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Revision 1.396 by root, Sat Feb 4 17:57:55 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_SIGNALFD>	430	=item C<EVFLAG_SIGNALFD>
376		431
377	When this flag is specified, then libev will attempt to use the	432	When this flag is specified, then libev will attempt to use the
378	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API	433	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
379	delivers signals synchronously, which makes is both faster and might make	434	delivers signals synchronously, which makes it both faster and might make
380	it possible to get the queued signal data.	435	it possible to get the queued signal data. It can also simplify signal
		436	handling with threads, as long as you properly block signals in your
		437	threads that are not interested in handling them.
381		438
382	Signalfd will not be used by default as this changes your signal mask, and	439	Signalfd will not be used by default as this changes your signal mask, and
383	there are a lot of shoddy libraries and programs (glib's threadpool for	440	there are a lot of shoddy libraries and programs (glib's threadpool for
384	example) that can't properly initialise their signal masks.	441	example) that can't properly initialise their signal masks.
		442
		443	=item C<EVFLAG_NOSIGMASK>
		444
		445	When this flag is specified, then libev will avoid to modify the signal
		446	mask. Specifically, this means you have to make sure signals are unblocked
		447	when you want to receive them.
		448
		449	This behaviour is useful when you want to do your own signal handling, or
		450	want to handle signals only in specific threads and want to avoid libev
		451	unblocking the signals.
		452
		453	It's also required by POSIX in a threaded program, as libev calls
		454	C<sigprocmask>, whose behaviour is officially unspecified.
		455
		456	This flag's behaviour will become the default in future versions of libev.
385		457
386	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	458	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
387		459
388	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
389	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,
…		…
417	=item C<EVBACKEND_EPOLL> (value 4, Linux)	489	=item C<EVBACKEND_EPOLL> (value 4, Linux)
418		490
419	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
420	kernels).	492	kernels).
421		493
422	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
423	but it scales phenomenally better. While poll and select usually scale	495	it scales phenomenally better. While poll and select usually scale like
424	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
425	epoll scales either O(1) or O(active_fds).	497	fd), epoll scales either O(1) or O(active_fds).
426		498
427	The epoll mechanism deserves honorable mention as the most misdesigned	499	The epoll mechanism deserves honorable mention as the most misdesigned
428	of the more advanced event mechanisms: mere annoyances include silently	500	of the more advanced event mechanisms: mere annoyances include silently
429	dropping file descriptors, requiring a system call per change per file	501	dropping file descriptors, requiring a system call per change per file
430	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
431	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
432	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
433	take considerable time (one syscall per file descriptor) and is of course	507	set, which can take considerable time (one syscall per file descriptor)
434	hard to detect.	508	and is of course hard to detect.
435		509
436	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	510	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
437	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
438	I<different> file descriptors (even already closed ones, so one cannot	512	totally I<different> file descriptors (even already closed ones, so
439	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
440	on SMP systems). Libev tries to counter these spurious notifications by	514	(especially on SMP systems). Libev tries to counter these spurious
441	employing an additional generation counter and comparing that against the	515	notifications by employing an additional generation counter and comparing
442	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...
443		526
444	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
445	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
446	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
447	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
…		…
513	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	596	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
514		597
515	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,
516	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)).
517		600
518	Please note that Solaris event ports can deliver a lot of spurious
519	notifications, so you need to use non-blocking I/O or other means to avoid
520	blocking when no data (or space) is available.
521
522	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
523	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
524	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	603	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
525	might perform better.	604	might perform better.
526		605
527	On the positive side, with the exception of the spurious readiness	606	On the positive side, this backend actually performed fully to
528	notifications, this backend actually performed fully to specification
529	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
530	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.
531		620
532	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
533	C<EVBACKEND_POLL>.	622	C<EVBACKEND_POLL>.
534		623
535	=item C<EVBACKEND_ALL>	624	=item C<EVBACKEND_ALL>
536		625
537	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
538	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
539	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	628	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
540		629
541	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).
542		639
543	=back	640	=back
544		641
545	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,
546	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
547	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
548	()> will be tried.	645	()> will be tried.
549		646
550	Example: This is the most typical usage.
551
552	if (!ev_default_loop (0))
553	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
554
555	Example: Restrict libev to the select and poll backends, and do not allow
556	environment settings to be taken into account:
557
558	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
559
560	Example: Use whatever libev has to offer, but make sure that kqueue is
561	used if available (warning, breaks stuff, best use only with your own
562	private event loop and only if you know the OS supports your types of
563	fds):
564
565	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
566
567	=item struct ev_loop *ev_loop_new (unsigned int flags)
568
569	Similar to C<ev_default_loop>, but always creates a new event loop that is
570	always distinct from the default loop. Unlike the default loop, it cannot
571	handle signal and child watchers, and attempts to do so will be greeted by
572	undefined behaviour (or a failed assertion if assertions are enabled).
573
574	Note that this function I<is> thread-safe, and the recommended way to use
575	libev with threads is indeed to create one loop per thread, and using the
576	default loop in the "main" or "initial" thread.
577
578	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.
579		648
580	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	649	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
581	if (!epoller)	650	if (!epoller)
582	fatal ("no epoll found here, maybe it hides under your chair");	651	fatal ("no epoll found here, maybe it hides under your chair");
583		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
584	=item ev_default_destroy ()	658	=item ev_loop_destroy (loop)
585		659
586	Destroys the default loop again (frees all memory and kernel state	660	Destroys an event loop object (frees all memory and kernel state
587	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
588	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
589	responsibility to either stop all watchers cleanly yourself I<before>	663	responsibility to either stop all watchers cleanly yourself I<before>
590	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
591	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
…		…
593		667
594	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
595	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
596	as signal and child watchers) would need to be stopped manually.	670	as signal and child watchers) would need to be stopped manually.
597		671
598	In general it is not advisable to call this function except in the	672	This function is normally used on loop objects allocated by
599	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.
600	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>
601	C<ev_loop_new> and C<ev_loop_destroy>.	679	and C<ev_loop_destroy>.
602		680
603	=item ev_loop_destroy (loop)	681	=item ev_loop_fork (loop)
604		682
605	Like C<ev_default_destroy>, but destroys an event loop created by an
606	earlier call to C<ev_loop_new>.
607
608	=item ev_default_fork ()
609
610	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
611	to reinitialise the kernel state for backends that have one. Despite the	684	reinitialise the kernel state for backends that have one. Despite the
612	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
613	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
614	sense). You I<must> call it in the child before using any of the libev	687	child before resuming or calling C<ev_run>.
615	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.
616		693
617	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
618	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
619	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).
620		700
621	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
622	it just in case after a fork. To make this easy, the function will fit in	702	it just in case after a fork.
623	quite nicely into a call to C<pthread_atfork>:
624		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	...
625	pthread_atfork (0, 0, ev_default_fork);	714	pthread_atfork (0, 0, post_fork_child);
626
627	=item ev_loop_fork (loop)
628
629	Like C<ev_default_fork>, but acts on an event loop created by
630	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
631	after fork that you want to re-use in the child, and how you do this is
632	entirely your own problem.
633		715
634	=item int ev_is_default_loop (loop)	716	=item int ev_is_default_loop (loop)
635		717
636	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
637	otherwise.	719	otherwise.
638		720
639	=item unsigned int ev_loop_count (loop)	721	=item unsigned int ev_iteration (loop)
640		722
641	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
642	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>
643	happily wraps around with enough iterations.	725	and happily wraps around with enough iterations.
644		726
645	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
646	"ticks" the number of loop iterations), as it roughly corresponds with	728	"ticks" the number of loop iterations), as it roughly corresponds with
647	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.
648		731
649	=item unsigned int ev_loop_depth (loop)	732	=item unsigned int ev_depth (loop)
650		733
651	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
652	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.
653		736
654	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
655	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),
656	in which case it is higher.	739	in which case it is higher.
657		740
658	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread	741	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
659	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.
660		745
661	=item unsigned int ev_backend (loop)	746	=item unsigned int ev_backend (loop)
662		747
663	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
664	use.	749	use.
…		…
673		758
674	=item ev_now_update (loop)	759	=item ev_now_update (loop)
675		760
676	Establishes the current time by querying the kernel, updating the time	761	Establishes the current time by querying the kernel, updating the time
677	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
678	is usually done automatically within C<ev_loop ()>.	763	is usually done automatically within C<ev_run ()>.
679		764
680	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
681	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
682	the current time is a good idea.	767	the current time is a good idea.
683		768
…		…
685		770
686	=item ev_suspend (loop)	771	=item ev_suspend (loop)
687		772
688	=item ev_resume (loop)	773	=item ev_resume (loop)
689		774
690	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
691	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.
692		777
693	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
694	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
695	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
696	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>
…		…
698	C<ev_resume> directly afterwards to resume timer processing.	783	C<ev_resume> directly afterwards to resume timer processing.
699		784
700	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
701	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
702	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
703	occured while suspended).	788	occurred while suspended).
704		789
705	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
706	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>
707	without a previous call to C<ev_suspend>.	792	without a previous call to C<ev_suspend>.
708		793
709	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
710	event loop time (see C<ev_now_update>).	795	event loop time (see C<ev_now_update>).
711		796
712	=item ev_loop (loop, int flags)	797	=item ev_run (loop, int flags)
713		798
714	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
715	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
716	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>.
717		804
718	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
719	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.
720		808
721	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
722	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
723	finished (especially in interactive programs), but having a program	811	finished (especially in interactive programs), but having a program
724	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
725	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
726	beauty.	814	beauty.
727		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
728	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
729	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
730	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
731	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.
732		826
733	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
734	necessary) and will handle those and any already outstanding ones. It	828	necessary) and will handle those and any already outstanding ones. It
735	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
736	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
737	user-registered callback will be called), and will return after one	831	user-registered callback will be called), and will return after one
738	iteration of the loop.	832	iteration of the loop.
739		833
740	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
741	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
742	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
743	usually a better approach for this kind of thing.	837	usually a better approach for this kind of thing.
744		838
745	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):
746		842
		843	- Increment loop depth.
		844	- Reset the ev_break status.
747	- Before the first iteration, call any pending watchers.	845	- Before the first iteration, call any pending watchers.
		846	LOOP:
748	* If EVFLAG_FORKCHECK was used, check for a fork.	847	- If EVFLAG_FORKCHECK was used, check for a fork.
749	- 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.
750	- Queue and call all prepare watchers.	849	- Queue and call all prepare watchers.
		850	- If ev_break was called, goto FINISH.
751	- If we have been forked, detach and recreate the kernel state	851	- If we have been forked, detach and recreate the kernel state
752	as to not disturb the other process.	852	as to not disturb the other process.
753	- Update the kernel state with all outstanding changes.	853	- Update the kernel state with all outstanding changes.
754	- Update the "event loop time" (ev_now ()).	854	- Update the "event loop time" (ev_now ()).
755	- Calculate for how long to sleep or block, if at all	855	- Calculate for how long to sleep or block, if at all
756	(active idle watchers, EVLOOP_NONBLOCK or not having	856	(active idle watchers, EVRUN_NOWAIT or not having
757	any active watchers at all will result in not sleeping).	857	any active watchers at all will result in not sleeping).
758	- 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.
759	- Block the process, waiting for any events.	860	- Block the process, waiting for any events.
760	- Queue all outstanding I/O (fd) events.	861	- Queue all outstanding I/O (fd) events.
761	- 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.
762	- Queue all expired timers.	863	- Queue all expired timers.
763	- Queue all expired periodics.	864	- Queue all expired periodics.
764	- Unless any events are pending now, queue all idle watchers.	865	- Queue all idle watchers with priority higher than that of pending events.
765	- Queue all check watchers.	866	- Queue all check watchers.
766	- 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).
767	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
768	be handled here by queueing them when their watcher gets executed.	869	be handled here by queueing them when their watcher gets executed.
769	- 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
770	were used, or there are no active watchers, return, otherwise	871	were used, or there are no active watchers, goto FINISH, otherwise
771	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.
772		877
773	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
774	anymore.	879	anymore.
775		880
776	... queue jobs here, make sure they register event watchers as long	881	... queue jobs here, make sure they register event watchers as long
777	... 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..)
778	ev_loop (my_loop, 0);	883	ev_run (my_loop, 0);
779	... jobs done or somebody called unloop. yeah!	884	... jobs done or somebody called break. yeah!
780		885
781	=item ev_unloop (loop, how)	886	=item ev_break (loop, how)
782		887
783	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
784	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
785	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
786	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.
787		892
788	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>.
789		894
790	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.
791		897
792	=item ev_ref (loop)	898	=item ev_ref (loop)
793		899
794	=item ev_unref (loop)	900	=item ev_unref (loop)
795		901
796	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
797	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
798	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.
799		905
800	This is useful when you have a watcher that you never intend to	906	This is useful when you have a watcher that you never intend to
801	unregister, but that nevertheless should not keep C<ev_loop> from	907	unregister, but that nevertheless should not keep C<ev_run> from
802	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>	908	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
803	before stopping it.	909	before stopping it.
804		910
805	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
806	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
807	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
808	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
809	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
810	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
811	before, respectively. Note also that libev might stop watchers itself	917	before, respectively. Note also that libev might stop watchers itself
812	(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>
813	in the callback).	919	in the callback).
814		920
815	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>
816	running when nothing else is active.	922	running when nothing else is active.
817		923
818	ev_signal exitsig;	924	ev_signal exitsig;
819	ev_signal_init (&exitsig, sig_cb, SIGINT);	925	ev_signal_init (&exitsig, sig_cb, SIGINT);
820	ev_signal_start (loop, &exitsig);	926	ev_signal_start (loop, &exitsig);
821	evf_unref (loop);	927	ev_unref (loop);
822		928
823	Example: For some weird reason, unregister the above signal handler again.	929	Example: For some weird reason, unregister the above signal handler again.
824		930
825	ev_ref (loop);	931	ev_ref (loop);
826	ev_signal_stop (loop, &exitsig);	932	ev_signal_stop (loop, &exitsig);
…		…
846	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.
847		953
848	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
849	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,
850	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
851	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
852	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
853	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
854	once per this interval, on average.	960	once per this interval, on average (as long as the host time resolution is
		961	good enough).
855		962
856	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
857	to spend more time collecting timeouts, at the expense of increased	964	to spend more time collecting timeouts, at the expense of increased
858	latency/jitter/inexactness (the watcher callback will be called	965	latency/jitter/inexactness (the watcher callback will be called
859	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
…		…
865	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>,
866	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
867	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
868	parallelity, then this setting will limit your transaction rate (if you	975	parallelity, then this setting will limit your transaction rate (if you
869	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,
870	then you can't do more than 100 transations per second).	977	then you can't do more than 100 transactions per second).
871		978
872	Setting the I<timeout collect interval> can improve the opportunity for	979	Setting the I<timeout collect interval> can improve the opportunity for
873	saving power, as the program will "bundle" timer callback invocations that	980	saving power, as the program will "bundle" timer callback invocations that
874	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
875	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
…		…
883	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	990	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
884		991
885	=item ev_invoke_pending (loop)	992	=item ev_invoke_pending (loop)
886		993
887	This call will simply invoke all pending watchers while resetting their	994	This call will simply invoke all pending watchers while resetting their
888	pending state. Normally, C<ev_loop> does this automatically when required,	995	pending state. Normally, C<ev_run> does this automatically when required,
889	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).
890		1001
891	=item int ev_pending_count (loop)	1002	=item int ev_pending_count (loop)
892		1003
893	Returns the number of pending watchers - zero indicates that no watchers	1004	Returns the number of pending watchers - zero indicates that no watchers
894	are pending.	1005	are pending.
895		1006
896	=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))
897		1008
898	This overrides the invoke pending functionality of the loop: Instead of	1009	This overrides the invoke pending functionality of the loop: Instead of
899	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
900	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
901	invoke the actual watchers inside another context (another thread etc.).	1012	invoke the actual watchers inside another context (another thread etc.).
902		1013
903	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
904	callback.	1015	callback.
…		…
907		1018
908	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
909	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
910	each call to a libev function.	1021	each call to a libev function.
911		1022
912	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
913	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
914	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
915	and I<acquire> callbacks on the loop.	1026	I<release> and I<acquire> callbacks on the loop.
916		1027
917	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
918	suspended waiting for new events, and C<acquire> is called just	1029	suspended waiting for new events, and C<acquire> is called just
919	afterwards.	1030	afterwards.
920		1031
…		…
923		1034
924	While event loop modifications are allowed between invocations of	1035	While event loop modifications are allowed between invocations of
925	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
926	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
927	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
928	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
929	to take note of any changes you made.	1040	to take note of any changes you made.
930		1041
931	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
932	invocations of C<release> and C<acquire>.	1043	invocations of C<release> and C<acquire>.
933		1044
934	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
935	document.	1046	document.
936		1047
937	=item ev_set_userdata (loop, void *data)	1048	=item ev_set_userdata (loop, void *data)
938		1049
939	=item ev_userdata (loop)	1050	=item void *ev_userdata (loop)
940		1051
941	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
942	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
943	C<0.>	1054	C<0>.
944		1055
945	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,
946	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
947	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
948	any other purpose as well.	1059	any other purpose as well.
949		1060
950	=item ev_loop_verify (loop)	1061	=item ev_verify (loop)
951		1062
952	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
953	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
954	through all internal structures and checks them for validity. If anything	1065	through all internal structures and checks them for validity. If anything
955	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
…		…
966		1077
967	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
968	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
969	watchers and C<ev_io_start> for I/O watchers.	1080	watchers and C<ev_io_start> for I/O watchers.
970		1081
971	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
972	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
973	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:
974		1086
975	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)
976	{	1088	{
977	ev_io_stop (w);	1089	ev_io_stop (w);
978	ev_unloop (loop, EVUNLOOP_ALL);	1090	ev_break (loop, EVBREAK_ALL);
979	}	1091	}
980		1092
981	struct ev_loop *loop = ev_default_loop (0);	1093	struct ev_loop *loop = ev_default_loop (0);
982		1094
983	ev_io stdin_watcher;	1095	ev_io stdin_watcher;
984		1096
985	ev_init (&stdin_watcher, my_cb);	1097	ev_init (&stdin_watcher, my_cb);
986	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1098	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
987	ev_io_start (loop, &stdin_watcher);	1099	ev_io_start (loop, &stdin_watcher);
988		1100
989	ev_loop (loop, 0);	1101	ev_run (loop, 0);
990		1102
991	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
992	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
993	stack).	1105	stack).
994		1106
995	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>
996	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).
997		1109
998	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
999	(watcher *, callback)>, which expects a callback to be provided. This	1111	*, callback)>, which expects a callback to be provided. This callback is
1000	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
1001	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
1002	is readable and/or writable).	1114	and/or writable).
1003		1115
1004	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 *, ...) >>
1005	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
1006	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<<
1007	ev_TYPE_init (watcher *, callback, ...) >>.	1119	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
1030	=item C<EV_WRITE>	1142	=item C<EV_WRITE>
1031		1143
1032	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
1033	writable.	1145	writable.
1034		1146
1035	=item C<EV_TIMEOUT>	1147	=item C<EV_TIMER>
1036		1148
1037	The C<ev_timer> watcher has timed out.	1149	The C<ev_timer> watcher has timed out.
1038		1150
1039	=item C<EV_PERIODIC>	1151	=item C<EV_PERIODIC>
1040		1152
…		…
1058		1170
1059	=item C<EV_PREPARE>	1171	=item C<EV_PREPARE>
1060		1172
1061	=item C<EV_CHECK>	1173	=item C<EV_CHECK>
1062		1174
1063	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
1064	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
1065	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
1066	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
1067	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
1068	(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
1069	C<ev_loop> from blocking).	1181	C<ev_run> from blocking).
1070		1182
1071	=item C<EV_EMBED>	1183	=item C<EV_EMBED>
1072		1184
1073	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.
1074		1186
1075	=item C<EV_FORK>	1187	=item C<EV_FORK>
1076		1188
1077	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
1078	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>).
1079		1195
1080	=item C<EV_ASYNC>	1196	=item C<EV_ASYNC>
1081		1197
1082	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>).
1083		1199
…		…
1256	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
1257	functions that do not need a watcher.	1373	functions that do not need a watcher.
1258		1374
1259	=back	1375	=back
1260		1376
		1377	See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR
		1378	OWN COMPOSITE WATCHERS> idioms.
1261		1379
1262	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1380	=head2 WATCHER STATES
1263		1381
1264	Each watcher has, by default, a member C<void *data> that you can change	1382	There are various watcher states mentioned throughout this manual -
1265	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
1266	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
1267	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".
1268	member, you can also "subclass" the watcher type and provide your own
1269	data:
1270		1386
1271	struct my_io	1387	=over 4
1272	{
1273	ev_io io;
1274	int otherfd;
1275	void *somedata;
1276	struct whatever *mostinteresting;
1277	};
1278		1388
1279	...	1389	=item initialiased
1280	struct my_io w;
1281	ev_io_init (&w.io, my_cb, fd, EV_READ);
1282		1390
1283	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
1284	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.
1285		1394
1286	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
1287	{	1396	use in an event loop. It can be moved around, freed, reused etc. at
1288	struct my_io *w = (struct my_io *)w_;	1397	will - as long as you either keep the memory contents intact, or call
1289	...	1398	C<ev_TYPE_init> again.
1290	}
1291		1399
1292	More interesting and less C-conformant ways of casting your callback type	1400	=item started/running/active
1293	instead have been omitted.
1294		1401
1295	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
1296	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.
1297		1407
1298	struct my_biggy	1408	=item pending
1299	{
1300	int some_data;
1301	ev_timer t1;
1302	ev_timer t2;
1303	}
1304		1409
1305	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
1306	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
1307	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
1308	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
1309	programmers):	1414	callback.
1310		1415
1311	#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.
1312		1422
1313	static void	1423	It is also possible to feed an event on a watcher that is not active (e.g.
1314	t1_cb (EV_P_ ev_timer *w, int revents)	1424	via C<ev_feed_event>), in which case it becomes pending without being
1315	{	1425	active.
1316	struct my_biggy big = (struct my_biggy *)
1317	(((char *)w) - offsetof (struct my_biggy, t1));
1318	}
1319		1426
1320	static void	1427	=item stopped
1321	t2_cb (EV_P_ ev_timer *w, int revents)	1428
1322	{	1429	A watcher can be stopped implicitly by libev (in which case it might still
1323	struct my_biggy big = (struct my_biggy *)	1430	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1324	(((char *)w) - offsetof (struct my_biggy, t2));	1431	latter will clear any pending state the watcher might be in, regardless
1325	}	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
1326		1441
1327	=head2 WATCHER PRIORITY MODELS	1442	=head2 WATCHER PRIORITY MODELS
1328		1443
1329	Many event loops support I<watcher priorities>, which are usually small	1444	Many event loops support I<watcher priorities>, which are usually small
1330	integers that influence the ordering of event callback invocation	1445	integers that influence the ordering of event callback invocation
…		…
1373		1488
1374	For example, to emulate how many other event libraries handle priorities,	1489	For example, to emulate how many other event libraries handle priorities,
1375	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
1376	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
1377	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
1378	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
1379	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
1380	workable.	1495	workable.
1381		1496
1382	Usually, however, the lock-out model implemented that way will perform	1497	Usually, however, the lock-out model implemented that way will perform
1383	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,
…		…
1397	{	1512	{
1398	// stop the I/O watcher, we received the event, but	1513	// stop the I/O watcher, we received the event, but
1399	// are not yet ready to handle it.	1514	// are not yet ready to handle it.
1400	ev_io_stop (EV_A_ w);	1515	ev_io_stop (EV_A_ w);
1401		1516
1402	// start the idle watcher to ahndle the actual event.	1517	// start the idle watcher to handle the actual event.
1403	// it will not be executed as long as other watchers	1518	// it will not be executed as long as other watchers
1404	// with the default priority are receiving events.	1519	// with the default priority are receiving events.
1405	ev_idle_start (EV_A_ &idle);	1520	ev_idle_start (EV_A_ &idle);
1406	}	1521	}
1407		1522
…		…
1457	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
1458	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
1459	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
1460	required if you know what you are doing).	1575	required if you know what you are doing).
1461		1576
1462	If you cannot use non-blocking mode, then force the use of a
1463	known-to-be-good backend (at the time of this writing, this includes only
1464	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1465	descriptors for which non-blocking operation makes no sense (such as
1466	files) - libev doesn't guarentee any specific behaviour in that case.
1467
1468	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
1469	receive "spurious" readiness notifications, that is your callback might	1578	receive "spurious" readiness notifications, that is, your callback might
1470	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
1471	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
1472	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
1473	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
1474	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1475	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1583	preferable to a program hanging until some data arrives.
1476		1584
1477	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
1478	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
1479	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
1480	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
1481	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
1482	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
1483	indefinitely.	1591	indefinitely.
1484		1592
1485	But really, best use non-blocking mode.	1593	But really, best use non-blocking mode.
1486		1594
…		…
1514		1622
1515	There is no workaround possible except not registering events	1623	There is no workaround possible except not registering events
1516	for potentially C<dup ()>'ed file descriptors, or to resort to	1624	for potentially C<dup ()>'ed file descriptors, or to resort to
1517	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1625	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1518		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
1519	=head3 The special problem of fork	1660	=head3 The special problem of fork
1520		1661
1521	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
1522	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
1523	it in the child.	1664	it in the child if you want to continue to use it in the child.
1524		1665
1525	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
1526	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
1527	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1668	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1528	C<EVBACKEND_POLL>.
1529		1669
1530	=head3 The special problem of SIGPIPE	1670	=head3 The special problem of SIGPIPE
1531		1671
1532	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>:
1533	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
…		…
1536		1676
1537	So when you encounter spurious, unexplained daemon exits, make sure you	1677	So when you encounter spurious, unexplained daemon exits, make sure you
1538	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
1539	somewhere, as that would have given you a big clue).	1679	somewhere, as that would have given you a big clue).
1540		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.
1541		1719
1542	=head3 Watcher-Specific Functions	1720	=head3 Watcher-Specific Functions
1543		1721
1544	=over 4	1722	=over 4
1545		1723
…		…
1577	...	1755	...
1578	struct ev_loop *loop = ev_default_init (0);	1756	struct ev_loop *loop = ev_default_init (0);
1579	ev_io stdin_readable;	1757	ev_io stdin_readable;
1580	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);
1581	ev_io_start (loop, &stdin_readable);	1759	ev_io_start (loop, &stdin_readable);
1582	ev_loop (loop, 0);	1760	ev_run (loop, 0);
1583		1761
1584		1762
1585	=head2 C<ev_timer> - relative and optionally repeating timeouts	1763	=head2 C<ev_timer> - relative and optionally repeating timeouts
1586		1764
1587	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
…		…
1593	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1771	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1594	monotonic clock option helps a lot here).	1772	monotonic clock option helps a lot here).
1595		1773
1596	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
1597	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
1598	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
1599	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
1600	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
1601	no longer true when a callback calls C<ev_loop> recursively).	1780	longer true when a callback calls C<ev_run> recursively).
1602		1781
1603	=head3 Be smart about timeouts	1782	=head3 Be smart about timeouts
1604		1783
1605	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
1606	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,
…		…
1681		1860
1682	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,
1683	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
1684	within the callback:	1863	within the callback:
1685		1864
		1865	ev_tstamp timeout = 60.;
1686	ev_tstamp last_activity; // time of last activity	1866	ev_tstamp last_activity; // time of last activity
		1867	ev_timer timer;
1687		1868
1688	static void	1869	static void
1689	callback (EV_P_ ev_timer *w, int revents)	1870	callback (EV_P_ ev_timer *w, int revents)
1690	{	1871	{
1691	ev_tstamp now = ev_now (EV_A);	1872	// calculate when the timeout would happen
1692	ev_tstamp timeout = last_activity + 60.;	1873	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1693		1874
1694	// if last_activity + 60. is older than now, we did time out	1875	// if negative, it means we the timeout already occured
1695	if (timeout < now)	1876	if (after < 0.)
1696	{	1877	{
1697	// timeout occured, take action	1878	// timeout occurred, take action
1698	}	1879	}
1699	else	1880	else
1700	{	1881	{
1701	// callback was invoked, but there was some activity, re-arm	1882	// callback was invoked, but there was some recent
1702	// the watcher to fire in last_activity + 60, which is	1883	// activity. simply restart the timer to time out
1703	// guaranteed to be in the future, so "again" is positive:	1884	// after "after" seconds, which is the earliest time
1704	w->repeat = timeout - now;	1885	// the timeout can occur.
		1886	ev_timer_set (w, after, 0.);
1705	ev_timer_again (EV_A_ w);	1887	ev_timer_start (EV_A_ w);
1706	}	1888	}
1707	}	1889	}
1708		1890
1709	To summarise the callback: first calculate the real timeout (defined	1891	To summarise the callback: first calculate in how many seconds the
1710	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,
1711	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
1712	the callback was invoked too early (C<timeout> is in the future), so	1894	(EV_A)> from that).
1713	re-schedule the timer to fire at that future time, to see if maybe we have
1714	a timeout then.
1715		1895
1716	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
1717	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.
1718		1905
1719	This scheme causes more callback invocations (about one every 60 seconds	1906	This scheme causes more callback invocations (about one every 60 seconds
1720	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
1721	libev to change the timeout.	1908	libev to change the timeout.
1722		1909
1723	To start the timer, simply initialise the watcher and set C<last_activity>	1910	To start the machinery, simply initialise the watcher and set
1724	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
1725	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:
1726		1914
		1915	last_activity = ev_now (EV_A);
1727	ev_init (timer, callback);	1916	ev_init (&timer, callback);
1728	last_activity = ev_now (loop);	1917	callback (EV_A_ &timer, 0);
1729	callback (loop, timer, EV_TIMEOUT);
1730		1918
1731	And when there is some activity, simply store the current time in	1919	When there is some activity, simply store the current time in
1732	C<last_activity>, no libev calls at all:	1920	C<last_activity>, no libev calls at all:
1733		1921
		1922	if (activity detected)
1734	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);
1735		1932
1736	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
1737	time-out is unlikely to be triggered, much more efficient.	1934	time-out is unlikely to be triggered, much more efficient.
1738
1739	Changing the timeout is trivial as well (if it isn't hard-coded in the
1740	callback :) - just change the timeout and invoke the callback, which will
1741	fix things for you.
1742		1935
1743	=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.
1744		1937
1745	If there is not one request, but many thousands (millions...), all	1938	If there is not one request, but many thousands (millions...), all
1746	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
…		…
1773	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
1774	rather complicated, but extremely efficient, something that really pays	1967	rather complicated, but extremely efficient, something that really pays
1775	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
1776	overkill :)	1969	overkill :)
1777		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
1778	=head3 The special problem of time updates	2008	=head3 The special problem of time updates
1779		2009
1780	Establishing the current time is a costly operation (it usually takes at	2010	Establishing the current time is a costly operation (it usually takes
1781	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
1782	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
1783	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
1784	lots of events in one iteration.	2014	lots of events in one iteration.
1785		2015
1786	The relative timeouts are calculated relative to the C<ev_now ()>	2016	The relative timeouts are calculated relative to the C<ev_now ()>
1787	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
…		…
1792	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2022	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1793		2023
1794	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
1795	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
1796	()>.	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.
1797		2060
1798	=head3 The special problems of suspended animation	2061	=head3 The special problems of suspended animation
1799		2062
1800	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
1801	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?
…		…
1845	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
1846	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.
1847		2110
1848	=item ev_timer_again (loop, ev_timer *)	2111	=item ev_timer_again (loop, ev_timer *)
1849		2112
1850	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
1851	repeating. The exact semantics are:	2114	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2115	timeout to the C<repeat> value and calling C<ev_timer_start>.
1852		2116
		2117	The exact semantics are as in the following rules, all of which will be
		2118	applied to the watcher:
		2119
		2120	=over 4
		2121
1853	If the timer is pending, its pending status is cleared.	2122	=item If the timer is pending, the pending status is always cleared.
1854		2123
1855	If the timer is started but non-repeating, stop it (as if it timed out).	2124	=item If the timer is started but non-repeating, stop it (as if it timed
		2125	out, without invoking it).
1856		2126
1857	If the timer is repeating, either start it if necessary (with the	2127	=item If the timer is repeating, make the C<repeat> value the new timeout
1858	C<repeat> value), or reset the running timer to the C<repeat> value.	2128	and start the timer, if necessary.
		2129
		2130	=back
1859		2131
1860	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2132	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1861	usage example.	2133	usage example.
1862		2134
1863	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)	2135	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
…		…
1865	Returns the remaining time until a timer fires. If the timer is active,	2137	Returns the remaining time until a timer fires. If the timer is active,
1866	then this time is relative to the current event loop time, otherwise it's	2138	then this time is relative to the current event loop time, otherwise it's
1867	the timeout value currently configured.	2139	the timeout value currently configured.
1868		2140
1869	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns	2141	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1870	C<5>. When the timer is started and one second passes, C<ev_timer_remain>	2142	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
1871	will return C<4>. When the timer expires and is restarted, it will return	2143	will return C<4>. When the timer expires and is restarted, it will return
1872	roughly C<7> (likely slightly less as callback invocation takes some time,	2144	roughly C<7> (likely slightly less as callback invocation takes some time,
1873	too), and so on.	2145	too), and so on.
1874		2146
1875	=item ev_tstamp repeat [read-write]	2147	=item ev_tstamp repeat [read-write]
…		…
1904	}	2176	}
1905		2177
1906	ev_timer mytimer;	2178	ev_timer mytimer;
1907	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2179	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1908	ev_timer_again (&mytimer); /* start timer */	2180	ev_timer_again (&mytimer); /* start timer */
1909	ev_loop (loop, 0);	2181	ev_run (loop, 0);
1910		2182
1911	// and in some piece of code that gets executed on any "activity":	2183	// and in some piece of code that gets executed on any "activity":
1912	// reset the timeout to start ticking again at 10 seconds	2184	// reset the timeout to start ticking again at 10 seconds
1913	ev_timer_again (&mytimer);	2185	ev_timer_again (&mytimer);
1914		2186
…		…
1940		2212
1941	As with timers, the callback is guaranteed to be invoked only when the	2213	As with timers, the callback is guaranteed to be invoked only when the
1942	point in time where it is supposed to trigger has passed. If multiple	2214	point in time where it is supposed to trigger has passed. If multiple
1943	timers become ready during the same loop iteration then the ones with	2215	timers become ready during the same loop iteration then the ones with
1944	earlier time-out values are invoked before ones with later time-out values	2216	earlier time-out values are invoked before ones with later time-out values
1945	(but this is no longer true when a callback calls C<ev_loop> recursively).	2217	(but this is no longer true when a callback calls C<ev_run> recursively).
1946		2218
1947	=head3 Watcher-Specific Functions and Data Members	2219	=head3 Watcher-Specific Functions and Data Members
1948		2220
1949	=over 4	2221	=over 4
1950		2222
…		…
1985		2257
1986	Another way to think about it (for the mathematically inclined) is that	2258	Another way to think about it (for the mathematically inclined) is that
1987	C<ev_periodic> will try to run the callback in this mode at the next possible	2259	C<ev_periodic> will try to run the callback in this mode at the next possible
1988	time where C<time = offset (mod interval)>, regardless of any time jumps.	2260	time where C<time = offset (mod interval)>, regardless of any time jumps.
1989		2261
1990	For numerical stability it is preferable that the C<offset> value is near	2262	The C<interval> I<MUST> be positive, and for numerical stability, the
1991	C<ev_now ()> (the current time), but there is no range requirement for	2263	interval value should be higher than C<1/8192> (which is around 100
1992	this value, and in fact is often specified as zero.	2264	microseconds) and C<offset> should be higher than C<0> and should have
		2265	at most a similar magnitude as the current time (say, within a factor of
		2266	ten). Typical values for offset are, in fact, C<0> or something between
		2267	C<0> and C<interval>, which is also the recommended range.
1993		2268
1994	Note also that there is an upper limit to how often a timer can fire (CPU	2269	Note also that there is an upper limit to how often a timer can fire (CPU
1995	speed for example), so if C<interval> is very small then timing stability	2270	speed for example), so if C<interval> is very small then timing stability
1996	will of course deteriorate. Libev itself tries to be exact to be about one	2271	will of course deteriorate. Libev itself tries to be exact to be about one
1997	millisecond (if the OS supports it and the machine is fast enough).	2272	millisecond (if the OS supports it and the machine is fast enough).
…		…
2078	Example: Call a callback every hour, or, more precisely, whenever the	2353	Example: Call a callback every hour, or, more precisely, whenever the
2079	system time is divisible by 3600. The callback invocation times have	2354	system time is divisible by 3600. The callback invocation times have
2080	potentially a lot of jitter, but good long-term stability.	2355	potentially a lot of jitter, but good long-term stability.
2081		2356
2082	static void	2357	static void
2083	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2358	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
2084	{	2359	{
2085	... its now a full hour (UTC, or TAI or whatever your clock follows)	2360	... its now a full hour (UTC, or TAI or whatever your clock follows)
2086	}	2361	}
2087		2362
2088	ev_periodic hourly_tick;	2363	ev_periodic hourly_tick;
…		…
2111		2386
2112	=head2 C<ev_signal> - signal me when a signal gets signalled!	2387	=head2 C<ev_signal> - signal me when a signal gets signalled!
2113		2388
2114	Signal watchers will trigger an event when the process receives a specific	2389	Signal watchers will trigger an event when the process receives a specific
2115	signal one or more times. Even though signals are very asynchronous, libev	2390	signal one or more times. Even though signals are very asynchronous, libev
2116	will try it's best to deliver signals synchronously, i.e. as part of the	2391	will try its best to deliver signals synchronously, i.e. as part of the
2117	normal event processing, like any other event.	2392	normal event processing, like any other event.
2118		2393
2119	If you want signals to be delivered truly asynchronously, just use	2394	If you want signals to be delivered truly asynchronously, just use
2120	C<sigaction> as you would do without libev and forget about sharing	2395	C<sigaction> as you would do without libev and forget about sharing
2121	the signal. You can even use C<ev_async> from a signal handler to	2396	the signal. You can even use C<ev_async> from a signal handler to
…		…
2140	=head3 The special problem of inheritance over fork/execve/pthread_create	2415	=head3 The special problem of inheritance over fork/execve/pthread_create
2141		2416
2142	Both the signal mask (C<sigprocmask>) and the signal disposition	2417	Both the signal mask (C<sigprocmask>) and the signal disposition
2143	(C<sigaction>) are unspecified after starting a signal watcher (and after	2418	(C<sigaction>) are unspecified after starting a signal watcher (and after
2144	stopping it again), that is, libev might or might not block the signal,	2419	stopping it again), that is, libev might or might not block the signal,
2145	and might or might not set or restore the installed signal handler.	2420	and might or might not set or restore the installed signal handler (but
		2421	see C<EVFLAG_NOSIGMASK>).
2146		2422
2147	While this does not matter for the signal disposition (libev never	2423	While this does not matter for the signal disposition (libev never
2148	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on	2424	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
2149	C<execve>), this matters for the signal mask: many programs do not expect	2425	C<execve>), this matters for the signal mask: many programs do not expect
2150	certain signals to be blocked.	2426	certain signals to be blocked.
…		…
2160	In current versions of libev, the signal will not be blocked indefinitely	2436	In current versions of libev, the signal will not be blocked indefinitely
2161	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces	2437	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
2162	the window of opportunity for problems, it will not go away, as libev	2438	the window of opportunity for problems, it will not go away, as libev
2163	I<has> to modify the signal mask, at least temporarily.	2439	I<has> to modify the signal mask, at least temporarily.
2164		2440
2165	So I can't stress this enough I<if you do not reset your signal mask	2441	So I can't stress this enough: I<If you do not reset your signal mask when
2166	when you expect it to be empty, you have a race condition in your	2442	you expect it to be empty, you have a race condition in your code>. This
2167	program>. This is not a libev-specific thing, this is true for most event	2443	is not a libev-specific thing, this is true for most event libraries.
2168	libraries.	2444
		2445	=head3 The special problem of threads signal handling
		2446
		2447	POSIX threads has problematic signal handling semantics, specifically,
		2448	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2449	threads in a process block signals, which is hard to achieve.
		2450
		2451	When you want to use sigwait (or mix libev signal handling with your own
		2452	for the same signals), you can tackle this problem by globally blocking
		2453	all signals before creating any threads (or creating them with a fully set
		2454	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2455	loops. Then designate one thread as "signal receiver thread" which handles
		2456	these signals. You can pass on any signals that libev might be interested
		2457	in by calling C<ev_feed_signal>.
2169		2458
2170	=head3 Watcher-Specific Functions and Data Members	2459	=head3 Watcher-Specific Functions and Data Members
2171		2460
2172	=over 4	2461	=over 4
2173		2462
…		…
2189	Example: Try to exit cleanly on SIGINT.	2478	Example: Try to exit cleanly on SIGINT.
2190		2479
2191	static void	2480	static void
2192	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2481	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2193	{	2482	{
2194	ev_unloop (loop, EVUNLOOP_ALL);	2483	ev_break (loop, EVBREAK_ALL);
2195	}	2484	}
2196		2485
2197	ev_signal signal_watcher;	2486	ev_signal signal_watcher;
2198	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2487	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2199	ev_signal_start (loop, &signal_watcher);	2488	ev_signal_start (loop, &signal_watcher);
…		…
2585		2874
2586	Prepare and check watchers are usually (but not always) used in pairs:	2875	Prepare and check watchers are usually (but not always) used in pairs:
2587	prepare watchers get invoked before the process blocks and check watchers	2876	prepare watchers get invoked before the process blocks and check watchers
2588	afterwards.	2877	afterwards.
2589		2878
2590	You I<must not> call C<ev_loop> or similar functions that enter	2879	You I<must not> call C<ev_run> or similar functions that enter
2591	the current event loop from either C<ev_prepare> or C<ev_check>	2880	the current event loop from either C<ev_prepare> or C<ev_check>
2592	watchers. Other loops than the current one are fine, however. The	2881	watchers. Other loops than the current one are fine, however. The
2593	rationale behind this is that you do not need to check for recursion in	2882	rationale behind this is that you do not need to check for recursion in
2594	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2883	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2595	C<ev_check> so if you have one watcher of each kind they will always be	2884	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2763		3052
2764	if (timeout >= 0)	3053	if (timeout >= 0)
2765	// create/start timer	3054	// create/start timer
2766		3055
2767	// poll	3056	// poll
2768	ev_loop (EV_A_ 0);	3057	ev_run (EV_A_ 0);
2769		3058
2770	// stop timer again	3059	// stop timer again
2771	if (timeout >= 0)	3060	if (timeout >= 0)
2772	ev_timer_stop (EV_A_ &to);	3061	ev_timer_stop (EV_A_ &to);
2773		3062
…		…
2851	if you do not want that, you need to temporarily stop the embed watcher).	3140	if you do not want that, you need to temporarily stop the embed watcher).
2852		3141
2853	=item ev_embed_sweep (loop, ev_embed *)	3142	=item ev_embed_sweep (loop, ev_embed *)
2854		3143
2855	Make a single, non-blocking sweep over the embedded loop. This works	3144	Make a single, non-blocking sweep over the embedded loop. This works
2856	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3145	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2857	appropriate way for embedded loops.	3146	appropriate way for embedded loops.
2858		3147
2859	=item struct ev_loop *other [read-only]	3148	=item struct ev_loop *other [read-only]
2860		3149
2861	The embedded event loop.	3150	The embedded event loop.
…		…
2921	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3210	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2922	handlers will be invoked, too, of course.	3211	handlers will be invoked, too, of course.
2923		3212
2924	=head3 The special problem of life after fork - how is it possible?	3213	=head3 The special problem of life after fork - how is it possible?
2925		3214
2926	Most uses of C<fork()> consist of forking, then some simple calls to ste	3215	Most uses of C<fork()> consist of forking, then some simple calls to set
2927	up/change the process environment, followed by a call to C<exec()>. This	3216	up/change the process environment, followed by a call to C<exec()>. This
2928	sequence should be handled by libev without any problems.	3217	sequence should be handled by libev without any problems.
2929		3218
2930	This changes when the application actually wants to do event handling	3219	This changes when the application actually wants to do event handling
2931	in the child, or both parent in child, in effect "continuing" after the	3220	in the child, or both parent in child, in effect "continuing" after the
…		…
2947	disadvantage of having to use multiple event loops (which do not support	3236	disadvantage of having to use multiple event loops (which do not support
2948	signal watchers).	3237	signal watchers).
2949		3238
2950	When this is not possible, or you want to use the default loop for	3239	When this is not possible, or you want to use the default loop for
2951	other reasons, then in the process that wants to start "fresh", call	3240	other reasons, then in the process that wants to start "fresh", call
2952	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3241	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
2953	the default loop will "orphan" (not stop) all registered watchers, so you	3242	Destroying the default loop will "orphan" (not stop) all registered
2954	have to be careful not to execute code that modifies those watchers. Note	3243	watchers, so you have to be careful not to execute code that modifies
2955	also that in that case, you have to re-register any signal watchers.	3244	those watchers. Note also that in that case, you have to re-register any
		3245	signal watchers.
2956		3246
2957	=head3 Watcher-Specific Functions and Data Members	3247	=head3 Watcher-Specific Functions and Data Members
2958		3248
2959	=over 4	3249	=over 4
2960		3250
2961	=item ev_fork_init (ev_signal *, callback)	3251	=item ev_fork_init (ev_fork *, callback)
2962		3252
2963	Initialises and configures the fork watcher - it has no parameters of any	3253	Initialises and configures the fork watcher - it has no parameters of any
2964	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3254	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2965	believe me.	3255	really.
2966		3256
2967	=back	3257	=back
2968		3258
2969		3259
		3260	=head2 C<ev_cleanup> - even the best things end
		3261
		3262	Cleanup watchers are called just before the event loop is being destroyed
		3263	by a call to C<ev_loop_destroy>.
		3264
		3265	While there is no guarantee that the event loop gets destroyed, cleanup
		3266	watchers provide a convenient method to install cleanup hooks for your
		3267	program, worker threads and so on - you just to make sure to destroy the
		3268	loop when you want them to be invoked.
		3269
		3270	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3271	all other watchers, they do not keep a reference to the event loop (which
		3272	makes a lot of sense if you think about it). Like all other watchers, you
		3273	can call libev functions in the callback, except C<ev_cleanup_start>.
		3274
		3275	=head3 Watcher-Specific Functions and Data Members
		3276
		3277	=over 4
		3278
		3279	=item ev_cleanup_init (ev_cleanup *, callback)
		3280
		3281	Initialises and configures the cleanup watcher - it has no parameters of
		3282	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3283	pointless, I assure you.
		3284
		3285	=back
		3286
		3287	Example: Register an atexit handler to destroy the default loop, so any
		3288	cleanup functions are called.
		3289
		3290	static void
		3291	program_exits (void)
		3292	{
		3293	ev_loop_destroy (EV_DEFAULT_UC);
		3294	}
		3295
		3296	...
		3297	atexit (program_exits);
		3298
		3299
2970	=head2 C<ev_async> - how to wake up another event loop	3300	=head2 C<ev_async> - how to wake up an event loop
2971		3301
2972	In general, you cannot use an C<ev_loop> from multiple threads or other	3302	In general, you cannot use an C<ev_loop> from multiple threads or other
2973	asynchronous sources such as signal handlers (as opposed to multiple event	3303	asynchronous sources such as signal handlers (as opposed to multiple event
2974	loops - those are of course safe to use in different threads).	3304	loops - those are of course safe to use in different threads).
2975		3305
2976	Sometimes, however, you need to wake up another event loop you do not	3306	Sometimes, however, you need to wake up an event loop you do not control,
2977	control, for example because it belongs to another thread. This is what	3307	for example because it belongs to another thread. This is what C<ev_async>
2978	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3308	watchers do: as long as the C<ev_async> watcher is active, you can signal
2979	can signal it by calling C<ev_async_send>, which is thread- and signal	3309	it by calling C<ev_async_send>, which is thread- and signal safe.
2980	safe.
2981		3310
2982	This functionality is very similar to C<ev_signal> watchers, as signals,	3311	This functionality is very similar to C<ev_signal> watchers, as signals,
2983	too, are asynchronous in nature, and signals, too, will be compressed	3312	too, are asynchronous in nature, and signals, too, will be compressed
2984	(i.e. the number of callback invocations may be less than the number of	3313	(i.e. the number of callback invocations may be less than the number of
2985	C<ev_async_sent> calls).	3314	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
2986		3315	of "global async watchers" by using a watcher on an otherwise unused
2987	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3316	signal, and C<ev_feed_signal> to signal this watcher from another thread,
2988	just the default loop.	3317	even without knowing which loop owns the signal.
2989		3318
2990	=head3 Queueing	3319	=head3 Queueing
2991		3320
2992	C<ev_async> does not support queueing of data in any way. The reason	3321	C<ev_async> does not support queueing of data in any way. The reason
2993	is that the author does not know of a simple (or any) algorithm for a	3322	is that the author does not know of a simple (or any) algorithm for a
…		…
3085	trust me.	3414	trust me.
3086		3415
3087	=item ev_async_send (loop, ev_async *)	3416	=item ev_async_send (loop, ev_async *)
3088		3417
3089	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3418	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3090	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3419	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3420	returns.
		3421
3091	C<ev_feed_event>, this call is safe to do from other threads, signal or	3422	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3092	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3423	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3093	section below on what exactly this means).	3424	embedding section below on what exactly this means).
3094		3425
3095	Note that, as with other watchers in libev, multiple events might get	3426	Note that, as with other watchers in libev, multiple events might get
3096	compressed into a single callback invocation (another way to look at this	3427	compressed into a single callback invocation (another way to look at
3097	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3428	this is that C<ev_async> watchers are level-triggered: they are set on
3098	reset when the event loop detects that).	3429	C<ev_async_send>, reset when the event loop detects that).
3099		3430
3100	This call incurs the overhead of a system call only once per event loop	3431	This call incurs the overhead of at most one extra system call per event
3101	iteration, so while the overhead might be noticeable, it doesn't apply to	3432	loop iteration, if the event loop is blocked, and no syscall at all if
3102	repeated calls to C<ev_async_send> for the same event loop.	3433	the event loop (or your program) is processing events. That means that
		3434	repeated calls are basically free (there is no need to avoid calls for
		3435	performance reasons) and that the overhead becomes smaller (typically
		3436	zero) under load.
3103		3437
3104	=item bool = ev_async_pending (ev_async *)	3438	=item bool = ev_async_pending (ev_async *)
3105		3439
3106	Returns a non-zero value when C<ev_async_send> has been called on the	3440	Returns a non-zero value when C<ev_async_send> has been called on the
3107	watcher but the event has not yet been processed (or even noted) by the	3441	watcher but the event has not yet been processed (or even noted) by the
…		…
3140		3474
3141	If C<timeout> is less than 0, then no timeout watcher will be	3475	If C<timeout> is less than 0, then no timeout watcher will be
3142	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3476	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
3143	repeat = 0) will be started. C<0> is a valid timeout.	3477	repeat = 0) will be started. C<0> is a valid timeout.
3144		3478
3145	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3479	The callback has the type C<void (*cb)(int revents, void *arg)> and is
3146	passed an C<revents> set like normal event callbacks (a combination of	3480	passed an C<revents> set like normal event callbacks (a combination of
3147	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3481	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
3148	value passed to C<ev_once>. Note that it is possible to receive I<both>	3482	value passed to C<ev_once>. Note that it is possible to receive I<both>
3149	a timeout and an io event at the same time - you probably should give io	3483	a timeout and an io event at the same time - you probably should give io
3150	events precedence.	3484	events precedence.
3151		3485
3152	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3486	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
3153		3487
3154	static void stdin_ready (int revents, void *arg)	3488	static void stdin_ready (int revents, void *arg)
3155	{	3489	{
3156	if (revents & EV_READ)	3490	if (revents & EV_READ)
3157	/* stdin might have data for us, joy! */;	3491	/* stdin might have data for us, joy! */;
3158	else if (revents & EV_TIMEOUT)	3492	else if (revents & EV_TIMER)
3159	/* doh, nothing entered */;	3493	/* doh, nothing entered */;
3160	}	3494	}
3161		3495
3162	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3496	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3163		3497
3164	=item ev_feed_fd_event (loop, int fd, int revents)	3498	=item ev_feed_fd_event (loop, int fd, int revents)
3165		3499
3166	Feed an event on the given fd, as if a file descriptor backend detected	3500	Feed an event on the given fd, as if a file descriptor backend detected
3167	the given events it.	3501	the given events.
3168		3502
3169	=item ev_feed_signal_event (loop, int signum)	3503	=item ev_feed_signal_event (loop, int signum)
3170		3504
3171	Feed an event as if the given signal occurred (C<loop> must be the default	3505	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3172	loop!).	3506	which is async-safe.
3173		3507
3174	=back	3508	=back
		3509
		3510
		3511	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3512
		3513	This section explains some common idioms that are not immediately
		3514	obvious. Note that examples are sprinkled over the whole manual, and this
		3515	section only contains stuff that wouldn't fit anywhere else.
		3516
		3517	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3518
		3519	Each watcher has, by default, a C<void *data> member that you can read
		3520	or modify at any time: libev will completely ignore it. This can be used
		3521	to associate arbitrary data with your watcher. If you need more data and
		3522	don't want to allocate memory separately and store a pointer to it in that
		3523	data member, you can also "subclass" the watcher type and provide your own
		3524	data:
		3525
		3526	struct my_io
		3527	{
		3528	ev_io io;
		3529	int otherfd;
		3530	void *somedata;
		3531	struct whatever *mostinteresting;
		3532	};
		3533
		3534	...
		3535	struct my_io w;
		3536	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3537
		3538	And since your callback will be called with a pointer to the watcher, you
		3539	can cast it back to your own type:
		3540
		3541	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3542	{
		3543	struct my_io *w = (struct my_io *)w_;
		3544	...
		3545	}
		3546
		3547	More interesting and less C-conformant ways of casting your callback
		3548	function type instead have been omitted.
		3549
		3550	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3551
		3552	Another common scenario is to use some data structure with multiple
		3553	embedded watchers, in effect creating your own watcher that combines
		3554	multiple libev event sources into one "super-watcher":
		3555
		3556	struct my_biggy
		3557	{
		3558	int some_data;
		3559	ev_timer t1;
		3560	ev_timer t2;
		3561	}
		3562
		3563	In this case getting the pointer to C<my_biggy> is a bit more
		3564	complicated: Either you store the address of your C<my_biggy> struct in
		3565	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3566	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3567	real programmers):
		3568
		3569	#include <stddef.h>
		3570
		3571	static void
		3572	t1_cb (EV_P_ ev_timer *w, int revents)
		3573	{
		3574	struct my_biggy big = (struct my_biggy *)
		3575	(((char *)w) - offsetof (struct my_biggy, t1));
		3576	}
		3577
		3578	static void
		3579	t2_cb (EV_P_ ev_timer *w, int revents)
		3580	{
		3581	struct my_biggy big = (struct my_biggy *)
		3582	(((char *)w) - offsetof (struct my_biggy, t2));
		3583	}
		3584
		3585	=head2 AVOIDING FINISHING BEFORE RETURNING
		3586
		3587	Often you have structures like this in event-based programs:
		3588
		3589	callback ()
		3590	{
		3591	free (request);
		3592	}
		3593
		3594	request = start_new_request (..., callback);
		3595
		3596	The intent is to start some "lengthy" operation. The C<request> could be
		3597	used to cancel the operation, or do other things with it.
		3598
		3599	It's not uncommon to have code paths in C<start_new_request> that
		3600	immediately invoke the callback, for example, to report errors. Or you add
		3601	some caching layer that finds that it can skip the lengthy aspects of the
		3602	operation and simply invoke the callback with the result.
		3603
		3604	The problem here is that this will happen I<before> C<start_new_request>
		3605	has returned, so C<request> is not set.
		3606
		3607	Even if you pass the request by some safer means to the callback, you
		3608	might want to do something to the request after starting it, such as
		3609	canceling it, which probably isn't working so well when the callback has
		3610	already been invoked.
		3611
		3612	A common way around all these issues is to make sure that
		3613	C<start_new_request> I<always> returns before the callback is invoked. If
		3614	C<start_new_request> immediately knows the result, it can artificially
		3615	delay invoking the callback by e.g. using a C<prepare> or C<idle> watcher
		3616	for example, or more sneakily, by reusing an existing (stopped) watcher
		3617	and pushing it into the pending queue:
		3618
		3619	ev_set_cb (watcher, callback);
		3620	ev_feed_event (EV_A_ watcher, 0);
		3621
		3622	This way, C<start_new_request> can safely return before the callback is
		3623	invoked, while not delaying callback invocation too much.
		3624
		3625	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3626
		3627	Often (especially in GUI toolkits) there are places where you have
		3628	I<modal> interaction, which is most easily implemented by recursively
		3629	invoking C<ev_run>.
		3630
		3631	This brings the problem of exiting - a callback might want to finish the
		3632	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3633	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3634	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3635	other combination: In these cases, C<ev_break> will not work alone.
		3636
		3637	The solution is to maintain "break this loop" variable for each C<ev_run>
		3638	invocation, and use a loop around C<ev_run> until the condition is
		3639	triggered, using C<EVRUN_ONCE>:
		3640
		3641	// main loop
		3642	int exit_main_loop = 0;
		3643
		3644	while (!exit_main_loop)
		3645	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3646
		3647	// in a modal watcher
		3648	int exit_nested_loop = 0;
		3649
		3650	while (!exit_nested_loop)
		3651	ev_run (EV_A_ EVRUN_ONCE);
		3652
		3653	To exit from any of these loops, just set the corresponding exit variable:
		3654
		3655	// exit modal loop
		3656	exit_nested_loop = 1;
		3657
		3658	// exit main program, after modal loop is finished
		3659	exit_main_loop = 1;
		3660
		3661	// exit both
		3662	exit_main_loop = exit_nested_loop = 1;
		3663
		3664	=head2 THREAD LOCKING EXAMPLE
		3665
		3666	Here is a fictitious example of how to run an event loop in a different
		3667	thread from where callbacks are being invoked and watchers are
		3668	created/added/removed.
		3669
		3670	For a real-world example, see the C<EV::Loop::Async> perl module,
		3671	which uses exactly this technique (which is suited for many high-level
		3672	languages).
		3673
		3674	The example uses a pthread mutex to protect the loop data, a condition
		3675	variable to wait for callback invocations, an async watcher to notify the
		3676	event loop thread and an unspecified mechanism to wake up the main thread.
		3677
		3678	First, you need to associate some data with the event loop:
		3679
		3680	typedef struct {
		3681	mutex_t lock; /* global loop lock */
		3682	ev_async async_w;
		3683	thread_t tid;
		3684	cond_t invoke_cv;
		3685	} userdata;
		3686
		3687	void prepare_loop (EV_P)
		3688	{
		3689	// for simplicity, we use a static userdata struct.
		3690	static userdata u;
		3691
		3692	ev_async_init (&u->async_w, async_cb);
		3693	ev_async_start (EV_A_ &u->async_w);
		3694
		3695	pthread_mutex_init (&u->lock, 0);
		3696	pthread_cond_init (&u->invoke_cv, 0);
		3697
		3698	// now associate this with the loop
		3699	ev_set_userdata (EV_A_ u);
		3700	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3701	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3702
		3703	// then create the thread running ev_run
		3704	pthread_create (&u->tid, 0, l_run, EV_A);
		3705	}
		3706
		3707	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3708	solely to wake up the event loop so it takes notice of any new watchers
		3709	that might have been added:
		3710
		3711	static void
		3712	async_cb (EV_P_ ev_async *w, int revents)
		3713	{
		3714	// just used for the side effects
		3715	}
		3716
		3717	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3718	protecting the loop data, respectively.
		3719
		3720	static void
		3721	l_release (EV_P)
		3722	{
		3723	userdata *u = ev_userdata (EV_A);
		3724	pthread_mutex_unlock (&u->lock);
		3725	}
		3726
		3727	static void
		3728	l_acquire (EV_P)
		3729	{
		3730	userdata *u = ev_userdata (EV_A);
		3731	pthread_mutex_lock (&u->lock);
		3732	}
		3733
		3734	The event loop thread first acquires the mutex, and then jumps straight
		3735	into C<ev_run>:
		3736
		3737	void *
		3738	l_run (void *thr_arg)
		3739	{
		3740	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3741
		3742	l_acquire (EV_A);
		3743	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3744	ev_run (EV_A_ 0);
		3745	l_release (EV_A);
		3746
		3747	return 0;
		3748	}
		3749
		3750	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3751	signal the main thread via some unspecified mechanism (signals? pipe
		3752	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3753	have been called (in a while loop because a) spurious wakeups are possible
		3754	and b) skipping inter-thread-communication when there are no pending
		3755	watchers is very beneficial):
		3756
		3757	static void
		3758	l_invoke (EV_P)
		3759	{
		3760	userdata *u = ev_userdata (EV_A);
		3761
		3762	while (ev_pending_count (EV_A))
		3763	{
		3764	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3765	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3766	}
		3767	}
		3768
		3769	Now, whenever the main thread gets told to invoke pending watchers, it
		3770	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3771	thread to continue:
		3772
		3773	static void
		3774	real_invoke_pending (EV_P)
		3775	{
		3776	userdata *u = ev_userdata (EV_A);
		3777
		3778	pthread_mutex_lock (&u->lock);
		3779	ev_invoke_pending (EV_A);
		3780	pthread_cond_signal (&u->invoke_cv);
		3781	pthread_mutex_unlock (&u->lock);
		3782	}
		3783
		3784	Whenever you want to start/stop a watcher or do other modifications to an
		3785	event loop, you will now have to lock:
		3786
		3787	ev_timer timeout_watcher;
		3788	userdata *u = ev_userdata (EV_A);
		3789
		3790	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3791
		3792	pthread_mutex_lock (&u->lock);
		3793	ev_timer_start (EV_A_ &timeout_watcher);
		3794	ev_async_send (EV_A_ &u->async_w);
		3795	pthread_mutex_unlock (&u->lock);
		3796
		3797	Note that sending the C<ev_async> watcher is required because otherwise
		3798	an event loop currently blocking in the kernel will have no knowledge
		3799	about the newly added timer. By waking up the loop it will pick up any new
		3800	watchers in the next event loop iteration.
		3801
		3802	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3803
		3804	While the overhead of a callback that e.g. schedules a thread is small, it
		3805	is still an overhead. If you embed libev, and your main usage is with some
		3806	kind of threads or coroutines, you might want to customise libev so that
		3807	doesn't need callbacks anymore.
		3808
		3809	Imagine you have coroutines that you can switch to using a function
		3810	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3811	and that due to some magic, the currently active coroutine is stored in a
		3812	global called C<current_coro>. Then you can build your own "wait for libev
		3813	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3814	the differing C<;> conventions):
		3815
		3816	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3817	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3818
		3819	That means instead of having a C callback function, you store the
		3820	coroutine to switch to in each watcher, and instead of having libev call
		3821	your callback, you instead have it switch to that coroutine.
		3822
		3823	A coroutine might now wait for an event with a function called
		3824	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3825	matter when, or whether the watcher is active or not when this function is
		3826	called):
		3827
		3828	void
		3829	wait_for_event (ev_watcher *w)
		3830	{
		3831	ev_cb_set (w) = current_coro;
		3832	switch_to (libev_coro);
		3833	}
		3834
		3835	That basically suspends the coroutine inside C<wait_for_event> and
		3836	continues the libev coroutine, which, when appropriate, switches back to
		3837	this or any other coroutine.
		3838
		3839	You can do similar tricks if you have, say, threads with an event queue -
		3840	instead of storing a coroutine, you store the queue object and instead of
		3841	switching to a coroutine, you push the watcher onto the queue and notify
		3842	any waiters.
		3843
		3844	To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two
		3845	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3846
		3847	// my_ev.h
		3848	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3849	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3850	#include "../libev/ev.h"
		3851
		3852	// my_ev.c
		3853	#define EV_H "my_ev.h"
		3854	#include "../libev/ev.c"
		3855
		3856	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3857	F<my_ev.c> into your project. When properly specifying include paths, you
		3858	can even use F<ev.h> as header file name directly.
3175		3859
3176		3860
3177	=head1 LIBEVENT EMULATION	3861	=head1 LIBEVENT EMULATION
3178		3862
3179	Libev offers a compatibility emulation layer for libevent. It cannot	3863	Libev offers a compatibility emulation layer for libevent. It cannot
3180	emulate the internals of libevent, so here are some usage hints:	3864	emulate the internals of libevent, so here are some usage hints:
3181		3865
3182	=over 4	3866	=over 4
		3867
		3868	=item * Only the libevent-1.4.1-beta API is being emulated.
		3869
		3870	This was the newest libevent version available when libev was implemented,
		3871	and is still mostly unchanged in 2010.
3183		3872
3184	=item * Use it by including <event.h>, as usual.	3873	=item * Use it by including <event.h>, as usual.
3185		3874
3186	=item * The following members are fully supported: ev_base, ev_callback,	3875	=item * The following members are fully supported: ev_base, ev_callback,
3187	ev_arg, ev_fd, ev_res, ev_events.	3876	ev_arg, ev_fd, ev_res, ev_events.
…		…
3193	=item * Priorities are not currently supported. Initialising priorities	3882	=item * Priorities are not currently supported. Initialising priorities
3194	will fail and all watchers will have the same priority, even though there	3883	will fail and all watchers will have the same priority, even though there
3195	is an ev_pri field.	3884	is an ev_pri field.
3196		3885
3197	=item * In libevent, the last base created gets the signals, in libev, the	3886	=item * In libevent, the last base created gets the signals, in libev, the
3198	first base created (== the default loop) gets the signals.	3887	base that registered the signal gets the signals.
3199		3888
3200	=item * Other members are not supported.	3889	=item * Other members are not supported.
3201		3890
3202	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3891	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3203	to use the libev header file and library.	3892	to use the libev header file and library.
…		…
3222	Care has been taken to keep the overhead low. The only data member the C++	3911	Care has been taken to keep the overhead low. The only data member the C++
3223	classes add (compared to plain C-style watchers) is the event loop pointer	3912	classes add (compared to plain C-style watchers) is the event loop pointer
3224	that the watcher is associated with (or no additional members at all if	3913	that the watcher is associated with (or no additional members at all if
3225	you disable C<EV_MULTIPLICITY> when embedding libev).	3914	you disable C<EV_MULTIPLICITY> when embedding libev).
3226		3915
3227	Currently, functions, and static and non-static member functions can be	3916	Currently, functions, static and non-static member functions and classes
3228	used as callbacks. Other types should be easy to add as long as they only	3917	with C<operator ()> can be used as callbacks. Other types should be easy
3229	need one additional pointer for context. If you need support for other	3918	to add as long as they only need one additional pointer for context. If
3230	types of functors please contact the author (preferably after implementing	3919	you need support for other types of functors please contact the author
3231	it).	3920	(preferably after implementing it).
3232		3921
3233	Here is a list of things available in the C<ev> namespace:	3922	Here is a list of things available in the C<ev> namespace:
3234		3923
3235	=over 4	3924	=over 4
3236		3925
…		…
3246	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	3935	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3247		3936
3248	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	3937	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
3249	the same name in the C<ev> namespace, with the exception of C<ev_signal>	3938	the same name in the C<ev> namespace, with the exception of C<ev_signal>
3250	which is called C<ev::sig> to avoid clashes with the C<signal> macro	3939	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3251	defines by many implementations.	3940	defined by many implementations.
3252		3941
3253	All of those classes have these methods:	3942	All of those classes have these methods:
3254		3943
3255	=over 4	3944	=over 4
3256		3945
…		…
3297	myclass obj;	3986	myclass obj;
3298	ev::io iow;	3987	ev::io iow;
3299	iow.set <myclass, &myclass::io_cb> (&obj);	3988	iow.set <myclass, &myclass::io_cb> (&obj);
3300		3989
3301	=item w->set (object *)	3990	=item w->set (object *)
3302
3303	This is an B<experimental> feature that might go away in a future version.
3304		3991
3305	This is a variation of a method callback - leaving out the method to call	3992	This is a variation of a method callback - leaving out the method to call
3306	will default the method to C<operator ()>, which makes it possible to use	3993	will default the method to C<operator ()>, which makes it possible to use
3307	functor objects without having to manually specify the C<operator ()> all	3994	functor objects without having to manually specify the C<operator ()> all
3308	the time. Incidentally, you can then also leave out the template argument	3995	the time. Incidentally, you can then also leave out the template argument
…		…
3348	Associates a different C<struct ev_loop> with this watcher. You can only	4035	Associates a different C<struct ev_loop> with this watcher. You can only
3349	do this when the watcher is inactive (and not pending either).	4036	do this when the watcher is inactive (and not pending either).
3350		4037
3351	=item w->set ([arguments])	4038	=item w->set ([arguments])
3352		4039
3353	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	4040	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
3354	called at least once. Unlike the C counterpart, an active watcher gets	4041	method or a suitable start method must be called at least once. Unlike the
3355	automatically stopped and restarted when reconfiguring it with this	4042	C counterpart, an active watcher gets automatically stopped and restarted
3356	method.	4043	when reconfiguring it with this method.
3357		4044
3358	=item w->start ()	4045	=item w->start ()
3359		4046
3360	Starts the watcher. Note that there is no C<loop> argument, as the	4047	Starts the watcher. Note that there is no C<loop> argument, as the
3361	constructor already stores the event loop.	4048	constructor already stores the event loop.
3362		4049
		4050	=item w->start ([arguments])
		4051
		4052	Instead of calling C<set> and C<start> methods separately, it is often
		4053	convenient to wrap them in one call. Uses the same type of arguments as
		4054	the configure C<set> method of the watcher.
		4055
3363	=item w->stop ()	4056	=item w->stop ()
3364		4057
3365	Stops the watcher if it is active. Again, no C<loop> argument.	4058	Stops the watcher if it is active. Again, no C<loop> argument.
3366		4059
3367	=item w->again () (C<ev::timer>, C<ev::periodic> only)	4060	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3379		4072
3380	=back	4073	=back
3381		4074
3382	=back	4075	=back
3383		4076
3384	Example: Define a class with an IO and idle watcher, start one of them in	4077	Example: Define a class with two I/O and idle watchers, start the I/O
3385	the constructor.	4078	watchers in the constructor.
3386		4079
3387	class myclass	4080	class myclass
3388	{	4081	{
3389	ev::io io ; void io_cb (ev::io &w, int revents);	4082	ev::io io ; void io_cb (ev::io &w, int revents);
		4083	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3390	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4084	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3391		4085
3392	myclass (int fd)	4086	myclass (int fd)
3393	{	4087	{
3394	io .set <myclass, &myclass::io_cb > (this);	4088	io .set <myclass, &myclass::io_cb > (this);
		4089	io2 .set <myclass, &myclass::io2_cb > (this);
3395	idle.set <myclass, &myclass::idle_cb> (this);	4090	idle.set <myclass, &myclass::idle_cb> (this);
3396		4091
3397	io.start (fd, ev::READ);	4092	io.set (fd, ev::WRITE); // configure the watcher
		4093	io.start (); // start it whenever convenient
		4094
		4095	io2.start (fd, ev::READ); // set + start in one call
3398	}	4096	}
3399	};	4097	};
3400		4098
3401		4099
3402	=head1 OTHER LANGUAGE BINDINGS	4100	=head1 OTHER LANGUAGE BINDINGS
…		…
3441	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4139	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3442		4140
3443	=item D	4141	=item D
3444		4142
3445	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4143	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3446	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4144	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3447		4145
3448	=item Ocaml	4146	=item Ocaml
3449		4147
3450	Erkki Seppala has written Ocaml bindings for libev, to be found at	4148	Erkki Seppala has written Ocaml bindings for libev, to be found at
3451	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4149	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
3452		4150
3453	=item Lua	4151	=item Lua
3454		4152
3455	Brian Maher has written a partial interface to libev	4153	Brian Maher has written a partial interface to libev for lua (at the
3456	for lua (only C<ev_io> and C<ev_timer>), to be found at	4154	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
3457	L<http://github.com/brimworks/lua-ev>.	4155	L<http://github.com/brimworks/lua-ev>.
3458		4156
3459	=back	4157	=back
3460		4158
3461		4159
…		…
3476	loop argument"). The C<EV_A> form is used when this is the sole argument,	4174	loop argument"). The C<EV_A> form is used when this is the sole argument,
3477	C<EV_A_> is used when other arguments are following. Example:	4175	C<EV_A_> is used when other arguments are following. Example:
3478		4176
3479	ev_unref (EV_A);	4177	ev_unref (EV_A);
3480	ev_timer_add (EV_A_ watcher);	4178	ev_timer_add (EV_A_ watcher);
3481	ev_loop (EV_A_ 0);	4179	ev_run (EV_A_ 0);
3482		4180
3483	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4181	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3484	which is often provided by the following macro.	4182	which is often provided by the following macro.
3485		4183
3486	=item C<EV_P>, C<EV_P_>	4184	=item C<EV_P>, C<EV_P_>
…		…
3499	suitable for use with C<EV_A>.	4197	suitable for use with C<EV_A>.
3500		4198
3501	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4199	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3502		4200
3503	Similar to the other two macros, this gives you the value of the default	4201	Similar to the other two macros, this gives you the value of the default
3504	loop, if multiple loops are supported ("ev loop default").	4202	loop, if multiple loops are supported ("ev loop default"). The default loop
		4203	will be initialised if it isn't already initialised.
		4204
		4205	For non-multiplicity builds, these macros do nothing, so you always have
		4206	to initialise the loop somewhere.
3505		4207
3506	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4208	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3507		4209
3508	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4210	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3509	default loop has been initialised (C<UC> == unchecked). Their behaviour	4211	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3526	}	4228	}
3527		4229
3528	ev_check check;	4230	ev_check check;
3529	ev_check_init (&check, check_cb);	4231	ev_check_init (&check, check_cb);
3530	ev_check_start (EV_DEFAULT_ &check);	4232	ev_check_start (EV_DEFAULT_ &check);
3531	ev_loop (EV_DEFAULT_ 0);	4233	ev_run (EV_DEFAULT_ 0);
3532		4234
3533	=head1 EMBEDDING	4235	=head1 EMBEDDING
3534		4236
3535	Libev can (and often is) directly embedded into host	4237	Libev can (and often is) directly embedded into host
3536	applications. Examples of applications that embed it include the Deliantra	4238	applications. Examples of applications that embed it include the Deliantra
…		…
3616	libev.m4	4318	libev.m4
3617		4319
3618	=head2 PREPROCESSOR SYMBOLS/MACROS	4320	=head2 PREPROCESSOR SYMBOLS/MACROS
3619		4321
3620	Libev can be configured via a variety of preprocessor symbols you have to	4322	Libev can be configured via a variety of preprocessor symbols you have to
3621	define before including any of its files. The default in the absence of	4323	define before including (or compiling) any of its files. The default in
3622	autoconf is documented for every option.	4324	the absence of autoconf is documented for every option.
		4325
		4326	Symbols marked with "(h)" do not change the ABI, and can have different
		4327	values when compiling libev vs. including F<ev.h>, so it is permissible
		4328	to redefine them before including F<ev.h> without breaking compatibility
		4329	to a compiled library. All other symbols change the ABI, which means all
		4330	users of libev and the libev code itself must be compiled with compatible
		4331	settings.
3623		4332
3624	=over 4	4333	=over 4
3625		4334
		4335	=item EV_COMPAT3 (h)
		4336
		4337	Backwards compatibility is a major concern for libev. This is why this
		4338	release of libev comes with wrappers for the functions and symbols that
		4339	have been renamed between libev version 3 and 4.
		4340
		4341	You can disable these wrappers (to test compatibility with future
		4342	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4343	sources. This has the additional advantage that you can drop the C<struct>
		4344	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4345	typedef in that case.
		4346
		4347	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4348	and in some even more future version the compatibility code will be
		4349	removed completely.
		4350
3626	=item EV_STANDALONE	4351	=item EV_STANDALONE (h)
3627		4352
3628	Must always be C<1> if you do not use autoconf configuration, which	4353	Must always be C<1> if you do not use autoconf configuration, which
3629	keeps libev from including F<config.h>, and it also defines dummy	4354	keeps libev from including F<config.h>, and it also defines dummy
3630	implementations for some libevent functions (such as logging, which is not	4355	implementations for some libevent functions (such as logging, which is not
3631	supported). It will also not define any of the structs usually found in	4356	supported). It will also not define any of the structs usually found in
3632	F<event.h> that are not directly supported by the libev core alone.	4357	F<event.h> that are not directly supported by the libev core alone.
3633		4358
3634	In standalone mode, libev will still try to automatically deduce the	4359	In standalone mode, libev will still try to automatically deduce the
3635	configuration, but has to be more conservative.	4360	configuration, but has to be more conservative.
		4361
		4362	=item EV_USE_FLOOR
		4363
		4364	If defined to be C<1>, libev will use the C<floor ()> function for its
		4365	periodic reschedule calculations, otherwise libev will fall back on a
		4366	portable (slower) implementation. If you enable this, you usually have to
		4367	link against libm or something equivalent. Enabling this when the C<floor>
		4368	function is not available will fail, so the safe default is to not enable
		4369	this.
3636		4370
3637	=item EV_USE_MONOTONIC	4371	=item EV_USE_MONOTONIC
3638		4372
3639	If defined to be C<1>, libev will try to detect the availability of the	4373	If defined to be C<1>, libev will try to detect the availability of the
3640	monotonic clock option at both compile time and runtime. Otherwise no	4374	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3770	If defined to be C<1>, libev will compile in support for the Linux inotify	4504	If defined to be C<1>, libev will compile in support for the Linux inotify
3771	interface to speed up C<ev_stat> watchers. Its actual availability will	4505	interface to speed up C<ev_stat> watchers. Its actual availability will
3772	be detected at runtime. If undefined, it will be enabled if the headers	4506	be detected at runtime. If undefined, it will be enabled if the headers
3773	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4507	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3774		4508
		4509	=item EV_NO_SMP
		4510
		4511	If defined to be C<1>, libev will assume that memory is always coherent
		4512	between threads, that is, threads can be used, but threads never run on
		4513	different cpus (or different cpu cores). This reduces dependencies
		4514	and makes libev faster.
		4515
		4516	=item EV_NO_THREADS
		4517
		4518	If defined to be C<1>, libev will assume that it will never be called
		4519	from different threads, which is a stronger assumption than C<EV_NO_SMP>,
		4520	above. This reduces dependencies and makes libev faster.
		4521
3775	=item EV_ATOMIC_T	4522	=item EV_ATOMIC_T
3776		4523
3777	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4524	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3778	access is atomic with respect to other threads or signal contexts. No such	4525	access is atomic and serialised with respect to other threads or signal
3779	type is easily found in the C language, so you can provide your own type	4526	contexts. No such type is easily found in the C language, so you can
3780	that you know is safe for your purposes. It is used both for signal handler "locking"	4527	provide your own type that you know is safe for your purposes. It is used
3781	as well as for signal and thread safety in C<ev_async> watchers.	4528	both for signal handler "locking" as well as for signal and thread safety
		4529	in C<ev_async> watchers.
3782		4530
3783	In the absence of this define, libev will use C<sig_atomic_t volatile>	4531	In the absence of this define, libev will use C<sig_atomic_t volatile>
3784	(from F<signal.h>), which is usually good enough on most platforms.	4532	(from F<signal.h>), which is usually good enough on most platforms,
		4533	although strictly speaking using a type that also implies a memory fence
		4534	is required.
3785		4535
3786	=item EV_H	4536	=item EV_H (h)
3787		4537
3788	The name of the F<ev.h> header file used to include it. The default if	4538	The name of the F<ev.h> header file used to include it. The default if
3789	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4539	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3790	used to virtually rename the F<ev.h> header file in case of conflicts.	4540	used to virtually rename the F<ev.h> header file in case of conflicts.
3791		4541
3792	=item EV_CONFIG_H	4542	=item EV_CONFIG_H (h)
3793		4543
3794	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4544	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3795	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4545	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3796	C<EV_H>, above.	4546	C<EV_H>, above.
3797		4547
3798	=item EV_EVENT_H	4548	=item EV_EVENT_H (h)
3799		4549
3800	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4550	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3801	of how the F<event.h> header can be found, the default is C<"event.h">.	4551	of how the F<event.h> header can be found, the default is C<"event.h">.
3802		4552
3803	=item EV_PROTOTYPES	4553	=item EV_PROTOTYPES (h)
3804		4554
3805	If defined to be C<0>, then F<ev.h> will not define any function	4555	If defined to be C<0>, then F<ev.h> will not define any function
3806	prototypes, but still define all the structs and other symbols. This is	4556	prototypes, but still define all the structs and other symbols. This is
3807	occasionally useful if you want to provide your own wrapper functions	4557	occasionally useful if you want to provide your own wrapper functions
3808	around libev functions.	4558	around libev functions.
…		…
3813	will have the C<struct ev_loop *> as first argument, and you can create	4563	will have the C<struct ev_loop *> as first argument, and you can create
3814	additional independent event loops. Otherwise there will be no support	4564	additional independent event loops. Otherwise there will be no support
3815	for multiple event loops and there is no first event loop pointer	4565	for multiple event loops and there is no first event loop pointer
3816	argument. Instead, all functions act on the single default loop.	4566	argument. Instead, all functions act on the single default loop.
3817		4567
		4568	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4569	default loop when multiplicity is switched off - you always have to
		4570	initialise the loop manually in this case.
		4571
3818	=item EV_MINPRI	4572	=item EV_MINPRI
3819		4573
3820	=item EV_MAXPRI	4574	=item EV_MAXPRI
3821		4575
3822	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4576	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3830	fine.	4584	fine.
3831		4585
3832	If your embedding application does not need any priorities, defining these	4586	If your embedding application does not need any priorities, defining these
3833	both to C<0> will save some memory and CPU.	4587	both to C<0> will save some memory and CPU.
3834		4588
3835	=item EV_PERIODIC_ENABLE	4589	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4590	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4591	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3836		4592
3837	If undefined or defined to be C<1>, then periodic timers are supported. If	4593	If undefined or defined to be C<1> (and the platform supports it), then
3838	defined to be C<0>, then they are not. Disabling them saves a few kB of	4594	the respective watcher type is supported. If defined to be C<0>, then it
3839	code.	4595	is not. Disabling watcher types mainly saves code size.
3840		4596
3841	=item EV_IDLE_ENABLE	4597	=item EV_FEATURES
3842
3843	If undefined or defined to be C<1>, then idle watchers are supported. If
3844	defined to be C<0>, then they are not. Disabling them saves a few kB of
3845	code.
3846
3847	=item EV_EMBED_ENABLE
3848
3849	If undefined or defined to be C<1>, then embed watchers are supported. If
3850	defined to be C<0>, then they are not. Embed watchers rely on most other
3851	watcher types, which therefore must not be disabled.
3852
3853	=item EV_STAT_ENABLE
3854
3855	If undefined or defined to be C<1>, then stat watchers are supported. If
3856	defined to be C<0>, then they are not.
3857
3858	=item EV_FORK_ENABLE
3859
3860	If undefined or defined to be C<1>, then fork watchers are supported. If
3861	defined to be C<0>, then they are not.
3862
3863	=item EV_ASYNC_ENABLE
3864
3865	If undefined or defined to be C<1>, then async watchers are supported. If
3866	defined to be C<0>, then they are not.
3867
3868	=item EV_MINIMAL
3869		4598
3870	If you need to shave off some kilobytes of code at the expense of some	4599	If you need to shave off some kilobytes of code at the expense of some
3871	speed (but with the full API), define this symbol to C<1>. Currently this	4600	speed (but with the full API), you can define this symbol to request
3872	is used to override some inlining decisions, saves roughly 30% code size	4601	certain subsets of functionality. The default is to enable all features
3873	on amd64. It also selects a much smaller 2-heap for timer management over	4602	that can be enabled on the platform.
3874	the default 4-heap.
3875		4603
3876	You can save even more by disabling watcher types you do not need	4604	A typical way to use this symbol is to define it to C<0> (or to a bitset
3877	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>	4605	with some broad features you want) and then selectively re-enable
3878	(C<-DNDEBUG>) will usually reduce code size a lot.	4606	additional parts you want, for example if you want everything minimal,
		4607	but multiple event loop support, async and child watchers and the poll
		4608	backend, use this:
3879		4609
3880	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to	4610	#define EV_FEATURES 0
3881	provide a bare-bones event library. See C<ev.h> for details on what parts	4611	#define EV_MULTIPLICITY 1
3882	of the API are still available, and do not complain if this subset changes	4612	#define EV_USE_POLL 1
3883	over time.	4613	#define EV_CHILD_ENABLE 1
		4614	#define EV_ASYNC_ENABLE 1
		4615
		4616	The actual value is a bitset, it can be a combination of the following
		4617	values:
		4618
		4619	=over 4
		4620
		4621	=item C<1> - faster/larger code
		4622
		4623	Use larger code to speed up some operations.
		4624
		4625	Currently this is used to override some inlining decisions (enlarging the
		4626	code size by roughly 30% on amd64).
		4627
		4628	When optimising for size, use of compiler flags such as C<-Os> with
		4629	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4630	assertions.
		4631
		4632	=item C<2> - faster/larger data structures
		4633
		4634	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4635	hash table sizes and so on. This will usually further increase code size
		4636	and can additionally have an effect on the size of data structures at
		4637	runtime.
		4638
		4639	=item C<4> - full API configuration
		4640
		4641	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4642	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4643
		4644	=item C<8> - full API
		4645
		4646	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4647	details on which parts of the API are still available without this
		4648	feature, and do not complain if this subset changes over time.
		4649
		4650	=item C<16> - enable all optional watcher types
		4651
		4652	Enables all optional watcher types. If you want to selectively enable
		4653	only some watcher types other than I/O and timers (e.g. prepare,
		4654	embed, async, child...) you can enable them manually by defining
		4655	C<EV_watchertype_ENABLE> to C<1> instead.
		4656
		4657	=item C<32> - enable all backends
		4658
		4659	This enables all backends - without this feature, you need to enable at
		4660	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4661
		4662	=item C<64> - enable OS-specific "helper" APIs
		4663
		4664	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4665	default.
		4666
		4667	=back
		4668
		4669	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4670	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4671	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4672	watchers, timers and monotonic clock support.
		4673
		4674	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4675	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4676	your program might be left out as well - a binary starting a timer and an
		4677	I/O watcher then might come out at only 5Kb.
		4678
		4679	=item EV_API_STATIC
		4680
		4681	If this symbol is defined (by default it is not), then all identifiers
		4682	will have static linkage. This means that libev will not export any
		4683	identifiers, and you cannot link against libev anymore. This can be useful
		4684	when you embed libev, only want to use libev functions in a single file,
		4685	and do not want its identifiers to be visible.
		4686
		4687	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4688	wants to use libev.
		4689
		4690	This option only works when libev is compiled with a C compiler, as C++
		4691	doesn't support the required declaration syntax.
		4692
		4693	=item EV_AVOID_STDIO
		4694
		4695	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4696	functions (printf, scanf, perror etc.). This will increase the code size
		4697	somewhat, but if your program doesn't otherwise depend on stdio and your
		4698	libc allows it, this avoids linking in the stdio library which is quite
		4699	big.
		4700
		4701	Note that error messages might become less precise when this option is
		4702	enabled.
3884		4703
3885	=item EV_NSIG	4704	=item EV_NSIG
3886		4705
3887	The highest supported signal number, +1 (or, the number of	4706	The highest supported signal number, +1 (or, the number of
3888	signals): Normally, libev tries to deduce the maximum number of signals	4707	signals): Normally, libev tries to deduce the maximum number of signals
3889	automatically, but sometimes this fails, in which case it can be	4708	automatically, but sometimes this fails, in which case it can be
3890	specified. Also, using a lower number than detected (C<32> should be	4709	specified. Also, using a lower number than detected (C<32> should be
3891	good for about any system in existance) can save some memory, as libev	4710	good for about any system in existence) can save some memory, as libev
3892	statically allocates some 12-24 bytes per signal number.	4711	statically allocates some 12-24 bytes per signal number.
3893		4712
3894	=item EV_PID_HASHSIZE	4713	=item EV_PID_HASHSIZE
3895		4714
3896	C<ev_child> watchers use a small hash table to distribute workload by	4715	C<ev_child> watchers use a small hash table to distribute workload by
3897	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4716	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3898	than enough. If you need to manage thousands of children you might want to	4717	usually more than enough. If you need to manage thousands of children you
3899	increase this value (I<must> be a power of two).	4718	might want to increase this value (I<must> be a power of two).
3900		4719
3901	=item EV_INOTIFY_HASHSIZE	4720	=item EV_INOTIFY_HASHSIZE
3902		4721
3903	C<ev_stat> watchers use a small hash table to distribute workload by	4722	C<ev_stat> watchers use a small hash table to distribute workload by
3904	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4723	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3905	usually more than enough. If you need to manage thousands of C<ev_stat>	4724	disabled), usually more than enough. If you need to manage thousands of
3906	watchers you might want to increase this value (I<must> be a power of	4725	C<ev_stat> watchers you might want to increase this value (I<must> be a
3907	two).	4726	power of two).
3908		4727
3909	=item EV_USE_4HEAP	4728	=item EV_USE_4HEAP
3910		4729
3911	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4730	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3912	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4731	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3913	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4732	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3914	faster performance with many (thousands) of watchers.	4733	faster performance with many (thousands) of watchers.
3915		4734
3916	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4735	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3917	(disabled).	4736	will be C<0>.
3918		4737
3919	=item EV_HEAP_CACHE_AT	4738	=item EV_HEAP_CACHE_AT
3920		4739
3921	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4740	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3922	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4741	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3923	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4742	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3924	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4743	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3925	but avoids random read accesses on heap changes. This improves performance	4744	but avoids random read accesses on heap changes. This improves performance
3926	noticeably with many (hundreds) of watchers.	4745	noticeably with many (hundreds) of watchers.
3927		4746
3928	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4747	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3929	(disabled).	4748	will be C<0>.
3930		4749
3931	=item EV_VERIFY	4750	=item EV_VERIFY
3932		4751
3933	Controls how much internal verification (see C<ev_loop_verify ()>) will	4752	Controls how much internal verification (see C<ev_verify ()>) will
3934	be done: If set to C<0>, no internal verification code will be compiled	4753	be done: If set to C<0>, no internal verification code will be compiled
3935	in. If set to C<1>, then verification code will be compiled in, but not	4754	in. If set to C<1>, then verification code will be compiled in, but not
3936	called. If set to C<2>, then the internal verification code will be	4755	called. If set to C<2>, then the internal verification code will be
3937	called once per loop, which can slow down libev. If set to C<3>, then the	4756	called once per loop, which can slow down libev. If set to C<3>, then the
3938	verification code will be called very frequently, which will slow down	4757	verification code will be called very frequently, which will slow down
3939	libev considerably.	4758	libev considerably.
3940		4759
3941	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4760	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3942	C<0>.	4761	will be C<0>.
3943		4762
3944	=item EV_COMMON	4763	=item EV_COMMON
3945		4764
3946	By default, all watchers have a C<void *data> member. By redefining	4765	By default, all watchers have a C<void *data> member. By redefining
3947	this macro to a something else you can include more and other types of	4766	this macro to something else you can include more and other types of
3948	members. You have to define it each time you include one of the files,	4767	members. You have to define it each time you include one of the files,
3949	though, and it must be identical each time.	4768	though, and it must be identical each time.
3950		4769
3951	For example, the perl EV module uses something like this:	4770	For example, the perl EV module uses something like this:
3952		4771
…		…
4005	file.	4824	file.
4006		4825
4007	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4826	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
4008	that everybody includes and which overrides some configure choices:	4827	that everybody includes and which overrides some configure choices:
4009		4828
4010	#define EV_MINIMAL 1	4829	#define EV_FEATURES 8
4011	#define EV_USE_POLL 0	4830	#define EV_USE_SELECT 1
4012	#define EV_MULTIPLICITY 0
4013	#define EV_PERIODIC_ENABLE 0	4831	#define EV_PREPARE_ENABLE 1
		4832	#define EV_IDLE_ENABLE 1
4014	#define EV_STAT_ENABLE 0	4833	#define EV_SIGNAL_ENABLE 1
4015	#define EV_FORK_ENABLE 0	4834	#define EV_CHILD_ENABLE 1
		4835	#define EV_USE_STDEXCEPT 0
4016	#define EV_CONFIG_H <config.h>	4836	#define EV_CONFIG_H <config.h>
4017	#define EV_MINPRI 0
4018	#define EV_MAXPRI 0
4019		4837
4020	#include "ev++.h"	4838	#include "ev++.h"
4021		4839
4022	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4840	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4023		4841
4024	#include "ev_cpp.h"	4842	#include "ev_cpp.h"
4025	#include "ev.c"	4843	#include "ev.c"
4026		4844
4027	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4845	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4028		4846
4029	=head2 THREADS AND COROUTINES	4847	=head2 THREADS AND COROUTINES
4030		4848
4031	=head3 THREADS	4849	=head3 THREADS
4032		4850
…		…
4083	default loop and triggering an C<ev_async> watcher from the default loop	4901	default loop and triggering an C<ev_async> watcher from the default loop
4084	watcher callback into the event loop interested in the signal.	4902	watcher callback into the event loop interested in the signal.
4085		4903
4086	=back	4904	=back
4087		4905
4088	=head4 THREAD LOCKING EXAMPLE	4906	See also L<THREAD LOCKING EXAMPLE>.
4089
4090	Here is a fictitious example of how to run an event loop in a different
4091	thread than where callbacks are being invoked and watchers are
4092	created/added/removed.
4093
4094	For a real-world example, see the C<EV::Loop::Async> perl module,
4095	which uses exactly this technique (which is suited for many high-level
4096	languages).
4097
4098	The example uses a pthread mutex to protect the loop data, a condition
4099	variable to wait for callback invocations, an async watcher to notify the
4100	event loop thread and an unspecified mechanism to wake up the main thread.
4101
4102	First, you need to associate some data with the event loop:
4103
4104	typedef struct {
4105	mutex_t lock; /* global loop lock */
4106	ev_async async_w;
4107	thread_t tid;
4108	cond_t invoke_cv;
4109	} userdata;
4110
4111	void prepare_loop (EV_P)
4112	{
4113	// for simplicity, we use a static userdata struct.
4114	static userdata u;
4115
4116	ev_async_init (&u->async_w, async_cb);
4117	ev_async_start (EV_A_ &u->async_w);
4118
4119	pthread_mutex_init (&u->lock, 0);
4120	pthread_cond_init (&u->invoke_cv, 0);
4121
4122	// now associate this with the loop
4123	ev_set_userdata (EV_A_ u);
4124	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4125	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4126
4127	// then create the thread running ev_loop
4128	pthread_create (&u->tid, 0, l_run, EV_A);
4129	}
4130
4131	The callback for the C<ev_async> watcher does nothing: the watcher is used
4132	solely to wake up the event loop so it takes notice of any new watchers
4133	that might have been added:
4134
4135	static void
4136	async_cb (EV_P_ ev_async *w, int revents)
4137	{
4138	// just used for the side effects
4139	}
4140
4141	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4142	protecting the loop data, respectively.
4143
4144	static void
4145	l_release (EV_P)
4146	{
4147	userdata *u = ev_userdata (EV_A);
4148	pthread_mutex_unlock (&u->lock);
4149	}
4150
4151	static void
4152	l_acquire (EV_P)
4153	{
4154	userdata *u = ev_userdata (EV_A);
4155	pthread_mutex_lock (&u->lock);
4156	}
4157
4158	The event loop thread first acquires the mutex, and then jumps straight
4159	into C<ev_loop>:
4160
4161	void *
4162	l_run (void *thr_arg)
4163	{
4164	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4165
4166	l_acquire (EV_A);
4167	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4168	ev_loop (EV_A_ 0);
4169	l_release (EV_A);
4170
4171	return 0;
4172	}
4173
4174	Instead of invoking all pending watchers, the C<l_invoke> callback will
4175	signal the main thread via some unspecified mechanism (signals? pipe
4176	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4177	have been called (in a while loop because a) spurious wakeups are possible
4178	and b) skipping inter-thread-communication when there are no pending
4179	watchers is very beneficial):
4180
4181	static void
4182	l_invoke (EV_P)
4183	{
4184	userdata *u = ev_userdata (EV_A);
4185
4186	while (ev_pending_count (EV_A))
4187	{
4188	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4189	pthread_cond_wait (&u->invoke_cv, &u->lock);
4190	}
4191	}
4192
4193	Now, whenever the main thread gets told to invoke pending watchers, it
4194	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4195	thread to continue:
4196
4197	static void
4198	real_invoke_pending (EV_P)
4199	{
4200	userdata *u = ev_userdata (EV_A);
4201
4202	pthread_mutex_lock (&u->lock);
4203	ev_invoke_pending (EV_A);
4204	pthread_cond_signal (&u->invoke_cv);
4205	pthread_mutex_unlock (&u->lock);
4206	}
4207
4208	Whenever you want to start/stop a watcher or do other modifications to an
4209	event loop, you will now have to lock:
4210
4211	ev_timer timeout_watcher;
4212	userdata *u = ev_userdata (EV_A);
4213
4214	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4215
4216	pthread_mutex_lock (&u->lock);
4217	ev_timer_start (EV_A_ &timeout_watcher);
4218	ev_async_send (EV_A_ &u->async_w);
4219	pthread_mutex_unlock (&u->lock);
4220
4221	Note that sending the C<ev_async> watcher is required because otherwise
4222	an event loop currently blocking in the kernel will have no knowledge
4223	about the newly added timer. By waking up the loop it will pick up any new
4224	watchers in the next event loop iteration.
4225		4907
4226	=head3 COROUTINES	4908	=head3 COROUTINES
4227		4909
4228	Libev is very accommodating to coroutines ("cooperative threads"):	4910	Libev is very accommodating to coroutines ("cooperative threads"):
4229	libev fully supports nesting calls to its functions from different	4911	libev fully supports nesting calls to its functions from different
4230	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4912	coroutines (e.g. you can call C<ev_run> on the same loop from two
4231	different coroutines, and switch freely between both coroutines running	4913	different coroutines, and switch freely between both coroutines running
4232	the loop, as long as you don't confuse yourself). The only exception is	4914	the loop, as long as you don't confuse yourself). The only exception is
4233	that you must not do this from C<ev_periodic> reschedule callbacks.	4915	that you must not do this from C<ev_periodic> reschedule callbacks.
4234		4916
4235	Care has been taken to ensure that libev does not keep local state inside	4917	Care has been taken to ensure that libev does not keep local state inside
4236	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4918	C<ev_run>, and other calls do not usually allow for coroutine switches as
4237	they do not call any callbacks.	4919	they do not call any callbacks.
4238		4920
4239	=head2 COMPILER WARNINGS	4921	=head2 COMPILER WARNINGS
4240		4922
4241	Depending on your compiler and compiler settings, you might get no or a	4923	Depending on your compiler and compiler settings, you might get no or a
…		…
4252	maintainable.	4934	maintainable.
4253		4935
4254	And of course, some compiler warnings are just plain stupid, or simply	4936	And of course, some compiler warnings are just plain stupid, or simply
4255	wrong (because they don't actually warn about the condition their message	4937	wrong (because they don't actually warn about the condition their message
4256	seems to warn about). For example, certain older gcc versions had some	4938	seems to warn about). For example, certain older gcc versions had some
4257	warnings that resulted an extreme number of false positives. These have	4939	warnings that resulted in an extreme number of false positives. These have
4258	been fixed, but some people still insist on making code warn-free with	4940	been fixed, but some people still insist on making code warn-free with
4259	such buggy versions.	4941	such buggy versions.
4260		4942
4261	While libev is written to generate as few warnings as possible,	4943	While libev is written to generate as few warnings as possible,
4262	"warn-free" code is not a goal, and it is recommended not to build libev	4944	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
4298	I suggest using suppression lists.	4980	I suggest using suppression lists.
4299		4981
4300		4982
4301	=head1 PORTABILITY NOTES	4983	=head1 PORTABILITY NOTES
4302		4984
		4985	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4986
		4987	GNU/Linux is the only common platform that supports 64 bit file/large file
		4988	interfaces but I<disables> them by default.
		4989
		4990	That means that libev compiled in the default environment doesn't support
		4991	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4992
		4993	Unfortunately, many programs try to work around this GNU/Linux issue
		4994	by enabling the large file API, which makes them incompatible with the
		4995	standard libev compiled for their system.
		4996
		4997	Likewise, libev cannot enable the large file API itself as this would
		4998	suddenly make it incompatible to the default compile time environment,
		4999	i.e. all programs not using special compile switches.
		5000
		5001	=head2 OS/X AND DARWIN BUGS
		5002
		5003	The whole thing is a bug if you ask me - basically any system interface
		5004	you touch is broken, whether it is locales, poll, kqueue or even the
		5005	OpenGL drivers.
		5006
		5007	=head3 C<kqueue> is buggy
		5008
		5009	The kqueue syscall is broken in all known versions - most versions support
		5010	only sockets, many support pipes.
		5011
		5012	Libev tries to work around this by not using C<kqueue> by default on this
		5013	rotten platform, but of course you can still ask for it when creating a
		5014	loop - embedding a socket-only kqueue loop into a select-based one is
		5015	probably going to work well.
		5016
		5017	=head3 C<poll> is buggy
		5018
		5019	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		5020	implementation by something calling C<kqueue> internally around the 10.5.6
		5021	release, so now C<kqueue> I<and> C<poll> are broken.
		5022
		5023	Libev tries to work around this by not using C<poll> by default on
		5024	this rotten platform, but of course you can still ask for it when creating
		5025	a loop.
		5026
		5027	=head3 C<select> is buggy
		5028
		5029	All that's left is C<select>, and of course Apple found a way to fuck this
		5030	one up as well: On OS/X, C<select> actively limits the number of file
		5031	descriptors you can pass in to 1024 - your program suddenly crashes when
		5032	you use more.
		5033
		5034	There is an undocumented "workaround" for this - defining
		5035	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		5036	work on OS/X.
		5037
		5038	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		5039
		5040	=head3 C<errno> reentrancy
		5041
		5042	The default compile environment on Solaris is unfortunately so
		5043	thread-unsafe that you can't even use components/libraries compiled
		5044	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		5045	defined by default. A valid, if stupid, implementation choice.
		5046
		5047	If you want to use libev in threaded environments you have to make sure
		5048	it's compiled with C<_REENTRANT> defined.
		5049
		5050	=head3 Event port backend
		5051
		5052	The scalable event interface for Solaris is called "event
		5053	ports". Unfortunately, this mechanism is very buggy in all major
		5054	releases. If you run into high CPU usage, your program freezes or you get
		5055	a large number of spurious wakeups, make sure you have all the relevant
		5056	and latest kernel patches applied. No, I don't know which ones, but there
		5057	are multiple ones to apply, and afterwards, event ports actually work
		5058	great.
		5059
		5060	If you can't get it to work, you can try running the program by setting
		5061	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		5062	C<select> backends.
		5063
		5064	=head2 AIX POLL BUG
		5065
		5066	AIX unfortunately has a broken C<poll.h> header. Libev works around
		5067	this by trying to avoid the poll backend altogether (i.e. it's not even
		5068	compiled in), which normally isn't a big problem as C<select> works fine
		5069	with large bitsets on AIX, and AIX is dead anyway.
		5070
4303	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5071	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		5072
		5073	=head3 General issues
4304		5074
4305	Win32 doesn't support any of the standards (e.g. POSIX) that libev	5075	Win32 doesn't support any of the standards (e.g. POSIX) that libev
4306	requires, and its I/O model is fundamentally incompatible with the POSIX	5076	requires, and its I/O model is fundamentally incompatible with the POSIX
4307	model. Libev still offers limited functionality on this platform in	5077	model. Libev still offers limited functionality on this platform in
4308	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5078	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4309	descriptors. This only applies when using Win32 natively, not when using	5079	descriptors. This only applies when using Win32 natively, not when using
4310	e.g. cygwin.	5080	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		5081	as every compiler comes with a slightly differently broken/incompatible
		5082	environment.
4311		5083
4312	Lifting these limitations would basically require the full	5084	Lifting these limitations would basically require the full
4313	re-implementation of the I/O system. If you are into these kinds of	5085	re-implementation of the I/O system. If you are into this kind of thing,
4314	things, then note that glib does exactly that for you in a very portable	5086	then note that glib does exactly that for you in a very portable way (note
4315	way (note also that glib is the slowest event library known to man).	5087	also that glib is the slowest event library known to man).
4316		5088
4317	There is no supported compilation method available on windows except	5089	There is no supported compilation method available on windows except
4318	embedding it into other applications.	5090	embedding it into other applications.
4319		5091
4320	Sensible signal handling is officially unsupported by Microsoft - libev	5092	Sensible signal handling is officially unsupported by Microsoft - libev
…		…
4348	you do I<not> compile the F<ev.c> or any other embedded source files!):	5120	you do I<not> compile the F<ev.c> or any other embedded source files!):
4349		5121
4350	#include "evwrap.h"	5122	#include "evwrap.h"
4351	#include "ev.c"	5123	#include "ev.c"
4352		5124
4353	=over 4
4354
4355	=item The winsocket select function	5125	=head3 The winsocket C<select> function
4356		5126
4357	The winsocket C<select> function doesn't follow POSIX in that it	5127	The winsocket C<select> function doesn't follow POSIX in that it
4358	requires socket I<handles> and not socket I<file descriptors> (it is	5128	requires socket I<handles> and not socket I<file descriptors> (it is
4359	also extremely buggy). This makes select very inefficient, and also	5129	also extremely buggy). This makes select very inefficient, and also
4360	requires a mapping from file descriptors to socket handles (the Microsoft	5130	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
4369	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	5139	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
4370		5140
4371	Note that winsockets handling of fd sets is O(n), so you can easily get a	5141	Note that winsockets handling of fd sets is O(n), so you can easily get a
4372	complexity in the O(n²) range when using win32.	5142	complexity in the O(n²) range when using win32.
4373		5143
4374	=item Limited number of file descriptors	5144	=head3 Limited number of file descriptors
4375		5145
4376	Windows has numerous arbitrary (and low) limits on things.	5146	Windows has numerous arbitrary (and low) limits on things.
4377		5147
4378	Early versions of winsocket's select only supported waiting for a maximum	5148	Early versions of winsocket's select only supported waiting for a maximum
4379	of C<64> handles (probably owning to the fact that all windows kernels	5149	of C<64> handles (probably owning to the fact that all windows kernels
…		…
4394	runtime libraries. This might get you to about C<512> or C<2048> sockets	5164	runtime libraries. This might get you to about C<512> or C<2048> sockets
4395	(depending on windows version and/or the phase of the moon). To get more,	5165	(depending on windows version and/or the phase of the moon). To get more,
4396	you need to wrap all I/O functions and provide your own fd management, but	5166	you need to wrap all I/O functions and provide your own fd management, but
4397	the cost of calling select (O(n²)) will likely make this unworkable.	5167	the cost of calling select (O(n²)) will likely make this unworkable.
4398		5168
4399	=back
4400
4401	=head2 PORTABILITY REQUIREMENTS	5169	=head2 PORTABILITY REQUIREMENTS
4402		5170
4403	In addition to a working ISO-C implementation and of course the	5171	In addition to a working ISO-C implementation and of course the
4404	backend-specific APIs, libev relies on a few additional extensions:	5172	backend-specific APIs, libev relies on a few additional extensions:
4405		5173
…		…
4411	Libev assumes not only that all watcher pointers have the same internal	5179	Libev assumes not only that all watcher pointers have the same internal
4412	structure (guaranteed by POSIX but not by ISO C for example), but it also	5180	structure (guaranteed by POSIX but not by ISO C for example), but it also
4413	assumes that the same (machine) code can be used to call any watcher	5181	assumes that the same (machine) code can be used to call any watcher
4414	callback: The watcher callbacks have different type signatures, but libev	5182	callback: The watcher callbacks have different type signatures, but libev
4415	calls them using an C<ev_watcher *> internally.	5183	calls them using an C<ev_watcher *> internally.
		5184
		5185	=item pointer accesses must be thread-atomic
		5186
		5187	Accessing a pointer value must be atomic, it must both be readable and
		5188	writable in one piece - this is the case on all current architectures.
4416		5189
4417	=item C<sig_atomic_t volatile> must be thread-atomic as well	5190	=item C<sig_atomic_t volatile> must be thread-atomic as well
4418		5191
4419	The type C<sig_atomic_t volatile> (or whatever is defined as	5192	The type C<sig_atomic_t volatile> (or whatever is defined as
4420	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5193	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
4443	watchers.	5216	watchers.
4444		5217
4445	=item C<double> must hold a time value in seconds with enough accuracy	5218	=item C<double> must hold a time value in seconds with enough accuracy
4446		5219
4447	The type C<double> is used to represent timestamps. It is required to	5220	The type C<double> is used to represent timestamps. It is required to
4448	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5221	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4449	enough for at least into the year 4000. This requirement is fulfilled by	5222	good enough for at least into the year 4000 with millisecond accuracy
		5223	(the design goal for libev). This requirement is overfulfilled by
4450	implementations implementing IEEE 754, which is basically all existing	5224	implementations using IEEE 754, which is basically all existing ones.
		5225
4451	ones. With IEEE 754 doubles, you get microsecond accuracy until at least	5226	With IEEE 754 doubles, you get microsecond accuracy until at least the
4452	2200.	5227	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5228	is either obsolete or somebody patched it to use C<long double> or
		5229	something like that, just kidding).
4453		5230
4454	=back	5231	=back
4455		5232
4456	If you know of other additional requirements drop me a note.	5233	If you know of other additional requirements drop me a note.
4457		5234
…		…
4519	=item Processing ev_async_send: O(number_of_async_watchers)	5296	=item Processing ev_async_send: O(number_of_async_watchers)
4520		5297
4521	=item Processing signals: O(max_signal_number)	5298	=item Processing signals: O(max_signal_number)
4522		5299
4523	Sending involves a system call I<iff> there were no other C<ev_async_send>	5300	Sending involves a system call I<iff> there were no other C<ev_async_send>
4524	calls in the current loop iteration. Checking for async and signal events	5301	calls in the current loop iteration and the loop is currently
		5302	blocked. Checking for async and signal events involves iterating over all
4525	involves iterating over all running async watchers or all signal numbers.	5303	running async watchers or all signal numbers.
4526		5304
4527	=back	5305	=back
4528		5306
4529		5307
		5308	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5309
		5310	The major version 4 introduced some incompatible changes to the API.
		5311
		5312	At the moment, the C<ev.h> header file provides compatibility definitions
		5313	for all changes, so most programs should still compile. The compatibility
		5314	layer might be removed in later versions of libev, so better update to the
		5315	new API early than late.
		5316
		5317	=over 4
		5318
		5319	=item C<EV_COMPAT3> backwards compatibility mechanism
		5320
		5321	The backward compatibility mechanism can be controlled by
		5322	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5323	section.
		5324
		5325	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5326
		5327	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5328
		5329	ev_loop_destroy (EV_DEFAULT_UC);
		5330	ev_loop_fork (EV_DEFAULT);
		5331
		5332	=item function/symbol renames
		5333
		5334	A number of functions and symbols have been renamed:
		5335
		5336	ev_loop => ev_run
		5337	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5338	EVLOOP_ONESHOT => EVRUN_ONCE
		5339
		5340	ev_unloop => ev_break
		5341	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5342	EVUNLOOP_ONE => EVBREAK_ONE
		5343	EVUNLOOP_ALL => EVBREAK_ALL
		5344
		5345	EV_TIMEOUT => EV_TIMER
		5346
		5347	ev_loop_count => ev_iteration
		5348	ev_loop_depth => ev_depth
		5349	ev_loop_verify => ev_verify
		5350
		5351	Most functions working on C<struct ev_loop> objects don't have an
		5352	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5353	associated constants have been renamed to not collide with the C<struct
		5354	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5355	as all other watcher types. Note that C<ev_loop_fork> is still called
		5356	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5357	typedef.
		5358
		5359	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5360
		5361	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5362	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5363	and work, but the library code will of course be larger.
		5364
		5365	=back
		5366
		5367
4530	=head1 GLOSSARY	5368	=head1 GLOSSARY
4531		5369
4532	=over 4	5370	=over 4
4533		5371
4534	=item active	5372	=item active
4535		5373
4536	A watcher is active as long as it has been started (has been attached to	5374	A watcher is active as long as it has been started and not yet stopped.
4537	an event loop) but not yet stopped (disassociated from the event loop).	5375	See L<WATCHER STATES> for details.
4538		5376
4539	=item application	5377	=item application
4540		5378
4541	In this document, an application is whatever is using libev.	5379	In this document, an application is whatever is using libev.
		5380
		5381	=item backend
		5382
		5383	The part of the code dealing with the operating system interfaces.
4542		5384
4543	=item callback	5385	=item callback
4544		5386
4545	The address of a function that is called when some event has been	5387	The address of a function that is called when some event has been
4546	detected. Callbacks are being passed the event loop, the watcher that	5388	detected. Callbacks are being passed the event loop, the watcher that
4547	received the event, and the actual event bitset.	5389	received the event, and the actual event bitset.
4548		5390
4549	=item callback invocation	5391	=item callback/watcher invocation
4550		5392
4551	The act of calling the callback associated with a watcher.	5393	The act of calling the callback associated with a watcher.
4552		5394
4553	=item event	5395	=item event
4554		5396
4555	A change of state of some external event, such as data now being available	5397	A change of state of some external event, such as data now being available
4556	for reading on a file descriptor, time having passed or simply not having	5398	for reading on a file descriptor, time having passed or simply not having
4557	any other events happening anymore.	5399	any other events happening anymore.
4558		5400
4559	In libev, events are represented as single bits (such as C<EV_READ> or	5401	In libev, events are represented as single bits (such as C<EV_READ> or
4560	C<EV_TIMEOUT>).	5402	C<EV_TIMER>).
4561		5403
4562	=item event library	5404	=item event library
4563		5405
4564	A software package implementing an event model and loop.	5406	A software package implementing an event model and loop.
4565		5407
…		…
4573	The model used to describe how an event loop handles and processes	5415	The model used to describe how an event loop handles and processes
4574	watchers and events.	5416	watchers and events.
4575		5417
4576	=item pending	5418	=item pending
4577		5419
4578	A watcher is pending as soon as the corresponding event has been detected,	5420	A watcher is pending as soon as the corresponding event has been
4579	and stops being pending as soon as the watcher will be invoked or its	5421	detected. See L<WATCHER STATES> for details.
4580	pending status is explicitly cleared by the application.
4581
4582	A watcher can be pending, but not active. Stopping a watcher also clears
4583	its pending status.
4584		5422
4585	=item real time	5423	=item real time
4586		5424
4587	The physical time that is observed. It is apparently strictly monotonic :)	5425	The physical time that is observed. It is apparently strictly monotonic :)
4588		5426
4589	=item wall-clock time	5427	=item wall-clock time
4590		5428
4591	The time and date as shown on clocks. Unlike real time, it can actually	5429	The time and date as shown on clocks. Unlike real time, it can actually
4592	be wrong and jump forwards and backwards, e.g. when the you adjust your	5430	be wrong and jump forwards and backwards, e.g. when you adjust your
4593	clock.	5431	clock.
4594		5432
4595	=item watcher	5433	=item watcher
4596		5434
4597	A data structure that describes interest in certain events. Watchers need	5435	A data structure that describes interest in certain events. Watchers need
4598	to be started (attached to an event loop) before they can receive events.	5436	to be started (attached to an event loop) before they can receive events.
4599		5437
4600	=item watcher invocation
4601
4602	The act of calling the callback associated with a watcher.
4603
4604	=back	5438	=back
4605		5439
4606	=head1 AUTHOR	5440	=head1 AUTHOR
4607		5441
4608	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5442	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5443	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4609		5444

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