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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
		861	=item ev_invoke_pending (loop)
		862
		863	This call will simply invoke all pending watchers while resetting their
		864	pending state. Normally, C<ev_loop> does this automatically when required,
		865	but when overriding the invoke callback this call comes handy.
		866
		867	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		868
		869	This overrides the invoke pending functionality of the loop: Instead of
		870	invoking all pending watchers when there are any, C<ev_loop> will call
		871	this callback instead. This is useful, for example, when you want to
		872	invoke the actual watchers inside another context (another thread etc.).
		873
		874	If you want to reset the callback, use C<ev_invoke_pending> as new
		875	callback.
		876
		877	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		878
		879	Sometimes you want to share the same loop between multiple threads. This
		880	can be done relatively simply by putting mutex_lock/unlock calls around
		881	each call to a libev function.
		882
		883	However, C<ev_loop> can run an indefinite time, so it is not feasible to
		884	wait for it to return. One way around this is to wake up the loop via
		885	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>
		886	and I<acquire> callbacks on the loop.
		887
		888	When set, then C<release> will be called just before the thread is
		889	suspended waiting for new events, and C<acquire> is called just
		890	afterwards.
		891
		892	Ideally, C<release> will just call your mutex_unlock function, and
		893	C<acquire> will just call the mutex_lock function again.
		894
		895	=item ev_set_userdata (loop, void *data)
		896
		897	=item ev_userdata (loop)
		898
		899	Set and retrieve a single C<void *> associated with a loop. When
		900	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		901	C<0.>
		902
		903	These two functions can be used to associate arbitrary data with a loop,
		904	and are intended solely for the C<invoke_pending_cb>, C<release> and
		905	C<acquire> callbacks described above, but of course can be (ab-)used for
		906	any other purpose as well.
		907
770	=item ev_loop_verify (loop)	908	=item ev_loop_verify (loop)
771		909
772	This function only does something when C<EV_VERIFY> support has been	910	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	911	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	912	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	913	is found to be inconsistent, it will print an error message to standard
776	error and call C<abort ()>.	914	error and call C<abort ()>.
777		915
778	This can be used to catch bugs inside libev itself: under normal	916	This can be used to catch bugs inside libev itself: under normal
…		…
782	=back	920	=back
783		921
784		922
785	=head1 ANATOMY OF A WATCHER	923	=head1 ANATOMY OF A WATCHER
786		924
		925	In the following description, uppercase C<TYPE> in names stands for the
		926	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		927	watchers and C<ev_io_start> for I/O watchers.
		928
787	A watcher is a structure that you create and register to record your	929	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	930	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:	931	become readable, you would create an C<ev_io> watcher for that:
790		932
791	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	933	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
792	{	934	{
793	ev_io_stop (w);	935	ev_io_stop (w);
794	ev_unloop (loop, EVUNLOOP_ALL);	936	ev_unloop (loop, EVUNLOOP_ALL);
795	}	937	}
796		938
797	struct ev_loop *loop = ev_default_loop (0);	939	struct ev_loop *loop = ev_default_loop (0);
		940
798	struct ev_io stdin_watcher;	941	ev_io stdin_watcher;
		942
799	ev_init (&stdin_watcher, my_cb);	943	ev_init (&stdin_watcher, my_cb);
800	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	944	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
801	ev_io_start (loop, &stdin_watcher);	945	ev_io_start (loop, &stdin_watcher);
		946
802	ev_loop (loop, 0);	947	ev_loop (loop, 0);
803		948
804	As you can see, you are responsible for allocating the memory for your	949	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,	950	watcher structures (and it is I<usually> a bad idea to do this on the
806	although this can sometimes be quite valid).	951	stack).
		952
		953	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		954	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
807		955
808	Each watcher structure must be initialised by a call to C<ev_init	956	Each watcher structure must be initialised by a call to C<ev_init
809	(watcher *, callback)>, which expects a callback to be provided. This	957	(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	958	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	959	watchers, each time the event loop detects that the file descriptor given
812	is readable and/or writable).	960	is readable and/or writable).
813		961
814	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	962	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	963	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	964	is also a macro to combine initialisation and setting in one call: C<<
817	(watcher *, callback, ...) >>.	965	ev_TYPE_init (watcher *, callback, ...) >>.
818		966
819	To make the watcher actually watch out for events, you have to start it	967	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	968	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	969	*) >>), and you can stop watching for events at any time by calling the
822	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	970	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
823		971
824	As long as your watcher is active (has been started but not stopped) you	972	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	973	must not touch the values stored in it. Most specifically you must never
826	reinitialise it or call its C<set> macro.	974	reinitialise it or call its C<ev_TYPE_set> macro.
827		975
828	Each and every callback receives the event loop pointer as first, the	976	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	977	registered watcher structure as second, and a bitset of received events as
830	third argument.	978	third argument.
831		979
…		…
889		1037
890	=item C<EV_ASYNC>	1038	=item C<EV_ASYNC>
891		1039
892	The given async watcher has been asynchronously notified (see C<ev_async>).	1040	The given async watcher has been asynchronously notified (see C<ev_async>).
893		1041
		1042	=item C<EV_CUSTOM>
		1043
		1044	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1045	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		1046
894	=item C<EV_ERROR>	1047	=item C<EV_ERROR>
895		1048
896	An unspecified error has occurred, the watcher has been stopped. This might	1049	An unspecified error has occurred, the watcher has been stopped. This might
897	happen because the watcher could not be properly started because libev	1050	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	1051	ran out of memory, a file descriptor was found to be closed or any other
…		…
912		1065
913	=back	1066	=back
914		1067
915	=head2 GENERIC WATCHER FUNCTIONS	1068	=head2 GENERIC WATCHER FUNCTIONS
916		1069
917	In the following description, C<TYPE> stands for the watcher type,
918	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
919
920	=over 4	1070	=over 4
921		1071
922	=item C<ev_init> (ev_TYPE *watcher, callback)	1072	=item C<ev_init> (ev_TYPE *watcher, callback)
923		1073
924	This macro initialises the generic portion of a watcher. The contents	1074	This macro initialises the generic portion of a watcher. The contents
…		…
929	which rolls both calls into one.	1079	which rolls both calls into one.
930		1080
931	You can reinitialise a watcher at any time as long as it has been stopped	1081	You can reinitialise a watcher at any time as long as it has been stopped
932	(or never started) and there are no pending events outstanding.	1082	(or never started) and there are no pending events outstanding.
933		1083
934	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1084	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
935	int revents)>.	1085	int revents)>.
936		1086
937	Example: Initialise an C<ev_io> watcher in two steps.	1087	Example: Initialise an C<ev_io> watcher in two steps.
938		1088
939	ev_io w;	1089	ev_io w;
…		…
1016	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1166	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1017	(default: C<-2>). Pending watchers with higher priority will be invoked	1167	(default: C<-2>). Pending watchers with higher priority will be invoked
1018	before watchers with lower priority, but priority will not keep watchers	1168	before watchers with lower priority, but priority will not keep watchers
1019	from being executed (except for C<ev_idle> watchers).	1169	from being executed (except for C<ev_idle> watchers).
1020		1170
1021	This means that priorities are I<only> used for ordering callback
1022	invocation after new events have been received. This is useful, for
1023	example, to reduce latency after idling, or more often, to bind two
1024	watchers on the same event and make sure one is called first.
1025
1026	If you need to suppress invocation when higher priority events are pending	1171	If you need to suppress invocation when higher priority events are pending
1027	you need to look at C<ev_idle> watchers, which provide this functionality.	1172	you need to look at C<ev_idle> watchers, which provide this functionality.
1028		1173
1029	You I<must not> change the priority of a watcher as long as it is active or	1174	You I<must not> change the priority of a watcher as long as it is active or
1030	pending.	1175	pending.
1031		1176
		1177	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1178	fine, as long as you do not mind that the priority value you query might
		1179	or might not have been clamped to the valid range.
		1180
1032	The default priority used by watchers when no priority has been set is	1181	The default priority used by watchers when no priority has been set is
1033	always C<0>, which is supposed to not be too high and not be too low :).	1182	always C<0>, which is supposed to not be too high and not be too low :).
1034		1183
1035	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1184	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1036	fine, as long as you do not mind that the priority value you query might	1185	priorities.
1037	or might not have been adjusted to be within valid range.
1038		1186
1039	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1187	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1040		1188
1041	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1189	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1042	C<loop> nor C<revents> need to be valid as long as the watcher callback	1190	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1064	member, you can also "subclass" the watcher type and provide your own	1212	member, you can also "subclass" the watcher type and provide your own
1065	data:	1213	data:
1066		1214
1067	struct my_io	1215	struct my_io
1068	{	1216	{
1069	struct ev_io io;	1217	ev_io io;
1070	int otherfd;	1218	int otherfd;
1071	void *somedata;	1219	void *somedata;
1072	struct whatever *mostinteresting;	1220	struct whatever *mostinteresting;
1073	};	1221	};
1074		1222
…		…
1077	ev_io_init (&w.io, my_cb, fd, EV_READ);	1225	ev_io_init (&w.io, my_cb, fd, EV_READ);
1078		1226
1079	And since your callback will be called with a pointer to the watcher, you	1227	And since your callback will be called with a pointer to the watcher, you
1080	can cast it back to your own type:	1228	can cast it back to your own type:
1081		1229
1082	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1230	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1083	{	1231	{
1084	struct my_io *w = (struct my_io *)w_;	1232	struct my_io *w = (struct my_io *)w_;
1085	...	1233	...
1086	}	1234	}
1087		1235
…		…
1105	programmers):	1253	programmers):
1106		1254
1107	#include <stddef.h>	1255	#include <stddef.h>
1108		1256
1109	static void	1257	static void
1110	t1_cb (EV_P_ struct ev_timer *w, int revents)	1258	t1_cb (EV_P_ ev_timer *w, int revents)
1111	{	1259	{
1112	struct my_biggy big = (struct my_biggy *	1260	struct my_biggy big = (struct my_biggy *)
1113	(((char *)w) - offsetof (struct my_biggy, t1));	1261	(((char *)w) - offsetof (struct my_biggy, t1));
1114	}	1262	}
1115		1263
1116	static void	1264	static void
1117	t2_cb (EV_P_ struct ev_timer *w, int revents)	1265	t2_cb (EV_P_ ev_timer *w, int revents)
1118	{	1266	{
1119	struct my_biggy big = (struct my_biggy *	1267	struct my_biggy big = (struct my_biggy *)
1120	(((char *)w) - offsetof (struct my_biggy, t2));	1268	(((char *)w) - offsetof (struct my_biggy, t2));
1121	}	1269	}
		1270
		1271	=head2 WATCHER PRIORITY MODELS
		1272
		1273	Many event loops support I<watcher priorities>, which are usually small
		1274	integers that influence the ordering of event callback invocation
		1275	between watchers in some way, all else being equal.
		1276
		1277	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1278	description for the more technical details such as the actual priority
		1279	range.
		1280
		1281	There are two common ways how these these priorities are being interpreted
		1282	by event loops:
		1283
		1284	In the more common lock-out model, higher priorities "lock out" invocation
		1285	of lower priority watchers, which means as long as higher priority
		1286	watchers receive events, lower priority watchers are not being invoked.
		1287
		1288	The less common only-for-ordering model uses priorities solely to order
		1289	callback invocation within a single event loop iteration: Higher priority
		1290	watchers are invoked before lower priority ones, but they all get invoked
		1291	before polling for new events.
		1292
		1293	Libev uses the second (only-for-ordering) model for all its watchers
		1294	except for idle watchers (which use the lock-out model).
		1295
		1296	The rationale behind this is that implementing the lock-out model for
		1297	watchers is not well supported by most kernel interfaces, and most event
		1298	libraries will just poll for the same events again and again as long as
		1299	their callbacks have not been executed, which is very inefficient in the
		1300	common case of one high-priority watcher locking out a mass of lower
		1301	priority ones.
		1302
		1303	Static (ordering) priorities are most useful when you have two or more
		1304	watchers handling the same resource: a typical usage example is having an
		1305	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1306	timeouts. Under load, data might be received while the program handles
		1307	other jobs, but since timers normally get invoked first, the timeout
		1308	handler will be executed before checking for data. In that case, giving
		1309	the timer a lower priority than the I/O watcher ensures that I/O will be
		1310	handled first even under adverse conditions (which is usually, but not
		1311	always, what you want).
		1312
		1313	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1314	will only be executed when no same or higher priority watchers have
		1315	received events, they can be used to implement the "lock-out" model when
		1316	required.
		1317
		1318	For example, to emulate how many other event libraries handle priorities,
		1319	you can associate an C<ev_idle> watcher to each such watcher, and in
		1320	the normal watcher callback, you just start the idle watcher. The real
		1321	processing is done in the idle watcher callback. This causes libev to
		1322	continously poll and process kernel event data for the watcher, but when
		1323	the lock-out case is known to be rare (which in turn is rare :), this is
		1324	workable.
		1325
		1326	Usually, however, the lock-out model implemented that way will perform
		1327	miserably under the type of load it was designed to handle. In that case,
		1328	it might be preferable to stop the real watcher before starting the
		1329	idle watcher, so the kernel will not have to process the event in case
		1330	the actual processing will be delayed for considerable time.
		1331
		1332	Here is an example of an I/O watcher that should run at a strictly lower
		1333	priority than the default, and which should only process data when no
		1334	other events are pending:
		1335
		1336	ev_idle idle; // actual processing watcher
		1337	ev_io io; // actual event watcher
		1338
		1339	static void
		1340	io_cb (EV_P_ ev_io *w, int revents)
		1341	{
		1342	// stop the I/O watcher, we received the event, but
		1343	// are not yet ready to handle it.
		1344	ev_io_stop (EV_A_ w);
		1345
		1346	// start the idle watcher to ahndle the actual event.
		1347	// it will not be executed as long as other watchers
		1348	// with the default priority are receiving events.
		1349	ev_idle_start (EV_A_ &idle);
		1350	}
		1351
		1352	static void
		1353	idle_cb (EV_P_ ev_idle *w, int revents)
		1354	{
		1355	// actual processing
		1356	read (STDIN_FILENO, ...);
		1357
		1358	// have to start the I/O watcher again, as
		1359	// we have handled the event
		1360	ev_io_start (EV_P_ &io);
		1361	}
		1362
		1363	// initialisation
		1364	ev_idle_init (&idle, idle_cb);
		1365	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1366	ev_io_start (EV_DEFAULT_ &io);
		1367
		1368	In the "real" world, it might also be beneficial to start a timer, so that
		1369	low-priority connections can not be locked out forever under load. This
		1370	enables your program to keep a lower latency for important connections
		1371	during short periods of high load, while not completely locking out less
		1372	important ones.
1122		1373
1123		1374
1124	=head1 WATCHER TYPES	1375	=head1 WATCHER TYPES
1125		1376
1126	This section describes each watcher in detail, but will not repeat	1377	This section describes each watcher in detail, but will not repeat
…		…
1152	descriptors to non-blocking mode is also usually a good idea (but not	1403	descriptors to non-blocking mode is also usually a good idea (but not
1153	required if you know what you are doing).	1404	required if you know what you are doing).
1154		1405
1155	If you cannot use non-blocking mode, then force the use of a	1406	If you cannot use non-blocking mode, then force the use of a
1156	known-to-be-good backend (at the time of this writing, this includes only	1407	known-to-be-good backend (at the time of this writing, this includes only
1157	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).	1408	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1409	descriptors for which non-blocking operation makes no sense (such as
		1410	files) - libev doesn't guarentee any specific behaviour in that case.
1158		1411
1159	Another thing you have to watch out for is that it is quite easy to	1412	Another thing you have to watch out for is that it is quite easy to
1160	receive "spurious" readiness notifications, that is your callback might	1413	receive "spurious" readiness notifications, that is your callback might
1161	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1414	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1162	because there is no data. Not only are some backends known to create a	1415	because there is no data. Not only are some backends known to create a
…		…
1257	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1510	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1258	readable, but only once. Since it is likely line-buffered, you could	1511	readable, but only once. Since it is likely line-buffered, you could
1259	attempt to read a whole line in the callback.	1512	attempt to read a whole line in the callback.
1260		1513
1261	static void	1514	static void
1262	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1515	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1263	{	1516	{
1264	ev_io_stop (loop, w);	1517	ev_io_stop (loop, w);
1265	.. read from stdin here (or from w->fd) and handle any I/O errors	1518	.. read from stdin here (or from w->fd) and handle any I/O errors
1266	}	1519	}
1267		1520
1268	...	1521	...
1269	struct ev_loop *loop = ev_default_init (0);	1522	struct ev_loop *loop = ev_default_init (0);
1270	struct ev_io stdin_readable;	1523	ev_io stdin_readable;
1271	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1524	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1272	ev_io_start (loop, &stdin_readable);	1525	ev_io_start (loop, &stdin_readable);
1273	ev_loop (loop, 0);	1526	ev_loop (loop, 0);
1274		1527
1275		1528
…		…
1283	year, it will still time out after (roughly) one hour. "Roughly" because	1536	year, it will still time out after (roughly) one hour. "Roughly" because
1284	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1537	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1285	monotonic clock option helps a lot here).	1538	monotonic clock option helps a lot here).
1286		1539
1287	The callback is guaranteed to be invoked only I<after> its timeout has	1540	The callback is guaranteed to be invoked only I<after> its timeout has
1288	passed, but if multiple timers become ready during the same loop iteration	1541	passed (not I<at>, so on systems with very low-resolution clocks this
1289	then order of execution is undefined.	1542	might introduce a small delay). If multiple timers become ready during the
		1543	same loop iteration then the ones with earlier time-out values are invoked
		1544	before ones of the same priority with later time-out values (but this is
		1545	no longer true when a callback calls C<ev_loop> recursively).
		1546
		1547	=head3 Be smart about timeouts
		1548
		1549	Many real-world problems involve some kind of timeout, usually for error
		1550	recovery. A typical example is an HTTP request - if the other side hangs,
		1551	you want to raise some error after a while.
		1552
		1553	What follows are some ways to handle this problem, from obvious and
		1554	inefficient to smart and efficient.
		1555
		1556	In the following, a 60 second activity timeout is assumed - a timeout that
		1557	gets reset to 60 seconds each time there is activity (e.g. each time some
		1558	data or other life sign was received).
		1559
		1560	=over 4
		1561
		1562	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1563
		1564	This is the most obvious, but not the most simple way: In the beginning,
		1565	start the watcher:
		1566
		1567	ev_timer_init (timer, callback, 60., 0.);
		1568	ev_timer_start (loop, timer);
		1569
		1570	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1571	and start it again:
		1572
		1573	ev_timer_stop (loop, timer);
		1574	ev_timer_set (timer, 60., 0.);
		1575	ev_timer_start (loop, timer);
		1576
		1577	This is relatively simple to implement, but means that each time there is
		1578	some activity, libev will first have to remove the timer from its internal
		1579	data structure and then add it again. Libev tries to be fast, but it's
		1580	still not a constant-time operation.
		1581
		1582	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1583
		1584	This is the easiest way, and involves using C<ev_timer_again> instead of
		1585	C<ev_timer_start>.
		1586
		1587	To implement this, configure an C<ev_timer> with a C<repeat> value
		1588	of C<60> and then call C<ev_timer_again> at start and each time you
		1589	successfully read or write some data. If you go into an idle state where
		1590	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1591	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1592
		1593	That means you can ignore both the C<ev_timer_start> function and the
		1594	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1595	member and C<ev_timer_again>.
		1596
		1597	At start:
		1598
		1599	ev_init (timer, callback);
		1600	timer->repeat = 60.;
		1601	ev_timer_again (loop, timer);
		1602
		1603	Each time there is some activity:
		1604
		1605	ev_timer_again (loop, timer);
		1606
		1607	It is even possible to change the time-out on the fly, regardless of
		1608	whether the watcher is active or not:
		1609
		1610	timer->repeat = 30.;
		1611	ev_timer_again (loop, timer);
		1612
		1613	This is slightly more efficient then stopping/starting the timer each time
		1614	you want to modify its timeout value, as libev does not have to completely
		1615	remove and re-insert the timer from/into its internal data structure.
		1616
		1617	It is, however, even simpler than the "obvious" way to do it.
		1618
		1619	=item 3. Let the timer time out, but then re-arm it as required.
		1620
		1621	This method is more tricky, but usually most efficient: Most timeouts are
		1622	relatively long compared to the intervals between other activity - in
		1623	our example, within 60 seconds, there are usually many I/O events with
		1624	associated activity resets.
		1625
		1626	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1627	but remember the time of last activity, and check for a real timeout only
		1628	within the callback:
		1629
		1630	ev_tstamp last_activity; // time of last activity
		1631
		1632	static void
		1633	callback (EV_P_ ev_timer *w, int revents)
		1634	{
		1635	ev_tstamp now = ev_now (EV_A);
		1636	ev_tstamp timeout = last_activity + 60.;
		1637
		1638	// if last_activity + 60. is older than now, we did time out
		1639	if (timeout < now)
		1640	{
		1641	// timeout occured, take action
		1642	}
		1643	else
		1644	{
		1645	// callback was invoked, but there was some activity, re-arm
		1646	// the watcher to fire in last_activity + 60, which is
		1647	// guaranteed to be in the future, so "again" is positive:
		1648	w->repeat = timeout - now;
		1649	ev_timer_again (EV_A_ w);
		1650	}
		1651	}
		1652
		1653	To summarise the callback: first calculate the real timeout (defined
		1654	as "60 seconds after the last activity"), then check if that time has
		1655	been reached, which means something I<did>, in fact, time out. Otherwise
		1656	the callback was invoked too early (C<timeout> is in the future), so
		1657	re-schedule the timer to fire at that future time, to see if maybe we have
		1658	a timeout then.
		1659
		1660	Note how C<ev_timer_again> is used, taking advantage of the
		1661	C<ev_timer_again> optimisation when the timer is already running.
		1662
		1663	This scheme causes more callback invocations (about one every 60 seconds
		1664	minus half the average time between activity), but virtually no calls to
		1665	libev to change the timeout.
		1666
		1667	To start the timer, simply initialise the watcher and set C<last_activity>
		1668	to the current time (meaning we just have some activity :), then call the
		1669	callback, which will "do the right thing" and start the timer:
		1670
		1671	ev_init (timer, callback);
		1672	last_activity = ev_now (loop);
		1673	callback (loop, timer, EV_TIMEOUT);
		1674
		1675	And when there is some activity, simply store the current time in
		1676	C<last_activity>, no libev calls at all:
		1677
		1678	last_actiivty = ev_now (loop);
		1679
		1680	This technique is slightly more complex, but in most cases where the
		1681	time-out is unlikely to be triggered, much more efficient.
		1682
		1683	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1684	callback :) - just change the timeout and invoke the callback, which will
		1685	fix things for you.
		1686
		1687	=item 4. Wee, just use a double-linked list for your timeouts.
		1688
		1689	If there is not one request, but many thousands (millions...), all
		1690	employing some kind of timeout with the same timeout value, then one can
		1691	do even better:
		1692
		1693	When starting the timeout, calculate the timeout value and put the timeout
		1694	at the I<end> of the list.
		1695
		1696	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1697	the list is expected to fire (for example, using the technique #3).
		1698
		1699	When there is some activity, remove the timer from the list, recalculate
		1700	the timeout, append it to the end of the list again, and make sure to
		1701	update the C<ev_timer> if it was taken from the beginning of the list.
		1702
		1703	This way, one can manage an unlimited number of timeouts in O(1) time for
		1704	starting, stopping and updating the timers, at the expense of a major
		1705	complication, and having to use a constant timeout. The constant timeout
		1706	ensures that the list stays sorted.
		1707
		1708	=back
		1709
		1710	So which method the best?
		1711
		1712	Method #2 is a simple no-brain-required solution that is adequate in most
		1713	situations. Method #3 requires a bit more thinking, but handles many cases
		1714	better, and isn't very complicated either. In most case, choosing either
		1715	one is fine, with #3 being better in typical situations.
		1716
		1717	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1718	rather complicated, but extremely efficient, something that really pays
		1719	off after the first million or so of active timers, i.e. it's usually
		1720	overkill :)
1290		1721
1291	=head3 The special problem of time updates	1722	=head3 The special problem of time updates
1292		1723
1293	Establishing the current time is a costly operation (it usually takes at	1724	Establishing the current time is a costly operation (it usually takes at
1294	least two system calls): EV therefore updates its idea of the current	1725	least two system calls): EV therefore updates its idea of the current
…		…
1338	If the timer is started but non-repeating, stop it (as if it timed out).	1769	If the timer is started but non-repeating, stop it (as if it timed out).
1339		1770
1340	If the timer is repeating, either start it if necessary (with the	1771	If the timer is repeating, either start it if necessary (with the
1341	C<repeat> value), or reset the running timer to the C<repeat> value.	1772	C<repeat> value), or reset the running timer to the C<repeat> value.
1342		1773
1343	This sounds a bit complicated, but here is a useful and typical	1774	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1344	example: Imagine you have a TCP connection and you want a so-called idle	1775	usage example.
1345	timeout, that is, you want to be called when there have been, say, 60
1346	seconds of inactivity on the socket. The easiest way to do this is to
1347	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1348	C<ev_timer_again> each time you successfully read or write some data. If
1349	you go into an idle state where you do not expect data to travel on the
1350	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1351	automatically restart it if need be.
1352
1353	That means you can ignore the C<after> value and C<ev_timer_start>
1354	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1355
1356	ev_timer_init (timer, callback, 0., 5.);
1357	ev_timer_again (loop, timer);
1358	...
1359	timer->again = 17.;
1360	ev_timer_again (loop, timer);
1361	...
1362	timer->again = 10.;
1363	ev_timer_again (loop, timer);
1364
1365	This is more slightly efficient then stopping/starting the timer each time
1366	you want to modify its timeout value.
1367
1368	Note, however, that it is often even more efficient to remember the
1369	time of the last activity and let the timer time-out naturally. In the
1370	callback, you then check whether the time-out is real, or, if there was
1371	some activity, you reschedule the watcher to time-out in "last_activity +
1372	timeout - ev_now ()" seconds.
1373		1776
1374	=item ev_tstamp repeat [read-write]	1777	=item ev_tstamp repeat [read-write]
1375		1778
1376	The current C<repeat> value. Will be used each time the watcher times out	1779	The current C<repeat> value. Will be used each time the watcher times out
1377	or C<ev_timer_again> is called, and determines the next timeout (if any),	1780	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1382	=head3 Examples	1785	=head3 Examples
1383		1786
1384	Example: Create a timer that fires after 60 seconds.	1787	Example: Create a timer that fires after 60 seconds.
1385		1788
1386	static void	1789	static void
1387	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1790	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1388	{	1791	{
1389	.. one minute over, w is actually stopped right here	1792	.. one minute over, w is actually stopped right here
1390	}	1793	}
1391		1794
1392	struct ev_timer mytimer;	1795	ev_timer mytimer;
1393	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1796	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1394	ev_timer_start (loop, &mytimer);	1797	ev_timer_start (loop, &mytimer);
1395		1798
1396	Example: Create a timeout timer that times out after 10 seconds of	1799	Example: Create a timeout timer that times out after 10 seconds of
1397	inactivity.	1800	inactivity.
1398		1801
1399	static void	1802	static void
1400	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1803	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1401	{	1804	{
1402	.. ten seconds without any activity	1805	.. ten seconds without any activity
1403	}	1806	}
1404		1807
1405	struct ev_timer mytimer;	1808	ev_timer mytimer;
1406	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1809	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1407	ev_timer_again (&mytimer); /* start timer */	1810	ev_timer_again (&mytimer); /* start timer */
1408	ev_loop (loop, 0);	1811	ev_loop (loop, 0);
1409		1812
1410	// and in some piece of code that gets executed on any "activity":	1813	// and in some piece of code that gets executed on any "activity":
…		…
1415	=head2 C<ev_periodic> - to cron or not to cron?	1818	=head2 C<ev_periodic> - to cron or not to cron?
1416		1819
1417	Periodic watchers are also timers of a kind, but they are very versatile	1820	Periodic watchers are also timers of a kind, but they are very versatile
1418	(and unfortunately a bit complex).	1821	(and unfortunately a bit complex).
1419		1822
1420	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1823	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1421	but on wall clock time (absolute time). You can tell a periodic watcher	1824	relative time, the physical time that passes) but on wall clock time
1422	to trigger after some specific point in time. For example, if you tell a	1825	(absolute time, the thing you can read on your calender or clock). The
1423	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	1826	difference is that wall clock time can run faster or slower than real
1424	+ 10.>, that is, an absolute time not a delay) and then reset your system	1827	time, and time jumps are not uncommon (e.g. when you adjust your
1425	clock to January of the previous year, then it will take more than year	1828	wrist-watch).
1426	to trigger the event (unlike an C<ev_timer>, which would still trigger
1427	roughly 10 seconds later as it uses a relative timeout).
1428		1829
		1830	You can tell a periodic watcher to trigger after some specific point
		1831	in time: for example, if you tell a periodic watcher to trigger "in 10
		1832	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1833	not a delay) and then reset your system clock to January of the previous
		1834	year, then it will take a year or more to trigger the event (unlike an
		1835	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1836	it, as it uses a relative timeout).
		1837
1429	C<ev_periodic>s can also be used to implement vastly more complex timers,	1838	C<ev_periodic> watchers can also be used to implement vastly more complex
1430	such as triggering an event on each "midnight, local time", or other	1839	timers, such as triggering an event on each "midnight, local time", or
1431	complicated rules.	1840	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1841	those cannot react to time jumps.
1432		1842
1433	As with timers, the callback is guaranteed to be invoked only when the	1843	As with timers, the callback is guaranteed to be invoked only when the
1434	time (C<at>) has passed, but if multiple periodic timers become ready	1844	point in time where it is supposed to trigger has passed. If multiple
1435	during the same loop iteration, then order of execution is undefined.	1845	timers become ready during the same loop iteration then the ones with
		1846	earlier time-out values are invoked before ones with later time-out values
		1847	(but this is no longer true when a callback calls C<ev_loop> recursively).
1436		1848
1437	=head3 Watcher-Specific Functions and Data Members	1849	=head3 Watcher-Specific Functions and Data Members
1438		1850
1439	=over 4	1851	=over 4
1440		1852
1441	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1853	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1442		1854
1443	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1855	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1444		1856
1445	Lots of arguments, lets sort it out... There are basically three modes of	1857	Lots of arguments, let's sort it out... There are basically three modes of
1446	operation, and we will explain them from simplest to most complex:	1858	operation, and we will explain them from simplest to most complex:
1447		1859
1448	=over 4	1860	=over 4
1449		1861
1450	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1862	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1451		1863
1452	In this configuration the watcher triggers an event after the wall clock	1864	In this configuration the watcher triggers an event after the wall clock
1453	time C<at> has passed. It will not repeat and will not adjust when a time	1865	time C<offset> has passed. It will not repeat and will not adjust when a
1454	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1866	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1455	only run when the system clock reaches or surpasses this time.	1867	will be stopped and invoked when the system clock reaches or surpasses
		1868	this point in time.
1456		1869
1457	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1870	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1458		1871
1459	In this mode the watcher will always be scheduled to time out at the next	1872	In this mode the watcher will always be scheduled to time out at the next
1460	C<at + N * interval> time (for some integer N, which can also be negative)	1873	C<offset + N * interval> time (for some integer N, which can also be
1461	and then repeat, regardless of any time jumps.	1874	negative) and then repeat, regardless of any time jumps. The C<offset>
		1875	argument is merely an offset into the C<interval> periods.
1462		1876
1463	This can be used to create timers that do not drift with respect to the	1877	This can be used to create timers that do not drift with respect to the
1464	system clock, for example, here is a C<ev_periodic> that triggers each	1878	system clock, for example, here is an C<ev_periodic> that triggers each
1465	hour, on the hour:	1879	hour, on the hour (with respect to UTC):
1466		1880
1467	ev_periodic_set (&periodic, 0., 3600., 0);	1881	ev_periodic_set (&periodic, 0., 3600., 0);
1468		1882
1469	This doesn't mean there will always be 3600 seconds in between triggers,	1883	This doesn't mean there will always be 3600 seconds in between triggers,
1470	but only that the callback will be called when the system time shows a	1884	but only that the callback will be called when the system time shows a
1471	full hour (UTC), or more correctly, when the system time is evenly divisible	1885	full hour (UTC), or more correctly, when the system time is evenly divisible
1472	by 3600.	1886	by 3600.
1473		1887
1474	Another way to think about it (for the mathematically inclined) is that	1888	Another way to think about it (for the mathematically inclined) is that
1475	C<ev_periodic> will try to run the callback in this mode at the next possible	1889	C<ev_periodic> will try to run the callback in this mode at the next possible
1476	time where C<time = at (mod interval)>, regardless of any time jumps.	1890	time where C<time = offset (mod interval)>, regardless of any time jumps.
1477		1891
1478	For numerical stability it is preferable that the C<at> value is near	1892	For numerical stability it is preferable that the C<offset> value is near
1479	C<ev_now ()> (the current time), but there is no range requirement for	1893	C<ev_now ()> (the current time), but there is no range requirement for
1480	this value, and in fact is often specified as zero.	1894	this value, and in fact is often specified as zero.
1481		1895
1482	Note also that there is an upper limit to how often a timer can fire (CPU	1896	Note also that there is an upper limit to how often a timer can fire (CPU
1483	speed for example), so if C<interval> is very small then timing stability	1897	speed for example), so if C<interval> is very small then timing stability
1484	will of course deteriorate. Libev itself tries to be exact to be about one	1898	will of course deteriorate. Libev itself tries to be exact to be about one
1485	millisecond (if the OS supports it and the machine is fast enough).	1899	millisecond (if the OS supports it and the machine is fast enough).
1486		1900
1487	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1901	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1488		1902
1489	In this mode the values for C<interval> and C<at> are both being	1903	In this mode the values for C<interval> and C<offset> are both being
1490	ignored. Instead, each time the periodic watcher gets scheduled, the	1904	ignored. Instead, each time the periodic watcher gets scheduled, the
1491	reschedule callback will be called with the watcher as first, and the	1905	reschedule callback will be called with the watcher as first, and the
1492	current time as second argument.	1906	current time as second argument.
1493		1907
1494	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1908	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1495	ever, or make ANY event loop modifications whatsoever>.	1909	or make ANY other event loop modifications whatsoever, unless explicitly
		1910	allowed by documentation here>.
1496		1911
1497	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1912	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1498	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	1913	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1499	only event loop modification you are allowed to do).	1914	only event loop modification you are allowed to do).
1500		1915
1501	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1916	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1502	*w, ev_tstamp now)>, e.g.:	1917	*w, ev_tstamp now)>, e.g.:
1503		1918
		1919	static ev_tstamp
1504	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1920	my_rescheduler (ev_periodic *w, ev_tstamp now)
1505	{	1921	{
1506	return now + 60.;	1922	return now + 60.;
1507	}	1923	}
1508		1924
1509	It must return the next time to trigger, based on the passed time value	1925	It must return the next time to trigger, based on the passed time value
…		…
1529	a different time than the last time it was called (e.g. in a crond like	1945	a different time than the last time it was called (e.g. in a crond like
1530	program when the crontabs have changed).	1946	program when the crontabs have changed).
1531		1947
1532	=item ev_tstamp ev_periodic_at (ev_periodic *)	1948	=item ev_tstamp ev_periodic_at (ev_periodic *)
1533		1949
1534	When active, returns the absolute time that the watcher is supposed to	1950	When active, returns the absolute time that the watcher is supposed
1535	trigger next.	1951	to trigger next. This is not the same as the C<offset> argument to
		1952	C<ev_periodic_set>, but indeed works even in interval and manual
		1953	rescheduling modes.
1536		1954
1537	=item ev_tstamp offset [read-write]	1955	=item ev_tstamp offset [read-write]
1538		1956
1539	When repeating, this contains the offset value, otherwise this is the	1957	When repeating, this contains the offset value, otherwise this is the
1540	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1958	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		1959	although libev might modify this value for better numerical stability).
1541		1960
1542	Can be modified any time, but changes only take effect when the periodic	1961	Can be modified any time, but changes only take effect when the periodic
1543	timer fires or C<ev_periodic_again> is being called.	1962	timer fires or C<ev_periodic_again> is being called.
1544		1963
1545	=item ev_tstamp interval [read-write]	1964	=item ev_tstamp interval [read-write]
1546		1965
1547	The current interval value. Can be modified any time, but changes only	1966	The current interval value. Can be modified any time, but changes only
1548	take effect when the periodic timer fires or C<ev_periodic_again> is being	1967	take effect when the periodic timer fires or C<ev_periodic_again> is being
1549	called.	1968	called.
1550		1969
1551	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1970	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1552		1971
1553	The current reschedule callback, or C<0>, if this functionality is	1972	The current reschedule callback, or C<0>, if this functionality is
1554	switched off. Can be changed any time, but changes only take effect when	1973	switched off. Can be changed any time, but changes only take effect when
1555	the periodic timer fires or C<ev_periodic_again> is being called.	1974	the periodic timer fires or C<ev_periodic_again> is being called.
1556		1975
…		…
1561	Example: Call a callback every hour, or, more precisely, whenever the	1980	Example: Call a callback every hour, or, more precisely, whenever the
1562	system time is divisible by 3600. The callback invocation times have	1981	system time is divisible by 3600. The callback invocation times have
1563	potentially a lot of jitter, but good long-term stability.	1982	potentially a lot of jitter, but good long-term stability.
1564		1983
1565	static void	1984	static void
1566	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1985	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1567	{	1986	{
1568	... its now a full hour (UTC, or TAI or whatever your clock follows)	1987	... its now a full hour (UTC, or TAI or whatever your clock follows)
1569	}	1988	}
1570		1989
1571	struct ev_periodic hourly_tick;	1990	ev_periodic hourly_tick;
1572	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1991	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1573	ev_periodic_start (loop, &hourly_tick);	1992	ev_periodic_start (loop, &hourly_tick);
1574		1993
1575	Example: The same as above, but use a reschedule callback to do it:	1994	Example: The same as above, but use a reschedule callback to do it:
1576		1995
1577	#include <math.h>	1996	#include <math.h>
1578		1997
1579	static ev_tstamp	1998	static ev_tstamp
1580	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1999	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1581	{	2000	{
1582	return now + (3600. - fmod (now, 3600.));	2001	return now + (3600. - fmod (now, 3600.));
1583	}	2002	}
1584		2003
1585	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2004	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1586		2005
1587	Example: Call a callback every hour, starting now:	2006	Example: Call a callback every hour, starting now:
1588		2007
1589	struct ev_periodic hourly_tick;	2008	ev_periodic hourly_tick;
1590	ev_periodic_init (&hourly_tick, clock_cb,	2009	ev_periodic_init (&hourly_tick, clock_cb,
1591	fmod (ev_now (loop), 3600.), 3600., 0);	2010	fmod (ev_now (loop), 3600.), 3600., 0);
1592	ev_periodic_start (loop, &hourly_tick);	2011	ev_periodic_start (loop, &hourly_tick);
1593		2012
1594		2013
…		…
1636	=head3 Examples	2055	=head3 Examples
1637		2056
1638	Example: Try to exit cleanly on SIGINT.	2057	Example: Try to exit cleanly on SIGINT.
1639		2058
1640	static void	2059	static void
1641	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2060	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1642	{	2061	{
1643	ev_unloop (loop, EVUNLOOP_ALL);	2062	ev_unloop (loop, EVUNLOOP_ALL);
1644	}	2063	}
1645		2064
1646	struct ev_signal signal_watcher;	2065	ev_signal signal_watcher;
1647	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2066	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1648	ev_signal_start (loop, &signal_watcher);	2067	ev_signal_start (loop, &signal_watcher);
1649		2068
1650		2069
1651	=head2 C<ev_child> - watch out for process status changes	2070	=head2 C<ev_child> - watch out for process status changes
…		…
1654	some child status changes (most typically when a child of yours dies or	2073	some child status changes (most typically when a child of yours dies or
1655	exits). It is permissible to install a child watcher I<after> the child	2074	exits). It is permissible to install a child watcher I<after> the child
1656	has been forked (which implies it might have already exited), as long	2075	has been forked (which implies it might have already exited), as long
1657	as the event loop isn't entered (or is continued from a watcher), i.e.,	2076	as the event loop isn't entered (or is continued from a watcher), i.e.,
1658	forking and then immediately registering a watcher for the child is fine,	2077	forking and then immediately registering a watcher for the child is fine,
1659	but forking and registering a watcher a few event loop iterations later is	2078	but forking and registering a watcher a few event loop iterations later or
1660	not.	2079	in the next callback invocation is not.
1661		2080
1662	Only the default event loop is capable of handling signals, and therefore	2081	Only the default event loop is capable of handling signals, and therefore
1663	you can only register child watchers in the default event loop.	2082	you can only register child watchers in the default event loop.
		2083
		2084	Due to some design glitches inside libev, child watchers will always be
		2085	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2086	libev)
1664		2087
1665	=head3 Process Interaction	2088	=head3 Process Interaction
1666		2089
1667	Libev grabs C<SIGCHLD> as soon as the default event loop is	2090	Libev grabs C<SIGCHLD> as soon as the default event loop is
1668	initialised. This is necessary to guarantee proper behaviour even if	2091	initialised. This is necessary to guarantee proper behaviour even if
…		…
1726	its completion.	2149	its completion.
1727		2150
1728	ev_child cw;	2151	ev_child cw;
1729		2152
1730	static void	2153	static void
1731	child_cb (EV_P_ struct ev_child *w, int revents)	2154	child_cb (EV_P_ ev_child *w, int revents)
1732	{	2155	{
1733	ev_child_stop (EV_A_ w);	2156	ev_child_stop (EV_A_ w);
1734	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2157	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1735	}	2158	}
1736		2159
…		…
1751		2174
1752		2175
1753	=head2 C<ev_stat> - did the file attributes just change?	2176	=head2 C<ev_stat> - did the file attributes just change?
1754		2177
1755	This watches a file system path for attribute changes. That is, it calls	2178	This watches a file system path for attribute changes. That is, it calls
1756	C<stat> regularly (or when the OS says it changed) and sees if it changed	2179	C<stat> on that path in regular intervals (or when the OS says it changed)
1757	compared to the last time, invoking the callback if it did.	2180	and sees if it changed compared to the last time, invoking the callback if
		2181	it did.
1758		2182
1759	The path does not need to exist: changing from "path exists" to "path does	2183	The path does not need to exist: changing from "path exists" to "path does
1760	not exist" is a status change like any other. The condition "path does	2184	not exist" is a status change like any other. The condition "path does not
1761	not exist" is signified by the C<st_nlink> field being zero (which is	2185	exist" (or more correctly "path cannot be stat'ed") is signified by the
1762	otherwise always forced to be at least one) and all the other fields of	2186	C<st_nlink> field being zero (which is otherwise always forced to be at
1763	the stat buffer having unspecified contents.	2187	least one) and all the other fields of the stat buffer having unspecified
		2188	contents.
1764		2189
1765	The path I<should> be absolute and I<must not> end in a slash. If it is	2190	The path I<must not> end in a slash or contain special components such as
		2191	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1766	relative and your working directory changes, the behaviour is undefined.	2192	your working directory changes, then the behaviour is undefined.
1767		2193
1768	Since there is no standard kernel interface to do this, the portable	2194	Since there is no portable change notification interface available, the
1769	implementation simply calls C<stat (2)> regularly on the path to see if	2195	portable implementation simply calls C<stat(2)> regularly on the path
1770	it changed somehow. You can specify a recommended polling interval for	2196	to see if it changed somehow. You can specify a recommended polling
1771	this case. If you specify a polling interval of C<0> (highly recommended!)	2197	interval for this case. If you specify a polling interval of C<0> (highly
1772	then a I<suitable, unspecified default> value will be used (which	2198	recommended!) then a I<suitable, unspecified default> value will be used
1773	you can expect to be around five seconds, although this might change	2199	(which you can expect to be around five seconds, although this might
1774	dynamically). Libev will also impose a minimum interval which is currently	2200	change dynamically). Libev will also impose a minimum interval which is
1775	around C<0.1>, but thats usually overkill.	2201	currently around C<0.1>, but that's usually overkill.
1776		2202
1777	This watcher type is not meant for massive numbers of stat watchers,	2203	This watcher type is not meant for massive numbers of stat watchers,
1778	as even with OS-supported change notifications, this can be	2204	as even with OS-supported change notifications, this can be
1779	resource-intensive.	2205	resource-intensive.
1780		2206
1781	At the time of this writing, the only OS-specific interface implemented	2207	At the time of this writing, the only OS-specific interface implemented
1782	is the Linux inotify interface (implementing kqueue support is left as	2208	is the Linux inotify interface (implementing kqueue support is left as an
1783	an exercise for the reader. Note, however, that the author sees no way	2209	exercise for the reader. Note, however, that the author sees no way of
1784	of implementing C<ev_stat> semantics with kqueue).	2210	implementing C<ev_stat> semantics with kqueue, except as a hint).
1785		2211
1786	=head3 ABI Issues (Largefile Support)	2212	=head3 ABI Issues (Largefile Support)
1787		2213
1788	Libev by default (unless the user overrides this) uses the default	2214	Libev by default (unless the user overrides this) uses the default
1789	compilation environment, which means that on systems with large file	2215	compilation environment, which means that on systems with large file
1790	support disabled by default, you get the 32 bit version of the stat	2216	support disabled by default, you get the 32 bit version of the stat
1791	structure. When using the library from programs that change the ABI to	2217	structure. When using the library from programs that change the ABI to
1792	use 64 bit file offsets the programs will fail. In that case you have to	2218	use 64 bit file offsets the programs will fail. In that case you have to
1793	compile libev with the same flags to get binary compatibility. This is	2219	compile libev with the same flags to get binary compatibility. This is
1794	obviously the case with any flags that change the ABI, but the problem is	2220	obviously the case with any flags that change the ABI, but the problem is
1795	most noticeably disabled with ev_stat and large file support.	2221	most noticeably displayed with ev_stat and large file support.
1796		2222
1797	The solution for this is to lobby your distribution maker to make large	2223	The solution for this is to lobby your distribution maker to make large
1798	file interfaces available by default (as e.g. FreeBSD does) and not	2224	file interfaces available by default (as e.g. FreeBSD does) and not
1799	optional. Libev cannot simply switch on large file support because it has	2225	optional. Libev cannot simply switch on large file support because it has
1800	to exchange stat structures with application programs compiled using the	2226	to exchange stat structures with application programs compiled using the
1801	default compilation environment.	2227	default compilation environment.
1802		2228
1803	=head3 Inotify and Kqueue	2229	=head3 Inotify and Kqueue
1804		2230
1805	When C<inotify (7)> support has been compiled into libev (generally	2231	When C<inotify (7)> support has been compiled into libev and present at
1806	only available with Linux 2.6.25 or above due to bugs in earlier	2232	runtime, it will be used to speed up change detection where possible. The
1807	implementations) and present at runtime, it will be used to speed up	2233	inotify descriptor will be created lazily when the first C<ev_stat>
1808	change detection where possible. The inotify descriptor will be created	2234	watcher is being started.
1809	lazily when the first C<ev_stat> watcher is being started.
1810		2235
1811	Inotify presence does not change the semantics of C<ev_stat> watchers	2236	Inotify presence does not change the semantics of C<ev_stat> watchers
1812	except that changes might be detected earlier, and in some cases, to avoid	2237	except that changes might be detected earlier, and in some cases, to avoid
1813	making regular C<stat> calls. Even in the presence of inotify support	2238	making regular C<stat> calls. Even in the presence of inotify support
1814	there are many cases where libev has to resort to regular C<stat> polling,	2239	there are many cases where libev has to resort to regular C<stat> polling,
1815	but as long as the path exists, libev usually gets away without polling.	2240	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2241	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2242	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2243	xfs are fully working) libev usually gets away without polling.
1816		2244
1817	There is no support for kqueue, as apparently it cannot be used to	2245	There is no support for kqueue, as apparently it cannot be used to
1818	implement this functionality, due to the requirement of having a file	2246	implement this functionality, due to the requirement of having a file
1819	descriptor open on the object at all times, and detecting renames, unlinks	2247	descriptor open on the object at all times, and detecting renames, unlinks
1820	etc. is difficult.	2248	etc. is difficult.
1821		2249
		2250	=head3 C<stat ()> is a synchronous operation
		2251
		2252	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2253	the process. The exception are C<ev_stat> watchers - those call C<stat
		2254	()>, which is a synchronous operation.
		2255
		2256	For local paths, this usually doesn't matter: unless the system is very
		2257	busy or the intervals between stat's are large, a stat call will be fast,
		2258	as the path data is usually in memory already (except when starting the
		2259	watcher).
		2260
		2261	For networked file systems, calling C<stat ()> can block an indefinite
		2262	time due to network issues, and even under good conditions, a stat call
		2263	often takes multiple milliseconds.
		2264
		2265	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2266	paths, although this is fully supported by libev.
		2267
1822	=head3 The special problem of stat time resolution	2268	=head3 The special problem of stat time resolution
1823		2269
1824	The C<stat ()> system call only supports full-second resolution portably, and	2270	The C<stat ()> system call only supports full-second resolution portably,
1825	even on systems where the resolution is higher, most file systems still	2271	and even on systems where the resolution is higher, most file systems
1826	only support whole seconds.	2272	still only support whole seconds.
1827		2273
1828	That means that, if the time is the only thing that changes, you can	2274	That means that, if the time is the only thing that changes, you can
1829	easily miss updates: on the first update, C<ev_stat> detects a change and	2275	easily miss updates: on the first update, C<ev_stat> detects a change and
1830	calls your callback, which does something. When there is another update	2276	calls your callback, which does something. When there is another update
1831	within the same second, C<ev_stat> will be unable to detect unless the	2277	within the same second, C<ev_stat> will be unable to detect unless the
…		…
1974		2420
1975	=head3 Watcher-Specific Functions and Data Members	2421	=head3 Watcher-Specific Functions and Data Members
1976		2422
1977	=over 4	2423	=over 4
1978		2424
1979	=item ev_idle_init (ev_signal *, callback)	2425	=item ev_idle_init (ev_idle *, callback)
1980		2426
1981	Initialises and configures the idle watcher - it has no parameters of any	2427	Initialises and configures the idle watcher - it has no parameters of any
1982	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2428	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1983	believe me.	2429	believe me.
1984		2430
…		…
1988		2434
1989	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2435	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1990	callback, free it. Also, use no error checking, as usual.	2436	callback, free it. Also, use no error checking, as usual.
1991		2437
1992	static void	2438	static void
1993	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2439	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1994	{	2440	{
1995	free (w);	2441	free (w);
1996	// now do something you wanted to do when the program has	2442	// now do something you wanted to do when the program has
1997	// no longer anything immediate to do.	2443	// no longer anything immediate to do.
1998	}	2444	}
1999		2445
2000	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2446	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2001	ev_idle_init (idle_watcher, idle_cb);	2447	ev_idle_init (idle_watcher, idle_cb);
2002	ev_idle_start (loop, idle_cb);	2448	ev_idle_start (loop, idle_watcher);
2003		2449
2004		2450
2005	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2451	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2006		2452
2007	Prepare and check watchers are usually (but not always) used in pairs:	2453	Prepare and check watchers are usually (but not always) used in pairs:
…		…
2086		2532
2087	static ev_io iow [nfd];	2533	static ev_io iow [nfd];
2088	static ev_timer tw;	2534	static ev_timer tw;
2089		2535
2090	static void	2536	static void
2091	io_cb (ev_loop *loop, ev_io *w, int revents)	2537	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2092	{	2538	{
2093	}	2539	}
2094		2540
2095	// create io watchers for each fd and a timer before blocking	2541	// create io watchers for each fd and a timer before blocking
2096	static void	2542	static void
2097	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2543	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2098	{	2544	{
2099	int timeout = 3600000;	2545	int timeout = 3600000;
2100	struct pollfd fds [nfd];	2546	struct pollfd fds [nfd];
2101	// actual code will need to loop here and realloc etc.	2547	// actual code will need to loop here and realloc etc.
2102	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2548	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2103		2549
2104	/* the callback is illegal, but won't be called as we stop during check */	2550	/* the callback is illegal, but won't be called as we stop during check */
2105	ev_timer_init (&tw, 0, timeout * 1e-3);	2551	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2106	ev_timer_start (loop, &tw);	2552	ev_timer_start (loop, &tw);
2107		2553
2108	// create one ev_io per pollfd	2554	// create one ev_io per pollfd
2109	for (int i = 0; i < nfd; ++i)	2555	for (int i = 0; i < nfd; ++i)
2110	{	2556	{
…		…
2117	}	2563	}
2118	}	2564	}
2119		2565
2120	// stop all watchers after blocking	2566	// stop all watchers after blocking
2121	static void	2567	static void
2122	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2568	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2123	{	2569	{
2124	ev_timer_stop (loop, &tw);	2570	ev_timer_stop (loop, &tw);
2125		2571
2126	for (int i = 0; i < nfd; ++i)	2572	for (int i = 0; i < nfd; ++i)
2127	{	2573	{
…		…
2223	some fds have to be watched and handled very quickly (with low latency),	2669	some fds have to be watched and handled very quickly (with low latency),
2224	and even priorities and idle watchers might have too much overhead. In	2670	and even priorities and idle watchers might have too much overhead. In
2225	this case you would put all the high priority stuff in one loop and all	2671	this case you would put all the high priority stuff in one loop and all
2226	the rest in a second one, and embed the second one in the first.	2672	the rest in a second one, and embed the second one in the first.
2227		2673
2228	As long as the watcher is active, the callback will be invoked every time	2674	As long as the watcher is active, the callback will be invoked every
2229	there might be events pending in the embedded loop. The callback must then	2675	time there might be events pending in the embedded loop. The callback
2230	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2676	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2231	their callbacks (you could also start an idle watcher to give the embedded	2677	sweep and invoke their callbacks (the callback doesn't need to invoke the
2232	loop strictly lower priority for example). You can also set the callback	2678	C<ev_embed_sweep> function directly, it could also start an idle watcher
2233	to C<0>, in which case the embed watcher will automatically execute the	2679	to give the embedded loop strictly lower priority for example).
2234	embedded loop sweep.
2235		2680
2236	As long as the watcher is started it will automatically handle events. The	2681	You can also set the callback to C<0>, in which case the embed watcher
2237	callback will be invoked whenever some events have been handled. You can	2682	will automatically execute the embedded loop sweep whenever necessary.
2238	set the callback to C<0> to avoid having to specify one if you are not
2239	interested in that.
2240		2683
2241	Also, there have not currently been made special provisions for forking:	2684	Fork detection will be handled transparently while the C<ev_embed> watcher
2242	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2685	is active, i.e., the embedded loop will automatically be forked when the
2243	but you will also have to stop and restart any C<ev_embed> watchers	2686	embedding loop forks. In other cases, the user is responsible for calling
2244	yourself - but you can use a fork watcher to handle this automatically,	2687	C<ev_loop_fork> on the embedded loop.
2245	and future versions of libev might do just that.
2246		2688
2247	Unfortunately, not all backends are embeddable: only the ones returned by	2689	Unfortunately, not all backends are embeddable: only the ones returned by
2248	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2690	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2249	portable one.	2691	portable one.
2250		2692
…		…
2295	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2737	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2296	used).	2738	used).
2297		2739
2298	struct ev_loop *loop_hi = ev_default_init (0);	2740	struct ev_loop *loop_hi = ev_default_init (0);
2299	struct ev_loop *loop_lo = 0;	2741	struct ev_loop *loop_lo = 0;
2300	struct ev_embed embed;	2742	ev_embed embed;
2301		2743
2302	// see if there is a chance of getting one that works	2744	// see if there is a chance of getting one that works
2303	// (remember that a flags value of 0 means autodetection)	2745	// (remember that a flags value of 0 means autodetection)
2304	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2746	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2305	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2747	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2319	kqueue implementation). Store the kqueue/socket-only event loop in	2761	kqueue implementation). Store the kqueue/socket-only event loop in
2320	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2762	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2321		2763
2322	struct ev_loop *loop = ev_default_init (0);	2764	struct ev_loop *loop = ev_default_init (0);
2323	struct ev_loop *loop_socket = 0;	2765	struct ev_loop *loop_socket = 0;
2324	struct ev_embed embed;	2766	ev_embed embed;
2325		2767
2326	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2768	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2327	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2769	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2328	{	2770	{
2329	ev_embed_init (&embed, 0, loop_socket);	2771	ev_embed_init (&embed, 0, loop_socket);
…		…
2344	event loop blocks next and before C<ev_check> watchers are being called,	2786	event loop blocks next and before C<ev_check> watchers are being called,
2345	and only in the child after the fork. If whoever good citizen calling	2787	and only in the child after the fork. If whoever good citizen calling
2346	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2788	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2347	handlers will be invoked, too, of course.	2789	handlers will be invoked, too, of course.
2348		2790
		2791	=head3 The special problem of life after fork - how is it possible?
		2792
		2793	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2794	up/change the process environment, followed by a call to C<exec()>. This
		2795	sequence should be handled by libev without any problems.
		2796
		2797	This changes when the application actually wants to do event handling
		2798	in the child, or both parent in child, in effect "continuing" after the
		2799	fork.
		2800
		2801	The default mode of operation (for libev, with application help to detect
		2802	forks) is to duplicate all the state in the child, as would be expected
		2803	when I<either> the parent I<or> the child process continues.
		2804
		2805	When both processes want to continue using libev, then this is usually the
		2806	wrong result. In that case, usually one process (typically the parent) is
		2807	supposed to continue with all watchers in place as before, while the other
		2808	process typically wants to start fresh, i.e. without any active watchers.
		2809
		2810	The cleanest and most efficient way to achieve that with libev is to
		2811	simply create a new event loop, which of course will be "empty", and
		2812	use that for new watchers. This has the advantage of not touching more
		2813	memory than necessary, and thus avoiding the copy-on-write, and the
		2814	disadvantage of having to use multiple event loops (which do not support
		2815	signal watchers).
		2816
		2817	When this is not possible, or you want to use the default loop for
		2818	other reasons, then in the process that wants to start "fresh", call
		2819	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2820	the default loop will "orphan" (not stop) all registered watchers, so you
		2821	have to be careful not to execute code that modifies those watchers. Note
		2822	also that in that case, you have to re-register any signal watchers.
		2823
2349	=head3 Watcher-Specific Functions and Data Members	2824	=head3 Watcher-Specific Functions and Data Members
2350		2825
2351	=over 4	2826	=over 4
2352		2827
2353	=item ev_fork_init (ev_signal *, callback)	2828	=item ev_fork_init (ev_signal *, callback)
…		…
2470	=over 4	2945	=over 4
2471		2946
2472	=item ev_async_init (ev_async *, callback)	2947	=item ev_async_init (ev_async *, callback)
2473		2948
2474	Initialises and configures the async watcher - it has no parameters of any	2949	Initialises and configures the async watcher - it has no parameters of any
2475	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2950	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2476	trust me.	2951	trust me.
2477		2952
2478	=item ev_async_send (loop, ev_async *)	2953	=item ev_async_send (loop, ev_async *)
2479		2954
2480	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2955	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2481	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2956	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2482	C<ev_feed_event>, this call is safe to do from other threads, signal or	2957	C<ev_feed_event>, this call is safe to do from other threads, signal or
2483	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	2958	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2484	section below on what exactly this means).	2959	section below on what exactly this means).
2485		2960
		2961	Note that, as with other watchers in libev, multiple events might get
		2962	compressed into a single callback invocation (another way to look at this
		2963	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		2964	reset when the event loop detects that).
		2965
2486	This call incurs the overhead of a system call only once per loop iteration,	2966	This call incurs the overhead of a system call only once per event loop
2487	so while the overhead might be noticeable, it doesn't apply to repeated	2967	iteration, so while the overhead might be noticeable, it doesn't apply to
2488	calls to C<ev_async_send>.	2968	repeated calls to C<ev_async_send> for the same event loop.
2489		2969
2490	=item bool = ev_async_pending (ev_async *)	2970	=item bool = ev_async_pending (ev_async *)
2491		2971
2492	Returns a non-zero value when C<ev_async_send> has been called on the	2972	Returns a non-zero value when C<ev_async_send> has been called on the
2493	watcher but the event has not yet been processed (or even noted) by the	2973	watcher but the event has not yet been processed (or even noted) by the
…		…
2496	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	2976	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2497	the loop iterates next and checks for the watcher to have become active,	2977	the loop iterates next and checks for the watcher to have become active,
2498	it will reset the flag again. C<ev_async_pending> can be used to very	2978	it will reset the flag again. C<ev_async_pending> can be used to very
2499	quickly check whether invoking the loop might be a good idea.	2979	quickly check whether invoking the loop might be a good idea.
2500		2980
2501	Not that this does I<not> check whether the watcher itself is pending, only	2981	Not that this does I<not> check whether the watcher itself is pending,
2502	whether it has been requested to make this watcher pending.	2982	only whether it has been requested to make this watcher pending: there
		2983	is a time window between the event loop checking and resetting the async
		2984	notification, and the callback being invoked.
2503		2985
2504	=back	2986	=back
2505		2987
2506		2988
2507	=head1 OTHER FUNCTIONS	2989	=head1 OTHER FUNCTIONS
…		…
2543	/* doh, nothing entered */;	3025	/* doh, nothing entered */;
2544	}	3026	}
2545		3027
2546	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3028	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2547		3029
2548	=item ev_feed_event (ev_loop *, watcher *, int revents)	3030	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2549		3031
2550	Feeds the given event set into the event loop, as if the specified event	3032	Feeds the given event set into the event loop, as if the specified event
2551	had happened for the specified watcher (which must be a pointer to an	3033	had happened for the specified watcher (which must be a pointer to an
2552	initialised but not necessarily started event watcher).	3034	initialised but not necessarily started event watcher).
2553		3035
2554	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3036	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2555		3037
2556	Feed an event on the given fd, as if a file descriptor backend detected	3038	Feed an event on the given fd, as if a file descriptor backend detected
2557	the given events it.	3039	the given events it.
2558		3040
2559	=item ev_feed_signal_event (ev_loop *loop, int signum)	3041	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2560		3042
2561	Feed an event as if the given signal occurred (C<loop> must be the default	3043	Feed an event as if the given signal occurred (C<loop> must be the default
2562	loop!).	3044	loop!).
2563		3045
2564	=back	3046	=back
…		…
2685	}	3167	}
2686		3168
2687	myclass obj;	3169	myclass obj;
2688	ev::io iow;	3170	ev::io iow;
2689	iow.set <myclass, &myclass::io_cb> (&obj);	3171	iow.set <myclass, &myclass::io_cb> (&obj);
		3172
		3173	=item w->set (object *)
		3174
		3175	This is an B<experimental> feature that might go away in a future version.
		3176
		3177	This is a variation of a method callback - leaving out the method to call
		3178	will default the method to C<operator ()>, which makes it possible to use
		3179	functor objects without having to manually specify the C<operator ()> all
		3180	the time. Incidentally, you can then also leave out the template argument
		3181	list.
		3182
		3183	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3184	int revents)>.
		3185
		3186	See the method-C<set> above for more details.
		3187
		3188	Example: use a functor object as callback.
		3189
		3190	struct myfunctor
		3191	{
		3192	void operator() (ev::io &w, int revents)
		3193	{
		3194	...
		3195	}
		3196	}
		3197
		3198	myfunctor f;
		3199
		3200	ev::io w;
		3201	w.set (&f);
2690		3202
2691	=item w->set<function> (void *data = 0)	3203	=item w->set<function> (void *data = 0)
2692		3204
2693	Also sets a callback, but uses a static method or plain function as	3205	Also sets a callback, but uses a static method or plain function as
2694	callback. The optional C<data> argument will be stored in the watcher's	3206	callback. The optional C<data> argument will be stored in the watcher's
…		…
2781	L<http://software.schmorp.de/pkg/EV>.	3293	L<http://software.schmorp.de/pkg/EV>.
2782		3294
2783	=item Python	3295	=item Python
2784		3296
2785	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3297	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2786	seems to be quite complete and well-documented. Note, however, that the	3298	seems to be quite complete and well-documented.
2787	patch they require for libev is outright dangerous as it breaks the ABI
2788	for everybody else, and therefore, should never be applied in an installed
2789	libev (if python requires an incompatible ABI then it needs to embed
2790	libev).
2791		3299
2792	=item Ruby	3300	=item Ruby
2793		3301
2794	Tony Arcieri has written a ruby extension that offers access to a subset	3302	Tony Arcieri has written a ruby extension that offers access to a subset
2795	of the libev API and adds file handle abstractions, asynchronous DNS and	3303	of the libev API and adds file handle abstractions, asynchronous DNS and
2796	more on top of it. It can be found via gem servers. Its homepage is at	3304	more on top of it. It can be found via gem servers. Its homepage is at
2797	L<http://rev.rubyforge.org/>.	3305	L<http://rev.rubyforge.org/>.
2798		3306
		3307	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3308	makes rev work even on mingw.
		3309
		3310	=item Haskell
		3311
		3312	A haskell binding to libev is available at
		3313	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3314
2799	=item D	3315	=item D
2800		3316
2801	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3317	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2802	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3318	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3319
		3320	=item Ocaml
		3321
		3322	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3323	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2803		3324
2804	=back	3325	=back
2805		3326
2806		3327
2807	=head1 MACRO MAGIC	3328	=head1 MACRO MAGIC
…		…
2908		3429
2909	#define EV_STANDALONE 1	3430	#define EV_STANDALONE 1
2910	#include "ev.h"	3431	#include "ev.h"
2911		3432
2912	Both header files and implementation files can be compiled with a C++	3433	Both header files and implementation files can be compiled with a C++
2913	compiler (at least, thats a stated goal, and breakage will be treated	3434	compiler (at least, that's a stated goal, and breakage will be treated
2914	as a bug).	3435	as a bug).
2915		3436
2916	You need the following files in your source tree, or in a directory	3437	You need the following files in your source tree, or in a directory
2917	in your include path (e.g. in libev/ when using -Ilibev):	3438	in your include path (e.g. in libev/ when using -Ilibev):
2918		3439
…		…
2974	keeps libev from including F<config.h>, and it also defines dummy	3495	keeps libev from including F<config.h>, and it also defines dummy
2975	implementations for some libevent functions (such as logging, which is not	3496	implementations for some libevent functions (such as logging, which is not
2976	supported). It will also not define any of the structs usually found in	3497	supported). It will also not define any of the structs usually found in
2977	F<event.h> that are not directly supported by the libev core alone.	3498	F<event.h> that are not directly supported by the libev core alone.
2978		3499
		3500	In stanbdalone mode, libev will still try to automatically deduce the
		3501	configuration, but has to be more conservative.
		3502
2979	=item EV_USE_MONOTONIC	3503	=item EV_USE_MONOTONIC
2980		3504
2981	If defined to be C<1>, libev will try to detect the availability of the	3505	If defined to be C<1>, libev will try to detect the availability of the
2982	monotonic clock option at both compile time and runtime. Otherwise no use	3506	monotonic clock option at both compile time and runtime. Otherwise no
2983	of the monotonic clock option will be attempted. If you enable this, you	3507	use of the monotonic clock option will be attempted. If you enable this,
2984	usually have to link against librt or something similar. Enabling it when	3508	you usually have to link against librt or something similar. Enabling it
2985	the functionality isn't available is safe, though, although you have	3509	when the functionality isn't available is safe, though, although you have
2986	to make sure you link against any libraries where the C<clock_gettime>	3510	to make sure you link against any libraries where the C<clock_gettime>
2987	function is hiding in (often F<-lrt>).	3511	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2988		3512
2989	=item EV_USE_REALTIME	3513	=item EV_USE_REALTIME
2990		3514
2991	If defined to be C<1>, libev will try to detect the availability of the	3515	If defined to be C<1>, libev will try to detect the availability of the
2992	real-time clock option at compile time (and assume its availability at	3516	real-time clock option at compile time (and assume its availability
2993	runtime if successful). Otherwise no use of the real-time clock option will	3517	at runtime if successful). Otherwise no use of the real-time clock
2994	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3518	option will be attempted. This effectively replaces C<gettimeofday>
2995	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3519	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2996	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3520	correctness. See the note about libraries in the description of
		3521	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3522	C<EV_USE_CLOCK_SYSCALL>.
		3523
		3524	=item EV_USE_CLOCK_SYSCALL
		3525
		3526	If defined to be C<1>, libev will try to use a direct syscall instead
		3527	of calling the system-provided C<clock_gettime> function. This option
		3528	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3529	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3530	programs needlessly. Using a direct syscall is slightly slower (in
		3531	theory), because no optimised vdso implementation can be used, but avoids
		3532	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3533	higher, as it simplifies linking (no need for C<-lrt>).
2997		3534
2998	=item EV_USE_NANOSLEEP	3535	=item EV_USE_NANOSLEEP
2999		3536
3000	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3537	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
3001	and will use it for delays. Otherwise it will use C<select ()>.	3538	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3017		3554
3018	=item EV_SELECT_USE_FD_SET	3555	=item EV_SELECT_USE_FD_SET
3019		3556
3020	If defined to C<1>, then the select backend will use the system C<fd_set>	3557	If defined to C<1>, then the select backend will use the system C<fd_set>
3021	structure. This is useful if libev doesn't compile due to a missing	3558	structure. This is useful if libev doesn't compile due to a missing
3022	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3559	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3023	exotic systems. This usually limits the range of file descriptors to some	3560	on exotic systems. This usually limits the range of file descriptors to
3024	low limit such as 1024 or might have other limitations (winsocket only	3561	some low limit such as 1024 or might have other limitations (winsocket
3025	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3562	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3026	influence the size of the C<fd_set> used.	3563	configures the maximum size of the C<fd_set>.
3027		3564
3028	=item EV_SELECT_IS_WINSOCKET	3565	=item EV_SELECT_IS_WINSOCKET
3029		3566
3030	When defined to C<1>, the select backend will assume that	3567	When defined to C<1>, the select backend will assume that
3031	select/socket/connect etc. don't understand file descriptors but	3568	select/socket/connect etc. don't understand file descriptors but
…		…
3181	defined to be C<0>, then they are not.	3718	defined to be C<0>, then they are not.
3182		3719
3183	=item EV_MINIMAL	3720	=item EV_MINIMAL
3184		3721
3185	If you need to shave off some kilobytes of code at the expense of some	3722	If you need to shave off some kilobytes of code at the expense of some
3186	speed, define this symbol to C<1>. Currently this is used to override some	3723	speed (but with the full API), define this symbol to C<1>. Currently this
3187	inlining decisions, saves roughly 30% code size on amd64. It also selects a	3724	is used to override some inlining decisions, saves roughly 30% code size
3188	much smaller 2-heap for timer management over the default 4-heap.	3725	on amd64. It also selects a much smaller 2-heap for timer management over
		3726	the default 4-heap.
		3727
		3728	You can save even more by disabling watcher types you do not need
		3729	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>
		3730	(C<-DNDEBUG>) will usually reduce code size a lot.
		3731
		3732	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to
		3733	provide a bare-bones event library. See C<ev.h> for details on what parts
		3734	of the API are still available, and do not complain if this subset changes
		3735	over time.
3189		3736
3190	=item EV_PID_HASHSIZE	3737	=item EV_PID_HASHSIZE
3191		3738
3192	C<ev_child> watchers use a small hash table to distribute workload by	3739	C<ev_child> watchers use a small hash table to distribute workload by
3193	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3740	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
3379	default loop and triggering an C<ev_async> watcher from the default loop	3926	default loop and triggering an C<ev_async> watcher from the default loop
3380	watcher callback into the event loop interested in the signal.	3927	watcher callback into the event loop interested in the signal.
3381		3928
3382	=back	3929	=back
3383		3930
		3931	=head4 THREAD LOCKING EXAMPLE
		3932
3384	=head3 COROUTINES	3933	=head3 COROUTINES
3385		3934
3386	Libev is very accommodating to coroutines ("cooperative threads"):	3935	Libev is very accommodating to coroutines ("cooperative threads"):
3387	libev fully supports nesting calls to its functions from different	3936	libev fully supports nesting calls to its functions from different
3388	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3937	coroutines (e.g. you can call C<ev_loop> on the same loop from two
…		…
3390	loop, as long as you don't confuse yourself). The only exception is that	3939	loop, as long as you don't confuse yourself). The only exception is that
3391	you must not do this from C<ev_periodic> reschedule callbacks.	3940	you must not do this from C<ev_periodic> reschedule callbacks.
3392		3941
3393	Care has been taken to ensure that libev does not keep local state inside	3942	Care has been taken to ensure that libev does not keep local state inside
3394	C<ev_loop>, and other calls do not usually allow for coroutine switches as	3943	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3395	they do not clal any callbacks.	3944	they do not call any callbacks.
3396		3945
3397	=head2 COMPILER WARNINGS	3946	=head2 COMPILER WARNINGS
3398		3947
3399	Depending on your compiler and compiler settings, you might get no or a	3948	Depending on your compiler and compiler settings, you might get no or a
3400	lot of warnings when compiling libev code. Some people are apparently	3949	lot of warnings when compiling libev code. Some people are apparently
…		…
3434	==2274== definitely lost: 0 bytes in 0 blocks.	3983	==2274== definitely lost: 0 bytes in 0 blocks.
3435	==2274== possibly lost: 0 bytes in 0 blocks.	3984	==2274== possibly lost: 0 bytes in 0 blocks.
3436	==2274== still reachable: 256 bytes in 1 blocks.	3985	==2274== still reachable: 256 bytes in 1 blocks.
3437		3986
3438	Then there is no memory leak, just as memory accounted to global variables	3987	Then there is no memory leak, just as memory accounted to global variables
3439	is not a memleak - the memory is still being refernced, and didn't leak.	3988	is not a memleak - the memory is still being referenced, and didn't leak.
3440		3989
3441	Similarly, under some circumstances, valgrind might report kernel bugs	3990	Similarly, under some circumstances, valgrind might report kernel bugs
3442	as if it were a bug in libev (e.g. in realloc or in the poll backend,	3991	as if it were a bug in libev (e.g. in realloc or in the poll backend,
3443	although an acceptable workaround has been found here), or it might be	3992	although an acceptable workaround has been found here), or it might be
3444	confused.	3993	confused.
…		…
3473	way (note also that glib is the slowest event library known to man).	4022	way (note also that glib is the slowest event library known to man).
3474		4023
3475	There is no supported compilation method available on windows except	4024	There is no supported compilation method available on windows except
3476	embedding it into other applications.	4025	embedding it into other applications.
3477		4026
		4027	Sensible signal handling is officially unsupported by Microsoft - libev
		4028	tries its best, but under most conditions, signals will simply not work.
		4029
3478	Not a libev limitation but worth mentioning: windows apparently doesn't	4030	Not a libev limitation but worth mentioning: windows apparently doesn't
3479	accept large writes: instead of resulting in a partial write, windows will	4031	accept large writes: instead of resulting in a partial write, windows will
3480	either accept everything or return C<ENOBUFS> if the buffer is too large,	4032	either accept everything or return C<ENOBUFS> if the buffer is too large,
3481	so make sure you only write small amounts into your sockets (less than a	4033	so make sure you only write small amounts into your sockets (less than a
3482	megabyte seems safe, but this apparently depends on the amount of memory	4034	megabyte seems safe, but this apparently depends on the amount of memory
…		…
3486	the abysmal performance of winsockets, using a large number of sockets	4038	the abysmal performance of winsockets, using a large number of sockets
3487	is not recommended (and not reasonable). If your program needs to use	4039	is not recommended (and not reasonable). If your program needs to use
3488	more than a hundred or so sockets, then likely it needs to use a totally	4040	more than a hundred or so sockets, then likely it needs to use a totally
3489	different implementation for windows, as libev offers the POSIX readiness	4041	different implementation for windows, as libev offers the POSIX readiness
3490	notification model, which cannot be implemented efficiently on windows	4042	notification model, which cannot be implemented efficiently on windows
3491	(Microsoft monopoly games).	4043	(due to Microsoft monopoly games).
3492		4044
3493	A typical way to use libev under windows is to embed it (see the embedding	4045	A typical way to use libev under windows is to embed it (see the embedding
3494	section for details) and use the following F<evwrap.h> header file instead	4046	section for details) and use the following F<evwrap.h> header file instead
3495	of F<ev.h>:	4047	of F<ev.h>:
3496		4048
…		…
3532		4084
3533	Early versions of winsocket's select only supported waiting for a maximum	4085	Early versions of winsocket's select only supported waiting for a maximum
3534	of C<64> handles (probably owning to the fact that all windows kernels	4086	of C<64> handles (probably owning to the fact that all windows kernels
3535	can only wait for C<64> things at the same time internally; Microsoft	4087	can only wait for C<64> things at the same time internally; Microsoft
3536	recommends spawning a chain of threads and wait for 63 handles and the	4088	recommends spawning a chain of threads and wait for 63 handles and the
3537	previous thread in each. Great).	4089	previous thread in each. Sounds great!).
3538		4090
3539	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4091	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3540	to some high number (e.g. C<2048>) before compiling the winsocket select	4092	to some high number (e.g. C<2048>) before compiling the winsocket select
3541	call (which might be in libev or elsewhere, for example, perl does its own	4093	call (which might be in libev or elsewhere, for example, perl and many
3542	select emulation on windows).	4094	other interpreters do their own select emulation on windows).
3543		4095
3544	Another limit is the number of file descriptors in the Microsoft runtime	4096	Another limit is the number of file descriptors in the Microsoft runtime
3545	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4097	libraries, which by default is C<64> (there must be a hidden I<64>
3546	or something like this inside Microsoft). You can increase this by calling	4098	fetish or something like this inside Microsoft). You can increase this
3547	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4099	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3548	arbitrary limit), but is broken in many versions of the Microsoft runtime	4100	(another arbitrary limit), but is broken in many versions of the Microsoft
3549	libraries.
3550
3551	This might get you to about C<512> or C<2048> sockets (depending on	4101	runtime libraries. This might get you to about C<512> or C<2048> sockets
3552	windows version and/or the phase of the moon). To get more, you need to	4102	(depending on windows version and/or the phase of the moon). To get more,
3553	wrap all I/O functions and provide your own fd management, but the cost of	4103	you need to wrap all I/O functions and provide your own fd management, but
3554	calling select (O(n²)) will likely make this unworkable.	4104	the cost of calling select (O(n²)) will likely make this unworkable.
3555		4105
3556	=back	4106	=back
3557		4107
3558	=head2 PORTABILITY REQUIREMENTS	4108	=head2 PORTABILITY REQUIREMENTS
3559		4109
…		…
3602	=item C<double> must hold a time value in seconds with enough accuracy	4152	=item C<double> must hold a time value in seconds with enough accuracy
3603		4153
3604	The type C<double> is used to represent timestamps. It is required to	4154	The type C<double> is used to represent timestamps. It is required to
3605	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4155	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
3606	enough for at least into the year 4000. This requirement is fulfilled by	4156	enough for at least into the year 4000. This requirement is fulfilled by
3607	implementations implementing IEEE 754 (basically all existing ones).	4157	implementations implementing IEEE 754, which is basically all existing
		4158	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4159	2200.
3608		4160
3609	=back	4161	=back
3610		4162
3611	If you know of other additional requirements drop me a note.	4163	If you know of other additional requirements drop me a note.
3612		4164
…		…
3680	involves iterating over all running async watchers or all signal numbers.	4232	involves iterating over all running async watchers or all signal numbers.
3681		4233
3682	=back	4234	=back
3683		4235
3684		4236
		4237	=head1 GLOSSARY
		4238
		4239	=over 4
		4240
		4241	=item active
		4242
		4243	A watcher is active as long as it has been started (has been attached to
		4244	an event loop) but not yet stopped (disassociated from the event loop).
		4245
		4246	=item application
		4247
		4248	In this document, an application is whatever is using libev.
		4249
		4250	=item callback
		4251
		4252	The address of a function that is called when some event has been
		4253	detected. Callbacks are being passed the event loop, the watcher that
		4254	received the event, and the actual event bitset.
		4255
		4256	=item callback invocation
		4257
		4258	The act of calling the callback associated with a watcher.
		4259
		4260	=item event
		4261
		4262	A change of state of some external event, such as data now being available
		4263	for reading on a file descriptor, time having passed or simply not having
		4264	any other events happening anymore.
		4265
		4266	In libev, events are represented as single bits (such as C<EV_READ> or
		4267	C<EV_TIMEOUT>).
		4268
		4269	=item event library
		4270
		4271	A software package implementing an event model and loop.
		4272
		4273	=item event loop
		4274
		4275	An entity that handles and processes external events and converts them
		4276	into callback invocations.
		4277
		4278	=item event model
		4279
		4280	The model used to describe how an event loop handles and processes
		4281	watchers and events.
		4282
		4283	=item pending
		4284
		4285	A watcher is pending as soon as the corresponding event has been detected,
		4286	and stops being pending as soon as the watcher will be invoked or its
		4287	pending status is explicitly cleared by the application.
		4288
		4289	A watcher can be pending, but not active. Stopping a watcher also clears
		4290	its pending status.
		4291
		4292	=item real time
		4293
		4294	The physical time that is observed. It is apparently strictly monotonic :)
		4295
		4296	=item wall-clock time
		4297
		4298	The time and date as shown on clocks. Unlike real time, it can actually
		4299	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4300	clock.
		4301
		4302	=item watcher
		4303
		4304	A data structure that describes interest in certain events. Watchers need
		4305	to be started (attached to an event loop) before they can receive events.
		4306
		4307	=item watcher invocation
		4308
		4309	The act of calling the callback associated with a watcher.
		4310
		4311	=back
		4312
3685	=head1 AUTHOR	4313	=head1 AUTHOR
3686		4314
3687	Marc Lehmann <libev@schmorp.de>.	4315	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3688		4316

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