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…		…
26	puts ("stdin ready");	26	puts ("stdin ready");
27	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
28	// with its corresponding stop function.	28	// with its corresponding stop function.
29	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
30		30
31	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_run's to stop iterating
32	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_break (EV_A_ EVBREAK_ALL);
33	}	33	}
34		34
35	// another callback, this time for a time-out	35	// another callback, this time for a time-out
36	static void	36	static void
37	timeout_cb (EV_P_ ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
38	{	38	{
39	puts ("timeout");	39	puts ("timeout");
40	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_run to stop iterating
41	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_break (EV_A_ EVBREAK_ONE);
42	}	42	}
43		43
44	int	44	int
45	main (void)	45	main (void)
46	{	46	{
47	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
48	struct ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = EV_DEFAULT;
49		49
50	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
51	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
53	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
…		…
56	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
58	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
59		59
60	// now wait for events to arrive	60	// now wait for events to arrive
61	ev_loop (loop, 0);	61	ev_run (loop, 0);
62		62
63	// unloop was called, so exit	63	// break was called, so exit
64	return 0;	64	return 0;
65	}	65	}
66		66
67	=head1 ABOUT THIS DOCUMENT	67	=head1 ABOUT THIS DOCUMENT
68		68
…		…
75	While this document tries to be as complete as possible in documenting	75	While this document tries to be as complete as possible in documenting
76	libev, its usage and the rationale behind its design, it is not a tutorial	76	libev, its usage and the rationale behind its design, it is not a tutorial
77	on event-based programming, nor will it introduce event-based programming	77	on event-based programming, nor will it introduce event-based programming
78	with libev.	78	with libev.
79		79
80	Familarity with event based programming techniques in general is assumed	80	Familiarity with event based programming techniques in general is assumed
81	throughout this document.	81	throughout this document.
		82
		83	=head1 WHAT TO READ WHEN IN A HURRY
		84
		85	This manual tries to be very detailed, but unfortunately, this also makes
		86	it very long. If you just want to know the basics of libev, I suggest
		87	reading L<ANATOMY OF A WATCHER>, then the L<EXAMPLE PROGRAM> above and
		88	look up the missing functions in L<GLOBAL FUNCTIONS> and the C<ev_io> and
		89	C<ev_timer> sections in L<WATCHER TYPES>.
82		90
83	=head1 ABOUT LIBEV	91	=head1 ABOUT LIBEV
84		92
85	Libev is an event loop: you register interest in certain events (such as a	93	Libev is an event loop: you register interest in certain events (such as a
86	file descriptor being readable or a timeout occurring), and it will manage	94	file descriptor being readable or a timeout occurring), and it will manage
…		…
124	this argument.	132	this argument.
125		133
126	=head2 TIME REPRESENTATION	134	=head2 TIME REPRESENTATION
127		135
128	Libev represents time as a single floating point number, representing	136	Libev represents time as a single floating point number, representing
129	the (fractional) number of seconds since the (POSIX) epoch (somewhere	137	the (fractional) number of seconds since the (POSIX) epoch (in practice
130	near the beginning of 1970, details are complicated, don't ask). This	138	somewhere near the beginning of 1970, details are complicated, don't
131	type is called C<ev_tstamp>, which is what you should use too. It usually	139	ask). This type is called C<ev_tstamp>, which is what you should use
132	aliases to the C<double> type in C. When you need to do any calculations	140	too. It usually aliases to the C<double> type in C. When you need to do
133	on it, you should treat it as some floating point value. Unlike the name	141	any calculations on it, you should treat it as some floating point value.
		142
134	component C<stamp> might indicate, it is also used for time differences	143	Unlike the name component C<stamp> might indicate, it is also used for
135	throughout libev.	144	time differences (e.g. delays) throughout libev.
136		145
137	=head1 ERROR HANDLING	146	=head1 ERROR HANDLING
138		147
139	Libev knows three classes of errors: operating system errors, usage errors	148	Libev knows three classes of errors: operating system errors, usage errors
140	and internal errors (bugs).	149	and internal errors (bugs).
…		…
164		173
165	=item ev_tstamp ev_time ()	174	=item ev_tstamp ev_time ()
166		175
167	Returns the current time as libev would use it. Please note that the	176	Returns the current time as libev would use it. Please note that the
168	C<ev_now> function is usually faster and also often returns the timestamp	177	C<ev_now> function is usually faster and also often returns the timestamp
169	you actually want to know.	178	you actually want to know. Also interesting is the combination of
		179	C<ev_now_update> and C<ev_now>.
170		180
171	=item ev_sleep (ev_tstamp interval)	181	=item ev_sleep (ev_tstamp interval)
172		182
173	Sleep for the given interval: The current thread will be blocked until	183	Sleep for the given interval: The current thread will be blocked
174	either it is interrupted or the given time interval has passed. Basically	184	until either it is interrupted or the given time interval has
		185	passed (approximately - it might return a bit earlier even if not
		186	interrupted). Returns immediately if C<< interval <= 0 >>.
		187
175	this is a sub-second-resolution C<sleep ()>.	188	Basically this is a sub-second-resolution C<sleep ()>.
		189
		190	The range of the C<interval> is limited - libev only guarantees to work
		191	with sleep times of up to one day (C<< interval <= 86400 >>).
176		192
177	=item int ev_version_major ()	193	=item int ev_version_major ()
178		194
179	=item int ev_version_minor ()	195	=item int ev_version_minor ()
180		196
…		…
191	as this indicates an incompatible change. Minor versions are usually	207	as this indicates an incompatible change. Minor versions are usually
192	compatible to older versions, so a larger minor version alone is usually	208	compatible to older versions, so a larger minor version alone is usually
193	not a problem.	209	not a problem.
194		210
195	Example: Make sure we haven't accidentally been linked against the wrong	211	Example: Make sure we haven't accidentally been linked against the wrong
196	version.	212	version (note, however, that this will not detect other ABI mismatches,
		213	such as LFS or reentrancy).
197		214
198	assert (("libev version mismatch",	215	assert (("libev version mismatch",
199	ev_version_major () == EV_VERSION_MAJOR	216	ev_version_major () == EV_VERSION_MAJOR
200	&& ev_version_minor () >= EV_VERSION_MINOR));	217	&& ev_version_minor () >= EV_VERSION_MINOR));
201		218
…		…
212	assert (("sorry, no epoll, no sex",	229	assert (("sorry, no epoll, no sex",
213	ev_supported_backends () & EVBACKEND_EPOLL));	230	ev_supported_backends () & EVBACKEND_EPOLL));
214		231
215	=item unsigned int ev_recommended_backends ()	232	=item unsigned int ev_recommended_backends ()
216		233
217	Return the set of all backends compiled into this binary of libev and also	234	Return the set of all backends compiled into this binary of libev and
218	recommended for this platform. This set is often smaller than the one	235	also recommended for this platform, meaning it will work for most file
		236	descriptor types. This set is often smaller than the one returned by
219	returned by C<ev_supported_backends>, as for example kqueue is broken on	237	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
220	most BSDs and will not be auto-detected unless you explicitly request it	238	and will not be auto-detected unless you explicitly request it (assuming
221	(assuming you know what you are doing). This is the set of backends that	239	you know what you are doing). This is the set of backends that libev will
222	libev will probe for if you specify no backends explicitly.	240	probe for if you specify no backends explicitly.
223		241
224	=item unsigned int ev_embeddable_backends ()	242	=item unsigned int ev_embeddable_backends ()
225		243
226	Returns the set of backends that are embeddable in other event loops. This	244	Returns the set of backends that are embeddable in other event loops. This
227	is the theoretical, all-platform, value. To find which backends	245	value is platform-specific but can include backends not available on the
228	might be supported on the current system, you would need to look at	246	current system. To find which embeddable backends might be supported on
229	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	247	the current system, you would need to look at C<ev_embeddable_backends ()
230	recommended ones.	248	& ev_supported_backends ()>, likewise for recommended ones.
231		249
232	See the description of C<ev_embed> watchers for more info.	250	See the description of C<ev_embed> watchers for more info.
233		251
234	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	252	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
235		253
236	Sets the allocation function to use (the prototype is similar - the	254	Sets the allocation function to use (the prototype is similar - the
237	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	255	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
238	used to allocate and free memory (no surprises here). If it returns zero	256	used to allocate and free memory (no surprises here). If it returns zero
239	when memory needs to be allocated (C<size != 0>), the library might abort	257	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
265	}	283	}
266		284
267	...	285	...
268	ev_set_allocator (persistent_realloc);	286	ev_set_allocator (persistent_realloc);
269		287
270	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	288	=item ev_set_syserr_cb (void (*cb)(const char *msg))
271		289
272	Set the callback function to call on a retryable system call error (such	290	Set the callback function to call on a retryable system call error (such
273	as failed select, poll, epoll_wait). The message is a printable string	291	as failed select, poll, epoll_wait). The message is a printable string
274	indicating the system call or subsystem causing the problem. If this	292	indicating the system call or subsystem causing the problem. If this
275	callback is set, then libev will expect it to remedy the situation, no	293	callback is set, then libev will expect it to remedy the situation, no
…		…
287	}	305	}
288		306
289	...	307	...
290	ev_set_syserr_cb (fatal_error);	308	ev_set_syserr_cb (fatal_error);
291		309
		310	=item ev_feed_signal (int signum)
		311
		312	This function can be used to "simulate" a signal receive. It is completely
		313	safe to call this function at any time, from any context, including signal
		314	handlers or random threads.
		315
		316	Its main use is to customise signal handling in your process, especially
		317	in the presence of threads. For example, you could block signals
		318	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		319	creating any loops), and in one thread, use C<sigwait> or any other
		320	mechanism to wait for signals, then "deliver" them to libev by calling
		321	C<ev_feed_signal>.
		322
292	=back	323	=back
293		324
294	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	325	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
295		326
296	An event loop is described by a C<struct ev_loop *> (the C<struct>	327	An event loop is described by a C<struct ev_loop *> (the C<struct> is
297	is I<not> optional in this case, as there is also an C<ev_loop>	328	I<not> optional in this case unless libev 3 compatibility is disabled, as
298	I<function>).	329	libev 3 had an C<ev_loop> function colliding with the struct name).
299		330
300	The library knows two types of such loops, the I<default> loop, which	331	The library knows two types of such loops, the I<default> loop, which
301	supports signals and child events, and dynamically created loops which do	332	supports child process events, and dynamically created event loops which
302	not.	333	do not.
303		334
304	=over 4	335	=over 4
305		336
306	=item struct ev_loop *ev_default_loop (unsigned int flags)	337	=item struct ev_loop *ev_default_loop (unsigned int flags)
307		338
308	This will initialise the default event loop if it hasn't been initialised	339	This returns the "default" event loop object, which is what you should
309	yet and return it. If the default loop could not be initialised, returns	340	normally use when you just need "the event loop". Event loop objects and
310	false. If it already was initialised it simply returns it (and ignores the	341	the C<flags> parameter are described in more detail in the entry for
311	flags. If that is troubling you, check C<ev_backend ()> afterwards).	342	C<ev_loop_new>.
		343
		344	If the default loop is already initialised then this function simply
		345	returns it (and ignores the flags. If that is troubling you, check
		346	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		347	flags, which should almost always be C<0>, unless the caller is also the
		348	one calling C<ev_run> or otherwise qualifies as "the main program".
312		349
313	If you don't know what event loop to use, use the one returned from this	350	If you don't know what event loop to use, use the one returned from this
314	function.	351	function (or via the C<EV_DEFAULT> macro).
315		352
316	Note that this function is I<not> thread-safe, so if you want to use it	353	Note that this function is I<not> thread-safe, so if you want to use it
317	from multiple threads, you have to lock (note also that this is unlikely,	354	from multiple threads, you have to employ some kind of mutex (note also
318	as loops cannot be shared easily between threads anyway).	355	that this case is unlikely, as loops cannot be shared easily between
		356	threads anyway).
319		357
320	The default loop is the only loop that can handle C<ev_signal> and	358	The default loop is the only loop that can handle C<ev_child> watchers,
321	C<ev_child> watchers, and to do this, it always registers a handler	359	and to do this, it always registers a handler for C<SIGCHLD>. If this is
322	for C<SIGCHLD>. If this is a problem for your application you can either	360	a problem for your application you can either create a dynamic loop with
323	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	361	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
324	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	362	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
325	C<ev_default_init>.	363
		364	Example: This is the most typical usage.
		365
		366	if (!ev_default_loop (0))
		367	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		368
		369	Example: Restrict libev to the select and poll backends, and do not allow
		370	environment settings to be taken into account:
		371
		372	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		373
		374	=item struct ev_loop *ev_loop_new (unsigned int flags)
		375
		376	This will create and initialise a new event loop object. If the loop
		377	could not be initialised, returns false.
		378
		379	This function is thread-safe, and one common way to use libev with
		380	threads is indeed to create one loop per thread, and using the default
		381	loop in the "main" or "initial" thread.
326		382
327	The flags argument can be used to specify special behaviour or specific	383	The flags argument can be used to specify special behaviour or specific
328	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	384	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
329		385
330	The following flags are supported:	386	The following flags are supported:
…		…
345	useful to try out specific backends to test their performance, or to work	401	useful to try out specific backends to test their performance, or to work
346	around bugs.	402	around bugs.
347		403
348	=item C<EVFLAG_FORKCHECK>	404	=item C<EVFLAG_FORKCHECK>
349		405
350	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	406	Instead of calling C<ev_loop_fork> manually after a fork, you can also
351	a fork, you can also make libev check for a fork in each iteration by	407	make libev check for a fork in each iteration by enabling this flag.
352	enabling this flag.
353		408
354	This works by calling C<getpid ()> on every iteration of the loop,	409	This works by calling C<getpid ()> on every iteration of the loop,
355	and thus this might slow down your event loop if you do a lot of loop	410	and thus this might slow down your event loop if you do a lot of loop
356	iterations and little real work, but is usually not noticeable (on my	411	iterations and little real work, but is usually not noticeable (on my
357	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	412	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
…		…
366	environment variable.	421	environment variable.
367		422
368	=item C<EVFLAG_NOINOTIFY>	423	=item C<EVFLAG_NOINOTIFY>
369		424
370	When this flag is specified, then libev will not attempt to use the	425	When this flag is specified, then libev will not attempt to use the
371	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and	426	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
372	testing, this flag can be useful to conserve inotify file descriptors, as	427	testing, this flag can be useful to conserve inotify file descriptors, as
373	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.	428	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
374		429
375	=item C<EVFLAG_SIGNALFD>	430	=item C<EVFLAG_SIGNALFD>
376		431
377	When this flag is specified, then libev will attempt to use the	432	When this flag is specified, then libev will attempt to use the
378	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API	433	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
379	delivers signals synchronously, which makes it both faster and might make	434	delivers signals synchronously, which makes it both faster and might make
380	it possible to get the queued signal data. It can also simplify signal	435	it possible to get the queued signal data. It can also simplify signal
381	handling with threads, as long as you properly block signals in your	436	handling with threads, as long as you properly block signals in your
382	threads that are not interested in handling them.	437	threads that are not interested in handling them.
383		438
384	Signalfd will not be used by default as this changes your signal mask, and	439	Signalfd will not be used by default as this changes your signal mask, and
385	there are a lot of shoddy libraries and programs (glib's threadpool for	440	there are a lot of shoddy libraries and programs (glib's threadpool for
386	example) that can't properly initialise their signal masks.	441	example) that can't properly initialise their signal masks.
		442
		443	=item C<EVFLAG_NOSIGMASK>
		444
		445	When this flag is specified, then libev will avoid to modify the signal
		446	mask. Specifically, this means you have to make sure signals are unblocked
		447	when you want to receive them.
		448
		449	This behaviour is useful when you want to do your own signal handling, or
		450	want to handle signals only in specific threads and want to avoid libev
		451	unblocking the signals.
		452
		453	It's also required by POSIX in a threaded program, as libev calls
		454	C<sigprocmask>, whose behaviour is officially unspecified.
		455
		456	This flag's behaviour will become the default in future versions of libev.
387		457
388	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	458	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
389		459
390	This is your standard select(2) backend. Not I<completely> standard, as	460	This is your standard select(2) backend. Not I<completely> standard, as
391	libev tries to roll its own fd_set with no limits on the number of fds,	461	libev tries to roll its own fd_set with no limits on the number of fds,
…		…
419	=item C<EVBACKEND_EPOLL> (value 4, Linux)	489	=item C<EVBACKEND_EPOLL> (value 4, Linux)
420		490
421	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9	491	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
422	kernels).	492	kernels).
423		493
424	For few fds, this backend is a bit little slower than poll and select,	494	For few fds, this backend is a bit little slower than poll and select, but
425	but it scales phenomenally better. While poll and select usually scale	495	it scales phenomenally better. While poll and select usually scale like
426	like O(total_fds) where n is the total number of fds (or the highest fd),	496	O(total_fds) where total_fds is the total number of fds (or the highest
427	epoll scales either O(1) or O(active_fds).	497	fd), epoll scales either O(1) or O(active_fds).
428		498
429	The epoll mechanism deserves honorable mention as the most misdesigned	499	The epoll mechanism deserves honorable mention as the most misdesigned
430	of the more advanced event mechanisms: mere annoyances include silently	500	of the more advanced event mechanisms: mere annoyances include silently
431	dropping file descriptors, requiring a system call per change per file	501	dropping file descriptors, requiring a system call per change per file
432	descriptor (and unnecessary guessing of parameters), problems with dup and	502	descriptor (and unnecessary guessing of parameters), problems with dup,
		503	returning before the timeout value, resulting in additional iterations
		504	(and only giving 5ms accuracy while select on the same platform gives
433	so on. The biggest issue is fork races, however - if a program forks then	505	0.1ms) and so on. The biggest issue is fork races, however - if a program
434	I<both> parent and child process have to recreate the epoll set, which can	506	forks then I<both> parent and child process have to recreate the epoll
435	take considerable time (one syscall per file descriptor) and is of course	507	set, which can take considerable time (one syscall per file descriptor)
436	hard to detect.	508	and is of course hard to detect.
437		509
438	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	510	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
439	of course I<doesn't>, and epoll just loves to report events for totally	511	but of course I<doesn't>, and epoll just loves to report events for
440	I<different> file descriptors (even already closed ones, so one cannot	512	totally I<different> file descriptors (even already closed ones, so
441	even remove them from the set) than registered in the set (especially	513	one cannot even remove them from the set) than registered in the set
442	on SMP systems). Libev tries to counter these spurious notifications by	514	(especially on SMP systems). Libev tries to counter these spurious
443	employing an additional generation counter and comparing that against the	515	notifications by employing an additional generation counter and comparing
444	events to filter out spurious ones, recreating the set when required.	516	that against the events to filter out spurious ones, recreating the set
		517	when required. Epoll also erroneously rounds down timeouts, but gives you
		518	no way to know when and by how much, so sometimes you have to busy-wait
		519	because epoll returns immediately despite a nonzero timeout. And last
		520	not least, it also refuses to work with some file descriptors which work
		521	perfectly fine with C<select> (files, many character devices...).
		522
		523	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
		524	cobbled together in a hurry, no thought to design or interaction with
		525	others. Oh, the pain, will it ever stop...
445		526
446	While stopping, setting and starting an I/O watcher in the same iteration	527	While stopping, setting and starting an I/O watcher in the same iteration
447	will result in some caching, there is still a system call per such	528	will result in some caching, there is still a system call per such
448	incident (because the same I<file descriptor> could point to a different	529	incident (because the same I<file descriptor> could point to a different
449	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	530	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
486		567
487	It scales in the same way as the epoll backend, but the interface to the	568	It scales in the same way as the epoll backend, but the interface to the
488	kernel is more efficient (which says nothing about its actual speed, of	569	kernel is more efficient (which says nothing about its actual speed, of
489	course). While stopping, setting and starting an I/O watcher does never	570	course). While stopping, setting and starting an I/O watcher does never
490	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	571	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
491	two event changes per incident. Support for C<fork ()> is very bad (but	572	two event changes per incident. Support for C<fork ()> is very bad (you
492	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect	573	might have to leak fd's on fork, but it's more sane than epoll) and it
493	cases	574	drops fds silently in similarly hard-to-detect cases
494		575
495	This backend usually performs well under most conditions.	576	This backend usually performs well under most conditions.
496		577
497	While nominally embeddable in other event loops, this doesn't work	578	While nominally embeddable in other event loops, this doesn't work
498	everywhere, so you might need to test for this. And since it is broken	579	everywhere, so you might need to test for this. And since it is broken
…		…
515	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	596	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
516		597
517	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	598	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
518	it's really slow, but it still scales very well (O(active_fds)).	599	it's really slow, but it still scales very well (O(active_fds)).
519		600
520	Please note that Solaris event ports can deliver a lot of spurious
521	notifications, so you need to use non-blocking I/O or other means to avoid
522	blocking when no data (or space) is available.
523
524	While this backend scales well, it requires one system call per active	601	While this backend scales well, it requires one system call per active
525	file descriptor per loop iteration. For small and medium numbers of file	602	file descriptor per loop iteration. For small and medium numbers of file
526	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	603	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
527	might perform better.	604	might perform better.
528		605
529	On the positive side, with the exception of the spurious readiness	606	On the positive side, this backend actually performed fully to
530	notifications, this backend actually performed fully to specification
531	in all tests and is fully embeddable, which is a rare feat among the	607	specification in all tests and is fully embeddable, which is a rare feat
532	OS-specific backends (I vastly prefer correctness over speed hacks).	608	among the OS-specific backends (I vastly prefer correctness over speed
		609	hacks).
		610
		611	On the negative side, the interface is I<bizarre> - so bizarre that
		612	even sun itself gets it wrong in their code examples: The event polling
		613	function sometimes returns events to the caller even though an error
		614	occurred, but with no indication whether it has done so or not (yes, it's
		615	even documented that way) - deadly for edge-triggered interfaces where you
		616	absolutely have to know whether an event occurred or not because you have
		617	to re-arm the watcher.
		618
		619	Fortunately libev seems to be able to work around these idiocies.
533		620
534	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	621	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
535	C<EVBACKEND_POLL>.	622	C<EVBACKEND_POLL>.
536		623
537	=item C<EVBACKEND_ALL>	624	=item C<EVBACKEND_ALL>
538		625
539	Try all backends (even potentially broken ones that wouldn't be tried	626	Try all backends (even potentially broken ones that wouldn't be tried
540	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	627	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
541	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	628	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
542		629
543	It is definitely not recommended to use this flag.	630	It is definitely not recommended to use this flag, use whatever
		631	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		632	at all.
		633
		634	=item C<EVBACKEND_MASK>
		635
		636	Not a backend at all, but a mask to select all backend bits from a
		637	C<flags> value, in case you want to mask out any backends from a flags
		638	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
544		639
545	=back	640	=back
546		641
547	If one or more of the backend flags are or'ed into the flags value,	642	If one or more of the backend flags are or'ed into the flags value,
548	then only these backends will be tried (in the reverse order as listed	643	then only these backends will be tried (in the reverse order as listed
549	here). If none are specified, all backends in C<ev_recommended_backends	644	here). If none are specified, all backends in C<ev_recommended_backends
550	()> will be tried.	645	()> will be tried.
551		646
552	Example: This is the most typical usage.
553
554	if (!ev_default_loop (0))
555	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
556
557	Example: Restrict libev to the select and poll backends, and do not allow
558	environment settings to be taken into account:
559
560	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
561
562	Example: Use whatever libev has to offer, but make sure that kqueue is
563	used if available (warning, breaks stuff, best use only with your own
564	private event loop and only if you know the OS supports your types of
565	fds):
566
567	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
568
569	=item struct ev_loop *ev_loop_new (unsigned int flags)
570
571	Similar to C<ev_default_loop>, but always creates a new event loop that is
572	always distinct from the default loop. Unlike the default loop, it cannot
573	handle signal and child watchers, and attempts to do so will be greeted by
574	undefined behaviour (or a failed assertion if assertions are enabled).
575
576	Note that this function I<is> thread-safe, and the recommended way to use
577	libev with threads is indeed to create one loop per thread, and using the
578	default loop in the "main" or "initial" thread.
579
580	Example: Try to create a event loop that uses epoll and nothing else.	647	Example: Try to create a event loop that uses epoll and nothing else.
581		648
582	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	649	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
583	if (!epoller)	650	if (!epoller)
584	fatal ("no epoll found here, maybe it hides under your chair");	651	fatal ("no epoll found here, maybe it hides under your chair");
585		652
		653	Example: Use whatever libev has to offer, but make sure that kqueue is
		654	used if available.
		655
		656	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		657
586	=item ev_default_destroy ()	658	=item ev_loop_destroy (loop)
587		659
588	Destroys the default loop again (frees all memory and kernel state	660	Destroys an event loop object (frees all memory and kernel state
589	etc.). None of the active event watchers will be stopped in the normal	661	etc.). None of the active event watchers will be stopped in the normal
590	sense, so e.g. C<ev_is_active> might still return true. It is your	662	sense, so e.g. C<ev_is_active> might still return true. It is your
591	responsibility to either stop all watchers cleanly yourself I<before>	663	responsibility to either stop all watchers cleanly yourself I<before>
592	calling this function, or cope with the fact afterwards (which is usually	664	calling this function, or cope with the fact afterwards (which is usually
593	the easiest thing, you can just ignore the watchers and/or C<free ()> them	665	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
595		667
596	Note that certain global state, such as signal state (and installed signal	668	Note that certain global state, such as signal state (and installed signal
597	handlers), will not be freed by this function, and related watchers (such	669	handlers), will not be freed by this function, and related watchers (such
598	as signal and child watchers) would need to be stopped manually.	670	as signal and child watchers) would need to be stopped manually.
599		671
600	In general it is not advisable to call this function except in the	672	This function is normally used on loop objects allocated by
601	rare occasion where you really need to free e.g. the signal handling	673	C<ev_loop_new>, but it can also be used on the default loop returned by
		674	C<ev_default_loop>, in which case it is not thread-safe.
		675
		676	Note that it is not advisable to call this function on the default loop
		677	except in the rare occasion where you really need to free its resources.
602	pipe fds. If you need dynamically allocated loops it is better to use	678	If you need dynamically allocated loops it is better to use C<ev_loop_new>
603	C<ev_loop_new> and C<ev_loop_destroy>.	679	and C<ev_loop_destroy>.
604		680
605	=item ev_loop_destroy (loop)	681	=item ev_loop_fork (loop)
606		682
607	Like C<ev_default_destroy>, but destroys an event loop created by an
608	earlier call to C<ev_loop_new>.
609
610	=item ev_default_fork ()
611
612	This function sets a flag that causes subsequent C<ev_loop> iterations	683	This function sets a flag that causes subsequent C<ev_run> iterations to
613	to reinitialise the kernel state for backends that have one. Despite the	684	reinitialise the kernel state for backends that have one. Despite the
614	name, you can call it anytime, but it makes most sense after forking, in	685	name, you can call it anytime, but it makes most sense after forking, in
615	the child process (or both child and parent, but that again makes little	686	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
616	sense). You I<must> call it in the child before using any of the libev	687	child before resuming or calling C<ev_run>.
617	functions, and it will only take effect at the next C<ev_loop> iteration.	688
		689	Again, you I<have> to call it on I<any> loop that you want to re-use after
		690	a fork, I<even if you do not plan to use the loop in the parent>. This is
		691	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		692	during fork.
618		693
619	On the other hand, you only need to call this function in the child	694	On the other hand, you only need to call this function in the child
620	process if and only if you want to use the event library in the child. If	695	process if and only if you want to use the event loop in the child. If
621	you just fork+exec, you don't have to call it at all.	696	you just fork+exec or create a new loop in the child, you don't have to
		697	call it at all (in fact, C<epoll> is so badly broken that it makes a
		698	difference, but libev will usually detect this case on its own and do a
		699	costly reset of the backend).
622		700
623	The function itself is quite fast and it's usually not a problem to call	701	The function itself is quite fast and it's usually not a problem to call
624	it just in case after a fork. To make this easy, the function will fit in	702	it just in case after a fork.
625	quite nicely into a call to C<pthread_atfork>:
626		703
		704	Example: Automate calling C<ev_loop_fork> on the default loop when
		705	using pthreads.
		706
		707	static void
		708	post_fork_child (void)
		709	{
		710	ev_loop_fork (EV_DEFAULT);
		711	}
		712
		713	...
627	pthread_atfork (0, 0, ev_default_fork);	714	pthread_atfork (0, 0, post_fork_child);
628
629	=item ev_loop_fork (loop)
630
631	Like C<ev_default_fork>, but acts on an event loop created by
632	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
633	after fork that you want to re-use in the child, and how you do this is
634	entirely your own problem.
635		715
636	=item int ev_is_default_loop (loop)	716	=item int ev_is_default_loop (loop)
637		717
638	Returns true when the given loop is, in fact, the default loop, and false	718	Returns true when the given loop is, in fact, the default loop, and false
639	otherwise.	719	otherwise.
640		720
641	=item unsigned int ev_loop_count (loop)	721	=item unsigned int ev_iteration (loop)
642		722
643	Returns the count of loop iterations for the loop, which is identical to	723	Returns the current iteration count for the event loop, which is identical
644	the number of times libev did poll for new events. It starts at C<0> and	724	to the number of times libev did poll for new events. It starts at C<0>
645	happily wraps around with enough iterations.	725	and happily wraps around with enough iterations.
646		726
647	This value can sometimes be useful as a generation counter of sorts (it	727	This value can sometimes be useful as a generation counter of sorts (it
648	"ticks" the number of loop iterations), as it roughly corresponds with	728	"ticks" the number of loop iterations), as it roughly corresponds with
649	C<ev_prepare> and C<ev_check> calls.	729	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		730	prepare and check phases.
650		731
651	=item unsigned int ev_loop_depth (loop)	732	=item unsigned int ev_depth (loop)
652		733
653	Returns the number of times C<ev_loop> was entered minus the number of	734	Returns the number of times C<ev_run> was entered minus the number of
654	times C<ev_loop> was exited, in other words, the recursion depth.	735	times C<ev_run> was exited normally, in other words, the recursion depth.
655		736
656	Outside C<ev_loop>, this number is zero. In a callback, this number is	737	Outside C<ev_run>, this number is zero. In a callback, this number is
657	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),	738	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
658	in which case it is higher.	739	in which case it is higher.
659		740
660	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread	741	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
661	etc.), doesn't count as exit.	742	throwing an exception etc.), doesn't count as "exit" - consider this
		743	as a hint to avoid such ungentleman-like behaviour unless it's really
		744	convenient, in which case it is fully supported.
662		745
663	=item unsigned int ev_backend (loop)	746	=item unsigned int ev_backend (loop)
664		747
665	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	748	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
666	use.	749	use.
…		…
675		758
676	=item ev_now_update (loop)	759	=item ev_now_update (loop)
677		760
678	Establishes the current time by querying the kernel, updating the time	761	Establishes the current time by querying the kernel, updating the time
679	returned by C<ev_now ()> in the progress. This is a costly operation and	762	returned by C<ev_now ()> in the progress. This is a costly operation and
680	is usually done automatically within C<ev_loop ()>.	763	is usually done automatically within C<ev_run ()>.
681		764
682	This function is rarely useful, but when some event callback runs for a	765	This function is rarely useful, but when some event callback runs for a
683	very long time without entering the event loop, updating libev's idea of	766	very long time without entering the event loop, updating libev's idea of
684	the current time is a good idea.	767	the current time is a good idea.
685		768
…		…
687		770
688	=item ev_suspend (loop)	771	=item ev_suspend (loop)
689		772
690	=item ev_resume (loop)	773	=item ev_resume (loop)
691		774
692	These two functions suspend and resume a loop, for use when the loop is	775	These two functions suspend and resume an event loop, for use when the
693	not used for a while and timeouts should not be processed.	776	loop is not used for a while and timeouts should not be processed.
694		777
695	A typical use case would be an interactive program such as a game: When	778	A typical use case would be an interactive program such as a game: When
696	the user presses C<^Z> to suspend the game and resumes it an hour later it	779	the user presses C<^Z> to suspend the game and resumes it an hour later it
697	would be best to handle timeouts as if no time had actually passed while	780	would be best to handle timeouts as if no time had actually passed while
698	the program was suspended. This can be achieved by calling C<ev_suspend>	781	the program was suspended. This can be achieved by calling C<ev_suspend>
…		…
700	C<ev_resume> directly afterwards to resume timer processing.	783	C<ev_resume> directly afterwards to resume timer processing.
701		784
702	Effectively, all C<ev_timer> watchers will be delayed by the time spend	785	Effectively, all C<ev_timer> watchers will be delayed by the time spend
703	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers	786	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
704	will be rescheduled (that is, they will lose any events that would have	787	will be rescheduled (that is, they will lose any events that would have
705	occured while suspended).	788	occurred while suspended).
706		789
707	After calling C<ev_suspend> you B<must not> call I<any> function on the	790	After calling C<ev_suspend> you B<must not> call I<any> function on the
708	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>	791	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
709	without a previous call to C<ev_suspend>.	792	without a previous call to C<ev_suspend>.
710		793
711	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	794	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
712	event loop time (see C<ev_now_update>).	795	event loop time (see C<ev_now_update>).
713		796
714	=item ev_loop (loop, int flags)	797	=item bool ev_run (loop, int flags)
715		798
716	Finally, this is it, the event handler. This function usually is called	799	Finally, this is it, the event handler. This function usually is called
717	after you have initialised all your watchers and you want to start	800	after you have initialised all your watchers and you want to start
718	handling events.	801	handling events. It will ask the operating system for any new events, call
		802	the watcher callbacks, and then repeat the whole process indefinitely: This
		803	is why event loops are called I<loops>.
719		804
720	If the flags argument is specified as C<0>, it will not return until	805	If the flags argument is specified as C<0>, it will keep handling events
721	either no event watchers are active anymore or C<ev_unloop> was called.	806	until either no event watchers are active anymore or C<ev_break> was
		807	called.
722		808
		809	The return value is false if there are no more active watchers (which
		810	usually means "all jobs done" or "deadlock"), and true in all other cases
		811	(which usually means " you should call C<ev_run> again").
		812
723	Please note that an explicit C<ev_unloop> is usually better than	813	Please note that an explicit C<ev_break> is usually better than
724	relying on all watchers to be stopped when deciding when a program has	814	relying on all watchers to be stopped when deciding when a program has
725	finished (especially in interactive programs), but having a program	815	finished (especially in interactive programs), but having a program
726	that automatically loops as long as it has to and no longer by virtue	816	that automatically loops as long as it has to and no longer by virtue
727	of relying on its watchers stopping correctly, that is truly a thing of	817	of relying on its watchers stopping correctly, that is truly a thing of
728	beauty.	818	beauty.
729		819
		820	This function is I<mostly> exception-safe - you can break out of a
		821	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		822	exception and so on. This does not decrement the C<ev_depth> value, nor
		823	will it clear any outstanding C<EVBREAK_ONE> breaks.
		824
730	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	825	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
731	those events and any already outstanding ones, but will not block your	826	those events and any already outstanding ones, but will not wait and
732	process in case there are no events and will return after one iteration of	827	block your process in case there are no events and will return after one
733	the loop.	828	iteration of the loop. This is sometimes useful to poll and handle new
		829	events while doing lengthy calculations, to keep the program responsive.
734		830
735	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	831	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
736	necessary) and will handle those and any already outstanding ones. It	832	necessary) and will handle those and any already outstanding ones. It
737	will block your process until at least one new event arrives (which could	833	will block your process until at least one new event arrives (which could
738	be an event internal to libev itself, so there is no guarantee that a	834	be an event internal to libev itself, so there is no guarantee that a
739	user-registered callback will be called), and will return after one	835	user-registered callback will be called), and will return after one
740	iteration of the loop.	836	iteration of the loop.
741		837
742	This is useful if you are waiting for some external event in conjunction	838	This is useful if you are waiting for some external event in conjunction
743	with something not expressible using other libev watchers (i.e. "roll your	839	with something not expressible using other libev watchers (i.e. "roll your
744	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	840	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
745	usually a better approach for this kind of thing.	841	usually a better approach for this kind of thing.
746		842
747	Here are the gory details of what C<ev_loop> does:	843	Here are the gory details of what C<ev_run> does (this is for your
		844	understanding, not a guarantee that things will work exactly like this in
		845	future versions):
748		846
		847	- Increment loop depth.
		848	- Reset the ev_break status.
749	- Before the first iteration, call any pending watchers.	849	- Before the first iteration, call any pending watchers.
		850	LOOP:
750	* If EVFLAG_FORKCHECK was used, check for a fork.	851	- If EVFLAG_FORKCHECK was used, check for a fork.
751	- If a fork was detected (by any means), queue and call all fork watchers.	852	- If a fork was detected (by any means), queue and call all fork watchers.
752	- Queue and call all prepare watchers.	853	- Queue and call all prepare watchers.
		854	- If ev_break was called, goto FINISH.
753	- If we have been forked, detach and recreate the kernel state	855	- If we have been forked, detach and recreate the kernel state
754	as to not disturb the other process.	856	as to not disturb the other process.
755	- Update the kernel state with all outstanding changes.	857	- Update the kernel state with all outstanding changes.
756	- Update the "event loop time" (ev_now ()).	858	- Update the "event loop time" (ev_now ()).
757	- Calculate for how long to sleep or block, if at all	859	- Calculate for how long to sleep or block, if at all
758	(active idle watchers, EVLOOP_NONBLOCK or not having	860	(active idle watchers, EVRUN_NOWAIT or not having
759	any active watchers at all will result in not sleeping).	861	any active watchers at all will result in not sleeping).
760	- Sleep if the I/O and timer collect interval say so.	862	- Sleep if the I/O and timer collect interval say so.
		863	- Increment loop iteration counter.
761	- Block the process, waiting for any events.	864	- Block the process, waiting for any events.
762	- Queue all outstanding I/O (fd) events.	865	- Queue all outstanding I/O (fd) events.
763	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	866	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
764	- Queue all expired timers.	867	- Queue all expired timers.
765	- Queue all expired periodics.	868	- Queue all expired periodics.
766	- Unless any events are pending now, queue all idle watchers.	869	- Queue all idle watchers with priority higher than that of pending events.
767	- Queue all check watchers.	870	- Queue all check watchers.
768	- Call all queued watchers in reverse order (i.e. check watchers first).	871	- Call all queued watchers in reverse order (i.e. check watchers first).
769	Signals and child watchers are implemented as I/O watchers, and will	872	Signals and child watchers are implemented as I/O watchers, and will
770	be handled here by queueing them when their watcher gets executed.	873	be handled here by queueing them when their watcher gets executed.
771	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	874	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
772	were used, or there are no active watchers, return, otherwise	875	were used, or there are no active watchers, goto FINISH, otherwise
773	continue with step *.	876	continue with step LOOP.
		877	FINISH:
		878	- Reset the ev_break status iff it was EVBREAK_ONE.
		879	- Decrement the loop depth.
		880	- Return.
774		881
775	Example: Queue some jobs and then loop until no events are outstanding	882	Example: Queue some jobs and then loop until no events are outstanding
776	anymore.	883	anymore.
777		884
778	... queue jobs here, make sure they register event watchers as long	885	... queue jobs here, make sure they register event watchers as long
779	... as they still have work to do (even an idle watcher will do..)	886	... as they still have work to do (even an idle watcher will do..)
780	ev_loop (my_loop, 0);	887	ev_run (my_loop, 0);
781	... jobs done or somebody called unloop. yeah!	888	... jobs done or somebody called break. yeah!
782		889
783	=item ev_unloop (loop, how)	890	=item ev_break (loop, how)
784		891
785	Can be used to make a call to C<ev_loop> return early (but only after it	892	Can be used to make a call to C<ev_run> return early (but only after it
786	has processed all outstanding events). The C<how> argument must be either	893	has processed all outstanding events). The C<how> argument must be either
787	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	894	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
788	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	895	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
789		896
790	This "unloop state" will be cleared when entering C<ev_loop> again.	897	This "break state" will be cleared on the next call to C<ev_run>.
791		898
792	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	899	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		900	which case it will have no effect.
793		901
794	=item ev_ref (loop)	902	=item ev_ref (loop)
795		903
796	=item ev_unref (loop)	904	=item ev_unref (loop)
797		905
798	Ref/unref can be used to add or remove a reference count on the event	906	Ref/unref can be used to add or remove a reference count on the event
799	loop: Every watcher keeps one reference, and as long as the reference	907	loop: Every watcher keeps one reference, and as long as the reference
800	count is nonzero, C<ev_loop> will not return on its own.	908	count is nonzero, C<ev_run> will not return on its own.
801		909
802	This is useful when you have a watcher that you never intend to	910	This is useful when you have a watcher that you never intend to
803	unregister, but that nevertheless should not keep C<ev_loop> from	911	unregister, but that nevertheless should not keep C<ev_run> from
804	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>	912	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
805	before stopping it.	913	before stopping it.
806		914
807	As an example, libev itself uses this for its internal signal pipe: It	915	As an example, libev itself uses this for its internal signal pipe: It
808	is not visible to the libev user and should not keep C<ev_loop> from	916	is not visible to the libev user and should not keep C<ev_run> from
809	exiting if no event watchers registered by it are active. It is also an	917	exiting if no event watchers registered by it are active. It is also an
810	excellent way to do this for generic recurring timers or from within	918	excellent way to do this for generic recurring timers or from within
811	third-party libraries. Just remember to I<unref after start> and I<ref	919	third-party libraries. Just remember to I<unref after start> and I<ref
812	before stop> (but only if the watcher wasn't active before, or was active	920	before stop> (but only if the watcher wasn't active before, or was active
813	before, respectively. Note also that libev might stop watchers itself	921	before, respectively. Note also that libev might stop watchers itself
814	(e.g. non-repeating timers) in which case you have to C<ev_ref>	922	(e.g. non-repeating timers) in which case you have to C<ev_ref>
815	in the callback).	923	in the callback).
816		924
817	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	925	Example: Create a signal watcher, but keep it from keeping C<ev_run>
818	running when nothing else is active.	926	running when nothing else is active.
819		927
820	ev_signal exitsig;	928	ev_signal exitsig;
821	ev_signal_init (&exitsig, sig_cb, SIGINT);	929	ev_signal_init (&exitsig, sig_cb, SIGINT);
822	ev_signal_start (loop, &exitsig);	930	ev_signal_start (loop, &exitsig);
823	evf_unref (loop);	931	ev_unref (loop);
824		932
825	Example: For some weird reason, unregister the above signal handler again.	933	Example: For some weird reason, unregister the above signal handler again.
826		934
827	ev_ref (loop);	935	ev_ref (loop);
828	ev_signal_stop (loop, &exitsig);	936	ev_signal_stop (loop, &exitsig);
…		…
848	overhead for the actual polling but can deliver many events at once.	956	overhead for the actual polling but can deliver many events at once.
849		957
850	By setting a higher I<io collect interval> you allow libev to spend more	958	By setting a higher I<io collect interval> you allow libev to spend more
851	time collecting I/O events, so you can handle more events per iteration,	959	time collecting I/O events, so you can handle more events per iteration,
852	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	960	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
853	C<ev_timer>) will be not affected. Setting this to a non-null value will	961	C<ev_timer>) will not be affected. Setting this to a non-null value will
854	introduce an additional C<ev_sleep ()> call into most loop iterations. The	962	introduce an additional C<ev_sleep ()> call into most loop iterations. The
855	sleep time ensures that libev will not poll for I/O events more often then	963	sleep time ensures that libev will not poll for I/O events more often then
856	once per this interval, on average.	964	once per this interval, on average (as long as the host time resolution is
		965	good enough).
857		966
858	Likewise, by setting a higher I<timeout collect interval> you allow libev	967	Likewise, by setting a higher I<timeout collect interval> you allow libev
859	to spend more time collecting timeouts, at the expense of increased	968	to spend more time collecting timeouts, at the expense of increased
860	latency/jitter/inexactness (the watcher callback will be called	969	latency/jitter/inexactness (the watcher callback will be called
861	later). C<ev_io> watchers will not be affected. Setting this to a non-null	970	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
867	usually doesn't make much sense to set it to a lower value than C<0.01>,	976	usually doesn't make much sense to set it to a lower value than C<0.01>,
868	as this approaches the timing granularity of most systems. Note that if	977	as this approaches the timing granularity of most systems. Note that if
869	you do transactions with the outside world and you can't increase the	978	you do transactions with the outside world and you can't increase the
870	parallelity, then this setting will limit your transaction rate (if you	979	parallelity, then this setting will limit your transaction rate (if you
871	need to poll once per transaction and the I/O collect interval is 0.01,	980	need to poll once per transaction and the I/O collect interval is 0.01,
872	then you can't do more than 100 transations per second).	981	then you can't do more than 100 transactions per second).
873		982
874	Setting the I<timeout collect interval> can improve the opportunity for	983	Setting the I<timeout collect interval> can improve the opportunity for
875	saving power, as the program will "bundle" timer callback invocations that	984	saving power, as the program will "bundle" timer callback invocations that
876	are "near" in time together, by delaying some, thus reducing the number of	985	are "near" in time together, by delaying some, thus reducing the number of
877	times the process sleeps and wakes up again. Another useful technique to	986	times the process sleeps and wakes up again. Another useful technique to
…		…
885	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	994	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
886		995
887	=item ev_invoke_pending (loop)	996	=item ev_invoke_pending (loop)
888		997
889	This call will simply invoke all pending watchers while resetting their	998	This call will simply invoke all pending watchers while resetting their
890	pending state. Normally, C<ev_loop> does this automatically when required,	999	pending state. Normally, C<ev_run> does this automatically when required,
891	but when overriding the invoke callback this call comes handy.	1000	but when overriding the invoke callback this call comes handy. This
		1001	function can be invoked from a watcher - this can be useful for example
		1002	when you want to do some lengthy calculation and want to pass further
		1003	event handling to another thread (you still have to make sure only one
		1004	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
892		1005
893	=item int ev_pending_count (loop)	1006	=item int ev_pending_count (loop)
894		1007
895	Returns the number of pending watchers - zero indicates that no watchers	1008	Returns the number of pending watchers - zero indicates that no watchers
896	are pending.	1009	are pending.
897		1010
898	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))	1011	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
899		1012
900	This overrides the invoke pending functionality of the loop: Instead of	1013	This overrides the invoke pending functionality of the loop: Instead of
901	invoking all pending watchers when there are any, C<ev_loop> will call	1014	invoking all pending watchers when there are any, C<ev_run> will call
902	this callback instead. This is useful, for example, when you want to	1015	this callback instead. This is useful, for example, when you want to
903	invoke the actual watchers inside another context (another thread etc.).	1016	invoke the actual watchers inside another context (another thread etc.).
904		1017
905	If you want to reset the callback, use C<ev_invoke_pending> as new	1018	If you want to reset the callback, use C<ev_invoke_pending> as new
906	callback.	1019	callback.
…		…
909		1022
910	Sometimes you want to share the same loop between multiple threads. This	1023	Sometimes you want to share the same loop between multiple threads. This
911	can be done relatively simply by putting mutex_lock/unlock calls around	1024	can be done relatively simply by putting mutex_lock/unlock calls around
912	each call to a libev function.	1025	each call to a libev function.
913		1026
914	However, C<ev_loop> can run an indefinite time, so it is not feasible to	1027	However, C<ev_run> can run an indefinite time, so it is not feasible
915	wait for it to return. One way around this is to wake up the loop via	1028	to wait for it to return. One way around this is to wake up the event
916	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>	1029	loop via C<ev_break> and C<ev_async_send>, another way is to set these
917	and I<acquire> callbacks on the loop.	1030	I<release> and I<acquire> callbacks on the loop.
918		1031
919	When set, then C<release> will be called just before the thread is	1032	When set, then C<release> will be called just before the thread is
920	suspended waiting for new events, and C<acquire> is called just	1033	suspended waiting for new events, and C<acquire> is called just
921	afterwards.	1034	afterwards.
922		1035
…		…
925		1038
926	While event loop modifications are allowed between invocations of	1039	While event loop modifications are allowed between invocations of
927	C<release> and C<acquire> (that's their only purpose after all), no	1040	C<release> and C<acquire> (that's their only purpose after all), no
928	modifications done will affect the event loop, i.e. adding watchers will	1041	modifications done will affect the event loop, i.e. adding watchers will
929	have no effect on the set of file descriptors being watched, or the time	1042	have no effect on the set of file descriptors being watched, or the time
930	waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it	1043	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
931	to take note of any changes you made.	1044	to take note of any changes you made.
932		1045
933	In theory, threads executing C<ev_loop> will be async-cancel safe between	1046	In theory, threads executing C<ev_run> will be async-cancel safe between
934	invocations of C<release> and C<acquire>.	1047	invocations of C<release> and C<acquire>.
935		1048
936	See also the locking example in the C<THREADS> section later in this	1049	See also the locking example in the C<THREADS> section later in this
937	document.	1050	document.
938		1051
939	=item ev_set_userdata (loop, void *data)	1052	=item ev_set_userdata (loop, void *data)
940		1053
941	=item ev_userdata (loop)	1054	=item void *ev_userdata (loop)
942		1055
943	Set and retrieve a single C<void *> associated with a loop. When	1056	Set and retrieve a single C<void *> associated with a loop. When
944	C<ev_set_userdata> has never been called, then C<ev_userdata> returns	1057	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
945	C<0.>	1058	C<0>.
946		1059
947	These two functions can be used to associate arbitrary data with a loop,	1060	These two functions can be used to associate arbitrary data with a loop,
948	and are intended solely for the C<invoke_pending_cb>, C<release> and	1061	and are intended solely for the C<invoke_pending_cb>, C<release> and
949	C<acquire> callbacks described above, but of course can be (ab-)used for	1062	C<acquire> callbacks described above, but of course can be (ab-)used for
950	any other purpose as well.	1063	any other purpose as well.
951		1064
952	=item ev_loop_verify (loop)	1065	=item ev_verify (loop)
953		1066
954	This function only does something when C<EV_VERIFY> support has been	1067	This function only does something when C<EV_VERIFY> support has been
955	compiled in, which is the default for non-minimal builds. It tries to go	1068	compiled in, which is the default for non-minimal builds. It tries to go
956	through all internal structures and checks them for validity. If anything	1069	through all internal structures and checks them for validity. If anything
957	is found to be inconsistent, it will print an error message to standard	1070	is found to be inconsistent, it will print an error message to standard
…		…
968		1081
969	In the following description, uppercase C<TYPE> in names stands for the	1082	In the following description, uppercase C<TYPE> in names stands for the
970	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1083	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
971	watchers and C<ev_io_start> for I/O watchers.	1084	watchers and C<ev_io_start> for I/O watchers.
972		1085
973	A watcher is a structure that you create and register to record your	1086	A watcher is an opaque structure that you allocate and register to record
974	interest in some event. For instance, if you want to wait for STDIN to	1087	your interest in some event. To make a concrete example, imagine you want
975	become readable, you would create an C<ev_io> watcher for that:	1088	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1089	for that:
976		1090
977	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1091	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
978	{	1092	{
979	ev_io_stop (w);	1093	ev_io_stop (w);
980	ev_unloop (loop, EVUNLOOP_ALL);	1094	ev_break (loop, EVBREAK_ALL);
981	}	1095	}
982		1096
983	struct ev_loop *loop = ev_default_loop (0);	1097	struct ev_loop *loop = ev_default_loop (0);
984		1098
985	ev_io stdin_watcher;	1099	ev_io stdin_watcher;
986		1100
987	ev_init (&stdin_watcher, my_cb);	1101	ev_init (&stdin_watcher, my_cb);
988	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1102	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
989	ev_io_start (loop, &stdin_watcher);	1103	ev_io_start (loop, &stdin_watcher);
990		1104
991	ev_loop (loop, 0);	1105	ev_run (loop, 0);
992		1106
993	As you can see, you are responsible for allocating the memory for your	1107	As you can see, you are responsible for allocating the memory for your
994	watcher structures (and it is I<usually> a bad idea to do this on the	1108	watcher structures (and it is I<usually> a bad idea to do this on the
995	stack).	1109	stack).
996		1110
997	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1111	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
998	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1112	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
999		1113
1000	Each watcher structure must be initialised by a call to C<ev_init	1114	Each watcher structure must be initialised by a call to C<ev_init (watcher
1001	(watcher *, callback)>, which expects a callback to be provided. This	1115	*, callback)>, which expects a callback to be provided. This callback is
1002	callback gets invoked each time the event occurs (or, in the case of I/O	1116	invoked each time the event occurs (or, in the case of I/O watchers, each
1003	watchers, each time the event loop detects that the file descriptor given	1117	time the event loop detects that the file descriptor given is readable
1004	is readable and/or writable).	1118	and/or writable).
1005		1119
1006	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1120	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
1007	macro to configure it, with arguments specific to the watcher type. There	1121	macro to configure it, with arguments specific to the watcher type. There
1008	is also a macro to combine initialisation and setting in one call: C<<	1122	is also a macro to combine initialisation and setting in one call: C<<
1009	ev_TYPE_init (watcher *, callback, ...) >>.	1123	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
1032	=item C<EV_WRITE>	1146	=item C<EV_WRITE>
1033		1147
1034	The file descriptor in the C<ev_io> watcher has become readable and/or	1148	The file descriptor in the C<ev_io> watcher has become readable and/or
1035	writable.	1149	writable.
1036		1150
1037	=item C<EV_TIMEOUT>	1151	=item C<EV_TIMER>
1038		1152
1039	The C<ev_timer> watcher has timed out.	1153	The C<ev_timer> watcher has timed out.
1040		1154
1041	=item C<EV_PERIODIC>	1155	=item C<EV_PERIODIC>
1042		1156
…		…
1060		1174
1061	=item C<EV_PREPARE>	1175	=item C<EV_PREPARE>
1062		1176
1063	=item C<EV_CHECK>	1177	=item C<EV_CHECK>
1064		1178
1065	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1179	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
1066	to gather new events, and all C<ev_check> watchers are invoked just after	1180	to gather new events, and all C<ev_check> watchers are invoked just after
1067	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1181	C<ev_run> has gathered them, but before it invokes any callbacks for any
1068	received events. Callbacks of both watcher types can start and stop as	1182	received events. Callbacks of both watcher types can start and stop as
1069	many watchers as they want, and all of them will be taken into account	1183	many watchers as they want, and all of them will be taken into account
1070	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1184	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
1071	C<ev_loop> from blocking).	1185	C<ev_run> from blocking).
1072		1186
1073	=item C<EV_EMBED>	1187	=item C<EV_EMBED>
1074		1188
1075	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1189	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1076		1190
1077	=item C<EV_FORK>	1191	=item C<EV_FORK>
1078		1192
1079	The event loop has been resumed in the child process after fork (see	1193	The event loop has been resumed in the child process after fork (see
1080	C<ev_fork>).	1194	C<ev_fork>).
		1195
		1196	=item C<EV_CLEANUP>
		1197
		1198	The event loop is about to be destroyed (see C<ev_cleanup>).
1081		1199
1082	=item C<EV_ASYNC>	1200	=item C<EV_ASYNC>
1083		1201
1084	The given async watcher has been asynchronously notified (see C<ev_async>).	1202	The given async watcher has been asynchronously notified (see C<ev_async>).
1085		1203
…		…
1258	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related	1376	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1259	functions that do not need a watcher.	1377	functions that do not need a watcher.
1260		1378
1261	=back	1379	=back
1262		1380
		1381	See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR
		1382	OWN COMPOSITE WATCHERS> idioms.
1263		1383
1264	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1384	=head2 WATCHER STATES
1265		1385
1266	Each watcher has, by default, a member C<void *data> that you can change	1386	There are various watcher states mentioned throughout this manual -
1267	and read at any time: libev will completely ignore it. This can be used	1387	active, pending and so on. In this section these states and the rules to
1268	to associate arbitrary data with your watcher. If you need more data and	1388	transition between them will be described in more detail - and while these
1269	don't want to allocate memory and store a pointer to it in that data	1389	rules might look complicated, they usually do "the right thing".
1270	member, you can also "subclass" the watcher type and provide your own
1271	data:
1272		1390
1273	struct my_io	1391	=over 4
1274	{
1275	ev_io io;
1276	int otherfd;
1277	void *somedata;
1278	struct whatever *mostinteresting;
1279	};
1280		1392
1281	...	1393	=item initialiased
1282	struct my_io w;
1283	ev_io_init (&w.io, my_cb, fd, EV_READ);
1284		1394
1285	And since your callback will be called with a pointer to the watcher, you	1395	Before a watcher can be registered with the event loop it has to be
1286	can cast it back to your own type:	1396	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1397	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1287		1398
1288	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)	1399	In this state it is simply some block of memory that is suitable for
1289	{	1400	use in an event loop. It can be moved around, freed, reused etc. at
1290	struct my_io *w = (struct my_io *)w_;	1401	will - as long as you either keep the memory contents intact, or call
1291	...	1402	C<ev_TYPE_init> again.
1292	}
1293		1403
1294	More interesting and less C-conformant ways of casting your callback type	1404	=item started/running/active
1295	instead have been omitted.
1296		1405
1297	Another common scenario is to use some data structure with multiple	1406	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1298	embedded watchers:	1407	property of the event loop, and is actively waiting for events. While in
		1408	this state it cannot be accessed (except in a few documented ways), moved,
		1409	freed or anything else - the only legal thing is to keep a pointer to it,
		1410	and call libev functions on it that are documented to work on active watchers.
1299		1411
1300	struct my_biggy	1412	=item pending
1301	{
1302	int some_data;
1303	ev_timer t1;
1304	ev_timer t2;
1305	}
1306		1413
1307	In this case getting the pointer to C<my_biggy> is a bit more	1414	If a watcher is active and libev determines that an event it is interested
1308	complicated: Either you store the address of your C<my_biggy> struct	1415	in has occurred (such as a timer expiring), it will become pending. It will
1309	in the C<data> member of the watcher (for woozies), or you need to use	1416	stay in this pending state until either it is stopped or its callback is
1310	some pointer arithmetic using C<offsetof> inside your watchers (for real	1417	about to be invoked, so it is not normally pending inside the watcher
1311	programmers):	1418	callback.
1312		1419
1313	#include <stddef.h>	1420	The watcher might or might not be active while it is pending (for example,
		1421	an expired non-repeating timer can be pending but no longer active). If it
		1422	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1423	but it is still property of the event loop at this time, so cannot be
		1424	moved, freed or reused. And if it is active the rules described in the
		1425	previous item still apply.
1314		1426
1315	static void	1427	It is also possible to feed an event on a watcher that is not active (e.g.
1316	t1_cb (EV_P_ ev_timer *w, int revents)	1428	via C<ev_feed_event>), in which case it becomes pending without being
1317	{	1429	active.
1318	struct my_biggy big = (struct my_biggy *)
1319	(((char *)w) - offsetof (struct my_biggy, t1));
1320	}
1321		1430
1322	static void	1431	=item stopped
1323	t2_cb (EV_P_ ev_timer *w, int revents)	1432
1324	{	1433	A watcher can be stopped implicitly by libev (in which case it might still
1325	struct my_biggy big = (struct my_biggy *)	1434	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1326	(((char *)w) - offsetof (struct my_biggy, t2));	1435	latter will clear any pending state the watcher might be in, regardless
1327	}	1436	of whether it was active or not, so stopping a watcher explicitly before
		1437	freeing it is often a good idea.
		1438
		1439	While stopped (and not pending) the watcher is essentially in the
		1440	initialised state, that is, it can be reused, moved, modified in any way
		1441	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1442	it again).
		1443
		1444	=back
1328		1445
1329	=head2 WATCHER PRIORITY MODELS	1446	=head2 WATCHER PRIORITY MODELS
1330		1447
1331	Many event loops support I<watcher priorities>, which are usually small	1448	Many event loops support I<watcher priorities>, which are usually small
1332	integers that influence the ordering of event callback invocation	1449	integers that influence the ordering of event callback invocation
…		…
1375		1492
1376	For example, to emulate how many other event libraries handle priorities,	1493	For example, to emulate how many other event libraries handle priorities,
1377	you can associate an C<ev_idle> watcher to each such watcher, and in	1494	you can associate an C<ev_idle> watcher to each such watcher, and in
1378	the normal watcher callback, you just start the idle watcher. The real	1495	the normal watcher callback, you just start the idle watcher. The real
1379	processing is done in the idle watcher callback. This causes libev to	1496	processing is done in the idle watcher callback. This causes libev to
1380	continously poll and process kernel event data for the watcher, but when	1497	continuously poll and process kernel event data for the watcher, but when
1381	the lock-out case is known to be rare (which in turn is rare :), this is	1498	the lock-out case is known to be rare (which in turn is rare :), this is
1382	workable.	1499	workable.
1383		1500
1384	Usually, however, the lock-out model implemented that way will perform	1501	Usually, however, the lock-out model implemented that way will perform
1385	miserably under the type of load it was designed to handle. In that case,	1502	miserably under the type of load it was designed to handle. In that case,
…		…
1399	{	1516	{
1400	// stop the I/O watcher, we received the event, but	1517	// stop the I/O watcher, we received the event, but
1401	// are not yet ready to handle it.	1518	// are not yet ready to handle it.
1402	ev_io_stop (EV_A_ w);	1519	ev_io_stop (EV_A_ w);
1403		1520
1404	// start the idle watcher to ahndle the actual event.	1521	// start the idle watcher to handle the actual event.
1405	// it will not be executed as long as other watchers	1522	// it will not be executed as long as other watchers
1406	// with the default priority are receiving events.	1523	// with the default priority are receiving events.
1407	ev_idle_start (EV_A_ &idle);	1524	ev_idle_start (EV_A_ &idle);
1408	}	1525	}
1409		1526
…		…
1459	In general you can register as many read and/or write event watchers per	1576	In general you can register as many read and/or write event watchers per
1460	fd as you want (as long as you don't confuse yourself). Setting all file	1577	fd as you want (as long as you don't confuse yourself). Setting all file
1461	descriptors to non-blocking mode is also usually a good idea (but not	1578	descriptors to non-blocking mode is also usually a good idea (but not
1462	required if you know what you are doing).	1579	required if you know what you are doing).
1463		1580
1464	If you cannot use non-blocking mode, then force the use of a
1465	known-to-be-good backend (at the time of this writing, this includes only
1466	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1467	descriptors for which non-blocking operation makes no sense (such as
1468	files) - libev doesn't guarentee any specific behaviour in that case.
1469
1470	Another thing you have to watch out for is that it is quite easy to	1581	Another thing you have to watch out for is that it is quite easy to
1471	receive "spurious" readiness notifications, that is your callback might	1582	receive "spurious" readiness notifications, that is, your callback might
1472	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1583	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1473	because there is no data. Not only are some backends known to create a	1584	because there is no data. It is very easy to get into this situation even
1474	lot of those (for example Solaris ports), it is very easy to get into	1585	with a relatively standard program structure. Thus it is best to always
1475	this situation even with a relatively standard program structure. Thus	1586	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1476	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1477	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1587	preferable to a program hanging until some data arrives.
1478		1588
1479	If you cannot run the fd in non-blocking mode (for example you should	1589	If you cannot run the fd in non-blocking mode (for example you should
1480	not play around with an Xlib connection), then you have to separately	1590	not play around with an Xlib connection), then you have to separately
1481	re-test whether a file descriptor is really ready with a known-to-be good	1591	re-test whether a file descriptor is really ready with a known-to-be good
1482	interface such as poll (fortunately in our Xlib example, Xlib already	1592	interface such as poll (fortunately in the case of Xlib, it already does
1483	does this on its own, so its quite safe to use). Some people additionally	1593	this on its own, so its quite safe to use). Some people additionally
1484	use C<SIGALRM> and an interval timer, just to be sure you won't block	1594	use C<SIGALRM> and an interval timer, just to be sure you won't block
1485	indefinitely.	1595	indefinitely.
1486		1596
1487	But really, best use non-blocking mode.	1597	But really, best use non-blocking mode.
1488		1598
…		…
1516		1626
1517	There is no workaround possible except not registering events	1627	There is no workaround possible except not registering events
1518	for potentially C<dup ()>'ed file descriptors, or to resort to	1628	for potentially C<dup ()>'ed file descriptors, or to resort to
1519	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1629	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1520		1630
		1631	=head3 The special problem of files
		1632
		1633	Many people try to use C<select> (or libev) on file descriptors
		1634	representing files, and expect it to become ready when their program
		1635	doesn't block on disk accesses (which can take a long time on their own).
		1636
		1637	However, this cannot ever work in the "expected" way - you get a readiness
		1638	notification as soon as the kernel knows whether and how much data is
		1639	there, and in the case of open files, that's always the case, so you
		1640	always get a readiness notification instantly, and your read (or possibly
		1641	write) will still block on the disk I/O.
		1642
		1643	Another way to view it is that in the case of sockets, pipes, character
		1644	devices and so on, there is another party (the sender) that delivers data
		1645	on its own, but in the case of files, there is no such thing: the disk
		1646	will not send data on its own, simply because it doesn't know what you
		1647	wish to read - you would first have to request some data.
		1648
		1649	Since files are typically not-so-well supported by advanced notification
		1650	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1651	to files, even though you should not use it. The reason for this is
		1652	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1653	usually a tty, often a pipe, but also sometimes files or special devices
		1654	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1655	F</dev/urandom>), and even though the file might better be served with
		1656	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1657	it "just works" instead of freezing.
		1658
		1659	So avoid file descriptors pointing to files when you know it (e.g. use
		1660	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1661	when you rarely read from a file instead of from a socket, and want to
		1662	reuse the same code path.
		1663
1521	=head3 The special problem of fork	1664	=head3 The special problem of fork
1522		1665
1523	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1666	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1524	useless behaviour. Libev fully supports fork, but needs to be told about	1667	useless behaviour. Libev fully supports fork, but needs to be told about
1525	it in the child.	1668	it in the child if you want to continue to use it in the child.
1526		1669
1527	To support fork in your programs, you either have to call	1670	To support fork in your child processes, you have to call C<ev_loop_fork
1528	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1671	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1529	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1672	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1530	C<EVBACKEND_POLL>.
1531		1673
1532	=head3 The special problem of SIGPIPE	1674	=head3 The special problem of SIGPIPE
1533		1675
1534	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1676	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1535	when writing to a pipe whose other end has been closed, your program gets	1677	when writing to a pipe whose other end has been closed, your program gets
…		…
1538		1680
1539	So when you encounter spurious, unexplained daemon exits, make sure you	1681	So when you encounter spurious, unexplained daemon exits, make sure you
1540	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1682	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1541	somewhere, as that would have given you a big clue).	1683	somewhere, as that would have given you a big clue).
1542		1684
		1685	=head3 The special problem of accept()ing when you can't
		1686
		1687	Many implementations of the POSIX C<accept> function (for example,
		1688	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1689	connection from the pending queue in all error cases.
		1690
		1691	For example, larger servers often run out of file descriptors (because
		1692	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1693	rejecting the connection, leading to libev signalling readiness on
		1694	the next iteration again (the connection still exists after all), and
		1695	typically causing the program to loop at 100% CPU usage.
		1696
		1697	Unfortunately, the set of errors that cause this issue differs between
		1698	operating systems, there is usually little the app can do to remedy the
		1699	situation, and no known thread-safe method of removing the connection to
		1700	cope with overload is known (to me).
		1701
		1702	One of the easiest ways to handle this situation is to just ignore it
		1703	- when the program encounters an overload, it will just loop until the
		1704	situation is over. While this is a form of busy waiting, no OS offers an
		1705	event-based way to handle this situation, so it's the best one can do.
		1706
		1707	A better way to handle the situation is to log any errors other than
		1708	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1709	messages, and continue as usual, which at least gives the user an idea of
		1710	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1711	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1712	usage.
		1713
		1714	If your program is single-threaded, then you could also keep a dummy file
		1715	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1716	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1717	close that fd, and create a new dummy fd. This will gracefully refuse
		1718	clients under typical overload conditions.
		1719
		1720	The last way to handle it is to simply log the error and C<exit>, as
		1721	is often done with C<malloc> failures, but this results in an easy
		1722	opportunity for a DoS attack.
1543		1723
1544	=head3 Watcher-Specific Functions	1724	=head3 Watcher-Specific Functions
1545		1725
1546	=over 4	1726	=over 4
1547		1727
…		…
1579	...	1759	...
1580	struct ev_loop *loop = ev_default_init (0);	1760	struct ev_loop *loop = ev_default_init (0);
1581	ev_io stdin_readable;	1761	ev_io stdin_readable;
1582	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1762	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1583	ev_io_start (loop, &stdin_readable);	1763	ev_io_start (loop, &stdin_readable);
1584	ev_loop (loop, 0);	1764	ev_run (loop, 0);
1585		1765
1586		1766
1587	=head2 C<ev_timer> - relative and optionally repeating timeouts	1767	=head2 C<ev_timer> - relative and optionally repeating timeouts
1588		1768
1589	Timer watchers are simple relative timers that generate an event after a	1769	Timer watchers are simple relative timers that generate an event after a
…		…
1595	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1775	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1596	monotonic clock option helps a lot here).	1776	monotonic clock option helps a lot here).
1597		1777
1598	The callback is guaranteed to be invoked only I<after> its timeout has	1778	The callback is guaranteed to be invoked only I<after> its timeout has
1599	passed (not I<at>, so on systems with very low-resolution clocks this	1779	passed (not I<at>, so on systems with very low-resolution clocks this
1600	might introduce a small delay). If multiple timers become ready during the	1780	might introduce a small delay, see "the special problem of being too
		1781	early", below). If multiple timers become ready during the same loop
1601	same loop iteration then the ones with earlier time-out values are invoked	1782	iteration then the ones with earlier time-out values are invoked before
1602	before ones of the same priority with later time-out values (but this is	1783	ones of the same priority with later time-out values (but this is no
1603	no longer true when a callback calls C<ev_loop> recursively).	1784	longer true when a callback calls C<ev_run> recursively).
1604		1785
1605	=head3 Be smart about timeouts	1786	=head3 Be smart about timeouts
1606		1787
1607	Many real-world problems involve some kind of timeout, usually for error	1788	Many real-world problems involve some kind of timeout, usually for error
1608	recovery. A typical example is an HTTP request - if the other side hangs,	1789	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1683		1864
1684	In this case, it would be more efficient to leave the C<ev_timer> alone,	1865	In this case, it would be more efficient to leave the C<ev_timer> alone,
1685	but remember the time of last activity, and check for a real timeout only	1866	but remember the time of last activity, and check for a real timeout only
1686	within the callback:	1867	within the callback:
1687		1868
		1869	ev_tstamp timeout = 60.;
1688	ev_tstamp last_activity; // time of last activity	1870	ev_tstamp last_activity; // time of last activity
		1871	ev_timer timer;
1689		1872
1690	static void	1873	static void
1691	callback (EV_P_ ev_timer *w, int revents)	1874	callback (EV_P_ ev_timer *w, int revents)
1692	{	1875	{
1693	ev_tstamp now = ev_now (EV_A);	1876	// calculate when the timeout would happen
1694	ev_tstamp timeout = last_activity + 60.;	1877	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1695		1878
1696	// if last_activity + 60. is older than now, we did time out	1879	// if negative, it means we the timeout already occured
1697	if (timeout < now)	1880	if (after < 0.)
1698	{	1881	{
1699	// timeout occured, take action	1882	// timeout occurred, take action
1700	}	1883	}
1701	else	1884	else
1702	{	1885	{
1703	// callback was invoked, but there was some activity, re-arm	1886	// callback was invoked, but there was some recent
1704	// the watcher to fire in last_activity + 60, which is	1887	// activity. simply restart the timer to time out
1705	// guaranteed to be in the future, so "again" is positive:	1888	// after "after" seconds, which is the earliest time
1706	w->repeat = timeout - now;	1889	// the timeout can occur.
		1890	ev_timer_set (w, after, 0.);
1707	ev_timer_again (EV_A_ w);	1891	ev_timer_start (EV_A_ w);
1708	}	1892	}
1709	}	1893	}
1710		1894
1711	To summarise the callback: first calculate the real timeout (defined	1895	To summarise the callback: first calculate in how many seconds the
1712	as "60 seconds after the last activity"), then check if that time has	1896	timeout will occur (by calculating the absolute time when it would occur,
1713	been reached, which means something I<did>, in fact, time out. Otherwise	1897	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1714	the callback was invoked too early (C<timeout> is in the future), so	1898	(EV_A)> from that).
1715	re-schedule the timer to fire at that future time, to see if maybe we have
1716	a timeout then.
1717		1899
1718	Note how C<ev_timer_again> is used, taking advantage of the	1900	If this value is negative, then we are already past the timeout, i.e. we
1719	C<ev_timer_again> optimisation when the timer is already running.	1901	timed out, and need to do whatever is needed in this case.
		1902
		1903	Otherwise, we now the earliest time at which the timeout would trigger,
		1904	and simply start the timer with this timeout value.
		1905
		1906	In other words, each time the callback is invoked it will check whether
		1907	the timeout cocured. If not, it will simply reschedule itself to check
		1908	again at the earliest time it could time out. Rinse. Repeat.
1720		1909
1721	This scheme causes more callback invocations (about one every 60 seconds	1910	This scheme causes more callback invocations (about one every 60 seconds
1722	minus half the average time between activity), but virtually no calls to	1911	minus half the average time between activity), but virtually no calls to
1723	libev to change the timeout.	1912	libev to change the timeout.
1724		1913
1725	To start the timer, simply initialise the watcher and set C<last_activity>	1914	To start the machinery, simply initialise the watcher and set
1726	to the current time (meaning we just have some activity :), then call the	1915	C<last_activity> to the current time (meaning there was some activity just
1727	callback, which will "do the right thing" and start the timer:	1916	now), then call the callback, which will "do the right thing" and start
		1917	the timer:
1728		1918
		1919	last_activity = ev_now (EV_A);
1729	ev_init (timer, callback);	1920	ev_init (&timer, callback);
1730	last_activity = ev_now (loop);	1921	callback (EV_A_ &timer, 0);
1731	callback (loop, timer, EV_TIMEOUT);
1732		1922
1733	And when there is some activity, simply store the current time in	1923	When there is some activity, simply store the current time in
1734	C<last_activity>, no libev calls at all:	1924	C<last_activity>, no libev calls at all:
1735		1925
		1926	if (activity detected)
1736	last_actiivty = ev_now (loop);	1927	last_activity = ev_now (EV_A);
		1928
		1929	When your timeout value changes, then the timeout can be changed by simply
		1930	providing a new value, stopping the timer and calling the callback, which
		1931	will agaion do the right thing (for example, time out immediately :).
		1932
		1933	timeout = new_value;
		1934	ev_timer_stop (EV_A_ &timer);
		1935	callback (EV_A_ &timer, 0);
1737		1936
1738	This technique is slightly more complex, but in most cases where the	1937	This technique is slightly more complex, but in most cases where the
1739	time-out is unlikely to be triggered, much more efficient.	1938	time-out is unlikely to be triggered, much more efficient.
1740
1741	Changing the timeout is trivial as well (if it isn't hard-coded in the
1742	callback :) - just change the timeout and invoke the callback, which will
1743	fix things for you.
1744		1939
1745	=item 4. Wee, just use a double-linked list for your timeouts.	1940	=item 4. Wee, just use a double-linked list for your timeouts.
1746		1941
1747	If there is not one request, but many thousands (millions...), all	1942	If there is not one request, but many thousands (millions...), all
1748	employing some kind of timeout with the same timeout value, then one can	1943	employing some kind of timeout with the same timeout value, then one can
…		…
1775	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	1970	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1776	rather complicated, but extremely efficient, something that really pays	1971	rather complicated, but extremely efficient, something that really pays
1777	off after the first million or so of active timers, i.e. it's usually	1972	off after the first million or so of active timers, i.e. it's usually
1778	overkill :)	1973	overkill :)
1779		1974
		1975	=head3 The special problem of being too early
		1976
		1977	If you ask a timer to call your callback after three seconds, then
		1978	you expect it to be invoked after three seconds - but of course, this
		1979	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		1980	guaranteed to any precision by libev - imagine somebody suspending the
		1981	process with a STOP signal for a few hours for example.
		1982
		1983	So, libev tries to invoke your callback as soon as possible I<after> the
		1984	delay has occurred, but cannot guarantee this.
		1985
		1986	A less obvious failure mode is calling your callback too early: many event
		1987	loops compare timestamps with a "elapsed delay >= requested delay", but
		1988	this can cause your callback to be invoked much earlier than you would
		1989	expect.
		1990
		1991	To see why, imagine a system with a clock that only offers full second
		1992	resolution (think windows if you can't come up with a broken enough OS
		1993	yourself). If you schedule a one-second timer at the time 500.9, then the
		1994	event loop will schedule your timeout to elapse at a system time of 500
		1995	(500.9 truncated to the resolution) + 1, or 501.
		1996
		1997	If an event library looks at the timeout 0.1s later, it will see "501 >=
		1998	501" and invoke the callback 0.1s after it was started, even though a
		1999	one-second delay was requested - this is being "too early", despite best
		2000	intentions.
		2001
		2002	This is the reason why libev will never invoke the callback if the elapsed
		2003	delay equals the requested delay, but only when the elapsed delay is
		2004	larger than the requested delay. In the example above, libev would only invoke
		2005	the callback at system time 502, or 1.1s after the timer was started.
		2006
		2007	So, while libev cannot guarantee that your callback will be invoked
		2008	exactly when requested, it I<can> and I<does> guarantee that the requested
		2009	delay has actually elapsed, or in other words, it always errs on the "too
		2010	late" side of things.
		2011
1780	=head3 The special problem of time updates	2012	=head3 The special problem of time updates
1781		2013
1782	Establishing the current time is a costly operation (it usually takes at	2014	Establishing the current time is a costly operation (it usually takes
1783	least two system calls): EV therefore updates its idea of the current	2015	at least one system call): EV therefore updates its idea of the current
1784	time only before and after C<ev_loop> collects new events, which causes a	2016	time only before and after C<ev_run> collects new events, which causes a
1785	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2017	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1786	lots of events in one iteration.	2018	lots of events in one iteration.
1787		2019
1788	The relative timeouts are calculated relative to the C<ev_now ()>	2020	The relative timeouts are calculated relative to the C<ev_now ()>
1789	time. This is usually the right thing as this timestamp refers to the time	2021	time. This is usually the right thing as this timestamp refers to the time
…		…
1794	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2026	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1795		2027
1796	If the event loop is suspended for a long time, you can also force an	2028	If the event loop is suspended for a long time, you can also force an
1797	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2029	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1798	()>.	2030	()>.
		2031
		2032	=head3 The special problem of unsynchronised clocks
		2033
		2034	Modern systems have a variety of clocks - libev itself uses the normal
		2035	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2036	jumps).
		2037
		2038	Neither of these clocks is synchronised with each other or any other clock
		2039	on the system, so C<ev_time ()> might return a considerably different time
		2040	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2041	a call to C<gettimeofday> might return a second count that is one higher
		2042	than a directly following call to C<time>.
		2043
		2044	The moral of this is to only compare libev-related timestamps with
		2045	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2046	a second or so.
		2047
		2048	One more problem arises due to this lack of synchronisation: if libev uses
		2049	the system monotonic clock and you compare timestamps from C<ev_time>
		2050	or C<ev_now> from when you started your timer and when your callback is
		2051	invoked, you will find that sometimes the callback is a bit "early".
		2052
		2053	This is because C<ev_timer>s work in real time, not wall clock time, so
		2054	libev makes sure your callback is not invoked before the delay happened,
		2055	I<measured according to the real time>, not the system clock.
		2056
		2057	If your timeouts are based on a physical timescale (e.g. "time out this
		2058	connection after 100 seconds") then this shouldn't bother you as it is
		2059	exactly the right behaviour.
		2060
		2061	If you want to compare wall clock/system timestamps to your timers, then
		2062	you need to use C<ev_periodic>s, as these are based on the wall clock
		2063	time, where your comparisons will always generate correct results.
1799		2064
1800	=head3 The special problems of suspended animation	2065	=head3 The special problems of suspended animation
1801		2066
1802	When you leave the server world it is quite customary to hit machines that	2067	When you leave the server world it is quite customary to hit machines that
1803	can suspend/hibernate - what happens to the clocks during such a suspend?	2068	can suspend/hibernate - what happens to the clocks during such a suspend?
…		…
1847	keep up with the timer (because it takes longer than those 10 seconds to	2112	keep up with the timer (because it takes longer than those 10 seconds to
1848	do stuff) the timer will not fire more than once per event loop iteration.	2113	do stuff) the timer will not fire more than once per event loop iteration.
1849		2114
1850	=item ev_timer_again (loop, ev_timer *)	2115	=item ev_timer_again (loop, ev_timer *)
1851		2116
1852	This will act as if the timer timed out and restart it again if it is	2117	This will act as if the timer timed out, and restarts it again if it is
1853	repeating. The exact semantics are:	2118	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2119	timeout to the C<repeat> value and calling C<ev_timer_start>.
1854		2120
		2121	The exact semantics are as in the following rules, all of which will be
		2122	applied to the watcher:
		2123
		2124	=over 4
		2125
1855	If the timer is pending, its pending status is cleared.	2126	=item If the timer is pending, the pending status is always cleared.
1856		2127
1857	If the timer is started but non-repeating, stop it (as if it timed out).	2128	=item If the timer is started but non-repeating, stop it (as if it timed
		2129	out, without invoking it).
1858		2130
1859	If the timer is repeating, either start it if necessary (with the	2131	=item If the timer is repeating, make the C<repeat> value the new timeout
1860	C<repeat> value), or reset the running timer to the C<repeat> value.	2132	and start the timer, if necessary.
		2133
		2134	=back
1861		2135
1862	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2136	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1863	usage example.	2137	usage example.
1864		2138
1865	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)	2139	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
…		…
1906	}	2180	}
1907		2181
1908	ev_timer mytimer;	2182	ev_timer mytimer;
1909	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2183	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1910	ev_timer_again (&mytimer); /* start timer */	2184	ev_timer_again (&mytimer); /* start timer */
1911	ev_loop (loop, 0);	2185	ev_run (loop, 0);
1912		2186
1913	// and in some piece of code that gets executed on any "activity":	2187	// and in some piece of code that gets executed on any "activity":
1914	// reset the timeout to start ticking again at 10 seconds	2188	// reset the timeout to start ticking again at 10 seconds
1915	ev_timer_again (&mytimer);	2189	ev_timer_again (&mytimer);
1916		2190
…		…
1942		2216
1943	As with timers, the callback is guaranteed to be invoked only when the	2217	As with timers, the callback is guaranteed to be invoked only when the
1944	point in time where it is supposed to trigger has passed. If multiple	2218	point in time where it is supposed to trigger has passed. If multiple
1945	timers become ready during the same loop iteration then the ones with	2219	timers become ready during the same loop iteration then the ones with
1946	earlier time-out values are invoked before ones with later time-out values	2220	earlier time-out values are invoked before ones with later time-out values
1947	(but this is no longer true when a callback calls C<ev_loop> recursively).	2221	(but this is no longer true when a callback calls C<ev_run> recursively).
1948		2222
1949	=head3 Watcher-Specific Functions and Data Members	2223	=head3 Watcher-Specific Functions and Data Members
1950		2224
1951	=over 4	2225	=over 4
1952		2226
…		…
1987		2261
1988	Another way to think about it (for the mathematically inclined) is that	2262	Another way to think about it (for the mathematically inclined) is that
1989	C<ev_periodic> will try to run the callback in this mode at the next possible	2263	C<ev_periodic> will try to run the callback in this mode at the next possible
1990	time where C<time = offset (mod interval)>, regardless of any time jumps.	2264	time where C<time = offset (mod interval)>, regardless of any time jumps.
1991		2265
1992	For numerical stability it is preferable that the C<offset> value is near	2266	The C<interval> I<MUST> be positive, and for numerical stability, the
1993	C<ev_now ()> (the current time), but there is no range requirement for	2267	interval value should be higher than C<1/8192> (which is around 100
1994	this value, and in fact is often specified as zero.	2268	microseconds) and C<offset> should be higher than C<0> and should have
		2269	at most a similar magnitude as the current time (say, within a factor of
		2270	ten). Typical values for offset are, in fact, C<0> or something between
		2271	C<0> and C<interval>, which is also the recommended range.
1995		2272
1996	Note also that there is an upper limit to how often a timer can fire (CPU	2273	Note also that there is an upper limit to how often a timer can fire (CPU
1997	speed for example), so if C<interval> is very small then timing stability	2274	speed for example), so if C<interval> is very small then timing stability
1998	will of course deteriorate. Libev itself tries to be exact to be about one	2275	will of course deteriorate. Libev itself tries to be exact to be about one
1999	millisecond (if the OS supports it and the machine is fast enough).	2276	millisecond (if the OS supports it and the machine is fast enough).
…		…
2080	Example: Call a callback every hour, or, more precisely, whenever the	2357	Example: Call a callback every hour, or, more precisely, whenever the
2081	system time is divisible by 3600. The callback invocation times have	2358	system time is divisible by 3600. The callback invocation times have
2082	potentially a lot of jitter, but good long-term stability.	2359	potentially a lot of jitter, but good long-term stability.
2083		2360
2084	static void	2361	static void
2085	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2362	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
2086	{	2363	{
2087	... its now a full hour (UTC, or TAI or whatever your clock follows)	2364	... its now a full hour (UTC, or TAI or whatever your clock follows)
2088	}	2365	}
2089		2366
2090	ev_periodic hourly_tick;	2367	ev_periodic hourly_tick;
…		…
2113		2390
2114	=head2 C<ev_signal> - signal me when a signal gets signalled!	2391	=head2 C<ev_signal> - signal me when a signal gets signalled!
2115		2392
2116	Signal watchers will trigger an event when the process receives a specific	2393	Signal watchers will trigger an event when the process receives a specific
2117	signal one or more times. Even though signals are very asynchronous, libev	2394	signal one or more times. Even though signals are very asynchronous, libev
2118	will try it's best to deliver signals synchronously, i.e. as part of the	2395	will try its best to deliver signals synchronously, i.e. as part of the
2119	normal event processing, like any other event.	2396	normal event processing, like any other event.
2120		2397
2121	If you want signals to be delivered truly asynchronously, just use	2398	If you want signals to be delivered truly asynchronously, just use
2122	C<sigaction> as you would do without libev and forget about sharing	2399	C<sigaction> as you would do without libev and forget about sharing
2123	the signal. You can even use C<ev_async> from a signal handler to	2400	the signal. You can even use C<ev_async> from a signal handler to
…		…
2142	=head3 The special problem of inheritance over fork/execve/pthread_create	2419	=head3 The special problem of inheritance over fork/execve/pthread_create
2143		2420
2144	Both the signal mask (C<sigprocmask>) and the signal disposition	2421	Both the signal mask (C<sigprocmask>) and the signal disposition
2145	(C<sigaction>) are unspecified after starting a signal watcher (and after	2422	(C<sigaction>) are unspecified after starting a signal watcher (and after
2146	stopping it again), that is, libev might or might not block the signal,	2423	stopping it again), that is, libev might or might not block the signal,
2147	and might or might not set or restore the installed signal handler.	2424	and might or might not set or restore the installed signal handler (but
		2425	see C<EVFLAG_NOSIGMASK>).
2148		2426
2149	While this does not matter for the signal disposition (libev never	2427	While this does not matter for the signal disposition (libev never
2150	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on	2428	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
2151	C<execve>), this matters for the signal mask: many programs do not expect	2429	C<execve>), this matters for the signal mask: many programs do not expect
2152	certain signals to be blocked.	2430	certain signals to be blocked.
…		…
2166		2444
2167	So I can't stress this enough: I<If you do not reset your signal mask when	2445	So I can't stress this enough: I<If you do not reset your signal mask when
2168	you expect it to be empty, you have a race condition in your code>. This	2446	you expect it to be empty, you have a race condition in your code>. This
2169	is not a libev-specific thing, this is true for most event libraries.	2447	is not a libev-specific thing, this is true for most event libraries.
2170		2448
		2449	=head3 The special problem of threads signal handling
		2450
		2451	POSIX threads has problematic signal handling semantics, specifically,
		2452	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2453	threads in a process block signals, which is hard to achieve.
		2454
		2455	When you want to use sigwait (or mix libev signal handling with your own
		2456	for the same signals), you can tackle this problem by globally blocking
		2457	all signals before creating any threads (or creating them with a fully set
		2458	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2459	loops. Then designate one thread as "signal receiver thread" which handles
		2460	these signals. You can pass on any signals that libev might be interested
		2461	in by calling C<ev_feed_signal>.
		2462
2171	=head3 Watcher-Specific Functions and Data Members	2463	=head3 Watcher-Specific Functions and Data Members
2172		2464
2173	=over 4	2465	=over 4
2174		2466
2175	=item ev_signal_init (ev_signal *, callback, int signum)	2467	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
2190	Example: Try to exit cleanly on SIGINT.	2482	Example: Try to exit cleanly on SIGINT.
2191		2483
2192	static void	2484	static void
2193	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2485	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2194	{	2486	{
2195	ev_unloop (loop, EVUNLOOP_ALL);	2487	ev_break (loop, EVBREAK_ALL);
2196	}	2488	}
2197		2489
2198	ev_signal signal_watcher;	2490	ev_signal signal_watcher;
2199	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2491	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2200	ev_signal_start (loop, &signal_watcher);	2492	ev_signal_start (loop, &signal_watcher);
…		…
2586		2878
2587	Prepare and check watchers are usually (but not always) used in pairs:	2879	Prepare and check watchers are usually (but not always) used in pairs:
2588	prepare watchers get invoked before the process blocks and check watchers	2880	prepare watchers get invoked before the process blocks and check watchers
2589	afterwards.	2881	afterwards.
2590		2882
2591	You I<must not> call C<ev_loop> or similar functions that enter	2883	You I<must not> call C<ev_run> or similar functions that enter
2592	the current event loop from either C<ev_prepare> or C<ev_check>	2884	the current event loop from either C<ev_prepare> or C<ev_check>
2593	watchers. Other loops than the current one are fine, however. The	2885	watchers. Other loops than the current one are fine, however. The
2594	rationale behind this is that you do not need to check for recursion in	2886	rationale behind this is that you do not need to check for recursion in
2595	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2887	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2596	C<ev_check> so if you have one watcher of each kind they will always be	2888	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2764		3056
2765	if (timeout >= 0)	3057	if (timeout >= 0)
2766	// create/start timer	3058	// create/start timer
2767		3059
2768	// poll	3060	// poll
2769	ev_loop (EV_A_ 0);	3061	ev_run (EV_A_ 0);
2770		3062
2771	// stop timer again	3063	// stop timer again
2772	if (timeout >= 0)	3064	if (timeout >= 0)
2773	ev_timer_stop (EV_A_ &to);	3065	ev_timer_stop (EV_A_ &to);
2774		3066
…		…
2852	if you do not want that, you need to temporarily stop the embed watcher).	3144	if you do not want that, you need to temporarily stop the embed watcher).
2853		3145
2854	=item ev_embed_sweep (loop, ev_embed *)	3146	=item ev_embed_sweep (loop, ev_embed *)
2855		3147
2856	Make a single, non-blocking sweep over the embedded loop. This works	3148	Make a single, non-blocking sweep over the embedded loop. This works
2857	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3149	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2858	appropriate way for embedded loops.	3150	appropriate way for embedded loops.
2859		3151
2860	=item struct ev_loop *other [read-only]	3152	=item struct ev_loop *other [read-only]
2861		3153
2862	The embedded event loop.	3154	The embedded event loop.
…		…
2922	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3214	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2923	handlers will be invoked, too, of course.	3215	handlers will be invoked, too, of course.
2924		3216
2925	=head3 The special problem of life after fork - how is it possible?	3217	=head3 The special problem of life after fork - how is it possible?
2926		3218
2927	Most uses of C<fork()> consist of forking, then some simple calls to ste	3219	Most uses of C<fork()> consist of forking, then some simple calls to set
2928	up/change the process environment, followed by a call to C<exec()>. This	3220	up/change the process environment, followed by a call to C<exec()>. This
2929	sequence should be handled by libev without any problems.	3221	sequence should be handled by libev without any problems.
2930		3222
2931	This changes when the application actually wants to do event handling	3223	This changes when the application actually wants to do event handling
2932	in the child, or both parent in child, in effect "continuing" after the	3224	in the child, or both parent in child, in effect "continuing" after the
…		…
2948	disadvantage of having to use multiple event loops (which do not support	3240	disadvantage of having to use multiple event loops (which do not support
2949	signal watchers).	3241	signal watchers).
2950		3242
2951	When this is not possible, or you want to use the default loop for	3243	When this is not possible, or you want to use the default loop for
2952	other reasons, then in the process that wants to start "fresh", call	3244	other reasons, then in the process that wants to start "fresh", call
2953	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3245	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
2954	the default loop will "orphan" (not stop) all registered watchers, so you	3246	Destroying the default loop will "orphan" (not stop) all registered
2955	have to be careful not to execute code that modifies those watchers. Note	3247	watchers, so you have to be careful not to execute code that modifies
2956	also that in that case, you have to re-register any signal watchers.	3248	those watchers. Note also that in that case, you have to re-register any
		3249	signal watchers.
2957		3250
2958	=head3 Watcher-Specific Functions and Data Members	3251	=head3 Watcher-Specific Functions and Data Members
2959		3252
2960	=over 4	3253	=over 4
2961		3254
2962	=item ev_fork_init (ev_signal *, callback)	3255	=item ev_fork_init (ev_fork *, callback)
2963		3256
2964	Initialises and configures the fork watcher - it has no parameters of any	3257	Initialises and configures the fork watcher - it has no parameters of any
2965	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3258	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2966	believe me.	3259	really.
2967		3260
2968	=back	3261	=back
2969		3262
2970		3263
		3264	=head2 C<ev_cleanup> - even the best things end
		3265
		3266	Cleanup watchers are called just before the event loop is being destroyed
		3267	by a call to C<ev_loop_destroy>.
		3268
		3269	While there is no guarantee that the event loop gets destroyed, cleanup
		3270	watchers provide a convenient method to install cleanup hooks for your
		3271	program, worker threads and so on - you just to make sure to destroy the
		3272	loop when you want them to be invoked.
		3273
		3274	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3275	all other watchers, they do not keep a reference to the event loop (which
		3276	makes a lot of sense if you think about it). Like all other watchers, you
		3277	can call libev functions in the callback, except C<ev_cleanup_start>.
		3278
		3279	=head3 Watcher-Specific Functions and Data Members
		3280
		3281	=over 4
		3282
		3283	=item ev_cleanup_init (ev_cleanup *, callback)
		3284
		3285	Initialises and configures the cleanup watcher - it has no parameters of
		3286	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3287	pointless, I assure you.
		3288
		3289	=back
		3290
		3291	Example: Register an atexit handler to destroy the default loop, so any
		3292	cleanup functions are called.
		3293
		3294	static void
		3295	program_exits (void)
		3296	{
		3297	ev_loop_destroy (EV_DEFAULT_UC);
		3298	}
		3299
		3300	...
		3301	atexit (program_exits);
		3302
		3303
2971	=head2 C<ev_async> - how to wake up another event loop	3304	=head2 C<ev_async> - how to wake up an event loop
2972		3305
2973	In general, you cannot use an C<ev_loop> from multiple threads or other	3306	In general, you cannot use an C<ev_loop> from multiple threads or other
2974	asynchronous sources such as signal handlers (as opposed to multiple event	3307	asynchronous sources such as signal handlers (as opposed to multiple event
2975	loops - those are of course safe to use in different threads).	3308	loops - those are of course safe to use in different threads).
2976		3309
2977	Sometimes, however, you need to wake up another event loop you do not	3310	Sometimes, however, you need to wake up an event loop you do not control,
2978	control, for example because it belongs to another thread. This is what	3311	for example because it belongs to another thread. This is what C<ev_async>
2979	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3312	watchers do: as long as the C<ev_async> watcher is active, you can signal
2980	can signal it by calling C<ev_async_send>, which is thread- and signal	3313	it by calling C<ev_async_send>, which is thread- and signal safe.
2981	safe.
2982		3314
2983	This functionality is very similar to C<ev_signal> watchers, as signals,	3315	This functionality is very similar to C<ev_signal> watchers, as signals,
2984	too, are asynchronous in nature, and signals, too, will be compressed	3316	too, are asynchronous in nature, and signals, too, will be compressed
2985	(i.e. the number of callback invocations may be less than the number of	3317	(i.e. the number of callback invocations may be less than the number of
2986	C<ev_async_sent> calls).	3318	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
2987		3319	of "global async watchers" by using a watcher on an otherwise unused
2988	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3320	signal, and C<ev_feed_signal> to signal this watcher from another thread,
2989	just the default loop.	3321	even without knowing which loop owns the signal.
2990		3322
2991	=head3 Queueing	3323	=head3 Queueing
2992		3324
2993	C<ev_async> does not support queueing of data in any way. The reason	3325	C<ev_async> does not support queueing of data in any way. The reason
2994	is that the author does not know of a simple (or any) algorithm for a	3326	is that the author does not know of a simple (or any) algorithm for a
…		…
3086	trust me.	3418	trust me.
3087		3419
3088	=item ev_async_send (loop, ev_async *)	3420	=item ev_async_send (loop, ev_async *)
3089		3421
3090	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3422	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3091	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3423	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3424	returns.
		3425
3092	C<ev_feed_event>, this call is safe to do from other threads, signal or	3426	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3093	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3427	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3094	section below on what exactly this means).	3428	embedding section below on what exactly this means).
3095		3429
3096	Note that, as with other watchers in libev, multiple events might get	3430	Note that, as with other watchers in libev, multiple events might get
3097	compressed into a single callback invocation (another way to look at this	3431	compressed into a single callback invocation (another way to look at
3098	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3432	this is that C<ev_async> watchers are level-triggered: they are set on
3099	reset when the event loop detects that).	3433	C<ev_async_send>, reset when the event loop detects that).
3100		3434
3101	This call incurs the overhead of a system call only once per event loop	3435	This call incurs the overhead of at most one extra system call per event
3102	iteration, so while the overhead might be noticeable, it doesn't apply to	3436	loop iteration, if the event loop is blocked, and no syscall at all if
3103	repeated calls to C<ev_async_send> for the same event loop.	3437	the event loop (or your program) is processing events. That means that
		3438	repeated calls are basically free (there is no need to avoid calls for
		3439	performance reasons) and that the overhead becomes smaller (typically
		3440	zero) under load.
3104		3441
3105	=item bool = ev_async_pending (ev_async *)	3442	=item bool = ev_async_pending (ev_async *)
3106		3443
3107	Returns a non-zero value when C<ev_async_send> has been called on the	3444	Returns a non-zero value when C<ev_async_send> has been called on the
3108	watcher but the event has not yet been processed (or even noted) by the	3445	watcher but the event has not yet been processed (or even noted) by the
…		…
3141		3478
3142	If C<timeout> is less than 0, then no timeout watcher will be	3479	If C<timeout> is less than 0, then no timeout watcher will be
3143	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3480	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
3144	repeat = 0) will be started. C<0> is a valid timeout.	3481	repeat = 0) will be started. C<0> is a valid timeout.
3145		3482
3146	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3483	The callback has the type C<void (*cb)(int revents, void *arg)> and is
3147	passed an C<revents> set like normal event callbacks (a combination of	3484	passed an C<revents> set like normal event callbacks (a combination of
3148	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3485	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
3149	value passed to C<ev_once>. Note that it is possible to receive I<both>	3486	value passed to C<ev_once>. Note that it is possible to receive I<both>
3150	a timeout and an io event at the same time - you probably should give io	3487	a timeout and an io event at the same time - you probably should give io
3151	events precedence.	3488	events precedence.
3152		3489
3153	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3490	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
3154		3491
3155	static void stdin_ready (int revents, void *arg)	3492	static void stdin_ready (int revents, void *arg)
3156	{	3493	{
3157	if (revents & EV_READ)	3494	if (revents & EV_READ)
3158	/* stdin might have data for us, joy! */;	3495	/* stdin might have data for us, joy! */;
3159	else if (revents & EV_TIMEOUT)	3496	else if (revents & EV_TIMER)
3160	/* doh, nothing entered */;	3497	/* doh, nothing entered */;
3161	}	3498	}
3162		3499
3163	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3500	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3164		3501
3165	=item ev_feed_fd_event (loop, int fd, int revents)	3502	=item ev_feed_fd_event (loop, int fd, int revents)
3166		3503
3167	Feed an event on the given fd, as if a file descriptor backend detected	3504	Feed an event on the given fd, as if a file descriptor backend detected
3168	the given events it.	3505	the given events.
3169		3506
3170	=item ev_feed_signal_event (loop, int signum)	3507	=item ev_feed_signal_event (loop, int signum)
3171		3508
3172	Feed an event as if the given signal occurred (C<loop> must be the default	3509	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3173	loop!).	3510	which is async-safe.
3174		3511
3175	=back	3512	=back
		3513
		3514
		3515	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3516
		3517	This section explains some common idioms that are not immediately
		3518	obvious. Note that examples are sprinkled over the whole manual, and this
		3519	section only contains stuff that wouldn't fit anywhere else.
		3520
		3521	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3522
		3523	Each watcher has, by default, a C<void *data> member that you can read
		3524	or modify at any time: libev will completely ignore it. This can be used
		3525	to associate arbitrary data with your watcher. If you need more data and
		3526	don't want to allocate memory separately and store a pointer to it in that
		3527	data member, you can also "subclass" the watcher type and provide your own
		3528	data:
		3529
		3530	struct my_io
		3531	{
		3532	ev_io io;
		3533	int otherfd;
		3534	void *somedata;
		3535	struct whatever *mostinteresting;
		3536	};
		3537
		3538	...
		3539	struct my_io w;
		3540	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3541
		3542	And since your callback will be called with a pointer to the watcher, you
		3543	can cast it back to your own type:
		3544
		3545	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3546	{
		3547	struct my_io *w = (struct my_io *)w_;
		3548	...
		3549	}
		3550
		3551	More interesting and less C-conformant ways of casting your callback
		3552	function type instead have been omitted.
		3553
		3554	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3555
		3556	Another common scenario is to use some data structure with multiple
		3557	embedded watchers, in effect creating your own watcher that combines
		3558	multiple libev event sources into one "super-watcher":
		3559
		3560	struct my_biggy
		3561	{
		3562	int some_data;
		3563	ev_timer t1;
		3564	ev_timer t2;
		3565	}
		3566
		3567	In this case getting the pointer to C<my_biggy> is a bit more
		3568	complicated: Either you store the address of your C<my_biggy> struct in
		3569	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3570	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3571	real programmers):
		3572
		3573	#include <stddef.h>
		3574
		3575	static void
		3576	t1_cb (EV_P_ ev_timer *w, int revents)
		3577	{
		3578	struct my_biggy big = (struct my_biggy *)
		3579	(((char *)w) - offsetof (struct my_biggy, t1));
		3580	}
		3581
		3582	static void
		3583	t2_cb (EV_P_ ev_timer *w, int revents)
		3584	{
		3585	struct my_biggy big = (struct my_biggy *)
		3586	(((char *)w) - offsetof (struct my_biggy, t2));
		3587	}
		3588
		3589	=head2 AVOIDING FINISHING BEFORE RETURNING
		3590
		3591	Often you have structures like this in event-based programs:
		3592
		3593	callback ()
		3594	{
		3595	free (request);
		3596	}
		3597
		3598	request = start_new_request (..., callback);
		3599
		3600	The intent is to start some "lengthy" operation. The C<request> could be
		3601	used to cancel the operation, or do other things with it.
		3602
		3603	It's not uncommon to have code paths in C<start_new_request> that
		3604	immediately invoke the callback, for example, to report errors. Or you add
		3605	some caching layer that finds that it can skip the lengthy aspects of the
		3606	operation and simply invoke the callback with the result.
		3607
		3608	The problem here is that this will happen I<before> C<start_new_request>
		3609	has returned, so C<request> is not set.
		3610
		3611	Even if you pass the request by some safer means to the callback, you
		3612	might want to do something to the request after starting it, such as
		3613	canceling it, which probably isn't working so well when the callback has
		3614	already been invoked.
		3615
		3616	A common way around all these issues is to make sure that
		3617	C<start_new_request> I<always> returns before the callback is invoked. If
		3618	C<start_new_request> immediately knows the result, it can artificially
		3619	delay invoking the callback by e.g. using a C<prepare> or C<idle> watcher
		3620	for example, or more sneakily, by reusing an existing (stopped) watcher
		3621	and pushing it into the pending queue:
		3622
		3623	ev_set_cb (watcher, callback);
		3624	ev_feed_event (EV_A_ watcher, 0);
		3625
		3626	This way, C<start_new_request> can safely return before the callback is
		3627	invoked, while not delaying callback invocation too much.
		3628
		3629	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3630
		3631	Often (especially in GUI toolkits) there are places where you have
		3632	I<modal> interaction, which is most easily implemented by recursively
		3633	invoking C<ev_run>.
		3634
		3635	This brings the problem of exiting - a callback might want to finish the
		3636	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3637	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3638	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3639	other combination: In these cases, C<ev_break> will not work alone.
		3640
		3641	The solution is to maintain "break this loop" variable for each C<ev_run>
		3642	invocation, and use a loop around C<ev_run> until the condition is
		3643	triggered, using C<EVRUN_ONCE>:
		3644
		3645	// main loop
		3646	int exit_main_loop = 0;
		3647
		3648	while (!exit_main_loop)
		3649	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3650
		3651	// in a modal watcher
		3652	int exit_nested_loop = 0;
		3653
		3654	while (!exit_nested_loop)
		3655	ev_run (EV_A_ EVRUN_ONCE);
		3656
		3657	To exit from any of these loops, just set the corresponding exit variable:
		3658
		3659	// exit modal loop
		3660	exit_nested_loop = 1;
		3661
		3662	// exit main program, after modal loop is finished
		3663	exit_main_loop = 1;
		3664
		3665	// exit both
		3666	exit_main_loop = exit_nested_loop = 1;
		3667
		3668	=head2 THREAD LOCKING EXAMPLE
		3669
		3670	Here is a fictitious example of how to run an event loop in a different
		3671	thread from where callbacks are being invoked and watchers are
		3672	created/added/removed.
		3673
		3674	For a real-world example, see the C<EV::Loop::Async> perl module,
		3675	which uses exactly this technique (which is suited for many high-level
		3676	languages).
		3677
		3678	The example uses a pthread mutex to protect the loop data, a condition
		3679	variable to wait for callback invocations, an async watcher to notify the
		3680	event loop thread and an unspecified mechanism to wake up the main thread.
		3681
		3682	First, you need to associate some data with the event loop:
		3683
		3684	typedef struct {
		3685	mutex_t lock; /* global loop lock */
		3686	ev_async async_w;
		3687	thread_t tid;
		3688	cond_t invoke_cv;
		3689	} userdata;
		3690
		3691	void prepare_loop (EV_P)
		3692	{
		3693	// for simplicity, we use a static userdata struct.
		3694	static userdata u;
		3695
		3696	ev_async_init (&u->async_w, async_cb);
		3697	ev_async_start (EV_A_ &u->async_w);
		3698
		3699	pthread_mutex_init (&u->lock, 0);
		3700	pthread_cond_init (&u->invoke_cv, 0);
		3701
		3702	// now associate this with the loop
		3703	ev_set_userdata (EV_A_ u);
		3704	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3705	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3706
		3707	// then create the thread running ev_run
		3708	pthread_create (&u->tid, 0, l_run, EV_A);
		3709	}
		3710
		3711	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3712	solely to wake up the event loop so it takes notice of any new watchers
		3713	that might have been added:
		3714
		3715	static void
		3716	async_cb (EV_P_ ev_async *w, int revents)
		3717	{
		3718	// just used for the side effects
		3719	}
		3720
		3721	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3722	protecting the loop data, respectively.
		3723
		3724	static void
		3725	l_release (EV_P)
		3726	{
		3727	userdata *u = ev_userdata (EV_A);
		3728	pthread_mutex_unlock (&u->lock);
		3729	}
		3730
		3731	static void
		3732	l_acquire (EV_P)
		3733	{
		3734	userdata *u = ev_userdata (EV_A);
		3735	pthread_mutex_lock (&u->lock);
		3736	}
		3737
		3738	The event loop thread first acquires the mutex, and then jumps straight
		3739	into C<ev_run>:
		3740
		3741	void *
		3742	l_run (void *thr_arg)
		3743	{
		3744	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3745
		3746	l_acquire (EV_A);
		3747	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3748	ev_run (EV_A_ 0);
		3749	l_release (EV_A);
		3750
		3751	return 0;
		3752	}
		3753
		3754	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3755	signal the main thread via some unspecified mechanism (signals? pipe
		3756	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3757	have been called (in a while loop because a) spurious wakeups are possible
		3758	and b) skipping inter-thread-communication when there are no pending
		3759	watchers is very beneficial):
		3760
		3761	static void
		3762	l_invoke (EV_P)
		3763	{
		3764	userdata *u = ev_userdata (EV_A);
		3765
		3766	while (ev_pending_count (EV_A))
		3767	{
		3768	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3769	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3770	}
		3771	}
		3772
		3773	Now, whenever the main thread gets told to invoke pending watchers, it
		3774	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3775	thread to continue:
		3776
		3777	static void
		3778	real_invoke_pending (EV_P)
		3779	{
		3780	userdata *u = ev_userdata (EV_A);
		3781
		3782	pthread_mutex_lock (&u->lock);
		3783	ev_invoke_pending (EV_A);
		3784	pthread_cond_signal (&u->invoke_cv);
		3785	pthread_mutex_unlock (&u->lock);
		3786	}
		3787
		3788	Whenever you want to start/stop a watcher or do other modifications to an
		3789	event loop, you will now have to lock:
		3790
		3791	ev_timer timeout_watcher;
		3792	userdata *u = ev_userdata (EV_A);
		3793
		3794	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3795
		3796	pthread_mutex_lock (&u->lock);
		3797	ev_timer_start (EV_A_ &timeout_watcher);
		3798	ev_async_send (EV_A_ &u->async_w);
		3799	pthread_mutex_unlock (&u->lock);
		3800
		3801	Note that sending the C<ev_async> watcher is required because otherwise
		3802	an event loop currently blocking in the kernel will have no knowledge
		3803	about the newly added timer. By waking up the loop it will pick up any new
		3804	watchers in the next event loop iteration.
		3805
		3806	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3807
		3808	While the overhead of a callback that e.g. schedules a thread is small, it
		3809	is still an overhead. If you embed libev, and your main usage is with some
		3810	kind of threads or coroutines, you might want to customise libev so that
		3811	doesn't need callbacks anymore.
		3812
		3813	Imagine you have coroutines that you can switch to using a function
		3814	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3815	and that due to some magic, the currently active coroutine is stored in a
		3816	global called C<current_coro>. Then you can build your own "wait for libev
		3817	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3818	the differing C<;> conventions):
		3819
		3820	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3821	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3822
		3823	That means instead of having a C callback function, you store the
		3824	coroutine to switch to in each watcher, and instead of having libev call
		3825	your callback, you instead have it switch to that coroutine.
		3826
		3827	A coroutine might now wait for an event with a function called
		3828	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3829	matter when, or whether the watcher is active or not when this function is
		3830	called):
		3831
		3832	void
		3833	wait_for_event (ev_watcher *w)
		3834	{
		3835	ev_cb_set (w) = current_coro;
		3836	switch_to (libev_coro);
		3837	}
		3838
		3839	That basically suspends the coroutine inside C<wait_for_event> and
		3840	continues the libev coroutine, which, when appropriate, switches back to
		3841	this or any other coroutine.
		3842
		3843	You can do similar tricks if you have, say, threads with an event queue -
		3844	instead of storing a coroutine, you store the queue object and instead of
		3845	switching to a coroutine, you push the watcher onto the queue and notify
		3846	any waiters.
		3847
		3848	To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two
		3849	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3850
		3851	// my_ev.h
		3852	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3853	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3854	#include "../libev/ev.h"
		3855
		3856	// my_ev.c
		3857	#define EV_H "my_ev.h"
		3858	#include "../libev/ev.c"
		3859
		3860	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3861	F<my_ev.c> into your project. When properly specifying include paths, you
		3862	can even use F<ev.h> as header file name directly.
3176		3863
3177		3864
3178	=head1 LIBEVENT EMULATION	3865	=head1 LIBEVENT EMULATION
3179		3866
3180	Libev offers a compatibility emulation layer for libevent. It cannot	3867	Libev offers a compatibility emulation layer for libevent. It cannot
3181	emulate the internals of libevent, so here are some usage hints:	3868	emulate the internals of libevent, so here are some usage hints:
3182		3869
3183	=over 4	3870	=over 4
		3871
		3872	=item * Only the libevent-1.4.1-beta API is being emulated.
		3873
		3874	This was the newest libevent version available when libev was implemented,
		3875	and is still mostly unchanged in 2010.
3184		3876
3185	=item * Use it by including <event.h>, as usual.	3877	=item * Use it by including <event.h>, as usual.
3186		3878
3187	=item * The following members are fully supported: ev_base, ev_callback,	3879	=item * The following members are fully supported: ev_base, ev_callback,
3188	ev_arg, ev_fd, ev_res, ev_events.	3880	ev_arg, ev_fd, ev_res, ev_events.
…		…
3194	=item * Priorities are not currently supported. Initialising priorities	3886	=item * Priorities are not currently supported. Initialising priorities
3195	will fail and all watchers will have the same priority, even though there	3887	will fail and all watchers will have the same priority, even though there
3196	is an ev_pri field.	3888	is an ev_pri field.
3197		3889
3198	=item * In libevent, the last base created gets the signals, in libev, the	3890	=item * In libevent, the last base created gets the signals, in libev, the
3199	first base created (== the default loop) gets the signals.	3891	base that registered the signal gets the signals.
3200		3892
3201	=item * Other members are not supported.	3893	=item * Other members are not supported.
3202		3894
3203	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3895	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3204	to use the libev header file and library.	3896	to use the libev header file and library.
…		…
3223	Care has been taken to keep the overhead low. The only data member the C++	3915	Care has been taken to keep the overhead low. The only data member the C++
3224	classes add (compared to plain C-style watchers) is the event loop pointer	3916	classes add (compared to plain C-style watchers) is the event loop pointer
3225	that the watcher is associated with (or no additional members at all if	3917	that the watcher is associated with (or no additional members at all if
3226	you disable C<EV_MULTIPLICITY> when embedding libev).	3918	you disable C<EV_MULTIPLICITY> when embedding libev).
3227		3919
3228	Currently, functions, and static and non-static member functions can be	3920	Currently, functions, static and non-static member functions and classes
3229	used as callbacks. Other types should be easy to add as long as they only	3921	with C<operator ()> can be used as callbacks. Other types should be easy
3230	need one additional pointer for context. If you need support for other	3922	to add as long as they only need one additional pointer for context. If
3231	types of functors please contact the author (preferably after implementing	3923	you need support for other types of functors please contact the author
3232	it).	3924	(preferably after implementing it).
		3925
		3926	For all this to work, your C++ compiler either has to use the same calling
		3927	conventions as your C compiler (for static member functions), or you have
		3928	to embed libev and compile libev itself as C++.
3233		3929
3234	Here is a list of things available in the C<ev> namespace:	3930	Here is a list of things available in the C<ev> namespace:
3235		3931
3236	=over 4	3932	=over 4
3237		3933
…		…
3247	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	3943	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3248		3944
3249	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	3945	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
3250	the same name in the C<ev> namespace, with the exception of C<ev_signal>	3946	the same name in the C<ev> namespace, with the exception of C<ev_signal>
3251	which is called C<ev::sig> to avoid clashes with the C<signal> macro	3947	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3252	defines by many implementations.	3948	defined by many implementations.
3253		3949
3254	All of those classes have these methods:	3950	All of those classes have these methods:
3255		3951
3256	=over 4	3952	=over 4
3257		3953
…		…
3298	myclass obj;	3994	myclass obj;
3299	ev::io iow;	3995	ev::io iow;
3300	iow.set <myclass, &myclass::io_cb> (&obj);	3996	iow.set <myclass, &myclass::io_cb> (&obj);
3301		3997
3302	=item w->set (object *)	3998	=item w->set (object *)
3303
3304	This is an B<experimental> feature that might go away in a future version.
3305		3999
3306	This is a variation of a method callback - leaving out the method to call	4000	This is a variation of a method callback - leaving out the method to call
3307	will default the method to C<operator ()>, which makes it possible to use	4001	will default the method to C<operator ()>, which makes it possible to use
3308	functor objects without having to manually specify the C<operator ()> all	4002	functor objects without having to manually specify the C<operator ()> all
3309	the time. Incidentally, you can then also leave out the template argument	4003	the time. Incidentally, you can then also leave out the template argument
…		…
3349	Associates a different C<struct ev_loop> with this watcher. You can only	4043	Associates a different C<struct ev_loop> with this watcher. You can only
3350	do this when the watcher is inactive (and not pending either).	4044	do this when the watcher is inactive (and not pending either).
3351		4045
3352	=item w->set ([arguments])	4046	=item w->set ([arguments])
3353		4047
3354	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	4048	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
3355	called at least once. Unlike the C counterpart, an active watcher gets	4049	method or a suitable start method must be called at least once. Unlike the
3356	automatically stopped and restarted when reconfiguring it with this	4050	C counterpart, an active watcher gets automatically stopped and restarted
3357	method.	4051	when reconfiguring it with this method.
3358		4052
3359	=item w->start ()	4053	=item w->start ()
3360		4054
3361	Starts the watcher. Note that there is no C<loop> argument, as the	4055	Starts the watcher. Note that there is no C<loop> argument, as the
3362	constructor already stores the event loop.	4056	constructor already stores the event loop.
3363		4057
		4058	=item w->start ([arguments])
		4059
		4060	Instead of calling C<set> and C<start> methods separately, it is often
		4061	convenient to wrap them in one call. Uses the same type of arguments as
		4062	the configure C<set> method of the watcher.
		4063
3364	=item w->stop ()	4064	=item w->stop ()
3365		4065
3366	Stops the watcher if it is active. Again, no C<loop> argument.	4066	Stops the watcher if it is active. Again, no C<loop> argument.
3367		4067
3368	=item w->again () (C<ev::timer>, C<ev::periodic> only)	4068	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3380		4080
3381	=back	4081	=back
3382		4082
3383	=back	4083	=back
3384		4084
3385	Example: Define a class with an IO and idle watcher, start one of them in	4085	Example: Define a class with two I/O and idle watchers, start the I/O
3386	the constructor.	4086	watchers in the constructor.
3387		4087
3388	class myclass	4088	class myclass
3389	{	4089	{
3390	ev::io io ; void io_cb (ev::io &w, int revents);	4090	ev::io io ; void io_cb (ev::io &w, int revents);
		4091	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3391	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4092	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3392		4093
3393	myclass (int fd)	4094	myclass (int fd)
3394	{	4095	{
3395	io .set <myclass, &myclass::io_cb > (this);	4096	io .set <myclass, &myclass::io_cb > (this);
		4097	io2 .set <myclass, &myclass::io2_cb > (this);
3396	idle.set <myclass, &myclass::idle_cb> (this);	4098	idle.set <myclass, &myclass::idle_cb> (this);
3397		4099
3398	io.start (fd, ev::READ);	4100	io.set (fd, ev::WRITE); // configure the watcher
		4101	io.start (); // start it whenever convenient
		4102
		4103	io2.start (fd, ev::READ); // set + start in one call
3399	}	4104	}
3400	};	4105	};
3401		4106
3402		4107
3403	=head1 OTHER LANGUAGE BINDINGS	4108	=head1 OTHER LANGUAGE BINDINGS
…		…
3442	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4147	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3443		4148
3444	=item D	4149	=item D
3445		4150
3446	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4151	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3447	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4152	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3448		4153
3449	=item Ocaml	4154	=item Ocaml
3450		4155
3451	Erkki Seppala has written Ocaml bindings for libev, to be found at	4156	Erkki Seppala has written Ocaml bindings for libev, to be found at
3452	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4157	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
…		…
3477	loop argument"). The C<EV_A> form is used when this is the sole argument,	4182	loop argument"). The C<EV_A> form is used when this is the sole argument,
3478	C<EV_A_> is used when other arguments are following. Example:	4183	C<EV_A_> is used when other arguments are following. Example:
3479		4184
3480	ev_unref (EV_A);	4185	ev_unref (EV_A);
3481	ev_timer_add (EV_A_ watcher);	4186	ev_timer_add (EV_A_ watcher);
3482	ev_loop (EV_A_ 0);	4187	ev_run (EV_A_ 0);
3483		4188
3484	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4189	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3485	which is often provided by the following macro.	4190	which is often provided by the following macro.
3486		4191
3487	=item C<EV_P>, C<EV_P_>	4192	=item C<EV_P>, C<EV_P_>
…		…
3500	suitable for use with C<EV_A>.	4205	suitable for use with C<EV_A>.
3501		4206
3502	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4207	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3503		4208
3504	Similar to the other two macros, this gives you the value of the default	4209	Similar to the other two macros, this gives you the value of the default
3505	loop, if multiple loops are supported ("ev loop default").	4210	loop, if multiple loops are supported ("ev loop default"). The default loop
		4211	will be initialised if it isn't already initialised.
		4212
		4213	For non-multiplicity builds, these macros do nothing, so you always have
		4214	to initialise the loop somewhere.
3506		4215
3507	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4216	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3508		4217
3509	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4218	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3510	default loop has been initialised (C<UC> == unchecked). Their behaviour	4219	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3527	}	4236	}
3528		4237
3529	ev_check check;	4238	ev_check check;
3530	ev_check_init (&check, check_cb);	4239	ev_check_init (&check, check_cb);
3531	ev_check_start (EV_DEFAULT_ &check);	4240	ev_check_start (EV_DEFAULT_ &check);
3532	ev_loop (EV_DEFAULT_ 0);	4241	ev_run (EV_DEFAULT_ 0);
3533		4242
3534	=head1 EMBEDDING	4243	=head1 EMBEDDING
3535		4244
3536	Libev can (and often is) directly embedded into host	4245	Libev can (and often is) directly embedded into host
3537	applications. Examples of applications that embed it include the Deliantra	4246	applications. Examples of applications that embed it include the Deliantra
…		…
3622	define before including (or compiling) any of its files. The default in	4331	define before including (or compiling) any of its files. The default in
3623	the absence of autoconf is documented for every option.	4332	the absence of autoconf is documented for every option.
3624		4333
3625	Symbols marked with "(h)" do not change the ABI, and can have different	4334	Symbols marked with "(h)" do not change the ABI, and can have different
3626	values when compiling libev vs. including F<ev.h>, so it is permissible	4335	values when compiling libev vs. including F<ev.h>, so it is permissible
3627	to redefine them before including F<ev.h> without breakign compatibility	4336	to redefine them before including F<ev.h> without breaking compatibility
3628	to a compiled library. All other symbols change the ABI, which means all	4337	to a compiled library. All other symbols change the ABI, which means all
3629	users of libev and the libev code itself must be compiled with compatible	4338	users of libev and the libev code itself must be compiled with compatible
3630	settings.	4339	settings.
3631		4340
3632	=over 4	4341	=over 4
		4342
		4343	=item EV_COMPAT3 (h)
		4344
		4345	Backwards compatibility is a major concern for libev. This is why this
		4346	release of libev comes with wrappers for the functions and symbols that
		4347	have been renamed between libev version 3 and 4.
		4348
		4349	You can disable these wrappers (to test compatibility with future
		4350	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4351	sources. This has the additional advantage that you can drop the C<struct>
		4352	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4353	typedef in that case.
		4354
		4355	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4356	and in some even more future version the compatibility code will be
		4357	removed completely.
3633		4358
3634	=item EV_STANDALONE (h)	4359	=item EV_STANDALONE (h)
3635		4360
3636	Must always be C<1> if you do not use autoconf configuration, which	4361	Must always be C<1> if you do not use autoconf configuration, which
3637	keeps libev from including F<config.h>, and it also defines dummy	4362	keeps libev from including F<config.h>, and it also defines dummy
…		…
3639	supported). It will also not define any of the structs usually found in	4364	supported). It will also not define any of the structs usually found in
3640	F<event.h> that are not directly supported by the libev core alone.	4365	F<event.h> that are not directly supported by the libev core alone.
3641		4366
3642	In standalone mode, libev will still try to automatically deduce the	4367	In standalone mode, libev will still try to automatically deduce the
3643	configuration, but has to be more conservative.	4368	configuration, but has to be more conservative.
		4369
		4370	=item EV_USE_FLOOR
		4371
		4372	If defined to be C<1>, libev will use the C<floor ()> function for its
		4373	periodic reschedule calculations, otherwise libev will fall back on a
		4374	portable (slower) implementation. If you enable this, you usually have to
		4375	link against libm or something equivalent. Enabling this when the C<floor>
		4376	function is not available will fail, so the safe default is to not enable
		4377	this.
3644		4378
3645	=item EV_USE_MONOTONIC	4379	=item EV_USE_MONOTONIC
3646		4380
3647	If defined to be C<1>, libev will try to detect the availability of the	4381	If defined to be C<1>, libev will try to detect the availability of the
3648	monotonic clock option at both compile time and runtime. Otherwise no	4382	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3778	If defined to be C<1>, libev will compile in support for the Linux inotify	4512	If defined to be C<1>, libev will compile in support for the Linux inotify
3779	interface to speed up C<ev_stat> watchers. Its actual availability will	4513	interface to speed up C<ev_stat> watchers. Its actual availability will
3780	be detected at runtime. If undefined, it will be enabled if the headers	4514	be detected at runtime. If undefined, it will be enabled if the headers
3781	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4515	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3782		4516
		4517	=item EV_NO_SMP
		4518
		4519	If defined to be C<1>, libev will assume that memory is always coherent
		4520	between threads, that is, threads can be used, but threads never run on
		4521	different cpus (or different cpu cores). This reduces dependencies
		4522	and makes libev faster.
		4523
		4524	=item EV_NO_THREADS
		4525
		4526	If defined to be C<1>, libev will assume that it will never be called
		4527	from different threads, which is a stronger assumption than C<EV_NO_SMP>,
		4528	above. This reduces dependencies and makes libev faster.
		4529
3783	=item EV_ATOMIC_T	4530	=item EV_ATOMIC_T
3784		4531
3785	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4532	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3786	access is atomic with respect to other threads or signal contexts. No such	4533	access is atomic and serialised with respect to other threads or signal
3787	type is easily found in the C language, so you can provide your own type	4534	contexts. No such type is easily found in the C language, so you can
3788	that you know is safe for your purposes. It is used both for signal handler "locking"	4535	provide your own type that you know is safe for your purposes. It is used
3789	as well as for signal and thread safety in C<ev_async> watchers.	4536	both for signal handler "locking" as well as for signal and thread safety
		4537	in C<ev_async> watchers.
3790		4538
3791	In the absence of this define, libev will use C<sig_atomic_t volatile>	4539	In the absence of this define, libev will use C<sig_atomic_t volatile>
3792	(from F<signal.h>), which is usually good enough on most platforms.	4540	(from F<signal.h>), which is usually good enough on most platforms,
		4541	although strictly speaking using a type that also implies a memory fence
		4542	is required.
3793		4543
3794	=item EV_H (h)	4544	=item EV_H (h)
3795		4545
3796	The name of the F<ev.h> header file used to include it. The default if	4546	The name of the F<ev.h> header file used to include it. The default if
3797	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4547	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
…		…
3821	will have the C<struct ev_loop *> as first argument, and you can create	4571	will have the C<struct ev_loop *> as first argument, and you can create
3822	additional independent event loops. Otherwise there will be no support	4572	additional independent event loops. Otherwise there will be no support
3823	for multiple event loops and there is no first event loop pointer	4573	for multiple event loops and there is no first event loop pointer
3824	argument. Instead, all functions act on the single default loop.	4574	argument. Instead, all functions act on the single default loop.
3825		4575
		4576	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4577	default loop when multiplicity is switched off - you always have to
		4578	initialise the loop manually in this case.
		4579
3826	=item EV_MINPRI	4580	=item EV_MINPRI
3827		4581
3828	=item EV_MAXPRI	4582	=item EV_MAXPRI
3829		4583
3830	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4584	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3844	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,	4598	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
3845	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.	4599	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3846		4600
3847	If undefined or defined to be C<1> (and the platform supports it), then	4601	If undefined or defined to be C<1> (and the platform supports it), then
3848	the respective watcher type is supported. If defined to be C<0>, then it	4602	the respective watcher type is supported. If defined to be C<0>, then it
3849	is not. Disabling watcher types mainly saves codesize.	4603	is not. Disabling watcher types mainly saves code size.
3850		4604
3851	=item EV_MINIMAL	4605	=item EV_FEATURES
3852		4606
3853	If you need to shave off some kilobytes of code at the expense of some	4607	If you need to shave off some kilobytes of code at the expense of some
3854	speed (but with the full API), define this symbol to C<1>. Currently this	4608	speed (but with the full API), you can define this symbol to request
3855	is used to override some inlining decisions, saves roughly 30% code size	4609	certain subsets of functionality. The default is to enable all features
3856	on amd64. It also selects a much smaller 2-heap for timer management over	4610	that can be enabled on the platform.
3857	the default 4-heap.
3858		4611
3859	You can save even more by disabling watcher types you do not need	4612	A typical way to use this symbol is to define it to C<0> (or to a bitset
3860	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>	4613	with some broad features you want) and then selectively re-enable
3861	(C<-DNDEBUG>) will usually reduce code size a lot. Disabling inotify,	4614	additional parts you want, for example if you want everything minimal,
3862	eventfd and signalfd will further help, and disabling backends one doesn't	4615	but multiple event loop support, async and child watchers and the poll
3863	need (e.g. poll, epoll, kqueue, ports) will help further.	4616	backend, use this:
3864		4617
3865	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to	4618	#define EV_FEATURES 0
3866	provide a bare-bones event library. See C<ev.h> for details on what parts
3867	of the API are still available, and do not complain if this subset changes
3868	over time.
3869
3870	This example set of settings reduces the compiled size of libev from
3871	23.9Kb to 7.7Kb on my GNU/Linux amd64 system (and leaves little
3872	in - there is also an effect on the amount of memory used). With
3873	an intelligent-enough linker (gcc+binutils do this when you use
3874	C<-Wl,--gc-sections -ffunction-sections>) further unused functions might
3875	be left out as well automatically - a binary starting a timer and an I/O
3876	watcher then might come out at only 5Kb.
3877
3878	// tuning and API changes
3879	#define EV_MINIMAL 2
3880	#define EV_MULTIPLICITY 0	4619	#define EV_MULTIPLICITY 1
3881	#define EV_MINPRI 0
3882	#define EV_MAXPRI 0
3883
3884	// OS-specific backends
3885	#define EV_USE_INOTIFY 0
3886	#define EV_USE_EVENTFD 0
3887	#define EV_USE_SIGNALFD 0
3888	#define EV_USE_REALTIME 0
3889	#define EV_USE_MONOTONIC 0
3890	#define EV_USE_CLOCK_SYSCALL 0
3891
3892	// disable all backends except select
3893	#define EV_USE_POLL 0	4620	#define EV_USE_POLL 1
3894	#define EV_USE_PORT 0
3895	#define EV_USE_KQUEUE 0
3896	#define EV_USE_EPOLL 0
3897
3898	// disable all watcher types that cna be disabled
3899	#define EV_STAT_ENABLE 0
3900	#define EV_PERIODIC_ENABLE 0
3901	#define EV_IDLE_ENABLE 0
3902	#define EV_CHECK_ENABLE 0
3903	#define EV_PREPARE_ENABLE 0
3904	#define EV_FORK_ENABLE 0
3905	#define EV_SIGNAL_ENABLE 0
3906	#define EV_CHILD_ENABLE 0	4621	#define EV_CHILD_ENABLE 1
3907	#define EV_ASYNC_ENABLE 0	4622	#define EV_ASYNC_ENABLE 1
3908	#define EV_EMBED_ENABLE 0	4623
		4624	The actual value is a bitset, it can be a combination of the following
		4625	values:
		4626
		4627	=over 4
		4628
		4629	=item C<1> - faster/larger code
		4630
		4631	Use larger code to speed up some operations.
		4632
		4633	Currently this is used to override some inlining decisions (enlarging the
		4634	code size by roughly 30% on amd64).
		4635
		4636	When optimising for size, use of compiler flags such as C<-Os> with
		4637	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4638	assertions.
		4639
		4640	=item C<2> - faster/larger data structures
		4641
		4642	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4643	hash table sizes and so on. This will usually further increase code size
		4644	and can additionally have an effect on the size of data structures at
		4645	runtime.
		4646
		4647	=item C<4> - full API configuration
		4648
		4649	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4650	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4651
		4652	=item C<8> - full API
		4653
		4654	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4655	details on which parts of the API are still available without this
		4656	feature, and do not complain if this subset changes over time.
		4657
		4658	=item C<16> - enable all optional watcher types
		4659
		4660	Enables all optional watcher types. If you want to selectively enable
		4661	only some watcher types other than I/O and timers (e.g. prepare,
		4662	embed, async, child...) you can enable them manually by defining
		4663	C<EV_watchertype_ENABLE> to C<1> instead.
		4664
		4665	=item C<32> - enable all backends
		4666
		4667	This enables all backends - without this feature, you need to enable at
		4668	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4669
		4670	=item C<64> - enable OS-specific "helper" APIs
		4671
		4672	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4673	default.
		4674
		4675	=back
		4676
		4677	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4678	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4679	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4680	watchers, timers and monotonic clock support.
		4681
		4682	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4683	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4684	your program might be left out as well - a binary starting a timer and an
		4685	I/O watcher then might come out at only 5Kb.
		4686
		4687	=item EV_API_STATIC
		4688
		4689	If this symbol is defined (by default it is not), then all identifiers
		4690	will have static linkage. This means that libev will not export any
		4691	identifiers, and you cannot link against libev anymore. This can be useful
		4692	when you embed libev, only want to use libev functions in a single file,
		4693	and do not want its identifiers to be visible.
		4694
		4695	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4696	wants to use libev.
		4697
		4698	This option only works when libev is compiled with a C compiler, as C++
		4699	doesn't support the required declaration syntax.
3909		4700
3910	=item EV_AVOID_STDIO	4701	=item EV_AVOID_STDIO
3911		4702
3912	If this is set to C<1> at compiletime, then libev will avoid using stdio	4703	If this is set to C<1> at compiletime, then libev will avoid using stdio
3913	functions (printf, scanf, perror etc.). This will increase the codesize	4704	functions (printf, scanf, perror etc.). This will increase the code size
3914	somewhat, but if your program doesn't otherwise depend on stdio and your	4705	somewhat, but if your program doesn't otherwise depend on stdio and your
3915	libc allows it, this avoids linking in the stdio library which is quite	4706	libc allows it, this avoids linking in the stdio library which is quite
3916	big.	4707	big.
3917		4708
3918	Note that error messages might become less precise when this option is	4709	Note that error messages might become less precise when this option is
…		…
3922		4713
3923	The highest supported signal number, +1 (or, the number of	4714	The highest supported signal number, +1 (or, the number of
3924	signals): Normally, libev tries to deduce the maximum number of signals	4715	signals): Normally, libev tries to deduce the maximum number of signals
3925	automatically, but sometimes this fails, in which case it can be	4716	automatically, but sometimes this fails, in which case it can be
3926	specified. Also, using a lower number than detected (C<32> should be	4717	specified. Also, using a lower number than detected (C<32> should be
3927	good for about any system in existance) can save some memory, as libev	4718	good for about any system in existence) can save some memory, as libev
3928	statically allocates some 12-24 bytes per signal number.	4719	statically allocates some 12-24 bytes per signal number.
3929		4720
3930	=item EV_PID_HASHSIZE	4721	=item EV_PID_HASHSIZE
3931		4722
3932	C<ev_child> watchers use a small hash table to distribute workload by	4723	C<ev_child> watchers use a small hash table to distribute workload by
3933	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4724	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3934	than enough. If you need to manage thousands of children you might want to	4725	usually more than enough. If you need to manage thousands of children you
3935	increase this value (I<must> be a power of two).	4726	might want to increase this value (I<must> be a power of two).
3936		4727
3937	=item EV_INOTIFY_HASHSIZE	4728	=item EV_INOTIFY_HASHSIZE
3938		4729
3939	C<ev_stat> watchers use a small hash table to distribute workload by	4730	C<ev_stat> watchers use a small hash table to distribute workload by
3940	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4731	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3941	usually more than enough. If you need to manage thousands of C<ev_stat>	4732	disabled), usually more than enough. If you need to manage thousands of
3942	watchers you might want to increase this value (I<must> be a power of	4733	C<ev_stat> watchers you might want to increase this value (I<must> be a
3943	two).	4734	power of two).
3944		4735
3945	=item EV_USE_4HEAP	4736	=item EV_USE_4HEAP
3946		4737
3947	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4738	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3948	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4739	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3949	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4740	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3950	faster performance with many (thousands) of watchers.	4741	faster performance with many (thousands) of watchers.
3951		4742
3952	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4743	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3953	(disabled).	4744	will be C<0>.
3954		4745
3955	=item EV_HEAP_CACHE_AT	4746	=item EV_HEAP_CACHE_AT
3956		4747
3957	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4748	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3958	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4749	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3959	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4750	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3960	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4751	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3961	but avoids random read accesses on heap changes. This improves performance	4752	but avoids random read accesses on heap changes. This improves performance
3962	noticeably with many (hundreds) of watchers.	4753	noticeably with many (hundreds) of watchers.
3963		4754
3964	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4755	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3965	(disabled).	4756	will be C<0>.
3966		4757
3967	=item EV_VERIFY	4758	=item EV_VERIFY
3968		4759
3969	Controls how much internal verification (see C<ev_loop_verify ()>) will	4760	Controls how much internal verification (see C<ev_verify ()>) will
3970	be done: If set to C<0>, no internal verification code will be compiled	4761	be done: If set to C<0>, no internal verification code will be compiled
3971	in. If set to C<1>, then verification code will be compiled in, but not	4762	in. If set to C<1>, then verification code will be compiled in, but not
3972	called. If set to C<2>, then the internal verification code will be	4763	called. If set to C<2>, then the internal verification code will be
3973	called once per loop, which can slow down libev. If set to C<3>, then the	4764	called once per loop, which can slow down libev. If set to C<3>, then the
3974	verification code will be called very frequently, which will slow down	4765	verification code will be called very frequently, which will slow down
3975	libev considerably.	4766	libev considerably.
3976		4767
3977	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4768	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3978	C<0>.	4769	will be C<0>.
3979		4770
3980	=item EV_COMMON	4771	=item EV_COMMON
3981		4772
3982	By default, all watchers have a C<void *data> member. By redefining	4773	By default, all watchers have a C<void *data> member. By redefining
3983	this macro to a something else you can include more and other types of	4774	this macro to something else you can include more and other types of
3984	members. You have to define it each time you include one of the files,	4775	members. You have to define it each time you include one of the files,
3985	though, and it must be identical each time.	4776	though, and it must be identical each time.
3986		4777
3987	For example, the perl EV module uses something like this:	4778	For example, the perl EV module uses something like this:
3988		4779
…		…
4041	file.	4832	file.
4042		4833
4043	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4834	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
4044	that everybody includes and which overrides some configure choices:	4835	that everybody includes and which overrides some configure choices:
4045		4836
4046	#define EV_MINIMAL 1	4837	#define EV_FEATURES 8
4047	#define EV_USE_POLL 0	4838	#define EV_USE_SELECT 1
4048	#define EV_MULTIPLICITY 0
4049	#define EV_PERIODIC_ENABLE 0	4839	#define EV_PREPARE_ENABLE 1
		4840	#define EV_IDLE_ENABLE 1
4050	#define EV_STAT_ENABLE 0	4841	#define EV_SIGNAL_ENABLE 1
4051	#define EV_FORK_ENABLE 0	4842	#define EV_CHILD_ENABLE 1
		4843	#define EV_USE_STDEXCEPT 0
4052	#define EV_CONFIG_H <config.h>	4844	#define EV_CONFIG_H <config.h>
4053	#define EV_MINPRI 0
4054	#define EV_MAXPRI 0
4055		4845
4056	#include "ev++.h"	4846	#include "ev++.h"
4057		4847
4058	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4848	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4059		4849
4060	#include "ev_cpp.h"	4850	#include "ev_cpp.h"
4061	#include "ev.c"	4851	#include "ev.c"
4062		4852
4063	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4853	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4064		4854
4065	=head2 THREADS AND COROUTINES	4855	=head2 THREADS AND COROUTINES
4066		4856
4067	=head3 THREADS	4857	=head3 THREADS
4068		4858
…		…
4119	default loop and triggering an C<ev_async> watcher from the default loop	4909	default loop and triggering an C<ev_async> watcher from the default loop
4120	watcher callback into the event loop interested in the signal.	4910	watcher callback into the event loop interested in the signal.
4121		4911
4122	=back	4912	=back
4123		4913
4124	=head4 THREAD LOCKING EXAMPLE	4914	See also L<THREAD LOCKING EXAMPLE>.
4125
4126	Here is a fictitious example of how to run an event loop in a different
4127	thread than where callbacks are being invoked and watchers are
4128	created/added/removed.
4129
4130	For a real-world example, see the C<EV::Loop::Async> perl module,
4131	which uses exactly this technique (which is suited for many high-level
4132	languages).
4133
4134	The example uses a pthread mutex to protect the loop data, a condition
4135	variable to wait for callback invocations, an async watcher to notify the
4136	event loop thread and an unspecified mechanism to wake up the main thread.
4137
4138	First, you need to associate some data with the event loop:
4139
4140	typedef struct {
4141	mutex_t lock; /* global loop lock */
4142	ev_async async_w;
4143	thread_t tid;
4144	cond_t invoke_cv;
4145	} userdata;
4146
4147	void prepare_loop (EV_P)
4148	{
4149	// for simplicity, we use a static userdata struct.
4150	static userdata u;
4151
4152	ev_async_init (&u->async_w, async_cb);
4153	ev_async_start (EV_A_ &u->async_w);
4154
4155	pthread_mutex_init (&u->lock, 0);
4156	pthread_cond_init (&u->invoke_cv, 0);
4157
4158	// now associate this with the loop
4159	ev_set_userdata (EV_A_ u);
4160	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4161	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4162
4163	// then create the thread running ev_loop
4164	pthread_create (&u->tid, 0, l_run, EV_A);
4165	}
4166
4167	The callback for the C<ev_async> watcher does nothing: the watcher is used
4168	solely to wake up the event loop so it takes notice of any new watchers
4169	that might have been added:
4170
4171	static void
4172	async_cb (EV_P_ ev_async *w, int revents)
4173	{
4174	// just used for the side effects
4175	}
4176
4177	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4178	protecting the loop data, respectively.
4179
4180	static void
4181	l_release (EV_P)
4182	{
4183	userdata *u = ev_userdata (EV_A);
4184	pthread_mutex_unlock (&u->lock);
4185	}
4186
4187	static void
4188	l_acquire (EV_P)
4189	{
4190	userdata *u = ev_userdata (EV_A);
4191	pthread_mutex_lock (&u->lock);
4192	}
4193
4194	The event loop thread first acquires the mutex, and then jumps straight
4195	into C<ev_loop>:
4196
4197	void *
4198	l_run (void *thr_arg)
4199	{
4200	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4201
4202	l_acquire (EV_A);
4203	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4204	ev_loop (EV_A_ 0);
4205	l_release (EV_A);
4206
4207	return 0;
4208	}
4209
4210	Instead of invoking all pending watchers, the C<l_invoke> callback will
4211	signal the main thread via some unspecified mechanism (signals? pipe
4212	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4213	have been called (in a while loop because a) spurious wakeups are possible
4214	and b) skipping inter-thread-communication when there are no pending
4215	watchers is very beneficial):
4216
4217	static void
4218	l_invoke (EV_P)
4219	{
4220	userdata *u = ev_userdata (EV_A);
4221
4222	while (ev_pending_count (EV_A))
4223	{
4224	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4225	pthread_cond_wait (&u->invoke_cv, &u->lock);
4226	}
4227	}
4228
4229	Now, whenever the main thread gets told to invoke pending watchers, it
4230	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4231	thread to continue:
4232
4233	static void
4234	real_invoke_pending (EV_P)
4235	{
4236	userdata *u = ev_userdata (EV_A);
4237
4238	pthread_mutex_lock (&u->lock);
4239	ev_invoke_pending (EV_A);
4240	pthread_cond_signal (&u->invoke_cv);
4241	pthread_mutex_unlock (&u->lock);
4242	}
4243
4244	Whenever you want to start/stop a watcher or do other modifications to an
4245	event loop, you will now have to lock:
4246
4247	ev_timer timeout_watcher;
4248	userdata *u = ev_userdata (EV_A);
4249
4250	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4251
4252	pthread_mutex_lock (&u->lock);
4253	ev_timer_start (EV_A_ &timeout_watcher);
4254	ev_async_send (EV_A_ &u->async_w);
4255	pthread_mutex_unlock (&u->lock);
4256
4257	Note that sending the C<ev_async> watcher is required because otherwise
4258	an event loop currently blocking in the kernel will have no knowledge
4259	about the newly added timer. By waking up the loop it will pick up any new
4260	watchers in the next event loop iteration.
4261		4915
4262	=head3 COROUTINES	4916	=head3 COROUTINES
4263		4917
4264	Libev is very accommodating to coroutines ("cooperative threads"):	4918	Libev is very accommodating to coroutines ("cooperative threads"):
4265	libev fully supports nesting calls to its functions from different	4919	libev fully supports nesting calls to its functions from different
4266	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4920	coroutines (e.g. you can call C<ev_run> on the same loop from two
4267	different coroutines, and switch freely between both coroutines running	4921	different coroutines, and switch freely between both coroutines running
4268	the loop, as long as you don't confuse yourself). The only exception is	4922	the loop, as long as you don't confuse yourself). The only exception is
4269	that you must not do this from C<ev_periodic> reschedule callbacks.	4923	that you must not do this from C<ev_periodic> reschedule callbacks.
4270		4924
4271	Care has been taken to ensure that libev does not keep local state inside	4925	Care has been taken to ensure that libev does not keep local state inside
4272	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4926	C<ev_run>, and other calls do not usually allow for coroutine switches as
4273	they do not call any callbacks.	4927	they do not call any callbacks.
4274		4928
4275	=head2 COMPILER WARNINGS	4929	=head2 COMPILER WARNINGS
4276		4930
4277	Depending on your compiler and compiler settings, you might get no or a	4931	Depending on your compiler and compiler settings, you might get no or a
…		…
4288	maintainable.	4942	maintainable.
4289		4943
4290	And of course, some compiler warnings are just plain stupid, or simply	4944	And of course, some compiler warnings are just plain stupid, or simply
4291	wrong (because they don't actually warn about the condition their message	4945	wrong (because they don't actually warn about the condition their message
4292	seems to warn about). For example, certain older gcc versions had some	4946	seems to warn about). For example, certain older gcc versions had some
4293	warnings that resulted an extreme number of false positives. These have	4947	warnings that resulted in an extreme number of false positives. These have
4294	been fixed, but some people still insist on making code warn-free with	4948	been fixed, but some people still insist on making code warn-free with
4295	such buggy versions.	4949	such buggy versions.
4296		4950
4297	While libev is written to generate as few warnings as possible,	4951	While libev is written to generate as few warnings as possible,
4298	"warn-free" code is not a goal, and it is recommended not to build libev	4952	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
4334	I suggest using suppression lists.	4988	I suggest using suppression lists.
4335		4989
4336		4990
4337	=head1 PORTABILITY NOTES	4991	=head1 PORTABILITY NOTES
4338		4992
		4993	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4994
		4995	GNU/Linux is the only common platform that supports 64 bit file/large file
		4996	interfaces but I<disables> them by default.
		4997
		4998	That means that libev compiled in the default environment doesn't support
		4999	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		5000
		5001	Unfortunately, many programs try to work around this GNU/Linux issue
		5002	by enabling the large file API, which makes them incompatible with the
		5003	standard libev compiled for their system.
		5004
		5005	Likewise, libev cannot enable the large file API itself as this would
		5006	suddenly make it incompatible to the default compile time environment,
		5007	i.e. all programs not using special compile switches.
		5008
		5009	=head2 OS/X AND DARWIN BUGS
		5010
		5011	The whole thing is a bug if you ask me - basically any system interface
		5012	you touch is broken, whether it is locales, poll, kqueue or even the
		5013	OpenGL drivers.
		5014
		5015	=head3 C<kqueue> is buggy
		5016
		5017	The kqueue syscall is broken in all known versions - most versions support
		5018	only sockets, many support pipes.
		5019
		5020	Libev tries to work around this by not using C<kqueue> by default on this
		5021	rotten platform, but of course you can still ask for it when creating a
		5022	loop - embedding a socket-only kqueue loop into a select-based one is
		5023	probably going to work well.
		5024
		5025	=head3 C<poll> is buggy
		5026
		5027	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		5028	implementation by something calling C<kqueue> internally around the 10.5.6
		5029	release, so now C<kqueue> I<and> C<poll> are broken.
		5030
		5031	Libev tries to work around this by not using C<poll> by default on
		5032	this rotten platform, but of course you can still ask for it when creating
		5033	a loop.
		5034
		5035	=head3 C<select> is buggy
		5036
		5037	All that's left is C<select>, and of course Apple found a way to fuck this
		5038	one up as well: On OS/X, C<select> actively limits the number of file
		5039	descriptors you can pass in to 1024 - your program suddenly crashes when
		5040	you use more.
		5041
		5042	There is an undocumented "workaround" for this - defining
		5043	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		5044	work on OS/X.
		5045
		5046	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		5047
		5048	=head3 C<errno> reentrancy
		5049
		5050	The default compile environment on Solaris is unfortunately so
		5051	thread-unsafe that you can't even use components/libraries compiled
		5052	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		5053	defined by default. A valid, if stupid, implementation choice.
		5054
		5055	If you want to use libev in threaded environments you have to make sure
		5056	it's compiled with C<_REENTRANT> defined.
		5057
		5058	=head3 Event port backend
		5059
		5060	The scalable event interface for Solaris is called "event
		5061	ports". Unfortunately, this mechanism is very buggy in all major
		5062	releases. If you run into high CPU usage, your program freezes or you get
		5063	a large number of spurious wakeups, make sure you have all the relevant
		5064	and latest kernel patches applied. No, I don't know which ones, but there
		5065	are multiple ones to apply, and afterwards, event ports actually work
		5066	great.
		5067
		5068	If you can't get it to work, you can try running the program by setting
		5069	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		5070	C<select> backends.
		5071
		5072	=head2 AIX POLL BUG
		5073
		5074	AIX unfortunately has a broken C<poll.h> header. Libev works around
		5075	this by trying to avoid the poll backend altogether (i.e. it's not even
		5076	compiled in), which normally isn't a big problem as C<select> works fine
		5077	with large bitsets on AIX, and AIX is dead anyway.
		5078
4339	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5079	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		5080
		5081	=head3 General issues
4340		5082
4341	Win32 doesn't support any of the standards (e.g. POSIX) that libev	5083	Win32 doesn't support any of the standards (e.g. POSIX) that libev
4342	requires, and its I/O model is fundamentally incompatible with the POSIX	5084	requires, and its I/O model is fundamentally incompatible with the POSIX
4343	model. Libev still offers limited functionality on this platform in	5085	model. Libev still offers limited functionality on this platform in
4344	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5086	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4345	descriptors. This only applies when using Win32 natively, not when using	5087	descriptors. This only applies when using Win32 natively, not when using
4346	e.g. cygwin.	5088	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		5089	as every compiler comes with a slightly differently broken/incompatible
		5090	environment.
4347		5091
4348	Lifting these limitations would basically require the full	5092	Lifting these limitations would basically require the full
4349	re-implementation of the I/O system. If you are into these kinds of	5093	re-implementation of the I/O system. If you are into this kind of thing,
4350	things, then note that glib does exactly that for you in a very portable	5094	then note that glib does exactly that for you in a very portable way (note
4351	way (note also that glib is the slowest event library known to man).	5095	also that glib is the slowest event library known to man).
4352		5096
4353	There is no supported compilation method available on windows except	5097	There is no supported compilation method available on windows except
4354	embedding it into other applications.	5098	embedding it into other applications.
4355		5099
4356	Sensible signal handling is officially unsupported by Microsoft - libev	5100	Sensible signal handling is officially unsupported by Microsoft - libev
…		…
4384	you do I<not> compile the F<ev.c> or any other embedded source files!):	5128	you do I<not> compile the F<ev.c> or any other embedded source files!):
4385		5129
4386	#include "evwrap.h"	5130	#include "evwrap.h"
4387	#include "ev.c"	5131	#include "ev.c"
4388		5132
4389	=over 4
4390
4391	=item The winsocket select function	5133	=head3 The winsocket C<select> function
4392		5134
4393	The winsocket C<select> function doesn't follow POSIX in that it	5135	The winsocket C<select> function doesn't follow POSIX in that it
4394	requires socket I<handles> and not socket I<file descriptors> (it is	5136	requires socket I<handles> and not socket I<file descriptors> (it is
4395	also extremely buggy). This makes select very inefficient, and also	5137	also extremely buggy). This makes select very inefficient, and also
4396	requires a mapping from file descriptors to socket handles (the Microsoft	5138	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
4405	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	5147	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
4406		5148
4407	Note that winsockets handling of fd sets is O(n), so you can easily get a	5149	Note that winsockets handling of fd sets is O(n), so you can easily get a
4408	complexity in the O(n²) range when using win32.	5150	complexity in the O(n²) range when using win32.
4409		5151
4410	=item Limited number of file descriptors	5152	=head3 Limited number of file descriptors
4411		5153
4412	Windows has numerous arbitrary (and low) limits on things.	5154	Windows has numerous arbitrary (and low) limits on things.
4413		5155
4414	Early versions of winsocket's select only supported waiting for a maximum	5156	Early versions of winsocket's select only supported waiting for a maximum
4415	of C<64> handles (probably owning to the fact that all windows kernels	5157	of C<64> handles (probably owning to the fact that all windows kernels
…		…
4430	runtime libraries. This might get you to about C<512> or C<2048> sockets	5172	runtime libraries. This might get you to about C<512> or C<2048> sockets
4431	(depending on windows version and/or the phase of the moon). To get more,	5173	(depending on windows version and/or the phase of the moon). To get more,
4432	you need to wrap all I/O functions and provide your own fd management, but	5174	you need to wrap all I/O functions and provide your own fd management, but
4433	the cost of calling select (O(n²)) will likely make this unworkable.	5175	the cost of calling select (O(n²)) will likely make this unworkable.
4434		5176
4435	=back
4436
4437	=head2 PORTABILITY REQUIREMENTS	5177	=head2 PORTABILITY REQUIREMENTS
4438		5178
4439	In addition to a working ISO-C implementation and of course the	5179	In addition to a working ISO-C implementation and of course the
4440	backend-specific APIs, libev relies on a few additional extensions:	5180	backend-specific APIs, libev relies on a few additional extensions:
4441		5181
…		…
4447	Libev assumes not only that all watcher pointers have the same internal	5187	Libev assumes not only that all watcher pointers have the same internal
4448	structure (guaranteed by POSIX but not by ISO C for example), but it also	5188	structure (guaranteed by POSIX but not by ISO C for example), but it also
4449	assumes that the same (machine) code can be used to call any watcher	5189	assumes that the same (machine) code can be used to call any watcher
4450	callback: The watcher callbacks have different type signatures, but libev	5190	callback: The watcher callbacks have different type signatures, but libev
4451	calls them using an C<ev_watcher *> internally.	5191	calls them using an C<ev_watcher *> internally.
		5192
		5193	=item pointer accesses must be thread-atomic
		5194
		5195	Accessing a pointer value must be atomic, it must both be readable and
		5196	writable in one piece - this is the case on all current architectures.
4452		5197
4453	=item C<sig_atomic_t volatile> must be thread-atomic as well	5198	=item C<sig_atomic_t volatile> must be thread-atomic as well
4454		5199
4455	The type C<sig_atomic_t volatile> (or whatever is defined as	5200	The type C<sig_atomic_t volatile> (or whatever is defined as
4456	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5201	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
4479	watchers.	5224	watchers.
4480		5225
4481	=item C<double> must hold a time value in seconds with enough accuracy	5226	=item C<double> must hold a time value in seconds with enough accuracy
4482		5227
4483	The type C<double> is used to represent timestamps. It is required to	5228	The type C<double> is used to represent timestamps. It is required to
4484	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5229	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4485	enough for at least into the year 4000. This requirement is fulfilled by	5230	good enough for at least into the year 4000 with millisecond accuracy
		5231	(the design goal for libev). This requirement is overfulfilled by
4486	implementations implementing IEEE 754, which is basically all existing	5232	implementations using IEEE 754, which is basically all existing ones.
		5233
4487	ones. With IEEE 754 doubles, you get microsecond accuracy until at least	5234	With IEEE 754 doubles, you get microsecond accuracy until at least the
4488	2200.	5235	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5236	is either obsolete or somebody patched it to use C<long double> or
		5237	something like that, just kidding).
4489		5238
4490	=back	5239	=back
4491		5240
4492	If you know of other additional requirements drop me a note.	5241	If you know of other additional requirements drop me a note.
4493		5242
…		…
4555	=item Processing ev_async_send: O(number_of_async_watchers)	5304	=item Processing ev_async_send: O(number_of_async_watchers)
4556		5305
4557	=item Processing signals: O(max_signal_number)	5306	=item Processing signals: O(max_signal_number)
4558		5307
4559	Sending involves a system call I<iff> there were no other C<ev_async_send>	5308	Sending involves a system call I<iff> there were no other C<ev_async_send>
4560	calls in the current loop iteration. Checking for async and signal events	5309	calls in the current loop iteration and the loop is currently
		5310	blocked. Checking for async and signal events involves iterating over all
4561	involves iterating over all running async watchers or all signal numbers.	5311	running async watchers or all signal numbers.
4562		5312
4563	=back	5313	=back
4564		5314
4565		5315
		5316	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5317
		5318	The major version 4 introduced some incompatible changes to the API.
		5319
		5320	At the moment, the C<ev.h> header file provides compatibility definitions
		5321	for all changes, so most programs should still compile. The compatibility
		5322	layer might be removed in later versions of libev, so better update to the
		5323	new API early than late.
		5324
		5325	=over 4
		5326
		5327	=item C<EV_COMPAT3> backwards compatibility mechanism
		5328
		5329	The backward compatibility mechanism can be controlled by
		5330	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5331	section.
		5332
		5333	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5334
		5335	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5336
		5337	ev_loop_destroy (EV_DEFAULT_UC);
		5338	ev_loop_fork (EV_DEFAULT);
		5339
		5340	=item function/symbol renames
		5341
		5342	A number of functions and symbols have been renamed:
		5343
		5344	ev_loop => ev_run
		5345	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5346	EVLOOP_ONESHOT => EVRUN_ONCE
		5347
		5348	ev_unloop => ev_break
		5349	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5350	EVUNLOOP_ONE => EVBREAK_ONE
		5351	EVUNLOOP_ALL => EVBREAK_ALL
		5352
		5353	EV_TIMEOUT => EV_TIMER
		5354
		5355	ev_loop_count => ev_iteration
		5356	ev_loop_depth => ev_depth
		5357	ev_loop_verify => ev_verify
		5358
		5359	Most functions working on C<struct ev_loop> objects don't have an
		5360	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5361	associated constants have been renamed to not collide with the C<struct
		5362	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5363	as all other watcher types. Note that C<ev_loop_fork> is still called
		5364	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5365	typedef.
		5366
		5367	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5368
		5369	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5370	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5371	and work, but the library code will of course be larger.
		5372
		5373	=back
		5374
		5375
4566	=head1 GLOSSARY	5376	=head1 GLOSSARY
4567		5377
4568	=over 4	5378	=over 4
4569		5379
4570	=item active	5380	=item active
4571		5381
4572	A watcher is active as long as it has been started (has been attached to	5382	A watcher is active as long as it has been started and not yet stopped.
4573	an event loop) but not yet stopped (disassociated from the event loop).	5383	See L<WATCHER STATES> for details.
4574		5384
4575	=item application	5385	=item application
4576		5386
4577	In this document, an application is whatever is using libev.	5387	In this document, an application is whatever is using libev.
		5388
		5389	=item backend
		5390
		5391	The part of the code dealing with the operating system interfaces.
4578		5392
4579	=item callback	5393	=item callback
4580		5394
4581	The address of a function that is called when some event has been	5395	The address of a function that is called when some event has been
4582	detected. Callbacks are being passed the event loop, the watcher that	5396	detected. Callbacks are being passed the event loop, the watcher that
4583	received the event, and the actual event bitset.	5397	received the event, and the actual event bitset.
4584		5398
4585	=item callback invocation	5399	=item callback/watcher invocation
4586		5400
4587	The act of calling the callback associated with a watcher.	5401	The act of calling the callback associated with a watcher.
4588		5402
4589	=item event	5403	=item event
4590		5404
4591	A change of state of some external event, such as data now being available	5405	A change of state of some external event, such as data now being available
4592	for reading on a file descriptor, time having passed or simply not having	5406	for reading on a file descriptor, time having passed or simply not having
4593	any other events happening anymore.	5407	any other events happening anymore.
4594		5408
4595	In libev, events are represented as single bits (such as C<EV_READ> or	5409	In libev, events are represented as single bits (such as C<EV_READ> or
4596	C<EV_TIMEOUT>).	5410	C<EV_TIMER>).
4597		5411
4598	=item event library	5412	=item event library
4599		5413
4600	A software package implementing an event model and loop.	5414	A software package implementing an event model and loop.
4601		5415
…		…
4609	The model used to describe how an event loop handles and processes	5423	The model used to describe how an event loop handles and processes
4610	watchers and events.	5424	watchers and events.
4611		5425
4612	=item pending	5426	=item pending
4613		5427
4614	A watcher is pending as soon as the corresponding event has been detected,	5428	A watcher is pending as soon as the corresponding event has been
4615	and stops being pending as soon as the watcher will be invoked or its	5429	detected. See L<WATCHER STATES> for details.
4616	pending status is explicitly cleared by the application.
4617
4618	A watcher can be pending, but not active. Stopping a watcher also clears
4619	its pending status.
4620		5430
4621	=item real time	5431	=item real time
4622		5432
4623	The physical time that is observed. It is apparently strictly monotonic :)	5433	The physical time that is observed. It is apparently strictly monotonic :)
4624		5434
4625	=item wall-clock time	5435	=item wall-clock time
4626		5436
4627	The time and date as shown on clocks. Unlike real time, it can actually	5437	The time and date as shown on clocks. Unlike real time, it can actually
4628	be wrong and jump forwards and backwards, e.g. when the you adjust your	5438	be wrong and jump forwards and backwards, e.g. when you adjust your
4629	clock.	5439	clock.
4630		5440
4631	=item watcher	5441	=item watcher
4632		5442
4633	A data structure that describes interest in certain events. Watchers need	5443	A data structure that describes interest in certain events. Watchers need
4634	to be started (attached to an event loop) before they can receive events.	5444	to be started (attached to an event loop) before they can receive events.
4635		5445
4636	=item watcher invocation
4637
4638	The act of calling the callback associated with a watcher.
4639
4640	=back	5446	=back
4641		5447
4642	=head1 AUTHOR	5448	=head1 AUTHOR
4643		5449
4644	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5450	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5451	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4645		5452

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