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		1	=encoding utf-8
		2
1	=head1 NAME	3	=head1 NAME
2		4
3	libev - a high performance full-featured event loop written in C	5	libev - a high performance full-featured event loop written in C
4		6
5	=head1 SYNOPSIS	7	=head1 SYNOPSIS
…		…
58	ev_timer_start (loop, &timeout_watcher);	60	ev_timer_start (loop, &timeout_watcher);
59		61
60	// now wait for events to arrive	62	// now wait for events to arrive
61	ev_run (loop, 0);	63	ev_run (loop, 0);
62		64
63	// unloop was called, so exit	65	// break was called, so exit
64	return 0;	66	return 0;
65	}	67	}
66		68
67	=head1 ABOUT THIS DOCUMENT	69	=head1 ABOUT THIS DOCUMENT
68		70
…		…
82		84
83	=head1 WHAT TO READ WHEN IN A HURRY	85	=head1 WHAT TO READ WHEN IN A HURRY
84		86
85	This manual tries to be very detailed, but unfortunately, this also makes	87	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	88	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	89	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	90	look up the missing functions in L</GLOBAL FUNCTIONS> and the C<ev_io> and
89	C<ev_timer> sections in L<WATCHER TYPES>.	91	C<ev_timer> sections in L</WATCHER TYPES>.
90		92
91	=head1 ABOUT LIBEV	93	=head1 ABOUT LIBEV
92		94
93	Libev is an event loop: you register interest in certain events (such as a	95	Libev is an event loop: you register interest in certain events (such as a
94	file descriptor being readable or a timeout occurring), and it will manage	96	file descriptor being readable or a timeout occurring), and it will manage
…		…
174	=item ev_tstamp ev_time ()	176	=item ev_tstamp ev_time ()
175		177
176	Returns the current time as libev would use it. Please note that the	178	Returns the current time as libev would use it. Please note that the
177	C<ev_now> function is usually faster and also often returns the timestamp	179	C<ev_now> function is usually faster and also often returns the timestamp
178	you actually want to know. Also interesting is the combination of	180	you actually want to know. Also interesting is the combination of
179	C<ev_update_now> and C<ev_now>.	181	C<ev_now_update> and C<ev_now>.
180		182
181	=item ev_sleep (ev_tstamp interval)	183	=item ev_sleep (ev_tstamp interval)
182		184
183	Sleep for the given interval: The current thread will be blocked until	185	Sleep for the given interval: The current thread will be blocked
184	either it is interrupted or the given time interval has passed. Basically	186	until either it is interrupted or the given time interval has
		187	passed (approximately - it might return a bit earlier even if not
		188	interrupted). Returns immediately if C<< interval <= 0 >>.
		189
185	this is a sub-second-resolution C<sleep ()>.	190	Basically this is a sub-second-resolution C<sleep ()>.
		191
		192	The range of the C<interval> is limited - libev only guarantees to work
		193	with sleep times of up to one day (C<< interval <= 86400 >>).
186		194
187	=item int ev_version_major ()	195	=item int ev_version_major ()
188		196
189	=item int ev_version_minor ()	197	=item int ev_version_minor ()
190		198
…		…
241	the current system, you would need to look at C<ev_embeddable_backends ()	249	the current system, you would need to look at C<ev_embeddable_backends ()
242	& ev_supported_backends ()>, likewise for recommended ones.	250	& ev_supported_backends ()>, likewise for recommended ones.
243		251
244	See the description of C<ev_embed> watchers for more info.	252	See the description of C<ev_embed> watchers for more info.
245		253
246	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	254	=item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())
247		255
248	Sets the allocation function to use (the prototype is similar - the	256	Sets the allocation function to use (the prototype is similar - the
249	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	257	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
250	used to allocate and free memory (no surprises here). If it returns zero	258	used to allocate and free memory (no surprises here). If it returns zero
251	when memory needs to be allocated (C<size != 0>), the library might abort	259	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
277	}	285	}
278		286
279	...	287	...
280	ev_set_allocator (persistent_realloc);	288	ev_set_allocator (persistent_realloc);
281		289
282	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	290	=item ev_set_syserr_cb (void (*cb)(const char *msg) throw ())
283		291
284	Set the callback function to call on a retryable system call error (such	292	Set the callback function to call on a retryable system call error (such
285	as failed select, poll, epoll_wait). The message is a printable string	293	as failed select, poll, epoll_wait). The message is a printable string
286	indicating the system call or subsystem causing the problem. If this	294	indicating the system call or subsystem causing the problem. If this
287	callback is set, then libev will expect it to remedy the situation, no	295	callback is set, then libev will expect it to remedy the situation, no
…		…
299	}	307	}
300		308
301	...	309	...
302	ev_set_syserr_cb (fatal_error);	310	ev_set_syserr_cb (fatal_error);
303		311
		312	=item ev_feed_signal (int signum)
		313
		314	This function can be used to "simulate" a signal receive. It is completely
		315	safe to call this function at any time, from any context, including signal
		316	handlers or random threads.
		317
		318	Its main use is to customise signal handling in your process, especially
		319	in the presence of threads. For example, you could block signals
		320	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		321	creating any loops), and in one thread, use C<sigwait> or any other
		322	mechanism to wait for signals, then "deliver" them to libev by calling
		323	C<ev_feed_signal>.
		324
304	=back	325	=back
305		326
306	=head1 FUNCTIONS CONTROLLING EVENT LOOPS	327	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
307		328
308	An event loop is described by a C<struct ev_loop *> (the C<struct> is	329	An event loop is described by a C<struct ev_loop *> (the C<struct> is
…		…
355	=item struct ev_loop *ev_loop_new (unsigned int flags)	376	=item struct ev_loop *ev_loop_new (unsigned int flags)
356		377
357	This will create and initialise a new event loop object. If the loop	378	This will create and initialise a new event loop object. If the loop
358	could not be initialised, returns false.	379	could not be initialised, returns false.
359		380
360	Note that this function I<is> thread-safe, and one common way to use	381	This function is thread-safe, and one common way to use libev with
361	libev with threads is indeed to create one loop per thread, and using the	382	threads is indeed to create one loop per thread, and using the default
362	default loop in the "main" or "initial" thread.	383	loop in the "main" or "initial" thread.
363		384
364	The flags argument can be used to specify special behaviour or specific	385	The flags argument can be used to specify special behaviour or specific
365	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	386	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
366		387
367	The following flags are supported:	388	The following flags are supported:
…		…
377		398
378	If this flag bit is or'ed into the flag value (or the program runs setuid	399	If this flag bit is or'ed into the flag value (or the program runs setuid
379	or setgid) then libev will I<not> look at the environment variable	400	or setgid) then libev will I<not> look at the environment variable
380	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	401	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
381	override the flags completely if it is found in the environment. This is	402	override the flags completely if it is found in the environment. This is
382	useful to try out specific backends to test their performance, or to work	403	useful to try out specific backends to test their performance, to work
383	around bugs.	404	around bugs, or to make libev threadsafe (accessing environment variables
		405	cannot be done in a threadsafe way, but usually it works if no other
		406	thread modifies them).
384		407
385	=item C<EVFLAG_FORKCHECK>	408	=item C<EVFLAG_FORKCHECK>
386		409
387	Instead of calling C<ev_loop_fork> manually after a fork, you can also	410	Instead of calling C<ev_loop_fork> manually after a fork, you can also
388	make libev check for a fork in each iteration by enabling this flag.	411	make libev check for a fork in each iteration by enabling this flag.
…		…
402	environment variable.	425	environment variable.
403		426
404	=item C<EVFLAG_NOINOTIFY>	427	=item C<EVFLAG_NOINOTIFY>
405		428
406	When this flag is specified, then libev will not attempt to use the	429	When this flag is specified, then libev will not attempt to use the
407	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and	430	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
408	testing, this flag can be useful to conserve inotify file descriptors, as	431	testing, this flag can be useful to conserve inotify file descriptors, as
409	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.	432	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
410		433
411	=item C<EVFLAG_SIGNALFD>	434	=item C<EVFLAG_SIGNALFD>
412		435
413	When this flag is specified, then libev will attempt to use the	436	When this flag is specified, then libev will attempt to use the
414	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API	437	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
415	delivers signals synchronously, which makes it both faster and might make	438	delivers signals synchronously, which makes it both faster and might make
416	it possible to get the queued signal data. It can also simplify signal	439	it possible to get the queued signal data. It can also simplify signal
417	handling with threads, as long as you properly block signals in your	440	handling with threads, as long as you properly block signals in your
418	threads that are not interested in handling them.	441	threads that are not interested in handling them.
419		442
420	Signalfd will not be used by default as this changes your signal mask, and	443	Signalfd will not be used by default as this changes your signal mask, and
421	there are a lot of shoddy libraries and programs (glib's threadpool for	444	there are a lot of shoddy libraries and programs (glib's threadpool for
422	example) that can't properly initialise their signal masks.	445	example) that can't properly initialise their signal masks.
		446
		447	=item C<EVFLAG_NOSIGMASK>
		448
		449	When this flag is specified, then libev will avoid to modify the signal
		450	mask. Specifically, this means you have to make sure signals are unblocked
		451	when you want to receive them.
		452
		453	This behaviour is useful when you want to do your own signal handling, or
		454	want to handle signals only in specific threads and want to avoid libev
		455	unblocking the signals.
		456
		457	It's also required by POSIX in a threaded program, as libev calls
		458	C<sigprocmask>, whose behaviour is officially unspecified.
		459
		460	This flag's behaviour will become the default in future versions of libev.
423		461
424	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	462	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
425		463
426	This is your standard select(2) backend. Not I<completely> standard, as	464	This is your standard select(2) backend. Not I<completely> standard, as
427	libev tries to roll its own fd_set with no limits on the number of fds,	465	libev tries to roll its own fd_set with no limits on the number of fds,
…		…
455	=item C<EVBACKEND_EPOLL> (value 4, Linux)	493	=item C<EVBACKEND_EPOLL> (value 4, Linux)
456		494
457	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9	495	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
458	kernels).	496	kernels).
459		497
460	For few fds, this backend is a bit little slower than poll and select,	498	For few fds, this backend is a bit little slower than poll and select, but
461	but it scales phenomenally better. While poll and select usually scale	499	it scales phenomenally better. While poll and select usually scale like
462	like O(total_fds) where n is the total number of fds (or the highest fd),	500	O(total_fds) where total_fds is the total number of fds (or the highest
463	epoll scales either O(1) or O(active_fds).	501	fd), epoll scales either O(1) or O(active_fds).
464		502
465	The epoll mechanism deserves honorable mention as the most misdesigned	503	The epoll mechanism deserves honorable mention as the most misdesigned
466	of the more advanced event mechanisms: mere annoyances include silently	504	of the more advanced event mechanisms: mere annoyances include silently
467	dropping file descriptors, requiring a system call per change per file	505	dropping file descriptors, requiring a system call per change per file
468	descriptor (and unnecessary guessing of parameters), problems with dup,	506	descriptor (and unnecessary guessing of parameters), problems with dup,
469	returning before the timeout value requiring additional iterations and so	507	returning before the timeout value, resulting in additional iterations
		508	(and only giving 5ms accuracy while select on the same platform gives
470	on. The biggest issue is fork races, however - if a program forks then	509	0.1ms) and so on. The biggest issue is fork races, however - if a program
471	I<both> parent and child process have to recreate the epoll set, which can	510	forks then I<both> parent and child process have to recreate the epoll
472	take considerable time (one syscall per file descriptor) and is of course	511	set, which can take considerable time (one syscall per file descriptor)
473	hard to detect.	512	and is of course hard to detect.
474		513
475	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	514	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
476	of course I<doesn't>, and epoll just loves to report events for totally	515	but of course I<doesn't>, and epoll just loves to report events for
477	I<different> file descriptors (even already closed ones, so one cannot	516	totally I<different> file descriptors (even already closed ones, so
478	even remove them from the set) than registered in the set (especially	517	one cannot even remove them from the set) than registered in the set
479	on SMP systems). Libev tries to counter these spurious notifications by	518	(especially on SMP systems). Libev tries to counter these spurious
480	employing an additional generation counter and comparing that against the	519	notifications by employing an additional generation counter and comparing
481	events to filter out spurious ones, recreating the set when required. Last	520	that against the events to filter out spurious ones, recreating the set
		521	when required. Epoll also erroneously rounds down timeouts, but gives you
		522	no way to know when and by how much, so sometimes you have to busy-wait
		523	because epoll returns immediately despite a nonzero timeout. And last
482	not least, it also refuses to work with some file descriptors which work	524	not least, it also refuses to work with some file descriptors which work
483	perfectly fine with C<select> (files, many character devices...).	525	perfectly fine with C<select> (files, many character devices...).
		526
		527	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
		528	cobbled together in a hurry, no thought to design or interaction with
		529	others. Oh, the pain, will it ever stop...
484		530
485	While stopping, setting and starting an I/O watcher in the same iteration	531	While stopping, setting and starting an I/O watcher in the same iteration
486	will result in some caching, there is still a system call per such	532	will result in some caching, there is still a system call per such
487	incident (because the same I<file descriptor> could point to a different	533	incident (because the same I<file descriptor> could point to a different
488	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	534	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
525		571
526	It scales in the same way as the epoll backend, but the interface to the	572	It scales in the same way as the epoll backend, but the interface to the
527	kernel is more efficient (which says nothing about its actual speed, of	573	kernel is more efficient (which says nothing about its actual speed, of
528	course). While stopping, setting and starting an I/O watcher does never	574	course). While stopping, setting and starting an I/O watcher does never
529	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	575	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
530	two event changes per incident. Support for C<fork ()> is very bad (but	576	two event changes per incident. Support for C<fork ()> is very bad (you
531	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect	577	might have to leak fd's on fork, but it's more sane than epoll) and it
532	cases	578	drops fds silently in similarly hard-to-detect cases.
533		579
534	This backend usually performs well under most conditions.	580	This backend usually performs well under most conditions.
535		581
536	While nominally embeddable in other event loops, this doesn't work	582	While nominally embeddable in other event loops, this doesn't work
537	everywhere, so you might need to test for this. And since it is broken	583	everywhere, so you might need to test for this. And since it is broken
…		…
554	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	600	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
555		601
556	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	602	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
557	it's really slow, but it still scales very well (O(active_fds)).	603	it's really slow, but it still scales very well (O(active_fds)).
558		604
559	Please note that Solaris event ports can deliver a lot of spurious
560	notifications, so you need to use non-blocking I/O or other means to avoid
561	blocking when no data (or space) is available.
562
563	While this backend scales well, it requires one system call per active	605	While this backend scales well, it requires one system call per active
564	file descriptor per loop iteration. For small and medium numbers of file	606	file descriptor per loop iteration. For small and medium numbers of file
565	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	607	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
566	might perform better.	608	might perform better.
567		609
568	On the positive side, with the exception of the spurious readiness	610	On the positive side, this backend actually performed fully to
569	notifications, this backend actually performed fully to specification
570	in all tests and is fully embeddable, which is a rare feat among the	611	specification in all tests and is fully embeddable, which is a rare feat
571	OS-specific backends (I vastly prefer correctness over speed hacks).	612	among the OS-specific backends (I vastly prefer correctness over speed
		613	hacks).
		614
		615	On the negative side, the interface is I<bizarre> - so bizarre that
		616	even sun itself gets it wrong in their code examples: The event polling
		617	function sometimes returns events to the caller even though an error
		618	occurred, but with no indication whether it has done so or not (yes, it's
		619	even documented that way) - deadly for edge-triggered interfaces where you
		620	absolutely have to know whether an event occurred or not because you have
		621	to re-arm the watcher.
		622
		623	Fortunately libev seems to be able to work around these idiocies.
572		624
573	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	625	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
574	C<EVBACKEND_POLL>.	626	C<EVBACKEND_POLL>.
575		627
576	=item C<EVBACKEND_ALL>	628	=item C<EVBACKEND_ALL>
577		629
578	Try all backends (even potentially broken ones that wouldn't be tried	630	Try all backends (even potentially broken ones that wouldn't be tried
579	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	631	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
580	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	632	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
581		633
582	It is definitely not recommended to use this flag.	634	It is definitely not recommended to use this flag, use whatever
		635	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		636	at all.
		637
		638	=item C<EVBACKEND_MASK>
		639
		640	Not a backend at all, but a mask to select all backend bits from a
		641	C<flags> value, in case you want to mask out any backends from a flags
		642	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
583		643
584	=back	644	=back
585		645
586	If one or more of the backend flags are or'ed into the flags value,	646	If one or more of the backend flags are or'ed into the flags value,
587	then only these backends will be tried (in the reverse order as listed	647	then only these backends will be tried (in the reverse order as listed
…		…
616	This function is normally used on loop objects allocated by	676	This function is normally used on loop objects allocated by
617	C<ev_loop_new>, but it can also be used on the default loop returned by	677	C<ev_loop_new>, but it can also be used on the default loop returned by
618	C<ev_default_loop>, in which case it is not thread-safe.	678	C<ev_default_loop>, in which case it is not thread-safe.
619		679
620	Note that it is not advisable to call this function on the default loop	680	Note that it is not advisable to call this function on the default loop
621	except in the rare occasion where you really need to free it's resources.	681	except in the rare occasion where you really need to free its resources.
622	If you need dynamically allocated loops it is better to use C<ev_loop_new>	682	If you need dynamically allocated loops it is better to use C<ev_loop_new>
623	and C<ev_loop_destroy>.	683	and C<ev_loop_destroy>.
624		684
625	=item ev_loop_fork (loop)	685	=item ev_loop_fork (loop)
626		686
…		…
628	reinitialise the kernel state for backends that have one. Despite the	688	reinitialise the kernel state for backends that have one. Despite the
629	name, you can call it anytime, but it makes most sense after forking, in	689	name, you can call it anytime, but it makes most sense after forking, in
630	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the	690	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
631	child before resuming or calling C<ev_run>.	691	child before resuming or calling C<ev_run>.
632		692
633	Again, you I<have> to call it on I<any> loop that you want to re-use after	693	Again, you I<have> to call it on I<any> loop that you want to re-use after
634	a fork, I<even if you do not plan to use the loop in the parent>. This is	694	a fork, I<even if you do not plan to use the loop in the parent>. This is
635	because some kernel interfaces *cough* I<kqueue> *cough* do funny things	695	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
636	during fork.	696	during fork.
637		697
638	On the other hand, you only need to call this function in the child	698	On the other hand, you only need to call this function in the child
…		…
674	prepare and check phases.	734	prepare and check phases.
675		735
676	=item unsigned int ev_depth (loop)	736	=item unsigned int ev_depth (loop)
677		737
678	Returns the number of times C<ev_run> was entered minus the number of	738	Returns the number of times C<ev_run> was entered minus the number of
679	times C<ev_run> was exited, in other words, the recursion depth.	739	times C<ev_run> was exited normally, in other words, the recursion depth.
680		740
681	Outside C<ev_run>, this number is zero. In a callback, this number is	741	Outside C<ev_run>, this number is zero. In a callback, this number is
682	C<1>, unless C<ev_run> was invoked recursively (or from another thread),	742	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
683	in which case it is higher.	743	in which case it is higher.
684		744
685	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread	745	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
686	etc.), doesn't count as "exit" - consider this as a hint to avoid such	746	throwing an exception etc.), doesn't count as "exit" - consider this
687	ungentleman-like behaviour unless it's really convenient.	747	as a hint to avoid such ungentleman-like behaviour unless it's really
		748	convenient, in which case it is fully supported.
688		749
689	=item unsigned int ev_backend (loop)	750	=item unsigned int ev_backend (loop)
690		751
691	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	752	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
692	use.	753	use.
…		…
707		768
708	This function is rarely useful, but when some event callback runs for a	769	This function is rarely useful, but when some event callback runs for a
709	very long time without entering the event loop, updating libev's idea of	770	very long time without entering the event loop, updating libev's idea of
710	the current time is a good idea.	771	the current time is a good idea.
711		772
712	See also L<The special problem of time updates> in the C<ev_timer> section.	773	See also L</The special problem of time updates> in the C<ev_timer> section.
713		774
714	=item ev_suspend (loop)	775	=item ev_suspend (loop)
715		776
716	=item ev_resume (loop)	777	=item ev_resume (loop)
717		778
…		…
735	without a previous call to C<ev_suspend>.	796	without a previous call to C<ev_suspend>.
736		797
737	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	798	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
738	event loop time (see C<ev_now_update>).	799	event loop time (see C<ev_now_update>).
739		800
740	=item ev_run (loop, int flags)	801	=item bool ev_run (loop, int flags)
741		802
742	Finally, this is it, the event handler. This function usually is called	803	Finally, this is it, the event handler. This function usually is called
743	after you have initialised all your watchers and you want to start	804	after you have initialised all your watchers and you want to start
744	handling events. It will ask the operating system for any new events, call	805	handling events. It will ask the operating system for any new events, call
745	the watcher callbacks, an then repeat the whole process indefinitely: This	806	the watcher callbacks, and then repeat the whole process indefinitely: This
746	is why event loops are called I<loops>.	807	is why event loops are called I<loops>.
747		808
748	If the flags argument is specified as C<0>, it will keep handling events	809	If the flags argument is specified as C<0>, it will keep handling events
749	until either no event watchers are active anymore or C<ev_break> was	810	until either no event watchers are active anymore or C<ev_break> was
750	called.	811	called.
		812
		813	The return value is false if there are no more active watchers (which
		814	usually means "all jobs done" or "deadlock"), and true in all other cases
		815	(which usually means " you should call C<ev_run> again").
751		816
752	Please note that an explicit C<ev_break> is usually better than	817	Please note that an explicit C<ev_break> is usually better than
753	relying on all watchers to be stopped when deciding when a program has	818	relying on all watchers to be stopped when deciding when a program has
754	finished (especially in interactive programs), but having a program	819	finished (especially in interactive programs), but having a program
755	that automatically loops as long as it has to and no longer by virtue	820	that automatically loops as long as it has to and no longer by virtue
756	of relying on its watchers stopping correctly, that is truly a thing of	821	of relying on its watchers stopping correctly, that is truly a thing of
757	beauty.	822	beauty.
758		823
		824	This function is I<mostly> exception-safe - you can break out of a
		825	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		826	exception and so on. This does not decrement the C<ev_depth> value, nor
		827	will it clear any outstanding C<EVBREAK_ONE> breaks.
		828
759	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle	829	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
760	those events and any already outstanding ones, but will not wait and	830	those events and any already outstanding ones, but will not wait and
761	block your process in case there are no events and will return after one	831	block your process in case there are no events and will return after one
762	iteration of the loop. This is sometimes useful to poll and handle new	832	iteration of the loop. This is sometimes useful to poll and handle new
763	events while doing lengthy calculations, to keep the program responsive.	833	events while doing lengthy calculations, to keep the program responsive.
…		…
772	This is useful if you are waiting for some external event in conjunction	842	This is useful if you are waiting for some external event in conjunction
773	with something not expressible using other libev watchers (i.e. "roll your	843	with something not expressible using other libev watchers (i.e. "roll your
774	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	844	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
775	usually a better approach for this kind of thing.	845	usually a better approach for this kind of thing.
776		846
777	Here are the gory details of what C<ev_run> does:	847	Here are the gory details of what C<ev_run> does (this is for your
		848	understanding, not a guarantee that things will work exactly like this in
		849	future versions):
778		850
779	- Increment loop depth.	851	- Increment loop depth.
780	- Reset the ev_break status.	852	- Reset the ev_break status.
781	- Before the first iteration, call any pending watchers.	853	- Before the first iteration, call any pending watchers.
782	LOOP:	854	LOOP:
…		…
815	anymore.	887	anymore.
816		888
817	... queue jobs here, make sure they register event watchers as long	889	... queue jobs here, make sure they register event watchers as long
818	... as they still have work to do (even an idle watcher will do..)	890	... as they still have work to do (even an idle watcher will do..)
819	ev_run (my_loop, 0);	891	ev_run (my_loop, 0);
820	... jobs done or somebody called unloop. yeah!	892	... jobs done or somebody called break. yeah!
821		893
822	=item ev_break (loop, how)	894	=item ev_break (loop, how)
823		895
824	Can be used to make a call to C<ev_run> return early (but only after it	896	Can be used to make a call to C<ev_run> return early (but only after it
825	has processed all outstanding events). The C<how> argument must be either	897	has processed all outstanding events). The C<how> argument must be either
826	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or	898	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
827	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.	899	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
828		900
829	This "break state" will be cleared when entering C<ev_run> again.	901	This "break state" will be cleared on the next call to C<ev_run>.
830		902
831	It is safe to call C<ev_break> from outside any C<ev_run> calls, too.	903	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		904	which case it will have no effect.
832		905
833	=item ev_ref (loop)	906	=item ev_ref (loop)
834		907
835	=item ev_unref (loop)	908	=item ev_unref (loop)
836		909
…		…
857	running when nothing else is active.	930	running when nothing else is active.
858		931
859	ev_signal exitsig;	932	ev_signal exitsig;
860	ev_signal_init (&exitsig, sig_cb, SIGINT);	933	ev_signal_init (&exitsig, sig_cb, SIGINT);
861	ev_signal_start (loop, &exitsig);	934	ev_signal_start (loop, &exitsig);
862	evf_unref (loop);	935	ev_unref (loop);
863		936
864	Example: For some weird reason, unregister the above signal handler again.	937	Example: For some weird reason, unregister the above signal handler again.
865		938
866	ev_ref (loop);	939	ev_ref (loop);
867	ev_signal_stop (loop, &exitsig);	940	ev_signal_stop (loop, &exitsig);
…		…
887	overhead for the actual polling but can deliver many events at once.	960	overhead for the actual polling but can deliver many events at once.
888		961
889	By setting a higher I<io collect interval> you allow libev to spend more	962	By setting a higher I<io collect interval> you allow libev to spend more
890	time collecting I/O events, so you can handle more events per iteration,	963	time collecting I/O events, so you can handle more events per iteration,
891	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	964	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
892	C<ev_timer>) will be not affected. Setting this to a non-null value will	965	C<ev_timer>) will not be affected. Setting this to a non-null value will
893	introduce an additional C<ev_sleep ()> call into most loop iterations. The	966	introduce an additional C<ev_sleep ()> call into most loop iterations. The
894	sleep time ensures that libev will not poll for I/O events more often then	967	sleep time ensures that libev will not poll for I/O events more often then
895	once per this interval, on average.	968	once per this interval, on average (as long as the host time resolution is
		969	good enough).
896		970
897	Likewise, by setting a higher I<timeout collect interval> you allow libev	971	Likewise, by setting a higher I<timeout collect interval> you allow libev
898	to spend more time collecting timeouts, at the expense of increased	972	to spend more time collecting timeouts, at the expense of increased
899	latency/jitter/inexactness (the watcher callback will be called	973	latency/jitter/inexactness (the watcher callback will be called
900	later). C<ev_io> watchers will not be affected. Setting this to a non-null	974	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
946	invoke the actual watchers inside another context (another thread etc.).	1020	invoke the actual watchers inside another context (another thread etc.).
947		1021
948	If you want to reset the callback, use C<ev_invoke_pending> as new	1022	If you want to reset the callback, use C<ev_invoke_pending> as new
949	callback.	1023	callback.
950		1024
951	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))	1025	=item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())
952		1026
953	Sometimes you want to share the same loop between multiple threads. This	1027	Sometimes you want to share the same loop between multiple threads. This
954	can be done relatively simply by putting mutex_lock/unlock calls around	1028	can be done relatively simply by putting mutex_lock/unlock calls around
955	each call to a libev function.	1029	each call to a libev function.
956		1030
957	However, C<ev_run> can run an indefinite time, so it is not feasible	1031	However, C<ev_run> can run an indefinite time, so it is not feasible
958	to wait for it to return. One way around this is to wake up the event	1032	to wait for it to return. One way around this is to wake up the event
959	loop via C<ev_break> and C<av_async_send>, another way is to set these	1033	loop via C<ev_break> and C<ev_async_send>, another way is to set these
960	I<release> and I<acquire> callbacks on the loop.	1034	I<release> and I<acquire> callbacks on the loop.
961		1035
962	When set, then C<release> will be called just before the thread is	1036	When set, then C<release> will be called just before the thread is
963	suspended waiting for new events, and C<acquire> is called just	1037	suspended waiting for new events, and C<acquire> is called just
964	afterwards.	1038	afterwards.
…		…
979	See also the locking example in the C<THREADS> section later in this	1053	See also the locking example in the C<THREADS> section later in this
980	document.	1054	document.
981		1055
982	=item ev_set_userdata (loop, void *data)	1056	=item ev_set_userdata (loop, void *data)
983		1057
984	=item ev_userdata (loop)	1058	=item void *ev_userdata (loop)
985		1059
986	Set and retrieve a single C<void *> associated with a loop. When	1060	Set and retrieve a single C<void *> associated with a loop. When
987	C<ev_set_userdata> has never been called, then C<ev_userdata> returns	1061	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
988	C<0.>	1062	C<0>.
989		1063
990	These two functions can be used to associate arbitrary data with a loop,	1064	These two functions can be used to associate arbitrary data with a loop,
991	and are intended solely for the C<invoke_pending_cb>, C<release> and	1065	and are intended solely for the C<invoke_pending_cb>, C<release> and
992	C<acquire> callbacks described above, but of course can be (ab-)used for	1066	C<acquire> callbacks described above, but of course can be (ab-)used for
993	any other purpose as well.	1067	any other purpose as well.
…		…
1104		1178
1105	=item C<EV_PREPARE>	1179	=item C<EV_PREPARE>
1106		1180
1107	=item C<EV_CHECK>	1181	=item C<EV_CHECK>
1108		1182
1109	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts	1183	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to
1110	to gather new events, and all C<ev_check> watchers are invoked just after	1184	gather new events, and all C<ev_check> watchers are queued (not invoked)
1111	C<ev_run> has gathered them, but before it invokes any callbacks for any	1185	just after C<ev_run> has gathered them, but before it queues any callbacks
		1186	for any received events. That means C<ev_prepare> watchers are the last
		1187	watchers invoked before the event loop sleeps or polls for new events, and
		1188	C<ev_check> watchers will be invoked before any other watchers of the same
		1189	or lower priority within an event loop iteration.
		1190
1112	received events. Callbacks of both watcher types can start and stop as	1191	Callbacks of both watcher types can start and stop as many watchers as
1113	many watchers as they want, and all of them will be taken into account	1192	they want, and all of them will be taken into account (for example, a
1114	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1193	C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from
1115	C<ev_run> from blocking).	1194	blocking).
1116		1195
1117	=item C<EV_EMBED>	1196	=item C<EV_EMBED>
1118		1197
1119	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1198	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1120		1199
…		…
1243		1322
1244	=item callback ev_cb (ev_TYPE *watcher)	1323	=item callback ev_cb (ev_TYPE *watcher)
1245		1324
1246	Returns the callback currently set on the watcher.	1325	Returns the callback currently set on the watcher.
1247		1326
1248	=item ev_cb_set (ev_TYPE *watcher, callback)	1327	=item ev_set_cb (ev_TYPE *watcher, callback)
1249		1328
1250	Change the callback. You can change the callback at virtually any time	1329	Change the callback. You can change the callback at virtually any time
1251	(modulo threads).	1330	(modulo threads).
1252		1331
1253	=item ev_set_priority (ev_TYPE *watcher, int priority)	1332	=item ev_set_priority (ev_TYPE *watcher, int priority)
…		…
1271	or might not have been clamped to the valid range.	1350	or might not have been clamped to the valid range.
1272		1351
1273	The default priority used by watchers when no priority has been set is	1352	The default priority used by watchers when no priority has been set is
1274	always C<0>, which is supposed to not be too high and not be too low :).	1353	always C<0>, which is supposed to not be too high and not be too low :).
1275		1354
1276	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of	1355	See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1277	priorities.	1356	priorities.
1278		1357
1279	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1358	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1280		1359
1281	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1360	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
…		…
1306	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related	1385	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1307	functions that do not need a watcher.	1386	functions that do not need a watcher.
1308		1387
1309	=back	1388	=back
1310		1389
1311	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1390	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
1312		1391	OWN COMPOSITE WATCHERS> idioms.
1313	Each watcher has, by default, a member C<void *data> that you can change
1314	and read at any time: libev will completely ignore it. This can be used
1315	to associate arbitrary data with your watcher. If you need more data and
1316	don't want to allocate memory and store a pointer to it in that data
1317	member, you can also "subclass" the watcher type and provide your own
1318	data:
1319
1320	struct my_io
1321	{
1322	ev_io io;
1323	int otherfd;
1324	void *somedata;
1325	struct whatever *mostinteresting;
1326	};
1327
1328	...
1329	struct my_io w;
1330	ev_io_init (&w.io, my_cb, fd, EV_READ);
1331
1332	And since your callback will be called with a pointer to the watcher, you
1333	can cast it back to your own type:
1334
1335	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1336	{
1337	struct my_io *w = (struct my_io *)w_;
1338	...
1339	}
1340
1341	More interesting and less C-conformant ways of casting your callback type
1342	instead have been omitted.
1343
1344	Another common scenario is to use some data structure with multiple
1345	embedded watchers:
1346
1347	struct my_biggy
1348	{
1349	int some_data;
1350	ev_timer t1;
1351	ev_timer t2;
1352	}
1353
1354	In this case getting the pointer to C<my_biggy> is a bit more
1355	complicated: Either you store the address of your C<my_biggy> struct
1356	in the C<data> member of the watcher (for woozies), or you need to use
1357	some pointer arithmetic using C<offsetof> inside your watchers (for real
1358	programmers):
1359
1360	#include <stddef.h>
1361
1362	static void
1363	t1_cb (EV_P_ ev_timer *w, int revents)
1364	{
1365	struct my_biggy big = (struct my_biggy *)
1366	(((char *)w) - offsetof (struct my_biggy, t1));
1367	}
1368
1369	static void
1370	t2_cb (EV_P_ ev_timer *w, int revents)
1371	{
1372	struct my_biggy big = (struct my_biggy *)
1373	(((char *)w) - offsetof (struct my_biggy, t2));
1374	}
1375		1392
1376	=head2 WATCHER STATES	1393	=head2 WATCHER STATES
1377		1394
1378	There are various watcher states mentioned throughout this manual -	1395	There are various watcher states mentioned throughout this manual -
1379	active, pending and so on. In this section these states and the rules to	1396	active, pending and so on. In this section these states and the rules to
1380	transition between them will be described in more detail - and while these	1397	transition between them will be described in more detail - and while these
1381	rules might look complicated, they usually do "the right thing".	1398	rules might look complicated, they usually do "the right thing".
1382		1399
1383	=over 4	1400	=over 4
1384		1401
1385	=item initialiased	1402	=item initialised
1386		1403
1387	Before a watcher can be registered with the event looop it has to be	1404	Before a watcher can be registered with the event loop it has to be
1388	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to	1405	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
1389	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.	1406	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1390		1407
1391	In this state it is simply some block of memory that is suitable for use	1408	In this state it is simply some block of memory that is suitable for
1392	in an event loop. It can be moved around, freed, reused etc. at will.	1409	use in an event loop. It can be moved around, freed, reused etc. at
		1410	will - as long as you either keep the memory contents intact, or call
		1411	C<ev_TYPE_init> again.
1393		1412
1394	=item started/running/active	1413	=item started/running/active
1395		1414
1396	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes	1415	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1397	property of the event loop, and is actively waiting for events. While in	1416	property of the event loop, and is actively waiting for events. While in
…		…
1425	latter will clear any pending state the watcher might be in, regardless	1444	latter will clear any pending state the watcher might be in, regardless
1426	of whether it was active or not, so stopping a watcher explicitly before	1445	of whether it was active or not, so stopping a watcher explicitly before
1427	freeing it is often a good idea.	1446	freeing it is often a good idea.
1428		1447
1429	While stopped (and not pending) the watcher is essentially in the	1448	While stopped (and not pending) the watcher is essentially in the
1430	initialised state, that is it can be reused, moved, modified in any way	1449	initialised state, that is, it can be reused, moved, modified in any way
1431	you wish.	1450	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1451	it again).
1432		1452
1433	=back	1453	=back
1434		1454
1435	=head2 WATCHER PRIORITY MODELS	1455	=head2 WATCHER PRIORITY MODELS
1436		1456
…		…
1565	In general you can register as many read and/or write event watchers per	1585	In general you can register as many read and/or write event watchers per
1566	fd as you want (as long as you don't confuse yourself). Setting all file	1586	fd as you want (as long as you don't confuse yourself). Setting all file
1567	descriptors to non-blocking mode is also usually a good idea (but not	1587	descriptors to non-blocking mode is also usually a good idea (but not
1568	required if you know what you are doing).	1588	required if you know what you are doing).
1569		1589
1570	If you cannot use non-blocking mode, then force the use of a
1571	known-to-be-good backend (at the time of this writing, this includes only
1572	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1573	descriptors for which non-blocking operation makes no sense (such as
1574	files) - libev doesn't guarantee any specific behaviour in that case.
1575
1576	Another thing you have to watch out for is that it is quite easy to	1590	Another thing you have to watch out for is that it is quite easy to
1577	receive "spurious" readiness notifications, that is your callback might	1591	receive "spurious" readiness notifications, that is, your callback might
1578	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1592	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1579	because there is no data. Not only are some backends known to create a	1593	because there is no data. It is very easy to get into this situation even
1580	lot of those (for example Solaris ports), it is very easy to get into	1594	with a relatively standard program structure. Thus it is best to always
1581	this situation even with a relatively standard program structure. Thus	1595	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1582	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1583	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1596	preferable to a program hanging until some data arrives.
1584		1597
1585	If you cannot run the fd in non-blocking mode (for example you should	1598	If you cannot run the fd in non-blocking mode (for example you should
1586	not play around with an Xlib connection), then you have to separately	1599	not play around with an Xlib connection), then you have to separately
1587	re-test whether a file descriptor is really ready with a known-to-be good	1600	re-test whether a file descriptor is really ready with a known-to-be good
1588	interface such as poll (fortunately in our Xlib example, Xlib already	1601	interface such as poll (fortunately in the case of Xlib, it already does
1589	does this on its own, so its quite safe to use). Some people additionally	1602	this on its own, so its quite safe to use). Some people additionally
1590	use C<SIGALRM> and an interval timer, just to be sure you won't block	1603	use C<SIGALRM> and an interval timer, just to be sure you won't block
1591	indefinitely.	1604	indefinitely.
1592		1605
1593	But really, best use non-blocking mode.	1606	But really, best use non-blocking mode.
1594		1607
…		…
1622		1635
1623	There is no workaround possible except not registering events	1636	There is no workaround possible except not registering events
1624	for potentially C<dup ()>'ed file descriptors, or to resort to	1637	for potentially C<dup ()>'ed file descriptors, or to resort to
1625	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1638	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1626		1639
		1640	=head3 The special problem of files
		1641
		1642	Many people try to use C<select> (or libev) on file descriptors
		1643	representing files, and expect it to become ready when their program
		1644	doesn't block on disk accesses (which can take a long time on their own).
		1645
		1646	However, this cannot ever work in the "expected" way - you get a readiness
		1647	notification as soon as the kernel knows whether and how much data is
		1648	there, and in the case of open files, that's always the case, so you
		1649	always get a readiness notification instantly, and your read (or possibly
		1650	write) will still block on the disk I/O.
		1651
		1652	Another way to view it is that in the case of sockets, pipes, character
		1653	devices and so on, there is another party (the sender) that delivers data
		1654	on its own, but in the case of files, there is no such thing: the disk
		1655	will not send data on its own, simply because it doesn't know what you
		1656	wish to read - you would first have to request some data.
		1657
		1658	Since files are typically not-so-well supported by advanced notification
		1659	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1660	to files, even though you should not use it. The reason for this is
		1661	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1662	usually a tty, often a pipe, but also sometimes files or special devices
		1663	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1664	F</dev/urandom>), and even though the file might better be served with
		1665	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1666	it "just works" instead of freezing.
		1667
		1668	So avoid file descriptors pointing to files when you know it (e.g. use
		1669	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1670	when you rarely read from a file instead of from a socket, and want to
		1671	reuse the same code path.
		1672
1627	=head3 The special problem of fork	1673	=head3 The special problem of fork
1628		1674
1629	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1675	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1630	useless behaviour. Libev fully supports fork, but needs to be told about	1676	useless behaviour. Libev fully supports fork, but needs to be told about
1631	it in the child.	1677	it in the child if you want to continue to use it in the child.
1632		1678
1633	To support fork in your programs, you either have to call	1679	To support fork in your child processes, you have to call C<ev_loop_fork
1634	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1680	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1635	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1681	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1636	C<EVBACKEND_POLL>.
1637		1682
1638	=head3 The special problem of SIGPIPE	1683	=head3 The special problem of SIGPIPE
1639		1684
1640	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1685	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1641	when writing to a pipe whose other end has been closed, your program gets	1686	when writing to a pipe whose other end has been closed, your program gets
…		…
1739	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1784	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1740	monotonic clock option helps a lot here).	1785	monotonic clock option helps a lot here).
1741		1786
1742	The callback is guaranteed to be invoked only I<after> its timeout has	1787	The callback is guaranteed to be invoked only I<after> its timeout has
1743	passed (not I<at>, so on systems with very low-resolution clocks this	1788	passed (not I<at>, so on systems with very low-resolution clocks this
1744	might introduce a small delay). If multiple timers become ready during the	1789	might introduce a small delay, see "the special problem of being too
		1790	early", below). If multiple timers become ready during the same loop
1745	same loop iteration then the ones with earlier time-out values are invoked	1791	iteration then the ones with earlier time-out values are invoked before
1746	before ones of the same priority with later time-out values (but this is	1792	ones of the same priority with later time-out values (but this is no
1747	no longer true when a callback calls C<ev_run> recursively).	1793	longer true when a callback calls C<ev_run> recursively).
1748		1794
1749	=head3 Be smart about timeouts	1795	=head3 Be smart about timeouts
1750		1796
1751	Many real-world problems involve some kind of timeout, usually for error	1797	Many real-world problems involve some kind of timeout, usually for error
1752	recovery. A typical example is an HTTP request - if the other side hangs,	1798	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1827		1873
1828	In this case, it would be more efficient to leave the C<ev_timer> alone,	1874	In this case, it would be more efficient to leave the C<ev_timer> alone,
1829	but remember the time of last activity, and check for a real timeout only	1875	but remember the time of last activity, and check for a real timeout only
1830	within the callback:	1876	within the callback:
1831		1877
		1878	ev_tstamp timeout = 60.;
1832	ev_tstamp last_activity; // time of last activity	1879	ev_tstamp last_activity; // time of last activity
		1880	ev_timer timer;
1833		1881
1834	static void	1882	static void
1835	callback (EV_P_ ev_timer *w, int revents)	1883	callback (EV_P_ ev_timer *w, int revents)
1836	{	1884	{
1837	ev_tstamp now = ev_now (EV_A);	1885	// calculate when the timeout would happen
1838	ev_tstamp timeout = last_activity + 60.;	1886	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1839		1887
1840	// if last_activity + 60. is older than now, we did time out	1888	// if negative, it means we the timeout already occurred
1841	if (timeout < now)	1889	if (after < 0.)
1842	{	1890	{
1843	// timeout occurred, take action	1891	// timeout occurred, take action
1844	}	1892	}
1845	else	1893	else
1846	{	1894	{
1847	// callback was invoked, but there was some activity, re-arm	1895	// callback was invoked, but there was some recent
1848	// the watcher to fire in last_activity + 60, which is	1896	// activity. simply restart the timer to time out
1849	// guaranteed to be in the future, so "again" is positive:	1897	// after "after" seconds, which is the earliest time
1850	w->repeat = timeout - now;	1898	// the timeout can occur.
		1899	ev_timer_set (w, after, 0.);
1851	ev_timer_again (EV_A_ w);	1900	ev_timer_start (EV_A_ w);
1852	}	1901	}
1853	}	1902	}
1854		1903
1855	To summarise the callback: first calculate the real timeout (defined	1904	To summarise the callback: first calculate in how many seconds the
1856	as "60 seconds after the last activity"), then check if that time has	1905	timeout will occur (by calculating the absolute time when it would occur,
1857	been reached, which means something I<did>, in fact, time out. Otherwise	1906	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1858	the callback was invoked too early (C<timeout> is in the future), so	1907	(EV_A)> from that).
1859	re-schedule the timer to fire at that future time, to see if maybe we have
1860	a timeout then.
1861		1908
1862	Note how C<ev_timer_again> is used, taking advantage of the	1909	If this value is negative, then we are already past the timeout, i.e. we
1863	C<ev_timer_again> optimisation when the timer is already running.	1910	timed out, and need to do whatever is needed in this case.
		1911
		1912	Otherwise, we now the earliest time at which the timeout would trigger,
		1913	and simply start the timer with this timeout value.
		1914
		1915	In other words, each time the callback is invoked it will check whether
		1916	the timeout occurred. If not, it will simply reschedule itself to check
		1917	again at the earliest time it could time out. Rinse. Repeat.
1864		1918
1865	This scheme causes more callback invocations (about one every 60 seconds	1919	This scheme causes more callback invocations (about one every 60 seconds
1866	minus half the average time between activity), but virtually no calls to	1920	minus half the average time between activity), but virtually no calls to
1867	libev to change the timeout.	1921	libev to change the timeout.
1868		1922
1869	To start the timer, simply initialise the watcher and set C<last_activity>	1923	To start the machinery, simply initialise the watcher and set
1870	to the current time (meaning we just have some activity :), then call the	1924	C<last_activity> to the current time (meaning there was some activity just
1871	callback, which will "do the right thing" and start the timer:	1925	now), then call the callback, which will "do the right thing" and start
		1926	the timer:
1872		1927
		1928	last_activity = ev_now (EV_A);
1873	ev_init (timer, callback);	1929	ev_init (&timer, callback);
1874	last_activity = ev_now (loop);	1930	callback (EV_A_ &timer, 0);
1875	callback (loop, timer, EV_TIMER);
1876		1931
1877	And when there is some activity, simply store the current time in	1932	When there is some activity, simply store the current time in
1878	C<last_activity>, no libev calls at all:	1933	C<last_activity>, no libev calls at all:
1879		1934
		1935	if (activity detected)
1880	last_activity = ev_now (loop);	1936	last_activity = ev_now (EV_A);
		1937
		1938	When your timeout value changes, then the timeout can be changed by simply
		1939	providing a new value, stopping the timer and calling the callback, which
		1940	will again do the right thing (for example, time out immediately :).
		1941
		1942	timeout = new_value;
		1943	ev_timer_stop (EV_A_ &timer);
		1944	callback (EV_A_ &timer, 0);
1881		1945
1882	This technique is slightly more complex, but in most cases where the	1946	This technique is slightly more complex, but in most cases where the
1883	time-out is unlikely to be triggered, much more efficient.	1947	time-out is unlikely to be triggered, much more efficient.
1884
1885	Changing the timeout is trivial as well (if it isn't hard-coded in the
1886	callback :) - just change the timeout and invoke the callback, which will
1887	fix things for you.
1888		1948
1889	=item 4. Wee, just use a double-linked list for your timeouts.	1949	=item 4. Wee, just use a double-linked list for your timeouts.
1890		1950
1891	If there is not one request, but many thousands (millions...), all	1951	If there is not one request, but many thousands (millions...), all
1892	employing some kind of timeout with the same timeout value, then one can	1952	employing some kind of timeout with the same timeout value, then one can
…		…
1919	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	1979	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1920	rather complicated, but extremely efficient, something that really pays	1980	rather complicated, but extremely efficient, something that really pays
1921	off after the first million or so of active timers, i.e. it's usually	1981	off after the first million or so of active timers, i.e. it's usually
1922	overkill :)	1982	overkill :)
1923		1983
		1984	=head3 The special problem of being too early
		1985
		1986	If you ask a timer to call your callback after three seconds, then
		1987	you expect it to be invoked after three seconds - but of course, this
		1988	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		1989	guaranteed to any precision by libev - imagine somebody suspending the
		1990	process with a STOP signal for a few hours for example.
		1991
		1992	So, libev tries to invoke your callback as soon as possible I<after> the
		1993	delay has occurred, but cannot guarantee this.
		1994
		1995	A less obvious failure mode is calling your callback too early: many event
		1996	loops compare timestamps with a "elapsed delay >= requested delay", but
		1997	this can cause your callback to be invoked much earlier than you would
		1998	expect.
		1999
		2000	To see why, imagine a system with a clock that only offers full second
		2001	resolution (think windows if you can't come up with a broken enough OS
		2002	yourself). If you schedule a one-second timer at the time 500.9, then the
		2003	event loop will schedule your timeout to elapse at a system time of 500
		2004	(500.9 truncated to the resolution) + 1, or 501.
		2005
		2006	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2007	501" and invoke the callback 0.1s after it was started, even though a
		2008	one-second delay was requested - this is being "too early", despite best
		2009	intentions.
		2010
		2011	This is the reason why libev will never invoke the callback if the elapsed
		2012	delay equals the requested delay, but only when the elapsed delay is
		2013	larger than the requested delay. In the example above, libev would only invoke
		2014	the callback at system time 502, or 1.1s after the timer was started.
		2015
		2016	So, while libev cannot guarantee that your callback will be invoked
		2017	exactly when requested, it I<can> and I<does> guarantee that the requested
		2018	delay has actually elapsed, or in other words, it always errs on the "too
		2019	late" side of things.
		2020
1924	=head3 The special problem of time updates	2021	=head3 The special problem of time updates
1925		2022
1926	Establishing the current time is a costly operation (it usually takes at	2023	Establishing the current time is a costly operation (it usually takes
1927	least two system calls): EV therefore updates its idea of the current	2024	at least one system call): EV therefore updates its idea of the current
1928	time only before and after C<ev_run> collects new events, which causes a	2025	time only before and after C<ev_run> collects new events, which causes a
1929	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2026	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1930	lots of events in one iteration.	2027	lots of events in one iteration.
1931		2028
1932	The relative timeouts are calculated relative to the C<ev_now ()>	2029	The relative timeouts are calculated relative to the C<ev_now ()>
…		…
1938	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2035	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1939		2036
1940	If the event loop is suspended for a long time, you can also force an	2037	If the event loop is suspended for a long time, you can also force an
1941	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2038	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1942	()>.	2039	()>.
		2040
		2041	=head3 The special problem of unsynchronised clocks
		2042
		2043	Modern systems have a variety of clocks - libev itself uses the normal
		2044	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2045	jumps).
		2046
		2047	Neither of these clocks is synchronised with each other or any other clock
		2048	on the system, so C<ev_time ()> might return a considerably different time
		2049	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2050	a call to C<gettimeofday> might return a second count that is one higher
		2051	than a directly following call to C<time>.
		2052
		2053	The moral of this is to only compare libev-related timestamps with
		2054	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2055	a second or so.
		2056
		2057	One more problem arises due to this lack of synchronisation: if libev uses
		2058	the system monotonic clock and you compare timestamps from C<ev_time>
		2059	or C<ev_now> from when you started your timer and when your callback is
		2060	invoked, you will find that sometimes the callback is a bit "early".
		2061
		2062	This is because C<ev_timer>s work in real time, not wall clock time, so
		2063	libev makes sure your callback is not invoked before the delay happened,
		2064	I<measured according to the real time>, not the system clock.
		2065
		2066	If your timeouts are based on a physical timescale (e.g. "time out this
		2067	connection after 100 seconds") then this shouldn't bother you as it is
		2068	exactly the right behaviour.
		2069
		2070	If you want to compare wall clock/system timestamps to your timers, then
		2071	you need to use C<ev_periodic>s, as these are based on the wall clock
		2072	time, where your comparisons will always generate correct results.
1943		2073
1944	=head3 The special problems of suspended animation	2074	=head3 The special problems of suspended animation
1945		2075
1946	When you leave the server world it is quite customary to hit machines that	2076	When you leave the server world it is quite customary to hit machines that
1947	can suspend/hibernate - what happens to the clocks during such a suspend?	2077	can suspend/hibernate - what happens to the clocks during such a suspend?
…		…
1991	keep up with the timer (because it takes longer than those 10 seconds to	2121	keep up with the timer (because it takes longer than those 10 seconds to
1992	do stuff) the timer will not fire more than once per event loop iteration.	2122	do stuff) the timer will not fire more than once per event loop iteration.
1993		2123
1994	=item ev_timer_again (loop, ev_timer *)	2124	=item ev_timer_again (loop, ev_timer *)
1995		2125
1996	This will act as if the timer timed out and restart it again if it is	2126	This will act as if the timer timed out, and restarts it again if it is
1997	repeating. The exact semantics are:	2127	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2128	timeout to the C<repeat> value and calling C<ev_timer_start>.
1998		2129
		2130	The exact semantics are as in the following rules, all of which will be
		2131	applied to the watcher:
		2132
		2133	=over 4
		2134
1999	If the timer is pending, its pending status is cleared.	2135	=item If the timer is pending, the pending status is always cleared.
2000		2136
2001	If the timer is started but non-repeating, stop it (as if it timed out).	2137	=item If the timer is started but non-repeating, stop it (as if it timed
		2138	out, without invoking it).
2002		2139
2003	If the timer is repeating, either start it if necessary (with the	2140	=item If the timer is repeating, make the C<repeat> value the new timeout
2004	C<repeat> value), or reset the running timer to the C<repeat> value.	2141	and start the timer, if necessary.
2005		2142
		2143	=back
		2144
2006	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2145	This sounds a bit complicated, see L</Be smart about timeouts>, above, for a
2007	usage example.	2146	usage example.
2008		2147
2009	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)	2148	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
2010		2149
2011	Returns the remaining time until a timer fires. If the timer is active,	2150	Returns the remaining time until a timer fires. If the timer is active,
…		…
2131		2270
2132	Another way to think about it (for the mathematically inclined) is that	2271	Another way to think about it (for the mathematically inclined) is that
2133	C<ev_periodic> will try to run the callback in this mode at the next possible	2272	C<ev_periodic> will try to run the callback in this mode at the next possible
2134	time where C<time = offset (mod interval)>, regardless of any time jumps.	2273	time where C<time = offset (mod interval)>, regardless of any time jumps.
2135		2274
2136	For numerical stability it is preferable that the C<offset> value is near	2275	The C<interval> I<MUST> be positive, and for numerical stability, the
2137	C<ev_now ()> (the current time), but there is no range requirement for	2276	interval value should be higher than C<1/8192> (which is around 100
2138	this value, and in fact is often specified as zero.	2277	microseconds) and C<offset> should be higher than C<0> and should have
		2278	at most a similar magnitude as the current time (say, within a factor of
		2279	ten). Typical values for offset are, in fact, C<0> or something between
		2280	C<0> and C<interval>, which is also the recommended range.
2139		2281
2140	Note also that there is an upper limit to how often a timer can fire (CPU	2282	Note also that there is an upper limit to how often a timer can fire (CPU
2141	speed for example), so if C<interval> is very small then timing stability	2283	speed for example), so if C<interval> is very small then timing stability
2142	will of course deteriorate. Libev itself tries to be exact to be about one	2284	will of course deteriorate. Libev itself tries to be exact to be about one
2143	millisecond (if the OS supports it and the machine is fast enough).	2285	millisecond (if the OS supports it and the machine is fast enough).
…		…
2257		2399
2258	=head2 C<ev_signal> - signal me when a signal gets signalled!	2400	=head2 C<ev_signal> - signal me when a signal gets signalled!
2259		2401
2260	Signal watchers will trigger an event when the process receives a specific	2402	Signal watchers will trigger an event when the process receives a specific
2261	signal one or more times. Even though signals are very asynchronous, libev	2403	signal one or more times. Even though signals are very asynchronous, libev
2262	will try it's best to deliver signals synchronously, i.e. as part of the	2404	will try its best to deliver signals synchronously, i.e. as part of the
2263	normal event processing, like any other event.	2405	normal event processing, like any other event.
2264		2406
2265	If you want signals to be delivered truly asynchronously, just use	2407	If you want signals to be delivered truly asynchronously, just use
2266	C<sigaction> as you would do without libev and forget about sharing	2408	C<sigaction> as you would do without libev and forget about sharing
2267	the signal. You can even use C<ev_async> from a signal handler to	2409	the signal. You can even use C<ev_async> from a signal handler to
…		…
2271	only within the same loop, i.e. you can watch for C<SIGINT> in your	2413	only within the same loop, i.e. you can watch for C<SIGINT> in your
2272	default loop and for C<SIGIO> in another loop, but you cannot watch for	2414	default loop and for C<SIGIO> in another loop, but you cannot watch for
2273	C<SIGINT> in both the default loop and another loop at the same time. At	2415	C<SIGINT> in both the default loop and another loop at the same time. At
2274	the moment, C<SIGCHLD> is permanently tied to the default loop.	2416	the moment, C<SIGCHLD> is permanently tied to the default loop.
2275		2417
2276	When the first watcher gets started will libev actually register something	2418	Only after the first watcher for a signal is started will libev actually
2277	with the kernel (thus it coexists with your own signal handlers as long as	2419	register something with the kernel. It thus coexists with your own signal
2278	you don't register any with libev for the same signal).	2420	handlers as long as you don't register any with libev for the same signal.
2279		2421
2280	If possible and supported, libev will install its handlers with	2422	If possible and supported, libev will install its handlers with
2281	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should	2423	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
2282	not be unduly interrupted. If you have a problem with system calls getting	2424	not be unduly interrupted. If you have a problem with system calls getting
2283	interrupted by signals you can block all signals in an C<ev_check> watcher	2425	interrupted by signals you can block all signals in an C<ev_check> watcher
…		…
2286	=head3 The special problem of inheritance over fork/execve/pthread_create	2428	=head3 The special problem of inheritance over fork/execve/pthread_create
2287		2429
2288	Both the signal mask (C<sigprocmask>) and the signal disposition	2430	Both the signal mask (C<sigprocmask>) and the signal disposition
2289	(C<sigaction>) are unspecified after starting a signal watcher (and after	2431	(C<sigaction>) are unspecified after starting a signal watcher (and after
2290	stopping it again), that is, libev might or might not block the signal,	2432	stopping it again), that is, libev might or might not block the signal,
2291	and might or might not set or restore the installed signal handler.	2433	and might or might not set or restore the installed signal handler (but
		2434	see C<EVFLAG_NOSIGMASK>).
2292		2435
2293	While this does not matter for the signal disposition (libev never	2436	While this does not matter for the signal disposition (libev never
2294	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on	2437	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
2295	C<execve>), this matters for the signal mask: many programs do not expect	2438	C<execve>), this matters for the signal mask: many programs do not expect
2296	certain signals to be blocked.	2439	certain signals to be blocked.
…		…
2309	I<has> to modify the signal mask, at least temporarily.	2452	I<has> to modify the signal mask, at least temporarily.
2310		2453
2311	So I can't stress this enough: I<If you do not reset your signal mask when	2454	So I can't stress this enough: I<If you do not reset your signal mask when
2312	you expect it to be empty, you have a race condition in your code>. This	2455	you expect it to be empty, you have a race condition in your code>. This
2313	is not a libev-specific thing, this is true for most event libraries.	2456	is not a libev-specific thing, this is true for most event libraries.
		2457
		2458	=head3 The special problem of threads signal handling
		2459
		2460	POSIX threads has problematic signal handling semantics, specifically,
		2461	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2462	threads in a process block signals, which is hard to achieve.
		2463
		2464	When you want to use sigwait (or mix libev signal handling with your own
		2465	for the same signals), you can tackle this problem by globally blocking
		2466	all signals before creating any threads (or creating them with a fully set
		2467	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2468	loops. Then designate one thread as "signal receiver thread" which handles
		2469	these signals. You can pass on any signals that libev might be interested
		2470	in by calling C<ev_feed_signal>.
2314		2471
2315	=head3 Watcher-Specific Functions and Data Members	2472	=head3 Watcher-Specific Functions and Data Members
2316		2473
2317	=over 4	2474	=over 4
2318		2475
…		…
2453		2610
2454	=head2 C<ev_stat> - did the file attributes just change?	2611	=head2 C<ev_stat> - did the file attributes just change?
2455		2612
2456	This watches a file system path for attribute changes. That is, it calls	2613	This watches a file system path for attribute changes. That is, it calls
2457	C<stat> on that path in regular intervals (or when the OS says it changed)	2614	C<stat> on that path in regular intervals (or when the OS says it changed)
2458	and sees if it changed compared to the last time, invoking the callback if	2615	and sees if it changed compared to the last time, invoking the callback
2459	it did.	2616	if it did. Starting the watcher C<stat>'s the file, so only changes that
		2617	happen after the watcher has been started will be reported.
2460		2618
2461	The path does not need to exist: changing from "path exists" to "path does	2619	The path does not need to exist: changing from "path exists" to "path does
2462	not exist" is a status change like any other. The condition "path does not	2620	not exist" is a status change like any other. The condition "path does not
2463	exist" (or more correctly "path cannot be stat'ed") is signified by the	2621	exist" (or more correctly "path cannot be stat'ed") is signified by the
2464	C<st_nlink> field being zero (which is otherwise always forced to be at	2622	C<st_nlink> field being zero (which is otherwise always forced to be at
…		…
2694	Apart from keeping your process non-blocking (which is a useful	2852	Apart from keeping your process non-blocking (which is a useful
2695	effect on its own sometimes), idle watchers are a good place to do	2853	effect on its own sometimes), idle watchers are a good place to do
2696	"pseudo-background processing", or delay processing stuff to after the	2854	"pseudo-background processing", or delay processing stuff to after the
2697	event loop has handled all outstanding events.	2855	event loop has handled all outstanding events.
2698		2856
		2857	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2858
		2859	As long as there is at least one active idle watcher, libev will never
		2860	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2861	For this to work, the idle watcher doesn't need to be invoked at all - the
		2862	lowest priority will do.
		2863
		2864	This mode of operation can be useful together with an C<ev_check> watcher,
		2865	to do something on each event loop iteration - for example to balance load
		2866	between different connections.
		2867
		2868	See L</Abusing an ev_check watcher for its side-effect> for a longer
		2869	example.
		2870
2699	=head3 Watcher-Specific Functions and Data Members	2871	=head3 Watcher-Specific Functions and Data Members
2700		2872
2701	=over 4	2873	=over 4
2702		2874
2703	=item ev_idle_init (ev_idle *, callback)	2875	=item ev_idle_init (ev_idle *, callback)
…		…
2714	callback, free it. Also, use no error checking, as usual.	2886	callback, free it. Also, use no error checking, as usual.
2715		2887
2716	static void	2888	static void
2717	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	2889	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2718	{	2890	{
		2891	// stop the watcher
		2892	ev_idle_stop (loop, w);
		2893
		2894	// now we can free it
2719	free (w);	2895	free (w);
		2896
2720	// now do something you wanted to do when the program has	2897	// now do something you wanted to do when the program has
2721	// no longer anything immediate to do.	2898	// no longer anything immediate to do.
2722	}	2899	}
2723		2900
2724	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2901	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
…		…
2726	ev_idle_start (loop, idle_watcher);	2903	ev_idle_start (loop, idle_watcher);
2727		2904
2728		2905
2729	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2906	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2730		2907
2731	Prepare and check watchers are usually (but not always) used in pairs:	2908	Prepare and check watchers are often (but not always) used in pairs:
2732	prepare watchers get invoked before the process blocks and check watchers	2909	prepare watchers get invoked before the process blocks and check watchers
2733	afterwards.	2910	afterwards.
2734		2911
2735	You I<must not> call C<ev_run> or similar functions that enter	2912	You I<must not> call C<ev_run> or similar functions that enter
2736	the current event loop from either C<ev_prepare> or C<ev_check>	2913	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
2764	with priority higher than or equal to the event loop and one coroutine	2941	with priority higher than or equal to the event loop and one coroutine
2765	of lower priority, but only once, using idle watchers to keep the event	2942	of lower priority, but only once, using idle watchers to keep the event
2766	loop from blocking if lower-priority coroutines are active, thus mapping	2943	loop from blocking if lower-priority coroutines are active, thus mapping
2767	low-priority coroutines to idle/background tasks).	2944	low-priority coroutines to idle/background tasks).
2768		2945
2769	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2946	When used for this purpose, it is recommended to give C<ev_check> watchers
2770	priority, to ensure that they are being run before any other watchers	2947	highest (C<EV_MAXPRI>) priority, to ensure that they are being run before
2771	after the poll (this doesn't matter for C<ev_prepare> watchers).	2948	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		2949	watchers).
2772		2950
2773	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	2951	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
2774	activate ("feed") events into libev. While libev fully supports this, they	2952	activate ("feed") events into libev. While libev fully supports this, they
2775	might get executed before other C<ev_check> watchers did their job. As	2953	might get executed before other C<ev_check> watchers did their job. As
2776	C<ev_check> watchers are often used to embed other (non-libev) event	2954	C<ev_check> watchers are often used to embed other (non-libev) event
2777	loops those other event loops might be in an unusable state until their	2955	loops those other event loops might be in an unusable state until their
2778	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	2956	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2779	others).	2957	others).
		2958
		2959	=head3 Abusing an C<ev_check> watcher for its side-effect
		2960
		2961	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		2962	useful because they are called once per event loop iteration. For
		2963	example, if you want to handle a large number of connections fairly, you
		2964	normally only do a bit of work for each active connection, and if there
		2965	is more work to do, you wait for the next event loop iteration, so other
		2966	connections have a chance of making progress.
		2967
		2968	Using an C<ev_check> watcher is almost enough: it will be called on the
		2969	next event loop iteration. However, that isn't as soon as possible -
		2970	without external events, your C<ev_check> watcher will not be invoked.
		2971
		2972	This is where C<ev_idle> watchers come in handy - all you need is a
		2973	single global idle watcher that is active as long as you have one active
		2974	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		2975	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		2976	invoked. Neither watcher alone can do that.
2780		2977
2781	=head3 Watcher-Specific Functions and Data Members	2978	=head3 Watcher-Specific Functions and Data Members
2782		2979
2783	=over 4	2980	=over 4
2784		2981
…		…
2985		3182
2986	=over 4	3183	=over 4
2987		3184
2988	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	3185	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
2989		3186
2990	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	3187	=item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)
2991		3188
2992	Configures the watcher to embed the given loop, which must be	3189	Configures the watcher to embed the given loop, which must be
2993	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	3190	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2994	invoked automatically, otherwise it is the responsibility of the callback	3191	invoked automatically, otherwise it is the responsibility of the callback
2995	to invoke it (it will continue to be called until the sweep has been done,	3192	to invoke it (it will continue to be called until the sweep has been done,
…		…
3058		3255
3059	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3256	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
3060		3257
3061	Fork watchers are called when a C<fork ()> was detected (usually because	3258	Fork watchers are called when a C<fork ()> was detected (usually because
3062	whoever is a good citizen cared to tell libev about it by calling	3259	whoever is a good citizen cared to tell libev about it by calling
3063	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the	3260	C<ev_loop_fork>). The invocation is done before the event loop blocks next
3064	event loop blocks next and before C<ev_check> watchers are being called,	3261	and before C<ev_check> watchers are being called, and only in the child
3065	and only in the child after the fork. If whoever good citizen calling	3262	after the fork. If whoever good citizen calling C<ev_default_fork> cheats
3066	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3263	and calls it in the wrong process, the fork handlers will be invoked, too,
3067	handlers will be invoked, too, of course.	3264	of course.
3068		3265
3069	=head3 The special problem of life after fork - how is it possible?	3266	=head3 The special problem of life after fork - how is it possible?
3070		3267
3071	Most uses of C<fork()> consist of forking, then some simple calls to set	3268	Most uses of C<fork()> consist of forking, then some simple calls to set
3072	up/change the process environment, followed by a call to C<exec()>. This	3269	up/change the process environment, followed by a call to C<exec()>. This
…		…
3153	atexit (program_exits);	3350	atexit (program_exits);
3154		3351
3155		3352
3156	=head2 C<ev_async> - how to wake up an event loop	3353	=head2 C<ev_async> - how to wake up an event loop
3157		3354
3158	In general, you cannot use an C<ev_run> from multiple threads or other	3355	In general, you cannot use an C<ev_loop> from multiple threads or other
3159	asynchronous sources such as signal handlers (as opposed to multiple event	3356	asynchronous sources such as signal handlers (as opposed to multiple event
3160	loops - those are of course safe to use in different threads).	3357	loops - those are of course safe to use in different threads).
3161		3358
3162	Sometimes, however, you need to wake up an event loop you do not control,	3359	Sometimes, however, you need to wake up an event loop you do not control,
3163	for example because it belongs to another thread. This is what C<ev_async>	3360	for example because it belongs to another thread. This is what C<ev_async>
…		…
3165	it by calling C<ev_async_send>, which is thread- and signal safe.	3362	it by calling C<ev_async_send>, which is thread- and signal safe.
3166		3363
3167	This functionality is very similar to C<ev_signal> watchers, as signals,	3364	This functionality is very similar to C<ev_signal> watchers, as signals,
3168	too, are asynchronous in nature, and signals, too, will be compressed	3365	too, are asynchronous in nature, and signals, too, will be compressed
3169	(i.e. the number of callback invocations may be less than the number of	3366	(i.e. the number of callback invocations may be less than the number of
3170	C<ev_async_sent> calls).	3367	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
3171		3368	of "global async watchers" by using a watcher on an otherwise unused
3172	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3369	signal, and C<ev_feed_signal> to signal this watcher from another thread,
3173	just the default loop.	3370	even without knowing which loop owns the signal.
3174		3371
3175	=head3 Queueing	3372	=head3 Queueing
3176		3373
3177	C<ev_async> does not support queueing of data in any way. The reason	3374	C<ev_async> does not support queueing of data in any way. The reason
3178	is that the author does not know of a simple (or any) algorithm for a	3375	is that the author does not know of a simple (or any) algorithm for a
…		…
3270	trust me.	3467	trust me.
3271		3468
3272	=item ev_async_send (loop, ev_async *)	3469	=item ev_async_send (loop, ev_async *)
3273		3470
3274	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3471	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3275	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3472	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3473	returns.
		3474
3276	C<ev_feed_event>, this call is safe to do from other threads, signal or	3475	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3277	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3476	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3278	section below on what exactly this means).	3477	embedding section below on what exactly this means).
3279		3478
3280	Note that, as with other watchers in libev, multiple events might get	3479	Note that, as with other watchers in libev, multiple events might get
3281	compressed into a single callback invocation (another way to look at this	3480	compressed into a single callback invocation (another way to look at
3282	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3481	this is that C<ev_async> watchers are level-triggered: they are set on
3283	reset when the event loop detects that).	3482	C<ev_async_send>, reset when the event loop detects that).
3284		3483
3285	This call incurs the overhead of a system call only once per event loop	3484	This call incurs the overhead of at most one extra system call per event
3286	iteration, so while the overhead might be noticeable, it doesn't apply to	3485	loop iteration, if the event loop is blocked, and no syscall at all if
3287	repeated calls to C<ev_async_send> for the same event loop.	3486	the event loop (or your program) is processing events. That means that
		3487	repeated calls are basically free (there is no need to avoid calls for
		3488	performance reasons) and that the overhead becomes smaller (typically
		3489	zero) under load.
3288		3490
3289	=item bool = ev_async_pending (ev_async *)	3491	=item bool = ev_async_pending (ev_async *)
3290		3492
3291	Returns a non-zero value when C<ev_async_send> has been called on the	3493	Returns a non-zero value when C<ev_async_send> has been called on the
3292	watcher but the event has not yet been processed (or even noted) by the	3494	watcher but the event has not yet been processed (or even noted) by the
…		…
3347	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3549	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3348		3550
3349	=item ev_feed_fd_event (loop, int fd, int revents)	3551	=item ev_feed_fd_event (loop, int fd, int revents)
3350		3552
3351	Feed an event on the given fd, as if a file descriptor backend detected	3553	Feed an event on the given fd, as if a file descriptor backend detected
3352	the given events it.	3554	the given events.
3353		3555
3354	=item ev_feed_signal_event (loop, int signum)	3556	=item ev_feed_signal_event (loop, int signum)
3355		3557
3356	Feed an event as if the given signal occurred (C<loop> must be the default	3558	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3357	loop!).	3559	which is async-safe.
3358		3560
3359	=back	3561	=back
		3562
		3563
		3564	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3565
		3566	This section explains some common idioms that are not immediately
		3567	obvious. Note that examples are sprinkled over the whole manual, and this
		3568	section only contains stuff that wouldn't fit anywhere else.
		3569
		3570	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3571
		3572	Each watcher has, by default, a C<void *data> member that you can read
		3573	or modify at any time: libev will completely ignore it. This can be used
		3574	to associate arbitrary data with your watcher. If you need more data and
		3575	don't want to allocate memory separately and store a pointer to it in that
		3576	data member, you can also "subclass" the watcher type and provide your own
		3577	data:
		3578
		3579	struct my_io
		3580	{
		3581	ev_io io;
		3582	int otherfd;
		3583	void *somedata;
		3584	struct whatever *mostinteresting;
		3585	};
		3586
		3587	...
		3588	struct my_io w;
		3589	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3590
		3591	And since your callback will be called with a pointer to the watcher, you
		3592	can cast it back to your own type:
		3593
		3594	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3595	{
		3596	struct my_io *w = (struct my_io *)w_;
		3597	...
		3598	}
		3599
		3600	More interesting and less C-conformant ways of casting your callback
		3601	function type instead have been omitted.
		3602
		3603	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3604
		3605	Another common scenario is to use some data structure with multiple
		3606	embedded watchers, in effect creating your own watcher that combines
		3607	multiple libev event sources into one "super-watcher":
		3608
		3609	struct my_biggy
		3610	{
		3611	int some_data;
		3612	ev_timer t1;
		3613	ev_timer t2;
		3614	}
		3615
		3616	In this case getting the pointer to C<my_biggy> is a bit more
		3617	complicated: Either you store the address of your C<my_biggy> struct in
		3618	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3619	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3620	real programmers):
		3621
		3622	#include <stddef.h>
		3623
		3624	static void
		3625	t1_cb (EV_P_ ev_timer *w, int revents)
		3626	{
		3627	struct my_biggy big = (struct my_biggy *)
		3628	(((char *)w) - offsetof (struct my_biggy, t1));
		3629	}
		3630
		3631	static void
		3632	t2_cb (EV_P_ ev_timer *w, int revents)
		3633	{
		3634	struct my_biggy big = (struct my_biggy *)
		3635	(((char *)w) - offsetof (struct my_biggy, t2));
		3636	}
		3637
		3638	=head2 AVOIDING FINISHING BEFORE RETURNING
		3639
		3640	Often you have structures like this in event-based programs:
		3641
		3642	callback ()
		3643	{
		3644	free (request);
		3645	}
		3646
		3647	request = start_new_request (..., callback);
		3648
		3649	The intent is to start some "lengthy" operation. The C<request> could be
		3650	used to cancel the operation, or do other things with it.
		3651
		3652	It's not uncommon to have code paths in C<start_new_request> that
		3653	immediately invoke the callback, for example, to report errors. Or you add
		3654	some caching layer that finds that it can skip the lengthy aspects of the
		3655	operation and simply invoke the callback with the result.
		3656
		3657	The problem here is that this will happen I<before> C<start_new_request>
		3658	has returned, so C<request> is not set.
		3659
		3660	Even if you pass the request by some safer means to the callback, you
		3661	might want to do something to the request after starting it, such as
		3662	canceling it, which probably isn't working so well when the callback has
		3663	already been invoked.
		3664
		3665	A common way around all these issues is to make sure that
		3666	C<start_new_request> I<always> returns before the callback is invoked. If
		3667	C<start_new_request> immediately knows the result, it can artificially
		3668	delay invoking the callback by using a C<prepare> or C<idle> watcher for
		3669	example, or more sneakily, by reusing an existing (stopped) watcher and
		3670	pushing it into the pending queue:
		3671
		3672	ev_set_cb (watcher, callback);
		3673	ev_feed_event (EV_A_ watcher, 0);
		3674
		3675	This way, C<start_new_request> can safely return before the callback is
		3676	invoked, while not delaying callback invocation too much.
		3677
		3678	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3679
		3680	Often (especially in GUI toolkits) there are places where you have
		3681	I<modal> interaction, which is most easily implemented by recursively
		3682	invoking C<ev_run>.
		3683
		3684	This brings the problem of exiting - a callback might want to finish the
		3685	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3686	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3687	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3688	other combination: In these cases, a simple C<ev_break> will not work.
		3689
		3690	The solution is to maintain "break this loop" variable for each C<ev_run>
		3691	invocation, and use a loop around C<ev_run> until the condition is
		3692	triggered, using C<EVRUN_ONCE>:
		3693
		3694	// main loop
		3695	int exit_main_loop = 0;
		3696
		3697	while (!exit_main_loop)
		3698	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3699
		3700	// in a modal watcher
		3701	int exit_nested_loop = 0;
		3702
		3703	while (!exit_nested_loop)
		3704	ev_run (EV_A_ EVRUN_ONCE);
		3705
		3706	To exit from any of these loops, just set the corresponding exit variable:
		3707
		3708	// exit modal loop
		3709	exit_nested_loop = 1;
		3710
		3711	// exit main program, after modal loop is finished
		3712	exit_main_loop = 1;
		3713
		3714	// exit both
		3715	exit_main_loop = exit_nested_loop = 1;
		3716
		3717	=head2 THREAD LOCKING EXAMPLE
		3718
		3719	Here is a fictitious example of how to run an event loop in a different
		3720	thread from where callbacks are being invoked and watchers are
		3721	created/added/removed.
		3722
		3723	For a real-world example, see the C<EV::Loop::Async> perl module,
		3724	which uses exactly this technique (which is suited for many high-level
		3725	languages).
		3726
		3727	The example uses a pthread mutex to protect the loop data, a condition
		3728	variable to wait for callback invocations, an async watcher to notify the
		3729	event loop thread and an unspecified mechanism to wake up the main thread.
		3730
		3731	First, you need to associate some data with the event loop:
		3732
		3733	typedef struct {
		3734	mutex_t lock; /* global loop lock */
		3735	ev_async async_w;
		3736	thread_t tid;
		3737	cond_t invoke_cv;
		3738	} userdata;
		3739
		3740	void prepare_loop (EV_P)
		3741	{
		3742	// for simplicity, we use a static userdata struct.
		3743	static userdata u;
		3744
		3745	ev_async_init (&u->async_w, async_cb);
		3746	ev_async_start (EV_A_ &u->async_w);
		3747
		3748	pthread_mutex_init (&u->lock, 0);
		3749	pthread_cond_init (&u->invoke_cv, 0);
		3750
		3751	// now associate this with the loop
		3752	ev_set_userdata (EV_A_ u);
		3753	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3754	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3755
		3756	// then create the thread running ev_run
		3757	pthread_create (&u->tid, 0, l_run, EV_A);
		3758	}
		3759
		3760	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3761	solely to wake up the event loop so it takes notice of any new watchers
		3762	that might have been added:
		3763
		3764	static void
		3765	async_cb (EV_P_ ev_async *w, int revents)
		3766	{
		3767	// just used for the side effects
		3768	}
		3769
		3770	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3771	protecting the loop data, respectively.
		3772
		3773	static void
		3774	l_release (EV_P)
		3775	{
		3776	userdata *u = ev_userdata (EV_A);
		3777	pthread_mutex_unlock (&u->lock);
		3778	}
		3779
		3780	static void
		3781	l_acquire (EV_P)
		3782	{
		3783	userdata *u = ev_userdata (EV_A);
		3784	pthread_mutex_lock (&u->lock);
		3785	}
		3786
		3787	The event loop thread first acquires the mutex, and then jumps straight
		3788	into C<ev_run>:
		3789
		3790	void *
		3791	l_run (void *thr_arg)
		3792	{
		3793	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3794
		3795	l_acquire (EV_A);
		3796	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3797	ev_run (EV_A_ 0);
		3798	l_release (EV_A);
		3799
		3800	return 0;
		3801	}
		3802
		3803	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3804	signal the main thread via some unspecified mechanism (signals? pipe
		3805	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3806	have been called (in a while loop because a) spurious wakeups are possible
		3807	and b) skipping inter-thread-communication when there are no pending
		3808	watchers is very beneficial):
		3809
		3810	static void
		3811	l_invoke (EV_P)
		3812	{
		3813	userdata *u = ev_userdata (EV_A);
		3814
		3815	while (ev_pending_count (EV_A))
		3816	{
		3817	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3818	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3819	}
		3820	}
		3821
		3822	Now, whenever the main thread gets told to invoke pending watchers, it
		3823	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3824	thread to continue:
		3825
		3826	static void
		3827	real_invoke_pending (EV_P)
		3828	{
		3829	userdata *u = ev_userdata (EV_A);
		3830
		3831	pthread_mutex_lock (&u->lock);
		3832	ev_invoke_pending (EV_A);
		3833	pthread_cond_signal (&u->invoke_cv);
		3834	pthread_mutex_unlock (&u->lock);
		3835	}
		3836
		3837	Whenever you want to start/stop a watcher or do other modifications to an
		3838	event loop, you will now have to lock:
		3839
		3840	ev_timer timeout_watcher;
		3841	userdata *u = ev_userdata (EV_A);
		3842
		3843	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3844
		3845	pthread_mutex_lock (&u->lock);
		3846	ev_timer_start (EV_A_ &timeout_watcher);
		3847	ev_async_send (EV_A_ &u->async_w);
		3848	pthread_mutex_unlock (&u->lock);
		3849
		3850	Note that sending the C<ev_async> watcher is required because otherwise
		3851	an event loop currently blocking in the kernel will have no knowledge
		3852	about the newly added timer. By waking up the loop it will pick up any new
		3853	watchers in the next event loop iteration.
		3854
		3855	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3856
		3857	While the overhead of a callback that e.g. schedules a thread is small, it
		3858	is still an overhead. If you embed libev, and your main usage is with some
		3859	kind of threads or coroutines, you might want to customise libev so that
		3860	doesn't need callbacks anymore.
		3861
		3862	Imagine you have coroutines that you can switch to using a function
		3863	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3864	and that due to some magic, the currently active coroutine is stored in a
		3865	global called C<current_coro>. Then you can build your own "wait for libev
		3866	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3867	the differing C<;> conventions):
		3868
		3869	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3870	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3871
		3872	That means instead of having a C callback function, you store the
		3873	coroutine to switch to in each watcher, and instead of having libev call
		3874	your callback, you instead have it switch to that coroutine.
		3875
		3876	A coroutine might now wait for an event with a function called
		3877	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3878	matter when, or whether the watcher is active or not when this function is
		3879	called):
		3880
		3881	void
		3882	wait_for_event (ev_watcher *w)
		3883	{
		3884	ev_set_cb (w, current_coro);
		3885	switch_to (libev_coro);
		3886	}
		3887
		3888	That basically suspends the coroutine inside C<wait_for_event> and
		3889	continues the libev coroutine, which, when appropriate, switches back to
		3890	this or any other coroutine.
		3891
		3892	You can do similar tricks if you have, say, threads with an event queue -
		3893	instead of storing a coroutine, you store the queue object and instead of
		3894	switching to a coroutine, you push the watcher onto the queue and notify
		3895	any waiters.
		3896
		3897	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		3898	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3899
		3900	// my_ev.h
		3901	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3902	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3903	#include "../libev/ev.h"
		3904
		3905	// my_ev.c
		3906	#define EV_H "my_ev.h"
		3907	#include "../libev/ev.c"
		3908
		3909	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3910	F<my_ev.c> into your project. When properly specifying include paths, you
		3911	can even use F<ev.h> as header file name directly.
3360		3912
3361		3913
3362	=head1 LIBEVENT EMULATION	3914	=head1 LIBEVENT EMULATION
3363		3915
3364	Libev offers a compatibility emulation layer for libevent. It cannot	3916	Libev offers a compatibility emulation layer for libevent. It cannot
3365	emulate the internals of libevent, so here are some usage hints:	3917	emulate the internals of libevent, so here are some usage hints:
3366		3918
3367	=over 4	3919	=over 4
		3920
		3921	=item * Only the libevent-1.4.1-beta API is being emulated.
		3922
		3923	This was the newest libevent version available when libev was implemented,
		3924	and is still mostly unchanged in 2010.
3368		3925
3369	=item * Use it by including <event.h>, as usual.	3926	=item * Use it by including <event.h>, as usual.
3370		3927
3371	=item * The following members are fully supported: ev_base, ev_callback,	3928	=item * The following members are fully supported: ev_base, ev_callback,
3372	ev_arg, ev_fd, ev_res, ev_events.	3929	ev_arg, ev_fd, ev_res, ev_events.
…		…
3378	=item * Priorities are not currently supported. Initialising priorities	3935	=item * Priorities are not currently supported. Initialising priorities
3379	will fail and all watchers will have the same priority, even though there	3936	will fail and all watchers will have the same priority, even though there
3380	is an ev_pri field.	3937	is an ev_pri field.
3381		3938
3382	=item * In libevent, the last base created gets the signals, in libev, the	3939	=item * In libevent, the last base created gets the signals, in libev, the
3383	first base created (== the default loop) gets the signals.	3940	base that registered the signal gets the signals.
3384		3941
3385	=item * Other members are not supported.	3942	=item * Other members are not supported.
3386		3943
3387	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3944	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3388	to use the libev header file and library.	3945	to use the libev header file and library.
3389		3946
3390	=back	3947	=back
3391		3948
3392	=head1 C++ SUPPORT	3949	=head1 C++ SUPPORT
		3950
		3951	=head2 C API
		3952
		3953	The normal C API should work fine when used from C++: both ev.h and the
		3954	libev sources can be compiled as C++. Therefore, code that uses the C API
		3955	will work fine.
		3956
		3957	Proper exception specifications might have to be added to callbacks passed
		3958	to libev: exceptions may be thrown only from watcher callbacks, all
		3959	other callbacks (allocator, syserr, loop acquire/release and periodic
		3960	reschedule callbacks) must not throw exceptions, and might need a C<throw
		3961	()> specification. If you have code that needs to be compiled as both C
		3962	and C++ you can use the C<EV_THROW> macro for this:
		3963
		3964	static void
		3965	fatal_error (const char *msg) EV_THROW
		3966	{
		3967	perror (msg);
		3968	abort ();
		3969	}
		3970
		3971	...
		3972	ev_set_syserr_cb (fatal_error);
		3973
		3974	The only API functions that can currently throw exceptions are C<ev_run>,
		3975	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		3976	because it runs cleanup watchers).
		3977
		3978	Throwing exceptions in watcher callbacks is only supported if libev itself
		3979	is compiled with a C++ compiler or your C and C++ environments allow
		3980	throwing exceptions through C libraries (most do).
		3981
		3982	=head2 C++ API
3393		3983
3394	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3984	Libev comes with some simplistic wrapper classes for C++ that mainly allow
3395	you to use some convenience methods to start/stop watchers and also change	3985	you to use some convenience methods to start/stop watchers and also change
3396	the callback model to a model using method callbacks on objects.	3986	the callback model to a model using method callbacks on objects.
3397		3987
3398	To use it,	3988	To use it,
3399		3989
3400	#include <ev++.h>	3990	#include <ev++.h>
3401		3991
3402	This automatically includes F<ev.h> and puts all of its definitions (many	3992	This automatically includes F<ev.h> and puts all of its definitions (many
3403	of them macros) into the global namespace. All C++ specific things are	3993	of them macros) into the global namespace. All C++ specific things are
3404	put into the C<ev> namespace. It should support all the same embedding	3994	put into the C<ev> namespace. It should support all the same embedding
…		…
3407	Care has been taken to keep the overhead low. The only data member the C++	3997	Care has been taken to keep the overhead low. The only data member the C++
3408	classes add (compared to plain C-style watchers) is the event loop pointer	3998	classes add (compared to plain C-style watchers) is the event loop pointer
3409	that the watcher is associated with (or no additional members at all if	3999	that the watcher is associated with (or no additional members at all if
3410	you disable C<EV_MULTIPLICITY> when embedding libev).	4000	you disable C<EV_MULTIPLICITY> when embedding libev).
3411		4001
3412	Currently, functions, and static and non-static member functions can be	4002	Currently, functions, static and non-static member functions and classes
3413	used as callbacks. Other types should be easy to add as long as they only	4003	with C<operator ()> can be used as callbacks. Other types should be easy
3414	need one additional pointer for context. If you need support for other	4004	to add as long as they only need one additional pointer for context. If
3415	types of functors please contact the author (preferably after implementing	4005	you need support for other types of functors please contact the author
3416	it).	4006	(preferably after implementing it).
		4007
		4008	For all this to work, your C++ compiler either has to use the same calling
		4009	conventions as your C compiler (for static member functions), or you have
		4010	to embed libev and compile libev itself as C++.
3417		4011
3418	Here is a list of things available in the C<ev> namespace:	4012	Here is a list of things available in the C<ev> namespace:
3419		4013
3420	=over 4	4014	=over 4
3421		4015
…		…
3431	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4025	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3432		4026
3433	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4027	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
3434	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4028	the same name in the C<ev> namespace, with the exception of C<ev_signal>
3435	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4029	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3436	defines by many implementations.	4030	defined by many implementations.
3437		4031
3438	All of those classes have these methods:	4032	All of those classes have these methods:
3439		4033
3440	=over 4	4034	=over 4
3441		4035
…		…
3531	Associates a different C<struct ev_loop> with this watcher. You can only	4125	Associates a different C<struct ev_loop> with this watcher. You can only
3532	do this when the watcher is inactive (and not pending either).	4126	do this when the watcher is inactive (and not pending either).
3533		4127
3534	=item w->set ([arguments])	4128	=item w->set ([arguments])
3535		4129
3536	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this	4130	Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>),
3537	method or a suitable start method must be called at least once. Unlike the	4131	with the same arguments. Either this method or a suitable start method
3538	C counterpart, an active watcher gets automatically stopped and restarted	4132	must be called at least once. Unlike the C counterpart, an active watcher
3539	when reconfiguring it with this method.	4133	gets automatically stopped and restarted when reconfiguring it with this
		4134	method.
		4135
		4136	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4137	clashing with the C<set (loop)> method.
3540		4138
3541	=item w->start ()	4139	=item w->start ()
3542		4140
3543	Starts the watcher. Note that there is no C<loop> argument, as the	4141	Starts the watcher. Note that there is no C<loop> argument, as the
3544	constructor already stores the event loop.	4142	constructor already stores the event loop.
…		…
3574	watchers in the constructor.	4172	watchers in the constructor.
3575		4173
3576	class myclass	4174	class myclass
3577	{	4175	{
3578	ev::io io ; void io_cb (ev::io &w, int revents);	4176	ev::io io ; void io_cb (ev::io &w, int revents);
3579	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);	4177	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3580	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4178	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3581		4179
3582	myclass (int fd)	4180	myclass (int fd)
3583	{	4181	{
3584	io .set <myclass, &myclass::io_cb > (this);	4182	io .set <myclass, &myclass::io_cb > (this);
…		…
3635	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4233	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3636		4234
3637	=item D	4235	=item D
3638		4236
3639	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4237	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3640	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4238	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3641		4239
3642	=item Ocaml	4240	=item Ocaml
3643		4241
3644	Erkki Seppala has written Ocaml bindings for libev, to be found at	4242	Erkki Seppala has written Ocaml bindings for libev, to be found at
3645	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4243	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
…		…
3648		4246
3649	Brian Maher has written a partial interface to libev for lua (at the	4247	Brian Maher has written a partial interface to libev for lua (at the
3650	time of this writing, only C<ev_io> and C<ev_timer>), to be found at	4248	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
3651	L<http://github.com/brimworks/lua-ev>.	4249	L<http://github.com/brimworks/lua-ev>.
3652		4250
		4251	=item Javascript
		4252
		4253	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4254
		4255	=item Others
		4256
		4257	There are others, and I stopped counting.
		4258
3653	=back	4259	=back
3654		4260
3655		4261
3656	=head1 MACRO MAGIC	4262	=head1 MACRO MAGIC
3657		4263
…		…
3693	suitable for use with C<EV_A>.	4299	suitable for use with C<EV_A>.
3694		4300
3695	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4301	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3696		4302
3697	Similar to the other two macros, this gives you the value of the default	4303	Similar to the other two macros, this gives you the value of the default
3698	loop, if multiple loops are supported ("ev loop default").	4304	loop, if multiple loops are supported ("ev loop default"). The default loop
		4305	will be initialised if it isn't already initialised.
		4306
		4307	For non-multiplicity builds, these macros do nothing, so you always have
		4308	to initialise the loop somewhere.
3699		4309
3700	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4310	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3701		4311
3702	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4312	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3703	default loop has been initialised (C<UC> == unchecked). Their behaviour	4313	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3848	supported). It will also not define any of the structs usually found in	4458	supported). It will also not define any of the structs usually found in
3849	F<event.h> that are not directly supported by the libev core alone.	4459	F<event.h> that are not directly supported by the libev core alone.
3850		4460
3851	In standalone mode, libev will still try to automatically deduce the	4461	In standalone mode, libev will still try to automatically deduce the
3852	configuration, but has to be more conservative.	4462	configuration, but has to be more conservative.
		4463
		4464	=item EV_USE_FLOOR
		4465
		4466	If defined to be C<1>, libev will use the C<floor ()> function for its
		4467	periodic reschedule calculations, otherwise libev will fall back on a
		4468	portable (slower) implementation. If you enable this, you usually have to
		4469	link against libm or something equivalent. Enabling this when the C<floor>
		4470	function is not available will fail, so the safe default is to not enable
		4471	this.
3853		4472
3854	=item EV_USE_MONOTONIC	4473	=item EV_USE_MONOTONIC
3855		4474
3856	If defined to be C<1>, libev will try to detect the availability of the	4475	If defined to be C<1>, libev will try to detect the availability of the
3857	monotonic clock option at both compile time and runtime. Otherwise no	4476	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3942		4561
3943	If programs implement their own fd to handle mapping on win32, then this	4562	If programs implement their own fd to handle mapping on win32, then this
3944	macro can be used to override the C<close> function, useful to unregister	4563	macro can be used to override the C<close> function, useful to unregister
3945	file descriptors again. Note that the replacement function has to close	4564	file descriptors again. Note that the replacement function has to close
3946	the underlying OS handle.	4565	the underlying OS handle.
		4566
		4567	=item EV_USE_WSASOCKET
		4568
		4569	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4570	communication socket, which works better in some environments. Otherwise,
		4571	the normal C<socket> function will be used, which works better in other
		4572	environments.
3947		4573
3948	=item EV_USE_POLL	4574	=item EV_USE_POLL
3949		4575
3950	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4576	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3951	backend. Otherwise it will be enabled on non-win32 platforms. It	4577	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3987	If defined to be C<1>, libev will compile in support for the Linux inotify	4613	If defined to be C<1>, libev will compile in support for the Linux inotify
3988	interface to speed up C<ev_stat> watchers. Its actual availability will	4614	interface to speed up C<ev_stat> watchers. Its actual availability will
3989	be detected at runtime. If undefined, it will be enabled if the headers	4615	be detected at runtime. If undefined, it will be enabled if the headers
3990	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4616	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3991		4617
		4618	=item EV_NO_SMP
		4619
		4620	If defined to be C<1>, libev will assume that memory is always coherent
		4621	between threads, that is, threads can be used, but threads never run on
		4622	different cpus (or different cpu cores). This reduces dependencies
		4623	and makes libev faster.
		4624
		4625	=item EV_NO_THREADS
		4626
		4627	If defined to be C<1>, libev will assume that it will never be called from
		4628	different threads (that includes signal handlers), which is a stronger
		4629	assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes
		4630	libev faster.
		4631
3992	=item EV_ATOMIC_T	4632	=item EV_ATOMIC_T
3993		4633
3994	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4634	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3995	access is atomic with respect to other threads or signal contexts. No such	4635	access is atomic with respect to other threads or signal contexts. No
3996	type is easily found in the C language, so you can provide your own type	4636	such type is easily found in the C language, so you can provide your own
3997	that you know is safe for your purposes. It is used both for signal handler "locking"	4637	type that you know is safe for your purposes. It is used both for signal
3998	as well as for signal and thread safety in C<ev_async> watchers.	4638	handler "locking" as well as for signal and thread safety in C<ev_async>
		4639	watchers.
3999		4640
4000	In the absence of this define, libev will use C<sig_atomic_t volatile>	4641	In the absence of this define, libev will use C<sig_atomic_t volatile>
4001	(from F<signal.h>), which is usually good enough on most platforms.	4642	(from F<signal.h>), which is usually good enough on most platforms.
4002		4643
4003	=item EV_H (h)	4644	=item EV_H (h)
…		…
4030	will have the C<struct ev_loop *> as first argument, and you can create	4671	will have the C<struct ev_loop *> as first argument, and you can create
4031	additional independent event loops. Otherwise there will be no support	4672	additional independent event loops. Otherwise there will be no support
4032	for multiple event loops and there is no first event loop pointer	4673	for multiple event loops and there is no first event loop pointer
4033	argument. Instead, all functions act on the single default loop.	4674	argument. Instead, all functions act on the single default loop.
4034		4675
		4676	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4677	default loop when multiplicity is switched off - you always have to
		4678	initialise the loop manually in this case.
		4679
4035	=item EV_MINPRI	4680	=item EV_MINPRI
4036		4681
4037	=item EV_MAXPRI	4682	=item EV_MAXPRI
4038		4683
4039	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4684	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
4075	#define EV_USE_POLL 1	4720	#define EV_USE_POLL 1
4076	#define EV_CHILD_ENABLE 1	4721	#define EV_CHILD_ENABLE 1
4077	#define EV_ASYNC_ENABLE 1	4722	#define EV_ASYNC_ENABLE 1
4078		4723
4079	The actual value is a bitset, it can be a combination of the following	4724	The actual value is a bitset, it can be a combination of the following
4080	values:	4725	values (by default, all of these are enabled):
4081		4726
4082	=over 4	4727	=over 4
4083		4728
4084	=item C<1> - faster/larger code	4729	=item C<1> - faster/larger code
4085		4730
…		…
4089	code size by roughly 30% on amd64).	4734	code size by roughly 30% on amd64).
4090		4735
4091	When optimising for size, use of compiler flags such as C<-Os> with	4736	When optimising for size, use of compiler flags such as C<-Os> with
4092	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of	4737	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
4093	assertions.	4738	assertions.
		4739
		4740	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4741	(e.g. gcc with C<-Os>).
4094		4742
4095	=item C<2> - faster/larger data structures	4743	=item C<2> - faster/larger data structures
4096		4744
4097	Replaces the small 2-heap for timer management by a faster 4-heap, larger	4745	Replaces the small 2-heap for timer management by a faster 4-heap, larger
4098	hash table sizes and so on. This will usually further increase code size	4746	hash table sizes and so on. This will usually further increase code size
4099	and can additionally have an effect on the size of data structures at	4747	and can additionally have an effect on the size of data structures at
4100	runtime.	4748	runtime.
4101		4749
		4750	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4751	(e.g. gcc with C<-Os>).
		4752
4102	=item C<4> - full API configuration	4753	=item C<4> - full API configuration
4103		4754
4104	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and	4755	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
4105	enables multiplicity (C<EV_MULTIPLICITY>=1).	4756	enables multiplicity (C<EV_MULTIPLICITY>=1).
4106		4757
…		…
4136		4787
4137	With an intelligent-enough linker (gcc+binutils are intelligent enough	4788	With an intelligent-enough linker (gcc+binutils are intelligent enough
4138	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by	4789	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
4139	your program might be left out as well - a binary starting a timer and an	4790	your program might be left out as well - a binary starting a timer and an
4140	I/O watcher then might come out at only 5Kb.	4791	I/O watcher then might come out at only 5Kb.
		4792
		4793	=item EV_API_STATIC
		4794
		4795	If this symbol is defined (by default it is not), then all identifiers
		4796	will have static linkage. This means that libev will not export any
		4797	identifiers, and you cannot link against libev anymore. This can be useful
		4798	when you embed libev, only want to use libev functions in a single file,
		4799	and do not want its identifiers to be visible.
		4800
		4801	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4802	wants to use libev.
		4803
		4804	This option only works when libev is compiled with a C compiler, as C++
		4805	doesn't support the required declaration syntax.
4141		4806
4142	=item EV_AVOID_STDIO	4807	=item EV_AVOID_STDIO
4143		4808
4144	If this is set to C<1> at compiletime, then libev will avoid using stdio	4809	If this is set to C<1> at compiletime, then libev will avoid using stdio
4145	functions (printf, scanf, perror etc.). This will increase the code size	4810	functions (printf, scanf, perror etc.). This will increase the code size
…		…
4289	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4954	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4290		4955
4291	#include "ev_cpp.h"	4956	#include "ev_cpp.h"
4292	#include "ev.c"	4957	#include "ev.c"
4293		4958
4294	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4959	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4295		4960
4296	=head2 THREADS AND COROUTINES	4961	=head2 THREADS AND COROUTINES
4297		4962
4298	=head3 THREADS	4963	=head3 THREADS
4299		4964
…		…
4350	default loop and triggering an C<ev_async> watcher from the default loop	5015	default loop and triggering an C<ev_async> watcher from the default loop
4351	watcher callback into the event loop interested in the signal.	5016	watcher callback into the event loop interested in the signal.
4352		5017
4353	=back	5018	=back
4354		5019
4355	=head4 THREAD LOCKING EXAMPLE	5020	See also L</THREAD LOCKING EXAMPLE>.
4356
4357	Here is a fictitious example of how to run an event loop in a different
4358	thread than where callbacks are being invoked and watchers are
4359	created/added/removed.
4360
4361	For a real-world example, see the C<EV::Loop::Async> perl module,
4362	which uses exactly this technique (which is suited for many high-level
4363	languages).
4364
4365	The example uses a pthread mutex to protect the loop data, a condition
4366	variable to wait for callback invocations, an async watcher to notify the
4367	event loop thread and an unspecified mechanism to wake up the main thread.
4368
4369	First, you need to associate some data with the event loop:
4370
4371	typedef struct {
4372	mutex_t lock; /* global loop lock */
4373	ev_async async_w;
4374	thread_t tid;
4375	cond_t invoke_cv;
4376	} userdata;
4377
4378	void prepare_loop (EV_P)
4379	{
4380	// for simplicity, we use a static userdata struct.
4381	static userdata u;
4382
4383	ev_async_init (&u->async_w, async_cb);
4384	ev_async_start (EV_A_ &u->async_w);
4385
4386	pthread_mutex_init (&u->lock, 0);
4387	pthread_cond_init (&u->invoke_cv, 0);
4388
4389	// now associate this with the loop
4390	ev_set_userdata (EV_A_ u);
4391	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4392	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4393
4394	// then create the thread running ev_loop
4395	pthread_create (&u->tid, 0, l_run, EV_A);
4396	}
4397
4398	The callback for the C<ev_async> watcher does nothing: the watcher is used
4399	solely to wake up the event loop so it takes notice of any new watchers
4400	that might have been added:
4401
4402	static void
4403	async_cb (EV_P_ ev_async *w, int revents)
4404	{
4405	// just used for the side effects
4406	}
4407
4408	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4409	protecting the loop data, respectively.
4410
4411	static void
4412	l_release (EV_P)
4413	{
4414	userdata *u = ev_userdata (EV_A);
4415	pthread_mutex_unlock (&u->lock);
4416	}
4417
4418	static void
4419	l_acquire (EV_P)
4420	{
4421	userdata *u = ev_userdata (EV_A);
4422	pthread_mutex_lock (&u->lock);
4423	}
4424
4425	The event loop thread first acquires the mutex, and then jumps straight
4426	into C<ev_run>:
4427
4428	void *
4429	l_run (void *thr_arg)
4430	{
4431	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4432
4433	l_acquire (EV_A);
4434	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4435	ev_run (EV_A_ 0);
4436	l_release (EV_A);
4437
4438	return 0;
4439	}
4440
4441	Instead of invoking all pending watchers, the C<l_invoke> callback will
4442	signal the main thread via some unspecified mechanism (signals? pipe
4443	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4444	have been called (in a while loop because a) spurious wakeups are possible
4445	and b) skipping inter-thread-communication when there are no pending
4446	watchers is very beneficial):
4447
4448	static void
4449	l_invoke (EV_P)
4450	{
4451	userdata *u = ev_userdata (EV_A);
4452
4453	while (ev_pending_count (EV_A))
4454	{
4455	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4456	pthread_cond_wait (&u->invoke_cv, &u->lock);
4457	}
4458	}
4459
4460	Now, whenever the main thread gets told to invoke pending watchers, it
4461	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4462	thread to continue:
4463
4464	static void
4465	real_invoke_pending (EV_P)
4466	{
4467	userdata *u = ev_userdata (EV_A);
4468
4469	pthread_mutex_lock (&u->lock);
4470	ev_invoke_pending (EV_A);
4471	pthread_cond_signal (&u->invoke_cv);
4472	pthread_mutex_unlock (&u->lock);
4473	}
4474
4475	Whenever you want to start/stop a watcher or do other modifications to an
4476	event loop, you will now have to lock:
4477
4478	ev_timer timeout_watcher;
4479	userdata *u = ev_userdata (EV_A);
4480
4481	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4482
4483	pthread_mutex_lock (&u->lock);
4484	ev_timer_start (EV_A_ &timeout_watcher);
4485	ev_async_send (EV_A_ &u->async_w);
4486	pthread_mutex_unlock (&u->lock);
4487
4488	Note that sending the C<ev_async> watcher is required because otherwise
4489	an event loop currently blocking in the kernel will have no knowledge
4490	about the newly added timer. By waking up the loop it will pick up any new
4491	watchers in the next event loop iteration.
4492		5021
4493	=head3 COROUTINES	5022	=head3 COROUTINES
4494		5023
4495	Libev is very accommodating to coroutines ("cooperative threads"):	5024	Libev is very accommodating to coroutines ("cooperative threads"):
4496	libev fully supports nesting calls to its functions from different	5025	libev fully supports nesting calls to its functions from different
…		…
4661	requires, and its I/O model is fundamentally incompatible with the POSIX	5190	requires, and its I/O model is fundamentally incompatible with the POSIX
4662	model. Libev still offers limited functionality on this platform in	5191	model. Libev still offers limited functionality on this platform in
4663	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5192	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4664	descriptors. This only applies when using Win32 natively, not when using	5193	descriptors. This only applies when using Win32 natively, not when using
4665	e.g. cygwin. Actually, it only applies to the microsofts own compilers,	5194	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
4666	as every compielr comes with a slightly differently broken/incompatible	5195	as every compiler comes with a slightly differently broken/incompatible
4667	environment.	5196	environment.
4668		5197
4669	Lifting these limitations would basically require the full	5198	Lifting these limitations would basically require the full
4670	re-implementation of the I/O system. If you are into this kind of thing,	5199	re-implementation of the I/O system. If you are into this kind of thing,
4671	then note that glib does exactly that for you in a very portable way (note	5200	then note that glib does exactly that for you in a very portable way (note
…		…
4787	thread" or will block signals process-wide, both behaviours would	5316	thread" or will block signals process-wide, both behaviours would
4788	be compatible with libev. Interaction between C<sigprocmask> and	5317	be compatible with libev. Interaction between C<sigprocmask> and
4789	C<pthread_sigmask> could complicate things, however.	5318	C<pthread_sigmask> could complicate things, however.
4790		5319
4791	The most portable way to handle signals is to block signals in all threads	5320	The most portable way to handle signals is to block signals in all threads
4792	except the initial one, and run the default loop in the initial thread as	5321	except the initial one, and run the signal handling loop in the initial
4793	well.	5322	thread as well.
4794		5323
4795	=item C<long> must be large enough for common memory allocation sizes	5324	=item C<long> must be large enough for common memory allocation sizes
4796		5325
4797	To improve portability and simplify its API, libev uses C<long> internally	5326	To improve portability and simplify its API, libev uses C<long> internally
4798	instead of C<size_t> when allocating its data structures. On non-POSIX	5327	instead of C<size_t> when allocating its data structures. On non-POSIX
…		…
4804		5333
4805	The type C<double> is used to represent timestamps. It is required to	5334	The type C<double> is used to represent timestamps. It is required to
4806	have at least 51 bits of mantissa (and 9 bits of exponent), which is	5335	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4807	good enough for at least into the year 4000 with millisecond accuracy	5336	good enough for at least into the year 4000 with millisecond accuracy
4808	(the design goal for libev). This requirement is overfulfilled by	5337	(the design goal for libev). This requirement is overfulfilled by
4809	implementations using IEEE 754, which is basically all existing ones. With	5338	implementations using IEEE 754, which is basically all existing ones.
		5339
4810	IEEE 754 doubles, you get microsecond accuracy until at least 2200.	5340	With IEEE 754 doubles, you get microsecond accuracy until at least the
		5341	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5342	is either obsolete or somebody patched it to use C<long double> or
		5343	something like that, just kidding).
4811		5344
4812	=back	5345	=back
4813		5346
4814	If you know of other additional requirements drop me a note.	5347	If you know of other additional requirements drop me a note.
4815		5348
…		…
4877	=item Processing ev_async_send: O(number_of_async_watchers)	5410	=item Processing ev_async_send: O(number_of_async_watchers)
4878		5411
4879	=item Processing signals: O(max_signal_number)	5412	=item Processing signals: O(max_signal_number)
4880		5413
4881	Sending involves a system call I<iff> there were no other C<ev_async_send>	5414	Sending involves a system call I<iff> there were no other C<ev_async_send>
4882	calls in the current loop iteration. Checking for async and signal events	5415	calls in the current loop iteration and the loop is currently
		5416	blocked. Checking for async and signal events involves iterating over all
4883	involves iterating over all running async watchers or all signal numbers.	5417	running async watchers or all signal numbers.
4884		5418
4885	=back	5419	=back
4886		5420
4887		5421
4888	=head1 PORTING FROM LIBEV 3.X TO 4.X	5422	=head1 PORTING FROM LIBEV 3.X TO 4.X
…		…
4897	=over 4	5431	=over 4
4898		5432
4899	=item C<EV_COMPAT3> backwards compatibility mechanism	5433	=item C<EV_COMPAT3> backwards compatibility mechanism
4900		5434
4901	The backward compatibility mechanism can be controlled by	5435	The backward compatibility mechanism can be controlled by
4902	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>	5436	C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING>
4903	section.	5437	section.
4904		5438
4905	=item C<ev_default_destroy> and C<ev_default_fork> have been removed	5439	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
4906		5440
4907	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:	5441	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
…		…
4950	=over 4	5484	=over 4
4951		5485
4952	=item active	5486	=item active
4953		5487
4954	A watcher is active as long as it has been started and not yet stopped.	5488	A watcher is active as long as it has been started and not yet stopped.
4955	See L<WATCHER STATES> for details.	5489	See L</WATCHER STATES> for details.
4956		5490
4957	=item application	5491	=item application
4958		5492
4959	In this document, an application is whatever is using libev.	5493	In this document, an application is whatever is using libev.
4960		5494
…		…
4996	watchers and events.	5530	watchers and events.
4997		5531
4998	=item pending	5532	=item pending
4999		5533
5000	A watcher is pending as soon as the corresponding event has been	5534	A watcher is pending as soon as the corresponding event has been
5001	detected. See L<WATCHER STATES> for details.	5535	detected. See L</WATCHER STATES> for details.
5002		5536
5003	=item real time	5537	=item real time
5004		5538
5005	The physical time that is observed. It is apparently strictly monotonic :)	5539	The physical time that is observed. It is apparently strictly monotonic :)
5006		5540
5007	=item wall-clock time	5541	=item wall-clock time
5008		5542
5009	The time and date as shown on clocks. Unlike real time, it can actually	5543	The time and date as shown on clocks. Unlike real time, it can actually
5010	be wrong and jump forwards and backwards, e.g. when the you adjust your	5544	be wrong and jump forwards and backwards, e.g. when you adjust your
5011	clock.	5545	clock.
5012		5546
5013	=item watcher	5547	=item watcher
5014		5548
5015	A data structure that describes interest in certain events. Watchers need	5549	A data structure that describes interest in certain events. Watchers need
…		…
5018	=back	5552	=back
5019		5553
5020	=head1 AUTHOR	5554	=head1 AUTHOR
5021		5555
5022	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael	5556	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
5023	Magnusson and Emanuele Giaquinta.	5557	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
5024		5558

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