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

Comparing libev/ev.pod (file contents):
Revision 1.314 by root, Fri Oct 22 06:06:31 2010 UTC vs.
Revision 1.337 by root, Sun Oct 31 20:20:20 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
…		…
124	this argument.	132	this argument.
125		133
126	=head2 TIME REPRESENTATION	134	=head2 TIME REPRESENTATION
127		135
128	Libev represents time as a single floating point number, representing	136	Libev represents time as a single floating point number, representing
129	the (fractional) number of seconds since the (POSIX) epoch (in practise	137	the (fractional) number of seconds since the (POSIX) epoch (in practice
130	somewhere near the beginning of 1970, details are complicated, don't	138	somewhere near the beginning of 1970, details are complicated, don't
131	ask). This type is called C<ev_tstamp>, which is what you should use	139	ask). This type is called C<ev_tstamp>, which is what you should use
132	too. It usually aliases to the C<double> type in C. When you need to do	140	too. It usually aliases to the C<double> type in C. When you need to do
133	any calculations on it, you should treat it as some floating point value.	141	any calculations on it, you should treat it as some floating point value.
134		142
…		…
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.	178	you actually want to know. Also interesting is the combination of
		179	C<ev_update_now> and C<ev_now>.
171		180
172	=item ev_sleep (ev_tstamp interval)	181	=item ev_sleep (ev_tstamp interval)
173		182
174	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
175	either it is interrupted or the given time interval has passed. Basically	184	either it is interrupted or the given time interval has passed. Basically
…		…
192	as this indicates an incompatible change. Minor versions are usually	201	as this indicates an incompatible change. Minor versions are usually
193	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
194	not a problem.	203	not a problem.
195		204
196	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
197	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).
198		208
199	assert (("libev version mismatch",	209	assert (("libev version mismatch",
200	ev_version_major () == EV_VERSION_MAJOR	210	ev_version_major () == EV_VERSION_MAJOR
201	&& ev_version_minor () >= EV_VERSION_MINOR));	211	&& ev_version_minor () >= EV_VERSION_MINOR));
202		212
…		…
213	assert (("sorry, no epoll, no sex",	223	assert (("sorry, no epoll, no sex",
214	ev_supported_backends () & EVBACKEND_EPOLL));	224	ev_supported_backends () & EVBACKEND_EPOLL));
215		225
216	=item unsigned int ev_recommended_backends ()	226	=item unsigned int ev_recommended_backends ()
217		227
218	Return the set of all backends compiled into this binary of libev and also	228	Return the set of all backends compiled into this binary of libev and
219	recommended for this platform. This set is often smaller than the one	229	also recommended for this platform, meaning it will work for most file
		230	descriptor types. This set is often smaller than the one returned by
220	returned by C<ev_supported_backends>, as for example kqueue is broken on	231	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
221	most BSDs and will not be auto-detected unless you explicitly request it	232	and will not be auto-detected unless you explicitly request it (assuming
222	(assuming you know what you are doing). This is the set of backends that	233	you know what you are doing). This is the set of backends that libev will
223	libev will probe for if you specify no backends explicitly.	234	probe for if you specify no backends explicitly.
224		235
225	=item unsigned int ev_embeddable_backends ()	236	=item unsigned int ev_embeddable_backends ()
226		237
227	Returns the set of backends that are embeddable in other event loops. This	238	Returns the set of backends that are embeddable in other event loops. This
228	is the theoretical, all-platform, value. To find which backends	239	value is platform-specific but can include backends not available on the
229	might be supported on the current system, you would need to look at	240	current system. To find which embeddable backends might be supported on
230	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	241	the current system, you would need to look at C<ev_embeddable_backends ()
231	recommended ones.	242	& ev_supported_backends ()>, likewise for recommended ones.
232		243
233	See the description of C<ev_embed> watchers for more info.	244	See the description of C<ev_embed> watchers for more info.
234		245
235	=item ev_set_allocator (void (cb)(void *ptr, long size)) [NOT REENTRANT]	246	=item ev_set_allocator (void (cb)(void *ptr, long size)) [NOT REENTRANT]
236		247
…		…
290	...	301	...
291	ev_set_syserr_cb (fatal_error);	302	ev_set_syserr_cb (fatal_error);
292		303
293	=back	304	=back
294		305
295	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	306	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
296		307
297	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
298	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
299	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).
300		311
301	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
302	supports signals and child events, and dynamically created event loops	313	supports child process events, and dynamically created event loops which
303	which do not.	314	do not.
304		315
305	=over 4	316	=over 4
306		317
307	=item struct ev_loop *ev_default_loop (unsigned int flags)	318	=item struct ev_loop *ev_default_loop (unsigned int flags)
308		319
309	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
310	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
311	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
312	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".
313		330
314	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
315	function.	332	function (or via the C<EV_DEFAULT> macro).
316		333
317	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
318	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
319	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).
320		338
321	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,
322	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
323	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
324	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
325	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	343	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
326	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.
327		363
328	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
329	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>).
330		366
331	The following flags are supported:	367	The following flags are supported:
…		…
427	epoll scales either O(1) or O(active_fds).	463	epoll scales either O(1) or O(active_fds).
428		464
429	The epoll mechanism deserves honorable mention as the most misdesigned	465	The epoll mechanism deserves honorable mention as the most misdesigned
430	of the more advanced event mechanisms: mere annoyances include silently	466	of the more advanced event mechanisms: mere annoyances include silently
431	dropping file descriptors, requiring a system call per change per file	467	dropping file descriptors, requiring a system call per change per file
432	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 requiring additional iterations and so
433	so on. The biggest issue is fork races, however - if a program forks then	470	on. The biggest issue is fork races, however - if a program forks then
434	I<both> parent and child process have to recreate the epoll set, which can	471	I<both> parent and child process have to recreate the epoll set, which can
435	take considerable time (one syscall per file descriptor) and is of course	472	take considerable time (one syscall per file descriptor) and is of course
436	hard to detect.	473	hard to detect.
437		474
438	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	475	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
…		…
549	If one or more of the backend flags are or'ed into the flags value,	586	If one or more of the backend flags are or'ed into the flags value,
550	then only these backends will be tried (in the reverse order as listed	587	then only these backends will be tried (in the reverse order as listed
551	here). If none are specified, all backends in C<ev_recommended_backends	588	here). If none are specified, all backends in C<ev_recommended_backends
552	()> will be tried.	589	()> will be tried.
553		590
554	Example: This is the most typical usage.
555
556	if (!ev_default_loop (0))
557	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
558
559	Example: Restrict libev to the select and poll backends, and do not allow
560	environment settings to be taken into account:
561
562	ev_default_loop (EVBACKEND_POLL \| EVBACKEND_SELECT \| EVFLAG_NOENV);
563
564	Example: Use whatever libev has to offer, but make sure that kqueue is
565	used if available (warning, breaks stuff, best use only with your own
566	private event loop and only if you know the OS supports your types of
567	fds):
568
569	ev_default_loop (ev_recommended_backends () \| EVBACKEND_KQUEUE);
570
571	=item struct ev_loop *ev_loop_new (unsigned int flags)
572
573	Similar to C<ev_default_loop>, but always creates a new event loop that is
574	always distinct from the default loop.
575
576	Note that this function I<is> thread-safe, and one common way to use
577	libev with threads is indeed to create one loop per thread, and using the
578	default loop in the "main" or "initial" thread.
579
580	Example: Try to create a event loop that uses epoll and nothing else.	591	Example: Try to create a event loop that uses epoll and nothing else.
581		592
582	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);	593	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);
583	if (!epoller)	594	if (!epoller)
584	fatal ("no epoll found here, maybe it hides under your chair");	595	fatal ("no epoll found here, maybe it hides under your chair");
585		596
		597	Example: Use whatever libev has to offer, but make sure that kqueue is
		598	used if available.
		599
		600	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () \| EVBACKEND_KQUEUE);
		601
586	=item ev_default_destroy ()	602	=item ev_loop_destroy (loop)
587		603
588	Destroys the default loop (frees all memory and kernel state etc.). None	604	Destroys an event loop object (frees all memory and kernel state
589	of the active event watchers will be stopped in the normal sense, so	605	etc.). None of the active event watchers will be stopped in the normal
590	e.g. C<ev_is_active> might still return true. It is your responsibility to	606	sense, so e.g. C<ev_is_active> might still return true. It is your
591	either stop all watchers cleanly yourself I<before> calling this function,	607	responsibility to either stop all watchers cleanly yourself I<before>
592	or cope with the fact afterwards (which is usually the easiest thing, you	608	calling this function, or cope with the fact afterwards (which is usually
593	can just ignore the watchers and/or C<free ()> them for example).	609	the easiest thing, you can just ignore the watchers and/or C<free ()> them
		610	for example).
594		611
595	Note that certain global state, such as signal state (and installed signal	612	Note that certain global state, such as signal state (and installed signal
596	handlers), will not be freed by this function, and related watchers (such	613	handlers), will not be freed by this function, and related watchers (such
597	as signal and child watchers) would need to be stopped manually.	614	as signal and child watchers) would need to be stopped manually.
598		615
599	In general it is not advisable to call this function except in the	616	This function is normally used on loop objects allocated by
600	rare occasion where you really need to free e.g. the signal handling	617	C<ev_loop_new>, but it can also be used on the default loop returned by
		618	C<ev_default_loop>, in which case it is not thread-safe.
		619
		620	Note that it is not advisable to call this function on the default loop
		621	except in the rare occasion where you really need to free it's resources.
601	pipe fds. If you need dynamically allocated loops it is better to use	622	If you need dynamically allocated loops it is better to use C<ev_loop_new>
602	C<ev_loop_new> and C<ev_loop_destroy>.	623	and C<ev_loop_destroy>.
603		624
604	=item ev_loop_destroy (loop)	625	=item ev_loop_fork (loop)
605		626
606	Like C<ev_default_destroy>, but destroys an event loop created by an
607	earlier call to C<ev_loop_new>.
608
609	=item ev_default_fork ()
610
611	This function sets a flag that causes subsequent C<ev_run> iterations	627	This function sets a flag that causes subsequent C<ev_run> iterations to
612	to reinitialise the kernel state for backends that have one. Despite the	628	reinitialise the kernel state for backends that have one. Despite the
613	name, you can call it anytime, but it makes most sense after forking, in	629	name, you can call it anytime, but it makes most sense after forking, in
614	the child process (or both child and parent, but that again makes little	630	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
615	sense). You I<must> call it in the child before using any of the libev	631	child before resuming or calling C<ev_run>.
616	functions, and it will only take effect at the next C<ev_run> iteration.
617		632
618	Again, you I<have> to call it on I<any> loop that you want to re-use after	633	Again, you I<have> to call it on I<any> loop that you want to re-use after
619	a fork, I<even if you do not plan to use the loop in the parent>. This is	634	a fork, I<even if you do not plan to use the loop in the parent>. This is
620	because some kernel interfaces cough I<kqueue> cough do funny things	635	because some kernel interfaces cough I<kqueue> cough do funny things
621	during fork.	636	during fork.
…		…
626	call it at all (in fact, C<epoll> is so badly broken that it makes a	641	call it at all (in fact, C<epoll> is so badly broken that it makes a
627	difference, but libev will usually detect this case on its own and do a	642	difference, but libev will usually detect this case on its own and do a
628	costly reset of the backend).	643	costly reset of the backend).
629		644
630	The function itself is quite fast and it's usually not a problem to call	645	The function itself is quite fast and it's usually not a problem to call
631	it just in case after a fork. To make this easy, the function will fit in	646	it just in case after a fork.
632	quite nicely into a call to C<pthread_atfork>:
633		647
		648	Example: Automate calling C<ev_loop_fork> on the default loop when
		649	using pthreads.
		650
		651	static void
		652	post_fork_child (void)
		653	{
		654	ev_loop_fork (EV_DEFAULT);
		655	}
		656
		657	...
634	pthread_atfork (0, 0, ev_default_fork);	658	pthread_atfork (0, 0, post_fork_child);
635
636	=item ev_loop_fork (loop)
637
638	Like C<ev_default_fork>, but acts on an event loop created by
639	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
640	after fork that you want to re-use in the child, and how you keep track of
641	them is entirely your own problem.
642		659
643	=item int ev_is_default_loop (loop)	660	=item int ev_is_default_loop (loop)
644		661
645	Returns true when the given loop is, in fact, the default loop, and false	662	Returns true when the given loop is, in fact, the default loop, and false
646	otherwise.	663	otherwise.
…		…
807	Can be used to make a call to C<ev_run> return early (but only after it	824	Can be used to make a call to C<ev_run> return early (but only after it
808	has processed all outstanding events). The C<how> argument must be either	825	has processed all outstanding events). The C<how> argument must be either
809	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or	826	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
810	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.	827	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
811		828
812	This "unloop state" will be cleared when entering C<ev_run> again.	829	This "break state" will be cleared when entering C<ev_run> again.
813		830
814	It is safe to call C<ev_break> from outside any C<ev_run> calls. ##TODO##	831	It is safe to call C<ev_break> from outside any C<ev_run> calls, too.
815		832
816	=item ev_ref (loop)	833	=item ev_ref (loop)
817		834
818	=item ev_unref (loop)	835	=item ev_unref (loop)
819		836
…		…
1104	=item C<EV_FORK>	1121	=item C<EV_FORK>
1105		1122
1106	The event loop has been resumed in the child process after fork (see	1123	The event loop has been resumed in the child process after fork (see
1107	C<ev_fork>).	1124	C<ev_fork>).
1108		1125
		1126	=item C<EV_CLEANUP>
		1127
		1128	The event loop is about to be destroyed (see C<ev_cleanup>).
		1129
1109	=item C<EV_ASYNC>	1130	=item C<EV_ASYNC>
1110		1131
1111	The given async watcher has been asynchronously notified (see C<ev_async>).	1132	The given async watcher has been asynchronously notified (see C<ev_async>).
1112		1133
1113	=item C<EV_CUSTOM>	1134	=item C<EV_CUSTOM>
…		…
1134	programs, though, as the fd could already be closed and reused for another	1155	programs, though, as the fd could already be closed and reused for another
1135	thing, so beware.	1156	thing, so beware.
1136		1157
1137	=back	1158	=back
1138		1159
1139	=head2 WATCHER STATES
1140
1141	There are various watcher states mentioned throughout this manual -
1142	active, pending and so on. In this section these states and the rules to
1143	transition between them will be described in more detail - and while these
1144	rules might look complicated, they usually do "the right thing".
1145
1146	=over 4
1147
1148	=item initialiased
1149
1150	Before a watcher can be registered with the event looop it has to be
1151	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
1152	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1153
1154	In this state it is simply some block of memory that is suitable for use
1155	in an event loop. It can be moved around, freed, reused etc. at will.
1156
1157	=item started/running/active
1158
1159	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1160	property of the event loop, and is actively waiting for events. While in
1161	this state it cannot be accessed (except in a few documented ways), moved,
1162	freed or anything else - the only legal thing is to keep a pointer to it,
1163	and call libev functions on it that are documented to work on active watchers.
1164
1165	=item pending
1166
1167	If a watcher is active and libev determines that an event it is interested
1168	in has occurred (such as a timer expiring), it will become pending. It will
1169	stay in this pending state until either it is stopped or its callback is
1170	about to be invoked, so it is not normally pending inside the watcher
1171	callback.
1172
1173	The watcher might or might not be active while it is pending (for example,
1174	an expired non-repeating timer can be pending but no longer active). If it
1175	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
1176	but it is still property of the event loop at this time, so cannot be
1177	moved, freed or reused. And if it is active the rules described in the
1178	previous item still apply.
1179
1180	It is also possible to feed an event on a watcher that is not active (e.g.
1181	via C<ev_feed_event>), in which case it becomes pending without being
1182	active.
1183
1184	=item stopped
1185
1186	A watcher can be stopped implicitly by libev (in which case it might still
1187	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1188	latter will clear any pending state the watcher might be in, regardless
1189	of whether it was active or not, so stopping a watcher explicitly before
1190	freeing it is often a good idea.
1191
1192	While stopped (and not pending) the watcher is essentially in the
1193	initialised state, that is it can be reused, moved, modified in any way
1194	you wish.
1195
1196	=back
1197
1198	=head2 GENERIC WATCHER FUNCTIONS	1160	=head2 GENERIC WATCHER FUNCTIONS
1199		1161
1200	=over 4	1162	=over 4
1201		1163
1202	=item C<ev_init> (ev_TYPE *watcher, callback)	1164	=item C<ev_init> (ev_TYPE *watcher, callback)
…		…
1343		1305
1344	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related	1306	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1345	functions that do not need a watcher.	1307	functions that do not need a watcher.
1346		1308
1347	=back	1309	=back
1348
1349		1310
1350	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1311	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1351		1312
1352	Each watcher has, by default, a member C<void *data> that you can change	1313	Each watcher has, by default, a member C<void *data> that you can change
1353	and read at any time: libev will completely ignore it. This can be used	1314	and read at any time: libev will completely ignore it. This can be used
…		…
1409	t2_cb (EV_P_ ev_timer *w, int revents)	1370	t2_cb (EV_P_ ev_timer *w, int revents)
1410	{	1371	{
1411	struct my_biggy big = (struct my_biggy *)	1372	struct my_biggy big = (struct my_biggy *)
1412	(((char *)w) - offsetof (struct my_biggy, t2));	1373	(((char *)w) - offsetof (struct my_biggy, t2));
1413	}	1374	}
		1375
		1376	=head2 WATCHER STATES
		1377
		1378	There are various watcher states mentioned throughout this manual -
		1379	active, pending and so on. In this section these states and the rules to
		1380	transition between them will be described in more detail - and while these
		1381	rules might look complicated, they usually do "the right thing".
		1382
		1383	=over 4
		1384
		1385	=item initialiased
		1386
		1387	Before a watcher can be registered with the event looop it has to be
		1388	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1389	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1390
		1391	In this state it is simply some block of memory that is suitable for use
		1392	in an event loop. It can be moved around, freed, reused etc. at will.
		1393
		1394	=item started/running/active
		1395
		1396	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1397	property of the event loop, and is actively waiting for events. While in
		1398	this state it cannot be accessed (except in a few documented ways), moved,
		1399	freed or anything else - the only legal thing is to keep a pointer to it,
		1400	and call libev functions on it that are documented to work on active watchers.
		1401
		1402	=item pending
		1403
		1404	If a watcher is active and libev determines that an event it is interested
		1405	in has occurred (such as a timer expiring), it will become pending. It will
		1406	stay in this pending state until either it is stopped or its callback is
		1407	about to be invoked, so it is not normally pending inside the watcher
		1408	callback.
		1409
		1410	The watcher might or might not be active while it is pending (for example,
		1411	an expired non-repeating timer can be pending but no longer active). If it
		1412	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1413	but it is still property of the event loop at this time, so cannot be
		1414	moved, freed or reused. And if it is active the rules described in the
		1415	previous item still apply.
		1416
		1417	It is also possible to feed an event on a watcher that is not active (e.g.
		1418	via C<ev_feed_event>), in which case it becomes pending without being
		1419	active.
		1420
		1421	=item stopped
		1422
		1423	A watcher can be stopped implicitly by libev (in which case it might still
		1424	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1425	latter will clear any pending state the watcher might be in, regardless
		1426	of whether it was active or not, so stopping a watcher explicitly before
		1427	freeing it is often a good idea.
		1428
		1429	While stopped (and not pending) the watcher is essentially in the
		1430	initialised state, that is it can be reused, moved, modified in any way
		1431	you wish.
		1432
		1433	=back
1414		1434
1415	=head2 WATCHER PRIORITY MODELS	1435	=head2 WATCHER PRIORITY MODELS
1416		1436
1417	Many event loops support I<watcher priorities>, which are usually small	1437	Many event loops support I<watcher priorities>, which are usually small
1418	integers that influence the ordering of event callback invocation	1438	integers that influence the ordering of event callback invocation
…		…
3072	disadvantage of having to use multiple event loops (which do not support	3092	disadvantage of having to use multiple event loops (which do not support
3073	signal watchers).	3093	signal watchers).
3074		3094
3075	When this is not possible, or you want to use the default loop for	3095	When this is not possible, or you want to use the default loop for
3076	other reasons, then in the process that wants to start "fresh", call	3096	other reasons, then in the process that wants to start "fresh", call
3077	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3097	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
3078	the default loop will "orphan" (not stop) all registered watchers, so you	3098	Destroying the default loop will "orphan" (not stop) all registered
3079	have to be careful not to execute code that modifies those watchers. Note	3099	watchers, so you have to be careful not to execute code that modifies
3080	also that in that case, you have to re-register any signal watchers.	3100	those watchers. Note also that in that case, you have to re-register any
		3101	signal watchers.
3081		3102
3082	=head3 Watcher-Specific Functions and Data Members	3103	=head3 Watcher-Specific Functions and Data Members
3083		3104
3084	=over 4	3105	=over 4
3085		3106
3086	=item ev_fork_init (ev_signal *, callback)	3107	=item ev_fork_init (ev_fork *, callback)
3087		3108
3088	Initialises and configures the fork watcher - it has no parameters of any	3109	Initialises and configures the fork watcher - it has no parameters of any
3089	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3110	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
3090	believe me.	3111	really.
3091		3112
3092	=back	3113	=back
		3114
		3115
		3116	=head2 C<ev_cleanup> - even the best things end
		3117
		3118	Cleanup watchers are called just before the event loop is being destroyed
		3119	by a call to C<ev_loop_destroy>.
		3120
		3121	While there is no guarantee that the event loop gets destroyed, cleanup
		3122	watchers provide a convenient method to install cleanup hooks for your
		3123	program, worker threads and so on - you just to make sure to destroy the
		3124	loop when you want them to be invoked.
		3125
		3126	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3127	all other watchers, they do not keep a reference to the event loop (which
		3128	makes a lot of sense if you think about it). Like all other watchers, you
		3129	can call libev functions in the callback, except C<ev_cleanup_start>.
		3130
		3131	=head3 Watcher-Specific Functions and Data Members
		3132
		3133	=over 4
		3134
		3135	=item ev_cleanup_init (ev_cleanup *, callback)
		3136
		3137	Initialises and configures the cleanup watcher - it has no parameters of
		3138	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3139	pointless, I assure you.
		3140
		3141	=back
		3142
		3143	Example: Register an atexit handler to destroy the default loop, so any
		3144	cleanup functions are called.
		3145
		3146	static void
		3147	program_exits (void)
		3148	{
		3149	ev_loop_destroy (EV_DEFAULT_UC);
		3150	}
		3151
		3152	...
		3153	atexit (program_exits);
3093		3154
3094		3155
3095	=head2 C<ev_async> - how to wake up an event loop	3156	=head2 C<ev_async> - how to wake up an event loop
3096		3157
3097	In general, you cannot use an C<ev_run> from multiple threads or other	3158	In general, you cannot use an C<ev_run> from multiple threads or other
…		…
4704	structure (guaranteed by POSIX but not by ISO C for example), but it also	4765	structure (guaranteed by POSIX but not by ISO C for example), but it also
4705	assumes that the same (machine) code can be used to call any watcher	4766	assumes that the same (machine) code can be used to call any watcher
4706	callback: The watcher callbacks have different type signatures, but libev	4767	callback: The watcher callbacks have different type signatures, but libev
4707	calls them using an C<ev_watcher *> internally.	4768	calls them using an C<ev_watcher *> internally.
4708		4769
		4770	=item pointer accesses must be thread-atomic
		4771
		4772	Accessing a pointer value must be atomic, it must both be readable and
		4773	writable in one piece - this is the case on all current architectures.
		4774
4709	=item C<sig_atomic_t volatile> must be thread-atomic as well	4775	=item C<sig_atomic_t volatile> must be thread-atomic as well
4710		4776
4711	The type C<sig_atomic_t volatile> (or whatever is defined as	4777	The type C<sig_atomic_t volatile> (or whatever is defined as
4712	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	4778	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
4713	threads. This is not part of the specification for C<sig_atomic_t>, but is	4779	threads. This is not part of the specification for C<sig_atomic_t>, but is
…		…
4819	=back	4885	=back
4820		4886
4821		4887
4822	=head1 PORTING FROM LIBEV 3.X TO 4.X	4888	=head1 PORTING FROM LIBEV 3.X TO 4.X
4823		4889
4824	The major version 4 introduced some minor incompatible changes to the API.	4890	The major version 4 introduced some incompatible changes to the API.
4825		4891
4826	At the moment, the C<ev.h> header file tries to implement superficial	4892	At the moment, the C<ev.h> header file provides compatibility definitions
4827	compatibility, so most programs should still compile. Those might be	4893	for all changes, so most programs should still compile. The compatibility
4828	removed in later versions of libev, so better update early than late.	4894	layer might be removed in later versions of libev, so better update to the
		4895	new API early than late.
4829		4896
4830	=over 4	4897	=over 4
		4898
		4899	=item C<EV_COMPAT3> backwards compatibility mechanism
		4900
		4901	The backward compatibility mechanism can be controlled by
		4902	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		4903	section.
		4904
		4905	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		4906
		4907	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		4908
		4909	ev_loop_destroy (EV_DEFAULT_UC);
		4910	ev_loop_fork (EV_DEFAULT);
4831		4911
4832	=item function/symbol renames	4912	=item function/symbol renames
4833		4913
4834	A number of functions and symbols have been renamed:	4914	A number of functions and symbols have been renamed:
4835		4915
…		…
4854	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme	4934	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
4855	as all other watcher types. Note that C<ev_loop_fork> is still called	4935	as all other watcher types. Note that C<ev_loop_fork> is still called
4856	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>	4936	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
4857	typedef.	4937	typedef.
4858		4938
4859	=item C<EV_COMPAT3> backwards compatibility mechanism
4860
4861	The backward compatibility mechanism can be controlled by
4862	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
4863	section.
4864
4865	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>	4939	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
4866		4940
4867	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different	4941	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
4868	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile	4942	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
4869	and work, but the library code will of course be larger.	4943	and work, but the library code will of course be larger.
…		…
4875		4949
4876	=over 4	4950	=over 4
4877		4951
4878	=item active	4952	=item active
4879		4953
4880	A watcher is active as long as it has been started (has been attached to	4954	A watcher is active as long as it has been started and not yet stopped.
4881	an event loop) but not yet stopped (disassociated from the event loop).	4955	See L<WATCHER STATES> for details.
4882		4956
4883	=item application	4957	=item application
4884		4958
4885	In this document, an application is whatever is using libev.	4959	In this document, an application is whatever is using libev.
		4960
		4961	=item backend
		4962
		4963	The part of the code dealing with the operating system interfaces.
4886		4964
4887	=item callback	4965	=item callback
4888		4966
4889	The address of a function that is called when some event has been	4967	The address of a function that is called when some event has been
4890	detected. Callbacks are being passed the event loop, the watcher that	4968	detected. Callbacks are being passed the event loop, the watcher that
4891	received the event, and the actual event bitset.	4969	received the event, and the actual event bitset.
4892		4970
4893	=item callback invocation	4971	=item callback/watcher invocation
4894		4972
4895	The act of calling the callback associated with a watcher.	4973	The act of calling the callback associated with a watcher.
4896		4974
4897	=item event	4975	=item event
4898		4976
…		…
4917	The model used to describe how an event loop handles and processes	4995	The model used to describe how an event loop handles and processes
4918	watchers and events.	4996	watchers and events.
4919		4997
4920	=item pending	4998	=item pending
4921		4999
4922	A watcher is pending as soon as the corresponding event has been detected,	5000	A watcher is pending as soon as the corresponding event has been
4923	and stops being pending as soon as the watcher will be invoked or its	5001	detected. See L<WATCHER STATES> for details.
4924	pending status is explicitly cleared by the application.
4925
4926	A watcher can be pending, but not active. Stopping a watcher also clears
4927	its pending status.
4928		5002
4929	=item real time	5003	=item real time
4930		5004
4931	The physical time that is observed. It is apparently strictly monotonic :)	5005	The physical time that is observed. It is apparently strictly monotonic :)
4932		5006
…		…
4939	=item watcher	5013	=item watcher
4940		5014
4941	A data structure that describes interest in certain events. Watchers need	5015	A data structure that describes interest in certain events. Watchers need
4942	to be started (attached to an event loop) before they can receive events.	5016	to be started (attached to an event loop) before they can receive events.
4943		5017
4944	=item watcher invocation
4945
4946	The act of calling the callback associated with a watcher.
4947
4948	=back	5018	=back
4949		5019
4950	=head1 AUTHOR	5020	=head1 AUTHOR
4951		5021
4952	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5022	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5023	Magnusson and Emanuele Giaquinta.
4953		5024

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Comparing libev/ev.pod (file contents): Revision 1.314 by root, Fri Oct 22 06:06:31 2010 UTC vs. Revision 1.337 by root, Sun Oct 31 20:20:20 2010 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.314 by root, Fri Oct 22 06:06:31 2010 UTC vs.
Revision 1.337 by root, Sun Oct 31 20:20:20 2010 UTC