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Revision 1.369 by root, Mon May 30 18:34:28 2011 UTC

…		…
26	puts ("stdin ready");	26	puts ("stdin ready");
27	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
28	// with its corresponding stop function.	28	// with its corresponding stop function.
29	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
30		30
31	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_run's to stop iterating
32	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_break (EV_A_ EVBREAK_ALL);
33	}	33	}
34		34
35	// another callback, this time for a time-out	35	// another callback, this time for a time-out
36	static void	36	static void
37	timeout_cb (EV_P_ ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
38	{	38	{
39	puts ("timeout");	39	puts ("timeout");
40	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_run to stop iterating
41	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_break (EV_A_ EVBREAK_ONE);
42	}	42	}
43		43
44	int	44	int
45	main (void)	45	main (void)
46	{	46	{
47	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
48	struct ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = EV_DEFAULT;
49		49
50	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
51	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
53	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
…		…
56	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
58	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
59		59
60	// now wait for events to arrive	60	// now wait for events to arrive
61	ev_loop (loop, 0);	61	ev_run (loop, 0);
62		62
63	// unloop was called, so exit	63	// break was called, so exit
64	return 0;	64	return 0;
65	}	65	}
66		66
67	=head1 ABOUT THIS DOCUMENT	67	=head1 ABOUT THIS DOCUMENT
68		68
…		…
75	While this document tries to be as complete as possible in documenting	75	While this document tries to be as complete as possible in documenting
76	libev, its usage and the rationale behind its design, it is not a tutorial	76	libev, its usage and the rationale behind its design, it is not a tutorial
77	on event-based programming, nor will it introduce event-based programming	77	on event-based programming, nor will it introduce event-based programming
78	with libev.	78	with libev.
79		79
80	Familarity with event based programming techniques in general is assumed	80	Familiarity with event based programming techniques in general is assumed
81	throughout this document.	81	throughout this document.
		82
		83	=head1 WHAT TO READ WHEN IN A HURRY
		84
		85	This manual tries to be very detailed, but unfortunately, this also makes
		86	it very long. If you just want to know the basics of libev, I suggest
		87	reading L<ANATOMY OF A WATCHER>, then the L<EXAMPLE PROGRAM> above and
		88	look up the missing functions in L<GLOBAL FUNCTIONS> and the C<ev_io> and
		89	C<ev_timer> sections in L<WATCHER TYPES>.
82		90
83	=head1 ABOUT LIBEV	91	=head1 ABOUT LIBEV
84		92
85	Libev is an event loop: you register interest in certain events (such as a	93	Libev is an event loop: you register interest in certain events (such as a
86	file descriptor being readable or a timeout occurring), and it will manage	94	file descriptor being readable or a timeout occurring), and it will manage
…		…
124	this argument.	132	this argument.
125		133
126	=head2 TIME REPRESENTATION	134	=head2 TIME REPRESENTATION
127		135
128	Libev represents time as a single floating point number, representing	136	Libev represents time as a single floating point number, representing
129	the (fractional) number of seconds since the (POSIX) epoch (somewhere	137	the (fractional) number of seconds since the (POSIX) epoch (in practice
130	near the beginning of 1970, details are complicated, don't ask). This	138	somewhere near the beginning of 1970, details are complicated, don't
131	type is called C<ev_tstamp>, which is what you should use too. It usually	139	ask). This type is called C<ev_tstamp>, which is what you should use
132	aliases to the C<double> type in C. When you need to do any calculations	140	too. It usually aliases to the C<double> type in C. When you need to do
133	on it, you should treat it as some floating point value. Unlike the name	141	any calculations on it, you should treat it as some floating point value.
		142
134	component C<stamp> might indicate, it is also used for time differences	143	Unlike the name component C<stamp> might indicate, it is also used for
135	throughout libev.	144	time differences (e.g. delays) throughout libev.
136		145
137	=head1 ERROR HANDLING	146	=head1 ERROR HANDLING
138		147
139	Libev knows three classes of errors: operating system errors, usage errors	148	Libev knows three classes of errors: operating system errors, usage errors
140	and internal errors (bugs).	149	and internal errors (bugs).
…		…
164		173
165	=item ev_tstamp ev_time ()	174	=item ev_tstamp ev_time ()
166		175
167	Returns the current time as libev would use it. Please note that the	176	Returns the current time as libev would use it. Please note that the
168	C<ev_now> function is usually faster and also often returns the timestamp	177	C<ev_now> function is usually faster and also often returns the timestamp
169	you actually want to know.	178	you actually want to know. Also interesting is the combination of
		179	C<ev_update_now> and C<ev_now>.
170		180
171	=item ev_sleep (ev_tstamp interval)	181	=item ev_sleep (ev_tstamp interval)
172		182
173	Sleep for the given interval: The current thread will be blocked until	183	Sleep for the given interval: The current thread will be blocked until
174	either it is interrupted or the given time interval has passed. Basically	184	either it is interrupted or the given time interval has passed. Basically
…		…
191	as this indicates an incompatible change. Minor versions are usually	201	as this indicates an incompatible change. Minor versions are usually
192	compatible to older versions, so a larger minor version alone is usually	202	compatible to older versions, so a larger minor version alone is usually
193	not a problem.	203	not a problem.
194		204
195	Example: Make sure we haven't accidentally been linked against the wrong	205	Example: Make sure we haven't accidentally been linked against the wrong
196	version.	206	version (note, however, that this will not detect other ABI mismatches,
		207	such as LFS or reentrancy).
197		208
198	assert (("libev version mismatch",	209	assert (("libev version mismatch",
199	ev_version_major () == EV_VERSION_MAJOR	210	ev_version_major () == EV_VERSION_MAJOR
200	&& ev_version_minor () >= EV_VERSION_MINOR));	211	&& ev_version_minor () >= EV_VERSION_MINOR));
201		212
…		…
212	assert (("sorry, no epoll, no sex",	223	assert (("sorry, no epoll, no sex",
213	ev_supported_backends () & EVBACKEND_EPOLL));	224	ev_supported_backends () & EVBACKEND_EPOLL));
214		225
215	=item unsigned int ev_recommended_backends ()	226	=item unsigned int ev_recommended_backends ()
216		227
217	Return the set of all backends compiled into this binary of libev and also	228	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	229	also recommended for this platform, meaning it will work for most file
		230	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	231	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	232	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	233	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.	234	probe for if you specify no backends explicitly.
223		235
224	=item unsigned int ev_embeddable_backends ()	236	=item unsigned int ev_embeddable_backends ()
225		237
226	Returns the set of backends that are embeddable in other event loops. This	238	Returns the set of backends that are embeddable in other event loops. This
227	is the theoretical, all-platform, value. To find which backends	239	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	240	current system. To find which embeddable backends might be supported on
229	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	241	the current system, you would need to look at C<ev_embeddable_backends ()
230	recommended ones.	242	& ev_supported_backends ()>, likewise for recommended ones.
231		243
232	See the description of C<ev_embed> watchers for more info.	244	See the description of C<ev_embed> watchers for more info.
233		245
234	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	246	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
235		247
236	Sets the allocation function to use (the prototype is similar - the	248	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	249	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	250	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	251	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
265	}	277	}
266		278
267	...	279	...
268	ev_set_allocator (persistent_realloc);	280	ev_set_allocator (persistent_realloc);
269		281
270	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	282	=item ev_set_syserr_cb (void (*cb)(const char *msg))
271		283
272	Set the callback function to call on a retryable system call error (such	284	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	285	as failed select, poll, epoll_wait). The message is a printable string
274	indicating the system call or subsystem causing the problem. If this	286	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	287	callback is set, then libev will expect it to remedy the situation, no
…		…
287	}	299	}
288		300
289	...	301	...
290	ev_set_syserr_cb (fatal_error);	302	ev_set_syserr_cb (fatal_error);
291		303
		304	=item ev_feed_signal (int signum)
		305
		306	This function can be used to "simulate" a signal receive. It is completely
		307	safe to call this function at any time, from any context, including signal
		308	handlers or random threads.
		309
		310	Its main use is to customise signal handling in your process, especially
		311	in the presence of threads. For example, you could block signals
		312	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		313	creating any loops), and in one thread, use C<sigwait> or any other
		314	mechanism to wait for signals, then "deliver" them to libev by calling
		315	C<ev_feed_signal>.
		316
292	=back	317	=back
293		318
294	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	319	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
295		320
296	An event loop is described by a C<struct ev_loop *> (the C<struct>	321	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>	322	I<not> optional in this case unless libev 3 compatibility is disabled, as
298	I<function>).	323	libev 3 had an C<ev_loop> function colliding with the struct name).
299		324
300	The library knows two types of such loops, the I<default> loop, which	325	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	326	supports child process events, and dynamically created event loops which
302	not.	327	do not.
303		328
304	=over 4	329	=over 4
305		330
306	=item struct ev_loop *ev_default_loop (unsigned int flags)	331	=item struct ev_loop *ev_default_loop (unsigned int flags)
307		332
308	This will initialise the default event loop if it hasn't been initialised	333	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	334	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	335	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).	336	C<ev_loop_new>.
		337
		338	If the default loop is already initialised then this function simply
		339	returns it (and ignores the flags. If that is troubling you, check
		340	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		341	flags, which should almost always be C<0>, unless the caller is also the
		342	one calling C<ev_run> or otherwise qualifies as "the main program".
312		343
313	If you don't know what event loop to use, use the one returned from this	344	If you don't know what event loop to use, use the one returned from this
314	function.	345	function (or via the C<EV_DEFAULT> macro).
315		346
316	Note that this function is I<not> thread-safe, so if you want to use it	347	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,	348	from multiple threads, you have to employ some kind of mutex (note also
318	as loops cannot be shared easily between threads anyway).	349	that this case is unlikely, as loops cannot be shared easily between
		350	threads anyway).
319		351
320	The default loop is the only loop that can handle C<ev_signal> and	352	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	353	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	354	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	355	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	356	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
325	C<ev_default_init>.	357
		358	Example: This is the most typical usage.
		359
		360	if (!ev_default_loop (0))
		361	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		362
		363	Example: Restrict libev to the select and poll backends, and do not allow
		364	environment settings to be taken into account:
		365
		366	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		367
		368	=item struct ev_loop *ev_loop_new (unsigned int flags)
		369
		370	This will create and initialise a new event loop object. If the loop
		371	could not be initialised, returns false.
		372
		373	This function is thread-safe, and one common way to use libev with
		374	threads is indeed to create one loop per thread, and using the default
		375	loop in the "main" or "initial" thread.
326		376
327	The flags argument can be used to specify special behaviour or specific	377	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>).	378	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
329		379
330	The following flags are supported:	380	The following flags are supported:
…		…
345	useful to try out specific backends to test their performance, or to work	395	useful to try out specific backends to test their performance, or to work
346	around bugs.	396	around bugs.
347		397
348	=item C<EVFLAG_FORKCHECK>	398	=item C<EVFLAG_FORKCHECK>
349		399
350	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	400	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	401	make libev check for a fork in each iteration by enabling this flag.
352	enabling this flag.
353		402
354	This works by calling C<getpid ()> on every iteration of the loop,	403	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	404	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	405	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	406	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
…		…
366	environment variable.	415	environment variable.
367		416
368	=item C<EVFLAG_NOINOTIFY>	417	=item C<EVFLAG_NOINOTIFY>
369		418
370	When this flag is specified, then libev will not attempt to use the	419	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	420	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	421	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.	422	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
374		423
375	=item C<EVFLAG_SIGNALFD>	424	=item C<EVFLAG_SIGNALFD>
376		425
377	When this flag is specified, then libev will attempt to use the	426	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	427	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	428	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	429	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	430	handling with threads, as long as you properly block signals in your
382	threads that are not interested in handling them.	431	threads that are not interested in handling them.
383		432
384	Signalfd will not be used by default as this changes your signal mask, and	433	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	434	there are a lot of shoddy libraries and programs (glib's threadpool for
386	example) that can't properly initialise their signal masks.	435	example) that can't properly initialise their signal masks.
		436
		437	=item C<EVFLAG_NOSIGMASK>
		438
		439	When this flag is specified, then libev will avoid to modify the signal
		440	mask. Specifically, this means you ahve to make sure signals are unblocked
		441	when you want to receive them.
		442
		443	This behaviour is useful when you want to do your own signal handling, or
		444	want to handle signals only in specific threads and want to avoid libev
		445	unblocking the signals.
		446
		447	It's also required by POSIX in a threaded program, as libev calls
		448	C<sigprocmask>, whose behaviour is officially unspecified.
		449
		450	This flag's behaviour will become the default in future versions of libev.
387		451
388	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	452	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
389		453
390	This is your standard select(2) backend. Not I<completely> standard, as	454	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,	455	libev tries to roll its own fd_set with no limits on the number of fds,
…		…
419	=item C<EVBACKEND_EPOLL> (value 4, Linux)	483	=item C<EVBACKEND_EPOLL> (value 4, Linux)
420		484
421	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9	485	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
422	kernels).	486	kernels).
423		487
424	For few fds, this backend is a bit little slower than poll and select,	488	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	489	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),	490	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).	491	fd), epoll scales either O(1) or O(active_fds).
428		492
429	The epoll mechanism deserves honorable mention as the most misdesigned	493	The epoll mechanism deserves honorable mention as the most misdesigned
430	of the more advanced event mechanisms: mere annoyances include silently	494	of the more advanced event mechanisms: mere annoyances include silently
431	dropping file descriptors, requiring a system call per change per file	495	dropping file descriptors, requiring a system call per change per file
432	descriptor (and unnecessary guessing of parameters), problems with dup and	496	descriptor (and unnecessary guessing of parameters), problems with dup,
		497	returning before the timeout value, resulting in additional iterations
		498	(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	499	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	500	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	501	set, which can take considerable time (one syscall per file descriptor)
436	hard to detect.	502	and is of course hard to detect.
437		503
438	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	504	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
439	of course I<doesn't>, and epoll just loves to report events for totally	505	of course I<doesn't>, and epoll just loves to report events for totally
440	I<different> file descriptors (even already closed ones, so one cannot	506	I<different> file descriptors (even already closed ones, so one cannot
441	even remove them from the set) than registered in the set (especially	507	even remove them from the set) than registered in the set (especially
442	on SMP systems). Libev tries to counter these spurious notifications by	508	on SMP systems). Libev tries to counter these spurious notifications by
443	employing an additional generation counter and comparing that against the	509	employing an additional generation counter and comparing that against the
444	events to filter out spurious ones, recreating the set when required.	510	events to filter out spurious ones, recreating the set when required. Last
		511	not least, it also refuses to work with some file descriptors which work
		512	perfectly fine with C<select> (files, many character devices...).
		513
		514	Epoll is truly the train wreck analog among event poll mechanisms,
		515	a frankenpoll, cobbled together in a hurry, no thought to design or
		516	interaction with others.
445		517
446	While stopping, setting and starting an I/O watcher in the same iteration	518	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	519	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	520	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	521	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
515	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	587	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
516		588
517	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	589	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)).	590	it's really slow, but it still scales very well (O(active_fds)).
519		591
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	592	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	593	file descriptor per loop iteration. For small and medium numbers of file
526	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	594	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
527	might perform better.	595	might perform better.
528		596
529	On the positive side, with the exception of the spurious readiness	597	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	598	specification in all tests and is fully embeddable, which is a rare feat
532	OS-specific backends (I vastly prefer correctness over speed hacks).	599	among the OS-specific backends (I vastly prefer correctness over speed
		600	hacks).
		601
		602	On the negative side, the interface is I<bizarre> - so bizarre that
		603	even sun itself gets it wrong in their code examples: The event polling
		604	function sometimes returning events to the caller even though an error
		605	occurred, but with no indication whether it has done so or not (yes, it's
		606	even documented that way) - deadly for edge-triggered interfaces where
		607	you absolutely have to know whether an event occurred or not because you
		608	have to re-arm the watcher.
		609
		610	Fortunately libev seems to be able to work around these idiocies.
533		611
534	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	612	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
535	C<EVBACKEND_POLL>.	613	C<EVBACKEND_POLL>.
536		614
537	=item C<EVBACKEND_ALL>	615	=item C<EVBACKEND_ALL>
538		616
539	Try all backends (even potentially broken ones that wouldn't be tried	617	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	618	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
541	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	619	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
542		620
543	It is definitely not recommended to use this flag.	621	It is definitely not recommended to use this flag, use whatever
		622	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		623	at all.
		624
		625	=item C<EVBACKEND_MASK>
		626
		627	Not a backend at all, but a mask to select all backend bits from a
		628	C<flags> value, in case you want to mask out any backends from a flags
		629	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
544		630
545	=back	631	=back
546		632
547	If one or more of the backend flags are or'ed into the flags value,	633	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	634	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	635	here). If none are specified, all backends in C<ev_recommended_backends
550	()> will be tried.	636	()> will be tried.
551		637
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.	638	Example: Try to create a event loop that uses epoll and nothing else.
581		639
582	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	640	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
583	if (!epoller)	641	if (!epoller)
584	fatal ("no epoll found here, maybe it hides under your chair");	642	fatal ("no epoll found here, maybe it hides under your chair");
585		643
		644	Example: Use whatever libev has to offer, but make sure that kqueue is
		645	used if available.
		646
		647	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		648
586	=item ev_default_destroy ()	649	=item ev_loop_destroy (loop)
587		650
588	Destroys the default loop again (frees all memory and kernel state	651	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	652	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	653	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>	654	responsibility to either stop all watchers cleanly yourself I<before>
592	calling this function, or cope with the fact afterwards (which is usually	655	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	656	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
595		658
596	Note that certain global state, such as signal state (and installed signal	659	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	660	handlers), will not be freed by this function, and related watchers (such
598	as signal and child watchers) would need to be stopped manually.	661	as signal and child watchers) would need to be stopped manually.
599		662
600	In general it is not advisable to call this function except in the	663	This function is normally used on loop objects allocated by
601	rare occasion where you really need to free e.g. the signal handling	664	C<ev_loop_new>, but it can also be used on the default loop returned by
		665	C<ev_default_loop>, in which case it is not thread-safe.
		666
		667	Note that it is not advisable to call this function on the default loop
		668	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	669	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>.	670	and C<ev_loop_destroy>.
604		671
605	=item ev_loop_destroy (loop)	672	=item ev_loop_fork (loop)
606		673
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	674	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	675	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	676	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	677	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	678	child before resuming or calling C<ev_run>.
617	functions, and it will only take effect at the next C<ev_loop> iteration.	679
		680	Again, you I<have> to call it on I<any> loop that you want to re-use after
		681	a fork, I<even if you do not plan to use the loop in the parent>. This is
		682	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		683	during fork.
618		684
619	On the other hand, you only need to call this function in the child	685	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	686	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.	687	you just fork+exec or create a new loop in the child, you don't have to
		688	call it at all (in fact, C<epoll> is so badly broken that it makes a
		689	difference, but libev will usually detect this case on its own and do a
		690	costly reset of the backend).
622		691
623	The function itself is quite fast and it's usually not a problem to call	692	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	693	it just in case after a fork.
625	quite nicely into a call to C<pthread_atfork>:
626		694
		695	Example: Automate calling C<ev_loop_fork> on the default loop when
		696	using pthreads.
		697
		698	static void
		699	post_fork_child (void)
		700	{
		701	ev_loop_fork (EV_DEFAULT);
		702	}
		703
		704	...
627	pthread_atfork (0, 0, ev_default_fork);	705	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		706
636	=item int ev_is_default_loop (loop)	707	=item int ev_is_default_loop (loop)
637		708
638	Returns true when the given loop is, in fact, the default loop, and false	709	Returns true when the given loop is, in fact, the default loop, and false
639	otherwise.	710	otherwise.
640		711
641	=item unsigned int ev_loop_count (loop)	712	=item unsigned int ev_iteration (loop)
642		713
643	Returns the count of loop iterations for the loop, which is identical to	714	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	715	to the number of times libev did poll for new events. It starts at C<0>
645	happily wraps around with enough iterations.	716	and happily wraps around with enough iterations.
646		717
647	This value can sometimes be useful as a generation counter of sorts (it	718	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	719	"ticks" the number of loop iterations), as it roughly corresponds with
649	C<ev_prepare> and C<ev_check> calls.	720	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		721	prepare and check phases.
650		722
651	=item unsigned int ev_loop_depth (loop)	723	=item unsigned int ev_depth (loop)
652		724
653	Returns the number of times C<ev_loop> was entered minus the number of	725	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.	726	times C<ev_run> was exited normally, in other words, the recursion depth.
655		727
656	Outside C<ev_loop>, this number is zero. In a callback, this number is	728	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),	729	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
658	in which case it is higher.	730	in which case it is higher.
659		731
660	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread	732	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
661	etc.), doesn't count as exit.	733	throwing an exception etc.), doesn't count as "exit" - consider this
		734	as a hint to avoid such ungentleman-like behaviour unless it's really
		735	convenient, in which case it is fully supported.
662		736
663	=item unsigned int ev_backend (loop)	737	=item unsigned int ev_backend (loop)
664		738
665	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	739	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
666	use.	740	use.
…		…
675		749
676	=item ev_now_update (loop)	750	=item ev_now_update (loop)
677		751
678	Establishes the current time by querying the kernel, updating the time	752	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	753	returned by C<ev_now ()> in the progress. This is a costly operation and
680	is usually done automatically within C<ev_loop ()>.	754	is usually done automatically within C<ev_run ()>.
681		755
682	This function is rarely useful, but when some event callback runs for a	756	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	757	very long time without entering the event loop, updating libev's idea of
684	the current time is a good idea.	758	the current time is a good idea.
685		759
…		…
687		761
688	=item ev_suspend (loop)	762	=item ev_suspend (loop)
689		763
690	=item ev_resume (loop)	764	=item ev_resume (loop)
691		765
692	These two functions suspend and resume a loop, for use when the loop is	766	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.	767	loop is not used for a while and timeouts should not be processed.
694		768
695	A typical use case would be an interactive program such as a game: When	769	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	770	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	771	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>	772	the program was suspended. This can be achieved by calling C<ev_suspend>
…		…
700	C<ev_resume> directly afterwards to resume timer processing.	774	C<ev_resume> directly afterwards to resume timer processing.
701		775
702	Effectively, all C<ev_timer> watchers will be delayed by the time spend	776	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	777	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	778	will be rescheduled (that is, they will lose any events that would have
705	occured while suspended).	779	occurred while suspended).
706		780
707	After calling C<ev_suspend> you B<must not> call I<any> function on the	781	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>	782	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>.	783	without a previous call to C<ev_suspend>.
710		784
711	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	785	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
712	event loop time (see C<ev_now_update>).	786	event loop time (see C<ev_now_update>).
713		787
714	=item ev_loop (loop, int flags)	788	=item ev_run (loop, int flags)
715		789
716	Finally, this is it, the event handler. This function usually is called	790	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	791	after you have initialised all your watchers and you want to start
718	handling events.	792	handling events. It will ask the operating system for any new events, call
		793	the watcher callbacks, an then repeat the whole process indefinitely: This
		794	is why event loops are called I<loops>.
719		795
720	If the flags argument is specified as C<0>, it will not return until	796	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.	797	until either no event watchers are active anymore or C<ev_break> was
		798	called.
722		799
723	Please note that an explicit C<ev_unloop> is usually better than	800	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	801	relying on all watchers to be stopped when deciding when a program has
725	finished (especially in interactive programs), but having a program	802	finished (especially in interactive programs), but having a program
726	that automatically loops as long as it has to and no longer by virtue	803	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	804	of relying on its watchers stopping correctly, that is truly a thing of
728	beauty.	805	beauty.
729		806
		807	This function is also I<mostly> exception-safe - you can break out of
		808	a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		809	exception and so on. This does not decrement the C<ev_depth> value, nor
		810	will it clear any outstanding C<EVBREAK_ONE> breaks.
		811
730	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	812	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	813	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	814	block your process in case there are no events and will return after one
733	the loop.	815	iteration of the loop. This is sometimes useful to poll and handle new
		816	events while doing lengthy calculations, to keep the program responsive.
734		817
735	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	818	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	819	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	820	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	821	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	822	user-registered callback will be called), and will return after one
740	iteration of the loop.	823	iteration of the loop.
741		824
742	This is useful if you are waiting for some external event in conjunction	825	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	826	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	827	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.	828	usually a better approach for this kind of thing.
746		829
747	Here are the gory details of what C<ev_loop> does:	830	Here are the gory details of what C<ev_run> does (this is for your
		831	understanding, not a guarantee that things will work exactly like this in
		832	future versions):
748		833
		834	- Increment loop depth.
		835	- Reset the ev_break status.
749	- Before the first iteration, call any pending watchers.	836	- Before the first iteration, call any pending watchers.
		837	LOOP:
750	* If EVFLAG_FORKCHECK was used, check for a fork.	838	- If EVFLAG_FORKCHECK was used, check for a fork.
751	- If a fork was detected (by any means), queue and call all fork watchers.	839	- If a fork was detected (by any means), queue and call all fork watchers.
752	- Queue and call all prepare watchers.	840	- Queue and call all prepare watchers.
		841	- If ev_break was called, goto FINISH.
753	- If we have been forked, detach and recreate the kernel state	842	- If we have been forked, detach and recreate the kernel state
754	as to not disturb the other process.	843	as to not disturb the other process.
755	- Update the kernel state with all outstanding changes.	844	- Update the kernel state with all outstanding changes.
756	- Update the "event loop time" (ev_now ()).	845	- Update the "event loop time" (ev_now ()).
757	- Calculate for how long to sleep or block, if at all	846	- Calculate for how long to sleep or block, if at all
758	(active idle watchers, EVLOOP_NONBLOCK or not having	847	(active idle watchers, EVRUN_NOWAIT or not having
759	any active watchers at all will result in not sleeping).	848	any active watchers at all will result in not sleeping).
760	- Sleep if the I/O and timer collect interval say so.	849	- Sleep if the I/O and timer collect interval say so.
		850	- Increment loop iteration counter.
761	- Block the process, waiting for any events.	851	- Block the process, waiting for any events.
762	- Queue all outstanding I/O (fd) events.	852	- Queue all outstanding I/O (fd) events.
763	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	853	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
764	- Queue all expired timers.	854	- Queue all expired timers.
765	- Queue all expired periodics.	855	- Queue all expired periodics.
766	- Unless any events are pending now, queue all idle watchers.	856	- Queue all idle watchers with priority higher than that of pending events.
767	- Queue all check watchers.	857	- Queue all check watchers.
768	- Call all queued watchers in reverse order (i.e. check watchers first).	858	- 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	859	Signals and child watchers are implemented as I/O watchers, and will
770	be handled here by queueing them when their watcher gets executed.	860	be handled here by queueing them when their watcher gets executed.
771	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	861	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
772	were used, or there are no active watchers, return, otherwise	862	were used, or there are no active watchers, goto FINISH, otherwise
773	continue with step *.	863	continue with step LOOP.
		864	FINISH:
		865	- Reset the ev_break status iff it was EVBREAK_ONE.
		866	- Decrement the loop depth.
		867	- Return.
774		868
775	Example: Queue some jobs and then loop until no events are outstanding	869	Example: Queue some jobs and then loop until no events are outstanding
776	anymore.	870	anymore.
777		871
778	... queue jobs here, make sure they register event watchers as long	872	... 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..)	873	... as they still have work to do (even an idle watcher will do..)
780	ev_loop (my_loop, 0);	874	ev_run (my_loop, 0);
781	... jobs done or somebody called unloop. yeah!	875	... jobs done or somebody called break. yeah!
782		876
783	=item ev_unloop (loop, how)	877	=item ev_break (loop, how)
784		878
785	Can be used to make a call to C<ev_loop> return early (but only after it	879	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	880	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	881	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.	882	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
789		883
790	This "unloop state" will be cleared when entering C<ev_loop> again.	884	This "break state" will be cleared on the next call to C<ev_run>.
791		885
792	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	886	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		887	which case it will have no effect.
793		888
794	=item ev_ref (loop)	889	=item ev_ref (loop)
795		890
796	=item ev_unref (loop)	891	=item ev_unref (loop)
797		892
798	Ref/unref can be used to add or remove a reference count on the event	893	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	894	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.	895	count is nonzero, C<ev_run> will not return on its own.
801		896
802	This is useful when you have a watcher that you never intend to	897	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	898	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>	899	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
805	before stopping it.	900	before stopping it.
806		901
807	As an example, libev itself uses this for its internal signal pipe: It	902	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	903	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	904	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	905	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	906	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	907	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	908	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>	909	(e.g. non-repeating timers) in which case you have to C<ev_ref>
815	in the callback).	910	in the callback).
816		911
817	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	912	Example: Create a signal watcher, but keep it from keeping C<ev_run>
818	running when nothing else is active.	913	running when nothing else is active.
819		914
820	ev_signal exitsig;	915	ev_signal exitsig;
821	ev_signal_init (&exitsig, sig_cb, SIGINT);	916	ev_signal_init (&exitsig, sig_cb, SIGINT);
822	ev_signal_start (loop, &exitsig);	917	ev_signal_start (loop, &exitsig);
823	evf_unref (loop);	918	ev_unref (loop);
824		919
825	Example: For some weird reason, unregister the above signal handler again.	920	Example: For some weird reason, unregister the above signal handler again.
826		921
827	ev_ref (loop);	922	ev_ref (loop);
828	ev_signal_stop (loop, &exitsig);	923	ev_signal_stop (loop, &exitsig);
…		…
867	usually doesn't make much sense to set it to a lower value than C<0.01>,	962	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	963	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	964	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	965	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,	966	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).	967	then you can't do more than 100 transactions per second).
873		968
874	Setting the I<timeout collect interval> can improve the opportunity for	969	Setting the I<timeout collect interval> can improve the opportunity for
875	saving power, as the program will "bundle" timer callback invocations that	970	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	971	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	972	times the process sleeps and wakes up again. Another useful technique to
…		…
885	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	980	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
886		981
887	=item ev_invoke_pending (loop)	982	=item ev_invoke_pending (loop)
888		983
889	This call will simply invoke all pending watchers while resetting their	984	This call will simply invoke all pending watchers while resetting their
890	pending state. Normally, C<ev_loop> does this automatically when required,	985	pending state. Normally, C<ev_run> does this automatically when required,
891	but when overriding the invoke callback this call comes handy.	986	but when overriding the invoke callback this call comes handy. This
		987	function can be invoked from a watcher - this can be useful for example
		988	when you want to do some lengthy calculation and want to pass further
		989	event handling to another thread (you still have to make sure only one
		990	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
892		991
893	=item int ev_pending_count (loop)	992	=item int ev_pending_count (loop)
894		993
895	Returns the number of pending watchers - zero indicates that no watchers	994	Returns the number of pending watchers - zero indicates that no watchers
896	are pending.	995	are pending.
897		996
898	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))	997	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
899		998
900	This overrides the invoke pending functionality of the loop: Instead of	999	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	1000	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	1001	this callback instead. This is useful, for example, when you want to
903	invoke the actual watchers inside another context (another thread etc.).	1002	invoke the actual watchers inside another context (another thread etc.).
904		1003
905	If you want to reset the callback, use C<ev_invoke_pending> as new	1004	If you want to reset the callback, use C<ev_invoke_pending> as new
906	callback.	1005	callback.
…		…
909		1008
910	Sometimes you want to share the same loop between multiple threads. This	1009	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	1010	can be done relatively simply by putting mutex_lock/unlock calls around
912	each call to a libev function.	1011	each call to a libev function.
913		1012
914	However, C<ev_loop> can run an indefinite time, so it is not feasible to	1013	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	1014	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>	1015	loop via C<ev_break> and C<av_async_send>, another way is to set these
917	and I<acquire> callbacks on the loop.	1016	I<release> and I<acquire> callbacks on the loop.
918		1017
919	When set, then C<release> will be called just before the thread is	1018	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	1019	suspended waiting for new events, and C<acquire> is called just
921	afterwards.	1020	afterwards.
922		1021
…		…
925		1024
926	While event loop modifications are allowed between invocations of	1025	While event loop modifications are allowed between invocations of
927	C<release> and C<acquire> (that's their only purpose after all), no	1026	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	1027	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	1028	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	1029	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.	1030	to take note of any changes you made.
932		1031
933	In theory, threads executing C<ev_loop> will be async-cancel safe between	1032	In theory, threads executing C<ev_run> will be async-cancel safe between
934	invocations of C<release> and C<acquire>.	1033	invocations of C<release> and C<acquire>.
935		1034
936	See also the locking example in the C<THREADS> section later in this	1035	See also the locking example in the C<THREADS> section later in this
937	document.	1036	document.
938		1037
939	=item ev_set_userdata (loop, void *data)	1038	=item ev_set_userdata (loop, void *data)
940		1039
941	=item ev_userdata (loop)	1040	=item void *ev_userdata (loop)
942		1041
943	Set and retrieve a single C<void *> associated with a loop. When	1042	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	1043	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
945	C<0.>	1044	C<0>.
946		1045
947	These two functions can be used to associate arbitrary data with a loop,	1046	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	1047	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	1048	C<acquire> callbacks described above, but of course can be (ab-)used for
950	any other purpose as well.	1049	any other purpose as well.
951		1050
952	=item ev_loop_verify (loop)	1051	=item ev_verify (loop)
953		1052
954	This function only does something when C<EV_VERIFY> support has been	1053	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	1054	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	1055	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	1056	is found to be inconsistent, it will print an error message to standard
…		…
968		1067
969	In the following description, uppercase C<TYPE> in names stands for the	1068	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	1069	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.	1070	watchers and C<ev_io_start> for I/O watchers.
972		1071
973	A watcher is a structure that you create and register to record your	1072	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	1073	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:	1074	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1075	for that:
976		1076
977	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1077	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
978	{	1078	{
979	ev_io_stop (w);	1079	ev_io_stop (w);
980	ev_unloop (loop, EVUNLOOP_ALL);	1080	ev_break (loop, EVBREAK_ALL);
981	}	1081	}
982		1082
983	struct ev_loop *loop = ev_default_loop (0);	1083	struct ev_loop *loop = ev_default_loop (0);
984		1084
985	ev_io stdin_watcher;	1085	ev_io stdin_watcher;
986		1086
987	ev_init (&stdin_watcher, my_cb);	1087	ev_init (&stdin_watcher, my_cb);
988	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1088	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
989	ev_io_start (loop, &stdin_watcher);	1089	ev_io_start (loop, &stdin_watcher);
990		1090
991	ev_loop (loop, 0);	1091	ev_run (loop, 0);
992		1092
993	As you can see, you are responsible for allocating the memory for your	1093	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	1094	watcher structures (and it is I<usually> a bad idea to do this on the
995	stack).	1095	stack).
996		1096
997	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1097	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).	1098	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
999		1099
1000	Each watcher structure must be initialised by a call to C<ev_init	1100	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	1101	*, 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	1102	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	1103	time the event loop detects that the file descriptor given is readable
1004	is readable and/or writable).	1104	and/or writable).
1005		1105
1006	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1106	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	1107	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<<	1108	is also a macro to combine initialisation and setting in one call: C<<
1009	ev_TYPE_init (watcher *, callback, ...) >>.	1109	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
1032	=item C<EV_WRITE>	1132	=item C<EV_WRITE>
1033		1133
1034	The file descriptor in the C<ev_io> watcher has become readable and/or	1134	The file descriptor in the C<ev_io> watcher has become readable and/or
1035	writable.	1135	writable.
1036		1136
1037	=item C<EV_TIMEOUT>	1137	=item C<EV_TIMER>
1038		1138
1039	The C<ev_timer> watcher has timed out.	1139	The C<ev_timer> watcher has timed out.
1040		1140
1041	=item C<EV_PERIODIC>	1141	=item C<EV_PERIODIC>
1042		1142
…		…
1060		1160
1061	=item C<EV_PREPARE>	1161	=item C<EV_PREPARE>
1062		1162
1063	=item C<EV_CHECK>	1163	=item C<EV_CHECK>
1064		1164
1065	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1165	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	1166	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	1167	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	1168	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	1169	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	1170	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
1071	C<ev_loop> from blocking).	1171	C<ev_run> from blocking).
1072		1172
1073	=item C<EV_EMBED>	1173	=item C<EV_EMBED>
1074		1174
1075	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1175	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1076		1176
1077	=item C<EV_FORK>	1177	=item C<EV_FORK>
1078		1178
1079	The event loop has been resumed in the child process after fork (see	1179	The event loop has been resumed in the child process after fork (see
1080	C<ev_fork>).	1180	C<ev_fork>).
		1181
		1182	=item C<EV_CLEANUP>
		1183
		1184	The event loop is about to be destroyed (see C<ev_cleanup>).
1081		1185
1082	=item C<EV_ASYNC>	1186	=item C<EV_ASYNC>
1083		1187
1084	The given async watcher has been asynchronously notified (see C<ev_async>).	1188	The given async watcher has been asynchronously notified (see C<ev_async>).
1085		1189
…		…
1258	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related	1362	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1259	functions that do not need a watcher.	1363	functions that do not need a watcher.
1260		1364
1261	=back	1365	=back
1262		1366
		1367	See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR
		1368	OWN COMPOSITE WATCHERS> idioms.
1263		1369
1264	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1370	=head2 WATCHER STATES
1265		1371
1266	Each watcher has, by default, a member C<void *data> that you can change	1372	There are various watcher states mentioned throughout this manual -
1267	and read at any time: libev will completely ignore it. This can be used	1373	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	1374	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	1375	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		1376
1273	struct my_io	1377	=over 4
1274	{
1275	ev_io io;
1276	int otherfd;
1277	void *somedata;
1278	struct whatever *mostinteresting;
1279	};
1280		1378
1281	...	1379	=item initialiased
1282	struct my_io w;
1283	ev_io_init (&w.io, my_cb, fd, EV_READ);
1284		1380
1285	And since your callback will be called with a pointer to the watcher, you	1381	Before a watcher can be registered with the event looop it has to be
1286	can cast it back to your own type:	1382	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1383	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1287		1384
1288	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)	1385	In this state it is simply some block of memory that is suitable for
1289	{	1386	use in an event loop. It can be moved around, freed, reused etc. at
1290	struct my_io *w = (struct my_io *)w_;	1387	will - as long as you either keep the memory contents intact, or call
1291	...	1388	C<ev_TYPE_init> again.
1292	}
1293		1389
1294	More interesting and less C-conformant ways of casting your callback type	1390	=item started/running/active
1295	instead have been omitted.
1296		1391
1297	Another common scenario is to use some data structure with multiple	1392	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1298	embedded watchers:	1393	property of the event loop, and is actively waiting for events. While in
		1394	this state it cannot be accessed (except in a few documented ways), moved,
		1395	freed or anything else - the only legal thing is to keep a pointer to it,
		1396	and call libev functions on it that are documented to work on active watchers.
1299		1397
1300	struct my_biggy	1398	=item pending
1301	{
1302	int some_data;
1303	ev_timer t1;
1304	ev_timer t2;
1305	}
1306		1399
1307	In this case getting the pointer to C<my_biggy> is a bit more	1400	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	1401	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	1402	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	1403	about to be invoked, so it is not normally pending inside the watcher
1311	programmers):	1404	callback.
1312		1405
1313	#include <stddef.h>	1406	The watcher might or might not be active while it is pending (for example,
		1407	an expired non-repeating timer can be pending but no longer active). If it
		1408	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1409	but it is still property of the event loop at this time, so cannot be
		1410	moved, freed or reused. And if it is active the rules described in the
		1411	previous item still apply.
1314		1412
1315	static void	1413	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)	1414	via C<ev_feed_event>), in which case it becomes pending without being
1317	{	1415	active.
1318	struct my_biggy big = (struct my_biggy *)
1319	(((char *)w) - offsetof (struct my_biggy, t1));
1320	}
1321		1416
1322	static void	1417	=item stopped
1323	t2_cb (EV_P_ ev_timer *w, int revents)	1418
1324	{	1419	A watcher can be stopped implicitly by libev (in which case it might still
1325	struct my_biggy big = (struct my_biggy *)	1420	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1326	(((char *)w) - offsetof (struct my_biggy, t2));	1421	latter will clear any pending state the watcher might be in, regardless
1327	}	1422	of whether it was active or not, so stopping a watcher explicitly before
		1423	freeing it is often a good idea.
		1424
		1425	While stopped (and not pending) the watcher is essentially in the
		1426	initialised state, that is, it can be reused, moved, modified in any way
		1427	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1428	it again).
		1429
		1430	=back
1328		1431
1329	=head2 WATCHER PRIORITY MODELS	1432	=head2 WATCHER PRIORITY MODELS
1330		1433
1331	Many event loops support I<watcher priorities>, which are usually small	1434	Many event loops support I<watcher priorities>, which are usually small
1332	integers that influence the ordering of event callback invocation	1435	integers that influence the ordering of event callback invocation
…		…
1375		1478
1376	For example, to emulate how many other event libraries handle priorities,	1479	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	1480	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	1481	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	1482	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	1483	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	1484	the lock-out case is known to be rare (which in turn is rare :), this is
1382	workable.	1485	workable.
1383		1486
1384	Usually, however, the lock-out model implemented that way will perform	1487	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,	1488	miserably under the type of load it was designed to handle. In that case,
…		…
1399	{	1502	{
1400	// stop the I/O watcher, we received the event, but	1503	// stop the I/O watcher, we received the event, but
1401	// are not yet ready to handle it.	1504	// are not yet ready to handle it.
1402	ev_io_stop (EV_A_ w);	1505	ev_io_stop (EV_A_ w);
1403		1506
1404	// start the idle watcher to ahndle the actual event.	1507	// start the idle watcher to handle the actual event.
1405	// it will not be executed as long as other watchers	1508	// it will not be executed as long as other watchers
1406	// with the default priority are receiving events.	1509	// with the default priority are receiving events.
1407	ev_idle_start (EV_A_ &idle);	1510	ev_idle_start (EV_A_ &idle);
1408	}	1511	}
1409		1512
…		…
1459	In general you can register as many read and/or write event watchers per	1562	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	1563	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	1564	descriptors to non-blocking mode is also usually a good idea (but not
1462	required if you know what you are doing).	1565	required if you know what you are doing).
1463		1566
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	1567	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	1568	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	1569	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	1570	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	1571	with a relatively standard program structure. Thus it is best to always
1475	this situation even with a relatively standard program structure. Thus	1572	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.	1573	preferable to a program hanging until some data arrives.
1478		1574
1479	If you cannot run the fd in non-blocking mode (for example you should	1575	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	1576	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	1577	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	1578	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	1579	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	1580	use C<SIGALRM> and an interval timer, just to be sure you won't block
1485	indefinitely.	1581	indefinitely.
1486		1582
1487	But really, best use non-blocking mode.	1583	But really, best use non-blocking mode.
1488		1584
…		…
1516		1612
1517	There is no workaround possible except not registering events	1613	There is no workaround possible except not registering events
1518	for potentially C<dup ()>'ed file descriptors, or to resort to	1614	for potentially C<dup ()>'ed file descriptors, or to resort to
1519	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1615	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1520		1616
		1617	=head3 The special problem of files
		1618
		1619	Many people try to use C<select> (or libev) on file descriptors
		1620	representing files, and expect it to become ready when their program
		1621	doesn't block on disk accesses (which can take a long time on their own).
		1622
		1623	However, this cannot ever work in the "expected" way - you get a readiness
		1624	notification as soon as the kernel knows whether and how much data is
		1625	there, and in the case of open files, that's always the case, so you
		1626	always get a readiness notification instantly, and your read (or possibly
		1627	write) will still block on the disk I/O.
		1628
		1629	Another way to view it is that in the case of sockets, pipes, character
		1630	devices and so on, there is another party (the sender) that delivers data
		1631	on its own, but in the case of files, there is no such thing: the disk
		1632	will not send data on its own, simply because it doesn't know what you
		1633	wish to read - you would first have to request some data.
		1634
		1635	Since files are typically not-so-well supported by advanced notification
		1636	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1637	to files, even though you should not use it. The reason for this is
		1638	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1639	usually a tty, often a pipe, but also sometimes files or special devices
		1640	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1641	F</dev/urandom>), and even though the file might better be served with
		1642	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1643	it "just works" instead of freezing.
		1644
		1645	So avoid file descriptors pointing to files when you know it (e.g. use
		1646	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1647	when you rarely read from a file instead of from a socket, and want to
		1648	reuse the same code path.
		1649
1521	=head3 The special problem of fork	1650	=head3 The special problem of fork
1522		1651
1523	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1652	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	1653	useless behaviour. Libev fully supports fork, but needs to be told about
1525	it in the child.	1654	it in the child if you want to continue to use it in the child.
1526		1655
1527	To support fork in your programs, you either have to call	1656	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,	1657	()> 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	1658	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1530	C<EVBACKEND_POLL>.
1531		1659
1532	=head3 The special problem of SIGPIPE	1660	=head3 The special problem of SIGPIPE
1533		1661
1534	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1662	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	1663	when writing to a pipe whose other end has been closed, your program gets
…		…
1541	somewhere, as that would have given you a big clue).	1669	somewhere, as that would have given you a big clue).
1542		1670
1543	=head3 The special problem of accept()ing when you can't	1671	=head3 The special problem of accept()ing when you can't
1544		1672
1545	Many implementations of the POSIX C<accept> function (for example,	1673	Many implementations of the POSIX C<accept> function (for example,
1546	found in port-2004 Linux) have the peculiar behaviour of not removing a	1674	found in post-2004 Linux) have the peculiar behaviour of not removing a
1547	connection from the pending queue in all error cases.	1675	connection from the pending queue in all error cases.
1548		1676
1549	For example, larger servers often run out of file descriptors (because	1677	For example, larger servers often run out of file descriptors (because
1550	of resource limits), causing C<accept> to fail with C<ENFILE> but not	1678	of resource limits), causing C<accept> to fail with C<ENFILE> but not
1551	rejecting the connection, leading to libev signalling readiness on	1679	rejecting the connection, leading to libev signalling readiness on
…		…
1617	...	1745	...
1618	struct ev_loop *loop = ev_default_init (0);	1746	struct ev_loop *loop = ev_default_init (0);
1619	ev_io stdin_readable;	1747	ev_io stdin_readable;
1620	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1748	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1621	ev_io_start (loop, &stdin_readable);	1749	ev_io_start (loop, &stdin_readable);
1622	ev_loop (loop, 0);	1750	ev_run (loop, 0);
1623		1751
1624		1752
1625	=head2 C<ev_timer> - relative and optionally repeating timeouts	1753	=head2 C<ev_timer> - relative and optionally repeating timeouts
1626		1754
1627	Timer watchers are simple relative timers that generate an event after a	1755	Timer watchers are simple relative timers that generate an event after a
…		…
1636	The callback is guaranteed to be invoked only I<after> its timeout has	1764	The callback is guaranteed to be invoked only I<after> its timeout has
1637	passed (not I<at>, so on systems with very low-resolution clocks this	1765	passed (not I<at>, so on systems with very low-resolution clocks this
1638	might introduce a small delay). If multiple timers become ready during the	1766	might introduce a small delay). If multiple timers become ready during the
1639	same loop iteration then the ones with earlier time-out values are invoked	1767	same loop iteration then the ones with earlier time-out values are invoked
1640	before ones of the same priority with later time-out values (but this is	1768	before ones of the same priority with later time-out values (but this is
1641	no longer true when a callback calls C<ev_loop> recursively).	1769	no longer true when a callback calls C<ev_run> recursively).
1642		1770
1643	=head3 Be smart about timeouts	1771	=head3 Be smart about timeouts
1644		1772
1645	Many real-world problems involve some kind of timeout, usually for error	1773	Many real-world problems involve some kind of timeout, usually for error
1646	recovery. A typical example is an HTTP request - if the other side hangs,	1774	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1732	ev_tstamp timeout = last_activity + 60.;	1860	ev_tstamp timeout = last_activity + 60.;
1733		1861
1734	// if last_activity + 60. is older than now, we did time out	1862	// if last_activity + 60. is older than now, we did time out
1735	if (timeout < now)	1863	if (timeout < now)
1736	{	1864	{
1737	// timeout occured, take action	1865	// timeout occurred, take action
1738	}	1866	}
1739	else	1867	else
1740	{	1868	{
1741	// callback was invoked, but there was some activity, re-arm	1869	// callback was invoked, but there was some activity, re-arm
1742	// the watcher to fire in last_activity + 60, which is	1870	// the watcher to fire in last_activity + 60, which is
…		…
1764	to the current time (meaning we just have some activity :), then call the	1892	to the current time (meaning we just have some activity :), then call the
1765	callback, which will "do the right thing" and start the timer:	1893	callback, which will "do the right thing" and start the timer:
1766		1894
1767	ev_init (timer, callback);	1895	ev_init (timer, callback);
1768	last_activity = ev_now (loop);	1896	last_activity = ev_now (loop);
1769	callback (loop, timer, EV_TIMEOUT);	1897	callback (loop, timer, EV_TIMER);
1770		1898
1771	And when there is some activity, simply store the current time in	1899	And when there is some activity, simply store the current time in
1772	C<last_activity>, no libev calls at all:	1900	C<last_activity>, no libev calls at all:
1773		1901
1774	last_actiivty = ev_now (loop);	1902	last_activity = ev_now (loop);
1775		1903
1776	This technique is slightly more complex, but in most cases where the	1904	This technique is slightly more complex, but in most cases where the
1777	time-out is unlikely to be triggered, much more efficient.	1905	time-out is unlikely to be triggered, much more efficient.
1778		1906
1779	Changing the timeout is trivial as well (if it isn't hard-coded in the	1907	Changing the timeout is trivial as well (if it isn't hard-coded in the
…		…
1817		1945
1818	=head3 The special problem of time updates	1946	=head3 The special problem of time updates
1819		1947
1820	Establishing the current time is a costly operation (it usually takes at	1948	Establishing the current time is a costly operation (it usually takes at
1821	least two system calls): EV therefore updates its idea of the current	1949	least two system calls): EV therefore updates its idea of the current
1822	time only before and after C<ev_loop> collects new events, which causes a	1950	time only before and after C<ev_run> collects new events, which causes a
1823	growing difference between C<ev_now ()> and C<ev_time ()> when handling	1951	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1824	lots of events in one iteration.	1952	lots of events in one iteration.
1825		1953
1826	The relative timeouts are calculated relative to the C<ev_now ()>	1954	The relative timeouts are calculated relative to the C<ev_now ()>
1827	time. This is usually the right thing as this timestamp refers to the time	1955	time. This is usually the right thing as this timestamp refers to the time
…		…
1944	}	2072	}
1945		2073
1946	ev_timer mytimer;	2074	ev_timer mytimer;
1947	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2075	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1948	ev_timer_again (&mytimer); /* start timer */	2076	ev_timer_again (&mytimer); /* start timer */
1949	ev_loop (loop, 0);	2077	ev_run (loop, 0);
1950		2078
1951	// and in some piece of code that gets executed on any "activity":	2079	// and in some piece of code that gets executed on any "activity":
1952	// reset the timeout to start ticking again at 10 seconds	2080	// reset the timeout to start ticking again at 10 seconds
1953	ev_timer_again (&mytimer);	2081	ev_timer_again (&mytimer);
1954		2082
…		…
1980		2108
1981	As with timers, the callback is guaranteed to be invoked only when the	2109	As with timers, the callback is guaranteed to be invoked only when the
1982	point in time where it is supposed to trigger has passed. If multiple	2110	point in time where it is supposed to trigger has passed. If multiple
1983	timers become ready during the same loop iteration then the ones with	2111	timers become ready during the same loop iteration then the ones with
1984	earlier time-out values are invoked before ones with later time-out values	2112	earlier time-out values are invoked before ones with later time-out values
1985	(but this is no longer true when a callback calls C<ev_loop> recursively).	2113	(but this is no longer true when a callback calls C<ev_run> recursively).
1986		2114
1987	=head3 Watcher-Specific Functions and Data Members	2115	=head3 Watcher-Specific Functions and Data Members
1988		2116
1989	=over 4	2117	=over 4
1990		2118
…		…
2025		2153
2026	Another way to think about it (for the mathematically inclined) is that	2154	Another way to think about it (for the mathematically inclined) is that
2027	C<ev_periodic> will try to run the callback in this mode at the next possible	2155	C<ev_periodic> will try to run the callback in this mode at the next possible
2028	time where C<time = offset (mod interval)>, regardless of any time jumps.	2156	time where C<time = offset (mod interval)>, regardless of any time jumps.
2029		2157
2030	For numerical stability it is preferable that the C<offset> value is near	2158	The C<interval> I<MUST> be positive, and for numerical stability, the
2031	C<ev_now ()> (the current time), but there is no range requirement for	2159	interval value should be higher than C<1/8192> (which is around 100
2032	this value, and in fact is often specified as zero.	2160	microseconds) and C<offset> should be higher than C<0> and should have
		2161	at most a similar magnitude as the current time (say, within a factor of
		2162	ten). Typical values for offset are, in fact, C<0> or something between
		2163	C<0> and C<interval>, which is also the recommended range.
2033		2164
2034	Note also that there is an upper limit to how often a timer can fire (CPU	2165	Note also that there is an upper limit to how often a timer can fire (CPU
2035	speed for example), so if C<interval> is very small then timing stability	2166	speed for example), so if C<interval> is very small then timing stability
2036	will of course deteriorate. Libev itself tries to be exact to be about one	2167	will of course deteriorate. Libev itself tries to be exact to be about one
2037	millisecond (if the OS supports it and the machine is fast enough).	2168	millisecond (if the OS supports it and the machine is fast enough).
…		…
2118	Example: Call a callback every hour, or, more precisely, whenever the	2249	Example: Call a callback every hour, or, more precisely, whenever the
2119	system time is divisible by 3600. The callback invocation times have	2250	system time is divisible by 3600. The callback invocation times have
2120	potentially a lot of jitter, but good long-term stability.	2251	potentially a lot of jitter, but good long-term stability.
2121		2252
2122	static void	2253	static void
2123	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2254	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
2124	{	2255	{
2125	... its now a full hour (UTC, or TAI or whatever your clock follows)	2256	... its now a full hour (UTC, or TAI or whatever your clock follows)
2126	}	2257	}
2127		2258
2128	ev_periodic hourly_tick;	2259	ev_periodic hourly_tick;
…		…
2151		2282
2152	=head2 C<ev_signal> - signal me when a signal gets signalled!	2283	=head2 C<ev_signal> - signal me when a signal gets signalled!
2153		2284
2154	Signal watchers will trigger an event when the process receives a specific	2285	Signal watchers will trigger an event when the process receives a specific
2155	signal one or more times. Even though signals are very asynchronous, libev	2286	signal one or more times. Even though signals are very asynchronous, libev
2156	will try it's best to deliver signals synchronously, i.e. as part of the	2287	will try its best to deliver signals synchronously, i.e. as part of the
2157	normal event processing, like any other event.	2288	normal event processing, like any other event.
2158		2289
2159	If you want signals to be delivered truly asynchronously, just use	2290	If you want signals to be delivered truly asynchronously, just use
2160	C<sigaction> as you would do without libev and forget about sharing	2291	C<sigaction> as you would do without libev and forget about sharing
2161	the signal. You can even use C<ev_async> from a signal handler to	2292	the signal. You can even use C<ev_async> from a signal handler to
…		…
2180	=head3 The special problem of inheritance over fork/execve/pthread_create	2311	=head3 The special problem of inheritance over fork/execve/pthread_create
2181		2312
2182	Both the signal mask (C<sigprocmask>) and the signal disposition	2313	Both the signal mask (C<sigprocmask>) and the signal disposition
2183	(C<sigaction>) are unspecified after starting a signal watcher (and after	2314	(C<sigaction>) are unspecified after starting a signal watcher (and after
2184	stopping it again), that is, libev might or might not block the signal,	2315	stopping it again), that is, libev might or might not block the signal,
2185	and might or might not set or restore the installed signal handler.	2316	and might or might not set or restore the installed signal handler (but
		2317	see C<EVFLAG_NOSIGMASK>).
2186		2318
2187	While this does not matter for the signal disposition (libev never	2319	While this does not matter for the signal disposition (libev never
2188	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on	2320	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
2189	C<execve>), this matters for the signal mask: many programs do not expect	2321	C<execve>), this matters for the signal mask: many programs do not expect
2190	certain signals to be blocked.	2322	certain signals to be blocked.
…		…
2204		2336
2205	So I can't stress this enough: I<If you do not reset your signal mask when	2337	So I can't stress this enough: I<If you do not reset your signal mask when
2206	you expect it to be empty, you have a race condition in your code>. This	2338	you expect it to be empty, you have a race condition in your code>. This
2207	is not a libev-specific thing, this is true for most event libraries.	2339	is not a libev-specific thing, this is true for most event libraries.
2208		2340
		2341	=head3 The special problem of threads signal handling
		2342
		2343	POSIX threads has problematic signal handling semantics, specifically,
		2344	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2345	threads in a process block signals, which is hard to achieve.
		2346
		2347	When you want to use sigwait (or mix libev signal handling with your own
		2348	for the same signals), you can tackle this problem by globally blocking
		2349	all signals before creating any threads (or creating them with a fully set
		2350	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2351	loops. Then designate one thread as "signal receiver thread" which handles
		2352	these signals. You can pass on any signals that libev might be interested
		2353	in by calling C<ev_feed_signal>.
		2354
2209	=head3 Watcher-Specific Functions and Data Members	2355	=head3 Watcher-Specific Functions and Data Members
2210		2356
2211	=over 4	2357	=over 4
2212		2358
2213	=item ev_signal_init (ev_signal *, callback, int signum)	2359	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
2228	Example: Try to exit cleanly on SIGINT.	2374	Example: Try to exit cleanly on SIGINT.
2229		2375
2230	static void	2376	static void
2231	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2377	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2232	{	2378	{
2233	ev_unloop (loop, EVUNLOOP_ALL);	2379	ev_break (loop, EVBREAK_ALL);
2234	}	2380	}
2235		2381
2236	ev_signal signal_watcher;	2382	ev_signal signal_watcher;
2237	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2383	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2238	ev_signal_start (loop, &signal_watcher);	2384	ev_signal_start (loop, &signal_watcher);
…		…
2624		2770
2625	Prepare and check watchers are usually (but not always) used in pairs:	2771	Prepare and check watchers are usually (but not always) used in pairs:
2626	prepare watchers get invoked before the process blocks and check watchers	2772	prepare watchers get invoked before the process blocks and check watchers
2627	afterwards.	2773	afterwards.
2628		2774
2629	You I<must not> call C<ev_loop> or similar functions that enter	2775	You I<must not> call C<ev_run> or similar functions that enter
2630	the current event loop from either C<ev_prepare> or C<ev_check>	2776	the current event loop from either C<ev_prepare> or C<ev_check>
2631	watchers. Other loops than the current one are fine, however. The	2777	watchers. Other loops than the current one are fine, however. The
2632	rationale behind this is that you do not need to check for recursion in	2778	rationale behind this is that you do not need to check for recursion in
2633	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2779	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2634	C<ev_check> so if you have one watcher of each kind they will always be	2780	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2802		2948
2803	if (timeout >= 0)	2949	if (timeout >= 0)
2804	// create/start timer	2950	// create/start timer
2805		2951
2806	// poll	2952	// poll
2807	ev_loop (EV_A_ 0);	2953	ev_run (EV_A_ 0);
2808		2954
2809	// stop timer again	2955	// stop timer again
2810	if (timeout >= 0)	2956	if (timeout >= 0)
2811	ev_timer_stop (EV_A_ &to);	2957	ev_timer_stop (EV_A_ &to);
2812		2958
…		…
2890	if you do not want that, you need to temporarily stop the embed watcher).	3036	if you do not want that, you need to temporarily stop the embed watcher).
2891		3037
2892	=item ev_embed_sweep (loop, ev_embed *)	3038	=item ev_embed_sweep (loop, ev_embed *)
2893		3039
2894	Make a single, non-blocking sweep over the embedded loop. This works	3040	Make a single, non-blocking sweep over the embedded loop. This works
2895	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3041	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2896	appropriate way for embedded loops.	3042	appropriate way for embedded loops.
2897		3043
2898	=item struct ev_loop *other [read-only]	3044	=item struct ev_loop *other [read-only]
2899		3045
2900	The embedded event loop.	3046	The embedded event loop.
…		…
2960	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3106	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2961	handlers will be invoked, too, of course.	3107	handlers will be invoked, too, of course.
2962		3108
2963	=head3 The special problem of life after fork - how is it possible?	3109	=head3 The special problem of life after fork - how is it possible?
2964		3110
2965	Most uses of C<fork()> consist of forking, then some simple calls to ste	3111	Most uses of C<fork()> consist of forking, then some simple calls to set
2966	up/change the process environment, followed by a call to C<exec()>. This	3112	up/change the process environment, followed by a call to C<exec()>. This
2967	sequence should be handled by libev without any problems.	3113	sequence should be handled by libev without any problems.
2968		3114
2969	This changes when the application actually wants to do event handling	3115	This changes when the application actually wants to do event handling
2970	in the child, or both parent in child, in effect "continuing" after the	3116	in the child, or both parent in child, in effect "continuing" after the
…		…
2986	disadvantage of having to use multiple event loops (which do not support	3132	disadvantage of having to use multiple event loops (which do not support
2987	signal watchers).	3133	signal watchers).
2988		3134
2989	When this is not possible, or you want to use the default loop for	3135	When this is not possible, or you want to use the default loop for
2990	other reasons, then in the process that wants to start "fresh", call	3136	other reasons, then in the process that wants to start "fresh", call
2991	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3137	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
2992	the default loop will "orphan" (not stop) all registered watchers, so you	3138	Destroying the default loop will "orphan" (not stop) all registered
2993	have to be careful not to execute code that modifies those watchers. Note	3139	watchers, so you have to be careful not to execute code that modifies
2994	also that in that case, you have to re-register any signal watchers.	3140	those watchers. Note also that in that case, you have to re-register any
		3141	signal watchers.
2995		3142
2996	=head3 Watcher-Specific Functions and Data Members	3143	=head3 Watcher-Specific Functions and Data Members
2997		3144
2998	=over 4	3145	=over 4
2999		3146
3000	=item ev_fork_init (ev_signal *, callback)	3147	=item ev_fork_init (ev_fork *, callback)
3001		3148
3002	Initialises and configures the fork watcher - it has no parameters of any	3149	Initialises and configures the fork watcher - it has no parameters of any
3003	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3150	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
3004	believe me.	3151	really.
3005		3152
3006	=back	3153	=back
3007		3154
3008		3155
		3156	=head2 C<ev_cleanup> - even the best things end
		3157
		3158	Cleanup watchers are called just before the event loop is being destroyed
		3159	by a call to C<ev_loop_destroy>.
		3160
		3161	While there is no guarantee that the event loop gets destroyed, cleanup
		3162	watchers provide a convenient method to install cleanup hooks for your
		3163	program, worker threads and so on - you just to make sure to destroy the
		3164	loop when you want them to be invoked.
		3165
		3166	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3167	all other watchers, they do not keep a reference to the event loop (which
		3168	makes a lot of sense if you think about it). Like all other watchers, you
		3169	can call libev functions in the callback, except C<ev_cleanup_start>.
		3170
		3171	=head3 Watcher-Specific Functions and Data Members
		3172
		3173	=over 4
		3174
		3175	=item ev_cleanup_init (ev_cleanup *, callback)
		3176
		3177	Initialises and configures the cleanup watcher - it has no parameters of
		3178	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3179	pointless, I assure you.
		3180
		3181	=back
		3182
		3183	Example: Register an atexit handler to destroy the default loop, so any
		3184	cleanup functions are called.
		3185
		3186	static void
		3187	program_exits (void)
		3188	{
		3189	ev_loop_destroy (EV_DEFAULT_UC);
		3190	}
		3191
		3192	...
		3193	atexit (program_exits);
		3194
		3195
3009	=head2 C<ev_async> - how to wake up another event loop	3196	=head2 C<ev_async> - how to wake up an event loop
3010		3197
3011	In general, you cannot use an C<ev_loop> from multiple threads or other	3198	In general, you cannot use an C<ev_loop> from multiple threads or other
3012	asynchronous sources such as signal handlers (as opposed to multiple event	3199	asynchronous sources such as signal handlers (as opposed to multiple event
3013	loops - those are of course safe to use in different threads).	3200	loops - those are of course safe to use in different threads).
3014		3201
3015	Sometimes, however, you need to wake up another event loop you do not	3202	Sometimes, however, you need to wake up an event loop you do not control,
3016	control, for example because it belongs to another thread. This is what	3203	for example because it belongs to another thread. This is what C<ev_async>
3017	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3204	watchers do: as long as the C<ev_async> watcher is active, you can signal
3018	can signal it by calling C<ev_async_send>, which is thread- and signal	3205	it by calling C<ev_async_send>, which is thread- and signal safe.
3019	safe.
3020		3206
3021	This functionality is very similar to C<ev_signal> watchers, as signals,	3207	This functionality is very similar to C<ev_signal> watchers, as signals,
3022	too, are asynchronous in nature, and signals, too, will be compressed	3208	too, are asynchronous in nature, and signals, too, will be compressed
3023	(i.e. the number of callback invocations may be less than the number of	3209	(i.e. the number of callback invocations may be less than the number of
3024	C<ev_async_sent> calls).	3210	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
		3211	of "global async watchers" by using a watcher on an otherwise unused
		3212	signal, and C<ev_feed_signal> to signal this watcher from another thread,
		3213	even without knowing which loop owns the signal.
3025		3214
3026	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3215	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
3027	just the default loop.	3216	just the default loop.
3028		3217
3029	=head3 Queueing	3218	=head3 Queueing
…		…
3124	trust me.	3313	trust me.
3125		3314
3126	=item ev_async_send (loop, ev_async *)	3315	=item ev_async_send (loop, ev_async *)
3127		3316
3128	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3317	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3129	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3318	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3319	returns.
		3320
3130	C<ev_feed_event>, this call is safe to do from other threads, signal or	3321	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3131	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3322	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3132	section below on what exactly this means).	3323	embedding section below on what exactly this means).
3133		3324
3134	Note that, as with other watchers in libev, multiple events might get	3325	Note that, as with other watchers in libev, multiple events might get
3135	compressed into a single callback invocation (another way to look at this	3326	compressed into a single callback invocation (another way to look at this
3136	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3327	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
3137	reset when the event loop detects that).	3328	reset when the event loop detects that).
…		…
3179		3370
3180	If C<timeout> is less than 0, then no timeout watcher will be	3371	If C<timeout> is less than 0, then no timeout watcher will be
3181	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3372	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
3182	repeat = 0) will be started. C<0> is a valid timeout.	3373	repeat = 0) will be started. C<0> is a valid timeout.
3183		3374
3184	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3375	The callback has the type C<void (*cb)(int revents, void *arg)> and is
3185	passed an C<revents> set like normal event callbacks (a combination of	3376	passed an C<revents> set like normal event callbacks (a combination of
3186	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3377	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
3187	value passed to C<ev_once>. Note that it is possible to receive I<both>	3378	value passed to C<ev_once>. Note that it is possible to receive I<both>
3188	a timeout and an io event at the same time - you probably should give io	3379	a timeout and an io event at the same time - you probably should give io
3189	events precedence.	3380	events precedence.
3190		3381
3191	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3382	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
3192		3383
3193	static void stdin_ready (int revents, void *arg)	3384	static void stdin_ready (int revents, void *arg)
3194	{	3385	{
3195	if (revents & EV_READ)	3386	if (revents & EV_READ)
3196	/* stdin might have data for us, joy! */;	3387	/* stdin might have data for us, joy! */;
3197	else if (revents & EV_TIMEOUT)	3388	else if (revents & EV_TIMER)
3198	/* doh, nothing entered */;	3389	/* doh, nothing entered */;
3199	}	3390	}
3200		3391
3201	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3392	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3202		3393
…		…
3205	Feed an event on the given fd, as if a file descriptor backend detected	3396	Feed an event on the given fd, as if a file descriptor backend detected
3206	the given events it.	3397	the given events it.
3207		3398
3208	=item ev_feed_signal_event (loop, int signum)	3399	=item ev_feed_signal_event (loop, int signum)
3209		3400
3210	Feed an event as if the given signal occurred (C<loop> must be the default	3401	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3211	loop!).	3402	which is async-safe.
3212		3403
3213	=back	3404	=back
		3405
		3406
		3407	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3408
		3409	This section explains some common idioms that are not immediately
		3410	obvious. Note that examples are sprinkled over the whole manual, and this
		3411	section only contains stuff that wouldn't fit anywhere else.
		3412
		3413	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3414
		3415	Each watcher has, by default, a C<void *data> member that you can read
		3416	or modify at any time: libev will completely ignore it. This can be used
		3417	to associate arbitrary data with your watcher. If you need more data and
		3418	don't want to allocate memory separately and store a pointer to it in that
		3419	data member, you can also "subclass" the watcher type and provide your own
		3420	data:
		3421
		3422	struct my_io
		3423	{
		3424	ev_io io;
		3425	int otherfd;
		3426	void *somedata;
		3427	struct whatever *mostinteresting;
		3428	};
		3429
		3430	...
		3431	struct my_io w;
		3432	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3433
		3434	And since your callback will be called with a pointer to the watcher, you
		3435	can cast it back to your own type:
		3436
		3437	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3438	{
		3439	struct my_io *w = (struct my_io *)w_;
		3440	...
		3441	}
		3442
		3443	More interesting and less C-conformant ways of casting your callback
		3444	function type instead have been omitted.
		3445
		3446	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3447
		3448	Another common scenario is to use some data structure with multiple
		3449	embedded watchers, in effect creating your own watcher that combines
		3450	multiple libev event sources into one "super-watcher":
		3451
		3452	struct my_biggy
		3453	{
		3454	int some_data;
		3455	ev_timer t1;
		3456	ev_timer t2;
		3457	}
		3458
		3459	In this case getting the pointer to C<my_biggy> is a bit more
		3460	complicated: Either you store the address of your C<my_biggy> struct in
		3461	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3462	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3463	real programmers):
		3464
		3465	#include <stddef.h>
		3466
		3467	static void
		3468	t1_cb (EV_P_ ev_timer *w, int revents)
		3469	{
		3470	struct my_biggy big = (struct my_biggy *)
		3471	(((char *)w) - offsetof (struct my_biggy, t1));
		3472	}
		3473
		3474	static void
		3475	t2_cb (EV_P_ ev_timer *w, int revents)
		3476	{
		3477	struct my_biggy big = (struct my_biggy *)
		3478	(((char *)w) - offsetof (struct my_biggy, t2));
		3479	}
		3480
		3481	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3482
		3483	Often (especially in GUI toolkits) there are places where you have
		3484	I<modal> interaction, which is most easily implemented by recursively
		3485	invoking C<ev_run>.
		3486
		3487	This brings the problem of exiting - a callback might want to finish the
		3488	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3489	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3490	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3491	other combination: In these cases, C<ev_break> will not work alone.
		3492
		3493	The solution is to maintain "break this loop" variable for each C<ev_run>
		3494	invocation, and use a loop around C<ev_run> until the condition is
		3495	triggered, using C<EVRUN_ONCE>:
		3496
		3497	// main loop
		3498	int exit_main_loop = 0;
		3499
		3500	while (!exit_main_loop)
		3501	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3502
		3503	// in a model watcher
		3504	int exit_nested_loop = 0;
		3505
		3506	while (!exit_nested_loop)
		3507	ev_run (EV_A_ EVRUN_ONCE);
		3508
		3509	To exit from any of these loops, just set the corresponding exit variable:
		3510
		3511	// exit modal loop
		3512	exit_nested_loop = 1;
		3513
		3514	// exit main program, after modal loop is finished
		3515	exit_main_loop = 1;
		3516
		3517	// exit both
		3518	exit_main_loop = exit_nested_loop = 1;
		3519
		3520	=head2 THREAD LOCKING EXAMPLE
		3521
		3522	Here is a fictitious example of how to run an event loop in a different
		3523	thread from where callbacks are being invoked and watchers are
		3524	created/added/removed.
		3525
		3526	For a real-world example, see the C<EV::Loop::Async> perl module,
		3527	which uses exactly this technique (which is suited for many high-level
		3528	languages).
		3529
		3530	The example uses a pthread mutex to protect the loop data, a condition
		3531	variable to wait for callback invocations, an async watcher to notify the
		3532	event loop thread and an unspecified mechanism to wake up the main thread.
		3533
		3534	First, you need to associate some data with the event loop:
		3535
		3536	typedef struct {
		3537	mutex_t lock; /* global loop lock */
		3538	ev_async async_w;
		3539	thread_t tid;
		3540	cond_t invoke_cv;
		3541	} userdata;
		3542
		3543	void prepare_loop (EV_P)
		3544	{
		3545	// for simplicity, we use a static userdata struct.
		3546	static userdata u;
		3547
		3548	ev_async_init (&u->async_w, async_cb);
		3549	ev_async_start (EV_A_ &u->async_w);
		3550
		3551	pthread_mutex_init (&u->lock, 0);
		3552	pthread_cond_init (&u->invoke_cv, 0);
		3553
		3554	// now associate this with the loop
		3555	ev_set_userdata (EV_A_ u);
		3556	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3557	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3558
		3559	// then create the thread running ev_run
		3560	pthread_create (&u->tid, 0, l_run, EV_A);
		3561	}
		3562
		3563	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3564	solely to wake up the event loop so it takes notice of any new watchers
		3565	that might have been added:
		3566
		3567	static void
		3568	async_cb (EV_P_ ev_async *w, int revents)
		3569	{
		3570	// just used for the side effects
		3571	}
		3572
		3573	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3574	protecting the loop data, respectively.
		3575
		3576	static void
		3577	l_release (EV_P)
		3578	{
		3579	userdata *u = ev_userdata (EV_A);
		3580	pthread_mutex_unlock (&u->lock);
		3581	}
		3582
		3583	static void
		3584	l_acquire (EV_P)
		3585	{
		3586	userdata *u = ev_userdata (EV_A);
		3587	pthread_mutex_lock (&u->lock);
		3588	}
		3589
		3590	The event loop thread first acquires the mutex, and then jumps straight
		3591	into C<ev_run>:
		3592
		3593	void *
		3594	l_run (void *thr_arg)
		3595	{
		3596	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3597
		3598	l_acquire (EV_A);
		3599	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3600	ev_run (EV_A_ 0);
		3601	l_release (EV_A);
		3602
		3603	return 0;
		3604	}
		3605
		3606	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3607	signal the main thread via some unspecified mechanism (signals? pipe
		3608	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3609	have been called (in a while loop because a) spurious wakeups are possible
		3610	and b) skipping inter-thread-communication when there are no pending
		3611	watchers is very beneficial):
		3612
		3613	static void
		3614	l_invoke (EV_P)
		3615	{
		3616	userdata *u = ev_userdata (EV_A);
		3617
		3618	while (ev_pending_count (EV_A))
		3619	{
		3620	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3621	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3622	}
		3623	}
		3624
		3625	Now, whenever the main thread gets told to invoke pending watchers, it
		3626	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3627	thread to continue:
		3628
		3629	static void
		3630	real_invoke_pending (EV_P)
		3631	{
		3632	userdata *u = ev_userdata (EV_A);
		3633
		3634	pthread_mutex_lock (&u->lock);
		3635	ev_invoke_pending (EV_A);
		3636	pthread_cond_signal (&u->invoke_cv);
		3637	pthread_mutex_unlock (&u->lock);
		3638	}
		3639
		3640	Whenever you want to start/stop a watcher or do other modifications to an
		3641	event loop, you will now have to lock:
		3642
		3643	ev_timer timeout_watcher;
		3644	userdata *u = ev_userdata (EV_A);
		3645
		3646	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3647
		3648	pthread_mutex_lock (&u->lock);
		3649	ev_timer_start (EV_A_ &timeout_watcher);
		3650	ev_async_send (EV_A_ &u->async_w);
		3651	pthread_mutex_unlock (&u->lock);
		3652
		3653	Note that sending the C<ev_async> watcher is required because otherwise
		3654	an event loop currently blocking in the kernel will have no knowledge
		3655	about the newly added timer. By waking up the loop it will pick up any new
		3656	watchers in the next event loop iteration.
		3657
		3658	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3659
		3660	While the overhead of a callback that e.g. schedules a thread is small, it
		3661	is still an overhead. If you embed libev, and your main usage is with some
		3662	kind of threads or coroutines, you might want to customise libev so that
		3663	doesn't need callbacks anymore.
		3664
		3665	Imagine you have coroutines that you can switch to using a function
		3666	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3667	and that due to some magic, the currently active coroutine is stored in a
		3668	global called C<current_coro>. Then you can build your own "wait for libev
		3669	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3670	the differing C<;> conventions):
		3671
		3672	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3673	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3674
		3675	That means instead of having a C callback function, you store the
		3676	coroutine to switch to in each watcher, and instead of having libev call
		3677	your callback, you instead have it switch to that coroutine.
		3678
		3679	A coroutine might now wait for an event with a function called
		3680	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3681	matter when, or whether the watcher is active or not when this function is
		3682	called):
		3683
		3684	void
		3685	wait_for_event (ev_watcher *w)
		3686	{
		3687	ev_cb_set (w) = current_coro;
		3688	switch_to (libev_coro);
		3689	}
		3690
		3691	That basically suspends the coroutine inside C<wait_for_event> and
		3692	continues the libev coroutine, which, when appropriate, switches back to
		3693	this or any other coroutine. I am sure if you sue this your own :)
		3694
		3695	You can do similar tricks if you have, say, threads with an event queue -
		3696	instead of storing a coroutine, you store the queue object and instead of
		3697	switching to a coroutine, you push the watcher onto the queue and notify
		3698	any waiters.
		3699
		3700	To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two
		3701	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3702
		3703	// my_ev.h
		3704	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3705	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3706	#include "../libev/ev.h"
		3707
		3708	// my_ev.c
		3709	#define EV_H "my_ev.h"
		3710	#include "../libev/ev.c"
		3711
		3712	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3713	F<my_ev.c> into your project. When properly specifying include paths, you
		3714	can even use F<ev.h> as header file name directly.
3214		3715
3215		3716
3216	=head1 LIBEVENT EMULATION	3717	=head1 LIBEVENT EMULATION
3217		3718
3218	Libev offers a compatibility emulation layer for libevent. It cannot	3719	Libev offers a compatibility emulation layer for libevent. It cannot
3219	emulate the internals of libevent, so here are some usage hints:	3720	emulate the internals of libevent, so here are some usage hints:
3220		3721
3221	=over 4	3722	=over 4
		3723
		3724	=item * Only the libevent-1.4.1-beta API is being emulated.
		3725
		3726	This was the newest libevent version available when libev was implemented,
		3727	and is still mostly unchanged in 2010.
3222		3728
3223	=item * Use it by including <event.h>, as usual.	3729	=item * Use it by including <event.h>, as usual.
3224		3730
3225	=item * The following members are fully supported: ev_base, ev_callback,	3731	=item * The following members are fully supported: ev_base, ev_callback,
3226	ev_arg, ev_fd, ev_res, ev_events.	3732	ev_arg, ev_fd, ev_res, ev_events.
…		…
3232	=item * Priorities are not currently supported. Initialising priorities	3738	=item * Priorities are not currently supported. Initialising priorities
3233	will fail and all watchers will have the same priority, even though there	3739	will fail and all watchers will have the same priority, even though there
3234	is an ev_pri field.	3740	is an ev_pri field.
3235		3741
3236	=item * In libevent, the last base created gets the signals, in libev, the	3742	=item * In libevent, the last base created gets the signals, in libev, the
3237	first base created (== the default loop) gets the signals.	3743	base that registered the signal gets the signals.
3238		3744
3239	=item * Other members are not supported.	3745	=item * Other members are not supported.
3240		3746
3241	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3747	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3242	to use the libev header file and library.	3748	to use the libev header file and library.
…		…
3261	Care has been taken to keep the overhead low. The only data member the C++	3767	Care has been taken to keep the overhead low. The only data member the C++
3262	classes add (compared to plain C-style watchers) is the event loop pointer	3768	classes add (compared to plain C-style watchers) is the event loop pointer
3263	that the watcher is associated with (or no additional members at all if	3769	that the watcher is associated with (or no additional members at all if
3264	you disable C<EV_MULTIPLICITY> when embedding libev).	3770	you disable C<EV_MULTIPLICITY> when embedding libev).
3265		3771
3266	Currently, functions, and static and non-static member functions can be	3772	Currently, functions, static and non-static member functions and classes
3267	used as callbacks. Other types should be easy to add as long as they only	3773	with C<operator ()> can be used as callbacks. Other types should be easy
3268	need one additional pointer for context. If you need support for other	3774	to add as long as they only need one additional pointer for context. If
3269	types of functors please contact the author (preferably after implementing	3775	you need support for other types of functors please contact the author
3270	it).	3776	(preferably after implementing it).
3271		3777
3272	Here is a list of things available in the C<ev> namespace:	3778	Here is a list of things available in the C<ev> namespace:
3273		3779
3274	=over 4	3780	=over 4
3275		3781
…		…
3336	myclass obj;	3842	myclass obj;
3337	ev::io iow;	3843	ev::io iow;
3338	iow.set <myclass, &myclass::io_cb> (&obj);	3844	iow.set <myclass, &myclass::io_cb> (&obj);
3339		3845
3340	=item w->set (object *)	3846	=item w->set (object *)
3341
3342	This is an B<experimental> feature that might go away in a future version.
3343		3847
3344	This is a variation of a method callback - leaving out the method to call	3848	This is a variation of a method callback - leaving out the method to call
3345	will default the method to C<operator ()>, which makes it possible to use	3849	will default the method to C<operator ()>, which makes it possible to use
3346	functor objects without having to manually specify the C<operator ()> all	3850	functor objects without having to manually specify the C<operator ()> all
3347	the time. Incidentally, you can then also leave out the template argument	3851	the time. Incidentally, you can then also leave out the template argument
…		…
3387	Associates a different C<struct ev_loop> with this watcher. You can only	3891	Associates a different C<struct ev_loop> with this watcher. You can only
3388	do this when the watcher is inactive (and not pending either).	3892	do this when the watcher is inactive (and not pending either).
3389		3893
3390	=item w->set ([arguments])	3894	=item w->set ([arguments])
3391		3895
3392	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3896	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
3393	called at least once. Unlike the C counterpart, an active watcher gets	3897	method or a suitable start method must be called at least once. Unlike the
3394	automatically stopped and restarted when reconfiguring it with this	3898	C counterpart, an active watcher gets automatically stopped and restarted
3395	method.	3899	when reconfiguring it with this method.
3396		3900
3397	=item w->start ()	3901	=item w->start ()
3398		3902
3399	Starts the watcher. Note that there is no C<loop> argument, as the	3903	Starts the watcher. Note that there is no C<loop> argument, as the
3400	constructor already stores the event loop.	3904	constructor already stores the event loop.
3401		3905
		3906	=item w->start ([arguments])
		3907
		3908	Instead of calling C<set> and C<start> methods separately, it is often
		3909	convenient to wrap them in one call. Uses the same type of arguments as
		3910	the configure C<set> method of the watcher.
		3911
3402	=item w->stop ()	3912	=item w->stop ()
3403		3913
3404	Stops the watcher if it is active. Again, no C<loop> argument.	3914	Stops the watcher if it is active. Again, no C<loop> argument.
3405		3915
3406	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3916	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3418		3928
3419	=back	3929	=back
3420		3930
3421	=back	3931	=back
3422		3932
3423	Example: Define a class with an IO and idle watcher, start one of them in	3933	Example: Define a class with two I/O and idle watchers, start the I/O
3424	the constructor.	3934	watchers in the constructor.
3425		3935
3426	class myclass	3936	class myclass
3427	{	3937	{
3428	ev::io io ; void io_cb (ev::io &w, int revents);	3938	ev::io io ; void io_cb (ev::io &w, int revents);
		3939	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
3429	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3940	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3430		3941
3431	myclass (int fd)	3942	myclass (int fd)
3432	{	3943	{
3433	io .set <myclass, &myclass::io_cb > (this);	3944	io .set <myclass, &myclass::io_cb > (this);
		3945	io2 .set <myclass, &myclass::io2_cb > (this);
3434	idle.set <myclass, &myclass::idle_cb> (this);	3946	idle.set <myclass, &myclass::idle_cb> (this);
3435		3947
3436	io.start (fd, ev::READ);	3948	io.set (fd, ev::WRITE); // configure the watcher
		3949	io.start (); // start it whenever convenient
		3950
		3951	io2.start (fd, ev::READ); // set + start in one call
3437	}	3952	}
3438	};	3953	};
3439		3954
3440		3955
3441	=head1 OTHER LANGUAGE BINDINGS	3956	=head1 OTHER LANGUAGE BINDINGS
…		…
3515	loop argument"). The C<EV_A> form is used when this is the sole argument,	4030	loop argument"). The C<EV_A> form is used when this is the sole argument,
3516	C<EV_A_> is used when other arguments are following. Example:	4031	C<EV_A_> is used when other arguments are following. Example:
3517		4032
3518	ev_unref (EV_A);	4033	ev_unref (EV_A);
3519	ev_timer_add (EV_A_ watcher);	4034	ev_timer_add (EV_A_ watcher);
3520	ev_loop (EV_A_ 0);	4035	ev_run (EV_A_ 0);
3521		4036
3522	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4037	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3523	which is often provided by the following macro.	4038	which is often provided by the following macro.
3524		4039
3525	=item C<EV_P>, C<EV_P_>	4040	=item C<EV_P>, C<EV_P_>
…		…
3565	}	4080	}
3566		4081
3567	ev_check check;	4082	ev_check check;
3568	ev_check_init (&check, check_cb);	4083	ev_check_init (&check, check_cb);
3569	ev_check_start (EV_DEFAULT_ &check);	4084	ev_check_start (EV_DEFAULT_ &check);
3570	ev_loop (EV_DEFAULT_ 0);	4085	ev_run (EV_DEFAULT_ 0);
3571		4086
3572	=head1 EMBEDDING	4087	=head1 EMBEDDING
3573		4088
3574	Libev can (and often is) directly embedded into host	4089	Libev can (and often is) directly embedded into host
3575	applications. Examples of applications that embed it include the Deliantra	4090	applications. Examples of applications that embed it include the Deliantra
…		…
3660	define before including (or compiling) any of its files. The default in	4175	define before including (or compiling) any of its files. The default in
3661	the absence of autoconf is documented for every option.	4176	the absence of autoconf is documented for every option.
3662		4177
3663	Symbols marked with "(h)" do not change the ABI, and can have different	4178	Symbols marked with "(h)" do not change the ABI, and can have different
3664	values when compiling libev vs. including F<ev.h>, so it is permissible	4179	values when compiling libev vs. including F<ev.h>, so it is permissible
3665	to redefine them before including F<ev.h> without breakign compatibility	4180	to redefine them before including F<ev.h> without breaking compatibility
3666	to a compiled library. All other symbols change the ABI, which means all	4181	to a compiled library. All other symbols change the ABI, which means all
3667	users of libev and the libev code itself must be compiled with compatible	4182	users of libev and the libev code itself must be compiled with compatible
3668	settings.	4183	settings.
3669		4184
3670	=over 4	4185	=over 4
		4186
		4187	=item EV_COMPAT3 (h)
		4188
		4189	Backwards compatibility is a major concern for libev. This is why this
		4190	release of libev comes with wrappers for the functions and symbols that
		4191	have been renamed between libev version 3 and 4.
		4192
		4193	You can disable these wrappers (to test compatibility with future
		4194	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4195	sources. This has the additional advantage that you can drop the C<struct>
		4196	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4197	typedef in that case.
		4198
		4199	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4200	and in some even more future version the compatibility code will be
		4201	removed completely.
3671		4202
3672	=item EV_STANDALONE (h)	4203	=item EV_STANDALONE (h)
3673		4204
3674	Must always be C<1> if you do not use autoconf configuration, which	4205	Must always be C<1> if you do not use autoconf configuration, which
3675	keeps libev from including F<config.h>, and it also defines dummy	4206	keeps libev from including F<config.h>, and it also defines dummy
…		…
3677	supported). It will also not define any of the structs usually found in	4208	supported). It will also not define any of the structs usually found in
3678	F<event.h> that are not directly supported by the libev core alone.	4209	F<event.h> that are not directly supported by the libev core alone.
3679		4210
3680	In standalone mode, libev will still try to automatically deduce the	4211	In standalone mode, libev will still try to automatically deduce the
3681	configuration, but has to be more conservative.	4212	configuration, but has to be more conservative.
		4213
		4214	=item EV_USE_FLOOR
		4215
		4216	If defined to be C<1>, libev will use the C<floor ()> function for its
		4217	periodic reschedule calculations, otherwise libev will fall back on a
		4218	portable (slower) implementation. If you enable this, you usually have to
		4219	link against libm or something equivalent. Enabling this when the C<floor>
		4220	function is not available will fail, so the safe default is to not enable
		4221	this.
3682		4222
3683	=item EV_USE_MONOTONIC	4223	=item EV_USE_MONOTONIC
3684		4224
3685	If defined to be C<1>, libev will try to detect the availability of the	4225	If defined to be C<1>, libev will try to detect the availability of the
3686	monotonic clock option at both compile time and runtime. Otherwise no	4226	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3882	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,	4422	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
3883	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.	4423	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3884		4424
3885	If undefined or defined to be C<1> (and the platform supports it), then	4425	If undefined or defined to be C<1> (and the platform supports it), then
3886	the respective watcher type is supported. If defined to be C<0>, then it	4426	the respective watcher type is supported. If defined to be C<0>, then it
3887	is not. Disabling watcher types mainly saves codesize.	4427	is not. Disabling watcher types mainly saves code size.
3888		4428
3889	=item EV_FEATURES	4429	=item EV_FEATURES
3890		4430
3891	If you need to shave off some kilobytes of code at the expense of some	4431	If you need to shave off some kilobytes of code at the expense of some
3892	speed (but with the full API), you can define this symbol to request	4432	speed (but with the full API), you can define this symbol to request
3893	certain subsets of functionality. The default is to enable all features	4433	certain subsets of functionality. The default is to enable all features
3894	that can be enabled on the platform.	4434	that can be enabled on the platform.
3895
3896	Note that using autoconf will usually override most of the features, so
3897	using this symbol makes sense mostly when embedding libev.
3898		4435
3899	A typical way to use this symbol is to define it to C<0> (or to a bitset	4436	A typical way to use this symbol is to define it to C<0> (or to a bitset
3900	with some broad features you want) and then selectively re-enable	4437	with some broad features you want) and then selectively re-enable
3901	additional parts you want, for example if you want everything minimal,	4438	additional parts you want, for example if you want everything minimal,
3902	but multiple event loop support, async and child watchers and the poll	4439	but multiple event loop support, async and child watchers and the poll
…		…
3915		4452
3916	=item C<1> - faster/larger code	4453	=item C<1> - faster/larger code
3917		4454
3918	Use larger code to speed up some operations.	4455	Use larger code to speed up some operations.
3919		4456
3920	Currently this is used to override some inlining decisions (enlarging the roughly	4457	Currently this is used to override some inlining decisions (enlarging the
3921	30% code size on amd64.	4458	code size by roughly 30% on amd64).
3922		4459
3923	When optimising for size, use of compiler flags such as C<-Os> with	4460	When optimising for size, use of compiler flags such as C<-Os> with
3924	gcc recommended, as well as C<-DNDEBUG>, as libev contains a number of	4461	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
3925	assertions.	4462	assertions.
3926		4463
3927	=item C<2> - faster/larger data structures	4464	=item C<2> - faster/larger data structures
3928		4465
3929	Replaces the small 2-heap for timer management by a faster 4-heap, larger	4466	Replaces the small 2-heap for timer management by a faster 4-heap, larger
3930	hash table sizes and so on. This will usually further increase codesize	4467	hash table sizes and so on. This will usually further increase code size
3931	and can additionally have an effect on the size of data structures at	4468	and can additionally have an effect on the size of data structures at
3932	runtime.	4469	runtime.
3933		4470
3934	=item C<4> - full API configuration	4471	=item C<4> - full API configuration
3935		4472
3936	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and	4473	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
3937	enables multiplicity (C<EV_MULTIPLICITY>=1).	4474	enables multiplicity (C<EV_MULTIPLICITY>=1).
3938		4475
		4476	=item C<8> - full API
		4477
3939	It also enables a lot of the "lesser used" core API functions. See C<ev.h>	4478	This enables a lot of the "lesser used" API functions. See C<ev.h> for
3940	for details on which parts of the API are still available without this	4479	details on which parts of the API are still available without this
3941	feature, and do not complain if this subset changes over time.	4480	feature, and do not complain if this subset changes over time.
3942		4481
3943	=item C<8> - enable all optional watcher types	4482	=item C<16> - enable all optional watcher types
3944		4483
3945	Enables all optional watcher types. If you want to selectively enable	4484	Enables all optional watcher types. If you want to selectively enable
3946	only some watcher types other than I/O and timers (e.g. prepare,	4485	only some watcher types other than I/O and timers (e.g. prepare,
3947	embed, async, child...) you can enable them manually by defining	4486	embed, async, child...) you can enable them manually by defining
3948	C<EV_watchertype_ENABLE> to C<1> instead.	4487	C<EV_watchertype_ENABLE> to C<1> instead.
3949		4488
3950	=item C<16> - enable all backends	4489	=item C<32> - enable all backends
3951		4490
3952	This enables all backends - without this feature, you need to enable at	4491	This enables all backends - without this feature, you need to enable at
3953	least one backend manually (C<EV_USE_SELECT> is a good choice).	4492	least one backend manually (C<EV_USE_SELECT> is a good choice).
3954		4493
3955	=item C<32> - enable OS-specific "helper" APIs	4494	=item C<64> - enable OS-specific "helper" APIs
3956		4495
3957	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by	4496	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
3958	default.	4497	default.
3959		4498
3960	=back	4499	=back
3961		4500
3962	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>	4501	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
3963	reduces the compiled size of libev from 24.7Kb to 6.5Kb on my GNU/Linux	4502	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
3964	amd64 system, while still giving you I/O watchers, timers and monotonic	4503	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
3965	clock support.	4504	watchers, timers and monotonic clock support.
3966		4505
3967	With an intelligent-enough linker (gcc+binutils are intelligent enough	4506	With an intelligent-enough linker (gcc+binutils are intelligent enough
3968	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by	4507	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
3969	your program might be left out as well - a binary starting a timer and an	4508	your program might be left out as well - a binary starting a timer and an
3970	I/O watcher then might come out at only 5Kb.	4509	I/O watcher then might come out at only 5Kb.
3971		4510
3972	=item EV_AVOID_STDIO	4511	=item EV_AVOID_STDIO
3973		4512
3974	If this is set to C<1> at compiletime, then libev will avoid using stdio	4513	If this is set to C<1> at compiletime, then libev will avoid using stdio
3975	functions (printf, scanf, perror etc.). This will increase the codesize	4514	functions (printf, scanf, perror etc.). This will increase the code size
3976	somewhat, but if your program doesn't otherwise depend on stdio and your	4515	somewhat, but if your program doesn't otherwise depend on stdio and your
3977	libc allows it, this avoids linking in the stdio library which is quite	4516	libc allows it, this avoids linking in the stdio library which is quite
3978	big.	4517	big.
3979		4518
3980	Note that error messages might become less precise when this option is	4519	Note that error messages might become less precise when this option is
…		…
3984		4523
3985	The highest supported signal number, +1 (or, the number of	4524	The highest supported signal number, +1 (or, the number of
3986	signals): Normally, libev tries to deduce the maximum number of signals	4525	signals): Normally, libev tries to deduce the maximum number of signals
3987	automatically, but sometimes this fails, in which case it can be	4526	automatically, but sometimes this fails, in which case it can be
3988	specified. Also, using a lower number than detected (C<32> should be	4527	specified. Also, using a lower number than detected (C<32> should be
3989	good for about any system in existance) can save some memory, as libev	4528	good for about any system in existence) can save some memory, as libev
3990	statically allocates some 12-24 bytes per signal number.	4529	statically allocates some 12-24 bytes per signal number.
3991		4530
3992	=item EV_PID_HASHSIZE	4531	=item EV_PID_HASHSIZE
3993		4532
3994	C<ev_child> watchers use a small hash table to distribute workload by	4533	C<ev_child> watchers use a small hash table to distribute workload by
…		…
4026	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it	4565	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
4027	will be C<0>.	4566	will be C<0>.
4028		4567
4029	=item EV_VERIFY	4568	=item EV_VERIFY
4030		4569
4031	Controls how much internal verification (see C<ev_loop_verify ()>) will	4570	Controls how much internal verification (see C<ev_verify ()>) will
4032	be done: If set to C<0>, no internal verification code will be compiled	4571	be done: If set to C<0>, no internal verification code will be compiled
4033	in. If set to C<1>, then verification code will be compiled in, but not	4572	in. If set to C<1>, then verification code will be compiled in, but not
4034	called. If set to C<2>, then the internal verification code will be	4573	called. If set to C<2>, then the internal verification code will be
4035	called once per loop, which can slow down libev. If set to C<3>, then the	4574	called once per loop, which can slow down libev. If set to C<3>, then the
4036	verification code will be called very frequently, which will slow down	4575	verification code will be called very frequently, which will slow down
…		…
4040	will be C<0>.	4579	will be C<0>.
4041		4580
4042	=item EV_COMMON	4581	=item EV_COMMON
4043		4582
4044	By default, all watchers have a C<void *data> member. By redefining	4583	By default, all watchers have a C<void *data> member. By redefining
4045	this macro to a something else you can include more and other types of	4584	this macro to something else you can include more and other types of
4046	members. You have to define it each time you include one of the files,	4585	members. You have to define it each time you include one of the files,
4047	though, and it must be identical each time.	4586	though, and it must be identical each time.
4048		4587
4049	For example, the perl EV module uses something like this:	4588	For example, the perl EV module uses something like this:
4050		4589
…		…
4103	file.	4642	file.
4104		4643
4105	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4644	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
4106	that everybody includes and which overrides some configure choices:	4645	that everybody includes and which overrides some configure choices:
4107		4646
4108	#define EV_FEATURES 0	4647	#define EV_FEATURES 8
4109	#define EV_USE_SELECT 1	4648	#define EV_USE_SELECT 1
		4649	#define EV_PREPARE_ENABLE 1
		4650	#define EV_IDLE_ENABLE 1
		4651	#define EV_SIGNAL_ENABLE 1
		4652	#define EV_CHILD_ENABLE 1
		4653	#define EV_USE_STDEXCEPT 0
4110	#define EV_CONFIG_H <config.h>	4654	#define EV_CONFIG_H <config.h>
4111		4655
4112	#include "ev++.h"	4656	#include "ev++.h"
4113		4657
4114	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4658	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4115		4659
4116	#include "ev_cpp.h"	4660	#include "ev_cpp.h"
4117	#include "ev.c"	4661	#include "ev.c"
4118		4662
4119	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4663	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4120		4664
4121	=head2 THREADS AND COROUTINES	4665	=head2 THREADS AND COROUTINES
4122		4666
4123	=head3 THREADS	4667	=head3 THREADS
4124		4668
…		…
4175	default loop and triggering an C<ev_async> watcher from the default loop	4719	default loop and triggering an C<ev_async> watcher from the default loop
4176	watcher callback into the event loop interested in the signal.	4720	watcher callback into the event loop interested in the signal.
4177		4721
4178	=back	4722	=back
4179		4723
4180	=head4 THREAD LOCKING EXAMPLE	4724	See also L<THREAD LOCKING EXAMPLE>.
4181
4182	Here is a fictitious example of how to run an event loop in a different
4183	thread than where callbacks are being invoked and watchers are
4184	created/added/removed.
4185
4186	For a real-world example, see the C<EV::Loop::Async> perl module,
4187	which uses exactly this technique (which is suited for many high-level
4188	languages).
4189
4190	The example uses a pthread mutex to protect the loop data, a condition
4191	variable to wait for callback invocations, an async watcher to notify the
4192	event loop thread and an unspecified mechanism to wake up the main thread.
4193
4194	First, you need to associate some data with the event loop:
4195
4196	typedef struct {
4197	mutex_t lock; /* global loop lock */
4198	ev_async async_w;
4199	thread_t tid;
4200	cond_t invoke_cv;
4201	} userdata;
4202
4203	void prepare_loop (EV_P)
4204	{
4205	// for simplicity, we use a static userdata struct.
4206	static userdata u;
4207
4208	ev_async_init (&u->async_w, async_cb);
4209	ev_async_start (EV_A_ &u->async_w);
4210
4211	pthread_mutex_init (&u->lock, 0);
4212	pthread_cond_init (&u->invoke_cv, 0);
4213
4214	// now associate this with the loop
4215	ev_set_userdata (EV_A_ u);
4216	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4217	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4218
4219	// then create the thread running ev_loop
4220	pthread_create (&u->tid, 0, l_run, EV_A);
4221	}
4222
4223	The callback for the C<ev_async> watcher does nothing: the watcher is used
4224	solely to wake up the event loop so it takes notice of any new watchers
4225	that might have been added:
4226
4227	static void
4228	async_cb (EV_P_ ev_async *w, int revents)
4229	{
4230	// just used for the side effects
4231	}
4232
4233	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4234	protecting the loop data, respectively.
4235
4236	static void
4237	l_release (EV_P)
4238	{
4239	userdata *u = ev_userdata (EV_A);
4240	pthread_mutex_unlock (&u->lock);
4241	}
4242
4243	static void
4244	l_acquire (EV_P)
4245	{
4246	userdata *u = ev_userdata (EV_A);
4247	pthread_mutex_lock (&u->lock);
4248	}
4249
4250	The event loop thread first acquires the mutex, and then jumps straight
4251	into C<ev_loop>:
4252
4253	void *
4254	l_run (void *thr_arg)
4255	{
4256	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4257
4258	l_acquire (EV_A);
4259	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4260	ev_loop (EV_A_ 0);
4261	l_release (EV_A);
4262
4263	return 0;
4264	}
4265
4266	Instead of invoking all pending watchers, the C<l_invoke> callback will
4267	signal the main thread via some unspecified mechanism (signals? pipe
4268	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4269	have been called (in a while loop because a) spurious wakeups are possible
4270	and b) skipping inter-thread-communication when there are no pending
4271	watchers is very beneficial):
4272
4273	static void
4274	l_invoke (EV_P)
4275	{
4276	userdata *u = ev_userdata (EV_A);
4277
4278	while (ev_pending_count (EV_A))
4279	{
4280	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4281	pthread_cond_wait (&u->invoke_cv, &u->lock);
4282	}
4283	}
4284
4285	Now, whenever the main thread gets told to invoke pending watchers, it
4286	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4287	thread to continue:
4288
4289	static void
4290	real_invoke_pending (EV_P)
4291	{
4292	userdata *u = ev_userdata (EV_A);
4293
4294	pthread_mutex_lock (&u->lock);
4295	ev_invoke_pending (EV_A);
4296	pthread_cond_signal (&u->invoke_cv);
4297	pthread_mutex_unlock (&u->lock);
4298	}
4299
4300	Whenever you want to start/stop a watcher or do other modifications to an
4301	event loop, you will now have to lock:
4302
4303	ev_timer timeout_watcher;
4304	userdata *u = ev_userdata (EV_A);
4305
4306	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4307
4308	pthread_mutex_lock (&u->lock);
4309	ev_timer_start (EV_A_ &timeout_watcher);
4310	ev_async_send (EV_A_ &u->async_w);
4311	pthread_mutex_unlock (&u->lock);
4312
4313	Note that sending the C<ev_async> watcher is required because otherwise
4314	an event loop currently blocking in the kernel will have no knowledge
4315	about the newly added timer. By waking up the loop it will pick up any new
4316	watchers in the next event loop iteration.
4317		4725
4318	=head3 COROUTINES	4726	=head3 COROUTINES
4319		4727
4320	Libev is very accommodating to coroutines ("cooperative threads"):	4728	Libev is very accommodating to coroutines ("cooperative threads"):
4321	libev fully supports nesting calls to its functions from different	4729	libev fully supports nesting calls to its functions from different
4322	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4730	coroutines (e.g. you can call C<ev_run> on the same loop from two
4323	different coroutines, and switch freely between both coroutines running	4731	different coroutines, and switch freely between both coroutines running
4324	the loop, as long as you don't confuse yourself). The only exception is	4732	the loop, as long as you don't confuse yourself). The only exception is
4325	that you must not do this from C<ev_periodic> reschedule callbacks.	4733	that you must not do this from C<ev_periodic> reschedule callbacks.
4326		4734
4327	Care has been taken to ensure that libev does not keep local state inside	4735	Care has been taken to ensure that libev does not keep local state inside
4328	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4736	C<ev_run>, and other calls do not usually allow for coroutine switches as
4329	they do not call any callbacks.	4737	they do not call any callbacks.
4330		4738
4331	=head2 COMPILER WARNINGS	4739	=head2 COMPILER WARNINGS
4332		4740
4333	Depending on your compiler and compiler settings, you might get no or a	4741	Depending on your compiler and compiler settings, you might get no or a
…		…
4344	maintainable.	4752	maintainable.
4345		4753
4346	And of course, some compiler warnings are just plain stupid, or simply	4754	And of course, some compiler warnings are just plain stupid, or simply
4347	wrong (because they don't actually warn about the condition their message	4755	wrong (because they don't actually warn about the condition their message
4348	seems to warn about). For example, certain older gcc versions had some	4756	seems to warn about). For example, certain older gcc versions had some
4349	warnings that resulted an extreme number of false positives. These have	4757	warnings that resulted in an extreme number of false positives. These have
4350	been fixed, but some people still insist on making code warn-free with	4758	been fixed, but some people still insist on making code warn-free with
4351	such buggy versions.	4759	such buggy versions.
4352		4760
4353	While libev is written to generate as few warnings as possible,	4761	While libev is written to generate as few warnings as possible,
4354	"warn-free" code is not a goal, and it is recommended not to build libev	4762	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
4390	I suggest using suppression lists.	4798	I suggest using suppression lists.
4391		4799
4392		4800
4393	=head1 PORTABILITY NOTES	4801	=head1 PORTABILITY NOTES
4394		4802
		4803	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4804
		4805	GNU/Linux is the only common platform that supports 64 bit file/large file
		4806	interfaces but I<disables> them by default.
		4807
		4808	That means that libev compiled in the default environment doesn't support
		4809	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4810
		4811	Unfortunately, many programs try to work around this GNU/Linux issue
		4812	by enabling the large file API, which makes them incompatible with the
		4813	standard libev compiled for their system.
		4814
		4815	Likewise, libev cannot enable the large file API itself as this would
		4816	suddenly make it incompatible to the default compile time environment,
		4817	i.e. all programs not using special compile switches.
		4818
		4819	=head2 OS/X AND DARWIN BUGS
		4820
		4821	The whole thing is a bug if you ask me - basically any system interface
		4822	you touch is broken, whether it is locales, poll, kqueue or even the
		4823	OpenGL drivers.
		4824
		4825	=head3 C<kqueue> is buggy
		4826
		4827	The kqueue syscall is broken in all known versions - most versions support
		4828	only sockets, many support pipes.
		4829
		4830	Libev tries to work around this by not using C<kqueue> by default on this
		4831	rotten platform, but of course you can still ask for it when creating a
		4832	loop - embedding a socket-only kqueue loop into a select-based one is
		4833	probably going to work well.
		4834
		4835	=head3 C<poll> is buggy
		4836
		4837	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4838	implementation by something calling C<kqueue> internally around the 10.5.6
		4839	release, so now C<kqueue> I<and> C<poll> are broken.
		4840
		4841	Libev tries to work around this by not using C<poll> by default on
		4842	this rotten platform, but of course you can still ask for it when creating
		4843	a loop.
		4844
		4845	=head3 C<select> is buggy
		4846
		4847	All that's left is C<select>, and of course Apple found a way to fuck this
		4848	one up as well: On OS/X, C<select> actively limits the number of file
		4849	descriptors you can pass in to 1024 - your program suddenly crashes when
		4850	you use more.
		4851
		4852	There is an undocumented "workaround" for this - defining
		4853	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4854	work on OS/X.
		4855
		4856	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4857
		4858	=head3 C<errno> reentrancy
		4859
		4860	The default compile environment on Solaris is unfortunately so
		4861	thread-unsafe that you can't even use components/libraries compiled
		4862	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4863	defined by default. A valid, if stupid, implementation choice.
		4864
		4865	If you want to use libev in threaded environments you have to make sure
		4866	it's compiled with C<_REENTRANT> defined.
		4867
		4868	=head3 Event port backend
		4869
		4870	The scalable event interface for Solaris is called "event
		4871	ports". Unfortunately, this mechanism is very buggy in all major
		4872	releases. If you run into high CPU usage, your program freezes or you get
		4873	a large number of spurious wakeups, make sure you have all the relevant
		4874	and latest kernel patches applied. No, I don't know which ones, but there
		4875	are multiple ones to apply, and afterwards, event ports actually work
		4876	great.
		4877
		4878	If you can't get it to work, you can try running the program by setting
		4879	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4880	C<select> backends.
		4881
		4882	=head2 AIX POLL BUG
		4883
		4884	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4885	this by trying to avoid the poll backend altogether (i.e. it's not even
		4886	compiled in), which normally isn't a big problem as C<select> works fine
		4887	with large bitsets on AIX, and AIX is dead anyway.
		4888
4395	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4889	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4890
		4891	=head3 General issues
4396		4892
4397	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4893	Win32 doesn't support any of the standards (e.g. POSIX) that libev
4398	requires, and its I/O model is fundamentally incompatible with the POSIX	4894	requires, and its I/O model is fundamentally incompatible with the POSIX
4399	model. Libev still offers limited functionality on this platform in	4895	model. Libev still offers limited functionality on this platform in
4400	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4896	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4401	descriptors. This only applies when using Win32 natively, not when using	4897	descriptors. This only applies when using Win32 natively, not when using
4402	e.g. cygwin.	4898	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4899	as every compielr comes with a slightly differently broken/incompatible
		4900	environment.
4403		4901
4404	Lifting these limitations would basically require the full	4902	Lifting these limitations would basically require the full
4405	re-implementation of the I/O system. If you are into these kinds of	4903	re-implementation of the I/O system. If you are into this kind of thing,
4406	things, then note that glib does exactly that for you in a very portable	4904	then note that glib does exactly that for you in a very portable way (note
4407	way (note also that glib is the slowest event library known to man).	4905	also that glib is the slowest event library known to man).
4408		4906
4409	There is no supported compilation method available on windows except	4907	There is no supported compilation method available on windows except
4410	embedding it into other applications.	4908	embedding it into other applications.
4411		4909
4412	Sensible signal handling is officially unsupported by Microsoft - libev	4910	Sensible signal handling is officially unsupported by Microsoft - libev
…		…
4440	you do I<not> compile the F<ev.c> or any other embedded source files!):	4938	you do I<not> compile the F<ev.c> or any other embedded source files!):
4441		4939
4442	#include "evwrap.h"	4940	#include "evwrap.h"
4443	#include "ev.c"	4941	#include "ev.c"
4444		4942
4445	=over 4
4446
4447	=item The winsocket select function	4943	=head3 The winsocket C<select> function
4448		4944
4449	The winsocket C<select> function doesn't follow POSIX in that it	4945	The winsocket C<select> function doesn't follow POSIX in that it
4450	requires socket I<handles> and not socket I<file descriptors> (it is	4946	requires socket I<handles> and not socket I<file descriptors> (it is
4451	also extremely buggy). This makes select very inefficient, and also	4947	also extremely buggy). This makes select very inefficient, and also
4452	requires a mapping from file descriptors to socket handles (the Microsoft	4948	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
4461	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4957	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
4462		4958
4463	Note that winsockets handling of fd sets is O(n), so you can easily get a	4959	Note that winsockets handling of fd sets is O(n), so you can easily get a
4464	complexity in the O(n²) range when using win32.	4960	complexity in the O(n²) range when using win32.
4465		4961
4466	=item Limited number of file descriptors	4962	=head3 Limited number of file descriptors
4467		4963
4468	Windows has numerous arbitrary (and low) limits on things.	4964	Windows has numerous arbitrary (and low) limits on things.
4469		4965
4470	Early versions of winsocket's select only supported waiting for a maximum	4966	Early versions of winsocket's select only supported waiting for a maximum
4471	of C<64> handles (probably owning to the fact that all windows kernels	4967	of C<64> handles (probably owning to the fact that all windows kernels
…		…
4486	runtime libraries. This might get you to about C<512> or C<2048> sockets	4982	runtime libraries. This might get you to about C<512> or C<2048> sockets
4487	(depending on windows version and/or the phase of the moon). To get more,	4983	(depending on windows version and/or the phase of the moon). To get more,
4488	you need to wrap all I/O functions and provide your own fd management, but	4984	you need to wrap all I/O functions and provide your own fd management, but
4489	the cost of calling select (O(n²)) will likely make this unworkable.	4985	the cost of calling select (O(n²)) will likely make this unworkable.
4490		4986
4491	=back
4492
4493	=head2 PORTABILITY REQUIREMENTS	4987	=head2 PORTABILITY REQUIREMENTS
4494		4988
4495	In addition to a working ISO-C implementation and of course the	4989	In addition to a working ISO-C implementation and of course the
4496	backend-specific APIs, libev relies on a few additional extensions:	4990	backend-specific APIs, libev relies on a few additional extensions:
4497		4991
…		…
4503	Libev assumes not only that all watcher pointers have the same internal	4997	Libev assumes not only that all watcher pointers have the same internal
4504	structure (guaranteed by POSIX but not by ISO C for example), but it also	4998	structure (guaranteed by POSIX but not by ISO C for example), but it also
4505	assumes that the same (machine) code can be used to call any watcher	4999	assumes that the same (machine) code can be used to call any watcher
4506	callback: The watcher callbacks have different type signatures, but libev	5000	callback: The watcher callbacks have different type signatures, but libev
4507	calls them using an C<ev_watcher *> internally.	5001	calls them using an C<ev_watcher *> internally.
		5002
		5003	=item pointer accesses must be thread-atomic
		5004
		5005	Accessing a pointer value must be atomic, it must both be readable and
		5006	writable in one piece - this is the case on all current architectures.
4508		5007
4509	=item C<sig_atomic_t volatile> must be thread-atomic as well	5008	=item C<sig_atomic_t volatile> must be thread-atomic as well
4510		5009
4511	The type C<sig_atomic_t volatile> (or whatever is defined as	5010	The type C<sig_atomic_t volatile> (or whatever is defined as
4512	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5011	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
4535	watchers.	5034	watchers.
4536		5035
4537	=item C<double> must hold a time value in seconds with enough accuracy	5036	=item C<double> must hold a time value in seconds with enough accuracy
4538		5037
4539	The type C<double> is used to represent timestamps. It is required to	5038	The type C<double> is used to represent timestamps. It is required to
4540	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5039	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4541	enough for at least into the year 4000. This requirement is fulfilled by	5040	good enough for at least into the year 4000 with millisecond accuracy
		5041	(the design goal for libev). This requirement is overfulfilled by
4542	implementations implementing IEEE 754, which is basically all existing	5042	implementations using IEEE 754, which is basically all existing ones. With
4543	ones. With IEEE 754 doubles, you get microsecond accuracy until at least	5043	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
4544	2200.
4545		5044
4546	=back	5045	=back
4547		5046
4548	If you know of other additional requirements drop me a note.	5047	If you know of other additional requirements drop me a note.
4549		5048
…		…
4617	involves iterating over all running async watchers or all signal numbers.	5116	involves iterating over all running async watchers or all signal numbers.
4618		5117
4619	=back	5118	=back
4620		5119
4621		5120
		5121	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5122
		5123	The major version 4 introduced some incompatible changes to the API.
		5124
		5125	At the moment, the C<ev.h> header file provides compatibility definitions
		5126	for all changes, so most programs should still compile. The compatibility
		5127	layer might be removed in later versions of libev, so better update to the
		5128	new API early than late.
		5129
		5130	=over 4
		5131
		5132	=item C<EV_COMPAT3> backwards compatibility mechanism
		5133
		5134	The backward compatibility mechanism can be controlled by
		5135	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5136	section.
		5137
		5138	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5139
		5140	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5141
		5142	ev_loop_destroy (EV_DEFAULT_UC);
		5143	ev_loop_fork (EV_DEFAULT);
		5144
		5145	=item function/symbol renames
		5146
		5147	A number of functions and symbols have been renamed:
		5148
		5149	ev_loop => ev_run
		5150	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5151	EVLOOP_ONESHOT => EVRUN_ONCE
		5152
		5153	ev_unloop => ev_break
		5154	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5155	EVUNLOOP_ONE => EVBREAK_ONE
		5156	EVUNLOOP_ALL => EVBREAK_ALL
		5157
		5158	EV_TIMEOUT => EV_TIMER
		5159
		5160	ev_loop_count => ev_iteration
		5161	ev_loop_depth => ev_depth
		5162	ev_loop_verify => ev_verify
		5163
		5164	Most functions working on C<struct ev_loop> objects don't have an
		5165	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5166	associated constants have been renamed to not collide with the C<struct
		5167	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5168	as all other watcher types. Note that C<ev_loop_fork> is still called
		5169	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5170	typedef.
		5171
		5172	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5173
		5174	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5175	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5176	and work, but the library code will of course be larger.
		5177
		5178	=back
		5179
		5180
4622	=head1 GLOSSARY	5181	=head1 GLOSSARY
4623		5182
4624	=over 4	5183	=over 4
4625		5184
4626	=item active	5185	=item active
4627		5186
4628	A watcher is active as long as it has been started (has been attached to	5187	A watcher is active as long as it has been started and not yet stopped.
4629	an event loop) but not yet stopped (disassociated from the event loop).	5188	See L<WATCHER STATES> for details.
4630		5189
4631	=item application	5190	=item application
4632		5191
4633	In this document, an application is whatever is using libev.	5192	In this document, an application is whatever is using libev.
		5193
		5194	=item backend
		5195
		5196	The part of the code dealing with the operating system interfaces.
4634		5197
4635	=item callback	5198	=item callback
4636		5199
4637	The address of a function that is called when some event has been	5200	The address of a function that is called when some event has been
4638	detected. Callbacks are being passed the event loop, the watcher that	5201	detected. Callbacks are being passed the event loop, the watcher that
4639	received the event, and the actual event bitset.	5202	received the event, and the actual event bitset.
4640		5203
4641	=item callback invocation	5204	=item callback/watcher invocation
4642		5205
4643	The act of calling the callback associated with a watcher.	5206	The act of calling the callback associated with a watcher.
4644		5207
4645	=item event	5208	=item event
4646		5209
4647	A change of state of some external event, such as data now being available	5210	A change of state of some external event, such as data now being available
4648	for reading on a file descriptor, time having passed or simply not having	5211	for reading on a file descriptor, time having passed or simply not having
4649	any other events happening anymore.	5212	any other events happening anymore.
4650		5213
4651	In libev, events are represented as single bits (such as C<EV_READ> or	5214	In libev, events are represented as single bits (such as C<EV_READ> or
4652	C<EV_TIMEOUT>).	5215	C<EV_TIMER>).
4653		5216
4654	=item event library	5217	=item event library
4655		5218
4656	A software package implementing an event model and loop.	5219	A software package implementing an event model and loop.
4657		5220
…		…
4665	The model used to describe how an event loop handles and processes	5228	The model used to describe how an event loop handles and processes
4666	watchers and events.	5229	watchers and events.
4667		5230
4668	=item pending	5231	=item pending
4669		5232
4670	A watcher is pending as soon as the corresponding event has been detected,	5233	A watcher is pending as soon as the corresponding event has been
4671	and stops being pending as soon as the watcher will be invoked or its	5234	detected. See L<WATCHER STATES> for details.
4672	pending status is explicitly cleared by the application.
4673
4674	A watcher can be pending, but not active. Stopping a watcher also clears
4675	its pending status.
4676		5235
4677	=item real time	5236	=item real time
4678		5237
4679	The physical time that is observed. It is apparently strictly monotonic :)	5238	The physical time that is observed. It is apparently strictly monotonic :)
4680		5239
4681	=item wall-clock time	5240	=item wall-clock time
4682		5241
4683	The time and date as shown on clocks. Unlike real time, it can actually	5242	The time and date as shown on clocks. Unlike real time, it can actually
4684	be wrong and jump forwards and backwards, e.g. when the you adjust your	5243	be wrong and jump forwards and backwards, e.g. when you adjust your
4685	clock.	5244	clock.
4686		5245
4687	=item watcher	5246	=item watcher
4688		5247
4689	A data structure that describes interest in certain events. Watchers need	5248	A data structure that describes interest in certain events. Watchers need
4690	to be started (attached to an event loop) before they can receive events.	5249	to be started (attached to an event loop) before they can receive events.
4691		5250
4692	=item watcher invocation
4693
4694	The act of calling the callback associated with a watcher.
4695
4696	=back	5251	=back
4697		5252
4698	=head1 AUTHOR	5253	=head1 AUTHOR
4699		5254
4700	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5255	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5256	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4701		5257

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