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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_NOSIGFD>
		376
		377	When this flag is specified, then libev will not attempt to use the
		378	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This is
		379	probably only useful to work around any bugs in libev. Consequently, this
		380	flag might go away once the signalfd functionality is considered stable,
		381	so it's useful mostly in environment variables and not in program code.
		382
349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	383	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
350		384
351	This is your standard select(2) backend. Not I<completely> standard, as	385	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,	386	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	387	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	411	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
378	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	412	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
379		413
380	=item C<EVBACKEND_EPOLL> (value 4, Linux)	414	=item C<EVBACKEND_EPOLL> (value 4, Linux)
381		415
		416	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		417	kernels).
		418
382	For few fds, this backend is a bit little slower than poll and select,	419	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	420	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),	421	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	422	epoll scales either O(1) or O(active_fds).
386	of shortcomings, such as silently dropping events in some hard-to-detect	423
387	cases and requiring a system call per fd change, no fork support and bad	424	The epoll mechanism deserves honorable mention as the most misdesigned
388	support for dup.	425	of the more advanced event mechanisms: mere annoyances include silently
		426	dropping file descriptors, requiring a system call per change per file
		427	descriptor (and unnecessary guessing of parameters), problems with dup and
		428	so on. The biggest issue is fork races, however - if a program forks then
		429	I<both> parent and child process have to recreate the epoll set, which can
		430	take considerable time (one syscall per file descriptor) and is of course
		431	hard to detect.
		432
		433	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		434	of course I<doesn't>, and epoll just loves to report events for totally
		435	I<different> file descriptors (even already closed ones, so one cannot
		436	even remove them from the set) than registered in the set (especially
		437	on SMP systems). Libev tries to counter these spurious notifications by
		438	employing an additional generation counter and comparing that against the
		439	events to filter out spurious ones, recreating the set when required.
389		440
390	While stopping, setting and starting an I/O watcher in the same iteration	441	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	442	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	443	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	444	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
394	very well if you register events for both fds.	445	file descriptors might not work very well if you register events for both
395		446	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		447
400	Best performance from this backend is achieved by not unregistering all	448	Best performance from this backend is achieved by not unregistering all
401	watchers for a file descriptor until it has been closed, if possible,	449	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	450	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	451	starting a watcher (without re-setting it) also usually doesn't cause
404	extra overhead.	452	extra overhead. A fork can both result in spurious notifications as well
		453	as in libev having to destroy and recreate the epoll object, which can
		454	take considerable time and thus should be avoided.
		455
		456	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		457	faster than epoll for maybe up to a hundred file descriptors, depending on
		458	the usage. So sad.
405		459
406	While nominally embeddable in other event loops, this feature is broken in	460	While nominally embeddable in other event loops, this feature is broken in
407	all kernel versions tested so far.	461	all kernel versions tested so far.
408		462
409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	463	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
410	C<EVBACKEND_POLL>.	464	C<EVBACKEND_POLL>.
411		465
412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	466	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
413		467
414	Kqueue deserves special mention, as at the time of this writing, it was	468	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	469	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	470	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	471	it's completely useless). Unlike epoll, however, whose brokenness
418	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or	472	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.	473	without API changes to existing programs. For this reason it's not being
		474	"auto-detected" unless you explicitly specify it in the flags (i.e. using
		475	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		476	system like NetBSD.
420		477
421	You still can embed kqueue into a normal poll or select backend and use it	478	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	479	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.	480	the target platform). See C<ev_embed> watchers for more info.
424		481
425	It scales in the same way as the epoll backend, but the interface to the	482	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	483	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	484	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	485	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	486	two event changes per incident. Support for C<fork ()> is very bad (but
430	drops fds silently in similarly hard-to-detect cases.	487	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		488	cases
431		489
432	This backend usually performs well under most conditions.	490	This backend usually performs well under most conditions.
433		491
434	While nominally embeddable in other event loops, this doesn't work	492	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	493	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	494	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	495	(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,	496	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
439	using it only for sockets.	497	also broken on OS X)) and, did I mention it, using it only for sockets.
440		498
441	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	499	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	500	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
443	C<NOTE_EOF>.	501	C<NOTE_EOF>.
444		502
…		…
464	might perform better.	522	might perform better.
465		523
466	On the positive side, with the exception of the spurious readiness	524	On the positive side, with the exception of the spurious readiness
467	notifications, this backend actually performed fully to specification	525	notifications, this backend actually performed fully to specification
468	in all tests and is fully embeddable, which is a rare feat among the	526	in all tests and is fully embeddable, which is a rare feat among the
469	OS-specific backends.	527	OS-specific backends (I vastly prefer correctness over speed hacks).
470		528
471	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	529	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
472	C<EVBACKEND_POLL>.	530	C<EVBACKEND_POLL>.
473		531
474	=item C<EVBACKEND_ALL>	532	=item C<EVBACKEND_ALL>
…		…
479		537
480	It is definitely not recommended to use this flag.	538	It is definitely not recommended to use this flag.
481		539
482	=back	540	=back
483		541
484	If one or more of these are or'ed into the flags value, then only these	542	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	543	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.	544	here). If none are specified, all backends in C<ev_recommended_backends
		545	()> will be tried.
487		546
488	Example: This is the most typical usage.	547	Example: This is the most typical usage.
489		548
490	if (!ev_default_loop (0))	549	if (!ev_default_loop (0))
491	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	550	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
527	responsibility to either stop all watchers cleanly yourself I<before>	586	responsibility to either stop all watchers cleanly yourself I<before>
528	calling this function, or cope with the fact afterwards (which is usually	587	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	588	the easiest thing, you can just ignore the watchers and/or C<free ()> them
530	for example).	589	for example).
531		590
532	Note that certain global state, such as signal state, will not be freed by	591	Note that certain global state, such as signal state (and installed signal
533	this function, and related watchers (such as signal and child watchers)	592	handlers), will not be freed by this function, and related watchers (such
534	would need to be stopped manually.	593	as signal and child watchers) would need to be stopped manually.
535		594
536	In general it is not advisable to call this function except in the	595	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	596	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	597	pipe fds. If you need dynamically allocated loops it is better to use
539	C<ev_loop_new> and C<ev_loop_destroy>).	598	C<ev_loop_new> and C<ev_loop_destroy>.
540		599
541	=item ev_loop_destroy (loop)	600	=item ev_loop_destroy (loop)
542		601
543	Like C<ev_default_destroy>, but destroys an event loop created by an	602	Like C<ev_default_destroy>, but destroys an event loop created by an
544	earlier call to C<ev_loop_new>.	603	earlier call to C<ev_loop_new>.
…		…
582		641
583	This value can sometimes be useful as a generation counter of sorts (it	642	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	643	"ticks" the number of loop iterations), as it roughly corresponds with
585	C<ev_prepare> and C<ev_check> calls.	644	C<ev_prepare> and C<ev_check> calls.
586		645
		646	=item unsigned int ev_loop_depth (loop)
		647
		648	Returns the number of times C<ev_loop> was entered minus the number of
		649	times C<ev_loop> was exited, in other words, the recursion depth.
		650
		651	Outside C<ev_loop>, this number is zero. In a callback, this number is
		652	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),
		653	in which case it is higher.
		654
		655	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread
		656	etc.), doesn't count as exit.
		657
587	=item unsigned int ev_backend (loop)	658	=item unsigned int ev_backend (loop)
588		659
589	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	660	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
590	use.	661	use.
591		662
…		…
605		676
606	This function is rarely useful, but when some event callback runs for a	677	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	678	very long time without entering the event loop, updating libev's idea of
608	the current time is a good idea.	679	the current time is a good idea.
609		680
610	See also "The special problem of time updates" in the C<ev_timer> section.	681	See also L<The special problem of time updates> in the C<ev_timer> section.
		682
		683	=item ev_suspend (loop)
		684
		685	=item ev_resume (loop)
		686
		687	These two functions suspend and resume a loop, for use when the loop is
		688	not used for a while and timeouts should not be processed.
		689
		690	A typical use case would be an interactive program such as a game: When
		691	the user presses C<^Z> to suspend the game and resumes it an hour later it
		692	would be best to handle timeouts as if no time had actually passed while
		693	the program was suspended. This can be achieved by calling C<ev_suspend>
		694	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		695	C<ev_resume> directly afterwards to resume timer processing.
		696
		697	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		698	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		699	will be rescheduled (that is, they will lose any events that would have
		700	occured while suspended).
		701
		702	After calling C<ev_suspend> you B<must not> call I<any> function on the
		703	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		704	without a previous call to C<ev_suspend>.
		705
		706	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		707	event loop time (see C<ev_now_update>).
611		708
612	=item ev_loop (loop, int flags)	709	=item ev_loop (loop, int flags)
613		710
614	Finally, this is it, the event handler. This function usually is called	711	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	712	after you have initialised all your watchers and you want to start
616	events.	713	handling events.
617		714
618	If the flags argument is specified as C<0>, it will not return until	715	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.	716	either no event watchers are active anymore or C<ev_unloop> was called.
620		717
621	Please note that an explicit C<ev_unloop> is usually better than	718	Please note that an explicit C<ev_unloop> is usually better than
…		…
631	the loop.	728	the loop.
632		729
633	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	730	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	731	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	732	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	733	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	734	user-registered callback will be called), and will return after one
638	iteration of the loop.	735	iteration of the loop.
639		736
640	This is useful if you are waiting for some external event in conjunction	737	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	738	with something not expressible using other libev watchers (i.e. "roll your
…		…
695		792
696	Ref/unref can be used to add or remove a reference count on the event	793	Ref/unref can be used to add or remove a reference count on the event
697	loop: Every watcher keeps one reference, and as long as the reference	794	loop: Every watcher keeps one reference, and as long as the reference
698	count is nonzero, C<ev_loop> will not return on its own.	795	count is nonzero, C<ev_loop> will not return on its own.
699		796
700	If you have a watcher you never unregister that should not keep C<ev_loop>	797	This is useful when you have a watcher that you never intend to
701	from returning, call ev_unref() after starting, and ev_ref() before	798	unregister, but that nevertheless should not keep C<ev_loop> from
		799	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
702	stopping it.	800	before stopping it.
703		801
704	As an example, libev itself uses this for its internal signal pipe: It is	802	As an example, libev itself uses this for its internal signal pipe: It
705	not visible to the libev user and should not keep C<ev_loop> from exiting	803	is not visible to the libev user and should not keep C<ev_loop> from
706	if no event watchers registered by it are active. It is also an excellent	804	exiting if no event watchers registered by it are active. It is also an
707	way to do this for generic recurring timers or from within third-party	805	excellent way to do this for generic recurring timers or from within
708	libraries. Just remember to I<unref after start> and I<ref before stop>	806	third-party libraries. Just remember to I<unref after start> and I<ref
709	(but only if the watcher wasn't active before, or was active before,	807	before stop> (but only if the watcher wasn't active before, or was active
710	respectively).	808	before, respectively. Note also that libev might stop watchers itself
		809	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		810	in the callback).
711		811
712	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	812	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
713	running when nothing else is active.	813	running when nothing else is active.
714		814
715	struct ev_signal exitsig;	815	ev_signal exitsig;
716	ev_signal_init (&exitsig, sig_cb, SIGINT);	816	ev_signal_init (&exitsig, sig_cb, SIGINT);
717	ev_signal_start (loop, &exitsig);	817	ev_signal_start (loop, &exitsig);
718	evf_unref (loop);	818	evf_unref (loop);
719		819
720	Example: For some weird reason, unregister the above signal handler again.	820	Example: For some weird reason, unregister the above signal handler again.
…		…
744		844
745	By setting a higher I<io collect interval> you allow libev to spend more	845	By setting a higher I<io collect interval> you allow libev to spend more
746	time collecting I/O events, so you can handle more events per iteration,	846	time collecting I/O events, so you can handle more events per iteration,
747	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	847	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
748	C<ev_timer>) will be not affected. Setting this to a non-null value will	848	C<ev_timer>) will be not affected. Setting this to a non-null value will
749	introduce an additional C<ev_sleep ()> call into most loop iterations.	849	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		850	sleep time ensures that libev will not poll for I/O events more often then
		851	once per this interval, on average.
750		852
751	Likewise, by setting a higher I<timeout collect interval> you allow libev	853	Likewise, by setting a higher I<timeout collect interval> you allow libev
752	to spend more time collecting timeouts, at the expense of increased	854	to spend more time collecting timeouts, at the expense of increased
753	latency/jitter/inexactness (the watcher callback will be called	855	latency/jitter/inexactness (the watcher callback will be called
754	later). C<ev_io> watchers will not be affected. Setting this to a non-null	856	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
756		858
757	Many (busy) programs can usually benefit by setting the I/O collect	859	Many (busy) programs can usually benefit by setting the I/O collect
758	interval to a value near C<0.1> or so, which is often enough for	860	interval to a value near C<0.1> or so, which is often enough for
759	interactive servers (of course not for games), likewise for timeouts. It	861	interactive servers (of course not for games), likewise for timeouts. It
760	usually doesn't make much sense to set it to a lower value than C<0.01>,	862	usually doesn't make much sense to set it to a lower value than C<0.01>,
761	as this approaches the timing granularity of most systems.	863	as this approaches the timing granularity of most systems. Note that if
		864	you do transactions with the outside world and you can't increase the
		865	parallelity, then this setting will limit your transaction rate (if you
		866	need to poll once per transaction and the I/O collect interval is 0.01,
		867	then you can't do more than 100 transations per second).
762		868
763	Setting the I<timeout collect interval> can improve the opportunity for	869	Setting the I<timeout collect interval> can improve the opportunity for
764	saving power, as the program will "bundle" timer callback invocations that	870	saving power, as the program will "bundle" timer callback invocations that
765	are "near" in time together, by delaying some, thus reducing the number of	871	are "near" in time together, by delaying some, thus reducing the number of
766	times the process sleeps and wakes up again. Another useful technique to	872	times the process sleeps and wakes up again. Another useful technique to
767	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	873	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
768	they fire on, say, one-second boundaries only.	874	they fire on, say, one-second boundaries only.
769		875
		876	Example: we only need 0.1s timeout granularity, and we wish not to poll
		877	more often than 100 times per second:
		878
		879	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		880	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		881
		882	=item ev_invoke_pending (loop)
		883
		884	This call will simply invoke all pending watchers while resetting their
		885	pending state. Normally, C<ev_loop> does this automatically when required,
		886	but when overriding the invoke callback this call comes handy.
		887
		888	=item int ev_pending_count (loop)
		889
		890	Returns the number of pending watchers - zero indicates that no watchers
		891	are pending.
		892
		893	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		894
		895	This overrides the invoke pending functionality of the loop: Instead of
		896	invoking all pending watchers when there are any, C<ev_loop> will call
		897	this callback instead. This is useful, for example, when you want to
		898	invoke the actual watchers inside another context (another thread etc.).
		899
		900	If you want to reset the callback, use C<ev_invoke_pending> as new
		901	callback.
		902
		903	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		904
		905	Sometimes you want to share the same loop between multiple threads. This
		906	can be done relatively simply by putting mutex_lock/unlock calls around
		907	each call to a libev function.
		908
		909	However, C<ev_loop> can run an indefinite time, so it is not feasible to
		910	wait for it to return. One way around this is to wake up the loop via
		911	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>
		912	and I<acquire> callbacks on the loop.
		913
		914	When set, then C<release> will be called just before the thread is
		915	suspended waiting for new events, and C<acquire> is called just
		916	afterwards.
		917
		918	Ideally, C<release> will just call your mutex_unlock function, and
		919	C<acquire> will just call the mutex_lock function again.
		920
		921	While event loop modifications are allowed between invocations of
		922	C<release> and C<acquire> (that's their only purpose after all), no
		923	modifications done will affect the event loop, i.e. adding watchers will
		924	have no effect on the set of file descriptors being watched, or the time
		925	waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it
		926	to take note of any changes you made.
		927
		928	In theory, threads executing C<ev_loop> will be async-cancel safe between
		929	invocations of C<release> and C<acquire>.
		930
		931	See also the locking example in the C<THREADS> section later in this
		932	document.
		933
		934	=item ev_set_userdata (loop, void *data)
		935
		936	=item ev_userdata (loop)
		937
		938	Set and retrieve a single C<void *> associated with a loop. When
		939	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		940	C<0.>
		941
		942	These two functions can be used to associate arbitrary data with a loop,
		943	and are intended solely for the C<invoke_pending_cb>, C<release> and
		944	C<acquire> callbacks described above, but of course can be (ab-)used for
		945	any other purpose as well.
		946
770	=item ev_loop_verify (loop)	947	=item ev_loop_verify (loop)
771		948
772	This function only does something when C<EV_VERIFY> support has been	949	This function only does something when C<EV_VERIFY> support has been
773	compiled in. which is the default for non-minimal builds. It tries to go	950	compiled in, which is the default for non-minimal builds. It tries to go
774	through all internal structures and checks them for validity. If anything	951	through all internal structures and checks them for validity. If anything
775	is found to be inconsistent, it will print an error message to standard	952	is found to be inconsistent, it will print an error message to standard
776	error and call C<abort ()>.	953	error and call C<abort ()>.
777		954
778	This can be used to catch bugs inside libev itself: under normal	955	This can be used to catch bugs inside libev itself: under normal
…		…
782	=back	959	=back
783		960
784		961
785	=head1 ANATOMY OF A WATCHER	962	=head1 ANATOMY OF A WATCHER
786		963
		964	In the following description, uppercase C<TYPE> in names stands for the
		965	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		966	watchers and C<ev_io_start> for I/O watchers.
		967
787	A watcher is a structure that you create and register to record your	968	A watcher is a structure that you create and register to record your
788	interest in some event. For instance, if you want to wait for STDIN to	969	interest in some event. For instance, if you want to wait for STDIN to
789	become readable, you would create an C<ev_io> watcher for that:	970	become readable, you would create an C<ev_io> watcher for that:
790		971
791	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	972	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
792	{	973	{
793	ev_io_stop (w);	974	ev_io_stop (w);
794	ev_unloop (loop, EVUNLOOP_ALL);	975	ev_unloop (loop, EVUNLOOP_ALL);
795	}	976	}
796		977
797	struct ev_loop *loop = ev_default_loop (0);	978	struct ev_loop *loop = ev_default_loop (0);
		979
798	struct ev_io stdin_watcher;	980	ev_io stdin_watcher;
		981
799	ev_init (&stdin_watcher, my_cb);	982	ev_init (&stdin_watcher, my_cb);
800	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	983	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
801	ev_io_start (loop, &stdin_watcher);	984	ev_io_start (loop, &stdin_watcher);
		985
802	ev_loop (loop, 0);	986	ev_loop (loop, 0);
803		987
804	As you can see, you are responsible for allocating the memory for your	988	As you can see, you are responsible for allocating the memory for your
805	watcher structures (and it is usually a bad idea to do this on the stack,	989	watcher structures (and it is I<usually> a bad idea to do this on the
806	although this can sometimes be quite valid).	990	stack).
		991
		992	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		993	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
807		994
808	Each watcher structure must be initialised by a call to C<ev_init	995	Each watcher structure must be initialised by a call to C<ev_init
809	(watcher *, callback)>, which expects a callback to be provided. This	996	(watcher *, callback)>, which expects a callback to be provided. This
810	callback gets invoked each time the event occurs (or, in the case of I/O	997	callback gets invoked each time the event occurs (or, in the case of I/O
811	watchers, each time the event loop detects that the file descriptor given	998	watchers, each time the event loop detects that the file descriptor given
812	is readable and/or writable).	999	is readable and/or writable).
813		1000
814	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1001	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
815	with arguments specific to this watcher type. There is also a macro	1002	macro to configure it, with arguments specific to the watcher type. There
816	to combine initialisation and setting in one call: C<< ev_<type>_init	1003	is also a macro to combine initialisation and setting in one call: C<<
817	(watcher *, callback, ...) >>.	1004	ev_TYPE_init (watcher *, callback, ...) >>.
818		1005
819	To make the watcher actually watch out for events, you have to start it	1006	To make the watcher actually watch out for events, you have to start it
820	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	1007	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
821	*) >>), and you can stop watching for events at any time by calling the	1008	*) >>), and you can stop watching for events at any time by calling the
822	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1009	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
823		1010
824	As long as your watcher is active (has been started but not stopped) you	1011	As long as your watcher is active (has been started but not stopped) you
825	must not touch the values stored in it. Most specifically you must never	1012	must not touch the values stored in it. Most specifically you must never
826	reinitialise it or call its C<set> macro.	1013	reinitialise it or call its C<ev_TYPE_set> macro.
827		1014
828	Each and every callback receives the event loop pointer as first, the	1015	Each and every callback receives the event loop pointer as first, the
829	registered watcher structure as second, and a bitset of received events as	1016	registered watcher structure as second, and a bitset of received events as
830	third argument.	1017	third argument.
831		1018
…		…
889		1076
890	=item C<EV_ASYNC>	1077	=item C<EV_ASYNC>
891		1078
892	The given async watcher has been asynchronously notified (see C<ev_async>).	1079	The given async watcher has been asynchronously notified (see C<ev_async>).
893		1080
		1081	=item C<EV_CUSTOM>
		1082
		1083	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1084	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		1085
894	=item C<EV_ERROR>	1086	=item C<EV_ERROR>
895		1087
896	An unspecified error has occurred, the watcher has been stopped. This might	1088	An unspecified error has occurred, the watcher has been stopped. This might
897	happen because the watcher could not be properly started because libev	1089	happen because the watcher could not be properly started because libev
898	ran out of memory, a file descriptor was found to be closed or any other	1090	ran out of memory, a file descriptor was found to be closed or any other
		1091	problem. Libev considers these application bugs.
		1092
899	problem. You best act on it by reporting the problem and somehow coping	1093	You best act on it by reporting the problem and somehow coping with the
900	with the watcher being stopped.	1094	watcher being stopped. Note that well-written programs should not receive
		1095	an error ever, so when your watcher receives it, this usually indicates a
		1096	bug in your program.
901		1097
902	Libev will usually signal a few "dummy" events together with an error, for	1098	Libev will usually signal a few "dummy" events together with an error, for
903	example it might indicate that a fd is readable or writable, and if your	1099	example it might indicate that a fd is readable or writable, and if your
904	callbacks is well-written it can just attempt the operation and cope with	1100	callbacks is well-written it can just attempt the operation and cope with
905	the error from read() or write(). This will not work in multi-threaded	1101	the error from read() or write(). This will not work in multi-threaded
…		…
908		1104
909	=back	1105	=back
910		1106
911	=head2 GENERIC WATCHER FUNCTIONS	1107	=head2 GENERIC WATCHER FUNCTIONS
912		1108
913	In the following description, C<TYPE> stands for the watcher type,
914	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
915
916	=over 4	1109	=over 4
917		1110
918	=item C<ev_init> (ev_TYPE *watcher, callback)	1111	=item C<ev_init> (ev_TYPE *watcher, callback)
919		1112
920	This macro initialises the generic portion of a watcher. The contents	1113	This macro initialises the generic portion of a watcher. The contents
…		…
925	which rolls both calls into one.	1118	which rolls both calls into one.
926		1119
927	You can reinitialise a watcher at any time as long as it has been stopped	1120	You can reinitialise a watcher at any time as long as it has been stopped
928	(or never started) and there are no pending events outstanding.	1121	(or never started) and there are no pending events outstanding.
929		1122
930	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1123	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
931	int revents)>.	1124	int revents)>.
932		1125
933	Example: Initialise an C<ev_io> watcher in two steps.	1126	Example: Initialise an C<ev_io> watcher in two steps.
934		1127
935	ev_io w;	1128	ev_io w;
936	ev_init (&w, my_cb);	1129	ev_init (&w, my_cb);
937	ev_io_set (&w, STDIN_FILENO, EV_READ);	1130	ev_io_set (&w, STDIN_FILENO, EV_READ);
938		1131
939	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1132	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
940		1133
941	This macro initialises the type-specific parts of a watcher. You need to	1134	This macro initialises the type-specific parts of a watcher. You need to
942	call C<ev_init> at least once before you call this macro, but you can	1135	call C<ev_init> at least once before you call this macro, but you can
943	call C<ev_TYPE_set> any number of times. You must not, however, call this	1136	call C<ev_TYPE_set> any number of times. You must not, however, call this
944	macro on a watcher that is active (it can be pending, however, which is a	1137	macro on a watcher that is active (it can be pending, however, which is a
…		…
957		1150
958	Example: Initialise and set an C<ev_io> watcher in one step.	1151	Example: Initialise and set an C<ev_io> watcher in one step.
959		1152
960	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1153	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
961		1154
962	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1155	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
963		1156
964	Starts (activates) the given watcher. Only active watchers will receive	1157	Starts (activates) the given watcher. Only active watchers will receive
965	events. If the watcher is already active nothing will happen.	1158	events. If the watcher is already active nothing will happen.
966		1159
967	Example: Start the C<ev_io> watcher that is being abused as example in this	1160	Example: Start the C<ev_io> watcher that is being abused as example in this
968	whole section.	1161	whole section.
969		1162
970	ev_io_start (EV_DEFAULT_UC, &w);	1163	ev_io_start (EV_DEFAULT_UC, &w);
971		1164
972	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1165	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
973		1166
974	Stops the given watcher again (if active) and clears the pending	1167	Stops the given watcher if active, and clears the pending status (whether
		1168	the watcher was active or not).
		1169
975	status. It is possible that stopped watchers are pending (for example,	1170	It is possible that stopped watchers are pending - for example,
976	non-repeating timers are being stopped when they become pending), but	1171	non-repeating timers are being stopped when they become pending - but
977	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1172	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
978	you want to free or reuse the memory used by the watcher it is therefore a	1173	pending. If you want to free or reuse the memory used by the watcher it is
979	good idea to always call its C<ev_TYPE_stop> function.	1174	therefore a good idea to always call its C<ev_TYPE_stop> function.
980		1175
981	=item bool ev_is_active (ev_TYPE *watcher)	1176	=item bool ev_is_active (ev_TYPE *watcher)
982		1177
983	Returns a true value iff the watcher is active (i.e. it has been started	1178	Returns a true value iff the watcher is active (i.e. it has been started
984	and not yet been stopped). As long as a watcher is active you must not modify	1179	and not yet been stopped). As long as a watcher is active you must not modify
…		…
1000	=item ev_cb_set (ev_TYPE *watcher, callback)	1195	=item ev_cb_set (ev_TYPE *watcher, callback)
1001		1196
1002	Change the callback. You can change the callback at virtually any time	1197	Change the callback. You can change the callback at virtually any time
1003	(modulo threads).	1198	(modulo threads).
1004		1199
1005	=item ev_set_priority (ev_TYPE *watcher, priority)	1200	=item ev_set_priority (ev_TYPE *watcher, int priority)
1006		1201
1007	=item int ev_priority (ev_TYPE *watcher)	1202	=item int ev_priority (ev_TYPE *watcher)
1008		1203
1009	Set and query the priority of the watcher. The priority is a small	1204	Set and query the priority of the watcher. The priority is a small
1010	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1205	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1011	(default: C<-2>). Pending watchers with higher priority will be invoked	1206	(default: C<-2>). Pending watchers with higher priority will be invoked
1012	before watchers with lower priority, but priority will not keep watchers	1207	before watchers with lower priority, but priority will not keep watchers
1013	from being executed (except for C<ev_idle> watchers).	1208	from being executed (except for C<ev_idle> watchers).
1014		1209
1015	This means that priorities are I<only> used for ordering callback
1016	invocation after new events have been received. This is useful, for
1017	example, to reduce latency after idling, or more often, to bind two
1018	watchers on the same event and make sure one is called first.
1019
1020	If you need to suppress invocation when higher priority events are pending	1210	If you need to suppress invocation when higher priority events are pending
1021	you need to look at C<ev_idle> watchers, which provide this functionality.	1211	you need to look at C<ev_idle> watchers, which provide this functionality.
1022		1212
1023	You I<must not> change the priority of a watcher as long as it is active or	1213	You I<must not> change the priority of a watcher as long as it is active or
1024	pending.	1214	pending.
1025		1215
		1216	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1217	fine, as long as you do not mind that the priority value you query might
		1218	or might not have been clamped to the valid range.
		1219
1026	The default priority used by watchers when no priority has been set is	1220	The default priority used by watchers when no priority has been set is
1027	always C<0>, which is supposed to not be too high and not be too low :).	1221	always C<0>, which is supposed to not be too high and not be too low :).
1028		1222
1029	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1223	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1030	fine, as long as you do not mind that the priority value you query might	1224	priorities.
1031	or might not have been adjusted to be within valid range.
1032		1225
1033	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1226	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1034		1227
1035	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1228	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1036	C<loop> nor C<revents> need to be valid as long as the watcher callback	1229	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1043	returns its C<revents> bitset (as if its callback was invoked). If the	1236	returns its C<revents> bitset (as if its callback was invoked). If the
1044	watcher isn't pending it does nothing and returns C<0>.	1237	watcher isn't pending it does nothing and returns C<0>.
1045		1238
1046	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1239	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1047	callback to be invoked, which can be accomplished with this function.	1240	callback to be invoked, which can be accomplished with this function.
		1241
		1242	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1243
		1244	Feeds the given event set into the event loop, as if the specified event
		1245	had happened for the specified watcher (which must be a pointer to an
		1246	initialised but not necessarily started event watcher). Obviously you must
		1247	not free the watcher as long as it has pending events.
		1248
		1249	Stopping the watcher, letting libev invoke it, or calling
		1250	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1251	not started in the first place.
		1252
		1253	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1254	functions that do not need a watcher.
1048		1255
1049	=back	1256	=back
1050		1257
1051		1258
1052	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1259	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
1058	member, you can also "subclass" the watcher type and provide your own	1265	member, you can also "subclass" the watcher type and provide your own
1059	data:	1266	data:
1060		1267
1061	struct my_io	1268	struct my_io
1062	{	1269	{
1063	struct ev_io io;	1270	ev_io io;
1064	int otherfd;	1271	int otherfd;
1065	void *somedata;	1272	void *somedata;
1066	struct whatever *mostinteresting;	1273	struct whatever *mostinteresting;
1067	};	1274	};
1068		1275
…		…
1071	ev_io_init (&w.io, my_cb, fd, EV_READ);	1278	ev_io_init (&w.io, my_cb, fd, EV_READ);
1072		1279
1073	And since your callback will be called with a pointer to the watcher, you	1280	And since your callback will be called with a pointer to the watcher, you
1074	can cast it back to your own type:	1281	can cast it back to your own type:
1075		1282
1076	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1283	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1077	{	1284	{
1078	struct my_io *w = (struct my_io *)w_;	1285	struct my_io *w = (struct my_io *)w_;
1079	...	1286	...
1080	}	1287	}
1081		1288
…		…
1099	programmers):	1306	programmers):
1100		1307
1101	#include <stddef.h>	1308	#include <stddef.h>
1102		1309
1103	static void	1310	static void
1104	t1_cb (EV_P_ struct ev_timer *w, int revents)	1311	t1_cb (EV_P_ ev_timer *w, int revents)
1105	{	1312	{
1106	struct my_biggy big = (struct my_biggy *	1313	struct my_biggy big = (struct my_biggy *)
1107	(((char *)w) - offsetof (struct my_biggy, t1));	1314	(((char *)w) - offsetof (struct my_biggy, t1));
1108	}	1315	}
1109		1316
1110	static void	1317	static void
1111	t2_cb (EV_P_ struct ev_timer *w, int revents)	1318	t2_cb (EV_P_ ev_timer *w, int revents)
1112	{	1319	{
1113	struct my_biggy big = (struct my_biggy *	1320	struct my_biggy big = (struct my_biggy *)
1114	(((char *)w) - offsetof (struct my_biggy, t2));	1321	(((char *)w) - offsetof (struct my_biggy, t2));
1115	}	1322	}
		1323
		1324	=head2 WATCHER PRIORITY MODELS
		1325
		1326	Many event loops support I<watcher priorities>, which are usually small
		1327	integers that influence the ordering of event callback invocation
		1328	between watchers in some way, all else being equal.
		1329
		1330	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1331	description for the more technical details such as the actual priority
		1332	range.
		1333
		1334	There are two common ways how these these priorities are being interpreted
		1335	by event loops:
		1336
		1337	In the more common lock-out model, higher priorities "lock out" invocation
		1338	of lower priority watchers, which means as long as higher priority
		1339	watchers receive events, lower priority watchers are not being invoked.
		1340
		1341	The less common only-for-ordering model uses priorities solely to order
		1342	callback invocation within a single event loop iteration: Higher priority
		1343	watchers are invoked before lower priority ones, but they all get invoked
		1344	before polling for new events.
		1345
		1346	Libev uses the second (only-for-ordering) model for all its watchers
		1347	except for idle watchers (which use the lock-out model).
		1348
		1349	The rationale behind this is that implementing the lock-out model for
		1350	watchers is not well supported by most kernel interfaces, and most event
		1351	libraries will just poll for the same events again and again as long as
		1352	their callbacks have not been executed, which is very inefficient in the
		1353	common case of one high-priority watcher locking out a mass of lower
		1354	priority ones.
		1355
		1356	Static (ordering) priorities are most useful when you have two or more
		1357	watchers handling the same resource: a typical usage example is having an
		1358	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1359	timeouts. Under load, data might be received while the program handles
		1360	other jobs, but since timers normally get invoked first, the timeout
		1361	handler will be executed before checking for data. In that case, giving
		1362	the timer a lower priority than the I/O watcher ensures that I/O will be
		1363	handled first even under adverse conditions (which is usually, but not
		1364	always, what you want).
		1365
		1366	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1367	will only be executed when no same or higher priority watchers have
		1368	received events, they can be used to implement the "lock-out" model when
		1369	required.
		1370
		1371	For example, to emulate how many other event libraries handle priorities,
		1372	you can associate an C<ev_idle> watcher to each such watcher, and in
		1373	the normal watcher callback, you just start the idle watcher. The real
		1374	processing is done in the idle watcher callback. This causes libev to
		1375	continously poll and process kernel event data for the watcher, but when
		1376	the lock-out case is known to be rare (which in turn is rare :), this is
		1377	workable.
		1378
		1379	Usually, however, the lock-out model implemented that way will perform
		1380	miserably under the type of load it was designed to handle. In that case,
		1381	it might be preferable to stop the real watcher before starting the
		1382	idle watcher, so the kernel will not have to process the event in case
		1383	the actual processing will be delayed for considerable time.
		1384
		1385	Here is an example of an I/O watcher that should run at a strictly lower
		1386	priority than the default, and which should only process data when no
		1387	other events are pending:
		1388
		1389	ev_idle idle; // actual processing watcher
		1390	ev_io io; // actual event watcher
		1391
		1392	static void
		1393	io_cb (EV_P_ ev_io *w, int revents)
		1394	{
		1395	// stop the I/O watcher, we received the event, but
		1396	// are not yet ready to handle it.
		1397	ev_io_stop (EV_A_ w);
		1398
		1399	// start the idle watcher to ahndle the actual event.
		1400	// it will not be executed as long as other watchers
		1401	// with the default priority are receiving events.
		1402	ev_idle_start (EV_A_ &idle);
		1403	}
		1404
		1405	static void
		1406	idle_cb (EV_P_ ev_idle *w, int revents)
		1407	{
		1408	// actual processing
		1409	read (STDIN_FILENO, ...);
		1410
		1411	// have to start the I/O watcher again, as
		1412	// we have handled the event
		1413	ev_io_start (EV_P_ &io);
		1414	}
		1415
		1416	// initialisation
		1417	ev_idle_init (&idle, idle_cb);
		1418	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1419	ev_io_start (EV_DEFAULT_ &io);
		1420
		1421	In the "real" world, it might also be beneficial to start a timer, so that
		1422	low-priority connections can not be locked out forever under load. This
		1423	enables your program to keep a lower latency for important connections
		1424	during short periods of high load, while not completely locking out less
		1425	important ones.
1116		1426
1117		1427
1118	=head1 WATCHER TYPES	1428	=head1 WATCHER TYPES
1119		1429
1120	This section describes each watcher in detail, but will not repeat	1430	This section describes each watcher in detail, but will not repeat
…		…
1146	descriptors to non-blocking mode is also usually a good idea (but not	1456	descriptors to non-blocking mode is also usually a good idea (but not
1147	required if you know what you are doing).	1457	required if you know what you are doing).
1148		1458
1149	If you cannot use non-blocking mode, then force the use of a	1459	If you cannot use non-blocking mode, then force the use of a
1150	known-to-be-good backend (at the time of this writing, this includes only	1460	known-to-be-good backend (at the time of this writing, this includes only
1151	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).	1461	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1462	descriptors for which non-blocking operation makes no sense (such as
		1463	files) - libev doesn't guarentee any specific behaviour in that case.
1152		1464
1153	Another thing you have to watch out for is that it is quite easy to	1465	Another thing you have to watch out for is that it is quite easy to
1154	receive "spurious" readiness notifications, that is your callback might	1466	receive "spurious" readiness notifications, that is your callback might
1155	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1467	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1156	because there is no data. Not only are some backends known to create a	1468	because there is no data. Not only are some backends known to create a
…		…
1251	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1563	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1252	readable, but only once. Since it is likely line-buffered, you could	1564	readable, but only once. Since it is likely line-buffered, you could
1253	attempt to read a whole line in the callback.	1565	attempt to read a whole line in the callback.
1254		1566
1255	static void	1567	static void
1256	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1568	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1257	{	1569	{
1258	ev_io_stop (loop, w);	1570	ev_io_stop (loop, w);
1259	.. read from stdin here (or from w->fd) and handle any I/O errors	1571	.. read from stdin here (or from w->fd) and handle any I/O errors
1260	}	1572	}
1261		1573
1262	...	1574	...
1263	struct ev_loop *loop = ev_default_init (0);	1575	struct ev_loop *loop = ev_default_init (0);
1264	struct ev_io stdin_readable;	1576	ev_io stdin_readable;
1265	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1577	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1266	ev_io_start (loop, &stdin_readable);	1578	ev_io_start (loop, &stdin_readable);
1267	ev_loop (loop, 0);	1579	ev_loop (loop, 0);
1268		1580
1269		1581
…		…
1277	year, it will still time out after (roughly) one hour. "Roughly" because	1589	year, it will still time out after (roughly) one hour. "Roughly" because
1278	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1590	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1279	monotonic clock option helps a lot here).	1591	monotonic clock option helps a lot here).
1280		1592
1281	The callback is guaranteed to be invoked only I<after> its timeout has	1593	The callback is guaranteed to be invoked only I<after> its timeout has
1282	passed, but if multiple timers become ready during the same loop iteration	1594	passed (not I<at>, so on systems with very low-resolution clocks this
1283	then order of execution is undefined.	1595	might introduce a small delay). If multiple timers become ready during the
		1596	same loop iteration then the ones with earlier time-out values are invoked
		1597	before ones of the same priority with later time-out values (but this is
		1598	no longer true when a callback calls C<ev_loop> recursively).
		1599
		1600	=head3 Be smart about timeouts
		1601
		1602	Many real-world problems involve some kind of timeout, usually for error
		1603	recovery. A typical example is an HTTP request - if the other side hangs,
		1604	you want to raise some error after a while.
		1605
		1606	What follows are some ways to handle this problem, from obvious and
		1607	inefficient to smart and efficient.
		1608
		1609	In the following, a 60 second activity timeout is assumed - a timeout that
		1610	gets reset to 60 seconds each time there is activity (e.g. each time some
		1611	data or other life sign was received).
		1612
		1613	=over 4
		1614
		1615	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1616
		1617	This is the most obvious, but not the most simple way: In the beginning,
		1618	start the watcher:
		1619
		1620	ev_timer_init (timer, callback, 60., 0.);
		1621	ev_timer_start (loop, timer);
		1622
		1623	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1624	and start it again:
		1625
		1626	ev_timer_stop (loop, timer);
		1627	ev_timer_set (timer, 60., 0.);
		1628	ev_timer_start (loop, timer);
		1629
		1630	This is relatively simple to implement, but means that each time there is
		1631	some activity, libev will first have to remove the timer from its internal
		1632	data structure and then add it again. Libev tries to be fast, but it's
		1633	still not a constant-time operation.
		1634
		1635	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1636
		1637	This is the easiest way, and involves using C<ev_timer_again> instead of
		1638	C<ev_timer_start>.
		1639
		1640	To implement this, configure an C<ev_timer> with a C<repeat> value
		1641	of C<60> and then call C<ev_timer_again> at start and each time you
		1642	successfully read or write some data. If you go into an idle state where
		1643	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1644	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1645
		1646	That means you can ignore both the C<ev_timer_start> function and the
		1647	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1648	member and C<ev_timer_again>.
		1649
		1650	At start:
		1651
		1652	ev_init (timer, callback);
		1653	timer->repeat = 60.;
		1654	ev_timer_again (loop, timer);
		1655
		1656	Each time there is some activity:
		1657
		1658	ev_timer_again (loop, timer);
		1659
		1660	It is even possible to change the time-out on the fly, regardless of
		1661	whether the watcher is active or not:
		1662
		1663	timer->repeat = 30.;
		1664	ev_timer_again (loop, timer);
		1665
		1666	This is slightly more efficient then stopping/starting the timer each time
		1667	you want to modify its timeout value, as libev does not have to completely
		1668	remove and re-insert the timer from/into its internal data structure.
		1669
		1670	It is, however, even simpler than the "obvious" way to do it.
		1671
		1672	=item 3. Let the timer time out, but then re-arm it as required.
		1673
		1674	This method is more tricky, but usually most efficient: Most timeouts are
		1675	relatively long compared to the intervals between other activity - in
		1676	our example, within 60 seconds, there are usually many I/O events with
		1677	associated activity resets.
		1678
		1679	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1680	but remember the time of last activity, and check for a real timeout only
		1681	within the callback:
		1682
		1683	ev_tstamp last_activity; // time of last activity
		1684
		1685	static void
		1686	callback (EV_P_ ev_timer *w, int revents)
		1687	{
		1688	ev_tstamp now = ev_now (EV_A);
		1689	ev_tstamp timeout = last_activity + 60.;
		1690
		1691	// if last_activity + 60. is older than now, we did time out
		1692	if (timeout < now)
		1693	{
		1694	// timeout occured, take action
		1695	}
		1696	else
		1697	{
		1698	// callback was invoked, but there was some activity, re-arm
		1699	// the watcher to fire in last_activity + 60, which is
		1700	// guaranteed to be in the future, so "again" is positive:
		1701	w->repeat = timeout - now;
		1702	ev_timer_again (EV_A_ w);
		1703	}
		1704	}
		1705
		1706	To summarise the callback: first calculate the real timeout (defined
		1707	as "60 seconds after the last activity"), then check if that time has
		1708	been reached, which means something I<did>, in fact, time out. Otherwise
		1709	the callback was invoked too early (C<timeout> is in the future), so
		1710	re-schedule the timer to fire at that future time, to see if maybe we have
		1711	a timeout then.
		1712
		1713	Note how C<ev_timer_again> is used, taking advantage of the
		1714	C<ev_timer_again> optimisation when the timer is already running.
		1715
		1716	This scheme causes more callback invocations (about one every 60 seconds
		1717	minus half the average time between activity), but virtually no calls to
		1718	libev to change the timeout.
		1719
		1720	To start the timer, simply initialise the watcher and set C<last_activity>
		1721	to the current time (meaning we just have some activity :), then call the
		1722	callback, which will "do the right thing" and start the timer:
		1723
		1724	ev_init (timer, callback);
		1725	last_activity = ev_now (loop);
		1726	callback (loop, timer, EV_TIMEOUT);
		1727
		1728	And when there is some activity, simply store the current time in
		1729	C<last_activity>, no libev calls at all:
		1730
		1731	last_actiivty = ev_now (loop);
		1732
		1733	This technique is slightly more complex, but in most cases where the
		1734	time-out is unlikely to be triggered, much more efficient.
		1735
		1736	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1737	callback :) - just change the timeout and invoke the callback, which will
		1738	fix things for you.
		1739
		1740	=item 4. Wee, just use a double-linked list for your timeouts.
		1741
		1742	If there is not one request, but many thousands (millions...), all
		1743	employing some kind of timeout with the same timeout value, then one can
		1744	do even better:
		1745
		1746	When starting the timeout, calculate the timeout value and put the timeout
		1747	at the I<end> of the list.
		1748
		1749	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1750	the list is expected to fire (for example, using the technique #3).
		1751
		1752	When there is some activity, remove the timer from the list, recalculate
		1753	the timeout, append it to the end of the list again, and make sure to
		1754	update the C<ev_timer> if it was taken from the beginning of the list.
		1755
		1756	This way, one can manage an unlimited number of timeouts in O(1) time for
		1757	starting, stopping and updating the timers, at the expense of a major
		1758	complication, and having to use a constant timeout. The constant timeout
		1759	ensures that the list stays sorted.
		1760
		1761	=back
		1762
		1763	So which method the best?
		1764
		1765	Method #2 is a simple no-brain-required solution that is adequate in most
		1766	situations. Method #3 requires a bit more thinking, but handles many cases
		1767	better, and isn't very complicated either. In most case, choosing either
		1768	one is fine, with #3 being better in typical situations.
		1769
		1770	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1771	rather complicated, but extremely efficient, something that really pays
		1772	off after the first million or so of active timers, i.e. it's usually
		1773	overkill :)
1284		1774
1285	=head3 The special problem of time updates	1775	=head3 The special problem of time updates
1286		1776
1287	Establishing the current time is a costly operation (it usually takes at	1777	Establishing the current time is a costly operation (it usually takes at
1288	least two system calls): EV therefore updates its idea of the current	1778	least two system calls): EV therefore updates its idea of the current
…		…
1300		1790
1301	If the event loop is suspended for a long time, you can also force an	1791	If the event loop is suspended for a long time, you can also force an
1302	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1792	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1303	()>.	1793	()>.
1304		1794
		1795	=head3 The special problems of suspended animation
		1796
		1797	When you leave the server world it is quite customary to hit machines that
		1798	can suspend/hibernate - what happens to the clocks during such a suspend?
		1799
		1800	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1801	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1802	to run until the system is suspended, but they will not advance while the
		1803	system is suspended. That means, on resume, it will be as if the program
		1804	was frozen for a few seconds, but the suspend time will not be counted
		1805	towards C<ev_timer> when a monotonic clock source is used. The real time
		1806	clock advanced as expected, but if it is used as sole clocksource, then a
		1807	long suspend would be detected as a time jump by libev, and timers would
		1808	be adjusted accordingly.
		1809
		1810	I would not be surprised to see different behaviour in different between
		1811	operating systems, OS versions or even different hardware.
		1812
		1813	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1814	time jump in the monotonic clocks and the realtime clock. If the program
		1815	is suspended for a very long time, and monotonic clock sources are in use,
		1816	then you can expect C<ev_timer>s to expire as the full suspension time
		1817	will be counted towards the timers. When no monotonic clock source is in
		1818	use, then libev will again assume a timejump and adjust accordingly.
		1819
		1820	It might be beneficial for this latter case to call C<ev_suspend>
		1821	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1822	deterministic behaviour in this case (you can do nothing against
		1823	C<SIGSTOP>).
		1824
1305	=head3 Watcher-Specific Functions and Data Members	1825	=head3 Watcher-Specific Functions and Data Members
1306		1826
1307	=over 4	1827	=over 4
1308		1828
1309	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1829	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1332	If the timer is started but non-repeating, stop it (as if it timed out).	1852	If the timer is started but non-repeating, stop it (as if it timed out).
1333		1853
1334	If the timer is repeating, either start it if necessary (with the	1854	If the timer is repeating, either start it if necessary (with the
1335	C<repeat> value), or reset the running timer to the C<repeat> value.	1855	C<repeat> value), or reset the running timer to the C<repeat> value.
1336		1856
1337	This sounds a bit complicated, but here is a useful and typical	1857	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1338	example: Imagine you have a TCP connection and you want a so-called idle	1858	usage example.
1339	timeout, that is, you want to be called when there have been, say, 60
1340	seconds of inactivity on the socket. The easiest way to do this is to
1341	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1342	C<ev_timer_again> each time you successfully read or write some data. If
1343	you go into an idle state where you do not expect data to travel on the
1344	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1345	automatically restart it if need be.
1346		1859
1347	That means you can ignore the C<after> value and C<ev_timer_start>	1860	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1348	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1349		1861
1350	ev_timer_init (timer, callback, 0., 5.);	1862	Returns the remaining time until a timer fires. If the timer is active,
1351	ev_timer_again (loop, timer);	1863	then this time is relative to the current event loop time, otherwise it's
1352	...	1864	the timeout value currently configured.
1353	timer->again = 17.;
1354	ev_timer_again (loop, timer);
1355	...
1356	timer->again = 10.;
1357	ev_timer_again (loop, timer);
1358		1865
1359	This is more slightly efficient then stopping/starting the timer each time	1866	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1360	you want to modify its timeout value.	1867	C<5>. When the timer is started and one second passes, C<ev_timer_remain>
1361		1868	will return C<4>. When the timer expires and is restarted, it will return
1362	Note, however, that it is often even more efficient to remember the	1869	roughly C<7> (likely slightly less as callback invocation takes some time,
1363	time of the last activity and let the timer time-out naturally. In the	1870	too), and so on.
1364	callback, you then check whether the time-out is real, or, if there was
1365	some activity, you reschedule the watcher to time-out in "last_activity +
1366	timeout - ev_now ()" seconds.
1367		1871
1368	=item ev_tstamp repeat [read-write]	1872	=item ev_tstamp repeat [read-write]
1369		1873
1370	The current C<repeat> value. Will be used each time the watcher times out	1874	The current C<repeat> value. Will be used each time the watcher times out
1371	or C<ev_timer_again> is called, and determines the next timeout (if any),	1875	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1376	=head3 Examples	1880	=head3 Examples
1377		1881
1378	Example: Create a timer that fires after 60 seconds.	1882	Example: Create a timer that fires after 60 seconds.
1379		1883
1380	static void	1884	static void
1381	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1885	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1382	{	1886	{
1383	.. one minute over, w is actually stopped right here	1887	.. one minute over, w is actually stopped right here
1384	}	1888	}
1385		1889
1386	struct ev_timer mytimer;	1890	ev_timer mytimer;
1387	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1891	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1388	ev_timer_start (loop, &mytimer);	1892	ev_timer_start (loop, &mytimer);
1389		1893
1390	Example: Create a timeout timer that times out after 10 seconds of	1894	Example: Create a timeout timer that times out after 10 seconds of
1391	inactivity.	1895	inactivity.
1392		1896
1393	static void	1897	static void
1394	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1898	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1395	{	1899	{
1396	.. ten seconds without any activity	1900	.. ten seconds without any activity
1397	}	1901	}
1398		1902
1399	struct ev_timer mytimer;	1903	ev_timer mytimer;
1400	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1904	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1401	ev_timer_again (&mytimer); /* start timer */	1905	ev_timer_again (&mytimer); /* start timer */
1402	ev_loop (loop, 0);	1906	ev_loop (loop, 0);
1403		1907
1404	// and in some piece of code that gets executed on any "activity":	1908	// and in some piece of code that gets executed on any "activity":
…		…
1409	=head2 C<ev_periodic> - to cron or not to cron?	1913	=head2 C<ev_periodic> - to cron or not to cron?
1410		1914
1411	Periodic watchers are also timers of a kind, but they are very versatile	1915	Periodic watchers are also timers of a kind, but they are very versatile
1412	(and unfortunately a bit complex).	1916	(and unfortunately a bit complex).
1413		1917
1414	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1918	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1415	but on wall clock time (absolute time). You can tell a periodic watcher	1919	relative time, the physical time that passes) but on wall clock time
1416	to trigger after some specific point in time. For example, if you tell a	1920	(absolute time, the thing you can read on your calender or clock). The
1417	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	1921	difference is that wall clock time can run faster or slower than real
1418	+ 10.>, that is, an absolute time not a delay) and then reset your system	1922	time, and time jumps are not uncommon (e.g. when you adjust your
1419	clock to January of the previous year, then it will take more than year	1923	wrist-watch).
1420	to trigger the event (unlike an C<ev_timer>, which would still trigger
1421	roughly 10 seconds later as it uses a relative timeout).
1422		1924
		1925	You can tell a periodic watcher to trigger after some specific point
		1926	in time: for example, if you tell a periodic watcher to trigger "in 10
		1927	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1928	not a delay) and then reset your system clock to January of the previous
		1929	year, then it will take a year or more to trigger the event (unlike an
		1930	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1931	it, as it uses a relative timeout).
		1932
1423	C<ev_periodic>s can also be used to implement vastly more complex timers,	1933	C<ev_periodic> watchers can also be used to implement vastly more complex
1424	such as triggering an event on each "midnight, local time", or other	1934	timers, such as triggering an event on each "midnight, local time", or
1425	complicated rules.	1935	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1936	those cannot react to time jumps.
1426		1937
1427	As with timers, the callback is guaranteed to be invoked only when the	1938	As with timers, the callback is guaranteed to be invoked only when the
1428	time (C<at>) has passed, but if multiple periodic timers become ready	1939	point in time where it is supposed to trigger has passed. If multiple
1429	during the same loop iteration, then order of execution is undefined.	1940	timers become ready during the same loop iteration then the ones with
		1941	earlier time-out values are invoked before ones with later time-out values
		1942	(but this is no longer true when a callback calls C<ev_loop> recursively).
1430		1943
1431	=head3 Watcher-Specific Functions and Data Members	1944	=head3 Watcher-Specific Functions and Data Members
1432		1945
1433	=over 4	1946	=over 4
1434		1947
1435	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1948	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1436		1949
1437	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1950	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1438		1951
1439	Lots of arguments, lets sort it out... There are basically three modes of	1952	Lots of arguments, let's sort it out... There are basically three modes of
1440	operation, and we will explain them from simplest to most complex:	1953	operation, and we will explain them from simplest to most complex:
1441		1954
1442	=over 4	1955	=over 4
1443		1956
1444	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1957	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1445		1958
1446	In this configuration the watcher triggers an event after the wall clock	1959	In this configuration the watcher triggers an event after the wall clock
1447	time C<at> has passed. It will not repeat and will not adjust when a time	1960	time C<offset> has passed. It will not repeat and will not adjust when a
1448	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1961	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1449	only run when the system clock reaches or surpasses this time.	1962	will be stopped and invoked when the system clock reaches or surpasses
		1963	this point in time.
1450		1964
1451	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1965	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1452		1966
1453	In this mode the watcher will always be scheduled to time out at the next	1967	In this mode the watcher will always be scheduled to time out at the next
1454	C<at + N * interval> time (for some integer N, which can also be negative)	1968	C<offset + N * interval> time (for some integer N, which can also be
1455	and then repeat, regardless of any time jumps.	1969	negative) and then repeat, regardless of any time jumps. The C<offset>
		1970	argument is merely an offset into the C<interval> periods.
1456		1971
1457	This can be used to create timers that do not drift with respect to the	1972	This can be used to create timers that do not drift with respect to the
1458	system clock, for example, here is a C<ev_periodic> that triggers each	1973	system clock, for example, here is an C<ev_periodic> that triggers each
1459	hour, on the hour:	1974	hour, on the hour (with respect to UTC):
1460		1975
1461	ev_periodic_set (&periodic, 0., 3600., 0);	1976	ev_periodic_set (&periodic, 0., 3600., 0);
1462		1977
1463	This doesn't mean there will always be 3600 seconds in between triggers,	1978	This doesn't mean there will always be 3600 seconds in between triggers,
1464	but only that the callback will be called when the system time shows a	1979	but only that the callback will be called when the system time shows a
1465	full hour (UTC), or more correctly, when the system time is evenly divisible	1980	full hour (UTC), or more correctly, when the system time is evenly divisible
1466	by 3600.	1981	by 3600.
1467		1982
1468	Another way to think about it (for the mathematically inclined) is that	1983	Another way to think about it (for the mathematically inclined) is that
1469	C<ev_periodic> will try to run the callback in this mode at the next possible	1984	C<ev_periodic> will try to run the callback in this mode at the next possible
1470	time where C<time = at (mod interval)>, regardless of any time jumps.	1985	time where C<time = offset (mod interval)>, regardless of any time jumps.
1471		1986
1472	For numerical stability it is preferable that the C<at> value is near	1987	For numerical stability it is preferable that the C<offset> value is near
1473	C<ev_now ()> (the current time), but there is no range requirement for	1988	C<ev_now ()> (the current time), but there is no range requirement for
1474	this value, and in fact is often specified as zero.	1989	this value, and in fact is often specified as zero.
1475		1990
1476	Note also that there is an upper limit to how often a timer can fire (CPU	1991	Note also that there is an upper limit to how often a timer can fire (CPU
1477	speed for example), so if C<interval> is very small then timing stability	1992	speed for example), so if C<interval> is very small then timing stability
1478	will of course deteriorate. Libev itself tries to be exact to be about one	1993	will of course deteriorate. Libev itself tries to be exact to be about one
1479	millisecond (if the OS supports it and the machine is fast enough).	1994	millisecond (if the OS supports it and the machine is fast enough).
1480		1995
1481	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1996	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1482		1997
1483	In this mode the values for C<interval> and C<at> are both being	1998	In this mode the values for C<interval> and C<offset> are both being
1484	ignored. Instead, each time the periodic watcher gets scheduled, the	1999	ignored. Instead, each time the periodic watcher gets scheduled, the
1485	reschedule callback will be called with the watcher as first, and the	2000	reschedule callback will be called with the watcher as first, and the
1486	current time as second argument.	2001	current time as second argument.
1487		2002
1488	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2003	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1489	ever, or make ANY event loop modifications whatsoever>.	2004	or make ANY other event loop modifications whatsoever, unless explicitly
		2005	allowed by documentation here>.
1490		2006
1491	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2007	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1492	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2008	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1493	only event loop modification you are allowed to do).	2009	only event loop modification you are allowed to do).
1494		2010
1495	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	2011	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1496	*w, ev_tstamp now)>, e.g.:	2012	*w, ev_tstamp now)>, e.g.:
1497		2013
		2014	static ev_tstamp
1498	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	2015	my_rescheduler (ev_periodic *w, ev_tstamp now)
1499	{	2016	{
1500	return now + 60.;	2017	return now + 60.;
1501	}	2018	}
1502		2019
1503	It must return the next time to trigger, based on the passed time value	2020	It must return the next time to trigger, based on the passed time value
…		…
1523	a different time than the last time it was called (e.g. in a crond like	2040	a different time than the last time it was called (e.g. in a crond like
1524	program when the crontabs have changed).	2041	program when the crontabs have changed).
1525		2042
1526	=item ev_tstamp ev_periodic_at (ev_periodic *)	2043	=item ev_tstamp ev_periodic_at (ev_periodic *)
1527		2044
1528	When active, returns the absolute time that the watcher is supposed to	2045	When active, returns the absolute time that the watcher is supposed
1529	trigger next.	2046	to trigger next. This is not the same as the C<offset> argument to
		2047	C<ev_periodic_set>, but indeed works even in interval and manual
		2048	rescheduling modes.
1530		2049
1531	=item ev_tstamp offset [read-write]	2050	=item ev_tstamp offset [read-write]
1532		2051
1533	When repeating, this contains the offset value, otherwise this is the	2052	When repeating, this contains the offset value, otherwise this is the
1534	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2053	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2054	although libev might modify this value for better numerical stability).
1535		2055
1536	Can be modified any time, but changes only take effect when the periodic	2056	Can be modified any time, but changes only take effect when the periodic
1537	timer fires or C<ev_periodic_again> is being called.	2057	timer fires or C<ev_periodic_again> is being called.
1538		2058
1539	=item ev_tstamp interval [read-write]	2059	=item ev_tstamp interval [read-write]
1540		2060
1541	The current interval value. Can be modified any time, but changes only	2061	The current interval value. Can be modified any time, but changes only
1542	take effect when the periodic timer fires or C<ev_periodic_again> is being	2062	take effect when the periodic timer fires or C<ev_periodic_again> is being
1543	called.	2063	called.
1544		2064
1545	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2065	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1546		2066
1547	The current reschedule callback, or C<0>, if this functionality is	2067	The current reschedule callback, or C<0>, if this functionality is
1548	switched off. Can be changed any time, but changes only take effect when	2068	switched off. Can be changed any time, but changes only take effect when
1549	the periodic timer fires or C<ev_periodic_again> is being called.	2069	the periodic timer fires or C<ev_periodic_again> is being called.
1550		2070
…		…
1555	Example: Call a callback every hour, or, more precisely, whenever the	2075	Example: Call a callback every hour, or, more precisely, whenever the
1556	system time is divisible by 3600. The callback invocation times have	2076	system time is divisible by 3600. The callback invocation times have
1557	potentially a lot of jitter, but good long-term stability.	2077	potentially a lot of jitter, but good long-term stability.
1558		2078
1559	static void	2079	static void
1560	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2080	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1561	{	2081	{
1562	... its now a full hour (UTC, or TAI or whatever your clock follows)	2082	... its now a full hour (UTC, or TAI or whatever your clock follows)
1563	}	2083	}
1564		2084
1565	struct ev_periodic hourly_tick;	2085	ev_periodic hourly_tick;
1566	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2086	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1567	ev_periodic_start (loop, &hourly_tick);	2087	ev_periodic_start (loop, &hourly_tick);
1568		2088
1569	Example: The same as above, but use a reschedule callback to do it:	2089	Example: The same as above, but use a reschedule callback to do it:
1570		2090
1571	#include <math.h>	2091	#include <math.h>
1572		2092
1573	static ev_tstamp	2093	static ev_tstamp
1574	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2094	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1575	{	2095	{
1576	return now + (3600. - fmod (now, 3600.));	2096	return now + (3600. - fmod (now, 3600.));
1577	}	2097	}
1578		2098
1579	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2099	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1580		2100
1581	Example: Call a callback every hour, starting now:	2101	Example: Call a callback every hour, starting now:
1582		2102
1583	struct ev_periodic hourly_tick;	2103	ev_periodic hourly_tick;
1584	ev_periodic_init (&hourly_tick, clock_cb,	2104	ev_periodic_init (&hourly_tick, clock_cb,
1585	fmod (ev_now (loop), 3600.), 3600., 0);	2105	fmod (ev_now (loop), 3600.), 3600., 0);
1586	ev_periodic_start (loop, &hourly_tick);	2106	ev_periodic_start (loop, &hourly_tick);
1587		2107
1588		2108
…		…
1591	Signal watchers will trigger an event when the process receives a specific	2111	Signal watchers will trigger an event when the process receives a specific
1592	signal one or more times. Even though signals are very asynchronous, libev	2112	signal one or more times. Even though signals are very asynchronous, libev
1593	will try it's best to deliver signals synchronously, i.e. as part of the	2113	will try it's best to deliver signals synchronously, i.e. as part of the
1594	normal event processing, like any other event.	2114	normal event processing, like any other event.
1595		2115
1596	If you want signals asynchronously, just use C<sigaction> as you would	2116	If you want signals to be delivered truly asynchronously, just use
1597	do without libev and forget about sharing the signal. You can even use	2117	C<sigaction> as you would do without libev and forget about sharing
1598	C<ev_async> from a signal handler to synchronously wake up an event loop.	2118	the signal. You can even use C<ev_async> from a signal handler to
		2119	synchronously wake up an event loop.
1599		2120
1600	You can configure as many watchers as you like per signal. Only when the	2121	You can configure as many watchers as you like for the same signal, but
		2122	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2123	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2124	C<SIGINT> in both the default loop and another loop at the same time. At
		2125	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2126
1601	first watcher gets started will libev actually register a signal handler	2127	When the first watcher gets started will libev actually register something
1602	with the kernel (thus it coexists with your own signal handlers as long as	2128	with the kernel (thus it coexists with your own signal handlers as long as
1603	you don't register any with libev for the same signal). Similarly, when	2129	you don't register any with libev for the same signal).
1604	the last signal watcher for a signal is stopped, libev will reset the
1605	signal handler to SIG_DFL (regardless of what it was set to before).
1606		2130
1607	If possible and supported, libev will install its handlers with	2131	If possible and supported, libev will install its handlers with
1608	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2132	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1609	interrupted. If you have a problem with system calls getting interrupted by	2133	not be unduly interrupted. If you have a problem with system calls getting
1610	signals you can block all signals in an C<ev_check> watcher and unblock	2134	interrupted by signals you can block all signals in an C<ev_check> watcher
1611	them in an C<ev_prepare> watcher.	2135	and unblock them in an C<ev_prepare> watcher.
		2136
		2137	=head3 The special problem of inheritance over execve
		2138
		2139	Both the signal mask (C<sigprocmask>) and the signal disposition
		2140	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2141	stopping it again), that is, libev might or might not block the signal,
		2142	and might or might not set or restore the installed signal handler.
		2143
		2144	While this does not matter for the signal disposition (libev never
		2145	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2146	C<execve>), this matters for the signal mask: many programs do not expect
		2147	certain signals to be blocked.
		2148
		2149	This means that before calling C<exec> (from the child) you should reset
		2150	the signal mask to whatever "default" you expect (all clear is a good
		2151	choice usually).
		2152
		2153	The simplest way to ensure that the signal mask is reset in the child is
		2154	to install a fork handler with C<pthread_atfork> that resets it. That will
		2155	catch fork calls done by libraries (such as the libc) as well.
		2156
		2157	In current versions of libev, you can also ensure that the signal mask is
		2158	not blocking any signals (except temporarily, so thread users watch out)
		2159	by specifying the C<EVFLAG_NOSIGFD> when creating the event loop. This
		2160	is not guaranteed for future versions, however.
1612		2161
1613	=head3 Watcher-Specific Functions and Data Members	2162	=head3 Watcher-Specific Functions and Data Members
1614		2163
1615	=over 4	2164	=over 4
1616		2165
…		…
1630	=head3 Examples	2179	=head3 Examples
1631		2180
1632	Example: Try to exit cleanly on SIGINT.	2181	Example: Try to exit cleanly on SIGINT.
1633		2182
1634	static void	2183	static void
1635	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2184	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1636	{	2185	{
1637	ev_unloop (loop, EVUNLOOP_ALL);	2186	ev_unloop (loop, EVUNLOOP_ALL);
1638	}	2187	}
1639		2188
1640	struct ev_signal signal_watcher;	2189	ev_signal signal_watcher;
1641	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2190	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1642	ev_signal_start (loop, &signal_watcher);	2191	ev_signal_start (loop, &signal_watcher);
1643		2192
1644		2193
1645	=head2 C<ev_child> - watch out for process status changes	2194	=head2 C<ev_child> - watch out for process status changes
…		…
1648	some child status changes (most typically when a child of yours dies or	2197	some child status changes (most typically when a child of yours dies or
1649	exits). It is permissible to install a child watcher I<after> the child	2198	exits). It is permissible to install a child watcher I<after> the child
1650	has been forked (which implies it might have already exited), as long	2199	has been forked (which implies it might have already exited), as long
1651	as the event loop isn't entered (or is continued from a watcher), i.e.,	2200	as the event loop isn't entered (or is continued from a watcher), i.e.,
1652	forking and then immediately registering a watcher for the child is fine,	2201	forking and then immediately registering a watcher for the child is fine,
1653	but forking and registering a watcher a few event loop iterations later is	2202	but forking and registering a watcher a few event loop iterations later or
1654	not.	2203	in the next callback invocation is not.
1655		2204
1656	Only the default event loop is capable of handling signals, and therefore	2205	Only the default event loop is capable of handling signals, and therefore
1657	you can only register child watchers in the default event loop.	2206	you can only register child watchers in the default event loop.
1658		2207
		2208	Due to some design glitches inside libev, child watchers will always be
		2209	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2210	libev)
		2211
1659	=head3 Process Interaction	2212	=head3 Process Interaction
1660		2213
1661	Libev grabs C<SIGCHLD> as soon as the default event loop is	2214	Libev grabs C<SIGCHLD> as soon as the default event loop is
1662	initialised. This is necessary to guarantee proper behaviour even if	2215	initialised. This is necessary to guarantee proper behaviour even if the
1663	the first child watcher is started after the child exits. The occurrence	2216	first child watcher is started after the child exits. The occurrence
1664	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2217	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1665	synchronously as part of the event loop processing. Libev always reaps all	2218	synchronously as part of the event loop processing. Libev always reaps all
1666	children, even ones not watched.	2219	children, even ones not watched.
1667		2220
1668	=head3 Overriding the Built-In Processing	2221	=head3 Overriding the Built-In Processing
…		…
1678	=head3 Stopping the Child Watcher	2231	=head3 Stopping the Child Watcher
1679		2232
1680	Currently, the child watcher never gets stopped, even when the	2233	Currently, the child watcher never gets stopped, even when the
1681	child terminates, so normally one needs to stop the watcher in the	2234	child terminates, so normally one needs to stop the watcher in the
1682	callback. Future versions of libev might stop the watcher automatically	2235	callback. Future versions of libev might stop the watcher automatically
1683	when a child exit is detected.	2236	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2237	problem).
1684		2238
1685	=head3 Watcher-Specific Functions and Data Members	2239	=head3 Watcher-Specific Functions and Data Members
1686		2240
1687	=over 4	2241	=over 4
1688		2242
…		…
1720	its completion.	2274	its completion.
1721		2275
1722	ev_child cw;	2276	ev_child cw;
1723		2277
1724	static void	2278	static void
1725	child_cb (EV_P_ struct ev_child *w, int revents)	2279	child_cb (EV_P_ ev_child *w, int revents)
1726	{	2280	{
1727	ev_child_stop (EV_A_ w);	2281	ev_child_stop (EV_A_ w);
1728	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2282	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1729	}	2283	}
1730		2284
…		…
1745		2299
1746		2300
1747	=head2 C<ev_stat> - did the file attributes just change?	2301	=head2 C<ev_stat> - did the file attributes just change?
1748		2302
1749	This watches a file system path for attribute changes. That is, it calls	2303	This watches a file system path for attribute changes. That is, it calls
1750	C<stat> regularly (or when the OS says it changed) and sees if it changed	2304	C<stat> on that path in regular intervals (or when the OS says it changed)
1751	compared to the last time, invoking the callback if it did.	2305	and sees if it changed compared to the last time, invoking the callback if
		2306	it did.
1752		2307
1753	The path does not need to exist: changing from "path exists" to "path does	2308	The path does not need to exist: changing from "path exists" to "path does
1754	not exist" is a status change like any other. The condition "path does	2309	not exist" is a status change like any other. The condition "path does not
1755	not exist" is signified by the C<st_nlink> field being zero (which is	2310	exist" (or more correctly "path cannot be stat'ed") is signified by the
1756	otherwise always forced to be at least one) and all the other fields of	2311	C<st_nlink> field being zero (which is otherwise always forced to be at
1757	the stat buffer having unspecified contents.	2312	least one) and all the other fields of the stat buffer having unspecified
		2313	contents.
1758		2314
1759	The path I<should> be absolute and I<must not> end in a slash. If it is	2315	The path I<must not> end in a slash or contain special components such as
		2316	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1760	relative and your working directory changes, the behaviour is undefined.	2317	your working directory changes, then the behaviour is undefined.
1761		2318
1762	Since there is no standard kernel interface to do this, the portable	2319	Since there is no portable change notification interface available, the
1763	implementation simply calls C<stat (2)> regularly on the path to see if	2320	portable implementation simply calls C<stat(2)> regularly on the path
1764	it changed somehow. You can specify a recommended polling interval for	2321	to see if it changed somehow. You can specify a recommended polling
1765	this case. If you specify a polling interval of C<0> (highly recommended!)	2322	interval for this case. If you specify a polling interval of C<0> (highly
1766	then a I<suitable, unspecified default> value will be used (which	2323	recommended!) then a I<suitable, unspecified default> value will be used
1767	you can expect to be around five seconds, although this might change	2324	(which you can expect to be around five seconds, although this might
1768	dynamically). Libev will also impose a minimum interval which is currently	2325	change dynamically). Libev will also impose a minimum interval which is
1769	around C<0.1>, but thats usually overkill.	2326	currently around C<0.1>, but that's usually overkill.
1770		2327
1771	This watcher type is not meant for massive numbers of stat watchers,	2328	This watcher type is not meant for massive numbers of stat watchers,
1772	as even with OS-supported change notifications, this can be	2329	as even with OS-supported change notifications, this can be
1773	resource-intensive.	2330	resource-intensive.
1774		2331
1775	At the time of this writing, the only OS-specific interface implemented	2332	At the time of this writing, the only OS-specific interface implemented
1776	is the Linux inotify interface (implementing kqueue support is left as	2333	is the Linux inotify interface (implementing kqueue support is left as an
1777	an exercise for the reader. Note, however, that the author sees no way	2334	exercise for the reader. Note, however, that the author sees no way of
1778	of implementing C<ev_stat> semantics with kqueue).	2335	implementing C<ev_stat> semantics with kqueue, except as a hint).
1779		2336
1780	=head3 ABI Issues (Largefile Support)	2337	=head3 ABI Issues (Largefile Support)
1781		2338
1782	Libev by default (unless the user overrides this) uses the default	2339	Libev by default (unless the user overrides this) uses the default
1783	compilation environment, which means that on systems with large file	2340	compilation environment, which means that on systems with large file
1784	support disabled by default, you get the 32 bit version of the stat	2341	support disabled by default, you get the 32 bit version of the stat
1785	structure. When using the library from programs that change the ABI to	2342	structure. When using the library from programs that change the ABI to
1786	use 64 bit file offsets the programs will fail. In that case you have to	2343	use 64 bit file offsets the programs will fail. In that case you have to
1787	compile libev with the same flags to get binary compatibility. This is	2344	compile libev with the same flags to get binary compatibility. This is
1788	obviously the case with any flags that change the ABI, but the problem is	2345	obviously the case with any flags that change the ABI, but the problem is
1789	most noticeably disabled with ev_stat and large file support.	2346	most noticeably displayed with ev_stat and large file support.
1790		2347
1791	The solution for this is to lobby your distribution maker to make large	2348	The solution for this is to lobby your distribution maker to make large
1792	file interfaces available by default (as e.g. FreeBSD does) and not	2349	file interfaces available by default (as e.g. FreeBSD does) and not
1793	optional. Libev cannot simply switch on large file support because it has	2350	optional. Libev cannot simply switch on large file support because it has
1794	to exchange stat structures with application programs compiled using the	2351	to exchange stat structures with application programs compiled using the
1795	default compilation environment.	2352	default compilation environment.
1796		2353
1797	=head3 Inotify and Kqueue	2354	=head3 Inotify and Kqueue
1798		2355
1799	When C<inotify (7)> support has been compiled into libev (generally only	2356	When C<inotify (7)> support has been compiled into libev and present at
1800	available with Linux) and present at runtime, it will be used to speed up	2357	runtime, it will be used to speed up change detection where possible. The
1801	change detection where possible. The inotify descriptor will be created lazily	2358	inotify descriptor will be created lazily when the first C<ev_stat>
1802	when the first C<ev_stat> watcher is being started.	2359	watcher is being started.
1803		2360
1804	Inotify presence does not change the semantics of C<ev_stat> watchers	2361	Inotify presence does not change the semantics of C<ev_stat> watchers
1805	except that changes might be detected earlier, and in some cases, to avoid	2362	except that changes might be detected earlier, and in some cases, to avoid
1806	making regular C<stat> calls. Even in the presence of inotify support	2363	making regular C<stat> calls. Even in the presence of inotify support
1807	there are many cases where libev has to resort to regular C<stat> polling,	2364	there are many cases where libev has to resort to regular C<stat> polling,
1808	but as long as the path exists, libev usually gets away without polling.	2365	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2366	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2367	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2368	xfs are fully working) libev usually gets away without polling.
1809		2369
1810	There is no support for kqueue, as apparently it cannot be used to	2370	There is no support for kqueue, as apparently it cannot be used to
1811	implement this functionality, due to the requirement of having a file	2371	implement this functionality, due to the requirement of having a file
1812	descriptor open on the object at all times, and detecting renames, unlinks	2372	descriptor open on the object at all times, and detecting renames, unlinks
1813	etc. is difficult.	2373	etc. is difficult.
1814		2374
		2375	=head3 C<stat ()> is a synchronous operation
		2376
		2377	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2378	the process. The exception are C<ev_stat> watchers - those call C<stat
		2379	()>, which is a synchronous operation.
		2380
		2381	For local paths, this usually doesn't matter: unless the system is very
		2382	busy or the intervals between stat's are large, a stat call will be fast,
		2383	as the path data is usually in memory already (except when starting the
		2384	watcher).
		2385
		2386	For networked file systems, calling C<stat ()> can block an indefinite
		2387	time due to network issues, and even under good conditions, a stat call
		2388	often takes multiple milliseconds.
		2389
		2390	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2391	paths, although this is fully supported by libev.
		2392
1815	=head3 The special problem of stat time resolution	2393	=head3 The special problem of stat time resolution
1816		2394
1817	The C<stat ()> system call only supports full-second resolution portably, and	2395	The C<stat ()> system call only supports full-second resolution portably,
1818	even on systems where the resolution is higher, most file systems still	2396	and even on systems where the resolution is higher, most file systems
1819	only support whole seconds.	2397	still only support whole seconds.
1820		2398
1821	That means that, if the time is the only thing that changes, you can	2399	That means that, if the time is the only thing that changes, you can
1822	easily miss updates: on the first update, C<ev_stat> detects a change and	2400	easily miss updates: on the first update, C<ev_stat> detects a change and
1823	calls your callback, which does something. When there is another update	2401	calls your callback, which does something. When there is another update
1824	within the same second, C<ev_stat> will be unable to detect unless the	2402	within the same second, C<ev_stat> will be unable to detect unless the
…		…
1967		2545
1968	=head3 Watcher-Specific Functions and Data Members	2546	=head3 Watcher-Specific Functions and Data Members
1969		2547
1970	=over 4	2548	=over 4
1971		2549
1972	=item ev_idle_init (ev_signal *, callback)	2550	=item ev_idle_init (ev_idle *, callback)
1973		2551
1974	Initialises and configures the idle watcher - it has no parameters of any	2552	Initialises and configures the idle watcher - it has no parameters of any
1975	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2553	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1976	believe me.	2554	believe me.
1977		2555
…		…
1981		2559
1982	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2560	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1983	callback, free it. Also, use no error checking, as usual.	2561	callback, free it. Also, use no error checking, as usual.
1984		2562
1985	static void	2563	static void
1986	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2564	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1987	{	2565	{
1988	free (w);	2566	free (w);
1989	// now do something you wanted to do when the program has	2567	// now do something you wanted to do when the program has
1990	// no longer anything immediate to do.	2568	// no longer anything immediate to do.
1991	}	2569	}
1992		2570
1993	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2571	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1994	ev_idle_init (idle_watcher, idle_cb);	2572	ev_idle_init (idle_watcher, idle_cb);
1995	ev_idle_start (loop, idle_cb);	2573	ev_idle_start (loop, idle_watcher);
1996		2574
1997		2575
1998	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2576	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1999		2577
2000	Prepare and check watchers are usually (but not always) used in pairs:	2578	Prepare and check watchers are usually (but not always) used in pairs:
…		…
2079		2657
2080	static ev_io iow [nfd];	2658	static ev_io iow [nfd];
2081	static ev_timer tw;	2659	static ev_timer tw;
2082		2660
2083	static void	2661	static void
2084	io_cb (ev_loop *loop, ev_io *w, int revents)	2662	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2085	{	2663	{
2086	}	2664	}
2087		2665
2088	// create io watchers for each fd and a timer before blocking	2666	// create io watchers for each fd and a timer before blocking
2089	static void	2667	static void
2090	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2668	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2091	{	2669	{
2092	int timeout = 3600000;	2670	int timeout = 3600000;
2093	struct pollfd fds [nfd];	2671	struct pollfd fds [nfd];
2094	// actual code will need to loop here and realloc etc.	2672	// actual code will need to loop here and realloc etc.
2095	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2673	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2096		2674
2097	/* the callback is illegal, but won't be called as we stop during check */	2675	/* the callback is illegal, but won't be called as we stop during check */
2098	ev_timer_init (&tw, 0, timeout * 1e-3);	2676	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2099	ev_timer_start (loop, &tw);	2677	ev_timer_start (loop, &tw);
2100		2678
2101	// create one ev_io per pollfd	2679	// create one ev_io per pollfd
2102	for (int i = 0; i < nfd; ++i)	2680	for (int i = 0; i < nfd; ++i)
2103	{	2681	{
…		…
2110	}	2688	}
2111	}	2689	}
2112		2690
2113	// stop all watchers after blocking	2691	// stop all watchers after blocking
2114	static void	2692	static void
2115	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2693	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2116	{	2694	{
2117	ev_timer_stop (loop, &tw);	2695	ev_timer_stop (loop, &tw);
2118		2696
2119	for (int i = 0; i < nfd; ++i)	2697	for (int i = 0; i < nfd; ++i)
2120	{	2698	{
…		…
2216	some fds have to be watched and handled very quickly (with low latency),	2794	some fds have to be watched and handled very quickly (with low latency),
2217	and even priorities and idle watchers might have too much overhead. In	2795	and even priorities and idle watchers might have too much overhead. In
2218	this case you would put all the high priority stuff in one loop and all	2796	this case you would put all the high priority stuff in one loop and all
2219	the rest in a second one, and embed the second one in the first.	2797	the rest in a second one, and embed the second one in the first.
2220		2798
2221	As long as the watcher is active, the callback will be invoked every time	2799	As long as the watcher is active, the callback will be invoked every
2222	there might be events pending in the embedded loop. The callback must then	2800	time there might be events pending in the embedded loop. The callback
2223	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2801	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2224	their callbacks (you could also start an idle watcher to give the embedded	2802	sweep and invoke their callbacks (the callback doesn't need to invoke the
2225	loop strictly lower priority for example). You can also set the callback	2803	C<ev_embed_sweep> function directly, it could also start an idle watcher
2226	to C<0>, in which case the embed watcher will automatically execute the	2804	to give the embedded loop strictly lower priority for example).
2227	embedded loop sweep.
2228		2805
2229	As long as the watcher is started it will automatically handle events. The	2806	You can also set the callback to C<0>, in which case the embed watcher
2230	callback will be invoked whenever some events have been handled. You can	2807	will automatically execute the embedded loop sweep whenever necessary.
2231	set the callback to C<0> to avoid having to specify one if you are not
2232	interested in that.
2233		2808
2234	Also, there have not currently been made special provisions for forking:	2809	Fork detection will be handled transparently while the C<ev_embed> watcher
2235	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2810	is active, i.e., the embedded loop will automatically be forked when the
2236	but you will also have to stop and restart any C<ev_embed> watchers	2811	embedding loop forks. In other cases, the user is responsible for calling
2237	yourself - but you can use a fork watcher to handle this automatically,	2812	C<ev_loop_fork> on the embedded loop.
2238	and future versions of libev might do just that.
2239		2813
2240	Unfortunately, not all backends are embeddable: only the ones returned by	2814	Unfortunately, not all backends are embeddable: only the ones returned by
2241	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2815	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2242	portable one.	2816	portable one.
2243		2817
…		…
2288	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2862	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2289	used).	2863	used).
2290		2864
2291	struct ev_loop *loop_hi = ev_default_init (0);	2865	struct ev_loop *loop_hi = ev_default_init (0);
2292	struct ev_loop *loop_lo = 0;	2866	struct ev_loop *loop_lo = 0;
2293	struct ev_embed embed;	2867	ev_embed embed;
2294		2868
2295	// see if there is a chance of getting one that works	2869	// see if there is a chance of getting one that works
2296	// (remember that a flags value of 0 means autodetection)	2870	// (remember that a flags value of 0 means autodetection)
2297	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2871	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2298	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2872	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2312	kqueue implementation). Store the kqueue/socket-only event loop in	2886	kqueue implementation). Store the kqueue/socket-only event loop in
2313	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2887	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2314		2888
2315	struct ev_loop *loop = ev_default_init (0);	2889	struct ev_loop *loop = ev_default_init (0);
2316	struct ev_loop *loop_socket = 0;	2890	struct ev_loop *loop_socket = 0;
2317	struct ev_embed embed;	2891	ev_embed embed;
2318		2892
2319	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2893	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2320	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2894	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2321	{	2895	{
2322	ev_embed_init (&embed, 0, loop_socket);	2896	ev_embed_init (&embed, 0, loop_socket);
…		…
2337	event loop blocks next and before C<ev_check> watchers are being called,	2911	event loop blocks next and before C<ev_check> watchers are being called,
2338	and only in the child after the fork. If whoever good citizen calling	2912	and only in the child after the fork. If whoever good citizen calling
2339	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2913	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2340	handlers will be invoked, too, of course.	2914	handlers will be invoked, too, of course.
2341		2915
		2916	=head3 The special problem of life after fork - how is it possible?
		2917
		2918	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2919	up/change the process environment, followed by a call to C<exec()>. This
		2920	sequence should be handled by libev without any problems.
		2921
		2922	This changes when the application actually wants to do event handling
		2923	in the child, or both parent in child, in effect "continuing" after the
		2924	fork.
		2925
		2926	The default mode of operation (for libev, with application help to detect
		2927	forks) is to duplicate all the state in the child, as would be expected
		2928	when I<either> the parent I<or> the child process continues.
		2929
		2930	When both processes want to continue using libev, then this is usually the
		2931	wrong result. In that case, usually one process (typically the parent) is
		2932	supposed to continue with all watchers in place as before, while the other
		2933	process typically wants to start fresh, i.e. without any active watchers.
		2934
		2935	The cleanest and most efficient way to achieve that with libev is to
		2936	simply create a new event loop, which of course will be "empty", and
		2937	use that for new watchers. This has the advantage of not touching more
		2938	memory than necessary, and thus avoiding the copy-on-write, and the
		2939	disadvantage of having to use multiple event loops (which do not support
		2940	signal watchers).
		2941
		2942	When this is not possible, or you want to use the default loop for
		2943	other reasons, then in the process that wants to start "fresh", call
		2944	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2945	the default loop will "orphan" (not stop) all registered watchers, so you
		2946	have to be careful not to execute code that modifies those watchers. Note
		2947	also that in that case, you have to re-register any signal watchers.
		2948
2342	=head3 Watcher-Specific Functions and Data Members	2949	=head3 Watcher-Specific Functions and Data Members
2343		2950
2344	=over 4	2951	=over 4
2345		2952
2346	=item ev_fork_init (ev_signal *, callback)	2953	=item ev_fork_init (ev_signal *, callback)
…		…
2375	=head3 Queueing	2982	=head3 Queueing
2376		2983
2377	C<ev_async> does not support queueing of data in any way. The reason	2984	C<ev_async> does not support queueing of data in any way. The reason
2378	is that the author does not know of a simple (or any) algorithm for a	2985	is that the author does not know of a simple (or any) algorithm for a
2379	multiple-writer-single-reader queue that works in all cases and doesn't	2986	multiple-writer-single-reader queue that works in all cases and doesn't
2380	need elaborate support such as pthreads.	2987	need elaborate support such as pthreads or unportable memory access
		2988	semantics.
2381		2989
2382	That means that if you want to queue data, you have to provide your own	2990	That means that if you want to queue data, you have to provide your own
2383	queue. But at least I can tell you how to implement locking around your	2991	queue. But at least I can tell you how to implement locking around your
2384	queue:	2992	queue:
2385		2993
…		…
2463	=over 4	3071	=over 4
2464		3072
2465	=item ev_async_init (ev_async *, callback)	3073	=item ev_async_init (ev_async *, callback)
2466		3074
2467	Initialises and configures the async watcher - it has no parameters of any	3075	Initialises and configures the async watcher - it has no parameters of any
2468	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3076	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2469	trust me.	3077	trust me.
2470		3078
2471	=item ev_async_send (loop, ev_async *)	3079	=item ev_async_send (loop, ev_async *)
2472		3080
2473	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3081	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2474	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3082	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2475	C<ev_feed_event>, this call is safe to do from other threads, signal or	3083	C<ev_feed_event>, this call is safe to do from other threads, signal or
2476	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3084	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2477	section below on what exactly this means).	3085	section below on what exactly this means).
2478		3086
		3087	Note that, as with other watchers in libev, multiple events might get
		3088	compressed into a single callback invocation (another way to look at this
		3089	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3090	reset when the event loop detects that).
		3091
2479	This call incurs the overhead of a system call only once per loop iteration,	3092	This call incurs the overhead of a system call only once per event loop
2480	so while the overhead might be noticeable, it doesn't apply to repeated	3093	iteration, so while the overhead might be noticeable, it doesn't apply to
2481	calls to C<ev_async_send>.	3094	repeated calls to C<ev_async_send> for the same event loop.
2482		3095
2483	=item bool = ev_async_pending (ev_async *)	3096	=item bool = ev_async_pending (ev_async *)
2484		3097
2485	Returns a non-zero value when C<ev_async_send> has been called on the	3098	Returns a non-zero value when C<ev_async_send> has been called on the
2486	watcher but the event has not yet been processed (or even noted) by the	3099	watcher but the event has not yet been processed (or even noted) by the
…		…
2489	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3102	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2490	the loop iterates next and checks for the watcher to have become active,	3103	the loop iterates next and checks for the watcher to have become active,
2491	it will reset the flag again. C<ev_async_pending> can be used to very	3104	it will reset the flag again. C<ev_async_pending> can be used to very
2492	quickly check whether invoking the loop might be a good idea.	3105	quickly check whether invoking the loop might be a good idea.
2493		3106
2494	Not that this does I<not> check whether the watcher itself is pending, only	3107	Not that this does I<not> check whether the watcher itself is pending,
2495	whether it has been requested to make this watcher pending.	3108	only whether it has been requested to make this watcher pending: there
		3109	is a time window between the event loop checking and resetting the async
		3110	notification, and the callback being invoked.
2496		3111
2497	=back	3112	=back
2498		3113
2499		3114
2500	=head1 OTHER FUNCTIONS	3115	=head1 OTHER FUNCTIONS
…		…
2536	/* doh, nothing entered */;	3151	/* doh, nothing entered */;
2537	}	3152	}
2538		3153
2539	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3154	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2540		3155
2541	=item ev_feed_event (ev_loop *, watcher *, int revents)
2542
2543	Feeds the given event set into the event loop, as if the specified event
2544	had happened for the specified watcher (which must be a pointer to an
2545	initialised but not necessarily started event watcher).
2546
2547	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3156	=item ev_feed_fd_event (loop, int fd, int revents)
2548		3157
2549	Feed an event on the given fd, as if a file descriptor backend detected	3158	Feed an event on the given fd, as if a file descriptor backend detected
2550	the given events it.	3159	the given events it.
2551		3160
2552	=item ev_feed_signal_event (ev_loop *loop, int signum)	3161	=item ev_feed_signal_event (loop, int signum)
2553		3162
2554	Feed an event as if the given signal occurred (C<loop> must be the default	3163	Feed an event as if the given signal occurred (C<loop> must be the default
2555	loop!).	3164	loop!).
2556		3165
2557	=back	3166	=back
…		…
2637		3246
2638	=over 4	3247	=over 4
2639		3248
2640	=item ev::TYPE::TYPE ()	3249	=item ev::TYPE::TYPE ()
2641		3250
2642	=item ev::TYPE::TYPE (struct ev_loop *)	3251	=item ev::TYPE::TYPE (loop)
2643		3252
2644	=item ev::TYPE::~TYPE	3253	=item ev::TYPE::~TYPE
2645		3254
2646	The constructor (optionally) takes an event loop to associate the watcher	3255	The constructor (optionally) takes an event loop to associate the watcher
2647	with. If it is omitted, it will use C<EV_DEFAULT>.	3256	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2679		3288
2680	myclass obj;	3289	myclass obj;
2681	ev::io iow;	3290	ev::io iow;
2682	iow.set <myclass, &myclass::io_cb> (&obj);	3291	iow.set <myclass, &myclass::io_cb> (&obj);
2683		3292
		3293	=item w->set (object *)
		3294
		3295	This is an B<experimental> feature that might go away in a future version.
		3296
		3297	This is a variation of a method callback - leaving out the method to call
		3298	will default the method to C<operator ()>, which makes it possible to use
		3299	functor objects without having to manually specify the C<operator ()> all
		3300	the time. Incidentally, you can then also leave out the template argument
		3301	list.
		3302
		3303	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3304	int revents)>.
		3305
		3306	See the method-C<set> above for more details.
		3307
		3308	Example: use a functor object as callback.
		3309
		3310	struct myfunctor
		3311	{
		3312	void operator() (ev::io &w, int revents)
		3313	{
		3314	...
		3315	}
		3316	}
		3317
		3318	myfunctor f;
		3319
		3320	ev::io w;
		3321	w.set (&f);
		3322
2684	=item w->set<function> (void *data = 0)	3323	=item w->set<function> (void *data = 0)
2685		3324
2686	Also sets a callback, but uses a static method or plain function as	3325	Also sets a callback, but uses a static method or plain function as
2687	callback. The optional C<data> argument will be stored in the watcher's	3326	callback. The optional C<data> argument will be stored in the watcher's
2688	C<data> member and is free for you to use.	3327	C<data> member and is free for you to use.
…		…
2694	Example: Use a plain function as callback.	3333	Example: Use a plain function as callback.
2695		3334
2696	static void io_cb (ev::io &w, int revents) { }	3335	static void io_cb (ev::io &w, int revents) { }
2697	iow.set <io_cb> ();	3336	iow.set <io_cb> ();
2698		3337
2699	=item w->set (struct ev_loop *)	3338	=item w->set (loop)
2700		3339
2701	Associates a different C<struct ev_loop> with this watcher. You can only	3340	Associates a different C<struct ev_loop> with this watcher. You can only
2702	do this when the watcher is inactive (and not pending either).	3341	do this when the watcher is inactive (and not pending either).
2703		3342
2704	=item w->set ([arguments])	3343	=item w->set ([arguments])
…		…
2774	L<http://software.schmorp.de/pkg/EV>.	3413	L<http://software.schmorp.de/pkg/EV>.
2775		3414
2776	=item Python	3415	=item Python
2777		3416
2778	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3417	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2779	seems to be quite complete and well-documented. Note, however, that the	3418	seems to be quite complete and well-documented.
2780	patch they require for libev is outright dangerous as it breaks the ABI
2781	for everybody else, and therefore, should never be applied in an installed
2782	libev (if python requires an incompatible ABI then it needs to embed
2783	libev).
2784		3419
2785	=item Ruby	3420	=item Ruby
2786		3421
2787	Tony Arcieri has written a ruby extension that offers access to a subset	3422	Tony Arcieri has written a ruby extension that offers access to a subset
2788	of the libev API and adds file handle abstractions, asynchronous DNS and	3423	of the libev API and adds file handle abstractions, asynchronous DNS and
2789	more on top of it. It can be found via gem servers. Its homepage is at	3424	more on top of it. It can be found via gem servers. Its homepage is at
2790	L<http://rev.rubyforge.org/>.	3425	L<http://rev.rubyforge.org/>.
2791		3426
		3427	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3428	makes rev work even on mingw.
		3429
		3430	=item Haskell
		3431
		3432	A haskell binding to libev is available at
		3433	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3434
2792	=item D	3435	=item D
2793		3436
2794	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3437	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2795	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3438	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3439
		3440	=item Ocaml
		3441
		3442	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3443	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3444
		3445	=item Lua
		3446
		3447	Brian Maher has written a partial interface to libev
		3448	for lua (only C<ev_io> and C<ev_timer>), to be found at
		3449	L<http://github.com/brimworks/lua-ev>.
2796		3450
2797	=back	3451	=back
2798		3452
2799		3453
2800	=head1 MACRO MAGIC	3454	=head1 MACRO MAGIC
…		…
2901		3555
2902	#define EV_STANDALONE 1	3556	#define EV_STANDALONE 1
2903	#include "ev.h"	3557	#include "ev.h"
2904		3558
2905	Both header files and implementation files can be compiled with a C++	3559	Both header files and implementation files can be compiled with a C++
2906	compiler (at least, thats a stated goal, and breakage will be treated	3560	compiler (at least, that's a stated goal, and breakage will be treated
2907	as a bug).	3561	as a bug).
2908		3562
2909	You need the following files in your source tree, or in a directory	3563	You need the following files in your source tree, or in a directory
2910	in your include path (e.g. in libev/ when using -Ilibev):	3564	in your include path (e.g. in libev/ when using -Ilibev):
2911		3565
…		…
2967	keeps libev from including F<config.h>, and it also defines dummy	3621	keeps libev from including F<config.h>, and it also defines dummy
2968	implementations for some libevent functions (such as logging, which is not	3622	implementations for some libevent functions (such as logging, which is not
2969	supported). It will also not define any of the structs usually found in	3623	supported). It will also not define any of the structs usually found in
2970	F<event.h> that are not directly supported by the libev core alone.	3624	F<event.h> that are not directly supported by the libev core alone.
2971		3625
		3626	In standalone mode, libev will still try to automatically deduce the
		3627	configuration, but has to be more conservative.
		3628
2972	=item EV_USE_MONOTONIC	3629	=item EV_USE_MONOTONIC
2973		3630
2974	If defined to be C<1>, libev will try to detect the availability of the	3631	If defined to be C<1>, libev will try to detect the availability of the
2975	monotonic clock option at both compile time and runtime. Otherwise no use	3632	monotonic clock option at both compile time and runtime. Otherwise no
2976	of the monotonic clock option will be attempted. If you enable this, you	3633	use of the monotonic clock option will be attempted. If you enable this,
2977	usually have to link against librt or something similar. Enabling it when	3634	you usually have to link against librt or something similar. Enabling it
2978	the functionality isn't available is safe, though, although you have	3635	when the functionality isn't available is safe, though, although you have
2979	to make sure you link against any libraries where the C<clock_gettime>	3636	to make sure you link against any libraries where the C<clock_gettime>
2980	function is hiding in (often F<-lrt>).	3637	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2981		3638
2982	=item EV_USE_REALTIME	3639	=item EV_USE_REALTIME
2983		3640
2984	If defined to be C<1>, libev will try to detect the availability of the	3641	If defined to be C<1>, libev will try to detect the availability of the
2985	real-time clock option at compile time (and assume its availability at	3642	real-time clock option at compile time (and assume its availability
2986	runtime if successful). Otherwise no use of the real-time clock option will	3643	at runtime if successful). Otherwise no use of the real-time clock
2987	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3644	option will be attempted. This effectively replaces C<gettimeofday>
2988	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3645	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2989	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3646	correctness. See the note about libraries in the description of
		3647	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3648	C<EV_USE_CLOCK_SYSCALL>.
		3649
		3650	=item EV_USE_CLOCK_SYSCALL
		3651
		3652	If defined to be C<1>, libev will try to use a direct syscall instead
		3653	of calling the system-provided C<clock_gettime> function. This option
		3654	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3655	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3656	programs needlessly. Using a direct syscall is slightly slower (in
		3657	theory), because no optimised vdso implementation can be used, but avoids
		3658	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3659	higher, as it simplifies linking (no need for C<-lrt>).
2990		3660
2991	=item EV_USE_NANOSLEEP	3661	=item EV_USE_NANOSLEEP
2992		3662
2993	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3663	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2994	and will use it for delays. Otherwise it will use C<select ()>.	3664	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3010		3680
3011	=item EV_SELECT_USE_FD_SET	3681	=item EV_SELECT_USE_FD_SET
3012		3682
3013	If defined to C<1>, then the select backend will use the system C<fd_set>	3683	If defined to C<1>, then the select backend will use the system C<fd_set>
3014	structure. This is useful if libev doesn't compile due to a missing	3684	structure. This is useful if libev doesn't compile due to a missing
3015	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3685	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3016	exotic systems. This usually limits the range of file descriptors to some	3686	on exotic systems. This usually limits the range of file descriptors to
3017	low limit such as 1024 or might have other limitations (winsocket only	3687	some low limit such as 1024 or might have other limitations (winsocket
3018	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3688	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3019	influence the size of the C<fd_set> used.	3689	configures the maximum size of the C<fd_set>.
3020		3690
3021	=item EV_SELECT_IS_WINSOCKET	3691	=item EV_SELECT_IS_WINSOCKET
3022		3692
3023	When defined to C<1>, the select backend will assume that	3693	When defined to C<1>, the select backend will assume that
3024	select/socket/connect etc. don't understand file descriptors but	3694	select/socket/connect etc. don't understand file descriptors but
…		…
3026	be used is the winsock select). This means that it will call	3696	be used is the winsock select). This means that it will call
3027	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3697	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3028	it is assumed that all these functions actually work on fds, even	3698	it is assumed that all these functions actually work on fds, even
3029	on win32. Should not be defined on non-win32 platforms.	3699	on win32. Should not be defined on non-win32 platforms.
3030		3700
3031	=item EV_FD_TO_WIN32_HANDLE	3701	=item EV_FD_TO_WIN32_HANDLE(fd)
3032		3702
3033	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3703	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3034	file descriptors to socket handles. When not defining this symbol (the	3704	file descriptors to socket handles. When not defining this symbol (the
3035	default), then libev will call C<_get_osfhandle>, which is usually	3705	default), then libev will call C<_get_osfhandle>, which is usually
3036	correct. In some cases, programs use their own file descriptor management,	3706	correct. In some cases, programs use their own file descriptor management,
3037	in which case they can provide this function to map fds to socket handles.	3707	in which case they can provide this function to map fds to socket handles.
		3708
		3709	=item EV_WIN32_HANDLE_TO_FD(handle)
		3710
		3711	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3712	using the standard C<_open_osfhandle> function. For programs implementing
		3713	their own fd to handle mapping, overwriting this function makes it easier
		3714	to do so. This can be done by defining this macro to an appropriate value.
		3715
		3716	=item EV_WIN32_CLOSE_FD(fd)
		3717
		3718	If programs implement their own fd to handle mapping on win32, then this
		3719	macro can be used to override the C<close> function, useful to unregister
		3720	file descriptors again. Note that the replacement function has to close
		3721	the underlying OS handle.
3038		3722
3039	=item EV_USE_POLL	3723	=item EV_USE_POLL
3040		3724
3041	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3725	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3042	backend. Otherwise it will be enabled on non-win32 platforms. It	3726	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3174	defined to be C<0>, then they are not.	3858	defined to be C<0>, then they are not.
3175		3859
3176	=item EV_MINIMAL	3860	=item EV_MINIMAL
3177		3861
3178	If you need to shave off some kilobytes of code at the expense of some	3862	If you need to shave off some kilobytes of code at the expense of some
3179	speed, define this symbol to C<1>. Currently this is used to override some	3863	speed (but with the full API), define this symbol to C<1>. Currently this
3180	inlining decisions, saves roughly 30% code size on amd64. It also selects a	3864	is used to override some inlining decisions, saves roughly 30% code size
3181	much smaller 2-heap for timer management over the default 4-heap.	3865	on amd64. It also selects a much smaller 2-heap for timer management over
		3866	the default 4-heap.
		3867
		3868	You can save even more by disabling watcher types you do not need
		3869	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>
		3870	(C<-DNDEBUG>) will usually reduce code size a lot.
		3871
		3872	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to
		3873	provide a bare-bones event library. See C<ev.h> for details on what parts
		3874	of the API are still available, and do not complain if this subset changes
		3875	over time.
		3876
		3877	=item EV_NSIG
		3878
		3879	The highest supported signal number, +1 (or, the number of
		3880	signals): Normally, libev tries to deduce the maximum number of signals
		3881	automatically, but sometimes this fails, in which case it can be
		3882	specified. Also, using a lower number than detected (C<32> should be
		3883	good for about any system in existance) can save some memory, as libev
		3884	statically allocates some 12-24 bytes per signal number.
3182		3885
3183	=item EV_PID_HASHSIZE	3886	=item EV_PID_HASHSIZE
3184		3887
3185	C<ev_child> watchers use a small hash table to distribute workload by	3888	C<ev_child> watchers use a small hash table to distribute workload by
3186	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3889	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
3372	default loop and triggering an C<ev_async> watcher from the default loop	4075	default loop and triggering an C<ev_async> watcher from the default loop
3373	watcher callback into the event loop interested in the signal.	4076	watcher callback into the event loop interested in the signal.
3374		4077
3375	=back	4078	=back
3376		4079
		4080	=head4 THREAD LOCKING EXAMPLE
		4081
		4082	Here is a fictitious example of how to run an event loop in a different
		4083	thread than where callbacks are being invoked and watchers are
		4084	created/added/removed.
		4085
		4086	For a real-world example, see the C<EV::Loop::Async> perl module,
		4087	which uses exactly this technique (which is suited for many high-level
		4088	languages).
		4089
		4090	The example uses a pthread mutex to protect the loop data, a condition
		4091	variable to wait for callback invocations, an async watcher to notify the
		4092	event loop thread and an unspecified mechanism to wake up the main thread.
		4093
		4094	First, you need to associate some data with the event loop:
		4095
		4096	typedef struct {
		4097	mutex_t lock; /* global loop lock */
		4098	ev_async async_w;
		4099	thread_t tid;
		4100	cond_t invoke_cv;
		4101	} userdata;
		4102
		4103	void prepare_loop (EV_P)
		4104	{
		4105	// for simplicity, we use a static userdata struct.
		4106	static userdata u;
		4107
		4108	ev_async_init (&u->async_w, async_cb);
		4109	ev_async_start (EV_A_ &u->async_w);
		4110
		4111	pthread_mutex_init (&u->lock, 0);
		4112	pthread_cond_init (&u->invoke_cv, 0);
		4113
		4114	// now associate this with the loop
		4115	ev_set_userdata (EV_A_ u);
		4116	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4117	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4118
		4119	// then create the thread running ev_loop
		4120	pthread_create (&u->tid, 0, l_run, EV_A);
		4121	}
		4122
		4123	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4124	solely to wake up the event loop so it takes notice of any new watchers
		4125	that might have been added:
		4126
		4127	static void
		4128	async_cb (EV_P_ ev_async *w, int revents)
		4129	{
		4130	// just used for the side effects
		4131	}
		4132
		4133	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4134	protecting the loop data, respectively.
		4135
		4136	static void
		4137	l_release (EV_P)
		4138	{
		4139	userdata *u = ev_userdata (EV_A);
		4140	pthread_mutex_unlock (&u->lock);
		4141	}
		4142
		4143	static void
		4144	l_acquire (EV_P)
		4145	{
		4146	userdata *u = ev_userdata (EV_A);
		4147	pthread_mutex_lock (&u->lock);
		4148	}
		4149
		4150	The event loop thread first acquires the mutex, and then jumps straight
		4151	into C<ev_loop>:
		4152
		4153	void *
		4154	l_run (void *thr_arg)
		4155	{
		4156	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4157
		4158	l_acquire (EV_A);
		4159	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4160	ev_loop (EV_A_ 0);
		4161	l_release (EV_A);
		4162
		4163	return 0;
		4164	}
		4165
		4166	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4167	signal the main thread via some unspecified mechanism (signals? pipe
		4168	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4169	have been called (in a while loop because a) spurious wakeups are possible
		4170	and b) skipping inter-thread-communication when there are no pending
		4171	watchers is very beneficial):
		4172
		4173	static void
		4174	l_invoke (EV_P)
		4175	{
		4176	userdata *u = ev_userdata (EV_A);
		4177
		4178	while (ev_pending_count (EV_A))
		4179	{
		4180	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4181	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4182	}
		4183	}
		4184
		4185	Now, whenever the main thread gets told to invoke pending watchers, it
		4186	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4187	thread to continue:
		4188
		4189	static void
		4190	real_invoke_pending (EV_P)
		4191	{
		4192	userdata *u = ev_userdata (EV_A);
		4193
		4194	pthread_mutex_lock (&u->lock);
		4195	ev_invoke_pending (EV_A);
		4196	pthread_cond_signal (&u->invoke_cv);
		4197	pthread_mutex_unlock (&u->lock);
		4198	}
		4199
		4200	Whenever you want to start/stop a watcher or do other modifications to an
		4201	event loop, you will now have to lock:
		4202
		4203	ev_timer timeout_watcher;
		4204	userdata *u = ev_userdata (EV_A);
		4205
		4206	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4207
		4208	pthread_mutex_lock (&u->lock);
		4209	ev_timer_start (EV_A_ &timeout_watcher);
		4210	ev_async_send (EV_A_ &u->async_w);
		4211	pthread_mutex_unlock (&u->lock);
		4212
		4213	Note that sending the C<ev_async> watcher is required because otherwise
		4214	an event loop currently blocking in the kernel will have no knowledge
		4215	about the newly added timer. By waking up the loop it will pick up any new
		4216	watchers in the next event loop iteration.
		4217
3377	=head3 COROUTINES	4218	=head3 COROUTINES
3378		4219
3379	Libev is very accommodating to coroutines ("cooperative threads"):	4220	Libev is very accommodating to coroutines ("cooperative threads"):
3380	libev fully supports nesting calls to its functions from different	4221	libev fully supports nesting calls to its functions from different
3381	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4222	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3382	different coroutines, and switch freely between both coroutines running the	4223	different coroutines, and switch freely between both coroutines running
3383	loop, as long as you don't confuse yourself). The only exception is that	4224	the loop, as long as you don't confuse yourself). The only exception is
3384	you must not do this from C<ev_periodic> reschedule callbacks.	4225	that you must not do this from C<ev_periodic> reschedule callbacks.
3385		4226
3386	Care has been taken to ensure that libev does not keep local state inside	4227	Care has been taken to ensure that libev does not keep local state inside
3387	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4228	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3388	they do not clal any callbacks.	4229	they do not call any callbacks.
3389		4230
3390	=head2 COMPILER WARNINGS	4231	=head2 COMPILER WARNINGS
3391		4232
3392	Depending on your compiler and compiler settings, you might get no or a	4233	Depending on your compiler and compiler settings, you might get no or a
3393	lot of warnings when compiling libev code. Some people are apparently	4234	lot of warnings when compiling libev code. Some people are apparently
…		…
3427	==2274== definitely lost: 0 bytes in 0 blocks.	4268	==2274== definitely lost: 0 bytes in 0 blocks.
3428	==2274== possibly lost: 0 bytes in 0 blocks.	4269	==2274== possibly lost: 0 bytes in 0 blocks.
3429	==2274== still reachable: 256 bytes in 1 blocks.	4270	==2274== still reachable: 256 bytes in 1 blocks.
3430		4271
3431	Then there is no memory leak, just as memory accounted to global variables	4272	Then there is no memory leak, just as memory accounted to global variables
3432	is not a memleak - the memory is still being refernced, and didn't leak.	4273	is not a memleak - the memory is still being referenced, and didn't leak.
3433		4274
3434	Similarly, under some circumstances, valgrind might report kernel bugs	4275	Similarly, under some circumstances, valgrind might report kernel bugs
3435	as if it were a bug in libev (e.g. in realloc or in the poll backend,	4276	as if it were a bug in libev (e.g. in realloc or in the poll backend,
3436	although an acceptable workaround has been found here), or it might be	4277	although an acceptable workaround has been found here), or it might be
3437	confused.	4278	confused.
…		…
3466	way (note also that glib is the slowest event library known to man).	4307	way (note also that glib is the slowest event library known to man).
3467		4308
3468	There is no supported compilation method available on windows except	4309	There is no supported compilation method available on windows except
3469	embedding it into other applications.	4310	embedding it into other applications.
3470		4311
		4312	Sensible signal handling is officially unsupported by Microsoft - libev
		4313	tries its best, but under most conditions, signals will simply not work.
		4314
3471	Not a libev limitation but worth mentioning: windows apparently doesn't	4315	Not a libev limitation but worth mentioning: windows apparently doesn't
3472	accept large writes: instead of resulting in a partial write, windows will	4316	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,	4317	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	4318	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	4319	megabyte seems safe, but this apparently depends on the amount of memory
…		…
3479	the abysmal performance of winsockets, using a large number of sockets	4323	the abysmal performance of winsockets, using a large number of sockets
3480	is not recommended (and not reasonable). If your program needs to use	4324	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	4325	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	4326	different implementation for windows, as libev offers the POSIX readiness
3483	notification model, which cannot be implemented efficiently on windows	4327	notification model, which cannot be implemented efficiently on windows
3484	(Microsoft monopoly games).	4328	(due to Microsoft monopoly games).
3485		4329
3486	A typical way to use libev under windows is to embed it (see the embedding	4330	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	4331	section for details) and use the following F<evwrap.h> header file instead
3488	of F<ev.h>:	4332	of F<ev.h>:
3489		4333
…		…
3525		4369
3526	Early versions of winsocket's select only supported waiting for a maximum	4370	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	4371	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	4372	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	4373	recommends spawning a chain of threads and wait for 63 handles and the
3530	previous thread in each. Great).	4374	previous thread in each. Sounds great!).
3531		4375
3532	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4376	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	4377	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	4378	call (which might be in libev or elsewhere, for example, perl and many
3535	select emulation on windows).	4379	other interpreters do their own select emulation on windows).
3536		4380
3537	Another limit is the number of file descriptors in the Microsoft runtime	4381	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	4382	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	4383	fetish or something like this inside Microsoft). You can increase this
3540	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4384	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	4385	(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	4386	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	4387	(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	4388	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.	4389	the cost of calling select (O(n²)) will likely make this unworkable.
3548		4390
3549	=back	4391	=back
3550		4392
3551	=head2 PORTABILITY REQUIREMENTS	4393	=head2 PORTABILITY REQUIREMENTS
3552		4394
…		…
3595	=item C<double> must hold a time value in seconds with enough accuracy	4437	=item C<double> must hold a time value in seconds with enough accuracy
3596		4438
3597	The type C<double> is used to represent timestamps. It is required to	4439	The type C<double> is used to represent timestamps. It is required to
3598	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4440	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
3599	enough for at least into the year 4000. This requirement is fulfilled by	4441	enough for at least into the year 4000. This requirement is fulfilled by
3600	implementations implementing IEEE 754 (basically all existing ones).	4442	implementations implementing IEEE 754, which is basically all existing
		4443	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4444	2200.
3601		4445
3602	=back	4446	=back
3603		4447
3604	If you know of other additional requirements drop me a note.	4448	If you know of other additional requirements drop me a note.
3605		4449
…		…
3673	involves iterating over all running async watchers or all signal numbers.	4517	involves iterating over all running async watchers or all signal numbers.
3674		4518
3675	=back	4519	=back
3676		4520
3677		4521
		4522	=head1 GLOSSARY
		4523
		4524	=over 4
		4525
		4526	=item active
		4527
		4528	A watcher is active as long as it has been started (has been attached to
		4529	an event loop) but not yet stopped (disassociated from the event loop).
		4530
		4531	=item application
		4532
		4533	In this document, an application is whatever is using libev.
		4534
		4535	=item callback
		4536
		4537	The address of a function that is called when some event has been
		4538	detected. Callbacks are being passed the event loop, the watcher that
		4539	received the event, and the actual event bitset.
		4540
		4541	=item callback invocation
		4542
		4543	The act of calling the callback associated with a watcher.
		4544
		4545	=item event
		4546
		4547	A change of state of some external event, such as data now being available
		4548	for reading on a file descriptor, time having passed or simply not having
		4549	any other events happening anymore.
		4550
		4551	In libev, events are represented as single bits (such as C<EV_READ> or
		4552	C<EV_TIMEOUT>).
		4553
		4554	=item event library
		4555
		4556	A software package implementing an event model and loop.
		4557
		4558	=item event loop
		4559
		4560	An entity that handles and processes external events and converts them
		4561	into callback invocations.
		4562
		4563	=item event model
		4564
		4565	The model used to describe how an event loop handles and processes
		4566	watchers and events.
		4567
		4568	=item pending
		4569
		4570	A watcher is pending as soon as the corresponding event has been detected,
		4571	and stops being pending as soon as the watcher will be invoked or its
		4572	pending status is explicitly cleared by the application.
		4573
		4574	A watcher can be pending, but not active. Stopping a watcher also clears
		4575	its pending status.
		4576
		4577	=item real time
		4578
		4579	The physical time that is observed. It is apparently strictly monotonic :)
		4580
		4581	=item wall-clock time
		4582
		4583	The time and date as shown on clocks. Unlike real time, it can actually
		4584	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4585	clock.
		4586
		4587	=item watcher
		4588
		4589	A data structure that describes interest in certain events. Watchers need
		4590	to be started (attached to an event loop) before they can receive events.
		4591
		4592	=item watcher invocation
		4593
		4594	The act of calling the callback associated with a watcher.
		4595
		4596	=back
		4597
3678	=head1 AUTHOR	4598	=head1 AUTHOR
3679		4599
3680	Marc Lehmann <libev@schmorp.de>.	4600	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3681		4601

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