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Revision 1.337 by root, Sun Oct 31 20:20:20 2010 UTC vs.
Revision 1.428 by root, Thu May 30 18:51:57 2013 UTC

…		…
58	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
59		59
60	// now wait for events to arrive	60	// now wait for events to arrive
61	ev_run (loop, 0);	61	ev_run (loop, 0);
62		62
63	// unloop was called, so exit	63	// break was called, so exit
64	return 0;	64	return 0;
65	}	65	}
66		66
67	=head1 ABOUT THIS DOCUMENT	67	=head1 ABOUT THIS DOCUMENT
68		68
…		…
82		82
83	=head1 WHAT TO READ WHEN IN A HURRY	83	=head1 WHAT TO READ WHEN IN A HURRY
84		84
85	This manual tries to be very detailed, but unfortunately, this also makes	85	This manual tries to be very detailed, but unfortunately, this also makes
86	it very long. If you just want to know the basics of libev, I suggest	86	it very long. If you just want to know the basics of libev, I suggest
87	reading L<ANATOMY OF A WATCHER>, then the L<EXAMPLE PROGRAM> above and	87	reading L</ANATOMY OF A WATCHER>, then the L</EXAMPLE PROGRAM> above and
88	look up the missing functions in L<GLOBAL FUNCTIONS> and the C<ev_io> and	88	look up the missing functions in L</GLOBAL FUNCTIONS> and the C<ev_io> and
89	C<ev_timer> sections in L<WATCHER TYPES>.	89	C<ev_timer> sections in L</WATCHER TYPES>.
90		90
91	=head1 ABOUT LIBEV	91	=head1 ABOUT LIBEV
92		92
93	Libev is an event loop: you register interest in certain events (such as a	93	Libev is an event loop: you register interest in certain events (such as a
94	file descriptor being readable or a timeout occurring), and it will manage	94	file descriptor being readable or a timeout occurring), and it will manage
…		…
174	=item ev_tstamp ev_time ()	174	=item ev_tstamp ev_time ()
175		175
176	Returns the current time as libev would use it. Please note that the	176	Returns the current time as libev would use it. Please note that the
177	C<ev_now> function is usually faster and also often returns the timestamp	177	C<ev_now> function is usually faster and also often returns the timestamp
178	you actually want to know. Also interesting is the combination of	178	you actually want to know. Also interesting is the combination of
179	C<ev_update_now> and C<ev_now>.	179	C<ev_now_update> and C<ev_now>.
180		180
181	=item ev_sleep (ev_tstamp interval)	181	=item ev_sleep (ev_tstamp interval)
182		182
183	Sleep for the given interval: The current thread will be blocked until	183	Sleep for the given interval: The current thread will be blocked
184	either it is interrupted or the given time interval has passed. Basically	184	until either it is interrupted or the given time interval has
		185	passed (approximately - it might return a bit earlier even if not
		186	interrupted). Returns immediately if C<< interval <= 0 >>.
		187
185	this is a sub-second-resolution C<sleep ()>.	188	Basically this is a sub-second-resolution C<sleep ()>.
		189
		190	The range of the C<interval> is limited - libev only guarantees to work
		191	with sleep times of up to one day (C<< interval <= 86400 >>).
186		192
187	=item int ev_version_major ()	193	=item int ev_version_major ()
188		194
189	=item int ev_version_minor ()	195	=item int ev_version_minor ()
190		196
…		…
241	the current system, you would need to look at C<ev_embeddable_backends ()	247	the current system, you would need to look at C<ev_embeddable_backends ()
242	& ev_supported_backends ()>, likewise for recommended ones.	248	& ev_supported_backends ()>, likewise for recommended ones.
243		249
244	See the description of C<ev_embed> watchers for more info.	250	See the description of C<ev_embed> watchers for more info.
245		251
246	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	252	=item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())
247		253
248	Sets the allocation function to use (the prototype is similar - the	254	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	255	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	256	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	257	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
277	}	283	}
278		284
279	...	285	...
280	ev_set_allocator (persistent_realloc);	286	ev_set_allocator (persistent_realloc);
281		287
282	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	288	=item ev_set_syserr_cb (void (*cb)(const char *msg) throw ())
283		289
284	Set the callback function to call on a retryable system call error (such	290	Set the callback function to call on a retryable system call error (such
285	as failed select, poll, epoll_wait). The message is a printable string	291	as failed select, poll, epoll_wait). The message is a printable string
286	indicating the system call or subsystem causing the problem. If this	292	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	293	callback is set, then libev will expect it to remedy the situation, no
…		…
299	}	305	}
300		306
301	...	307	...
302	ev_set_syserr_cb (fatal_error);	308	ev_set_syserr_cb (fatal_error);
303		309
		310	=item ev_feed_signal (int signum)
		311
		312	This function can be used to "simulate" a signal receive. It is completely
		313	safe to call this function at any time, from any context, including signal
		314	handlers or random threads.
		315
		316	Its main use is to customise signal handling in your process, especially
		317	in the presence of threads. For example, you could block signals
		318	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		319	creating any loops), and in one thread, use C<sigwait> or any other
		320	mechanism to wait for signals, then "deliver" them to libev by calling
		321	C<ev_feed_signal>.
		322
304	=back	323	=back
305		324
306	=head1 FUNCTIONS CONTROLLING EVENT LOOPS	325	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
307		326
308	An event loop is described by a C<struct ev_loop *> (the C<struct> is	327	An event loop is described by a C<struct ev_loop *> (the C<struct> is
…		…
355	=item struct ev_loop *ev_loop_new (unsigned int flags)	374	=item struct ev_loop *ev_loop_new (unsigned int flags)
356		375
357	This will create and initialise a new event loop object. If the loop	376	This will create and initialise a new event loop object. If the loop
358	could not be initialised, returns false.	377	could not be initialised, returns false.
359		378
360	Note that this function I<is> thread-safe, and one common way to use	379	This function is thread-safe, and one common way to use libev with
361	libev with threads is indeed to create one loop per thread, and using the	380	threads is indeed to create one loop per thread, and using the default
362	default loop in the "main" or "initial" thread.	381	loop in the "main" or "initial" thread.
363		382
364	The flags argument can be used to specify special behaviour or specific	383	The flags argument can be used to specify special behaviour or specific
365	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	384	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
366		385
367	The following flags are supported:	386	The following flags are supported:
…		…
377		396
378	If this flag bit is or'ed into the flag value (or the program runs setuid	397	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	398	or setgid) then libev will I<not> look at the environment variable
380	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	399	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
381	override the flags completely if it is found in the environment. This is	400	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	401	useful to try out specific backends to test their performance, to work
383	around bugs.	402	around bugs, or to make libev threadsafe (accessing environment variables
		403	cannot be done in a threadsafe way, but usually it works if no other
		404	thread modifies them).
384		405
385	=item C<EVFLAG_FORKCHECK>	406	=item C<EVFLAG_FORKCHECK>
386		407
387	Instead of calling C<ev_loop_fork> manually after a fork, you can also	408	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.	409	make libev check for a fork in each iteration by enabling this flag.
…		…
402	environment variable.	423	environment variable.
403		424
404	=item C<EVFLAG_NOINOTIFY>	425	=item C<EVFLAG_NOINOTIFY>
405		426
406	When this flag is specified, then libev will not attempt to use the	427	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	428	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	429	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.	430	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
410		431
411	=item C<EVFLAG_SIGNALFD>	432	=item C<EVFLAG_SIGNALFD>
412		433
413	When this flag is specified, then libev will attempt to use the	434	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	435	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	436	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	437	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	438	handling with threads, as long as you properly block signals in your
418	threads that are not interested in handling them.	439	threads that are not interested in handling them.
419		440
420	Signalfd will not be used by default as this changes your signal mask, and	441	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	442	there are a lot of shoddy libraries and programs (glib's threadpool for
422	example) that can't properly initialise their signal masks.	443	example) that can't properly initialise their signal masks.
		444
		445	=item C<EVFLAG_NOSIGMASK>
		446
		447	When this flag is specified, then libev will avoid to modify the signal
		448	mask. Specifically, this means you have to make sure signals are unblocked
		449	when you want to receive them.
		450
		451	This behaviour is useful when you want to do your own signal handling, or
		452	want to handle signals only in specific threads and want to avoid libev
		453	unblocking the signals.
		454
		455	It's also required by POSIX in a threaded program, as libev calls
		456	C<sigprocmask>, whose behaviour is officially unspecified.
		457
		458	This flag's behaviour will become the default in future versions of libev.
423		459
424	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	460	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
425		461
426	This is your standard select(2) backend. Not I<completely> standard, as	462	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,	463	libev tries to roll its own fd_set with no limits on the number of fds,
…		…
455	=item C<EVBACKEND_EPOLL> (value 4, Linux)	491	=item C<EVBACKEND_EPOLL> (value 4, Linux)
456		492
457	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9	493	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
458	kernels).	494	kernels).
459		495
460	For few fds, this backend is a bit little slower than poll and select,	496	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	497	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),	498	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).	499	fd), epoll scales either O(1) or O(active_fds).
464		500
465	The epoll mechanism deserves honorable mention as the most misdesigned	501	The epoll mechanism deserves honorable mention as the most misdesigned
466	of the more advanced event mechanisms: mere annoyances include silently	502	of the more advanced event mechanisms: mere annoyances include silently
467	dropping file descriptors, requiring a system call per change per file	503	dropping file descriptors, requiring a system call per change per file
468	descriptor (and unnecessary guessing of parameters), problems with dup,	504	descriptor (and unnecessary guessing of parameters), problems with dup,
469	returning before the timeout value requiring additional iterations and so	505	returning before the timeout value, resulting in additional iterations
		506	(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	507	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	508	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	509	set, which can take considerable time (one syscall per file descriptor)
473	hard to detect.	510	and is of course hard to detect.
474		511
475	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	512	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	513	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	514	totally I<different> file descriptors (even already closed ones, so
478	even remove them from the set) than registered in the set (especially	515	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	516	(especially on SMP systems). Libev tries to counter these spurious
480	employing an additional generation counter and comparing that against the	517	notifications by employing an additional generation counter and comparing
481	events to filter out spurious ones, recreating the set when required. Last	518	that against the events to filter out spurious ones, recreating the set
		519	when required. Epoll also erroneously rounds down timeouts, but gives you
		520	no way to know when and by how much, so sometimes you have to busy-wait
		521	because epoll returns immediately despite a nonzero timeout. And last
482	not least, it also refuses to work with some file descriptors which work	522	not least, it also refuses to work with some file descriptors which work
483	perfectly fine with C<select> (files, many character devices...).	523	perfectly fine with C<select> (files, many character devices...).
		524
		525	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
		526	cobbled together in a hurry, no thought to design or interaction with
		527	others. Oh, the pain, will it ever stop...
484		528
485	While stopping, setting and starting an I/O watcher in the same iteration	529	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	530	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	531	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	532	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
525		569
526	It scales in the same way as the epoll backend, but the interface to the	570	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	571	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	572	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	573	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	574	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	575	might have to leak fd's on fork, but it's more sane than epoll) and it
532	cases	576	drops fds silently in similarly hard-to-detect cases.
533		577
534	This backend usually performs well under most conditions.	578	This backend usually performs well under most conditions.
535		579
536	While nominally embeddable in other event loops, this doesn't work	580	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	581	everywhere, so you might need to test for this. And since it is broken
…		…
554	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	598	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
555		599
556	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	600	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)).	601	it's really slow, but it still scales very well (O(active_fds)).
558		602
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	603	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	604	file descriptor per loop iteration. For small and medium numbers of file
565	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	605	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
566	might perform better.	606	might perform better.
567		607
568	On the positive side, with the exception of the spurious readiness	608	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	609	specification in all tests and is fully embeddable, which is a rare feat
571	OS-specific backends (I vastly prefer correctness over speed hacks).	610	among the OS-specific backends (I vastly prefer correctness over speed
		611	hacks).
		612
		613	On the negative side, the interface is I<bizarre> - so bizarre that
		614	even sun itself gets it wrong in their code examples: The event polling
		615	function sometimes returns events to the caller even though an error
		616	occurred, but with no indication whether it has done so or not (yes, it's
		617	even documented that way) - deadly for edge-triggered interfaces where you
		618	absolutely have to know whether an event occurred or not because you have
		619	to re-arm the watcher.
		620
		621	Fortunately libev seems to be able to work around these idiocies.
572		622
573	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	623	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
574	C<EVBACKEND_POLL>.	624	C<EVBACKEND_POLL>.
575		625
576	=item C<EVBACKEND_ALL>	626	=item C<EVBACKEND_ALL>
577		627
578	Try all backends (even potentially broken ones that wouldn't be tried	628	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	629	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
580	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	630	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
581		631
582	It is definitely not recommended to use this flag.	632	It is definitely not recommended to use this flag, use whatever
		633	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		634	at all.
		635
		636	=item C<EVBACKEND_MASK>
		637
		638	Not a backend at all, but a mask to select all backend bits from a
		639	C<flags> value, in case you want to mask out any backends from a flags
		640	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
583		641
584	=back	642	=back
585		643
586	If one or more of the backend flags are or'ed into the flags value,	644	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	645	then only these backends will be tried (in the reverse order as listed
…		…
616	This function is normally used on loop objects allocated by	674	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	675	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.	676	C<ev_default_loop>, in which case it is not thread-safe.
619		677
620	Note that it is not advisable to call this function on the default loop	678	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.	679	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>	680	If you need dynamically allocated loops it is better to use C<ev_loop_new>
623	and C<ev_loop_destroy>.	681	and C<ev_loop_destroy>.
624		682
625	=item ev_loop_fork (loop)	683	=item ev_loop_fork (loop)
626		684
…		…
674	prepare and check phases.	732	prepare and check phases.
675		733
676	=item unsigned int ev_depth (loop)	734	=item unsigned int ev_depth (loop)
677		735
678	Returns the number of times C<ev_run> was entered minus the number of	736	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.	737	times C<ev_run> was exited normally, in other words, the recursion depth.
680		738
681	Outside C<ev_run>, this number is zero. In a callback, this number is	739	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),	740	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
683	in which case it is higher.	741	in which case it is higher.
684		742
685	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread	743	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	744	throwing an exception etc.), doesn't count as "exit" - consider this
687	ungentleman-like behaviour unless it's really convenient.	745	as a hint to avoid such ungentleman-like behaviour unless it's really
		746	convenient, in which case it is fully supported.
688		747
689	=item unsigned int ev_backend (loop)	748	=item unsigned int ev_backend (loop)
690		749
691	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	750	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
692	use.	751	use.
…		…
707		766
708	This function is rarely useful, but when some event callback runs for a	767	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	768	very long time without entering the event loop, updating libev's idea of
710	the current time is a good idea.	769	the current time is a good idea.
711		770
712	See also L<The special problem of time updates> in the C<ev_timer> section.	771	See also L</The special problem of time updates> in the C<ev_timer> section.
713		772
714	=item ev_suspend (loop)	773	=item ev_suspend (loop)
715		774
716	=item ev_resume (loop)	775	=item ev_resume (loop)
717		776
…		…
735	without a previous call to C<ev_suspend>.	794	without a previous call to C<ev_suspend>.
736		795
737	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	796	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
738	event loop time (see C<ev_now_update>).	797	event loop time (see C<ev_now_update>).
739		798
740	=item ev_run (loop, int flags)	799	=item bool ev_run (loop, int flags)
741		800
742	Finally, this is it, the event handler. This function usually is called	801	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	802	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	803	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	804	the watcher callbacks, and then repeat the whole process indefinitely: This
746	is why event loops are called I<loops>.	805	is why event loops are called I<loops>.
747		806
748	If the flags argument is specified as C<0>, it will keep handling events	807	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	808	until either no event watchers are active anymore or C<ev_break> was
750	called.	809	called.
		810
		811	The return value is false if there are no more active watchers (which
		812	usually means "all jobs done" or "deadlock"), and true in all other cases
		813	(which usually means " you should call C<ev_run> again").
751		814
752	Please note that an explicit C<ev_break> is usually better than	815	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	816	relying on all watchers to be stopped when deciding when a program has
754	finished (especially in interactive programs), but having a program	817	finished (especially in interactive programs), but having a program
755	that automatically loops as long as it has to and no longer by virtue	818	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	819	of relying on its watchers stopping correctly, that is truly a thing of
757	beauty.	820	beauty.
758		821
		822	This function is I<mostly> exception-safe - you can break out of a
		823	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		824	exception and so on. This does not decrement the C<ev_depth> value, nor
		825	will it clear any outstanding C<EVBREAK_ONE> breaks.
		826
759	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle	827	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	828	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	829	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	830	iteration of the loop. This is sometimes useful to poll and handle new
763	events while doing lengthy calculations, to keep the program responsive.	831	events while doing lengthy calculations, to keep the program responsive.
…		…
772	This is useful if you are waiting for some external event in conjunction	840	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	841	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	842	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.	843	usually a better approach for this kind of thing.
776		844
777	Here are the gory details of what C<ev_run> does:	845	Here are the gory details of what C<ev_run> does (this is for your
		846	understanding, not a guarantee that things will work exactly like this in
		847	future versions):
778		848
779	- Increment loop depth.	849	- Increment loop depth.
780	- Reset the ev_break status.	850	- Reset the ev_break status.
781	- Before the first iteration, call any pending watchers.	851	- Before the first iteration, call any pending watchers.
782	LOOP:	852	LOOP:
…		…
815	anymore.	885	anymore.
816		886
817	... queue jobs here, make sure they register event watchers as long	887	... 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..)	888	... as they still have work to do (even an idle watcher will do..)
819	ev_run (my_loop, 0);	889	ev_run (my_loop, 0);
820	... jobs done or somebody called unloop. yeah!	890	... jobs done or somebody called break. yeah!
821		891
822	=item ev_break (loop, how)	892	=item ev_break (loop, how)
823		893
824	Can be used to make a call to C<ev_run> return early (but only after it	894	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	895	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	896	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.	897	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
828		898
829	This "break state" will be cleared when entering C<ev_run> again.	899	This "break state" will be cleared on the next call to C<ev_run>.
830		900
831	It is safe to call C<ev_break> from outside any C<ev_run> calls, too.	901	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		902	which case it will have no effect.
832		903
833	=item ev_ref (loop)	904	=item ev_ref (loop)
834		905
835	=item ev_unref (loop)	906	=item ev_unref (loop)
836		907
…		…
857	running when nothing else is active.	928	running when nothing else is active.
858		929
859	ev_signal exitsig;	930	ev_signal exitsig;
860	ev_signal_init (&exitsig, sig_cb, SIGINT);	931	ev_signal_init (&exitsig, sig_cb, SIGINT);
861	ev_signal_start (loop, &exitsig);	932	ev_signal_start (loop, &exitsig);
862	evf_unref (loop);	933	ev_unref (loop);
863		934
864	Example: For some weird reason, unregister the above signal handler again.	935	Example: For some weird reason, unregister the above signal handler again.
865		936
866	ev_ref (loop);	937	ev_ref (loop);
867	ev_signal_stop (loop, &exitsig);	938	ev_signal_stop (loop, &exitsig);
…		…
887	overhead for the actual polling but can deliver many events at once.	958	overhead for the actual polling but can deliver many events at once.
888		959
889	By setting a higher I<io collect interval> you allow libev to spend more	960	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,	961	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	962	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	963	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	964	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	965	sleep time ensures that libev will not poll for I/O events more often then
895	once per this interval, on average.	966	once per this interval, on average (as long as the host time resolution is
		967	good enough).
896		968
897	Likewise, by setting a higher I<timeout collect interval> you allow libev	969	Likewise, by setting a higher I<timeout collect interval> you allow libev
898	to spend more time collecting timeouts, at the expense of increased	970	to spend more time collecting timeouts, at the expense of increased
899	latency/jitter/inexactness (the watcher callback will be called	971	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	972	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.).	1018	invoke the actual watchers inside another context (another thread etc.).
947		1019
948	If you want to reset the callback, use C<ev_invoke_pending> as new	1020	If you want to reset the callback, use C<ev_invoke_pending> as new
949	callback.	1021	callback.
950		1022
951	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))	1023	=item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())
952		1024
953	Sometimes you want to share the same loop between multiple threads. This	1025	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	1026	can be done relatively simply by putting mutex_lock/unlock calls around
955	each call to a libev function.	1027	each call to a libev function.
956		1028
957	However, C<ev_run> can run an indefinite time, so it is not feasible	1029	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	1030	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	1031	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.	1032	I<release> and I<acquire> callbacks on the loop.
961		1033
962	When set, then C<release> will be called just before the thread is	1034	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	1035	suspended waiting for new events, and C<acquire> is called just
964	afterwards.	1036	afterwards.
…		…
979	See also the locking example in the C<THREADS> section later in this	1051	See also the locking example in the C<THREADS> section later in this
980	document.	1052	document.
981		1053
982	=item ev_set_userdata (loop, void *data)	1054	=item ev_set_userdata (loop, void *data)
983		1055
984	=item ev_userdata (loop)	1056	=item void *ev_userdata (loop)
985		1057
986	Set and retrieve a single C<void *> associated with a loop. When	1058	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	1059	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
988	C<0.>	1060	C<0>.
989		1061
990	These two functions can be used to associate arbitrary data with a loop,	1062	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	1063	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	1064	C<acquire> callbacks described above, but of course can be (ab-)used for
993	any other purpose as well.	1065	any other purpose as well.
…		…
1104		1176
1105	=item C<EV_PREPARE>	1177	=item C<EV_PREPARE>
1106		1178
1107	=item C<EV_CHECK>	1179	=item C<EV_CHECK>
1108		1180
1109	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts	1181	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	1182	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	1183	just after C<ev_run> has gathered them, but before it queues any callbacks
		1184	for any received events. That means C<ev_prepare> watchers are the last
		1185	watchers invoked before the event loop sleeps or polls for new events, and
		1186	C<ev_check> watchers will be invoked before any other watchers of the same
		1187	or lower priority within an event loop iteration.
		1188
1112	received events. Callbacks of both watcher types can start and stop as	1189	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	1190	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	1191	C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from
1115	C<ev_run> from blocking).	1192	blocking).
1116		1193
1117	=item C<EV_EMBED>	1194	=item C<EV_EMBED>
1118		1195
1119	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1196	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1120		1197
…		…
1243		1320
1244	=item callback ev_cb (ev_TYPE *watcher)	1321	=item callback ev_cb (ev_TYPE *watcher)
1245		1322
1246	Returns the callback currently set on the watcher.	1323	Returns the callback currently set on the watcher.
1247		1324
1248	=item ev_cb_set (ev_TYPE *watcher, callback)	1325	=item ev_set_cb (ev_TYPE *watcher, callback)
1249		1326
1250	Change the callback. You can change the callback at virtually any time	1327	Change the callback. You can change the callback at virtually any time
1251	(modulo threads).	1328	(modulo threads).
1252		1329
1253	=item ev_set_priority (ev_TYPE *watcher, int priority)	1330	=item ev_set_priority (ev_TYPE *watcher, int priority)
…		…
1271	or might not have been clamped to the valid range.	1348	or might not have been clamped to the valid range.
1272		1349
1273	The default priority used by watchers when no priority has been set is	1350	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 :).	1351	always C<0>, which is supposed to not be too high and not be too low :).
1275		1352
1276	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of	1353	See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1277	priorities.	1354	priorities.
1278		1355
1279	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1356	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1280		1357
1281	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1358	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	1383	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1307	functions that do not need a watcher.	1384	functions that do not need a watcher.
1308		1385
1309	=back	1386	=back
1310		1387
1311	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1388	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
1312		1389	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		1390
1376	=head2 WATCHER STATES	1391	=head2 WATCHER STATES
1377		1392
1378	There are various watcher states mentioned throughout this manual -	1393	There are various watcher states mentioned throughout this manual -
1379	active, pending and so on. In this section these states and the rules to	1394	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	1395	transition between them will be described in more detail - and while these
1381	rules might look complicated, they usually do "the right thing".	1396	rules might look complicated, they usually do "the right thing".
1382		1397
1383	=over 4	1398	=over 4
1384		1399
1385	=item initialiased	1400	=item initialised
1386		1401
1387	Before a watcher can be registered with the event looop it has to be	1402	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	1403	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.	1404	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1390		1405
1391	In this state it is simply some block of memory that is suitable for use	1406	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.	1407	use in an event loop. It can be moved around, freed, reused etc. at
		1408	will - as long as you either keep the memory contents intact, or call
		1409	C<ev_TYPE_init> again.
1393		1410
1394	=item started/running/active	1411	=item started/running/active
1395		1412
1396	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes	1413	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	1414	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	1442	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	1443	of whether it was active or not, so stopping a watcher explicitly before
1427	freeing it is often a good idea.	1444	freeing it is often a good idea.
1428		1445
1429	While stopped (and not pending) the watcher is essentially in the	1446	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	1447	initialised state, that is, it can be reused, moved, modified in any way
1431	you wish.	1448	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1449	it again).
1432		1450
1433	=back	1451	=back
1434		1452
1435	=head2 WATCHER PRIORITY MODELS	1453	=head2 WATCHER PRIORITY MODELS
1436		1454
…		…
1565	In general you can register as many read and/or write event watchers per	1583	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	1584	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	1585	descriptors to non-blocking mode is also usually a good idea (but not
1568	required if you know what you are doing).	1586	required if you know what you are doing).
1569		1587
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	1588	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	1589	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	1590	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	1591	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	1592	with a relatively standard program structure. Thus it is best to always
1581	this situation even with a relatively standard program structure. Thus	1593	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.	1594	preferable to a program hanging until some data arrives.
1584		1595
1585	If you cannot run the fd in non-blocking mode (for example you should	1596	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	1597	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	1598	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	1599	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	1600	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	1601	use C<SIGALRM> and an interval timer, just to be sure you won't block
1591	indefinitely.	1602	indefinitely.
1592		1603
1593	But really, best use non-blocking mode.	1604	But really, best use non-blocking mode.
1594		1605
…		…
1622		1633
1623	There is no workaround possible except not registering events	1634	There is no workaround possible except not registering events
1624	for potentially C<dup ()>'ed file descriptors, or to resort to	1635	for potentially C<dup ()>'ed file descriptors, or to resort to
1625	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1636	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1626		1637
		1638	=head3 The special problem of files
		1639
		1640	Many people try to use C<select> (or libev) on file descriptors
		1641	representing files, and expect it to become ready when their program
		1642	doesn't block on disk accesses (which can take a long time on their own).
		1643
		1644	However, this cannot ever work in the "expected" way - you get a readiness
		1645	notification as soon as the kernel knows whether and how much data is
		1646	there, and in the case of open files, that's always the case, so you
		1647	always get a readiness notification instantly, and your read (or possibly
		1648	write) will still block on the disk I/O.
		1649
		1650	Another way to view it is that in the case of sockets, pipes, character
		1651	devices and so on, there is another party (the sender) that delivers data
		1652	on its own, but in the case of files, there is no such thing: the disk
		1653	will not send data on its own, simply because it doesn't know what you
		1654	wish to read - you would first have to request some data.
		1655
		1656	Since files are typically not-so-well supported by advanced notification
		1657	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1658	to files, even though you should not use it. The reason for this is
		1659	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1660	usually a tty, often a pipe, but also sometimes files or special devices
		1661	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1662	F</dev/urandom>), and even though the file might better be served with
		1663	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1664	it "just works" instead of freezing.
		1665
		1666	So avoid file descriptors pointing to files when you know it (e.g. use
		1667	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1668	when you rarely read from a file instead of from a socket, and want to
		1669	reuse the same code path.
		1670
1627	=head3 The special problem of fork	1671	=head3 The special problem of fork
1628		1672
1629	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1673	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	1674	useless behaviour. Libev fully supports fork, but needs to be told about
1631	it in the child.	1675	it in the child if you want to continue to use it in the child.
1632		1676
1633	To support fork in your programs, you either have to call	1677	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,	1678	()> 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	1679	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1636	C<EVBACKEND_POLL>.
1637		1680
1638	=head3 The special problem of SIGPIPE	1681	=head3 The special problem of SIGPIPE
1639		1682
1640	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1683	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	1684	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	1782	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1740	monotonic clock option helps a lot here).	1783	monotonic clock option helps a lot here).
1741		1784
1742	The callback is guaranteed to be invoked only I<after> its timeout has	1785	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	1786	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	1787	might introduce a small delay, see "the special problem of being too
		1788	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	1789	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	1790	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).	1791	longer true when a callback calls C<ev_run> recursively).
1748		1792
1749	=head3 Be smart about timeouts	1793	=head3 Be smart about timeouts
1750		1794
1751	Many real-world problems involve some kind of timeout, usually for error	1795	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,	1796	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1827		1871
1828	In this case, it would be more efficient to leave the C<ev_timer> alone,	1872	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	1873	but remember the time of last activity, and check for a real timeout only
1830	within the callback:	1874	within the callback:
1831		1875
		1876	ev_tstamp timeout = 60.;
1832	ev_tstamp last_activity; // time of last activity	1877	ev_tstamp last_activity; // time of last activity
		1878	ev_timer timer;
1833		1879
1834	static void	1880	static void
1835	callback (EV_P_ ev_timer *w, int revents)	1881	callback (EV_P_ ev_timer *w, int revents)
1836	{	1882	{
1837	ev_tstamp now = ev_now (EV_A);	1883	// calculate when the timeout would happen
1838	ev_tstamp timeout = last_activity + 60.;	1884	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1839		1885
1840	// if last_activity + 60. is older than now, we did time out	1886	// if negative, it means we the timeout already occurred
1841	if (timeout < now)	1887	if (after < 0.)
1842	{	1888	{
1843	// timeout occurred, take action	1889	// timeout occurred, take action
1844	}	1890	}
1845	else	1891	else
1846	{	1892	{
1847	// callback was invoked, but there was some activity, re-arm	1893	// callback was invoked, but there was some recent
1848	// the watcher to fire in last_activity + 60, which is	1894	// activity. simply restart the timer to time out
1849	// guaranteed to be in the future, so "again" is positive:	1895	// after "after" seconds, which is the earliest time
1850	w->repeat = timeout - now;	1896	// the timeout can occur.
		1897	ev_timer_set (w, after, 0.);
1851	ev_timer_again (EV_A_ w);	1898	ev_timer_start (EV_A_ w);
1852	}	1899	}
1853	}	1900	}
1854		1901
1855	To summarise the callback: first calculate the real timeout (defined	1902	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	1903	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	1904	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	1905	(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		1906
1862	Note how C<ev_timer_again> is used, taking advantage of the	1907	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.	1908	timed out, and need to do whatever is needed in this case.
		1909
		1910	Otherwise, we now the earliest time at which the timeout would trigger,
		1911	and simply start the timer with this timeout value.
		1912
		1913	In other words, each time the callback is invoked it will check whether
		1914	the timeout occurred. If not, it will simply reschedule itself to check
		1915	again at the earliest time it could time out. Rinse. Repeat.
1864		1916
1865	This scheme causes more callback invocations (about one every 60 seconds	1917	This scheme causes more callback invocations (about one every 60 seconds
1866	minus half the average time between activity), but virtually no calls to	1918	minus half the average time between activity), but virtually no calls to
1867	libev to change the timeout.	1919	libev to change the timeout.
1868		1920
1869	To start the timer, simply initialise the watcher and set C<last_activity>	1921	To start the machinery, simply initialise the watcher and set
1870	to the current time (meaning we just have some activity :), then call the	1922	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:	1923	now), then call the callback, which will "do the right thing" and start
		1924	the timer:
1872		1925
		1926	last_activity = ev_now (EV_A);
1873	ev_init (timer, callback);	1927	ev_init (&timer, callback);
1874	last_activity = ev_now (loop);	1928	callback (EV_A_ &timer, 0);
1875	callback (loop, timer, EV_TIMER);
1876		1929
1877	And when there is some activity, simply store the current time in	1930	When there is some activity, simply store the current time in
1878	C<last_activity>, no libev calls at all:	1931	C<last_activity>, no libev calls at all:
1879		1932
		1933	if (activity detected)
1880	last_activity = ev_now (loop);	1934	last_activity = ev_now (EV_A);
		1935
		1936	When your timeout value changes, then the timeout can be changed by simply
		1937	providing a new value, stopping the timer and calling the callback, which
		1938	will again do the right thing (for example, time out immediately :).
		1939
		1940	timeout = new_value;
		1941	ev_timer_stop (EV_A_ &timer);
		1942	callback (EV_A_ &timer, 0);
1881		1943
1882	This technique is slightly more complex, but in most cases where the	1944	This technique is slightly more complex, but in most cases where the
1883	time-out is unlikely to be triggered, much more efficient.	1945	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		1946
1889	=item 4. Wee, just use a double-linked list for your timeouts.	1947	=item 4. Wee, just use a double-linked list for your timeouts.
1890		1948
1891	If there is not one request, but many thousands (millions...), all	1949	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	1950	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	1977	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	1978	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	1979	off after the first million or so of active timers, i.e. it's usually
1922	overkill :)	1980	overkill :)
1923		1981
		1982	=head3 The special problem of being too early
		1983
		1984	If you ask a timer to call your callback after three seconds, then
		1985	you expect it to be invoked after three seconds - but of course, this
		1986	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		1987	guaranteed to any precision by libev - imagine somebody suspending the
		1988	process with a STOP signal for a few hours for example.
		1989
		1990	So, libev tries to invoke your callback as soon as possible I<after> the
		1991	delay has occurred, but cannot guarantee this.
		1992
		1993	A less obvious failure mode is calling your callback too early: many event
		1994	loops compare timestamps with a "elapsed delay >= requested delay", but
		1995	this can cause your callback to be invoked much earlier than you would
		1996	expect.
		1997
		1998	To see why, imagine a system with a clock that only offers full second
		1999	resolution (think windows if you can't come up with a broken enough OS
		2000	yourself). If you schedule a one-second timer at the time 500.9, then the
		2001	event loop will schedule your timeout to elapse at a system time of 500
		2002	(500.9 truncated to the resolution) + 1, or 501.
		2003
		2004	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2005	501" and invoke the callback 0.1s after it was started, even though a
		2006	one-second delay was requested - this is being "too early", despite best
		2007	intentions.
		2008
		2009	This is the reason why libev will never invoke the callback if the elapsed
		2010	delay equals the requested delay, but only when the elapsed delay is
		2011	larger than the requested delay. In the example above, libev would only invoke
		2012	the callback at system time 502, or 1.1s after the timer was started.
		2013
		2014	So, while libev cannot guarantee that your callback will be invoked
		2015	exactly when requested, it I<can> and I<does> guarantee that the requested
		2016	delay has actually elapsed, or in other words, it always errs on the "too
		2017	late" side of things.
		2018
1924	=head3 The special problem of time updates	2019	=head3 The special problem of time updates
1925		2020
1926	Establishing the current time is a costly operation (it usually takes at	2021	Establishing the current time is a costly operation (it usually takes
1927	least two system calls): EV therefore updates its idea of the current	2022	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	2023	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	2024	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1930	lots of events in one iteration.	2025	lots of events in one iteration.
1931		2026
1932	The relative timeouts are calculated relative to the C<ev_now ()>	2027	The relative timeouts are calculated relative to the C<ev_now ()>
…		…
1938	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2033	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1939		2034
1940	If the event loop is suspended for a long time, you can also force an	2035	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	2036	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1942	()>.	2037	()>.
		2038
		2039	=head3 The special problem of unsynchronised clocks
		2040
		2041	Modern systems have a variety of clocks - libev itself uses the normal
		2042	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2043	jumps).
		2044
		2045	Neither of these clocks is synchronised with each other or any other clock
		2046	on the system, so C<ev_time ()> might return a considerably different time
		2047	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2048	a call to C<gettimeofday> might return a second count that is one higher
		2049	than a directly following call to C<time>.
		2050
		2051	The moral of this is to only compare libev-related timestamps with
		2052	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2053	a second or so.
		2054
		2055	One more problem arises due to this lack of synchronisation: if libev uses
		2056	the system monotonic clock and you compare timestamps from C<ev_time>
		2057	or C<ev_now> from when you started your timer and when your callback is
		2058	invoked, you will find that sometimes the callback is a bit "early".
		2059
		2060	This is because C<ev_timer>s work in real time, not wall clock time, so
		2061	libev makes sure your callback is not invoked before the delay happened,
		2062	I<measured according to the real time>, not the system clock.
		2063
		2064	If your timeouts are based on a physical timescale (e.g. "time out this
		2065	connection after 100 seconds") then this shouldn't bother you as it is
		2066	exactly the right behaviour.
		2067
		2068	If you want to compare wall clock/system timestamps to your timers, then
		2069	you need to use C<ev_periodic>s, as these are based on the wall clock
		2070	time, where your comparisons will always generate correct results.
1943		2071
1944	=head3 The special problems of suspended animation	2072	=head3 The special problems of suspended animation
1945		2073
1946	When you leave the server world it is quite customary to hit machines that	2074	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?	2075	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	2119	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.	2120	do stuff) the timer will not fire more than once per event loop iteration.
1993		2121
1994	=item ev_timer_again (loop, ev_timer *)	2122	=item ev_timer_again (loop, ev_timer *)
1995		2123
1996	This will act as if the timer timed out and restart it again if it is	2124	This will act as if the timer timed out, and restarts it again if it is
1997	repeating. The exact semantics are:	2125	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2126	timeout to the C<repeat> value and calling C<ev_timer_start>.
1998		2127
		2128	The exact semantics are as in the following rules, all of which will be
		2129	applied to the watcher:
		2130
		2131	=over 4
		2132
1999	If the timer is pending, its pending status is cleared.	2133	=item If the timer is pending, the pending status is always cleared.
2000		2134
2001	If the timer is started but non-repeating, stop it (as if it timed out).	2135	=item If the timer is started but non-repeating, stop it (as if it timed
		2136	out, without invoking it).
2002		2137
2003	If the timer is repeating, either start it if necessary (with the	2138	=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.	2139	and start the timer, if necessary.
2005		2140
		2141	=back
		2142
2006	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2143	This sounds a bit complicated, see L</Be smart about timeouts>, above, for a
2007	usage example.	2144	usage example.
2008		2145
2009	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)	2146	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
2010		2147
2011	Returns the remaining time until a timer fires. If the timer is active,	2148	Returns the remaining time until a timer fires. If the timer is active,
…		…
2131		2268
2132	Another way to think about it (for the mathematically inclined) is that	2269	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	2270	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.	2271	time where C<time = offset (mod interval)>, regardless of any time jumps.
2135		2272
2136	For numerical stability it is preferable that the C<offset> value is near	2273	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	2274	interval value should be higher than C<1/8192> (which is around 100
2138	this value, and in fact is often specified as zero.	2275	microseconds) and C<offset> should be higher than C<0> and should have
		2276	at most a similar magnitude as the current time (say, within a factor of
		2277	ten). Typical values for offset are, in fact, C<0> or something between
		2278	C<0> and C<interval>, which is also the recommended range.
2139		2279
2140	Note also that there is an upper limit to how often a timer can fire (CPU	2280	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	2281	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	2282	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).	2283	millisecond (if the OS supports it and the machine is fast enough).
…		…
2257		2397
2258	=head2 C<ev_signal> - signal me when a signal gets signalled!	2398	=head2 C<ev_signal> - signal me when a signal gets signalled!
2259		2399
2260	Signal watchers will trigger an event when the process receives a specific	2400	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	2401	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	2402	will try its best to deliver signals synchronously, i.e. as part of the
2263	normal event processing, like any other event.	2403	normal event processing, like any other event.
2264		2404
2265	If you want signals to be delivered truly asynchronously, just use	2405	If you want signals to be delivered truly asynchronously, just use
2266	C<sigaction> as you would do without libev and forget about sharing	2406	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	2407	the signal. You can even use C<ev_async> from a signal handler to
…		…
2286	=head3 The special problem of inheritance over fork/execve/pthread_create	2426	=head3 The special problem of inheritance over fork/execve/pthread_create
2287		2427
2288	Both the signal mask (C<sigprocmask>) and the signal disposition	2428	Both the signal mask (C<sigprocmask>) and the signal disposition
2289	(C<sigaction>) are unspecified after starting a signal watcher (and after	2429	(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,	2430	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.	2431	and might or might not set or restore the installed signal handler (but
		2432	see C<EVFLAG_NOSIGMASK>).
2292		2433
2293	While this does not matter for the signal disposition (libev never	2434	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	2435	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	2436	C<execve>), this matters for the signal mask: many programs do not expect
2296	certain signals to be blocked.	2437	certain signals to be blocked.
…		…
2309	I<has> to modify the signal mask, at least temporarily.	2450	I<has> to modify the signal mask, at least temporarily.
2310		2451
2311	So I can't stress this enough: I<If you do not reset your signal mask when	2452	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	2453	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.	2454	is not a libev-specific thing, this is true for most event libraries.
		2455
		2456	=head3 The special problem of threads signal handling
		2457
		2458	POSIX threads has problematic signal handling semantics, specifically,
		2459	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2460	threads in a process block signals, which is hard to achieve.
		2461
		2462	When you want to use sigwait (or mix libev signal handling with your own
		2463	for the same signals), you can tackle this problem by globally blocking
		2464	all signals before creating any threads (or creating them with a fully set
		2465	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2466	loops. Then designate one thread as "signal receiver thread" which handles
		2467	these signals. You can pass on any signals that libev might be interested
		2468	in by calling C<ev_feed_signal>.
2314		2469
2315	=head3 Watcher-Specific Functions and Data Members	2470	=head3 Watcher-Specific Functions and Data Members
2316		2471
2317	=over 4	2472	=over 4
2318		2473
…		…
2453		2608
2454	=head2 C<ev_stat> - did the file attributes just change?	2609	=head2 C<ev_stat> - did the file attributes just change?
2455		2610
2456	This watches a file system path for attribute changes. That is, it calls	2611	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)	2612	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	2613	and sees if it changed compared to the last time, invoking the callback
2459	it did.	2614	if it did. Starting the watcher C<stat>'s the file, so only changes that
		2615	happen after the watcher has been started will be reported.
2460		2616
2461	The path does not need to exist: changing from "path exists" to "path does	2617	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	2618	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	2619	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	2620	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	2850	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	2851	effect on its own sometimes), idle watchers are a good place to do
2696	"pseudo-background processing", or delay processing stuff to after the	2852	"pseudo-background processing", or delay processing stuff to after the
2697	event loop has handled all outstanding events.	2853	event loop has handled all outstanding events.
2698		2854
		2855	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2856
		2857	As long as there is at least one active idle watcher, libev will never
		2858	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2859	For this to work, the idle watcher doesn't need to be invoked at all - the
		2860	lowest priority will do.
		2861
		2862	This mode of operation can be useful together with an C<ev_check> watcher,
		2863	to do something on each event loop iteration - for example to balance load
		2864	between different connections.
		2865
		2866	See L</Abusing an ev_check watcher for its side-effect> for a longer
		2867	example.
		2868
2699	=head3 Watcher-Specific Functions and Data Members	2869	=head3 Watcher-Specific Functions and Data Members
2700		2870
2701	=over 4	2871	=over 4
2702		2872
2703	=item ev_idle_init (ev_idle *, callback)	2873	=item ev_idle_init (ev_idle *, callback)
…		…
2714	callback, free it. Also, use no error checking, as usual.	2884	callback, free it. Also, use no error checking, as usual.
2715		2885
2716	static void	2886	static void
2717	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	2887	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2718	{	2888	{
		2889	// stop the watcher
		2890	ev_idle_stop (loop, w);
		2891
		2892	// now we can free it
2719	free (w);	2893	free (w);
		2894
2720	// now do something you wanted to do when the program has	2895	// now do something you wanted to do when the program has
2721	// no longer anything immediate to do.	2896	// no longer anything immediate to do.
2722	}	2897	}
2723		2898
2724	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2899	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
…		…
2726	ev_idle_start (loop, idle_watcher);	2901	ev_idle_start (loop, idle_watcher);
2727		2902
2728		2903
2729	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2904	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2730		2905
2731	Prepare and check watchers are usually (but not always) used in pairs:	2906	Prepare and check watchers are often (but not always) used in pairs:
2732	prepare watchers get invoked before the process blocks and check watchers	2907	prepare watchers get invoked before the process blocks and check watchers
2733	afterwards.	2908	afterwards.
2734		2909
2735	You I<must not> call C<ev_run> or similar functions that enter	2910	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>	2911	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	2939	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	2940	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	2941	loop from blocking if lower-priority coroutines are active, thus mapping
2767	low-priority coroutines to idle/background tasks).	2942	low-priority coroutines to idle/background tasks).
2768		2943
2769	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2944	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	2945	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).	2946	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		2947	watchers).
2772		2948
2773	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	2949	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	2950	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	2951	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	2952	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	2953	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	2954	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2779	others).	2955	others).
		2956
		2957	=head3 Abusing an C<ev_check> watcher for its side-effect
		2958
		2959	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		2960	useful because they are called once per event loop iteration. For
		2961	example, if you want to handle a large number of connections fairly, you
		2962	normally only do a bit of work for each active connection, and if there
		2963	is more work to do, you wait for the next event loop iteration, so other
		2964	connections have a chance of making progress.
		2965
		2966	Using an C<ev_check> watcher is almost enough: it will be called on the
		2967	next event loop iteration. However, that isn't as soon as possible -
		2968	without external events, your C<ev_check> watcher will not be invoked.
		2969
		2970	This is where C<ev_idle> watchers come in handy - all you need is a
		2971	single global idle watcher that is active as long as you have one active
		2972	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		2973	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		2974	invoked. Neither watcher alone can do that.
2780		2975
2781	=head3 Watcher-Specific Functions and Data Members	2976	=head3 Watcher-Specific Functions and Data Members
2782		2977
2783	=over 4	2978	=over 4
2784		2979
…		…
2985		3180
2986	=over 4	3181	=over 4
2987		3182
2988	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	3183	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
2989		3184
2990	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	3185	=item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)
2991		3186
2992	Configures the watcher to embed the given loop, which must be	3187	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	3188	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	3189	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,	3190	to invoke it (it will continue to be called until the sweep has been done,
…		…
3058		3253
3059	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3254	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
3060		3255
3061	Fork watchers are called when a C<fork ()> was detected (usually because	3256	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	3257	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	3258	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,	3259	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	3260	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	3261	and calls it in the wrong process, the fork handlers will be invoked, too,
3067	handlers will be invoked, too, of course.	3262	of course.
3068		3263
3069	=head3 The special problem of life after fork - how is it possible?	3264	=head3 The special problem of life after fork - how is it possible?
3070		3265
3071	Most uses of C<fork()> consist of forking, then some simple calls to set	3266	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	3267	up/change the process environment, followed by a call to C<exec()>. This
…		…
3153	atexit (program_exits);	3348	atexit (program_exits);
3154		3349
3155		3350
3156	=head2 C<ev_async> - how to wake up an event loop	3351	=head2 C<ev_async> - how to wake up an event loop
3157		3352
3158	In general, you cannot use an C<ev_run> from multiple threads or other	3353	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	3354	asynchronous sources such as signal handlers (as opposed to multiple event
3160	loops - those are of course safe to use in different threads).	3355	loops - those are of course safe to use in different threads).
3161		3356
3162	Sometimes, however, you need to wake up an event loop you do not control,	3357	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>	3358	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.	3360	it by calling C<ev_async_send>, which is thread- and signal safe.
3166		3361
3167	This functionality is very similar to C<ev_signal> watchers, as signals,	3362	This functionality is very similar to C<ev_signal> watchers, as signals,
3168	too, are asynchronous in nature, and signals, too, will be compressed	3363	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	3364	(i.e. the number of callback invocations may be less than the number of
3170	C<ev_async_sent> calls).	3365	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
3171		3366	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	3367	signal, and C<ev_feed_signal> to signal this watcher from another thread,
3173	just the default loop.	3368	even without knowing which loop owns the signal.
3174		3369
3175	=head3 Queueing	3370	=head3 Queueing
3176		3371
3177	C<ev_async> does not support queueing of data in any way. The reason	3372	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	3373	is that the author does not know of a simple (or any) algorithm for a
…		…
3270	trust me.	3465	trust me.
3271		3466
3272	=item ev_async_send (loop, ev_async *)	3467	=item ev_async_send (loop, ev_async *)
3273		3468
3274	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3469	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	3470	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3471	returns.
		3472
3276	C<ev_feed_event>, this call is safe to do from other threads, signal or	3473	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	3474	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3278	section below on what exactly this means).	3475	embedding section below on what exactly this means).
3279		3476
3280	Note that, as with other watchers in libev, multiple events might get	3477	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	3478	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>,	3479	this is that C<ev_async> watchers are level-triggered: they are set on
3283	reset when the event loop detects that).	3480	C<ev_async_send>, reset when the event loop detects that).
3284		3481
3285	This call incurs the overhead of a system call only once per event loop	3482	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	3483	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.	3484	the event loop (or your program) is processing events. That means that
		3485	repeated calls are basically free (there is no need to avoid calls for
		3486	performance reasons) and that the overhead becomes smaller (typically
		3487	zero) under load.
3288		3488
3289	=item bool = ev_async_pending (ev_async *)	3489	=item bool = ev_async_pending (ev_async *)
3290		3490
3291	Returns a non-zero value when C<ev_async_send> has been called on the	3491	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	3492	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);	3547	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3348		3548
3349	=item ev_feed_fd_event (loop, int fd, int revents)	3549	=item ev_feed_fd_event (loop, int fd, int revents)
3350		3550
3351	Feed an event on the given fd, as if a file descriptor backend detected	3551	Feed an event on the given fd, as if a file descriptor backend detected
3352	the given events it.	3552	the given events.
3353		3553
3354	=item ev_feed_signal_event (loop, int signum)	3554	=item ev_feed_signal_event (loop, int signum)
3355		3555
3356	Feed an event as if the given signal occurred (C<loop> must be the default	3556	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3357	loop!).	3557	which is async-safe.
3358		3558
3359	=back	3559	=back
		3560
		3561
		3562	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3563
		3564	This section explains some common idioms that are not immediately
		3565	obvious. Note that examples are sprinkled over the whole manual, and this
		3566	section only contains stuff that wouldn't fit anywhere else.
		3567
		3568	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3569
		3570	Each watcher has, by default, a C<void *data> member that you can read
		3571	or modify at any time: libev will completely ignore it. This can be used
		3572	to associate arbitrary data with your watcher. If you need more data and
		3573	don't want to allocate memory separately and store a pointer to it in that
		3574	data member, you can also "subclass" the watcher type and provide your own
		3575	data:
		3576
		3577	struct my_io
		3578	{
		3579	ev_io io;
		3580	int otherfd;
		3581	void *somedata;
		3582	struct whatever *mostinteresting;
		3583	};
		3584
		3585	...
		3586	struct my_io w;
		3587	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3588
		3589	And since your callback will be called with a pointer to the watcher, you
		3590	can cast it back to your own type:
		3591
		3592	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3593	{
		3594	struct my_io *w = (struct my_io *)w_;
		3595	...
		3596	}
		3597
		3598	More interesting and less C-conformant ways of casting your callback
		3599	function type instead have been omitted.
		3600
		3601	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3602
		3603	Another common scenario is to use some data structure with multiple
		3604	embedded watchers, in effect creating your own watcher that combines
		3605	multiple libev event sources into one "super-watcher":
		3606
		3607	struct my_biggy
		3608	{
		3609	int some_data;
		3610	ev_timer t1;
		3611	ev_timer t2;
		3612	}
		3613
		3614	In this case getting the pointer to C<my_biggy> is a bit more
		3615	complicated: Either you store the address of your C<my_biggy> struct in
		3616	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3617	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3618	real programmers):
		3619
		3620	#include <stddef.h>
		3621
		3622	static void
		3623	t1_cb (EV_P_ ev_timer *w, int revents)
		3624	{
		3625	struct my_biggy big = (struct my_biggy *)
		3626	(((char *)w) - offsetof (struct my_biggy, t1));
		3627	}
		3628
		3629	static void
		3630	t2_cb (EV_P_ ev_timer *w, int revents)
		3631	{
		3632	struct my_biggy big = (struct my_biggy *)
		3633	(((char *)w) - offsetof (struct my_biggy, t2));
		3634	}
		3635
		3636	=head2 AVOIDING FINISHING BEFORE RETURNING
		3637
		3638	Often you have structures like this in event-based programs:
		3639
		3640	callback ()
		3641	{
		3642	free (request);
		3643	}
		3644
		3645	request = start_new_request (..., callback);
		3646
		3647	The intent is to start some "lengthy" operation. The C<request> could be
		3648	used to cancel the operation, or do other things with it.
		3649
		3650	It's not uncommon to have code paths in C<start_new_request> that
		3651	immediately invoke the callback, for example, to report errors. Or you add
		3652	some caching layer that finds that it can skip the lengthy aspects of the
		3653	operation and simply invoke the callback with the result.
		3654
		3655	The problem here is that this will happen I<before> C<start_new_request>
		3656	has returned, so C<request> is not set.
		3657
		3658	Even if you pass the request by some safer means to the callback, you
		3659	might want to do something to the request after starting it, such as
		3660	canceling it, which probably isn't working so well when the callback has
		3661	already been invoked.
		3662
		3663	A common way around all these issues is to make sure that
		3664	C<start_new_request> I<always> returns before the callback is invoked. If
		3665	C<start_new_request> immediately knows the result, it can artificially
		3666	delay invoking the callback by using a C<prepare> or C<idle> watcher for
		3667	example, or more sneakily, by reusing an existing (stopped) watcher and
		3668	pushing it into the pending queue:
		3669
		3670	ev_set_cb (watcher, callback);
		3671	ev_feed_event (EV_A_ watcher, 0);
		3672
		3673	This way, C<start_new_request> can safely return before the callback is
		3674	invoked, while not delaying callback invocation too much.
		3675
		3676	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3677
		3678	Often (especially in GUI toolkits) there are places where you have
		3679	I<modal> interaction, which is most easily implemented by recursively
		3680	invoking C<ev_run>.
		3681
		3682	This brings the problem of exiting - a callback might want to finish the
		3683	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3684	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3685	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3686	other combination: In these cases, a simple C<ev_break> will not work.
		3687
		3688	The solution is to maintain "break this loop" variable for each C<ev_run>
		3689	invocation, and use a loop around C<ev_run> until the condition is
		3690	triggered, using C<EVRUN_ONCE>:
		3691
		3692	// main loop
		3693	int exit_main_loop = 0;
		3694
		3695	while (!exit_main_loop)
		3696	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3697
		3698	// in a modal watcher
		3699	int exit_nested_loop = 0;
		3700
		3701	while (!exit_nested_loop)
		3702	ev_run (EV_A_ EVRUN_ONCE);
		3703
		3704	To exit from any of these loops, just set the corresponding exit variable:
		3705
		3706	// exit modal loop
		3707	exit_nested_loop = 1;
		3708
		3709	// exit main program, after modal loop is finished
		3710	exit_main_loop = 1;
		3711
		3712	// exit both
		3713	exit_main_loop = exit_nested_loop = 1;
		3714
		3715	=head2 THREAD LOCKING EXAMPLE
		3716
		3717	Here is a fictitious example of how to run an event loop in a different
		3718	thread from where callbacks are being invoked and watchers are
		3719	created/added/removed.
		3720
		3721	For a real-world example, see the C<EV::Loop::Async> perl module,
		3722	which uses exactly this technique (which is suited for many high-level
		3723	languages).
		3724
		3725	The example uses a pthread mutex to protect the loop data, a condition
		3726	variable to wait for callback invocations, an async watcher to notify the
		3727	event loop thread and an unspecified mechanism to wake up the main thread.
		3728
		3729	First, you need to associate some data with the event loop:
		3730
		3731	typedef struct {
		3732	mutex_t lock; /* global loop lock */
		3733	ev_async async_w;
		3734	thread_t tid;
		3735	cond_t invoke_cv;
		3736	} userdata;
		3737
		3738	void prepare_loop (EV_P)
		3739	{
		3740	// for simplicity, we use a static userdata struct.
		3741	static userdata u;
		3742
		3743	ev_async_init (&u->async_w, async_cb);
		3744	ev_async_start (EV_A_ &u->async_w);
		3745
		3746	pthread_mutex_init (&u->lock, 0);
		3747	pthread_cond_init (&u->invoke_cv, 0);
		3748
		3749	// now associate this with the loop
		3750	ev_set_userdata (EV_A_ u);
		3751	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3752	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3753
		3754	// then create the thread running ev_run
		3755	pthread_create (&u->tid, 0, l_run, EV_A);
		3756	}
		3757
		3758	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3759	solely to wake up the event loop so it takes notice of any new watchers
		3760	that might have been added:
		3761
		3762	static void
		3763	async_cb (EV_P_ ev_async *w, int revents)
		3764	{
		3765	// just used for the side effects
		3766	}
		3767
		3768	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3769	protecting the loop data, respectively.
		3770
		3771	static void
		3772	l_release (EV_P)
		3773	{
		3774	userdata *u = ev_userdata (EV_A);
		3775	pthread_mutex_unlock (&u->lock);
		3776	}
		3777
		3778	static void
		3779	l_acquire (EV_P)
		3780	{
		3781	userdata *u = ev_userdata (EV_A);
		3782	pthread_mutex_lock (&u->lock);
		3783	}
		3784
		3785	The event loop thread first acquires the mutex, and then jumps straight
		3786	into C<ev_run>:
		3787
		3788	void *
		3789	l_run (void *thr_arg)
		3790	{
		3791	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3792
		3793	l_acquire (EV_A);
		3794	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3795	ev_run (EV_A_ 0);
		3796	l_release (EV_A);
		3797
		3798	return 0;
		3799	}
		3800
		3801	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3802	signal the main thread via some unspecified mechanism (signals? pipe
		3803	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3804	have been called (in a while loop because a) spurious wakeups are possible
		3805	and b) skipping inter-thread-communication when there are no pending
		3806	watchers is very beneficial):
		3807
		3808	static void
		3809	l_invoke (EV_P)
		3810	{
		3811	userdata *u = ev_userdata (EV_A);
		3812
		3813	while (ev_pending_count (EV_A))
		3814	{
		3815	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3816	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3817	}
		3818	}
		3819
		3820	Now, whenever the main thread gets told to invoke pending watchers, it
		3821	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3822	thread to continue:
		3823
		3824	static void
		3825	real_invoke_pending (EV_P)
		3826	{
		3827	userdata *u = ev_userdata (EV_A);
		3828
		3829	pthread_mutex_lock (&u->lock);
		3830	ev_invoke_pending (EV_A);
		3831	pthread_cond_signal (&u->invoke_cv);
		3832	pthread_mutex_unlock (&u->lock);
		3833	}
		3834
		3835	Whenever you want to start/stop a watcher or do other modifications to an
		3836	event loop, you will now have to lock:
		3837
		3838	ev_timer timeout_watcher;
		3839	userdata *u = ev_userdata (EV_A);
		3840
		3841	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3842
		3843	pthread_mutex_lock (&u->lock);
		3844	ev_timer_start (EV_A_ &timeout_watcher);
		3845	ev_async_send (EV_A_ &u->async_w);
		3846	pthread_mutex_unlock (&u->lock);
		3847
		3848	Note that sending the C<ev_async> watcher is required because otherwise
		3849	an event loop currently blocking in the kernel will have no knowledge
		3850	about the newly added timer. By waking up the loop it will pick up any new
		3851	watchers in the next event loop iteration.
		3852
		3853	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3854
		3855	While the overhead of a callback that e.g. schedules a thread is small, it
		3856	is still an overhead. If you embed libev, and your main usage is with some
		3857	kind of threads or coroutines, you might want to customise libev so that
		3858	doesn't need callbacks anymore.
		3859
		3860	Imagine you have coroutines that you can switch to using a function
		3861	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3862	and that due to some magic, the currently active coroutine is stored in a
		3863	global called C<current_coro>. Then you can build your own "wait for libev
		3864	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3865	the differing C<;> conventions):
		3866
		3867	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3868	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3869
		3870	That means instead of having a C callback function, you store the
		3871	coroutine to switch to in each watcher, and instead of having libev call
		3872	your callback, you instead have it switch to that coroutine.
		3873
		3874	A coroutine might now wait for an event with a function called
		3875	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3876	matter when, or whether the watcher is active or not when this function is
		3877	called):
		3878
		3879	void
		3880	wait_for_event (ev_watcher *w)
		3881	{
		3882	ev_set_cb (w, current_coro);
		3883	switch_to (libev_coro);
		3884	}
		3885
		3886	That basically suspends the coroutine inside C<wait_for_event> and
		3887	continues the libev coroutine, which, when appropriate, switches back to
		3888	this or any other coroutine.
		3889
		3890	You can do similar tricks if you have, say, threads with an event queue -
		3891	instead of storing a coroutine, you store the queue object and instead of
		3892	switching to a coroutine, you push the watcher onto the queue and notify
		3893	any waiters.
		3894
		3895	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		3896	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3897
		3898	// my_ev.h
		3899	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3900	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3901	#include "../libev/ev.h"
		3902
		3903	// my_ev.c
		3904	#define EV_H "my_ev.h"
		3905	#include "../libev/ev.c"
		3906
		3907	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3908	F<my_ev.c> into your project. When properly specifying include paths, you
		3909	can even use F<ev.h> as header file name directly.
3360		3910
3361		3911
3362	=head1 LIBEVENT EMULATION	3912	=head1 LIBEVENT EMULATION
3363		3913
3364	Libev offers a compatibility emulation layer for libevent. It cannot	3914	Libev offers a compatibility emulation layer for libevent. It cannot
3365	emulate the internals of libevent, so here are some usage hints:	3915	emulate the internals of libevent, so here are some usage hints:
3366		3916
3367	=over 4	3917	=over 4
		3918
		3919	=item * Only the libevent-1.4.1-beta API is being emulated.
		3920
		3921	This was the newest libevent version available when libev was implemented,
		3922	and is still mostly unchanged in 2010.
3368		3923
3369	=item * Use it by including <event.h>, as usual.	3924	=item * Use it by including <event.h>, as usual.
3370		3925
3371	=item * The following members are fully supported: ev_base, ev_callback,	3926	=item * The following members are fully supported: ev_base, ev_callback,
3372	ev_arg, ev_fd, ev_res, ev_events.	3927	ev_arg, ev_fd, ev_res, ev_events.
…		…
3378	=item * Priorities are not currently supported. Initialising priorities	3933	=item * Priorities are not currently supported. Initialising priorities
3379	will fail and all watchers will have the same priority, even though there	3934	will fail and all watchers will have the same priority, even though there
3380	is an ev_pri field.	3935	is an ev_pri field.
3381		3936
3382	=item * In libevent, the last base created gets the signals, in libev, the	3937	=item * In libevent, the last base created gets the signals, in libev, the
3383	first base created (== the default loop) gets the signals.	3938	base that registered the signal gets the signals.
3384		3939
3385	=item * Other members are not supported.	3940	=item * Other members are not supported.
3386		3941
3387	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3942	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3388	to use the libev header file and library.	3943	to use the libev header file and library.
3389		3944
3390	=back	3945	=back
3391		3946
3392	=head1 C++ SUPPORT	3947	=head1 C++ SUPPORT
		3948
		3949	=head2 C API
		3950
		3951	The normal C API should work fine when used from C++: both ev.h and the
		3952	libev sources can be compiled as C++. Therefore, code that uses the C API
		3953	will work fine.
		3954
		3955	Proper exception specifications might have to be added to callbacks passed
		3956	to libev: exceptions may be thrown only from watcher callbacks, all
		3957	other callbacks (allocator, syserr, loop acquire/release and periodic
		3958	reschedule callbacks) must not throw exceptions, and might need a C<throw
		3959	()> specification. If you have code that needs to be compiled as both C
		3960	and C++ you can use the C<EV_THROW> macro for this:
		3961
		3962	static void
		3963	fatal_error (const char *msg) EV_THROW
		3964	{
		3965	perror (msg);
		3966	abort ();
		3967	}
		3968
		3969	...
		3970	ev_set_syserr_cb (fatal_error);
		3971
		3972	The only API functions that can currently throw exceptions are C<ev_run>,
		3973	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		3974	because it runs cleanup watchers).
		3975
		3976	Throwing exceptions in watcher callbacks is only supported if libev itself
		3977	is compiled with a C++ compiler or your C and C++ environments allow
		3978	throwing exceptions through C libraries (most do).
		3979
		3980	=head2 C++ API
3393		3981
3394	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3982	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	3983	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.	3984	the callback model to a model using method callbacks on objects.
3397		3985
3398	To use it,	3986	To use it,
3399		3987
3400	#include <ev++.h>	3988	#include <ev++.h>
3401		3989
3402	This automatically includes F<ev.h> and puts all of its definitions (many	3990	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	3991	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	3992	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++	3995	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	3996	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	3997	that the watcher is associated with (or no additional members at all if
3410	you disable C<EV_MULTIPLICITY> when embedding libev).	3998	you disable C<EV_MULTIPLICITY> when embedding libev).
3411		3999
3412	Currently, functions, and static and non-static member functions can be	4000	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	4001	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	4002	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	4003	you need support for other types of functors please contact the author
3416	it).	4004	(preferably after implementing it).
		4005
		4006	For all this to work, your C++ compiler either has to use the same calling
		4007	conventions as your C compiler (for static member functions), or you have
		4008	to embed libev and compile libev itself as C++.
3417		4009
3418	Here is a list of things available in the C<ev> namespace:	4010	Here is a list of things available in the C<ev> namespace:
3419		4011
3420	=over 4	4012	=over 4
3421		4013
…		…
3431	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4023	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3432		4024
3433	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4025	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>	4026	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	4027	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3436	defines by many implementations.	4028	defined by many implementations.
3437		4029
3438	All of those classes have these methods:	4030	All of those classes have these methods:
3439		4031
3440	=over 4	4032	=over 4
3441		4033
…		…
3531	Associates a different C<struct ev_loop> with this watcher. You can only	4123	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).	4124	do this when the watcher is inactive (and not pending either).
3533		4125
3534	=item w->set ([arguments])	4126	=item w->set ([arguments])
3535		4127
3536	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this	4128	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	4129	with the same arguments. Either this method or a suitable start method
3538	C counterpart, an active watcher gets automatically stopped and restarted	4130	must be called at least once. Unlike the C counterpart, an active watcher
3539	when reconfiguring it with this method.	4131	gets automatically stopped and restarted when reconfiguring it with this
		4132	method.
		4133
		4134	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4135	clashing with the C<set (loop)> method.
3540		4136
3541	=item w->start ()	4137	=item w->start ()
3542		4138
3543	Starts the watcher. Note that there is no C<loop> argument, as the	4139	Starts the watcher. Note that there is no C<loop> argument, as the
3544	constructor already stores the event loop.	4140	constructor already stores the event loop.
…		…
3574	watchers in the constructor.	4170	watchers in the constructor.
3575		4171
3576	class myclass	4172	class myclass
3577	{	4173	{
3578	ev::io io ; void io_cb (ev::io &w, int revents);	4174	ev::io io ; void io_cb (ev::io &w, int revents);
3579	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);	4175	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3580	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4176	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3581		4177
3582	myclass (int fd)	4178	myclass (int fd)
3583	{	4179	{
3584	io .set <myclass, &myclass::io_cb > (this);	4180	io .set <myclass, &myclass::io_cb > (this);
…		…
3635	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4231	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3636		4232
3637	=item D	4233	=item D
3638		4234
3639	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4235	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>.	4236	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3641		4237
3642	=item Ocaml	4238	=item Ocaml
3643		4239
3644	Erkki Seppala has written Ocaml bindings for libev, to be found at	4240	Erkki Seppala has written Ocaml bindings for libev, to be found at
3645	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4241	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
…		…
3648		4244
3649	Brian Maher has written a partial interface to libev for lua (at the	4245	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	4246	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
3651	L<http://github.com/brimworks/lua-ev>.	4247	L<http://github.com/brimworks/lua-ev>.
3652		4248
		4249	=item Javascript
		4250
		4251	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4252
		4253	=item Others
		4254
		4255	There are others, and I stopped counting.
		4256
3653	=back	4257	=back
3654		4258
3655		4259
3656	=head1 MACRO MAGIC	4260	=head1 MACRO MAGIC
3657		4261
…		…
3693	suitable for use with C<EV_A>.	4297	suitable for use with C<EV_A>.
3694		4298
3695	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4299	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3696		4300
3697	Similar to the other two macros, this gives you the value of the default	4301	Similar to the other two macros, this gives you the value of the default
3698	loop, if multiple loops are supported ("ev loop default").	4302	loop, if multiple loops are supported ("ev loop default"). The default loop
		4303	will be initialised if it isn't already initialised.
		4304
		4305	For non-multiplicity builds, these macros do nothing, so you always have
		4306	to initialise the loop somewhere.
3699		4307
3700	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4308	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3701		4309
3702	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4310	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	4311	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3848	supported). It will also not define any of the structs usually found in	4456	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.	4457	F<event.h> that are not directly supported by the libev core alone.
3850		4458
3851	In standalone mode, libev will still try to automatically deduce the	4459	In standalone mode, libev will still try to automatically deduce the
3852	configuration, but has to be more conservative.	4460	configuration, but has to be more conservative.
		4461
		4462	=item EV_USE_FLOOR
		4463
		4464	If defined to be C<1>, libev will use the C<floor ()> function for its
		4465	periodic reschedule calculations, otherwise libev will fall back on a
		4466	portable (slower) implementation. If you enable this, you usually have to
		4467	link against libm or something equivalent. Enabling this when the C<floor>
		4468	function is not available will fail, so the safe default is to not enable
		4469	this.
3853		4470
3854	=item EV_USE_MONOTONIC	4471	=item EV_USE_MONOTONIC
3855		4472
3856	If defined to be C<1>, libev will try to detect the availability of the	4473	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	4474	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3942		4559
3943	If programs implement their own fd to handle mapping on win32, then this	4560	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	4561	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	4562	file descriptors again. Note that the replacement function has to close
3946	the underlying OS handle.	4563	the underlying OS handle.
		4564
		4565	=item EV_USE_WSASOCKET
		4566
		4567	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4568	communication socket, which works better in some environments. Otherwise,
		4569	the normal C<socket> function will be used, which works better in other
		4570	environments.
3947		4571
3948	=item EV_USE_POLL	4572	=item EV_USE_POLL
3949		4573
3950	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4574	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	4575	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	4611	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	4612	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	4613	be detected at runtime. If undefined, it will be enabled if the headers
3990	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4614	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3991		4615
		4616	=item EV_NO_SMP
		4617
		4618	If defined to be C<1>, libev will assume that memory is always coherent
		4619	between threads, that is, threads can be used, but threads never run on
		4620	different cpus (or different cpu cores). This reduces dependencies
		4621	and makes libev faster.
		4622
		4623	=item EV_NO_THREADS
		4624
		4625	If defined to be C<1>, libev will assume that it will never be called from
		4626	different threads (that includes signal handlers), which is a stronger
		4627	assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes
		4628	libev faster.
		4629
3992	=item EV_ATOMIC_T	4630	=item EV_ATOMIC_T
3993		4631
3994	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4632	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	4633	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	4634	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"	4635	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.	4636	handler "locking" as well as for signal and thread safety in C<ev_async>
		4637	watchers.
3999		4638
4000	In the absence of this define, libev will use C<sig_atomic_t volatile>	4639	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.	4640	(from F<signal.h>), which is usually good enough on most platforms.
4002		4641
4003	=item EV_H (h)	4642	=item EV_H (h)
…		…
4030	will have the C<struct ev_loop *> as first argument, and you can create	4669	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	4670	additional independent event loops. Otherwise there will be no support
4032	for multiple event loops and there is no first event loop pointer	4671	for multiple event loops and there is no first event loop pointer
4033	argument. Instead, all functions act on the single default loop.	4672	argument. Instead, all functions act on the single default loop.
4034		4673
		4674	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4675	default loop when multiplicity is switched off - you always have to
		4676	initialise the loop manually in this case.
		4677
4035	=item EV_MINPRI	4678	=item EV_MINPRI
4036		4679
4037	=item EV_MAXPRI	4680	=item EV_MAXPRI
4038		4681
4039	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4682	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
4075	#define EV_USE_POLL 1	4718	#define EV_USE_POLL 1
4076	#define EV_CHILD_ENABLE 1	4719	#define EV_CHILD_ENABLE 1
4077	#define EV_ASYNC_ENABLE 1	4720	#define EV_ASYNC_ENABLE 1
4078		4721
4079	The actual value is a bitset, it can be a combination of the following	4722	The actual value is a bitset, it can be a combination of the following
4080	values:	4723	values (by default, all of these are enabled):
4081		4724
4082	=over 4	4725	=over 4
4083		4726
4084	=item C<1> - faster/larger code	4727	=item C<1> - faster/larger code
4085		4728
…		…
4089	code size by roughly 30% on amd64).	4732	code size by roughly 30% on amd64).
4090		4733
4091	When optimising for size, use of compiler flags such as C<-Os> with	4734	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	4735	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
4093	assertions.	4736	assertions.
		4737
		4738	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4739	(e.g. gcc with C<-Os>).
4094		4740
4095	=item C<2> - faster/larger data structures	4741	=item C<2> - faster/larger data structures
4096		4742
4097	Replaces the small 2-heap for timer management by a faster 4-heap, larger	4743	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	4744	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	4745	and can additionally have an effect on the size of data structures at
4100	runtime.	4746	runtime.
4101		4747
		4748	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4749	(e.g. gcc with C<-Os>).
		4750
4102	=item C<4> - full API configuration	4751	=item C<4> - full API configuration
4103		4752
4104	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and	4753	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
4105	enables multiplicity (C<EV_MULTIPLICITY>=1).	4754	enables multiplicity (C<EV_MULTIPLICITY>=1).
4106		4755
…		…
4136		4785
4137	With an intelligent-enough linker (gcc+binutils are intelligent enough	4786	With an intelligent-enough linker (gcc+binutils are intelligent enough
4138	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by	4787	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	4788	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.	4789	I/O watcher then might come out at only 5Kb.
		4790
		4791	=item EV_API_STATIC
		4792
		4793	If this symbol is defined (by default it is not), then all identifiers
		4794	will have static linkage. This means that libev will not export any
		4795	identifiers, and you cannot link against libev anymore. This can be useful
		4796	when you embed libev, only want to use libev functions in a single file,
		4797	and do not want its identifiers to be visible.
		4798
		4799	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4800	wants to use libev.
		4801
		4802	This option only works when libev is compiled with a C compiler, as C++
		4803	doesn't support the required declaration syntax.
4141		4804
4142	=item EV_AVOID_STDIO	4805	=item EV_AVOID_STDIO
4143		4806
4144	If this is set to C<1> at compiletime, then libev will avoid using stdio	4807	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	4808	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:	4952	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4290		4953
4291	#include "ev_cpp.h"	4954	#include "ev_cpp.h"
4292	#include "ev.c"	4955	#include "ev.c"
4293		4956
4294	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4957	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4295		4958
4296	=head2 THREADS AND COROUTINES	4959	=head2 THREADS AND COROUTINES
4297		4960
4298	=head3 THREADS	4961	=head3 THREADS
4299		4962
…		…
4350	default loop and triggering an C<ev_async> watcher from the default loop	5013	default loop and triggering an C<ev_async> watcher from the default loop
4351	watcher callback into the event loop interested in the signal.	5014	watcher callback into the event loop interested in the signal.
4352		5015
4353	=back	5016	=back
4354		5017
4355	=head4 THREAD LOCKING EXAMPLE	5018	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		5019
4493	=head3 COROUTINES	5020	=head3 COROUTINES
4494		5021
4495	Libev is very accommodating to coroutines ("cooperative threads"):	5022	Libev is very accommodating to coroutines ("cooperative threads"):
4496	libev fully supports nesting calls to its functions from different	5023	libev fully supports nesting calls to its functions from different
…		…
4661	requires, and its I/O model is fundamentally incompatible with the POSIX	5188	requires, and its I/O model is fundamentally incompatible with the POSIX
4662	model. Libev still offers limited functionality on this platform in	5189	model. Libev still offers limited functionality on this platform in
4663	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5190	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4664	descriptors. This only applies when using Win32 natively, not when using	5191	descriptors. This only applies when using Win32 natively, not when using
4665	e.g. cygwin. Actually, it only applies to the microsofts own compilers,	5192	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
4666	as every compielr comes with a slightly differently broken/incompatible	5193	as every compiler comes with a slightly differently broken/incompatible
4667	environment.	5194	environment.
4668		5195
4669	Lifting these limitations would basically require the full	5196	Lifting these limitations would basically require the full
4670	re-implementation of the I/O system. If you are into this kind of thing,	5197	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	5198	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	5314	thread" or will block signals process-wide, both behaviours would
4788	be compatible with libev. Interaction between C<sigprocmask> and	5315	be compatible with libev. Interaction between C<sigprocmask> and
4789	C<pthread_sigmask> could complicate things, however.	5316	C<pthread_sigmask> could complicate things, however.
4790		5317
4791	The most portable way to handle signals is to block signals in all threads	5318	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	5319	except the initial one, and run the signal handling loop in the initial
4793	well.	5320	thread as well.
4794		5321
4795	=item C<long> must be large enough for common memory allocation sizes	5322	=item C<long> must be large enough for common memory allocation sizes
4796		5323
4797	To improve portability and simplify its API, libev uses C<long> internally	5324	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	5325	instead of C<size_t> when allocating its data structures. On non-POSIX
…		…
4804		5331
4805	The type C<double> is used to represent timestamps. It is required to	5332	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	5333	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	5334	good enough for at least into the year 4000 with millisecond accuracy
4808	(the design goal for libev). This requirement is overfulfilled by	5335	(the design goal for libev). This requirement is overfulfilled by
4809	implementations using IEEE 754, which is basically all existing ones. With	5336	implementations using IEEE 754, which is basically all existing ones.
		5337
4810	IEEE 754 doubles, you get microsecond accuracy until at least 2200.	5338	With IEEE 754 doubles, you get microsecond accuracy until at least the
		5339	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5340	is either obsolete or somebody patched it to use C<long double> or
		5341	something like that, just kidding).
4811		5342
4812	=back	5343	=back
4813		5344
4814	If you know of other additional requirements drop me a note.	5345	If you know of other additional requirements drop me a note.
4815		5346
…		…
4877	=item Processing ev_async_send: O(number_of_async_watchers)	5408	=item Processing ev_async_send: O(number_of_async_watchers)
4878		5409
4879	=item Processing signals: O(max_signal_number)	5410	=item Processing signals: O(max_signal_number)
4880		5411
4881	Sending involves a system call I<iff> there were no other C<ev_async_send>	5412	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	5413	calls in the current loop iteration and the loop is currently
		5414	blocked. Checking for async and signal events involves iterating over all
4883	involves iterating over all running async watchers or all signal numbers.	5415	running async watchers or all signal numbers.
4884		5416
4885	=back	5417	=back
4886		5418
4887		5419
4888	=head1 PORTING FROM LIBEV 3.X TO 4.X	5420	=head1 PORTING FROM LIBEV 3.X TO 4.X
…		…
4897	=over 4	5429	=over 4
4898		5430
4899	=item C<EV_COMPAT3> backwards compatibility mechanism	5431	=item C<EV_COMPAT3> backwards compatibility mechanism
4900		5432
4901	The backward compatibility mechanism can be controlled by	5433	The backward compatibility mechanism can be controlled by
4902	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>	5434	C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING>
4903	section.	5435	section.
4904		5436
4905	=item C<ev_default_destroy> and C<ev_default_fork> have been removed	5437	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
4906		5438
4907	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:	5439	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
…		…
4950	=over 4	5482	=over 4
4951		5483
4952	=item active	5484	=item active
4953		5485
4954	A watcher is active as long as it has been started and not yet stopped.	5486	A watcher is active as long as it has been started and not yet stopped.
4955	See L<WATCHER STATES> for details.	5487	See L</WATCHER STATES> for details.
4956		5488
4957	=item application	5489	=item application
4958		5490
4959	In this document, an application is whatever is using libev.	5491	In this document, an application is whatever is using libev.
4960		5492
…		…
4996	watchers and events.	5528	watchers and events.
4997		5529
4998	=item pending	5530	=item pending
4999		5531
5000	A watcher is pending as soon as the corresponding event has been	5532	A watcher is pending as soon as the corresponding event has been
5001	detected. See L<WATCHER STATES> for details.	5533	detected. See L</WATCHER STATES> for details.
5002		5534
5003	=item real time	5535	=item real time
5004		5536
5005	The physical time that is observed. It is apparently strictly monotonic :)	5537	The physical time that is observed. It is apparently strictly monotonic :)
5006		5538
5007	=item wall-clock time	5539	=item wall-clock time
5008		5540
5009	The time and date as shown on clocks. Unlike real time, it can actually	5541	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	5542	be wrong and jump forwards and backwards, e.g. when you adjust your
5011	clock.	5543	clock.
5012		5544
5013	=item watcher	5545	=item watcher
5014		5546
5015	A data structure that describes interest in certain events. Watchers need	5547	A data structure that describes interest in certain events. Watchers need
…		…
5018	=back	5550	=back
5019		5551
5020	=head1 AUTHOR	5552	=head1 AUTHOR
5021		5553
5022	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael	5554	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
5023	Magnusson and Emanuele Giaquinta.	5555	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
5024		5556

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