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…		…
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
		14	#include <stdio.h> // for puts
		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
18		20
19	// all watcher callbacks have a similar signature	21	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	22	// this callback is called when data is readable on stdin
21	static void	23	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	24	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	25	{
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
…		…
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	33	}
32		34
33	// another callback, this time for a time-out	35	// another callback, this time for a time-out
34	static void	36	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	38	{
37	puts ("timeout");	39	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	42	}
…		…
60		62
61	// unloop was called, so exit	63	// unloop was called, so exit
62	return 0;	64	return 0;
63	}	65	}
64		66
65	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
66		70
67	The newest version of this document is also available as an html-formatted	71	The newest version of this document is also available as an html-formatted
68	web page you might find easier to navigate when reading it for the first	72	web page you might find easier to navigate when reading it for the first
69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.	73	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		74
		75	While this document tries to be as complete as possible in documenting
		76	libev, its usage and the rationale behind its design, it is not a tutorial
		77	on event-based programming, nor will it introduce event-based programming
		78	with libev.
		79
		80	Familarity with event based programming techniques in general is assumed
		81	throughout this document.
		82
		83	=head1 ABOUT LIBEV
70		84
71	Libev is an event loop: you register interest in certain events (such as a	85	Libev is an event loop: you register interest in certain events (such as a
72	file descriptor being readable or a timeout occurring), and it will manage	86	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	87	these event sources and provide your program with events.
74		88
…		…
103	Libev is very configurable. In this manual the default (and most common)	117	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	118	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	119	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	120	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	121	for multiple event loops, then all functions taking an initial argument of
108	name C<loop> (which is always of type C<struct ev_loop *>) will not have	122	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	123	this argument.
110		124
111	=head2 TIME REPRESENTATION	125	=head2 TIME REPRESENTATION
112		126
113	Libev represents time as a single floating point number, representing the	127	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	128	the (fractional) number of seconds since the (POSIX) epoch (somewhere
115	the beginning of 1970, details are complicated, don't ask). This type is	129	near the beginning of 1970, details are complicated, don't ask). This
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	130	type is called C<ev_tstamp>, which is what you should use too. It usually
117	to the C<double> type in C, and when you need to do any calculations on	131	aliases to the C<double> type in C. When you need to do any calculations
118	it, you should treat it as some floating point value. Unlike the name	132	on it, you should treat it as some floating point value. Unlike the name
119	component C<stamp> might indicate, it is also used for time differences	133	component C<stamp> might indicate, it is also used for time differences
120	throughout libev.	134	throughout libev.
121		135
122	=head1 ERROR HANDLING	136	=head1 ERROR HANDLING
123		137
…		…
276		290
277	=back	291	=back
278		292
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	293	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
280		294
281	An event loop is described by a C<struct ev_loop *>. The library knows two	295	An event loop is described by a C<struct ev_loop *> (the C<struct>
282	types of such loops, the I<default> loop, which supports signals and child	296	is I<not> optional in this case, as there is also an C<ev_loop>
283	events, and dynamically created loops which do not.	297	I<function>).
		298
		299	The library knows two types of such loops, the I<default> loop, which
		300	supports signals and child events, and dynamically created loops which do
		301	not.
284		302
285	=over 4	303	=over 4
286		304
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	305	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		306
…		…
294	If you don't know what event loop to use, use the one returned from this	312	If you don't know what event loop to use, use the one returned from this
295	function.	313	function.
296		314
297	Note that this function is I<not> thread-safe, so if you want to use it	315	Note that this function is I<not> thread-safe, so if you want to use it
298	from multiple threads, you have to lock (note also that this is unlikely,	316	from multiple threads, you have to lock (note also that this is unlikely,
299	as loops cannot bes hared easily between threads anyway).	317	as loops cannot be shared easily between threads anyway).
300		318
301	The default loop is the only loop that can handle C<ev_signal> and	319	The default loop is the only loop that can handle C<ev_signal> and
302	C<ev_child> watchers, and to do this, it always registers a handler	320	C<ev_child> watchers, and to do this, it always registers a handler
303	for C<SIGCHLD>. If this is a problem for your application you can either	321	for C<SIGCHLD>. If this is a problem for your application you can either
304	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	322	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
…		…
380	=item C<EVBACKEND_EPOLL> (value 4, Linux)	398	=item C<EVBACKEND_EPOLL> (value 4, Linux)
381		399
382	For few fds, this backend is a bit little slower than poll and select,	400	For few fds, this backend is a bit little slower than poll and select,
383	but it scales phenomenally better. While poll and select usually scale	401	but it scales phenomenally better. While poll and select usually scale
384	like O(total_fds) where n is the total number of fds (or the highest fd),	402	like O(total_fds) where n is the total number of fds (or the highest fd),
385	epoll scales either O(1) or O(active_fds). The epoll design has a number	403	epoll scales either O(1) or O(active_fds).
386	of shortcomings, such as silently dropping events in some hard-to-detect	404
387	cases and requiring a system call per fd change, no fork support and bad	405	The epoll mechanism deserves honorable mention as the most misdesigned
388	support for dup.	406	of the more advanced event mechanisms: mere annoyances include silently
		407	dropping file descriptors, requiring a system call per change per file
		408	descriptor (and unnecessary guessing of parameters), problems with dup and
		409	so on. The biggest issue is fork races, however - if a program forks then
		410	I<both> parent and child process have to recreate the epoll set, which can
		411	take considerable time (one syscall per file descriptor) and is of course
		412	hard to detect.
		413
		414	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		415	of course I<doesn't>, and epoll just loves to report events for totally
		416	I<different> file descriptors (even already closed ones, so one cannot
		417	even remove them from the set) than registered in the set (especially
		418	on SMP systems). Libev tries to counter these spurious notifications by
		419	employing an additional generation counter and comparing that against the
		420	events to filter out spurious ones, recreating the set when required.
389		421
390	While stopping, setting and starting an I/O watcher in the same iteration	422	While stopping, setting and starting an I/O watcher in the same iteration
391	will result in some caching, there is still a system call per such incident	423	will result in some caching, there is still a system call per such
392	(because the fd could point to a different file description now), so its	424	incident (because the same I<file descriptor> could point to a different
393	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	425	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
394	very well if you register events for both fds.	426	file descriptors might not work very well if you register events for both
395		427	file descriptors.
396	Please note that epoll sometimes generates spurious notifications, so you
397	need to use non-blocking I/O or other means to avoid blocking when no data
398	(or space) is available.
399		428
400	Best performance from this backend is achieved by not unregistering all	429	Best performance from this backend is achieved by not unregistering all
401	watchers for a file descriptor until it has been closed, if possible,	430	watchers for a file descriptor until it has been closed, if possible,
402	i.e. keep at least one watcher active per fd at all times. Stopping and	431	i.e. keep at least one watcher active per fd at all times. Stopping and
403	starting a watcher (without re-setting it) also usually doesn't cause	432	starting a watcher (without re-setting it) also usually doesn't cause
404	extra overhead.	433	extra overhead. A fork can both result in spurious notifications as well
		434	as in libev having to destroy and recreate the epoll object, which can
		435	take considerable time and thus should be avoided.
		436
		437	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		438	faster than epoll for maybe up to a hundred file descriptors, depending on
		439	the usage. So sad.
405		440
406	While nominally embeddable in other event loops, this feature is broken in	441	While nominally embeddable in other event loops, this feature is broken in
407	all kernel versions tested so far.	442	all kernel versions tested so far.
408		443
409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	444	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
410	C<EVBACKEND_POLL>.	445	C<EVBACKEND_POLL>.
411		446
412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	447	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
413		448
414	Kqueue deserves special mention, as at the time of this writing, it was	449	Kqueue deserves special mention, as at the time of this writing, it
415	broken on all BSDs except NetBSD (usually it doesn't work reliably with	450	was broken on all BSDs except NetBSD (usually it doesn't work reliably
416	anything but sockets and pipes, except on Darwin, where of course it's	451	with anything but sockets and pipes, except on Darwin, where of course
417	completely useless). For this reason it's not being "auto-detected" unless	452	it's completely useless). Unlike epoll, however, whose brokenness
418	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or	453	is by design, these kqueue bugs can (and eventually will) be fixed
419	libev was compiled on a known-to-be-good (-enough) system like NetBSD.	454	without API changes to existing programs. For this reason it's not being
		455	"auto-detected" unless you explicitly specify it in the flags (i.e. using
		456	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		457	system like NetBSD.
420		458
421	You still can embed kqueue into a normal poll or select backend and use it	459	You still can embed kqueue into a normal poll or select backend and use it
422	only for sockets (after having made sure that sockets work with kqueue on	460	only for sockets (after having made sure that sockets work with kqueue on
423	the target platform). See C<ev_embed> watchers for more info.	461	the target platform). See C<ev_embed> watchers for more info.
424		462
425	It scales in the same way as the epoll backend, but the interface to the	463	It scales in the same way as the epoll backend, but the interface to the
426	kernel is more efficient (which says nothing about its actual speed, of	464	kernel is more efficient (which says nothing about its actual speed, of
427	course). While stopping, setting and starting an I/O watcher does never	465	course). While stopping, setting and starting an I/O watcher does never
428	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	466	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
429	two event changes per incident. Support for C<fork ()> is very bad and it	467	two event changes per incident. Support for C<fork ()> is very bad (but
430	drops fds silently in similarly hard-to-detect cases.	468	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		469	cases
431		470
432	This backend usually performs well under most conditions.	471	This backend usually performs well under most conditions.
433		472
434	While nominally embeddable in other event loops, this doesn't work	473	While nominally embeddable in other event loops, this doesn't work
435	everywhere, so you might need to test for this. And since it is broken	474	everywhere, so you might need to test for this. And since it is broken
436	almost everywhere, you should only use it when you have a lot of sockets	475	almost everywhere, you should only use it when you have a lot of sockets
437	(for which it usually works), by embedding it into another event loop	476	(for which it usually works), by embedding it into another event loop
438	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,	477	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
439	using it only for sockets.	478	also broken on OS X)) and, did I mention it, using it only for sockets.
440		479
441	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	480	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
442	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with	481	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
443	C<NOTE_EOF>.	482	C<NOTE_EOF>.
444		483
…		…
464	might perform better.	503	might perform better.
465		504
466	On the positive side, with the exception of the spurious readiness	505	On the positive side, with the exception of the spurious readiness
467	notifications, this backend actually performed fully to specification	506	notifications, this backend actually performed fully to specification
468	in all tests and is fully embeddable, which is a rare feat among the	507	in all tests and is fully embeddable, which is a rare feat among the
469	OS-specific backends.	508	OS-specific backends (I vastly prefer correctness over speed hacks).
470		509
471	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	510	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
472	C<EVBACKEND_POLL>.	511	C<EVBACKEND_POLL>.
473		512
474	=item C<EVBACKEND_ALL>	513	=item C<EVBACKEND_ALL>
…		…
527	responsibility to either stop all watchers cleanly yourself I<before>	566	responsibility to either stop all watchers cleanly yourself I<before>
528	calling this function, or cope with the fact afterwards (which is usually	567	calling this function, or cope with the fact afterwards (which is usually
529	the easiest thing, you can just ignore the watchers and/or C<free ()> them	568	the easiest thing, you can just ignore the watchers and/or C<free ()> them
530	for example).	569	for example).
531		570
532	Note that certain global state, such as signal state, will not be freed by	571	Note that certain global state, such as signal state (and installed signal
533	this function, and related watchers (such as signal and child watchers)	572	handlers), will not be freed by this function, and related watchers (such
534	would need to be stopped manually.	573	as signal and child watchers) would need to be stopped manually.
535		574
536	In general it is not advisable to call this function except in the	575	In general it is not advisable to call this function except in the
537	rare occasion where you really need to free e.g. the signal handling	576	rare occasion where you really need to free e.g. the signal handling
538	pipe fds. If you need dynamically allocated loops it is better to use	577	pipe fds. If you need dynamically allocated loops it is better to use
539	C<ev_loop_new> and C<ev_loop_destroy>).	578	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
582		621
583	This value can sometimes be useful as a generation counter of sorts (it	622	This value can sometimes be useful as a generation counter of sorts (it
584	"ticks" the number of loop iterations), as it roughly corresponds with	623	"ticks" the number of loop iterations), as it roughly corresponds with
585	C<ev_prepare> and C<ev_check> calls.	624	C<ev_prepare> and C<ev_check> calls.
586		625
		626	=item unsigned int ev_loop_depth (loop)
		627
		628	Returns the number of times C<ev_loop> was entered minus the number of
		629	times C<ev_loop> was exited, in other words, the recursion depth.
		630
		631	Outside C<ev_loop>, this number is zero. In a callback, this number is
		632	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),
		633	in which case it is higher.
		634
		635	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread
		636	etc.), doesn't count as exit.
		637
587	=item unsigned int ev_backend (loop)	638	=item unsigned int ev_backend (loop)
588		639
589	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	640	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
590	use.	641	use.
591		642
…		…
605		656
606	This function is rarely useful, but when some event callback runs for a	657	This function is rarely useful, but when some event callback runs for a
607	very long time without entering the event loop, updating libev's idea of	658	very long time without entering the event loop, updating libev's idea of
608	the current time is a good idea.	659	the current time is a good idea.
609		660
610	See also "The special problem of time updates" in the C<ev_timer> section.	661	See also L<The special problem of time updates> in the C<ev_timer> section.
		662
		663	=item ev_suspend (loop)
		664
		665	=item ev_resume (loop)
		666
		667	These two functions suspend and resume a loop, for use when the loop is
		668	not used for a while and timeouts should not be processed.
		669
		670	A typical use case would be an interactive program such as a game: When
		671	the user presses C<^Z> to suspend the game and resumes it an hour later it
		672	would be best to handle timeouts as if no time had actually passed while
		673	the program was suspended. This can be achieved by calling C<ev_suspend>
		674	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		675	C<ev_resume> directly afterwards to resume timer processing.
		676
		677	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		678	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		679	will be rescheduled (that is, they will lose any events that would have
		680	occured while suspended).
		681
		682	After calling C<ev_suspend> you B<must not> call I<any> function on the
		683	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		684	without a previous call to C<ev_suspend>.
		685
		686	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		687	event loop time (see C<ev_now_update>).
611		688
612	=item ev_loop (loop, int flags)	689	=item ev_loop (loop, int flags)
613		690
614	Finally, this is it, the event handler. This function usually is called	691	Finally, this is it, the event handler. This function usually is called
615	after you initialised all your watchers and you want to start handling	692	after you initialised all your watchers and you want to start handling
…		…
631	the loop.	708	the loop.
632		709
633	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	710	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
634	necessary) and will handle those and any already outstanding ones. It	711	necessary) and will handle those and any already outstanding ones. It
635	will block your process until at least one new event arrives (which could	712	will block your process until at least one new event arrives (which could
636	be an event internal to libev itself, so there is no guarentee that a	713	be an event internal to libev itself, so there is no guarantee that a
637	user-registered callback will be called), and will return after one	714	user-registered callback will be called), and will return after one
638	iteration of the loop.	715	iteration of the loop.
639		716
640	This is useful if you are waiting for some external event in conjunction	717	This is useful if you are waiting for some external event in conjunction
641	with something not expressible using other libev watchers (i.e. "roll your	718	with something not expressible using other libev watchers (i.e. "roll your
…		…
685	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	762	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
686	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	763	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
687		764
688	This "unloop state" will be cleared when entering C<ev_loop> again.	765	This "unloop state" will be cleared when entering C<ev_loop> again.
689		766
		767	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		768
690	=item ev_ref (loop)	769	=item ev_ref (loop)
691		770
692	=item ev_unref (loop)	771	=item ev_unref (loop)
693		772
694	Ref/unref can be used to add or remove a reference count on the event	773	Ref/unref can be used to add or remove a reference count on the event
…		…
697		776
698	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>
699	from returning, call ev_unref() after starting, and ev_ref() before	778	from returning, call ev_unref() after starting, and ev_ref() before
700	stopping it.	779	stopping it.
701		780
702	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
703	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
704	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
705	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
706	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
707	(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
708	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).
709		790
710	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>
711	running when nothing else is active.	792	running when nothing else is active.
712		793
713	struct ev_signal exitsig;	794	ev_signal exitsig;
714	ev_signal_init (&exitsig, sig_cb, SIGINT);	795	ev_signal_init (&exitsig, sig_cb, SIGINT);
715	ev_signal_start (loop, &exitsig);	796	ev_signal_start (loop, &exitsig);
716	evf_unref (loop);	797	evf_unref (loop);
717		798
718	Example: For some weird reason, unregister the above signal handler again.	799	Example: For some weird reason, unregister the above signal handler again.
…		…
742		823
743	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
744	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,
745	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
746	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
747	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.
748		831
749	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
750	to spend more time collecting timeouts, at the expense of increased	833	to spend more time collecting timeouts, at the expense of increased
751	latency/jitter/inexactness (the watcher callback will be called	834	latency/jitter/inexactness (the watcher callback will be called
752	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
…		…
754		837
755	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
756	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
757	interactive servers (of course not for games), likewise for timeouts. It	840	interactive servers (of course not for games), likewise for timeouts. It
758	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>,
759	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).
760		847
761	Setting the I<timeout collect interval> can improve the opportunity for	848	Setting the I<timeout collect interval> can improve the opportunity for
762	saving power, as the program will "bundle" timer callback invocations that	849	saving power, as the program will "bundle" timer callback invocations that
763	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
764	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
765	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
766	they fire on, say, one-second boundaries only.	853	they fire on, say, one-second boundaries only.
767		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
768	=item ev_loop_verify (loop)	861	=item ev_loop_verify (loop)
769		862
770	This function only does something when C<EV_VERIFY> support has been	863	This function only does something when C<EV_VERIFY> support has been
771	compiled in. which is the default for non-minimal builds. It tries to go	864	compiled in, which is the default for non-minimal builds. It tries to go
772	through all internal structures and checks them for validity. If anything	865	through all internal structures and checks them for validity. If anything
773	is found to be inconsistent, it will print an error message to standard	866	is found to be inconsistent, it will print an error message to standard
774	error and call C<abort ()>.	867	error and call C<abort ()>.
775		868
776	This can be used to catch bugs inside libev itself: under normal	869	This can be used to catch bugs inside libev itself: under normal
…		…
780	=back	873	=back
781		874
782		875
783	=head1 ANATOMY OF A WATCHER	876	=head1 ANATOMY OF A WATCHER
784		877
		878	In the following description, uppercase C<TYPE> in names stands for the
		879	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		880	watchers and C<ev_io_start> for I/O watchers.
		881
785	A watcher is a structure that you create and register to record your	882	A watcher is a structure that you create and register to record your
786	interest in some event. For instance, if you want to wait for STDIN to	883	interest in some event. For instance, if you want to wait for STDIN to
787	become readable, you would create an C<ev_io> watcher for that:	884	become readable, you would create an C<ev_io> watcher for that:
788		885
789	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	886	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
790	{	887	{
791	ev_io_stop (w);	888	ev_io_stop (w);
792	ev_unloop (loop, EVUNLOOP_ALL);	889	ev_unloop (loop, EVUNLOOP_ALL);
793	}	890	}
794		891
795	struct ev_loop *loop = ev_default_loop (0);	892	struct ev_loop *loop = ev_default_loop (0);
		893
796	struct ev_io stdin_watcher;	894	ev_io stdin_watcher;
		895
797	ev_init (&stdin_watcher, my_cb);	896	ev_init (&stdin_watcher, my_cb);
798	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	897	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
799	ev_io_start (loop, &stdin_watcher);	898	ev_io_start (loop, &stdin_watcher);
		899
800	ev_loop (loop, 0);	900	ev_loop (loop, 0);
801		901
802	As you can see, you are responsible for allocating the memory for your	902	As you can see, you are responsible for allocating the memory for your
803	watcher structures (and it is usually a bad idea to do this on the stack,	903	watcher structures (and it is I<usually> a bad idea to do this on the
804	although this can sometimes be quite valid).	904	stack).
		905
		906	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		907	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
805		908
806	Each watcher structure must be initialised by a call to C<ev_init	909	Each watcher structure must be initialised by a call to C<ev_init
807	(watcher *, callback)>, which expects a callback to be provided. This	910	(watcher *, callback)>, which expects a callback to be provided. This
808	callback gets invoked each time the event occurs (or, in the case of I/O	911	callback gets invoked each time the event occurs (or, in the case of I/O
809	watchers, each time the event loop detects that the file descriptor given	912	watchers, each time the event loop detects that the file descriptor given
810	is readable and/or writable).	913	is readable and/or writable).
811		914
812	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	915	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
813	with arguments specific to this watcher type. There is also a macro	916	macro to configure it, with arguments specific to the watcher type. There
814	to combine initialisation and setting in one call: C<< ev_<type>_init	917	is also a macro to combine initialisation and setting in one call: C<<
815	(watcher *, callback, ...) >>.	918	ev_TYPE_init (watcher *, callback, ...) >>.
816		919
817	To make the watcher actually watch out for events, you have to start it	920	To make the watcher actually watch out for events, you have to start it
818	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	921	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
819	*) >>), and you can stop watching for events at any time by calling the	922	*) >>), and you can stop watching for events at any time by calling the
820	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	923	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
821		924
822	As long as your watcher is active (has been started but not stopped) you	925	As long as your watcher is active (has been started but not stopped) you
823	must not touch the values stored in it. Most specifically you must never	926	must not touch the values stored in it. Most specifically you must never
824	reinitialise it or call its C<set> macro.	927	reinitialise it or call its C<ev_TYPE_set> macro.
825		928
826	Each and every callback receives the event loop pointer as first, the	929	Each and every callback receives the event loop pointer as first, the
827	registered watcher structure as second, and a bitset of received events as	930	registered watcher structure as second, and a bitset of received events as
828	third argument.	931	third argument.
829		932
…		…
887		990
888	=item C<EV_ASYNC>	991	=item C<EV_ASYNC>
889		992
890	The given async watcher has been asynchronously notified (see C<ev_async>).	993	The given async watcher has been asynchronously notified (see C<ev_async>).
891		994
		995	=item C<EV_CUSTOM>
		996
		997	Not ever sent (or otherwise used) by libev itself, but can be freely used
		998	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		999
892	=item C<EV_ERROR>	1000	=item C<EV_ERROR>
893		1001
894	An unspecified error has occurred, the watcher has been stopped. This might	1002	An unspecified error has occurred, the watcher has been stopped. This might
895	happen because the watcher could not be properly started because libev	1003	happen because the watcher could not be properly started because libev
896	ran out of memory, a file descriptor was found to be closed or any other	1004	ran out of memory, a file descriptor was found to be closed or any other
		1005	problem. Libev considers these application bugs.
		1006
897	problem. You best act on it by reporting the problem and somehow coping	1007	You best act on it by reporting the problem and somehow coping with the
898	with the watcher being stopped.	1008	watcher being stopped. Note that well-written programs should not receive
		1009	an error ever, so when your watcher receives it, this usually indicates a
		1010	bug in your program.
899		1011
900	Libev will usually signal a few "dummy" events together with an error, for	1012	Libev will usually signal a few "dummy" events together with an error, for
901	example it might indicate that a fd is readable or writable, and if your	1013	example it might indicate that a fd is readable or writable, and if your
902	callbacks is well-written it can just attempt the operation and cope with	1014	callbacks is well-written it can just attempt the operation and cope with
903	the error from read() or write(). This will not work in multi-threaded	1015	the error from read() or write(). This will not work in multi-threaded
…		…
906		1018
907	=back	1019	=back
908		1020
909	=head2 GENERIC WATCHER FUNCTIONS	1021	=head2 GENERIC WATCHER FUNCTIONS
910		1022
911	In the following description, C<TYPE> stands for the watcher type,
912	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
913
914	=over 4	1023	=over 4
915		1024
916	=item C<ev_init> (ev_TYPE *watcher, callback)	1025	=item C<ev_init> (ev_TYPE *watcher, callback)
917		1026
918	This macro initialises the generic portion of a watcher. The contents	1027	This macro initialises the generic portion of a watcher. The contents
…		…
923	which rolls both calls into one.	1032	which rolls both calls into one.
924		1033
925	You can reinitialise a watcher at any time as long as it has been stopped	1034	You can reinitialise a watcher at any time as long as it has been stopped
926	(or never started) and there are no pending events outstanding.	1035	(or never started) and there are no pending events outstanding.
927		1036
928	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1037	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
929	int revents)>.	1038	int revents)>.
930		1039
931	Example: Initialise an C<ev_io> watcher in two steps.	1040	Example: Initialise an C<ev_io> watcher in two steps.
932		1041
933	ev_io w;	1042	ev_io w;
…		…
967		1076
968	ev_io_start (EV_DEFAULT_UC, &w);	1077	ev_io_start (EV_DEFAULT_UC, &w);
969		1078
970	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1079	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
971		1080
972	Stops the given watcher again (if active) and clears the pending	1081	Stops the given watcher if active, and clears the pending status (whether
		1082	the watcher was active or not).
		1083
973	status. It is possible that stopped watchers are pending (for example,	1084	It is possible that stopped watchers are pending - for example,
974	non-repeating timers are being stopped when they become pending), but	1085	non-repeating timers are being stopped when they become pending - but
975	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1086	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
976	you want to free or reuse the memory used by the watcher it is therefore a	1087	pending. If you want to free or reuse the memory used by the watcher it is
977	good idea to always call its C<ev_TYPE_stop> function.	1088	therefore a good idea to always call its C<ev_TYPE_stop> function.
978		1089
979	=item bool ev_is_active (ev_TYPE *watcher)	1090	=item bool ev_is_active (ev_TYPE *watcher)
980		1091
981	Returns a true value iff the watcher is active (i.e. it has been started	1092	Returns a true value iff the watcher is active (i.e. it has been started
982	and not yet been stopped). As long as a watcher is active you must not modify	1093	and not yet been stopped). As long as a watcher is active you must not modify
…		…
1008	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1119	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1009	(default: C<-2>). Pending watchers with higher priority will be invoked	1120	(default: C<-2>). Pending watchers with higher priority will be invoked
1010	before watchers with lower priority, but priority will not keep watchers	1121	before watchers with lower priority, but priority will not keep watchers
1011	from being executed (except for C<ev_idle> watchers).	1122	from being executed (except for C<ev_idle> watchers).
1012		1123
1013	This means that priorities are I<only> used for ordering callback
1014	invocation after new events have been received. This is useful, for
1015	example, to reduce latency after idling, or more often, to bind two
1016	watchers on the same event and make sure one is called first.
1017
1018	If you need to suppress invocation when higher priority events are pending	1124	If you need to suppress invocation when higher priority events are pending
1019	you need to look at C<ev_idle> watchers, which provide this functionality.	1125	you need to look at C<ev_idle> watchers, which provide this functionality.
1020		1126
1021	You I<must not> change the priority of a watcher as long as it is active or	1127	You I<must not> change the priority of a watcher as long as it is active or
1022	pending.	1128	pending.
1023		1129
		1130	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1131	fine, as long as you do not mind that the priority value you query might
		1132	or might not have been clamped to the valid range.
		1133
1024	The default priority used by watchers when no priority has been set is	1134	The default priority used by watchers when no priority has been set is
1025	always C<0>, which is supposed to not be too high and not be too low :).	1135	always C<0>, which is supposed to not be too high and not be too low :).
1026		1136
1027	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1137	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1028	fine, as long as you do not mind that the priority value you query might	1138	priorities.
1029	or might not have been adjusted to be within valid range.
1030		1139
1031	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1140	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1032		1141
1033	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1142	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1034	C<loop> nor C<revents> need to be valid as long as the watcher callback	1143	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1056	member, you can also "subclass" the watcher type and provide your own	1165	member, you can also "subclass" the watcher type and provide your own
1057	data:	1166	data:
1058		1167
1059	struct my_io	1168	struct my_io
1060	{	1169	{
1061	struct ev_io io;	1170	ev_io io;
1062	int otherfd;	1171	int otherfd;
1063	void *somedata;	1172	void *somedata;
1064	struct whatever *mostinteresting;	1173	struct whatever *mostinteresting;
1065	};	1174	};
1066		1175
…		…
1069	ev_io_init (&w.io, my_cb, fd, EV_READ);	1178	ev_io_init (&w.io, my_cb, fd, EV_READ);
1070		1179
1071	And since your callback will be called with a pointer to the watcher, you	1180	And since your callback will be called with a pointer to the watcher, you
1072	can cast it back to your own type:	1181	can cast it back to your own type:
1073		1182
1074	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1183	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1075	{	1184	{
1076	struct my_io *w = (struct my_io *)w_;	1185	struct my_io *w = (struct my_io *)w_;
1077	...	1186	...
1078	}	1187	}
1079		1188
…		…
1097	programmers):	1206	programmers):
1098		1207
1099	#include <stddef.h>	1208	#include <stddef.h>
1100		1209
1101	static void	1210	static void
1102	t1_cb (EV_P_ struct ev_timer *w, int revents)	1211	t1_cb (EV_P_ ev_timer *w, int revents)
1103	{	1212	{
1104	struct my_biggy big = (struct my_biggy *	1213	struct my_biggy big = (struct my_biggy *)
1105	(((char *)w) - offsetof (struct my_biggy, t1));	1214	(((char *)w) - offsetof (struct my_biggy, t1));
1106	}	1215	}
1107		1216
1108	static void	1217	static void
1109	t2_cb (EV_P_ struct ev_timer *w, int revents)	1218	t2_cb (EV_P_ ev_timer *w, int revents)
1110	{	1219	{
1111	struct my_biggy big = (struct my_biggy *	1220	struct my_biggy big = (struct my_biggy *)
1112	(((char *)w) - offsetof (struct my_biggy, t2));	1221	(((char *)w) - offsetof (struct my_biggy, t2));
1113	}	1222	}
		1223
		1224	=head2 WATCHER PRIORITY MODELS
		1225
		1226	Many event loops support I<watcher priorities>, which are usually small
		1227	integers that influence the ordering of event callback invocation
		1228	between watchers in some way, all else being equal.
		1229
		1230	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1231	description for the more technical details such as the actual priority
		1232	range.
		1233
		1234	There are two common ways how these these priorities are being interpreted
		1235	by event loops:
		1236
		1237	In the more common lock-out model, higher priorities "lock out" invocation
		1238	of lower priority watchers, which means as long as higher priority
		1239	watchers receive events, lower priority watchers are not being invoked.
		1240
		1241	The less common only-for-ordering model uses priorities solely to order
		1242	callback invocation within a single event loop iteration: Higher priority
		1243	watchers are invoked before lower priority ones, but they all get invoked
		1244	before polling for new events.
		1245
		1246	Libev uses the second (only-for-ordering) model for all its watchers
		1247	except for idle watchers (which use the lock-out model).
		1248
		1249	The rationale behind this is that implementing the lock-out model for
		1250	watchers is not well supported by most kernel interfaces, and most event
		1251	libraries will just poll for the same events again and again as long as
		1252	their callbacks have not been executed, which is very inefficient in the
		1253	common case of one high-priority watcher locking out a mass of lower
		1254	priority ones.
		1255
		1256	Static (ordering) priorities are most useful when you have two or more
		1257	watchers handling the same resource: a typical usage example is having an
		1258	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1259	timeouts. Under load, data might be received while the program handles
		1260	other jobs, but since timers normally get invoked first, the timeout
		1261	handler will be executed before checking for data. In that case, giving
		1262	the timer a lower priority than the I/O watcher ensures that I/O will be
		1263	handled first even under adverse conditions (which is usually, but not
		1264	always, what you want).
		1265
		1266	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1267	will only be executed when no same or higher priority watchers have
		1268	received events, they can be used to implement the "lock-out" model when
		1269	required.
		1270
		1271	For example, to emulate how many other event libraries handle priorities,
		1272	you can associate an C<ev_idle> watcher to each such watcher, and in
		1273	the normal watcher callback, you just start the idle watcher. The real
		1274	processing is done in the idle watcher callback. This causes libev to
		1275	continously poll and process kernel event data for the watcher, but when
		1276	the lock-out case is known to be rare (which in turn is rare :), this is
		1277	workable.
		1278
		1279	Usually, however, the lock-out model implemented that way will perform
		1280	miserably under the type of load it was designed to handle. In that case,
		1281	it might be preferable to stop the real watcher before starting the
		1282	idle watcher, so the kernel will not have to process the event in case
		1283	the actual processing will be delayed for considerable time.
		1284
		1285	Here is an example of an I/O watcher that should run at a strictly lower
		1286	priority than the default, and which should only process data when no
		1287	other events are pending:
		1288
		1289	ev_idle idle; // actual processing watcher
		1290	ev_io io; // actual event watcher
		1291
		1292	static void
		1293	io_cb (EV_P_ ev_io *w, int revents)
		1294	{
		1295	// stop the I/O watcher, we received the event, but
		1296	// are not yet ready to handle it.
		1297	ev_io_stop (EV_A_ w);
		1298
		1299	// start the idle watcher to ahndle the actual event.
		1300	// it will not be executed as long as other watchers
		1301	// with the default priority are receiving events.
		1302	ev_idle_start (EV_A_ &idle);
		1303	}
		1304
		1305	static void
		1306	idle_cb (EV_P_ ev_idle *w, int revents)
		1307	{
		1308	// actual processing
		1309	read (STDIN_FILENO, ...);
		1310
		1311	// have to start the I/O watcher again, as
		1312	// we have handled the event
		1313	ev_io_start (EV_P_ &io);
		1314	}
		1315
		1316	// initialisation
		1317	ev_idle_init (&idle, idle_cb);
		1318	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1319	ev_io_start (EV_DEFAULT_ &io);
		1320
		1321	In the "real" world, it might also be beneficial to start a timer, so that
		1322	low-priority connections can not be locked out forever under load. This
		1323	enables your program to keep a lower latency for important connections
		1324	during short periods of high load, while not completely locking out less
		1325	important ones.
1114		1326
1115		1327
1116	=head1 WATCHER TYPES	1328	=head1 WATCHER TYPES
1117		1329
1118	This section describes each watcher in detail, but will not repeat	1330	This section describes each watcher in detail, but will not repeat
…		…
1144	descriptors to non-blocking mode is also usually a good idea (but not	1356	descriptors to non-blocking mode is also usually a good idea (but not
1145	required if you know what you are doing).	1357	required if you know what you are doing).
1146		1358
1147	If you cannot use non-blocking mode, then force the use of a	1359	If you cannot use non-blocking mode, then force the use of a
1148	known-to-be-good backend (at the time of this writing, this includes only	1360	known-to-be-good backend (at the time of this writing, this includes only
1149	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).	1361	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1362	descriptors for which non-blocking operation makes no sense (such as
		1363	files) - libev doesn't guarentee any specific behaviour in that case.
1150		1364
1151	Another thing you have to watch out for is that it is quite easy to	1365	Another thing you have to watch out for is that it is quite easy to
1152	receive "spurious" readiness notifications, that is your callback might	1366	receive "spurious" readiness notifications, that is your callback might
1153	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1367	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1154	because there is no data. Not only are some backends known to create a	1368	because there is no data. Not only are some backends known to create a
…		…
1249	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1463	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1250	readable, but only once. Since it is likely line-buffered, you could	1464	readable, but only once. Since it is likely line-buffered, you could
1251	attempt to read a whole line in the callback.	1465	attempt to read a whole line in the callback.
1252		1466
1253	static void	1467	static void
1254	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1468	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1255	{	1469	{
1256	ev_io_stop (loop, w);	1470	ev_io_stop (loop, w);
1257	.. read from stdin here (or from w->fd) and handle any I/O errors	1471	.. read from stdin here (or from w->fd) and handle any I/O errors
1258	}	1472	}
1259		1473
1260	...	1474	...
1261	struct ev_loop *loop = ev_default_init (0);	1475	struct ev_loop *loop = ev_default_init (0);
1262	struct ev_io stdin_readable;	1476	ev_io stdin_readable;
1263	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1477	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1264	ev_io_start (loop, &stdin_readable);	1478	ev_io_start (loop, &stdin_readable);
1265	ev_loop (loop, 0);	1479	ev_loop (loop, 0);
1266		1480
1267		1481
…		…
1275	year, it will still time out after (roughly) one hour. "Roughly" because	1489	year, it will still time out after (roughly) one hour. "Roughly" because
1276	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1490	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1277	monotonic clock option helps a lot here).	1491	monotonic clock option helps a lot here).
1278		1492
1279	The callback is guaranteed to be invoked only I<after> its timeout has	1493	The callback is guaranteed to be invoked only I<after> its timeout has
1280	passed, but if multiple timers become ready during the same loop iteration	1494	passed (not I<at>, so on systems with very low-resolution clocks this
1281	then order of execution is undefined.	1495	might introduce a small delay). If multiple timers become ready during the
		1496	same loop iteration then the ones with earlier time-out values are invoked
		1497	before ones with later time-out values (but this is no longer true when a
		1498	callback calls C<ev_loop> recursively).
		1499
		1500	=head3 Be smart about timeouts
		1501
		1502	Many real-world problems involve some kind of timeout, usually for error
		1503	recovery. A typical example is an HTTP request - if the other side hangs,
		1504	you want to raise some error after a while.
		1505
		1506	What follows are some ways to handle this problem, from obvious and
		1507	inefficient to smart and efficient.
		1508
		1509	In the following, a 60 second activity timeout is assumed - a timeout that
		1510	gets reset to 60 seconds each time there is activity (e.g. each time some
		1511	data or other life sign was received).
		1512
		1513	=over 4
		1514
		1515	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1516
		1517	This is the most obvious, but not the most simple way: In the beginning,
		1518	start the watcher:
		1519
		1520	ev_timer_init (timer, callback, 60., 0.);
		1521	ev_timer_start (loop, timer);
		1522
		1523	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1524	and start it again:
		1525
		1526	ev_timer_stop (loop, timer);
		1527	ev_timer_set (timer, 60., 0.);
		1528	ev_timer_start (loop, timer);
		1529
		1530	This is relatively simple to implement, but means that each time there is
		1531	some activity, libev will first have to remove the timer from its internal
		1532	data structure and then add it again. Libev tries to be fast, but it's
		1533	still not a constant-time operation.
		1534
		1535	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1536
		1537	This is the easiest way, and involves using C<ev_timer_again> instead of
		1538	C<ev_timer_start>.
		1539
		1540	To implement this, configure an C<ev_timer> with a C<repeat> value
		1541	of C<60> and then call C<ev_timer_again> at start and each time you
		1542	successfully read or write some data. If you go into an idle state where
		1543	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1544	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1545
		1546	That means you can ignore both the C<ev_timer_start> function and the
		1547	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1548	member and C<ev_timer_again>.
		1549
		1550	At start:
		1551
		1552	ev_init (timer, callback);
		1553	timer->repeat = 60.;
		1554	ev_timer_again (loop, timer);
		1555
		1556	Each time there is some activity:
		1557
		1558	ev_timer_again (loop, timer);
		1559
		1560	It is even possible to change the time-out on the fly, regardless of
		1561	whether the watcher is active or not:
		1562
		1563	timer->repeat = 30.;
		1564	ev_timer_again (loop, timer);
		1565
		1566	This is slightly more efficient then stopping/starting the timer each time
		1567	you want to modify its timeout value, as libev does not have to completely
		1568	remove and re-insert the timer from/into its internal data structure.
		1569
		1570	It is, however, even simpler than the "obvious" way to do it.
		1571
		1572	=item 3. Let the timer time out, but then re-arm it as required.
		1573
		1574	This method is more tricky, but usually most efficient: Most timeouts are
		1575	relatively long compared to the intervals between other activity - in
		1576	our example, within 60 seconds, there are usually many I/O events with
		1577	associated activity resets.
		1578
		1579	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1580	but remember the time of last activity, and check for a real timeout only
		1581	within the callback:
		1582
		1583	ev_tstamp last_activity; // time of last activity
		1584
		1585	static void
		1586	callback (EV_P_ ev_timer *w, int revents)
		1587	{
		1588	ev_tstamp now = ev_now (EV_A);
		1589	ev_tstamp timeout = last_activity + 60.;
		1590
		1591	// if last_activity + 60. is older than now, we did time out
		1592	if (timeout < now)
		1593	{
		1594	// timeout occured, take action
		1595	}
		1596	else
		1597	{
		1598	// callback was invoked, but there was some activity, re-arm
		1599	// the watcher to fire in last_activity + 60, which is
		1600	// guaranteed to be in the future, so "again" is positive:
		1601	w->repeat = timeout - now;
		1602	ev_timer_again (EV_A_ w);
		1603	}
		1604	}
		1605
		1606	To summarise the callback: first calculate the real timeout (defined
		1607	as "60 seconds after the last activity"), then check if that time has
		1608	been reached, which means something I<did>, in fact, time out. Otherwise
		1609	the callback was invoked too early (C<timeout> is in the future), so
		1610	re-schedule the timer to fire at that future time, to see if maybe we have
		1611	a timeout then.
		1612
		1613	Note how C<ev_timer_again> is used, taking advantage of the
		1614	C<ev_timer_again> optimisation when the timer is already running.
		1615
		1616	This scheme causes more callback invocations (about one every 60 seconds
		1617	minus half the average time between activity), but virtually no calls to
		1618	libev to change the timeout.
		1619
		1620	To start the timer, simply initialise the watcher and set C<last_activity>
		1621	to the current time (meaning we just have some activity :), then call the
		1622	callback, which will "do the right thing" and start the timer:
		1623
		1624	ev_init (timer, callback);
		1625	last_activity = ev_now (loop);
		1626	callback (loop, timer, EV_TIMEOUT);
		1627
		1628	And when there is some activity, simply store the current time in
		1629	C<last_activity>, no libev calls at all:
		1630
		1631	last_actiivty = ev_now (loop);
		1632
		1633	This technique is slightly more complex, but in most cases where the
		1634	time-out is unlikely to be triggered, much more efficient.
		1635
		1636	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1637	callback :) - just change the timeout and invoke the callback, which will
		1638	fix things for you.
		1639
		1640	=item 4. Wee, just use a double-linked list for your timeouts.
		1641
		1642	If there is not one request, but many thousands (millions...), all
		1643	employing some kind of timeout with the same timeout value, then one can
		1644	do even better:
		1645
		1646	When starting the timeout, calculate the timeout value and put the timeout
		1647	at the I<end> of the list.
		1648
		1649	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1650	the list is expected to fire (for example, using the technique #3).
		1651
		1652	When there is some activity, remove the timer from the list, recalculate
		1653	the timeout, append it to the end of the list again, and make sure to
		1654	update the C<ev_timer> if it was taken from the beginning of the list.
		1655
		1656	This way, one can manage an unlimited number of timeouts in O(1) time for
		1657	starting, stopping and updating the timers, at the expense of a major
		1658	complication, and having to use a constant timeout. The constant timeout
		1659	ensures that the list stays sorted.
		1660
		1661	=back
		1662
		1663	So which method the best?
		1664
		1665	Method #2 is a simple no-brain-required solution that is adequate in most
		1666	situations. Method #3 requires a bit more thinking, but handles many cases
		1667	better, and isn't very complicated either. In most case, choosing either
		1668	one is fine, with #3 being better in typical situations.
		1669
		1670	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1671	rather complicated, but extremely efficient, something that really pays
		1672	off after the first million or so of active timers, i.e. it's usually
		1673	overkill :)
1282		1674
1283	=head3 The special problem of time updates	1675	=head3 The special problem of time updates
1284		1676
1285	Establishing the current time is a costly operation (it usually takes at	1677	Establishing the current time is a costly operation (it usually takes at
1286	least two system calls): EV therefore updates its idea of the current	1678	least two system calls): EV therefore updates its idea of the current
…		…
1330	If the timer is started but non-repeating, stop it (as if it timed out).	1722	If the timer is started but non-repeating, stop it (as if it timed out).
1331		1723
1332	If the timer is repeating, either start it if necessary (with the	1724	If the timer is repeating, either start it if necessary (with the
1333	C<repeat> value), or reset the running timer to the C<repeat> value.	1725	C<repeat> value), or reset the running timer to the C<repeat> value.
1334		1726
1335	This sounds a bit complicated, but here is a useful and typical	1727	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1336	example: Imagine you have a TCP connection and you want a so-called idle	1728	usage example.
1337	timeout, that is, you want to be called when there have been, say, 60
1338	seconds of inactivity on the socket. The easiest way to do this is to
1339	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1340	C<ev_timer_again> each time you successfully read or write some data. If
1341	you go into an idle state where you do not expect data to travel on the
1342	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1343	automatically restart it if need be.
1344
1345	That means you can ignore the C<after> value and C<ev_timer_start>
1346	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1347
1348	ev_timer_init (timer, callback, 0., 5.);
1349	ev_timer_again (loop, timer);
1350	...
1351	timer->again = 17.;
1352	ev_timer_again (loop, timer);
1353	...
1354	timer->again = 10.;
1355	ev_timer_again (loop, timer);
1356
1357	This is more slightly efficient then stopping/starting the timer each time
1358	you want to modify its timeout value.
1359
1360	Note, however, that it is often even more efficient to remember the
1361	time of the last activity and let the timer time-out naturally. In the
1362	callback, you then check whether the time-out is real, or, if there was
1363	some activity, you reschedule the watcher to time-out in "last_activity +
1364	timeout - ev_now ()" seconds.
1365		1729
1366	=item ev_tstamp repeat [read-write]	1730	=item ev_tstamp repeat [read-write]
1367		1731
1368	The current C<repeat> value. Will be used each time the watcher times out	1732	The current C<repeat> value. Will be used each time the watcher times out
1369	or C<ev_timer_again> is called, and determines the next timeout (if any),	1733	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1374	=head3 Examples	1738	=head3 Examples
1375		1739
1376	Example: Create a timer that fires after 60 seconds.	1740	Example: Create a timer that fires after 60 seconds.
1377		1741
1378	static void	1742	static void
1379	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1743	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1380	{	1744	{
1381	.. one minute over, w is actually stopped right here	1745	.. one minute over, w is actually stopped right here
1382	}	1746	}
1383		1747
1384	struct ev_timer mytimer;	1748	ev_timer mytimer;
1385	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1749	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1386	ev_timer_start (loop, &mytimer);	1750	ev_timer_start (loop, &mytimer);
1387		1751
1388	Example: Create a timeout timer that times out after 10 seconds of	1752	Example: Create a timeout timer that times out after 10 seconds of
1389	inactivity.	1753	inactivity.
1390		1754
1391	static void	1755	static void
1392	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1756	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1393	{	1757	{
1394	.. ten seconds without any activity	1758	.. ten seconds without any activity
1395	}	1759	}
1396		1760
1397	struct ev_timer mytimer;	1761	ev_timer mytimer;
1398	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1762	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1399	ev_timer_again (&mytimer); /* start timer */	1763	ev_timer_again (&mytimer); /* start timer */
1400	ev_loop (loop, 0);	1764	ev_loop (loop, 0);
1401		1765
1402	// and in some piece of code that gets executed on any "activity":	1766	// and in some piece of code that gets executed on any "activity":
…		…
1407	=head2 C<ev_periodic> - to cron or not to cron?	1771	=head2 C<ev_periodic> - to cron or not to cron?
1408		1772
1409	Periodic watchers are also timers of a kind, but they are very versatile	1773	Periodic watchers are also timers of a kind, but they are very versatile
1410	(and unfortunately a bit complex).	1774	(and unfortunately a bit complex).
1411		1775
1412	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1776	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1413	but on wall clock time (absolute time). You can tell a periodic watcher	1777	relative time, the physical time that passes) but on wall clock time
1414	to trigger after some specific point in time. For example, if you tell a	1778	(absolute time, the thing you can read on your calender or clock). The
1415	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	1779	difference is that wall clock time can run faster or slower than real
1416	+ 10.>, that is, an absolute time not a delay) and then reset your system	1780	time, and time jumps are not uncommon (e.g. when you adjust your
1417	clock to January of the previous year, then it will take more than year	1781	wrist-watch).
1418	to trigger the event (unlike an C<ev_timer>, which would still trigger
1419	roughly 10 seconds later as it uses a relative timeout).
1420		1782
		1783	You can tell a periodic watcher to trigger after some specific point
		1784	in time: for example, if you tell a periodic watcher to trigger "in 10
		1785	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1786	not a delay) and then reset your system clock to January of the previous
		1787	year, then it will take a year or more to trigger the event (unlike an
		1788	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1789	it, as it uses a relative timeout).
		1790
1421	C<ev_periodic>s can also be used to implement vastly more complex timers,	1791	C<ev_periodic> watchers can also be used to implement vastly more complex
1422	such as triggering an event on each "midnight, local time", or other	1792	timers, such as triggering an event on each "midnight, local time", or
1423	complicated rules.	1793	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1794	those cannot react to time jumps.
1424		1795
1425	As with timers, the callback is guaranteed to be invoked only when the	1796	As with timers, the callback is guaranteed to be invoked only when the
1426	time (C<at>) has passed, but if multiple periodic timers become ready	1797	point in time where it is supposed to trigger has passed. If multiple
1427	during the same loop iteration, then order of execution is undefined.	1798	timers become ready during the same loop iteration then the ones with
		1799	earlier time-out values are invoked before ones with later time-out values
		1800	(but this is no longer true when a callback calls C<ev_loop> recursively).
1428		1801
1429	=head3 Watcher-Specific Functions and Data Members	1802	=head3 Watcher-Specific Functions and Data Members
1430		1803
1431	=over 4	1804	=over 4
1432		1805
1433	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1806	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1434		1807
1435	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1808	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1436		1809
1437	Lots of arguments, lets sort it out... There are basically three modes of	1810	Lots of arguments, let's sort it out... There are basically three modes of
1438	operation, and we will explain them from simplest to most complex:	1811	operation, and we will explain them from simplest to most complex:
1439		1812
1440	=over 4	1813	=over 4
1441		1814
1442	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1815	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1443		1816
1444	In this configuration the watcher triggers an event after the wall clock	1817	In this configuration the watcher triggers an event after the wall clock
1445	time C<at> has passed. It will not repeat and will not adjust when a time	1818	time C<offset> has passed. It will not repeat and will not adjust when a
1446	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1819	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1447	only run when the system clock reaches or surpasses this time.	1820	will be stopped and invoked when the system clock reaches or surpasses
		1821	this point in time.
1448		1822
1449	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1823	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1450		1824
1451	In this mode the watcher will always be scheduled to time out at the next	1825	In this mode the watcher will always be scheduled to time out at the next
1452	C<at + N * interval> time (for some integer N, which can also be negative)	1826	C<offset + N * interval> time (for some integer N, which can also be
1453	and then repeat, regardless of any time jumps.	1827	negative) and then repeat, regardless of any time jumps. The C<offset>
		1828	argument is merely an offset into the C<interval> periods.
1454		1829
1455	This can be used to create timers that do not drift with respect to the	1830	This can be used to create timers that do not drift with respect to the
1456	system clock, for example, here is a C<ev_periodic> that triggers each	1831	system clock, for example, here is an C<ev_periodic> that triggers each
1457	hour, on the hour:	1832	hour, on the hour (with respect to UTC):
1458		1833
1459	ev_periodic_set (&periodic, 0., 3600., 0);	1834	ev_periodic_set (&periodic, 0., 3600., 0);
1460		1835
1461	This doesn't mean there will always be 3600 seconds in between triggers,	1836	This doesn't mean there will always be 3600 seconds in between triggers,
1462	but only that the callback will be called when the system time shows a	1837	but only that the callback will be called when the system time shows a
1463	full hour (UTC), or more correctly, when the system time is evenly divisible	1838	full hour (UTC), or more correctly, when the system time is evenly divisible
1464	by 3600.	1839	by 3600.
1465		1840
1466	Another way to think about it (for the mathematically inclined) is that	1841	Another way to think about it (for the mathematically inclined) is that
1467	C<ev_periodic> will try to run the callback in this mode at the next possible	1842	C<ev_periodic> will try to run the callback in this mode at the next possible
1468	time where C<time = at (mod interval)>, regardless of any time jumps.	1843	time where C<time = offset (mod interval)>, regardless of any time jumps.
1469		1844
1470	For numerical stability it is preferable that the C<at> value is near	1845	For numerical stability it is preferable that the C<offset> value is near
1471	C<ev_now ()> (the current time), but there is no range requirement for	1846	C<ev_now ()> (the current time), but there is no range requirement for
1472	this value, and in fact is often specified as zero.	1847	this value, and in fact is often specified as zero.
1473		1848
1474	Note also that there is an upper limit to how often a timer can fire (CPU	1849	Note also that there is an upper limit to how often a timer can fire (CPU
1475	speed for example), so if C<interval> is very small then timing stability	1850	speed for example), so if C<interval> is very small then timing stability
1476	will of course deteriorate. Libev itself tries to be exact to be about one	1851	will of course deteriorate. Libev itself tries to be exact to be about one
1477	millisecond (if the OS supports it and the machine is fast enough).	1852	millisecond (if the OS supports it and the machine is fast enough).
1478		1853
1479	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1854	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1480		1855
1481	In this mode the values for C<interval> and C<at> are both being	1856	In this mode the values for C<interval> and C<offset> are both being
1482	ignored. Instead, each time the periodic watcher gets scheduled, the	1857	ignored. Instead, each time the periodic watcher gets scheduled, the
1483	reschedule callback will be called with the watcher as first, and the	1858	reschedule callback will be called with the watcher as first, and the
1484	current time as second argument.	1859	current time as second argument.
1485		1860
1486	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1861	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1487	ever, or make ANY event loop modifications whatsoever>.	1862	or make ANY other event loop modifications whatsoever, unless explicitly
		1863	allowed by documentation here>.
1488		1864
1489	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1865	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1490	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	1866	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1491	only event loop modification you are allowed to do).	1867	only event loop modification you are allowed to do).
1492		1868
1493	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1869	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1494	*w, ev_tstamp now)>, e.g.:	1870	*w, ev_tstamp now)>, e.g.:
1495		1871
		1872	static ev_tstamp
1496	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1873	my_rescheduler (ev_periodic *w, ev_tstamp now)
1497	{	1874	{
1498	return now + 60.;	1875	return now + 60.;
1499	}	1876	}
1500		1877
1501	It must return the next time to trigger, based on the passed time value	1878	It must return the next time to trigger, based on the passed time value
…		…
1521	a different time than the last time it was called (e.g. in a crond like	1898	a different time than the last time it was called (e.g. in a crond like
1522	program when the crontabs have changed).	1899	program when the crontabs have changed).
1523		1900
1524	=item ev_tstamp ev_periodic_at (ev_periodic *)	1901	=item ev_tstamp ev_periodic_at (ev_periodic *)
1525		1902
1526	When active, returns the absolute time that the watcher is supposed to	1903	When active, returns the absolute time that the watcher is supposed
1527	trigger next.	1904	to trigger next. This is not the same as the C<offset> argument to
		1905	C<ev_periodic_set>, but indeed works even in interval and manual
		1906	rescheduling modes.
1528		1907
1529	=item ev_tstamp offset [read-write]	1908	=item ev_tstamp offset [read-write]
1530		1909
1531	When repeating, this contains the offset value, otherwise this is the	1910	When repeating, this contains the offset value, otherwise this is the
1532	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1911	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		1912	although libev might modify this value for better numerical stability).
1533		1913
1534	Can be modified any time, but changes only take effect when the periodic	1914	Can be modified any time, but changes only take effect when the periodic
1535	timer fires or C<ev_periodic_again> is being called.	1915	timer fires or C<ev_periodic_again> is being called.
1536		1916
1537	=item ev_tstamp interval [read-write]	1917	=item ev_tstamp interval [read-write]
1538		1918
1539	The current interval value. Can be modified any time, but changes only	1919	The current interval value. Can be modified any time, but changes only
1540	take effect when the periodic timer fires or C<ev_periodic_again> is being	1920	take effect when the periodic timer fires or C<ev_periodic_again> is being
1541	called.	1921	called.
1542		1922
1543	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1923	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1544		1924
1545	The current reschedule callback, or C<0>, if this functionality is	1925	The current reschedule callback, or C<0>, if this functionality is
1546	switched off. Can be changed any time, but changes only take effect when	1926	switched off. Can be changed any time, but changes only take effect when
1547	the periodic timer fires or C<ev_periodic_again> is being called.	1927	the periodic timer fires or C<ev_periodic_again> is being called.
1548		1928
…		…
1553	Example: Call a callback every hour, or, more precisely, whenever the	1933	Example: Call a callback every hour, or, more precisely, whenever the
1554	system time is divisible by 3600. The callback invocation times have	1934	system time is divisible by 3600. The callback invocation times have
1555	potentially a lot of jitter, but good long-term stability.	1935	potentially a lot of jitter, but good long-term stability.
1556		1936
1557	static void	1937	static void
1558	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1938	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1559	{	1939	{
1560	... its now a full hour (UTC, or TAI or whatever your clock follows)	1940	... its now a full hour (UTC, or TAI or whatever your clock follows)
1561	}	1941	}
1562		1942
1563	struct ev_periodic hourly_tick;	1943	ev_periodic hourly_tick;
1564	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1944	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1565	ev_periodic_start (loop, &hourly_tick);	1945	ev_periodic_start (loop, &hourly_tick);
1566		1946
1567	Example: The same as above, but use a reschedule callback to do it:	1947	Example: The same as above, but use a reschedule callback to do it:
1568		1948
1569	#include <math.h>	1949	#include <math.h>
1570		1950
1571	static ev_tstamp	1951	static ev_tstamp
1572	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1952	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1573	{	1953	{
1574	return now + (3600. - fmod (now, 3600.));	1954	return now + (3600. - fmod (now, 3600.));
1575	}	1955	}
1576		1956
1577	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1957	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1578		1958
1579	Example: Call a callback every hour, starting now:	1959	Example: Call a callback every hour, starting now:
1580		1960
1581	struct ev_periodic hourly_tick;	1961	ev_periodic hourly_tick;
1582	ev_periodic_init (&hourly_tick, clock_cb,	1962	ev_periodic_init (&hourly_tick, clock_cb,
1583	fmod (ev_now (loop), 3600.), 3600., 0);	1963	fmod (ev_now (loop), 3600.), 3600., 0);
1584	ev_periodic_start (loop, &hourly_tick);	1964	ev_periodic_start (loop, &hourly_tick);
1585		1965
1586		1966
…		…
1625		2005
1626	=back	2006	=back
1627		2007
1628	=head3 Examples	2008	=head3 Examples
1629		2009
1630	Example: Try to exit cleanly on SIGINT and SIGTERM.	2010	Example: Try to exit cleanly on SIGINT.
1631		2011
1632	static void	2012	static void
1633	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2013	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1634	{	2014	{
1635	ev_unloop (loop, EVUNLOOP_ALL);	2015	ev_unloop (loop, EVUNLOOP_ALL);
1636	}	2016	}
1637		2017
1638	struct ev_signal signal_watcher;	2018	ev_signal signal_watcher;
1639	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2019	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1640	ev_signal_start (loop, &sigint_cb);	2020	ev_signal_start (loop, &signal_watcher);
1641		2021
1642		2022
1643	=head2 C<ev_child> - watch out for process status changes	2023	=head2 C<ev_child> - watch out for process status changes
1644		2024
1645	Child watchers trigger when your process receives a SIGCHLD in response to	2025	Child watchers trigger when your process receives a SIGCHLD in response to
1646	some child status changes (most typically when a child of yours dies or	2026	some child status changes (most typically when a child of yours dies or
1647	exits). It is permissible to install a child watcher I<after> the child	2027	exits). It is permissible to install a child watcher I<after> the child
1648	has been forked (which implies it might have already exited), as long	2028	has been forked (which implies it might have already exited), as long
1649	as the event loop isn't entered (or is continued from a watcher), i.e.,	2029	as the event loop isn't entered (or is continued from a watcher), i.e.,
1650	forking and then immediately registering a watcher for the child is fine,	2030	forking and then immediately registering a watcher for the child is fine,
1651	but forking and registering a watcher a few event loop iterations later is	2031	but forking and registering a watcher a few event loop iterations later or
1652	not.	2032	in the next callback invocation is not.
1653		2033
1654	Only the default event loop is capable of handling signals, and therefore	2034	Only the default event loop is capable of handling signals, and therefore
1655	you can only register child watchers in the default event loop.	2035	you can only register child watchers in the default event loop.
1656		2036
1657	=head3 Process Interaction	2037	=head3 Process Interaction
…		…
1718	its completion.	2098	its completion.
1719		2099
1720	ev_child cw;	2100	ev_child cw;
1721		2101
1722	static void	2102	static void
1723	child_cb (EV_P_ struct ev_child *w, int revents)	2103	child_cb (EV_P_ ev_child *w, int revents)
1724	{	2104	{
1725	ev_child_stop (EV_A_ w);	2105	ev_child_stop (EV_A_ w);
1726	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2106	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1727	}	2107	}
1728		2108
…		…
1743		2123
1744		2124
1745	=head2 C<ev_stat> - did the file attributes just change?	2125	=head2 C<ev_stat> - did the file attributes just change?
1746		2126
1747	This watches a file system path for attribute changes. That is, it calls	2127	This watches a file system path for attribute changes. That is, it calls
1748	C<stat> regularly (or when the OS says it changed) and sees if it changed	2128	C<stat> on that path in regular intervals (or when the OS says it changed)
1749	compared to the last time, invoking the callback if it did.	2129	and sees if it changed compared to the last time, invoking the callback if
		2130	it did.
1750		2131
1751	The path does not need to exist: changing from "path exists" to "path does	2132	The path does not need to exist: changing from "path exists" to "path does
1752	not exist" is a status change like any other. The condition "path does	2133	not exist" is a status change like any other. The condition "path does not
1753	not exist" is signified by the C<st_nlink> field being zero (which is	2134	exist" (or more correctly "path cannot be stat'ed") is signified by the
1754	otherwise always forced to be at least one) and all the other fields of	2135	C<st_nlink> field being zero (which is otherwise always forced to be at
1755	the stat buffer having unspecified contents.	2136	least one) and all the other fields of the stat buffer having unspecified
		2137	contents.
1756		2138
1757	The path I<should> be absolute and I<must not> end in a slash. If it is	2139	The path I<must not> end in a slash or contain special components such as
		2140	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1758	relative and your working directory changes, the behaviour is undefined.	2141	your working directory changes, then the behaviour is undefined.
1759		2142
1760	Since there is no standard kernel interface to do this, the portable	2143	Since there is no portable change notification interface available, the
1761	implementation simply calls C<stat (2)> regularly on the path to see if	2144	portable implementation simply calls C<stat(2)> regularly on the path
1762	it changed somehow. You can specify a recommended polling interval for	2145	to see if it changed somehow. You can specify a recommended polling
1763	this case. If you specify a polling interval of C<0> (highly recommended!)	2146	interval for this case. If you specify a polling interval of C<0> (highly
1764	then a I<suitable, unspecified default> value will be used (which	2147	recommended!) then a I<suitable, unspecified default> value will be used
1765	you can expect to be around five seconds, although this might change	2148	(which you can expect to be around five seconds, although this might
1766	dynamically). Libev will also impose a minimum interval which is currently	2149	change dynamically). Libev will also impose a minimum interval which is
1767	around C<0.1>, but thats usually overkill.	2150	currently around C<0.1>, but that's usually overkill.
1768		2151
1769	This watcher type is not meant for massive numbers of stat watchers,	2152	This watcher type is not meant for massive numbers of stat watchers,
1770	as even with OS-supported change notifications, this can be	2153	as even with OS-supported change notifications, this can be
1771	resource-intensive.	2154	resource-intensive.
1772		2155
1773	At the time of this writing, the only OS-specific interface implemented	2156	At the time of this writing, the only OS-specific interface implemented
1774	is the Linux inotify interface (implementing kqueue support is left as	2157	is the Linux inotify interface (implementing kqueue support is left as an
1775	an exercise for the reader. Note, however, that the author sees no way	2158	exercise for the reader. Note, however, that the author sees no way of
1776	of implementing C<ev_stat> semantics with kqueue).	2159	implementing C<ev_stat> semantics with kqueue, except as a hint).
1777		2160
1778	=head3 ABI Issues (Largefile Support)	2161	=head3 ABI Issues (Largefile Support)
1779		2162
1780	Libev by default (unless the user overrides this) uses the default	2163	Libev by default (unless the user overrides this) uses the default
1781	compilation environment, which means that on systems with large file	2164	compilation environment, which means that on systems with large file
1782	support disabled by default, you get the 32 bit version of the stat	2165	support disabled by default, you get the 32 bit version of the stat
1783	structure. When using the library from programs that change the ABI to	2166	structure. When using the library from programs that change the ABI to
1784	use 64 bit file offsets the programs will fail. In that case you have to	2167	use 64 bit file offsets the programs will fail. In that case you have to
1785	compile libev with the same flags to get binary compatibility. This is	2168	compile libev with the same flags to get binary compatibility. This is
1786	obviously the case with any flags that change the ABI, but the problem is	2169	obviously the case with any flags that change the ABI, but the problem is
1787	most noticeably disabled with ev_stat and large file support.	2170	most noticeably displayed with ev_stat and large file support.
1788		2171
1789	The solution for this is to lobby your distribution maker to make large	2172	The solution for this is to lobby your distribution maker to make large
1790	file interfaces available by default (as e.g. FreeBSD does) and not	2173	file interfaces available by default (as e.g. FreeBSD does) and not
1791	optional. Libev cannot simply switch on large file support because it has	2174	optional. Libev cannot simply switch on large file support because it has
1792	to exchange stat structures with application programs compiled using the	2175	to exchange stat structures with application programs compiled using the
1793	default compilation environment.	2176	default compilation environment.
1794		2177
1795	=head3 Inotify and Kqueue	2178	=head3 Inotify and Kqueue
1796		2179
1797	When C<inotify (7)> support has been compiled into libev (generally only	2180	When C<inotify (7)> support has been compiled into libev and present at
1798	available with Linux) and present at runtime, it will be used to speed up	2181	runtime, it will be used to speed up change detection where possible. The
1799	change detection where possible. The inotify descriptor will be created lazily	2182	inotify descriptor will be created lazily when the first C<ev_stat>
1800	when the first C<ev_stat> watcher is being started.	2183	watcher is being started.
1801		2184
1802	Inotify presence does not change the semantics of C<ev_stat> watchers	2185	Inotify presence does not change the semantics of C<ev_stat> watchers
1803	except that changes might be detected earlier, and in some cases, to avoid	2186	except that changes might be detected earlier, and in some cases, to avoid
1804	making regular C<stat> calls. Even in the presence of inotify support	2187	making regular C<stat> calls. Even in the presence of inotify support
1805	there are many cases where libev has to resort to regular C<stat> polling,	2188	there are many cases where libev has to resort to regular C<stat> polling,
1806	but as long as the path exists, libev usually gets away without polling.	2189	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2190	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2191	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2192	xfs are fully working) libev usually gets away without polling.
1807		2193
1808	There is no support for kqueue, as apparently it cannot be used to	2194	There is no support for kqueue, as apparently it cannot be used to
1809	implement this functionality, due to the requirement of having a file	2195	implement this functionality, due to the requirement of having a file
1810	descriptor open on the object at all times, and detecting renames, unlinks	2196	descriptor open on the object at all times, and detecting renames, unlinks
1811	etc. is difficult.	2197	etc. is difficult.
1812		2198
		2199	=head3 C<stat ()> is a synchronous operation
		2200
		2201	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2202	the process. The exception are C<ev_stat> watchers - those call C<stat
		2203	()>, which is a synchronous operation.
		2204
		2205	For local paths, this usually doesn't matter: unless the system is very
		2206	busy or the intervals between stat's are large, a stat call will be fast,
		2207	as the path data is usually in memory already (except when starting the
		2208	watcher).
		2209
		2210	For networked file systems, calling C<stat ()> can block an indefinite
		2211	time due to network issues, and even under good conditions, a stat call
		2212	often takes multiple milliseconds.
		2213
		2214	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2215	paths, although this is fully supported by libev.
		2216
1813	=head3 The special problem of stat time resolution	2217	=head3 The special problem of stat time resolution
1814		2218
1815	The C<stat ()> system call only supports full-second resolution portably, and	2219	The C<stat ()> system call only supports full-second resolution portably,
1816	even on systems where the resolution is higher, most file systems still	2220	and even on systems where the resolution is higher, most file systems
1817	only support whole seconds.	2221	still only support whole seconds.
1818		2222
1819	That means that, if the time is the only thing that changes, you can	2223	That means that, if the time is the only thing that changes, you can
1820	easily miss updates: on the first update, C<ev_stat> detects a change and	2224	easily miss updates: on the first update, C<ev_stat> detects a change and
1821	calls your callback, which does something. When there is another update	2225	calls your callback, which does something. When there is another update
1822	within the same second, C<ev_stat> will be unable to detect unless the	2226	within the same second, C<ev_stat> will be unable to detect unless the
…		…
1965		2369
1966	=head3 Watcher-Specific Functions and Data Members	2370	=head3 Watcher-Specific Functions and Data Members
1967		2371
1968	=over 4	2372	=over 4
1969		2373
1970	=item ev_idle_init (ev_signal *, callback)	2374	=item ev_idle_init (ev_idle *, callback)
1971		2375
1972	Initialises and configures the idle watcher - it has no parameters of any	2376	Initialises and configures the idle watcher - it has no parameters of any
1973	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2377	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1974	believe me.	2378	believe me.
1975		2379
…		…
1979		2383
1980	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2384	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1981	callback, free it. Also, use no error checking, as usual.	2385	callback, free it. Also, use no error checking, as usual.
1982		2386
1983	static void	2387	static void
1984	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2388	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1985	{	2389	{
1986	free (w);	2390	free (w);
1987	// now do something you wanted to do when the program has	2391	// now do something you wanted to do when the program has
1988	// no longer anything immediate to do.	2392	// no longer anything immediate to do.
1989	}	2393	}
1990		2394
1991	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2395	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1992	ev_idle_init (idle_watcher, idle_cb);	2396	ev_idle_init (idle_watcher, idle_cb);
1993	ev_idle_start (loop, idle_cb);	2397	ev_idle_start (loop, idle_watcher);
1994		2398
1995		2399
1996	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2400	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1997		2401
1998	Prepare and check watchers are usually (but not always) used in pairs:	2402	Prepare and check watchers are usually (but not always) used in pairs:
…		…
2077		2481
2078	static ev_io iow [nfd];	2482	static ev_io iow [nfd];
2079	static ev_timer tw;	2483	static ev_timer tw;
2080		2484
2081	static void	2485	static void
2082	io_cb (ev_loop *loop, ev_io *w, int revents)	2486	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2083	{	2487	{
2084	}	2488	}
2085		2489
2086	// create io watchers for each fd and a timer before blocking	2490	// create io watchers for each fd and a timer before blocking
2087	static void	2491	static void
2088	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2492	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2089	{	2493	{
2090	int timeout = 3600000;	2494	int timeout = 3600000;
2091	struct pollfd fds [nfd];	2495	struct pollfd fds [nfd];
2092	// actual code will need to loop here and realloc etc.	2496	// actual code will need to loop here and realloc etc.
2093	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2497	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2094		2498
2095	/* the callback is illegal, but won't be called as we stop during check */	2499	/* the callback is illegal, but won't be called as we stop during check */
2096	ev_timer_init (&tw, 0, timeout * 1e-3);	2500	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2097	ev_timer_start (loop, &tw);	2501	ev_timer_start (loop, &tw);
2098		2502
2099	// create one ev_io per pollfd	2503	// create one ev_io per pollfd
2100	for (int i = 0; i < nfd; ++i)	2504	for (int i = 0; i < nfd; ++i)
2101	{	2505	{
…		…
2108	}	2512	}
2109	}	2513	}
2110		2514
2111	// stop all watchers after blocking	2515	// stop all watchers after blocking
2112	static void	2516	static void
2113	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2517	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2114	{	2518	{
2115	ev_timer_stop (loop, &tw);	2519	ev_timer_stop (loop, &tw);
2116		2520
2117	for (int i = 0; i < nfd; ++i)	2521	for (int i = 0; i < nfd; ++i)
2118	{	2522	{
…		…
2214	some fds have to be watched and handled very quickly (with low latency),	2618	some fds have to be watched and handled very quickly (with low latency),
2215	and even priorities and idle watchers might have too much overhead. In	2619	and even priorities and idle watchers might have too much overhead. In
2216	this case you would put all the high priority stuff in one loop and all	2620	this case you would put all the high priority stuff in one loop and all
2217	the rest in a second one, and embed the second one in the first.	2621	the rest in a second one, and embed the second one in the first.
2218		2622
2219	As long as the watcher is active, the callback will be invoked every time	2623	As long as the watcher is active, the callback will be invoked every
2220	there might be events pending in the embedded loop. The callback must then	2624	time there might be events pending in the embedded loop. The callback
2221	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2625	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2222	their callbacks (you could also start an idle watcher to give the embedded	2626	sweep and invoke their callbacks (the callback doesn't need to invoke the
2223	loop strictly lower priority for example). You can also set the callback	2627	C<ev_embed_sweep> function directly, it could also start an idle watcher
2224	to C<0>, in which case the embed watcher will automatically execute the	2628	to give the embedded loop strictly lower priority for example).
2225	embedded loop sweep.
2226		2629
2227	As long as the watcher is started it will automatically handle events. The	2630	You can also set the callback to C<0>, in which case the embed watcher
2228	callback will be invoked whenever some events have been handled. You can	2631	will automatically execute the embedded loop sweep whenever necessary.
2229	set the callback to C<0> to avoid having to specify one if you are not
2230	interested in that.
2231		2632
2232	Also, there have not currently been made special provisions for forking:	2633	Fork detection will be handled transparently while the C<ev_embed> watcher
2233	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2634	is active, i.e., the embedded loop will automatically be forked when the
2234	but you will also have to stop and restart any C<ev_embed> watchers	2635	embedding loop forks. In other cases, the user is responsible for calling
2235	yourself - but you can use a fork watcher to handle this automatically,	2636	C<ev_loop_fork> on the embedded loop.
2236	and future versions of libev might do just that.
2237		2637
2238	Unfortunately, not all backends are embeddable: only the ones returned by	2638	Unfortunately, not all backends are embeddable: only the ones returned by
2239	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2639	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2240	portable one.	2640	portable one.
2241		2641
…		…
2286	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2686	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2287	used).	2687	used).
2288		2688
2289	struct ev_loop *loop_hi = ev_default_init (0);	2689	struct ev_loop *loop_hi = ev_default_init (0);
2290	struct ev_loop *loop_lo = 0;	2690	struct ev_loop *loop_lo = 0;
2291	struct ev_embed embed;	2691	ev_embed embed;
2292		2692
2293	// see if there is a chance of getting one that works	2693	// see if there is a chance of getting one that works
2294	// (remember that a flags value of 0 means autodetection)	2694	// (remember that a flags value of 0 means autodetection)
2295	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2695	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2296	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2696	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2310	kqueue implementation). Store the kqueue/socket-only event loop in	2710	kqueue implementation). Store the kqueue/socket-only event loop in
2311	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2711	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2312		2712
2313	struct ev_loop *loop = ev_default_init (0);	2713	struct ev_loop *loop = ev_default_init (0);
2314	struct ev_loop *loop_socket = 0;	2714	struct ev_loop *loop_socket = 0;
2315	struct ev_embed embed;	2715	ev_embed embed;
2316		2716
2317	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2717	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2318	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2718	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2319	{	2719	{
2320	ev_embed_init (&embed, 0, loop_socket);	2720	ev_embed_init (&embed, 0, loop_socket);
…		…
2335	event loop blocks next and before C<ev_check> watchers are being called,	2735	event loop blocks next and before C<ev_check> watchers are being called,
2336	and only in the child after the fork. If whoever good citizen calling	2736	and only in the child after the fork. If whoever good citizen calling
2337	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2737	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2338	handlers will be invoked, too, of course.	2738	handlers will be invoked, too, of course.
2339		2739
		2740	=head3 The special problem of life after fork - how is it possible?
		2741
		2742	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2743	up/change the process environment, followed by a call to C<exec()>. This
		2744	sequence should be handled by libev without any problems.
		2745
		2746	This changes when the application actually wants to do event handling
		2747	in the child, or both parent in child, in effect "continuing" after the
		2748	fork.
		2749
		2750	The default mode of operation (for libev, with application help to detect
		2751	forks) is to duplicate all the state in the child, as would be expected
		2752	when I<either> the parent I<or> the child process continues.
		2753
		2754	When both processes want to continue using libev, then this is usually the
		2755	wrong result. In that case, usually one process (typically the parent) is
		2756	supposed to continue with all watchers in place as before, while the other
		2757	process typically wants to start fresh, i.e. without any active watchers.
		2758
		2759	The cleanest and most efficient way to achieve that with libev is to
		2760	simply create a new event loop, which of course will be "empty", and
		2761	use that for new watchers. This has the advantage of not touching more
		2762	memory than necessary, and thus avoiding the copy-on-write, and the
		2763	disadvantage of having to use multiple event loops (which do not support
		2764	signal watchers).
		2765
		2766	When this is not possible, or you want to use the default loop for
		2767	other reasons, then in the process that wants to start "fresh", call
		2768	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2769	the default loop will "orphan" (not stop) all registered watchers, so you
		2770	have to be careful not to execute code that modifies those watchers. Note
		2771	also that in that case, you have to re-register any signal watchers.
		2772
2340	=head3 Watcher-Specific Functions and Data Members	2773	=head3 Watcher-Specific Functions and Data Members
2341		2774
2342	=over 4	2775	=over 4
2343		2776
2344	=item ev_fork_init (ev_signal *, callback)	2777	=item ev_fork_init (ev_signal *, callback)
…		…
2384	=over 4	2817	=over 4
2385		2818
2386	=item queueing from a signal handler context	2819	=item queueing from a signal handler context
2387		2820
2388	To implement race-free queueing, you simply add to the queue in the signal	2821	To implement race-free queueing, you simply add to the queue in the signal
2389	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2822	handler but you block the signal handler in the watcher callback. Here is
2390	some fictitious SIGUSR1 handler:	2823	an example that does that for some fictitious SIGUSR1 handler:
2391		2824
2392	static ev_async mysig;	2825	static ev_async mysig;
2393		2826
2394	static void	2827	static void
2395	sigusr1_handler (void)	2828	sigusr1_handler (void)
…		…
2461	=over 4	2894	=over 4
2462		2895
2463	=item ev_async_init (ev_async *, callback)	2896	=item ev_async_init (ev_async *, callback)
2464		2897
2465	Initialises and configures the async watcher - it has no parameters of any	2898	Initialises and configures the async watcher - it has no parameters of any
2466	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2899	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2467	trust me.	2900	trust me.
2468		2901
2469	=item ev_async_send (loop, ev_async *)	2902	=item ev_async_send (loop, ev_async *)
2470		2903
2471	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2904	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2472	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2905	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2473	C<ev_feed_event>, this call is safe to do from other threads, signal or	2906	C<ev_feed_event>, this call is safe to do from other threads, signal or
2474	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	2907	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2475	section below on what exactly this means).	2908	section below on what exactly this means).
2476		2909
		2910	Note that, as with other watchers in libev, multiple events might get
		2911	compressed into a single callback invocation (another way to look at this
		2912	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		2913	reset when the event loop detects that).
		2914
2477	This call incurs the overhead of a system call only once per loop iteration,	2915	This call incurs the overhead of a system call only once per event loop
2478	so while the overhead might be noticeable, it doesn't apply to repeated	2916	iteration, so while the overhead might be noticeable, it doesn't apply to
2479	calls to C<ev_async_send>.	2917	repeated calls to C<ev_async_send> for the same event loop.
2480		2918
2481	=item bool = ev_async_pending (ev_async *)	2919	=item bool = ev_async_pending (ev_async *)
2482		2920
2483	Returns a non-zero value when C<ev_async_send> has been called on the	2921	Returns a non-zero value when C<ev_async_send> has been called on the
2484	watcher but the event has not yet been processed (or even noted) by the	2922	watcher but the event has not yet been processed (or even noted) by the
…		…
2487	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	2925	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2488	the loop iterates next and checks for the watcher to have become active,	2926	the loop iterates next and checks for the watcher to have become active,
2489	it will reset the flag again. C<ev_async_pending> can be used to very	2927	it will reset the flag again. C<ev_async_pending> can be used to very
2490	quickly check whether invoking the loop might be a good idea.	2928	quickly check whether invoking the loop might be a good idea.
2491		2929
2492	Not that this does I<not> check whether the watcher itself is pending, only	2930	Not that this does I<not> check whether the watcher itself is pending,
2493	whether it has been requested to make this watcher pending.	2931	only whether it has been requested to make this watcher pending: there
		2932	is a time window between the event loop checking and resetting the async
		2933	notification, and the callback being invoked.
2494		2934
2495	=back	2935	=back
2496		2936
2497		2937
2498	=head1 OTHER FUNCTIONS	2938	=head1 OTHER FUNCTIONS
…		…
2502	=over 4	2942	=over 4
2503		2943
2504	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2944	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2505		2945
2506	This function combines a simple timer and an I/O watcher, calls your	2946	This function combines a simple timer and an I/O watcher, calls your
2507	callback on whichever event happens first and automatically stop both	2947	callback on whichever event happens first and automatically stops both
2508	watchers. This is useful if you want to wait for a single event on an fd	2948	watchers. This is useful if you want to wait for a single event on an fd
2509	or timeout without having to allocate/configure/start/stop/free one or	2949	or timeout without having to allocate/configure/start/stop/free one or
2510	more watchers yourself.	2950	more watchers yourself.
2511		2951
2512	If C<fd> is less than 0, then no I/O watcher will be started and events	2952	If C<fd> is less than 0, then no I/O watcher will be started and the
2513	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2953	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2514	C<events> set will be created and started.	2954	the given C<fd> and C<events> set will be created and started.
2515		2955
2516	If C<timeout> is less than 0, then no timeout watcher will be	2956	If C<timeout> is less than 0, then no timeout watcher will be
2517	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2957	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2518	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2958	repeat = 0) will be started. C<0> is a valid timeout.
2519	dubious value.
2520		2959
2521	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2960	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2522	passed an C<revents> set like normal event callbacks (a combination of	2961	passed an C<revents> set like normal event callbacks (a combination of
2523	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2962	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2524	value passed to C<ev_once>:	2963	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2964	a timeout and an io event at the same time - you probably should give io
		2965	events precedence.
		2966
		2967	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2525		2968
2526	static void stdin_ready (int revents, void *arg)	2969	static void stdin_ready (int revents, void *arg)
2527	{	2970	{
		2971	if (revents & EV_READ)
		2972	/* stdin might have data for us, joy! */;
2528	if (revents & EV_TIMEOUT)	2973	else if (revents & EV_TIMEOUT)
2529	/* doh, nothing entered */;	2974	/* doh, nothing entered */;
2530	else if (revents & EV_READ)
2531	/* stdin might have data for us, joy! */;
2532	}	2975	}
2533		2976
2534	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2977	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2535		2978
2536	=item ev_feed_event (ev_loop *, watcher *, int revents)	2979	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2537		2980
2538	Feeds the given event set into the event loop, as if the specified event	2981	Feeds the given event set into the event loop, as if the specified event
2539	had happened for the specified watcher (which must be a pointer to an	2982	had happened for the specified watcher (which must be a pointer to an
2540	initialised but not necessarily started event watcher).	2983	initialised but not necessarily started event watcher).
2541		2984
2542	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2985	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2543		2986
2544	Feed an event on the given fd, as if a file descriptor backend detected	2987	Feed an event on the given fd, as if a file descriptor backend detected
2545	the given events it.	2988	the given events it.
2546		2989
2547	=item ev_feed_signal_event (ev_loop *loop, int signum)	2990	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2548		2991
2549	Feed an event as if the given signal occurred (C<loop> must be the default	2992	Feed an event as if the given signal occurred (C<loop> must be the default
2550	loop!).	2993	loop!).
2551		2994
2552	=back	2995	=back
…		…
2673	}	3116	}
2674		3117
2675	myclass obj;	3118	myclass obj;
2676	ev::io iow;	3119	ev::io iow;
2677	iow.set <myclass, &myclass::io_cb> (&obj);	3120	iow.set <myclass, &myclass::io_cb> (&obj);
		3121
		3122	=item w->set (object *)
		3123
		3124	This is an B<experimental> feature that might go away in a future version.
		3125
		3126	This is a variation of a method callback - leaving out the method to call
		3127	will default the method to C<operator ()>, which makes it possible to use
		3128	functor objects without having to manually specify the C<operator ()> all
		3129	the time. Incidentally, you can then also leave out the template argument
		3130	list.
		3131
		3132	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3133	int revents)>.
		3134
		3135	See the method-C<set> above for more details.
		3136
		3137	Example: use a functor object as callback.
		3138
		3139	struct myfunctor
		3140	{
		3141	void operator() (ev::io &w, int revents)
		3142	{
		3143	...
		3144	}
		3145	}
		3146
		3147	myfunctor f;
		3148
		3149	ev::io w;
		3150	w.set (&f);
2678		3151
2679	=item w->set<function> (void *data = 0)	3152	=item w->set<function> (void *data = 0)
2680		3153
2681	Also sets a callback, but uses a static method or plain function as	3154	Also sets a callback, but uses a static method or plain function as
2682	callback. The optional C<data> argument will be stored in the watcher's	3155	callback. The optional C<data> argument will be stored in the watcher's
…		…
2769	L<http://software.schmorp.de/pkg/EV>.	3242	L<http://software.schmorp.de/pkg/EV>.
2770		3243
2771	=item Python	3244	=item Python
2772		3245
2773	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3246	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2774	seems to be quite complete and well-documented. Note, however, that the	3247	seems to be quite complete and well-documented.
2775	patch they require for libev is outright dangerous as it breaks the ABI
2776	for everybody else, and therefore, should never be applied in an installed
2777	libev (if python requires an incompatible ABI then it needs to embed
2778	libev).
2779		3248
2780	=item Ruby	3249	=item Ruby
2781		3250
2782	Tony Arcieri has written a ruby extension that offers access to a subset	3251	Tony Arcieri has written a ruby extension that offers access to a subset
2783	of the libev API and adds file handle abstractions, asynchronous DNS and	3252	of the libev API and adds file handle abstractions, asynchronous DNS and
2784	more on top of it. It can be found via gem servers. Its homepage is at	3253	more on top of it. It can be found via gem servers. Its homepage is at
2785	L<http://rev.rubyforge.org/>.	3254	L<http://rev.rubyforge.org/>.
2786		3255
		3256	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3257	makes rev work even on mingw.
		3258
		3259	=item Haskell
		3260
		3261	A haskell binding to libev is available at
		3262	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3263
2787	=item D	3264	=item D
2788		3265
2789	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3266	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2790	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3267	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3268
		3269	=item Ocaml
		3270
		3271	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3272	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2791		3273
2792	=back	3274	=back
2793		3275
2794		3276
2795	=head1 MACRO MAGIC	3277	=head1 MACRO MAGIC
…		…
2896		3378
2897	#define EV_STANDALONE 1	3379	#define EV_STANDALONE 1
2898	#include "ev.h"	3380	#include "ev.h"
2899		3381
2900	Both header files and implementation files can be compiled with a C++	3382	Both header files and implementation files can be compiled with a C++
2901	compiler (at least, thats a stated goal, and breakage will be treated	3383	compiler (at least, that's a stated goal, and breakage will be treated
2902	as a bug).	3384	as a bug).
2903		3385
2904	You need the following files in your source tree, or in a directory	3386	You need the following files in your source tree, or in a directory
2905	in your include path (e.g. in libev/ when using -Ilibev):	3387	in your include path (e.g. in libev/ when using -Ilibev):
2906		3388
…		…
2962	keeps libev from including F<config.h>, and it also defines dummy	3444	keeps libev from including F<config.h>, and it also defines dummy
2963	implementations for some libevent functions (such as logging, which is not	3445	implementations for some libevent functions (such as logging, which is not
2964	supported). It will also not define any of the structs usually found in	3446	supported). It will also not define any of the structs usually found in
2965	F<event.h> that are not directly supported by the libev core alone.	3447	F<event.h> that are not directly supported by the libev core alone.
2966		3448
		3449	In stanbdalone mode, libev will still try to automatically deduce the
		3450	configuration, but has to be more conservative.
		3451
2967	=item EV_USE_MONOTONIC	3452	=item EV_USE_MONOTONIC
2968		3453
2969	If defined to be C<1>, libev will try to detect the availability of the	3454	If defined to be C<1>, libev will try to detect the availability of the
2970	monotonic clock option at both compile time and runtime. Otherwise no use	3455	monotonic clock option at both compile time and runtime. Otherwise no
2971	of the monotonic clock option will be attempted. If you enable this, you	3456	use of the monotonic clock option will be attempted. If you enable this,
2972	usually have to link against librt or something similar. Enabling it when	3457	you usually have to link against librt or something similar. Enabling it
2973	the functionality isn't available is safe, though, although you have	3458	when the functionality isn't available is safe, though, although you have
2974	to make sure you link against any libraries where the C<clock_gettime>	3459	to make sure you link against any libraries where the C<clock_gettime>
2975	function is hiding in (often F<-lrt>).	3460	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2976		3461
2977	=item EV_USE_REALTIME	3462	=item EV_USE_REALTIME
2978		3463
2979	If defined to be C<1>, libev will try to detect the availability of the	3464	If defined to be C<1>, libev will try to detect the availability of the
2980	real-time clock option at compile time (and assume its availability at	3465	real-time clock option at compile time (and assume its availability
2981	runtime if successful). Otherwise no use of the real-time clock option will	3466	at runtime if successful). Otherwise no use of the real-time clock
2982	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3467	option will be attempted. This effectively replaces C<gettimeofday>
2983	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3468	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2984	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3469	correctness. See the note about libraries in the description of
		3470	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3471	C<EV_USE_CLOCK_SYSCALL>.
		3472
		3473	=item EV_USE_CLOCK_SYSCALL
		3474
		3475	If defined to be C<1>, libev will try to use a direct syscall instead
		3476	of calling the system-provided C<clock_gettime> function. This option
		3477	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3478	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3479	programs needlessly. Using a direct syscall is slightly slower (in
		3480	theory), because no optimised vdso implementation can be used, but avoids
		3481	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3482	higher, as it simplifies linking (no need for C<-lrt>).
2985		3483
2986	=item EV_USE_NANOSLEEP	3484	=item EV_USE_NANOSLEEP
2987		3485
2988	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3486	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2989	and will use it for delays. Otherwise it will use C<select ()>.	3487	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3005		3503
3006	=item EV_SELECT_USE_FD_SET	3504	=item EV_SELECT_USE_FD_SET
3007		3505
3008	If defined to C<1>, then the select backend will use the system C<fd_set>	3506	If defined to C<1>, then the select backend will use the system C<fd_set>
3009	structure. This is useful if libev doesn't compile due to a missing	3507	structure. This is useful if libev doesn't compile due to a missing
3010	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3508	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3011	exotic systems. This usually limits the range of file descriptors to some	3509	on exotic systems. This usually limits the range of file descriptors to
3012	low limit such as 1024 or might have other limitations (winsocket only	3510	some low limit such as 1024 or might have other limitations (winsocket
3013	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3511	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3014	influence the size of the C<fd_set> used.	3512	configures the maximum size of the C<fd_set>.
3015		3513
3016	=item EV_SELECT_IS_WINSOCKET	3514	=item EV_SELECT_IS_WINSOCKET
3017		3515
3018	When defined to C<1>, the select backend will assume that	3516	When defined to C<1>, the select backend will assume that
3019	select/socket/connect etc. don't understand file descriptors but	3517	select/socket/connect etc. don't understand file descriptors but
…		…
3306	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3804	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3307		3805
3308	#include "ev_cpp.h"	3806	#include "ev_cpp.h"
3309	#include "ev.c"	3807	#include "ev.c"
3310		3808
		3809	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3311		3810
3312	=head1 THREADS AND COROUTINES	3811	=head2 THREADS AND COROUTINES
3313		3812
3314	=head2 THREADS	3813	=head3 THREADS
3315		3814
3316	All libev functions are reentrant and thread-safe unless explicitly	3815	All libev functions are reentrant and thread-safe unless explicitly
3317	documented otherwise, but it uses no locking itself. This means that you	3816	documented otherwise, but libev implements no locking itself. This means
3318	can use as many loops as you want in parallel, as long as there are no	3817	that you can use as many loops as you want in parallel, as long as there
3319	concurrent calls into any libev function with the same loop parameter	3818	are no concurrent calls into any libev function with the same loop
3320	(C<ev_default_*> calls have an implicit default loop parameter, of	3819	parameter (C<ev_default_*> calls have an implicit default loop parameter,
3321	course): libev guarantees that different event loops share no data	3820	of course): libev guarantees that different event loops share no data
3322	structures that need any locking.	3821	structures that need any locking.
3323		3822
3324	Or to put it differently: calls with different loop parameters can be done	3823	Or to put it differently: calls with different loop parameters can be done
3325	concurrently from multiple threads, calls with the same loop parameter	3824	concurrently from multiple threads, calls with the same loop parameter
3326	must be done serially (but can be done from different threads, as long as	3825	must be done serially (but can be done from different threads, as long as
…		…
3366	default loop and triggering an C<ev_async> watcher from the default loop	3865	default loop and triggering an C<ev_async> watcher from the default loop
3367	watcher callback into the event loop interested in the signal.	3866	watcher callback into the event loop interested in the signal.
3368		3867
3369	=back	3868	=back
3370		3869
3371	=head2 COROUTINES	3870	=head3 COROUTINES
3372		3871
3373	Libev is much more accommodating to coroutines ("cooperative threads"):	3872	Libev is very accommodating to coroutines ("cooperative threads"):
3374	libev fully supports nesting calls to it's functions from different	3873	libev fully supports nesting calls to its functions from different
3375	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3874	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3376	different coroutines and switch freely between both coroutines running the	3875	different coroutines, and switch freely between both coroutines running the
3377	loop, as long as you don't confuse yourself). The only exception is that	3876	loop, as long as you don't confuse yourself). The only exception is that
3378	you must not do this from C<ev_periodic> reschedule callbacks.	3877	you must not do this from C<ev_periodic> reschedule callbacks.
3379		3878
3380	Care has been taken to ensure that libev does not keep local state inside	3879	Care has been taken to ensure that libev does not keep local state inside
3381	C<ev_loop>, and other calls do not usually allow coroutine switches.	3880	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		3881	they do not call any callbacks.
3382		3882
		3883	=head2 COMPILER WARNINGS
3383		3884
3384	=head1 COMPLEXITIES	3885	Depending on your compiler and compiler settings, you might get no or a
		3886	lot of warnings when compiling libev code. Some people are apparently
		3887	scared by this.
3385		3888
3386	In this section the complexities of (many of) the algorithms used inside	3889	However, these are unavoidable for many reasons. For one, each compiler
3387	libev will be explained. For complexity discussions about backends see the	3890	has different warnings, and each user has different tastes regarding
3388	documentation for C<ev_default_init>.	3891	warning options. "Warn-free" code therefore cannot be a goal except when
		3892	targeting a specific compiler and compiler-version.
3389		3893
3390	All of the following are about amortised time: If an array needs to be	3894	Another reason is that some compiler warnings require elaborate
3391	extended, libev needs to realloc and move the whole array, but this	3895	workarounds, or other changes to the code that make it less clear and less
3392	happens asymptotically never with higher number of elements, so O(1) might	3896	maintainable.
3393	mean it might do a lengthy realloc operation in rare cases, but on average
3394	it is much faster and asymptotically approaches constant time.
3395		3897
3396	=over 4	3898	And of course, some compiler warnings are just plain stupid, or simply
		3899	wrong (because they don't actually warn about the condition their message
		3900	seems to warn about). For example, certain older gcc versions had some
		3901	warnings that resulted an extreme number of false positives. These have
		3902	been fixed, but some people still insist on making code warn-free with
		3903	such buggy versions.
3397		3904
3398	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3905	While libev is written to generate as few warnings as possible,
		3906	"warn-free" code is not a goal, and it is recommended not to build libev
		3907	with any compiler warnings enabled unless you are prepared to cope with
		3908	them (e.g. by ignoring them). Remember that warnings are just that:
		3909	warnings, not errors, or proof of bugs.
3399		3910
3400	This means that, when you have a watcher that triggers in one hour and
3401	there are 100 watchers that would trigger before that then inserting will
3402	have to skip roughly seven (C<ld 100>) of these watchers.
3403		3911
3404	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3912	=head2 VALGRIND
3405		3913
3406	That means that changing a timer costs less than removing/adding them	3914	Valgrind has a special section here because it is a popular tool that is
3407	as only the relative motion in the event queue has to be paid for.	3915	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3408		3916
3409	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3917	If you think you found a bug (memory leak, uninitialised data access etc.)
		3918	in libev, then check twice: If valgrind reports something like:
3410		3919
3411	These just add the watcher into an array or at the head of a list.	3920	==2274== definitely lost: 0 bytes in 0 blocks.
		3921	==2274== possibly lost: 0 bytes in 0 blocks.
		3922	==2274== still reachable: 256 bytes in 1 blocks.
3412		3923
3413	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3924	Then there is no memory leak, just as memory accounted to global variables
		3925	is not a memleak - the memory is still being referenced, and didn't leak.
3414		3926
3415	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3927	Similarly, under some circumstances, valgrind might report kernel bugs
		3928	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3929	although an acceptable workaround has been found here), or it might be
		3930	confused.
3416		3931
3417	These watchers are stored in lists then need to be walked to find the	3932	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3418	correct watcher to remove. The lists are usually short (you don't usually	3933	make it into some kind of religion.
3419	have many watchers waiting for the same fd or signal).
3420		3934
3421	=item Finding the next timer in each loop iteration: O(1)	3935	If you are unsure about something, feel free to contact the mailing list
		3936	with the full valgrind report and an explanation on why you think this
		3937	is a bug in libev (best check the archives, too :). However, don't be
		3938	annoyed when you get a brisk "this is no bug" answer and take the chance
		3939	of learning how to interpret valgrind properly.
3422		3940
3423	By virtue of using a binary or 4-heap, the next timer is always found at a	3941	If you need, for some reason, empty reports from valgrind for your project
3424	fixed position in the storage array.	3942	I suggest using suppression lists.
3425		3943
3426	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3427		3944
3428	A change means an I/O watcher gets started or stopped, which requires	3945	=head1 PORTABILITY NOTES
3429	libev to recalculate its status (and possibly tell the kernel, depending
3430	on backend and whether C<ev_io_set> was used).
3431		3946
3432	=item Activating one watcher (putting it into the pending state): O(1)
3433
3434	=item Priority handling: O(number_of_priorities)
3435
3436	Priorities are implemented by allocating some space for each
3437	priority. When doing priority-based operations, libev usually has to
3438	linearly search all the priorities, but starting/stopping and activating
3439	watchers becomes O(1) with respect to priority handling.
3440
3441	=item Sending an ev_async: O(1)
3442
3443	=item Processing ev_async_send: O(number_of_async_watchers)
3444
3445	=item Processing signals: O(max_signal_number)
3446
3447	Sending involves a system call I<iff> there were no other C<ev_async_send>
3448	calls in the current loop iteration. Checking for async and signal events
3449	involves iterating over all running async watchers or all signal numbers.
3450
3451	=back
3452
3453
3454	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	3947	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3455		3948
3456	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3949	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3457	requires, and its I/O model is fundamentally incompatible with the POSIX	3950	requires, and its I/O model is fundamentally incompatible with the POSIX
3458	model. Libev still offers limited functionality on this platform in	3951	model. Libev still offers limited functionality on this platform in
3459	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3952	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3466	way (note also that glib is the slowest event library known to man).	3959	way (note also that glib is the slowest event library known to man).
3467		3960
3468	There is no supported compilation method available on windows except	3961	There is no supported compilation method available on windows except
3469	embedding it into other applications.	3962	embedding it into other applications.
3470		3963
		3964	Sensible signal handling is officially unsupported by Microsoft - libev
		3965	tries its best, but under most conditions, signals will simply not work.
		3966
3471	Not a libev limitation but worth mentioning: windows apparently doesn't	3967	Not a libev limitation but worth mentioning: windows apparently doesn't
3472	accept large writes: instead of resulting in a partial write, windows will	3968	accept large writes: instead of resulting in a partial write, windows will
3473	either accept everything or return C<ENOBUFS> if the buffer is too large,	3969	either accept everything or return C<ENOBUFS> if the buffer is too large,
3474	so make sure you only write small amounts into your sockets (less than a	3970	so make sure you only write small amounts into your sockets (less than a
3475	megabyte seems safe, but this apparently depends on the amount of memory	3971	megabyte seems safe, but this apparently depends on the amount of memory
…		…
3479	the abysmal performance of winsockets, using a large number of sockets	3975	the abysmal performance of winsockets, using a large number of sockets
3480	is not recommended (and not reasonable). If your program needs to use	3976	is not recommended (and not reasonable). If your program needs to use
3481	more than a hundred or so sockets, then likely it needs to use a totally	3977	more than a hundred or so sockets, then likely it needs to use a totally
3482	different implementation for windows, as libev offers the POSIX readiness	3978	different implementation for windows, as libev offers the POSIX readiness
3483	notification model, which cannot be implemented efficiently on windows	3979	notification model, which cannot be implemented efficiently on windows
3484	(Microsoft monopoly games).	3980	(due to Microsoft monopoly games).
3485		3981
3486	A typical way to use libev under windows is to embed it (see the embedding	3982	A typical way to use libev under windows is to embed it (see the embedding
3487	section for details) and use the following F<evwrap.h> header file instead	3983	section for details) and use the following F<evwrap.h> header file instead
3488	of F<ev.h>:	3984	of F<ev.h>:
3489		3985
…		…
3525		4021
3526	Early versions of winsocket's select only supported waiting for a maximum	4022	Early versions of winsocket's select only supported waiting for a maximum
3527	of C<64> handles (probably owning to the fact that all windows kernels	4023	of C<64> handles (probably owning to the fact that all windows kernels
3528	can only wait for C<64> things at the same time internally; Microsoft	4024	can only wait for C<64> things at the same time internally; Microsoft
3529	recommends spawning a chain of threads and wait for 63 handles and the	4025	recommends spawning a chain of threads and wait for 63 handles and the
3530	previous thread in each. Great).	4026	previous thread in each. Sounds great!).
3531		4027
3532	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4028	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3533	to some high number (e.g. C<2048>) before compiling the winsocket select	4029	to some high number (e.g. C<2048>) before compiling the winsocket select
3534	call (which might be in libev or elsewhere, for example, perl does its own	4030	call (which might be in libev or elsewhere, for example, perl and many
3535	select emulation on windows).	4031	other interpreters do their own select emulation on windows).
3536		4032
3537	Another limit is the number of file descriptors in the Microsoft runtime	4033	Another limit is the number of file descriptors in the Microsoft runtime
3538	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4034	libraries, which by default is C<64> (there must be a hidden I<64>
3539	or something like this inside Microsoft). You can increase this by calling	4035	fetish or something like this inside Microsoft). You can increase this
3540	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4036	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3541	arbitrary limit), but is broken in many versions of the Microsoft runtime	4037	(another arbitrary limit), but is broken in many versions of the Microsoft
3542	libraries.
3543
3544	This might get you to about C<512> or C<2048> sockets (depending on	4038	runtime libraries. This might get you to about C<512> or C<2048> sockets
3545	windows version and/or the phase of the moon). To get more, you need to	4039	(depending on windows version and/or the phase of the moon). To get more,
3546	wrap all I/O functions and provide your own fd management, but the cost of	4040	you need to wrap all I/O functions and provide your own fd management, but
3547	calling select (O(n²)) will likely make this unworkable.	4041	the cost of calling select (O(n²)) will likely make this unworkable.
3548		4042
3549	=back	4043	=back
3550		4044
3551
3552	=head1 PORTABILITY REQUIREMENTS	4045	=head2 PORTABILITY REQUIREMENTS
3553		4046
3554	In addition to a working ISO-C implementation, libev relies on a few	4047	In addition to a working ISO-C implementation and of course the
3555	additional extensions:	4048	backend-specific APIs, libev relies on a few additional extensions:
3556		4049
3557	=over 4	4050	=over 4
3558		4051
3559	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	4052	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3560	calling conventions regardless of C<ev_watcher_type *>.	4053	calling conventions regardless of C<ev_watcher_type *>.
…		…
3585	except the initial one, and run the default loop in the initial thread as	4078	except the initial one, and run the default loop in the initial thread as
3586	well.	4079	well.
3587		4080
3588	=item C<long> must be large enough for common memory allocation sizes	4081	=item C<long> must be large enough for common memory allocation sizes
3589		4082
3590	To improve portability and simplify using libev, libev uses C<long>	4083	To improve portability and simplify its API, libev uses C<long> internally
3591	internally instead of C<size_t> when allocating its data structures. On	4084	instead of C<size_t> when allocating its data structures. On non-POSIX
3592	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4085	systems (Microsoft...) this might be unexpectedly low, but is still at
3593	is still at least 31 bits everywhere, which is enough for hundreds of	4086	least 31 bits everywhere, which is enough for hundreds of millions of
3594	millions of watchers.	4087	watchers.
3595		4088
3596	=item C<double> must hold a time value in seconds with enough accuracy	4089	=item C<double> must hold a time value in seconds with enough accuracy
3597		4090
3598	The type C<double> is used to represent timestamps. It is required to	4091	The type C<double> is used to represent timestamps. It is required to
3599	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4092	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
3600	enough for at least into the year 4000. This requirement is fulfilled by	4093	enough for at least into the year 4000. This requirement is fulfilled by
3601	implementations implementing IEEE 754 (basically all existing ones).	4094	implementations implementing IEEE 754, which is basically all existing
		4095	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4096	2200.
3602		4097
3603	=back	4098	=back
3604		4099
3605	If you know of other additional requirements drop me a note.	4100	If you know of other additional requirements drop me a note.
3606		4101
3607		4102
3608	=head1 COMPILER WARNINGS	4103	=head1 ALGORITHMIC COMPLEXITIES
3609		4104
3610	Depending on your compiler and compiler settings, you might get no or a	4105	In this section the complexities of (many of) the algorithms used inside
3611	lot of warnings when compiling libev code. Some people are apparently	4106	libev will be documented. For complexity discussions about backends see
3612	scared by this.	4107	the documentation for C<ev_default_init>.
3613		4108
3614	However, these are unavoidable for many reasons. For one, each compiler	4109	All of the following are about amortised time: If an array needs to be
3615	has different warnings, and each user has different tastes regarding	4110	extended, libev needs to realloc and move the whole array, but this
3616	warning options. "Warn-free" code therefore cannot be a goal except when	4111	happens asymptotically rarer with higher number of elements, so O(1) might
3617	targeting a specific compiler and compiler-version.	4112	mean that libev does a lengthy realloc operation in rare cases, but on
		4113	average it is much faster and asymptotically approaches constant time.
3618		4114
3619	Another reason is that some compiler warnings require elaborate	4115	=over 4
3620	workarounds, or other changes to the code that make it less clear and less
3621	maintainable.
3622		4116
3623	And of course, some compiler warnings are just plain stupid, or simply	4117	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3624	wrong (because they don't actually warn about the condition their message
3625	seems to warn about).
3626		4118
3627	While libev is written to generate as few warnings as possible,	4119	This means that, when you have a watcher that triggers in one hour and
3628	"warn-free" code is not a goal, and it is recommended not to build libev	4120	there are 100 watchers that would trigger before that, then inserting will
3629	with any compiler warnings enabled unless you are prepared to cope with	4121	have to skip roughly seven (C<ld 100>) of these watchers.
3630	them (e.g. by ignoring them). Remember that warnings are just that:
3631	warnings, not errors, or proof of bugs.
3632		4122
		4123	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3633		4124
3634	=head1 VALGRIND	4125	That means that changing a timer costs less than removing/adding them,
		4126	as only the relative motion in the event queue has to be paid for.
3635		4127
3636	Valgrind has a special section here because it is a popular tool that is	4128	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3637	highly useful, but valgrind reports are very hard to interpret.
3638		4129
3639	If you think you found a bug (memory leak, uninitialised data access etc.)	4130	These just add the watcher into an array or at the head of a list.
3640	in libev, then check twice: If valgrind reports something like:
3641		4131
3642	==2274== definitely lost: 0 bytes in 0 blocks.	4132	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3643	==2274== possibly lost: 0 bytes in 0 blocks.
3644	==2274== still reachable: 256 bytes in 1 blocks.
3645		4133
3646	Then there is no memory leak. Similarly, under some circumstances,	4134	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3647	valgrind might report kernel bugs as if it were a bug in libev, or it
3648	might be confused (it is a very good tool, but only a tool).
3649		4135
3650	If you are unsure about something, feel free to contact the mailing list	4136	These watchers are stored in lists, so they need to be walked to find the
3651	with the full valgrind report and an explanation on why you think this is	4137	correct watcher to remove. The lists are usually short (you don't usually
3652	a bug in libev. However, don't be annoyed when you get a brisk "this is	4138	have many watchers waiting for the same fd or signal: one is typical, two
3653	no bug" answer and take the chance of learning how to interpret valgrind	4139	is rare).
3654	properly.
3655		4140
3656	If you need, for some reason, empty reports from valgrind for your project	4141	=item Finding the next timer in each loop iteration: O(1)
3657	I suggest using suppression lists.
3658		4142
		4143	By virtue of using a binary or 4-heap, the next timer is always found at a
		4144	fixed position in the storage array.
		4145
		4146	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4147
		4148	A change means an I/O watcher gets started or stopped, which requires
		4149	libev to recalculate its status (and possibly tell the kernel, depending
		4150	on backend and whether C<ev_io_set> was used).
		4151
		4152	=item Activating one watcher (putting it into the pending state): O(1)
		4153
		4154	=item Priority handling: O(number_of_priorities)
		4155
		4156	Priorities are implemented by allocating some space for each
		4157	priority. When doing priority-based operations, libev usually has to
		4158	linearly search all the priorities, but starting/stopping and activating
		4159	watchers becomes O(1) with respect to priority handling.
		4160
		4161	=item Sending an ev_async: O(1)
		4162
		4163	=item Processing ev_async_send: O(number_of_async_watchers)
		4164
		4165	=item Processing signals: O(max_signal_number)
		4166
		4167	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4168	calls in the current loop iteration. Checking for async and signal events
		4169	involves iterating over all running async watchers or all signal numbers.
		4170
		4171	=back
		4172
		4173
		4174	=head1 GLOSSARY
		4175
		4176	=over 4
		4177
		4178	=item active
		4179
		4180	A watcher is active as long as it has been started (has been attached to
		4181	an event loop) but not yet stopped (disassociated from the event loop).
		4182
		4183	=item application
		4184
		4185	In this document, an application is whatever is using libev.
		4186
		4187	=item callback
		4188
		4189	The address of a function that is called when some event has been
		4190	detected. Callbacks are being passed the event loop, the watcher that
		4191	received the event, and the actual event bitset.
		4192
		4193	=item callback invocation
		4194
		4195	The act of calling the callback associated with a watcher.
		4196
		4197	=item event
		4198
		4199	A change of state of some external event, such as data now being available
		4200	for reading on a file descriptor, time having passed or simply not having
		4201	any other events happening anymore.
		4202
		4203	In libev, events are represented as single bits (such as C<EV_READ> or
		4204	C<EV_TIMEOUT>).
		4205
		4206	=item event library
		4207
		4208	A software package implementing an event model and loop.
		4209
		4210	=item event loop
		4211
		4212	An entity that handles and processes external events and converts them
		4213	into callback invocations.
		4214
		4215	=item event model
		4216
		4217	The model used to describe how an event loop handles and processes
		4218	watchers and events.
		4219
		4220	=item pending
		4221
		4222	A watcher is pending as soon as the corresponding event has been detected,
		4223	and stops being pending as soon as the watcher will be invoked or its
		4224	pending status is explicitly cleared by the application.
		4225
		4226	A watcher can be pending, but not active. Stopping a watcher also clears
		4227	its pending status.
		4228
		4229	=item real time
		4230
		4231	The physical time that is observed. It is apparently strictly monotonic :)
		4232
		4233	=item wall-clock time
		4234
		4235	The time and date as shown on clocks. Unlike real time, it can actually
		4236	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4237	clock.
		4238
		4239	=item watcher
		4240
		4241	A data structure that describes interest in certain events. Watchers need
		4242	to be started (attached to an event loop) before they can receive events.
		4243
		4244	=item watcher invocation
		4245
		4246	The act of calling the callback associated with a watcher.
		4247
		4248	=back
3659		4249
3660	=head1 AUTHOR	4250	=head1 AUTHOR
3661		4251
3662	Marc Lehmann <libev@schmorp.de>.	4252	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3663		4253

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