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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
…		…
344	flag.	362	flag.
345		363
346	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	364	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
347	environment variable.	365	environment variable.
348		366
		367	=item C<EVFLAG_NOINOTIFY>
		368
		369	When this flag is specified, then libev will not attempt to use the
		370	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and
		371	testing, this flag can be useful to conserve inotify file descriptors, as
		372	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		373
		374	=item C<EVFLAG_NOSIGNALFD>
		375
		376	When this flag is specified, then libev will not attempt to use the
		377	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This is
		378	probably only useful to work around any bugs in libev. Consequently, this
		379	flag might go away once the signalfd functionality is considered stable,
		380	so it's useful mostly in environment variables and not in program code.
		381
349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	382	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
350		383
351	This is your standard select(2) backend. Not I<completely> standard, as	384	This is your standard select(2) backend. Not I<completely> standard, as
352	libev tries to roll its own fd_set with no limits on the number of fds,	385	libev tries to roll its own fd_set with no limits on the number of fds,
353	but if that fails, expect a fairly low limit on the number of fds when	386	but if that fails, expect a fairly low limit on the number of fds when
…		…
380	=item C<EVBACKEND_EPOLL> (value 4, Linux)	413	=item C<EVBACKEND_EPOLL> (value 4, Linux)
381		414
382	For few fds, this backend is a bit little slower than poll and select,	415	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	416	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),	417	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	418	epoll scales either O(1) or O(active_fds).
386	of shortcomings, such as silently dropping events in some hard-to-detect	419
387	cases and requiring a system call per fd change, no fork support and bad	420	The epoll mechanism deserves honorable mention as the most misdesigned
388	support for dup.	421	of the more advanced event mechanisms: mere annoyances include silently
		422	dropping file descriptors, requiring a system call per change per file
		423	descriptor (and unnecessary guessing of parameters), problems with dup and
		424	so on. The biggest issue is fork races, however - if a program forks then
		425	I<both> parent and child process have to recreate the epoll set, which can
		426	take considerable time (one syscall per file descriptor) and is of course
		427	hard to detect.
		428
		429	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		430	of course I<doesn't>, and epoll just loves to report events for totally
		431	I<different> file descriptors (even already closed ones, so one cannot
		432	even remove them from the set) than registered in the set (especially
		433	on SMP systems). Libev tries to counter these spurious notifications by
		434	employing an additional generation counter and comparing that against the
		435	events to filter out spurious ones, recreating the set when required.
389		436
390	While stopping, setting and starting an I/O watcher in the same iteration	437	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	438	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	439	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	440	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
394	very well if you register events for both fds.	441	file descriptors might not work very well if you register events for both
395		442	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		443
400	Best performance from this backend is achieved by not unregistering all	444	Best performance from this backend is achieved by not unregistering all
401	watchers for a file descriptor until it has been closed, if possible,	445	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	446	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	447	starting a watcher (without re-setting it) also usually doesn't cause
404	extra overhead.	448	extra overhead. A fork can both result in spurious notifications as well
		449	as in libev having to destroy and recreate the epoll object, which can
		450	take considerable time and thus should be avoided.
		451
		452	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		453	faster than epoll for maybe up to a hundred file descriptors, depending on
		454	the usage. So sad.
405		455
406	While nominally embeddable in other event loops, this feature is broken in	456	While nominally embeddable in other event loops, this feature is broken in
407	all kernel versions tested so far.	457	all kernel versions tested so far.
408		458
409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	459	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
410	C<EVBACKEND_POLL>.	460	C<EVBACKEND_POLL>.
411		461
412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	462	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
413		463
414	Kqueue deserves special mention, as at the time of this writing, it was	464	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	465	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	466	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	467	it's completely useless). Unlike epoll, however, whose brokenness
418	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or	468	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.	469	without API changes to existing programs. For this reason it's not being
		470	"auto-detected" unless you explicitly specify it in the flags (i.e. using
		471	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		472	system like NetBSD.
420		473
421	You still can embed kqueue into a normal poll or select backend and use it	474	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	475	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.	476	the target platform). See C<ev_embed> watchers for more info.
424		477
425	It scales in the same way as the epoll backend, but the interface to the	478	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	479	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	480	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	481	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	482	two event changes per incident. Support for C<fork ()> is very bad (but
430	drops fds silently in similarly hard-to-detect cases.	483	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		484	cases
431		485
432	This backend usually performs well under most conditions.	486	This backend usually performs well under most conditions.
433		487
434	While nominally embeddable in other event loops, this doesn't work	488	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	489	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	490	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	491	(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,	492	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
439	using it only for sockets.	493	also broken on OS X)) and, did I mention it, using it only for sockets.
440		494
441	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	495	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	496	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
443	C<NOTE_EOF>.	497	C<NOTE_EOF>.
444		498
…		…
464	might perform better.	518	might perform better.
465		519
466	On the positive side, with the exception of the spurious readiness	520	On the positive side, with the exception of the spurious readiness
467	notifications, this backend actually performed fully to specification	521	notifications, this backend actually performed fully to specification
468	in all tests and is fully embeddable, which is a rare feat among the	522	in all tests and is fully embeddable, which is a rare feat among the
469	OS-specific backends.	523	OS-specific backends (I vastly prefer correctness over speed hacks).
470		524
471	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	525	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
472	C<EVBACKEND_POLL>.	526	C<EVBACKEND_POLL>.
473		527
474	=item C<EVBACKEND_ALL>	528	=item C<EVBACKEND_ALL>
…		…
479		533
480	It is definitely not recommended to use this flag.	534	It is definitely not recommended to use this flag.
481		535
482	=back	536	=back
483		537
484	If one or more of these are or'ed into the flags value, then only these	538	If one or more of the backend flags are or'ed into the flags value,
485	backends will be tried (in the reverse order as listed here). If none are	539	then only these backends will be tried (in the reverse order as listed
486	specified, all backends in C<ev_recommended_backends ()> will be tried.	540	here). If none are specified, all backends in C<ev_recommended_backends
		541	()> will be tried.
487		542
488	Example: This is the most typical usage.	543	Example: This is the most typical usage.
489		544
490	if (!ev_default_loop (0))	545	if (!ev_default_loop (0))
491	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	546	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
527	responsibility to either stop all watchers cleanly yourself I<before>	582	responsibility to either stop all watchers cleanly yourself I<before>
528	calling this function, or cope with the fact afterwards (which is usually	583	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	584	the easiest thing, you can just ignore the watchers and/or C<free ()> them
530	for example).	585	for example).
531		586
532	Note that certain global state, such as signal state, will not be freed by	587	Note that certain global state, such as signal state (and installed signal
533	this function, and related watchers (such as signal and child watchers)	588	handlers), will not be freed by this function, and related watchers (such
534	would need to be stopped manually.	589	as signal and child watchers) would need to be stopped manually.
535		590
536	In general it is not advisable to call this function except in the	591	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	592	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	593	pipe fds. If you need dynamically allocated loops it is better to use
539	C<ev_loop_new> and C<ev_loop_destroy>).	594	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
582		637
583	This value can sometimes be useful as a generation counter of sorts (it	638	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	639	"ticks" the number of loop iterations), as it roughly corresponds with
585	C<ev_prepare> and C<ev_check> calls.	640	C<ev_prepare> and C<ev_check> calls.
586		641
		642	=item unsigned int ev_loop_depth (loop)
		643
		644	Returns the number of times C<ev_loop> was entered minus the number of
		645	times C<ev_loop> was exited, in other words, the recursion depth.
		646
		647	Outside C<ev_loop>, this number is zero. In a callback, this number is
		648	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),
		649	in which case it is higher.
		650
		651	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread
		652	etc.), doesn't count as exit.
		653
587	=item unsigned int ev_backend (loop)	654	=item unsigned int ev_backend (loop)
588		655
589	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	656	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
590	use.	657	use.
591		658
…		…
605		672
606	This function is rarely useful, but when some event callback runs for a	673	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	674	very long time without entering the event loop, updating libev's idea of
608	the current time is a good idea.	675	the current time is a good idea.
609		676
610	See also "The special problem of time updates" in the C<ev_timer> section.	677	See also L<The special problem of time updates> in the C<ev_timer> section.
		678
		679	=item ev_suspend (loop)
		680
		681	=item ev_resume (loop)
		682
		683	These two functions suspend and resume a loop, for use when the loop is
		684	not used for a while and timeouts should not be processed.
		685
		686	A typical use case would be an interactive program such as a game: When
		687	the user presses C<^Z> to suspend the game and resumes it an hour later it
		688	would be best to handle timeouts as if no time had actually passed while
		689	the program was suspended. This can be achieved by calling C<ev_suspend>
		690	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		691	C<ev_resume> directly afterwards to resume timer processing.
		692
		693	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		694	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		695	will be rescheduled (that is, they will lose any events that would have
		696	occured while suspended).
		697
		698	After calling C<ev_suspend> you B<must not> call I<any> function on the
		699	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		700	without a previous call to C<ev_suspend>.
		701
		702	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		703	event loop time (see C<ev_now_update>).
611		704
612	=item ev_loop (loop, int flags)	705	=item ev_loop (loop, int flags)
613		706
614	Finally, this is it, the event handler. This function usually is called	707	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	708	after you initialised all your watchers and you want to start handling
…		…
631	the loop.	724	the loop.
632		725
633	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	726	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	727	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	728	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	729	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	730	user-registered callback will be called), and will return after one
638	iteration of the loop.	731	iteration of the loop.
639		732
640	This is useful if you are waiting for some external event in conjunction	733	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	734	with something not expressible using other libev watchers (i.e. "roll your
…		…
699		792
700	If you have a watcher you never unregister that should not keep C<ev_loop>	793	If you have a watcher you never unregister that should not keep C<ev_loop>
701	from returning, call ev_unref() after starting, and ev_ref() before	794	from returning, call ev_unref() after starting, and ev_ref() before
702	stopping it.	795	stopping it.
703		796
704	As an example, libev itself uses this for its internal signal pipe: It is	797	As an example, libev itself uses this for its internal signal pipe: It
705	not visible to the libev user and should not keep C<ev_loop> from exiting	798	is not visible to the libev user and should not keep C<ev_loop> from
706	if no event watchers registered by it are active. It is also an excellent	799	exiting if no event watchers registered by it are active. It is also an
707	way to do this for generic recurring timers or from within third-party	800	excellent way to do this for generic recurring timers or from within
708	libraries. Just remember to I<unref after start> and I<ref before stop>	801	third-party libraries. Just remember to I<unref after start> and I<ref
709	(but only if the watcher wasn't active before, or was active before,	802	before stop> (but only if the watcher wasn't active before, or was active
710	respectively).	803	before, respectively. Note also that libev might stop watchers itself
		804	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		805	in the callback).
711		806
712	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	807	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
713	running when nothing else is active.	808	running when nothing else is active.
714		809
715	struct ev_signal exitsig;	810	ev_signal exitsig;
716	ev_signal_init (&exitsig, sig_cb, SIGINT);	811	ev_signal_init (&exitsig, sig_cb, SIGINT);
717	ev_signal_start (loop, &exitsig);	812	ev_signal_start (loop, &exitsig);
718	evf_unref (loop);	813	evf_unref (loop);
719		814
720	Example: For some weird reason, unregister the above signal handler again.	815	Example: For some weird reason, unregister the above signal handler again.
…		…
744		839
745	By setting a higher I<io collect interval> you allow libev to spend more	840	By setting a higher I<io collect interval> you allow libev to spend more
746	time collecting I/O events, so you can handle more events per iteration,	841	time collecting I/O events, so you can handle more events per iteration,
747	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	842	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
748	C<ev_timer>) will be not affected. Setting this to a non-null value will	843	C<ev_timer>) will be not affected. Setting this to a non-null value will
749	introduce an additional C<ev_sleep ()> call into most loop iterations.	844	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		845	sleep time ensures that libev will not poll for I/O events more often then
		846	once per this interval, on average.
750		847
751	Likewise, by setting a higher I<timeout collect interval> you allow libev	848	Likewise, by setting a higher I<timeout collect interval> you allow libev
752	to spend more time collecting timeouts, at the expense of increased	849	to spend more time collecting timeouts, at the expense of increased
753	latency/jitter/inexactness (the watcher callback will be called	850	latency/jitter/inexactness (the watcher callback will be called
754	later). C<ev_io> watchers will not be affected. Setting this to a non-null	851	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
756		853
757	Many (busy) programs can usually benefit by setting the I/O collect	854	Many (busy) programs can usually benefit by setting the I/O collect
758	interval to a value near C<0.1> or so, which is often enough for	855	interval to a value near C<0.1> or so, which is often enough for
759	interactive servers (of course not for games), likewise for timeouts. It	856	interactive servers (of course not for games), likewise for timeouts. It
760	usually doesn't make much sense to set it to a lower value than C<0.01>,	857	usually doesn't make much sense to set it to a lower value than C<0.01>,
761	as this approaches the timing granularity of most systems.	858	as this approaches the timing granularity of most systems. Note that if
		859	you do transactions with the outside world and you can't increase the
		860	parallelity, then this setting will limit your transaction rate (if you
		861	need to poll once per transaction and the I/O collect interval is 0.01,
		862	then you can't do more than 100 transations per second).
762		863
763	Setting the I<timeout collect interval> can improve the opportunity for	864	Setting the I<timeout collect interval> can improve the opportunity for
764	saving power, as the program will "bundle" timer callback invocations that	865	saving power, as the program will "bundle" timer callback invocations that
765	are "near" in time together, by delaying some, thus reducing the number of	866	are "near" in time together, by delaying some, thus reducing the number of
766	times the process sleeps and wakes up again. Another useful technique to	867	times the process sleeps and wakes up again. Another useful technique to
767	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	868	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
768	they fire on, say, one-second boundaries only.	869	they fire on, say, one-second boundaries only.
769		870
		871	Example: we only need 0.1s timeout granularity, and we wish not to poll
		872	more often than 100 times per second:
		873
		874	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		875	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		876
		877	=item ev_invoke_pending (loop)
		878
		879	This call will simply invoke all pending watchers while resetting their
		880	pending state. Normally, C<ev_loop> does this automatically when required,
		881	but when overriding the invoke callback this call comes handy.
		882
		883	=item int ev_pending_count (loop)
		884
		885	Returns the number of pending watchers - zero indicates that no watchers
		886	are pending.
		887
		888	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		889
		890	This overrides the invoke pending functionality of the loop: Instead of
		891	invoking all pending watchers when there are any, C<ev_loop> will call
		892	this callback instead. This is useful, for example, when you want to
		893	invoke the actual watchers inside another context (another thread etc.).
		894
		895	If you want to reset the callback, use C<ev_invoke_pending> as new
		896	callback.
		897
		898	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		899
		900	Sometimes you want to share the same loop between multiple threads. This
		901	can be done relatively simply by putting mutex_lock/unlock calls around
		902	each call to a libev function.
		903
		904	However, C<ev_loop> can run an indefinite time, so it is not feasible to
		905	wait for it to return. One way around this is to wake up the loop via
		906	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>
		907	and I<acquire> callbacks on the loop.
		908
		909	When set, then C<release> will be called just before the thread is
		910	suspended waiting for new events, and C<acquire> is called just
		911	afterwards.
		912
		913	Ideally, C<release> will just call your mutex_unlock function, and
		914	C<acquire> will just call the mutex_lock function again.
		915
		916	While event loop modifications are allowed between invocations of
		917	C<release> and C<acquire> (that's their only purpose after all), no
		918	modifications done will affect the event loop, i.e. adding watchers will
		919	have no effect on the set of file descriptors being watched, or the time
		920	waited. USe an C<ev_async> watcher to wake up C<ev_loop> when you want it
		921	to take note of any changes you made.
		922
		923	In theory, threads executing C<ev_loop> will be async-cancel safe between
		924	invocations of C<release> and C<acquire>.
		925
		926	See also the locking example in the C<THREADS> section later in this
		927	document.
		928
		929	=item ev_set_userdata (loop, void *data)
		930
		931	=item ev_userdata (loop)
		932
		933	Set and retrieve a single C<void *> associated with a loop. When
		934	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		935	C<0.>
		936
		937	These two functions can be used to associate arbitrary data with a loop,
		938	and are intended solely for the C<invoke_pending_cb>, C<release> and
		939	C<acquire> callbacks described above, but of course can be (ab-)used for
		940	any other purpose as well.
		941
770	=item ev_loop_verify (loop)	942	=item ev_loop_verify (loop)
771		943
772	This function only does something when C<EV_VERIFY> support has been	944	This function only does something when C<EV_VERIFY> support has been
773	compiled in. which is the default for non-minimal builds. It tries to go	945	compiled in, which is the default for non-minimal builds. It tries to go
774	through all internal structures and checks them for validity. If anything	946	through all internal structures and checks them for validity. If anything
775	is found to be inconsistent, it will print an error message to standard	947	is found to be inconsistent, it will print an error message to standard
776	error and call C<abort ()>.	948	error and call C<abort ()>.
777		949
778	This can be used to catch bugs inside libev itself: under normal	950	This can be used to catch bugs inside libev itself: under normal
…		…
782	=back	954	=back
783		955
784		956
785	=head1 ANATOMY OF A WATCHER	957	=head1 ANATOMY OF A WATCHER
786		958
		959	In the following description, uppercase C<TYPE> in names stands for the
		960	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		961	watchers and C<ev_io_start> for I/O watchers.
		962
787	A watcher is a structure that you create and register to record your	963	A watcher is a structure that you create and register to record your
788	interest in some event. For instance, if you want to wait for STDIN to	964	interest in some event. For instance, if you want to wait for STDIN to
789	become readable, you would create an C<ev_io> watcher for that:	965	become readable, you would create an C<ev_io> watcher for that:
790		966
791	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	967	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
792	{	968	{
793	ev_io_stop (w);	969	ev_io_stop (w);
794	ev_unloop (loop, EVUNLOOP_ALL);	970	ev_unloop (loop, EVUNLOOP_ALL);
795	}	971	}
796		972
797	struct ev_loop *loop = ev_default_loop (0);	973	struct ev_loop *loop = ev_default_loop (0);
		974
798	struct ev_io stdin_watcher;	975	ev_io stdin_watcher;
		976
799	ev_init (&stdin_watcher, my_cb);	977	ev_init (&stdin_watcher, my_cb);
800	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	978	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
801	ev_io_start (loop, &stdin_watcher);	979	ev_io_start (loop, &stdin_watcher);
		980
802	ev_loop (loop, 0);	981	ev_loop (loop, 0);
803		982
804	As you can see, you are responsible for allocating the memory for your	983	As you can see, you are responsible for allocating the memory for your
805	watcher structures (and it is usually a bad idea to do this on the stack,	984	watcher structures (and it is I<usually> a bad idea to do this on the
806	although this can sometimes be quite valid).	985	stack).
		986
		987	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		988	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
807		989
808	Each watcher structure must be initialised by a call to C<ev_init	990	Each watcher structure must be initialised by a call to C<ev_init
809	(watcher *, callback)>, which expects a callback to be provided. This	991	(watcher *, callback)>, which expects a callback to be provided. This
810	callback gets invoked each time the event occurs (or, in the case of I/O	992	callback gets invoked each time the event occurs (or, in the case of I/O
811	watchers, each time the event loop detects that the file descriptor given	993	watchers, each time the event loop detects that the file descriptor given
812	is readable and/or writable).	994	is readable and/or writable).
813		995
814	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	996	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
815	with arguments specific to this watcher type. There is also a macro	997	macro to configure it, with arguments specific to the watcher type. There
816	to combine initialisation and setting in one call: C<< ev_<type>_init	998	is also a macro to combine initialisation and setting in one call: C<<
817	(watcher *, callback, ...) >>.	999	ev_TYPE_init (watcher *, callback, ...) >>.
818		1000
819	To make the watcher actually watch out for events, you have to start it	1001	To make the watcher actually watch out for events, you have to start it
820	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	1002	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
821	*) >>), and you can stop watching for events at any time by calling the	1003	*) >>), and you can stop watching for events at any time by calling the
822	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1004	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
823		1005
824	As long as your watcher is active (has been started but not stopped) you	1006	As long as your watcher is active (has been started but not stopped) you
825	must not touch the values stored in it. Most specifically you must never	1007	must not touch the values stored in it. Most specifically you must never
826	reinitialise it or call its C<set> macro.	1008	reinitialise it or call its C<ev_TYPE_set> macro.
827		1009
828	Each and every callback receives the event loop pointer as first, the	1010	Each and every callback receives the event loop pointer as first, the
829	registered watcher structure as second, and a bitset of received events as	1011	registered watcher structure as second, and a bitset of received events as
830	third argument.	1012	third argument.
831		1013
…		…
889		1071
890	=item C<EV_ASYNC>	1072	=item C<EV_ASYNC>
891		1073
892	The given async watcher has been asynchronously notified (see C<ev_async>).	1074	The given async watcher has been asynchronously notified (see C<ev_async>).
893		1075
		1076	=item C<EV_CUSTOM>
		1077
		1078	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1079	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		1080
894	=item C<EV_ERROR>	1081	=item C<EV_ERROR>
895		1082
896	An unspecified error has occurred, the watcher has been stopped. This might	1083	An unspecified error has occurred, the watcher has been stopped. This might
897	happen because the watcher could not be properly started because libev	1084	happen because the watcher could not be properly started because libev
898	ran out of memory, a file descriptor was found to be closed or any other	1085	ran out of memory, a file descriptor was found to be closed or any other
…		…
912		1099
913	=back	1100	=back
914		1101
915	=head2 GENERIC WATCHER FUNCTIONS	1102	=head2 GENERIC WATCHER FUNCTIONS
916		1103
917	In the following description, C<TYPE> stands for the watcher type,
918	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
919
920	=over 4	1104	=over 4
921		1105
922	=item C<ev_init> (ev_TYPE *watcher, callback)	1106	=item C<ev_init> (ev_TYPE *watcher, callback)
923		1107
924	This macro initialises the generic portion of a watcher. The contents	1108	This macro initialises the generic portion of a watcher. The contents
…		…
929	which rolls both calls into one.	1113	which rolls both calls into one.
930		1114
931	You can reinitialise a watcher at any time as long as it has been stopped	1115	You can reinitialise a watcher at any time as long as it has been stopped
932	(or never started) and there are no pending events outstanding.	1116	(or never started) and there are no pending events outstanding.
933		1117
934	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1118	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
935	int revents)>.	1119	int revents)>.
936		1120
937	Example: Initialise an C<ev_io> watcher in two steps.	1121	Example: Initialise an C<ev_io> watcher in two steps.
938		1122
939	ev_io w;	1123	ev_io w;
…		…
1016	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1200	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1017	(default: C<-2>). Pending watchers with higher priority will be invoked	1201	(default: C<-2>). Pending watchers with higher priority will be invoked
1018	before watchers with lower priority, but priority will not keep watchers	1202	before watchers with lower priority, but priority will not keep watchers
1019	from being executed (except for C<ev_idle> watchers).	1203	from being executed (except for C<ev_idle> watchers).
1020		1204
1021	This means that priorities are I<only> used for ordering callback
1022	invocation after new events have been received. This is useful, for
1023	example, to reduce latency after idling, or more often, to bind two
1024	watchers on the same event and make sure one is called first.
1025
1026	If you need to suppress invocation when higher priority events are pending	1205	If you need to suppress invocation when higher priority events are pending
1027	you need to look at C<ev_idle> watchers, which provide this functionality.	1206	you need to look at C<ev_idle> watchers, which provide this functionality.
1028		1207
1029	You I<must not> change the priority of a watcher as long as it is active or	1208	You I<must not> change the priority of a watcher as long as it is active or
1030	pending.	1209	pending.
1031		1210
		1211	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1212	fine, as long as you do not mind that the priority value you query might
		1213	or might not have been clamped to the valid range.
		1214
1032	The default priority used by watchers when no priority has been set is	1215	The default priority used by watchers when no priority has been set is
1033	always C<0>, which is supposed to not be too high and not be too low :).	1216	always C<0>, which is supposed to not be too high and not be too low :).
1034		1217
1035	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1218	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1036	fine, as long as you do not mind that the priority value you query might	1219	priorities.
1037	or might not have been adjusted to be within valid range.
1038		1220
1039	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1221	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1040		1222
1041	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1223	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1042	C<loop> nor C<revents> need to be valid as long as the watcher callback	1224	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1064	member, you can also "subclass" the watcher type and provide your own	1246	member, you can also "subclass" the watcher type and provide your own
1065	data:	1247	data:
1066		1248
1067	struct my_io	1249	struct my_io
1068	{	1250	{
1069	struct ev_io io;	1251	ev_io io;
1070	int otherfd;	1252	int otherfd;
1071	void *somedata;	1253	void *somedata;
1072	struct whatever *mostinteresting;	1254	struct whatever *mostinteresting;
1073	};	1255	};
1074		1256
…		…
1077	ev_io_init (&w.io, my_cb, fd, EV_READ);	1259	ev_io_init (&w.io, my_cb, fd, EV_READ);
1078		1260
1079	And since your callback will be called with a pointer to the watcher, you	1261	And since your callback will be called with a pointer to the watcher, you
1080	can cast it back to your own type:	1262	can cast it back to your own type:
1081		1263
1082	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1264	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1083	{	1265	{
1084	struct my_io *w = (struct my_io *)w_;	1266	struct my_io *w = (struct my_io *)w_;
1085	...	1267	...
1086	}	1268	}
1087		1269
…		…
1105	programmers):	1287	programmers):
1106		1288
1107	#include <stddef.h>	1289	#include <stddef.h>
1108		1290
1109	static void	1291	static void
1110	t1_cb (EV_P_ struct ev_timer *w, int revents)	1292	t1_cb (EV_P_ ev_timer *w, int revents)
1111	{	1293	{
1112	struct my_biggy big = (struct my_biggy *	1294	struct my_biggy big = (struct my_biggy *)
1113	(((char *)w) - offsetof (struct my_biggy, t1));	1295	(((char *)w) - offsetof (struct my_biggy, t1));
1114	}	1296	}
1115		1297
1116	static void	1298	static void
1117	t2_cb (EV_P_ struct ev_timer *w, int revents)	1299	t2_cb (EV_P_ ev_timer *w, int revents)
1118	{	1300	{
1119	struct my_biggy big = (struct my_biggy *	1301	struct my_biggy big = (struct my_biggy *)
1120	(((char *)w) - offsetof (struct my_biggy, t2));	1302	(((char *)w) - offsetof (struct my_biggy, t2));
1121	}	1303	}
		1304
		1305	=head2 WATCHER PRIORITY MODELS
		1306
		1307	Many event loops support I<watcher priorities>, which are usually small
		1308	integers that influence the ordering of event callback invocation
		1309	between watchers in some way, all else being equal.
		1310
		1311	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1312	description for the more technical details such as the actual priority
		1313	range.
		1314
		1315	There are two common ways how these these priorities are being interpreted
		1316	by event loops:
		1317
		1318	In the more common lock-out model, higher priorities "lock out" invocation
		1319	of lower priority watchers, which means as long as higher priority
		1320	watchers receive events, lower priority watchers are not being invoked.
		1321
		1322	The less common only-for-ordering model uses priorities solely to order
		1323	callback invocation within a single event loop iteration: Higher priority
		1324	watchers are invoked before lower priority ones, but they all get invoked
		1325	before polling for new events.
		1326
		1327	Libev uses the second (only-for-ordering) model for all its watchers
		1328	except for idle watchers (which use the lock-out model).
		1329
		1330	The rationale behind this is that implementing the lock-out model for
		1331	watchers is not well supported by most kernel interfaces, and most event
		1332	libraries will just poll for the same events again and again as long as
		1333	their callbacks have not been executed, which is very inefficient in the
		1334	common case of one high-priority watcher locking out a mass of lower
		1335	priority ones.
		1336
		1337	Static (ordering) priorities are most useful when you have two or more
		1338	watchers handling the same resource: a typical usage example is having an
		1339	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1340	timeouts. Under load, data might be received while the program handles
		1341	other jobs, but since timers normally get invoked first, the timeout
		1342	handler will be executed before checking for data. In that case, giving
		1343	the timer a lower priority than the I/O watcher ensures that I/O will be
		1344	handled first even under adverse conditions (which is usually, but not
		1345	always, what you want).
		1346
		1347	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1348	will only be executed when no same or higher priority watchers have
		1349	received events, they can be used to implement the "lock-out" model when
		1350	required.
		1351
		1352	For example, to emulate how many other event libraries handle priorities,
		1353	you can associate an C<ev_idle> watcher to each such watcher, and in
		1354	the normal watcher callback, you just start the idle watcher. The real
		1355	processing is done in the idle watcher callback. This causes libev to
		1356	continously poll and process kernel event data for the watcher, but when
		1357	the lock-out case is known to be rare (which in turn is rare :), this is
		1358	workable.
		1359
		1360	Usually, however, the lock-out model implemented that way will perform
		1361	miserably under the type of load it was designed to handle. In that case,
		1362	it might be preferable to stop the real watcher before starting the
		1363	idle watcher, so the kernel will not have to process the event in case
		1364	the actual processing will be delayed for considerable time.
		1365
		1366	Here is an example of an I/O watcher that should run at a strictly lower
		1367	priority than the default, and which should only process data when no
		1368	other events are pending:
		1369
		1370	ev_idle idle; // actual processing watcher
		1371	ev_io io; // actual event watcher
		1372
		1373	static void
		1374	io_cb (EV_P_ ev_io *w, int revents)
		1375	{
		1376	// stop the I/O watcher, we received the event, but
		1377	// are not yet ready to handle it.
		1378	ev_io_stop (EV_A_ w);
		1379
		1380	// start the idle watcher to ahndle the actual event.
		1381	// it will not be executed as long as other watchers
		1382	// with the default priority are receiving events.
		1383	ev_idle_start (EV_A_ &idle);
		1384	}
		1385
		1386	static void
		1387	idle_cb (EV_P_ ev_idle *w, int revents)
		1388	{
		1389	// actual processing
		1390	read (STDIN_FILENO, ...);
		1391
		1392	// have to start the I/O watcher again, as
		1393	// we have handled the event
		1394	ev_io_start (EV_P_ &io);
		1395	}
		1396
		1397	// initialisation
		1398	ev_idle_init (&idle, idle_cb);
		1399	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1400	ev_io_start (EV_DEFAULT_ &io);
		1401
		1402	In the "real" world, it might also be beneficial to start a timer, so that
		1403	low-priority connections can not be locked out forever under load. This
		1404	enables your program to keep a lower latency for important connections
		1405	during short periods of high load, while not completely locking out less
		1406	important ones.
1122		1407
1123		1408
1124	=head1 WATCHER TYPES	1409	=head1 WATCHER TYPES
1125		1410
1126	This section describes each watcher in detail, but will not repeat	1411	This section describes each watcher in detail, but will not repeat
…		…
1152	descriptors to non-blocking mode is also usually a good idea (but not	1437	descriptors to non-blocking mode is also usually a good idea (but not
1153	required if you know what you are doing).	1438	required if you know what you are doing).
1154		1439
1155	If you cannot use non-blocking mode, then force the use of a	1440	If you cannot use non-blocking mode, then force the use of a
1156	known-to-be-good backend (at the time of this writing, this includes only	1441	known-to-be-good backend (at the time of this writing, this includes only
1157	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).	1442	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1443	descriptors for which non-blocking operation makes no sense (such as
		1444	files) - libev doesn't guarentee any specific behaviour in that case.
1158		1445
1159	Another thing you have to watch out for is that it is quite easy to	1446	Another thing you have to watch out for is that it is quite easy to
1160	receive "spurious" readiness notifications, that is your callback might	1447	receive "spurious" readiness notifications, that is your callback might
1161	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1448	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1162	because there is no data. Not only are some backends known to create a	1449	because there is no data. Not only are some backends known to create a
…		…
1257	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1544	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1258	readable, but only once. Since it is likely line-buffered, you could	1545	readable, but only once. Since it is likely line-buffered, you could
1259	attempt to read a whole line in the callback.	1546	attempt to read a whole line in the callback.
1260		1547
1261	static void	1548	static void
1262	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1549	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1263	{	1550	{
1264	ev_io_stop (loop, w);	1551	ev_io_stop (loop, w);
1265	.. read from stdin here (or from w->fd) and handle any I/O errors	1552	.. read from stdin here (or from w->fd) and handle any I/O errors
1266	}	1553	}
1267		1554
1268	...	1555	...
1269	struct ev_loop *loop = ev_default_init (0);	1556	struct ev_loop *loop = ev_default_init (0);
1270	struct ev_io stdin_readable;	1557	ev_io stdin_readable;
1271	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1558	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1272	ev_io_start (loop, &stdin_readable);	1559	ev_io_start (loop, &stdin_readable);
1273	ev_loop (loop, 0);	1560	ev_loop (loop, 0);
1274		1561
1275		1562
…		…
1283	year, it will still time out after (roughly) one hour. "Roughly" because	1570	year, it will still time out after (roughly) one hour. "Roughly" because
1284	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1571	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1285	monotonic clock option helps a lot here).	1572	monotonic clock option helps a lot here).
1286		1573
1287	The callback is guaranteed to be invoked only I<after> its timeout has	1574	The callback is guaranteed to be invoked only I<after> its timeout has
1288	passed, but if multiple timers become ready during the same loop iteration	1575	passed (not I<at>, so on systems with very low-resolution clocks this
1289	then order of execution is undefined.	1576	might introduce a small delay). If multiple timers become ready during the
		1577	same loop iteration then the ones with earlier time-out values are invoked
		1578	before ones of the same priority with later time-out values (but this is
		1579	no longer true when a callback calls C<ev_loop> recursively).
		1580
		1581	=head3 Be smart about timeouts
		1582
		1583	Many real-world problems involve some kind of timeout, usually for error
		1584	recovery. A typical example is an HTTP request - if the other side hangs,
		1585	you want to raise some error after a while.
		1586
		1587	What follows are some ways to handle this problem, from obvious and
		1588	inefficient to smart and efficient.
		1589
		1590	In the following, a 60 second activity timeout is assumed - a timeout that
		1591	gets reset to 60 seconds each time there is activity (e.g. each time some
		1592	data or other life sign was received).
		1593
		1594	=over 4
		1595
		1596	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1597
		1598	This is the most obvious, but not the most simple way: In the beginning,
		1599	start the watcher:
		1600
		1601	ev_timer_init (timer, callback, 60., 0.);
		1602	ev_timer_start (loop, timer);
		1603
		1604	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1605	and start it again:
		1606
		1607	ev_timer_stop (loop, timer);
		1608	ev_timer_set (timer, 60., 0.);
		1609	ev_timer_start (loop, timer);
		1610
		1611	This is relatively simple to implement, but means that each time there is
		1612	some activity, libev will first have to remove the timer from its internal
		1613	data structure and then add it again. Libev tries to be fast, but it's
		1614	still not a constant-time operation.
		1615
		1616	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1617
		1618	This is the easiest way, and involves using C<ev_timer_again> instead of
		1619	C<ev_timer_start>.
		1620
		1621	To implement this, configure an C<ev_timer> with a C<repeat> value
		1622	of C<60> and then call C<ev_timer_again> at start and each time you
		1623	successfully read or write some data. If you go into an idle state where
		1624	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1625	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1626
		1627	That means you can ignore both the C<ev_timer_start> function and the
		1628	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1629	member and C<ev_timer_again>.
		1630
		1631	At start:
		1632
		1633	ev_init (timer, callback);
		1634	timer->repeat = 60.;
		1635	ev_timer_again (loop, timer);
		1636
		1637	Each time there is some activity:
		1638
		1639	ev_timer_again (loop, timer);
		1640
		1641	It is even possible to change the time-out on the fly, regardless of
		1642	whether the watcher is active or not:
		1643
		1644	timer->repeat = 30.;
		1645	ev_timer_again (loop, timer);
		1646
		1647	This is slightly more efficient then stopping/starting the timer each time
		1648	you want to modify its timeout value, as libev does not have to completely
		1649	remove and re-insert the timer from/into its internal data structure.
		1650
		1651	It is, however, even simpler than the "obvious" way to do it.
		1652
		1653	=item 3. Let the timer time out, but then re-arm it as required.
		1654
		1655	This method is more tricky, but usually most efficient: Most timeouts are
		1656	relatively long compared to the intervals between other activity - in
		1657	our example, within 60 seconds, there are usually many I/O events with
		1658	associated activity resets.
		1659
		1660	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1661	but remember the time of last activity, and check for a real timeout only
		1662	within the callback:
		1663
		1664	ev_tstamp last_activity; // time of last activity
		1665
		1666	static void
		1667	callback (EV_P_ ev_timer *w, int revents)
		1668	{
		1669	ev_tstamp now = ev_now (EV_A);
		1670	ev_tstamp timeout = last_activity + 60.;
		1671
		1672	// if last_activity + 60. is older than now, we did time out
		1673	if (timeout < now)
		1674	{
		1675	// timeout occured, take action
		1676	}
		1677	else
		1678	{
		1679	// callback was invoked, but there was some activity, re-arm
		1680	// the watcher to fire in last_activity + 60, which is
		1681	// guaranteed to be in the future, so "again" is positive:
		1682	w->repeat = timeout - now;
		1683	ev_timer_again (EV_A_ w);
		1684	}
		1685	}
		1686
		1687	To summarise the callback: first calculate the real timeout (defined
		1688	as "60 seconds after the last activity"), then check if that time has
		1689	been reached, which means something I<did>, in fact, time out. Otherwise
		1690	the callback was invoked too early (C<timeout> is in the future), so
		1691	re-schedule the timer to fire at that future time, to see if maybe we have
		1692	a timeout then.
		1693
		1694	Note how C<ev_timer_again> is used, taking advantage of the
		1695	C<ev_timer_again> optimisation when the timer is already running.
		1696
		1697	This scheme causes more callback invocations (about one every 60 seconds
		1698	minus half the average time between activity), but virtually no calls to
		1699	libev to change the timeout.
		1700
		1701	To start the timer, simply initialise the watcher and set C<last_activity>
		1702	to the current time (meaning we just have some activity :), then call the
		1703	callback, which will "do the right thing" and start the timer:
		1704
		1705	ev_init (timer, callback);
		1706	last_activity = ev_now (loop);
		1707	callback (loop, timer, EV_TIMEOUT);
		1708
		1709	And when there is some activity, simply store the current time in
		1710	C<last_activity>, no libev calls at all:
		1711
		1712	last_actiivty = ev_now (loop);
		1713
		1714	This technique is slightly more complex, but in most cases where the
		1715	time-out is unlikely to be triggered, much more efficient.
		1716
		1717	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1718	callback :) - just change the timeout and invoke the callback, which will
		1719	fix things for you.
		1720
		1721	=item 4. Wee, just use a double-linked list for your timeouts.
		1722
		1723	If there is not one request, but many thousands (millions...), all
		1724	employing some kind of timeout with the same timeout value, then one can
		1725	do even better:
		1726
		1727	When starting the timeout, calculate the timeout value and put the timeout
		1728	at the I<end> of the list.
		1729
		1730	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1731	the list is expected to fire (for example, using the technique #3).
		1732
		1733	When there is some activity, remove the timer from the list, recalculate
		1734	the timeout, append it to the end of the list again, and make sure to
		1735	update the C<ev_timer> if it was taken from the beginning of the list.
		1736
		1737	This way, one can manage an unlimited number of timeouts in O(1) time for
		1738	starting, stopping and updating the timers, at the expense of a major
		1739	complication, and having to use a constant timeout. The constant timeout
		1740	ensures that the list stays sorted.
		1741
		1742	=back
		1743
		1744	So which method the best?
		1745
		1746	Method #2 is a simple no-brain-required solution that is adequate in most
		1747	situations. Method #3 requires a bit more thinking, but handles many cases
		1748	better, and isn't very complicated either. In most case, choosing either
		1749	one is fine, with #3 being better in typical situations.
		1750
		1751	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1752	rather complicated, but extremely efficient, something that really pays
		1753	off after the first million or so of active timers, i.e. it's usually
		1754	overkill :)
1290		1755
1291	=head3 The special problem of time updates	1756	=head3 The special problem of time updates
1292		1757
1293	Establishing the current time is a costly operation (it usually takes at	1758	Establishing the current time is a costly operation (it usually takes at
1294	least two system calls): EV therefore updates its idea of the current	1759	least two system calls): EV therefore updates its idea of the current
…		…
1306		1771
1307	If the event loop is suspended for a long time, you can also force an	1772	If the event loop is suspended for a long time, you can also force an
1308	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1773	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1309	()>.	1774	()>.
1310		1775
		1776	=head3 The special problems of suspended animation
		1777
		1778	When you leave the server world it is quite customary to hit machines that
		1779	can suspend/hibernate - what happens to the clocks during such a suspend?
		1780
		1781	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1782	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1783	to run until the system is suspended, but they will not advance while the
		1784	system is suspended. That means, on resume, it will be as if the program
		1785	was frozen for a few seconds, but the suspend time will not be counted
		1786	towards C<ev_timer> when a monotonic clock source is used. The real time
		1787	clock advanced as expected, but if it is used as sole clocksource, then a
		1788	long suspend would be detected as a time jump by libev, and timers would
		1789	be adjusted accordingly.
		1790
		1791	I would not be surprised to see different behaviour in different between
		1792	operating systems, OS versions or even different hardware.
		1793
		1794	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1795	time jump in the monotonic clocks and the realtime clock. If the program
		1796	is suspended for a very long time, and monotonic clock sources are in use,
		1797	then you can expect C<ev_timer>s to expire as the full suspension time
		1798	will be counted towards the timers. When no monotonic clock source is in
		1799	use, then libev will again assume a timejump and adjust accordingly.
		1800
		1801	It might be beneficial for this latter case to call C<ev_suspend>
		1802	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1803	deterministic behaviour in this case (you can do nothing against
		1804	C<SIGSTOP>).
		1805
1311	=head3 Watcher-Specific Functions and Data Members	1806	=head3 Watcher-Specific Functions and Data Members
1312		1807
1313	=over 4	1808	=over 4
1314		1809
1315	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1810	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1338	If the timer is started but non-repeating, stop it (as if it timed out).	1833	If the timer is started but non-repeating, stop it (as if it timed out).
1339		1834
1340	If the timer is repeating, either start it if necessary (with the	1835	If the timer is repeating, either start it if necessary (with the
1341	C<repeat> value), or reset the running timer to the C<repeat> value.	1836	C<repeat> value), or reset the running timer to the C<repeat> value.
1342		1837
1343	This sounds a bit complicated, but here is a useful and typical	1838	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1344	example: Imagine you have a TCP connection and you want a so-called idle	1839	usage example.
1345	timeout, that is, you want to be called when there have been, say, 60
1346	seconds of inactivity on the socket. The easiest way to do this is to
1347	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1348	C<ev_timer_again> each time you successfully read or write some data. If
1349	you go into an idle state where you do not expect data to travel on the
1350	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1351	automatically restart it if need be.
1352		1840
1353	That means you can ignore the C<after> value and C<ev_timer_start>	1841	=item ev_timer_remaining (loop, ev_timer *)
1354	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1355		1842
1356	ev_timer_init (timer, callback, 0., 5.);	1843	Returns the remaining time until a timer fires. If the timer is active,
1357	ev_timer_again (loop, timer);	1844	then this time is relative to the current event loop time, otherwise it's
1358	...	1845	the timeout value currently configured.
1359	timer->again = 17.;
1360	ev_timer_again (loop, timer);
1361	...
1362	timer->again = 10.;
1363	ev_timer_again (loop, timer);
1364		1846
1365	This is more slightly efficient then stopping/starting the timer each time	1847	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1366	you want to modify its timeout value.	1848	C<5>. When the timer is started and one second passes, C<ev_timer_remain>
1367		1849	will return C<4>. When the timer expires and is restarted, it will return
1368	Note, however, that it is often even more efficient to remember the	1850	roughly C<7> (likely slightly less as callback invocation takes some time,
1369	time of the last activity and let the timer time-out naturally. In the	1851	too), and so on.
1370	callback, you then check whether the time-out is real, or, if there was
1371	some activity, you reschedule the watcher to time-out in "last_activity +
1372	timeout - ev_now ()" seconds.
1373		1852
1374	=item ev_tstamp repeat [read-write]	1853	=item ev_tstamp repeat [read-write]
1375		1854
1376	The current C<repeat> value. Will be used each time the watcher times out	1855	The current C<repeat> value. Will be used each time the watcher times out
1377	or C<ev_timer_again> is called, and determines the next timeout (if any),	1856	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1382	=head3 Examples	1861	=head3 Examples
1383		1862
1384	Example: Create a timer that fires after 60 seconds.	1863	Example: Create a timer that fires after 60 seconds.
1385		1864
1386	static void	1865	static void
1387	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1866	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1388	{	1867	{
1389	.. one minute over, w is actually stopped right here	1868	.. one minute over, w is actually stopped right here
1390	}	1869	}
1391		1870
1392	struct ev_timer mytimer;	1871	ev_timer mytimer;
1393	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1872	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1394	ev_timer_start (loop, &mytimer);	1873	ev_timer_start (loop, &mytimer);
1395		1874
1396	Example: Create a timeout timer that times out after 10 seconds of	1875	Example: Create a timeout timer that times out after 10 seconds of
1397	inactivity.	1876	inactivity.
1398		1877
1399	static void	1878	static void
1400	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1879	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1401	{	1880	{
1402	.. ten seconds without any activity	1881	.. ten seconds without any activity
1403	}	1882	}
1404		1883
1405	struct ev_timer mytimer;	1884	ev_timer mytimer;
1406	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1885	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1407	ev_timer_again (&mytimer); /* start timer */	1886	ev_timer_again (&mytimer); /* start timer */
1408	ev_loop (loop, 0);	1887	ev_loop (loop, 0);
1409		1888
1410	// and in some piece of code that gets executed on any "activity":	1889	// and in some piece of code that gets executed on any "activity":
…		…
1415	=head2 C<ev_periodic> - to cron or not to cron?	1894	=head2 C<ev_periodic> - to cron or not to cron?
1416		1895
1417	Periodic watchers are also timers of a kind, but they are very versatile	1896	Periodic watchers are also timers of a kind, but they are very versatile
1418	(and unfortunately a bit complex).	1897	(and unfortunately a bit complex).
1419		1898
1420	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1899	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1421	but on wall clock time (absolute time). You can tell a periodic watcher	1900	relative time, the physical time that passes) but on wall clock time
1422	to trigger after some specific point in time. For example, if you tell a	1901	(absolute time, the thing you can read on your calender or clock). The
1423	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	1902	difference is that wall clock time can run faster or slower than real
1424	+ 10.>, that is, an absolute time not a delay) and then reset your system	1903	time, and time jumps are not uncommon (e.g. when you adjust your
1425	clock to January of the previous year, then it will take more than year	1904	wrist-watch).
1426	to trigger the event (unlike an C<ev_timer>, which would still trigger
1427	roughly 10 seconds later as it uses a relative timeout).
1428		1905
		1906	You can tell a periodic watcher to trigger after some specific point
		1907	in time: for example, if you tell a periodic watcher to trigger "in 10
		1908	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1909	not a delay) and then reset your system clock to January of the previous
		1910	year, then it will take a year or more to trigger the event (unlike an
		1911	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1912	it, as it uses a relative timeout).
		1913
1429	C<ev_periodic>s can also be used to implement vastly more complex timers,	1914	C<ev_periodic> watchers can also be used to implement vastly more complex
1430	such as triggering an event on each "midnight, local time", or other	1915	timers, such as triggering an event on each "midnight, local time", or
1431	complicated rules.	1916	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1917	those cannot react to time jumps.
1432		1918
1433	As with timers, the callback is guaranteed to be invoked only when the	1919	As with timers, the callback is guaranteed to be invoked only when the
1434	time (C<at>) has passed, but if multiple periodic timers become ready	1920	point in time where it is supposed to trigger has passed. If multiple
1435	during the same loop iteration, then order of execution is undefined.	1921	timers become ready during the same loop iteration then the ones with
		1922	earlier time-out values are invoked before ones with later time-out values
		1923	(but this is no longer true when a callback calls C<ev_loop> recursively).
1436		1924
1437	=head3 Watcher-Specific Functions and Data Members	1925	=head3 Watcher-Specific Functions and Data Members
1438		1926
1439	=over 4	1927	=over 4
1440		1928
1441	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1929	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1442		1930
1443	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1931	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1444		1932
1445	Lots of arguments, lets sort it out... There are basically three modes of	1933	Lots of arguments, let's sort it out... There are basically three modes of
1446	operation, and we will explain them from simplest to most complex:	1934	operation, and we will explain them from simplest to most complex:
1447		1935
1448	=over 4	1936	=over 4
1449		1937
1450	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1938	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1451		1939
1452	In this configuration the watcher triggers an event after the wall clock	1940	In this configuration the watcher triggers an event after the wall clock
1453	time C<at> has passed. It will not repeat and will not adjust when a time	1941	time C<offset> has passed. It will not repeat and will not adjust when a
1454	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1942	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1455	only run when the system clock reaches or surpasses this time.	1943	will be stopped and invoked when the system clock reaches or surpasses
		1944	this point in time.
1456		1945
1457	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1946	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1458		1947
1459	In this mode the watcher will always be scheduled to time out at the next	1948	In this mode the watcher will always be scheduled to time out at the next
1460	C<at + N * interval> time (for some integer N, which can also be negative)	1949	C<offset + N * interval> time (for some integer N, which can also be
1461	and then repeat, regardless of any time jumps.	1950	negative) and then repeat, regardless of any time jumps. The C<offset>
		1951	argument is merely an offset into the C<interval> periods.
1462		1952
1463	This can be used to create timers that do not drift with respect to the	1953	This can be used to create timers that do not drift with respect to the
1464	system clock, for example, here is a C<ev_periodic> that triggers each	1954	system clock, for example, here is an C<ev_periodic> that triggers each
1465	hour, on the hour:	1955	hour, on the hour (with respect to UTC):
1466		1956
1467	ev_periodic_set (&periodic, 0., 3600., 0);	1957	ev_periodic_set (&periodic, 0., 3600., 0);
1468		1958
1469	This doesn't mean there will always be 3600 seconds in between triggers,	1959	This doesn't mean there will always be 3600 seconds in between triggers,
1470	but only that the callback will be called when the system time shows a	1960	but only that the callback will be called when the system time shows a
1471	full hour (UTC), or more correctly, when the system time is evenly divisible	1961	full hour (UTC), or more correctly, when the system time is evenly divisible
1472	by 3600.	1962	by 3600.
1473		1963
1474	Another way to think about it (for the mathematically inclined) is that	1964	Another way to think about it (for the mathematically inclined) is that
1475	C<ev_periodic> will try to run the callback in this mode at the next possible	1965	C<ev_periodic> will try to run the callback in this mode at the next possible
1476	time where C<time = at (mod interval)>, regardless of any time jumps.	1966	time where C<time = offset (mod interval)>, regardless of any time jumps.
1477		1967
1478	For numerical stability it is preferable that the C<at> value is near	1968	For numerical stability it is preferable that the C<offset> value is near
1479	C<ev_now ()> (the current time), but there is no range requirement for	1969	C<ev_now ()> (the current time), but there is no range requirement for
1480	this value, and in fact is often specified as zero.	1970	this value, and in fact is often specified as zero.
1481		1971
1482	Note also that there is an upper limit to how often a timer can fire (CPU	1972	Note also that there is an upper limit to how often a timer can fire (CPU
1483	speed for example), so if C<interval> is very small then timing stability	1973	speed for example), so if C<interval> is very small then timing stability
1484	will of course deteriorate. Libev itself tries to be exact to be about one	1974	will of course deteriorate. Libev itself tries to be exact to be about one
1485	millisecond (if the OS supports it and the machine is fast enough).	1975	millisecond (if the OS supports it and the machine is fast enough).
1486		1976
1487	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1977	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1488		1978
1489	In this mode the values for C<interval> and C<at> are both being	1979	In this mode the values for C<interval> and C<offset> are both being
1490	ignored. Instead, each time the periodic watcher gets scheduled, the	1980	ignored. Instead, each time the periodic watcher gets scheduled, the
1491	reschedule callback will be called with the watcher as first, and the	1981	reschedule callback will be called with the watcher as first, and the
1492	current time as second argument.	1982	current time as second argument.
1493		1983
1494	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1984	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1495	ever, or make ANY event loop modifications whatsoever>.	1985	or make ANY other event loop modifications whatsoever, unless explicitly
		1986	allowed by documentation here>.
1496		1987
1497	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1988	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1498	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	1989	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1499	only event loop modification you are allowed to do).	1990	only event loop modification you are allowed to do).
1500		1991
1501	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1992	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1502	*w, ev_tstamp now)>, e.g.:	1993	*w, ev_tstamp now)>, e.g.:
1503		1994
		1995	static ev_tstamp
1504	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1996	my_rescheduler (ev_periodic *w, ev_tstamp now)
1505	{	1997	{
1506	return now + 60.;	1998	return now + 60.;
1507	}	1999	}
1508		2000
1509	It must return the next time to trigger, based on the passed time value	2001	It must return the next time to trigger, based on the passed time value
…		…
1529	a different time than the last time it was called (e.g. in a crond like	2021	a different time than the last time it was called (e.g. in a crond like
1530	program when the crontabs have changed).	2022	program when the crontabs have changed).
1531		2023
1532	=item ev_tstamp ev_periodic_at (ev_periodic *)	2024	=item ev_tstamp ev_periodic_at (ev_periodic *)
1533		2025
1534	When active, returns the absolute time that the watcher is supposed to	2026	When active, returns the absolute time that the watcher is supposed
1535	trigger next.	2027	to trigger next. This is not the same as the C<offset> argument to
		2028	C<ev_periodic_set>, but indeed works even in interval and manual
		2029	rescheduling modes.
1536		2030
1537	=item ev_tstamp offset [read-write]	2031	=item ev_tstamp offset [read-write]
1538		2032
1539	When repeating, this contains the offset value, otherwise this is the	2033	When repeating, this contains the offset value, otherwise this is the
1540	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2034	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2035	although libev might modify this value for better numerical stability).
1541		2036
1542	Can be modified any time, but changes only take effect when the periodic	2037	Can be modified any time, but changes only take effect when the periodic
1543	timer fires or C<ev_periodic_again> is being called.	2038	timer fires or C<ev_periodic_again> is being called.
1544		2039
1545	=item ev_tstamp interval [read-write]	2040	=item ev_tstamp interval [read-write]
1546		2041
1547	The current interval value. Can be modified any time, but changes only	2042	The current interval value. Can be modified any time, but changes only
1548	take effect when the periodic timer fires or C<ev_periodic_again> is being	2043	take effect when the periodic timer fires or C<ev_periodic_again> is being
1549	called.	2044	called.
1550		2045
1551	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2046	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1552		2047
1553	The current reschedule callback, or C<0>, if this functionality is	2048	The current reschedule callback, or C<0>, if this functionality is
1554	switched off. Can be changed any time, but changes only take effect when	2049	switched off. Can be changed any time, but changes only take effect when
1555	the periodic timer fires or C<ev_periodic_again> is being called.	2050	the periodic timer fires or C<ev_periodic_again> is being called.
1556		2051
…		…
1561	Example: Call a callback every hour, or, more precisely, whenever the	2056	Example: Call a callback every hour, or, more precisely, whenever the
1562	system time is divisible by 3600. The callback invocation times have	2057	system time is divisible by 3600. The callback invocation times have
1563	potentially a lot of jitter, but good long-term stability.	2058	potentially a lot of jitter, but good long-term stability.
1564		2059
1565	static void	2060	static void
1566	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2061	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1567	{	2062	{
1568	... its now a full hour (UTC, or TAI or whatever your clock follows)	2063	... its now a full hour (UTC, or TAI or whatever your clock follows)
1569	}	2064	}
1570		2065
1571	struct ev_periodic hourly_tick;	2066	ev_periodic hourly_tick;
1572	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2067	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1573	ev_periodic_start (loop, &hourly_tick);	2068	ev_periodic_start (loop, &hourly_tick);
1574		2069
1575	Example: The same as above, but use a reschedule callback to do it:	2070	Example: The same as above, but use a reschedule callback to do it:
1576		2071
1577	#include <math.h>	2072	#include <math.h>
1578		2073
1579	static ev_tstamp	2074	static ev_tstamp
1580	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2075	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1581	{	2076	{
1582	return now + (3600. - fmod (now, 3600.));	2077	return now + (3600. - fmod (now, 3600.));
1583	}	2078	}
1584		2079
1585	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2080	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1586		2081
1587	Example: Call a callback every hour, starting now:	2082	Example: Call a callback every hour, starting now:
1588		2083
1589	struct ev_periodic hourly_tick;	2084	ev_periodic hourly_tick;
1590	ev_periodic_init (&hourly_tick, clock_cb,	2085	ev_periodic_init (&hourly_tick, clock_cb,
1591	fmod (ev_now (loop), 3600.), 3600., 0);	2086	fmod (ev_now (loop), 3600.), 3600., 0);
1592	ev_periodic_start (loop, &hourly_tick);	2087	ev_periodic_start (loop, &hourly_tick);
1593		2088
1594		2089
…		…
1597	Signal watchers will trigger an event when the process receives a specific	2092	Signal watchers will trigger an event when the process receives a specific
1598	signal one or more times. Even though signals are very asynchronous, libev	2093	signal one or more times. Even though signals are very asynchronous, libev
1599	will try it's best to deliver signals synchronously, i.e. as part of the	2094	will try it's best to deliver signals synchronously, i.e. as part of the
1600	normal event processing, like any other event.	2095	normal event processing, like any other event.
1601		2096
1602	If you want signals asynchronously, just use C<sigaction> as you would	2097	If you want signals to be delivered truly asynchronously, just use
1603	do without libev and forget about sharing the signal. You can even use	2098	C<sigaction> as you would do without libev and forget about sharing
1604	C<ev_async> from a signal handler to synchronously wake up an event loop.	2099	the signal. You can even use C<ev_async> from a signal handler to
		2100	synchronously wake up an event loop.
1605		2101
1606	You can configure as many watchers as you like per signal. Only when the	2102	You can configure as many watchers as you like for the same signal, but
		2103	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2104	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2105	C<SIGINT> in both the default loop and another loop at the same time. At
		2106	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2107
1607	first watcher gets started will libev actually register a signal handler	2108	When the first watcher gets started will libev actually register something
1608	with the kernel (thus it coexists with your own signal handlers as long as	2109	with the kernel (thus it coexists with your own signal handlers as long as
1609	you don't register any with libev for the same signal). Similarly, when	2110	you don't register any with libev for the same signal).
1610	the last signal watcher for a signal is stopped, libev will reset the	2111
1611	signal handler to SIG_DFL (regardless of what it was set to before).	2112	Both the signal mask state (C<sigprocmask>) and the signal handler state
		2113	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2114	sotpping it again), that is, libev might or might not block the signal,
		2115	and might or might not set or restore the installed signal handler.
1612		2116
1613	If possible and supported, libev will install its handlers with	2117	If possible and supported, libev will install its handlers with
1614	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2118	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1615	interrupted. If you have a problem with system calls getting interrupted by	2119	not be unduly interrupted. If you have a problem with system calls getting
1616	signals you can block all signals in an C<ev_check> watcher and unblock	2120	interrupted by signals you can block all signals in an C<ev_check> watcher
1617	them in an C<ev_prepare> watcher.	2121	and unblock them in an C<ev_prepare> watcher.
1618		2122
1619	=head3 Watcher-Specific Functions and Data Members	2123	=head3 Watcher-Specific Functions and Data Members
1620		2124
1621	=over 4	2125	=over 4
1622		2126
…		…
1636	=head3 Examples	2140	=head3 Examples
1637		2141
1638	Example: Try to exit cleanly on SIGINT.	2142	Example: Try to exit cleanly on SIGINT.
1639		2143
1640	static void	2144	static void
1641	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2145	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1642	{	2146	{
1643	ev_unloop (loop, EVUNLOOP_ALL);	2147	ev_unloop (loop, EVUNLOOP_ALL);
1644	}	2148	}
1645		2149
1646	struct ev_signal signal_watcher;	2150	ev_signal signal_watcher;
1647	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2151	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1648	ev_signal_start (loop, &signal_watcher);	2152	ev_signal_start (loop, &signal_watcher);
1649		2153
1650		2154
1651	=head2 C<ev_child> - watch out for process status changes	2155	=head2 C<ev_child> - watch out for process status changes
…		…
1654	some child status changes (most typically when a child of yours dies or	2158	some child status changes (most typically when a child of yours dies or
1655	exits). It is permissible to install a child watcher I<after> the child	2159	exits). It is permissible to install a child watcher I<after> the child
1656	has been forked (which implies it might have already exited), as long	2160	has been forked (which implies it might have already exited), as long
1657	as the event loop isn't entered (or is continued from a watcher), i.e.,	2161	as the event loop isn't entered (or is continued from a watcher), i.e.,
1658	forking and then immediately registering a watcher for the child is fine,	2162	forking and then immediately registering a watcher for the child is fine,
1659	but forking and registering a watcher a few event loop iterations later is	2163	but forking and registering a watcher a few event loop iterations later or
1660	not.	2164	in the next callback invocation is not.
1661		2165
1662	Only the default event loop is capable of handling signals, and therefore	2166	Only the default event loop is capable of handling signals, and therefore
1663	you can only register child watchers in the default event loop.	2167	you can only register child watchers in the default event loop.
1664		2168
		2169	Due to some design glitches inside libev, child watchers will always be
		2170	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2171	libev)
		2172
1665	=head3 Process Interaction	2173	=head3 Process Interaction
1666		2174
1667	Libev grabs C<SIGCHLD> as soon as the default event loop is	2175	Libev grabs C<SIGCHLD> as soon as the default event loop is
1668	initialised. This is necessary to guarantee proper behaviour even if	2176	initialised. This is necessary to guarantee proper behaviour even if the
1669	the first child watcher is started after the child exits. The occurrence	2177	first child watcher is started after the child exits. The occurrence
1670	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2178	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1671	synchronously as part of the event loop processing. Libev always reaps all	2179	synchronously as part of the event loop processing. Libev always reaps all
1672	children, even ones not watched.	2180	children, even ones not watched.
1673		2181
1674	=head3 Overriding the Built-In Processing	2182	=head3 Overriding the Built-In Processing
…		…
1684	=head3 Stopping the Child Watcher	2192	=head3 Stopping the Child Watcher
1685		2193
1686	Currently, the child watcher never gets stopped, even when the	2194	Currently, the child watcher never gets stopped, even when the
1687	child terminates, so normally one needs to stop the watcher in the	2195	child terminates, so normally one needs to stop the watcher in the
1688	callback. Future versions of libev might stop the watcher automatically	2196	callback. Future versions of libev might stop the watcher automatically
1689	when a child exit is detected.	2197	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2198	problem).
1690		2199
1691	=head3 Watcher-Specific Functions and Data Members	2200	=head3 Watcher-Specific Functions and Data Members
1692		2201
1693	=over 4	2202	=over 4
1694		2203
…		…
1726	its completion.	2235	its completion.
1727		2236
1728	ev_child cw;	2237	ev_child cw;
1729		2238
1730	static void	2239	static void
1731	child_cb (EV_P_ struct ev_child *w, int revents)	2240	child_cb (EV_P_ ev_child *w, int revents)
1732	{	2241	{
1733	ev_child_stop (EV_A_ w);	2242	ev_child_stop (EV_A_ w);
1734	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2243	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1735	}	2244	}
1736		2245
…		…
1751		2260
1752		2261
1753	=head2 C<ev_stat> - did the file attributes just change?	2262	=head2 C<ev_stat> - did the file attributes just change?
1754		2263
1755	This watches a file system path for attribute changes. That is, it calls	2264	This watches a file system path for attribute changes. That is, it calls
1756	C<stat> regularly (or when the OS says it changed) and sees if it changed	2265	C<stat> on that path in regular intervals (or when the OS says it changed)
1757	compared to the last time, invoking the callback if it did.	2266	and sees if it changed compared to the last time, invoking the callback if
		2267	it did.
1758		2268
1759	The path does not need to exist: changing from "path exists" to "path does	2269	The path does not need to exist: changing from "path exists" to "path does
1760	not exist" is a status change like any other. The condition "path does	2270	not exist" is a status change like any other. The condition "path does not
1761	not exist" is signified by the C<st_nlink> field being zero (which is	2271	exist" (or more correctly "path cannot be stat'ed") is signified by the
1762	otherwise always forced to be at least one) and all the other fields of	2272	C<st_nlink> field being zero (which is otherwise always forced to be at
1763	the stat buffer having unspecified contents.	2273	least one) and all the other fields of the stat buffer having unspecified
		2274	contents.
1764		2275
1765	The path I<should> be absolute and I<must not> end in a slash. If it is	2276	The path I<must not> end in a slash or contain special components such as
		2277	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1766	relative and your working directory changes, the behaviour is undefined.	2278	your working directory changes, then the behaviour is undefined.
1767		2279
1768	Since there is no standard kernel interface to do this, the portable	2280	Since there is no portable change notification interface available, the
1769	implementation simply calls C<stat (2)> regularly on the path to see if	2281	portable implementation simply calls C<stat(2)> regularly on the path
1770	it changed somehow. You can specify a recommended polling interval for	2282	to see if it changed somehow. You can specify a recommended polling
1771	this case. If you specify a polling interval of C<0> (highly recommended!)	2283	interval for this case. If you specify a polling interval of C<0> (highly
1772	then a I<suitable, unspecified default> value will be used (which	2284	recommended!) then a I<suitable, unspecified default> value will be used
1773	you can expect to be around five seconds, although this might change	2285	(which you can expect to be around five seconds, although this might
1774	dynamically). Libev will also impose a minimum interval which is currently	2286	change dynamically). Libev will also impose a minimum interval which is
1775	around C<0.1>, but thats usually overkill.	2287	currently around C<0.1>, but that's usually overkill.
1776		2288
1777	This watcher type is not meant for massive numbers of stat watchers,	2289	This watcher type is not meant for massive numbers of stat watchers,
1778	as even with OS-supported change notifications, this can be	2290	as even with OS-supported change notifications, this can be
1779	resource-intensive.	2291	resource-intensive.
1780		2292
1781	At the time of this writing, the only OS-specific interface implemented	2293	At the time of this writing, the only OS-specific interface implemented
1782	is the Linux inotify interface (implementing kqueue support is left as	2294	is the Linux inotify interface (implementing kqueue support is left as an
1783	an exercise for the reader. Note, however, that the author sees no way	2295	exercise for the reader. Note, however, that the author sees no way of
1784	of implementing C<ev_stat> semantics with kqueue).	2296	implementing C<ev_stat> semantics with kqueue, except as a hint).
1785		2297
1786	=head3 ABI Issues (Largefile Support)	2298	=head3 ABI Issues (Largefile Support)
1787		2299
1788	Libev by default (unless the user overrides this) uses the default	2300	Libev by default (unless the user overrides this) uses the default
1789	compilation environment, which means that on systems with large file	2301	compilation environment, which means that on systems with large file
1790	support disabled by default, you get the 32 bit version of the stat	2302	support disabled by default, you get the 32 bit version of the stat
1791	structure. When using the library from programs that change the ABI to	2303	structure. When using the library from programs that change the ABI to
1792	use 64 bit file offsets the programs will fail. In that case you have to	2304	use 64 bit file offsets the programs will fail. In that case you have to
1793	compile libev with the same flags to get binary compatibility. This is	2305	compile libev with the same flags to get binary compatibility. This is
1794	obviously the case with any flags that change the ABI, but the problem is	2306	obviously the case with any flags that change the ABI, but the problem is
1795	most noticeably disabled with ev_stat and large file support.	2307	most noticeably displayed with ev_stat and large file support.
1796		2308
1797	The solution for this is to lobby your distribution maker to make large	2309	The solution for this is to lobby your distribution maker to make large
1798	file interfaces available by default (as e.g. FreeBSD does) and not	2310	file interfaces available by default (as e.g. FreeBSD does) and not
1799	optional. Libev cannot simply switch on large file support because it has	2311	optional. Libev cannot simply switch on large file support because it has
1800	to exchange stat structures with application programs compiled using the	2312	to exchange stat structures with application programs compiled using the
1801	default compilation environment.	2313	default compilation environment.
1802		2314
1803	=head3 Inotify and Kqueue	2315	=head3 Inotify and Kqueue
1804		2316
1805	When C<inotify (7)> support has been compiled into libev (generally	2317	When C<inotify (7)> support has been compiled into libev and present at
1806	only available with Linux 2.6.25 or above due to bugs in earlier	2318	runtime, it will be used to speed up change detection where possible. The
1807	implementations) and present at runtime, it will be used to speed up	2319	inotify descriptor will be created lazily when the first C<ev_stat>
1808	change detection where possible. The inotify descriptor will be created	2320	watcher is being started.
1809	lazily when the first C<ev_stat> watcher is being started.
1810		2321
1811	Inotify presence does not change the semantics of C<ev_stat> watchers	2322	Inotify presence does not change the semantics of C<ev_stat> watchers
1812	except that changes might be detected earlier, and in some cases, to avoid	2323	except that changes might be detected earlier, and in some cases, to avoid
1813	making regular C<stat> calls. Even in the presence of inotify support	2324	making regular C<stat> calls. Even in the presence of inotify support
1814	there are many cases where libev has to resort to regular C<stat> polling,	2325	there are many cases where libev has to resort to regular C<stat> polling,
1815	but as long as the path exists, libev usually gets away without polling.	2326	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2327	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2328	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2329	xfs are fully working) libev usually gets away without polling.
1816		2330
1817	There is no support for kqueue, as apparently it cannot be used to	2331	There is no support for kqueue, as apparently it cannot be used to
1818	implement this functionality, due to the requirement of having a file	2332	implement this functionality, due to the requirement of having a file
1819	descriptor open on the object at all times, and detecting renames, unlinks	2333	descriptor open on the object at all times, and detecting renames, unlinks
1820	etc. is difficult.	2334	etc. is difficult.
1821		2335
		2336	=head3 C<stat ()> is a synchronous operation
		2337
		2338	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2339	the process. The exception are C<ev_stat> watchers - those call C<stat
		2340	()>, which is a synchronous operation.
		2341
		2342	For local paths, this usually doesn't matter: unless the system is very
		2343	busy or the intervals between stat's are large, a stat call will be fast,
		2344	as the path data is usually in memory already (except when starting the
		2345	watcher).
		2346
		2347	For networked file systems, calling C<stat ()> can block an indefinite
		2348	time due to network issues, and even under good conditions, a stat call
		2349	often takes multiple milliseconds.
		2350
		2351	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2352	paths, although this is fully supported by libev.
		2353
1822	=head3 The special problem of stat time resolution	2354	=head3 The special problem of stat time resolution
1823		2355
1824	The C<stat ()> system call only supports full-second resolution portably, and	2356	The C<stat ()> system call only supports full-second resolution portably,
1825	even on systems where the resolution is higher, most file systems still	2357	and even on systems where the resolution is higher, most file systems
1826	only support whole seconds.	2358	still only support whole seconds.
1827		2359
1828	That means that, if the time is the only thing that changes, you can	2360	That means that, if the time is the only thing that changes, you can
1829	easily miss updates: on the first update, C<ev_stat> detects a change and	2361	easily miss updates: on the first update, C<ev_stat> detects a change and
1830	calls your callback, which does something. When there is another update	2362	calls your callback, which does something. When there is another update
1831	within the same second, C<ev_stat> will be unable to detect unless the	2363	within the same second, C<ev_stat> will be unable to detect unless the
…		…
1974		2506
1975	=head3 Watcher-Specific Functions and Data Members	2507	=head3 Watcher-Specific Functions and Data Members
1976		2508
1977	=over 4	2509	=over 4
1978		2510
1979	=item ev_idle_init (ev_signal *, callback)	2511	=item ev_idle_init (ev_idle *, callback)
1980		2512
1981	Initialises and configures the idle watcher - it has no parameters of any	2513	Initialises and configures the idle watcher - it has no parameters of any
1982	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2514	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1983	believe me.	2515	believe me.
1984		2516
…		…
1988		2520
1989	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2521	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1990	callback, free it. Also, use no error checking, as usual.	2522	callback, free it. Also, use no error checking, as usual.
1991		2523
1992	static void	2524	static void
1993	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2525	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1994	{	2526	{
1995	free (w);	2527	free (w);
1996	// now do something you wanted to do when the program has	2528	// now do something you wanted to do when the program has
1997	// no longer anything immediate to do.	2529	// no longer anything immediate to do.
1998	}	2530	}
1999		2531
2000	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2532	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2001	ev_idle_init (idle_watcher, idle_cb);	2533	ev_idle_init (idle_watcher, idle_cb);
2002	ev_idle_start (loop, idle_cb);	2534	ev_idle_start (loop, idle_watcher);
2003		2535
2004		2536
2005	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2537	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2006		2538
2007	Prepare and check watchers are usually (but not always) used in pairs:	2539	Prepare and check watchers are usually (but not always) used in pairs:
…		…
2086		2618
2087	static ev_io iow [nfd];	2619	static ev_io iow [nfd];
2088	static ev_timer tw;	2620	static ev_timer tw;
2089		2621
2090	static void	2622	static void
2091	io_cb (ev_loop *loop, ev_io *w, int revents)	2623	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2092	{	2624	{
2093	}	2625	}
2094		2626
2095	// create io watchers for each fd and a timer before blocking	2627	// create io watchers for each fd and a timer before blocking
2096	static void	2628	static void
2097	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2629	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2098	{	2630	{
2099	int timeout = 3600000;	2631	int timeout = 3600000;
2100	struct pollfd fds [nfd];	2632	struct pollfd fds [nfd];
2101	// actual code will need to loop here and realloc etc.	2633	// actual code will need to loop here and realloc etc.
2102	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2634	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2103		2635
2104	/* the callback is illegal, but won't be called as we stop during check */	2636	/* the callback is illegal, but won't be called as we stop during check */
2105	ev_timer_init (&tw, 0, timeout * 1e-3);	2637	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2106	ev_timer_start (loop, &tw);	2638	ev_timer_start (loop, &tw);
2107		2639
2108	// create one ev_io per pollfd	2640	// create one ev_io per pollfd
2109	for (int i = 0; i < nfd; ++i)	2641	for (int i = 0; i < nfd; ++i)
2110	{	2642	{
…		…
2117	}	2649	}
2118	}	2650	}
2119		2651
2120	// stop all watchers after blocking	2652	// stop all watchers after blocking
2121	static void	2653	static void
2122	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2654	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2123	{	2655	{
2124	ev_timer_stop (loop, &tw);	2656	ev_timer_stop (loop, &tw);
2125		2657
2126	for (int i = 0; i < nfd; ++i)	2658	for (int i = 0; i < nfd; ++i)
2127	{	2659	{
…		…
2223	some fds have to be watched and handled very quickly (with low latency),	2755	some fds have to be watched and handled very quickly (with low latency),
2224	and even priorities and idle watchers might have too much overhead. In	2756	and even priorities and idle watchers might have too much overhead. In
2225	this case you would put all the high priority stuff in one loop and all	2757	this case you would put all the high priority stuff in one loop and all
2226	the rest in a second one, and embed the second one in the first.	2758	the rest in a second one, and embed the second one in the first.
2227		2759
2228	As long as the watcher is active, the callback will be invoked every time	2760	As long as the watcher is active, the callback will be invoked every
2229	there might be events pending in the embedded loop. The callback must then	2761	time there might be events pending in the embedded loop. The callback
2230	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2762	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2231	their callbacks (you could also start an idle watcher to give the embedded	2763	sweep and invoke their callbacks (the callback doesn't need to invoke the
2232	loop strictly lower priority for example). You can also set the callback	2764	C<ev_embed_sweep> function directly, it could also start an idle watcher
2233	to C<0>, in which case the embed watcher will automatically execute the	2765	to give the embedded loop strictly lower priority for example).
2234	embedded loop sweep.
2235		2766
2236	As long as the watcher is started it will automatically handle events. The	2767	You can also set the callback to C<0>, in which case the embed watcher
2237	callback will be invoked whenever some events have been handled. You can	2768	will automatically execute the embedded loop sweep whenever necessary.
2238	set the callback to C<0> to avoid having to specify one if you are not
2239	interested in that.
2240		2769
2241	Also, there have not currently been made special provisions for forking:	2770	Fork detection will be handled transparently while the C<ev_embed> watcher
2242	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2771	is active, i.e., the embedded loop will automatically be forked when the
2243	but you will also have to stop and restart any C<ev_embed> watchers	2772	embedding loop forks. In other cases, the user is responsible for calling
2244	yourself - but you can use a fork watcher to handle this automatically,	2773	C<ev_loop_fork> on the embedded loop.
2245	and future versions of libev might do just that.
2246		2774
2247	Unfortunately, not all backends are embeddable: only the ones returned by	2775	Unfortunately, not all backends are embeddable: only the ones returned by
2248	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2776	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2249	portable one.	2777	portable one.
2250		2778
…		…
2295	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2823	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2296	used).	2824	used).
2297		2825
2298	struct ev_loop *loop_hi = ev_default_init (0);	2826	struct ev_loop *loop_hi = ev_default_init (0);
2299	struct ev_loop *loop_lo = 0;	2827	struct ev_loop *loop_lo = 0;
2300	struct ev_embed embed;	2828	ev_embed embed;
2301		2829
2302	// see if there is a chance of getting one that works	2830	// see if there is a chance of getting one that works
2303	// (remember that a flags value of 0 means autodetection)	2831	// (remember that a flags value of 0 means autodetection)
2304	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2832	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2305	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2833	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2319	kqueue implementation). Store the kqueue/socket-only event loop in	2847	kqueue implementation). Store the kqueue/socket-only event loop in
2320	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2848	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2321		2849
2322	struct ev_loop *loop = ev_default_init (0);	2850	struct ev_loop *loop = ev_default_init (0);
2323	struct ev_loop *loop_socket = 0;	2851	struct ev_loop *loop_socket = 0;
2324	struct ev_embed embed;	2852	ev_embed embed;
2325		2853
2326	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2854	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2327	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2855	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2328	{	2856	{
2329	ev_embed_init (&embed, 0, loop_socket);	2857	ev_embed_init (&embed, 0, loop_socket);
…		…
2344	event loop blocks next and before C<ev_check> watchers are being called,	2872	event loop blocks next and before C<ev_check> watchers are being called,
2345	and only in the child after the fork. If whoever good citizen calling	2873	and only in the child after the fork. If whoever good citizen calling
2346	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2874	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2347	handlers will be invoked, too, of course.	2875	handlers will be invoked, too, of course.
2348		2876
		2877	=head3 The special problem of life after fork - how is it possible?
		2878
		2879	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2880	up/change the process environment, followed by a call to C<exec()>. This
		2881	sequence should be handled by libev without any problems.
		2882
		2883	This changes when the application actually wants to do event handling
		2884	in the child, or both parent in child, in effect "continuing" after the
		2885	fork.
		2886
		2887	The default mode of operation (for libev, with application help to detect
		2888	forks) is to duplicate all the state in the child, as would be expected
		2889	when I<either> the parent I<or> the child process continues.
		2890
		2891	When both processes want to continue using libev, then this is usually the
		2892	wrong result. In that case, usually one process (typically the parent) is
		2893	supposed to continue with all watchers in place as before, while the other
		2894	process typically wants to start fresh, i.e. without any active watchers.
		2895
		2896	The cleanest and most efficient way to achieve that with libev is to
		2897	simply create a new event loop, which of course will be "empty", and
		2898	use that for new watchers. This has the advantage of not touching more
		2899	memory than necessary, and thus avoiding the copy-on-write, and the
		2900	disadvantage of having to use multiple event loops (which do not support
		2901	signal watchers).
		2902
		2903	When this is not possible, or you want to use the default loop for
		2904	other reasons, then in the process that wants to start "fresh", call
		2905	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2906	the default loop will "orphan" (not stop) all registered watchers, so you
		2907	have to be careful not to execute code that modifies those watchers. Note
		2908	also that in that case, you have to re-register any signal watchers.
		2909
2349	=head3 Watcher-Specific Functions and Data Members	2910	=head3 Watcher-Specific Functions and Data Members
2350		2911
2351	=over 4	2912	=over 4
2352		2913
2353	=item ev_fork_init (ev_signal *, callback)	2914	=item ev_fork_init (ev_signal *, callback)
…		…
2470	=over 4	3031	=over 4
2471		3032
2472	=item ev_async_init (ev_async *, callback)	3033	=item ev_async_init (ev_async *, callback)
2473		3034
2474	Initialises and configures the async watcher - it has no parameters of any	3035	Initialises and configures the async watcher - it has no parameters of any
2475	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3036	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2476	trust me.	3037	trust me.
2477		3038
2478	=item ev_async_send (loop, ev_async *)	3039	=item ev_async_send (loop, ev_async *)
2479		3040
2480	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3041	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2481	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3042	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2482	C<ev_feed_event>, this call is safe to do from other threads, signal or	3043	C<ev_feed_event>, this call is safe to do from other threads, signal or
2483	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3044	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2484	section below on what exactly this means).	3045	section below on what exactly this means).
2485		3046
		3047	Note that, as with other watchers in libev, multiple events might get
		3048	compressed into a single callback invocation (another way to look at this
		3049	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3050	reset when the event loop detects that).
		3051
2486	This call incurs the overhead of a system call only once per loop iteration,	3052	This call incurs the overhead of a system call only once per event loop
2487	so while the overhead might be noticeable, it doesn't apply to repeated	3053	iteration, so while the overhead might be noticeable, it doesn't apply to
2488	calls to C<ev_async_send>.	3054	repeated calls to C<ev_async_send> for the same event loop.
2489		3055
2490	=item bool = ev_async_pending (ev_async *)	3056	=item bool = ev_async_pending (ev_async *)
2491		3057
2492	Returns a non-zero value when C<ev_async_send> has been called on the	3058	Returns a non-zero value when C<ev_async_send> has been called on the
2493	watcher but the event has not yet been processed (or even noted) by the	3059	watcher but the event has not yet been processed (or even noted) by the
…		…
2496	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3062	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2497	the loop iterates next and checks for the watcher to have become active,	3063	the loop iterates next and checks for the watcher to have become active,
2498	it will reset the flag again. C<ev_async_pending> can be used to very	3064	it will reset the flag again. C<ev_async_pending> can be used to very
2499	quickly check whether invoking the loop might be a good idea.	3065	quickly check whether invoking the loop might be a good idea.
2500		3066
2501	Not that this does I<not> check whether the watcher itself is pending, only	3067	Not that this does I<not> check whether the watcher itself is pending,
2502	whether it has been requested to make this watcher pending.	3068	only whether it has been requested to make this watcher pending: there
		3069	is a time window between the event loop checking and resetting the async
		3070	notification, and the callback being invoked.
2503		3071
2504	=back	3072	=back
2505		3073
2506		3074
2507	=head1 OTHER FUNCTIONS	3075	=head1 OTHER FUNCTIONS
…		…
2543	/* doh, nothing entered */;	3111	/* doh, nothing entered */;
2544	}	3112	}
2545		3113
2546	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3114	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2547		3115
2548	=item ev_feed_event (ev_loop *, watcher *, int revents)	3116	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2549		3117
2550	Feeds the given event set into the event loop, as if the specified event	3118	Feeds the given event set into the event loop, as if the specified event
2551	had happened for the specified watcher (which must be a pointer to an	3119	had happened for the specified watcher (which must be a pointer to an
2552	initialised but not necessarily started event watcher).	3120	initialised but not necessarily started event watcher).
2553		3121
2554	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3122	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2555		3123
2556	Feed an event on the given fd, as if a file descriptor backend detected	3124	Feed an event on the given fd, as if a file descriptor backend detected
2557	the given events it.	3125	the given events it.
2558		3126
2559	=item ev_feed_signal_event (ev_loop *loop, int signum)	3127	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2560		3128
2561	Feed an event as if the given signal occurred (C<loop> must be the default	3129	Feed an event as if the given signal occurred (C<loop> must be the default
2562	loop!).	3130	loop!).
2563		3131
2564	=back	3132	=back
…		…
2685	}	3253	}
2686		3254
2687	myclass obj;	3255	myclass obj;
2688	ev::io iow;	3256	ev::io iow;
2689	iow.set <myclass, &myclass::io_cb> (&obj);	3257	iow.set <myclass, &myclass::io_cb> (&obj);
		3258
		3259	=item w->set (object *)
		3260
		3261	This is an B<experimental> feature that might go away in a future version.
		3262
		3263	This is a variation of a method callback - leaving out the method to call
		3264	will default the method to C<operator ()>, which makes it possible to use
		3265	functor objects without having to manually specify the C<operator ()> all
		3266	the time. Incidentally, you can then also leave out the template argument
		3267	list.
		3268
		3269	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3270	int revents)>.
		3271
		3272	See the method-C<set> above for more details.
		3273
		3274	Example: use a functor object as callback.
		3275
		3276	struct myfunctor
		3277	{
		3278	void operator() (ev::io &w, int revents)
		3279	{
		3280	...
		3281	}
		3282	}
		3283
		3284	myfunctor f;
		3285
		3286	ev::io w;
		3287	w.set (&f);
2690		3288
2691	=item w->set<function> (void *data = 0)	3289	=item w->set<function> (void *data = 0)
2692		3290
2693	Also sets a callback, but uses a static method or plain function as	3291	Also sets a callback, but uses a static method or plain function as
2694	callback. The optional C<data> argument will be stored in the watcher's	3292	callback. The optional C<data> argument will be stored in the watcher's
…		…
2781	L<http://software.schmorp.de/pkg/EV>.	3379	L<http://software.schmorp.de/pkg/EV>.
2782		3380
2783	=item Python	3381	=item Python
2784		3382
2785	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3383	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2786	seems to be quite complete and well-documented. Note, however, that the	3384	seems to be quite complete and well-documented.
2787	patch they require for libev is outright dangerous as it breaks the ABI
2788	for everybody else, and therefore, should never be applied in an installed
2789	libev (if python requires an incompatible ABI then it needs to embed
2790	libev).
2791		3385
2792	=item Ruby	3386	=item Ruby
2793		3387
2794	Tony Arcieri has written a ruby extension that offers access to a subset	3388	Tony Arcieri has written a ruby extension that offers access to a subset
2795	of the libev API and adds file handle abstractions, asynchronous DNS and	3389	of the libev API and adds file handle abstractions, asynchronous DNS and
2796	more on top of it. It can be found via gem servers. Its homepage is at	3390	more on top of it. It can be found via gem servers. Its homepage is at
2797	L<http://rev.rubyforge.org/>.	3391	L<http://rev.rubyforge.org/>.
2798		3392
		3393	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3394	makes rev work even on mingw.
		3395
		3396	=item Haskell
		3397
		3398	A haskell binding to libev is available at
		3399	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3400
2799	=item D	3401	=item D
2800		3402
2801	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3403	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2802	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3404	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3405
		3406	=item Ocaml
		3407
		3408	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3409	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2803		3410
2804	=back	3411	=back
2805		3412
2806		3413
2807	=head1 MACRO MAGIC	3414	=head1 MACRO MAGIC
…		…
2908		3515
2909	#define EV_STANDALONE 1	3516	#define EV_STANDALONE 1
2910	#include "ev.h"	3517	#include "ev.h"
2911		3518
2912	Both header files and implementation files can be compiled with a C++	3519	Both header files and implementation files can be compiled with a C++
2913	compiler (at least, thats a stated goal, and breakage will be treated	3520	compiler (at least, that's a stated goal, and breakage will be treated
2914	as a bug).	3521	as a bug).
2915		3522
2916	You need the following files in your source tree, or in a directory	3523	You need the following files in your source tree, or in a directory
2917	in your include path (e.g. in libev/ when using -Ilibev):	3524	in your include path (e.g. in libev/ when using -Ilibev):
2918		3525
…		…
2974	keeps libev from including F<config.h>, and it also defines dummy	3581	keeps libev from including F<config.h>, and it also defines dummy
2975	implementations for some libevent functions (such as logging, which is not	3582	implementations for some libevent functions (such as logging, which is not
2976	supported). It will also not define any of the structs usually found in	3583	supported). It will also not define any of the structs usually found in
2977	F<event.h> that are not directly supported by the libev core alone.	3584	F<event.h> that are not directly supported by the libev core alone.
2978		3585
		3586	In stanbdalone mode, libev will still try to automatically deduce the
		3587	configuration, but has to be more conservative.
		3588
2979	=item EV_USE_MONOTONIC	3589	=item EV_USE_MONOTONIC
2980		3590
2981	If defined to be C<1>, libev will try to detect the availability of the	3591	If defined to be C<1>, libev will try to detect the availability of the
2982	monotonic clock option at both compile time and runtime. Otherwise no use	3592	monotonic clock option at both compile time and runtime. Otherwise no
2983	of the monotonic clock option will be attempted. If you enable this, you	3593	use of the monotonic clock option will be attempted. If you enable this,
2984	usually have to link against librt or something similar. Enabling it when	3594	you usually have to link against librt or something similar. Enabling it
2985	the functionality isn't available is safe, though, although you have	3595	when the functionality isn't available is safe, though, although you have
2986	to make sure you link against any libraries where the C<clock_gettime>	3596	to make sure you link against any libraries where the C<clock_gettime>
2987	function is hiding in (often F<-lrt>).	3597	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2988		3598
2989	=item EV_USE_REALTIME	3599	=item EV_USE_REALTIME
2990		3600
2991	If defined to be C<1>, libev will try to detect the availability of the	3601	If defined to be C<1>, libev will try to detect the availability of the
2992	real-time clock option at compile time (and assume its availability at	3602	real-time clock option at compile time (and assume its availability
2993	runtime if successful). Otherwise no use of the real-time clock option will	3603	at runtime if successful). Otherwise no use of the real-time clock
2994	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3604	option will be attempted. This effectively replaces C<gettimeofday>
2995	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3605	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2996	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3606	correctness. See the note about libraries in the description of
		3607	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3608	C<EV_USE_CLOCK_SYSCALL>.
		3609
		3610	=item EV_USE_CLOCK_SYSCALL
		3611
		3612	If defined to be C<1>, libev will try to use a direct syscall instead
		3613	of calling the system-provided C<clock_gettime> function. This option
		3614	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3615	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3616	programs needlessly. Using a direct syscall is slightly slower (in
		3617	theory), because no optimised vdso implementation can be used, but avoids
		3618	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3619	higher, as it simplifies linking (no need for C<-lrt>).
2997		3620
2998	=item EV_USE_NANOSLEEP	3621	=item EV_USE_NANOSLEEP
2999		3622
3000	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3623	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
3001	and will use it for delays. Otherwise it will use C<select ()>.	3624	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3017		3640
3018	=item EV_SELECT_USE_FD_SET	3641	=item EV_SELECT_USE_FD_SET
3019		3642
3020	If defined to C<1>, then the select backend will use the system C<fd_set>	3643	If defined to C<1>, then the select backend will use the system C<fd_set>
3021	structure. This is useful if libev doesn't compile due to a missing	3644	structure. This is useful if libev doesn't compile due to a missing
3022	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3645	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3023	exotic systems. This usually limits the range of file descriptors to some	3646	on exotic systems. This usually limits the range of file descriptors to
3024	low limit such as 1024 or might have other limitations (winsocket only	3647	some low limit such as 1024 or might have other limitations (winsocket
3025	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3648	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3026	influence the size of the C<fd_set> used.	3649	configures the maximum size of the C<fd_set>.
3027		3650
3028	=item EV_SELECT_IS_WINSOCKET	3651	=item EV_SELECT_IS_WINSOCKET
3029		3652
3030	When defined to C<1>, the select backend will assume that	3653	When defined to C<1>, the select backend will assume that
3031	select/socket/connect etc. don't understand file descriptors but	3654	select/socket/connect etc. don't understand file descriptors but
…		…
3181	defined to be C<0>, then they are not.	3804	defined to be C<0>, then they are not.
3182		3805
3183	=item EV_MINIMAL	3806	=item EV_MINIMAL
3184		3807
3185	If you need to shave off some kilobytes of code at the expense of some	3808	If you need to shave off some kilobytes of code at the expense of some
3186	speed, define this symbol to C<1>. Currently this is used to override some	3809	speed (but with the full API), define this symbol to C<1>. Currently this
3187	inlining decisions, saves roughly 30% code size on amd64. It also selects a	3810	is used to override some inlining decisions, saves roughly 30% code size
3188	much smaller 2-heap for timer management over the default 4-heap.	3811	on amd64. It also selects a much smaller 2-heap for timer management over
		3812	the default 4-heap.
		3813
		3814	You can save even more by disabling watcher types you do not need
		3815	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>
		3816	(C<-DNDEBUG>) will usually reduce code size a lot.
		3817
		3818	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to
		3819	provide a bare-bones event library. See C<ev.h> for details on what parts
		3820	of the API are still available, and do not complain if this subset changes
		3821	over time.
		3822
		3823	=item EV_NSIG
		3824
		3825	The highest supported signal number, +1 (or, the number of
		3826	signals): Normally, libev tries to deduce the maximum number of signals
		3827	automatically, but sometimes this fails, in which case it can be
		3828	specified. Also, using a lower number than detected (C<32> should be
		3829	good for about any system in existance) can save some memory, as libev
		3830	statically allocates some 12-24 bytes per signal number.
3189		3831
3190	=item EV_PID_HASHSIZE	3832	=item EV_PID_HASHSIZE
3191		3833
3192	C<ev_child> watchers use a small hash table to distribute workload by	3834	C<ev_child> watchers use a small hash table to distribute workload by
3193	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3835	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
3379	default loop and triggering an C<ev_async> watcher from the default loop	4021	default loop and triggering an C<ev_async> watcher from the default loop
3380	watcher callback into the event loop interested in the signal.	4022	watcher callback into the event loop interested in the signal.
3381		4023
3382	=back	4024	=back
3383		4025
		4026	=head4 THREAD LOCKING EXAMPLE
		4027
		4028	Here is a fictitious example of how to run an event loop in a different
		4029	thread than where callbacks are being invoked and watchers are
		4030	created/added/removed.
		4031
		4032	For a real-world example, see the C<EV::Loop::Async> perl module,
		4033	which uses exactly this technique (which is suited for many high-level
		4034	languages).
		4035
		4036	The example uses a pthread mutex to protect the loop data, a condition
		4037	variable to wait for callback invocations, an async watcher to notify the
		4038	event loop thread and an unspecified mechanism to wake up the main thread.
		4039
		4040	First, you need to associate some data with the event loop:
		4041
		4042	typedef struct {
		4043	mutex_t lock; /* global loop lock */
		4044	ev_async async_w;
		4045	thread_t tid;
		4046	cond_t invoke_cv;
		4047	} userdata;
		4048
		4049	void prepare_loop (EV_P)
		4050	{
		4051	// for simplicity, we use a static userdata struct.
		4052	static userdata u;
		4053
		4054	ev_async_init (&u->async_w, async_cb);
		4055	ev_async_start (EV_A_ &u->async_w);
		4056
		4057	pthread_mutex_init (&u->lock, 0);
		4058	pthread_cond_init (&u->invoke_cv, 0);
		4059
		4060	// now associate this with the loop
		4061	ev_set_userdata (EV_A_ u);
		4062	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4063	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4064
		4065	// then create the thread running ev_loop
		4066	pthread_create (&u->tid, 0, l_run, EV_A);
		4067	}
		4068
		4069	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4070	solely to wake up the event loop so it takes notice of any new watchers
		4071	that might have been added:
		4072
		4073	static void
		4074	async_cb (EV_P_ ev_async *w, int revents)
		4075	{
		4076	// just used for the side effects
		4077	}
		4078
		4079	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4080	protecting the loop data, respectively.
		4081
		4082	static void
		4083	l_release (EV_P)
		4084	{
		4085	userdata *u = ev_userdata (EV_A);
		4086	pthread_mutex_unlock (&u->lock);
		4087	}
		4088
		4089	static void
		4090	l_acquire (EV_P)
		4091	{
		4092	userdata *u = ev_userdata (EV_A);
		4093	pthread_mutex_lock (&u->lock);
		4094	}
		4095
		4096	The event loop thread first acquires the mutex, and then jumps straight
		4097	into C<ev_loop>:
		4098
		4099	void *
		4100	l_run (void *thr_arg)
		4101	{
		4102	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4103
		4104	l_acquire (EV_A);
		4105	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4106	ev_loop (EV_A_ 0);
		4107	l_release (EV_A);
		4108
		4109	return 0;
		4110	}
		4111
		4112	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4113	signal the main thread via some unspecified mechanism (signals? pipe
		4114	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4115	have been called (in a while loop because a) spurious wakeups are possible
		4116	and b) skipping inter-thread-communication when there are no pending
		4117	watchers is very beneficial):
		4118
		4119	static void
		4120	l_invoke (EV_P)
		4121	{
		4122	userdata *u = ev_userdata (EV_A);
		4123
		4124	while (ev_pending_count (EV_A))
		4125	{
		4126	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4127	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4128	}
		4129	}
		4130
		4131	Now, whenever the main thread gets told to invoke pending watchers, it
		4132	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4133	thread to continue:
		4134
		4135	static void
		4136	real_invoke_pending (EV_P)
		4137	{
		4138	userdata *u = ev_userdata (EV_A);
		4139
		4140	pthread_mutex_lock (&u->lock);
		4141	ev_invoke_pending (EV_A);
		4142	pthread_cond_signal (&u->invoke_cv);
		4143	pthread_mutex_unlock (&u->lock);
		4144	}
		4145
		4146	Whenever you want to start/stop a watcher or do other modifications to an
		4147	event loop, you will now have to lock:
		4148
		4149	ev_timer timeout_watcher;
		4150	userdata *u = ev_userdata (EV_A);
		4151
		4152	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4153
		4154	pthread_mutex_lock (&u->lock);
		4155	ev_timer_start (EV_A_ &timeout_watcher);
		4156	ev_async_send (EV_A_ &u->async_w);
		4157	pthread_mutex_unlock (&u->lock);
		4158
		4159	Note that sending the C<ev_async> watcher is required because otherwise
		4160	an event loop currently blocking in the kernel will have no knowledge
		4161	about the newly added timer. By waking up the loop it will pick up any new
		4162	watchers in the next event loop iteration.
		4163
3384	=head3 COROUTINES	4164	=head3 COROUTINES
3385		4165
3386	Libev is very accommodating to coroutines ("cooperative threads"):	4166	Libev is very accommodating to coroutines ("cooperative threads"):
3387	libev fully supports nesting calls to its functions from different	4167	libev fully supports nesting calls to its functions from different
3388	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4168	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3389	different coroutines, and switch freely between both coroutines running the	4169	different coroutines, and switch freely between both coroutines running
3390	loop, as long as you don't confuse yourself). The only exception is that	4170	the loop, as long as you don't confuse yourself). The only exception is
3391	you must not do this from C<ev_periodic> reschedule callbacks.	4171	that you must not do this from C<ev_periodic> reschedule callbacks.
3392		4172
3393	Care has been taken to ensure that libev does not keep local state inside	4173	Care has been taken to ensure that libev does not keep local state inside
3394	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4174	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3395	they do not clal any callbacks.	4175	they do not call any callbacks.
3396		4176
3397	=head2 COMPILER WARNINGS	4177	=head2 COMPILER WARNINGS
3398		4178
3399	Depending on your compiler and compiler settings, you might get no or a	4179	Depending on your compiler and compiler settings, you might get no or a
3400	lot of warnings when compiling libev code. Some people are apparently	4180	lot of warnings when compiling libev code. Some people are apparently
…		…
3434	==2274== definitely lost: 0 bytes in 0 blocks.	4214	==2274== definitely lost: 0 bytes in 0 blocks.
3435	==2274== possibly lost: 0 bytes in 0 blocks.	4215	==2274== possibly lost: 0 bytes in 0 blocks.
3436	==2274== still reachable: 256 bytes in 1 blocks.	4216	==2274== still reachable: 256 bytes in 1 blocks.
3437		4217
3438	Then there is no memory leak, just as memory accounted to global variables	4218	Then there is no memory leak, just as memory accounted to global variables
3439	is not a memleak - the memory is still being refernced, and didn't leak.	4219	is not a memleak - the memory is still being referenced, and didn't leak.
3440		4220
3441	Similarly, under some circumstances, valgrind might report kernel bugs	4221	Similarly, under some circumstances, valgrind might report kernel bugs
3442	as if it were a bug in libev (e.g. in realloc or in the poll backend,	4222	as if it were a bug in libev (e.g. in realloc or in the poll backend,
3443	although an acceptable workaround has been found here), or it might be	4223	although an acceptable workaround has been found here), or it might be
3444	confused.	4224	confused.
…		…
3473	way (note also that glib is the slowest event library known to man).	4253	way (note also that glib is the slowest event library known to man).
3474		4254
3475	There is no supported compilation method available on windows except	4255	There is no supported compilation method available on windows except
3476	embedding it into other applications.	4256	embedding it into other applications.
3477		4257
		4258	Sensible signal handling is officially unsupported by Microsoft - libev
		4259	tries its best, but under most conditions, signals will simply not work.
		4260
3478	Not a libev limitation but worth mentioning: windows apparently doesn't	4261	Not a libev limitation but worth mentioning: windows apparently doesn't
3479	accept large writes: instead of resulting in a partial write, windows will	4262	accept large writes: instead of resulting in a partial write, windows will
3480	either accept everything or return C<ENOBUFS> if the buffer is too large,	4263	either accept everything or return C<ENOBUFS> if the buffer is too large,
3481	so make sure you only write small amounts into your sockets (less than a	4264	so make sure you only write small amounts into your sockets (less than a
3482	megabyte seems safe, but this apparently depends on the amount of memory	4265	megabyte seems safe, but this apparently depends on the amount of memory
…		…
3486	the abysmal performance of winsockets, using a large number of sockets	4269	the abysmal performance of winsockets, using a large number of sockets
3487	is not recommended (and not reasonable). If your program needs to use	4270	is not recommended (and not reasonable). If your program needs to use
3488	more than a hundred or so sockets, then likely it needs to use a totally	4271	more than a hundred or so sockets, then likely it needs to use a totally
3489	different implementation for windows, as libev offers the POSIX readiness	4272	different implementation for windows, as libev offers the POSIX readiness
3490	notification model, which cannot be implemented efficiently on windows	4273	notification model, which cannot be implemented efficiently on windows
3491	(Microsoft monopoly games).	4274	(due to Microsoft monopoly games).
3492		4275
3493	A typical way to use libev under windows is to embed it (see the embedding	4276	A typical way to use libev under windows is to embed it (see the embedding
3494	section for details) and use the following F<evwrap.h> header file instead	4277	section for details) and use the following F<evwrap.h> header file instead
3495	of F<ev.h>:	4278	of F<ev.h>:
3496		4279
…		…
3532		4315
3533	Early versions of winsocket's select only supported waiting for a maximum	4316	Early versions of winsocket's select only supported waiting for a maximum
3534	of C<64> handles (probably owning to the fact that all windows kernels	4317	of C<64> handles (probably owning to the fact that all windows kernels
3535	can only wait for C<64> things at the same time internally; Microsoft	4318	can only wait for C<64> things at the same time internally; Microsoft
3536	recommends spawning a chain of threads and wait for 63 handles and the	4319	recommends spawning a chain of threads and wait for 63 handles and the
3537	previous thread in each. Great).	4320	previous thread in each. Sounds great!).
3538		4321
3539	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4322	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3540	to some high number (e.g. C<2048>) before compiling the winsocket select	4323	to some high number (e.g. C<2048>) before compiling the winsocket select
3541	call (which might be in libev or elsewhere, for example, perl does its own	4324	call (which might be in libev or elsewhere, for example, perl and many
3542	select emulation on windows).	4325	other interpreters do their own select emulation on windows).
3543		4326
3544	Another limit is the number of file descriptors in the Microsoft runtime	4327	Another limit is the number of file descriptors in the Microsoft runtime
3545	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4328	libraries, which by default is C<64> (there must be a hidden I<64>
3546	or something like this inside Microsoft). You can increase this by calling	4329	fetish or something like this inside Microsoft). You can increase this
3547	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4330	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3548	arbitrary limit), but is broken in many versions of the Microsoft runtime	4331	(another arbitrary limit), but is broken in many versions of the Microsoft
3549	libraries.
3550
3551	This might get you to about C<512> or C<2048> sockets (depending on	4332	runtime libraries. This might get you to about C<512> or C<2048> sockets
3552	windows version and/or the phase of the moon). To get more, you need to	4333	(depending on windows version and/or the phase of the moon). To get more,
3553	wrap all I/O functions and provide your own fd management, but the cost of	4334	you need to wrap all I/O functions and provide your own fd management, but
3554	calling select (O(n²)) will likely make this unworkable.	4335	the cost of calling select (O(n²)) will likely make this unworkable.
3555		4336
3556	=back	4337	=back
3557		4338
3558	=head2 PORTABILITY REQUIREMENTS	4339	=head2 PORTABILITY REQUIREMENTS
3559		4340
…		…
3602	=item C<double> must hold a time value in seconds with enough accuracy	4383	=item C<double> must hold a time value in seconds with enough accuracy
3603		4384
3604	The type C<double> is used to represent timestamps. It is required to	4385	The type C<double> is used to represent timestamps. It is required to
3605	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4386	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
3606	enough for at least into the year 4000. This requirement is fulfilled by	4387	enough for at least into the year 4000. This requirement is fulfilled by
3607	implementations implementing IEEE 754 (basically all existing ones).	4388	implementations implementing IEEE 754, which is basically all existing
		4389	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4390	2200.
3608		4391
3609	=back	4392	=back
3610		4393
3611	If you know of other additional requirements drop me a note.	4394	If you know of other additional requirements drop me a note.
3612		4395
…		…
3680	involves iterating over all running async watchers or all signal numbers.	4463	involves iterating over all running async watchers or all signal numbers.
3681		4464
3682	=back	4465	=back
3683		4466
3684		4467
		4468	=head1 GLOSSARY
		4469
		4470	=over 4
		4471
		4472	=item active
		4473
		4474	A watcher is active as long as it has been started (has been attached to
		4475	an event loop) but not yet stopped (disassociated from the event loop).
		4476
		4477	=item application
		4478
		4479	In this document, an application is whatever is using libev.
		4480
		4481	=item callback
		4482
		4483	The address of a function that is called when some event has been
		4484	detected. Callbacks are being passed the event loop, the watcher that
		4485	received the event, and the actual event bitset.
		4486
		4487	=item callback invocation
		4488
		4489	The act of calling the callback associated with a watcher.
		4490
		4491	=item event
		4492
		4493	A change of state of some external event, such as data now being available
		4494	for reading on a file descriptor, time having passed or simply not having
		4495	any other events happening anymore.
		4496
		4497	In libev, events are represented as single bits (such as C<EV_READ> or
		4498	C<EV_TIMEOUT>).
		4499
		4500	=item event library
		4501
		4502	A software package implementing an event model and loop.
		4503
		4504	=item event loop
		4505
		4506	An entity that handles and processes external events and converts them
		4507	into callback invocations.
		4508
		4509	=item event model
		4510
		4511	The model used to describe how an event loop handles and processes
		4512	watchers and events.
		4513
		4514	=item pending
		4515
		4516	A watcher is pending as soon as the corresponding event has been detected,
		4517	and stops being pending as soon as the watcher will be invoked or its
		4518	pending status is explicitly cleared by the application.
		4519
		4520	A watcher can be pending, but not active. Stopping a watcher also clears
		4521	its pending status.
		4522
		4523	=item real time
		4524
		4525	The physical time that is observed. It is apparently strictly monotonic :)
		4526
		4527	=item wall-clock time
		4528
		4529	The time and date as shown on clocks. Unlike real time, it can actually
		4530	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4531	clock.
		4532
		4533	=item watcher
		4534
		4535	A data structure that describes interest in certain events. Watchers need
		4536	to be started (attached to an event loop) before they can receive events.
		4537
		4538	=item watcher invocation
		4539
		4540	The act of calling the callback associated with a watcher.
		4541
		4542	=back
		4543
3685	=head1 AUTHOR	4544	=head1 AUTHOR
3686		4545
3687	Marc Lehmann <libev@schmorp.de>.	4546	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3688		4547

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