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…		…
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 it both faster and might make	434	delivers signals synchronously, which makes it both faster and might make
380	it possible to get the queued signal data. It can also simplify signal	435	it possible to get the queued signal data. It can also simplify signal
381	handling with threads, as long as you properly block signals in your	436	handling with threads, as long as you properly block signals in your
382	threads that are not interested in handling them.	437	threads that are not interested in handling them.
383		438
384	Signalfd will not be used by default as this changes your signal mask, and	439	Signalfd will not be used by default as this changes your signal mask, and
385	there are a lot of shoddy libraries and programs (glib's threadpool for	440	there are a lot of shoddy libraries and programs (glib's threadpool for
386	example) that can't properly initialise their signal masks.	441	example) that can't properly initialise their signal masks.
		442
		443	=item C<EVFLAG_NOSIGMASK>
		444
		445	When this flag is specified, then libev will avoid to modify the signal
		446	mask. Specifically, this means you have to make sure signals are unblocked
		447	when you want to receive them.
		448
		449	This behaviour is useful when you want to do your own signal handling, or
		450	want to handle signals only in specific threads and want to avoid libev
		451	unblocking the signals.
		452
		453	It's also required by POSIX in a threaded program, as libev calls
		454	C<sigprocmask>, whose behaviour is officially unspecified.
		455
		456	This flag's behaviour will become the default in future versions of libev.
387		457
388	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	458	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
389		459
390	This is your standard select(2) backend. Not I<completely> standard, as	460	This is your standard select(2) backend. Not I<completely> standard, as
391	libev tries to roll its own fd_set with no limits on the number of fds,	461	libev tries to roll its own fd_set with no limits on the number of fds,
…		…
419	=item C<EVBACKEND_EPOLL> (value 4, Linux)	489	=item C<EVBACKEND_EPOLL> (value 4, Linux)
420		490
421	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9	491	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
422	kernels).	492	kernels).
423		493
424	For few fds, this backend is a bit little slower than poll and select,	494	For few fds, this backend is a bit little slower than poll and select, but
425	but it scales phenomenally better. While poll and select usually scale	495	it scales phenomenally better. While poll and select usually scale like
426	like O(total_fds) where n is the total number of fds (or the highest fd),	496	O(total_fds) where total_fds is the total number of fds (or the highest
427	epoll scales either O(1) or O(active_fds).	497	fd), epoll scales either O(1) or O(active_fds).
428		498
429	The epoll mechanism deserves honorable mention as the most misdesigned	499	The epoll mechanism deserves honorable mention as the most misdesigned
430	of the more advanced event mechanisms: mere annoyances include silently	500	of the more advanced event mechanisms: mere annoyances include silently
431	dropping file descriptors, requiring a system call per change per file	501	dropping file descriptors, requiring a system call per change per file
432	descriptor (and unnecessary guessing of parameters), problems with dup and	502	descriptor (and unnecessary guessing of parameters), problems with dup,
		503	returning before the timeout value, resulting in additional iterations
		504	(and only giving 5ms accuracy while select on the same platform gives
433	so on. The biggest issue is fork races, however - if a program forks then	505	0.1ms) and so on. The biggest issue is fork races, however - if a program
434	I<both> parent and child process have to recreate the epoll set, which can	506	forks then I<both> parent and child process have to recreate the epoll
435	take considerable time (one syscall per file descriptor) and is of course	507	set, which can take considerable time (one syscall per file descriptor)
436	hard to detect.	508	and is of course hard to detect.
437		509
438	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	510	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
439	of course I<doesn't>, and epoll just loves to report events for totally	511	but of course I<doesn't>, and epoll just loves to report events for
440	I<different> file descriptors (even already closed ones, so one cannot	512	totally I<different> file descriptors (even already closed ones, so
441	even remove them from the set) than registered in the set (especially	513	one cannot even remove them from the set) than registered in the set
442	on SMP systems). Libev tries to counter these spurious notifications by	514	(especially on SMP systems). Libev tries to counter these spurious
443	employing an additional generation counter and comparing that against the	515	notifications by employing an additional generation counter and comparing
444	events to filter out spurious ones, recreating the set when required.	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...
445		526
446	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
447	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
448	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
449	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
…		…
515	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	596	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
516		597
517	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,
518	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)).
519		600
520	Please note that Solaris event ports can deliver a lot of spurious
521	notifications, so you need to use non-blocking I/O or other means to avoid
522	blocking when no data (or space) is available.
523
524	While this backend scales well, it requires one system call per active	601	While this backend scales well, it requires one system call per active
525	file descriptor per loop iteration. For small and medium numbers of file	602	file descriptor per loop iteration. For small and medium numbers of file
526	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	603	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
527	might perform better.	604	might perform better.
528		605
529	On the positive side, with the exception of the spurious readiness	606	On the positive side, this backend actually performed fully to
530	notifications, this backend actually performed fully to specification
531	in all tests and is fully embeddable, which is a rare feat among the	607	specification in all tests and is fully embeddable, which is a rare feat
532	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.
533		620
534	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
535	C<EVBACKEND_POLL>.	622	C<EVBACKEND_POLL>.
536		623
537	=item C<EVBACKEND_ALL>	624	=item C<EVBACKEND_ALL>
538		625
539	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
540	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
541	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	628	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
542		629
543	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).
544		639
545	=back	640	=back
546		641
547	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,
548	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
549	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
550	()> will be tried.	645	()> will be tried.
551		646
552	Example: This is the most typical usage.
553
554	if (!ev_default_loop (0))
555	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
556
557	Example: Restrict libev to the select and poll backends, and do not allow
558	environment settings to be taken into account:
559
560	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
561
562	Example: Use whatever libev has to offer, but make sure that kqueue is
563	used if available (warning, breaks stuff, best use only with your own
564	private event loop and only if you know the OS supports your types of
565	fds):
566
567	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
568
569	=item struct ev_loop *ev_loop_new (unsigned int flags)
570
571	Similar to C<ev_default_loop>, but always creates a new event loop that is
572	always distinct from the default loop. Unlike the default loop, it cannot
573	handle signal and child watchers, and attempts to do so will be greeted by
574	undefined behaviour (or a failed assertion if assertions are enabled).
575
576	Note that this function I<is> thread-safe, and the recommended way to use
577	libev with threads is indeed to create one loop per thread, and using the
578	default loop in the "main" or "initial" thread.
579
580	Example: Try to create a event loop that uses epoll and nothing else.	647	Example: Try to create a event loop that uses epoll and nothing else.
581		648
582	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	649	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
583	if (!epoller)	650	if (!epoller)
584	fatal ("no epoll found here, maybe it hides under your chair");	651	fatal ("no epoll found here, maybe it hides under your chair");
585		652
		653	Example: Use whatever libev has to offer, but make sure that kqueue is
		654	used if available.
		655
		656	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		657
586	=item ev_default_destroy ()	658	=item ev_loop_destroy (loop)
587		659
588	Destroys the default loop again (frees all memory and kernel state	660	Destroys an event loop object (frees all memory and kernel state
589	etc.). None of the active event watchers will be stopped in the normal	661	etc.). None of the active event watchers will be stopped in the normal
590	sense, so e.g. C<ev_is_active> might still return true. It is your	662	sense, so e.g. C<ev_is_active> might still return true. It is your
591	responsibility to either stop all watchers cleanly yourself I<before>	663	responsibility to either stop all watchers cleanly yourself I<before>
592	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
593	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
…		…
595		667
596	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
597	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
598	as signal and child watchers) would need to be stopped manually.	670	as signal and child watchers) would need to be stopped manually.
599		671
600	In general it is not advisable to call this function except in the	672	This function is normally used on loop objects allocated by
601	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.
602	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>
603	C<ev_loop_new> and C<ev_loop_destroy>.	679	and C<ev_loop_destroy>.
604		680
605	=item ev_loop_destroy (loop)	681	=item ev_loop_fork (loop)
606		682
607	Like C<ev_default_destroy>, but destroys an event loop created by an
608	earlier call to C<ev_loop_new>.
609
610	=item ev_default_fork ()
611
612	This function sets a flag that causes subsequent C<ev_loop> iterations	683	This function sets a flag that causes subsequent C<ev_run> iterations to
613	to reinitialise the kernel state for backends that have one. Despite the	684	reinitialise the kernel state for backends that have one. Despite the
614	name, you can call it anytime, but it makes most sense after forking, in	685	name, you can call it anytime, but it makes most sense after forking, in
615	the child process (or both child and parent, but that again makes little	686	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
616	sense). You I<must> call it in the child before using any of the libev	687	child before resuming or calling C<ev_run>.
617	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.
618		693
619	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
620	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
621	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).
622		700
623	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
624	it just in case after a fork. To make this easy, the function will fit in	702	it just in case after a fork.
625	quite nicely into a call to C<pthread_atfork>:
626		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	...
627	pthread_atfork (0, 0, ev_default_fork);	714	pthread_atfork (0, 0, post_fork_child);
628
629	=item ev_loop_fork (loop)
630
631	Like C<ev_default_fork>, but acts on an event loop created by
632	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
633	after fork that you want to re-use in the child, and how you do this is
634	entirely your own problem.
635		715
636	=item int ev_is_default_loop (loop)	716	=item int ev_is_default_loop (loop)
637		717
638	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
639	otherwise.	719	otherwise.
640		720
641	=item unsigned int ev_loop_count (loop)	721	=item unsigned int ev_iteration (loop)
642		722
643	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
644	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>
645	happily wraps around with enough iterations.	725	and happily wraps around with enough iterations.
646		726
647	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
648	"ticks" the number of loop iterations), as it roughly corresponds with	728	"ticks" the number of loop iterations), as it roughly corresponds with
649	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.
650		731
651	=item unsigned int ev_loop_depth (loop)	732	=item unsigned int ev_depth (loop)
652		733
653	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
654	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.
655		736
656	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
657	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),
658	in which case it is higher.	739	in which case it is higher.
659		740
660	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread	741	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
661	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.
662		745
663	=item unsigned int ev_backend (loop)	746	=item unsigned int ev_backend (loop)
664		747
665	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
666	use.	749	use.
…		…
675		758
676	=item ev_now_update (loop)	759	=item ev_now_update (loop)
677		760
678	Establishes the current time by querying the kernel, updating the time	761	Establishes the current time by querying the kernel, updating the time
679	returned by C<ev_now ()> in the progress. This is a costly operation and	762	returned by C<ev_now ()> in the progress. This is a costly operation and
680	is usually done automatically within C<ev_loop ()>.	763	is usually done automatically within C<ev_run ()>.
681		764
682	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
683	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
684	the current time is a good idea.	767	the current time is a good idea.
685		768
…		…
687		770
688	=item ev_suspend (loop)	771	=item ev_suspend (loop)
689		772
690	=item ev_resume (loop)	773	=item ev_resume (loop)
691		774
692	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
693	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.
694		777
695	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
696	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
697	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
698	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>
…		…
700	C<ev_resume> directly afterwards to resume timer processing.	783	C<ev_resume> directly afterwards to resume timer processing.
701		784
702	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
703	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
704	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
705	occured while suspended).	788	occurred while suspended).
706		789
707	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
708	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>
709	without a previous call to C<ev_suspend>.	792	without a previous call to C<ev_suspend>.
710		793
711	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
712	event loop time (see C<ev_now_update>).	795	event loop time (see C<ev_now_update>).
713		796
714	=item ev_loop (loop, int flags)	797	=item ev_run (loop, int flags)
715		798
716	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
717	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
718	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>.
719		804
720	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
721	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.
722		808
723	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
724	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
725	finished (especially in interactive programs), but having a program	811	finished (especially in interactive programs), but having a program
726	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
727	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
728	beauty.	814	beauty.
729		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
730	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
731	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
732	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
733	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.
734		826
735	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
736	necessary) and will handle those and any already outstanding ones. It	828	necessary) and will handle those and any already outstanding ones. It
737	will block your process until at least one new event arrives (which could	829	will block your process until at least one new event arrives (which could
738	be an event internal to libev itself, so there is no guarantee that a	830	be an event internal to libev itself, so there is no guarantee that a
739	user-registered callback will be called), and will return after one	831	user-registered callback will be called), and will return after one
740	iteration of the loop.	832	iteration of the loop.
741		833
742	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
743	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
744	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
745	usually a better approach for this kind of thing.	837	usually a better approach for this kind of thing.
746		838
747	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):
748		842
		843	- Increment loop depth.
		844	- Reset the ev_break status.
749	- Before the first iteration, call any pending watchers.	845	- Before the first iteration, call any pending watchers.
		846	LOOP:
750	* If EVFLAG_FORKCHECK was used, check for a fork.	847	- If EVFLAG_FORKCHECK was used, check for a fork.
751	- 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.
752	- Queue and call all prepare watchers.	849	- Queue and call all prepare watchers.
		850	- If ev_break was called, goto FINISH.
753	- If we have been forked, detach and recreate the kernel state	851	- If we have been forked, detach and recreate the kernel state
754	as to not disturb the other process.	852	as to not disturb the other process.
755	- Update the kernel state with all outstanding changes.	853	- Update the kernel state with all outstanding changes.
756	- Update the "event loop time" (ev_now ()).	854	- Update the "event loop time" (ev_now ()).
757	- Calculate for how long to sleep or block, if at all	855	- Calculate for how long to sleep or block, if at all
758	(active idle watchers, EVLOOP_NONBLOCK or not having	856	(active idle watchers, EVRUN_NOWAIT or not having
759	any active watchers at all will result in not sleeping).	857	any active watchers at all will result in not sleeping).
760	- 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.
761	- Block the process, waiting for any events.	860	- Block the process, waiting for any events.
762	- Queue all outstanding I/O (fd) events.	861	- Queue all outstanding I/O (fd) events.
763	- 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.
764	- Queue all expired timers.	863	- Queue all expired timers.
765	- Queue all expired periodics.	864	- Queue all expired periodics.
766	- Unless any events are pending now, queue all idle watchers.	865	- Queue all idle watchers with priority higher than that of pending events.
767	- Queue all check watchers.	866	- Queue all check watchers.
768	- 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).
769	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
770	be handled here by queueing them when their watcher gets executed.	869	be handled here by queueing them when their watcher gets executed.
771	- 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
772	were used, or there are no active watchers, return, otherwise	871	were used, or there are no active watchers, goto FINISH, otherwise
773	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.
774		877
775	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
776	anymore.	879	anymore.
777		880
778	... queue jobs here, make sure they register event watchers as long	881	... queue jobs here, make sure they register event watchers as long
779	... as they still have work to do (even an idle watcher will do..)	882	... as they still have work to do (even an idle watcher will do..)
780	ev_loop (my_loop, 0);	883	ev_run (my_loop, 0);
781	... jobs done or somebody called unloop. yeah!	884	... jobs done or somebody called break. yeah!
782		885
783	=item ev_unloop (loop, how)	886	=item ev_break (loop, how)
784		887
785	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
786	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
787	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
788	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.
789		892
790	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>.
791		894
792	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.
793		897
794	=item ev_ref (loop)	898	=item ev_ref (loop)
795		899
796	=item ev_unref (loop)	900	=item ev_unref (loop)
797		901
798	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
799	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
800	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.
801		905
802	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
803	unregister, but that nevertheless should not keep C<ev_loop> from	907	unregister, but that nevertheless should not keep C<ev_run> from
804	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>	908	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
805	before stopping it.	909	before stopping it.
806		910
807	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
808	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
809	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
810	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
811	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
812	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
813	before, respectively. Note also that libev might stop watchers itself	917	before, respectively. Note also that libev might stop watchers itself
814	(e.g. non-repeating timers) in which case you have to C<ev_ref>	918	(e.g. non-repeating timers) in which case you have to C<ev_ref>
815	in the callback).	919	in the callback).
816		920
817	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>
818	running when nothing else is active.	922	running when nothing else is active.
819		923
820	ev_signal exitsig;	924	ev_signal exitsig;
821	ev_signal_init (&exitsig, sig_cb, SIGINT);	925	ev_signal_init (&exitsig, sig_cb, SIGINT);
822	ev_signal_start (loop, &exitsig);	926	ev_signal_start (loop, &exitsig);
823	evf_unref (loop);	927	ev_unref (loop);
824		928
825	Example: For some weird reason, unregister the above signal handler again.	929	Example: For some weird reason, unregister the above signal handler again.
826		930
827	ev_ref (loop);	931	ev_ref (loop);
828	ev_signal_stop (loop, &exitsig);	932	ev_signal_stop (loop, &exitsig);
…		…
848	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.
849		953
850	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
851	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,
852	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
853	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
854	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
855	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
856	once per this interval, on average.	960	once per this interval, on average (as long as the host time resolution is
		961	good enough).
857		962
858	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
859	to spend more time collecting timeouts, at the expense of increased	964	to spend more time collecting timeouts, at the expense of increased
860	latency/jitter/inexactness (the watcher callback will be called	965	latency/jitter/inexactness (the watcher callback will be called
861	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
…		…
867	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>,
868	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
869	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
870	parallelity, then this setting will limit your transaction rate (if you	975	parallelity, then this setting will limit your transaction rate (if you
871	need to poll once per transaction and the I/O collect interval is 0.01,	976	need to poll once per transaction and the I/O collect interval is 0.01,
872	then you can't do more than 100 transations per second).	977	then you can't do more than 100 transactions per second).
873		978
874	Setting the I<timeout collect interval> can improve the opportunity for	979	Setting the I<timeout collect interval> can improve the opportunity for
875	saving power, as the program will "bundle" timer callback invocations that	980	saving power, as the program will "bundle" timer callback invocations that
876	are "near" in time together, by delaying some, thus reducing the number of	981	are "near" in time together, by delaying some, thus reducing the number of
877	times the process sleeps and wakes up again. Another useful technique to	982	times the process sleeps and wakes up again. Another useful technique to
…		…
885	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	990	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
886		991
887	=item ev_invoke_pending (loop)	992	=item ev_invoke_pending (loop)
888		993
889	This call will simply invoke all pending watchers while resetting their	994	This call will simply invoke all pending watchers while resetting their
890	pending state. Normally, C<ev_loop> does this automatically when required,	995	pending state. Normally, C<ev_run> does this automatically when required,
891	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).
892		1001
893	=item int ev_pending_count (loop)	1002	=item int ev_pending_count (loop)
894		1003
895	Returns the number of pending watchers - zero indicates that no watchers	1004	Returns the number of pending watchers - zero indicates that no watchers
896	are pending.	1005	are pending.
897		1006
898	=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))
899		1008
900	This overrides the invoke pending functionality of the loop: Instead of	1009	This overrides the invoke pending functionality of the loop: Instead of
901	invoking all pending watchers when there are any, C<ev_loop> will call	1010	invoking all pending watchers when there are any, C<ev_run> will call
902	this callback instead. This is useful, for example, when you want to	1011	this callback instead. This is useful, for example, when you want to
903	invoke the actual watchers inside another context (another thread etc.).	1012	invoke the actual watchers inside another context (another thread etc.).
904		1013
905	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
906	callback.	1015	callback.
…		…
909		1018
910	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
911	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
912	each call to a libev function.	1021	each call to a libev function.
913		1022
914	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
915	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
916	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
917	and I<acquire> callbacks on the loop.	1026	I<release> and I<acquire> callbacks on the loop.
918		1027
919	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
920	suspended waiting for new events, and C<acquire> is called just	1029	suspended waiting for new events, and C<acquire> is called just
921	afterwards.	1030	afterwards.
922		1031
…		…
925		1034
926	While event loop modifications are allowed between invocations of	1035	While event loop modifications are allowed between invocations of
927	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
928	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
929	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
930	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
931	to take note of any changes you made.	1040	to take note of any changes you made.
932		1041
933	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
934	invocations of C<release> and C<acquire>.	1043	invocations of C<release> and C<acquire>.
935		1044
936	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
937	document.	1046	document.
938		1047
939	=item ev_set_userdata (loop, void *data)	1048	=item ev_set_userdata (loop, void *data)
940		1049
941	=item ev_userdata (loop)	1050	=item void *ev_userdata (loop)
942		1051
943	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
944	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
945	C<0.>	1054	C<0>.
946		1055
947	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,
948	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
949	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
950	any other purpose as well.	1059	any other purpose as well.
951		1060
952	=item ev_loop_verify (loop)	1061	=item ev_verify (loop)
953		1062
954	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
955	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
956	through all internal structures and checks them for validity. If anything	1065	through all internal structures and checks them for validity. If anything
957	is found to be inconsistent, it will print an error message to standard	1066	is found to be inconsistent, it will print an error message to standard
…		…
968		1077
969	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
970	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
971	watchers and C<ev_io_start> for I/O watchers.	1080	watchers and C<ev_io_start> for I/O watchers.
972		1081
973	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
974	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
975	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:
976		1086
977	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)
978	{	1088	{
979	ev_io_stop (w);	1089	ev_io_stop (w);
980	ev_unloop (loop, EVUNLOOP_ALL);	1090	ev_break (loop, EVBREAK_ALL);
981	}	1091	}
982		1092
983	struct ev_loop *loop = ev_default_loop (0);	1093	struct ev_loop *loop = ev_default_loop (0);
984		1094
985	ev_io stdin_watcher;	1095	ev_io stdin_watcher;
986		1096
987	ev_init (&stdin_watcher, my_cb);	1097	ev_init (&stdin_watcher, my_cb);
988	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1098	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
989	ev_io_start (loop, &stdin_watcher);	1099	ev_io_start (loop, &stdin_watcher);
990		1100
991	ev_loop (loop, 0);	1101	ev_run (loop, 0);
992		1102
993	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
994	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
995	stack).	1105	stack).
996		1106
997	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>
998	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).
999		1109
1000	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
1001	(watcher *, callback)>, which expects a callback to be provided. This	1111	*, callback)>, which expects a callback to be provided. This callback is
1002	callback gets invoked each time the event occurs (or, in the case of I/O	1112	invoked each time the event occurs (or, in the case of I/O watchers, each
1003	watchers, each time the event loop detects that the file descriptor given	1113	time the event loop detects that the file descriptor given is readable
1004	is readable and/or writable).	1114	and/or writable).
1005		1115
1006	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 *, ...) >>
1007	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
1008	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<<
1009	ev_TYPE_init (watcher *, callback, ...) >>.	1119	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
1032	=item C<EV_WRITE>	1142	=item C<EV_WRITE>
1033		1143
1034	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
1035	writable.	1145	writable.
1036		1146
1037	=item C<EV_TIMEOUT>	1147	=item C<EV_TIMER>
1038		1148
1039	The C<ev_timer> watcher has timed out.	1149	The C<ev_timer> watcher has timed out.
1040		1150
1041	=item C<EV_PERIODIC>	1151	=item C<EV_PERIODIC>
1042		1152
…		…
1060		1170
1061	=item C<EV_PREPARE>	1171	=item C<EV_PREPARE>
1062		1172
1063	=item C<EV_CHECK>	1173	=item C<EV_CHECK>
1064		1174
1065	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
1066	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
1067	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
1068	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
1069	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
1070	(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
1071	C<ev_loop> from blocking).	1181	C<ev_run> from blocking).
1072		1182
1073	=item C<EV_EMBED>	1183	=item C<EV_EMBED>
1074		1184
1075	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.
1076		1186
1077	=item C<EV_FORK>	1187	=item C<EV_FORK>
1078		1188
1079	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
1080	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>).
1081		1195
1082	=item C<EV_ASYNC>	1196	=item C<EV_ASYNC>
1083		1197
1084	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>).
1085		1199
…		…
1258	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
1259	functions that do not need a watcher.	1373	functions that do not need a watcher.
1260		1374
1261	=back	1375	=back
1262		1376
		1377	See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR
		1378	OWN COMPOSITE WATCHERS> idioms.
1263		1379
1264	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1380	=head2 WATCHER STATES
1265		1381
1266	Each watcher has, by default, a member C<void *data> that you can change	1382	There are various watcher states mentioned throughout this manual -
1267	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
1268	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
1269	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".
1270	member, you can also "subclass" the watcher type and provide your own
1271	data:
1272		1386
1273	struct my_io	1387	=over 4
1274	{
1275	ev_io io;
1276	int otherfd;
1277	void *somedata;
1278	struct whatever *mostinteresting;
1279	};
1280		1388
1281	...	1389	=item initialiased
1282	struct my_io w;
1283	ev_io_init (&w.io, my_cb, fd, EV_READ);
1284		1390
1285	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
1286	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.
1287		1394
1288	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
1289	{	1396	use in an event loop. It can be moved around, freed, reused etc. at
1290	struct my_io *w = (struct my_io *)w_;	1397	will - as long as you either keep the memory contents intact, or call
1291	...	1398	C<ev_TYPE_init> again.
1292	}
1293		1399
1294	More interesting and less C-conformant ways of casting your callback type	1400	=item started/running/active
1295	instead have been omitted.
1296		1401
1297	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
1298	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.
1299		1407
1300	struct my_biggy	1408	=item pending
1301	{
1302	int some_data;
1303	ev_timer t1;
1304	ev_timer t2;
1305	}
1306		1409
1307	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
1308	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
1309	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
1310	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
1311	programmers):	1414	callback.
1312		1415
1313	#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.
1314		1422
1315	static void	1423	It is also possible to feed an event on a watcher that is not active (e.g.
1316	t1_cb (EV_P_ ev_timer *w, int revents)	1424	via C<ev_feed_event>), in which case it becomes pending without being
1317	{	1425	active.
1318	struct my_biggy big = (struct my_biggy *)
1319	(((char *)w) - offsetof (struct my_biggy, t1));
1320	}
1321		1426
1322	static void	1427	=item stopped
1323	t2_cb (EV_P_ ev_timer *w, int revents)	1428
1324	{	1429	A watcher can be stopped implicitly by libev (in which case it might still
1325	struct my_biggy big = (struct my_biggy *)	1430	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1326	(((char *)w) - offsetof (struct my_biggy, t2));	1431	latter will clear any pending state the watcher might be in, regardless
1327	}	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
1328		1441
1329	=head2 WATCHER PRIORITY MODELS	1442	=head2 WATCHER PRIORITY MODELS
1330		1443
1331	Many event loops support I<watcher priorities>, which are usually small	1444	Many event loops support I<watcher priorities>, which are usually small
1332	integers that influence the ordering of event callback invocation	1445	integers that influence the ordering of event callback invocation
…		…
1375		1488
1376	For example, to emulate how many other event libraries handle priorities,	1489	For example, to emulate how many other event libraries handle priorities,
1377	you can associate an C<ev_idle> watcher to each such watcher, and in	1490	you can associate an C<ev_idle> watcher to each such watcher, and in
1378	the normal watcher callback, you just start the idle watcher. The real	1491	the normal watcher callback, you just start the idle watcher. The real
1379	processing is done in the idle watcher callback. This causes libev to	1492	processing is done in the idle watcher callback. This causes libev to
1380	continously poll and process kernel event data for the watcher, but when	1493	continuously poll and process kernel event data for the watcher, but when
1381	the lock-out case is known to be rare (which in turn is rare :), this is	1494	the lock-out case is known to be rare (which in turn is rare :), this is
1382	workable.	1495	workable.
1383		1496
1384	Usually, however, the lock-out model implemented that way will perform	1497	Usually, however, the lock-out model implemented that way will perform
1385	miserably under the type of load it was designed to handle. In that case,	1498	miserably under the type of load it was designed to handle. In that case,
…		…
1399	{	1512	{
1400	// stop the I/O watcher, we received the event, but	1513	// stop the I/O watcher, we received the event, but
1401	// are not yet ready to handle it.	1514	// are not yet ready to handle it.
1402	ev_io_stop (EV_A_ w);	1515	ev_io_stop (EV_A_ w);
1403		1516
1404	// start the idle watcher to ahndle the actual event.	1517	// start the idle watcher to handle the actual event.
1405	// it will not be executed as long as other watchers	1518	// it will not be executed as long as other watchers
1406	// with the default priority are receiving events.	1519	// with the default priority are receiving events.
1407	ev_idle_start (EV_A_ &idle);	1520	ev_idle_start (EV_A_ &idle);
1408	}	1521	}
1409		1522
…		…
1459	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
1460	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
1461	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
1462	required if you know what you are doing).	1575	required if you know what you are doing).
1463		1576
1464	If you cannot use non-blocking mode, then force the use of a
1465	known-to-be-good backend (at the time of this writing, this includes only
1466	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1467	descriptors for which non-blocking operation makes no sense (such as
1468	files) - libev doesn't guarentee any specific behaviour in that case.
1469
1470	Another thing you have to watch out for is that it is quite easy to	1577	Another thing you have to watch out for is that it is quite easy to
1471	receive "spurious" readiness notifications, that is your callback might	1578	receive "spurious" readiness notifications, that is, your callback might
1472	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1579	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1473	because there is no data. Not only are some backends known to create a	1580	because there is no data. It is very easy to get into this situation even
1474	lot of those (for example Solaris ports), it is very easy to get into	1581	with a relatively standard program structure. Thus it is best to always
1475	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
1476	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1477	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1583	preferable to a program hanging until some data arrives.
1478		1584
1479	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
1480	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
1481	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
1482	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
1483	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
1484	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
1485	indefinitely.	1591	indefinitely.
1486		1592
1487	But really, best use non-blocking mode.	1593	But really, best use non-blocking mode.
1488		1594
…		…
1516		1622
1517	There is no workaround possible except not registering events	1623	There is no workaround possible except not registering events
1518	for potentially C<dup ()>'ed file descriptors, or to resort to	1624	for potentially C<dup ()>'ed file descriptors, or to resort to
1519	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1625	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1520		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
1521	=head3 The special problem of fork	1660	=head3 The special problem of fork
1522		1661
1523	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
1524	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
1525	it in the child.	1664	it in the child if you want to continue to use it in the child.
1526		1665
1527	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
1528	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
1529	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1668	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1530	C<EVBACKEND_POLL>.
1531		1669
1532	=head3 The special problem of SIGPIPE	1670	=head3 The special problem of SIGPIPE
1533		1671
1534	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>:
1535	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
…		…
1538		1676
1539	So when you encounter spurious, unexplained daemon exits, make sure you	1677	So when you encounter spurious, unexplained daemon exits, make sure you
1540	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1678	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1541	somewhere, as that would have given you a big clue).	1679	somewhere, as that would have given you a big clue).
1542		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.
1543		1719
1544	=head3 Watcher-Specific Functions	1720	=head3 Watcher-Specific Functions
1545		1721
1546	=over 4	1722	=over 4
1547		1723
…		…
1579	...	1755	...
1580	struct ev_loop *loop = ev_default_init (0);	1756	struct ev_loop *loop = ev_default_init (0);
1581	ev_io stdin_readable;	1757	ev_io stdin_readable;
1582	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);
1583	ev_io_start (loop, &stdin_readable);	1759	ev_io_start (loop, &stdin_readable);
1584	ev_loop (loop, 0);	1760	ev_run (loop, 0);
1585		1761
1586		1762
1587	=head2 C<ev_timer> - relative and optionally repeating timeouts	1763	=head2 C<ev_timer> - relative and optionally repeating timeouts
1588		1764
1589	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
…		…
1595	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1771	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1596	monotonic clock option helps a lot here).	1772	monotonic clock option helps a lot here).
1597		1773
1598	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
1599	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
1600	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
1601	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
1602	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
1603	no longer true when a callback calls C<ev_loop> recursively).	1780	longer true when a callback calls C<ev_run> recursively).
1604		1781
1605	=head3 Be smart about timeouts	1782	=head3 Be smart about timeouts
1606		1783
1607	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
1608	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,
…		…
1683		1860
1684	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,
1685	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
1686	within the callback:	1863	within the callback:
1687		1864
		1865	ev_tstamp timeout = 60.;
1688	ev_tstamp last_activity; // time of last activity	1866	ev_tstamp last_activity; // time of last activity
		1867	ev_timer timer;
1689		1868
1690	static void	1869	static void
1691	callback (EV_P_ ev_timer *w, int revents)	1870	callback (EV_P_ ev_timer *w, int revents)
1692	{	1871	{
1693	ev_tstamp now = ev_now (EV_A);	1872	// calculate when the timeout would happen
1694	ev_tstamp timeout = last_activity + 60.;	1873	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1695		1874
1696	// if last_activity + 60. is older than now, we did time out	1875	// if negative, it means we the timeout already occured
1697	if (timeout < now)	1876	if (after < 0.)
1698	{	1877	{
1699	// timeout occured, take action	1878	// timeout occurred, take action
1700	}	1879	}
1701	else	1880	else
1702	{	1881	{
1703	// callback was invoked, but there was some activity, re-arm	1882	// callback was invoked, but there was some recent
1704	// the watcher to fire in last_activity + 60, which is	1883	// activity. simply restart the timer to time out
1705	// guaranteed to be in the future, so "again" is positive:	1884	// after "after" seconds, which is the earliest time
1706	w->repeat = timeout - now;	1885	// the timeout can occur.
		1886	ev_timer_set (w, after, 0.);
1707	ev_timer_again (EV_A_ w);	1887	ev_timer_start (EV_A_ w);
1708	}	1888	}
1709	}	1889	}
1710		1890
1711	To summarise the callback: first calculate the real timeout (defined	1891	To summarise the callback: first calculate in how many seconds the
1712	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,
1713	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
1714	the callback was invoked too early (C<timeout> is in the future), so	1894	(EV_A)> from that).
1715	re-schedule the timer to fire at that future time, to see if maybe we have
1716	a timeout then.
1717		1895
1718	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
1719	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.
1720		1905
1721	This scheme causes more callback invocations (about one every 60 seconds	1906	This scheme causes more callback invocations (about one every 60 seconds
1722	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
1723	libev to change the timeout.	1908	libev to change the timeout.
1724		1909
1725	To start the timer, simply initialise the watcher and set C<last_activity>	1910	To start the machinery, simply initialise the watcher and set
1726	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
1727	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:
1728		1914
		1915	last_activity = ev_now (EV_A);
1729	ev_init (timer, callback);	1916	ev_init (&timer, callback);
1730	last_activity = ev_now (loop);	1917	callback (EV_A_ &timer, 0);
1731	callback (loop, timer, EV_TIMEOUT);
1732		1918
1733	And when there is some activity, simply store the current time in	1919	When there is some activity, simply store the current time in
1734	C<last_activity>, no libev calls at all:	1920	C<last_activity>, no libev calls at all:
1735		1921
		1922	if (activity detected)
1736	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);
1737		1932
1738	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
1739	time-out is unlikely to be triggered, much more efficient.	1934	time-out is unlikely to be triggered, much more efficient.
1740
1741	Changing the timeout is trivial as well (if it isn't hard-coded in the
1742	callback :) - just change the timeout and invoke the callback, which will
1743	fix things for you.
1744		1935
1745	=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.
1746		1937
1747	If there is not one request, but many thousands (millions...), all	1938	If there is not one request, but many thousands (millions...), all
1748	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
…		…
1775	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
1776	rather complicated, but extremely efficient, something that really pays	1967	rather complicated, but extremely efficient, something that really pays
1777	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
1778	overkill :)	1969	overkill :)
1779		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
1780	=head3 The special problem of time updates	2008	=head3 The special problem of time updates
1781		2009
1782	Establishing the current time is a costly operation (it usually takes at	2010	Establishing the current time is a costly operation (it usually takes
1783	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
1784	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
1785	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
1786	lots of events in one iteration.	2014	lots of events in one iteration.
1787		2015
1788	The relative timeouts are calculated relative to the C<ev_now ()>	2016	The relative timeouts are calculated relative to the C<ev_now ()>
1789	time. This is usually the right thing as this timestamp refers to the time	2017	time. This is usually the right thing as this timestamp refers to the time
…		…
1794	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2022	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1795		2023
1796	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
1797	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
1798	()>.	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.
1799		2060
1800	=head3 The special problems of suspended animation	2061	=head3 The special problems of suspended animation
1801		2062
1802	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
1803	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?
…		…
1847	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
1848	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.
1849		2110
1850	=item ev_timer_again (loop, ev_timer *)	2111	=item ev_timer_again (loop, ev_timer *)
1851		2112
1852	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
1853	repeating. The exact semantics are:	2114	repeating. The exact semantics are:
1854		2115
1855	If the timer is pending, its pending status is cleared.	2116	If the timer is pending, its pending status is cleared.
1856		2117
1857	If the timer is started but non-repeating, stop it (as if it timed out).	2118	If the timer is started but non-repeating, stop it (as if it timed out).
…		…
1906	}	2167	}
1907		2168
1908	ev_timer mytimer;	2169	ev_timer mytimer;
1909	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2170	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1910	ev_timer_again (&mytimer); /* start timer */	2171	ev_timer_again (&mytimer); /* start timer */
1911	ev_loop (loop, 0);	2172	ev_run (loop, 0);
1912		2173
1913	// and in some piece of code that gets executed on any "activity":	2174	// and in some piece of code that gets executed on any "activity":
1914	// reset the timeout to start ticking again at 10 seconds	2175	// reset the timeout to start ticking again at 10 seconds
1915	ev_timer_again (&mytimer);	2176	ev_timer_again (&mytimer);
1916		2177
…		…
1942		2203
1943	As with timers, the callback is guaranteed to be invoked only when the	2204	As with timers, the callback is guaranteed to be invoked only when the
1944	point in time where it is supposed to trigger has passed. If multiple	2205	point in time where it is supposed to trigger has passed. If multiple
1945	timers become ready during the same loop iteration then the ones with	2206	timers become ready during the same loop iteration then the ones with
1946	earlier time-out values are invoked before ones with later time-out values	2207	earlier time-out values are invoked before ones with later time-out values
1947	(but this is no longer true when a callback calls C<ev_loop> recursively).	2208	(but this is no longer true when a callback calls C<ev_run> recursively).
1948		2209
1949	=head3 Watcher-Specific Functions and Data Members	2210	=head3 Watcher-Specific Functions and Data Members
1950		2211
1951	=over 4	2212	=over 4
1952		2213
…		…
1987		2248
1988	Another way to think about it (for the mathematically inclined) is that	2249	Another way to think about it (for the mathematically inclined) is that
1989	C<ev_periodic> will try to run the callback in this mode at the next possible	2250	C<ev_periodic> will try to run the callback in this mode at the next possible
1990	time where C<time = offset (mod interval)>, regardless of any time jumps.	2251	time where C<time = offset (mod interval)>, regardless of any time jumps.
1991		2252
1992	For numerical stability it is preferable that the C<offset> value is near	2253	The C<interval> I<MUST> be positive, and for numerical stability, the
1993	C<ev_now ()> (the current time), but there is no range requirement for	2254	interval value should be higher than C<1/8192> (which is around 100
1994	this value, and in fact is often specified as zero.	2255	microseconds) and C<offset> should be higher than C<0> and should have
		2256	at most a similar magnitude as the current time (say, within a factor of
		2257	ten). Typical values for offset are, in fact, C<0> or something between
		2258	C<0> and C<interval>, which is also the recommended range.
1995		2259
1996	Note also that there is an upper limit to how often a timer can fire (CPU	2260	Note also that there is an upper limit to how often a timer can fire (CPU
1997	speed for example), so if C<interval> is very small then timing stability	2261	speed for example), so if C<interval> is very small then timing stability
1998	will of course deteriorate. Libev itself tries to be exact to be about one	2262	will of course deteriorate. Libev itself tries to be exact to be about one
1999	millisecond (if the OS supports it and the machine is fast enough).	2263	millisecond (if the OS supports it and the machine is fast enough).
…		…
2080	Example: Call a callback every hour, or, more precisely, whenever the	2344	Example: Call a callback every hour, or, more precisely, whenever the
2081	system time is divisible by 3600. The callback invocation times have	2345	system time is divisible by 3600. The callback invocation times have
2082	potentially a lot of jitter, but good long-term stability.	2346	potentially a lot of jitter, but good long-term stability.
2083		2347
2084	static void	2348	static void
2085	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2349	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
2086	{	2350	{
2087	... its now a full hour (UTC, or TAI or whatever your clock follows)	2351	... its now a full hour (UTC, or TAI or whatever your clock follows)
2088	}	2352	}
2089		2353
2090	ev_periodic hourly_tick;	2354	ev_periodic hourly_tick;
…		…
2113		2377
2114	=head2 C<ev_signal> - signal me when a signal gets signalled!	2378	=head2 C<ev_signal> - signal me when a signal gets signalled!
2115		2379
2116	Signal watchers will trigger an event when the process receives a specific	2380	Signal watchers will trigger an event when the process receives a specific
2117	signal one or more times. Even though signals are very asynchronous, libev	2381	signal one or more times. Even though signals are very asynchronous, libev
2118	will try it's best to deliver signals synchronously, i.e. as part of the	2382	will try its best to deliver signals synchronously, i.e. as part of the
2119	normal event processing, like any other event.	2383	normal event processing, like any other event.
2120		2384
2121	If you want signals to be delivered truly asynchronously, just use	2385	If you want signals to be delivered truly asynchronously, just use
2122	C<sigaction> as you would do without libev and forget about sharing	2386	C<sigaction> as you would do without libev and forget about sharing
2123	the signal. You can even use C<ev_async> from a signal handler to	2387	the signal. You can even use C<ev_async> from a signal handler to
…		…
2142	=head3 The special problem of inheritance over fork/execve/pthread_create	2406	=head3 The special problem of inheritance over fork/execve/pthread_create
2143		2407
2144	Both the signal mask (C<sigprocmask>) and the signal disposition	2408	Both the signal mask (C<sigprocmask>) and the signal disposition
2145	(C<sigaction>) are unspecified after starting a signal watcher (and after	2409	(C<sigaction>) are unspecified after starting a signal watcher (and after
2146	stopping it again), that is, libev might or might not block the signal,	2410	stopping it again), that is, libev might or might not block the signal,
2147	and might or might not set or restore the installed signal handler.	2411	and might or might not set or restore the installed signal handler (but
		2412	see C<EVFLAG_NOSIGMASK>).
2148		2413
2149	While this does not matter for the signal disposition (libev never	2414	While this does not matter for the signal disposition (libev never
2150	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on	2415	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
2151	C<execve>), this matters for the signal mask: many programs do not expect	2416	C<execve>), this matters for the signal mask: many programs do not expect
2152	certain signals to be blocked.	2417	certain signals to be blocked.
…		…
2166		2431
2167	So I can't stress this enough: I<If you do not reset your signal mask when	2432	So I can't stress this enough: I<If you do not reset your signal mask when
2168	you expect it to be empty, you have a race condition in your code>. This	2433	you expect it to be empty, you have a race condition in your code>. This
2169	is not a libev-specific thing, this is true for most event libraries.	2434	is not a libev-specific thing, this is true for most event libraries.
2170		2435
		2436	=head3 The special problem of threads signal handling
		2437
		2438	POSIX threads has problematic signal handling semantics, specifically,
		2439	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2440	threads in a process block signals, which is hard to achieve.
		2441
		2442	When you want to use sigwait (or mix libev signal handling with your own
		2443	for the same signals), you can tackle this problem by globally blocking
		2444	all signals before creating any threads (or creating them with a fully set
		2445	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2446	loops. Then designate one thread as "signal receiver thread" which handles
		2447	these signals. You can pass on any signals that libev might be interested
		2448	in by calling C<ev_feed_signal>.
		2449
2171	=head3 Watcher-Specific Functions and Data Members	2450	=head3 Watcher-Specific Functions and Data Members
2172		2451
2173	=over 4	2452	=over 4
2174		2453
2175	=item ev_signal_init (ev_signal *, callback, int signum)	2454	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
2190	Example: Try to exit cleanly on SIGINT.	2469	Example: Try to exit cleanly on SIGINT.
2191		2470
2192	static void	2471	static void
2193	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2472	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2194	{	2473	{
2195	ev_unloop (loop, EVUNLOOP_ALL);	2474	ev_break (loop, EVBREAK_ALL);
2196	}	2475	}
2197		2476
2198	ev_signal signal_watcher;	2477	ev_signal signal_watcher;
2199	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2478	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2200	ev_signal_start (loop, &signal_watcher);	2479	ev_signal_start (loop, &signal_watcher);
…		…
2586		2865
2587	Prepare and check watchers are usually (but not always) used in pairs:	2866	Prepare and check watchers are usually (but not always) used in pairs:
2588	prepare watchers get invoked before the process blocks and check watchers	2867	prepare watchers get invoked before the process blocks and check watchers
2589	afterwards.	2868	afterwards.
2590		2869
2591	You I<must not> call C<ev_loop> or similar functions that enter	2870	You I<must not> call C<ev_run> or similar functions that enter
2592	the current event loop from either C<ev_prepare> or C<ev_check>	2871	the current event loop from either C<ev_prepare> or C<ev_check>
2593	watchers. Other loops than the current one are fine, however. The	2872	watchers. Other loops than the current one are fine, however. The
2594	rationale behind this is that you do not need to check for recursion in	2873	rationale behind this is that you do not need to check for recursion in
2595	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2874	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2596	C<ev_check> so if you have one watcher of each kind they will always be	2875	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2764		3043
2765	if (timeout >= 0)	3044	if (timeout >= 0)
2766	// create/start timer	3045	// create/start timer
2767		3046
2768	// poll	3047	// poll
2769	ev_loop (EV_A_ 0);	3048	ev_run (EV_A_ 0);
2770		3049
2771	// stop timer again	3050	// stop timer again
2772	if (timeout >= 0)	3051	if (timeout >= 0)
2773	ev_timer_stop (EV_A_ &to);	3052	ev_timer_stop (EV_A_ &to);
2774		3053
…		…
2852	if you do not want that, you need to temporarily stop the embed watcher).	3131	if you do not want that, you need to temporarily stop the embed watcher).
2853		3132
2854	=item ev_embed_sweep (loop, ev_embed *)	3133	=item ev_embed_sweep (loop, ev_embed *)
2855		3134
2856	Make a single, non-blocking sweep over the embedded loop. This works	3135	Make a single, non-blocking sweep over the embedded loop. This works
2857	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3136	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2858	appropriate way for embedded loops.	3137	appropriate way for embedded loops.
2859		3138
2860	=item struct ev_loop *other [read-only]	3139	=item struct ev_loop *other [read-only]
2861		3140
2862	The embedded event loop.	3141	The embedded event loop.
…		…
2922	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3201	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2923	handlers will be invoked, too, of course.	3202	handlers will be invoked, too, of course.
2924		3203
2925	=head3 The special problem of life after fork - how is it possible?	3204	=head3 The special problem of life after fork - how is it possible?
2926		3205
2927	Most uses of C<fork()> consist of forking, then some simple calls to ste	3206	Most uses of C<fork()> consist of forking, then some simple calls to set
2928	up/change the process environment, followed by a call to C<exec()>. This	3207	up/change the process environment, followed by a call to C<exec()>. This
2929	sequence should be handled by libev without any problems.	3208	sequence should be handled by libev without any problems.
2930		3209
2931	This changes when the application actually wants to do event handling	3210	This changes when the application actually wants to do event handling
2932	in the child, or both parent in child, in effect "continuing" after the	3211	in the child, or both parent in child, in effect "continuing" after the
…		…
2948	disadvantage of having to use multiple event loops (which do not support	3227	disadvantage of having to use multiple event loops (which do not support
2949	signal watchers).	3228	signal watchers).
2950		3229
2951	When this is not possible, or you want to use the default loop for	3230	When this is not possible, or you want to use the default loop for
2952	other reasons, then in the process that wants to start "fresh", call	3231	other reasons, then in the process that wants to start "fresh", call
2953	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3232	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
2954	the default loop will "orphan" (not stop) all registered watchers, so you	3233	Destroying the default loop will "orphan" (not stop) all registered
2955	have to be careful not to execute code that modifies those watchers. Note	3234	watchers, so you have to be careful not to execute code that modifies
2956	also that in that case, you have to re-register any signal watchers.	3235	those watchers. Note also that in that case, you have to re-register any
		3236	signal watchers.
2957		3237
2958	=head3 Watcher-Specific Functions and Data Members	3238	=head3 Watcher-Specific Functions and Data Members
2959		3239
2960	=over 4	3240	=over 4
2961		3241
2962	=item ev_fork_init (ev_signal *, callback)	3242	=item ev_fork_init (ev_fork *, callback)
2963		3243
2964	Initialises and configures the fork watcher - it has no parameters of any	3244	Initialises and configures the fork watcher - it has no parameters of any
2965	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3245	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2966	believe me.	3246	really.
2967		3247
2968	=back	3248	=back
2969		3249
2970		3250
		3251	=head2 C<ev_cleanup> - even the best things end
		3252
		3253	Cleanup watchers are called just before the event loop is being destroyed
		3254	by a call to C<ev_loop_destroy>.
		3255
		3256	While there is no guarantee that the event loop gets destroyed, cleanup
		3257	watchers provide a convenient method to install cleanup hooks for your
		3258	program, worker threads and so on - you just to make sure to destroy the
		3259	loop when you want them to be invoked.
		3260
		3261	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3262	all other watchers, they do not keep a reference to the event loop (which
		3263	makes a lot of sense if you think about it). Like all other watchers, you
		3264	can call libev functions in the callback, except C<ev_cleanup_start>.
		3265
		3266	=head3 Watcher-Specific Functions and Data Members
		3267
		3268	=over 4
		3269
		3270	=item ev_cleanup_init (ev_cleanup *, callback)
		3271
		3272	Initialises and configures the cleanup watcher - it has no parameters of
		3273	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3274	pointless, I assure you.
		3275
		3276	=back
		3277
		3278	Example: Register an atexit handler to destroy the default loop, so any
		3279	cleanup functions are called.
		3280
		3281	static void
		3282	program_exits (void)
		3283	{
		3284	ev_loop_destroy (EV_DEFAULT_UC);
		3285	}
		3286
		3287	...
		3288	atexit (program_exits);
		3289
		3290
2971	=head2 C<ev_async> - how to wake up another event loop	3291	=head2 C<ev_async> - how to wake up an event loop
2972		3292
2973	In general, you cannot use an C<ev_loop> from multiple threads or other	3293	In general, you cannot use an C<ev_loop> from multiple threads or other
2974	asynchronous sources such as signal handlers (as opposed to multiple event	3294	asynchronous sources such as signal handlers (as opposed to multiple event
2975	loops - those are of course safe to use in different threads).	3295	loops - those are of course safe to use in different threads).
2976		3296
2977	Sometimes, however, you need to wake up another event loop you do not	3297	Sometimes, however, you need to wake up an event loop you do not control,
2978	control, for example because it belongs to another thread. This is what	3298	for example because it belongs to another thread. This is what C<ev_async>
2979	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3299	watchers do: as long as the C<ev_async> watcher is active, you can signal
2980	can signal it by calling C<ev_async_send>, which is thread- and signal	3300	it by calling C<ev_async_send>, which is thread- and signal safe.
2981	safe.
2982		3301
2983	This functionality is very similar to C<ev_signal> watchers, as signals,	3302	This functionality is very similar to C<ev_signal> watchers, as signals,
2984	too, are asynchronous in nature, and signals, too, will be compressed	3303	too, are asynchronous in nature, and signals, too, will be compressed
2985	(i.e. the number of callback invocations may be less than the number of	3304	(i.e. the number of callback invocations may be less than the number of
2986	C<ev_async_sent> calls).	3305	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
2987		3306	of "global async watchers" by using a watcher on an otherwise unused
2988	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3307	signal, and C<ev_feed_signal> to signal this watcher from another thread,
2989	just the default loop.	3308	even without knowing which loop owns the signal.
2990		3309
2991	=head3 Queueing	3310	=head3 Queueing
2992		3311
2993	C<ev_async> does not support queueing of data in any way. The reason	3312	C<ev_async> does not support queueing of data in any way. The reason
2994	is that the author does not know of a simple (or any) algorithm for a	3313	is that the author does not know of a simple (or any) algorithm for a
…		…
3086	trust me.	3405	trust me.
3087		3406
3088	=item ev_async_send (loop, ev_async *)	3407	=item ev_async_send (loop, ev_async *)
3089		3408
3090	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3409	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3091	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3410	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3411	returns.
		3412
3092	C<ev_feed_event>, this call is safe to do from other threads, signal or	3413	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3093	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3414	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3094	section below on what exactly this means).	3415	embedding section below on what exactly this means).
3095		3416
3096	Note that, as with other watchers in libev, multiple events might get	3417	Note that, as with other watchers in libev, multiple events might get
3097	compressed into a single callback invocation (another way to look at this	3418	compressed into a single callback invocation (another way to look at
3098	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3419	this is that C<ev_async> watchers are level-triggered: they are set on
3099	reset when the event loop detects that).	3420	C<ev_async_send>, reset when the event loop detects that).
3100		3421
3101	This call incurs the overhead of a system call only once per event loop	3422	This call incurs the overhead of at most one extra system call per event
3102	iteration, so while the overhead might be noticeable, it doesn't apply to	3423	loop iteration, if the event loop is blocked, and no syscall at all if
3103	repeated calls to C<ev_async_send> for the same event loop.	3424	the event loop (or your program) is processing events. That means that
		3425	repeated calls are basically free (there is no need to avoid calls for
		3426	performance reasons) and that the overhead becomes smaller (typically
		3427	zero) under load.
3104		3428
3105	=item bool = ev_async_pending (ev_async *)	3429	=item bool = ev_async_pending (ev_async *)
3106		3430
3107	Returns a non-zero value when C<ev_async_send> has been called on the	3431	Returns a non-zero value when C<ev_async_send> has been called on the
3108	watcher but the event has not yet been processed (or even noted) by the	3432	watcher but the event has not yet been processed (or even noted) by the
…		…
3141		3465
3142	If C<timeout> is less than 0, then no timeout watcher will be	3466	If C<timeout> is less than 0, then no timeout watcher will be
3143	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3467	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
3144	repeat = 0) will be started. C<0> is a valid timeout.	3468	repeat = 0) will be started. C<0> is a valid timeout.
3145		3469
3146	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3470	The callback has the type C<void (*cb)(int revents, void *arg)> and is
3147	passed an C<revents> set like normal event callbacks (a combination of	3471	passed an C<revents> set like normal event callbacks (a combination of
3148	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3472	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
3149	value passed to C<ev_once>. Note that it is possible to receive I<both>	3473	value passed to C<ev_once>. Note that it is possible to receive I<both>
3150	a timeout and an io event at the same time - you probably should give io	3474	a timeout and an io event at the same time - you probably should give io
3151	events precedence.	3475	events precedence.
3152		3476
3153	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3477	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
3154		3478
3155	static void stdin_ready (int revents, void *arg)	3479	static void stdin_ready (int revents, void *arg)
3156	{	3480	{
3157	if (revents & EV_READ)	3481	if (revents & EV_READ)
3158	/* stdin might have data for us, joy! */;	3482	/* stdin might have data for us, joy! */;
3159	else if (revents & EV_TIMEOUT)	3483	else if (revents & EV_TIMER)
3160	/* doh, nothing entered */;	3484	/* doh, nothing entered */;
3161	}	3485	}
3162		3486
3163	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3487	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3164		3488
3165	=item ev_feed_fd_event (loop, int fd, int revents)	3489	=item ev_feed_fd_event (loop, int fd, int revents)
3166		3490
3167	Feed an event on the given fd, as if a file descriptor backend detected	3491	Feed an event on the given fd, as if a file descriptor backend detected
3168	the given events it.	3492	the given events.
3169		3493
3170	=item ev_feed_signal_event (loop, int signum)	3494	=item ev_feed_signal_event (loop, int signum)
3171		3495
3172	Feed an event as if the given signal occurred (C<loop> must be the default	3496	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3173	loop!).	3497	which is async-safe.
3174		3498
3175	=back	3499	=back
		3500
		3501
		3502	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3503
		3504	This section explains some common idioms that are not immediately
		3505	obvious. Note that examples are sprinkled over the whole manual, and this
		3506	section only contains stuff that wouldn't fit anywhere else.
		3507
		3508	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3509
		3510	Each watcher has, by default, a C<void *data> member that you can read
		3511	or modify at any time: libev will completely ignore it. This can be used
		3512	to associate arbitrary data with your watcher. If you need more data and
		3513	don't want to allocate memory separately and store a pointer to it in that
		3514	data member, you can also "subclass" the watcher type and provide your own
		3515	data:
		3516
		3517	struct my_io
		3518	{
		3519	ev_io io;
		3520	int otherfd;
		3521	void *somedata;
		3522	struct whatever *mostinteresting;
		3523	};
		3524
		3525	...
		3526	struct my_io w;
		3527	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3528
		3529	And since your callback will be called with a pointer to the watcher, you
		3530	can cast it back to your own type:
		3531
		3532	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3533	{
		3534	struct my_io *w = (struct my_io *)w_;
		3535	...
		3536	}
		3537
		3538	More interesting and less C-conformant ways of casting your callback
		3539	function type instead have been omitted.
		3540
		3541	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3542
		3543	Another common scenario is to use some data structure with multiple
		3544	embedded watchers, in effect creating your own watcher that combines
		3545	multiple libev event sources into one "super-watcher":
		3546
		3547	struct my_biggy
		3548	{
		3549	int some_data;
		3550	ev_timer t1;
		3551	ev_timer t2;
		3552	}
		3553
		3554	In this case getting the pointer to C<my_biggy> is a bit more
		3555	complicated: Either you store the address of your C<my_biggy> struct in
		3556	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3557	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3558	real programmers):
		3559
		3560	#include <stddef.h>
		3561
		3562	static void
		3563	t1_cb (EV_P_ ev_timer *w, int revents)
		3564	{
		3565	struct my_biggy big = (struct my_biggy *)
		3566	(((char *)w) - offsetof (struct my_biggy, t1));
		3567	}
		3568
		3569	static void
		3570	t2_cb (EV_P_ ev_timer *w, int revents)
		3571	{
		3572	struct my_biggy big = (struct my_biggy *)
		3573	(((char *)w) - offsetof (struct my_biggy, t2));
		3574	}
		3575
		3576	=head2 AVOIDING FINISHING BEFORE RETURNING
		3577
		3578	Often you have structures like this in event-based programs:
		3579
		3580	callback ()
		3581	{
		3582	free (request);
		3583	}
		3584
		3585	request = start_new_request (..., callback);
		3586
		3587	The intent is to start some "lengthy" operation. The C<request> could be
		3588	used to cancel the operation, or do other things with it.
		3589
		3590	It's not uncommon to have code paths in C<start_new_request> that
		3591	immediately invoke the callback, for example, to report errors. Or you add
		3592	some caching layer that finds that it can skip the lengthy aspects of the
		3593	operation and simply invoke the callback with the result.
		3594
		3595	The problem here is that this will happen I<before> C<start_new_request>
		3596	has returned, so C<request> is not set.
		3597
		3598	Even if you pass the request by some safer means to the callback, you
		3599	might want to do something to the request after starting it, such as
		3600	canceling it, which probably isn't working so well when the callback has
		3601	already been invoked.
		3602
		3603	A common way around all these issues is to make sure that
		3604	C<start_new_request> I<always> returns before the callback is invoked. If
		3605	C<start_new_request> immediately knows the result, it can artificially
		3606	delay invoking the callback by e.g. using a C<prepare> or C<idle> watcher
		3607	for example, or more sneakily, by reusing an existing (stopped) watcher
		3608	and pushing it into the pending queue:
		3609
		3610	ev_set_cb (watcher, callback);
		3611	ev_feed_event (EV_A_ watcher, 0);
		3612
		3613	This way, C<start_new_request> can safely return before the callback is
		3614	invoked, while not delaying callback invocation too much.
		3615
		3616	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3617
		3618	Often (especially in GUI toolkits) there are places where you have
		3619	I<modal> interaction, which is most easily implemented by recursively
		3620	invoking C<ev_run>.
		3621
		3622	This brings the problem of exiting - a callback might want to finish the
		3623	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3624	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3625	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3626	other combination: In these cases, C<ev_break> will not work alone.
		3627
		3628	The solution is to maintain "break this loop" variable for each C<ev_run>
		3629	invocation, and use a loop around C<ev_run> until the condition is
		3630	triggered, using C<EVRUN_ONCE>:
		3631
		3632	// main loop
		3633	int exit_main_loop = 0;
		3634
		3635	while (!exit_main_loop)
		3636	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3637
		3638	// in a modal watcher
		3639	int exit_nested_loop = 0;
		3640
		3641	while (!exit_nested_loop)
		3642	ev_run (EV_A_ EVRUN_ONCE);
		3643
		3644	To exit from any of these loops, just set the corresponding exit variable:
		3645
		3646	// exit modal loop
		3647	exit_nested_loop = 1;
		3648
		3649	// exit main program, after modal loop is finished
		3650	exit_main_loop = 1;
		3651
		3652	// exit both
		3653	exit_main_loop = exit_nested_loop = 1;
		3654
		3655	=head2 THREAD LOCKING EXAMPLE
		3656
		3657	Here is a fictitious example of how to run an event loop in a different
		3658	thread from where callbacks are being invoked and watchers are
		3659	created/added/removed.
		3660
		3661	For a real-world example, see the C<EV::Loop::Async> perl module,
		3662	which uses exactly this technique (which is suited for many high-level
		3663	languages).
		3664
		3665	The example uses a pthread mutex to protect the loop data, a condition
		3666	variable to wait for callback invocations, an async watcher to notify the
		3667	event loop thread and an unspecified mechanism to wake up the main thread.
		3668
		3669	First, you need to associate some data with the event loop:
		3670
		3671	typedef struct {
		3672	mutex_t lock; /* global loop lock */
		3673	ev_async async_w;
		3674	thread_t tid;
		3675	cond_t invoke_cv;
		3676	} userdata;
		3677
		3678	void prepare_loop (EV_P)
		3679	{
		3680	// for simplicity, we use a static userdata struct.
		3681	static userdata u;
		3682
		3683	ev_async_init (&u->async_w, async_cb);
		3684	ev_async_start (EV_A_ &u->async_w);
		3685
		3686	pthread_mutex_init (&u->lock, 0);
		3687	pthread_cond_init (&u->invoke_cv, 0);
		3688
		3689	// now associate this with the loop
		3690	ev_set_userdata (EV_A_ u);
		3691	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3692	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3693
		3694	// then create the thread running ev_run
		3695	pthread_create (&u->tid, 0, l_run, EV_A);
		3696	}
		3697
		3698	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3699	solely to wake up the event loop so it takes notice of any new watchers
		3700	that might have been added:
		3701
		3702	static void
		3703	async_cb (EV_P_ ev_async *w, int revents)
		3704	{
		3705	// just used for the side effects
		3706	}
		3707
		3708	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3709	protecting the loop data, respectively.
		3710
		3711	static void
		3712	l_release (EV_P)
		3713	{
		3714	userdata *u = ev_userdata (EV_A);
		3715	pthread_mutex_unlock (&u->lock);
		3716	}
		3717
		3718	static void
		3719	l_acquire (EV_P)
		3720	{
		3721	userdata *u = ev_userdata (EV_A);
		3722	pthread_mutex_lock (&u->lock);
		3723	}
		3724
		3725	The event loop thread first acquires the mutex, and then jumps straight
		3726	into C<ev_run>:
		3727
		3728	void *
		3729	l_run (void *thr_arg)
		3730	{
		3731	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3732
		3733	l_acquire (EV_A);
		3734	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3735	ev_run (EV_A_ 0);
		3736	l_release (EV_A);
		3737
		3738	return 0;
		3739	}
		3740
		3741	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3742	signal the main thread via some unspecified mechanism (signals? pipe
		3743	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3744	have been called (in a while loop because a) spurious wakeups are possible
		3745	and b) skipping inter-thread-communication when there are no pending
		3746	watchers is very beneficial):
		3747
		3748	static void
		3749	l_invoke (EV_P)
		3750	{
		3751	userdata *u = ev_userdata (EV_A);
		3752
		3753	while (ev_pending_count (EV_A))
		3754	{
		3755	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3756	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3757	}
		3758	}
		3759
		3760	Now, whenever the main thread gets told to invoke pending watchers, it
		3761	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3762	thread to continue:
		3763
		3764	static void
		3765	real_invoke_pending (EV_P)
		3766	{
		3767	userdata *u = ev_userdata (EV_A);
		3768
		3769	pthread_mutex_lock (&u->lock);
		3770	ev_invoke_pending (EV_A);
		3771	pthread_cond_signal (&u->invoke_cv);
		3772	pthread_mutex_unlock (&u->lock);
		3773	}
		3774
		3775	Whenever you want to start/stop a watcher or do other modifications to an
		3776	event loop, you will now have to lock:
		3777
		3778	ev_timer timeout_watcher;
		3779	userdata *u = ev_userdata (EV_A);
		3780
		3781	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3782
		3783	pthread_mutex_lock (&u->lock);
		3784	ev_timer_start (EV_A_ &timeout_watcher);
		3785	ev_async_send (EV_A_ &u->async_w);
		3786	pthread_mutex_unlock (&u->lock);
		3787
		3788	Note that sending the C<ev_async> watcher is required because otherwise
		3789	an event loop currently blocking in the kernel will have no knowledge
		3790	about the newly added timer. By waking up the loop it will pick up any new
		3791	watchers in the next event loop iteration.
		3792
		3793	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3794
		3795	While the overhead of a callback that e.g. schedules a thread is small, it
		3796	is still an overhead. If you embed libev, and your main usage is with some
		3797	kind of threads or coroutines, you might want to customise libev so that
		3798	doesn't need callbacks anymore.
		3799
		3800	Imagine you have coroutines that you can switch to using a function
		3801	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3802	and that due to some magic, the currently active coroutine is stored in a
		3803	global called C<current_coro>. Then you can build your own "wait for libev
		3804	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3805	the differing C<;> conventions):
		3806
		3807	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3808	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3809
		3810	That means instead of having a C callback function, you store the
		3811	coroutine to switch to in each watcher, and instead of having libev call
		3812	your callback, you instead have it switch to that coroutine.
		3813
		3814	A coroutine might now wait for an event with a function called
		3815	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3816	matter when, or whether the watcher is active or not when this function is
		3817	called):
		3818
		3819	void
		3820	wait_for_event (ev_watcher *w)
		3821	{
		3822	ev_cb_set (w) = current_coro;
		3823	switch_to (libev_coro);
		3824	}
		3825
		3826	That basically suspends the coroutine inside C<wait_for_event> and
		3827	continues the libev coroutine, which, when appropriate, switches back to
		3828	this or any other coroutine.
		3829
		3830	You can do similar tricks if you have, say, threads with an event queue -
		3831	instead of storing a coroutine, you store the queue object and instead of
		3832	switching to a coroutine, you push the watcher onto the queue and notify
		3833	any waiters.
		3834
		3835	To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two
		3836	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3837
		3838	// my_ev.h
		3839	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3840	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3841	#include "../libev/ev.h"
		3842
		3843	// my_ev.c
		3844	#define EV_H "my_ev.h"
		3845	#include "../libev/ev.c"
		3846
		3847	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3848	F<my_ev.c> into your project. When properly specifying include paths, you
		3849	can even use F<ev.h> as header file name directly.
3176		3850
3177		3851
3178	=head1 LIBEVENT EMULATION	3852	=head1 LIBEVENT EMULATION
3179		3853
3180	Libev offers a compatibility emulation layer for libevent. It cannot	3854	Libev offers a compatibility emulation layer for libevent. It cannot
3181	emulate the internals of libevent, so here are some usage hints:	3855	emulate the internals of libevent, so here are some usage hints:
3182		3856
3183	=over 4	3857	=over 4
		3858
		3859	=item * Only the libevent-1.4.1-beta API is being emulated.
		3860
		3861	This was the newest libevent version available when libev was implemented,
		3862	and is still mostly unchanged in 2010.
3184		3863
3185	=item * Use it by including <event.h>, as usual.	3864	=item * Use it by including <event.h>, as usual.
3186		3865
3187	=item * The following members are fully supported: ev_base, ev_callback,	3866	=item * The following members are fully supported: ev_base, ev_callback,
3188	ev_arg, ev_fd, ev_res, ev_events.	3867	ev_arg, ev_fd, ev_res, ev_events.
…		…
3194	=item * Priorities are not currently supported. Initialising priorities	3873	=item * Priorities are not currently supported. Initialising priorities
3195	will fail and all watchers will have the same priority, even though there	3874	will fail and all watchers will have the same priority, even though there
3196	is an ev_pri field.	3875	is an ev_pri field.
3197		3876
3198	=item * In libevent, the last base created gets the signals, in libev, the	3877	=item * In libevent, the last base created gets the signals, in libev, the
3199	first base created (== the default loop) gets the signals.	3878	base that registered the signal gets the signals.
3200		3879
3201	=item * Other members are not supported.	3880	=item * Other members are not supported.
3202		3881
3203	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3882	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3204	to use the libev header file and library.	3883	to use the libev header file and library.
…		…
3223	Care has been taken to keep the overhead low. The only data member the C++	3902	Care has been taken to keep the overhead low. The only data member the C++
3224	classes add (compared to plain C-style watchers) is the event loop pointer	3903	classes add (compared to plain C-style watchers) is the event loop pointer
3225	that the watcher is associated with (or no additional members at all if	3904	that the watcher is associated with (or no additional members at all if
3226	you disable C<EV_MULTIPLICITY> when embedding libev).	3905	you disable C<EV_MULTIPLICITY> when embedding libev).
3227		3906
3228	Currently, functions, and static and non-static member functions can be	3907	Currently, functions, static and non-static member functions and classes
3229	used as callbacks. Other types should be easy to add as long as they only	3908	with C<operator ()> can be used as callbacks. Other types should be easy
3230	need one additional pointer for context. If you need support for other	3909	to add as long as they only need one additional pointer for context. If
3231	types of functors please contact the author (preferably after implementing	3910	you need support for other types of functors please contact the author
3232	it).	3911	(preferably after implementing it).
3233		3912
3234	Here is a list of things available in the C<ev> namespace:	3913	Here is a list of things available in the C<ev> namespace:
3235		3914
3236	=over 4	3915	=over 4
3237		3916
…		…
3247	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	3926	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3248		3927
3249	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	3928	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
3250	the same name in the C<ev> namespace, with the exception of C<ev_signal>	3929	the same name in the C<ev> namespace, with the exception of C<ev_signal>
3251	which is called C<ev::sig> to avoid clashes with the C<signal> macro	3930	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3252	defines by many implementations.	3931	defined by many implementations.
3253		3932
3254	All of those classes have these methods:	3933	All of those classes have these methods:
3255		3934
3256	=over 4	3935	=over 4
3257		3936
…		…
3298	myclass obj;	3977	myclass obj;
3299	ev::io iow;	3978	ev::io iow;
3300	iow.set <myclass, &myclass::io_cb> (&obj);	3979	iow.set <myclass, &myclass::io_cb> (&obj);
3301		3980
3302	=item w->set (object *)	3981	=item w->set (object *)
3303
3304	This is an B<experimental> feature that might go away in a future version.
3305		3982
3306	This is a variation of a method callback - leaving out the method to call	3983	This is a variation of a method callback - leaving out the method to call
3307	will default the method to C<operator ()>, which makes it possible to use	3984	will default the method to C<operator ()>, which makes it possible to use
3308	functor objects without having to manually specify the C<operator ()> all	3985	functor objects without having to manually specify the C<operator ()> all
3309	the time. Incidentally, you can then also leave out the template argument	3986	the time. Incidentally, you can then also leave out the template argument
…		…
3349	Associates a different C<struct ev_loop> with this watcher. You can only	4026	Associates a different C<struct ev_loop> with this watcher. You can only
3350	do this when the watcher is inactive (and not pending either).	4027	do this when the watcher is inactive (and not pending either).
3351		4028
3352	=item w->set ([arguments])	4029	=item w->set ([arguments])
3353		4030
3354	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	4031	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
3355	called at least once. Unlike the C counterpart, an active watcher gets	4032	method or a suitable start method must be called at least once. Unlike the
3356	automatically stopped and restarted when reconfiguring it with this	4033	C counterpart, an active watcher gets automatically stopped and restarted
3357	method.	4034	when reconfiguring it with this method.
3358		4035
3359	=item w->start ()	4036	=item w->start ()
3360		4037
3361	Starts the watcher. Note that there is no C<loop> argument, as the	4038	Starts the watcher. Note that there is no C<loop> argument, as the
3362	constructor already stores the event loop.	4039	constructor already stores the event loop.
3363		4040
		4041	=item w->start ([arguments])
		4042
		4043	Instead of calling C<set> and C<start> methods separately, it is often
		4044	convenient to wrap them in one call. Uses the same type of arguments as
		4045	the configure C<set> method of the watcher.
		4046
3364	=item w->stop ()	4047	=item w->stop ()
3365		4048
3366	Stops the watcher if it is active. Again, no C<loop> argument.	4049	Stops the watcher if it is active. Again, no C<loop> argument.
3367		4050
3368	=item w->again () (C<ev::timer>, C<ev::periodic> only)	4051	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3380		4063
3381	=back	4064	=back
3382		4065
3383	=back	4066	=back
3384		4067
3385	Example: Define a class with an IO and idle watcher, start one of them in	4068	Example: Define a class with two I/O and idle watchers, start the I/O
3386	the constructor.	4069	watchers in the constructor.
3387		4070
3388	class myclass	4071	class myclass
3389	{	4072	{
3390	ev::io io ; void io_cb (ev::io &w, int revents);	4073	ev::io io ; void io_cb (ev::io &w, int revents);
		4074	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3391	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4075	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3392		4076
3393	myclass (int fd)	4077	myclass (int fd)
3394	{	4078	{
3395	io .set <myclass, &myclass::io_cb > (this);	4079	io .set <myclass, &myclass::io_cb > (this);
		4080	io2 .set <myclass, &myclass::io2_cb > (this);
3396	idle.set <myclass, &myclass::idle_cb> (this);	4081	idle.set <myclass, &myclass::idle_cb> (this);
3397		4082
3398	io.start (fd, ev::READ);	4083	io.set (fd, ev::WRITE); // configure the watcher
		4084	io.start (); // start it whenever convenient
		4085
		4086	io2.start (fd, ev::READ); // set + start in one call
3399	}	4087	}
3400	};	4088	};
3401		4089
3402		4090
3403	=head1 OTHER LANGUAGE BINDINGS	4091	=head1 OTHER LANGUAGE BINDINGS
…		…
3442	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4130	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3443		4131
3444	=item D	4132	=item D
3445		4133
3446	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4134	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3447	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4135	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3448		4136
3449	=item Ocaml	4137	=item Ocaml
3450		4138
3451	Erkki Seppala has written Ocaml bindings for libev, to be found at	4139	Erkki Seppala has written Ocaml bindings for libev, to be found at
3452	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4140	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
…		…
3477	loop argument"). The C<EV_A> form is used when this is the sole argument,	4165	loop argument"). The C<EV_A> form is used when this is the sole argument,
3478	C<EV_A_> is used when other arguments are following. Example:	4166	C<EV_A_> is used when other arguments are following. Example:
3479		4167
3480	ev_unref (EV_A);	4168	ev_unref (EV_A);
3481	ev_timer_add (EV_A_ watcher);	4169	ev_timer_add (EV_A_ watcher);
3482	ev_loop (EV_A_ 0);	4170	ev_run (EV_A_ 0);
3483		4171
3484	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4172	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3485	which is often provided by the following macro.	4173	which is often provided by the following macro.
3486		4174
3487	=item C<EV_P>, C<EV_P_>	4175	=item C<EV_P>, C<EV_P_>
…		…
3500	suitable for use with C<EV_A>.	4188	suitable for use with C<EV_A>.
3501		4189
3502	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4190	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3503		4191
3504	Similar to the other two macros, this gives you the value of the default	4192	Similar to the other two macros, this gives you the value of the default
3505	loop, if multiple loops are supported ("ev loop default").	4193	loop, if multiple loops are supported ("ev loop default"). The default loop
		4194	will be initialised if it isn't already initialised.
		4195
		4196	For non-multiplicity builds, these macros do nothing, so you always have
		4197	to initialise the loop somewhere.
3506		4198
3507	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4199	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3508		4200
3509	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4201	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3510	default loop has been initialised (C<UC> == unchecked). Their behaviour	4202	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3527	}	4219	}
3528		4220
3529	ev_check check;	4221	ev_check check;
3530	ev_check_init (&check, check_cb);	4222	ev_check_init (&check, check_cb);
3531	ev_check_start (EV_DEFAULT_ &check);	4223	ev_check_start (EV_DEFAULT_ &check);
3532	ev_loop (EV_DEFAULT_ 0);	4224	ev_run (EV_DEFAULT_ 0);
3533		4225
3534	=head1 EMBEDDING	4226	=head1 EMBEDDING
3535		4227
3536	Libev can (and often is) directly embedded into host	4228	Libev can (and often is) directly embedded into host
3537	applications. Examples of applications that embed it include the Deliantra	4229	applications. Examples of applications that embed it include the Deliantra
…		…
3622	define before including (or compiling) any of its files. The default in	4314	define before including (or compiling) any of its files. The default in
3623	the absence of autoconf is documented for every option.	4315	the absence of autoconf is documented for every option.
3624		4316
3625	Symbols marked with "(h)" do not change the ABI, and can have different	4317	Symbols marked with "(h)" do not change the ABI, and can have different
3626	values when compiling libev vs. including F<ev.h>, so it is permissible	4318	values when compiling libev vs. including F<ev.h>, so it is permissible
3627	to redefine them before including F<ev.h> without breakign compatibility	4319	to redefine them before including F<ev.h> without breaking compatibility
3628	to a compiled library. All other symbols change the ABI, which means all	4320	to a compiled library. All other symbols change the ABI, which means all
3629	users of libev and the libev code itself must be compiled with compatible	4321	users of libev and the libev code itself must be compiled with compatible
3630	settings.	4322	settings.
3631		4323
3632	=over 4	4324	=over 4
		4325
		4326	=item EV_COMPAT3 (h)
		4327
		4328	Backwards compatibility is a major concern for libev. This is why this
		4329	release of libev comes with wrappers for the functions and symbols that
		4330	have been renamed between libev version 3 and 4.
		4331
		4332	You can disable these wrappers (to test compatibility with future
		4333	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4334	sources. This has the additional advantage that you can drop the C<struct>
		4335	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4336	typedef in that case.
		4337
		4338	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4339	and in some even more future version the compatibility code will be
		4340	removed completely.
3633		4341
3634	=item EV_STANDALONE (h)	4342	=item EV_STANDALONE (h)
3635		4343
3636	Must always be C<1> if you do not use autoconf configuration, which	4344	Must always be C<1> if you do not use autoconf configuration, which
3637	keeps libev from including F<config.h>, and it also defines dummy	4345	keeps libev from including F<config.h>, and it also defines dummy
…		…
3639	supported). It will also not define any of the structs usually found in	4347	supported). It will also not define any of the structs usually found in
3640	F<event.h> that are not directly supported by the libev core alone.	4348	F<event.h> that are not directly supported by the libev core alone.
3641		4349
3642	In standalone mode, libev will still try to automatically deduce the	4350	In standalone mode, libev will still try to automatically deduce the
3643	configuration, but has to be more conservative.	4351	configuration, but has to be more conservative.
		4352
		4353	=item EV_USE_FLOOR
		4354
		4355	If defined to be C<1>, libev will use the C<floor ()> function for its
		4356	periodic reschedule calculations, otherwise libev will fall back on a
		4357	portable (slower) implementation. If you enable this, you usually have to
		4358	link against libm or something equivalent. Enabling this when the C<floor>
		4359	function is not available will fail, so the safe default is to not enable
		4360	this.
3644		4361
3645	=item EV_USE_MONOTONIC	4362	=item EV_USE_MONOTONIC
3646		4363
3647	If defined to be C<1>, libev will try to detect the availability of the	4364	If defined to be C<1>, libev will try to detect the availability of the
3648	monotonic clock option at both compile time and runtime. Otherwise no	4365	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3781	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4498	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3782		4499
3783	=item EV_ATOMIC_T	4500	=item EV_ATOMIC_T
3784		4501
3785	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4502	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3786	access is atomic with respect to other threads or signal contexts. No such	4503	access is atomic and serialised with respect to other threads or signal
3787	type is easily found in the C language, so you can provide your own type	4504	contexts. No such type is easily found in the C language, so you can
3788	that you know is safe for your purposes. It is used both for signal handler "locking"	4505	provide your own type that you know is safe for your purposes. It is used
3789	as well as for signal and thread safety in C<ev_async> watchers.	4506	both for signal handler "locking" as well as for signal and thread safety
		4507	in C<ev_async> watchers.
3790		4508
3791	In the absence of this define, libev will use C<sig_atomic_t volatile>	4509	In the absence of this define, libev will use C<sig_atomic_t volatile>
3792	(from F<signal.h>), which is usually good enough on most platforms.	4510	(from F<signal.h>), which is usually good enough on most platforms,
		4511	although strictly speaking using a type that also implies a memory fence
		4512	is required.
3793		4513
3794	=item EV_H (h)	4514	=item EV_H (h)
3795		4515
3796	The name of the F<ev.h> header file used to include it. The default if	4516	The name of the F<ev.h> header file used to include it. The default if
3797	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4517	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
…		…
3821	will have the C<struct ev_loop *> as first argument, and you can create	4541	will have the C<struct ev_loop *> as first argument, and you can create
3822	additional independent event loops. Otherwise there will be no support	4542	additional independent event loops. Otherwise there will be no support
3823	for multiple event loops and there is no first event loop pointer	4543	for multiple event loops and there is no first event loop pointer
3824	argument. Instead, all functions act on the single default loop.	4544	argument. Instead, all functions act on the single default loop.
3825		4545
		4546	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4547	default loop when multiplicity is switched off - you always have to
		4548	initialise the loop manually in this case.
		4549
3826	=item EV_MINPRI	4550	=item EV_MINPRI
3827		4551
3828	=item EV_MAXPRI	4552	=item EV_MAXPRI
3829		4553
3830	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4554	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3838	fine.	4562	fine.
3839		4563
3840	If your embedding application does not need any priorities, defining these	4564	If your embedding application does not need any priorities, defining these
3841	both to C<0> will save some memory and CPU.	4565	both to C<0> will save some memory and CPU.
3842		4566
3843	=item EV_PERIODIC_ENABLE	4567	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4568	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4569	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3844		4570
3845	If undefined or defined to be C<1>, then periodic timers are supported. If	4571	If undefined or defined to be C<1> (and the platform supports it), then
3846	defined to be C<0>, then they are not. Disabling them saves a few kB of	4572	the respective watcher type is supported. If defined to be C<0>, then it
3847	code.	4573	is not. Disabling watcher types mainly saves code size.
3848		4574
3849	=item EV_IDLE_ENABLE	4575	=item EV_FEATURES
3850
3851	If undefined or defined to be C<1>, then idle watchers are supported. If
3852	defined to be C<0>, then they are not. Disabling them saves a few kB of
3853	code.
3854
3855	=item EV_EMBED_ENABLE
3856
3857	If undefined or defined to be C<1>, then embed watchers are supported. If
3858	defined to be C<0>, then they are not. Embed watchers rely on most other
3859	watcher types, which therefore must not be disabled.
3860
3861	=item EV_STAT_ENABLE
3862
3863	If undefined or defined to be C<1>, then stat watchers are supported. If
3864	defined to be C<0>, then they are not.
3865
3866	=item EV_FORK_ENABLE
3867
3868	If undefined or defined to be C<1>, then fork watchers are supported. If
3869	defined to be C<0>, then they are not.
3870
3871	=item EV_SIGNAL_ENABLE
3872
3873	If undefined or defined to be C<1>, then signal watchers are supported. If
3874	defined to be C<0>, then they are not.
3875
3876	=item EV_ASYNC_ENABLE
3877
3878	If undefined or defined to be C<1>, then async watchers are supported. If
3879	defined to be C<0>, then they are not.
3880
3881	=item EV_CHILD_ENABLE
3882
3883	If undefined or defined to be C<1> (and C<_WIN32> is not defined), then
3884	child watchers are supported. If defined to be C<0>, then they are not.
3885
3886	=item EV_MINIMAL
3887		4576
3888	If you need to shave off some kilobytes of code at the expense of some	4577	If you need to shave off some kilobytes of code at the expense of some
3889	speed (but with the full API), define this symbol to C<1>. Currently this	4578	speed (but with the full API), you can define this symbol to request
3890	is used to override some inlining decisions, saves roughly 30% code size	4579	certain subsets of functionality. The default is to enable all features
3891	on amd64. It also selects a much smaller 2-heap for timer management over	4580	that can be enabled on the platform.
3892	the default 4-heap.
3893		4581
3894	You can save even more by disabling watcher types you do not need	4582	A typical way to use this symbol is to define it to C<0> (or to a bitset
3895	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>	4583	with some broad features you want) and then selectively re-enable
3896	(C<-DNDEBUG>) will usually reduce code size a lot. Disabling inotify,	4584	additional parts you want, for example if you want everything minimal,
3897	eventfd and signalfd will further help, and disabling backends one doesn't	4585	but multiple event loop support, async and child watchers and the poll
3898	need (e.g. poll, epoll, kqueue, ports) will help further.	4586	backend, use this:
3899		4587
3900	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to	4588	#define EV_FEATURES 0
3901	provide a bare-bones event library. See C<ev.h> for details on what parts
3902	of the API are still available, and do not complain if this subset changes
3903	over time.
3904
3905	This example set of settings reduces the compiled size of libev from 24Kb
3906	to 8Kb on my GNU/Linux amd64 system (and leaves little in - there is also
3907	an effect on the amount of memory used). With an intelligent-enough linker
3908	further unused functions might be left out as well automatically.
3909
3910	// tuning and API changes
3911	#define EV_MINIMAL 2
3912	#define EV_MULTIPLICITY 0	4589	#define EV_MULTIPLICITY 1
3913	#define EV_MINPRI 0
3914	#define EV_MAXPRI 0
3915
3916	// OS-specific backends
3917	#define EV_USE_INOTIFY 0
3918	#define EV_USE_EVENTFD 0
3919	#define EV_USE_SIGNALFD 0
3920	#define EV_USE_REALTIME 0
3921	#define EV_USE_MONOTONIC 0
3922	#define EV_USE_CLOCK_SYSCALL 0
3923
3924	// disable all backends except select
3925	#define EV_USE_POLL 0	4590	#define EV_USE_POLL 1
3926	#define EV_USE_PORT 0
3927	#define EV_USE_KQUEUE 0
3928	#define EV_USE_EPOLL 0
3929
3930	// disable all watcher types that cna be disabled
3931	#define EV_STAT_ENABLE 0
3932	#define EV_PERIODIC_ENABLE 0
3933	#define EV_IDLE_ENABLE 0
3934	#define EV_FORK_ENABLE 0
3935	#define EV_SIGNAL_ENABLE 0
3936	#define EV_CHILD_ENABLE 0	4591	#define EV_CHILD_ENABLE 1
3937	#define EV_ASYNC_ENABLE 0	4592	#define EV_ASYNC_ENABLE 1
3938	#define EV_EMBED_ENABLE 0	4593
		4594	The actual value is a bitset, it can be a combination of the following
		4595	values:
		4596
		4597	=over 4
		4598
		4599	=item C<1> - faster/larger code
		4600
		4601	Use larger code to speed up some operations.
		4602
		4603	Currently this is used to override some inlining decisions (enlarging the
		4604	code size by roughly 30% on amd64).
		4605
		4606	When optimising for size, use of compiler flags such as C<-Os> with
		4607	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4608	assertions.
		4609
		4610	=item C<2> - faster/larger data structures
		4611
		4612	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4613	hash table sizes and so on. This will usually further increase code size
		4614	and can additionally have an effect on the size of data structures at
		4615	runtime.
		4616
		4617	=item C<4> - full API configuration
		4618
		4619	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4620	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4621
		4622	=item C<8> - full API
		4623
		4624	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4625	details on which parts of the API are still available without this
		4626	feature, and do not complain if this subset changes over time.
		4627
		4628	=item C<16> - enable all optional watcher types
		4629
		4630	Enables all optional watcher types. If you want to selectively enable
		4631	only some watcher types other than I/O and timers (e.g. prepare,
		4632	embed, async, child...) you can enable them manually by defining
		4633	C<EV_watchertype_ENABLE> to C<1> instead.
		4634
		4635	=item C<32> - enable all backends
		4636
		4637	This enables all backends - without this feature, you need to enable at
		4638	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4639
		4640	=item C<64> - enable OS-specific "helper" APIs
		4641
		4642	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4643	default.
		4644
		4645	=back
		4646
		4647	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4648	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4649	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4650	watchers, timers and monotonic clock support.
		4651
		4652	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4653	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4654	your program might be left out as well - a binary starting a timer and an
		4655	I/O watcher then might come out at only 5Kb.
		4656
		4657	=item EV_API_STATIC
		4658
		4659	If this symbol is defined (by default it is not), then all identifiers
		4660	will have static linkage. This means that libev will not export any
		4661	identifiers, and you cannot link against libev anymore. This can be useful
		4662	when you embed libev, only want to use libev functions in a single file,
		4663	and do not want its identifiers to be visible.
		4664
		4665	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4666	wants to use libev.
3939		4667
3940	=item EV_AVOID_STDIO	4668	=item EV_AVOID_STDIO
3941		4669
3942	If this is set to C<1> at compiletime, then libev will avoid using stdio	4670	If this is set to C<1> at compiletime, then libev will avoid using stdio
3943	functions (printf, scanf, perror etc.). This will increase the codesize	4671	functions (printf, scanf, perror etc.). This will increase the code size
3944	somewhat, but if your program doesn't otherwise depend on stdio and your	4672	somewhat, but if your program doesn't otherwise depend on stdio and your
3945	libc allows it, this avoids linking in the stdio library which is quite	4673	libc allows it, this avoids linking in the stdio library which is quite
3946	big.	4674	big.
3947		4675
3948	Note that error messages might become less precise when this option is	4676	Note that error messages might become less precise when this option is
…		…
3952		4680
3953	The highest supported signal number, +1 (or, the number of	4681	The highest supported signal number, +1 (or, the number of
3954	signals): Normally, libev tries to deduce the maximum number of signals	4682	signals): Normally, libev tries to deduce the maximum number of signals
3955	automatically, but sometimes this fails, in which case it can be	4683	automatically, but sometimes this fails, in which case it can be
3956	specified. Also, using a lower number than detected (C<32> should be	4684	specified. Also, using a lower number than detected (C<32> should be
3957	good for about any system in existance) can save some memory, as libev	4685	good for about any system in existence) can save some memory, as libev
3958	statically allocates some 12-24 bytes per signal number.	4686	statically allocates some 12-24 bytes per signal number.
3959		4687
3960	=item EV_PID_HASHSIZE	4688	=item EV_PID_HASHSIZE
3961		4689
3962	C<ev_child> watchers use a small hash table to distribute workload by	4690	C<ev_child> watchers use a small hash table to distribute workload by
3963	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4691	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3964	than enough. If you need to manage thousands of children you might want to	4692	usually more than enough. If you need to manage thousands of children you
3965	increase this value (I<must> be a power of two).	4693	might want to increase this value (I<must> be a power of two).
3966		4694
3967	=item EV_INOTIFY_HASHSIZE	4695	=item EV_INOTIFY_HASHSIZE
3968		4696
3969	C<ev_stat> watchers use a small hash table to distribute workload by	4697	C<ev_stat> watchers use a small hash table to distribute workload by
3970	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4698	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3971	usually more than enough. If you need to manage thousands of C<ev_stat>	4699	disabled), usually more than enough. If you need to manage thousands of
3972	watchers you might want to increase this value (I<must> be a power of	4700	C<ev_stat> watchers you might want to increase this value (I<must> be a
3973	two).	4701	power of two).
3974		4702
3975	=item EV_USE_4HEAP	4703	=item EV_USE_4HEAP
3976		4704
3977	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4705	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3978	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4706	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3979	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4707	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3980	faster performance with many (thousands) of watchers.	4708	faster performance with many (thousands) of watchers.
3981		4709
3982	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4710	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3983	(disabled).	4711	will be C<0>.
3984		4712
3985	=item EV_HEAP_CACHE_AT	4713	=item EV_HEAP_CACHE_AT
3986		4714
3987	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4715	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3988	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4716	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3989	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4717	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3990	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4718	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3991	but avoids random read accesses on heap changes. This improves performance	4719	but avoids random read accesses on heap changes. This improves performance
3992	noticeably with many (hundreds) of watchers.	4720	noticeably with many (hundreds) of watchers.
3993		4721
3994	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4722	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3995	(disabled).	4723	will be C<0>.
3996		4724
3997	=item EV_VERIFY	4725	=item EV_VERIFY
3998		4726
3999	Controls how much internal verification (see C<ev_loop_verify ()>) will	4727	Controls how much internal verification (see C<ev_verify ()>) will
4000	be done: If set to C<0>, no internal verification code will be compiled	4728	be done: If set to C<0>, no internal verification code will be compiled
4001	in. If set to C<1>, then verification code will be compiled in, but not	4729	in. If set to C<1>, then verification code will be compiled in, but not
4002	called. If set to C<2>, then the internal verification code will be	4730	called. If set to C<2>, then the internal verification code will be
4003	called once per loop, which can slow down libev. If set to C<3>, then the	4731	called once per loop, which can slow down libev. If set to C<3>, then the
4004	verification code will be called very frequently, which will slow down	4732	verification code will be called very frequently, which will slow down
4005	libev considerably.	4733	libev considerably.
4006		4734
4007	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4735	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
4008	C<0>.	4736	will be C<0>.
4009		4737
4010	=item EV_COMMON	4738	=item EV_COMMON
4011		4739
4012	By default, all watchers have a C<void *data> member. By redefining	4740	By default, all watchers have a C<void *data> member. By redefining
4013	this macro to a something else you can include more and other types of	4741	this macro to something else you can include more and other types of
4014	members. You have to define it each time you include one of the files,	4742	members. You have to define it each time you include one of the files,
4015	though, and it must be identical each time.	4743	though, and it must be identical each time.
4016		4744
4017	For example, the perl EV module uses something like this:	4745	For example, the perl EV module uses something like this:
4018		4746
…		…
4071	file.	4799	file.
4072		4800
4073	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4801	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
4074	that everybody includes and which overrides some configure choices:	4802	that everybody includes and which overrides some configure choices:
4075		4803
4076	#define EV_MINIMAL 1	4804	#define EV_FEATURES 8
4077	#define EV_USE_POLL 0	4805	#define EV_USE_SELECT 1
4078	#define EV_MULTIPLICITY 0
4079	#define EV_PERIODIC_ENABLE 0	4806	#define EV_PREPARE_ENABLE 1
		4807	#define EV_IDLE_ENABLE 1
4080	#define EV_STAT_ENABLE 0	4808	#define EV_SIGNAL_ENABLE 1
4081	#define EV_FORK_ENABLE 0	4809	#define EV_CHILD_ENABLE 1
		4810	#define EV_USE_STDEXCEPT 0
4082	#define EV_CONFIG_H <config.h>	4811	#define EV_CONFIG_H <config.h>
4083	#define EV_MINPRI 0
4084	#define EV_MAXPRI 0
4085		4812
4086	#include "ev++.h"	4813	#include "ev++.h"
4087		4814
4088	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4815	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4089		4816
4090	#include "ev_cpp.h"	4817	#include "ev_cpp.h"
4091	#include "ev.c"	4818	#include "ev.c"
4092		4819
4093	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4820	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4094		4821
4095	=head2 THREADS AND COROUTINES	4822	=head2 THREADS AND COROUTINES
4096		4823
4097	=head3 THREADS	4824	=head3 THREADS
4098		4825
…		…
4149	default loop and triggering an C<ev_async> watcher from the default loop	4876	default loop and triggering an C<ev_async> watcher from the default loop
4150	watcher callback into the event loop interested in the signal.	4877	watcher callback into the event loop interested in the signal.
4151		4878
4152	=back	4879	=back
4153		4880
4154	=head4 THREAD LOCKING EXAMPLE	4881	See also L<THREAD LOCKING EXAMPLE>.
4155
4156	Here is a fictitious example of how to run an event loop in a different
4157	thread than where callbacks are being invoked and watchers are
4158	created/added/removed.
4159
4160	For a real-world example, see the C<EV::Loop::Async> perl module,
4161	which uses exactly this technique (which is suited for many high-level
4162	languages).
4163
4164	The example uses a pthread mutex to protect the loop data, a condition
4165	variable to wait for callback invocations, an async watcher to notify the
4166	event loop thread and an unspecified mechanism to wake up the main thread.
4167
4168	First, you need to associate some data with the event loop:
4169
4170	typedef struct {
4171	mutex_t lock; /* global loop lock */
4172	ev_async async_w;
4173	thread_t tid;
4174	cond_t invoke_cv;
4175	} userdata;
4176
4177	void prepare_loop (EV_P)
4178	{
4179	// for simplicity, we use a static userdata struct.
4180	static userdata u;
4181
4182	ev_async_init (&u->async_w, async_cb);
4183	ev_async_start (EV_A_ &u->async_w);
4184
4185	pthread_mutex_init (&u->lock, 0);
4186	pthread_cond_init (&u->invoke_cv, 0);
4187
4188	// now associate this with the loop
4189	ev_set_userdata (EV_A_ u);
4190	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4191	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4192
4193	// then create the thread running ev_loop
4194	pthread_create (&u->tid, 0, l_run, EV_A);
4195	}
4196
4197	The callback for the C<ev_async> watcher does nothing: the watcher is used
4198	solely to wake up the event loop so it takes notice of any new watchers
4199	that might have been added:
4200
4201	static void
4202	async_cb (EV_P_ ev_async *w, int revents)
4203	{
4204	// just used for the side effects
4205	}
4206
4207	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4208	protecting the loop data, respectively.
4209
4210	static void
4211	l_release (EV_P)
4212	{
4213	userdata *u = ev_userdata (EV_A);
4214	pthread_mutex_unlock (&u->lock);
4215	}
4216
4217	static void
4218	l_acquire (EV_P)
4219	{
4220	userdata *u = ev_userdata (EV_A);
4221	pthread_mutex_lock (&u->lock);
4222	}
4223
4224	The event loop thread first acquires the mutex, and then jumps straight
4225	into C<ev_loop>:
4226
4227	void *
4228	l_run (void *thr_arg)
4229	{
4230	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4231
4232	l_acquire (EV_A);
4233	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4234	ev_loop (EV_A_ 0);
4235	l_release (EV_A);
4236
4237	return 0;
4238	}
4239
4240	Instead of invoking all pending watchers, the C<l_invoke> callback will
4241	signal the main thread via some unspecified mechanism (signals? pipe
4242	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4243	have been called (in a while loop because a) spurious wakeups are possible
4244	and b) skipping inter-thread-communication when there are no pending
4245	watchers is very beneficial):
4246
4247	static void
4248	l_invoke (EV_P)
4249	{
4250	userdata *u = ev_userdata (EV_A);
4251
4252	while (ev_pending_count (EV_A))
4253	{
4254	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4255	pthread_cond_wait (&u->invoke_cv, &u->lock);
4256	}
4257	}
4258
4259	Now, whenever the main thread gets told to invoke pending watchers, it
4260	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4261	thread to continue:
4262
4263	static void
4264	real_invoke_pending (EV_P)
4265	{
4266	userdata *u = ev_userdata (EV_A);
4267
4268	pthread_mutex_lock (&u->lock);
4269	ev_invoke_pending (EV_A);
4270	pthread_cond_signal (&u->invoke_cv);
4271	pthread_mutex_unlock (&u->lock);
4272	}
4273
4274	Whenever you want to start/stop a watcher or do other modifications to an
4275	event loop, you will now have to lock:
4276
4277	ev_timer timeout_watcher;
4278	userdata *u = ev_userdata (EV_A);
4279
4280	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4281
4282	pthread_mutex_lock (&u->lock);
4283	ev_timer_start (EV_A_ &timeout_watcher);
4284	ev_async_send (EV_A_ &u->async_w);
4285	pthread_mutex_unlock (&u->lock);
4286
4287	Note that sending the C<ev_async> watcher is required because otherwise
4288	an event loop currently blocking in the kernel will have no knowledge
4289	about the newly added timer. By waking up the loop it will pick up any new
4290	watchers in the next event loop iteration.
4291		4882
4292	=head3 COROUTINES	4883	=head3 COROUTINES
4293		4884
4294	Libev is very accommodating to coroutines ("cooperative threads"):	4885	Libev is very accommodating to coroutines ("cooperative threads"):
4295	libev fully supports nesting calls to its functions from different	4886	libev fully supports nesting calls to its functions from different
4296	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4887	coroutines (e.g. you can call C<ev_run> on the same loop from two
4297	different coroutines, and switch freely between both coroutines running	4888	different coroutines, and switch freely between both coroutines running
4298	the loop, as long as you don't confuse yourself). The only exception is	4889	the loop, as long as you don't confuse yourself). The only exception is
4299	that you must not do this from C<ev_periodic> reschedule callbacks.	4890	that you must not do this from C<ev_periodic> reschedule callbacks.
4300		4891
4301	Care has been taken to ensure that libev does not keep local state inside	4892	Care has been taken to ensure that libev does not keep local state inside
4302	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4893	C<ev_run>, and other calls do not usually allow for coroutine switches as
4303	they do not call any callbacks.	4894	they do not call any callbacks.
4304		4895
4305	=head2 COMPILER WARNINGS	4896	=head2 COMPILER WARNINGS
4306		4897
4307	Depending on your compiler and compiler settings, you might get no or a	4898	Depending on your compiler and compiler settings, you might get no or a
…		…
4318	maintainable.	4909	maintainable.
4319		4910
4320	And of course, some compiler warnings are just plain stupid, or simply	4911	And of course, some compiler warnings are just plain stupid, or simply
4321	wrong (because they don't actually warn about the condition their message	4912	wrong (because they don't actually warn about the condition their message
4322	seems to warn about). For example, certain older gcc versions had some	4913	seems to warn about). For example, certain older gcc versions had some
4323	warnings that resulted an extreme number of false positives. These have	4914	warnings that resulted in an extreme number of false positives. These have
4324	been fixed, but some people still insist on making code warn-free with	4915	been fixed, but some people still insist on making code warn-free with
4325	such buggy versions.	4916	such buggy versions.
4326		4917
4327	While libev is written to generate as few warnings as possible,	4918	While libev is written to generate as few warnings as possible,
4328	"warn-free" code is not a goal, and it is recommended not to build libev	4919	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
4364	I suggest using suppression lists.	4955	I suggest using suppression lists.
4365		4956
4366		4957
4367	=head1 PORTABILITY NOTES	4958	=head1 PORTABILITY NOTES
4368		4959
		4960	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4961
		4962	GNU/Linux is the only common platform that supports 64 bit file/large file
		4963	interfaces but I<disables> them by default.
		4964
		4965	That means that libev compiled in the default environment doesn't support
		4966	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4967
		4968	Unfortunately, many programs try to work around this GNU/Linux issue
		4969	by enabling the large file API, which makes them incompatible with the
		4970	standard libev compiled for their system.
		4971
		4972	Likewise, libev cannot enable the large file API itself as this would
		4973	suddenly make it incompatible to the default compile time environment,
		4974	i.e. all programs not using special compile switches.
		4975
		4976	=head2 OS/X AND DARWIN BUGS
		4977
		4978	The whole thing is a bug if you ask me - basically any system interface
		4979	you touch is broken, whether it is locales, poll, kqueue or even the
		4980	OpenGL drivers.
		4981
		4982	=head3 C<kqueue> is buggy
		4983
		4984	The kqueue syscall is broken in all known versions - most versions support
		4985	only sockets, many support pipes.
		4986
		4987	Libev tries to work around this by not using C<kqueue> by default on this
		4988	rotten platform, but of course you can still ask for it when creating a
		4989	loop - embedding a socket-only kqueue loop into a select-based one is
		4990	probably going to work well.
		4991
		4992	=head3 C<poll> is buggy
		4993
		4994	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4995	implementation by something calling C<kqueue> internally around the 10.5.6
		4996	release, so now C<kqueue> I<and> C<poll> are broken.
		4997
		4998	Libev tries to work around this by not using C<poll> by default on
		4999	this rotten platform, but of course you can still ask for it when creating
		5000	a loop.
		5001
		5002	=head3 C<select> is buggy
		5003
		5004	All that's left is C<select>, and of course Apple found a way to fuck this
		5005	one up as well: On OS/X, C<select> actively limits the number of file
		5006	descriptors you can pass in to 1024 - your program suddenly crashes when
		5007	you use more.
		5008
		5009	There is an undocumented "workaround" for this - defining
		5010	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		5011	work on OS/X.
		5012
		5013	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		5014
		5015	=head3 C<errno> reentrancy
		5016
		5017	The default compile environment on Solaris is unfortunately so
		5018	thread-unsafe that you can't even use components/libraries compiled
		5019	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		5020	defined by default. A valid, if stupid, implementation choice.
		5021
		5022	If you want to use libev in threaded environments you have to make sure
		5023	it's compiled with C<_REENTRANT> defined.
		5024
		5025	=head3 Event port backend
		5026
		5027	The scalable event interface for Solaris is called "event
		5028	ports". Unfortunately, this mechanism is very buggy in all major
		5029	releases. If you run into high CPU usage, your program freezes or you get
		5030	a large number of spurious wakeups, make sure you have all the relevant
		5031	and latest kernel patches applied. No, I don't know which ones, but there
		5032	are multiple ones to apply, and afterwards, event ports actually work
		5033	great.
		5034
		5035	If you can't get it to work, you can try running the program by setting
		5036	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		5037	C<select> backends.
		5038
		5039	=head2 AIX POLL BUG
		5040
		5041	AIX unfortunately has a broken C<poll.h> header. Libev works around
		5042	this by trying to avoid the poll backend altogether (i.e. it's not even
		5043	compiled in), which normally isn't a big problem as C<select> works fine
		5044	with large bitsets on AIX, and AIX is dead anyway.
		5045
4369	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5046	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		5047
		5048	=head3 General issues
4370		5049
4371	Win32 doesn't support any of the standards (e.g. POSIX) that libev	5050	Win32 doesn't support any of the standards (e.g. POSIX) that libev
4372	requires, and its I/O model is fundamentally incompatible with the POSIX	5051	requires, and its I/O model is fundamentally incompatible with the POSIX
4373	model. Libev still offers limited functionality on this platform in	5052	model. Libev still offers limited functionality on this platform in
4374	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5053	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4375	descriptors. This only applies when using Win32 natively, not when using	5054	descriptors. This only applies when using Win32 natively, not when using
4376	e.g. cygwin.	5055	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		5056	as every compiler comes with a slightly differently broken/incompatible
		5057	environment.
4377		5058
4378	Lifting these limitations would basically require the full	5059	Lifting these limitations would basically require the full
4379	re-implementation of the I/O system. If you are into these kinds of	5060	re-implementation of the I/O system. If you are into this kind of thing,
4380	things, then note that glib does exactly that for you in a very portable	5061	then note that glib does exactly that for you in a very portable way (note
4381	way (note also that glib is the slowest event library known to man).	5062	also that glib is the slowest event library known to man).
4382		5063
4383	There is no supported compilation method available on windows except	5064	There is no supported compilation method available on windows except
4384	embedding it into other applications.	5065	embedding it into other applications.
4385		5066
4386	Sensible signal handling is officially unsupported by Microsoft - libev	5067	Sensible signal handling is officially unsupported by Microsoft - libev
…		…
4414	you do I<not> compile the F<ev.c> or any other embedded source files!):	5095	you do I<not> compile the F<ev.c> or any other embedded source files!):
4415		5096
4416	#include "evwrap.h"	5097	#include "evwrap.h"
4417	#include "ev.c"	5098	#include "ev.c"
4418		5099
4419	=over 4
4420
4421	=item The winsocket select function	5100	=head3 The winsocket C<select> function
4422		5101
4423	The winsocket C<select> function doesn't follow POSIX in that it	5102	The winsocket C<select> function doesn't follow POSIX in that it
4424	requires socket I<handles> and not socket I<file descriptors> (it is	5103	requires socket I<handles> and not socket I<file descriptors> (it is
4425	also extremely buggy). This makes select very inefficient, and also	5104	also extremely buggy). This makes select very inefficient, and also
4426	requires a mapping from file descriptors to socket handles (the Microsoft	5105	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
4435	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	5114	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
4436		5115
4437	Note that winsockets handling of fd sets is O(n), so you can easily get a	5116	Note that winsockets handling of fd sets is O(n), so you can easily get a
4438	complexity in the O(n²) range when using win32.	5117	complexity in the O(n²) range when using win32.
4439		5118
4440	=item Limited number of file descriptors	5119	=head3 Limited number of file descriptors
4441		5120
4442	Windows has numerous arbitrary (and low) limits on things.	5121	Windows has numerous arbitrary (and low) limits on things.
4443		5122
4444	Early versions of winsocket's select only supported waiting for a maximum	5123	Early versions of winsocket's select only supported waiting for a maximum
4445	of C<64> handles (probably owning to the fact that all windows kernels	5124	of C<64> handles (probably owning to the fact that all windows kernels
…		…
4460	runtime libraries. This might get you to about C<512> or C<2048> sockets	5139	runtime libraries. This might get you to about C<512> or C<2048> sockets
4461	(depending on windows version and/or the phase of the moon). To get more,	5140	(depending on windows version and/or the phase of the moon). To get more,
4462	you need to wrap all I/O functions and provide your own fd management, but	5141	you need to wrap all I/O functions and provide your own fd management, but
4463	the cost of calling select (O(n²)) will likely make this unworkable.	5142	the cost of calling select (O(n²)) will likely make this unworkable.
4464		5143
4465	=back
4466
4467	=head2 PORTABILITY REQUIREMENTS	5144	=head2 PORTABILITY REQUIREMENTS
4468		5145
4469	In addition to a working ISO-C implementation and of course the	5146	In addition to a working ISO-C implementation and of course the
4470	backend-specific APIs, libev relies on a few additional extensions:	5147	backend-specific APIs, libev relies on a few additional extensions:
4471		5148
…		…
4477	Libev assumes not only that all watcher pointers have the same internal	5154	Libev assumes not only that all watcher pointers have the same internal
4478	structure (guaranteed by POSIX but not by ISO C for example), but it also	5155	structure (guaranteed by POSIX but not by ISO C for example), but it also
4479	assumes that the same (machine) code can be used to call any watcher	5156	assumes that the same (machine) code can be used to call any watcher
4480	callback: The watcher callbacks have different type signatures, but libev	5157	callback: The watcher callbacks have different type signatures, but libev
4481	calls them using an C<ev_watcher *> internally.	5158	calls them using an C<ev_watcher *> internally.
		5159
		5160	=item pointer accesses must be thread-atomic
		5161
		5162	Accessing a pointer value must be atomic, it must both be readable and
		5163	writable in one piece - this is the case on all current architectures.
4482		5164
4483	=item C<sig_atomic_t volatile> must be thread-atomic as well	5165	=item C<sig_atomic_t volatile> must be thread-atomic as well
4484		5166
4485	The type C<sig_atomic_t volatile> (or whatever is defined as	5167	The type C<sig_atomic_t volatile> (or whatever is defined as
4486	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5168	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
4509	watchers.	5191	watchers.
4510		5192
4511	=item C<double> must hold a time value in seconds with enough accuracy	5193	=item C<double> must hold a time value in seconds with enough accuracy
4512		5194
4513	The type C<double> is used to represent timestamps. It is required to	5195	The type C<double> is used to represent timestamps. It is required to
4514	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5196	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4515	enough for at least into the year 4000. This requirement is fulfilled by	5197	good enough for at least into the year 4000 with millisecond accuracy
		5198	(the design goal for libev). This requirement is overfulfilled by
4516	implementations implementing IEEE 754, which is basically all existing	5199	implementations using IEEE 754, which is basically all existing ones.
		5200
4517	ones. With IEEE 754 doubles, you get microsecond accuracy until at least	5201	With IEEE 754 doubles, you get microsecond accuracy until at least the
4518	2200.	5202	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5203	is either obsolete or somebody patched it to use C<long double> or
		5204	something like that, just kidding).
4519		5205
4520	=back	5206	=back
4521		5207
4522	If you know of other additional requirements drop me a note.	5208	If you know of other additional requirements drop me a note.
4523		5209
…		…
4585	=item Processing ev_async_send: O(number_of_async_watchers)	5271	=item Processing ev_async_send: O(number_of_async_watchers)
4586		5272
4587	=item Processing signals: O(max_signal_number)	5273	=item Processing signals: O(max_signal_number)
4588		5274
4589	Sending involves a system call I<iff> there were no other C<ev_async_send>	5275	Sending involves a system call I<iff> there were no other C<ev_async_send>
4590	calls in the current loop iteration. Checking for async and signal events	5276	calls in the current loop iteration and the loop is currently
		5277	blocked. Checking for async and signal events involves iterating over all
4591	involves iterating over all running async watchers or all signal numbers.	5278	running async watchers or all signal numbers.
4592		5279
4593	=back	5280	=back
4594		5281
4595		5282
		5283	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5284
		5285	The major version 4 introduced some incompatible changes to the API.
		5286
		5287	At the moment, the C<ev.h> header file provides compatibility definitions
		5288	for all changes, so most programs should still compile. The compatibility
		5289	layer might be removed in later versions of libev, so better update to the
		5290	new API early than late.
		5291
		5292	=over 4
		5293
		5294	=item C<EV_COMPAT3> backwards compatibility mechanism
		5295
		5296	The backward compatibility mechanism can be controlled by
		5297	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5298	section.
		5299
		5300	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5301
		5302	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5303
		5304	ev_loop_destroy (EV_DEFAULT_UC);
		5305	ev_loop_fork (EV_DEFAULT);
		5306
		5307	=item function/symbol renames
		5308
		5309	A number of functions and symbols have been renamed:
		5310
		5311	ev_loop => ev_run
		5312	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5313	EVLOOP_ONESHOT => EVRUN_ONCE
		5314
		5315	ev_unloop => ev_break
		5316	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5317	EVUNLOOP_ONE => EVBREAK_ONE
		5318	EVUNLOOP_ALL => EVBREAK_ALL
		5319
		5320	EV_TIMEOUT => EV_TIMER
		5321
		5322	ev_loop_count => ev_iteration
		5323	ev_loop_depth => ev_depth
		5324	ev_loop_verify => ev_verify
		5325
		5326	Most functions working on C<struct ev_loop> objects don't have an
		5327	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5328	associated constants have been renamed to not collide with the C<struct
		5329	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5330	as all other watcher types. Note that C<ev_loop_fork> is still called
		5331	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5332	typedef.
		5333
		5334	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5335
		5336	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5337	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5338	and work, but the library code will of course be larger.
		5339
		5340	=back
		5341
		5342
4596	=head1 GLOSSARY	5343	=head1 GLOSSARY
4597		5344
4598	=over 4	5345	=over 4
4599		5346
4600	=item active	5347	=item active
4601		5348
4602	A watcher is active as long as it has been started (has been attached to	5349	A watcher is active as long as it has been started and not yet stopped.
4603	an event loop) but not yet stopped (disassociated from the event loop).	5350	See L<WATCHER STATES> for details.
4604		5351
4605	=item application	5352	=item application
4606		5353
4607	In this document, an application is whatever is using libev.	5354	In this document, an application is whatever is using libev.
		5355
		5356	=item backend
		5357
		5358	The part of the code dealing with the operating system interfaces.
4608		5359
4609	=item callback	5360	=item callback
4610		5361
4611	The address of a function that is called when some event has been	5362	The address of a function that is called when some event has been
4612	detected. Callbacks are being passed the event loop, the watcher that	5363	detected. Callbacks are being passed the event loop, the watcher that
4613	received the event, and the actual event bitset.	5364	received the event, and the actual event bitset.
4614		5365
4615	=item callback invocation	5366	=item callback/watcher invocation
4616		5367
4617	The act of calling the callback associated with a watcher.	5368	The act of calling the callback associated with a watcher.
4618		5369
4619	=item event	5370	=item event
4620		5371
4621	A change of state of some external event, such as data now being available	5372	A change of state of some external event, such as data now being available
4622	for reading on a file descriptor, time having passed or simply not having	5373	for reading on a file descriptor, time having passed or simply not having
4623	any other events happening anymore.	5374	any other events happening anymore.
4624		5375
4625	In libev, events are represented as single bits (such as C<EV_READ> or	5376	In libev, events are represented as single bits (such as C<EV_READ> or
4626	C<EV_TIMEOUT>).	5377	C<EV_TIMER>).
4627		5378
4628	=item event library	5379	=item event library
4629		5380
4630	A software package implementing an event model and loop.	5381	A software package implementing an event model and loop.
4631		5382
…		…
4639	The model used to describe how an event loop handles and processes	5390	The model used to describe how an event loop handles and processes
4640	watchers and events.	5391	watchers and events.
4641		5392
4642	=item pending	5393	=item pending
4643		5394
4644	A watcher is pending as soon as the corresponding event has been detected,	5395	A watcher is pending as soon as the corresponding event has been
4645	and stops being pending as soon as the watcher will be invoked or its	5396	detected. See L<WATCHER STATES> for details.
4646	pending status is explicitly cleared by the application.
4647
4648	A watcher can be pending, but not active. Stopping a watcher also clears
4649	its pending status.
4650		5397
4651	=item real time	5398	=item real time
4652		5399
4653	The physical time that is observed. It is apparently strictly monotonic :)	5400	The physical time that is observed. It is apparently strictly monotonic :)
4654		5401
4655	=item wall-clock time	5402	=item wall-clock time
4656		5403
4657	The time and date as shown on clocks. Unlike real time, it can actually	5404	The time and date as shown on clocks. Unlike real time, it can actually
4658	be wrong and jump forwards and backwards, e.g. when the you adjust your	5405	be wrong and jump forwards and backwards, e.g. when you adjust your
4659	clock.	5406	clock.
4660		5407
4661	=item watcher	5408	=item watcher
4662		5409
4663	A data structure that describes interest in certain events. Watchers need	5410	A data structure that describes interest in certain events. Watchers need
4664	to be started (attached to an event loop) before they can receive events.	5411	to be started (attached to an event loop) before they can receive events.
4665		5412
4666	=item watcher invocation
4667
4668	The act of calling the callback associated with a watcher.
4669
4670	=back	5413	=back
4671		5414
4672	=head1 AUTHOR	5415	=head1 AUTHOR
4673		5416
4674	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5417	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5418	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4675		5419

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