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Revision 1.371 by root, Sat Jun 4 05:25:03 2011 UTC

…		…
26	puts ("stdin ready");	26	puts ("stdin ready");
27	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
28	// with its corresponding stop function.	28	// with its corresponding stop function.
29	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
30		30
31	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_run's to stop iterating
32	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_break (EV_A_ EVBREAK_ALL);
33	}	33	}
34		34
35	// another callback, this time for a time-out	35	// another callback, this time for a time-out
36	static void	36	static void
37	timeout_cb (EV_P_ ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
38	{	38	{
39	puts ("timeout");	39	puts ("timeout");
40	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_run to stop iterating
41	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_break (EV_A_ EVBREAK_ONE);
42	}	42	}
43		43
44	int	44	int
45	main (void)	45	main (void)
46	{	46	{
47	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
48	struct ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = EV_DEFAULT;
49		49
50	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
51	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
53	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
…		…
56	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
58	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
59		59
60	// now wait for events to arrive	60	// now wait for events to arrive
61	ev_loop (loop, 0);	61	ev_run (loop, 0);
62		62
63	// unloop was called, so exit	63	// break was called, so exit
64	return 0;	64	return 0;
65	}	65	}
66		66
67	=head1 ABOUT THIS DOCUMENT	67	=head1 ABOUT THIS DOCUMENT
68		68
…		…
75	While this document tries to be as complete as possible in documenting	75	While this document tries to be as complete as possible in documenting
76	libev, its usage and the rationale behind its design, it is not a tutorial	76	libev, its usage and the rationale behind its design, it is not a tutorial
77	on event-based programming, nor will it introduce event-based programming	77	on event-based programming, nor will it introduce event-based programming
78	with libev.	78	with libev.
79		79
80	Familarity with event based programming techniques in general is assumed	80	Familiarity with event based programming techniques in general is assumed
81	throughout this document.	81	throughout this document.
		82
		83	=head1 WHAT TO READ WHEN IN A HURRY
		84
		85	This manual tries to be very detailed, but unfortunately, this also makes
		86	it very long. If you just want to know the basics of libev, I suggest
		87	reading L<ANATOMY OF A WATCHER>, then the L<EXAMPLE PROGRAM> above and
		88	look up the missing functions in L<GLOBAL FUNCTIONS> and the C<ev_io> and
		89	C<ev_timer> sections in L<WATCHER TYPES>.
82		90
83	=head1 ABOUT LIBEV	91	=head1 ABOUT LIBEV
84		92
85	Libev is an event loop: you register interest in certain events (such as a	93	Libev is an event loop: you register interest in certain events (such as a
86	file descriptor being readable or a timeout occurring), and it will manage	94	file descriptor being readable or a timeout occurring), and it will manage
…		…
124	this argument.	132	this argument.
125		133
126	=head2 TIME REPRESENTATION	134	=head2 TIME REPRESENTATION
127		135
128	Libev represents time as a single floating point number, representing	136	Libev represents time as a single floating point number, representing
129	the (fractional) number of seconds since the (POSIX) epoch (somewhere	137	the (fractional) number of seconds since the (POSIX) epoch (in practice
130	near the beginning of 1970, details are complicated, don't ask). This	138	somewhere near the beginning of 1970, details are complicated, don't
131	type is called C<ev_tstamp>, which is what you should use too. It usually	139	ask). This type is called C<ev_tstamp>, which is what you should use
132	aliases to the C<double> type in C. When you need to do any calculations	140	too. It usually aliases to the C<double> type in C. When you need to do
133	on it, you should treat it as some floating point value. Unlike the name	141	any calculations on it, you should treat it as some floating point value.
		142
134	component C<stamp> might indicate, it is also used for time differences	143	Unlike the name component C<stamp> might indicate, it is also used for
135	throughout libev.	144	time differences (e.g. delays) throughout libev.
136		145
137	=head1 ERROR HANDLING	146	=head1 ERROR HANDLING
138		147
139	Libev knows three classes of errors: operating system errors, usage errors	148	Libev knows three classes of errors: operating system errors, usage errors
140	and internal errors (bugs).	149	and internal errors (bugs).
…		…
164		173
165	=item ev_tstamp ev_time ()	174	=item ev_tstamp ev_time ()
166		175
167	Returns the current time as libev would use it. Please note that the	176	Returns the current time as libev would use it. Please note that the
168	C<ev_now> function is usually faster and also often returns the timestamp	177	C<ev_now> function is usually faster and also often returns the timestamp
169	you actually want to know.	178	you actually want to know. Also interesting is the combination of
		179	C<ev_update_now> and C<ev_now>.
170		180
171	=item ev_sleep (ev_tstamp interval)	181	=item ev_sleep (ev_tstamp interval)
172		182
173	Sleep for the given interval: The current thread will be blocked until	183	Sleep for the given interval: The current thread will be blocked
174	either it is interrupted or the given time interval has passed. Basically	184	until either it is interrupted or the given time interval has
		185	passed (approximately - it might return a bit earlier even if not
		186	interrupted). Returns immediately if C<< interval <= 0 >>.
		187
175	this is a sub-second-resolution C<sleep ()>.	188	Basically this is a sub-second-resolution C<sleep ()>.
		189
		190	The range of the C<interval> is limited - libev only guarantees to work
		191	with sleep times of up to one day (C<< interval <= 86400 >>).
176		192
177	=item int ev_version_major ()	193	=item int ev_version_major ()
178		194
179	=item int ev_version_minor ()	195	=item int ev_version_minor ()
180		196
…		…
191	as this indicates an incompatible change. Minor versions are usually	207	as this indicates an incompatible change. Minor versions are usually
192	compatible to older versions, so a larger minor version alone is usually	208	compatible to older versions, so a larger minor version alone is usually
193	not a problem.	209	not a problem.
194		210
195	Example: Make sure we haven't accidentally been linked against the wrong	211	Example: Make sure we haven't accidentally been linked against the wrong
196	version.	212	version (note, however, that this will not detect other ABI mismatches,
		213	such as LFS or reentrancy).
197		214
198	assert (("libev version mismatch",	215	assert (("libev version mismatch",
199	ev_version_major () == EV_VERSION_MAJOR	216	ev_version_major () == EV_VERSION_MAJOR
200	&& ev_version_minor () >= EV_VERSION_MINOR));	217	&& ev_version_minor () >= EV_VERSION_MINOR));
201		218
…		…
212	assert (("sorry, no epoll, no sex",	229	assert (("sorry, no epoll, no sex",
213	ev_supported_backends () & EVBACKEND_EPOLL));	230	ev_supported_backends () & EVBACKEND_EPOLL));
214		231
215	=item unsigned int ev_recommended_backends ()	232	=item unsigned int ev_recommended_backends ()
216		233
217	Return the set of all backends compiled into this binary of libev and also	234	Return the set of all backends compiled into this binary of libev and
218	recommended for this platform. This set is often smaller than the one	235	also recommended for this platform, meaning it will work for most file
		236	descriptor types. This set is often smaller than the one returned by
219	returned by C<ev_supported_backends>, as for example kqueue is broken on	237	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
220	most BSDs and will not be auto-detected unless you explicitly request it	238	and will not be auto-detected unless you explicitly request it (assuming
221	(assuming you know what you are doing). This is the set of backends that	239	you know what you are doing). This is the set of backends that libev will
222	libev will probe for if you specify no backends explicitly.	240	probe for if you specify no backends explicitly.
223		241
224	=item unsigned int ev_embeddable_backends ()	242	=item unsigned int ev_embeddable_backends ()
225		243
226	Returns the set of backends that are embeddable in other event loops. This	244	Returns the set of backends that are embeddable in other event loops. This
227	is the theoretical, all-platform, value. To find which backends	245	value is platform-specific but can include backends not available on the
228	might be supported on the current system, you would need to look at	246	current system. To find which embeddable backends might be supported on
229	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	247	the current system, you would need to look at C<ev_embeddable_backends ()
230	recommended ones.	248	& ev_supported_backends ()>, likewise for recommended ones.
231		249
232	See the description of C<ev_embed> watchers for more info.	250	See the description of C<ev_embed> watchers for more info.
233		251
234	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	252	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
235		253
236	Sets the allocation function to use (the prototype is similar - the	254	Sets the allocation function to use (the prototype is similar - the
237	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	255	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
238	used to allocate and free memory (no surprises here). If it returns zero	256	used to allocate and free memory (no surprises here). If it returns zero
239	when memory needs to be allocated (C<size != 0>), the library might abort	257	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
265	}	283	}
266		284
267	...	285	...
268	ev_set_allocator (persistent_realloc);	286	ev_set_allocator (persistent_realloc);
269		287
270	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	288	=item ev_set_syserr_cb (void (*cb)(const char *msg))
271		289
272	Set the callback function to call on a retryable system call error (such	290	Set the callback function to call on a retryable system call error (such
273	as failed select, poll, epoll_wait). The message is a printable string	291	as failed select, poll, epoll_wait). The message is a printable string
274	indicating the system call or subsystem causing the problem. If this	292	indicating the system call or subsystem causing the problem. If this
275	callback is set, then libev will expect it to remedy the situation, no	293	callback is set, then libev will expect it to remedy the situation, no
…		…
287	}	305	}
288		306
289	...	307	...
290	ev_set_syserr_cb (fatal_error);	308	ev_set_syserr_cb (fatal_error);
291		309
		310	=item ev_feed_signal (int signum)
		311
		312	This function can be used to "simulate" a signal receive. It is completely
		313	safe to call this function at any time, from any context, including signal
		314	handlers or random threads.
		315
		316	Its main use is to customise signal handling in your process, especially
		317	in the presence of threads. For example, you could block signals
		318	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		319	creating any loops), and in one thread, use C<sigwait> or any other
		320	mechanism to wait for signals, then "deliver" them to libev by calling
		321	C<ev_feed_signal>.
		322
292	=back	323	=back
293		324
294	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	325	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
295		326
296	An event loop is described by a C<struct ev_loop *> (the C<struct>	327	An event loop is described by a C<struct ev_loop *> (the C<struct> is
297	is I<not> optional in this case, as there is also an C<ev_loop>	328	I<not> optional in this case unless libev 3 compatibility is disabled, as
298	I<function>).	329	libev 3 had an C<ev_loop> function colliding with the struct name).
299		330
300	The library knows two types of such loops, the I<default> loop, which	331	The library knows two types of such loops, the I<default> loop, which
301	supports signals and child events, and dynamically created loops which do	332	supports child process events, and dynamically created event loops which
302	not.	333	do not.
303		334
304	=over 4	335	=over 4
305		336
306	=item struct ev_loop *ev_default_loop (unsigned int flags)	337	=item struct ev_loop *ev_default_loop (unsigned int flags)
307		338
308	This will initialise the default event loop if it hasn't been initialised	339	This returns the "default" event loop object, which is what you should
309	yet and return it. If the default loop could not be initialised, returns	340	normally use when you just need "the event loop". Event loop objects and
310	false. If it already was initialised it simply returns it (and ignores the	341	the C<flags> parameter are described in more detail in the entry for
311	flags. If that is troubling you, check C<ev_backend ()> afterwards).	342	C<ev_loop_new>.
		343
		344	If the default loop is already initialised then this function simply
		345	returns it (and ignores the flags. If that is troubling you, check
		346	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		347	flags, which should almost always be C<0>, unless the caller is also the
		348	one calling C<ev_run> or otherwise qualifies as "the main program".
312		349
313	If you don't know what event loop to use, use the one returned from this	350	If you don't know what event loop to use, use the one returned from this
314	function.	351	function (or via the C<EV_DEFAULT> macro).
315		352
316	Note that this function is I<not> thread-safe, so if you want to use it	353	Note that this function is I<not> thread-safe, so if you want to use it
317	from multiple threads, you have to lock (note also that this is unlikely,	354	from multiple threads, you have to employ some kind of mutex (note also
318	as loops cannot be shared easily between threads anyway).	355	that this case is unlikely, as loops cannot be shared easily between
		356	threads anyway).
319		357
320	The default loop is the only loop that can handle C<ev_signal> and	358	The default loop is the only loop that can handle C<ev_child> watchers,
321	C<ev_child> watchers, and to do this, it always registers a handler	359	and to do this, it always registers a handler for C<SIGCHLD>. If this is
322	for C<SIGCHLD>. If this is a problem for your application you can either	360	a problem for your application you can either create a dynamic loop with
323	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	361	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
324	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	362	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
325	C<ev_default_init>.	363
		364	Example: This is the most typical usage.
		365
		366	if (!ev_default_loop (0))
		367	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		368
		369	Example: Restrict libev to the select and poll backends, and do not allow
		370	environment settings to be taken into account:
		371
		372	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		373
		374	=item struct ev_loop *ev_loop_new (unsigned int flags)
		375
		376	This will create and initialise a new event loop object. If the loop
		377	could not be initialised, returns false.
		378
		379	This function is thread-safe, and one common way to use libev with
		380	threads is indeed to create one loop per thread, and using the default
		381	loop in the "main" or "initial" thread.
326		382
327	The flags argument can be used to specify special behaviour or specific	383	The flags argument can be used to specify special behaviour or specific
328	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	384	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
329		385
330	The following flags are supported:	386	The following flags are supported:
…		…
345	useful to try out specific backends to test their performance, or to work	401	useful to try out specific backends to test their performance, or to work
346	around bugs.	402	around bugs.
347		403
348	=item C<EVFLAG_FORKCHECK>	404	=item C<EVFLAG_FORKCHECK>
349		405
350	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	406	Instead of calling C<ev_loop_fork> manually after a fork, you can also
351	a fork, you can also make libev check for a fork in each iteration by	407	make libev check for a fork in each iteration by enabling this flag.
352	enabling this flag.
353		408
354	This works by calling C<getpid ()> on every iteration of the loop,	409	This works by calling C<getpid ()> on every iteration of the loop,
355	and thus this might slow down your event loop if you do a lot of loop	410	and thus this might slow down your event loop if you do a lot of loop
356	iterations and little real work, but is usually not noticeable (on my	411	iterations and little real work, but is usually not noticeable (on my
357	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	412	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
…		…
366	environment variable.	421	environment variable.
367		422
368	=item C<EVFLAG_NOINOTIFY>	423	=item C<EVFLAG_NOINOTIFY>
369		424
370	When this flag is specified, then libev will not attempt to use the	425	When this flag is specified, then libev will not attempt to use the
371	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and	426	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
372	testing, this flag can be useful to conserve inotify file descriptors, as	427	testing, this flag can be useful to conserve inotify file descriptors, as
373	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.	428	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
374		429
375	=item C<EVFLAG_SIGNALFD>	430	=item C<EVFLAG_SIGNALFD>
376		431
377	When this flag is specified, then libev will attempt to use the	432	When this flag is specified, then libev will attempt to use the
378	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API	433	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
379	delivers signals synchronously, which makes it both faster and might make	434	delivers signals synchronously, which makes it both faster and might make
380	it possible to get the queued signal data. It can also simplify signal	435	it possible to get the queued signal data. It can also simplify signal
381	handling with threads, as long as you properly block signals in your	436	handling with threads, as long as you properly block signals in your
382	threads that are not interested in handling them.	437	threads that are not interested in handling them.
383		438
384	Signalfd will not be used by default as this changes your signal mask, and	439	Signalfd will not be used by default as this changes your signal mask, and
385	there are a lot of shoddy libraries and programs (glib's threadpool for	440	there are a lot of shoddy libraries and programs (glib's threadpool for
386	example) that can't properly initialise their signal masks.	441	example) that can't properly initialise their signal masks.
		442
		443	=item C<EVFLAG_NOSIGMASK>
		444
		445	When this flag is specified, then libev will avoid to modify the signal
		446	mask. Specifically, this means you ahve to make sure signals are unblocked
		447	when you want to receive them.
		448
		449	This behaviour is useful when you want to do your own signal handling, or
		450	want to handle signals only in specific threads and want to avoid libev
		451	unblocking the signals.
		452
		453	It's also required by POSIX in a threaded program, as libev calls
		454	C<sigprocmask>, whose behaviour is officially unspecified.
		455
		456	This flag's behaviour will become the default in future versions of libev.
387		457
388	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	458	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
389		459
390	This is your standard select(2) backend. Not I<completely> standard, as	460	This is your standard select(2) backend. Not I<completely> standard, as
391	libev tries to roll its own fd_set with no limits on the number of fds,	461	libev tries to roll its own fd_set with no limits on the number of fds,
…		…
419	=item C<EVBACKEND_EPOLL> (value 4, Linux)	489	=item C<EVBACKEND_EPOLL> (value 4, Linux)
420		490
421	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9	491	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
422	kernels).	492	kernels).
423		493
424	For few fds, this backend is a bit little slower than poll and select,	494	For few fds, this backend is a bit little slower than poll and select, but
425	but it scales phenomenally better. While poll and select usually scale	495	it scales phenomenally better. While poll and select usually scale like
426	like O(total_fds) where n is the total number of fds (or the highest fd),	496	O(total_fds) where total_fds is the total number of fds (or the highest
427	epoll scales either O(1) or O(active_fds).	497	fd), epoll scales either O(1) or O(active_fds).
428		498
429	The epoll mechanism deserves honorable mention as the most misdesigned	499	The epoll mechanism deserves honorable mention as the most misdesigned
430	of the more advanced event mechanisms: mere annoyances include silently	500	of the more advanced event mechanisms: mere annoyances include silently
431	dropping file descriptors, requiring a system call per change per file	501	dropping file descriptors, requiring a system call per change per file
432	descriptor (and unnecessary guessing of parameters), problems with dup and	502	descriptor (and unnecessary guessing of parameters), problems with dup,
		503	returning before the timeout value, resulting in additional iterations
		504	(and only giving 5ms accuracy while select on the same platform gives
433	so on. The biggest issue is fork races, however - if a program forks then	505	0.1ms) and so on. The biggest issue is fork races, however - if a program
434	I<both> parent and child process have to recreate the epoll set, which can	506	forks then I<both> parent and child process have to recreate the epoll
435	take considerable time (one syscall per file descriptor) and is of course	507	set, which can take considerable time (one syscall per file descriptor)
436	hard to detect.	508	and is of course hard to detect.
437		509
438	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	510	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
439	of course I<doesn't>, and epoll just loves to report events for totally	511	but of course I<doesn't>, and epoll just loves to report events for
440	I<different> file descriptors (even already closed ones, so one cannot	512	totally I<different> file descriptors (even already closed ones, so
441	even remove them from the set) than registered in the set (especially	513	one cannot even remove them from the set) than registered in the set
442	on SMP systems). Libev tries to counter these spurious notifications by	514	(especially on SMP systems). Libev tries to counter these spurious
443	employing an additional generation counter and comparing that against the	515	notifications by employing an additional generation counter and comparing
444	events to filter out spurious ones, recreating the set when required.	516	that against the events to filter out spurious ones, recreating the set
		517	when required. Epoll also errornously rounds down timeouts, but gives you
		518	no way to know when and by how much, so sometimes you have to busy-wait
		519	because epoll returns immediately despite a nonzero timeout. And last
		520	not least, it also refuses to work with some file descriptors which work
		521	perfectly fine with C<select> (files, many character devices...).
		522
		523	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
		524	cobbled together in a hurry, no thought to design or interaction with
		525	others. Oh, the pain, will it ever stop...
445		526
446	While stopping, setting and starting an I/O watcher in the same iteration	527	While stopping, setting and starting an I/O watcher in the same iteration
447	will result in some caching, there is still a system call per such	528	will result in some caching, there is still a system call per such
448	incident (because the same I<file descriptor> could point to a different	529	incident (because the same I<file descriptor> could point to a different
449	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	530	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
515	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	596	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
516		597
517	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	598	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
518	it's really slow, but it still scales very well (O(active_fds)).	599	it's really slow, but it still scales very well (O(active_fds)).
519		600
520	Please note that Solaris event ports can deliver a lot of spurious
521	notifications, so you need to use non-blocking I/O or other means to avoid
522	blocking when no data (or space) is available.
523
524	While this backend scales well, it requires one system call per active	601	While this backend scales well, it requires one system call per active
525	file descriptor per loop iteration. For small and medium numbers of file	602	file descriptor per loop iteration. For small and medium numbers of file
526	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	603	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
527	might perform better.	604	might perform better.
528		605
529	On the positive side, with the exception of the spurious readiness	606	On the positive side, this backend actually performed fully to
530	notifications, this backend actually performed fully to specification
531	in all tests and is fully embeddable, which is a rare feat among the	607	specification in all tests and is fully embeddable, which is a rare feat
532	OS-specific backends (I vastly prefer correctness over speed hacks).	608	among the OS-specific backends (I vastly prefer correctness over speed
		609	hacks).
		610
		611	On the negative side, the interface is I<bizarre> - so bizarre that
		612	even sun itself gets it wrong in their code examples: The event polling
		613	function sometimes returning 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
		616	you absolutely have to know whether an event occurred or not because you
		617	have to re-arm the watcher.
		618
		619	Fortunately libev seems to be able to work around these idiocies.
533		620
534	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	621	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
535	C<EVBACKEND_POLL>.	622	C<EVBACKEND_POLL>.
536		623
537	=item C<EVBACKEND_ALL>	624	=item C<EVBACKEND_ALL>
538		625
539	Try all backends (even potentially broken ones that wouldn't be tried	626	Try all backends (even potentially broken ones that wouldn't be tried
540	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	627	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
541	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	628	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
542		629
543	It is definitely not recommended to use this flag.	630	It is definitely not recommended to use this flag, use whatever
		631	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		632	at all.
		633
		634	=item C<EVBACKEND_MASK>
		635
		636	Not a backend at all, but a mask to select all backend bits from a
		637	C<flags> value, in case you want to mask out any backends from a flags
		638	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
544		639
545	=back	640	=back
546		641
547	If one or more of the backend flags are or'ed into the flags value,	642	If one or more of the backend flags are or'ed into the flags value,
548	then only these backends will be tried (in the reverse order as listed	643	then only these backends will be tried (in the reverse order as listed
549	here). If none are specified, all backends in C<ev_recommended_backends	644	here). If none are specified, all backends in C<ev_recommended_backends
550	()> will be tried.	645	()> will be tried.
551		646
552	Example: This is the most typical usage.
553
554	if (!ev_default_loop (0))
555	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
556
557	Example: Restrict libev to the select and poll backends, and do not allow
558	environment settings to be taken into account:
559
560	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
561
562	Example: Use whatever libev has to offer, but make sure that kqueue is
563	used if available (warning, breaks stuff, best use only with your own
564	private event loop and only if you know the OS supports your types of
565	fds):
566
567	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
568
569	=item struct ev_loop *ev_loop_new (unsigned int flags)
570
571	Similar to C<ev_default_loop>, but always creates a new event loop that is
572	always distinct from the default loop.
573
574	Note that this function I<is> thread-safe, and one common way to use
575	libev with threads is indeed to create one loop per thread, and using the
576	default loop in the "main" or "initial" thread.
577
578	Example: Try to create a event loop that uses epoll and nothing else.	647	Example: Try to create a event loop that uses epoll and nothing else.
579		648
580	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	649	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
581	if (!epoller)	650	if (!epoller)
582	fatal ("no epoll found here, maybe it hides under your chair");	651	fatal ("no epoll found here, maybe it hides under your chair");
583		652
		653	Example: Use whatever libev has to offer, but make sure that kqueue is
		654	used if available.
		655
		656	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		657
584	=item ev_default_destroy ()	658	=item ev_loop_destroy (loop)
585		659
586	Destroys the default loop (frees all memory and kernel state etc.). None	660	Destroys an event loop object (frees all memory and kernel state
587	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
588	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
589	either stop all watchers cleanly yourself I<before> calling this function,	663	responsibility to either stop all watchers cleanly yourself I<before>
590	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
591	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).
592		667
593	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
594	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
595	as signal and child watchers) would need to be stopped manually.	670	as signal and child watchers) would need to be stopped manually.
596		671
597	In general it is not advisable to call this function except in the	672	This function is normally used on loop objects allocated by
598	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.
599	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>
600	C<ev_loop_new> and C<ev_loop_destroy>.	679	and C<ev_loop_destroy>.
601		680
602	=item ev_loop_destroy (loop)	681	=item ev_loop_fork (loop)
603		682
604	Like C<ev_default_destroy>, but destroys an event loop created by an
605	earlier call to C<ev_loop_new>.
606
607	=item ev_default_fork ()
608
609	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
610	to reinitialise the kernel state for backends that have one. Despite the	684	reinitialise the kernel state for backends that have one. Despite the
611	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
612	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
613	sense). You I<must> call it in the child before using any of the libev	687	child before resuming or calling C<ev_run>.
614	functions, and it will only take effect at the next C<ev_loop> iteration.	688
		689	Again, you I<have> to call it on I<any> loop that you want to re-use after
		690	a fork, I<even if you do not plan to use the loop in the parent>. This is
		691	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		692	during fork.
615		693
616	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
617	process if and only if you want to use the event library in the child. If	695	process if and only if you want to use the event loop in the child. If
618	you just fork+exec, you don't have to call it at all.	696	you just fork+exec or create a new loop in the child, you don't have to
		697	call it at all (in fact, C<epoll> is so badly broken that it makes a
		698	difference, but libev will usually detect this case on its own and do a
		699	costly reset of the backend).
619		700
620	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
621	it just in case after a fork. To make this easy, the function will fit in	702	it just in case after a fork.
622	quite nicely into a call to C<pthread_atfork>:
623		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	...
624	pthread_atfork (0, 0, ev_default_fork);	714	pthread_atfork (0, 0, post_fork_child);
625
626	=item ev_loop_fork (loop)
627
628	Like C<ev_default_fork>, but acts on an event loop created by
629	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
630	after fork that you want to re-use in the child, and how you do this is
631	entirely your own problem.
632		715
633	=item int ev_is_default_loop (loop)	716	=item int ev_is_default_loop (loop)
634		717
635	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
636	otherwise.	719	otherwise.
637		720
638	=item unsigned int ev_loop_count (loop)	721	=item unsigned int ev_iteration (loop)
639		722
640	Returns the count of loop iterations for the loop, which is identical to	723	Returns the current iteration count for the event loop, which is identical
641	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>
642	happily wraps around with enough iterations.	725	and happily wraps around with enough iterations.
643		726
644	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
645	"ticks" the number of loop iterations), as it roughly corresponds with	728	"ticks" the number of loop iterations), as it roughly corresponds with
646	C<ev_prepare> and C<ev_check> calls.	729	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		730	prepare and check phases.
647		731
648	=item unsigned int ev_loop_depth (loop)	732	=item unsigned int ev_depth (loop)
649		733
650	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
651	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.
652		736
653	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
654	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),
655	in which case it is higher.	739	in which case it is higher.
656		740
657	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread	741	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
658	etc.), doesn't count as exit.	742	throwing an exception etc.), doesn't count as "exit" - consider this
		743	as a hint to avoid such ungentleman-like behaviour unless it's really
		744	convenient, in which case it is fully supported.
659		745
660	=item unsigned int ev_backend (loop)	746	=item unsigned int ev_backend (loop)
661		747
662	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
663	use.	749	use.
…		…
672		758
673	=item ev_now_update (loop)	759	=item ev_now_update (loop)
674		760
675	Establishes the current time by querying the kernel, updating the time	761	Establishes the current time by querying the kernel, updating the time
676	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
677	is usually done automatically within C<ev_loop ()>.	763	is usually done automatically within C<ev_run ()>.
678		764
679	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
680	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
681	the current time is a good idea.	767	the current time is a good idea.
682		768
…		…
684		770
685	=item ev_suspend (loop)	771	=item ev_suspend (loop)
686		772
687	=item ev_resume (loop)	773	=item ev_resume (loop)
688		774
689	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
690	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.
691		777
692	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
693	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
694	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
695	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>
…		…
697	C<ev_resume> directly afterwards to resume timer processing.	783	C<ev_resume> directly afterwards to resume timer processing.
698		784
699	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
700	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
701	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
702	occured while suspended).	788	occurred while suspended).
703		789
704	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
705	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>
706	without a previous call to C<ev_suspend>.	792	without a previous call to C<ev_suspend>.
707		793
708	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
709	event loop time (see C<ev_now_update>).	795	event loop time (see C<ev_now_update>).
710		796
711	=item ev_loop (loop, int flags)	797	=item ev_run (loop, int flags)
712		798
713	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
714	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
715	handling events.	801	handling events. It will ask the operating system for any new events, call
		802	the watcher callbacks, an then repeat the whole process indefinitely: This
		803	is why event loops are called I<loops>.
716		804
717	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
718	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.
719		808
720	Please note that an explicit C<ev_unloop> is usually better than	809	Please note that an explicit C<ev_break> is usually better than
721	relying on all watchers to be stopped when deciding when a program has	810	relying on all watchers to be stopped when deciding when a program has
722	finished (especially in interactive programs), but having a program	811	finished (especially in interactive programs), but having a program
723	that automatically loops as long as it has to and no longer by virtue	812	that automatically loops as long as it has to and no longer by virtue
724	of relying on its watchers stopping correctly, that is truly a thing of	813	of relying on its watchers stopping correctly, that is truly a thing of
725	beauty.	814	beauty.
726		815
		816	This function is also I<mostly> exception-safe - you can break out of
		817	a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		818	exception and so on. This does not decrement the C<ev_depth> value, nor
		819	will it clear any outstanding C<EVBREAK_ONE> breaks.
		820
727	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	821	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
728	those events and any already outstanding ones, but will not block your	822	those events and any already outstanding ones, but will not wait and
729	process in case there are no events and will return after one iteration of	823	block your process in case there are no events and will return after one
730	the loop.	824	iteration of the loop. This is sometimes useful to poll and handle new
		825	events while doing lengthy calculations, to keep the program responsive.
731		826
732	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	827	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
733	necessary) and will handle those and any already outstanding ones. It	828	necessary) and will handle those and any already outstanding ones. It
734	will block your process until at least one new event arrives (which could	829	will block your process until at least one new event arrives (which could
735	be an event internal to libev itself, so there is no guarantee that a	830	be an event internal to libev itself, so there is no guarantee that a
736	user-registered callback will be called), and will return after one	831	user-registered callback will be called), and will return after one
737	iteration of the loop.	832	iteration of the loop.
738		833
739	This is useful if you are waiting for some external event in conjunction	834	This is useful if you are waiting for some external event in conjunction
740	with something not expressible using other libev watchers (i.e. "roll your	835	with something not expressible using other libev watchers (i.e. "roll your
741	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	836	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
742	usually a better approach for this kind of thing.	837	usually a better approach for this kind of thing.
743		838
744	Here are the gory details of what C<ev_loop> does:	839	Here are the gory details of what C<ev_run> does (this is for your
		840	understanding, not a guarantee that things will work exactly like this in
		841	future versions):
745		842
		843	- Increment loop depth.
		844	- Reset the ev_break status.
746	- Before the first iteration, call any pending watchers.	845	- Before the first iteration, call any pending watchers.
		846	LOOP:
747	* If EVFLAG_FORKCHECK was used, check for a fork.	847	- If EVFLAG_FORKCHECK was used, check for a fork.
748	- If a fork was detected (by any means), queue and call all fork watchers.	848	- If a fork was detected (by any means), queue and call all fork watchers.
749	- Queue and call all prepare watchers.	849	- Queue and call all prepare watchers.
		850	- If ev_break was called, goto FINISH.
750	- If we have been forked, detach and recreate the kernel state	851	- If we have been forked, detach and recreate the kernel state
751	as to not disturb the other process.	852	as to not disturb the other process.
752	- Update the kernel state with all outstanding changes.	853	- Update the kernel state with all outstanding changes.
753	- Update the "event loop time" (ev_now ()).	854	- Update the "event loop time" (ev_now ()).
754	- Calculate for how long to sleep or block, if at all	855	- Calculate for how long to sleep or block, if at all
755	(active idle watchers, EVLOOP_NONBLOCK or not having	856	(active idle watchers, EVRUN_NOWAIT or not having
756	any active watchers at all will result in not sleeping).	857	any active watchers at all will result in not sleeping).
757	- Sleep if the I/O and timer collect interval say so.	858	- Sleep if the I/O and timer collect interval say so.
		859	- Increment loop iteration counter.
758	- Block the process, waiting for any events.	860	- Block the process, waiting for any events.
759	- Queue all outstanding I/O (fd) events.	861	- Queue all outstanding I/O (fd) events.
760	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	862	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
761	- Queue all expired timers.	863	- Queue all expired timers.
762	- Queue all expired periodics.	864	- Queue all expired periodics.
763	- Unless any events are pending now, queue all idle watchers.	865	- Queue all idle watchers with priority higher than that of pending events.
764	- Queue all check watchers.	866	- Queue all check watchers.
765	- Call all queued watchers in reverse order (i.e. check watchers first).	867	- Call all queued watchers in reverse order (i.e. check watchers first).
766	Signals and child watchers are implemented as I/O watchers, and will	868	Signals and child watchers are implemented as I/O watchers, and will
767	be handled here by queueing them when their watcher gets executed.	869	be handled here by queueing them when their watcher gets executed.
768	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	870	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
769	were used, or there are no active watchers, return, otherwise	871	were used, or there are no active watchers, goto FINISH, otherwise
770	continue with step *.	872	continue with step LOOP.
		873	FINISH:
		874	- Reset the ev_break status iff it was EVBREAK_ONE.
		875	- Decrement the loop depth.
		876	- Return.
771		877
772	Example: Queue some jobs and then loop until no events are outstanding	878	Example: Queue some jobs and then loop until no events are outstanding
773	anymore.	879	anymore.
774		880
775	... queue jobs here, make sure they register event watchers as long	881	... queue jobs here, make sure they register event watchers as long
776	... as they still have work to do (even an idle watcher will do..)	882	... as they still have work to do (even an idle watcher will do..)
777	ev_loop (my_loop, 0);	883	ev_run (my_loop, 0);
778	... jobs done or somebody called unloop. yeah!	884	... jobs done or somebody called break. yeah!
779		885
780	=item ev_unloop (loop, how)	886	=item ev_break (loop, how)
781		887
782	Can be used to make a call to C<ev_loop> return early (but only after it	888	Can be used to make a call to C<ev_run> return early (but only after it
783	has processed all outstanding events). The C<how> argument must be either	889	has processed all outstanding events). The C<how> argument must be either
784	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	890	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
785	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	891	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
786		892
787	This "unloop state" will be cleared when entering C<ev_loop> again.	893	This "break state" will be cleared on the next call to C<ev_run>.
788		894
789	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	895	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		896	which case it will have no effect.
790		897
791	=item ev_ref (loop)	898	=item ev_ref (loop)
792		899
793	=item ev_unref (loop)	900	=item ev_unref (loop)
794		901
795	Ref/unref can be used to add or remove a reference count on the event	902	Ref/unref can be used to add or remove a reference count on the event
796	loop: Every watcher keeps one reference, and as long as the reference	903	loop: Every watcher keeps one reference, and as long as the reference
797	count is nonzero, C<ev_loop> will not return on its own.	904	count is nonzero, C<ev_run> will not return on its own.
798		905
799	This is useful when you have a watcher that you never intend to	906	This is useful when you have a watcher that you never intend to
800	unregister, but that nevertheless should not keep C<ev_loop> from	907	unregister, but that nevertheless should not keep C<ev_run> from
801	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>	908	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
802	before stopping it.	909	before stopping it.
803		910
804	As an example, libev itself uses this for its internal signal pipe: It	911	As an example, libev itself uses this for its internal signal pipe: It
805	is not visible to the libev user and should not keep C<ev_loop> from	912	is not visible to the libev user and should not keep C<ev_run> from
806	exiting if no event watchers registered by it are active. It is also an	913	exiting if no event watchers registered by it are active. It is also an
807	excellent way to do this for generic recurring timers or from within	914	excellent way to do this for generic recurring timers or from within
808	third-party libraries. Just remember to I<unref after start> and I<ref	915	third-party libraries. Just remember to I<unref after start> and I<ref
809	before stop> (but only if the watcher wasn't active before, or was active	916	before stop> (but only if the watcher wasn't active before, or was active
810	before, respectively. Note also that libev might stop watchers itself	917	before, respectively. Note also that libev might stop watchers itself
811	(e.g. non-repeating timers) in which case you have to C<ev_ref>	918	(e.g. non-repeating timers) in which case you have to C<ev_ref>
812	in the callback).	919	in the callback).
813		920
814	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	921	Example: Create a signal watcher, but keep it from keeping C<ev_run>
815	running when nothing else is active.	922	running when nothing else is active.
816		923
817	ev_signal exitsig;	924	ev_signal exitsig;
818	ev_signal_init (&exitsig, sig_cb, SIGINT);	925	ev_signal_init (&exitsig, sig_cb, SIGINT);
819	ev_signal_start (loop, &exitsig);	926	ev_signal_start (loop, &exitsig);
820	evf_unref (loop);	927	ev_unref (loop);
821		928
822	Example: For some weird reason, unregister the above signal handler again.	929	Example: For some weird reason, unregister the above signal handler again.
823		930
824	ev_ref (loop);	931	ev_ref (loop);
825	ev_signal_stop (loop, &exitsig);	932	ev_signal_stop (loop, &exitsig);
…		…
864	usually doesn't make much sense to set it to a lower value than C<0.01>,	971	usually doesn't make much sense to set it to a lower value than C<0.01>,
865	as this approaches the timing granularity of most systems. Note that if	972	as this approaches the timing granularity of most systems. Note that if
866	you do transactions with the outside world and you can't increase the	973	you do transactions with the outside world and you can't increase the
867	parallelity, then this setting will limit your transaction rate (if you	974	parallelity, then this setting will limit your transaction rate (if you
868	need to poll once per transaction and the I/O collect interval is 0.01,	975	need to poll once per transaction and the I/O collect interval is 0.01,
869	then you can't do more than 100 transations per second).	976	then you can't do more than 100 transactions per second).
870		977
871	Setting the I<timeout collect interval> can improve the opportunity for	978	Setting the I<timeout collect interval> can improve the opportunity for
872	saving power, as the program will "bundle" timer callback invocations that	979	saving power, as the program will "bundle" timer callback invocations that
873	are "near" in time together, by delaying some, thus reducing the number of	980	are "near" in time together, by delaying some, thus reducing the number of
874	times the process sleeps and wakes up again. Another useful technique to	981	times the process sleeps and wakes up again. Another useful technique to
…		…
882	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	989	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
883		990
884	=item ev_invoke_pending (loop)	991	=item ev_invoke_pending (loop)
885		992
886	This call will simply invoke all pending watchers while resetting their	993	This call will simply invoke all pending watchers while resetting their
887	pending state. Normally, C<ev_loop> does this automatically when required,	994	pending state. Normally, C<ev_run> does this automatically when required,
888	but when overriding the invoke callback this call comes handy.	995	but when overriding the invoke callback this call comes handy. This
		996	function can be invoked from a watcher - this can be useful for example
		997	when you want to do some lengthy calculation and want to pass further
		998	event handling to another thread (you still have to make sure only one
		999	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
889		1000
890	=item int ev_pending_count (loop)	1001	=item int ev_pending_count (loop)
891		1002
892	Returns the number of pending watchers - zero indicates that no watchers	1003	Returns the number of pending watchers - zero indicates that no watchers
893	are pending.	1004	are pending.
894		1005
895	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))	1006	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
896		1007
897	This overrides the invoke pending functionality of the loop: Instead of	1008	This overrides the invoke pending functionality of the loop: Instead of
898	invoking all pending watchers when there are any, C<ev_loop> will call	1009	invoking all pending watchers when there are any, C<ev_run> will call
899	this callback instead. This is useful, for example, when you want to	1010	this callback instead. This is useful, for example, when you want to
900	invoke the actual watchers inside another context (another thread etc.).	1011	invoke the actual watchers inside another context (another thread etc.).
901		1012
902	If you want to reset the callback, use C<ev_invoke_pending> as new	1013	If you want to reset the callback, use C<ev_invoke_pending> as new
903	callback.	1014	callback.
…		…
906		1017
907	Sometimes you want to share the same loop between multiple threads. This	1018	Sometimes you want to share the same loop between multiple threads. This
908	can be done relatively simply by putting mutex_lock/unlock calls around	1019	can be done relatively simply by putting mutex_lock/unlock calls around
909	each call to a libev function.	1020	each call to a libev function.
910		1021
911	However, C<ev_loop> can run an indefinite time, so it is not feasible to	1022	However, C<ev_run> can run an indefinite time, so it is not feasible
912	wait for it to return. One way around this is to wake up the loop via	1023	to wait for it to return. One way around this is to wake up the event
913	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>	1024	loop via C<ev_break> and C<av_async_send>, another way is to set these
914	and I<acquire> callbacks on the loop.	1025	I<release> and I<acquire> callbacks on the loop.
915		1026
916	When set, then C<release> will be called just before the thread is	1027	When set, then C<release> will be called just before the thread is
917	suspended waiting for new events, and C<acquire> is called just	1028	suspended waiting for new events, and C<acquire> is called just
918	afterwards.	1029	afterwards.
919		1030
…		…
922		1033
923	While event loop modifications are allowed between invocations of	1034	While event loop modifications are allowed between invocations of
924	C<release> and C<acquire> (that's their only purpose after all), no	1035	C<release> and C<acquire> (that's their only purpose after all), no
925	modifications done will affect the event loop, i.e. adding watchers will	1036	modifications done will affect the event loop, i.e. adding watchers will
926	have no effect on the set of file descriptors being watched, or the time	1037	have no effect on the set of file descriptors being watched, or the time
927	waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it	1038	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
928	to take note of any changes you made.	1039	to take note of any changes you made.
929		1040
930	In theory, threads executing C<ev_loop> will be async-cancel safe between	1041	In theory, threads executing C<ev_run> will be async-cancel safe between
931	invocations of C<release> and C<acquire>.	1042	invocations of C<release> and C<acquire>.
932		1043
933	See also the locking example in the C<THREADS> section later in this	1044	See also the locking example in the C<THREADS> section later in this
934	document.	1045	document.
935		1046
936	=item ev_set_userdata (loop, void *data)	1047	=item ev_set_userdata (loop, void *data)
937		1048
938	=item ev_userdata (loop)	1049	=item void *ev_userdata (loop)
939		1050
940	Set and retrieve a single C<void *> associated with a loop. When	1051	Set and retrieve a single C<void *> associated with a loop. When
941	C<ev_set_userdata> has never been called, then C<ev_userdata> returns	1052	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
942	C<0.>	1053	C<0>.
943		1054
944	These two functions can be used to associate arbitrary data with a loop,	1055	These two functions can be used to associate arbitrary data with a loop,
945	and are intended solely for the C<invoke_pending_cb>, C<release> and	1056	and are intended solely for the C<invoke_pending_cb>, C<release> and
946	C<acquire> callbacks described above, but of course can be (ab-)used for	1057	C<acquire> callbacks described above, but of course can be (ab-)used for
947	any other purpose as well.	1058	any other purpose as well.
948		1059
949	=item ev_loop_verify (loop)	1060	=item ev_verify (loop)
950		1061
951	This function only does something when C<EV_VERIFY> support has been	1062	This function only does something when C<EV_VERIFY> support has been
952	compiled in, which is the default for non-minimal builds. It tries to go	1063	compiled in, which is the default for non-minimal builds. It tries to go
953	through all internal structures and checks them for validity. If anything	1064	through all internal structures and checks them for validity. If anything
954	is found to be inconsistent, it will print an error message to standard	1065	is found to be inconsistent, it will print an error message to standard
…		…
965		1076
966	In the following description, uppercase C<TYPE> in names stands for the	1077	In the following description, uppercase C<TYPE> in names stands for the
967	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1078	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
968	watchers and C<ev_io_start> for I/O watchers.	1079	watchers and C<ev_io_start> for I/O watchers.
969		1080
970	A watcher is a structure that you create and register to record your	1081	A watcher is an opaque structure that you allocate and register to record
971	interest in some event. For instance, if you want to wait for STDIN to	1082	your interest in some event. To make a concrete example, imagine you want
972	become readable, you would create an C<ev_io> watcher for that:	1083	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1084	for that:
973		1085
974	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1086	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
975	{	1087	{
976	ev_io_stop (w);	1088	ev_io_stop (w);
977	ev_unloop (loop, EVUNLOOP_ALL);	1089	ev_break (loop, EVBREAK_ALL);
978	}	1090	}
979		1091
980	struct ev_loop *loop = ev_default_loop (0);	1092	struct ev_loop *loop = ev_default_loop (0);
981		1093
982	ev_io stdin_watcher;	1094	ev_io stdin_watcher;
983		1095
984	ev_init (&stdin_watcher, my_cb);	1096	ev_init (&stdin_watcher, my_cb);
985	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1097	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
986	ev_io_start (loop, &stdin_watcher);	1098	ev_io_start (loop, &stdin_watcher);
987		1099
988	ev_loop (loop, 0);	1100	ev_run (loop, 0);
989		1101
990	As you can see, you are responsible for allocating the memory for your	1102	As you can see, you are responsible for allocating the memory for your
991	watcher structures (and it is I<usually> a bad idea to do this on the	1103	watcher structures (and it is I<usually> a bad idea to do this on the
992	stack).	1104	stack).
993		1105
994	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1106	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
995	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1107	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
996		1108
997	Each watcher structure must be initialised by a call to C<ev_init	1109	Each watcher structure must be initialised by a call to C<ev_init (watcher
998	(watcher *, callback)>, which expects a callback to be provided. This	1110	*, callback)>, which expects a callback to be provided. This callback is
999	callback gets invoked each time the event occurs (or, in the case of I/O	1111	invoked each time the event occurs (or, in the case of I/O watchers, each
1000	watchers, each time the event loop detects that the file descriptor given	1112	time the event loop detects that the file descriptor given is readable
1001	is readable and/or writable).	1113	and/or writable).
1002		1114
1003	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1115	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
1004	macro to configure it, with arguments specific to the watcher type. There	1116	macro to configure it, with arguments specific to the watcher type. There
1005	is also a macro to combine initialisation and setting in one call: C<<	1117	is also a macro to combine initialisation and setting in one call: C<<
1006	ev_TYPE_init (watcher *, callback, ...) >>.	1118	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
1057		1169
1058	=item C<EV_PREPARE>	1170	=item C<EV_PREPARE>
1059		1171
1060	=item C<EV_CHECK>	1172	=item C<EV_CHECK>
1061		1173
1062	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1174	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
1063	to gather new events, and all C<ev_check> watchers are invoked just after	1175	to gather new events, and all C<ev_check> watchers are invoked just after
1064	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1176	C<ev_run> has gathered them, but before it invokes any callbacks for any
1065	received events. Callbacks of both watcher types can start and stop as	1177	received events. Callbacks of both watcher types can start and stop as
1066	many watchers as they want, and all of them will be taken into account	1178	many watchers as they want, and all of them will be taken into account
1067	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1179	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
1068	C<ev_loop> from blocking).	1180	C<ev_run> from blocking).
1069		1181
1070	=item C<EV_EMBED>	1182	=item C<EV_EMBED>
1071		1183
1072	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1184	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1073		1185
1074	=item C<EV_FORK>	1186	=item C<EV_FORK>
1075		1187
1076	The event loop has been resumed in the child process after fork (see	1188	The event loop has been resumed in the child process after fork (see
1077	C<ev_fork>).	1189	C<ev_fork>).
		1190
		1191	=item C<EV_CLEANUP>
		1192
		1193	The event loop is about to be destroyed (see C<ev_cleanup>).
1078		1194
1079	=item C<EV_ASYNC>	1195	=item C<EV_ASYNC>
1080		1196
1081	The given async watcher has been asynchronously notified (see C<ev_async>).	1197	The given async watcher has been asynchronously notified (see C<ev_async>).
1082		1198
…		…
1255	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related	1371	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1256	functions that do not need a watcher.	1372	functions that do not need a watcher.
1257		1373
1258	=back	1374	=back
1259		1375
		1376	See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR
		1377	OWN COMPOSITE WATCHERS> idioms.
1260		1378
1261	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1379	=head2 WATCHER STATES
1262		1380
1263	Each watcher has, by default, a member C<void *data> that you can change	1381	There are various watcher states mentioned throughout this manual -
1264	and read at any time: libev will completely ignore it. This can be used	1382	active, pending and so on. In this section these states and the rules to
1265	to associate arbitrary data with your watcher. If you need more data and	1383	transition between them will be described in more detail - and while these
1266	don't want to allocate memory and store a pointer to it in that data	1384	rules might look complicated, they usually do "the right thing".
1267	member, you can also "subclass" the watcher type and provide your own
1268	data:
1269		1385
1270	struct my_io	1386	=over 4
1271	{
1272	ev_io io;
1273	int otherfd;
1274	void *somedata;
1275	struct whatever *mostinteresting;
1276	};
1277		1387
1278	...	1388	=item initialiased
1279	struct my_io w;
1280	ev_io_init (&w.io, my_cb, fd, EV_READ);
1281		1389
1282	And since your callback will be called with a pointer to the watcher, you	1390	Before a watcher can be registered with the event looop it has to be
1283	can cast it back to your own type:	1391	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1392	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1284		1393
1285	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)	1394	In this state it is simply some block of memory that is suitable for
1286	{	1395	use in an event loop. It can be moved around, freed, reused etc. at
1287	struct my_io *w = (struct my_io *)w_;	1396	will - as long as you either keep the memory contents intact, or call
1288	...	1397	C<ev_TYPE_init> again.
1289	}
1290		1398
1291	More interesting and less C-conformant ways of casting your callback type	1399	=item started/running/active
1292	instead have been omitted.
1293		1400
1294	Another common scenario is to use some data structure with multiple	1401	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1295	embedded watchers:	1402	property of the event loop, and is actively waiting for events. While in
		1403	this state it cannot be accessed (except in a few documented ways), moved,
		1404	freed or anything else - the only legal thing is to keep a pointer to it,
		1405	and call libev functions on it that are documented to work on active watchers.
1296		1406
1297	struct my_biggy	1407	=item pending
1298	{
1299	int some_data;
1300	ev_timer t1;
1301	ev_timer t2;
1302	}
1303		1408
1304	In this case getting the pointer to C<my_biggy> is a bit more	1409	If a watcher is active and libev determines that an event it is interested
1305	complicated: Either you store the address of your C<my_biggy> struct	1410	in has occurred (such as a timer expiring), it will become pending. It will
1306	in the C<data> member of the watcher (for woozies), or you need to use	1411	stay in this pending state until either it is stopped or its callback is
1307	some pointer arithmetic using C<offsetof> inside your watchers (for real	1412	about to be invoked, so it is not normally pending inside the watcher
1308	programmers):	1413	callback.
1309		1414
1310	#include <stddef.h>	1415	The watcher might or might not be active while it is pending (for example,
		1416	an expired non-repeating timer can be pending but no longer active). If it
		1417	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1418	but it is still property of the event loop at this time, so cannot be
		1419	moved, freed or reused. And if it is active the rules described in the
		1420	previous item still apply.
1311		1421
1312	static void	1422	It is also possible to feed an event on a watcher that is not active (e.g.
1313	t1_cb (EV_P_ ev_timer *w, int revents)	1423	via C<ev_feed_event>), in which case it becomes pending without being
1314	{	1424	active.
1315	struct my_biggy big = (struct my_biggy *)
1316	(((char *)w) - offsetof (struct my_biggy, t1));
1317	}
1318		1425
1319	static void	1426	=item stopped
1320	t2_cb (EV_P_ ev_timer *w, int revents)	1427
1321	{	1428	A watcher can be stopped implicitly by libev (in which case it might still
1322	struct my_biggy big = (struct my_biggy *)	1429	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1323	(((char *)w) - offsetof (struct my_biggy, t2));	1430	latter will clear any pending state the watcher might be in, regardless
1324	}	1431	of whether it was active or not, so stopping a watcher explicitly before
		1432	freeing it is often a good idea.
		1433
		1434	While stopped (and not pending) the watcher is essentially in the
		1435	initialised state, that is, it can be reused, moved, modified in any way
		1436	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1437	it again).
		1438
		1439	=back
1325		1440
1326	=head2 WATCHER PRIORITY MODELS	1441	=head2 WATCHER PRIORITY MODELS
1327		1442
1328	Many event loops support I<watcher priorities>, which are usually small	1443	Many event loops support I<watcher priorities>, which are usually small
1329	integers that influence the ordering of event callback invocation	1444	integers that influence the ordering of event callback invocation
…		…
1372		1487
1373	For example, to emulate how many other event libraries handle priorities,	1488	For example, to emulate how many other event libraries handle priorities,
1374	you can associate an C<ev_idle> watcher to each such watcher, and in	1489	you can associate an C<ev_idle> watcher to each such watcher, and in
1375	the normal watcher callback, you just start the idle watcher. The real	1490	the normal watcher callback, you just start the idle watcher. The real
1376	processing is done in the idle watcher callback. This causes libev to	1491	processing is done in the idle watcher callback. This causes libev to
1377	continously poll and process kernel event data for the watcher, but when	1492	continuously poll and process kernel event data for the watcher, but when
1378	the lock-out case is known to be rare (which in turn is rare :), this is	1493	the lock-out case is known to be rare (which in turn is rare :), this is
1379	workable.	1494	workable.
1380		1495
1381	Usually, however, the lock-out model implemented that way will perform	1496	Usually, however, the lock-out model implemented that way will perform
1382	miserably under the type of load it was designed to handle. In that case,	1497	miserably under the type of load it was designed to handle. In that case,
…		…
1396	{	1511	{
1397	// stop the I/O watcher, we received the event, but	1512	// stop the I/O watcher, we received the event, but
1398	// are not yet ready to handle it.	1513	// are not yet ready to handle it.
1399	ev_io_stop (EV_A_ w);	1514	ev_io_stop (EV_A_ w);
1400		1515
1401	// start the idle watcher to ahndle the actual event.	1516	// start the idle watcher to handle the actual event.
1402	// it will not be executed as long as other watchers	1517	// it will not be executed as long as other watchers
1403	// with the default priority are receiving events.	1518	// with the default priority are receiving events.
1404	ev_idle_start (EV_A_ &idle);	1519	ev_idle_start (EV_A_ &idle);
1405	}	1520	}
1406		1521
…		…
1456	In general you can register as many read and/or write event watchers per	1571	In general you can register as many read and/or write event watchers per
1457	fd as you want (as long as you don't confuse yourself). Setting all file	1572	fd as you want (as long as you don't confuse yourself). Setting all file
1458	descriptors to non-blocking mode is also usually a good idea (but not	1573	descriptors to non-blocking mode is also usually a good idea (but not
1459	required if you know what you are doing).	1574	required if you know what you are doing).
1460		1575
1461	If you cannot use non-blocking mode, then force the use of a
1462	known-to-be-good backend (at the time of this writing, this includes only
1463	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1464	descriptors for which non-blocking operation makes no sense (such as
1465	files) - libev doesn't guarentee any specific behaviour in that case.
1466
1467	Another thing you have to watch out for is that it is quite easy to	1576	Another thing you have to watch out for is that it is quite easy to
1468	receive "spurious" readiness notifications, that is your callback might	1577	receive "spurious" readiness notifications, that is, your callback might
1469	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1578	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1470	because there is no data. Not only are some backends known to create a	1579	because there is no data. It is very easy to get into this situation even
1471	lot of those (for example Solaris ports), it is very easy to get into	1580	with a relatively standard program structure. Thus it is best to always
1472	this situation even with a relatively standard program structure. Thus	1581	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1473	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1474	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1582	preferable to a program hanging until some data arrives.
1475		1583
1476	If you cannot run the fd in non-blocking mode (for example you should	1584	If you cannot run the fd in non-blocking mode (for example you should
1477	not play around with an Xlib connection), then you have to separately	1585	not play around with an Xlib connection), then you have to separately
1478	re-test whether a file descriptor is really ready with a known-to-be good	1586	re-test whether a file descriptor is really ready with a known-to-be good
1479	interface such as poll (fortunately in our Xlib example, Xlib already	1587	interface such as poll (fortunately in the case of Xlib, it already does
1480	does this on its own, so its quite safe to use). Some people additionally	1588	this on its own, so its quite safe to use). Some people additionally
1481	use C<SIGALRM> and an interval timer, just to be sure you won't block	1589	use C<SIGALRM> and an interval timer, just to be sure you won't block
1482	indefinitely.	1590	indefinitely.
1483		1591
1484	But really, best use non-blocking mode.	1592	But really, best use non-blocking mode.
1485		1593
…		…
1513		1621
1514	There is no workaround possible except not registering events	1622	There is no workaround possible except not registering events
1515	for potentially C<dup ()>'ed file descriptors, or to resort to	1623	for potentially C<dup ()>'ed file descriptors, or to resort to
1516	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1624	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1517		1625
		1626	=head3 The special problem of files
		1627
		1628	Many people try to use C<select> (or libev) on file descriptors
		1629	representing files, and expect it to become ready when their program
		1630	doesn't block on disk accesses (which can take a long time on their own).
		1631
		1632	However, this cannot ever work in the "expected" way - you get a readiness
		1633	notification as soon as the kernel knows whether and how much data is
		1634	there, and in the case of open files, that's always the case, so you
		1635	always get a readiness notification instantly, and your read (or possibly
		1636	write) will still block on the disk I/O.
		1637
		1638	Another way to view it is that in the case of sockets, pipes, character
		1639	devices and so on, there is another party (the sender) that delivers data
		1640	on its own, but in the case of files, there is no such thing: the disk
		1641	will not send data on its own, simply because it doesn't know what you
		1642	wish to read - you would first have to request some data.
		1643
		1644	Since files are typically not-so-well supported by advanced notification
		1645	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1646	to files, even though you should not use it. The reason for this is
		1647	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1648	usually a tty, often a pipe, but also sometimes files or special devices
		1649	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1650	F</dev/urandom>), and even though the file might better be served with
		1651	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1652	it "just works" instead of freezing.
		1653
		1654	So avoid file descriptors pointing to files when you know it (e.g. use
		1655	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1656	when you rarely read from a file instead of from a socket, and want to
		1657	reuse the same code path.
		1658
1518	=head3 The special problem of fork	1659	=head3 The special problem of fork
1519		1660
1520	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1661	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1521	useless behaviour. Libev fully supports fork, but needs to be told about	1662	useless behaviour. Libev fully supports fork, but needs to be told about
1522	it in the child.	1663	it in the child if you want to continue to use it in the child.
1523		1664
1524	To support fork in your programs, you either have to call	1665	To support fork in your child processes, you have to call C<ev_loop_fork
1525	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1666	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1526	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1667	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1527	C<EVBACKEND_POLL>.
1528		1668
1529	=head3 The special problem of SIGPIPE	1669	=head3 The special problem of SIGPIPE
1530		1670
1531	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1671	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1532	when writing to a pipe whose other end has been closed, your program gets	1672	when writing to a pipe whose other end has been closed, your program gets
…		…
1538	somewhere, as that would have given you a big clue).	1678	somewhere, as that would have given you a big clue).
1539		1679
1540	=head3 The special problem of accept()ing when you can't	1680	=head3 The special problem of accept()ing when you can't
1541		1681
1542	Many implementations of the POSIX C<accept> function (for example,	1682	Many implementations of the POSIX C<accept> function (for example,
1543	found in port-2004 Linux) have the peculiar behaviour of not removing a	1683	found in post-2004 Linux) have the peculiar behaviour of not removing a
1544	connection from the pending queue in all error cases.	1684	connection from the pending queue in all error cases.
1545		1685
1546	For example, larger servers often run out of file descriptors (because	1686	For example, larger servers often run out of file descriptors (because
1547	of resource limits), causing C<accept> to fail with C<ENFILE> but not	1687	of resource limits), causing C<accept> to fail with C<ENFILE> but not
1548	rejecting the connection, leading to libev signalling readiness on	1688	rejecting the connection, leading to libev signalling readiness on
…		…
1614	...	1754	...
1615	struct ev_loop *loop = ev_default_init (0);	1755	struct ev_loop *loop = ev_default_init (0);
1616	ev_io stdin_readable;	1756	ev_io stdin_readable;
1617	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1757	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1618	ev_io_start (loop, &stdin_readable);	1758	ev_io_start (loop, &stdin_readable);
1619	ev_loop (loop, 0);	1759	ev_run (loop, 0);
1620		1760
1621		1761
1622	=head2 C<ev_timer> - relative and optionally repeating timeouts	1762	=head2 C<ev_timer> - relative and optionally repeating timeouts
1623		1763
1624	Timer watchers are simple relative timers that generate an event after a	1764	Timer watchers are simple relative timers that generate an event after a
…		…
1633	The callback is guaranteed to be invoked only I<after> its timeout has	1773	The callback is guaranteed to be invoked only I<after> its timeout has
1634	passed (not I<at>, so on systems with very low-resolution clocks this	1774	passed (not I<at>, so on systems with very low-resolution clocks this
1635	might introduce a small delay). If multiple timers become ready during the	1775	might introduce a small delay). If multiple timers become ready during the
1636	same loop iteration then the ones with earlier time-out values are invoked	1776	same loop iteration then the ones with earlier time-out values are invoked
1637	before ones of the same priority with later time-out values (but this is	1777	before ones of the same priority with later time-out values (but this is
1638	no longer true when a callback calls C<ev_loop> recursively).	1778	no longer true when a callback calls C<ev_run> recursively).
1639		1779
1640	=head3 Be smart about timeouts	1780	=head3 Be smart about timeouts
1641		1781
1642	Many real-world problems involve some kind of timeout, usually for error	1782	Many real-world problems involve some kind of timeout, usually for error
1643	recovery. A typical example is an HTTP request - if the other side hangs,	1783	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1729	ev_tstamp timeout = last_activity + 60.;	1869	ev_tstamp timeout = last_activity + 60.;
1730		1870
1731	// if last_activity + 60. is older than now, we did time out	1871	// if last_activity + 60. is older than now, we did time out
1732	if (timeout < now)	1872	if (timeout < now)
1733	{	1873	{
1734	// timeout occured, take action	1874	// timeout occurred, take action
1735	}	1875	}
1736	else	1876	else
1737	{	1877	{
1738	// callback was invoked, but there was some activity, re-arm	1878	// callback was invoked, but there was some activity, re-arm
1739	// the watcher to fire in last_activity + 60, which is	1879	// the watcher to fire in last_activity + 60, which is
…		…
1766	callback (loop, timer, EV_TIMER);	1906	callback (loop, timer, EV_TIMER);
1767		1907
1768	And when there is some activity, simply store the current time in	1908	And when there is some activity, simply store the current time in
1769	C<last_activity>, no libev calls at all:	1909	C<last_activity>, no libev calls at all:
1770		1910
1771	last_actiivty = ev_now (loop);	1911	last_activity = ev_now (loop);
1772		1912
1773	This technique is slightly more complex, but in most cases where the	1913	This technique is slightly more complex, but in most cases where the
1774	time-out is unlikely to be triggered, much more efficient.	1914	time-out is unlikely to be triggered, much more efficient.
1775		1915
1776	Changing the timeout is trivial as well (if it isn't hard-coded in the	1916	Changing the timeout is trivial as well (if it isn't hard-coded in the
…		…
1814		1954
1815	=head3 The special problem of time updates	1955	=head3 The special problem of time updates
1816		1956
1817	Establishing the current time is a costly operation (it usually takes at	1957	Establishing the current time is a costly operation (it usually takes at
1818	least two system calls): EV therefore updates its idea of the current	1958	least two system calls): EV therefore updates its idea of the current
1819	time only before and after C<ev_loop> collects new events, which causes a	1959	time only before and after C<ev_run> collects new events, which causes a
1820	growing difference between C<ev_now ()> and C<ev_time ()> when handling	1960	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1821	lots of events in one iteration.	1961	lots of events in one iteration.
1822		1962
1823	The relative timeouts are calculated relative to the C<ev_now ()>	1963	The relative timeouts are calculated relative to the C<ev_now ()>
1824	time. This is usually the right thing as this timestamp refers to the time	1964	time. This is usually the right thing as this timestamp refers to the time
…		…
1941	}	2081	}
1942		2082
1943	ev_timer mytimer;	2083	ev_timer mytimer;
1944	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2084	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1945	ev_timer_again (&mytimer); /* start timer */	2085	ev_timer_again (&mytimer); /* start timer */
1946	ev_loop (loop, 0);	2086	ev_run (loop, 0);
1947		2087
1948	// and in some piece of code that gets executed on any "activity":	2088	// and in some piece of code that gets executed on any "activity":
1949	// reset the timeout to start ticking again at 10 seconds	2089	// reset the timeout to start ticking again at 10 seconds
1950	ev_timer_again (&mytimer);	2090	ev_timer_again (&mytimer);
1951		2091
…		…
1977		2117
1978	As with timers, the callback is guaranteed to be invoked only when the	2118	As with timers, the callback is guaranteed to be invoked only when the
1979	point in time where it is supposed to trigger has passed. If multiple	2119	point in time where it is supposed to trigger has passed. If multiple
1980	timers become ready during the same loop iteration then the ones with	2120	timers become ready during the same loop iteration then the ones with
1981	earlier time-out values are invoked before ones with later time-out values	2121	earlier time-out values are invoked before ones with later time-out values
1982	(but this is no longer true when a callback calls C<ev_loop> recursively).	2122	(but this is no longer true when a callback calls C<ev_run> recursively).
1983		2123
1984	=head3 Watcher-Specific Functions and Data Members	2124	=head3 Watcher-Specific Functions and Data Members
1985		2125
1986	=over 4	2126	=over 4
1987		2127
…		…
2022		2162
2023	Another way to think about it (for the mathematically inclined) is that	2163	Another way to think about it (for the mathematically inclined) is that
2024	C<ev_periodic> will try to run the callback in this mode at the next possible	2164	C<ev_periodic> will try to run the callback in this mode at the next possible
2025	time where C<time = offset (mod interval)>, regardless of any time jumps.	2165	time where C<time = offset (mod interval)>, regardless of any time jumps.
2026		2166
2027	For numerical stability it is preferable that the C<offset> value is near	2167	The C<interval> I<MUST> be positive, and for numerical stability, the
2028	C<ev_now ()> (the current time), but there is no range requirement for	2168	interval value should be higher than C<1/8192> (which is around 100
2029	this value, and in fact is often specified as zero.	2169	microseconds) and C<offset> should be higher than C<0> and should have
		2170	at most a similar magnitude as the current time (say, within a factor of
		2171	ten). Typical values for offset are, in fact, C<0> or something between
		2172	C<0> and C<interval>, which is also the recommended range.
2030		2173
2031	Note also that there is an upper limit to how often a timer can fire (CPU	2174	Note also that there is an upper limit to how often a timer can fire (CPU
2032	speed for example), so if C<interval> is very small then timing stability	2175	speed for example), so if C<interval> is very small then timing stability
2033	will of course deteriorate. Libev itself tries to be exact to be about one	2176	will of course deteriorate. Libev itself tries to be exact to be about one
2034	millisecond (if the OS supports it and the machine is fast enough).	2177	millisecond (if the OS supports it and the machine is fast enough).
…		…
2115	Example: Call a callback every hour, or, more precisely, whenever the	2258	Example: Call a callback every hour, or, more precisely, whenever the
2116	system time is divisible by 3600. The callback invocation times have	2259	system time is divisible by 3600. The callback invocation times have
2117	potentially a lot of jitter, but good long-term stability.	2260	potentially a lot of jitter, but good long-term stability.
2118		2261
2119	static void	2262	static void
2120	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2263	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
2121	{	2264	{
2122	... its now a full hour (UTC, or TAI or whatever your clock follows)	2265	... its now a full hour (UTC, or TAI or whatever your clock follows)
2123	}	2266	}
2124		2267
2125	ev_periodic hourly_tick;	2268	ev_periodic hourly_tick;
…		…
2148		2291
2149	=head2 C<ev_signal> - signal me when a signal gets signalled!	2292	=head2 C<ev_signal> - signal me when a signal gets signalled!
2150		2293
2151	Signal watchers will trigger an event when the process receives a specific	2294	Signal watchers will trigger an event when the process receives a specific
2152	signal one or more times. Even though signals are very asynchronous, libev	2295	signal one or more times. Even though signals are very asynchronous, libev
2153	will try it's best to deliver signals synchronously, i.e. as part of the	2296	will try its best to deliver signals synchronously, i.e. as part of the
2154	normal event processing, like any other event.	2297	normal event processing, like any other event.
2155		2298
2156	If you want signals to be delivered truly asynchronously, just use	2299	If you want signals to be delivered truly asynchronously, just use
2157	C<sigaction> as you would do without libev and forget about sharing	2300	C<sigaction> as you would do without libev and forget about sharing
2158	the signal. You can even use C<ev_async> from a signal handler to	2301	the signal. You can even use C<ev_async> from a signal handler to
…		…
2177	=head3 The special problem of inheritance over fork/execve/pthread_create	2320	=head3 The special problem of inheritance over fork/execve/pthread_create
2178		2321
2179	Both the signal mask (C<sigprocmask>) and the signal disposition	2322	Both the signal mask (C<sigprocmask>) and the signal disposition
2180	(C<sigaction>) are unspecified after starting a signal watcher (and after	2323	(C<sigaction>) are unspecified after starting a signal watcher (and after
2181	stopping it again), that is, libev might or might not block the signal,	2324	stopping it again), that is, libev might or might not block the signal,
2182	and might or might not set or restore the installed signal handler.	2325	and might or might not set or restore the installed signal handler (but
		2326	see C<EVFLAG_NOSIGMASK>).
2183		2327
2184	While this does not matter for the signal disposition (libev never	2328	While this does not matter for the signal disposition (libev never
2185	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on	2329	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
2186	C<execve>), this matters for the signal mask: many programs do not expect	2330	C<execve>), this matters for the signal mask: many programs do not expect
2187	certain signals to be blocked.	2331	certain signals to be blocked.
…		…
2201		2345
2202	So I can't stress this enough: I<If you do not reset your signal mask when	2346	So I can't stress this enough: I<If you do not reset your signal mask when
2203	you expect it to be empty, you have a race condition in your code>. This	2347	you expect it to be empty, you have a race condition in your code>. This
2204	is not a libev-specific thing, this is true for most event libraries.	2348	is not a libev-specific thing, this is true for most event libraries.
2205		2349
		2350	=head3 The special problem of threads signal handling
		2351
		2352	POSIX threads has problematic signal handling semantics, specifically,
		2353	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2354	threads in a process block signals, which is hard to achieve.
		2355
		2356	When you want to use sigwait (or mix libev signal handling with your own
		2357	for the same signals), you can tackle this problem by globally blocking
		2358	all signals before creating any threads (or creating them with a fully set
		2359	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2360	loops. Then designate one thread as "signal receiver thread" which handles
		2361	these signals. You can pass on any signals that libev might be interested
		2362	in by calling C<ev_feed_signal>.
		2363
2206	=head3 Watcher-Specific Functions and Data Members	2364	=head3 Watcher-Specific Functions and Data Members
2207		2365
2208	=over 4	2366	=over 4
2209		2367
2210	=item ev_signal_init (ev_signal *, callback, int signum)	2368	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
2225	Example: Try to exit cleanly on SIGINT.	2383	Example: Try to exit cleanly on SIGINT.
2226		2384
2227	static void	2385	static void
2228	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2386	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2229	{	2387	{
2230	ev_unloop (loop, EVUNLOOP_ALL);	2388	ev_break (loop, EVBREAK_ALL);
2231	}	2389	}
2232		2390
2233	ev_signal signal_watcher;	2391	ev_signal signal_watcher;
2234	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2392	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2235	ev_signal_start (loop, &signal_watcher);	2393	ev_signal_start (loop, &signal_watcher);
…		…
2621		2779
2622	Prepare and check watchers are usually (but not always) used in pairs:	2780	Prepare and check watchers are usually (but not always) used in pairs:
2623	prepare watchers get invoked before the process blocks and check watchers	2781	prepare watchers get invoked before the process blocks and check watchers
2624	afterwards.	2782	afterwards.
2625		2783
2626	You I<must not> call C<ev_loop> or similar functions that enter	2784	You I<must not> call C<ev_run> or similar functions that enter
2627	the current event loop from either C<ev_prepare> or C<ev_check>	2785	the current event loop from either C<ev_prepare> or C<ev_check>
2628	watchers. Other loops than the current one are fine, however. The	2786	watchers. Other loops than the current one are fine, however. The
2629	rationale behind this is that you do not need to check for recursion in	2787	rationale behind this is that you do not need to check for recursion in
2630	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2788	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2631	C<ev_check> so if you have one watcher of each kind they will always be	2789	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2799		2957
2800	if (timeout >= 0)	2958	if (timeout >= 0)
2801	// create/start timer	2959	// create/start timer
2802		2960
2803	// poll	2961	// poll
2804	ev_loop (EV_A_ 0);	2962	ev_run (EV_A_ 0);
2805		2963
2806	// stop timer again	2964	// stop timer again
2807	if (timeout >= 0)	2965	if (timeout >= 0)
2808	ev_timer_stop (EV_A_ &to);	2966	ev_timer_stop (EV_A_ &to);
2809		2967
…		…
2887	if you do not want that, you need to temporarily stop the embed watcher).	3045	if you do not want that, you need to temporarily stop the embed watcher).
2888		3046
2889	=item ev_embed_sweep (loop, ev_embed *)	3047	=item ev_embed_sweep (loop, ev_embed *)
2890		3048
2891	Make a single, non-blocking sweep over the embedded loop. This works	3049	Make a single, non-blocking sweep over the embedded loop. This works
2892	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3050	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2893	appropriate way for embedded loops.	3051	appropriate way for embedded loops.
2894		3052
2895	=item struct ev_loop *other [read-only]	3053	=item struct ev_loop *other [read-only]
2896		3054
2897	The embedded event loop.	3055	The embedded event loop.
…		…
2957	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3115	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2958	handlers will be invoked, too, of course.	3116	handlers will be invoked, too, of course.
2959		3117
2960	=head3 The special problem of life after fork - how is it possible?	3118	=head3 The special problem of life after fork - how is it possible?
2961		3119
2962	Most uses of C<fork()> consist of forking, then some simple calls to ste	3120	Most uses of C<fork()> consist of forking, then some simple calls to set
2963	up/change the process environment, followed by a call to C<exec()>. This	3121	up/change the process environment, followed by a call to C<exec()>. This
2964	sequence should be handled by libev without any problems.	3122	sequence should be handled by libev without any problems.
2965		3123
2966	This changes when the application actually wants to do event handling	3124	This changes when the application actually wants to do event handling
2967	in the child, or both parent in child, in effect "continuing" after the	3125	in the child, or both parent in child, in effect "continuing" after the
…		…
2983	disadvantage of having to use multiple event loops (which do not support	3141	disadvantage of having to use multiple event loops (which do not support
2984	signal watchers).	3142	signal watchers).
2985		3143
2986	When this is not possible, or you want to use the default loop for	3144	When this is not possible, or you want to use the default loop for
2987	other reasons, then in the process that wants to start "fresh", call	3145	other reasons, then in the process that wants to start "fresh", call
2988	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3146	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
2989	the default loop will "orphan" (not stop) all registered watchers, so you	3147	Destroying the default loop will "orphan" (not stop) all registered
2990	have to be careful not to execute code that modifies those watchers. Note	3148	watchers, so you have to be careful not to execute code that modifies
2991	also that in that case, you have to re-register any signal watchers.	3149	those watchers. Note also that in that case, you have to re-register any
		3150	signal watchers.
2992		3151
2993	=head3 Watcher-Specific Functions and Data Members	3152	=head3 Watcher-Specific Functions and Data Members
2994		3153
2995	=over 4	3154	=over 4
2996		3155
2997	=item ev_fork_init (ev_signal *, callback)	3156	=item ev_fork_init (ev_fork *, callback)
2998		3157
2999	Initialises and configures the fork watcher - it has no parameters of any	3158	Initialises and configures the fork watcher - it has no parameters of any
3000	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3159	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
3001	believe me.	3160	really.
3002		3161
3003	=back	3162	=back
3004		3163
3005		3164
		3165	=head2 C<ev_cleanup> - even the best things end
		3166
		3167	Cleanup watchers are called just before the event loop is being destroyed
		3168	by a call to C<ev_loop_destroy>.
		3169
		3170	While there is no guarantee that the event loop gets destroyed, cleanup
		3171	watchers provide a convenient method to install cleanup hooks for your
		3172	program, worker threads and so on - you just to make sure to destroy the
		3173	loop when you want them to be invoked.
		3174
		3175	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3176	all other watchers, they do not keep a reference to the event loop (which
		3177	makes a lot of sense if you think about it). Like all other watchers, you
		3178	can call libev functions in the callback, except C<ev_cleanup_start>.
		3179
		3180	=head3 Watcher-Specific Functions and Data Members
		3181
		3182	=over 4
		3183
		3184	=item ev_cleanup_init (ev_cleanup *, callback)
		3185
		3186	Initialises and configures the cleanup watcher - it has no parameters of
		3187	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3188	pointless, I assure you.
		3189
		3190	=back
		3191
		3192	Example: Register an atexit handler to destroy the default loop, so any
		3193	cleanup functions are called.
		3194
		3195	static void
		3196	program_exits (void)
		3197	{
		3198	ev_loop_destroy (EV_DEFAULT_UC);
		3199	}
		3200
		3201	...
		3202	atexit (program_exits);
		3203
		3204
3006	=head2 C<ev_async> - how to wake up another event loop	3205	=head2 C<ev_async> - how to wake up an event loop
3007		3206
3008	In general, you cannot use an C<ev_loop> from multiple threads or other	3207	In general, you cannot use an C<ev_loop> from multiple threads or other
3009	asynchronous sources such as signal handlers (as opposed to multiple event	3208	asynchronous sources such as signal handlers (as opposed to multiple event
3010	loops - those are of course safe to use in different threads).	3209	loops - those are of course safe to use in different threads).
3011		3210
3012	Sometimes, however, you need to wake up another event loop you do not	3211	Sometimes, however, you need to wake up an event loop you do not control,
3013	control, for example because it belongs to another thread. This is what	3212	for example because it belongs to another thread. This is what C<ev_async>
3014	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3213	watchers do: as long as the C<ev_async> watcher is active, you can signal
3015	can signal it by calling C<ev_async_send>, which is thread- and signal	3214	it by calling C<ev_async_send>, which is thread- and signal safe.
3016	safe.
3017		3215
3018	This functionality is very similar to C<ev_signal> watchers, as signals,	3216	This functionality is very similar to C<ev_signal> watchers, as signals,
3019	too, are asynchronous in nature, and signals, too, will be compressed	3217	too, are asynchronous in nature, and signals, too, will be compressed
3020	(i.e. the number of callback invocations may be less than the number of	3218	(i.e. the number of callback invocations may be less than the number of
3021	C<ev_async_sent> calls).	3219	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
		3220	of "global async watchers" by using a watcher on an otherwise unused
		3221	signal, and C<ev_feed_signal> to signal this watcher from another thread,
		3222	even without knowing which loop owns the signal.
3022		3223
3023	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3224	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
3024	just the default loop.	3225	just the default loop.
3025		3226
3026	=head3 Queueing	3227	=head3 Queueing
…		…
3121	trust me.	3322	trust me.
3122		3323
3123	=item ev_async_send (loop, ev_async *)	3324	=item ev_async_send (loop, ev_async *)
3124		3325
3125	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3326	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3126	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3327	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3328	returns.
		3329
3127	C<ev_feed_event>, this call is safe to do from other threads, signal or	3330	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3128	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3331	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3129	section below on what exactly this means).	3332	embedding section below on what exactly this means).
3130		3333
3131	Note that, as with other watchers in libev, multiple events might get	3334	Note that, as with other watchers in libev, multiple events might get
3132	compressed into a single callback invocation (another way to look at this	3335	compressed into a single callback invocation (another way to look at this
3133	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3336	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
3134	reset when the event loop detects that).	3337	reset when the event loop detects that).
…		…
3202	Feed an event on the given fd, as if a file descriptor backend detected	3405	Feed an event on the given fd, as if a file descriptor backend detected
3203	the given events it.	3406	the given events it.
3204		3407
3205	=item ev_feed_signal_event (loop, int signum)	3408	=item ev_feed_signal_event (loop, int signum)
3206		3409
3207	Feed an event as if the given signal occurred (C<loop> must be the default	3410	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3208	loop!).	3411	which is async-safe.
3209		3412
3210	=back	3413	=back
		3414
		3415
		3416	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3417
		3418	This section explains some common idioms that are not immediately
		3419	obvious. Note that examples are sprinkled over the whole manual, and this
		3420	section only contains stuff that wouldn't fit anywhere else.
		3421
		3422	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3423
		3424	Each watcher has, by default, a C<void *data> member that you can read
		3425	or modify at any time: libev will completely ignore it. This can be used
		3426	to associate arbitrary data with your watcher. If you need more data and
		3427	don't want to allocate memory separately and store a pointer to it in that
		3428	data member, you can also "subclass" the watcher type and provide your own
		3429	data:
		3430
		3431	struct my_io
		3432	{
		3433	ev_io io;
		3434	int otherfd;
		3435	void *somedata;
		3436	struct whatever *mostinteresting;
		3437	};
		3438
		3439	...
		3440	struct my_io w;
		3441	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3442
		3443	And since your callback will be called with a pointer to the watcher, you
		3444	can cast it back to your own type:
		3445
		3446	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3447	{
		3448	struct my_io *w = (struct my_io *)w_;
		3449	...
		3450	}
		3451
		3452	More interesting and less C-conformant ways of casting your callback
		3453	function type instead have been omitted.
		3454
		3455	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3456
		3457	Another common scenario is to use some data structure with multiple
		3458	embedded watchers, in effect creating your own watcher that combines
		3459	multiple libev event sources into one "super-watcher":
		3460
		3461	struct my_biggy
		3462	{
		3463	int some_data;
		3464	ev_timer t1;
		3465	ev_timer t2;
		3466	}
		3467
		3468	In this case getting the pointer to C<my_biggy> is a bit more
		3469	complicated: Either you store the address of your C<my_biggy> struct in
		3470	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3471	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3472	real programmers):
		3473
		3474	#include <stddef.h>
		3475
		3476	static void
		3477	t1_cb (EV_P_ ev_timer *w, int revents)
		3478	{
		3479	struct my_biggy big = (struct my_biggy *)
		3480	(((char *)w) - offsetof (struct my_biggy, t1));
		3481	}
		3482
		3483	static void
		3484	t2_cb (EV_P_ ev_timer *w, int revents)
		3485	{
		3486	struct my_biggy big = (struct my_biggy *)
		3487	(((char *)w) - offsetof (struct my_biggy, t2));
		3488	}
		3489
		3490	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3491
		3492	Often (especially in GUI toolkits) there are places where you have
		3493	I<modal> interaction, which is most easily implemented by recursively
		3494	invoking C<ev_run>.
		3495
		3496	This brings the problem of exiting - a callback might want to finish the
		3497	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3498	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3499	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3500	other combination: In these cases, C<ev_break> will not work alone.
		3501
		3502	The solution is to maintain "break this loop" variable for each C<ev_run>
		3503	invocation, and use a loop around C<ev_run> until the condition is
		3504	triggered, using C<EVRUN_ONCE>:
		3505
		3506	// main loop
		3507	int exit_main_loop = 0;
		3508
		3509	while (!exit_main_loop)
		3510	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3511
		3512	// in a model watcher
		3513	int exit_nested_loop = 0;
		3514
		3515	while (!exit_nested_loop)
		3516	ev_run (EV_A_ EVRUN_ONCE);
		3517
		3518	To exit from any of these loops, just set the corresponding exit variable:
		3519
		3520	// exit modal loop
		3521	exit_nested_loop = 1;
		3522
		3523	// exit main program, after modal loop is finished
		3524	exit_main_loop = 1;
		3525
		3526	// exit both
		3527	exit_main_loop = exit_nested_loop = 1;
		3528
		3529	=head2 THREAD LOCKING EXAMPLE
		3530
		3531	Here is a fictitious example of how to run an event loop in a different
		3532	thread from where callbacks are being invoked and watchers are
		3533	created/added/removed.
		3534
		3535	For a real-world example, see the C<EV::Loop::Async> perl module,
		3536	which uses exactly this technique (which is suited for many high-level
		3537	languages).
		3538
		3539	The example uses a pthread mutex to protect the loop data, a condition
		3540	variable to wait for callback invocations, an async watcher to notify the
		3541	event loop thread and an unspecified mechanism to wake up the main thread.
		3542
		3543	First, you need to associate some data with the event loop:
		3544
		3545	typedef struct {
		3546	mutex_t lock; /* global loop lock */
		3547	ev_async async_w;
		3548	thread_t tid;
		3549	cond_t invoke_cv;
		3550	} userdata;
		3551
		3552	void prepare_loop (EV_P)
		3553	{
		3554	// for simplicity, we use a static userdata struct.
		3555	static userdata u;
		3556
		3557	ev_async_init (&u->async_w, async_cb);
		3558	ev_async_start (EV_A_ &u->async_w);
		3559
		3560	pthread_mutex_init (&u->lock, 0);
		3561	pthread_cond_init (&u->invoke_cv, 0);
		3562
		3563	// now associate this with the loop
		3564	ev_set_userdata (EV_A_ u);
		3565	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3566	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3567
		3568	// then create the thread running ev_run
		3569	pthread_create (&u->tid, 0, l_run, EV_A);
		3570	}
		3571
		3572	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3573	solely to wake up the event loop so it takes notice of any new watchers
		3574	that might have been added:
		3575
		3576	static void
		3577	async_cb (EV_P_ ev_async *w, int revents)
		3578	{
		3579	// just used for the side effects
		3580	}
		3581
		3582	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3583	protecting the loop data, respectively.
		3584
		3585	static void
		3586	l_release (EV_P)
		3587	{
		3588	userdata *u = ev_userdata (EV_A);
		3589	pthread_mutex_unlock (&u->lock);
		3590	}
		3591
		3592	static void
		3593	l_acquire (EV_P)
		3594	{
		3595	userdata *u = ev_userdata (EV_A);
		3596	pthread_mutex_lock (&u->lock);
		3597	}
		3598
		3599	The event loop thread first acquires the mutex, and then jumps straight
		3600	into C<ev_run>:
		3601
		3602	void *
		3603	l_run (void *thr_arg)
		3604	{
		3605	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3606
		3607	l_acquire (EV_A);
		3608	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3609	ev_run (EV_A_ 0);
		3610	l_release (EV_A);
		3611
		3612	return 0;
		3613	}
		3614
		3615	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3616	signal the main thread via some unspecified mechanism (signals? pipe
		3617	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3618	have been called (in a while loop because a) spurious wakeups are possible
		3619	and b) skipping inter-thread-communication when there are no pending
		3620	watchers is very beneficial):
		3621
		3622	static void
		3623	l_invoke (EV_P)
		3624	{
		3625	userdata *u = ev_userdata (EV_A);
		3626
		3627	while (ev_pending_count (EV_A))
		3628	{
		3629	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3630	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3631	}
		3632	}
		3633
		3634	Now, whenever the main thread gets told to invoke pending watchers, it
		3635	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3636	thread to continue:
		3637
		3638	static void
		3639	real_invoke_pending (EV_P)
		3640	{
		3641	userdata *u = ev_userdata (EV_A);
		3642
		3643	pthread_mutex_lock (&u->lock);
		3644	ev_invoke_pending (EV_A);
		3645	pthread_cond_signal (&u->invoke_cv);
		3646	pthread_mutex_unlock (&u->lock);
		3647	}
		3648
		3649	Whenever you want to start/stop a watcher or do other modifications to an
		3650	event loop, you will now have to lock:
		3651
		3652	ev_timer timeout_watcher;
		3653	userdata *u = ev_userdata (EV_A);
		3654
		3655	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3656
		3657	pthread_mutex_lock (&u->lock);
		3658	ev_timer_start (EV_A_ &timeout_watcher);
		3659	ev_async_send (EV_A_ &u->async_w);
		3660	pthread_mutex_unlock (&u->lock);
		3661
		3662	Note that sending the C<ev_async> watcher is required because otherwise
		3663	an event loop currently blocking in the kernel will have no knowledge
		3664	about the newly added timer. By waking up the loop it will pick up any new
		3665	watchers in the next event loop iteration.
		3666
		3667	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3668
		3669	While the overhead of a callback that e.g. schedules a thread is small, it
		3670	is still an overhead. If you embed libev, and your main usage is with some
		3671	kind of threads or coroutines, you might want to customise libev so that
		3672	doesn't need callbacks anymore.
		3673
		3674	Imagine you have coroutines that you can switch to using a function
		3675	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3676	and that due to some magic, the currently active coroutine is stored in a
		3677	global called C<current_coro>. Then you can build your own "wait for libev
		3678	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3679	the differing C<;> conventions):
		3680
		3681	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3682	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3683
		3684	That means instead of having a C callback function, you store the
		3685	coroutine to switch to in each watcher, and instead of having libev call
		3686	your callback, you instead have it switch to that coroutine.
		3687
		3688	A coroutine might now wait for an event with a function called
		3689	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3690	matter when, or whether the watcher is active or not when this function is
		3691	called):
		3692
		3693	void
		3694	wait_for_event (ev_watcher *w)
		3695	{
		3696	ev_cb_set (w) = current_coro;
		3697	switch_to (libev_coro);
		3698	}
		3699
		3700	That basically suspends the coroutine inside C<wait_for_event> and
		3701	continues the libev coroutine, which, when appropriate, switches back to
		3702	this or any other coroutine. I am sure if you sue this your own :)
		3703
		3704	You can do similar tricks if you have, say, threads with an event queue -
		3705	instead of storing a coroutine, you store the queue object and instead of
		3706	switching to a coroutine, you push the watcher onto the queue and notify
		3707	any waiters.
		3708
		3709	To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two
		3710	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3711
		3712	// my_ev.h
		3713	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3714	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3715	#include "../libev/ev.h"
		3716
		3717	// my_ev.c
		3718	#define EV_H "my_ev.h"
		3719	#include "../libev/ev.c"
		3720
		3721	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3722	F<my_ev.c> into your project. When properly specifying include paths, you
		3723	can even use F<ev.h> as header file name directly.
3211		3724
3212		3725
3213	=head1 LIBEVENT EMULATION	3726	=head1 LIBEVENT EMULATION
3214		3727
3215	Libev offers a compatibility emulation layer for libevent. It cannot	3728	Libev offers a compatibility emulation layer for libevent. It cannot
3216	emulate the internals of libevent, so here are some usage hints:	3729	emulate the internals of libevent, so here are some usage hints:
3217		3730
3218	=over 4	3731	=over 4
		3732
		3733	=item * Only the libevent-1.4.1-beta API is being emulated.
		3734
		3735	This was the newest libevent version available when libev was implemented,
		3736	and is still mostly unchanged in 2010.
3219		3737
3220	=item * Use it by including <event.h>, as usual.	3738	=item * Use it by including <event.h>, as usual.
3221		3739
3222	=item * The following members are fully supported: ev_base, ev_callback,	3740	=item * The following members are fully supported: ev_base, ev_callback,
3223	ev_arg, ev_fd, ev_res, ev_events.	3741	ev_arg, ev_fd, ev_res, ev_events.
…		…
3229	=item * Priorities are not currently supported. Initialising priorities	3747	=item * Priorities are not currently supported. Initialising priorities
3230	will fail and all watchers will have the same priority, even though there	3748	will fail and all watchers will have the same priority, even though there
3231	is an ev_pri field.	3749	is an ev_pri field.
3232		3750
3233	=item * In libevent, the last base created gets the signals, in libev, the	3751	=item * In libevent, the last base created gets the signals, in libev, the
3234	first base created (== the default loop) gets the signals.	3752	base that registered the signal gets the signals.
3235		3753
3236	=item * Other members are not supported.	3754	=item * Other members are not supported.
3237		3755
3238	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3756	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3239	to use the libev header file and library.	3757	to use the libev header file and library.
…		…
3258	Care has been taken to keep the overhead low. The only data member the C++	3776	Care has been taken to keep the overhead low. The only data member the C++
3259	classes add (compared to plain C-style watchers) is the event loop pointer	3777	classes add (compared to plain C-style watchers) is the event loop pointer
3260	that the watcher is associated with (or no additional members at all if	3778	that the watcher is associated with (or no additional members at all if
3261	you disable C<EV_MULTIPLICITY> when embedding libev).	3779	you disable C<EV_MULTIPLICITY> when embedding libev).
3262		3780
3263	Currently, functions, and static and non-static member functions can be	3781	Currently, functions, static and non-static member functions and classes
3264	used as callbacks. Other types should be easy to add as long as they only	3782	with C<operator ()> can be used as callbacks. Other types should be easy
3265	need one additional pointer for context. If you need support for other	3783	to add as long as they only need one additional pointer for context. If
3266	types of functors please contact the author (preferably after implementing	3784	you need support for other types of functors please contact the author
3267	it).	3785	(preferably after implementing it).
3268		3786
3269	Here is a list of things available in the C<ev> namespace:	3787	Here is a list of things available in the C<ev> namespace:
3270		3788
3271	=over 4	3789	=over 4
3272		3790
…		…
3333	myclass obj;	3851	myclass obj;
3334	ev::io iow;	3852	ev::io iow;
3335	iow.set <myclass, &myclass::io_cb> (&obj);	3853	iow.set <myclass, &myclass::io_cb> (&obj);
3336		3854
3337	=item w->set (object *)	3855	=item w->set (object *)
3338
3339	This is an B<experimental> feature that might go away in a future version.
3340		3856
3341	This is a variation of a method callback - leaving out the method to call	3857	This is a variation of a method callback - leaving out the method to call
3342	will default the method to C<operator ()>, which makes it possible to use	3858	will default the method to C<operator ()>, which makes it possible to use
3343	functor objects without having to manually specify the C<operator ()> all	3859	functor objects without having to manually specify the C<operator ()> all
3344	the time. Incidentally, you can then also leave out the template argument	3860	the time. Incidentally, you can then also leave out the template argument
…		…
3384	Associates a different C<struct ev_loop> with this watcher. You can only	3900	Associates a different C<struct ev_loop> with this watcher. You can only
3385	do this when the watcher is inactive (and not pending either).	3901	do this when the watcher is inactive (and not pending either).
3386		3902
3387	=item w->set ([arguments])	3903	=item w->set ([arguments])
3388		3904
3389	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3905	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
3390	called at least once. Unlike the C counterpart, an active watcher gets	3906	method or a suitable start method must be called at least once. Unlike the
3391	automatically stopped and restarted when reconfiguring it with this	3907	C counterpart, an active watcher gets automatically stopped and restarted
3392	method.	3908	when reconfiguring it with this method.
3393		3909
3394	=item w->start ()	3910	=item w->start ()
3395		3911
3396	Starts the watcher. Note that there is no C<loop> argument, as the	3912	Starts the watcher. Note that there is no C<loop> argument, as the
3397	constructor already stores the event loop.	3913	constructor already stores the event loop.
3398		3914
		3915	=item w->start ([arguments])
		3916
		3917	Instead of calling C<set> and C<start> methods separately, it is often
		3918	convenient to wrap them in one call. Uses the same type of arguments as
		3919	the configure C<set> method of the watcher.
		3920
3399	=item w->stop ()	3921	=item w->stop ()
3400		3922
3401	Stops the watcher if it is active. Again, no C<loop> argument.	3923	Stops the watcher if it is active. Again, no C<loop> argument.
3402		3924
3403	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3925	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3415		3937
3416	=back	3938	=back
3417		3939
3418	=back	3940	=back
3419		3941
3420	Example: Define a class with an IO and idle watcher, start one of them in	3942	Example: Define a class with two I/O and idle watchers, start the I/O
3421	the constructor.	3943	watchers in the constructor.
3422		3944
3423	class myclass	3945	class myclass
3424	{	3946	{
3425	ev::io io ; void io_cb (ev::io &w, int revents);	3947	ev::io io ; void io_cb (ev::io &w, int revents);
		3948	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
3426	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3949	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3427		3950
3428	myclass (int fd)	3951	myclass (int fd)
3429	{	3952	{
3430	io .set <myclass, &myclass::io_cb > (this);	3953	io .set <myclass, &myclass::io_cb > (this);
		3954	io2 .set <myclass, &myclass::io2_cb > (this);
3431	idle.set <myclass, &myclass::idle_cb> (this);	3955	idle.set <myclass, &myclass::idle_cb> (this);
3432		3956
3433	io.start (fd, ev::READ);	3957	io.set (fd, ev::WRITE); // configure the watcher
		3958	io.start (); // start it whenever convenient
		3959
		3960	io2.start (fd, ev::READ); // set + start in one call
3434	}	3961	}
3435	};	3962	};
3436		3963
3437		3964
3438	=head1 OTHER LANGUAGE BINDINGS	3965	=head1 OTHER LANGUAGE BINDINGS
…		…
3512	loop argument"). The C<EV_A> form is used when this is the sole argument,	4039	loop argument"). The C<EV_A> form is used when this is the sole argument,
3513	C<EV_A_> is used when other arguments are following. Example:	4040	C<EV_A_> is used when other arguments are following. Example:
3514		4041
3515	ev_unref (EV_A);	4042	ev_unref (EV_A);
3516	ev_timer_add (EV_A_ watcher);	4043	ev_timer_add (EV_A_ watcher);
3517	ev_loop (EV_A_ 0);	4044	ev_run (EV_A_ 0);
3518		4045
3519	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4046	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3520	which is often provided by the following macro.	4047	which is often provided by the following macro.
3521		4048
3522	=item C<EV_P>, C<EV_P_>	4049	=item C<EV_P>, C<EV_P_>
…		…
3562	}	4089	}
3563		4090
3564	ev_check check;	4091	ev_check check;
3565	ev_check_init (&check, check_cb);	4092	ev_check_init (&check, check_cb);
3566	ev_check_start (EV_DEFAULT_ &check);	4093	ev_check_start (EV_DEFAULT_ &check);
3567	ev_loop (EV_DEFAULT_ 0);	4094	ev_run (EV_DEFAULT_ 0);
3568		4095
3569	=head1 EMBEDDING	4096	=head1 EMBEDDING
3570		4097
3571	Libev can (and often is) directly embedded into host	4098	Libev can (and often is) directly embedded into host
3572	applications. Examples of applications that embed it include the Deliantra	4099	applications. Examples of applications that embed it include the Deliantra
…		…
3657	define before including (or compiling) any of its files. The default in	4184	define before including (or compiling) any of its files. The default in
3658	the absence of autoconf is documented for every option.	4185	the absence of autoconf is documented for every option.
3659		4186
3660	Symbols marked with "(h)" do not change the ABI, and can have different	4187	Symbols marked with "(h)" do not change the ABI, and can have different
3661	values when compiling libev vs. including F<ev.h>, so it is permissible	4188	values when compiling libev vs. including F<ev.h>, so it is permissible
3662	to redefine them before including F<ev.h> without breakign compatibility	4189	to redefine them before including F<ev.h> without breaking compatibility
3663	to a compiled library. All other symbols change the ABI, which means all	4190	to a compiled library. All other symbols change the ABI, which means all
3664	users of libev and the libev code itself must be compiled with compatible	4191	users of libev and the libev code itself must be compiled with compatible
3665	settings.	4192	settings.
3666		4193
3667	=over 4	4194	=over 4
		4195
		4196	=item EV_COMPAT3 (h)
		4197
		4198	Backwards compatibility is a major concern for libev. This is why this
		4199	release of libev comes with wrappers for the functions and symbols that
		4200	have been renamed between libev version 3 and 4.
		4201
		4202	You can disable these wrappers (to test compatibility with future
		4203	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4204	sources. This has the additional advantage that you can drop the C<struct>
		4205	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4206	typedef in that case.
		4207
		4208	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4209	and in some even more future version the compatibility code will be
		4210	removed completely.
3668		4211
3669	=item EV_STANDALONE (h)	4212	=item EV_STANDALONE (h)
3670		4213
3671	Must always be C<1> if you do not use autoconf configuration, which	4214	Must always be C<1> if you do not use autoconf configuration, which
3672	keeps libev from including F<config.h>, and it also defines dummy	4215	keeps libev from including F<config.h>, and it also defines dummy
…		…
3674	supported). It will also not define any of the structs usually found in	4217	supported). It will also not define any of the structs usually found in
3675	F<event.h> that are not directly supported by the libev core alone.	4218	F<event.h> that are not directly supported by the libev core alone.
3676		4219
3677	In standalone mode, libev will still try to automatically deduce the	4220	In standalone mode, libev will still try to automatically deduce the
3678	configuration, but has to be more conservative.	4221	configuration, but has to be more conservative.
		4222
		4223	=item EV_USE_FLOOR
		4224
		4225	If defined to be C<1>, libev will use the C<floor ()> function for its
		4226	periodic reschedule calculations, otherwise libev will fall back on a
		4227	portable (slower) implementation. If you enable this, you usually have to
		4228	link against libm or something equivalent. Enabling this when the C<floor>
		4229	function is not available will fail, so the safe default is to not enable
		4230	this.
3679		4231
3680	=item EV_USE_MONOTONIC	4232	=item EV_USE_MONOTONIC
3681		4233
3682	If defined to be C<1>, libev will try to detect the availability of the	4234	If defined to be C<1>, libev will try to detect the availability of the
3683	monotonic clock option at both compile time and runtime. Otherwise no	4235	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3879	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,	4431	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
3880	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.	4432	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3881		4433
3882	If undefined or defined to be C<1> (and the platform supports it), then	4434	If undefined or defined to be C<1> (and the platform supports it), then
3883	the respective watcher type is supported. If defined to be C<0>, then it	4435	the respective watcher type is supported. If defined to be C<0>, then it
3884	is not. Disabling watcher types mainly saves codesize.	4436	is not. Disabling watcher types mainly saves code size.
3885		4437
3886	=item EV_FEATURES	4438	=item EV_FEATURES
3887		4439
3888	If you need to shave off some kilobytes of code at the expense of some	4440	If you need to shave off some kilobytes of code at the expense of some
3889	speed (but with the full API), you can define this symbol to request	4441	speed (but with the full API), you can define this symbol to request
…		…
3909		4461
3910	=item C<1> - faster/larger code	4462	=item C<1> - faster/larger code
3911		4463
3912	Use larger code to speed up some operations.	4464	Use larger code to speed up some operations.
3913		4465
3914	Currently this is used to override some inlining decisions (enlarging the roughly	4466	Currently this is used to override some inlining decisions (enlarging the
3915	30% code size on amd64.	4467	code size by roughly 30% on amd64).
3916		4468
3917	When optimising for size, use of compiler flags such as C<-Os> with	4469	When optimising for size, use of compiler flags such as C<-Os> with
3918	gcc recommended, as well as C<-DNDEBUG>, as libev contains a number of	4470	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
3919	assertions.	4471	assertions.
3920		4472
3921	=item C<2> - faster/larger data structures	4473	=item C<2> - faster/larger data structures
3922		4474
3923	Replaces the small 2-heap for timer management by a faster 4-heap, larger	4475	Replaces the small 2-heap for timer management by a faster 4-heap, larger
3924	hash table sizes and so on. This will usually further increase codesize	4476	hash table sizes and so on. This will usually further increase code size
3925	and can additionally have an effect on the size of data structures at	4477	and can additionally have an effect on the size of data structures at
3926	runtime.	4478	runtime.
3927		4479
3928	=item C<4> - full API configuration	4480	=item C<4> - full API configuration
3929		4481
…		…
3966	I/O watcher then might come out at only 5Kb.	4518	I/O watcher then might come out at only 5Kb.
3967		4519
3968	=item EV_AVOID_STDIO	4520	=item EV_AVOID_STDIO
3969		4521
3970	If this is set to C<1> at compiletime, then libev will avoid using stdio	4522	If this is set to C<1> at compiletime, then libev will avoid using stdio
3971	functions (printf, scanf, perror etc.). This will increase the codesize	4523	functions (printf, scanf, perror etc.). This will increase the code size
3972	somewhat, but if your program doesn't otherwise depend on stdio and your	4524	somewhat, but if your program doesn't otherwise depend on stdio and your
3973	libc allows it, this avoids linking in the stdio library which is quite	4525	libc allows it, this avoids linking in the stdio library which is quite
3974	big.	4526	big.
3975		4527
3976	Note that error messages might become less precise when this option is	4528	Note that error messages might become less precise when this option is
…		…
3980		4532
3981	The highest supported signal number, +1 (or, the number of	4533	The highest supported signal number, +1 (or, the number of
3982	signals): Normally, libev tries to deduce the maximum number of signals	4534	signals): Normally, libev tries to deduce the maximum number of signals
3983	automatically, but sometimes this fails, in which case it can be	4535	automatically, but sometimes this fails, in which case it can be
3984	specified. Also, using a lower number than detected (C<32> should be	4536	specified. Also, using a lower number than detected (C<32> should be
3985	good for about any system in existance) can save some memory, as libev	4537	good for about any system in existence) can save some memory, as libev
3986	statically allocates some 12-24 bytes per signal number.	4538	statically allocates some 12-24 bytes per signal number.
3987		4539
3988	=item EV_PID_HASHSIZE	4540	=item EV_PID_HASHSIZE
3989		4541
3990	C<ev_child> watchers use a small hash table to distribute workload by	4542	C<ev_child> watchers use a small hash table to distribute workload by
…		…
4022	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it	4574	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
4023	will be C<0>.	4575	will be C<0>.
4024		4576
4025	=item EV_VERIFY	4577	=item EV_VERIFY
4026		4578
4027	Controls how much internal verification (see C<ev_loop_verify ()>) will	4579	Controls how much internal verification (see C<ev_verify ()>) will
4028	be done: If set to C<0>, no internal verification code will be compiled	4580	be done: If set to C<0>, no internal verification code will be compiled
4029	in. If set to C<1>, then verification code will be compiled in, but not	4581	in. If set to C<1>, then verification code will be compiled in, but not
4030	called. If set to C<2>, then the internal verification code will be	4582	called. If set to C<2>, then the internal verification code will be
4031	called once per loop, which can slow down libev. If set to C<3>, then the	4583	called once per loop, which can slow down libev. If set to C<3>, then the
4032	verification code will be called very frequently, which will slow down	4584	verification code will be called very frequently, which will slow down
…		…
4036	will be C<0>.	4588	will be C<0>.
4037		4589
4038	=item EV_COMMON	4590	=item EV_COMMON
4039		4591
4040	By default, all watchers have a C<void *data> member. By redefining	4592	By default, all watchers have a C<void *data> member. By redefining
4041	this macro to a something else you can include more and other types of	4593	this macro to something else you can include more and other types of
4042	members. You have to define it each time you include one of the files,	4594	members. You have to define it each time you include one of the files,
4043	though, and it must be identical each time.	4595	though, and it must be identical each time.
4044		4596
4045	For example, the perl EV module uses something like this:	4597	For example, the perl EV module uses something like this:
4046		4598
…		…
4115	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4667	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4116		4668
4117	#include "ev_cpp.h"	4669	#include "ev_cpp.h"
4118	#include "ev.c"	4670	#include "ev.c"
4119		4671
4120	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4672	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4121		4673
4122	=head2 THREADS AND COROUTINES	4674	=head2 THREADS AND COROUTINES
4123		4675
4124	=head3 THREADS	4676	=head3 THREADS
4125		4677
…		…
4176	default loop and triggering an C<ev_async> watcher from the default loop	4728	default loop and triggering an C<ev_async> watcher from the default loop
4177	watcher callback into the event loop interested in the signal.	4729	watcher callback into the event loop interested in the signal.
4178		4730
4179	=back	4731	=back
4180		4732
4181	=head4 THREAD LOCKING EXAMPLE	4733	See also L<THREAD LOCKING EXAMPLE>.
4182
4183	Here is a fictitious example of how to run an event loop in a different
4184	thread than where callbacks are being invoked and watchers are
4185	created/added/removed.
4186
4187	For a real-world example, see the C<EV::Loop::Async> perl module,
4188	which uses exactly this technique (which is suited for many high-level
4189	languages).
4190
4191	The example uses a pthread mutex to protect the loop data, a condition
4192	variable to wait for callback invocations, an async watcher to notify the
4193	event loop thread and an unspecified mechanism to wake up the main thread.
4194
4195	First, you need to associate some data with the event loop:
4196
4197	typedef struct {
4198	mutex_t lock; /* global loop lock */
4199	ev_async async_w;
4200	thread_t tid;
4201	cond_t invoke_cv;
4202	} userdata;
4203
4204	void prepare_loop (EV_P)
4205	{
4206	// for simplicity, we use a static userdata struct.
4207	static userdata u;
4208
4209	ev_async_init (&u->async_w, async_cb);
4210	ev_async_start (EV_A_ &u->async_w);
4211
4212	pthread_mutex_init (&u->lock, 0);
4213	pthread_cond_init (&u->invoke_cv, 0);
4214
4215	// now associate this with the loop
4216	ev_set_userdata (EV_A_ u);
4217	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4218	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4219
4220	// then create the thread running ev_loop
4221	pthread_create (&u->tid, 0, l_run, EV_A);
4222	}
4223
4224	The callback for the C<ev_async> watcher does nothing: the watcher is used
4225	solely to wake up the event loop so it takes notice of any new watchers
4226	that might have been added:
4227
4228	static void
4229	async_cb (EV_P_ ev_async *w, int revents)
4230	{
4231	// just used for the side effects
4232	}
4233
4234	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4235	protecting the loop data, respectively.
4236
4237	static void
4238	l_release (EV_P)
4239	{
4240	userdata *u = ev_userdata (EV_A);
4241	pthread_mutex_unlock (&u->lock);
4242	}
4243
4244	static void
4245	l_acquire (EV_P)
4246	{
4247	userdata *u = ev_userdata (EV_A);
4248	pthread_mutex_lock (&u->lock);
4249	}
4250
4251	The event loop thread first acquires the mutex, and then jumps straight
4252	into C<ev_loop>:
4253
4254	void *
4255	l_run (void *thr_arg)
4256	{
4257	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4258
4259	l_acquire (EV_A);
4260	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4261	ev_loop (EV_A_ 0);
4262	l_release (EV_A);
4263
4264	return 0;
4265	}
4266
4267	Instead of invoking all pending watchers, the C<l_invoke> callback will
4268	signal the main thread via some unspecified mechanism (signals? pipe
4269	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4270	have been called (in a while loop because a) spurious wakeups are possible
4271	and b) skipping inter-thread-communication when there are no pending
4272	watchers is very beneficial):
4273
4274	static void
4275	l_invoke (EV_P)
4276	{
4277	userdata *u = ev_userdata (EV_A);
4278
4279	while (ev_pending_count (EV_A))
4280	{
4281	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4282	pthread_cond_wait (&u->invoke_cv, &u->lock);
4283	}
4284	}
4285
4286	Now, whenever the main thread gets told to invoke pending watchers, it
4287	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4288	thread to continue:
4289
4290	static void
4291	real_invoke_pending (EV_P)
4292	{
4293	userdata *u = ev_userdata (EV_A);
4294
4295	pthread_mutex_lock (&u->lock);
4296	ev_invoke_pending (EV_A);
4297	pthread_cond_signal (&u->invoke_cv);
4298	pthread_mutex_unlock (&u->lock);
4299	}
4300
4301	Whenever you want to start/stop a watcher or do other modifications to an
4302	event loop, you will now have to lock:
4303
4304	ev_timer timeout_watcher;
4305	userdata *u = ev_userdata (EV_A);
4306
4307	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4308
4309	pthread_mutex_lock (&u->lock);
4310	ev_timer_start (EV_A_ &timeout_watcher);
4311	ev_async_send (EV_A_ &u->async_w);
4312	pthread_mutex_unlock (&u->lock);
4313
4314	Note that sending the C<ev_async> watcher is required because otherwise
4315	an event loop currently blocking in the kernel will have no knowledge
4316	about the newly added timer. By waking up the loop it will pick up any new
4317	watchers in the next event loop iteration.
4318		4734
4319	=head3 COROUTINES	4735	=head3 COROUTINES
4320		4736
4321	Libev is very accommodating to coroutines ("cooperative threads"):	4737	Libev is very accommodating to coroutines ("cooperative threads"):
4322	libev fully supports nesting calls to its functions from different	4738	libev fully supports nesting calls to its functions from different
4323	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4739	coroutines (e.g. you can call C<ev_run> on the same loop from two
4324	different coroutines, and switch freely between both coroutines running	4740	different coroutines, and switch freely between both coroutines running
4325	the loop, as long as you don't confuse yourself). The only exception is	4741	the loop, as long as you don't confuse yourself). The only exception is
4326	that you must not do this from C<ev_periodic> reschedule callbacks.	4742	that you must not do this from C<ev_periodic> reschedule callbacks.
4327		4743
4328	Care has been taken to ensure that libev does not keep local state inside	4744	Care has been taken to ensure that libev does not keep local state inside
4329	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4745	C<ev_run>, and other calls do not usually allow for coroutine switches as
4330	they do not call any callbacks.	4746	they do not call any callbacks.
4331		4747
4332	=head2 COMPILER WARNINGS	4748	=head2 COMPILER WARNINGS
4333		4749
4334	Depending on your compiler and compiler settings, you might get no or a	4750	Depending on your compiler and compiler settings, you might get no or a
…		…
4345	maintainable.	4761	maintainable.
4346		4762
4347	And of course, some compiler warnings are just plain stupid, or simply	4763	And of course, some compiler warnings are just plain stupid, or simply
4348	wrong (because they don't actually warn about the condition their message	4764	wrong (because they don't actually warn about the condition their message
4349	seems to warn about). For example, certain older gcc versions had some	4765	seems to warn about). For example, certain older gcc versions had some
4350	warnings that resulted an extreme number of false positives. These have	4766	warnings that resulted in an extreme number of false positives. These have
4351	been fixed, but some people still insist on making code warn-free with	4767	been fixed, but some people still insist on making code warn-free with
4352	such buggy versions.	4768	such buggy versions.
4353		4769
4354	While libev is written to generate as few warnings as possible,	4770	While libev is written to generate as few warnings as possible,
4355	"warn-free" code is not a goal, and it is recommended not to build libev	4771	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
4391	I suggest using suppression lists.	4807	I suggest using suppression lists.
4392		4808
4393		4809
4394	=head1 PORTABILITY NOTES	4810	=head1 PORTABILITY NOTES
4395		4811
		4812	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4813
		4814	GNU/Linux is the only common platform that supports 64 bit file/large file
		4815	interfaces but I<disables> them by default.
		4816
		4817	That means that libev compiled in the default environment doesn't support
		4818	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4819
		4820	Unfortunately, many programs try to work around this GNU/Linux issue
		4821	by enabling the large file API, which makes them incompatible with the
		4822	standard libev compiled for their system.
		4823
		4824	Likewise, libev cannot enable the large file API itself as this would
		4825	suddenly make it incompatible to the default compile time environment,
		4826	i.e. all programs not using special compile switches.
		4827
		4828	=head2 OS/X AND DARWIN BUGS
		4829
		4830	The whole thing is a bug if you ask me - basically any system interface
		4831	you touch is broken, whether it is locales, poll, kqueue or even the
		4832	OpenGL drivers.
		4833
		4834	=head3 C<kqueue> is buggy
		4835
		4836	The kqueue syscall is broken in all known versions - most versions support
		4837	only sockets, many support pipes.
		4838
		4839	Libev tries to work around this by not using C<kqueue> by default on this
		4840	rotten platform, but of course you can still ask for it when creating a
		4841	loop - embedding a socket-only kqueue loop into a select-based one is
		4842	probably going to work well.
		4843
		4844	=head3 C<poll> is buggy
		4845
		4846	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4847	implementation by something calling C<kqueue> internally around the 10.5.6
		4848	release, so now C<kqueue> I<and> C<poll> are broken.
		4849
		4850	Libev tries to work around this by not using C<poll> by default on
		4851	this rotten platform, but of course you can still ask for it when creating
		4852	a loop.
		4853
		4854	=head3 C<select> is buggy
		4855
		4856	All that's left is C<select>, and of course Apple found a way to fuck this
		4857	one up as well: On OS/X, C<select> actively limits the number of file
		4858	descriptors you can pass in to 1024 - your program suddenly crashes when
		4859	you use more.
		4860
		4861	There is an undocumented "workaround" for this - defining
		4862	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4863	work on OS/X.
		4864
		4865	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4866
		4867	=head3 C<errno> reentrancy
		4868
		4869	The default compile environment on Solaris is unfortunately so
		4870	thread-unsafe that you can't even use components/libraries compiled
		4871	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4872	defined by default. A valid, if stupid, implementation choice.
		4873
		4874	If you want to use libev in threaded environments you have to make sure
		4875	it's compiled with C<_REENTRANT> defined.
		4876
		4877	=head3 Event port backend
		4878
		4879	The scalable event interface for Solaris is called "event
		4880	ports". Unfortunately, this mechanism is very buggy in all major
		4881	releases. If you run into high CPU usage, your program freezes or you get
		4882	a large number of spurious wakeups, make sure you have all the relevant
		4883	and latest kernel patches applied. No, I don't know which ones, but there
		4884	are multiple ones to apply, and afterwards, event ports actually work
		4885	great.
		4886
		4887	If you can't get it to work, you can try running the program by setting
		4888	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4889	C<select> backends.
		4890
		4891	=head2 AIX POLL BUG
		4892
		4893	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4894	this by trying to avoid the poll backend altogether (i.e. it's not even
		4895	compiled in), which normally isn't a big problem as C<select> works fine
		4896	with large bitsets on AIX, and AIX is dead anyway.
		4897
4396	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4898	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4899
		4900	=head3 General issues
4397		4901
4398	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4902	Win32 doesn't support any of the standards (e.g. POSIX) that libev
4399	requires, and its I/O model is fundamentally incompatible with the POSIX	4903	requires, and its I/O model is fundamentally incompatible with the POSIX
4400	model. Libev still offers limited functionality on this platform in	4904	model. Libev still offers limited functionality on this platform in
4401	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4905	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4402	descriptors. This only applies when using Win32 natively, not when using	4906	descriptors. This only applies when using Win32 natively, not when using
4403	e.g. cygwin.	4907	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4908	as every compielr comes with a slightly differently broken/incompatible
		4909	environment.
4404		4910
4405	Lifting these limitations would basically require the full	4911	Lifting these limitations would basically require the full
4406	re-implementation of the I/O system. If you are into these kinds of	4912	re-implementation of the I/O system. If you are into this kind of thing,
4407	things, then note that glib does exactly that for you in a very portable	4913	then note that glib does exactly that for you in a very portable way (note
4408	way (note also that glib is the slowest event library known to man).	4914	also that glib is the slowest event library known to man).
4409		4915
4410	There is no supported compilation method available on windows except	4916	There is no supported compilation method available on windows except
4411	embedding it into other applications.	4917	embedding it into other applications.
4412		4918
4413	Sensible signal handling is officially unsupported by Microsoft - libev	4919	Sensible signal handling is officially unsupported by Microsoft - libev
…		…
4441	you do I<not> compile the F<ev.c> or any other embedded source files!):	4947	you do I<not> compile the F<ev.c> or any other embedded source files!):
4442		4948
4443	#include "evwrap.h"	4949	#include "evwrap.h"
4444	#include "ev.c"	4950	#include "ev.c"
4445		4951
4446	=over 4
4447
4448	=item The winsocket select function	4952	=head3 The winsocket C<select> function
4449		4953
4450	The winsocket C<select> function doesn't follow POSIX in that it	4954	The winsocket C<select> function doesn't follow POSIX in that it
4451	requires socket I<handles> and not socket I<file descriptors> (it is	4955	requires socket I<handles> and not socket I<file descriptors> (it is
4452	also extremely buggy). This makes select very inefficient, and also	4956	also extremely buggy). This makes select very inefficient, and also
4453	requires a mapping from file descriptors to socket handles (the Microsoft	4957	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
4462	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4966	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
4463		4967
4464	Note that winsockets handling of fd sets is O(n), so you can easily get a	4968	Note that winsockets handling of fd sets is O(n), so you can easily get a
4465	complexity in the O(n²) range when using win32.	4969	complexity in the O(n²) range when using win32.
4466		4970
4467	=item Limited number of file descriptors	4971	=head3 Limited number of file descriptors
4468		4972
4469	Windows has numerous arbitrary (and low) limits on things.	4973	Windows has numerous arbitrary (and low) limits on things.
4470		4974
4471	Early versions of winsocket's select only supported waiting for a maximum	4975	Early versions of winsocket's select only supported waiting for a maximum
4472	of C<64> handles (probably owning to the fact that all windows kernels	4976	of C<64> handles (probably owning to the fact that all windows kernels
…		…
4487	runtime libraries. This might get you to about C<512> or C<2048> sockets	4991	runtime libraries. This might get you to about C<512> or C<2048> sockets
4488	(depending on windows version and/or the phase of the moon). To get more,	4992	(depending on windows version and/or the phase of the moon). To get more,
4489	you need to wrap all I/O functions and provide your own fd management, but	4993	you need to wrap all I/O functions and provide your own fd management, but
4490	the cost of calling select (O(n²)) will likely make this unworkable.	4994	the cost of calling select (O(n²)) will likely make this unworkable.
4491		4995
4492	=back
4493
4494	=head2 PORTABILITY REQUIREMENTS	4996	=head2 PORTABILITY REQUIREMENTS
4495		4997
4496	In addition to a working ISO-C implementation and of course the	4998	In addition to a working ISO-C implementation and of course the
4497	backend-specific APIs, libev relies on a few additional extensions:	4999	backend-specific APIs, libev relies on a few additional extensions:
4498		5000
…		…
4504	Libev assumes not only that all watcher pointers have the same internal	5006	Libev assumes not only that all watcher pointers have the same internal
4505	structure (guaranteed by POSIX but not by ISO C for example), but it also	5007	structure (guaranteed by POSIX but not by ISO C for example), but it also
4506	assumes that the same (machine) code can be used to call any watcher	5008	assumes that the same (machine) code can be used to call any watcher
4507	callback: The watcher callbacks have different type signatures, but libev	5009	callback: The watcher callbacks have different type signatures, but libev
4508	calls them using an C<ev_watcher *> internally.	5010	calls them using an C<ev_watcher *> internally.
		5011
		5012	=item pointer accesses must be thread-atomic
		5013
		5014	Accessing a pointer value must be atomic, it must both be readable and
		5015	writable in one piece - this is the case on all current architectures.
4509		5016
4510	=item C<sig_atomic_t volatile> must be thread-atomic as well	5017	=item C<sig_atomic_t volatile> must be thread-atomic as well
4511		5018
4512	The type C<sig_atomic_t volatile> (or whatever is defined as	5019	The type C<sig_atomic_t volatile> (or whatever is defined as
4513	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5020	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
4536	watchers.	5043	watchers.
4537		5044
4538	=item C<double> must hold a time value in seconds with enough accuracy	5045	=item C<double> must hold a time value in seconds with enough accuracy
4539		5046
4540	The type C<double> is used to represent timestamps. It is required to	5047	The type C<double> is used to represent timestamps. It is required to
4541	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5048	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4542	enough for at least into the year 4000. This requirement is fulfilled by	5049	good enough for at least into the year 4000 with millisecond accuracy
		5050	(the design goal for libev). This requirement is overfulfilled by
4543	implementations implementing IEEE 754, which is basically all existing	5051	implementations using IEEE 754, which is basically all existing ones. With
4544	ones. With IEEE 754 doubles, you get microsecond accuracy until at least	5052	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
4545	2200.
4546		5053
4547	=back	5054	=back
4548		5055
4549	If you know of other additional requirements drop me a note.	5056	If you know of other additional requirements drop me a note.
4550		5057
…		…
4618	involves iterating over all running async watchers or all signal numbers.	5125	involves iterating over all running async watchers or all signal numbers.
4619		5126
4620	=back	5127	=back
4621		5128
4622		5129
4623	=head1 PORTING FROM 3.X TO 4.X	5130	=head1 PORTING FROM LIBEV 3.X TO 4.X
4624		5131
4625	The major version 4 introduced some minor incompatible changes to the API.	5132	The major version 4 introduced some incompatible changes to the API.
		5133
		5134	At the moment, the C<ev.h> header file provides compatibility definitions
		5135	for all changes, so most programs should still compile. The compatibility
		5136	layer might be removed in later versions of libev, so better update to the
		5137	new API early than late.
4626		5138
4627	=over 4	5139	=over 4
4628		5140
4629	=item C<EV_TIMEOUT> replaced by C<EV_TIMER> in C<revents>	5141	=item C<EV_COMPAT3> backwards compatibility mechanism
4630		5142
4631	This is a simple rename - all other watcher types use their name	5143	The backward compatibility mechanism can be controlled by
4632	as revents flag, and now C<ev_timer> does, too.	5144	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5145	section.
4633		5146
4634	Both C<EV_TIMER> and C<EV_TIMEOUT> symbols were present in 3.x versions	5147	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
4635	and continue to be present for the forseeable future, so this is mostly a	5148
4636	documentation change.	5149	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5150
		5151	ev_loop_destroy (EV_DEFAULT_UC);
		5152	ev_loop_fork (EV_DEFAULT);
		5153
		5154	=item function/symbol renames
		5155
		5156	A number of functions and symbols have been renamed:
		5157
		5158	ev_loop => ev_run
		5159	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5160	EVLOOP_ONESHOT => EVRUN_ONCE
		5161
		5162	ev_unloop => ev_break
		5163	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5164	EVUNLOOP_ONE => EVBREAK_ONE
		5165	EVUNLOOP_ALL => EVBREAK_ALL
		5166
		5167	EV_TIMEOUT => EV_TIMER
		5168
		5169	ev_loop_count => ev_iteration
		5170	ev_loop_depth => ev_depth
		5171	ev_loop_verify => ev_verify
		5172
		5173	Most functions working on C<struct ev_loop> objects don't have an
		5174	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5175	associated constants have been renamed to not collide with the C<struct
		5176	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5177	as all other watcher types. Note that C<ev_loop_fork> is still called
		5178	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5179	typedef.
4637		5180
4638	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>	5181	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
4639		5182
4640	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different	5183	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
4641	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile	5184	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
…		…
4648		5191
4649	=over 4	5192	=over 4
4650		5193
4651	=item active	5194	=item active
4652		5195
4653	A watcher is active as long as it has been started (has been attached to	5196	A watcher is active as long as it has been started and not yet stopped.
4654	an event loop) but not yet stopped (disassociated from the event loop).	5197	See L<WATCHER STATES> for details.
4655		5198
4656	=item application	5199	=item application
4657		5200
4658	In this document, an application is whatever is using libev.	5201	In this document, an application is whatever is using libev.
		5202
		5203	=item backend
		5204
		5205	The part of the code dealing with the operating system interfaces.
4659		5206
4660	=item callback	5207	=item callback
4661		5208
4662	The address of a function that is called when some event has been	5209	The address of a function that is called when some event has been
4663	detected. Callbacks are being passed the event loop, the watcher that	5210	detected. Callbacks are being passed the event loop, the watcher that
4664	received the event, and the actual event bitset.	5211	received the event, and the actual event bitset.
4665		5212
4666	=item callback invocation	5213	=item callback/watcher invocation
4667		5214
4668	The act of calling the callback associated with a watcher.	5215	The act of calling the callback associated with a watcher.
4669		5216
4670	=item event	5217	=item event
4671		5218
…		…
4690	The model used to describe how an event loop handles and processes	5237	The model used to describe how an event loop handles and processes
4691	watchers and events.	5238	watchers and events.
4692		5239
4693	=item pending	5240	=item pending
4694		5241
4695	A watcher is pending as soon as the corresponding event has been detected,	5242	A watcher is pending as soon as the corresponding event has been
4696	and stops being pending as soon as the watcher will be invoked or its	5243	detected. See L<WATCHER STATES> for details.
4697	pending status is explicitly cleared by the application.
4698
4699	A watcher can be pending, but not active. Stopping a watcher also clears
4700	its pending status.
4701		5244
4702	=item real time	5245	=item real time
4703		5246
4704	The physical time that is observed. It is apparently strictly monotonic :)	5247	The physical time that is observed. It is apparently strictly monotonic :)
4705		5248
4706	=item wall-clock time	5249	=item wall-clock time
4707		5250
4708	The time and date as shown on clocks. Unlike real time, it can actually	5251	The time and date as shown on clocks. Unlike real time, it can actually
4709	be wrong and jump forwards and backwards, e.g. when the you adjust your	5252	be wrong and jump forwards and backwards, e.g. when you adjust your
4710	clock.	5253	clock.
4711		5254
4712	=item watcher	5255	=item watcher
4713		5256
4714	A data structure that describes interest in certain events. Watchers need	5257	A data structure that describes interest in certain events. Watchers need
4715	to be started (attached to an event loop) before they can receive events.	5258	to be started (attached to an event loop) before they can receive events.
4716		5259
4717	=item watcher invocation
4718
4719	The act of calling the callback associated with a watcher.
4720
4721	=back	5260	=back
4722		5261
4723	=head1 AUTHOR	5262	=head1 AUTHOR
4724		5263
4725	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5264	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5265	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4726		5266

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