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Revision 1.370 by root, Thu Jun 2 23:42:40 2011 UTC

…		…
26	puts ("stdin ready");	26	puts ("stdin ready");
27	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
28	// with its corresponding stop function.	28	// with its corresponding stop function.
29	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
30		30
31	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_run's to stop iterating
32	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_break (EV_A_ EVBREAK_ALL);
33	}	33	}
34		34
35	// another callback, this time for a time-out	35	// another callback, this time for a time-out
36	static void	36	static void
37	timeout_cb (EV_P_ ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
38	{	38	{
39	puts ("timeout");	39	puts ("timeout");
40	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_run to stop iterating
41	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_break (EV_A_ EVBREAK_ONE);
42	}	42	}
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);
…		…
56	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
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_loop (loop, 0);	61	ev_run (loop, 0);
62		62
63	// unloop was called, so exit	63	// break was called, so exit
64	return 0;	64	return 0;
65	}	65	}
66		66
67	=head1 ABOUT THIS DOCUMENT	67	=head1 ABOUT THIS DOCUMENT
68		68
…		…
77	on event-based programming, nor will it introduce event-based programming	77	on event-based programming, nor will it introduce event-based programming
78	with libev.	78	with libev.
79		79
80	Familiarity with event based programming techniques in general is assumed	80	Familiarity with event based programming techniques in general is assumed
81	throughout this document.	81	throughout this document.
		82
		83	=head1 WHAT TO READ WHEN IN A HURRY
		84
		85	This manual tries to be very detailed, but unfortunately, this also makes
		86	it very long. If you just want to know the basics of libev, I suggest
		87	reading L<ANATOMY OF A WATCHER>, then the L<EXAMPLE PROGRAM> above and
		88	look up the missing functions in L<GLOBAL FUNCTIONS> and the C<ev_io> and
		89	C<ev_timer> sections in L<WATCHER TYPES>.
82		90
83	=head1 ABOUT LIBEV	91	=head1 ABOUT LIBEV
84		92
85	Libev is an event loop: you register interest in certain events (such as a	93	Libev is an event loop: you register interest in certain events (such as a
86	file descriptor being readable or a timeout occurring), and it will manage	94	file descriptor being readable or a timeout occurring), and it will manage
…		…
124	this argument.	132	this argument.
125		133
126	=head2 TIME REPRESENTATION	134	=head2 TIME REPRESENTATION
127		135
128	Libev represents time as a single floating point number, representing	136	Libev represents time as a single floating point number, representing
129	the (fractional) number of seconds since the (POSIX) epoch (in practise	137	the (fractional) number of seconds since the (POSIX) epoch (in practice
130	somewhere near the beginning of 1970, details are complicated, don't	138	somewhere near the beginning of 1970, details are complicated, don't
131	ask). This type is called C<ev_tstamp>, which is what you should use	139	ask). This type is called C<ev_tstamp>, which is what you should use
132	too. It usually aliases to the C<double> type in C. When you need to do	140	too. It usually aliases to the C<double> type in C. When you need to do
133	any calculations on it, you should treat it as some floating point value.	141	any calculations on it, you should treat it as some floating point value.
134		142
…		…
165		173
166	=item ev_tstamp ev_time ()	174	=item ev_tstamp ev_time ()
167		175
168	Returns the current time as libev would use it. Please note that the	176	Returns the current time as libev would use it. Please note that the
169	C<ev_now> function is usually faster and also often returns the timestamp	177	C<ev_now> function is usually faster and also often returns the timestamp
170	you actually want to know.	178	you actually want to know. Also interesting is the combination of
		179	C<ev_update_now> and C<ev_now>.
171		180
172	=item ev_sleep (ev_tstamp interval)	181	=item ev_sleep (ev_tstamp interval)
173		182
174	Sleep for the given interval: The current thread will be blocked until	183	Sleep for the given interval: The current thread will be blocked until
175	either it is interrupted or the given time interval has passed. Basically	184	either it is interrupted or the given time interval has passed. Basically
…		…
192	as this indicates an incompatible change. Minor versions are usually	201	as this indicates an incompatible change. Minor versions are usually
193	compatible to older versions, so a larger minor version alone is usually	202	compatible to older versions, so a larger minor version alone is usually
194	not a problem.	203	not a problem.
195		204
196	Example: Make sure we haven't accidentally been linked against the wrong	205	Example: Make sure we haven't accidentally been linked against the wrong
197	version (note, however, that this will not detect ABI mismatches :).	206	version (note, however, that this will not detect other ABI mismatches,
		207	such as LFS or reentrancy).
198		208
199	assert (("libev version mismatch",	209	assert (("libev version mismatch",
200	ev_version_major () == EV_VERSION_MAJOR	210	ev_version_major () == EV_VERSION_MAJOR
201	&& ev_version_minor () >= EV_VERSION_MINOR));	211	&& ev_version_minor () >= EV_VERSION_MINOR));
202		212
…		…
213	assert (("sorry, no epoll, no sex",	223	assert (("sorry, no epoll, no sex",
214	ev_supported_backends () & EVBACKEND_EPOLL));	224	ev_supported_backends () & EVBACKEND_EPOLL));
215		225
216	=item unsigned int ev_recommended_backends ()	226	=item unsigned int ev_recommended_backends ()
217		227
218	Return the set of all backends compiled into this binary of libev and also	228	Return the set of all backends compiled into this binary of libev and
219	recommended for this platform. This set is often smaller than the one	229	also recommended for this platform, meaning it will work for most file
		230	descriptor types. This set is often smaller than the one returned by
220	returned by C<ev_supported_backends>, as for example kqueue is broken on	231	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
221	most BSDs and will not be auto-detected unless you explicitly request it	232	and will not be auto-detected unless you explicitly request it (assuming
222	(assuming you know what you are doing). This is the set of backends that	233	you know what you are doing). This is the set of backends that libev will
223	libev will probe for if you specify no backends explicitly.	234	probe for if you specify no backends explicitly.
224		235
225	=item unsigned int ev_embeddable_backends ()	236	=item unsigned int ev_embeddable_backends ()
226		237
227	Returns the set of backends that are embeddable in other event loops. This	238	Returns the set of backends that are embeddable in other event loops. This
228	is the theoretical, all-platform, value. To find which backends	239	value is platform-specific but can include backends not available on the
229	might be supported on the current system, you would need to look at	240	current system. To find which embeddable backends might be supported on
230	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	241	the current system, you would need to look at C<ev_embeddable_backends ()
231	recommended ones.	242	& ev_supported_backends ()>, likewise for recommended ones.
232		243
233	See the description of C<ev_embed> watchers for more info.	244	See the description of C<ev_embed> watchers for more info.
234		245
235	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	246	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
236		247
237	Sets the allocation function to use (the prototype is similar - the	248	Sets the allocation function to use (the prototype is similar - the
238	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	249	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
239	used to allocate and free memory (no surprises here). If it returns zero	250	used to allocate and free memory (no surprises here). If it returns zero
240	when memory needs to be allocated (C<size != 0>), the library might abort	251	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
266	}	277	}
267		278
268	...	279	...
269	ev_set_allocator (persistent_realloc);	280	ev_set_allocator (persistent_realloc);
270		281
271	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	282	=item ev_set_syserr_cb (void (*cb)(const char *msg))
272		283
273	Set the callback function to call on a retryable system call error (such	284	Set the callback function to call on a retryable system call error (such
274	as failed select, poll, epoll_wait). The message is a printable string	285	as failed select, poll, epoll_wait). The message is a printable string
275	indicating the system call or subsystem causing the problem. If this	286	indicating the system call or subsystem causing the problem. If this
276	callback is set, then libev will expect it to remedy the situation, no	287	callback is set, then libev will expect it to remedy the situation, no
…		…
288	}	299	}
289		300
290	...	301	...
291	ev_set_syserr_cb (fatal_error);	302	ev_set_syserr_cb (fatal_error);
292		303
		304	=item ev_feed_signal (int signum)
		305
		306	This function can be used to "simulate" a signal receive. It is completely
		307	safe to call this function at any time, from any context, including signal
		308	handlers or random threads.
		309
		310	Its main use is to customise signal handling in your process, especially
		311	in the presence of threads. For example, you could block signals
		312	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		313	creating any loops), and in one thread, use C<sigwait> or any other
		314	mechanism to wait for signals, then "deliver" them to libev by calling
		315	C<ev_feed_signal>.
		316
293	=back	317	=back
294		318
295	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	319	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
296		320
297	An event loop is described by a C<struct ev_loop *> (the C<struct>	321	An event loop is described by a C<struct ev_loop *> (the C<struct> is
298	is I<not> optional in this case, as there is also an C<ev_loop>	322	I<not> optional in this case unless libev 3 compatibility is disabled, as
299	I<function>).	323	libev 3 had an C<ev_loop> function colliding with the struct name).
300		324
301	The library knows two types of such loops, the I<default> loop, which	325	The library knows two types of such loops, the I<default> loop, which
302	supports signals and child events, and dynamically created loops which do	326	supports child process events, and dynamically created event loops which
303	not.	327	do not.
304		328
305	=over 4	329	=over 4
306		330
307	=item struct ev_loop *ev_default_loop (unsigned int flags)	331	=item struct ev_loop *ev_default_loop (unsigned int flags)
308		332
309	This will initialise the default event loop if it hasn't been initialised	333	This returns the "default" event loop object, which is what you should
310	yet and return it. If the default loop could not be initialised, returns	334	normally use when you just need "the event loop". Event loop objects and
311	false. If it already was initialised it simply returns it (and ignores the	335	the C<flags> parameter are described in more detail in the entry for
312	flags. If that is troubling you, check C<ev_backend ()> afterwards).	336	C<ev_loop_new>.
		337
		338	If the default loop is already initialised then this function simply
		339	returns it (and ignores the flags. If that is troubling you, check
		340	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		341	flags, which should almost always be C<0>, unless the caller is also the
		342	one calling C<ev_run> or otherwise qualifies as "the main program".
313		343
314	If you don't know what event loop to use, use the one returned from this	344	If you don't know what event loop to use, use the one returned from this
315	function.	345	function (or via the C<EV_DEFAULT> macro).
316		346
317	Note that this function is I<not> thread-safe, so if you want to use it	347	Note that this function is I<not> thread-safe, so if you want to use it
318	from multiple threads, you have to lock (note also that this is unlikely,	348	from multiple threads, you have to employ some kind of mutex (note also
319	as loops cannot be shared easily between threads anyway).	349	that this case is unlikely, as loops cannot be shared easily between
		350	threads anyway).
320		351
321	The default loop is the only loop that can handle C<ev_signal> and	352	The default loop is the only loop that can handle C<ev_child> watchers,
322	C<ev_child> watchers, and to do this, it always registers a handler	353	and to do this, it always registers a handler for C<SIGCHLD>. If this is
323	for C<SIGCHLD>. If this is a problem for your application you can either	354	a problem for your application you can either create a dynamic loop with
324	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	355	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
325	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	356	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
326	C<ev_default_init>.	357
		358	Example: This is the most typical usage.
		359
		360	if (!ev_default_loop (0))
		361	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		362
		363	Example: Restrict libev to the select and poll backends, and do not allow
		364	environment settings to be taken into account:
		365
		366	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		367
		368	=item struct ev_loop *ev_loop_new (unsigned int flags)
		369
		370	This will create and initialise a new event loop object. If the loop
		371	could not be initialised, returns false.
		372
		373	This function is thread-safe, and one common way to use libev with
		374	threads is indeed to create one loop per thread, and using the default
		375	loop in the "main" or "initial" thread.
327		376
328	The flags argument can be used to specify special behaviour or specific	377	The flags argument can be used to specify special behaviour or specific
329	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	378	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
330		379
331	The following flags are supported:	380	The following flags are supported:
…		…
366	environment variable.	415	environment variable.
367		416
368	=item C<EVFLAG_NOINOTIFY>	417	=item C<EVFLAG_NOINOTIFY>
369		418
370	When this flag is specified, then libev will not attempt to use the	419	When this flag is specified, then libev will not attempt to use the
371	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and	420	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
372	testing, this flag can be useful to conserve inotify file descriptors, as	421	testing, this flag can be useful to conserve inotify file descriptors, as
373	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.	422	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
374		423
375	=item C<EVFLAG_SIGNALFD>	424	=item C<EVFLAG_SIGNALFD>
376		425
377	When this flag is specified, then libev will attempt to use the	426	When this flag is specified, then libev will attempt to use the
378	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API	427	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
379	delivers signals synchronously, which makes it both faster and might make	428	delivers signals synchronously, which makes it both faster and might make
380	it possible to get the queued signal data. It can also simplify signal	429	it possible to get the queued signal data. It can also simplify signal
381	handling with threads, as long as you properly block signals in your	430	handling with threads, as long as you properly block signals in your
382	threads that are not interested in handling them.	431	threads that are not interested in handling them.
383		432
384	Signalfd will not be used by default as this changes your signal mask, and	433	Signalfd will not be used by default as this changes your signal mask, and
385	there are a lot of shoddy libraries and programs (glib's threadpool for	434	there are a lot of shoddy libraries and programs (glib's threadpool for
386	example) that can't properly initialise their signal masks.	435	example) that can't properly initialise their signal masks.
		436
		437	=item C<EVFLAG_NOSIGMASK>
		438
		439	When this flag is specified, then libev will avoid to modify the signal
		440	mask. Specifically, this means you ahve to make sure signals are unblocked
		441	when you want to receive them.
		442
		443	This behaviour is useful when you want to do your own signal handling, or
		444	want to handle signals only in specific threads and want to avoid libev
		445	unblocking the signals.
		446
		447	It's also required by POSIX in a threaded program, as libev calls
		448	C<sigprocmask>, whose behaviour is officially unspecified.
		449
		450	This flag's behaviour will become the default in future versions of libev.
387		451
388	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	452	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
389		453
390	This is your standard select(2) backend. Not I<completely> standard, as	454	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,	455	libev tries to roll its own fd_set with no limits on the number of fds,
…		…
419	=item C<EVBACKEND_EPOLL> (value 4, Linux)	483	=item C<EVBACKEND_EPOLL> (value 4, Linux)
420		484
421	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9	485	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
422	kernels).	486	kernels).
423		487
424	For few fds, this backend is a bit little slower than poll and select,	488	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	489	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),	490	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).	491	fd), epoll scales either O(1) or O(active_fds).
428		492
429	The epoll mechanism deserves honorable mention as the most misdesigned	493	The epoll mechanism deserves honorable mention as the most misdesigned
430	of the more advanced event mechanisms: mere annoyances include silently	494	of the more advanced event mechanisms: mere annoyances include silently
431	dropping file descriptors, requiring a system call per change per file	495	dropping file descriptors, requiring a system call per change per file
432	descriptor (and unnecessary guessing of parameters), problems with dup and	496	descriptor (and unnecessary guessing of parameters), problems with dup,
		497	returning before the timeout value, resulting in additional iterations
		498	(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	499	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	500	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	501	set, which can take considerable time (one syscall per file descriptor)
436	hard to detect.	502	and is of course hard to detect.
437		503
438	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	504	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	505	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	506	totally I<different> file descriptors (even already closed ones, so
441	even remove them from the set) than registered in the set (especially	507	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	508	(especially on SMP systems). Libev tries to counter these spurious
443	employing an additional generation counter and comparing that against the	509	notifications by employing an additional generation counter and comparing
444	events to filter out spurious ones, recreating the set when required. Last	510	that against the events to filter out spurious ones, recreating the set
		511	when required. Epoll also errornously rounds down timeouts, but gives you
		512	no way to know when and by how much, so sometimes you have to busy-wait
		513	because epoll returns immediately despite a nonzero timeout. And last
445	not least, it also refuses to work with some file descriptors which work	514	not least, it also refuses to work with some file descriptors which work
446	perfectly fine with C<select> (files, many character devices...).	515	perfectly fine with C<select> (files, many character devices...).
		516
		517	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
		518	cobbled together in a hurry, no thought to design or interaction with
		519	others. Oh, the pain, will it ever stop...
447		520
448	While stopping, setting and starting an I/O watcher in the same iteration	521	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	522	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	523	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	524	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
517	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	590	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
518		591
519	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	592	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)).	593	it's really slow, but it still scales very well (O(active_fds)).
521		594
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	595	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	596	file descriptor per loop iteration. For small and medium numbers of file
528	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	597	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
529	might perform better.	598	might perform better.
530		599
531	On the positive side, with the exception of the spurious readiness	600	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	601	specification in all tests and is fully embeddable, which is a rare feat
534	OS-specific backends (I vastly prefer correctness over speed hacks).	602	among the OS-specific backends (I vastly prefer correctness over speed
		603	hacks).
		604
		605	On the negative side, the interface is I<bizarre> - so bizarre that
		606	even sun itself gets it wrong in their code examples: The event polling
		607	function sometimes returning events to the caller even though an error
		608	occurred, but with no indication whether it has done so or not (yes, it's
		609	even documented that way) - deadly for edge-triggered interfaces where
		610	you absolutely have to know whether an event occurred or not because you
		611	have to re-arm the watcher.
		612
		613	Fortunately libev seems to be able to work around these idiocies.
535		614
536	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	615	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
537	C<EVBACKEND_POLL>.	616	C<EVBACKEND_POLL>.
538		617
539	=item C<EVBACKEND_ALL>	618	=item C<EVBACKEND_ALL>
540		619
541	Try all backends (even potentially broken ones that wouldn't be tried	620	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	621	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
543	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	622	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
544		623
545	It is definitely not recommended to use this flag.	624	It is definitely not recommended to use this flag, use whatever
		625	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		626	at all.
		627
		628	=item C<EVBACKEND_MASK>
		629
		630	Not a backend at all, but a mask to select all backend bits from a
		631	C<flags> value, in case you want to mask out any backends from a flags
		632	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
546		633
547	=back	634	=back
548		635
549	If one or more of the backend flags are or'ed into the flags value,	636	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	637	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	638	here). If none are specified, all backends in C<ev_recommended_backends
552	()> will be tried.	639	()> will be tried.
553		640
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.	641	Example: Try to create a event loop that uses epoll and nothing else.
581		642
582	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	643	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
583	if (!epoller)	644	if (!epoller)
584	fatal ("no epoll found here, maybe it hides under your chair");	645	fatal ("no epoll found here, maybe it hides under your chair");
585		646
		647	Example: Use whatever libev has to offer, but make sure that kqueue is
		648	used if available.
		649
		650	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		651
586	=item ev_default_destroy ()	652	=item ev_loop_destroy (loop)
587		653
588	Destroys the default loop (frees all memory and kernel state etc.). None	654	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	655	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	656	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,	657	responsibility to either stop all watchers cleanly yourself I<before>
592	or cope with the fact afterwards (which is usually the easiest thing, you	658	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).	659	the easiest thing, you can just ignore the watchers and/or C<free ()> them
		660	for example).
594		661
595	Note that certain global state, such as signal state (and installed signal	662	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	663	handlers), will not be freed by this function, and related watchers (such
597	as signal and child watchers) would need to be stopped manually.	664	as signal and child watchers) would need to be stopped manually.
598		665
599	In general it is not advisable to call this function except in the	666	This function is normally used on loop objects allocated by
600	rare occasion where you really need to free e.g. the signal handling	667	C<ev_loop_new>, but it can also be used on the default loop returned by
		668	C<ev_default_loop>, in which case it is not thread-safe.
		669
		670	Note that it is not advisable to call this function on the default loop
		671	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	672	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>.	673	and C<ev_loop_destroy>.
603		674
604	=item ev_loop_destroy (loop)	675	=item ev_loop_fork (loop)
605		676
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_loop> iterations	677	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	678	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	679	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	680	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	681	child before resuming or calling C<ev_run>.
616	functions, and it will only take effect at the next C<ev_loop> iteration.
617		682
618	Again, you I<have> to call it on I<any> loop that you want to re-use after	683	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	684	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	685	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
621	during fork.	686	during fork.
622		687
623	On the other hand, you only need to call this function in the child	688	On the other hand, you only need to call this function in the child
624	process if and only if you want to use the event loop in the child. If you	689	process if and only if you want to use the event loop in the child. If
625	just fork+exec or create a new loop in the child, you don't have to call	690	you just fork+exec or create a new loop in the child, you don't have to
626	it at all.	691	call it at all (in fact, C<epoll> is so badly broken that it makes a
		692	difference, but libev will usually detect this case on its own and do a
		693	costly reset of the backend).
627		694
628	The function itself is quite fast and it's usually not a problem to call	695	The function itself is quite fast and it's usually not a problem to call
629	it just in case after a fork. To make this easy, the function will fit in	696	it just in case after a fork.
630	quite nicely into a call to C<pthread_atfork>:
631		697
		698	Example: Automate calling C<ev_loop_fork> on the default loop when
		699	using pthreads.
		700
		701	static void
		702	post_fork_child (void)
		703	{
		704	ev_loop_fork (EV_DEFAULT);
		705	}
		706
		707	...
632	pthread_atfork (0, 0, ev_default_fork);	708	pthread_atfork (0, 0, post_fork_child);
633
634	=item ev_loop_fork (loop)
635
636	Like C<ev_default_fork>, but acts on an event loop created by
637	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
638	after fork that you want to re-use in the child, and how you keep track of
639	them is entirely your own problem.
640		709
641	=item int ev_is_default_loop (loop)	710	=item int ev_is_default_loop (loop)
642		711
643	Returns true when the given loop is, in fact, the default loop, and false	712	Returns true when the given loop is, in fact, the default loop, and false
644	otherwise.	713	otherwise.
645		714
646	=item unsigned int ev_iteration (loop)	715	=item unsigned int ev_iteration (loop)
647		716
648	Returns the current iteration count for the loop, which is identical to	717	Returns the current iteration count for the event loop, which is identical
649	the number of times libev did poll for new events. It starts at C<0> and	718	to the number of times libev did poll for new events. It starts at C<0>
650	happily wraps around with enough iterations.	719	and happily wraps around with enough iterations.
651		720
652	This value can sometimes be useful as a generation counter of sorts (it	721	This value can sometimes be useful as a generation counter of sorts (it
653	"ticks" the number of loop iterations), as it roughly corresponds with	722	"ticks" the number of loop iterations), as it roughly corresponds with
654	C<ev_prepare> and C<ev_check> calls - and is incremented between the	723	C<ev_prepare> and C<ev_check> calls - and is incremented between the
655	prepare and check phases.	724	prepare and check phases.
656		725
657	=item unsigned int ev_depth (loop)	726	=item unsigned int ev_depth (loop)
658		727
659	Returns the number of times C<ev_loop> was entered minus the number of	728	Returns the number of times C<ev_run> was entered minus the number of
660	times C<ev_loop> was exited, in other words, the recursion depth.	729	times C<ev_run> was exited normally, in other words, the recursion depth.
661		730
662	Outside C<ev_loop>, this number is zero. In a callback, this number is	731	Outside C<ev_run>, this number is zero. In a callback, this number is
663	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),	732	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
664	in which case it is higher.	733	in which case it is higher.
665		734
666	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread	735	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
667	etc.), doesn't count as "exit" - consider this as a hint to avoid such	736	throwing an exception etc.), doesn't count as "exit" - consider this
668	ungentleman behaviour unless it's really convenient.	737	as a hint to avoid such ungentleman-like behaviour unless it's really
		738	convenient, in which case it is fully supported.
669		739
670	=item unsigned int ev_backend (loop)	740	=item unsigned int ev_backend (loop)
671		741
672	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	742	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
673	use.	743	use.
…		…
682		752
683	=item ev_now_update (loop)	753	=item ev_now_update (loop)
684		754
685	Establishes the current time by querying the kernel, updating the time	755	Establishes the current time by querying the kernel, updating the time
686	returned by C<ev_now ()> in the progress. This is a costly operation and	756	returned by C<ev_now ()> in the progress. This is a costly operation and
687	is usually done automatically within C<ev_loop ()>.	757	is usually done automatically within C<ev_run ()>.
688		758
689	This function is rarely useful, but when some event callback runs for a	759	This function is rarely useful, but when some event callback runs for a
690	very long time without entering the event loop, updating libev's idea of	760	very long time without entering the event loop, updating libev's idea of
691	the current time is a good idea.	761	the current time is a good idea.
692		762
…		…
694		764
695	=item ev_suspend (loop)	765	=item ev_suspend (loop)
696		766
697	=item ev_resume (loop)	767	=item ev_resume (loop)
698		768
699	These two functions suspend and resume a loop, for use when the loop is	769	These two functions suspend and resume an event loop, for use when the
700	not used for a while and timeouts should not be processed.	770	loop is not used for a while and timeouts should not be processed.
701		771
702	A typical use case would be an interactive program such as a game: When	772	A typical use case would be an interactive program such as a game: When
703	the user presses C<^Z> to suspend the game and resumes it an hour later it	773	the user presses C<^Z> to suspend the game and resumes it an hour later it
704	would be best to handle timeouts as if no time had actually passed while	774	would be best to handle timeouts as if no time had actually passed while
705	the program was suspended. This can be achieved by calling C<ev_suspend>	775	the program was suspended. This can be achieved by calling C<ev_suspend>
…		…
716	without a previous call to C<ev_suspend>.	786	without a previous call to C<ev_suspend>.
717		787
718	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	788	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
719	event loop time (see C<ev_now_update>).	789	event loop time (see C<ev_now_update>).
720		790
721	=item ev_loop (loop, int flags)	791	=item ev_run (loop, int flags)
722		792
723	Finally, this is it, the event handler. This function usually is called	793	Finally, this is it, the event handler. This function usually is called
724	after you have initialised all your watchers and you want to start	794	after you have initialised all your watchers and you want to start
725	handling events.	795	handling events. It will ask the operating system for any new events, call
		796	the watcher callbacks, an then repeat the whole process indefinitely: This
		797	is why event loops are called I<loops>.
726		798
727	If the flags argument is specified as C<0>, it will not return until	799	If the flags argument is specified as C<0>, it will keep handling events
728	either no event watchers are active anymore or C<ev_unloop> was called.	800	until either no event watchers are active anymore or C<ev_break> was
		801	called.
729		802
730	Please note that an explicit C<ev_unloop> is usually better than	803	Please note that an explicit C<ev_break> is usually better than
731	relying on all watchers to be stopped when deciding when a program has	804	relying on all watchers to be stopped when deciding when a program has
732	finished (especially in interactive programs), but having a program	805	finished (especially in interactive programs), but having a program
733	that automatically loops as long as it has to and no longer by virtue	806	that automatically loops as long as it has to and no longer by virtue
734	of relying on its watchers stopping correctly, that is truly a thing of	807	of relying on its watchers stopping correctly, that is truly a thing of
735	beauty.	808	beauty.
736		809
		810	This function is also I<mostly> exception-safe - you can break out of
		811	a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		812	exception and so on. This does not decrement the C<ev_depth> value, nor
		813	will it clear any outstanding C<EVBREAK_ONE> breaks.
		814
737	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	815	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
738	those events and any already outstanding ones, but will not block your	816	those events and any already outstanding ones, but will not wait and
739	process in case there are no events and will return after one iteration of	817	block your process in case there are no events and will return after one
740	the loop.	818	iteration of the loop. This is sometimes useful to poll and handle new
		819	events while doing lengthy calculations, to keep the program responsive.
741		820
742	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	821	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
743	necessary) and will handle those and any already outstanding ones. It	822	necessary) and will handle those and any already outstanding ones. It
744	will block your process until at least one new event arrives (which could	823	will block your process until at least one new event arrives (which could
745	be an event internal to libev itself, so there is no guarantee that a	824	be an event internal to libev itself, so there is no guarantee that a
746	user-registered callback will be called), and will return after one	825	user-registered callback will be called), and will return after one
747	iteration of the loop.	826	iteration of the loop.
748		827
749	This is useful if you are waiting for some external event in conjunction	828	This is useful if you are waiting for some external event in conjunction
750	with something not expressible using other libev watchers (i.e. "roll your	829	with something not expressible using other libev watchers (i.e. "roll your
751	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	830	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
752	usually a better approach for this kind of thing.	831	usually a better approach for this kind of thing.
753		832
754	Here are the gory details of what C<ev_loop> does:	833	Here are the gory details of what C<ev_run> does (this is for your
		834	understanding, not a guarantee that things will work exactly like this in
		835	future versions):
755		836
		837	- Increment loop depth.
		838	- Reset the ev_break status.
756	- Before the first iteration, call any pending watchers.	839	- Before the first iteration, call any pending watchers.
		840	LOOP:
757	* If EVFLAG_FORKCHECK was used, check for a fork.	841	- If EVFLAG_FORKCHECK was used, check for a fork.
758	- If a fork was detected (by any means), queue and call all fork watchers.	842	- If a fork was detected (by any means), queue and call all fork watchers.
759	- Queue and call all prepare watchers.	843	- Queue and call all prepare watchers.
		844	- If ev_break was called, goto FINISH.
760	- If we have been forked, detach and recreate the kernel state	845	- If we have been forked, detach and recreate the kernel state
761	as to not disturb the other process.	846	as to not disturb the other process.
762	- Update the kernel state with all outstanding changes.	847	- Update the kernel state with all outstanding changes.
763	- Update the "event loop time" (ev_now ()).	848	- Update the "event loop time" (ev_now ()).
764	- Calculate for how long to sleep or block, if at all	849	- Calculate for how long to sleep or block, if at all
765	(active idle watchers, EVLOOP_NONBLOCK or not having	850	(active idle watchers, EVRUN_NOWAIT or not having
766	any active watchers at all will result in not sleeping).	851	any active watchers at all will result in not sleeping).
767	- Sleep if the I/O and timer collect interval say so.	852	- Sleep if the I/O and timer collect interval say so.
		853	- Increment loop iteration counter.
768	- Block the process, waiting for any events.	854	- Block the process, waiting for any events.
769	- Queue all outstanding I/O (fd) events.	855	- Queue all outstanding I/O (fd) events.
770	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	856	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
771	- Queue all expired timers.	857	- Queue all expired timers.
772	- Queue all expired periodics.	858	- Queue all expired periodics.
773	- Unless any events are pending now, queue all idle watchers.	859	- Queue all idle watchers with priority higher than that of pending events.
774	- Queue all check watchers.	860	- Queue all check watchers.
775	- Call all queued watchers in reverse order (i.e. check watchers first).	861	- Call all queued watchers in reverse order (i.e. check watchers first).
776	Signals and child watchers are implemented as I/O watchers, and will	862	Signals and child watchers are implemented as I/O watchers, and will
777	be handled here by queueing them when their watcher gets executed.	863	be handled here by queueing them when their watcher gets executed.
778	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	864	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
779	were used, or there are no active watchers, return, otherwise	865	were used, or there are no active watchers, goto FINISH, otherwise
780	continue with step *.	866	continue with step LOOP.
		867	FINISH:
		868	- Reset the ev_break status iff it was EVBREAK_ONE.
		869	- Decrement the loop depth.
		870	- Return.
781		871
782	Example: Queue some jobs and then loop until no events are outstanding	872	Example: Queue some jobs and then loop until no events are outstanding
783	anymore.	873	anymore.
784		874
785	... queue jobs here, make sure they register event watchers as long	875	... queue jobs here, make sure they register event watchers as long
786	... as they still have work to do (even an idle watcher will do..)	876	... as they still have work to do (even an idle watcher will do..)
787	ev_loop (my_loop, 0);	877	ev_run (my_loop, 0);
788	... jobs done or somebody called unloop. yeah!	878	... jobs done or somebody called break. yeah!
789		879
790	=item ev_unloop (loop, how)	880	=item ev_break (loop, how)
791		881
792	Can be used to make a call to C<ev_loop> return early (but only after it	882	Can be used to make a call to C<ev_run> return early (but only after it
793	has processed all outstanding events). The C<how> argument must be either	883	has processed all outstanding events). The C<how> argument must be either
794	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	884	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
795	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	885	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
796		886
797	This "unloop state" will be cleared when entering C<ev_loop> again.	887	This "break state" will be cleared on the next call to C<ev_run>.
798		888
799	It is safe to call C<ev_unloop> from outside any C<ev_loop> calls.	889	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		890	which case it will have no effect.
800		891
801	=item ev_ref (loop)	892	=item ev_ref (loop)
802		893
803	=item ev_unref (loop)	894	=item ev_unref (loop)
804		895
805	Ref/unref can be used to add or remove a reference count on the event	896	Ref/unref can be used to add or remove a reference count on the event
806	loop: Every watcher keeps one reference, and as long as the reference	897	loop: Every watcher keeps one reference, and as long as the reference
807	count is nonzero, C<ev_loop> will not return on its own.	898	count is nonzero, C<ev_run> will not return on its own.
808		899
809	This is useful when you have a watcher that you never intend to	900	This is useful when you have a watcher that you never intend to
810	unregister, but that nevertheless should not keep C<ev_loop> from	901	unregister, but that nevertheless should not keep C<ev_run> from
811	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>	902	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
812	before stopping it.	903	before stopping it.
813		904
814	As an example, libev itself uses this for its internal signal pipe: It	905	As an example, libev itself uses this for its internal signal pipe: It
815	is not visible to the libev user and should not keep C<ev_loop> from	906	is not visible to the libev user and should not keep C<ev_run> from
816	exiting if no event watchers registered by it are active. It is also an	907	exiting if no event watchers registered by it are active. It is also an
817	excellent way to do this for generic recurring timers or from within	908	excellent way to do this for generic recurring timers or from within
818	third-party libraries. Just remember to I<unref after start> and I<ref	909	third-party libraries. Just remember to I<unref after start> and I<ref
819	before stop> (but only if the watcher wasn't active before, or was active	910	before stop> (but only if the watcher wasn't active before, or was active
820	before, respectively. Note also that libev might stop watchers itself	911	before, respectively. Note also that libev might stop watchers itself
821	(e.g. non-repeating timers) in which case you have to C<ev_ref>	912	(e.g. non-repeating timers) in which case you have to C<ev_ref>
822	in the callback).	913	in the callback).
823		914
824	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	915	Example: Create a signal watcher, but keep it from keeping C<ev_run>
825	running when nothing else is active.	916	running when nothing else is active.
826		917
827	ev_signal exitsig;	918	ev_signal exitsig;
828	ev_signal_init (&exitsig, sig_cb, SIGINT);	919	ev_signal_init (&exitsig, sig_cb, SIGINT);
829	ev_signal_start (loop, &exitsig);	920	ev_signal_start (loop, &exitsig);
830	evf_unref (loop);	921	ev_unref (loop);
831		922
832	Example: For some weird reason, unregister the above signal handler again.	923	Example: For some weird reason, unregister the above signal handler again.
833		924
834	ev_ref (loop);	925	ev_ref (loop);
835	ev_signal_stop (loop, &exitsig);	926	ev_signal_stop (loop, &exitsig);
…		…
892	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	983	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
893		984
894	=item ev_invoke_pending (loop)	985	=item ev_invoke_pending (loop)
895		986
896	This call will simply invoke all pending watchers while resetting their	987	This call will simply invoke all pending watchers while resetting their
897	pending state. Normally, C<ev_loop> does this automatically when required,	988	pending state. Normally, C<ev_run> does this automatically when required,
898	but when overriding the invoke callback this call comes handy.	989	but when overriding the invoke callback this call comes handy. This
		990	function can be invoked from a watcher - this can be useful for example
		991	when you want to do some lengthy calculation and want to pass further
		992	event handling to another thread (you still have to make sure only one
		993	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
899		994
900	=item int ev_pending_count (loop)	995	=item int ev_pending_count (loop)
901		996
902	Returns the number of pending watchers - zero indicates that no watchers	997	Returns the number of pending watchers - zero indicates that no watchers
903	are pending.	998	are pending.
904		999
905	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))	1000	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
906		1001
907	This overrides the invoke pending functionality of the loop: Instead of	1002	This overrides the invoke pending functionality of the loop: Instead of
908	invoking all pending watchers when there are any, C<ev_loop> will call	1003	invoking all pending watchers when there are any, C<ev_run> will call
909	this callback instead. This is useful, for example, when you want to	1004	this callback instead. This is useful, for example, when you want to
910	invoke the actual watchers inside another context (another thread etc.).	1005	invoke the actual watchers inside another context (another thread etc.).
911		1006
912	If you want to reset the callback, use C<ev_invoke_pending> as new	1007	If you want to reset the callback, use C<ev_invoke_pending> as new
913	callback.	1008	callback.
…		…
916		1011
917	Sometimes you want to share the same loop between multiple threads. This	1012	Sometimes you want to share the same loop between multiple threads. This
918	can be done relatively simply by putting mutex_lock/unlock calls around	1013	can be done relatively simply by putting mutex_lock/unlock calls around
919	each call to a libev function.	1014	each call to a libev function.
920		1015
921	However, C<ev_loop> can run an indefinite time, so it is not feasible to	1016	However, C<ev_run> can run an indefinite time, so it is not feasible
922	wait for it to return. One way around this is to wake up the loop via	1017	to wait for it to return. One way around this is to wake up the event
923	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>	1018	loop via C<ev_break> and C<av_async_send>, another way is to set these
924	and I<acquire> callbacks on the loop.	1019	I<release> and I<acquire> callbacks on the loop.
925		1020
926	When set, then C<release> will be called just before the thread is	1021	When set, then C<release> will be called just before the thread is
927	suspended waiting for new events, and C<acquire> is called just	1022	suspended waiting for new events, and C<acquire> is called just
928	afterwards.	1023	afterwards.
929		1024
…		…
932		1027
933	While event loop modifications are allowed between invocations of	1028	While event loop modifications are allowed between invocations of
934	C<release> and C<acquire> (that's their only purpose after all), no	1029	C<release> and C<acquire> (that's their only purpose after all), no
935	modifications done will affect the event loop, i.e. adding watchers will	1030	modifications done will affect the event loop, i.e. adding watchers will
936	have no effect on the set of file descriptors being watched, or the time	1031	have no effect on the set of file descriptors being watched, or the time
937	waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it	1032	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
938	to take note of any changes you made.	1033	to take note of any changes you made.
939		1034
940	In theory, threads executing C<ev_loop> will be async-cancel safe between	1035	In theory, threads executing C<ev_run> will be async-cancel safe between
941	invocations of C<release> and C<acquire>.	1036	invocations of C<release> and C<acquire>.
942		1037
943	See also the locking example in the C<THREADS> section later in this	1038	See also the locking example in the C<THREADS> section later in this
944	document.	1039	document.
945		1040
946	=item ev_set_userdata (loop, void *data)	1041	=item ev_set_userdata (loop, void *data)
947		1042
948	=item ev_userdata (loop)	1043	=item void *ev_userdata (loop)
949		1044
950	Set and retrieve a single C<void *> associated with a loop. When	1045	Set and retrieve a single C<void *> associated with a loop. When
951	C<ev_set_userdata> has never been called, then C<ev_userdata> returns	1046	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
952	C<0.>	1047	C<0>.
953		1048
954	These two functions can be used to associate arbitrary data with a loop,	1049	These two functions can be used to associate arbitrary data with a loop,
955	and are intended solely for the C<invoke_pending_cb>, C<release> and	1050	and are intended solely for the C<invoke_pending_cb>, C<release> and
956	C<acquire> callbacks described above, but of course can be (ab-)used for	1051	C<acquire> callbacks described above, but of course can be (ab-)used for
957	any other purpose as well.	1052	any other purpose as well.
958		1053
959	=item ev_loop_verify (loop)	1054	=item ev_verify (loop)
960		1055
961	This function only does something when C<EV_VERIFY> support has been	1056	This function only does something when C<EV_VERIFY> support has been
962	compiled in, which is the default for non-minimal builds. It tries to go	1057	compiled in, which is the default for non-minimal builds. It tries to go
963	through all internal structures and checks them for validity. If anything	1058	through all internal structures and checks them for validity. If anything
964	is found to be inconsistent, it will print an error message to standard	1059	is found to be inconsistent, it will print an error message to standard
…		…
975		1070
976	In the following description, uppercase C<TYPE> in names stands for the	1071	In the following description, uppercase C<TYPE> in names stands for the
977	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1072	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
978	watchers and C<ev_io_start> for I/O watchers.	1073	watchers and C<ev_io_start> for I/O watchers.
979		1074
980	A watcher is a structure that you create and register to record your	1075	A watcher is an opaque structure that you allocate and register to record
981	interest in some event. For instance, if you want to wait for STDIN to	1076	your interest in some event. To make a concrete example, imagine you want
982	become readable, you would create an C<ev_io> watcher for that:	1077	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1078	for that:
983		1079
984	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1080	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
985	{	1081	{
986	ev_io_stop (w);	1082	ev_io_stop (w);
987	ev_unloop (loop, EVUNLOOP_ALL);	1083	ev_break (loop, EVBREAK_ALL);
988	}	1084	}
989		1085
990	struct ev_loop *loop = ev_default_loop (0);	1086	struct ev_loop *loop = ev_default_loop (0);
991		1087
992	ev_io stdin_watcher;	1088	ev_io stdin_watcher;
993		1089
994	ev_init (&stdin_watcher, my_cb);	1090	ev_init (&stdin_watcher, my_cb);
995	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1091	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
996	ev_io_start (loop, &stdin_watcher);	1092	ev_io_start (loop, &stdin_watcher);
997		1093
998	ev_loop (loop, 0);	1094	ev_run (loop, 0);
999		1095
1000	As you can see, you are responsible for allocating the memory for your	1096	As you can see, you are responsible for allocating the memory for your
1001	watcher structures (and it is I<usually> a bad idea to do this on the	1097	watcher structures (and it is I<usually> a bad idea to do this on the
1002	stack).	1098	stack).
1003		1099
1004	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1100	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
1005	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1101	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
1006		1102
1007	Each watcher structure must be initialised by a call to C<ev_init	1103	Each watcher structure must be initialised by a call to C<ev_init (watcher
1008	(watcher *, callback)>, which expects a callback to be provided. This	1104	*, callback)>, which expects a callback to be provided. This callback is
1009	callback gets invoked each time the event occurs (or, in the case of I/O	1105	invoked each time the event occurs (or, in the case of I/O watchers, each
1010	watchers, each time the event loop detects that the file descriptor given	1106	time the event loop detects that the file descriptor given is readable
1011	is readable and/or writable).	1107	and/or writable).
1012		1108
1013	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1109	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
1014	macro to configure it, with arguments specific to the watcher type. There	1110	macro to configure it, with arguments specific to the watcher type. There
1015	is also a macro to combine initialisation and setting in one call: C<<	1111	is also a macro to combine initialisation and setting in one call: C<<
1016	ev_TYPE_init (watcher *, callback, ...) >>.	1112	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
1067		1163
1068	=item C<EV_PREPARE>	1164	=item C<EV_PREPARE>
1069		1165
1070	=item C<EV_CHECK>	1166	=item C<EV_CHECK>
1071		1167
1072	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1168	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
1073	to gather new events, and all C<ev_check> watchers are invoked just after	1169	to gather new events, and all C<ev_check> watchers are invoked just after
1074	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1170	C<ev_run> has gathered them, but before it invokes any callbacks for any
1075	received events. Callbacks of both watcher types can start and stop as	1171	received events. Callbacks of both watcher types can start and stop as
1076	many watchers as they want, and all of them will be taken into account	1172	many watchers as they want, and all of them will be taken into account
1077	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1173	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
1078	C<ev_loop> from blocking).	1174	C<ev_run> from blocking).
1079		1175
1080	=item C<EV_EMBED>	1176	=item C<EV_EMBED>
1081		1177
1082	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1178	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1083		1179
1084	=item C<EV_FORK>	1180	=item C<EV_FORK>
1085		1181
1086	The event loop has been resumed in the child process after fork (see	1182	The event loop has been resumed in the child process after fork (see
1087	C<ev_fork>).	1183	C<ev_fork>).
		1184
		1185	=item C<EV_CLEANUP>
		1186
		1187	The event loop is about to be destroyed (see C<ev_cleanup>).
1088		1188
1089	=item C<EV_ASYNC>	1189	=item C<EV_ASYNC>
1090		1190
1091	The given async watcher has been asynchronously notified (see C<ev_async>).	1191	The given async watcher has been asynchronously notified (see C<ev_async>).
1092		1192
…		…
1265	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related	1365	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1266	functions that do not need a watcher.	1366	functions that do not need a watcher.
1267		1367
1268	=back	1368	=back
1269		1369
		1370	See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR
		1371	OWN COMPOSITE WATCHERS> idioms.
1270		1372
1271	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1373	=head2 WATCHER STATES
1272		1374
1273	Each watcher has, by default, a member C<void *data> that you can change	1375	There are various watcher states mentioned throughout this manual -
1274	and read at any time: libev will completely ignore it. This can be used	1376	active, pending and so on. In this section these states and the rules to
1275	to associate arbitrary data with your watcher. If you need more data and	1377	transition between them will be described in more detail - and while these
1276	don't want to allocate memory and store a pointer to it in that data	1378	rules might look complicated, they usually do "the right thing".
1277	member, you can also "subclass" the watcher type and provide your own
1278	data:
1279		1379
1280	struct my_io	1380	=over 4
1281	{
1282	ev_io io;
1283	int otherfd;
1284	void *somedata;
1285	struct whatever *mostinteresting;
1286	};
1287		1381
1288	...	1382	=item initialiased
1289	struct my_io w;
1290	ev_io_init (&w.io, my_cb, fd, EV_READ);
1291		1383
1292	And since your callback will be called with a pointer to the watcher, you	1384	Before a watcher can be registered with the event looop it has to be
1293	can cast it back to your own type:	1385	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1386	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1294		1387
1295	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)	1388	In this state it is simply some block of memory that is suitable for
1296	{	1389	use in an event loop. It can be moved around, freed, reused etc. at
1297	struct my_io *w = (struct my_io *)w_;	1390	will - as long as you either keep the memory contents intact, or call
1298	...	1391	C<ev_TYPE_init> again.
1299	}
1300		1392
1301	More interesting and less C-conformant ways of casting your callback type	1393	=item started/running/active
1302	instead have been omitted.
1303		1394
1304	Another common scenario is to use some data structure with multiple	1395	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1305	embedded watchers:	1396	property of the event loop, and is actively waiting for events. While in
		1397	this state it cannot be accessed (except in a few documented ways), moved,
		1398	freed or anything else - the only legal thing is to keep a pointer to it,
		1399	and call libev functions on it that are documented to work on active watchers.
1306		1400
1307	struct my_biggy	1401	=item pending
1308	{
1309	int some_data;
1310	ev_timer t1;
1311	ev_timer t2;
1312	}
1313		1402
1314	In this case getting the pointer to C<my_biggy> is a bit more	1403	If a watcher is active and libev determines that an event it is interested
1315	complicated: Either you store the address of your C<my_biggy> struct	1404	in has occurred (such as a timer expiring), it will become pending. It will
1316	in the C<data> member of the watcher (for woozies), or you need to use	1405	stay in this pending state until either it is stopped or its callback is
1317	some pointer arithmetic using C<offsetof> inside your watchers (for real	1406	about to be invoked, so it is not normally pending inside the watcher
1318	programmers):	1407	callback.
1319		1408
1320	#include <stddef.h>	1409	The watcher might or might not be active while it is pending (for example,
		1410	an expired non-repeating timer can be pending but no longer active). If it
		1411	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1412	but it is still property of the event loop at this time, so cannot be
		1413	moved, freed or reused. And if it is active the rules described in the
		1414	previous item still apply.
1321		1415
1322	static void	1416	It is also possible to feed an event on a watcher that is not active (e.g.
1323	t1_cb (EV_P_ ev_timer *w, int revents)	1417	via C<ev_feed_event>), in which case it becomes pending without being
1324	{	1418	active.
1325	struct my_biggy big = (struct my_biggy *)
1326	(((char *)w) - offsetof (struct my_biggy, t1));
1327	}
1328		1419
1329	static void	1420	=item stopped
1330	t2_cb (EV_P_ ev_timer *w, int revents)	1421
1331	{	1422	A watcher can be stopped implicitly by libev (in which case it might still
1332	struct my_biggy big = (struct my_biggy *)	1423	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1333	(((char *)w) - offsetof (struct my_biggy, t2));	1424	latter will clear any pending state the watcher might be in, regardless
1334	}	1425	of whether it was active or not, so stopping a watcher explicitly before
		1426	freeing it is often a good idea.
		1427
		1428	While stopped (and not pending) the watcher is essentially in the
		1429	initialised state, that is, it can be reused, moved, modified in any way
		1430	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1431	it again).
		1432
		1433	=back
1335		1434
1336	=head2 WATCHER PRIORITY MODELS	1435	=head2 WATCHER PRIORITY MODELS
1337		1436
1338	Many event loops support I<watcher priorities>, which are usually small	1437	Many event loops support I<watcher priorities>, which are usually small
1339	integers that influence the ordering of event callback invocation	1438	integers that influence the ordering of event callback invocation
…		…
1466	In general you can register as many read and/or write event watchers per	1565	In general you can register as many read and/or write event watchers per
1467	fd as you want (as long as you don't confuse yourself). Setting all file	1566	fd as you want (as long as you don't confuse yourself). Setting all file
1468	descriptors to non-blocking mode is also usually a good idea (but not	1567	descriptors to non-blocking mode is also usually a good idea (but not
1469	required if you know what you are doing).	1568	required if you know what you are doing).
1470		1569
1471	If you cannot use non-blocking mode, then force the use of a
1472	known-to-be-good backend (at the time of this writing, this includes only
1473	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1474	descriptors for which non-blocking operation makes no sense (such as
1475	files) - libev doesn't guarantee any specific behaviour in that case.
1476
1477	Another thing you have to watch out for is that it is quite easy to	1570	Another thing you have to watch out for is that it is quite easy to
1478	receive "spurious" readiness notifications, that is your callback might	1571	receive "spurious" readiness notifications, that is, your callback might
1479	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1572	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1480	because there is no data. Not only are some backends known to create a	1573	because there is no data. It is very easy to get into this situation even
1481	lot of those (for example Solaris ports), it is very easy to get into	1574	with a relatively standard program structure. Thus it is best to always
1482	this situation even with a relatively standard program structure. Thus	1575	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1483	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1484	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1576	preferable to a program hanging until some data arrives.
1485		1577
1486	If you cannot run the fd in non-blocking mode (for example you should	1578	If you cannot run the fd in non-blocking mode (for example you should
1487	not play around with an Xlib connection), then you have to separately	1579	not play around with an Xlib connection), then you have to separately
1488	re-test whether a file descriptor is really ready with a known-to-be good	1580	re-test whether a file descriptor is really ready with a known-to-be good
1489	interface such as poll (fortunately in our Xlib example, Xlib already	1581	interface such as poll (fortunately in the case of Xlib, it already does
1490	does this on its own, so its quite safe to use). Some people additionally	1582	this on its own, so its quite safe to use). Some people additionally
1491	use C<SIGALRM> and an interval timer, just to be sure you won't block	1583	use C<SIGALRM> and an interval timer, just to be sure you won't block
1492	indefinitely.	1584	indefinitely.
1493		1585
1494	But really, best use non-blocking mode.	1586	But really, best use non-blocking mode.
1495		1587
…		…
1523		1615
1524	There is no workaround possible except not registering events	1616	There is no workaround possible except not registering events
1525	for potentially C<dup ()>'ed file descriptors, or to resort to	1617	for potentially C<dup ()>'ed file descriptors, or to resort to
1526	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1618	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1527		1619
		1620	=head3 The special problem of files
		1621
		1622	Many people try to use C<select> (or libev) on file descriptors
		1623	representing files, and expect it to become ready when their program
		1624	doesn't block on disk accesses (which can take a long time on their own).
		1625
		1626	However, this cannot ever work in the "expected" way - you get a readiness
		1627	notification as soon as the kernel knows whether and how much data is
		1628	there, and in the case of open files, that's always the case, so you
		1629	always get a readiness notification instantly, and your read (or possibly
		1630	write) will still block on the disk I/O.
		1631
		1632	Another way to view it is that in the case of sockets, pipes, character
		1633	devices and so on, there is another party (the sender) that delivers data
		1634	on its own, but in the case of files, there is no such thing: the disk
		1635	will not send data on its own, simply because it doesn't know what you
		1636	wish to read - you would first have to request some data.
		1637
		1638	Since files are typically not-so-well supported by advanced notification
		1639	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1640	to files, even though you should not use it. The reason for this is
		1641	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1642	usually a tty, often a pipe, but also sometimes files or special devices
		1643	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1644	F</dev/urandom>), and even though the file might better be served with
		1645	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1646	it "just works" instead of freezing.
		1647
		1648	So avoid file descriptors pointing to files when you know it (e.g. use
		1649	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1650	when you rarely read from a file instead of from a socket, and want to
		1651	reuse the same code path.
		1652
1528	=head3 The special problem of fork	1653	=head3 The special problem of fork
1529		1654
1530	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1655	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1531	useless behaviour. Libev fully supports fork, but needs to be told about	1656	useless behaviour. Libev fully supports fork, but needs to be told about
1532	it in the child.	1657	it in the child if you want to continue to use it in the child.
1533		1658
1534	To support fork in your programs, you either have to call	1659	To support fork in your child processes, you have to call C<ev_loop_fork
1535	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1660	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1536	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1661	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1537	C<EVBACKEND_POLL>.
1538		1662
1539	=head3 The special problem of SIGPIPE	1663	=head3 The special problem of SIGPIPE
1540		1664
1541	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1665	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1542	when writing to a pipe whose other end has been closed, your program gets	1666	when writing to a pipe whose other end has been closed, your program gets
…		…
1624	...	1748	...
1625	struct ev_loop *loop = ev_default_init (0);	1749	struct ev_loop *loop = ev_default_init (0);
1626	ev_io stdin_readable;	1750	ev_io stdin_readable;
1627	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1751	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1628	ev_io_start (loop, &stdin_readable);	1752	ev_io_start (loop, &stdin_readable);
1629	ev_loop (loop, 0);	1753	ev_run (loop, 0);
1630		1754
1631		1755
1632	=head2 C<ev_timer> - relative and optionally repeating timeouts	1756	=head2 C<ev_timer> - relative and optionally repeating timeouts
1633		1757
1634	Timer watchers are simple relative timers that generate an event after a	1758	Timer watchers are simple relative timers that generate an event after a
…		…
1643	The callback is guaranteed to be invoked only I<after> its timeout has	1767	The callback is guaranteed to be invoked only I<after> its timeout has
1644	passed (not I<at>, so on systems with very low-resolution clocks this	1768	passed (not I<at>, so on systems with very low-resolution clocks this
1645	might introduce a small delay). If multiple timers become ready during the	1769	might introduce a small delay). If multiple timers become ready during the
1646	same loop iteration then the ones with earlier time-out values are invoked	1770	same loop iteration then the ones with earlier time-out values are invoked
1647	before ones of the same priority with later time-out values (but this is	1771	before ones of the same priority with later time-out values (but this is
1648	no longer true when a callback calls C<ev_loop> recursively).	1772	no longer true when a callback calls C<ev_run> recursively).
1649		1773
1650	=head3 Be smart about timeouts	1774	=head3 Be smart about timeouts
1651		1775
1652	Many real-world problems involve some kind of timeout, usually for error	1776	Many real-world problems involve some kind of timeout, usually for error
1653	recovery. A typical example is an HTTP request - if the other side hangs,	1777	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1824		1948
1825	=head3 The special problem of time updates	1949	=head3 The special problem of time updates
1826		1950
1827	Establishing the current time is a costly operation (it usually takes at	1951	Establishing the current time is a costly operation (it usually takes at
1828	least two system calls): EV therefore updates its idea of the current	1952	least two system calls): EV therefore updates its idea of the current
1829	time only before and after C<ev_loop> collects new events, which causes a	1953	time only before and after C<ev_run> collects new events, which causes a
1830	growing difference between C<ev_now ()> and C<ev_time ()> when handling	1954	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1831	lots of events in one iteration.	1955	lots of events in one iteration.
1832		1956
1833	The relative timeouts are calculated relative to the C<ev_now ()>	1957	The relative timeouts are calculated relative to the C<ev_now ()>
1834	time. This is usually the right thing as this timestamp refers to the time	1958	time. This is usually the right thing as this timestamp refers to the time
…		…
1951	}	2075	}
1952		2076
1953	ev_timer mytimer;	2077	ev_timer mytimer;
1954	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2078	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1955	ev_timer_again (&mytimer); /* start timer */	2079	ev_timer_again (&mytimer); /* start timer */
1956	ev_loop (loop, 0);	2080	ev_run (loop, 0);
1957		2081
1958	// and in some piece of code that gets executed on any "activity":	2082	// and in some piece of code that gets executed on any "activity":
1959	// reset the timeout to start ticking again at 10 seconds	2083	// reset the timeout to start ticking again at 10 seconds
1960	ev_timer_again (&mytimer);	2084	ev_timer_again (&mytimer);
1961		2085
…		…
1987		2111
1988	As with timers, the callback is guaranteed to be invoked only when the	2112	As with timers, the callback is guaranteed to be invoked only when the
1989	point in time where it is supposed to trigger has passed. If multiple	2113	point in time where it is supposed to trigger has passed. If multiple
1990	timers become ready during the same loop iteration then the ones with	2114	timers become ready during the same loop iteration then the ones with
1991	earlier time-out values are invoked before ones with later time-out values	2115	earlier time-out values are invoked before ones with later time-out values
1992	(but this is no longer true when a callback calls C<ev_loop> recursively).	2116	(but this is no longer true when a callback calls C<ev_run> recursively).
1993		2117
1994	=head3 Watcher-Specific Functions and Data Members	2118	=head3 Watcher-Specific Functions and Data Members
1995		2119
1996	=over 4	2120	=over 4
1997		2121
…		…
2032		2156
2033	Another way to think about it (for the mathematically inclined) is that	2157	Another way to think about it (for the mathematically inclined) is that
2034	C<ev_periodic> will try to run the callback in this mode at the next possible	2158	C<ev_periodic> will try to run the callback in this mode at the next possible
2035	time where C<time = offset (mod interval)>, regardless of any time jumps.	2159	time where C<time = offset (mod interval)>, regardless of any time jumps.
2036		2160
2037	For numerical stability it is preferable that the C<offset> value is near	2161	The C<interval> I<MUST> be positive, and for numerical stability, the
2038	C<ev_now ()> (the current time), but there is no range requirement for	2162	interval value should be higher than C<1/8192> (which is around 100
2039	this value, and in fact is often specified as zero.	2163	microseconds) and C<offset> should be higher than C<0> and should have
		2164	at most a similar magnitude as the current time (say, within a factor of
		2165	ten). Typical values for offset are, in fact, C<0> or something between
		2166	C<0> and C<interval>, which is also the recommended range.
2040		2167
2041	Note also that there is an upper limit to how often a timer can fire (CPU	2168	Note also that there is an upper limit to how often a timer can fire (CPU
2042	speed for example), so if C<interval> is very small then timing stability	2169	speed for example), so if C<interval> is very small then timing stability
2043	will of course deteriorate. Libev itself tries to be exact to be about one	2170	will of course deteriorate. Libev itself tries to be exact to be about one
2044	millisecond (if the OS supports it and the machine is fast enough).	2171	millisecond (if the OS supports it and the machine is fast enough).
…		…
2158		2285
2159	=head2 C<ev_signal> - signal me when a signal gets signalled!	2286	=head2 C<ev_signal> - signal me when a signal gets signalled!
2160		2287
2161	Signal watchers will trigger an event when the process receives a specific	2288	Signal watchers will trigger an event when the process receives a specific
2162	signal one or more times. Even though signals are very asynchronous, libev	2289	signal one or more times. Even though signals are very asynchronous, libev
2163	will try it's best to deliver signals synchronously, i.e. as part of the	2290	will try its best to deliver signals synchronously, i.e. as part of the
2164	normal event processing, like any other event.	2291	normal event processing, like any other event.
2165		2292
2166	If you want signals to be delivered truly asynchronously, just use	2293	If you want signals to be delivered truly asynchronously, just use
2167	C<sigaction> as you would do without libev and forget about sharing	2294	C<sigaction> as you would do without libev and forget about sharing
2168	the signal. You can even use C<ev_async> from a signal handler to	2295	the signal. You can even use C<ev_async> from a signal handler to
…		…
2187	=head3 The special problem of inheritance over fork/execve/pthread_create	2314	=head3 The special problem of inheritance over fork/execve/pthread_create
2188		2315
2189	Both the signal mask (C<sigprocmask>) and the signal disposition	2316	Both the signal mask (C<sigprocmask>) and the signal disposition
2190	(C<sigaction>) are unspecified after starting a signal watcher (and after	2317	(C<sigaction>) are unspecified after starting a signal watcher (and after
2191	stopping it again), that is, libev might or might not block the signal,	2318	stopping it again), that is, libev might or might not block the signal,
2192	and might or might not set or restore the installed signal handler.	2319	and might or might not set or restore the installed signal handler (but
		2320	see C<EVFLAG_NOSIGMASK>).
2193		2321
2194	While this does not matter for the signal disposition (libev never	2322	While this does not matter for the signal disposition (libev never
2195	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on	2323	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
2196	C<execve>), this matters for the signal mask: many programs do not expect	2324	C<execve>), this matters for the signal mask: many programs do not expect
2197	certain signals to be blocked.	2325	certain signals to be blocked.
…		…
2211		2339
2212	So I can't stress this enough: I<If you do not reset your signal mask when	2340	So I can't stress this enough: I<If you do not reset your signal mask when
2213	you expect it to be empty, you have a race condition in your code>. This	2341	you expect it to be empty, you have a race condition in your code>. This
2214	is not a libev-specific thing, this is true for most event libraries.	2342	is not a libev-specific thing, this is true for most event libraries.
2215		2343
		2344	=head3 The special problem of threads signal handling
		2345
		2346	POSIX threads has problematic signal handling semantics, specifically,
		2347	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2348	threads in a process block signals, which is hard to achieve.
		2349
		2350	When you want to use sigwait (or mix libev signal handling with your own
		2351	for the same signals), you can tackle this problem by globally blocking
		2352	all signals before creating any threads (or creating them with a fully set
		2353	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2354	loops. Then designate one thread as "signal receiver thread" which handles
		2355	these signals. You can pass on any signals that libev might be interested
		2356	in by calling C<ev_feed_signal>.
		2357
2216	=head3 Watcher-Specific Functions and Data Members	2358	=head3 Watcher-Specific Functions and Data Members
2217		2359
2218	=over 4	2360	=over 4
2219		2361
2220	=item ev_signal_init (ev_signal *, callback, int signum)	2362	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
2235	Example: Try to exit cleanly on SIGINT.	2377	Example: Try to exit cleanly on SIGINT.
2236		2378
2237	static void	2379	static void
2238	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2380	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2239	{	2381	{
2240	ev_unloop (loop, EVUNLOOP_ALL);	2382	ev_break (loop, EVBREAK_ALL);
2241	}	2383	}
2242		2384
2243	ev_signal signal_watcher;	2385	ev_signal signal_watcher;
2244	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2386	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2245	ev_signal_start (loop, &signal_watcher);	2387	ev_signal_start (loop, &signal_watcher);
…		…
2631		2773
2632	Prepare and check watchers are usually (but not always) used in pairs:	2774	Prepare and check watchers are usually (but not always) used in pairs:
2633	prepare watchers get invoked before the process blocks and check watchers	2775	prepare watchers get invoked before the process blocks and check watchers
2634	afterwards.	2776	afterwards.
2635		2777
2636	You I<must not> call C<ev_loop> or similar functions that enter	2778	You I<must not> call C<ev_run> or similar functions that enter
2637	the current event loop from either C<ev_prepare> or C<ev_check>	2779	the current event loop from either C<ev_prepare> or C<ev_check>
2638	watchers. Other loops than the current one are fine, however. The	2780	watchers. Other loops than the current one are fine, however. The
2639	rationale behind this is that you do not need to check for recursion in	2781	rationale behind this is that you do not need to check for recursion in
2640	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2782	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2641	C<ev_check> so if you have one watcher of each kind they will always be	2783	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2809		2951
2810	if (timeout >= 0)	2952	if (timeout >= 0)
2811	// create/start timer	2953	// create/start timer
2812		2954
2813	// poll	2955	// poll
2814	ev_loop (EV_A_ 0);	2956	ev_run (EV_A_ 0);
2815		2957
2816	// stop timer again	2958	// stop timer again
2817	if (timeout >= 0)	2959	if (timeout >= 0)
2818	ev_timer_stop (EV_A_ &to);	2960	ev_timer_stop (EV_A_ &to);
2819		2961
…		…
2897	if you do not want that, you need to temporarily stop the embed watcher).	3039	if you do not want that, you need to temporarily stop the embed watcher).
2898		3040
2899	=item ev_embed_sweep (loop, ev_embed *)	3041	=item ev_embed_sweep (loop, ev_embed *)
2900		3042
2901	Make a single, non-blocking sweep over the embedded loop. This works	3043	Make a single, non-blocking sweep over the embedded loop. This works
2902	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3044	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2903	appropriate way for embedded loops.	3045	appropriate way for embedded loops.
2904		3046
2905	=item struct ev_loop *other [read-only]	3047	=item struct ev_loop *other [read-only]
2906		3048
2907	The embedded event loop.	3049	The embedded event loop.
…		…
2993	disadvantage of having to use multiple event loops (which do not support	3135	disadvantage of having to use multiple event loops (which do not support
2994	signal watchers).	3136	signal watchers).
2995		3137
2996	When this is not possible, or you want to use the default loop for	3138	When this is not possible, or you want to use the default loop for
2997	other reasons, then in the process that wants to start "fresh", call	3139	other reasons, then in the process that wants to start "fresh", call
2998	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3140	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
2999	the default loop will "orphan" (not stop) all registered watchers, so you	3141	Destroying the default loop will "orphan" (not stop) all registered
3000	have to be careful not to execute code that modifies those watchers. Note	3142	watchers, so you have to be careful not to execute code that modifies
3001	also that in that case, you have to re-register any signal watchers.	3143	those watchers. Note also that in that case, you have to re-register any
		3144	signal watchers.
3002		3145
3003	=head3 Watcher-Specific Functions and Data Members	3146	=head3 Watcher-Specific Functions and Data Members
3004		3147
3005	=over 4	3148	=over 4
3006		3149
3007	=item ev_fork_init (ev_signal *, callback)	3150	=item ev_fork_init (ev_fork *, callback)
3008		3151
3009	Initialises and configures the fork watcher - it has no parameters of any	3152	Initialises and configures the fork watcher - it has no parameters of any
3010	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3153	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
3011	believe me.	3154	really.
3012		3155
3013	=back	3156	=back
		3157
		3158
		3159	=head2 C<ev_cleanup> - even the best things end
		3160
		3161	Cleanup watchers are called just before the event loop is being destroyed
		3162	by a call to C<ev_loop_destroy>.
		3163
		3164	While there is no guarantee that the event loop gets destroyed, cleanup
		3165	watchers provide a convenient method to install cleanup hooks for your
		3166	program, worker threads and so on - you just to make sure to destroy the
		3167	loop when you want them to be invoked.
		3168
		3169	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3170	all other watchers, they do not keep a reference to the event loop (which
		3171	makes a lot of sense if you think about it). Like all other watchers, you
		3172	can call libev functions in the callback, except C<ev_cleanup_start>.
		3173
		3174	=head3 Watcher-Specific Functions and Data Members
		3175
		3176	=over 4
		3177
		3178	=item ev_cleanup_init (ev_cleanup *, callback)
		3179
		3180	Initialises and configures the cleanup watcher - it has no parameters of
		3181	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3182	pointless, I assure you.
		3183
		3184	=back
		3185
		3186	Example: Register an atexit handler to destroy the default loop, so any
		3187	cleanup functions are called.
		3188
		3189	static void
		3190	program_exits (void)
		3191	{
		3192	ev_loop_destroy (EV_DEFAULT_UC);
		3193	}
		3194
		3195	...
		3196	atexit (program_exits);
3014		3197
3015		3198
3016	=head2 C<ev_async> - how to wake up an event loop	3199	=head2 C<ev_async> - how to wake up an event loop
3017		3200
3018	In general, you cannot use an C<ev_loop> from multiple threads or other	3201	In general, you cannot use an C<ev_loop> from multiple threads or other
…		…
3025	it by calling C<ev_async_send>, which is thread- and signal safe.	3208	it by calling C<ev_async_send>, which is thread- and signal safe.
3026		3209
3027	This functionality is very similar to C<ev_signal> watchers, as signals,	3210	This functionality is very similar to C<ev_signal> watchers, as signals,
3028	too, are asynchronous in nature, and signals, too, will be compressed	3211	too, are asynchronous in nature, and signals, too, will be compressed
3029	(i.e. the number of callback invocations may be less than the number of	3212	(i.e. the number of callback invocations may be less than the number of
3030	C<ev_async_sent> calls).	3213	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
		3214	of "global async watchers" by using a watcher on an otherwise unused
		3215	signal, and C<ev_feed_signal> to signal this watcher from another thread,
		3216	even without knowing which loop owns the signal.
3031		3217
3032	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3218	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
3033	just the default loop.	3219	just the default loop.
3034		3220
3035	=head3 Queueing	3221	=head3 Queueing
…		…
3130	trust me.	3316	trust me.
3131		3317
3132	=item ev_async_send (loop, ev_async *)	3318	=item ev_async_send (loop, ev_async *)
3133		3319
3134	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3320	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3135	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3321	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3322	returns.
		3323
3136	C<ev_feed_event>, this call is safe to do from other threads, signal or	3324	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3137	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3325	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3138	section below on what exactly this means).	3326	embedding section below on what exactly this means).
3139		3327
3140	Note that, as with other watchers in libev, multiple events might get	3328	Note that, as with other watchers in libev, multiple events might get
3141	compressed into a single callback invocation (another way to look at this	3329	compressed into a single callback invocation (another way to look at this
3142	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3330	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
3143	reset when the event loop detects that).	3331	reset when the event loop detects that).
…		…
3211	Feed an event on the given fd, as if a file descriptor backend detected	3399	Feed an event on the given fd, as if a file descriptor backend detected
3212	the given events it.	3400	the given events it.
3213		3401
3214	=item ev_feed_signal_event (loop, int signum)	3402	=item ev_feed_signal_event (loop, int signum)
3215		3403
3216	Feed an event as if the given signal occurred (C<loop> must be the default	3404	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3217	loop!).	3405	which is async-safe.
3218		3406
3219	=back	3407	=back
		3408
		3409
		3410	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3411
		3412	This section explains some common idioms that are not immediately
		3413	obvious. Note that examples are sprinkled over the whole manual, and this
		3414	section only contains stuff that wouldn't fit anywhere else.
		3415
		3416	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3417
		3418	Each watcher has, by default, a C<void *data> member that you can read
		3419	or modify at any time: libev will completely ignore it. This can be used
		3420	to associate arbitrary data with your watcher. If you need more data and
		3421	don't want to allocate memory separately and store a pointer to it in that
		3422	data member, you can also "subclass" the watcher type and provide your own
		3423	data:
		3424
		3425	struct my_io
		3426	{
		3427	ev_io io;
		3428	int otherfd;
		3429	void *somedata;
		3430	struct whatever *mostinteresting;
		3431	};
		3432
		3433	...
		3434	struct my_io w;
		3435	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3436
		3437	And since your callback will be called with a pointer to the watcher, you
		3438	can cast it back to your own type:
		3439
		3440	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3441	{
		3442	struct my_io *w = (struct my_io *)w_;
		3443	...
		3444	}
		3445
		3446	More interesting and less C-conformant ways of casting your callback
		3447	function type instead have been omitted.
		3448
		3449	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3450
		3451	Another common scenario is to use some data structure with multiple
		3452	embedded watchers, in effect creating your own watcher that combines
		3453	multiple libev event sources into one "super-watcher":
		3454
		3455	struct my_biggy
		3456	{
		3457	int some_data;
		3458	ev_timer t1;
		3459	ev_timer t2;
		3460	}
		3461
		3462	In this case getting the pointer to C<my_biggy> is a bit more
		3463	complicated: Either you store the address of your C<my_biggy> struct in
		3464	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3465	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3466	real programmers):
		3467
		3468	#include <stddef.h>
		3469
		3470	static void
		3471	t1_cb (EV_P_ ev_timer *w, int revents)
		3472	{
		3473	struct my_biggy big = (struct my_biggy *)
		3474	(((char *)w) - offsetof (struct my_biggy, t1));
		3475	}
		3476
		3477	static void
		3478	t2_cb (EV_P_ ev_timer *w, int revents)
		3479	{
		3480	struct my_biggy big = (struct my_biggy *)
		3481	(((char *)w) - offsetof (struct my_biggy, t2));
		3482	}
		3483
		3484	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3485
		3486	Often (especially in GUI toolkits) there are places where you have
		3487	I<modal> interaction, which is most easily implemented by recursively
		3488	invoking C<ev_run>.
		3489
		3490	This brings the problem of exiting - a callback might want to finish the
		3491	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3492	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3493	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3494	other combination: In these cases, C<ev_break> will not work alone.
		3495
		3496	The solution is to maintain "break this loop" variable for each C<ev_run>
		3497	invocation, and use a loop around C<ev_run> until the condition is
		3498	triggered, using C<EVRUN_ONCE>:
		3499
		3500	// main loop
		3501	int exit_main_loop = 0;
		3502
		3503	while (!exit_main_loop)
		3504	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3505
		3506	// in a model watcher
		3507	int exit_nested_loop = 0;
		3508
		3509	while (!exit_nested_loop)
		3510	ev_run (EV_A_ EVRUN_ONCE);
		3511
		3512	To exit from any of these loops, just set the corresponding exit variable:
		3513
		3514	// exit modal loop
		3515	exit_nested_loop = 1;
		3516
		3517	// exit main program, after modal loop is finished
		3518	exit_main_loop = 1;
		3519
		3520	// exit both
		3521	exit_main_loop = exit_nested_loop = 1;
		3522
		3523	=head2 THREAD LOCKING EXAMPLE
		3524
		3525	Here is a fictitious example of how to run an event loop in a different
		3526	thread from where callbacks are being invoked and watchers are
		3527	created/added/removed.
		3528
		3529	For a real-world example, see the C<EV::Loop::Async> perl module,
		3530	which uses exactly this technique (which is suited for many high-level
		3531	languages).
		3532
		3533	The example uses a pthread mutex to protect the loop data, a condition
		3534	variable to wait for callback invocations, an async watcher to notify the
		3535	event loop thread and an unspecified mechanism to wake up the main thread.
		3536
		3537	First, you need to associate some data with the event loop:
		3538
		3539	typedef struct {
		3540	mutex_t lock; /* global loop lock */
		3541	ev_async async_w;
		3542	thread_t tid;
		3543	cond_t invoke_cv;
		3544	} userdata;
		3545
		3546	void prepare_loop (EV_P)
		3547	{
		3548	// for simplicity, we use a static userdata struct.
		3549	static userdata u;
		3550
		3551	ev_async_init (&u->async_w, async_cb);
		3552	ev_async_start (EV_A_ &u->async_w);
		3553
		3554	pthread_mutex_init (&u->lock, 0);
		3555	pthread_cond_init (&u->invoke_cv, 0);
		3556
		3557	// now associate this with the loop
		3558	ev_set_userdata (EV_A_ u);
		3559	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3560	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3561
		3562	// then create the thread running ev_run
		3563	pthread_create (&u->tid, 0, l_run, EV_A);
		3564	}
		3565
		3566	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3567	solely to wake up the event loop so it takes notice of any new watchers
		3568	that might have been added:
		3569
		3570	static void
		3571	async_cb (EV_P_ ev_async *w, int revents)
		3572	{
		3573	// just used for the side effects
		3574	}
		3575
		3576	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3577	protecting the loop data, respectively.
		3578
		3579	static void
		3580	l_release (EV_P)
		3581	{
		3582	userdata *u = ev_userdata (EV_A);
		3583	pthread_mutex_unlock (&u->lock);
		3584	}
		3585
		3586	static void
		3587	l_acquire (EV_P)
		3588	{
		3589	userdata *u = ev_userdata (EV_A);
		3590	pthread_mutex_lock (&u->lock);
		3591	}
		3592
		3593	The event loop thread first acquires the mutex, and then jumps straight
		3594	into C<ev_run>:
		3595
		3596	void *
		3597	l_run (void *thr_arg)
		3598	{
		3599	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3600
		3601	l_acquire (EV_A);
		3602	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3603	ev_run (EV_A_ 0);
		3604	l_release (EV_A);
		3605
		3606	return 0;
		3607	}
		3608
		3609	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3610	signal the main thread via some unspecified mechanism (signals? pipe
		3611	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3612	have been called (in a while loop because a) spurious wakeups are possible
		3613	and b) skipping inter-thread-communication when there are no pending
		3614	watchers is very beneficial):
		3615
		3616	static void
		3617	l_invoke (EV_P)
		3618	{
		3619	userdata *u = ev_userdata (EV_A);
		3620
		3621	while (ev_pending_count (EV_A))
		3622	{
		3623	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3624	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3625	}
		3626	}
		3627
		3628	Now, whenever the main thread gets told to invoke pending watchers, it
		3629	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3630	thread to continue:
		3631
		3632	static void
		3633	real_invoke_pending (EV_P)
		3634	{
		3635	userdata *u = ev_userdata (EV_A);
		3636
		3637	pthread_mutex_lock (&u->lock);
		3638	ev_invoke_pending (EV_A);
		3639	pthread_cond_signal (&u->invoke_cv);
		3640	pthread_mutex_unlock (&u->lock);
		3641	}
		3642
		3643	Whenever you want to start/stop a watcher or do other modifications to an
		3644	event loop, you will now have to lock:
		3645
		3646	ev_timer timeout_watcher;
		3647	userdata *u = ev_userdata (EV_A);
		3648
		3649	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3650
		3651	pthread_mutex_lock (&u->lock);
		3652	ev_timer_start (EV_A_ &timeout_watcher);
		3653	ev_async_send (EV_A_ &u->async_w);
		3654	pthread_mutex_unlock (&u->lock);
		3655
		3656	Note that sending the C<ev_async> watcher is required because otherwise
		3657	an event loop currently blocking in the kernel will have no knowledge
		3658	about the newly added timer. By waking up the loop it will pick up any new
		3659	watchers in the next event loop iteration.
		3660
		3661	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3662
		3663	While the overhead of a callback that e.g. schedules a thread is small, it
		3664	is still an overhead. If you embed libev, and your main usage is with some
		3665	kind of threads or coroutines, you might want to customise libev so that
		3666	doesn't need callbacks anymore.
		3667
		3668	Imagine you have coroutines that you can switch to using a function
		3669	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3670	and that due to some magic, the currently active coroutine is stored in a
		3671	global called C<current_coro>. Then you can build your own "wait for libev
		3672	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3673	the differing C<;> conventions):
		3674
		3675	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3676	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3677
		3678	That means instead of having a C callback function, you store the
		3679	coroutine to switch to in each watcher, and instead of having libev call
		3680	your callback, you instead have it switch to that coroutine.
		3681
		3682	A coroutine might now wait for an event with a function called
		3683	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3684	matter when, or whether the watcher is active or not when this function is
		3685	called):
		3686
		3687	void
		3688	wait_for_event (ev_watcher *w)
		3689	{
		3690	ev_cb_set (w) = current_coro;
		3691	switch_to (libev_coro);
		3692	}
		3693
		3694	That basically suspends the coroutine inside C<wait_for_event> and
		3695	continues the libev coroutine, which, when appropriate, switches back to
		3696	this or any other coroutine. I am sure if you sue this your own :)
		3697
		3698	You can do similar tricks if you have, say, threads with an event queue -
		3699	instead of storing a coroutine, you store the queue object and instead of
		3700	switching to a coroutine, you push the watcher onto the queue and notify
		3701	any waiters.
		3702
		3703	To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two
		3704	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3705
		3706	// my_ev.h
		3707	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3708	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3709	#include "../libev/ev.h"
		3710
		3711	// my_ev.c
		3712	#define EV_H "my_ev.h"
		3713	#include "../libev/ev.c"
		3714
		3715	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3716	F<my_ev.c> into your project. When properly specifying include paths, you
		3717	can even use F<ev.h> as header file name directly.
3220		3718
3221		3719
3222	=head1 LIBEVENT EMULATION	3720	=head1 LIBEVENT EMULATION
3223		3721
3224	Libev offers a compatibility emulation layer for libevent. It cannot	3722	Libev offers a compatibility emulation layer for libevent. It cannot
3225	emulate the internals of libevent, so here are some usage hints:	3723	emulate the internals of libevent, so here are some usage hints:
3226		3724
3227	=over 4	3725	=over 4
		3726
		3727	=item * Only the libevent-1.4.1-beta API is being emulated.
		3728
		3729	This was the newest libevent version available when libev was implemented,
		3730	and is still mostly unchanged in 2010.
3228		3731
3229	=item * Use it by including <event.h>, as usual.	3732	=item * Use it by including <event.h>, as usual.
3230		3733
3231	=item * The following members are fully supported: ev_base, ev_callback,	3734	=item * The following members are fully supported: ev_base, ev_callback,
3232	ev_arg, ev_fd, ev_res, ev_events.	3735	ev_arg, ev_fd, ev_res, ev_events.
…		…
3238	=item * Priorities are not currently supported. Initialising priorities	3741	=item * Priorities are not currently supported. Initialising priorities
3239	will fail and all watchers will have the same priority, even though there	3742	will fail and all watchers will have the same priority, even though there
3240	is an ev_pri field.	3743	is an ev_pri field.
3241		3744
3242	=item * In libevent, the last base created gets the signals, in libev, the	3745	=item * In libevent, the last base created gets the signals, in libev, the
3243	first base created (== the default loop) gets the signals.	3746	base that registered the signal gets the signals.
3244		3747
3245	=item * Other members are not supported.	3748	=item * Other members are not supported.
3246		3749
3247	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3750	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3248	to use the libev header file and library.	3751	to use the libev header file and library.
…		…
3267	Care has been taken to keep the overhead low. The only data member the C++	3770	Care has been taken to keep the overhead low. The only data member the C++
3268	classes add (compared to plain C-style watchers) is the event loop pointer	3771	classes add (compared to plain C-style watchers) is the event loop pointer
3269	that the watcher is associated with (or no additional members at all if	3772	that the watcher is associated with (or no additional members at all if
3270	you disable C<EV_MULTIPLICITY> when embedding libev).	3773	you disable C<EV_MULTIPLICITY> when embedding libev).
3271		3774
3272	Currently, functions, and static and non-static member functions can be	3775	Currently, functions, static and non-static member functions and classes
3273	used as callbacks. Other types should be easy to add as long as they only	3776	with C<operator ()> can be used as callbacks. Other types should be easy
3274	need one additional pointer for context. If you need support for other	3777	to add as long as they only need one additional pointer for context. If
3275	types of functors please contact the author (preferably after implementing	3778	you need support for other types of functors please contact the author
3276	it).	3779	(preferably after implementing it).
3277		3780
3278	Here is a list of things available in the C<ev> namespace:	3781	Here is a list of things available in the C<ev> namespace:
3279		3782
3280	=over 4	3783	=over 4
3281		3784
…		…
3391	Associates a different C<struct ev_loop> with this watcher. You can only	3894	Associates a different C<struct ev_loop> with this watcher. You can only
3392	do this when the watcher is inactive (and not pending either).	3895	do this when the watcher is inactive (and not pending either).
3393		3896
3394	=item w->set ([arguments])	3897	=item w->set ([arguments])
3395		3898
3396	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3899	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
3397	called at least once. Unlike the C counterpart, an active watcher gets	3900	method or a suitable start method must be called at least once. Unlike the
3398	automatically stopped and restarted when reconfiguring it with this	3901	C counterpart, an active watcher gets automatically stopped and restarted
3399	method.	3902	when reconfiguring it with this method.
3400		3903
3401	=item w->start ()	3904	=item w->start ()
3402		3905
3403	Starts the watcher. Note that there is no C<loop> argument, as the	3906	Starts the watcher. Note that there is no C<loop> argument, as the
3404	constructor already stores the event loop.	3907	constructor already stores the event loop.
3405		3908
		3909	=item w->start ([arguments])
		3910
		3911	Instead of calling C<set> and C<start> methods separately, it is often
		3912	convenient to wrap them in one call. Uses the same type of arguments as
		3913	the configure C<set> method of the watcher.
		3914
3406	=item w->stop ()	3915	=item w->stop ()
3407		3916
3408	Stops the watcher if it is active. Again, no C<loop> argument.	3917	Stops the watcher if it is active. Again, no C<loop> argument.
3409		3918
3410	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3919	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3422		3931
3423	=back	3932	=back
3424		3933
3425	=back	3934	=back
3426		3935
3427	Example: Define a class with an IO and idle watcher, start one of them in	3936	Example: Define a class with two I/O and idle watchers, start the I/O
3428	the constructor.	3937	watchers in the constructor.
3429		3938
3430	class myclass	3939	class myclass
3431	{	3940	{
3432	ev::io io ; void io_cb (ev::io &w, int revents);	3941	ev::io io ; void io_cb (ev::io &w, int revents);
		3942	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
3433	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3943	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3434		3944
3435	myclass (int fd)	3945	myclass (int fd)
3436	{	3946	{
3437	io .set <myclass, &myclass::io_cb > (this);	3947	io .set <myclass, &myclass::io_cb > (this);
		3948	io2 .set <myclass, &myclass::io2_cb > (this);
3438	idle.set <myclass, &myclass::idle_cb> (this);	3949	idle.set <myclass, &myclass::idle_cb> (this);
3439		3950
3440	io.start (fd, ev::READ);	3951	io.set (fd, ev::WRITE); // configure the watcher
		3952	io.start (); // start it whenever convenient
		3953
		3954	io2.start (fd, ev::READ); // set + start in one call
3441	}	3955	}
3442	};	3956	};
3443		3957
3444		3958
3445	=head1 OTHER LANGUAGE BINDINGS	3959	=head1 OTHER LANGUAGE BINDINGS
…		…
3519	loop argument"). The C<EV_A> form is used when this is the sole argument,	4033	loop argument"). The C<EV_A> form is used when this is the sole argument,
3520	C<EV_A_> is used when other arguments are following. Example:	4034	C<EV_A_> is used when other arguments are following. Example:
3521		4035
3522	ev_unref (EV_A);	4036	ev_unref (EV_A);
3523	ev_timer_add (EV_A_ watcher);	4037	ev_timer_add (EV_A_ watcher);
3524	ev_loop (EV_A_ 0);	4038	ev_run (EV_A_ 0);
3525		4039
3526	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4040	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3527	which is often provided by the following macro.	4041	which is often provided by the following macro.
3528		4042
3529	=item C<EV_P>, C<EV_P_>	4043	=item C<EV_P>, C<EV_P_>
…		…
3569	}	4083	}
3570		4084
3571	ev_check check;	4085	ev_check check;
3572	ev_check_init (&check, check_cb);	4086	ev_check_init (&check, check_cb);
3573	ev_check_start (EV_DEFAULT_ &check);	4087	ev_check_start (EV_DEFAULT_ &check);
3574	ev_loop (EV_DEFAULT_ 0);	4088	ev_run (EV_DEFAULT_ 0);
3575		4089
3576	=head1 EMBEDDING	4090	=head1 EMBEDDING
3577		4091
3578	Libev can (and often is) directly embedded into host	4092	Libev can (and often is) directly embedded into host
3579	applications. Examples of applications that embed it include the Deliantra	4093	applications. Examples of applications that embed it include the Deliantra
…		…
3671	users of libev and the libev code itself must be compiled with compatible	4185	users of libev and the libev code itself must be compiled with compatible
3672	settings.	4186	settings.
3673		4187
3674	=over 4	4188	=over 4
3675		4189
		4190	=item EV_COMPAT3 (h)
		4191
		4192	Backwards compatibility is a major concern for libev. This is why this
		4193	release of libev comes with wrappers for the functions and symbols that
		4194	have been renamed between libev version 3 and 4.
		4195
		4196	You can disable these wrappers (to test compatibility with future
		4197	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4198	sources. This has the additional advantage that you can drop the C<struct>
		4199	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4200	typedef in that case.
		4201
		4202	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4203	and in some even more future version the compatibility code will be
		4204	removed completely.
		4205
3676	=item EV_STANDALONE (h)	4206	=item EV_STANDALONE (h)
3677		4207
3678	Must always be C<1> if you do not use autoconf configuration, which	4208	Must always be C<1> if you do not use autoconf configuration, which
3679	keeps libev from including F<config.h>, and it also defines dummy	4209	keeps libev from including F<config.h>, and it also defines dummy
3680	implementations for some libevent functions (such as logging, which is not	4210	implementations for some libevent functions (such as logging, which is not
3681	supported). It will also not define any of the structs usually found in	4211	supported). It will also not define any of the structs usually found in
3682	F<event.h> that are not directly supported by the libev core alone.	4212	F<event.h> that are not directly supported by the libev core alone.
3683		4213
3684	In standalone mode, libev will still try to automatically deduce the	4214	In standalone mode, libev will still try to automatically deduce the
3685	configuration, but has to be more conservative.	4215	configuration, but has to be more conservative.
		4216
		4217	=item EV_USE_FLOOR
		4218
		4219	If defined to be C<1>, libev will use the C<floor ()> function for its
		4220	periodic reschedule calculations, otherwise libev will fall back on a
		4221	portable (slower) implementation. If you enable this, you usually have to
		4222	link against libm or something equivalent. Enabling this when the C<floor>
		4223	function is not available will fail, so the safe default is to not enable
		4224	this.
3686		4225
3687	=item EV_USE_MONOTONIC	4226	=item EV_USE_MONOTONIC
3688		4227
3689	If defined to be C<1>, libev will try to detect the availability of the	4228	If defined to be C<1>, libev will try to detect the availability of the
3690	monotonic clock option at both compile time and runtime. Otherwise no	4229	monotonic clock option at both compile time and runtime. Otherwise no
…		…
4029	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it	4568	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
4030	will be C<0>.	4569	will be C<0>.
4031		4570
4032	=item EV_VERIFY	4571	=item EV_VERIFY
4033		4572
4034	Controls how much internal verification (see C<ev_loop_verify ()>) will	4573	Controls how much internal verification (see C<ev_verify ()>) will
4035	be done: If set to C<0>, no internal verification code will be compiled	4574	be done: If set to C<0>, no internal verification code will be compiled
4036	in. If set to C<1>, then verification code will be compiled in, but not	4575	in. If set to C<1>, then verification code will be compiled in, but not
4037	called. If set to C<2>, then the internal verification code will be	4576	called. If set to C<2>, then the internal verification code will be
4038	called once per loop, which can slow down libev. If set to C<3>, then the	4577	called once per loop, which can slow down libev. If set to C<3>, then the
4039	verification code will be called very frequently, which will slow down	4578	verification code will be called very frequently, which will slow down
…		…
4122	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4661	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4123		4662
4124	#include "ev_cpp.h"	4663	#include "ev_cpp.h"
4125	#include "ev.c"	4664	#include "ev.c"
4126		4665
4127	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4666	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4128		4667
4129	=head2 THREADS AND COROUTINES	4668	=head2 THREADS AND COROUTINES
4130		4669
4131	=head3 THREADS	4670	=head3 THREADS
4132		4671
…		…
4183	default loop and triggering an C<ev_async> watcher from the default loop	4722	default loop and triggering an C<ev_async> watcher from the default loop
4184	watcher callback into the event loop interested in the signal.	4723	watcher callback into the event loop interested in the signal.
4185		4724
4186	=back	4725	=back
4187		4726
4188	=head4 THREAD LOCKING EXAMPLE	4727	See also L<THREAD LOCKING EXAMPLE>.
4189
4190	Here is a fictitious example of how to run an event loop in a different
4191	thread than where callbacks are being invoked and watchers are
4192	created/added/removed.
4193
4194	For a real-world example, see the C<EV::Loop::Async> perl module,
4195	which uses exactly this technique (which is suited for many high-level
4196	languages).
4197
4198	The example uses a pthread mutex to protect the loop data, a condition
4199	variable to wait for callback invocations, an async watcher to notify the
4200	event loop thread and an unspecified mechanism to wake up the main thread.
4201
4202	First, you need to associate some data with the event loop:
4203
4204	typedef struct {
4205	mutex_t lock; /* global loop lock */
4206	ev_async async_w;
4207	thread_t tid;
4208	cond_t invoke_cv;
4209	} userdata;
4210
4211	void prepare_loop (EV_P)
4212	{
4213	// for simplicity, we use a static userdata struct.
4214	static userdata u;
4215
4216	ev_async_init (&u->async_w, async_cb);
4217	ev_async_start (EV_A_ &u->async_w);
4218
4219	pthread_mutex_init (&u->lock, 0);
4220	pthread_cond_init (&u->invoke_cv, 0);
4221
4222	// now associate this with the loop
4223	ev_set_userdata (EV_A_ u);
4224	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4225	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4226
4227	// then create the thread running ev_loop
4228	pthread_create (&u->tid, 0, l_run, EV_A);
4229	}
4230
4231	The callback for the C<ev_async> watcher does nothing: the watcher is used
4232	solely to wake up the event loop so it takes notice of any new watchers
4233	that might have been added:
4234
4235	static void
4236	async_cb (EV_P_ ev_async *w, int revents)
4237	{
4238	// just used for the side effects
4239	}
4240
4241	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4242	protecting the loop data, respectively.
4243
4244	static void
4245	l_release (EV_P)
4246	{
4247	userdata *u = ev_userdata (EV_A);
4248	pthread_mutex_unlock (&u->lock);
4249	}
4250
4251	static void
4252	l_acquire (EV_P)
4253	{
4254	userdata *u = ev_userdata (EV_A);
4255	pthread_mutex_lock (&u->lock);
4256	}
4257
4258	The event loop thread first acquires the mutex, and then jumps straight
4259	into C<ev_loop>:
4260
4261	void *
4262	l_run (void *thr_arg)
4263	{
4264	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4265
4266	l_acquire (EV_A);
4267	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4268	ev_loop (EV_A_ 0);
4269	l_release (EV_A);
4270
4271	return 0;
4272	}
4273
4274	Instead of invoking all pending watchers, the C<l_invoke> callback will
4275	signal the main thread via some unspecified mechanism (signals? pipe
4276	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4277	have been called (in a while loop because a) spurious wakeups are possible
4278	and b) skipping inter-thread-communication when there are no pending
4279	watchers is very beneficial):
4280
4281	static void
4282	l_invoke (EV_P)
4283	{
4284	userdata *u = ev_userdata (EV_A);
4285
4286	while (ev_pending_count (EV_A))
4287	{
4288	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4289	pthread_cond_wait (&u->invoke_cv, &u->lock);
4290	}
4291	}
4292
4293	Now, whenever the main thread gets told to invoke pending watchers, it
4294	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4295	thread to continue:
4296
4297	static void
4298	real_invoke_pending (EV_P)
4299	{
4300	userdata *u = ev_userdata (EV_A);
4301
4302	pthread_mutex_lock (&u->lock);
4303	ev_invoke_pending (EV_A);
4304	pthread_cond_signal (&u->invoke_cv);
4305	pthread_mutex_unlock (&u->lock);
4306	}
4307
4308	Whenever you want to start/stop a watcher or do other modifications to an
4309	event loop, you will now have to lock:
4310
4311	ev_timer timeout_watcher;
4312	userdata *u = ev_userdata (EV_A);
4313
4314	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4315
4316	pthread_mutex_lock (&u->lock);
4317	ev_timer_start (EV_A_ &timeout_watcher);
4318	ev_async_send (EV_A_ &u->async_w);
4319	pthread_mutex_unlock (&u->lock);
4320
4321	Note that sending the C<ev_async> watcher is required because otherwise
4322	an event loop currently blocking in the kernel will have no knowledge
4323	about the newly added timer. By waking up the loop it will pick up any new
4324	watchers in the next event loop iteration.
4325		4728
4326	=head3 COROUTINES	4729	=head3 COROUTINES
4327		4730
4328	Libev is very accommodating to coroutines ("cooperative threads"):	4731	Libev is very accommodating to coroutines ("cooperative threads"):
4329	libev fully supports nesting calls to its functions from different	4732	libev fully supports nesting calls to its functions from different
4330	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4733	coroutines (e.g. you can call C<ev_run> on the same loop from two
4331	different coroutines, and switch freely between both coroutines running	4734	different coroutines, and switch freely between both coroutines running
4332	the loop, as long as you don't confuse yourself). The only exception is	4735	the loop, as long as you don't confuse yourself). The only exception is
4333	that you must not do this from C<ev_periodic> reschedule callbacks.	4736	that you must not do this from C<ev_periodic> reschedule callbacks.
4334		4737
4335	Care has been taken to ensure that libev does not keep local state inside	4738	Care has been taken to ensure that libev does not keep local state inside
4336	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4739	C<ev_run>, and other calls do not usually allow for coroutine switches as
4337	they do not call any callbacks.	4740	they do not call any callbacks.
4338		4741
4339	=head2 COMPILER WARNINGS	4742	=head2 COMPILER WARNINGS
4340		4743
4341	Depending on your compiler and compiler settings, you might get no or a	4744	Depending on your compiler and compiler settings, you might get no or a
…		…
4425	=head3 C<kqueue> is buggy	4828	=head3 C<kqueue> is buggy
4426		4829
4427	The kqueue syscall is broken in all known versions - most versions support	4830	The kqueue syscall is broken in all known versions - most versions support
4428	only sockets, many support pipes.	4831	only sockets, many support pipes.
4429		4832
4430	Libev tries to work around this by not using C<kqueue> by default on	4833	Libev tries to work around this by not using C<kqueue> by default on this
4431	this rotten platform, but of course you can still ask for it when creating	4834	rotten platform, but of course you can still ask for it when creating a
4432	a loop.	4835	loop - embedding a socket-only kqueue loop into a select-based one is
		4836	probably going to work well.
4433		4837
4434	=head3 C<poll> is buggy	4838	=head3 C<poll> is buggy
4435		4839
4436	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>	4840	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
4437	implementation by something calling C<kqueue> internally around the 10.5.6	4841	implementation by something calling C<kqueue> internally around the 10.5.6
…		…
4456		4860
4457	=head3 C<errno> reentrancy	4861	=head3 C<errno> reentrancy
4458		4862
4459	The default compile environment on Solaris is unfortunately so	4863	The default compile environment on Solaris is unfortunately so
4460	thread-unsafe that you can't even use components/libraries compiled	4864	thread-unsafe that you can't even use components/libraries compiled
4461	without C<-D_REENTRANT> (as long as they use C<errno>), which, of course,	4865	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
4462	isn't defined by default.	4866	defined by default. A valid, if stupid, implementation choice.
4463		4867
4464	If you want to use libev in threaded environments you have to make sure	4868	If you want to use libev in threaded environments you have to make sure
4465	it's compiled with C<_REENTRANT> defined.	4869	it's compiled with C<_REENTRANT> defined.
4466		4870
4467	=head3 Event port backend	4871	=head3 Event port backend
4468		4872
4469	The scalable event interface for Solaris is called "event ports". Unfortunately,	4873	The scalable event interface for Solaris is called "event
4470	this mechanism is very buggy. If you run into high CPU usage, your program	4874	ports". Unfortunately, this mechanism is very buggy in all major
		4875	releases. If you run into high CPU usage, your program freezes or you get
4471	freezes or you get a large number of spurious wakeups, make sure you have	4876	a large number of spurious wakeups, make sure you have all the relevant
4472	all the relevant and latest kernel patches applied. No, I don't know which	4877	and latest kernel patches applied. No, I don't know which ones, but there
4473	ones, but there are multiple ones.	4878	are multiple ones to apply, and afterwards, event ports actually work
		4879	great.
4474		4880
4475	If you can't get it to work, you can try running the program by setting	4881	If you can't get it to work, you can try running the program by setting
4476	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and	4882	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
4477	C<select> backends.	4883	C<select> backends.
4478		4884
4479	=head2 AIX POLL BUG	4885	=head2 AIX POLL BUG
4480		4886
4481	AIX unfortunately has a broken C<poll.h> header. Libev works around	4887	AIX unfortunately has a broken C<poll.h> header. Libev works around
4482	this by trying to avoid the poll backend altogether (i.e. it's not even	4888	this by trying to avoid the poll backend altogether (i.e. it's not even
4483	compiled in), which normally isn't a big problem as C<select> works fine	4889	compiled in), which normally isn't a big problem as C<select> works fine
4484	with large bitsets, and AIX is dead anyway.	4890	with large bitsets on AIX, and AIX is dead anyway.
4485		4891
4486	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4892	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
4487		4893
4488	=head3 General issues	4894	=head3 General issues
4489		4895
…		…
4595	structure (guaranteed by POSIX but not by ISO C for example), but it also	5001	structure (guaranteed by POSIX but not by ISO C for example), but it also
4596	assumes that the same (machine) code can be used to call any watcher	5002	assumes that the same (machine) code can be used to call any watcher
4597	callback: The watcher callbacks have different type signatures, but libev	5003	callback: The watcher callbacks have different type signatures, but libev
4598	calls them using an C<ev_watcher *> internally.	5004	calls them using an C<ev_watcher *> internally.
4599		5005
		5006	=item pointer accesses must be thread-atomic
		5007
		5008	Accessing a pointer value must be atomic, it must both be readable and
		5009	writable in one piece - this is the case on all current architectures.
		5010
4600	=item C<sig_atomic_t volatile> must be thread-atomic as well	5011	=item C<sig_atomic_t volatile> must be thread-atomic as well
4601		5012
4602	The type C<sig_atomic_t volatile> (or whatever is defined as	5013	The type C<sig_atomic_t volatile> (or whatever is defined as
4603	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5014	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
4604	threads. This is not part of the specification for C<sig_atomic_t>, but is	5015	threads. This is not part of the specification for C<sig_atomic_t>, but is
…		…
4626	watchers.	5037	watchers.
4627		5038
4628	=item C<double> must hold a time value in seconds with enough accuracy	5039	=item C<double> must hold a time value in seconds with enough accuracy
4629		5040
4630	The type C<double> is used to represent timestamps. It is required to	5041	The type C<double> is used to represent timestamps. It is required to
4631	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5042	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4632	enough for at least into the year 4000. This requirement is fulfilled by	5043	good enough for at least into the year 4000 with millisecond accuracy
		5044	(the design goal for libev). This requirement is overfulfilled by
4633	implementations implementing IEEE 754, which is basically all existing	5045	implementations using IEEE 754, which is basically all existing ones. With
4634	ones. With IEEE 754 doubles, you get microsecond accuracy until at least	5046	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
4635	2200.
4636		5047
4637	=back	5048	=back
4638		5049
4639	If you know of other additional requirements drop me a note.	5050	If you know of other additional requirements drop me a note.
4640		5051
…		…
4710	=back	5121	=back
4711		5122
4712		5123
4713	=head1 PORTING FROM LIBEV 3.X TO 4.X	5124	=head1 PORTING FROM LIBEV 3.X TO 4.X
4714		5125
4715	The major version 4 introduced some minor incompatible changes to the API.	5126	The major version 4 introduced some incompatible changes to the API.
4716		5127
4717	At the moment, the C<ev.h> header file tries to implement superficial	5128	At the moment, the C<ev.h> header file provides compatibility definitions
4718	compatibility, so most programs should still compile. Those might be	5129	for all changes, so most programs should still compile. The compatibility
4719	removed in later versions of libev, so better update early than late.	5130	layer might be removed in later versions of libev, so better update to the
		5131	new API early than late.
4720		5132
4721	=over 4	5133	=over 4
4722		5134
4723	=item C<ev_loop_count> renamed to C<ev_iteration>	5135	=item C<EV_COMPAT3> backwards compatibility mechanism
4724		5136
4725	=item C<ev_loop_depth> renamed to C<ev_depth>	5137	The backward compatibility mechanism can be controlled by
		5138	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5139	section.
4726		5140
4727	=item C<ev_loop_verify> renamed to C<ev_verify>	5141	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5142
		5143	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5144
		5145	ev_loop_destroy (EV_DEFAULT_UC);
		5146	ev_loop_fork (EV_DEFAULT);
		5147
		5148	=item function/symbol renames
		5149
		5150	A number of functions and symbols have been renamed:
		5151
		5152	ev_loop => ev_run
		5153	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5154	EVLOOP_ONESHOT => EVRUN_ONCE
		5155
		5156	ev_unloop => ev_break
		5157	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5158	EVUNLOOP_ONE => EVBREAK_ONE
		5159	EVUNLOOP_ALL => EVBREAK_ALL
		5160
		5161	EV_TIMEOUT => EV_TIMER
		5162
		5163	ev_loop_count => ev_iteration
		5164	ev_loop_depth => ev_depth
		5165	ev_loop_verify => ev_verify
4728		5166
4729	Most functions working on C<struct ev_loop> objects don't have an	5167	Most functions working on C<struct ev_loop> objects don't have an
4730	C<ev_loop_> prefix, so it was removed. Note that C<ev_loop_fork> is	5168	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5169	associated constants have been renamed to not collide with the C<struct
		5170	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5171	as all other watcher types. Note that C<ev_loop_fork> is still called
4731	still called C<ev_loop_fork> because it would otherwise clash with the	5172	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
4732	C<ev_fork> typedef.	5173	typedef.
4733
4734	=item C<EV_TIMEOUT> renamed to C<EV_TIMER> in C<revents>
4735
4736	This is a simple rename - all other watcher types use their name
4737	as revents flag, and now C<ev_timer> does, too.
4738
4739	Both C<EV_TIMER> and C<EV_TIMEOUT> symbols were present in 3.x versions
4740	and continue to be present for the foreseeable future, so this is mostly a
4741	documentation change.
4742		5174
4743	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>	5175	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
4744		5176
4745	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different	5177	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
4746	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile	5178	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
…		…
4753		5185
4754	=over 4	5186	=over 4
4755		5187
4756	=item active	5188	=item active
4757		5189
4758	A watcher is active as long as it has been started (has been attached to	5190	A watcher is active as long as it has been started and not yet stopped.
4759	an event loop) but not yet stopped (disassociated from the event loop).	5191	See L<WATCHER STATES> for details.
4760		5192
4761	=item application	5193	=item application
4762		5194
4763	In this document, an application is whatever is using libev.	5195	In this document, an application is whatever is using libev.
		5196
		5197	=item backend
		5198
		5199	The part of the code dealing with the operating system interfaces.
4764		5200
4765	=item callback	5201	=item callback
4766		5202
4767	The address of a function that is called when some event has been	5203	The address of a function that is called when some event has been
4768	detected. Callbacks are being passed the event loop, the watcher that	5204	detected. Callbacks are being passed the event loop, the watcher that
4769	received the event, and the actual event bitset.	5205	received the event, and the actual event bitset.
4770		5206
4771	=item callback invocation	5207	=item callback/watcher invocation
4772		5208
4773	The act of calling the callback associated with a watcher.	5209	The act of calling the callback associated with a watcher.
4774		5210
4775	=item event	5211	=item event
4776		5212
…		…
4795	The model used to describe how an event loop handles and processes	5231	The model used to describe how an event loop handles and processes
4796	watchers and events.	5232	watchers and events.
4797		5233
4798	=item pending	5234	=item pending
4799		5235
4800	A watcher is pending as soon as the corresponding event has been detected,	5236	A watcher is pending as soon as the corresponding event has been
4801	and stops being pending as soon as the watcher will be invoked or its	5237	detected. See L<WATCHER STATES> for details.
4802	pending status is explicitly cleared by the application.
4803
4804	A watcher can be pending, but not active. Stopping a watcher also clears
4805	its pending status.
4806		5238
4807	=item real time	5239	=item real time
4808		5240
4809	The physical time that is observed. It is apparently strictly monotonic :)	5241	The physical time that is observed. It is apparently strictly monotonic :)
4810		5242
4811	=item wall-clock time	5243	=item wall-clock time
4812		5244
4813	The time and date as shown on clocks. Unlike real time, it can actually	5245	The time and date as shown on clocks. Unlike real time, it can actually
4814	be wrong and jump forwards and backwards, e.g. when the you adjust your	5246	be wrong and jump forwards and backwards, e.g. when you adjust your
4815	clock.	5247	clock.
4816		5248
4817	=item watcher	5249	=item watcher
4818		5250
4819	A data structure that describes interest in certain events. Watchers need	5251	A data structure that describes interest in certain events. Watchers need
4820	to be started (attached to an event loop) before they can receive events.	5252	to be started (attached to an event loop) before they can receive events.
4821		5253
4822	=item watcher invocation
4823
4824	The act of calling the callback associated with a watcher.
4825
4826	=back	5254	=back
4827		5255
4828	=head1 AUTHOR	5256	=head1 AUTHOR
4829		5257
4830	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5258	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5259	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4831		5260

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