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

Comparing libev/ev.pod (file contents):
Revision 1.319 by root, Fri Oct 22 10:09:12 2010 UTC vs.
Revision 1.340 by root, Wed Nov 3 20:03:21 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
…		…
193	as this indicates an incompatible change. Minor versions are usually	201	as this indicates an incompatible change. Minor versions are usually
194	compatible to older versions, so a larger minor version alone is usually	202	compatible to older versions, so a larger minor version alone is usually
195	not a problem.	203	not a problem.
196		204
197	Example: Make sure we haven't accidentally been linked against the wrong	205	Example: Make sure we haven't accidentally been linked against the wrong
198	version (note, however, that this will not detect ABI mismatches :).	206	version (note, however, that this will not detect other ABI mismatches,
		207	such as LFS or reentrancy).
199		208
200	assert (("libev version mismatch",	209	assert (("libev version mismatch",
201	ev_version_major () == EV_VERSION_MAJOR	210	ev_version_major () == EV_VERSION_MAJOR
202	&& ev_version_minor () >= EV_VERSION_MINOR));	211	&& ev_version_minor () >= EV_VERSION_MINOR));
203		212
…		…
232	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 ()
233	& ev_supported_backends ()>, likewise for recommended ones.	242	& ev_supported_backends ()>, likewise for recommended ones.
234		243
235	See the description of C<ev_embed> watchers for more info.	244	See the description of C<ev_embed> watchers for more info.
236		245
237	=item ev_set_allocator (void (cb)(void *ptr, long size)) [NOT REENTRANT]	246	=item ev_set_allocator (void (cb)(void *ptr, long size))
238		247
239	Sets the allocation function to use (the prototype is similar - the	248	Sets the allocation function to use (the prototype is similar - the
240	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
241	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
242	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
…		…
268	}	277	}
269		278
270	...	279	...
271	ev_set_allocator (persistent_realloc);	280	ev_set_allocator (persistent_realloc);
272		281
273	=item ev_set_syserr_cb (void (cb)(const char msg)); [NOT REENTRANT]	282	=item ev_set_syserr_cb (void (cb)(const char msg))
274		283
275	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
276	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
277	indicating the system call or subsystem causing the problem. If this	286	indicating the system call or subsystem causing the problem. If this
278	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
…		…
292	...	301	...
293	ev_set_syserr_cb (fatal_error);	302	ev_set_syserr_cb (fatal_error);
294		303
295	=back	304	=back
296		305
297	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	306	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
298		307
299	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
300	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
301	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).
302		311
303	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
304	supports signals and child events, and dynamically created event loops	313	supports child process events, and dynamically created event loops which
305	which do not.	314	do not.
306		315
307	=over 4	316	=over 4
308		317
309	=item struct ev_loop *ev_default_loop (unsigned int flags)	318	=item struct ev_loop *ev_default_loop (unsigned int flags)
310		319
311	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
312	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
313	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
314	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".
315		330
316	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
317	function.	332	function (or via the C<EV_DEFAULT> macro).
318		333
319	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
320	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
321	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).
322		338
323	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,
324	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
325	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
326	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
327	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	343	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
328	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	Note that this function I<is> thread-safe, and one common way to use
		361	libev with threads is indeed to create one loop per thread, and using the
		362	default loop in the "main" or "initial" thread.
329		363
330	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
331	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>).
332		366
333	The following flags are supported:	367	The following flags are supported:
…		…
368	environment variable.	402	environment variable.
369		403
370	=item C<EVFLAG_NOINOTIFY>	404	=item C<EVFLAG_NOINOTIFY>
371		405
372	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
373	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
374	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
375	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.
376		410
377	=item C<EVFLAG_SIGNALFD>	411	=item C<EVFLAG_SIGNALFD>
378		412
379	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
380	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
381	delivers signals synchronously, which makes it both faster and might make	415	delivers signals synchronously, which makes it both faster and might make
382	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
383	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
384	threads that are not interested in handling them.	418	threads that are not interested in handling them.
385		419
…		…
429	epoll scales either O(1) or O(active_fds).	463	epoll scales either O(1) or O(active_fds).
430		464
431	The epoll mechanism deserves honorable mention as the most misdesigned	465	The epoll mechanism deserves honorable mention as the most misdesigned
432	of the more advanced event mechanisms: mere annoyances include silently	466	of the more advanced event mechanisms: mere annoyances include silently
433	dropping file descriptors, requiring a system call per change per file	467	dropping file descriptors, requiring a system call per change per file
434	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
435	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
436	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
437	take considerable time (one syscall per file descriptor) and is of course	473	set, which can take considerable time (one syscall per file descriptor)
438	hard to detect.	474	and is of course hard to detect.
439		475
440	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
441	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
442	I<different> file descriptors (even already closed ones, so one cannot	478	I<different> file descriptors (even already closed ones, so one cannot
443	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
…		…
445	employing an additional generation counter and comparing that against the	481	employing an additional generation counter and comparing that against the
446	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
447	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
448	perfectly fine with C<select> (files, many character devices...).	484	perfectly fine with C<select> (files, many character devices...).
449		485
		486	Epoll is truly the train wreck analog among event poll mechanisms.
		487
450	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
451	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
452	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
453	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
454	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
…		…
551	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,
552	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
553	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
554	()> will be tried.	592	()> will be tried.
555		593
556	Example: This is the most typical usage.
557
558	if (!ev_default_loop (0))
559	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
560
561	Example: Restrict libev to the select and poll backends, and do not allow
562	environment settings to be taken into account:
563
564	ev_default_loop (EVBACKEND_POLL \| EVBACKEND_SELECT \| EVFLAG_NOENV);
565
566	Example: Use whatever libev has to offer, but make sure that kqueue is
567	used if available (warning, breaks stuff, best use only with your own
568	private event loop and only if you know the OS supports your types of
569	fds):
570
571	ev_default_loop (ev_recommended_backends () \| EVBACKEND_KQUEUE);
572
573	=item struct ev_loop *ev_loop_new (unsigned int flags)
574
575	Similar to C<ev_default_loop>, but always creates a new event loop that is
576	always distinct from the default loop.
577
578	Note that this function I<is> thread-safe, and one common way to use
579	libev with threads is indeed to create one loop per thread, and using the
580	default loop in the "main" or "initial" thread.
581
582	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.
583		595
584	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);	596	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);
585	if (!epoller)	597	if (!epoller)
586	fatal ("no epoll found here, maybe it hides under your chair");	598	fatal ("no epoll found here, maybe it hides under your chair");
587		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
588	=item ev_default_destroy ()	605	=item ev_loop_destroy (loop)
589		606
590	Destroys the default loop (frees all memory and kernel state etc.). None	607	Destroys an event loop object (frees all memory and kernel state
591	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
592	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
593	either stop all watchers cleanly yourself I<before> calling this function,	610	responsibility to either stop all watchers cleanly yourself I<before>
594	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
595	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).
596		614
597	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
598	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
599	as signal and child watchers) would need to be stopped manually.	617	as signal and child watchers) would need to be stopped manually.
600		618
601	In general it is not advisable to call this function except in the	619	This function is normally used on loop objects allocated by
602	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.
603	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>
604	C<ev_loop_new> and C<ev_loop_destroy>.	626	and C<ev_loop_destroy>.
605		627
606	=item ev_loop_destroy (loop)	628	=item ev_loop_fork (loop)
607		629
608	Like C<ev_default_destroy>, but destroys an event loop created by an
609	earlier call to C<ev_loop_new>.
610
611	=item ev_default_fork ()
612
613	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
614	to reinitialise the kernel state for backends that have one. Despite the	631	reinitialise the kernel state for backends that have one. Despite the
615	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
616	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
617	sense). You I<must> call it in the child before using any of the libev	634	child before resuming or calling C<ev_run>.
618	functions, and it will only take effect at the next C<ev_run> iteration.
619		635
620	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
621	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
622	because some kernel interfaces cough I<kqueue> cough do funny things	638	because some kernel interfaces cough I<kqueue> cough do funny things
623	during fork.	639	during fork.
…		…
628	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
629	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
630	costly reset of the backend).	646	costly reset of the backend).
631		647
632	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
633	it just in case after a fork. To make this easy, the function will fit in	649	it just in case after a fork.
634	quite nicely into a call to C<pthread_atfork>:
635		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	...
636	pthread_atfork (0, 0, ev_default_fork);	661	pthread_atfork (0, 0, post_fork_child);
637
638	=item ev_loop_fork (loop)
639
640	Like C<ev_default_fork>, but acts on an event loop created by
641	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
642	after fork that you want to re-use in the child, and how you keep track of
643	them is entirely your own problem.
644		662
645	=item int ev_is_default_loop (loop)	663	=item int ev_is_default_loop (loop)
646		664
647	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
648	otherwise.	666	otherwise.
…		…
809	Can be used to make a call to C<ev_run> return early (but only after it	827	Can be used to make a call to C<ev_run> return early (but only after it
810	has processed all outstanding events). The C<how> argument must be either	828	has processed all outstanding events). The C<how> argument must be either
811	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or	829	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
812	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.	830	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
813		831
814	This "unloop state" will be cleared when entering C<ev_run> again.	832	This "break state" will be cleared when entering C<ev_run> again.
815		833
816	It is safe to call C<ev_break> from outside any C<ev_run> calls. ##TODO##	834	It is safe to call C<ev_break> from outside any C<ev_run> calls, too.
817		835
818	=item ev_ref (loop)	836	=item ev_ref (loop)
819		837
820	=item ev_unref (loop)	838	=item ev_unref (loop)
821		839
…		…
1106	=item C<EV_FORK>	1124	=item C<EV_FORK>
1107		1125
1108	The event loop has been resumed in the child process after fork (see	1126	The event loop has been resumed in the child process after fork (see
1109	C<ev_fork>).	1127	C<ev_fork>).
1110		1128
		1129	=item C<EV_CLEANUP>
		1130
		1131	The event loop is about to be destroyed (see C<ev_cleanup>).
		1132
1111	=item C<EV_ASYNC>	1133	=item C<EV_ASYNC>
1112		1134
1113	The given async watcher has been asynchronously notified (see C<ev_async>).	1135	The given async watcher has been asynchronously notified (see C<ev_async>).
1114		1136
1115	=item C<EV_CUSTOM>	1137	=item C<EV_CUSTOM>
…		…
1136	programs, though, as the fd could already be closed and reused for another	1158	programs, though, as the fd could already be closed and reused for another
1137	thing, so beware.	1159	thing, so beware.
1138		1160
1139	=back	1161	=back
1140		1162
1141	=head2 WATCHER STATES
1142
1143	There are various watcher states mentioned throughout this manual -
1144	active, pending and so on. In this section these states and the rules to
1145	transition between them will be described in more detail - and while these
1146	rules might look complicated, they usually do "the right thing".
1147
1148	=over 4
1149
1150	=item initialiased
1151
1152	Before a watcher can be registered with the event looop it has to be
1153	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
1154	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1155
1156	In this state it is simply some block of memory that is suitable for use
1157	in an event loop. It can be moved around, freed, reused etc. at will.
1158
1159	=item started/running/active
1160
1161	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1162	property of the event loop, and is actively waiting for events. While in
1163	this state it cannot be accessed (except in a few documented ways), moved,
1164	freed or anything else - the only legal thing is to keep a pointer to it,
1165	and call libev functions on it that are documented to work on active watchers.
1166
1167	=item pending
1168
1169	If a watcher is active and libev determines that an event it is interested
1170	in has occurred (such as a timer expiring), it will become pending. It will
1171	stay in this pending state until either it is stopped or its callback is
1172	about to be invoked, so it is not normally pending inside the watcher
1173	callback.
1174
1175	The watcher might or might not be active while it is pending (for example,
1176	an expired non-repeating timer can be pending but no longer active). If it
1177	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
1178	but it is still property of the event loop at this time, so cannot be
1179	moved, freed or reused. And if it is active the rules described in the
1180	previous item still apply.
1181
1182	It is also possible to feed an event on a watcher that is not active (e.g.
1183	via C<ev_feed_event>), in which case it becomes pending without being
1184	active.
1185
1186	=item stopped
1187
1188	A watcher can be stopped implicitly by libev (in which case it might still
1189	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1190	latter will clear any pending state the watcher might be in, regardless
1191	of whether it was active or not, so stopping a watcher explicitly before
1192	freeing it is often a good idea.
1193
1194	While stopped (and not pending) the watcher is essentially in the
1195	initialised state, that is it can be reused, moved, modified in any way
1196	you wish.
1197
1198	=back
1199
1200	=head2 GENERIC WATCHER FUNCTIONS	1163	=head2 GENERIC WATCHER FUNCTIONS
1201		1164
1202	=over 4	1165	=over 4
1203		1166
1204	=item C<ev_init> (ev_TYPE *watcher, callback)	1167	=item C<ev_init> (ev_TYPE *watcher, callback)
…		…
1345		1308
1346	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related	1309	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1347	functions that do not need a watcher.	1310	functions that do not need a watcher.
1348		1311
1349	=back	1312	=back
1350
1351		1313
1352	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1314	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1353		1315
1354	Each watcher has, by default, a member C<void *data> that you can change	1316	Each watcher has, by default, a member C<void *data> that you can change
1355	and read at any time: libev will completely ignore it. This can be used	1317	and read at any time: libev will completely ignore it. This can be used
…		…
1411	t2_cb (EV_P_ ev_timer *w, int revents)	1373	t2_cb (EV_P_ ev_timer *w, int revents)
1412	{	1374	{
1413	struct my_biggy big = (struct my_biggy *)	1375	struct my_biggy big = (struct my_biggy *)
1414	(((char *)w) - offsetof (struct my_biggy, t2));	1376	(((char *)w) - offsetof (struct my_biggy, t2));
1415	}	1377	}
		1378
		1379	=head2 WATCHER STATES
		1380
		1381	There are various watcher states mentioned throughout this manual -
		1382	active, pending and so on. In this section these states and the rules to
		1383	transition between them will be described in more detail - and while these
		1384	rules might look complicated, they usually do "the right thing".
		1385
		1386	=over 4
		1387
		1388	=item initialiased
		1389
		1390	Before a watcher can be registered with the event looop it has to be
		1391	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1392	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1393
		1394	In this state it is simply some block of memory that is suitable for use
		1395	in an event loop. It can be moved around, freed, reused etc. at will.
		1396
		1397	=item started/running/active
		1398
		1399	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1400	property of the event loop, and is actively waiting for events. While in
		1401	this state it cannot be accessed (except in a few documented ways), moved,
		1402	freed or anything else - the only legal thing is to keep a pointer to it,
		1403	and call libev functions on it that are documented to work on active watchers.
		1404
		1405	=item pending
		1406
		1407	If a watcher is active and libev determines that an event it is interested
		1408	in has occurred (such as a timer expiring), it will become pending. It will
		1409	stay in this pending state until either it is stopped or its callback is
		1410	about to be invoked, so it is not normally pending inside the watcher
		1411	callback.
		1412
		1413	The watcher might or might not be active while it is pending (for example,
		1414	an expired non-repeating timer can be pending but no longer active). If it
		1415	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1416	but it is still property of the event loop at this time, so cannot be
		1417	moved, freed or reused. And if it is active the rules described in the
		1418	previous item still apply.
		1419
		1420	It is also possible to feed an event on a watcher that is not active (e.g.
		1421	via C<ev_feed_event>), in which case it becomes pending without being
		1422	active.
		1423
		1424	=item stopped
		1425
		1426	A watcher can be stopped implicitly by libev (in which case it might still
		1427	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1428	latter will clear any pending state the watcher might be in, regardless
		1429	of whether it was active or not, so stopping a watcher explicitly before
		1430	freeing it is often a good idea.
		1431
		1432	While stopped (and not pending) the watcher is essentially in the
		1433	initialised state, that is it can be reused, moved, modified in any way
		1434	you wish.
		1435
		1436	=back
1416		1437
1417	=head2 WATCHER PRIORITY MODELS	1438	=head2 WATCHER PRIORITY MODELS
1418		1439
1419	Many event loops support I<watcher priorities>, which are usually small	1440	Many event loops support I<watcher priorities>, which are usually small
1420	integers that influence the ordering of event callback invocation	1441	integers that influence the ordering of event callback invocation
…		…
2239		2260
2240	=head2 C<ev_signal> - signal me when a signal gets signalled!	2261	=head2 C<ev_signal> - signal me when a signal gets signalled!
2241		2262
2242	Signal watchers will trigger an event when the process receives a specific	2263	Signal watchers will trigger an event when the process receives a specific
2243	signal one or more times. Even though signals are very asynchronous, libev	2264	signal one or more times. Even though signals are very asynchronous, libev
2244	will try it's best to deliver signals synchronously, i.e. as part of the	2265	will try its best to deliver signals synchronously, i.e. as part of the
2245	normal event processing, like any other event.	2266	normal event processing, like any other event.
2246		2267
2247	If you want signals to be delivered truly asynchronously, just use	2268	If you want signals to be delivered truly asynchronously, just use
2248	C<sigaction> as you would do without libev and forget about sharing	2269	C<sigaction> as you would do without libev and forget about sharing
2249	the signal. You can even use C<ev_async> from a signal handler to	2270	the signal. You can even use C<ev_async> from a signal handler to
…		…
3074	disadvantage of having to use multiple event loops (which do not support	3095	disadvantage of having to use multiple event loops (which do not support
3075	signal watchers).	3096	signal watchers).
3076		3097
3077	When this is not possible, or you want to use the default loop for	3098	When this is not possible, or you want to use the default loop for
3078	other reasons, then in the process that wants to start "fresh", call	3099	other reasons, then in the process that wants to start "fresh", call
3079	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3100	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
3080	the default loop will "orphan" (not stop) all registered watchers, so you	3101	Destroying the default loop will "orphan" (not stop) all registered
3081	have to be careful not to execute code that modifies those watchers. Note	3102	watchers, so you have to be careful not to execute code that modifies
3082	also that in that case, you have to re-register any signal watchers.	3103	those watchers. Note also that in that case, you have to re-register any
		3104	signal watchers.
3083		3105
3084	=head3 Watcher-Specific Functions and Data Members	3106	=head3 Watcher-Specific Functions and Data Members
3085		3107
3086	=over 4	3108	=over 4
3087		3109
3088	=item ev_fork_init (ev_signal *, callback)	3110	=item ev_fork_init (ev_fork *, callback)
3089		3111
3090	Initialises and configures the fork watcher - it has no parameters of any	3112	Initialises and configures the fork watcher - it has no parameters of any
3091	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3113	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
3092	believe me.	3114	really.
3093		3115
3094	=back	3116	=back
		3117
		3118
		3119	=head2 C<ev_cleanup> - even the best things end
		3120
		3121	Cleanup watchers are called just before the event loop is being destroyed
		3122	by a call to C<ev_loop_destroy>.
		3123
		3124	While there is no guarantee that the event loop gets destroyed, cleanup
		3125	watchers provide a convenient method to install cleanup hooks for your
		3126	program, worker threads and so on - you just to make sure to destroy the
		3127	loop when you want them to be invoked.
		3128
		3129	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3130	all other watchers, they do not keep a reference to the event loop (which
		3131	makes a lot of sense if you think about it). Like all other watchers, you
		3132	can call libev functions in the callback, except C<ev_cleanup_start>.
		3133
		3134	=head3 Watcher-Specific Functions and Data Members
		3135
		3136	=over 4
		3137
		3138	=item ev_cleanup_init (ev_cleanup *, callback)
		3139
		3140	Initialises and configures the cleanup watcher - it has no parameters of
		3141	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3142	pointless, I assure you.
		3143
		3144	=back
		3145
		3146	Example: Register an atexit handler to destroy the default loop, so any
		3147	cleanup functions are called.
		3148
		3149	static void
		3150	program_exits (void)
		3151	{
		3152	ev_loop_destroy (EV_DEFAULT_UC);
		3153	}
		3154
		3155	...
		3156	atexit (program_exits);
3095		3157
3096		3158
3097	=head2 C<ev_async> - how to wake up an event loop	3159	=head2 C<ev_async> - how to wake up an event loop
3098		3160
3099	In general, you cannot use an C<ev_run> from multiple threads or other	3161	In general, you cannot use an C<ev_run> from multiple threads or other
…		…
4706	structure (guaranteed by POSIX but not by ISO C for example), but it also	4768	structure (guaranteed by POSIX but not by ISO C for example), but it also
4707	assumes that the same (machine) code can be used to call any watcher	4769	assumes that the same (machine) code can be used to call any watcher
4708	callback: The watcher callbacks have different type signatures, but libev	4770	callback: The watcher callbacks have different type signatures, but libev
4709	calls them using an C<ev_watcher *> internally.	4771	calls them using an C<ev_watcher *> internally.
4710		4772
		4773	=item pointer accesses must be thread-atomic
		4774
		4775	Accessing a pointer value must be atomic, it must both be readable and
		4776	writable in one piece - this is the case on all current architectures.
		4777
4711	=item C<sig_atomic_t volatile> must be thread-atomic as well	4778	=item C<sig_atomic_t volatile> must be thread-atomic as well
4712		4779
4713	The type C<sig_atomic_t volatile> (or whatever is defined as	4780	The type C<sig_atomic_t volatile> (or whatever is defined as
4714	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	4781	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
4715	threads. This is not part of the specification for C<sig_atomic_t>, but is	4782	threads. This is not part of the specification for C<sig_atomic_t>, but is
…		…
4821	=back	4888	=back
4822		4889
4823		4890
4824	=head1 PORTING FROM LIBEV 3.X TO 4.X	4891	=head1 PORTING FROM LIBEV 3.X TO 4.X
4825		4892
4826	The major version 4 introduced some minor incompatible changes to the API.	4893	The major version 4 introduced some incompatible changes to the API.
4827		4894
4828	At the moment, the C<ev.h> header file tries to implement superficial	4895	At the moment, the C<ev.h> header file provides compatibility definitions
4829	compatibility, so most programs should still compile. Those might be	4896	for all changes, so most programs should still compile. The compatibility
4830	removed in later versions of libev, so better update early than late.	4897	layer might be removed in later versions of libev, so better update to the
		4898	new API early than late.
4831		4899
4832	=over 4	4900	=over 4
		4901
		4902	=item C<EV_COMPAT3> backwards compatibility mechanism
		4903
		4904	The backward compatibility mechanism can be controlled by
		4905	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		4906	section.
		4907
		4908	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		4909
		4910	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		4911
		4912	ev_loop_destroy (EV_DEFAULT_UC);
		4913	ev_loop_fork (EV_DEFAULT);
4833		4914
4834	=item function/symbol renames	4915	=item function/symbol renames
4835		4916
4836	A number of functions and symbols have been renamed:	4917	A number of functions and symbols have been renamed:
4837		4918
…		…
4856	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme	4937	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
4857	as all other watcher types. Note that C<ev_loop_fork> is still called	4938	as all other watcher types. Note that C<ev_loop_fork> is still called
4858	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>	4939	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
4859	typedef.	4940	typedef.
4860		4941
4861	=item C<EV_COMPAT3> backwards compatibility mechanism
4862
4863	The backward compatibility mechanism can be controlled by
4864	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
4865	section.
4866
4867	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>	4942	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
4868		4943
4869	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different	4944	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
4870	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile	4945	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
4871	and work, but the library code will of course be larger.	4946	and work, but the library code will of course be larger.
…		…
4945		5020
4946	=back	5021	=back
4947		5022
4948	=head1 AUTHOR	5023	=head1 AUTHOR
4949		5024
4950	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5025	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5026	Magnusson and Emanuele Giaquinta.
4951		5027

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Comparing libev/ev.pod (file contents): Revision 1.319 by root, Fri Oct 22 10:09:12 2010 UTC vs. Revision 1.340 by root, Wed Nov 3 20:03:21 2010 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.319 by root, Fri Oct 22 10:09:12 2010 UTC vs.
Revision 1.340 by root, Wed Nov 3 20:03:21 2010 UTC