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…		…
8		8
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
		13
		14	#include <stdio.h> // for puts
13		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_TYPE	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
…		…
41		43
42	int	44	int
43	main (void)	45	main (void)
44	{	46	{
45	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
46	ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = ev_default_loop (0);
47		49
48	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
…		…
60		62
61	// unloop was called, so exit	63	// unloop was called, so exit
62	return 0;	64	return 0;
63	}	65	}
64		66
65	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
66		70
67	The newest version of this document is also available as an html-formatted	71	The newest version of this document is also available as an html-formatted
68	web page you might find easier to navigate when reading it for the first	72	web page you might find easier to navigate when reading it for the first
69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.	73	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		74
		75	While this document tries to be as complete as possible in documenting
		76	libev, its usage and the rationale behind its design, it is not a tutorial
		77	on event-based programming, nor will it introduce event-based programming
		78	with libev.
		79
		80	Familarity with event based programming techniques in general is assumed
		81	throughout this document.
		82
		83	=head1 ABOUT LIBEV
70		84
71	Libev is an event loop: you register interest in certain events (such as a	85	Libev is an event loop: you register interest in certain events (such as a
72	file descriptor being readable or a timeout occurring), and it will manage	86	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	87	these event sources and provide your program with events.
74		88
…		…
108	name C<loop> (which is always of type C<ev_loop *>) will not have	122	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	123	this argument.
110		124
111	=head2 TIME REPRESENTATION	125	=head2 TIME REPRESENTATION
112		126
113	Libev represents time as a single floating point number, representing the	127	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	128	the (fractional) number of seconds since the (POSIX) epoch (somewhere
115	the beginning of 1970, details are complicated, don't ask). This type is	129	near the beginning of 1970, details are complicated, don't ask). This
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	130	type is called C<ev_tstamp>, which is what you should use too. It usually
117	to the C<double> type in C, and when you need to do any calculations on	131	aliases to the C<double> type in C. When you need to do any calculations
118	it, you should treat it as some floating point value. Unlike the name	132	on it, you should treat it as some floating point value. Unlike the name
119	component C<stamp> might indicate, it is also used for time differences	133	component C<stamp> might indicate, it is also used for time differences
120	throughout libev.	134	throughout libev.
121		135
122	=head1 ERROR HANDLING	136	=head1 ERROR HANDLING
123		137
…		…
298	If you don't know what event loop to use, use the one returned from this	312	If you don't know what event loop to use, use the one returned from this
299	function.	313	function.
300		314
301	Note that this function is I<not> thread-safe, so if you want to use it	315	Note that this function is I<not> thread-safe, so if you want to use it
302	from multiple threads, you have to lock (note also that this is unlikely,	316	from multiple threads, you have to lock (note also that this is unlikely,
303	as loops cannot bes hared easily between threads anyway).	317	as loops cannot be shared easily between threads anyway).
304		318
305	The default loop is the only loop that can handle C<ev_signal> and	319	The default loop is the only loop that can handle C<ev_signal> and
306	C<ev_child> watchers, and to do this, it always registers a handler	320	C<ev_child> watchers, and to do this, it always registers a handler
307	for C<SIGCHLD>. If this is a problem for your application you can either	321	for C<SIGCHLD>. If this is a problem for your application you can either
308	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	322	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
…		…
348	flag.	362	flag.
349		363
350	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>
351	environment variable.	365	environment variable.
352		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
353	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	382	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
354		383
355	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
356	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,
357	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
…		…
384	=item C<EVBACKEND_EPOLL> (value 4, Linux)	413	=item C<EVBACKEND_EPOLL> (value 4, Linux)
385		414
386	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,
387	but it scales phenomenally better. While poll and select usually scale	416	but it scales phenomenally better. While poll and select usually scale
388	like O(total_fds) where n is the total number of fds (or the highest fd),	417	like O(total_fds) where n is the total number of fds (or the highest fd),
389	epoll scales either O(1) or O(active_fds). The epoll design has a number	418	epoll scales either O(1) or O(active_fds).
390	of shortcomings, such as silently dropping events in some hard-to-detect	419
391	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
392	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.
393		436
394	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
395	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
396	(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
397	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
398	very well if you register events for both fds.	441	file descriptors might not work very well if you register events for both
399		442	file descriptors.
400	Please note that epoll sometimes generates spurious notifications, so you
401	need to use non-blocking I/O or other means to avoid blocking when no data
402	(or space) is available.
403		443
404	Best performance from this backend is achieved by not unregistering all	444	Best performance from this backend is achieved by not unregistering all
405	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,
406	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
407	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
408	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.
409		455
410	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
411	all kernel versions tested so far.	457	all kernel versions tested so far.
412		458
413	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
414	C<EVBACKEND_POLL>.	460	C<EVBACKEND_POLL>.
415		461
416	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	462	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
417		463
418	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
419	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
420	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
421	completely useless). For this reason it's not being "auto-detected" unless	467	it's completely useless). Unlike epoll, however, whose brokenness
422	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
423	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.
424		473
425	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
426	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
427	the target platform). See C<ev_embed> watchers for more info.	476	the target platform). See C<ev_embed> watchers for more info.
428		477
429	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
430	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
431	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
432	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
433	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
434	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
435		485
436	This backend usually performs well under most conditions.	486	This backend usually performs well under most conditions.
437		487
438	While nominally embeddable in other event loops, this doesn't work	488	While nominally embeddable in other event loops, this doesn't work
439	everywhere, so you might need to test for this. And since it is broken	489	everywhere, so you might need to test for this. And since it is broken
440	almost everywhere, you should only use it when you have a lot of sockets	490	almost everywhere, you should only use it when you have a lot of sockets
441	(for which it usually works), by embedding it into another event loop	491	(for which it usually works), by embedding it into another event loop
442	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,	492	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
443	using it only for sockets.	493	also broken on OS X)) and, did I mention it, using it only for sockets.
444		494
445	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
446	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
447	C<NOTE_EOF>.	497	C<NOTE_EOF>.
448		498
…		…
468	might perform better.	518	might perform better.
469		519
470	On the positive side, with the exception of the spurious readiness	520	On the positive side, with the exception of the spurious readiness
471	notifications, this backend actually performed fully to specification	521	notifications, this backend actually performed fully to specification
472	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
473	OS-specific backends.	523	OS-specific backends (I vastly prefer correctness over speed hacks).
474		524
475	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
476	C<EVBACKEND_POLL>.	526	C<EVBACKEND_POLL>.
477		527
478	=item C<EVBACKEND_ALL>	528	=item C<EVBACKEND_ALL>
…		…
483		533
484	It is definitely not recommended to use this flag.	534	It is definitely not recommended to use this flag.
485		535
486	=back	536	=back
487		537
488	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,
489	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
490	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.
491		542
492	Example: This is the most typical usage.	543	Example: This is the most typical usage.
493		544
494	if (!ev_default_loop (0))	545	if (!ev_default_loop (0))
495	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	546	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
531	responsibility to either stop all watchers cleanly yourself I<before>	582	responsibility to either stop all watchers cleanly yourself I<before>
532	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
533	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
534	for example).	585	for example).
535		586
536	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
537	this function, and related watchers (such as signal and child watchers)	588	handlers), will not be freed by this function, and related watchers (such
538	would need to be stopped manually.	589	as signal and child watchers) would need to be stopped manually.
539		590
540	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
541	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
542	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
543	C<ev_loop_new> and C<ev_loop_destroy>).	594	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
586		637
587	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
588	"ticks" the number of loop iterations), as it roughly corresponds with	639	"ticks" the number of loop iterations), as it roughly corresponds with
589	C<ev_prepare> and C<ev_check> calls.	640	C<ev_prepare> and C<ev_check> calls.
590		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
591	=item unsigned int ev_backend (loop)	654	=item unsigned int ev_backend (loop)
592		655
593	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
594	use.	657	use.
595		658
…		…
609		672
610	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
611	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
612	the current time is a good idea.	675	the current time is a good idea.
613		676
614	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>).
615		704
616	=item ev_loop (loop, int flags)	705	=item ev_loop (loop, int flags)
617		706
618	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
619	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
…		…
635	the loop.	724	the loop.
636		725
637	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
638	necessary) and will handle those and any already outstanding ones. It	727	necessary) and will handle those and any already outstanding ones. It
639	will block your process until at least one new event arrives (which could	728	will block your process until at least one new event arrives (which could
640	be an event internal to libev itself, so there is no guarentee that a	729	be an event internal to libev itself, so there is no guarantee that a
641	user-registered callback will be called), and will return after one	730	user-registered callback will be called), and will return after one
642	iteration of the loop.	731	iteration of the loop.
643		732
644	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
645	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
…		…
703		792
704	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>
705	from returning, call ev_unref() after starting, and ev_ref() before	794	from returning, call ev_unref() after starting, and ev_ref() before
706	stopping it.	795	stopping it.
707		796
708	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
709	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
710	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
711	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
712	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
713	(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
714	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).
715		806
716	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>
717	running when nothing else is active.	808	running when nothing else is active.
718		809
719	ev_signal exitsig;	810	ev_signal exitsig;
…		…
748		839
749	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
750	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,
751	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
752	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
753	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.
754		847
755	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
756	to spend more time collecting timeouts, at the expense of increased	849	to spend more time collecting timeouts, at the expense of increased
757	latency/jitter/inexactness (the watcher callback will be called	850	latency/jitter/inexactness (the watcher callback will be called
758	later). C<ev_io> watchers will not be affected. Setting this to a non-null	851	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
760		853
761	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
762	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
763	interactive servers (of course not for games), likewise for timeouts. It	856	interactive servers (of course not for games), likewise for timeouts. It
764	usually doesn't make much sense to set it to a lower value than C<0.01>,	857	usually doesn't make much sense to set it to a lower value than C<0.01>,
765	as this approaches the timing granularity of most systems.	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).
766		863
767	Setting the I<timeout collect interval> can improve the opportunity for	864	Setting the I<timeout collect interval> can improve the opportunity for
768	saving power, as the program will "bundle" timer callback invocations that	865	saving power, as the program will "bundle" timer callback invocations that
769	are "near" in time together, by delaying some, thus reducing the number of	866	are "near" in time together, by delaying some, thus reducing the number of
770	times the process sleeps and wakes up again. Another useful technique to	867	times the process sleeps and wakes up again. Another useful technique to
771	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	868	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
772	they fire on, say, one-second boundaries only.	869	they fire on, say, one-second boundaries only.
		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.
773		941
774	=item ev_loop_verify (loop)	942	=item ev_loop_verify (loop)
775		943
776	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
777	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
…		…
903		1071
904	=item C<EV_ASYNC>	1072	=item C<EV_ASYNC>
905		1073
906	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>).
907		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
908	=item C<EV_ERROR>	1081	=item C<EV_ERROR>
909		1082
910	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
911	happen because the watcher could not be properly started because libev	1084	happen because the watcher could not be properly started because libev
912	ran out of memory, a file descriptor was found to be closed or any other	1085	ran out of memory, a file descriptor was found to be closed or any other
…		…
1027	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1200	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1028	(default: C<-2>). Pending watchers with higher priority will be invoked	1201	(default: C<-2>). Pending watchers with higher priority will be invoked
1029	before watchers with lower priority, but priority will not keep watchers	1202	before watchers with lower priority, but priority will not keep watchers
1030	from being executed (except for C<ev_idle> watchers).	1203	from being executed (except for C<ev_idle> watchers).
1031		1204
1032	This means that priorities are I<only> used for ordering callback
1033	invocation after new events have been received. This is useful, for
1034	example, to reduce latency after idling, or more often, to bind two
1035	watchers on the same event and make sure one is called first.
1036
1037	If you need to suppress invocation when higher priority events are pending	1205	If you need to suppress invocation when higher priority events are pending
1038	you need to look at C<ev_idle> watchers, which provide this functionality.	1206	you need to look at C<ev_idle> watchers, which provide this functionality.
1039		1207
1040	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
1041	pending.	1209	pending.
1042
1043	The default priority used by watchers when no priority has been set is
1044	always C<0>, which is supposed to not be too high and not be too low :).
1045		1210
1046	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1211	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1047	fine, as long as you do not mind that the priority value you query might	1212	fine, as long as you do not mind that the priority value you query might
1048	or might not have been clamped to the valid range.	1213	or might not have been clamped to the valid range.
		1214
		1215	The default priority used by watchers when no priority has been set is
		1216	always C<0>, which is supposed to not be too high and not be too low :).
		1217
		1218	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
		1219	priorities.
1049		1220
1050	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1221	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1051		1222
1052	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
1053	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
…		…
1118	#include <stddef.h>	1289	#include <stddef.h>
1119		1290
1120	static void	1291	static void
1121	t1_cb (EV_P_ ev_timer *w, int revents)	1292	t1_cb (EV_P_ ev_timer *w, int revents)
1122	{	1293	{
1123	struct my_biggy big = (struct my_biggy *	1294	struct my_biggy big = (struct my_biggy *)
1124	(((char *)w) - offsetof (struct my_biggy, t1));	1295	(((char *)w) - offsetof (struct my_biggy, t1));
1125	}	1296	}
1126		1297
1127	static void	1298	static void
1128	t2_cb (EV_P_ ev_timer *w, int revents)	1299	t2_cb (EV_P_ ev_timer *w, int revents)
1129	{	1300	{
1130	struct my_biggy big = (struct my_biggy *	1301	struct my_biggy big = (struct my_biggy *)
1131	(((char *)w) - offsetof (struct my_biggy, t2));	1302	(((char *)w) - offsetof (struct my_biggy, t2));
1132	}	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.
1133		1407
1134		1408
1135	=head1 WATCHER TYPES	1409	=head1 WATCHER TYPES
1136		1410
1137	This section describes each watcher in detail, but will not repeat	1411	This section describes each watcher in detail, but will not repeat
…		…
1163	descriptors to non-blocking mode is also usually a good idea (but not	1437	descriptors to non-blocking mode is also usually a good idea (but not
1164	required if you know what you are doing).	1438	required if you know what you are doing).
1165		1439
1166	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
1167	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
1168	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.
1169		1445
1170	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
1171	receive "spurious" readiness notifications, that is your callback might	1447	receive "spurious" readiness notifications, that is your callback might
1172	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1448	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1173	because there is no data. Not only are some backends known to create a	1449	because there is no data. Not only are some backends known to create a
…		…
1294	year, it will still time out after (roughly) one hour. "Roughly" because	1570	year, it will still time out after (roughly) one hour. "Roughly" because
1295	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1571	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1296	monotonic clock option helps a lot here).	1572	monotonic clock option helps a lot here).
1297		1573
1298	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
1299	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
1300	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).
1301		1580
1302	=head3 Be smart about timeouts	1581	=head3 Be smart about timeouts
1303		1582
1304	Many real-world problems involve some kind of timeout, usually for error	1583	Many real-world problems involve some kind of timeout, usually for error
1305	recovery. A typical example is an HTTP request - if the other side hangs,	1584	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1349	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>	1628	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
1350	member and C<ev_timer_again>.	1629	member and C<ev_timer_again>.
1351		1630
1352	At start:	1631	At start:
1353		1632
1354	ev_timer_init (timer, callback);	1633	ev_init (timer, callback);
1355	timer->repeat = 60.;	1634	timer->repeat = 60.;
1356	ev_timer_again (loop, timer);	1635	ev_timer_again (loop, timer);
1357		1636
1358	Each time there is some activity:	1637	Each time there is some activity:
1359		1638
…		…
1398	else	1677	else
1399	{	1678	{
1400	// callback was invoked, but there was some activity, re-arm	1679	// callback was invoked, but there was some activity, re-arm
1401	// the watcher to fire in last_activity + 60, which is	1680	// the watcher to fire in last_activity + 60, which is
1402	// guaranteed to be in the future, so "again" is positive:	1681	// guaranteed to be in the future, so "again" is positive:
1403	w->again = timeout - now;	1682	w->repeat = timeout - now;
1404	ev_timer_again (EV_A_ w);	1683	ev_timer_again (EV_A_ w);
1405	}	1684	}
1406	}	1685	}
1407		1686
1408	To summarise the callback: first calculate the real timeout (defined	1687	To summarise the callback: first calculate the real timeout (defined
…		…
1421		1700
1422	To start the timer, simply initialise the watcher and set C<last_activity>	1701	To start the timer, simply initialise the watcher and set C<last_activity>
1423	to the current time (meaning we just have some activity :), then call the	1702	to the current time (meaning we just have some activity :), then call the
1424	callback, which will "do the right thing" and start the timer:	1703	callback, which will "do the right thing" and start the timer:
1425		1704
1426	ev_timer_init (timer, callback);	1705	ev_init (timer, callback);
1427	last_activity = ev_now (loop);	1706	last_activity = ev_now (loop);
1428	callback (loop, timer, EV_TIMEOUT);	1707	callback (loop, timer, EV_TIMEOUT);
1429		1708
1430	And when there is some activity, simply store the current time in	1709	And when there is some activity, simply store the current time in
1431	C<last_activity>, no libev calls at all:	1710	C<last_activity>, no libev calls at all:
…		…
1492		1771
1493	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
1494	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
1495	()>.	1774	()>.
1496		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
1497	=head3 Watcher-Specific Functions and Data Members	1806	=head3 Watcher-Specific Functions and Data Members
1498		1807
1499	=over 4	1808	=over 4
1500		1809
1501	=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)
…		…
1524	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).
1525		1834
1526	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
1527	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.
1528		1837
1529	This sounds a bit complicated, see "Be smart about timeouts", above, for a	1838	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1530	usage example.	1839	usage example.
		1840
		1841	=item ev_timer_remaining (loop, ev_timer *)
		1842
		1843	Returns the remaining time until a timer fires. If the timer is active,
		1844	then this time is relative to the current event loop time, otherwise it's
		1845	the timeout value currently configured.
		1846
		1847	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		1848	C<5>. When the timer is started and one second passes, C<ev_timer_remain>
		1849	will return C<4>. When the timer expires and is restarted, it will return
		1850	roughly C<7> (likely slightly less as callback invocation takes some time,
		1851	too), and so on.
1531		1852
1532	=item ev_tstamp repeat [read-write]	1853	=item ev_tstamp repeat [read-write]
1533		1854
1534	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
1535	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),
…		…
1573	=head2 C<ev_periodic> - to cron or not to cron?	1894	=head2 C<ev_periodic> - to cron or not to cron?
1574		1895
1575	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
1576	(and unfortunately a bit complex).	1897	(and unfortunately a bit complex).
1577		1898
1578	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
1579	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
1580	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
1581	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
1582	+ 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
1583	clock to January of the previous year, then it will take more than year	1904	wrist-watch).
1584	to trigger the event (unlike an C<ev_timer>, which would still trigger
1585	roughly 10 seconds later as it uses a relative timeout).
1586		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
1587	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
1588	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
1589	complicated rules.	1916	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1917	those cannot react to time jumps.
1590		1918
1591	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
1592	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
1593	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).
1594		1924
1595	=head3 Watcher-Specific Functions and Data Members	1925	=head3 Watcher-Specific Functions and Data Members
1596		1926
1597	=over 4	1927	=over 4
1598		1928
1599	=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)
1600		1930
1601	=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)
1602		1932
1603	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
1604	operation, and we will explain them from simplest to most complex:	1934	operation, and we will explain them from simplest to most complex:
1605		1935
1606	=over 4	1936	=over 4
1607		1937
1608	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1938	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1609		1939
1610	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
1611	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
1612	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
1613	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.
1614		1945
1615	=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)
1616		1947
1617	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
1618	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
1619	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.
1620		1952
1621	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
1622	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
1623	hour, on the hour:	1955	hour, on the hour (with respect to UTC):
1624		1956
1625	ev_periodic_set (&periodic, 0., 3600., 0);	1957	ev_periodic_set (&periodic, 0., 3600., 0);
1626		1958
1627	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,
1628	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
1629	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
1630	by 3600.	1962	by 3600.
1631		1963
1632	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
1633	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
1634	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.
1635		1967
1636	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
1637	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
1638	this value, and in fact is often specified as zero.	1970	this value, and in fact is often specified as zero.
1639		1971
1640	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
1641	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
1642	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
1643	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).
1644		1976
1645	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1977	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1646		1978
1647	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
1648	ignored. Instead, each time the periodic watcher gets scheduled, the	1980	ignored. Instead, each time the periodic watcher gets scheduled, the
1649	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
1650	current time as second argument.	1982	current time as second argument.
1651		1983
1652	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,
1653	ever, or make ANY event loop modifications whatsoever>.	1985	or make ANY other event loop modifications whatsoever, unless explicitly
		1986	allowed by documentation here>.
1654		1987
1655	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
1656	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
1657	only event loop modification you are allowed to do).	1990	only event loop modification you are allowed to do).
1658		1991
…		…
1688	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
1689	program when the crontabs have changed).	2022	program when the crontabs have changed).
1690		2023
1691	=item ev_tstamp ev_periodic_at (ev_periodic *)	2024	=item ev_tstamp ev_periodic_at (ev_periodic *)
1692		2025
1693	When active, returns the absolute time that the watcher is supposed to	2026	When active, returns the absolute time that the watcher is supposed
1694	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.
1695		2030
1696	=item ev_tstamp offset [read-write]	2031	=item ev_tstamp offset [read-write]
1697		2032
1698	When repeating, this contains the offset value, otherwise this is the	2033	When repeating, this contains the offset value, otherwise this is the
1699	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	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).
1700		2036
1701	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
1702	timer fires or C<ev_periodic_again> is being called.	2038	timer fires or C<ev_periodic_again> is being called.
1703		2039
1704	=item ev_tstamp interval [read-write]	2040	=item ev_tstamp interval [read-write]
…		…
1756	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
1757	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
1758	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
1759	normal event processing, like any other event.	2095	normal event processing, like any other event.
1760		2096
1761	If you want signals asynchronously, just use C<sigaction> as you would	2097	If you want signals to be delivered truly asynchronously, just use
1762	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
1763	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.
1764		2101
1765	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
1766	first watcher gets started will libev actually register a signal handler	2108	When the first watcher gets started will libev actually register something
1767	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
1768	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).
1769	the last signal watcher for a signal is stopped, libev will reset the	2111
1770	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.
1771		2116
1772	If possible and supported, libev will install its handlers with	2117	If possible and supported, libev will install its handlers with
1773	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2118	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1774	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
1775	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
1776	them in an C<ev_prepare> watcher.	2121	and unblock them in an C<ev_prepare> watcher.
1777		2122
1778	=head3 Watcher-Specific Functions and Data Members	2123	=head3 Watcher-Specific Functions and Data Members
1779		2124
1780	=over 4	2125	=over 4
1781		2126
…		…
1813	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
1814	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
1815	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
1816	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.,
1817	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,
1818	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
1819	not.	2164	in the next callback invocation is not.
1820		2165
1821	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
1822	you can only register child watchers in the default event loop.	2167	you can only register child watchers in the default event loop.
1823		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
1824	=head3 Process Interaction	2173	=head3 Process Interaction
1825		2174
1826	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
1827	initialised. This is necessary to guarantee proper behaviour even if	2176	initialised. This is necessary to guarantee proper behaviour even if the
1828	the first child watcher is started after the child exits. The occurrence	2177	first child watcher is started after the child exits. The occurrence
1829	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2178	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1830	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
1831	children, even ones not watched.	2180	children, even ones not watched.
1832		2181
1833	=head3 Overriding the Built-In Processing	2182	=head3 Overriding the Built-In Processing
…		…
1843	=head3 Stopping the Child Watcher	2192	=head3 Stopping the Child Watcher
1844		2193
1845	Currently, the child watcher never gets stopped, even when the	2194	Currently, the child watcher never gets stopped, even when the
1846	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
1847	callback. Future versions of libev might stop the watcher automatically	2196	callback. Future versions of libev might stop the watcher automatically
1848	when a child exit is detected.	2197	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2198	problem).
1849		2199
1850	=head3 Watcher-Specific Functions and Data Members	2200	=head3 Watcher-Specific Functions and Data Members
1851		2201
1852	=over 4	2202	=over 4
1853		2203
…		…
1910		2260
1911		2261
1912	=head2 C<ev_stat> - did the file attributes just change?	2262	=head2 C<ev_stat> - did the file attributes just change?
1913		2263
1914	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
1915	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)
1916	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.
1917		2268
1918	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
1919	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
1920	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
1921	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
1922	the stat buffer having unspecified contents.	2273	least one) and all the other fields of the stat buffer having unspecified
		2274	contents.
1923		2275
1924	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
1925	relative and your working directory changes, the behaviour is undefined.	2278	your working directory changes, then the behaviour is undefined.
1926		2279
1927	Since there is no standard kernel interface to do this, the portable	2280	Since there is no portable change notification interface available, the
1928	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
1929	it changed somehow. You can specify a recommended polling interval for	2282	to see if it changed somehow. You can specify a recommended polling
1930	this case. If you specify a polling interval of C<0> (highly recommended!)	2283	interval for this case. If you specify a polling interval of C<0> (highly
1931	then a I<suitable, unspecified default> value will be used (which	2284	recommended!) then a I<suitable, unspecified default> value will be used
1932	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
1933	dynamically). Libev will also impose a minimum interval which is currently	2286	change dynamically). Libev will also impose a minimum interval which is
1934	around C<0.1>, but thats usually overkill.	2287	currently around C<0.1>, but that's usually overkill.
1935		2288
1936	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,
1937	as even with OS-supported change notifications, this can be	2290	as even with OS-supported change notifications, this can be
1938	resource-intensive.	2291	resource-intensive.
1939		2292
1940	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
1941	is the Linux inotify interface (implementing kqueue support is left as	2294	is the Linux inotify interface (implementing kqueue support is left as an
1942	an exercise for the reader. Note, however, that the author sees no way	2295	exercise for the reader. Note, however, that the author sees no way of
1943	of implementing C<ev_stat> semantics with kqueue).	2296	implementing C<ev_stat> semantics with kqueue, except as a hint).
1944		2297
1945	=head3 ABI Issues (Largefile Support)	2298	=head3 ABI Issues (Largefile Support)
1946		2299
1947	Libev by default (unless the user overrides this) uses the default	2300	Libev by default (unless the user overrides this) uses the default
1948	compilation environment, which means that on systems with large file	2301	compilation environment, which means that on systems with large file
1949	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
1950	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
1951	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
1952	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
1953	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
1954	most noticeably disabled with ev_stat and large file support.	2307	most noticeably displayed with ev_stat and large file support.
1955		2308
1956	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
1957	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
1958	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
1959	to exchange stat structures with application programs compiled using the	2312	to exchange stat structures with application programs compiled using the
1960	default compilation environment.	2313	default compilation environment.
1961		2314
1962	=head3 Inotify and Kqueue	2315	=head3 Inotify and Kqueue
1963		2316
1964	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
1965	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
1966	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>
1967	change detection where possible. The inotify descriptor will be created	2320	watcher is being started.
1968	lazily when the first C<ev_stat> watcher is being started.
1969		2321
1970	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
1971	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
1972	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
1973	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,
1974	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.
1975		2330
1976	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
1977	implement this functionality, due to the requirement of having a file	2332	implement this functionality, due to the requirement of having a file
1978	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
1979	etc. is difficult.	2334	etc. is difficult.
1980		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
1981	=head3 The special problem of stat time resolution	2354	=head3 The special problem of stat time resolution
1982		2355
1983	The C<stat ()> system call only supports full-second resolution portably, and	2356	The C<stat ()> system call only supports full-second resolution portably,
1984	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
1985	only support whole seconds.	2358	still only support whole seconds.
1986		2359
1987	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
1988	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
1989	calls your callback, which does something. When there is another update	2362	calls your callback, which does something. When there is another update
1990	within the same second, C<ev_stat> will be unable to detect unless the	2363	within the same second, C<ev_stat> will be unable to detect unless the
…		…
2133		2506
2134	=head3 Watcher-Specific Functions and Data Members	2507	=head3 Watcher-Specific Functions and Data Members
2135		2508
2136	=over 4	2509	=over 4
2137		2510
2138	=item ev_idle_init (ev_signal *, callback)	2511	=item ev_idle_init (ev_idle *, callback)
2139		2512
2140	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
2141	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,
2142	believe me.	2515	believe me.
2143		2516
…		…
2156	// no longer anything immediate to do.	2529	// no longer anything immediate to do.
2157	}	2530	}
2158		2531
2159	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2532	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2160	ev_idle_init (idle_watcher, idle_cb);	2533	ev_idle_init (idle_watcher, idle_cb);
2161	ev_idle_start (loop, idle_cb);	2534	ev_idle_start (loop, idle_watcher);
2162		2535
2163		2536
2164	=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!
2165		2538
2166	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:
…		…
2259	struct pollfd fds [nfd];	2632	struct pollfd fds [nfd];
2260	// actual code will need to loop here and realloc etc.	2633	// actual code will need to loop here and realloc etc.
2261	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2634	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2262		2635
2263	/* 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 */
2264	ev_timer_init (&tw, 0, timeout * 1e-3);	2637	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2265	ev_timer_start (loop, &tw);	2638	ev_timer_start (loop, &tw);
2266		2639
2267	// create one ev_io per pollfd	2640	// create one ev_io per pollfd
2268	for (int i = 0; i < nfd; ++i)	2641	for (int i = 0; i < nfd; ++i)
2269	{	2642	{
…		…
2382	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),
2383	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
2384	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
2385	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.
2386		2759
2387	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
2388	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
2389	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
2390	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
2391	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
2392	to C<0>, in which case the embed watcher will automatically execute the	2765	to give the embedded loop strictly lower priority for example).
2393	embedded loop sweep.
2394		2766
2395	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
2396	callback will be invoked whenever some events have been handled. You can	2768	will automatically execute the embedded loop sweep whenever necessary.
2397	set the callback to C<0> to avoid having to specify one if you are not
2398	interested in that.
2399		2769
2400	Also, there have not currently been made special provisions for forking:	2770	Fork detection will be handled transparently while the C<ev_embed> watcher
2401	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2771	is active, i.e., the embedded loop will automatically be forked when the
2402	but you will also have to stop and restart any C<ev_embed> watchers	2772	embedding loop forks. In other cases, the user is responsible for calling
2403	yourself - but you can use a fork watcher to handle this automatically,	2773	C<ev_loop_fork> on the embedded loop.
2404	and future versions of libev might do just that.
2405		2774
2406	Unfortunately, not all backends are embeddable: only the ones returned by	2775	Unfortunately, not all backends are embeddable: only the ones returned by
2407	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2776	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2408	portable one.	2777	portable one.
2409		2778
…		…
2503	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,
2504	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
2505	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
2506	handlers will be invoked, too, of course.	2875	handlers will be invoked, too, of course.
2507		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
2508	=head3 Watcher-Specific Functions and Data Members	2910	=head3 Watcher-Specific Functions and Data Members
2509		2911
2510	=over 4	2912	=over 4
2511		2913
2512	=item ev_fork_init (ev_signal *, callback)	2914	=item ev_fork_init (ev_signal *, callback)
…		…
2629	=over 4	3031	=over 4
2630		3032
2631	=item ev_async_init (ev_async *, callback)	3033	=item ev_async_init (ev_async *, callback)
2632		3034
2633	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
2634	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,
2635	trust me.	3037	trust me.
2636		3038
2637	=item ev_async_send (loop, ev_async *)	3039	=item ev_async_send (loop, ev_async *)
2638		3040
2639	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
2640	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
2641	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
2642	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
2643	section below on what exactly this means).	3045	section below on what exactly this means).
2644		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
2645	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
2646	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
2647	calls to C<ev_async_send>.	3054	repeated calls to C<ev_async_send> for the same event loop.
2648		3055
2649	=item bool = ev_async_pending (ev_async *)	3056	=item bool = ev_async_pending (ev_async *)
2650		3057
2651	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
2652	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
…		…
2655	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
2656	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,
2657	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
2658	quickly check whether invoking the loop might be a good idea.	3065	quickly check whether invoking the loop might be a good idea.
2659		3066
2660	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,
2661	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.
2662		3071
2663	=back	3072	=back
2664		3073
2665		3074
2666	=head1 OTHER FUNCTIONS	3075	=head1 OTHER FUNCTIONS
…		…
2845		3254
2846	myclass obj;	3255	myclass obj;
2847	ev::io iow;	3256	ev::io iow;
2848	iow.set <myclass, &myclass::io_cb> (&obj);	3257	iow.set <myclass, &myclass::io_cb> (&obj);
2849		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);
		3288
2850	=item w->set<function> (void *data = 0)	3289	=item w->set<function> (void *data = 0)
2851		3290
2852	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
2853	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
2854	C<data> member and is free for you to use.	3293	C<data> member and is free for you to use.
…		…
2940	L<http://software.schmorp.de/pkg/EV>.	3379	L<http://software.schmorp.de/pkg/EV>.
2941		3380
2942	=item Python	3381	=item Python
2943		3382
2944	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
2945	seems to be quite complete and well-documented. Note, however, that the	3384	seems to be quite complete and well-documented.
2946	patch they require for libev is outright dangerous as it breaks the ABI
2947	for everybody else, and therefore, should never be applied in an installed
2948	libev (if python requires an incompatible ABI then it needs to embed
2949	libev).
2950		3385
2951	=item Ruby	3386	=item Ruby
2952		3387
2953	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
2954	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
2955	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
2956	L<http://rev.rubyforge.org/>.	3391	L<http://rev.rubyforge.org/>.
		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>.
2957		3400
2958	=item D	3401	=item D
2959		3402
2960	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
2961	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3404	be found at L<http://proj.llucax.com.ar/wiki/evd>.
…		…
3072		3515
3073	#define EV_STANDALONE 1	3516	#define EV_STANDALONE 1
3074	#include "ev.h"	3517	#include "ev.h"
3075		3518
3076	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++
3077	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
3078	as a bug).	3521	as a bug).
3079		3522
3080	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
3081	in your include path (e.g. in libev/ when using -Ilibev):	3524	in your include path (e.g. in libev/ when using -Ilibev):
3082		3525
…		…
3138	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
3139	implementations for some libevent functions (such as logging, which is not	3582	implementations for some libevent functions (such as logging, which is not
3140	supported). It will also not define any of the structs usually found in	3583	supported). It will also not define any of the structs usually found in
3141	F<event.h> that are not directly supported by the libev core alone.	3584	F<event.h> that are not directly supported by the libev core alone.
3142		3585
		3586	In stanbdalone mode, libev will still try to automatically deduce the
		3587	configuration, but has to be more conservative.
		3588
3143	=item EV_USE_MONOTONIC	3589	=item EV_USE_MONOTONIC
3144		3590
3145	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
3146	monotonic clock option at both compile time and runtime. Otherwise no use	3592	monotonic clock option at both compile time and runtime. Otherwise no
3147	of the monotonic clock option will be attempted. If you enable this, you	3593	use of the monotonic clock option will be attempted. If you enable this,
3148	usually have to link against librt or something similar. Enabling it when	3594	you usually have to link against librt or something similar. Enabling it
3149	the functionality isn't available is safe, though, although you have	3595	when the functionality isn't available is safe, though, although you have
3150	to make sure you link against any libraries where the C<clock_gettime>	3596	to make sure you link against any libraries where the C<clock_gettime>
3151	function is hiding in (often F<-lrt>).	3597	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
3152		3598
3153	=item EV_USE_REALTIME	3599	=item EV_USE_REALTIME
3154		3600
3155	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
3156	real-time clock option at compile time (and assume its availability at	3602	real-time clock option at compile time (and assume its availability
3157	runtime if successful). Otherwise no use of the real-time clock option will	3603	at runtime if successful). Otherwise no use of the real-time clock
3158	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3604	option will be attempted. This effectively replaces C<gettimeofday>
3159	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3605	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
3160	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>).
3161		3620
3162	=item EV_USE_NANOSLEEP	3621	=item EV_USE_NANOSLEEP
3163		3622
3164	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
3165	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 ()>.
…		…
3181		3640
3182	=item EV_SELECT_USE_FD_SET	3641	=item EV_SELECT_USE_FD_SET
3183		3642
3184	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>
3185	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
3186	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
3187	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
3188	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
3189	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,
3190	influence the size of the C<fd_set> used.	3649	configures the maximum size of the C<fd_set>.
3191		3650
3192	=item EV_SELECT_IS_WINSOCKET	3651	=item EV_SELECT_IS_WINSOCKET
3193		3652
3194	When defined to C<1>, the select backend will assume that	3653	When defined to C<1>, the select backend will assume that
3195	select/socket/connect etc. don't understand file descriptors but	3654	select/socket/connect etc. don't understand file descriptors but
…		…
3345	defined to be C<0>, then they are not.	3804	defined to be C<0>, then they are not.
3346		3805
3347	=item EV_MINIMAL	3806	=item EV_MINIMAL
3348		3807
3349	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
3350	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
3351	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
3352	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.
3353		3831
3354	=item EV_PID_HASHSIZE	3832	=item EV_PID_HASHSIZE
3355		3833
3356	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
3357	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
…		…
3543	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
3544	watcher callback into the event loop interested in the signal.	4022	watcher callback into the event loop interested in the signal.
3545		4023
3546	=back	4024	=back
3547		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
3548	=head3 COROUTINES	4164	=head3 COROUTINES
3549		4165
3550	Libev is very accommodating to coroutines ("cooperative threads"):	4166	Libev is very accommodating to coroutines ("cooperative threads"):
3551	libev fully supports nesting calls to its functions from different	4167	libev fully supports nesting calls to its functions from different
3552	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4168	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3553	different coroutines, and switch freely between both coroutines running the	4169	different coroutines, and switch freely between both coroutines running
3554	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
3555	you must not do this from C<ev_periodic> reschedule callbacks.	4171	that you must not do this from C<ev_periodic> reschedule callbacks.
3556		4172
3557	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
3558	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
3559	they do not clal any callbacks.	4175	they do not call any callbacks.
3560		4176
3561	=head2 COMPILER WARNINGS	4177	=head2 COMPILER WARNINGS
3562		4178
3563	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
3564	lot of warnings when compiling libev code. Some people are apparently	4180	lot of warnings when compiling libev code. Some people are apparently
…		…
3598	==2274== definitely lost: 0 bytes in 0 blocks.	4214	==2274== definitely lost: 0 bytes in 0 blocks.
3599	==2274== possibly lost: 0 bytes in 0 blocks.	4215	==2274== possibly lost: 0 bytes in 0 blocks.
3600	==2274== still reachable: 256 bytes in 1 blocks.	4216	==2274== still reachable: 256 bytes in 1 blocks.
3601		4217
3602	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
3603	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.
3604		4220
3605	Similarly, under some circumstances, valgrind might report kernel bugs	4221	Similarly, under some circumstances, valgrind might report kernel bugs
3606	as if it were a bug in libev (e.g. in realloc or in the poll backend,	4222	as if it were a bug in libev (e.g. in realloc or in the poll backend,
3607	although an acceptable workaround has been found here), or it might be	4223	although an acceptable workaround has been found here), or it might be
3608	confused.	4224	confused.
…		…
3637	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).
3638		4254
3639	There is no supported compilation method available on windows except	4255	There is no supported compilation method available on windows except
3640	embedding it into other applications.	4256	embedding it into other applications.
3641		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
3642	Not a libev limitation but worth mentioning: windows apparently doesn't	4261	Not a libev limitation but worth mentioning: windows apparently doesn't
3643	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
3644	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,
3645	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
3646	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
…		…
3650	the abysmal performance of winsockets, using a large number of sockets	4269	the abysmal performance of winsockets, using a large number of sockets
3651	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
3652	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
3653	different implementation for windows, as libev offers the POSIX readiness	4272	different implementation for windows, as libev offers the POSIX readiness
3654	notification model, which cannot be implemented efficiently on windows	4273	notification model, which cannot be implemented efficiently on windows
3655	(Microsoft monopoly games).	4274	(due to Microsoft monopoly games).
3656		4275
3657	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
3658	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
3659	of F<ev.h>:	4278	of F<ev.h>:
3660		4279
…		…
3696		4315
3697	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
3698	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
3699	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
3700	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
3701	previous thread in each. Great).	4320	previous thread in each. Sounds great!).
3702		4321
3703	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>
3704	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
3705	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
3706	select emulation on windows).	4325	other interpreters do their own select emulation on windows).
3707		4326
3708	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
3709	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>
3710	or something like this inside Microsoft). You can increase this by calling	4329	fetish or something like this inside Microsoft). You can increase this
3711	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4330	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3712	arbitrary limit), but is broken in many versions of the Microsoft runtime	4331	(another arbitrary limit), but is broken in many versions of the Microsoft
3713	libraries.
3714
3715	This might get you to about C<512> or C<2048> sockets (depending on	4332	runtime libraries. This might get you to about C<512> or C<2048> sockets
3716	windows version and/or the phase of the moon). To get more, you need to	4333	(depending on windows version and/or the phase of the moon). To get more,
3717	wrap all I/O functions and provide your own fd management, but the cost of	4334	you need to wrap all I/O functions and provide your own fd management, but
3718	calling select (O(n²)) will likely make this unworkable.	4335	the cost of calling select (O(n²)) will likely make this unworkable.
3719		4336
3720	=back	4337	=back
3721		4338
3722	=head2 PORTABILITY REQUIREMENTS	4339	=head2 PORTABILITY REQUIREMENTS
3723		4340
…		…
3766	=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
3767		4384
3768	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
3769	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
3770	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
3771	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.
3772		4391
3773	=back	4392	=back
3774		4393
3775	If you know of other additional requirements drop me a note.	4394	If you know of other additional requirements drop me a note.
3776		4395
…		…
3844	involves iterating over all running async watchers or all signal numbers.	4463	involves iterating over all running async watchers or all signal numbers.
3845		4464
3846	=back	4465	=back
3847		4466
3848		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
3849	=head1 AUTHOR	4544	=head1 AUTHOR
3850		4545
3851	Marc Lehmann <libev@schmorp.de>.	4546	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3852		4547

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