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…		…
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
…		…
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 interesting 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 EVENT LOOPS	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
…		…
342	Example: Restrict libev to the select and poll backends, and do not allow	369	Example: Restrict libev to the select and poll backends, and do not allow
343	environment settings to be taken into account:	370	environment settings to be taken into account:
344		371
345	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	372	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
346		373
347	Example: Use whatever libev has to offer, but make sure that kqueue is
348	used if available (warning, breaks stuff, best use only with your own
349	private event loop and only if you know the OS supports your types of
350	fds):
351
352	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
353
354	=item struct ev_loop *ev_loop_new (unsigned int flags)	374	=item struct ev_loop *ev_loop_new (unsigned int flags)
355		375
356	This will create and initialise a new event loop object. If the loop	376	This will create and initialise a new event loop object. If the loop
357	could not be initialised, returns false.	377	could not be initialised, returns false.
358		378
359	Note that this function I<is> thread-safe, and one common way to use	379	This function is thread-safe, and one common way to use libev with
360	libev with threads is indeed to create one loop per thread, and using the	380	threads is indeed to create one loop per thread, and using the default
361	default loop in the "main" or "initial" thread.	381	loop in the "main" or "initial" thread.
362		382
363	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
364	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>).
365		385
366	The following flags are supported:	386	The following flags are supported:
…		…
401	environment variable.	421	environment variable.
402		422
403	=item C<EVFLAG_NOINOTIFY>	423	=item C<EVFLAG_NOINOTIFY>
404		424
405	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
406	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
407	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
408	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.
409		429
410	=item C<EVFLAG_SIGNALFD>	430	=item C<EVFLAG_SIGNALFD>
411		431
412	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
413	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
414	delivers signals synchronously, which makes it both faster and might make	434	delivers signals synchronously, which makes it both faster and might make
415	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
416	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
417	threads that are not interested in handling them.	437	threads that are not interested in handling them.
418		438
419	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
420	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
421	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.
422		457
423	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	458	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
424		459
425	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
426	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,
…		…
454	=item C<EVBACKEND_EPOLL> (value 4, Linux)	489	=item C<EVBACKEND_EPOLL> (value 4, Linux)
455		490
456	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
457	kernels).	492	kernels).
458		493
459	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
460	but it scales phenomenally better. While poll and select usually scale	495	it scales phenomenally better. While poll and select usually scale like
461	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
462	epoll scales either O(1) or O(active_fds).	497	fd), epoll scales either O(1) or O(active_fds).
463		498
464	The epoll mechanism deserves honorable mention as the most misdesigned	499	The epoll mechanism deserves honorable mention as the most misdesigned
465	of the more advanced event mechanisms: mere annoyances include silently	500	of the more advanced event mechanisms: mere annoyances include silently
466	dropping file descriptors, requiring a system call per change per file	501	dropping file descriptors, requiring a system call per change per file
467	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
468	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
469	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
470	take considerable time (one syscall per file descriptor) and is of course	507	set, which can take considerable time (one syscall per file descriptor)
471	hard to detect.	508	and is of course hard to detect.
472		509
473	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	510	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
474	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
475	I<different> file descriptors (even already closed ones, so one cannot	512	totally I<different> file descriptors (even already closed ones, so
476	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
477	on SMP systems). Libev tries to counter these spurious notifications by	514	(especially on SMP systems). Libev tries to counter these spurious
478	employing an additional generation counter and comparing that against the	515	notifications by employing an additional generation counter and comparing
479	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
480	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
481	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...
482		526
483	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
484	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
485	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
486	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
…		…
523		567
524	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
525	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
526	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
527	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
528	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
529	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
530	cases	574	drops fds silently in similarly hard-to-detect cases
531		575
532	This backend usually performs well under most conditions.	576	This backend usually performs well under most conditions.
533		577
534	While nominally embeddable in other event loops, this doesn't work	578	While nominally embeddable in other event loops, this doesn't work
535	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
…		…
552	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	596	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
553		597
554	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,
555	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)).
556		600
557	Please note that Solaris event ports can deliver a lot of spurious
558	notifications, so you need to use non-blocking I/O or other means to avoid
559	blocking when no data (or space) is available.
560
561	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
562	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
563	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	603	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
564	might perform better.	604	might perform better.
565		605
566	On the positive side, with the exception of the spurious readiness	606	On the positive side, this backend actually performed fully to
567	notifications, this backend actually performed fully to specification
568	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
569	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.
570		620
571	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
572	C<EVBACKEND_POLL>.	622	C<EVBACKEND_POLL>.
573		623
574	=item C<EVBACKEND_ALL>	624	=item C<EVBACKEND_ALL>
575		625
576	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
577	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
578	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	628	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
579		629
580	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).
581		639
582	=back	640	=back
583		641
584	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,
585	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
…		…
589	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.
590		648
591	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	649	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
592	if (!epoller)	650	if (!epoller)
593	fatal ("no epoll found here, maybe it hides under your chair");	651	fatal ("no epoll found here, maybe it hides under your chair");
		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);
594		657
595	=item ev_loop_destroy (loop)	658	=item ev_loop_destroy (loop)
596		659
597	Destroys an event loop object (frees all memory and kernel state	660	Destroys an event loop object (frees all memory and kernel state
598	etc.). None of the active event watchers will be stopped in the normal	661	etc.). None of the active event watchers will be stopped in the normal
…		…
609	This function is normally used on loop objects allocated by	672	This function is normally used on loop objects allocated by
610	C<ev_loop_new>, but it can also be used on the default loop returned by	673	C<ev_loop_new>, but it can also be used on the default loop returned by
611	C<ev_default_loop>, in which case it is not thread-safe.	674	C<ev_default_loop>, in which case it is not thread-safe.
612		675
613	Note that it is not advisable to call this function on the default loop	676	Note that it is not advisable to call this function on the default loop
614	except in the rare occasion where you really need to free it's resources.	677	except in the rare occasion where you really need to free its resources.
615	If you need dynamically allocated loops it is better to use C<ev_loop_new>	678	If you need dynamically allocated loops it is better to use C<ev_loop_new>
616	and C<ev_loop_destroy>.	679	and C<ev_loop_destroy>.
617		680
618	=item ev_loop_fork (loop)	681	=item ev_loop_fork (loop)
619		682
…		…
667	prepare and check phases.	730	prepare and check phases.
668		731
669	=item unsigned int ev_depth (loop)	732	=item unsigned int ev_depth (loop)
670		733
671	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
672	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.
673		736
674	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
675	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),
676	in which case it is higher.	739	in which case it is higher.
677		740
678	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread	741	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
679	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
680	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.
681		745
682	=item unsigned int ev_backend (loop)	746	=item unsigned int ev_backend (loop)
683		747
684	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
685	use.	749	use.
…		…
728	without a previous call to C<ev_suspend>.	792	without a previous call to C<ev_suspend>.
729		793
730	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
731	event loop time (see C<ev_now_update>).	795	event loop time (see C<ev_now_update>).
732		796
733	=item ev_run (loop, int flags)	797	=item bool ev_run (loop, int flags)
734		798
735	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
736	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
737	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
738	the watcher callbacks, an then repeat the whole process indefinitely: This	802	the watcher callbacks, and then repeat the whole process indefinitely: This
739	is why event loops are called I<loops>.	803	is why event loops are called I<loops>.
740		804
741	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
742	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
743	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").
744		812
745	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
746	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
747	finished (especially in interactive programs), but having a program	815	finished (especially in interactive programs), but having a program
748	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
749	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
750	beauty.	818	beauty.
751		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
752	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
753	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
754	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
755	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
756	events while doing lengthy calculations, to keep the program responsive.	829	events while doing lengthy calculations, to keep the program responsive.
…		…
765	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
766	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
767	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
768	usually a better approach for this kind of thing.	841	usually a better approach for this kind of thing.
769		842
770	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):
771		846
772	- Increment loop depth.	847	- Increment loop depth.
773	- Reset the ev_break status.	848	- Reset the ev_break status.
774	- Before the first iteration, call any pending watchers.	849	- Before the first iteration, call any pending watchers.
775	LOOP:	850	LOOP:
…		…
808	anymore.	883	anymore.
809		884
810	... queue jobs here, make sure they register event watchers as long	885	... queue jobs here, make sure they register event watchers as long
811	... 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..)
812	ev_run (my_loop, 0);	887	ev_run (my_loop, 0);
813	... jobs done or somebody called unloop. yeah!	888	... jobs done or somebody called break. yeah!
814		889
815	=item ev_break (loop, how)	890	=item ev_break (loop, how)
816		891
817	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
818	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
819	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
820	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.
821		896
822	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>.
823		898
824	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.
825		901
826	=item ev_ref (loop)	902	=item ev_ref (loop)
827		903
828	=item ev_unref (loop)	904	=item ev_unref (loop)
829		905
…		…
850	running when nothing else is active.	926	running when nothing else is active.
851		927
852	ev_signal exitsig;	928	ev_signal exitsig;
853	ev_signal_init (&exitsig, sig_cb, SIGINT);	929	ev_signal_init (&exitsig, sig_cb, SIGINT);
854	ev_signal_start (loop, &exitsig);	930	ev_signal_start (loop, &exitsig);
855	evf_unref (loop);	931	ev_unref (loop);
856		932
857	Example: For some weird reason, unregister the above signal handler again.	933	Example: For some weird reason, unregister the above signal handler again.
858		934
859	ev_ref (loop);	935	ev_ref (loop);
860	ev_signal_stop (loop, &exitsig);	936	ev_signal_stop (loop, &exitsig);
…		…
880	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.
881		957
882	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
883	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,
884	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
885	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
886	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
887	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
888	once per this interval, on average.	964	once per this interval, on average (as long as the host time resolution is
		965	good enough).
889		966
890	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
891	to spend more time collecting timeouts, at the expense of increased	968	to spend more time collecting timeouts, at the expense of increased
892	latency/jitter/inexactness (the watcher callback will be called	969	latency/jitter/inexactness (the watcher callback will be called
893	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
…		…
947	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
948	each call to a libev function.	1025	each call to a libev function.
949		1026
950	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
951	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
952	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
953	I<release> and I<acquire> callbacks on the loop.	1030	I<release> and I<acquire> callbacks on the loop.
954		1031
955	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
956	suspended waiting for new events, and C<acquire> is called just	1033	suspended waiting for new events, and C<acquire> is called just
957	afterwards.	1034	afterwards.
…		…
972	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
973	document.	1050	document.
974		1051
975	=item ev_set_userdata (loop, void *data)	1052	=item ev_set_userdata (loop, void *data)
976		1053
977	=item ev_userdata (loop)	1054	=item void *ev_userdata (loop)
978		1055
979	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
980	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
981	C<0.>	1058	C<0>.
982		1059
983	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,
984	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
985	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
986	any other purpose as well.	1063	any other purpose as well.
…		…
1114	=item C<EV_FORK>	1191	=item C<EV_FORK>
1115		1192
1116	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
1117	C<ev_fork>).	1194	C<ev_fork>).
1118		1195
		1196	=item C<EV_CLEANUP>
		1197
		1198	The event loop is about to be destroyed (see C<ev_cleanup>).
		1199
1119	=item C<EV_ASYNC>	1200	=item C<EV_ASYNC>
1120		1201
1121	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>).
1122		1203
1123	=item C<EV_CUSTOM>	1204	=item C<EV_CUSTOM>
…		…
1144	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
1145	thing, so beware.	1226	thing, so beware.
1146		1227
1147	=back	1228	=back
1148		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
1149	=head2 WATCHER STATES	1384	=head2 WATCHER STATES
1150		1385
1151	There are various watcher states mentioned throughout this manual -	1386	There are various watcher states mentioned throughout this manual -
1152	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
1153	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
…		…
1155		1390
1156	=over 4	1391	=over 4
1157		1392
1158	=item initialiased	1393	=item initialiased
1159		1394
1160	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
1161	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
1162	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.
1163		1398
1164	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
1165	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.
1166		1403
1167	=item started/running/active	1404	=item started/running/active
1168		1405
1169	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
1170	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
…		…
1198	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
1199	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
1200	freeing it is often a good idea.	1437	freeing it is often a good idea.
1201		1438
1202	While stopped (and not pending) the watcher is essentially in the	1439	While stopped (and not pending) the watcher is essentially in the
1203	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
1204	you wish.	1441	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1442	it again).
1205		1443
1206	=back	1444	=back
1207
1208	=head2 GENERIC WATCHER FUNCTIONS
1209
1210	=over 4
1211
1212	=item C<ev_init> (ev_TYPE *watcher, callback)
1213
1214	This macro initialises the generic portion of a watcher. The contents
1215	of the watcher object can be arbitrary (so C<malloc> will do). Only
1216	the generic parts of the watcher are initialised, you I<need> to call
1217	the type-specific C<ev_TYPE_set> macro afterwards to initialise the
1218	type-specific parts. For each type there is also a C<ev_TYPE_init> macro
1219	which rolls both calls into one.
1220
1221	You can reinitialise a watcher at any time as long as it has been stopped
1222	(or never started) and there are no pending events outstanding.
1223
1224	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
1225	int revents)>.
1226
1227	Example: Initialise an C<ev_io> watcher in two steps.
1228
1229	ev_io w;
1230	ev_init (&w, my_cb);
1231	ev_io_set (&w, STDIN_FILENO, EV_READ);
1232
1233	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
1234
1235	This macro initialises the type-specific parts of a watcher. You need to
1236	call C<ev_init> at least once before you call this macro, but you can
1237	call C<ev_TYPE_set> any number of times. You must not, however, call this
1238	macro on a watcher that is active (it can be pending, however, which is a
1239	difference to the C<ev_init> macro).
1240
1241	Although some watcher types do not have type-specific arguments
1242	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
1243
1244	See C<ev_init>, above, for an example.
1245
1246	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
1247
1248	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
1249	calls into a single call. This is the most convenient method to initialise
1250	a watcher. The same limitations apply, of course.
1251
1252	Example: Initialise and set an C<ev_io> watcher in one step.
1253
1254	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1255
1256	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1257
1258	Starts (activates) the given watcher. Only active watchers will receive
1259	events. If the watcher is already active nothing will happen.
1260
1261	Example: Start the C<ev_io> watcher that is being abused as example in this
1262	whole section.
1263
1264	ev_io_start (EV_DEFAULT_UC, &w);
1265
1266	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1267
1268	Stops the given watcher if active, and clears the pending status (whether
1269	the watcher was active or not).
1270
1271	It is possible that stopped watchers are pending - for example,
1272	non-repeating timers are being stopped when they become pending - but
1273	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
1274	pending. If you want to free or reuse the memory used by the watcher it is
1275	therefore a good idea to always call its C<ev_TYPE_stop> function.
1276
1277	=item bool ev_is_active (ev_TYPE *watcher)
1278
1279	Returns a true value iff the watcher is active (i.e. it has been started
1280	and not yet been stopped). As long as a watcher is active you must not modify
1281	it.
1282
1283	=item bool ev_is_pending (ev_TYPE *watcher)
1284
1285	Returns a true value iff the watcher is pending, (i.e. it has outstanding
1286	events but its callback has not yet been invoked). As long as a watcher
1287	is pending (but not active) you must not call an init function on it (but
1288	C<ev_TYPE_set> is safe), you must not change its priority, and you must
1289	make sure the watcher is available to libev (e.g. you cannot C<free ()>
1290	it).
1291
1292	=item callback ev_cb (ev_TYPE *watcher)
1293
1294	Returns the callback currently set on the watcher.
1295
1296	=item ev_cb_set (ev_TYPE *watcher, callback)
1297
1298	Change the callback. You can change the callback at virtually any time
1299	(modulo threads).
1300
1301	=item ev_set_priority (ev_TYPE *watcher, int priority)
1302
1303	=item int ev_priority (ev_TYPE *watcher)
1304
1305	Set and query the priority of the watcher. The priority is a small
1306	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1307	(default: C<-2>). Pending watchers with higher priority will be invoked
1308	before watchers with lower priority, but priority will not keep watchers
1309	from being executed (except for C<ev_idle> watchers).
1310
1311	If you need to suppress invocation when higher priority events are pending
1312	you need to look at C<ev_idle> watchers, which provide this functionality.
1313
1314	You I<must not> change the priority of a watcher as long as it is active or
1315	pending.
1316
1317	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1318	fine, as long as you do not mind that the priority value you query might
1319	or might not have been clamped to the valid range.
1320
1321	The default priority used by watchers when no priority has been set is
1322	always C<0>, which is supposed to not be too high and not be too low :).
1323
1324	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1325	priorities.
1326
1327	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1328
1329	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1330	C<loop> nor C<revents> need to be valid as long as the watcher callback
1331	can deal with that fact, as both are simply passed through to the
1332	callback.
1333
1334	=item int ev_clear_pending (loop, ev_TYPE *watcher)
1335
1336	If the watcher is pending, this function clears its pending status and
1337	returns its C<revents> bitset (as if its callback was invoked). If the
1338	watcher isn't pending it does nothing and returns C<0>.
1339
1340	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1341	callback to be invoked, which can be accomplished with this function.
1342
1343	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
1344
1345	Feeds the given event set into the event loop, as if the specified event
1346	had happened for the specified watcher (which must be a pointer to an
1347	initialised but not necessarily started event watcher). Obviously you must
1348	not free the watcher as long as it has pending events.
1349
1350	Stopping the watcher, letting libev invoke it, or calling
1351	C<ev_clear_pending> will clear the pending event, even if the watcher was
1352	not started in the first place.
1353
1354	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1355	functions that do not need a watcher.
1356
1357	=back
1358
1359
1360	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1361
1362	Each watcher has, by default, a member C<void *data> that you can change
1363	and read at any time: libev will completely ignore it. This can be used
1364	to associate arbitrary data with your watcher. If you need more data and
1365	don't want to allocate memory and store a pointer to it in that data
1366	member, you can also "subclass" the watcher type and provide your own
1367	data:
1368
1369	struct my_io
1370	{
1371	ev_io io;
1372	int otherfd;
1373	void *somedata;
1374	struct whatever *mostinteresting;
1375	};
1376
1377	...
1378	struct my_io w;
1379	ev_io_init (&w.io, my_cb, fd, EV_READ);
1380
1381	And since your callback will be called with a pointer to the watcher, you
1382	can cast it back to your own type:
1383
1384	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1385	{
1386	struct my_io *w = (struct my_io *)w_;
1387	...
1388	}
1389
1390	More interesting and less C-conformant ways of casting your callback type
1391	instead have been omitted.
1392
1393	Another common scenario is to use some data structure with multiple
1394	embedded watchers:
1395
1396	struct my_biggy
1397	{
1398	int some_data;
1399	ev_timer t1;
1400	ev_timer t2;
1401	}
1402
1403	In this case getting the pointer to C<my_biggy> is a bit more
1404	complicated: Either you store the address of your C<my_biggy> struct
1405	in the C<data> member of the watcher (for woozies), or you need to use
1406	some pointer arithmetic using C<offsetof> inside your watchers (for real
1407	programmers):
1408
1409	#include <stddef.h>
1410
1411	static void
1412	t1_cb (EV_P_ ev_timer *w, int revents)
1413	{
1414	struct my_biggy big = (struct my_biggy *)
1415	(((char *)w) - offsetof (struct my_biggy, t1));
1416	}
1417
1418	static void
1419	t2_cb (EV_P_ ev_timer *w, int revents)
1420	{
1421	struct my_biggy big = (struct my_biggy *)
1422	(((char *)w) - offsetof (struct my_biggy, t2));
1423	}
1424		1445
1425	=head2 WATCHER PRIORITY MODELS	1446	=head2 WATCHER PRIORITY MODELS
1426		1447
1427	Many event loops support I<watcher priorities>, which are usually small	1448	Many event loops support I<watcher priorities>, which are usually small
1428	integers that influence the ordering of event callback invocation	1449	integers that influence the ordering of event callback invocation
…		…
1555	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
1556	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
1557	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
1558	required if you know what you are doing).	1579	required if you know what you are doing).
1559		1580
1560	If you cannot use non-blocking mode, then force the use of a
1561	known-to-be-good backend (at the time of this writing, this includes only
1562	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1563	descriptors for which non-blocking operation makes no sense (such as
1564	files) - libev doesn't guarantee any specific behaviour in that case.
1565
1566	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
1567	receive "spurious" readiness notifications, that is your callback might	1582	receive "spurious" readiness notifications, that is, your callback might
1568	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
1569	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
1570	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
1571	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
1572	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1573	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1587	preferable to a program hanging until some data arrives.
1574		1588
1575	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
1576	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
1577	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
1578	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
1579	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
1580	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
1581	indefinitely.	1595	indefinitely.
1582		1596
1583	But really, best use non-blocking mode.	1597	But really, best use non-blocking mode.
1584		1598
…		…
1612		1626
1613	There is no workaround possible except not registering events	1627	There is no workaround possible except not registering events
1614	for potentially C<dup ()>'ed file descriptors, or to resort to	1628	for potentially C<dup ()>'ed file descriptors, or to resort to
1615	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1629	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1616		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
1617	=head3 The special problem of fork	1664	=head3 The special problem of fork
1618		1665
1619	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
1620	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
1621	it in the child.	1668	it in the child if you want to continue to use it in the child.
1622		1669
1623	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
1624	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
1625	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1672	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1626	C<EVBACKEND_POLL>.
1627		1673
1628	=head3 The special problem of SIGPIPE	1674	=head3 The special problem of SIGPIPE
1629		1675
1630	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>:
1631	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
…		…
1729	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1775	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1730	monotonic clock option helps a lot here).	1776	monotonic clock option helps a lot here).
1731		1777
1732	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
1733	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
1734	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
1735	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
1736	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
1737	no longer true when a callback calls C<ev_run> recursively).	1784	longer true when a callback calls C<ev_run> recursively).
1738		1785
1739	=head3 Be smart about timeouts	1786	=head3 Be smart about timeouts
1740		1787
1741	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
1742	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,
…		…
1817		1864
1818	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,
1819	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
1820	within the callback:	1867	within the callback:
1821		1868
		1869	ev_tstamp timeout = 60.;
1822	ev_tstamp last_activity; // time of last activity	1870	ev_tstamp last_activity; // time of last activity
		1871	ev_timer timer;
1823		1872
1824	static void	1873	static void
1825	callback (EV_P_ ev_timer *w, int revents)	1874	callback (EV_P_ ev_timer *w, int revents)
1826	{	1875	{
1827	ev_tstamp now = ev_now (EV_A);	1876	// calculate when the timeout would happen
1828	ev_tstamp timeout = last_activity + 60.;	1877	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1829		1878
1830	// if last_activity + 60. is older than now, we did time out	1879	// if negative, it means we the timeout already occured
1831	if (timeout < now)	1880	if (after < 0.)
1832	{	1881	{
1833	// timeout occurred, take action	1882	// timeout occurred, take action
1834	}	1883	}
1835	else	1884	else
1836	{	1885	{
1837	// callback was invoked, but there was some activity, re-arm	1886	// callback was invoked, but there was some recent
1838	// the watcher to fire in last_activity + 60, which is	1887	// activity. simply restart the timer to time out
1839	// guaranteed to be in the future, so "again" is positive:	1888	// after "after" seconds, which is the earliest time
1840	w->repeat = timeout - now;	1889	// the timeout can occur.
		1890	ev_timer_set (w, after, 0.);
1841	ev_timer_again (EV_A_ w);	1891	ev_timer_start (EV_A_ w);
1842	}	1892	}
1843	}	1893	}
1844		1894
1845	To summarise the callback: first calculate the real timeout (defined	1895	To summarise the callback: first calculate in how many seconds the
1846	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,
1847	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
1848	the callback was invoked too early (C<timeout> is in the future), so	1898	(EV_A)> from that).
1849	re-schedule the timer to fire at that future time, to see if maybe we have
1850	a timeout then.
1851		1899
1852	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
1853	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.
1854		1909
1855	This scheme causes more callback invocations (about one every 60 seconds	1910	This scheme causes more callback invocations (about one every 60 seconds
1856	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
1857	libev to change the timeout.	1912	libev to change the timeout.
1858		1913
1859	To start the timer, simply initialise the watcher and set C<last_activity>	1914	To start the machinery, simply initialise the watcher and set
1860	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
1861	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:
1862		1918
		1919	last_activity = ev_now (EV_A);
1863	ev_init (timer, callback);	1920	ev_init (&timer, callback);
1864	last_activity = ev_now (loop);	1921	callback (EV_A_ &timer, 0);
1865	callback (loop, timer, EV_TIMER);
1866		1922
1867	And when there is some activity, simply store the current time in	1923	When there is some activity, simply store the current time in
1868	C<last_activity>, no libev calls at all:	1924	C<last_activity>, no libev calls at all:
1869		1925
		1926	if (activity detected)
1870	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);
1871		1936
1872	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
1873	time-out is unlikely to be triggered, much more efficient.	1938	time-out is unlikely to be triggered, much more efficient.
1874
1875	Changing the timeout is trivial as well (if it isn't hard-coded in the
1876	callback :) - just change the timeout and invoke the callback, which will
1877	fix things for you.
1878		1939
1879	=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.
1880		1941
1881	If there is not one request, but many thousands (millions...), all	1942	If there is not one request, but many thousands (millions...), all
1882	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
…		…
1909	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
1910	rather complicated, but extremely efficient, something that really pays	1971	rather complicated, but extremely efficient, something that really pays
1911	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
1912	overkill :)	1973	overkill :)
1913		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
1914	=head3 The special problem of time updates	2012	=head3 The special problem of time updates
1915		2013
1916	Establishing the current time is a costly operation (it usually takes at	2014	Establishing the current time is a costly operation (it usually takes
1917	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
1918	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
1919	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
1920	lots of events in one iteration.	2018	lots of events in one iteration.
1921		2019
1922	The relative timeouts are calculated relative to the C<ev_now ()>	2020	The relative timeouts are calculated relative to the C<ev_now ()>
…		…
1928	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2026	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1929		2027
1930	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
1931	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
1932	()>.	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.
1933		2064
1934	=head3 The special problems of suspended animation	2065	=head3 The special problems of suspended animation
1935		2066
1936	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
1937	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?
…		…
1981	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
1982	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.
1983		2114
1984	=item ev_timer_again (loop, ev_timer *)	2115	=item ev_timer_again (loop, ev_timer *)
1985		2116
1986	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
1987	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>.
1988		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
1989	If the timer is pending, its pending status is cleared.	2126	=item If the timer is pending, the pending status is always cleared.
1990		2127
1991	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).
1992		2130
1993	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
1994	C<repeat> value), or reset the running timer to the C<repeat> value.	2132	and start the timer, if necessary.
		2133
		2134	=back
1995		2135
1996	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
1997	usage example.	2137	usage example.
1998		2138
1999	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)	2139	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
…		…
2121		2261
2122	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
2123	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
2124	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.
2125		2265
2126	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
2127	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
2128	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.
2129		2272
2130	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
2131	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
2132	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
2133	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).
…		…
2247		2390
2248	=head2 C<ev_signal> - signal me when a signal gets signalled!	2391	=head2 C<ev_signal> - signal me when a signal gets signalled!
2249		2392
2250	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
2251	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
2252	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
2253	normal event processing, like any other event.	2396	normal event processing, like any other event.
2254		2397
2255	If you want signals to be delivered truly asynchronously, just use	2398	If you want signals to be delivered truly asynchronously, just use
2256	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
2257	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
…		…
2276	=head3 The special problem of inheritance over fork/execve/pthread_create	2419	=head3 The special problem of inheritance over fork/execve/pthread_create
2277		2420
2278	Both the signal mask (C<sigprocmask>) and the signal disposition	2421	Both the signal mask (C<sigprocmask>) and the signal disposition
2279	(C<sigaction>) are unspecified after starting a signal watcher (and after	2422	(C<sigaction>) are unspecified after starting a signal watcher (and after
2280	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,
2281	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>).
2282		2426
2283	While this does not matter for the signal disposition (libev never	2427	While this does not matter for the signal disposition (libev never
2284	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
2285	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
2286	certain signals to be blocked.	2430	certain signals to be blocked.
…		…
2299	I<has> to modify the signal mask, at least temporarily.	2443	I<has> to modify the signal mask, at least temporarily.
2300		2444
2301	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
2302	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
2303	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>.
2304		2462
2305	=head3 Watcher-Specific Functions and Data Members	2463	=head3 Watcher-Specific Functions and Data Members
2306		2464
2307	=over 4	2465	=over 4
2308		2466
…		…
3092		3250
3093	=head3 Watcher-Specific Functions and Data Members	3251	=head3 Watcher-Specific Functions and Data Members
3094		3252
3095	=over 4	3253	=over 4
3096		3254
3097	=item ev_fork_init (ev_signal *, callback)	3255	=item ev_fork_init (ev_fork *, callback)
3098		3256
3099	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
3100	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,
3101	believe me.	3259	really.
3102		3260
3103	=back	3261	=back
3104		3262
3105		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
3106	=head2 C<ev_async> - how to wake up an event loop	3304	=head2 C<ev_async> - how to wake up an event loop
3107		3305
3108	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
3109	asynchronous sources such as signal handlers (as opposed to multiple event	3307	asynchronous sources such as signal handlers (as opposed to multiple event
3110	loops - those are of course safe to use in different threads).	3308	loops - those are of course safe to use in different threads).
3111		3309
3112	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,
3113	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>
…		…
3115	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.
3116		3314
3117	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,
3118	too, are asynchronous in nature, and signals, too, will be compressed	3316	too, are asynchronous in nature, and signals, too, will be compressed
3119	(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
3120	C<ev_async_sent> calls).	3318	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
3121		3319	of "global async watchers" by using a watcher on an otherwise unused
3122	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,
3123	just the default loop.	3321	even without knowing which loop owns the signal.
3124		3322
3125	=head3 Queueing	3323	=head3 Queueing
3126		3324
3127	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
3128	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
…		…
3220	trust me.	3418	trust me.
3221		3419
3222	=item ev_async_send (loop, ev_async *)	3420	=item ev_async_send (loop, ev_async *)
3223		3421
3224	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
3225	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
3226	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,
3227	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
3228	section below on what exactly this means).	3428	embedding section below on what exactly this means).
3229		3429
3230	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
3231	compressed into a single callback invocation (another way to look at this	3431	compressed into a single callback invocation (another way to look at
3232	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
3233	reset when the event loop detects that).	3433	C<ev_async_send>, reset when the event loop detects that).
3234		3434
3235	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
3236	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
3237	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.
3238		3441
3239	=item bool = ev_async_pending (ev_async *)	3442	=item bool = ev_async_pending (ev_async *)
3240		3443
3241	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
3242	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
…		…
3297	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3500	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3298		3501
3299	=item ev_feed_fd_event (loop, int fd, int revents)	3502	=item ev_feed_fd_event (loop, int fd, int revents)
3300		3503
3301	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
3302	the given events it.	3505	the given events.
3303		3506
3304	=item ev_feed_signal_event (loop, int signum)	3507	=item ev_feed_signal_event (loop, int signum)
3305		3508
3306	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>,
3307	loop!).	3510	which is async-safe.
3308		3511
3309	=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.
3310		3863
3311		3864
3312	=head1 LIBEVENT EMULATION	3865	=head1 LIBEVENT EMULATION
3313		3866
3314	Libev offers a compatibility emulation layer for libevent. It cannot	3867	Libev offers a compatibility emulation layer for libevent. It cannot
3315	emulate the internals of libevent, so here are some usage hints:	3868	emulate the internals of libevent, so here are some usage hints:
3316		3869
3317	=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.
3318		3876
3319	=item * Use it by including <event.h>, as usual.	3877	=item * Use it by including <event.h>, as usual.
3320		3878
3321	=item * The following members are fully supported: ev_base, ev_callback,	3879	=item * The following members are fully supported: ev_base, ev_callback,
3322	ev_arg, ev_fd, ev_res, ev_events.	3880	ev_arg, ev_fd, ev_res, ev_events.
…		…
3328	=item * Priorities are not currently supported. Initialising priorities	3886	=item * Priorities are not currently supported. Initialising priorities
3329	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
3330	is an ev_pri field.	3888	is an ev_pri field.
3331		3889
3332	=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
3333	first base created (== the default loop) gets the signals.	3891	base that registered the signal gets the signals.
3334		3892
3335	=item * Other members are not supported.	3893	=item * Other members are not supported.
3336		3894
3337	=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
3338	to use the libev header file and library.	3896	to use the libev header file and library.
…		…
3357	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++
3358	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
3359	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
3360	you disable C<EV_MULTIPLICITY> when embedding libev).	3918	you disable C<EV_MULTIPLICITY> when embedding libev).
3361		3919
3362	Currently, functions, and static and non-static member functions can be	3920	Currently, functions, static and non-static member functions and classes
3363	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
3364	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
3365	types of functors please contact the author (preferably after implementing	3923	you need support for other types of functors please contact the author
3366	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++.
3367		3929
3368	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:
3369		3931
3370	=over 4	3932	=over 4
3371		3933
…		…
3381	=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.
3382		3944
3383	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
3384	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>
3385	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
3386	defines by many implementations.	3948	defined by many implementations.
3387		3949
3388	All of those classes have these methods:	3950	All of those classes have these methods:
3389		3951
3390	=over 4	3952	=over 4
3391		3953
…		…
3524	watchers in the constructor.	4086	watchers in the constructor.
3525		4087
3526	class myclass	4088	class myclass
3527	{	4089	{
3528	ev::io io ; void io_cb (ev::io &w, int revents);	4090	ev::io io ; void io_cb (ev::io &w, int revents);
3529	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);	4091	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3530	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4092	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3531		4093
3532	myclass (int fd)	4094	myclass (int fd)
3533	{	4095	{
3534	io .set <myclass, &myclass::io_cb > (this);	4096	io .set <myclass, &myclass::io_cb > (this);
…		…
3585	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4147	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3586		4148
3587	=item D	4149	=item D
3588		4150
3589	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
3590	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>.
3591		4153
3592	=item Ocaml	4154	=item Ocaml
3593		4155
3594	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
3595	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4157	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
…		…
3643	suitable for use with C<EV_A>.	4205	suitable for use with C<EV_A>.
3644		4206
3645	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4207	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3646		4208
3647	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
3648	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.
3649		4215
3650	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4216	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3651		4217
3652	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
3653	default loop has been initialised (C<UC> == unchecked). Their behaviour	4219	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3798	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
3799	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.
3800		4366
3801	In standalone mode, libev will still try to automatically deduce the	4367	In standalone mode, libev will still try to automatically deduce the
3802	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.
3803		4378
3804	=item EV_USE_MONOTONIC	4379	=item EV_USE_MONOTONIC
3805		4380
3806	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
3807	monotonic clock option at both compile time and runtime. Otherwise no	4382	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3937	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
3938	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
3939	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
3940	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4515	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3941		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
3942	=item EV_ATOMIC_T	4530	=item EV_ATOMIC_T
3943		4531
3944	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
3945	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
3946	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
3947	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
3948	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.
3949		4538
3950	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>
3951	(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.
3952		4543
3953	=item EV_H (h)	4544	=item EV_H (h)
3954		4545
3955	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
3956	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
…		…
3980	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
3981	additional independent event loops. Otherwise there will be no support	4572	additional independent event loops. Otherwise there will be no support
3982	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
3983	argument. Instead, all functions act on the single default loop.	4574	argument. Instead, all functions act on the single default loop.
3984		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
3985	=item EV_MINPRI	4580	=item EV_MINPRI
3986		4581
3987	=item EV_MAXPRI	4582	=item EV_MAXPRI
3988		4583
3989	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
…		…
4086		4681
4087	With an intelligent-enough linker (gcc+binutils are intelligent enough	4682	With an intelligent-enough linker (gcc+binutils are intelligent enough
4088	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
4089	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
4090	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.
4091		4700
4092	=item EV_AVOID_STDIO	4701	=item EV_AVOID_STDIO
4093		4702
4094	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
4095	functions (printf, scanf, perror etc.). This will increase the code size	4704	functions (printf, scanf, perror etc.). This will increase the code size
…		…
4239	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:
4240		4849
4241	#include "ev_cpp.h"	4850	#include "ev_cpp.h"
4242	#include "ev.c"	4851	#include "ev.c"
4243		4852
4244	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4853	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4245		4854
4246	=head2 THREADS AND COROUTINES	4855	=head2 THREADS AND COROUTINES
4247		4856
4248	=head3 THREADS	4857	=head3 THREADS
4249		4858
…		…
4300	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
4301	watcher callback into the event loop interested in the signal.	4910	watcher callback into the event loop interested in the signal.
4302		4911
4303	=back	4912	=back
4304		4913
4305	=head4 THREAD LOCKING EXAMPLE	4914	See also L<THREAD LOCKING EXAMPLE>.
4306
4307	Here is a fictitious example of how to run an event loop in a different
4308	thread than where callbacks are being invoked and watchers are
4309	created/added/removed.
4310
4311	For a real-world example, see the C<EV::Loop::Async> perl module,
4312	which uses exactly this technique (which is suited for many high-level
4313	languages).
4314
4315	The example uses a pthread mutex to protect the loop data, a condition
4316	variable to wait for callback invocations, an async watcher to notify the
4317	event loop thread and an unspecified mechanism to wake up the main thread.
4318
4319	First, you need to associate some data with the event loop:
4320
4321	typedef struct {
4322	mutex_t lock; /* global loop lock */
4323	ev_async async_w;
4324	thread_t tid;
4325	cond_t invoke_cv;
4326	} userdata;
4327
4328	void prepare_loop (EV_P)
4329	{
4330	// for simplicity, we use a static userdata struct.
4331	static userdata u;
4332
4333	ev_async_init (&u->async_w, async_cb);
4334	ev_async_start (EV_A_ &u->async_w);
4335
4336	pthread_mutex_init (&u->lock, 0);
4337	pthread_cond_init (&u->invoke_cv, 0);
4338
4339	// now associate this with the loop
4340	ev_set_userdata (EV_A_ u);
4341	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4342	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4343
4344	// then create the thread running ev_loop
4345	pthread_create (&u->tid, 0, l_run, EV_A);
4346	}
4347
4348	The callback for the C<ev_async> watcher does nothing: the watcher is used
4349	solely to wake up the event loop so it takes notice of any new watchers
4350	that might have been added:
4351
4352	static void
4353	async_cb (EV_P_ ev_async *w, int revents)
4354	{
4355	// just used for the side effects
4356	}
4357
4358	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4359	protecting the loop data, respectively.
4360
4361	static void
4362	l_release (EV_P)
4363	{
4364	userdata *u = ev_userdata (EV_A);
4365	pthread_mutex_unlock (&u->lock);
4366	}
4367
4368	static void
4369	l_acquire (EV_P)
4370	{
4371	userdata *u = ev_userdata (EV_A);
4372	pthread_mutex_lock (&u->lock);
4373	}
4374
4375	The event loop thread first acquires the mutex, and then jumps straight
4376	into C<ev_run>:
4377
4378	void *
4379	l_run (void *thr_arg)
4380	{
4381	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4382
4383	l_acquire (EV_A);
4384	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4385	ev_run (EV_A_ 0);
4386	l_release (EV_A);
4387
4388	return 0;
4389	}
4390
4391	Instead of invoking all pending watchers, the C<l_invoke> callback will
4392	signal the main thread via some unspecified mechanism (signals? pipe
4393	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4394	have been called (in a while loop because a) spurious wakeups are possible
4395	and b) skipping inter-thread-communication when there are no pending
4396	watchers is very beneficial):
4397
4398	static void
4399	l_invoke (EV_P)
4400	{
4401	userdata *u = ev_userdata (EV_A);
4402
4403	while (ev_pending_count (EV_A))
4404	{
4405	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4406	pthread_cond_wait (&u->invoke_cv, &u->lock);
4407	}
4408	}
4409
4410	Now, whenever the main thread gets told to invoke pending watchers, it
4411	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4412	thread to continue:
4413
4414	static void
4415	real_invoke_pending (EV_P)
4416	{
4417	userdata *u = ev_userdata (EV_A);
4418
4419	pthread_mutex_lock (&u->lock);
4420	ev_invoke_pending (EV_A);
4421	pthread_cond_signal (&u->invoke_cv);
4422	pthread_mutex_unlock (&u->lock);
4423	}
4424
4425	Whenever you want to start/stop a watcher or do other modifications to an
4426	event loop, you will now have to lock:
4427
4428	ev_timer timeout_watcher;
4429	userdata *u = ev_userdata (EV_A);
4430
4431	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4432
4433	pthread_mutex_lock (&u->lock);
4434	ev_timer_start (EV_A_ &timeout_watcher);
4435	ev_async_send (EV_A_ &u->async_w);
4436	pthread_mutex_unlock (&u->lock);
4437
4438	Note that sending the C<ev_async> watcher is required because otherwise
4439	an event loop currently blocking in the kernel will have no knowledge
4440	about the newly added timer. By waking up the loop it will pick up any new
4441	watchers in the next event loop iteration.
4442		4915
4443	=head3 COROUTINES	4916	=head3 COROUTINES
4444		4917
4445	Libev is very accommodating to coroutines ("cooperative threads"):	4918	Libev is very accommodating to coroutines ("cooperative threads"):
4446	libev fully supports nesting calls to its functions from different	4919	libev fully supports nesting calls to its functions from different
…		…
4611	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
4612	model. Libev still offers limited functionality on this platform in	5085	model. Libev still offers limited functionality on this platform in
4613	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
4614	descriptors. This only applies when using Win32 natively, not when using	5087	descriptors. This only applies when using Win32 natively, not when using
4615	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,
4616	as every compielr comes with a slightly differently broken/incompatible	5089	as every compiler comes with a slightly differently broken/incompatible
4617	environment.	5090	environment.
4618		5091
4619	Lifting these limitations would basically require the full	5092	Lifting these limitations would basically require the full
4620	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,
4621	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
…		…
4715	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
4716	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
4717	callback: The watcher callbacks have different type signatures, but libev	5190	callback: The watcher callbacks have different type signatures, but libev
4718	calls them using an C<ev_watcher *> internally.	5191	calls them using an C<ev_watcher *> internally.
4719		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
4720	=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
4721		5199
4722	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
4723	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
4724	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
…		…
4749		5227
4750	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
4751	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
4752	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
4753	(the design goal for libev). This requirement is overfulfilled by	5231	(the design goal for libev). This requirement is overfulfilled by
4754	implementations using IEEE 754, which is basically all existing ones. With	5232	implementations using IEEE 754, which is basically all existing ones.
		5233
4755	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).
4756		5238
4757	=back	5239	=back
4758		5240
4759	If you know of other additional requirements drop me a note.	5241	If you know of other additional requirements drop me a note.
4760		5242
…		…
4822	=item Processing ev_async_send: O(number_of_async_watchers)	5304	=item Processing ev_async_send: O(number_of_async_watchers)
4823		5305
4824	=item Processing signals: O(max_signal_number)	5306	=item Processing signals: O(max_signal_number)
4825		5307
4826	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>
4827	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
4828	involves iterating over all running async watchers or all signal numbers.	5311	running async watchers or all signal numbers.
4829		5312
4830	=back	5313	=back
4831		5314
4832		5315
4833	=head1 PORTING FROM LIBEV 3.X TO 4.X	5316	=head1 PORTING FROM LIBEV 3.X TO 4.X
4834		5317
4835	The major version 4 introduced some minor incompatible changes to the API.	5318	The major version 4 introduced some incompatible changes to the API.
4836		5319
4837	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
4838	compatibility, so most programs should still compile. Those might be	5321	for all changes, so most programs should still compile. The compatibility
4839	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.
4840		5324
4841	=over 4	5325	=over 4
4842		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
4843	=item C<ev_default_destroy> and C<ev_default_fork> have been removed	5333	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
4844		5334
4845	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:	5335	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
4846		5336
4847	ev_loop_destroy (EV_DEFAULT);	5337	ev_loop_destroy (EV_DEFAULT_UC);
4848	ev_loop_fork (EV_DEFAULT);	5338	ev_loop_fork (EV_DEFAULT);
4849		5339
4850	=item function/symbol renames	5340	=item function/symbol renames
4851		5341
4852	A number of functions and symbols have been renamed:	5342	A number of functions and symbols have been renamed:
…		…
4872	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
4873	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
4874	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>
4875	typedef.	5365	typedef.
4876		5366
4877	=item C<EV_COMPAT3> backwards compatibility mechanism
4878
4879	The backward compatibility mechanism can be controlled by
4880	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
4881	section.
4882
4883	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>	5367	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
4884		5368
4885	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
4886	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile	5370	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
4887	and work, but the library code will of course be larger.	5371	and work, but the library code will of course be larger.
…		…
4949	The physical time that is observed. It is apparently strictly monotonic :)	5433	The physical time that is observed. It is apparently strictly monotonic :)
4950		5434
4951	=item wall-clock time	5435	=item wall-clock time
4952		5436
4953	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
4954	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
4955	clock.	5439	clock.
4956		5440
4957	=item watcher	5441	=item watcher
4958		5442
4959	A data structure that describes interest in certain events. Watchers need	5443	A data structure that describes interest in certain events. Watchers need
…		…
4961		5445
4962	=back	5446	=back
4963		5447
4964	=head1 AUTHOR	5448	=head1 AUTHOR
4965		5449
4966	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.
4967		5452

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