[ViewVC] Diff of: cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.34 by root, Fri Nov 23 16:17:12 2007 UTC vs.
Revision 1.48 by root, Tue Nov 27 08:11:52 2007 UTC

…		…
106	returned by C<ev_supported_backends>, as for example kqueue is broken on	106	returned by C<ev_supported_backends>, as for example kqueue is broken on
107	most BSDs and will not be autodetected unless you explicitly request it	107	most BSDs and will not be autodetected unless you explicitly request it
108	(assuming you know what you are doing). This is the set of backends that	108	(assuming you know what you are doing). This is the set of backends that
109	libev will probe for if you specify no backends explicitly.	109	libev will probe for if you specify no backends explicitly.
110		110
		111	=item unsigned int ev_embeddable_backends ()
		112
		113	Returns the set of backends that are embeddable in other event loops. This
		114	is the theoretical, all-platform, value. To find which backends
		115	might be supported on the current system, you would need to look at
		116	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
		117	recommended ones.
		118
		119	See the description of C<ev_embed> watchers for more info.
		120
111	=item ev_set_allocator (void (cb)(void *ptr, long size))	121	=item ev_set_allocator (void (cb)(void *ptr, long size))
112		122
113	Sets the allocation function to use (the prototype is similar to the	123	Sets the allocation function to use (the prototype is similar to the
114	realloc C function, the semantics are identical). It is used to allocate	124	realloc C function, the semantics are identical). It is used to allocate
115	and free memory (no surprises here). If it returns zero when memory	125	and free memory (no surprises here). If it returns zero when memory
…		…
313	fatal ("no epoll found here, maybe it hides under your chair");	323	fatal ("no epoll found here, maybe it hides under your chair");
314		324
315	=item ev_default_destroy ()	325	=item ev_default_destroy ()
316		326
317	Destroys the default loop again (frees all memory and kernel state	327	Destroys the default loop again (frees all memory and kernel state
318	etc.). This stops all registered event watchers (by not touching them in	328	etc.). None of the active event watchers will be stopped in the normal
319	any way whatsoever, although you cannot rely on this :).	329	sense, so e.g. C<ev_is_active> might still return true. It is your
		330	responsibility to either stop all watchers cleanly yoursef I<before>
		331	calling this function, or cope with the fact afterwards (which is usually
		332	the easiest thing, youc na just ignore the watchers and/or C<free ()> them
		333	for example).
320		334
321	=item ev_loop_destroy (loop)	335	=item ev_loop_destroy (loop)
322		336
323	Like C<ev_default_destroy>, but destroys an event loop created by an	337	Like C<ev_default_destroy>, but destroys an event loop created by an
324	earlier call to C<ev_loop_new>.	338	earlier call to C<ev_loop_new>.
…		…
454	ev_ref (myloop);	468	ev_ref (myloop);
455	ev_signal_stop (myloop, &exitsig);	469	ev_signal_stop (myloop, &exitsig);
456		470
457	=back	471	=back
458		472
		473
459	=head1 ANATOMY OF A WATCHER	474	=head1 ANATOMY OF A WATCHER
460		475
461	A watcher is a structure that you create and register to record your	476	A watcher is a structure that you create and register to record your
462	interest in some event. For instance, if you want to wait for STDIN to	477	interest in some event. For instance, if you want to wait for STDIN to
463	become readable, you would create an C<ev_io> watcher for that:	478	become readable, you would create an C<ev_io> watcher for that:
…		…
495	*) >>), and you can stop watching for events at any time by calling the	510	*) >>), and you can stop watching for events at any time by calling the
496	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	511	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.
497		512
498	As long as your watcher is active (has been started but not stopped) you	513	As long as your watcher is active (has been started but not stopped) you
499	must not touch the values stored in it. Most specifically you must never	514	must not touch the values stored in it. Most specifically you must never
500	reinitialise it or call its set macro.	515	reinitialise it or call its C<set> macro.
501
502	You can check whether an event is active by calling the C<ev_is_active
503	(watcher *)> macro. To see whether an event is outstanding (but the
504	callback for it has not been called yet) you can use the C<ev_is_pending
505	(watcher *)> macro.
506		516
507	Each and every callback receives the event loop pointer as first, the	517	Each and every callback receives the event loop pointer as first, the
508	registered watcher structure as second, and a bitset of received events as	518	registered watcher structure as second, and a bitset of received events as
509	third argument.	519	third argument.
510		520
…		…
534	The signal specified in the C<ev_signal> watcher has been received by a thread.	544	The signal specified in the C<ev_signal> watcher has been received by a thread.
535		545
536	=item C<EV_CHILD>	546	=item C<EV_CHILD>
537		547
538	The pid specified in the C<ev_child> watcher has received a status change.	548	The pid specified in the C<ev_child> watcher has received a status change.
		549
		550	=item C<EV_STAT>
		551
		552	The path specified in the C<ev_stat> watcher changed its attributes somehow.
539		553
540	=item C<EV_IDLE>	554	=item C<EV_IDLE>
541		555
542	The C<ev_idle> watcher has determined that you have nothing better to do.	556	The C<ev_idle> watcher has determined that you have nothing better to do.
543		557
…		…
567	with the error from read() or write(). This will not work in multithreaded	581	with the error from read() or write(). This will not work in multithreaded
568	programs, though, so beware.	582	programs, though, so beware.
569		583
570	=back	584	=back
571		585
		586	=head2 GENERIC WATCHER FUNCTIONS
		587
		588	In the following description, C<TYPE> stands for the watcher type,
		589	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
		590
		591	=over 4
		592
		593	=item C<ev_init> (ev_TYPE *watcher, callback)
		594
		595	This macro initialises the generic portion of a watcher. The contents
		596	of the watcher object can be arbitrary (so C<malloc> will do). Only
		597	the generic parts of the watcher are initialised, you I<need> to call
		598	the type-specific C<ev_TYPE_set> macro afterwards to initialise the
		599	type-specific parts. For each type there is also a C<ev_TYPE_init> macro
		600	which rolls both calls into one.
		601
		602	You can reinitialise a watcher at any time as long as it has been stopped
		603	(or never started) and there are no pending events outstanding.
		604
		605	The callback is always of type C<void ()(ev_loop loop, ev_TYPE *watcher,
		606	int revents)>.
		607
		608	=item C<ev_TYPE_set> (ev_TYPE *, [args])
		609
		610	This macro initialises the type-specific parts of a watcher. You need to
		611	call C<ev_init> at least once before you call this macro, but you can
		612	call C<ev_TYPE_set> any number of times. You must not, however, call this
		613	macro on a watcher that is active (it can be pending, however, which is a
		614	difference to the C<ev_init> macro).
		615
		616	Although some watcher types do not have type-specific arguments
		617	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
		618
		619	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
		620
		621	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
		622	calls into a single call. This is the most convinient method to initialise
		623	a watcher. The same limitations apply, of course.
		624
		625	=item C<ev_TYPE_start> (loop , ev_TYPE watcher)
		626
		627	Starts (activates) the given watcher. Only active watchers will receive
		628	events. If the watcher is already active nothing will happen.
		629
		630	=item C<ev_TYPE_stop> (loop , ev_TYPE watcher)
		631
		632	Stops the given watcher again (if active) and clears the pending
		633	status. It is possible that stopped watchers are pending (for example,
		634	non-repeating timers are being stopped when they become pending), but
		635	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If
		636	you want to free or reuse the memory used by the watcher it is therefore a
		637	good idea to always call its C<ev_TYPE_stop> function.
		638
		639	=item bool ev_is_active (ev_TYPE *watcher)
		640
		641	Returns a true value iff the watcher is active (i.e. it has been started
		642	and not yet been stopped). As long as a watcher is active you must not modify
		643	it.
		644
		645	=item bool ev_is_pending (ev_TYPE *watcher)
		646
		647	Returns a true value iff the watcher is pending, (i.e. it has outstanding
		648	events but its callback has not yet been invoked). As long as a watcher
		649	is pending (but not active) you must not call an init function on it (but
		650	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to
		651	libev (e.g. you cnanot C<free ()> it).
		652
		653	=item callback = ev_cb (ev_TYPE *watcher)
		654
		655	Returns the callback currently set on the watcher.
		656
		657	=item ev_cb_set (ev_TYPE *watcher, callback)
		658
		659	Change the callback. You can change the callback at virtually any time
		660	(modulo threads).
		661
		662	=back
		663
		664
572	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	665	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
573		666
574	Each watcher has, by default, a member C<void *data> that you can change	667	Each watcher has, by default, a member C<void *data> that you can change
575	and read at any time, libev will completely ignore it. This can be used	668	and read at any time, libev will completely ignore it. This can be used
576	to associate arbitrary data with your watcher. If you need more data and	669	to associate arbitrary data with your watcher. If you need more data and
…		…
600		693
601		694
602	=head1 WATCHER TYPES	695	=head1 WATCHER TYPES
603		696
604	This section describes each watcher in detail, but will not repeat	697	This section describes each watcher in detail, but will not repeat
605	information given in the last section.	698	information given in the last section. Any initialisation/set macros,
		699	functions and members specific to the watcher type are explained.
606		700
		701	Members are additionally marked with either I<[read-only]>, meaning that,
		702	while the watcher is active, you can look at the member and expect some
		703	sensible content, but you must not modify it (you can modify it while the
		704	watcher is stopped to your hearts content), or I<[read-write]>, which
		705	means you can expect it to have some sensible content while the watcher
		706	is active, but you can also modify it. Modifying it may not do something
		707	sensible or take immediate effect (or do anything at all), but libev will
		708	not crash or malfunction in any way.
607		709
		710
608	=head2 C<ev_io> - is this file descriptor readable or writable	711	=head2 C<ev_io> - is this file descriptor readable or writable?
609		712
610	I/O watchers check whether a file descriptor is readable or writable	713	I/O watchers check whether a file descriptor is readable or writable
611	in each iteration of the event loop (This behaviour is called	714	in each iteration of the event loop, or, more precisely, when reading
612	level-triggering because you keep receiving events as long as the	715	would not block the process and writing would at least be able to write
613	condition persists. Remember you can stop the watcher if you don't want to	716	some data. This behaviour is called level-triggering because you keep
614	act on the event and neither want to receive future events).	717	receiving events as long as the condition persists. Remember you can stop
		718	the watcher if you don't want to act on the event and neither want to
		719	receive future events.
615		720
616	In general you can register as many read and/or write event watchers per	721	In general you can register as many read and/or write event watchers per
617	fd as you want (as long as you don't confuse yourself). Setting all file	722	fd as you want (as long as you don't confuse yourself). Setting all file
618	descriptors to non-blocking mode is also usually a good idea (but not	723	descriptors to non-blocking mode is also usually a good idea (but not
619	required if you know what you are doing).	724	required if you know what you are doing).
620		725
621	You have to be careful with dup'ed file descriptors, though. Some backends	726	You have to be careful with dup'ed file descriptors, though. Some backends
622	(the linux epoll backend is a notable example) cannot handle dup'ed file	727	(the linux epoll backend is a notable example) cannot handle dup'ed file
623	descriptors correctly if you register interest in two or more fds pointing	728	descriptors correctly if you register interest in two or more fds pointing
624	to the same underlying file/socket etc. description (that is, they share	729	to the same underlying file/socket/etc. description (that is, they share
625	the same underlying "file open").	730	the same underlying "file open").
626		731
627	If you must do this, then force the use of a known-to-be-good backend	732	If you must do this, then force the use of a known-to-be-good backend
628	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	733	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
629	C<EVBACKEND_POLL>).	734	C<EVBACKEND_POLL>).
630		735
		736	Another thing you have to watch out for is that it is quite easy to
		737	receive "spurious" readyness notifications, that is your callback might
		738	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
		739	because there is no data. Not only are some backends known to create a
		740	lot of those (for example solaris ports), it is very easy to get into
		741	this situation even with a relatively standard program structure. Thus
		742	it is best to always use non-blocking I/O: An extra C<read>(2) returning
		743	C<EAGAIN> is far preferable to a program hanging until some data arrives.
		744
		745	If you cannot run the fd in non-blocking mode (for example you should not
		746	play around with an Xlib connection), then you have to seperately re-test
		747	wether a file descriptor is really ready with a known-to-be good interface
		748	such as poll (fortunately in our Xlib example, Xlib already does this on
		749	its own, so its quite safe to use).
		750
631	=over 4	751	=over 4
632		752
633	=item ev_io_init (ev_io *, callback, int fd, int events)	753	=item ev_io_init (ev_io *, callback, int fd, int events)
634		754
635	=item ev_io_set (ev_io *, int fd, int events)	755	=item ev_io_set (ev_io *, int fd, int events)
636		756
637	Configures an C<ev_io> watcher. The fd is the file descriptor to rceeive	757	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
638	events for and events is either C<EV_READ>, C<EV_WRITE> or C<EV_READ \|	758	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or
639	EV_WRITE> to receive the given events.	759	C<EV_READ \| EV_WRITE> to receive the given events.
640		760
641	Please note that most of the more scalable backend mechanisms (for example	761	=item int fd [read-only]
642	epoll and solaris ports) can result in spurious readyness notifications	762
643	for file descriptors, so you practically need to use non-blocking I/O (and	763	The file descriptor being watched.
644	treat callback invocation as hint only), or retest separately with a safe	764
645	interface before doing I/O (XLib can do this), or force the use of either	765	=item int events [read-only]
646	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>, which don't suffer from this	766
647	problem. Also note that it is quite easy to have your callback invoked	767	The events being watched.
648	when the readyness condition is no longer valid even when employing
649	typical ways of handling events, so its a good idea to use non-blocking
650	I/O unconditionally.
651		768
652	=back	769	=back
653		770
654	Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well	771	Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well
655	readable, but only once. Since it is likely line-buffered, you could	772	readable, but only once. Since it is likely line-buffered, you could
…		…
668	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	785	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
669	ev_io_start (loop, &stdin_readable);	786	ev_io_start (loop, &stdin_readable);
670	ev_loop (loop, 0);	787	ev_loop (loop, 0);
671		788
672		789
673	=head2 C<ev_timer> - relative and optionally recurring timeouts	790	=head2 C<ev_timer> - relative and optionally repeating timeouts
674		791
675	Timer watchers are simple relative timers that generate an event after a	792	Timer watchers are simple relative timers that generate an event after a
676	given time, and optionally repeating in regular intervals after that.	793	given time, and optionally repeating in regular intervals after that.
677		794
678	The timers are based on real time, that is, if you register an event that	795	The timers are based on real time, that is, if you register an event that
…		…
719		836
720	If the timer is repeating, either start it if necessary (with the repeat	837	If the timer is repeating, either start it if necessary (with the repeat
721	value), or reset the running timer to the repeat value.	838	value), or reset the running timer to the repeat value.
722		839
723	This sounds a bit complicated, but here is a useful and typical	840	This sounds a bit complicated, but here is a useful and typical
724	example: Imagine you have a tcp connection and you want a so-called idle	841	example: Imagine you have a tcp connection and you want a so-called
725	timeout, that is, you want to be called when there have been, say, 60	842	idle timeout, that is, you want to be called when there have been,
726	seconds of inactivity on the socket. The easiest way to do this is to	843	say, 60 seconds of inactivity on the socket. The easiest way to do
727	configure an C<ev_timer> with after=repeat=60 and calling ev_timer_again each	844	this is to configure an C<ev_timer> with C<after>=C<repeat>=C<60> and calling
728	time you successfully read or write some data. If you go into an idle	845	C<ev_timer_again> each time you successfully read or write some data. If
729	state where you do not expect data to travel on the socket, you can stop	846	you go into an idle state where you do not expect data to travel on the
730	the timer, and again will automatically restart it if need be.	847	socket, you can stop the timer, and again will automatically restart it if
		848	need be.
		849
		850	You can also ignore the C<after> value and C<ev_timer_start> altogether
		851	and only ever use the C<repeat> value:
		852
		853	ev_timer_init (timer, callback, 0., 5.);
		854	ev_timer_again (loop, timer);
		855	...
		856	timer->again = 17.;
		857	ev_timer_again (loop, timer);
		858	...
		859	timer->again = 10.;
		860	ev_timer_again (loop, timer);
		861
		862	This is more efficient then stopping/starting the timer eahc time you want
		863	to modify its timeout value.
		864
		865	=item ev_tstamp repeat [read-write]
		866
		867	The current C<repeat> value. Will be used each time the watcher times out
		868	or C<ev_timer_again> is called and determines the next timeout (if any),
		869	which is also when any modifications are taken into account.
731		870
732	=back	871	=back
733		872
734	Example: create a timer that fires after 60 seconds.	873	Example: create a timer that fires after 60 seconds.
735		874
…		…
760	// and in some piece of code that gets executed on any "activity":	899	// and in some piece of code that gets executed on any "activity":
761	// reset the timeout to start ticking again at 10 seconds	900	// reset the timeout to start ticking again at 10 seconds
762	ev_timer_again (&mytimer);	901	ev_timer_again (&mytimer);
763		902
764		903
765	=head2 C<ev_periodic> - to cron or not to cron	904	=head2 C<ev_periodic> - to cron or not to cron?
766		905
767	Periodic watchers are also timers of a kind, but they are very versatile	906	Periodic watchers are also timers of a kind, but they are very versatile
768	(and unfortunately a bit complex).	907	(and unfortunately a bit complex).
769		908
770	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	909	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
771	but on wallclock time (absolute time). You can tell a periodic watcher	910	but on wallclock time (absolute time). You can tell a periodic watcher
772	to trigger "at" some specific point in time. For example, if you tell a	911	to trigger "at" some specific point in time. For example, if you tell a
773	periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now ()	912	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
774	+ 10.>) and then reset your system clock to the last year, then it will	913	+ 10.>) and then reset your system clock to the last year, then it will
775	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	914	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
776	roughly 10 seconds later and of course not if you reset your system time	915	roughly 10 seconds later and of course not if you reset your system time
777	again).	916	again).
778		917
…		…
862	Simply stops and restarts the periodic watcher again. This is only useful	1001	Simply stops and restarts the periodic watcher again. This is only useful
863	when you changed some parameters or the reschedule callback would return	1002	when you changed some parameters or the reschedule callback would return
864	a different time than the last time it was called (e.g. in a crond like	1003	a different time than the last time it was called (e.g. in a crond like
865	program when the crontabs have changed).	1004	program when the crontabs have changed).
866		1005
		1006	=item ev_tstamp interval [read-write]
		1007
		1008	The current interval value. Can be modified any time, but changes only
		1009	take effect when the periodic timer fires or C<ev_periodic_again> is being
		1010	called.
		1011
		1012	=item ev_tstamp (reschedule_cb)(struct ev_periodic w, ev_tstamp now) [read-write]
		1013
		1014	The current reschedule callback, or C<0>, if this functionality is
		1015	switched off. Can be changed any time, but changes only take effect when
		1016	the periodic timer fires or C<ev_periodic_again> is being called.
		1017
867	=back	1018	=back
868		1019
869	Example: call a callback every hour, or, more precisely, whenever the	1020	Example: call a callback every hour, or, more precisely, whenever the
870	system clock is divisible by 3600. The callback invocation times have	1021	system clock is divisible by 3600. The callback invocation times have
871	potentially a lot of jittering, but good long-term stability.	1022	potentially a lot of jittering, but good long-term stability.
…		…
898	ev_periodic_init (&hourly_tick, clock_cb,	1049	ev_periodic_init (&hourly_tick, clock_cb,
899	fmod (ev_now (loop), 3600.), 3600., 0);	1050	fmod (ev_now (loop), 3600.), 3600., 0);
900	ev_periodic_start (loop, &hourly_tick);	1051	ev_periodic_start (loop, &hourly_tick);
901		1052
902		1053
903	=head2 C<ev_signal> - signal me when a signal gets signalled	1054	=head2 C<ev_signal> - signal me when a signal gets signalled!
904		1055
905	Signal watchers will trigger an event when the process receives a specific	1056	Signal watchers will trigger an event when the process receives a specific
906	signal one or more times. Even though signals are very asynchronous, libev	1057	signal one or more times. Even though signals are very asynchronous, libev
907	will try it's best to deliver signals synchronously, i.e. as part of the	1058	will try it's best to deliver signals synchronously, i.e. as part of the
908	normal event processing, like any other event.	1059	normal event processing, like any other event.
…		…
921	=item ev_signal_set (ev_signal *, int signum)	1072	=item ev_signal_set (ev_signal *, int signum)
922		1073
923	Configures the watcher to trigger on the given signal number (usually one	1074	Configures the watcher to trigger on the given signal number (usually one
924	of the C<SIGxxx> constants).	1075	of the C<SIGxxx> constants).
925		1076
		1077	=item int signum [read-only]
		1078
		1079	The signal the watcher watches out for.
		1080
926	=back	1081	=back
927		1082
		1083
928	=head2 C<ev_child> - wait for pid status changes	1084	=head2 C<ev_child> - watch out for process status changes
929		1085
930	Child watchers trigger when your process receives a SIGCHLD in response to	1086	Child watchers trigger when your process receives a SIGCHLD in response to
931	some child status changes (most typically when a child of yours dies).	1087	some child status changes (most typically when a child of yours dies).
932		1088
933	=over 4	1089	=over 4
…		…
941	at the C<rstatus> member of the C<ev_child> watcher structure to see	1097	at the C<rstatus> member of the C<ev_child> watcher structure to see
942	the status word (use the macros from C<sys/wait.h> and see your systems	1098	the status word (use the macros from C<sys/wait.h> and see your systems
943	C<waitpid> documentation). The C<rpid> member contains the pid of the	1099	C<waitpid> documentation). The C<rpid> member contains the pid of the
944	process causing the status change.	1100	process causing the status change.
945		1101
		1102	=item int pid [read-only]
		1103
		1104	The process id this watcher watches out for, or C<0>, meaning any process id.
		1105
		1106	=item int rpid [read-write]
		1107
		1108	The process id that detected a status change.
		1109
		1110	=item int rstatus [read-write]
		1111
		1112	The process exit/trace status caused by C<rpid> (see your systems
		1113	C<waitpid> and C<sys/wait.h> documentation for details).
		1114
946	=back	1115	=back
947		1116
948	Example: try to exit cleanly on SIGINT and SIGTERM.	1117	Example: try to exit cleanly on SIGINT and SIGTERM.
949		1118
950	static void	1119	static void
…		…
956	struct ev_signal signal_watcher;	1125	struct ev_signal signal_watcher;
957	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1126	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
958	ev_signal_start (loop, &sigint_cb);	1127	ev_signal_start (loop, &sigint_cb);
959		1128
960		1129
		1130	=head2 C<ev_stat> - did the file attributes just change?
		1131
		1132	This watches a filesystem path for attribute changes. That is, it calls
		1133	C<stat> regularly (or when the OS says it changed) and sees if it changed
		1134	compared to the last time, invoking the callback if it did.
		1135
		1136	The path does not need to exist: changing from "path exists" to "path does
		1137	not exist" is a status change like any other. The condition "path does
		1138	not exist" is signified by the C<st_nlink> field being zero (which is
		1139	otherwise always forced to be at least one) and all the other fields of
		1140	the stat buffer having unspecified contents.
		1141
		1142	Since there is no standard to do this, the portable implementation simply
		1143	calls C<stat (2)> regulalry on the path to see if it changed somehow. You
		1144	can specify a recommended polling interval for this case. If you specify
		1145	a polling interval of C<0> (highly recommended!) then a I<suitable,
		1146	unspecified default> value will be used (which you can expect to be around
		1147	five seconds, although this might change dynamically). Libev will also
		1148	impose a minimum interval which is currently around C<0.1>, but thats
		1149	usually overkill.
		1150
		1151	This watcher type is not meant for massive numbers of stat watchers,
		1152	as even with OS-supported change notifications, this can be
		1153	resource-intensive.
		1154
		1155	At the time of this writing, no specific OS backends are implemented, but
		1156	if demand increases, at least a kqueue and inotify backend will be added.
		1157
		1158	=over 4
		1159
		1160	=item ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)
		1161
		1162	=item ev_stat_set (ev_stat , const char path, ev_tstamp interval)
		1163
		1164	Configures the watcher to wait for status changes of the given
		1165	C<path>. The C<interval> is a hint on how quickly a change is expected to
		1166	be detected and should normally be specified as C<0> to let libev choose
		1167	a suitable value. The memory pointed to by C<path> must point to the same
		1168	path for as long as the watcher is active.
		1169
		1170	The callback will be receive C<EV_STAT> when a change was detected,
		1171	relative to the attributes at the time the watcher was started (or the
		1172	last change was detected).
		1173
		1174	=item ev_stat_stat (ev_stat *)
		1175
		1176	Updates the stat buffer immediately with new values. If you change the
		1177	watched path in your callback, you could call this fucntion to avoid
		1178	detecting this change (while introducing a race condition). Can also be
		1179	useful simply to find out the new values.
		1180
		1181	=item ev_statdata attr [read-only]
		1182
		1183	The most-recently detected attributes of the file. Although the type is of
		1184	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
		1185	suitable for your system. If the C<st_nlink> member is C<0>, then there
		1186	was some error while C<stat>ing the file.
		1187
		1188	=item ev_statdata prev [read-only]
		1189
		1190	The previous attributes of the file. The callback gets invoked whenever
		1191	C<prev> != C<attr>.
		1192
		1193	=item ev_tstamp interval [read-only]
		1194
		1195	The specified interval.
		1196
		1197	=item const char *path [read-only]
		1198
		1199	The filesystem path that is being watched.
		1200
		1201	=back
		1202
		1203	Example: Watch C</etc/passwd> for attribute changes.
		1204
		1205	static void
		1206	passwd_cb (struct ev_loop loop, ev_stat w, int revents)
		1207	{
		1208	/* /etc/passwd changed in some way */
		1209	if (w->attr.st_nlink)
		1210	{
		1211	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1212	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1213	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1214	}
		1215	else
		1216	/* you shalt not abuse printf for puts */
		1217	puts ("wow, /etc/passwd is not there, expect problems. "
		1218	"if this is windows, they already arrived\n");
		1219	}
		1220
		1221	...
		1222	ev_stat passwd;
		1223
		1224	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
		1225	ev_stat_start (loop, &passwd);
		1226
		1227
961	=head2 C<ev_idle> - when you've got nothing better to do	1228	=head2 C<ev_idle> - when you've got nothing better to do...
962		1229
963	Idle watchers trigger events when there are no other events are pending	1230	Idle watchers trigger events when there are no other events are pending
964	(prepare, check and other idle watchers do not count). That is, as long	1231	(prepare, check and other idle watchers do not count). That is, as long
965	as your process is busy handling sockets or timeouts (or even signals,	1232	as your process is busy handling sockets or timeouts (or even signals,
966	imagine) it will not be triggered. But when your process is idle all idle	1233	imagine) it will not be triggered. But when your process is idle all idle
…		…
1000	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1267	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1001	ev_idle_init (idle_watcher, idle_cb);	1268	ev_idle_init (idle_watcher, idle_cb);
1002	ev_idle_start (loop, idle_cb);	1269	ev_idle_start (loop, idle_cb);
1003		1270
1004		1271
1005	=head2 C<ev_prepare> and C<ev_check> - customise your event loop	1272	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1006		1273
1007	Prepare and check watchers are usually (but not always) used in tandem:	1274	Prepare and check watchers are usually (but not always) used in tandem:
1008	prepare watchers get invoked before the process blocks and check watchers	1275	prepare watchers get invoked before the process blocks and check watchers
1009	afterwards.	1276	afterwards.
1010		1277
		1278	You I<must not> call C<ev_loop> or similar functions that enter
		1279	the current event loop from either C<ev_prepare> or C<ev_check>
		1280	watchers. Other loops than the current one are fine, however. The
		1281	rationale behind this is that you do not need to check for recursion in
		1282	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
		1283	C<ev_check> so if you have one watcher of each kind they will always be
		1284	called in pairs bracketing the blocking call.
		1285
1011	Their main purpose is to integrate other event mechanisms into libev. This	1286	Their main purpose is to integrate other event mechanisms into libev and
1012	could be used, for example, to track variable changes, implement your own	1287	their use is somewhat advanced. This could be used, for example, to track
1013	watchers, integrate net-snmp or a coroutine library and lots more.	1288	variable changes, implement your own watchers, integrate net-snmp or a
		1289	coroutine library and lots more. They are also occasionally useful if
		1290	you cache some data and want to flush it before blocking (for example,
		1291	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
		1292	watcher).
1014		1293
1015	This is done by examining in each prepare call which file descriptors need	1294	This is done by examining in each prepare call which file descriptors need
1016	to be watched by the other library, registering C<ev_io> watchers for	1295	to be watched by the other library, registering C<ev_io> watchers for
1017	them and starting an C<ev_timer> watcher for any timeouts (many libraries	1296	them and starting an C<ev_timer> watcher for any timeouts (many libraries
1018	provide just this functionality). Then, in the check watcher you check for	1297	provide just this functionality). Then, in the check watcher you check for
…		…
1040	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1319	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1041	macros, but using them is utterly, utterly and completely pointless.	1320	macros, but using them is utterly, utterly and completely pointless.
1042		1321
1043	=back	1322	=back
1044		1323
1045	Example: TODO.	1324	Example: To include a library such as adns, you would add IO watchers
		1325	and a timeout watcher in a prepare handler, as required by libadns, and
		1326	in a check watcher, destroy them and call into libadns. What follows is
		1327	pseudo-code only of course:
		1328
		1329	static ev_io iow [nfd];
		1330	static ev_timer tw;
		1331
		1332	static void
		1333	io_cb (ev_loop loop, ev_io w, int revents)
		1334	{
		1335	// set the relevant poll flags
		1336	// could also call adns_processreadable etc. here
		1337	struct pollfd fd = (struct pollfd )w->data;
		1338	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
		1339	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
		1340	}
		1341
		1342	// create io watchers for each fd and a timer before blocking
		1343	static void
		1344	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)
		1345	{
		1346	int timeout = 3600000;truct pollfd fds [nfd];
		1347	// actual code will need to loop here and realloc etc.
		1348	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1349
		1350	/* the callback is illegal, but won't be called as we stop during check */
		1351	ev_timer_init (&tw, 0, timeout * 1e-3);
		1352	ev_timer_start (loop, &tw);
		1353
		1354	// create on ev_io per pollfd
		1355	for (int i = 0; i < nfd; ++i)
		1356	{
		1357	ev_io_init (iow + i, io_cb, fds [i].fd,
		1358	((fds [i].events & POLLIN ? EV_READ : 0)
		1359	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		1360
		1361	fds [i].revents = 0;
		1362	iow [i].data = fds + i;
		1363	ev_io_start (loop, iow + i);
		1364	}
		1365	}
		1366
		1367	// stop all watchers after blocking
		1368	static void
		1369	adns_check_cb (ev_loop loop, ev_check w, int revents)
		1370	{
		1371	ev_timer_stop (loop, &tw);
		1372
		1373	for (int i = 0; i < nfd; ++i)
		1374	ev_io_stop (loop, iow + i);
		1375
		1376	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1377	}
		1378
		1379
		1380	=head2 C<ev_embed> - when one backend isn't enough...
		1381
		1382	This is a rather advanced watcher type that lets you embed one event loop
		1383	into another (currently only C<ev_io> events are supported in the embedded
		1384	loop, other types of watchers might be handled in a delayed or incorrect
		1385	fashion and must not be used).
		1386
		1387	There are primarily two reasons you would want that: work around bugs and
		1388	prioritise I/O.
		1389
		1390	As an example for a bug workaround, the kqueue backend might only support
		1391	sockets on some platform, so it is unusable as generic backend, but you
		1392	still want to make use of it because you have many sockets and it scales
		1393	so nicely. In this case, you would create a kqueue-based loop and embed it
		1394	into your default loop (which might use e.g. poll). Overall operation will
		1395	be a bit slower because first libev has to poll and then call kevent, but
		1396	at least you can use both at what they are best.
		1397
		1398	As for prioritising I/O: rarely you have the case where some fds have
		1399	to be watched and handled very quickly (with low latency), and even
		1400	priorities and idle watchers might have too much overhead. In this case
		1401	you would put all the high priority stuff in one loop and all the rest in
		1402	a second one, and embed the second one in the first.
		1403
		1404	As long as the watcher is active, the callback will be invoked every time
		1405	there might be events pending in the embedded loop. The callback must then
		1406	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
		1407	their callbacks (you could also start an idle watcher to give the embedded
		1408	loop strictly lower priority for example). You can also set the callback
		1409	to C<0>, in which case the embed watcher will automatically execute the
		1410	embedded loop sweep.
		1411
		1412	As long as the watcher is started it will automatically handle events. The
		1413	callback will be invoked whenever some events have been handled. You can
		1414	set the callback to C<0> to avoid having to specify one if you are not
		1415	interested in that.
		1416
		1417	Also, there have not currently been made special provisions for forking:
		1418	when you fork, you not only have to call C<ev_loop_fork> on both loops,
		1419	but you will also have to stop and restart any C<ev_embed> watchers
		1420	yourself.
		1421
		1422	Unfortunately, not all backends are embeddable, only the ones returned by
		1423	C<ev_embeddable_backends> are, which, unfortunately, does not include any
		1424	portable one.
		1425
		1426	So when you want to use this feature you will always have to be prepared
		1427	that you cannot get an embeddable loop. The recommended way to get around
		1428	this is to have a separate variables for your embeddable loop, try to
		1429	create it, and if that fails, use the normal loop for everything:
		1430
		1431	struct ev_loop *loop_hi = ev_default_init (0);
		1432	struct ev_loop *loop_lo = 0;
		1433	struct ev_embed embed;
		1434
		1435	// see if there is a chance of getting one that works
		1436	// (remember that a flags value of 0 means autodetection)
		1437	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		1438	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		1439	: 0;
		1440
		1441	// if we got one, then embed it, otherwise default to loop_hi
		1442	if (loop_lo)
		1443	{
		1444	ev_embed_init (&embed, 0, loop_lo);
		1445	ev_embed_start (loop_hi, &embed);
		1446	}
		1447	else
		1448	loop_lo = loop_hi;
		1449
		1450	=over 4
		1451
		1452	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)
		1453
		1454	=item ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)
		1455
		1456	Configures the watcher to embed the given loop, which must be
		1457	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		1458	invoked automatically, otherwise it is the responsibility of the callback
		1459	to invoke it (it will continue to be called until the sweep has been done,
		1460	if you do not want thta, you need to temporarily stop the embed watcher).
		1461
		1462	=item ev_embed_sweep (loop, ev_embed *)
		1463
		1464	Make a single, non-blocking sweep over the embedded loop. This works
		1465	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		1466	apropriate way for embedded loops.
		1467
		1468	=item struct ev_loop *loop [read-only]
		1469
		1470	The embedded event loop.
		1471
		1472	=back
1046		1473
1047		1474
1048	=head1 OTHER FUNCTIONS	1475	=head1 OTHER FUNCTIONS
1049		1476
1050	There are some other functions of possible interest. Described. Here. Now.	1477	There are some other functions of possible interest. Described. Here. Now.
…		…
1081	/* stdin might have data for us, joy! */;	1508	/* stdin might have data for us, joy! */;
1082	}	1509	}
1083		1510
1084	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	1511	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
1085		1512
1086	=item ev_feed_event (loop, watcher, int events)	1513	=item ev_feed_event (ev_loop , watcher , int revents)
1087		1514
1088	Feeds the given event set into the event loop, as if the specified event	1515	Feeds the given event set into the event loop, as if the specified event
1089	had happened for the specified watcher (which must be a pointer to an	1516	had happened for the specified watcher (which must be a pointer to an
1090	initialised but not necessarily started event watcher).	1517	initialised but not necessarily started event watcher).
1091		1518
1092	=item ev_feed_fd_event (loop, int fd, int revents)	1519	=item ev_feed_fd_event (ev_loop *, int fd, int revents)
1093		1520
1094	Feed an event on the given fd, as if a file descriptor backend detected	1521	Feed an event on the given fd, as if a file descriptor backend detected
1095	the given events it.	1522	the given events it.
1096		1523
1097	=item ev_feed_signal_event (loop, int signum)	1524	=item ev_feed_signal_event (ev_loop *loop, int signum)
1098		1525
1099	Feed an event as if the given signal occured (loop must be the default loop!).	1526	Feed an event as if the given signal occured (C<loop> must be the default
		1527	loop!).
1100		1528
1101	=back	1529	=back
1102		1530
1103		1531
1104	=head1 LIBEVENT EMULATION	1532	=head1 LIBEVENT EMULATION
…		…
1128		1556
1129	=back	1557	=back
1130		1558
1131	=head1 C++ SUPPORT	1559	=head1 C++ SUPPORT
1132		1560
1133	TBD.	1561	Libev comes with some simplistic wrapper classes for C++ that mainly allow
		1562	you to use some convinience methods to start/stop watchers and also change
		1563	the callback model to a model using method callbacks on objects.
		1564
		1565	To use it,
		1566
		1567	#include <ev++.h>
		1568
		1569	(it is not installed by default). This automatically includes F<ev.h>
		1570	and puts all of its definitions (many of them macros) into the global
		1571	namespace. All C++ specific things are put into the C<ev> namespace.
		1572
		1573	It should support all the same embedding options as F<ev.h>, most notably
		1574	C<EV_MULTIPLICITY>.
		1575
		1576	Here is a list of things available in the C<ev> namespace:
		1577
		1578	=over 4
		1579
		1580	=item C<ev::READ>, C<ev::WRITE> etc.
		1581
		1582	These are just enum values with the same values as the C<EV_READ> etc.
		1583	macros from F<ev.h>.
		1584
		1585	=item C<ev::tstamp>, C<ev::now>
		1586
		1587	Aliases to the same types/functions as with the C<ev_> prefix.
		1588
		1589	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
		1590
		1591	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
		1592	the same name in the C<ev> namespace, with the exception of C<ev_signal>
		1593	which is called C<ev::sig> to avoid clashes with the C<signal> macro
		1594	defines by many implementations.
		1595
		1596	All of those classes have these methods:
		1597
		1598	=over 4
		1599
		1600	=item ev::TYPE::TYPE (object , object::method )
		1601
		1602	=item ev::TYPE::TYPE (object , object::method , struct ev_loop *)
		1603
		1604	=item ev::TYPE::~TYPE
		1605
		1606	The constructor takes a pointer to an object and a method pointer to
		1607	the event handler callback to call in this class. The constructor calls
		1608	C<ev_init> for you, which means you have to call the C<set> method
		1609	before starting it. If you do not specify a loop then the constructor
		1610	automatically associates the default loop with this watcher.
		1611
		1612	The destructor automatically stops the watcher if it is active.
		1613
		1614	=item w->set (struct ev_loop *)
		1615
		1616	Associates a different C<struct ev_loop> with this watcher. You can only
		1617	do this when the watcher is inactive (and not pending either).
		1618
		1619	=item w->set ([args])
		1620
		1621	Basically the same as C<ev_TYPE_set>, with the same args. Must be
		1622	called at least once. Unlike the C counterpart, an active watcher gets
		1623	automatically stopped and restarted.
		1624
		1625	=item w->start ()
		1626
		1627	Starts the watcher. Note that there is no C<loop> argument as the
		1628	constructor already takes the loop.
		1629
		1630	=item w->stop ()
		1631
		1632	Stops the watcher if it is active. Again, no C<loop> argument.
		1633
		1634	=item w->again () C<ev::timer>, C<ev::periodic> only
		1635
		1636	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
		1637	C<ev_TYPE_again> function.
		1638
		1639	=item w->sweep () C<ev::embed> only
		1640
		1641	Invokes C<ev_embed_sweep>.
		1642
		1643	=back
		1644
		1645	=back
		1646
		1647	Example: Define a class with an IO and idle watcher, start one of them in
		1648	the constructor.
		1649
		1650	class myclass
		1651	{
		1652	ev_io io; void io_cb (ev::io &w, int revents);
		1653	ev_idle idle void idle_cb (ev::idle &w, int revents);
		1654
		1655	myclass ();
		1656	}
		1657
		1658	myclass::myclass (int fd)
		1659	: io (this, &myclass::io_cb),
		1660	idle (this, &myclass::idle_cb)
		1661	{
		1662	io.start (fd, ev::READ);
		1663	}
		1664
		1665	=head1 EMBEDDING
		1666
		1667	Libev can (and often is) directly embedded into host
		1668	applications. Examples of applications that embed it include the Deliantra
		1669	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
		1670	and rxvt-unicode.
		1671
		1672	The goal is to enable you to just copy the neecssary files into your
		1673	source directory without having to change even a single line in them, so
		1674	you can easily upgrade by simply copying (or having a checked-out copy of
		1675	libev somewhere in your source tree).
		1676
		1677	=head2 FILESETS
		1678
		1679	Depending on what features you need you need to include one or more sets of files
		1680	in your app.
		1681
		1682	=head3 CORE EVENT LOOP
		1683
		1684	To include only the libev core (all the C<ev_*> functions), with manual
		1685	configuration (no autoconf):
		1686
		1687	#define EV_STANDALONE 1
		1688	#include "ev.c"
		1689
		1690	This will automatically include F<ev.h>, too, and should be done in a
		1691	single C source file only to provide the function implementations. To use
		1692	it, do the same for F<ev.h> in all files wishing to use this API (best
		1693	done by writing a wrapper around F<ev.h> that you can include instead and
		1694	where you can put other configuration options):
		1695
		1696	#define EV_STANDALONE 1
		1697	#include "ev.h"
		1698
		1699	Both header files and implementation files can be compiled with a C++
		1700	compiler (at least, thats a stated goal, and breakage will be treated
		1701	as a bug).
		1702
		1703	You need the following files in your source tree, or in a directory
		1704	in your include path (e.g. in libev/ when using -Ilibev):
		1705
		1706	ev.h
		1707	ev.c
		1708	ev_vars.h
		1709	ev_wrap.h
		1710
		1711	ev_win32.c required on win32 platforms only
		1712
		1713	ev_select.c only when select backend is enabled (which is by default)
		1714	ev_poll.c only when poll backend is enabled (disabled by default)
		1715	ev_epoll.c only when the epoll backend is enabled (disabled by default)
		1716	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
		1717	ev_port.c only when the solaris port backend is enabled (disabled by default)
		1718
		1719	F<ev.c> includes the backend files directly when enabled, so you only need
		1720	to compile this single file.
		1721
		1722	=head3 LIBEVENT COMPATIBILITY API
		1723
		1724	To include the libevent compatibility API, also include:
		1725
		1726	#include "event.c"
		1727
		1728	in the file including F<ev.c>, and:
		1729
		1730	#include "event.h"
		1731
		1732	in the files that want to use the libevent API. This also includes F<ev.h>.
		1733
		1734	You need the following additional files for this:
		1735
		1736	event.h
		1737	event.c
		1738
		1739	=head3 AUTOCONF SUPPORT
		1740
		1741	Instead of using C<EV_STANDALONE=1> and providing your config in
		1742	whatever way you want, you can also C<m4_include([libev.m4])> in your
		1743	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
		1744	include F<config.h> and configure itself accordingly.
		1745
		1746	For this of course you need the m4 file:
		1747
		1748	libev.m4
		1749
		1750	=head2 PREPROCESSOR SYMBOLS/MACROS
		1751
		1752	Libev can be configured via a variety of preprocessor symbols you have to define
		1753	before including any of its files. The default is not to build for multiplicity
		1754	and only include the select backend.
		1755
		1756	=over 4
		1757
		1758	=item EV_STANDALONE
		1759
		1760	Must always be C<1> if you do not use autoconf configuration, which
		1761	keeps libev from including F<config.h>, and it also defines dummy
		1762	implementations for some libevent functions (such as logging, which is not
		1763	supported). It will also not define any of the structs usually found in
		1764	F<event.h> that are not directly supported by the libev core alone.
		1765
		1766	=item EV_USE_MONOTONIC
		1767
		1768	If defined to be C<1>, libev will try to detect the availability of the
		1769	monotonic clock option at both compiletime and runtime. Otherwise no use
		1770	of the monotonic clock option will be attempted. If you enable this, you
		1771	usually have to link against librt or something similar. Enabling it when
		1772	the functionality isn't available is safe, though, althoguh you have
		1773	to make sure you link against any libraries where the C<clock_gettime>
		1774	function is hiding in (often F<-lrt>).
		1775
		1776	=item EV_USE_REALTIME
		1777
		1778	If defined to be C<1>, libev will try to detect the availability of the
		1779	realtime clock option at compiletime (and assume its availability at
		1780	runtime if successful). Otherwise no use of the realtime clock option will
		1781	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
		1782	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries
		1783	in the description of C<EV_USE_MONOTONIC>, though.
		1784
		1785	=item EV_USE_SELECT
		1786
		1787	If undefined or defined to be C<1>, libev will compile in support for the
		1788	C<select>(2) backend. No attempt at autodetection will be done: if no
		1789	other method takes over, select will be it. Otherwise the select backend
		1790	will not be compiled in.
		1791
		1792	=item EV_SELECT_USE_FD_SET
		1793
		1794	If defined to C<1>, then the select backend will use the system C<fd_set>
		1795	structure. This is useful if libev doesn't compile due to a missing
		1796	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on
		1797	exotic systems. This usually limits the range of file descriptors to some
		1798	low limit such as 1024 or might have other limitations (winsocket only
		1799	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
		1800	influence the size of the C<fd_set> used.
		1801
		1802	=item EV_SELECT_IS_WINSOCKET
		1803
		1804	When defined to C<1>, the select backend will assume that
		1805	select/socket/connect etc. don't understand file descriptors but
		1806	wants osf handles on win32 (this is the case when the select to
		1807	be used is the winsock select). This means that it will call
		1808	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
		1809	it is assumed that all these functions actually work on fds, even
		1810	on win32. Should not be defined on non-win32 platforms.
		1811
		1812	=item EV_USE_POLL
		1813
		1814	If defined to be C<1>, libev will compile in support for the C<poll>(2)
		1815	backend. Otherwise it will be enabled on non-win32 platforms. It
		1816	takes precedence over select.
		1817
		1818	=item EV_USE_EPOLL
		1819
		1820	If defined to be C<1>, libev will compile in support for the Linux
		1821	C<epoll>(7) backend. Its availability will be detected at runtime,
		1822	otherwise another method will be used as fallback. This is the
		1823	preferred backend for GNU/Linux systems.
		1824
		1825	=item EV_USE_KQUEUE
		1826
		1827	If defined to be C<1>, libev will compile in support for the BSD style
		1828	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
		1829	otherwise another method will be used as fallback. This is the preferred
		1830	backend for BSD and BSD-like systems, although on most BSDs kqueue only
		1831	supports some types of fds correctly (the only platform we found that
		1832	supports ptys for example was NetBSD), so kqueue might be compiled in, but
		1833	not be used unless explicitly requested. The best way to use it is to find
		1834	out whether kqueue supports your type of fd properly and use an embedded
		1835	kqueue loop.
		1836
		1837	=item EV_USE_PORT
		1838
		1839	If defined to be C<1>, libev will compile in support for the Solaris
		1840	10 port style backend. Its availability will be detected at runtime,
		1841	otherwise another method will be used as fallback. This is the preferred
		1842	backend for Solaris 10 systems.
		1843
		1844	=item EV_USE_DEVPOLL
		1845
		1846	reserved for future expansion, works like the USE symbols above.
		1847
		1848	=item EV_H
		1849
		1850	The name of the F<ev.h> header file used to include it. The default if
		1851	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This
		1852	can be used to virtually rename the F<ev.h> header file in case of conflicts.
		1853
		1854	=item EV_CONFIG_H
		1855
		1856	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
		1857	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
		1858	C<EV_H>, above.
		1859
		1860	=item EV_EVENT_H
		1861
		1862	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
		1863	of how the F<event.h> header can be found.
		1864
		1865	=item EV_PROTOTYPES
		1866
		1867	If defined to be C<0>, then F<ev.h> will not define any function
		1868	prototypes, but still define all the structs and other symbols. This is
		1869	occasionally useful if you want to provide your own wrapper functions
		1870	around libev functions.
		1871
		1872	=item EV_MULTIPLICITY
		1873
		1874	If undefined or defined to C<1>, then all event-loop-specific functions
		1875	will have the C<struct ev_loop *> as first argument, and you can create
		1876	additional independent event loops. Otherwise there will be no support
		1877	for multiple event loops and there is no first event loop pointer
		1878	argument. Instead, all functions act on the single default loop.
		1879
		1880	=item EV_PERIODIC_ENABLE
		1881
		1882	If undefined or defined to be C<1>, then periodic timers are supported. If
		1883	defined to be C<0>, then they are not. Disabling them saves a few kB of
		1884	code.
		1885
		1886	=item EV_EMBED_ENABLE
		1887
		1888	If undefined or defined to be C<1>, then embed watchers are supported. If
		1889	defined to be C<0>, then they are not.
		1890
		1891	=item EV_STAT_ENABLE
		1892
		1893	If undefined or defined to be C<1>, then stat watchers are supported. If
		1894	defined to be C<0>, then they are not.
		1895
		1896	=item EV_MINIMAL
		1897
		1898	If you need to shave off some kilobytes of code at the expense of some
		1899	speed, define this symbol to C<1>. Currently only used for gcc to override
		1900	some inlining decisions, saves roughly 30% codesize of amd64.
		1901
		1902	=item EV_COMMON
		1903
		1904	By default, all watchers have a C<void *data> member. By redefining
		1905	this macro to a something else you can include more and other types of
		1906	members. You have to define it each time you include one of the files,
		1907	though, and it must be identical each time.
		1908
		1909	For example, the perl EV module uses something like this:
		1910
		1911	#define EV_COMMON \
		1912	SV self; / contains this struct */ \
		1913	SV cb_sv, fh /* note no trailing ";" */
		1914
		1915	=item EV_CB_DECLARE (type)
		1916
		1917	=item EV_CB_INVOKE (watcher, revents)
		1918
		1919	=item ev_set_cb (ev, cb)
		1920
		1921	Can be used to change the callback member declaration in each watcher,
		1922	and the way callbacks are invoked and set. Must expand to a struct member
		1923	definition and a statement, respectively. See the F<ev.v> header file for
		1924	their default definitions. One possible use for overriding these is to
		1925	avoid the C<struct ev_loop *> as first argument in all cases, or to use
		1926	method calls instead of plain function calls in C++.
		1927
		1928	=head2 EXAMPLES
		1929
		1930	For a real-world example of a program the includes libev
		1931	verbatim, you can have a look at the EV perl module
		1932	(L<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
		1933	the F<libev/> subdirectory and includes them in the F<EV/EVAPI.h> (public
		1934	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
		1935	will be compiled. It is pretty complex because it provides its own header
		1936	file.
		1937
		1938	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
		1939	that everybody includes and which overrides some autoconf choices:
		1940
		1941	#define EV_USE_POLL 0
		1942	#define EV_MULTIPLICITY 0
		1943	#define EV_PERIODICS 0
		1944	#define EV_CONFIG_H <config.h>
		1945
		1946	#include "ev++.h"
		1947
		1948	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
		1949
		1950	#include "ev_cpp.h"
		1951	#include "ev.c"
		1952
		1953
		1954	=head1 COMPLEXITIES
		1955
		1956	In this section the complexities of (many of) the algorithms used inside
		1957	libev will be explained. For complexity discussions about backends see the
		1958	documentation for C<ev_default_init>.
		1959
		1960	=over 4
		1961
		1962	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		1963
		1964	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
		1965
		1966	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
		1967
		1968	=item Stopping check/prepare/idle watchers: O(1)
		1969
		1970	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))
		1971
		1972	=item Finding the next timer per loop iteration: O(1)
		1973
		1974	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		1975
		1976	=item Activating one watcher: O(1)
		1977
		1978	=back
		1979
1134		1980
1135	=head1 AUTHOR	1981	=head1 AUTHOR
1136		1982
1137	Marc Lehmann <libev@schmorp.de>.	1983	Marc Lehmann <libev@schmorp.de>.
1138		1984

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Revision 1.48 by root, Tue Nov 27 08:11:52 2007 UTC