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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
…		…
75	While this document tries to be as complete as possible in documenting	75	While this document tries to be as complete as possible in documenting
76	libev, its usage and the rationale behind its design, it is not a tutorial	76	libev, its usage and the rationale behind its design, it is not a tutorial
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	Familarity 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 (somewhere	137	the (fractional) number of seconds since the (POSIX) epoch (in practice
130	near the beginning of 1970, details are complicated, don't ask). This	138	somewhere near the beginning of 1970, details are complicated, don't
131	type is called C<ev_tstamp>, which is what you should use too. It usually	139	ask). This type is called C<ev_tstamp>, which is what you should use
132	aliases to the C<double> type in C. When you need to do any calculations	140	too. It usually aliases to the C<double> type in C. When you need to do
133	on it, you should treat it as some floating point value. Unlike the name	141	any calculations on it, you should treat it as some floating point value.
		142
134	component C<stamp> might indicate, it is also used for time differences	143	Unlike the name component C<stamp> might indicate, it is also used for
135	throughout libev.	144	time differences (e.g. delays) throughout libev.
136		145
137	=head1 ERROR HANDLING	146	=head1 ERROR HANDLING
138		147
139	Libev knows three classes of errors: operating system errors, usage errors	148	Libev knows three classes of errors: operating system errors, usage errors
140	and internal errors (bugs).	149	and internal errors (bugs).
…		…
164		173
165	=item ev_tstamp ev_time ()	174	=item ev_tstamp ev_time ()
166		175
167	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
168	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
169	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>.
170		180
171	=item ev_sleep (ev_tstamp interval)	181	=item ev_sleep (ev_tstamp interval)
172		182
173	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
174	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
…		…
191	as this indicates an incompatible change. Minor versions are usually	201	as this indicates an incompatible change. Minor versions are usually
192	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
193	not a problem.	203	not a problem.
194		204
195	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
196	version.	206	version (note, however, that this will not detect other ABI mismatches,
		207	such as LFS or reentrancy).
197		208
198	assert (("libev version mismatch",	209	assert (("libev version mismatch",
199	ev_version_major () == EV_VERSION_MAJOR	210	ev_version_major () == EV_VERSION_MAJOR
200	&& ev_version_minor () >= EV_VERSION_MINOR));	211	&& ev_version_minor () >= EV_VERSION_MINOR));
201		212
…		…
212	assert (("sorry, no epoll, no sex",	223	assert (("sorry, no epoll, no sex",
213	ev_supported_backends () & EVBACKEND_EPOLL));	224	ev_supported_backends () & EVBACKEND_EPOLL));
214		225
215	=item unsigned int ev_recommended_backends ()	226	=item unsigned int ev_recommended_backends ()
216		227
217	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
218	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
219	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
220	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
221	(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
222	libev will probe for if you specify no backends explicitly.	234	probe for if you specify no backends explicitly.
223		235
224	=item unsigned int ev_embeddable_backends ()	236	=item unsigned int ev_embeddable_backends ()
225		237
226	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
227	is the theoretical, all-platform, value. To find which backends	239	value is platform-specific but can include backends not available on the
228	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
229	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	241	the current system, you would need to look at C<ev_embeddable_backends ()
230	recommended ones.	242	& ev_supported_backends ()>, likewise for recommended ones.
231		243
232	See the description of C<ev_embed> watchers for more info.	244	See the description of C<ev_embed> watchers for more info.
233		245
234	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	246	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
235		247
236	Sets the allocation function to use (the prototype is similar - the	248	Sets the allocation function to use (the prototype is similar - the
237	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
238	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
239	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
…		…
265	}	277	}
266		278
267	...	279	...
268	ev_set_allocator (persistent_realloc);	280	ev_set_allocator (persistent_realloc);
269		281
270	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	282	=item ev_set_syserr_cb (void (*cb)(const char *msg))
271		283
272	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
273	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
274	indicating the system call or subsystem causing the problem. If this	286	indicating the system call or subsystem causing the problem. If this
275	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
…		…
287	}	299	}
288		300
289	...	301	...
290	ev_set_syserr_cb (fatal_error);	302	ev_set_syserr_cb (fatal_error);
291		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
292	=back	317	=back
293		318
294	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	319	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
295		320
296	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
297	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
298	I<function>).	323	libev 3 had an C<ev_loop> function colliding with the struct name).
299		324
300	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
301	supports signals and child events, and dynamically created loops which do	326	supports child process events, and dynamically created event loops which
302	not.	327	do not.
303		328
304	=over 4	329	=over 4
305		330
306	=item struct ev_loop *ev_default_loop (unsigned int flags)	331	=item struct ev_loop *ev_default_loop (unsigned int flags)
307		332
308	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
309	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
310	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
311	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".
312		343
313	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
314	function.	345	function (or via the C<EV_DEFAULT> macro).
315		346
316	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
317	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
318	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).
319		351
320	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,
321	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
322	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
323	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
324	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	356	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
325	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.
326		376
327	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
328	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>).
329		379
330	The following flags are supported:	380	The following flags are supported:
…		…
345	useful to try out specific backends to test their performance, or to work	395	useful to try out specific backends to test their performance, or to work
346	around bugs.	396	around bugs.
347		397
348	=item C<EVFLAG_FORKCHECK>	398	=item C<EVFLAG_FORKCHECK>
349		399
350	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	400	Instead of calling C<ev_loop_fork> manually after a fork, you can also
351	a fork, you can also make libev check for a fork in each iteration by	401	make libev check for a fork in each iteration by enabling this flag.
352	enabling this flag.
353		402
354	This works by calling C<getpid ()> on every iteration of the loop,	403	This works by calling C<getpid ()> on every iteration of the loop,
355	and thus this might slow down your event loop if you do a lot of loop	404	and thus this might slow down your event loop if you do a lot of loop
356	iterations and little real work, but is usually not noticeable (on my	405	iterations and little real work, but is usually not noticeable (on my
357	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	406	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
…		…
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.	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
		514	not least, it also refuses to work with some file descriptors which work
		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...
445		520
446	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
447	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
448	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
449	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
…		…
515	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	590	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
516		591
517	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,
518	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)).
519		594
520	Please note that Solaris event ports can deliver a lot of spurious
521	notifications, so you need to use non-blocking I/O or other means to avoid
522	blocking when no data (or space) is available.
523
524	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
525	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
526	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	597	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
527	might perform better.	598	might perform better.
528		599
529	On the positive side, with the exception of the spurious readiness	600	On the positive side, this backend actually performed fully to
530	notifications, this backend actually performed fully to specification
531	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
532	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.
533		614
534	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
535	C<EVBACKEND_POLL>.	616	C<EVBACKEND_POLL>.
536		617
537	=item C<EVBACKEND_ALL>	618	=item C<EVBACKEND_ALL>
538		619
539	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
540	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
541	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	622	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
542		623
543	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).
544		633
545	=back	634	=back
546		635
547	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,
548	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
549	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
550	()> will be tried.	639	()> will be tried.
551		640
552	Example: This is the most typical usage.
553
554	if (!ev_default_loop (0))
555	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
556
557	Example: Restrict libev to the select and poll backends, and do not allow
558	environment settings to be taken into account:
559
560	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
561
562	Example: Use whatever libev has to offer, but make sure that kqueue is
563	used if available (warning, breaks stuff, best use only with your own
564	private event loop and only if you know the OS supports your types of
565	fds):
566
567	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
568
569	=item struct ev_loop *ev_loop_new (unsigned int flags)
570
571	Similar to C<ev_default_loop>, but always creates a new event loop that is
572	always distinct from the default loop. Unlike the default loop, it cannot
573	handle signal and child watchers, and attempts to do so will be greeted by
574	undefined behaviour (or a failed assertion if assertions are enabled).
575
576	Note that this function I<is> thread-safe, and the recommended 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 again (frees all memory and kernel state	654	Destroys an event loop object (frees all memory and kernel state
589	etc.). None of the active event watchers will be stopped in the normal	655	etc.). None of the active event watchers will be stopped in the normal
590	sense, so e.g. C<ev_is_active> might still return true. It is your	656	sense, so e.g. C<ev_is_active> might still return true. It is your
591	responsibility to either stop all watchers cleanly yourself I<before>	657	responsibility to either stop all watchers cleanly yourself I<before>
592	calling this function, or cope with the fact afterwards (which is usually	658	calling this function, or cope with the fact afterwards (which is usually
593	the easiest thing, you can just ignore the watchers and/or C<free ()> them	659	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
595		661
596	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
597	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
598	as signal and child watchers) would need to be stopped manually.	664	as signal and child watchers) would need to be stopped manually.
599		665
600	In general it is not advisable to call this function except in the	666	This function is normally used on loop objects allocated by
601	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.
602	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>
603	C<ev_loop_new> and C<ev_loop_destroy>.	673	and C<ev_loop_destroy>.
604		674
605	=item ev_loop_destroy (loop)	675	=item ev_loop_fork (loop)
606		676
607	Like C<ev_default_destroy>, but destroys an event loop created by an
608	earlier call to C<ev_loop_new>.
609
610	=item ev_default_fork ()
611
612	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
613	to reinitialise the kernel state for backends that have one. Despite the	678	reinitialise the kernel state for backends that have one. Despite the
614	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
615	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
616	sense). You I<must> call it in the child before using any of the libev	681	child before resuming or calling C<ev_run>.
617	functions, and it will only take effect at the next C<ev_loop> iteration.	682
		683	Again, you I<have> to call it on I<any> loop that you want to re-use after
		684	a fork, I<even if you do not plan to use the loop in the parent>. This is
		685	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		686	during fork.
618		687
619	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
620	process if and only if you want to use the event library in the child. If	689	process if and only if you want to use the event loop in the child. If
621	you just fork+exec, you don't have to call it at all.	690	you just fork+exec or create a new loop in the child, you don't have to
		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).
622		694
623	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
624	it just in case after a fork. To make this easy, the function will fit in	696	it just in case after a fork.
625	quite nicely into a call to C<pthread_atfork>:
626		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	...
627	pthread_atfork (0, 0, ev_default_fork);	708	pthread_atfork (0, 0, post_fork_child);
628
629	=item ev_loop_fork (loop)
630
631	Like C<ev_default_fork>, but acts on an event loop created by
632	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
633	after fork that you want to re-use in the child, and how you do this is
634	entirely your own problem.
635		709
636	=item int ev_is_default_loop (loop)	710	=item int ev_is_default_loop (loop)
637		711
638	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
639	otherwise.	713	otherwise.
640		714
641	=item unsigned int ev_loop_count (loop)	715	=item unsigned int ev_iteration (loop)
642		716
643	Returns the count of loop iterations for the loop, which is identical to	717	Returns the current iteration count for the event loop, which is identical
644	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>
645	happily wraps around with enough iterations.	719	and happily wraps around with enough iterations.
646		720
647	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
648	"ticks" the number of loop iterations), as it roughly corresponds with	722	"ticks" the number of loop iterations), as it roughly corresponds with
649	C<ev_prepare> and C<ev_check> calls.	723	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		724	prepare and check phases.
650		725
651	=item unsigned int ev_loop_depth (loop)	726	=item unsigned int ev_depth (loop)
652		727
653	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
654	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.
655		730
656	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
657	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),
658	in which case it is higher.	733	in which case it is higher.
659		734
660	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread	735	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
661	etc.), doesn't count as exit.	736	throwing an exception etc.), doesn't count as "exit" - consider this
		737	as a hint to avoid such ungentleman-like behaviour unless it's really
		738	convenient, in which case it is fully supported.
662		739
663	=item unsigned int ev_backend (loop)	740	=item unsigned int ev_backend (loop)
664		741
665	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
666	use.	743	use.
…		…
675		752
676	=item ev_now_update (loop)	753	=item ev_now_update (loop)
677		754
678	Establishes the current time by querying the kernel, updating the time	755	Establishes the current time by querying the kernel, updating the time
679	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
680	is usually done automatically within C<ev_loop ()>.	757	is usually done automatically within C<ev_run ()>.
681		758
682	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
683	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
684	the current time is a good idea.	761	the current time is a good idea.
685		762
…		…
687		764
688	=item ev_suspend (loop)	765	=item ev_suspend (loop)
689		766
690	=item ev_resume (loop)	767	=item ev_resume (loop)
691		768
692	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
693	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.
694		771
695	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
696	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
697	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
698	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>
…		…
700	C<ev_resume> directly afterwards to resume timer processing.	777	C<ev_resume> directly afterwards to resume timer processing.
701		778
702	Effectively, all C<ev_timer> watchers will be delayed by the time spend	779	Effectively, all C<ev_timer> watchers will be delayed by the time spend
703	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers	780	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
704	will be rescheduled (that is, they will lose any events that would have	781	will be rescheduled (that is, they will lose any events that would have
705	occured while suspended).	782	occurred while suspended).
706		783
707	After calling C<ev_suspend> you B<must not> call I<any> function on the	784	After calling C<ev_suspend> you B<must not> call I<any> function on the
708	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>	785	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
709	without a previous call to C<ev_suspend>.	786	without a previous call to C<ev_suspend>.
710		787
711	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
712	event loop time (see C<ev_now_update>).	789	event loop time (see C<ev_now_update>).
713		790
714	=item ev_loop (loop, int flags)	791	=item ev_run (loop, int flags)
715		792
716	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
717	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
718	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>.
719		798
720	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
721	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.
722		802
723	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
724	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
725	finished (especially in interactive programs), but having a program	805	finished (especially in interactive programs), but having a program
726	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
727	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
728	beauty.	808	beauty.
729		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
730	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
731	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
732	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
733	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.
734		820
735	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
736	necessary) and will handle those and any already outstanding ones. It	822	necessary) and will handle those and any already outstanding ones. It
737	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
738	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
739	user-registered callback will be called), and will return after one	825	user-registered callback will be called), and will return after one
740	iteration of the loop.	826	iteration of the loop.
741		827
742	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
743	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
744	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
745	usually a better approach for this kind of thing.	831	usually a better approach for this kind of thing.
746		832
747	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):
748		836
		837	- Increment loop depth.
		838	- Reset the ev_break status.
749	- Before the first iteration, call any pending watchers.	839	- Before the first iteration, call any pending watchers.
		840	LOOP:
750	* If EVFLAG_FORKCHECK was used, check for a fork.	841	- If EVFLAG_FORKCHECK was used, check for a fork.
751	- 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.
752	- Queue and call all prepare watchers.	843	- Queue and call all prepare watchers.
		844	- If ev_break was called, goto FINISH.
753	- If we have been forked, detach and recreate the kernel state	845	- If we have been forked, detach and recreate the kernel state
754	as to not disturb the other process.	846	as to not disturb the other process.
755	- Update the kernel state with all outstanding changes.	847	- Update the kernel state with all outstanding changes.
756	- Update the "event loop time" (ev_now ()).	848	- Update the "event loop time" (ev_now ()).
757	- Calculate for how long to sleep or block, if at all	849	- Calculate for how long to sleep or block, if at all
758	(active idle watchers, EVLOOP_NONBLOCK or not having	850	(active idle watchers, EVRUN_NOWAIT or not having
759	any active watchers at all will result in not sleeping).	851	any active watchers at all will result in not sleeping).
760	- 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.
761	- Block the process, waiting for any events.	854	- Block the process, waiting for any events.
762	- Queue all outstanding I/O (fd) events.	855	- Queue all outstanding I/O (fd) events.
763	- 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.
764	- Queue all expired timers.	857	- Queue all expired timers.
765	- Queue all expired periodics.	858	- Queue all expired periodics.
766	- Unless any events are pending now, queue all idle watchers.	859	- Queue all idle watchers with priority higher than that of pending events.
767	- Queue all check watchers.	860	- Queue all check watchers.
768	- 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).
769	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
770	be handled here by queueing them when their watcher gets executed.	863	be handled here by queueing them when their watcher gets executed.
771	- 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
772	were used, or there are no active watchers, return, otherwise	865	were used, or there are no active watchers, goto FINISH, otherwise
773	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.
774		871
775	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
776	anymore.	873	anymore.
777		874
778	... queue jobs here, make sure they register event watchers as long	875	... queue jobs here, make sure they register event watchers as long
779	... 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..)
780	ev_loop (my_loop, 0);	877	ev_run (my_loop, 0);
781	... jobs done or somebody called unloop. yeah!	878	... jobs done or somebody called break. yeah!
782		879
783	=item ev_unloop (loop, how)	880	=item ev_break (loop, how)
784		881
785	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
786	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
787	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
788	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.
789		886
790	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>.
791		888
792	It is safe to call C<ev_unloop> from otuside 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.
793		891
794	=item ev_ref (loop)	892	=item ev_ref (loop)
795		893
796	=item ev_unref (loop)	894	=item ev_unref (loop)
797		895
798	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
799	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
800	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.
801		899
802	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
803	unregister, but that nevertheless should not keep C<ev_loop> from	901	unregister, but that nevertheless should not keep C<ev_run> from
804	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>
805	before stopping it.	903	before stopping it.
806		904
807	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
808	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
809	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
810	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
811	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
812	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
813	before, respectively. Note also that libev might stop watchers itself	911	before, respectively. Note also that libev might stop watchers itself
814	(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>
815	in the callback).	913	in the callback).
816		914
817	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>
818	running when nothing else is active.	916	running when nothing else is active.
819		917
820	ev_signal exitsig;	918	ev_signal exitsig;
821	ev_signal_init (&exitsig, sig_cb, SIGINT);	919	ev_signal_init (&exitsig, sig_cb, SIGINT);
822	ev_signal_start (loop, &exitsig);	920	ev_signal_start (loop, &exitsig);
823	evf_unref (loop);	921	ev_unref (loop);
824		922
825	Example: For some weird reason, unregister the above signal handler again.	923	Example: For some weird reason, unregister the above signal handler again.
826		924
827	ev_ref (loop);	925	ev_ref (loop);
828	ev_signal_stop (loop, &exitsig);	926	ev_signal_stop (loop, &exitsig);
…		…
867	usually doesn't make much sense to set it to a lower value than C<0.01>,	965	usually doesn't make much sense to set it to a lower value than C<0.01>,
868	as this approaches the timing granularity of most systems. Note that if	966	as this approaches the timing granularity of most systems. Note that if
869	you do transactions with the outside world and you can't increase the	967	you do transactions with the outside world and you can't increase the
870	parallelity, then this setting will limit your transaction rate (if you	968	parallelity, then this setting will limit your transaction rate (if you
871	need to poll once per transaction and the I/O collect interval is 0.01,	969	need to poll once per transaction and the I/O collect interval is 0.01,
872	then you can't do more than 100 transations per second).	970	then you can't do more than 100 transactions per second).
873		971
874	Setting the I<timeout collect interval> can improve the opportunity for	972	Setting the I<timeout collect interval> can improve the opportunity for
875	saving power, as the program will "bundle" timer callback invocations that	973	saving power, as the program will "bundle" timer callback invocations that
876	are "near" in time together, by delaying some, thus reducing the number of	974	are "near" in time together, by delaying some, thus reducing the number of
877	times the process sleeps and wakes up again. Another useful technique to	975	times the process sleeps and wakes up again. Another useful technique to
…		…
885	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	983	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
886		984
887	=item ev_invoke_pending (loop)	985	=item ev_invoke_pending (loop)
888		986
889	This call will simply invoke all pending watchers while resetting their	987	This call will simply invoke all pending watchers while resetting their
890	pending state. Normally, C<ev_loop> does this automatically when required,	988	pending state. Normally, C<ev_run> does this automatically when required,
891	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).
892		994
893	=item int ev_pending_count (loop)	995	=item int ev_pending_count (loop)
894		996
895	Returns the number of pending watchers - zero indicates that no watchers	997	Returns the number of pending watchers - zero indicates that no watchers
896	are pending.	998	are pending.
897		999
898	=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))
899		1001
900	This overrides the invoke pending functionality of the loop: Instead of	1002	This overrides the invoke pending functionality of the loop: Instead of
901	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
902	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
903	invoke the actual watchers inside another context (another thread etc.).	1005	invoke the actual watchers inside another context (another thread etc.).
904		1006
905	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
906	callback.	1008	callback.
…		…
909		1011
910	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
911	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
912	each call to a libev function.	1014	each call to a libev function.
913		1015
914	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
915	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
916	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
917	and I<acquire> callbacks on the loop.	1019	I<release> and I<acquire> callbacks on the loop.
918		1020
919	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
920	suspended waiting for new events, and C<acquire> is called just	1022	suspended waiting for new events, and C<acquire> is called just
921	afterwards.	1023	afterwards.
922		1024
…		…
925		1027
926	While event loop modifications are allowed between invocations of	1028	While event loop modifications are allowed between invocations of
927	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
928	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
929	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
930	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
931	to take note of any changes you made.	1033	to take note of any changes you made.
932		1034
933	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
934	invocations of C<release> and C<acquire>.	1036	invocations of C<release> and C<acquire>.
935		1037
936	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
937	document.	1039	document.
938		1040
939	=item ev_set_userdata (loop, void *data)	1041	=item ev_set_userdata (loop, void *data)
940		1042
941	=item ev_userdata (loop)	1043	=item void *ev_userdata (loop)
942		1044
943	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
944	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
945	C<0.>	1047	C<0>.
946		1048
947	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,
948	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
949	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
950	any other purpose as well.	1052	any other purpose as well.
951		1053
952	=item ev_loop_verify (loop)	1054	=item ev_verify (loop)
953		1055
954	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
955	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
956	through all internal structures and checks them for validity. If anything	1058	through all internal structures and checks them for validity. If anything
957	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
…		…
968		1070
969	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
970	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
971	watchers and C<ev_io_start> for I/O watchers.	1073	watchers and C<ev_io_start> for I/O watchers.
972		1074
973	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
974	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
975	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:
976		1079
977	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)
978	{	1081	{
979	ev_io_stop (w);	1082	ev_io_stop (w);
980	ev_unloop (loop, EVUNLOOP_ALL);	1083	ev_break (loop, EVBREAK_ALL);
981	}	1084	}
982		1085
983	struct ev_loop *loop = ev_default_loop (0);	1086	struct ev_loop *loop = ev_default_loop (0);
984		1087
985	ev_io stdin_watcher;	1088	ev_io stdin_watcher;
986		1089
987	ev_init (&stdin_watcher, my_cb);	1090	ev_init (&stdin_watcher, my_cb);
988	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1091	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
989	ev_io_start (loop, &stdin_watcher);	1092	ev_io_start (loop, &stdin_watcher);
990		1093
991	ev_loop (loop, 0);	1094	ev_run (loop, 0);
992		1095
993	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
994	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
995	stack).	1098	stack).
996		1099
997	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>
998	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).
999		1102
1000	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
1001	(watcher *, callback)>, which expects a callback to be provided. This	1104	*, callback)>, which expects a callback to be provided. This callback is
1002	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
1003	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
1004	is readable and/or writable).	1107	and/or writable).
1005		1108
1006	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 *, ...) >>
1007	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
1008	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<<
1009	ev_TYPE_init (watcher *, callback, ...) >>.	1112	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
1032	=item C<EV_WRITE>	1135	=item C<EV_WRITE>
1033		1136
1034	The file descriptor in the C<ev_io> watcher has become readable and/or	1137	The file descriptor in the C<ev_io> watcher has become readable and/or
1035	writable.	1138	writable.
1036		1139
1037	=item C<EV_TIMEOUT>	1140	=item C<EV_TIMER>
1038		1141
1039	The C<ev_timer> watcher has timed out.	1142	The C<ev_timer> watcher has timed out.
1040		1143
1041	=item C<EV_PERIODIC>	1144	=item C<EV_PERIODIC>
1042		1145
…		…
1060		1163
1061	=item C<EV_PREPARE>	1164	=item C<EV_PREPARE>
1062		1165
1063	=item C<EV_CHECK>	1166	=item C<EV_CHECK>
1064		1167
1065	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
1066	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
1067	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
1068	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
1069	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
1070	(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
1071	C<ev_loop> from blocking).	1174	C<ev_run> from blocking).
1072		1175
1073	=item C<EV_EMBED>	1176	=item C<EV_EMBED>
1074		1177
1075	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.
1076		1179
1077	=item C<EV_FORK>	1180	=item C<EV_FORK>
1078		1181
1079	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
1080	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>).
1081		1188
1082	=item C<EV_ASYNC>	1189	=item C<EV_ASYNC>
1083		1190
1084	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>).
1085		1192
…		…
1258	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
1259	functions that do not need a watcher.	1366	functions that do not need a watcher.
1260		1367
1261	=back	1368	=back
1262		1369
		1370	See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR
		1371	OWN COMPOSITE WATCHERS> idioms.
1263		1372
1264	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1373	=head2 WATCHER STATES
1265		1374
1266	Each watcher has, by default, a member C<void *data> that you can change	1375	There are various watcher states mentioned throughout this manual -
1267	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
1268	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
1269	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".
1270	member, you can also "subclass" the watcher type and provide your own
1271	data:
1272		1379
1273	struct my_io	1380	=over 4
1274	{
1275	ev_io io;
1276	int otherfd;
1277	void *somedata;
1278	struct whatever *mostinteresting;
1279	};
1280		1381
1281	...	1382	=item initialiased
1282	struct my_io w;
1283	ev_io_init (&w.io, my_cb, fd, EV_READ);
1284		1383
1285	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
1286	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.
1287		1387
1288	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
1289	{	1389	use in an event loop. It can be moved around, freed, reused etc. at
1290	struct my_io *w = (struct my_io *)w_;	1390	will - as long as you either keep the memory contents intact, or call
1291	...	1391	C<ev_TYPE_init> again.
1292	}
1293		1392
1294	More interesting and less C-conformant ways of casting your callback type	1393	=item started/running/active
1295	instead have been omitted.
1296		1394
1297	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
1298	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.
1299		1400
1300	struct my_biggy	1401	=item pending
1301	{
1302	int some_data;
1303	ev_timer t1;
1304	ev_timer t2;
1305	}
1306		1402
1307	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
1308	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
1309	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
1310	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
1311	programmers):	1407	callback.
1312		1408
1313	#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.
1314		1415
1315	static void	1416	It is also possible to feed an event on a watcher that is not active (e.g.
1316	t1_cb (EV_P_ ev_timer *w, int revents)	1417	via C<ev_feed_event>), in which case it becomes pending without being
1317	{	1418	active.
1318	struct my_biggy big = (struct my_biggy *)
1319	(((char *)w) - offsetof (struct my_biggy, t1));
1320	}
1321		1419
1322	static void	1420	=item stopped
1323	t2_cb (EV_P_ ev_timer *w, int revents)	1421
1324	{	1422	A watcher can be stopped implicitly by libev (in which case it might still
1325	struct my_biggy big = (struct my_biggy *)	1423	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1326	(((char *)w) - offsetof (struct my_biggy, t2));	1424	latter will clear any pending state the watcher might be in, regardless
1327	}	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
1328		1434
1329	=head2 WATCHER PRIORITY MODELS	1435	=head2 WATCHER PRIORITY MODELS
1330		1436
1331	Many event loops support I<watcher priorities>, which are usually small	1437	Many event loops support I<watcher priorities>, which are usually small
1332	integers that influence the ordering of event callback invocation	1438	integers that influence the ordering of event callback invocation
…		…
1375		1481
1376	For example, to emulate how many other event libraries handle priorities,	1482	For example, to emulate how many other event libraries handle priorities,
1377	you can associate an C<ev_idle> watcher to each such watcher, and in	1483	you can associate an C<ev_idle> watcher to each such watcher, and in
1378	the normal watcher callback, you just start the idle watcher. The real	1484	the normal watcher callback, you just start the idle watcher. The real
1379	processing is done in the idle watcher callback. This causes libev to	1485	processing is done in the idle watcher callback. This causes libev to
1380	continously poll and process kernel event data for the watcher, but when	1486	continuously poll and process kernel event data for the watcher, but when
1381	the lock-out case is known to be rare (which in turn is rare :), this is	1487	the lock-out case is known to be rare (which in turn is rare :), this is
1382	workable.	1488	workable.
1383		1489
1384	Usually, however, the lock-out model implemented that way will perform	1490	Usually, however, the lock-out model implemented that way will perform
1385	miserably under the type of load it was designed to handle. In that case,	1491	miserably under the type of load it was designed to handle. In that case,
…		…
1399	{	1505	{
1400	// stop the I/O watcher, we received the event, but	1506	// stop the I/O watcher, we received the event, but
1401	// are not yet ready to handle it.	1507	// are not yet ready to handle it.
1402	ev_io_stop (EV_A_ w);	1508	ev_io_stop (EV_A_ w);
1403		1509
1404	// start the idle watcher to ahndle the actual event.	1510	// start the idle watcher to handle the actual event.
1405	// it will not be executed as long as other watchers	1511	// it will not be executed as long as other watchers
1406	// with the default priority are receiving events.	1512	// with the default priority are receiving events.
1407	ev_idle_start (EV_A_ &idle);	1513	ev_idle_start (EV_A_ &idle);
1408	}	1514	}
1409		1515
…		…
1459	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
1460	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
1461	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
1462	required if you know what you are doing).	1568	required if you know what you are doing).
1463		1569
1464	If you cannot use non-blocking mode, then force the use of a
1465	known-to-be-good backend (at the time of this writing, this includes only
1466	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1467	descriptors for which non-blocking operation makes no sense (such as
1468	files) - libev doesn't guarentee any specific behaviour in that case.
1469
1470	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
1471	receive "spurious" readiness notifications, that is your callback might	1571	receive "spurious" readiness notifications, that is, your callback might
1472	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
1473	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
1474	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
1475	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
1476	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1477	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1576	preferable to a program hanging until some data arrives.
1478		1577
1479	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
1480	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
1481	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
1482	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
1483	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
1484	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
1485	indefinitely.	1584	indefinitely.
1486		1585
1487	But really, best use non-blocking mode.	1586	But really, best use non-blocking mode.
1488		1587
…		…
1516		1615
1517	There is no workaround possible except not registering events	1616	There is no workaround possible except not registering events
1518	for potentially C<dup ()>'ed file descriptors, or to resort to	1617	for potentially C<dup ()>'ed file descriptors, or to resort to
1519	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1618	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1520		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
1521	=head3 The special problem of fork	1653	=head3 The special problem of fork
1522		1654
1523	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
1524	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
1525	it in the child.	1657	it in the child if you want to continue to use it in the child.
1526		1658
1527	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
1528	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
1529	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1661	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1530	C<EVBACKEND_POLL>.
1531		1662
1532	=head3 The special problem of SIGPIPE	1663	=head3 The special problem of SIGPIPE
1533		1664
1534	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>:
1535	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
…		…
1538		1669
1539	So when you encounter spurious, unexplained daemon exits, make sure you	1670	So when you encounter spurious, unexplained daemon exits, make sure you
1540	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1671	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1541	somewhere, as that would have given you a big clue).	1672	somewhere, as that would have given you a big clue).
1542		1673
		1674	=head3 The special problem of accept()ing when you can't
		1675
		1676	Many implementations of the POSIX C<accept> function (for example,
		1677	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1678	connection from the pending queue in all error cases.
		1679
		1680	For example, larger servers often run out of file descriptors (because
		1681	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1682	rejecting the connection, leading to libev signalling readiness on
		1683	the next iteration again (the connection still exists after all), and
		1684	typically causing the program to loop at 100% CPU usage.
		1685
		1686	Unfortunately, the set of errors that cause this issue differs between
		1687	operating systems, there is usually little the app can do to remedy the
		1688	situation, and no known thread-safe method of removing the connection to
		1689	cope with overload is known (to me).
		1690
		1691	One of the easiest ways to handle this situation is to just ignore it
		1692	- when the program encounters an overload, it will just loop until the
		1693	situation is over. While this is a form of busy waiting, no OS offers an
		1694	event-based way to handle this situation, so it's the best one can do.
		1695
		1696	A better way to handle the situation is to log any errors other than
		1697	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1698	messages, and continue as usual, which at least gives the user an idea of
		1699	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1700	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1701	usage.
		1702
		1703	If your program is single-threaded, then you could also keep a dummy file
		1704	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1705	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1706	close that fd, and create a new dummy fd. This will gracefully refuse
		1707	clients under typical overload conditions.
		1708
		1709	The last way to handle it is to simply log the error and C<exit>, as
		1710	is often done with C<malloc> failures, but this results in an easy
		1711	opportunity for a DoS attack.
1543		1712
1544	=head3 Watcher-Specific Functions	1713	=head3 Watcher-Specific Functions
1545		1714
1546	=over 4	1715	=over 4
1547		1716
…		…
1579	...	1748	...
1580	struct ev_loop *loop = ev_default_init (0);	1749	struct ev_loop *loop = ev_default_init (0);
1581	ev_io stdin_readable;	1750	ev_io stdin_readable;
1582	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);
1583	ev_io_start (loop, &stdin_readable);	1752	ev_io_start (loop, &stdin_readable);
1584	ev_loop (loop, 0);	1753	ev_run (loop, 0);
1585		1754
1586		1755
1587	=head2 C<ev_timer> - relative and optionally repeating timeouts	1756	=head2 C<ev_timer> - relative and optionally repeating timeouts
1588		1757
1589	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
…		…
1598	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
1599	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
1600	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
1601	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
1602	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
1603	no longer true when a callback calls C<ev_loop> recursively).	1772	no longer true when a callback calls C<ev_run> recursively).
1604		1773
1605	=head3 Be smart about timeouts	1774	=head3 Be smart about timeouts
1606		1775
1607	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
1608	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,
…		…
1694	ev_tstamp timeout = last_activity + 60.;	1863	ev_tstamp timeout = last_activity + 60.;
1695		1864
1696	// if last_activity + 60. is older than now, we did time out	1865	// if last_activity + 60. is older than now, we did time out
1697	if (timeout < now)	1866	if (timeout < now)
1698	{	1867	{
1699	// timeout occured, take action	1868	// timeout occurred, take action
1700	}	1869	}
1701	else	1870	else
1702	{	1871	{
1703	// callback was invoked, but there was some activity, re-arm	1872	// callback was invoked, but there was some activity, re-arm
1704	// the watcher to fire in last_activity + 60, which is	1873	// the watcher to fire in last_activity + 60, which is
…		…
1726	to the current time (meaning we just have some activity :), then call the	1895	to the current time (meaning we just have some activity :), then call the
1727	callback, which will "do the right thing" and start the timer:	1896	callback, which will "do the right thing" and start the timer:
1728		1897
1729	ev_init (timer, callback);	1898	ev_init (timer, callback);
1730	last_activity = ev_now (loop);	1899	last_activity = ev_now (loop);
1731	callback (loop, timer, EV_TIMEOUT);	1900	callback (loop, timer, EV_TIMER);
1732		1901
1733	And when there is some activity, simply store the current time in	1902	And when there is some activity, simply store the current time in
1734	C<last_activity>, no libev calls at all:	1903	C<last_activity>, no libev calls at all:
1735		1904
1736	last_actiivty = ev_now (loop);	1905	last_activity = ev_now (loop);
1737		1906
1738	This technique is slightly more complex, but in most cases where the	1907	This technique is slightly more complex, but in most cases where the
1739	time-out is unlikely to be triggered, much more efficient.	1908	time-out is unlikely to be triggered, much more efficient.
1740		1909
1741	Changing the timeout is trivial as well (if it isn't hard-coded in the	1910	Changing the timeout is trivial as well (if it isn't hard-coded in the
…		…
1779		1948
1780	=head3 The special problem of time updates	1949	=head3 The special problem of time updates
1781		1950
1782	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
1783	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
1784	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
1785	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
1786	lots of events in one iteration.	1955	lots of events in one iteration.
1787		1956
1788	The relative timeouts are calculated relative to the C<ev_now ()>	1957	The relative timeouts are calculated relative to the C<ev_now ()>
1789	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
…		…
1906	}	2075	}
1907		2076
1908	ev_timer mytimer;	2077	ev_timer mytimer;
1909	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 */
1910	ev_timer_again (&mytimer); /* start timer */	2079	ev_timer_again (&mytimer); /* start timer */
1911	ev_loop (loop, 0);	2080	ev_run (loop, 0);
1912		2081
1913	// 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":
1914	// reset the timeout to start ticking again at 10 seconds	2083	// reset the timeout to start ticking again at 10 seconds
1915	ev_timer_again (&mytimer);	2084	ev_timer_again (&mytimer);
1916		2085
…		…
1942		2111
1943	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
1944	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
1945	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
1946	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
1947	(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).
1948		2117
1949	=head3 Watcher-Specific Functions and Data Members	2118	=head3 Watcher-Specific Functions and Data Members
1950		2119
1951	=over 4	2120	=over 4
1952		2121
…		…
1987		2156
1988	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
1989	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
1990	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.
1991		2160
1992	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
1993	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
1994	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.
1995		2167
1996	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
1997	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
1998	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
1999	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).
…		…
2080	Example: Call a callback every hour, or, more precisely, whenever the	2252	Example: Call a callback every hour, or, more precisely, whenever the
2081	system time is divisible by 3600. The callback invocation times have	2253	system time is divisible by 3600. The callback invocation times have
2082	potentially a lot of jitter, but good long-term stability.	2254	potentially a lot of jitter, but good long-term stability.
2083		2255
2084	static void	2256	static void
2085	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2257	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
2086	{	2258	{
2087	... its now a full hour (UTC, or TAI or whatever your clock follows)	2259	... its now a full hour (UTC, or TAI or whatever your clock follows)
2088	}	2260	}
2089		2261
2090	ev_periodic hourly_tick;	2262	ev_periodic hourly_tick;
…		…
2113		2285
2114	=head2 C<ev_signal> - signal me when a signal gets signalled!	2286	=head2 C<ev_signal> - signal me when a signal gets signalled!
2115		2287
2116	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
2117	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
2118	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
2119	normal event processing, like any other event.	2291	normal event processing, like any other event.
2120		2292
2121	If you want signals to be delivered truly asynchronously, just use	2293	If you want signals to be delivered truly asynchronously, just use
2122	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
2123	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
…		…
2142	=head3 The special problem of inheritance over fork/execve/pthread_create	2314	=head3 The special problem of inheritance over fork/execve/pthread_create
2143		2315
2144	Both the signal mask (C<sigprocmask>) and the signal disposition	2316	Both the signal mask (C<sigprocmask>) and the signal disposition
2145	(C<sigaction>) are unspecified after starting a signal watcher (and after	2317	(C<sigaction>) are unspecified after starting a signal watcher (and after
2146	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,
2147	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>).
2148		2321
2149	While this does not matter for the signal disposition (libev never	2322	While this does not matter for the signal disposition (libev never
2150	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
2151	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
2152	certain signals to be blocked.	2325	certain signals to be blocked.
…		…
2166		2339
2167	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
2168	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
2169	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.
2170		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
2171	=head3 Watcher-Specific Functions and Data Members	2358	=head3 Watcher-Specific Functions and Data Members
2172		2359
2173	=over 4	2360	=over 4
2174		2361
2175	=item ev_signal_init (ev_signal *, callback, int signum)	2362	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
2190	Example: Try to exit cleanly on SIGINT.	2377	Example: Try to exit cleanly on SIGINT.
2191		2378
2192	static void	2379	static void
2193	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2380	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2194	{	2381	{
2195	ev_unloop (loop, EVUNLOOP_ALL);	2382	ev_break (loop, EVBREAK_ALL);
2196	}	2383	}
2197		2384
2198	ev_signal signal_watcher;	2385	ev_signal signal_watcher;
2199	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2386	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2200	ev_signal_start (loop, &signal_watcher);	2387	ev_signal_start (loop, &signal_watcher);
…		…
2586		2773
2587	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:
2588	prepare watchers get invoked before the process blocks and check watchers	2775	prepare watchers get invoked before the process blocks and check watchers
2589	afterwards.	2776	afterwards.
2590		2777
2591	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
2592	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>
2593	watchers. Other loops than the current one are fine, however. The	2780	watchers. Other loops than the current one are fine, however. The
2594	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
2595	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,
2596	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
…		…
2764		2951
2765	if (timeout >= 0)	2952	if (timeout >= 0)
2766	// create/start timer	2953	// create/start timer
2767		2954
2768	// poll	2955	// poll
2769	ev_loop (EV_A_ 0);	2956	ev_run (EV_A_ 0);
2770		2957
2771	// stop timer again	2958	// stop timer again
2772	if (timeout >= 0)	2959	if (timeout >= 0)
2773	ev_timer_stop (EV_A_ &to);	2960	ev_timer_stop (EV_A_ &to);
2774		2961
…		…
2852	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).
2853		3040
2854	=item ev_embed_sweep (loop, ev_embed *)	3041	=item ev_embed_sweep (loop, ev_embed *)
2855		3042
2856	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
2857	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
2858	appropriate way for embedded loops.	3045	appropriate way for embedded loops.
2859		3046
2860	=item struct ev_loop *other [read-only]	3047	=item struct ev_loop *other [read-only]
2861		3048
2862	The embedded event loop.	3049	The embedded event loop.
…		…
2922	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3109	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2923	handlers will be invoked, too, of course.	3110	handlers will be invoked, too, of course.
2924		3111
2925	=head3 The special problem of life after fork - how is it possible?	3112	=head3 The special problem of life after fork - how is it possible?
2926		3113
2927	Most uses of C<fork()> consist of forking, then some simple calls to ste	3114	Most uses of C<fork()> consist of forking, then some simple calls to set
2928	up/change the process environment, followed by a call to C<exec()>. This	3115	up/change the process environment, followed by a call to C<exec()>. This
2929	sequence should be handled by libev without any problems.	3116	sequence should be handled by libev without any problems.
2930		3117
2931	This changes when the application actually wants to do event handling	3118	This changes when the application actually wants to do event handling
2932	in the child, or both parent in child, in effect "continuing" after the	3119	in the child, or both parent in child, in effect "continuing" after the
…		…
2948	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
2949	signal watchers).	3136	signal watchers).
2950		3137
2951	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
2952	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
2953	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3140	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
2954	the default loop will "orphan" (not stop) all registered watchers, so you	3141	Destroying the default loop will "orphan" (not stop) all registered
2955	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
2956	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.
2957		3145
2958	=head3 Watcher-Specific Functions and Data Members	3146	=head3 Watcher-Specific Functions and Data Members
2959		3147
2960	=over 4	3148	=over 4
2961		3149
2962	=item ev_fork_init (ev_signal *, callback)	3150	=item ev_fork_init (ev_fork *, callback)
2963		3151
2964	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
2965	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,
2966	believe me.	3154	really.
2967		3155
2968	=back	3156	=back
2969		3157
2970		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);
		3197
		3198
2971	=head2 C<ev_async> - how to wake up another event loop	3199	=head2 C<ev_async> - how to wake up an event loop
2972		3200
2973	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
2974	asynchronous sources such as signal handlers (as opposed to multiple event	3202	asynchronous sources such as signal handlers (as opposed to multiple event
2975	loops - those are of course safe to use in different threads).	3203	loops - those are of course safe to use in different threads).
2976		3204
2977	Sometimes, however, you need to wake up another event loop you do not	3205	Sometimes, however, you need to wake up an event loop you do not control,
2978	control, for example because it belongs to another thread. This is what	3206	for example because it belongs to another thread. This is what C<ev_async>
2979	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3207	watchers do: as long as the C<ev_async> watcher is active, you can signal
2980	can signal it by calling C<ev_async_send>, which is thread- and signal	3208	it by calling C<ev_async_send>, which is thread- and signal safe.
2981	safe.
2982		3209
2983	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,
2984	too, are asynchronous in nature, and signals, too, will be compressed	3211	too, are asynchronous in nature, and signals, too, will be compressed
2985	(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
2986	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.
2987		3217
2988	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
2989	just the default loop.	3219	just the default loop.
2990		3220
2991	=head3 Queueing	3221	=head3 Queueing
…		…
3086	trust me.	3316	trust me.
3087		3317
3088	=item ev_async_send (loop, ev_async *)	3318	=item ev_async_send (loop, ev_async *)
3089		3319
3090	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
3091	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
3092	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,
3093	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
3094	section below on what exactly this means).	3326	embedding section below on what exactly this means).
3095		3327
3096	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
3097	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
3098	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>,
3099	reset when the event loop detects that).	3331	reset when the event loop detects that).
…		…
3141		3373
3142	If C<timeout> is less than 0, then no timeout watcher will be	3374	If C<timeout> is less than 0, then no timeout watcher will be
3143	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3375	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
3144	repeat = 0) will be started. C<0> is a valid timeout.	3376	repeat = 0) will be started. C<0> is a valid timeout.
3145		3377
3146	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3378	The callback has the type C<void (*cb)(int revents, void *arg)> and is
3147	passed an C<revents> set like normal event callbacks (a combination of	3379	passed an C<revents> set like normal event callbacks (a combination of
3148	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3380	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
3149	value passed to C<ev_once>. Note that it is possible to receive I<both>	3381	value passed to C<ev_once>. Note that it is possible to receive I<both>
3150	a timeout and an io event at the same time - you probably should give io	3382	a timeout and an io event at the same time - you probably should give io
3151	events precedence.	3383	events precedence.
3152		3384
3153	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3385	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
3154		3386
3155	static void stdin_ready (int revents, void *arg)	3387	static void stdin_ready (int revents, void *arg)
3156	{	3388	{
3157	if (revents & EV_READ)	3389	if (revents & EV_READ)
3158	/* stdin might have data for us, joy! */;	3390	/* stdin might have data for us, joy! */;
3159	else if (revents & EV_TIMEOUT)	3391	else if (revents & EV_TIMER)
3160	/* doh, nothing entered */;	3392	/* doh, nothing entered */;
3161	}	3393	}
3162		3394
3163	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3395	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3164		3396
…		…
3167	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
3168	the given events it.	3400	the given events it.
3169		3401
3170	=item ev_feed_signal_event (loop, int signum)	3402	=item ev_feed_signal_event (loop, int signum)
3171		3403
3172	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>,
3173	loop!).	3405	which is async-safe.
3174		3406
3175	=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.
3176		3718
3177		3719
3178	=head1 LIBEVENT EMULATION	3720	=head1 LIBEVENT EMULATION
3179		3721
3180	Libev offers a compatibility emulation layer for libevent. It cannot	3722	Libev offers a compatibility emulation layer for libevent. It cannot
3181	emulate the internals of libevent, so here are some usage hints:	3723	emulate the internals of libevent, so here are some usage hints:
3182		3724
3183	=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.
3184		3731
3185	=item * Use it by including <event.h>, as usual.	3732	=item * Use it by including <event.h>, as usual.
3186		3733
3187	=item * The following members are fully supported: ev_base, ev_callback,	3734	=item * The following members are fully supported: ev_base, ev_callback,
3188	ev_arg, ev_fd, ev_res, ev_events.	3735	ev_arg, ev_fd, ev_res, ev_events.
…		…
3194	=item * Priorities are not currently supported. Initialising priorities	3741	=item * Priorities are not currently supported. Initialising priorities
3195	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
3196	is an ev_pri field.	3743	is an ev_pri field.
3197		3744
3198	=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
3199	first base created (== the default loop) gets the signals.	3746	base that registered the signal gets the signals.
3200		3747
3201	=item * Other members are not supported.	3748	=item * Other members are not supported.
3202		3749
3203	=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
3204	to use the libev header file and library.	3751	to use the libev header file and library.
…		…
3223	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++
3224	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
3225	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
3226	you disable C<EV_MULTIPLICITY> when embedding libev).	3773	you disable C<EV_MULTIPLICITY> when embedding libev).
3227		3774
3228	Currently, functions, and static and non-static member functions can be	3775	Currently, functions, static and non-static member functions and classes
3229	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
3230	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
3231	types of functors please contact the author (preferably after implementing	3778	you need support for other types of functors please contact the author
3232	it).	3779	(preferably after implementing it).
3233		3780
3234	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:
3235		3782
3236	=over 4	3783	=over 4
3237		3784
…		…
3298	myclass obj;	3845	myclass obj;
3299	ev::io iow;	3846	ev::io iow;
3300	iow.set <myclass, &myclass::io_cb> (&obj);	3847	iow.set <myclass, &myclass::io_cb> (&obj);
3301		3848
3302	=item w->set (object *)	3849	=item w->set (object *)
3303
3304	This is an B<experimental> feature that might go away in a future version.
3305		3850
3306	This is a variation of a method callback - leaving out the method to call	3851	This is a variation of a method callback - leaving out the method to call
3307	will default the method to C<operator ()>, which makes it possible to use	3852	will default the method to C<operator ()>, which makes it possible to use
3308	functor objects without having to manually specify the C<operator ()> all	3853	functor objects without having to manually specify the C<operator ()> all
3309	the time. Incidentally, you can then also leave out the template argument	3854	the time. Incidentally, you can then also leave out the template argument
…		…
3349	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
3350	do this when the watcher is inactive (and not pending either).	3895	do this when the watcher is inactive (and not pending either).
3351		3896
3352	=item w->set ([arguments])	3897	=item w->set ([arguments])
3353		3898
3354	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
3355	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
3356	automatically stopped and restarted when reconfiguring it with this	3901	C counterpart, an active watcher gets automatically stopped and restarted
3357	method.	3902	when reconfiguring it with this method.
3358		3903
3359	=item w->start ()	3904	=item w->start ()
3360		3905
3361	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
3362	constructor already stores the event loop.	3907	constructor already stores the event loop.
3363		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
3364	=item w->stop ()	3915	=item w->stop ()
3365		3916
3366	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.
3367		3918
3368	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3919	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3380		3931
3381	=back	3932	=back
3382		3933
3383	=back	3934	=back
3384		3935
3385	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
3386	the constructor.	3937	watchers in the constructor.
3387		3938
3388	class myclass	3939	class myclass
3389	{	3940	{
3390	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);
3391	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3943	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3392		3944
3393	myclass (int fd)	3945	myclass (int fd)
3394	{	3946	{
3395	io .set <myclass, &myclass::io_cb > (this);	3947	io .set <myclass, &myclass::io_cb > (this);
		3948	io2 .set <myclass, &myclass::io2_cb > (this);
3396	idle.set <myclass, &myclass::idle_cb> (this);	3949	idle.set <myclass, &myclass::idle_cb> (this);
3397		3950
3398	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
3399	}	3955	}
3400	};	3956	};
3401		3957
3402		3958
3403	=head1 OTHER LANGUAGE BINDINGS	3959	=head1 OTHER LANGUAGE BINDINGS
…		…
3477	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,
3478	C<EV_A_> is used when other arguments are following. Example:	4034	C<EV_A_> is used when other arguments are following. Example:
3479		4035
3480	ev_unref (EV_A);	4036	ev_unref (EV_A);
3481	ev_timer_add (EV_A_ watcher);	4037	ev_timer_add (EV_A_ watcher);
3482	ev_loop (EV_A_ 0);	4038	ev_run (EV_A_ 0);
3483		4039
3484	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,
3485	which is often provided by the following macro.	4041	which is often provided by the following macro.
3486		4042
3487	=item C<EV_P>, C<EV_P_>	4043	=item C<EV_P>, C<EV_P_>
…		…
3527	}	4083	}
3528		4084
3529	ev_check check;	4085	ev_check check;
3530	ev_check_init (&check, check_cb);	4086	ev_check_init (&check, check_cb);
3531	ev_check_start (EV_DEFAULT_ &check);	4087	ev_check_start (EV_DEFAULT_ &check);
3532	ev_loop (EV_DEFAULT_ 0);	4088	ev_run (EV_DEFAULT_ 0);
3533		4089
3534	=head1 EMBEDDING	4090	=head1 EMBEDDING
3535		4091
3536	Libev can (and often is) directly embedded into host	4092	Libev can (and often is) directly embedded into host
3537	applications. Examples of applications that embed it include the Deliantra	4093	applications. Examples of applications that embed it include the Deliantra
…		…
3622	define before including (or compiling) any of its files. The default in	4178	define before including (or compiling) any of its files. The default in
3623	the absence of autoconf is documented for every option.	4179	the absence of autoconf is documented for every option.
3624		4180
3625	Symbols marked with "(h)" do not change the ABI, and can have different	4181	Symbols marked with "(h)" do not change the ABI, and can have different
3626	values when compiling libev vs. including F<ev.h>, so it is permissible	4182	values when compiling libev vs. including F<ev.h>, so it is permissible
3627	to redefine them before including F<ev.h> without breakign compatibility	4183	to redefine them before including F<ev.h> without breaking compatibility
3628	to a compiled library. All other symbols change the ABI, which means all	4184	to a compiled library. All other symbols change the ABI, which means all
3629	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
3630	settings.	4186	settings.
3631		4187
3632	=over 4	4188	=over 4
		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.
3633		4205
3634	=item EV_STANDALONE (h)	4206	=item EV_STANDALONE (h)
3635		4207
3636	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
3637	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
…		…
3639	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
3640	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.
3641		4213
3642	In standalone mode, libev will still try to automatically deduce the	4214	In standalone mode, libev will still try to automatically deduce the
3643	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.
3644		4225
3645	=item EV_USE_MONOTONIC	4226	=item EV_USE_MONOTONIC
3646		4227
3647	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
3648	monotonic clock option at both compile time and runtime. Otherwise no	4229	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3838	fine.	4419	fine.
3839		4420
3840	If your embedding application does not need any priorities, defining these	4421	If your embedding application does not need any priorities, defining these
3841	both to C<0> will save some memory and CPU.	4422	both to C<0> will save some memory and CPU.
3842		4423
3843	=item EV_PERIODIC_ENABLE	4424	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4425	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4426	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3844		4427
3845	If undefined or defined to be C<1>, then periodic timers are supported. If	4428	If undefined or defined to be C<1> (and the platform supports it), then
3846	defined to be C<0>, then they are not. Disabling them saves a few kB of	4429	the respective watcher type is supported. If defined to be C<0>, then it
3847	code.	4430	is not. Disabling watcher types mainly saves code size.
3848		4431
3849	=item EV_IDLE_ENABLE	4432	=item EV_FEATURES
3850
3851	If undefined or defined to be C<1>, then idle watchers are supported. If
3852	defined to be C<0>, then they are not. Disabling them saves a few kB of
3853	code.
3854
3855	=item EV_EMBED_ENABLE
3856
3857	If undefined or defined to be C<1>, then embed watchers are supported. If
3858	defined to be C<0>, then they are not. Embed watchers rely on most other
3859	watcher types, which therefore must not be disabled.
3860
3861	=item EV_STAT_ENABLE
3862
3863	If undefined or defined to be C<1>, then stat watchers are supported. If
3864	defined to be C<0>, then they are not.
3865
3866	=item EV_FORK_ENABLE
3867
3868	If undefined or defined to be C<1>, then fork watchers are supported. If
3869	defined to be C<0>, then they are not.
3870
3871	=item EV_SIGNAL_ENABLE
3872
3873	If undefined or defined to be C<1>, then signal watchers are supported. If
3874	defined to be C<0>, then they are not.
3875
3876	=item EV_ASYNC_ENABLE
3877
3878	If undefined or defined to be C<1>, then async watchers are supported. If
3879	defined to be C<0>, then they are not.
3880
3881	=item EV_CHILD_ENABLE
3882
3883	If undefined or defined to be C<1> (and C<_WIN32> is not defined), then
3884	child watchers are supported. If defined to be C<0>, then they are not.
3885
3886	=item EV_MINIMAL
3887		4433
3888	If you need to shave off some kilobytes of code at the expense of some	4434	If you need to shave off some kilobytes of code at the expense of some
3889	speed (but with the full API), define this symbol to C<1>. Currently this	4435	speed (but with the full API), you can define this symbol to request
3890	is used to override some inlining decisions, saves roughly 30% code size	4436	certain subsets of functionality. The default is to enable all features
3891	on amd64. It also selects a much smaller 2-heap for timer management over	4437	that can be enabled on the platform.
3892	the default 4-heap.
3893		4438
3894	You can save even more by disabling watcher types you do not need	4439	A typical way to use this symbol is to define it to C<0> (or to a bitset
3895	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>	4440	with some broad features you want) and then selectively re-enable
3896	(C<-DNDEBUG>) will usually reduce code size a lot. Disabling inotify,	4441	additional parts you want, for example if you want everything minimal,
3897	eventfd and signalfd will further help, and disabling backends one doesn't	4442	but multiple event loop support, async and child watchers and the poll
3898	need (e.g. poll, epoll, kqueue, ports) will help further.	4443	backend, use this:
3899		4444
3900	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to	4445	#define EV_FEATURES 0
3901	provide a bare-bones event library. See C<ev.h> for details on what parts
3902	of the API are still available, and do not complain if this subset changes
3903	over time.
3904
3905	This example set of settings reduces the compiled size of libev from 24Kb
3906	to 8Kb on my GNU/Linux amd64 system (and leaves little in - there is also
3907	an effect on the amount of memory used). With an intelligent-enough linker
3908	further unused functions might be left out as well automatically.
3909
3910	// tuning and API changes
3911	#define EV_MINIMAL 2
3912	#define EV_MULTIPLICITY 0	4446	#define EV_MULTIPLICITY 1
3913	#define EV_MINPRI 0
3914	#define EV_MAXPRI 0
3915
3916	// OS-specific backends
3917	#define EV_USE_INOTIFY 0
3918	#define EV_USE_EVENTFD 0
3919	#define EV_USE_SIGNALFD 0
3920	#define EV_USE_REALTIME 0
3921	#define EV_USE_MONOTONIC 0
3922	#define EV_USE_CLOCK_SYSCALL 0
3923
3924	// disable all backends except select
3925	#define EV_USE_POLL 0	4447	#define EV_USE_POLL 1
3926	#define EV_USE_PORT 0
3927	#define EV_USE_KQUEUE 0
3928	#define EV_USE_EPOLL 0
3929
3930	// disable all watcher types that cna be disabled
3931	#define EV_STAT_ENABLE 0
3932	#define EV_PERIODIC_ENABLE 0
3933	#define EV_IDLE_ENABLE 0
3934	#define EV_FORK_ENABLE 0
3935	#define EV_SIGNAL_ENABLE 0
3936	#define EV_CHILD_ENABLE 0	4448	#define EV_CHILD_ENABLE 1
3937	#define EV_ASYNC_ENABLE 0	4449	#define EV_ASYNC_ENABLE 1
3938	#define EV_EMBED_ENABLE 0	4450
		4451	The actual value is a bitset, it can be a combination of the following
		4452	values:
		4453
		4454	=over 4
		4455
		4456	=item C<1> - faster/larger code
		4457
		4458	Use larger code to speed up some operations.
		4459
		4460	Currently this is used to override some inlining decisions (enlarging the
		4461	code size by roughly 30% on amd64).
		4462
		4463	When optimising for size, use of compiler flags such as C<-Os> with
		4464	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4465	assertions.
		4466
		4467	=item C<2> - faster/larger data structures
		4468
		4469	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4470	hash table sizes and so on. This will usually further increase code size
		4471	and can additionally have an effect on the size of data structures at
		4472	runtime.
		4473
		4474	=item C<4> - full API configuration
		4475
		4476	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4477	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4478
		4479	=item C<8> - full API
		4480
		4481	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4482	details on which parts of the API are still available without this
		4483	feature, and do not complain if this subset changes over time.
		4484
		4485	=item C<16> - enable all optional watcher types
		4486
		4487	Enables all optional watcher types. If you want to selectively enable
		4488	only some watcher types other than I/O and timers (e.g. prepare,
		4489	embed, async, child...) you can enable them manually by defining
		4490	C<EV_watchertype_ENABLE> to C<1> instead.
		4491
		4492	=item C<32> - enable all backends
		4493
		4494	This enables all backends - without this feature, you need to enable at
		4495	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4496
		4497	=item C<64> - enable OS-specific "helper" APIs
		4498
		4499	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4500	default.
		4501
		4502	=back
		4503
		4504	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4505	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4506	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4507	watchers, timers and monotonic clock support.
		4508
		4509	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4510	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4511	your program might be left out as well - a binary starting a timer and an
		4512	I/O watcher then might come out at only 5Kb.
3939		4513
3940	=item EV_AVOID_STDIO	4514	=item EV_AVOID_STDIO
3941		4515
3942	If this is set to C<1> at compiletime, then libev will avoid using stdio	4516	If this is set to C<1> at compiletime, then libev will avoid using stdio
3943	functions (printf, scanf, perror etc.). This will increase the codesize	4517	functions (printf, scanf, perror etc.). This will increase the code size
3944	somewhat, but if your program doesn't otherwise depend on stdio and your	4518	somewhat, but if your program doesn't otherwise depend on stdio and your
3945	libc allows it, this avoids linking in the stdio library which is quite	4519	libc allows it, this avoids linking in the stdio library which is quite
3946	big.	4520	big.
3947		4521
3948	Note that error messages might become less precise when this option is	4522	Note that error messages might become less precise when this option is
…		…
3952		4526
3953	The highest supported signal number, +1 (or, the number of	4527	The highest supported signal number, +1 (or, the number of
3954	signals): Normally, libev tries to deduce the maximum number of signals	4528	signals): Normally, libev tries to deduce the maximum number of signals
3955	automatically, but sometimes this fails, in which case it can be	4529	automatically, but sometimes this fails, in which case it can be
3956	specified. Also, using a lower number than detected (C<32> should be	4530	specified. Also, using a lower number than detected (C<32> should be
3957	good for about any system in existance) can save some memory, as libev	4531	good for about any system in existence) can save some memory, as libev
3958	statically allocates some 12-24 bytes per signal number.	4532	statically allocates some 12-24 bytes per signal number.
3959		4533
3960	=item EV_PID_HASHSIZE	4534	=item EV_PID_HASHSIZE
3961		4535
3962	C<ev_child> watchers use a small hash table to distribute workload by	4536	C<ev_child> watchers use a small hash table to distribute workload by
3963	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4537	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3964	than enough. If you need to manage thousands of children you might want to	4538	usually more than enough. If you need to manage thousands of children you
3965	increase this value (I<must> be a power of two).	4539	might want to increase this value (I<must> be a power of two).
3966		4540
3967	=item EV_INOTIFY_HASHSIZE	4541	=item EV_INOTIFY_HASHSIZE
3968		4542
3969	C<ev_stat> watchers use a small hash table to distribute workload by	4543	C<ev_stat> watchers use a small hash table to distribute workload by
3970	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4544	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3971	usually more than enough. If you need to manage thousands of C<ev_stat>	4545	disabled), usually more than enough. If you need to manage thousands of
3972	watchers you might want to increase this value (I<must> be a power of	4546	C<ev_stat> watchers you might want to increase this value (I<must> be a
3973	two).	4547	power of two).
3974		4548
3975	=item EV_USE_4HEAP	4549	=item EV_USE_4HEAP
3976		4550
3977	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4551	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3978	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4552	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3979	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4553	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3980	faster performance with many (thousands) of watchers.	4554	faster performance with many (thousands) of watchers.
3981		4555
3982	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4556	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3983	(disabled).	4557	will be C<0>.
3984		4558
3985	=item EV_HEAP_CACHE_AT	4559	=item EV_HEAP_CACHE_AT
3986		4560
3987	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4561	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3988	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4562	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3989	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4563	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3990	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4564	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3991	but avoids random read accesses on heap changes. This improves performance	4565	but avoids random read accesses on heap changes. This improves performance
3992	noticeably with many (hundreds) of watchers.	4566	noticeably with many (hundreds) of watchers.
3993		4567
3994	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4568	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3995	(disabled).	4569	will be C<0>.
3996		4570
3997	=item EV_VERIFY	4571	=item EV_VERIFY
3998		4572
3999	Controls how much internal verification (see C<ev_loop_verify ()>) will	4573	Controls how much internal verification (see C<ev_verify ()>) will
4000	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
4001	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
4002	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
4003	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
4004	verification code will be called very frequently, which will slow down	4578	verification code will be called very frequently, which will slow down
4005	libev considerably.	4579	libev considerably.
4006		4580
4007	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4581	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
4008	C<0>.	4582	will be C<0>.
4009		4583
4010	=item EV_COMMON	4584	=item EV_COMMON
4011		4585
4012	By default, all watchers have a C<void *data> member. By redefining	4586	By default, all watchers have a C<void *data> member. By redefining
4013	this macro to a something else you can include more and other types of	4587	this macro to something else you can include more and other types of
4014	members. You have to define it each time you include one of the files,	4588	members. You have to define it each time you include one of the files,
4015	though, and it must be identical each time.	4589	though, and it must be identical each time.
4016		4590
4017	For example, the perl EV module uses something like this:	4591	For example, the perl EV module uses something like this:
4018		4592
…		…
4071	file.	4645	file.
4072		4646
4073	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4647	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
4074	that everybody includes and which overrides some configure choices:	4648	that everybody includes and which overrides some configure choices:
4075		4649
4076	#define EV_MINIMAL 1	4650	#define EV_FEATURES 8
4077	#define EV_USE_POLL 0	4651	#define EV_USE_SELECT 1
4078	#define EV_MULTIPLICITY 0
4079	#define EV_PERIODIC_ENABLE 0	4652	#define EV_PREPARE_ENABLE 1
		4653	#define EV_IDLE_ENABLE 1
4080	#define EV_STAT_ENABLE 0	4654	#define EV_SIGNAL_ENABLE 1
4081	#define EV_FORK_ENABLE 0	4655	#define EV_CHILD_ENABLE 1
		4656	#define EV_USE_STDEXCEPT 0
4082	#define EV_CONFIG_H <config.h>	4657	#define EV_CONFIG_H <config.h>
4083	#define EV_MINPRI 0
4084	#define EV_MAXPRI 0
4085		4658
4086	#include "ev++.h"	4659	#include "ev++.h"
4087		4660
4088	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:
4089		4662
4090	#include "ev_cpp.h"	4663	#include "ev_cpp.h"
4091	#include "ev.c"	4664	#include "ev.c"
4092		4665
4093	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4666	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4094		4667
4095	=head2 THREADS AND COROUTINES	4668	=head2 THREADS AND COROUTINES
4096		4669
4097	=head3 THREADS	4670	=head3 THREADS
4098		4671
…		…
4149	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
4150	watcher callback into the event loop interested in the signal.	4723	watcher callback into the event loop interested in the signal.
4151		4724
4152	=back	4725	=back
4153		4726
4154	=head4 THREAD LOCKING EXAMPLE	4727	See also L<THREAD LOCKING EXAMPLE>.
4155
4156	Here is a fictitious example of how to run an event loop in a different
4157	thread than where callbacks are being invoked and watchers are
4158	created/added/removed.
4159
4160	For a real-world example, see the C<EV::Loop::Async> perl module,
4161	which uses exactly this technique (which is suited for many high-level
4162	languages).
4163
4164	The example uses a pthread mutex to protect the loop data, a condition
4165	variable to wait for callback invocations, an async watcher to notify the
4166	event loop thread and an unspecified mechanism to wake up the main thread.
4167
4168	First, you need to associate some data with the event loop:
4169
4170	typedef struct {
4171	mutex_t lock; /* global loop lock */
4172	ev_async async_w;
4173	thread_t tid;
4174	cond_t invoke_cv;
4175	} userdata;
4176
4177	void prepare_loop (EV_P)
4178	{
4179	// for simplicity, we use a static userdata struct.
4180	static userdata u;
4181
4182	ev_async_init (&u->async_w, async_cb);
4183	ev_async_start (EV_A_ &u->async_w);
4184
4185	pthread_mutex_init (&u->lock, 0);
4186	pthread_cond_init (&u->invoke_cv, 0);
4187
4188	// now associate this with the loop
4189	ev_set_userdata (EV_A_ u);
4190	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4191	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4192
4193	// then create the thread running ev_loop
4194	pthread_create (&u->tid, 0, l_run, EV_A);
4195	}
4196
4197	The callback for the C<ev_async> watcher does nothing: the watcher is used
4198	solely to wake up the event loop so it takes notice of any new watchers
4199	that might have been added:
4200
4201	static void
4202	async_cb (EV_P_ ev_async *w, int revents)
4203	{
4204	// just used for the side effects
4205	}
4206
4207	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4208	protecting the loop data, respectively.
4209
4210	static void
4211	l_release (EV_P)
4212	{
4213	userdata *u = ev_userdata (EV_A);
4214	pthread_mutex_unlock (&u->lock);
4215	}
4216
4217	static void
4218	l_acquire (EV_P)
4219	{
4220	userdata *u = ev_userdata (EV_A);
4221	pthread_mutex_lock (&u->lock);
4222	}
4223
4224	The event loop thread first acquires the mutex, and then jumps straight
4225	into C<ev_loop>:
4226
4227	void *
4228	l_run (void *thr_arg)
4229	{
4230	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4231
4232	l_acquire (EV_A);
4233	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4234	ev_loop (EV_A_ 0);
4235	l_release (EV_A);
4236
4237	return 0;
4238	}
4239
4240	Instead of invoking all pending watchers, the C<l_invoke> callback will
4241	signal the main thread via some unspecified mechanism (signals? pipe
4242	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4243	have been called (in a while loop because a) spurious wakeups are possible
4244	and b) skipping inter-thread-communication when there are no pending
4245	watchers is very beneficial):
4246
4247	static void
4248	l_invoke (EV_P)
4249	{
4250	userdata *u = ev_userdata (EV_A);
4251
4252	while (ev_pending_count (EV_A))
4253	{
4254	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4255	pthread_cond_wait (&u->invoke_cv, &u->lock);
4256	}
4257	}
4258
4259	Now, whenever the main thread gets told to invoke pending watchers, it
4260	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4261	thread to continue:
4262
4263	static void
4264	real_invoke_pending (EV_P)
4265	{
4266	userdata *u = ev_userdata (EV_A);
4267
4268	pthread_mutex_lock (&u->lock);
4269	ev_invoke_pending (EV_A);
4270	pthread_cond_signal (&u->invoke_cv);
4271	pthread_mutex_unlock (&u->lock);
4272	}
4273
4274	Whenever you want to start/stop a watcher or do other modifications to an
4275	event loop, you will now have to lock:
4276
4277	ev_timer timeout_watcher;
4278	userdata *u = ev_userdata (EV_A);
4279
4280	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4281
4282	pthread_mutex_lock (&u->lock);
4283	ev_timer_start (EV_A_ &timeout_watcher);
4284	ev_async_send (EV_A_ &u->async_w);
4285	pthread_mutex_unlock (&u->lock);
4286
4287	Note that sending the C<ev_async> watcher is required because otherwise
4288	an event loop currently blocking in the kernel will have no knowledge
4289	about the newly added timer. By waking up the loop it will pick up any new
4290	watchers in the next event loop iteration.
4291		4728
4292	=head3 COROUTINES	4729	=head3 COROUTINES
4293		4730
4294	Libev is very accommodating to coroutines ("cooperative threads"):	4731	Libev is very accommodating to coroutines ("cooperative threads"):
4295	libev fully supports nesting calls to its functions from different	4732	libev fully supports nesting calls to its functions from different
4296	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
4297	different coroutines, and switch freely between both coroutines running	4734	different coroutines, and switch freely between both coroutines running
4298	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
4299	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.
4300		4737
4301	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
4302	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
4303	they do not call any callbacks.	4740	they do not call any callbacks.
4304		4741
4305	=head2 COMPILER WARNINGS	4742	=head2 COMPILER WARNINGS
4306		4743
4307	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
…		…
4318	maintainable.	4755	maintainable.
4319		4756
4320	And of course, some compiler warnings are just plain stupid, or simply	4757	And of course, some compiler warnings are just plain stupid, or simply
4321	wrong (because they don't actually warn about the condition their message	4758	wrong (because they don't actually warn about the condition their message
4322	seems to warn about). For example, certain older gcc versions had some	4759	seems to warn about). For example, certain older gcc versions had some
4323	warnings that resulted an extreme number of false positives. These have	4760	warnings that resulted in an extreme number of false positives. These have
4324	been fixed, but some people still insist on making code warn-free with	4761	been fixed, but some people still insist on making code warn-free with
4325	such buggy versions.	4762	such buggy versions.
4326		4763
4327	While libev is written to generate as few warnings as possible,	4764	While libev is written to generate as few warnings as possible,
4328	"warn-free" code is not a goal, and it is recommended not to build libev	4765	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
4364	I suggest using suppression lists.	4801	I suggest using suppression lists.
4365		4802
4366		4803
4367	=head1 PORTABILITY NOTES	4804	=head1 PORTABILITY NOTES
4368		4805
		4806	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4807
		4808	GNU/Linux is the only common platform that supports 64 bit file/large file
		4809	interfaces but I<disables> them by default.
		4810
		4811	That means that libev compiled in the default environment doesn't support
		4812	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4813
		4814	Unfortunately, many programs try to work around this GNU/Linux issue
		4815	by enabling the large file API, which makes them incompatible with the
		4816	standard libev compiled for their system.
		4817
		4818	Likewise, libev cannot enable the large file API itself as this would
		4819	suddenly make it incompatible to the default compile time environment,
		4820	i.e. all programs not using special compile switches.
		4821
		4822	=head2 OS/X AND DARWIN BUGS
		4823
		4824	The whole thing is a bug if you ask me - basically any system interface
		4825	you touch is broken, whether it is locales, poll, kqueue or even the
		4826	OpenGL drivers.
		4827
		4828	=head3 C<kqueue> is buggy
		4829
		4830	The kqueue syscall is broken in all known versions - most versions support
		4831	only sockets, many support pipes.
		4832
		4833	Libev tries to work around this by not using C<kqueue> by default on this
		4834	rotten platform, but of course you can still ask for it when creating a
		4835	loop - embedding a socket-only kqueue loop into a select-based one is
		4836	probably going to work well.
		4837
		4838	=head3 C<poll> is buggy
		4839
		4840	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4841	implementation by something calling C<kqueue> internally around the 10.5.6
		4842	release, so now C<kqueue> I<and> C<poll> are broken.
		4843
		4844	Libev tries to work around this by not using C<poll> by default on
		4845	this rotten platform, but of course you can still ask for it when creating
		4846	a loop.
		4847
		4848	=head3 C<select> is buggy
		4849
		4850	All that's left is C<select>, and of course Apple found a way to fuck this
		4851	one up as well: On OS/X, C<select> actively limits the number of file
		4852	descriptors you can pass in to 1024 - your program suddenly crashes when
		4853	you use more.
		4854
		4855	There is an undocumented "workaround" for this - defining
		4856	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4857	work on OS/X.
		4858
		4859	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4860
		4861	=head3 C<errno> reentrancy
		4862
		4863	The default compile environment on Solaris is unfortunately so
		4864	thread-unsafe that you can't even use components/libraries compiled
		4865	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4866	defined by default. A valid, if stupid, implementation choice.
		4867
		4868	If you want to use libev in threaded environments you have to make sure
		4869	it's compiled with C<_REENTRANT> defined.
		4870
		4871	=head3 Event port backend
		4872
		4873	The scalable event interface for Solaris is called "event
		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
		4876	a large number of spurious wakeups, make sure you have all the relevant
		4877	and latest kernel patches applied. No, I don't know which ones, but there
		4878	are multiple ones to apply, and afterwards, event ports actually work
		4879	great.
		4880
		4881	If you can't get it to work, you can try running the program by setting
		4882	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4883	C<select> backends.
		4884
		4885	=head2 AIX POLL BUG
		4886
		4887	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4888	this by trying to avoid the poll backend altogether (i.e. it's not even
		4889	compiled in), which normally isn't a big problem as C<select> works fine
		4890	with large bitsets on AIX, and AIX is dead anyway.
		4891
4369	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4892	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4893
		4894	=head3 General issues
4370		4895
4371	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4896	Win32 doesn't support any of the standards (e.g. POSIX) that libev
4372	requires, and its I/O model is fundamentally incompatible with the POSIX	4897	requires, and its I/O model is fundamentally incompatible with the POSIX
4373	model. Libev still offers limited functionality on this platform in	4898	model. Libev still offers limited functionality on this platform in
4374	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4899	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4375	descriptors. This only applies when using Win32 natively, not when using	4900	descriptors. This only applies when using Win32 natively, not when using
4376	e.g. cygwin.	4901	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4902	as every compielr comes with a slightly differently broken/incompatible
		4903	environment.
4377		4904
4378	Lifting these limitations would basically require the full	4905	Lifting these limitations would basically require the full
4379	re-implementation of the I/O system. If you are into these kinds of	4906	re-implementation of the I/O system. If you are into this kind of thing,
4380	things, then note that glib does exactly that for you in a very portable	4907	then note that glib does exactly that for you in a very portable way (note
4381	way (note also that glib is the slowest event library known to man).	4908	also that glib is the slowest event library known to man).
4382		4909
4383	There is no supported compilation method available on windows except	4910	There is no supported compilation method available on windows except
4384	embedding it into other applications.	4911	embedding it into other applications.
4385		4912
4386	Sensible signal handling is officially unsupported by Microsoft - libev	4913	Sensible signal handling is officially unsupported by Microsoft - libev
…		…
4414	you do I<not> compile the F<ev.c> or any other embedded source files!):	4941	you do I<not> compile the F<ev.c> or any other embedded source files!):
4415		4942
4416	#include "evwrap.h"	4943	#include "evwrap.h"
4417	#include "ev.c"	4944	#include "ev.c"
4418		4945
4419	=over 4
4420
4421	=item The winsocket select function	4946	=head3 The winsocket C<select> function
4422		4947
4423	The winsocket C<select> function doesn't follow POSIX in that it	4948	The winsocket C<select> function doesn't follow POSIX in that it
4424	requires socket I<handles> and not socket I<file descriptors> (it is	4949	requires socket I<handles> and not socket I<file descriptors> (it is
4425	also extremely buggy). This makes select very inefficient, and also	4950	also extremely buggy). This makes select very inefficient, and also
4426	requires a mapping from file descriptors to socket handles (the Microsoft	4951	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
4435	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4960	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
4436		4961
4437	Note that winsockets handling of fd sets is O(n), so you can easily get a	4962	Note that winsockets handling of fd sets is O(n), so you can easily get a
4438	complexity in the O(n²) range when using win32.	4963	complexity in the O(n²) range when using win32.
4439		4964
4440	=item Limited number of file descriptors	4965	=head3 Limited number of file descriptors
4441		4966
4442	Windows has numerous arbitrary (and low) limits on things.	4967	Windows has numerous arbitrary (and low) limits on things.
4443		4968
4444	Early versions of winsocket's select only supported waiting for a maximum	4969	Early versions of winsocket's select only supported waiting for a maximum
4445	of C<64> handles (probably owning to the fact that all windows kernels	4970	of C<64> handles (probably owning to the fact that all windows kernels
…		…
4460	runtime libraries. This might get you to about C<512> or C<2048> sockets	4985	runtime libraries. This might get you to about C<512> or C<2048> sockets
4461	(depending on windows version and/or the phase of the moon). To get more,	4986	(depending on windows version and/or the phase of the moon). To get more,
4462	you need to wrap all I/O functions and provide your own fd management, but	4987	you need to wrap all I/O functions and provide your own fd management, but
4463	the cost of calling select (O(n²)) will likely make this unworkable.	4988	the cost of calling select (O(n²)) will likely make this unworkable.
4464		4989
4465	=back
4466
4467	=head2 PORTABILITY REQUIREMENTS	4990	=head2 PORTABILITY REQUIREMENTS
4468		4991
4469	In addition to a working ISO-C implementation and of course the	4992	In addition to a working ISO-C implementation and of course the
4470	backend-specific APIs, libev relies on a few additional extensions:	4993	backend-specific APIs, libev relies on a few additional extensions:
4471		4994
…		…
4477	Libev assumes not only that all watcher pointers have the same internal	5000	Libev assumes not only that all watcher pointers have the same internal
4478	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
4479	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
4480	callback: The watcher callbacks have different type signatures, but libev	5003	callback: The watcher callbacks have different type signatures, but libev
4481	calls them using an C<ev_watcher *> internally.	5004	calls them using an C<ev_watcher *> internally.
		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.
4482		5010
4483	=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
4484		5012
4485	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
4486	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
…		…
4509	watchers.	5037	watchers.
4510		5038
4511	=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
4512		5040
4513	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
4514	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
4515	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
4516	implementations implementing IEEE 754, which is basically all existing	5045	implementations using IEEE 754, which is basically all existing ones. With
4517	ones. With IEEE 754 doubles, you get microsecond accuracy until at least	5046	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
4518	2200.
4519		5047
4520	=back	5048	=back
4521		5049
4522	If you know of other additional requirements drop me a note.	5050	If you know of other additional requirements drop me a note.
4523		5051
…		…
4591	involves iterating over all running async watchers or all signal numbers.	5119	involves iterating over all running async watchers or all signal numbers.
4592		5120
4593	=back	5121	=back
4594		5122
4595		5123
		5124	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5125
		5126	The major version 4 introduced some incompatible changes to the API.
		5127
		5128	At the moment, the C<ev.h> header file provides compatibility definitions
		5129	for all changes, so most programs should still compile. The compatibility
		5130	layer might be removed in later versions of libev, so better update to the
		5131	new API early than late.
		5132
		5133	=over 4
		5134
		5135	=item C<EV_COMPAT3> backwards compatibility mechanism
		5136
		5137	The backward compatibility mechanism can be controlled by
		5138	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5139	section.
		5140
		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
		5166
		5167	Most functions working on C<struct ev_loop> objects don't have an
		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
		5172	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5173	typedef.
		5174
		5175	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5176
		5177	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5178	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5179	and work, but the library code will of course be larger.
		5180
		5181	=back
		5182
		5183
4596	=head1 GLOSSARY	5184	=head1 GLOSSARY
4597		5185
4598	=over 4	5186	=over 4
4599		5187
4600	=item active	5188	=item active
4601		5189
4602	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.
4603	an event loop) but not yet stopped (disassociated from the event loop).	5191	See L<WATCHER STATES> for details.
4604		5192
4605	=item application	5193	=item application
4606		5194
4607	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.
4608		5200
4609	=item callback	5201	=item callback
4610		5202
4611	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
4612	detected. Callbacks are being passed the event loop, the watcher that	5204	detected. Callbacks are being passed the event loop, the watcher that
4613	received the event, and the actual event bitset.	5205	received the event, and the actual event bitset.
4614		5206
4615	=item callback invocation	5207	=item callback/watcher invocation
4616		5208
4617	The act of calling the callback associated with a watcher.	5209	The act of calling the callback associated with a watcher.
4618		5210
4619	=item event	5211	=item event
4620		5212
4621	A change of state of some external event, such as data now being available	5213	A change of state of some external event, such as data now being available
4622	for reading on a file descriptor, time having passed or simply not having	5214	for reading on a file descriptor, time having passed or simply not having
4623	any other events happening anymore.	5215	any other events happening anymore.
4624		5216
4625	In libev, events are represented as single bits (such as C<EV_READ> or	5217	In libev, events are represented as single bits (such as C<EV_READ> or
4626	C<EV_TIMEOUT>).	5218	C<EV_TIMER>).
4627		5219
4628	=item event library	5220	=item event library
4629		5221
4630	A software package implementing an event model and loop.	5222	A software package implementing an event model and loop.
4631		5223
…		…
4639	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
4640	watchers and events.	5232	watchers and events.
4641		5233
4642	=item pending	5234	=item pending
4643		5235
4644	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
4645	and stops being pending as soon as the watcher will be invoked or its	5237	detected. See L<WATCHER STATES> for details.
4646	pending status is explicitly cleared by the application.
4647
4648	A watcher can be pending, but not active. Stopping a watcher also clears
4649	its pending status.
4650		5238
4651	=item real time	5239	=item real time
4652		5240
4653	The physical time that is observed. It is apparently strictly monotonic :)	5241	The physical time that is observed. It is apparently strictly monotonic :)
4654		5242
4655	=item wall-clock time	5243	=item wall-clock time
4656		5244
4657	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
4658	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
4659	clock.	5247	clock.
4660		5248
4661	=item watcher	5249	=item watcher
4662		5250
4663	A data structure that describes interest in certain events. Watchers need	5251	A data structure that describes interest in certain events. Watchers need
4664	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.
4665		5253
4666	=item watcher invocation
4667
4668	The act of calling the callback associated with a watcher.
4669
4670	=back	5254	=back
4671		5255
4672	=head1 AUTHOR	5256	=head1 AUTHOR
4673		5257
4674	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.
4675		5260

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