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Revision 1.312 by root, Thu Oct 21 15:14:49 2010 UTC vs.
Revision 1.355 by root, Tue Jan 11 01:41:56 2011 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))
236		247
237	Sets the allocation function to use (the prototype is similar - the	248	Sets the allocation function to use (the prototype is similar - the
238	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
239	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
240	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
…		…
266	}	277	}
267		278
268	...	279	...
269	ev_set_allocator (persistent_realloc);	280	ev_set_allocator (persistent_realloc);
270		281
271	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	282	=item ev_set_syserr_cb (void (*cb)(const char *msg))
272		283
273	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
274	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
275	indicating the system call or subsystem causing the problem. If this	286	indicating the system call or subsystem causing the problem. If this
276	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
…		…
288	}	299	}
289		300
290	...	301	...
291	ev_set_syserr_cb (fatal_error);	302	ev_set_syserr_cb (fatal_error);
292		303
		304	=item ev_feed_signal (int signum)
		305
		306	This function can be used to "simulate" a signal receive. It is completely
		307	safe to call this function at any time, from any context, including signal
		308	handlers or random threads.
		309
		310	Its main use is to customise signal handling in your process, especially
		311	in the presence of threads. For example, you could block signals
		312	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		313	creating any loops), and in one thread, use C<sigwait> or any other
		314	mechanism to wait for signals, then "deliver" them to libev by calling
		315	C<ev_feed_signal>.
		316
293	=back	317	=back
294		318
295	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	319	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
296		320
297	An event loop is described by a C<struct ev_loop *> (the C<struct> is	321	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	322	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).	323	libev 3 had an C<ev_loop> function colliding with the struct name).
300		324
301	The library knows two types of such loops, the I<default> loop, which	325	The library knows two types of such loops, the I<default> loop, which
302	supports signals and child events, and dynamically created event loops	326	supports child process events, and dynamically created event loops which
303	which do not.	327	do not.
304		328
305	=over 4	329	=over 4
306		330
307	=item struct ev_loop *ev_default_loop (unsigned int flags)	331	=item struct ev_loop *ev_default_loop (unsigned int flags)
308		332
309	This will initialise the default event loop if it hasn't been initialised	333	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	334	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	335	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).	336	C<ev_loop_new>.
		337
		338	If the default loop is already initialised then this function simply
		339	returns it (and ignores the flags. If that is troubling you, check
		340	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		341	flags, which should almost always be C<0>, unless the caller is also the
		342	one calling C<ev_run> or otherwise qualifies as "the main program".
313		343
314	If you don't know what event loop to use, use the one returned from this	344	If you don't know what event loop to use, use the one returned from this
315	function.	345	function (or via the C<EV_DEFAULT> macro).
316		346
317	Note that this function is I<not> thread-safe, so if you want to use it	347	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,	348	from multiple threads, you have to employ some kind of mutex (note also
319	as loops cannot be shared easily between threads anyway).	349	that this case is unlikely, as loops cannot be shared easily between
		350	threads anyway).
320		351
321	The default loop is the only loop that can handle C<ev_signal> and	352	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	353	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	354	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	355	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	356	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
326	C<ev_default_init>.	357
		358	Example: This is the most typical usage.
		359
		360	if (!ev_default_loop (0))
		361	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		362
		363	Example: Restrict libev to the select and poll backends, and do not allow
		364	environment settings to be taken into account:
		365
		366	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		367
		368	=item struct ev_loop *ev_loop_new (unsigned int flags)
		369
		370	This will create and initialise a new event loop object. If the loop
		371	could not be initialised, returns false.
		372
		373	This function is thread-safe, and one common way to use libev with
		374	threads is indeed to create one loop per thread, and using the default
		375	loop in the "main" or "initial" thread.
327		376
328	The flags argument can be used to specify special behaviour or specific	377	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>).	378	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
330		379
331	The following flags are supported:	380	The following flags are supported:
…		…
366	environment variable.	415	environment variable.
367		416
368	=item C<EVFLAG_NOINOTIFY>	417	=item C<EVFLAG_NOINOTIFY>
369		418
370	When this flag is specified, then libev will not attempt to use the	419	When this flag is specified, then libev will not attempt to use the
371	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and	420	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
372	testing, this flag can be useful to conserve inotify file descriptors, as	421	testing, this flag can be useful to conserve inotify file descriptors, as
373	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.	422	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
374		423
375	=item C<EVFLAG_SIGNALFD>	424	=item C<EVFLAG_SIGNALFD>
376		425
377	When this flag is specified, then libev will attempt to use the	426	When this flag is specified, then libev will attempt to use the
378	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API	427	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
379	delivers signals synchronously, which makes it both faster and might make	428	delivers signals synchronously, which makes it both faster and might make
380	it possible to get the queued signal data. It can also simplify signal	429	it possible to get the queued signal data. It can also simplify signal
381	handling with threads, as long as you properly block signals in your	430	handling with threads, as long as you properly block signals in your
382	threads that are not interested in handling them.	431	threads that are not interested in handling them.
383		432
384	Signalfd will not be used by default as this changes your signal mask, and	433	Signalfd will not be used by default as this changes your signal mask, and
385	there are a lot of shoddy libraries and programs (glib's threadpool for	434	there are a lot of shoddy libraries and programs (glib's threadpool for
386	example) that can't properly initialise their signal masks.	435	example) that can't properly initialise their signal masks.
		436
		437	=item C<EVFLAG_NOSIGMASK>
		438
		439	When this flag is specified, then libev will avoid to modify the signal
		440	mask. Specifically, this means you ahve to make sure signals are unblocked
		441	when you want to receive them.
		442
		443	This behaviour is useful when you want to do your own signal handling, or
		444	want to handle signals only in specific threads and want to avoid libev
		445	unblocking the signals.
		446
		447	This flag's behaviour will become the default in future versions of libev.
387		448
388	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	449	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
389		450
390	This is your standard select(2) backend. Not I<completely> standard, as	451	This is your standard select(2) backend. Not I<completely> standard, as
391	libev tries to roll its own fd_set with no limits on the number of fds,	452	libev tries to roll its own fd_set with no limits on the number of fds,
…		…
427	epoll scales either O(1) or O(active_fds).	488	epoll scales either O(1) or O(active_fds).
428		489
429	The epoll mechanism deserves honorable mention as the most misdesigned	490	The epoll mechanism deserves honorable mention as the most misdesigned
430	of the more advanced event mechanisms: mere annoyances include silently	491	of the more advanced event mechanisms: mere annoyances include silently
431	dropping file descriptors, requiring a system call per change per file	492	dropping file descriptors, requiring a system call per change per file
432	descriptor (and unnecessary guessing of parameters), problems with dup and	493	descriptor (and unnecessary guessing of parameters), problems with dup,
		494	returning before the timeout value, resulting in additional iterations
		495	(and only giving 5ms accuracy while select on the same platform gives
433	so on. The biggest issue is fork races, however - if a program forks then	496	0.1ms) and so on. The biggest issue is fork races, however - if a program
434	I<both> parent and child process have to recreate the epoll set, which can	497	forks then I<both> parent and child process have to recreate the epoll
435	take considerable time (one syscall per file descriptor) and is of course	498	set, which can take considerable time (one syscall per file descriptor)
436	hard to detect.	499	and is of course hard to detect.
437		500
438	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	501	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
439	of course I<doesn't>, and epoll just loves to report events for totally	502	of course I<doesn't>, and epoll just loves to report events for totally
440	I<different> file descriptors (even already closed ones, so one cannot	503	I<different> file descriptors (even already closed ones, so one cannot
441	even remove them from the set) than registered in the set (especially	504	even remove them from the set) than registered in the set (especially
…		…
443	employing an additional generation counter and comparing that against the	506	employing an additional generation counter and comparing that against the
444	events to filter out spurious ones, recreating the set when required. Last	507	events to filter out spurious ones, recreating the set when required. Last
445	not least, it also refuses to work with some file descriptors which work	508	not least, it also refuses to work with some file descriptors which work
446	perfectly fine with C<select> (files, many character devices...).	509	perfectly fine with C<select> (files, many character devices...).
447		510
		511	Epoll is truly the train wreck analog among event poll mechanisms,
		512	a frankenpoll, cobbled together in a hurry, no thought to design or
		513	interaction with others.
		514
448	While stopping, setting and starting an I/O watcher in the same iteration	515	While stopping, setting and starting an I/O watcher in the same iteration
449	will result in some caching, there is still a system call per such	516	will result in some caching, there is still a system call per such
450	incident (because the same I<file descriptor> could point to a different	517	incident (because the same I<file descriptor> could point to a different
451	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	518	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
452	file descriptors might not work very well if you register events for both	519	file descriptors might not work very well if you register events for both
…		…
517	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	584	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
518		585
519	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	586	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
520	it's really slow, but it still scales very well (O(active_fds)).	587	it's really slow, but it still scales very well (O(active_fds)).
521		588
522	Please note that Solaris event ports can deliver a lot of spurious
523	notifications, so you need to use non-blocking I/O or other means to avoid
524	blocking when no data (or space) is available.
525
526	While this backend scales well, it requires one system call per active	589	While this backend scales well, it requires one system call per active
527	file descriptor per loop iteration. For small and medium numbers of file	590	file descriptor per loop iteration. For small and medium numbers of file
528	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	591	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
529	might perform better.	592	might perform better.
530		593
531	On the positive side, with the exception of the spurious readiness	594	On the positive side, this backend actually performed fully to
532	notifications, this backend actually performed fully to specification
533	in all tests and is fully embeddable, which is a rare feat among the	595	specification in all tests and is fully embeddable, which is a rare feat
534	OS-specific backends (I vastly prefer correctness over speed hacks).	596	among the OS-specific backends (I vastly prefer correctness over speed
		597	hacks).
		598
		599	On the negative side, the interface is I<bizarre> - so bizarre that
		600	even sun itself gets it wrong in their code examples: The event polling
		601	function sometimes returning events to the caller even though an error
		602	occurred, but with no indication whether it has done so or not (yes, it's
		603	even documented that way) - deadly for edge-triggered interfaces where
		604	you absolutely have to know whether an event occurred or not because you
		605	have to re-arm the watcher.
		606
		607	Fortunately libev seems to be able to work around these idiocies.
535		608
536	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	609	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
537	C<EVBACKEND_POLL>.	610	C<EVBACKEND_POLL>.
538		611
539	=item C<EVBACKEND_ALL>	612	=item C<EVBACKEND_ALL>
540		613
541	Try all backends (even potentially broken ones that wouldn't be tried	614	Try all backends (even potentially broken ones that wouldn't be tried
542	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	615	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
543	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	616	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
544		617
545	It is definitely not recommended to use this flag.	618	It is definitely not recommended to use this flag, use whatever
		619	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		620	at all.
		621
		622	=item C<EVBACKEND_MASK>
		623
		624	Not a backend at all, but a mask to select all backend bits from a
		625	C<flags> value, in case you want to mask out any backends from a flags
		626	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
546		627
547	=back	628	=back
548		629
549	If one or more of the backend flags are or'ed into the flags value,	630	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	631	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	632	here). If none are specified, all backends in C<ev_recommended_backends
552	()> will be tried.	633	()> will be tried.
553		634
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.	635	Example: Try to create a event loop that uses epoll and nothing else.
581		636
582	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	637	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
583	if (!epoller)	638	if (!epoller)
584	fatal ("no epoll found here, maybe it hides under your chair");	639	fatal ("no epoll found here, maybe it hides under your chair");
585		640
		641	Example: Use whatever libev has to offer, but make sure that kqueue is
		642	used if available.
		643
		644	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		645
586	=item ev_default_destroy ()	646	=item ev_loop_destroy (loop)
587		647
588	Destroys the default loop (frees all memory and kernel state etc.). None	648	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	649	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	650	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,	651	responsibility to either stop all watchers cleanly yourself I<before>
592	or cope with the fact afterwards (which is usually the easiest thing, you	652	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).	653	the easiest thing, you can just ignore the watchers and/or C<free ()> them
		654	for example).
594		655
595	Note that certain global state, such as signal state (and installed signal	656	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	657	handlers), will not be freed by this function, and related watchers (such
597	as signal and child watchers) would need to be stopped manually.	658	as signal and child watchers) would need to be stopped manually.
598		659
599	In general it is not advisable to call this function except in the	660	This function is normally used on loop objects allocated by
600	rare occasion where you really need to free e.g. the signal handling	661	C<ev_loop_new>, but it can also be used on the default loop returned by
		662	C<ev_default_loop>, in which case it is not thread-safe.
		663
		664	Note that it is not advisable to call this function on the default loop
		665	except in the rare occasion where you really need to free its resources.
601	pipe fds. If you need dynamically allocated loops it is better to use	666	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>.	667	and C<ev_loop_destroy>.
603		668
604	=item ev_loop_destroy (loop)	669	=item ev_loop_fork (loop)
605		670
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	671	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	672	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	673	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	674	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	675	child before resuming or calling C<ev_run>.
616	functions, and it will only take effect at the next C<ev_run> iteration.
617		676
618	Again, you I<have> to call it on I<any> loop that you want to re-use after	677	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	678	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	679	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
621	during fork.	680	during fork.
…		…
626	call it at all (in fact, C<epoll> is so badly broken that it makes a	685	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	686	difference, but libev will usually detect this case on its own and do a
628	costly reset of the backend).	687	costly reset of the backend).
629		688
630	The function itself is quite fast and it's usually not a problem to call	689	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	690	it just in case after a fork.
632	quite nicely into a call to C<pthread_atfork>:
633		691
		692	Example: Automate calling C<ev_loop_fork> on the default loop when
		693	using pthreads.
		694
		695	static void
		696	post_fork_child (void)
		697	{
		698	ev_loop_fork (EV_DEFAULT);
		699	}
		700
		701	...
634	pthread_atfork (0, 0, ev_default_fork);	702	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		703
643	=item int ev_is_default_loop (loop)	704	=item int ev_is_default_loop (loop)
644		705
645	Returns true when the given loop is, in fact, the default loop, and false	706	Returns true when the given loop is, in fact, the default loop, and false
646	otherwise.	707	otherwise.
…		…
657	prepare and check phases.	718	prepare and check phases.
658		719
659	=item unsigned int ev_depth (loop)	720	=item unsigned int ev_depth (loop)
660		721
661	Returns the number of times C<ev_run> was entered minus the number of	722	Returns the number of times C<ev_run> was entered minus the number of
662	times C<ev_run> was exited, in other words, the recursion depth.	723	times C<ev_run> was exited normally, in other words, the recursion depth.
663		724
664	Outside C<ev_run>, this number is zero. In a callback, this number is	725	Outside C<ev_run>, this number is zero. In a callback, this number is
665	C<1>, unless C<ev_run> was invoked recursively (or from another thread),	726	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
666	in which case it is higher.	727	in which case it is higher.
667		728
668	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread	729	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
669	etc.), doesn't count as "exit" - consider this as a hint to avoid such	730	throwing an exception etc.), doesn't count as "exit" - consider this
670	ungentleman-like behaviour unless it's really convenient.	731	as a hint to avoid such ungentleman-like behaviour unless it's really
		732	convenient, in which case it is fully supported.
671		733
672	=item unsigned int ev_backend (loop)	734	=item unsigned int ev_backend (loop)
673		735
674	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	736	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
675	use.	737	use.
…		…
736	relying on all watchers to be stopped when deciding when a program has	798	relying on all watchers to be stopped when deciding when a program has
737	finished (especially in interactive programs), but having a program	799	finished (especially in interactive programs), but having a program
738	that automatically loops as long as it has to and no longer by virtue	800	that automatically loops as long as it has to and no longer by virtue
739	of relying on its watchers stopping correctly, that is truly a thing of	801	of relying on its watchers stopping correctly, that is truly a thing of
740	beauty.	802	beauty.
		803
		804	This function is also I<mostly> exception-safe - you can break out of
		805	a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		806	exception and so on. This does not decrement the C<ev_depth> value, nor
		807	will it clear any outstanding C<EVBREAK_ONE> breaks.
741		808
742	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle	809	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
743	those events and any already outstanding ones, but will not wait and	810	those events and any already outstanding ones, but will not wait and
744	block your process in case there are no events and will return after one	811	block your process in case there are no events and will return after one
745	iteration of the loop. This is sometimes useful to poll and handle new	812	iteration of the loop. This is sometimes useful to poll and handle new
…		…
807	Can be used to make a call to C<ev_run> return early (but only after it	874	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	875	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	876	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.	877	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
811		878
812	This "unloop state" will be cleared when entering C<ev_run> again.	879	This "break state" will be cleared on the next call to C<ev_run>.
813		880
814	It is safe to call C<ev_break> from outside any C<ev_run> calls. ##TODO##	881	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		882	which case it will have no effect.
815		883
816	=item ev_ref (loop)	884	=item ev_ref (loop)
817		885
818	=item ev_unref (loop)	886	=item ev_unref (loop)
819		887
…		…
840	running when nothing else is active.	908	running when nothing else is active.
841		909
842	ev_signal exitsig;	910	ev_signal exitsig;
843	ev_signal_init (&exitsig, sig_cb, SIGINT);	911	ev_signal_init (&exitsig, sig_cb, SIGINT);
844	ev_signal_start (loop, &exitsig);	912	ev_signal_start (loop, &exitsig);
845	evf_unref (loop);	913	ev_unref (loop);
846		914
847	Example: For some weird reason, unregister the above signal handler again.	915	Example: For some weird reason, unregister the above signal handler again.
848		916
849	ev_ref (loop);	917	ev_ref (loop);
850	ev_signal_stop (loop, &exitsig);	918	ev_signal_stop (loop, &exitsig);
…		…
908		976
909	=item ev_invoke_pending (loop)	977	=item ev_invoke_pending (loop)
910		978
911	This call will simply invoke all pending watchers while resetting their	979	This call will simply invoke all pending watchers while resetting their
912	pending state. Normally, C<ev_run> does this automatically when required,	980	pending state. Normally, C<ev_run> does this automatically when required,
913	but when overriding the invoke callback this call comes handy.	981	but when overriding the invoke callback this call comes handy. This
		982	function can be invoked from a watcher - this can be useful for example
		983	when you want to do some lengthy calculation and want to pass further
		984	event handling to another thread (you still have to make sure only one
		985	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
914		986
915	=item int ev_pending_count (loop)	987	=item int ev_pending_count (loop)
916		988
917	Returns the number of pending watchers - zero indicates that no watchers	989	Returns the number of pending watchers - zero indicates that no watchers
918	are pending.	990	are pending.
…		…
958	See also the locking example in the C<THREADS> section later in this	1030	See also the locking example in the C<THREADS> section later in this
959	document.	1031	document.
960		1032
961	=item ev_set_userdata (loop, void *data)	1033	=item ev_set_userdata (loop, void *data)
962		1034
963	=item ev_userdata (loop)	1035	=item void *ev_userdata (loop)
964		1036
965	Set and retrieve a single C<void *> associated with a loop. When	1037	Set and retrieve a single C<void *> associated with a loop. When
966	C<ev_set_userdata> has never been called, then C<ev_userdata> returns	1038	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
967	C<0.>	1039	C<0>.
968		1040
969	These two functions can be used to associate arbitrary data with a loop,	1041	These two functions can be used to associate arbitrary data with a loop,
970	and are intended solely for the C<invoke_pending_cb>, C<release> and	1042	and are intended solely for the C<invoke_pending_cb>, C<release> and
971	C<acquire> callbacks described above, but of course can be (ab-)used for	1043	C<acquire> callbacks described above, but of course can be (ab-)used for
972	any other purpose as well.	1044	any other purpose as well.
…		…
1100	=item C<EV_FORK>	1172	=item C<EV_FORK>
1101		1173
1102	The event loop has been resumed in the child process after fork (see	1174	The event loop has been resumed in the child process after fork (see
1103	C<ev_fork>).	1175	C<ev_fork>).
1104		1176
		1177	=item C<EV_CLEANUP>
		1178
		1179	The event loop is about to be destroyed (see C<ev_cleanup>).
		1180
1105	=item C<EV_ASYNC>	1181	=item C<EV_ASYNC>
1106		1182
1107	The given async watcher has been asynchronously notified (see C<ev_async>).	1183	The given async watcher has been asynchronously notified (see C<ev_async>).
1108		1184
1109	=item C<EV_CUSTOM>	1185	=item C<EV_CUSTOM>
…		…
1130	programs, though, as the fd could already be closed and reused for another	1206	programs, though, as the fd could already be closed and reused for another
1131	thing, so beware.	1207	thing, so beware.
1132		1208
1133	=back	1209	=back
1134		1210
1135	=head2 WATCHER STATES
1136
1137	There are various watcher states mentioned throughout this manual -
1138	active, pending and so on. In this section these states and the rules to
1139	transition between them will be described in more detail - and while these
1140	rules might look complicated, they usually do "the right thing".
1141
1142	=over 4
1143
1144	=item initialiased
1145
1146	Before a watcher can be registered with the event looop it has to be
1147	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
1148	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1149
1150	In this state it is simply some block of memory that is suitable for use
1151	in an event loop. It can be moved around, freed, reused etc. at will.
1152
1153	=item started/running/active
1154
1155	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1156	property of the event loop, and is actively waiting for events. While in
1157	this state it cannot be accessed (except in a few documented ways), moved,
1158	freed or anything else - the only legal thing is to keep a pointer to it,
1159	and call libev functions on it that are documented to work on active watchers.
1160
1161	=item pending
1162
1163	If a watcher is active and libev determines that an event it is interested
1164	in has occurred (such as a timer expiring), it will become pending. It will
1165	stay in this pending state until either it is stopped or its callback is
1166	about to be invoked, so it is not normally pending inside the watcher
1167	callback.
1168
1169	The watcher might or might not be active while it is pending (for example,
1170	an expired non-repeating timer can be pending but no longer active). If it
1171	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
1172	but it is still property of the event loop at this time, so cannot be
1173	moved, freed or reused. And if it is active the rules described in the
1174	previous item still apply.
1175
1176	It is also possible to feed an event on a watcher that is not active (e.g.
1177	via C<ev_feed_event>), in which case it becomes pending without being
1178	active.
1179
1180	=item stopped
1181
1182	A watcher can be stopped implicitly by libev (in which case it might still
1183	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1184	latter will clear any pending state the watcher might be in, regardless
1185	of whether it was active or not, so stopping a watcher explicitly before
1186	freeing it is often a good idea.
1187
1188	While stopped (and not pending) the watcher is essentially in the
1189	initialised state, that is it can be reused, moved, modified in any way
1190	you wish.
1191
1192	=back
1193
1194	=head2 GENERIC WATCHER FUNCTIONS	1211	=head2 GENERIC WATCHER FUNCTIONS
1195		1212
1196	=over 4	1213	=over 4
1197		1214
1198	=item C<ev_init> (ev_TYPE *watcher, callback)	1215	=item C<ev_init> (ev_TYPE *watcher, callback)
…		…
1339		1356
1340	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related	1357	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1341	functions that do not need a watcher.	1358	functions that do not need a watcher.
1342		1359
1343	=back	1360	=back
1344
1345		1361
1346	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1362	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1347		1363
1348	Each watcher has, by default, a member C<void *data> that you can change	1364	Each watcher has, by default, a member C<void *data> that you can change
1349	and read at any time: libev will completely ignore it. This can be used	1365	and read at any time: libev will completely ignore it. This can be used
…		…
1405	t2_cb (EV_P_ ev_timer *w, int revents)	1421	t2_cb (EV_P_ ev_timer *w, int revents)
1406	{	1422	{
1407	struct my_biggy big = (struct my_biggy *)	1423	struct my_biggy big = (struct my_biggy *)
1408	(((char *)w) - offsetof (struct my_biggy, t2));	1424	(((char *)w) - offsetof (struct my_biggy, t2));
1409	}	1425	}
		1426
		1427	=head2 WATCHER STATES
		1428
		1429	There are various watcher states mentioned throughout this manual -
		1430	active, pending and so on. In this section these states and the rules to
		1431	transition between them will be described in more detail - and while these
		1432	rules might look complicated, they usually do "the right thing".
		1433
		1434	=over 4
		1435
		1436	=item initialiased
		1437
		1438	Before a watcher can be registered with the event looop it has to be
		1439	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1440	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1441
		1442	In this state it is simply some block of memory that is suitable for use
		1443	in an event loop. It can be moved around, freed, reused etc. at will.
		1444
		1445	=item started/running/active
		1446
		1447	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1448	property of the event loop, and is actively waiting for events. While in
		1449	this state it cannot be accessed (except in a few documented ways), moved,
		1450	freed or anything else - the only legal thing is to keep a pointer to it,
		1451	and call libev functions on it that are documented to work on active watchers.
		1452
		1453	=item pending
		1454
		1455	If a watcher is active and libev determines that an event it is interested
		1456	in has occurred (such as a timer expiring), it will become pending. It will
		1457	stay in this pending state until either it is stopped or its callback is
		1458	about to be invoked, so it is not normally pending inside the watcher
		1459	callback.
		1460
		1461	The watcher might or might not be active while it is pending (for example,
		1462	an expired non-repeating timer can be pending but no longer active). If it
		1463	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1464	but it is still property of the event loop at this time, so cannot be
		1465	moved, freed or reused. And if it is active the rules described in the
		1466	previous item still apply.
		1467
		1468	It is also possible to feed an event on a watcher that is not active (e.g.
		1469	via C<ev_feed_event>), in which case it becomes pending without being
		1470	active.
		1471
		1472	=item stopped
		1473
		1474	A watcher can be stopped implicitly by libev (in which case it might still
		1475	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1476	latter will clear any pending state the watcher might be in, regardless
		1477	of whether it was active or not, so stopping a watcher explicitly before
		1478	freeing it is often a good idea.
		1479
		1480	While stopped (and not pending) the watcher is essentially in the
		1481	initialised state, that is it can be reused, moved, modified in any way
		1482	you wish.
		1483
		1484	=back
1410		1485
1411	=head2 WATCHER PRIORITY MODELS	1486	=head2 WATCHER PRIORITY MODELS
1412		1487
1413	Many event loops support I<watcher priorities>, which are usually small	1488	Many event loops support I<watcher priorities>, which are usually small
1414	integers that influence the ordering of event callback invocation	1489	integers that influence the ordering of event callback invocation
…		…
1541	In general you can register as many read and/or write event watchers per	1616	In general you can register as many read and/or write event watchers per
1542	fd as you want (as long as you don't confuse yourself). Setting all file	1617	fd as you want (as long as you don't confuse yourself). Setting all file
1543	descriptors to non-blocking mode is also usually a good idea (but not	1618	descriptors to non-blocking mode is also usually a good idea (but not
1544	required if you know what you are doing).	1619	required if you know what you are doing).
1545		1620
1546	If you cannot use non-blocking mode, then force the use of a
1547	known-to-be-good backend (at the time of this writing, this includes only
1548	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1549	descriptors for which non-blocking operation makes no sense (such as
1550	files) - libev doesn't guarantee any specific behaviour in that case.
1551
1552	Another thing you have to watch out for is that it is quite easy to	1621	Another thing you have to watch out for is that it is quite easy to
1553	receive "spurious" readiness notifications, that is your callback might	1622	receive "spurious" readiness notifications, that is, your callback might
1554	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1623	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1555	because there is no data. Not only are some backends known to create a	1624	because there is no data. It is very easy to get into this situation even
1556	lot of those (for example Solaris ports), it is very easy to get into	1625	with a relatively standard program structure. Thus it is best to always
1557	this situation even with a relatively standard program structure. Thus	1626	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1558	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1559	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1627	preferable to a program hanging until some data arrives.
1560		1628
1561	If you cannot run the fd in non-blocking mode (for example you should	1629	If you cannot run the fd in non-blocking mode (for example you should
1562	not play around with an Xlib connection), then you have to separately	1630	not play around with an Xlib connection), then you have to separately
1563	re-test whether a file descriptor is really ready with a known-to-be good	1631	re-test whether a file descriptor is really ready with a known-to-be good
1564	interface such as poll (fortunately in our Xlib example, Xlib already	1632	interface such as poll (fortunately in the case of Xlib, it already does
1565	does this on its own, so its quite safe to use). Some people additionally	1633	this on its own, so its quite safe to use). Some people additionally
1566	use C<SIGALRM> and an interval timer, just to be sure you won't block	1634	use C<SIGALRM> and an interval timer, just to be sure you won't block
1567	indefinitely.	1635	indefinitely.
1568		1636
1569	But really, best use non-blocking mode.	1637	But really, best use non-blocking mode.
1570		1638
…		…
1598		1666
1599	There is no workaround possible except not registering events	1667	There is no workaround possible except not registering events
1600	for potentially C<dup ()>'ed file descriptors, or to resort to	1668	for potentially C<dup ()>'ed file descriptors, or to resort to
1601	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1669	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1602		1670
		1671	=head3 The special problem of files
		1672
		1673	Many people try to use C<select> (or libev) on file descriptors
		1674	representing files, and expect it to become ready when their program
		1675	doesn't block on disk accesses (which can take a long time on their own).
		1676
		1677	However, this cannot ever work in the "expected" way - you get a readiness
		1678	notification as soon as the kernel knows whether and how much data is
		1679	there, and in the case of open files, that's always the case, so you
		1680	always get a readiness notification instantly, and your read (or possibly
		1681	write) will still block on the disk I/O.
		1682
		1683	Another way to view it is that in the case of sockets, pipes, character
		1684	devices and so on, there is another party (the sender) that delivers data
		1685	on it's own, but in the case of files, there is no such thing: the disk
		1686	will not send data on it's own, simply because it doesn't know what you
		1687	wish to read - you would first have to request some data.
		1688
		1689	Since files are typically not-so-well supported by advanced notification
		1690	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1691	to files, even though you should not use it. The reason for this is
		1692	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1693	usually a tty, often a pipe, but also sometimes files or special devices
		1694	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1695	F</dev/urandom>), and even though the file might better be served with
		1696	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1697	it "just works" instead of freezing.
		1698
		1699	So avoid file descriptors pointing to files when you know it (e.g. use
		1700	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1701	when you rarely read from a file instead of from a socket, and want to
		1702	reuse the same code path.
		1703
1603	=head3 The special problem of fork	1704	=head3 The special problem of fork
1604		1705
1605	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1706	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1606	useless behaviour. Libev fully supports fork, but needs to be told about	1707	useless behaviour. Libev fully supports fork, but needs to be told about
1607	it in the child.	1708	it in the child if you want to continue to use it in the child.
1608		1709
1609	To support fork in your programs, you either have to call	1710	To support fork in your child processes, you have to call C<ev_loop_fork
1610	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1711	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1611	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1712	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1612	C<EVBACKEND_POLL>.
1613		1713
1614	=head3 The special problem of SIGPIPE	1714	=head3 The special problem of SIGPIPE
1615		1715
1616	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1716	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1617	when writing to a pipe whose other end has been closed, your program gets	1717	when writing to a pipe whose other end has been closed, your program gets
…		…
2233		2333
2234	=head2 C<ev_signal> - signal me when a signal gets signalled!	2334	=head2 C<ev_signal> - signal me when a signal gets signalled!
2235		2335
2236	Signal watchers will trigger an event when the process receives a specific	2336	Signal watchers will trigger an event when the process receives a specific
2237	signal one or more times. Even though signals are very asynchronous, libev	2337	signal one or more times. Even though signals are very asynchronous, libev
2238	will try it's best to deliver signals synchronously, i.e. as part of the	2338	will try its best to deliver signals synchronously, i.e. as part of the
2239	normal event processing, like any other event.	2339	normal event processing, like any other event.
2240		2340
2241	If you want signals to be delivered truly asynchronously, just use	2341	If you want signals to be delivered truly asynchronously, just use
2242	C<sigaction> as you would do without libev and forget about sharing	2342	C<sigaction> as you would do without libev and forget about sharing
2243	the signal. You can even use C<ev_async> from a signal handler to	2343	the signal. You can even use C<ev_async> from a signal handler to
…		…
2285	I<has> to modify the signal mask, at least temporarily.	2385	I<has> to modify the signal mask, at least temporarily.
2286		2386
2287	So I can't stress this enough: I<If you do not reset your signal mask when	2387	So I can't stress this enough: I<If you do not reset your signal mask when
2288	you expect it to be empty, you have a race condition in your code>. This	2388	you expect it to be empty, you have a race condition in your code>. This
2289	is not a libev-specific thing, this is true for most event libraries.	2389	is not a libev-specific thing, this is true for most event libraries.
		2390
		2391	=head3 The special problem of threads signal handling
		2392
		2393	POSIX threads has problematic signal handling semantics, specifically,
		2394	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2395	threads in a process block signals, which is hard to achieve.
		2396
		2397	When you want to use sigwait (or mix libev signal handling with your own
		2398	for the same signals), you can tackle this problem by globally blocking
		2399	all signals before creating any threads (or creating them with a fully set
		2400	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2401	loops. Then designate one thread as "signal receiver thread" which handles
		2402	these signals. You can pass on any signals that libev might be interested
		2403	in by calling C<ev_feed_signal>.
2290		2404
2291	=head3 Watcher-Specific Functions and Data Members	2405	=head3 Watcher-Specific Functions and Data Members
2292		2406
2293	=over 4	2407	=over 4
2294		2408
…		…
3068	disadvantage of having to use multiple event loops (which do not support	3182	disadvantage of having to use multiple event loops (which do not support
3069	signal watchers).	3183	signal watchers).
3070		3184
3071	When this is not possible, or you want to use the default loop for	3185	When this is not possible, or you want to use the default loop for
3072	other reasons, then in the process that wants to start "fresh", call	3186	other reasons, then in the process that wants to start "fresh", call
3073	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3187	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
3074	the default loop will "orphan" (not stop) all registered watchers, so you	3188	Destroying the default loop will "orphan" (not stop) all registered
3075	have to be careful not to execute code that modifies those watchers. Note	3189	watchers, so you have to be careful not to execute code that modifies
3076	also that in that case, you have to re-register any signal watchers.	3190	those watchers. Note also that in that case, you have to re-register any
		3191	signal watchers.
3077		3192
3078	=head3 Watcher-Specific Functions and Data Members	3193	=head3 Watcher-Specific Functions and Data Members
3079		3194
3080	=over 4	3195	=over 4
3081		3196
3082	=item ev_fork_init (ev_signal *, callback)	3197	=item ev_fork_init (ev_fork *, callback)
3083		3198
3084	Initialises and configures the fork watcher - it has no parameters of any	3199	Initialises and configures the fork watcher - it has no parameters of any
3085	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3200	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
3086	believe me.	3201	really.
3087		3202
3088	=back	3203	=back
		3204
		3205
		3206	=head2 C<ev_cleanup> - even the best things end
		3207
		3208	Cleanup watchers are called just before the event loop is being destroyed
		3209	by a call to C<ev_loop_destroy>.
		3210
		3211	While there is no guarantee that the event loop gets destroyed, cleanup
		3212	watchers provide a convenient method to install cleanup hooks for your
		3213	program, worker threads and so on - you just to make sure to destroy the
		3214	loop when you want them to be invoked.
		3215
		3216	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3217	all other watchers, they do not keep a reference to the event loop (which
		3218	makes a lot of sense if you think about it). Like all other watchers, you
		3219	can call libev functions in the callback, except C<ev_cleanup_start>.
		3220
		3221	=head3 Watcher-Specific Functions and Data Members
		3222
		3223	=over 4
		3224
		3225	=item ev_cleanup_init (ev_cleanup *, callback)
		3226
		3227	Initialises and configures the cleanup watcher - it has no parameters of
		3228	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3229	pointless, I assure you.
		3230
		3231	=back
		3232
		3233	Example: Register an atexit handler to destroy the default loop, so any
		3234	cleanup functions are called.
		3235
		3236	static void
		3237	program_exits (void)
		3238	{
		3239	ev_loop_destroy (EV_DEFAULT_UC);
		3240	}
		3241
		3242	...
		3243	atexit (program_exits);
3089		3244
3090		3245
3091	=head2 C<ev_async> - how to wake up an event loop	3246	=head2 C<ev_async> - how to wake up an event loop
3092		3247
3093	In general, you cannot use an C<ev_run> from multiple threads or other	3248	In general, you cannot use an C<ev_run> from multiple threads or other
…		…
3100	it by calling C<ev_async_send>, which is thread- and signal safe.	3255	it by calling C<ev_async_send>, which is thread- and signal safe.
3101		3256
3102	This functionality is very similar to C<ev_signal> watchers, as signals,	3257	This functionality is very similar to C<ev_signal> watchers, as signals,
3103	too, are asynchronous in nature, and signals, too, will be compressed	3258	too, are asynchronous in nature, and signals, too, will be compressed
3104	(i.e. the number of callback invocations may be less than the number of	3259	(i.e. the number of callback invocations may be less than the number of
3105	C<ev_async_sent> calls).	3260	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
		3261	of "global async watchers" by using a watcher on an otherwise unused
		3262	signal, and C<ev_feed_signal> to signal this watcher from another thread,
		3263	even without knowing which loop owns the signal.
3106		3264
3107	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3265	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
3108	just the default loop.	3266	just the default loop.
3109		3267
3110	=head3 Queueing	3268	=head3 Queueing
…		…
3286	Feed an event on the given fd, as if a file descriptor backend detected	3444	Feed an event on the given fd, as if a file descriptor backend detected
3287	the given events it.	3445	the given events it.
3288		3446
3289	=item ev_feed_signal_event (loop, int signum)	3447	=item ev_feed_signal_event (loop, int signum)
3290		3448
3291	Feed an event as if the given signal occurred (C<loop> must be the default	3449	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3292	loop!).	3450	which is async-safe.
		3451
		3452	=back
		3453
		3454
		3455	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3456
		3457	This section explains some common idioms that are not immediately
		3458	obvious. Note that examples are sprinkled over the whole manual, and this
		3459	section only contains stuff that wouldn't fit anywhere else.
		3460
		3461	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3462
		3463	Often (especially in GUI toolkits) there are places where you have
		3464	I<modal> interaction, which is most easily implemented by recursively
		3465	invoking C<ev_run>.
		3466
		3467	This brings the problem of exiting - a callback might want to finish the
		3468	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3469	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3470	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3471	other combination: In these cases, C<ev_break> will not work alone.
		3472
		3473	The solution is to maintain "break this loop" variable for each C<ev_run>
		3474	invocation, and use a loop around C<ev_run> until the condition is
		3475	triggered, using C<EVRUN_ONCE>:
		3476
		3477	// main loop
		3478	int exit_main_loop = 0;
		3479
		3480	while (!exit_main_loop)
		3481	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3482
		3483	// in a model watcher
		3484	int exit_nested_loop = 0;
		3485
		3486	while (!exit_nested_loop)
		3487	ev_run (EV_A_ EVRUN_ONCE);
		3488
		3489	To exit from any of these loops, just set the corresponding exit variable:
		3490
		3491	// exit modal loop
		3492	exit_nested_loop = 1;
		3493
		3494	// exit main program, after modal loop is finished
		3495	exit_main_loop = 1;
		3496
		3497	// exit both
		3498	exit_main_loop = exit_nested_loop = 1;
		3499
		3500	=head2 THREAD LOCKING EXAMPLE
		3501
		3502	Here is a fictitious example of how to run an event loop in a different
		3503	thread than where callbacks are being invoked and watchers are
		3504	created/added/removed.
		3505
		3506	For a real-world example, see the C<EV::Loop::Async> perl module,
		3507	which uses exactly this technique (which is suited for many high-level
		3508	languages).
		3509
		3510	The example uses a pthread mutex to protect the loop data, a condition
		3511	variable to wait for callback invocations, an async watcher to notify the
		3512	event loop thread and an unspecified mechanism to wake up the main thread.
		3513
		3514	First, you need to associate some data with the event loop:
		3515
		3516	typedef struct {
		3517	mutex_t lock; /* global loop lock */
		3518	ev_async async_w;
		3519	thread_t tid;
		3520	cond_t invoke_cv;
		3521	} userdata;
		3522
		3523	void prepare_loop (EV_P)
		3524	{
		3525	// for simplicity, we use a static userdata struct.
		3526	static userdata u;
		3527
		3528	ev_async_init (&u->async_w, async_cb);
		3529	ev_async_start (EV_A_ &u->async_w);
		3530
		3531	pthread_mutex_init (&u->lock, 0);
		3532	pthread_cond_init (&u->invoke_cv, 0);
		3533
		3534	// now associate this with the loop
		3535	ev_set_userdata (EV_A_ u);
		3536	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3537	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3538
		3539	// then create the thread running ev_loop
		3540	pthread_create (&u->tid, 0, l_run, EV_A);
		3541	}
		3542
		3543	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3544	solely to wake up the event loop so it takes notice of any new watchers
		3545	that might have been added:
		3546
		3547	static void
		3548	async_cb (EV_P_ ev_async *w, int revents)
		3549	{
		3550	// just used for the side effects
		3551	}
		3552
		3553	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3554	protecting the loop data, respectively.
		3555
		3556	static void
		3557	l_release (EV_P)
		3558	{
		3559	userdata *u = ev_userdata (EV_A);
		3560	pthread_mutex_unlock (&u->lock);
		3561	}
		3562
		3563	static void
		3564	l_acquire (EV_P)
		3565	{
		3566	userdata *u = ev_userdata (EV_A);
		3567	pthread_mutex_lock (&u->lock);
		3568	}
		3569
		3570	The event loop thread first acquires the mutex, and then jumps straight
		3571	into C<ev_run>:
		3572
		3573	void *
		3574	l_run (void *thr_arg)
		3575	{
		3576	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3577
		3578	l_acquire (EV_A);
		3579	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3580	ev_run (EV_A_ 0);
		3581	l_release (EV_A);
		3582
		3583	return 0;
		3584	}
		3585
		3586	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3587	signal the main thread via some unspecified mechanism (signals? pipe
		3588	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3589	have been called (in a while loop because a) spurious wakeups are possible
		3590	and b) skipping inter-thread-communication when there are no pending
		3591	watchers is very beneficial):
		3592
		3593	static void
		3594	l_invoke (EV_P)
		3595	{
		3596	userdata *u = ev_userdata (EV_A);
		3597
		3598	while (ev_pending_count (EV_A))
		3599	{
		3600	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3601	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3602	}
		3603	}
		3604
		3605	Now, whenever the main thread gets told to invoke pending watchers, it
		3606	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3607	thread to continue:
		3608
		3609	static void
		3610	real_invoke_pending (EV_P)
		3611	{
		3612	userdata *u = ev_userdata (EV_A);
		3613
		3614	pthread_mutex_lock (&u->lock);
		3615	ev_invoke_pending (EV_A);
		3616	pthread_cond_signal (&u->invoke_cv);
		3617	pthread_mutex_unlock (&u->lock);
		3618	}
		3619
		3620	Whenever you want to start/stop a watcher or do other modifications to an
		3621	event loop, you will now have to lock:
		3622
		3623	ev_timer timeout_watcher;
		3624	userdata *u = ev_userdata (EV_A);
		3625
		3626	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3627
		3628	pthread_mutex_lock (&u->lock);
		3629	ev_timer_start (EV_A_ &timeout_watcher);
		3630	ev_async_send (EV_A_ &u->async_w);
		3631	pthread_mutex_unlock (&u->lock);
		3632
		3633	Note that sending the C<ev_async> watcher is required because otherwise
		3634	an event loop currently blocking in the kernel will have no knowledge
		3635	about the newly added timer. By waking up the loop it will pick up any new
		3636	watchers in the next event loop iteration.
3293		3637
3294	=back	3638	=back
3295		3639
3296		3640
3297	=head1 LIBEVENT EMULATION	3641	=head1 LIBEVENT EMULATION
3298		3642
3299	Libev offers a compatibility emulation layer for libevent. It cannot	3643	Libev offers a compatibility emulation layer for libevent. It cannot
3300	emulate the internals of libevent, so here are some usage hints:	3644	emulate the internals of libevent, so here are some usage hints:
3301		3645
3302	=over 4	3646	=over 4
		3647
		3648	=item * Only the libevent-1.4.1-beta API is being emulated.
		3649
		3650	This was the newest libevent version available when libev was implemented,
		3651	and is still mostly unchanged in 2010.
3303		3652
3304	=item * Use it by including <event.h>, as usual.	3653	=item * Use it by including <event.h>, as usual.
3305		3654
3306	=item * The following members are fully supported: ev_base, ev_callback,	3655	=item * The following members are fully supported: ev_base, ev_callback,
3307	ev_arg, ev_fd, ev_res, ev_events.	3656	ev_arg, ev_fd, ev_res, ev_events.
…		…
3313	=item * Priorities are not currently supported. Initialising priorities	3662	=item * Priorities are not currently supported. Initialising priorities
3314	will fail and all watchers will have the same priority, even though there	3663	will fail and all watchers will have the same priority, even though there
3315	is an ev_pri field.	3664	is an ev_pri field.
3316		3665
3317	=item * In libevent, the last base created gets the signals, in libev, the	3666	=item * In libevent, the last base created gets the signals, in libev, the
3318	first base created (== the default loop) gets the signals.	3667	base that registered the signal gets the signals.
3319		3668
3320	=item * Other members are not supported.	3669	=item * Other members are not supported.
3321		3670
3322	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3671	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3323	to use the libev header file and library.	3672	to use the libev header file and library.
…		…
3342	Care has been taken to keep the overhead low. The only data member the C++	3691	Care has been taken to keep the overhead low. The only data member the C++
3343	classes add (compared to plain C-style watchers) is the event loop pointer	3692	classes add (compared to plain C-style watchers) is the event loop pointer
3344	that the watcher is associated with (or no additional members at all if	3693	that the watcher is associated with (or no additional members at all if
3345	you disable C<EV_MULTIPLICITY> when embedding libev).	3694	you disable C<EV_MULTIPLICITY> when embedding libev).
3346		3695
3347	Currently, functions, and static and non-static member functions can be	3696	Currently, functions, static and non-static member functions and classes
3348	used as callbacks. Other types should be easy to add as long as they only	3697	with C<operator ()> can be used as callbacks. Other types should be easy
3349	need one additional pointer for context. If you need support for other	3698	to add as long as they only need one additional pointer for context. If
3350	types of functors please contact the author (preferably after implementing	3699	you need support for other types of functors please contact the author
3351	it).	3700	(preferably after implementing it).
3352		3701
3353	Here is a list of things available in the C<ev> namespace:	3702	Here is a list of things available in the C<ev> namespace:
3354		3703
3355	=over 4	3704	=over 4
3356		3705
…		…
4285	default loop and triggering an C<ev_async> watcher from the default loop	4634	default loop and triggering an C<ev_async> watcher from the default loop
4286	watcher callback into the event loop interested in the signal.	4635	watcher callback into the event loop interested in the signal.
4287		4636
4288	=back	4637	=back
4289		4638
4290	=head4 THREAD LOCKING EXAMPLE	4639	See also L<THREAD LOCKING EXAMPLE>.
4291
4292	Here is a fictitious example of how to run an event loop in a different
4293	thread than where callbacks are being invoked and watchers are
4294	created/added/removed.
4295
4296	For a real-world example, see the C<EV::Loop::Async> perl module,
4297	which uses exactly this technique (which is suited for many high-level
4298	languages).
4299
4300	The example uses a pthread mutex to protect the loop data, a condition
4301	variable to wait for callback invocations, an async watcher to notify the
4302	event loop thread and an unspecified mechanism to wake up the main thread.
4303
4304	First, you need to associate some data with the event loop:
4305
4306	typedef struct {
4307	mutex_t lock; /* global loop lock */
4308	ev_async async_w;
4309	thread_t tid;
4310	cond_t invoke_cv;
4311	} userdata;
4312
4313	void prepare_loop (EV_P)
4314	{
4315	// for simplicity, we use a static userdata struct.
4316	static userdata u;
4317
4318	ev_async_init (&u->async_w, async_cb);
4319	ev_async_start (EV_A_ &u->async_w);
4320
4321	pthread_mutex_init (&u->lock, 0);
4322	pthread_cond_init (&u->invoke_cv, 0);
4323
4324	// now associate this with the loop
4325	ev_set_userdata (EV_A_ u);
4326	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4327	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4328
4329	// then create the thread running ev_loop
4330	pthread_create (&u->tid, 0, l_run, EV_A);
4331	}
4332
4333	The callback for the C<ev_async> watcher does nothing: the watcher is used
4334	solely to wake up the event loop so it takes notice of any new watchers
4335	that might have been added:
4336
4337	static void
4338	async_cb (EV_P_ ev_async *w, int revents)
4339	{
4340	// just used for the side effects
4341	}
4342
4343	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4344	protecting the loop data, respectively.
4345
4346	static void
4347	l_release (EV_P)
4348	{
4349	userdata *u = ev_userdata (EV_A);
4350	pthread_mutex_unlock (&u->lock);
4351	}
4352
4353	static void
4354	l_acquire (EV_P)
4355	{
4356	userdata *u = ev_userdata (EV_A);
4357	pthread_mutex_lock (&u->lock);
4358	}
4359
4360	The event loop thread first acquires the mutex, and then jumps straight
4361	into C<ev_run>:
4362
4363	void *
4364	l_run (void *thr_arg)
4365	{
4366	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4367
4368	l_acquire (EV_A);
4369	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4370	ev_run (EV_A_ 0);
4371	l_release (EV_A);
4372
4373	return 0;
4374	}
4375
4376	Instead of invoking all pending watchers, the C<l_invoke> callback will
4377	signal the main thread via some unspecified mechanism (signals? pipe
4378	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4379	have been called (in a while loop because a) spurious wakeups are possible
4380	and b) skipping inter-thread-communication when there are no pending
4381	watchers is very beneficial):
4382
4383	static void
4384	l_invoke (EV_P)
4385	{
4386	userdata *u = ev_userdata (EV_A);
4387
4388	while (ev_pending_count (EV_A))
4389	{
4390	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4391	pthread_cond_wait (&u->invoke_cv, &u->lock);
4392	}
4393	}
4394
4395	Now, whenever the main thread gets told to invoke pending watchers, it
4396	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4397	thread to continue:
4398
4399	static void
4400	real_invoke_pending (EV_P)
4401	{
4402	userdata *u = ev_userdata (EV_A);
4403
4404	pthread_mutex_lock (&u->lock);
4405	ev_invoke_pending (EV_A);
4406	pthread_cond_signal (&u->invoke_cv);
4407	pthread_mutex_unlock (&u->lock);
4408	}
4409
4410	Whenever you want to start/stop a watcher or do other modifications to an
4411	event loop, you will now have to lock:
4412
4413	ev_timer timeout_watcher;
4414	userdata *u = ev_userdata (EV_A);
4415
4416	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4417
4418	pthread_mutex_lock (&u->lock);
4419	ev_timer_start (EV_A_ &timeout_watcher);
4420	ev_async_send (EV_A_ &u->async_w);
4421	pthread_mutex_unlock (&u->lock);
4422
4423	Note that sending the C<ev_async> watcher is required because otherwise
4424	an event loop currently blocking in the kernel will have no knowledge
4425	about the newly added timer. By waking up the loop it will pick up any new
4426	watchers in the next event loop iteration.
4427		4640
4428	=head3 COROUTINES	4641	=head3 COROUTINES
4429		4642
4430	Libev is very accommodating to coroutines ("cooperative threads"):	4643	Libev is very accommodating to coroutines ("cooperative threads"):
4431	libev fully supports nesting calls to its functions from different	4644	libev fully supports nesting calls to its functions from different
…		…
4527	=head3 C<kqueue> is buggy	4740	=head3 C<kqueue> is buggy
4528		4741
4529	The kqueue syscall is broken in all known versions - most versions support	4742	The kqueue syscall is broken in all known versions - most versions support
4530	only sockets, many support pipes.	4743	only sockets, many support pipes.
4531		4744
4532	Libev tries to work around this by not using C<kqueue> by default on	4745	Libev tries to work around this by not using C<kqueue> by default on this
4533	this rotten platform, but of course you can still ask for it when creating	4746	rotten platform, but of course you can still ask for it when creating a
4534	a loop.	4747	loop - embedding a socket-only kqueue loop into a select-based one is
		4748	probably going to work well.
4535		4749
4536	=head3 C<poll> is buggy	4750	=head3 C<poll> is buggy
4537		4751
4538	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>	4752	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
4539	implementation by something calling C<kqueue> internally around the 10.5.6	4753	implementation by something calling C<kqueue> internally around the 10.5.6
…		…
4558		4772
4559	=head3 C<errno> reentrancy	4773	=head3 C<errno> reentrancy
4560		4774
4561	The default compile environment on Solaris is unfortunately so	4775	The default compile environment on Solaris is unfortunately so
4562	thread-unsafe that you can't even use components/libraries compiled	4776	thread-unsafe that you can't even use components/libraries compiled
4563	without C<-D_REENTRANT> (as long as they use C<errno>), which, of course,	4777	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
4564	isn't defined by default.	4778	defined by default. A valid, if stupid, implementation choice.
4565		4779
4566	If you want to use libev in threaded environments you have to make sure	4780	If you want to use libev in threaded environments you have to make sure
4567	it's compiled with C<_REENTRANT> defined.	4781	it's compiled with C<_REENTRANT> defined.
4568		4782
4569	=head3 Event port backend	4783	=head3 Event port backend
4570		4784
4571	The scalable event interface for Solaris is called "event ports". Unfortunately,	4785	The scalable event interface for Solaris is called "event
4572	this mechanism is very buggy. If you run into high CPU usage, your program	4786	ports". Unfortunately, this mechanism is very buggy in all major
		4787	releases. If you run into high CPU usage, your program freezes or you get
4573	freezes or you get a large number of spurious wakeups, make sure you have	4788	a large number of spurious wakeups, make sure you have all the relevant
4574	all the relevant and latest kernel patches applied. No, I don't know which	4789	and latest kernel patches applied. No, I don't know which ones, but there
4575	ones, but there are multiple ones.	4790	are multiple ones to apply, and afterwards, event ports actually work
		4791	great.
4576		4792
4577	If you can't get it to work, you can try running the program by setting	4793	If you can't get it to work, you can try running the program by setting
4578	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and	4794	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
4579	C<select> backends.	4795	C<select> backends.
4580		4796
4581	=head2 AIX POLL BUG	4797	=head2 AIX POLL BUG
4582		4798
4583	AIX unfortunately has a broken C<poll.h> header. Libev works around	4799	AIX unfortunately has a broken C<poll.h> header. Libev works around
4584	this by trying to avoid the poll backend altogether (i.e. it's not even	4800	this by trying to avoid the poll backend altogether (i.e. it's not even
4585	compiled in), which normally isn't a big problem as C<select> works fine	4801	compiled in), which normally isn't a big problem as C<select> works fine
4586	with large bitsets, and AIX is dead anyway.	4802	with large bitsets on AIX, and AIX is dead anyway.
4587		4803
4588	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4804	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
4589		4805
4590	=head3 General issues	4806	=head3 General issues
4591		4807
…		…
4697	structure (guaranteed by POSIX but not by ISO C for example), but it also	4913	structure (guaranteed by POSIX but not by ISO C for example), but it also
4698	assumes that the same (machine) code can be used to call any watcher	4914	assumes that the same (machine) code can be used to call any watcher
4699	callback: The watcher callbacks have different type signatures, but libev	4915	callback: The watcher callbacks have different type signatures, but libev
4700	calls them using an C<ev_watcher *> internally.	4916	calls them using an C<ev_watcher *> internally.
4701		4917
		4918	=item pointer accesses must be thread-atomic
		4919
		4920	Accessing a pointer value must be atomic, it must both be readable and
		4921	writable in one piece - this is the case on all current architectures.
		4922
4702	=item C<sig_atomic_t volatile> must be thread-atomic as well	4923	=item C<sig_atomic_t volatile> must be thread-atomic as well
4703		4924
4704	The type C<sig_atomic_t volatile> (or whatever is defined as	4925	The type C<sig_atomic_t volatile> (or whatever is defined as
4705	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	4926	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
4706	threads. This is not part of the specification for C<sig_atomic_t>, but is	4927	threads. This is not part of the specification for C<sig_atomic_t>, but is
…		…
4812	=back	5033	=back
4813		5034
4814		5035
4815	=head1 PORTING FROM LIBEV 3.X TO 4.X	5036	=head1 PORTING FROM LIBEV 3.X TO 4.X
4816		5037
4817	The major version 4 introduced some minor incompatible changes to the API.	5038	The major version 4 introduced some incompatible changes to the API.
4818		5039
4819	At the moment, the C<ev.h> header file tries to implement superficial	5040	At the moment, the C<ev.h> header file provides compatibility definitions
4820	compatibility, so most programs should still compile. Those might be	5041	for all changes, so most programs should still compile. The compatibility
4821	removed in later versions of libev, so better update early than late.	5042	layer might be removed in later versions of libev, so better update to the
		5043	new API early than late.
4822		5044
4823	=over 4	5045	=over 4
		5046
		5047	=item C<EV_COMPAT3> backwards compatibility mechanism
		5048
		5049	The backward compatibility mechanism can be controlled by
		5050	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5051	section.
		5052
		5053	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5054
		5055	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5056
		5057	ev_loop_destroy (EV_DEFAULT_UC);
		5058	ev_loop_fork (EV_DEFAULT);
4824		5059
4825	=item function/symbol renames	5060	=item function/symbol renames
4826		5061
4827	A number of functions and symbols have been renamed:	5062	A number of functions and symbols have been renamed:
4828		5063
…		…
4847	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme	5082	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
4848	as all other watcher types. Note that C<ev_loop_fork> is still called	5083	as all other watcher types. Note that C<ev_loop_fork> is still called
4849	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>	5084	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
4850	typedef.	5085	typedef.
4851		5086
4852	=item C<EV_COMPAT3> backwards compatibility mechanism
4853
4854	The backward compatibility mechanism can be controlled by
4855	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
4856	section.
4857
4858	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>	5087	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
4859		5088
4860	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different	5089	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
4861	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile	5090	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
4862	and work, but the library code will of course be larger.	5091	and work, but the library code will of course be larger.
…		…
4868		5097
4869	=over 4	5098	=over 4
4870		5099
4871	=item active	5100	=item active
4872		5101
4873	A watcher is active as long as it has been started (has been attached to	5102	A watcher is active as long as it has been started and not yet stopped.
4874	an event loop) but not yet stopped (disassociated from the event loop).	5103	See L<WATCHER STATES> for details.
4875		5104
4876	=item application	5105	=item application
4877		5106
4878	In this document, an application is whatever is using libev.	5107	In this document, an application is whatever is using libev.
		5108
		5109	=item backend
		5110
		5111	The part of the code dealing with the operating system interfaces.
4879		5112
4880	=item callback	5113	=item callback
4881		5114
4882	The address of a function that is called when some event has been	5115	The address of a function that is called when some event has been
4883	detected. Callbacks are being passed the event loop, the watcher that	5116	detected. Callbacks are being passed the event loop, the watcher that
4884	received the event, and the actual event bitset.	5117	received the event, and the actual event bitset.
4885		5118
4886	=item callback invocation	5119	=item callback/watcher invocation
4887		5120
4888	The act of calling the callback associated with a watcher.	5121	The act of calling the callback associated with a watcher.
4889		5122
4890	=item event	5123	=item event
4891		5124
…		…
4910	The model used to describe how an event loop handles and processes	5143	The model used to describe how an event loop handles and processes
4911	watchers and events.	5144	watchers and events.
4912		5145
4913	=item pending	5146	=item pending
4914		5147
4915	A watcher is pending as soon as the corresponding event has been detected,	5148	A watcher is pending as soon as the corresponding event has been
4916	and stops being pending as soon as the watcher will be invoked or its	5149	detected. See L<WATCHER STATES> for details.
4917	pending status is explicitly cleared by the application.
4918
4919	A watcher can be pending, but not active. Stopping a watcher also clears
4920	its pending status.
4921		5150
4922	=item real time	5151	=item real time
4923		5152
4924	The physical time that is observed. It is apparently strictly monotonic :)	5153	The physical time that is observed. It is apparently strictly monotonic :)
4925		5154
…		…
4932	=item watcher	5161	=item watcher
4933		5162
4934	A data structure that describes interest in certain events. Watchers need	5163	A data structure that describes interest in certain events. Watchers need
4935	to be started (attached to an event loop) before they can receive events.	5164	to be started (attached to an event loop) before they can receive events.
4936		5165
4937	=item watcher invocation
4938
4939	The act of calling the callback associated with a watcher.
4940
4941	=back	5166	=back
4942		5167
4943	=head1 AUTHOR	5168	=head1 AUTHOR
4944		5169
4945	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5170	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5171	Magnusson and Emanuele Giaquinta.
4946		5172

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