify special behaviour or specific	364	The flags argument can be used to specify special behaviour or specific
332	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	365	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
333		366
334	The following flags are supported:	367	The following flags are supported:
…		…
369	environment variable.	402	environment variable.
370		403
371	=item C<EVFLAG_NOINOTIFY>	404	=item C<EVFLAG_NOINOTIFY>
372		405
373	When this flag is specified, then libev will not attempt to use the	406	When this flag is specified, then libev will not attempt to use the
374	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and	407	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
375	testing, this flag can be useful to conserve inotify file descriptors, as	408	testing, this flag can be useful to conserve inotify file descriptors, as
376	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.	409	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
377		410
378	=item C<EVFLAG_SIGNALFD>	411	=item C<EVFLAG_SIGNALFD>
379		412
380	When this flag is specified, then libev will attempt to use the	413	When this flag is specified, then libev will attempt to use the
381	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API	414	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
382	delivers signals synchronously, which makes it both faster and might make	415	delivers signals synchronously, which makes it both faster and might make
383	it possible to get the queued signal data. It can also simplify signal	416	it possible to get the queued signal data. It can also simplify signal
384	handling with threads, as long as you properly block signals in your	417	handling with threads, as long as you properly block signals in your
385	threads that are not interested in handling them.	418	threads that are not interested in handling them.
386		419
…		…
430	epoll scales either O(1) or O(active_fds).	463	epoll scales either O(1) or O(active_fds).
431		464
432	The epoll mechanism deserves honorable mention as the most misdesigned	465	The epoll mechanism deserves honorable mention as the most misdesigned
433	of the more advanced event mechanisms: mere annoyances include silently	466	of the more advanced event mechanisms: mere annoyances include silently
434	dropping file descriptors, requiring a system call per change per file	467	dropping file descriptors, requiring a system call per change per file
435	descriptor (and unnecessary guessing of parameters), problems with dup and	468	descriptor (and unnecessary guessing of parameters), problems with dup,
		469	returning before the timeout value, resulting in additional iterations
		470	(and only giving 5ms accuracy while select on the same platform gives
436	so on. The biggest issue is fork races, however - if a program forks then	471	0.1ms) and so on. The biggest issue is fork races, however - if a program
437	I<both> parent and child process have to recreate the epoll set, which can	472	forks then I<both> parent and child process have to recreate the epoll
438	take considerable time (one syscall per file descriptor) and is of course	473	set, which can take considerable time (one syscall per file descriptor)
439	hard to detect.	474	and is of course hard to detect.
440		475
441	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	476	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
442	of course I<doesn't>, and epoll just loves to report events for totally	477	of course I<doesn't>, and epoll just loves to report events for totally
443	I<different> file descriptors (even already closed ones, so one cannot	478	I<different> file descriptors (even already closed ones, so one cannot
444	even remove them from the set) than registered in the set (especially	479	even remove them from the set) than registered in the set (especially
…		…
446	employing an additional generation counter and comparing that against the	481	employing an additional generation counter and comparing that against the
447	events to filter out spurious ones, recreating the set when required. Last	482	events to filter out spurious ones, recreating the set when required. Last
448	not least, it also refuses to work with some file descriptors which work	483	not least, it also refuses to work with some file descriptors which work
449	perfectly fine with C<select> (files, many character devices...).	484	perfectly fine with C<select> (files, many character devices...).
450		485
		486	Epoll is truly the train wreck analog among event poll mechanisms.
		487
451	While stopping, setting and starting an I/O watcher in the same iteration	488	While stopping, setting and starting an I/O watcher in the same iteration
452	will result in some caching, there is still a system call per such	489	will result in some caching, there is still a system call per such
453	incident (because the same I<file descriptor> could point to a different	490	incident (because the same I<file descriptor> could point to a different
454	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	491	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
455	file descriptors might not work very well if you register events for both	492	file descriptors might not work very well if you register events for both
…		…
552	If one or more of the backend flags are or'ed into the flags value,	589	If one or more of the backend flags are or'ed into the flags value,
553	then only these backends will be tried (in the reverse order as listed	590	then only these backends will be tried (in the reverse order as listed
554	here). If none are specified, all backends in C<ev_recommended_backends	591	here). If none are specified, all backends in C<ev_recommended_backends
555	()> will be tried.	592	()> will be tried.
556		593
557	Example: This is the most typical usage.
558
559	if (!ev_default_loop (0))
560	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
561
562	Example: Restrict libev to the select and poll backends, and do not allow
563	environment settings to be taken into account:
564
565	ev_default_loop (EVBACKEND_POLL \| EVBACKEND_SELECT \| EVFLAG_NOENV);
566
567	Example: Use whatever libev has to offer, but make sure that kqueue is
568	used if available (warning, breaks stuff, best use only with your own
569	private event loop and only if you know the OS supports your types of
570	fds):
571
572	ev_default_loop (ev_recommended_backends () \| EVBACKEND_KQUEUE);
573
574	=item struct ev_loop *ev_loop_new (unsigned int flags)
575
576	Similar to C<ev_default_loop>, but always creates a new event loop that is
577	always distinct from the default loop.
578
579	Note that this function I<is> thread-safe, and one common way to use
580	libev with threads is indeed to create one loop per thread, and using the
581	default loop in the "main" or "initial" thread.
582
583	Example: Try to create a event loop that uses epoll and nothing else.	594	Example: Try to create a event loop that uses epoll and nothing else.
584		595
585	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);	596	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);
586	if (!epoller)	597	if (!epoller)
587	fatal ("no epoll found here, maybe it hides under your chair");	598	fatal ("no epoll found here, maybe it hides under your chair");
588		599
		600	Example: Use whatever libev has to offer, but make sure that kqueue is
		601	used if available.
		602
		603	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () \| EVBACKEND_KQUEUE);
		604
589	=item ev_default_destroy ()	605	=item ev_loop_destroy (loop)
590		606
591	Destroys the default loop (frees all memory and kernel state etc.). None	607	Destroys an event loop object (frees all memory and kernel state
592	of the active event watchers will be stopped in the normal sense, so	608	etc.). None of the active event watchers will be stopped in the normal
593	e.g. C<ev_is_active> might still return true. It is your responsibility to	609	sense, so e.g. C<ev_is_active> might still return true. It is your
594	either stop all watchers cleanly yourself I<before> calling this function,	610	responsibility to either stop all watchers cleanly yourself I<before>
595	or cope with the fact afterwards (which is usually the easiest thing, you	611	calling this function, or cope with the fact afterwards (which is usually
596	can just ignore the watchers and/or C<free ()> them for example).	612	the easiest thing, you can just ignore the watchers and/or C<free ()> them
		613	for example).
597		614
598	Note that certain global state, such as signal state (and installed signal	615	Note that certain global state, such as signal state (and installed signal
599	handlers), will not be freed by this function, and related watchers (such	616	handlers), will not be freed by this function, and related watchers (such
600	as signal and child watchers) would need to be stopped manually.	617	as signal and child watchers) would need to be stopped manually.
601		618
602	In general it is not advisable to call this function except in the	619	This function is normally used on loop objects allocated by
603	rare occasion where you really need to free e.g. the signal handling	620	C<ev_loop_new>, but it can also be used on the default loop returned by
		621	C<ev_default_loop>, in which case it is not thread-safe.
		622
		623	Note that it is not advisable to call this function on the default loop
		624	except in the rare occasion where you really need to free its resources.
604	pipe fds. If you need dynamically allocated loops it is better to use	625	If you need dynamically allocated loops it is better to use C<ev_loop_new>
605	C<ev_loop_new> and C<ev_loop_destroy>.	626	and C<ev_loop_destroy>.
606		627
607	=item ev_loop_destroy (loop)	628	=item ev_loop_fork (loop)
608		629
609	Like C<ev_default_destroy>, but destroys an event loop created by an
610	earlier call to C<ev_loop_new>.
611
612	=item ev_default_fork ()
613
614	This function sets a flag that causes subsequent C<ev_run> iterations	630	This function sets a flag that causes subsequent C<ev_run> iterations to
615	to reinitialise the kernel state for backends that have one. Despite the	631	reinitialise the kernel state for backends that have one. Despite the
616	name, you can call it anytime, but it makes most sense after forking, in	632	name, you can call it anytime, but it makes most sense after forking, in
617	the child process (or both child and parent, but that again makes little	633	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
618	sense). You I<must> call it in the child before using any of the libev	634	child before resuming or calling C<ev_run>.
619	functions, and it will only take effect at the next C<ev_run> iteration.
620		635
621	Again, you I<have> to call it on I<any> loop that you want to re-use after	636	Again, you I<have> to call it on I<any> loop that you want to re-use after
622	a fork, I<even if you do not plan to use the loop in the parent>. This is	637	a fork, I<even if you do not plan to use the loop in the parent>. This is
623	because some kernel interfaces cough I<kqueue> cough do funny things	638	because some kernel interfaces cough I<kqueue> cough do funny things
624	during fork.	639	during fork.
…		…
629	call it at all (in fact, C<epoll> is so badly broken that it makes a	644	call it at all (in fact, C<epoll> is so badly broken that it makes a
630	difference, but libev will usually detect this case on its own and do a	645	difference, but libev will usually detect this case on its own and do a
631	costly reset of the backend).	646	costly reset of the backend).
632		647
633	The function itself is quite fast and it's usually not a problem to call	648	The function itself is quite fast and it's usually not a problem to call
634	it just in case after a fork. To make this easy, the function will fit in	649	it just in case after a fork.
635	quite nicely into a call to C<pthread_atfork>:
636		650
		651	Example: Automate calling C<ev_loop_fork> on the default loop when
		652	using pthreads.
		653
		654	static void
		655	post_fork_child (void)
		656	{
		657	ev_loop_fork (EV_DEFAULT);
		658	}
		659
		660	...
637	pthread_atfork (0, 0, ev_default_fork);	661	pthread_atfork (0, 0, post_fork_child);
638
639	=item ev_loop_fork (loop)
640
641	Like C<ev_default_fork>, but acts on an event loop created by
642	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
643	after fork that you want to re-use in the child, and how you keep track of
644	them is entirely your own problem.
645		662
646	=item int ev_is_default_loop (loop)	663	=item int ev_is_default_loop (loop)
647		664
648	Returns true when the given loop is, in fact, the default loop, and false	665	Returns true when the given loop is, in fact, the default loop, and false
649	otherwise.	666	otherwise.
…		…
660	prepare and check phases.	677	prepare and check phases.
661		678
662	=item unsigned int ev_depth (loop)	679	=item unsigned int ev_depth (loop)
663		680
664	Returns the number of times C<ev_run> was entered minus the number of	681	Returns the number of times C<ev_run> was entered minus the number of
665	times C<ev_run> was exited, in other words, the recursion depth.	682	times C<ev_run> was exited normally, in other words, the recursion depth.
666		683
667	Outside C<ev_run>, this number is zero. In a callback, this number is	684	Outside C<ev_run>, this number is zero. In a callback, this number is
668	C<1>, unless C<ev_run> was invoked recursively (or from another thread),	685	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
669	in which case it is higher.	686	in which case it is higher.
670		687
671	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread	688	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
672	etc.), doesn't count as "exit" - consider this as a hint to avoid such	689	throwing an exception etc.), doesn't count as "exit" - consider this
673	ungentleman-like behaviour unless it's really convenient.	690	as a hint to avoid such ungentleman-like behaviour unless it's really
		691	convenient, in which case it is fully supported.
674		692
675	=item unsigned int ev_backend (loop)	693	=item unsigned int ev_backend (loop)
676		694
677	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	695	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
678	use.	696	use.
…		…
739	relying on all watchers to be stopped when deciding when a program has	757	relying on all watchers to be stopped when deciding when a program has
740	finished (especially in interactive programs), but having a program	758	finished (especially in interactive programs), but having a program
741	that automatically loops as long as it has to and no longer by virtue	759	that automatically loops as long as it has to and no longer by virtue
742	of relying on its watchers stopping correctly, that is truly a thing of	760	of relying on its watchers stopping correctly, that is truly a thing of
743	beauty.	761	beauty.
		762
		763	This function is also I<mostly> exception-safe - you can break out of
		764	a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		765	exception and so on. This does not decrement the C<ev_depth> value, nor
		766	will it clear any outstanding C<EVBREAK_ONE> breaks.
744		767
745	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle	768	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
746	those events and any already outstanding ones, but will not wait and	769	those events and any already outstanding ones, but will not wait and
747	block your process in case there are no events and will return after one	770	block your process in case there are no events and will return after one
748	iteration of the loop. This is sometimes useful to poll and handle new	771	iteration of the loop. This is sometimes useful to poll and handle new
…		…
810	Can be used to make a call to C<ev_run> return early (but only after it	833	Can be used to make a call to C<ev_run> return early (but only after it
811	has processed all outstanding events). The C<how> argument must be either	834	has processed all outstanding events). The C<how> argument must be either
812	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or	835	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
813	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.	836	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
814		837
815	This "unloop state" will be cleared when entering C<ev_run> again.	838	This "break state" will be cleared on the next call to C<ev_run>.
816		839
817	It is safe to call C<ev_break> from outside any C<ev_run> calls. ##TODO##	840	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		841	which case it will have no effect.
818		842
819	=item ev_ref (loop)	843	=item ev_ref (loop)
820		844
821	=item ev_unref (loop)	845	=item ev_unref (loop)
822		846
…		…
965	See also the locking example in the C<THREADS> section later in this	989	See also the locking example in the C<THREADS> section later in this
966	document.	990	document.
967		991
968	=item ev_set_userdata (loop, void *data)	992	=item ev_set_userdata (loop, void *data)
969		993
970	=item ev_userdata (loop)	994	=item void *ev_userdata (loop)
971		995
972	Set and retrieve a single C<void *> associated with a loop. When	996	Set and retrieve a single C<void *> associated with a loop. When
973	C<ev_set_userdata> has never been called, then C<ev_userdata> returns	997	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
974	C<0.>	998	C<0>.
975		999
976	These two functions can be used to associate arbitrary data with a loop,	1000	These two functions can be used to associate arbitrary data with a loop,
977	and are intended solely for the C<invoke_pending_cb>, C<release> and	1001	and are intended solely for the C<invoke_pending_cb>, C<release> and
978	C<acquire> callbacks described above, but of course can be (ab-)used for	1002	C<acquire> callbacks described above, but of course can be (ab-)used for
979	any other purpose as well.	1003	any other purpose as well.
…		…
1107	=item C<EV_FORK>	1131	=item C<EV_FORK>
1108		1132
1109	The event loop has been resumed in the child process after fork (see	1133	The event loop has been resumed in the child process after fork (see
1110	C<ev_fork>).	1134	C<ev_fork>).
1111		1135
		1136	=item C<EV_CLEANUP>
		1137
		1138	The event loop is about to be destroyed (see C<ev_cleanup>).
		1139
1112	=item C<EV_ASYNC>	1140	=item C<EV_ASYNC>
1113		1141
1114	The given async watcher has been asynchronously notified (see C<ev_async>).	1142	The given async watcher has been asynchronously notified (see C<ev_async>).
1115		1143
1116	=item C<EV_CUSTOM>	1144	=item C<EV_CUSTOM>
…		…
1137	programs, though, as the fd could already be closed and reused for another	1165	programs, though, as the fd could already be closed and reused for another
1138	thing, so beware.	1166	thing, so beware.
1139		1167
1140	=back	1168	=back
1141		1169
1142	=head2 WATCHER STATES
1143
1144	There are various watcher states mentioned throughout this manual -
1145	active, pending and so on. In this section these states and the rules to
1146	transition between them will be described in more detail - and while these
1147	rules might look complicated, they usually do "the right thing".
1148
1149	=over 4
1150
1151	=item initialiased
1152
1153	Before a watcher can be registered with the event looop it has to be
1154	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
1155	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1156
1157	In this state it is simply some block of memory that is suitable for use
1158	in an event loop. It can be moved around, freed, reused etc. at will.
1159
1160	=item started/running/active
1161
1162	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1163	property of the event loop, and is actively waiting for events. While in
1164	this state it cannot be accessed (except in a few documented ways), moved,
1165	freed or anything else - the only legal thing is to keep a pointer to it,
1166	and call libev functions on it that are documented to work on active watchers.
1167
1168	=item pending
1169
1170	If a watcher is active and libev determines that an event it is interested
1171	in has occurred (such as a timer expiring), it will become pending. It will
1172	stay in this pending state until either it is stopped or its callback is
1173	about to be invoked, so it is not normally pending inside the watcher
1174	callback.
1175
1176	The watcher might or might not be active while it is pending (for example,
1177	an expired non-repeating timer can be pending but no longer active). If it
1178	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
1179	but it is still property of the event loop at this time, so cannot be
1180	moved, freed or reused. And if it is active the rules described in the
1181	previous item still apply.
1182
1183	It is also possible to feed an event on a watcher that is not active (e.g.
1184	via C<ev_feed_event>), in which case it becomes pending without being
1185	active.
1186
1187	=item stopped
1188
1189	A watcher can be stopped implicitly by libev (in which case it might still
1190	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1191	latter will clear any pending state the watcher might be in, regardless
1192	of whether it was active or not, so stopping a watcher explicitly before
1193	freeing it is often a good idea.
1194
1195	While stopped (and not pending) the watcher is essentially in the
1196	initialised state, that is it can be reused, moved, modified in any way
1197	you wish.
1198
1199	=back
1200
1201	=head2 GENERIC WATCHER FUNCTIONS	1170	=head2 GENERIC WATCHER FUNCTIONS
1202		1171
1203	=over 4	1172	=over 4
1204		1173
1205	=item C<ev_init> (ev_TYPE *watcher, callback)	1174	=item C<ev_init> (ev_TYPE *watcher, callback)
…		…
1346		1315
1347	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related	1316	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1348	functions that do not need a watcher.	1317	functions that do not need a watcher.
1349		1318
1350	=back	1319	=back
1351
1352		1320
1353	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1321	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1354		1322
1355	Each watcher has, by default, a member C<void *data> that you can change	1323	Each watcher has, by default, a member C<void *data> that you can change
1356	and read at any time: libev will completely ignore it. This can be used	1324	and read at any time: libev will completely ignore it. This can be used
…		…
1412	t2_cb (EV_P_ ev_timer *w, int revents)	1380	t2_cb (EV_P_ ev_timer *w, int revents)
1413	{	1381	{
1414	struct my_biggy big = (struct my_biggy *)	1382	struct my_biggy big = (struct my_biggy *)
1415	(((char *)w) - offsetof (struct my_biggy, t2));	1383	(((char *)w) - offsetof (struct my_biggy, t2));
1416	}	1384	}
		1385
		1386	=head2 WATCHER STATES
		1387
		1388	There are various watcher states mentioned throughout this manual -
		1389	active, pending and so on. In this section these states and the rules to
		1390	transition between them will be described in more detail - and while these
		1391	rules might look complicated, they usually do "the right thing".
		1392
		1393	=over 4
		1394
		1395	=item initialiased
		1396
		1397	Before a watcher can be registered with the event looop it has to be
		1398	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1399	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1400
		1401	In this state it is simply some block of memory that is suitable for use
		1402	in an event loop. It can be moved around, freed, reused etc. at will.
		1403
		1404	=item started/running/active
		1405
		1406	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1407	property of the event loop, and is actively waiting for events. While in
		1408	this state it cannot be accessed (except in a few documented ways), moved,
		1409	freed or anything else - the only legal thing is to keep a pointer to it,
		1410	and call libev functions on it that are documented to work on active watchers.
		1411
		1412	=item pending
		1413
		1414	If a watcher is active and libev determines that an event it is interested
		1415	in has occurred (such as a timer expiring), it will become pending. It will
		1416	stay in this pending state until either it is stopped or its callback is
		1417	about to be invoked, so it is not normally pending inside the watcher
		1418	callback.
		1419
		1420	The watcher might or might not be active while it is pending (for example,
		1421	an expired non-repeating timer can be pending but no longer active). If it
		1422	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1423	but it is still property of the event loop at this time, so cannot be
		1424	moved, freed or reused. And if it is active the rules described in the
		1425	previous item still apply.
		1426
		1427	It is also possible to feed an event on a watcher that is not active (e.g.
		1428	via C<ev_feed_event>), in which case it becomes pending without being
		1429	active.
		1430
		1431	=item stopped
		1432
		1433	A watcher can be stopped implicitly by libev (in which case it might still
		1434	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1435	latter will clear any pending state the watcher might be in, regardless
		1436	of whether it was active or not, so stopping a watcher explicitly before
		1437	freeing it is often a good idea.
		1438
		1439	While stopped (and not pending) the watcher is essentially in the
		1440	initialised state, that is it can be reused, moved, modified in any way
		1441	you wish.
		1442
		1443	=back
1417		1444
1418	=head2 WATCHER PRIORITY MODELS	1445	=head2 WATCHER PRIORITY MODELS
1419		1446
1420	Many event loops support I<watcher priorities>, which are usually small	1447	Many event loops support I<watcher priorities>, which are usually small
1421	integers that influence the ordering of event callback invocation	1448	integers that influence the ordering of event callback invocation
…		…
2240		2267
2241	=head2 C<ev_signal> - signal me when a signal gets signalled!	2268	=head2 C<ev_signal> - signal me when a signal gets signalled!
2242		2269
2243	Signal watchers will trigger an event when the process receives a specific	2270	Signal watchers will trigger an event when the process receives a specific
2244	signal one or more times. Even though signals are very asynchronous, libev	2271	signal one or more times. Even though signals are very asynchronous, libev
2245	will try it's best to deliver signals synchronously, i.e. as part of the	2272	will try its best to deliver signals synchronously, i.e. as part of the
2246	normal event processing, like any other event.	2273	normal event processing, like any other event.
2247		2274
2248	If you want signals to be delivered truly asynchronously, just use	2275	If you want signals to be delivered truly asynchronously, just use
2249	C<sigaction> as you would do without libev and forget about sharing	2276	C<sigaction> as you would do without libev and forget about sharing
2250	the signal. You can even use C<ev_async> from a signal handler to	2277	the signal. You can even use C<ev_async> from a signal handler to
…		…
3075	disadvantage of having to use multiple event loops (which do not support	3102	disadvantage of having to use multiple event loops (which do not support
3076	signal watchers).	3103	signal watchers).
3077		3104
3078	When this is not possible, or you want to use the default loop for	3105	When this is not possible, or you want to use the default loop for
3079	other reasons, then in the process that wants to start "fresh", call	3106	other reasons, then in the process that wants to start "fresh", call
3080	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3107	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
3081	the default loop will "orphan" (not stop) all registered watchers, so you	3108	Destroying the default loop will "orphan" (not stop) all registered
3082	have to be careful not to execute code that modifies those watchers. Note	3109	watchers, so you have to be careful not to execute code that modifies
3083	also that in that case, you have to re-register any signal watchers.	3110	those watchers. Note also that in that case, you have to re-register any
		3111	signal watchers.
3084		3112
3085	=head3 Watcher-Specific Functions and Data Members	3113	=head3 Watcher-Specific Functions and Data Members
3086		3114
3087	=over 4	3115	=over 4
3088		3116
3089	=item ev_fork_init (ev_signal *, callback)	3117	=item ev_fork_init (ev_fork *, callback)
3090		3118
3091	Initialises and configures the fork watcher - it has no parameters of any	3119	Initialises and configures the fork watcher - it has no parameters of any
3092	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3120	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
3093	believe me.	3121	really.
3094		3122
3095	=back	3123	=back
		3124
		3125
		3126	=head2 C<ev_cleanup> - even the best things end
		3127
		3128	Cleanup watchers are called just before the event loop is being destroyed
		3129	by a call to C<ev_loop_destroy>.
		3130
		3131	While there is no guarantee that the event loop gets destroyed, cleanup
		3132	watchers provide a convenient method to install cleanup hooks for your
		3133	program, worker threads and so on - you just to make sure to destroy the
		3134	loop when you want them to be invoked.
		3135
		3136	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3137	all other watchers, they do not keep a reference to the event loop (which
		3138	makes a lot of sense if you think about it). Like all other watchers, you
		3139	can call libev functions in the callback, except C<ev_cleanup_start>.
		3140
		3141	=head3 Watcher-Specific Functions and Data Members
		3142
		3143	=over 4
		3144
		3145	=item ev_cleanup_init (ev_cleanup *, callback)
		3146
		3147	Initialises and configures the cleanup watcher - it has no parameters of
		3148	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3149	pointless, I assure you.
		3150
		3151	=back
		3152
		3153	Example: Register an atexit handler to destroy the default loop, so any
		3154	cleanup functions are called.
		3155
		3156	static void
		3157	program_exits (void)
		3158	{
		3159	ev_loop_destroy (EV_DEFAULT_UC);
		3160	}
		3161
		3162	...
		3163	atexit (program_exits);
3096		3164
3097		3165
3098	=head2 C<ev_async> - how to wake up an event loop	3166	=head2 C<ev_async> - how to wake up an event loop
3099		3167
3100	In general, you cannot use an C<ev_run> from multiple threads or other	3168	In general, you cannot use an C<ev_run> from multiple threads or other
…		…
3299	loop!).	3367	loop!).
3300		3368
3301	=back	3369	=back
3302		3370
3303		3371
		3372	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3373
		3374	This section explains some common idioms that are not immediately
		3375	obvious. Note that examples are sprinkled over the whole manual, and this
		3376	section only contains stuff that wouldn't fit anywhere else.
		3377
		3378	=over 4
		3379
		3380	=item Model/nested event loop invocations and exit conditions.
		3381
		3382	Often (especially in GUI toolkits) there are places where you have
		3383	I<modal> interaction, which is most easily implemented by recursively
		3384	invoking C<ev_run>.
		3385
		3386	This brings the problem of exiting - a callback might want to finish the
		3387	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3388	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3389	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3390	other combination: In these cases, C<ev_break> will not work alone.
		3391
		3392	The solution is to maintain "break this loop" variable for each C<ev_run>
		3393	invocation, and use a loop around C<ev_run> until the condition is
		3394	triggered, using C<EVRUN_ONCE>:
		3395
		3396	// main loop
		3397	int exit_main_loop = 0;
		3398
		3399	while (!exit_main_loop)
		3400	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3401
		3402	// in a model watcher
		3403	int exit_nested_loop = 0;
		3404
		3405	while (!exit_nested_loop)
		3406	ev_run (EV_A_ EVRUN_ONCE);
		3407
		3408	To exit from any of these loops, just set the corresponding exit variable:
		3409
		3410	// exit modal loop
		3411	exit_nested_loop = 1;
		3412
		3413	// exit main program, after modal loop is finished
		3414	exit_main_loop = 1;
		3415
		3416	// exit both
		3417	exit_main_loop = exit_nested_loop = 1;
		3418
		3419	=back
		3420
		3421
3304	=head1 LIBEVENT EMULATION	3422	=head1 LIBEVENT EMULATION
3305		3423
3306	Libev offers a compatibility emulation layer for libevent. It cannot	3424	Libev offers a compatibility emulation layer for libevent. It cannot
3307	emulate the internals of libevent, so here are some usage hints:	3425	emulate the internals of libevent, so here are some usage hints:
3308		3426
3309	=over 4	3427	=over 4
		3428
		3429	=item * Only the libevent-1.4.1-beta API is being emulated.
		3430
		3431	This was the newest libevent version available when libev was implemented,
		3432	and is still mostly uncanged in 2010.
3310		3433
3311	=item * Use it by including <event.h>, as usual.	3434	=item * Use it by including <event.h>, as usual.
3312		3435
3313	=item * The following members are fully supported: ev_base, ev_callback,	3436	=item * The following members are fully supported: ev_base, ev_callback,
3314	ev_arg, ev_fd, ev_res, ev_events.	3437	ev_arg, ev_fd, ev_res, ev_events.
…		…
3320	=item * Priorities are not currently supported. Initialising priorities	3443	=item * Priorities are not currently supported. Initialising priorities
3321	will fail and all watchers will have the same priority, even though there	3444	will fail and all watchers will have the same priority, even though there
3322	is an ev_pri field.	3445	is an ev_pri field.
3323		3446
3324	=item * In libevent, the last base created gets the signals, in libev, the	3447	=item * In libevent, the last base created gets the signals, in libev, the
3325	first base created (== the default loop) gets the signals.	3448	base that registered the signal gets the signals.
3326		3449
3327	=item * Other members are not supported.	3450	=item * Other members are not supported.
3328		3451
3329	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3452	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3330	to use the libev header file and library.	3453	to use the libev header file and library.
…		…
3349	Care has been taken to keep the overhead low. The only data member the C++	3472	Care has been taken to keep the overhead low. The only data member the C++
3350	classes add (compared to plain C-style watchers) is the event loop pointer	3473	classes add (compared to plain C-style watchers) is the event loop pointer
3351	that the watcher is associated with (or no additional members at all if	3474	that the watcher is associated with (or no additional members at all if
3352	you disable C<EV_MULTIPLICITY> when embedding libev).	3475	you disable C<EV_MULTIPLICITY> when embedding libev).
3353		3476
3354	Currently, functions, and static and non-static member functions can be	3477	Currently, functions, static and non-static member functions and classes
3355	used as callbacks. Other types should be easy to add as long as they only	3478	with C<operator ()> can be used as callbacks. Other types should be easy
3356	need one additional pointer for context. If you need support for other	3479	to add as long as they only need one additional pointer for context. If
3357	types of functors please contact the author (preferably after implementing	3480	you need support for other types of functors please contact the author
3358	it).	3481	(preferably after implementing it).
3359		3482
3360	Here is a list of things available in the C<ev> namespace:	3483	Here is a list of things available in the C<ev> namespace:
3361		3484
3362	=over 4	3485	=over 4
3363		3486
…		…
4707	structure (guaranteed by POSIX but not by ISO C for example), but it also	4830	structure (guaranteed by POSIX but not by ISO C for example), but it also
4708	assumes that the same (machine) code can be used to call any watcher	4831	assumes that the same (machine) code can be used to call any watcher
4709	callback: The watcher callbacks have different type signatures, but libev	4832	callback: The watcher callbacks have different type signatures, but libev
4710	calls them using an C<ev_watcher *> internally.	4833	calls them using an C<ev_watcher *> internally.
4711		4834
		4835	=item pointer accesses must be thread-atomic
		4836
		4837	Accessing a pointer value must be atomic, it must both be readable and
		4838	writable in one piece - this is the case on all current architectures.
		4839
4712	=item C<sig_atomic_t volatile> must be thread-atomic as well	4840	=item C<sig_atomic_t volatile> must be thread-atomic as well
4713		4841
4714	The type C<sig_atomic_t volatile> (or whatever is defined as	4842	The type C<sig_atomic_t volatile> (or whatever is defined as
4715	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	4843	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
4716	threads. This is not part of the specification for C<sig_atomic_t>, but is	4844	threads. This is not part of the specification for C<sig_atomic_t>, but is
…		…
4822	=back	4950	=back
4823		4951
4824		4952
4825	=head1 PORTING FROM LIBEV 3.X TO 4.X	4953	=head1 PORTING FROM LIBEV 3.X TO 4.X
4826		4954
4827	The major version 4 introduced some minor incompatible changes to the API.	4955	The major version 4 introduced some incompatible changes to the API.
4828		4956
4829	At the moment, the C<ev.h> header file tries to implement superficial	4957	At the moment, the C<ev.h> header file provides compatibility definitions
4830	compatibility, so most programs should still compile. Those might be	4958	for all changes, so most programs should still compile. The compatibility
4831	removed in later versions of libev, so better update early than late.	4959	layer might be removed in later versions of libev, so better update to the
		4960	new API early than late.
4832		4961
4833	=over 4	4962	=over 4
		4963
		4964	=item C<EV_COMPAT3> backwards compatibility mechanism
		4965
		4966	The backward compatibility mechanism can be controlled by
		4967	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		4968	section.
		4969
		4970	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		4971
		4972	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		4973
		4974	ev_loop_destroy (EV_DEFAULT_UC);
		4975	ev_loop_fork (EV_DEFAULT);
4834		4976
4835	=item function/symbol renames	4977	=item function/symbol renames
4836		4978
4837	A number of functions and symbols have been renamed:	4979	A number of functions and symbols have been renamed:
4838		4980
…		…
4857	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme	4999	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
4858	as all other watcher types. Note that C<ev_loop_fork> is still called	5000	as all other watcher types. Note that C<ev_loop_fork> is still called
4859	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>	5001	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
4860	typedef.	5002	typedef.
4861		5003
4862	=item C<EV_COMPAT3> backwards compatibility mechanism
4863
4864	The backward compatibility mechanism can be controlled by
4865	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
4866	section.
4867
4868	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>	5004	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
4869		5005
4870	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different	5006	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
4871	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile	5007	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
4872	and work, but the library code will of course be larger.	5008	and work, but the library code will of course be larger.
…		…
4946		5082
4947	=back	5083	=back
4948		5084
4949	=head1 AUTHOR	5085	=head1 AUTHOR
4950		5086
4951	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5087	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5088	Magnusson and Emanuele Giaquinta.
4952		5089

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Comparing libev/ev.pod (file contents): Revision 1.320 by root, Fri Oct 22 10:48:54 2010 UTC vs. Revision 1.346 by root, Wed Nov 10 14:50:54 2010 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.320 by root, Fri Oct 22 10:48:54 2010 UTC vs.
Revision 1.346 by root, Wed Nov 10 14:50:54 2010 UTC