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…		…
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
		14	#include <stdio.h> // for puts
		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
18		20
19	// all watcher callbacks have a similar signature	21	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	22	// this callback is called when data is readable on stdin
21	static void	23	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	24	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	25	{
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
…		…
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	33	}
32		34
33	// another callback, this time for a time-out	35	// another callback, this time for a time-out
34	static void	36	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	38	{
37	puts ("timeout");	39	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	42	}
…		…
60		62
61	// unloop was called, so exit	63	// unloop was called, so exit
62	return 0;	64	return 0;
63	}	65	}
64		66
65	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
66		70
67	The newest version of this document is also available as an html-formatted	71	The newest version of this document is also available as an html-formatted
68	web page you might find easier to navigate when reading it for the first	72	web page you might find easier to navigate when reading it for the first
69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.	73	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		74
		75	While this document tries to be as complete as possible in documenting
		76	libev, its usage and the rationale behind its design, it is not a tutorial
		77	on event-based programming, nor will it introduce event-based programming
		78	with libev.
		79
		80	Familarity with event based programming techniques in general is assumed
		81	throughout this document.
		82
		83	=head1 ABOUT LIBEV
70		84
71	Libev is an event loop: you register interest in certain events (such as a	85	Libev is an event loop: you register interest in certain events (such as a
72	file descriptor being readable or a timeout occurring), and it will manage	86	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	87	these event sources and provide your program with events.
74		88
…		…
103	Libev is very configurable. In this manual the default (and most common)	117	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	118	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	119	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	120	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	121	for multiple event loops, then all functions taking an initial argument of
108	name C<loop> (which is always of type C<struct ev_loop *>) will not have	122	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	123	this argument.
110		124
111	=head2 TIME REPRESENTATION	125	=head2 TIME REPRESENTATION
112		126
113	Libev represents time as a single floating point number, representing the	127	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	128	the (fractional) number of seconds since the (POSIX) epoch (somewhere
115	the beginning of 1970, details are complicated, don't ask). This type is	129	near the beginning of 1970, details are complicated, don't ask). This
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	130	type is called C<ev_tstamp>, which is what you should use too. It usually
117	to the C<double> type in C, and when you need to do any calculations on	131	aliases to the C<double> type in C. When you need to do any calculations
118	it, you should treat it as some floating point value. Unlike the name	132	on it, you should treat it as some floating point value. Unlike the name
119	component C<stamp> might indicate, it is also used for time differences	133	component C<stamp> might indicate, it is also used for time differences
120	throughout libev.	134	throughout libev.
121		135
122	=head1 ERROR HANDLING	136	=head1 ERROR HANDLING
123		137
…		…
276		290
277	=back	291	=back
278		292
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	293	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
280		294
281	An event loop is described by a C<struct ev_loop *>. The library knows two	295	An event loop is described by a C<struct ev_loop *> (the C<struct>
282	types of such loops, the I<default> loop, which supports signals and child	296	is I<not> optional in this case, as there is also an C<ev_loop>
283	events, and dynamically created loops which do not.	297	I<function>).
		298
		299	The library knows two types of such loops, the I<default> loop, which
		300	supports signals and child events, and dynamically created loops which do
		301	not.
284		302
285	=over 4	303	=over 4
286		304
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	305	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		306
…		…
294	If you don't know what event loop to use, use the one returned from this	312	If you don't know what event loop to use, use the one returned from this
295	function.	313	function.
296		314
297	Note that this function is I<not> thread-safe, so if you want to use it	315	Note that this function is I<not> thread-safe, so if you want to use it
298	from multiple threads, you have to lock (note also that this is unlikely,	316	from multiple threads, you have to lock (note also that this is unlikely,
299	as loops cannot bes hared easily between threads anyway).	317	as loops cannot be shared easily between threads anyway).
300		318
301	The default loop is the only loop that can handle C<ev_signal> and	319	The default loop is the only loop that can handle C<ev_signal> and
302	C<ev_child> watchers, and to do this, it always registers a handler	320	C<ev_child> watchers, and to do this, it always registers a handler
303	for C<SIGCHLD>. If this is a problem for your application you can either	321	for C<SIGCHLD>. If this is a problem for your application you can either
304	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	322	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
…		…
380	=item C<EVBACKEND_EPOLL> (value 4, Linux)	398	=item C<EVBACKEND_EPOLL> (value 4, Linux)
381		399
382	For few fds, this backend is a bit little slower than poll and select,	400	For few fds, this backend is a bit little slower than poll and select,
383	but it scales phenomenally better. While poll and select usually scale	401	but it scales phenomenally better. While poll and select usually scale
384	like O(total_fds) where n is the total number of fds (or the highest fd),	402	like O(total_fds) where n is the total number of fds (or the highest fd),
385	epoll scales either O(1) or O(active_fds). The epoll design has a number	403	epoll scales either O(1) or O(active_fds).
386	of shortcomings, such as silently dropping events in some hard-to-detect	404
387	cases and requiring a system call per fd change, no fork support and bad	405	The epoll mechanism deserves honorable mention as the most misdesigned
388	support for dup.	406	of the more advanced event mechanisms: mere annoyances include silently
		407	dropping file descriptors, requiring a system call per change per file
		408	descriptor (and unnecessary guessing of parameters), problems with dup and
		409	so on. The biggest issue is fork races, however - if a program forks then
		410	I<both> parent and child process have to recreate the epoll set, which can
		411	take considerable time (one syscall per file descriptor) and is of course
		412	hard to detect.
		413
		414	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		415	of course I<doesn't>, and epoll just loves to report events for totally
		416	I<different> file descriptors (even already closed ones, so one cannot
		417	even remove them from the set) than registered in the set (especially
		418	on SMP systems). Libev tries to counter these spurious notifications by
		419	employing an additional generation counter and comparing that against the
		420	events to filter out spurious ones, recreating the set when required.
389		421
390	While stopping, setting and starting an I/O watcher in the same iteration	422	While stopping, setting and starting an I/O watcher in the same iteration
391	will result in some caching, there is still a system call per such incident	423	will result in some caching, there is still a system call per such
392	(because the fd could point to a different file description now), so its	424	incident (because the same I<file descriptor> could point to a different
393	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	425	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
394	very well if you register events for both fds.	426	file descriptors might not work very well if you register events for both
395		427	file descriptors.
396	Please note that epoll sometimes generates spurious notifications, so you
397	need to use non-blocking I/O or other means to avoid blocking when no data
398	(or space) is available.
399		428
400	Best performance from this backend is achieved by not unregistering all	429	Best performance from this backend is achieved by not unregistering all
401	watchers for a file descriptor until it has been closed, if possible,	430	watchers for a file descriptor until it has been closed, if possible,
402	i.e. keep at least one watcher active per fd at all times. Stopping and	431	i.e. keep at least one watcher active per fd at all times. Stopping and
403	starting a watcher (without re-setting it) also usually doesn't cause	432	starting a watcher (without re-setting it) also usually doesn't cause
404	extra overhead.	433	extra overhead. A fork can both result in spurious notifications as well
		434	as in libev having to destroy and recreate the epoll object, which can
		435	take considerable time and thus should be avoided.
		436
		437	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		438	faster than epoll for maybe up to a hundred file descriptors, depending on
		439	the usage. So sad.
405		440
406	While nominally embeddable in other event loops, this feature is broken in	441	While nominally embeddable in other event loops, this feature is broken in
407	all kernel versions tested so far.	442	all kernel versions tested so far.
408		443
409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	444	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
410	C<EVBACKEND_POLL>.	445	C<EVBACKEND_POLL>.
411		446
412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	447	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
413		448
414	Kqueue deserves special mention, as at the time of this writing, it was	449	Kqueue deserves special mention, as at the time of this writing, it
415	broken on all BSDs except NetBSD (usually it doesn't work reliably with	450	was broken on all BSDs except NetBSD (usually it doesn't work reliably
416	anything but sockets and pipes, except on Darwin, where of course it's	451	with anything but sockets and pipes, except on Darwin, where of course
417	completely useless). For this reason it's not being "auto-detected" unless	452	it's completely useless). Unlike epoll, however, whose brokenness
418	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or	453	is by design, these kqueue bugs can (and eventually will) be fixed
419	libev was compiled on a known-to-be-good (-enough) system like NetBSD.	454	without API changes to existing programs. For this reason it's not being
		455	"auto-detected" unless you explicitly specify it in the flags (i.e. using
		456	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		457	system like NetBSD.
420		458
421	You still can embed kqueue into a normal poll or select backend and use it	459	You still can embed kqueue into a normal poll or select backend and use it
422	only for sockets (after having made sure that sockets work with kqueue on	460	only for sockets (after having made sure that sockets work with kqueue on
423	the target platform). See C<ev_embed> watchers for more info.	461	the target platform). See C<ev_embed> watchers for more info.
424		462
425	It scales in the same way as the epoll backend, but the interface to the	463	It scales in the same way as the epoll backend, but the interface to the
426	kernel is more efficient (which says nothing about its actual speed, of	464	kernel is more efficient (which says nothing about its actual speed, of
427	course). While stopping, setting and starting an I/O watcher does never	465	course). While stopping, setting and starting an I/O watcher does never
428	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	466	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
429	two event changes per incident. Support for C<fork ()> is very bad and it	467	two event changes per incident. Support for C<fork ()> is very bad (but
430	drops fds silently in similarly hard-to-detect cases.	468	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		469	cases
431		470
432	This backend usually performs well under most conditions.	471	This backend usually performs well under most conditions.
433		472
434	While nominally embeddable in other event loops, this doesn't work	473	While nominally embeddable in other event loops, this doesn't work
435	everywhere, so you might need to test for this. And since it is broken	474	everywhere, so you might need to test for this. And since it is broken
436	almost everywhere, you should only use it when you have a lot of sockets	475	almost everywhere, you should only use it when you have a lot of sockets
437	(for which it usually works), by embedding it into another event loop	476	(for which it usually works), by embedding it into another event loop
438	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,	477	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
439	using it only for sockets.	478	also broken on OS X)) and, did I mention it, using it only for sockets.
440		479
441	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	480	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
442	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with	481	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
443	C<NOTE_EOF>.	482	C<NOTE_EOF>.
444		483
…		…
464	might perform better.	503	might perform better.
465		504
466	On the positive side, with the exception of the spurious readiness	505	On the positive side, with the exception of the spurious readiness
467	notifications, this backend actually performed fully to specification	506	notifications, this backend actually performed fully to specification
468	in all tests and is fully embeddable, which is a rare feat among the	507	in all tests and is fully embeddable, which is a rare feat among the
469	OS-specific backends.	508	OS-specific backends (I vastly prefer correctness over speed hacks).
470		509
471	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	510	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
472	C<EVBACKEND_POLL>.	511	C<EVBACKEND_POLL>.
473		512
474	=item C<EVBACKEND_ALL>	513	=item C<EVBACKEND_ALL>
…		…
527	responsibility to either stop all watchers cleanly yourself I<before>	566	responsibility to either stop all watchers cleanly yourself I<before>
528	calling this function, or cope with the fact afterwards (which is usually	567	calling this function, or cope with the fact afterwards (which is usually
529	the easiest thing, you can just ignore the watchers and/or C<free ()> them	568	the easiest thing, you can just ignore the watchers and/or C<free ()> them
530	for example).	569	for example).
531		570
532	Note that certain global state, such as signal state, will not be freed by	571	Note that certain global state, such as signal state (and installed signal
533	this function, and related watchers (such as signal and child watchers)	572	handlers), will not be freed by this function, and related watchers (such
534	would need to be stopped manually.	573	as signal and child watchers) would need to be stopped manually.
535		574
536	In general it is not advisable to call this function except in the	575	In general it is not advisable to call this function except in the
537	rare occasion where you really need to free e.g. the signal handling	576	rare occasion where you really need to free e.g. the signal handling
538	pipe fds. If you need dynamically allocated loops it is better to use	577	pipe fds. If you need dynamically allocated loops it is better to use
539	C<ev_loop_new> and C<ev_loop_destroy>).	578	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
582		621
583	This value can sometimes be useful as a generation counter of sorts (it	622	This value can sometimes be useful as a generation counter of sorts (it
584	"ticks" the number of loop iterations), as it roughly corresponds with	623	"ticks" the number of loop iterations), as it roughly corresponds with
585	C<ev_prepare> and C<ev_check> calls.	624	C<ev_prepare> and C<ev_check> calls.
586		625
		626	=item unsigned int ev_loop_depth (loop)
		627
		628	Returns the number of times C<ev_loop> was entered minus the number of
		629	times C<ev_loop> was exited, in other words, the recursion depth.
		630
		631	Outside C<ev_loop>, this number is zero. In a callback, this number is
		632	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),
		633	in which case it is higher.
		634
		635	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread
		636	etc.), doesn't count as exit.
		637
587	=item unsigned int ev_backend (loop)	638	=item unsigned int ev_backend (loop)
588		639
589	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	640	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
590	use.	641	use.
591		642
…		…
605		656
606	This function is rarely useful, but when some event callback runs for a	657	This function is rarely useful, but when some event callback runs for a
607	very long time without entering the event loop, updating libev's idea of	658	very long time without entering the event loop, updating libev's idea of
608	the current time is a good idea.	659	the current time is a good idea.
609		660
610	See also "The special problem of time updates" in the C<ev_timer> section.	661	See also L<The special problem of time updates> in the C<ev_timer> section.
		662
		663	=item ev_suspend (loop)
		664
		665	=item ev_resume (loop)
		666
		667	These two functions suspend and resume a loop, for use when the loop is
		668	not used for a while and timeouts should not be processed.
		669
		670	A typical use case would be an interactive program such as a game: When
		671	the user presses C<^Z> to suspend the game and resumes it an hour later it
		672	would be best to handle timeouts as if no time had actually passed while
		673	the program was suspended. This can be achieved by calling C<ev_suspend>
		674	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		675	C<ev_resume> directly afterwards to resume timer processing.
		676
		677	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		678	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		679	will be rescheduled (that is, they will lose any events that would have
		680	occured while suspended).
		681
		682	After calling C<ev_suspend> you B<must not> call I<any> function on the
		683	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		684	without a previous call to C<ev_suspend>.
		685
		686	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		687	event loop time (see C<ev_now_update>).
611		688
612	=item ev_loop (loop, int flags)	689	=item ev_loop (loop, int flags)
613		690
614	Finally, this is it, the event handler. This function usually is called	691	Finally, this is it, the event handler. This function usually is called
615	after you initialised all your watchers and you want to start handling	692	after you initialised all your watchers and you want to start handling
…		…
631	the loop.	708	the loop.
632		709
633	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	710	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
634	necessary) and will handle those and any already outstanding ones. It	711	necessary) and will handle those and any already outstanding ones. It
635	will block your process until at least one new event arrives (which could	712	will block your process until at least one new event arrives (which could
636	be an event internal to libev itself, so there is no guarentee that a	713	be an event internal to libev itself, so there is no guarantee that a
637	user-registered callback will be called), and will return after one	714	user-registered callback will be called), and will return after one
638	iteration of the loop.	715	iteration of the loop.
639		716
640	This is useful if you are waiting for some external event in conjunction	717	This is useful if you are waiting for some external event in conjunction
641	with something not expressible using other libev watchers (i.e. "roll your	718	with something not expressible using other libev watchers (i.e. "roll your
…		…
699		776
700	If you have a watcher you never unregister that should not keep C<ev_loop>	777	If you have a watcher you never unregister that should not keep C<ev_loop>
701	from returning, call ev_unref() after starting, and ev_ref() before	778	from returning, call ev_unref() after starting, and ev_ref() before
702	stopping it.	779	stopping it.
703		780
704	As an example, libev itself uses this for its internal signal pipe: It is	781	As an example, libev itself uses this for its internal signal pipe: It
705	not visible to the libev user and should not keep C<ev_loop> from exiting	782	is not visible to the libev user and should not keep C<ev_loop> from
706	if no event watchers registered by it are active. It is also an excellent	783	exiting if no event watchers registered by it are active. It is also an
707	way to do this for generic recurring timers or from within third-party	784	excellent way to do this for generic recurring timers or from within
708	libraries. Just remember to I<unref after start> and I<ref before stop>	785	third-party libraries. Just remember to I<unref after start> and I<ref
709	(but only if the watcher wasn't active before, or was active before,	786	before stop> (but only if the watcher wasn't active before, or was active
710	respectively).	787	before, respectively. Note also that libev might stop watchers itself
		788	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		789	in the callback).
711		790
712	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	791	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
713	running when nothing else is active.	792	running when nothing else is active.
714		793
715	struct ev_signal exitsig;	794	ev_signal exitsig;
716	ev_signal_init (&exitsig, sig_cb, SIGINT);	795	ev_signal_init (&exitsig, sig_cb, SIGINT);
717	ev_signal_start (loop, &exitsig);	796	ev_signal_start (loop, &exitsig);
718	evf_unref (loop);	797	evf_unref (loop);
719		798
720	Example: For some weird reason, unregister the above signal handler again.	799	Example: For some weird reason, unregister the above signal handler again.
…		…
744		823
745	By setting a higher I<io collect interval> you allow libev to spend more	824	By setting a higher I<io collect interval> you allow libev to spend more
746	time collecting I/O events, so you can handle more events per iteration,	825	time collecting I/O events, so you can handle more events per iteration,
747	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	826	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
748	C<ev_timer>) will be not affected. Setting this to a non-null value will	827	C<ev_timer>) will be not affected. Setting this to a non-null value will
749	introduce an additional C<ev_sleep ()> call into most loop iterations.	828	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		829	sleep time ensures that libev will not poll for I/O events more often then
		830	once per this interval, on average.
750		831
751	Likewise, by setting a higher I<timeout collect interval> you allow libev	832	Likewise, by setting a higher I<timeout collect interval> you allow libev
752	to spend more time collecting timeouts, at the expense of increased	833	to spend more time collecting timeouts, at the expense of increased
753	latency/jitter/inexactness (the watcher callback will be called	834	latency/jitter/inexactness (the watcher callback will be called
754	later). C<ev_io> watchers will not be affected. Setting this to a non-null	835	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
756		837
757	Many (busy) programs can usually benefit by setting the I/O collect	838	Many (busy) programs can usually benefit by setting the I/O collect
758	interval to a value near C<0.1> or so, which is often enough for	839	interval to a value near C<0.1> or so, which is often enough for
759	interactive servers (of course not for games), likewise for timeouts. It	840	interactive servers (of course not for games), likewise for timeouts. It
760	usually doesn't make much sense to set it to a lower value than C<0.01>,	841	usually doesn't make much sense to set it to a lower value than C<0.01>,
761	as this approaches the timing granularity of most systems.	842	as this approaches the timing granularity of most systems. Note that if
		843	you do transactions with the outside world and you can't increase the
		844	parallelity, then this setting will limit your transaction rate (if you
		845	need to poll once per transaction and the I/O collect interval is 0.01,
		846	then you can't do more than 100 transations per second).
762		847
763	Setting the I<timeout collect interval> can improve the opportunity for	848	Setting the I<timeout collect interval> can improve the opportunity for
764	saving power, as the program will "bundle" timer callback invocations that	849	saving power, as the program will "bundle" timer callback invocations that
765	are "near" in time together, by delaying some, thus reducing the number of	850	are "near" in time together, by delaying some, thus reducing the number of
766	times the process sleeps and wakes up again. Another useful technique to	851	times the process sleeps and wakes up again. Another useful technique to
767	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	852	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
768	they fire on, say, one-second boundaries only.	853	they fire on, say, one-second boundaries only.
769		854
		855	Example: we only need 0.1s timeout granularity, and we wish not to poll
		856	more often than 100 times per second:
		857
		858	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		859	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		860
770	=item ev_loop_verify (loop)	861	=item ev_loop_verify (loop)
771		862
772	This function only does something when C<EV_VERIFY> support has been	863	This function only does something when C<EV_VERIFY> support has been
773	compiled in. which is the default for non-minimal builds. It tries to go	864	compiled in, which is the default for non-minimal builds. It tries to go
774	through all internal structures and checks them for validity. If anything	865	through all internal structures and checks them for validity. If anything
775	is found to be inconsistent, it will print an error message to standard	866	is found to be inconsistent, it will print an error message to standard
776	error and call C<abort ()>.	867	error and call C<abort ()>.
777		868
778	This can be used to catch bugs inside libev itself: under normal	869	This can be used to catch bugs inside libev itself: under normal
…		…
782	=back	873	=back
783		874
784		875
785	=head1 ANATOMY OF A WATCHER	876	=head1 ANATOMY OF A WATCHER
786		877
		878	In the following description, uppercase C<TYPE> in names stands for the
		879	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		880	watchers and C<ev_io_start> for I/O watchers.
		881
787	A watcher is a structure that you create and register to record your	882	A watcher is a structure that you create and register to record your
788	interest in some event. For instance, if you want to wait for STDIN to	883	interest in some event. For instance, if you want to wait for STDIN to
789	become readable, you would create an C<ev_io> watcher for that:	884	become readable, you would create an C<ev_io> watcher for that:
790		885
791	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	886	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
792	{	887	{
793	ev_io_stop (w);	888	ev_io_stop (w);
794	ev_unloop (loop, EVUNLOOP_ALL);	889	ev_unloop (loop, EVUNLOOP_ALL);
795	}	890	}
796		891
797	struct ev_loop *loop = ev_default_loop (0);	892	struct ev_loop *loop = ev_default_loop (0);
		893
798	struct ev_io stdin_watcher;	894	ev_io stdin_watcher;
		895
799	ev_init (&stdin_watcher, my_cb);	896	ev_init (&stdin_watcher, my_cb);
800	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	897	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
801	ev_io_start (loop, &stdin_watcher);	898	ev_io_start (loop, &stdin_watcher);
		899
802	ev_loop (loop, 0);	900	ev_loop (loop, 0);
803		901
804	As you can see, you are responsible for allocating the memory for your	902	As you can see, you are responsible for allocating the memory for your
805	watcher structures (and it is usually a bad idea to do this on the stack,	903	watcher structures (and it is I<usually> a bad idea to do this on the
806	although this can sometimes be quite valid).	904	stack).
		905
		906	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		907	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
807		908
808	Each watcher structure must be initialised by a call to C<ev_init	909	Each watcher structure must be initialised by a call to C<ev_init
809	(watcher *, callback)>, which expects a callback to be provided. This	910	(watcher *, callback)>, which expects a callback to be provided. This
810	callback gets invoked each time the event occurs (or, in the case of I/O	911	callback gets invoked each time the event occurs (or, in the case of I/O
811	watchers, each time the event loop detects that the file descriptor given	912	watchers, each time the event loop detects that the file descriptor given
812	is readable and/or writable).	913	is readable and/or writable).
813		914
814	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	915	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
815	with arguments specific to this watcher type. There is also a macro	916	macro to configure it, with arguments specific to the watcher type. There
816	to combine initialisation and setting in one call: C<< ev_<type>_init	917	is also a macro to combine initialisation and setting in one call: C<<
817	(watcher *, callback, ...) >>.	918	ev_TYPE_init (watcher *, callback, ...) >>.
818		919
819	To make the watcher actually watch out for events, you have to start it	920	To make the watcher actually watch out for events, you have to start it
820	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	921	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
821	*) >>), and you can stop watching for events at any time by calling the	922	*) >>), and you can stop watching for events at any time by calling the
822	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	923	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
823		924
824	As long as your watcher is active (has been started but not stopped) you	925	As long as your watcher is active (has been started but not stopped) you
825	must not touch the values stored in it. Most specifically you must never	926	must not touch the values stored in it. Most specifically you must never
826	reinitialise it or call its C<set> macro.	927	reinitialise it or call its C<ev_TYPE_set> macro.
827		928
828	Each and every callback receives the event loop pointer as first, the	929	Each and every callback receives the event loop pointer as first, the
829	registered watcher structure as second, and a bitset of received events as	930	registered watcher structure as second, and a bitset of received events as
830	third argument.	931	third argument.
831		932
…		…
889		990
890	=item C<EV_ASYNC>	991	=item C<EV_ASYNC>
891		992
892	The given async watcher has been asynchronously notified (see C<ev_async>).	993	The given async watcher has been asynchronously notified (see C<ev_async>).
893		994
		995	=item C<EV_CUSTOM>
		996
		997	Not ever sent (or otherwise used) by libev itself, but can be freely used
		998	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		999
894	=item C<EV_ERROR>	1000	=item C<EV_ERROR>
895		1001
896	An unspecified error has occurred, the watcher has been stopped. This might	1002	An unspecified error has occurred, the watcher has been stopped. This might
897	happen because the watcher could not be properly started because libev	1003	happen because the watcher could not be properly started because libev
898	ran out of memory, a file descriptor was found to be closed or any other	1004	ran out of memory, a file descriptor was found to be closed or any other
		1005	problem. Libev considers these application bugs.
		1006
899	problem. You best act on it by reporting the problem and somehow coping	1007	You best act on it by reporting the problem and somehow coping with the
900	with the watcher being stopped.	1008	watcher being stopped. Note that well-written programs should not receive
		1009	an error ever, so when your watcher receives it, this usually indicates a
		1010	bug in your program.
901		1011
902	Libev will usually signal a few "dummy" events together with an error, for	1012	Libev will usually signal a few "dummy" events together with an error, for
903	example it might indicate that a fd is readable or writable, and if your	1013	example it might indicate that a fd is readable or writable, and if your
904	callbacks is well-written it can just attempt the operation and cope with	1014	callbacks is well-written it can just attempt the operation and cope with
905	the error from read() or write(). This will not work in multi-threaded	1015	the error from read() or write(). This will not work in multi-threaded
…		…
908		1018
909	=back	1019	=back
910		1020
911	=head2 GENERIC WATCHER FUNCTIONS	1021	=head2 GENERIC WATCHER FUNCTIONS
912		1022
913	In the following description, C<TYPE> stands for the watcher type,
914	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
915
916	=over 4	1023	=over 4
917		1024
918	=item C<ev_init> (ev_TYPE *watcher, callback)	1025	=item C<ev_init> (ev_TYPE *watcher, callback)
919		1026
920	This macro initialises the generic portion of a watcher. The contents	1027	This macro initialises the generic portion of a watcher. The contents
…		…
925	which rolls both calls into one.	1032	which rolls both calls into one.
926		1033
927	You can reinitialise a watcher at any time as long as it has been stopped	1034	You can reinitialise a watcher at any time as long as it has been stopped
928	(or never started) and there are no pending events outstanding.	1035	(or never started) and there are no pending events outstanding.
929		1036
930	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1037	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
931	int revents)>.	1038	int revents)>.
932		1039
933	Example: Initialise an C<ev_io> watcher in two steps.	1040	Example: Initialise an C<ev_io> watcher in two steps.
934		1041
935	ev_io w;	1042	ev_io w;
…		…
1012	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1119	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1013	(default: C<-2>). Pending watchers with higher priority will be invoked	1120	(default: C<-2>). Pending watchers with higher priority will be invoked
1014	before watchers with lower priority, but priority will not keep watchers	1121	before watchers with lower priority, but priority will not keep watchers
1015	from being executed (except for C<ev_idle> watchers).	1122	from being executed (except for C<ev_idle> watchers).
1016		1123
1017	This means that priorities are I<only> used for ordering callback
1018	invocation after new events have been received. This is useful, for
1019	example, to reduce latency after idling, or more often, to bind two
1020	watchers on the same event and make sure one is called first.
1021
1022	If you need to suppress invocation when higher priority events are pending	1124	If you need to suppress invocation when higher priority events are pending
1023	you need to look at C<ev_idle> watchers, which provide this functionality.	1125	you need to look at C<ev_idle> watchers, which provide this functionality.
1024		1126
1025	You I<must not> change the priority of a watcher as long as it is active or	1127	You I<must not> change the priority of a watcher as long as it is active or
1026	pending.	1128	pending.
1027		1129
		1130	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1131	fine, as long as you do not mind that the priority value you query might
		1132	or might not have been clamped to the valid range.
		1133
1028	The default priority used by watchers when no priority has been set is	1134	The default priority used by watchers when no priority has been set is
1029	always C<0>, which is supposed to not be too high and not be too low :).	1135	always C<0>, which is supposed to not be too high and not be too low :).
1030		1136
1031	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1137	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1032	fine, as long as you do not mind that the priority value you query might	1138	priorities.
1033	or might not have been adjusted to be within valid range.
1034		1139
1035	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1140	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1036		1141
1037	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1142	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1038	C<loop> nor C<revents> need to be valid as long as the watcher callback	1143	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1060	member, you can also "subclass" the watcher type and provide your own	1165	member, you can also "subclass" the watcher type and provide your own
1061	data:	1166	data:
1062		1167
1063	struct my_io	1168	struct my_io
1064	{	1169	{
1065	struct ev_io io;	1170	ev_io io;
1066	int otherfd;	1171	int otherfd;
1067	void *somedata;	1172	void *somedata;
1068	struct whatever *mostinteresting;	1173	struct whatever *mostinteresting;
1069	};	1174	};
1070		1175
…		…
1073	ev_io_init (&w.io, my_cb, fd, EV_READ);	1178	ev_io_init (&w.io, my_cb, fd, EV_READ);
1074		1179
1075	And since your callback will be called with a pointer to the watcher, you	1180	And since your callback will be called with a pointer to the watcher, you
1076	can cast it back to your own type:	1181	can cast it back to your own type:
1077		1182
1078	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1183	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1079	{	1184	{
1080	struct my_io *w = (struct my_io *)w_;	1185	struct my_io *w = (struct my_io *)w_;
1081	...	1186	...
1082	}	1187	}
1083		1188
…		…
1101	programmers):	1206	programmers):
1102		1207
1103	#include <stddef.h>	1208	#include <stddef.h>
1104		1209
1105	static void	1210	static void
1106	t1_cb (EV_P_ struct ev_timer *w, int revents)	1211	t1_cb (EV_P_ ev_timer *w, int revents)
1107	{	1212	{
1108	struct my_biggy big = (struct my_biggy *	1213	struct my_biggy big = (struct my_biggy *)
1109	(((char *)w) - offsetof (struct my_biggy, t1));	1214	(((char *)w) - offsetof (struct my_biggy, t1));
1110	}	1215	}
1111		1216
1112	static void	1217	static void
1113	t2_cb (EV_P_ struct ev_timer *w, int revents)	1218	t2_cb (EV_P_ ev_timer *w, int revents)
1114	{	1219	{
1115	struct my_biggy big = (struct my_biggy *	1220	struct my_biggy big = (struct my_biggy *)
1116	(((char *)w) - offsetof (struct my_biggy, t2));	1221	(((char *)w) - offsetof (struct my_biggy, t2));
1117	}	1222	}
		1223
		1224	=head2 WATCHER PRIORITY MODELS
		1225
		1226	Many event loops support I<watcher priorities>, which are usually small
		1227	integers that influence the ordering of event callback invocation
		1228	between watchers in some way, all else being equal.
		1229
		1230	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1231	description for the more technical details such as the actual priority
		1232	range.
		1233
		1234	There are two common ways how these these priorities are being interpreted
		1235	by event loops:
		1236
		1237	In the more common lock-out model, higher priorities "lock out" invocation
		1238	of lower priority watchers, which means as long as higher priority
		1239	watchers receive events, lower priority watchers are not being invoked.
		1240
		1241	The less common only-for-ordering model uses priorities solely to order
		1242	callback invocation within a single event loop iteration: Higher priority
		1243	watchers are invoked before lower priority ones, but they all get invoked
		1244	before polling for new events.
		1245
		1246	Libev uses the second (only-for-ordering) model for all its watchers
		1247	except for idle watchers (which use the lock-out model).
		1248
		1249	The rationale behind this is that implementing the lock-out model for
		1250	watchers is not well supported by most kernel interfaces, and most event
		1251	libraries will just poll for the same events again and again as long as
		1252	their callbacks have not been executed, which is very inefficient in the
		1253	common case of one high-priority watcher locking out a mass of lower
		1254	priority ones.
		1255
		1256	Static (ordering) priorities are most useful when you have two or more
		1257	watchers handling the same resource: a typical usage example is having an
		1258	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1259	timeouts. Under load, data might be received while the program handles
		1260	other jobs, but since timers normally get invoked first, the timeout
		1261	handler will be executed before checking for data. In that case, giving
		1262	the timer a lower priority than the I/O watcher ensures that I/O will be
		1263	handled first even under adverse conditions (which is usually, but not
		1264	always, what you want).
		1265
		1266	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1267	will only be executed when no same or higher priority watchers have
		1268	received events, they can be used to implement the "lock-out" model when
		1269	required.
		1270
		1271	For example, to emulate how many other event libraries handle priorities,
		1272	you can associate an C<ev_idle> watcher to each such watcher, and in
		1273	the normal watcher callback, you just start the idle watcher. The real
		1274	processing is done in the idle watcher callback. This causes libev to
		1275	continously poll and process kernel event data for the watcher, but when
		1276	the lock-out case is known to be rare (which in turn is rare :), this is
		1277	workable.
		1278
		1279	Usually, however, the lock-out model implemented that way will perform
		1280	miserably under the type of load it was designed to handle. In that case,
		1281	it might be preferable to stop the real watcher before starting the
		1282	idle watcher, so the kernel will not have to process the event in case
		1283	the actual processing will be delayed for considerable time.
		1284
		1285	Here is an example of an I/O watcher that should run at a strictly lower
		1286	priority than the default, and which should only process data when no
		1287	other events are pending:
		1288
		1289	ev_idle idle; // actual processing watcher
		1290	ev_io io; // actual event watcher
		1291
		1292	static void
		1293	io_cb (EV_P_ ev_io *w, int revents)
		1294	{
		1295	// stop the I/O watcher, we received the event, but
		1296	// are not yet ready to handle it.
		1297	ev_io_stop (EV_A_ w);
		1298
		1299	// start the idle watcher to ahndle the actual event.
		1300	// it will not be executed as long as other watchers
		1301	// with the default priority are receiving events.
		1302	ev_idle_start (EV_A_ &idle);
		1303	}
		1304
		1305	static void
		1306	idle_cb (EV_P_ ev_idle *w, int revents)
		1307	{
		1308	// actual processing
		1309	read (STDIN_FILENO, ...);
		1310
		1311	// have to start the I/O watcher again, as
		1312	// we have handled the event
		1313	ev_io_start (EV_P_ &io);
		1314	}
		1315
		1316	// initialisation
		1317	ev_idle_init (&idle, idle_cb);
		1318	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1319	ev_io_start (EV_DEFAULT_ &io);
		1320
		1321	In the "real" world, it might also be beneficial to start a timer, so that
		1322	low-priority connections can not be locked out forever under load. This
		1323	enables your program to keep a lower latency for important connections
		1324	during short periods of high load, while not completely locking out less
		1325	important ones.
1118		1326
1119		1327
1120	=head1 WATCHER TYPES	1328	=head1 WATCHER TYPES
1121		1329
1122	This section describes each watcher in detail, but will not repeat	1330	This section describes each watcher in detail, but will not repeat
…		…
1148	descriptors to non-blocking mode is also usually a good idea (but not	1356	descriptors to non-blocking mode is also usually a good idea (but not
1149	required if you know what you are doing).	1357	required if you know what you are doing).
1150		1358
1151	If you cannot use non-blocking mode, then force the use of a	1359	If you cannot use non-blocking mode, then force the use of a
1152	known-to-be-good backend (at the time of this writing, this includes only	1360	known-to-be-good backend (at the time of this writing, this includes only
1153	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).	1361	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1362	descriptors for which non-blocking operation makes no sense (such as
		1363	files) - libev doesn't guarentee any specific behaviour in that case.
1154		1364
1155	Another thing you have to watch out for is that it is quite easy to	1365	Another thing you have to watch out for is that it is quite easy to
1156	receive "spurious" readiness notifications, that is your callback might	1366	receive "spurious" readiness notifications, that is your callback might
1157	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1367	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1158	because there is no data. Not only are some backends known to create a	1368	because there is no data. Not only are some backends known to create a
…		…
1253	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1463	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1254	readable, but only once. Since it is likely line-buffered, you could	1464	readable, but only once. Since it is likely line-buffered, you could
1255	attempt to read a whole line in the callback.	1465	attempt to read a whole line in the callback.
1256		1466
1257	static void	1467	static void
1258	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1468	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1259	{	1469	{
1260	ev_io_stop (loop, w);	1470	ev_io_stop (loop, w);
1261	.. read from stdin here (or from w->fd) and handle any I/O errors	1471	.. read from stdin here (or from w->fd) and handle any I/O errors
1262	}	1472	}
1263		1473
1264	...	1474	...
1265	struct ev_loop *loop = ev_default_init (0);	1475	struct ev_loop *loop = ev_default_init (0);
1266	struct ev_io stdin_readable;	1476	ev_io stdin_readable;
1267	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1477	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1268	ev_io_start (loop, &stdin_readable);	1478	ev_io_start (loop, &stdin_readable);
1269	ev_loop (loop, 0);	1479	ev_loop (loop, 0);
1270		1480
1271		1481
…		…
1279	year, it will still time out after (roughly) one hour. "Roughly" because	1489	year, it will still time out after (roughly) one hour. "Roughly" because
1280	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1490	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1281	monotonic clock option helps a lot here).	1491	monotonic clock option helps a lot here).
1282		1492
1283	The callback is guaranteed to be invoked only I<after> its timeout has	1493	The callback is guaranteed to be invoked only I<after> its timeout has
1284	passed, but if multiple timers become ready during the same loop iteration	1494	passed (not I<at>, so on systems with very low-resolution clocks this
1285	then order of execution is undefined.	1495	might introduce a small delay). If multiple timers become ready during the
		1496	same loop iteration then the ones with earlier time-out values are invoked
		1497	before ones of the same priority with later time-out values (but this is
		1498	no longer true when a callback calls C<ev_loop> recursively).
		1499
		1500	=head3 Be smart about timeouts
		1501
		1502	Many real-world problems involve some kind of timeout, usually for error
		1503	recovery. A typical example is an HTTP request - if the other side hangs,
		1504	you want to raise some error after a while.
		1505
		1506	What follows are some ways to handle this problem, from obvious and
		1507	inefficient to smart and efficient.
		1508
		1509	In the following, a 60 second activity timeout is assumed - a timeout that
		1510	gets reset to 60 seconds each time there is activity (e.g. each time some
		1511	data or other life sign was received).
		1512
		1513	=over 4
		1514
		1515	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1516
		1517	This is the most obvious, but not the most simple way: In the beginning,
		1518	start the watcher:
		1519
		1520	ev_timer_init (timer, callback, 60., 0.);
		1521	ev_timer_start (loop, timer);
		1522
		1523	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1524	and start it again:
		1525
		1526	ev_timer_stop (loop, timer);
		1527	ev_timer_set (timer, 60., 0.);
		1528	ev_timer_start (loop, timer);
		1529
		1530	This is relatively simple to implement, but means that each time there is
		1531	some activity, libev will first have to remove the timer from its internal
		1532	data structure and then add it again. Libev tries to be fast, but it's
		1533	still not a constant-time operation.
		1534
		1535	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1536
		1537	This is the easiest way, and involves using C<ev_timer_again> instead of
		1538	C<ev_timer_start>.
		1539
		1540	To implement this, configure an C<ev_timer> with a C<repeat> value
		1541	of C<60> and then call C<ev_timer_again> at start and each time you
		1542	successfully read or write some data. If you go into an idle state where
		1543	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1544	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1545
		1546	That means you can ignore both the C<ev_timer_start> function and the
		1547	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1548	member and C<ev_timer_again>.
		1549
		1550	At start:
		1551
		1552	ev_init (timer, callback);
		1553	timer->repeat = 60.;
		1554	ev_timer_again (loop, timer);
		1555
		1556	Each time there is some activity:
		1557
		1558	ev_timer_again (loop, timer);
		1559
		1560	It is even possible to change the time-out on the fly, regardless of
		1561	whether the watcher is active or not:
		1562
		1563	timer->repeat = 30.;
		1564	ev_timer_again (loop, timer);
		1565
		1566	This is slightly more efficient then stopping/starting the timer each time
		1567	you want to modify its timeout value, as libev does not have to completely
		1568	remove and re-insert the timer from/into its internal data structure.
		1569
		1570	It is, however, even simpler than the "obvious" way to do it.
		1571
		1572	=item 3. Let the timer time out, but then re-arm it as required.
		1573
		1574	This method is more tricky, but usually most efficient: Most timeouts are
		1575	relatively long compared to the intervals between other activity - in
		1576	our example, within 60 seconds, there are usually many I/O events with
		1577	associated activity resets.
		1578
		1579	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1580	but remember the time of last activity, and check for a real timeout only
		1581	within the callback:
		1582
		1583	ev_tstamp last_activity; // time of last activity
		1584
		1585	static void
		1586	callback (EV_P_ ev_timer *w, int revents)
		1587	{
		1588	ev_tstamp now = ev_now (EV_A);
		1589	ev_tstamp timeout = last_activity + 60.;
		1590
		1591	// if last_activity + 60. is older than now, we did time out
		1592	if (timeout < now)
		1593	{
		1594	// timeout occured, take action
		1595	}
		1596	else
		1597	{
		1598	// callback was invoked, but there was some activity, re-arm
		1599	// the watcher to fire in last_activity + 60, which is
		1600	// guaranteed to be in the future, so "again" is positive:
		1601	w->repeat = timeout - now;
		1602	ev_timer_again (EV_A_ w);
		1603	}
		1604	}
		1605
		1606	To summarise the callback: first calculate the real timeout (defined
		1607	as "60 seconds after the last activity"), then check if that time has
		1608	been reached, which means something I<did>, in fact, time out. Otherwise
		1609	the callback was invoked too early (C<timeout> is in the future), so
		1610	re-schedule the timer to fire at that future time, to see if maybe we have
		1611	a timeout then.
		1612
		1613	Note how C<ev_timer_again> is used, taking advantage of the
		1614	C<ev_timer_again> optimisation when the timer is already running.
		1615
		1616	This scheme causes more callback invocations (about one every 60 seconds
		1617	minus half the average time between activity), but virtually no calls to
		1618	libev to change the timeout.
		1619
		1620	To start the timer, simply initialise the watcher and set C<last_activity>
		1621	to the current time (meaning we just have some activity :), then call the
		1622	callback, which will "do the right thing" and start the timer:
		1623
		1624	ev_init (timer, callback);
		1625	last_activity = ev_now (loop);
		1626	callback (loop, timer, EV_TIMEOUT);
		1627
		1628	And when there is some activity, simply store the current time in
		1629	C<last_activity>, no libev calls at all:
		1630
		1631	last_actiivty = ev_now (loop);
		1632
		1633	This technique is slightly more complex, but in most cases where the
		1634	time-out is unlikely to be triggered, much more efficient.
		1635
		1636	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1637	callback :) - just change the timeout and invoke the callback, which will
		1638	fix things for you.
		1639
		1640	=item 4. Wee, just use a double-linked list for your timeouts.
		1641
		1642	If there is not one request, but many thousands (millions...), all
		1643	employing some kind of timeout with the same timeout value, then one can
		1644	do even better:
		1645
		1646	When starting the timeout, calculate the timeout value and put the timeout
		1647	at the I<end> of the list.
		1648
		1649	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1650	the list is expected to fire (for example, using the technique #3).
		1651
		1652	When there is some activity, remove the timer from the list, recalculate
		1653	the timeout, append it to the end of the list again, and make sure to
		1654	update the C<ev_timer> if it was taken from the beginning of the list.
		1655
		1656	This way, one can manage an unlimited number of timeouts in O(1) time for
		1657	starting, stopping and updating the timers, at the expense of a major
		1658	complication, and having to use a constant timeout. The constant timeout
		1659	ensures that the list stays sorted.
		1660
		1661	=back
		1662
		1663	So which method the best?
		1664
		1665	Method #2 is a simple no-brain-required solution that is adequate in most
		1666	situations. Method #3 requires a bit more thinking, but handles many cases
		1667	better, and isn't very complicated either. In most case, choosing either
		1668	one is fine, with #3 being better in typical situations.
		1669
		1670	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1671	rather complicated, but extremely efficient, something that really pays
		1672	off after the first million or so of active timers, i.e. it's usually
		1673	overkill :)
1286		1674
1287	=head3 The special problem of time updates	1675	=head3 The special problem of time updates
1288		1676
1289	Establishing the current time is a costly operation (it usually takes at	1677	Establishing the current time is a costly operation (it usually takes at
1290	least two system calls): EV therefore updates its idea of the current	1678	least two system calls): EV therefore updates its idea of the current
…		…
1334	If the timer is started but non-repeating, stop it (as if it timed out).	1722	If the timer is started but non-repeating, stop it (as if it timed out).
1335		1723
1336	If the timer is repeating, either start it if necessary (with the	1724	If the timer is repeating, either start it if necessary (with the
1337	C<repeat> value), or reset the running timer to the C<repeat> value.	1725	C<repeat> value), or reset the running timer to the C<repeat> value.
1338		1726
1339	This sounds a bit complicated, but here is a useful and typical	1727	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1340	example: Imagine you have a TCP connection and you want a so-called idle	1728	usage example.
1341	timeout, that is, you want to be called when there have been, say, 60
1342	seconds of inactivity on the socket. The easiest way to do this is to
1343	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1344	C<ev_timer_again> each time you successfully read or write some data. If
1345	you go into an idle state where you do not expect data to travel on the
1346	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1347	automatically restart it if need be.
1348
1349	That means you can ignore the C<after> value and C<ev_timer_start>
1350	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1351
1352	ev_timer_init (timer, callback, 0., 5.);
1353	ev_timer_again (loop, timer);
1354	...
1355	timer->again = 17.;
1356	ev_timer_again (loop, timer);
1357	...
1358	timer->again = 10.;
1359	ev_timer_again (loop, timer);
1360
1361	This is more slightly efficient then stopping/starting the timer each time
1362	you want to modify its timeout value.
1363
1364	Note, however, that it is often even more efficient to remember the
1365	time of the last activity and let the timer time-out naturally. In the
1366	callback, you then check whether the time-out is real, or, if there was
1367	some activity, you reschedule the watcher to time-out in "last_activity +
1368	timeout - ev_now ()" seconds.
1369		1729
1370	=item ev_tstamp repeat [read-write]	1730	=item ev_tstamp repeat [read-write]
1371		1731
1372	The current C<repeat> value. Will be used each time the watcher times out	1732	The current C<repeat> value. Will be used each time the watcher times out
1373	or C<ev_timer_again> is called, and determines the next timeout (if any),	1733	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1378	=head3 Examples	1738	=head3 Examples
1379		1739
1380	Example: Create a timer that fires after 60 seconds.	1740	Example: Create a timer that fires after 60 seconds.
1381		1741
1382	static void	1742	static void
1383	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1743	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1384	{	1744	{
1385	.. one minute over, w is actually stopped right here	1745	.. one minute over, w is actually stopped right here
1386	}	1746	}
1387		1747
1388	struct ev_timer mytimer;	1748	ev_timer mytimer;
1389	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1749	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1390	ev_timer_start (loop, &mytimer);	1750	ev_timer_start (loop, &mytimer);
1391		1751
1392	Example: Create a timeout timer that times out after 10 seconds of	1752	Example: Create a timeout timer that times out after 10 seconds of
1393	inactivity.	1753	inactivity.
1394		1754
1395	static void	1755	static void
1396	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1756	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1397	{	1757	{
1398	.. ten seconds without any activity	1758	.. ten seconds without any activity
1399	}	1759	}
1400		1760
1401	struct ev_timer mytimer;	1761	ev_timer mytimer;
1402	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1762	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1403	ev_timer_again (&mytimer); /* start timer */	1763	ev_timer_again (&mytimer); /* start timer */
1404	ev_loop (loop, 0);	1764	ev_loop (loop, 0);
1405		1765
1406	// and in some piece of code that gets executed on any "activity":	1766	// and in some piece of code that gets executed on any "activity":
…		…
1411	=head2 C<ev_periodic> - to cron or not to cron?	1771	=head2 C<ev_periodic> - to cron or not to cron?
1412		1772
1413	Periodic watchers are also timers of a kind, but they are very versatile	1773	Periodic watchers are also timers of a kind, but they are very versatile
1414	(and unfortunately a bit complex).	1774	(and unfortunately a bit complex).
1415		1775
1416	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1776	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1417	but on wall clock time (absolute time). You can tell a periodic watcher	1777	relative time, the physical time that passes) but on wall clock time
1418	to trigger after some specific point in time. For example, if you tell a	1778	(absolute time, the thing you can read on your calender or clock). The
1419	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	1779	difference is that wall clock time can run faster or slower than real
1420	+ 10.>, that is, an absolute time not a delay) and then reset your system	1780	time, and time jumps are not uncommon (e.g. when you adjust your
1421	clock to January of the previous year, then it will take more than year	1781	wrist-watch).
1422	to trigger the event (unlike an C<ev_timer>, which would still trigger
1423	roughly 10 seconds later as it uses a relative timeout).
1424		1782
		1783	You can tell a periodic watcher to trigger after some specific point
		1784	in time: for example, if you tell a periodic watcher to trigger "in 10
		1785	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1786	not a delay) and then reset your system clock to January of the previous
		1787	year, then it will take a year or more to trigger the event (unlike an
		1788	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1789	it, as it uses a relative timeout).
		1790
1425	C<ev_periodic>s can also be used to implement vastly more complex timers,	1791	C<ev_periodic> watchers can also be used to implement vastly more complex
1426	such as triggering an event on each "midnight, local time", or other	1792	timers, such as triggering an event on each "midnight, local time", or
1427	complicated rules.	1793	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1794	those cannot react to time jumps.
1428		1795
1429	As with timers, the callback is guaranteed to be invoked only when the	1796	As with timers, the callback is guaranteed to be invoked only when the
1430	time (C<at>) has passed, but if multiple periodic timers become ready	1797	point in time where it is supposed to trigger has passed. If multiple
1431	during the same loop iteration, then order of execution is undefined.	1798	timers become ready during the same loop iteration then the ones with
		1799	earlier time-out values are invoked before ones with later time-out values
		1800	(but this is no longer true when a callback calls C<ev_loop> recursively).
1432		1801
1433	=head3 Watcher-Specific Functions and Data Members	1802	=head3 Watcher-Specific Functions and Data Members
1434		1803
1435	=over 4	1804	=over 4
1436		1805
1437	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1806	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1438		1807
1439	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1808	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1440		1809
1441	Lots of arguments, lets sort it out... There are basically three modes of	1810	Lots of arguments, let's sort it out... There are basically three modes of
1442	operation, and we will explain them from simplest to most complex:	1811	operation, and we will explain them from simplest to most complex:
1443		1812
1444	=over 4	1813	=over 4
1445		1814
1446	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1815	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1447		1816
1448	In this configuration the watcher triggers an event after the wall clock	1817	In this configuration the watcher triggers an event after the wall clock
1449	time C<at> has passed. It will not repeat and will not adjust when a time	1818	time C<offset> has passed. It will not repeat and will not adjust when a
1450	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1819	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1451	only run when the system clock reaches or surpasses this time.	1820	will be stopped and invoked when the system clock reaches or surpasses
		1821	this point in time.
1452		1822
1453	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1823	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1454		1824
1455	In this mode the watcher will always be scheduled to time out at the next	1825	In this mode the watcher will always be scheduled to time out at the next
1456	C<at + N * interval> time (for some integer N, which can also be negative)	1826	C<offset + N * interval> time (for some integer N, which can also be
1457	and then repeat, regardless of any time jumps.	1827	negative) and then repeat, regardless of any time jumps. The C<offset>
		1828	argument is merely an offset into the C<interval> periods.
1458		1829
1459	This can be used to create timers that do not drift with respect to the	1830	This can be used to create timers that do not drift with respect to the
1460	system clock, for example, here is a C<ev_periodic> that triggers each	1831	system clock, for example, here is an C<ev_periodic> that triggers each
1461	hour, on the hour:	1832	hour, on the hour (with respect to UTC):
1462		1833
1463	ev_periodic_set (&periodic, 0., 3600., 0);	1834	ev_periodic_set (&periodic, 0., 3600., 0);
1464		1835
1465	This doesn't mean there will always be 3600 seconds in between triggers,	1836	This doesn't mean there will always be 3600 seconds in between triggers,
1466	but only that the callback will be called when the system time shows a	1837	but only that the callback will be called when the system time shows a
1467	full hour (UTC), or more correctly, when the system time is evenly divisible	1838	full hour (UTC), or more correctly, when the system time is evenly divisible
1468	by 3600.	1839	by 3600.
1469		1840
1470	Another way to think about it (for the mathematically inclined) is that	1841	Another way to think about it (for the mathematically inclined) is that
1471	C<ev_periodic> will try to run the callback in this mode at the next possible	1842	C<ev_periodic> will try to run the callback in this mode at the next possible
1472	time where C<time = at (mod interval)>, regardless of any time jumps.	1843	time where C<time = offset (mod interval)>, regardless of any time jumps.
1473		1844
1474	For numerical stability it is preferable that the C<at> value is near	1845	For numerical stability it is preferable that the C<offset> value is near
1475	C<ev_now ()> (the current time), but there is no range requirement for	1846	C<ev_now ()> (the current time), but there is no range requirement for
1476	this value, and in fact is often specified as zero.	1847	this value, and in fact is often specified as zero.
1477		1848
1478	Note also that there is an upper limit to how often a timer can fire (CPU	1849	Note also that there is an upper limit to how often a timer can fire (CPU
1479	speed for example), so if C<interval> is very small then timing stability	1850	speed for example), so if C<interval> is very small then timing stability
1480	will of course deteriorate. Libev itself tries to be exact to be about one	1851	will of course deteriorate. Libev itself tries to be exact to be about one
1481	millisecond (if the OS supports it and the machine is fast enough).	1852	millisecond (if the OS supports it and the machine is fast enough).
1482		1853
1483	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1854	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1484		1855
1485	In this mode the values for C<interval> and C<at> are both being	1856	In this mode the values for C<interval> and C<offset> are both being
1486	ignored. Instead, each time the periodic watcher gets scheduled, the	1857	ignored. Instead, each time the periodic watcher gets scheduled, the
1487	reschedule callback will be called with the watcher as first, and the	1858	reschedule callback will be called with the watcher as first, and the
1488	current time as second argument.	1859	current time as second argument.
1489		1860
1490	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1861	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1491	ever, or make ANY event loop modifications whatsoever>.	1862	or make ANY other event loop modifications whatsoever, unless explicitly
		1863	allowed by documentation here>.
1492		1864
1493	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1865	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1494	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	1866	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1495	only event loop modification you are allowed to do).	1867	only event loop modification you are allowed to do).
1496		1868
1497	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1869	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1498	*w, ev_tstamp now)>, e.g.:	1870	*w, ev_tstamp now)>, e.g.:
1499		1871
		1872	static ev_tstamp
1500	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1873	my_rescheduler (ev_periodic *w, ev_tstamp now)
1501	{	1874	{
1502	return now + 60.;	1875	return now + 60.;
1503	}	1876	}
1504		1877
1505	It must return the next time to trigger, based on the passed time value	1878	It must return the next time to trigger, based on the passed time value
…		…
1525	a different time than the last time it was called (e.g. in a crond like	1898	a different time than the last time it was called (e.g. in a crond like
1526	program when the crontabs have changed).	1899	program when the crontabs have changed).
1527		1900
1528	=item ev_tstamp ev_periodic_at (ev_periodic *)	1901	=item ev_tstamp ev_periodic_at (ev_periodic *)
1529		1902
1530	When active, returns the absolute time that the watcher is supposed to	1903	When active, returns the absolute time that the watcher is supposed
1531	trigger next.	1904	to trigger next. This is not the same as the C<offset> argument to
		1905	C<ev_periodic_set>, but indeed works even in interval and manual
		1906	rescheduling modes.
1532		1907
1533	=item ev_tstamp offset [read-write]	1908	=item ev_tstamp offset [read-write]
1534		1909
1535	When repeating, this contains the offset value, otherwise this is the	1910	When repeating, this contains the offset value, otherwise this is the
1536	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1911	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		1912	although libev might modify this value for better numerical stability).
1537		1913
1538	Can be modified any time, but changes only take effect when the periodic	1914	Can be modified any time, but changes only take effect when the periodic
1539	timer fires or C<ev_periodic_again> is being called.	1915	timer fires or C<ev_periodic_again> is being called.
1540		1916
1541	=item ev_tstamp interval [read-write]	1917	=item ev_tstamp interval [read-write]
1542		1918
1543	The current interval value. Can be modified any time, but changes only	1919	The current interval value. Can be modified any time, but changes only
1544	take effect when the periodic timer fires or C<ev_periodic_again> is being	1920	take effect when the periodic timer fires or C<ev_periodic_again> is being
1545	called.	1921	called.
1546		1922
1547	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1923	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1548		1924
1549	The current reschedule callback, or C<0>, if this functionality is	1925	The current reschedule callback, or C<0>, if this functionality is
1550	switched off. Can be changed any time, but changes only take effect when	1926	switched off. Can be changed any time, but changes only take effect when
1551	the periodic timer fires or C<ev_periodic_again> is being called.	1927	the periodic timer fires or C<ev_periodic_again> is being called.
1552		1928
…		…
1557	Example: Call a callback every hour, or, more precisely, whenever the	1933	Example: Call a callback every hour, or, more precisely, whenever the
1558	system time is divisible by 3600. The callback invocation times have	1934	system time is divisible by 3600. The callback invocation times have
1559	potentially a lot of jitter, but good long-term stability.	1935	potentially a lot of jitter, but good long-term stability.
1560		1936
1561	static void	1937	static void
1562	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1938	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1563	{	1939	{
1564	... its now a full hour (UTC, or TAI or whatever your clock follows)	1940	... its now a full hour (UTC, or TAI or whatever your clock follows)
1565	}	1941	}
1566		1942
1567	struct ev_periodic hourly_tick;	1943	ev_periodic hourly_tick;
1568	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1944	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1569	ev_periodic_start (loop, &hourly_tick);	1945	ev_periodic_start (loop, &hourly_tick);
1570		1946
1571	Example: The same as above, but use a reschedule callback to do it:	1947	Example: The same as above, but use a reschedule callback to do it:
1572		1948
1573	#include <math.h>	1949	#include <math.h>
1574		1950
1575	static ev_tstamp	1951	static ev_tstamp
1576	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1952	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1577	{	1953	{
1578	return now + (3600. - fmod (now, 3600.));	1954	return now + (3600. - fmod (now, 3600.));
1579	}	1955	}
1580		1956
1581	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1957	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1582		1958
1583	Example: Call a callback every hour, starting now:	1959	Example: Call a callback every hour, starting now:
1584		1960
1585	struct ev_periodic hourly_tick;	1961	ev_periodic hourly_tick;
1586	ev_periodic_init (&hourly_tick, clock_cb,	1962	ev_periodic_init (&hourly_tick, clock_cb,
1587	fmod (ev_now (loop), 3600.), 3600., 0);	1963	fmod (ev_now (loop), 3600.), 3600., 0);
1588	ev_periodic_start (loop, &hourly_tick);	1964	ev_periodic_start (loop, &hourly_tick);
1589		1965
1590		1966
…		…
1632	=head3 Examples	2008	=head3 Examples
1633		2009
1634	Example: Try to exit cleanly on SIGINT.	2010	Example: Try to exit cleanly on SIGINT.
1635		2011
1636	static void	2012	static void
1637	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2013	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1638	{	2014	{
1639	ev_unloop (loop, EVUNLOOP_ALL);	2015	ev_unloop (loop, EVUNLOOP_ALL);
1640	}	2016	}
1641		2017
1642	struct ev_signal signal_watcher;	2018	ev_signal signal_watcher;
1643	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2019	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1644	ev_signal_start (loop, &signal_watcher);	2020	ev_signal_start (loop, &signal_watcher);
1645		2021
1646		2022
1647	=head2 C<ev_child> - watch out for process status changes	2023	=head2 C<ev_child> - watch out for process status changes
…		…
1650	some child status changes (most typically when a child of yours dies or	2026	some child status changes (most typically when a child of yours dies or
1651	exits). It is permissible to install a child watcher I<after> the child	2027	exits). It is permissible to install a child watcher I<after> the child
1652	has been forked (which implies it might have already exited), as long	2028	has been forked (which implies it might have already exited), as long
1653	as the event loop isn't entered (or is continued from a watcher), i.e.,	2029	as the event loop isn't entered (or is continued from a watcher), i.e.,
1654	forking and then immediately registering a watcher for the child is fine,	2030	forking and then immediately registering a watcher for the child is fine,
1655	but forking and registering a watcher a few event loop iterations later is	2031	but forking and registering a watcher a few event loop iterations later or
1656	not.	2032	in the next callback invocation is not.
1657		2033
1658	Only the default event loop is capable of handling signals, and therefore	2034	Only the default event loop is capable of handling signals, and therefore
1659	you can only register child watchers in the default event loop.	2035	you can only register child watchers in the default event loop.
		2036
		2037	Due to some design glitches inside libev, child watchers will always be
		2038	handled at maximum priority (their priority is set to EV_MAXPRI by libev)
1660		2039
1661	=head3 Process Interaction	2040	=head3 Process Interaction
1662		2041
1663	Libev grabs C<SIGCHLD> as soon as the default event loop is	2042	Libev grabs C<SIGCHLD> as soon as the default event loop is
1664	initialised. This is necessary to guarantee proper behaviour even if	2043	initialised. This is necessary to guarantee proper behaviour even if
…		…
1722	its completion.	2101	its completion.
1723		2102
1724	ev_child cw;	2103	ev_child cw;
1725		2104
1726	static void	2105	static void
1727	child_cb (EV_P_ struct ev_child *w, int revents)	2106	child_cb (EV_P_ ev_child *w, int revents)
1728	{	2107	{
1729	ev_child_stop (EV_A_ w);	2108	ev_child_stop (EV_A_ w);
1730	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2109	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1731	}	2110	}
1732		2111
…		…
1747		2126
1748		2127
1749	=head2 C<ev_stat> - did the file attributes just change?	2128	=head2 C<ev_stat> - did the file attributes just change?
1750		2129
1751	This watches a file system path for attribute changes. That is, it calls	2130	This watches a file system path for attribute changes. That is, it calls
1752	C<stat> regularly (or when the OS says it changed) and sees if it changed	2131	C<stat> on that path in regular intervals (or when the OS says it changed)
1753	compared to the last time, invoking the callback if it did.	2132	and sees if it changed compared to the last time, invoking the callback if
		2133	it did.
1754		2134
1755	The path does not need to exist: changing from "path exists" to "path does	2135	The path does not need to exist: changing from "path exists" to "path does
1756	not exist" is a status change like any other. The condition "path does	2136	not exist" is a status change like any other. The condition "path does not
1757	not exist" is signified by the C<st_nlink> field being zero (which is	2137	exist" (or more correctly "path cannot be stat'ed") is signified by the
1758	otherwise always forced to be at least one) and all the other fields of	2138	C<st_nlink> field being zero (which is otherwise always forced to be at
1759	the stat buffer having unspecified contents.	2139	least one) and all the other fields of the stat buffer having unspecified
		2140	contents.
1760		2141
1761	The path I<should> be absolute and I<must not> end in a slash. If it is	2142	The path I<must not> end in a slash or contain special components such as
		2143	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1762	relative and your working directory changes, the behaviour is undefined.	2144	your working directory changes, then the behaviour is undefined.
1763		2145
1764	Since there is no standard kernel interface to do this, the portable	2146	Since there is no portable change notification interface available, the
1765	implementation simply calls C<stat (2)> regularly on the path to see if	2147	portable implementation simply calls C<stat(2)> regularly on the path
1766	it changed somehow. You can specify a recommended polling interval for	2148	to see if it changed somehow. You can specify a recommended polling
1767	this case. If you specify a polling interval of C<0> (highly recommended!)	2149	interval for this case. If you specify a polling interval of C<0> (highly
1768	then a I<suitable, unspecified default> value will be used (which	2150	recommended!) then a I<suitable, unspecified default> value will be used
1769	you can expect to be around five seconds, although this might change	2151	(which you can expect to be around five seconds, although this might
1770	dynamically). Libev will also impose a minimum interval which is currently	2152	change dynamically). Libev will also impose a minimum interval which is
1771	around C<0.1>, but thats usually overkill.	2153	currently around C<0.1>, but that's usually overkill.
1772		2154
1773	This watcher type is not meant for massive numbers of stat watchers,	2155	This watcher type is not meant for massive numbers of stat watchers,
1774	as even with OS-supported change notifications, this can be	2156	as even with OS-supported change notifications, this can be
1775	resource-intensive.	2157	resource-intensive.
1776		2158
1777	At the time of this writing, the only OS-specific interface implemented	2159	At the time of this writing, the only OS-specific interface implemented
1778	is the Linux inotify interface (implementing kqueue support is left as	2160	is the Linux inotify interface (implementing kqueue support is left as an
1779	an exercise for the reader. Note, however, that the author sees no way	2161	exercise for the reader. Note, however, that the author sees no way of
1780	of implementing C<ev_stat> semantics with kqueue).	2162	implementing C<ev_stat> semantics with kqueue, except as a hint).
1781		2163
1782	=head3 ABI Issues (Largefile Support)	2164	=head3 ABI Issues (Largefile Support)
1783		2165
1784	Libev by default (unless the user overrides this) uses the default	2166	Libev by default (unless the user overrides this) uses the default
1785	compilation environment, which means that on systems with large file	2167	compilation environment, which means that on systems with large file
1786	support disabled by default, you get the 32 bit version of the stat	2168	support disabled by default, you get the 32 bit version of the stat
1787	structure. When using the library from programs that change the ABI to	2169	structure. When using the library from programs that change the ABI to
1788	use 64 bit file offsets the programs will fail. In that case you have to	2170	use 64 bit file offsets the programs will fail. In that case you have to
1789	compile libev with the same flags to get binary compatibility. This is	2171	compile libev with the same flags to get binary compatibility. This is
1790	obviously the case with any flags that change the ABI, but the problem is	2172	obviously the case with any flags that change the ABI, but the problem is
1791	most noticeably disabled with ev_stat and large file support.	2173	most noticeably displayed with ev_stat and large file support.
1792		2174
1793	The solution for this is to lobby your distribution maker to make large	2175	The solution for this is to lobby your distribution maker to make large
1794	file interfaces available by default (as e.g. FreeBSD does) and not	2176	file interfaces available by default (as e.g. FreeBSD does) and not
1795	optional. Libev cannot simply switch on large file support because it has	2177	optional. Libev cannot simply switch on large file support because it has
1796	to exchange stat structures with application programs compiled using the	2178	to exchange stat structures with application programs compiled using the
1797	default compilation environment.	2179	default compilation environment.
1798		2180
1799	=head3 Inotify and Kqueue	2181	=head3 Inotify and Kqueue
1800		2182
1801	When C<inotify (7)> support has been compiled into libev (generally	2183	When C<inotify (7)> support has been compiled into libev and present at
1802	only available with Linux 2.6.25 or above due to bugs in earlier	2184	runtime, it will be used to speed up change detection where possible. The
1803	implementations) and present at runtime, it will be used to speed up	2185	inotify descriptor will be created lazily when the first C<ev_stat>
1804	change detection where possible. The inotify descriptor will be created	2186	watcher is being started.
1805	lazily when the first C<ev_stat> watcher is being started.
1806		2187
1807	Inotify presence does not change the semantics of C<ev_stat> watchers	2188	Inotify presence does not change the semantics of C<ev_stat> watchers
1808	except that changes might be detected earlier, and in some cases, to avoid	2189	except that changes might be detected earlier, and in some cases, to avoid
1809	making regular C<stat> calls. Even in the presence of inotify support	2190	making regular C<stat> calls. Even in the presence of inotify support
1810	there are many cases where libev has to resort to regular C<stat> polling,	2191	there are many cases where libev has to resort to regular C<stat> polling,
1811	but as long as the path exists, libev usually gets away without polling.	2192	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2193	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2194	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2195	xfs are fully working) libev usually gets away without polling.
1812		2196
1813	There is no support for kqueue, as apparently it cannot be used to	2197	There is no support for kqueue, as apparently it cannot be used to
1814	implement this functionality, due to the requirement of having a file	2198	implement this functionality, due to the requirement of having a file
1815	descriptor open on the object at all times, and detecting renames, unlinks	2199	descriptor open on the object at all times, and detecting renames, unlinks
1816	etc. is difficult.	2200	etc. is difficult.
1817		2201
		2202	=head3 C<stat ()> is a synchronous operation
		2203
		2204	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2205	the process. The exception are C<ev_stat> watchers - those call C<stat
		2206	()>, which is a synchronous operation.
		2207
		2208	For local paths, this usually doesn't matter: unless the system is very
		2209	busy or the intervals between stat's are large, a stat call will be fast,
		2210	as the path data is usually in memory already (except when starting the
		2211	watcher).
		2212
		2213	For networked file systems, calling C<stat ()> can block an indefinite
		2214	time due to network issues, and even under good conditions, a stat call
		2215	often takes multiple milliseconds.
		2216
		2217	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2218	paths, although this is fully supported by libev.
		2219
1818	=head3 The special problem of stat time resolution	2220	=head3 The special problem of stat time resolution
1819		2221
1820	The C<stat ()> system call only supports full-second resolution portably, and	2222	The C<stat ()> system call only supports full-second resolution portably,
1821	even on systems where the resolution is higher, most file systems still	2223	and even on systems where the resolution is higher, most file systems
1822	only support whole seconds.	2224	still only support whole seconds.
1823		2225
1824	That means that, if the time is the only thing that changes, you can	2226	That means that, if the time is the only thing that changes, you can
1825	easily miss updates: on the first update, C<ev_stat> detects a change and	2227	easily miss updates: on the first update, C<ev_stat> detects a change and
1826	calls your callback, which does something. When there is another update	2228	calls your callback, which does something. When there is another update
1827	within the same second, C<ev_stat> will be unable to detect unless the	2229	within the same second, C<ev_stat> will be unable to detect unless the
…		…
1970		2372
1971	=head3 Watcher-Specific Functions and Data Members	2373	=head3 Watcher-Specific Functions and Data Members
1972		2374
1973	=over 4	2375	=over 4
1974		2376
1975	=item ev_idle_init (ev_signal *, callback)	2377	=item ev_idle_init (ev_idle *, callback)
1976		2378
1977	Initialises and configures the idle watcher - it has no parameters of any	2379	Initialises and configures the idle watcher - it has no parameters of any
1978	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2380	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1979	believe me.	2381	believe me.
1980		2382
…		…
1984		2386
1985	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2387	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1986	callback, free it. Also, use no error checking, as usual.	2388	callback, free it. Also, use no error checking, as usual.
1987		2389
1988	static void	2390	static void
1989	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2391	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1990	{	2392	{
1991	free (w);	2393	free (w);
1992	// now do something you wanted to do when the program has	2394	// now do something you wanted to do when the program has
1993	// no longer anything immediate to do.	2395	// no longer anything immediate to do.
1994	}	2396	}
1995		2397
1996	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2398	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1997	ev_idle_init (idle_watcher, idle_cb);	2399	ev_idle_init (idle_watcher, idle_cb);
1998	ev_idle_start (loop, idle_cb);	2400	ev_idle_start (loop, idle_watcher);
1999		2401
2000		2402
2001	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2403	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2002		2404
2003	Prepare and check watchers are usually (but not always) used in pairs:	2405	Prepare and check watchers are usually (but not always) used in pairs:
…		…
2082		2484
2083	static ev_io iow [nfd];	2485	static ev_io iow [nfd];
2084	static ev_timer tw;	2486	static ev_timer tw;
2085		2487
2086	static void	2488	static void
2087	io_cb (ev_loop *loop, ev_io *w, int revents)	2489	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2088	{	2490	{
2089	}	2491	}
2090		2492
2091	// create io watchers for each fd and a timer before blocking	2493	// create io watchers for each fd and a timer before blocking
2092	static void	2494	static void
2093	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2495	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2094	{	2496	{
2095	int timeout = 3600000;	2497	int timeout = 3600000;
2096	struct pollfd fds [nfd];	2498	struct pollfd fds [nfd];
2097	// actual code will need to loop here and realloc etc.	2499	// actual code will need to loop here and realloc etc.
2098	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2500	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2099		2501
2100	/* the callback is illegal, but won't be called as we stop during check */	2502	/* the callback is illegal, but won't be called as we stop during check */
2101	ev_timer_init (&tw, 0, timeout * 1e-3);	2503	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2102	ev_timer_start (loop, &tw);	2504	ev_timer_start (loop, &tw);
2103		2505
2104	// create one ev_io per pollfd	2506	// create one ev_io per pollfd
2105	for (int i = 0; i < nfd; ++i)	2507	for (int i = 0; i < nfd; ++i)
2106	{	2508	{
…		…
2113	}	2515	}
2114	}	2516	}
2115		2517
2116	// stop all watchers after blocking	2518	// stop all watchers after blocking
2117	static void	2519	static void
2118	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2520	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2119	{	2521	{
2120	ev_timer_stop (loop, &tw);	2522	ev_timer_stop (loop, &tw);
2121		2523
2122	for (int i = 0; i < nfd; ++i)	2524	for (int i = 0; i < nfd; ++i)
2123	{	2525	{
…		…
2219	some fds have to be watched and handled very quickly (with low latency),	2621	some fds have to be watched and handled very quickly (with low latency),
2220	and even priorities and idle watchers might have too much overhead. In	2622	and even priorities and idle watchers might have too much overhead. In
2221	this case you would put all the high priority stuff in one loop and all	2623	this case you would put all the high priority stuff in one loop and all
2222	the rest in a second one, and embed the second one in the first.	2624	the rest in a second one, and embed the second one in the first.
2223		2625
2224	As long as the watcher is active, the callback will be invoked every time	2626	As long as the watcher is active, the callback will be invoked every
2225	there might be events pending in the embedded loop. The callback must then	2627	time there might be events pending in the embedded loop. The callback
2226	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2628	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2227	their callbacks (you could also start an idle watcher to give the embedded	2629	sweep and invoke their callbacks (the callback doesn't need to invoke the
2228	loop strictly lower priority for example). You can also set the callback	2630	C<ev_embed_sweep> function directly, it could also start an idle watcher
2229	to C<0>, in which case the embed watcher will automatically execute the	2631	to give the embedded loop strictly lower priority for example).
2230	embedded loop sweep.
2231		2632
2232	As long as the watcher is started it will automatically handle events. The	2633	You can also set the callback to C<0>, in which case the embed watcher
2233	callback will be invoked whenever some events have been handled. You can	2634	will automatically execute the embedded loop sweep whenever necessary.
2234	set the callback to C<0> to avoid having to specify one if you are not
2235	interested in that.
2236		2635
2237	Also, there have not currently been made special provisions for forking:	2636	Fork detection will be handled transparently while the C<ev_embed> watcher
2238	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2637	is active, i.e., the embedded loop will automatically be forked when the
2239	but you will also have to stop and restart any C<ev_embed> watchers	2638	embedding loop forks. In other cases, the user is responsible for calling
2240	yourself - but you can use a fork watcher to handle this automatically,	2639	C<ev_loop_fork> on the embedded loop.
2241	and future versions of libev might do just that.
2242		2640
2243	Unfortunately, not all backends are embeddable: only the ones returned by	2641	Unfortunately, not all backends are embeddable: only the ones returned by
2244	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2642	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2245	portable one.	2643	portable one.
2246		2644
…		…
2291	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2689	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2292	used).	2690	used).
2293		2691
2294	struct ev_loop *loop_hi = ev_default_init (0);	2692	struct ev_loop *loop_hi = ev_default_init (0);
2295	struct ev_loop *loop_lo = 0;	2693	struct ev_loop *loop_lo = 0;
2296	struct ev_embed embed;	2694	ev_embed embed;
2297		2695
2298	// see if there is a chance of getting one that works	2696	// see if there is a chance of getting one that works
2299	// (remember that a flags value of 0 means autodetection)	2697	// (remember that a flags value of 0 means autodetection)
2300	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2698	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2301	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2699	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2315	kqueue implementation). Store the kqueue/socket-only event loop in	2713	kqueue implementation). Store the kqueue/socket-only event loop in
2316	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2714	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2317		2715
2318	struct ev_loop *loop = ev_default_init (0);	2716	struct ev_loop *loop = ev_default_init (0);
2319	struct ev_loop *loop_socket = 0;	2717	struct ev_loop *loop_socket = 0;
2320	struct ev_embed embed;	2718	ev_embed embed;
2321		2719
2322	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2720	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2323	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2721	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2324	{	2722	{
2325	ev_embed_init (&embed, 0, loop_socket);	2723	ev_embed_init (&embed, 0, loop_socket);
…		…
2340	event loop blocks next and before C<ev_check> watchers are being called,	2738	event loop blocks next and before C<ev_check> watchers are being called,
2341	and only in the child after the fork. If whoever good citizen calling	2739	and only in the child after the fork. If whoever good citizen calling
2342	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2740	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2343	handlers will be invoked, too, of course.	2741	handlers will be invoked, too, of course.
2344		2742
		2743	=head3 The special problem of life after fork - how is it possible?
		2744
		2745	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2746	up/change the process environment, followed by a call to C<exec()>. This
		2747	sequence should be handled by libev without any problems.
		2748
		2749	This changes when the application actually wants to do event handling
		2750	in the child, or both parent in child, in effect "continuing" after the
		2751	fork.
		2752
		2753	The default mode of operation (for libev, with application help to detect
		2754	forks) is to duplicate all the state in the child, as would be expected
		2755	when I<either> the parent I<or> the child process continues.
		2756
		2757	When both processes want to continue using libev, then this is usually the
		2758	wrong result. In that case, usually one process (typically the parent) is
		2759	supposed to continue with all watchers in place as before, while the other
		2760	process typically wants to start fresh, i.e. without any active watchers.
		2761
		2762	The cleanest and most efficient way to achieve that with libev is to
		2763	simply create a new event loop, which of course will be "empty", and
		2764	use that for new watchers. This has the advantage of not touching more
		2765	memory than necessary, and thus avoiding the copy-on-write, and the
		2766	disadvantage of having to use multiple event loops (which do not support
		2767	signal watchers).
		2768
		2769	When this is not possible, or you want to use the default loop for
		2770	other reasons, then in the process that wants to start "fresh", call
		2771	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2772	the default loop will "orphan" (not stop) all registered watchers, so you
		2773	have to be careful not to execute code that modifies those watchers. Note
		2774	also that in that case, you have to re-register any signal watchers.
		2775
2345	=head3 Watcher-Specific Functions and Data Members	2776	=head3 Watcher-Specific Functions and Data Members
2346		2777
2347	=over 4	2778	=over 4
2348		2779
2349	=item ev_fork_init (ev_signal *, callback)	2780	=item ev_fork_init (ev_signal *, callback)
…		…
2466	=over 4	2897	=over 4
2467		2898
2468	=item ev_async_init (ev_async *, callback)	2899	=item ev_async_init (ev_async *, callback)
2469		2900
2470	Initialises and configures the async watcher - it has no parameters of any	2901	Initialises and configures the async watcher - it has no parameters of any
2471	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2902	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2472	trust me.	2903	trust me.
2473		2904
2474	=item ev_async_send (loop, ev_async *)	2905	=item ev_async_send (loop, ev_async *)
2475		2906
2476	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2907	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2477	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2908	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2478	C<ev_feed_event>, this call is safe to do from other threads, signal or	2909	C<ev_feed_event>, this call is safe to do from other threads, signal or
2479	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	2910	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2480	section below on what exactly this means).	2911	section below on what exactly this means).
2481		2912
		2913	Note that, as with other watchers in libev, multiple events might get
		2914	compressed into a single callback invocation (another way to look at this
		2915	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		2916	reset when the event loop detects that).
		2917
2482	This call incurs the overhead of a system call only once per loop iteration,	2918	This call incurs the overhead of a system call only once per event loop
2483	so while the overhead might be noticeable, it doesn't apply to repeated	2919	iteration, so while the overhead might be noticeable, it doesn't apply to
2484	calls to C<ev_async_send>.	2920	repeated calls to C<ev_async_send> for the same event loop.
2485		2921
2486	=item bool = ev_async_pending (ev_async *)	2922	=item bool = ev_async_pending (ev_async *)
2487		2923
2488	Returns a non-zero value when C<ev_async_send> has been called on the	2924	Returns a non-zero value when C<ev_async_send> has been called on the
2489	watcher but the event has not yet been processed (or even noted) by the	2925	watcher but the event has not yet been processed (or even noted) by the
…		…
2492	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	2928	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2493	the loop iterates next and checks for the watcher to have become active,	2929	the loop iterates next and checks for the watcher to have become active,
2494	it will reset the flag again. C<ev_async_pending> can be used to very	2930	it will reset the flag again. C<ev_async_pending> can be used to very
2495	quickly check whether invoking the loop might be a good idea.	2931	quickly check whether invoking the loop might be a good idea.
2496		2932
2497	Not that this does I<not> check whether the watcher itself is pending, only	2933	Not that this does I<not> check whether the watcher itself is pending,
2498	whether it has been requested to make this watcher pending.	2934	only whether it has been requested to make this watcher pending: there
		2935	is a time window between the event loop checking and resetting the async
		2936	notification, and the callback being invoked.
2499		2937
2500	=back	2938	=back
2501		2939
2502		2940
2503	=head1 OTHER FUNCTIONS	2941	=head1 OTHER FUNCTIONS
…		…
2539	/* doh, nothing entered */;	2977	/* doh, nothing entered */;
2540	}	2978	}
2541		2979
2542	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2980	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2543		2981
2544	=item ev_feed_event (ev_loop *, watcher *, int revents)	2982	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2545		2983
2546	Feeds the given event set into the event loop, as if the specified event	2984	Feeds the given event set into the event loop, as if the specified event
2547	had happened for the specified watcher (which must be a pointer to an	2985	had happened for the specified watcher (which must be a pointer to an
2548	initialised but not necessarily started event watcher).	2986	initialised but not necessarily started event watcher).
2549		2987
2550	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2988	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2551		2989
2552	Feed an event on the given fd, as if a file descriptor backend detected	2990	Feed an event on the given fd, as if a file descriptor backend detected
2553	the given events it.	2991	the given events it.
2554		2992
2555	=item ev_feed_signal_event (ev_loop *loop, int signum)	2993	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2556		2994
2557	Feed an event as if the given signal occurred (C<loop> must be the default	2995	Feed an event as if the given signal occurred (C<loop> must be the default
2558	loop!).	2996	loop!).
2559		2997
2560	=back	2998	=back
…		…
2681	}	3119	}
2682		3120
2683	myclass obj;	3121	myclass obj;
2684	ev::io iow;	3122	ev::io iow;
2685	iow.set <myclass, &myclass::io_cb> (&obj);	3123	iow.set <myclass, &myclass::io_cb> (&obj);
		3124
		3125	=item w->set (object *)
		3126
		3127	This is an B<experimental> feature that might go away in a future version.
		3128
		3129	This is a variation of a method callback - leaving out the method to call
		3130	will default the method to C<operator ()>, which makes it possible to use
		3131	functor objects without having to manually specify the C<operator ()> all
		3132	the time. Incidentally, you can then also leave out the template argument
		3133	list.
		3134
		3135	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3136	int revents)>.
		3137
		3138	See the method-C<set> above for more details.
		3139
		3140	Example: use a functor object as callback.
		3141
		3142	struct myfunctor
		3143	{
		3144	void operator() (ev::io &w, int revents)
		3145	{
		3146	...
		3147	}
		3148	}
		3149
		3150	myfunctor f;
		3151
		3152	ev::io w;
		3153	w.set (&f);
2686		3154
2687	=item w->set<function> (void *data = 0)	3155	=item w->set<function> (void *data = 0)
2688		3156
2689	Also sets a callback, but uses a static method or plain function as	3157	Also sets a callback, but uses a static method or plain function as
2690	callback. The optional C<data> argument will be stored in the watcher's	3158	callback. The optional C<data> argument will be stored in the watcher's
…		…
2777	L<http://software.schmorp.de/pkg/EV>.	3245	L<http://software.schmorp.de/pkg/EV>.
2778		3246
2779	=item Python	3247	=item Python
2780		3248
2781	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3249	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2782	seems to be quite complete and well-documented. Note, however, that the	3250	seems to be quite complete and well-documented.
2783	patch they require for libev is outright dangerous as it breaks the ABI
2784	for everybody else, and therefore, should never be applied in an installed
2785	libev (if python requires an incompatible ABI then it needs to embed
2786	libev).
2787		3251
2788	=item Ruby	3252	=item Ruby
2789		3253
2790	Tony Arcieri has written a ruby extension that offers access to a subset	3254	Tony Arcieri has written a ruby extension that offers access to a subset
2791	of the libev API and adds file handle abstractions, asynchronous DNS and	3255	of the libev API and adds file handle abstractions, asynchronous DNS and
2792	more on top of it. It can be found via gem servers. Its homepage is at	3256	more on top of it. It can be found via gem servers. Its homepage is at
2793	L<http://rev.rubyforge.org/>.	3257	L<http://rev.rubyforge.org/>.
2794		3258
		3259	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3260	makes rev work even on mingw.
		3261
		3262	=item Haskell
		3263
		3264	A haskell binding to libev is available at
		3265	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3266
2795	=item D	3267	=item D
2796		3268
2797	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3269	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2798	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3270	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3271
		3272	=item Ocaml
		3273
		3274	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3275	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2799		3276
2800	=back	3277	=back
2801		3278
2802		3279
2803	=head1 MACRO MAGIC	3280	=head1 MACRO MAGIC
…		…
2904		3381
2905	#define EV_STANDALONE 1	3382	#define EV_STANDALONE 1
2906	#include "ev.h"	3383	#include "ev.h"
2907		3384
2908	Both header files and implementation files can be compiled with a C++	3385	Both header files and implementation files can be compiled with a C++
2909	compiler (at least, thats a stated goal, and breakage will be treated	3386	compiler (at least, that's a stated goal, and breakage will be treated
2910	as a bug).	3387	as a bug).
2911		3388
2912	You need the following files in your source tree, or in a directory	3389	You need the following files in your source tree, or in a directory
2913	in your include path (e.g. in libev/ when using -Ilibev):	3390	in your include path (e.g. in libev/ when using -Ilibev):
2914		3391
…		…
2970	keeps libev from including F<config.h>, and it also defines dummy	3447	keeps libev from including F<config.h>, and it also defines dummy
2971	implementations for some libevent functions (such as logging, which is not	3448	implementations for some libevent functions (such as logging, which is not
2972	supported). It will also not define any of the structs usually found in	3449	supported). It will also not define any of the structs usually found in
2973	F<event.h> that are not directly supported by the libev core alone.	3450	F<event.h> that are not directly supported by the libev core alone.
2974		3451
		3452	In stanbdalone mode, libev will still try to automatically deduce the
		3453	configuration, but has to be more conservative.
		3454
2975	=item EV_USE_MONOTONIC	3455	=item EV_USE_MONOTONIC
2976		3456
2977	If defined to be C<1>, libev will try to detect the availability of the	3457	If defined to be C<1>, libev will try to detect the availability of the
2978	monotonic clock option at both compile time and runtime. Otherwise no use	3458	monotonic clock option at both compile time and runtime. Otherwise no
2979	of the monotonic clock option will be attempted. If you enable this, you	3459	use of the monotonic clock option will be attempted. If you enable this,
2980	usually have to link against librt or something similar. Enabling it when	3460	you usually have to link against librt or something similar. Enabling it
2981	the functionality isn't available is safe, though, although you have	3461	when the functionality isn't available is safe, though, although you have
2982	to make sure you link against any libraries where the C<clock_gettime>	3462	to make sure you link against any libraries where the C<clock_gettime>
2983	function is hiding in (often F<-lrt>).	3463	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2984		3464
2985	=item EV_USE_REALTIME	3465	=item EV_USE_REALTIME
2986		3466
2987	If defined to be C<1>, libev will try to detect the availability of the	3467	If defined to be C<1>, libev will try to detect the availability of the
2988	real-time clock option at compile time (and assume its availability at	3468	real-time clock option at compile time (and assume its availability
2989	runtime if successful). Otherwise no use of the real-time clock option will	3469	at runtime if successful). Otherwise no use of the real-time clock
2990	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3470	option will be attempted. This effectively replaces C<gettimeofday>
2991	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3471	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2992	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3472	correctness. See the note about libraries in the description of
		3473	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3474	C<EV_USE_CLOCK_SYSCALL>.
		3475
		3476	=item EV_USE_CLOCK_SYSCALL
		3477
		3478	If defined to be C<1>, libev will try to use a direct syscall instead
		3479	of calling the system-provided C<clock_gettime> function. This option
		3480	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3481	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3482	programs needlessly. Using a direct syscall is slightly slower (in
		3483	theory), because no optimised vdso implementation can be used, but avoids
		3484	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3485	higher, as it simplifies linking (no need for C<-lrt>).
2993		3486
2994	=item EV_USE_NANOSLEEP	3487	=item EV_USE_NANOSLEEP
2995		3488
2996	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3489	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2997	and will use it for delays. Otherwise it will use C<select ()>.	3490	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3013		3506
3014	=item EV_SELECT_USE_FD_SET	3507	=item EV_SELECT_USE_FD_SET
3015		3508
3016	If defined to C<1>, then the select backend will use the system C<fd_set>	3509	If defined to C<1>, then the select backend will use the system C<fd_set>
3017	structure. This is useful if libev doesn't compile due to a missing	3510	structure. This is useful if libev doesn't compile due to a missing
3018	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3511	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3019	exotic systems. This usually limits the range of file descriptors to some	3512	on exotic systems. This usually limits the range of file descriptors to
3020	low limit such as 1024 or might have other limitations (winsocket only	3513	some low limit such as 1024 or might have other limitations (winsocket
3021	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3514	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3022	influence the size of the C<fd_set> used.	3515	configures the maximum size of the C<fd_set>.
3023		3516
3024	=item EV_SELECT_IS_WINSOCKET	3517	=item EV_SELECT_IS_WINSOCKET
3025		3518
3026	When defined to C<1>, the select backend will assume that	3519	When defined to C<1>, the select backend will assume that
3027	select/socket/connect etc. don't understand file descriptors but	3520	select/socket/connect etc. don't understand file descriptors but
…		…
3386	loop, as long as you don't confuse yourself). The only exception is that	3879	loop, as long as you don't confuse yourself). The only exception is that
3387	you must not do this from C<ev_periodic> reschedule callbacks.	3880	you must not do this from C<ev_periodic> reschedule callbacks.
3388		3881
3389	Care has been taken to ensure that libev does not keep local state inside	3882	Care has been taken to ensure that libev does not keep local state inside
3390	C<ev_loop>, and other calls do not usually allow for coroutine switches as	3883	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3391	they do not clal any callbacks.	3884	they do not call any callbacks.
3392		3885
3393	=head2 COMPILER WARNINGS	3886	=head2 COMPILER WARNINGS
3394		3887
3395	Depending on your compiler and compiler settings, you might get no or a	3888	Depending on your compiler and compiler settings, you might get no or a
3396	lot of warnings when compiling libev code. Some people are apparently	3889	lot of warnings when compiling libev code. Some people are apparently
…		…
3430	==2274== definitely lost: 0 bytes in 0 blocks.	3923	==2274== definitely lost: 0 bytes in 0 blocks.
3431	==2274== possibly lost: 0 bytes in 0 blocks.	3924	==2274== possibly lost: 0 bytes in 0 blocks.
3432	==2274== still reachable: 256 bytes in 1 blocks.	3925	==2274== still reachable: 256 bytes in 1 blocks.
3433		3926
3434	Then there is no memory leak, just as memory accounted to global variables	3927	Then there is no memory leak, just as memory accounted to global variables
3435	is not a memleak - the memory is still being refernced, and didn't leak.	3928	is not a memleak - the memory is still being referenced, and didn't leak.
3436		3929
3437	Similarly, under some circumstances, valgrind might report kernel bugs	3930	Similarly, under some circumstances, valgrind might report kernel bugs
3438	as if it were a bug in libev (e.g. in realloc or in the poll backend,	3931	as if it were a bug in libev (e.g. in realloc or in the poll backend,
3439	although an acceptable workaround has been found here), or it might be	3932	although an acceptable workaround has been found here), or it might be
3440	confused.	3933	confused.
…		…
3469	way (note also that glib is the slowest event library known to man).	3962	way (note also that glib is the slowest event library known to man).
3470		3963
3471	There is no supported compilation method available on windows except	3964	There is no supported compilation method available on windows except
3472	embedding it into other applications.	3965	embedding it into other applications.
3473		3966
		3967	Sensible signal handling is officially unsupported by Microsoft - libev
		3968	tries its best, but under most conditions, signals will simply not work.
		3969
3474	Not a libev limitation but worth mentioning: windows apparently doesn't	3970	Not a libev limitation but worth mentioning: windows apparently doesn't
3475	accept large writes: instead of resulting in a partial write, windows will	3971	accept large writes: instead of resulting in a partial write, windows will
3476	either accept everything or return C<ENOBUFS> if the buffer is too large,	3972	either accept everything or return C<ENOBUFS> if the buffer is too large,
3477	so make sure you only write small amounts into your sockets (less than a	3973	so make sure you only write small amounts into your sockets (less than a
3478	megabyte seems safe, but this apparently depends on the amount of memory	3974	megabyte seems safe, but this apparently depends on the amount of memory
…		…
3482	the abysmal performance of winsockets, using a large number of sockets	3978	the abysmal performance of winsockets, using a large number of sockets
3483	is not recommended (and not reasonable). If your program needs to use	3979	is not recommended (and not reasonable). If your program needs to use
3484	more than a hundred or so sockets, then likely it needs to use a totally	3980	more than a hundred or so sockets, then likely it needs to use a totally
3485	different implementation for windows, as libev offers the POSIX readiness	3981	different implementation for windows, as libev offers the POSIX readiness
3486	notification model, which cannot be implemented efficiently on windows	3982	notification model, which cannot be implemented efficiently on windows
3487	(Microsoft monopoly games).	3983	(due to Microsoft monopoly games).
3488		3984
3489	A typical way to use libev under windows is to embed it (see the embedding	3985	A typical way to use libev under windows is to embed it (see the embedding
3490	section for details) and use the following F<evwrap.h> header file instead	3986	section for details) and use the following F<evwrap.h> header file instead
3491	of F<ev.h>:	3987	of F<ev.h>:
3492		3988
…		…
3528		4024
3529	Early versions of winsocket's select only supported waiting for a maximum	4025	Early versions of winsocket's select only supported waiting for a maximum
3530	of C<64> handles (probably owning to the fact that all windows kernels	4026	of C<64> handles (probably owning to the fact that all windows kernels
3531	can only wait for C<64> things at the same time internally; Microsoft	4027	can only wait for C<64> things at the same time internally; Microsoft
3532	recommends spawning a chain of threads and wait for 63 handles and the	4028	recommends spawning a chain of threads and wait for 63 handles and the
3533	previous thread in each. Great).	4029	previous thread in each. Sounds great!).
3534		4030
3535	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4031	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3536	to some high number (e.g. C<2048>) before compiling the winsocket select	4032	to some high number (e.g. C<2048>) before compiling the winsocket select
3537	call (which might be in libev or elsewhere, for example, perl does its own	4033	call (which might be in libev or elsewhere, for example, perl and many
3538	select emulation on windows).	4034	other interpreters do their own select emulation on windows).
3539		4035
3540	Another limit is the number of file descriptors in the Microsoft runtime	4036	Another limit is the number of file descriptors in the Microsoft runtime
3541	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4037	libraries, which by default is C<64> (there must be a hidden I<64>
3542	or something like this inside Microsoft). You can increase this by calling	4038	fetish or something like this inside Microsoft). You can increase this
3543	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4039	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3544	arbitrary limit), but is broken in many versions of the Microsoft runtime	4040	(another arbitrary limit), but is broken in many versions of the Microsoft
3545	libraries.
3546
3547	This might get you to about C<512> or C<2048> sockets (depending on	4041	runtime libraries. This might get you to about C<512> or C<2048> sockets
3548	windows version and/or the phase of the moon). To get more, you need to	4042	(depending on windows version and/or the phase of the moon). To get more,
3549	wrap all I/O functions and provide your own fd management, but the cost of	4043	you need to wrap all I/O functions and provide your own fd management, but
3550	calling select (O(n²)) will likely make this unworkable.	4044	the cost of calling select (O(n²)) will likely make this unworkable.
3551		4045
3552	=back	4046	=back
3553		4047
3554	=head2 PORTABILITY REQUIREMENTS	4048	=head2 PORTABILITY REQUIREMENTS
3555		4049
…		…
3598	=item C<double> must hold a time value in seconds with enough accuracy	4092	=item C<double> must hold a time value in seconds with enough accuracy
3599		4093
3600	The type C<double> is used to represent timestamps. It is required to	4094	The type C<double> is used to represent timestamps. It is required to
3601	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4095	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
3602	enough for at least into the year 4000. This requirement is fulfilled by	4096	enough for at least into the year 4000. This requirement is fulfilled by
3603	implementations implementing IEEE 754 (basically all existing ones).	4097	implementations implementing IEEE 754, which is basically all existing
		4098	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4099	2200.
3604		4100
3605	=back	4101	=back
3606		4102
3607	If you know of other additional requirements drop me a note.	4103	If you know of other additional requirements drop me a note.
3608		4104
…		…
3676	involves iterating over all running async watchers or all signal numbers.	4172	involves iterating over all running async watchers or all signal numbers.
3677		4173
3678	=back	4174	=back
3679		4175
3680		4176
		4177	=head1 GLOSSARY
		4178
		4179	=over 4
		4180
		4181	=item active
		4182
		4183	A watcher is active as long as it has been started (has been attached to
		4184	an event loop) but not yet stopped (disassociated from the event loop).
		4185
		4186	=item application
		4187
		4188	In this document, an application is whatever is using libev.
		4189
		4190	=item callback
		4191
		4192	The address of a function that is called when some event has been
		4193	detected. Callbacks are being passed the event loop, the watcher that
		4194	received the event, and the actual event bitset.
		4195
		4196	=item callback invocation
		4197
		4198	The act of calling the callback associated with a watcher.
		4199
		4200	=item event
		4201
		4202	A change of state of some external event, such as data now being available
		4203	for reading on a file descriptor, time having passed or simply not having
		4204	any other events happening anymore.
		4205
		4206	In libev, events are represented as single bits (such as C<EV_READ> or
		4207	C<EV_TIMEOUT>).
		4208
		4209	=item event library
		4210
		4211	A software package implementing an event model and loop.
		4212
		4213	=item event loop
		4214
		4215	An entity that handles and processes external events and converts them
		4216	into callback invocations.
		4217
		4218	=item event model
		4219
		4220	The model used to describe how an event loop handles and processes
		4221	watchers and events.
		4222
		4223	=item pending
		4224
		4225	A watcher is pending as soon as the corresponding event has been detected,
		4226	and stops being pending as soon as the watcher will be invoked or its
		4227	pending status is explicitly cleared by the application.
		4228
		4229	A watcher can be pending, but not active. Stopping a watcher also clears
		4230	its pending status.
		4231
		4232	=item real time
		4233
		4234	The physical time that is observed. It is apparently strictly monotonic :)
		4235
		4236	=item wall-clock time
		4237
		4238	The time and date as shown on clocks. Unlike real time, it can actually
		4239	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4240	clock.
		4241
		4242	=item watcher
		4243
		4244	A data structure that describes interest in certain events. Watchers need
		4245	to be started (attached to an event loop) before they can receive events.
		4246
		4247	=item watcher invocation
		4248
		4249	The act of calling the callback associated with a watcher.
		4250
		4251	=back
		4252
3681	=head1 AUTHOR	4253	=head1 AUTHOR
3682		4254
3683	Marc Lehmann <libev@schmorp.de>.	4255	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3684		4256

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