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…		…
8		8
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
		14	#include <stdio.h> // for puts
13		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;
…		…
41		43
42	int	44	int
43	main (void)	45	main (void)
44	{	46	{
45	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
46	ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = ev_default_loop (0);
47		49
48	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
…		…
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
…		…
108	name C<loop> (which is always of type C<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
…		…
298	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
299	function.	313	function.
300		314
301	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
302	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,
303	as loops cannot bes hared easily between threads anyway).	317	as loops cannot be shared easily between threads anyway).
304		318
305	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
306	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
307	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
308	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
…		…
384	=item C<EVBACKEND_EPOLL> (value 4, Linux)	398	=item C<EVBACKEND_EPOLL> (value 4, Linux)
385		399
386	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,
387	but it scales phenomenally better. While poll and select usually scale	401	but it scales phenomenally better. While poll and select usually scale
388	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),
389	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).
390	of shortcomings, such as silently dropping events in some hard-to-detect	404
391	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
392	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.
393		421
394	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
395	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
396	(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
397	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
398	very well if you register events for both fds.	426	file descriptors might not work very well if you register events for both
399		427	file descriptors.
400	Please note that epoll sometimes generates spurious notifications, so you
401	need to use non-blocking I/O or other means to avoid blocking when no data
402	(or space) is available.
403		428
404	Best performance from this backend is achieved by not unregistering all	429	Best performance from this backend is achieved by not unregistering all
405	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,
406	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
407	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
408	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.
409		440
410	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
411	all kernel versions tested so far.	442	all kernel versions tested so far.
412		443
413	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
414	C<EVBACKEND_POLL>.	445	C<EVBACKEND_POLL>.
415		446
416	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	447	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
417		448
418	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
419	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
420	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
421	completely useless). For this reason it's not being "auto-detected" unless	452	it's completely useless). Unlike epoll, however, whose brokenness
422	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
423	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.
424		458
425	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
426	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
427	the target platform). See C<ev_embed> watchers for more info.	461	the target platform). See C<ev_embed> watchers for more info.
428		462
429	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
430	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
431	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
432	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
433	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
434	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
435		470
436	This backend usually performs well under most conditions.	471	This backend usually performs well under most conditions.
437		472
438	While nominally embeddable in other event loops, this doesn't work	473	While nominally embeddable in other event loops, this doesn't work
439	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
440	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
441	(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
442	(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
443	using it only for sockets.	478	also broken on OS X)) and, did I mention it, using it only for sockets.
444		479
445	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
446	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
447	C<NOTE_EOF>.	482	C<NOTE_EOF>.
448		483
…		…
468	might perform better.	503	might perform better.
469		504
470	On the positive side, with the exception of the spurious readiness	505	On the positive side, with the exception of the spurious readiness
471	notifications, this backend actually performed fully to specification	506	notifications, this backend actually performed fully to specification
472	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
473	OS-specific backends.	508	OS-specific backends (I vastly prefer correctness over speed hacks).
474		509
475	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
476	C<EVBACKEND_POLL>.	511	C<EVBACKEND_POLL>.
477		512
478	=item C<EVBACKEND_ALL>	513	=item C<EVBACKEND_ALL>
…		…
531	responsibility to either stop all watchers cleanly yourself I<before>	566	responsibility to either stop all watchers cleanly yourself I<before>
532	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
533	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
534	for example).	569	for example).
535		570
536	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
537	this function, and related watchers (such as signal and child watchers)	572	handlers), will not be freed by this function, and related watchers (such
538	would need to be stopped manually.	573	as signal and child watchers) would need to be stopped manually.
539		574
540	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
541	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
542	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
543	C<ev_loop_new> and C<ev_loop_destroy>).	578	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
586		621
587	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
588	"ticks" the number of loop iterations), as it roughly corresponds with	623	"ticks" the number of loop iterations), as it roughly corresponds with
589	C<ev_prepare> and C<ev_check> calls.	624	C<ev_prepare> and C<ev_check> calls.
590		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
591	=item unsigned int ev_backend (loop)	638	=item unsigned int ev_backend (loop)
592		639
593	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
594	use.	641	use.
595		642
…		…
609		656
610	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
611	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
612	the current time is a good idea.	659	the current time is a good idea.
613		660
614	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>).
615		688
616	=item ev_loop (loop, int flags)	689	=item ev_loop (loop, int flags)
617		690
618	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
619	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
…		…
635	the loop.	708	the loop.
636		709
637	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
638	necessary) and will handle those and any already outstanding ones. It	711	necessary) and will handle those and any already outstanding ones. It
639	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
640	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
641	user-registered callback will be called), and will return after one	714	user-registered callback will be called), and will return after one
642	iteration of the loop.	715	iteration of the loop.
643		716
644	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
645	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
…		…
703		776
704	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>
705	from returning, call ev_unref() after starting, and ev_ref() before	778	from returning, call ev_unref() after starting, and ev_ref() before
706	stopping it.	779	stopping it.
707		780
708	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
709	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
710	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
711	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
712	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
713	(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
714	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).
715		790
716	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>
717	running when nothing else is active.	792	running when nothing else is active.
718		793
719	ev_signal exitsig;	794	ev_signal exitsig;
…		…
748		823
749	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
750	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,
751	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
752	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
753	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.
754		831
755	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
756	to spend more time collecting timeouts, at the expense of increased	833	to spend more time collecting timeouts, at the expense of increased
757	latency/jitter/inexactness (the watcher callback will be called	834	latency/jitter/inexactness (the watcher callback will be called
758	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
…		…
760		837
761	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
762	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
763	interactive servers (of course not for games), likewise for timeouts. It	840	interactive servers (of course not for games), likewise for timeouts. It
764	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>,
765	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).
766		847
767	Setting the I<timeout collect interval> can improve the opportunity for	848	Setting the I<timeout collect interval> can improve the opportunity for
768	saving power, as the program will "bundle" timer callback invocations that	849	saving power, as the program will "bundle" timer callback invocations that
769	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
770	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
771	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
772	they fire on, say, one-second boundaries only.	853	they fire on, say, one-second boundaries only.
		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	While event loop modifications are allowed between invocations of
		896	C<release> and C<acquire> (that's their only purpose after all), no
		897	modifications done will affect the event loop, i.e. adding watchers will
		898	have no effect on the set of file descriptors being watched, or the time
		899	waited. USe an C<ev_async> watcher to wake up C<ev_loop> when you want it
		900	to take note of any changes you made.
		901
		902	In theory, threads executing C<ev_loop> will be async-cancel safe between
		903	invocations of C<release> and C<acquire>.
		904
		905	See also the locking example in the C<THREADS> section later in this
		906	document.
		907
		908	=item ev_set_userdata (loop, void *data)
		909
		910	=item ev_userdata (loop)
		911
		912	Set and retrieve a single C<void *> associated with a loop. When
		913	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		914	C<0.>
		915
		916	These two functions can be used to associate arbitrary data with a loop,
		917	and are intended solely for the C<invoke_pending_cb>, C<release> and
		918	C<acquire> callbacks described above, but of course can be (ab-)used for
		919	any other purpose as well.
773		920
774	=item ev_loop_verify (loop)	921	=item ev_loop_verify (loop)
775		922
776	This function only does something when C<EV_VERIFY> support has been	923	This function only does something when C<EV_VERIFY> support has been
777	compiled in, which is the default for non-minimal builds. It tries to go	924	compiled in, which is the default for non-minimal builds. It tries to go
…		…
903		1050
904	=item C<EV_ASYNC>	1051	=item C<EV_ASYNC>
905		1052
906	The given async watcher has been asynchronously notified (see C<ev_async>).	1053	The given async watcher has been asynchronously notified (see C<ev_async>).
907		1054
		1055	=item C<EV_CUSTOM>
		1056
		1057	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1058	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		1059
908	=item C<EV_ERROR>	1060	=item C<EV_ERROR>
909		1061
910	An unspecified error has occurred, the watcher has been stopped. This might	1062	An unspecified error has occurred, the watcher has been stopped. This might
911	happen because the watcher could not be properly started because libev	1063	happen because the watcher could not be properly started because libev
912	ran out of memory, a file descriptor was found to be closed or any other	1064	ran out of memory, a file descriptor was found to be closed or any other
…		…
1027	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1179	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1028	(default: C<-2>). Pending watchers with higher priority will be invoked	1180	(default: C<-2>). Pending watchers with higher priority will be invoked
1029	before watchers with lower priority, but priority will not keep watchers	1181	before watchers with lower priority, but priority will not keep watchers
1030	from being executed (except for C<ev_idle> watchers).	1182	from being executed (except for C<ev_idle> watchers).
1031		1183
1032	This means that priorities are I<only> used for ordering callback
1033	invocation after new events have been received. This is useful, for
1034	example, to reduce latency after idling, or more often, to bind two
1035	watchers on the same event and make sure one is called first.
1036
1037	If you need to suppress invocation when higher priority events are pending	1184	If you need to suppress invocation when higher priority events are pending
1038	you need to look at C<ev_idle> watchers, which provide this functionality.	1185	you need to look at C<ev_idle> watchers, which provide this functionality.
1039		1186
1040	You I<must not> change the priority of a watcher as long as it is active or	1187	You I<must not> change the priority of a watcher as long as it is active or
1041	pending.	1188	pending.
1042
1043	The default priority used by watchers when no priority has been set is
1044	always C<0>, which is supposed to not be too high and not be too low :).
1045		1189
1046	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1190	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1047	fine, as long as you do not mind that the priority value you query might	1191	fine, as long as you do not mind that the priority value you query might
1048	or might not have been clamped to the valid range.	1192	or might not have been clamped to the valid range.
		1193
		1194	The default priority used by watchers when no priority has been set is
		1195	always C<0>, which is supposed to not be too high and not be too low :).
		1196
		1197	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
		1198	priorities.
1049		1199
1050	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1200	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1051		1201
1052	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1202	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1053	C<loop> nor C<revents> need to be valid as long as the watcher callback	1203	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1118	#include <stddef.h>	1268	#include <stddef.h>
1119		1269
1120	static void	1270	static void
1121	t1_cb (EV_P_ ev_timer *w, int revents)	1271	t1_cb (EV_P_ ev_timer *w, int revents)
1122	{	1272	{
1123	struct my_biggy big = (struct my_biggy *	1273	struct my_biggy big = (struct my_biggy *)
1124	(((char *)w) - offsetof (struct my_biggy, t1));	1274	(((char *)w) - offsetof (struct my_biggy, t1));
1125	}	1275	}
1126		1276
1127	static void	1277	static void
1128	t2_cb (EV_P_ ev_timer *w, int revents)	1278	t2_cb (EV_P_ ev_timer *w, int revents)
1129	{	1279	{
1130	struct my_biggy big = (struct my_biggy *	1280	struct my_biggy big = (struct my_biggy *)
1131	(((char *)w) - offsetof (struct my_biggy, t2));	1281	(((char *)w) - offsetof (struct my_biggy, t2));
1132	}	1282	}
		1283
		1284	=head2 WATCHER PRIORITY MODELS
		1285
		1286	Many event loops support I<watcher priorities>, which are usually small
		1287	integers that influence the ordering of event callback invocation
		1288	between watchers in some way, all else being equal.
		1289
		1290	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1291	description for the more technical details such as the actual priority
		1292	range.
		1293
		1294	There are two common ways how these these priorities are being interpreted
		1295	by event loops:
		1296
		1297	In the more common lock-out model, higher priorities "lock out" invocation
		1298	of lower priority watchers, which means as long as higher priority
		1299	watchers receive events, lower priority watchers are not being invoked.
		1300
		1301	The less common only-for-ordering model uses priorities solely to order
		1302	callback invocation within a single event loop iteration: Higher priority
		1303	watchers are invoked before lower priority ones, but they all get invoked
		1304	before polling for new events.
		1305
		1306	Libev uses the second (only-for-ordering) model for all its watchers
		1307	except for idle watchers (which use the lock-out model).
		1308
		1309	The rationale behind this is that implementing the lock-out model for
		1310	watchers is not well supported by most kernel interfaces, and most event
		1311	libraries will just poll for the same events again and again as long as
		1312	their callbacks have not been executed, which is very inefficient in the
		1313	common case of one high-priority watcher locking out a mass of lower
		1314	priority ones.
		1315
		1316	Static (ordering) priorities are most useful when you have two or more
		1317	watchers handling the same resource: a typical usage example is having an
		1318	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1319	timeouts. Under load, data might be received while the program handles
		1320	other jobs, but since timers normally get invoked first, the timeout
		1321	handler will be executed before checking for data. In that case, giving
		1322	the timer a lower priority than the I/O watcher ensures that I/O will be
		1323	handled first even under adverse conditions (which is usually, but not
		1324	always, what you want).
		1325
		1326	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1327	will only be executed when no same or higher priority watchers have
		1328	received events, they can be used to implement the "lock-out" model when
		1329	required.
		1330
		1331	For example, to emulate how many other event libraries handle priorities,
		1332	you can associate an C<ev_idle> watcher to each such watcher, and in
		1333	the normal watcher callback, you just start the idle watcher. The real
		1334	processing is done in the idle watcher callback. This causes libev to
		1335	continously poll and process kernel event data for the watcher, but when
		1336	the lock-out case is known to be rare (which in turn is rare :), this is
		1337	workable.
		1338
		1339	Usually, however, the lock-out model implemented that way will perform
		1340	miserably under the type of load it was designed to handle. In that case,
		1341	it might be preferable to stop the real watcher before starting the
		1342	idle watcher, so the kernel will not have to process the event in case
		1343	the actual processing will be delayed for considerable time.
		1344
		1345	Here is an example of an I/O watcher that should run at a strictly lower
		1346	priority than the default, and which should only process data when no
		1347	other events are pending:
		1348
		1349	ev_idle idle; // actual processing watcher
		1350	ev_io io; // actual event watcher
		1351
		1352	static void
		1353	io_cb (EV_P_ ev_io *w, int revents)
		1354	{
		1355	// stop the I/O watcher, we received the event, but
		1356	// are not yet ready to handle it.
		1357	ev_io_stop (EV_A_ w);
		1358
		1359	// start the idle watcher to ahndle the actual event.
		1360	// it will not be executed as long as other watchers
		1361	// with the default priority are receiving events.
		1362	ev_idle_start (EV_A_ &idle);
		1363	}
		1364
		1365	static void
		1366	idle_cb (EV_P_ ev_idle *w, int revents)
		1367	{
		1368	// actual processing
		1369	read (STDIN_FILENO, ...);
		1370
		1371	// have to start the I/O watcher again, as
		1372	// we have handled the event
		1373	ev_io_start (EV_P_ &io);
		1374	}
		1375
		1376	// initialisation
		1377	ev_idle_init (&idle, idle_cb);
		1378	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1379	ev_io_start (EV_DEFAULT_ &io);
		1380
		1381	In the "real" world, it might also be beneficial to start a timer, so that
		1382	low-priority connections can not be locked out forever under load. This
		1383	enables your program to keep a lower latency for important connections
		1384	during short periods of high load, while not completely locking out less
		1385	important ones.
1133		1386
1134		1387
1135	=head1 WATCHER TYPES	1388	=head1 WATCHER TYPES
1136		1389
1137	This section describes each watcher in detail, but will not repeat	1390	This section describes each watcher in detail, but will not repeat
…		…
1163	descriptors to non-blocking mode is also usually a good idea (but not	1416	descriptors to non-blocking mode is also usually a good idea (but not
1164	required if you know what you are doing).	1417	required if you know what you are doing).
1165		1418
1166	If you cannot use non-blocking mode, then force the use of a	1419	If you cannot use non-blocking mode, then force the use of a
1167	known-to-be-good backend (at the time of this writing, this includes only	1420	known-to-be-good backend (at the time of this writing, this includes only
1168	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).	1421	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1422	descriptors for which non-blocking operation makes no sense (such as
		1423	files) - libev doesn't guarentee any specific behaviour in that case.
1169		1424
1170	Another thing you have to watch out for is that it is quite easy to	1425	Another thing you have to watch out for is that it is quite easy to
1171	receive "spurious" readiness notifications, that is your callback might	1426	receive "spurious" readiness notifications, that is your callback might
1172	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1427	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1173	because there is no data. Not only are some backends known to create a	1428	because there is no data. Not only are some backends known to create a
…		…
1294	year, it will still time out after (roughly) one hour. "Roughly" because	1549	year, it will still time out after (roughly) one hour. "Roughly" because
1295	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1550	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1296	monotonic clock option helps a lot here).	1551	monotonic clock option helps a lot here).
1297		1552
1298	The callback is guaranteed to be invoked only I<after> its timeout has	1553	The callback is guaranteed to be invoked only I<after> its timeout has
1299	passed, but if multiple timers become ready during the same loop iteration	1554	passed (not I<at>, so on systems with very low-resolution clocks this
1300	then order of execution is undefined.	1555	might introduce a small delay). If multiple timers become ready during the
		1556	same loop iteration then the ones with earlier time-out values are invoked
		1557	before ones of the same priority with later time-out values (but this is
		1558	no longer true when a callback calls C<ev_loop> recursively).
1301		1559
1302	=head3 Be smart about timeouts	1560	=head3 Be smart about timeouts
1303		1561
1304	Many real-world problems involve some kind of timeout, usually for error	1562	Many real-world problems involve some kind of timeout, usually for error
1305	recovery. A typical example is an HTTP request - if the other side hangs,	1563	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1349	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>	1607	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
1350	member and C<ev_timer_again>.	1608	member and C<ev_timer_again>.
1351		1609
1352	At start:	1610	At start:
1353		1611
1354	ev_timer_init (timer, callback);	1612	ev_init (timer, callback);
1355	timer->repeat = 60.;	1613	timer->repeat = 60.;
1356	ev_timer_again (loop, timer);	1614	ev_timer_again (loop, timer);
1357		1615
1358	Each time there is some activity:	1616	Each time there is some activity:
1359		1617
…		…
1398	else	1656	else
1399	{	1657	{
1400	// callback was invoked, but there was some activity, re-arm	1658	// callback was invoked, but there was some activity, re-arm
1401	// the watcher to fire in last_activity + 60, which is	1659	// the watcher to fire in last_activity + 60, which is
1402	// guaranteed to be in the future, so "again" is positive:	1660	// guaranteed to be in the future, so "again" is positive:
1403	w->again = timeout - now;	1661	w->repeat = timeout - now;
1404	ev_timer_again (EV_A_ w);	1662	ev_timer_again (EV_A_ w);
1405	}	1663	}
1406	}	1664	}
1407		1665
1408	To summarise the callback: first calculate the real timeout (defined	1666	To summarise the callback: first calculate the real timeout (defined
…		…
1421		1679
1422	To start the timer, simply initialise the watcher and set C<last_activity>	1680	To start the timer, simply initialise the watcher and set C<last_activity>
1423	to the current time (meaning we just have some activity :), then call the	1681	to the current time (meaning we just have some activity :), then call the
1424	callback, which will "do the right thing" and start the timer:	1682	callback, which will "do the right thing" and start the timer:
1425		1683
1426	ev_timer_init (timer, callback);	1684	ev_init (timer, callback);
1427	last_activity = ev_now (loop);	1685	last_activity = ev_now (loop);
1428	callback (loop, timer, EV_TIMEOUT);	1686	callback (loop, timer, EV_TIMEOUT);
1429		1687
1430	And when there is some activity, simply store the current time in	1688	And when there is some activity, simply store the current time in
1431	C<last_activity>, no libev calls at all:	1689	C<last_activity>, no libev calls at all:
…		…
1524	If the timer is started but non-repeating, stop it (as if it timed out).	1782	If the timer is started but non-repeating, stop it (as if it timed out).
1525		1783
1526	If the timer is repeating, either start it if necessary (with the	1784	If the timer is repeating, either start it if necessary (with the
1527	C<repeat> value), or reset the running timer to the C<repeat> value.	1785	C<repeat> value), or reset the running timer to the C<repeat> value.
1528		1786
1529	This sounds a bit complicated, see "Be smart about timeouts", above, for a	1787	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1530	usage example.	1788	usage example.
1531		1789
1532	=item ev_tstamp repeat [read-write]	1790	=item ev_tstamp repeat [read-write]
1533		1791
1534	The current C<repeat> value. Will be used each time the watcher times out	1792	The current C<repeat> value. Will be used each time the watcher times out
…		…
1573	=head2 C<ev_periodic> - to cron or not to cron?	1831	=head2 C<ev_periodic> - to cron or not to cron?
1574		1832
1575	Periodic watchers are also timers of a kind, but they are very versatile	1833	Periodic watchers are also timers of a kind, but they are very versatile
1576	(and unfortunately a bit complex).	1834	(and unfortunately a bit complex).
1577		1835
1578	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1836	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1579	but on wall clock time (absolute time). You can tell a periodic watcher	1837	relative time, the physical time that passes) but on wall clock time
1580	to trigger after some specific point in time. For example, if you tell a	1838	(absolute time, the thing you can read on your calender or clock). The
1581	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	1839	difference is that wall clock time can run faster or slower than real
1582	+ 10.>, that is, an absolute time not a delay) and then reset your system	1840	time, and time jumps are not uncommon (e.g. when you adjust your
1583	clock to January of the previous year, then it will take more than year	1841	wrist-watch).
1584	to trigger the event (unlike an C<ev_timer>, which would still trigger
1585	roughly 10 seconds later as it uses a relative timeout).
1586		1842
		1843	You can tell a periodic watcher to trigger after some specific point
		1844	in time: for example, if you tell a periodic watcher to trigger "in 10
		1845	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1846	not a delay) and then reset your system clock to January of the previous
		1847	year, then it will take a year or more to trigger the event (unlike an
		1848	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1849	it, as it uses a relative timeout).
		1850
1587	C<ev_periodic>s can also be used to implement vastly more complex timers,	1851	C<ev_periodic> watchers can also be used to implement vastly more complex
1588	such as triggering an event on each "midnight, local time", or other	1852	timers, such as triggering an event on each "midnight, local time", or
1589	complicated rules.	1853	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1854	those cannot react to time jumps.
1590		1855
1591	As with timers, the callback is guaranteed to be invoked only when the	1856	As with timers, the callback is guaranteed to be invoked only when the
1592	time (C<at>) has passed, but if multiple periodic timers become ready	1857	point in time where it is supposed to trigger has passed. If multiple
1593	during the same loop iteration, then order of execution is undefined.	1858	timers become ready during the same loop iteration then the ones with
		1859	earlier time-out values are invoked before ones with later time-out values
		1860	(but this is no longer true when a callback calls C<ev_loop> recursively).
1594		1861
1595	=head3 Watcher-Specific Functions and Data Members	1862	=head3 Watcher-Specific Functions and Data Members
1596		1863
1597	=over 4	1864	=over 4
1598		1865
1599	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1866	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1600		1867
1601	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1868	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1602		1869
1603	Lots of arguments, lets sort it out... There are basically three modes of	1870	Lots of arguments, let's sort it out... There are basically three modes of
1604	operation, and we will explain them from simplest to most complex:	1871	operation, and we will explain them from simplest to most complex:
1605		1872
1606	=over 4	1873	=over 4
1607		1874
1608	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1875	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1609		1876
1610	In this configuration the watcher triggers an event after the wall clock	1877	In this configuration the watcher triggers an event after the wall clock
1611	time C<at> has passed. It will not repeat and will not adjust when a time	1878	time C<offset> has passed. It will not repeat and will not adjust when a
1612	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1879	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1613	only run when the system clock reaches or surpasses this time.	1880	will be stopped and invoked when the system clock reaches or surpasses
		1881	this point in time.
1614		1882
1615	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1883	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1616		1884
1617	In this mode the watcher will always be scheduled to time out at the next	1885	In this mode the watcher will always be scheduled to time out at the next
1618	C<at + N * interval> time (for some integer N, which can also be negative)	1886	C<offset + N * interval> time (for some integer N, which can also be
1619	and then repeat, regardless of any time jumps.	1887	negative) and then repeat, regardless of any time jumps. The C<offset>
		1888	argument is merely an offset into the C<interval> periods.
1620		1889
1621	This can be used to create timers that do not drift with respect to the	1890	This can be used to create timers that do not drift with respect to the
1622	system clock, for example, here is a C<ev_periodic> that triggers each	1891	system clock, for example, here is an C<ev_periodic> that triggers each
1623	hour, on the hour:	1892	hour, on the hour (with respect to UTC):
1624		1893
1625	ev_periodic_set (&periodic, 0., 3600., 0);	1894	ev_periodic_set (&periodic, 0., 3600., 0);
1626		1895
1627	This doesn't mean there will always be 3600 seconds in between triggers,	1896	This doesn't mean there will always be 3600 seconds in between triggers,
1628	but only that the callback will be called when the system time shows a	1897	but only that the callback will be called when the system time shows a
1629	full hour (UTC), or more correctly, when the system time is evenly divisible	1898	full hour (UTC), or more correctly, when the system time is evenly divisible
1630	by 3600.	1899	by 3600.
1631		1900
1632	Another way to think about it (for the mathematically inclined) is that	1901	Another way to think about it (for the mathematically inclined) is that
1633	C<ev_periodic> will try to run the callback in this mode at the next possible	1902	C<ev_periodic> will try to run the callback in this mode at the next possible
1634	time where C<time = at (mod interval)>, regardless of any time jumps.	1903	time where C<time = offset (mod interval)>, regardless of any time jumps.
1635		1904
1636	For numerical stability it is preferable that the C<at> value is near	1905	For numerical stability it is preferable that the C<offset> value is near
1637	C<ev_now ()> (the current time), but there is no range requirement for	1906	C<ev_now ()> (the current time), but there is no range requirement for
1638	this value, and in fact is often specified as zero.	1907	this value, and in fact is often specified as zero.
1639		1908
1640	Note also that there is an upper limit to how often a timer can fire (CPU	1909	Note also that there is an upper limit to how often a timer can fire (CPU
1641	speed for example), so if C<interval> is very small then timing stability	1910	speed for example), so if C<interval> is very small then timing stability
1642	will of course deteriorate. Libev itself tries to be exact to be about one	1911	will of course deteriorate. Libev itself tries to be exact to be about one
1643	millisecond (if the OS supports it and the machine is fast enough).	1912	millisecond (if the OS supports it and the machine is fast enough).
1644		1913
1645	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1914	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1646		1915
1647	In this mode the values for C<interval> and C<at> are both being	1916	In this mode the values for C<interval> and C<offset> are both being
1648	ignored. Instead, each time the periodic watcher gets scheduled, the	1917	ignored. Instead, each time the periodic watcher gets scheduled, the
1649	reschedule callback will be called with the watcher as first, and the	1918	reschedule callback will be called with the watcher as first, and the
1650	current time as second argument.	1919	current time as second argument.
1651		1920
1652	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1921	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1653	ever, or make ANY event loop modifications whatsoever>.	1922	or make ANY other event loop modifications whatsoever, unless explicitly
		1923	allowed by documentation here>.
1654		1924
1655	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1925	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1656	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	1926	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1657	only event loop modification you are allowed to do).	1927	only event loop modification you are allowed to do).
1658		1928
…		…
1688	a different time than the last time it was called (e.g. in a crond like	1958	a different time than the last time it was called (e.g. in a crond like
1689	program when the crontabs have changed).	1959	program when the crontabs have changed).
1690		1960
1691	=item ev_tstamp ev_periodic_at (ev_periodic *)	1961	=item ev_tstamp ev_periodic_at (ev_periodic *)
1692		1962
1693	When active, returns the absolute time that the watcher is supposed to	1963	When active, returns the absolute time that the watcher is supposed
1694	trigger next.	1964	to trigger next. This is not the same as the C<offset> argument to
		1965	C<ev_periodic_set>, but indeed works even in interval and manual
		1966	rescheduling modes.
1695		1967
1696	=item ev_tstamp offset [read-write]	1968	=item ev_tstamp offset [read-write]
1697		1969
1698	When repeating, this contains the offset value, otherwise this is the	1970	When repeating, this contains the offset value, otherwise this is the
1699	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1971	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		1972	although libev might modify this value for better numerical stability).
1700		1973
1701	Can be modified any time, but changes only take effect when the periodic	1974	Can be modified any time, but changes only take effect when the periodic
1702	timer fires or C<ev_periodic_again> is being called.	1975	timer fires or C<ev_periodic_again> is being called.
1703		1976
1704	=item ev_tstamp interval [read-write]	1977	=item ev_tstamp interval [read-write]
…		…
1813	some child status changes (most typically when a child of yours dies or	2086	some child status changes (most typically when a child of yours dies or
1814	exits). It is permissible to install a child watcher I<after> the child	2087	exits). It is permissible to install a child watcher I<after> the child
1815	has been forked (which implies it might have already exited), as long	2088	has been forked (which implies it might have already exited), as long
1816	as the event loop isn't entered (or is continued from a watcher), i.e.,	2089	as the event loop isn't entered (or is continued from a watcher), i.e.,
1817	forking and then immediately registering a watcher for the child is fine,	2090	forking and then immediately registering a watcher for the child is fine,
1818	but forking and registering a watcher a few event loop iterations later is	2091	but forking and registering a watcher a few event loop iterations later or
1819	not.	2092	in the next callback invocation is not.
1820		2093
1821	Only the default event loop is capable of handling signals, and therefore	2094	Only the default event loop is capable of handling signals, and therefore
1822	you can only register child watchers in the default event loop.	2095	you can only register child watchers in the default event loop.
		2096
		2097	Due to some design glitches inside libev, child watchers will always be
		2098	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2099	libev)
1823		2100
1824	=head3 Process Interaction	2101	=head3 Process Interaction
1825		2102
1826	Libev grabs C<SIGCHLD> as soon as the default event loop is	2103	Libev grabs C<SIGCHLD> as soon as the default event loop is
1827	initialised. This is necessary to guarantee proper behaviour even if	2104	initialised. This is necessary to guarantee proper behaviour even if
…		…
1910		2187
1911		2188
1912	=head2 C<ev_stat> - did the file attributes just change?	2189	=head2 C<ev_stat> - did the file attributes just change?
1913		2190
1914	This watches a file system path for attribute changes. That is, it calls	2191	This watches a file system path for attribute changes. That is, it calls
1915	C<stat> regularly (or when the OS says it changed) and sees if it changed	2192	C<stat> on that path in regular intervals (or when the OS says it changed)
1916	compared to the last time, invoking the callback if it did.	2193	and sees if it changed compared to the last time, invoking the callback if
		2194	it did.
1917		2195
1918	The path does not need to exist: changing from "path exists" to "path does	2196	The path does not need to exist: changing from "path exists" to "path does
1919	not exist" is a status change like any other. The condition "path does	2197	not exist" is a status change like any other. The condition "path does not
1920	not exist" is signified by the C<st_nlink> field being zero (which is	2198	exist" (or more correctly "path cannot be stat'ed") is signified by the
1921	otherwise always forced to be at least one) and all the other fields of	2199	C<st_nlink> field being zero (which is otherwise always forced to be at
1922	the stat buffer having unspecified contents.	2200	least one) and all the other fields of the stat buffer having unspecified
		2201	contents.
1923		2202
1924	The path I<should> be absolute and I<must not> end in a slash. If it is	2203	The path I<must not> end in a slash or contain special components such as
		2204	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1925	relative and your working directory changes, the behaviour is undefined.	2205	your working directory changes, then the behaviour is undefined.
1926		2206
1927	Since there is no standard kernel interface to do this, the portable	2207	Since there is no portable change notification interface available, the
1928	implementation simply calls C<stat (2)> regularly on the path to see if	2208	portable implementation simply calls C<stat(2)> regularly on the path
1929	it changed somehow. You can specify a recommended polling interval for	2209	to see if it changed somehow. You can specify a recommended polling
1930	this case. If you specify a polling interval of C<0> (highly recommended!)	2210	interval for this case. If you specify a polling interval of C<0> (highly
1931	then a I<suitable, unspecified default> value will be used (which	2211	recommended!) then a I<suitable, unspecified default> value will be used
1932	you can expect to be around five seconds, although this might change	2212	(which you can expect to be around five seconds, although this might
1933	dynamically). Libev will also impose a minimum interval which is currently	2213	change dynamically). Libev will also impose a minimum interval which is
1934	around C<0.1>, but thats usually overkill.	2214	currently around C<0.1>, but that's usually overkill.
1935		2215
1936	This watcher type is not meant for massive numbers of stat watchers,	2216	This watcher type is not meant for massive numbers of stat watchers,
1937	as even with OS-supported change notifications, this can be	2217	as even with OS-supported change notifications, this can be
1938	resource-intensive.	2218	resource-intensive.
1939		2219
1940	At the time of this writing, the only OS-specific interface implemented	2220	At the time of this writing, the only OS-specific interface implemented
1941	is the Linux inotify interface (implementing kqueue support is left as	2221	is the Linux inotify interface (implementing kqueue support is left as an
1942	an exercise for the reader. Note, however, that the author sees no way	2222	exercise for the reader. Note, however, that the author sees no way of
1943	of implementing C<ev_stat> semantics with kqueue).	2223	implementing C<ev_stat> semantics with kqueue, except as a hint).
1944		2224
1945	=head3 ABI Issues (Largefile Support)	2225	=head3 ABI Issues (Largefile Support)
1946		2226
1947	Libev by default (unless the user overrides this) uses the default	2227	Libev by default (unless the user overrides this) uses the default
1948	compilation environment, which means that on systems with large file	2228	compilation environment, which means that on systems with large file
1949	support disabled by default, you get the 32 bit version of the stat	2229	support disabled by default, you get the 32 bit version of the stat
1950	structure. When using the library from programs that change the ABI to	2230	structure. When using the library from programs that change the ABI to
1951	use 64 bit file offsets the programs will fail. In that case you have to	2231	use 64 bit file offsets the programs will fail. In that case you have to
1952	compile libev with the same flags to get binary compatibility. This is	2232	compile libev with the same flags to get binary compatibility. This is
1953	obviously the case with any flags that change the ABI, but the problem is	2233	obviously the case with any flags that change the ABI, but the problem is
1954	most noticeably disabled with ev_stat and large file support.	2234	most noticeably displayed with ev_stat and large file support.
1955		2235
1956	The solution for this is to lobby your distribution maker to make large	2236	The solution for this is to lobby your distribution maker to make large
1957	file interfaces available by default (as e.g. FreeBSD does) and not	2237	file interfaces available by default (as e.g. FreeBSD does) and not
1958	optional. Libev cannot simply switch on large file support because it has	2238	optional. Libev cannot simply switch on large file support because it has
1959	to exchange stat structures with application programs compiled using the	2239	to exchange stat structures with application programs compiled using the
1960	default compilation environment.	2240	default compilation environment.
1961		2241
1962	=head3 Inotify and Kqueue	2242	=head3 Inotify and Kqueue
1963		2243
1964	When C<inotify (7)> support has been compiled into libev (generally	2244	When C<inotify (7)> support has been compiled into libev and present at
1965	only available with Linux 2.6.25 or above due to bugs in earlier	2245	runtime, it will be used to speed up change detection where possible. The
1966	implementations) and present at runtime, it will be used to speed up	2246	inotify descriptor will be created lazily when the first C<ev_stat>
1967	change detection where possible. The inotify descriptor will be created	2247	watcher is being started.
1968	lazily when the first C<ev_stat> watcher is being started.
1969		2248
1970	Inotify presence does not change the semantics of C<ev_stat> watchers	2249	Inotify presence does not change the semantics of C<ev_stat> watchers
1971	except that changes might be detected earlier, and in some cases, to avoid	2250	except that changes might be detected earlier, and in some cases, to avoid
1972	making regular C<stat> calls. Even in the presence of inotify support	2251	making regular C<stat> calls. Even in the presence of inotify support
1973	there are many cases where libev has to resort to regular C<stat> polling,	2252	there are many cases where libev has to resort to regular C<stat> polling,
1974	but as long as the path exists, libev usually gets away without polling.	2253	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2254	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2255	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2256	xfs are fully working) libev usually gets away without polling.
1975		2257
1976	There is no support for kqueue, as apparently it cannot be used to	2258	There is no support for kqueue, as apparently it cannot be used to
1977	implement this functionality, due to the requirement of having a file	2259	implement this functionality, due to the requirement of having a file
1978	descriptor open on the object at all times, and detecting renames, unlinks	2260	descriptor open on the object at all times, and detecting renames, unlinks
1979	etc. is difficult.	2261	etc. is difficult.
1980		2262
		2263	=head3 C<stat ()> is a synchronous operation
		2264
		2265	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2266	the process. The exception are C<ev_stat> watchers - those call C<stat
		2267	()>, which is a synchronous operation.
		2268
		2269	For local paths, this usually doesn't matter: unless the system is very
		2270	busy or the intervals between stat's are large, a stat call will be fast,
		2271	as the path data is usually in memory already (except when starting the
		2272	watcher).
		2273
		2274	For networked file systems, calling C<stat ()> can block an indefinite
		2275	time due to network issues, and even under good conditions, a stat call
		2276	often takes multiple milliseconds.
		2277
		2278	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2279	paths, although this is fully supported by libev.
		2280
1981	=head3 The special problem of stat time resolution	2281	=head3 The special problem of stat time resolution
1982		2282
1983	The C<stat ()> system call only supports full-second resolution portably, and	2283	The C<stat ()> system call only supports full-second resolution portably,
1984	even on systems where the resolution is higher, most file systems still	2284	and even on systems where the resolution is higher, most file systems
1985	only support whole seconds.	2285	still only support whole seconds.
1986		2286
1987	That means that, if the time is the only thing that changes, you can	2287	That means that, if the time is the only thing that changes, you can
1988	easily miss updates: on the first update, C<ev_stat> detects a change and	2288	easily miss updates: on the first update, C<ev_stat> detects a change and
1989	calls your callback, which does something. When there is another update	2289	calls your callback, which does something. When there is another update
1990	within the same second, C<ev_stat> will be unable to detect unless the	2290	within the same second, C<ev_stat> will be unable to detect unless the
…		…
2133		2433
2134	=head3 Watcher-Specific Functions and Data Members	2434	=head3 Watcher-Specific Functions and Data Members
2135		2435
2136	=over 4	2436	=over 4
2137		2437
2138	=item ev_idle_init (ev_signal *, callback)	2438	=item ev_idle_init (ev_idle *, callback)
2139		2439
2140	Initialises and configures the idle watcher - it has no parameters of any	2440	Initialises and configures the idle watcher - it has no parameters of any
2141	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2441	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
2142	believe me.	2442	believe me.
2143		2443
…		…
2156	// no longer anything immediate to do.	2456	// no longer anything immediate to do.
2157	}	2457	}
2158		2458
2159	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2459	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2160	ev_idle_init (idle_watcher, idle_cb);	2460	ev_idle_init (idle_watcher, idle_cb);
2161	ev_idle_start (loop, idle_cb);	2461	ev_idle_start (loop, idle_watcher);
2162		2462
2163		2463
2164	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2464	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2165		2465
2166	Prepare and check watchers are usually (but not always) used in pairs:	2466	Prepare and check watchers are usually (but not always) used in pairs:
…		…
2259	struct pollfd fds [nfd];	2559	struct pollfd fds [nfd];
2260	// actual code will need to loop here and realloc etc.	2560	// actual code will need to loop here and realloc etc.
2261	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2561	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2262		2562
2263	/* the callback is illegal, but won't be called as we stop during check */	2563	/* the callback is illegal, but won't be called as we stop during check */
2264	ev_timer_init (&tw, 0, timeout * 1e-3);	2564	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2265	ev_timer_start (loop, &tw);	2565	ev_timer_start (loop, &tw);
2266		2566
2267	// create one ev_io per pollfd	2567	// create one ev_io per pollfd
2268	for (int i = 0; i < nfd; ++i)	2568	for (int i = 0; i < nfd; ++i)
2269	{	2569	{
…		…
2382	some fds have to be watched and handled very quickly (with low latency),	2682	some fds have to be watched and handled very quickly (with low latency),
2383	and even priorities and idle watchers might have too much overhead. In	2683	and even priorities and idle watchers might have too much overhead. In
2384	this case you would put all the high priority stuff in one loop and all	2684	this case you would put all the high priority stuff in one loop and all
2385	the rest in a second one, and embed the second one in the first.	2685	the rest in a second one, and embed the second one in the first.
2386		2686
2387	As long as the watcher is active, the callback will be invoked every time	2687	As long as the watcher is active, the callback will be invoked every
2388	there might be events pending in the embedded loop. The callback must then	2688	time there might be events pending in the embedded loop. The callback
2389	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2689	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2390	their callbacks (you could also start an idle watcher to give the embedded	2690	sweep and invoke their callbacks (the callback doesn't need to invoke the
2391	loop strictly lower priority for example). You can also set the callback	2691	C<ev_embed_sweep> function directly, it could also start an idle watcher
2392	to C<0>, in which case the embed watcher will automatically execute the	2692	to give the embedded loop strictly lower priority for example).
2393	embedded loop sweep.
2394		2693
2395	As long as the watcher is started it will automatically handle events. The	2694	You can also set the callback to C<0>, in which case the embed watcher
2396	callback will be invoked whenever some events have been handled. You can	2695	will automatically execute the embedded loop sweep whenever necessary.
2397	set the callback to C<0> to avoid having to specify one if you are not
2398	interested in that.
2399		2696
2400	Also, there have not currently been made special provisions for forking:	2697	Fork detection will be handled transparently while the C<ev_embed> watcher
2401	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2698	is active, i.e., the embedded loop will automatically be forked when the
2402	but you will also have to stop and restart any C<ev_embed> watchers	2699	embedding loop forks. In other cases, the user is responsible for calling
2403	yourself - but you can use a fork watcher to handle this automatically,	2700	C<ev_loop_fork> on the embedded loop.
2404	and future versions of libev might do just that.
2405		2701
2406	Unfortunately, not all backends are embeddable: only the ones returned by	2702	Unfortunately, not all backends are embeddable: only the ones returned by
2407	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2703	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2408	portable one.	2704	portable one.
2409		2705
…		…
2503	event loop blocks next and before C<ev_check> watchers are being called,	2799	event loop blocks next and before C<ev_check> watchers are being called,
2504	and only in the child after the fork. If whoever good citizen calling	2800	and only in the child after the fork. If whoever good citizen calling
2505	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2801	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2506	handlers will be invoked, too, of course.	2802	handlers will be invoked, too, of course.
2507		2803
		2804	=head3 The special problem of life after fork - how is it possible?
		2805
		2806	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2807	up/change the process environment, followed by a call to C<exec()>. This
		2808	sequence should be handled by libev without any problems.
		2809
		2810	This changes when the application actually wants to do event handling
		2811	in the child, or both parent in child, in effect "continuing" after the
		2812	fork.
		2813
		2814	The default mode of operation (for libev, with application help to detect
		2815	forks) is to duplicate all the state in the child, as would be expected
		2816	when I<either> the parent I<or> the child process continues.
		2817
		2818	When both processes want to continue using libev, then this is usually the
		2819	wrong result. In that case, usually one process (typically the parent) is
		2820	supposed to continue with all watchers in place as before, while the other
		2821	process typically wants to start fresh, i.e. without any active watchers.
		2822
		2823	The cleanest and most efficient way to achieve that with libev is to
		2824	simply create a new event loop, which of course will be "empty", and
		2825	use that for new watchers. This has the advantage of not touching more
		2826	memory than necessary, and thus avoiding the copy-on-write, and the
		2827	disadvantage of having to use multiple event loops (which do not support
		2828	signal watchers).
		2829
		2830	When this is not possible, or you want to use the default loop for
		2831	other reasons, then in the process that wants to start "fresh", call
		2832	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2833	the default loop will "orphan" (not stop) all registered watchers, so you
		2834	have to be careful not to execute code that modifies those watchers. Note
		2835	also that in that case, you have to re-register any signal watchers.
		2836
2508	=head3 Watcher-Specific Functions and Data Members	2837	=head3 Watcher-Specific Functions and Data Members
2509		2838
2510	=over 4	2839	=over 4
2511		2840
2512	=item ev_fork_init (ev_signal *, callback)	2841	=item ev_fork_init (ev_signal *, callback)
…		…
2629	=over 4	2958	=over 4
2630		2959
2631	=item ev_async_init (ev_async *, callback)	2960	=item ev_async_init (ev_async *, callback)
2632		2961
2633	Initialises and configures the async watcher - it has no parameters of any	2962	Initialises and configures the async watcher - it has no parameters of any
2634	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2963	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2635	trust me.	2964	trust me.
2636		2965
2637	=item ev_async_send (loop, ev_async *)	2966	=item ev_async_send (loop, ev_async *)
2638		2967
2639	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2968	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2640	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2969	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2641	C<ev_feed_event>, this call is safe to do from other threads, signal or	2970	C<ev_feed_event>, this call is safe to do from other threads, signal or
2642	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	2971	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2643	section below on what exactly this means).	2972	section below on what exactly this means).
2644		2973
		2974	Note that, as with other watchers in libev, multiple events might get
		2975	compressed into a single callback invocation (another way to look at this
		2976	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		2977	reset when the event loop detects that).
		2978
2645	This call incurs the overhead of a system call only once per loop iteration,	2979	This call incurs the overhead of a system call only once per event loop
2646	so while the overhead might be noticeable, it doesn't apply to repeated	2980	iteration, so while the overhead might be noticeable, it doesn't apply to
2647	calls to C<ev_async_send>.	2981	repeated calls to C<ev_async_send> for the same event loop.
2648		2982
2649	=item bool = ev_async_pending (ev_async *)	2983	=item bool = ev_async_pending (ev_async *)
2650		2984
2651	Returns a non-zero value when C<ev_async_send> has been called on the	2985	Returns a non-zero value when C<ev_async_send> has been called on the
2652	watcher but the event has not yet been processed (or even noted) by the	2986	watcher but the event has not yet been processed (or even noted) by the
…		…
2655	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	2989	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2656	the loop iterates next and checks for the watcher to have become active,	2990	the loop iterates next and checks for the watcher to have become active,
2657	it will reset the flag again. C<ev_async_pending> can be used to very	2991	it will reset the flag again. C<ev_async_pending> can be used to very
2658	quickly check whether invoking the loop might be a good idea.	2992	quickly check whether invoking the loop might be a good idea.
2659		2993
2660	Not that this does I<not> check whether the watcher itself is pending, only	2994	Not that this does I<not> check whether the watcher itself is pending,
2661	whether it has been requested to make this watcher pending.	2995	only whether it has been requested to make this watcher pending: there
		2996	is a time window between the event loop checking and resetting the async
		2997	notification, and the callback being invoked.
2662		2998
2663	=back	2999	=back
2664		3000
2665		3001
2666	=head1 OTHER FUNCTIONS	3002	=head1 OTHER FUNCTIONS
…		…
2845		3181
2846	myclass obj;	3182	myclass obj;
2847	ev::io iow;	3183	ev::io iow;
2848	iow.set <myclass, &myclass::io_cb> (&obj);	3184	iow.set <myclass, &myclass::io_cb> (&obj);
2849		3185
		3186	=item w->set (object *)
		3187
		3188	This is an B<experimental> feature that might go away in a future version.
		3189
		3190	This is a variation of a method callback - leaving out the method to call
		3191	will default the method to C<operator ()>, which makes it possible to use
		3192	functor objects without having to manually specify the C<operator ()> all
		3193	the time. Incidentally, you can then also leave out the template argument
		3194	list.
		3195
		3196	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3197	int revents)>.
		3198
		3199	See the method-C<set> above for more details.
		3200
		3201	Example: use a functor object as callback.
		3202
		3203	struct myfunctor
		3204	{
		3205	void operator() (ev::io &w, int revents)
		3206	{
		3207	...
		3208	}
		3209	}
		3210
		3211	myfunctor f;
		3212
		3213	ev::io w;
		3214	w.set (&f);
		3215
2850	=item w->set<function> (void *data = 0)	3216	=item w->set<function> (void *data = 0)
2851		3217
2852	Also sets a callback, but uses a static method or plain function as	3218	Also sets a callback, but uses a static method or plain function as
2853	callback. The optional C<data> argument will be stored in the watcher's	3219	callback. The optional C<data> argument will be stored in the watcher's
2854	C<data> member and is free for you to use.	3220	C<data> member and is free for you to use.
…		…
2940	L<http://software.schmorp.de/pkg/EV>.	3306	L<http://software.schmorp.de/pkg/EV>.
2941		3307
2942	=item Python	3308	=item Python
2943		3309
2944	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3310	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2945	seems to be quite complete and well-documented. Note, however, that the	3311	seems to be quite complete and well-documented.
2946	patch they require for libev is outright dangerous as it breaks the ABI
2947	for everybody else, and therefore, should never be applied in an installed
2948	libev (if python requires an incompatible ABI then it needs to embed
2949	libev).
2950		3312
2951	=item Ruby	3313	=item Ruby
2952		3314
2953	Tony Arcieri has written a ruby extension that offers access to a subset	3315	Tony Arcieri has written a ruby extension that offers access to a subset
2954	of the libev API and adds file handle abstractions, asynchronous DNS and	3316	of the libev API and adds file handle abstractions, asynchronous DNS and
2955	more on top of it. It can be found via gem servers. Its homepage is at	3317	more on top of it. It can be found via gem servers. Its homepage is at
2956	L<http://rev.rubyforge.org/>.	3318	L<http://rev.rubyforge.org/>.
		3319
		3320	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3321	makes rev work even on mingw.
		3322
		3323	=item Haskell
		3324
		3325	A haskell binding to libev is available at
		3326	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
2957		3327
2958	=item D	3328	=item D
2959		3329
2960	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3330	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2961	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3331	be found at L<http://proj.llucax.com.ar/wiki/evd>.
…		…
3072		3442
3073	#define EV_STANDALONE 1	3443	#define EV_STANDALONE 1
3074	#include "ev.h"	3444	#include "ev.h"
3075		3445
3076	Both header files and implementation files can be compiled with a C++	3446	Both header files and implementation files can be compiled with a C++
3077	compiler (at least, thats a stated goal, and breakage will be treated	3447	compiler (at least, that's a stated goal, and breakage will be treated
3078	as a bug).	3448	as a bug).
3079		3449
3080	You need the following files in your source tree, or in a directory	3450	You need the following files in your source tree, or in a directory
3081	in your include path (e.g. in libev/ when using -Ilibev):	3451	in your include path (e.g. in libev/ when using -Ilibev):
3082		3452
…		…
3138	keeps libev from including F<config.h>, and it also defines dummy	3508	keeps libev from including F<config.h>, and it also defines dummy
3139	implementations for some libevent functions (such as logging, which is not	3509	implementations for some libevent functions (such as logging, which is not
3140	supported). It will also not define any of the structs usually found in	3510	supported). It will also not define any of the structs usually found in
3141	F<event.h> that are not directly supported by the libev core alone.	3511	F<event.h> that are not directly supported by the libev core alone.
3142		3512
		3513	In stanbdalone mode, libev will still try to automatically deduce the
		3514	configuration, but has to be more conservative.
		3515
3143	=item EV_USE_MONOTONIC	3516	=item EV_USE_MONOTONIC
3144		3517
3145	If defined to be C<1>, libev will try to detect the availability of the	3518	If defined to be C<1>, libev will try to detect the availability of the
3146	monotonic clock option at both compile time and runtime. Otherwise no use	3519	monotonic clock option at both compile time and runtime. Otherwise no
3147	of the monotonic clock option will be attempted. If you enable this, you	3520	use of the monotonic clock option will be attempted. If you enable this,
3148	usually have to link against librt or something similar. Enabling it when	3521	you usually have to link against librt or something similar. Enabling it
3149	the functionality isn't available is safe, though, although you have	3522	when the functionality isn't available is safe, though, although you have
3150	to make sure you link against any libraries where the C<clock_gettime>	3523	to make sure you link against any libraries where the C<clock_gettime>
3151	function is hiding in (often F<-lrt>).	3524	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
3152		3525
3153	=item EV_USE_REALTIME	3526	=item EV_USE_REALTIME
3154		3527
3155	If defined to be C<1>, libev will try to detect the availability of the	3528	If defined to be C<1>, libev will try to detect the availability of the
3156	real-time clock option at compile time (and assume its availability at	3529	real-time clock option at compile time (and assume its availability
3157	runtime if successful). Otherwise no use of the real-time clock option will	3530	at runtime if successful). Otherwise no use of the real-time clock
3158	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3531	option will be attempted. This effectively replaces C<gettimeofday>
3159	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3532	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
3160	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3533	correctness. See the note about libraries in the description of
		3534	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3535	C<EV_USE_CLOCK_SYSCALL>.
		3536
		3537	=item EV_USE_CLOCK_SYSCALL
		3538
		3539	If defined to be C<1>, libev will try to use a direct syscall instead
		3540	of calling the system-provided C<clock_gettime> function. This option
		3541	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3542	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3543	programs needlessly. Using a direct syscall is slightly slower (in
		3544	theory), because no optimised vdso implementation can be used, but avoids
		3545	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3546	higher, as it simplifies linking (no need for C<-lrt>).
3161		3547
3162	=item EV_USE_NANOSLEEP	3548	=item EV_USE_NANOSLEEP
3163		3549
3164	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3550	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
3165	and will use it for delays. Otherwise it will use C<select ()>.	3551	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3181		3567
3182	=item EV_SELECT_USE_FD_SET	3568	=item EV_SELECT_USE_FD_SET
3183		3569
3184	If defined to C<1>, then the select backend will use the system C<fd_set>	3570	If defined to C<1>, then the select backend will use the system C<fd_set>
3185	structure. This is useful if libev doesn't compile due to a missing	3571	structure. This is useful if libev doesn't compile due to a missing
3186	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3572	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3187	exotic systems. This usually limits the range of file descriptors to some	3573	on exotic systems. This usually limits the range of file descriptors to
3188	low limit such as 1024 or might have other limitations (winsocket only	3574	some low limit such as 1024 or might have other limitations (winsocket
3189	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3575	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3190	influence the size of the C<fd_set> used.	3576	configures the maximum size of the C<fd_set>.
3191		3577
3192	=item EV_SELECT_IS_WINSOCKET	3578	=item EV_SELECT_IS_WINSOCKET
3193		3579
3194	When defined to C<1>, the select backend will assume that	3580	When defined to C<1>, the select backend will assume that
3195	select/socket/connect etc. don't understand file descriptors but	3581	select/socket/connect etc. don't understand file descriptors but
…		…
3345	defined to be C<0>, then they are not.	3731	defined to be C<0>, then they are not.
3346		3732
3347	=item EV_MINIMAL	3733	=item EV_MINIMAL
3348		3734
3349	If you need to shave off some kilobytes of code at the expense of some	3735	If you need to shave off some kilobytes of code at the expense of some
3350	speed, define this symbol to C<1>. Currently this is used to override some	3736	speed (but with the full API), define this symbol to C<1>. Currently this
3351	inlining decisions, saves roughly 30% code size on amd64. It also selects a	3737	is used to override some inlining decisions, saves roughly 30% code size
3352	much smaller 2-heap for timer management over the default 4-heap.	3738	on amd64. It also selects a much smaller 2-heap for timer management over
		3739	the default 4-heap.
		3740
		3741	You can save even more by disabling watcher types you do not need
		3742	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>
		3743	(C<-DNDEBUG>) will usually reduce code size a lot.
		3744
		3745	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to
		3746	provide a bare-bones event library. See C<ev.h> for details on what parts
		3747	of the API are still available, and do not complain if this subset changes
		3748	over time.
3353		3749
3354	=item EV_PID_HASHSIZE	3750	=item EV_PID_HASHSIZE
3355		3751
3356	C<ev_child> watchers use a small hash table to distribute workload by	3752	C<ev_child> watchers use a small hash table to distribute workload by
3357	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3753	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
3543	default loop and triggering an C<ev_async> watcher from the default loop	3939	default loop and triggering an C<ev_async> watcher from the default loop
3544	watcher callback into the event loop interested in the signal.	3940	watcher callback into the event loop interested in the signal.
3545		3941
3546	=back	3942	=back
3547		3943
		3944	=head4 THREAD LOCKING EXAMPLE
		3945
		3946	Here is a fictitious example of how to run an event loop in a different
		3947	thread than where callbacks are being invoked and watchers are
		3948	created/added/removed.
		3949
		3950	For a real-world example, see the C<EV::Loop::Async> perl module,
		3951	which uses exactly this technique (which is suited for many high-level
		3952	languages).
		3953
		3954	The example uses a pthread mutex to protect the loop data, a condition
		3955	variable to wait for callback invocations, an async watcher to notify the
		3956	event loop thread and an unspecified mechanism to wake up the main thread.
		3957
		3958	First, you need to associate some data with the event loop:
		3959
		3960	typedef struct {
		3961	mutex_t lock; /* global loop lock */
		3962	ev_async async_w;
		3963	thread_t tid;
		3964	cond_t invoke_cv;
		3965	} userdata;
		3966
		3967	void prepare_loop (EV_P)
		3968	{
		3969	// for simplicity, we use a static userdata struct.
		3970	static userdata u;
		3971
		3972	ev_async_init (&u->async_w, async_cb);
		3973	ev_async_start (EV_A_ &u->async_w);
		3974
		3975	pthread_mutex_init (&u->lock, 0);
		3976	pthread_cond_init (&u->invoke_cv, 0);
		3977
		3978	// now associate this with the loop
		3979	ev_set_userdata (EV_A_ u);
		3980	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3981	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3982
		3983	// then create the thread running ev_loop
		3984	pthread_create (&u->tid, 0, l_run, EV_A);
		3985	}
		3986
		3987	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3988	solely to wake up the event loop so it takes notice of any new watchers
		3989	that might have been added:
		3990
		3991	static void
		3992	async_cb (EV_P_ ev_async *w, int revents)
		3993	{
		3994	// just used for the side effects
		3995	}
		3996
		3997	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3998	protecting the loop data, respectively.
		3999
		4000	static void
		4001	l_release (EV_P)
		4002	{
		4003	userdata *u = ev_userdata (EV_A);
		4004	pthread_mutex_unlock (&u->lock);
		4005	}
		4006
		4007	static void
		4008	l_acquire (EV_P)
		4009	{
		4010	userdata *u = ev_userdata (EV_A);
		4011	pthread_mutex_lock (&u->lock);
		4012	}
		4013
		4014	The event loop thread first acquires the mutex, and then jumps straight
		4015	into C<ev_loop>:
		4016
		4017	void *
		4018	l_run (void *thr_arg)
		4019	{
		4020	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4021
		4022	l_acquire (EV_A);
		4023	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4024	ev_loop (EV_A_ 0);
		4025	l_release (EV_A);
		4026
		4027	return 0;
		4028	}
		4029
		4030	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4031	signal the main thread via some unspecified mechanism (signals? pipe
		4032	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4033	have been called:
		4034
		4035	static void
		4036	l_invoke (EV_P)
		4037	{
		4038	userdata *u = ev_userdata (EV_A);
		4039
		4040	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4041
		4042	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4043	}
		4044
		4045	Now, whenever the main thread gets told to invoke pending watchers, it
		4046	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4047	thread to continue:
		4048
		4049	static void
		4050	real_invoke_pending (EV_P)
		4051	{
		4052	userdata *u = ev_userdata (EV_A);
		4053
		4054	pthread_mutex_lock (&u->lock);
		4055	ev_invoke_pending (EV_A);
		4056	pthread_cond_signal (&u->invoke_cv);
		4057	pthread_mutex_unlock (&u->lock);
		4058	}
		4059
		4060	Whenever you want to start/stop a watcher or do other modifications to an
		4061	event loop, you will now have to lock:
		4062
		4063	ev_timer timeout_watcher;
		4064	userdata *u = ev_userdata (EV_A);
		4065
		4066	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4067
		4068	pthread_mutex_lock (&u->lock);
		4069	ev_timer_start (EV_A_ &timeout_watcher);
		4070	ev_async_send (EV_A_ &u->async_w);
		4071	pthread_mutex_unlock (&u->lock);
		4072
		4073	Note that sending the C<ev_async> watcher is required because otherwise
		4074	an event loop currently blocking in the kernel will have no knowledge
		4075	about the newly added timer. By waking up the loop it will pick up any new
		4076	watchers in the next event loop iteration.
		4077
3548	=head3 COROUTINES	4078	=head3 COROUTINES
3549		4079
3550	Libev is very accommodating to coroutines ("cooperative threads"):	4080	Libev is very accommodating to coroutines ("cooperative threads"):
3551	libev fully supports nesting calls to its functions from different	4081	libev fully supports nesting calls to its functions from different
3552	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4082	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3553	different coroutines, and switch freely between both coroutines running the	4083	different coroutines, and switch freely between both coroutines running
3554	loop, as long as you don't confuse yourself). The only exception is that	4084	the loop, as long as you don't confuse yourself). The only exception is
3555	you must not do this from C<ev_periodic> reschedule callbacks.	4085	that you must not do this from C<ev_periodic> reschedule callbacks.
3556		4086
3557	Care has been taken to ensure that libev does not keep local state inside	4087	Care has been taken to ensure that libev does not keep local state inside
3558	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4088	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3559	they do not clal any callbacks.	4089	they do not call any callbacks.
3560		4090
3561	=head2 COMPILER WARNINGS	4091	=head2 COMPILER WARNINGS
3562		4092
3563	Depending on your compiler and compiler settings, you might get no or a	4093	Depending on your compiler and compiler settings, you might get no or a
3564	lot of warnings when compiling libev code. Some people are apparently	4094	lot of warnings when compiling libev code. Some people are apparently
…		…
3598	==2274== definitely lost: 0 bytes in 0 blocks.	4128	==2274== definitely lost: 0 bytes in 0 blocks.
3599	==2274== possibly lost: 0 bytes in 0 blocks.	4129	==2274== possibly lost: 0 bytes in 0 blocks.
3600	==2274== still reachable: 256 bytes in 1 blocks.	4130	==2274== still reachable: 256 bytes in 1 blocks.
3601		4131
3602	Then there is no memory leak, just as memory accounted to global variables	4132	Then there is no memory leak, just as memory accounted to global variables
3603	is not a memleak - the memory is still being refernced, and didn't leak.	4133	is not a memleak - the memory is still being referenced, and didn't leak.
3604		4134
3605	Similarly, under some circumstances, valgrind might report kernel bugs	4135	Similarly, under some circumstances, valgrind might report kernel bugs
3606	as if it were a bug in libev (e.g. in realloc or in the poll backend,	4136	as if it were a bug in libev (e.g. in realloc or in the poll backend,
3607	although an acceptable workaround has been found here), or it might be	4137	although an acceptable workaround has been found here), or it might be
3608	confused.	4138	confused.
…		…
3637	way (note also that glib is the slowest event library known to man).	4167	way (note also that glib is the slowest event library known to man).
3638		4168
3639	There is no supported compilation method available on windows except	4169	There is no supported compilation method available on windows except
3640	embedding it into other applications.	4170	embedding it into other applications.
3641		4171
		4172	Sensible signal handling is officially unsupported by Microsoft - libev
		4173	tries its best, but under most conditions, signals will simply not work.
		4174
3642	Not a libev limitation but worth mentioning: windows apparently doesn't	4175	Not a libev limitation but worth mentioning: windows apparently doesn't
3643	accept large writes: instead of resulting in a partial write, windows will	4176	accept large writes: instead of resulting in a partial write, windows will
3644	either accept everything or return C<ENOBUFS> if the buffer is too large,	4177	either accept everything or return C<ENOBUFS> if the buffer is too large,
3645	so make sure you only write small amounts into your sockets (less than a	4178	so make sure you only write small amounts into your sockets (less than a
3646	megabyte seems safe, but this apparently depends on the amount of memory	4179	megabyte seems safe, but this apparently depends on the amount of memory
…		…
3650	the abysmal performance of winsockets, using a large number of sockets	4183	the abysmal performance of winsockets, using a large number of sockets
3651	is not recommended (and not reasonable). If your program needs to use	4184	is not recommended (and not reasonable). If your program needs to use
3652	more than a hundred or so sockets, then likely it needs to use a totally	4185	more than a hundred or so sockets, then likely it needs to use a totally
3653	different implementation for windows, as libev offers the POSIX readiness	4186	different implementation for windows, as libev offers the POSIX readiness
3654	notification model, which cannot be implemented efficiently on windows	4187	notification model, which cannot be implemented efficiently on windows
3655	(Microsoft monopoly games).	4188	(due to Microsoft monopoly games).
3656		4189
3657	A typical way to use libev under windows is to embed it (see the embedding	4190	A typical way to use libev under windows is to embed it (see the embedding
3658	section for details) and use the following F<evwrap.h> header file instead	4191	section for details) and use the following F<evwrap.h> header file instead
3659	of F<ev.h>:	4192	of F<ev.h>:
3660		4193
…		…
3696		4229
3697	Early versions of winsocket's select only supported waiting for a maximum	4230	Early versions of winsocket's select only supported waiting for a maximum
3698	of C<64> handles (probably owning to the fact that all windows kernels	4231	of C<64> handles (probably owning to the fact that all windows kernels
3699	can only wait for C<64> things at the same time internally; Microsoft	4232	can only wait for C<64> things at the same time internally; Microsoft
3700	recommends spawning a chain of threads and wait for 63 handles and the	4233	recommends spawning a chain of threads and wait for 63 handles and the
3701	previous thread in each. Great).	4234	previous thread in each. Sounds great!).
3702		4235
3703	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4236	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3704	to some high number (e.g. C<2048>) before compiling the winsocket select	4237	to some high number (e.g. C<2048>) before compiling the winsocket select
3705	call (which might be in libev or elsewhere, for example, perl does its own	4238	call (which might be in libev or elsewhere, for example, perl and many
3706	select emulation on windows).	4239	other interpreters do their own select emulation on windows).
3707		4240
3708	Another limit is the number of file descriptors in the Microsoft runtime	4241	Another limit is the number of file descriptors in the Microsoft runtime
3709	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4242	libraries, which by default is C<64> (there must be a hidden I<64>
3710	or something like this inside Microsoft). You can increase this by calling	4243	fetish or something like this inside Microsoft). You can increase this
3711	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4244	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3712	arbitrary limit), but is broken in many versions of the Microsoft runtime	4245	(another arbitrary limit), but is broken in many versions of the Microsoft
3713	libraries.
3714
3715	This might get you to about C<512> or C<2048> sockets (depending on	4246	runtime libraries. This might get you to about C<512> or C<2048> sockets
3716	windows version and/or the phase of the moon). To get more, you need to	4247	(depending on windows version and/or the phase of the moon). To get more,
3717	wrap all I/O functions and provide your own fd management, but the cost of	4248	you need to wrap all I/O functions and provide your own fd management, but
3718	calling select (O(n²)) will likely make this unworkable.	4249	the cost of calling select (O(n²)) will likely make this unworkable.
3719		4250
3720	=back	4251	=back
3721		4252
3722	=head2 PORTABILITY REQUIREMENTS	4253	=head2 PORTABILITY REQUIREMENTS
3723		4254
…		…
3766	=item C<double> must hold a time value in seconds with enough accuracy	4297	=item C<double> must hold a time value in seconds with enough accuracy
3767		4298
3768	The type C<double> is used to represent timestamps. It is required to	4299	The type C<double> is used to represent timestamps. It is required to
3769	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4300	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
3770	enough for at least into the year 4000. This requirement is fulfilled by	4301	enough for at least into the year 4000. This requirement is fulfilled by
3771	implementations implementing IEEE 754 (basically all existing ones).	4302	implementations implementing IEEE 754, which is basically all existing
		4303	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4304	2200.
3772		4305
3773	=back	4306	=back
3774		4307
3775	If you know of other additional requirements drop me a note.	4308	If you know of other additional requirements drop me a note.
3776		4309
…		…
3844	involves iterating over all running async watchers or all signal numbers.	4377	involves iterating over all running async watchers or all signal numbers.
3845		4378
3846	=back	4379	=back
3847		4380
3848		4381
		4382	=head1 GLOSSARY
		4383
		4384	=over 4
		4385
		4386	=item active
		4387
		4388	A watcher is active as long as it has been started (has been attached to
		4389	an event loop) but not yet stopped (disassociated from the event loop).
		4390
		4391	=item application
		4392
		4393	In this document, an application is whatever is using libev.
		4394
		4395	=item callback
		4396
		4397	The address of a function that is called when some event has been
		4398	detected. Callbacks are being passed the event loop, the watcher that
		4399	received the event, and the actual event bitset.
		4400
		4401	=item callback invocation
		4402
		4403	The act of calling the callback associated with a watcher.
		4404
		4405	=item event
		4406
		4407	A change of state of some external event, such as data now being available
		4408	for reading on a file descriptor, time having passed or simply not having
		4409	any other events happening anymore.
		4410
		4411	In libev, events are represented as single bits (such as C<EV_READ> or
		4412	C<EV_TIMEOUT>).
		4413
		4414	=item event library
		4415
		4416	A software package implementing an event model and loop.
		4417
		4418	=item event loop
		4419
		4420	An entity that handles and processes external events and converts them
		4421	into callback invocations.
		4422
		4423	=item event model
		4424
		4425	The model used to describe how an event loop handles and processes
		4426	watchers and events.
		4427
		4428	=item pending
		4429
		4430	A watcher is pending as soon as the corresponding event has been detected,
		4431	and stops being pending as soon as the watcher will be invoked or its
		4432	pending status is explicitly cleared by the application.
		4433
		4434	A watcher can be pending, but not active. Stopping a watcher also clears
		4435	its pending status.
		4436
		4437	=item real time
		4438
		4439	The physical time that is observed. It is apparently strictly monotonic :)
		4440
		4441	=item wall-clock time
		4442
		4443	The time and date as shown on clocks. Unlike real time, it can actually
		4444	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4445	clock.
		4446
		4447	=item watcher
		4448
		4449	A data structure that describes interest in certain events. Watchers need
		4450	to be started (attached to an event loop) before they can receive events.
		4451
		4452	=item watcher invocation
		4453
		4454	The act of calling the callback associated with a watcher.
		4455
		4456	=back
		4457
3849	=head1 AUTHOR	4458	=head1 AUTHOR
3850		4459
3851	Marc Lehmann <libev@schmorp.de>.	4460	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3852		4461

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