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Revision 1.371 by root, Sat Jun 4 05:25:03 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);
…		…
58	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
59		59
60	// now wait for events to arrive	60	// now wait for events to arrive
61	ev_run (loop, 0);	61	ev_run (loop, 0);
62		62
63	// unloop was called, so exit	63	// break was called, so exit
64	return 0;	64	return 0;
65	}	65	}
66		66
67	=head1 ABOUT THIS DOCUMENT	67	=head1 ABOUT THIS DOCUMENT
68		68
…		…
77	on event-based programming, nor will it introduce event-based programming	77	on event-based programming, nor will it introduce event-based programming
78	with libev.	78	with libev.
79		79
80	Familiarity with event based programming techniques in general is assumed	80	Familiarity with event based programming techniques in general is assumed
81	throughout this document.	81	throughout this document.
		82
		83	=head1 WHAT TO READ WHEN IN A HURRY
		84
		85	This manual tries to be very detailed, but unfortunately, this also makes
		86	it very long. If you just want to know the basics of libev, I suggest
		87	reading L<ANATOMY OF A WATCHER>, then the L<EXAMPLE PROGRAM> above and
		88	look up the missing functions in L<GLOBAL FUNCTIONS> and the C<ev_io> and
		89	C<ev_timer> sections in L<WATCHER TYPES>.
82		90
83	=head1 ABOUT LIBEV	91	=head1 ABOUT LIBEV
84		92
85	Libev is an event loop: you register interest in certain events (such as a	93	Libev is an event loop: you register interest in certain events (such as a
86	file descriptor being readable or a timeout occurring), and it will manage	94	file descriptor being readable or a timeout occurring), and it will manage
…		…
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
175	either it is interrupted or the given time interval has passed. Basically	184	until either it is interrupted or the given time interval has
		185	passed (approximately - it might return a bit earlier even if not
		186	interrupted). Returns immediately if C<< interval <= 0 >>.
		187
176	this is a sub-second-resolution C<sleep ()>.	188	Basically this is a sub-second-resolution C<sleep ()>.
		189
		190	The range of the C<interval> is limited - libev only guarantees to work
		191	with sleep times of up to one day (C<< interval <= 86400 >>).
177		192
178	=item int ev_version_major ()	193	=item int ev_version_major ()
179		194
180	=item int ev_version_minor ()	195	=item int ev_version_minor ()
181		196
…		…
192	as this indicates an incompatible change. Minor versions are usually	207	as this indicates an incompatible change. Minor versions are usually
193	compatible to older versions, so a larger minor version alone is usually	208	compatible to older versions, so a larger minor version alone is usually
194	not a problem.	209	not a problem.
195		210
196	Example: Make sure we haven't accidentally been linked against the wrong	211	Example: Make sure we haven't accidentally been linked against the wrong
197	version (note, however, that this will not detect ABI mismatches :).	212	version (note, however, that this will not detect other ABI mismatches,
		213	such as LFS or reentrancy).
198		214
199	assert (("libev version mismatch",	215	assert (("libev version mismatch",
200	ev_version_major () == EV_VERSION_MAJOR	216	ev_version_major () == EV_VERSION_MAJOR
201	&& ev_version_minor () >= EV_VERSION_MINOR));	217	&& ev_version_minor () >= EV_VERSION_MINOR));
202		218
…		…
213	assert (("sorry, no epoll, no sex",	229	assert (("sorry, no epoll, no sex",
214	ev_supported_backends () & EVBACKEND_EPOLL));	230	ev_supported_backends () & EVBACKEND_EPOLL));
215		231
216	=item unsigned int ev_recommended_backends ()	232	=item unsigned int ev_recommended_backends ()
217		233
218	Return the set of all backends compiled into this binary of libev and also	234	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	235	also recommended for this platform, meaning it will work for most file
		236	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	237	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	238	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	239	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.	240	probe for if you specify no backends explicitly.
224		241
225	=item unsigned int ev_embeddable_backends ()	242	=item unsigned int ev_embeddable_backends ()
226		243
227	Returns the set of backends that are embeddable in other event loops. This	244	Returns the set of backends that are embeddable in other event loops. This
228	is the theoretical, all-platform, value. To find which backends	245	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	246	current system. To find which embeddable backends might be supported on
230	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	247	the current system, you would need to look at C<ev_embeddable_backends ()
231	recommended ones.	248	& ev_supported_backends ()>, likewise for recommended ones.
232		249
233	See the description of C<ev_embed> watchers for more info.	250	See the description of C<ev_embed> watchers for more info.
234		251
235	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	252	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
236		253
237	Sets the allocation function to use (the prototype is similar - the	254	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	255	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	256	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	257	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
266	}	283	}
267		284
268	...	285	...
269	ev_set_allocator (persistent_realloc);	286	ev_set_allocator (persistent_realloc);
270		287
271	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	288	=item ev_set_syserr_cb (void (*cb)(const char *msg))
272		289
273	Set the callback function to call on a retryable system call error (such	290	Set the callback function to call on a retryable system call error (such
274	as failed select, poll, epoll_wait). The message is a printable string	291	as failed select, poll, epoll_wait). The message is a printable string
275	indicating the system call or subsystem causing the problem. If this	292	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	293	callback is set, then libev will expect it to remedy the situation, no
…		…
288	}	305	}
289		306
290	...	307	...
291	ev_set_syserr_cb (fatal_error);	308	ev_set_syserr_cb (fatal_error);
292		309
		310	=item ev_feed_signal (int signum)
		311
		312	This function can be used to "simulate" a signal receive. It is completely
		313	safe to call this function at any time, from any context, including signal
		314	handlers or random threads.
		315
		316	Its main use is to customise signal handling in your process, especially
		317	in the presence of threads. For example, you could block signals
		318	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		319	creating any loops), and in one thread, use C<sigwait> or any other
		320	mechanism to wait for signals, then "deliver" them to libev by calling
		321	C<ev_feed_signal>.
		322
293	=back	323	=back
294		324
295	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	325	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
296		326
297	An event loop is described by a C<struct ev_loop *> (the C<struct> is	327	An event loop is described by a C<struct ev_loop *> (the C<struct> is
298	I<not> optional in this case unless libev 3 compatibility is disabled, as	328	I<not> optional in this case unless libev 3 compatibility is disabled, as
299	libev 3 had an C<ev_loop> function colliding with the struct name).	329	libev 3 had an C<ev_loop> function colliding with the struct name).
300		330
301	The library knows two types of such loops, the I<default> loop, which	331	The library knows two types of such loops, the I<default> loop, which
302	supports signals and child events, and dynamically created event loops	332	supports child process events, and dynamically created event loops which
303	which do not.	333	do not.
304		334
305	=over 4	335	=over 4
306		336
307	=item struct ev_loop *ev_default_loop (unsigned int flags)	337	=item struct ev_loop *ev_default_loop (unsigned int flags)
308		338
309	This will initialise the default event loop if it hasn't been initialised	339	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	340	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	341	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).	342	C<ev_loop_new>.
		343
		344	If the default loop is already initialised then this function simply
		345	returns it (and ignores the flags. If that is troubling you, check
		346	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		347	flags, which should almost always be C<0>, unless the caller is also the
		348	one calling C<ev_run> or otherwise qualifies as "the main program".
313		349
314	If you don't know what event loop to use, use the one returned from this	350	If you don't know what event loop to use, use the one returned from this
315	function.	351	function (or via the C<EV_DEFAULT> macro).
316		352
317	Note that this function is I<not> thread-safe, so if you want to use it	353	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,	354	from multiple threads, you have to employ some kind of mutex (note also
319	as loops cannot be shared easily between threads anyway).	355	that this case is unlikely, as loops cannot be shared easily between
		356	threads anyway).
320		357
321	The default loop is the only loop that can handle C<ev_signal> and	358	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	359	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	360	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	361	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	362	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
326	C<ev_default_init>.	363
		364	Example: This is the most typical usage.
		365
		366	if (!ev_default_loop (0))
		367	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		368
		369	Example: Restrict libev to the select and poll backends, and do not allow
		370	environment settings to be taken into account:
		371
		372	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		373
		374	=item struct ev_loop *ev_loop_new (unsigned int flags)
		375
		376	This will create and initialise a new event loop object. If the loop
		377	could not be initialised, returns false.
		378
		379	This function is thread-safe, and one common way to use libev with
		380	threads is indeed to create one loop per thread, and using the default
		381	loop in the "main" or "initial" thread.
327		382
328	The flags argument can be used to specify special behaviour or specific	383	The flags argument can be used to specify special behaviour or specific
329	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	384	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
330		385
331	The following flags are supported:	386	The following flags are supported:
…		…
366	environment variable.	421	environment variable.
367		422
368	=item C<EVFLAG_NOINOTIFY>	423	=item C<EVFLAG_NOINOTIFY>
369		424
370	When this flag is specified, then libev will not attempt to use the	425	When this flag is specified, then libev will not attempt to use the
371	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and	426	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
372	testing, this flag can be useful to conserve inotify file descriptors, as	427	testing, this flag can be useful to conserve inotify file descriptors, as
373	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.	428	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
374		429
375	=item C<EVFLAG_SIGNALFD>	430	=item C<EVFLAG_SIGNALFD>
376		431
377	When this flag is specified, then libev will attempt to use the	432	When this flag is specified, then libev will attempt to use the
378	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API	433	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
379	delivers signals synchronously, which makes it both faster and might make	434	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	435	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	436	handling with threads, as long as you properly block signals in your
382	threads that are not interested in handling them.	437	threads that are not interested in handling them.
383		438
384	Signalfd will not be used by default as this changes your signal mask, and	439	Signalfd will not be used by default as this changes your signal mask, and
385	there are a lot of shoddy libraries and programs (glib's threadpool for	440	there are a lot of shoddy libraries and programs (glib's threadpool for
386	example) that can't properly initialise their signal masks.	441	example) that can't properly initialise their signal masks.
		442
		443	=item C<EVFLAG_NOSIGMASK>
		444
		445	When this flag is specified, then libev will avoid to modify the signal
		446	mask. Specifically, this means you ahve to make sure signals are unblocked
		447	when you want to receive them.
		448
		449	This behaviour is useful when you want to do your own signal handling, or
		450	want to handle signals only in specific threads and want to avoid libev
		451	unblocking the signals.
		452
		453	It's also required by POSIX in a threaded program, as libev calls
		454	C<sigprocmask>, whose behaviour is officially unspecified.
		455
		456	This flag's behaviour will become the default in future versions of libev.
387		457
388	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	458	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
389		459
390	This is your standard select(2) backend. Not I<completely> standard, as	460	This is your standard select(2) backend. Not I<completely> standard, as
391	libev tries to roll its own fd_set with no limits on the number of fds,	461	libev tries to roll its own fd_set with no limits on the number of fds,
…		…
419	=item C<EVBACKEND_EPOLL> (value 4, Linux)	489	=item C<EVBACKEND_EPOLL> (value 4, Linux)
420		490
421	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9	491	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
422	kernels).	492	kernels).
423		493
424	For few fds, this backend is a bit little slower than poll and select,	494	For few fds, this backend is a bit little slower than poll and select, but
425	but it scales phenomenally better. While poll and select usually scale	495	it scales phenomenally better. While poll and select usually scale like
426	like O(total_fds) where n is the total number of fds (or the highest fd),	496	O(total_fds) where total_fds is the total number of fds (or the highest
427	epoll scales either O(1) or O(active_fds).	497	fd), epoll scales either O(1) or O(active_fds).
428		498
429	The epoll mechanism deserves honorable mention as the most misdesigned	499	The epoll mechanism deserves honorable mention as the most misdesigned
430	of the more advanced event mechanisms: mere annoyances include silently	500	of the more advanced event mechanisms: mere annoyances include silently
431	dropping file descriptors, requiring a system call per change per file	501	dropping file descriptors, requiring a system call per change per file
432	descriptor (and unnecessary guessing of parameters), problems with dup and	502	descriptor (and unnecessary guessing of parameters), problems with dup,
		503	returning before the timeout value, resulting in additional iterations
		504	(and only giving 5ms accuracy while select on the same platform gives
433	so on. The biggest issue is fork races, however - if a program forks then	505	0.1ms) and so on. The biggest issue is fork races, however - if a program
434	I<both> parent and child process have to recreate the epoll set, which can	506	forks then I<both> parent and child process have to recreate the epoll
435	take considerable time (one syscall per file descriptor) and is of course	507	set, which can take considerable time (one syscall per file descriptor)
436	hard to detect.	508	and is of course hard to detect.
437		509
438	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	510	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
439	of course I<doesn't>, and epoll just loves to report events for totally	511	but of course I<doesn't>, and epoll just loves to report events for
440	I<different> file descriptors (even already closed ones, so one cannot	512	totally I<different> file descriptors (even already closed ones, so
441	even remove them from the set) than registered in the set (especially	513	one cannot even remove them from the set) than registered in the set
442	on SMP systems). Libev tries to counter these spurious notifications by	514	(especially on SMP systems). Libev tries to counter these spurious
443	employing an additional generation counter and comparing that against the	515	notifications by employing an additional generation counter and comparing
444	events to filter out spurious ones, recreating the set when required. Last	516	that against the events to filter out spurious ones, recreating the set
		517	when required. Epoll also errornously rounds down timeouts, but gives you
		518	no way to know when and by how much, so sometimes you have to busy-wait
		519	because epoll returns immediately despite a nonzero timeout. And last
445	not least, it also refuses to work with some file descriptors which work	520	not least, it also refuses to work with some file descriptors which work
446	perfectly fine with C<select> (files, many character devices...).	521	perfectly fine with C<select> (files, many character devices...).
		522
		523	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
		524	cobbled together in a hurry, no thought to design or interaction with
		525	others. Oh, the pain, will it ever stop...
447		526
448	While stopping, setting and starting an I/O watcher in the same iteration	527	While stopping, setting and starting an I/O watcher in the same iteration
449	will result in some caching, there is still a system call per such	528	will result in some caching, there is still a system call per such
450	incident (because the same I<file descriptor> could point to a different	529	incident (because the same I<file descriptor> could point to a different
451	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	530	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
517	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	596	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
518		597
519	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	598	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
520	it's really slow, but it still scales very well (O(active_fds)).	599	it's really slow, but it still scales very well (O(active_fds)).
521		600
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	601	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	602	file descriptor per loop iteration. For small and medium numbers of file
528	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	603	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
529	might perform better.	604	might perform better.
530		605
531	On the positive side, with the exception of the spurious readiness	606	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	607	specification in all tests and is fully embeddable, which is a rare feat
534	OS-specific backends (I vastly prefer correctness over speed hacks).	608	among the OS-specific backends (I vastly prefer correctness over speed
		609	hacks).
		610
		611	On the negative side, the interface is I<bizarre> - so bizarre that
		612	even sun itself gets it wrong in their code examples: The event polling
		613	function sometimes returning events to the caller even though an error
		614	occurred, but with no indication whether it has done so or not (yes, it's
		615	even documented that way) - deadly for edge-triggered interfaces where
		616	you absolutely have to know whether an event occurred or not because you
		617	have to re-arm the watcher.
		618
		619	Fortunately libev seems to be able to work around these idiocies.
535		620
536	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	621	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
537	C<EVBACKEND_POLL>.	622	C<EVBACKEND_POLL>.
538		623
539	=item C<EVBACKEND_ALL>	624	=item C<EVBACKEND_ALL>
540		625
541	Try all backends (even potentially broken ones that wouldn't be tried	626	Try all backends (even potentially broken ones that wouldn't be tried
542	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	627	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
543	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	628	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
544		629
545	It is definitely not recommended to use this flag.	630	It is definitely not recommended to use this flag, use whatever
		631	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		632	at all.
		633
		634	=item C<EVBACKEND_MASK>
		635
		636	Not a backend at all, but a mask to select all backend bits from a
		637	C<flags> value, in case you want to mask out any backends from a flags
		638	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
546		639
547	=back	640	=back
548		641
549	If one or more of the backend flags are or'ed into the flags value,	642	If one or more of the backend flags are or'ed into the flags value,
550	then only these backends will be tried (in the reverse order as listed	643	then only these backends will be tried (in the reverse order as listed
551	here). If none are specified, all backends in C<ev_recommended_backends	644	here). If none are specified, all backends in C<ev_recommended_backends
552	()> will be tried.	645	()> will be tried.
553		646
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.	647	Example: Try to create a event loop that uses epoll and nothing else.
581		648
582	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	649	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
583	if (!epoller)	650	if (!epoller)
584	fatal ("no epoll found here, maybe it hides under your chair");	651	fatal ("no epoll found here, maybe it hides under your chair");
585		652
		653	Example: Use whatever libev has to offer, but make sure that kqueue is
		654	used if available.
		655
		656	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		657
586	=item ev_default_destroy ()	658	=item ev_loop_destroy (loop)
587		659
588	Destroys the default loop (frees all memory and kernel state etc.). None	660	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	661	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	662	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,	663	responsibility to either stop all watchers cleanly yourself I<before>
592	or cope with the fact afterwards (which is usually the easiest thing, you	664	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).	665	the easiest thing, you can just ignore the watchers and/or C<free ()> them
		666	for example).
594		667
595	Note that certain global state, such as signal state (and installed signal	668	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	669	handlers), will not be freed by this function, and related watchers (such
597	as signal and child watchers) would need to be stopped manually.	670	as signal and child watchers) would need to be stopped manually.
598		671
599	In general it is not advisable to call this function except in the	672	This function is normally used on loop objects allocated by
600	rare occasion where you really need to free e.g. the signal handling	673	C<ev_loop_new>, but it can also be used on the default loop returned by
		674	C<ev_default_loop>, in which case it is not thread-safe.
		675
		676	Note that it is not advisable to call this function on the default loop
		677	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	678	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>.	679	and C<ev_loop_destroy>.
603		680
604	=item ev_loop_destroy (loop)	681	=item ev_loop_fork (loop)
605		682
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	683	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	684	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	685	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	686	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	687	child before resuming or calling C<ev_run>.
616	functions, and it will only take effect at the next C<ev_run> iteration.
617		688
618	Again, you I<have> to call it on I<any> loop that you want to re-use after	689	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	690	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	691	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
621	during fork.	692	during fork.
…		…
626	call it at all (in fact, C<epoll> is so badly broken that it makes a	697	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	698	difference, but libev will usually detect this case on its own and do a
628	costly reset of the backend).	699	costly reset of the backend).
629		700
630	The function itself is quite fast and it's usually not a problem to call	701	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	702	it just in case after a fork.
632	quite nicely into a call to C<pthread_atfork>:
633		703
		704	Example: Automate calling C<ev_loop_fork> on the default loop when
		705	using pthreads.
		706
		707	static void
		708	post_fork_child (void)
		709	{
		710	ev_loop_fork (EV_DEFAULT);
		711	}
		712
		713	...
634	pthread_atfork (0, 0, ev_default_fork);	714	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		715
643	=item int ev_is_default_loop (loop)	716	=item int ev_is_default_loop (loop)
644		717
645	Returns true when the given loop is, in fact, the default loop, and false	718	Returns true when the given loop is, in fact, the default loop, and false
646	otherwise.	719	otherwise.
…		…
657	prepare and check phases.	730	prepare and check phases.
658		731
659	=item unsigned int ev_depth (loop)	732	=item unsigned int ev_depth (loop)
660		733
661	Returns the number of times C<ev_run> was entered minus the number of	734	Returns the number of times C<ev_run> was entered minus the number of
662	times C<ev_run> was exited, in other words, the recursion depth.	735	times C<ev_run> was exited normally, in other words, the recursion depth.
663		736
664	Outside C<ev_run>, this number is zero. In a callback, this number is	737	Outside C<ev_run>, this number is zero. In a callback, this number is
665	C<1>, unless C<ev_run> was invoked recursively (or from another thread),	738	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
666	in which case it is higher.	739	in which case it is higher.
667		740
668	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread	741	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	742	throwing an exception etc.), doesn't count as "exit" - consider this
670	ungentleman-like behaviour unless it's really convenient.	743	as a hint to avoid such ungentleman-like behaviour unless it's really
		744	convenient, in which case it is fully supported.
671		745
672	=item unsigned int ev_backend (loop)	746	=item unsigned int ev_backend (loop)
673		747
674	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	748	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
675	use.	749	use.
…		…
737	finished (especially in interactive programs), but having a program	811	finished (especially in interactive programs), but having a program
738	that automatically loops as long as it has to and no longer by virtue	812	that automatically loops as long as it has to and no longer by virtue
739	of relying on its watchers stopping correctly, that is truly a thing of	813	of relying on its watchers stopping correctly, that is truly a thing of
740	beauty.	814	beauty.
741		815
		816	This function is also I<mostly> exception-safe - you can break out of
		817	a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		818	exception and so on. This does not decrement the C<ev_depth> value, nor
		819	will it clear any outstanding C<EVBREAK_ONE> breaks.
		820
742	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle	821	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
743	those events and any already outstanding ones, but will not wait and	822	those events and any already outstanding ones, but will not wait and
744	block your process in case there are no events and will return after one	823	block your process in case there are no events and will return after one
745	iteration of the loop. This is sometimes useful to poll and handle new	824	iteration of the loop. This is sometimes useful to poll and handle new
746	events while doing lengthy calculations, to keep the program responsive.	825	events while doing lengthy calculations, to keep the program responsive.
…		…
755	This is useful if you are waiting for some external event in conjunction	834	This is useful if you are waiting for some external event in conjunction
756	with something not expressible using other libev watchers (i.e. "roll your	835	with something not expressible using other libev watchers (i.e. "roll your
757	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	836	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
758	usually a better approach for this kind of thing.	837	usually a better approach for this kind of thing.
759		838
760	Here are the gory details of what C<ev_run> does:	839	Here are the gory details of what C<ev_run> does (this is for your
		840	understanding, not a guarantee that things will work exactly like this in
		841	future versions):
761		842
762	- Increment loop depth.	843	- Increment loop depth.
763	- Reset the ev_break status.	844	- Reset the ev_break status.
764	- Before the first iteration, call any pending watchers.	845	- Before the first iteration, call any pending watchers.
765	LOOP:	846	LOOP:
…		…
798	anymore.	879	anymore.
799		880
800	... queue jobs here, make sure they register event watchers as long	881	... queue jobs here, make sure they register event watchers as long
801	... as they still have work to do (even an idle watcher will do..)	882	... as they still have work to do (even an idle watcher will do..)
802	ev_run (my_loop, 0);	883	ev_run (my_loop, 0);
803	... jobs done or somebody called unloop. yeah!	884	... jobs done or somebody called break. yeah!
804		885
805	=item ev_break (loop, how)	886	=item ev_break (loop, how)
806		887
807	Can be used to make a call to C<ev_run> return early (but only after it	888	Can be used to make a call to C<ev_run> return early (but only after it
808	has processed all outstanding events). The C<how> argument must be either	889	has processed all outstanding events). The C<how> argument must be either
809	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or	890	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
810	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.	891	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
811		892
812	This "unloop state" will be cleared when entering C<ev_run> again.	893	This "break state" will be cleared on the next call to C<ev_run>.
813		894
814	It is safe to call C<ev_break> from outside any C<ev_run> calls. ##TODO##	895	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		896	which case it will have no effect.
815		897
816	=item ev_ref (loop)	898	=item ev_ref (loop)
817		899
818	=item ev_unref (loop)	900	=item ev_unref (loop)
819		901
…		…
840	running when nothing else is active.	922	running when nothing else is active.
841		923
842	ev_signal exitsig;	924	ev_signal exitsig;
843	ev_signal_init (&exitsig, sig_cb, SIGINT);	925	ev_signal_init (&exitsig, sig_cb, SIGINT);
844	ev_signal_start (loop, &exitsig);	926	ev_signal_start (loop, &exitsig);
845	evf_unref (loop);	927	ev_unref (loop);
846		928
847	Example: For some weird reason, unregister the above signal handler again.	929	Example: For some weird reason, unregister the above signal handler again.
848		930
849	ev_ref (loop);	931	ev_ref (loop);
850	ev_signal_stop (loop, &exitsig);	932	ev_signal_stop (loop, &exitsig);
…		…
962	See also the locking example in the C<THREADS> section later in this	1044	See also the locking example in the C<THREADS> section later in this
963	document.	1045	document.
964		1046
965	=item ev_set_userdata (loop, void *data)	1047	=item ev_set_userdata (loop, void *data)
966		1048
967	=item ev_userdata (loop)	1049	=item void *ev_userdata (loop)
968		1050
969	Set and retrieve a single C<void *> associated with a loop. When	1051	Set and retrieve a single C<void *> associated with a loop. When
970	C<ev_set_userdata> has never been called, then C<ev_userdata> returns	1052	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
971	C<0.>	1053	C<0>.
972		1054
973	These two functions can be used to associate arbitrary data with a loop,	1055	These two functions can be used to associate arbitrary data with a loop,
974	and are intended solely for the C<invoke_pending_cb>, C<release> and	1056	and are intended solely for the C<invoke_pending_cb>, C<release> and
975	C<acquire> callbacks described above, but of course can be (ab-)used for	1057	C<acquire> callbacks described above, but of course can be (ab-)used for
976	any other purpose as well.	1058	any other purpose as well.
…		…
1104	=item C<EV_FORK>	1186	=item C<EV_FORK>
1105		1187
1106	The event loop has been resumed in the child process after fork (see	1188	The event loop has been resumed in the child process after fork (see
1107	C<ev_fork>).	1189	C<ev_fork>).
1108		1190
		1191	=item C<EV_CLEANUP>
		1192
		1193	The event loop is about to be destroyed (see C<ev_cleanup>).
		1194
1109	=item C<EV_ASYNC>	1195	=item C<EV_ASYNC>
1110		1196
1111	The given async watcher has been asynchronously notified (see C<ev_async>).	1197	The given async watcher has been asynchronously notified (see C<ev_async>).
1112		1198
1113	=item C<EV_CUSTOM>	1199	=item C<EV_CUSTOM>
…		…
1134	programs, though, as the fd could already be closed and reused for another	1220	programs, though, as the fd could already be closed and reused for another
1135	thing, so beware.	1221	thing, so beware.
1136		1222
1137	=back	1223	=back
1138		1224
		1225	=head2 GENERIC WATCHER FUNCTIONS
		1226
		1227	=over 4
		1228
		1229	=item C<ev_init> (ev_TYPE *watcher, callback)
		1230
		1231	This macro initialises the generic portion of a watcher. The contents
		1232	of the watcher object can be arbitrary (so C<malloc> will do). Only
		1233	the generic parts of the watcher are initialised, you I<need> to call
		1234	the type-specific C<ev_TYPE_set> macro afterwards to initialise the
		1235	type-specific parts. For each type there is also a C<ev_TYPE_init> macro
		1236	which rolls both calls into one.
		1237
		1238	You can reinitialise a watcher at any time as long as it has been stopped
		1239	(or never started) and there are no pending events outstanding.
		1240
		1241	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
		1242	int revents)>.
		1243
		1244	Example: Initialise an C<ev_io> watcher in two steps.
		1245
		1246	ev_io w;
		1247	ev_init (&w, my_cb);
		1248	ev_io_set (&w, STDIN_FILENO, EV_READ);
		1249
		1250	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
		1251
		1252	This macro initialises the type-specific parts of a watcher. You need to
		1253	call C<ev_init> at least once before you call this macro, but you can
		1254	call C<ev_TYPE_set> any number of times. You must not, however, call this
		1255	macro on a watcher that is active (it can be pending, however, which is a
		1256	difference to the C<ev_init> macro).
		1257
		1258	Although some watcher types do not have type-specific arguments
		1259	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
		1260
		1261	See C<ev_init>, above, for an example.
		1262
		1263	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
		1264
		1265	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
		1266	calls into a single call. This is the most convenient method to initialise
		1267	a watcher. The same limitations apply, of course.
		1268
		1269	Example: Initialise and set an C<ev_io> watcher in one step.
		1270
		1271	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1272
		1273	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
		1274
		1275	Starts (activates) the given watcher. Only active watchers will receive
		1276	events. If the watcher is already active nothing will happen.
		1277
		1278	Example: Start the C<ev_io> watcher that is being abused as example in this
		1279	whole section.
		1280
		1281	ev_io_start (EV_DEFAULT_UC, &w);
		1282
		1283	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
		1284
		1285	Stops the given watcher if active, and clears the pending status (whether
		1286	the watcher was active or not).
		1287
		1288	It is possible that stopped watchers are pending - for example,
		1289	non-repeating timers are being stopped when they become pending - but
		1290	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
		1291	pending. If you want to free or reuse the memory used by the watcher it is
		1292	therefore a good idea to always call its C<ev_TYPE_stop> function.
		1293
		1294	=item bool ev_is_active (ev_TYPE *watcher)
		1295
		1296	Returns a true value iff the watcher is active (i.e. it has been started
		1297	and not yet been stopped). As long as a watcher is active you must not modify
		1298	it.
		1299
		1300	=item bool ev_is_pending (ev_TYPE *watcher)
		1301
		1302	Returns a true value iff the watcher is pending, (i.e. it has outstanding
		1303	events but its callback has not yet been invoked). As long as a watcher
		1304	is pending (but not active) you must not call an init function on it (but
		1305	C<ev_TYPE_set> is safe), you must not change its priority, and you must
		1306	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		1307	it).
		1308
		1309	=item callback ev_cb (ev_TYPE *watcher)
		1310
		1311	Returns the callback currently set on the watcher.
		1312
		1313	=item ev_cb_set (ev_TYPE *watcher, callback)
		1314
		1315	Change the callback. You can change the callback at virtually any time
		1316	(modulo threads).
		1317
		1318	=item ev_set_priority (ev_TYPE *watcher, int priority)
		1319
		1320	=item int ev_priority (ev_TYPE *watcher)
		1321
		1322	Set and query the priority of the watcher. The priority is a small
		1323	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		1324	(default: C<-2>). Pending watchers with higher priority will be invoked
		1325	before watchers with lower priority, but priority will not keep watchers
		1326	from being executed (except for C<ev_idle> watchers).
		1327
		1328	If you need to suppress invocation when higher priority events are pending
		1329	you need to look at C<ev_idle> watchers, which provide this functionality.
		1330
		1331	You I<must not> change the priority of a watcher as long as it is active or
		1332	pending.
		1333
		1334	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1335	fine, as long as you do not mind that the priority value you query might
		1336	or might not have been clamped to the valid range.
		1337
		1338	The default priority used by watchers when no priority has been set is
		1339	always C<0>, which is supposed to not be too high and not be too low :).
		1340
		1341	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
		1342	priorities.
		1343
		1344	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		1345
		1346	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		1347	C<loop> nor C<revents> need to be valid as long as the watcher callback
		1348	can deal with that fact, as both are simply passed through to the
		1349	callback.
		1350
		1351	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		1352
		1353	If the watcher is pending, this function clears its pending status and
		1354	returns its C<revents> bitset (as if its callback was invoked). If the
		1355	watcher isn't pending it does nothing and returns C<0>.
		1356
		1357	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1358	callback to be invoked, which can be accomplished with this function.
		1359
		1360	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1361
		1362	Feeds the given event set into the event loop, as if the specified event
		1363	had happened for the specified watcher (which must be a pointer to an
		1364	initialised but not necessarily started event watcher). Obviously you must
		1365	not free the watcher as long as it has pending events.
		1366
		1367	Stopping the watcher, letting libev invoke it, or calling
		1368	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1369	not started in the first place.
		1370
		1371	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1372	functions that do not need a watcher.
		1373
		1374	=back
		1375
		1376	See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR
		1377	OWN COMPOSITE WATCHERS> idioms.
		1378
1139	=head2 WATCHER STATES	1379	=head2 WATCHER STATES
1140		1380
1141	There are various watcher states mentioned throughout this manual -	1381	There are various watcher states mentioned throughout this manual -
1142	active, pending and so on. In this section these states and the rules to	1382	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	1383	transition between them will be described in more detail - and while these
…		…
1149		1389
1150	Before a watcher can be registered with the event looop it has to be	1390	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	1391	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.	1392	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1153		1393
1154	In this state it is simply some block of memory that is suitable for use	1394	In this state it is simply some block of memory that is suitable for
1155	in an event loop. It can be moved around, freed, reused etc. at will.	1395	use in an event loop. It can be moved around, freed, reused etc. at
		1396	will - as long as you either keep the memory contents intact, or call
		1397	C<ev_TYPE_init> again.
1156		1398
1157	=item started/running/active	1399	=item started/running/active
1158		1400
1159	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes	1401	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	1402	property of the event loop, and is actively waiting for events. While in
…		…
1188	latter will clear any pending state the watcher might be in, regardless	1430	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	1431	of whether it was active or not, so stopping a watcher explicitly before
1190	freeing it is often a good idea.	1432	freeing it is often a good idea.
1191		1433
1192	While stopped (and not pending) the watcher is essentially in the	1434	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	1435	initialised state, that is, it can be reused, moved, modified in any way
1194	you wish.	1436	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1437	it again).
1195		1438
1196	=back	1439	=back
1197
1198	=head2 GENERIC WATCHER FUNCTIONS
1199
1200	=over 4
1201
1202	=item C<ev_init> (ev_TYPE *watcher, callback)
1203
1204	This macro initialises the generic portion of a watcher. The contents
1205	of the watcher object can be arbitrary (so C<malloc> will do). Only
1206	the generic parts of the watcher are initialised, you I<need> to call
1207	the type-specific C<ev_TYPE_set> macro afterwards to initialise the
1208	type-specific parts. For each type there is also a C<ev_TYPE_init> macro
1209	which rolls both calls into one.
1210
1211	You can reinitialise a watcher at any time as long as it has been stopped
1212	(or never started) and there are no pending events outstanding.
1213
1214	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
1215	int revents)>.
1216
1217	Example: Initialise an C<ev_io> watcher in two steps.
1218
1219	ev_io w;
1220	ev_init (&w, my_cb);
1221	ev_io_set (&w, STDIN_FILENO, EV_READ);
1222
1223	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
1224
1225	This macro initialises the type-specific parts of a watcher. You need to
1226	call C<ev_init> at least once before you call this macro, but you can
1227	call C<ev_TYPE_set> any number of times. You must not, however, call this
1228	macro on a watcher that is active (it can be pending, however, which is a
1229	difference to the C<ev_init> macro).
1230
1231	Although some watcher types do not have type-specific arguments
1232	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
1233
1234	See C<ev_init>, above, for an example.
1235
1236	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
1237
1238	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
1239	calls into a single call. This is the most convenient method to initialise
1240	a watcher. The same limitations apply, of course.
1241
1242	Example: Initialise and set an C<ev_io> watcher in one step.
1243
1244	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1245
1246	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1247
1248	Starts (activates) the given watcher. Only active watchers will receive
1249	events. If the watcher is already active nothing will happen.
1250
1251	Example: Start the C<ev_io> watcher that is being abused as example in this
1252	whole section.
1253
1254	ev_io_start (EV_DEFAULT_UC, &w);
1255
1256	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1257
1258	Stops the given watcher if active, and clears the pending status (whether
1259	the watcher was active or not).
1260
1261	It is possible that stopped watchers are pending - for example,
1262	non-repeating timers are being stopped when they become pending - but
1263	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
1264	pending. If you want to free or reuse the memory used by the watcher it is
1265	therefore a good idea to always call its C<ev_TYPE_stop> function.
1266
1267	=item bool ev_is_active (ev_TYPE *watcher)
1268
1269	Returns a true value iff the watcher is active (i.e. it has been started
1270	and not yet been stopped). As long as a watcher is active you must not modify
1271	it.
1272
1273	=item bool ev_is_pending (ev_TYPE *watcher)
1274
1275	Returns a true value iff the watcher is pending, (i.e. it has outstanding
1276	events but its callback has not yet been invoked). As long as a watcher
1277	is pending (but not active) you must not call an init function on it (but
1278	C<ev_TYPE_set> is safe), you must not change its priority, and you must
1279	make sure the watcher is available to libev (e.g. you cannot C<free ()>
1280	it).
1281
1282	=item callback ev_cb (ev_TYPE *watcher)
1283
1284	Returns the callback currently set on the watcher.
1285
1286	=item ev_cb_set (ev_TYPE *watcher, callback)
1287
1288	Change the callback. You can change the callback at virtually any time
1289	(modulo threads).
1290
1291	=item ev_set_priority (ev_TYPE *watcher, int priority)
1292
1293	=item int ev_priority (ev_TYPE *watcher)
1294
1295	Set and query the priority of the watcher. The priority is a small
1296	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1297	(default: C<-2>). Pending watchers with higher priority will be invoked
1298	before watchers with lower priority, but priority will not keep watchers
1299	from being executed (except for C<ev_idle> watchers).
1300
1301	If you need to suppress invocation when higher priority events are pending
1302	you need to look at C<ev_idle> watchers, which provide this functionality.
1303
1304	You I<must not> change the priority of a watcher as long as it is active or
1305	pending.
1306
1307	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1308	fine, as long as you do not mind that the priority value you query might
1309	or might not have been clamped to the valid range.
1310
1311	The default priority used by watchers when no priority has been set is
1312	always C<0>, which is supposed to not be too high and not be too low :).
1313
1314	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1315	priorities.
1316
1317	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1318
1319	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1320	C<loop> nor C<revents> need to be valid as long as the watcher callback
1321	can deal with that fact, as both are simply passed through to the
1322	callback.
1323
1324	=item int ev_clear_pending (loop, ev_TYPE *watcher)
1325
1326	If the watcher is pending, this function clears its pending status and
1327	returns its C<revents> bitset (as if its callback was invoked). If the
1328	watcher isn't pending it does nothing and returns C<0>.
1329
1330	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1331	callback to be invoked, which can be accomplished with this function.
1332
1333	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
1334
1335	Feeds the given event set into the event loop, as if the specified event
1336	had happened for the specified watcher (which must be a pointer to an
1337	initialised but not necessarily started event watcher). Obviously you must
1338	not free the watcher as long as it has pending events.
1339
1340	Stopping the watcher, letting libev invoke it, or calling
1341	C<ev_clear_pending> will clear the pending event, even if the watcher was
1342	not started in the first place.
1343
1344	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1345	functions that do not need a watcher.
1346
1347	=back
1348
1349
1350	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1351
1352	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
1354	to associate arbitrary data with your watcher. If you need more data and
1355	don't want to allocate memory and store a pointer to it in that data
1356	member, you can also "subclass" the watcher type and provide your own
1357	data:
1358
1359	struct my_io
1360	{
1361	ev_io io;
1362	int otherfd;
1363	void *somedata;
1364	struct whatever *mostinteresting;
1365	};
1366
1367	...
1368	struct my_io w;
1369	ev_io_init (&w.io, my_cb, fd, EV_READ);
1370
1371	And since your callback will be called with a pointer to the watcher, you
1372	can cast it back to your own type:
1373
1374	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1375	{
1376	struct my_io *w = (struct my_io *)w_;
1377	...
1378	}
1379
1380	More interesting and less C-conformant ways of casting your callback type
1381	instead have been omitted.
1382
1383	Another common scenario is to use some data structure with multiple
1384	embedded watchers:
1385
1386	struct my_biggy
1387	{
1388	int some_data;
1389	ev_timer t1;
1390	ev_timer t2;
1391	}
1392
1393	In this case getting the pointer to C<my_biggy> is a bit more
1394	complicated: Either you store the address of your C<my_biggy> struct
1395	in the C<data> member of the watcher (for woozies), or you need to use
1396	some pointer arithmetic using C<offsetof> inside your watchers (for real
1397	programmers):
1398
1399	#include <stddef.h>
1400
1401	static void
1402	t1_cb (EV_P_ ev_timer *w, int revents)
1403	{
1404	struct my_biggy big = (struct my_biggy *)
1405	(((char *)w) - offsetof (struct my_biggy, t1));
1406	}
1407
1408	static void
1409	t2_cb (EV_P_ ev_timer *w, int revents)
1410	{
1411	struct my_biggy big = (struct my_biggy *)
1412	(((char *)w) - offsetof (struct my_biggy, t2));
1413	}
1414		1440
1415	=head2 WATCHER PRIORITY MODELS	1441	=head2 WATCHER PRIORITY MODELS
1416		1442
1417	Many event loops support I<watcher priorities>, which are usually small	1443	Many event loops support I<watcher priorities>, which are usually small
1418	integers that influence the ordering of event callback invocation	1444	integers that influence the ordering of event callback invocation
…		…
1545	In general you can register as many read and/or write event watchers per	1571	In general you can register as many read and/or write event watchers per
1546	fd as you want (as long as you don't confuse yourself). Setting all file	1572	fd as you want (as long as you don't confuse yourself). Setting all file
1547	descriptors to non-blocking mode is also usually a good idea (but not	1573	descriptors to non-blocking mode is also usually a good idea (but not
1548	required if you know what you are doing).	1574	required if you know what you are doing).
1549		1575
1550	If you cannot use non-blocking mode, then force the use of a
1551	known-to-be-good backend (at the time of this writing, this includes only
1552	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1553	descriptors for which non-blocking operation makes no sense (such as
1554	files) - libev doesn't guarantee any specific behaviour in that case.
1555
1556	Another thing you have to watch out for is that it is quite easy to	1576	Another thing you have to watch out for is that it is quite easy to
1557	receive "spurious" readiness notifications, that is your callback might	1577	receive "spurious" readiness notifications, that is, your callback might
1558	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1578	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1559	because there is no data. Not only are some backends known to create a	1579	because there is no data. It is very easy to get into this situation even
1560	lot of those (for example Solaris ports), it is very easy to get into	1580	with a relatively standard program structure. Thus it is best to always
1561	this situation even with a relatively standard program structure. Thus	1581	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1562	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1563	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1582	preferable to a program hanging until some data arrives.
1564		1583
1565	If you cannot run the fd in non-blocking mode (for example you should	1584	If you cannot run the fd in non-blocking mode (for example you should
1566	not play around with an Xlib connection), then you have to separately	1585	not play around with an Xlib connection), then you have to separately
1567	re-test whether a file descriptor is really ready with a known-to-be good	1586	re-test whether a file descriptor is really ready with a known-to-be good
1568	interface such as poll (fortunately in our Xlib example, Xlib already	1587	interface such as poll (fortunately in the case of Xlib, it already does
1569	does this on its own, so its quite safe to use). Some people additionally	1588	this on its own, so its quite safe to use). Some people additionally
1570	use C<SIGALRM> and an interval timer, just to be sure you won't block	1589	use C<SIGALRM> and an interval timer, just to be sure you won't block
1571	indefinitely.	1590	indefinitely.
1572		1591
1573	But really, best use non-blocking mode.	1592	But really, best use non-blocking mode.
1574		1593
…		…
1602		1621
1603	There is no workaround possible except not registering events	1622	There is no workaround possible except not registering events
1604	for potentially C<dup ()>'ed file descriptors, or to resort to	1623	for potentially C<dup ()>'ed file descriptors, or to resort to
1605	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1624	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1606		1625
		1626	=head3 The special problem of files
		1627
		1628	Many people try to use C<select> (or libev) on file descriptors
		1629	representing files, and expect it to become ready when their program
		1630	doesn't block on disk accesses (which can take a long time on their own).
		1631
		1632	However, this cannot ever work in the "expected" way - you get a readiness
		1633	notification as soon as the kernel knows whether and how much data is
		1634	there, and in the case of open files, that's always the case, so you
		1635	always get a readiness notification instantly, and your read (or possibly
		1636	write) will still block on the disk I/O.
		1637
		1638	Another way to view it is that in the case of sockets, pipes, character
		1639	devices and so on, there is another party (the sender) that delivers data
		1640	on its own, but in the case of files, there is no such thing: the disk
		1641	will not send data on its own, simply because it doesn't know what you
		1642	wish to read - you would first have to request some data.
		1643
		1644	Since files are typically not-so-well supported by advanced notification
		1645	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1646	to files, even though you should not use it. The reason for this is
		1647	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1648	usually a tty, often a pipe, but also sometimes files or special devices
		1649	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1650	F</dev/urandom>), and even though the file might better be served with
		1651	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1652	it "just works" instead of freezing.
		1653
		1654	So avoid file descriptors pointing to files when you know it (e.g. use
		1655	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1656	when you rarely read from a file instead of from a socket, and want to
		1657	reuse the same code path.
		1658
1607	=head3 The special problem of fork	1659	=head3 The special problem of fork
1608		1660
1609	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1661	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1610	useless behaviour. Libev fully supports fork, but needs to be told about	1662	useless behaviour. Libev fully supports fork, but needs to be told about
1611	it in the child.	1663	it in the child if you want to continue to use it in the child.
1612		1664
1613	To support fork in your programs, you either have to call	1665	To support fork in your child processes, you have to call C<ev_loop_fork
1614	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1666	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1615	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1667	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1616	C<EVBACKEND_POLL>.
1617		1668
1618	=head3 The special problem of SIGPIPE	1669	=head3 The special problem of SIGPIPE
1619		1670
1620	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1671	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1621	when writing to a pipe whose other end has been closed, your program gets	1672	when writing to a pipe whose other end has been closed, your program gets
…		…
2111		2162
2112	Another way to think about it (for the mathematically inclined) is that	2163	Another way to think about it (for the mathematically inclined) is that
2113	C<ev_periodic> will try to run the callback in this mode at the next possible	2164	C<ev_periodic> will try to run the callback in this mode at the next possible
2114	time where C<time = offset (mod interval)>, regardless of any time jumps.	2165	time where C<time = offset (mod interval)>, regardless of any time jumps.
2115		2166
2116	For numerical stability it is preferable that the C<offset> value is near	2167	The C<interval> I<MUST> be positive, and for numerical stability, the
2117	C<ev_now ()> (the current time), but there is no range requirement for	2168	interval value should be higher than C<1/8192> (which is around 100
2118	this value, and in fact is often specified as zero.	2169	microseconds) and C<offset> should be higher than C<0> and should have
		2170	at most a similar magnitude as the current time (say, within a factor of
		2171	ten). Typical values for offset are, in fact, C<0> or something between
		2172	C<0> and C<interval>, which is also the recommended range.
2119		2173
2120	Note also that there is an upper limit to how often a timer can fire (CPU	2174	Note also that there is an upper limit to how often a timer can fire (CPU
2121	speed for example), so if C<interval> is very small then timing stability	2175	speed for example), so if C<interval> is very small then timing stability
2122	will of course deteriorate. Libev itself tries to be exact to be about one	2176	will of course deteriorate. Libev itself tries to be exact to be about one
2123	millisecond (if the OS supports it and the machine is fast enough).	2177	millisecond (if the OS supports it and the machine is fast enough).
…		…
2237		2291
2238	=head2 C<ev_signal> - signal me when a signal gets signalled!	2292	=head2 C<ev_signal> - signal me when a signal gets signalled!
2239		2293
2240	Signal watchers will trigger an event when the process receives a specific	2294	Signal watchers will trigger an event when the process receives a specific
2241	signal one or more times. Even though signals are very asynchronous, libev	2295	signal one or more times. Even though signals are very asynchronous, libev
2242	will try it's best to deliver signals synchronously, i.e. as part of the	2296	will try its best to deliver signals synchronously, i.e. as part of the
2243	normal event processing, like any other event.	2297	normal event processing, like any other event.
2244		2298
2245	If you want signals to be delivered truly asynchronously, just use	2299	If you want signals to be delivered truly asynchronously, just use
2246	C<sigaction> as you would do without libev and forget about sharing	2300	C<sigaction> as you would do without libev and forget about sharing
2247	the signal. You can even use C<ev_async> from a signal handler to	2301	the signal. You can even use C<ev_async> from a signal handler to
…		…
2266	=head3 The special problem of inheritance over fork/execve/pthread_create	2320	=head3 The special problem of inheritance over fork/execve/pthread_create
2267		2321
2268	Both the signal mask (C<sigprocmask>) and the signal disposition	2322	Both the signal mask (C<sigprocmask>) and the signal disposition
2269	(C<sigaction>) are unspecified after starting a signal watcher (and after	2323	(C<sigaction>) are unspecified after starting a signal watcher (and after
2270	stopping it again), that is, libev might or might not block the signal,	2324	stopping it again), that is, libev might or might not block the signal,
2271	and might or might not set or restore the installed signal handler.	2325	and might or might not set or restore the installed signal handler (but
		2326	see C<EVFLAG_NOSIGMASK>).
2272		2327
2273	While this does not matter for the signal disposition (libev never	2328	While this does not matter for the signal disposition (libev never
2274	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on	2329	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
2275	C<execve>), this matters for the signal mask: many programs do not expect	2330	C<execve>), this matters for the signal mask: many programs do not expect
2276	certain signals to be blocked.	2331	certain signals to be blocked.
…		…
2289	I<has> to modify the signal mask, at least temporarily.	2344	I<has> to modify the signal mask, at least temporarily.
2290		2345
2291	So I can't stress this enough: I<If you do not reset your signal mask when	2346	So I can't stress this enough: I<If you do not reset your signal mask when
2292	you expect it to be empty, you have a race condition in your code>. This	2347	you expect it to be empty, you have a race condition in your code>. This
2293	is not a libev-specific thing, this is true for most event libraries.	2348	is not a libev-specific thing, this is true for most event libraries.
		2349
		2350	=head3 The special problem of threads signal handling
		2351
		2352	POSIX threads has problematic signal handling semantics, specifically,
		2353	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2354	threads in a process block signals, which is hard to achieve.
		2355
		2356	When you want to use sigwait (or mix libev signal handling with your own
		2357	for the same signals), you can tackle this problem by globally blocking
		2358	all signals before creating any threads (or creating them with a fully set
		2359	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2360	loops. Then designate one thread as "signal receiver thread" which handles
		2361	these signals. You can pass on any signals that libev might be interested
		2362	in by calling C<ev_feed_signal>.
2294		2363
2295	=head3 Watcher-Specific Functions and Data Members	2364	=head3 Watcher-Specific Functions and Data Members
2296		2365
2297	=over 4	2366	=over 4
2298		2367
…		…
3072	disadvantage of having to use multiple event loops (which do not support	3141	disadvantage of having to use multiple event loops (which do not support
3073	signal watchers).	3142	signal watchers).
3074		3143
3075	When this is not possible, or you want to use the default loop for	3144	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	3145	other reasons, then in the process that wants to start "fresh", call
3077	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3146	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	3147	Destroying the default loop will "orphan" (not stop) all registered
3079	have to be careful not to execute code that modifies those watchers. Note	3148	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.	3149	those watchers. Note also that in that case, you have to re-register any
		3150	signal watchers.
3081		3151
3082	=head3 Watcher-Specific Functions and Data Members	3152	=head3 Watcher-Specific Functions and Data Members
3083		3153
3084	=over 4	3154	=over 4
3085		3155
3086	=item ev_fork_init (ev_signal *, callback)	3156	=item ev_fork_init (ev_fork *, callback)
3087		3157
3088	Initialises and configures the fork watcher - it has no parameters of any	3158	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,	3159	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
3090	believe me.	3160	really.
3091		3161
3092	=back	3162	=back
3093		3163
3094		3164
		3165	=head2 C<ev_cleanup> - even the best things end
		3166
		3167	Cleanup watchers are called just before the event loop is being destroyed
		3168	by a call to C<ev_loop_destroy>.
		3169
		3170	While there is no guarantee that the event loop gets destroyed, cleanup
		3171	watchers provide a convenient method to install cleanup hooks for your
		3172	program, worker threads and so on - you just to make sure to destroy the
		3173	loop when you want them to be invoked.
		3174
		3175	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3176	all other watchers, they do not keep a reference to the event loop (which
		3177	makes a lot of sense if you think about it). Like all other watchers, you
		3178	can call libev functions in the callback, except C<ev_cleanup_start>.
		3179
		3180	=head3 Watcher-Specific Functions and Data Members
		3181
		3182	=over 4
		3183
		3184	=item ev_cleanup_init (ev_cleanup *, callback)
		3185
		3186	Initialises and configures the cleanup watcher - it has no parameters of
		3187	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3188	pointless, I assure you.
		3189
		3190	=back
		3191
		3192	Example: Register an atexit handler to destroy the default loop, so any
		3193	cleanup functions are called.
		3194
		3195	static void
		3196	program_exits (void)
		3197	{
		3198	ev_loop_destroy (EV_DEFAULT_UC);
		3199	}
		3200
		3201	...
		3202	atexit (program_exits);
		3203
		3204
3095	=head2 C<ev_async> - how to wake up an event loop	3205	=head2 C<ev_async> - how to wake up an event loop
3096		3206
3097	In general, you cannot use an C<ev_run> from multiple threads or other	3207	In general, you cannot use an C<ev_loop> from multiple threads or other
3098	asynchronous sources such as signal handlers (as opposed to multiple event	3208	asynchronous sources such as signal handlers (as opposed to multiple event
3099	loops - those are of course safe to use in different threads).	3209	loops - those are of course safe to use in different threads).
3100		3210
3101	Sometimes, however, you need to wake up an event loop you do not control,	3211	Sometimes, however, you need to wake up an event loop you do not control,
3102	for example because it belongs to another thread. This is what C<ev_async>	3212	for example because it belongs to another thread. This is what C<ev_async>
…		…
3104	it by calling C<ev_async_send>, which is thread- and signal safe.	3214	it by calling C<ev_async_send>, which is thread- and signal safe.
3105		3215
3106	This functionality is very similar to C<ev_signal> watchers, as signals,	3216	This functionality is very similar to C<ev_signal> watchers, as signals,
3107	too, are asynchronous in nature, and signals, too, will be compressed	3217	too, are asynchronous in nature, and signals, too, will be compressed
3108	(i.e. the number of callback invocations may be less than the number of	3218	(i.e. the number of callback invocations may be less than the number of
3109	C<ev_async_sent> calls).	3219	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
		3220	of "global async watchers" by using a watcher on an otherwise unused
		3221	signal, and C<ev_feed_signal> to signal this watcher from another thread,
		3222	even without knowing which loop owns the signal.
3110		3223
3111	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3224	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
3112	just the default loop.	3225	just the default loop.
3113		3226
3114	=head3 Queueing	3227	=head3 Queueing
…		…
3209	trust me.	3322	trust me.
3210		3323
3211	=item ev_async_send (loop, ev_async *)	3324	=item ev_async_send (loop, ev_async *)
3212		3325
3213	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3326	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3214	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3327	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3328	returns.
		3329
3215	C<ev_feed_event>, this call is safe to do from other threads, signal or	3330	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3216	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3331	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3217	section below on what exactly this means).	3332	embedding section below on what exactly this means).
3218		3333
3219	Note that, as with other watchers in libev, multiple events might get	3334	Note that, as with other watchers in libev, multiple events might get
3220	compressed into a single callback invocation (another way to look at this	3335	compressed into a single callback invocation (another way to look at this
3221	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3336	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
3222	reset when the event loop detects that).	3337	reset when the event loop detects that).
…		…
3290	Feed an event on the given fd, as if a file descriptor backend detected	3405	Feed an event on the given fd, as if a file descriptor backend detected
3291	the given events it.	3406	the given events it.
3292		3407
3293	=item ev_feed_signal_event (loop, int signum)	3408	=item ev_feed_signal_event (loop, int signum)
3294		3409
3295	Feed an event as if the given signal occurred (C<loop> must be the default	3410	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3296	loop!).	3411	which is async-safe.
3297		3412
3298	=back	3413	=back
		3414
		3415
		3416	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3417
		3418	This section explains some common idioms that are not immediately
		3419	obvious. Note that examples are sprinkled over the whole manual, and this
		3420	section only contains stuff that wouldn't fit anywhere else.
		3421
		3422	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3423
		3424	Each watcher has, by default, a C<void *data> member that you can read
		3425	or modify at any time: libev will completely ignore it. This can be used
		3426	to associate arbitrary data with your watcher. If you need more data and
		3427	don't want to allocate memory separately and store a pointer to it in that
		3428	data member, you can also "subclass" the watcher type and provide your own
		3429	data:
		3430
		3431	struct my_io
		3432	{
		3433	ev_io io;
		3434	int otherfd;
		3435	void *somedata;
		3436	struct whatever *mostinteresting;
		3437	};
		3438
		3439	...
		3440	struct my_io w;
		3441	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3442
		3443	And since your callback will be called with a pointer to the watcher, you
		3444	can cast it back to your own type:
		3445
		3446	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3447	{
		3448	struct my_io *w = (struct my_io *)w_;
		3449	...
		3450	}
		3451
		3452	More interesting and less C-conformant ways of casting your callback
		3453	function type instead have been omitted.
		3454
		3455	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3456
		3457	Another common scenario is to use some data structure with multiple
		3458	embedded watchers, in effect creating your own watcher that combines
		3459	multiple libev event sources into one "super-watcher":
		3460
		3461	struct my_biggy
		3462	{
		3463	int some_data;
		3464	ev_timer t1;
		3465	ev_timer t2;
		3466	}
		3467
		3468	In this case getting the pointer to C<my_biggy> is a bit more
		3469	complicated: Either you store the address of your C<my_biggy> struct in
		3470	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3471	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3472	real programmers):
		3473
		3474	#include <stddef.h>
		3475
		3476	static void
		3477	t1_cb (EV_P_ ev_timer *w, int revents)
		3478	{
		3479	struct my_biggy big = (struct my_biggy *)
		3480	(((char *)w) - offsetof (struct my_biggy, t1));
		3481	}
		3482
		3483	static void
		3484	t2_cb (EV_P_ ev_timer *w, int revents)
		3485	{
		3486	struct my_biggy big = (struct my_biggy *)
		3487	(((char *)w) - offsetof (struct my_biggy, t2));
		3488	}
		3489
		3490	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3491
		3492	Often (especially in GUI toolkits) there are places where you have
		3493	I<modal> interaction, which is most easily implemented by recursively
		3494	invoking C<ev_run>.
		3495
		3496	This brings the problem of exiting - a callback might want to finish the
		3497	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3498	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3499	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3500	other combination: In these cases, C<ev_break> will not work alone.
		3501
		3502	The solution is to maintain "break this loop" variable for each C<ev_run>
		3503	invocation, and use a loop around C<ev_run> until the condition is
		3504	triggered, using C<EVRUN_ONCE>:
		3505
		3506	// main loop
		3507	int exit_main_loop = 0;
		3508
		3509	while (!exit_main_loop)
		3510	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3511
		3512	// in a model watcher
		3513	int exit_nested_loop = 0;
		3514
		3515	while (!exit_nested_loop)
		3516	ev_run (EV_A_ EVRUN_ONCE);
		3517
		3518	To exit from any of these loops, just set the corresponding exit variable:
		3519
		3520	// exit modal loop
		3521	exit_nested_loop = 1;
		3522
		3523	// exit main program, after modal loop is finished
		3524	exit_main_loop = 1;
		3525
		3526	// exit both
		3527	exit_main_loop = exit_nested_loop = 1;
		3528
		3529	=head2 THREAD LOCKING EXAMPLE
		3530
		3531	Here is a fictitious example of how to run an event loop in a different
		3532	thread from where callbacks are being invoked and watchers are
		3533	created/added/removed.
		3534
		3535	For a real-world example, see the C<EV::Loop::Async> perl module,
		3536	which uses exactly this technique (which is suited for many high-level
		3537	languages).
		3538
		3539	The example uses a pthread mutex to protect the loop data, a condition
		3540	variable to wait for callback invocations, an async watcher to notify the
		3541	event loop thread and an unspecified mechanism to wake up the main thread.
		3542
		3543	First, you need to associate some data with the event loop:
		3544
		3545	typedef struct {
		3546	mutex_t lock; /* global loop lock */
		3547	ev_async async_w;
		3548	thread_t tid;
		3549	cond_t invoke_cv;
		3550	} userdata;
		3551
		3552	void prepare_loop (EV_P)
		3553	{
		3554	// for simplicity, we use a static userdata struct.
		3555	static userdata u;
		3556
		3557	ev_async_init (&u->async_w, async_cb);
		3558	ev_async_start (EV_A_ &u->async_w);
		3559
		3560	pthread_mutex_init (&u->lock, 0);
		3561	pthread_cond_init (&u->invoke_cv, 0);
		3562
		3563	// now associate this with the loop
		3564	ev_set_userdata (EV_A_ u);
		3565	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3566	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3567
		3568	// then create the thread running ev_run
		3569	pthread_create (&u->tid, 0, l_run, EV_A);
		3570	}
		3571
		3572	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3573	solely to wake up the event loop so it takes notice of any new watchers
		3574	that might have been added:
		3575
		3576	static void
		3577	async_cb (EV_P_ ev_async *w, int revents)
		3578	{
		3579	// just used for the side effects
		3580	}
		3581
		3582	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3583	protecting the loop data, respectively.
		3584
		3585	static void
		3586	l_release (EV_P)
		3587	{
		3588	userdata *u = ev_userdata (EV_A);
		3589	pthread_mutex_unlock (&u->lock);
		3590	}
		3591
		3592	static void
		3593	l_acquire (EV_P)
		3594	{
		3595	userdata *u = ev_userdata (EV_A);
		3596	pthread_mutex_lock (&u->lock);
		3597	}
		3598
		3599	The event loop thread first acquires the mutex, and then jumps straight
		3600	into C<ev_run>:
		3601
		3602	void *
		3603	l_run (void *thr_arg)
		3604	{
		3605	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3606
		3607	l_acquire (EV_A);
		3608	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3609	ev_run (EV_A_ 0);
		3610	l_release (EV_A);
		3611
		3612	return 0;
		3613	}
		3614
		3615	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3616	signal the main thread via some unspecified mechanism (signals? pipe
		3617	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3618	have been called (in a while loop because a) spurious wakeups are possible
		3619	and b) skipping inter-thread-communication when there are no pending
		3620	watchers is very beneficial):
		3621
		3622	static void
		3623	l_invoke (EV_P)
		3624	{
		3625	userdata *u = ev_userdata (EV_A);
		3626
		3627	while (ev_pending_count (EV_A))
		3628	{
		3629	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3630	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3631	}
		3632	}
		3633
		3634	Now, whenever the main thread gets told to invoke pending watchers, it
		3635	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3636	thread to continue:
		3637
		3638	static void
		3639	real_invoke_pending (EV_P)
		3640	{
		3641	userdata *u = ev_userdata (EV_A);
		3642
		3643	pthread_mutex_lock (&u->lock);
		3644	ev_invoke_pending (EV_A);
		3645	pthread_cond_signal (&u->invoke_cv);
		3646	pthread_mutex_unlock (&u->lock);
		3647	}
		3648
		3649	Whenever you want to start/stop a watcher or do other modifications to an
		3650	event loop, you will now have to lock:
		3651
		3652	ev_timer timeout_watcher;
		3653	userdata *u = ev_userdata (EV_A);
		3654
		3655	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3656
		3657	pthread_mutex_lock (&u->lock);
		3658	ev_timer_start (EV_A_ &timeout_watcher);
		3659	ev_async_send (EV_A_ &u->async_w);
		3660	pthread_mutex_unlock (&u->lock);
		3661
		3662	Note that sending the C<ev_async> watcher is required because otherwise
		3663	an event loop currently blocking in the kernel will have no knowledge
		3664	about the newly added timer. By waking up the loop it will pick up any new
		3665	watchers in the next event loop iteration.
		3666
		3667	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3668
		3669	While the overhead of a callback that e.g. schedules a thread is small, it
		3670	is still an overhead. If you embed libev, and your main usage is with some
		3671	kind of threads or coroutines, you might want to customise libev so that
		3672	doesn't need callbacks anymore.
		3673
		3674	Imagine you have coroutines that you can switch to using a function
		3675	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3676	and that due to some magic, the currently active coroutine is stored in a
		3677	global called C<current_coro>. Then you can build your own "wait for libev
		3678	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3679	the differing C<;> conventions):
		3680
		3681	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3682	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3683
		3684	That means instead of having a C callback function, you store the
		3685	coroutine to switch to in each watcher, and instead of having libev call
		3686	your callback, you instead have it switch to that coroutine.
		3687
		3688	A coroutine might now wait for an event with a function called
		3689	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3690	matter when, or whether the watcher is active or not when this function is
		3691	called):
		3692
		3693	void
		3694	wait_for_event (ev_watcher *w)
		3695	{
		3696	ev_cb_set (w) = current_coro;
		3697	switch_to (libev_coro);
		3698	}
		3699
		3700	That basically suspends the coroutine inside C<wait_for_event> and
		3701	continues the libev coroutine, which, when appropriate, switches back to
		3702	this or any other coroutine. I am sure if you sue this your own :)
		3703
		3704	You can do similar tricks if you have, say, threads with an event queue -
		3705	instead of storing a coroutine, you store the queue object and instead of
		3706	switching to a coroutine, you push the watcher onto the queue and notify
		3707	any waiters.
		3708
		3709	To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two
		3710	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3711
		3712	// my_ev.h
		3713	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3714	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3715	#include "../libev/ev.h"
		3716
		3717	// my_ev.c
		3718	#define EV_H "my_ev.h"
		3719	#include "../libev/ev.c"
		3720
		3721	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3722	F<my_ev.c> into your project. When properly specifying include paths, you
		3723	can even use F<ev.h> as header file name directly.
3299		3724
3300		3725
3301	=head1 LIBEVENT EMULATION	3726	=head1 LIBEVENT EMULATION
3302		3727
3303	Libev offers a compatibility emulation layer for libevent. It cannot	3728	Libev offers a compatibility emulation layer for libevent. It cannot
3304	emulate the internals of libevent, so here are some usage hints:	3729	emulate the internals of libevent, so here are some usage hints:
3305		3730
3306	=over 4	3731	=over 4
		3732
		3733	=item * Only the libevent-1.4.1-beta API is being emulated.
		3734
		3735	This was the newest libevent version available when libev was implemented,
		3736	and is still mostly unchanged in 2010.
3307		3737
3308	=item * Use it by including <event.h>, as usual.	3738	=item * Use it by including <event.h>, as usual.
3309		3739
3310	=item * The following members are fully supported: ev_base, ev_callback,	3740	=item * The following members are fully supported: ev_base, ev_callback,
3311	ev_arg, ev_fd, ev_res, ev_events.	3741	ev_arg, ev_fd, ev_res, ev_events.
…		…
3317	=item * Priorities are not currently supported. Initialising priorities	3747	=item * Priorities are not currently supported. Initialising priorities
3318	will fail and all watchers will have the same priority, even though there	3748	will fail and all watchers will have the same priority, even though there
3319	is an ev_pri field.	3749	is an ev_pri field.
3320		3750
3321	=item * In libevent, the last base created gets the signals, in libev, the	3751	=item * In libevent, the last base created gets the signals, in libev, the
3322	first base created (== the default loop) gets the signals.	3752	base that registered the signal gets the signals.
3323		3753
3324	=item * Other members are not supported.	3754	=item * Other members are not supported.
3325		3755
3326	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3756	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3327	to use the libev header file and library.	3757	to use the libev header file and library.
…		…
3346	Care has been taken to keep the overhead low. The only data member the C++	3776	Care has been taken to keep the overhead low. The only data member the C++
3347	classes add (compared to plain C-style watchers) is the event loop pointer	3777	classes add (compared to plain C-style watchers) is the event loop pointer
3348	that the watcher is associated with (or no additional members at all if	3778	that the watcher is associated with (or no additional members at all if
3349	you disable C<EV_MULTIPLICITY> when embedding libev).	3779	you disable C<EV_MULTIPLICITY> when embedding libev).
3350		3780
3351	Currently, functions, and static and non-static member functions can be	3781	Currently, functions, static and non-static member functions and classes
3352	used as callbacks. Other types should be easy to add as long as they only	3782	with C<operator ()> can be used as callbacks. Other types should be easy
3353	need one additional pointer for context. If you need support for other	3783	to add as long as they only need one additional pointer for context. If
3354	types of functors please contact the author (preferably after implementing	3784	you need support for other types of functors please contact the author
3355	it).	3785	(preferably after implementing it).
3356		3786
3357	Here is a list of things available in the C<ev> namespace:	3787	Here is a list of things available in the C<ev> namespace:
3358		3788
3359	=over 4	3789	=over 4
3360		3790
…		…
3788	F<event.h> that are not directly supported by the libev core alone.	4218	F<event.h> that are not directly supported by the libev core alone.
3789		4219
3790	In standalone mode, libev will still try to automatically deduce the	4220	In standalone mode, libev will still try to automatically deduce the
3791	configuration, but has to be more conservative.	4221	configuration, but has to be more conservative.
3792		4222
		4223	=item EV_USE_FLOOR
		4224
		4225	If defined to be C<1>, libev will use the C<floor ()> function for its
		4226	periodic reschedule calculations, otherwise libev will fall back on a
		4227	portable (slower) implementation. If you enable this, you usually have to
		4228	link against libm or something equivalent. Enabling this when the C<floor>
		4229	function is not available will fail, so the safe default is to not enable
		4230	this.
		4231
3793	=item EV_USE_MONOTONIC	4232	=item EV_USE_MONOTONIC
3794		4233
3795	If defined to be C<1>, libev will try to detect the availability of the	4234	If defined to be C<1>, libev will try to detect the availability of the
3796	monotonic clock option at both compile time and runtime. Otherwise no	4235	monotonic clock option at both compile time and runtime. Otherwise no
3797	use of the monotonic clock option will be attempted. If you enable this,	4236	use of the monotonic clock option will be attempted. If you enable this,
…		…
4228	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4667	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4229		4668
4230	#include "ev_cpp.h"	4669	#include "ev_cpp.h"
4231	#include "ev.c"	4670	#include "ev.c"
4232		4671
4233	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4672	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4234		4673
4235	=head2 THREADS AND COROUTINES	4674	=head2 THREADS AND COROUTINES
4236		4675
4237	=head3 THREADS	4676	=head3 THREADS
4238		4677
…		…
4289	default loop and triggering an C<ev_async> watcher from the default loop	4728	default loop and triggering an C<ev_async> watcher from the default loop
4290	watcher callback into the event loop interested in the signal.	4729	watcher callback into the event loop interested in the signal.
4291		4730
4292	=back	4731	=back
4293		4732
4294	=head4 THREAD LOCKING EXAMPLE	4733	See also L<THREAD LOCKING EXAMPLE>.
4295
4296	Here is a fictitious example of how to run an event loop in a different
4297	thread than where callbacks are being invoked and watchers are
4298	created/added/removed.
4299
4300	For a real-world example, see the C<EV::Loop::Async> perl module,
4301	which uses exactly this technique (which is suited for many high-level
4302	languages).
4303
4304	The example uses a pthread mutex to protect the loop data, a condition
4305	variable to wait for callback invocations, an async watcher to notify the
4306	event loop thread and an unspecified mechanism to wake up the main thread.
4307
4308	First, you need to associate some data with the event loop:
4309
4310	typedef struct {
4311	mutex_t lock; /* global loop lock */
4312	ev_async async_w;
4313	thread_t tid;
4314	cond_t invoke_cv;
4315	} userdata;
4316
4317	void prepare_loop (EV_P)
4318	{
4319	// for simplicity, we use a static userdata struct.
4320	static userdata u;
4321
4322	ev_async_init (&u->async_w, async_cb);
4323	ev_async_start (EV_A_ &u->async_w);
4324
4325	pthread_mutex_init (&u->lock, 0);
4326	pthread_cond_init (&u->invoke_cv, 0);
4327
4328	// now associate this with the loop
4329	ev_set_userdata (EV_A_ u);
4330	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4331	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4332
4333	// then create the thread running ev_loop
4334	pthread_create (&u->tid, 0, l_run, EV_A);
4335	}
4336
4337	The callback for the C<ev_async> watcher does nothing: the watcher is used
4338	solely to wake up the event loop so it takes notice of any new watchers
4339	that might have been added:
4340
4341	static void
4342	async_cb (EV_P_ ev_async *w, int revents)
4343	{
4344	// just used for the side effects
4345	}
4346
4347	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4348	protecting the loop data, respectively.
4349
4350	static void
4351	l_release (EV_P)
4352	{
4353	userdata *u = ev_userdata (EV_A);
4354	pthread_mutex_unlock (&u->lock);
4355	}
4356
4357	static void
4358	l_acquire (EV_P)
4359	{
4360	userdata *u = ev_userdata (EV_A);
4361	pthread_mutex_lock (&u->lock);
4362	}
4363
4364	The event loop thread first acquires the mutex, and then jumps straight
4365	into C<ev_run>:
4366
4367	void *
4368	l_run (void *thr_arg)
4369	{
4370	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4371
4372	l_acquire (EV_A);
4373	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4374	ev_run (EV_A_ 0);
4375	l_release (EV_A);
4376
4377	return 0;
4378	}
4379
4380	Instead of invoking all pending watchers, the C<l_invoke> callback will
4381	signal the main thread via some unspecified mechanism (signals? pipe
4382	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4383	have been called (in a while loop because a) spurious wakeups are possible
4384	and b) skipping inter-thread-communication when there are no pending
4385	watchers is very beneficial):
4386
4387	static void
4388	l_invoke (EV_P)
4389	{
4390	userdata *u = ev_userdata (EV_A);
4391
4392	while (ev_pending_count (EV_A))
4393	{
4394	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4395	pthread_cond_wait (&u->invoke_cv, &u->lock);
4396	}
4397	}
4398
4399	Now, whenever the main thread gets told to invoke pending watchers, it
4400	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4401	thread to continue:
4402
4403	static void
4404	real_invoke_pending (EV_P)
4405	{
4406	userdata *u = ev_userdata (EV_A);
4407
4408	pthread_mutex_lock (&u->lock);
4409	ev_invoke_pending (EV_A);
4410	pthread_cond_signal (&u->invoke_cv);
4411	pthread_mutex_unlock (&u->lock);
4412	}
4413
4414	Whenever you want to start/stop a watcher or do other modifications to an
4415	event loop, you will now have to lock:
4416
4417	ev_timer timeout_watcher;
4418	userdata *u = ev_userdata (EV_A);
4419
4420	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4421
4422	pthread_mutex_lock (&u->lock);
4423	ev_timer_start (EV_A_ &timeout_watcher);
4424	ev_async_send (EV_A_ &u->async_w);
4425	pthread_mutex_unlock (&u->lock);
4426
4427	Note that sending the C<ev_async> watcher is required because otherwise
4428	an event loop currently blocking in the kernel will have no knowledge
4429	about the newly added timer. By waking up the loop it will pick up any new
4430	watchers in the next event loop iteration.
4431		4734
4432	=head3 COROUTINES	4735	=head3 COROUTINES
4433		4736
4434	Libev is very accommodating to coroutines ("cooperative threads"):	4737	Libev is very accommodating to coroutines ("cooperative threads"):
4435	libev fully supports nesting calls to its functions from different	4738	libev fully supports nesting calls to its functions from different
…		…
4531	=head3 C<kqueue> is buggy	4834	=head3 C<kqueue> is buggy
4532		4835
4533	The kqueue syscall is broken in all known versions - most versions support	4836	The kqueue syscall is broken in all known versions - most versions support
4534	only sockets, many support pipes.	4837	only sockets, many support pipes.
4535		4838
4536	Libev tries to work around this by not using C<kqueue> by default on	4839	Libev tries to work around this by not using C<kqueue> by default on this
4537	this rotten platform, but of course you can still ask for it when creating	4840	rotten platform, but of course you can still ask for it when creating a
4538	a loop.	4841	loop - embedding a socket-only kqueue loop into a select-based one is
		4842	probably going to work well.
4539		4843
4540	=head3 C<poll> is buggy	4844	=head3 C<poll> is buggy
4541		4845
4542	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>	4846	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
4543	implementation by something calling C<kqueue> internally around the 10.5.6	4847	implementation by something calling C<kqueue> internally around the 10.5.6
…		…
4562		4866
4563	=head3 C<errno> reentrancy	4867	=head3 C<errno> reentrancy
4564		4868
4565	The default compile environment on Solaris is unfortunately so	4869	The default compile environment on Solaris is unfortunately so
4566	thread-unsafe that you can't even use components/libraries compiled	4870	thread-unsafe that you can't even use components/libraries compiled
4567	without C<-D_REENTRANT> (as long as they use C<errno>), which, of course,	4871	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
4568	isn't defined by default.	4872	defined by default. A valid, if stupid, implementation choice.
4569		4873
4570	If you want to use libev in threaded environments you have to make sure	4874	If you want to use libev in threaded environments you have to make sure
4571	it's compiled with C<_REENTRANT> defined.	4875	it's compiled with C<_REENTRANT> defined.
4572		4876
4573	=head3 Event port backend	4877	=head3 Event port backend
4574		4878
4575	The scalable event interface for Solaris is called "event ports". Unfortunately,	4879	The scalable event interface for Solaris is called "event
4576	this mechanism is very buggy. If you run into high CPU usage, your program	4880	ports". Unfortunately, this mechanism is very buggy in all major
		4881	releases. If you run into high CPU usage, your program freezes or you get
4577	freezes or you get a large number of spurious wakeups, make sure you have	4882	a large number of spurious wakeups, make sure you have all the relevant
4578	all the relevant and latest kernel patches applied. No, I don't know which	4883	and latest kernel patches applied. No, I don't know which ones, but there
4579	ones, but there are multiple ones.	4884	are multiple ones to apply, and afterwards, event ports actually work
		4885	great.
4580		4886
4581	If you can't get it to work, you can try running the program by setting	4887	If you can't get it to work, you can try running the program by setting
4582	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and	4888	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
4583	C<select> backends.	4889	C<select> backends.
4584		4890
4585	=head2 AIX POLL BUG	4891	=head2 AIX POLL BUG
4586		4892
4587	AIX unfortunately has a broken C<poll.h> header. Libev works around	4893	AIX unfortunately has a broken C<poll.h> header. Libev works around
4588	this by trying to avoid the poll backend altogether (i.e. it's not even	4894	this by trying to avoid the poll backend altogether (i.e. it's not even
4589	compiled in), which normally isn't a big problem as C<select> works fine	4895	compiled in), which normally isn't a big problem as C<select> works fine
4590	with large bitsets, and AIX is dead anyway.	4896	with large bitsets on AIX, and AIX is dead anyway.
4591		4897
4592	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4898	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
4593		4899
4594	=head3 General issues	4900	=head3 General issues
4595		4901
…		…
4701	structure (guaranteed by POSIX but not by ISO C for example), but it also	5007	structure (guaranteed by POSIX but not by ISO C for example), but it also
4702	assumes that the same (machine) code can be used to call any watcher	5008	assumes that the same (machine) code can be used to call any watcher
4703	callback: The watcher callbacks have different type signatures, but libev	5009	callback: The watcher callbacks have different type signatures, but libev
4704	calls them using an C<ev_watcher *> internally.	5010	calls them using an C<ev_watcher *> internally.
4705		5011
		5012	=item pointer accesses must be thread-atomic
		5013
		5014	Accessing a pointer value must be atomic, it must both be readable and
		5015	writable in one piece - this is the case on all current architectures.
		5016
4706	=item C<sig_atomic_t volatile> must be thread-atomic as well	5017	=item C<sig_atomic_t volatile> must be thread-atomic as well
4707		5018
4708	The type C<sig_atomic_t volatile> (or whatever is defined as	5019	The type C<sig_atomic_t volatile> (or whatever is defined as
4709	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5020	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
4710	threads. This is not part of the specification for C<sig_atomic_t>, but is	5021	threads. This is not part of the specification for C<sig_atomic_t>, but is
…		…
4816	=back	5127	=back
4817		5128
4818		5129
4819	=head1 PORTING FROM LIBEV 3.X TO 4.X	5130	=head1 PORTING FROM LIBEV 3.X TO 4.X
4820		5131
4821	The major version 4 introduced some minor incompatible changes to the API.	5132	The major version 4 introduced some incompatible changes to the API.
4822		5133
4823	At the moment, the C<ev.h> header file tries to implement superficial	5134	At the moment, the C<ev.h> header file provides compatibility definitions
4824	compatibility, so most programs should still compile. Those might be	5135	for all changes, so most programs should still compile. The compatibility
4825	removed in later versions of libev, so better update early than late.	5136	layer might be removed in later versions of libev, so better update to the
		5137	new API early than late.
4826		5138
4827	=over 4	5139	=over 4
		5140
		5141	=item C<EV_COMPAT3> backwards compatibility mechanism
		5142
		5143	The backward compatibility mechanism can be controlled by
		5144	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5145	section.
		5146
		5147	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5148
		5149	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5150
		5151	ev_loop_destroy (EV_DEFAULT_UC);
		5152	ev_loop_fork (EV_DEFAULT);
4828		5153
4829	=item function/symbol renames	5154	=item function/symbol renames
4830		5155
4831	A number of functions and symbols have been renamed:	5156	A number of functions and symbols have been renamed:
4832		5157
…		…
4851	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme	5176	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
4852	as all other watcher types. Note that C<ev_loop_fork> is still called	5177	as all other watcher types. Note that C<ev_loop_fork> is still called
4853	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>	5178	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
4854	typedef.	5179	typedef.
4855		5180
4856	=item C<EV_COMPAT3> backwards compatibility mechanism
4857
4858	The backward compatibility mechanism can be controlled by
4859	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
4860	section.
4861
4862	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>	5181	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
4863		5182
4864	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different	5183	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
4865	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile	5184	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
4866	and work, but the library code will of course be larger.	5185	and work, but the library code will of course be larger.
…		…
4872		5191
4873	=over 4	5192	=over 4
4874		5193
4875	=item active	5194	=item active
4876		5195
4877	A watcher is active as long as it has been started (has been attached to	5196	A watcher is active as long as it has been started and not yet stopped.
4878	an event loop) but not yet stopped (disassociated from the event loop).	5197	See L<WATCHER STATES> for details.
4879		5198
4880	=item application	5199	=item application
4881		5200
4882	In this document, an application is whatever is using libev.	5201	In this document, an application is whatever is using libev.
		5202
		5203	=item backend
		5204
		5205	The part of the code dealing with the operating system interfaces.
4883		5206
4884	=item callback	5207	=item callback
4885		5208
4886	The address of a function that is called when some event has been	5209	The address of a function that is called when some event has been
4887	detected. Callbacks are being passed the event loop, the watcher that	5210	detected. Callbacks are being passed the event loop, the watcher that
4888	received the event, and the actual event bitset.	5211	received the event, and the actual event bitset.
4889		5212
4890	=item callback invocation	5213	=item callback/watcher invocation
4891		5214
4892	The act of calling the callback associated with a watcher.	5215	The act of calling the callback associated with a watcher.
4893		5216
4894	=item event	5217	=item event
4895		5218
…		…
4914	The model used to describe how an event loop handles and processes	5237	The model used to describe how an event loop handles and processes
4915	watchers and events.	5238	watchers and events.
4916		5239
4917	=item pending	5240	=item pending
4918		5241
4919	A watcher is pending as soon as the corresponding event has been detected,	5242	A watcher is pending as soon as the corresponding event has been
4920	and stops being pending as soon as the watcher will be invoked or its	5243	detected. See L<WATCHER STATES> for details.
4921	pending status is explicitly cleared by the application.
4922
4923	A watcher can be pending, but not active. Stopping a watcher also clears
4924	its pending status.
4925		5244
4926	=item real time	5245	=item real time
4927		5246
4928	The physical time that is observed. It is apparently strictly monotonic :)	5247	The physical time that is observed. It is apparently strictly monotonic :)
4929		5248
4930	=item wall-clock time	5249	=item wall-clock time
4931		5250
4932	The time and date as shown on clocks. Unlike real time, it can actually	5251	The time and date as shown on clocks. Unlike real time, it can actually
4933	be wrong and jump forwards and backwards, e.g. when the you adjust your	5252	be wrong and jump forwards and backwards, e.g. when you adjust your
4934	clock.	5253	clock.
4935		5254
4936	=item watcher	5255	=item watcher
4937		5256
4938	A data structure that describes interest in certain events. Watchers need	5257	A data structure that describes interest in certain events. Watchers need
4939	to be started (attached to an event loop) before they can receive events.	5258	to be started (attached to an event loop) before they can receive events.
4940		5259
4941	=item watcher invocation
4942
4943	The act of calling the callback associated with a watcher.
4944
4945	=back	5260	=back
4946		5261
4947	=head1 AUTHOR	5262	=head1 AUTHOR
4948		5263
4949	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5264	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5265	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4950		5266

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