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Revision 1.275 by root, Sat Dec 26 09:21:54 2009 UTC vs.
Revision 1.393 by root, Sat Jan 21 12:23:45 2012 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_now_update> 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
174	either it is interrupted or the given time interval has passed. Basically	184	until either it is interrupted or the given time interval has
		185	passed (approximately - it might return a bit earlier even if not
		186	interrupted). Returns immediately if C<< interval <= 0 >>.
		187
175	this is a sub-second-resolution C<sleep ()>.	188	Basically this is a sub-second-resolution C<sleep ()>.
		189
		190	The range of the C<interval> is limited - libev only guarantees to work
		191	with sleep times of up to one day (C<< interval <= 86400 >>).
176		192
177	=item int ev_version_major ()	193	=item int ev_version_major ()
178		194
179	=item int ev_version_minor ()	195	=item int ev_version_minor ()
180		196
…		…
191	as this indicates an incompatible change. Minor versions are usually	207	as this indicates an incompatible change. Minor versions are usually
192	compatible to older versions, so a larger minor version alone is usually	208	compatible to older versions, so a larger minor version alone is usually
193	not a problem.	209	not a problem.
194		210
195	Example: Make sure we haven't accidentally been linked against the wrong	211	Example: Make sure we haven't accidentally been linked against the wrong
196	version.	212	version (note, however, that this will not detect other ABI mismatches,
		213	such as LFS or reentrancy).
197		214
198	assert (("libev version mismatch",	215	assert (("libev version mismatch",
199	ev_version_major () == EV_VERSION_MAJOR	216	ev_version_major () == EV_VERSION_MAJOR
200	&& ev_version_minor () >= EV_VERSION_MINOR));	217	&& ev_version_minor () >= EV_VERSION_MINOR));
201		218
…		…
212	assert (("sorry, no epoll, no sex",	229	assert (("sorry, no epoll, no sex",
213	ev_supported_backends () & EVBACKEND_EPOLL));	230	ev_supported_backends () & EVBACKEND_EPOLL));
214		231
215	=item unsigned int ev_recommended_backends ()	232	=item unsigned int ev_recommended_backends ()
216		233
217	Return the set of all backends compiled into this binary of libev and also	234	Return the set of all backends compiled into this binary of libev and
218	recommended for this platform. This set is often smaller than the one	235	also recommended for this platform, meaning it will work for most file
		236	descriptor types. This set is often smaller than the one returned by
219	returned by C<ev_supported_backends>, as for example kqueue is broken on	237	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
220	most BSDs and will not be auto-detected unless you explicitly request it	238	and will not be auto-detected unless you explicitly request it (assuming
221	(assuming you know what you are doing). This is the set of backends that	239	you know what you are doing). This is the set of backends that libev will
222	libev will probe for if you specify no backends explicitly.	240	probe for if you specify no backends explicitly.
223		241
224	=item unsigned int ev_embeddable_backends ()	242	=item unsigned int ev_embeddable_backends ()
225		243
226	Returns the set of backends that are embeddable in other event loops. This	244	Returns the set of backends that are embeddable in other event loops. This
227	is the theoretical, all-platform, value. To find which backends	245	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	246	current system. To find which embeddable backends might be supported on
229	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	247	the current system, you would need to look at C<ev_embeddable_backends ()
230	recommended ones.	248	& ev_supported_backends ()>, likewise for recommended ones.
231		249
232	See the description of C<ev_embed> watchers for more info.	250	See the description of C<ev_embed> watchers for more info.
233		251
234	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	252	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
235		253
236	Sets the allocation function to use (the prototype is similar - the	254	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	255	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	256	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	257	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
265	}	283	}
266		284
267	...	285	...
268	ev_set_allocator (persistent_realloc);	286	ev_set_allocator (persistent_realloc);
269		287
270	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	288	=item ev_set_syserr_cb (void (*cb)(const char *msg))
271		289
272	Set the callback function to call on a retryable system call error (such	290	Set the callback function to call on a retryable system call error (such
273	as failed select, poll, epoll_wait). The message is a printable string	291	as failed select, poll, epoll_wait). The message is a printable string
274	indicating the system call or subsystem causing the problem. If this	292	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	293	callback is set, then libev will expect it to remedy the situation, no
…		…
287	}	305	}
288		306
289	...	307	...
290	ev_set_syserr_cb (fatal_error);	308	ev_set_syserr_cb (fatal_error);
291		309
		310	=item ev_feed_signal (int signum)
		311
		312	This function can be used to "simulate" a signal receive. It is completely
		313	safe to call this function at any time, from any context, including signal
		314	handlers or random threads.
		315
		316	Its main use is to customise signal handling in your process, especially
		317	in the presence of threads. For example, you could block signals
		318	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		319	creating any loops), and in one thread, use C<sigwait> or any other
		320	mechanism to wait for signals, then "deliver" them to libev by calling
		321	C<ev_feed_signal>.
		322
292	=back	323	=back
293		324
294	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	325	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
295		326
296	An event loop is described by a C<struct ev_loop *> (the C<struct>	327	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>	328	I<not> optional in this case unless libev 3 compatibility is disabled, as
298	I<function>).	329	libev 3 had an C<ev_loop> function colliding with the struct name).
299		330
300	The library knows two types of such loops, the I<default> loop, which	331	The library knows two types of such loops, the I<default> loop, which
301	supports signals and child events, and dynamically created loops which do	332	supports child process events, and dynamically created event loops which
302	not.	333	do not.
303		334
304	=over 4	335	=over 4
305		336
306	=item struct ev_loop *ev_default_loop (unsigned int flags)	337	=item struct ev_loop *ev_default_loop (unsigned int flags)
307		338
308	This will initialise the default event loop if it hasn't been initialised	339	This returns the "default" event loop object, which is what you should
309	yet and return it. If the default loop could not be initialised, returns	340	normally use when you just need "the event loop". Event loop objects and
310	false. If it already was initialised it simply returns it (and ignores the	341	the C<flags> parameter are described in more detail in the entry for
311	flags. If that is troubling you, check C<ev_backend ()> afterwards).	342	C<ev_loop_new>.
		343
		344	If the default loop is already initialised then this function simply
		345	returns it (and ignores the flags. If that is troubling you, check
		346	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		347	flags, which should almost always be C<0>, unless the caller is also the
		348	one calling C<ev_run> or otherwise qualifies as "the main program".
312		349
313	If you don't know what event loop to use, use the one returned from this	350	If you don't know what event loop to use, use the one returned from this
314	function.	351	function (or via the C<EV_DEFAULT> macro).
315		352
316	Note that this function is I<not> thread-safe, so if you want to use it	353	Note that this function is I<not> thread-safe, so if you want to use it
317	from multiple threads, you have to lock (note also that this is unlikely,	354	from multiple threads, you have to employ some kind of mutex (note also
318	as loops cannot be shared easily between threads anyway).	355	that this case is unlikely, as loops cannot be shared easily between
		356	threads anyway).
319		357
320	The default loop is the only loop that can handle C<ev_signal> and	358	The default loop is the only loop that can handle C<ev_child> watchers,
321	C<ev_child> watchers, and to do this, it always registers a handler	359	and to do this, it always registers a handler for C<SIGCHLD>. If this is
322	for C<SIGCHLD>. If this is a problem for your application you can either	360	a problem for your application you can either create a dynamic loop with
323	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	361	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
324	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	362	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
325	C<ev_default_init>.	363
		364	Example: This is the most typical usage.
		365
		366	if (!ev_default_loop (0))
		367	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		368
		369	Example: Restrict libev to the select and poll backends, and do not allow
		370	environment settings to be taken into account:
		371
		372	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		373
		374	=item struct ev_loop *ev_loop_new (unsigned int flags)
		375
		376	This will create and initialise a new event loop object. If the loop
		377	could not be initialised, returns false.
		378
		379	This function is thread-safe, and one common way to use libev with
		380	threads is indeed to create one loop per thread, and using the default
		381	loop in the "main" or "initial" thread.
326		382
327	The flags argument can be used to specify special behaviour or specific	383	The flags argument can be used to specify special behaviour or specific
328	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	384	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
329		385
330	The following flags are supported:	386	The following flags are supported:
…		…
345	useful to try out specific backends to test their performance, or to work	401	useful to try out specific backends to test their performance, or to work
346	around bugs.	402	around bugs.
347		403
348	=item C<EVFLAG_FORKCHECK>	404	=item C<EVFLAG_FORKCHECK>
349		405
350	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	406	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	407	make libev check for a fork in each iteration by enabling this flag.
352	enabling this flag.
353		408
354	This works by calling C<getpid ()> on every iteration of the loop,	409	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	410	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	411	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	412	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
…		…
366	environment variable.	421	environment variable.
367		422
368	=item C<EVFLAG_NOINOTIFY>	423	=item C<EVFLAG_NOINOTIFY>
369		424
370	When this flag is specified, then libev will not attempt to use the	425	When this flag is specified, then libev will not attempt to use the
371	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and	426	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
372	testing, this flag can be useful to conserve inotify file descriptors, as	427	testing, this flag can be useful to conserve inotify file descriptors, as
373	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.	428	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
374		429
375	=item C<EVFLAG_NOSIGFD>	430	=item C<EVFLAG_SIGNALFD>
376		431
377	When this flag is specified, then libev will not attempt to use the	432	When this flag is specified, then libev will attempt to use the
378	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This is	433	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
379	probably only useful to work around any bugs in libev. Consequently, this	434	delivers signals synchronously, which makes it both faster and might make
380	flag might go away once the signalfd functionality is considered stable,	435	it possible to get the queued signal data. It can also simplify signal
381	so it's useful mostly in environment variables and not in program code.	436	handling with threads, as long as you properly block signals in your
		437	threads that are not interested in handling them.
		438
		439	Signalfd will not be used by default as this changes your signal mask, and
		440	there are a lot of shoddy libraries and programs (glib's threadpool for
		441	example) that can't properly initialise their signal masks.
		442
		443	=item C<EVFLAG_NOSIGMASK>
		444
		445	When this flag is specified, then libev will avoid to modify the signal
		446	mask. Specifically, this means you have to make sure signals are unblocked
		447	when you want to receive them.
		448
		449	This behaviour is useful when you want to do your own signal handling, or
		450	want to handle signals only in specific threads and want to avoid libev
		451	unblocking the signals.
		452
		453	It's also required by POSIX in a threaded program, as libev calls
		454	C<sigprocmask>, whose behaviour is officially unspecified.
		455
		456	This flag's behaviour will become the default in future versions of libev.
382		457
383	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	458	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
384		459
385	This is your standard select(2) backend. Not I<completely> standard, as	460	This is your standard select(2) backend. Not I<completely> standard, as
386	libev tries to roll its own fd_set with no limits on the number of fds,	461	libev tries to roll its own fd_set with no limits on the number of fds,
…		…
414	=item C<EVBACKEND_EPOLL> (value 4, Linux)	489	=item C<EVBACKEND_EPOLL> (value 4, Linux)
415		490
416	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9	491	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
417	kernels).	492	kernels).
418		493
419	For few fds, this backend is a bit little slower than poll and select,	494	For few fds, this backend is a bit little slower than poll and select, but
420	but it scales phenomenally better. While poll and select usually scale	495	it scales phenomenally better. While poll and select usually scale like
421	like O(total_fds) where n is the total number of fds (or the highest fd),	496	O(total_fds) where total_fds is the total number of fds (or the highest
422	epoll scales either O(1) or O(active_fds).	497	fd), epoll scales either O(1) or O(active_fds).
423		498
424	The epoll mechanism deserves honorable mention as the most misdesigned	499	The epoll mechanism deserves honorable mention as the most misdesigned
425	of the more advanced event mechanisms: mere annoyances include silently	500	of the more advanced event mechanisms: mere annoyances include silently
426	dropping file descriptors, requiring a system call per change per file	501	dropping file descriptors, requiring a system call per change per file
427	descriptor (and unnecessary guessing of parameters), problems with dup and	502	descriptor (and unnecessary guessing of parameters), problems with dup,
		503	returning before the timeout value, resulting in additional iterations
		504	(and only giving 5ms accuracy while select on the same platform gives
428	so on. The biggest issue is fork races, however - if a program forks then	505	0.1ms) and so on. The biggest issue is fork races, however - if a program
429	I<both> parent and child process have to recreate the epoll set, which can	506	forks then I<both> parent and child process have to recreate the epoll
430	take considerable time (one syscall per file descriptor) and is of course	507	set, which can take considerable time (one syscall per file descriptor)
431	hard to detect.	508	and is of course hard to detect.
432		509
433	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	510	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
434	of course I<doesn't>, and epoll just loves to report events for totally	511	but of course I<doesn't>, and epoll just loves to report events for
435	I<different> file descriptors (even already closed ones, so one cannot	512	totally I<different> file descriptors (even already closed ones, so
436	even remove them from the set) than registered in the set (especially	513	one cannot even remove them from the set) than registered in the set
437	on SMP systems). Libev tries to counter these spurious notifications by	514	(especially on SMP systems). Libev tries to counter these spurious
438	employing an additional generation counter and comparing that against the	515	notifications by employing an additional generation counter and comparing
439	events to filter out spurious ones, recreating the set when required.	516	that against the events to filter out spurious ones, recreating the set
		517	when required. Epoll also erroneously rounds down timeouts, but gives you
		518	no way to know when and by how much, so sometimes you have to busy-wait
		519	because epoll returns immediately despite a nonzero timeout. And last
		520	not least, it also refuses to work with some file descriptors which work
		521	perfectly fine with C<select> (files, many character devices...).
		522
		523	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
		524	cobbled together in a hurry, no thought to design or interaction with
		525	others. Oh, the pain, will it ever stop...
440		526
441	While stopping, setting and starting an I/O watcher in the same iteration	527	While stopping, setting and starting an I/O watcher in the same iteration
442	will result in some caching, there is still a system call per such	528	will result in some caching, there is still a system call per such
443	incident (because the same I<file descriptor> could point to a different	529	incident (because the same I<file descriptor> could point to a different
444	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	530	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
510	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	596	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
511		597
512	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	598	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
513	it's really slow, but it still scales very well (O(active_fds)).	599	it's really slow, but it still scales very well (O(active_fds)).
514		600
515	Please note that Solaris event ports can deliver a lot of spurious
516	notifications, so you need to use non-blocking I/O or other means to avoid
517	blocking when no data (or space) is available.
518
519	While this backend scales well, it requires one system call per active	601	While this backend scales well, it requires one system call per active
520	file descriptor per loop iteration. For small and medium numbers of file	602	file descriptor per loop iteration. For small and medium numbers of file
521	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	603	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
522	might perform better.	604	might perform better.
523		605
524	On the positive side, with the exception of the spurious readiness	606	On the positive side, this backend actually performed fully to
525	notifications, this backend actually performed fully to specification
526	in all tests and is fully embeddable, which is a rare feat among the	607	specification in all tests and is fully embeddable, which is a rare feat
527	OS-specific backends (I vastly prefer correctness over speed hacks).	608	among the OS-specific backends (I vastly prefer correctness over speed
		609	hacks).
		610
		611	On the negative side, the interface is I<bizarre> - so bizarre that
		612	even sun itself gets it wrong in their code examples: The event polling
		613	function sometimes returns events to the caller even though an error
		614	occurred, but with no indication whether it has done so or not (yes, it's
		615	even documented that way) - deadly for edge-triggered interfaces where you
		616	absolutely have to know whether an event occurred or not because you have
		617	to re-arm the watcher.
		618
		619	Fortunately libev seems to be able to work around these idiocies.
528		620
529	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	621	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
530	C<EVBACKEND_POLL>.	622	C<EVBACKEND_POLL>.
531		623
532	=item C<EVBACKEND_ALL>	624	=item C<EVBACKEND_ALL>
533		625
534	Try all backends (even potentially broken ones that wouldn't be tried	626	Try all backends (even potentially broken ones that wouldn't be tried
535	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	627	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
536	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	628	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
537		629
538	It is definitely not recommended to use this flag.	630	It is definitely not recommended to use this flag, use whatever
		631	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		632	at all.
		633
		634	=item C<EVBACKEND_MASK>
		635
		636	Not a backend at all, but a mask to select all backend bits from a
		637	C<flags> value, in case you want to mask out any backends from a flags
		638	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
539		639
540	=back	640	=back
541		641
542	If one or more of the backend flags are or'ed into the flags value,	642	If one or more of the backend flags are or'ed into the flags value,
543	then only these backends will be tried (in the reverse order as listed	643	then only these backends will be tried (in the reverse order as listed
544	here). If none are specified, all backends in C<ev_recommended_backends	644	here). If none are specified, all backends in C<ev_recommended_backends
545	()> will be tried.	645	()> will be tried.
546		646
547	Example: This is the most typical usage.
548
549	if (!ev_default_loop (0))
550	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
551
552	Example: Restrict libev to the select and poll backends, and do not allow
553	environment settings to be taken into account:
554
555	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
556
557	Example: Use whatever libev has to offer, but make sure that kqueue is
558	used if available (warning, breaks stuff, best use only with your own
559	private event loop and only if you know the OS supports your types of
560	fds):
561
562	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
563
564	=item struct ev_loop *ev_loop_new (unsigned int flags)
565
566	Similar to C<ev_default_loop>, but always creates a new event loop that is
567	always distinct from the default loop. Unlike the default loop, it cannot
568	handle signal and child watchers, and attempts to do so will be greeted by
569	undefined behaviour (or a failed assertion if assertions are enabled).
570
571	Note that this function I<is> thread-safe, and the recommended way to use
572	libev with threads is indeed to create one loop per thread, and using the
573	default loop in the "main" or "initial" thread.
574
575	Example: Try to create a event loop that uses epoll and nothing else.	647	Example: Try to create a event loop that uses epoll and nothing else.
576		648
577	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	649	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
578	if (!epoller)	650	if (!epoller)
579	fatal ("no epoll found here, maybe it hides under your chair");	651	fatal ("no epoll found here, maybe it hides under your chair");
580		652
		653	Example: Use whatever libev has to offer, but make sure that kqueue is
		654	used if available.
		655
		656	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		657
581	=item ev_default_destroy ()	658	=item ev_loop_destroy (loop)
582		659
583	Destroys the default loop again (frees all memory and kernel state	660	Destroys an event loop object (frees all memory and kernel state
584	etc.). None of the active event watchers will be stopped in the normal	661	etc.). None of the active event watchers will be stopped in the normal
585	sense, so e.g. C<ev_is_active> might still return true. It is your	662	sense, so e.g. C<ev_is_active> might still return true. It is your
586	responsibility to either stop all watchers cleanly yourself I<before>	663	responsibility to either stop all watchers cleanly yourself I<before>
587	calling this function, or cope with the fact afterwards (which is usually	664	calling this function, or cope with the fact afterwards (which is usually
588	the easiest thing, you can just ignore the watchers and/or C<free ()> them	665	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
590		667
591	Note that certain global state, such as signal state (and installed signal	668	Note that certain global state, such as signal state (and installed signal
592	handlers), will not be freed by this function, and related watchers (such	669	handlers), will not be freed by this function, and related watchers (such
593	as signal and child watchers) would need to be stopped manually.	670	as signal and child watchers) would need to be stopped manually.
594		671
595	In general it is not advisable to call this function except in the	672	This function is normally used on loop objects allocated by
596	rare occasion where you really need to free e.g. the signal handling	673	C<ev_loop_new>, but it can also be used on the default loop returned by
		674	C<ev_default_loop>, in which case it is not thread-safe.
		675
		676	Note that it is not advisable to call this function on the default loop
		677	except in the rare occasion where you really need to free its resources.
597	pipe fds. If you need dynamically allocated loops it is better to use	678	If you need dynamically allocated loops it is better to use C<ev_loop_new>
598	C<ev_loop_new> and C<ev_loop_destroy>.	679	and C<ev_loop_destroy>.
599		680
600	=item ev_loop_destroy (loop)	681	=item ev_loop_fork (loop)
601		682
602	Like C<ev_default_destroy>, but destroys an event loop created by an
603	earlier call to C<ev_loop_new>.
604
605	=item ev_default_fork ()
606
607	This function sets a flag that causes subsequent C<ev_loop> iterations	683	This function sets a flag that causes subsequent C<ev_run> iterations to
608	to reinitialise the kernel state for backends that have one. Despite the	684	reinitialise the kernel state for backends that have one. Despite the
609	name, you can call it anytime, but it makes most sense after forking, in	685	name, you can call it anytime, but it makes most sense after forking, in
610	the child process (or both child and parent, but that again makes little	686	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
611	sense). You I<must> call it in the child before using any of the libev	687	child before resuming or calling C<ev_run>.
612	functions, and it will only take effect at the next C<ev_loop> iteration.	688
		689	Again, you I<have> to call it on I<any> loop that you want to re-use after
		690	a fork, I<even if you do not plan to use the loop in the parent>. This is
		691	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		692	during fork.
613		693
614	On the other hand, you only need to call this function in the child	694	On the other hand, you only need to call this function in the child
615	process if and only if you want to use the event library in the child. If	695	process if and only if you want to use the event loop in the child. If
616	you just fork+exec, you don't have to call it at all.	696	you just fork+exec or create a new loop in the child, you don't have to
		697	call it at all (in fact, C<epoll> is so badly broken that it makes a
		698	difference, but libev will usually detect this case on its own and do a
		699	costly reset of the backend).
617		700
618	The function itself is quite fast and it's usually not a problem to call	701	The function itself is quite fast and it's usually not a problem to call
619	it just in case after a fork. To make this easy, the function will fit in	702	it just in case after a fork.
620	quite nicely into a call to C<pthread_atfork>:
621		703
		704	Example: Automate calling C<ev_loop_fork> on the default loop when
		705	using pthreads.
		706
		707	static void
		708	post_fork_child (void)
		709	{
		710	ev_loop_fork (EV_DEFAULT);
		711	}
		712
		713	...
622	pthread_atfork (0, 0, ev_default_fork);	714	pthread_atfork (0, 0, post_fork_child);
623
624	=item ev_loop_fork (loop)
625
626	Like C<ev_default_fork>, but acts on an event loop created by
627	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
628	after fork that you want to re-use in the child, and how you do this is
629	entirely your own problem.
630		715
631	=item int ev_is_default_loop (loop)	716	=item int ev_is_default_loop (loop)
632		717
633	Returns true when the given loop is, in fact, the default loop, and false	718	Returns true when the given loop is, in fact, the default loop, and false
634	otherwise.	719	otherwise.
635		720
636	=item unsigned int ev_loop_count (loop)	721	=item unsigned int ev_iteration (loop)
637		722
638	Returns the count of loop iterations for the loop, which is identical to	723	Returns the current iteration count for the event loop, which is identical
639	the number of times libev did poll for new events. It starts at C<0> and	724	to the number of times libev did poll for new events. It starts at C<0>
640	happily wraps around with enough iterations.	725	and happily wraps around with enough iterations.
641		726
642	This value can sometimes be useful as a generation counter of sorts (it	727	This value can sometimes be useful as a generation counter of sorts (it
643	"ticks" the number of loop iterations), as it roughly corresponds with	728	"ticks" the number of loop iterations), as it roughly corresponds with
644	C<ev_prepare> and C<ev_check> calls.	729	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		730	prepare and check phases.
645		731
646	=item unsigned int ev_loop_depth (loop)	732	=item unsigned int ev_depth (loop)
647		733
648	Returns the number of times C<ev_loop> was entered minus the number of	734	Returns the number of times C<ev_run> was entered minus the number of
649	times C<ev_loop> was exited, in other words, the recursion depth.	735	times C<ev_run> was exited normally, in other words, the recursion depth.
650		736
651	Outside C<ev_loop>, this number is zero. In a callback, this number is	737	Outside C<ev_run>, this number is zero. In a callback, this number is
652	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),	738	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
653	in which case it is higher.	739	in which case it is higher.
654		740
655	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread	741	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
656	etc.), doesn't count as exit.	742	throwing an exception etc.), doesn't count as "exit" - consider this
		743	as a hint to avoid such ungentleman-like behaviour unless it's really
		744	convenient, in which case it is fully supported.
657		745
658	=item unsigned int ev_backend (loop)	746	=item unsigned int ev_backend (loop)
659		747
660	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	748	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
661	use.	749	use.
…		…
670		758
671	=item ev_now_update (loop)	759	=item ev_now_update (loop)
672		760
673	Establishes the current time by querying the kernel, updating the time	761	Establishes the current time by querying the kernel, updating the time
674	returned by C<ev_now ()> in the progress. This is a costly operation and	762	returned by C<ev_now ()> in the progress. This is a costly operation and
675	is usually done automatically within C<ev_loop ()>.	763	is usually done automatically within C<ev_run ()>.
676		764
677	This function is rarely useful, but when some event callback runs for a	765	This function is rarely useful, but when some event callback runs for a
678	very long time without entering the event loop, updating libev's idea of	766	very long time without entering the event loop, updating libev's idea of
679	the current time is a good idea.	767	the current time is a good idea.
680		768
…		…
682		770
683	=item ev_suspend (loop)	771	=item ev_suspend (loop)
684		772
685	=item ev_resume (loop)	773	=item ev_resume (loop)
686		774
687	These two functions suspend and resume a loop, for use when the loop is	775	These two functions suspend and resume an event loop, for use when the
688	not used for a while and timeouts should not be processed.	776	loop is not used for a while and timeouts should not be processed.
689		777
690	A typical use case would be an interactive program such as a game: When	778	A typical use case would be an interactive program such as a game: When
691	the user presses C<^Z> to suspend the game and resumes it an hour later it	779	the user presses C<^Z> to suspend the game and resumes it an hour later it
692	would be best to handle timeouts as if no time had actually passed while	780	would be best to handle timeouts as if no time had actually passed while
693	the program was suspended. This can be achieved by calling C<ev_suspend>	781	the program was suspended. This can be achieved by calling C<ev_suspend>
…		…
695	C<ev_resume> directly afterwards to resume timer processing.	783	C<ev_resume> directly afterwards to resume timer processing.
696		784
697	Effectively, all C<ev_timer> watchers will be delayed by the time spend	785	Effectively, all C<ev_timer> watchers will be delayed by the time spend
698	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers	786	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
699	will be rescheduled (that is, they will lose any events that would have	787	will be rescheduled (that is, they will lose any events that would have
700	occured while suspended).	788	occurred while suspended).
701		789
702	After calling C<ev_suspend> you B<must not> call I<any> function on the	790	After calling C<ev_suspend> you B<must not> call I<any> function on the
703	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>	791	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
704	without a previous call to C<ev_suspend>.	792	without a previous call to C<ev_suspend>.
705		793
706	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	794	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
707	event loop time (see C<ev_now_update>).	795	event loop time (see C<ev_now_update>).
708		796
709	=item ev_loop (loop, int flags)	797	=item ev_run (loop, int flags)
710		798
711	Finally, this is it, the event handler. This function usually is called	799	Finally, this is it, the event handler. This function usually is called
712	after you have initialised all your watchers and you want to start	800	after you have initialised all your watchers and you want to start
713	handling events.	801	handling events. It will ask the operating system for any new events, call
		802	the watcher callbacks, an then repeat the whole process indefinitely: This
		803	is why event loops are called I<loops>.
714		804
715	If the flags argument is specified as C<0>, it will not return until	805	If the flags argument is specified as C<0>, it will keep handling events
716	either no event watchers are active anymore or C<ev_unloop> was called.	806	until either no event watchers are active anymore or C<ev_break> was
		807	called.
717		808
718	Please note that an explicit C<ev_unloop> is usually better than	809	Please note that an explicit C<ev_break> is usually better than
719	relying on all watchers to be stopped when deciding when a program has	810	relying on all watchers to be stopped when deciding when a program has
720	finished (especially in interactive programs), but having a program	811	finished (especially in interactive programs), but having a program
721	that automatically loops as long as it has to and no longer by virtue	812	that automatically loops as long as it has to and no longer by virtue
722	of relying on its watchers stopping correctly, that is truly a thing of	813	of relying on its watchers stopping correctly, that is truly a thing of
723	beauty.	814	beauty.
724		815
		816	This function is also I<mostly> exception-safe - you can break out of
		817	a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		818	exception and so on. This does not decrement the C<ev_depth> value, nor
		819	will it clear any outstanding C<EVBREAK_ONE> breaks.
		820
725	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	821	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
726	those events and any already outstanding ones, but will not block your	822	those events and any already outstanding ones, but will not wait and
727	process in case there are no events and will return after one iteration of	823	block your process in case there are no events and will return after one
728	the loop.	824	iteration of the loop. This is sometimes useful to poll and handle new
		825	events while doing lengthy calculations, to keep the program responsive.
729		826
730	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	827	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
731	necessary) and will handle those and any already outstanding ones. It	828	necessary) and will handle those and any already outstanding ones. It
732	will block your process until at least one new event arrives (which could	829	will block your process until at least one new event arrives (which could
733	be an event internal to libev itself, so there is no guarantee that a	830	be an event internal to libev itself, so there is no guarantee that a
734	user-registered callback will be called), and will return after one	831	user-registered callback will be called), and will return after one
735	iteration of the loop.	832	iteration of the loop.
736		833
737	This is useful if you are waiting for some external event in conjunction	834	This is useful if you are waiting for some external event in conjunction
738	with something not expressible using other libev watchers (i.e. "roll your	835	with something not expressible using other libev watchers (i.e. "roll your
739	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	836	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
740	usually a better approach for this kind of thing.	837	usually a better approach for this kind of thing.
741		838
742	Here are the gory details of what C<ev_loop> does:	839	Here are the gory details of what C<ev_run> does (this is for your
		840	understanding, not a guarantee that things will work exactly like this in
		841	future versions):
743		842
		843	- Increment loop depth.
		844	- Reset the ev_break status.
744	- Before the first iteration, call any pending watchers.	845	- Before the first iteration, call any pending watchers.
		846	LOOP:
745	* If EVFLAG_FORKCHECK was used, check for a fork.	847	- If EVFLAG_FORKCHECK was used, check for a fork.
746	- If a fork was detected (by any means), queue and call all fork watchers.	848	- If a fork was detected (by any means), queue and call all fork watchers.
747	- Queue and call all prepare watchers.	849	- Queue and call all prepare watchers.
		850	- If ev_break was called, goto FINISH.
748	- If we have been forked, detach and recreate the kernel state	851	- If we have been forked, detach and recreate the kernel state
749	as to not disturb the other process.	852	as to not disturb the other process.
750	- Update the kernel state with all outstanding changes.	853	- Update the kernel state with all outstanding changes.
751	- Update the "event loop time" (ev_now ()).	854	- Update the "event loop time" (ev_now ()).
752	- Calculate for how long to sleep or block, if at all	855	- Calculate for how long to sleep or block, if at all
753	(active idle watchers, EVLOOP_NONBLOCK or not having	856	(active idle watchers, EVRUN_NOWAIT or not having
754	any active watchers at all will result in not sleeping).	857	any active watchers at all will result in not sleeping).
755	- Sleep if the I/O and timer collect interval say so.	858	- Sleep if the I/O and timer collect interval say so.
		859	- Increment loop iteration counter.
756	- Block the process, waiting for any events.	860	- Block the process, waiting for any events.
757	- Queue all outstanding I/O (fd) events.	861	- Queue all outstanding I/O (fd) events.
758	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	862	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
759	- Queue all expired timers.	863	- Queue all expired timers.
760	- Queue all expired periodics.	864	- Queue all expired periodics.
761	- Unless any events are pending now, queue all idle watchers.	865	- Queue all idle watchers with priority higher than that of pending events.
762	- Queue all check watchers.	866	- Queue all check watchers.
763	- Call all queued watchers in reverse order (i.e. check watchers first).	867	- Call all queued watchers in reverse order (i.e. check watchers first).
764	Signals and child watchers are implemented as I/O watchers, and will	868	Signals and child watchers are implemented as I/O watchers, and will
765	be handled here by queueing them when their watcher gets executed.	869	be handled here by queueing them when their watcher gets executed.
766	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	870	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
767	were used, or there are no active watchers, return, otherwise	871	were used, or there are no active watchers, goto FINISH, otherwise
768	continue with step *.	872	continue with step LOOP.
		873	FINISH:
		874	- Reset the ev_break status iff it was EVBREAK_ONE.
		875	- Decrement the loop depth.
		876	- Return.
769		877
770	Example: Queue some jobs and then loop until no events are outstanding	878	Example: Queue some jobs and then loop until no events are outstanding
771	anymore.	879	anymore.
772		880
773	... queue jobs here, make sure they register event watchers as long	881	... queue jobs here, make sure they register event watchers as long
774	... as they still have work to do (even an idle watcher will do..)	882	... as they still have work to do (even an idle watcher will do..)
775	ev_loop (my_loop, 0);	883	ev_run (my_loop, 0);
776	... jobs done or somebody called unloop. yeah!	884	... jobs done or somebody called break. yeah!
777		885
778	=item ev_unloop (loop, how)	886	=item ev_break (loop, how)
779		887
780	Can be used to make a call to C<ev_loop> return early (but only after it	888	Can be used to make a call to C<ev_run> return early (but only after it
781	has processed all outstanding events). The C<how> argument must be either	889	has processed all outstanding events). The C<how> argument must be either
782	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	890	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
783	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	891	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
784		892
785	This "unloop state" will be cleared when entering C<ev_loop> again.	893	This "break state" will be cleared on the next call to C<ev_run>.
786		894
787	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	895	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		896	which case it will have no effect.
788		897
789	=item ev_ref (loop)	898	=item ev_ref (loop)
790		899
791	=item ev_unref (loop)	900	=item ev_unref (loop)
792		901
793	Ref/unref can be used to add or remove a reference count on the event	902	Ref/unref can be used to add or remove a reference count on the event
794	loop: Every watcher keeps one reference, and as long as the reference	903	loop: Every watcher keeps one reference, and as long as the reference
795	count is nonzero, C<ev_loop> will not return on its own.	904	count is nonzero, C<ev_run> will not return on its own.
796		905
797	If you have a watcher you never unregister that should not keep C<ev_loop>	906	This is useful when you have a watcher that you never intend to
798	from returning, call ev_unref() after starting, and ev_ref() before	907	unregister, but that nevertheless should not keep C<ev_run> from
		908	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
799	stopping it.	909	before stopping it.
800		910
801	As an example, libev itself uses this for its internal signal pipe: It	911	As an example, libev itself uses this for its internal signal pipe: It
802	is not visible to the libev user and should not keep C<ev_loop> from	912	is not visible to the libev user and should not keep C<ev_run> from
803	exiting if no event watchers registered by it are active. It is also an	913	exiting if no event watchers registered by it are active. It is also an
804	excellent way to do this for generic recurring timers or from within	914	excellent way to do this for generic recurring timers or from within
805	third-party libraries. Just remember to I<unref after start> and I<ref	915	third-party libraries. Just remember to I<unref after start> and I<ref
806	before stop> (but only if the watcher wasn't active before, or was active	916	before stop> (but only if the watcher wasn't active before, or was active
807	before, respectively. Note also that libev might stop watchers itself	917	before, respectively. Note also that libev might stop watchers itself
808	(e.g. non-repeating timers) in which case you have to C<ev_ref>	918	(e.g. non-repeating timers) in which case you have to C<ev_ref>
809	in the callback).	919	in the callback).
810		920
811	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	921	Example: Create a signal watcher, but keep it from keeping C<ev_run>
812	running when nothing else is active.	922	running when nothing else is active.
813		923
814	ev_signal exitsig;	924	ev_signal exitsig;
815	ev_signal_init (&exitsig, sig_cb, SIGINT);	925	ev_signal_init (&exitsig, sig_cb, SIGINT);
816	ev_signal_start (loop, &exitsig);	926	ev_signal_start (loop, &exitsig);
817	evf_unref (loop);	927	ev_unref (loop);
818		928
819	Example: For some weird reason, unregister the above signal handler again.	929	Example: For some weird reason, unregister the above signal handler again.
820		930
821	ev_ref (loop);	931	ev_ref (loop);
822	ev_signal_stop (loop, &exitsig);	932	ev_signal_stop (loop, &exitsig);
…		…
842	overhead for the actual polling but can deliver many events at once.	952	overhead for the actual polling but can deliver many events at once.
843		953
844	By setting a higher I<io collect interval> you allow libev to spend more	954	By setting a higher I<io collect interval> you allow libev to spend more
845	time collecting I/O events, so you can handle more events per iteration,	955	time collecting I/O events, so you can handle more events per iteration,
846	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	956	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
847	C<ev_timer>) will be not affected. Setting this to a non-null value will	957	C<ev_timer>) will not be affected. Setting this to a non-null value will
848	introduce an additional C<ev_sleep ()> call into most loop iterations. The	958	introduce an additional C<ev_sleep ()> call into most loop iterations. The
849	sleep time ensures that libev will not poll for I/O events more often then	959	sleep time ensures that libev will not poll for I/O events more often then
850	once per this interval, on average.	960	once per this interval, on average (as long as the host time resolution is
		961	good enough).
851		962
852	Likewise, by setting a higher I<timeout collect interval> you allow libev	963	Likewise, by setting a higher I<timeout collect interval> you allow libev
853	to spend more time collecting timeouts, at the expense of increased	964	to spend more time collecting timeouts, at the expense of increased
854	latency/jitter/inexactness (the watcher callback will be called	965	latency/jitter/inexactness (the watcher callback will be called
855	later). C<ev_io> watchers will not be affected. Setting this to a non-null	966	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
861	usually doesn't make much sense to set it to a lower value than C<0.01>,	972	usually doesn't make much sense to set it to a lower value than C<0.01>,
862	as this approaches the timing granularity of most systems. Note that if	973	as this approaches the timing granularity of most systems. Note that if
863	you do transactions with the outside world and you can't increase the	974	you do transactions with the outside world and you can't increase the
864	parallelity, then this setting will limit your transaction rate (if you	975	parallelity, then this setting will limit your transaction rate (if you
865	need to poll once per transaction and the I/O collect interval is 0.01,	976	need to poll once per transaction and the I/O collect interval is 0.01,
866	then you can't do more than 100 transations per second).	977	then you can't do more than 100 transactions per second).
867		978
868	Setting the I<timeout collect interval> can improve the opportunity for	979	Setting the I<timeout collect interval> can improve the opportunity for
869	saving power, as the program will "bundle" timer callback invocations that	980	saving power, as the program will "bundle" timer callback invocations that
870	are "near" in time together, by delaying some, thus reducing the number of	981	are "near" in time together, by delaying some, thus reducing the number of
871	times the process sleeps and wakes up again. Another useful technique to	982	times the process sleeps and wakes up again. Another useful technique to
…		…
879	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	990	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
880		991
881	=item ev_invoke_pending (loop)	992	=item ev_invoke_pending (loop)
882		993
883	This call will simply invoke all pending watchers while resetting their	994	This call will simply invoke all pending watchers while resetting their
884	pending state. Normally, C<ev_loop> does this automatically when required,	995	pending state. Normally, C<ev_run> does this automatically when required,
885	but when overriding the invoke callback this call comes handy.	996	but when overriding the invoke callback this call comes handy. This
		997	function can be invoked from a watcher - this can be useful for example
		998	when you want to do some lengthy calculation and want to pass further
		999	event handling to another thread (you still have to make sure only one
		1000	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
886		1001
887	=item int ev_pending_count (loop)	1002	=item int ev_pending_count (loop)
888		1003
889	Returns the number of pending watchers - zero indicates that no watchers	1004	Returns the number of pending watchers - zero indicates that no watchers
890	are pending.	1005	are pending.
891		1006
892	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))	1007	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
893		1008
894	This overrides the invoke pending functionality of the loop: Instead of	1009	This overrides the invoke pending functionality of the loop: Instead of
895	invoking all pending watchers when there are any, C<ev_loop> will call	1010	invoking all pending watchers when there are any, C<ev_run> will call
896	this callback instead. This is useful, for example, when you want to	1011	this callback instead. This is useful, for example, when you want to
897	invoke the actual watchers inside another context (another thread etc.).	1012	invoke the actual watchers inside another context (another thread etc.).
898		1013
899	If you want to reset the callback, use C<ev_invoke_pending> as new	1014	If you want to reset the callback, use C<ev_invoke_pending> as new
900	callback.	1015	callback.
…		…
903		1018
904	Sometimes you want to share the same loop between multiple threads. This	1019	Sometimes you want to share the same loop between multiple threads. This
905	can be done relatively simply by putting mutex_lock/unlock calls around	1020	can be done relatively simply by putting mutex_lock/unlock calls around
906	each call to a libev function.	1021	each call to a libev function.
907		1022
908	However, C<ev_loop> can run an indefinite time, so it is not feasible to	1023	However, C<ev_run> can run an indefinite time, so it is not feasible
909	wait for it to return. One way around this is to wake up the loop via	1024	to wait for it to return. One way around this is to wake up the event
910	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>	1025	loop via C<ev_break> and C<ev_async_send>, another way is to set these
911	and I<acquire> callbacks on the loop.	1026	I<release> and I<acquire> callbacks on the loop.
912		1027
913	When set, then C<release> will be called just before the thread is	1028	When set, then C<release> will be called just before the thread is
914	suspended waiting for new events, and C<acquire> is called just	1029	suspended waiting for new events, and C<acquire> is called just
915	afterwards.	1030	afterwards.
916		1031
…		…
919		1034
920	While event loop modifications are allowed between invocations of	1035	While event loop modifications are allowed between invocations of
921	C<release> and C<acquire> (that's their only purpose after all), no	1036	C<release> and C<acquire> (that's their only purpose after all), no
922	modifications done will affect the event loop, i.e. adding watchers will	1037	modifications done will affect the event loop, i.e. adding watchers will
923	have no effect on the set of file descriptors being watched, or the time	1038	have no effect on the set of file descriptors being watched, or the time
924	waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it	1039	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
925	to take note of any changes you made.	1040	to take note of any changes you made.
926		1041
927	In theory, threads executing C<ev_loop> will be async-cancel safe between	1042	In theory, threads executing C<ev_run> will be async-cancel safe between
928	invocations of C<release> and C<acquire>.	1043	invocations of C<release> and C<acquire>.
929		1044
930	See also the locking example in the C<THREADS> section later in this	1045	See also the locking example in the C<THREADS> section later in this
931	document.	1046	document.
932		1047
933	=item ev_set_userdata (loop, void *data)	1048	=item ev_set_userdata (loop, void *data)
934		1049
935	=item ev_userdata (loop)	1050	=item void *ev_userdata (loop)
936		1051
937	Set and retrieve a single C<void *> associated with a loop. When	1052	Set and retrieve a single C<void *> associated with a loop. When
938	C<ev_set_userdata> has never been called, then C<ev_userdata> returns	1053	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
939	C<0.>	1054	C<0>.
940		1055
941	These two functions can be used to associate arbitrary data with a loop,	1056	These two functions can be used to associate arbitrary data with a loop,
942	and are intended solely for the C<invoke_pending_cb>, C<release> and	1057	and are intended solely for the C<invoke_pending_cb>, C<release> and
943	C<acquire> callbacks described above, but of course can be (ab-)used for	1058	C<acquire> callbacks described above, but of course can be (ab-)used for
944	any other purpose as well.	1059	any other purpose as well.
945		1060
946	=item ev_loop_verify (loop)	1061	=item ev_verify (loop)
947		1062
948	This function only does something when C<EV_VERIFY> support has been	1063	This function only does something when C<EV_VERIFY> support has been
949	compiled in, which is the default for non-minimal builds. It tries to go	1064	compiled in, which is the default for non-minimal builds. It tries to go
950	through all internal structures and checks them for validity. If anything	1065	through all internal structures and checks them for validity. If anything
951	is found to be inconsistent, it will print an error message to standard	1066	is found to be inconsistent, it will print an error message to standard
…		…
962		1077
963	In the following description, uppercase C<TYPE> in names stands for the	1078	In the following description, uppercase C<TYPE> in names stands for the
964	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1079	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
965	watchers and C<ev_io_start> for I/O watchers.	1080	watchers and C<ev_io_start> for I/O watchers.
966		1081
967	A watcher is a structure that you create and register to record your	1082	A watcher is an opaque structure that you allocate and register to record
968	interest in some event. For instance, if you want to wait for STDIN to	1083	your interest in some event. To make a concrete example, imagine you want
969	become readable, you would create an C<ev_io> watcher for that:	1084	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1085	for that:
970		1086
971	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1087	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
972	{	1088	{
973	ev_io_stop (w);	1089	ev_io_stop (w);
974	ev_unloop (loop, EVUNLOOP_ALL);	1090	ev_break (loop, EVBREAK_ALL);
975	}	1091	}
976		1092
977	struct ev_loop *loop = ev_default_loop (0);	1093	struct ev_loop *loop = ev_default_loop (0);
978		1094
979	ev_io stdin_watcher;	1095	ev_io stdin_watcher;
980		1096
981	ev_init (&stdin_watcher, my_cb);	1097	ev_init (&stdin_watcher, my_cb);
982	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1098	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
983	ev_io_start (loop, &stdin_watcher);	1099	ev_io_start (loop, &stdin_watcher);
984		1100
985	ev_loop (loop, 0);	1101	ev_run (loop, 0);
986		1102
987	As you can see, you are responsible for allocating the memory for your	1103	As you can see, you are responsible for allocating the memory for your
988	watcher structures (and it is I<usually> a bad idea to do this on the	1104	watcher structures (and it is I<usually> a bad idea to do this on the
989	stack).	1105	stack).
990		1106
991	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1107	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
992	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1108	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
993		1109
994	Each watcher structure must be initialised by a call to C<ev_init	1110	Each watcher structure must be initialised by a call to C<ev_init (watcher
995	(watcher *, callback)>, which expects a callback to be provided. This	1111	*, callback)>, which expects a callback to be provided. This callback is
996	callback gets invoked each time the event occurs (or, in the case of I/O	1112	invoked each time the event occurs (or, in the case of I/O watchers, each
997	watchers, each time the event loop detects that the file descriptor given	1113	time the event loop detects that the file descriptor given is readable
998	is readable and/or writable).	1114	and/or writable).
999		1115
1000	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1116	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
1001	macro to configure it, with arguments specific to the watcher type. There	1117	macro to configure it, with arguments specific to the watcher type. There
1002	is also a macro to combine initialisation and setting in one call: C<<	1118	is also a macro to combine initialisation and setting in one call: C<<
1003	ev_TYPE_init (watcher *, callback, ...) >>.	1119	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
1026	=item C<EV_WRITE>	1142	=item C<EV_WRITE>
1027		1143
1028	The file descriptor in the C<ev_io> watcher has become readable and/or	1144	The file descriptor in the C<ev_io> watcher has become readable and/or
1029	writable.	1145	writable.
1030		1146
1031	=item C<EV_TIMEOUT>	1147	=item C<EV_TIMER>
1032		1148
1033	The C<ev_timer> watcher has timed out.	1149	The C<ev_timer> watcher has timed out.
1034		1150
1035	=item C<EV_PERIODIC>	1151	=item C<EV_PERIODIC>
1036		1152
…		…
1054		1170
1055	=item C<EV_PREPARE>	1171	=item C<EV_PREPARE>
1056		1172
1057	=item C<EV_CHECK>	1173	=item C<EV_CHECK>
1058		1174
1059	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1175	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
1060	to gather new events, and all C<ev_check> watchers are invoked just after	1176	to gather new events, and all C<ev_check> watchers are invoked just after
1061	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1177	C<ev_run> has gathered them, but before it invokes any callbacks for any
1062	received events. Callbacks of both watcher types can start and stop as	1178	received events. Callbacks of both watcher types can start and stop as
1063	many watchers as they want, and all of them will be taken into account	1179	many watchers as they want, and all of them will be taken into account
1064	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1180	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
1065	C<ev_loop> from blocking).	1181	C<ev_run> from blocking).
1066		1182
1067	=item C<EV_EMBED>	1183	=item C<EV_EMBED>
1068		1184
1069	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1185	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1070		1186
1071	=item C<EV_FORK>	1187	=item C<EV_FORK>
1072		1188
1073	The event loop has been resumed in the child process after fork (see	1189	The event loop has been resumed in the child process after fork (see
1074	C<ev_fork>).	1190	C<ev_fork>).
		1191
		1192	=item C<EV_CLEANUP>
		1193
		1194	The event loop is about to be destroyed (see C<ev_cleanup>).
1075		1195
1076	=item C<EV_ASYNC>	1196	=item C<EV_ASYNC>
1077		1197
1078	The given async watcher has been asynchronously notified (see C<ev_async>).	1198	The given async watcher has been asynchronously notified (see C<ev_async>).
1079		1199
…		…
1252	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related	1372	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1253	functions that do not need a watcher.	1373	functions that do not need a watcher.
1254		1374
1255	=back	1375	=back
1256		1376
		1377	See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR
		1378	OWN COMPOSITE WATCHERS> idioms.
1257		1379
1258	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1380	=head2 WATCHER STATES
1259		1381
1260	Each watcher has, by default, a member C<void *data> that you can change	1382	There are various watcher states mentioned throughout this manual -
1261	and read at any time: libev will completely ignore it. This can be used	1383	active, pending and so on. In this section these states and the rules to
1262	to associate arbitrary data with your watcher. If you need more data and	1384	transition between them will be described in more detail - and while these
1263	don't want to allocate memory and store a pointer to it in that data	1385	rules might look complicated, they usually do "the right thing".
1264	member, you can also "subclass" the watcher type and provide your own
1265	data:
1266		1386
1267	struct my_io	1387	=over 4
1268	{
1269	ev_io io;
1270	int otherfd;
1271	void *somedata;
1272	struct whatever *mostinteresting;
1273	};
1274		1388
1275	...	1389	=item initialiased
1276	struct my_io w;
1277	ev_io_init (&w.io, my_cb, fd, EV_READ);
1278		1390
1279	And since your callback will be called with a pointer to the watcher, you	1391	Before a watcher can be registered with the event loop it has to be
1280	can cast it back to your own type:	1392	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1393	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1281		1394
1282	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)	1395	In this state it is simply some block of memory that is suitable for
1283	{	1396	use in an event loop. It can be moved around, freed, reused etc. at
1284	struct my_io *w = (struct my_io *)w_;	1397	will - as long as you either keep the memory contents intact, or call
1285	...	1398	C<ev_TYPE_init> again.
1286	}
1287		1399
1288	More interesting and less C-conformant ways of casting your callback type	1400	=item started/running/active
1289	instead have been omitted.
1290		1401
1291	Another common scenario is to use some data structure with multiple	1402	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1292	embedded watchers:	1403	property of the event loop, and is actively waiting for events. While in
		1404	this state it cannot be accessed (except in a few documented ways), moved,
		1405	freed or anything else - the only legal thing is to keep a pointer to it,
		1406	and call libev functions on it that are documented to work on active watchers.
1293		1407
1294	struct my_biggy	1408	=item pending
1295	{
1296	int some_data;
1297	ev_timer t1;
1298	ev_timer t2;
1299	}
1300		1409
1301	In this case getting the pointer to C<my_biggy> is a bit more	1410	If a watcher is active and libev determines that an event it is interested
1302	complicated: Either you store the address of your C<my_biggy> struct	1411	in has occurred (such as a timer expiring), it will become pending. It will
1303	in the C<data> member of the watcher (for woozies), or you need to use	1412	stay in this pending state until either it is stopped or its callback is
1304	some pointer arithmetic using C<offsetof> inside your watchers (for real	1413	about to be invoked, so it is not normally pending inside the watcher
1305	programmers):	1414	callback.
1306		1415
1307	#include <stddef.h>	1416	The watcher might or might not be active while it is pending (for example,
		1417	an expired non-repeating timer can be pending but no longer active). If it
		1418	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1419	but it is still property of the event loop at this time, so cannot be
		1420	moved, freed or reused. And if it is active the rules described in the
		1421	previous item still apply.
1308		1422
1309	static void	1423	It is also possible to feed an event on a watcher that is not active (e.g.
1310	t1_cb (EV_P_ ev_timer *w, int revents)	1424	via C<ev_feed_event>), in which case it becomes pending without being
1311	{	1425	active.
1312	struct my_biggy big = (struct my_biggy *)
1313	(((char *)w) - offsetof (struct my_biggy, t1));
1314	}
1315		1426
1316	static void	1427	=item stopped
1317	t2_cb (EV_P_ ev_timer *w, int revents)	1428
1318	{	1429	A watcher can be stopped implicitly by libev (in which case it might still
1319	struct my_biggy big = (struct my_biggy *)	1430	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1320	(((char *)w) - offsetof (struct my_biggy, t2));	1431	latter will clear any pending state the watcher might be in, regardless
1321	}	1432	of whether it was active or not, so stopping a watcher explicitly before
		1433	freeing it is often a good idea.
		1434
		1435	While stopped (and not pending) the watcher is essentially in the
		1436	initialised state, that is, it can be reused, moved, modified in any way
		1437	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1438	it again).
		1439
		1440	=back
1322		1441
1323	=head2 WATCHER PRIORITY MODELS	1442	=head2 WATCHER PRIORITY MODELS
1324		1443
1325	Many event loops support I<watcher priorities>, which are usually small	1444	Many event loops support I<watcher priorities>, which are usually small
1326	integers that influence the ordering of event callback invocation	1445	integers that influence the ordering of event callback invocation
…		…
1369		1488
1370	For example, to emulate how many other event libraries handle priorities,	1489	For example, to emulate how many other event libraries handle priorities,
1371	you can associate an C<ev_idle> watcher to each such watcher, and in	1490	you can associate an C<ev_idle> watcher to each such watcher, and in
1372	the normal watcher callback, you just start the idle watcher. The real	1491	the normal watcher callback, you just start the idle watcher. The real
1373	processing is done in the idle watcher callback. This causes libev to	1492	processing is done in the idle watcher callback. This causes libev to
1374	continously poll and process kernel event data for the watcher, but when	1493	continuously poll and process kernel event data for the watcher, but when
1375	the lock-out case is known to be rare (which in turn is rare :), this is	1494	the lock-out case is known to be rare (which in turn is rare :), this is
1376	workable.	1495	workable.
1377		1496
1378	Usually, however, the lock-out model implemented that way will perform	1497	Usually, however, the lock-out model implemented that way will perform
1379	miserably under the type of load it was designed to handle. In that case,	1498	miserably under the type of load it was designed to handle. In that case,
…		…
1393	{	1512	{
1394	// stop the I/O watcher, we received the event, but	1513	// stop the I/O watcher, we received the event, but
1395	// are not yet ready to handle it.	1514	// are not yet ready to handle it.
1396	ev_io_stop (EV_A_ w);	1515	ev_io_stop (EV_A_ w);
1397		1516
1398	// start the idle watcher to ahndle the actual event.	1517	// start the idle watcher to handle the actual event.
1399	// it will not be executed as long as other watchers	1518	// it will not be executed as long as other watchers
1400	// with the default priority are receiving events.	1519	// with the default priority are receiving events.
1401	ev_idle_start (EV_A_ &idle);	1520	ev_idle_start (EV_A_ &idle);
1402	}	1521	}
1403		1522
…		…
1453	In general you can register as many read and/or write event watchers per	1572	In general you can register as many read and/or write event watchers per
1454	fd as you want (as long as you don't confuse yourself). Setting all file	1573	fd as you want (as long as you don't confuse yourself). Setting all file
1455	descriptors to non-blocking mode is also usually a good idea (but not	1574	descriptors to non-blocking mode is also usually a good idea (but not
1456	required if you know what you are doing).	1575	required if you know what you are doing).
1457		1576
1458	If you cannot use non-blocking mode, then force the use of a
1459	known-to-be-good backend (at the time of this writing, this includes only
1460	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1461	descriptors for which non-blocking operation makes no sense (such as
1462	files) - libev doesn't guarentee any specific behaviour in that case.
1463
1464	Another thing you have to watch out for is that it is quite easy to	1577	Another thing you have to watch out for is that it is quite easy to
1465	receive "spurious" readiness notifications, that is your callback might	1578	receive "spurious" readiness notifications, that is, your callback might
1466	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1579	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1467	because there is no data. Not only are some backends known to create a	1580	because there is no data. It is very easy to get into this situation even
1468	lot of those (for example Solaris ports), it is very easy to get into	1581	with a relatively standard program structure. Thus it is best to always
1469	this situation even with a relatively standard program structure. Thus	1582	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1470	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1471	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1583	preferable to a program hanging until some data arrives.
1472		1584
1473	If you cannot run the fd in non-blocking mode (for example you should	1585	If you cannot run the fd in non-blocking mode (for example you should
1474	not play around with an Xlib connection), then you have to separately	1586	not play around with an Xlib connection), then you have to separately
1475	re-test whether a file descriptor is really ready with a known-to-be good	1587	re-test whether a file descriptor is really ready with a known-to-be good
1476	interface such as poll (fortunately in our Xlib example, Xlib already	1588	interface such as poll (fortunately in the case of Xlib, it already does
1477	does this on its own, so its quite safe to use). Some people additionally	1589	this on its own, so its quite safe to use). Some people additionally
1478	use C<SIGALRM> and an interval timer, just to be sure you won't block	1590	use C<SIGALRM> and an interval timer, just to be sure you won't block
1479	indefinitely.	1591	indefinitely.
1480		1592
1481	But really, best use non-blocking mode.	1593	But really, best use non-blocking mode.
1482		1594
…		…
1510		1622
1511	There is no workaround possible except not registering events	1623	There is no workaround possible except not registering events
1512	for potentially C<dup ()>'ed file descriptors, or to resort to	1624	for potentially C<dup ()>'ed file descriptors, or to resort to
1513	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1625	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1514		1626
		1627	=head3 The special problem of files
		1628
		1629	Many people try to use C<select> (or libev) on file descriptors
		1630	representing files, and expect it to become ready when their program
		1631	doesn't block on disk accesses (which can take a long time on their own).
		1632
		1633	However, this cannot ever work in the "expected" way - you get a readiness
		1634	notification as soon as the kernel knows whether and how much data is
		1635	there, and in the case of open files, that's always the case, so you
		1636	always get a readiness notification instantly, and your read (or possibly
		1637	write) will still block on the disk I/O.
		1638
		1639	Another way to view it is that in the case of sockets, pipes, character
		1640	devices and so on, there is another party (the sender) that delivers data
		1641	on its own, but in the case of files, there is no such thing: the disk
		1642	will not send data on its own, simply because it doesn't know what you
		1643	wish to read - you would first have to request some data.
		1644
		1645	Since files are typically not-so-well supported by advanced notification
		1646	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1647	to files, even though you should not use it. The reason for this is
		1648	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1649	usually a tty, often a pipe, but also sometimes files or special devices
		1650	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1651	F</dev/urandom>), and even though the file might better be served with
		1652	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1653	it "just works" instead of freezing.
		1654
		1655	So avoid file descriptors pointing to files when you know it (e.g. use
		1656	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1657	when you rarely read from a file instead of from a socket, and want to
		1658	reuse the same code path.
		1659
1515	=head3 The special problem of fork	1660	=head3 The special problem of fork
1516		1661
1517	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1662	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1518	useless behaviour. Libev fully supports fork, but needs to be told about	1663	useless behaviour. Libev fully supports fork, but needs to be told about
1519	it in the child.	1664	it in the child if you want to continue to use it in the child.
1520		1665
1521	To support fork in your programs, you either have to call	1666	To support fork in your child processes, you have to call C<ev_loop_fork
1522	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1667	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1523	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1668	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1524	C<EVBACKEND_POLL>.
1525		1669
1526	=head3 The special problem of SIGPIPE	1670	=head3 The special problem of SIGPIPE
1527		1671
1528	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1672	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1529	when writing to a pipe whose other end has been closed, your program gets	1673	when writing to a pipe whose other end has been closed, your program gets
…		…
1532		1676
1533	So when you encounter spurious, unexplained daemon exits, make sure you	1677	So when you encounter spurious, unexplained daemon exits, make sure you
1534	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1678	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1535	somewhere, as that would have given you a big clue).	1679	somewhere, as that would have given you a big clue).
1536		1680
		1681	=head3 The special problem of accept()ing when you can't
		1682
		1683	Many implementations of the POSIX C<accept> function (for example,
		1684	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1685	connection from the pending queue in all error cases.
		1686
		1687	For example, larger servers often run out of file descriptors (because
		1688	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1689	rejecting the connection, leading to libev signalling readiness on
		1690	the next iteration again (the connection still exists after all), and
		1691	typically causing the program to loop at 100% CPU usage.
		1692
		1693	Unfortunately, the set of errors that cause this issue differs between
		1694	operating systems, there is usually little the app can do to remedy the
		1695	situation, and no known thread-safe method of removing the connection to
		1696	cope with overload is known (to me).
		1697
		1698	One of the easiest ways to handle this situation is to just ignore it
		1699	- when the program encounters an overload, it will just loop until the
		1700	situation is over. While this is a form of busy waiting, no OS offers an
		1701	event-based way to handle this situation, so it's the best one can do.
		1702
		1703	A better way to handle the situation is to log any errors other than
		1704	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1705	messages, and continue as usual, which at least gives the user an idea of
		1706	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1707	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1708	usage.
		1709
		1710	If your program is single-threaded, then you could also keep a dummy file
		1711	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1712	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1713	close that fd, and create a new dummy fd. This will gracefully refuse
		1714	clients under typical overload conditions.
		1715
		1716	The last way to handle it is to simply log the error and C<exit>, as
		1717	is often done with C<malloc> failures, but this results in an easy
		1718	opportunity for a DoS attack.
1537		1719
1538	=head3 Watcher-Specific Functions	1720	=head3 Watcher-Specific Functions
1539		1721
1540	=over 4	1722	=over 4
1541		1723
…		…
1573	...	1755	...
1574	struct ev_loop *loop = ev_default_init (0);	1756	struct ev_loop *loop = ev_default_init (0);
1575	ev_io stdin_readable;	1757	ev_io stdin_readable;
1576	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1758	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1577	ev_io_start (loop, &stdin_readable);	1759	ev_io_start (loop, &stdin_readable);
1578	ev_loop (loop, 0);	1760	ev_run (loop, 0);
1579		1761
1580		1762
1581	=head2 C<ev_timer> - relative and optionally repeating timeouts	1763	=head2 C<ev_timer> - relative and optionally repeating timeouts
1582		1764
1583	Timer watchers are simple relative timers that generate an event after a	1765	Timer watchers are simple relative timers that generate an event after a
…		…
1589	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1771	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1590	monotonic clock option helps a lot here).	1772	monotonic clock option helps a lot here).
1591		1773
1592	The callback is guaranteed to be invoked only I<after> its timeout has	1774	The callback is guaranteed to be invoked only I<after> its timeout has
1593	passed (not I<at>, so on systems with very low-resolution clocks this	1775	passed (not I<at>, so on systems with very low-resolution clocks this
1594	might introduce a small delay). If multiple timers become ready during the	1776	might introduce a small delay, see "the special problem of being too
		1777	early", below). If multiple timers become ready during the same loop
1595	same loop iteration then the ones with earlier time-out values are invoked	1778	iteration then the ones with earlier time-out values are invoked before
1596	before ones of the same priority with later time-out values (but this is	1779	ones of the same priority with later time-out values (but this is no
1597	no longer true when a callback calls C<ev_loop> recursively).	1780	longer true when a callback calls C<ev_run> recursively).
1598		1781
1599	=head3 Be smart about timeouts	1782	=head3 Be smart about timeouts
1600		1783
1601	Many real-world problems involve some kind of timeout, usually for error	1784	Many real-world problems involve some kind of timeout, usually for error
1602	recovery. A typical example is an HTTP request - if the other side hangs,	1785	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1677		1860
1678	In this case, it would be more efficient to leave the C<ev_timer> alone,	1861	In this case, it would be more efficient to leave the C<ev_timer> alone,
1679	but remember the time of last activity, and check for a real timeout only	1862	but remember the time of last activity, and check for a real timeout only
1680	within the callback:	1863	within the callback:
1681		1864
		1865	ev_tstamp timeout = 60.;
1682	ev_tstamp last_activity; // time of last activity	1866	ev_tstamp last_activity; // time of last activity
		1867	ev_timer timer;
1683		1868
1684	static void	1869	static void
1685	callback (EV_P_ ev_timer *w, int revents)	1870	callback (EV_P_ ev_timer *w, int revents)
1686	{	1871	{
1687	ev_tstamp now = ev_now (EV_A);	1872	// calculate when the timeout would happen
1688	ev_tstamp timeout = last_activity + 60.;	1873	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1689		1874
1690	// if last_activity + 60. is older than now, we did time out	1875	// if negative, it means we the timeout already occured
1691	if (timeout < now)	1876	if (after < 0.)
1692	{	1877	{
1693	// timeout occured, take action	1878	// timeout occurred, take action
1694	}	1879	}
1695	else	1880	else
1696	{	1881	{
1697	// callback was invoked, but there was some activity, re-arm	1882	// callback was invoked, but there was some recent
1698	// the watcher to fire in last_activity + 60, which is	1883	// activity. simply restart the timer to time out
1699	// guaranteed to be in the future, so "again" is positive:	1884	// after "after" seconds, which is the earliest time
1700	w->repeat = timeout - now;	1885	// the timeout can occur.
		1886	ev_timer_set (w, after, 0.);
1701	ev_timer_again (EV_A_ w);	1887	ev_timer_start (EV_A_ w);
1702	}	1888	}
1703	}	1889	}
1704		1890
1705	To summarise the callback: first calculate the real timeout (defined	1891	To summarise the callback: first calculate in how many seconds the
1706	as "60 seconds after the last activity"), then check if that time has	1892	timeout will occur (by calculating the absolute time when it would occur,
1707	been reached, which means something I<did>, in fact, time out. Otherwise	1893	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1708	the callback was invoked too early (C<timeout> is in the future), so	1894	(EV_A)> from that).
1709	re-schedule the timer to fire at that future time, to see if maybe we have
1710	a timeout then.
1711		1895
1712	Note how C<ev_timer_again> is used, taking advantage of the	1896	If this value is negative, then we are already past the timeout, i.e. we
1713	C<ev_timer_again> optimisation when the timer is already running.	1897	timed out, and need to do whatever is needed in this case.
		1898
		1899	Otherwise, we now the earliest time at which the timeout would trigger,
		1900	and simply start the timer with this timeout value.
		1901
		1902	In other words, each time the callback is invoked it will check whether
		1903	the timeout cocured. If not, it will simply reschedule itself to check
		1904	again at the earliest time it could time out. Rinse. Repeat.
1714		1905
1715	This scheme causes more callback invocations (about one every 60 seconds	1906	This scheme causes more callback invocations (about one every 60 seconds
1716	minus half the average time between activity), but virtually no calls to	1907	minus half the average time between activity), but virtually no calls to
1717	libev to change the timeout.	1908	libev to change the timeout.
1718		1909
1719	To start the timer, simply initialise the watcher and set C<last_activity>	1910	To start the machinery, simply initialise the watcher and set
1720	to the current time (meaning we just have some activity :), then call the	1911	C<last_activity> to the current time (meaning there was some activity just
1721	callback, which will "do the right thing" and start the timer:	1912	now), then call the callback, which will "do the right thing" and start
		1913	the timer:
1722		1914
		1915	last_activity = ev_now (EV_A);
1723	ev_init (timer, callback);	1916	ev_init (&timer, callback);
1724	last_activity = ev_now (loop);	1917	callback (EV_A_ &timer, 0);
1725	callback (loop, timer, EV_TIMEOUT);
1726		1918
1727	And when there is some activity, simply store the current time in	1919	When there is some activity, simply store the current time in
1728	C<last_activity>, no libev calls at all:	1920	C<last_activity>, no libev calls at all:
1729		1921
		1922	if (activity detected)
1730	last_actiivty = ev_now (loop);	1923	last_activity = ev_now (EV_A);
		1924
		1925	When your timeout value changes, then the timeout can be changed by simply
		1926	providing a new value, stopping the timer and calling the callback, which
		1927	will agaion do the right thing (for example, time out immediately :).
		1928
		1929	timeout = new_value;
		1930	ev_timer_stop (EV_A_ &timer);
		1931	callback (EV_A_ &timer, 0);
1731		1932
1732	This technique is slightly more complex, but in most cases where the	1933	This technique is slightly more complex, but in most cases where the
1733	time-out is unlikely to be triggered, much more efficient.	1934	time-out is unlikely to be triggered, much more efficient.
1734
1735	Changing the timeout is trivial as well (if it isn't hard-coded in the
1736	callback :) - just change the timeout and invoke the callback, which will
1737	fix things for you.
1738		1935
1739	=item 4. Wee, just use a double-linked list for your timeouts.	1936	=item 4. Wee, just use a double-linked list for your timeouts.
1740		1937
1741	If there is not one request, but many thousands (millions...), all	1938	If there is not one request, but many thousands (millions...), all
1742	employing some kind of timeout with the same timeout value, then one can	1939	employing some kind of timeout with the same timeout value, then one can
…		…
1769	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	1966	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1770	rather complicated, but extremely efficient, something that really pays	1967	rather complicated, but extremely efficient, something that really pays
1771	off after the first million or so of active timers, i.e. it's usually	1968	off after the first million or so of active timers, i.e. it's usually
1772	overkill :)	1969	overkill :)
1773		1970
		1971	=head3 The special problem of being too early
		1972
		1973	If you ask a timer to call your callback after three seconds, then
		1974	you expect it to be invoked after three seconds - but of course, this
		1975	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		1976	guaranteed to any precision by libev - imagine somebody suspending the
		1977	process with a STOP signal for a few hours for example.
		1978
		1979	So, libev tries to invoke your callback as soon as possible I<after> the
		1980	delay has occurred, but cannot guarantee this.
		1981
		1982	A less obvious failure mode is calling your callback too early: many event
		1983	loops compare timestamps with a "elapsed delay >= requested delay", but
		1984	this can cause your callback to be invoked much earlier than you would
		1985	expect.
		1986
		1987	To see why, imagine a system with a clock that only offers full second
		1988	resolution (think windows if you can't come up with a broken enough OS
		1989	yourself). If you schedule a one-second timer at the time 500.9, then the
		1990	event loop will schedule your timeout to elapse at a system time of 500
		1991	(500.9 truncated to the resolution) + 1, or 501.
		1992
		1993	If an event library looks at the timeout 0.1s later, it will see "501 >=
		1994	501" and invoke the callback 0.1s after it was started, even though a
		1995	one-second delay was requested - this is being "too early", despite best
		1996	intentions.
		1997
		1998	This is the reason why libev will never invoke the callback if the elapsed
		1999	delay equals the requested delay, but only when the elapsed delay is
		2000	larger than the requested delay. In the example above, libev would only invoke
		2001	the callback at system time 502, or 1.1s after the timer was started.
		2002
		2003	So, while libev cannot guarantee that your callback will be invoked
		2004	exactly when requested, it I<can> and I<does> guarantee that the requested
		2005	delay has actually elapsed, or in other words, it always errs on the "too
		2006	late" side of things.
		2007
1774	=head3 The special problem of time updates	2008	=head3 The special problem of time updates
1775		2009
1776	Establishing the current time is a costly operation (it usually takes at	2010	Establishing the current time is a costly operation (it usually takes
1777	least two system calls): EV therefore updates its idea of the current	2011	at least one system call): EV therefore updates its idea of the current
1778	time only before and after C<ev_loop> collects new events, which causes a	2012	time only before and after C<ev_run> collects new events, which causes a
1779	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2013	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1780	lots of events in one iteration.	2014	lots of events in one iteration.
1781		2015
1782	The relative timeouts are calculated relative to the C<ev_now ()>	2016	The relative timeouts are calculated relative to the C<ev_now ()>
1783	time. This is usually the right thing as this timestamp refers to the time	2017	time. This is usually the right thing as this timestamp refers to the time
…		…
1788	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2022	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1789		2023
1790	If the event loop is suspended for a long time, you can also force an	2024	If the event loop is suspended for a long time, you can also force an
1791	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2025	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1792	()>.	2026	()>.
		2027
		2028	=head3 The special problem of unsynchronised clocks
		2029
		2030	Modern systems have a variety of clocks - libev itself uses the normal
		2031	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2032	jumps).
		2033
		2034	Neither of these clocks is synchronised with each other or any other clock
		2035	on the system, so C<ev_time ()> might return a considerably different time
		2036	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2037	a call to C<gettimeofday> might return a second count that is one higher
		2038	than a directly following call to C<time>.
		2039
		2040	The moral of this is to only compare libev-related timestamps with
		2041	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2042	a second or so.
		2043
		2044	One more problem arises due to this lack of synchronisation: if libev uses
		2045	the system monotonic clock and you compare timestamps from C<ev_time>
		2046	or C<ev_now> from when you started your timer and when your callback is
		2047	invoked, you will find that sometimes the callback is a bit "early".
		2048
		2049	This is because C<ev_timer>s work in real time, not wall clock time, so
		2050	libev makes sure your callback is not invoked before the delay happened,
		2051	I<measured according to the real time>, not the system clock.
		2052
		2053	If your timeouts are based on a physical timescale (e.g. "time out this
		2054	connection after 100 seconds") then this shouldn't bother you as it is
		2055	exactly the right behaviour.
		2056
		2057	If you want to compare wall clock/system timestamps to your timers, then
		2058	you need to use C<ev_periodic>s, as these are based on the wall clock
		2059	time, where your comparisons will always generate correct results.
1793		2060
1794	=head3 The special problems of suspended animation	2061	=head3 The special problems of suspended animation
1795		2062
1796	When you leave the server world it is quite customary to hit machines that	2063	When you leave the server world it is quite customary to hit machines that
1797	can suspend/hibernate - what happens to the clocks during such a suspend?	2064	can suspend/hibernate - what happens to the clocks during such a suspend?
…		…
1841	keep up with the timer (because it takes longer than those 10 seconds to	2108	keep up with the timer (because it takes longer than those 10 seconds to
1842	do stuff) the timer will not fire more than once per event loop iteration.	2109	do stuff) the timer will not fire more than once per event loop iteration.
1843		2110
1844	=item ev_timer_again (loop, ev_timer *)	2111	=item ev_timer_again (loop, ev_timer *)
1845		2112
1846	This will act as if the timer timed out and restart it again if it is	2113	This will act as if the timer timed out and restarts it again if it is
1847	repeating. The exact semantics are:	2114	repeating. The exact semantics are:
1848		2115
1849	If the timer is pending, its pending status is cleared.	2116	If the timer is pending, its pending status is cleared.
1850		2117
1851	If the timer is started but non-repeating, stop it (as if it timed out).	2118	If the timer is started but non-repeating, stop it (as if it timed out).
…		…
1861	Returns the remaining time until a timer fires. If the timer is active,	2128	Returns the remaining time until a timer fires. If the timer is active,
1862	then this time is relative to the current event loop time, otherwise it's	2129	then this time is relative to the current event loop time, otherwise it's
1863	the timeout value currently configured.	2130	the timeout value currently configured.
1864		2131
1865	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns	2132	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1866	C<5>. When the timer is started and one second passes, C<ev_timer_remain>	2133	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
1867	will return C<4>. When the timer expires and is restarted, it will return	2134	will return C<4>. When the timer expires and is restarted, it will return
1868	roughly C<7> (likely slightly less as callback invocation takes some time,	2135	roughly C<7> (likely slightly less as callback invocation takes some time,
1869	too), and so on.	2136	too), and so on.
1870		2137
1871	=item ev_tstamp repeat [read-write]	2138	=item ev_tstamp repeat [read-write]
…		…
1900	}	2167	}
1901		2168
1902	ev_timer mytimer;	2169	ev_timer mytimer;
1903	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2170	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1904	ev_timer_again (&mytimer); /* start timer */	2171	ev_timer_again (&mytimer); /* start timer */
1905	ev_loop (loop, 0);	2172	ev_run (loop, 0);
1906		2173
1907	// and in some piece of code that gets executed on any "activity":	2174	// and in some piece of code that gets executed on any "activity":
1908	// reset the timeout to start ticking again at 10 seconds	2175	// reset the timeout to start ticking again at 10 seconds
1909	ev_timer_again (&mytimer);	2176	ev_timer_again (&mytimer);
1910		2177
…		…
1936		2203
1937	As with timers, the callback is guaranteed to be invoked only when the	2204	As with timers, the callback is guaranteed to be invoked only when the
1938	point in time where it is supposed to trigger has passed. If multiple	2205	point in time where it is supposed to trigger has passed. If multiple
1939	timers become ready during the same loop iteration then the ones with	2206	timers become ready during the same loop iteration then the ones with
1940	earlier time-out values are invoked before ones with later time-out values	2207	earlier time-out values are invoked before ones with later time-out values
1941	(but this is no longer true when a callback calls C<ev_loop> recursively).	2208	(but this is no longer true when a callback calls C<ev_run> recursively).
1942		2209
1943	=head3 Watcher-Specific Functions and Data Members	2210	=head3 Watcher-Specific Functions and Data Members
1944		2211
1945	=over 4	2212	=over 4
1946		2213
…		…
1981		2248
1982	Another way to think about it (for the mathematically inclined) is that	2249	Another way to think about it (for the mathematically inclined) is that
1983	C<ev_periodic> will try to run the callback in this mode at the next possible	2250	C<ev_periodic> will try to run the callback in this mode at the next possible
1984	time where C<time = offset (mod interval)>, regardless of any time jumps.	2251	time where C<time = offset (mod interval)>, regardless of any time jumps.
1985		2252
1986	For numerical stability it is preferable that the C<offset> value is near	2253	The C<interval> I<MUST> be positive, and for numerical stability, the
1987	C<ev_now ()> (the current time), but there is no range requirement for	2254	interval value should be higher than C<1/8192> (which is around 100
1988	this value, and in fact is often specified as zero.	2255	microseconds) and C<offset> should be higher than C<0> and should have
		2256	at most a similar magnitude as the current time (say, within a factor of
		2257	ten). Typical values for offset are, in fact, C<0> or something between
		2258	C<0> and C<interval>, which is also the recommended range.
1989		2259
1990	Note also that there is an upper limit to how often a timer can fire (CPU	2260	Note also that there is an upper limit to how often a timer can fire (CPU
1991	speed for example), so if C<interval> is very small then timing stability	2261	speed for example), so if C<interval> is very small then timing stability
1992	will of course deteriorate. Libev itself tries to be exact to be about one	2262	will of course deteriorate. Libev itself tries to be exact to be about one
1993	millisecond (if the OS supports it and the machine is fast enough).	2263	millisecond (if the OS supports it and the machine is fast enough).
…		…
2074	Example: Call a callback every hour, or, more precisely, whenever the	2344	Example: Call a callback every hour, or, more precisely, whenever the
2075	system time is divisible by 3600. The callback invocation times have	2345	system time is divisible by 3600. The callback invocation times have
2076	potentially a lot of jitter, but good long-term stability.	2346	potentially a lot of jitter, but good long-term stability.
2077		2347
2078	static void	2348	static void
2079	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2349	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
2080	{	2350	{
2081	... its now a full hour (UTC, or TAI or whatever your clock follows)	2351	... its now a full hour (UTC, or TAI or whatever your clock follows)
2082	}	2352	}
2083		2353
2084	ev_periodic hourly_tick;	2354	ev_periodic hourly_tick;
…		…
2107		2377
2108	=head2 C<ev_signal> - signal me when a signal gets signalled!	2378	=head2 C<ev_signal> - signal me when a signal gets signalled!
2109		2379
2110	Signal watchers will trigger an event when the process receives a specific	2380	Signal watchers will trigger an event when the process receives a specific
2111	signal one or more times. Even though signals are very asynchronous, libev	2381	signal one or more times. Even though signals are very asynchronous, libev
2112	will try it's best to deliver signals synchronously, i.e. as part of the	2382	will try its best to deliver signals synchronously, i.e. as part of the
2113	normal event processing, like any other event.	2383	normal event processing, like any other event.
2114		2384
2115	If you want signals to be delivered truly asynchronously, just use	2385	If you want signals to be delivered truly asynchronously, just use
2116	C<sigaction> as you would do without libev and forget about sharing	2386	C<sigaction> as you would do without libev and forget about sharing
2117	the signal. You can even use C<ev_async> from a signal handler to	2387	the signal. You can even use C<ev_async> from a signal handler to
…		…
2131	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should	2401	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
2132	not be unduly interrupted. If you have a problem with system calls getting	2402	not be unduly interrupted. If you have a problem with system calls getting
2133	interrupted by signals you can block all signals in an C<ev_check> watcher	2403	interrupted by signals you can block all signals in an C<ev_check> watcher
2134	and unblock them in an C<ev_prepare> watcher.	2404	and unblock them in an C<ev_prepare> watcher.
2135		2405
2136	=head3 The special problem of inheritance over execve	2406	=head3 The special problem of inheritance over fork/execve/pthread_create
2137		2407
2138	Both the signal mask (C<sigprocmask>) and the signal disposition	2408	Both the signal mask (C<sigprocmask>) and the signal disposition
2139	(C<sigaction>) are unspecified after starting a signal watcher (and after	2409	(C<sigaction>) are unspecified after starting a signal watcher (and after
2140	stopping it again), that is, libev might or might not block the signal,	2410	stopping it again), that is, libev might or might not block the signal,
2141	and might or might not set or restore the installed signal handler.	2411	and might or might not set or restore the installed signal handler (but
		2412	see C<EVFLAG_NOSIGMASK>).
2142		2413
2143	While this does not matter for the signal disposition (libev never	2414	While this does not matter for the signal disposition (libev never
2144	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on	2415	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
2145	C<execve>), this matters for the signal mask: many programs do not expect	2416	C<execve>), this matters for the signal mask: many programs do not expect
2146	certain signals to be blocked.	2417	certain signals to be blocked.
…		…
2151		2422
2152	The simplest way to ensure that the signal mask is reset in the child is	2423	The simplest way to ensure that the signal mask is reset in the child is
2153	to install a fork handler with C<pthread_atfork> that resets it. That will	2424	to install a fork handler with C<pthread_atfork> that resets it. That will
2154	catch fork calls done by libraries (such as the libc) as well.	2425	catch fork calls done by libraries (such as the libc) as well.
2155		2426
2156	In current versions of libev, you can also ensure that the signal mask is	2427	In current versions of libev, the signal will not be blocked indefinitely
2157	not blocking any signals (except temporarily, so thread users watch out)	2428	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
2158	by specifying the C<EVFLAG_NOSIGFD> when creating the event loop. This	2429	the window of opportunity for problems, it will not go away, as libev
2159	is not guaranteed for future versions, however.	2430	I<has> to modify the signal mask, at least temporarily.
		2431
		2432	So I can't stress this enough: I<If you do not reset your signal mask when
		2433	you expect it to be empty, you have a race condition in your code>. This
		2434	is not a libev-specific thing, this is true for most event libraries.
		2435
		2436	=head3 The special problem of threads signal handling
		2437
		2438	POSIX threads has problematic signal handling semantics, specifically,
		2439	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2440	threads in a process block signals, which is hard to achieve.
		2441
		2442	When you want to use sigwait (or mix libev signal handling with your own
		2443	for the same signals), you can tackle this problem by globally blocking
		2444	all signals before creating any threads (or creating them with a fully set
		2445	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2446	loops. Then designate one thread as "signal receiver thread" which handles
		2447	these signals. You can pass on any signals that libev might be interested
		2448	in by calling C<ev_feed_signal>.
2160		2449
2161	=head3 Watcher-Specific Functions and Data Members	2450	=head3 Watcher-Specific Functions and Data Members
2162		2451
2163	=over 4	2452	=over 4
2164		2453
…		…
2180	Example: Try to exit cleanly on SIGINT.	2469	Example: Try to exit cleanly on SIGINT.
2181		2470
2182	static void	2471	static void
2183	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2472	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2184	{	2473	{
2185	ev_unloop (loop, EVUNLOOP_ALL);	2474	ev_break (loop, EVBREAK_ALL);
2186	}	2475	}
2187		2476
2188	ev_signal signal_watcher;	2477	ev_signal signal_watcher;
2189	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2478	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2190	ev_signal_start (loop, &signal_watcher);	2479	ev_signal_start (loop, &signal_watcher);
…		…
2576		2865
2577	Prepare and check watchers are usually (but not always) used in pairs:	2866	Prepare and check watchers are usually (but not always) used in pairs:
2578	prepare watchers get invoked before the process blocks and check watchers	2867	prepare watchers get invoked before the process blocks and check watchers
2579	afterwards.	2868	afterwards.
2580		2869
2581	You I<must not> call C<ev_loop> or similar functions that enter	2870	You I<must not> call C<ev_run> or similar functions that enter
2582	the current event loop from either C<ev_prepare> or C<ev_check>	2871	the current event loop from either C<ev_prepare> or C<ev_check>
2583	watchers. Other loops than the current one are fine, however. The	2872	watchers. Other loops than the current one are fine, however. The
2584	rationale behind this is that you do not need to check for recursion in	2873	rationale behind this is that you do not need to check for recursion in
2585	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2874	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2586	C<ev_check> so if you have one watcher of each kind they will always be	2875	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2754		3043
2755	if (timeout >= 0)	3044	if (timeout >= 0)
2756	// create/start timer	3045	// create/start timer
2757		3046
2758	// poll	3047	// poll
2759	ev_loop (EV_A_ 0);	3048	ev_run (EV_A_ 0);
2760		3049
2761	// stop timer again	3050	// stop timer again
2762	if (timeout >= 0)	3051	if (timeout >= 0)
2763	ev_timer_stop (EV_A_ &to);	3052	ev_timer_stop (EV_A_ &to);
2764		3053
…		…
2842	if you do not want that, you need to temporarily stop the embed watcher).	3131	if you do not want that, you need to temporarily stop the embed watcher).
2843		3132
2844	=item ev_embed_sweep (loop, ev_embed *)	3133	=item ev_embed_sweep (loop, ev_embed *)
2845		3134
2846	Make a single, non-blocking sweep over the embedded loop. This works	3135	Make a single, non-blocking sweep over the embedded loop. This works
2847	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3136	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2848	appropriate way for embedded loops.	3137	appropriate way for embedded loops.
2849		3138
2850	=item struct ev_loop *other [read-only]	3139	=item struct ev_loop *other [read-only]
2851		3140
2852	The embedded event loop.	3141	The embedded event loop.
…		…
2912	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3201	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2913	handlers will be invoked, too, of course.	3202	handlers will be invoked, too, of course.
2914		3203
2915	=head3 The special problem of life after fork - how is it possible?	3204	=head3 The special problem of life after fork - how is it possible?
2916		3205
2917	Most uses of C<fork()> consist of forking, then some simple calls to ste	3206	Most uses of C<fork()> consist of forking, then some simple calls to set
2918	up/change the process environment, followed by a call to C<exec()>. This	3207	up/change the process environment, followed by a call to C<exec()>. This
2919	sequence should be handled by libev without any problems.	3208	sequence should be handled by libev without any problems.
2920		3209
2921	This changes when the application actually wants to do event handling	3210	This changes when the application actually wants to do event handling
2922	in the child, or both parent in child, in effect "continuing" after the	3211	in the child, or both parent in child, in effect "continuing" after the
…		…
2938	disadvantage of having to use multiple event loops (which do not support	3227	disadvantage of having to use multiple event loops (which do not support
2939	signal watchers).	3228	signal watchers).
2940		3229
2941	When this is not possible, or you want to use the default loop for	3230	When this is not possible, or you want to use the default loop for
2942	other reasons, then in the process that wants to start "fresh", call	3231	other reasons, then in the process that wants to start "fresh", call
2943	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3232	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
2944	the default loop will "orphan" (not stop) all registered watchers, so you	3233	Destroying the default loop will "orphan" (not stop) all registered
2945	have to be careful not to execute code that modifies those watchers. Note	3234	watchers, so you have to be careful not to execute code that modifies
2946	also that in that case, you have to re-register any signal watchers.	3235	those watchers. Note also that in that case, you have to re-register any
		3236	signal watchers.
2947		3237
2948	=head3 Watcher-Specific Functions and Data Members	3238	=head3 Watcher-Specific Functions and Data Members
2949		3239
2950	=over 4	3240	=over 4
2951		3241
2952	=item ev_fork_init (ev_signal *, callback)	3242	=item ev_fork_init (ev_fork *, callback)
2953		3243
2954	Initialises and configures the fork watcher - it has no parameters of any	3244	Initialises and configures the fork watcher - it has no parameters of any
2955	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3245	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2956	believe me.	3246	really.
2957		3247
2958	=back	3248	=back
2959		3249
2960		3250
		3251	=head2 C<ev_cleanup> - even the best things end
		3252
		3253	Cleanup watchers are called just before the event loop is being destroyed
		3254	by a call to C<ev_loop_destroy>.
		3255
		3256	While there is no guarantee that the event loop gets destroyed, cleanup
		3257	watchers provide a convenient method to install cleanup hooks for your
		3258	program, worker threads and so on - you just to make sure to destroy the
		3259	loop when you want them to be invoked.
		3260
		3261	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3262	all other watchers, they do not keep a reference to the event loop (which
		3263	makes a lot of sense if you think about it). Like all other watchers, you
		3264	can call libev functions in the callback, except C<ev_cleanup_start>.
		3265
		3266	=head3 Watcher-Specific Functions and Data Members
		3267
		3268	=over 4
		3269
		3270	=item ev_cleanup_init (ev_cleanup *, callback)
		3271
		3272	Initialises and configures the cleanup watcher - it has no parameters of
		3273	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3274	pointless, I assure you.
		3275
		3276	=back
		3277
		3278	Example: Register an atexit handler to destroy the default loop, so any
		3279	cleanup functions are called.
		3280
		3281	static void
		3282	program_exits (void)
		3283	{
		3284	ev_loop_destroy (EV_DEFAULT_UC);
		3285	}
		3286
		3287	...
		3288	atexit (program_exits);
		3289
		3290
2961	=head2 C<ev_async> - how to wake up another event loop	3291	=head2 C<ev_async> - how to wake up an event loop
2962		3292
2963	In general, you cannot use an C<ev_loop> from multiple threads or other	3293	In general, you cannot use an C<ev_loop> from multiple threads or other
2964	asynchronous sources such as signal handlers (as opposed to multiple event	3294	asynchronous sources such as signal handlers (as opposed to multiple event
2965	loops - those are of course safe to use in different threads).	3295	loops - those are of course safe to use in different threads).
2966		3296
2967	Sometimes, however, you need to wake up another event loop you do not	3297	Sometimes, however, you need to wake up an event loop you do not control,
2968	control, for example because it belongs to another thread. This is what	3298	for example because it belongs to another thread. This is what C<ev_async>
2969	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3299	watchers do: as long as the C<ev_async> watcher is active, you can signal
2970	can signal it by calling C<ev_async_send>, which is thread- and signal	3300	it by calling C<ev_async_send>, which is thread- and signal safe.
2971	safe.
2972		3301
2973	This functionality is very similar to C<ev_signal> watchers, as signals,	3302	This functionality is very similar to C<ev_signal> watchers, as signals,
2974	too, are asynchronous in nature, and signals, too, will be compressed	3303	too, are asynchronous in nature, and signals, too, will be compressed
2975	(i.e. the number of callback invocations may be less than the number of	3304	(i.e. the number of callback invocations may be less than the number of
2976	C<ev_async_sent> calls).	3305	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
2977		3306	of "global async watchers" by using a watcher on an otherwise unused
2978	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3307	signal, and C<ev_feed_signal> to signal this watcher from another thread,
2979	just the default loop.	3308	even without knowing which loop owns the signal.
2980		3309
2981	=head3 Queueing	3310	=head3 Queueing
2982		3311
2983	C<ev_async> does not support queueing of data in any way. The reason	3312	C<ev_async> does not support queueing of data in any way. The reason
2984	is that the author does not know of a simple (or any) algorithm for a	3313	is that the author does not know of a simple (or any) algorithm for a
…		…
3076	trust me.	3405	trust me.
3077		3406
3078	=item ev_async_send (loop, ev_async *)	3407	=item ev_async_send (loop, ev_async *)
3079		3408
3080	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3409	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3081	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3410	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3411	returns.
		3412
3082	C<ev_feed_event>, this call is safe to do from other threads, signal or	3413	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3083	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3414	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3084	section below on what exactly this means).	3415	embedding section below on what exactly this means).
3085		3416
3086	Note that, as with other watchers in libev, multiple events might get	3417	Note that, as with other watchers in libev, multiple events might get
3087	compressed into a single callback invocation (another way to look at this	3418	compressed into a single callback invocation (another way to look at
3088	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3419	this is that C<ev_async> watchers are level-triggered: they are set on
3089	reset when the event loop detects that).	3420	C<ev_async_send>, reset when the event loop detects that).
3090		3421
3091	This call incurs the overhead of a system call only once per event loop	3422	This call incurs the overhead of at most one extra system call per event
3092	iteration, so while the overhead might be noticeable, it doesn't apply to	3423	loop iteration, if the event loop is blocked, and no syscall at all if
3093	repeated calls to C<ev_async_send> for the same event loop.	3424	the event loop (or your program) is processing events. That means that
		3425	repeated calls are basically free (there is no need to avoid calls for
		3426	performance reasons) and that the overhead becomes smaller (typically
		3427	zero) under load.
3094		3428
3095	=item bool = ev_async_pending (ev_async *)	3429	=item bool = ev_async_pending (ev_async *)
3096		3430
3097	Returns a non-zero value when C<ev_async_send> has been called on the	3431	Returns a non-zero value when C<ev_async_send> has been called on the
3098	watcher but the event has not yet been processed (or even noted) by the	3432	watcher but the event has not yet been processed (or even noted) by the
…		…
3131		3465
3132	If C<timeout> is less than 0, then no timeout watcher will be	3466	If C<timeout> is less than 0, then no timeout watcher will be
3133	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3467	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
3134	repeat = 0) will be started. C<0> is a valid timeout.	3468	repeat = 0) will be started. C<0> is a valid timeout.
3135		3469
3136	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3470	The callback has the type C<void (*cb)(int revents, void *arg)> and is
3137	passed an C<revents> set like normal event callbacks (a combination of	3471	passed an C<revents> set like normal event callbacks (a combination of
3138	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3472	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
3139	value passed to C<ev_once>. Note that it is possible to receive I<both>	3473	value passed to C<ev_once>. Note that it is possible to receive I<both>
3140	a timeout and an io event at the same time - you probably should give io	3474	a timeout and an io event at the same time - you probably should give io
3141	events precedence.	3475	events precedence.
3142		3476
3143	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3477	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
3144		3478
3145	static void stdin_ready (int revents, void *arg)	3479	static void stdin_ready (int revents, void *arg)
3146	{	3480	{
3147	if (revents & EV_READ)	3481	if (revents & EV_READ)
3148	/* stdin might have data for us, joy! */;	3482	/* stdin might have data for us, joy! */;
3149	else if (revents & EV_TIMEOUT)	3483	else if (revents & EV_TIMER)
3150	/* doh, nothing entered */;	3484	/* doh, nothing entered */;
3151	}	3485	}
3152		3486
3153	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3487	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3154		3488
3155	=item ev_feed_fd_event (loop, int fd, int revents)	3489	=item ev_feed_fd_event (loop, int fd, int revents)
3156		3490
3157	Feed an event on the given fd, as if a file descriptor backend detected	3491	Feed an event on the given fd, as if a file descriptor backend detected
3158	the given events it.	3492	the given events.
3159		3493
3160	=item ev_feed_signal_event (loop, int signum)	3494	=item ev_feed_signal_event (loop, int signum)
3161		3495
3162	Feed an event as if the given signal occurred (C<loop> must be the default	3496	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3163	loop!).	3497	which is async-safe.
3164		3498
3165	=back	3499	=back
		3500
		3501
		3502	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3503
		3504	This section explains some common idioms that are not immediately
		3505	obvious. Note that examples are sprinkled over the whole manual, and this
		3506	section only contains stuff that wouldn't fit anywhere else.
		3507
		3508	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3509
		3510	Each watcher has, by default, a C<void *data> member that you can read
		3511	or modify at any time: libev will completely ignore it. This can be used
		3512	to associate arbitrary data with your watcher. If you need more data and
		3513	don't want to allocate memory separately and store a pointer to it in that
		3514	data member, you can also "subclass" the watcher type and provide your own
		3515	data:
		3516
		3517	struct my_io
		3518	{
		3519	ev_io io;
		3520	int otherfd;
		3521	void *somedata;
		3522	struct whatever *mostinteresting;
		3523	};
		3524
		3525	...
		3526	struct my_io w;
		3527	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3528
		3529	And since your callback will be called with a pointer to the watcher, you
		3530	can cast it back to your own type:
		3531
		3532	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3533	{
		3534	struct my_io *w = (struct my_io *)w_;
		3535	...
		3536	}
		3537
		3538	More interesting and less C-conformant ways of casting your callback
		3539	function type instead have been omitted.
		3540
		3541	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3542
		3543	Another common scenario is to use some data structure with multiple
		3544	embedded watchers, in effect creating your own watcher that combines
		3545	multiple libev event sources into one "super-watcher":
		3546
		3547	struct my_biggy
		3548	{
		3549	int some_data;
		3550	ev_timer t1;
		3551	ev_timer t2;
		3552	}
		3553
		3554	In this case getting the pointer to C<my_biggy> is a bit more
		3555	complicated: Either you store the address of your C<my_biggy> struct in
		3556	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3557	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3558	real programmers):
		3559
		3560	#include <stddef.h>
		3561
		3562	static void
		3563	t1_cb (EV_P_ ev_timer *w, int revents)
		3564	{
		3565	struct my_biggy big = (struct my_biggy *)
		3566	(((char *)w) - offsetof (struct my_biggy, t1));
		3567	}
		3568
		3569	static void
		3570	t2_cb (EV_P_ ev_timer *w, int revents)
		3571	{
		3572	struct my_biggy big = (struct my_biggy *)
		3573	(((char *)w) - offsetof (struct my_biggy, t2));
		3574	}
		3575
		3576	=head2 AVOIDING FINISHING BEFORE RETURNING
		3577
		3578	Often you have structures like this in event-based programs:
		3579
		3580	callback ()
		3581	{
		3582	free (request);
		3583	}
		3584
		3585	request = start_new_request (..., callback);
		3586
		3587	The intent is to start some "lengthy" operation. The C<request> could be
		3588	used to cancel the operation, or do other things with it.
		3589
		3590	It's not uncommon to have code paths in C<start_new_request> that
		3591	immediately invoke the callback, for example, to report errors. Or you add
		3592	some caching layer that finds that it can skip the lengthy aspects of the
		3593	operation and simply invoke the callback with the result.
		3594
		3595	The problem here is that this will happen I<before> C<start_new_request>
		3596	has returned, so C<request> is not set.
		3597
		3598	Even if you pass the request by some safer means to the callback, you
		3599	might want to do something to the request after starting it, such as
		3600	canceling it, which probably isn't working so well when the callback has
		3601	already been invoked.
		3602
		3603	A common way around all these issues is to make sure that
		3604	C<start_new_request> I<always> returns before the callback is invoked. If
		3605	C<start_new_request> immediately knows the result, it can artificially
		3606	delay invoking the callback by e.g. using a C<prepare> or C<idle> watcher
		3607	for example, or more sneakily, by reusing an existing (stopped) watcher
		3608	and pushing it into the pending queue:
		3609
		3610	ev_set_cb (watcher, callback);
		3611	ev_feed_event (EV_A_ watcher, 0);
		3612
		3613	This way, C<start_new_request> can safely return before the callback is
		3614	invoked, while not delaying callback invocation too much.
		3615
		3616	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3617
		3618	Often (especially in GUI toolkits) there are places where you have
		3619	I<modal> interaction, which is most easily implemented by recursively
		3620	invoking C<ev_run>.
		3621
		3622	This brings the problem of exiting - a callback might want to finish the
		3623	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3624	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3625	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3626	other combination: In these cases, C<ev_break> will not work alone.
		3627
		3628	The solution is to maintain "break this loop" variable for each C<ev_run>
		3629	invocation, and use a loop around C<ev_run> until the condition is
		3630	triggered, using C<EVRUN_ONCE>:
		3631
		3632	// main loop
		3633	int exit_main_loop = 0;
		3634
		3635	while (!exit_main_loop)
		3636	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3637
		3638	// in a modal watcher
		3639	int exit_nested_loop = 0;
		3640
		3641	while (!exit_nested_loop)
		3642	ev_run (EV_A_ EVRUN_ONCE);
		3643
		3644	To exit from any of these loops, just set the corresponding exit variable:
		3645
		3646	// exit modal loop
		3647	exit_nested_loop = 1;
		3648
		3649	// exit main program, after modal loop is finished
		3650	exit_main_loop = 1;
		3651
		3652	// exit both
		3653	exit_main_loop = exit_nested_loop = 1;
		3654
		3655	=head2 THREAD LOCKING EXAMPLE
		3656
		3657	Here is a fictitious example of how to run an event loop in a different
		3658	thread from where callbacks are being invoked and watchers are
		3659	created/added/removed.
		3660
		3661	For a real-world example, see the C<EV::Loop::Async> perl module,
		3662	which uses exactly this technique (which is suited for many high-level
		3663	languages).
		3664
		3665	The example uses a pthread mutex to protect the loop data, a condition
		3666	variable to wait for callback invocations, an async watcher to notify the
		3667	event loop thread and an unspecified mechanism to wake up the main thread.
		3668
		3669	First, you need to associate some data with the event loop:
		3670
		3671	typedef struct {
		3672	mutex_t lock; /* global loop lock */
		3673	ev_async async_w;
		3674	thread_t tid;
		3675	cond_t invoke_cv;
		3676	} userdata;
		3677
		3678	void prepare_loop (EV_P)
		3679	{
		3680	// for simplicity, we use a static userdata struct.
		3681	static userdata u;
		3682
		3683	ev_async_init (&u->async_w, async_cb);
		3684	ev_async_start (EV_A_ &u->async_w);
		3685
		3686	pthread_mutex_init (&u->lock, 0);
		3687	pthread_cond_init (&u->invoke_cv, 0);
		3688
		3689	// now associate this with the loop
		3690	ev_set_userdata (EV_A_ u);
		3691	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3692	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3693
		3694	// then create the thread running ev_run
		3695	pthread_create (&u->tid, 0, l_run, EV_A);
		3696	}
		3697
		3698	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3699	solely to wake up the event loop so it takes notice of any new watchers
		3700	that might have been added:
		3701
		3702	static void
		3703	async_cb (EV_P_ ev_async *w, int revents)
		3704	{
		3705	// just used for the side effects
		3706	}
		3707
		3708	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3709	protecting the loop data, respectively.
		3710
		3711	static void
		3712	l_release (EV_P)
		3713	{
		3714	userdata *u = ev_userdata (EV_A);
		3715	pthread_mutex_unlock (&u->lock);
		3716	}
		3717
		3718	static void
		3719	l_acquire (EV_P)
		3720	{
		3721	userdata *u = ev_userdata (EV_A);
		3722	pthread_mutex_lock (&u->lock);
		3723	}
		3724
		3725	The event loop thread first acquires the mutex, and then jumps straight
		3726	into C<ev_run>:
		3727
		3728	void *
		3729	l_run (void *thr_arg)
		3730	{
		3731	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3732
		3733	l_acquire (EV_A);
		3734	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3735	ev_run (EV_A_ 0);
		3736	l_release (EV_A);
		3737
		3738	return 0;
		3739	}
		3740
		3741	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3742	signal the main thread via some unspecified mechanism (signals? pipe
		3743	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3744	have been called (in a while loop because a) spurious wakeups are possible
		3745	and b) skipping inter-thread-communication when there are no pending
		3746	watchers is very beneficial):
		3747
		3748	static void
		3749	l_invoke (EV_P)
		3750	{
		3751	userdata *u = ev_userdata (EV_A);
		3752
		3753	while (ev_pending_count (EV_A))
		3754	{
		3755	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3756	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3757	}
		3758	}
		3759
		3760	Now, whenever the main thread gets told to invoke pending watchers, it
		3761	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3762	thread to continue:
		3763
		3764	static void
		3765	real_invoke_pending (EV_P)
		3766	{
		3767	userdata *u = ev_userdata (EV_A);
		3768
		3769	pthread_mutex_lock (&u->lock);
		3770	ev_invoke_pending (EV_A);
		3771	pthread_cond_signal (&u->invoke_cv);
		3772	pthread_mutex_unlock (&u->lock);
		3773	}
		3774
		3775	Whenever you want to start/stop a watcher or do other modifications to an
		3776	event loop, you will now have to lock:
		3777
		3778	ev_timer timeout_watcher;
		3779	userdata *u = ev_userdata (EV_A);
		3780
		3781	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3782
		3783	pthread_mutex_lock (&u->lock);
		3784	ev_timer_start (EV_A_ &timeout_watcher);
		3785	ev_async_send (EV_A_ &u->async_w);
		3786	pthread_mutex_unlock (&u->lock);
		3787
		3788	Note that sending the C<ev_async> watcher is required because otherwise
		3789	an event loop currently blocking in the kernel will have no knowledge
		3790	about the newly added timer. By waking up the loop it will pick up any new
		3791	watchers in the next event loop iteration.
		3792
		3793	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3794
		3795	While the overhead of a callback that e.g. schedules a thread is small, it
		3796	is still an overhead. If you embed libev, and your main usage is with some
		3797	kind of threads or coroutines, you might want to customise libev so that
		3798	doesn't need callbacks anymore.
		3799
		3800	Imagine you have coroutines that you can switch to using a function
		3801	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3802	and that due to some magic, the currently active coroutine is stored in a
		3803	global called C<current_coro>. Then you can build your own "wait for libev
		3804	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3805	the differing C<;> conventions):
		3806
		3807	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3808	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3809
		3810	That means instead of having a C callback function, you store the
		3811	coroutine to switch to in each watcher, and instead of having libev call
		3812	your callback, you instead have it switch to that coroutine.
		3813
		3814	A coroutine might now wait for an event with a function called
		3815	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3816	matter when, or whether the watcher is active or not when this function is
		3817	called):
		3818
		3819	void
		3820	wait_for_event (ev_watcher *w)
		3821	{
		3822	ev_cb_set (w) = current_coro;
		3823	switch_to (libev_coro);
		3824	}
		3825
		3826	That basically suspends the coroutine inside C<wait_for_event> and
		3827	continues the libev coroutine, which, when appropriate, switches back to
		3828	this or any other coroutine.
		3829
		3830	You can do similar tricks if you have, say, threads with an event queue -
		3831	instead of storing a coroutine, you store the queue object and instead of
		3832	switching to a coroutine, you push the watcher onto the queue and notify
		3833	any waiters.
		3834
		3835	To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two
		3836	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3837
		3838	// my_ev.h
		3839	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3840	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3841	#include "../libev/ev.h"
		3842
		3843	// my_ev.c
		3844	#define EV_H "my_ev.h"
		3845	#include "../libev/ev.c"
		3846
		3847	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3848	F<my_ev.c> into your project. When properly specifying include paths, you
		3849	can even use F<ev.h> as header file name directly.
3166		3850
3167		3851
3168	=head1 LIBEVENT EMULATION	3852	=head1 LIBEVENT EMULATION
3169		3853
3170	Libev offers a compatibility emulation layer for libevent. It cannot	3854	Libev offers a compatibility emulation layer for libevent. It cannot
3171	emulate the internals of libevent, so here are some usage hints:	3855	emulate the internals of libevent, so here are some usage hints:
3172		3856
3173	=over 4	3857	=over 4
		3858
		3859	=item * Only the libevent-1.4.1-beta API is being emulated.
		3860
		3861	This was the newest libevent version available when libev was implemented,
		3862	and is still mostly unchanged in 2010.
3174		3863
3175	=item * Use it by including <event.h>, as usual.	3864	=item * Use it by including <event.h>, as usual.
3176		3865
3177	=item * The following members are fully supported: ev_base, ev_callback,	3866	=item * The following members are fully supported: ev_base, ev_callback,
3178	ev_arg, ev_fd, ev_res, ev_events.	3867	ev_arg, ev_fd, ev_res, ev_events.
…		…
3184	=item * Priorities are not currently supported. Initialising priorities	3873	=item * Priorities are not currently supported. Initialising priorities
3185	will fail and all watchers will have the same priority, even though there	3874	will fail and all watchers will have the same priority, even though there
3186	is an ev_pri field.	3875	is an ev_pri field.
3187		3876
3188	=item * In libevent, the last base created gets the signals, in libev, the	3877	=item * In libevent, the last base created gets the signals, in libev, the
3189	first base created (== the default loop) gets the signals.	3878	base that registered the signal gets the signals.
3190		3879
3191	=item * Other members are not supported.	3880	=item * Other members are not supported.
3192		3881
3193	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3882	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3194	to use the libev header file and library.	3883	to use the libev header file and library.
…		…
3213	Care has been taken to keep the overhead low. The only data member the C++	3902	Care has been taken to keep the overhead low. The only data member the C++
3214	classes add (compared to plain C-style watchers) is the event loop pointer	3903	classes add (compared to plain C-style watchers) is the event loop pointer
3215	that the watcher is associated with (or no additional members at all if	3904	that the watcher is associated with (or no additional members at all if
3216	you disable C<EV_MULTIPLICITY> when embedding libev).	3905	you disable C<EV_MULTIPLICITY> when embedding libev).
3217		3906
3218	Currently, functions, and static and non-static member functions can be	3907	Currently, functions, static and non-static member functions and classes
3219	used as callbacks. Other types should be easy to add as long as they only	3908	with C<operator ()> can be used as callbacks. Other types should be easy
3220	need one additional pointer for context. If you need support for other	3909	to add as long as they only need one additional pointer for context. If
3221	types of functors please contact the author (preferably after implementing	3910	you need support for other types of functors please contact the author
3222	it).	3911	(preferably after implementing it).
3223		3912
3224	Here is a list of things available in the C<ev> namespace:	3913	Here is a list of things available in the C<ev> namespace:
3225		3914
3226	=over 4	3915	=over 4
3227		3916
…		…
3237	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	3926	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3238		3927
3239	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	3928	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
3240	the same name in the C<ev> namespace, with the exception of C<ev_signal>	3929	the same name in the C<ev> namespace, with the exception of C<ev_signal>
3241	which is called C<ev::sig> to avoid clashes with the C<signal> macro	3930	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3242	defines by many implementations.	3931	defined by many implementations.
3243		3932
3244	All of those classes have these methods:	3933	All of those classes have these methods:
3245		3934
3246	=over 4	3935	=over 4
3247		3936
…		…
3288	myclass obj;	3977	myclass obj;
3289	ev::io iow;	3978	ev::io iow;
3290	iow.set <myclass, &myclass::io_cb> (&obj);	3979	iow.set <myclass, &myclass::io_cb> (&obj);
3291		3980
3292	=item w->set (object *)	3981	=item w->set (object *)
3293
3294	This is an B<experimental> feature that might go away in a future version.
3295		3982
3296	This is a variation of a method callback - leaving out the method to call	3983	This is a variation of a method callback - leaving out the method to call
3297	will default the method to C<operator ()>, which makes it possible to use	3984	will default the method to C<operator ()>, which makes it possible to use
3298	functor objects without having to manually specify the C<operator ()> all	3985	functor objects without having to manually specify the C<operator ()> all
3299	the time. Incidentally, you can then also leave out the template argument	3986	the time. Incidentally, you can then also leave out the template argument
…		…
3339	Associates a different C<struct ev_loop> with this watcher. You can only	4026	Associates a different C<struct ev_loop> with this watcher. You can only
3340	do this when the watcher is inactive (and not pending either).	4027	do this when the watcher is inactive (and not pending either).
3341		4028
3342	=item w->set ([arguments])	4029	=item w->set ([arguments])
3343		4030
3344	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	4031	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
3345	called at least once. Unlike the C counterpart, an active watcher gets	4032	method or a suitable start method must be called at least once. Unlike the
3346	automatically stopped and restarted when reconfiguring it with this	4033	C counterpart, an active watcher gets automatically stopped and restarted
3347	method.	4034	when reconfiguring it with this method.
3348		4035
3349	=item w->start ()	4036	=item w->start ()
3350		4037
3351	Starts the watcher. Note that there is no C<loop> argument, as the	4038	Starts the watcher. Note that there is no C<loop> argument, as the
3352	constructor already stores the event loop.	4039	constructor already stores the event loop.
3353		4040
		4041	=item w->start ([arguments])
		4042
		4043	Instead of calling C<set> and C<start> methods separately, it is often
		4044	convenient to wrap them in one call. Uses the same type of arguments as
		4045	the configure C<set> method of the watcher.
		4046
3354	=item w->stop ()	4047	=item w->stop ()
3355		4048
3356	Stops the watcher if it is active. Again, no C<loop> argument.	4049	Stops the watcher if it is active. Again, no C<loop> argument.
3357		4050
3358	=item w->again () (C<ev::timer>, C<ev::periodic> only)	4051	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3370		4063
3371	=back	4064	=back
3372		4065
3373	=back	4066	=back
3374		4067
3375	Example: Define a class with an IO and idle watcher, start one of them in	4068	Example: Define a class with two I/O and idle watchers, start the I/O
3376	the constructor.	4069	watchers in the constructor.
3377		4070
3378	class myclass	4071	class myclass
3379	{	4072	{
3380	ev::io io ; void io_cb (ev::io &w, int revents);	4073	ev::io io ; void io_cb (ev::io &w, int revents);
		4074	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3381	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4075	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3382		4076
3383	myclass (int fd)	4077	myclass (int fd)
3384	{	4078	{
3385	io .set <myclass, &myclass::io_cb > (this);	4079	io .set <myclass, &myclass::io_cb > (this);
		4080	io2 .set <myclass, &myclass::io2_cb > (this);
3386	idle.set <myclass, &myclass::idle_cb> (this);	4081	idle.set <myclass, &myclass::idle_cb> (this);
3387		4082
3388	io.start (fd, ev::READ);	4083	io.set (fd, ev::WRITE); // configure the watcher
		4084	io.start (); // start it whenever convenient
		4085
		4086	io2.start (fd, ev::READ); // set + start in one call
3389	}	4087	}
3390	};	4088	};
3391		4089
3392		4090
3393	=head1 OTHER LANGUAGE BINDINGS	4091	=head1 OTHER LANGUAGE BINDINGS
…		…
3432	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4130	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3433		4131
3434	=item D	4132	=item D
3435		4133
3436	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4134	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3437	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4135	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3438		4136
3439	=item Ocaml	4137	=item Ocaml
3440		4138
3441	Erkki Seppala has written Ocaml bindings for libev, to be found at	4139	Erkki Seppala has written Ocaml bindings for libev, to be found at
3442	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4140	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
3443		4141
3444	=item Lua	4142	=item Lua
3445		4143
3446	Brian Maher has written a partial interface to libev	4144	Brian Maher has written a partial interface to libev for lua (at the
3447	for lua (only C<ev_io> and C<ev_timer>), to be found at	4145	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
3448	L<http://github.com/brimworks/lua-ev>.	4146	L<http://github.com/brimworks/lua-ev>.
3449		4147
3450	=back	4148	=back
3451		4149
3452		4150
…		…
3467	loop argument"). The C<EV_A> form is used when this is the sole argument,	4165	loop argument"). The C<EV_A> form is used when this is the sole argument,
3468	C<EV_A_> is used when other arguments are following. Example:	4166	C<EV_A_> is used when other arguments are following. Example:
3469		4167
3470	ev_unref (EV_A);	4168	ev_unref (EV_A);
3471	ev_timer_add (EV_A_ watcher);	4169	ev_timer_add (EV_A_ watcher);
3472	ev_loop (EV_A_ 0);	4170	ev_run (EV_A_ 0);
3473		4171
3474	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4172	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3475	which is often provided by the following macro.	4173	which is often provided by the following macro.
3476		4174
3477	=item C<EV_P>, C<EV_P_>	4175	=item C<EV_P>, C<EV_P_>
…		…
3490	suitable for use with C<EV_A>.	4188	suitable for use with C<EV_A>.
3491		4189
3492	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4190	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3493		4191
3494	Similar to the other two macros, this gives you the value of the default	4192	Similar to the other two macros, this gives you the value of the default
3495	loop, if multiple loops are supported ("ev loop default").	4193	loop, if multiple loops are supported ("ev loop default"). The default loop
		4194	will be initialised if it isn't already initialised.
		4195
		4196	For non-multiplicity builds, these macros do nothing, so you always have
		4197	to initialise the loop somewhere.
3496		4198
3497	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4199	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3498		4200
3499	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4201	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3500	default loop has been initialised (C<UC> == unchecked). Their behaviour	4202	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3517	}	4219	}
3518		4220
3519	ev_check check;	4221	ev_check check;
3520	ev_check_init (&check, check_cb);	4222	ev_check_init (&check, check_cb);
3521	ev_check_start (EV_DEFAULT_ &check);	4223	ev_check_start (EV_DEFAULT_ &check);
3522	ev_loop (EV_DEFAULT_ 0);	4224	ev_run (EV_DEFAULT_ 0);
3523		4225
3524	=head1 EMBEDDING	4226	=head1 EMBEDDING
3525		4227
3526	Libev can (and often is) directly embedded into host	4228	Libev can (and often is) directly embedded into host
3527	applications. Examples of applications that embed it include the Deliantra	4229	applications. Examples of applications that embed it include the Deliantra
…		…
3607	libev.m4	4309	libev.m4
3608		4310
3609	=head2 PREPROCESSOR SYMBOLS/MACROS	4311	=head2 PREPROCESSOR SYMBOLS/MACROS
3610		4312
3611	Libev can be configured via a variety of preprocessor symbols you have to	4313	Libev can be configured via a variety of preprocessor symbols you have to
3612	define before including any of its files. The default in the absence of	4314	define before including (or compiling) any of its files. The default in
3613	autoconf is documented for every option.	4315	the absence of autoconf is documented for every option.
		4316
		4317	Symbols marked with "(h)" do not change the ABI, and can have different
		4318	values when compiling libev vs. including F<ev.h>, so it is permissible
		4319	to redefine them before including F<ev.h> without breaking compatibility
		4320	to a compiled library. All other symbols change the ABI, which means all
		4321	users of libev and the libev code itself must be compiled with compatible
		4322	settings.
3614		4323
3615	=over 4	4324	=over 4
3616		4325
		4326	=item EV_COMPAT3 (h)
		4327
		4328	Backwards compatibility is a major concern for libev. This is why this
		4329	release of libev comes with wrappers for the functions and symbols that
		4330	have been renamed between libev version 3 and 4.
		4331
		4332	You can disable these wrappers (to test compatibility with future
		4333	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4334	sources. This has the additional advantage that you can drop the C<struct>
		4335	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4336	typedef in that case.
		4337
		4338	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4339	and in some even more future version the compatibility code will be
		4340	removed completely.
		4341
3617	=item EV_STANDALONE	4342	=item EV_STANDALONE (h)
3618		4343
3619	Must always be C<1> if you do not use autoconf configuration, which	4344	Must always be C<1> if you do not use autoconf configuration, which
3620	keeps libev from including F<config.h>, and it also defines dummy	4345	keeps libev from including F<config.h>, and it also defines dummy
3621	implementations for some libevent functions (such as logging, which is not	4346	implementations for some libevent functions (such as logging, which is not
3622	supported). It will also not define any of the structs usually found in	4347	supported). It will also not define any of the structs usually found in
3623	F<event.h> that are not directly supported by the libev core alone.	4348	F<event.h> that are not directly supported by the libev core alone.
3624		4349
3625	In standalone mode, libev will still try to automatically deduce the	4350	In standalone mode, libev will still try to automatically deduce the
3626	configuration, but has to be more conservative.	4351	configuration, but has to be more conservative.
		4352
		4353	=item EV_USE_FLOOR
		4354
		4355	If defined to be C<1>, libev will use the C<floor ()> function for its
		4356	periodic reschedule calculations, otherwise libev will fall back on a
		4357	portable (slower) implementation. If you enable this, you usually have to
		4358	link against libm or something equivalent. Enabling this when the C<floor>
		4359	function is not available will fail, so the safe default is to not enable
		4360	this.
3627		4361
3628	=item EV_USE_MONOTONIC	4362	=item EV_USE_MONOTONIC
3629		4363
3630	If defined to be C<1>, libev will try to detect the availability of the	4364	If defined to be C<1>, libev will try to detect the availability of the
3631	monotonic clock option at both compile time and runtime. Otherwise no	4365	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3764	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4498	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3765		4499
3766	=item EV_ATOMIC_T	4500	=item EV_ATOMIC_T
3767		4501
3768	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4502	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3769	access is atomic with respect to other threads or signal contexts. No such	4503	access is atomic and serialised with respect to other threads or signal
3770	type is easily found in the C language, so you can provide your own type	4504	contexts. No such type is easily found in the C language, so you can
3771	that you know is safe for your purposes. It is used both for signal handler "locking"	4505	provide your own type that you know is safe for your purposes. It is used
3772	as well as for signal and thread safety in C<ev_async> watchers.	4506	both for signal handler "locking" as well as for signal and thread safety
		4507	in C<ev_async> watchers.
3773		4508
3774	In the absence of this define, libev will use C<sig_atomic_t volatile>	4509	In the absence of this define, libev will use C<sig_atomic_t volatile>
3775	(from F<signal.h>), which is usually good enough on most platforms.	4510	(from F<signal.h>), which is usually good enough on most platforms,
		4511	although strictly speaking using a type that also implies a memory fence
		4512	is required.
3776		4513
3777	=item EV_H	4514	=item EV_H (h)
3778		4515
3779	The name of the F<ev.h> header file used to include it. The default if	4516	The name of the F<ev.h> header file used to include it. The default if
3780	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4517	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3781	used to virtually rename the F<ev.h> header file in case of conflicts.	4518	used to virtually rename the F<ev.h> header file in case of conflicts.
3782		4519
3783	=item EV_CONFIG_H	4520	=item EV_CONFIG_H (h)
3784		4521
3785	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4522	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3786	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4523	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3787	C<EV_H>, above.	4524	C<EV_H>, above.
3788		4525
3789	=item EV_EVENT_H	4526	=item EV_EVENT_H (h)
3790		4527
3791	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4528	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3792	of how the F<event.h> header can be found, the default is C<"event.h">.	4529	of how the F<event.h> header can be found, the default is C<"event.h">.
3793		4530
3794	=item EV_PROTOTYPES	4531	=item EV_PROTOTYPES (h)
3795		4532
3796	If defined to be C<0>, then F<ev.h> will not define any function	4533	If defined to be C<0>, then F<ev.h> will not define any function
3797	prototypes, but still define all the structs and other symbols. This is	4534	prototypes, but still define all the structs and other symbols. This is
3798	occasionally useful if you want to provide your own wrapper functions	4535	occasionally useful if you want to provide your own wrapper functions
3799	around libev functions.	4536	around libev functions.
…		…
3804	will have the C<struct ev_loop *> as first argument, and you can create	4541	will have the C<struct ev_loop *> as first argument, and you can create
3805	additional independent event loops. Otherwise there will be no support	4542	additional independent event loops. Otherwise there will be no support
3806	for multiple event loops and there is no first event loop pointer	4543	for multiple event loops and there is no first event loop pointer
3807	argument. Instead, all functions act on the single default loop.	4544	argument. Instead, all functions act on the single default loop.
3808		4545
		4546	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4547	default loop when multiplicity is switched off - you always have to
		4548	initialise the loop manually in this case.
		4549
3809	=item EV_MINPRI	4550	=item EV_MINPRI
3810		4551
3811	=item EV_MAXPRI	4552	=item EV_MAXPRI
3812		4553
3813	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4554	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3821	fine.	4562	fine.
3822		4563
3823	If your embedding application does not need any priorities, defining these	4564	If your embedding application does not need any priorities, defining these
3824	both to C<0> will save some memory and CPU.	4565	both to C<0> will save some memory and CPU.
3825		4566
3826	=item EV_PERIODIC_ENABLE	4567	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4568	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4569	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3827		4570
3828	If undefined or defined to be C<1>, then periodic timers are supported. If	4571	If undefined or defined to be C<1> (and the platform supports it), then
3829	defined to be C<0>, then they are not. Disabling them saves a few kB of	4572	the respective watcher type is supported. If defined to be C<0>, then it
3830	code.	4573	is not. Disabling watcher types mainly saves code size.
3831		4574
3832	=item EV_IDLE_ENABLE	4575	=item EV_FEATURES
3833
3834	If undefined or defined to be C<1>, then idle watchers are supported. If
3835	defined to be C<0>, then they are not. Disabling them saves a few kB of
3836	code.
3837
3838	=item EV_EMBED_ENABLE
3839
3840	If undefined or defined to be C<1>, then embed watchers are supported. If
3841	defined to be C<0>, then they are not. Embed watchers rely on most other
3842	watcher types, which therefore must not be disabled.
3843
3844	=item EV_STAT_ENABLE
3845
3846	If undefined or defined to be C<1>, then stat watchers are supported. If
3847	defined to be C<0>, then they are not.
3848
3849	=item EV_FORK_ENABLE
3850
3851	If undefined or defined to be C<1>, then fork watchers are supported. If
3852	defined to be C<0>, then they are not.
3853
3854	=item EV_ASYNC_ENABLE
3855
3856	If undefined or defined to be C<1>, then async watchers are supported. If
3857	defined to be C<0>, then they are not.
3858
3859	=item EV_MINIMAL
3860		4576
3861	If you need to shave off some kilobytes of code at the expense of some	4577	If you need to shave off some kilobytes of code at the expense of some
3862	speed (but with the full API), define this symbol to C<1>. Currently this	4578	speed (but with the full API), you can define this symbol to request
3863	is used to override some inlining decisions, saves roughly 30% code size	4579	certain subsets of functionality. The default is to enable all features
3864	on amd64. It also selects a much smaller 2-heap for timer management over	4580	that can be enabled on the platform.
3865	the default 4-heap.
3866		4581
3867	You can save even more by disabling watcher types you do not need	4582	A typical way to use this symbol is to define it to C<0> (or to a bitset
3868	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>	4583	with some broad features you want) and then selectively re-enable
3869	(C<-DNDEBUG>) will usually reduce code size a lot.	4584	additional parts you want, for example if you want everything minimal,
		4585	but multiple event loop support, async and child watchers and the poll
		4586	backend, use this:
3870		4587
3871	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to	4588	#define EV_FEATURES 0
3872	provide a bare-bones event library. See C<ev.h> for details on what parts	4589	#define EV_MULTIPLICITY 1
3873	of the API are still available, and do not complain if this subset changes	4590	#define EV_USE_POLL 1
3874	over time.	4591	#define EV_CHILD_ENABLE 1
		4592	#define EV_ASYNC_ENABLE 1
		4593
		4594	The actual value is a bitset, it can be a combination of the following
		4595	values:
		4596
		4597	=over 4
		4598
		4599	=item C<1> - faster/larger code
		4600
		4601	Use larger code to speed up some operations.
		4602
		4603	Currently this is used to override some inlining decisions (enlarging the
		4604	code size by roughly 30% on amd64).
		4605
		4606	When optimising for size, use of compiler flags such as C<-Os> with
		4607	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4608	assertions.
		4609
		4610	=item C<2> - faster/larger data structures
		4611
		4612	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4613	hash table sizes and so on. This will usually further increase code size
		4614	and can additionally have an effect on the size of data structures at
		4615	runtime.
		4616
		4617	=item C<4> - full API configuration
		4618
		4619	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4620	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4621
		4622	=item C<8> - full API
		4623
		4624	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4625	details on which parts of the API are still available without this
		4626	feature, and do not complain if this subset changes over time.
		4627
		4628	=item C<16> - enable all optional watcher types
		4629
		4630	Enables all optional watcher types. If you want to selectively enable
		4631	only some watcher types other than I/O and timers (e.g. prepare,
		4632	embed, async, child...) you can enable them manually by defining
		4633	C<EV_watchertype_ENABLE> to C<1> instead.
		4634
		4635	=item C<32> - enable all backends
		4636
		4637	This enables all backends - without this feature, you need to enable at
		4638	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4639
		4640	=item C<64> - enable OS-specific "helper" APIs
		4641
		4642	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4643	default.
		4644
		4645	=back
		4646
		4647	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4648	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4649	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4650	watchers, timers and monotonic clock support.
		4651
		4652	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4653	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4654	your program might be left out as well - a binary starting a timer and an
		4655	I/O watcher then might come out at only 5Kb.
		4656
		4657	=item EV_API_STATIC
		4658
		4659	If this symbol is defined (by default it is not), then all identifiers
		4660	will have static linkage. This means that libev will not export any
		4661	identifiers, and you cannot link against libev anymore. This can be useful
		4662	when you embed libev, only want to use libev functions in a single file,
		4663	and do not want its identifiers to be visible.
		4664
		4665	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4666	wants to use libev.
		4667
		4668	This option only works when libev is compiled with a C compiler, as C++
		4669	doesn't support the required declaration syntax.
		4670
		4671	=item EV_AVOID_STDIO
		4672
		4673	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4674	functions (printf, scanf, perror etc.). This will increase the code size
		4675	somewhat, but if your program doesn't otherwise depend on stdio and your
		4676	libc allows it, this avoids linking in the stdio library which is quite
		4677	big.
		4678
		4679	Note that error messages might become less precise when this option is
		4680	enabled.
3875		4681
3876	=item EV_NSIG	4682	=item EV_NSIG
3877		4683
3878	The highest supported signal number, +1 (or, the number of	4684	The highest supported signal number, +1 (or, the number of
3879	signals): Normally, libev tries to deduce the maximum number of signals	4685	signals): Normally, libev tries to deduce the maximum number of signals
3880	automatically, but sometimes this fails, in which case it can be	4686	automatically, but sometimes this fails, in which case it can be
3881	specified. Also, using a lower number than detected (C<32> should be	4687	specified. Also, using a lower number than detected (C<32> should be
3882	good for about any system in existance) can save some memory, as libev	4688	good for about any system in existence) can save some memory, as libev
3883	statically allocates some 12-24 bytes per signal number.	4689	statically allocates some 12-24 bytes per signal number.
3884		4690
3885	=item EV_PID_HASHSIZE	4691	=item EV_PID_HASHSIZE
3886		4692
3887	C<ev_child> watchers use a small hash table to distribute workload by	4693	C<ev_child> watchers use a small hash table to distribute workload by
3888	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4694	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3889	than enough. If you need to manage thousands of children you might want to	4695	usually more than enough. If you need to manage thousands of children you
3890	increase this value (I<must> be a power of two).	4696	might want to increase this value (I<must> be a power of two).
3891		4697
3892	=item EV_INOTIFY_HASHSIZE	4698	=item EV_INOTIFY_HASHSIZE
3893		4699
3894	C<ev_stat> watchers use a small hash table to distribute workload by	4700	C<ev_stat> watchers use a small hash table to distribute workload by
3895	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4701	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3896	usually more than enough. If you need to manage thousands of C<ev_stat>	4702	disabled), usually more than enough. If you need to manage thousands of
3897	watchers you might want to increase this value (I<must> be a power of	4703	C<ev_stat> watchers you might want to increase this value (I<must> be a
3898	two).	4704	power of two).
3899		4705
3900	=item EV_USE_4HEAP	4706	=item EV_USE_4HEAP
3901		4707
3902	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4708	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3903	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4709	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3904	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4710	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3905	faster performance with many (thousands) of watchers.	4711	faster performance with many (thousands) of watchers.
3906		4712
3907	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4713	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3908	(disabled).	4714	will be C<0>.
3909		4715
3910	=item EV_HEAP_CACHE_AT	4716	=item EV_HEAP_CACHE_AT
3911		4717
3912	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4718	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3913	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4719	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3914	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4720	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3915	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4721	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3916	but avoids random read accesses on heap changes. This improves performance	4722	but avoids random read accesses on heap changes. This improves performance
3917	noticeably with many (hundreds) of watchers.	4723	noticeably with many (hundreds) of watchers.
3918		4724
3919	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4725	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3920	(disabled).	4726	will be C<0>.
3921		4727
3922	=item EV_VERIFY	4728	=item EV_VERIFY
3923		4729
3924	Controls how much internal verification (see C<ev_loop_verify ()>) will	4730	Controls how much internal verification (see C<ev_verify ()>) will
3925	be done: If set to C<0>, no internal verification code will be compiled	4731	be done: If set to C<0>, no internal verification code will be compiled
3926	in. If set to C<1>, then verification code will be compiled in, but not	4732	in. If set to C<1>, then verification code will be compiled in, but not
3927	called. If set to C<2>, then the internal verification code will be	4733	called. If set to C<2>, then the internal verification code will be
3928	called once per loop, which can slow down libev. If set to C<3>, then the	4734	called once per loop, which can slow down libev. If set to C<3>, then the
3929	verification code will be called very frequently, which will slow down	4735	verification code will be called very frequently, which will slow down
3930	libev considerably.	4736	libev considerably.
3931		4737
3932	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4738	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3933	C<0>.	4739	will be C<0>.
3934		4740
3935	=item EV_COMMON	4741	=item EV_COMMON
3936		4742
3937	By default, all watchers have a C<void *data> member. By redefining	4743	By default, all watchers have a C<void *data> member. By redefining
3938	this macro to a something else you can include more and other types of	4744	this macro to something else you can include more and other types of
3939	members. You have to define it each time you include one of the files,	4745	members. You have to define it each time you include one of the files,
3940	though, and it must be identical each time.	4746	though, and it must be identical each time.
3941		4747
3942	For example, the perl EV module uses something like this:	4748	For example, the perl EV module uses something like this:
3943		4749
…		…
3996	file.	4802	file.
3997		4803
3998	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4804	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3999	that everybody includes and which overrides some configure choices:	4805	that everybody includes and which overrides some configure choices:
4000		4806
4001	#define EV_MINIMAL 1	4807	#define EV_FEATURES 8
4002	#define EV_USE_POLL 0	4808	#define EV_USE_SELECT 1
4003	#define EV_MULTIPLICITY 0
4004	#define EV_PERIODIC_ENABLE 0	4809	#define EV_PREPARE_ENABLE 1
		4810	#define EV_IDLE_ENABLE 1
4005	#define EV_STAT_ENABLE 0	4811	#define EV_SIGNAL_ENABLE 1
4006	#define EV_FORK_ENABLE 0	4812	#define EV_CHILD_ENABLE 1
		4813	#define EV_USE_STDEXCEPT 0
4007	#define EV_CONFIG_H <config.h>	4814	#define EV_CONFIG_H <config.h>
4008	#define EV_MINPRI 0
4009	#define EV_MAXPRI 0
4010		4815
4011	#include "ev++.h"	4816	#include "ev++.h"
4012		4817
4013	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4818	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4014		4819
4015	#include "ev_cpp.h"	4820	#include "ev_cpp.h"
4016	#include "ev.c"	4821	#include "ev.c"
4017		4822
4018	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4823	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4019		4824
4020	=head2 THREADS AND COROUTINES	4825	=head2 THREADS AND COROUTINES
4021		4826
4022	=head3 THREADS	4827	=head3 THREADS
4023		4828
…		…
4074	default loop and triggering an C<ev_async> watcher from the default loop	4879	default loop and triggering an C<ev_async> watcher from the default loop
4075	watcher callback into the event loop interested in the signal.	4880	watcher callback into the event loop interested in the signal.
4076		4881
4077	=back	4882	=back
4078		4883
4079	=head4 THREAD LOCKING EXAMPLE	4884	See also L<THREAD LOCKING EXAMPLE>.
4080
4081	Here is a fictitious example of how to run an event loop in a different
4082	thread than where callbacks are being invoked and watchers are
4083	created/added/removed.
4084
4085	For a real-world example, see the C<EV::Loop::Async> perl module,
4086	which uses exactly this technique (which is suited for many high-level
4087	languages).
4088
4089	The example uses a pthread mutex to protect the loop data, a condition
4090	variable to wait for callback invocations, an async watcher to notify the
4091	event loop thread and an unspecified mechanism to wake up the main thread.
4092
4093	First, you need to associate some data with the event loop:
4094
4095	typedef struct {
4096	mutex_t lock; /* global loop lock */
4097	ev_async async_w;
4098	thread_t tid;
4099	cond_t invoke_cv;
4100	} userdata;
4101
4102	void prepare_loop (EV_P)
4103	{
4104	// for simplicity, we use a static userdata struct.
4105	static userdata u;
4106
4107	ev_async_init (&u->async_w, async_cb);
4108	ev_async_start (EV_A_ &u->async_w);
4109
4110	pthread_mutex_init (&u->lock, 0);
4111	pthread_cond_init (&u->invoke_cv, 0);
4112
4113	// now associate this with the loop
4114	ev_set_userdata (EV_A_ u);
4115	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4116	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4117
4118	// then create the thread running ev_loop
4119	pthread_create (&u->tid, 0, l_run, EV_A);
4120	}
4121
4122	The callback for the C<ev_async> watcher does nothing: the watcher is used
4123	solely to wake up the event loop so it takes notice of any new watchers
4124	that might have been added:
4125
4126	static void
4127	async_cb (EV_P_ ev_async *w, int revents)
4128	{
4129	// just used for the side effects
4130	}
4131
4132	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4133	protecting the loop data, respectively.
4134
4135	static void
4136	l_release (EV_P)
4137	{
4138	userdata *u = ev_userdata (EV_A);
4139	pthread_mutex_unlock (&u->lock);
4140	}
4141
4142	static void
4143	l_acquire (EV_P)
4144	{
4145	userdata *u = ev_userdata (EV_A);
4146	pthread_mutex_lock (&u->lock);
4147	}
4148
4149	The event loop thread first acquires the mutex, and then jumps straight
4150	into C<ev_loop>:
4151
4152	void *
4153	l_run (void *thr_arg)
4154	{
4155	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4156
4157	l_acquire (EV_A);
4158	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4159	ev_loop (EV_A_ 0);
4160	l_release (EV_A);
4161
4162	return 0;
4163	}
4164
4165	Instead of invoking all pending watchers, the C<l_invoke> callback will
4166	signal the main thread via some unspecified mechanism (signals? pipe
4167	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4168	have been called (in a while loop because a) spurious wakeups are possible
4169	and b) skipping inter-thread-communication when there are no pending
4170	watchers is very beneficial):
4171
4172	static void
4173	l_invoke (EV_P)
4174	{
4175	userdata *u = ev_userdata (EV_A);
4176
4177	while (ev_pending_count (EV_A))
4178	{
4179	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4180	pthread_cond_wait (&u->invoke_cv, &u->lock);
4181	}
4182	}
4183
4184	Now, whenever the main thread gets told to invoke pending watchers, it
4185	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4186	thread to continue:
4187
4188	static void
4189	real_invoke_pending (EV_P)
4190	{
4191	userdata *u = ev_userdata (EV_A);
4192
4193	pthread_mutex_lock (&u->lock);
4194	ev_invoke_pending (EV_A);
4195	pthread_cond_signal (&u->invoke_cv);
4196	pthread_mutex_unlock (&u->lock);
4197	}
4198
4199	Whenever you want to start/stop a watcher or do other modifications to an
4200	event loop, you will now have to lock:
4201
4202	ev_timer timeout_watcher;
4203	userdata *u = ev_userdata (EV_A);
4204
4205	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4206
4207	pthread_mutex_lock (&u->lock);
4208	ev_timer_start (EV_A_ &timeout_watcher);
4209	ev_async_send (EV_A_ &u->async_w);
4210	pthread_mutex_unlock (&u->lock);
4211
4212	Note that sending the C<ev_async> watcher is required because otherwise
4213	an event loop currently blocking in the kernel will have no knowledge
4214	about the newly added timer. By waking up the loop it will pick up any new
4215	watchers in the next event loop iteration.
4216		4885
4217	=head3 COROUTINES	4886	=head3 COROUTINES
4218		4887
4219	Libev is very accommodating to coroutines ("cooperative threads"):	4888	Libev is very accommodating to coroutines ("cooperative threads"):
4220	libev fully supports nesting calls to its functions from different	4889	libev fully supports nesting calls to its functions from different
4221	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4890	coroutines (e.g. you can call C<ev_run> on the same loop from two
4222	different coroutines, and switch freely between both coroutines running	4891	different coroutines, and switch freely between both coroutines running
4223	the loop, as long as you don't confuse yourself). The only exception is	4892	the loop, as long as you don't confuse yourself). The only exception is
4224	that you must not do this from C<ev_periodic> reschedule callbacks.	4893	that you must not do this from C<ev_periodic> reschedule callbacks.
4225		4894
4226	Care has been taken to ensure that libev does not keep local state inside	4895	Care has been taken to ensure that libev does not keep local state inside
4227	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4896	C<ev_run>, and other calls do not usually allow for coroutine switches as
4228	they do not call any callbacks.	4897	they do not call any callbacks.
4229		4898
4230	=head2 COMPILER WARNINGS	4899	=head2 COMPILER WARNINGS
4231		4900
4232	Depending on your compiler and compiler settings, you might get no or a	4901	Depending on your compiler and compiler settings, you might get no or a
…		…
4243	maintainable.	4912	maintainable.
4244		4913
4245	And of course, some compiler warnings are just plain stupid, or simply	4914	And of course, some compiler warnings are just plain stupid, or simply
4246	wrong (because they don't actually warn about the condition their message	4915	wrong (because they don't actually warn about the condition their message
4247	seems to warn about). For example, certain older gcc versions had some	4916	seems to warn about). For example, certain older gcc versions had some
4248	warnings that resulted an extreme number of false positives. These have	4917	warnings that resulted in an extreme number of false positives. These have
4249	been fixed, but some people still insist on making code warn-free with	4918	been fixed, but some people still insist on making code warn-free with
4250	such buggy versions.	4919	such buggy versions.
4251		4920
4252	While libev is written to generate as few warnings as possible,	4921	While libev is written to generate as few warnings as possible,
4253	"warn-free" code is not a goal, and it is recommended not to build libev	4922	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
4289	I suggest using suppression lists.	4958	I suggest using suppression lists.
4290		4959
4291		4960
4292	=head1 PORTABILITY NOTES	4961	=head1 PORTABILITY NOTES
4293		4962
		4963	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4964
		4965	GNU/Linux is the only common platform that supports 64 bit file/large file
		4966	interfaces but I<disables> them by default.
		4967
		4968	That means that libev compiled in the default environment doesn't support
		4969	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4970
		4971	Unfortunately, many programs try to work around this GNU/Linux issue
		4972	by enabling the large file API, which makes them incompatible with the
		4973	standard libev compiled for their system.
		4974
		4975	Likewise, libev cannot enable the large file API itself as this would
		4976	suddenly make it incompatible to the default compile time environment,
		4977	i.e. all programs not using special compile switches.
		4978
		4979	=head2 OS/X AND DARWIN BUGS
		4980
		4981	The whole thing is a bug if you ask me - basically any system interface
		4982	you touch is broken, whether it is locales, poll, kqueue or even the
		4983	OpenGL drivers.
		4984
		4985	=head3 C<kqueue> is buggy
		4986
		4987	The kqueue syscall is broken in all known versions - most versions support
		4988	only sockets, many support pipes.
		4989
		4990	Libev tries to work around this by not using C<kqueue> by default on this
		4991	rotten platform, but of course you can still ask for it when creating a
		4992	loop - embedding a socket-only kqueue loop into a select-based one is
		4993	probably going to work well.
		4994
		4995	=head3 C<poll> is buggy
		4996
		4997	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4998	implementation by something calling C<kqueue> internally around the 10.5.6
		4999	release, so now C<kqueue> I<and> C<poll> are broken.
		5000
		5001	Libev tries to work around this by not using C<poll> by default on
		5002	this rotten platform, but of course you can still ask for it when creating
		5003	a loop.
		5004
		5005	=head3 C<select> is buggy
		5006
		5007	All that's left is C<select>, and of course Apple found a way to fuck this
		5008	one up as well: On OS/X, C<select> actively limits the number of file
		5009	descriptors you can pass in to 1024 - your program suddenly crashes when
		5010	you use more.
		5011
		5012	There is an undocumented "workaround" for this - defining
		5013	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		5014	work on OS/X.
		5015
		5016	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		5017
		5018	=head3 C<errno> reentrancy
		5019
		5020	The default compile environment on Solaris is unfortunately so
		5021	thread-unsafe that you can't even use components/libraries compiled
		5022	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		5023	defined by default. A valid, if stupid, implementation choice.
		5024
		5025	If you want to use libev in threaded environments you have to make sure
		5026	it's compiled with C<_REENTRANT> defined.
		5027
		5028	=head3 Event port backend
		5029
		5030	The scalable event interface for Solaris is called "event
		5031	ports". Unfortunately, this mechanism is very buggy in all major
		5032	releases. If you run into high CPU usage, your program freezes or you get
		5033	a large number of spurious wakeups, make sure you have all the relevant
		5034	and latest kernel patches applied. No, I don't know which ones, but there
		5035	are multiple ones to apply, and afterwards, event ports actually work
		5036	great.
		5037
		5038	If you can't get it to work, you can try running the program by setting
		5039	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		5040	C<select> backends.
		5041
		5042	=head2 AIX POLL BUG
		5043
		5044	AIX unfortunately has a broken C<poll.h> header. Libev works around
		5045	this by trying to avoid the poll backend altogether (i.e. it's not even
		5046	compiled in), which normally isn't a big problem as C<select> works fine
		5047	with large bitsets on AIX, and AIX is dead anyway.
		5048
4294	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5049	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		5050
		5051	=head3 General issues
4295		5052
4296	Win32 doesn't support any of the standards (e.g. POSIX) that libev	5053	Win32 doesn't support any of the standards (e.g. POSIX) that libev
4297	requires, and its I/O model is fundamentally incompatible with the POSIX	5054	requires, and its I/O model is fundamentally incompatible with the POSIX
4298	model. Libev still offers limited functionality on this platform in	5055	model. Libev still offers limited functionality on this platform in
4299	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5056	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4300	descriptors. This only applies when using Win32 natively, not when using	5057	descriptors. This only applies when using Win32 natively, not when using
4301	e.g. cygwin.	5058	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		5059	as every compiler comes with a slightly differently broken/incompatible
		5060	environment.
4302		5061
4303	Lifting these limitations would basically require the full	5062	Lifting these limitations would basically require the full
4304	re-implementation of the I/O system. If you are into these kinds of	5063	re-implementation of the I/O system. If you are into this kind of thing,
4305	things, then note that glib does exactly that for you in a very portable	5064	then note that glib does exactly that for you in a very portable way (note
4306	way (note also that glib is the slowest event library known to man).	5065	also that glib is the slowest event library known to man).
4307		5066
4308	There is no supported compilation method available on windows except	5067	There is no supported compilation method available on windows except
4309	embedding it into other applications.	5068	embedding it into other applications.
4310		5069
4311	Sensible signal handling is officially unsupported by Microsoft - libev	5070	Sensible signal handling is officially unsupported by Microsoft - libev
…		…
4339	you do I<not> compile the F<ev.c> or any other embedded source files!):	5098	you do I<not> compile the F<ev.c> or any other embedded source files!):
4340		5099
4341	#include "evwrap.h"	5100	#include "evwrap.h"
4342	#include "ev.c"	5101	#include "ev.c"
4343		5102
4344	=over 4
4345
4346	=item The winsocket select function	5103	=head3 The winsocket C<select> function
4347		5104
4348	The winsocket C<select> function doesn't follow POSIX in that it	5105	The winsocket C<select> function doesn't follow POSIX in that it
4349	requires socket I<handles> and not socket I<file descriptors> (it is	5106	requires socket I<handles> and not socket I<file descriptors> (it is
4350	also extremely buggy). This makes select very inefficient, and also	5107	also extremely buggy). This makes select very inefficient, and also
4351	requires a mapping from file descriptors to socket handles (the Microsoft	5108	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
4360	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	5117	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
4361		5118
4362	Note that winsockets handling of fd sets is O(n), so you can easily get a	5119	Note that winsockets handling of fd sets is O(n), so you can easily get a
4363	complexity in the O(n²) range when using win32.	5120	complexity in the O(n²) range when using win32.
4364		5121
4365	=item Limited number of file descriptors	5122	=head3 Limited number of file descriptors
4366		5123
4367	Windows has numerous arbitrary (and low) limits on things.	5124	Windows has numerous arbitrary (and low) limits on things.
4368		5125
4369	Early versions of winsocket's select only supported waiting for a maximum	5126	Early versions of winsocket's select only supported waiting for a maximum
4370	of C<64> handles (probably owning to the fact that all windows kernels	5127	of C<64> handles (probably owning to the fact that all windows kernels
…		…
4385	runtime libraries. This might get you to about C<512> or C<2048> sockets	5142	runtime libraries. This might get you to about C<512> or C<2048> sockets
4386	(depending on windows version and/or the phase of the moon). To get more,	5143	(depending on windows version and/or the phase of the moon). To get more,
4387	you need to wrap all I/O functions and provide your own fd management, but	5144	you need to wrap all I/O functions and provide your own fd management, but
4388	the cost of calling select (O(n²)) will likely make this unworkable.	5145	the cost of calling select (O(n²)) will likely make this unworkable.
4389		5146
4390	=back
4391
4392	=head2 PORTABILITY REQUIREMENTS	5147	=head2 PORTABILITY REQUIREMENTS
4393		5148
4394	In addition to a working ISO-C implementation and of course the	5149	In addition to a working ISO-C implementation and of course the
4395	backend-specific APIs, libev relies on a few additional extensions:	5150	backend-specific APIs, libev relies on a few additional extensions:
4396		5151
…		…
4402	Libev assumes not only that all watcher pointers have the same internal	5157	Libev assumes not only that all watcher pointers have the same internal
4403	structure (guaranteed by POSIX but not by ISO C for example), but it also	5158	structure (guaranteed by POSIX but not by ISO C for example), but it also
4404	assumes that the same (machine) code can be used to call any watcher	5159	assumes that the same (machine) code can be used to call any watcher
4405	callback: The watcher callbacks have different type signatures, but libev	5160	callback: The watcher callbacks have different type signatures, but libev
4406	calls them using an C<ev_watcher *> internally.	5161	calls them using an C<ev_watcher *> internally.
		5162
		5163	=item pointer accesses must be thread-atomic
		5164
		5165	Accessing a pointer value must be atomic, it must both be readable and
		5166	writable in one piece - this is the case on all current architectures.
4407		5167
4408	=item C<sig_atomic_t volatile> must be thread-atomic as well	5168	=item C<sig_atomic_t volatile> must be thread-atomic as well
4409		5169
4410	The type C<sig_atomic_t volatile> (or whatever is defined as	5170	The type C<sig_atomic_t volatile> (or whatever is defined as
4411	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5171	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
4434	watchers.	5194	watchers.
4435		5195
4436	=item C<double> must hold a time value in seconds with enough accuracy	5196	=item C<double> must hold a time value in seconds with enough accuracy
4437		5197
4438	The type C<double> is used to represent timestamps. It is required to	5198	The type C<double> is used to represent timestamps. It is required to
4439	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5199	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4440	enough for at least into the year 4000. This requirement is fulfilled by	5200	good enough for at least into the year 4000 with millisecond accuracy
		5201	(the design goal for libev). This requirement is overfulfilled by
4441	implementations implementing IEEE 754, which is basically all existing	5202	implementations using IEEE 754, which is basically all existing ones.
		5203
4442	ones. With IEEE 754 doubles, you get microsecond accuracy until at least	5204	With IEEE 754 doubles, you get microsecond accuracy until at least the
4443	2200.	5205	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5206	is either obsolete or somebody patched it to use C<long double> or
		5207	something like that, just kidding).
4444		5208
4445	=back	5209	=back
4446		5210
4447	If you know of other additional requirements drop me a note.	5211	If you know of other additional requirements drop me a note.
4448		5212
…		…
4510	=item Processing ev_async_send: O(number_of_async_watchers)	5274	=item Processing ev_async_send: O(number_of_async_watchers)
4511		5275
4512	=item Processing signals: O(max_signal_number)	5276	=item Processing signals: O(max_signal_number)
4513		5277
4514	Sending involves a system call I<iff> there were no other C<ev_async_send>	5278	Sending involves a system call I<iff> there were no other C<ev_async_send>
4515	calls in the current loop iteration. Checking for async and signal events	5279	calls in the current loop iteration and the loop is currently
		5280	blocked. Checking for async and signal events involves iterating over all
4516	involves iterating over all running async watchers or all signal numbers.	5281	running async watchers or all signal numbers.
4517		5282
4518	=back	5283	=back
4519		5284
4520		5285
		5286	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5287
		5288	The major version 4 introduced some incompatible changes to the API.
		5289
		5290	At the moment, the C<ev.h> header file provides compatibility definitions
		5291	for all changes, so most programs should still compile. The compatibility
		5292	layer might be removed in later versions of libev, so better update to the
		5293	new API early than late.
		5294
		5295	=over 4
		5296
		5297	=item C<EV_COMPAT3> backwards compatibility mechanism
		5298
		5299	The backward compatibility mechanism can be controlled by
		5300	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5301	section.
		5302
		5303	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5304
		5305	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5306
		5307	ev_loop_destroy (EV_DEFAULT_UC);
		5308	ev_loop_fork (EV_DEFAULT);
		5309
		5310	=item function/symbol renames
		5311
		5312	A number of functions and symbols have been renamed:
		5313
		5314	ev_loop => ev_run
		5315	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5316	EVLOOP_ONESHOT => EVRUN_ONCE
		5317
		5318	ev_unloop => ev_break
		5319	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5320	EVUNLOOP_ONE => EVBREAK_ONE
		5321	EVUNLOOP_ALL => EVBREAK_ALL
		5322
		5323	EV_TIMEOUT => EV_TIMER
		5324
		5325	ev_loop_count => ev_iteration
		5326	ev_loop_depth => ev_depth
		5327	ev_loop_verify => ev_verify
		5328
		5329	Most functions working on C<struct ev_loop> objects don't have an
		5330	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5331	associated constants have been renamed to not collide with the C<struct
		5332	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5333	as all other watcher types. Note that C<ev_loop_fork> is still called
		5334	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5335	typedef.
		5336
		5337	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5338
		5339	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5340	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5341	and work, but the library code will of course be larger.
		5342
		5343	=back
		5344
		5345
4521	=head1 GLOSSARY	5346	=head1 GLOSSARY
4522		5347
4523	=over 4	5348	=over 4
4524		5349
4525	=item active	5350	=item active
4526		5351
4527	A watcher is active as long as it has been started (has been attached to	5352	A watcher is active as long as it has been started and not yet stopped.
4528	an event loop) but not yet stopped (disassociated from the event loop).	5353	See L<WATCHER STATES> for details.
4529		5354
4530	=item application	5355	=item application
4531		5356
4532	In this document, an application is whatever is using libev.	5357	In this document, an application is whatever is using libev.
		5358
		5359	=item backend
		5360
		5361	The part of the code dealing with the operating system interfaces.
4533		5362
4534	=item callback	5363	=item callback
4535		5364
4536	The address of a function that is called when some event has been	5365	The address of a function that is called when some event has been
4537	detected. Callbacks are being passed the event loop, the watcher that	5366	detected. Callbacks are being passed the event loop, the watcher that
4538	received the event, and the actual event bitset.	5367	received the event, and the actual event bitset.
4539		5368
4540	=item callback invocation	5369	=item callback/watcher invocation
4541		5370
4542	The act of calling the callback associated with a watcher.	5371	The act of calling the callback associated with a watcher.
4543		5372
4544	=item event	5373	=item event
4545		5374
4546	A change of state of some external event, such as data now being available	5375	A change of state of some external event, such as data now being available
4547	for reading on a file descriptor, time having passed or simply not having	5376	for reading on a file descriptor, time having passed or simply not having
4548	any other events happening anymore.	5377	any other events happening anymore.
4549		5378
4550	In libev, events are represented as single bits (such as C<EV_READ> or	5379	In libev, events are represented as single bits (such as C<EV_READ> or
4551	C<EV_TIMEOUT>).	5380	C<EV_TIMER>).
4552		5381
4553	=item event library	5382	=item event library
4554		5383
4555	A software package implementing an event model and loop.	5384	A software package implementing an event model and loop.
4556		5385
…		…
4564	The model used to describe how an event loop handles and processes	5393	The model used to describe how an event loop handles and processes
4565	watchers and events.	5394	watchers and events.
4566		5395
4567	=item pending	5396	=item pending
4568		5397
4569	A watcher is pending as soon as the corresponding event has been detected,	5398	A watcher is pending as soon as the corresponding event has been
4570	and stops being pending as soon as the watcher will be invoked or its	5399	detected. See L<WATCHER STATES> for details.
4571	pending status is explicitly cleared by the application.
4572
4573	A watcher can be pending, but not active. Stopping a watcher also clears
4574	its pending status.
4575		5400
4576	=item real time	5401	=item real time
4577		5402
4578	The physical time that is observed. It is apparently strictly monotonic :)	5403	The physical time that is observed. It is apparently strictly monotonic :)
4579		5404
4580	=item wall-clock time	5405	=item wall-clock time
4581		5406
4582	The time and date as shown on clocks. Unlike real time, it can actually	5407	The time and date as shown on clocks. Unlike real time, it can actually
4583	be wrong and jump forwards and backwards, e.g. when the you adjust your	5408	be wrong and jump forwards and backwards, e.g. when you adjust your
4584	clock.	5409	clock.
4585		5410
4586	=item watcher	5411	=item watcher
4587		5412
4588	A data structure that describes interest in certain events. Watchers need	5413	A data structure that describes interest in certain events. Watchers need
4589	to be started (attached to an event loop) before they can receive events.	5414	to be started (attached to an event loop) before they can receive events.
4590		5415
4591	=item watcher invocation
4592
4593	The act of calling the callback associated with a watcher.
4594
4595	=back	5416	=back
4596		5417
4597	=head1 AUTHOR	5418	=head1 AUTHOR
4598		5419
4599	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5420	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5421	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4600		5422

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