ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.310 by root, Thu Oct 21 12:32:47 2010 UTC vs.
Revision 1.384 by sf-exg, Sun Oct 16 11:02:57 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_now_update> 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 case unless libev 3 compatibility is disabled, as libev	328	I<not> optional in this case unless libev 3 compatibility is disabled, as
299	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 have 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 erroneously 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 returns 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 you
		616	absolutely have to know whether an event occurred or not because you have
		617	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);
…		…
870	overhead for the actual polling but can deliver many events at once.	952	overhead for the actual polling but can deliver many events at once.
871		953
872	By setting a higher I<io collect interval> you allow libev to spend more	954	By setting a higher I<io collect interval> you allow libev to spend more
873	time collecting I/O events, so you can handle more events per iteration,	955	time collecting I/O events, so you can handle more events per iteration,
874	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	956	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
875	C<ev_timer>) will be not affected. Setting this to a non-null value will	957	C<ev_timer>) will not be affected. Setting this to a non-null value will
876	introduce an additional C<ev_sleep ()> call into most loop iterations. The	958	introduce an additional C<ev_sleep ()> call into most loop iterations. The
877	sleep time ensures that libev will not poll for I/O events more often then	959	sleep time ensures that libev will not poll for I/O events more often then
878	once per this interval, on average.	960	once per this interval, on average (as long as the host time resolution is
		961	good enough).
879		962
880	Likewise, by setting a higher I<timeout collect interval> you allow libev	963	Likewise, by setting a higher I<timeout collect interval> you allow libev
881	to spend more time collecting timeouts, at the expense of increased	964	to spend more time collecting timeouts, at the expense of increased
882	latency/jitter/inexactness (the watcher callback will be called	965	latency/jitter/inexactness (the watcher callback will be called
883	later). C<ev_io> watchers will not be affected. Setting this to a non-null	966	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
908		991
909	=item ev_invoke_pending (loop)	992	=item ev_invoke_pending (loop)
910		993
911	This call will simply invoke all pending watchers while resetting their	994	This call will simply invoke all pending watchers while resetting their
912	pending state. Normally, C<ev_run> does this automatically when required,	995	pending state. Normally, C<ev_run> does this automatically when required,
913	but when overriding the invoke callback this call comes handy.	996	but when overriding the invoke callback this call comes handy. This
		997	function can be invoked from a watcher - this can be useful for example
		998	when you want to do some lengthy calculation and want to pass further
		999	event handling to another thread (you still have to make sure only one
		1000	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
914		1001
915	=item int ev_pending_count (loop)	1002	=item int ev_pending_count (loop)
916		1003
917	Returns the number of pending watchers - zero indicates that no watchers	1004	Returns the number of pending watchers - zero indicates that no watchers
918	are pending.	1005	are pending.
…		…
958	See also the locking example in the C<THREADS> section later in this	1045	See also the locking example in the C<THREADS> section later in this
959	document.	1046	document.
960		1047
961	=item ev_set_userdata (loop, void *data)	1048	=item ev_set_userdata (loop, void *data)
962		1049
963	=item ev_userdata (loop)	1050	=item void *ev_userdata (loop)
964		1051
965	Set and retrieve a single C<void *> associated with a loop. When	1052	Set and retrieve a single C<void *> associated with a loop. When
966	C<ev_set_userdata> has never been called, then C<ev_userdata> returns	1053	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
967	C<0.>	1054	C<0>.
968		1055
969	These two functions can be used to associate arbitrary data with a loop,	1056	These two functions can be used to associate arbitrary data with a loop,
970	and are intended solely for the C<invoke_pending_cb>, C<release> and	1057	and are intended solely for the C<invoke_pending_cb>, C<release> and
971	C<acquire> callbacks described above, but of course can be (ab-)used for	1058	C<acquire> callbacks described above, but of course can be (ab-)used for
972	any other purpose as well.	1059	any other purpose as well.
…		…
990		1077
991	In the following description, uppercase C<TYPE> in names stands for the	1078	In the following description, uppercase C<TYPE> in names stands for the
992	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1079	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
993	watchers and C<ev_io_start> for I/O watchers.	1080	watchers and C<ev_io_start> for I/O watchers.
994		1081
995	A watcher is a structure that you create and register to record your	1082	A watcher is an opaque structure that you allocate and register to record
996	interest in some event. For instance, if you want to wait for STDIN to	1083	your interest in some event. To make a concrete example, imagine you want
997	become readable, you would create an C<ev_io> watcher for that:	1084	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1085	for that:
998		1086
999	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1087	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
1000	{	1088	{
1001	ev_io_stop (w);	1089	ev_io_stop (w);
1002	ev_break (loop, EVBREAK_ALL);	1090	ev_break (loop, EVBREAK_ALL);
…		…
1017	stack).	1105	stack).
1018		1106
1019	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1107	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
1020	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1108	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
1021		1109
1022	Each watcher structure must be initialised by a call to C<ev_init	1110	Each watcher structure must be initialised by a call to C<ev_init (watcher
1023	(watcher *, callback)>, which expects a callback to be provided. This	1111	*, callback)>, which expects a callback to be provided. This callback is
1024	callback gets invoked each time the event occurs (or, in the case of I/O	1112	invoked each time the event occurs (or, in the case of I/O watchers, each
1025	watchers, each time the event loop detects that the file descriptor given	1113	time the event loop detects that the file descriptor given is readable
1026	is readable and/or writable).	1114	and/or writable).
1027		1115
1028	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1116	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
1029	macro to configure it, with arguments specific to the watcher type. There	1117	macro to configure it, with arguments specific to the watcher type. There
1030	is also a macro to combine initialisation and setting in one call: C<<	1118	is also a macro to combine initialisation and setting in one call: C<<
1031	ev_TYPE_init (watcher *, callback, ...) >>.	1119	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
1099	=item C<EV_FORK>	1187	=item C<EV_FORK>
1100		1188
1101	The event loop has been resumed in the child process after fork (see	1189	The event loop has been resumed in the child process after fork (see
1102	C<ev_fork>).	1190	C<ev_fork>).
1103		1191
		1192	=item C<EV_CLEANUP>
		1193
		1194	The event loop is about to be destroyed (see C<ev_cleanup>).
		1195
1104	=item C<EV_ASYNC>	1196	=item C<EV_ASYNC>
1105		1197
1106	The given async watcher has been asynchronously notified (see C<ev_async>).	1198	The given async watcher has been asynchronously notified (see C<ev_async>).
1107		1199
1108	=item C<EV_CUSTOM>	1200	=item C<EV_CUSTOM>
…		…
1280	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related	1372	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1281	functions that do not need a watcher.	1373	functions that do not need a watcher.
1282		1374
1283	=back	1375	=back
1284		1376
		1377	See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR
		1378	OWN COMPOSITE WATCHERS> idioms.
1285		1379
1286	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1380	=head2 WATCHER STATES
1287		1381
1288	Each watcher has, by default, a member C<void *data> that you can change	1382	There are various watcher states mentioned throughout this manual -
1289	and read at any time: libev will completely ignore it. This can be used	1383	active, pending and so on. In this section these states and the rules to
1290	to associate arbitrary data with your watcher. If you need more data and	1384	transition between them will be described in more detail - and while these
1291	don't want to allocate memory and store a pointer to it in that data	1385	rules might look complicated, they usually do "the right thing".
1292	member, you can also "subclass" the watcher type and provide your own
1293	data:
1294		1386
1295	struct my_io	1387	=over 4
1296	{
1297	ev_io io;
1298	int otherfd;
1299	void *somedata;
1300	struct whatever *mostinteresting;
1301	};
1302		1388
1303	...	1389	=item initialiased
1304	struct my_io w;
1305	ev_io_init (&w.io, my_cb, fd, EV_READ);
1306		1390
1307	And since your callback will be called with a pointer to the watcher, you	1391	Before a watcher can be registered with the event loop it has to be
1308	can cast it back to your own type:	1392	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1393	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1309		1394
1310	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)	1395	In this state it is simply some block of memory that is suitable for
1311	{	1396	use in an event loop. It can be moved around, freed, reused etc. at
1312	struct my_io *w = (struct my_io *)w_;	1397	will - as long as you either keep the memory contents intact, or call
1313	...	1398	C<ev_TYPE_init> again.
1314	}
1315		1399
1316	More interesting and less C-conformant ways of casting your callback type	1400	=item started/running/active
1317	instead have been omitted.
1318		1401
1319	Another common scenario is to use some data structure with multiple	1402	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1320	embedded watchers:	1403	property of the event loop, and is actively waiting for events. While in
		1404	this state it cannot be accessed (except in a few documented ways), moved,
		1405	freed or anything else - the only legal thing is to keep a pointer to it,
		1406	and call libev functions on it that are documented to work on active watchers.
1321		1407
1322	struct my_biggy	1408	=item pending
1323	{
1324	int some_data;
1325	ev_timer t1;
1326	ev_timer t2;
1327	}
1328		1409
1329	In this case getting the pointer to C<my_biggy> is a bit more	1410	If a watcher is active and libev determines that an event it is interested
1330	complicated: Either you store the address of your C<my_biggy> struct	1411	in has occurred (such as a timer expiring), it will become pending. It will
1331	in the C<data> member of the watcher (for woozies), or you need to use	1412	stay in this pending state until either it is stopped or its callback is
1332	some pointer arithmetic using C<offsetof> inside your watchers (for real	1413	about to be invoked, so it is not normally pending inside the watcher
1333	programmers):	1414	callback.
1334		1415
1335	#include <stddef.h>	1416	The watcher might or might not be active while it is pending (for example,
		1417	an expired non-repeating timer can be pending but no longer active). If it
		1418	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1419	but it is still property of the event loop at this time, so cannot be
		1420	moved, freed or reused. And if it is active the rules described in the
		1421	previous item still apply.
1336		1422
1337	static void	1423	It is also possible to feed an event on a watcher that is not active (e.g.
1338	t1_cb (EV_P_ ev_timer *w, int revents)	1424	via C<ev_feed_event>), in which case it becomes pending without being
1339	{	1425	active.
1340	struct my_biggy big = (struct my_biggy *)
1341	(((char *)w) - offsetof (struct my_biggy, t1));
1342	}
1343		1426
1344	static void	1427	=item stopped
1345	t2_cb (EV_P_ ev_timer *w, int revents)	1428
1346	{	1429	A watcher can be stopped implicitly by libev (in which case it might still
1347	struct my_biggy big = (struct my_biggy *)	1430	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1348	(((char *)w) - offsetof (struct my_biggy, t2));	1431	latter will clear any pending state the watcher might be in, regardless
1349	}	1432	of whether it was active or not, so stopping a watcher explicitly before
		1433	freeing it is often a good idea.
		1434
		1435	While stopped (and not pending) the watcher is essentially in the
		1436	initialised state, that is, it can be reused, moved, modified in any way
		1437	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1438	it again).
		1439
		1440	=back
1350		1441
1351	=head2 WATCHER PRIORITY MODELS	1442	=head2 WATCHER PRIORITY MODELS
1352		1443
1353	Many event loops support I<watcher priorities>, which are usually small	1444	Many event loops support I<watcher priorities>, which are usually small
1354	integers that influence the ordering of event callback invocation	1445	integers that influence the ordering of event callback invocation
…		…
1481	In general you can register as many read and/or write event watchers per	1572	In general you can register as many read and/or write event watchers per
1482	fd as you want (as long as you don't confuse yourself). Setting all file	1573	fd as you want (as long as you don't confuse yourself). Setting all file
1483	descriptors to non-blocking mode is also usually a good idea (but not	1574	descriptors to non-blocking mode is also usually a good idea (but not
1484	required if you know what you are doing).	1575	required if you know what you are doing).
1485		1576
1486	If you cannot use non-blocking mode, then force the use of a
1487	known-to-be-good backend (at the time of this writing, this includes only
1488	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1489	descriptors for which non-blocking operation makes no sense (such as
1490	files) - libev doesn't guarantee any specific behaviour in that case.
1491
1492	Another thing you have to watch out for is that it is quite easy to	1577	Another thing you have to watch out for is that it is quite easy to
1493	receive "spurious" readiness notifications, that is your callback might	1578	receive "spurious" readiness notifications, that is, your callback might
1494	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1579	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1495	because there is no data. Not only are some backends known to create a	1580	because there is no data. It is very easy to get into this situation even
1496	lot of those (for example Solaris ports), it is very easy to get into	1581	with a relatively standard program structure. Thus it is best to always
1497	this situation even with a relatively standard program structure. Thus	1582	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1498	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1499	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1583	preferable to a program hanging until some data arrives.
1500		1584
1501	If you cannot run the fd in non-blocking mode (for example you should	1585	If you cannot run the fd in non-blocking mode (for example you should
1502	not play around with an Xlib connection), then you have to separately	1586	not play around with an Xlib connection), then you have to separately
1503	re-test whether a file descriptor is really ready with a known-to-be good	1587	re-test whether a file descriptor is really ready with a known-to-be good
1504	interface such as poll (fortunately in our Xlib example, Xlib already	1588	interface such as poll (fortunately in the case of Xlib, it already does
1505	does this on its own, so its quite safe to use). Some people additionally	1589	this on its own, so its quite safe to use). Some people additionally
1506	use C<SIGALRM> and an interval timer, just to be sure you won't block	1590	use C<SIGALRM> and an interval timer, just to be sure you won't block
1507	indefinitely.	1591	indefinitely.
1508		1592
1509	But really, best use non-blocking mode.	1593	But really, best use non-blocking mode.
1510		1594
…		…
1538		1622
1539	There is no workaround possible except not registering events	1623	There is no workaround possible except not registering events
1540	for potentially C<dup ()>'ed file descriptors, or to resort to	1624	for potentially C<dup ()>'ed file descriptors, or to resort to
1541	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1625	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1542		1626
		1627	=head3 The special problem of files
		1628
		1629	Many people try to use C<select> (or libev) on file descriptors
		1630	representing files, and expect it to become ready when their program
		1631	doesn't block on disk accesses (which can take a long time on their own).
		1632
		1633	However, this cannot ever work in the "expected" way - you get a readiness
		1634	notification as soon as the kernel knows whether and how much data is
		1635	there, and in the case of open files, that's always the case, so you
		1636	always get a readiness notification instantly, and your read (or possibly
		1637	write) will still block on the disk I/O.
		1638
		1639	Another way to view it is that in the case of sockets, pipes, character
		1640	devices and so on, there is another party (the sender) that delivers data
		1641	on its own, but in the case of files, there is no such thing: the disk
		1642	will not send data on its own, simply because it doesn't know what you
		1643	wish to read - you would first have to request some data.
		1644
		1645	Since files are typically not-so-well supported by advanced notification
		1646	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1647	to files, even though you should not use it. The reason for this is
		1648	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1649	usually a tty, often a pipe, but also sometimes files or special devices
		1650	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1651	F</dev/urandom>), and even though the file might better be served with
		1652	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1653	it "just works" instead of freezing.
		1654
		1655	So avoid file descriptors pointing to files when you know it (e.g. use
		1656	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1657	when you rarely read from a file instead of from a socket, and want to
		1658	reuse the same code path.
		1659
1543	=head3 The special problem of fork	1660	=head3 The special problem of fork
1544		1661
1545	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1662	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1546	useless behaviour. Libev fully supports fork, but needs to be told about	1663	useless behaviour. Libev fully supports fork, but needs to be told about
1547	it in the child.	1664	it in the child if you want to continue to use it in the child.
1548		1665
1549	To support fork in your programs, you either have to call	1666	To support fork in your child processes, you have to call C<ev_loop_fork
1550	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1667	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1551	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1668	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1552	C<EVBACKEND_POLL>.
1553		1669
1554	=head3 The special problem of SIGPIPE	1670	=head3 The special problem of SIGPIPE
1555		1671
1556	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1672	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1557	when writing to a pipe whose other end has been closed, your program gets	1673	when writing to a pipe whose other end has been closed, your program gets
…		…
1655	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1771	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1656	monotonic clock option helps a lot here).	1772	monotonic clock option helps a lot here).
1657		1773
1658	The callback is guaranteed to be invoked only I<after> its timeout has	1774	The callback is guaranteed to be invoked only I<after> its timeout has
1659	passed (not I<at>, so on systems with very low-resolution clocks this	1775	passed (not I<at>, so on systems with very low-resolution clocks this
1660	might introduce a small delay). If multiple timers become ready during the	1776	might introduce a small delay, see "the special problem of being too
		1777	early", below). If multiple timers become ready during the same loop
1661	same loop iteration then the ones with earlier time-out values are invoked	1778	iteration then the ones with earlier time-out values are invoked before
1662	before ones of the same priority with later time-out values (but this is	1779	ones of the same priority with later time-out values (but this is no
1663	no longer true when a callback calls C<ev_run> recursively).	1780	longer true when a callback calls C<ev_run> recursively).
1664		1781
1665	=head3 Be smart about timeouts	1782	=head3 Be smart about timeouts
1666		1783
1667	Many real-world problems involve some kind of timeout, usually for error	1784	Many real-world problems involve some kind of timeout, usually for error
1668	recovery. A typical example is an HTTP request - if the other side hangs,	1785	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1835	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	1952	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1836	rather complicated, but extremely efficient, something that really pays	1953	rather complicated, but extremely efficient, something that really pays
1837	off after the first million or so of active timers, i.e. it's usually	1954	off after the first million or so of active timers, i.e. it's usually
1838	overkill :)	1955	overkill :)
1839		1956
		1957	=head3 The special problem of being too early
		1958
		1959	If you ask a timer to call your callback after three seconds, then
		1960	you expect it to be invoked after three seconds - but of course, this
		1961	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		1962	guaranteed to any precision by libev - imagine somebody suspending the
		1963	process a STOP signal for a few hours for example.
		1964
		1965	So, libev tries to invoke your callback as soon as possible I<after> the
		1966	delay has occurred, but cannot guarantee this.
		1967
		1968	A less obvious failure mode is calling your callback too early: many event
		1969	loops compare timestamps with a "elapsed delay >= requested delay", but
		1970	this can cause your callback to be invoked much earlier than you would
		1971	expect.
		1972
		1973	To see why, imagine a system with a clock that only offers full second
		1974	resolution (think windows if you can't come up with a broken enough OS
		1975	yourself). If you schedule a one-second timer at the time 500.9, then the
		1976	event loop will schedule your timeout to elapse at a system time of 500
		1977	(500.9 truncated to the resolution) + 1, or 501.
		1978
		1979	If an event library looks at the timeout 0.1s later, it will see "501 >=
		1980	501" and invoke the callback 0.1s after it was started, even though a
		1981	one-second delay was requested - this is being "too early", despite best
		1982	intentions.
		1983
		1984	This is the reason why libev will never invoke the callback if the elapsed
		1985	delay equals the requested delay, but only when the elapsed delay is
		1986	larger than the requested delay. In the example above, libev would only invoke
		1987	the callback at system time 502, or 1.1s after the timer was started.
		1988
		1989	So, while libev cannot guarantee that your callback will be invoked
		1990	exactly when requested, it I<can> and I<does> guarantee that the requested
		1991	delay has actually elapsed, or in other words, it always errs on the "too
		1992	late" side of things.
		1993
1840	=head3 The special problem of time updates	1994	=head3 The special problem of time updates
1841		1995
1842	Establishing the current time is a costly operation (it usually takes at	1996	Establishing the current time is a costly operation (it usually takes
1843	least two system calls): EV therefore updates its idea of the current	1997	at least one system call): EV therefore updates its idea of the current
1844	time only before and after C<ev_run> collects new events, which causes a	1998	time only before and after C<ev_run> collects new events, which causes a
1845	growing difference between C<ev_now ()> and C<ev_time ()> when handling	1999	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1846	lots of events in one iteration.	2000	lots of events in one iteration.
1847		2001
1848	The relative timeouts are calculated relative to the C<ev_now ()>	2002	The relative timeouts are calculated relative to the C<ev_now ()>
…		…
1854	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2008	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1855		2009
1856	If the event loop is suspended for a long time, you can also force an	2010	If the event loop is suspended for a long time, you can also force an
1857	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2011	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1858	()>.	2012	()>.
		2013
		2014	=head3 The special problem of unsynchronised clocks
		2015
		2016	Modern systems have a variety of clocks - libev itself uses the normal
		2017	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2018	jumps).
		2019
		2020	Neither of these clocks is synchronised with each other or any other clock
		2021	on the system, so C<ev_time ()> might return a considerably different time
		2022	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2023	a call to C<gettimeofday> might return a second count that is one higher
		2024	than a directly following call to C<time>.
		2025
		2026	The moral of this is to only compare libev-related timestamps with
		2027	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2028	a second or so.
		2029
		2030	One more problem arises due to this lack of synchronisation: if libev uses
		2031	the system monotonic clock and you compare timestamps from C<ev_time>
		2032	or C<ev_now> from when you started your timer and when your callback is
		2033	invoked, you will find that sometimes the callback is a bit "early".
		2034
		2035	This is because C<ev_timer>s work in real time, not wall clock time, so
		2036	libev makes sure your callback is not invoked before the delay happened,
		2037	I<measured according to the real time>, not the system clock.
		2038
		2039	If your timeouts are based on a physical timescale (e.g. "time out this
		2040	connection after 100 seconds") then this shouldn't bother you as it is
		2041	exactly the right behaviour.
		2042
		2043	If you want to compare wall clock/system timestamps to your timers, then
		2044	you need to use C<ev_periodic>s, as these are based on the wall clock
		2045	time, where your comparisons will always generate correct results.
1859		2046
1860	=head3 The special problems of suspended animation	2047	=head3 The special problems of suspended animation
1861		2048
1862	When you leave the server world it is quite customary to hit machines that	2049	When you leave the server world it is quite customary to hit machines that
1863	can suspend/hibernate - what happens to the clocks during such a suspend?	2050	can suspend/hibernate - what happens to the clocks during such a suspend?
…		…
1907	keep up with the timer (because it takes longer than those 10 seconds to	2094	keep up with the timer (because it takes longer than those 10 seconds to
1908	do stuff) the timer will not fire more than once per event loop iteration.	2095	do stuff) the timer will not fire more than once per event loop iteration.
1909		2096
1910	=item ev_timer_again (loop, ev_timer *)	2097	=item ev_timer_again (loop, ev_timer *)
1911		2098
1912	This will act as if the timer timed out and restart it again if it is	2099	This will act as if the timer timed out and restarts it again if it is
1913	repeating. The exact semantics are:	2100	repeating. The exact semantics are:
1914		2101
1915	If the timer is pending, its pending status is cleared.	2102	If the timer is pending, its pending status is cleared.
1916		2103
1917	If the timer is started but non-repeating, stop it (as if it timed out).	2104	If the timer is started but non-repeating, stop it (as if it timed out).
…		…
2047		2234
2048	Another way to think about it (for the mathematically inclined) is that	2235	Another way to think about it (for the mathematically inclined) is that
2049	C<ev_periodic> will try to run the callback in this mode at the next possible	2236	C<ev_periodic> will try to run the callback in this mode at the next possible
2050	time where C<time = offset (mod interval)>, regardless of any time jumps.	2237	time where C<time = offset (mod interval)>, regardless of any time jumps.
2051		2238
2052	For numerical stability it is preferable that the C<offset> value is near	2239	The C<interval> I<MUST> be positive, and for numerical stability, the
2053	C<ev_now ()> (the current time), but there is no range requirement for	2240	interval value should be higher than C<1/8192> (which is around 100
2054	this value, and in fact is often specified as zero.	2241	microseconds) and C<offset> should be higher than C<0> and should have
		2242	at most a similar magnitude as the current time (say, within a factor of
		2243	ten). Typical values for offset are, in fact, C<0> or something between
		2244	C<0> and C<interval>, which is also the recommended range.
2055		2245
2056	Note also that there is an upper limit to how often a timer can fire (CPU	2246	Note also that there is an upper limit to how often a timer can fire (CPU
2057	speed for example), so if C<interval> is very small then timing stability	2247	speed for example), so if C<interval> is very small then timing stability
2058	will of course deteriorate. Libev itself tries to be exact to be about one	2248	will of course deteriorate. Libev itself tries to be exact to be about one
2059	millisecond (if the OS supports it and the machine is fast enough).	2249	millisecond (if the OS supports it and the machine is fast enough).
…		…
2173		2363
2174	=head2 C<ev_signal> - signal me when a signal gets signalled!	2364	=head2 C<ev_signal> - signal me when a signal gets signalled!
2175		2365
2176	Signal watchers will trigger an event when the process receives a specific	2366	Signal watchers will trigger an event when the process receives a specific
2177	signal one or more times. Even though signals are very asynchronous, libev	2367	signal one or more times. Even though signals are very asynchronous, libev
2178	will try it's best to deliver signals synchronously, i.e. as part of the	2368	will try its best to deliver signals synchronously, i.e. as part of the
2179	normal event processing, like any other event.	2369	normal event processing, like any other event.
2180		2370
2181	If you want signals to be delivered truly asynchronously, just use	2371	If you want signals to be delivered truly asynchronously, just use
2182	C<sigaction> as you would do without libev and forget about sharing	2372	C<sigaction> as you would do without libev and forget about sharing
2183	the signal. You can even use C<ev_async> from a signal handler to	2373	the signal. You can even use C<ev_async> from a signal handler to
…		…
2202	=head3 The special problem of inheritance over fork/execve/pthread_create	2392	=head3 The special problem of inheritance over fork/execve/pthread_create
2203		2393
2204	Both the signal mask (C<sigprocmask>) and the signal disposition	2394	Both the signal mask (C<sigprocmask>) and the signal disposition
2205	(C<sigaction>) are unspecified after starting a signal watcher (and after	2395	(C<sigaction>) are unspecified after starting a signal watcher (and after
2206	stopping it again), that is, libev might or might not block the signal,	2396	stopping it again), that is, libev might or might not block the signal,
2207	and might or might not set or restore the installed signal handler.	2397	and might or might not set or restore the installed signal handler (but
		2398	see C<EVFLAG_NOSIGMASK>).
2208		2399
2209	While this does not matter for the signal disposition (libev never	2400	While this does not matter for the signal disposition (libev never
2210	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on	2401	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
2211	C<execve>), this matters for the signal mask: many programs do not expect	2402	C<execve>), this matters for the signal mask: many programs do not expect
2212	certain signals to be blocked.	2403	certain signals to be blocked.
…		…
2225	I<has> to modify the signal mask, at least temporarily.	2416	I<has> to modify the signal mask, at least temporarily.
2226		2417
2227	So I can't stress this enough: I<If you do not reset your signal mask when	2418	So I can't stress this enough: I<If you do not reset your signal mask when
2228	you expect it to be empty, you have a race condition in your code>. This	2419	you expect it to be empty, you have a race condition in your code>. This
2229	is not a libev-specific thing, this is true for most event libraries.	2420	is not a libev-specific thing, this is true for most event libraries.
		2421
		2422	=head3 The special problem of threads signal handling
		2423
		2424	POSIX threads has problematic signal handling semantics, specifically,
		2425	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2426	threads in a process block signals, which is hard to achieve.
		2427
		2428	When you want to use sigwait (or mix libev signal handling with your own
		2429	for the same signals), you can tackle this problem by globally blocking
		2430	all signals before creating any threads (or creating them with a fully set
		2431	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2432	loops. Then designate one thread as "signal receiver thread" which handles
		2433	these signals. You can pass on any signals that libev might be interested
		2434	in by calling C<ev_feed_signal>.
2230		2435
2231	=head3 Watcher-Specific Functions and Data Members	2436	=head3 Watcher-Specific Functions and Data Members
2232		2437
2233	=over 4	2438	=over 4
2234		2439
…		…
3008	disadvantage of having to use multiple event loops (which do not support	3213	disadvantage of having to use multiple event loops (which do not support
3009	signal watchers).	3214	signal watchers).
3010		3215
3011	When this is not possible, or you want to use the default loop for	3216	When this is not possible, or you want to use the default loop for
3012	other reasons, then in the process that wants to start "fresh", call	3217	other reasons, then in the process that wants to start "fresh", call
3013	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3218	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
3014	the default loop will "orphan" (not stop) all registered watchers, so you	3219	Destroying the default loop will "orphan" (not stop) all registered
3015	have to be careful not to execute code that modifies those watchers. Note	3220	watchers, so you have to be careful not to execute code that modifies
3016	also that in that case, you have to re-register any signal watchers.	3221	those watchers. Note also that in that case, you have to re-register any
		3222	signal watchers.
3017		3223
3018	=head3 Watcher-Specific Functions and Data Members	3224	=head3 Watcher-Specific Functions and Data Members
3019		3225
3020	=over 4	3226	=over 4
3021		3227
3022	=item ev_fork_init (ev_signal *, callback)	3228	=item ev_fork_init (ev_fork *, callback)
3023		3229
3024	Initialises and configures the fork watcher - it has no parameters of any	3230	Initialises and configures the fork watcher - it has no parameters of any
3025	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3231	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
3026	believe me.	3232	really.
3027		3233
3028	=back	3234	=back
3029		3235
3030		3236
		3237	=head2 C<ev_cleanup> - even the best things end
		3238
		3239	Cleanup watchers are called just before the event loop is being destroyed
		3240	by a call to C<ev_loop_destroy>.
		3241
		3242	While there is no guarantee that the event loop gets destroyed, cleanup
		3243	watchers provide a convenient method to install cleanup hooks for your
		3244	program, worker threads and so on - you just to make sure to destroy the
		3245	loop when you want them to be invoked.
		3246
		3247	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3248	all other watchers, they do not keep a reference to the event loop (which
		3249	makes a lot of sense if you think about it). Like all other watchers, you
		3250	can call libev functions in the callback, except C<ev_cleanup_start>.
		3251
		3252	=head3 Watcher-Specific Functions and Data Members
		3253
		3254	=over 4
		3255
		3256	=item ev_cleanup_init (ev_cleanup *, callback)
		3257
		3258	Initialises and configures the cleanup watcher - it has no parameters of
		3259	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3260	pointless, I assure you.
		3261
		3262	=back
		3263
		3264	Example: Register an atexit handler to destroy the default loop, so any
		3265	cleanup functions are called.
		3266
		3267	static void
		3268	program_exits (void)
		3269	{
		3270	ev_loop_destroy (EV_DEFAULT_UC);
		3271	}
		3272
		3273	...
		3274	atexit (program_exits);
		3275
		3276
3031	=head2 C<ev_async> - how to wake up an event loop	3277	=head2 C<ev_async> - how to wake up an event loop
3032		3278
3033	In general, you cannot use an C<ev_run> from multiple threads or other	3279	In general, you cannot use an C<ev_loop> from multiple threads or other
3034	asynchronous sources such as signal handlers (as opposed to multiple event	3280	asynchronous sources such as signal handlers (as opposed to multiple event
3035	loops - those are of course safe to use in different threads).	3281	loops - those are of course safe to use in different threads).
3036		3282
3037	Sometimes, however, you need to wake up an event loop you do not control,	3283	Sometimes, however, you need to wake up an event loop you do not control,
3038	for example because it belongs to another thread. This is what C<ev_async>	3284	for example because it belongs to another thread. This is what C<ev_async>
…		…
3040	it by calling C<ev_async_send>, which is thread- and signal safe.	3286	it by calling C<ev_async_send>, which is thread- and signal safe.
3041		3287
3042	This functionality is very similar to C<ev_signal> watchers, as signals,	3288	This functionality is very similar to C<ev_signal> watchers, as signals,
3043	too, are asynchronous in nature, and signals, too, will be compressed	3289	too, are asynchronous in nature, and signals, too, will be compressed
3044	(i.e. the number of callback invocations may be less than the number of	3290	(i.e. the number of callback invocations may be less than the number of
3045	C<ev_async_sent> calls).	3291	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
3046		3292	of "global async watchers" by using a watcher on an otherwise unused
3047	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3293	signal, and C<ev_feed_signal> to signal this watcher from another thread,
3048	just the default loop.	3294	even without knowing which loop owns the signal.
3049		3295
3050	=head3 Queueing	3296	=head3 Queueing
3051		3297
3052	C<ev_async> does not support queueing of data in any way. The reason	3298	C<ev_async> does not support queueing of data in any way. The reason
3053	is that the author does not know of a simple (or any) algorithm for a	3299	is that the author does not know of a simple (or any) algorithm for a
…		…
3145	trust me.	3391	trust me.
3146		3392
3147	=item ev_async_send (loop, ev_async *)	3393	=item ev_async_send (loop, ev_async *)
3148		3394
3149	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3395	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3150	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3396	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3397	returns.
		3398
3151	C<ev_feed_event>, this call is safe to do from other threads, signal or	3399	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3152	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3400	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3153	section below on what exactly this means).	3401	embedding section below on what exactly this means).
3154		3402
3155	Note that, as with other watchers in libev, multiple events might get	3403	Note that, as with other watchers in libev, multiple events might get
3156	compressed into a single callback invocation (another way to look at this	3404	compressed into a single callback invocation (another way to look at
3157	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3405	this is that C<ev_async> watchers are level-triggered: they are set on
3158	reset when the event loop detects that).	3406	C<ev_async_send>, reset when the event loop detects that).
3159		3407
3160	This call incurs the overhead of a system call only once per event loop	3408	This call incurs the overhead of at most one extra system call per event
3161	iteration, so while the overhead might be noticeable, it doesn't apply to	3409	loop iteration, if the event loop is blocked, and no syscall at all if
3162	repeated calls to C<ev_async_send> for the same event loop.	3410	the event loop (or your program) is processing events. That means that
		3411	repeated calls are basically free (there is no need to avoid calls for
		3412	performance reasons) and that the overhead becomes smaller (typically
		3413	zero) under load.
3163		3414
3164	=item bool = ev_async_pending (ev_async *)	3415	=item bool = ev_async_pending (ev_async *)
3165		3416
3166	Returns a non-zero value when C<ev_async_send> has been called on the	3417	Returns a non-zero value when C<ev_async_send> has been called on the
3167	watcher but the event has not yet been processed (or even noted) by the	3418	watcher but the event has not yet been processed (or even noted) by the
…		…
3226	Feed an event on the given fd, as if a file descriptor backend detected	3477	Feed an event on the given fd, as if a file descriptor backend detected
3227	the given events it.	3478	the given events it.
3228		3479
3229	=item ev_feed_signal_event (loop, int signum)	3480	=item ev_feed_signal_event (loop, int signum)
3230		3481
3231	Feed an event as if the given signal occurred (C<loop> must be the default	3482	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3232	loop!).	3483	which is async-safe.
3233		3484
3234	=back	3485	=back
		3486
		3487
		3488	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3489
		3490	This section explains some common idioms that are not immediately
		3491	obvious. Note that examples are sprinkled over the whole manual, and this
		3492	section only contains stuff that wouldn't fit anywhere else.
		3493
		3494	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3495
		3496	Each watcher has, by default, a C<void *data> member that you can read
		3497	or modify at any time: libev will completely ignore it. This can be used
		3498	to associate arbitrary data with your watcher. If you need more data and
		3499	don't want to allocate memory separately and store a pointer to it in that
		3500	data member, you can also "subclass" the watcher type and provide your own
		3501	data:
		3502
		3503	struct my_io
		3504	{
		3505	ev_io io;
		3506	int otherfd;
		3507	void *somedata;
		3508	struct whatever *mostinteresting;
		3509	};
		3510
		3511	...
		3512	struct my_io w;
		3513	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3514
		3515	And since your callback will be called with a pointer to the watcher, you
		3516	can cast it back to your own type:
		3517
		3518	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3519	{
		3520	struct my_io *w = (struct my_io *)w_;
		3521	...
		3522	}
		3523
		3524	More interesting and less C-conformant ways of casting your callback
		3525	function type instead have been omitted.
		3526
		3527	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3528
		3529	Another common scenario is to use some data structure with multiple
		3530	embedded watchers, in effect creating your own watcher that combines
		3531	multiple libev event sources into one "super-watcher":
		3532
		3533	struct my_biggy
		3534	{
		3535	int some_data;
		3536	ev_timer t1;
		3537	ev_timer t2;
		3538	}
		3539
		3540	In this case getting the pointer to C<my_biggy> is a bit more
		3541	complicated: Either you store the address of your C<my_biggy> struct in
		3542	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3543	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3544	real programmers):
		3545
		3546	#include <stddef.h>
		3547
		3548	static void
		3549	t1_cb (EV_P_ ev_timer *w, int revents)
		3550	{
		3551	struct my_biggy big = (struct my_biggy *)
		3552	(((char *)w) - offsetof (struct my_biggy, t1));
		3553	}
		3554
		3555	static void
		3556	t2_cb (EV_P_ ev_timer *w, int revents)
		3557	{
		3558	struct my_biggy big = (struct my_biggy *)
		3559	(((char *)w) - offsetof (struct my_biggy, t2));
		3560	}
		3561
		3562	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3563
		3564	Often (especially in GUI toolkits) there are places where you have
		3565	I<modal> interaction, which is most easily implemented by recursively
		3566	invoking C<ev_run>.
		3567
		3568	This brings the problem of exiting - a callback might want to finish the
		3569	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3570	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3571	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3572	other combination: In these cases, C<ev_break> will not work alone.
		3573
		3574	The solution is to maintain "break this loop" variable for each C<ev_run>
		3575	invocation, and use a loop around C<ev_run> until the condition is
		3576	triggered, using C<EVRUN_ONCE>:
		3577
		3578	// main loop
		3579	int exit_main_loop = 0;
		3580
		3581	while (!exit_main_loop)
		3582	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3583
		3584	// in a model watcher
		3585	int exit_nested_loop = 0;
		3586
		3587	while (!exit_nested_loop)
		3588	ev_run (EV_A_ EVRUN_ONCE);
		3589
		3590	To exit from any of these loops, just set the corresponding exit variable:
		3591
		3592	// exit modal loop
		3593	exit_nested_loop = 1;
		3594
		3595	// exit main program, after modal loop is finished
		3596	exit_main_loop = 1;
		3597
		3598	// exit both
		3599	exit_main_loop = exit_nested_loop = 1;
		3600
		3601	=head2 THREAD LOCKING EXAMPLE
		3602
		3603	Here is a fictitious example of how to run an event loop in a different
		3604	thread from where callbacks are being invoked and watchers are
		3605	created/added/removed.
		3606
		3607	For a real-world example, see the C<EV::Loop::Async> perl module,
		3608	which uses exactly this technique (which is suited for many high-level
		3609	languages).
		3610
		3611	The example uses a pthread mutex to protect the loop data, a condition
		3612	variable to wait for callback invocations, an async watcher to notify the
		3613	event loop thread and an unspecified mechanism to wake up the main thread.
		3614
		3615	First, you need to associate some data with the event loop:
		3616
		3617	typedef struct {
		3618	mutex_t lock; /* global loop lock */
		3619	ev_async async_w;
		3620	thread_t tid;
		3621	cond_t invoke_cv;
		3622	} userdata;
		3623
		3624	void prepare_loop (EV_P)
		3625	{
		3626	// for simplicity, we use a static userdata struct.
		3627	static userdata u;
		3628
		3629	ev_async_init (&u->async_w, async_cb);
		3630	ev_async_start (EV_A_ &u->async_w);
		3631
		3632	pthread_mutex_init (&u->lock, 0);
		3633	pthread_cond_init (&u->invoke_cv, 0);
		3634
		3635	// now associate this with the loop
		3636	ev_set_userdata (EV_A_ u);
		3637	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3638	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3639
		3640	// then create the thread running ev_run
		3641	pthread_create (&u->tid, 0, l_run, EV_A);
		3642	}
		3643
		3644	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3645	solely to wake up the event loop so it takes notice of any new watchers
		3646	that might have been added:
		3647
		3648	static void
		3649	async_cb (EV_P_ ev_async *w, int revents)
		3650	{
		3651	// just used for the side effects
		3652	}
		3653
		3654	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3655	protecting the loop data, respectively.
		3656
		3657	static void
		3658	l_release (EV_P)
		3659	{
		3660	userdata *u = ev_userdata (EV_A);
		3661	pthread_mutex_unlock (&u->lock);
		3662	}
		3663
		3664	static void
		3665	l_acquire (EV_P)
		3666	{
		3667	userdata *u = ev_userdata (EV_A);
		3668	pthread_mutex_lock (&u->lock);
		3669	}
		3670
		3671	The event loop thread first acquires the mutex, and then jumps straight
		3672	into C<ev_run>:
		3673
		3674	void *
		3675	l_run (void *thr_arg)
		3676	{
		3677	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3678
		3679	l_acquire (EV_A);
		3680	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3681	ev_run (EV_A_ 0);
		3682	l_release (EV_A);
		3683
		3684	return 0;
		3685	}
		3686
		3687	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3688	signal the main thread via some unspecified mechanism (signals? pipe
		3689	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3690	have been called (in a while loop because a) spurious wakeups are possible
		3691	and b) skipping inter-thread-communication when there are no pending
		3692	watchers is very beneficial):
		3693
		3694	static void
		3695	l_invoke (EV_P)
		3696	{
		3697	userdata *u = ev_userdata (EV_A);
		3698
		3699	while (ev_pending_count (EV_A))
		3700	{
		3701	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3702	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3703	}
		3704	}
		3705
		3706	Now, whenever the main thread gets told to invoke pending watchers, it
		3707	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3708	thread to continue:
		3709
		3710	static void
		3711	real_invoke_pending (EV_P)
		3712	{
		3713	userdata *u = ev_userdata (EV_A);
		3714
		3715	pthread_mutex_lock (&u->lock);
		3716	ev_invoke_pending (EV_A);
		3717	pthread_cond_signal (&u->invoke_cv);
		3718	pthread_mutex_unlock (&u->lock);
		3719	}
		3720
		3721	Whenever you want to start/stop a watcher or do other modifications to an
		3722	event loop, you will now have to lock:
		3723
		3724	ev_timer timeout_watcher;
		3725	userdata *u = ev_userdata (EV_A);
		3726
		3727	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3728
		3729	pthread_mutex_lock (&u->lock);
		3730	ev_timer_start (EV_A_ &timeout_watcher);
		3731	ev_async_send (EV_A_ &u->async_w);
		3732	pthread_mutex_unlock (&u->lock);
		3733
		3734	Note that sending the C<ev_async> watcher is required because otherwise
		3735	an event loop currently blocking in the kernel will have no knowledge
		3736	about the newly added timer. By waking up the loop it will pick up any new
		3737	watchers in the next event loop iteration.
		3738
		3739	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3740
		3741	While the overhead of a callback that e.g. schedules a thread is small, it
		3742	is still an overhead. If you embed libev, and your main usage is with some
		3743	kind of threads or coroutines, you might want to customise libev so that
		3744	doesn't need callbacks anymore.
		3745
		3746	Imagine you have coroutines that you can switch to using a function
		3747	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3748	and that due to some magic, the currently active coroutine is stored in a
		3749	global called C<current_coro>. Then you can build your own "wait for libev
		3750	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3751	the differing C<;> conventions):
		3752
		3753	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3754	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3755
		3756	That means instead of having a C callback function, you store the
		3757	coroutine to switch to in each watcher, and instead of having libev call
		3758	your callback, you instead have it switch to that coroutine.
		3759
		3760	A coroutine might now wait for an event with a function called
		3761	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3762	matter when, or whether the watcher is active or not when this function is
		3763	called):
		3764
		3765	void
		3766	wait_for_event (ev_watcher *w)
		3767	{
		3768	ev_cb_set (w) = current_coro;
		3769	switch_to (libev_coro);
		3770	}
		3771
		3772	That basically suspends the coroutine inside C<wait_for_event> and
		3773	continues the libev coroutine, which, when appropriate, switches back to
		3774	this or any other coroutine. I am sure if you sue this your own :)
		3775
		3776	You can do similar tricks if you have, say, threads with an event queue -
		3777	instead of storing a coroutine, you store the queue object and instead of
		3778	switching to a coroutine, you push the watcher onto the queue and notify
		3779	any waiters.
		3780
		3781	To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two
		3782	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3783
		3784	// my_ev.h
		3785	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3786	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3787	#include "../libev/ev.h"
		3788
		3789	// my_ev.c
		3790	#define EV_H "my_ev.h"
		3791	#include "../libev/ev.c"
		3792
		3793	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3794	F<my_ev.c> into your project. When properly specifying include paths, you
		3795	can even use F<ev.h> as header file name directly.
3235		3796
3236		3797
3237	=head1 LIBEVENT EMULATION	3798	=head1 LIBEVENT EMULATION
3238		3799
3239	Libev offers a compatibility emulation layer for libevent. It cannot	3800	Libev offers a compatibility emulation layer for libevent. It cannot
3240	emulate the internals of libevent, so here are some usage hints:	3801	emulate the internals of libevent, so here are some usage hints:
3241		3802
3242	=over 4	3803	=over 4
		3804
		3805	=item * Only the libevent-1.4.1-beta API is being emulated.
		3806
		3807	This was the newest libevent version available when libev was implemented,
		3808	and is still mostly unchanged in 2010.
3243		3809
3244	=item * Use it by including <event.h>, as usual.	3810	=item * Use it by including <event.h>, as usual.
3245		3811
3246	=item * The following members are fully supported: ev_base, ev_callback,	3812	=item * The following members are fully supported: ev_base, ev_callback,
3247	ev_arg, ev_fd, ev_res, ev_events.	3813	ev_arg, ev_fd, ev_res, ev_events.
…		…
3253	=item * Priorities are not currently supported. Initialising priorities	3819	=item * Priorities are not currently supported. Initialising priorities
3254	will fail and all watchers will have the same priority, even though there	3820	will fail and all watchers will have the same priority, even though there
3255	is an ev_pri field.	3821	is an ev_pri field.
3256		3822
3257	=item * In libevent, the last base created gets the signals, in libev, the	3823	=item * In libevent, the last base created gets the signals, in libev, the
3258	first base created (== the default loop) gets the signals.	3824	base that registered the signal gets the signals.
3259		3825
3260	=item * Other members are not supported.	3826	=item * Other members are not supported.
3261		3827
3262	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3828	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3263	to use the libev header file and library.	3829	to use the libev header file and library.
…		…
3282	Care has been taken to keep the overhead low. The only data member the C++	3848	Care has been taken to keep the overhead low. The only data member the C++
3283	classes add (compared to plain C-style watchers) is the event loop pointer	3849	classes add (compared to plain C-style watchers) is the event loop pointer
3284	that the watcher is associated with (or no additional members at all if	3850	that the watcher is associated with (or no additional members at all if
3285	you disable C<EV_MULTIPLICITY> when embedding libev).	3851	you disable C<EV_MULTIPLICITY> when embedding libev).
3286		3852
3287	Currently, functions, and static and non-static member functions can be	3853	Currently, functions, static and non-static member functions and classes
3288	used as callbacks. Other types should be easy to add as long as they only	3854	with C<operator ()> can be used as callbacks. Other types should be easy
3289	need one additional pointer for context. If you need support for other	3855	to add as long as they only need one additional pointer for context. If
3290	types of functors please contact the author (preferably after implementing	3856	you need support for other types of functors please contact the author
3291	it).	3857	(preferably after implementing it).
3292		3858
3293	Here is a list of things available in the C<ev> namespace:	3859	Here is a list of things available in the C<ev> namespace:
3294		3860
3295	=over 4	3861	=over 4
3296		3862
…		…
3449	watchers in the constructor.	4015	watchers in the constructor.
3450		4016
3451	class myclass	4017	class myclass
3452	{	4018	{
3453	ev::io io ; void io_cb (ev::io &w, int revents);	4019	ev::io io ; void io_cb (ev::io &w, int revents);
3454	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);	4020	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3455	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4021	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3456		4022
3457	myclass (int fd)	4023	myclass (int fd)
3458	{	4024	{
3459	io .set <myclass, &myclass::io_cb > (this);	4025	io .set <myclass, &myclass::io_cb > (this);
…		…
3510	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4076	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3511		4077
3512	=item D	4078	=item D
3513		4079
3514	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4080	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3515	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4081	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3516		4082
3517	=item Ocaml	4083	=item Ocaml
3518		4084
3519	Erkki Seppala has written Ocaml bindings for libev, to be found at	4085	Erkki Seppala has written Ocaml bindings for libev, to be found at
3520	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4086	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
…		…
3568	suitable for use with C<EV_A>.	4134	suitable for use with C<EV_A>.
3569		4135
3570	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4136	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3571		4137
3572	Similar to the other two macros, this gives you the value of the default	4138	Similar to the other two macros, this gives you the value of the default
3573	loop, if multiple loops are supported ("ev loop default").	4139	loop, if multiple loops are supported ("ev loop default"). The default loop
		4140	will be initialised if it isn't already initialised.
		4141
		4142	For non-multiplicity builds, these macros do nothing, so you always have
		4143	to initialise the loop somewhere.
3574		4144
3575	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4145	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3576		4146
3577	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4147	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3578	default loop has been initialised (C<UC> == unchecked). Their behaviour	4148	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3723	supported). It will also not define any of the structs usually found in	4293	supported). It will also not define any of the structs usually found in
3724	F<event.h> that are not directly supported by the libev core alone.	4294	F<event.h> that are not directly supported by the libev core alone.
3725		4295
3726	In standalone mode, libev will still try to automatically deduce the	4296	In standalone mode, libev will still try to automatically deduce the
3727	configuration, but has to be more conservative.	4297	configuration, but has to be more conservative.
		4298
		4299	=item EV_USE_FLOOR
		4300
		4301	If defined to be C<1>, libev will use the C<floor ()> function for its
		4302	periodic reschedule calculations, otherwise libev will fall back on a
		4303	portable (slower) implementation. If you enable this, you usually have to
		4304	link against libm or something equivalent. Enabling this when the C<floor>
		4305	function is not available will fail, so the safe default is to not enable
		4306	this.
3728		4307
3729	=item EV_USE_MONOTONIC	4308	=item EV_USE_MONOTONIC
3730		4309
3731	If defined to be C<1>, libev will try to detect the availability of the	4310	If defined to be C<1>, libev will try to detect the availability of the
3732	monotonic clock option at both compile time and runtime. Otherwise no	4311	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3865	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4444	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3866		4445
3867	=item EV_ATOMIC_T	4446	=item EV_ATOMIC_T
3868		4447
3869	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4448	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3870	access is atomic with respect to other threads or signal contexts. No such	4449	access is atomic and serialised with respect to other threads or signal
3871	type is easily found in the C language, so you can provide your own type	4450	contexts. No such type is easily found in the C language, so you can
3872	that you know is safe for your purposes. It is used both for signal handler "locking"	4451	provide your own type that you know is safe for your purposes. It is used
3873	as well as for signal and thread safety in C<ev_async> watchers.	4452	both for signal handler "locking" as well as for signal and thread safety
		4453	in C<ev_async> watchers.
3874		4454
3875	In the absence of this define, libev will use C<sig_atomic_t volatile>	4455	In the absence of this define, libev will use C<sig_atomic_t volatile>
3876	(from F<signal.h>), which is usually good enough on most platforms.	4456	(from F<signal.h>), which is usually good enough on most platforms,
		4457	although strictly speaking using a type that also implies a memory fence
		4458	is required.
3877		4459
3878	=item EV_H (h)	4460	=item EV_H (h)
3879		4461
3880	The name of the F<ev.h> header file used to include it. The default if	4462	The name of the F<ev.h> header file used to include it. The default if
3881	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4463	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
…		…
3904	If undefined or defined to C<1>, then all event-loop-specific functions	4486	If undefined or defined to C<1>, then all event-loop-specific functions
3905	will have the C<struct ev_loop *> as first argument, and you can create	4487	will have the C<struct ev_loop *> as first argument, and you can create
3906	additional independent event loops. Otherwise there will be no support	4488	additional independent event loops. Otherwise there will be no support
3907	for multiple event loops and there is no first event loop pointer	4489	for multiple event loops and there is no first event loop pointer
3908	argument. Instead, all functions act on the single default loop.	4490	argument. Instead, all functions act on the single default loop.
		4491
		4492	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4493	default loop when multiplicity is switched off - you always have to
		4494	initialise the loop manually in this case.
3909		4495
3910	=item EV_MINPRI	4496	=item EV_MINPRI
3911		4497
3912	=item EV_MAXPRI	4498	=item EV_MAXPRI
3913		4499
…		…
4164	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4750	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4165		4751
4166	#include "ev_cpp.h"	4752	#include "ev_cpp.h"
4167	#include "ev.c"	4753	#include "ev.c"
4168		4754
4169	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4755	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4170		4756
4171	=head2 THREADS AND COROUTINES	4757	=head2 THREADS AND COROUTINES
4172		4758
4173	=head3 THREADS	4759	=head3 THREADS
4174		4760
…		…
4225	default loop and triggering an C<ev_async> watcher from the default loop	4811	default loop and triggering an C<ev_async> watcher from the default loop
4226	watcher callback into the event loop interested in the signal.	4812	watcher callback into the event loop interested in the signal.
4227		4813
4228	=back	4814	=back
4229		4815
4230	=head4 THREAD LOCKING EXAMPLE	4816	See also L<THREAD LOCKING EXAMPLE>.
4231
4232	Here is a fictitious example of how to run an event loop in a different
4233	thread than where callbacks are being invoked and watchers are
4234	created/added/removed.
4235
4236	For a real-world example, see the C<EV::Loop::Async> perl module,
4237	which uses exactly this technique (which is suited for many high-level
4238	languages).
4239
4240	The example uses a pthread mutex to protect the loop data, a condition
4241	variable to wait for callback invocations, an async watcher to notify the
4242	event loop thread and an unspecified mechanism to wake up the main thread.
4243
4244	First, you need to associate some data with the event loop:
4245
4246	typedef struct {
4247	mutex_t lock; /* global loop lock */
4248	ev_async async_w;
4249	thread_t tid;
4250	cond_t invoke_cv;
4251	} userdata;
4252
4253	void prepare_loop (EV_P)
4254	{
4255	// for simplicity, we use a static userdata struct.
4256	static userdata u;
4257
4258	ev_async_init (&u->async_w, async_cb);
4259	ev_async_start (EV_A_ &u->async_w);
4260
4261	pthread_mutex_init (&u->lock, 0);
4262	pthread_cond_init (&u->invoke_cv, 0);
4263
4264	// now associate this with the loop
4265	ev_set_userdata (EV_A_ u);
4266	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4267	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4268
4269	// then create the thread running ev_loop
4270	pthread_create (&u->tid, 0, l_run, EV_A);
4271	}
4272
4273	The callback for the C<ev_async> watcher does nothing: the watcher is used
4274	solely to wake up the event loop so it takes notice of any new watchers
4275	that might have been added:
4276
4277	static void
4278	async_cb (EV_P_ ev_async *w, int revents)
4279	{
4280	// just used for the side effects
4281	}
4282
4283	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4284	protecting the loop data, respectively.
4285
4286	static void
4287	l_release (EV_P)
4288	{
4289	userdata *u = ev_userdata (EV_A);
4290	pthread_mutex_unlock (&u->lock);
4291	}
4292
4293	static void
4294	l_acquire (EV_P)
4295	{
4296	userdata *u = ev_userdata (EV_A);
4297	pthread_mutex_lock (&u->lock);
4298	}
4299
4300	The event loop thread first acquires the mutex, and then jumps straight
4301	into C<ev_run>:
4302
4303	void *
4304	l_run (void *thr_arg)
4305	{
4306	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4307
4308	l_acquire (EV_A);
4309	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4310	ev_run (EV_A_ 0);
4311	l_release (EV_A);
4312
4313	return 0;
4314	}
4315
4316	Instead of invoking all pending watchers, the C<l_invoke> callback will
4317	signal the main thread via some unspecified mechanism (signals? pipe
4318	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4319	have been called (in a while loop because a) spurious wakeups are possible
4320	and b) skipping inter-thread-communication when there are no pending
4321	watchers is very beneficial):
4322
4323	static void
4324	l_invoke (EV_P)
4325	{
4326	userdata *u = ev_userdata (EV_A);
4327
4328	while (ev_pending_count (EV_A))
4329	{
4330	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4331	pthread_cond_wait (&u->invoke_cv, &u->lock);
4332	}
4333	}
4334
4335	Now, whenever the main thread gets told to invoke pending watchers, it
4336	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4337	thread to continue:
4338
4339	static void
4340	real_invoke_pending (EV_P)
4341	{
4342	userdata *u = ev_userdata (EV_A);
4343
4344	pthread_mutex_lock (&u->lock);
4345	ev_invoke_pending (EV_A);
4346	pthread_cond_signal (&u->invoke_cv);
4347	pthread_mutex_unlock (&u->lock);
4348	}
4349
4350	Whenever you want to start/stop a watcher or do other modifications to an
4351	event loop, you will now have to lock:
4352
4353	ev_timer timeout_watcher;
4354	userdata *u = ev_userdata (EV_A);
4355
4356	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4357
4358	pthread_mutex_lock (&u->lock);
4359	ev_timer_start (EV_A_ &timeout_watcher);
4360	ev_async_send (EV_A_ &u->async_w);
4361	pthread_mutex_unlock (&u->lock);
4362
4363	Note that sending the C<ev_async> watcher is required because otherwise
4364	an event loop currently blocking in the kernel will have no knowledge
4365	about the newly added timer. By waking up the loop it will pick up any new
4366	watchers in the next event loop iteration.
4367		4817
4368	=head3 COROUTINES	4818	=head3 COROUTINES
4369		4819
4370	Libev is very accommodating to coroutines ("cooperative threads"):	4820	Libev is very accommodating to coroutines ("cooperative threads"):
4371	libev fully supports nesting calls to its functions from different	4821	libev fully supports nesting calls to its functions from different
…		…
4467	=head3 C<kqueue> is buggy	4917	=head3 C<kqueue> is buggy
4468		4918
4469	The kqueue syscall is broken in all known versions - most versions support	4919	The kqueue syscall is broken in all known versions - most versions support
4470	only sockets, many support pipes.	4920	only sockets, many support pipes.
4471		4921
4472	Libev tries to work around this by not using C<kqueue> by default on	4922	Libev tries to work around this by not using C<kqueue> by default on this
4473	this rotten platform, but of course you can still ask for it when creating	4923	rotten platform, but of course you can still ask for it when creating a
4474	a loop.	4924	loop - embedding a socket-only kqueue loop into a select-based one is
		4925	probably going to work well.
4475		4926
4476	=head3 C<poll> is buggy	4927	=head3 C<poll> is buggy
4477		4928
4478	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>	4929	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
4479	implementation by something calling C<kqueue> internally around the 10.5.6	4930	implementation by something calling C<kqueue> internally around the 10.5.6
…		…
4498		4949
4499	=head3 C<errno> reentrancy	4950	=head3 C<errno> reentrancy
4500		4951
4501	The default compile environment on Solaris is unfortunately so	4952	The default compile environment on Solaris is unfortunately so
4502	thread-unsafe that you can't even use components/libraries compiled	4953	thread-unsafe that you can't even use components/libraries compiled
4503	without C<-D_REENTRANT> (as long as they use C<errno>), which, of course,	4954	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
4504	isn't defined by default.	4955	defined by default. A valid, if stupid, implementation choice.
4505		4956
4506	If you want to use libev in threaded environments you have to make sure	4957	If you want to use libev in threaded environments you have to make sure
4507	it's compiled with C<_REENTRANT> defined.	4958	it's compiled with C<_REENTRANT> defined.
4508		4959
4509	=head3 Event port backend	4960	=head3 Event port backend
4510		4961
4511	The scalable event interface for Solaris is called "event ports". Unfortunately,	4962	The scalable event interface for Solaris is called "event
4512	this mechanism is very buggy. If you run into high CPU usage, your program	4963	ports". Unfortunately, this mechanism is very buggy in all major
		4964	releases. If you run into high CPU usage, your program freezes or you get
4513	freezes or you get a large number of spurious wakeups, make sure you have	4965	a large number of spurious wakeups, make sure you have all the relevant
4514	all the relevant and latest kernel patches applied. No, I don't know which	4966	and latest kernel patches applied. No, I don't know which ones, but there
4515	ones, but there are multiple ones.	4967	are multiple ones to apply, and afterwards, event ports actually work
		4968	great.
4516		4969
4517	If you can't get it to work, you can try running the program by setting	4970	If you can't get it to work, you can try running the program by setting
4518	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and	4971	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
4519	C<select> backends.	4972	C<select> backends.
4520		4973
4521	=head2 AIX POLL BUG	4974	=head2 AIX POLL BUG
4522		4975
4523	AIX unfortunately has a broken C<poll.h> header. Libev works around	4976	AIX unfortunately has a broken C<poll.h> header. Libev works around
4524	this by trying to avoid the poll backend altogether (i.e. it's not even	4977	this by trying to avoid the poll backend altogether (i.e. it's not even
4525	compiled in), which normally isn't a big problem as C<select> works fine	4978	compiled in), which normally isn't a big problem as C<select> works fine
4526	with large bitsets, and AIX is dead anyway.	4979	with large bitsets on AIX, and AIX is dead anyway.
4527		4980
4528	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4981	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
4529		4982
4530	=head3 General issues	4983	=head3 General issues
4531		4984
…		…
4533	requires, and its I/O model is fundamentally incompatible with the POSIX	4986	requires, and its I/O model is fundamentally incompatible with the POSIX
4534	model. Libev still offers limited functionality on this platform in	4987	model. Libev still offers limited functionality on this platform in
4535	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4988	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4536	descriptors. This only applies when using Win32 natively, not when using	4989	descriptors. This only applies when using Win32 natively, not when using
4537	e.g. cygwin. Actually, it only applies to the microsofts own compilers,	4990	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
4538	as every compielr comes with a slightly differently broken/incompatible	4991	as every compiler comes with a slightly differently broken/incompatible
4539	environment.	4992	environment.
4540		4993
4541	Lifting these limitations would basically require the full	4994	Lifting these limitations would basically require the full
4542	re-implementation of the I/O system. If you are into this kind of thing,	4995	re-implementation of the I/O system. If you are into this kind of thing,
4543	then note that glib does exactly that for you in a very portable way (note	4996	then note that glib does exactly that for you in a very portable way (note
…		…
4637	structure (guaranteed by POSIX but not by ISO C for example), but it also	5090	structure (guaranteed by POSIX but not by ISO C for example), but it also
4638	assumes that the same (machine) code can be used to call any watcher	5091	assumes that the same (machine) code can be used to call any watcher
4639	callback: The watcher callbacks have different type signatures, but libev	5092	callback: The watcher callbacks have different type signatures, but libev
4640	calls them using an C<ev_watcher *> internally.	5093	calls them using an C<ev_watcher *> internally.
4641		5094
		5095	=item pointer accesses must be thread-atomic
		5096
		5097	Accessing a pointer value must be atomic, it must both be readable and
		5098	writable in one piece - this is the case on all current architectures.
		5099
4642	=item C<sig_atomic_t volatile> must be thread-atomic as well	5100	=item C<sig_atomic_t volatile> must be thread-atomic as well
4643		5101
4644	The type C<sig_atomic_t volatile> (or whatever is defined as	5102	The type C<sig_atomic_t volatile> (or whatever is defined as
4645	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5103	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
4646	threads. This is not part of the specification for C<sig_atomic_t>, but is	5104	threads. This is not part of the specification for C<sig_atomic_t>, but is
…		…
4671		5129
4672	The type C<double> is used to represent timestamps. It is required to	5130	The type C<double> is used to represent timestamps. It is required to
4673	have at least 51 bits of mantissa (and 9 bits of exponent), which is	5131	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4674	good enough for at least into the year 4000 with millisecond accuracy	5132	good enough for at least into the year 4000 with millisecond accuracy
4675	(the design goal for libev). This requirement is overfulfilled by	5133	(the design goal for libev). This requirement is overfulfilled by
4676	implementations using IEEE 754, which is basically all existing ones. With	5134	implementations using IEEE 754, which is basically all existing ones.
		5135
4677	IEEE 754 doubles, you get microsecond accuracy until at least 2200.	5136	With IEEE 754 doubles, you get microsecond accuracy until at least the
		5137	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5138	is either obsolete or somebody patched it to use C<long double> or
		5139	something like that, just kidding).
4678		5140
4679	=back	5141	=back
4680		5142
4681	If you know of other additional requirements drop me a note.	5143	If you know of other additional requirements drop me a note.
4682		5144
…		…
4744	=item Processing ev_async_send: O(number_of_async_watchers)	5206	=item Processing ev_async_send: O(number_of_async_watchers)
4745		5207
4746	=item Processing signals: O(max_signal_number)	5208	=item Processing signals: O(max_signal_number)
4747		5209
4748	Sending involves a system call I<iff> there were no other C<ev_async_send>	5210	Sending involves a system call I<iff> there were no other C<ev_async_send>
4749	calls in the current loop iteration. Checking for async and signal events	5211	calls in the current loop iteration and the loop is currently
		5212	blocked. Checking for async and signal events involves iterating over all
4750	involves iterating over all running async watchers or all signal numbers.	5213	running async watchers or all signal numbers.
4751		5214
4752	=back	5215	=back
4753		5216
4754		5217
4755	=head1 PORTING FROM LIBEV 3.X TO 4.X	5218	=head1 PORTING FROM LIBEV 3.X TO 4.X
4756		5219
4757	The major version 4 introduced some minor incompatible changes to the API.	5220	The major version 4 introduced some incompatible changes to the API.
4758		5221
4759	At the moment, the C<ev.h> header file tries to implement superficial	5222	At the moment, the C<ev.h> header file provides compatibility definitions
4760	compatibility, so most programs should still compile. Those might be	5223	for all changes, so most programs should still compile. The compatibility
4761	removed in later versions of libev, so better update early than late.	5224	layer might be removed in later versions of libev, so better update to the
		5225	new API early than late.
4762		5226
4763	=over 4	5227	=over 4
		5228
		5229	=item C<EV_COMPAT3> backwards compatibility mechanism
		5230
		5231	The backward compatibility mechanism can be controlled by
		5232	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5233	section.
		5234
		5235	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5236
		5237	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5238
		5239	ev_loop_destroy (EV_DEFAULT_UC);
		5240	ev_loop_fork (EV_DEFAULT);
4764		5241
4765	=item function/symbol renames	5242	=item function/symbol renames
4766		5243
4767	A number of functions and symbols have been renamed:	5244	A number of functions and symbols have been renamed:
4768		5245
…		…
4787	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme	5264	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
4788	as all other watcher types. Note that C<ev_loop_fork> is still called	5265	as all other watcher types. Note that C<ev_loop_fork> is still called
4789	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>	5266	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
4790	typedef.	5267	typedef.
4791		5268
4792	=item C<EV_COMPAT3> backwards compatibility mechanism
4793
4794	The backward compatibility mechanism can be controlled by
4795	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
4796	section.
4797
4798	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>	5269	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
4799		5270
4800	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different	5271	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
4801	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile	5272	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
4802	and work, but the library code will of course be larger.	5273	and work, but the library code will of course be larger.
…		…
4808		5279
4809	=over 4	5280	=over 4
4810		5281
4811	=item active	5282	=item active
4812		5283
4813	A watcher is active as long as it has been started (has been attached to	5284	A watcher is active as long as it has been started and not yet stopped.
4814	an event loop) but not yet stopped (disassociated from the event loop).	5285	See L<WATCHER STATES> for details.
4815		5286
4816	=item application	5287	=item application
4817		5288
4818	In this document, an application is whatever is using libev.	5289	In this document, an application is whatever is using libev.
		5290
		5291	=item backend
		5292
		5293	The part of the code dealing with the operating system interfaces.
4819		5294
4820	=item callback	5295	=item callback
4821		5296
4822	The address of a function that is called when some event has been	5297	The address of a function that is called when some event has been
4823	detected. Callbacks are being passed the event loop, the watcher that	5298	detected. Callbacks are being passed the event loop, the watcher that
4824	received the event, and the actual event bitset.	5299	received the event, and the actual event bitset.
4825		5300
4826	=item callback invocation	5301	=item callback/watcher invocation
4827		5302
4828	The act of calling the callback associated with a watcher.	5303	The act of calling the callback associated with a watcher.
4829		5304
4830	=item event	5305	=item event
4831		5306
…		…
4850	The model used to describe how an event loop handles and processes	5325	The model used to describe how an event loop handles and processes
4851	watchers and events.	5326	watchers and events.
4852		5327
4853	=item pending	5328	=item pending
4854		5329
4855	A watcher is pending as soon as the corresponding event has been detected,	5330	A watcher is pending as soon as the corresponding event has been
4856	and stops being pending as soon as the watcher will be invoked or its	5331	detected. See L<WATCHER STATES> for details.
4857	pending status is explicitly cleared by the application.
4858
4859	A watcher can be pending, but not active. Stopping a watcher also clears
4860	its pending status.
4861		5332
4862	=item real time	5333	=item real time
4863		5334
4864	The physical time that is observed. It is apparently strictly monotonic :)	5335	The physical time that is observed. It is apparently strictly monotonic :)
4865		5336
4866	=item wall-clock time	5337	=item wall-clock time
4867		5338
4868	The time and date as shown on clocks. Unlike real time, it can actually	5339	The time and date as shown on clocks. Unlike real time, it can actually
4869	be wrong and jump forwards and backwards, e.g. when the you adjust your	5340	be wrong and jump forwards and backwards, e.g. when you adjust your
4870	clock.	5341	clock.
4871		5342
4872	=item watcher	5343	=item watcher
4873		5344
4874	A data structure that describes interest in certain events. Watchers need	5345	A data structure that describes interest in certain events. Watchers need
4875	to be started (attached to an event loop) before they can receive events.	5346	to be started (attached to an event loop) before they can receive events.
4876		5347
4877	=item watcher invocation
4878
4879	The act of calling the callback associated with a watcher.
4880
4881	=back	5348	=back
4882		5349
4883	=head1 AUTHOR	5350	=head1 AUTHOR
4884		5351
4885	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5352	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5353	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4886		5354

Diff Legend

–	Removed lines
+	Added lines
<	Changed lines
>	Changed lines