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Revision 1.292 by sf-exg, Mon Mar 22 09:57:01 2010 UTC vs.
Revision 1.425 by root, Tue Jan 22 03:53:01 2013 UTC

…		…
26	puts ("stdin ready");	26	puts ("stdin ready");
27	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
28	// with its corresponding stop function.	28	// with its corresponding stop function.
29	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
30		30
31	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_run's to stop iterating
32	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_break (EV_A_ EVBREAK_ALL);
33	}	33	}
34		34
35	// another callback, this time for a time-out	35	// another callback, this time for a time-out
36	static void	36	static void
37	timeout_cb (EV_P_ ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
38	{	38	{
39	puts ("timeout");	39	puts ("timeout");
40	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_run to stop iterating
41	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_break (EV_A_ EVBREAK_ONE);
42	}	42	}
43		43
44	int	44	int
45	main (void)	45	main (void)
46	{	46	{
47	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
48	struct ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = EV_DEFAULT;
49		49
50	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
51	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
53	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
…		…
56	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
58	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
59		59
60	// now wait for events to arrive	60	// now wait for events to arrive
61	ev_loop (loop, 0);	61	ev_run (loop, 0);
62		62
63	// unloop was called, so exit	63	// break was called, so exit
64	return 0;	64	return 0;
65	}	65	}
66		66
67	=head1 ABOUT THIS DOCUMENT	67	=head1 ABOUT THIS DOCUMENT
68		68
…		…
75	While this document tries to be as complete as possible in documenting	75	While this document tries to be as complete as possible in documenting
76	libev, its usage and the rationale behind its design, it is not a tutorial	76	libev, its usage and the rationale behind its design, it is not a tutorial
77	on event-based programming, nor will it introduce event-based programming	77	on event-based programming, nor will it introduce event-based programming
78	with libev.	78	with libev.
79		79
80	Familarity with event based programming techniques in general is assumed	80	Familiarity with event based programming techniques in general is assumed
81	throughout this document.	81	throughout this document.
		82
		83	=head1 WHAT TO READ WHEN IN A HURRY
		84
		85	This manual tries to be very detailed, but unfortunately, this also makes
		86	it very long. If you just want to know the basics of libev, I suggest
		87	reading L</ANATOMY OF A WATCHER>, then the L</EXAMPLE PROGRAM> above and
		88	look up the missing functions in L</GLOBAL FUNCTIONS> and the C<ev_io> and
		89	C<ev_timer> sections in L</WATCHER TYPES>.
82		90
83	=head1 ABOUT LIBEV	91	=head1 ABOUT LIBEV
84		92
85	Libev is an event loop: you register interest in certain events (such as a	93	Libev is an event loop: you register interest in certain events (such as a
86	file descriptor being readable or a timeout occurring), and it will manage	94	file descriptor being readable or a timeout occurring), and it will manage
…		…
124	this argument.	132	this argument.
125		133
126	=head2 TIME REPRESENTATION	134	=head2 TIME REPRESENTATION
127		135
128	Libev represents time as a single floating point number, representing	136	Libev represents time as a single floating point number, representing
129	the (fractional) number of seconds since the (POSIX) epoch (somewhere	137	the (fractional) number of seconds since the (POSIX) epoch (in practice
130	near the beginning of 1970, details are complicated, don't ask). This	138	somewhere near the beginning of 1970, details are complicated, don't
131	type is called C<ev_tstamp>, which is what you should use too. It usually	139	ask). This type is called C<ev_tstamp>, which is what you should use
132	aliases to the C<double> type in C. When you need to do any calculations	140	too. It usually aliases to the C<double> type in C. When you need to do
133	on it, you should treat it as some floating point value. Unlike the name	141	any calculations on it, you should treat it as some floating point value.
		142
134	component C<stamp> might indicate, it is also used for time differences	143	Unlike the name component C<stamp> might indicate, it is also used for
135	throughout libev.	144	time differences (e.g. delays) throughout libev.
136		145
137	=head1 ERROR HANDLING	146	=head1 ERROR HANDLING
138		147
139	Libev knows three classes of errors: operating system errors, usage errors	148	Libev knows three classes of errors: operating system errors, usage errors
140	and internal errors (bugs).	149	and internal errors (bugs).
…		…
164		173
165	=item ev_tstamp ev_time ()	174	=item ev_tstamp ev_time ()
166		175
167	Returns the current time as libev would use it. Please note that the	176	Returns the current time as libev would use it. Please note that the
168	C<ev_now> function is usually faster and also often returns the timestamp	177	C<ev_now> function is usually faster and also often returns the timestamp
169	you actually want to know.	178	you actually want to know. Also interesting is the combination of
		179	C<ev_now_update> and C<ev_now>.
170		180
171	=item ev_sleep (ev_tstamp interval)	181	=item ev_sleep (ev_tstamp interval)
172		182
173	Sleep for the given interval: The current thread will be blocked until	183	Sleep for the given interval: The current thread will be blocked
174	either it is interrupted or the given time interval has passed. Basically	184	until either it is interrupted or the given time interval has
		185	passed (approximately - it might return a bit earlier even if not
		186	interrupted). Returns immediately if C<< interval <= 0 >>.
		187
175	this is a sub-second-resolution C<sleep ()>.	188	Basically this is a sub-second-resolution C<sleep ()>.
		189
		190	The range of the C<interval> is limited - libev only guarantees to work
		191	with sleep times of up to one day (C<< interval <= 86400 >>).
176		192
177	=item int ev_version_major ()	193	=item int ev_version_major ()
178		194
179	=item int ev_version_minor ()	195	=item int ev_version_minor ()
180		196
…		…
191	as this indicates an incompatible change. Minor versions are usually	207	as this indicates an incompatible change. Minor versions are usually
192	compatible to older versions, so a larger minor version alone is usually	208	compatible to older versions, so a larger minor version alone is usually
193	not a problem.	209	not a problem.
194		210
195	Example: Make sure we haven't accidentally been linked against the wrong	211	Example: Make sure we haven't accidentally been linked against the wrong
196	version.	212	version (note, however, that this will not detect other ABI mismatches,
		213	such as LFS or reentrancy).
197		214
198	assert (("libev version mismatch",	215	assert (("libev version mismatch",
199	ev_version_major () == EV_VERSION_MAJOR	216	ev_version_major () == EV_VERSION_MAJOR
200	&& ev_version_minor () >= EV_VERSION_MINOR));	217	&& ev_version_minor () >= EV_VERSION_MINOR));
201		218
…		…
212	assert (("sorry, no epoll, no sex",	229	assert (("sorry, no epoll, no sex",
213	ev_supported_backends () & EVBACKEND_EPOLL));	230	ev_supported_backends () & EVBACKEND_EPOLL));
214		231
215	=item unsigned int ev_recommended_backends ()	232	=item unsigned int ev_recommended_backends ()
216		233
217	Return the set of all backends compiled into this binary of libev and also	234	Return the set of all backends compiled into this binary of libev and
218	recommended for this platform. This set is often smaller than the one	235	also recommended for this platform, meaning it will work for most file
		236	descriptor types. This set is often smaller than the one returned by
219	returned by C<ev_supported_backends>, as for example kqueue is broken on	237	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
220	most BSDs and will not be auto-detected unless you explicitly request it	238	and will not be auto-detected unless you explicitly request it (assuming
221	(assuming you know what you are doing). This is the set of backends that	239	you know what you are doing). This is the set of backends that libev will
222	libev will probe for if you specify no backends explicitly.	240	probe for if you specify no backends explicitly.
223		241
224	=item unsigned int ev_embeddable_backends ()	242	=item unsigned int ev_embeddable_backends ()
225		243
226	Returns the set of backends that are embeddable in other event loops. This	244	Returns the set of backends that are embeddable in other event loops. This
227	is the theoretical, all-platform, value. To find which backends	245	value is platform-specific but can include backends not available on the
228	might be supported on the current system, you would need to look at	246	current system. To find which embeddable backends might be supported on
229	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	247	the current system, you would need to look at C<ev_embeddable_backends ()
230	recommended ones.	248	& ev_supported_backends ()>, likewise for recommended ones.
231		249
232	See the description of C<ev_embed> watchers for more info.	250	See the description of C<ev_embed> watchers for more info.
233		251
234	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	252	=item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())
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) throw ())
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:
…		…
365	environment variable.	421	environment variable.
366		422
367	=item C<EVFLAG_NOINOTIFY>	423	=item C<EVFLAG_NOINOTIFY>
368		424
369	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
370	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
371	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
372	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.
373		429
374	=item C<EVFLAG_SIGNALFD>	430	=item C<EVFLAG_SIGNALFD>
375		431
376	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
377	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
378	delivers signals synchronously, which makes it both faster and might make	434	delivers signals synchronously, which makes it both faster and might make
379	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
380	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
381	threads that are not interested in handling them.	437	threads that are not interested in handling them.
382		438
383	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
384	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
385	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.
386		457
387	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	458	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
388		459
389	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
390	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,
…		…
418	=item C<EVBACKEND_EPOLL> (value 4, Linux)	489	=item C<EVBACKEND_EPOLL> (value 4, Linux)
419		490
420	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
421	kernels).	492	kernels).
422		493
423	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
424	but it scales phenomenally better. While poll and select usually scale	495	it scales phenomenally better. While poll and select usually scale like
425	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
426	epoll scales either O(1) or O(active_fds).	497	fd), epoll scales either O(1) or O(active_fds).
427		498
428	The epoll mechanism deserves honorable mention as the most misdesigned	499	The epoll mechanism deserves honorable mention as the most misdesigned
429	of the more advanced event mechanisms: mere annoyances include silently	500	of the more advanced event mechanisms: mere annoyances include silently
430	dropping file descriptors, requiring a system call per change per file	501	dropping file descriptors, requiring a system call per change per file
431	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
432	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
433	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
434	take considerable time (one syscall per file descriptor) and is of course	507	set, which can take considerable time (one syscall per file descriptor)
435	hard to detect.	508	and is of course hard to detect.
436		509
437	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	510	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
438	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
439	I<different> file descriptors (even already closed ones, so one cannot	512	totally I<different> file descriptors (even already closed ones, so
440	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
441	on SMP systems). Libev tries to counter these spurious notifications by	514	(especially on SMP systems). Libev tries to counter these spurious
442	employing an additional generation counter and comparing that against the	515	notifications by employing an additional generation counter and comparing
443	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...
444		526
445	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
446	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
447	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
448	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
…		…
485		567
486	It scales in the same way as the epoll backend, but the interface to the	568	It scales in the same way as the epoll backend, but the interface to the
487	kernel is more efficient (which says nothing about its actual speed, of	569	kernel is more efficient (which says nothing about its actual speed, of
488	course). While stopping, setting and starting an I/O watcher does never	570	course). While stopping, setting and starting an I/O watcher does never
489	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	571	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
490	two event changes per incident. Support for C<fork ()> is very bad (but	572	two event changes per incident. Support for C<fork ()> is very bad (you
491	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect	573	might have to leak fd's on fork, but it's more sane than epoll) and it
492	cases	574	drops fds silently in similarly hard-to-detect cases.
493		575
494	This backend usually performs well under most conditions.	576	This backend usually performs well under most conditions.
495		577
496	While nominally embeddable in other event loops, this doesn't work	578	While nominally embeddable in other event loops, this doesn't work
497	everywhere, so you might need to test for this. And since it is broken	579	everywhere, so you might need to test for this. And since it is broken
…		…
514	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	596	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
515		597
516	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,
517	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)).
518		600
519	Please note that Solaris event ports can deliver a lot of spurious
520	notifications, so you need to use non-blocking I/O or other means to avoid
521	blocking when no data (or space) is available.
522
523	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
524	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
525	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	603	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
526	might perform better.	604	might perform better.
527		605
528	On the positive side, with the exception of the spurious readiness	606	On the positive side, this backend actually performed fully to
529	notifications, this backend actually performed fully to specification
530	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
531	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.
532		620
533	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
534	C<EVBACKEND_POLL>.	622	C<EVBACKEND_POLL>.
535		623
536	=item C<EVBACKEND_ALL>	624	=item C<EVBACKEND_ALL>
537		625
538	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
539	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
540	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	628	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
541		629
542	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).
543		639
544	=back	640	=back
545		641
546	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,
547	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
548	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
549	()> will be tried.	645	()> will be tried.
550		646
551	Example: This is the most typical usage.
552
553	if (!ev_default_loop (0))
554	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
555
556	Example: Restrict libev to the select and poll backends, and do not allow
557	environment settings to be taken into account:
558
559	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
560
561	Example: Use whatever libev has to offer, but make sure that kqueue is
562	used if available (warning, breaks stuff, best use only with your own
563	private event loop and only if you know the OS supports your types of
564	fds):
565
566	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
567
568	=item struct ev_loop *ev_loop_new (unsigned int flags)
569
570	Similar to C<ev_default_loop>, but always creates a new event loop that is
571	always distinct from the default loop.
572
573	Note that this function I<is> thread-safe, and one common way to use
574	libev with threads is indeed to create one loop per thread, and using the
575	default loop in the "main" or "initial" thread.
576
577	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.
578		648
579	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	649	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
580	if (!epoller)	650	if (!epoller)
581	fatal ("no epoll found here, maybe it hides under your chair");	651	fatal ("no epoll found here, maybe it hides under your chair");
582		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
583	=item ev_default_destroy ()	658	=item ev_loop_destroy (loop)
584		659
585	Destroys the default loop (frees all memory and kernel state etc.). None	660	Destroys an event loop object (frees all memory and kernel state
586	of the active event watchers will be stopped in the normal sense, so	661	etc.). None of the active event watchers will be stopped in the normal
587	e.g. C<ev_is_active> might still return true. It is your responsibility to	662	sense, so e.g. C<ev_is_active> might still return true. It is your
588	either stop all watchers cleanly yourself I<before> calling this function,	663	responsibility to either stop all watchers cleanly yourself I<before>
589	or cope with the fact afterwards (which is usually the easiest thing, you	664	calling this function, or cope with the fact afterwards (which is usually
590	can just ignore the watchers and/or C<free ()> them for example).	665	the easiest thing, you can just ignore the watchers and/or C<free ()> them
		666	for example).
591		667
592	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
593	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
594	as signal and child watchers) would need to be stopped manually.	670	as signal and child watchers) would need to be stopped manually.
595		671
596	In general it is not advisable to call this function except in the	672	This function is normally used on loop objects allocated by
597	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.
598	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>
599	C<ev_loop_new> and C<ev_loop_destroy>.	679	and C<ev_loop_destroy>.
600		680
601	=item ev_loop_destroy (loop)	681	=item ev_loop_fork (loop)
602		682
603	Like C<ev_default_destroy>, but destroys an event loop created by an
604	earlier call to C<ev_loop_new>.
605
606	=item ev_default_fork ()
607
608	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
609	to reinitialise the kernel state for backends that have one. Despite the	684	reinitialise the kernel state for backends that have one. Despite the
610	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
611	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
612	sense). You I<must> call it in the child before using any of the libev	687	child before resuming or calling C<ev_run>.
613	functions, and it will only take effect at the next C<ev_loop> iteration.
614		688
615	Again, you I<have> to call it on I<any> loop that you want to re-use after	689	Again, you I<have> to call it on I<any> loop that you want to re-use after
616	a fork, I<even if you do not plan to use the loop in the parent>. This is	690	a fork, I<even if you do not plan to use the loop in the parent>. This is
617	because some kernel interfaces *cough* I<kqueue> *cough* do funny things	691	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
618	during fork.	692	during fork.
619		693
620	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
621	process if and only if you want to use the event loop in the child. If you	695	process if and only if you want to use the event loop in the child. If
622	just fork+exec or create a new loop in the child, you don't have to call	696	you just fork+exec or create a new loop in the child, you don't have to
623	it at all.	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).
624		700
625	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
626	it just in case after a fork. To make this easy, the function will fit in	702	it just in case after a fork.
627	quite nicely into a call to C<pthread_atfork>:
628		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	...
629	pthread_atfork (0, 0, ev_default_fork);	714	pthread_atfork (0, 0, post_fork_child);
630
631	=item ev_loop_fork (loop)
632
633	Like C<ev_default_fork>, but acts on an event loop created by
634	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
635	after fork that you want to re-use in the child, and how you keep track of
636	them is entirely your own problem.
637		715
638	=item int ev_is_default_loop (loop)	716	=item int ev_is_default_loop (loop)
639		717
640	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
641	otherwise.	719	otherwise.
642		720
643	=item unsigned int ev_iteration (loop)	721	=item unsigned int ev_iteration (loop)
644		722
645	Returns the current iteration count for the loop, which is identical to	723	Returns the current iteration count for the event loop, which is identical
646	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>
647	happily wraps around with enough iterations.	725	and happily wraps around with enough iterations.
648		726
649	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
650	"ticks" the number of loop iterations), as it roughly corresponds with	728	"ticks" the number of loop iterations), as it roughly corresponds with
651	C<ev_prepare> and C<ev_check> calls - and is incremented between the	729	C<ev_prepare> and C<ev_check> calls - and is incremented between the
652	prepare and check phases.	730	prepare and check phases.
653		731
654	=item unsigned int ev_depth (loop)	732	=item unsigned int ev_depth (loop)
655		733
656	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
657	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.
658		736
659	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
660	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),
661	in which case it is higher.	739	in which case it is higher.
662		740
663	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread	741	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
664	etc.), doesn't count as "exit" - consider this as a hint to avoid such	742	throwing an exception etc.), doesn't count as "exit" - consider this
665	ungentleman behaviour unless it's really convenient.	743	as a hint to avoid such ungentleman-like behaviour unless it's really
		744	convenient, in which case it is fully supported.
666		745
667	=item unsigned int ev_backend (loop)	746	=item unsigned int ev_backend (loop)
668		747
669	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
670	use.	749	use.
…		…
679		758
680	=item ev_now_update (loop)	759	=item ev_now_update (loop)
681		760
682	Establishes the current time by querying the kernel, updating the time	761	Establishes the current time by querying the kernel, updating the time
683	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
684	is usually done automatically within C<ev_loop ()>.	763	is usually done automatically within C<ev_run ()>.
685		764
686	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
687	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
688	the current time is a good idea.	767	the current time is a good idea.
689		768
690	See also L<The special problem of time updates> in the C<ev_timer> section.	769	See also L</The special problem of time updates> in the C<ev_timer> section.
691		770
692	=item ev_suspend (loop)	771	=item ev_suspend (loop)
693		772
694	=item ev_resume (loop)	773	=item ev_resume (loop)
695		774
696	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
697	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.
698		777
699	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
700	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
701	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
702	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>
…		…
704	C<ev_resume> directly afterwards to resume timer processing.	783	C<ev_resume> directly afterwards to resume timer processing.
705		784
706	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
707	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
708	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
709	occured while suspended).	788	occurred while suspended).
710		789
711	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
712	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>
713	without a previous call to C<ev_suspend>.	792	without a previous call to C<ev_suspend>.
714		793
715	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
716	event loop time (see C<ev_now_update>).	795	event loop time (see C<ev_now_update>).
717		796
718	=item ev_loop (loop, int flags)	797	=item bool ev_run (loop, int flags)
719		798
720	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
721	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
722	handling events.	801	handling events. It will ask the operating system for any new events, call
		802	the watcher callbacks, and then repeat the whole process indefinitely: This
		803	is why event loops are called I<loops>.
723		804
724	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
725	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.
726		808
		809	The return value is false if there are no more active watchers (which
		810	usually means "all jobs done" or "deadlock"), and true in all other cases
		811	(which usually means " you should call C<ev_run> again").
		812
727	Please note that an explicit C<ev_unloop> is usually better than	813	Please note that an explicit C<ev_break> is usually better than
728	relying on all watchers to be stopped when deciding when a program has	814	relying on all watchers to be stopped when deciding when a program has
729	finished (especially in interactive programs), but having a program	815	finished (especially in interactive programs), but having a program
730	that automatically loops as long as it has to and no longer by virtue	816	that automatically loops as long as it has to and no longer by virtue
731	of relying on its watchers stopping correctly, that is truly a thing of	817	of relying on its watchers stopping correctly, that is truly a thing of
732	beauty.	818	beauty.
733		819
		820	This function is I<mostly> exception-safe - you can break out of a
		821	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		822	exception and so on. This does not decrement the C<ev_depth> value, nor
		823	will it clear any outstanding C<EVBREAK_ONE> breaks.
		824
734	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	825	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
735	those events and any already outstanding ones, but will not block your	826	those events and any already outstanding ones, but will not wait and
736	process in case there are no events and will return after one iteration of	827	block your process in case there are no events and will return after one
737	the loop.	828	iteration of the loop. This is sometimes useful to poll and handle new
		829	events while doing lengthy calculations, to keep the program responsive.
738		830
739	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	831	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
740	necessary) and will handle those and any already outstanding ones. It	832	necessary) and will handle those and any already outstanding ones. It
741	will block your process until at least one new event arrives (which could	833	will block your process until at least one new event arrives (which could
742	be an event internal to libev itself, so there is no guarantee that a	834	be an event internal to libev itself, so there is no guarantee that a
743	user-registered callback will be called), and will return after one	835	user-registered callback will be called), and will return after one
744	iteration of the loop.	836	iteration of the loop.
745		837
746	This is useful if you are waiting for some external event in conjunction	838	This is useful if you are waiting for some external event in conjunction
747	with something not expressible using other libev watchers (i.e. "roll your	839	with something not expressible using other libev watchers (i.e. "roll your
748	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	840	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
749	usually a better approach for this kind of thing.	841	usually a better approach for this kind of thing.
750		842
751	Here are the gory details of what C<ev_loop> does:	843	Here are the gory details of what C<ev_run> does (this is for your
		844	understanding, not a guarantee that things will work exactly like this in
		845	future versions):
752		846
		847	- Increment loop depth.
		848	- Reset the ev_break status.
753	- Before the first iteration, call any pending watchers.	849	- Before the first iteration, call any pending watchers.
		850	LOOP:
754	* If EVFLAG_FORKCHECK was used, check for a fork.	851	- If EVFLAG_FORKCHECK was used, check for a fork.
755	- If a fork was detected (by any means), queue and call all fork watchers.	852	- If a fork was detected (by any means), queue and call all fork watchers.
756	- Queue and call all prepare watchers.	853	- Queue and call all prepare watchers.
		854	- If ev_break was called, goto FINISH.
757	- If we have been forked, detach and recreate the kernel state	855	- If we have been forked, detach and recreate the kernel state
758	as to not disturb the other process.	856	as to not disturb the other process.
759	- Update the kernel state with all outstanding changes.	857	- Update the kernel state with all outstanding changes.
760	- Update the "event loop time" (ev_now ()).	858	- Update the "event loop time" (ev_now ()).
761	- Calculate for how long to sleep or block, if at all	859	- Calculate for how long to sleep or block, if at all
762	(active idle watchers, EVLOOP_NONBLOCK or not having	860	(active idle watchers, EVRUN_NOWAIT or not having
763	any active watchers at all will result in not sleeping).	861	any active watchers at all will result in not sleeping).
764	- Sleep if the I/O and timer collect interval say so.	862	- Sleep if the I/O and timer collect interval say so.
		863	- Increment loop iteration counter.
765	- Block the process, waiting for any events.	864	- Block the process, waiting for any events.
766	- Queue all outstanding I/O (fd) events.	865	- Queue all outstanding I/O (fd) events.
767	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	866	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
768	- Queue all expired timers.	867	- Queue all expired timers.
769	- Queue all expired periodics.	868	- Queue all expired periodics.
770	- Unless any events are pending now, queue all idle watchers.	869	- Queue all idle watchers with priority higher than that of pending events.
771	- Queue all check watchers.	870	- Queue all check watchers.
772	- Call all queued watchers in reverse order (i.e. check watchers first).	871	- Call all queued watchers in reverse order (i.e. check watchers first).
773	Signals and child watchers are implemented as I/O watchers, and will	872	Signals and child watchers are implemented as I/O watchers, and will
774	be handled here by queueing them when their watcher gets executed.	873	be handled here by queueing them when their watcher gets executed.
775	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	874	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
776	were used, or there are no active watchers, return, otherwise	875	were used, or there are no active watchers, goto FINISH, otherwise
777	continue with step *.	876	continue with step LOOP.
		877	FINISH:
		878	- Reset the ev_break status iff it was EVBREAK_ONE.
		879	- Decrement the loop depth.
		880	- Return.
778		881
779	Example: Queue some jobs and then loop until no events are outstanding	882	Example: Queue some jobs and then loop until no events are outstanding
780	anymore.	883	anymore.
781		884
782	... queue jobs here, make sure they register event watchers as long	885	... queue jobs here, make sure they register event watchers as long
783	... as they still have work to do (even an idle watcher will do..)	886	... as they still have work to do (even an idle watcher will do..)
784	ev_loop (my_loop, 0);	887	ev_run (my_loop, 0);
785	... jobs done or somebody called unloop. yeah!	888	... jobs done or somebody called break. yeah!
786		889
787	=item ev_unloop (loop, how)	890	=item ev_break (loop, how)
788		891
789	Can be used to make a call to C<ev_loop> return early (but only after it	892	Can be used to make a call to C<ev_run> return early (but only after it
790	has processed all outstanding events). The C<how> argument must be either	893	has processed all outstanding events). The C<how> argument must be either
791	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	894	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
792	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	895	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
793		896
794	This "unloop state" will be cleared when entering C<ev_loop> again.	897	This "break state" will be cleared on the next call to C<ev_run>.
795		898
796	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	899	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		900	which case it will have no effect.
797		901
798	=item ev_ref (loop)	902	=item ev_ref (loop)
799		903
800	=item ev_unref (loop)	904	=item ev_unref (loop)
801		905
802	Ref/unref can be used to add or remove a reference count on the event	906	Ref/unref can be used to add or remove a reference count on the event
803	loop: Every watcher keeps one reference, and as long as the reference	907	loop: Every watcher keeps one reference, and as long as the reference
804	count is nonzero, C<ev_loop> will not return on its own.	908	count is nonzero, C<ev_run> will not return on its own.
805		909
806	This is useful when you have a watcher that you never intend to	910	This is useful when you have a watcher that you never intend to
807	unregister, but that nevertheless should not keep C<ev_loop> from	911	unregister, but that nevertheless should not keep C<ev_run> from
808	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>	912	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
809	before stopping it.	913	before stopping it.
810		914
811	As an example, libev itself uses this for its internal signal pipe: It	915	As an example, libev itself uses this for its internal signal pipe: It
812	is not visible to the libev user and should not keep C<ev_loop> from	916	is not visible to the libev user and should not keep C<ev_run> from
813	exiting if no event watchers registered by it are active. It is also an	917	exiting if no event watchers registered by it are active. It is also an
814	excellent way to do this for generic recurring timers or from within	918	excellent way to do this for generic recurring timers or from within
815	third-party libraries. Just remember to I<unref after start> and I<ref	919	third-party libraries. Just remember to I<unref after start> and I<ref
816	before stop> (but only if the watcher wasn't active before, or was active	920	before stop> (but only if the watcher wasn't active before, or was active
817	before, respectively. Note also that libev might stop watchers itself	921	before, respectively. Note also that libev might stop watchers itself
818	(e.g. non-repeating timers) in which case you have to C<ev_ref>	922	(e.g. non-repeating timers) in which case you have to C<ev_ref>
819	in the callback).	923	in the callback).
820		924
821	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	925	Example: Create a signal watcher, but keep it from keeping C<ev_run>
822	running when nothing else is active.	926	running when nothing else is active.
823		927
824	ev_signal exitsig;	928	ev_signal exitsig;
825	ev_signal_init (&exitsig, sig_cb, SIGINT);	929	ev_signal_init (&exitsig, sig_cb, SIGINT);
826	ev_signal_start (loop, &exitsig);	930	ev_signal_start (loop, &exitsig);
827	evf_unref (loop);	931	ev_unref (loop);
828		932
829	Example: For some weird reason, unregister the above signal handler again.	933	Example: For some weird reason, unregister the above signal handler again.
830		934
831	ev_ref (loop);	935	ev_ref (loop);
832	ev_signal_stop (loop, &exitsig);	936	ev_signal_stop (loop, &exitsig);
…		…
852	overhead for the actual polling but can deliver many events at once.	956	overhead for the actual polling but can deliver many events at once.
853		957
854	By setting a higher I<io collect interval> you allow libev to spend more	958	By setting a higher I<io collect interval> you allow libev to spend more
855	time collecting I/O events, so you can handle more events per iteration,	959	time collecting I/O events, so you can handle more events per iteration,
856	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	960	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
857	C<ev_timer>) will be not affected. Setting this to a non-null value will	961	C<ev_timer>) will not be affected. Setting this to a non-null value will
858	introduce an additional C<ev_sleep ()> call into most loop iterations. The	962	introduce an additional C<ev_sleep ()> call into most loop iterations. The
859	sleep time ensures that libev will not poll for I/O events more often then	963	sleep time ensures that libev will not poll for I/O events more often then
860	once per this interval, on average.	964	once per this interval, on average (as long as the host time resolution is
		965	good enough).
861		966
862	Likewise, by setting a higher I<timeout collect interval> you allow libev	967	Likewise, by setting a higher I<timeout collect interval> you allow libev
863	to spend more time collecting timeouts, at the expense of increased	968	to spend more time collecting timeouts, at the expense of increased
864	latency/jitter/inexactness (the watcher callback will be called	969	latency/jitter/inexactness (the watcher callback will be called
865	later). C<ev_io> watchers will not be affected. Setting this to a non-null	970	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
871	usually doesn't make much sense to set it to a lower value than C<0.01>,	976	usually doesn't make much sense to set it to a lower value than C<0.01>,
872	as this approaches the timing granularity of most systems. Note that if	977	as this approaches the timing granularity of most systems. Note that if
873	you do transactions with the outside world and you can't increase the	978	you do transactions with the outside world and you can't increase the
874	parallelity, then this setting will limit your transaction rate (if you	979	parallelity, then this setting will limit your transaction rate (if you
875	need to poll once per transaction and the I/O collect interval is 0.01,	980	need to poll once per transaction and the I/O collect interval is 0.01,
876	then you can't do more than 100 transations per second).	981	then you can't do more than 100 transactions per second).
877		982
878	Setting the I<timeout collect interval> can improve the opportunity for	983	Setting the I<timeout collect interval> can improve the opportunity for
879	saving power, as the program will "bundle" timer callback invocations that	984	saving power, as the program will "bundle" timer callback invocations that
880	are "near" in time together, by delaying some, thus reducing the number of	985	are "near" in time together, by delaying some, thus reducing the number of
881	times the process sleeps and wakes up again. Another useful technique to	986	times the process sleeps and wakes up again. Another useful technique to
…		…
889	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	994	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
890		995
891	=item ev_invoke_pending (loop)	996	=item ev_invoke_pending (loop)
892		997
893	This call will simply invoke all pending watchers while resetting their	998	This call will simply invoke all pending watchers while resetting their
894	pending state. Normally, C<ev_loop> does this automatically when required,	999	pending state. Normally, C<ev_run> does this automatically when required,
895	but when overriding the invoke callback this call comes handy.	1000	but when overriding the invoke callback this call comes handy. This
		1001	function can be invoked from a watcher - this can be useful for example
		1002	when you want to do some lengthy calculation and want to pass further
		1003	event handling to another thread (you still have to make sure only one
		1004	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
896		1005
897	=item int ev_pending_count (loop)	1006	=item int ev_pending_count (loop)
898		1007
899	Returns the number of pending watchers - zero indicates that no watchers	1008	Returns the number of pending watchers - zero indicates that no watchers
900	are pending.	1009	are pending.
901		1010
902	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))	1011	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
903		1012
904	This overrides the invoke pending functionality of the loop: Instead of	1013	This overrides the invoke pending functionality of the loop: Instead of
905	invoking all pending watchers when there are any, C<ev_loop> will call	1014	invoking all pending watchers when there are any, C<ev_run> will call
906	this callback instead. This is useful, for example, when you want to	1015	this callback instead. This is useful, for example, when you want to
907	invoke the actual watchers inside another context (another thread etc.).	1016	invoke the actual watchers inside another context (another thread etc.).
908		1017
909	If you want to reset the callback, use C<ev_invoke_pending> as new	1018	If you want to reset the callback, use C<ev_invoke_pending> as new
910	callback.	1019	callback.
911		1020
912	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))	1021	=item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())
913		1022
914	Sometimes you want to share the same loop between multiple threads. This	1023	Sometimes you want to share the same loop between multiple threads. This
915	can be done relatively simply by putting mutex_lock/unlock calls around	1024	can be done relatively simply by putting mutex_lock/unlock calls around
916	each call to a libev function.	1025	each call to a libev function.
917		1026
918	However, C<ev_loop> can run an indefinite time, so it is not feasible to	1027	However, C<ev_run> can run an indefinite time, so it is not feasible
919	wait for it to return. One way around this is to wake up the loop via	1028	to wait for it to return. One way around this is to wake up the event
920	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>	1029	loop via C<ev_break> and C<ev_async_send>, another way is to set these
921	and I<acquire> callbacks on the loop.	1030	I<release> and I<acquire> callbacks on the loop.
922		1031
923	When set, then C<release> will be called just before the thread is	1032	When set, then C<release> will be called just before the thread is
924	suspended waiting for new events, and C<acquire> is called just	1033	suspended waiting for new events, and C<acquire> is called just
925	afterwards.	1034	afterwards.
926		1035
…		…
929		1038
930	While event loop modifications are allowed between invocations of	1039	While event loop modifications are allowed between invocations of
931	C<release> and C<acquire> (that's their only purpose after all), no	1040	C<release> and C<acquire> (that's their only purpose after all), no
932	modifications done will affect the event loop, i.e. adding watchers will	1041	modifications done will affect the event loop, i.e. adding watchers will
933	have no effect on the set of file descriptors being watched, or the time	1042	have no effect on the set of file descriptors being watched, or the time
934	waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it	1043	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
935	to take note of any changes you made.	1044	to take note of any changes you made.
936		1045
937	In theory, threads executing C<ev_loop> will be async-cancel safe between	1046	In theory, threads executing C<ev_run> will be async-cancel safe between
938	invocations of C<release> and C<acquire>.	1047	invocations of C<release> and C<acquire>.
939		1048
940	See also the locking example in the C<THREADS> section later in this	1049	See also the locking example in the C<THREADS> section later in this
941	document.	1050	document.
942		1051
943	=item ev_set_userdata (loop, void *data)	1052	=item ev_set_userdata (loop, void *data)
944		1053
945	=item ev_userdata (loop)	1054	=item void *ev_userdata (loop)
946		1055
947	Set and retrieve a single C<void *> associated with a loop. When	1056	Set and retrieve a single C<void *> associated with a loop. When
948	C<ev_set_userdata> has never been called, then C<ev_userdata> returns	1057	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
949	C<0.>	1058	C<0>.
950		1059
951	These two functions can be used to associate arbitrary data with a loop,	1060	These two functions can be used to associate arbitrary data with a loop,
952	and are intended solely for the C<invoke_pending_cb>, C<release> and	1061	and are intended solely for the C<invoke_pending_cb>, C<release> and
953	C<acquire> callbacks described above, but of course can be (ab-)used for	1062	C<acquire> callbacks described above, but of course can be (ab-)used for
954	any other purpose as well.	1063	any other purpose as well.
955		1064
956	=item ev_loop_verify (loop)	1065	=item ev_verify (loop)
957		1066
958	This function only does something when C<EV_VERIFY> support has been	1067	This function only does something when C<EV_VERIFY> support has been
959	compiled in, which is the default for non-minimal builds. It tries to go	1068	compiled in, which is the default for non-minimal builds. It tries to go
960	through all internal structures and checks them for validity. If anything	1069	through all internal structures and checks them for validity. If anything
961	is found to be inconsistent, it will print an error message to standard	1070	is found to be inconsistent, it will print an error message to standard
…		…
972		1081
973	In the following description, uppercase C<TYPE> in names stands for the	1082	In the following description, uppercase C<TYPE> in names stands for the
974	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1083	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
975	watchers and C<ev_io_start> for I/O watchers.	1084	watchers and C<ev_io_start> for I/O watchers.
976		1085
977	A watcher is a structure that you create and register to record your	1086	A watcher is an opaque structure that you allocate and register to record
978	interest in some event. For instance, if you want to wait for STDIN to	1087	your interest in some event. To make a concrete example, imagine you want
979	become readable, you would create an C<ev_io> watcher for that:	1088	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1089	for that:
980		1090
981	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1091	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
982	{	1092	{
983	ev_io_stop (w);	1093	ev_io_stop (w);
984	ev_unloop (loop, EVUNLOOP_ALL);	1094	ev_break (loop, EVBREAK_ALL);
985	}	1095	}
986		1096
987	struct ev_loop *loop = ev_default_loop (0);	1097	struct ev_loop *loop = ev_default_loop (0);
988		1098
989	ev_io stdin_watcher;	1099	ev_io stdin_watcher;
990		1100
991	ev_init (&stdin_watcher, my_cb);	1101	ev_init (&stdin_watcher, my_cb);
992	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1102	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
993	ev_io_start (loop, &stdin_watcher);	1103	ev_io_start (loop, &stdin_watcher);
994		1104
995	ev_loop (loop, 0);	1105	ev_run (loop, 0);
996		1106
997	As you can see, you are responsible for allocating the memory for your	1107	As you can see, you are responsible for allocating the memory for your
998	watcher structures (and it is I<usually> a bad idea to do this on the	1108	watcher structures (and it is I<usually> a bad idea to do this on the
999	stack).	1109	stack).
1000		1110
1001	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1111	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
1002	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1112	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
1003		1113
1004	Each watcher structure must be initialised by a call to C<ev_init	1114	Each watcher structure must be initialised by a call to C<ev_init (watcher
1005	(watcher *, callback)>, which expects a callback to be provided. This	1115	*, callback)>, which expects a callback to be provided. This callback is
1006	callback gets invoked each time the event occurs (or, in the case of I/O	1116	invoked each time the event occurs (or, in the case of I/O watchers, each
1007	watchers, each time the event loop detects that the file descriptor given	1117	time the event loop detects that the file descriptor given is readable
1008	is readable and/or writable).	1118	and/or writable).
1009		1119
1010	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1120	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
1011	macro to configure it, with arguments specific to the watcher type. There	1121	macro to configure it, with arguments specific to the watcher type. There
1012	is also a macro to combine initialisation and setting in one call: C<<	1122	is also a macro to combine initialisation and setting in one call: C<<
1013	ev_TYPE_init (watcher *, callback, ...) >>.	1123	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
1064		1174
1065	=item C<EV_PREPARE>	1175	=item C<EV_PREPARE>
1066		1176
1067	=item C<EV_CHECK>	1177	=item C<EV_CHECK>
1068		1178
1069	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1179	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to
1070	to gather new events, and all C<ev_check> watchers are invoked just after	1180	gather new events, and all C<ev_check> watchers are queued (not invoked)
1071	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1181	just after C<ev_run> has gathered them, but before it queues any callbacks
		1182	for any received events. That means C<ev_prepare> watchers are the last
		1183	watchers invoked before the event loop sleeps or polls for new events, and
		1184	C<ev_check> watchers will be invoked before any other watchers of the same
		1185	or lower priority within an event loop iteration.
		1186
1072	received events. Callbacks of both watcher types can start and stop as	1187	Callbacks of both watcher types can start and stop as many watchers as
1073	many watchers as they want, and all of them will be taken into account	1188	they want, and all of them will be taken into account (for example, a
1074	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1189	C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from
1075	C<ev_loop> from blocking).	1190	blocking).
1076		1191
1077	=item C<EV_EMBED>	1192	=item C<EV_EMBED>
1078		1193
1079	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1194	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1080		1195
1081	=item C<EV_FORK>	1196	=item C<EV_FORK>
1082		1197
1083	The event loop has been resumed in the child process after fork (see	1198	The event loop has been resumed in the child process after fork (see
1084	C<ev_fork>).	1199	C<ev_fork>).
		1200
		1201	=item C<EV_CLEANUP>
		1202
		1203	The event loop is about to be destroyed (see C<ev_cleanup>).
1085		1204
1086	=item C<EV_ASYNC>	1205	=item C<EV_ASYNC>
1087		1206
1088	The given async watcher has been asynchronously notified (see C<ev_async>).	1207	The given async watcher has been asynchronously notified (see C<ev_async>).
1089		1208
…		…
1199		1318
1200	=item callback ev_cb (ev_TYPE *watcher)	1319	=item callback ev_cb (ev_TYPE *watcher)
1201		1320
1202	Returns the callback currently set on the watcher.	1321	Returns the callback currently set on the watcher.
1203		1322
1204	=item ev_cb_set (ev_TYPE *watcher, callback)	1323	=item ev_set_cb (ev_TYPE *watcher, callback)
1205		1324
1206	Change the callback. You can change the callback at virtually any time	1325	Change the callback. You can change the callback at virtually any time
1207	(modulo threads).	1326	(modulo threads).
1208		1327
1209	=item ev_set_priority (ev_TYPE *watcher, int priority)	1328	=item ev_set_priority (ev_TYPE *watcher, int priority)
…		…
1227	or might not have been clamped to the valid range.	1346	or might not have been clamped to the valid range.
1228		1347
1229	The default priority used by watchers when no priority has been set is	1348	The default priority used by watchers when no priority has been set is
1230	always C<0>, which is supposed to not be too high and not be too low :).	1349	always C<0>, which is supposed to not be too high and not be too low :).
1231		1350
1232	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of	1351	See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1233	priorities.	1352	priorities.
1234		1353
1235	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1354	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1236		1355
1237	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1356	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
…		…
1262	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related	1381	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1263	functions that do not need a watcher.	1382	functions that do not need a watcher.
1264		1383
1265	=back	1384	=back
1266		1385
		1386	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
		1387	OWN COMPOSITE WATCHERS> idioms.
1267		1388
1268	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1389	=head2 WATCHER STATES
1269		1390
1270	Each watcher has, by default, a member C<void *data> that you can change	1391	There are various watcher states mentioned throughout this manual -
1271	and read at any time: libev will completely ignore it. This can be used	1392	active, pending and so on. In this section these states and the rules to
1272	to associate arbitrary data with your watcher. If you need more data and	1393	transition between them will be described in more detail - and while these
1273	don't want to allocate memory and store a pointer to it in that data	1394	rules might look complicated, they usually do "the right thing".
1274	member, you can also "subclass" the watcher type and provide your own
1275	data:
1276		1395
1277	struct my_io	1396	=over 4
1278	{
1279	ev_io io;
1280	int otherfd;
1281	void *somedata;
1282	struct whatever *mostinteresting;
1283	};
1284		1397
1285	...	1398	=item initialised
1286	struct my_io w;
1287	ev_io_init (&w.io, my_cb, fd, EV_READ);
1288		1399
1289	And since your callback will be called with a pointer to the watcher, you	1400	Before a watcher can be registered with the event loop it has to be
1290	can cast it back to your own type:	1401	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1402	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1291		1403
1292	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)	1404	In this state it is simply some block of memory that is suitable for
1293	{	1405	use in an event loop. It can be moved around, freed, reused etc. at
1294	struct my_io *w = (struct my_io *)w_;	1406	will - as long as you either keep the memory contents intact, or call
1295	...	1407	C<ev_TYPE_init> again.
1296	}
1297		1408
1298	More interesting and less C-conformant ways of casting your callback type	1409	=item started/running/active
1299	instead have been omitted.
1300		1410
1301	Another common scenario is to use some data structure with multiple	1411	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1302	embedded watchers:	1412	property of the event loop, and is actively waiting for events. While in
		1413	this state it cannot be accessed (except in a few documented ways), moved,
		1414	freed or anything else - the only legal thing is to keep a pointer to it,
		1415	and call libev functions on it that are documented to work on active watchers.
1303		1416
1304	struct my_biggy	1417	=item pending
1305	{
1306	int some_data;
1307	ev_timer t1;
1308	ev_timer t2;
1309	}
1310		1418
1311	In this case getting the pointer to C<my_biggy> is a bit more	1419	If a watcher is active and libev determines that an event it is interested
1312	complicated: Either you store the address of your C<my_biggy> struct	1420	in has occurred (such as a timer expiring), it will become pending. It will
1313	in the C<data> member of the watcher (for woozies), or you need to use	1421	stay in this pending state until either it is stopped or its callback is
1314	some pointer arithmetic using C<offsetof> inside your watchers (for real	1422	about to be invoked, so it is not normally pending inside the watcher
1315	programmers):	1423	callback.
1316		1424
1317	#include <stddef.h>	1425	The watcher might or might not be active while it is pending (for example,
		1426	an expired non-repeating timer can be pending but no longer active). If it
		1427	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1428	but it is still property of the event loop at this time, so cannot be
		1429	moved, freed or reused. And if it is active the rules described in the
		1430	previous item still apply.
1318		1431
1319	static void	1432	It is also possible to feed an event on a watcher that is not active (e.g.
1320	t1_cb (EV_P_ ev_timer *w, int revents)	1433	via C<ev_feed_event>), in which case it becomes pending without being
1321	{	1434	active.
1322	struct my_biggy big = (struct my_biggy *)
1323	(((char *)w) - offsetof (struct my_biggy, t1));
1324	}
1325		1435
1326	static void	1436	=item stopped
1327	t2_cb (EV_P_ ev_timer *w, int revents)	1437
1328	{	1438	A watcher can be stopped implicitly by libev (in which case it might still
1329	struct my_biggy big = (struct my_biggy *)	1439	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1330	(((char *)w) - offsetof (struct my_biggy, t2));	1440	latter will clear any pending state the watcher might be in, regardless
1331	}	1441	of whether it was active or not, so stopping a watcher explicitly before
		1442	freeing it is often a good idea.
		1443
		1444	While stopped (and not pending) the watcher is essentially in the
		1445	initialised state, that is, it can be reused, moved, modified in any way
		1446	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1447	it again).
		1448
		1449	=back
1332		1450
1333	=head2 WATCHER PRIORITY MODELS	1451	=head2 WATCHER PRIORITY MODELS
1334		1452
1335	Many event loops support I<watcher priorities>, which are usually small	1453	Many event loops support I<watcher priorities>, which are usually small
1336	integers that influence the ordering of event callback invocation	1454	integers that influence the ordering of event callback invocation
…		…
1379		1497
1380	For example, to emulate how many other event libraries handle priorities,	1498	For example, to emulate how many other event libraries handle priorities,
1381	you can associate an C<ev_idle> watcher to each such watcher, and in	1499	you can associate an C<ev_idle> watcher to each such watcher, and in
1382	the normal watcher callback, you just start the idle watcher. The real	1500	the normal watcher callback, you just start the idle watcher. The real
1383	processing is done in the idle watcher callback. This causes libev to	1501	processing is done in the idle watcher callback. This causes libev to
1384	continously poll and process kernel event data for the watcher, but when	1502	continuously poll and process kernel event data for the watcher, but when
1385	the lock-out case is known to be rare (which in turn is rare :), this is	1503	the lock-out case is known to be rare (which in turn is rare :), this is
1386	workable.	1504	workable.
1387		1505
1388	Usually, however, the lock-out model implemented that way will perform	1506	Usually, however, the lock-out model implemented that way will perform
1389	miserably under the type of load it was designed to handle. In that case,	1507	miserably under the type of load it was designed to handle. In that case,
…		…
1403	{	1521	{
1404	// stop the I/O watcher, we received the event, but	1522	// stop the I/O watcher, we received the event, but
1405	// are not yet ready to handle it.	1523	// are not yet ready to handle it.
1406	ev_io_stop (EV_A_ w);	1524	ev_io_stop (EV_A_ w);
1407		1525
1408	// start the idle watcher to ahndle the actual event.	1526	// start the idle watcher to handle the actual event.
1409	// it will not be executed as long as other watchers	1527	// it will not be executed as long as other watchers
1410	// with the default priority are receiving events.	1528	// with the default priority are receiving events.
1411	ev_idle_start (EV_A_ &idle);	1529	ev_idle_start (EV_A_ &idle);
1412	}	1530	}
1413		1531
…		…
1463	In general you can register as many read and/or write event watchers per	1581	In general you can register as many read and/or write event watchers per
1464	fd as you want (as long as you don't confuse yourself). Setting all file	1582	fd as you want (as long as you don't confuse yourself). Setting all file
1465	descriptors to non-blocking mode is also usually a good idea (but not	1583	descriptors to non-blocking mode is also usually a good idea (but not
1466	required if you know what you are doing).	1584	required if you know what you are doing).
1467		1585
1468	If you cannot use non-blocking mode, then force the use of a
1469	known-to-be-good backend (at the time of this writing, this includes only
1470	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1471	descriptors for which non-blocking operation makes no sense (such as
1472	files) - libev doesn't guarentee any specific behaviour in that case.
1473
1474	Another thing you have to watch out for is that it is quite easy to	1586	Another thing you have to watch out for is that it is quite easy to
1475	receive "spurious" readiness notifications, that is your callback might	1587	receive "spurious" readiness notifications, that is, your callback might
1476	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1588	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1477	because there is no data. Not only are some backends known to create a	1589	because there is no data. It is very easy to get into this situation even
1478	lot of those (for example Solaris ports), it is very easy to get into	1590	with a relatively standard program structure. Thus it is best to always
1479	this situation even with a relatively standard program structure. Thus	1591	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1480	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1481	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1592	preferable to a program hanging until some data arrives.
1482		1593
1483	If you cannot run the fd in non-blocking mode (for example you should	1594	If you cannot run the fd in non-blocking mode (for example you should
1484	not play around with an Xlib connection), then you have to separately	1595	not play around with an Xlib connection), then you have to separately
1485	re-test whether a file descriptor is really ready with a known-to-be good	1596	re-test whether a file descriptor is really ready with a known-to-be good
1486	interface such as poll (fortunately in our Xlib example, Xlib already	1597	interface such as poll (fortunately in the case of Xlib, it already does
1487	does this on its own, so its quite safe to use). Some people additionally	1598	this on its own, so its quite safe to use). Some people additionally
1488	use C<SIGALRM> and an interval timer, just to be sure you won't block	1599	use C<SIGALRM> and an interval timer, just to be sure you won't block
1489	indefinitely.	1600	indefinitely.
1490		1601
1491	But really, best use non-blocking mode.	1602	But really, best use non-blocking mode.
1492		1603
…		…
1520		1631
1521	There is no workaround possible except not registering events	1632	There is no workaround possible except not registering events
1522	for potentially C<dup ()>'ed file descriptors, or to resort to	1633	for potentially C<dup ()>'ed file descriptors, or to resort to
1523	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1634	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1524		1635
		1636	=head3 The special problem of files
		1637
		1638	Many people try to use C<select> (or libev) on file descriptors
		1639	representing files, and expect it to become ready when their program
		1640	doesn't block on disk accesses (which can take a long time on their own).
		1641
		1642	However, this cannot ever work in the "expected" way - you get a readiness
		1643	notification as soon as the kernel knows whether and how much data is
		1644	there, and in the case of open files, that's always the case, so you
		1645	always get a readiness notification instantly, and your read (or possibly
		1646	write) will still block on the disk I/O.
		1647
		1648	Another way to view it is that in the case of sockets, pipes, character
		1649	devices and so on, there is another party (the sender) that delivers data
		1650	on its own, but in the case of files, there is no such thing: the disk
		1651	will not send data on its own, simply because it doesn't know what you
		1652	wish to read - you would first have to request some data.
		1653
		1654	Since files are typically not-so-well supported by advanced notification
		1655	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1656	to files, even though you should not use it. The reason for this is
		1657	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1658	usually a tty, often a pipe, but also sometimes files or special devices
		1659	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1660	F</dev/urandom>), and even though the file might better be served with
		1661	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1662	it "just works" instead of freezing.
		1663
		1664	So avoid file descriptors pointing to files when you know it (e.g. use
		1665	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1666	when you rarely read from a file instead of from a socket, and want to
		1667	reuse the same code path.
		1668
1525	=head3 The special problem of fork	1669	=head3 The special problem of fork
1526		1670
1527	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1671	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1528	useless behaviour. Libev fully supports fork, but needs to be told about	1672	useless behaviour. Libev fully supports fork, but needs to be told about
1529	it in the child.	1673	it in the child if you want to continue to use it in the child.
1530		1674
1531	To support fork in your programs, you either have to call	1675	To support fork in your child processes, you have to call C<ev_loop_fork
1532	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1676	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1533	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1677	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1534	C<EVBACKEND_POLL>.
1535		1678
1536	=head3 The special problem of SIGPIPE	1679	=head3 The special problem of SIGPIPE
1537		1680
1538	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1681	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1539	when writing to a pipe whose other end has been closed, your program gets	1682	when writing to a pipe whose other end has been closed, your program gets
…		…
1621	...	1764	...
1622	struct ev_loop *loop = ev_default_init (0);	1765	struct ev_loop *loop = ev_default_init (0);
1623	ev_io stdin_readable;	1766	ev_io stdin_readable;
1624	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1767	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1625	ev_io_start (loop, &stdin_readable);	1768	ev_io_start (loop, &stdin_readable);
1626	ev_loop (loop, 0);	1769	ev_run (loop, 0);
1627		1770
1628		1771
1629	=head2 C<ev_timer> - relative and optionally repeating timeouts	1772	=head2 C<ev_timer> - relative and optionally repeating timeouts
1630		1773
1631	Timer watchers are simple relative timers that generate an event after a	1774	Timer watchers are simple relative timers that generate an event after a
…		…
1637	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1780	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1638	monotonic clock option helps a lot here).	1781	monotonic clock option helps a lot here).
1639		1782
1640	The callback is guaranteed to be invoked only I<after> its timeout has	1783	The callback is guaranteed to be invoked only I<after> its timeout has
1641	passed (not I<at>, so on systems with very low-resolution clocks this	1784	passed (not I<at>, so on systems with very low-resolution clocks this
1642	might introduce a small delay). If multiple timers become ready during the	1785	might introduce a small delay, see "the special problem of being too
		1786	early", below). If multiple timers become ready during the same loop
1643	same loop iteration then the ones with earlier time-out values are invoked	1787	iteration then the ones with earlier time-out values are invoked before
1644	before ones of the same priority with later time-out values (but this is	1788	ones of the same priority with later time-out values (but this is no
1645	no longer true when a callback calls C<ev_loop> recursively).	1789	longer true when a callback calls C<ev_run> recursively).
1646		1790
1647	=head3 Be smart about timeouts	1791	=head3 Be smart about timeouts
1648		1792
1649	Many real-world problems involve some kind of timeout, usually for error	1793	Many real-world problems involve some kind of timeout, usually for error
1650	recovery. A typical example is an HTTP request - if the other side hangs,	1794	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1725		1869
1726	In this case, it would be more efficient to leave the C<ev_timer> alone,	1870	In this case, it would be more efficient to leave the C<ev_timer> alone,
1727	but remember the time of last activity, and check for a real timeout only	1871	but remember the time of last activity, and check for a real timeout only
1728	within the callback:	1872	within the callback:
1729		1873
		1874	ev_tstamp timeout = 60.;
1730	ev_tstamp last_activity; // time of last activity	1875	ev_tstamp last_activity; // time of last activity
		1876	ev_timer timer;
1731		1877
1732	static void	1878	static void
1733	callback (EV_P_ ev_timer *w, int revents)	1879	callback (EV_P_ ev_timer *w, int revents)
1734	{	1880	{
1735	ev_tstamp now = ev_now (EV_A);	1881	// calculate when the timeout would happen
1736	ev_tstamp timeout = last_activity + 60.;	1882	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1737		1883
1738	// if last_activity + 60. is older than now, we did time out	1884	// if negative, it means we the timeout already occurred
1739	if (timeout < now)	1885	if (after < 0.)
1740	{	1886	{
1741	// timeout occured, take action	1887	// timeout occurred, take action
1742	}	1888	}
1743	else	1889	else
1744	{	1890	{
1745	// callback was invoked, but there was some activity, re-arm	1891	// callback was invoked, but there was some recent
1746	// the watcher to fire in last_activity + 60, which is	1892	// activity. simply restart the timer to time out
1747	// guaranteed to be in the future, so "again" is positive:	1893	// after "after" seconds, which is the earliest time
1748	w->repeat = timeout - now;	1894	// the timeout can occur.
		1895	ev_timer_set (w, after, 0.);
1749	ev_timer_again (EV_A_ w);	1896	ev_timer_start (EV_A_ w);
1750	}	1897	}
1751	}	1898	}
1752		1899
1753	To summarise the callback: first calculate the real timeout (defined	1900	To summarise the callback: first calculate in how many seconds the
1754	as "60 seconds after the last activity"), then check if that time has	1901	timeout will occur (by calculating the absolute time when it would occur,
1755	been reached, which means something I<did>, in fact, time out. Otherwise	1902	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1756	the callback was invoked too early (C<timeout> is in the future), so	1903	(EV_A)> from that).
1757	re-schedule the timer to fire at that future time, to see if maybe we have
1758	a timeout then.
1759		1904
1760	Note how C<ev_timer_again> is used, taking advantage of the	1905	If this value is negative, then we are already past the timeout, i.e. we
1761	C<ev_timer_again> optimisation when the timer is already running.	1906	timed out, and need to do whatever is needed in this case.
		1907
		1908	Otherwise, we now the earliest time at which the timeout would trigger,
		1909	and simply start the timer with this timeout value.
		1910
		1911	In other words, each time the callback is invoked it will check whether
		1912	the timeout occurred. If not, it will simply reschedule itself to check
		1913	again at the earliest time it could time out. Rinse. Repeat.
1762		1914
1763	This scheme causes more callback invocations (about one every 60 seconds	1915	This scheme causes more callback invocations (about one every 60 seconds
1764	minus half the average time between activity), but virtually no calls to	1916	minus half the average time between activity), but virtually no calls to
1765	libev to change the timeout.	1917	libev to change the timeout.
1766		1918
1767	To start the timer, simply initialise the watcher and set C<last_activity>	1919	To start the machinery, simply initialise the watcher and set
1768	to the current time (meaning we just have some activity :), then call the	1920	C<last_activity> to the current time (meaning there was some activity just
1769	callback, which will "do the right thing" and start the timer:	1921	now), then call the callback, which will "do the right thing" and start
		1922	the timer:
1770		1923
		1924	last_activity = ev_now (EV_A);
1771	ev_init (timer, callback);	1925	ev_init (&timer, callback);
1772	last_activity = ev_now (loop);	1926	callback (EV_A_ &timer, 0);
1773	callback (loop, timer, EV_TIMER);
1774		1927
1775	And when there is some activity, simply store the current time in	1928	When there is some activity, simply store the current time in
1776	C<last_activity>, no libev calls at all:	1929	C<last_activity>, no libev calls at all:
1777		1930
		1931	if (activity detected)
1778	last_actiivty = ev_now (loop);	1932	last_activity = ev_now (EV_A);
		1933
		1934	When your timeout value changes, then the timeout can be changed by simply
		1935	providing a new value, stopping the timer and calling the callback, which
		1936	will again do the right thing (for example, time out immediately :).
		1937
		1938	timeout = new_value;
		1939	ev_timer_stop (EV_A_ &timer);
		1940	callback (EV_A_ &timer, 0);
1779		1941
1780	This technique is slightly more complex, but in most cases where the	1942	This technique is slightly more complex, but in most cases where the
1781	time-out is unlikely to be triggered, much more efficient.	1943	time-out is unlikely to be triggered, much more efficient.
1782
1783	Changing the timeout is trivial as well (if it isn't hard-coded in the
1784	callback :) - just change the timeout and invoke the callback, which will
1785	fix things for you.
1786		1944
1787	=item 4. Wee, just use a double-linked list for your timeouts.	1945	=item 4. Wee, just use a double-linked list for your timeouts.
1788		1946
1789	If there is not one request, but many thousands (millions...), all	1947	If there is not one request, but many thousands (millions...), all
1790	employing some kind of timeout with the same timeout value, then one can	1948	employing some kind of timeout with the same timeout value, then one can
…		…
1817	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	1975	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1818	rather complicated, but extremely efficient, something that really pays	1976	rather complicated, but extremely efficient, something that really pays
1819	off after the first million or so of active timers, i.e. it's usually	1977	off after the first million or so of active timers, i.e. it's usually
1820	overkill :)	1978	overkill :)
1821		1979
		1980	=head3 The special problem of being too early
		1981
		1982	If you ask a timer to call your callback after three seconds, then
		1983	you expect it to be invoked after three seconds - but of course, this
		1984	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		1985	guaranteed to any precision by libev - imagine somebody suspending the
		1986	process with a STOP signal for a few hours for example.
		1987
		1988	So, libev tries to invoke your callback as soon as possible I<after> the
		1989	delay has occurred, but cannot guarantee this.
		1990
		1991	A less obvious failure mode is calling your callback too early: many event
		1992	loops compare timestamps with a "elapsed delay >= requested delay", but
		1993	this can cause your callback to be invoked much earlier than you would
		1994	expect.
		1995
		1996	To see why, imagine a system with a clock that only offers full second
		1997	resolution (think windows if you can't come up with a broken enough OS
		1998	yourself). If you schedule a one-second timer at the time 500.9, then the
		1999	event loop will schedule your timeout to elapse at a system time of 500
		2000	(500.9 truncated to the resolution) + 1, or 501.
		2001
		2002	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2003	501" and invoke the callback 0.1s after it was started, even though a
		2004	one-second delay was requested - this is being "too early", despite best
		2005	intentions.
		2006
		2007	This is the reason why libev will never invoke the callback if the elapsed
		2008	delay equals the requested delay, but only when the elapsed delay is
		2009	larger than the requested delay. In the example above, libev would only invoke
		2010	the callback at system time 502, or 1.1s after the timer was started.
		2011
		2012	So, while libev cannot guarantee that your callback will be invoked
		2013	exactly when requested, it I<can> and I<does> guarantee that the requested
		2014	delay has actually elapsed, or in other words, it always errs on the "too
		2015	late" side of things.
		2016
1822	=head3 The special problem of time updates	2017	=head3 The special problem of time updates
1823		2018
1824	Establishing the current time is a costly operation (it usually takes at	2019	Establishing the current time is a costly operation (it usually takes
1825	least two system calls): EV therefore updates its idea of the current	2020	at least one system call): EV therefore updates its idea of the current
1826	time only before and after C<ev_loop> collects new events, which causes a	2021	time only before and after C<ev_run> collects new events, which causes a
1827	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2022	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1828	lots of events in one iteration.	2023	lots of events in one iteration.
1829		2024
1830	The relative timeouts are calculated relative to the C<ev_now ()>	2025	The relative timeouts are calculated relative to the C<ev_now ()>
1831	time. This is usually the right thing as this timestamp refers to the time	2026	time. This is usually the right thing as this timestamp refers to the time
…		…
1836	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2031	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1837		2032
1838	If the event loop is suspended for a long time, you can also force an	2033	If the event loop is suspended for a long time, you can also force an
1839	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2034	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1840	()>.	2035	()>.
		2036
		2037	=head3 The special problem of unsynchronised clocks
		2038
		2039	Modern systems have a variety of clocks - libev itself uses the normal
		2040	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2041	jumps).
		2042
		2043	Neither of these clocks is synchronised with each other or any other clock
		2044	on the system, so C<ev_time ()> might return a considerably different time
		2045	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2046	a call to C<gettimeofday> might return a second count that is one higher
		2047	than a directly following call to C<time>.
		2048
		2049	The moral of this is to only compare libev-related timestamps with
		2050	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2051	a second or so.
		2052
		2053	One more problem arises due to this lack of synchronisation: if libev uses
		2054	the system monotonic clock and you compare timestamps from C<ev_time>
		2055	or C<ev_now> from when you started your timer and when your callback is
		2056	invoked, you will find that sometimes the callback is a bit "early".
		2057
		2058	This is because C<ev_timer>s work in real time, not wall clock time, so
		2059	libev makes sure your callback is not invoked before the delay happened,
		2060	I<measured according to the real time>, not the system clock.
		2061
		2062	If your timeouts are based on a physical timescale (e.g. "time out this
		2063	connection after 100 seconds") then this shouldn't bother you as it is
		2064	exactly the right behaviour.
		2065
		2066	If you want to compare wall clock/system timestamps to your timers, then
		2067	you need to use C<ev_periodic>s, as these are based on the wall clock
		2068	time, where your comparisons will always generate correct results.
1841		2069
1842	=head3 The special problems of suspended animation	2070	=head3 The special problems of suspended animation
1843		2071
1844	When you leave the server world it is quite customary to hit machines that	2072	When you leave the server world it is quite customary to hit machines that
1845	can suspend/hibernate - what happens to the clocks during such a suspend?	2073	can suspend/hibernate - what happens to the clocks during such a suspend?
…		…
1889	keep up with the timer (because it takes longer than those 10 seconds to	2117	keep up with the timer (because it takes longer than those 10 seconds to
1890	do stuff) the timer will not fire more than once per event loop iteration.	2118	do stuff) the timer will not fire more than once per event loop iteration.
1891		2119
1892	=item ev_timer_again (loop, ev_timer *)	2120	=item ev_timer_again (loop, ev_timer *)
1893		2121
1894	This will act as if the timer timed out and restart it again if it is	2122	This will act as if the timer timed out, and restarts it again if it is
1895	repeating. The exact semantics are:	2123	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2124	timeout to the C<repeat> value and calling C<ev_timer_start>.
1896		2125
		2126	The exact semantics are as in the following rules, all of which will be
		2127	applied to the watcher:
		2128
		2129	=over 4
		2130
1897	If the timer is pending, its pending status is cleared.	2131	=item If the timer is pending, the pending status is always cleared.
1898		2132
1899	If the timer is started but non-repeating, stop it (as if it timed out).	2133	=item If the timer is started but non-repeating, stop it (as if it timed
		2134	out, without invoking it).
1900		2135
1901	If the timer is repeating, either start it if necessary (with the	2136	=item If the timer is repeating, make the C<repeat> value the new timeout
1902	C<repeat> value), or reset the running timer to the C<repeat> value.	2137	and start the timer, if necessary.
1903		2138
		2139	=back
		2140
1904	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2141	This sounds a bit complicated, see L</Be smart about timeouts>, above, for a
1905	usage example.	2142	usage example.
1906		2143
1907	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)	2144	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1908		2145
1909	Returns the remaining time until a timer fires. If the timer is active,	2146	Returns the remaining time until a timer fires. If the timer is active,
…		…
1948	}	2185	}
1949		2186
1950	ev_timer mytimer;	2187	ev_timer mytimer;
1951	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2188	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1952	ev_timer_again (&mytimer); /* start timer */	2189	ev_timer_again (&mytimer); /* start timer */
1953	ev_loop (loop, 0);	2190	ev_run (loop, 0);
1954		2191
1955	// and in some piece of code that gets executed on any "activity":	2192	// and in some piece of code that gets executed on any "activity":
1956	// reset the timeout to start ticking again at 10 seconds	2193	// reset the timeout to start ticking again at 10 seconds
1957	ev_timer_again (&mytimer);	2194	ev_timer_again (&mytimer);
1958		2195
…		…
1984		2221
1985	As with timers, the callback is guaranteed to be invoked only when the	2222	As with timers, the callback is guaranteed to be invoked only when the
1986	point in time where it is supposed to trigger has passed. If multiple	2223	point in time where it is supposed to trigger has passed. If multiple
1987	timers become ready during the same loop iteration then the ones with	2224	timers become ready during the same loop iteration then the ones with
1988	earlier time-out values are invoked before ones with later time-out values	2225	earlier time-out values are invoked before ones with later time-out values
1989	(but this is no longer true when a callback calls C<ev_loop> recursively).	2226	(but this is no longer true when a callback calls C<ev_run> recursively).
1990		2227
1991	=head3 Watcher-Specific Functions and Data Members	2228	=head3 Watcher-Specific Functions and Data Members
1992		2229
1993	=over 4	2230	=over 4
1994		2231
…		…
2029		2266
2030	Another way to think about it (for the mathematically inclined) is that	2267	Another way to think about it (for the mathematically inclined) is that
2031	C<ev_periodic> will try to run the callback in this mode at the next possible	2268	C<ev_periodic> will try to run the callback in this mode at the next possible
2032	time where C<time = offset (mod interval)>, regardless of any time jumps.	2269	time where C<time = offset (mod interval)>, regardless of any time jumps.
2033		2270
2034	For numerical stability it is preferable that the C<offset> value is near	2271	The C<interval> I<MUST> be positive, and for numerical stability, the
2035	C<ev_now ()> (the current time), but there is no range requirement for	2272	interval value should be higher than C<1/8192> (which is around 100
2036	this value, and in fact is often specified as zero.	2273	microseconds) and C<offset> should be higher than C<0> and should have
		2274	at most a similar magnitude as the current time (say, within a factor of
		2275	ten). Typical values for offset are, in fact, C<0> or something between
		2276	C<0> and C<interval>, which is also the recommended range.
2037		2277
2038	Note also that there is an upper limit to how often a timer can fire (CPU	2278	Note also that there is an upper limit to how often a timer can fire (CPU
2039	speed for example), so if C<interval> is very small then timing stability	2279	speed for example), so if C<interval> is very small then timing stability
2040	will of course deteriorate. Libev itself tries to be exact to be about one	2280	will of course deteriorate. Libev itself tries to be exact to be about one
2041	millisecond (if the OS supports it and the machine is fast enough).	2281	millisecond (if the OS supports it and the machine is fast enough).
…		…
2122	Example: Call a callback every hour, or, more precisely, whenever the	2362	Example: Call a callback every hour, or, more precisely, whenever the
2123	system time is divisible by 3600. The callback invocation times have	2363	system time is divisible by 3600. The callback invocation times have
2124	potentially a lot of jitter, but good long-term stability.	2364	potentially a lot of jitter, but good long-term stability.
2125		2365
2126	static void	2366	static void
2127	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2367	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
2128	{	2368	{
2129	... its now a full hour (UTC, or TAI or whatever your clock follows)	2369	... its now a full hour (UTC, or TAI or whatever your clock follows)
2130	}	2370	}
2131		2371
2132	ev_periodic hourly_tick;	2372	ev_periodic hourly_tick;
…		…
2155		2395
2156	=head2 C<ev_signal> - signal me when a signal gets signalled!	2396	=head2 C<ev_signal> - signal me when a signal gets signalled!
2157		2397
2158	Signal watchers will trigger an event when the process receives a specific	2398	Signal watchers will trigger an event when the process receives a specific
2159	signal one or more times. Even though signals are very asynchronous, libev	2399	signal one or more times. Even though signals are very asynchronous, libev
2160	will try it's best to deliver signals synchronously, i.e. as part of the	2400	will try its best to deliver signals synchronously, i.e. as part of the
2161	normal event processing, like any other event.	2401	normal event processing, like any other event.
2162		2402
2163	If you want signals to be delivered truly asynchronously, just use	2403	If you want signals to be delivered truly asynchronously, just use
2164	C<sigaction> as you would do without libev and forget about sharing	2404	C<sigaction> as you would do without libev and forget about sharing
2165	the signal. You can even use C<ev_async> from a signal handler to	2405	the signal. You can even use C<ev_async> from a signal handler to
…		…
2184	=head3 The special problem of inheritance over fork/execve/pthread_create	2424	=head3 The special problem of inheritance over fork/execve/pthread_create
2185		2425
2186	Both the signal mask (C<sigprocmask>) and the signal disposition	2426	Both the signal mask (C<sigprocmask>) and the signal disposition
2187	(C<sigaction>) are unspecified after starting a signal watcher (and after	2427	(C<sigaction>) are unspecified after starting a signal watcher (and after
2188	stopping it again), that is, libev might or might not block the signal,	2428	stopping it again), that is, libev might or might not block the signal,
2189	and might or might not set or restore the installed signal handler.	2429	and might or might not set or restore the installed signal handler (but
		2430	see C<EVFLAG_NOSIGMASK>).
2190		2431
2191	While this does not matter for the signal disposition (libev never	2432	While this does not matter for the signal disposition (libev never
2192	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on	2433	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
2193	C<execve>), this matters for the signal mask: many programs do not expect	2434	C<execve>), this matters for the signal mask: many programs do not expect
2194	certain signals to be blocked.	2435	certain signals to be blocked.
…		…
2208		2449
2209	So I can't stress this enough: I<If you do not reset your signal mask when	2450	So I can't stress this enough: I<If you do not reset your signal mask when
2210	you expect it to be empty, you have a race condition in your code>. This	2451	you expect it to be empty, you have a race condition in your code>. This
2211	is not a libev-specific thing, this is true for most event libraries.	2452	is not a libev-specific thing, this is true for most event libraries.
2212		2453
		2454	=head3 The special problem of threads signal handling
		2455
		2456	POSIX threads has problematic signal handling semantics, specifically,
		2457	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2458	threads in a process block signals, which is hard to achieve.
		2459
		2460	When you want to use sigwait (or mix libev signal handling with your own
		2461	for the same signals), you can tackle this problem by globally blocking
		2462	all signals before creating any threads (or creating them with a fully set
		2463	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2464	loops. Then designate one thread as "signal receiver thread" which handles
		2465	these signals. You can pass on any signals that libev might be interested
		2466	in by calling C<ev_feed_signal>.
		2467
2213	=head3 Watcher-Specific Functions and Data Members	2468	=head3 Watcher-Specific Functions and Data Members
2214		2469
2215	=over 4	2470	=over 4
2216		2471
2217	=item ev_signal_init (ev_signal *, callback, int signum)	2472	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
2232	Example: Try to exit cleanly on SIGINT.	2487	Example: Try to exit cleanly on SIGINT.
2233		2488
2234	static void	2489	static void
2235	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2490	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2236	{	2491	{
2237	ev_unloop (loop, EVUNLOOP_ALL);	2492	ev_break (loop, EVBREAK_ALL);
2238	}	2493	}
2239		2494
2240	ev_signal signal_watcher;	2495	ev_signal signal_watcher;
2241	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2496	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2242	ev_signal_start (loop, &signal_watcher);	2497	ev_signal_start (loop, &signal_watcher);
…		…
2351		2606
2352	=head2 C<ev_stat> - did the file attributes just change?	2607	=head2 C<ev_stat> - did the file attributes just change?
2353		2608
2354	This watches a file system path for attribute changes. That is, it calls	2609	This watches a file system path for attribute changes. That is, it calls
2355	C<stat> on that path in regular intervals (or when the OS says it changed)	2610	C<stat> on that path in regular intervals (or when the OS says it changed)
2356	and sees if it changed compared to the last time, invoking the callback if	2611	and sees if it changed compared to the last time, invoking the callback
2357	it did.	2612	if it did. Starting the watcher C<stat>'s the file, so only changes that
		2613	happen after the watcher has been started will be reported.
2358		2614
2359	The path does not need to exist: changing from "path exists" to "path does	2615	The path does not need to exist: changing from "path exists" to "path does
2360	not exist" is a status change like any other. The condition "path does not	2616	not exist" is a status change like any other. The condition "path does not
2361	exist" (or more correctly "path cannot be stat'ed") is signified by the	2617	exist" (or more correctly "path cannot be stat'ed") is signified by the
2362	C<st_nlink> field being zero (which is otherwise always forced to be at	2618	C<st_nlink> field being zero (which is otherwise always forced to be at
…		…
2592	Apart from keeping your process non-blocking (which is a useful	2848	Apart from keeping your process non-blocking (which is a useful
2593	effect on its own sometimes), idle watchers are a good place to do	2849	effect on its own sometimes), idle watchers are a good place to do
2594	"pseudo-background processing", or delay processing stuff to after the	2850	"pseudo-background processing", or delay processing stuff to after the
2595	event loop has handled all outstanding events.	2851	event loop has handled all outstanding events.
2596		2852
		2853	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2854
		2855	As long as there is at least one active idle watcher, libev will never
		2856	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2857	For this to work, the idle watcher doesn't need to be invoked at all - the
		2858	lowest priority will do.
		2859
		2860	This mode of operation can be useful together with an C<ev_check> watcher,
		2861	to do something on each event loop iteration - for example to balance load
		2862	between different connections.
		2863
		2864	See L</Abusing an ev_check watcher for its side-effect> for a longer
		2865	example.
		2866
2597	=head3 Watcher-Specific Functions and Data Members	2867	=head3 Watcher-Specific Functions and Data Members
2598		2868
2599	=over 4	2869	=over 4
2600		2870
2601	=item ev_idle_init (ev_idle *, callback)	2871	=item ev_idle_init (ev_idle *, callback)
…		…
2612	callback, free it. Also, use no error checking, as usual.	2882	callback, free it. Also, use no error checking, as usual.
2613		2883
2614	static void	2884	static void
2615	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	2885	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2616	{	2886	{
		2887	// stop the watcher
		2888	ev_idle_stop (loop, w);
		2889
		2890	// now we can free it
2617	free (w);	2891	free (w);
		2892
2618	// now do something you wanted to do when the program has	2893	// now do something you wanted to do when the program has
2619	// no longer anything immediate to do.	2894	// no longer anything immediate to do.
2620	}	2895	}
2621		2896
2622	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2897	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
…		…
2624	ev_idle_start (loop, idle_watcher);	2899	ev_idle_start (loop, idle_watcher);
2625		2900
2626		2901
2627	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2902	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2628		2903
2629	Prepare and check watchers are usually (but not always) used in pairs:	2904	Prepare and check watchers are often (but not always) used in pairs:
2630	prepare watchers get invoked before the process blocks and check watchers	2905	prepare watchers get invoked before the process blocks and check watchers
2631	afterwards.	2906	afterwards.
2632		2907
2633	You I<must not> call C<ev_loop> or similar functions that enter	2908	You I<must not> call C<ev_run> or similar functions that enter
2634	the current event loop from either C<ev_prepare> or C<ev_check>	2909	the current event loop from either C<ev_prepare> or C<ev_check>
2635	watchers. Other loops than the current one are fine, however. The	2910	watchers. Other loops than the current one are fine, however. The
2636	rationale behind this is that you do not need to check for recursion in	2911	rationale behind this is that you do not need to check for recursion in
2637	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2912	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2638	C<ev_check> so if you have one watcher of each kind they will always be	2913	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2662	with priority higher than or equal to the event loop and one coroutine	2937	with priority higher than or equal to the event loop and one coroutine
2663	of lower priority, but only once, using idle watchers to keep the event	2938	of lower priority, but only once, using idle watchers to keep the event
2664	loop from blocking if lower-priority coroutines are active, thus mapping	2939	loop from blocking if lower-priority coroutines are active, thus mapping
2665	low-priority coroutines to idle/background tasks).	2940	low-priority coroutines to idle/background tasks).
2666		2941
2667	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2942	When used for this purpose, it is recommended to give C<ev_check> watchers
2668	priority, to ensure that they are being run before any other watchers	2943	highest (C<EV_MAXPRI>) priority, to ensure that they are being run before
2669	after the poll (this doesn't matter for C<ev_prepare> watchers).	2944	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		2945	watchers).
2670		2946
2671	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	2947	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
2672	activate ("feed") events into libev. While libev fully supports this, they	2948	activate ("feed") events into libev. While libev fully supports this, they
2673	might get executed before other C<ev_check> watchers did their job. As	2949	might get executed before other C<ev_check> watchers did their job. As
2674	C<ev_check> watchers are often used to embed other (non-libev) event	2950	C<ev_check> watchers are often used to embed other (non-libev) event
2675	loops those other event loops might be in an unusable state until their	2951	loops those other event loops might be in an unusable state until their
2676	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	2952	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2677	others).	2953	others).
		2954
		2955	=head3 Abusing an C<ev_check> watcher for its side-effect
		2956
		2957	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		2958	useful because they are called once per event loop iteration. For
		2959	example, if you want to handle a large number of connections fairly, you
		2960	normally only do a bit of work for each active connection, and if there
		2961	is more work to do, you wait for the next event loop iteration, so other
		2962	connections have a chance of making progress.
		2963
		2964	Using an C<ev_check> watcher is almost enough: it will be called on the
		2965	next event loop iteration. However, that isn't as soon as possible -
		2966	without external events, your C<ev_check> watcher will not be invoked.
		2967
		2968	This is where C<ev_idle> watchers come in handy - all you need is a
		2969	single global idle watcher that is active as long as you have one active
		2970	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		2971	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		2972	invoked. Neither watcher alone can do that.
2678		2973
2679	=head3 Watcher-Specific Functions and Data Members	2974	=head3 Watcher-Specific Functions and Data Members
2680		2975
2681	=over 4	2976	=over 4
2682		2977
…		…
2806		3101
2807	if (timeout >= 0)	3102	if (timeout >= 0)
2808	// create/start timer	3103	// create/start timer
2809		3104
2810	// poll	3105	// poll
2811	ev_loop (EV_A_ 0);	3106	ev_run (EV_A_ 0);
2812		3107
2813	// stop timer again	3108	// stop timer again
2814	if (timeout >= 0)	3109	if (timeout >= 0)
2815	ev_timer_stop (EV_A_ &to);	3110	ev_timer_stop (EV_A_ &to);
2816		3111
…		…
2883		3178
2884	=over 4	3179	=over 4
2885		3180
2886	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	3181	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
2887		3182
2888	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	3183	=item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)
2889		3184
2890	Configures the watcher to embed the given loop, which must be	3185	Configures the watcher to embed the given loop, which must be
2891	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	3186	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2892	invoked automatically, otherwise it is the responsibility of the callback	3187	invoked automatically, otherwise it is the responsibility of the callback
2893	to invoke it (it will continue to be called until the sweep has been done,	3188	to invoke it (it will continue to be called until the sweep has been done,
2894	if you do not want that, you need to temporarily stop the embed watcher).	3189	if you do not want that, you need to temporarily stop the embed watcher).
2895		3190
2896	=item ev_embed_sweep (loop, ev_embed *)	3191	=item ev_embed_sweep (loop, ev_embed *)
2897		3192
2898	Make a single, non-blocking sweep over the embedded loop. This works	3193	Make a single, non-blocking sweep over the embedded loop. This works
2899	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3194	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2900	appropriate way for embedded loops.	3195	appropriate way for embedded loops.
2901		3196
2902	=item struct ev_loop *other [read-only]	3197	=item struct ev_loop *other [read-only]
2903		3198
2904	The embedded event loop.	3199	The embedded event loop.
…		…
2956		3251
2957	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3252	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2958		3253
2959	Fork watchers are called when a C<fork ()> was detected (usually because	3254	Fork watchers are called when a C<fork ()> was detected (usually because
2960	whoever is a good citizen cared to tell libev about it by calling	3255	whoever is a good citizen cared to tell libev about it by calling
2961	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the	3256	C<ev_loop_fork>). The invocation is done before the event loop blocks next
2962	event loop blocks next and before C<ev_check> watchers are being called,	3257	and before C<ev_check> watchers are being called, and only in the child
2963	and only in the child after the fork. If whoever good citizen calling	3258	after the fork. If whoever good citizen calling C<ev_default_fork> cheats
2964	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3259	and calls it in the wrong process, the fork handlers will be invoked, too,
2965	handlers will be invoked, too, of course.	3260	of course.
2966		3261
2967	=head3 The special problem of life after fork - how is it possible?	3262	=head3 The special problem of life after fork - how is it possible?
2968		3263
2969	Most uses of C<fork()> consist of forking, then some simple calls to ste	3264	Most uses of C<fork()> consist of forking, then some simple calls to set
2970	up/change the process environment, followed by a call to C<exec()>. This	3265	up/change the process environment, followed by a call to C<exec()>. This
2971	sequence should be handled by libev without any problems.	3266	sequence should be handled by libev without any problems.
2972		3267
2973	This changes when the application actually wants to do event handling	3268	This changes when the application actually wants to do event handling
2974	in the child, or both parent in child, in effect "continuing" after the	3269	in the child, or both parent in child, in effect "continuing" after the
…		…
2990	disadvantage of having to use multiple event loops (which do not support	3285	disadvantage of having to use multiple event loops (which do not support
2991	signal watchers).	3286	signal watchers).
2992		3287
2993	When this is not possible, or you want to use the default loop for	3288	When this is not possible, or you want to use the default loop for
2994	other reasons, then in the process that wants to start "fresh", call	3289	other reasons, then in the process that wants to start "fresh", call
2995	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3290	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
2996	the default loop will "orphan" (not stop) all registered watchers, so you	3291	Destroying the default loop will "orphan" (not stop) all registered
2997	have to be careful not to execute code that modifies those watchers. Note	3292	watchers, so you have to be careful not to execute code that modifies
2998	also that in that case, you have to re-register any signal watchers.	3293	those watchers. Note also that in that case, you have to re-register any
		3294	signal watchers.
2999		3295
3000	=head3 Watcher-Specific Functions and Data Members	3296	=head3 Watcher-Specific Functions and Data Members
3001		3297
3002	=over 4	3298	=over 4
3003		3299
3004	=item ev_fork_init (ev_signal *, callback)	3300	=item ev_fork_init (ev_fork *, callback)
3005		3301
3006	Initialises and configures the fork watcher - it has no parameters of any	3302	Initialises and configures the fork watcher - it has no parameters of any
3007	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3303	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
3008	believe me.	3304	really.
3009		3305
3010	=back	3306	=back
3011		3307
3012		3308
		3309	=head2 C<ev_cleanup> - even the best things end
		3310
		3311	Cleanup watchers are called just before the event loop is being destroyed
		3312	by a call to C<ev_loop_destroy>.
		3313
		3314	While there is no guarantee that the event loop gets destroyed, cleanup
		3315	watchers provide a convenient method to install cleanup hooks for your
		3316	program, worker threads and so on - you just to make sure to destroy the
		3317	loop when you want them to be invoked.
		3318
		3319	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3320	all other watchers, they do not keep a reference to the event loop (which
		3321	makes a lot of sense if you think about it). Like all other watchers, you
		3322	can call libev functions in the callback, except C<ev_cleanup_start>.
		3323
		3324	=head3 Watcher-Specific Functions and Data Members
		3325
		3326	=over 4
		3327
		3328	=item ev_cleanup_init (ev_cleanup *, callback)
		3329
		3330	Initialises and configures the cleanup watcher - it has no parameters of
		3331	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3332	pointless, I assure you.
		3333
		3334	=back
		3335
		3336	Example: Register an atexit handler to destroy the default loop, so any
		3337	cleanup functions are called.
		3338
		3339	static void
		3340	program_exits (void)
		3341	{
		3342	ev_loop_destroy (EV_DEFAULT_UC);
		3343	}
		3344
		3345	...
		3346	atexit (program_exits);
		3347
		3348
3013	=head2 C<ev_async> - how to wake up another event loop	3349	=head2 C<ev_async> - how to wake up an event loop
3014		3350
3015	In general, you cannot use an C<ev_loop> from multiple threads or other	3351	In general, you cannot use an C<ev_loop> from multiple threads or other
3016	asynchronous sources such as signal handlers (as opposed to multiple event	3352	asynchronous sources such as signal handlers (as opposed to multiple event
3017	loops - those are of course safe to use in different threads).	3353	loops - those are of course safe to use in different threads).
3018		3354
3019	Sometimes, however, you need to wake up another event loop you do not	3355	Sometimes, however, you need to wake up an event loop you do not control,
3020	control, for example because it belongs to another thread. This is what	3356	for example because it belongs to another thread. This is what C<ev_async>
3021	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3357	watchers do: as long as the C<ev_async> watcher is active, you can signal
3022	can signal it by calling C<ev_async_send>, which is thread- and signal	3358	it by calling C<ev_async_send>, which is thread- and signal safe.
3023	safe.
3024		3359
3025	This functionality is very similar to C<ev_signal> watchers, as signals,	3360	This functionality is very similar to C<ev_signal> watchers, as signals,
3026	too, are asynchronous in nature, and signals, too, will be compressed	3361	too, are asynchronous in nature, and signals, too, will be compressed
3027	(i.e. the number of callback invocations may be less than the number of	3362	(i.e. the number of callback invocations may be less than the number of
3028	C<ev_async_sent> calls).	3363	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
3029		3364	of "global async watchers" by using a watcher on an otherwise unused
3030	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3365	signal, and C<ev_feed_signal> to signal this watcher from another thread,
3031	just the default loop.	3366	even without knowing which loop owns the signal.
3032		3367
3033	=head3 Queueing	3368	=head3 Queueing
3034		3369
3035	C<ev_async> does not support queueing of data in any way. The reason	3370	C<ev_async> does not support queueing of data in any way. The reason
3036	is that the author does not know of a simple (or any) algorithm for a	3371	is that the author does not know of a simple (or any) algorithm for a
…		…
3128	trust me.	3463	trust me.
3129		3464
3130	=item ev_async_send (loop, ev_async *)	3465	=item ev_async_send (loop, ev_async *)
3131		3466
3132	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3467	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3133	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3468	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3469	returns.
		3470
3134	C<ev_feed_event>, this call is safe to do from other threads, signal or	3471	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3135	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3472	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3136	section below on what exactly this means).	3473	embedding section below on what exactly this means).
3137		3474
3138	Note that, as with other watchers in libev, multiple events might get	3475	Note that, as with other watchers in libev, multiple events might get
3139	compressed into a single callback invocation (another way to look at this	3476	compressed into a single callback invocation (another way to look at
3140	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3477	this is that C<ev_async> watchers are level-triggered: they are set on
3141	reset when the event loop detects that).	3478	C<ev_async_send>, reset when the event loop detects that).
3142		3479
3143	This call incurs the overhead of a system call only once per event loop	3480	This call incurs the overhead of at most one extra system call per event
3144	iteration, so while the overhead might be noticeable, it doesn't apply to	3481	loop iteration, if the event loop is blocked, and no syscall at all if
3145	repeated calls to C<ev_async_send> for the same event loop.	3482	the event loop (or your program) is processing events. That means that
		3483	repeated calls are basically free (there is no need to avoid calls for
		3484	performance reasons) and that the overhead becomes smaller (typically
		3485	zero) under load.
3146		3486
3147	=item bool = ev_async_pending (ev_async *)	3487	=item bool = ev_async_pending (ev_async *)
3148		3488
3149	Returns a non-zero value when C<ev_async_send> has been called on the	3489	Returns a non-zero value when C<ev_async_send> has been called on the
3150	watcher but the event has not yet been processed (or even noted) by the	3490	watcher but the event has not yet been processed (or even noted) by the
…		…
3205	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3545	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3206		3546
3207	=item ev_feed_fd_event (loop, int fd, int revents)	3547	=item ev_feed_fd_event (loop, int fd, int revents)
3208		3548
3209	Feed an event on the given fd, as if a file descriptor backend detected	3549	Feed an event on the given fd, as if a file descriptor backend detected
3210	the given events it.	3550	the given events.
3211		3551
3212	=item ev_feed_signal_event (loop, int signum)	3552	=item ev_feed_signal_event (loop, int signum)
3213		3553
3214	Feed an event as if the given signal occurred (C<loop> must be the default	3554	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3215	loop!).	3555	which is async-safe.
3216		3556
3217	=back	3557	=back
		3558
		3559
		3560	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3561
		3562	This section explains some common idioms that are not immediately
		3563	obvious. Note that examples are sprinkled over the whole manual, and this
		3564	section only contains stuff that wouldn't fit anywhere else.
		3565
		3566	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3567
		3568	Each watcher has, by default, a C<void *data> member that you can read
		3569	or modify at any time: libev will completely ignore it. This can be used
		3570	to associate arbitrary data with your watcher. If you need more data and
		3571	don't want to allocate memory separately and store a pointer to it in that
		3572	data member, you can also "subclass" the watcher type and provide your own
		3573	data:
		3574
		3575	struct my_io
		3576	{
		3577	ev_io io;
		3578	int otherfd;
		3579	void *somedata;
		3580	struct whatever *mostinteresting;
		3581	};
		3582
		3583	...
		3584	struct my_io w;
		3585	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3586
		3587	And since your callback will be called with a pointer to the watcher, you
		3588	can cast it back to your own type:
		3589
		3590	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3591	{
		3592	struct my_io *w = (struct my_io *)w_;
		3593	...
		3594	}
		3595
		3596	More interesting and less C-conformant ways of casting your callback
		3597	function type instead have been omitted.
		3598
		3599	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3600
		3601	Another common scenario is to use some data structure with multiple
		3602	embedded watchers, in effect creating your own watcher that combines
		3603	multiple libev event sources into one "super-watcher":
		3604
		3605	struct my_biggy
		3606	{
		3607	int some_data;
		3608	ev_timer t1;
		3609	ev_timer t2;
		3610	}
		3611
		3612	In this case getting the pointer to C<my_biggy> is a bit more
		3613	complicated: Either you store the address of your C<my_biggy> struct in
		3614	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3615	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3616	real programmers):
		3617
		3618	#include <stddef.h>
		3619
		3620	static void
		3621	t1_cb (EV_P_ ev_timer *w, int revents)
		3622	{
		3623	struct my_biggy big = (struct my_biggy *)
		3624	(((char *)w) - offsetof (struct my_biggy, t1));
		3625	}
		3626
		3627	static void
		3628	t2_cb (EV_P_ ev_timer *w, int revents)
		3629	{
		3630	struct my_biggy big = (struct my_biggy *)
		3631	(((char *)w) - offsetof (struct my_biggy, t2));
		3632	}
		3633
		3634	=head2 AVOIDING FINISHING BEFORE RETURNING
		3635
		3636	Often you have structures like this in event-based programs:
		3637
		3638	callback ()
		3639	{
		3640	free (request);
		3641	}
		3642
		3643	request = start_new_request (..., callback);
		3644
		3645	The intent is to start some "lengthy" operation. The C<request> could be
		3646	used to cancel the operation, or do other things with it.
		3647
		3648	It's not uncommon to have code paths in C<start_new_request> that
		3649	immediately invoke the callback, for example, to report errors. Or you add
		3650	some caching layer that finds that it can skip the lengthy aspects of the
		3651	operation and simply invoke the callback with the result.
		3652
		3653	The problem here is that this will happen I<before> C<start_new_request>
		3654	has returned, so C<request> is not set.
		3655
		3656	Even if you pass the request by some safer means to the callback, you
		3657	might want to do something to the request after starting it, such as
		3658	canceling it, which probably isn't working so well when the callback has
		3659	already been invoked.
		3660
		3661	A common way around all these issues is to make sure that
		3662	C<start_new_request> I<always> returns before the callback is invoked. If
		3663	C<start_new_request> immediately knows the result, it can artificially
		3664	delay invoking the callback by using a C<prepare> or C<idle> watcher for
		3665	example, or more sneakily, by reusing an existing (stopped) watcher and
		3666	pushing it into the pending queue:
		3667
		3668	ev_set_cb (watcher, callback);
		3669	ev_feed_event (EV_A_ watcher, 0);
		3670
		3671	This way, C<start_new_request> can safely return before the callback is
		3672	invoked, while not delaying callback invocation too much.
		3673
		3674	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3675
		3676	Often (especially in GUI toolkits) there are places where you have
		3677	I<modal> interaction, which is most easily implemented by recursively
		3678	invoking C<ev_run>.
		3679
		3680	This brings the problem of exiting - a callback might want to finish the
		3681	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3682	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3683	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3684	other combination: In these cases, a simple C<ev_break> will not work.
		3685
		3686	The solution is to maintain "break this loop" variable for each C<ev_run>
		3687	invocation, and use a loop around C<ev_run> until the condition is
		3688	triggered, using C<EVRUN_ONCE>:
		3689
		3690	// main loop
		3691	int exit_main_loop = 0;
		3692
		3693	while (!exit_main_loop)
		3694	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3695
		3696	// in a modal watcher
		3697	int exit_nested_loop = 0;
		3698
		3699	while (!exit_nested_loop)
		3700	ev_run (EV_A_ EVRUN_ONCE);
		3701
		3702	To exit from any of these loops, just set the corresponding exit variable:
		3703
		3704	// exit modal loop
		3705	exit_nested_loop = 1;
		3706
		3707	// exit main program, after modal loop is finished
		3708	exit_main_loop = 1;
		3709
		3710	// exit both
		3711	exit_main_loop = exit_nested_loop = 1;
		3712
		3713	=head2 THREAD LOCKING EXAMPLE
		3714
		3715	Here is a fictitious example of how to run an event loop in a different
		3716	thread from where callbacks are being invoked and watchers are
		3717	created/added/removed.
		3718
		3719	For a real-world example, see the C<EV::Loop::Async> perl module,
		3720	which uses exactly this technique (which is suited for many high-level
		3721	languages).
		3722
		3723	The example uses a pthread mutex to protect the loop data, a condition
		3724	variable to wait for callback invocations, an async watcher to notify the
		3725	event loop thread and an unspecified mechanism to wake up the main thread.
		3726
		3727	First, you need to associate some data with the event loop:
		3728
		3729	typedef struct {
		3730	mutex_t lock; /* global loop lock */
		3731	ev_async async_w;
		3732	thread_t tid;
		3733	cond_t invoke_cv;
		3734	} userdata;
		3735
		3736	void prepare_loop (EV_P)
		3737	{
		3738	// for simplicity, we use a static userdata struct.
		3739	static userdata u;
		3740
		3741	ev_async_init (&u->async_w, async_cb);
		3742	ev_async_start (EV_A_ &u->async_w);
		3743
		3744	pthread_mutex_init (&u->lock, 0);
		3745	pthread_cond_init (&u->invoke_cv, 0);
		3746
		3747	// now associate this with the loop
		3748	ev_set_userdata (EV_A_ u);
		3749	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3750	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3751
		3752	// then create the thread running ev_run
		3753	pthread_create (&u->tid, 0, l_run, EV_A);
		3754	}
		3755
		3756	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3757	solely to wake up the event loop so it takes notice of any new watchers
		3758	that might have been added:
		3759
		3760	static void
		3761	async_cb (EV_P_ ev_async *w, int revents)
		3762	{
		3763	// just used for the side effects
		3764	}
		3765
		3766	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3767	protecting the loop data, respectively.
		3768
		3769	static void
		3770	l_release (EV_P)
		3771	{
		3772	userdata *u = ev_userdata (EV_A);
		3773	pthread_mutex_unlock (&u->lock);
		3774	}
		3775
		3776	static void
		3777	l_acquire (EV_P)
		3778	{
		3779	userdata *u = ev_userdata (EV_A);
		3780	pthread_mutex_lock (&u->lock);
		3781	}
		3782
		3783	The event loop thread first acquires the mutex, and then jumps straight
		3784	into C<ev_run>:
		3785
		3786	void *
		3787	l_run (void *thr_arg)
		3788	{
		3789	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3790
		3791	l_acquire (EV_A);
		3792	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3793	ev_run (EV_A_ 0);
		3794	l_release (EV_A);
		3795
		3796	return 0;
		3797	}
		3798
		3799	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3800	signal the main thread via some unspecified mechanism (signals? pipe
		3801	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3802	have been called (in a while loop because a) spurious wakeups are possible
		3803	and b) skipping inter-thread-communication when there are no pending
		3804	watchers is very beneficial):
		3805
		3806	static void
		3807	l_invoke (EV_P)
		3808	{
		3809	userdata *u = ev_userdata (EV_A);
		3810
		3811	while (ev_pending_count (EV_A))
		3812	{
		3813	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3814	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3815	}
		3816	}
		3817
		3818	Now, whenever the main thread gets told to invoke pending watchers, it
		3819	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3820	thread to continue:
		3821
		3822	static void
		3823	real_invoke_pending (EV_P)
		3824	{
		3825	userdata *u = ev_userdata (EV_A);
		3826
		3827	pthread_mutex_lock (&u->lock);
		3828	ev_invoke_pending (EV_A);
		3829	pthread_cond_signal (&u->invoke_cv);
		3830	pthread_mutex_unlock (&u->lock);
		3831	}
		3832
		3833	Whenever you want to start/stop a watcher or do other modifications to an
		3834	event loop, you will now have to lock:
		3835
		3836	ev_timer timeout_watcher;
		3837	userdata *u = ev_userdata (EV_A);
		3838
		3839	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3840
		3841	pthread_mutex_lock (&u->lock);
		3842	ev_timer_start (EV_A_ &timeout_watcher);
		3843	ev_async_send (EV_A_ &u->async_w);
		3844	pthread_mutex_unlock (&u->lock);
		3845
		3846	Note that sending the C<ev_async> watcher is required because otherwise
		3847	an event loop currently blocking in the kernel will have no knowledge
		3848	about the newly added timer. By waking up the loop it will pick up any new
		3849	watchers in the next event loop iteration.
		3850
		3851	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3852
		3853	While the overhead of a callback that e.g. schedules a thread is small, it
		3854	is still an overhead. If you embed libev, and your main usage is with some
		3855	kind of threads or coroutines, you might want to customise libev so that
		3856	doesn't need callbacks anymore.
		3857
		3858	Imagine you have coroutines that you can switch to using a function
		3859	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3860	and that due to some magic, the currently active coroutine is stored in a
		3861	global called C<current_coro>. Then you can build your own "wait for libev
		3862	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3863	the differing C<;> conventions):
		3864
		3865	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3866	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3867
		3868	That means instead of having a C callback function, you store the
		3869	coroutine to switch to in each watcher, and instead of having libev call
		3870	your callback, you instead have it switch to that coroutine.
		3871
		3872	A coroutine might now wait for an event with a function called
		3873	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3874	matter when, or whether the watcher is active or not when this function is
		3875	called):
		3876
		3877	void
		3878	wait_for_event (ev_watcher *w)
		3879	{
		3880	ev_set_cb (w, current_coro);
		3881	switch_to (libev_coro);
		3882	}
		3883
		3884	That basically suspends the coroutine inside C<wait_for_event> and
		3885	continues the libev coroutine, which, when appropriate, switches back to
		3886	this or any other coroutine.
		3887
		3888	You can do similar tricks if you have, say, threads with an event queue -
		3889	instead of storing a coroutine, you store the queue object and instead of
		3890	switching to a coroutine, you push the watcher onto the queue and notify
		3891	any waiters.
		3892
		3893	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		3894	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3895
		3896	// my_ev.h
		3897	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3898	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3899	#include "../libev/ev.h"
		3900
		3901	// my_ev.c
		3902	#define EV_H "my_ev.h"
		3903	#include "../libev/ev.c"
		3904
		3905	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3906	F<my_ev.c> into your project. When properly specifying include paths, you
		3907	can even use F<ev.h> as header file name directly.
3218		3908
3219		3909
3220	=head1 LIBEVENT EMULATION	3910	=head1 LIBEVENT EMULATION
3221		3911
3222	Libev offers a compatibility emulation layer for libevent. It cannot	3912	Libev offers a compatibility emulation layer for libevent. It cannot
3223	emulate the internals of libevent, so here are some usage hints:	3913	emulate the internals of libevent, so here are some usage hints:
3224		3914
3225	=over 4	3915	=over 4
		3916
		3917	=item * Only the libevent-1.4.1-beta API is being emulated.
		3918
		3919	This was the newest libevent version available when libev was implemented,
		3920	and is still mostly unchanged in 2010.
3226		3921
3227	=item * Use it by including <event.h>, as usual.	3922	=item * Use it by including <event.h>, as usual.
3228		3923
3229	=item * The following members are fully supported: ev_base, ev_callback,	3924	=item * The following members are fully supported: ev_base, ev_callback,
3230	ev_arg, ev_fd, ev_res, ev_events.	3925	ev_arg, ev_fd, ev_res, ev_events.
…		…
3236	=item * Priorities are not currently supported. Initialising priorities	3931	=item * Priorities are not currently supported. Initialising priorities
3237	will fail and all watchers will have the same priority, even though there	3932	will fail and all watchers will have the same priority, even though there
3238	is an ev_pri field.	3933	is an ev_pri field.
3239		3934
3240	=item * In libevent, the last base created gets the signals, in libev, the	3935	=item * In libevent, the last base created gets the signals, in libev, the
3241	first base created (== the default loop) gets the signals.	3936	base that registered the signal gets the signals.
3242		3937
3243	=item * Other members are not supported.	3938	=item * Other members are not supported.
3244		3939
3245	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3940	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3246	to use the libev header file and library.	3941	to use the libev header file and library.
3247		3942
3248	=back	3943	=back
3249		3944
3250	=head1 C++ SUPPORT	3945	=head1 C++ SUPPORT
		3946
		3947	=head2 C API
		3948
		3949	The normal C API should work fine when used from C++: both ev.h and the
		3950	libev sources can be compiled as C++. Therefore, code that uses the C API
		3951	will work fine.
		3952
		3953	Proper exception specifications might have to be added to callbacks passed
		3954	to libev: exceptions may be thrown only from watcher callbacks, all
		3955	other callbacks (allocator, syserr, loop acquire/release and periodic
		3956	reschedule callbacks) must not throw exceptions, and might need a C<throw
		3957	()> specification. If you have code that needs to be compiled as both C
		3958	and C++ you can use the C<EV_THROW> macro for this:
		3959
		3960	static void
		3961	fatal_error (const char *msg) EV_THROW
		3962	{
		3963	perror (msg);
		3964	abort ();
		3965	}
		3966
		3967	...
		3968	ev_set_syserr_cb (fatal_error);
		3969
		3970	The only API functions that can currently throw exceptions are C<ev_run>,
		3971	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		3972	because it runs cleanup watchers).
		3973
		3974	Throwing exceptions in watcher callbacks is only supported if libev itself
		3975	is compiled with a C++ compiler or your C and C++ environments allow
		3976	throwing exceptions through C libraries (most do).
		3977
		3978	=head2 C++ API
3251		3979
3252	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3980	Libev comes with some simplistic wrapper classes for C++ that mainly allow
3253	you to use some convenience methods to start/stop watchers and also change	3981	you to use some convenience methods to start/stop watchers and also change
3254	the callback model to a model using method callbacks on objects.	3982	the callback model to a model using method callbacks on objects.
3255		3983
…		…
3265	Care has been taken to keep the overhead low. The only data member the C++	3993	Care has been taken to keep the overhead low. The only data member the C++
3266	classes add (compared to plain C-style watchers) is the event loop pointer	3994	classes add (compared to plain C-style watchers) is the event loop pointer
3267	that the watcher is associated with (or no additional members at all if	3995	that the watcher is associated with (or no additional members at all if
3268	you disable C<EV_MULTIPLICITY> when embedding libev).	3996	you disable C<EV_MULTIPLICITY> when embedding libev).
3269		3997
3270	Currently, functions, and static and non-static member functions can be	3998	Currently, functions, static and non-static member functions and classes
3271	used as callbacks. Other types should be easy to add as long as they only	3999	with C<operator ()> can be used as callbacks. Other types should be easy
3272	need one additional pointer for context. If you need support for other	4000	to add as long as they only need one additional pointer for context. If
3273	types of functors please contact the author (preferably after implementing	4001	you need support for other types of functors please contact the author
3274	it).	4002	(preferably after implementing it).
		4003
		4004	For all this to work, your C++ compiler either has to use the same calling
		4005	conventions as your C compiler (for static member functions), or you have
		4006	to embed libev and compile libev itself as C++.
3275		4007
3276	Here is a list of things available in the C<ev> namespace:	4008	Here is a list of things available in the C<ev> namespace:
3277		4009
3278	=over 4	4010	=over 4
3279		4011
…		…
3289	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4021	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3290		4022
3291	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4023	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
3292	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4024	the same name in the C<ev> namespace, with the exception of C<ev_signal>
3293	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4025	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3294	defines by many implementations.	4026	defined by many implementations.
3295		4027
3296	All of those classes have these methods:	4028	All of those classes have these methods:
3297		4029
3298	=over 4	4030	=over 4
3299		4031
…		…
3340	myclass obj;	4072	myclass obj;
3341	ev::io iow;	4073	ev::io iow;
3342	iow.set <myclass, &myclass::io_cb> (&obj);	4074	iow.set <myclass, &myclass::io_cb> (&obj);
3343		4075
3344	=item w->set (object *)	4076	=item w->set (object *)
3345
3346	This is an B<experimental> feature that might go away in a future version.
3347		4077
3348	This is a variation of a method callback - leaving out the method to call	4078	This is a variation of a method callback - leaving out the method to call
3349	will default the method to C<operator ()>, which makes it possible to use	4079	will default the method to C<operator ()>, which makes it possible to use
3350	functor objects without having to manually specify the C<operator ()> all	4080	functor objects without having to manually specify the C<operator ()> all
3351	the time. Incidentally, you can then also leave out the template argument	4081	the time. Incidentally, you can then also leave out the template argument
…		…
3391	Associates a different C<struct ev_loop> with this watcher. You can only	4121	Associates a different C<struct ev_loop> with this watcher. You can only
3392	do this when the watcher is inactive (and not pending either).	4122	do this when the watcher is inactive (and not pending either).
3393		4123
3394	=item w->set ([arguments])	4124	=item w->set ([arguments])
3395		4125
3396	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	4126	Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>),
		4127	with the same arguments. Either this method or a suitable start method
3397	called at least once. Unlike the C counterpart, an active watcher gets	4128	must be called at least once. Unlike the C counterpart, an active watcher
3398	automatically stopped and restarted when reconfiguring it with this	4129	gets automatically stopped and restarted when reconfiguring it with this
3399	method.	4130	method.
		4131
		4132	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4133	clashing with the C<set (loop)> method.
3400		4134
3401	=item w->start ()	4135	=item w->start ()
3402		4136
3403	Starts the watcher. Note that there is no C<loop> argument, as the	4137	Starts the watcher. Note that there is no C<loop> argument, as the
3404	constructor already stores the event loop.	4138	constructor already stores the event loop.
3405		4139
		4140	=item w->start ([arguments])
		4141
		4142	Instead of calling C<set> and C<start> methods separately, it is often
		4143	convenient to wrap them in one call. Uses the same type of arguments as
		4144	the configure C<set> method of the watcher.
		4145
3406	=item w->stop ()	4146	=item w->stop ()
3407		4147
3408	Stops the watcher if it is active. Again, no C<loop> argument.	4148	Stops the watcher if it is active. Again, no C<loop> argument.
3409		4149
3410	=item w->again () (C<ev::timer>, C<ev::periodic> only)	4150	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3422		4162
3423	=back	4163	=back
3424		4164
3425	=back	4165	=back
3426		4166
3427	Example: Define a class with an IO and idle watcher, start one of them in	4167	Example: Define a class with two I/O and idle watchers, start the I/O
3428	the constructor.	4168	watchers in the constructor.
3429		4169
3430	class myclass	4170	class myclass
3431	{	4171	{
3432	ev::io io ; void io_cb (ev::io &w, int revents);	4172	ev::io io ; void io_cb (ev::io &w, int revents);
		4173	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3433	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4174	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3434		4175
3435	myclass (int fd)	4176	myclass (int fd)
3436	{	4177	{
3437	io .set <myclass, &myclass::io_cb > (this);	4178	io .set <myclass, &myclass::io_cb > (this);
		4179	io2 .set <myclass, &myclass::io2_cb > (this);
3438	idle.set <myclass, &myclass::idle_cb> (this);	4180	idle.set <myclass, &myclass::idle_cb> (this);
3439		4181
3440	io.start (fd, ev::READ);	4182	io.set (fd, ev::WRITE); // configure the watcher
		4183	io.start (); // start it whenever convenient
		4184
		4185	io2.start (fd, ev::READ); // set + start in one call
3441	}	4186	}
3442	};	4187	};
3443		4188
3444		4189
3445	=head1 OTHER LANGUAGE BINDINGS	4190	=head1 OTHER LANGUAGE BINDINGS
…		…
3484	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4229	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3485		4230
3486	=item D	4231	=item D
3487		4232
3488	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4233	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3489	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4234	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3490		4235
3491	=item Ocaml	4236	=item Ocaml
3492		4237
3493	Erkki Seppala has written Ocaml bindings for libev, to be found at	4238	Erkki Seppala has written Ocaml bindings for libev, to be found at
3494	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4239	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
…		…
3497		4242
3498	Brian Maher has written a partial interface to libev for lua (at the	4243	Brian Maher has written a partial interface to libev for lua (at the
3499	time of this writing, only C<ev_io> and C<ev_timer>), to be found at	4244	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
3500	L<http://github.com/brimworks/lua-ev>.	4245	L<http://github.com/brimworks/lua-ev>.
3501		4246
		4247	=item Javascript
		4248
		4249	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4250
		4251	=item Others
		4252
		4253	There are others, and I stopped counting.
		4254
3502	=back	4255	=back
3503		4256
3504		4257
3505	=head1 MACRO MAGIC	4258	=head1 MACRO MAGIC
3506		4259
…		…
3519	loop argument"). The C<EV_A> form is used when this is the sole argument,	4272	loop argument"). The C<EV_A> form is used when this is the sole argument,
3520	C<EV_A_> is used when other arguments are following. Example:	4273	C<EV_A_> is used when other arguments are following. Example:
3521		4274
3522	ev_unref (EV_A);	4275	ev_unref (EV_A);
3523	ev_timer_add (EV_A_ watcher);	4276	ev_timer_add (EV_A_ watcher);
3524	ev_loop (EV_A_ 0);	4277	ev_run (EV_A_ 0);
3525		4278
3526	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4279	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3527	which is often provided by the following macro.	4280	which is often provided by the following macro.
3528		4281
3529	=item C<EV_P>, C<EV_P_>	4282	=item C<EV_P>, C<EV_P_>
…		…
3542	suitable for use with C<EV_A>.	4295	suitable for use with C<EV_A>.
3543		4296
3544	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4297	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3545		4298
3546	Similar to the other two macros, this gives you the value of the default	4299	Similar to the other two macros, this gives you the value of the default
3547	loop, if multiple loops are supported ("ev loop default").	4300	loop, if multiple loops are supported ("ev loop default"). The default loop
		4301	will be initialised if it isn't already initialised.
		4302
		4303	For non-multiplicity builds, these macros do nothing, so you always have
		4304	to initialise the loop somewhere.
3548		4305
3549	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4306	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3550		4307
3551	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4308	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3552	default loop has been initialised (C<UC> == unchecked). Their behaviour	4309	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3569	}	4326	}
3570		4327
3571	ev_check check;	4328	ev_check check;
3572	ev_check_init (&check, check_cb);	4329	ev_check_init (&check, check_cb);
3573	ev_check_start (EV_DEFAULT_ &check);	4330	ev_check_start (EV_DEFAULT_ &check);
3574	ev_loop (EV_DEFAULT_ 0);	4331	ev_run (EV_DEFAULT_ 0);
3575		4332
3576	=head1 EMBEDDING	4333	=head1 EMBEDDING
3577		4334
3578	Libev can (and often is) directly embedded into host	4335	Libev can (and often is) directly embedded into host
3579	applications. Examples of applications that embed it include the Deliantra	4336	applications. Examples of applications that embed it include the Deliantra
…		…
3671	users of libev and the libev code itself must be compiled with compatible	4428	users of libev and the libev code itself must be compiled with compatible
3672	settings.	4429	settings.
3673		4430
3674	=over 4	4431	=over 4
3675		4432
		4433	=item EV_COMPAT3 (h)
		4434
		4435	Backwards compatibility is a major concern for libev. This is why this
		4436	release of libev comes with wrappers for the functions and symbols that
		4437	have been renamed between libev version 3 and 4.
		4438
		4439	You can disable these wrappers (to test compatibility with future
		4440	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4441	sources. This has the additional advantage that you can drop the C<struct>
		4442	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4443	typedef in that case.
		4444
		4445	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4446	and in some even more future version the compatibility code will be
		4447	removed completely.
		4448
3676	=item EV_STANDALONE (h)	4449	=item EV_STANDALONE (h)
3677		4450
3678	Must always be C<1> if you do not use autoconf configuration, which	4451	Must always be C<1> if you do not use autoconf configuration, which
3679	keeps libev from including F<config.h>, and it also defines dummy	4452	keeps libev from including F<config.h>, and it also defines dummy
3680	implementations for some libevent functions (such as logging, which is not	4453	implementations for some libevent functions (such as logging, which is not
3681	supported). It will also not define any of the structs usually found in	4454	supported). It will also not define any of the structs usually found in
3682	F<event.h> that are not directly supported by the libev core alone.	4455	F<event.h> that are not directly supported by the libev core alone.
3683		4456
3684	In standalone mode, libev will still try to automatically deduce the	4457	In standalone mode, libev will still try to automatically deduce the
3685	configuration, but has to be more conservative.	4458	configuration, but has to be more conservative.
		4459
		4460	=item EV_USE_FLOOR
		4461
		4462	If defined to be C<1>, libev will use the C<floor ()> function for its
		4463	periodic reschedule calculations, otherwise libev will fall back on a
		4464	portable (slower) implementation. If you enable this, you usually have to
		4465	link against libm or something equivalent. Enabling this when the C<floor>
		4466	function is not available will fail, so the safe default is to not enable
		4467	this.
3686		4468
3687	=item EV_USE_MONOTONIC	4469	=item EV_USE_MONOTONIC
3688		4470
3689	If defined to be C<1>, libev will try to detect the availability of the	4471	If defined to be C<1>, libev will try to detect the availability of the
3690	monotonic clock option at both compile time and runtime. Otherwise no	4472	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3775		4557
3776	If programs implement their own fd to handle mapping on win32, then this	4558	If programs implement their own fd to handle mapping on win32, then this
3777	macro can be used to override the C<close> function, useful to unregister	4559	macro can be used to override the C<close> function, useful to unregister
3778	file descriptors again. Note that the replacement function has to close	4560	file descriptors again. Note that the replacement function has to close
3779	the underlying OS handle.	4561	the underlying OS handle.
		4562
		4563	=item EV_USE_WSASOCKET
		4564
		4565	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4566	communication socket, which works better in some environments. Otherwise,
		4567	the normal C<socket> function will be used, which works better in other
		4568	environments.
3780		4569
3781	=item EV_USE_POLL	4570	=item EV_USE_POLL
3782		4571
3783	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4572	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3784	backend. Otherwise it will be enabled on non-win32 platforms. It	4573	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3820	If defined to be C<1>, libev will compile in support for the Linux inotify	4609	If defined to be C<1>, libev will compile in support for the Linux inotify
3821	interface to speed up C<ev_stat> watchers. Its actual availability will	4610	interface to speed up C<ev_stat> watchers. Its actual availability will
3822	be detected at runtime. If undefined, it will be enabled if the headers	4611	be detected at runtime. If undefined, it will be enabled if the headers
3823	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4612	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3824		4613
		4614	=item EV_NO_SMP
		4615
		4616	If defined to be C<1>, libev will assume that memory is always coherent
		4617	between threads, that is, threads can be used, but threads never run on
		4618	different cpus (or different cpu cores). This reduces dependencies
		4619	and makes libev faster.
		4620
		4621	=item EV_NO_THREADS
		4622
		4623	If defined to be C<1>, libev will assume that it will never be called
		4624	from different threads, which is a stronger assumption than C<EV_NO_SMP>,
		4625	above. This reduces dependencies and makes libev faster.
		4626
3825	=item EV_ATOMIC_T	4627	=item EV_ATOMIC_T
3826		4628
3827	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4629	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3828	access is atomic with respect to other threads or signal contexts. No such	4630	access is atomic with respect to other threads or signal contexts. No
3829	type is easily found in the C language, so you can provide your own type	4631	such type is easily found in the C language, so you can provide your own
3830	that you know is safe for your purposes. It is used both for signal handler "locking"	4632	type that you know is safe for your purposes. It is used both for signal
3831	as well as for signal and thread safety in C<ev_async> watchers.	4633	handler "locking" as well as for signal and thread safety in C<ev_async>
		4634	watchers.
3832		4635
3833	In the absence of this define, libev will use C<sig_atomic_t volatile>	4636	In the absence of this define, libev will use C<sig_atomic_t volatile>
3834	(from F<signal.h>), which is usually good enough on most platforms.	4637	(from F<signal.h>), which is usually good enough on most platforms.
3835		4638
3836	=item EV_H (h)	4639	=item EV_H (h)
…		…
3863	will have the C<struct ev_loop *> as first argument, and you can create	4666	will have the C<struct ev_loop *> as first argument, and you can create
3864	additional independent event loops. Otherwise there will be no support	4667	additional independent event loops. Otherwise there will be no support
3865	for multiple event loops and there is no first event loop pointer	4668	for multiple event loops and there is no first event loop pointer
3866	argument. Instead, all functions act on the single default loop.	4669	argument. Instead, all functions act on the single default loop.
3867		4670
		4671	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4672	default loop when multiplicity is switched off - you always have to
		4673	initialise the loop manually in this case.
		4674
3868	=item EV_MINPRI	4675	=item EV_MINPRI
3869		4676
3870	=item EV_MAXPRI	4677	=item EV_MAXPRI
3871		4678
3872	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4679	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3886	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,	4693	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
3887	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.	4694	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3888		4695
3889	If undefined or defined to be C<1> (and the platform supports it), then	4696	If undefined or defined to be C<1> (and the platform supports it), then
3890	the respective watcher type is supported. If defined to be C<0>, then it	4697	the respective watcher type is supported. If defined to be C<0>, then it
3891	is not. Disabling watcher types mainly saves codesize.	4698	is not. Disabling watcher types mainly saves code size.
3892		4699
3893	=item EV_FEATURES	4700	=item EV_FEATURES
3894		4701
3895	If you need to shave off some kilobytes of code at the expense of some	4702	If you need to shave off some kilobytes of code at the expense of some
3896	speed (but with the full API), you can define this symbol to request	4703	speed (but with the full API), you can define this symbol to request
…		…
3908	#define EV_USE_POLL 1	4715	#define EV_USE_POLL 1
3909	#define EV_CHILD_ENABLE 1	4716	#define EV_CHILD_ENABLE 1
3910	#define EV_ASYNC_ENABLE 1	4717	#define EV_ASYNC_ENABLE 1
3911		4718
3912	The actual value is a bitset, it can be a combination of the following	4719	The actual value is a bitset, it can be a combination of the following
3913	values:	4720	values (by default, all of these are enabled):
3914		4721
3915	=over 4	4722	=over 4
3916		4723
3917	=item C<1> - faster/larger code	4724	=item C<1> - faster/larger code
3918		4725
3919	Use larger code to speed up some operations.	4726	Use larger code to speed up some operations.
3920		4727
3921	Currently this is used to override some inlining decisions (enlarging the roughly	4728	Currently this is used to override some inlining decisions (enlarging the
3922	30% code size on amd64.	4729	code size by roughly 30% on amd64).
3923		4730
3924	When optimising for size, use of compiler flags such as C<-Os> with	4731	When optimising for size, use of compiler flags such as C<-Os> with
3925	gcc recommended, as well as C<-DNDEBUG>, as libev contains a number of	4732	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
3926	assertions.	4733	assertions.
3927		4734
		4735	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4736	(e.g. gcc with C<-Os>).
		4737
3928	=item C<2> - faster/larger data structures	4738	=item C<2> - faster/larger data structures
3929		4739
3930	Replaces the small 2-heap for timer management by a faster 4-heap, larger	4740	Replaces the small 2-heap for timer management by a faster 4-heap, larger
3931	hash table sizes and so on. This will usually further increase codesize	4741	hash table sizes and so on. This will usually further increase code size
3932	and can additionally have an effect on the size of data structures at	4742	and can additionally have an effect on the size of data structures at
3933	runtime.	4743	runtime.
		4744
		4745	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4746	(e.g. gcc with C<-Os>).
3934		4747
3935	=item C<4> - full API configuration	4748	=item C<4> - full API configuration
3936		4749
3937	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and	4750	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
3938	enables multiplicity (C<EV_MULTIPLICITY>=1).	4751	enables multiplicity (C<EV_MULTIPLICITY>=1).
…		…
3970	With an intelligent-enough linker (gcc+binutils are intelligent enough	4783	With an intelligent-enough linker (gcc+binutils are intelligent enough
3971	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by	4784	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
3972	your program might be left out as well - a binary starting a timer and an	4785	your program might be left out as well - a binary starting a timer and an
3973	I/O watcher then might come out at only 5Kb.	4786	I/O watcher then might come out at only 5Kb.
3974		4787
		4788	=item EV_API_STATIC
		4789
		4790	If this symbol is defined (by default it is not), then all identifiers
		4791	will have static linkage. This means that libev will not export any
		4792	identifiers, and you cannot link against libev anymore. This can be useful
		4793	when you embed libev, only want to use libev functions in a single file,
		4794	and do not want its identifiers to be visible.
		4795
		4796	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4797	wants to use libev.
		4798
		4799	This option only works when libev is compiled with a C compiler, as C++
		4800	doesn't support the required declaration syntax.
		4801
3975	=item EV_AVOID_STDIO	4802	=item EV_AVOID_STDIO
3976		4803
3977	If this is set to C<1> at compiletime, then libev will avoid using stdio	4804	If this is set to C<1> at compiletime, then libev will avoid using stdio
3978	functions (printf, scanf, perror etc.). This will increase the codesize	4805	functions (printf, scanf, perror etc.). This will increase the code size
3979	somewhat, but if your program doesn't otherwise depend on stdio and your	4806	somewhat, but if your program doesn't otherwise depend on stdio and your
3980	libc allows it, this avoids linking in the stdio library which is quite	4807	libc allows it, this avoids linking in the stdio library which is quite
3981	big.	4808	big.
3982		4809
3983	Note that error messages might become less precise when this option is	4810	Note that error messages might become less precise when this option is
…		…
3987		4814
3988	The highest supported signal number, +1 (or, the number of	4815	The highest supported signal number, +1 (or, the number of
3989	signals): Normally, libev tries to deduce the maximum number of signals	4816	signals): Normally, libev tries to deduce the maximum number of signals
3990	automatically, but sometimes this fails, in which case it can be	4817	automatically, but sometimes this fails, in which case it can be
3991	specified. Also, using a lower number than detected (C<32> should be	4818	specified. Also, using a lower number than detected (C<32> should be
3992	good for about any system in existance) can save some memory, as libev	4819	good for about any system in existence) can save some memory, as libev
3993	statically allocates some 12-24 bytes per signal number.	4820	statically allocates some 12-24 bytes per signal number.
3994		4821
3995	=item EV_PID_HASHSIZE	4822	=item EV_PID_HASHSIZE
3996		4823
3997	C<ev_child> watchers use a small hash table to distribute workload by	4824	C<ev_child> watchers use a small hash table to distribute workload by
…		…
4029	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it	4856	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
4030	will be C<0>.	4857	will be C<0>.
4031		4858
4032	=item EV_VERIFY	4859	=item EV_VERIFY
4033		4860
4034	Controls how much internal verification (see C<ev_loop_verify ()>) will	4861	Controls how much internal verification (see C<ev_verify ()>) will
4035	be done: If set to C<0>, no internal verification code will be compiled	4862	be done: If set to C<0>, no internal verification code will be compiled
4036	in. If set to C<1>, then verification code will be compiled in, but not	4863	in. If set to C<1>, then verification code will be compiled in, but not
4037	called. If set to C<2>, then the internal verification code will be	4864	called. If set to C<2>, then the internal verification code will be
4038	called once per loop, which can slow down libev. If set to C<3>, then the	4865	called once per loop, which can slow down libev. If set to C<3>, then the
4039	verification code will be called very frequently, which will slow down	4866	verification code will be called very frequently, which will slow down
…		…
4043	will be C<0>.	4870	will be C<0>.
4044		4871
4045	=item EV_COMMON	4872	=item EV_COMMON
4046		4873
4047	By default, all watchers have a C<void *data> member. By redefining	4874	By default, all watchers have a C<void *data> member. By redefining
4048	this macro to a something else you can include more and other types of	4875	this macro to something else you can include more and other types of
4049	members. You have to define it each time you include one of the files,	4876	members. You have to define it each time you include one of the files,
4050	though, and it must be identical each time.	4877	though, and it must be identical each time.
4051		4878
4052	For example, the perl EV module uses something like this:	4879	For example, the perl EV module uses something like this:
4053		4880
…		…
4122	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4949	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4123		4950
4124	#include "ev_cpp.h"	4951	#include "ev_cpp.h"
4125	#include "ev.c"	4952	#include "ev.c"
4126		4953
4127	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4954	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4128		4955
4129	=head2 THREADS AND COROUTINES	4956	=head2 THREADS AND COROUTINES
4130		4957
4131	=head3 THREADS	4958	=head3 THREADS
4132		4959
…		…
4183	default loop and triggering an C<ev_async> watcher from the default loop	5010	default loop and triggering an C<ev_async> watcher from the default loop
4184	watcher callback into the event loop interested in the signal.	5011	watcher callback into the event loop interested in the signal.
4185		5012
4186	=back	5013	=back
4187		5014
4188	=head4 THREAD LOCKING EXAMPLE	5015	See also L</THREAD LOCKING EXAMPLE>.
4189
4190	Here is a fictitious example of how to run an event loop in a different
4191	thread than where callbacks are being invoked and watchers are
4192	created/added/removed.
4193
4194	For a real-world example, see the C<EV::Loop::Async> perl module,
4195	which uses exactly this technique (which is suited for many high-level
4196	languages).
4197
4198	The example uses a pthread mutex to protect the loop data, a condition
4199	variable to wait for callback invocations, an async watcher to notify the
4200	event loop thread and an unspecified mechanism to wake up the main thread.
4201
4202	First, you need to associate some data with the event loop:
4203
4204	typedef struct {
4205	mutex_t lock; /* global loop lock */
4206	ev_async async_w;
4207	thread_t tid;
4208	cond_t invoke_cv;
4209	} userdata;
4210
4211	void prepare_loop (EV_P)
4212	{
4213	// for simplicity, we use a static userdata struct.
4214	static userdata u;
4215
4216	ev_async_init (&u->async_w, async_cb);
4217	ev_async_start (EV_A_ &u->async_w);
4218
4219	pthread_mutex_init (&u->lock, 0);
4220	pthread_cond_init (&u->invoke_cv, 0);
4221
4222	// now associate this with the loop
4223	ev_set_userdata (EV_A_ u);
4224	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4225	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4226
4227	// then create the thread running ev_loop
4228	pthread_create (&u->tid, 0, l_run, EV_A);
4229	}
4230
4231	The callback for the C<ev_async> watcher does nothing: the watcher is used
4232	solely to wake up the event loop so it takes notice of any new watchers
4233	that might have been added:
4234
4235	static void
4236	async_cb (EV_P_ ev_async *w, int revents)
4237	{
4238	// just used for the side effects
4239	}
4240
4241	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4242	protecting the loop data, respectively.
4243
4244	static void
4245	l_release (EV_P)
4246	{
4247	userdata *u = ev_userdata (EV_A);
4248	pthread_mutex_unlock (&u->lock);
4249	}
4250
4251	static void
4252	l_acquire (EV_P)
4253	{
4254	userdata *u = ev_userdata (EV_A);
4255	pthread_mutex_lock (&u->lock);
4256	}
4257
4258	The event loop thread first acquires the mutex, and then jumps straight
4259	into C<ev_loop>:
4260
4261	void *
4262	l_run (void *thr_arg)
4263	{
4264	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4265
4266	l_acquire (EV_A);
4267	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4268	ev_loop (EV_A_ 0);
4269	l_release (EV_A);
4270
4271	return 0;
4272	}
4273
4274	Instead of invoking all pending watchers, the C<l_invoke> callback will
4275	signal the main thread via some unspecified mechanism (signals? pipe
4276	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4277	have been called (in a while loop because a) spurious wakeups are possible
4278	and b) skipping inter-thread-communication when there are no pending
4279	watchers is very beneficial):
4280
4281	static void
4282	l_invoke (EV_P)
4283	{
4284	userdata *u = ev_userdata (EV_A);
4285
4286	while (ev_pending_count (EV_A))
4287	{
4288	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4289	pthread_cond_wait (&u->invoke_cv, &u->lock);
4290	}
4291	}
4292
4293	Now, whenever the main thread gets told to invoke pending watchers, it
4294	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4295	thread to continue:
4296
4297	static void
4298	real_invoke_pending (EV_P)
4299	{
4300	userdata *u = ev_userdata (EV_A);
4301
4302	pthread_mutex_lock (&u->lock);
4303	ev_invoke_pending (EV_A);
4304	pthread_cond_signal (&u->invoke_cv);
4305	pthread_mutex_unlock (&u->lock);
4306	}
4307
4308	Whenever you want to start/stop a watcher or do other modifications to an
4309	event loop, you will now have to lock:
4310
4311	ev_timer timeout_watcher;
4312	userdata *u = ev_userdata (EV_A);
4313
4314	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4315
4316	pthread_mutex_lock (&u->lock);
4317	ev_timer_start (EV_A_ &timeout_watcher);
4318	ev_async_send (EV_A_ &u->async_w);
4319	pthread_mutex_unlock (&u->lock);
4320
4321	Note that sending the C<ev_async> watcher is required because otherwise
4322	an event loop currently blocking in the kernel will have no knowledge
4323	about the newly added timer. By waking up the loop it will pick up any new
4324	watchers in the next event loop iteration.
4325		5016
4326	=head3 COROUTINES	5017	=head3 COROUTINES
4327		5018
4328	Libev is very accommodating to coroutines ("cooperative threads"):	5019	Libev is very accommodating to coroutines ("cooperative threads"):
4329	libev fully supports nesting calls to its functions from different	5020	libev fully supports nesting calls to its functions from different
4330	coroutines (e.g. you can call C<ev_loop> on the same loop from two	5021	coroutines (e.g. you can call C<ev_run> on the same loop from two
4331	different coroutines, and switch freely between both coroutines running	5022	different coroutines, and switch freely between both coroutines running
4332	the loop, as long as you don't confuse yourself). The only exception is	5023	the loop, as long as you don't confuse yourself). The only exception is
4333	that you must not do this from C<ev_periodic> reschedule callbacks.	5024	that you must not do this from C<ev_periodic> reschedule callbacks.
4334		5025
4335	Care has been taken to ensure that libev does not keep local state inside	5026	Care has been taken to ensure that libev does not keep local state inside
4336	C<ev_loop>, and other calls do not usually allow for coroutine switches as	5027	C<ev_run>, and other calls do not usually allow for coroutine switches as
4337	they do not call any callbacks.	5028	they do not call any callbacks.
4338		5029
4339	=head2 COMPILER WARNINGS	5030	=head2 COMPILER WARNINGS
4340		5031
4341	Depending on your compiler and compiler settings, you might get no or a	5032	Depending on your compiler and compiler settings, you might get no or a
…		…
4352	maintainable.	5043	maintainable.
4353		5044
4354	And of course, some compiler warnings are just plain stupid, or simply	5045	And of course, some compiler warnings are just plain stupid, or simply
4355	wrong (because they don't actually warn about the condition their message	5046	wrong (because they don't actually warn about the condition their message
4356	seems to warn about). For example, certain older gcc versions had some	5047	seems to warn about). For example, certain older gcc versions had some
4357	warnings that resulted an extreme number of false positives. These have	5048	warnings that resulted in an extreme number of false positives. These have
4358	been fixed, but some people still insist on making code warn-free with	5049	been fixed, but some people still insist on making code warn-free with
4359	such buggy versions.	5050	such buggy versions.
4360		5051
4361	While libev is written to generate as few warnings as possible,	5052	While libev is written to generate as few warnings as possible,
4362	"warn-free" code is not a goal, and it is recommended not to build libev	5053	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
4398	I suggest using suppression lists.	5089	I suggest using suppression lists.
4399		5090
4400		5091
4401	=head1 PORTABILITY NOTES	5092	=head1 PORTABILITY NOTES
4402		5093
		5094	=head2 GNU/LINUX 32 BIT LIMITATIONS
		5095
		5096	GNU/Linux is the only common platform that supports 64 bit file/large file
		5097	interfaces but I<disables> them by default.
		5098
		5099	That means that libev compiled in the default environment doesn't support
		5100	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		5101
		5102	Unfortunately, many programs try to work around this GNU/Linux issue
		5103	by enabling the large file API, which makes them incompatible with the
		5104	standard libev compiled for their system.
		5105
		5106	Likewise, libev cannot enable the large file API itself as this would
		5107	suddenly make it incompatible to the default compile time environment,
		5108	i.e. all programs not using special compile switches.
		5109
		5110	=head2 OS/X AND DARWIN BUGS
		5111
		5112	The whole thing is a bug if you ask me - basically any system interface
		5113	you touch is broken, whether it is locales, poll, kqueue or even the
		5114	OpenGL drivers.
		5115
		5116	=head3 C<kqueue> is buggy
		5117
		5118	The kqueue syscall is broken in all known versions - most versions support
		5119	only sockets, many support pipes.
		5120
		5121	Libev tries to work around this by not using C<kqueue> by default on this
		5122	rotten platform, but of course you can still ask for it when creating a
		5123	loop - embedding a socket-only kqueue loop into a select-based one is
		5124	probably going to work well.
		5125
		5126	=head3 C<poll> is buggy
		5127
		5128	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		5129	implementation by something calling C<kqueue> internally around the 10.5.6
		5130	release, so now C<kqueue> I<and> C<poll> are broken.
		5131
		5132	Libev tries to work around this by not using C<poll> by default on
		5133	this rotten platform, but of course you can still ask for it when creating
		5134	a loop.
		5135
		5136	=head3 C<select> is buggy
		5137
		5138	All that's left is C<select>, and of course Apple found a way to fuck this
		5139	one up as well: On OS/X, C<select> actively limits the number of file
		5140	descriptors you can pass in to 1024 - your program suddenly crashes when
		5141	you use more.
		5142
		5143	There is an undocumented "workaround" for this - defining
		5144	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		5145	work on OS/X.
		5146
		5147	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		5148
		5149	=head3 C<errno> reentrancy
		5150
		5151	The default compile environment on Solaris is unfortunately so
		5152	thread-unsafe that you can't even use components/libraries compiled
		5153	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		5154	defined by default. A valid, if stupid, implementation choice.
		5155
		5156	If you want to use libev in threaded environments you have to make sure
		5157	it's compiled with C<_REENTRANT> defined.
		5158
		5159	=head3 Event port backend
		5160
		5161	The scalable event interface for Solaris is called "event
		5162	ports". Unfortunately, this mechanism is very buggy in all major
		5163	releases. If you run into high CPU usage, your program freezes or you get
		5164	a large number of spurious wakeups, make sure you have all the relevant
		5165	and latest kernel patches applied. No, I don't know which ones, but there
		5166	are multiple ones to apply, and afterwards, event ports actually work
		5167	great.
		5168
		5169	If you can't get it to work, you can try running the program by setting
		5170	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		5171	C<select> backends.
		5172
		5173	=head2 AIX POLL BUG
		5174
		5175	AIX unfortunately has a broken C<poll.h> header. Libev works around
		5176	this by trying to avoid the poll backend altogether (i.e. it's not even
		5177	compiled in), which normally isn't a big problem as C<select> works fine
		5178	with large bitsets on AIX, and AIX is dead anyway.
		5179
4403	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5180	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		5181
		5182	=head3 General issues
4404		5183
4405	Win32 doesn't support any of the standards (e.g. POSIX) that libev	5184	Win32 doesn't support any of the standards (e.g. POSIX) that libev
4406	requires, and its I/O model is fundamentally incompatible with the POSIX	5185	requires, and its I/O model is fundamentally incompatible with the POSIX
4407	model. Libev still offers limited functionality on this platform in	5186	model. Libev still offers limited functionality on this platform in
4408	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5187	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4409	descriptors. This only applies when using Win32 natively, not when using	5188	descriptors. This only applies when using Win32 natively, not when using
4410	e.g. cygwin.	5189	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		5190	as every compiler comes with a slightly differently broken/incompatible
		5191	environment.
4411		5192
4412	Lifting these limitations would basically require the full	5193	Lifting these limitations would basically require the full
4413	re-implementation of the I/O system. If you are into these kinds of	5194	re-implementation of the I/O system. If you are into this kind of thing,
4414	things, then note that glib does exactly that for you in a very portable	5195	then note that glib does exactly that for you in a very portable way (note
4415	way (note also that glib is the slowest event library known to man).	5196	also that glib is the slowest event library known to man).
4416		5197
4417	There is no supported compilation method available on windows except	5198	There is no supported compilation method available on windows except
4418	embedding it into other applications.	5199	embedding it into other applications.
4419		5200
4420	Sensible signal handling is officially unsupported by Microsoft - libev	5201	Sensible signal handling is officially unsupported by Microsoft - libev
…		…
4448	you do I<not> compile the F<ev.c> or any other embedded source files!):	5229	you do I<not> compile the F<ev.c> or any other embedded source files!):
4449		5230
4450	#include "evwrap.h"	5231	#include "evwrap.h"
4451	#include "ev.c"	5232	#include "ev.c"
4452		5233
4453	=over 4
4454
4455	=item The winsocket select function	5234	=head3 The winsocket C<select> function
4456		5235
4457	The winsocket C<select> function doesn't follow POSIX in that it	5236	The winsocket C<select> function doesn't follow POSIX in that it
4458	requires socket I<handles> and not socket I<file descriptors> (it is	5237	requires socket I<handles> and not socket I<file descriptors> (it is
4459	also extremely buggy). This makes select very inefficient, and also	5238	also extremely buggy). This makes select very inefficient, and also
4460	requires a mapping from file descriptors to socket handles (the Microsoft	5239	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
4469	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	5248	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
4470		5249
4471	Note that winsockets handling of fd sets is O(n), so you can easily get a	5250	Note that winsockets handling of fd sets is O(n), so you can easily get a
4472	complexity in the O(n²) range when using win32.	5251	complexity in the O(n²) range when using win32.
4473		5252
4474	=item Limited number of file descriptors	5253	=head3 Limited number of file descriptors
4475		5254
4476	Windows has numerous arbitrary (and low) limits on things.	5255	Windows has numerous arbitrary (and low) limits on things.
4477		5256
4478	Early versions of winsocket's select only supported waiting for a maximum	5257	Early versions of winsocket's select only supported waiting for a maximum
4479	of C<64> handles (probably owning to the fact that all windows kernels	5258	of C<64> handles (probably owning to the fact that all windows kernels
…		…
4494	runtime libraries. This might get you to about C<512> or C<2048> sockets	5273	runtime libraries. This might get you to about C<512> or C<2048> sockets
4495	(depending on windows version and/or the phase of the moon). To get more,	5274	(depending on windows version and/or the phase of the moon). To get more,
4496	you need to wrap all I/O functions and provide your own fd management, but	5275	you need to wrap all I/O functions and provide your own fd management, but
4497	the cost of calling select (O(n²)) will likely make this unworkable.	5276	the cost of calling select (O(n²)) will likely make this unworkable.
4498		5277
4499	=back
4500
4501	=head2 PORTABILITY REQUIREMENTS	5278	=head2 PORTABILITY REQUIREMENTS
4502		5279
4503	In addition to a working ISO-C implementation and of course the	5280	In addition to a working ISO-C implementation and of course the
4504	backend-specific APIs, libev relies on a few additional extensions:	5281	backend-specific APIs, libev relies on a few additional extensions:
4505		5282
…		…
4511	Libev assumes not only that all watcher pointers have the same internal	5288	Libev assumes not only that all watcher pointers have the same internal
4512	structure (guaranteed by POSIX but not by ISO C for example), but it also	5289	structure (guaranteed by POSIX but not by ISO C for example), but it also
4513	assumes that the same (machine) code can be used to call any watcher	5290	assumes that the same (machine) code can be used to call any watcher
4514	callback: The watcher callbacks have different type signatures, but libev	5291	callback: The watcher callbacks have different type signatures, but libev
4515	calls them using an C<ev_watcher *> internally.	5292	calls them using an C<ev_watcher *> internally.
		5293
		5294	=item pointer accesses must be thread-atomic
		5295
		5296	Accessing a pointer value must be atomic, it must both be readable and
		5297	writable in one piece - this is the case on all current architectures.
4516		5298
4517	=item C<sig_atomic_t volatile> must be thread-atomic as well	5299	=item C<sig_atomic_t volatile> must be thread-atomic as well
4518		5300
4519	The type C<sig_atomic_t volatile> (or whatever is defined as	5301	The type C<sig_atomic_t volatile> (or whatever is defined as
4520	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5302	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
4529	thread" or will block signals process-wide, both behaviours would	5311	thread" or will block signals process-wide, both behaviours would
4530	be compatible with libev. Interaction between C<sigprocmask> and	5312	be compatible with libev. Interaction between C<sigprocmask> and
4531	C<pthread_sigmask> could complicate things, however.	5313	C<pthread_sigmask> could complicate things, however.
4532		5314
4533	The most portable way to handle signals is to block signals in all threads	5315	The most portable way to handle signals is to block signals in all threads
4534	except the initial one, and run the default loop in the initial thread as	5316	except the initial one, and run the signal handling loop in the initial
4535	well.	5317	thread as well.
4536		5318
4537	=item C<long> must be large enough for common memory allocation sizes	5319	=item C<long> must be large enough for common memory allocation sizes
4538		5320
4539	To improve portability and simplify its API, libev uses C<long> internally	5321	To improve portability and simplify its API, libev uses C<long> internally
4540	instead of C<size_t> when allocating its data structures. On non-POSIX	5322	instead of C<size_t> when allocating its data structures. On non-POSIX
…		…
4543	watchers.	5325	watchers.
4544		5326
4545	=item C<double> must hold a time value in seconds with enough accuracy	5327	=item C<double> must hold a time value in seconds with enough accuracy
4546		5328
4547	The type C<double> is used to represent timestamps. It is required to	5329	The type C<double> is used to represent timestamps. It is required to
4548	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5330	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4549	enough for at least into the year 4000. This requirement is fulfilled by	5331	good enough for at least into the year 4000 with millisecond accuracy
		5332	(the design goal for libev). This requirement is overfulfilled by
4550	implementations implementing IEEE 754, which is basically all existing	5333	implementations using IEEE 754, which is basically all existing ones.
		5334
4551	ones. With IEEE 754 doubles, you get microsecond accuracy until at least	5335	With IEEE 754 doubles, you get microsecond accuracy until at least the
4552	2200.	5336	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5337	is either obsolete or somebody patched it to use C<long double> or
		5338	something like that, just kidding).
4553		5339
4554	=back	5340	=back
4555		5341
4556	If you know of other additional requirements drop me a note.	5342	If you know of other additional requirements drop me a note.
4557		5343
…		…
4619	=item Processing ev_async_send: O(number_of_async_watchers)	5405	=item Processing ev_async_send: O(number_of_async_watchers)
4620		5406
4621	=item Processing signals: O(max_signal_number)	5407	=item Processing signals: O(max_signal_number)
4622		5408
4623	Sending involves a system call I<iff> there were no other C<ev_async_send>	5409	Sending involves a system call I<iff> there were no other C<ev_async_send>
4624	calls in the current loop iteration. Checking for async and signal events	5410	calls in the current loop iteration and the loop is currently
		5411	blocked. Checking for async and signal events involves iterating over all
4625	involves iterating over all running async watchers or all signal numbers.	5412	running async watchers or all signal numbers.
4626		5413
4627	=back	5414	=back
4628		5415
4629		5416
4630	=head1 PORTING FROM LIBEV 3.X TO 4.X	5417	=head1 PORTING FROM LIBEV 3.X TO 4.X
4631		5418
4632	The major version 4 introduced some minor incompatible changes to the API.	5419	The major version 4 introduced some incompatible changes to the API.
4633		5420
4634	At the moment, the C<ev.h> header file tries to implement superficial	5421	At the moment, the C<ev.h> header file provides compatibility definitions
4635	compatibility, so most programs should still compile. Those might be	5422	for all changes, so most programs should still compile. The compatibility
4636	removed in later versions of libev, so better update early than late.	5423	layer might be removed in later versions of libev, so better update to the
		5424	new API early than late.
4637		5425
4638	=over 4	5426	=over 4
4639		5427
4640	=item C<ev_loop_count> renamed to C<ev_iteration>	5428	=item C<EV_COMPAT3> backwards compatibility mechanism
4641		5429
4642	=item C<ev_loop_depth> renamed to C<ev_depth>	5430	The backward compatibility mechanism can be controlled by
		5431	C<EV_COMPAT3>. See L</PREPROCESSOR SYMBOLS/MACROS> in the L</EMBEDDING>
		5432	section.
4643		5433
4644	=item C<ev_loop_verify> renamed to C<ev_verify>	5434	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5435
		5436	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5437
		5438	ev_loop_destroy (EV_DEFAULT_UC);
		5439	ev_loop_fork (EV_DEFAULT);
		5440
		5441	=item function/symbol renames
		5442
		5443	A number of functions and symbols have been renamed:
		5444
		5445	ev_loop => ev_run
		5446	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5447	EVLOOP_ONESHOT => EVRUN_ONCE
		5448
		5449	ev_unloop => ev_break
		5450	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5451	EVUNLOOP_ONE => EVBREAK_ONE
		5452	EVUNLOOP_ALL => EVBREAK_ALL
		5453
		5454	EV_TIMEOUT => EV_TIMER
		5455
		5456	ev_loop_count => ev_iteration
		5457	ev_loop_depth => ev_depth
		5458	ev_loop_verify => ev_verify
4645		5459
4646	Most functions working on C<struct ev_loop> objects don't have an	5460	Most functions working on C<struct ev_loop> objects don't have an
4647	C<ev_loop_> prefix, so it was removed. Note that C<ev_loop_fork> is	5461	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5462	associated constants have been renamed to not collide with the C<struct
		5463	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5464	as all other watcher types. Note that C<ev_loop_fork> is still called
4648	still called C<ev_loop_fork> because it would otherwise clash with the	5465	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
4649	C<ev_fork> typedef.	5466	typedef.
4650
4651	=item C<EV_TIMEOUT> renamed to C<EV_TIMER> in C<revents>
4652
4653	This is a simple rename - all other watcher types use their name
4654	as revents flag, and now C<ev_timer> does, too.
4655
4656	Both C<EV_TIMER> and C<EV_TIMEOUT> symbols were present in 3.x versions
4657	and continue to be present for the forseeable future, so this is mostly a
4658	documentation change.
4659		5467
4660	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>	5468	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
4661		5469
4662	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different	5470	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
4663	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile	5471	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
…		…
4670		5478
4671	=over 4	5479	=over 4
4672		5480
4673	=item active	5481	=item active
4674		5482
4675	A watcher is active as long as it has been started (has been attached to	5483	A watcher is active as long as it has been started and not yet stopped.
4676	an event loop) but not yet stopped (disassociated from the event loop).	5484	See L</WATCHER STATES> for details.
4677		5485
4678	=item application	5486	=item application
4679		5487
4680	In this document, an application is whatever is using libev.	5488	In this document, an application is whatever is using libev.
		5489
		5490	=item backend
		5491
		5492	The part of the code dealing with the operating system interfaces.
4681		5493
4682	=item callback	5494	=item callback
4683		5495
4684	The address of a function that is called when some event has been	5496	The address of a function that is called when some event has been
4685	detected. Callbacks are being passed the event loop, the watcher that	5497	detected. Callbacks are being passed the event loop, the watcher that
4686	received the event, and the actual event bitset.	5498	received the event, and the actual event bitset.
4687		5499
4688	=item callback invocation	5500	=item callback/watcher invocation
4689		5501
4690	The act of calling the callback associated with a watcher.	5502	The act of calling the callback associated with a watcher.
4691		5503
4692	=item event	5504	=item event
4693		5505
…		…
4712	The model used to describe how an event loop handles and processes	5524	The model used to describe how an event loop handles and processes
4713	watchers and events.	5525	watchers and events.
4714		5526
4715	=item pending	5527	=item pending
4716		5528
4717	A watcher is pending as soon as the corresponding event has been detected,	5529	A watcher is pending as soon as the corresponding event has been
4718	and stops being pending as soon as the watcher will be invoked or its	5530	detected. See L</WATCHER STATES> for details.
4719	pending status is explicitly cleared by the application.
4720
4721	A watcher can be pending, but not active. Stopping a watcher also clears
4722	its pending status.
4723		5531
4724	=item real time	5532	=item real time
4725		5533
4726	The physical time that is observed. It is apparently strictly monotonic :)	5534	The physical time that is observed. It is apparently strictly monotonic :)
4727		5535
4728	=item wall-clock time	5536	=item wall-clock time
4729		5537
4730	The time and date as shown on clocks. Unlike real time, it can actually	5538	The time and date as shown on clocks. Unlike real time, it can actually
4731	be wrong and jump forwards and backwards, e.g. when the you adjust your	5539	be wrong and jump forwards and backwards, e.g. when you adjust your
4732	clock.	5540	clock.
4733		5541
4734	=item watcher	5542	=item watcher
4735		5543
4736	A data structure that describes interest in certain events. Watchers need	5544	A data structure that describes interest in certain events. Watchers need
4737	to be started (attached to an event loop) before they can receive events.	5545	to be started (attached to an event loop) before they can receive events.
4738		5546
4739	=item watcher invocation
4740
4741	The act of calling the callback associated with a watcher.
4742
4743	=back	5547	=back
4744		5548
4745	=head1 AUTHOR	5549	=head1 AUTHOR
4746		5550
4747	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5551	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5552	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4748		5553

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