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Revision 1.399 by root, Mon Apr 2 23:14:41 2012 UTC

…		…
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);
…		…
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_run (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
…		…
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	Familiarity 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
…		…
165		173
166	=item ev_tstamp ev_time ()	174	=item ev_tstamp ev_time ()
167		175
168	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
169	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
170	you actually want to know. Also interetsing is the combination of	178	you actually want to know. Also interesting is the combination of
171	C<ev_update_now> and C<ev_now>.	179	C<ev_now_update> and C<ev_now>.
172		180
173	=item ev_sleep (ev_tstamp interval)	181	=item ev_sleep (ev_tstamp interval)
174		182
175	Sleep for the given interval: The current thread will be blocked until	183	Sleep for the given interval: The current thread will be blocked
176	either it is interrupted or the given time interval has passed. Basically	184	until either it is interrupted or the given time interval has
		185	passed (approximately - it might return a bit earlier even if not
		186	interrupted). Returns immediately if C<< interval <= 0 >>.
		187
177	this is a sub-second-resolution C<sleep ()>.	188	Basically this is a sub-second-resolution C<sleep ()>.
		189
		190	The range of the C<interval> is limited - libev only guarantees to work
		191	with sleep times of up to one day (C<< interval <= 86400 >>).
178		192
179	=item int ev_version_major ()	193	=item int ev_version_major ()
180		194
181	=item int ev_version_minor ()	195	=item int ev_version_minor ()
182		196
…		…
233	the current system, you would need to look at C<ev_embeddable_backends ()	247	the current system, you would need to look at C<ev_embeddable_backends ()
234	& ev_supported_backends ()>, likewise for recommended ones.	248	& ev_supported_backends ()>, likewise for recommended ones.
235		249
236	See the description of C<ev_embed> watchers for more info.	250	See the description of C<ev_embed> watchers for more info.
237		251
238	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	252	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
239		253
240	Sets the allocation function to use (the prototype is similar - the	254	Sets the allocation function to use (the prototype is similar - the
241	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	255	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
242	used to allocate and free memory (no surprises here). If it returns zero	256	used to allocate and free memory (no surprises here). If it returns zero
243	when memory needs to be allocated (C<size != 0>), the library might abort	257	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
269	}	283	}
270		284
271	...	285	...
272	ev_set_allocator (persistent_realloc);	286	ev_set_allocator (persistent_realloc);
273		287
274	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	288	=item ev_set_syserr_cb (void (*cb)(const char *msg))
275		289
276	Set the callback function to call on a retryable system call error (such	290	Set the callback function to call on a retryable system call error (such
277	as failed select, poll, epoll_wait). The message is a printable string	291	as failed select, poll, epoll_wait). The message is a printable string
278	indicating the system call or subsystem causing the problem. If this	292	indicating the system call or subsystem causing the problem. If this
279	callback is set, then libev will expect it to remedy the situation, no	293	callback is set, then libev will expect it to remedy the situation, no
…		…
291	}	305	}
292		306
293	...	307	...
294	ev_set_syserr_cb (fatal_error);	308	ev_set_syserr_cb (fatal_error);
295		309
		310	=item ev_feed_signal (int signum)
		311
		312	This function can be used to "simulate" a signal receive. It is completely
		313	safe to call this function at any time, from any context, including signal
		314	handlers or random threads.
		315
		316	Its main use is to customise signal handling in your process, especially
		317	in the presence of threads. For example, you could block signals
		318	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		319	creating any loops), and in one thread, use C<sigwait> or any other
		320	mechanism to wait for signals, then "deliver" them to libev by calling
		321	C<ev_feed_signal>.
		322
296	=back	323	=back
297		324
298	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	325	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
299		326
300	An event loop is described by a C<struct ev_loop *> (the C<struct> is	327	An event loop is described by a C<struct ev_loop *> (the C<struct> is
301	I<not> optional in this case unless libev 3 compatibility is disabled, as	328	I<not> optional in this case unless libev 3 compatibility is disabled, as
302	libev 3 had an C<ev_loop> function colliding with the struct name).	329	libev 3 had an C<ev_loop> function colliding with the struct name).
303		330
304	The library knows two types of such loops, the I<default> loop, which	331	The library knows two types of such loops, the I<default> loop, which
305	supports signals and child events, and dynamically created event loops	332	supports child process events, and dynamically created event loops which
306	which do not.	333	do not.
307		334
308	=over 4	335	=over 4
309		336
310	=item struct ev_loop *ev_default_loop (unsigned int flags)	337	=item struct ev_loop *ev_default_loop (unsigned int flags)
311		338
312	This will initialise the default event loop if it hasn't been initialised	339	This returns the "default" event loop object, which is what you should
313	yet and return it. If the default loop could not be initialised, returns	340	normally use when you just need "the event loop". Event loop objects and
314	false. If it already was initialised it simply returns it (and ignores the	341	the C<flags> parameter are described in more detail in the entry for
315	flags. If that is troubling you, check C<ev_backend ()> afterwards).	342	C<ev_loop_new>.
		343
		344	If the default loop is already initialised then this function simply
		345	returns it (and ignores the flags. If that is troubling you, check
		346	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		347	flags, which should almost always be C<0>, unless the caller is also the
		348	one calling C<ev_run> or otherwise qualifies as "the main program".
316		349
317	If you don't know what event loop to use, use the one returned from this	350	If you don't know what event loop to use, use the one returned from this
318	function.	351	function (or via the C<EV_DEFAULT> macro).
319		352
320	Note that this function is I<not> thread-safe, so if you want to use it	353	Note that this function is I<not> thread-safe, so if you want to use it
321	from multiple threads, you have to lock (note also that this is unlikely,	354	from multiple threads, you have to employ some kind of mutex (note also
322	as loops cannot be shared easily between threads anyway).	355	that this case is unlikely, as loops cannot be shared easily between
		356	threads anyway).
323		357
324	The default loop is the only loop that can handle C<ev_signal> and	358	The default loop is the only loop that can handle C<ev_child> watchers,
325	C<ev_child> watchers, and to do this, it always registers a handler	359	and to do this, it always registers a handler for C<SIGCHLD>. If this is
326	for C<SIGCHLD>. If this is a problem for your application you can either	360	a problem for your application you can either create a dynamic loop with
327	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	361	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
328	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	362	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
329	C<ev_default_init>.	363
		364	Example: This is the most typical usage.
		365
		366	if (!ev_default_loop (0))
		367	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		368
		369	Example: Restrict libev to the select and poll backends, and do not allow
		370	environment settings to be taken into account:
		371
		372	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		373
		374	=item struct ev_loop *ev_loop_new (unsigned int flags)
		375
		376	This will create and initialise a new event loop object. If the loop
		377	could not be initialised, returns false.
		378
		379	This function is thread-safe, and one common way to use libev with
		380	threads is indeed to create one loop per thread, and using the default
		381	loop in the "main" or "initial" thread.
330		382
331	The flags argument can be used to specify special behaviour or specific	383	The flags argument can be used to specify special behaviour or specific
332	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	384	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
333		385
334	The following flags are supported:	386	The following flags are supported:
…		…
369	environment variable.	421	environment variable.
370		422
371	=item C<EVFLAG_NOINOTIFY>	423	=item C<EVFLAG_NOINOTIFY>
372		424
373	When this flag is specified, then libev will not attempt to use the	425	When this flag is specified, then libev will not attempt to use the
374	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and	426	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
375	testing, this flag can be useful to conserve inotify file descriptors, as	427	testing, this flag can be useful to conserve inotify file descriptors, as
376	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.	428	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
377		429
378	=item C<EVFLAG_SIGNALFD>	430	=item C<EVFLAG_SIGNALFD>
379		431
380	When this flag is specified, then libev will attempt to use the	432	When this flag is specified, then libev will attempt to use the
381	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API	433	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
382	delivers signals synchronously, which makes it both faster and might make	434	delivers signals synchronously, which makes it both faster and might make
383	it possible to get the queued signal data. It can also simplify signal	435	it possible to get the queued signal data. It can also simplify signal
384	handling with threads, as long as you properly block signals in your	436	handling with threads, as long as you properly block signals in your
385	threads that are not interested in handling them.	437	threads that are not interested in handling them.
386		438
387	Signalfd will not be used by default as this changes your signal mask, and	439	Signalfd will not be used by default as this changes your signal mask, and
388	there are a lot of shoddy libraries and programs (glib's threadpool for	440	there are a lot of shoddy libraries and programs (glib's threadpool for
389	example) that can't properly initialise their signal masks.	441	example) that can't properly initialise their signal masks.
		442
		443	=item C<EVFLAG_NOSIGMASK>
		444
		445	When this flag is specified, then libev will avoid to modify the signal
		446	mask. Specifically, this means you have to make sure signals are unblocked
		447	when you want to receive them.
		448
		449	This behaviour is useful when you want to do your own signal handling, or
		450	want to handle signals only in specific threads and want to avoid libev
		451	unblocking the signals.
		452
		453	It's also required by POSIX in a threaded program, as libev calls
		454	C<sigprocmask>, whose behaviour is officially unspecified.
		455
		456	This flag's behaviour will become the default in future versions of libev.
390		457
391	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	458	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
392		459
393	This is your standard select(2) backend. Not I<completely> standard, as	460	This is your standard select(2) backend. Not I<completely> standard, as
394	libev tries to roll its own fd_set with no limits on the number of fds,	461	libev tries to roll its own fd_set with no limits on the number of fds,
…		…
422	=item C<EVBACKEND_EPOLL> (value 4, Linux)	489	=item C<EVBACKEND_EPOLL> (value 4, Linux)
423		490
424	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9	491	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
425	kernels).	492	kernels).
426		493
427	For few fds, this backend is a bit little slower than poll and select,	494	For few fds, this backend is a bit little slower than poll and select, but
428	but it scales phenomenally better. While poll and select usually scale	495	it scales phenomenally better. While poll and select usually scale like
429	like O(total_fds) where n is the total number of fds (or the highest fd),	496	O(total_fds) where total_fds is the total number of fds (or the highest
430	epoll scales either O(1) or O(active_fds).	497	fd), epoll scales either O(1) or O(active_fds).
431		498
432	The epoll mechanism deserves honorable mention as the most misdesigned	499	The epoll mechanism deserves honorable mention as the most misdesigned
433	of the more advanced event mechanisms: mere annoyances include silently	500	of the more advanced event mechanisms: mere annoyances include silently
434	dropping file descriptors, requiring a system call per change per file	501	dropping file descriptors, requiring a system call per change per file
435	descriptor (and unnecessary guessing of parameters), problems with dup and	502	descriptor (and unnecessary guessing of parameters), problems with dup,
		503	returning before the timeout value, resulting in additional iterations
		504	(and only giving 5ms accuracy while select on the same platform gives
436	so on. The biggest issue is fork races, however - if a program forks then	505	0.1ms) and so on. The biggest issue is fork races, however - if a program
437	I<both> parent and child process have to recreate the epoll set, which can	506	forks then I<both> parent and child process have to recreate the epoll
438	take considerable time (one syscall per file descriptor) and is of course	507	set, which can take considerable time (one syscall per file descriptor)
439	hard to detect.	508	and is of course hard to detect.
440		509
441	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	510	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
442	of course I<doesn't>, and epoll just loves to report events for totally	511	but of course I<doesn't>, and epoll just loves to report events for
443	I<different> file descriptors (even already closed ones, so one cannot	512	totally I<different> file descriptors (even already closed ones, so
444	even remove them from the set) than registered in the set (especially	513	one cannot even remove them from the set) than registered in the set
445	on SMP systems). Libev tries to counter these spurious notifications by	514	(especially on SMP systems). Libev tries to counter these spurious
446	employing an additional generation counter and comparing that against the	515	notifications by employing an additional generation counter and comparing
447	events to filter out spurious ones, recreating the set when required. Last	516	that against the events to filter out spurious ones, recreating the set
		517	when required. Epoll also erroneously rounds down timeouts, but gives you
		518	no way to know when and by how much, so sometimes you have to busy-wait
		519	because epoll returns immediately despite a nonzero timeout. And last
448	not least, it also refuses to work with some file descriptors which work	520	not least, it also refuses to work with some file descriptors which work
449	perfectly fine with C<select> (files, many character devices...).	521	perfectly fine with C<select> (files, many character devices...).
		522
		523	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
		524	cobbled together in a hurry, no thought to design or interaction with
		525	others. Oh, the pain, will it ever stop...
450		526
451	While stopping, setting and starting an I/O watcher in the same iteration	527	While stopping, setting and starting an I/O watcher in the same iteration
452	will result in some caching, there is still a system call per such	528	will result in some caching, there is still a system call per such
453	incident (because the same I<file descriptor> could point to a different	529	incident (because the same I<file descriptor> could point to a different
454	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	530	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
491		567
492	It scales in the same way as the epoll backend, but the interface to the	568	It scales in the same way as the epoll backend, but the interface to the
493	kernel is more efficient (which says nothing about its actual speed, of	569	kernel is more efficient (which says nothing about its actual speed, of
494	course). While stopping, setting and starting an I/O watcher does never	570	course). While stopping, setting and starting an I/O watcher does never
495	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	571	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
496	two event changes per incident. Support for C<fork ()> is very bad (but	572	two event changes per incident. Support for C<fork ()> is very bad (you
497	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect	573	might have to leak fd's on fork, but it's more sane than epoll) and it
498	cases	574	drops fds silently in similarly hard-to-detect cases
499		575
500	This backend usually performs well under most conditions.	576	This backend usually performs well under most conditions.
501		577
502	While nominally embeddable in other event loops, this doesn't work	578	While nominally embeddable in other event loops, this doesn't work
503	everywhere, so you might need to test for this. And since it is broken	579	everywhere, so you might need to test for this. And since it is broken
…		…
520	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	596	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
521		597
522	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	598	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
523	it's really slow, but it still scales very well (O(active_fds)).	599	it's really slow, but it still scales very well (O(active_fds)).
524		600
525	Please note that Solaris event ports can deliver a lot of spurious
526	notifications, so you need to use non-blocking I/O or other means to avoid
527	blocking when no data (or space) is available.
528
529	While this backend scales well, it requires one system call per active	601	While this backend scales well, it requires one system call per active
530	file descriptor per loop iteration. For small and medium numbers of file	602	file descriptor per loop iteration. For small and medium numbers of file
531	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	603	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
532	might perform better.	604	might perform better.
533		605
534	On the positive side, with the exception of the spurious readiness	606	On the positive side, this backend actually performed fully to
535	notifications, this backend actually performed fully to specification
536	in all tests and is fully embeddable, which is a rare feat among the	607	specification in all tests and is fully embeddable, which is a rare feat
537	OS-specific backends (I vastly prefer correctness over speed hacks).	608	among the OS-specific backends (I vastly prefer correctness over speed
		609	hacks).
		610
		611	On the negative side, the interface is I<bizarre> - so bizarre that
		612	even sun itself gets it wrong in their code examples: The event polling
		613	function sometimes returns events to the caller even though an error
		614	occurred, but with no indication whether it has done so or not (yes, it's
		615	even documented that way) - deadly for edge-triggered interfaces where you
		616	absolutely have to know whether an event occurred or not because you have
		617	to re-arm the watcher.
		618
		619	Fortunately libev seems to be able to work around these idiocies.
538		620
539	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	621	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
540	C<EVBACKEND_POLL>.	622	C<EVBACKEND_POLL>.
541		623
542	=item C<EVBACKEND_ALL>	624	=item C<EVBACKEND_ALL>
543		625
544	Try all backends (even potentially broken ones that wouldn't be tried	626	Try all backends (even potentially broken ones that wouldn't be tried
545	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	627	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
546	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	628	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
547		629
548	It is definitely not recommended to use this flag.	630	It is definitely not recommended to use this flag, use whatever
		631	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		632	at all.
		633
		634	=item C<EVBACKEND_MASK>
		635
		636	Not a backend at all, but a mask to select all backend bits from a
		637	C<flags> value, in case you want to mask out any backends from a flags
		638	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
549		639
550	=back	640	=back
551		641
552	If one or more of the backend flags are or'ed into the flags value,	642	If one or more of the backend flags are or'ed into the flags value,
553	then only these backends will be tried (in the reverse order as listed	643	then only these backends will be tried (in the reverse order as listed
554	here). If none are specified, all backends in C<ev_recommended_backends	644	here). If none are specified, all backends in C<ev_recommended_backends
555	()> will be tried.	645	()> will be tried.
556		646
557	Example: This is the most typical usage.
558
559	if (!ev_default_loop (0))
560	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
561
562	Example: Restrict libev to the select and poll backends, and do not allow
563	environment settings to be taken into account:
564
565	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
566
567	Example: Use whatever libev has to offer, but make sure that kqueue is
568	used if available (warning, breaks stuff, best use only with your own
569	private event loop and only if you know the OS supports your types of
570	fds):
571
572	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
573
574	=item struct ev_loop *ev_loop_new (unsigned int flags)
575
576	Similar to C<ev_default_loop>, but always creates a new event loop that is
577	always distinct from the default loop.
578
579	Note that this function I<is> thread-safe, and one common way to use
580	libev with threads is indeed to create one loop per thread, and using the
581	default loop in the "main" or "initial" thread.
582
583	Example: Try to create a event loop that uses epoll and nothing else.	647	Example: Try to create a event loop that uses epoll and nothing else.
584		648
585	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	649	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
586	if (!epoller)	650	if (!epoller)
587	fatal ("no epoll found here, maybe it hides under your chair");	651	fatal ("no epoll found here, maybe it hides under your chair");
588		652
		653	Example: Use whatever libev has to offer, but make sure that kqueue is
		654	used if available.
		655
		656	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		657
589	=item ev_default_destroy ()	658	=item ev_loop_destroy (loop)
590		659
591	Destroys the default loop (frees all memory and kernel state etc.). None	660	Destroys an event loop object (frees all memory and kernel state
592	of the active event watchers will be stopped in the normal sense, so	661	etc.). None of the active event watchers will be stopped in the normal
593	e.g. C<ev_is_active> might still return true. It is your responsibility to	662	sense, so e.g. C<ev_is_active> might still return true. It is your
594	either stop all watchers cleanly yourself I<before> calling this function,	663	responsibility to either stop all watchers cleanly yourself I<before>
595	or cope with the fact afterwards (which is usually the easiest thing, you	664	calling this function, or cope with the fact afterwards (which is usually
596	can just ignore the watchers and/or C<free ()> them for example).	665	the easiest thing, you can just ignore the watchers and/or C<free ()> them
		666	for example).
597		667
598	Note that certain global state, such as signal state (and installed signal	668	Note that certain global state, such as signal state (and installed signal
599	handlers), will not be freed by this function, and related watchers (such	669	handlers), will not be freed by this function, and related watchers (such
600	as signal and child watchers) would need to be stopped manually.	670	as signal and child watchers) would need to be stopped manually.
601		671
602	In general it is not advisable to call this function except in the	672	This function is normally used on loop objects allocated by
603	rare occasion where you really need to free e.g. the signal handling	673	C<ev_loop_new>, but it can also be used on the default loop returned by
		674	C<ev_default_loop>, in which case it is not thread-safe.
		675
		676	Note that it is not advisable to call this function on the default loop
		677	except in the rare occasion where you really need to free its resources.
604	pipe fds. If you need dynamically allocated loops it is better to use	678	If you need dynamically allocated loops it is better to use C<ev_loop_new>
605	C<ev_loop_new> and C<ev_loop_destroy>.	679	and C<ev_loop_destroy>.
606		680
607	=item ev_loop_destroy (loop)	681	=item ev_loop_fork (loop)
608		682
609	Like C<ev_default_destroy>, but destroys an event loop created by an
610	earlier call to C<ev_loop_new>.
611
612	=item ev_default_fork ()
613
614	This function sets a flag that causes subsequent C<ev_run> iterations	683	This function sets a flag that causes subsequent C<ev_run> iterations to
615	to reinitialise the kernel state for backends that have one. Despite the	684	reinitialise the kernel state for backends that have one. Despite the
616	name, you can call it anytime, but it makes most sense after forking, in	685	name, you can call it anytime, but it makes most sense after forking, in
617	the child process (or both child and parent, but that again makes little	686	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
618	sense). You I<must> call it in the child before using any of the libev	687	child before resuming or calling C<ev_run>.
619	functions, and it will only take effect at the next C<ev_run> iteration.
620		688
621	Again, you I<have> to call it on I<any> loop that you want to re-use after	689	Again, you I<have> to call it on I<any> loop that you want to re-use after
622	a fork, I<even if you do not plan to use the loop in the parent>. This is	690	a fork, I<even if you do not plan to use the loop in the parent>. This is
623	because some kernel interfaces *cough* I<kqueue> *cough* do funny things	691	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
624	during fork.	692	during fork.
…		…
629	call it at all (in fact, C<epoll> is so badly broken that it makes a	697	call it at all (in fact, C<epoll> is so badly broken that it makes a
630	difference, but libev will usually detect this case on its own and do a	698	difference, but libev will usually detect this case on its own and do a
631	costly reset of the backend).	699	costly reset of the backend).
632		700
633	The function itself is quite fast and it's usually not a problem to call	701	The function itself is quite fast and it's usually not a problem to call
634	it just in case after a fork. To make this easy, the function will fit in	702	it just in case after a fork.
635	quite nicely into a call to C<pthread_atfork>:
636		703
		704	Example: Automate calling C<ev_loop_fork> on the default loop when
		705	using pthreads.
		706
		707	static void
		708	post_fork_child (void)
		709	{
		710	ev_loop_fork (EV_DEFAULT);
		711	}
		712
		713	...
637	pthread_atfork (0, 0, ev_default_fork);	714	pthread_atfork (0, 0, post_fork_child);
638
639	=item ev_loop_fork (loop)
640
641	Like C<ev_default_fork>, but acts on an event loop created by
642	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
643	after fork that you want to re-use in the child, and how you keep track of
644	them is entirely your own problem.
645		715
646	=item int ev_is_default_loop (loop)	716	=item int ev_is_default_loop (loop)
647		717
648	Returns true when the given loop is, in fact, the default loop, and false	718	Returns true when the given loop is, in fact, the default loop, and false
649	otherwise.	719	otherwise.
…		…
660	prepare and check phases.	730	prepare and check phases.
661		731
662	=item unsigned int ev_depth (loop)	732	=item unsigned int ev_depth (loop)
663		733
664	Returns the number of times C<ev_run> was entered minus the number of	734	Returns the number of times C<ev_run> was entered minus the number of
665	times C<ev_run> was exited, in other words, the recursion depth.	735	times C<ev_run> was exited normally, in other words, the recursion depth.
666		736
667	Outside C<ev_run>, this number is zero. In a callback, this number is	737	Outside C<ev_run>, this number is zero. In a callback, this number is
668	C<1>, unless C<ev_run> was invoked recursively (or from another thread),	738	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
669	in which case it is higher.	739	in which case it is higher.
670		740
671	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread	741	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
672	etc.), doesn't count as "exit" - consider this as a hint to avoid such	742	throwing an exception etc.), doesn't count as "exit" - consider this
673	ungentleman-like behaviour unless it's really convenient.	743	as a hint to avoid such ungentleman-like behaviour unless it's really
		744	convenient, in which case it is fully supported.
674		745
675	=item unsigned int ev_backend (loop)	746	=item unsigned int ev_backend (loop)
676		747
677	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	748	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
678	use.	749	use.
…		…
721	without a previous call to C<ev_suspend>.	792	without a previous call to C<ev_suspend>.
722		793
723	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	794	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
724	event loop time (see C<ev_now_update>).	795	event loop time (see C<ev_now_update>).
725		796
726	=item ev_run (loop, int flags)	797	=item bool ev_run (loop, int flags)
727		798
728	Finally, this is it, the event handler. This function usually is called	799	Finally, this is it, the event handler. This function usually is called
729	after you have initialised all your watchers and you want to start	800	after you have initialised all your watchers and you want to start
730	handling events. It will ask the operating system for any new events, call	801	handling events. It will ask the operating system for any new events, call
731	the watcher callbacks, an then repeat the whole process indefinitely: This	802	the watcher callbacks, and then repeat the whole process indefinitely: This
732	is why event loops are called I<loops>.	803	is why event loops are called I<loops>.
733		804
734	If the flags argument is specified as C<0>, it will keep handling events	805	If the flags argument is specified as C<0>, it will keep handling events
735	until either no event watchers are active anymore or C<ev_break> was	806	until either no event watchers are active anymore or C<ev_break> was
736	called.	807	called.
		808
		809	The return value is false if there are no more active watchers (which
		810	usually means "all jobs done" or "deadlock"), and true in all other cases
		811	(which usually means " you should call C<ev_run> again").
737		812
738	Please note that an explicit C<ev_break> is usually better than	813	Please note that an explicit C<ev_break> is usually better than
739	relying on all watchers to be stopped when deciding when a program has	814	relying on all watchers to be stopped when deciding when a program has
740	finished (especially in interactive programs), but having a program	815	finished (especially in interactive programs), but having a program
741	that automatically loops as long as it has to and no longer by virtue	816	that automatically loops as long as it has to and no longer by virtue
742	of relying on its watchers stopping correctly, that is truly a thing of	817	of relying on its watchers stopping correctly, that is truly a thing of
743	beauty.	818	beauty.
744		819
		820	This function is I<mostly> exception-safe - you can break out of a
		821	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		822	exception and so on. This does not decrement the C<ev_depth> value, nor
		823	will it clear any outstanding C<EVBREAK_ONE> breaks.
		824
745	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle	825	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
746	those events and any already outstanding ones, but will not wait and	826	those events and any already outstanding ones, but will not wait and
747	block your process in case there are no events and will return after one	827	block your process in case there are no events and will return after one
748	iteration of the loop. This is sometimes useful to poll and handle new	828	iteration of the loop. This is sometimes useful to poll and handle new
749	events while doing lengthy calculations, to keep the program responsive.	829	events while doing lengthy calculations, to keep the program responsive.
…		…
758	This is useful if you are waiting for some external event in conjunction	838	This is useful if you are waiting for some external event in conjunction
759	with something not expressible using other libev watchers (i.e. "roll your	839	with something not expressible using other libev watchers (i.e. "roll your
760	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	840	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
761	usually a better approach for this kind of thing.	841	usually a better approach for this kind of thing.
762		842
763	Here are the gory details of what C<ev_run> does:	843	Here are the gory details of what C<ev_run> does (this is for your
		844	understanding, not a guarantee that things will work exactly like this in
		845	future versions):
764		846
765	- Increment loop depth.	847	- Increment loop depth.
766	- Reset the ev_break status.	848	- Reset the ev_break status.
767	- Before the first iteration, call any pending watchers.	849	- Before the first iteration, call any pending watchers.
768	LOOP:	850	LOOP:
…		…
801	anymore.	883	anymore.
802		884
803	... queue jobs here, make sure they register event watchers as long	885	... queue jobs here, make sure they register event watchers as long
804	... as they still have work to do (even an idle watcher will do..)	886	... as they still have work to do (even an idle watcher will do..)
805	ev_run (my_loop, 0);	887	ev_run (my_loop, 0);
806	... jobs done or somebody called unloop. yeah!	888	... jobs done or somebody called break. yeah!
807		889
808	=item ev_break (loop, how)	890	=item ev_break (loop, how)
809		891
810	Can be used to make a call to C<ev_run> return early (but only after it	892	Can be used to make a call to C<ev_run> return early (but only after it
811	has processed all outstanding events). The C<how> argument must be either	893	has processed all outstanding events). The C<how> argument must be either
812	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or	894	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
813	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.	895	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
814		896
815	This "unloop state" will be cleared when entering C<ev_run> again.	897	This "break state" will be cleared on the next call to C<ev_run>.
816		898
817	It is safe to call C<ev_break> from outside any C<ev_run> calls. ##TODO##	899	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		900	which case it will have no effect.
818		901
819	=item ev_ref (loop)	902	=item ev_ref (loop)
820		903
821	=item ev_unref (loop)	904	=item ev_unref (loop)
822		905
…		…
843	running when nothing else is active.	926	running when nothing else is active.
844		927
845	ev_signal exitsig;	928	ev_signal exitsig;
846	ev_signal_init (&exitsig, sig_cb, SIGINT);	929	ev_signal_init (&exitsig, sig_cb, SIGINT);
847	ev_signal_start (loop, &exitsig);	930	ev_signal_start (loop, &exitsig);
848	evf_unref (loop);	931	ev_unref (loop);
849		932
850	Example: For some weird reason, unregister the above signal handler again.	933	Example: For some weird reason, unregister the above signal handler again.
851		934
852	ev_ref (loop);	935	ev_ref (loop);
853	ev_signal_stop (loop, &exitsig);	936	ev_signal_stop (loop, &exitsig);
…		…
873	overhead for the actual polling but can deliver many events at once.	956	overhead for the actual polling but can deliver many events at once.
874		957
875	By setting a higher I<io collect interval> you allow libev to spend more	958	By setting a higher I<io collect interval> you allow libev to spend more
876	time collecting I/O events, so you can handle more events per iteration,	959	time collecting I/O events, so you can handle more events per iteration,
877	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	960	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
878	C<ev_timer>) will be not affected. Setting this to a non-null value will	961	C<ev_timer>) will not be affected. Setting this to a non-null value will
879	introduce an additional C<ev_sleep ()> call into most loop iterations. The	962	introduce an additional C<ev_sleep ()> call into most loop iterations. The
880	sleep time ensures that libev will not poll for I/O events more often then	963	sleep time ensures that libev will not poll for I/O events more often then
881	once per this interval, on average.	964	once per this interval, on average (as long as the host time resolution is
		965	good enough).
882		966
883	Likewise, by setting a higher I<timeout collect interval> you allow libev	967	Likewise, by setting a higher I<timeout collect interval> you allow libev
884	to spend more time collecting timeouts, at the expense of increased	968	to spend more time collecting timeouts, at the expense of increased
885	latency/jitter/inexactness (the watcher callback will be called	969	latency/jitter/inexactness (the watcher callback will be called
886	later). C<ev_io> watchers will not be affected. Setting this to a non-null	970	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
940	can be done relatively simply by putting mutex_lock/unlock calls around	1024	can be done relatively simply by putting mutex_lock/unlock calls around
941	each call to a libev function.	1025	each call to a libev function.
942		1026
943	However, C<ev_run> can run an indefinite time, so it is not feasible	1027	However, C<ev_run> can run an indefinite time, so it is not feasible
944	to wait for it to return. One way around this is to wake up the event	1028	to wait for it to return. One way around this is to wake up the event
945	loop via C<ev_break> and C<av_async_send>, another way is to set these	1029	loop via C<ev_break> and C<ev_async_send>, another way is to set these
946	I<release> and I<acquire> callbacks on the loop.	1030	I<release> and I<acquire> callbacks on the loop.
947		1031
948	When set, then C<release> will be called just before the thread is	1032	When set, then C<release> will be called just before the thread is
949	suspended waiting for new events, and C<acquire> is called just	1033	suspended waiting for new events, and C<acquire> is called just
950	afterwards.	1034	afterwards.
…		…
965	See also the locking example in the C<THREADS> section later in this	1049	See also the locking example in the C<THREADS> section later in this
966	document.	1050	document.
967		1051
968	=item ev_set_userdata (loop, void *data)	1052	=item ev_set_userdata (loop, void *data)
969		1053
970	=item ev_userdata (loop)	1054	=item void *ev_userdata (loop)
971		1055
972	Set and retrieve a single C<void *> associated with a loop. When	1056	Set and retrieve a single C<void *> associated with a loop. When
973	C<ev_set_userdata> has never been called, then C<ev_userdata> returns	1057	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
974	C<0.>	1058	C<0>.
975		1059
976	These two functions can be used to associate arbitrary data with a loop,	1060	These two functions can be used to associate arbitrary data with a loop,
977	and are intended solely for the C<invoke_pending_cb>, C<release> and	1061	and are intended solely for the C<invoke_pending_cb>, C<release> and
978	C<acquire> callbacks described above, but of course can be (ab-)used for	1062	C<acquire> callbacks described above, but of course can be (ab-)used for
979	any other purpose as well.	1063	any other purpose as well.
…		…
1107	=item C<EV_FORK>	1191	=item C<EV_FORK>
1108		1192
1109	The event loop has been resumed in the child process after fork (see	1193	The event loop has been resumed in the child process after fork (see
1110	C<ev_fork>).	1194	C<ev_fork>).
1111		1195
		1196	=item C<EV_CLEANUP>
		1197
		1198	The event loop is about to be destroyed (see C<ev_cleanup>).
		1199
1112	=item C<EV_ASYNC>	1200	=item C<EV_ASYNC>
1113		1201
1114	The given async watcher has been asynchronously notified (see C<ev_async>).	1202	The given async watcher has been asynchronously notified (see C<ev_async>).
1115		1203
1116	=item C<EV_CUSTOM>	1204	=item C<EV_CUSTOM>
…		…
1137	programs, though, as the fd could already be closed and reused for another	1225	programs, though, as the fd could already be closed and reused for another
1138	thing, so beware.	1226	thing, so beware.
1139		1227
1140	=back	1228	=back
1141		1229
		1230	=head2 GENERIC WATCHER FUNCTIONS
		1231
		1232	=over 4
		1233
		1234	=item C<ev_init> (ev_TYPE *watcher, callback)
		1235
		1236	This macro initialises the generic portion of a watcher. The contents
		1237	of the watcher object can be arbitrary (so C<malloc> will do). Only
		1238	the generic parts of the watcher are initialised, you I<need> to call
		1239	the type-specific C<ev_TYPE_set> macro afterwards to initialise the
		1240	type-specific parts. For each type there is also a C<ev_TYPE_init> macro
		1241	which rolls both calls into one.
		1242
		1243	You can reinitialise a watcher at any time as long as it has been stopped
		1244	(or never started) and there are no pending events outstanding.
		1245
		1246	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
		1247	int revents)>.
		1248
		1249	Example: Initialise an C<ev_io> watcher in two steps.
		1250
		1251	ev_io w;
		1252	ev_init (&w, my_cb);
		1253	ev_io_set (&w, STDIN_FILENO, EV_READ);
		1254
		1255	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
		1256
		1257	This macro initialises the type-specific parts of a watcher. You need to
		1258	call C<ev_init> at least once before you call this macro, but you can
		1259	call C<ev_TYPE_set> any number of times. You must not, however, call this
		1260	macro on a watcher that is active (it can be pending, however, which is a
		1261	difference to the C<ev_init> macro).
		1262
		1263	Although some watcher types do not have type-specific arguments
		1264	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
		1265
		1266	See C<ev_init>, above, for an example.
		1267
		1268	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
		1269
		1270	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
		1271	calls into a single call. This is the most convenient method to initialise
		1272	a watcher. The same limitations apply, of course.
		1273
		1274	Example: Initialise and set an C<ev_io> watcher in one step.
		1275
		1276	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1277
		1278	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
		1279
		1280	Starts (activates) the given watcher. Only active watchers will receive
		1281	events. If the watcher is already active nothing will happen.
		1282
		1283	Example: Start the C<ev_io> watcher that is being abused as example in this
		1284	whole section.
		1285
		1286	ev_io_start (EV_DEFAULT_UC, &w);
		1287
		1288	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
		1289
		1290	Stops the given watcher if active, and clears the pending status (whether
		1291	the watcher was active or not).
		1292
		1293	It is possible that stopped watchers are pending - for example,
		1294	non-repeating timers are being stopped when they become pending - but
		1295	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
		1296	pending. If you want to free or reuse the memory used by the watcher it is
		1297	therefore a good idea to always call its C<ev_TYPE_stop> function.
		1298
		1299	=item bool ev_is_active (ev_TYPE *watcher)
		1300
		1301	Returns a true value iff the watcher is active (i.e. it has been started
		1302	and not yet been stopped). As long as a watcher is active you must not modify
		1303	it.
		1304
		1305	=item bool ev_is_pending (ev_TYPE *watcher)
		1306
		1307	Returns a true value iff the watcher is pending, (i.e. it has outstanding
		1308	events but its callback has not yet been invoked). As long as a watcher
		1309	is pending (but not active) you must not call an init function on it (but
		1310	C<ev_TYPE_set> is safe), you must not change its priority, and you must
		1311	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		1312	it).
		1313
		1314	=item callback ev_cb (ev_TYPE *watcher)
		1315
		1316	Returns the callback currently set on the watcher.
		1317
		1318	=item ev_cb_set (ev_TYPE *watcher, callback)
		1319
		1320	Change the callback. You can change the callback at virtually any time
		1321	(modulo threads).
		1322
		1323	=item ev_set_priority (ev_TYPE *watcher, int priority)
		1324
		1325	=item int ev_priority (ev_TYPE *watcher)
		1326
		1327	Set and query the priority of the watcher. The priority is a small
		1328	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		1329	(default: C<-2>). Pending watchers with higher priority will be invoked
		1330	before watchers with lower priority, but priority will not keep watchers
		1331	from being executed (except for C<ev_idle> watchers).
		1332
		1333	If you need to suppress invocation when higher priority events are pending
		1334	you need to look at C<ev_idle> watchers, which provide this functionality.
		1335
		1336	You I<must not> change the priority of a watcher as long as it is active or
		1337	pending.
		1338
		1339	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1340	fine, as long as you do not mind that the priority value you query might
		1341	or might not have been clamped to the valid range.
		1342
		1343	The default priority used by watchers when no priority has been set is
		1344	always C<0>, which is supposed to not be too high and not be too low :).
		1345
		1346	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
		1347	priorities.
		1348
		1349	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		1350
		1351	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		1352	C<loop> nor C<revents> need to be valid as long as the watcher callback
		1353	can deal with that fact, as both are simply passed through to the
		1354	callback.
		1355
		1356	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		1357
		1358	If the watcher is pending, this function clears its pending status and
		1359	returns its C<revents> bitset (as if its callback was invoked). If the
		1360	watcher isn't pending it does nothing and returns C<0>.
		1361
		1362	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1363	callback to be invoked, which can be accomplished with this function.
		1364
		1365	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1366
		1367	Feeds the given event set into the event loop, as if the specified event
		1368	had happened for the specified watcher (which must be a pointer to an
		1369	initialised but not necessarily started event watcher). Obviously you must
		1370	not free the watcher as long as it has pending events.
		1371
		1372	Stopping the watcher, letting libev invoke it, or calling
		1373	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1374	not started in the first place.
		1375
		1376	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1377	functions that do not need a watcher.
		1378
		1379	=back
		1380
		1381	See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR
		1382	OWN COMPOSITE WATCHERS> idioms.
		1383
1142	=head2 WATCHER STATES	1384	=head2 WATCHER STATES
1143		1385
1144	There are various watcher states mentioned throughout this manual -	1386	There are various watcher states mentioned throughout this manual -
1145	active, pending and so on. In this section these states and the rules to	1387	active, pending and so on. In this section these states and the rules to
1146	transition between them will be described in more detail - and while these	1388	transition between them will be described in more detail - and while these
…		…
1148		1390
1149	=over 4	1391	=over 4
1150		1392
1151	=item initialiased	1393	=item initialiased
1152		1394
1153	Before a watcher can be registered with the event looop it has to be	1395	Before a watcher can be registered with the event loop it has to be
1154	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to	1396	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
1155	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.	1397	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1156		1398
1157	In this state it is simply some block of memory that is suitable for use	1399	In this state it is simply some block of memory that is suitable for
1158	in an event loop. It can be moved around, freed, reused etc. at will.	1400	use in an event loop. It can be moved around, freed, reused etc. at
		1401	will - as long as you either keep the memory contents intact, or call
		1402	C<ev_TYPE_init> again.
1159		1403
1160	=item started/running/active	1404	=item started/running/active
1161		1405
1162	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes	1406	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1163	property of the event loop, and is actively waiting for events. While in	1407	property of the event loop, and is actively waiting for events. While in
…		…
1191	latter will clear any pending state the watcher might be in, regardless	1435	latter will clear any pending state the watcher might be in, regardless
1192	of whether it was active or not, so stopping a watcher explicitly before	1436	of whether it was active or not, so stopping a watcher explicitly before
1193	freeing it is often a good idea.	1437	freeing it is often a good idea.
1194		1438
1195	While stopped (and not pending) the watcher is essentially in the	1439	While stopped (and not pending) the watcher is essentially in the
1196	initialised state, that is it can be reused, moved, modified in any way	1440	initialised state, that is, it can be reused, moved, modified in any way
1197	you wish.	1441	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1442	it again).
1198		1443
1199	=back	1444	=back
1200
1201	=head2 GENERIC WATCHER FUNCTIONS
1202
1203	=over 4
1204
1205	=item C<ev_init> (ev_TYPE *watcher, callback)
1206
1207	This macro initialises the generic portion of a watcher. The contents
1208	of the watcher object can be arbitrary (so C<malloc> will do). Only
1209	the generic parts of the watcher are initialised, you I<need> to call
1210	the type-specific C<ev_TYPE_set> macro afterwards to initialise the
1211	type-specific parts. For each type there is also a C<ev_TYPE_init> macro
1212	which rolls both calls into one.
1213
1214	You can reinitialise a watcher at any time as long as it has been stopped
1215	(or never started) and there are no pending events outstanding.
1216
1217	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
1218	int revents)>.
1219
1220	Example: Initialise an C<ev_io> watcher in two steps.
1221
1222	ev_io w;
1223	ev_init (&w, my_cb);
1224	ev_io_set (&w, STDIN_FILENO, EV_READ);
1225
1226	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
1227
1228	This macro initialises the type-specific parts of a watcher. You need to
1229	call C<ev_init> at least once before you call this macro, but you can
1230	call C<ev_TYPE_set> any number of times. You must not, however, call this
1231	macro on a watcher that is active (it can be pending, however, which is a
1232	difference to the C<ev_init> macro).
1233
1234	Although some watcher types do not have type-specific arguments
1235	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
1236
1237	See C<ev_init>, above, for an example.
1238
1239	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
1240
1241	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
1242	calls into a single call. This is the most convenient method to initialise
1243	a watcher. The same limitations apply, of course.
1244
1245	Example: Initialise and set an C<ev_io> watcher in one step.
1246
1247	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1248
1249	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1250
1251	Starts (activates) the given watcher. Only active watchers will receive
1252	events. If the watcher is already active nothing will happen.
1253
1254	Example: Start the C<ev_io> watcher that is being abused as example in this
1255	whole section.
1256
1257	ev_io_start (EV_DEFAULT_UC, &w);
1258
1259	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1260
1261	Stops the given watcher if active, and clears the pending status (whether
1262	the watcher was active or not).
1263
1264	It is possible that stopped watchers are pending - for example,
1265	non-repeating timers are being stopped when they become pending - but
1266	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
1267	pending. If you want to free or reuse the memory used by the watcher it is
1268	therefore a good idea to always call its C<ev_TYPE_stop> function.
1269
1270	=item bool ev_is_active (ev_TYPE *watcher)
1271
1272	Returns a true value iff the watcher is active (i.e. it has been started
1273	and not yet been stopped). As long as a watcher is active you must not modify
1274	it.
1275
1276	=item bool ev_is_pending (ev_TYPE *watcher)
1277
1278	Returns a true value iff the watcher is pending, (i.e. it has outstanding
1279	events but its callback has not yet been invoked). As long as a watcher
1280	is pending (but not active) you must not call an init function on it (but
1281	C<ev_TYPE_set> is safe), you must not change its priority, and you must
1282	make sure the watcher is available to libev (e.g. you cannot C<free ()>
1283	it).
1284
1285	=item callback ev_cb (ev_TYPE *watcher)
1286
1287	Returns the callback currently set on the watcher.
1288
1289	=item ev_cb_set (ev_TYPE *watcher, callback)
1290
1291	Change the callback. You can change the callback at virtually any time
1292	(modulo threads).
1293
1294	=item ev_set_priority (ev_TYPE *watcher, int priority)
1295
1296	=item int ev_priority (ev_TYPE *watcher)
1297
1298	Set and query the priority of the watcher. The priority is a small
1299	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1300	(default: C<-2>). Pending watchers with higher priority will be invoked
1301	before watchers with lower priority, but priority will not keep watchers
1302	from being executed (except for C<ev_idle> watchers).
1303
1304	If you need to suppress invocation when higher priority events are pending
1305	you need to look at C<ev_idle> watchers, which provide this functionality.
1306
1307	You I<must not> change the priority of a watcher as long as it is active or
1308	pending.
1309
1310	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1311	fine, as long as you do not mind that the priority value you query might
1312	or might not have been clamped to the valid range.
1313
1314	The default priority used by watchers when no priority has been set is
1315	always C<0>, which is supposed to not be too high and not be too low :).
1316
1317	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1318	priorities.
1319
1320	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1321
1322	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1323	C<loop> nor C<revents> need to be valid as long as the watcher callback
1324	can deal with that fact, as both are simply passed through to the
1325	callback.
1326
1327	=item int ev_clear_pending (loop, ev_TYPE *watcher)
1328
1329	If the watcher is pending, this function clears its pending status and
1330	returns its C<revents> bitset (as if its callback was invoked). If the
1331	watcher isn't pending it does nothing and returns C<0>.
1332
1333	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1334	callback to be invoked, which can be accomplished with this function.
1335
1336	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
1337
1338	Feeds the given event set into the event loop, as if the specified event
1339	had happened for the specified watcher (which must be a pointer to an
1340	initialised but not necessarily started event watcher). Obviously you must
1341	not free the watcher as long as it has pending events.
1342
1343	Stopping the watcher, letting libev invoke it, or calling
1344	C<ev_clear_pending> will clear the pending event, even if the watcher was
1345	not started in the first place.
1346
1347	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1348	functions that do not need a watcher.
1349
1350	=back
1351
1352
1353	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1354
1355	Each watcher has, by default, a member C<void *data> that you can change
1356	and read at any time: libev will completely ignore it. This can be used
1357	to associate arbitrary data with your watcher. If you need more data and
1358	don't want to allocate memory and store a pointer to it in that data
1359	member, you can also "subclass" the watcher type and provide your own
1360	data:
1361
1362	struct my_io
1363	{
1364	ev_io io;
1365	int otherfd;
1366	void *somedata;
1367	struct whatever *mostinteresting;
1368	};
1369
1370	...
1371	struct my_io w;
1372	ev_io_init (&w.io, my_cb, fd, EV_READ);
1373
1374	And since your callback will be called with a pointer to the watcher, you
1375	can cast it back to your own type:
1376
1377	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1378	{
1379	struct my_io *w = (struct my_io *)w_;
1380	...
1381	}
1382
1383	More interesting and less C-conformant ways of casting your callback type
1384	instead have been omitted.
1385
1386	Another common scenario is to use some data structure with multiple
1387	embedded watchers:
1388
1389	struct my_biggy
1390	{
1391	int some_data;
1392	ev_timer t1;
1393	ev_timer t2;
1394	}
1395
1396	In this case getting the pointer to C<my_biggy> is a bit more
1397	complicated: Either you store the address of your C<my_biggy> struct
1398	in the C<data> member of the watcher (for woozies), or you need to use
1399	some pointer arithmetic using C<offsetof> inside your watchers (for real
1400	programmers):
1401
1402	#include <stddef.h>
1403
1404	static void
1405	t1_cb (EV_P_ ev_timer *w, int revents)
1406	{
1407	struct my_biggy big = (struct my_biggy *)
1408	(((char *)w) - offsetof (struct my_biggy, t1));
1409	}
1410
1411	static void
1412	t2_cb (EV_P_ ev_timer *w, int revents)
1413	{
1414	struct my_biggy big = (struct my_biggy *)
1415	(((char *)w) - offsetof (struct my_biggy, t2));
1416	}
1417		1445
1418	=head2 WATCHER PRIORITY MODELS	1446	=head2 WATCHER PRIORITY MODELS
1419		1447
1420	Many event loops support I<watcher priorities>, which are usually small	1448	Many event loops support I<watcher priorities>, which are usually small
1421	integers that influence the ordering of event callback invocation	1449	integers that influence the ordering of event callback invocation
…		…
1548	In general you can register as many read and/or write event watchers per	1576	In general you can register as many read and/or write event watchers per
1549	fd as you want (as long as you don't confuse yourself). Setting all file	1577	fd as you want (as long as you don't confuse yourself). Setting all file
1550	descriptors to non-blocking mode is also usually a good idea (but not	1578	descriptors to non-blocking mode is also usually a good idea (but not
1551	required if you know what you are doing).	1579	required if you know what you are doing).
1552		1580
1553	If you cannot use non-blocking mode, then force the use of a
1554	known-to-be-good backend (at the time of this writing, this includes only
1555	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1556	descriptors for which non-blocking operation makes no sense (such as
1557	files) - libev doesn't guarantee any specific behaviour in that case.
1558
1559	Another thing you have to watch out for is that it is quite easy to	1581	Another thing you have to watch out for is that it is quite easy to
1560	receive "spurious" readiness notifications, that is your callback might	1582	receive "spurious" readiness notifications, that is, your callback might
1561	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1583	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1562	because there is no data. Not only are some backends known to create a	1584	because there is no data. It is very easy to get into this situation even
1563	lot of those (for example Solaris ports), it is very easy to get into	1585	with a relatively standard program structure. Thus it is best to always
1564	this situation even with a relatively standard program structure. Thus	1586	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1565	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1566	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1587	preferable to a program hanging until some data arrives.
1567		1588
1568	If you cannot run the fd in non-blocking mode (for example you should	1589	If you cannot run the fd in non-blocking mode (for example you should
1569	not play around with an Xlib connection), then you have to separately	1590	not play around with an Xlib connection), then you have to separately
1570	re-test whether a file descriptor is really ready with a known-to-be good	1591	re-test whether a file descriptor is really ready with a known-to-be good
1571	interface such as poll (fortunately in our Xlib example, Xlib already	1592	interface such as poll (fortunately in the case of Xlib, it already does
1572	does this on its own, so its quite safe to use). Some people additionally	1593	this on its own, so its quite safe to use). Some people additionally
1573	use C<SIGALRM> and an interval timer, just to be sure you won't block	1594	use C<SIGALRM> and an interval timer, just to be sure you won't block
1574	indefinitely.	1595	indefinitely.
1575		1596
1576	But really, best use non-blocking mode.	1597	But really, best use non-blocking mode.
1577		1598
…		…
1605		1626
1606	There is no workaround possible except not registering events	1627	There is no workaround possible except not registering events
1607	for potentially C<dup ()>'ed file descriptors, or to resort to	1628	for potentially C<dup ()>'ed file descriptors, or to resort to
1608	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1629	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1609		1630
		1631	=head3 The special problem of files
		1632
		1633	Many people try to use C<select> (or libev) on file descriptors
		1634	representing files, and expect it to become ready when their program
		1635	doesn't block on disk accesses (which can take a long time on their own).
		1636
		1637	However, this cannot ever work in the "expected" way - you get a readiness
		1638	notification as soon as the kernel knows whether and how much data is
		1639	there, and in the case of open files, that's always the case, so you
		1640	always get a readiness notification instantly, and your read (or possibly
		1641	write) will still block on the disk I/O.
		1642
		1643	Another way to view it is that in the case of sockets, pipes, character
		1644	devices and so on, there is another party (the sender) that delivers data
		1645	on its own, but in the case of files, there is no such thing: the disk
		1646	will not send data on its own, simply because it doesn't know what you
		1647	wish to read - you would first have to request some data.
		1648
		1649	Since files are typically not-so-well supported by advanced notification
		1650	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1651	to files, even though you should not use it. The reason for this is
		1652	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1653	usually a tty, often a pipe, but also sometimes files or special devices
		1654	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1655	F</dev/urandom>), and even though the file might better be served with
		1656	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1657	it "just works" instead of freezing.
		1658
		1659	So avoid file descriptors pointing to files when you know it (e.g. use
		1660	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1661	when you rarely read from a file instead of from a socket, and want to
		1662	reuse the same code path.
		1663
1610	=head3 The special problem of fork	1664	=head3 The special problem of fork
1611		1665
1612	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1666	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1613	useless behaviour. Libev fully supports fork, but needs to be told about	1667	useless behaviour. Libev fully supports fork, but needs to be told about
1614	it in the child.	1668	it in the child if you want to continue to use it in the child.
1615		1669
1616	To support fork in your programs, you either have to call	1670	To support fork in your child processes, you have to call C<ev_loop_fork
1617	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1671	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1618	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1672	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1619	C<EVBACKEND_POLL>.
1620		1673
1621	=head3 The special problem of SIGPIPE	1674	=head3 The special problem of SIGPIPE
1622		1675
1623	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1676	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1624	when writing to a pipe whose other end has been closed, your program gets	1677	when writing to a pipe whose other end has been closed, your program gets
…		…
1722	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1775	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1723	monotonic clock option helps a lot here).	1776	monotonic clock option helps a lot here).
1724		1777
1725	The callback is guaranteed to be invoked only I<after> its timeout has	1778	The callback is guaranteed to be invoked only I<after> its timeout has
1726	passed (not I<at>, so on systems with very low-resolution clocks this	1779	passed (not I<at>, so on systems with very low-resolution clocks this
1727	might introduce a small delay). If multiple timers become ready during the	1780	might introduce a small delay, see "the special problem of being too
		1781	early", below). If multiple timers become ready during the same loop
1728	same loop iteration then the ones with earlier time-out values are invoked	1782	iteration then the ones with earlier time-out values are invoked before
1729	before ones of the same priority with later time-out values (but this is	1783	ones of the same priority with later time-out values (but this is no
1730	no longer true when a callback calls C<ev_run> recursively).	1784	longer true when a callback calls C<ev_run> recursively).
1731		1785
1732	=head3 Be smart about timeouts	1786	=head3 Be smart about timeouts
1733		1787
1734	Many real-world problems involve some kind of timeout, usually for error	1788	Many real-world problems involve some kind of timeout, usually for error
1735	recovery. A typical example is an HTTP request - if the other side hangs,	1789	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1810		1864
1811	In this case, it would be more efficient to leave the C<ev_timer> alone,	1865	In this case, it would be more efficient to leave the C<ev_timer> alone,
1812	but remember the time of last activity, and check for a real timeout only	1866	but remember the time of last activity, and check for a real timeout only
1813	within the callback:	1867	within the callback:
1814		1868
		1869	ev_tstamp timeout = 60.;
1815	ev_tstamp last_activity; // time of last activity	1870	ev_tstamp last_activity; // time of last activity
		1871	ev_timer timer;
1816		1872
1817	static void	1873	static void
1818	callback (EV_P_ ev_timer *w, int revents)	1874	callback (EV_P_ ev_timer *w, int revents)
1819	{	1875	{
1820	ev_tstamp now = ev_now (EV_A);	1876	// calculate when the timeout would happen
1821	ev_tstamp timeout = last_activity + 60.;	1877	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1822		1878
1823	// if last_activity + 60. is older than now, we did time out	1879	// if negative, it means we the timeout already occured
1824	if (timeout < now)	1880	if (after < 0.)
1825	{	1881	{
1826	// timeout occurred, take action	1882	// timeout occurred, take action
1827	}	1883	}
1828	else	1884	else
1829	{	1885	{
1830	// callback was invoked, but there was some activity, re-arm	1886	// callback was invoked, but there was some recent
1831	// the watcher to fire in last_activity + 60, which is	1887	// activity. simply restart the timer to time out
1832	// guaranteed to be in the future, so "again" is positive:	1888	// after "after" seconds, which is the earliest time
1833	w->repeat = timeout - now;	1889	// the timeout can occur.
		1890	ev_timer_set (w, after, 0.);
1834	ev_timer_again (EV_A_ w);	1891	ev_timer_start (EV_A_ w);
1835	}	1892	}
1836	}	1893	}
1837		1894
1838	To summarise the callback: first calculate the real timeout (defined	1895	To summarise the callback: first calculate in how many seconds the
1839	as "60 seconds after the last activity"), then check if that time has	1896	timeout will occur (by calculating the absolute time when it would occur,
1840	been reached, which means something I<did>, in fact, time out. Otherwise	1897	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1841	the callback was invoked too early (C<timeout> is in the future), so	1898	(EV_A)> from that).
1842	re-schedule the timer to fire at that future time, to see if maybe we have
1843	a timeout then.
1844		1899
1845	Note how C<ev_timer_again> is used, taking advantage of the	1900	If this value is negative, then we are already past the timeout, i.e. we
1846	C<ev_timer_again> optimisation when the timer is already running.	1901	timed out, and need to do whatever is needed in this case.
		1902
		1903	Otherwise, we now the earliest time at which the timeout would trigger,
		1904	and simply start the timer with this timeout value.
		1905
		1906	In other words, each time the callback is invoked it will check whether
		1907	the timeout cocured. If not, it will simply reschedule itself to check
		1908	again at the earliest time it could time out. Rinse. Repeat.
1847		1909
1848	This scheme causes more callback invocations (about one every 60 seconds	1910	This scheme causes more callback invocations (about one every 60 seconds
1849	minus half the average time between activity), but virtually no calls to	1911	minus half the average time between activity), but virtually no calls to
1850	libev to change the timeout.	1912	libev to change the timeout.
1851		1913
1852	To start the timer, simply initialise the watcher and set C<last_activity>	1914	To start the machinery, simply initialise the watcher and set
1853	to the current time (meaning we just have some activity :), then call the	1915	C<last_activity> to the current time (meaning there was some activity just
1854	callback, which will "do the right thing" and start the timer:	1916	now), then call the callback, which will "do the right thing" and start
		1917	the timer:
1855		1918
		1919	last_activity = ev_now (EV_A);
1856	ev_init (timer, callback);	1920	ev_init (&timer, callback);
1857	last_activity = ev_now (loop);	1921	callback (EV_A_ &timer, 0);
1858	callback (loop, timer, EV_TIMER);
1859		1922
1860	And when there is some activity, simply store the current time in	1923	When there is some activity, simply store the current time in
1861	C<last_activity>, no libev calls at all:	1924	C<last_activity>, no libev calls at all:
1862		1925
		1926	if (activity detected)
1863	last_activity = ev_now (loop);	1927	last_activity = ev_now (EV_A);
		1928
		1929	When your timeout value changes, then the timeout can be changed by simply
		1930	providing a new value, stopping the timer and calling the callback, which
		1931	will agaion do the right thing (for example, time out immediately :).
		1932
		1933	timeout = new_value;
		1934	ev_timer_stop (EV_A_ &timer);
		1935	callback (EV_A_ &timer, 0);
1864		1936
1865	This technique is slightly more complex, but in most cases where the	1937	This technique is slightly more complex, but in most cases where the
1866	time-out is unlikely to be triggered, much more efficient.	1938	time-out is unlikely to be triggered, much more efficient.
1867
1868	Changing the timeout is trivial as well (if it isn't hard-coded in the
1869	callback :) - just change the timeout and invoke the callback, which will
1870	fix things for you.
1871		1939
1872	=item 4. Wee, just use a double-linked list for your timeouts.	1940	=item 4. Wee, just use a double-linked list for your timeouts.
1873		1941
1874	If there is not one request, but many thousands (millions...), all	1942	If there is not one request, but many thousands (millions...), all
1875	employing some kind of timeout with the same timeout value, then one can	1943	employing some kind of timeout with the same timeout value, then one can
…		…
1902	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	1970	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1903	rather complicated, but extremely efficient, something that really pays	1971	rather complicated, but extremely efficient, something that really pays
1904	off after the first million or so of active timers, i.e. it's usually	1972	off after the first million or so of active timers, i.e. it's usually
1905	overkill :)	1973	overkill :)
1906		1974
		1975	=head3 The special problem of being too early
		1976
		1977	If you ask a timer to call your callback after three seconds, then
		1978	you expect it to be invoked after three seconds - but of course, this
		1979	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		1980	guaranteed to any precision by libev - imagine somebody suspending the
		1981	process with a STOP signal for a few hours for example.
		1982
		1983	So, libev tries to invoke your callback as soon as possible I<after> the
		1984	delay has occurred, but cannot guarantee this.
		1985
		1986	A less obvious failure mode is calling your callback too early: many event
		1987	loops compare timestamps with a "elapsed delay >= requested delay", but
		1988	this can cause your callback to be invoked much earlier than you would
		1989	expect.
		1990
		1991	To see why, imagine a system with a clock that only offers full second
		1992	resolution (think windows if you can't come up with a broken enough OS
		1993	yourself). If you schedule a one-second timer at the time 500.9, then the
		1994	event loop will schedule your timeout to elapse at a system time of 500
		1995	(500.9 truncated to the resolution) + 1, or 501.
		1996
		1997	If an event library looks at the timeout 0.1s later, it will see "501 >=
		1998	501" and invoke the callback 0.1s after it was started, even though a
		1999	one-second delay was requested - this is being "too early", despite best
		2000	intentions.
		2001
		2002	This is the reason why libev will never invoke the callback if the elapsed
		2003	delay equals the requested delay, but only when the elapsed delay is
		2004	larger than the requested delay. In the example above, libev would only invoke
		2005	the callback at system time 502, or 1.1s after the timer was started.
		2006
		2007	So, while libev cannot guarantee that your callback will be invoked
		2008	exactly when requested, it I<can> and I<does> guarantee that the requested
		2009	delay has actually elapsed, or in other words, it always errs on the "too
		2010	late" side of things.
		2011
1907	=head3 The special problem of time updates	2012	=head3 The special problem of time updates
1908		2013
1909	Establishing the current time is a costly operation (it usually takes at	2014	Establishing the current time is a costly operation (it usually takes
1910	least two system calls): EV therefore updates its idea of the current	2015	at least one system call): EV therefore updates its idea of the current
1911	time only before and after C<ev_run> collects new events, which causes a	2016	time only before and after C<ev_run> collects new events, which causes a
1912	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2017	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1913	lots of events in one iteration.	2018	lots of events in one iteration.
1914		2019
1915	The relative timeouts are calculated relative to the C<ev_now ()>	2020	The relative timeouts are calculated relative to the C<ev_now ()>
…		…
1921	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2026	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1922		2027
1923	If the event loop is suspended for a long time, you can also force an	2028	If the event loop is suspended for a long time, you can also force an
1924	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2029	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1925	()>.	2030	()>.
		2031
		2032	=head3 The special problem of unsynchronised clocks
		2033
		2034	Modern systems have a variety of clocks - libev itself uses the normal
		2035	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2036	jumps).
		2037
		2038	Neither of these clocks is synchronised with each other or any other clock
		2039	on the system, so C<ev_time ()> might return a considerably different time
		2040	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2041	a call to C<gettimeofday> might return a second count that is one higher
		2042	than a directly following call to C<time>.
		2043
		2044	The moral of this is to only compare libev-related timestamps with
		2045	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2046	a second or so.
		2047
		2048	One more problem arises due to this lack of synchronisation: if libev uses
		2049	the system monotonic clock and you compare timestamps from C<ev_time>
		2050	or C<ev_now> from when you started your timer and when your callback is
		2051	invoked, you will find that sometimes the callback is a bit "early".
		2052
		2053	This is because C<ev_timer>s work in real time, not wall clock time, so
		2054	libev makes sure your callback is not invoked before the delay happened,
		2055	I<measured according to the real time>, not the system clock.
		2056
		2057	If your timeouts are based on a physical timescale (e.g. "time out this
		2058	connection after 100 seconds") then this shouldn't bother you as it is
		2059	exactly the right behaviour.
		2060
		2061	If you want to compare wall clock/system timestamps to your timers, then
		2062	you need to use C<ev_periodic>s, as these are based on the wall clock
		2063	time, where your comparisons will always generate correct results.
1926		2064
1927	=head3 The special problems of suspended animation	2065	=head3 The special problems of suspended animation
1928		2066
1929	When you leave the server world it is quite customary to hit machines that	2067	When you leave the server world it is quite customary to hit machines that
1930	can suspend/hibernate - what happens to the clocks during such a suspend?	2068	can suspend/hibernate - what happens to the clocks during such a suspend?
…		…
1974	keep up with the timer (because it takes longer than those 10 seconds to	2112	keep up with the timer (because it takes longer than those 10 seconds to
1975	do stuff) the timer will not fire more than once per event loop iteration.	2113	do stuff) the timer will not fire more than once per event loop iteration.
1976		2114
1977	=item ev_timer_again (loop, ev_timer *)	2115	=item ev_timer_again (loop, ev_timer *)
1978		2116
1979	This will act as if the timer timed out and restart it again if it is	2117	This will act as if the timer timed out, and restarts it again if it is
1980	repeating. The exact semantics are:	2118	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2119	timeout to the C<repeat> value and calling C<ev_timer_start>.
1981		2120
		2121	The exact semantics are as in the following rules, all of which will be
		2122	applied to the watcher:
		2123
		2124	=over 4
		2125
1982	If the timer is pending, its pending status is cleared.	2126	=item If the timer is pending, the pending status is always cleared.
1983		2127
1984	If the timer is started but non-repeating, stop it (as if it timed out).	2128	=item If the timer is started but non-repeating, stop it (as if it timed
		2129	out, without invoking it).
1985		2130
1986	If the timer is repeating, either start it if necessary (with the	2131	=item If the timer is repeating, make the C<repeat> value the new timeout
1987	C<repeat> value), or reset the running timer to the C<repeat> value.	2132	and start the timer, if necessary.
		2133
		2134	=back
1988		2135
1989	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2136	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1990	usage example.	2137	usage example.
1991		2138
1992	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)	2139	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
…		…
2114		2261
2115	Another way to think about it (for the mathematically inclined) is that	2262	Another way to think about it (for the mathematically inclined) is that
2116	C<ev_periodic> will try to run the callback in this mode at the next possible	2263	C<ev_periodic> will try to run the callback in this mode at the next possible
2117	time where C<time = offset (mod interval)>, regardless of any time jumps.	2264	time where C<time = offset (mod interval)>, regardless of any time jumps.
2118		2265
2119	For numerical stability it is preferable that the C<offset> value is near	2266	The C<interval> I<MUST> be positive, and for numerical stability, the
2120	C<ev_now ()> (the current time), but there is no range requirement for	2267	interval value should be higher than C<1/8192> (which is around 100
2121	this value, and in fact is often specified as zero.	2268	microseconds) and C<offset> should be higher than C<0> and should have
		2269	at most a similar magnitude as the current time (say, within a factor of
		2270	ten). Typical values for offset are, in fact, C<0> or something between
		2271	C<0> and C<interval>, which is also the recommended range.
2122		2272
2123	Note also that there is an upper limit to how often a timer can fire (CPU	2273	Note also that there is an upper limit to how often a timer can fire (CPU
2124	speed for example), so if C<interval> is very small then timing stability	2274	speed for example), so if C<interval> is very small then timing stability
2125	will of course deteriorate. Libev itself tries to be exact to be about one	2275	will of course deteriorate. Libev itself tries to be exact to be about one
2126	millisecond (if the OS supports it and the machine is fast enough).	2276	millisecond (if the OS supports it and the machine is fast enough).
…		…
2240		2390
2241	=head2 C<ev_signal> - signal me when a signal gets signalled!	2391	=head2 C<ev_signal> - signal me when a signal gets signalled!
2242		2392
2243	Signal watchers will trigger an event when the process receives a specific	2393	Signal watchers will trigger an event when the process receives a specific
2244	signal one or more times. Even though signals are very asynchronous, libev	2394	signal one or more times. Even though signals are very asynchronous, libev
2245	will try it's best to deliver signals synchronously, i.e. as part of the	2395	will try its best to deliver signals synchronously, i.e. as part of the
2246	normal event processing, like any other event.	2396	normal event processing, like any other event.
2247		2397
2248	If you want signals to be delivered truly asynchronously, just use	2398	If you want signals to be delivered truly asynchronously, just use
2249	C<sigaction> as you would do without libev and forget about sharing	2399	C<sigaction> as you would do without libev and forget about sharing
2250	the signal. You can even use C<ev_async> from a signal handler to	2400	the signal. You can even use C<ev_async> from a signal handler to
…		…
2269	=head3 The special problem of inheritance over fork/execve/pthread_create	2419	=head3 The special problem of inheritance over fork/execve/pthread_create
2270		2420
2271	Both the signal mask (C<sigprocmask>) and the signal disposition	2421	Both the signal mask (C<sigprocmask>) and the signal disposition
2272	(C<sigaction>) are unspecified after starting a signal watcher (and after	2422	(C<sigaction>) are unspecified after starting a signal watcher (and after
2273	stopping it again), that is, libev might or might not block the signal,	2423	stopping it again), that is, libev might or might not block the signal,
2274	and might or might not set or restore the installed signal handler.	2424	and might or might not set or restore the installed signal handler (but
		2425	see C<EVFLAG_NOSIGMASK>).
2275		2426
2276	While this does not matter for the signal disposition (libev never	2427	While this does not matter for the signal disposition (libev never
2277	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on	2428	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
2278	C<execve>), this matters for the signal mask: many programs do not expect	2429	C<execve>), this matters for the signal mask: many programs do not expect
2279	certain signals to be blocked.	2430	certain signals to be blocked.
…		…
2292	I<has> to modify the signal mask, at least temporarily.	2443	I<has> to modify the signal mask, at least temporarily.
2293		2444
2294	So I can't stress this enough: I<If you do not reset your signal mask when	2445	So I can't stress this enough: I<If you do not reset your signal mask when
2295	you expect it to be empty, you have a race condition in your code>. This	2446	you expect it to be empty, you have a race condition in your code>. This
2296	is not a libev-specific thing, this is true for most event libraries.	2447	is not a libev-specific thing, this is true for most event libraries.
		2448
		2449	=head3 The special problem of threads signal handling
		2450
		2451	POSIX threads has problematic signal handling semantics, specifically,
		2452	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2453	threads in a process block signals, which is hard to achieve.
		2454
		2455	When you want to use sigwait (or mix libev signal handling with your own
		2456	for the same signals), you can tackle this problem by globally blocking
		2457	all signals before creating any threads (or creating them with a fully set
		2458	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2459	loops. Then designate one thread as "signal receiver thread" which handles
		2460	these signals. You can pass on any signals that libev might be interested
		2461	in by calling C<ev_feed_signal>.
2297		2462
2298	=head3 Watcher-Specific Functions and Data Members	2463	=head3 Watcher-Specific Functions and Data Members
2299		2464
2300	=over 4	2465	=over 4
2301		2466
…		…
3075	disadvantage of having to use multiple event loops (which do not support	3240	disadvantage of having to use multiple event loops (which do not support
3076	signal watchers).	3241	signal watchers).
3077		3242
3078	When this is not possible, or you want to use the default loop for	3243	When this is not possible, or you want to use the default loop for
3079	other reasons, then in the process that wants to start "fresh", call	3244	other reasons, then in the process that wants to start "fresh", call
3080	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3245	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
3081	the default loop will "orphan" (not stop) all registered watchers, so you	3246	Destroying the default loop will "orphan" (not stop) all registered
3082	have to be careful not to execute code that modifies those watchers. Note	3247	watchers, so you have to be careful not to execute code that modifies
3083	also that in that case, you have to re-register any signal watchers.	3248	those watchers. Note also that in that case, you have to re-register any
		3249	signal watchers.
3084		3250
3085	=head3 Watcher-Specific Functions and Data Members	3251	=head3 Watcher-Specific Functions and Data Members
3086		3252
3087	=over 4	3253	=over 4
3088		3254
3089	=item ev_fork_init (ev_signal *, callback)	3255	=item ev_fork_init (ev_fork *, callback)
3090		3256
3091	Initialises and configures the fork watcher - it has no parameters of any	3257	Initialises and configures the fork watcher - it has no parameters of any
3092	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3258	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
3093	believe me.	3259	really.
3094		3260
3095	=back	3261	=back
3096		3262
3097		3263
		3264	=head2 C<ev_cleanup> - even the best things end
		3265
		3266	Cleanup watchers are called just before the event loop is being destroyed
		3267	by a call to C<ev_loop_destroy>.
		3268
		3269	While there is no guarantee that the event loop gets destroyed, cleanup
		3270	watchers provide a convenient method to install cleanup hooks for your
		3271	program, worker threads and so on - you just to make sure to destroy the
		3272	loop when you want them to be invoked.
		3273
		3274	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3275	all other watchers, they do not keep a reference to the event loop (which
		3276	makes a lot of sense if you think about it). Like all other watchers, you
		3277	can call libev functions in the callback, except C<ev_cleanup_start>.
		3278
		3279	=head3 Watcher-Specific Functions and Data Members
		3280
		3281	=over 4
		3282
		3283	=item ev_cleanup_init (ev_cleanup *, callback)
		3284
		3285	Initialises and configures the cleanup watcher - it has no parameters of
		3286	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3287	pointless, I assure you.
		3288
		3289	=back
		3290
		3291	Example: Register an atexit handler to destroy the default loop, so any
		3292	cleanup functions are called.
		3293
		3294	static void
		3295	program_exits (void)
		3296	{
		3297	ev_loop_destroy (EV_DEFAULT_UC);
		3298	}
		3299
		3300	...
		3301	atexit (program_exits);
		3302
		3303
3098	=head2 C<ev_async> - how to wake up an event loop	3304	=head2 C<ev_async> - how to wake up an event loop
3099		3305
3100	In general, you cannot use an C<ev_run> from multiple threads or other	3306	In general, you cannot use an C<ev_loop> from multiple threads or other
3101	asynchronous sources such as signal handlers (as opposed to multiple event	3307	asynchronous sources such as signal handlers (as opposed to multiple event
3102	loops - those are of course safe to use in different threads).	3308	loops - those are of course safe to use in different threads).
3103		3309
3104	Sometimes, however, you need to wake up an event loop you do not control,	3310	Sometimes, however, you need to wake up an event loop you do not control,
3105	for example because it belongs to another thread. This is what C<ev_async>	3311	for example because it belongs to another thread. This is what C<ev_async>
…		…
3107	it by calling C<ev_async_send>, which is thread- and signal safe.	3313	it by calling C<ev_async_send>, which is thread- and signal safe.
3108		3314
3109	This functionality is very similar to C<ev_signal> watchers, as signals,	3315	This functionality is very similar to C<ev_signal> watchers, as signals,
3110	too, are asynchronous in nature, and signals, too, will be compressed	3316	too, are asynchronous in nature, and signals, too, will be compressed
3111	(i.e. the number of callback invocations may be less than the number of	3317	(i.e. the number of callback invocations may be less than the number of
3112	C<ev_async_sent> calls).	3318	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
3113		3319	of "global async watchers" by using a watcher on an otherwise unused
3114	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3320	signal, and C<ev_feed_signal> to signal this watcher from another thread,
3115	just the default loop.	3321	even without knowing which loop owns the signal.
3116		3322
3117	=head3 Queueing	3323	=head3 Queueing
3118		3324
3119	C<ev_async> does not support queueing of data in any way. The reason	3325	C<ev_async> does not support queueing of data in any way. The reason
3120	is that the author does not know of a simple (or any) algorithm for a	3326	is that the author does not know of a simple (or any) algorithm for a
…		…
3212	trust me.	3418	trust me.
3213		3419
3214	=item ev_async_send (loop, ev_async *)	3420	=item ev_async_send (loop, ev_async *)
3215		3421
3216	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3422	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3217	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3423	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3424	returns.
		3425
3218	C<ev_feed_event>, this call is safe to do from other threads, signal or	3426	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3219	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3427	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3220	section below on what exactly this means).	3428	embedding section below on what exactly this means).
3221		3429
3222	Note that, as with other watchers in libev, multiple events might get	3430	Note that, as with other watchers in libev, multiple events might get
3223	compressed into a single callback invocation (another way to look at this	3431	compressed into a single callback invocation (another way to look at
3224	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3432	this is that C<ev_async> watchers are level-triggered: they are set on
3225	reset when the event loop detects that).	3433	C<ev_async_send>, reset when the event loop detects that).
3226		3434
3227	This call incurs the overhead of a system call only once per event loop	3435	This call incurs the overhead of at most one extra system call per event
3228	iteration, so while the overhead might be noticeable, it doesn't apply to	3436	loop iteration, if the event loop is blocked, and no syscall at all if
3229	repeated calls to C<ev_async_send> for the same event loop.	3437	the event loop (or your program) is processing events. That means that
		3438	repeated calls are basically free (there is no need to avoid calls for
		3439	performance reasons) and that the overhead becomes smaller (typically
		3440	zero) under load.
3230		3441
3231	=item bool = ev_async_pending (ev_async *)	3442	=item bool = ev_async_pending (ev_async *)
3232		3443
3233	Returns a non-zero value when C<ev_async_send> has been called on the	3444	Returns a non-zero value when C<ev_async_send> has been called on the
3234	watcher but the event has not yet been processed (or even noted) by the	3445	watcher but the event has not yet been processed (or even noted) by the
…		…
3289	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3500	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3290		3501
3291	=item ev_feed_fd_event (loop, int fd, int revents)	3502	=item ev_feed_fd_event (loop, int fd, int revents)
3292		3503
3293	Feed an event on the given fd, as if a file descriptor backend detected	3504	Feed an event on the given fd, as if a file descriptor backend detected
3294	the given events it.	3505	the given events.
3295		3506
3296	=item ev_feed_signal_event (loop, int signum)	3507	=item ev_feed_signal_event (loop, int signum)
3297		3508
3298	Feed an event as if the given signal occurred (C<loop> must be the default	3509	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3299	loop!).	3510	which is async-safe.
3300		3511
3301	=back	3512	=back
		3513
		3514
		3515	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3516
		3517	This section explains some common idioms that are not immediately
		3518	obvious. Note that examples are sprinkled over the whole manual, and this
		3519	section only contains stuff that wouldn't fit anywhere else.
		3520
		3521	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3522
		3523	Each watcher has, by default, a C<void *data> member that you can read
		3524	or modify at any time: libev will completely ignore it. This can be used
		3525	to associate arbitrary data with your watcher. If you need more data and
		3526	don't want to allocate memory separately and store a pointer to it in that
		3527	data member, you can also "subclass" the watcher type and provide your own
		3528	data:
		3529
		3530	struct my_io
		3531	{
		3532	ev_io io;
		3533	int otherfd;
		3534	void *somedata;
		3535	struct whatever *mostinteresting;
		3536	};
		3537
		3538	...
		3539	struct my_io w;
		3540	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3541
		3542	And since your callback will be called with a pointer to the watcher, you
		3543	can cast it back to your own type:
		3544
		3545	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3546	{
		3547	struct my_io *w = (struct my_io *)w_;
		3548	...
		3549	}
		3550
		3551	More interesting and less C-conformant ways of casting your callback
		3552	function type instead have been omitted.
		3553
		3554	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3555
		3556	Another common scenario is to use some data structure with multiple
		3557	embedded watchers, in effect creating your own watcher that combines
		3558	multiple libev event sources into one "super-watcher":
		3559
		3560	struct my_biggy
		3561	{
		3562	int some_data;
		3563	ev_timer t1;
		3564	ev_timer t2;
		3565	}
		3566
		3567	In this case getting the pointer to C<my_biggy> is a bit more
		3568	complicated: Either you store the address of your C<my_biggy> struct in
		3569	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3570	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3571	real programmers):
		3572
		3573	#include <stddef.h>
		3574
		3575	static void
		3576	t1_cb (EV_P_ ev_timer *w, int revents)
		3577	{
		3578	struct my_biggy big = (struct my_biggy *)
		3579	(((char *)w) - offsetof (struct my_biggy, t1));
		3580	}
		3581
		3582	static void
		3583	t2_cb (EV_P_ ev_timer *w, int revents)
		3584	{
		3585	struct my_biggy big = (struct my_biggy *)
		3586	(((char *)w) - offsetof (struct my_biggy, t2));
		3587	}
		3588
		3589	=head2 AVOIDING FINISHING BEFORE RETURNING
		3590
		3591	Often you have structures like this in event-based programs:
		3592
		3593	callback ()
		3594	{
		3595	free (request);
		3596	}
		3597
		3598	request = start_new_request (..., callback);
		3599
		3600	The intent is to start some "lengthy" operation. The C<request> could be
		3601	used to cancel the operation, or do other things with it.
		3602
		3603	It's not uncommon to have code paths in C<start_new_request> that
		3604	immediately invoke the callback, for example, to report errors. Or you add
		3605	some caching layer that finds that it can skip the lengthy aspects of the
		3606	operation and simply invoke the callback with the result.
		3607
		3608	The problem here is that this will happen I<before> C<start_new_request>
		3609	has returned, so C<request> is not set.
		3610
		3611	Even if you pass the request by some safer means to the callback, you
		3612	might want to do something to the request after starting it, such as
		3613	canceling it, which probably isn't working so well when the callback has
		3614	already been invoked.
		3615
		3616	A common way around all these issues is to make sure that
		3617	C<start_new_request> I<always> returns before the callback is invoked. If
		3618	C<start_new_request> immediately knows the result, it can artificially
		3619	delay invoking the callback by e.g. using a C<prepare> or C<idle> watcher
		3620	for example, or more sneakily, by reusing an existing (stopped) watcher
		3621	and pushing it into the pending queue:
		3622
		3623	ev_set_cb (watcher, callback);
		3624	ev_feed_event (EV_A_ watcher, 0);
		3625
		3626	This way, C<start_new_request> can safely return before the callback is
		3627	invoked, while not delaying callback invocation too much.
		3628
		3629	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3630
		3631	Often (especially in GUI toolkits) there are places where you have
		3632	I<modal> interaction, which is most easily implemented by recursively
		3633	invoking C<ev_run>.
		3634
		3635	This brings the problem of exiting - a callback might want to finish the
		3636	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3637	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3638	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3639	other combination: In these cases, C<ev_break> will not work alone.
		3640
		3641	The solution is to maintain "break this loop" variable for each C<ev_run>
		3642	invocation, and use a loop around C<ev_run> until the condition is
		3643	triggered, using C<EVRUN_ONCE>:
		3644
		3645	// main loop
		3646	int exit_main_loop = 0;
		3647
		3648	while (!exit_main_loop)
		3649	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3650
		3651	// in a modal watcher
		3652	int exit_nested_loop = 0;
		3653
		3654	while (!exit_nested_loop)
		3655	ev_run (EV_A_ EVRUN_ONCE);
		3656
		3657	To exit from any of these loops, just set the corresponding exit variable:
		3658
		3659	// exit modal loop
		3660	exit_nested_loop = 1;
		3661
		3662	// exit main program, after modal loop is finished
		3663	exit_main_loop = 1;
		3664
		3665	// exit both
		3666	exit_main_loop = exit_nested_loop = 1;
		3667
		3668	=head2 THREAD LOCKING EXAMPLE
		3669
		3670	Here is a fictitious example of how to run an event loop in a different
		3671	thread from where callbacks are being invoked and watchers are
		3672	created/added/removed.
		3673
		3674	For a real-world example, see the C<EV::Loop::Async> perl module,
		3675	which uses exactly this technique (which is suited for many high-level
		3676	languages).
		3677
		3678	The example uses a pthread mutex to protect the loop data, a condition
		3679	variable to wait for callback invocations, an async watcher to notify the
		3680	event loop thread and an unspecified mechanism to wake up the main thread.
		3681
		3682	First, you need to associate some data with the event loop:
		3683
		3684	typedef struct {
		3685	mutex_t lock; /* global loop lock */
		3686	ev_async async_w;
		3687	thread_t tid;
		3688	cond_t invoke_cv;
		3689	} userdata;
		3690
		3691	void prepare_loop (EV_P)
		3692	{
		3693	// for simplicity, we use a static userdata struct.
		3694	static userdata u;
		3695
		3696	ev_async_init (&u->async_w, async_cb);
		3697	ev_async_start (EV_A_ &u->async_w);
		3698
		3699	pthread_mutex_init (&u->lock, 0);
		3700	pthread_cond_init (&u->invoke_cv, 0);
		3701
		3702	// now associate this with the loop
		3703	ev_set_userdata (EV_A_ u);
		3704	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3705	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3706
		3707	// then create the thread running ev_run
		3708	pthread_create (&u->tid, 0, l_run, EV_A);
		3709	}
		3710
		3711	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3712	solely to wake up the event loop so it takes notice of any new watchers
		3713	that might have been added:
		3714
		3715	static void
		3716	async_cb (EV_P_ ev_async *w, int revents)
		3717	{
		3718	// just used for the side effects
		3719	}
		3720
		3721	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3722	protecting the loop data, respectively.
		3723
		3724	static void
		3725	l_release (EV_P)
		3726	{
		3727	userdata *u = ev_userdata (EV_A);
		3728	pthread_mutex_unlock (&u->lock);
		3729	}
		3730
		3731	static void
		3732	l_acquire (EV_P)
		3733	{
		3734	userdata *u = ev_userdata (EV_A);
		3735	pthread_mutex_lock (&u->lock);
		3736	}
		3737
		3738	The event loop thread first acquires the mutex, and then jumps straight
		3739	into C<ev_run>:
		3740
		3741	void *
		3742	l_run (void *thr_arg)
		3743	{
		3744	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3745
		3746	l_acquire (EV_A);
		3747	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3748	ev_run (EV_A_ 0);
		3749	l_release (EV_A);
		3750
		3751	return 0;
		3752	}
		3753
		3754	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3755	signal the main thread via some unspecified mechanism (signals? pipe
		3756	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3757	have been called (in a while loop because a) spurious wakeups are possible
		3758	and b) skipping inter-thread-communication when there are no pending
		3759	watchers is very beneficial):
		3760
		3761	static void
		3762	l_invoke (EV_P)
		3763	{
		3764	userdata *u = ev_userdata (EV_A);
		3765
		3766	while (ev_pending_count (EV_A))
		3767	{
		3768	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3769	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3770	}
		3771	}
		3772
		3773	Now, whenever the main thread gets told to invoke pending watchers, it
		3774	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3775	thread to continue:
		3776
		3777	static void
		3778	real_invoke_pending (EV_P)
		3779	{
		3780	userdata *u = ev_userdata (EV_A);
		3781
		3782	pthread_mutex_lock (&u->lock);
		3783	ev_invoke_pending (EV_A);
		3784	pthread_cond_signal (&u->invoke_cv);
		3785	pthread_mutex_unlock (&u->lock);
		3786	}
		3787
		3788	Whenever you want to start/stop a watcher or do other modifications to an
		3789	event loop, you will now have to lock:
		3790
		3791	ev_timer timeout_watcher;
		3792	userdata *u = ev_userdata (EV_A);
		3793
		3794	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3795
		3796	pthread_mutex_lock (&u->lock);
		3797	ev_timer_start (EV_A_ &timeout_watcher);
		3798	ev_async_send (EV_A_ &u->async_w);
		3799	pthread_mutex_unlock (&u->lock);
		3800
		3801	Note that sending the C<ev_async> watcher is required because otherwise
		3802	an event loop currently blocking in the kernel will have no knowledge
		3803	about the newly added timer. By waking up the loop it will pick up any new
		3804	watchers in the next event loop iteration.
		3805
		3806	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3807
		3808	While the overhead of a callback that e.g. schedules a thread is small, it
		3809	is still an overhead. If you embed libev, and your main usage is with some
		3810	kind of threads or coroutines, you might want to customise libev so that
		3811	doesn't need callbacks anymore.
		3812
		3813	Imagine you have coroutines that you can switch to using a function
		3814	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3815	and that due to some magic, the currently active coroutine is stored in a
		3816	global called C<current_coro>. Then you can build your own "wait for libev
		3817	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3818	the differing C<;> conventions):
		3819
		3820	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3821	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3822
		3823	That means instead of having a C callback function, you store the
		3824	coroutine to switch to in each watcher, and instead of having libev call
		3825	your callback, you instead have it switch to that coroutine.
		3826
		3827	A coroutine might now wait for an event with a function called
		3828	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3829	matter when, or whether the watcher is active or not when this function is
		3830	called):
		3831
		3832	void
		3833	wait_for_event (ev_watcher *w)
		3834	{
		3835	ev_cb_set (w) = current_coro;
		3836	switch_to (libev_coro);
		3837	}
		3838
		3839	That basically suspends the coroutine inside C<wait_for_event> and
		3840	continues the libev coroutine, which, when appropriate, switches back to
		3841	this or any other coroutine.
		3842
		3843	You can do similar tricks if you have, say, threads with an event queue -
		3844	instead of storing a coroutine, you store the queue object and instead of
		3845	switching to a coroutine, you push the watcher onto the queue and notify
		3846	any waiters.
		3847
		3848	To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two
		3849	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3850
		3851	// my_ev.h
		3852	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3853	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3854	#include "../libev/ev.h"
		3855
		3856	// my_ev.c
		3857	#define EV_H "my_ev.h"
		3858	#include "../libev/ev.c"
		3859
		3860	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3861	F<my_ev.c> into your project. When properly specifying include paths, you
		3862	can even use F<ev.h> as header file name directly.
3302		3863
3303		3864
3304	=head1 LIBEVENT EMULATION	3865	=head1 LIBEVENT EMULATION
3305		3866
3306	Libev offers a compatibility emulation layer for libevent. It cannot	3867	Libev offers a compatibility emulation layer for libevent. It cannot
3307	emulate the internals of libevent, so here are some usage hints:	3868	emulate the internals of libevent, so here are some usage hints:
3308		3869
3309	=over 4	3870	=over 4
		3871
		3872	=item * Only the libevent-1.4.1-beta API is being emulated.
		3873
		3874	This was the newest libevent version available when libev was implemented,
		3875	and is still mostly unchanged in 2010.
3310		3876
3311	=item * Use it by including <event.h>, as usual.	3877	=item * Use it by including <event.h>, as usual.
3312		3878
3313	=item * The following members are fully supported: ev_base, ev_callback,	3879	=item * The following members are fully supported: ev_base, ev_callback,
3314	ev_arg, ev_fd, ev_res, ev_events.	3880	ev_arg, ev_fd, ev_res, ev_events.
…		…
3320	=item * Priorities are not currently supported. Initialising priorities	3886	=item * Priorities are not currently supported. Initialising priorities
3321	will fail and all watchers will have the same priority, even though there	3887	will fail and all watchers will have the same priority, even though there
3322	is an ev_pri field.	3888	is an ev_pri field.
3323		3889
3324	=item * In libevent, the last base created gets the signals, in libev, the	3890	=item * In libevent, the last base created gets the signals, in libev, the
3325	first base created (== the default loop) gets the signals.	3891	base that registered the signal gets the signals.
3326		3892
3327	=item * Other members are not supported.	3893	=item * Other members are not supported.
3328		3894
3329	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3895	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3330	to use the libev header file and library.	3896	to use the libev header file and library.
…		…
3349	Care has been taken to keep the overhead low. The only data member the C++	3915	Care has been taken to keep the overhead low. The only data member the C++
3350	classes add (compared to plain C-style watchers) is the event loop pointer	3916	classes add (compared to plain C-style watchers) is the event loop pointer
3351	that the watcher is associated with (or no additional members at all if	3917	that the watcher is associated with (or no additional members at all if
3352	you disable C<EV_MULTIPLICITY> when embedding libev).	3918	you disable C<EV_MULTIPLICITY> when embedding libev).
3353		3919
3354	Currently, functions, and static and non-static member functions can be	3920	Currently, functions, static and non-static member functions and classes
3355	used as callbacks. Other types should be easy to add as long as they only	3921	with C<operator ()> can be used as callbacks. Other types should be easy
3356	need one additional pointer for context. If you need support for other	3922	to add as long as they only need one additional pointer for context. If
3357	types of functors please contact the author (preferably after implementing	3923	you need support for other types of functors please contact the author
3358	it).	3924	(preferably after implementing it).
		3925
		3926	For all this to work, your C++ compiler either has to use the same calling
		3927	conventions as your C compiler (for static member functions), or you have
		3928	to embed libev and compile libev itself as C++.
3359		3929
3360	Here is a list of things available in the C<ev> namespace:	3930	Here is a list of things available in the C<ev> namespace:
3361		3931
3362	=over 4	3932	=over 4
3363		3933
…		…
3373	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	3943	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3374		3944
3375	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	3945	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
3376	the same name in the C<ev> namespace, with the exception of C<ev_signal>	3946	the same name in the C<ev> namespace, with the exception of C<ev_signal>
3377	which is called C<ev::sig> to avoid clashes with the C<signal> macro	3947	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3378	defines by many implementations.	3948	defined by many implementations.
3379		3949
3380	All of those classes have these methods:	3950	All of those classes have these methods:
3381		3951
3382	=over 4	3952	=over 4
3383		3953
…		…
3516	watchers in the constructor.	4086	watchers in the constructor.
3517		4087
3518	class myclass	4088	class myclass
3519	{	4089	{
3520	ev::io io ; void io_cb (ev::io &w, int revents);	4090	ev::io io ; void io_cb (ev::io &w, int revents);
3521	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);	4091	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3522	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4092	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3523		4093
3524	myclass (int fd)	4094	myclass (int fd)
3525	{	4095	{
3526	io .set <myclass, &myclass::io_cb > (this);	4096	io .set <myclass, &myclass::io_cb > (this);
…		…
3577	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4147	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3578		4148
3579	=item D	4149	=item D
3580		4150
3581	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4151	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3582	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4152	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3583		4153
3584	=item Ocaml	4154	=item Ocaml
3585		4155
3586	Erkki Seppala has written Ocaml bindings for libev, to be found at	4156	Erkki Seppala has written Ocaml bindings for libev, to be found at
3587	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4157	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
…		…
3635	suitable for use with C<EV_A>.	4205	suitable for use with C<EV_A>.
3636		4206
3637	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4207	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3638		4208
3639	Similar to the other two macros, this gives you the value of the default	4209	Similar to the other two macros, this gives you the value of the default
3640	loop, if multiple loops are supported ("ev loop default").	4210	loop, if multiple loops are supported ("ev loop default"). The default loop
		4211	will be initialised if it isn't already initialised.
		4212
		4213	For non-multiplicity builds, these macros do nothing, so you always have
		4214	to initialise the loop somewhere.
3641		4215
3642	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4216	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3643		4217
3644	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4218	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3645	default loop has been initialised (C<UC> == unchecked). Their behaviour	4219	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3790	supported). It will also not define any of the structs usually found in	4364	supported). It will also not define any of the structs usually found in
3791	F<event.h> that are not directly supported by the libev core alone.	4365	F<event.h> that are not directly supported by the libev core alone.
3792		4366
3793	In standalone mode, libev will still try to automatically deduce the	4367	In standalone mode, libev will still try to automatically deduce the
3794	configuration, but has to be more conservative.	4368	configuration, but has to be more conservative.
		4369
		4370	=item EV_USE_FLOOR
		4371
		4372	If defined to be C<1>, libev will use the C<floor ()> function for its
		4373	periodic reschedule calculations, otherwise libev will fall back on a
		4374	portable (slower) implementation. If you enable this, you usually have to
		4375	link against libm or something equivalent. Enabling this when the C<floor>
		4376	function is not available will fail, so the safe default is to not enable
		4377	this.
3795		4378
3796	=item EV_USE_MONOTONIC	4379	=item EV_USE_MONOTONIC
3797		4380
3798	If defined to be C<1>, libev will try to detect the availability of the	4381	If defined to be C<1>, libev will try to detect the availability of the
3799	monotonic clock option at both compile time and runtime. Otherwise no	4382	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3929	If defined to be C<1>, libev will compile in support for the Linux inotify	4512	If defined to be C<1>, libev will compile in support for the Linux inotify
3930	interface to speed up C<ev_stat> watchers. Its actual availability will	4513	interface to speed up C<ev_stat> watchers. Its actual availability will
3931	be detected at runtime. If undefined, it will be enabled if the headers	4514	be detected at runtime. If undefined, it will be enabled if the headers
3932	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4515	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3933		4516
		4517	=item EV_NO_SMP
		4518
		4519	If defined to be C<1>, libev will assume that memory is always coherent
		4520	between threads, that is, threads can be used, but threads never run on
		4521	different cpus (or different cpu cores). This reduces dependencies
		4522	and makes libev faster.
		4523
		4524	=item EV_NO_THREADS
		4525
		4526	If defined to be C<1>, libev will assume that it will never be called
		4527	from different threads, which is a stronger assumption than C<EV_NO_SMP>,
		4528	above. This reduces dependencies and makes libev faster.
		4529
3934	=item EV_ATOMIC_T	4530	=item EV_ATOMIC_T
3935		4531
3936	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4532	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3937	access is atomic with respect to other threads or signal contexts. No such	4533	access is atomic and serialised with respect to other threads or signal
3938	type is easily found in the C language, so you can provide your own type	4534	contexts. No such type is easily found in the C language, so you can
3939	that you know is safe for your purposes. It is used both for signal handler "locking"	4535	provide your own type that you know is safe for your purposes. It is used
3940	as well as for signal and thread safety in C<ev_async> watchers.	4536	both for signal handler "locking" as well as for signal and thread safety
		4537	in C<ev_async> watchers.
3941		4538
3942	In the absence of this define, libev will use C<sig_atomic_t volatile>	4539	In the absence of this define, libev will use C<sig_atomic_t volatile>
3943	(from F<signal.h>), which is usually good enough on most platforms.	4540	(from F<signal.h>), which is usually good enough on most platforms,
		4541	although strictly speaking using a type that also implies a memory fence
		4542	is required.
3944		4543
3945	=item EV_H (h)	4544	=item EV_H (h)
3946		4545
3947	The name of the F<ev.h> header file used to include it. The default if	4546	The name of the F<ev.h> header file used to include it. The default if
3948	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4547	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
…		…
3972	will have the C<struct ev_loop *> as first argument, and you can create	4571	will have the C<struct ev_loop *> as first argument, and you can create
3973	additional independent event loops. Otherwise there will be no support	4572	additional independent event loops. Otherwise there will be no support
3974	for multiple event loops and there is no first event loop pointer	4573	for multiple event loops and there is no first event loop pointer
3975	argument. Instead, all functions act on the single default loop.	4574	argument. Instead, all functions act on the single default loop.
3976		4575
		4576	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4577	default loop when multiplicity is switched off - you always have to
		4578	initialise the loop manually in this case.
		4579
3977	=item EV_MINPRI	4580	=item EV_MINPRI
3978		4581
3979	=item EV_MAXPRI	4582	=item EV_MAXPRI
3980		4583
3981	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4584	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
4078		4681
4079	With an intelligent-enough linker (gcc+binutils are intelligent enough	4682	With an intelligent-enough linker (gcc+binutils are intelligent enough
4080	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by	4683	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
4081	your program might be left out as well - a binary starting a timer and an	4684	your program might be left out as well - a binary starting a timer and an
4082	I/O watcher then might come out at only 5Kb.	4685	I/O watcher then might come out at only 5Kb.
		4686
		4687	=item EV_API_STATIC
		4688
		4689	If this symbol is defined (by default it is not), then all identifiers
		4690	will have static linkage. This means that libev will not export any
		4691	identifiers, and you cannot link against libev anymore. This can be useful
		4692	when you embed libev, only want to use libev functions in a single file,
		4693	and do not want its identifiers to be visible.
		4694
		4695	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4696	wants to use libev.
		4697
		4698	This option only works when libev is compiled with a C compiler, as C++
		4699	doesn't support the required declaration syntax.
4083		4700
4084	=item EV_AVOID_STDIO	4701	=item EV_AVOID_STDIO
4085		4702
4086	If this is set to C<1> at compiletime, then libev will avoid using stdio	4703	If this is set to C<1> at compiletime, then libev will avoid using stdio
4087	functions (printf, scanf, perror etc.). This will increase the code size	4704	functions (printf, scanf, perror etc.). This will increase the code size
…		…
4231	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4848	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4232		4849
4233	#include "ev_cpp.h"	4850	#include "ev_cpp.h"
4234	#include "ev.c"	4851	#include "ev.c"
4235		4852
4236	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4853	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4237		4854
4238	=head2 THREADS AND COROUTINES	4855	=head2 THREADS AND COROUTINES
4239		4856
4240	=head3 THREADS	4857	=head3 THREADS
4241		4858
…		…
4292	default loop and triggering an C<ev_async> watcher from the default loop	4909	default loop and triggering an C<ev_async> watcher from the default loop
4293	watcher callback into the event loop interested in the signal.	4910	watcher callback into the event loop interested in the signal.
4294		4911
4295	=back	4912	=back
4296		4913
4297	=head4 THREAD LOCKING EXAMPLE	4914	See also L<THREAD LOCKING EXAMPLE>.
4298
4299	Here is a fictitious example of how to run an event loop in a different
4300	thread than where callbacks are being invoked and watchers are
4301	created/added/removed.
4302
4303	For a real-world example, see the C<EV::Loop::Async> perl module,
4304	which uses exactly this technique (which is suited for many high-level
4305	languages).
4306
4307	The example uses a pthread mutex to protect the loop data, a condition
4308	variable to wait for callback invocations, an async watcher to notify the
4309	event loop thread and an unspecified mechanism to wake up the main thread.
4310
4311	First, you need to associate some data with the event loop:
4312
4313	typedef struct {
4314	mutex_t lock; /* global loop lock */
4315	ev_async async_w;
4316	thread_t tid;
4317	cond_t invoke_cv;
4318	} userdata;
4319
4320	void prepare_loop (EV_P)
4321	{
4322	// for simplicity, we use a static userdata struct.
4323	static userdata u;
4324
4325	ev_async_init (&u->async_w, async_cb);
4326	ev_async_start (EV_A_ &u->async_w);
4327
4328	pthread_mutex_init (&u->lock, 0);
4329	pthread_cond_init (&u->invoke_cv, 0);
4330
4331	// now associate this with the loop
4332	ev_set_userdata (EV_A_ u);
4333	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4334	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4335
4336	// then create the thread running ev_loop
4337	pthread_create (&u->tid, 0, l_run, EV_A);
4338	}
4339
4340	The callback for the C<ev_async> watcher does nothing: the watcher is used
4341	solely to wake up the event loop so it takes notice of any new watchers
4342	that might have been added:
4343
4344	static void
4345	async_cb (EV_P_ ev_async *w, int revents)
4346	{
4347	// just used for the side effects
4348	}
4349
4350	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4351	protecting the loop data, respectively.
4352
4353	static void
4354	l_release (EV_P)
4355	{
4356	userdata *u = ev_userdata (EV_A);
4357	pthread_mutex_unlock (&u->lock);
4358	}
4359
4360	static void
4361	l_acquire (EV_P)
4362	{
4363	userdata *u = ev_userdata (EV_A);
4364	pthread_mutex_lock (&u->lock);
4365	}
4366
4367	The event loop thread first acquires the mutex, and then jumps straight
4368	into C<ev_run>:
4369
4370	void *
4371	l_run (void *thr_arg)
4372	{
4373	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4374
4375	l_acquire (EV_A);
4376	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4377	ev_run (EV_A_ 0);
4378	l_release (EV_A);
4379
4380	return 0;
4381	}
4382
4383	Instead of invoking all pending watchers, the C<l_invoke> callback will
4384	signal the main thread via some unspecified mechanism (signals? pipe
4385	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4386	have been called (in a while loop because a) spurious wakeups are possible
4387	and b) skipping inter-thread-communication when there are no pending
4388	watchers is very beneficial):
4389
4390	static void
4391	l_invoke (EV_P)
4392	{
4393	userdata *u = ev_userdata (EV_A);
4394
4395	while (ev_pending_count (EV_A))
4396	{
4397	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4398	pthread_cond_wait (&u->invoke_cv, &u->lock);
4399	}
4400	}
4401
4402	Now, whenever the main thread gets told to invoke pending watchers, it
4403	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4404	thread to continue:
4405
4406	static void
4407	real_invoke_pending (EV_P)
4408	{
4409	userdata *u = ev_userdata (EV_A);
4410
4411	pthread_mutex_lock (&u->lock);
4412	ev_invoke_pending (EV_A);
4413	pthread_cond_signal (&u->invoke_cv);
4414	pthread_mutex_unlock (&u->lock);
4415	}
4416
4417	Whenever you want to start/stop a watcher or do other modifications to an
4418	event loop, you will now have to lock:
4419
4420	ev_timer timeout_watcher;
4421	userdata *u = ev_userdata (EV_A);
4422
4423	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4424
4425	pthread_mutex_lock (&u->lock);
4426	ev_timer_start (EV_A_ &timeout_watcher);
4427	ev_async_send (EV_A_ &u->async_w);
4428	pthread_mutex_unlock (&u->lock);
4429
4430	Note that sending the C<ev_async> watcher is required because otherwise
4431	an event loop currently blocking in the kernel will have no knowledge
4432	about the newly added timer. By waking up the loop it will pick up any new
4433	watchers in the next event loop iteration.
4434		4915
4435	=head3 COROUTINES	4916	=head3 COROUTINES
4436		4917
4437	Libev is very accommodating to coroutines ("cooperative threads"):	4918	Libev is very accommodating to coroutines ("cooperative threads"):
4438	libev fully supports nesting calls to its functions from different	4919	libev fully supports nesting calls to its functions from different
…		…
4603	requires, and its I/O model is fundamentally incompatible with the POSIX	5084	requires, and its I/O model is fundamentally incompatible with the POSIX
4604	model. Libev still offers limited functionality on this platform in	5085	model. Libev still offers limited functionality on this platform in
4605	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5086	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4606	descriptors. This only applies when using Win32 natively, not when using	5087	descriptors. This only applies when using Win32 natively, not when using
4607	e.g. cygwin. Actually, it only applies to the microsofts own compilers,	5088	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
4608	as every compielr comes with a slightly differently broken/incompatible	5089	as every compiler comes with a slightly differently broken/incompatible
4609	environment.	5090	environment.
4610		5091
4611	Lifting these limitations would basically require the full	5092	Lifting these limitations would basically require the full
4612	re-implementation of the I/O system. If you are into this kind of thing,	5093	re-implementation of the I/O system. If you are into this kind of thing,
4613	then note that glib does exactly that for you in a very portable way (note	5094	then note that glib does exactly that for you in a very portable way (note
…		…
4707	structure (guaranteed by POSIX but not by ISO C for example), but it also	5188	structure (guaranteed by POSIX but not by ISO C for example), but it also
4708	assumes that the same (machine) code can be used to call any watcher	5189	assumes that the same (machine) code can be used to call any watcher
4709	callback: The watcher callbacks have different type signatures, but libev	5190	callback: The watcher callbacks have different type signatures, but libev
4710	calls them using an C<ev_watcher *> internally.	5191	calls them using an C<ev_watcher *> internally.
4711		5192
		5193	=item pointer accesses must be thread-atomic
		5194
		5195	Accessing a pointer value must be atomic, it must both be readable and
		5196	writable in one piece - this is the case on all current architectures.
		5197
4712	=item C<sig_atomic_t volatile> must be thread-atomic as well	5198	=item C<sig_atomic_t volatile> must be thread-atomic as well
4713		5199
4714	The type C<sig_atomic_t volatile> (or whatever is defined as	5200	The type C<sig_atomic_t volatile> (or whatever is defined as
4715	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5201	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
4716	threads. This is not part of the specification for C<sig_atomic_t>, but is	5202	threads. This is not part of the specification for C<sig_atomic_t>, but is
…		…
4741		5227
4742	The type C<double> is used to represent timestamps. It is required to	5228	The type C<double> is used to represent timestamps. It is required to
4743	have at least 51 bits of mantissa (and 9 bits of exponent), which is	5229	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4744	good enough for at least into the year 4000 with millisecond accuracy	5230	good enough for at least into the year 4000 with millisecond accuracy
4745	(the design goal for libev). This requirement is overfulfilled by	5231	(the design goal for libev). This requirement is overfulfilled by
4746	implementations using IEEE 754, which is basically all existing ones. With	5232	implementations using IEEE 754, which is basically all existing ones.
		5233
4747	IEEE 754 doubles, you get microsecond accuracy until at least 2200.	5234	With IEEE 754 doubles, you get microsecond accuracy until at least the
		5235	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5236	is either obsolete or somebody patched it to use C<long double> or
		5237	something like that, just kidding).
4748		5238
4749	=back	5239	=back
4750		5240
4751	If you know of other additional requirements drop me a note.	5241	If you know of other additional requirements drop me a note.
4752		5242
…		…
4814	=item Processing ev_async_send: O(number_of_async_watchers)	5304	=item Processing ev_async_send: O(number_of_async_watchers)
4815		5305
4816	=item Processing signals: O(max_signal_number)	5306	=item Processing signals: O(max_signal_number)
4817		5307
4818	Sending involves a system call I<iff> there were no other C<ev_async_send>	5308	Sending involves a system call I<iff> there were no other C<ev_async_send>
4819	calls in the current loop iteration. Checking for async and signal events	5309	calls in the current loop iteration and the loop is currently
		5310	blocked. Checking for async and signal events involves iterating over all
4820	involves iterating over all running async watchers or all signal numbers.	5311	running async watchers or all signal numbers.
4821		5312
4822	=back	5313	=back
4823		5314
4824		5315
4825	=head1 PORTING FROM LIBEV 3.X TO 4.X	5316	=head1 PORTING FROM LIBEV 3.X TO 4.X
4826		5317
4827	The major version 4 introduced some minor incompatible changes to the API.	5318	The major version 4 introduced some incompatible changes to the API.
4828		5319
4829	At the moment, the C<ev.h> header file tries to implement superficial	5320	At the moment, the C<ev.h> header file provides compatibility definitions
4830	compatibility, so most programs should still compile. Those might be	5321	for all changes, so most programs should still compile. The compatibility
4831	removed in later versions of libev, so better update early than late.	5322	layer might be removed in later versions of libev, so better update to the
		5323	new API early than late.
4832		5324
4833	=over 4	5325	=over 4
		5326
		5327	=item C<EV_COMPAT3> backwards compatibility mechanism
		5328
		5329	The backward compatibility mechanism can be controlled by
		5330	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5331	section.
		5332
		5333	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5334
		5335	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5336
		5337	ev_loop_destroy (EV_DEFAULT_UC);
		5338	ev_loop_fork (EV_DEFAULT);
4834		5339
4835	=item function/symbol renames	5340	=item function/symbol renames
4836		5341
4837	A number of functions and symbols have been renamed:	5342	A number of functions and symbols have been renamed:
4838		5343
…		…
4857	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme	5362	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
4858	as all other watcher types. Note that C<ev_loop_fork> is still called	5363	as all other watcher types. Note that C<ev_loop_fork> is still called
4859	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>	5364	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
4860	typedef.	5365	typedef.
4861		5366
4862	=item C<EV_COMPAT3> backwards compatibility mechanism
4863
4864	The backward compatibility mechanism can be controlled by
4865	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
4866	section.
4867
4868	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>	5367	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
4869		5368
4870	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different	5369	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
4871	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile	5370	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
4872	and work, but the library code will of course be larger.	5371	and work, but the library code will of course be larger.
…		…
4934	The physical time that is observed. It is apparently strictly monotonic :)	5433	The physical time that is observed. It is apparently strictly monotonic :)
4935		5434
4936	=item wall-clock time	5435	=item wall-clock time
4937		5436
4938	The time and date as shown on clocks. Unlike real time, it can actually	5437	The time and date as shown on clocks. Unlike real time, it can actually
4939	be wrong and jump forwards and backwards, e.g. when the you adjust your	5438	be wrong and jump forwards and backwards, e.g. when you adjust your
4940	clock.	5439	clock.
4941		5440
4942	=item watcher	5441	=item watcher
4943		5442
4944	A data structure that describes interest in certain events. Watchers need	5443	A data structure that describes interest in certain events. Watchers need
…		…
4946		5445
4947	=back	5446	=back
4948		5447
4949	=head1 AUTHOR	5448	=head1 AUTHOR
4950		5449
4951	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5450	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5451	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4952		5452

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