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…		…
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
		14	#include <stdio.h> // for puts
		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
18		20
19	// all watcher callbacks have a similar signature	21	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	22	// this callback is called when data is readable on stdin
21	static void	23	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	24	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	25	{
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
…		…
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	33	}
32		34
33	// another callback, this time for a time-out	35	// another callback, this time for a time-out
34	static void	36	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	38	{
37	puts ("timeout");	39	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	42	}
…		…
60		62
61	// unloop was called, so exit	63	// unloop was called, so exit
62	return 0;	64	return 0;
63	}	65	}
64		66
65	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
66		70
67	The newest version of this document is also available as an html-formatted	71	The newest version of this document is also available as an html-formatted
68	web page you might find easier to navigate when reading it for the first	72	web page you might find easier to navigate when reading it for the first
69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.	73	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		74
		75	While this document tries to be as complete as possible in documenting
		76	libev, its usage and the rationale behind its design, it is not a tutorial
		77	on event-based programming, nor will it introduce event-based programming
		78	with libev.
		79
		80	Familarity with event based programming techniques in general is assumed
		81	throughout this document.
		82
		83	=head1 ABOUT LIBEV
70		84
71	Libev is an event loop: you register interest in certain events (such as a	85	Libev is an event loop: you register interest in certain events (such as a
72	file descriptor being readable or a timeout occurring), and it will manage	86	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	87	these event sources and provide your program with events.
74		88
…		…
84	=head2 FEATURES	98	=head2 FEATURES
85		99
86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	100	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	101	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	102	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	103	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
90	with customised rescheduling (C<ev_periodic>), synchronous signals	104	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
91	(C<ev_signal>), process status change events (C<ev_child>), and event	105	timers (C<ev_timer>), absolute timers with customised rescheduling
92	watchers dealing with the event loop mechanism itself (C<ev_idle>,	106	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
93	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	107	change events (C<ev_child>), and event watchers dealing with the event
94	file watchers (C<ev_stat>) and even limited support for fork events	108	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
95	(C<ev_fork>).	109	C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even
		110	limited support for fork events (C<ev_fork>).
96		111
97	It also is quite fast (see this	112	It also is quite fast (see this
98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	113	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
99	for example).	114	for example).
100		115
…		…
108	name C<loop> (which is always of type C<struct ev_loop *>) will not have	123	name C<loop> (which is always of type C<struct ev_loop *>) will not have
109	this argument.	124	this argument.
110		125
111	=head2 TIME REPRESENTATION	126	=head2 TIME REPRESENTATION
112		127
113	Libev represents time as a single floating point number, representing the	128	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	129	the (fractional) number of seconds since the (POSIX) epoch (somewhere
115	the beginning of 1970, details are complicated, don't ask). This type is	130	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	131	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	132	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	133	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	134	component C<stamp> might indicate, it is also used for time differences
120	throughout libev.	135	throughout libev.
121		136
122	=head1 ERROR HANDLING	137	=head1 ERROR HANDLING
123		138
…		…
276		291
277	=back	292	=back
278		293
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	294	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
280		295
281	An event loop is described by a C<struct ev_loop *>. The library knows two	296	An event loop is described by a C<struct ev_loop *> (the C<struct>
282	types of such loops, the I<default> loop, which supports signals and child	297	is I<not> optional in this case, as there is also an C<ev_loop>
283	events, and dynamically created loops which do not.	298	I<function>).
		299
		300	The library knows two types of such loops, the I<default> loop, which
		301	supports signals and child events, and dynamically created loops which do
		302	not.
284		303
285	=over 4	304	=over 4
286		305
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	306	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		307
…		…
294	If you don't know what event loop to use, use the one returned from this	313	If you don't know what event loop to use, use the one returned from this
295	function.	314	function.
296		315
297	Note that this function is I<not> thread-safe, so if you want to use it	316	Note that this function is I<not> thread-safe, so if you want to use it
298	from multiple threads, you have to lock (note also that this is unlikely,	317	from multiple threads, you have to lock (note also that this is unlikely,
299	as loops cannot bes hared easily between threads anyway).	318	as loops cannot be shared easily between threads anyway).
300		319
301	The default loop is the only loop that can handle C<ev_signal> and	320	The default loop is the only loop that can handle C<ev_signal> and
302	C<ev_child> watchers, and to do this, it always registers a handler	321	C<ev_child> watchers, and to do this, it always registers a handler
303	for C<SIGCHLD>. If this is a problem for your application you can either	322	for C<SIGCHLD>. If this is a problem for your application you can either
304	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	323	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
…		…
344	flag.	363	flag.
345		364
346	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	365	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
347	environment variable.	366	environment variable.
348		367
		368	=item C<EVFLAG_NOINOTIFY>
		369
		370	When this flag is specified, then libev will not attempt to use the
		371	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and
		372	testing, this flag can be useful to conserve inotify file descriptors, as
		373	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		374
		375	=item C<EVFLAG_SIGNALFD>
		376
		377	When this flag is specified, then libev will attempt to use the
		378	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API
		379	delivers signals synchronously, which makes is both faster and might make
		380	it possible to get the queued signal data.
		381
		382	Signalfd will not be used by default as this changes your signal mask, and
		383	there are a lot of shoddy libraries and programs (glib's threadpool for
		384	example) that can't properly initialise their signal masks.
		385
349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	386	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
350		387
351	This is your standard select(2) backend. Not I<completely> standard, as	388	This is your standard select(2) backend. Not I<completely> standard, as
352	libev tries to roll its own fd_set with no limits on the number of fds,	389	libev tries to roll its own fd_set with no limits on the number of fds,
353	but if that fails, expect a fairly low limit on the number of fds when	390	but if that fails, expect a fairly low limit on the number of fds when
…		…
377	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and	414	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
378	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	415	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
379		416
380	=item C<EVBACKEND_EPOLL> (value 4, Linux)	417	=item C<EVBACKEND_EPOLL> (value 4, Linux)
381		418
		419	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		420	kernels).
		421
382	For few fds, this backend is a bit little slower than poll and select,	422	For few fds, this backend is a bit little slower than poll and select,
383	but it scales phenomenally better. While poll and select usually scale	423	but it scales phenomenally better. While poll and select usually scale
384	like O(total_fds) where n is the total number of fds (or the highest fd),	424	like O(total_fds) where n is the total number of fds (or the highest fd),
385	epoll scales either O(1) or O(active_fds). The epoll design has a number	425	epoll scales either O(1) or O(active_fds).
386	of shortcomings, such as silently dropping events in some hard-to-detect	426
387	cases and requiring a system call per fd change, no fork support and bad	427	The epoll mechanism deserves honorable mention as the most misdesigned
388	support for dup.	428	of the more advanced event mechanisms: mere annoyances include silently
		429	dropping file descriptors, requiring a system call per change per file
		430	descriptor (and unnecessary guessing of parameters), problems with dup and
		431	so on. The biggest issue is fork races, however - if a program forks then
		432	I<both> parent and child process have to recreate the epoll set, which can
		433	take considerable time (one syscall per file descriptor) and is of course
		434	hard to detect.
		435
		436	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		437	of course I<doesn't>, and epoll just loves to report events for totally
		438	I<different> file descriptors (even already closed ones, so one cannot
		439	even remove them from the set) than registered in the set (especially
		440	on SMP systems). Libev tries to counter these spurious notifications by
		441	employing an additional generation counter and comparing that against the
		442	events to filter out spurious ones, recreating the set when required.
389		443
390	While stopping, setting and starting an I/O watcher in the same iteration	444	While stopping, setting and starting an I/O watcher in the same iteration
391	will result in some caching, there is still a system call per such incident	445	will result in some caching, there is still a system call per such
392	(because the fd could point to a different file description now), so its	446	incident (because the same I<file descriptor> could point to a different
393	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	447	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
394	very well if you register events for both fds.	448	file descriptors might not work very well if you register events for both
395		449	file descriptors.
396	Please note that epoll sometimes generates spurious notifications, so you
397	need to use non-blocking I/O or other means to avoid blocking when no data
398	(or space) is available.
399		450
400	Best performance from this backend is achieved by not unregistering all	451	Best performance from this backend is achieved by not unregistering all
401	watchers for a file descriptor until it has been closed, if possible,	452	watchers for a file descriptor until it has been closed, if possible,
402	i.e. keep at least one watcher active per fd at all times. Stopping and	453	i.e. keep at least one watcher active per fd at all times. Stopping and
403	starting a watcher (without re-setting it) also usually doesn't cause	454	starting a watcher (without re-setting it) also usually doesn't cause
404	extra overhead.	455	extra overhead. A fork can both result in spurious notifications as well
		456	as in libev having to destroy and recreate the epoll object, which can
		457	take considerable time and thus should be avoided.
		458
		459	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		460	faster than epoll for maybe up to a hundred file descriptors, depending on
		461	the usage. So sad.
405		462
406	While nominally embeddable in other event loops, this feature is broken in	463	While nominally embeddable in other event loops, this feature is broken in
407	all kernel versions tested so far.	464	all kernel versions tested so far.
408		465
409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	466	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
410	C<EVBACKEND_POLL>.	467	C<EVBACKEND_POLL>.
411		468
412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	469	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
413		470
414	Kqueue deserves special mention, as at the time of this writing, it was	471	Kqueue deserves special mention, as at the time of this writing, it
415	broken on all BSDs except NetBSD (usually it doesn't work reliably with	472	was broken on all BSDs except NetBSD (usually it doesn't work reliably
416	anything but sockets and pipes, except on Darwin, where of course it's	473	with anything but sockets and pipes, except on Darwin, where of course
417	completely useless). For this reason it's not being "auto-detected" unless	474	it's completely useless). Unlike epoll, however, whose brokenness
418	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or	475	is by design, these kqueue bugs can (and eventually will) be fixed
419	libev was compiled on a known-to-be-good (-enough) system like NetBSD.	476	without API changes to existing programs. For this reason it's not being
		477	"auto-detected" unless you explicitly specify it in the flags (i.e. using
		478	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		479	system like NetBSD.
420		480
421	You still can embed kqueue into a normal poll or select backend and use it	481	You still can embed kqueue into a normal poll or select backend and use it
422	only for sockets (after having made sure that sockets work with kqueue on	482	only for sockets (after having made sure that sockets work with kqueue on
423	the target platform). See C<ev_embed> watchers for more info.	483	the target platform). See C<ev_embed> watchers for more info.
424		484
425	It scales in the same way as the epoll backend, but the interface to the	485	It scales in the same way as the epoll backend, but the interface to the
426	kernel is more efficient (which says nothing about its actual speed, of	486	kernel is more efficient (which says nothing about its actual speed, of
427	course). While stopping, setting and starting an I/O watcher does never	487	course). While stopping, setting and starting an I/O watcher does never
428	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	488	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
429	two event changes per incident. Support for C<fork ()> is very bad and it	489	two event changes per incident. Support for C<fork ()> is very bad (but
430	drops fds silently in similarly hard-to-detect cases.	490	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		491	cases
431		492
432	This backend usually performs well under most conditions.	493	This backend usually performs well under most conditions.
433		494
434	While nominally embeddable in other event loops, this doesn't work	495	While nominally embeddable in other event loops, this doesn't work
435	everywhere, so you might need to test for this. And since it is broken	496	everywhere, so you might need to test for this. And since it is broken
436	almost everywhere, you should only use it when you have a lot of sockets	497	almost everywhere, you should only use it when you have a lot of sockets
437	(for which it usually works), by embedding it into another event loop	498	(for which it usually works), by embedding it into another event loop
438	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,	499	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
439	using it only for sockets.	500	also broken on OS X)) and, did I mention it, using it only for sockets.
440		501
441	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	502	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
442	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with	503	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
443	C<NOTE_EOF>.	504	C<NOTE_EOF>.
444		505
…		…
464	might perform better.	525	might perform better.
465		526
466	On the positive side, with the exception of the spurious readiness	527	On the positive side, with the exception of the spurious readiness
467	notifications, this backend actually performed fully to specification	528	notifications, this backend actually performed fully to specification
468	in all tests and is fully embeddable, which is a rare feat among the	529	in all tests and is fully embeddable, which is a rare feat among the
469	OS-specific backends.	530	OS-specific backends (I vastly prefer correctness over speed hacks).
470		531
471	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	532	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
472	C<EVBACKEND_POLL>.	533	C<EVBACKEND_POLL>.
473		534
474	=item C<EVBACKEND_ALL>	535	=item C<EVBACKEND_ALL>
…		…
479		540
480	It is definitely not recommended to use this flag.	541	It is definitely not recommended to use this flag.
481		542
482	=back	543	=back
483		544
484	If one or more of these are or'ed into the flags value, then only these	545	If one or more of the backend flags are or'ed into the flags value,
485	backends will be tried (in the reverse order as listed here). If none are	546	then only these backends will be tried (in the reverse order as listed
486	specified, all backends in C<ev_recommended_backends ()> will be tried.	547	here). If none are specified, all backends in C<ev_recommended_backends
		548	()> will be tried.
487		549
488	Example: This is the most typical usage.	550	Example: This is the most typical usage.
489		551
490	if (!ev_default_loop (0))	552	if (!ev_default_loop (0))
491	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	553	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
527	responsibility to either stop all watchers cleanly yourself I<before>	589	responsibility to either stop all watchers cleanly yourself I<before>
528	calling this function, or cope with the fact afterwards (which is usually	590	calling this function, or cope with the fact afterwards (which is usually
529	the easiest thing, you can just ignore the watchers and/or C<free ()> them	591	the easiest thing, you can just ignore the watchers and/or C<free ()> them
530	for example).	592	for example).
531		593
532	Note that certain global state, such as signal state, will not be freed by	594	Note that certain global state, such as signal state (and installed signal
533	this function, and related watchers (such as signal and child watchers)	595	handlers), will not be freed by this function, and related watchers (such
534	would need to be stopped manually.	596	as signal and child watchers) would need to be stopped manually.
535		597
536	In general it is not advisable to call this function except in the	598	In general it is not advisable to call this function except in the
537	rare occasion where you really need to free e.g. the signal handling	599	rare occasion where you really need to free e.g. the signal handling
538	pipe fds. If you need dynamically allocated loops it is better to use	600	pipe fds. If you need dynamically allocated loops it is better to use
539	C<ev_loop_new> and C<ev_loop_destroy>).	601	C<ev_loop_new> and C<ev_loop_destroy>.
540		602
541	=item ev_loop_destroy (loop)	603	=item ev_loop_destroy (loop)
542		604
543	Like C<ev_default_destroy>, but destroys an event loop created by an	605	Like C<ev_default_destroy>, but destroys an event loop created by an
544	earlier call to C<ev_loop_new>.	606	earlier call to C<ev_loop_new>.
…		…
582		644
583	This value can sometimes be useful as a generation counter of sorts (it	645	This value can sometimes be useful as a generation counter of sorts (it
584	"ticks" the number of loop iterations), as it roughly corresponds with	646	"ticks" the number of loop iterations), as it roughly corresponds with
585	C<ev_prepare> and C<ev_check> calls.	647	C<ev_prepare> and C<ev_check> calls.
586		648
		649	=item unsigned int ev_loop_depth (loop)
		650
		651	Returns the number of times C<ev_loop> was entered minus the number of
		652	times C<ev_loop> was exited, in other words, the recursion depth.
		653
		654	Outside C<ev_loop>, this number is zero. In a callback, this number is
		655	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),
		656	in which case it is higher.
		657
		658	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread
		659	etc.), doesn't count as exit.
		660
587	=item unsigned int ev_backend (loop)	661	=item unsigned int ev_backend (loop)
588		662
589	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	663	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
590	use.	664	use.
591		665
…		…
605		679
606	This function is rarely useful, but when some event callback runs for a	680	This function is rarely useful, but when some event callback runs for a
607	very long time without entering the event loop, updating libev's idea of	681	very long time without entering the event loop, updating libev's idea of
608	the current time is a good idea.	682	the current time is a good idea.
609		683
610	See also "The special problem of time updates" in the C<ev_timer> section.	684	See also L<The special problem of time updates> in the C<ev_timer> section.
		685
		686	=item ev_suspend (loop)
		687
		688	=item ev_resume (loop)
		689
		690	These two functions suspend and resume a loop, for use when the loop is
		691	not used for a while and timeouts should not be processed.
		692
		693	A typical use case would be an interactive program such as a game: When
		694	the user presses C<^Z> to suspend the game and resumes it an hour later it
		695	would be best to handle timeouts as if no time had actually passed while
		696	the program was suspended. This can be achieved by calling C<ev_suspend>
		697	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		698	C<ev_resume> directly afterwards to resume timer processing.
		699
		700	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		701	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		702	will be rescheduled (that is, they will lose any events that would have
		703	occured while suspended).
		704
		705	After calling C<ev_suspend> you B<must not> call I<any> function on the
		706	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		707	without a previous call to C<ev_suspend>.
		708
		709	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		710	event loop time (see C<ev_now_update>).
611		711
612	=item ev_loop (loop, int flags)	712	=item ev_loop (loop, int flags)
613		713
614	Finally, this is it, the event handler. This function usually is called	714	Finally, this is it, the event handler. This function usually is called
615	after you initialised all your watchers and you want to start handling	715	after you have initialised all your watchers and you want to start
616	events.	716	handling events.
617		717
618	If the flags argument is specified as C<0>, it will not return until	718	If the flags argument is specified as C<0>, it will not return until
619	either no event watchers are active anymore or C<ev_unloop> was called.	719	either no event watchers are active anymore or C<ev_unloop> was called.
620		720
621	Please note that an explicit C<ev_unloop> is usually better than	721	Please note that an explicit C<ev_unloop> is usually better than
…		…
631	the loop.	731	the loop.
632		732
633	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	733	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
634	necessary) and will handle those and any already outstanding ones. It	734	necessary) and will handle those and any already outstanding ones. It
635	will block your process until at least one new event arrives (which could	735	will block your process until at least one new event arrives (which could
636	be an event internal to libev itself, so there is no guarentee that a	736	be an event internal to libev itself, so there is no guarantee that a
637	user-registered callback will be called), and will return after one	737	user-registered callback will be called), and will return after one
638	iteration of the loop.	738	iteration of the loop.
639		739
640	This is useful if you are waiting for some external event in conjunction	740	This is useful if you are waiting for some external event in conjunction
641	with something not expressible using other libev watchers (i.e. "roll your	741	with something not expressible using other libev watchers (i.e. "roll your
…		…
685	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	785	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
686	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	786	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
687		787
688	This "unloop state" will be cleared when entering C<ev_loop> again.	788	This "unloop state" will be cleared when entering C<ev_loop> again.
689		789
		790	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		791
690	=item ev_ref (loop)	792	=item ev_ref (loop)
691		793
692	=item ev_unref (loop)	794	=item ev_unref (loop)
693		795
694	Ref/unref can be used to add or remove a reference count on the event	796	Ref/unref can be used to add or remove a reference count on the event
695	loop: Every watcher keeps one reference, and as long as the reference	797	loop: Every watcher keeps one reference, and as long as the reference
696	count is nonzero, C<ev_loop> will not return on its own.	798	count is nonzero, C<ev_loop> will not return on its own.
697		799
698	If you have a watcher you never unregister that should not keep C<ev_loop>	800	This is useful when you have a watcher that you never intend to
699	from returning, call ev_unref() after starting, and ev_ref() before	801	unregister, but that nevertheless should not keep C<ev_loop> from
		802	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
700	stopping it.	803	before stopping it.
701		804
702	As an example, libev itself uses this for its internal signal pipe: It is	805	As an example, libev itself uses this for its internal signal pipe: It
703	not visible to the libev user and should not keep C<ev_loop> from exiting	806	is not visible to the libev user and should not keep C<ev_loop> from
704	if no event watchers registered by it are active. It is also an excellent	807	exiting if no event watchers registered by it are active. It is also an
705	way to do this for generic recurring timers or from within third-party	808	excellent way to do this for generic recurring timers or from within
706	libraries. Just remember to I<unref after start> and I<ref before stop>	809	third-party libraries. Just remember to I<unref after start> and I<ref
707	(but only if the watcher wasn't active before, or was active before,	810	before stop> (but only if the watcher wasn't active before, or was active
708	respectively).	811	before, respectively. Note also that libev might stop watchers itself
		812	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		813	in the callback).
709		814
710	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	815	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
711	running when nothing else is active.	816	running when nothing else is active.
712		817
713	struct ev_signal exitsig;	818	ev_signal exitsig;
714	ev_signal_init (&exitsig, sig_cb, SIGINT);	819	ev_signal_init (&exitsig, sig_cb, SIGINT);
715	ev_signal_start (loop, &exitsig);	820	ev_signal_start (loop, &exitsig);
716	evf_unref (loop);	821	evf_unref (loop);
717		822
718	Example: For some weird reason, unregister the above signal handler again.	823	Example: For some weird reason, unregister the above signal handler again.
…		…
742		847
743	By setting a higher I<io collect interval> you allow libev to spend more	848	By setting a higher I<io collect interval> you allow libev to spend more
744	time collecting I/O events, so you can handle more events per iteration,	849	time collecting I/O events, so you can handle more events per iteration,
745	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	850	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
746	C<ev_timer>) will be not affected. Setting this to a non-null value will	851	C<ev_timer>) will be not affected. Setting this to a non-null value will
747	introduce an additional C<ev_sleep ()> call into most loop iterations.	852	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		853	sleep time ensures that libev will not poll for I/O events more often then
		854	once per this interval, on average.
748		855
749	Likewise, by setting a higher I<timeout collect interval> you allow libev	856	Likewise, by setting a higher I<timeout collect interval> you allow libev
750	to spend more time collecting timeouts, at the expense of increased	857	to spend more time collecting timeouts, at the expense of increased
751	latency/jitter/inexactness (the watcher callback will be called	858	latency/jitter/inexactness (the watcher callback will be called
752	later). C<ev_io> watchers will not be affected. Setting this to a non-null	859	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
754		861
755	Many (busy) programs can usually benefit by setting the I/O collect	862	Many (busy) programs can usually benefit by setting the I/O collect
756	interval to a value near C<0.1> or so, which is often enough for	863	interval to a value near C<0.1> or so, which is often enough for
757	interactive servers (of course not for games), likewise for timeouts. It	864	interactive servers (of course not for games), likewise for timeouts. It
758	usually doesn't make much sense to set it to a lower value than C<0.01>,	865	usually doesn't make much sense to set it to a lower value than C<0.01>,
759	as this approaches the timing granularity of most systems.	866	as this approaches the timing granularity of most systems. Note that if
		867	you do transactions with the outside world and you can't increase the
		868	parallelity, then this setting will limit your transaction rate (if you
		869	need to poll once per transaction and the I/O collect interval is 0.01,
		870	then you can't do more than 100 transations per second).
760		871
761	Setting the I<timeout collect interval> can improve the opportunity for	872	Setting the I<timeout collect interval> can improve the opportunity for
762	saving power, as the program will "bundle" timer callback invocations that	873	saving power, as the program will "bundle" timer callback invocations that
763	are "near" in time together, by delaying some, thus reducing the number of	874	are "near" in time together, by delaying some, thus reducing the number of
764	times the process sleeps and wakes up again. Another useful technique to	875	times the process sleeps and wakes up again. Another useful technique to
765	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	876	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
766	they fire on, say, one-second boundaries only.	877	they fire on, say, one-second boundaries only.
767		878
		879	Example: we only need 0.1s timeout granularity, and we wish not to poll
		880	more often than 100 times per second:
		881
		882	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		883	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		884
		885	=item ev_invoke_pending (loop)
		886
		887	This call will simply invoke all pending watchers while resetting their
		888	pending state. Normally, C<ev_loop> does this automatically when required,
		889	but when overriding the invoke callback this call comes handy.
		890
		891	=item int ev_pending_count (loop)
		892
		893	Returns the number of pending watchers - zero indicates that no watchers
		894	are pending.
		895
		896	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		897
		898	This overrides the invoke pending functionality of the loop: Instead of
		899	invoking all pending watchers when there are any, C<ev_loop> will call
		900	this callback instead. This is useful, for example, when you want to
		901	invoke the actual watchers inside another context (another thread etc.).
		902
		903	If you want to reset the callback, use C<ev_invoke_pending> as new
		904	callback.
		905
		906	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		907
		908	Sometimes you want to share the same loop between multiple threads. This
		909	can be done relatively simply by putting mutex_lock/unlock calls around
		910	each call to a libev function.
		911
		912	However, C<ev_loop> can run an indefinite time, so it is not feasible to
		913	wait for it to return. One way around this is to wake up the loop via
		914	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>
		915	and I<acquire> callbacks on the loop.
		916
		917	When set, then C<release> will be called just before the thread is
		918	suspended waiting for new events, and C<acquire> is called just
		919	afterwards.
		920
		921	Ideally, C<release> will just call your mutex_unlock function, and
		922	C<acquire> will just call the mutex_lock function again.
		923
		924	While event loop modifications are allowed between invocations of
		925	C<release> and C<acquire> (that's their only purpose after all), no
		926	modifications done will affect the event loop, i.e. adding watchers will
		927	have no effect on the set of file descriptors being watched, or the time
		928	waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it
		929	to take note of any changes you made.
		930
		931	In theory, threads executing C<ev_loop> will be async-cancel safe between
		932	invocations of C<release> and C<acquire>.
		933
		934	See also the locking example in the C<THREADS> section later in this
		935	document.
		936
		937	=item ev_set_userdata (loop, void *data)
		938
		939	=item ev_userdata (loop)
		940
		941	Set and retrieve a single C<void *> associated with a loop. When
		942	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		943	C<0.>
		944
		945	These two functions can be used to associate arbitrary data with a loop,
		946	and are intended solely for the C<invoke_pending_cb>, C<release> and
		947	C<acquire> callbacks described above, but of course can be (ab-)used for
		948	any other purpose as well.
		949
768	=item ev_loop_verify (loop)	950	=item ev_loop_verify (loop)
769		951
770	This function only does something when C<EV_VERIFY> support has been	952	This function only does something when C<EV_VERIFY> support has been
771	compiled in. which is the default for non-minimal builds. It tries to go	953	compiled in, which is the default for non-minimal builds. It tries to go
772	through all internal structures and checks them for validity. If anything	954	through all internal structures and checks them for validity. If anything
773	is found to be inconsistent, it will print an error message to standard	955	is found to be inconsistent, it will print an error message to standard
774	error and call C<abort ()>.	956	error and call C<abort ()>.
775		957
776	This can be used to catch bugs inside libev itself: under normal	958	This can be used to catch bugs inside libev itself: under normal
…		…
780	=back	962	=back
781		963
782		964
783	=head1 ANATOMY OF A WATCHER	965	=head1 ANATOMY OF A WATCHER
784		966
		967	In the following description, uppercase C<TYPE> in names stands for the
		968	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		969	watchers and C<ev_io_start> for I/O watchers.
		970
785	A watcher is a structure that you create and register to record your	971	A watcher is a structure that you create and register to record your
786	interest in some event. For instance, if you want to wait for STDIN to	972	interest in some event. For instance, if you want to wait for STDIN to
787	become readable, you would create an C<ev_io> watcher for that:	973	become readable, you would create an C<ev_io> watcher for that:
788		974
789	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	975	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
790	{	976	{
791	ev_io_stop (w);	977	ev_io_stop (w);
792	ev_unloop (loop, EVUNLOOP_ALL);	978	ev_unloop (loop, EVUNLOOP_ALL);
793	}	979	}
794		980
795	struct ev_loop *loop = ev_default_loop (0);	981	struct ev_loop *loop = ev_default_loop (0);
		982
796	struct ev_io stdin_watcher;	983	ev_io stdin_watcher;
		984
797	ev_init (&stdin_watcher, my_cb);	985	ev_init (&stdin_watcher, my_cb);
798	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	986	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
799	ev_io_start (loop, &stdin_watcher);	987	ev_io_start (loop, &stdin_watcher);
		988
800	ev_loop (loop, 0);	989	ev_loop (loop, 0);
801		990
802	As you can see, you are responsible for allocating the memory for your	991	As you can see, you are responsible for allocating the memory for your
803	watcher structures (and it is usually a bad idea to do this on the stack,	992	watcher structures (and it is I<usually> a bad idea to do this on the
804	although this can sometimes be quite valid).	993	stack).
		994
		995	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		996	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
805		997
806	Each watcher structure must be initialised by a call to C<ev_init	998	Each watcher structure must be initialised by a call to C<ev_init
807	(watcher *, callback)>, which expects a callback to be provided. This	999	(watcher *, callback)>, which expects a callback to be provided. This
808	callback gets invoked each time the event occurs (or, in the case of I/O	1000	callback gets invoked each time the event occurs (or, in the case of I/O
809	watchers, each time the event loop detects that the file descriptor given	1001	watchers, each time the event loop detects that the file descriptor given
810	is readable and/or writable).	1002	is readable and/or writable).
811		1003
812	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1004	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
813	with arguments specific to this watcher type. There is also a macro	1005	macro to configure it, with arguments specific to the watcher type. There
814	to combine initialisation and setting in one call: C<< ev_<type>_init	1006	is also a macro to combine initialisation and setting in one call: C<<
815	(watcher *, callback, ...) >>.	1007	ev_TYPE_init (watcher *, callback, ...) >>.
816		1008
817	To make the watcher actually watch out for events, you have to start it	1009	To make the watcher actually watch out for events, you have to start it
818	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	1010	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
819	*) >>), and you can stop watching for events at any time by calling the	1011	*) >>), and you can stop watching for events at any time by calling the
820	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1012	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
821		1013
822	As long as your watcher is active (has been started but not stopped) you	1014	As long as your watcher is active (has been started but not stopped) you
823	must not touch the values stored in it. Most specifically you must never	1015	must not touch the values stored in it. Most specifically you must never
824	reinitialise it or call its C<set> macro.	1016	reinitialise it or call its C<ev_TYPE_set> macro.
825		1017
826	Each and every callback receives the event loop pointer as first, the	1018	Each and every callback receives the event loop pointer as first, the
827	registered watcher structure as second, and a bitset of received events as	1019	registered watcher structure as second, and a bitset of received events as
828	third argument.	1020	third argument.
829		1021
…		…
887		1079
888	=item C<EV_ASYNC>	1080	=item C<EV_ASYNC>
889		1081
890	The given async watcher has been asynchronously notified (see C<ev_async>).	1082	The given async watcher has been asynchronously notified (see C<ev_async>).
891		1083
		1084	=item C<EV_CUSTOM>
		1085
		1086	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1087	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		1088
892	=item C<EV_ERROR>	1089	=item C<EV_ERROR>
893		1090
894	An unspecified error has occurred, the watcher has been stopped. This might	1091	An unspecified error has occurred, the watcher has been stopped. This might
895	happen because the watcher could not be properly started because libev	1092	happen because the watcher could not be properly started because libev
896	ran out of memory, a file descriptor was found to be closed or any other	1093	ran out of memory, a file descriptor was found to be closed or any other
		1094	problem. Libev considers these application bugs.
		1095
897	problem. You best act on it by reporting the problem and somehow coping	1096	You best act on it by reporting the problem and somehow coping with the
898	with the watcher being stopped.	1097	watcher being stopped. Note that well-written programs should not receive
		1098	an error ever, so when your watcher receives it, this usually indicates a
		1099	bug in your program.
899		1100
900	Libev will usually signal a few "dummy" events together with an error, for	1101	Libev will usually signal a few "dummy" events together with an error, for
901	example it might indicate that a fd is readable or writable, and if your	1102	example it might indicate that a fd is readable or writable, and if your
902	callbacks is well-written it can just attempt the operation and cope with	1103	callbacks is well-written it can just attempt the operation and cope with
903	the error from read() or write(). This will not work in multi-threaded	1104	the error from read() or write(). This will not work in multi-threaded
…		…
906		1107
907	=back	1108	=back
908		1109
909	=head2 GENERIC WATCHER FUNCTIONS	1110	=head2 GENERIC WATCHER FUNCTIONS
910		1111
911	In the following description, C<TYPE> stands for the watcher type,
912	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
913
914	=over 4	1112	=over 4
915		1113
916	=item C<ev_init> (ev_TYPE *watcher, callback)	1114	=item C<ev_init> (ev_TYPE *watcher, callback)
917		1115
918	This macro initialises the generic portion of a watcher. The contents	1116	This macro initialises the generic portion of a watcher. The contents
…		…
923	which rolls both calls into one.	1121	which rolls both calls into one.
924		1122
925	You can reinitialise a watcher at any time as long as it has been stopped	1123	You can reinitialise a watcher at any time as long as it has been stopped
926	(or never started) and there are no pending events outstanding.	1124	(or never started) and there are no pending events outstanding.
927		1125
928	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1126	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
929	int revents)>.	1127	int revents)>.
930		1128
931	Example: Initialise an C<ev_io> watcher in two steps.	1129	Example: Initialise an C<ev_io> watcher in two steps.
932		1130
933	ev_io w;	1131	ev_io w;
934	ev_init (&w, my_cb);	1132	ev_init (&w, my_cb);
935	ev_io_set (&w, STDIN_FILENO, EV_READ);	1133	ev_io_set (&w, STDIN_FILENO, EV_READ);
936		1134
937	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1135	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
938		1136
939	This macro initialises the type-specific parts of a watcher. You need to	1137	This macro initialises the type-specific parts of a watcher. You need to
940	call C<ev_init> at least once before you call this macro, but you can	1138	call C<ev_init> at least once before you call this macro, but you can
941	call C<ev_TYPE_set> any number of times. You must not, however, call this	1139	call C<ev_TYPE_set> any number of times. You must not, however, call this
942	macro on a watcher that is active (it can be pending, however, which is a	1140	macro on a watcher that is active (it can be pending, however, which is a
…		…
955		1153
956	Example: Initialise and set an C<ev_io> watcher in one step.	1154	Example: Initialise and set an C<ev_io> watcher in one step.
957		1155
958	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1156	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
959		1157
960	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1158	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
961		1159
962	Starts (activates) the given watcher. Only active watchers will receive	1160	Starts (activates) the given watcher. Only active watchers will receive
963	events. If the watcher is already active nothing will happen.	1161	events. If the watcher is already active nothing will happen.
964		1162
965	Example: Start the C<ev_io> watcher that is being abused as example in this	1163	Example: Start the C<ev_io> watcher that is being abused as example in this
966	whole section.	1164	whole section.
967		1165
968	ev_io_start (EV_DEFAULT_UC, &w);	1166	ev_io_start (EV_DEFAULT_UC, &w);
969		1167
970	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1168	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
971		1169
972	Stops the given watcher again (if active) and clears the pending	1170	Stops the given watcher if active, and clears the pending status (whether
		1171	the watcher was active or not).
		1172
973	status. It is possible that stopped watchers are pending (for example,	1173	It is possible that stopped watchers are pending - for example,
974	non-repeating timers are being stopped when they become pending), but	1174	non-repeating timers are being stopped when they become pending - but
975	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1175	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
976	you want to free or reuse the memory used by the watcher it is therefore a	1176	pending. If you want to free or reuse the memory used by the watcher it is
977	good idea to always call its C<ev_TYPE_stop> function.	1177	therefore a good idea to always call its C<ev_TYPE_stop> function.
978		1178
979	=item bool ev_is_active (ev_TYPE *watcher)	1179	=item bool ev_is_active (ev_TYPE *watcher)
980		1180
981	Returns a true value iff the watcher is active (i.e. it has been started	1181	Returns a true value iff the watcher is active (i.e. it has been started
982	and not yet been stopped). As long as a watcher is active you must not modify	1182	and not yet been stopped). As long as a watcher is active you must not modify
…		…
998	=item ev_cb_set (ev_TYPE *watcher, callback)	1198	=item ev_cb_set (ev_TYPE *watcher, callback)
999		1199
1000	Change the callback. You can change the callback at virtually any time	1200	Change the callback. You can change the callback at virtually any time
1001	(modulo threads).	1201	(modulo threads).
1002		1202
1003	=item ev_set_priority (ev_TYPE *watcher, priority)	1203	=item ev_set_priority (ev_TYPE *watcher, int priority)
1004		1204
1005	=item int ev_priority (ev_TYPE *watcher)	1205	=item int ev_priority (ev_TYPE *watcher)
1006		1206
1007	Set and query the priority of the watcher. The priority is a small	1207	Set and query the priority of the watcher. The priority is a small
1008	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1208	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1009	(default: C<-2>). Pending watchers with higher priority will be invoked	1209	(default: C<-2>). Pending watchers with higher priority will be invoked
1010	before watchers with lower priority, but priority will not keep watchers	1210	before watchers with lower priority, but priority will not keep watchers
1011	from being executed (except for C<ev_idle> watchers).	1211	from being executed (except for C<ev_idle> watchers).
1012		1212
1013	This means that priorities are I<only> used for ordering callback
1014	invocation after new events have been received. This is useful, for
1015	example, to reduce latency after idling, or more often, to bind two
1016	watchers on the same event and make sure one is called first.
1017
1018	If you need to suppress invocation when higher priority events are pending	1213	If you need to suppress invocation when higher priority events are pending
1019	you need to look at C<ev_idle> watchers, which provide this functionality.	1214	you need to look at C<ev_idle> watchers, which provide this functionality.
1020		1215
1021	You I<must not> change the priority of a watcher as long as it is active or	1216	You I<must not> change the priority of a watcher as long as it is active or
1022	pending.	1217	pending.
1023		1218
		1219	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1220	fine, as long as you do not mind that the priority value you query might
		1221	or might not have been clamped to the valid range.
		1222
1024	The default priority used by watchers when no priority has been set is	1223	The default priority used by watchers when no priority has been set is
1025	always C<0>, which is supposed to not be too high and not be too low :).	1224	always C<0>, which is supposed to not be too high and not be too low :).
1026		1225
1027	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1226	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1028	fine, as long as you do not mind that the priority value you query might	1227	priorities.
1029	or might not have been adjusted to be within valid range.
1030		1228
1031	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1229	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1032		1230
1033	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1231	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1034	C<loop> nor C<revents> need to be valid as long as the watcher callback	1232	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1041	returns its C<revents> bitset (as if its callback was invoked). If the	1239	returns its C<revents> bitset (as if its callback was invoked). If the
1042	watcher isn't pending it does nothing and returns C<0>.	1240	watcher isn't pending it does nothing and returns C<0>.
1043		1241
1044	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1242	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1045	callback to be invoked, which can be accomplished with this function.	1243	callback to be invoked, which can be accomplished with this function.
		1244
		1245	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1246
		1247	Feeds the given event set into the event loop, as if the specified event
		1248	had happened for the specified watcher (which must be a pointer to an
		1249	initialised but not necessarily started event watcher). Obviously you must
		1250	not free the watcher as long as it has pending events.
		1251
		1252	Stopping the watcher, letting libev invoke it, or calling
		1253	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1254	not started in the first place.
		1255
		1256	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1257	functions that do not need a watcher.
1046		1258
1047	=back	1259	=back
1048		1260
1049		1261
1050	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1262	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
1056	member, you can also "subclass" the watcher type and provide your own	1268	member, you can also "subclass" the watcher type and provide your own
1057	data:	1269	data:
1058		1270
1059	struct my_io	1271	struct my_io
1060	{	1272	{
1061	struct ev_io io;	1273	ev_io io;
1062	int otherfd;	1274	int otherfd;
1063	void *somedata;	1275	void *somedata;
1064	struct whatever *mostinteresting;	1276	struct whatever *mostinteresting;
1065	};	1277	};
1066		1278
…		…
1069	ev_io_init (&w.io, my_cb, fd, EV_READ);	1281	ev_io_init (&w.io, my_cb, fd, EV_READ);
1070		1282
1071	And since your callback will be called with a pointer to the watcher, you	1283	And since your callback will be called with a pointer to the watcher, you
1072	can cast it back to your own type:	1284	can cast it back to your own type:
1073		1285
1074	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1286	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1075	{	1287	{
1076	struct my_io *w = (struct my_io *)w_;	1288	struct my_io *w = (struct my_io *)w_;
1077	...	1289	...
1078	}	1290	}
1079		1291
…		…
1097	programmers):	1309	programmers):
1098		1310
1099	#include <stddef.h>	1311	#include <stddef.h>
1100		1312
1101	static void	1313	static void
1102	t1_cb (EV_P_ struct ev_timer *w, int revents)	1314	t1_cb (EV_P_ ev_timer *w, int revents)
1103	{	1315	{
1104	struct my_biggy big = (struct my_biggy *	1316	struct my_biggy big = (struct my_biggy *)
1105	(((char *)w) - offsetof (struct my_biggy, t1));	1317	(((char *)w) - offsetof (struct my_biggy, t1));
1106	}	1318	}
1107		1319
1108	static void	1320	static void
1109	t2_cb (EV_P_ struct ev_timer *w, int revents)	1321	t2_cb (EV_P_ ev_timer *w, int revents)
1110	{	1322	{
1111	struct my_biggy big = (struct my_biggy *	1323	struct my_biggy big = (struct my_biggy *)
1112	(((char *)w) - offsetof (struct my_biggy, t2));	1324	(((char *)w) - offsetof (struct my_biggy, t2));
1113	}	1325	}
		1326
		1327	=head2 WATCHER PRIORITY MODELS
		1328
		1329	Many event loops support I<watcher priorities>, which are usually small
		1330	integers that influence the ordering of event callback invocation
		1331	between watchers in some way, all else being equal.
		1332
		1333	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1334	description for the more technical details such as the actual priority
		1335	range.
		1336
		1337	There are two common ways how these these priorities are being interpreted
		1338	by event loops:
		1339
		1340	In the more common lock-out model, higher priorities "lock out" invocation
		1341	of lower priority watchers, which means as long as higher priority
		1342	watchers receive events, lower priority watchers are not being invoked.
		1343
		1344	The less common only-for-ordering model uses priorities solely to order
		1345	callback invocation within a single event loop iteration: Higher priority
		1346	watchers are invoked before lower priority ones, but they all get invoked
		1347	before polling for new events.
		1348
		1349	Libev uses the second (only-for-ordering) model for all its watchers
		1350	except for idle watchers (which use the lock-out model).
		1351
		1352	The rationale behind this is that implementing the lock-out model for
		1353	watchers is not well supported by most kernel interfaces, and most event
		1354	libraries will just poll for the same events again and again as long as
		1355	their callbacks have not been executed, which is very inefficient in the
		1356	common case of one high-priority watcher locking out a mass of lower
		1357	priority ones.
		1358
		1359	Static (ordering) priorities are most useful when you have two or more
		1360	watchers handling the same resource: a typical usage example is having an
		1361	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1362	timeouts. Under load, data might be received while the program handles
		1363	other jobs, but since timers normally get invoked first, the timeout
		1364	handler will be executed before checking for data. In that case, giving
		1365	the timer a lower priority than the I/O watcher ensures that I/O will be
		1366	handled first even under adverse conditions (which is usually, but not
		1367	always, what you want).
		1368
		1369	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1370	will only be executed when no same or higher priority watchers have
		1371	received events, they can be used to implement the "lock-out" model when
		1372	required.
		1373
		1374	For example, to emulate how many other event libraries handle priorities,
		1375	you can associate an C<ev_idle> watcher to each such watcher, and in
		1376	the normal watcher callback, you just start the idle watcher. The real
		1377	processing is done in the idle watcher callback. This causes libev to
		1378	continously poll and process kernel event data for the watcher, but when
		1379	the lock-out case is known to be rare (which in turn is rare :), this is
		1380	workable.
		1381
		1382	Usually, however, the lock-out model implemented that way will perform
		1383	miserably under the type of load it was designed to handle. In that case,
		1384	it might be preferable to stop the real watcher before starting the
		1385	idle watcher, so the kernel will not have to process the event in case
		1386	the actual processing will be delayed for considerable time.
		1387
		1388	Here is an example of an I/O watcher that should run at a strictly lower
		1389	priority than the default, and which should only process data when no
		1390	other events are pending:
		1391
		1392	ev_idle idle; // actual processing watcher
		1393	ev_io io; // actual event watcher
		1394
		1395	static void
		1396	io_cb (EV_P_ ev_io *w, int revents)
		1397	{
		1398	// stop the I/O watcher, we received the event, but
		1399	// are not yet ready to handle it.
		1400	ev_io_stop (EV_A_ w);
		1401
		1402	// start the idle watcher to ahndle the actual event.
		1403	// it will not be executed as long as other watchers
		1404	// with the default priority are receiving events.
		1405	ev_idle_start (EV_A_ &idle);
		1406	}
		1407
		1408	static void
		1409	idle_cb (EV_P_ ev_idle *w, int revents)
		1410	{
		1411	// actual processing
		1412	read (STDIN_FILENO, ...);
		1413
		1414	// have to start the I/O watcher again, as
		1415	// we have handled the event
		1416	ev_io_start (EV_P_ &io);
		1417	}
		1418
		1419	// initialisation
		1420	ev_idle_init (&idle, idle_cb);
		1421	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1422	ev_io_start (EV_DEFAULT_ &io);
		1423
		1424	In the "real" world, it might also be beneficial to start a timer, so that
		1425	low-priority connections can not be locked out forever under load. This
		1426	enables your program to keep a lower latency for important connections
		1427	during short periods of high load, while not completely locking out less
		1428	important ones.
1114		1429
1115		1430
1116	=head1 WATCHER TYPES	1431	=head1 WATCHER TYPES
1117		1432
1118	This section describes each watcher in detail, but will not repeat	1433	This section describes each watcher in detail, but will not repeat
…		…
1144	descriptors to non-blocking mode is also usually a good idea (but not	1459	descriptors to non-blocking mode is also usually a good idea (but not
1145	required if you know what you are doing).	1460	required if you know what you are doing).
1146		1461
1147	If you cannot use non-blocking mode, then force the use of a	1462	If you cannot use non-blocking mode, then force the use of a
1148	known-to-be-good backend (at the time of this writing, this includes only	1463	known-to-be-good backend (at the time of this writing, this includes only
1149	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).	1464	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1465	descriptors for which non-blocking operation makes no sense (such as
		1466	files) - libev doesn't guarentee any specific behaviour in that case.
1150		1467
1151	Another thing you have to watch out for is that it is quite easy to	1468	Another thing you have to watch out for is that it is quite easy to
1152	receive "spurious" readiness notifications, that is your callback might	1469	receive "spurious" readiness notifications, that is your callback might
1153	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1470	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1154	because there is no data. Not only are some backends known to create a	1471	because there is no data. Not only are some backends known to create a
…		…
1249	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1566	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1250	readable, but only once. Since it is likely line-buffered, you could	1567	readable, but only once. Since it is likely line-buffered, you could
1251	attempt to read a whole line in the callback.	1568	attempt to read a whole line in the callback.
1252		1569
1253	static void	1570	static void
1254	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1571	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1255	{	1572	{
1256	ev_io_stop (loop, w);	1573	ev_io_stop (loop, w);
1257	.. read from stdin here (or from w->fd) and handle any I/O errors	1574	.. read from stdin here (or from w->fd) and handle any I/O errors
1258	}	1575	}
1259		1576
1260	...	1577	...
1261	struct ev_loop *loop = ev_default_init (0);	1578	struct ev_loop *loop = ev_default_init (0);
1262	struct ev_io stdin_readable;	1579	ev_io stdin_readable;
1263	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1580	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1264	ev_io_start (loop, &stdin_readable);	1581	ev_io_start (loop, &stdin_readable);
1265	ev_loop (loop, 0);	1582	ev_loop (loop, 0);
1266		1583
1267		1584
…		…
1275	year, it will still time out after (roughly) one hour. "Roughly" because	1592	year, it will still time out after (roughly) one hour. "Roughly" because
1276	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1593	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1277	monotonic clock option helps a lot here).	1594	monotonic clock option helps a lot here).
1278		1595
1279	The callback is guaranteed to be invoked only I<after> its timeout has	1596	The callback is guaranteed to be invoked only I<after> its timeout has
1280	passed, but if multiple timers become ready during the same loop iteration	1597	passed (not I<at>, so on systems with very low-resolution clocks this
1281	then order of execution is undefined.	1598	might introduce a small delay). If multiple timers become ready during the
		1599	same loop iteration then the ones with earlier time-out values are invoked
		1600	before ones of the same priority with later time-out values (but this is
		1601	no longer true when a callback calls C<ev_loop> recursively).
		1602
		1603	=head3 Be smart about timeouts
		1604
		1605	Many real-world problems involve some kind of timeout, usually for error
		1606	recovery. A typical example is an HTTP request - if the other side hangs,
		1607	you want to raise some error after a while.
		1608
		1609	What follows are some ways to handle this problem, from obvious and
		1610	inefficient to smart and efficient.
		1611
		1612	In the following, a 60 second activity timeout is assumed - a timeout that
		1613	gets reset to 60 seconds each time there is activity (e.g. each time some
		1614	data or other life sign was received).
		1615
		1616	=over 4
		1617
		1618	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1619
		1620	This is the most obvious, but not the most simple way: In the beginning,
		1621	start the watcher:
		1622
		1623	ev_timer_init (timer, callback, 60., 0.);
		1624	ev_timer_start (loop, timer);
		1625
		1626	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1627	and start it again:
		1628
		1629	ev_timer_stop (loop, timer);
		1630	ev_timer_set (timer, 60., 0.);
		1631	ev_timer_start (loop, timer);
		1632
		1633	This is relatively simple to implement, but means that each time there is
		1634	some activity, libev will first have to remove the timer from its internal
		1635	data structure and then add it again. Libev tries to be fast, but it's
		1636	still not a constant-time operation.
		1637
		1638	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1639
		1640	This is the easiest way, and involves using C<ev_timer_again> instead of
		1641	C<ev_timer_start>.
		1642
		1643	To implement this, configure an C<ev_timer> with a C<repeat> value
		1644	of C<60> and then call C<ev_timer_again> at start and each time you
		1645	successfully read or write some data. If you go into an idle state where
		1646	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1647	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1648
		1649	That means you can ignore both the C<ev_timer_start> function and the
		1650	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1651	member and C<ev_timer_again>.
		1652
		1653	At start:
		1654
		1655	ev_init (timer, callback);
		1656	timer->repeat = 60.;
		1657	ev_timer_again (loop, timer);
		1658
		1659	Each time there is some activity:
		1660
		1661	ev_timer_again (loop, timer);
		1662
		1663	It is even possible to change the time-out on the fly, regardless of
		1664	whether the watcher is active or not:
		1665
		1666	timer->repeat = 30.;
		1667	ev_timer_again (loop, timer);
		1668
		1669	This is slightly more efficient then stopping/starting the timer each time
		1670	you want to modify its timeout value, as libev does not have to completely
		1671	remove and re-insert the timer from/into its internal data structure.
		1672
		1673	It is, however, even simpler than the "obvious" way to do it.
		1674
		1675	=item 3. Let the timer time out, but then re-arm it as required.
		1676
		1677	This method is more tricky, but usually most efficient: Most timeouts are
		1678	relatively long compared to the intervals between other activity - in
		1679	our example, within 60 seconds, there are usually many I/O events with
		1680	associated activity resets.
		1681
		1682	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1683	but remember the time of last activity, and check for a real timeout only
		1684	within the callback:
		1685
		1686	ev_tstamp last_activity; // time of last activity
		1687
		1688	static void
		1689	callback (EV_P_ ev_timer *w, int revents)
		1690	{
		1691	ev_tstamp now = ev_now (EV_A);
		1692	ev_tstamp timeout = last_activity + 60.;
		1693
		1694	// if last_activity + 60. is older than now, we did time out
		1695	if (timeout < now)
		1696	{
		1697	// timeout occured, take action
		1698	}
		1699	else
		1700	{
		1701	// callback was invoked, but there was some activity, re-arm
		1702	// the watcher to fire in last_activity + 60, which is
		1703	// guaranteed to be in the future, so "again" is positive:
		1704	w->repeat = timeout - now;
		1705	ev_timer_again (EV_A_ w);
		1706	}
		1707	}
		1708
		1709	To summarise the callback: first calculate the real timeout (defined
		1710	as "60 seconds after the last activity"), then check if that time has
		1711	been reached, which means something I<did>, in fact, time out. Otherwise
		1712	the callback was invoked too early (C<timeout> is in the future), so
		1713	re-schedule the timer to fire at that future time, to see if maybe we have
		1714	a timeout then.
		1715
		1716	Note how C<ev_timer_again> is used, taking advantage of the
		1717	C<ev_timer_again> optimisation when the timer is already running.
		1718
		1719	This scheme causes more callback invocations (about one every 60 seconds
		1720	minus half the average time between activity), but virtually no calls to
		1721	libev to change the timeout.
		1722
		1723	To start the timer, simply initialise the watcher and set C<last_activity>
		1724	to the current time (meaning we just have some activity :), then call the
		1725	callback, which will "do the right thing" and start the timer:
		1726
		1727	ev_init (timer, callback);
		1728	last_activity = ev_now (loop);
		1729	callback (loop, timer, EV_TIMEOUT);
		1730
		1731	And when there is some activity, simply store the current time in
		1732	C<last_activity>, no libev calls at all:
		1733
		1734	last_actiivty = ev_now (loop);
		1735
		1736	This technique is slightly more complex, but in most cases where the
		1737	time-out is unlikely to be triggered, much more efficient.
		1738
		1739	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1740	callback :) - just change the timeout and invoke the callback, which will
		1741	fix things for you.
		1742
		1743	=item 4. Wee, just use a double-linked list for your timeouts.
		1744
		1745	If there is not one request, but many thousands (millions...), all
		1746	employing some kind of timeout with the same timeout value, then one can
		1747	do even better:
		1748
		1749	When starting the timeout, calculate the timeout value and put the timeout
		1750	at the I<end> of the list.
		1751
		1752	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1753	the list is expected to fire (for example, using the technique #3).
		1754
		1755	When there is some activity, remove the timer from the list, recalculate
		1756	the timeout, append it to the end of the list again, and make sure to
		1757	update the C<ev_timer> if it was taken from the beginning of the list.
		1758
		1759	This way, one can manage an unlimited number of timeouts in O(1) time for
		1760	starting, stopping and updating the timers, at the expense of a major
		1761	complication, and having to use a constant timeout. The constant timeout
		1762	ensures that the list stays sorted.
		1763
		1764	=back
		1765
		1766	So which method the best?
		1767
		1768	Method #2 is a simple no-brain-required solution that is adequate in most
		1769	situations. Method #3 requires a bit more thinking, but handles many cases
		1770	better, and isn't very complicated either. In most case, choosing either
		1771	one is fine, with #3 being better in typical situations.
		1772
		1773	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1774	rather complicated, but extremely efficient, something that really pays
		1775	off after the first million or so of active timers, i.e. it's usually
		1776	overkill :)
1282		1777
1283	=head3 The special problem of time updates	1778	=head3 The special problem of time updates
1284		1779
1285	Establishing the current time is a costly operation (it usually takes at	1780	Establishing the current time is a costly operation (it usually takes at
1286	least two system calls): EV therefore updates its idea of the current	1781	least two system calls): EV therefore updates its idea of the current
…		…
1298		1793
1299	If the event loop is suspended for a long time, you can also force an	1794	If the event loop is suspended for a long time, you can also force an
1300	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1795	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1301	()>.	1796	()>.
1302		1797
		1798	=head3 The special problems of suspended animation
		1799
		1800	When you leave the server world it is quite customary to hit machines that
		1801	can suspend/hibernate - what happens to the clocks during such a suspend?
		1802
		1803	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1804	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1805	to run until the system is suspended, but they will not advance while the
		1806	system is suspended. That means, on resume, it will be as if the program
		1807	was frozen for a few seconds, but the suspend time will not be counted
		1808	towards C<ev_timer> when a monotonic clock source is used. The real time
		1809	clock advanced as expected, but if it is used as sole clocksource, then a
		1810	long suspend would be detected as a time jump by libev, and timers would
		1811	be adjusted accordingly.
		1812
		1813	I would not be surprised to see different behaviour in different between
		1814	operating systems, OS versions or even different hardware.
		1815
		1816	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1817	time jump in the monotonic clocks and the realtime clock. If the program
		1818	is suspended for a very long time, and monotonic clock sources are in use,
		1819	then you can expect C<ev_timer>s to expire as the full suspension time
		1820	will be counted towards the timers. When no monotonic clock source is in
		1821	use, then libev will again assume a timejump and adjust accordingly.
		1822
		1823	It might be beneficial for this latter case to call C<ev_suspend>
		1824	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1825	deterministic behaviour in this case (you can do nothing against
		1826	C<SIGSTOP>).
		1827
1303	=head3 Watcher-Specific Functions and Data Members	1828	=head3 Watcher-Specific Functions and Data Members
1304		1829
1305	=over 4	1830	=over 4
1306		1831
1307	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1832	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1330	If the timer is started but non-repeating, stop it (as if it timed out).	1855	If the timer is started but non-repeating, stop it (as if it timed out).
1331		1856
1332	If the timer is repeating, either start it if necessary (with the	1857	If the timer is repeating, either start it if necessary (with the
1333	C<repeat> value), or reset the running timer to the C<repeat> value.	1858	C<repeat> value), or reset the running timer to the C<repeat> value.
1334		1859
1335	This sounds a bit complicated, but here is a useful and typical	1860	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1336	example: Imagine you have a TCP connection and you want a so-called idle	1861	usage example.
1337	timeout, that is, you want to be called when there have been, say, 60
1338	seconds of inactivity on the socket. The easiest way to do this is to
1339	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1340	C<ev_timer_again> each time you successfully read or write some data. If
1341	you go into an idle state where you do not expect data to travel on the
1342	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1343	automatically restart it if need be.
1344		1862
1345	That means you can ignore the C<after> value and C<ev_timer_start>	1863	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1346	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1347		1864
1348	ev_timer_init (timer, callback, 0., 5.);	1865	Returns the remaining time until a timer fires. If the timer is active,
1349	ev_timer_again (loop, timer);	1866	then this time is relative to the current event loop time, otherwise it's
1350	...	1867	the timeout value currently configured.
1351	timer->again = 17.;
1352	ev_timer_again (loop, timer);
1353	...
1354	timer->again = 10.;
1355	ev_timer_again (loop, timer);
1356		1868
1357	This is more slightly efficient then stopping/starting the timer each time	1869	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1358	you want to modify its timeout value.	1870	C<5>. When the timer is started and one second passes, C<ev_timer_remain>
1359		1871	will return C<4>. When the timer expires and is restarted, it will return
1360	Note, however, that it is often even more efficient to remember the	1872	roughly C<7> (likely slightly less as callback invocation takes some time,
1361	time of the last activity and let the timer time-out naturally. In the	1873	too), and so on.
1362	callback, you then check whether the time-out is real, or, if there was
1363	some activity, you reschedule the watcher to time-out in "last_activity +
1364	timeout - ev_now ()" seconds.
1365		1874
1366	=item ev_tstamp repeat [read-write]	1875	=item ev_tstamp repeat [read-write]
1367		1876
1368	The current C<repeat> value. Will be used each time the watcher times out	1877	The current C<repeat> value. Will be used each time the watcher times out
1369	or C<ev_timer_again> is called, and determines the next timeout (if any),	1878	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1374	=head3 Examples	1883	=head3 Examples
1375		1884
1376	Example: Create a timer that fires after 60 seconds.	1885	Example: Create a timer that fires after 60 seconds.
1377		1886
1378	static void	1887	static void
1379	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1888	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1380	{	1889	{
1381	.. one minute over, w is actually stopped right here	1890	.. one minute over, w is actually stopped right here
1382	}	1891	}
1383		1892
1384	struct ev_timer mytimer;	1893	ev_timer mytimer;
1385	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1894	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1386	ev_timer_start (loop, &mytimer);	1895	ev_timer_start (loop, &mytimer);
1387		1896
1388	Example: Create a timeout timer that times out after 10 seconds of	1897	Example: Create a timeout timer that times out after 10 seconds of
1389	inactivity.	1898	inactivity.
1390		1899
1391	static void	1900	static void
1392	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1901	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1393	{	1902	{
1394	.. ten seconds without any activity	1903	.. ten seconds without any activity
1395	}	1904	}
1396		1905
1397	struct ev_timer mytimer;	1906	ev_timer mytimer;
1398	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1907	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1399	ev_timer_again (&mytimer); /* start timer */	1908	ev_timer_again (&mytimer); /* start timer */
1400	ev_loop (loop, 0);	1909	ev_loop (loop, 0);
1401		1910
1402	// and in some piece of code that gets executed on any "activity":	1911	// and in some piece of code that gets executed on any "activity":
…		…
1407	=head2 C<ev_periodic> - to cron or not to cron?	1916	=head2 C<ev_periodic> - to cron or not to cron?
1408		1917
1409	Periodic watchers are also timers of a kind, but they are very versatile	1918	Periodic watchers are also timers of a kind, but they are very versatile
1410	(and unfortunately a bit complex).	1919	(and unfortunately a bit complex).
1411		1920
1412	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1921	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1413	but on wall clock time (absolute time). You can tell a periodic watcher	1922	relative time, the physical time that passes) but on wall clock time
1414	to trigger after some specific point in time. For example, if you tell a	1923	(absolute time, the thing you can read on your calender or clock). The
1415	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	1924	difference is that wall clock time can run faster or slower than real
1416	+ 10.>, that is, an absolute time not a delay) and then reset your system	1925	time, and time jumps are not uncommon (e.g. when you adjust your
1417	clock to January of the previous year, then it will take more than year	1926	wrist-watch).
1418	to trigger the event (unlike an C<ev_timer>, which would still trigger
1419	roughly 10 seconds later as it uses a relative timeout).
1420		1927
		1928	You can tell a periodic watcher to trigger after some specific point
		1929	in time: for example, if you tell a periodic watcher to trigger "in 10
		1930	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1931	not a delay) and then reset your system clock to January of the previous
		1932	year, then it will take a year or more to trigger the event (unlike an
		1933	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1934	it, as it uses a relative timeout).
		1935
1421	C<ev_periodic>s can also be used to implement vastly more complex timers,	1936	C<ev_periodic> watchers can also be used to implement vastly more complex
1422	such as triggering an event on each "midnight, local time", or other	1937	timers, such as triggering an event on each "midnight, local time", or
1423	complicated rules.	1938	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1939	those cannot react to time jumps.
1424		1940
1425	As with timers, the callback is guaranteed to be invoked only when the	1941	As with timers, the callback is guaranteed to be invoked only when the
1426	time (C<at>) has passed, but if multiple periodic timers become ready	1942	point in time where it is supposed to trigger has passed. If multiple
1427	during the same loop iteration, then order of execution is undefined.	1943	timers become ready during the same loop iteration then the ones with
		1944	earlier time-out values are invoked before ones with later time-out values
		1945	(but this is no longer true when a callback calls C<ev_loop> recursively).
1428		1946
1429	=head3 Watcher-Specific Functions and Data Members	1947	=head3 Watcher-Specific Functions and Data Members
1430		1948
1431	=over 4	1949	=over 4
1432		1950
1433	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1951	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1434		1952
1435	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1953	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1436		1954
1437	Lots of arguments, lets sort it out... There are basically three modes of	1955	Lots of arguments, let's sort it out... There are basically three modes of
1438	operation, and we will explain them from simplest to most complex:	1956	operation, and we will explain them from simplest to most complex:
1439		1957
1440	=over 4	1958	=over 4
1441		1959
1442	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1960	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1443		1961
1444	In this configuration the watcher triggers an event after the wall clock	1962	In this configuration the watcher triggers an event after the wall clock
1445	time C<at> has passed. It will not repeat and will not adjust when a time	1963	time C<offset> has passed. It will not repeat and will not adjust when a
1446	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1964	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1447	only run when the system clock reaches or surpasses this time.	1965	will be stopped and invoked when the system clock reaches or surpasses
		1966	this point in time.
1448		1967
1449	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1968	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1450		1969
1451	In this mode the watcher will always be scheduled to time out at the next	1970	In this mode the watcher will always be scheduled to time out at the next
1452	C<at + N * interval> time (for some integer N, which can also be negative)	1971	C<offset + N * interval> time (for some integer N, which can also be
1453	and then repeat, regardless of any time jumps.	1972	negative) and then repeat, regardless of any time jumps. The C<offset>
		1973	argument is merely an offset into the C<interval> periods.
1454		1974
1455	This can be used to create timers that do not drift with respect to the	1975	This can be used to create timers that do not drift with respect to the
1456	system clock, for example, here is a C<ev_periodic> that triggers each	1976	system clock, for example, here is an C<ev_periodic> that triggers each
1457	hour, on the hour:	1977	hour, on the hour (with respect to UTC):
1458		1978
1459	ev_periodic_set (&periodic, 0., 3600., 0);	1979	ev_periodic_set (&periodic, 0., 3600., 0);
1460		1980
1461	This doesn't mean there will always be 3600 seconds in between triggers,	1981	This doesn't mean there will always be 3600 seconds in between triggers,
1462	but only that the callback will be called when the system time shows a	1982	but only that the callback will be called when the system time shows a
1463	full hour (UTC), or more correctly, when the system time is evenly divisible	1983	full hour (UTC), or more correctly, when the system time is evenly divisible
1464	by 3600.	1984	by 3600.
1465		1985
1466	Another way to think about it (for the mathematically inclined) is that	1986	Another way to think about it (for the mathematically inclined) is that
1467	C<ev_periodic> will try to run the callback in this mode at the next possible	1987	C<ev_periodic> will try to run the callback in this mode at the next possible
1468	time where C<time = at (mod interval)>, regardless of any time jumps.	1988	time where C<time = offset (mod interval)>, regardless of any time jumps.
1469		1989
1470	For numerical stability it is preferable that the C<at> value is near	1990	For numerical stability it is preferable that the C<offset> value is near
1471	C<ev_now ()> (the current time), but there is no range requirement for	1991	C<ev_now ()> (the current time), but there is no range requirement for
1472	this value, and in fact is often specified as zero.	1992	this value, and in fact is often specified as zero.
1473		1993
1474	Note also that there is an upper limit to how often a timer can fire (CPU	1994	Note also that there is an upper limit to how often a timer can fire (CPU
1475	speed for example), so if C<interval> is very small then timing stability	1995	speed for example), so if C<interval> is very small then timing stability
1476	will of course deteriorate. Libev itself tries to be exact to be about one	1996	will of course deteriorate. Libev itself tries to be exact to be about one
1477	millisecond (if the OS supports it and the machine is fast enough).	1997	millisecond (if the OS supports it and the machine is fast enough).
1478		1998
1479	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1999	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1480		2000
1481	In this mode the values for C<interval> and C<at> are both being	2001	In this mode the values for C<interval> and C<offset> are both being
1482	ignored. Instead, each time the periodic watcher gets scheduled, the	2002	ignored. Instead, each time the periodic watcher gets scheduled, the
1483	reschedule callback will be called with the watcher as first, and the	2003	reschedule callback will be called with the watcher as first, and the
1484	current time as second argument.	2004	current time as second argument.
1485		2005
1486	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2006	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1487	ever, or make ANY event loop modifications whatsoever>.	2007	or make ANY other event loop modifications whatsoever, unless explicitly
		2008	allowed by documentation here>.
1488		2009
1489	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2010	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1490	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2011	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1491	only event loop modification you are allowed to do).	2012	only event loop modification you are allowed to do).
1492		2013
1493	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	2014	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1494	*w, ev_tstamp now)>, e.g.:	2015	*w, ev_tstamp now)>, e.g.:
1495		2016
		2017	static ev_tstamp
1496	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	2018	my_rescheduler (ev_periodic *w, ev_tstamp now)
1497	{	2019	{
1498	return now + 60.;	2020	return now + 60.;
1499	}	2021	}
1500		2022
1501	It must return the next time to trigger, based on the passed time value	2023	It must return the next time to trigger, based on the passed time value
…		…
1521	a different time than the last time it was called (e.g. in a crond like	2043	a different time than the last time it was called (e.g. in a crond like
1522	program when the crontabs have changed).	2044	program when the crontabs have changed).
1523		2045
1524	=item ev_tstamp ev_periodic_at (ev_periodic *)	2046	=item ev_tstamp ev_periodic_at (ev_periodic *)
1525		2047
1526	When active, returns the absolute time that the watcher is supposed to	2048	When active, returns the absolute time that the watcher is supposed
1527	trigger next.	2049	to trigger next. This is not the same as the C<offset> argument to
		2050	C<ev_periodic_set>, but indeed works even in interval and manual
		2051	rescheduling modes.
1528		2052
1529	=item ev_tstamp offset [read-write]	2053	=item ev_tstamp offset [read-write]
1530		2054
1531	When repeating, this contains the offset value, otherwise this is the	2055	When repeating, this contains the offset value, otherwise this is the
1532	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2056	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2057	although libev might modify this value for better numerical stability).
1533		2058
1534	Can be modified any time, but changes only take effect when the periodic	2059	Can be modified any time, but changes only take effect when the periodic
1535	timer fires or C<ev_periodic_again> is being called.	2060	timer fires or C<ev_periodic_again> is being called.
1536		2061
1537	=item ev_tstamp interval [read-write]	2062	=item ev_tstamp interval [read-write]
1538		2063
1539	The current interval value. Can be modified any time, but changes only	2064	The current interval value. Can be modified any time, but changes only
1540	take effect when the periodic timer fires or C<ev_periodic_again> is being	2065	take effect when the periodic timer fires or C<ev_periodic_again> is being
1541	called.	2066	called.
1542		2067
1543	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2068	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1544		2069
1545	The current reschedule callback, or C<0>, if this functionality is	2070	The current reschedule callback, or C<0>, if this functionality is
1546	switched off. Can be changed any time, but changes only take effect when	2071	switched off. Can be changed any time, but changes only take effect when
1547	the periodic timer fires or C<ev_periodic_again> is being called.	2072	the periodic timer fires or C<ev_periodic_again> is being called.
1548		2073
…		…
1553	Example: Call a callback every hour, or, more precisely, whenever the	2078	Example: Call a callback every hour, or, more precisely, whenever the
1554	system time is divisible by 3600. The callback invocation times have	2079	system time is divisible by 3600. The callback invocation times have
1555	potentially a lot of jitter, but good long-term stability.	2080	potentially a lot of jitter, but good long-term stability.
1556		2081
1557	static void	2082	static void
1558	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2083	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1559	{	2084	{
1560	... its now a full hour (UTC, or TAI or whatever your clock follows)	2085	... its now a full hour (UTC, or TAI or whatever your clock follows)
1561	}	2086	}
1562		2087
1563	struct ev_periodic hourly_tick;	2088	ev_periodic hourly_tick;
1564	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2089	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1565	ev_periodic_start (loop, &hourly_tick);	2090	ev_periodic_start (loop, &hourly_tick);
1566		2091
1567	Example: The same as above, but use a reschedule callback to do it:	2092	Example: The same as above, but use a reschedule callback to do it:
1568		2093
1569	#include <math.h>	2094	#include <math.h>
1570		2095
1571	static ev_tstamp	2096	static ev_tstamp
1572	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2097	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1573	{	2098	{
1574	return now + (3600. - fmod (now, 3600.));	2099	return now + (3600. - fmod (now, 3600.));
1575	}	2100	}
1576		2101
1577	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2102	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1578		2103
1579	Example: Call a callback every hour, starting now:	2104	Example: Call a callback every hour, starting now:
1580		2105
1581	struct ev_periodic hourly_tick;	2106	ev_periodic hourly_tick;
1582	ev_periodic_init (&hourly_tick, clock_cb,	2107	ev_periodic_init (&hourly_tick, clock_cb,
1583	fmod (ev_now (loop), 3600.), 3600., 0);	2108	fmod (ev_now (loop), 3600.), 3600., 0);
1584	ev_periodic_start (loop, &hourly_tick);	2109	ev_periodic_start (loop, &hourly_tick);
1585		2110
1586		2111
…		…
1589	Signal watchers will trigger an event when the process receives a specific	2114	Signal watchers will trigger an event when the process receives a specific
1590	signal one or more times. Even though signals are very asynchronous, libev	2115	signal one or more times. Even though signals are very asynchronous, libev
1591	will try it's best to deliver signals synchronously, i.e. as part of the	2116	will try it's best to deliver signals synchronously, i.e. as part of the
1592	normal event processing, like any other event.	2117	normal event processing, like any other event.
1593		2118
1594	If you want signals asynchronously, just use C<sigaction> as you would	2119	If you want signals to be delivered truly asynchronously, just use
1595	do without libev and forget about sharing the signal. You can even use	2120	C<sigaction> as you would do without libev and forget about sharing
1596	C<ev_async> from a signal handler to synchronously wake up an event loop.	2121	the signal. You can even use C<ev_async> from a signal handler to
		2122	synchronously wake up an event loop.
1597		2123
1598	You can configure as many watchers as you like per signal. Only when the	2124	You can configure as many watchers as you like for the same signal, but
		2125	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2126	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2127	C<SIGINT> in both the default loop and another loop at the same time. At
		2128	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2129
1599	first watcher gets started will libev actually register a signal handler	2130	When the first watcher gets started will libev actually register something
1600	with the kernel (thus it coexists with your own signal handlers as long as	2131	with the kernel (thus it coexists with your own signal handlers as long as
1601	you don't register any with libev for the same signal). Similarly, when	2132	you don't register any with libev for the same signal).
1602	the last signal watcher for a signal is stopped, libev will reset the
1603	signal handler to SIG_DFL (regardless of what it was set to before).
1604		2133
1605	If possible and supported, libev will install its handlers with	2134	If possible and supported, libev will install its handlers with
1606	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2135	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1607	interrupted. If you have a problem with system calls getting interrupted by	2136	not be unduly interrupted. If you have a problem with system calls getting
1608	signals you can block all signals in an C<ev_check> watcher and unblock	2137	interrupted by signals you can block all signals in an C<ev_check> watcher
1609	them in an C<ev_prepare> watcher.	2138	and unblock them in an C<ev_prepare> watcher.
		2139
		2140	=head3 The special problem of inheritance over fork/execve/pthread_create
		2141
		2142	Both the signal mask (C<sigprocmask>) and the signal disposition
		2143	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2144	stopping it again), that is, libev might or might not block the signal,
		2145	and might or might not set or restore the installed signal handler.
		2146
		2147	While this does not matter for the signal disposition (libev never
		2148	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2149	C<execve>), this matters for the signal mask: many programs do not expect
		2150	certain signals to be blocked.
		2151
		2152	This means that before calling C<exec> (from the child) you should reset
		2153	the signal mask to whatever "default" you expect (all clear is a good
		2154	choice usually).
		2155
		2156	The simplest way to ensure that the signal mask is reset in the child is
		2157	to install a fork handler with C<pthread_atfork> that resets it. That will
		2158	catch fork calls done by libraries (such as the libc) as well.
		2159
		2160	In current versions of libev, the signal will not be blocked indefinitely
		2161	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2162	the window of opportunity for problems, it will not go away, as libev
		2163	I<has> to modify the signal mask, at least temporarily.
		2164
		2165	So I can't stress this enough I<if you do not reset your signal mask
		2166	when you expect it to be empty, you have a race condition in your
		2167	program>. This is not a libev-specific thing, this is true for most event
		2168	libraries.
1610		2169
1611	=head3 Watcher-Specific Functions and Data Members	2170	=head3 Watcher-Specific Functions and Data Members
1612		2171
1613	=over 4	2172	=over 4
1614		2173
…		…
1625		2184
1626	=back	2185	=back
1627		2186
1628	=head3 Examples	2187	=head3 Examples
1629		2188
1630	Example: Try to exit cleanly on SIGINT and SIGTERM.	2189	Example: Try to exit cleanly on SIGINT.
1631		2190
1632	static void	2191	static void
1633	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2192	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1634	{	2193	{
1635	ev_unloop (loop, EVUNLOOP_ALL);	2194	ev_unloop (loop, EVUNLOOP_ALL);
1636	}	2195	}
1637		2196
1638	struct ev_signal signal_watcher;	2197	ev_signal signal_watcher;
1639	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2198	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1640	ev_signal_start (loop, &sigint_cb);	2199	ev_signal_start (loop, &signal_watcher);
1641		2200
1642		2201
1643	=head2 C<ev_child> - watch out for process status changes	2202	=head2 C<ev_child> - watch out for process status changes
1644		2203
1645	Child watchers trigger when your process receives a SIGCHLD in response to	2204	Child watchers trigger when your process receives a SIGCHLD in response to
1646	some child status changes (most typically when a child of yours dies or	2205	some child status changes (most typically when a child of yours dies or
1647	exits). It is permissible to install a child watcher I<after> the child	2206	exits). It is permissible to install a child watcher I<after> the child
1648	has been forked (which implies it might have already exited), as long	2207	has been forked (which implies it might have already exited), as long
1649	as the event loop isn't entered (or is continued from a watcher), i.e.,	2208	as the event loop isn't entered (or is continued from a watcher), i.e.,
1650	forking and then immediately registering a watcher for the child is fine,	2209	forking and then immediately registering a watcher for the child is fine,
1651	but forking and registering a watcher a few event loop iterations later is	2210	but forking and registering a watcher a few event loop iterations later or
1652	not.	2211	in the next callback invocation is not.
1653		2212
1654	Only the default event loop is capable of handling signals, and therefore	2213	Only the default event loop is capable of handling signals, and therefore
1655	you can only register child watchers in the default event loop.	2214	you can only register child watchers in the default event loop.
1656		2215
		2216	Due to some design glitches inside libev, child watchers will always be
		2217	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2218	libev)
		2219
1657	=head3 Process Interaction	2220	=head3 Process Interaction
1658		2221
1659	Libev grabs C<SIGCHLD> as soon as the default event loop is	2222	Libev grabs C<SIGCHLD> as soon as the default event loop is
1660	initialised. This is necessary to guarantee proper behaviour even if	2223	initialised. This is necessary to guarantee proper behaviour even if the
1661	the first child watcher is started after the child exits. The occurrence	2224	first child watcher is started after the child exits. The occurrence
1662	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2225	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1663	synchronously as part of the event loop processing. Libev always reaps all	2226	synchronously as part of the event loop processing. Libev always reaps all
1664	children, even ones not watched.	2227	children, even ones not watched.
1665		2228
1666	=head3 Overriding the Built-In Processing	2229	=head3 Overriding the Built-In Processing
…		…
1676	=head3 Stopping the Child Watcher	2239	=head3 Stopping the Child Watcher
1677		2240
1678	Currently, the child watcher never gets stopped, even when the	2241	Currently, the child watcher never gets stopped, even when the
1679	child terminates, so normally one needs to stop the watcher in the	2242	child terminates, so normally one needs to stop the watcher in the
1680	callback. Future versions of libev might stop the watcher automatically	2243	callback. Future versions of libev might stop the watcher automatically
1681	when a child exit is detected.	2244	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2245	problem).
1682		2246
1683	=head3 Watcher-Specific Functions and Data Members	2247	=head3 Watcher-Specific Functions and Data Members
1684		2248
1685	=over 4	2249	=over 4
1686		2250
…		…
1718	its completion.	2282	its completion.
1719		2283
1720	ev_child cw;	2284	ev_child cw;
1721		2285
1722	static void	2286	static void
1723	child_cb (EV_P_ struct ev_child *w, int revents)	2287	child_cb (EV_P_ ev_child *w, int revents)
1724	{	2288	{
1725	ev_child_stop (EV_A_ w);	2289	ev_child_stop (EV_A_ w);
1726	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2290	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1727	}	2291	}
1728		2292
…		…
1743		2307
1744		2308
1745	=head2 C<ev_stat> - did the file attributes just change?	2309	=head2 C<ev_stat> - did the file attributes just change?
1746		2310
1747	This watches a file system path for attribute changes. That is, it calls	2311	This watches a file system path for attribute changes. That is, it calls
1748	C<stat> regularly (or when the OS says it changed) and sees if it changed	2312	C<stat> on that path in regular intervals (or when the OS says it changed)
1749	compared to the last time, invoking the callback if it did.	2313	and sees if it changed compared to the last time, invoking the callback if
		2314	it did.
1750		2315
1751	The path does not need to exist: changing from "path exists" to "path does	2316	The path does not need to exist: changing from "path exists" to "path does
1752	not exist" is a status change like any other. The condition "path does	2317	not exist" is a status change like any other. The condition "path does not
1753	not exist" is signified by the C<st_nlink> field being zero (which is	2318	exist" (or more correctly "path cannot be stat'ed") is signified by the
1754	otherwise always forced to be at least one) and all the other fields of	2319	C<st_nlink> field being zero (which is otherwise always forced to be at
1755	the stat buffer having unspecified contents.	2320	least one) and all the other fields of the stat buffer having unspecified
		2321	contents.
1756		2322
1757	The path I<should> be absolute and I<must not> end in a slash. If it is	2323	The path I<must not> end in a slash or contain special components such as
		2324	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1758	relative and your working directory changes, the behaviour is undefined.	2325	your working directory changes, then the behaviour is undefined.
1759		2326
1760	Since there is no standard kernel interface to do this, the portable	2327	Since there is no portable change notification interface available, the
1761	implementation simply calls C<stat (2)> regularly on the path to see if	2328	portable implementation simply calls C<stat(2)> regularly on the path
1762	it changed somehow. You can specify a recommended polling interval for	2329	to see if it changed somehow. You can specify a recommended polling
1763	this case. If you specify a polling interval of C<0> (highly recommended!)	2330	interval for this case. If you specify a polling interval of C<0> (highly
1764	then a I<suitable, unspecified default> value will be used (which	2331	recommended!) then a I<suitable, unspecified default> value will be used
1765	you can expect to be around five seconds, although this might change	2332	(which you can expect to be around five seconds, although this might
1766	dynamically). Libev will also impose a minimum interval which is currently	2333	change dynamically). Libev will also impose a minimum interval which is
1767	around C<0.1>, but thats usually overkill.	2334	currently around C<0.1>, but that's usually overkill.
1768		2335
1769	This watcher type is not meant for massive numbers of stat watchers,	2336	This watcher type is not meant for massive numbers of stat watchers,
1770	as even with OS-supported change notifications, this can be	2337	as even with OS-supported change notifications, this can be
1771	resource-intensive.	2338	resource-intensive.
1772		2339
1773	At the time of this writing, the only OS-specific interface implemented	2340	At the time of this writing, the only OS-specific interface implemented
1774	is the Linux inotify interface (implementing kqueue support is left as	2341	is the Linux inotify interface (implementing kqueue support is left as an
1775	an exercise for the reader. Note, however, that the author sees no way	2342	exercise for the reader. Note, however, that the author sees no way of
1776	of implementing C<ev_stat> semantics with kqueue).	2343	implementing C<ev_stat> semantics with kqueue, except as a hint).
1777		2344
1778	=head3 ABI Issues (Largefile Support)	2345	=head3 ABI Issues (Largefile Support)
1779		2346
1780	Libev by default (unless the user overrides this) uses the default	2347	Libev by default (unless the user overrides this) uses the default
1781	compilation environment, which means that on systems with large file	2348	compilation environment, which means that on systems with large file
1782	support disabled by default, you get the 32 bit version of the stat	2349	support disabled by default, you get the 32 bit version of the stat
1783	structure. When using the library from programs that change the ABI to	2350	structure. When using the library from programs that change the ABI to
1784	use 64 bit file offsets the programs will fail. In that case you have to	2351	use 64 bit file offsets the programs will fail. In that case you have to
1785	compile libev with the same flags to get binary compatibility. This is	2352	compile libev with the same flags to get binary compatibility. This is
1786	obviously the case with any flags that change the ABI, but the problem is	2353	obviously the case with any flags that change the ABI, but the problem is
1787	most noticeably disabled with ev_stat and large file support.	2354	most noticeably displayed with ev_stat and large file support.
1788		2355
1789	The solution for this is to lobby your distribution maker to make large	2356	The solution for this is to lobby your distribution maker to make large
1790	file interfaces available by default (as e.g. FreeBSD does) and not	2357	file interfaces available by default (as e.g. FreeBSD does) and not
1791	optional. Libev cannot simply switch on large file support because it has	2358	optional. Libev cannot simply switch on large file support because it has
1792	to exchange stat structures with application programs compiled using the	2359	to exchange stat structures with application programs compiled using the
1793	default compilation environment.	2360	default compilation environment.
1794		2361
1795	=head3 Inotify and Kqueue	2362	=head3 Inotify and Kqueue
1796		2363
1797	When C<inotify (7)> support has been compiled into libev (generally only	2364	When C<inotify (7)> support has been compiled into libev and present at
1798	available with Linux) and present at runtime, it will be used to speed up	2365	runtime, it will be used to speed up change detection where possible. The
1799	change detection where possible. The inotify descriptor will be created lazily	2366	inotify descriptor will be created lazily when the first C<ev_stat>
1800	when the first C<ev_stat> watcher is being started.	2367	watcher is being started.
1801		2368
1802	Inotify presence does not change the semantics of C<ev_stat> watchers	2369	Inotify presence does not change the semantics of C<ev_stat> watchers
1803	except that changes might be detected earlier, and in some cases, to avoid	2370	except that changes might be detected earlier, and in some cases, to avoid
1804	making regular C<stat> calls. Even in the presence of inotify support	2371	making regular C<stat> calls. Even in the presence of inotify support
1805	there are many cases where libev has to resort to regular C<stat> polling,	2372	there are many cases where libev has to resort to regular C<stat> polling,
1806	but as long as the path exists, libev usually gets away without polling.	2373	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2374	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2375	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2376	xfs are fully working) libev usually gets away without polling.
1807		2377
1808	There is no support for kqueue, as apparently it cannot be used to	2378	There is no support for kqueue, as apparently it cannot be used to
1809	implement this functionality, due to the requirement of having a file	2379	implement this functionality, due to the requirement of having a file
1810	descriptor open on the object at all times, and detecting renames, unlinks	2380	descriptor open on the object at all times, and detecting renames, unlinks
1811	etc. is difficult.	2381	etc. is difficult.
1812		2382
		2383	=head3 C<stat ()> is a synchronous operation
		2384
		2385	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2386	the process. The exception are C<ev_stat> watchers - those call C<stat
		2387	()>, which is a synchronous operation.
		2388
		2389	For local paths, this usually doesn't matter: unless the system is very
		2390	busy or the intervals between stat's are large, a stat call will be fast,
		2391	as the path data is usually in memory already (except when starting the
		2392	watcher).
		2393
		2394	For networked file systems, calling C<stat ()> can block an indefinite
		2395	time due to network issues, and even under good conditions, a stat call
		2396	often takes multiple milliseconds.
		2397
		2398	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2399	paths, although this is fully supported by libev.
		2400
1813	=head3 The special problem of stat time resolution	2401	=head3 The special problem of stat time resolution
1814		2402
1815	The C<stat ()> system call only supports full-second resolution portably, and	2403	The C<stat ()> system call only supports full-second resolution portably,
1816	even on systems where the resolution is higher, most file systems still	2404	and even on systems where the resolution is higher, most file systems
1817	only support whole seconds.	2405	still only support whole seconds.
1818		2406
1819	That means that, if the time is the only thing that changes, you can	2407	That means that, if the time is the only thing that changes, you can
1820	easily miss updates: on the first update, C<ev_stat> detects a change and	2408	easily miss updates: on the first update, C<ev_stat> detects a change and
1821	calls your callback, which does something. When there is another update	2409	calls your callback, which does something. When there is another update
1822	within the same second, C<ev_stat> will be unable to detect unless the	2410	within the same second, C<ev_stat> will be unable to detect unless the
…		…
1965		2553
1966	=head3 Watcher-Specific Functions and Data Members	2554	=head3 Watcher-Specific Functions and Data Members
1967		2555
1968	=over 4	2556	=over 4
1969		2557
1970	=item ev_idle_init (ev_signal *, callback)	2558	=item ev_idle_init (ev_idle *, callback)
1971		2559
1972	Initialises and configures the idle watcher - it has no parameters of any	2560	Initialises and configures the idle watcher - it has no parameters of any
1973	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2561	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1974	believe me.	2562	believe me.
1975		2563
…		…
1979		2567
1980	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2568	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1981	callback, free it. Also, use no error checking, as usual.	2569	callback, free it. Also, use no error checking, as usual.
1982		2570
1983	static void	2571	static void
1984	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2572	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1985	{	2573	{
1986	free (w);	2574	free (w);
1987	// now do something you wanted to do when the program has	2575	// now do something you wanted to do when the program has
1988	// no longer anything immediate to do.	2576	// no longer anything immediate to do.
1989	}	2577	}
1990		2578
1991	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2579	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1992	ev_idle_init (idle_watcher, idle_cb);	2580	ev_idle_init (idle_watcher, idle_cb);
1993	ev_idle_start (loop, idle_cb);	2581	ev_idle_start (loop, idle_watcher);
1994		2582
1995		2583
1996	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2584	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1997		2585
1998	Prepare and check watchers are usually (but not always) used in pairs:	2586	Prepare and check watchers are usually (but not always) used in pairs:
…		…
2077		2665
2078	static ev_io iow [nfd];	2666	static ev_io iow [nfd];
2079	static ev_timer tw;	2667	static ev_timer tw;
2080		2668
2081	static void	2669	static void
2082	io_cb (ev_loop *loop, ev_io *w, int revents)	2670	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2083	{	2671	{
2084	}	2672	}
2085		2673
2086	// create io watchers for each fd and a timer before blocking	2674	// create io watchers for each fd and a timer before blocking
2087	static void	2675	static void
2088	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2676	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2089	{	2677	{
2090	int timeout = 3600000;	2678	int timeout = 3600000;
2091	struct pollfd fds [nfd];	2679	struct pollfd fds [nfd];
2092	// actual code will need to loop here and realloc etc.	2680	// actual code will need to loop here and realloc etc.
2093	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2681	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2094		2682
2095	/* the callback is illegal, but won't be called as we stop during check */	2683	/* the callback is illegal, but won't be called as we stop during check */
2096	ev_timer_init (&tw, 0, timeout * 1e-3);	2684	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2097	ev_timer_start (loop, &tw);	2685	ev_timer_start (loop, &tw);
2098		2686
2099	// create one ev_io per pollfd	2687	// create one ev_io per pollfd
2100	for (int i = 0; i < nfd; ++i)	2688	for (int i = 0; i < nfd; ++i)
2101	{	2689	{
…		…
2108	}	2696	}
2109	}	2697	}
2110		2698
2111	// stop all watchers after blocking	2699	// stop all watchers after blocking
2112	static void	2700	static void
2113	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2701	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2114	{	2702	{
2115	ev_timer_stop (loop, &tw);	2703	ev_timer_stop (loop, &tw);
2116		2704
2117	for (int i = 0; i < nfd; ++i)	2705	for (int i = 0; i < nfd; ++i)
2118	{	2706	{
…		…
2214	some fds have to be watched and handled very quickly (with low latency),	2802	some fds have to be watched and handled very quickly (with low latency),
2215	and even priorities and idle watchers might have too much overhead. In	2803	and even priorities and idle watchers might have too much overhead. In
2216	this case you would put all the high priority stuff in one loop and all	2804	this case you would put all the high priority stuff in one loop and all
2217	the rest in a second one, and embed the second one in the first.	2805	the rest in a second one, and embed the second one in the first.
2218		2806
2219	As long as the watcher is active, the callback will be invoked every time	2807	As long as the watcher is active, the callback will be invoked every
2220	there might be events pending in the embedded loop. The callback must then	2808	time there might be events pending in the embedded loop. The callback
2221	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2809	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2222	their callbacks (you could also start an idle watcher to give the embedded	2810	sweep and invoke their callbacks (the callback doesn't need to invoke the
2223	loop strictly lower priority for example). You can also set the callback	2811	C<ev_embed_sweep> function directly, it could also start an idle watcher
2224	to C<0>, in which case the embed watcher will automatically execute the	2812	to give the embedded loop strictly lower priority for example).
2225	embedded loop sweep.
2226		2813
2227	As long as the watcher is started it will automatically handle events. The	2814	You can also set the callback to C<0>, in which case the embed watcher
2228	callback will be invoked whenever some events have been handled. You can	2815	will automatically execute the embedded loop sweep whenever necessary.
2229	set the callback to C<0> to avoid having to specify one if you are not
2230	interested in that.
2231		2816
2232	Also, there have not currently been made special provisions for forking:	2817	Fork detection will be handled transparently while the C<ev_embed> watcher
2233	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2818	is active, i.e., the embedded loop will automatically be forked when the
2234	but you will also have to stop and restart any C<ev_embed> watchers	2819	embedding loop forks. In other cases, the user is responsible for calling
2235	yourself - but you can use a fork watcher to handle this automatically,	2820	C<ev_loop_fork> on the embedded loop.
2236	and future versions of libev might do just that.
2237		2821
2238	Unfortunately, not all backends are embeddable: only the ones returned by	2822	Unfortunately, not all backends are embeddable: only the ones returned by
2239	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2823	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2240	portable one.	2824	portable one.
2241		2825
…		…
2286	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2870	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2287	used).	2871	used).
2288		2872
2289	struct ev_loop *loop_hi = ev_default_init (0);	2873	struct ev_loop *loop_hi = ev_default_init (0);
2290	struct ev_loop *loop_lo = 0;	2874	struct ev_loop *loop_lo = 0;
2291	struct ev_embed embed;	2875	ev_embed embed;
2292		2876
2293	// see if there is a chance of getting one that works	2877	// see if there is a chance of getting one that works
2294	// (remember that a flags value of 0 means autodetection)	2878	// (remember that a flags value of 0 means autodetection)
2295	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2879	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2296	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2880	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2310	kqueue implementation). Store the kqueue/socket-only event loop in	2894	kqueue implementation). Store the kqueue/socket-only event loop in
2311	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2895	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2312		2896
2313	struct ev_loop *loop = ev_default_init (0);	2897	struct ev_loop *loop = ev_default_init (0);
2314	struct ev_loop *loop_socket = 0;	2898	struct ev_loop *loop_socket = 0;
2315	struct ev_embed embed;	2899	ev_embed embed;
2316		2900
2317	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2901	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2318	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2902	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2319	{	2903	{
2320	ev_embed_init (&embed, 0, loop_socket);	2904	ev_embed_init (&embed, 0, loop_socket);
…		…
2335	event loop blocks next and before C<ev_check> watchers are being called,	2919	event loop blocks next and before C<ev_check> watchers are being called,
2336	and only in the child after the fork. If whoever good citizen calling	2920	and only in the child after the fork. If whoever good citizen calling
2337	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2921	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2338	handlers will be invoked, too, of course.	2922	handlers will be invoked, too, of course.
2339		2923
		2924	=head3 The special problem of life after fork - how is it possible?
		2925
		2926	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2927	up/change the process environment, followed by a call to C<exec()>. This
		2928	sequence should be handled by libev without any problems.
		2929
		2930	This changes when the application actually wants to do event handling
		2931	in the child, or both parent in child, in effect "continuing" after the
		2932	fork.
		2933
		2934	The default mode of operation (for libev, with application help to detect
		2935	forks) is to duplicate all the state in the child, as would be expected
		2936	when I<either> the parent I<or> the child process continues.
		2937
		2938	When both processes want to continue using libev, then this is usually the
		2939	wrong result. In that case, usually one process (typically the parent) is
		2940	supposed to continue with all watchers in place as before, while the other
		2941	process typically wants to start fresh, i.e. without any active watchers.
		2942
		2943	The cleanest and most efficient way to achieve that with libev is to
		2944	simply create a new event loop, which of course will be "empty", and
		2945	use that for new watchers. This has the advantage of not touching more
		2946	memory than necessary, and thus avoiding the copy-on-write, and the
		2947	disadvantage of having to use multiple event loops (which do not support
		2948	signal watchers).
		2949
		2950	When this is not possible, or you want to use the default loop for
		2951	other reasons, then in the process that wants to start "fresh", call
		2952	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2953	the default loop will "orphan" (not stop) all registered watchers, so you
		2954	have to be careful not to execute code that modifies those watchers. Note
		2955	also that in that case, you have to re-register any signal watchers.
		2956
2340	=head3 Watcher-Specific Functions and Data Members	2957	=head3 Watcher-Specific Functions and Data Members
2341		2958
2342	=over 4	2959	=over 4
2343		2960
2344	=item ev_fork_init (ev_signal *, callback)	2961	=item ev_fork_init (ev_signal *, callback)
…		…
2373	=head3 Queueing	2990	=head3 Queueing
2374		2991
2375	C<ev_async> does not support queueing of data in any way. The reason	2992	C<ev_async> does not support queueing of data in any way. The reason
2376	is that the author does not know of a simple (or any) algorithm for a	2993	is that the author does not know of a simple (or any) algorithm for a
2377	multiple-writer-single-reader queue that works in all cases and doesn't	2994	multiple-writer-single-reader queue that works in all cases and doesn't
2378	need elaborate support such as pthreads.	2995	need elaborate support such as pthreads or unportable memory access
		2996	semantics.
2379		2997
2380	That means that if you want to queue data, you have to provide your own	2998	That means that if you want to queue data, you have to provide your own
2381	queue. But at least I can tell you how to implement locking around your	2999	queue. But at least I can tell you how to implement locking around your
2382	queue:	3000	queue:
2383		3001
2384	=over 4	3002	=over 4
2385		3003
2386	=item queueing from a signal handler context	3004	=item queueing from a signal handler context
2387		3005
2388	To implement race-free queueing, you simply add to the queue in the signal	3006	To implement race-free queueing, you simply add to the queue in the signal
2389	handler but you block the signal handler in the watcher callback. Here is an example that does that for	3007	handler but you block the signal handler in the watcher callback. Here is
2390	some fictitious SIGUSR1 handler:	3008	an example that does that for some fictitious SIGUSR1 handler:
2391		3009
2392	static ev_async mysig;	3010	static ev_async mysig;
2393		3011
2394	static void	3012	static void
2395	sigusr1_handler (void)	3013	sigusr1_handler (void)
…		…
2461	=over 4	3079	=over 4
2462		3080
2463	=item ev_async_init (ev_async *, callback)	3081	=item ev_async_init (ev_async *, callback)
2464		3082
2465	Initialises and configures the async watcher - it has no parameters of any	3083	Initialises and configures the async watcher - it has no parameters of any
2466	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3084	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2467	trust me.	3085	trust me.
2468		3086
2469	=item ev_async_send (loop, ev_async *)	3087	=item ev_async_send (loop, ev_async *)
2470		3088
2471	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3089	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2472	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3090	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2473	C<ev_feed_event>, this call is safe to do from other threads, signal or	3091	C<ev_feed_event>, this call is safe to do from other threads, signal or
2474	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3092	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2475	section below on what exactly this means).	3093	section below on what exactly this means).
2476		3094
		3095	Note that, as with other watchers in libev, multiple events might get
		3096	compressed into a single callback invocation (another way to look at this
		3097	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3098	reset when the event loop detects that).
		3099
2477	This call incurs the overhead of a system call only once per loop iteration,	3100	This call incurs the overhead of a system call only once per event loop
2478	so while the overhead might be noticeable, it doesn't apply to repeated	3101	iteration, so while the overhead might be noticeable, it doesn't apply to
2479	calls to C<ev_async_send>.	3102	repeated calls to C<ev_async_send> for the same event loop.
2480		3103
2481	=item bool = ev_async_pending (ev_async *)	3104	=item bool = ev_async_pending (ev_async *)
2482		3105
2483	Returns a non-zero value when C<ev_async_send> has been called on the	3106	Returns a non-zero value when C<ev_async_send> has been called on the
2484	watcher but the event has not yet been processed (or even noted) by the	3107	watcher but the event has not yet been processed (or even noted) by the
…		…
2487	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3110	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2488	the loop iterates next and checks for the watcher to have become active,	3111	the loop iterates next and checks for the watcher to have become active,
2489	it will reset the flag again. C<ev_async_pending> can be used to very	3112	it will reset the flag again. C<ev_async_pending> can be used to very
2490	quickly check whether invoking the loop might be a good idea.	3113	quickly check whether invoking the loop might be a good idea.
2491		3114
2492	Not that this does I<not> check whether the watcher itself is pending, only	3115	Not that this does I<not> check whether the watcher itself is pending,
2493	whether it has been requested to make this watcher pending.	3116	only whether it has been requested to make this watcher pending: there
		3117	is a time window between the event loop checking and resetting the async
		3118	notification, and the callback being invoked.
2494		3119
2495	=back	3120	=back
2496		3121
2497		3122
2498	=head1 OTHER FUNCTIONS	3123	=head1 OTHER FUNCTIONS
…		…
2502	=over 4	3127	=over 4
2503		3128
2504	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3129	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2505		3130
2506	This function combines a simple timer and an I/O watcher, calls your	3131	This function combines a simple timer and an I/O watcher, calls your
2507	callback on whichever event happens first and automatically stop both	3132	callback on whichever event happens first and automatically stops both
2508	watchers. This is useful if you want to wait for a single event on an fd	3133	watchers. This is useful if you want to wait for a single event on an fd
2509	or timeout without having to allocate/configure/start/stop/free one or	3134	or timeout without having to allocate/configure/start/stop/free one or
2510	more watchers yourself.	3135	more watchers yourself.
2511		3136
2512	If C<fd> is less than 0, then no I/O watcher will be started and events	3137	If C<fd> is less than 0, then no I/O watcher will be started and the
2513	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	3138	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2514	C<events> set will be created and started.	3139	the given C<fd> and C<events> set will be created and started.
2515		3140
2516	If C<timeout> is less than 0, then no timeout watcher will be	3141	If C<timeout> is less than 0, then no timeout watcher will be
2517	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3142	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2518	repeat = 0) will be started. While C<0> is a valid timeout, it is of	3143	repeat = 0) will be started. C<0> is a valid timeout.
2519	dubious value.
2520		3144
2521	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3145	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2522	passed an C<revents> set like normal event callbacks (a combination of	3146	passed an C<revents> set like normal event callbacks (a combination of
2523	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3147	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2524	value passed to C<ev_once>:	3148	value passed to C<ev_once>. Note that it is possible to receive I<both>
		3149	a timeout and an io event at the same time - you probably should give io
		3150	events precedence.
		3151
		3152	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2525		3153
2526	static void stdin_ready (int revents, void *arg)	3154	static void stdin_ready (int revents, void *arg)
2527	{	3155	{
		3156	if (revents & EV_READ)
		3157	/* stdin might have data for us, joy! */;
2528	if (revents & EV_TIMEOUT)	3158	else if (revents & EV_TIMEOUT)
2529	/* doh, nothing entered */;	3159	/* doh, nothing entered */;
2530	else if (revents & EV_READ)
2531	/* stdin might have data for us, joy! */;
2532	}	3160	}
2533		3161
2534	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3162	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2535		3163
2536	=item ev_feed_event (ev_loop *, watcher *, int revents)
2537
2538	Feeds the given event set into the event loop, as if the specified event
2539	had happened for the specified watcher (which must be a pointer to an
2540	initialised but not necessarily started event watcher).
2541
2542	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3164	=item ev_feed_fd_event (loop, int fd, int revents)
2543		3165
2544	Feed an event on the given fd, as if a file descriptor backend detected	3166	Feed an event on the given fd, as if a file descriptor backend detected
2545	the given events it.	3167	the given events it.
2546		3168
2547	=item ev_feed_signal_event (ev_loop *loop, int signum)	3169	=item ev_feed_signal_event (loop, int signum)
2548		3170
2549	Feed an event as if the given signal occurred (C<loop> must be the default	3171	Feed an event as if the given signal occurred (C<loop> must be the default
2550	loop!).	3172	loop!).
2551		3173
2552	=back	3174	=back
…		…
2632		3254
2633	=over 4	3255	=over 4
2634		3256
2635	=item ev::TYPE::TYPE ()	3257	=item ev::TYPE::TYPE ()
2636		3258
2637	=item ev::TYPE::TYPE (struct ev_loop *)	3259	=item ev::TYPE::TYPE (loop)
2638		3260
2639	=item ev::TYPE::~TYPE	3261	=item ev::TYPE::~TYPE
2640		3262
2641	The constructor (optionally) takes an event loop to associate the watcher	3263	The constructor (optionally) takes an event loop to associate the watcher
2642	with. If it is omitted, it will use C<EV_DEFAULT>.	3264	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2674		3296
2675	myclass obj;	3297	myclass obj;
2676	ev::io iow;	3298	ev::io iow;
2677	iow.set <myclass, &myclass::io_cb> (&obj);	3299	iow.set <myclass, &myclass::io_cb> (&obj);
2678		3300
		3301	=item w->set (object *)
		3302
		3303	This is an B<experimental> feature that might go away in a future version.
		3304
		3305	This is a variation of a method callback - leaving out the method to call
		3306	will default the method to C<operator ()>, which makes it possible to use
		3307	functor objects without having to manually specify the C<operator ()> all
		3308	the time. Incidentally, you can then also leave out the template argument
		3309	list.
		3310
		3311	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3312	int revents)>.
		3313
		3314	See the method-C<set> above for more details.
		3315
		3316	Example: use a functor object as callback.
		3317
		3318	struct myfunctor
		3319	{
		3320	void operator() (ev::io &w, int revents)
		3321	{
		3322	...
		3323	}
		3324	}
		3325
		3326	myfunctor f;
		3327
		3328	ev::io w;
		3329	w.set (&f);
		3330
2679	=item w->set<function> (void *data = 0)	3331	=item w->set<function> (void *data = 0)
2680		3332
2681	Also sets a callback, but uses a static method or plain function as	3333	Also sets a callback, but uses a static method or plain function as
2682	callback. The optional C<data> argument will be stored in the watcher's	3334	callback. The optional C<data> argument will be stored in the watcher's
2683	C<data> member and is free for you to use.	3335	C<data> member and is free for you to use.
…		…
2689	Example: Use a plain function as callback.	3341	Example: Use a plain function as callback.
2690		3342
2691	static void io_cb (ev::io &w, int revents) { }	3343	static void io_cb (ev::io &w, int revents) { }
2692	iow.set <io_cb> ();	3344	iow.set <io_cb> ();
2693		3345
2694	=item w->set (struct ev_loop *)	3346	=item w->set (loop)
2695		3347
2696	Associates a different C<struct ev_loop> with this watcher. You can only	3348	Associates a different C<struct ev_loop> with this watcher. You can only
2697	do this when the watcher is inactive (and not pending either).	3349	do this when the watcher is inactive (and not pending either).
2698		3350
2699	=item w->set ([arguments])	3351	=item w->set ([arguments])
…		…
2769	L<http://software.schmorp.de/pkg/EV>.	3421	L<http://software.schmorp.de/pkg/EV>.
2770		3422
2771	=item Python	3423	=item Python
2772		3424
2773	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3425	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2774	seems to be quite complete and well-documented. Note, however, that the	3426	seems to be quite complete and well-documented.
2775	patch they require for libev is outright dangerous as it breaks the ABI
2776	for everybody else, and therefore, should never be applied in an installed
2777	libev (if python requires an incompatible ABI then it needs to embed
2778	libev).
2779		3427
2780	=item Ruby	3428	=item Ruby
2781		3429
2782	Tony Arcieri has written a ruby extension that offers access to a subset	3430	Tony Arcieri has written a ruby extension that offers access to a subset
2783	of the libev API and adds file handle abstractions, asynchronous DNS and	3431	of the libev API and adds file handle abstractions, asynchronous DNS and
2784	more on top of it. It can be found via gem servers. Its homepage is at	3432	more on top of it. It can be found via gem servers. Its homepage is at
2785	L<http://rev.rubyforge.org/>.	3433	L<http://rev.rubyforge.org/>.
2786		3434
		3435	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3436	makes rev work even on mingw.
		3437
		3438	=item Haskell
		3439
		3440	A haskell binding to libev is available at
		3441	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3442
2787	=item D	3443	=item D
2788		3444
2789	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3445	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2790	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3446	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3447
		3448	=item Ocaml
		3449
		3450	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3451	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3452
		3453	=item Lua
		3454
		3455	Brian Maher has written a partial interface to libev
		3456	for lua (only C<ev_io> and C<ev_timer>), to be found at
		3457	L<http://github.com/brimworks/lua-ev>.
2791		3458
2792	=back	3459	=back
2793		3460
2794		3461
2795	=head1 MACRO MAGIC	3462	=head1 MACRO MAGIC
…		…
2896		3563
2897	#define EV_STANDALONE 1	3564	#define EV_STANDALONE 1
2898	#include "ev.h"	3565	#include "ev.h"
2899		3566
2900	Both header files and implementation files can be compiled with a C++	3567	Both header files and implementation files can be compiled with a C++
2901	compiler (at least, thats a stated goal, and breakage will be treated	3568	compiler (at least, that's a stated goal, and breakage will be treated
2902	as a bug).	3569	as a bug).
2903		3570
2904	You need the following files in your source tree, or in a directory	3571	You need the following files in your source tree, or in a directory
2905	in your include path (e.g. in libev/ when using -Ilibev):	3572	in your include path (e.g. in libev/ when using -Ilibev):
2906		3573
…		…
2962	keeps libev from including F<config.h>, and it also defines dummy	3629	keeps libev from including F<config.h>, and it also defines dummy
2963	implementations for some libevent functions (such as logging, which is not	3630	implementations for some libevent functions (such as logging, which is not
2964	supported). It will also not define any of the structs usually found in	3631	supported). It will also not define any of the structs usually found in
2965	F<event.h> that are not directly supported by the libev core alone.	3632	F<event.h> that are not directly supported by the libev core alone.
2966		3633
		3634	In standalone mode, libev will still try to automatically deduce the
		3635	configuration, but has to be more conservative.
		3636
2967	=item EV_USE_MONOTONIC	3637	=item EV_USE_MONOTONIC
2968		3638
2969	If defined to be C<1>, libev will try to detect the availability of the	3639	If defined to be C<1>, libev will try to detect the availability of the
2970	monotonic clock option at both compile time and runtime. Otherwise no use	3640	monotonic clock option at both compile time and runtime. Otherwise no
2971	of the monotonic clock option will be attempted. If you enable this, you	3641	use of the monotonic clock option will be attempted. If you enable this,
2972	usually have to link against librt or something similar. Enabling it when	3642	you usually have to link against librt or something similar. Enabling it
2973	the functionality isn't available is safe, though, although you have	3643	when the functionality isn't available is safe, though, although you have
2974	to make sure you link against any libraries where the C<clock_gettime>	3644	to make sure you link against any libraries where the C<clock_gettime>
2975	function is hiding in (often F<-lrt>).	3645	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2976		3646
2977	=item EV_USE_REALTIME	3647	=item EV_USE_REALTIME
2978		3648
2979	If defined to be C<1>, libev will try to detect the availability of the	3649	If defined to be C<1>, libev will try to detect the availability of the
2980	real-time clock option at compile time (and assume its availability at	3650	real-time clock option at compile time (and assume its availability
2981	runtime if successful). Otherwise no use of the real-time clock option will	3651	at runtime if successful). Otherwise no use of the real-time clock
2982	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3652	option will be attempted. This effectively replaces C<gettimeofday>
2983	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3653	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2984	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3654	correctness. See the note about libraries in the description of
		3655	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3656	C<EV_USE_CLOCK_SYSCALL>.
		3657
		3658	=item EV_USE_CLOCK_SYSCALL
		3659
		3660	If defined to be C<1>, libev will try to use a direct syscall instead
		3661	of calling the system-provided C<clock_gettime> function. This option
		3662	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3663	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3664	programs needlessly. Using a direct syscall is slightly slower (in
		3665	theory), because no optimised vdso implementation can be used, but avoids
		3666	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3667	higher, as it simplifies linking (no need for C<-lrt>).
2985		3668
2986	=item EV_USE_NANOSLEEP	3669	=item EV_USE_NANOSLEEP
2987		3670
2988	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3671	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2989	and will use it for delays. Otherwise it will use C<select ()>.	3672	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3005		3688
3006	=item EV_SELECT_USE_FD_SET	3689	=item EV_SELECT_USE_FD_SET
3007		3690
3008	If defined to C<1>, then the select backend will use the system C<fd_set>	3691	If defined to C<1>, then the select backend will use the system C<fd_set>
3009	structure. This is useful if libev doesn't compile due to a missing	3692	structure. This is useful if libev doesn't compile due to a missing
3010	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3693	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3011	exotic systems. This usually limits the range of file descriptors to some	3694	on exotic systems. This usually limits the range of file descriptors to
3012	low limit such as 1024 or might have other limitations (winsocket only	3695	some low limit such as 1024 or might have other limitations (winsocket
3013	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3696	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3014	influence the size of the C<fd_set> used.	3697	configures the maximum size of the C<fd_set>.
3015		3698
3016	=item EV_SELECT_IS_WINSOCKET	3699	=item EV_SELECT_IS_WINSOCKET
3017		3700
3018	When defined to C<1>, the select backend will assume that	3701	When defined to C<1>, the select backend will assume that
3019	select/socket/connect etc. don't understand file descriptors but	3702	select/socket/connect etc. don't understand file descriptors but
…		…
3021	be used is the winsock select). This means that it will call	3704	be used is the winsock select). This means that it will call
3022	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3705	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3023	it is assumed that all these functions actually work on fds, even	3706	it is assumed that all these functions actually work on fds, even
3024	on win32. Should not be defined on non-win32 platforms.	3707	on win32. Should not be defined on non-win32 platforms.
3025		3708
3026	=item EV_FD_TO_WIN32_HANDLE	3709	=item EV_FD_TO_WIN32_HANDLE(fd)
3027		3710
3028	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3711	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3029	file descriptors to socket handles. When not defining this symbol (the	3712	file descriptors to socket handles. When not defining this symbol (the
3030	default), then libev will call C<_get_osfhandle>, which is usually	3713	default), then libev will call C<_get_osfhandle>, which is usually
3031	correct. In some cases, programs use their own file descriptor management,	3714	correct. In some cases, programs use their own file descriptor management,
3032	in which case they can provide this function to map fds to socket handles.	3715	in which case they can provide this function to map fds to socket handles.
		3716
		3717	=item EV_WIN32_HANDLE_TO_FD(handle)
		3718
		3719	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3720	using the standard C<_open_osfhandle> function. For programs implementing
		3721	their own fd to handle mapping, overwriting this function makes it easier
		3722	to do so. This can be done by defining this macro to an appropriate value.
		3723
		3724	=item EV_WIN32_CLOSE_FD(fd)
		3725
		3726	If programs implement their own fd to handle mapping on win32, then this
		3727	macro can be used to override the C<close> function, useful to unregister
		3728	file descriptors again. Note that the replacement function has to close
		3729	the underlying OS handle.
3033		3730
3034	=item EV_USE_POLL	3731	=item EV_USE_POLL
3035		3732
3036	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3733	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3037	backend. Otherwise it will be enabled on non-win32 platforms. It	3734	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3169	defined to be C<0>, then they are not.	3866	defined to be C<0>, then they are not.
3170		3867
3171	=item EV_MINIMAL	3868	=item EV_MINIMAL
3172		3869
3173	If you need to shave off some kilobytes of code at the expense of some	3870	If you need to shave off some kilobytes of code at the expense of some
3174	speed, define this symbol to C<1>. Currently this is used to override some	3871	speed (but with the full API), define this symbol to C<1>. Currently this
3175	inlining decisions, saves roughly 30% code size on amd64. It also selects a	3872	is used to override some inlining decisions, saves roughly 30% code size
3176	much smaller 2-heap for timer management over the default 4-heap.	3873	on amd64. It also selects a much smaller 2-heap for timer management over
		3874	the default 4-heap.
		3875
		3876	You can save even more by disabling watcher types you do not need
		3877	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>
		3878	(C<-DNDEBUG>) will usually reduce code size a lot.
		3879
		3880	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to
		3881	provide a bare-bones event library. See C<ev.h> for details on what parts
		3882	of the API are still available, and do not complain if this subset changes
		3883	over time.
		3884
		3885	=item EV_NSIG
		3886
		3887	The highest supported signal number, +1 (or, the number of
		3888	signals): Normally, libev tries to deduce the maximum number of signals
		3889	automatically, but sometimes this fails, in which case it can be
		3890	specified. Also, using a lower number than detected (C<32> should be
		3891	good for about any system in existance) can save some memory, as libev
		3892	statically allocates some 12-24 bytes per signal number.
3177		3893
3178	=item EV_PID_HASHSIZE	3894	=item EV_PID_HASHSIZE
3179		3895
3180	C<ev_child> watchers use a small hash table to distribute workload by	3896	C<ev_child> watchers use a small hash table to distribute workload by
3181	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3897	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
3306	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4022	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3307		4023
3308	#include "ev_cpp.h"	4024	#include "ev_cpp.h"
3309	#include "ev.c"	4025	#include "ev.c"
3310		4026
		4027	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3311		4028
3312	=head1 THREADS AND COROUTINES	4029	=head2 THREADS AND COROUTINES
3313		4030
3314	=head2 THREADS	4031	=head3 THREADS
3315		4032
3316	All libev functions are reentrant and thread-safe unless explicitly	4033	All libev functions are reentrant and thread-safe unless explicitly
3317	documented otherwise, but it uses no locking itself. This means that you	4034	documented otherwise, but libev implements no locking itself. This means
3318	can use as many loops as you want in parallel, as long as there are no	4035	that you can use as many loops as you want in parallel, as long as there
3319	concurrent calls into any libev function with the same loop parameter	4036	are no concurrent calls into any libev function with the same loop
3320	(C<ev_default_*> calls have an implicit default loop parameter, of	4037	parameter (C<ev_default_*> calls have an implicit default loop parameter,
3321	course): libev guarantees that different event loops share no data	4038	of course): libev guarantees that different event loops share no data
3322	structures that need any locking.	4039	structures that need any locking.
3323		4040
3324	Or to put it differently: calls with different loop parameters can be done	4041	Or to put it differently: calls with different loop parameters can be done
3325	concurrently from multiple threads, calls with the same loop parameter	4042	concurrently from multiple threads, calls with the same loop parameter
3326	must be done serially (but can be done from different threads, as long as	4043	must be done serially (but can be done from different threads, as long as
…		…
3366	default loop and triggering an C<ev_async> watcher from the default loop	4083	default loop and triggering an C<ev_async> watcher from the default loop
3367	watcher callback into the event loop interested in the signal.	4084	watcher callback into the event loop interested in the signal.
3368		4085
3369	=back	4086	=back
3370		4087
		4088	=head4 THREAD LOCKING EXAMPLE
		4089
		4090	Here is a fictitious example of how to run an event loop in a different
		4091	thread than where callbacks are being invoked and watchers are
		4092	created/added/removed.
		4093
		4094	For a real-world example, see the C<EV::Loop::Async> perl module,
		4095	which uses exactly this technique (which is suited for many high-level
		4096	languages).
		4097
		4098	The example uses a pthread mutex to protect the loop data, a condition
		4099	variable to wait for callback invocations, an async watcher to notify the
		4100	event loop thread and an unspecified mechanism to wake up the main thread.
		4101
		4102	First, you need to associate some data with the event loop:
		4103
		4104	typedef struct {
		4105	mutex_t lock; /* global loop lock */
		4106	ev_async async_w;
		4107	thread_t tid;
		4108	cond_t invoke_cv;
		4109	} userdata;
		4110
		4111	void prepare_loop (EV_P)
		4112	{
		4113	// for simplicity, we use a static userdata struct.
		4114	static userdata u;
		4115
		4116	ev_async_init (&u->async_w, async_cb);
		4117	ev_async_start (EV_A_ &u->async_w);
		4118
		4119	pthread_mutex_init (&u->lock, 0);
		4120	pthread_cond_init (&u->invoke_cv, 0);
		4121
		4122	// now associate this with the loop
		4123	ev_set_userdata (EV_A_ u);
		4124	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4125	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4126
		4127	// then create the thread running ev_loop
		4128	pthread_create (&u->tid, 0, l_run, EV_A);
		4129	}
		4130
		4131	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4132	solely to wake up the event loop so it takes notice of any new watchers
		4133	that might have been added:
		4134
		4135	static void
		4136	async_cb (EV_P_ ev_async *w, int revents)
		4137	{
		4138	// just used for the side effects
		4139	}
		4140
		4141	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4142	protecting the loop data, respectively.
		4143
		4144	static void
		4145	l_release (EV_P)
		4146	{
		4147	userdata *u = ev_userdata (EV_A);
		4148	pthread_mutex_unlock (&u->lock);
		4149	}
		4150
		4151	static void
		4152	l_acquire (EV_P)
		4153	{
		4154	userdata *u = ev_userdata (EV_A);
		4155	pthread_mutex_lock (&u->lock);
		4156	}
		4157
		4158	The event loop thread first acquires the mutex, and then jumps straight
		4159	into C<ev_loop>:
		4160
		4161	void *
		4162	l_run (void *thr_arg)
		4163	{
		4164	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4165
		4166	l_acquire (EV_A);
		4167	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4168	ev_loop (EV_A_ 0);
		4169	l_release (EV_A);
		4170
		4171	return 0;
		4172	}
		4173
		4174	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4175	signal the main thread via some unspecified mechanism (signals? pipe
		4176	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4177	have been called (in a while loop because a) spurious wakeups are possible
		4178	and b) skipping inter-thread-communication when there are no pending
		4179	watchers is very beneficial):
		4180
		4181	static void
		4182	l_invoke (EV_P)
		4183	{
		4184	userdata *u = ev_userdata (EV_A);
		4185
		4186	while (ev_pending_count (EV_A))
		4187	{
		4188	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4189	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4190	}
		4191	}
		4192
		4193	Now, whenever the main thread gets told to invoke pending watchers, it
		4194	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4195	thread to continue:
		4196
		4197	static void
		4198	real_invoke_pending (EV_P)
		4199	{
		4200	userdata *u = ev_userdata (EV_A);
		4201
		4202	pthread_mutex_lock (&u->lock);
		4203	ev_invoke_pending (EV_A);
		4204	pthread_cond_signal (&u->invoke_cv);
		4205	pthread_mutex_unlock (&u->lock);
		4206	}
		4207
		4208	Whenever you want to start/stop a watcher or do other modifications to an
		4209	event loop, you will now have to lock:
		4210
		4211	ev_timer timeout_watcher;
		4212	userdata *u = ev_userdata (EV_A);
		4213
		4214	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4215
		4216	pthread_mutex_lock (&u->lock);
		4217	ev_timer_start (EV_A_ &timeout_watcher);
		4218	ev_async_send (EV_A_ &u->async_w);
		4219	pthread_mutex_unlock (&u->lock);
		4220
		4221	Note that sending the C<ev_async> watcher is required because otherwise
		4222	an event loop currently blocking in the kernel will have no knowledge
		4223	about the newly added timer. By waking up the loop it will pick up any new
		4224	watchers in the next event loop iteration.
		4225
3371	=head2 COROUTINES	4226	=head3 COROUTINES
3372		4227
3373	Libev is much more accommodating to coroutines ("cooperative threads"):	4228	Libev is very accommodating to coroutines ("cooperative threads"):
3374	libev fully supports nesting calls to it's functions from different	4229	libev fully supports nesting calls to its functions from different
3375	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4230	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3376	different coroutines and switch freely between both coroutines running the	4231	different coroutines, and switch freely between both coroutines running
3377	loop, as long as you don't confuse yourself). The only exception is that	4232	the loop, as long as you don't confuse yourself). The only exception is
3378	you must not do this from C<ev_periodic> reschedule callbacks.	4233	that you must not do this from C<ev_periodic> reschedule callbacks.
3379		4234
3380	Care has been taken to ensure that libev does not keep local state inside	4235	Care has been taken to ensure that libev does not keep local state inside
3381	C<ev_loop>, and other calls do not usually allow coroutine switches.	4236	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		4237	they do not call any callbacks.
3382		4238
		4239	=head2 COMPILER WARNINGS
3383		4240
3384	=head1 COMPLEXITIES	4241	Depending on your compiler and compiler settings, you might get no or a
		4242	lot of warnings when compiling libev code. Some people are apparently
		4243	scared by this.
3385		4244
3386	In this section the complexities of (many of) the algorithms used inside	4245	However, these are unavoidable for many reasons. For one, each compiler
3387	libev will be explained. For complexity discussions about backends see the	4246	has different warnings, and each user has different tastes regarding
3388	documentation for C<ev_default_init>.	4247	warning options. "Warn-free" code therefore cannot be a goal except when
		4248	targeting a specific compiler and compiler-version.
3389		4249
3390	All of the following are about amortised time: If an array needs to be	4250	Another reason is that some compiler warnings require elaborate
3391	extended, libev needs to realloc and move the whole array, but this	4251	workarounds, or other changes to the code that make it less clear and less
3392	happens asymptotically never with higher number of elements, so O(1) might	4252	maintainable.
3393	mean it might do a lengthy realloc operation in rare cases, but on average
3394	it is much faster and asymptotically approaches constant time.
3395		4253
3396	=over 4	4254	And of course, some compiler warnings are just plain stupid, or simply
		4255	wrong (because they don't actually warn about the condition their message
		4256	seems to warn about). For example, certain older gcc versions had some
		4257	warnings that resulted an extreme number of false positives. These have
		4258	been fixed, but some people still insist on making code warn-free with
		4259	such buggy versions.
3397		4260
3398	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	4261	While libev is written to generate as few warnings as possible,
		4262	"warn-free" code is not a goal, and it is recommended not to build libev
		4263	with any compiler warnings enabled unless you are prepared to cope with
		4264	them (e.g. by ignoring them). Remember that warnings are just that:
		4265	warnings, not errors, or proof of bugs.
3399		4266
3400	This means that, when you have a watcher that triggers in one hour and
3401	there are 100 watchers that would trigger before that then inserting will
3402	have to skip roughly seven (C<ld 100>) of these watchers.
3403		4267
3404	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	4268	=head2 VALGRIND
3405		4269
3406	That means that changing a timer costs less than removing/adding them	4270	Valgrind has a special section here because it is a popular tool that is
3407	as only the relative motion in the event queue has to be paid for.	4271	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3408		4272
3409	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	4273	If you think you found a bug (memory leak, uninitialised data access etc.)
		4274	in libev, then check twice: If valgrind reports something like:
3410		4275
3411	These just add the watcher into an array or at the head of a list.	4276	==2274== definitely lost: 0 bytes in 0 blocks.
		4277	==2274== possibly lost: 0 bytes in 0 blocks.
		4278	==2274== still reachable: 256 bytes in 1 blocks.
3412		4279
3413	=item Stopping check/prepare/idle/fork/async watchers: O(1)	4280	Then there is no memory leak, just as memory accounted to global variables
		4281	is not a memleak - the memory is still being referenced, and didn't leak.
3414		4282
3415	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	4283	Similarly, under some circumstances, valgrind might report kernel bugs
		4284	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		4285	although an acceptable workaround has been found here), or it might be
		4286	confused.
3416		4287
3417	These watchers are stored in lists then need to be walked to find the	4288	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3418	correct watcher to remove. The lists are usually short (you don't usually	4289	make it into some kind of religion.
3419	have many watchers waiting for the same fd or signal).
3420		4290
3421	=item Finding the next timer in each loop iteration: O(1)	4291	If you are unsure about something, feel free to contact the mailing list
		4292	with the full valgrind report and an explanation on why you think this
		4293	is a bug in libev (best check the archives, too :). However, don't be
		4294	annoyed when you get a brisk "this is no bug" answer and take the chance
		4295	of learning how to interpret valgrind properly.
3422		4296
3423	By virtue of using a binary or 4-heap, the next timer is always found at a	4297	If you need, for some reason, empty reports from valgrind for your project
3424	fixed position in the storage array.	4298	I suggest using suppression lists.
3425		4299
3426	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3427		4300
3428	A change means an I/O watcher gets started or stopped, which requires	4301	=head1 PORTABILITY NOTES
3429	libev to recalculate its status (and possibly tell the kernel, depending
3430	on backend and whether C<ev_io_set> was used).
3431		4302
3432	=item Activating one watcher (putting it into the pending state): O(1)
3433
3434	=item Priority handling: O(number_of_priorities)
3435
3436	Priorities are implemented by allocating some space for each
3437	priority. When doing priority-based operations, libev usually has to
3438	linearly search all the priorities, but starting/stopping and activating
3439	watchers becomes O(1) with respect to priority handling.
3440
3441	=item Sending an ev_async: O(1)
3442
3443	=item Processing ev_async_send: O(number_of_async_watchers)
3444
3445	=item Processing signals: O(max_signal_number)
3446
3447	Sending involves a system call I<iff> there were no other C<ev_async_send>
3448	calls in the current loop iteration. Checking for async and signal events
3449	involves iterating over all running async watchers or all signal numbers.
3450
3451	=back
3452
3453
3454	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4303	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3455		4304
3456	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4305	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3457	requires, and its I/O model is fundamentally incompatible with the POSIX	4306	requires, and its I/O model is fundamentally incompatible with the POSIX
3458	model. Libev still offers limited functionality on this platform in	4307	model. Libev still offers limited functionality on this platform in
3459	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4308	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3466	way (note also that glib is the slowest event library known to man).	4315	way (note also that glib is the slowest event library known to man).
3467		4316
3468	There is no supported compilation method available on windows except	4317	There is no supported compilation method available on windows except
3469	embedding it into other applications.	4318	embedding it into other applications.
3470		4319
		4320	Sensible signal handling is officially unsupported by Microsoft - libev
		4321	tries its best, but under most conditions, signals will simply not work.
		4322
3471	Not a libev limitation but worth mentioning: windows apparently doesn't	4323	Not a libev limitation but worth mentioning: windows apparently doesn't
3472	accept large writes: instead of resulting in a partial write, windows will	4324	accept large writes: instead of resulting in a partial write, windows will
3473	either accept everything or return C<ENOBUFS> if the buffer is too large,	4325	either accept everything or return C<ENOBUFS> if the buffer is too large,
3474	so make sure you only write small amounts into your sockets (less than a	4326	so make sure you only write small amounts into your sockets (less than a
3475	megabyte seems safe, but this apparently depends on the amount of memory	4327	megabyte seems safe, but this apparently depends on the amount of memory
…		…
3479	the abysmal performance of winsockets, using a large number of sockets	4331	the abysmal performance of winsockets, using a large number of sockets
3480	is not recommended (and not reasonable). If your program needs to use	4332	is not recommended (and not reasonable). If your program needs to use
3481	more than a hundred or so sockets, then likely it needs to use a totally	4333	more than a hundred or so sockets, then likely it needs to use a totally
3482	different implementation for windows, as libev offers the POSIX readiness	4334	different implementation for windows, as libev offers the POSIX readiness
3483	notification model, which cannot be implemented efficiently on windows	4335	notification model, which cannot be implemented efficiently on windows
3484	(Microsoft monopoly games).	4336	(due to Microsoft monopoly games).
3485		4337
3486	A typical way to use libev under windows is to embed it (see the embedding	4338	A typical way to use libev under windows is to embed it (see the embedding
3487	section for details) and use the following F<evwrap.h> header file instead	4339	section for details) and use the following F<evwrap.h> header file instead
3488	of F<ev.h>:	4340	of F<ev.h>:
3489		4341
…		…
3525		4377
3526	Early versions of winsocket's select only supported waiting for a maximum	4378	Early versions of winsocket's select only supported waiting for a maximum
3527	of C<64> handles (probably owning to the fact that all windows kernels	4379	of C<64> handles (probably owning to the fact that all windows kernels
3528	can only wait for C<64> things at the same time internally; Microsoft	4380	can only wait for C<64> things at the same time internally; Microsoft
3529	recommends spawning a chain of threads and wait for 63 handles and the	4381	recommends spawning a chain of threads and wait for 63 handles and the
3530	previous thread in each. Great).	4382	previous thread in each. Sounds great!).
3531		4383
3532	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4384	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3533	to some high number (e.g. C<2048>) before compiling the winsocket select	4385	to some high number (e.g. C<2048>) before compiling the winsocket select
3534	call (which might be in libev or elsewhere, for example, perl does its own	4386	call (which might be in libev or elsewhere, for example, perl and many
3535	select emulation on windows).	4387	other interpreters do their own select emulation on windows).
3536		4388
3537	Another limit is the number of file descriptors in the Microsoft runtime	4389	Another limit is the number of file descriptors in the Microsoft runtime
3538	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4390	libraries, which by default is C<64> (there must be a hidden I<64>
3539	or something like this inside Microsoft). You can increase this by calling	4391	fetish or something like this inside Microsoft). You can increase this
3540	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4392	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3541	arbitrary limit), but is broken in many versions of the Microsoft runtime	4393	(another arbitrary limit), but is broken in many versions of the Microsoft
3542	libraries.
3543
3544	This might get you to about C<512> or C<2048> sockets (depending on	4394	runtime libraries. This might get you to about C<512> or C<2048> sockets
3545	windows version and/or the phase of the moon). To get more, you need to	4395	(depending on windows version and/or the phase of the moon). To get more,
3546	wrap all I/O functions and provide your own fd management, but the cost of	4396	you need to wrap all I/O functions and provide your own fd management, but
3547	calling select (O(n²)) will likely make this unworkable.	4397	the cost of calling select (O(n²)) will likely make this unworkable.
3548		4398
3549	=back	4399	=back
3550		4400
3551
3552	=head1 PORTABILITY REQUIREMENTS	4401	=head2 PORTABILITY REQUIREMENTS
3553		4402
3554	In addition to a working ISO-C implementation, libev relies on a few	4403	In addition to a working ISO-C implementation and of course the
3555	additional extensions:	4404	backend-specific APIs, libev relies on a few additional extensions:
3556		4405
3557	=over 4	4406	=over 4
3558		4407
3559	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	4408	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3560	calling conventions regardless of C<ev_watcher_type *>.	4409	calling conventions regardless of C<ev_watcher_type *>.
…		…
3585	except the initial one, and run the default loop in the initial thread as	4434	except the initial one, and run the default loop in the initial thread as
3586	well.	4435	well.
3587		4436
3588	=item C<long> must be large enough for common memory allocation sizes	4437	=item C<long> must be large enough for common memory allocation sizes
3589		4438
3590	To improve portability and simplify using libev, libev uses C<long>	4439	To improve portability and simplify its API, libev uses C<long> internally
3591	internally instead of C<size_t> when allocating its data structures. On	4440	instead of C<size_t> when allocating its data structures. On non-POSIX
3592	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4441	systems (Microsoft...) this might be unexpectedly low, but is still at
3593	is still at least 31 bits everywhere, which is enough for hundreds of	4442	least 31 bits everywhere, which is enough for hundreds of millions of
3594	millions of watchers.	4443	watchers.
3595		4444
3596	=item C<double> must hold a time value in seconds with enough accuracy	4445	=item C<double> must hold a time value in seconds with enough accuracy
3597		4446
3598	The type C<double> is used to represent timestamps. It is required to	4447	The type C<double> is used to represent timestamps. It is required to
3599	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4448	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
3600	enough for at least into the year 4000. This requirement is fulfilled by	4449	enough for at least into the year 4000. This requirement is fulfilled by
3601	implementations implementing IEEE 754 (basically all existing ones).	4450	implementations implementing IEEE 754, which is basically all existing
		4451	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4452	2200.
3602		4453
3603	=back	4454	=back
3604		4455
3605	If you know of other additional requirements drop me a note.	4456	If you know of other additional requirements drop me a note.
3606		4457
3607		4458
3608	=head1 COMPILER WARNINGS	4459	=head1 ALGORITHMIC COMPLEXITIES
3609		4460
3610	Depending on your compiler and compiler settings, you might get no or a	4461	In this section the complexities of (many of) the algorithms used inside
3611	lot of warnings when compiling libev code. Some people are apparently	4462	libev will be documented. For complexity discussions about backends see
3612	scared by this.	4463	the documentation for C<ev_default_init>.
3613		4464
3614	However, these are unavoidable for many reasons. For one, each compiler	4465	All of the following are about amortised time: If an array needs to be
3615	has different warnings, and each user has different tastes regarding	4466	extended, libev needs to realloc and move the whole array, but this
3616	warning options. "Warn-free" code therefore cannot be a goal except when	4467	happens asymptotically rarer with higher number of elements, so O(1) might
3617	targeting a specific compiler and compiler-version.	4468	mean that libev does a lengthy realloc operation in rare cases, but on
		4469	average it is much faster and asymptotically approaches constant time.
3618		4470
3619	Another reason is that some compiler warnings require elaborate	4471	=over 4
3620	workarounds, or other changes to the code that make it less clear and less
3621	maintainable.
3622		4472
3623	And of course, some compiler warnings are just plain stupid, or simply	4473	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3624	wrong (because they don't actually warn about the condition their message
3625	seems to warn about).
3626		4474
3627	While libev is written to generate as few warnings as possible,	4475	This means that, when you have a watcher that triggers in one hour and
3628	"warn-free" code is not a goal, and it is recommended not to build libev	4476	there are 100 watchers that would trigger before that, then inserting will
3629	with any compiler warnings enabled unless you are prepared to cope with	4477	have to skip roughly seven (C<ld 100>) of these watchers.
3630	them (e.g. by ignoring them). Remember that warnings are just that:
3631	warnings, not errors, or proof of bugs.
3632		4478
		4479	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3633		4480
3634	=head1 VALGRIND	4481	That means that changing a timer costs less than removing/adding them,
		4482	as only the relative motion in the event queue has to be paid for.
3635		4483
3636	Valgrind has a special section here because it is a popular tool that is	4484	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3637	highly useful, but valgrind reports are very hard to interpret.
3638		4485
3639	If you think you found a bug (memory leak, uninitialised data access etc.)	4486	These just add the watcher into an array or at the head of a list.
3640	in libev, then check twice: If valgrind reports something like:
3641		4487
3642	==2274== definitely lost: 0 bytes in 0 blocks.	4488	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3643	==2274== possibly lost: 0 bytes in 0 blocks.
3644	==2274== still reachable: 256 bytes in 1 blocks.
3645		4489
3646	Then there is no memory leak. Similarly, under some circumstances,	4490	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3647	valgrind might report kernel bugs as if it were a bug in libev, or it
3648	might be confused (it is a very good tool, but only a tool).
3649		4491
3650	If you are unsure about something, feel free to contact the mailing list	4492	These watchers are stored in lists, so they need to be walked to find the
3651	with the full valgrind report and an explanation on why you think this is	4493	correct watcher to remove. The lists are usually short (you don't usually
3652	a bug in libev. However, don't be annoyed when you get a brisk "this is	4494	have many watchers waiting for the same fd or signal: one is typical, two
3653	no bug" answer and take the chance of learning how to interpret valgrind	4495	is rare).
3654	properly.
3655		4496
3656	If you need, for some reason, empty reports from valgrind for your project	4497	=item Finding the next timer in each loop iteration: O(1)
3657	I suggest using suppression lists.
3658		4498
		4499	By virtue of using a binary or 4-heap, the next timer is always found at a
		4500	fixed position in the storage array.
		4501
		4502	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4503
		4504	A change means an I/O watcher gets started or stopped, which requires
		4505	libev to recalculate its status (and possibly tell the kernel, depending
		4506	on backend and whether C<ev_io_set> was used).
		4507
		4508	=item Activating one watcher (putting it into the pending state): O(1)
		4509
		4510	=item Priority handling: O(number_of_priorities)
		4511
		4512	Priorities are implemented by allocating some space for each
		4513	priority. When doing priority-based operations, libev usually has to
		4514	linearly search all the priorities, but starting/stopping and activating
		4515	watchers becomes O(1) with respect to priority handling.
		4516
		4517	=item Sending an ev_async: O(1)
		4518
		4519	=item Processing ev_async_send: O(number_of_async_watchers)
		4520
		4521	=item Processing signals: O(max_signal_number)
		4522
		4523	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4524	calls in the current loop iteration. Checking for async and signal events
		4525	involves iterating over all running async watchers or all signal numbers.
		4526
		4527	=back
		4528
		4529
		4530	=head1 GLOSSARY
		4531
		4532	=over 4
		4533
		4534	=item active
		4535
		4536	A watcher is active as long as it has been started (has been attached to
		4537	an event loop) but not yet stopped (disassociated from the event loop).
		4538
		4539	=item application
		4540
		4541	In this document, an application is whatever is using libev.
		4542
		4543	=item callback
		4544
		4545	The address of a function that is called when some event has been
		4546	detected. Callbacks are being passed the event loop, the watcher that
		4547	received the event, and the actual event bitset.
		4548
		4549	=item callback invocation
		4550
		4551	The act of calling the callback associated with a watcher.
		4552
		4553	=item event
		4554
		4555	A change of state of some external event, such as data now being available
		4556	for reading on a file descriptor, time having passed or simply not having
		4557	any other events happening anymore.
		4558
		4559	In libev, events are represented as single bits (such as C<EV_READ> or
		4560	C<EV_TIMEOUT>).
		4561
		4562	=item event library
		4563
		4564	A software package implementing an event model and loop.
		4565
		4566	=item event loop
		4567
		4568	An entity that handles and processes external events and converts them
		4569	into callback invocations.
		4570
		4571	=item event model
		4572
		4573	The model used to describe how an event loop handles and processes
		4574	watchers and events.
		4575
		4576	=item pending
		4577
		4578	A watcher is pending as soon as the corresponding event has been detected,
		4579	and stops being pending as soon as the watcher will be invoked or its
		4580	pending status is explicitly cleared by the application.
		4581
		4582	A watcher can be pending, but not active. Stopping a watcher also clears
		4583	its pending status.
		4584
		4585	=item real time
		4586
		4587	The physical time that is observed. It is apparently strictly monotonic :)
		4588
		4589	=item wall-clock time
		4590
		4591	The time and date as shown on clocks. Unlike real time, it can actually
		4592	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4593	clock.
		4594
		4595	=item watcher
		4596
		4597	A data structure that describes interest in certain events. Watchers need
		4598	to be started (attached to an event loop) before they can receive events.
		4599
		4600	=item watcher invocation
		4601
		4602	The act of calling the callback associated with a watcher.
		4603
		4604	=back
3659		4605
3660	=head1 AUTHOR	4606	=head1 AUTHOR
3661		4607
3662	Marc Lehmann <libev@schmorp.de>.	4608	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3663		4609

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